blob: eec3e6f9956cad798b6cc930cf7b799a64fca911 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
5 *
6 * Implementation of the Transmission Control Protocol(TCP).
7 *
Jesper Juhl02c30a82005-05-05 16:16:16 -07008 * Authors: Ross Biro
Linus Torvalds1da177e2005-04-16 15:20:36 -07009 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
10 * Mark Evans, <evansmp@uhura.aston.ac.uk>
11 * Corey Minyard <wf-rch!minyard@relay.EU.net>
12 * Florian La Roche, <flla@stud.uni-sb.de>
13 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
14 * Linus Torvalds, <torvalds@cs.helsinki.fi>
15 * Alan Cox, <gw4pts@gw4pts.ampr.org>
16 * Matthew Dillon, <dillon@apollo.west.oic.com>
17 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
18 * Jorge Cwik, <jorge@laser.satlink.net>
19 */
20
21/*
22 * Changes:
23 * Pedro Roque : Fast Retransmit/Recovery.
24 * Two receive queues.
25 * Retransmit queue handled by TCP.
26 * Better retransmit timer handling.
27 * New congestion avoidance.
28 * Header prediction.
29 * Variable renaming.
30 *
31 * Eric : Fast Retransmit.
32 * Randy Scott : MSS option defines.
33 * Eric Schenk : Fixes to slow start algorithm.
34 * Eric Schenk : Yet another double ACK bug.
35 * Eric Schenk : Delayed ACK bug fixes.
36 * Eric Schenk : Floyd style fast retrans war avoidance.
37 * David S. Miller : Don't allow zero congestion window.
38 * Eric Schenk : Fix retransmitter so that it sends
39 * next packet on ack of previous packet.
40 * Andi Kleen : Moved open_request checking here
41 * and process RSTs for open_requests.
42 * Andi Kleen : Better prune_queue, and other fixes.
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -080043 * Andrey Savochkin: Fix RTT measurements in the presence of
Linus Torvalds1da177e2005-04-16 15:20:36 -070044 * timestamps.
45 * Andrey Savochkin: Check sequence numbers correctly when
46 * removing SACKs due to in sequence incoming
47 * data segments.
48 * Andi Kleen: Make sure we never ack data there is not
49 * enough room for. Also make this condition
50 * a fatal error if it might still happen.
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +090051 * Andi Kleen: Add tcp_measure_rcv_mss to make
Linus Torvalds1da177e2005-04-16 15:20:36 -070052 * connections with MSS<min(MTU,ann. MSS)
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +090053 * work without delayed acks.
Linus Torvalds1da177e2005-04-16 15:20:36 -070054 * Andi Kleen: Process packets with PSH set in the
55 * fast path.
56 * J Hadi Salim: ECN support
57 * Andrei Gurtov,
58 * Pasi Sarolahti,
59 * Panu Kuhlberg: Experimental audit of TCP (re)transmission
60 * engine. Lots of bugs are found.
61 * Pasi Sarolahti: F-RTO for dealing with spurious RTOs
Linus Torvalds1da177e2005-04-16 15:20:36 -070062 */
63
Linus Torvalds1da177e2005-04-16 15:20:36 -070064#include <linux/mm.h>
65#include <linux/module.h>
66#include <linux/sysctl.h>
Ilpo Järvinena0bffff2009-03-21 13:36:17 -070067#include <linux/kernel.h>
Satoru SATOH5ffc02a2008-05-04 22:14:42 -070068#include <net/dst.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070069#include <net/tcp.h>
70#include <net/inet_common.h>
71#include <linux/ipsec.h>
72#include <asm/unaligned.h>
Chris Leech1a2449a2006-05-23 18:05:53 -070073#include <net/netdma.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070074
Brian Haleyab32ea52006-09-22 14:15:41 -070075int sysctl_tcp_timestamps __read_mostly = 1;
76int sysctl_tcp_window_scaling __read_mostly = 1;
77int sysctl_tcp_sack __read_mostly = 1;
78int sysctl_tcp_fack __read_mostly = 1;
79int sysctl_tcp_reordering __read_mostly = TCP_FASTRETRANS_THRESH;
80int sysctl_tcp_ecn __read_mostly;
81int sysctl_tcp_dsack __read_mostly = 1;
82int sysctl_tcp_app_win __read_mostly = 31;
83int sysctl_tcp_adv_win_scale __read_mostly = 2;
Linus Torvalds1da177e2005-04-16 15:20:36 -070084
Brian Haleyab32ea52006-09-22 14:15:41 -070085int sysctl_tcp_stdurg __read_mostly;
86int sysctl_tcp_rfc1337 __read_mostly;
87int sysctl_tcp_max_orphans __read_mostly = NR_FILE;
Ilpo Järvinenc96fd3d2007-09-20 11:36:37 -070088int sysctl_tcp_frto __read_mostly = 2;
Ilpo Järvinen3cfe3ba2007-02-27 10:09:49 -080089int sysctl_tcp_frto_response __read_mostly;
Brian Haleyab32ea52006-09-22 14:15:41 -070090int sysctl_tcp_nometrics_save __read_mostly;
Linus Torvalds1da177e2005-04-16 15:20:36 -070091
Brian Haleyab32ea52006-09-22 14:15:41 -070092int sysctl_tcp_moderate_rcvbuf __read_mostly = 1;
93int sysctl_tcp_abc __read_mostly;
Linus Torvalds1da177e2005-04-16 15:20:36 -070094
Linus Torvalds1da177e2005-04-16 15:20:36 -070095#define FLAG_DATA 0x01 /* Incoming frame contained data. */
96#define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
97#define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
98#define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
99#define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
100#define FLAG_DATA_SACKED 0x20 /* New SACK. */
101#define FLAG_ECE 0x40 /* ECE in this ACK */
102#define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */
103#define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
Ilpo Järvinen4dc26652007-02-21 23:16:11 -0800104#define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */
Ilpo Järvinen2e605292007-08-02 19:46:58 -0700105#define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
Ryousei Takano564262c12007-10-25 23:03:52 -0700106#define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
Ilpo Järvinen009a2e32007-09-20 11:34:38 -0700107#define FLAG_NONHEAD_RETRANS_ACKED 0x1000 /* Non-head rexmitted data was ACKed */
Ilpo Järvinencadbd032007-12-31 04:49:21 -0800108#define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700109
110#define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
111#define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
112#define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
113#define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
Ilpo Järvinen2e605292007-08-02 19:46:58 -0700114#define FLAG_ANY_PROGRESS (FLAG_FORWARD_PROGRESS|FLAG_SND_UNA_ADVANCED)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115
Linus Torvalds1da177e2005-04-16 15:20:36 -0700116#define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
Ilpo Järvinenbdf1ee52007-05-27 02:04:16 -0700117#define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700118
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900119/* Adapt the MSS value used to make delayed ack decision to the
Linus Torvalds1da177e2005-04-16 15:20:36 -0700120 * real world.
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900121 */
Ilpo Järvinen056834d2007-12-31 14:57:14 -0800122static void tcp_measure_rcv_mss(struct sock *sk, const struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700123{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700124 struct inet_connection_sock *icsk = inet_csk(sk);
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900125 const unsigned int lss = icsk->icsk_ack.last_seg_size;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700126 unsigned int len;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700127
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900128 icsk->icsk_ack.last_seg_size = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700129
130 /* skb->len may jitter because of SACKs, even if peer
131 * sends good full-sized frames.
132 */
Ilpo Järvinen056834d2007-12-31 14:57:14 -0800133 len = skb_shinfo(skb)->gso_size ? : skb->len;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700134 if (len >= icsk->icsk_ack.rcv_mss) {
135 icsk->icsk_ack.rcv_mss = len;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700136 } else {
137 /* Otherwise, we make more careful check taking into account,
138 * that SACKs block is variable.
139 *
140 * "len" is invariant segment length, including TCP header.
141 */
Arnaldo Carvalho de Melo9c702202007-04-25 18:04:18 -0700142 len += skb->data - skb_transport_header(skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700143 if (len >= TCP_MIN_RCVMSS + sizeof(struct tcphdr) ||
144 /* If PSH is not set, packet should be
145 * full sized, provided peer TCP is not badly broken.
146 * This observation (if it is correct 8)) allows
147 * to handle super-low mtu links fairly.
148 */
149 (len >= TCP_MIN_MSS + sizeof(struct tcphdr) &&
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -0700150 !(tcp_flag_word(tcp_hdr(skb)) & TCP_REMNANT))) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700151 /* Subtract also invariant (if peer is RFC compliant),
152 * tcp header plus fixed timestamp option length.
153 * Resulting "len" is MSS free of SACK jitter.
154 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700155 len -= tcp_sk(sk)->tcp_header_len;
156 icsk->icsk_ack.last_seg_size = len;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700157 if (len == lss) {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700158 icsk->icsk_ack.rcv_mss = len;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700159 return;
160 }
161 }
Alexey Kuznetsov1ef96962006-09-19 12:52:50 -0700162 if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED)
163 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700164 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700165 }
166}
167
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700168static void tcp_incr_quickack(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700169{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700170 struct inet_connection_sock *icsk = inet_csk(sk);
171 unsigned quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700172
Ilpo Järvinen056834d2007-12-31 14:57:14 -0800173 if (quickacks == 0)
174 quickacks = 2;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700175 if (quickacks > icsk->icsk_ack.quick)
176 icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700177}
178
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700179void tcp_enter_quickack_mode(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700180{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700181 struct inet_connection_sock *icsk = inet_csk(sk);
182 tcp_incr_quickack(sk);
183 icsk->icsk_ack.pingpong = 0;
184 icsk->icsk_ack.ato = TCP_ATO_MIN;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700185}
186
187/* Send ACKs quickly, if "quick" count is not exhausted
188 * and the session is not interactive.
189 */
190
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700191static inline int tcp_in_quickack_mode(const struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700192{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700193 const struct inet_connection_sock *icsk = inet_csk(sk);
194 return icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700195}
196
Ilpo Järvinenbdf1ee52007-05-27 02:04:16 -0700197static inline void TCP_ECN_queue_cwr(struct tcp_sock *tp)
198{
Ilpo Järvinen056834d2007-12-31 14:57:14 -0800199 if (tp->ecn_flags & TCP_ECN_OK)
Ilpo Järvinenbdf1ee52007-05-27 02:04:16 -0700200 tp->ecn_flags |= TCP_ECN_QUEUE_CWR;
201}
202
203static inline void TCP_ECN_accept_cwr(struct tcp_sock *tp, struct sk_buff *skb)
204{
205 if (tcp_hdr(skb)->cwr)
206 tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
207}
208
209static inline void TCP_ECN_withdraw_cwr(struct tcp_sock *tp)
210{
211 tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
212}
213
214static inline void TCP_ECN_check_ce(struct tcp_sock *tp, struct sk_buff *skb)
215{
Ilpo Järvinen056834d2007-12-31 14:57:14 -0800216 if (tp->ecn_flags & TCP_ECN_OK) {
Ilpo Järvinenbdf1ee52007-05-27 02:04:16 -0700217 if (INET_ECN_is_ce(TCP_SKB_CB(skb)->flags))
218 tp->ecn_flags |= TCP_ECN_DEMAND_CWR;
219 /* Funny extension: if ECT is not set on a segment,
220 * it is surely retransmit. It is not in ECN RFC,
221 * but Linux follows this rule. */
222 else if (INET_ECN_is_not_ect((TCP_SKB_CB(skb)->flags)))
223 tcp_enter_quickack_mode((struct sock *)tp);
224 }
225}
226
227static inline void TCP_ECN_rcv_synack(struct tcp_sock *tp, struct tcphdr *th)
228{
Ilpo Järvinen056834d2007-12-31 14:57:14 -0800229 if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || th->cwr))
Ilpo Järvinenbdf1ee52007-05-27 02:04:16 -0700230 tp->ecn_flags &= ~TCP_ECN_OK;
231}
232
233static inline void TCP_ECN_rcv_syn(struct tcp_sock *tp, struct tcphdr *th)
234{
Ilpo Järvinen056834d2007-12-31 14:57:14 -0800235 if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || !th->cwr))
Ilpo Järvinenbdf1ee52007-05-27 02:04:16 -0700236 tp->ecn_flags &= ~TCP_ECN_OK;
237}
238
239static inline int TCP_ECN_rcv_ecn_echo(struct tcp_sock *tp, struct tcphdr *th)
240{
Ilpo Järvinen056834d2007-12-31 14:57:14 -0800241 if (th->ece && !th->syn && (tp->ecn_flags & TCP_ECN_OK))
Ilpo Järvinenbdf1ee52007-05-27 02:04:16 -0700242 return 1;
243 return 0;
244}
245
Linus Torvalds1da177e2005-04-16 15:20:36 -0700246/* Buffer size and advertised window tuning.
247 *
248 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
249 */
250
251static void tcp_fixup_sndbuf(struct sock *sk)
252{
253 int sndmem = tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER + 16 +
254 sizeof(struct sk_buff);
255
256 if (sk->sk_sndbuf < 3 * sndmem)
257 sk->sk_sndbuf = min(3 * sndmem, sysctl_tcp_wmem[2]);
258}
259
260/* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
261 *
262 * All tcp_full_space() is split to two parts: "network" buffer, allocated
263 * forward and advertised in receiver window (tp->rcv_wnd) and
264 * "application buffer", required to isolate scheduling/application
265 * latencies from network.
266 * window_clamp is maximal advertised window. It can be less than
267 * tcp_full_space(), in this case tcp_full_space() - window_clamp
268 * is reserved for "application" buffer. The less window_clamp is
269 * the smoother our behaviour from viewpoint of network, but the lower
270 * throughput and the higher sensitivity of the connection to losses. 8)
271 *
272 * rcv_ssthresh is more strict window_clamp used at "slow start"
273 * phase to predict further behaviour of this connection.
274 * It is used for two goals:
275 * - to enforce header prediction at sender, even when application
276 * requires some significant "application buffer". It is check #1.
277 * - to prevent pruning of receive queue because of misprediction
278 * of receiver window. Check #2.
279 *
280 * The scheme does not work when sender sends good segments opening
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800281 * window and then starts to feed us spaghetti. But it should work
Linus Torvalds1da177e2005-04-16 15:20:36 -0700282 * in common situations. Otherwise, we have to rely on queue collapsing.
283 */
284
285/* Slow part of check#2. */
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -0700286static int __tcp_grow_window(const struct sock *sk, const struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700287{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -0700288 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700289 /* Optimize this! */
Eric Dumazetdfd4f0a2007-12-21 06:07:53 -0800290 int truesize = tcp_win_from_space(skb->truesize) >> 1;
291 int window = tcp_win_from_space(sysctl_tcp_rmem[2]) >> 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700292
293 while (tp->rcv_ssthresh <= window) {
294 if (truesize <= skb->len)
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700295 return 2 * inet_csk(sk)->icsk_ack.rcv_mss;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700296
297 truesize >>= 1;
298 window >>= 1;
299 }
300 return 0;
301}
302
Ilpo Järvinen056834d2007-12-31 14:57:14 -0800303static void tcp_grow_window(struct sock *sk, struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700304{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -0700305 struct tcp_sock *tp = tcp_sk(sk);
306
Linus Torvalds1da177e2005-04-16 15:20:36 -0700307 /* Check #1 */
308 if (tp->rcv_ssthresh < tp->window_clamp &&
309 (int)tp->rcv_ssthresh < tcp_space(sk) &&
310 !tcp_memory_pressure) {
311 int incr;
312
313 /* Check #2. Increase window, if skb with such overhead
314 * will fit to rcvbuf in future.
315 */
316 if (tcp_win_from_space(skb->truesize) <= skb->len)
Ilpo Järvinen056834d2007-12-31 14:57:14 -0800317 incr = 2 * tp->advmss;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700318 else
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -0700319 incr = __tcp_grow_window(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700320
321 if (incr) {
Ilpo Järvinen056834d2007-12-31 14:57:14 -0800322 tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr,
323 tp->window_clamp);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700324 inet_csk(sk)->icsk_ack.quick |= 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700325 }
326 }
327}
328
329/* 3. Tuning rcvbuf, when connection enters established state. */
330
331static void tcp_fixup_rcvbuf(struct sock *sk)
332{
333 struct tcp_sock *tp = tcp_sk(sk);
334 int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff);
335
336 /* Try to select rcvbuf so that 4 mss-sized segments
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800337 * will fit to window and corresponding skbs will fit to our rcvbuf.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700338 * (was 3; 4 is minimum to allow fast retransmit to work.)
339 */
340 while (tcp_win_from_space(rcvmem) < tp->advmss)
341 rcvmem += 128;
342 if (sk->sk_rcvbuf < 4 * rcvmem)
343 sk->sk_rcvbuf = min(4 * rcvmem, sysctl_tcp_rmem[2]);
344}
345
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800346/* 4. Try to fixup all. It is made immediately after connection enters
Linus Torvalds1da177e2005-04-16 15:20:36 -0700347 * established state.
348 */
349static void tcp_init_buffer_space(struct sock *sk)
350{
351 struct tcp_sock *tp = tcp_sk(sk);
352 int maxwin;
353
354 if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK))
355 tcp_fixup_rcvbuf(sk);
356 if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK))
357 tcp_fixup_sndbuf(sk);
358
359 tp->rcvq_space.space = tp->rcv_wnd;
360
361 maxwin = tcp_full_space(sk);
362
363 if (tp->window_clamp >= maxwin) {
364 tp->window_clamp = maxwin;
365
366 if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss)
367 tp->window_clamp = max(maxwin -
368 (maxwin >> sysctl_tcp_app_win),
369 4 * tp->advmss);
370 }
371
372 /* Force reservation of one segment. */
373 if (sysctl_tcp_app_win &&
374 tp->window_clamp > 2 * tp->advmss &&
375 tp->window_clamp + tp->advmss > maxwin)
376 tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss);
377
378 tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp);
379 tp->snd_cwnd_stamp = tcp_time_stamp;
380}
381
Linus Torvalds1da177e2005-04-16 15:20:36 -0700382/* 5. Recalculate window clamp after socket hit its memory bounds. */
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -0700383static void tcp_clamp_window(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700384{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -0700385 struct tcp_sock *tp = tcp_sk(sk);
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300386 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700387
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300388 icsk->icsk_ack.quick = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700389
John Heffner326f36e2005-11-10 17:11:48 -0800390 if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] &&
391 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) &&
392 !tcp_memory_pressure &&
393 atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) {
394 sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc),
395 sysctl_tcp_rmem[2]);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700396 }
John Heffner326f36e2005-11-10 17:11:48 -0800397 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf)
Ilpo Järvinen056834d2007-12-31 14:57:14 -0800398 tp->rcv_ssthresh = min(tp->window_clamp, 2U * tp->advmss);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700399}
400
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800401/* Initialize RCV_MSS value.
402 * RCV_MSS is an our guess about MSS used by the peer.
403 * We haven't any direct information about the MSS.
404 * It's better to underestimate the RCV_MSS rather than overestimate.
405 * Overestimations make us ACKing less frequently than needed.
406 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
407 */
408void tcp_initialize_rcv_mss(struct sock *sk)
409{
410 struct tcp_sock *tp = tcp_sk(sk);
411 unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache);
412
Ilpo Järvinen056834d2007-12-31 14:57:14 -0800413 hint = min(hint, tp->rcv_wnd / 2);
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800414 hint = min(hint, TCP_MIN_RCVMSS);
415 hint = max(hint, TCP_MIN_MSS);
416
417 inet_csk(sk)->icsk_ack.rcv_mss = hint;
418}
419
Linus Torvalds1da177e2005-04-16 15:20:36 -0700420/* Receiver "autotuning" code.
421 *
422 * The algorithm for RTT estimation w/o timestamps is based on
423 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
424 * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps>
425 *
426 * More detail on this code can be found at
427 * <http://www.psc.edu/~jheffner/senior_thesis.ps>,
428 * though this reference is out of date. A new paper
429 * is pending.
430 */
431static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep)
432{
433 u32 new_sample = tp->rcv_rtt_est.rtt;
434 long m = sample;
435
436 if (m == 0)
437 m = 1;
438
439 if (new_sample != 0) {
440 /* If we sample in larger samples in the non-timestamp
441 * case, we could grossly overestimate the RTT especially
442 * with chatty applications or bulk transfer apps which
443 * are stalled on filesystem I/O.
444 *
445 * Also, since we are only going for a minimum in the
Stephen Hemminger31f34262005-11-15 15:17:10 -0800446 * non-timestamp case, we do not smooth things out
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800447 * else with timestamps disabled convergence takes too
Linus Torvalds1da177e2005-04-16 15:20:36 -0700448 * long.
449 */
450 if (!win_dep) {
451 m -= (new_sample >> 3);
452 new_sample += m;
453 } else if (m < new_sample)
454 new_sample = m << 3;
455 } else {
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800456 /* No previous measure. */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700457 new_sample = m << 3;
458 }
459
460 if (tp->rcv_rtt_est.rtt != new_sample)
461 tp->rcv_rtt_est.rtt = new_sample;
462}
463
464static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp)
465{
466 if (tp->rcv_rtt_est.time == 0)
467 goto new_measure;
468 if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq))
469 return;
Ilpo Järvinen056834d2007-12-31 14:57:14 -0800470 tcp_rcv_rtt_update(tp, jiffies - tp->rcv_rtt_est.time, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700471
472new_measure:
473 tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd;
474 tp->rcv_rtt_est.time = tcp_time_stamp;
475}
476
Ilpo Järvinen056834d2007-12-31 14:57:14 -0800477static inline void tcp_rcv_rtt_measure_ts(struct sock *sk,
478 const struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700479{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700480 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700481 if (tp->rx_opt.rcv_tsecr &&
482 (TCP_SKB_CB(skb)->end_seq -
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700483 TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700484 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0);
485}
486
487/*
488 * This function should be called every time data is copied to user space.
489 * It calculates the appropriate TCP receive buffer space.
490 */
491void tcp_rcv_space_adjust(struct sock *sk)
492{
493 struct tcp_sock *tp = tcp_sk(sk);
494 int time;
495 int space;
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900496
Linus Torvalds1da177e2005-04-16 15:20:36 -0700497 if (tp->rcvq_space.time == 0)
498 goto new_measure;
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900499
Linus Torvalds1da177e2005-04-16 15:20:36 -0700500 time = tcp_time_stamp - tp->rcvq_space.time;
Ilpo Järvinen056834d2007-12-31 14:57:14 -0800501 if (time < (tp->rcv_rtt_est.rtt >> 3) || tp->rcv_rtt_est.rtt == 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700502 return;
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900503
Linus Torvalds1da177e2005-04-16 15:20:36 -0700504 space = 2 * (tp->copied_seq - tp->rcvq_space.seq);
505
506 space = max(tp->rcvq_space.space, space);
507
508 if (tp->rcvq_space.space != space) {
509 int rcvmem;
510
511 tp->rcvq_space.space = space;
512
John Heffner6fcf9412006-02-09 17:06:57 -0800513 if (sysctl_tcp_moderate_rcvbuf &&
514 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700515 int new_clamp = space;
516
517 /* Receive space grows, normalize in order to
518 * take into account packet headers and sk_buff
519 * structure overhead.
520 */
521 space /= tp->advmss;
522 if (!space)
523 space = 1;
524 rcvmem = (tp->advmss + MAX_TCP_HEADER +
525 16 + sizeof(struct sk_buff));
526 while (tcp_win_from_space(rcvmem) < tp->advmss)
527 rcvmem += 128;
528 space *= rcvmem;
529 space = min(space, sysctl_tcp_rmem[2]);
530 if (space > sk->sk_rcvbuf) {
531 sk->sk_rcvbuf = space;
532
533 /* Make the window clamp follow along. */
534 tp->window_clamp = new_clamp;
535 }
536 }
537 }
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900538
Linus Torvalds1da177e2005-04-16 15:20:36 -0700539new_measure:
540 tp->rcvq_space.seq = tp->copied_seq;
541 tp->rcvq_space.time = tcp_time_stamp;
542}
543
544/* There is something which you must keep in mind when you analyze the
545 * behavior of the tp->ato delayed ack timeout interval. When a
546 * connection starts up, we want to ack as quickly as possible. The
547 * problem is that "good" TCP's do slow start at the beginning of data
548 * transmission. The means that until we send the first few ACK's the
549 * sender will sit on his end and only queue most of his data, because
550 * he can only send snd_cwnd unacked packets at any given time. For
551 * each ACK we send, he increments snd_cwnd and transmits more of his
552 * queue. -DaveM
553 */
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -0700554static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700555{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -0700556 struct tcp_sock *tp = tcp_sk(sk);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700557 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700558 u32 now;
559
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700560 inet_csk_schedule_ack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700561
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700562 tcp_measure_rcv_mss(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700563
564 tcp_rcv_rtt_measure(tp);
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900565
Linus Torvalds1da177e2005-04-16 15:20:36 -0700566 now = tcp_time_stamp;
567
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700568 if (!icsk->icsk_ack.ato) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700569 /* The _first_ data packet received, initialize
570 * delayed ACK engine.
571 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700572 tcp_incr_quickack(sk);
573 icsk->icsk_ack.ato = TCP_ATO_MIN;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700574 } else {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700575 int m = now - icsk->icsk_ack.lrcvtime;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700576
Ilpo Järvinen056834d2007-12-31 14:57:14 -0800577 if (m <= TCP_ATO_MIN / 2) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700578 /* The fastest case is the first. */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700579 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2;
580 } else if (m < icsk->icsk_ack.ato) {
581 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m;
582 if (icsk->icsk_ack.ato > icsk->icsk_rto)
583 icsk->icsk_ack.ato = icsk->icsk_rto;
584 } else if (m > icsk->icsk_rto) {
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800585 /* Too long gap. Apparently sender failed to
Linus Torvalds1da177e2005-04-16 15:20:36 -0700586 * restart window, so that we send ACKs quickly.
587 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700588 tcp_incr_quickack(sk);
Hideo Aoki3ab224b2007-12-31 00:11:19 -0800589 sk_mem_reclaim(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700590 }
591 }
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700592 icsk->icsk_ack.lrcvtime = now;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700593
594 TCP_ECN_check_ce(tp, skb);
595
596 if (skb->len >= 128)
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -0700597 tcp_grow_window(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700598}
599
Linus Torvalds1da177e2005-04-16 15:20:36 -0700600/* Called to compute a smoothed rtt estimate. The data fed to this
601 * routine either comes from timestamps, or from segments that were
602 * known _not_ to have been retransmitted [see Karn/Partridge
603 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
604 * piece by Van Jacobson.
605 * NOTE: the next three routines used to be one big routine.
606 * To save cycles in the RFC 1323 implementation it was better to break
607 * it up into three procedures. -- erics
608 */
Stephen Hemminger2d2abba2005-11-10 16:56:12 -0800609static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700610{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300611 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700612 long m = mrtt; /* RTT */
613
Linus Torvalds1da177e2005-04-16 15:20:36 -0700614 /* The following amusing code comes from Jacobson's
615 * article in SIGCOMM '88. Note that rtt and mdev
616 * are scaled versions of rtt and mean deviation.
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900617 * This is designed to be as fast as possible
Linus Torvalds1da177e2005-04-16 15:20:36 -0700618 * m stands for "measurement".
619 *
620 * On a 1990 paper the rto value is changed to:
621 * RTO = rtt + 4 * mdev
622 *
623 * Funny. This algorithm seems to be very broken.
624 * These formulae increase RTO, when it should be decreased, increase
Stephen Hemminger31f34262005-11-15 15:17:10 -0800625 * too slowly, when it should be increased quickly, decrease too quickly
Linus Torvalds1da177e2005-04-16 15:20:36 -0700626 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
627 * does not matter how to _calculate_ it. Seems, it was trap
628 * that VJ failed to avoid. 8)
629 */
Stephen Hemminger2de979b2007-03-08 20:45:19 -0800630 if (m == 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700631 m = 1;
632 if (tp->srtt != 0) {
633 m -= (tp->srtt >> 3); /* m is now error in rtt est */
634 tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */
635 if (m < 0) {
636 m = -m; /* m is now abs(error) */
637 m -= (tp->mdev >> 2); /* similar update on mdev */
638 /* This is similar to one of Eifel findings.
639 * Eifel blocks mdev updates when rtt decreases.
640 * This solution is a bit different: we use finer gain
641 * for mdev in this case (alpha*beta).
642 * Like Eifel it also prevents growth of rto,
643 * but also it limits too fast rto decreases,
644 * happening in pure Eifel.
645 */
646 if (m > 0)
647 m >>= 3;
648 } else {
649 m -= (tp->mdev >> 2); /* similar update on mdev */
650 }
651 tp->mdev += m; /* mdev = 3/4 mdev + 1/4 new */
652 if (tp->mdev > tp->mdev_max) {
653 tp->mdev_max = tp->mdev;
654 if (tp->mdev_max > tp->rttvar)
655 tp->rttvar = tp->mdev_max;
656 }
657 if (after(tp->snd_una, tp->rtt_seq)) {
658 if (tp->mdev_max < tp->rttvar)
Ilpo Järvinen056834d2007-12-31 14:57:14 -0800659 tp->rttvar -= (tp->rttvar - tp->mdev_max) >> 2;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700660 tp->rtt_seq = tp->snd_nxt;
David S. Miller05bb1fa2007-08-30 22:10:28 -0700661 tp->mdev_max = tcp_rto_min(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700662 }
663 } else {
664 /* no previous measure. */
Ilpo Järvinen056834d2007-12-31 14:57:14 -0800665 tp->srtt = m << 3; /* take the measured time to be rtt */
666 tp->mdev = m << 1; /* make sure rto = 3*rtt */
David S. Miller05bb1fa2007-08-30 22:10:28 -0700667 tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700668 tp->rtt_seq = tp->snd_nxt;
669 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700670}
671
672/* Calculate rto without backoff. This is the second half of Van Jacobson's
673 * routine referred to above.
674 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700675static inline void tcp_set_rto(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700676{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700677 const struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700678 /* Old crap is replaced with new one. 8)
679 *
680 * More seriously:
681 * 1. If rtt variance happened to be less 50msec, it is hallucination.
682 * It cannot be less due to utterly erratic ACK generation made
683 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
684 * to do with delayed acks, because at cwnd>2 true delack timeout
685 * is invisible. Actually, Linux-2.4 also generates erratic
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800686 * ACKs in some circumstances.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700687 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700688 inet_csk(sk)->icsk_rto = (tp->srtt >> 3) + tp->rttvar;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700689
690 /* 2. Fixups made earlier cannot be right.
691 * If we do not estimate RTO correctly without them,
692 * all the algo is pure shit and should be replaced
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800693 * with correct one. It is exactly, which we pretend to do.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700694 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700695
Ilpo Järvinenee6aac52008-12-05 22:43:08 -0800696 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
697 * guarantees that rto is higher.
698 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700699 if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
700 inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700701}
702
703/* Save metrics learned by this TCP session.
704 This function is called only, when TCP finishes successfully
705 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
706 */
707void tcp_update_metrics(struct sock *sk)
708{
709 struct tcp_sock *tp = tcp_sk(sk);
710 struct dst_entry *dst = __sk_dst_get(sk);
711
712 if (sysctl_tcp_nometrics_save)
713 return;
714
715 dst_confirm(dst);
716
Ilpo Järvinen056834d2007-12-31 14:57:14 -0800717 if (dst && (dst->flags & DST_HOST)) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300718 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700719 int m;
Stephen Hemmingerc1e20f72008-07-18 23:02:15 -0700720 unsigned long rtt;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700721
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300722 if (icsk->icsk_backoff || !tp->srtt) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700723 /* This session failed to estimate rtt. Why?
724 * Probably, no packets returned in time.
725 * Reset our results.
726 */
727 if (!(dst_metric_locked(dst, RTAX_RTT)))
Ilpo Järvinen056834d2007-12-31 14:57:14 -0800728 dst->metrics[RTAX_RTT - 1] = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700729 return;
730 }
731
Stephen Hemmingerc1e20f72008-07-18 23:02:15 -0700732 rtt = dst_metric_rtt(dst, RTAX_RTT);
733 m = rtt - tp->srtt;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700734
735 /* If newly calculated rtt larger than stored one,
736 * store new one. Otherwise, use EWMA. Remember,
737 * rtt overestimation is always better than underestimation.
738 */
739 if (!(dst_metric_locked(dst, RTAX_RTT))) {
740 if (m <= 0)
Stephen Hemmingerc1e20f72008-07-18 23:02:15 -0700741 set_dst_metric_rtt(dst, RTAX_RTT, tp->srtt);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700742 else
Stephen Hemmingerc1e20f72008-07-18 23:02:15 -0700743 set_dst_metric_rtt(dst, RTAX_RTT, rtt - (m >> 3));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700744 }
745
746 if (!(dst_metric_locked(dst, RTAX_RTTVAR))) {
Stephen Hemmingerc1e20f72008-07-18 23:02:15 -0700747 unsigned long var;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700748 if (m < 0)
749 m = -m;
750
751 /* Scale deviation to rttvar fixed point */
752 m >>= 1;
753 if (m < tp->mdev)
754 m = tp->mdev;
755
Stephen Hemmingerc1e20f72008-07-18 23:02:15 -0700756 var = dst_metric_rtt(dst, RTAX_RTTVAR);
757 if (m >= var)
758 var = m;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700759 else
Stephen Hemmingerc1e20f72008-07-18 23:02:15 -0700760 var -= (var - m) >> 2;
761
762 set_dst_metric_rtt(dst, RTAX_RTTVAR, var);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700763 }
764
765 if (tp->snd_ssthresh >= 0xFFFF) {
766 /* Slow start still did not finish. */
767 if (dst_metric(dst, RTAX_SSTHRESH) &&
768 !dst_metric_locked(dst, RTAX_SSTHRESH) &&
769 (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH))
770 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1;
771 if (!dst_metric_locked(dst, RTAX_CWND) &&
772 tp->snd_cwnd > dst_metric(dst, RTAX_CWND))
Ilpo Järvinen056834d2007-12-31 14:57:14 -0800773 dst->metrics[RTAX_CWND - 1] = tp->snd_cwnd;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700774 } else if (tp->snd_cwnd > tp->snd_ssthresh &&
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300775 icsk->icsk_ca_state == TCP_CA_Open) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700776 /* Cong. avoidance phase, cwnd is reliable. */
777 if (!dst_metric_locked(dst, RTAX_SSTHRESH))
778 dst->metrics[RTAX_SSTHRESH-1] =
779 max(tp->snd_cwnd >> 1, tp->snd_ssthresh);
780 if (!dst_metric_locked(dst, RTAX_CWND))
Satoru SATOH5ffc02a2008-05-04 22:14:42 -0700781 dst->metrics[RTAX_CWND-1] = (dst_metric(dst, RTAX_CWND) + tp->snd_cwnd) >> 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700782 } else {
783 /* Else slow start did not finish, cwnd is non-sense,
784 ssthresh may be also invalid.
