blob: 9288220b73a8d80abf9a7fff748269930d8f8a8a [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 *
8 * Version: $Id: tcp_input.c,v 1.243 2002/02/01 22:01:04 davem Exp $
9 *
Jesper Juhl02c30a82005-05-05 16:16:16 -070010 * Authors: Ross Biro
Linus Torvalds1da177e2005-04-16 15:20:36 -070011 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
12 * Mark Evans, <evansmp@uhura.aston.ac.uk>
13 * Corey Minyard <wf-rch!minyard@relay.EU.net>
14 * Florian La Roche, <flla@stud.uni-sb.de>
15 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
16 * Linus Torvalds, <torvalds@cs.helsinki.fi>
17 * Alan Cox, <gw4pts@gw4pts.ampr.org>
18 * Matthew Dillon, <dillon@apollo.west.oic.com>
19 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
20 * Jorge Cwik, <jorge@laser.satlink.net>
21 */
22
23/*
24 * Changes:
25 * Pedro Roque : Fast Retransmit/Recovery.
26 * Two receive queues.
27 * Retransmit queue handled by TCP.
28 * Better retransmit timer handling.
29 * New congestion avoidance.
30 * Header prediction.
31 * Variable renaming.
32 *
33 * Eric : Fast Retransmit.
34 * Randy Scott : MSS option defines.
35 * Eric Schenk : Fixes to slow start algorithm.
36 * Eric Schenk : Yet another double ACK bug.
37 * Eric Schenk : Delayed ACK bug fixes.
38 * Eric Schenk : Floyd style fast retrans war avoidance.
39 * David S. Miller : Don't allow zero congestion window.
40 * Eric Schenk : Fix retransmitter so that it sends
41 * next packet on ack of previous packet.
42 * Andi Kleen : Moved open_request checking here
43 * and process RSTs for open_requests.
44 * Andi Kleen : Better prune_queue, and other fixes.
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -080045 * Andrey Savochkin: Fix RTT measurements in the presence of
Linus Torvalds1da177e2005-04-16 15:20:36 -070046 * timestamps.
47 * Andrey Savochkin: Check sequence numbers correctly when
48 * removing SACKs due to in sequence incoming
49 * data segments.
50 * Andi Kleen: Make sure we never ack data there is not
51 * enough room for. Also make this condition
52 * a fatal error if it might still happen.
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +090053 * Andi Kleen: Add tcp_measure_rcv_mss to make
Linus Torvalds1da177e2005-04-16 15:20:36 -070054 * connections with MSS<min(MTU,ann. MSS)
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +090055 * work without delayed acks.
Linus Torvalds1da177e2005-04-16 15:20:36 -070056 * Andi Kleen: Process packets with PSH set in the
57 * fast path.
58 * J Hadi Salim: ECN support
59 * Andrei Gurtov,
60 * Pasi Sarolahti,
61 * Panu Kuhlberg: Experimental audit of TCP (re)transmission
62 * engine. Lots of bugs are found.
63 * Pasi Sarolahti: F-RTO for dealing with spurious RTOs
Linus Torvalds1da177e2005-04-16 15:20:36 -070064 */
65
Linus Torvalds1da177e2005-04-16 15:20:36 -070066#include <linux/mm.h>
67#include <linux/module.h>
68#include <linux/sysctl.h>
69#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) */
Ilpo Järvinen49ff4bb2007-08-02 19:47:59 -0700106#define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained DSACK info */
Ilpo Järvinen009a2e32007-09-20 11:34:38 -0700107#define FLAG_NONHEAD_RETRANS_ACKED 0x1000 /* Non-head rexmitted data was ACKed */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700108
109#define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
110#define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
111#define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
112#define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
Ilpo Järvinen2e605292007-08-02 19:46:58 -0700113#define FLAG_ANY_PROGRESS (FLAG_FORWARD_PROGRESS|FLAG_SND_UNA_ADVANCED)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700114
Ilpo Järvinen4dc26652007-02-21 23:16:11 -0800115#define IsSackFrto() (sysctl_tcp_frto == 0x2)
116
Linus Torvalds1da177e2005-04-16 15:20:36 -0700117#define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
Ilpo Järvinenbdf1ee52007-05-27 02:04:16 -0700118#define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700119
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900120/* Adapt the MSS value used to make delayed ack decision to the
Linus Torvalds1da177e2005-04-16 15:20:36 -0700121 * real world.