785 */
786 if (!dst_metric_locked(dst, RTAX_CWND))
Satoru SATOH5ffc02a2008-05-04 22:14:42 -0700787 dst->metrics[RTAX_CWND-1] = (dst_metric(dst, RTAX_CWND) + tp->snd_ssthresh) >> 1;
788 if (dst_metric(dst, RTAX_SSTHRESH) &&
Linus Torvalds1da177e2005-04-16 15:20:36 -0700789 !dst_metric_locked(dst, RTAX_SSTHRESH) &&
Satoru SATOH5ffc02a2008-05-04 22:14:42 -0700790 tp->snd_ssthresh > dst_metric(dst, RTAX_SSTHRESH))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700791 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh;
792 }
793
794 if (!dst_metric_locked(dst, RTAX_REORDERING)) {
Satoru SATOH5ffc02a2008-05-04 22:14:42 -0700795 if (dst_metric(dst, RTAX_REORDERING) < tp->reordering &&
Linus Torvalds1da177e2005-04-16 15:20:36 -0700796 tp->reordering != sysctl_tcp_reordering)
797 dst->metrics[RTAX_REORDERING-1] = tp->reordering;
798 }
799 }
800}
801
Gerrit Renker410e27a2008-09-09 13:27:22 +0200802/* Numbers are taken from RFC3390.
803 *
804 * John Heffner states:
805 *
806 * The RFC specifies a window of no more than 4380 bytes
807 * unless 2*MSS > 4380. Reading the pseudocode in the RFC
808 * is a bit misleading because they use a clamp at 4380 bytes
809 * rather than use a multiplier in the relevant range.
810 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700811__u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst)
812{
813 __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0);
814
Gerrit Renker410e27a2008-09-09 13:27:22 +0200815 if (!cwnd) {
816 if (tp->mss_cache > 1460)
817 cwnd = 2;
818 else
819 cwnd = (tp->mss_cache > 1095) ? 3 : 4;
820 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700821 return min_t(__u32, cwnd, tp->snd_cwnd_clamp);
822}
823
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800824/* Set slow start threshold and cwnd not falling to slow start */
Ilpo Järvinen3cfe3ba2007-02-27 10:09:49 -0800825void tcp_enter_cwr(struct sock *sk, const int set_ssthresh)
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800826{
827 struct tcp_sock *tp = tcp_sk(sk);
Ilpo Järvinen3cfe3ba2007-02-27 10:09:49 -0800828 const struct inet_connection_sock *icsk = inet_csk(sk);
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800829
830 tp->prior_ssthresh = 0;
831 tp->bytes_acked = 0;
Ilpo Järvinene01f9d72007-03-02 13:27:25 -0800832 if (icsk->icsk_ca_state < TCP_CA_CWR) {
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800833 tp->undo_marker = 0;
Ilpo Järvinen3cfe3ba2007-02-27 10:09:49 -0800834 if (set_ssthresh)
835 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800836 tp->snd_cwnd = min(tp->snd_cwnd,
837 tcp_packets_in_flight(tp) + 1U);
838 tp->snd_cwnd_cnt = 0;
839 tp->high_seq = tp->snd_nxt;
840 tp->snd_cwnd_stamp = tcp_time_stamp;
841 TCP_ECN_queue_cwr(tp);
842
843 tcp_set_ca_state(sk, TCP_CA_CWR);
844 }
845}
846
Ilpo Järvinene60402d2007-08-09 15:14:46 +0300847/*
848 * Packet counting of FACK is based on in-order assumptions, therefore TCP
849 * disables it when reordering is detected
850 */
851static void tcp_disable_fack(struct tcp_sock *tp)
852{
Ilpo Järvinen85cc3912007-11-15 19:39:31 -0800853 /* RFC3517 uses different metric in lost marker => reset on change */
854 if (tcp_is_fack(tp))
855 tp->lost_skb_hint = NULL;
Ilpo Järvinene60402d2007-08-09 15:14:46 +0300856 tp->rx_opt.sack_ok &= ~2;
857}
858
Ryousei Takano564262c12007-10-25 23:03:52 -0700859/* Take a notice that peer is sending D-SACKs */
Ilpo Järvinene60402d2007-08-09 15:14:46 +0300860static void tcp_dsack_seen(struct tcp_sock *tp)
861{
862 tp->rx_opt.sack_ok |= 4;
863}
864
Linus Torvalds1da177e2005-04-16 15:20:36 -0700865/* Initialize metrics on socket. */
866
867static void tcp_init_metrics(struct sock *sk)
868{
869 struct tcp_sock *tp = tcp_sk(sk);
870 struct dst_entry *dst = __sk_dst_get(sk);
871
872 if (dst == NULL)
873 goto reset;
874
875 dst_confirm(dst);
876
877 if (dst_metric_locked(dst, RTAX_CWND))
878 tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND);
879 if (dst_metric(dst, RTAX_SSTHRESH)) {
880 tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH);
881 if (tp->snd_ssthresh > tp->snd_cwnd_clamp)
882 tp->snd_ssthresh = tp->snd_cwnd_clamp;
883 }
884 if (dst_metric(dst, RTAX_REORDERING) &&
885 tp->reordering != dst_metric(dst, RTAX_REORDERING)) {
Ilpo Järvinene60402d2007-08-09 15:14:46 +0300886 tcp_disable_fack(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700887 tp->reordering = dst_metric(dst, RTAX_REORDERING);
888 }
889
890 if (dst_metric(dst, RTAX_RTT) == 0)
891 goto reset;
892
Stephen Hemmingerc1e20f72008-07-18 23:02:15 -0700893 if (!tp->srtt && dst_metric_rtt(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700894 goto reset;
895
896 /* Initial rtt is determined from SYN,SYN-ACK.
897 * The segment is small and rtt may appear much
898 * less than real one. Use per-dst memory
899 * to make it more realistic.
900 *
901 * A bit of theory. RTT is time passed after "normal" sized packet
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800902 * is sent until it is ACKed. In normal circumstances sending small
Linus Torvalds1da177e2005-04-16 15:20:36 -0700903 * packets force peer to delay ACKs and calculation is correct too.
904 * The algorithm is adaptive and, provided we follow specs, it
905 * NEVER underestimate RTT. BUT! If peer tries to make some clever
906 * tricks sort of "quick acks" for time long enough to decrease RTT
907 * to low value, and then abruptly stops to do it and starts to delay
908 * ACKs, wait for troubles.
909 */
Stephen Hemmingerc1e20f72008-07-18 23:02:15 -0700910 if (dst_metric_rtt(dst, RTAX_RTT) > tp->srtt) {
911 tp->srtt = dst_metric_rtt(dst, RTAX_RTT);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700912 tp->rtt_seq = tp->snd_nxt;
913 }
Stephen Hemmingerc1e20f72008-07-18 23:02:15 -0700914 if (dst_metric_rtt(dst, RTAX_RTTVAR) > tp->mdev) {
915 tp->mdev = dst_metric_rtt(dst, RTAX_RTTVAR);
Satoru SATOH488faa22007-12-16 14:00:19 -0800916 tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700917 }
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700918 tcp_set_rto(sk);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700919 if (inet_csk(sk)->icsk_rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700920 goto reset;
Ilpo Järvinen86bceba2009-04-14 02:08:53 -0700921
922cwnd:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700923 tp->snd_cwnd = tcp_init_cwnd(tp, dst);
924 tp->snd_cwnd_stamp = tcp_time_stamp;
925 return;
926
927reset:
928 /* Play conservative. If timestamps are not
929 * supported, TCP will fail to recalculate correct
930 * rtt, if initial rto is too small. FORGET ALL AND RESET!
931 */
932 if (!tp->rx_opt.saw_tstamp && tp->srtt) {
933 tp->srtt = 0;
934 tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700935 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700936 }
Ilpo Järvinen86bceba2009-04-14 02:08:53 -0700937 goto cwnd;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700938}
939
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300940static void tcp_update_reordering(struct sock *sk, const int metric,
941 const int ts)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700942{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300943 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700944 if (metric > tp->reordering) {
Pavel Emelyanov40b215e2008-07-03 01:05:41 -0700945 int mib_idx;
946
Linus Torvalds1da177e2005-04-16 15:20:36 -0700947 tp->reordering = min(TCP_MAX_REORDERING, metric);
948
949 /* This exciting event is worth to be remembered. 8) */
950 if (ts)
Pavel Emelyanov40b215e2008-07-03 01:05:41 -0700951 mib_idx = LINUX_MIB_TCPTSREORDER;
Ilpo Järvinene60402d2007-08-09 15:14:46 +0300952 else if (tcp_is_reno(tp))
Pavel Emelyanov40b215e2008-07-03 01:05:41 -0700953 mib_idx = LINUX_MIB_TCPRENOREORDER;
Ilpo Järvinene60402d2007-08-09 15:14:46 +0300954 else if (tcp_is_fack(tp))
Pavel Emelyanov40b215e2008-07-03 01:05:41 -0700955 mib_idx = LINUX_MIB_TCPFACKREORDER;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700956 else
Pavel Emelyanov40b215e2008-07-03 01:05:41 -0700957 mib_idx = LINUX_MIB_TCPSACKREORDER;
958
Pavel Emelyanovde0744a2008-07-16 20:31:16 -0700959 NET_INC_STATS_BH(sock_net(sk), mib_idx);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700960#if FASTRETRANS_DEBUG > 1
961 printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n",
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300962 tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700963 tp->reordering,
964 tp->fackets_out,
965 tp->sacked_out,
966 tp->undo_marker ? tp->undo_retrans : 0);
967#endif
Ilpo Järvinene60402d2007-08-09 15:14:46 +0300968 tcp_disable_fack(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700969 }
970}
971
Ilpo Järvinen006f5822008-09-20 21:20:20 -0700972/* This must be called before lost_out is incremented */
Ilpo Järvinenc8c213f2008-09-20 21:18:55 -0700973static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb)
974{
Ilpo Järvinen006f5822008-09-20 21:20:20 -0700975 if ((tp->retransmit_skb_hint == NULL) ||
Ilpo Järvinenc8c213f2008-09-20 21:18:55 -0700976 before(TCP_SKB_CB(skb)->seq,
977 TCP_SKB_CB(tp->retransmit_skb_hint)->seq))
Ilpo Järvinen006f5822008-09-20 21:20:20 -0700978 tp->retransmit_skb_hint = skb;
979
980 if (!tp->lost_out ||
981 after(TCP_SKB_CB(skb)->end_seq, tp->retransmit_high))
982 tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;
Ilpo Järvinenc8c213f2008-09-20 21:18:55 -0700983}
984
Ilpo Järvinen41ea36e2008-09-20 21:19:22 -0700985static void tcp_skb_mark_lost(struct tcp_sock *tp, struct sk_buff *skb)
986{
987 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {
988 tcp_verify_retransmit_hint(tp, skb);
989
990 tp->lost_out += tcp_skb_pcount(skb);
991 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
992 }
993}
994
Ilpo Järvinene1aa6802008-11-24 21:11:55 -0800995static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp,
996 struct sk_buff *skb)
Ilpo Järvinen006f5822008-09-20 21:20:20 -0700997{
998 tcp_verify_retransmit_hint(tp, skb);
999
1000 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {
1001 tp->lost_out += tcp_skb_pcount(skb);
1002 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1003 }
1004}
1005
Linus Torvalds1da177e2005-04-16 15:20:36 -07001006/* This procedure tags the retransmission queue when SACKs arrive.
1007 *
1008 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
1009 * Packets in queue with these bits set are counted in variables
1010 * sacked_out, retrans_out and lost_out, correspondingly.
1011 *
1012 * Valid combinations are:
1013 * Tag InFlight Description
1014 * 0 1 - orig segment is in flight.
1015 * S 0 - nothing flies, orig reached receiver.
1016 * L 0 - nothing flies, orig lost by net.
1017 * R 2 - both orig and retransmit are in flight.
1018 * L|R 1 - orig is lost, retransmit is in flight.
1019 * S|R 1 - orig reached receiver, retrans is still in flight.
1020 * (L|S|R is logically valid, it could occur when L|R is sacked,
1021 * but it is equivalent to plain S and code short-curcuits it to S.
1022 * L|S is logically invalid, it would mean -1 packet in flight 8))
1023 *
1024 * These 6 states form finite state machine, controlled by the following events:
1025 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
1026 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
1027 * 3. Loss detection event of one of three flavors:
1028 * A. Scoreboard estimator decided the packet is lost.
1029 * A'. Reno "three dupacks" marks head of queue lost.
1030 * A''. Its FACK modfication, head until snd.fack is lost.
1031 * B. SACK arrives sacking data transmitted after never retransmitted
1032 * hole was sent out.
1033 * C. SACK arrives sacking SND.NXT at the moment, when the
1034 * segment was retransmitted.
1035 * 4. D-SACK added new rule: D-SACK changes any tag to S.
1036 *
1037 * It is pleasant to note, that state diagram turns out to be commutative,
1038 * so that we are allowed not to be bothered by order of our actions,
1039 * when multiple events arrive simultaneously. (see the function below).
1040 *
1041 * Reordering detection.
1042 * --------------------
1043 * Reordering metric is maximal distance, which a packet can be displaced
1044 * in packet stream. With SACKs we can estimate it:
1045 *
1046 * 1. SACK fills old hole and the corresponding segment was not
1047 * ever retransmitted -> reordering. Alas, we cannot use it
1048 * when segment was retransmitted.
1049 * 2. The last flaw is solved with D-SACK. D-SACK arrives
1050 * for retransmitted and already SACKed segment -> reordering..
1051 * Both of these heuristics are not used in Loss state, when we cannot
1052 * account for retransmits accurately.
Ilpo Järvinen5b3c9882007-08-24 22:54:44 -07001053 *
1054 * SACK block validation.
1055 * ----------------------
1056 *
1057 * SACK block range validation checks that the received SACK block fits to
1058 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
1059 * Note that SND.UNA is not included to the range though being valid because
Ilpo Järvinen0e835332007-10-01 15:28:17 -07001060 * it means that the receiver is rather inconsistent with itself reporting
1061 * SACK reneging when it should advance SND.UNA. Such SACK block this is
1062 * perfectly valid, however, in light of RFC2018 which explicitly states
1063 * that "SACK block MUST reflect the newest segment. Even if the newest
1064 * segment is going to be discarded ...", not that it looks very clever
1065 * in case of head skb. Due to potentional receiver driven attacks, we
1066 * choose to avoid immediate execution of a walk in write queue due to
1067 * reneging and defer head skb's loss recovery to standard loss recovery
1068 * procedure that will eventually trigger (nothing forbids us doing this).
Ilpo Järvinen5b3c9882007-08-24 22:54:44 -07001069 *
1070 * Implements also blockage to start_seq wrap-around. Problem lies in the
1071 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
1072 * there's no guarantee that it will be before snd_nxt (n). The problem
1073 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
1074 * wrap (s_w):
1075 *
1076 * <- outs wnd -> <- wrapzone ->
1077 * u e n u_w e_w s n_w
1078 * | | | | | | |
1079 * |<------------+------+----- TCP seqno space --------------+---------->|
1080 * ...-- <2^31 ->| |<--------...
1081 * ...---- >2^31 ------>| |<--------...
1082 *
1083 * Current code wouldn't be vulnerable but it's better still to discard such
1084 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
1085 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
1086 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
1087 * equal to the ideal case (infinite seqno space without wrap caused issues).
1088 *
1089 * With D-SACK the lower bound is extended to cover sequence space below
1090 * SND.UNA down to undo_marker, which is the last point of interest. Yet
Ryousei Takano564262c12007-10-25 23:03:52 -07001091 * again, D-SACK block must not to go across snd_una (for the same reason as
Ilpo Järvinen5b3c9882007-08-24 22:54:44 -07001092 * for the normal SACK blocks, explained above). But there all simplicity
1093 * ends, TCP might receive valid D-SACKs below that. As long as they reside
1094 * fully below undo_marker they do not affect behavior in anyway and can
1095 * therefore be safely ignored. In rare cases (which are more or less
1096 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
1097 * fragmentation and packet reordering past skb's retransmission. To consider
1098 * them correctly, the acceptable range must be extended even more though
1099 * the exact amount is rather hard to quantify. However, tp->max_window can
1100 * be used as an exaggerated estimate.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001101 */
Ilpo Järvinen5b3c9882007-08-24 22:54:44 -07001102static int tcp_is_sackblock_valid(struct tcp_sock *tp, int is_dsack,
1103 u32 start_seq, u32 end_seq)
1104{
1105 /* Too far in future, or reversed (interpretation is ambiguous) */
1106 if (after(end_seq, tp->snd_nxt) || !before(start_seq, end_seq))
1107 return 0;
1108
1109 /* Nasty start_seq wrap-around check (see comments above) */
1110 if (!before(start_seq, tp->snd_nxt))
1111 return 0;
1112
Ryousei Takano564262c12007-10-25 23:03:52 -07001113 /* In outstanding window? ...This is valid exit for D-SACKs too.
Ilpo Järvinen5b3c9882007-08-24 22:54:44 -07001114 * start_seq == snd_una is non-sensical (see comments above)
1115 */
1116 if (after(start_seq, tp->snd_una))
1117 return 1;
1118
1119 if (!is_dsack || !tp->undo_marker)
1120 return 0;
1121
1122 /* ...Then it's D-SACK, and must reside below snd_una completely */
1123 if (!after(end_seq, tp->snd_una))
1124 return 0;
1125
1126 if (!before(start_seq, tp->undo_marker))
1127 return 1;
1128
1129 /* Too old */
1130 if (!after(end_seq, tp->undo_marker))
1131 return 0;
1132
1133 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1134 * start_seq < undo_marker and end_seq >= undo_marker.
1135 */
1136 return !before(start_seq, end_seq - tp->max_window);
1137}
1138
Ilpo Järvinen1c1e87e2007-10-10 02:45:32 -07001139/* Check for lost retransmit. This superb idea is borrowed from "ratehalving".
1140 * Event "C". Later note: FACK people cheated me again 8), we have to account
1141 * for reordering! Ugly, but should help.
Ilpo Järvinenf785a8e2007-10-11 17:35:41 -07001142 *
1143 * Search retransmitted skbs from write_queue that were sent when snd_nxt was
1144 * less than what is now known to be received by the other end (derived from
Ilpo Järvinen9f58f3b2007-11-15 19:42:54 -08001145 * highest SACK block). Also calculate the lowest snd_nxt among the remaining
1146 * retransmitted skbs to avoid some costly processing per ACKs.
Ilpo Järvinen1c1e87e2007-10-10 02:45:32 -07001147 */
Ilpo Järvinen407ef1d2007-12-02 00:47:57 +02001148static void tcp_mark_lost_retrans(struct sock *sk)
Ilpo Järvinen1c1e87e2007-10-10 02:45:32 -07001149{
Ilpo Järvinen9f58f3b2007-11-15 19:42:54 -08001150 const struct inet_connection_sock *icsk = inet_csk(sk);
Ilpo Järvinen1c1e87e2007-10-10 02:45:32 -07001151 struct tcp_sock *tp = tcp_sk(sk);
1152 struct sk_buff *skb;
Ilpo Järvinenf785a8e2007-10-11 17:35:41 -07001153 int cnt = 0;
Ilpo Järvinendf2e0142007-10-18 05:07:57 -07001154 u32 new_low_seq = tp->snd_nxt;
Ilpo Järvinen6859d492007-12-02 00:48:06 +02001155 u32 received_upto = tcp_highest_sack_seq(tp);
Ilpo Järvinen9f58f3b2007-11-15 19:42:54 -08001156
1157 if (!tcp_is_fack(tp) || !tp->retrans_out ||
1158 !after(received_upto, tp->lost_retrans_low) ||
1159 icsk->icsk_ca_state != TCP_CA_Recovery)
Ilpo Järvinen407ef1d2007-12-02 00:47:57 +02001160 return;
Ilpo Järvinen1c1e87e2007-10-10 02:45:32 -07001161
1162 tcp_for_write_queue(skb, sk) {
1163 u32 ack_seq = TCP_SKB_CB(skb)->ack_seq;
1164
1165 if (skb == tcp_send_head(sk))
1166 break;
Ilpo Järvinenf785a8e2007-10-11 17:35:41 -07001167 if (cnt == tp->retrans_out)
Ilpo Järvinen1c1e87e2007-10-10 02:45:32 -07001168 break;
1169 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
1170 continue;
1171
Ilpo Järvinenf785a8e2007-10-11 17:35:41 -07001172 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS))
1173 continue;
1174
Ilpo Järvinend0af4162009-02-28 04:44:32 +00001175 /* TODO: We would like to get rid of tcp_is_fack(tp) only
1176 * constraint here (see above) but figuring out that at
1177 * least tp->reordering SACK blocks reside between ack_seq
1178 * and received_upto is not easy task to do cheaply with
1179 * the available datastructures.
1180 *
1181 * Whether FACK should check here for tp->reordering segs
1182 * in-between one could argue for either way (it would be
1183 * rather simple to implement as we could count fack_count
1184 * during the walk and do tp->fackets_out - fack_count).
1185 */
1186 if (after(received_upto, ack_seq)) {
Ilpo Järvinen1c1e87e2007-10-10 02:45:32 -07001187 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1188 tp->retrans_out -= tcp_skb_pcount(skb);
1189
Ilpo Järvinen006f5822008-09-20 21:20:20 -07001190 tcp_skb_mark_lost_uncond_verify(tp, skb);
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07001191 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSTRETRANSMIT);
Ilpo Järvinenf785a8e2007-10-11 17:35:41 -07001192 } else {
Ilpo Järvinendf2e0142007-10-18 05:07:57 -07001193 if (before(ack_seq, new_low_seq))
Ilpo Järvinenb08d6cb2007-10-11 17:36:13 -07001194 new_low_seq = ack_seq;
Ilpo Järvinenf785a8e2007-10-11 17:35:41 -07001195 cnt += tcp_skb_pcount(skb);
Ilpo Järvinen1c1e87e2007-10-10 02:45:32 -07001196 }
1197 }
Ilpo Järvinenb08d6cb2007-10-11 17:36:13 -07001198
1199 if (tp->retrans_out)
1200 tp->lost_retrans_low = new_low_seq;
Ilpo Järvinen1c1e87e2007-10-10 02:45:32 -07001201}
Ilpo Järvinen5b3c9882007-08-24 22:54:44 -07001202
Pavel Emelyanov1ed83462008-07-16 20:29:51 -07001203static int tcp_check_dsack(struct sock *sk, struct sk_buff *ack_skb,
David S. Millerd06e0212007-06-18 22:43:06 -07001204 struct tcp_sack_block_wire *sp, int num_sacks,
1205 u32 prior_snd_una)
1206{
Pavel Emelyanov1ed83462008-07-16 20:29:51 -07001207 struct tcp_sock *tp = tcp_sk(sk);
Harvey Harrisond3e2ce32008-05-02 16:26:16 -07001208 u32 start_seq_0 = get_unaligned_be32(&sp[0].start_seq);
1209 u32 end_seq_0 = get_unaligned_be32(&sp[0].end_seq);
David S. Millerd06e0212007-06-18 22:43:06 -07001210 int dup_sack = 0;
1211
1212 if (before(start_seq_0, TCP_SKB_CB(ack_skb)->ack_seq)) {
1213 dup_sack = 1;
Ilpo Järvinene60402d2007-08-09 15:14:46 +03001214 tcp_dsack_seen(tp);
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07001215 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKRECV);
David S. Millerd06e0212007-06-18 22:43:06 -07001216 } else if (num_sacks > 1) {
Harvey Harrisond3e2ce32008-05-02 16:26:16 -07001217 u32 end_seq_1 = get_unaligned_be32(&sp[1].end_seq);
1218 u32 start_seq_1 = get_unaligned_be32(&sp[1].start_seq);
David S. Millerd06e0212007-06-18 22:43:06 -07001219
1220 if (!after(end_seq_0, end_seq_1) &&
1221 !before(start_seq_0, start_seq_1)) {
1222 dup_sack = 1;
Ilpo Järvinene60402d2007-08-09 15:14:46 +03001223 tcp_dsack_seen(tp);
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07001224 NET_INC_STATS_BH(sock_net(sk),
1225 LINUX_MIB_TCPDSACKOFORECV);
David S. Millerd06e0212007-06-18 22:43:06 -07001226 }
1227 }
1228
1229 /* D-SACK for already forgotten data... Do dumb counting. */
1230 if (dup_sack &&
1231 !after(end_seq_0, prior_snd_una) &&
1232 after(end_seq_0, tp->undo_marker))
1233 tp->undo_retrans--;
1234
1235 return dup_sack;
1236}
1237
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001238struct tcp_sacktag_state {
1239 int reord;
1240 int fack_count;
1241 int flag;
1242};
1243
Ilpo Järvinend1935942007-10-11 17:34:25 -07001244/* Check if skb is fully within the SACK block. In presence of GSO skbs,
1245 * the incoming SACK may not exactly match but we can find smaller MSS
1246 * aligned portion of it that matches. Therefore we might need to fragment
1247 * which may fail and creates some hassle (caller must handle error case
1248 * returns).
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001249 *
1250 * FIXME: this could be merged to shift decision code
Ilpo Järvinend1935942007-10-11 17:34:25 -07001251 */
Adrian Bunk0f79efd2007-10-26 03:57:36 -07001252static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb,
1253 u32 start_seq, u32 end_seq)
Ilpo Järvinend1935942007-10-11 17:34:25 -07001254{
1255 int in_sack, err;
1256 unsigned int pkt_len;
Ilpo Järvinenadb92db2008-11-24 21:13:50 -08001257 unsigned int mss;
Ilpo Järvinend1935942007-10-11 17:34:25 -07001258
1259 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
1260 !before(end_seq, TCP_SKB_CB(skb)->end_seq);
1261
1262 if (tcp_skb_pcount(skb) > 1 && !in_sack &&
1263 after(TCP_SKB_CB(skb)->end_seq, start_seq)) {
Ilpo Järvinenadb92db2008-11-24 21:13:50 -08001264 mss = tcp_skb_mss(skb);
Ilpo Järvinend1935942007-10-11 17:34:25 -07001265 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq);
1266
Ilpo Järvinenadb92db2008-11-24 21:13:50 -08001267 if (!in_sack) {
Ilpo Järvinend1935942007-10-11 17:34:25 -07001268 pkt_len = start_seq - TCP_SKB_CB(skb)->seq;
Ilpo Järvinenadb92db2008-11-24 21:13:50 -08001269 if (pkt_len < mss)
1270 pkt_len = mss;
1271 } else {
Ilpo Järvinend1935942007-10-11 17:34:25 -07001272 pkt_len = end_seq - TCP_SKB_CB(skb)->seq;
Ilpo Järvinenadb92db2008-11-24 21:13:50 -08001273 if (pkt_len < mss)
1274 return -EINVAL;
1275 }
1276
1277 /* Round if necessary so that SACKs cover only full MSSes
1278 * and/or the remaining small portion (if present)
1279 */
1280 if (pkt_len > mss) {
1281 unsigned int new_len = (pkt_len / mss) * mss;
1282 if (!in_sack && new_len < pkt_len) {
1283 new_len += mss;
1284 if (new_len > skb->len)
1285 return 0;
1286 }
1287 pkt_len = new_len;
1288 }
1289 err = tcp_fragment(sk, skb, pkt_len, mss);
Ilpo Järvinend1935942007-10-11 17:34:25 -07001290 if (err < 0)
1291 return err;
1292 }
1293
1294 return in_sack;
1295}
1296
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001297static u8 tcp_sacktag_one(struct sk_buff *skb, struct sock *sk,
1298 struct tcp_sacktag_state *state,
1299 int dup_sack, int pcount)
Ilpo Järvinen9e10c47c2007-11-15 19:44:56 -08001300{
Ilpo Järvinen6859d492007-12-02 00:48:06 +02001301 struct tcp_sock *tp = tcp_sk(sk);
Ilpo Järvinen9e10c47c2007-11-15 19:44:56 -08001302 u8 sacked = TCP_SKB_CB(skb)->sacked;
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001303 int fack_count = state->fack_count;
Ilpo Järvinen9e10c47c2007-11-15 19:44:56 -08001304
1305 /* Account D-SACK for retransmitted packet. */
1306 if (dup_sack && (sacked & TCPCB_RETRANS)) {
1307 if (after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
1308 tp->undo_retrans--;
Ilpo Järvinenede9f3b2007-12-02 00:47:58 +02001309 if (sacked & TCPCB_SACKED_ACKED)
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001310 state->reord = min(fack_count, state->reord);
Ilpo Järvinen9e10c47c2007-11-15 19:44:56 -08001311 }
1312
1313 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1314 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001315 return sacked;
Ilpo Järvinen9e10c47c2007-11-15 19:44:56 -08001316
1317 if (!(sacked & TCPCB_SACKED_ACKED)) {
1318 if (sacked & TCPCB_SACKED_RETRANS) {
1319 /* If the segment is not tagged as lost,
1320 * we do not clear RETRANS, believing
1321 * that retransmission is still in flight.
1322 */
1323 if (sacked & TCPCB_LOST) {
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001324 sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
Ilpo Järvinenf58b22f2008-11-24 21:14:43 -08001325 tp->lost_out -= pcount;
1326 tp->retrans_out -= pcount;
Ilpo Järvinen9e10c47c2007-11-15 19:44:56 -08001327 }
1328 } else {
1329 if (!(sacked & TCPCB_RETRANS)) {
1330 /* New sack for not retransmitted frame,
1331 * which was in hole. It is reordering.
1332 */
1333 if (before(TCP_SKB_CB(skb)->seq,
1334 tcp_highest_sack_seq(tp)))
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001335 state->reord = min(fack_count,
1336 state->reord);
Ilpo Järvinen9e10c47c2007-11-15 19:44:56 -08001337
1338 /* SACK enhanced F-RTO (RFC4138; Appendix B) */
1339 if (!after(TCP_SKB_CB(skb)->end_seq, tp->frto_highmark))
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001340 state->flag |= FLAG_ONLY_ORIG_SACKED;
Ilpo Järvinen9e10c47c2007-11-15 19:44:56 -08001341 }
1342
1343 if (sacked & TCPCB_LOST) {
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001344 sacked &= ~TCPCB_LOST;
Ilpo Järvinenf58b22f2008-11-24 21:14:43 -08001345 tp->lost_out -= pcount;
Ilpo Järvinen9e10c47c2007-11-15 19:44:56 -08001346 }
1347 }
1348
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001349 sacked |= TCPCB_SACKED_ACKED;
1350 state->flag |= FLAG_DATA_SACKED;
Ilpo Järvinenf58b22f2008-11-24 21:14:43 -08001351 tp->sacked_out += pcount;
Ilpo Järvinen9e10c47c2007-11-15 19:44:56 -08001352
Ilpo Järvinenf58b22f2008-11-24 21:14:43 -08001353 fack_count += pcount;
Ilpo Järvinen9e10c47c2007-11-15 19:44:56 -08001354
1355 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1356 if (!tcp_is_fack(tp) && (tp->lost_skb_hint != NULL) &&
1357 before(TCP_SKB_CB(skb)->seq,
1358 TCP_SKB_CB(tp->lost_skb_hint)->seq))
Ilpo Järvinenf58b22f2008-11-24 21:14:43 -08001359 tp->lost_cnt_hint += pcount;
Ilpo Järvinen9e10c47c2007-11-15 19:44:56 -08001360
1361 if (fack_count > tp->fackets_out)
1362 tp->fackets_out = fack_count;
Ilpo Järvinen9e10c47c2007-11-15 19:44:56 -08001363 }
1364
1365 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1366 * frames and clear it. undo_retrans is decreased above, L|R frames
1367 * are accounted above as well.
1368 */
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001369 if (dup_sack && (sacked & TCPCB_SACKED_RETRANS)) {
1370 sacked &= ~TCPCB_SACKED_RETRANS;
Ilpo Järvinenf58b22f2008-11-24 21:14:43 -08001371 tp->retrans_out -= pcount;
Ilpo Järvinen9e10c47c2007-11-15 19:44:56 -08001372 }
1373
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001374 return sacked;
Ilpo Järvinen9e10c47c2007-11-15 19:44:56 -08001375}
1376
Ilpo Järvinen50133162008-12-05 22:42:41 -08001377static int tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001378 struct tcp_sacktag_state *state,
Ilpo Järvinen9ec06ff2009-03-01 00:21:36 -08001379 unsigned int pcount, int shifted, int mss,
1380 int dup_sack)
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001381{
1382 struct tcp_sock *tp = tcp_sk(sk);
Ilpo Järvinen50133162008-12-05 22:42:41 -08001383 struct sk_buff *prev = tcp_write_queue_prev(sk, skb);
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001384
1385 BUG_ON(!pcount);
1386
Ilpo Järvinen92ee76b2008-11-24 21:26:56 -08001387 /* Tweak before seqno plays */
1388 if (!tcp_is_fack(tp) && tcp_is_sack(tp) && tp->lost_skb_hint &&
1389 !before(TCP_SKB_CB(tp->lost_skb_hint)->seq, TCP_SKB_CB(skb)->seq))
1390 tp->lost_cnt_hint += pcount;
1391
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001392 TCP_SKB_CB(prev)->end_seq += shifted;
1393 TCP_SKB_CB(skb)->seq += shifted;
1394
1395 skb_shinfo(prev)->gso_segs += pcount;
1396 BUG_ON(skb_shinfo(skb)->gso_segs < pcount);
1397 skb_shinfo(skb)->gso_segs -= pcount;
1398
1399 /* When we're adding to gso_segs == 1, gso_size will be zero,
1400 * in theory this shouldn't be necessary but as long as DSACK
1401 * code can come after this skb later on it's better to keep
1402 * setting gso_size to something.
1403 */
1404 if (!skb_shinfo(prev)->gso_size) {
1405 skb_shinfo(prev)->gso_size = mss;
1406 skb_shinfo(prev)->gso_type = sk->sk_gso_type;
1407 }
1408
1409 /* CHECKME: To clear or not to clear? Mimics normal skb currently */
1410 if (skb_shinfo(skb)->gso_segs <= 1) {
1411 skb_shinfo(skb)->gso_size = 0;
1412 skb_shinfo(skb)->gso_type = 0;
1413 }
1414
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001415 /* We discard results */
Ilpo Järvinen9ec06ff2009-03-01 00:21:36 -08001416 tcp_sacktag_one(skb, sk, state, dup_sack, pcount);
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001417
1418 /* Difference in this won't matter, both ACKed by the same cumul. ACK */
1419 TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS);
1420
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001421 if (skb->len > 0) {
1422 BUG_ON(!tcp_skb_pcount(skb));
Ilpo Järvinen111cc8b2008-11-24 21:27:22 -08001423 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTED);
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001424 return 0;
1425 }
1426
1427 /* Whole SKB was eaten :-) */
1428
Ilpo Järvinen92ee76b2008-11-24 21:26:56 -08001429 if (skb == tp->retransmit_skb_hint)
1430 tp->retransmit_skb_hint = prev;
1431 if (skb == tp->scoreboard_skb_hint)
1432 tp->scoreboard_skb_hint = prev;
1433 if (skb == tp->lost_skb_hint) {
1434 tp->lost_skb_hint = prev;
1435 tp->lost_cnt_hint -= tcp_skb_pcount(prev);
1436 }
1437
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001438 TCP_SKB_CB(skb)->flags |= TCP_SKB_CB(prev)->flags;
1439 if (skb == tcp_highest_sack(sk))
1440 tcp_advance_highest_sack(sk, skb);
1441
1442 tcp_unlink_write_queue(skb, sk);
1443 sk_wmem_free_skb(sk, skb);
1444
Ilpo Järvinen111cc8b2008-11-24 21:27:22 -08001445 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKMERGED);
1446
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001447 return 1;
1448}
1449
1450/* I wish gso_size would have a bit more sane initialization than
1451 * something-or-zero which complicates things
1452 */
Ilpo Järvinen775ffab2008-12-05 22:41:26 -08001453static int tcp_skb_seglen(struct sk_buff *skb)
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001454{
Ilpo Järvinen775ffab2008-12-05 22:41:26 -08001455 return tcp_skb_pcount(skb) == 1 ? skb->len : tcp_skb_mss(skb);
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001456}
1457
1458/* Shifting pages past head area doesn't work */
1459static int skb_can_shift(struct sk_buff *skb)
1460{
1461 return !skb_headlen(skb) && skb_is_nonlinear(skb);
1462}
1463
1464/* Try collapsing SACK blocks spanning across multiple skbs to a single
1465 * skb.
1466 */
1467static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001468 struct tcp_sacktag_state *state,
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001469 u32 start_seq, u32 end_seq,
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001470 int dup_sack)
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001471{
1472 struct tcp_sock *tp = tcp_sk(sk);
1473 struct sk_buff *prev;
1474 int mss;
1475 int pcount = 0;
1476 int len;
1477 int in_sack;
1478
1479 if (!sk_can_gso(sk))
1480 goto fallback;
1481
1482 /* Normally R but no L won't result in plain S */
1483 if (!dup_sack &&
Ilpo Järvinen9969ca52008-12-05 22:41:06 -08001484 (TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_RETRANS)) == TCPCB_SACKED_RETRANS)
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001485 goto fallback;
1486 if (!skb_can_shift(skb))
1487 goto fallback;
1488 /* This frame is about to be dropped (was ACKed). */
1489 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
1490 goto fallback;
1491
1492 /* Can only happen with delayed DSACK + discard craziness */
1493 if (unlikely(skb == tcp_write_queue_head(sk)))
1494 goto fallback;
1495 prev = tcp_write_queue_prev(sk, skb);
1496
1497 if ((TCP_SKB_CB(prev)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED)
1498 goto fallback;
1499
1500 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
1501 !before(end_seq, TCP_SKB_CB(skb)->end_seq);
1502
1503 if (in_sack) {
1504 len = skb->len;
1505 pcount = tcp_skb_pcount(skb);
Ilpo Järvinen775ffab2008-12-05 22:41:26 -08001506 mss = tcp_skb_seglen(skb);
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001507
1508 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1509 * drop this restriction as unnecessary
1510 */
Ilpo Järvinen775ffab2008-12-05 22:41:26 -08001511 if (mss != tcp_skb_seglen(prev))
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001512 goto fallback;
1513 } else {
1514 if (!after(TCP_SKB_CB(skb)->end_seq, start_seq))
1515 goto noop;
1516 /* CHECKME: This is non-MSS split case only?, this will
1517 * cause skipped skbs due to advancing loop btw, original
1518 * has that feature too
1519 */
1520 if (tcp_skb_pcount(skb) <= 1)
1521 goto noop;
1522
1523 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq);
1524 if (!in_sack) {
1525 /* TODO: head merge to next could be attempted here
1526 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
1527 * though it might not be worth of the additional hassle
1528 *
1529 * ...we can probably just fallback to what was done
1530 * previously. We could try merging non-SACKed ones
1531 * as well but it probably isn't going to buy off
1532 * because later SACKs might again split them, and
1533 * it would make skb timestamp tracking considerably
1534 * harder problem.
1535 */
1536 goto fallback;
1537 }
1538
1539 len = end_seq - TCP_SKB_CB(skb)->seq;
1540 BUG_ON(len < 0);
1541 BUG_ON(len > skb->len);
1542
1543 /* MSS boundaries should be honoured or else pcount will
1544 * severely break even though it makes things bit trickier.
1545 * Optimize common case to avoid most of the divides
1546 */
1547 mss = tcp_skb_mss(skb);
1548
1549 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1550 * drop this restriction as unnecessary
1551 */
Ilpo Järvinen775ffab2008-12-05 22:41:26 -08001552 if (mss != tcp_skb_seglen(prev))
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001553 goto fallback;
1554
1555 if (len == mss) {
1556 pcount = 1;
1557 } else if (len < mss) {
1558 goto noop;
1559 } else {
1560 pcount = len / mss;
1561 len = pcount * mss;
1562 }
1563 }
1564
1565 if (!skb_shift(prev, skb, len))
1566 goto fallback;
Ilpo Järvinen9ec06ff2009-03-01 00:21:36 -08001567 if (!tcp_shifted_skb(sk, skb, state, pcount, len, mss, dup_sack))
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001568 goto out;
1569
1570 /* Hole filled allows collapsing with the next as well, this is very
1571 * useful when hole on every nth skb pattern happens
1572 */
1573 if (prev == tcp_write_queue_tail(sk))
1574 goto out;
1575 skb = tcp_write_queue_next(sk, prev);
1576
Ilpo Järvinenf0bc52f2008-12-05 22:40:47 -08001577 if (!skb_can_shift(skb) ||
1578 (skb == tcp_send_head(sk)) ||
1579 ((TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) ||
Ilpo Järvinen775ffab2008-12-05 22:41:26 -08001580 (mss != tcp_skb_seglen(skb)))
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001581 goto out;
1582
1583 len = skb->len;
1584 if (skb_shift(prev, skb, len)) {
1585 pcount += tcp_skb_pcount(skb);
Ilpo Järvinen9ec06ff2009-03-01 00:21:36 -08001586 tcp_shifted_skb(sk, skb, state, tcp_skb_pcount(skb), len, mss, 0);
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001587 }
1588
1589out:
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001590 state->fack_count += pcount;
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001591 return prev;
1592
1593noop:
1594 return skb;
1595
1596fallback:
Ilpo Järvinen111cc8b2008-11-24 21:27:22 -08001597 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTFALLBACK);
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001598 return NULL;
1599}
1600
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001601static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk,
1602 struct tcp_sack_block *next_dup,
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001603 struct tcp_sacktag_state *state,
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001604 u32 start_seq, u32 end_seq,
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001605 int dup_sack_in)
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001606{
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001607 struct tcp_sock *tp = tcp_sk(sk);
1608 struct sk_buff *tmp;
1609
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001610 tcp_for_write_queue_from(skb, sk) {
1611 int in_sack = 0;
1612 int dup_sack = dup_sack_in;
1613
1614 if (skb == tcp_send_head(sk))
1615 break;
1616
1617 /* queue is in-order => we can short-circuit the walk early */
1618 if (!before(TCP_SKB_CB(skb)->seq, end_seq))
1619 break;
1620
1621 if ((next_dup != NULL) &&
1622 before(TCP_SKB_CB(skb)->seq, next_dup->end_seq)) {
1623 in_sack = tcp_match_skb_to_sack(sk, skb,
1624 next_dup->start_seq,
1625 next_dup->end_seq);
1626 if (in_sack > 0)
1627 dup_sack = 1;
1628 }
1629
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001630 /* skb reference here is a bit tricky to get right, since
1631 * shifting can eat and free both this skb and the next,
1632 * so not even _safe variant of the loop is enough.
1633 */
1634 if (in_sack <= 0) {
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001635 tmp = tcp_shift_skb_data(sk, skb, state,
1636 start_seq, end_seq, dup_sack);
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001637 if (tmp != NULL) {
1638 if (tmp != skb) {
1639 skb = tmp;
1640 continue;
1641 }
1642
1643 in_sack = 0;
1644 } else {
1645 in_sack = tcp_match_skb_to_sack(sk, skb,
1646 start_seq,
1647 end_seq);
1648 }
1649 }
1650
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001651 if (unlikely(in_sack < 0))
1652 break;
1653
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001654 if (in_sack) {
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001655 TCP_SKB_CB(skb)->sacked = tcp_sacktag_one(skb, sk,
1656 state,
1657 dup_sack,
1658 tcp_skb_pcount(skb));
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001659
Ilpo Järvinen832d11c2008-11-24 21:20:15 -08001660 if (!before(TCP_SKB_CB(skb)->seq,
1661 tcp_highest_sack_seq(tp)))
1662 tcp_advance_highest_sack(sk, skb);
1663 }
1664
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001665 state->fack_count += tcp_skb_pcount(skb);
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001666 }
1667 return skb;
1668}
1669
1670/* Avoid all extra work that is being done by sacktag while walking in
1671 * a normal way
1672 */
1673static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk,
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001674 struct tcp_sacktag_state *state,
1675 u32 skip_to_seq)
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001676{
1677 tcp_for_write_queue_from(skb, sk) {
1678 if (skb == tcp_send_head(sk))
1679 break;
1680
Ilpo Järvinene8bae272008-11-24 21:12:28 -08001681 if (after(TCP_SKB_CB(skb)->end_seq, skip_to_seq))
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001682 break;
Ilpo Järvinend152a7d2008-03-03 12:10:16 -08001683
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001684 state->fack_count += tcp_skb_pcount(skb);
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001685 }
1686 return skb;
1687}
1688
1689static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb,
1690 struct sock *sk,
1691 struct tcp_sack_block *next_dup,
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001692 struct tcp_sacktag_state *state,
1693 u32 skip_to_seq)
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001694{
1695 if (next_dup == NULL)
1696 return skb;
1697
1698 if (before(next_dup->start_seq, skip_to_seq)) {
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001699 skb = tcp_sacktag_skip(skb, sk, state, next_dup->start_seq);
1700 skb = tcp_sacktag_walk(skb, sk, NULL, state,
1701 next_dup->start_seq, next_dup->end_seq,
1702 1);
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001703 }
1704
1705 return skb;
1706}
1707
1708static int tcp_sack_cache_ok(struct tcp_sock *tp, struct tcp_sack_block *cache)
1709{
1710 return cache < tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache);
1711}
1712
Linus Torvalds1da177e2005-04-16 15:20:36 -07001713static int
Ilpo Järvinen056834d2007-12-31 14:57:14 -08001714tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
1715 u32 prior_snd_una)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001716{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001717 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001718 struct tcp_sock *tp = tcp_sk(sk);
Arnaldo Carvalho de Melo9c702202007-04-25 18:04:18 -07001719 unsigned char *ptr = (skb_transport_header(ack_skb) +
1720 TCP_SKB_CB(ack_skb)->sacked);
Ilpo Järvinenfd6dad62007-11-15 19:49:47 -08001721 struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2);
Adam Langley4389dde2008-07-19 00:07:02 -07001722 struct tcp_sack_block sp[TCP_NUM_SACKS];
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001723 struct tcp_sack_block *cache;
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001724 struct tcp_sacktag_state state;
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001725 struct sk_buff *skb;
Adam Langley4389dde2008-07-19 00:07:02 -07001726 int num_sacks = min(TCP_NUM_SACKS, (ptr[1] - TCPOLEN_SACK_BASE) >> 3);
Ilpo Järvinenfd6dad62007-11-15 19:49:47 -08001727 int used_sacks;
Ilpo Järvinen7769f402007-06-15 15:14:04 -07001728 int found_dup_sack = 0;
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001729 int i, j;
Baruch Evenfda03fb2007-02-04 23:35:57 -08001730 int first_sack_index;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001731
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001732 state.flag = 0;
1733 state.reord = tp->packets_out;
1734
Ilpo Järvinend738cd82007-03-24 21:03:23 -07001735 if (!tp->sacked_out) {
Ilpo Järvinende83c052007-10-07 23:37:55 -07001736 if (WARN_ON(tp->fackets_out))
1737 tp->fackets_out = 0;
Ilpo Järvinen6859d492007-12-02 00:48:06 +02001738 tcp_highest_sack_reset(sk);
Ilpo Järvinend738cd82007-03-24 21:03:23 -07001739 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001740
Pavel Emelyanov1ed83462008-07-16 20:29:51 -07001741 found_dup_sack = tcp_check_dsack(sk, ack_skb, sp_wire,
David S. Millerd06e0212007-06-18 22:43:06 -07001742 num_sacks, prior_snd_una);
1743 if (found_dup_sack)
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001744 state.flag |= FLAG_DSACKING_ACK;
Baruch Even6f746512007-02-04 23:36:42 -08001745
1746 /* Eliminate too old ACKs, but take into
1747 * account more or less fresh ones, they can
1748 * contain valid SACK info.
1749 */
1750 if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window))
1751 return 0;
1752
Ilpo Järvinen96a2d412007-11-14 15:47:18 -08001753 if (!tp->packets_out)
1754 goto out;
1755
Ilpo Järvinenfd6dad62007-11-15 19:49:47 -08001756 used_sacks = 0;
1757 first_sack_index = 0;
1758 for (i = 0; i < num_sacks; i++) {
1759 int dup_sack = !i && found_dup_sack;
1760
Harvey Harrisond3e2ce32008-05-02 16:26:16 -07001761 sp[used_sacks].start_seq = get_unaligned_be32(&sp_wire[i].start_seq);
1762 sp[used_sacks].end_seq = get_unaligned_be32(&sp_wire[i].end_seq);
Ilpo Järvinenfd6dad62007-11-15 19:49:47 -08001763
1764 if (!tcp_is_sackblock_valid(tp, dup_sack,
1765 sp[used_sacks].start_seq,
1766 sp[used_sacks].end_seq)) {
Pavel Emelyanov40b215e2008-07-03 01:05:41 -07001767 int mib_idx;
1768
Ilpo Järvinenfd6dad62007-11-15 19:49:47 -08001769 if (dup_sack) {
1770 if (!tp->undo_marker)
Pavel Emelyanov40b215e2008-07-03 01:05:41 -07001771 mib_idx = LINUX_MIB_TCPDSACKIGNOREDNOUNDO;
Ilpo Järvinenfd6dad62007-11-15 19:49:47 -08001772 else
Pavel Emelyanov40b215e2008-07-03 01:05:41 -07001773 mib_idx = LINUX_MIB_TCPDSACKIGNOREDOLD;
Ilpo Järvinenfd6dad62007-11-15 19:49:47 -08001774 } else {
1775 /* Don't count olds caused by ACK reordering */
1776 if ((TCP_SKB_CB(ack_skb)->ack_seq != tp->snd_una) &&
1777 !after(sp[used_sacks].end_seq, tp->snd_una))
1778 continue;
Pavel Emelyanov40b215e2008-07-03 01:05:41 -07001779 mib_idx = LINUX_MIB_TCPSACKDISCARD;
Ilpo Järvinenfd6dad62007-11-15 19:49:47 -08001780 }
Pavel Emelyanov40b215e2008-07-03 01:05:41 -07001781
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07001782 NET_INC_STATS_BH(sock_net(sk), mib_idx);
Ilpo Järvinenfd6dad62007-11-15 19:49:47 -08001783 if (i == 0)
1784 first_sack_index = -1;
1785 continue;
1786 }
1787
1788 /* Ignore very old stuff early */
1789 if (!after(sp[used_sacks].end_seq, prior_snd_una))
1790 continue;
1791
1792 used_sacks++;
1793 }
1794
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001795 /* order SACK blocks to allow in order walk of the retrans queue */
1796 for (i = used_sacks - 1; i > 0; i--) {
Ilpo Järvinen056834d2007-12-31 14:57:14 -08001797 for (j = 0; j < i; j++) {
1798 if (after(sp[j].start_seq, sp[j + 1].start_seq)) {
Ilpo Järvinena0bffff2009-03-21 13:36:17 -07001799 swap(sp[j], sp[j + 1]);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001800
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001801 /* Track where the first SACK block goes to */
1802 if (j == first_sack_index)
Ilpo Järvinen056834d2007-12-31 14:57:14 -08001803 first_sack_index = j + 1;
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001804 }
1805 }
1806 }
1807
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001808 skb = tcp_write_queue_head(sk);
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001809 state.fack_count = 0;
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001810 i = 0;
1811
1812 if (!tp->sacked_out) {
1813 /* It's already past, so skip checking against it */
1814 cache = tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache);
1815 } else {
1816 cache = tp->recv_sack_cache;
1817 /* Skip empty blocks in at head of the cache */
1818 while (tcp_sack_cache_ok(tp, cache) && !cache->start_seq &&
1819 !cache->end_seq)
1820 cache++;
Baruch Evenfda03fb2007-02-04 23:35:57 -08001821 }
1822
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001823 while (i < used_sacks) {
Ilpo Järvinenfd6dad62007-11-15 19:49:47 -08001824 u32 start_seq = sp[i].start_seq;
1825 u32 end_seq = sp[i].end_seq;
Ilpo Järvinen7769f402007-06-15 15:14:04 -07001826 int dup_sack = (found_dup_sack && (i == first_sack_index));
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001827 struct tcp_sack_block *next_dup = NULL;
Ilpo Järvinene56d6cd2007-11-01 00:09:37 -07001828
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001829 if (found_dup_sack && ((i + 1) == first_sack_index))
1830 next_dup = &sp[i + 1];
Linus Torvalds1da177e2005-04-16 15:20:36 -07001831
1832 /* Event "B" in the comment above. */
1833 if (after(end_seq, tp->high_seq))
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001834 state.flag |= FLAG_DATA_LOST;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001835
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001836 /* Skip too early cached blocks */
1837 while (tcp_sack_cache_ok(tp, cache) &&
1838 !before(start_seq, cache->end_seq))
1839 cache++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001840
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001841 /* Can skip some work by looking recv_sack_cache? */
1842 if (tcp_sack_cache_ok(tp, cache) && !dup_sack &&
1843 after(end_seq, cache->start_seq)) {
David S. Millerfe067e82007-03-07 12:12:44 -08001844
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001845 /* Head todo? */
1846 if (before(start_seq, cache->start_seq)) {
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001847 skb = tcp_sacktag_skip(skb, sk, &state,
1848 start_seq);
Ilpo Järvinen056834d2007-12-31 14:57:14 -08001849 skb = tcp_sacktag_walk(skb, sk, next_dup,
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001850 &state,
Ilpo Järvinen056834d2007-12-31 14:57:14 -08001851 start_seq,
1852 cache->start_seq,
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001853 dup_sack);
Baruch Evenfda03fb2007-02-04 23:35:57 -08001854 }
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001855
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001856 /* Rest of the block already fully processed? */
Ilpo Järvinen20de20b2007-11-16 16:17:05 -08001857 if (!after(end_seq, cache->end_seq))
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001858 goto advance_sp;
Ilpo Järvinen20de20b2007-11-16 16:17:05 -08001859
Ilpo Järvinen056834d2007-12-31 14:57:14 -08001860 skb = tcp_maybe_skipping_dsack(skb, sk, next_dup,
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001861 &state,
1862 cache->end_seq);
Ilpo Järvinene56d6cd2007-11-01 00:09:37 -07001863
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001864 /* ...tail remains todo... */
Ilpo Järvinen6859d492007-12-02 00:48:06 +02001865 if (tcp_highest_sack_seq(tp) == cache->end_seq) {
Ilpo Järvinen20de20b2007-11-16 16:17:05 -08001866 /* ...but better entrypoint exists! */
Ilpo Järvinen6859d492007-12-02 00:48:06 +02001867 skb = tcp_highest_sack(sk);
1868 if (skb == NULL)
1869 break;
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001870 state.fack_count = tp->fackets_out;
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001871 cache++;
1872 goto walk;
1873 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001874
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001875 skb = tcp_sacktag_skip(skb, sk, &state, cache->end_seq);
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001876 /* Check overlap against next cached too (past this one already) */
1877 cache++;
1878 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001879 }
Ilpo Järvinenfbd52eb2007-11-10 21:24:19 -08001880
Ilpo Järvinen6859d492007-12-02 00:48:06 +02001881 if (!before(start_seq, tcp_highest_sack_seq(tp))) {
1882 skb = tcp_highest_sack(sk);
1883 if (skb == NULL)
1884 break;
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001885 state.fack_count = tp->fackets_out;
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001886 }
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001887 skb = tcp_sacktag_skip(skb, sk, &state, start_seq);
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001888
1889walk:
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001890 skb = tcp_sacktag_walk(skb, sk, next_dup, &state,
1891 start_seq, end_seq, dup_sack);
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001892
1893advance_sp:
Ilpo Järvinenfbd52eb2007-11-10 21:24:19 -08001894 /* SACK enhanced FRTO (RFC4138, Appendix B): Clearing correct
1895 * due to in-order walk
1896 */
1897 if (after(end_seq, tp->frto_highmark))
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001898 state.flag &= ~FLAG_ONLY_ORIG_SACKED;
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001899
1900 i++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001901 }
1902
Ilpo Järvinen68f83532007-11-15 19:50:37 -08001903 /* Clear the head of the cache sack blocks so we can skip it next time */
1904 for (i = 0; i < ARRAY_SIZE(tp->recv_sack_cache) - used_sacks; i++) {
1905 tp->recv_sack_cache[i].start_seq = 0;
1906 tp->recv_sack_cache[i].end_seq = 0;
1907 }
1908 for (j = 0; j < used_sacks; j++)
1909 tp->recv_sack_cache[i++] = sp[j];
1910
Ilpo Järvinen407ef1d2007-12-02 00:47:57 +02001911 tcp_mark_lost_retrans(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001912
Ilpo Järvinen86426c22007-08-09 14:45:17 +03001913 tcp_verify_left_out(tp);
1914
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001915 if ((state.reord < tp->fackets_out) &&
Ilpo Järvinenf5771112007-11-15 19:35:11 -08001916 ((icsk->icsk_ca_state != TCP_CA_Loss) || tp->undo_marker) &&
Ilpo Järvinenc5e7af02007-02-23 16:22:06 -08001917 (!tp->frto_highmark || after(tp->snd_una, tp->frto_highmark)))
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001918 tcp_update_reordering(sk, tp->fackets_out - state.reord, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001919
Ilpo Järvinen96a2d412007-11-14 15:47:18 -08001920out:
1921
Linus Torvalds1da177e2005-04-16 15:20:36 -07001922#if FASTRETRANS_DEBUG > 0
Ilpo Järvinen547b7922008-07-25 21:43:18 -07001923 WARN_ON((int)tp->sacked_out < 0);
1924 WARN_ON((int)tp->lost_out < 0);
1925 WARN_ON((int)tp->retrans_out < 0);
1926 WARN_ON((int)tcp_packets_in_flight(tp) < 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001927#endif
Ilpo Järvinena1197f52008-12-05 22:42:22 -08001928 return state.flag;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001929}
1930
Ilpo Järvinen882beba2008-04-07 22:33:07 -07001931/* Limits sacked_out so that sum with lost_out isn't ever larger than
1932 * packets_out. Returns zero if sacked_out adjustement wasn't necessary.
Ilpo Järvinen30935cf2007-02-21 23:01:36 -08001933 */
Ilpo Järvinen8eecaba2008-11-25 13:45:29 -08001934static int tcp_limit_reno_sacked(struct tcp_sock *tp)
Ilpo Järvinen4ddf6672007-05-27 01:52:00 -07001935{
Ilpo Järvinen4ddf6672007-05-27 01:52:00 -07001936 u32 holes;
1937
1938 holes = max(tp->lost_out, 1U);
1939 holes = min(holes, tp->packets_out);
1940
1941 if ((tp->sacked_out + holes) > tp->packets_out) {
1942 tp->sacked_out = tp->packets_out - holes;
Ilpo Järvinen882beba2008-04-07 22:33:07 -07001943 return 1;
Ilpo Järvinen4ddf6672007-05-27 01:52:00 -07001944 }
Ilpo Järvinen882beba2008-04-07 22:33:07 -07001945 return 0;
1946}
1947
1948/* If we receive more dupacks than we expected counting segments
1949 * in assumption of absent reordering, interpret this as reordering.
1950 * The only another reason could be bug in receiver TCP.
1951 */
1952static void tcp_check_reno_reordering(struct sock *sk, const int addend)
1953{
1954 struct tcp_sock *tp = tcp_sk(sk);
1955 if (tcp_limit_reno_sacked(tp))
1956 tcp_update_reordering(sk, tp->packets_out + addend, 0);
Ilpo Järvinen4ddf6672007-05-27 01:52:00 -07001957}
1958
1959/* Emulate SACKs for SACKless connection: account for a new dupack. */
1960
1961static void tcp_add_reno_sack(struct sock *sk)
1962{
1963 struct tcp_sock *tp = tcp_sk(sk);
1964 tp->sacked_out++;
1965 tcp_check_reno_reordering(sk, 0);
Ilpo Järvinen005903b2007-08-09 14:44:16 +03001966 tcp_verify_left_out(tp);
Ilpo Järvinen4ddf6672007-05-27 01:52:00 -07001967}
1968
1969/* Account for ACK, ACKing some data in Reno Recovery phase. */
1970
1971static void tcp_remove_reno_sacks(struct sock *sk, int acked)
1972{
1973 struct tcp_sock *tp = tcp_sk(sk);
1974
1975 if (acked > 0) {
1976 /* One ACK acked hole. The rest eat duplicate ACKs. */
Ilpo Järvinen056834d2007-12-31 14:57:14 -08001977 if (acked - 1 >= tp->sacked_out)
Ilpo Järvinen4ddf6672007-05-27 01:52:00 -07001978 tp->sacked_out = 0;
1979 else
Ilpo Järvinen056834d2007-12-31 14:57:14 -08001980 tp->sacked_out -= acked - 1;
Ilpo Järvinen4ddf6672007-05-27 01:52:00 -07001981 }
1982 tcp_check_reno_reordering(sk, acked);
Ilpo Järvinen005903b2007-08-09 14:44:16 +03001983 tcp_verify_left_out(tp);
Ilpo Järvinen4ddf6672007-05-27 01:52:00 -07001984}
1985
1986static inline void tcp_reset_reno_sack(struct tcp_sock *tp)
1987{
1988 tp->sacked_out = 0;
Ilpo Järvinen4ddf6672007-05-27 01:52:00 -07001989}
1990
Ilpo Järvinen62ab2222008-05-08 01:09:11 -07001991static int tcp_is_sackfrto(const struct tcp_sock *tp)
1992{
1993 return (sysctl_tcp_frto == 0x2) && !tcp_is_reno(tp);
1994}
1995
Ilpo Järvinen95eacd22007-10-01 15:27:42 -07001996/* F-RTO can only be used if TCP has never retransmitted anything other than
1997 * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here)
1998 */
Ilpo Järvinen46d0de42007-02-21 23:10:39 -08001999int tcp_use_frto(struct sock *sk)
Ilpo Järvinenbdaae172007-02-21 22:59:58 -08002000{
2001 const struct tcp_sock *tp = tcp_sk(sk);
Ilpo Järvinen6adb4f72008-04-07 22:33:57 -07002002 const struct inet_connection_sock *icsk = inet_csk(sk);
Ilpo Järvinen46d0de42007-02-21 23:10:39 -08002003 struct sk_buff *skb;
Ilpo Järvinenbdaae172007-02-21 22:59:58 -08002004
Ilpo Järvinen575ee712007-04-30 00:39:55 -07002005 if (!sysctl_tcp_frto)
Ilpo Järvinen46d0de42007-02-21 23:10:39 -08002006 return 0;
2007
Ilpo Järvinen6adb4f72008-04-07 22:33:57 -07002008 /* MTU probe and F-RTO won't really play nicely along currently */
2009 if (icsk->icsk_mtup.probe_size)
2010 return 0;
2011
Ilpo Järvinen62ab2222008-05-08 01:09:11 -07002012 if (tcp_is_sackfrto(tp))
Ilpo Järvinen4dc26652007-02-21 23:16:11 -08002013 return 1;
2014
Ilpo Järvinen46d0de42007-02-21 23:10:39 -08002015 /* Avoid expensive walking of rexmit queue if possible */
2016 if (tp->retrans_out > 1)
2017 return 0;
2018
David S. Millerfe067e82007-03-07 12:12:44 -08002019 skb = tcp_write_queue_head(sk);
David S. Miller28e34872008-09-23 02:51:41 -07002020 if (tcp_skb_is_last(sk, skb))
2021 return 1;
David S. Millerfe067e82007-03-07 12:12:44 -08002022 skb = tcp_write_queue_next(sk, skb); /* Skips head */
2023 tcp_for_write_queue_from(skb, sk) {
2024 if (skb == tcp_send_head(sk))
2025 break;
Ilpo Järvinen056834d2007-12-31 14:57:14 -08002026 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS)
Ilpo Järvinen46d0de42007-02-21 23:10:39 -08002027 return 0;
2028 /* Short-circuit when first non-SACKed skb has been checked */
Ilpo Järvinen056834d2007-12-31 14:57:14 -08002029 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
Ilpo Järvinen46d0de42007-02-21 23:10:39 -08002030 break;
2031 }
2032 return 1;
Ilpo Järvinenbdaae172007-02-21 22:59:58 -08002033}
2034
Ilpo Järvinen30935cf2007-02-21 23:01:36 -08002035/* RTO occurred, but do not yet enter Loss state. Instead, defer RTO
2036 * recovery a bit and use heuristics in tcp_process_frto() to detect if
Ilpo Järvinend1a54c62007-02-21 23:11:57 -08002037 * the RTO was spurious. Only clear SACKED_RETRANS of the head here to
2038 * keep retrans_out counting accurate (with SACK F-RTO, other than head
2039 * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS
2040 * bits are handled if the Loss state is really to be entered (in
2041 * tcp_enter_frto_loss).
Ilpo Järvinen7487c482007-02-21 23:02:30 -08002042 *
2043 * Do like tcp_enter_loss() would; when RTO expires the second time it
2044 * does:
2045 * "Reduce ssthresh if it has not yet been made inside this window."
Linus Torvalds1da177e2005-04-16 15:20:36 -07002046 */
2047void tcp_enter_frto(struct sock *sk)
2048{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002049 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002050 struct tcp_sock *tp = tcp_sk(sk);
2051 struct sk_buff *skb;
2052
Ilpo Järvinen7487c482007-02-21 23:02:30 -08002053 if ((!tp->frto_counter && icsk->icsk_ca_state <= TCP_CA_Disorder) ||
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09002054 tp->snd_una == tp->high_seq ||
Ilpo Järvinen7487c482007-02-21 23:02:30 -08002055 ((icsk->icsk_ca_state == TCP_CA_Loss || tp->frto_counter) &&
2056 !icsk->icsk_retransmits)) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002057 tp->prior_ssthresh = tcp_current_ssthresh(sk);
Ilpo Järvinen66e93e42007-02-21 23:13:47 -08002058 /* Our state is too optimistic in ssthresh() call because cwnd
Ryousei Takano564262c12007-10-25 23:03:52 -07002059 * is not reduced until tcp_enter_frto_loss() when previous F-RTO
Ilpo Järvinen66e93e42007-02-21 23:13:47 -08002060 * recovery has not yet completed. Pattern would be this: RTO,
2061 * Cumulative ACK, RTO (2xRTO for the same segment does not end
2062 * up here twice).
2063 * RFC4138 should be more specific on what to do, even though
2064 * RTO is quite unlikely to occur after the first Cumulative ACK
2065 * due to back-off and complexity of triggering events ...
2066 */
2067 if (tp->frto_counter) {
2068 u32 stored_cwnd;
2069 stored_cwnd = tp->snd_cwnd;
2070 tp->snd_cwnd = 2;
2071 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
2072 tp->snd_cwnd = stored_cwnd;
2073 } else {
2074 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
2075 }
2076 /* ... in theory, cong.control module could do "any tricks" in
2077 * ssthresh(), which means that ca_state, lost bits and lost_out
2078 * counter would have to be faked before the call occurs. We
2079 * consider that too expensive, unlikely and hacky, so modules
2080 * using these in ssthresh() must deal these incompatibility
2081 * issues if they receives CA_EVENT_FRTO and frto_counter != 0
2082 */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002083 tcp_ca_event(sk, CA_EVENT_FRTO);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002084 }
2085
Linus Torvalds1da177e2005-04-16 15:20:36 -07002086 tp->undo_marker = tp->snd_una;
2087 tp->undo_retrans = 0;
2088
David S. Millerfe067e82007-03-07 12:12:44 -08002089 skb = tcp_write_queue_head(sk);
Ilpo Järvinen009a2e32007-09-20 11:34:38 -07002090 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS)
2091 tp->undo_marker = 0;
Ilpo Järvinend1a54c62007-02-21 23:11:57 -08002092 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
Ilpo Järvinen522e7542007-02-21 22:54:52 -08002093 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
Ilpo Järvinend1a54c62007-02-21 23:11:57 -08002094 tp->retrans_out -= tcp_skb_pcount(skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002095 }
Ilpo Järvinen005903b2007-08-09 14:44:16 +03002096 tcp_verify_left_out(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002097
Ilpo Järvinen746aa322007-11-13 21:01:23 -08002098 /* Too bad if TCP was application limited */
2099 tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp) + 1);
2100
Ilpo Järvinen4dc26652007-02-21 23:16:11 -08002101 /* Earlier loss recovery underway (see RFC4138; Appendix B).
2102 * The last condition is necessary at least in tp->frto_counter case.
2103 */
Ilpo Järvinen62ab2222008-05-08 01:09:11 -07002104 if (tcp_is_sackfrto(tp) && (tp->frto_counter ||
Ilpo Järvinen4dc26652007-02-21 23:16:11 -08002105 ((1 << icsk->icsk_ca_state) & (TCPF_CA_Recovery|TCPF_CA_Loss))) &&
2106 after(tp->high_seq, tp->snd_una)) {
2107 tp->frto_highmark = tp->high_seq;
2108 } else {
2109 tp->frto_highmark = tp->snd_nxt;
2110 }
Ilpo Järvinen7b0eb222007-02-21 23:03:35 -08002111 tcp_set_ca_state(sk, TCP_CA_Disorder);
2112 tp->high_seq = tp->snd_nxt;
Ilpo Järvinen7487c482007-02-21 23:02:30 -08002113 tp->frto_counter = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002114}
2115
2116/* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
2117 * which indicates that we should follow the traditional RTO recovery,
2118 * i.e. mark everything lost and do go-back-N retransmission.
2119 */
Ilpo Järvinend1a54c62007-02-21 23:11:57 -08002120static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002121{
2122 struct tcp_sock *tp = tcp_sk(sk);
2123 struct sk_buff *skb;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002124
Linus Torvalds1da177e2005-04-16 15:20:36 -07002125 tp->lost_out = 0;
Ilpo Järvinend1a54c62007-02-21 23:11:57 -08002126 tp->retrans_out = 0;
Ilpo Järvinene60402d2007-08-09 15:14:46 +03002127 if (tcp_is_reno(tp))
Ilpo Järvinen9bff40f2007-05-27 01:53:49 -07002128 tcp_reset_reno_sack(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002129
David S. Millerfe067e82007-03-07 12:12:44 -08002130 tcp_for_write_queue(skb, sk) {
2131 if (skb == tcp_send_head(sk))
2132 break;
Ilpo Järvinen23aeeec2007-11-13 21:03:13 -08002133
2134 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
Ilpo Järvinend1a54c62007-02-21 23:11:57 -08002135 /*
2136 * Count the retransmission made on RTO correctly (only when
2137 * waiting for the first ACK and did not get it)...
2138 */
Ilpo Järvinen056834d2007-12-31 14:57:14 -08002139 if ((tp->frto_counter == 1) && !(flag & FLAG_DATA_ACKED)) {
Ilpo Järvinen0a9f2a42007-07-15 00:19:29 -07002140 /* For some reason this R-bit might get cleared? */
2141 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
2142 tp->retrans_out += tcp_skb_pcount(skb);
Ilpo Järvinend1a54c62007-02-21 23:11:57 -08002143 /* ...enter this if branch just for the first segment */
2144 flag |= FLAG_DATA_ACKED;
2145 } else {
Ilpo Järvinen009a2e32007-09-20 11:34:38 -07002146 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS)
2147 tp->undo_marker = 0;
Ilpo Järvinen23aeeec2007-11-13 21:03:13 -08002148 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
Ilpo Järvinend1a54c62007-02-21 23:11:57 -08002149 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002150
Ilpo Järvinen79d445162008-05-13 02:54:19 -07002151 /* Marking forward transmissions that were made after RTO lost
2152 * can cause unnecessary retransmissions in some scenarios,
2153 * SACK blocks will mitigate that in some but not in all cases.
2154 * We used to not mark them but it was causing break-ups with
2155 * receivers that do only in-order receival.
2156 *
2157 * TODO: we could detect presence of such receiver and select
2158 * different behavior per flow.
2159 */
2160 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
Ilpo Järvinen9bff40f2007-05-27 01:53:49 -07002161 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
2162 tp->lost_out += tcp_skb_pcount(skb);
Ilpo Järvinen006f5822008-09-20 21:20:20 -07002163 tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002164 }
2165 }
Ilpo Järvinen005903b2007-08-09 14:44:16 +03002166 tcp_verify_left_out(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002167
Ilpo Järvinen95c49222007-02-21 23:05:18 -08002168 tp->snd_cwnd = tcp_packets_in_flight(tp) + allowed_segments;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002169 tp->snd_cwnd_cnt = 0;
2170 tp->snd_cwnd_stamp = tcp_time_stamp;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002171 tp->frto_counter = 0;
Ilpo Järvinen16e90682007-10-11 17:32:31 -07002172 tp->bytes_acked = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002173
2174 tp->reordering = min_t(unsigned int, tp->reordering,
Ilpo Järvinen056834d2007-12-31 14:57:14 -08002175 sysctl_tcp_reordering);
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002176 tcp_set_ca_state(sk, TCP_CA_Loss);
Ilpo Järvinen79d445162008-05-13 02:54:19 -07002177 tp->high_seq = tp->snd_nxt;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002178 TCP_ECN_queue_cwr(tp);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08002179
Ilpo Järvinen64edc272008-09-20 21:18:32 -07002180 tcp_clear_all_retrans_hints(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002181}
2182
Ilpo Järvinen4cd82992007-10-11 17:34:57 -07002183static void tcp_clear_retrans_partial(struct tcp_sock *tp)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002184{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002185 tp->retrans_out = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002186 tp->lost_out = 0;
2187
2188 tp->undo_marker = 0;
2189 tp->undo_retrans = 0;
2190}
2191
Ilpo Järvinen4cd82992007-10-11 17:34:57 -07002192void tcp_clear_retrans(struct tcp_sock *tp)
2193{
2194 tcp_clear_retrans_partial(tp);
2195
2196 tp->fackets_out = 0;
2197 tp->sacked_out = 0;
2198}
2199
Linus Torvalds1da177e2005-04-16 15:20:36 -07002200/* Enter Loss state. If "how" is not zero, forget all SACK information
2201 * and reset tags completely, otherwise preserve SACKs. If receiver
2202 * dropped its ofo queue, we will know this due to reneging detection.
2203 */
2204void tcp_enter_loss(struct sock *sk, int how)
2205{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002206 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002207 struct tcp_sock *tp = tcp_sk(sk);
2208 struct sk_buff *skb;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002209
2210 /* Reduce ssthresh if it has not yet been made inside this window. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002211 if (icsk->icsk_ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq ||
2212 (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
2213 tp->prior_ssthresh = tcp_current_ssthresh(sk);
2214 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
2215 tcp_ca_event(sk, CA_EVENT_LOSS);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002216 }
2217 tp->snd_cwnd = 1;
2218 tp->snd_cwnd_cnt = 0;
2219 tp->snd_cwnd_stamp = tcp_time_stamp;
2220
Stephen Hemminger9772efb2005-11-10 17:09:53 -08002221 tp->bytes_acked = 0;
Ilpo Järvinen4cd82992007-10-11 17:34:57 -07002222 tcp_clear_retrans_partial(tp);
2223
2224 if (tcp_is_reno(tp))
2225 tcp_reset_reno_sack(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002226
Ilpo Järvinenb7689202007-09-20 11:37:19 -07002227 if (!how) {
2228 /* Push undo marker, if it was plain RTO and nothing
2229 * was retransmitted. */
Linus Torvalds1da177e2005-04-16 15:20:36 -07002230 tp->undo_marker = tp->snd_una;
Ilpo Järvinenb7689202007-09-20 11:37:19 -07002231 } else {
Ilpo Järvinen4cd82992007-10-11 17:34:57 -07002232 tp->sacked_out = 0;
2233 tp->fackets_out = 0;
Ilpo Järvinenb7689202007-09-20 11:37:19 -07002234 }
Ilpo Järvinen64edc272008-09-20 21:18:32 -07002235 tcp_clear_all_retrans_hints(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002236
David S. Millerfe067e82007-03-07 12:12:44 -08002237 tcp_for_write_queue(skb, sk) {
2238 if (skb == tcp_send_head(sk))
2239 break;
Ilpo Järvinen4cd82992007-10-11 17:34:57 -07002240
Ilpo Järvinen056834d2007-12-31 14:57:14 -08002241 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002242 tp->undo_marker = 0;
2243 TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED;
2244 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) {
2245 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
2246 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
2247 tp->lost_out += tcp_skb_pcount(skb);
Ilpo Järvinen006f5822008-09-20 21:20:20 -07002248 tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002249 }
2250 }
Ilpo Järvinen005903b2007-08-09 14:44:16 +03002251 tcp_verify_left_out(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002252
2253 tp->reordering = min_t(unsigned int, tp->reordering,
Ilpo Järvinen056834d2007-12-31 14:57:14 -08002254 sysctl_tcp_reordering);
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002255 tcp_set_ca_state(sk, TCP_CA_Loss);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002256 tp->high_seq = tp->snd_nxt;
2257 TCP_ECN_queue_cwr(tp);
Ryousei Takano564262c12007-10-25 23:03:52 -07002258 /* Abort F-RTO algorithm if one is in progress */
Ilpo Järvinen580e5722007-05-19 13:56:57 -07002259 tp->frto_counter = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002260}
2261
Ilpo Järvinencadbd032007-12-31 04:49:21 -08002262/* If ACK arrived pointing to a remembered SACK, it means that our
2263 * remembered SACKs do not reflect real state of receiver i.e.
2264 * receiver _host_ is heavily congested (or buggy).
2265 *
2266 * Do processing similar to RTO timeout.
2267 */
2268static int tcp_check_sack_reneging(struct sock *sk, int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002269{
Ilpo Järvinencadbd032007-12-31 04:49:21 -08002270 if (flag & FLAG_SACK_RENEGING) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002271 struct inet_connection_sock *icsk = inet_csk(sk);
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07002272 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSACKRENEGING);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002273
2274 tcp_enter_loss(sk, 1);
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002275 icsk->icsk_retransmits++;
David S. Millerfe067e82007-03-07 12:12:44 -08002276 tcp_retransmit_skb(sk, tcp_write_queue_head(sk));
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002277 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002278 icsk->icsk_rto, TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002279 return 1;
2280 }
2281 return 0;
2282}
2283
2284static inline int tcp_fackets_out(struct tcp_sock *tp)
2285{
Ilpo Järvinen056834d2007-12-31 14:57:14 -08002286 return tcp_is_reno(tp) ? tp->sacked_out + 1 : tp->fackets_out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002287}
2288
Ilpo Järvinen85cc3912007-11-15 19:39:31 -08002289/* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
2290 * counter when SACK is enabled (without SACK, sacked_out is used for
2291 * that purpose).
2292 *
2293 * Instead, with FACK TCP uses fackets_out that includes both SACKed
2294 * segments up to the highest received SACK block so far and holes in
2295 * between them.
2296 *
2297 * With reordering, holes may still be in flight, so RFC3517 recovery
2298 * uses pure sacked_out (total number of SACKed segments) even though
2299 * it violates the RFC that uses duplicate ACKs, often these are equal
2300 * but when e.g. out-of-window ACKs or packet duplication occurs,
2301 * they differ. Since neither occurs due to loss, TCP should really
2302 * ignore them.
2303 */
2304static inline int tcp_dupack_heurestics(struct tcp_sock *tp)
2305{
2306 return tcp_is_fack(tp) ? tp->fackets_out : tp->sacked_out + 1;
2307}
2308
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002309static inline int tcp_skb_timedout(struct sock *sk, struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002310{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002311 return (tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002312}
2313
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002314static inline int tcp_head_timedout(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002315{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002316 struct tcp_sock *tp = tcp_sk(sk);
2317
Linus Torvalds1da177e2005-04-16 15:20:36 -07002318 return tp->packets_out &&
David S. Millerfe067e82007-03-07 12:12:44 -08002319 tcp_skb_timedout(sk, tcp_write_queue_head(sk));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002320}
2321
2322/* Linux NewReno/SACK/FACK/ECN state machine.
2323 * --------------------------------------
2324 *
2325 * "Open" Normal state, no dubious events, fast path.
2326 * "Disorder" In all the respects it is "Open",
2327 * but requires a bit more attention. It is entered when
2328 * we see some SACKs or dupacks. It is split of "Open"
2329 * mainly to move some processing from fast path to slow one.
2330 * "CWR" CWND was reduced due to some Congestion Notification event.
2331 * It can be ECN, ICMP source quench, local device congestion.
2332 * "Recovery" CWND was reduced, we are fast-retransmitting.
2333 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2334 *
2335 * tcp_fastretrans_alert() is entered:
2336 * - each incoming ACK, if state is not "Open"
2337 * - when arrived ACK is unusual, namely:
2338 * * SACK
2339 * * Duplicate ACK.
2340 * * ECN ECE.
2341 *
2342 * Counting packets in flight is pretty simple.
2343 *
2344 * in_flight = packets_out - left_out + retrans_out
2345 *
2346 * packets_out is SND.NXT-SND.UNA counted in packets.
2347 *
2348 * retrans_out is number of retransmitted segments.
2349 *
2350 * left_out is number of segments left network, but not ACKed yet.
2351 *
2352 * left_out = sacked_out + lost_out
2353 *
2354 * sacked_out: Packets, which arrived to receiver out of order
2355 * and hence not ACKed. With SACKs this number is simply
2356 * amount of SACKed data. Even without SACKs
2357 * it is easy to give pretty reliable estimate of this number,
2358 * counting duplicate ACKs.
2359 *
2360 * lost_out: Packets lost by network. TCP has no explicit
2361 * "loss notification" feedback from network (for now).
2362 * It means that this number can be only _guessed_.
2363 * Actually, it is the heuristics to predict lossage that
2364 * distinguishes different algorithms.
2365 *
2366 * F.e. after RTO, when all the queue is considered as lost,
2367 * lost_out = packets_out and in_flight = retrans_out.
2368 *
2369 * Essentially, we have now two algorithms counting
2370 * lost packets.
2371 *
2372 * FACK: It is the simplest heuristics. As soon as we decided
2373 * that something is lost, we decide that _all_ not SACKed
2374 * packets until the most forward SACK are lost. I.e.
2375 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
2376 * It is absolutely correct estimate, if network does not reorder
2377 * packets. And it loses any connection to reality when reordering
2378 * takes place. We use FACK by default until reordering
2379 * is suspected on the path to this destination.
2380 *
2381 * NewReno: when Recovery is entered, we assume that one segment
2382 * is lost (classic Reno). While we are in Recovery and
2383 * a partial ACK arrives, we assume that one more packet
2384 * is lost (NewReno). This heuristics are the same in NewReno
2385 * and SACK.
2386 *
2387 * Imagine, that's all! Forget about all this shamanism about CWND inflation
2388 * deflation etc. CWND is real congestion window, never inflated, changes
2389 * only according to classic VJ rules.
2390 *
2391 * Really tricky (and requiring careful tuning) part of algorithm
2392 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2393 * The first determines the moment _when_ we should reduce CWND and,
2394 * hence, slow down forward transmission. In fact, it determines the moment
2395 * when we decide that hole is caused by loss, rather than by a reorder.
2396 *
2397 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2398 * holes, caused by lost packets.
2399 *
2400 * And the most logically complicated part of algorithm is undo
2401 * heuristics. We detect false retransmits due to both too early
2402 * fast retransmit (reordering) and underestimated RTO, analyzing
2403 * timestamps and D-SACKs. When we detect that some segments were
2404 * retransmitted by mistake and CWND reduction was wrong, we undo
2405 * window reduction and abort recovery phase. This logic is hidden
2406 * inside several functions named tcp_try_undo_<something>.
2407 */
2408
2409/* This function decides, when we should leave Disordered state
2410 * and enter Recovery phase, reducing congestion window.
2411 *
2412 * Main question: may we further continue forward transmission
2413 * with the same cwnd?
2414 */
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002415static int tcp_time_to_recover(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002416{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002417 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002418 __u32 packets_out;
2419
Ryousei Takano564262c12007-10-25 23:03:52 -07002420 /* Do not perform any recovery during F-RTO algorithm */
Ilpo Järvinen52c63f12007-02-21 23:06:52 -08002421 if (tp->frto_counter)
2422 return 0;
2423
Linus Torvalds1da177e2005-04-16 15:20:36 -07002424 /* Trick#1: The loss is proven. */
2425 if (tp->lost_out)
2426 return 1;
2427
2428 /* Not-A-Trick#2 : Classic rule... */
Ilpo Järvinen85cc3912007-11-15 19:39:31 -08002429 if (tcp_dupack_heurestics(tp) > tp->reordering)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002430 return 1;
2431
2432 /* Trick#3 : when we use RFC2988 timer restart, fast
2433 * retransmit can be triggered by timeout of queue head.
2434 */
Ilpo Järvinen85cc3912007-11-15 19:39:31 -08002435 if (tcp_is_fack(tp) && tcp_head_timedout(sk))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002436 return 1;
2437
2438 /* Trick#4: It is still not OK... But will it be useful to delay
2439 * recovery more?
2440 */
2441 packets_out = tp->packets_out;
2442 if (packets_out <= tp->reordering &&
2443 tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) &&
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002444 !tcp_may_send_now(sk)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002445 /* We have nothing to send. This connection is limited
2446 * either by receiver window or by application.
2447 */
2448 return 1;
2449 }
2450
2451 return 0;
2452}
2453
Ilpo Järvinen7363a5b2009-02-28 04:44:33 +00002454/* New heuristics: it is possible only after we switched to restart timer
2455 * each time when something is ACKed. Hence, we can detect timed out packets
2456 * during fast retransmit without falling to slow start.
2457 *
2458 * Usefulness of this as is very questionable, since we should know which of
2459 * the segments is the next to timeout which is relatively expensive to find
2460 * in general case unless we add some data structure just for that. The
2461 * current approach certainly won't find the right one too often and when it
2462 * finally does find _something_ it usually marks large part of the window
2463 * right away (because a retransmission with a larger timestamp blocks the
2464 * loop from advancing). -ij
2465 */
2466static void tcp_timeout_skbs(struct sock *sk)
2467{
2468 struct tcp_sock *tp = tcp_sk(sk);
2469 struct sk_buff *skb;
2470
2471 if (!tcp_is_fack(tp) || !tcp_head_timedout(sk))
2472 return;
2473
2474 skb = tp->scoreboard_skb_hint;
2475 if (tp->scoreboard_skb_hint == NULL)
2476 skb = tcp_write_queue_head(sk);
2477
2478 tcp_for_write_queue_from(skb, sk) {
2479 if (skb == tcp_send_head(sk))
2480 break;
2481 if (!tcp_skb_timedout(sk, skb))
2482 break;
2483
2484 tcp_skb_mark_lost(tp, skb);
2485 }
2486
2487 tp->scoreboard_skb_hint = skb;
2488
2489 tcp_verify_left_out(tp);
2490}
2491
Ilpo Järvinen85cc3912007-11-15 19:39:31 -08002492/* Mark head of queue up as lost. With RFC3517 SACK, the packets is
2493 * is against sacked "cnt", otherwise it's against facked "cnt"
2494 */
Ilpo Järvinen1b69d742008-04-07 22:31:38 -07002495static void tcp_mark_head_lost(struct sock *sk, int packets)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002496{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002497 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002498 struct sk_buff *skb;
Ilpo Järvinenc137f3d2008-04-07 22:32:38 -07002499 int cnt, oldcnt;
2500 int err;
2501 unsigned int mss;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002502
Ilpo Järvinen547b7922008-07-25 21:43:18 -07002503 WARN_ON(packets > tp->packets_out);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08002504 if (tp->lost_skb_hint) {
2505 skb = tp->lost_skb_hint;
2506 cnt = tp->lost_cnt_hint;
2507 } else {
David S. Millerfe067e82007-03-07 12:12:44 -08002508 skb = tcp_write_queue_head(sk);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08002509 cnt = 0;
2510 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002511
David S. Millerfe067e82007-03-07 12:12:44 -08002512 tcp_for_write_queue_from(skb, sk) {
2513 if (skb == tcp_send_head(sk))
2514 break;
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08002515 /* TODO: do this better */
2516 /* this is not the most efficient way to do this... */
2517 tp->lost_skb_hint = skb;
2518 tp->lost_cnt_hint = cnt;
Ilpo Järvinen85cc3912007-11-15 19:39:31 -08002519
Ilpo Järvinenc137f3d2008-04-07 22:32:38 -07002520 if (after(TCP_SKB_CB(skb)->end_seq, tp->high_seq))
2521 break;
2522
2523 oldcnt = cnt;
Ilpo Järvinenad1984e2008-01-30 20:06:02 -08002524 if (tcp_is_fack(tp) || tcp_is_reno(tp) ||
Ilpo Järvinen85cc3912007-11-15 19:39:31 -08002525 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
2526 cnt += tcp_skb_pcount(skb);
2527
Ilpo Järvinenc137f3d2008-04-07 22:32:38 -07002528 if (cnt > packets) {
2529 if (tcp_is_sack(tp) || (oldcnt >= packets))
2530 break;
2531
2532 mss = skb_shinfo(skb)->gso_size;
2533 err = tcp_fragment(sk, skb, (packets - oldcnt) * mss, mss);
2534 if (err < 0)
2535 break;
2536 cnt = packets;
2537 }
2538
Ilpo Järvinen41ea36e2008-09-20 21:19:22 -07002539 tcp_skb_mark_lost(tp, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002540 }
Ilpo Järvinen005903b2007-08-09 14:44:16 +03002541 tcp_verify_left_out(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002542}
2543
2544/* Account newly detected lost packet(s) */
2545
Ilpo Järvinen85cc3912007-11-15 19:39:31 -08002546static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002547{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002548 struct tcp_sock *tp = tcp_sk(sk);
2549
Ilpo Järvinen85cc3912007-11-15 19:39:31 -08002550 if (tcp_is_reno(tp)) {
Ilpo Järvinen1b69d742008-04-07 22:31:38 -07002551 tcp_mark_head_lost(sk, 1);
Ilpo Järvinen85cc3912007-11-15 19:39:31 -08002552 } else if (tcp_is_fack(tp)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002553 int lost = tp->fackets_out - tp->reordering;
2554 if (lost <= 0)
2555 lost = 1;
Ilpo Järvinen1b69d742008-04-07 22:31:38 -07002556 tcp_mark_head_lost(sk, lost);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002557 } else {
Ilpo Järvinen85cc3912007-11-15 19:39:31 -08002558 int sacked_upto = tp->sacked_out - tp->reordering;
Ilpo Järvinen1b69d742008-04-07 22:31:38 -07002559 if (sacked_upto < fast_rexmit)
2560 sacked_upto = fast_rexmit;
2561 tcp_mark_head_lost(sk, sacked_upto);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002562 }
2563
Ilpo Järvinen7363a5b2009-02-28 04:44:33 +00002564 tcp_timeout_skbs(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002565}
2566
2567/* CWND moderation, preventing bursts due to too big ACKs
2568 * in dubious situations.
2569 */
2570static inline void tcp_moderate_cwnd(struct tcp_sock *tp)
2571{
2572 tp->snd_cwnd = min(tp->snd_cwnd,
Ilpo Järvinen056834d2007-12-31 14:57:14 -08002573 tcp_packets_in_flight(tp) + tcp_max_burst(tp));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002574 tp->snd_cwnd_stamp = tcp_time_stamp;
2575}
2576
Stephen Hemminger72dc5b92006-06-05 17:30:08 -07002577/* Lower bound on congestion window is slow start threshold
2578 * unless congestion avoidance choice decides to overide it.
2579 */
2580static inline u32 tcp_cwnd_min(const struct sock *sk)
2581{
2582 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
2583
2584 return ca_ops->min_cwnd ? ca_ops->min_cwnd(sk) : tcp_sk(sk)->snd_ssthresh;
2585}
2586
Linus Torvalds1da177e2005-04-16 15:20:36 -07002587/* Decrease cwnd each second ack. */
Ilpo Järvinen1e757f92007-07-30 19:48:37 -07002588static void tcp_cwnd_down(struct sock *sk, int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002589{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002590 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002591 int decr = tp->snd_cwnd_cnt + 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002592
Ilpo Järvinen056834d2007-12-31 14:57:14 -08002593 if ((flag & (FLAG_ANY_PROGRESS | FLAG_DSACKING_ACK)) ||
2594 (tcp_is_reno(tp) && !(flag & FLAG_NOT_DUP))) {
2595 tp->snd_cwnd_cnt = decr & 1;
Ilpo Järvinen1e757f92007-07-30 19:48:37 -07002596 decr >>= 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002597
Ilpo Järvinen1e757f92007-07-30 19:48:37 -07002598 if (decr && tp->snd_cwnd > tcp_cwnd_min(sk))
2599 tp->snd_cwnd -= decr;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002600
Ilpo Järvinen056834d2007-12-31 14:57:14 -08002601 tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp) + 1);
Ilpo Järvinen1e757f92007-07-30 19:48:37 -07002602 tp->snd_cwnd_stamp = tcp_time_stamp;
2603 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002604}
2605
2606/* Nothing was retransmitted or returned timestamp is less
2607 * than timestamp of the first retransmission.
2608 */
2609static inline int tcp_packet_delayed(struct tcp_sock *tp)
2610{
2611 return !tp->retrans_stamp ||
2612 (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
Arnd Hannemannd7ee1472008-04-21 14:46:22 -07002613 before(tp->rx_opt.rcv_tsecr, tp->retrans_stamp));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002614}
2615
2616/* Undo procedures. */
2617
2618#if FASTRETRANS_DEBUG > 1
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002619static void DBGUNDO(struct sock *sk, const char *msg)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002620{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002621 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002622 struct inet_sock *inet = inet_sk(sk);
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002623
YOSHIFUJI Hideaki569508c2008-04-14 04:09:36 -07002624 if (sk->sk_family == AF_INET) {
Harvey Harrison673d57e2008-10-31 00:53:57 -07002625 printk(KERN_DEBUG "Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
YOSHIFUJI Hideaki569508c2008-04-14 04:09:36 -07002626 msg,
Harvey Harrison673d57e2008-10-31 00:53:57 -07002627 &inet->daddr, ntohs(inet->dport),
YOSHIFUJI Hideaki569508c2008-04-14 04:09:36 -07002628 tp->snd_cwnd, tcp_left_out(tp),
2629 tp->snd_ssthresh, tp->prior_ssthresh,
2630 tp->packets_out);
2631 }
2632#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
2633 else if (sk->sk_family == AF_INET6) {
2634 struct ipv6_pinfo *np = inet6_sk(sk);
Harvey Harrison5b095d9892008-10-29 12:52:50 -07002635 printk(KERN_DEBUG "Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
YOSHIFUJI Hideaki569508c2008-04-14 04:09:36 -07002636 msg,
Harvey Harrison0c6ce782008-10-28 16:09:23 -07002637 &np->daddr, ntohs(inet->dport),
YOSHIFUJI Hideaki569508c2008-04-14 04:09:36 -07002638 tp->snd_cwnd, tcp_left_out(tp),
2639 tp->snd_ssthresh, tp->prior_ssthresh,
2640 tp->packets_out);
2641 }
2642#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -07002643}
2644#else
2645#define DBGUNDO(x...) do { } while (0)
2646#endif
2647
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002648static void tcp_undo_cwr(struct sock *sk, const int undo)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002649{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002650 struct tcp_sock *tp = tcp_sk(sk);
2651
Linus Torvalds1da177e2005-04-16 15:20:36 -07002652 if (tp->prior_ssthresh) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002653 const struct inet_connection_sock *icsk = inet_csk(sk);
2654
2655 if (icsk->icsk_ca_ops->undo_cwnd)
2656 tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002657 else
Ilpo Järvinen056834d2007-12-31 14:57:14 -08002658 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh << 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002659
2660 if (undo && tp->prior_ssthresh > tp->snd_ssthresh) {
2661 tp->snd_ssthresh = tp->prior_ssthresh;
2662 TCP_ECN_withdraw_cwr(tp);
2663 }
2664 } else {
2665 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh);
2666 }
2667 tcp_moderate_cwnd(tp);
2668 tp->snd_cwnd_stamp = tcp_time_stamp;
2669}
2670
2671static inline int tcp_may_undo(struct tcp_sock *tp)
2672{
Ilpo Järvinen056834d2007-12-31 14:57:14 -08002673 return tp->undo_marker && (!tp->undo_retrans || tcp_packet_delayed(tp));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002674}
2675
2676/* People celebrate: "We love our President!" */
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002677static int tcp_try_undo_recovery(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002678{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002679 struct tcp_sock *tp = tcp_sk(sk);
2680
Linus Torvalds1da177e2005-04-16 15:20:36 -07002681 if (tcp_may_undo(tp)) {
Pavel Emelyanov40b215e2008-07-03 01:05:41 -07002682 int mib_idx;
2683
Linus Torvalds1da177e2005-04-16 15:20:36 -07002684 /* Happy end! We did not retransmit anything
2685 * or our original transmission succeeded.
2686 */
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002687 DBGUNDO(sk, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans");
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002688 tcp_undo_cwr(sk, 1);
2689 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss)
Pavel Emelyanov40b215e2008-07-03 01:05:41 -07002690 mib_idx = LINUX_MIB_TCPLOSSUNDO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002691 else
Pavel Emelyanov40b215e2008-07-03 01:05:41 -07002692 mib_idx = LINUX_MIB_TCPFULLUNDO;
2693
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07002694 NET_INC_STATS_BH(sock_net(sk), mib_idx);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002695 tp->undo_marker = 0;
2696 }
Ilpo Järvinene60402d2007-08-09 15:14:46 +03002697 if (tp->snd_una == tp->high_seq && tcp_is_reno(tp)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002698 /* Hold old state until something *above* high_seq
2699 * is ACKed. For Reno it is MUST to prevent false
2700 * fast retransmits (RFC2582). SACK TCP is safe. */
2701 tcp_moderate_cwnd(tp);
2702 return 1;
2703 }
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002704 tcp_set_ca_state(sk, TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002705 return 0;
2706}
2707
2708/* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002709static void tcp_try_undo_dsack(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002710{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002711 struct tcp_sock *tp = tcp_sk(sk);
2712
Linus Torvalds1da177e2005-04-16 15:20:36 -07002713 if (tp->undo_marker && !tp->undo_retrans) {
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002714 DBGUNDO(sk, "D-SACK");
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002715 tcp_undo_cwr(sk, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002716 tp->undo_marker = 0;
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07002717 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKUNDO);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002718 }
2719}
2720
2721/* Undo during fast recovery after partial ACK. */
2722
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002723static int tcp_try_undo_partial(struct sock *sk, int acked)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002724{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002725 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002726 /* Partial ACK arrived. Force Hoe's retransmit. */
Ilpo Järvinen85cc3912007-11-15 19:39:31 -08002727 int failed = tcp_is_reno(tp) || (tcp_fackets_out(tp) > tp->reordering);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002728
2729 if (tcp_may_undo(tp)) {
2730 /* Plain luck! Hole if filled with delayed
2731 * packet, rather than with a retransmit.
2732 */
2733 if (tp->retrans_out == 0)
2734 tp->retrans_stamp = 0;
2735
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002736 tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002737
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002738 DBGUNDO(sk, "Hoe");
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002739 tcp_undo_cwr(sk, 0);
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07002740 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPARTIALUNDO);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002741
2742 /* So... Do not make Hoe's retransmit yet.
2743 * If the first packet was delayed, the rest
2744 * ones are most probably delayed as well.
2745 */
2746 failed = 0;
2747 }
2748 return failed;
2749}
2750
2751/* Undo during loss recovery after partial ACK. */
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002752static int tcp_try_undo_loss(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002753{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002754 struct tcp_sock *tp = tcp_sk(sk);
2755
Linus Torvalds1da177e2005-04-16 15:20:36 -07002756 if (tcp_may_undo(tp)) {
2757 struct sk_buff *skb;
David S. Millerfe067e82007-03-07 12:12:44 -08002758 tcp_for_write_queue(skb, sk) {
2759 if (skb == tcp_send_head(sk))
2760 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002761 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
2762 }
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08002763
Ilpo Järvinen5af4ec22007-09-20 11:30:48 -07002764 tcp_clear_all_retrans_hints(tp);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08002765
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002766 DBGUNDO(sk, "partial loss");
Linus Torvalds1da177e2005-04-16 15:20:36 -07002767 tp->lost_out = 0;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002768 tcp_undo_cwr(sk, 1);
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07002769 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSSUNDO);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002770 inet_csk(sk)->icsk_retransmits = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002771 tp->undo_marker = 0;
Ilpo Järvinene60402d2007-08-09 15:14:46 +03002772 if (tcp_is_sack(tp))
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002773 tcp_set_ca_state(sk, TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002774 return 1;
2775 }
2776 return 0;
2777}
2778
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002779static inline void tcp_complete_cwr(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002780{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002781 struct tcp_sock *tp = tcp_sk(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -07002782 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002783 tp->snd_cwnd_stamp = tcp_time_stamp;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002784 tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002785}
2786
Ilpo Järvinen8aca6cb2008-06-04 11:34:22 -07002787static void tcp_try_keep_open(struct sock *sk)
2788{
2789 struct tcp_sock *tp = tcp_sk(sk);
2790 int state = TCP_CA_Open;
2791
2792 if (tcp_left_out(tp) || tp->retrans_out || tp->undo_marker)
2793 state = TCP_CA_Disorder;
2794
2795 if (inet_csk(sk)->icsk_ca_state != state) {
2796 tcp_set_ca_state(sk, state);
2797 tp->high_seq = tp->snd_nxt;
2798 }
2799}
2800
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002801static void tcp_try_to_open(struct sock *sk, int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002802{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002803 struct tcp_sock *tp = tcp_sk(sk);
2804
Ilpo Järvinen86426c22007-08-09 14:45:17 +03002805 tcp_verify_left_out(tp);
2806
Ilpo Järvinena1c1f282008-05-13 02:53:26 -07002807 if (!tp->frto_counter && tp->retrans_out == 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002808 tp->retrans_stamp = 0;
2809
Ilpo Järvinen056834d2007-12-31 14:57:14 -08002810 if (flag & FLAG_ECE)
Ilpo Järvinen3cfe3ba2007-02-27 10:09:49 -08002811 tcp_enter_cwr(sk, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002812
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002813 if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) {
Ilpo Järvinen8aca6cb2008-06-04 11:34:22 -07002814 tcp_try_keep_open(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002815 tcp_moderate_cwnd(tp);
2816 } else {
Ilpo Järvinen1e757f92007-07-30 19:48:37 -07002817 tcp_cwnd_down(sk, flag);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002818 }
2819}
2820
John Heffner5d424d52006-03-20 17:53:41 -08002821static void tcp_mtup_probe_failed(struct sock *sk)
2822{
2823 struct inet_connection_sock *icsk = inet_csk(sk);
2824
2825 icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1;
2826 icsk->icsk_mtup.probe_size = 0;
2827}
2828
Ilpo Järvinen72211e92009-03-14 14:23:04 +00002829static void tcp_mtup_probe_success(struct sock *sk)
John Heffner5d424d52006-03-20 17:53:41 -08002830{
2831 struct tcp_sock *tp = tcp_sk(sk);
2832 struct inet_connection_sock *icsk = inet_csk(sk);
2833
2834 /* FIXME: breaks with very large cwnd */
2835 tp->prior_ssthresh = tcp_current_ssthresh(sk);
2836 tp->snd_cwnd = tp->snd_cwnd *
2837 tcp_mss_to_mtu(sk, tp->mss_cache) /
2838 icsk->icsk_mtup.probe_size;
2839 tp->snd_cwnd_cnt = 0;
2840 tp->snd_cwnd_stamp = tcp_time_stamp;
2841 tp->rcv_ssthresh = tcp_current_ssthresh(sk);
2842
2843 icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size;
2844 icsk->icsk_mtup.probe_size = 0;
2845 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
2846}
2847
Ilpo Järvinene1aa6802008-11-24 21:11:55 -08002848/* Do a simple retransmit without using the backoff mechanisms in
2849 * tcp_timer. This is used for path mtu discovery.
2850 * The socket is already locked here.
2851 */
2852void tcp_simple_retransmit(struct sock *sk)
2853{
2854 const struct inet_connection_sock *icsk = inet_csk(sk);
2855 struct tcp_sock *tp = tcp_sk(sk);
2856 struct sk_buff *skb;
Ilpo Järvinen0c54b852009-03-14 14:23:05 +00002857 unsigned int mss = tcp_current_mss(sk);
Ilpo Järvinene1aa6802008-11-24 21:11:55 -08002858 u32 prior_lost = tp->lost_out;
2859
2860 tcp_for_write_queue(skb, sk) {
2861 if (skb == tcp_send_head(sk))
2862 break;
Ilpo Järvinen775ffab2008-12-05 22:41:26 -08002863 if (tcp_skb_seglen(skb) > mss &&
Ilpo Järvinene1aa6802008-11-24 21:11:55 -08002864 !(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
2865 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2866 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
2867 tp->retrans_out -= tcp_skb_pcount(skb);
2868 }
2869 tcp_skb_mark_lost_uncond_verify(tp, skb);
2870 }
2871 }
2872
2873 tcp_clear_retrans_hints_partial(tp);
2874
2875 if (prior_lost == tp->lost_out)
2876 return;
2877
2878 if (tcp_is_reno(tp))
2879 tcp_limit_reno_sacked(tp);
2880
2881 tcp_verify_left_out(tp);
2882
2883 /* Don't muck with the congestion window here.
2884 * Reason is that we do not increase amount of _data_
2885 * in network, but units changed and effective
2886 * cwnd/ssthresh really reduced now.
2887 */
2888 if (icsk->icsk_ca_state != TCP_CA_Loss) {
2889 tp->high_seq = tp->snd_nxt;
2890 tp->snd_ssthresh = tcp_current_ssthresh(sk);
2891 tp->prior_ssthresh = 0;
2892 tp->undo_marker = 0;
2893 tcp_set_ca_state(sk, TCP_CA_Loss);
2894 }
2895 tcp_xmit_retransmit_queue(sk);
2896}
2897
Linus Torvalds1da177e2005-04-16 15:20:36 -07002898/* Process an event, which can update packets-in-flight not trivially.
2899 * Main goal of this function is to calculate new estimate for left_out,
2900 * taking into account both packets sitting in receiver's buffer and
2901 * packets lost by network.
2902 *
2903 * Besides that it does CWND reduction, when packet loss is detected
2904 * and changes state of machine.
2905 *
2906 * It does _not_ decide what to send, it is made in function
2907 * tcp_xmit_retransmit_queue().
2908 */
Ilpo Järvinen056834d2007-12-31 14:57:14 -08002909static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002910{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002911 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002912 struct tcp_sock *tp = tcp_sk(sk);
Ilpo Järvinen056834d2007-12-31 14:57:14 -08002913 int is_dupack = !(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP));
2914 int do_lost = is_dupack || ((flag & FLAG_DATA_SACKED) &&
Ilpo Järvinen85cc3912007-11-15 19:39:31 -08002915 (tcp_fackets_out(tp) > tp->reordering));
Pavel Emelyanov40b215e2008-07-03 01:05:41 -07002916 int fast_rexmit = 0, mib_idx;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002917
Ilpo Järvinen3ccd3132007-12-31 04:43:32 -08002918 if (WARN_ON(!tp->packets_out && tp->sacked_out))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002919 tp->sacked_out = 0;
Ilpo Järvinen91fed7a2007-10-09 01:24:15 -07002920 if (WARN_ON(!tp->sacked_out && tp->fackets_out))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002921 tp->fackets_out = 0;
2922
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09002923 /* Now state machine starts.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002924 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
Ilpo Järvinen056834d2007-12-31 14:57:14 -08002925 if (flag & FLAG_ECE)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002926 tp->prior_ssthresh = 0;
2927
2928 /* B. In all the states check for reneging SACKs. */
Ilpo Järvinencadbd032007-12-31 04:49:21 -08002929 if (tcp_check_sack_reneging(sk, flag))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002930 return;
2931
2932 /* C. Process data loss notification, provided it is valid. */
Ilpo Järvinen85cc3912007-11-15 19:39:31 -08002933 if (tcp_is_fack(tp) && (flag & FLAG_DATA_LOST) &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07002934 before(tp->snd_una, tp->high_seq) &&
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002935 icsk->icsk_ca_state != TCP_CA_Open &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07002936 tp->fackets_out > tp->reordering) {
Ilpo Järvinen1b69d742008-04-07 22:31:38 -07002937 tcp_mark_head_lost(sk, tp->fackets_out - tp->reordering);
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07002938 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSS);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002939 }
2940
Ilpo Järvinen005903b2007-08-09 14:44:16 +03002941 /* D. Check consistency of the current state. */
2942 tcp_verify_left_out(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002943
2944 /* E. Check state exit conditions. State can be terminated
2945 * when high_seq is ACKed. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002946 if (icsk->icsk_ca_state == TCP_CA_Open) {
Ilpo Järvinen547b7922008-07-25 21:43:18 -07002947 WARN_ON(tp->retrans_out != 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002948 tp->retrans_stamp = 0;
2949 } else if (!before(tp->snd_una, tp->high_seq)) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002950 switch (icsk->icsk_ca_state) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002951 case TCP_CA_Loss:
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002952 icsk->icsk_retransmits = 0;
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002953 if (tcp_try_undo_recovery(sk))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002954 return;
2955 break;
2956
2957 case TCP_CA_CWR:
2958 /* CWR is to be held something *above* high_seq
2959 * is ACKed for CWR bit to reach receiver. */
2960 if (tp->snd_una != tp->high_seq) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002961 tcp_complete_cwr(sk);
2962 tcp_set_ca_state(sk, TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002963 }
2964 break;
2965
2966 case TCP_CA_Disorder:
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002967 tcp_try_undo_dsack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002968 if (!tp->undo_marker ||
2969 /* For SACK case do not Open to allow to undo
2970 * catching for all duplicate ACKs. */
Ilpo Järvinene60402d2007-08-09 15:14:46 +03002971 tcp_is_reno(tp) || tp->snd_una != tp->high_seq) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002972 tp->undo_marker = 0;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002973 tcp_set_ca_state(sk, TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002974 }
2975 break;
2976
2977 case TCP_CA_Recovery:
Ilpo Järvinene60402d2007-08-09 15:14:46 +03002978 if (tcp_is_reno(tp))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002979 tcp_reset_reno_sack(tp);
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002980 if (tcp_try_undo_recovery(sk))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002981 return;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002982 tcp_complete_cwr(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002983 break;
2984 }
2985 }
2986
2987 /* F. Process state. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002988 switch (icsk->icsk_ca_state) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002989 case TCP_CA_Recovery:
Ilpo Järvinen2e605292007-08-02 19:46:58 -07002990 if (!(flag & FLAG_SND_UNA_ADVANCED)) {
Ilpo Järvinene60402d2007-08-09 15:14:46 +03002991 if (tcp_is_reno(tp) && is_dupack)
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002992 tcp_add_reno_sack(sk);
Ilpo Järvinen1b6d427b2007-08-09 14:53:36 +03002993 } else
2994 do_lost = tcp_try_undo_partial(sk, pkts_acked);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002995 break;
2996 case TCP_CA_Loss:
Ilpo Järvinen056834d2007-12-31 14:57:14 -08002997 if (flag & FLAG_DATA_ACKED)
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002998 icsk->icsk_retransmits = 0;
Ilpo Järvinen882beba2008-04-07 22:33:07 -07002999 if (tcp_is_reno(tp) && flag & FLAG_SND_UNA_ADVANCED)
3000 tcp_reset_reno_sack(tp);
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07003001 if (!tcp_try_undo_loss(sk)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003002 tcp_moderate_cwnd(tp);
3003 tcp_xmit_retransmit_queue(sk);
3004 return;
3005 }
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003006 if (icsk->icsk_ca_state != TCP_CA_Open)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003007 return;
3008 /* Loss is undone; fall through to processing in Open state. */
3009 default:
Ilpo Järvinene60402d2007-08-09 15:14:46 +03003010 if (tcp_is_reno(tp)) {
Ilpo Järvinen2e605292007-08-02 19:46:58 -07003011 if (flag & FLAG_SND_UNA_ADVANCED)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003012 tcp_reset_reno_sack(tp);
3013 if (is_dupack)
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003014 tcp_add_reno_sack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003015 }
3016
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003017 if (icsk->icsk_ca_state == TCP_CA_Disorder)
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07003018 tcp_try_undo_dsack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003019
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07003020 if (!tcp_time_to_recover(sk)) {
3021 tcp_try_to_open(sk, flag);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003022 return;
3023 }
3024
John Heffner5d424d52006-03-20 17:53:41 -08003025 /* MTU probe failure: don't reduce cwnd */
3026 if (icsk->icsk_ca_state < TCP_CA_CWR &&
3027 icsk->icsk_mtup.probe_size &&
John Heffner0e7b1362006-03-20 21:32:58 -08003028 tp->snd_una == tp->mtu_probe.probe_seq_start) {
John Heffner5d424d52006-03-20 17:53:41 -08003029 tcp_mtup_probe_failed(sk);
3030 /* Restores the reduction we did in tcp_mtup_probe() */
3031 tp->snd_cwnd++;
3032 tcp_simple_retransmit(sk);
3033 return;
3034 }
3035
Linus Torvalds1da177e2005-04-16 15:20:36 -07003036 /* Otherwise enter Recovery state */
3037
Ilpo Järvinene60402d2007-08-09 15:14:46 +03003038 if (tcp_is_reno(tp))
Pavel Emelyanov40b215e2008-07-03 01:05:41 -07003039 mib_idx = LINUX_MIB_TCPRENORECOVERY;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003040 else
Pavel Emelyanov40b215e2008-07-03 01:05:41 -07003041 mib_idx = LINUX_MIB_TCPSACKRECOVERY;
3042
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07003043 NET_INC_STATS_BH(sock_net(sk), mib_idx);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003044
3045 tp->high_seq = tp->snd_nxt;
3046 tp->prior_ssthresh = 0;
3047 tp->undo_marker = tp->snd_una;
3048 tp->undo_retrans = tp->retrans_out;
3049
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003050 if (icsk->icsk_ca_state < TCP_CA_CWR) {
Ilpo Järvinen056834d2007-12-31 14:57:14 -08003051 if (!(flag & FLAG_ECE))
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003052 tp->prior_ssthresh = tcp_current_ssthresh(sk);
3053 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003054 TCP_ECN_queue_cwr(tp);
3055 }
3056
Stephen Hemminger9772efb2005-11-10 17:09:53 -08003057 tp->bytes_acked = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003058 tp->snd_cwnd_cnt = 0;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003059 tcp_set_ca_state(sk, TCP_CA_Recovery);
Ilpo Järvinen85cc3912007-11-15 19:39:31 -08003060 fast_rexmit = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003061 }
3062
Ilpo Järvinen85cc3912007-11-15 19:39:31 -08003063 if (do_lost || (tcp_is_fack(tp) && tcp_head_timedout(sk)))
3064 tcp_update_scoreboard(sk, fast_rexmit);
Ilpo Järvinen1e757f92007-07-30 19:48:37 -07003065 tcp_cwnd_down(sk, flag);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003066 tcp_xmit_retransmit_queue(sk);
3067}
3068
Ilpo Järvinen41834b72008-12-05 22:43:26 -08003069static void tcp_valid_rtt_meas(struct sock *sk, u32 seq_rtt)
3070{
3071 tcp_rtt_estimator(sk, seq_rtt);
3072 tcp_set_rto(sk);
3073 inet_csk(sk)->icsk_backoff = 0;
3074}
3075
Linus Torvalds1da177e2005-04-16 15:20:36 -07003076/* Read draft-ietf-tcplw-high-performance before mucking
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08003077 * with this code. (Supersedes RFC1323)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003078 */
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08003079static void tcp_ack_saw_tstamp(struct sock *sk, int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003080{
Linus Torvalds1da177e2005-04-16 15:20:36 -07003081 /* RTTM Rule: A TSecr value received in a segment is used to
3082 * update the averaged RTT measurement only if the segment
3083 * acknowledges some new data, i.e., only if it advances the
3084 * left edge of the send window.
3085 *
3086 * See draft-ietf-tcplw-high-performance-00, section 3.3.
3087 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
3088 *
3089 * Changed: reset backoff as soon as we see the first valid sample.
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08003090 * If we do not, we get strongly overestimated rto. With timestamps
Linus Torvalds1da177e2005-04-16 15:20:36 -07003091 * samples are accepted even from very old segments: f.e., when rtt=1
3092 * increases to 8, we retransmit 5 times and after 8 seconds delayed
3093 * answer arrives rto becomes 120 seconds! If at least one of segments
3094 * in window is lost... Voila. --ANK (010210)
3095 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003096 struct tcp_sock *tp = tcp_sk(sk);
Ilpo Järvinen41834b72008-12-05 22:43:26 -08003097
3098 tcp_valid_rtt_meas(sk, tcp_time_stamp - tp->rx_opt.rcv_tsecr);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003099}
3100
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08003101static void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003102{
3103 /* We don't have a timestamp. Can only use
3104 * packets that are not retransmitted to determine
3105 * rtt estimates. Also, we must not reset the
3106 * backoff for rto until we get a non-retransmitted
3107 * packet. This allows us to deal with a situation
3108 * where the network delay has increased suddenly.
3109 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
3110 */
3111
3112 if (flag & FLAG_RETRANS_DATA_ACKED)
3113 return;
3114
Ilpo Järvinen41834b72008-12-05 22:43:26 -08003115 tcp_valid_rtt_meas(sk, seq_rtt);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003116}
3117
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003118static inline void tcp_ack_update_rtt(struct sock *sk, const int flag,
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08003119 const s32 seq_rtt)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003120{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003121 const struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003122 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
3123 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08003124 tcp_ack_saw_tstamp(sk, flag);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003125 else if (seq_rtt >= 0)
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08003126 tcp_ack_no_tstamp(sk, seq_rtt, flag);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003127}
3128
Ilpo Järvinenc3a05c62007-12-02 00:47:59 +02003129static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003130{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003131 const struct inet_connection_sock *icsk = inet_csk(sk);
Ilpo Järvinenc3a05c62007-12-02 00:47:59 +02003132 icsk->icsk_ca_ops->cong_avoid(sk, ack, in_flight);
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003133 tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003134}
3135
Linus Torvalds1da177e2005-04-16 15:20:36 -07003136/* Restart timer after forward progress on connection.
3137 * RFC2988 recommends to restart timer to now+rto.
3138 */
Ilpo Järvinen6728e7d2007-08-24 22:53:26 -07003139static void tcp_rearm_rto(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003140{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07003141 struct tcp_sock *tp = tcp_sk(sk);
3142
Linus Torvalds1da177e2005-04-16 15:20:36 -07003143 if (!tp->packets_out) {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003144 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003145 } else {
Ilpo Järvinen056834d2007-12-31 14:57:14 -08003146 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
3147 inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003148 }
3149}
3150
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07003151/* If we get here, the whole TSO packet has not been acked. */
Ilpo Järvinen13fcf852007-10-09 01:28:45 -07003152static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003153{
3154 struct tcp_sock *tp = tcp_sk(sk);
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07003155 u32 packets_acked;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003156
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07003157 BUG_ON(!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una));
Linus Torvalds1da177e2005-04-16 15:20:36 -07003158
3159 packets_acked = tcp_skb_pcount(skb);
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07003160 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003161 return 0;
3162 packets_acked -= tcp_skb_pcount(skb);
3163
3164 if (packets_acked) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003165 BUG_ON(tcp_skb_pcount(skb) == 0);
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07003166 BUG_ON(!before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq));
Linus Torvalds1da177e2005-04-16 15:20:36 -07003167 }
3168
Ilpo Järvinen13fcf852007-10-09 01:28:45 -07003169 return packets_acked;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003170}
3171
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07003172/* Remove acknowledged frames from the retransmission queue. If our packet
3173 * is before the ack sequence we can discard it as it's confirmed to have
3174 * arrived at the other end.
3175 */
Ilpo Järvinen33f5f572008-10-07 14:43:06 -07003176static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
3177 u32 prior_snd_una)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003178{
3179 struct tcp_sock *tp = tcp_sk(sk);
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08003180 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003181 struct sk_buff *skb;
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07003182 u32 now = tcp_time_stamp;
Ilpo Järvinen13fcf852007-10-09 01:28:45 -07003183 int fully_acked = 1;
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07003184 int flag = 0;
Ilpo Järvinen72018832007-12-30 04:37:55 -08003185 u32 pkts_acked = 0;
Ilpo Järvinenc7caf8d2007-11-10 21:22:18 -08003186 u32 reord = tp->packets_out;
Ilpo Järvinen90638a02008-09-20 21:25:52 -07003187 u32 prior_sacked = tp->sacked_out;
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07003188 s32 seq_rtt = -1;
Gavin McCullagh2072c222007-12-29 19:11:21 -08003189 s32 ca_seq_rtt = -1;
Ilpo Järvinenb9ce2042007-06-15 15:08:43 -07003190 ktime_t last_ackt = net_invalid_timestamp();
Linus Torvalds1da177e2005-04-16 15:20:36 -07003191
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07003192 while ((skb = tcp_write_queue_head(sk)) && skb != tcp_send_head(sk)) {
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09003193 struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
Ilpo Järvinen72018832007-12-30 04:37:55 -08003194 u32 acked_pcount;
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07003195 u8 sacked = scb->sacked;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003196
Gavin McCullagh2072c222007-12-29 19:11:21 -08003197 /* Determine how many packets and what bytes were acked, tso and else */
Linus Torvalds1da177e2005-04-16 15:20:36 -07003198 if (after(scb->end_seq, tp->snd_una)) {
Ilpo Järvinen13fcf852007-10-09 01:28:45 -07003199 if (tcp_skb_pcount(skb) == 1 ||
3200 !after(tp->snd_una, scb->seq))
3201 break;
3202
Ilpo Järvinen72018832007-12-30 04:37:55 -08003203 acked_pcount = tcp_tso_acked(sk, skb);
3204 if (!acked_pcount)
Ilpo Järvinen13fcf852007-10-09 01:28:45 -07003205 break;
3206
3207 fully_acked = 0;
Ilpo Järvinen13fcf852007-10-09 01:28:45 -07003208 } else {
Ilpo Järvinen72018832007-12-30 04:37:55 -08003209 acked_pcount = tcp_skb_pcount(skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003210 }
3211
Ilpo Järvinen89d478f2007-12-30 04:35:27 -08003212 if (sacked & TCPCB_RETRANS) {
3213 if (sacked & TCPCB_SACKED_RETRANS)
Ilpo Järvinen72018832007-12-30 04:37:55 -08003214 tp->retrans_out -= acked_pcount;
Ilpo Järvinen89d478f2007-12-30 04:35:27 -08003215 flag |= FLAG_RETRANS_DATA_ACKED;
3216 ca_seq_rtt = -1;
3217 seq_rtt = -1;
Ilpo Järvinen056834d2007-12-31 14:57:14 -08003218 if ((flag & FLAG_DATA_ACKED) || (acked_pcount > 1))
Ilpo Järvinen89d478f2007-12-30 04:35:27 -08003219 flag |= FLAG_NONHEAD_RETRANS_ACKED;
Ilpo Järvinenc7caf8d2007-11-10 21:22:18 -08003220 } else {
Gavin McCullagh2072c222007-12-29 19:11:21 -08003221 ca_seq_rtt = now - scb->when;
3222 last_ackt = skb->tstamp;
Ilpo Järvinenc7caf8d2007-11-10 21:22:18 -08003223 if (seq_rtt < 0) {
Gavin McCullagh2072c222007-12-29 19:11:21 -08003224 seq_rtt = ca_seq_rtt;
Ilpo Järvinenc7caf8d2007-11-10 21:22:18 -08003225 }
Ilpo Järvinen89d478f2007-12-30 04:35:27 -08003226 if (!(sacked & TCPCB_SACKED_ACKED))
Ilpo Järvinen72018832007-12-30 04:37:55 -08003227 reord = min(pkts_acked, reord);
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08003228 }
Ilpo Järvinen89d478f2007-12-30 04:35:27 -08003229
3230 if (sacked & TCPCB_SACKED_ACKED)
Ilpo Järvinen72018832007-12-30 04:37:55 -08003231 tp->sacked_out -= acked_pcount;
Ilpo Järvinen89d478f2007-12-30 04:35:27 -08003232 if (sacked & TCPCB_LOST)
Ilpo Järvinen72018832007-12-30 04:37:55 -08003233 tp->lost_out -= acked_pcount;
Ilpo Järvinen89d478f2007-12-30 04:35:27 -08003234
Ilpo Järvinen72018832007-12-30 04:37:55 -08003235 tp->packets_out -= acked_pcount;
3236 pkts_acked += acked_pcount;
Ilpo Järvinen13fcf852007-10-09 01:28:45 -07003237
Ilpo Järvinen009a2e32007-09-20 11:34:38 -07003238 /* Initial outgoing SYN's get put onto the write_queue
3239 * just like anything else we transmit. It is not
3240 * true data, and if we misinform our callers that
3241 * this ACK acks real data, we will erroneously exit
3242 * connection startup slow start one packet too
3243 * quickly. This is severely frowned upon behavior.
3244 */
3245 if (!(scb->flags & TCPCB_FLAG_SYN)) {
3246 flag |= FLAG_DATA_ACKED;
3247 } else {
3248 flag |= FLAG_SYN_ACKED;
3249 tp->retrans_stamp = 0;
3250 }
3251
Ilpo Järvinen13fcf852007-10-09 01:28:45 -07003252 if (!fully_acked)
3253 break;
3254
David S. Millerfe067e82007-03-07 12:12:44 -08003255 tcp_unlink_write_queue(skb, sk);
Hideo Aoki3ab224b2007-12-31 00:11:19 -08003256 sk_wmem_free_skb(sk, skb);
Ilpo Järvinen90638a02008-09-20 21:25:52 -07003257 tp->scoreboard_skb_hint = NULL;
Ilpo Järvinenef9da472008-09-20 21:25:15 -07003258 if (skb == tp->retransmit_skb_hint)
3259 tp->retransmit_skb_hint = NULL;
Ilpo Järvinen90638a02008-09-20 21:25:52 -07003260 if (skb == tp->lost_skb_hint)
3261 tp->lost_skb_hint = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003262 }
3263
Ilpo Järvinen33f5f572008-10-07 14:43:06 -07003264 if (likely(between(tp->snd_up, prior_snd_una, tp->snd_una)))
3265 tp->snd_up = tp->snd_una;
3266
Ilpo Järvinencadbd032007-12-31 04:49:21 -08003267 if (skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
3268 flag |= FLAG_SACK_RENEGING;
3269
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07003270 if (flag & FLAG_ACKED) {
Stephen Hemminger164891a2007-04-23 22:26:16 -07003271 const struct tcp_congestion_ops *ca_ops
3272 = inet_csk(sk)->icsk_ca_ops;
3273
Ilpo Järvinen72211e92009-03-14 14:23:04 +00003274 if (unlikely(icsk->icsk_mtup.probe_size &&
3275 !after(tp->mtu_probe.probe_seq_end, tp->snd_una))) {
3276 tcp_mtup_probe_success(sk);
3277 }
3278
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07003279 tcp_ack_update_rtt(sk, flag, seq_rtt);
Ilpo Järvinen6728e7d2007-08-24 22:53:26 -07003280 tcp_rearm_rto(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -07003281
Ilpo Järvinenc7caf8d2007-11-10 21:22:18 -08003282 if (tcp_is_reno(tp)) {
3283 tcp_remove_reno_sacks(sk, pkts_acked);
3284 } else {
Ilpo Järvinen59a08cb2009-02-28 04:44:28 +00003285 int delta;
3286
Ilpo Järvinenc7caf8d2007-11-10 21:22:18 -08003287 /* Non-retransmitted hole got filled? That's reordering */
3288 if (reord < prior_fackets)
3289 tcp_update_reordering(sk, tp->fackets_out - reord, 0);
Ilpo Järvinen90638a02008-09-20 21:25:52 -07003290
Ilpo Järvinen59a08cb2009-02-28 04:44:28 +00003291 delta = tcp_is_fack(tp) ? pkts_acked :
3292 prior_sacked - tp->sacked_out;
3293 tp->lost_cnt_hint -= min(tp->lost_cnt_hint, delta);
Ilpo Järvinenc7caf8d2007-11-10 21:22:18 -08003294 }
3295
Ilpo Järvinen91fed7a2007-10-09 01:24:15 -07003296 tp->fackets_out -= min(pkts_acked, tp->fackets_out);
Ilpo Järvinen68f83532007-11-15 19:50:37 -08003297
Stephen Hemminger30cfd0b2007-07-25 23:49:34 -07003298 if (ca_ops->pkts_acked) {
3299 s32 rtt_us = -1;
Ilpo Järvinenb9ce2042007-06-15 15:08:43 -07003300
Stephen Hemminger30cfd0b2007-07-25 23:49:34 -07003301 /* Is the ACK triggering packet unambiguous? */
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07003302 if (!(flag & FLAG_RETRANS_DATA_ACKED)) {
Stephen Hemminger30cfd0b2007-07-25 23:49:34 -07003303 /* High resolution needed and available? */
3304 if (ca_ops->flags & TCP_CONG_RTT_STAMP &&
3305 !ktime_equal(last_ackt,
3306 net_invalid_timestamp()))
3307 rtt_us = ktime_us_delta(ktime_get_real(),
3308 last_ackt);
Gavin McCullagh2072c222007-12-29 19:11:21 -08003309 else if (ca_seq_rtt > 0)
3310 rtt_us = jiffies_to_usecs(ca_seq_rtt);
Stephen Hemminger30cfd0b2007-07-25 23:49:34 -07003311 }
3312
3313 ca_ops->pkts_acked(sk, pkts_acked, rtt_us);
3314 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07003315 }
3316
3317#if FASTRETRANS_DEBUG > 0
Ilpo Järvinen547b7922008-07-25 21:43:18 -07003318 WARN_ON((int)tp->sacked_out < 0);
3319 WARN_ON((int)tp->lost_out < 0);
3320 WARN_ON((int)tp->retrans_out < 0);
Ilpo Järvinene60402d2007-08-09 15:14:46 +03003321 if (!tp->packets_out && tcp_is_sack(tp)) {
Stephen Hemmingercfcabdc2007-10-09 01:59:42 -07003322 icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003323 if (tp->lost_out) {
3324 printk(KERN_DEBUG "Leak l=%u %d\n",
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003325 tp->lost_out, icsk->icsk_ca_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003326 tp->lost_out = 0;
3327 }
3328 if (tp->sacked_out) {
3329 printk(KERN_DEBUG "Leak s=%u %d\n",
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003330 tp->sacked_out, icsk->icsk_ca_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003331 tp->sacked_out = 0;
3332 }
3333 if (tp->retrans_out) {
3334 printk(KERN_DEBUG "Leak r=%u %d\n",
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003335 tp->retrans_out, icsk->icsk_ca_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003336 tp->retrans_out = 0;
3337 }
3338 }
3339#endif
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07003340 return flag;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003341}
3342
3343static void tcp_ack_probe(struct sock *sk)
3344{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003345 const struct tcp_sock *tp = tcp_sk(sk);
3346 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003347
3348 /* Was it a usable window open? */
3349
Ilpo Järvinen90840de2007-12-31 04:48:41 -08003350 if (!after(TCP_SKB_CB(tcp_send_head(sk))->end_seq, tcp_wnd_end(tp))) {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003351 icsk->icsk_backoff = 0;
3352 inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003353 /* Socket must be waked up by subsequent tcp_data_snd_check().
3354 * This function is not for random using!
3355 */
3356 } else {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003357 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
Arnaldo Carvalho de Melo3f421ba2005-08-09 20:11:08 -07003358 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
3359 TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003360 }
3361}
3362
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003363static inline int tcp_ack_is_dubious(const struct sock *sk, const int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003364{
3365 return (!(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) ||
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003366 inet_csk(sk)->icsk_ca_state != TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003367}
3368
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003369static inline int tcp_may_raise_cwnd(const struct sock *sk, const int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003370{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003371 const struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003372 return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) &&
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003373 !((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_Recovery | TCPF_CA_CWR));
Linus Torvalds1da177e2005-04-16 15:20:36 -07003374}
3375
3376/* Check that window update is acceptable.
3377 * The function assumes that snd_una<=ack<=snd_next.
3378 */
Ilpo Järvinen056834d2007-12-31 14:57:14 -08003379static inline int tcp_may_update_window(const struct tcp_sock *tp,
3380 const u32 ack, const u32 ack_seq,
3381 const u32 nwin)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003382{
3383 return (after(ack, tp->snd_una) ||
3384 after(ack_seq, tp->snd_wl1) ||
3385 (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd));
3386}
3387
3388/* Update our send window.
3389 *
3390 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
3391 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
3392 */
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07003393static int tcp_ack_update_window(struct sock *sk, struct sk_buff *skb, u32 ack,
3394 u32 ack_seq)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003395{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07003396 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003397 int flag = 0;
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -07003398 u32 nwin = ntohs(tcp_hdr(skb)->window);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003399
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -07003400 if (likely(!tcp_hdr(skb)->syn))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003401 nwin <<= tp->rx_opt.snd_wscale;
3402
3403 if (tcp_may_update_window(tp, ack, ack_seq, nwin)) {
3404 flag |= FLAG_WIN_UPDATE;
Hantzis Fotisee7537b2009-03-02 22:42:02 -08003405 tcp_update_wl(tp, ack_seq);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003406
3407 if (tp->snd_wnd != nwin) {
3408 tp->snd_wnd = nwin;
3409
3410 /* Note, it is the only place, where
3411 * fast path is recovered for sending TCP.
3412 */
Herbert Xu2ad41062005-10-27 18:47:46 +10003413 tp->pred_flags = 0;
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07003414 tcp_fast_path_check(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003415
3416 if (nwin > tp->max_window) {
3417 tp->max_window = nwin;
Arnaldo Carvalho de Melod83d8462005-12-13 23:26:10 -08003418 tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003419 }
3420 }
3421 }
3422
3423 tp->snd_una = ack;
3424
3425 return flag;
3426}
3427
Ilpo Järvinen9ead9a12007-02-21 22:56:19 -08003428/* A very conservative spurious RTO response algorithm: reduce cwnd and
3429 * continue in congestion avoidance.
3430 */
3431static void tcp_conservative_spur_to_response(struct tcp_sock *tp)
3432{
3433 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
Ilpo Järvinenaa8b6a72007-02-21 23:06:03 -08003434 tp->snd_cwnd_cnt = 0;
Ilpo Järvinen16e90682007-10-11 17:32:31 -07003435 tp->bytes_acked = 0;
Ilpo Järvinen46323652007-05-19 13:56:23 -07003436 TCP_ECN_queue_cwr(tp);
Ilpo Järvinen9ead9a12007-02-21 22:56:19 -08003437 tcp_moderate_cwnd(tp);
3438}
3439
Ilpo Järvinen3cfe3ba2007-02-27 10:09:49 -08003440/* A conservative spurious RTO response algorithm: reduce cwnd using
3441 * rate halving and continue in congestion avoidance.
3442 */
3443static void tcp_ratehalving_spur_to_response(struct sock *sk)
3444{
Ilpo Järvinen3cfe3ba2007-02-27 10:09:49 -08003445 tcp_enter_cwr(sk, 0);
Ilpo Järvinen3cfe3ba2007-02-27 10:09:49 -08003446}
3447
Ilpo Järvinene317f6f2007-03-02 13:34:19 -08003448static void tcp_undo_spur_to_response(struct sock *sk, int flag)
Ilpo Järvinen3cfe3ba2007-02-27 10:09:49 -08003449{
Ilpo Järvinen056834d2007-12-31 14:57:14 -08003450 if (flag & FLAG_ECE)
Ilpo Järvinene317f6f2007-03-02 13:34:19 -08003451 tcp_ratehalving_spur_to_response(sk);
3452 else
3453 tcp_undo_cwr(sk, 1);
Ilpo Järvinen3cfe3ba2007-02-27 10:09:49 -08003454}
3455
Ilpo Järvinen30935cf2007-02-21 23:01:36 -08003456/* F-RTO spurious RTO detection algorithm (RFC4138)
3457 *
Ilpo Järvinen6408d202007-02-21 23:04:11 -08003458 * F-RTO affects during two new ACKs following RTO (well, almost, see inline
3459 * comments). State (ACK number) is kept in frto_counter. When ACK advances
3460 * window (but not to or beyond highest sequence sent before RTO):
Ilpo Järvinen30935cf2007-02-21 23:01:36 -08003461 * On First ACK, send two new segments out.
3462 * On Second ACK, RTO was likely spurious. Do spurious response (response
3463 * algorithm is not part of the F-RTO detection algorithm
3464 * given in RFC4138 but can be selected separately).
3465 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss
Ilpo Järvinend551e452007-04-30 00:42:20 -07003466 * and TCP falls back to conventional RTO recovery. F-RTO allows overriding
3467 * of Nagle, this is done using frto_counter states 2 and 3, when a new data
3468 * segment of any size sent during F-RTO, state 2 is upgraded to 3.
Ilpo Järvinen30935cf2007-02-21 23:01:36 -08003469 *
3470 * Rationale: if the RTO was spurious, new ACKs should arrive from the
3471 * original window even after we transmit two new data segments.
3472 *
Ilpo Järvinen4dc26652007-02-21 23:16:11 -08003473 * SACK version:
3474 * on first step, wait until first cumulative ACK arrives, then move to
3475 * the second step. In second step, the next ACK decides.
3476 *
Ilpo Järvinen30935cf2007-02-21 23:01:36 -08003477 * F-RTO is implemented (mainly) in four functions:
3478 * - tcp_use_frto() is used to determine if TCP is can use F-RTO
3479 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is
3480 * called when tcp_use_frto() showed green light
3481 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm
3482 * - tcp_enter_frto_loss() is called if there is not enough evidence
3483 * to prove that the RTO is indeed spurious. It transfers the control
3484 * from F-RTO to the conventional RTO recovery
3485 */
Ilpo Järvinen2e605292007-08-02 19:46:58 -07003486static int tcp_process_frto(struct sock *sk, int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003487{
3488 struct tcp_sock *tp = tcp_sk(sk);
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09003489
Ilpo Järvinen005903b2007-08-09 14:44:16 +03003490 tcp_verify_left_out(tp);
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09003491
Ilpo Järvinen7487c482007-02-21 23:02:30 -08003492 /* Duplicate the behavior from Loss state (fastretrans_alert) */
Ilpo Järvinen056834d2007-12-31 14:57:14 -08003493 if (flag & FLAG_DATA_ACKED)
Ilpo Järvinen7487c482007-02-21 23:02:30 -08003494 inet_csk(sk)->icsk_retransmits = 0;
3495
Ilpo Järvinen009a2e32007-09-20 11:34:38 -07003496 if ((flag & FLAG_NONHEAD_RETRANS_ACKED) ||
3497 ((tp->frto_counter >= 2) && (flag & FLAG_RETRANS_DATA_ACKED)))
3498 tp->undo_marker = 0;
3499
Ilpo Järvinen95c49222007-02-21 23:05:18 -08003500 if (!before(tp->snd_una, tp->frto_highmark)) {
Ilpo Järvinend551e452007-04-30 00:42:20 -07003501 tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 2 : 3), flag);
Ilpo Järvinen7c9a4a52007-02-21 23:08:34 -08003502 return 1;
Ilpo Järvinen95c49222007-02-21 23:05:18 -08003503 }
3504
Ilpo Järvinen62ab2222008-05-08 01:09:11 -07003505 if (!tcp_is_sackfrto(tp)) {
Ilpo Järvinen4dc26652007-02-21 23:16:11 -08003506 /* RFC4138 shortcoming in step 2; should also have case c):
3507 * ACK isn't duplicate nor advances window, e.g., opposite dir
3508 * data, winupdate
3509 */
Ilpo Järvinen056834d2007-12-31 14:57:14 -08003510 if (!(flag & FLAG_ANY_PROGRESS) && (flag & FLAG_NOT_DUP))
Ilpo Järvinen4dc26652007-02-21 23:16:11 -08003511 return 1;
Ilpo Järvinen6408d202007-02-21 23:04:11 -08003512
Ilpo Järvinen056834d2007-12-31 14:57:14 -08003513 if (!(flag & FLAG_DATA_ACKED)) {
Ilpo Järvinen4dc26652007-02-21 23:16:11 -08003514 tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 0 : 3),
3515 flag);
3516 return 1;
3517 }
3518 } else {
Ilpo Järvinen056834d2007-12-31 14:57:14 -08003519 if (!(flag & FLAG_DATA_ACKED) && (tp->frto_counter == 1)) {
Ilpo Järvinen4dc26652007-02-21 23:16:11 -08003520 /* Prevent sending of new data. */
3521 tp->snd_cwnd = min(tp->snd_cwnd,
3522 tcp_packets_in_flight(tp));
3523 return 1;
3524 }
3525
Ilpo Järvinend551e452007-04-30 00:42:20 -07003526 if ((tp->frto_counter >= 2) &&
Ilpo Järvinen056834d2007-12-31 14:57:14 -08003527 (!(flag & FLAG_FORWARD_PROGRESS) ||
3528 ((flag & FLAG_DATA_SACKED) &&
3529 !(flag & FLAG_ONLY_ORIG_SACKED)))) {
Ilpo Järvinen4dc26652007-02-21 23:16:11 -08003530 /* RFC4138 shortcoming (see comment above) */
Ilpo Järvinen056834d2007-12-31 14:57:14 -08003531 if (!(flag & FLAG_FORWARD_PROGRESS) &&
3532 (flag & FLAG_NOT_DUP))
Ilpo Järvinen4dc26652007-02-21 23:16:11 -08003533 return 1;
3534
3535 tcp_enter_frto_loss(sk, 3, flag);
3536 return 1;
3537 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07003538 }
3539
3540 if (tp->frto_counter == 1) {
Ilpo Järvinen3e6f0492007-12-05 02:20:21 -08003541 /* tcp_may_send_now needs to see updated state */
Linus Torvalds1da177e2005-04-16 15:20:36 -07003542 tp->snd_cwnd = tcp_packets_in_flight(tp) + 2;
Ilpo Järvinen94d0ea72007-02-21 23:07:27 -08003543 tp->frto_counter = 2;
Ilpo Järvinen3e6f0492007-12-05 02:20:21 -08003544
3545 if (!tcp_may_send_now(sk))
3546 tcp_enter_frto_loss(sk, 2, flag);
3547
Ilpo Järvinen7c9a4a52007-02-21 23:08:34 -08003548 return 1;
Ilpo Järvinend551e452007-04-30 00:42:20 -07003549 } else {
Ilpo Järvinen3cfe3ba2007-02-27 10:09:49 -08003550 switch (sysctl_tcp_frto_response) {
3551 case 2:
Ilpo Järvinene317f6f2007-03-02 13:34:19 -08003552 tcp_undo_spur_to_response(sk, flag);
Ilpo Järvinen3cfe3ba2007-02-27 10:09:49 -08003553 break;
3554 case 1:
3555 tcp_conservative_spur_to_response(tp);
3556 break;
3557 default:
3558 tcp_ratehalving_spur_to_response(sk);
3559 break;
Stephen Hemminger3ff50b72007-04-20 17:09:22 -07003560 }
Ilpo Järvinen94d0ea72007-02-21 23:07:27 -08003561 tp->frto_counter = 0;
Ilpo Järvinen009a2e32007-09-20 11:34:38 -07003562 tp->undo_marker = 0;
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07003563 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSPURIOUSRTOS);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003564 }
Ilpo Järvinen7c9a4a52007-02-21 23:08:34 -08003565 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003566}
3567
Linus Torvalds1da177e2005-04-16 15:20:36 -07003568/* This routine deals with incoming acks, but not outgoing ones. */
3569static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
3570{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003571 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003572 struct tcp_sock *tp = tcp_sk(sk);
3573 u32 prior_snd_una = tp->snd_una;
3574 u32 ack_seq = TCP_SKB_CB(skb)->seq;
3575 u32 ack = TCP_SKB_CB(skb)->ack_seq;
3576 u32 prior_in_flight;
Ilpo Järvinenc7caf8d2007-11-10 21:22:18 -08003577 u32 prior_fackets;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003578 int prior_packets;
Ilpo Järvinen7c9a4a52007-02-21 23:08:34 -08003579 int frto_cwnd = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003580
John Dykstra96e0bf42009-03-22 21:49:57 -07003581 /* If the ack is older than previous acks
Linus Torvalds1da177e2005-04-16 15:20:36 -07003582 * then we can probably ignore it.
3583 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07003584 if (before(ack, prior_snd_una))
3585 goto old_ack;
3586
John Dykstra96e0bf42009-03-22 21:49:57 -07003587 /* If the ack includes data we haven't sent yet, discard
3588 * this segment (RFC793 Section 3.9).
3589 */
3590 if (after(ack, tp->snd_nxt))
3591 goto invalid_ack;
3592
Ilpo Järvinen2e605292007-08-02 19:46:58 -07003593 if (after(ack, prior_snd_una))
3594 flag |= FLAG_SND_UNA_ADVANCED;
3595
Daikichi Osuga3fdf3f02006-08-29 02:01:44 -07003596 if (sysctl_tcp_abc) {
3597 if (icsk->icsk_ca_state < TCP_CA_CWR)
3598 tp->bytes_acked += ack - prior_snd_una;
3599 else if (icsk->icsk_ca_state == TCP_CA_Loss)
3600 /* we assume just one segment left network */
Ilpo Järvinen056834d2007-12-31 14:57:14 -08003601 tp->bytes_acked += min(ack - prior_snd_una,
3602 tp->mss_cache);
Daikichi Osuga3fdf3f02006-08-29 02:01:44 -07003603 }
Stephen Hemminger9772efb2005-11-10 17:09:53 -08003604
Ilpo Järvinenc7caf8d2007-11-10 21:22:18 -08003605 prior_fackets = tp->fackets_out;
Ilpo Järvinen52d34082007-12-05 02:21:35 -08003606 prior_in_flight = tcp_packets_in_flight(tp);
Ilpo Järvinenc7caf8d2007-11-10 21:22:18 -08003607
Ilpo Järvinen056834d2007-12-31 14:57:14 -08003608 if (!(flag & FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003609 /* Window is constant, pure forward advance.
3610 * No more checks are required.
3611 * Note, we use the fact that SND.UNA>=SND.WL2.
3612 */
Hantzis Fotisee7537b2009-03-02 22:42:02 -08003613 tcp_update_wl(tp, ack_seq);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003614 tp->snd_una = ack;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003615 flag |= FLAG_WIN_UPDATE;
3616
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003617 tcp_ca_event(sk, CA_EVENT_FAST_ACK);
Stephen Hemminger317a76f2005-06-23 12:19:55 -07003618
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07003619 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPACKS);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003620 } else {
3621 if (ack_seq != TCP_SKB_CB(skb)->end_seq)
3622 flag |= FLAG_DATA;
3623 else
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07003624 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPUREACKS);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003625
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07003626 flag |= tcp_ack_update_window(sk, skb, ack, ack_seq);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003627
3628 if (TCP_SKB_CB(skb)->sacked)
3629 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una);
3630
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -07003631 if (TCP_ECN_rcv_ecn_echo(tp, tcp_hdr(skb)))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003632 flag |= FLAG_ECE;
3633
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003634 tcp_ca_event(sk, CA_EVENT_SLOW_ACK);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003635 }
3636
3637 /* We passed data and got it acked, remove any soft error
3638 * log. Something worked...
3639 */
3640 sk->sk_err_soft = 0;
David S. Miller4b53fb62008-07-23 16:38:45 -07003641 icsk->icsk_probes_out = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003642 tp->rcv_tstamp = tcp_time_stamp;
3643 prior_packets = tp->packets_out;
3644 if (!prior_packets)
3645 goto no_queue;
3646
Linus Torvalds1da177e2005-04-16 15:20:36 -07003647 /* See if we can take anything off of the retransmit queue. */
Ilpo Järvinen33f5f572008-10-07 14:43:06 -07003648 flag |= tcp_clean_rtx_queue(sk, prior_fackets, prior_snd_una);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003649
Ilpo Järvinene1cd8f72007-11-14 15:55:09 -08003650 if (tp->frto_counter)
3651 frto_cwnd = tcp_process_frto(sk, flag);
Ilpo Järvinen3de96472007-10-01 15:28:48 -07003652 /* Guarantee sacktag reordering detection against wrap-arounds */
3653 if (before(tp->frto_highmark, tp->snd_una))
3654 tp->frto_highmark = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003655
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003656 if (tcp_ack_is_dubious(sk, flag)) {
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08003657 /* Advance CWND, if state allows this. */
Ilpo Järvinen7c9a4a52007-02-21 23:08:34 -08003658 if ((flag & FLAG_DATA_ACKED) && !frto_cwnd &&
3659 tcp_may_raise_cwnd(sk, flag))
Ilpo Järvinenc3a05c62007-12-02 00:47:59 +02003660 tcp_cong_avoid(sk, ack, prior_in_flight);
Ilpo Järvinen056834d2007-12-31 14:57:14 -08003661 tcp_fastretrans_alert(sk, prior_packets - tp->packets_out,
3662 flag);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003663 } else {
Ilpo Järvinen7c9a4a52007-02-21 23:08:34 -08003664 if ((flag & FLAG_DATA_ACKED) && !frto_cwnd)
Ilpo Järvinenc3a05c62007-12-02 00:47:59 +02003665 tcp_cong_avoid(sk, ack, prior_in_flight);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003666 }
3667
Ilpo Järvinen056834d2007-12-31 14:57:14 -08003668 if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003669 dst_confirm(sk->sk_dst_cache);
3670
3671 return 1;
3672
3673no_queue:
Linus Torvalds1da177e2005-04-16 15:20:36 -07003674 /* If this ack opens up a zero window, clear backoff. It was
3675 * being used to time the probes, and is probably far higher than
3676 * it needs to be for normal retransmission.
3677 */
David S. Millerfe067e82007-03-07 12:12:44 -08003678 if (tcp_send_head(sk))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003679 tcp_ack_probe(sk);
3680 return 1;
3681
John Dykstra96e0bf42009-03-22 21:49:57 -07003682invalid_ack:
3683 SOCK_DEBUG(sk, "Ack %u after %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
3684 return -1;
3685
Linus Torvalds1da177e2005-04-16 15:20:36 -07003686old_ack:
Ilpo Järvinen8aca6cb2008-06-04 11:34:22 -07003687 if (TCP_SKB_CB(skb)->sacked) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003688 tcp_sacktag_write_queue(sk, skb, prior_snd_una);
Ilpo Järvinen8aca6cb2008-06-04 11:34:22 -07003689 if (icsk->icsk_ca_state == TCP_CA_Open)
3690 tcp_try_keep_open(sk);
3691 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07003692
John Dykstra96e0bf42009-03-22 21:49:57 -07003693 SOCK_DEBUG(sk, "Ack %u before %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003694 return 0;
3695}
3696
Linus Torvalds1da177e2005-04-16 15:20:36 -07003697/* Look for tcp options. Normally only called on SYN and SYNACK packets.
3698 * But, this can also be called on packets in the established flow when
3699 * the fast version below fails.
3700 */
Ilpo Järvinen056834d2007-12-31 14:57:14 -08003701void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx,
3702 int estab)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003703{
3704 unsigned char *ptr;
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -07003705 struct tcphdr *th = tcp_hdr(skb);
Ilpo Järvinen056834d2007-12-31 14:57:14 -08003706 int length = (th->doff * 4) - sizeof(struct tcphdr);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003707
3708 ptr = (unsigned char *)(th + 1);
3709 opt_rx->saw_tstamp = 0;
3710
Stephen Hemminger2de979b2007-03-08 20:45:19 -08003711 while (length > 0) {
Ilpo Järvinen056834d2007-12-31 14:57:14 -08003712 int opcode = *ptr++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003713 int opsize;
3714
3715 switch (opcode) {
Ilpo Järvinenf038ac82008-01-03 20:36:55 -08003716 case TCPOPT_EOL:
3717 return;
3718 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
3719 length--;
3720 continue;
3721 default:
3722 opsize = *ptr++;
3723 if (opsize < 2) /* "silly options" */
Linus Torvalds1da177e2005-04-16 15:20:36 -07003724 return;
Ilpo Järvinenf038ac82008-01-03 20:36:55 -08003725 if (opsize > length)
3726 return; /* don't parse partial options */
3727 switch (opcode) {
3728 case TCPOPT_MSS:
3729 if (opsize == TCPOLEN_MSS && th->syn && !estab) {
Harvey Harrisond3e2ce32008-05-02 16:26:16 -07003730 u16 in_mss = get_unaligned_be16(ptr);
Ilpo Järvinenf038ac82008-01-03 20:36:55 -08003731 if (in_mss) {
3732 if (opt_rx->user_mss &&
3733 opt_rx->user_mss < in_mss)
3734 in_mss = opt_rx->user_mss;
3735 opt_rx->mss_clamp = in_mss;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003736 }
Stephen Hemminger3ff50b72007-04-20 17:09:22 -07003737 }
Ilpo Järvinenf038ac82008-01-03 20:36:55 -08003738 break;
3739 case TCPOPT_WINDOW:
3740 if (opsize == TCPOLEN_WINDOW && th->syn &&
3741 !estab && sysctl_tcp_window_scaling) {
3742 __u8 snd_wscale = *(__u8 *)ptr;
3743 opt_rx->wscale_ok = 1;
3744 if (snd_wscale > 14) {
3745 if (net_ratelimit())
3746 printk(KERN_INFO "tcp_parse_options: Illegal window "
3747 "scaling value %d >14 received.\n",
3748 snd_wscale);
3749 snd_wscale = 14;
3750 }
3751 opt_rx->snd_wscale = snd_wscale;
3752 }
3753 break;
3754 case TCPOPT_TIMESTAMP:
3755 if ((opsize == TCPOLEN_TIMESTAMP) &&
3756 ((estab && opt_rx->tstamp_ok) ||
3757 (!estab && sysctl_tcp_timestamps))) {
3758 opt_rx->saw_tstamp = 1;
Harvey Harrisond3e2ce32008-05-02 16:26:16 -07003759 opt_rx->rcv_tsval = get_unaligned_be32(ptr);
3760 opt_rx->rcv_tsecr = get_unaligned_be32(ptr + 4);
Ilpo Järvinenf038ac82008-01-03 20:36:55 -08003761 }
3762 break;
3763 case TCPOPT_SACK_PERM:
3764 if (opsize == TCPOLEN_SACK_PERM && th->syn &&
3765 !estab && sysctl_tcp_sack) {
3766 opt_rx->sack_ok = 1;
3767 tcp_sack_reset(opt_rx);
3768 }
3769 break;
Stephen Hemminger3ff50b72007-04-20 17:09:22 -07003770
Ilpo Järvinenf038ac82008-01-03 20:36:55 -08003771 case TCPOPT_SACK:
3772 if ((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) &&
3773 !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) &&
3774 opt_rx->sack_ok) {
3775 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th;
3776 }
3777 break;
3778#ifdef CONFIG_TCP_MD5SIG
3779 case TCPOPT_MD5SIG:
3780 /*
3781 * The MD5 Hash has already been
3782 * checked (see tcp_v{4,6}_do_rcv()).
3783 */
3784 break;
3785#endif
3786 }
3787
3788 ptr += opsize-2;
3789 length -= opsize;
Stephen Hemminger3ff50b72007-04-20 17:09:22 -07003790 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07003791 }
3792}
3793
Ilpo Järvinena4356b22008-08-23 05:12:29 -07003794static int tcp_parse_aligned_timestamp(struct tcp_sock *tp, struct tcphdr *th)
3795{
3796 __be32 *ptr = (__be32 *)(th + 1);
3797
3798 if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
3799 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
3800 tp->rx_opt.saw_tstamp = 1;
3801 ++ptr;
3802 tp->rx_opt.rcv_tsval = ntohl(*ptr);
3803 ++ptr;
3804 tp->rx_opt.rcv_tsecr = ntohl(*ptr);
3805 return 1;
3806 }
3807 return 0;
3808}
3809
Linus Torvalds1da177e2005-04-16 15:20:36 -07003810/* Fast parse options. This hopes to only see timestamps.
3811 * If it is wrong it falls back on tcp_parse_options().
3812 */
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08003813static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th,
3814 struct tcp_sock *tp)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003815{
Ilpo Järvinen056834d2007-12-31 14:57:14 -08003816 if (th->doff == sizeof(struct tcphdr) >> 2) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003817 tp->rx_opt.saw_tstamp = 0;
3818 return 0;
3819 } else if (tp->rx_opt.tstamp_ok &&
3820 th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) {
Ilpo Järvinena4356b22008-08-23 05:12:29 -07003821 if (tcp_parse_aligned_timestamp(tp, th))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003822 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003823 }
3824 tcp_parse_options(skb, &tp->rx_opt, 1);
3825 return 1;
3826}
3827
YOSHIFUJI Hideaki7d5d5522008-04-17 12:29:53 +09003828#ifdef CONFIG_TCP_MD5SIG
3829/*
3830 * Parse MD5 Signature option
3831 */
3832u8 *tcp_parse_md5sig_option(struct tcphdr *th)
3833{
3834 int length = (th->doff << 2) - sizeof (*th);
3835 u8 *ptr = (u8*)(th + 1);
3836
3837 /* If the TCP option is too short, we can short cut */
3838 if (length < TCPOLEN_MD5SIG)
3839 return NULL;
3840
3841 while (length > 0) {
3842 int opcode = *ptr++;
3843 int opsize;
3844
3845 switch(opcode) {
3846 case TCPOPT_EOL:
3847 return NULL;
3848 case TCPOPT_NOP:
3849 length--;
3850 continue;
3851 default:
3852 opsize = *ptr++;
3853 if (opsize < 2 || opsize > length)
3854 return NULL;
3855 if (opcode == TCPOPT_MD5SIG)
3856 return ptr;
3857 }
3858 ptr += opsize - 2;
3859 length -= opsize;
3860 }
3861 return NULL;
3862}
3863#endif
3864
Linus Torvalds1da177e2005-04-16 15:20:36 -07003865static inline void tcp_store_ts_recent(struct tcp_sock *tp)
3866{
3867 tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval;
James Morris9d729f72007-03-04 16:12:44 -08003868 tp->rx_opt.ts_recent_stamp = get_seconds();
Linus Torvalds1da177e2005-04-16 15:20:36 -07003869}
3870
3871static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)
3872{
3873 if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) {
3874 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3875 * extra check below makes sure this can only happen
3876 * for pure ACK frames. -DaveM
3877 *
3878 * Not only, also it occurs for expired timestamps.
3879 */
3880
Ilpo Järvinenc887e6d2009-03-14 14:23:03 +00003881 if (tcp_paws_check(&tp->rx_opt, 0))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003882 tcp_store_ts_recent(tp);
3883 }
3884}
3885
3886/* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3887 *
3888 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3889 * it can pass through stack. So, the following predicate verifies that
3890 * this segment is not used for anything but congestion avoidance or
3891 * fast retransmit. Moreover, we even are able to eliminate most of such
3892 * second order effects, if we apply some small "replay" window (~RTO)
3893 * to timestamp space.
3894 *
3895 * All these measures still do not guarantee that we reject wrapped ACKs
3896 * on networks with high bandwidth, when sequence space is recycled fastly,
3897 * but it guarantees that such events will be very rare and do not affect
3898 * connection seriously. This doesn't look nice, but alas, PAWS is really
3899 * buggy extension.
3900 *
3901 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3902 * states that events when retransmit arrives after original data are rare.
3903 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3904 * the biggest problem on large power networks even with minor reordering.
3905 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3906 * up to bandwidth of 18Gigabit/sec. 8) ]
3907 */
3908
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003909static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003910{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003911 struct tcp_sock *tp = tcp_sk(sk);
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -07003912 struct tcphdr *th = tcp_hdr(skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003913 u32 seq = TCP_SKB_CB(skb)->seq;
3914 u32 ack = TCP_SKB_CB(skb)->ack_seq;
3915
3916 return (/* 1. Pure ACK with correct sequence number. */
3917 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) &&
3918
3919 /* 2. ... and duplicate ACK. */
3920 ack == tp->snd_una &&
3921
3922 /* 3. ... and does not update window. */
3923 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) &&
3924
3925 /* 4. ... and sits in replay window. */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003926 (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003927}
3928
Ilpo Järvinen056834d2007-12-31 14:57:14 -08003929static inline int tcp_paws_discard(const struct sock *sk,
3930 const struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003931{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003932 const struct tcp_sock *tp = tcp_sk(sk);
Ilpo Järvinenc887e6d2009-03-14 14:23:03 +00003933
3934 return !tcp_paws_check(&tp->rx_opt, TCP_PAWS_WINDOW) &&
3935 !tcp_disordered_ack(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003936}
3937
3938/* Check segment sequence number for validity.
3939 *
3940 * Segment controls are considered valid, if the segment
3941 * fits to the window after truncation to the window. Acceptability
3942 * of data (and SYN, FIN, of course) is checked separately.
3943 * See tcp_data_queue(), for example.
3944 *
3945 * Also, controls (RST is main one) are accepted using RCV.WUP instead
3946 * of RCV.NXT. Peer still did not advance his SND.UNA when we
3947 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
3948 * (borrowed from freebsd)
3949 */
3950
3951static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq)
3952{
3953 return !before(end_seq, tp->rcv_wup) &&
3954 !after(seq, tp->rcv_nxt + tcp_receive_window(tp));
3955}
3956
3957/* When we get a reset we do this. */
3958static void tcp_reset(struct sock *sk)
3959{
3960 /* We want the right error as BSD sees it (and indeed as we do). */
3961 switch (sk->sk_state) {
Ilpo Järvinen056834d2007-12-31 14:57:14 -08003962 case TCP_SYN_SENT:
3963 sk->sk_err = ECONNREFUSED;
3964 break;
3965 case TCP_CLOSE_WAIT:
3966 sk->sk_err = EPIPE;
3967 break;
3968 case TCP_CLOSE:
3969 return;
3970 default:
3971 sk->sk_err = ECONNRESET;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003972 }
3973
3974 if (!sock_flag(sk, SOCK_DEAD))
3975 sk->sk_error_report(sk);
3976
3977 tcp_done(sk);
3978}
3979
3980/*
3981 * Process the FIN bit. This now behaves as it is supposed to work
3982 * and the FIN takes effect when it is validly part of sequence
3983 * space. Not before when we get holes.
3984 *
3985 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
3986 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
3987 * TIME-WAIT)
3988 *
3989 * If we are in FINWAIT-1, a received FIN indicates simultaneous
3990 * close and we go into CLOSING (and later onto TIME-WAIT)
3991 *
3992 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
3993 */
3994static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th)
3995{
3996 struct tcp_sock *tp = tcp_sk(sk);
3997
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003998 inet_csk_schedule_ack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003999
4000 sk->sk_shutdown |= RCV_SHUTDOWN;
4001 sock_set_flag(sk, SOCK_DONE);
4002
4003 switch (sk->sk_state) {
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004004 case TCP_SYN_RECV:
4005 case TCP_ESTABLISHED:
4006 /* Move to CLOSE_WAIT */
4007 tcp_set_state(sk, TCP_CLOSE_WAIT);
4008 inet_csk(sk)->icsk_ack.pingpong = 1;
4009 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07004010
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004011 case TCP_CLOSE_WAIT:
4012 case TCP_CLOSING:
4013 /* Received a retransmission of the FIN, do
4014 * nothing.
4015 */
4016 break;
4017 case TCP_LAST_ACK:
4018 /* RFC793: Remain in the LAST-ACK state. */
4019 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07004020
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004021 case TCP_FIN_WAIT1:
4022 /* This case occurs when a simultaneous close
4023 * happens, we must ack the received FIN and
4024 * enter the CLOSING state.
4025 */
4026 tcp_send_ack(sk);
4027 tcp_set_state(sk, TCP_CLOSING);
4028 break;
4029 case TCP_FIN_WAIT2:
4030 /* Received a FIN -- send ACK and enter TIME_WAIT. */
4031 tcp_send_ack(sk);
4032 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
4033 break;
4034 default:
4035 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
4036 * cases we should never reach this piece of code.
4037 */
4038 printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n",
Harvey Harrison0dc47872008-03-05 20:47:47 -08004039 __func__, sk->sk_state);
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004040 break;
Stephen Hemminger3ff50b72007-04-20 17:09:22 -07004041 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07004042
4043 /* It _is_ possible, that we have something out-of-order _after_ FIN.
4044 * Probably, we should reset in this case. For now drop them.
4045 */
4046 __skb_queue_purge(&tp->out_of_order_queue);
Ilpo Järvinene60402d2007-08-09 15:14:46 +03004047 if (tcp_is_sack(tp))
Linus Torvalds1da177e2005-04-16 15:20:36 -07004048 tcp_sack_reset(&tp->rx_opt);
Hideo Aoki3ab224b2007-12-31 00:11:19 -08004049 sk_mem_reclaim(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004050
4051 if (!sock_flag(sk, SOCK_DEAD)) {
4052 sk->sk_state_change(sk);
4053
4054 /* Do not send POLL_HUP for half duplex close. */
4055 if (sk->sk_shutdown == SHUTDOWN_MASK ||
4056 sk->sk_state == TCP_CLOSE)
Pavel Emelyanov8d8ad9d2007-11-26 20:10:50 +08004057 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004058 else
Pavel Emelyanov8d8ad9d2007-11-26 20:10:50 +08004059 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004060 }
4061}
4062
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004063static inline int tcp_sack_extend(struct tcp_sack_block *sp, u32 seq,
4064 u32 end_seq)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004065{
4066 if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) {
4067 if (before(seq, sp->start_seq))
4068 sp->start_seq = seq;
4069 if (after(end_seq, sp->end_seq))
4070 sp->end_seq = end_seq;
4071 return 1;
4072 }
4073 return 0;
4074}
4075
Pavel Emelyanov1ed83462008-07-16 20:29:51 -07004076static void tcp_dsack_set(struct sock *sk, u32 seq, u32 end_seq)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004077{
Pavel Emelyanov1ed83462008-07-16 20:29:51 -07004078 struct tcp_sock *tp = tcp_sk(sk);
4079
Ilpo Järvinene60402d2007-08-09 15:14:46 +03004080 if (tcp_is_sack(tp) && sysctl_tcp_dsack) {
Pavel Emelyanov40b215e2008-07-03 01:05:41 -07004081 int mib_idx;
4082
Linus Torvalds1da177e2005-04-16 15:20:36 -07004083 if (before(seq, tp->rcv_nxt))
Pavel Emelyanov40b215e2008-07-03 01:05:41 -07004084 mib_idx = LINUX_MIB_TCPDSACKOLDSENT;
Linus Torvalds1da177e2005-04-16 15:20:36 -07004085 else
Pavel Emelyanov40b215e2008-07-03 01:05:41 -07004086 mib_idx = LINUX_MIB_TCPDSACKOFOSENT;
4087
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07004088 NET_INC_STATS_BH(sock_net(sk), mib_idx);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004089
4090 tp->rx_opt.dsack = 1;
4091 tp->duplicate_sack[0].start_seq = seq;
4092 tp->duplicate_sack[0].end_seq = end_seq;
Linus Torvalds1da177e2005-04-16 15:20:36 -07004093 }
4094}
4095
Pavel Emelyanov1ed83462008-07-16 20:29:51 -07004096static void tcp_dsack_extend(struct sock *sk, u32 seq, u32 end_seq)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004097{
Pavel Emelyanov1ed83462008-07-16 20:29:51 -07004098 struct tcp_sock *tp = tcp_sk(sk);
4099
Linus Torvalds1da177e2005-04-16 15:20:36 -07004100 if (!tp->rx_opt.dsack)
Pavel Emelyanov1ed83462008-07-16 20:29:51 -07004101 tcp_dsack_set(sk, seq, end_seq);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004102 else
4103 tcp_sack_extend(tp->duplicate_sack, seq, end_seq);
4104}
4105
4106static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb)
4107{
4108 struct tcp_sock *tp = tcp_sk(sk);
4109
4110 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
4111 before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07004112 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOST);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004113 tcp_enter_quickack_mode(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004114
Ilpo Järvinene60402d2007-08-09 15:14:46 +03004115 if (tcp_is_sack(tp) && sysctl_tcp_dsack) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004116 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
4117
4118 if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))
4119 end_seq = tp->rcv_nxt;
Pavel Emelyanov1ed83462008-07-16 20:29:51 -07004120 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, end_seq);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004121 }
4122 }
4123
4124 tcp_send_ack(sk);
4125}
4126
4127/* These routines update the SACK block as out-of-order packets arrive or
4128 * in-order packets close up the sequence space.
4129 */
4130static void tcp_sack_maybe_coalesce(struct tcp_sock *tp)
4131{
4132 int this_sack;
4133 struct tcp_sack_block *sp = &tp->selective_acks[0];
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004134 struct tcp_sack_block *swalk = sp + 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07004135
4136 /* See if the recent change to the first SACK eats into
4137 * or hits the sequence space of other SACK blocks, if so coalesce.
4138 */
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004139 for (this_sack = 1; this_sack < tp->rx_opt.num_sacks;) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004140 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) {
4141 int i;
4142
4143 /* Zap SWALK, by moving every further SACK up by one slot.
4144 * Decrease num_sacks.
4145 */
4146 tp->rx_opt.num_sacks--;
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004147 for (i = this_sack; i < tp->rx_opt.num_sacks; i++)
4148 sp[i] = sp[i + 1];
Linus Torvalds1da177e2005-04-16 15:20:36 -07004149 continue;
4150 }
4151 this_sack++, swalk++;
4152 }
4153}
4154
Linus Torvalds1da177e2005-04-16 15:20:36 -07004155static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq)
4156{
4157 struct tcp_sock *tp = tcp_sk(sk);
4158 struct tcp_sack_block *sp = &tp->selective_acks[0];
4159 int cur_sacks = tp->rx_opt.num_sacks;
4160 int this_sack;
4161
4162 if (!cur_sacks)
4163 goto new_sack;
4164
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004165 for (this_sack = 0; this_sack < cur_sacks; this_sack++, sp++) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004166 if (tcp_sack_extend(sp, seq, end_seq)) {
4167 /* Rotate this_sack to the first one. */
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004168 for (; this_sack > 0; this_sack--, sp--)
Ilpo Järvinena0bffff2009-03-21 13:36:17 -07004169 swap(*sp, *(sp - 1));
Linus Torvalds1da177e2005-04-16 15:20:36 -07004170 if (cur_sacks > 1)
4171 tcp_sack_maybe_coalesce(tp);
4172 return;
4173 }
4174 }
4175
4176 /* Could not find an adjacent existing SACK, build a new one,
4177 * put it at the front, and shift everyone else down. We
4178 * always know there is at least one SACK present already here.
4179 *
4180 * If the sack array is full, forget about the last one.
4181 */
Adam Langley4389dde2008-07-19 00:07:02 -07004182 if (this_sack >= TCP_NUM_SACKS) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004183 this_sack--;
4184 tp->rx_opt.num_sacks--;
4185 sp--;
4186 }
Stephen Hemminger2de979b2007-03-08 20:45:19 -08004187 for (; this_sack > 0; this_sack--, sp--)
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004188 *sp = *(sp - 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004189
4190new_sack:
4191 /* Build the new head SACK, and we're done. */
4192 sp->start_seq = seq;
4193 sp->end_seq = end_seq;
4194 tp->rx_opt.num_sacks++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07004195}
4196
4197/* RCV.NXT advances, some SACKs should be eaten. */
4198
4199static void tcp_sack_remove(struct tcp_sock *tp)
4200{
4201 struct tcp_sack_block *sp = &tp->selective_acks[0];
4202 int num_sacks = tp->rx_opt.num_sacks;
4203 int this_sack;
4204
4205 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
David S. Millerb03efcf2005-07-08 14:57:23 -07004206 if (skb_queue_empty(&tp->out_of_order_queue)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004207 tp->rx_opt.num_sacks = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07004208 return;
4209 }
4210
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004211 for (this_sack = 0; this_sack < num_sacks;) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004212 /* Check if the start of the sack is covered by RCV.NXT. */
4213 if (!before(tp->rcv_nxt, sp->start_seq)) {
4214 int i;
4215
4216 /* RCV.NXT must cover all the block! */
Ilpo Järvinen547b7922008-07-25 21:43:18 -07004217 WARN_ON(before(tp->rcv_nxt, sp->end_seq));
Linus Torvalds1da177e2005-04-16 15:20:36 -07004218
4219 /* Zap this SACK, by moving forward any other SACKS. */
4220 for (i=this_sack+1; i < num_sacks; i++)
4221 tp->selective_acks[i-1] = tp->selective_acks[i];
4222 num_sacks--;
4223 continue;
4224 }
4225 this_sack++;
4226 sp++;
4227 }
Ilpo Järvinen5861f8e2009-03-14 14:23:01 +00004228 tp->rx_opt.num_sacks = num_sacks;
Linus Torvalds1da177e2005-04-16 15:20:36 -07004229}
4230
4231/* This one checks to see if we can put data from the
4232 * out_of_order queue into the receive_queue.
4233 */
4234static void tcp_ofo_queue(struct sock *sk)
4235{
4236 struct tcp_sock *tp = tcp_sk(sk);
4237 __u32 dsack_high = tp->rcv_nxt;
4238 struct sk_buff *skb;
4239
4240 while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) {
4241 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
4242 break;
4243
4244 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) {
4245 __u32 dsack = dsack_high;
4246 if (before(TCP_SKB_CB(skb)->end_seq, dsack_high))
4247 dsack_high = TCP_SKB_CB(skb)->end_seq;
Pavel Emelyanov1ed83462008-07-16 20:29:51 -07004248 tcp_dsack_extend(sk, TCP_SKB_CB(skb)->seq, dsack);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004249 }
4250
4251 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
4252 SOCK_DEBUG(sk, "ofo packet was already received \n");
David S. Miller8728b832005-08-09 19:25:21 -07004253 __skb_unlink(skb, &tp->out_of_order_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004254 __kfree_skb(skb);
4255 continue;
4256 }
4257 SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n",
4258 tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
4259 TCP_SKB_CB(skb)->end_seq);
4260
David S. Miller8728b832005-08-09 19:25:21 -07004261 __skb_unlink(skb, &tp->out_of_order_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004262 __skb_queue_tail(&sk->sk_receive_queue, skb);
4263 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -07004264 if (tcp_hdr(skb)->fin)
4265 tcp_fin(skb, sk, tcp_hdr(skb));
Linus Torvalds1da177e2005-04-16 15:20:36 -07004266 }
4267}
4268
Vitaliy Gusev56f367b2008-04-15 20:26:34 -07004269static int tcp_prune_ofo_queue(struct sock *sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004270static int tcp_prune_queue(struct sock *sk);
4271
Vitaliy Gusevb000cd32008-04-15 00:33:38 -07004272static inline int tcp_try_rmem_schedule(struct sock *sk, unsigned int size)
4273{
4274 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
4275 !sk_rmem_schedule(sk, size)) {
4276
4277 if (tcp_prune_queue(sk) < 0)
4278 return -1;
4279
4280 if (!sk_rmem_schedule(sk, size)) {
Vitaliy Gusev56f367b2008-04-15 20:26:34 -07004281 if (!tcp_prune_ofo_queue(sk))
4282 return -1;
4283
Vitaliy Gusevb000cd32008-04-15 00:33:38 -07004284 if (!sk_rmem_schedule(sk, size))
4285 return -1;
4286 }
4287 }
4288 return 0;
4289}
4290
Linus Torvalds1da177e2005-04-16 15:20:36 -07004291static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
4292{
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -07004293 struct tcphdr *th = tcp_hdr(skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004294 struct tcp_sock *tp = tcp_sk(sk);
4295 int eaten = -1;
4296
4297 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq)
4298 goto drop;
4299
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004300 __skb_pull(skb, th->doff * 4);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004301
4302 TCP_ECN_accept_cwr(tp, skb);
4303
Ilpo Järvinen5861f8e2009-03-14 14:23:01 +00004304 tp->rx_opt.dsack = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07004305
4306 /* Queue data for delivery to the user.
4307 * Packets in sequence go to the receive queue.
4308 * Out of sequence packets to the out_of_order_queue.
4309 */
4310 if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
4311 if (tcp_receive_window(tp) == 0)
4312 goto out_of_window;
4313
4314 /* Ok. In sequence. In window. */
4315 if (tp->ucopy.task == current &&
4316 tp->copied_seq == tp->rcv_nxt && tp->ucopy.len &&
4317 sock_owned_by_user(sk) && !tp->urg_data) {
4318 int chunk = min_t(unsigned int, skb->len,
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004319 tp->ucopy.len);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004320
4321 __set_current_state(TASK_RUNNING);
4322
4323 local_bh_enable();
4324 if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) {
4325 tp->ucopy.len -= chunk;
4326 tp->copied_seq += chunk;
4327 eaten = (chunk == skb->len && !th->fin);
4328 tcp_rcv_space_adjust(sk);
4329 }
4330 local_bh_disable();
4331 }
4332
4333 if (eaten <= 0) {
4334queue_and_out:
4335 if (eaten < 0 &&
Vitaliy Gusevb000cd32008-04-15 00:33:38 -07004336 tcp_try_rmem_schedule(sk, skb->truesize))
4337 goto drop;
4338
Hideo Aoki3ab224b2007-12-31 00:11:19 -08004339 skb_set_owner_r(skb, sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004340 __skb_queue_tail(&sk->sk_receive_queue, skb);
4341 }
4342 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
Stephen Hemminger2de979b2007-03-08 20:45:19 -08004343 if (skb->len)
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07004344 tcp_event_data_recv(sk, skb);
Stephen Hemminger2de979b2007-03-08 20:45:19 -08004345 if (th->fin)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004346 tcp_fin(skb, sk, th);
4347
David S. Millerb03efcf2005-07-08 14:57:23 -07004348 if (!skb_queue_empty(&tp->out_of_order_queue)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004349 tcp_ofo_queue(sk);
4350
4351 /* RFC2581. 4.2. SHOULD send immediate ACK, when
4352 * gap in queue is filled.
4353 */
David S. Millerb03efcf2005-07-08 14:57:23 -07004354 if (skb_queue_empty(&tp->out_of_order_queue))
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004355 inet_csk(sk)->icsk_ack.pingpong = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07004356 }
4357
4358 if (tp->rx_opt.num_sacks)
4359 tcp_sack_remove(tp);
4360
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07004361 tcp_fast_path_check(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004362
4363 if (eaten > 0)
4364 __kfree_skb(skb);
4365 else if (!sock_flag(sk, SOCK_DEAD))
4366 sk->sk_data_ready(sk, 0);
4367 return;
4368 }
4369
4370 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
4371 /* A retransmit, 2nd most common case. Force an immediate ack. */
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07004372 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOST);
Pavel Emelyanov1ed83462008-07-16 20:29:51 -07004373 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004374
4375out_of_window:
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004376 tcp_enter_quickack_mode(sk);
4377 inet_csk_schedule_ack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004378drop:
4379 __kfree_skb(skb);
4380 return;
4381 }
4382
4383 /* Out of window. F.e. zero window probe. */
4384 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp)))
4385 goto out_of_window;
4386
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004387 tcp_enter_quickack_mode(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004388
4389 if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4390 /* Partial packet, seq < rcv_next < end_seq */
4391 SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n",
4392 tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
4393 TCP_SKB_CB(skb)->end_seq);
4394
Pavel Emelyanov1ed83462008-07-16 20:29:51 -07004395 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, tp->rcv_nxt);
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004396
Linus Torvalds1da177e2005-04-16 15:20:36 -07004397 /* If window is closed, drop tail of packet. But after
4398 * remembering D-SACK for its head made in previous line.
4399 */
4400 if (!tcp_receive_window(tp))
4401 goto out_of_window;
4402 goto queue_and_out;
4403 }
4404
4405 TCP_ECN_check_ce(tp, skb);
4406
Vitaliy Gusevb000cd32008-04-15 00:33:38 -07004407 if (tcp_try_rmem_schedule(sk, skb->truesize))
4408 goto drop;
Linus Torvalds1da177e2005-04-16 15:20:36 -07004409
4410 /* Disable header prediction. */
4411 tp->pred_flags = 0;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004412 inet_csk_schedule_ack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004413
4414 SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n",
4415 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
4416
Hideo Aoki3ab224b2007-12-31 00:11:19 -08004417 skb_set_owner_r(skb, sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004418
4419 if (!skb_peek(&tp->out_of_order_queue)) {
4420 /* Initial out of order segment, build 1 SACK. */
Ilpo Järvinene60402d2007-08-09 15:14:46 +03004421 if (tcp_is_sack(tp)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004422 tp->rx_opt.num_sacks = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07004423 tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
4424 tp->selective_acks[0].end_seq =
4425 TCP_SKB_CB(skb)->end_seq;
4426 }
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004427 __skb_queue_head(&tp->out_of_order_queue, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004428 } else {
4429 struct sk_buff *skb1 = tp->out_of_order_queue.prev;
4430 u32 seq = TCP_SKB_CB(skb)->seq;
4431 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
4432
4433 if (seq == TCP_SKB_CB(skb1)->end_seq) {
Gerrit Renker7de6c032008-04-14 00:05:09 -07004434 __skb_queue_after(&tp->out_of_order_queue, skb1, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004435
4436 if (!tp->rx_opt.num_sacks ||
4437 tp->selective_acks[0].end_seq != seq)
4438 goto add_sack;
4439
4440 /* Common case: data arrive in order after hole. */
4441 tp->selective_acks[0].end_seq = end_seq;
4442 return;
4443 }
4444
4445 /* Find place to insert this segment. */
4446 do {
4447 if (!after(TCP_SKB_CB(skb1)->seq, seq))
4448 break;
4449 } while ((skb1 = skb1->prev) !=
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004450 (struct sk_buff *)&tp->out_of_order_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004451
4452 /* Do skb overlap to previous one? */
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004453 if (skb1 != (struct sk_buff *)&tp->out_of_order_queue &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07004454 before(seq, TCP_SKB_CB(skb1)->end_seq)) {
4455 if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
4456 /* All the bits are present. Drop. */
4457 __kfree_skb(skb);
Pavel Emelyanov1ed83462008-07-16 20:29:51 -07004458 tcp_dsack_set(sk, seq, end_seq);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004459 goto add_sack;
4460 }
4461 if (after(seq, TCP_SKB_CB(skb1)->seq)) {
4462 /* Partial overlap. */
Pavel Emelyanov1ed83462008-07-16 20:29:51 -07004463 tcp_dsack_set(sk, seq,
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004464 TCP_SKB_CB(skb1)->end_seq);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004465 } else {
4466 skb1 = skb1->prev;
4467 }
4468 }
David S. Miller43f59c82008-09-21 21:28:51 -07004469 __skb_queue_after(&tp->out_of_order_queue, skb1, skb);
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004470
Linus Torvalds1da177e2005-04-16 15:20:36 -07004471 /* And clean segments covered by new one as whole. */
4472 while ((skb1 = skb->next) !=
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004473 (struct sk_buff *)&tp->out_of_order_queue &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07004474 after(end_seq, TCP_SKB_CB(skb1)->seq)) {
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004475 if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
Pavel Emelyanov1ed83462008-07-16 20:29:51 -07004476 tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004477 end_seq);
4478 break;
4479 }
4480 __skb_unlink(skb1, &tp->out_of_order_queue);
Pavel Emelyanov1ed83462008-07-16 20:29:51 -07004481 tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004482 TCP_SKB_CB(skb1)->end_seq);
4483 __kfree_skb(skb1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004484 }
4485
4486add_sack:
Ilpo Järvinene60402d2007-08-09 15:14:46 +03004487 if (tcp_is_sack(tp))
Linus Torvalds1da177e2005-04-16 15:20:36 -07004488 tcp_sack_new_ofo_skb(sk, seq, end_seq);
4489 }
4490}
4491
Ilpo Järvinen2cf46632008-08-23 05:11:41 -07004492static struct sk_buff *tcp_collapse_one(struct sock *sk, struct sk_buff *skb,
4493 struct sk_buff_head *list)
4494{
4495 struct sk_buff *next = skb->next;
4496
4497 __skb_unlink(skb, list);
4498 __kfree_skb(skb);
4499 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOLLAPSED);
4500
4501 return next;
4502}
4503
Linus Torvalds1da177e2005-04-16 15:20:36 -07004504/* Collapse contiguous sequence of skbs head..tail with
4505 * sequence numbers start..end.
4506 * Segments with FIN/SYN are not collapsed (only because this
4507 * simplifies code)
4508 */
4509static void
David S. Miller8728b832005-08-09 19:25:21 -07004510tcp_collapse(struct sock *sk, struct sk_buff_head *list,
4511 struct sk_buff *head, struct sk_buff *tail,
4512 u32 start, u32 end)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004513{
4514 struct sk_buff *skb;
4515
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08004516 /* First, check that queue is collapsible and find
Linus Torvalds1da177e2005-04-16 15:20:36 -07004517 * the point where collapsing can be useful. */
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004518 for (skb = head; skb != tail;) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004519 /* No new bits? It is possible on ofo queue. */
4520 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
Ilpo Järvinen2cf46632008-08-23 05:11:41 -07004521 skb = tcp_collapse_one(sk, skb, list);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004522 continue;
4523 }
4524
4525 /* The first skb to collapse is:
4526 * - not SYN/FIN and
4527 * - bloated or contains data before "start" or
4528 * overlaps to the next one.
4529 */
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -07004530 if (!tcp_hdr(skb)->syn && !tcp_hdr(skb)->fin &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07004531 (tcp_win_from_space(skb->truesize) > skb->len ||
4532 before(TCP_SKB_CB(skb)->seq, start) ||
4533 (skb->next != tail &&
4534 TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb->next)->seq)))
4535 break;
4536
4537 /* Decided to skip this, advance start seq. */
4538 start = TCP_SKB_CB(skb)->end_seq;
4539 skb = skb->next;
4540 }
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -07004541 if (skb == tail || tcp_hdr(skb)->syn || tcp_hdr(skb)->fin)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004542 return;
4543
4544 while (before(start, end)) {
4545 struct sk_buff *nskb;
Chuck Leverc2636b42007-10-23 21:07:32 -07004546 unsigned int header = skb_headroom(skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004547 int copy = SKB_MAX_ORDER(header, 0);
4548
4549 /* Too big header? This can happen with IPv6. */
4550 if (copy < 0)
4551 return;
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004552 if (end - start < copy)
4553 copy = end - start;
4554 nskb = alloc_skb(copy + header, GFP_ATOMIC);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004555 if (!nskb)
4556 return;
Arnaldo Carvalho de Meloc51957d2007-03-10 12:47:22 -03004557
Arnaldo Carvalho de Melo98e399f2007-03-19 15:33:04 -07004558 skb_set_mac_header(nskb, skb_mac_header(skb) - skb->head);
Arnaldo Carvalho de Melo9c702202007-04-25 18:04:18 -07004559 skb_set_network_header(nskb, (skb_network_header(skb) -
4560 skb->head));
4561 skb_set_transport_header(nskb, (skb_transport_header(skb) -
4562 skb->head));
Linus Torvalds1da177e2005-04-16 15:20:36 -07004563 skb_reserve(nskb, header);
4564 memcpy(nskb->head, skb->head, header);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004565 memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
4566 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start;
David S. Miller43f59c82008-09-21 21:28:51 -07004567 __skb_queue_before(list, skb, nskb);
Hideo Aoki3ab224b2007-12-31 00:11:19 -08004568 skb_set_owner_r(nskb, sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004569
4570 /* Copy data, releasing collapsed skbs. */
4571 while (copy > 0) {
4572 int offset = start - TCP_SKB_CB(skb)->seq;
4573 int size = TCP_SKB_CB(skb)->end_seq - start;
4574
Kris Katterjohn09a62662006-01-08 22:24:28 -08004575 BUG_ON(offset < 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004576 if (size > 0) {
4577 size = min(copy, size);
4578 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size))
4579 BUG();
4580 TCP_SKB_CB(nskb)->end_seq += size;
4581 copy -= size;
4582 start += size;
4583 }
4584 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
Ilpo Järvinen2cf46632008-08-23 05:11:41 -07004585 skb = tcp_collapse_one(sk, skb, list);
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -07004586 if (skb == tail ||
4587 tcp_hdr(skb)->syn ||
4588 tcp_hdr(skb)->fin)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004589 return;
4590 }
4591 }
4592 }
4593}
4594
4595/* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
4596 * and tcp_collapse() them until all the queue is collapsed.
4597 */
4598static void tcp_collapse_ofo_queue(struct sock *sk)
4599{
4600 struct tcp_sock *tp = tcp_sk(sk);
4601 struct sk_buff *skb = skb_peek(&tp->out_of_order_queue);
4602 struct sk_buff *head;
4603 u32 start, end;
4604
4605 if (skb == NULL)
4606 return;
4607
4608 start = TCP_SKB_CB(skb)->seq;
4609 end = TCP_SKB_CB(skb)->end_seq;
4610 head = skb;
4611
4612 for (;;) {
4613 skb = skb->next;
4614
4615 /* Segment is terminated when we see gap or when
4616 * we are at the end of all the queue. */
4617 if (skb == (struct sk_buff *)&tp->out_of_order_queue ||
4618 after(TCP_SKB_CB(skb)->seq, end) ||
4619 before(TCP_SKB_CB(skb)->end_seq, start)) {
David S. Miller8728b832005-08-09 19:25:21 -07004620 tcp_collapse(sk, &tp->out_of_order_queue,
4621 head, skb, start, end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004622 head = skb;
4623 if (skb == (struct sk_buff *)&tp->out_of_order_queue)
4624 break;
4625 /* Start new segment */
4626 start = TCP_SKB_CB(skb)->seq;
4627 end = TCP_SKB_CB(skb)->end_seq;
4628 } else {
4629 if (before(TCP_SKB_CB(skb)->seq, start))
4630 start = TCP_SKB_CB(skb)->seq;
4631 if (after(TCP_SKB_CB(skb)->end_seq, end))
4632 end = TCP_SKB_CB(skb)->end_seq;
4633 }
4634 }
4635}
4636
Vitaliy Gusevb000cd32008-04-15 00:33:38 -07004637/*
4638 * Purge the out-of-order queue.
Vitaliy Gusev56f367b2008-04-15 20:26:34 -07004639 * Return true if queue was pruned.
Vitaliy Gusevb000cd32008-04-15 00:33:38 -07004640 */
Vitaliy Gusev56f367b2008-04-15 20:26:34 -07004641static int tcp_prune_ofo_queue(struct sock *sk)
Vitaliy Gusevb000cd32008-04-15 00:33:38 -07004642{
4643 struct tcp_sock *tp = tcp_sk(sk);
Vitaliy Gusev56f367b2008-04-15 20:26:34 -07004644 int res = 0;
Vitaliy Gusevb000cd32008-04-15 00:33:38 -07004645
4646 if (!skb_queue_empty(&tp->out_of_order_queue)) {
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07004647 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_OFOPRUNED);
Vitaliy Gusevb000cd32008-04-15 00:33:38 -07004648 __skb_queue_purge(&tp->out_of_order_queue);
4649
4650 /* Reset SACK state. A conforming SACK implementation will
4651 * do the same at a timeout based retransmit. When a connection
4652 * is in a sad state like this, we care only about integrity
4653 * of the connection not performance.
4654 */
4655 if (tp->rx_opt.sack_ok)
4656 tcp_sack_reset(&tp->rx_opt);
4657 sk_mem_reclaim(sk);
Vitaliy Gusev56f367b2008-04-15 20:26:34 -07004658 res = 1;
Vitaliy Gusevb000cd32008-04-15 00:33:38 -07004659 }
Vitaliy Gusev56f367b2008-04-15 20:26:34 -07004660 return res;
Vitaliy Gusevb000cd32008-04-15 00:33:38 -07004661}
4662
Linus Torvalds1da177e2005-04-16 15:20:36 -07004663/* Reduce allocated memory if we can, trying to get
4664 * the socket within its memory limits again.
4665 *
4666 * Return less than zero if we should start dropping frames
4667 * until the socket owning process reads some of the data
4668 * to stabilize the situation.
4669 */
4670static int tcp_prune_queue(struct sock *sk)
4671{
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004672 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004673
4674 SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq);
4675
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07004676 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PRUNECALLED);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004677
4678 if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07004679 tcp_clamp_window(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004680 else if (tcp_memory_pressure)
4681 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss);
4682
4683 tcp_collapse_ofo_queue(sk);
David S. Miller8728b832005-08-09 19:25:21 -07004684 tcp_collapse(sk, &sk->sk_receive_queue,
4685 sk->sk_receive_queue.next,
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004686 (struct sk_buff *)&sk->sk_receive_queue,
Linus Torvalds1da177e2005-04-16 15:20:36 -07004687 tp->copied_seq, tp->rcv_nxt);
Hideo Aoki3ab224b2007-12-31 00:11:19 -08004688 sk_mem_reclaim(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004689
4690 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
4691 return 0;
4692
4693 /* Collapsing did not help, destructive actions follow.
4694 * This must not ever occur. */
4695
Vitaliy Gusevb000cd32008-04-15 00:33:38 -07004696 tcp_prune_ofo_queue(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004697
4698 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
4699 return 0;
4700
4701 /* If we are really being abused, tell the caller to silently
4702 * drop receive data on the floor. It will get retransmitted
4703 * and hopefully then we'll have sufficient space.
4704 */
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07004705 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_RCVPRUNED);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004706
4707 /* Massive buffer overcommit. */
4708 tp->pred_flags = 0;
4709 return -1;
4710}
4711
Linus Torvalds1da177e2005-04-16 15:20:36 -07004712/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
4713 * As additional protections, we do not touch cwnd in retransmission phases,
4714 * and if application hit its sndbuf limit recently.
4715 */
4716void tcp_cwnd_application_limited(struct sock *sk)
4717{
4718 struct tcp_sock *tp = tcp_sk(sk);
4719
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03004720 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07004721 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
4722 /* Limited by application or receiver window. */
Ilpo Järvinend254bcd2006-08-04 16:57:42 -07004723 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk));
4724 u32 win_used = max(tp->snd_cwnd_used, init_win);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004725 if (win_used < tp->snd_cwnd) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03004726 tp->snd_ssthresh = tcp_current_ssthresh(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004727 tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
4728 }
4729 tp->snd_cwnd_used = 0;
4730 }
4731 tp->snd_cwnd_stamp = tcp_time_stamp;
4732}
4733
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07004734static int tcp_should_expand_sndbuf(struct sock *sk)
David S. Miller0d9901d2005-07-05 15:21:10 -07004735{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07004736 struct tcp_sock *tp = tcp_sk(sk);
4737
David S. Miller0d9901d2005-07-05 15:21:10 -07004738 /* If the user specified a specific send buffer setting, do
4739 * not modify it.
4740 */
4741 if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
4742 return 0;
4743
4744 /* If we are under global TCP memory pressure, do not expand. */
4745 if (tcp_memory_pressure)
4746 return 0;
4747
4748 /* If we are under soft global TCP memory pressure, do not expand. */
4749 if (atomic_read(&tcp_memory_allocated) >= sysctl_tcp_mem[0])
4750 return 0;
4751
4752 /* If we filled the congestion window, do not expand. */
4753 if (tp->packets_out >= tp->snd_cwnd)
4754 return 0;
4755
4756 return 1;
4757}
Linus Torvalds1da177e2005-04-16 15:20:36 -07004758
4759/* When incoming ACK allowed to free some skb from write_queue,
4760 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
4761 * on the exit from tcp input handler.
4762 *
4763 * PROBLEM: sndbuf expansion does not work well with largesend.
4764 */
4765static void tcp_new_space(struct sock *sk)
4766{
4767 struct tcp_sock *tp = tcp_sk(sk);
4768
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07004769 if (tcp_should_expand_sndbuf(sk)) {
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004770 int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) +
Ilpo Järvinen4a7e5602008-10-07 14:43:31 -07004771 MAX_TCP_HEADER + 16 + sizeof(struct sk_buff);
4772 int demanded = max_t(unsigned int, tp->snd_cwnd,
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004773 tp->reordering + 1);
4774 sndmem *= 2 * demanded;
Linus Torvalds1da177e2005-04-16 15:20:36 -07004775 if (sndmem > sk->sk_sndbuf)
4776 sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]);
4777 tp->snd_cwnd_stamp = tcp_time_stamp;
4778 }
4779
4780 sk->sk_write_space(sk);
4781}
4782
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08004783static void tcp_check_space(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004784{
4785 if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
4786 sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
4787 if (sk->sk_socket &&
4788 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
4789 tcp_new_space(sk);
4790 }
4791}
4792
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07004793static inline void tcp_data_snd_check(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004794{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07004795 tcp_push_pending_frames(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004796 tcp_check_space(sk);
4797}
4798
4799/*
4800 * Check if sending an ack is needed.
4801 */
4802static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
4803{
4804 struct tcp_sock *tp = tcp_sk(sk);
4805
4806 /* More than one full frame received... */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004807 if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss
Linus Torvalds1da177e2005-04-16 15:20:36 -07004808 /* ... and right edge of window advances far enough.
4809 * (tcp_recvmsg() will send ACK otherwise). Or...
4810 */
4811 && __tcp_select_window(sk) >= tp->rcv_wnd) ||
4812 /* We ACK each frame or... */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004813 tcp_in_quickack_mode(sk) ||
Linus Torvalds1da177e2005-04-16 15:20:36 -07004814 /* We have out of order data. */
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004815 (ofo_possible && skb_peek(&tp->out_of_order_queue))) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004816 /* Then ack it now */
4817 tcp_send_ack(sk);
4818 } else {
4819 /* Else, send delayed ack. */
4820 tcp_send_delayed_ack(sk);
4821 }
4822}
4823
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08004824static inline void tcp_ack_snd_check(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004825{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004826 if (!inet_csk_ack_scheduled(sk)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004827 /* We sent a data segment already. */
4828 return;
4829 }
4830 __tcp_ack_snd_check(sk, 1);
4831}
4832
4833/*
4834 * This routine is only called when we have urgent data
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08004835 * signaled. Its the 'slow' part of tcp_urg. It could be
Linus Torvalds1da177e2005-04-16 15:20:36 -07004836 * moved inline now as tcp_urg is only called from one
4837 * place. We handle URGent data wrong. We have to - as
4838 * BSD still doesn't use the correction from RFC961.
4839 * For 1003.1g we should support a new option TCP_STDURG to permit
4840 * either form (or just set the sysctl tcp_stdurg).
4841 */
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004842
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004843static void tcp_check_urg(struct sock *sk, struct tcphdr *th)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004844{
4845 struct tcp_sock *tp = tcp_sk(sk);
4846 u32 ptr = ntohs(th->urg_ptr);
4847
4848 if (ptr && !sysctl_tcp_stdurg)
4849 ptr--;
4850 ptr += ntohl(th->seq);
4851
4852 /* Ignore urgent data that we've already seen and read. */
4853 if (after(tp->copied_seq, ptr))
4854 return;
4855
4856 /* Do not replay urg ptr.
4857 *
4858 * NOTE: interesting situation not covered by specs.
4859 * Misbehaving sender may send urg ptr, pointing to segment,
4860 * which we already have in ofo queue. We are not able to fetch
4861 * such data and will stay in TCP_URG_NOTYET until will be eaten
4862 * by recvmsg(). Seems, we are not obliged to handle such wicked
4863 * situations. But it is worth to think about possibility of some
4864 * DoSes using some hypothetical application level deadlock.
4865 */
4866 if (before(ptr, tp->rcv_nxt))
4867 return;
4868
4869 /* Do we already have a newer (or duplicate) urgent pointer? */
4870 if (tp->urg_data && !after(ptr, tp->urg_seq))
4871 return;
4872
4873 /* Tell the world about our new urgent pointer. */
4874 sk_send_sigurg(sk);
4875
4876 /* We may be adding urgent data when the last byte read was
4877 * urgent. To do this requires some care. We cannot just ignore
4878 * tp->copied_seq since we would read the last urgent byte again
4879 * as data, nor can we alter copied_seq until this data arrives
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08004880 * or we break the semantics of SIOCATMARK (and thus sockatmark())
Linus Torvalds1da177e2005-04-16 15:20:36 -07004881 *
4882 * NOTE. Double Dutch. Rendering to plain English: author of comment
4883 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
4884 * and expect that both A and B disappear from stream. This is _wrong_.
4885 * Though this happens in BSD with high probability, this is occasional.
4886 * Any application relying on this is buggy. Note also, that fix "works"
4887 * only in this artificial test. Insert some normal data between A and B and we will
4888 * decline of BSD again. Verdict: it is better to remove to trap
4889 * buggy users.
4890 */
4891 if (tp->urg_seq == tp->copied_seq && tp->urg_data &&
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004892 !sock_flag(sk, SOCK_URGINLINE) && tp->copied_seq != tp->rcv_nxt) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004893 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
4894 tp->copied_seq++;
4895 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) {
David S. Miller8728b832005-08-09 19:25:21 -07004896 __skb_unlink(skb, &sk->sk_receive_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004897 __kfree_skb(skb);
4898 }
4899 }
4900
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004901 tp->urg_data = TCP_URG_NOTYET;
4902 tp->urg_seq = ptr;
Linus Torvalds1da177e2005-04-16 15:20:36 -07004903
4904 /* Disable header prediction. */
4905 tp->pred_flags = 0;
4906}
4907
4908/* This is the 'fast' part of urgent handling. */
4909static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th)
4910{
4911 struct tcp_sock *tp = tcp_sk(sk);
4912
4913 /* Check if we get a new urgent pointer - normally not. */
4914 if (th->urg)
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004915 tcp_check_urg(sk, th);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004916
4917 /* Do we wait for any urgent data? - normally not... */
4918 if (tp->urg_data == TCP_URG_NOTYET) {
4919 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) -
4920 th->syn;
4921
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004922 /* Is the urgent pointer pointing into this packet? */
Linus Torvalds1da177e2005-04-16 15:20:36 -07004923 if (ptr < skb->len) {
4924 u8 tmp;
4925 if (skb_copy_bits(skb, ptr, &tmp, 1))
4926 BUG();
4927 tp->urg_data = TCP_URG_VALID | tmp;
4928 if (!sock_flag(sk, SOCK_DEAD))
4929 sk->sk_data_ready(sk, 0);
4930 }
4931 }
4932}
4933
4934static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen)
4935{
4936 struct tcp_sock *tp = tcp_sk(sk);
4937 int chunk = skb->len - hlen;
4938 int err;
4939
4940 local_bh_enable();
Herbert Xu60476372007-04-09 11:59:39 -07004941 if (skb_csum_unnecessary(skb))
Linus Torvalds1da177e2005-04-16 15:20:36 -07004942 err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk);
4943 else
4944 err = skb_copy_and_csum_datagram_iovec(skb, hlen,
4945 tp->ucopy.iov);
4946
4947 if (!err) {
4948 tp->ucopy.len -= chunk;
4949 tp->copied_seq += chunk;
4950 tcp_rcv_space_adjust(sk);
4951 }
4952
4953 local_bh_disable();
4954 return err;
4955}
4956
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004957static __sum16 __tcp_checksum_complete_user(struct sock *sk,
4958 struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004959{
Al Virob51655b2006-11-14 21:40:42 -08004960 __sum16 result;
Linus Torvalds1da177e2005-04-16 15:20:36 -07004961
4962 if (sock_owned_by_user(sk)) {
4963 local_bh_enable();
4964 result = __tcp_checksum_complete(skb);
4965 local_bh_disable();
4966 } else {
4967 result = __tcp_checksum_complete(skb);
4968 }
4969 return result;
4970}
4971
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004972static inline int tcp_checksum_complete_user(struct sock *sk,
4973 struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004974{
Herbert Xu60476372007-04-09 11:59:39 -07004975 return !skb_csum_unnecessary(skb) &&
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004976 __tcp_checksum_complete_user(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004977}
4978
Chris Leech1a2449a2006-05-23 18:05:53 -07004979#ifdef CONFIG_NET_DMA
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004980static int tcp_dma_try_early_copy(struct sock *sk, struct sk_buff *skb,
4981 int hlen)
Chris Leech1a2449a2006-05-23 18:05:53 -07004982{
4983 struct tcp_sock *tp = tcp_sk(sk);
4984 int chunk = skb->len - hlen;
4985 int dma_cookie;
4986 int copied_early = 0;
4987
4988 if (tp->ucopy.wakeup)
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004989 return 0;
Chris Leech1a2449a2006-05-23 18:05:53 -07004990
4991 if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list)
Dan Williamsf67b4592009-01-06 11:38:15 -07004992 tp->ucopy.dma_chan = dma_find_channel(DMA_MEMCPY);
Chris Leech1a2449a2006-05-23 18:05:53 -07004993
Herbert Xu60476372007-04-09 11:59:39 -07004994 if (tp->ucopy.dma_chan && skb_csum_unnecessary(skb)) {
Chris Leech1a2449a2006-05-23 18:05:53 -07004995
4996 dma_cookie = dma_skb_copy_datagram_iovec(tp->ucopy.dma_chan,
Ilpo Järvinen056834d2007-12-31 14:57:14 -08004997 skb, hlen,
4998 tp->ucopy.iov, chunk,
4999 tp->ucopy.pinned_list);
Chris Leech1a2449a2006-05-23 18:05:53 -07005000
5001 if (dma_cookie < 0)
5002 goto out;
5003
5004 tp->ucopy.dma_cookie = dma_cookie;
5005 copied_early = 1;
5006
5007 tp->ucopy.len -= chunk;
5008 tp->copied_seq += chunk;
5009 tcp_rcv_space_adjust(sk);
5010
5011 if ((tp->ucopy.len == 0) ||
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -07005012 (tcp_flag_word(tcp_hdr(skb)) & TCP_FLAG_PSH) ||
Chris Leech1a2449a2006-05-23 18:05:53 -07005013 (atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1))) {
5014 tp->ucopy.wakeup = 1;
5015 sk->sk_data_ready(sk, 0);
5016 }
5017 } else if (chunk > 0) {
5018 tp->ucopy.wakeup = 1;
5019 sk->sk_data_ready(sk, 0);
5020 }
5021out:
5022 return copied_early;
5023}
5024#endif /* CONFIG_NET_DMA */
5025
Ilpo Järvinencbe2d122008-08-23 05:10:12 -07005026/* Does PAWS and seqno based validation of an incoming segment, flags will
5027 * play significant role here.
5028 */
5029static int tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
5030 struct tcphdr *th, int syn_inerr)
5031{
5032 struct tcp_sock *tp = tcp_sk(sk);
5033
5034 /* RFC1323: H1. Apply PAWS check first. */
5035 if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
5036 tcp_paws_discard(sk, skb)) {
5037 if (!th->rst) {
5038 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
5039 tcp_send_dupack(sk, skb);
5040 goto discard;
5041 }
5042 /* Reset is accepted even if it did not pass PAWS. */
5043 }
5044
5045 /* Step 1: check sequence number */
5046 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
5047 /* RFC793, page 37: "In all states except SYN-SENT, all reset
5048 * (RST) segments are validated by checking their SEQ-fields."
5049 * And page 69: "If an incoming segment is not acceptable,
5050 * an acknowledgment should be sent in reply (unless the RST
5051 * bit is set, if so drop the segment and return)".
5052 */
5053 if (!th->rst)
5054 tcp_send_dupack(sk, skb);
5055 goto discard;
5056 }
5057
5058 /* Step 2: check RST bit */
5059 if (th->rst) {
5060 tcp_reset(sk);
5061 goto discard;
5062 }
5063
5064 /* ts_recent update must be made after we are sure that the packet
5065 * is in window.
5066 */
5067 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
5068
5069 /* step 3: check security and precedence [ignored] */
5070
5071 /* step 4: Check for a SYN in window. */
5072 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
5073 if (syn_inerr)
5074 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
5075 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONSYN);
5076 tcp_reset(sk);
5077 return -1;
5078 }
5079
5080 return 1;
5081
5082discard:
5083 __kfree_skb(skb);
5084 return 0;
5085}
5086
Linus Torvalds1da177e2005-04-16 15:20:36 -07005087/*
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09005088 * TCP receive function for the ESTABLISHED state.
Linus Torvalds1da177e2005-04-16 15:20:36 -07005089 *
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09005090 * It is split into a fast path and a slow path. The fast path is
Linus Torvalds1da177e2005-04-16 15:20:36 -07005091 * disabled when:
5092 * - A zero window was announced from us - zero window probing
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09005093 * is only handled properly in the slow path.
Linus Torvalds1da177e2005-04-16 15:20:36 -07005094 * - Out of order segments arrived.
5095 * - Urgent data is expected.
5096 * - There is no buffer space left
5097 * - Unexpected TCP flags/window values/header lengths are received
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09005098 * (detected by checking the TCP header against pred_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07005099 * - Data is sent in both directions. Fast path only supports pure senders
5100 * or pure receivers (this means either the sequence number or the ack
5101 * value must stay constant)
5102 * - Unexpected TCP option.
5103 *
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09005104 * When these conditions are not satisfied it drops into a standard
Linus Torvalds1da177e2005-04-16 15:20:36 -07005105 * receive procedure patterned after RFC793 to handle all cases.
5106 * The first three cases are guaranteed by proper pred_flags setting,
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09005107 * the rest is checked inline. Fast processing is turned on in
Linus Torvalds1da177e2005-04-16 15:20:36 -07005108 * tcp_data_queue when everything is OK.
5109 */
5110int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
5111 struct tcphdr *th, unsigned len)
5112{
5113 struct tcp_sock *tp = tcp_sk(sk);
Ilpo Järvinencbe2d122008-08-23 05:10:12 -07005114 int res;
Linus Torvalds1da177e2005-04-16 15:20:36 -07005115
5116 /*
5117 * Header prediction.
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09005118 * The code loosely follows the one in the famous
Linus Torvalds1da177e2005-04-16 15:20:36 -07005119 * "30 instruction TCP receive" Van Jacobson mail.
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09005120 *
5121 * Van's trick is to deposit buffers into socket queue
Linus Torvalds1da177e2005-04-16 15:20:36 -07005122 * on a device interrupt, to call tcp_recv function
5123 * on the receive process context and checksum and copy
5124 * the buffer to user space. smart...
5125 *
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09005126 * Our current scheme is not silly either but we take the
Linus Torvalds1da177e2005-04-16 15:20:36 -07005127 * extra cost of the net_bh soft interrupt processing...
5128 * We do checksum and copy also but from device to kernel.
5129 */
5130
5131 tp->rx_opt.saw_tstamp = 0;
5132
5133 /* pred_flags is 0xS?10 << 16 + snd_wnd
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08005134 * if header_prediction is to be made
Linus Torvalds1da177e2005-04-16 15:20:36 -07005135 * 'S' will always be tp->tcp_header_len >> 2
5136 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09005137 * turn it off (when there are holes in the receive
Linus Torvalds1da177e2005-04-16 15:20:36 -07005138 * space for instance)
5139 * PSH flag is ignored.
5140 */
5141
5142 if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags &&
John Dykstra96e0bf42009-03-22 21:49:57 -07005143 TCP_SKB_CB(skb)->seq == tp->rcv_nxt &&
5144 !after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07005145 int tcp_header_len = tp->tcp_header_len;
5146
5147 /* Timestamp header prediction: tcp_header_len
5148 * is automatically equal to th->doff*4 due to pred_flags
5149 * match.
5150 */
5151
5152 /* Check timestamp */
5153 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07005154 /* No? Slow path! */
Ilpo Järvinena4356b22008-08-23 05:12:29 -07005155 if (!tcp_parse_aligned_timestamp(tp, th))
Linus Torvalds1da177e2005-04-16 15:20:36 -07005156 goto slow_path;
5157
Linus Torvalds1da177e2005-04-16 15:20:36 -07005158 /* If PAWS failed, check it more carefully in slow path */
5159 if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0)
5160 goto slow_path;
5161
5162 /* DO NOT update ts_recent here, if checksum fails
5163 * and timestamp was corrupted part, it will result
5164 * in a hung connection since we will drop all
5165 * future packets due to the PAWS test.
5166 */
5167 }
5168
5169 if (len <= tcp_header_len) {
5170 /* Bulk data transfer: sender */
5171 if (len == tcp_header_len) {
5172 /* Predicted packet is in window by definition.
5173 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5174 * Hence, check seq<=rcv_wup reduces to:
5175 */
5176 if (tcp_header_len ==
5177 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
5178 tp->rcv_nxt == tp->rcv_wup)
5179 tcp_store_ts_recent(tp);
5180
Linus Torvalds1da177e2005-04-16 15:20:36 -07005181 /* We know that such packets are checksummed
5182 * on entry.
5183 */
5184 tcp_ack(sk, skb, 0);
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09005185 __kfree_skb(skb);
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07005186 tcp_data_snd_check(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005187 return 0;
5188 } else { /* Header too small */
Pavel Emelyanov63231bd2008-07-16 20:22:25 -07005189 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005190 goto discard;
5191 }
5192 } else {
5193 int eaten = 0;
Chris Leech1a2449a2006-05-23 18:05:53 -07005194 int copied_early = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07005195
Chris Leech1a2449a2006-05-23 18:05:53 -07005196 if (tp->copied_seq == tp->rcv_nxt &&
5197 len - tcp_header_len <= tp->ucopy.len) {
5198#ifdef CONFIG_NET_DMA
5199 if (tcp_dma_try_early_copy(sk, skb, tcp_header_len)) {
5200 copied_early = 1;
5201 eaten = 1;
5202 }
5203#endif
Ilpo Järvinen056834d2007-12-31 14:57:14 -08005204 if (tp->ucopy.task == current &&
5205 sock_owned_by_user(sk) && !copied_early) {
Chris Leech1a2449a2006-05-23 18:05:53 -07005206 __set_current_state(TASK_RUNNING);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005207
Chris Leech1a2449a2006-05-23 18:05:53 -07005208 if (!tcp_copy_to_iovec(sk, skb, tcp_header_len))
5209 eaten = 1;
5210 }
5211 if (eaten) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07005212 /* Predicted packet is in window by definition.
5213 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5214 * Hence, check seq<=rcv_wup reduces to:
5215 */
5216 if (tcp_header_len ==
5217 (sizeof(struct tcphdr) +
5218 TCPOLEN_TSTAMP_ALIGNED) &&
5219 tp->rcv_nxt == tp->rcv_wup)
5220 tcp_store_ts_recent(tp);
5221
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07005222 tcp_rcv_rtt_measure_ts(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005223
5224 __skb_pull(skb, tcp_header_len);
5225 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07005226 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPHITSTOUSER);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005227 }
Chris Leech1a2449a2006-05-23 18:05:53 -07005228 if (copied_early)
5229 tcp_cleanup_rbuf(sk, skb->len);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005230 }
5231 if (!eaten) {
5232 if (tcp_checksum_complete_user(sk, skb))
5233 goto csum_error;
5234
5235 /* Predicted packet is in window by definition.
5236 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5237 * Hence, check seq<=rcv_wup reduces to:
5238 */
5239 if (tcp_header_len ==
5240 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
5241 tp->rcv_nxt == tp->rcv_wup)
5242 tcp_store_ts_recent(tp);
5243
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07005244 tcp_rcv_rtt_measure_ts(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005245
5246 if ((int)skb->truesize > sk->sk_forward_alloc)
5247 goto step5;
5248
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07005249 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPHITS);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005250
5251 /* Bulk data transfer: receiver */
Ilpo Järvinen056834d2007-12-31 14:57:14 -08005252 __skb_pull(skb, tcp_header_len);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005253 __skb_queue_tail(&sk->sk_receive_queue, skb);
Hideo Aoki3ab224b2007-12-31 00:11:19 -08005254 skb_set_owner_r(skb, sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005255 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
5256 }
5257
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07005258 tcp_event_data_recv(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005259
5260 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) {
5261 /* Well, only one small jumplet in fast path... */
5262 tcp_ack(sk, skb, FLAG_DATA);
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07005263 tcp_data_snd_check(sk);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07005264 if (!inet_csk_ack_scheduled(sk))
Linus Torvalds1da177e2005-04-16 15:20:36 -07005265 goto no_ack;
5266 }
5267
Ali Saidi53240c22008-10-07 15:31:19 -07005268 if (!copied_early || tp->rcv_nxt != tp->rcv_wup)
5269 __tcp_ack_snd_check(sk, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005270no_ack:
Chris Leech1a2449a2006-05-23 18:05:53 -07005271#ifdef CONFIG_NET_DMA
5272 if (copied_early)
5273 __skb_queue_tail(&sk->sk_async_wait_queue, skb);
5274 else
5275#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -07005276 if (eaten)
5277 __kfree_skb(skb);
5278 else
5279 sk->sk_data_ready(sk, 0);
5280 return 0;
5281 }
5282 }
5283
5284slow_path:
Ilpo Järvinen056834d2007-12-31 14:57:14 -08005285 if (len < (th->doff << 2) || tcp_checksum_complete_user(sk, skb))
Linus Torvalds1da177e2005-04-16 15:20:36 -07005286 goto csum_error;
5287
5288 /*
Linus Torvalds1da177e2005-04-16 15:20:36 -07005289 * Standard slow path.
5290 */
5291
Ilpo Järvinencbe2d122008-08-23 05:10:12 -07005292 res = tcp_validate_incoming(sk, skb, th, 1);
5293 if (res <= 0)
5294 return -res;
Linus Torvalds1da177e2005-04-16 15:20:36 -07005295
5296step5:
John Dykstra96e0bf42009-03-22 21:49:57 -07005297 if (th->ack && tcp_ack(sk, skb, FLAG_SLOWPATH) < 0)
5298 goto discard;
Linus Torvalds1da177e2005-04-16 15:20:36 -07005299
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07005300 tcp_rcv_rtt_measure_ts(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005301
5302 /* Process urgent data. */
5303 tcp_urg(sk, skb, th);
5304
5305 /* step 7: process the segment text */
5306 tcp_data_queue(sk, skb);
5307
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07005308 tcp_data_snd_check(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005309 tcp_ack_snd_check(sk);
5310 return 0;
5311
5312csum_error:
Pavel Emelyanov63231bd2008-07-16 20:22:25 -07005313 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005314
5315discard:
5316 __kfree_skb(skb);
5317 return 0;
5318}
5319
5320static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
5321 struct tcphdr *th, unsigned len)
5322{
5323 struct tcp_sock *tp = tcp_sk(sk);
Arnaldo Carvalho de Melod83d8462005-12-13 23:26:10 -08005324 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005325 int saved_clamp = tp->rx_opt.mss_clamp;
5326
5327 tcp_parse_options(skb, &tp->rx_opt, 0);
5328
5329 if (th->ack) {
5330 /* rfc793:
5331 * "If the state is SYN-SENT then
5332 * first check the ACK bit
5333 * If the ACK bit is set
5334 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
5335 * a reset (unless the RST bit is set, if so drop
5336 * the segment and return)"
5337 *
5338 * We do not send data with SYN, so that RFC-correct
5339 * test reduces to:
5340 */
5341 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt)
5342 goto reset_and_undo;
5343
5344 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
5345 !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp,
5346 tcp_time_stamp)) {
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07005347 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSACTIVEREJECTED);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005348 goto reset_and_undo;
5349 }
5350
5351 /* Now ACK is acceptable.
5352 *
5353 * "If the RST bit is set
5354 * If the ACK was acceptable then signal the user "error:
5355 * connection reset", drop the segment, enter CLOSED state,
5356 * delete TCB, and return."
5357 */
5358
5359 if (th->rst) {
5360 tcp_reset(sk);
5361 goto discard;
5362 }
5363
5364 /* rfc793:
5365 * "fifth, if neither of the SYN or RST bits is set then
5366 * drop the segment and return."
5367 *
5368 * See note below!
5369 * --ANK(990513)
5370 */
5371 if (!th->syn)
5372 goto discard_and_undo;
5373
5374 /* rfc793:
5375 * "If the SYN bit is on ...
5376 * are acceptable then ...
5377 * (our SYN has been ACKed), change the connection
5378 * state to ESTABLISHED..."
5379 */
5380
5381 TCP_ECN_rcv_synack(tp, th);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005382
5383 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
5384 tcp_ack(sk, skb, FLAG_SLOWPATH);
5385
5386 /* Ok.. it's good. Set up sequence numbers and
5387 * move to established.
5388 */
5389 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
5390 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
5391
5392 /* RFC1323: The window in SYN & SYN/ACK segments is
5393 * never scaled.
5394 */
5395 tp->snd_wnd = ntohs(th->window);
Hantzis Fotisee7537b2009-03-02 22:42:02 -08005396 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005397
5398 if (!tp->rx_opt.wscale_ok) {
5399 tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0;
5400 tp->window_clamp = min(tp->window_clamp, 65535U);
5401 }
5402
5403 if (tp->rx_opt.saw_tstamp) {
5404 tp->rx_opt.tstamp_ok = 1;
5405 tp->tcp_header_len =
5406 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
5407 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
5408 tcp_store_ts_recent(tp);
5409 } else {
5410 tp->tcp_header_len = sizeof(struct tcphdr);
5411 }
5412
Ilpo Järvinene60402d2007-08-09 15:14:46 +03005413 if (tcp_is_sack(tp) && sysctl_tcp_fack)
5414 tcp_enable_fack(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005415
John Heffner5d424d52006-03-20 17:53:41 -08005416 tcp_mtup_init(sk);
Arnaldo Carvalho de Melod83d8462005-12-13 23:26:10 -08005417 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005418 tcp_initialize_rcv_mss(sk);
5419
5420 /* Remember, tcp_poll() does not lock socket!
5421 * Change state from SYN-SENT only after copied_seq
5422 * is initialized. */
5423 tp->copied_seq = tp->rcv_nxt;
Ralf Baechlee16aa202006-12-07 00:11:33 -08005424 smp_mb();
Linus Torvalds1da177e2005-04-16 15:20:36 -07005425 tcp_set_state(sk, TCP_ESTABLISHED);
5426
Venkat Yekkirala6b877692006-11-08 17:04:09 -06005427 security_inet_conn_established(sk, skb);
5428
Linus Torvalds1da177e2005-04-16 15:20:36 -07005429 /* Make sure socket is routed, for correct metrics. */
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -08005430 icsk->icsk_af_ops->rebuild_header(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005431
5432 tcp_init_metrics(sk);
5433
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03005434 tcp_init_congestion_control(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -07005435
Linus Torvalds1da177e2005-04-16 15:20:36 -07005436 /* Prevent spurious tcp_cwnd_restart() on first data
5437 * packet.
5438 */
5439 tp->lsndtime = tcp_time_stamp;
5440
5441 tcp_init_buffer_space(sk);
5442
5443 if (sock_flag(sk, SOCK_KEEPOPEN))
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07005444 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp));
Linus Torvalds1da177e2005-04-16 15:20:36 -07005445
5446 if (!tp->rx_opt.snd_wscale)
5447 __tcp_fast_path_on(tp, tp->snd_wnd);
5448 else
5449 tp->pred_flags = 0;
5450
5451 if (!sock_flag(sk, SOCK_DEAD)) {
5452 sk->sk_state_change(sk);
Pavel Emelyanov8d8ad9d2007-11-26 20:10:50 +08005453 sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005454 }
5455
Arnaldo Carvalho de Melo295f7322005-08-09 20:11:56 -07005456 if (sk->sk_write_pending ||
5457 icsk->icsk_accept_queue.rskq_defer_accept ||
5458 icsk->icsk_ack.pingpong) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07005459 /* Save one ACK. Data will be ready after
5460 * several ticks, if write_pending is set.
5461 *
5462 * It may be deleted, but with this feature tcpdumps
5463 * look so _wonderfully_ clever, that I was not able
5464 * to stand against the temptation 8) --ANK
5465 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07005466 inet_csk_schedule_ack(sk);
Arnaldo Carvalho de Melo295f7322005-08-09 20:11:56 -07005467 icsk->icsk_ack.lrcvtime = tcp_time_stamp;
5468 icsk->icsk_ack.ato = TCP_ATO_MIN;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07005469 tcp_incr_quickack(sk);
5470 tcp_enter_quickack_mode(sk);
Arnaldo Carvalho de Melo3f421ba2005-08-09 20:11:08 -07005471 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
5472 TCP_DELACK_MAX, TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005473
5474discard:
5475 __kfree_skb(skb);
5476 return 0;
5477 } else {
5478 tcp_send_ack(sk);
5479 }
5480 return -1;
5481 }
5482
5483 /* No ACK in the segment */
5484
5485 if (th->rst) {
5486 /* rfc793:
5487 * "If the RST bit is set
5488 *
5489 * Otherwise (no ACK) drop the segment and return."
5490 */
5491
5492 goto discard_and_undo;
5493 }
5494
5495 /* PAWS check. */
Ilpo Järvinen056834d2007-12-31 14:57:14 -08005496 if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp &&
Ilpo Järvinenc887e6d2009-03-14 14:23:03 +00005497 tcp_paws_reject(&tp->rx_opt, 0))
Linus Torvalds1da177e2005-04-16 15:20:36 -07005498 goto discard_and_undo;
5499
5500 if (th->syn) {
5501 /* We see SYN without ACK. It is attempt of
5502 * simultaneous connect with crossed SYNs.
5503 * Particularly, it can be connect to self.
5504 */
5505 tcp_set_state(sk, TCP_SYN_RECV);
5506
5507 if (tp->rx_opt.saw_tstamp) {
5508 tp->rx_opt.tstamp_ok = 1;
5509 tcp_store_ts_recent(tp);
5510 tp->tcp_header_len =
5511 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
5512 } else {
5513 tp->tcp_header_len = sizeof(struct tcphdr);
5514 }
5515
5516 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
5517 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
5518
5519 /* RFC1323: The window in SYN & SYN/ACK segments is
5520 * never scaled.
5521 */
5522 tp->snd_wnd = ntohs(th->window);
5523 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
5524 tp->max_window = tp->snd_wnd;
5525
5526 TCP_ECN_rcv_syn(tp, th);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005527
John Heffner5d424d52006-03-20 17:53:41 -08005528 tcp_mtup_init(sk);
Arnaldo Carvalho de Melod83d8462005-12-13 23:26:10 -08005529 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005530 tcp_initialize_rcv_mss(sk);
5531
Linus Torvalds1da177e2005-04-16 15:20:36 -07005532 tcp_send_synack(sk);
5533#if 0
5534 /* Note, we could accept data and URG from this segment.
5535 * There are no obstacles to make this.
5536 *
5537 * However, if we ignore data in ACKless segments sometimes,
5538 * we have no reasons to accept it sometimes.
5539 * Also, seems the code doing it in step6 of tcp_rcv_state_process
5540 * is not flawless. So, discard packet for sanity.
5541 * Uncomment this return to process the data.
5542 */
5543 return -1;
5544#else
5545 goto discard;
5546#endif
5547 }
5548 /* "fifth, if neither of the SYN or RST bits is set then
5549 * drop the segment and return."
5550 */
5551
5552discard_and_undo:
5553 tcp_clear_options(&tp->rx_opt);
5554 tp->rx_opt.mss_clamp = saved_clamp;
5555 goto discard;
5556
5557reset_and_undo:
5558 tcp_clear_options(&tp->rx_opt);
5559 tp->rx_opt.mss_clamp = saved_clamp;
5560 return 1;
5561}
5562
Linus Torvalds1da177e2005-04-16 15:20:36 -07005563/*
5564 * This function implements the receiving procedure of RFC 793 for
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09005565 * all states except ESTABLISHED and TIME_WAIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -07005566 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
5567 * address independent.
5568 */
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09005569
Linus Torvalds1da177e2005-04-16 15:20:36 -07005570int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
5571 struct tcphdr *th, unsigned len)
5572{
5573 struct tcp_sock *tp = tcp_sk(sk);
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -08005574 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005575 int queued = 0;
Ilpo Järvinencbe2d122008-08-23 05:10:12 -07005576 int res;
Linus Torvalds1da177e2005-04-16 15:20:36 -07005577
5578 tp->rx_opt.saw_tstamp = 0;
5579
5580 switch (sk->sk_state) {
5581 case TCP_CLOSE:
5582 goto discard;
5583
5584 case TCP_LISTEN:
Stephen Hemminger2de979b2007-03-08 20:45:19 -08005585 if (th->ack)
Linus Torvalds1da177e2005-04-16 15:20:36 -07005586 return 1;
5587
Stephen Hemminger2de979b2007-03-08 20:45:19 -08005588 if (th->rst)
Linus Torvalds1da177e2005-04-16 15:20:36 -07005589 goto discard;
5590
Stephen Hemminger2de979b2007-03-08 20:45:19 -08005591 if (th->syn) {
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -08005592 if (icsk->icsk_af_ops->conn_request(sk, skb) < 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07005593 return 1;
5594
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09005595 /* Now we have several options: In theory there is
5596 * nothing else in the frame. KA9Q has an option to
Linus Torvalds1da177e2005-04-16 15:20:36 -07005597 * send data with the syn, BSD accepts data with the
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09005598 * syn up to the [to be] advertised window and
5599 * Solaris 2.1 gives you a protocol error. For now
5600 * we just ignore it, that fits the spec precisely
Linus Torvalds1da177e2005-04-16 15:20:36 -07005601 * and avoids incompatibilities. It would be nice in
5602 * future to drop through and process the data.
5603 *
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09005604 * Now that TTCP is starting to be used we ought to
Linus Torvalds1da177e2005-04-16 15:20:36 -07005605 * queue this data.
5606 * But, this leaves one open to an easy denial of
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09005607 * service attack, and SYN cookies can't defend
Linus Torvalds1da177e2005-04-16 15:20:36 -07005608 * against this problem. So, we drop the data
Masayuki Nakagawafb7e2392007-01-23 20:15:06 -08005609 * in the interest of security over speed unless
5610 * it's still in use.
Linus Torvalds1da177e2005-04-16 15:20:36 -07005611 */
Masayuki Nakagawafb7e2392007-01-23 20:15:06 -08005612 kfree_skb(skb);
5613 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07005614 }
5615 goto discard;
5616
5617 case TCP_SYN_SENT:
Linus Torvalds1da177e2005-04-16 15:20:36 -07005618 queued = tcp_rcv_synsent_state_process(sk, skb, th, len);
5619 if (queued >= 0)
5620 return queued;
5621
5622 /* Do step6 onward by hand. */
5623 tcp_urg(sk, skb, th);
5624 __kfree_skb(skb);
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07005625 tcp_data_snd_check(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005626 return 0;
5627 }
5628
Ilpo Järvinencbe2d122008-08-23 05:10:12 -07005629 res = tcp_validate_incoming(sk, skb, th, 0);
5630 if (res <= 0)
5631 return -res;
Linus Torvalds1da177e2005-04-16 15:20:36 -07005632
5633 /* step 5: check the ACK field */
5634 if (th->ack) {
John Dykstra96e0bf42009-03-22 21:49:57 -07005635 int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH) > 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07005636
Stephen Hemminger2de979b2007-03-08 20:45:19 -08005637 switch (sk->sk_state) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07005638 case TCP_SYN_RECV:
5639 if (acceptable) {
5640 tp->copied_seq = tp->rcv_nxt;
Ralf Baechlee16aa202006-12-07 00:11:33 -08005641 smp_mb();
Linus Torvalds1da177e2005-04-16 15:20:36 -07005642 tcp_set_state(sk, TCP_ESTABLISHED);
5643 sk->sk_state_change(sk);
5644
5645 /* Note, that this wakeup is only for marginal
5646 * crossed SYN case. Passively open sockets
5647 * are not waked up, because sk->sk_sleep ==
5648 * NULL and sk->sk_socket == NULL.
5649 */
Pavel Emelyanov8d8ad9d2007-11-26 20:10:50 +08005650 if (sk->sk_socket)
5651 sk_wake_async(sk,
Ilpo Järvinen056834d2007-12-31 14:57:14 -08005652 SOCK_WAKE_IO, POLL_OUT);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005653
5654 tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
5655 tp->snd_wnd = ntohs(th->window) <<
5656 tp->rx_opt.snd_wscale;
Hantzis Fotisee7537b2009-03-02 22:42:02 -08005657 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005658
5659 /* tcp_ack considers this ACK as duplicate
5660 * and does not calculate rtt.
5661 * Fix it at least with timestamps.
5662 */
Ilpo Järvinen056834d2007-12-31 14:57:14 -08005663 if (tp->rx_opt.saw_tstamp &&
5664 tp->rx_opt.rcv_tsecr && !tp->srtt)
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08005665 tcp_ack_saw_tstamp(sk, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005666
5667 if (tp->rx_opt.tstamp_ok)
5668 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
5669
5670 /* Make sure socket is routed, for
5671 * correct metrics.
5672 */
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -08005673 icsk->icsk_af_ops->rebuild_header(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005674
5675 tcp_init_metrics(sk);
5676
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03005677 tcp_init_congestion_control(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -07005678
Linus Torvalds1da177e2005-04-16 15:20:36 -07005679 /* Prevent spurious tcp_cwnd_restart() on
5680 * first data packet.
5681 */
5682 tp->lsndtime = tcp_time_stamp;
5683
John Heffner5d424d52006-03-20 17:53:41 -08005684 tcp_mtup_init(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005685 tcp_initialize_rcv_mss(sk);
5686 tcp_init_buffer_space(sk);
5687 tcp_fast_path_on(tp);
5688 } else {
5689 return 1;
5690 }
5691 break;
5692
5693 case TCP_FIN_WAIT1:
5694 if (tp->snd_una == tp->write_seq) {
5695 tcp_set_state(sk, TCP_FIN_WAIT2);
5696 sk->sk_shutdown |= SEND_SHUTDOWN;
5697 dst_confirm(sk->sk_dst_cache);
5698
5699 if (!sock_flag(sk, SOCK_DEAD))
5700 /* Wake up lingering close() */
5701 sk->sk_state_change(sk);
5702 else {
5703 int tmo;
5704
5705 if (tp->linger2 < 0 ||
5706 (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
5707 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) {
5708 tcp_done(sk);
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07005709 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONDATA);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005710 return 1;
5711 }
5712
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07005713 tmo = tcp_fin_time(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005714 if (tmo > TCP_TIMEWAIT_LEN) {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07005715 inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005716 } else if (th->fin || sock_owned_by_user(sk)) {
5717 /* Bad case. We could lose such FIN otherwise.
5718 * It is not a big problem, but it looks confusing
5719 * and not so rare event. We still can lose it now,
5720 * if it spins in bh_lock_sock(), but it is really
5721 * marginal case.
5722 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07005723 inet_csk_reset_keepalive_timer(sk, tmo);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005724 } else {
5725 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
5726 goto discard;
5727 }
5728 }
5729 }
5730 break;
5731
5732 case TCP_CLOSING:
5733 if (tp->snd_una == tp->write_seq) {
5734 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
5735 goto discard;
5736 }
5737 break;
5738
5739 case TCP_LAST_ACK:
5740 if (tp->snd_una == tp->write_seq) {
5741 tcp_update_metrics(sk);
5742 tcp_done(sk);
5743 goto discard;
5744 }
5745 break;
5746 }
5747 } else
5748 goto discard;
5749
5750 /* step 6: check the URG bit */
5751 tcp_urg(sk, skb, th);
5752
5753 /* step 7: process the segment text */
5754 switch (sk->sk_state) {
5755 case TCP_CLOSE_WAIT:
5756 case TCP_CLOSING:
5757 case TCP_LAST_ACK:
5758 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
5759 break;
5760 case TCP_FIN_WAIT1:
5761 case TCP_FIN_WAIT2:
5762 /* RFC 793 says to queue data in these states,
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09005763 * RFC 1122 says we MUST send a reset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07005764 * BSD 4.4 also does reset.
5765 */
5766 if (sk->sk_shutdown & RCV_SHUTDOWN) {
5767 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
5768 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
Pavel Emelyanovde0744a2008-07-16 20:31:16 -07005769 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONDATA);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005770 tcp_reset(sk);
5771 return 1;
5772 }
5773 }
5774 /* Fall through */
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09005775 case TCP_ESTABLISHED:
Linus Torvalds1da177e2005-04-16 15:20:36 -07005776 tcp_data_queue(sk, skb);
5777 queued = 1;
5778 break;
5779 }
5780
5781 /* tcp_data could move socket to TIME-WAIT */
5782 if (sk->sk_state != TCP_CLOSE) {
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07005783 tcp_data_snd_check(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005784 tcp_ack_snd_check(sk);
5785 }
5786
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09005787 if (!queued) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07005788discard:
5789 __kfree_skb(skb);
5790 }
5791 return 0;
5792}
5793
5794EXPORT_SYMBOL(sysctl_tcp_ecn);
5795EXPORT_SYMBOL(sysctl_tcp_reordering);
Glenn Griffinc6aefaf2008-02-07 21:49:26 -08005796EXPORT_SYMBOL(sysctl_tcp_adv_win_scale);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005797EXPORT_SYMBOL(tcp_parse_options);
YOSHIFUJI Hideaki7d5d5522008-04-17 12:29:53 +09005798#ifdef CONFIG_TCP_MD5SIG
5799EXPORT_SYMBOL(tcp_parse_md5sig_option);
5800#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -07005801EXPORT_SYMBOL(tcp_rcv_established);
5802EXPORT_SYMBOL(tcp_rcv_state_process);
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08005803EXPORT_SYMBOL(tcp_initialize_rcv_mss);