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900122 */
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800123static void tcp_measure_rcv_mss(struct sock *sk,
124 const struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700125{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700126 struct inet_connection_sock *icsk = inet_csk(sk);
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900127 const unsigned int lss = icsk->icsk_ack.last_seg_size;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700128 unsigned int len;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700129
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900130 icsk->icsk_ack.last_seg_size = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700131
132 /* skb->len may jitter because of SACKs, even if peer
133 * sends good full-sized frames.
134 */
Herbert Xuff9b5e02006-08-31 15:11:02 -0700135 len = skb_shinfo(skb)->gso_size ?: skb->len;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700136 if (len >= icsk->icsk_ack.rcv_mss) {
137 icsk->icsk_ack.rcv_mss = len;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700138 } else {
139 /* Otherwise, we make more careful check taking into account,
140 * that SACKs block is variable.
141 *
142 * "len" is invariant segment length, including TCP header.
143 */
Arnaldo Carvalho de Melo9c702202007-04-25 18:04:18 -0700144 len += skb->data - skb_transport_header(skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700145 if (len >= TCP_MIN_RCVMSS + sizeof(struct tcphdr) ||
146 /* If PSH is not set, packet should be
147 * full sized, provided peer TCP is not badly broken.
148 * This observation (if it is correct 8)) allows
149 * to handle super-low mtu links fairly.
150 */
151 (len >= TCP_MIN_MSS + sizeof(struct tcphdr) &&
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -0700152 !(tcp_flag_word(tcp_hdr(skb)) & TCP_REMNANT))) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700153 /* Subtract also invariant (if peer is RFC compliant),
154 * tcp header plus fixed timestamp option length.
155 * Resulting "len" is MSS free of SACK jitter.
156 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700157 len -= tcp_sk(sk)->tcp_header_len;
158 icsk->icsk_ack.last_seg_size = len;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700159 if (len == lss) {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700160 icsk->icsk_ack.rcv_mss = len;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700161 return;
162 }
163 }
Alexey Kuznetsov1ef96962006-09-19 12:52:50 -0700164 if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED)
165 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700166 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700167 }
168}
169
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700170static void tcp_incr_quickack(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700171{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700172 struct inet_connection_sock *icsk = inet_csk(sk);
173 unsigned quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700174
175 if (quickacks==0)
176 quickacks=2;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700177 if (quickacks > icsk->icsk_ack.quick)
178 icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700179}
180
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700181void tcp_enter_quickack_mode(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700182{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700183 struct inet_connection_sock *icsk = inet_csk(sk);
184 tcp_incr_quickack(sk);
185 icsk->icsk_ack.pingpong = 0;
186 icsk->icsk_ack.ato = TCP_ATO_MIN;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700187}
188
189/* Send ACKs quickly, if "quick" count is not exhausted
190 * and the session is not interactive.
191 */
192
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700193static inline int tcp_in_quickack_mode(const struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700194{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700195 const struct inet_connection_sock *icsk = inet_csk(sk);
196 return icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700197}
198
Ilpo Järvinenbdf1ee52007-05-27 02:04:16 -0700199static inline void TCP_ECN_queue_cwr(struct tcp_sock *tp)
200{
201 if (tp->ecn_flags&TCP_ECN_OK)
202 tp->ecn_flags |= TCP_ECN_QUEUE_CWR;
203}
204
205static inline void TCP_ECN_accept_cwr(struct tcp_sock *tp, struct sk_buff *skb)
206{
207 if (tcp_hdr(skb)->cwr)
208 tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
209}
210
211static inline void TCP_ECN_withdraw_cwr(struct tcp_sock *tp)
212{
213 tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
214}
215
216static inline void TCP_ECN_check_ce(struct tcp_sock *tp, struct sk_buff *skb)
217{
218 if (tp->ecn_flags&TCP_ECN_OK) {
219 if (INET_ECN_is_ce(TCP_SKB_CB(skb)->flags))
220 tp->ecn_flags |= TCP_ECN_DEMAND_CWR;
221 /* Funny extension: if ECT is not set on a segment,
222 * it is surely retransmit. It is not in ECN RFC,
223 * but Linux follows this rule. */
224 else if (INET_ECN_is_not_ect((TCP_SKB_CB(skb)->flags)))
225 tcp_enter_quickack_mode((struct sock *)tp);
226 }
227}
228
229static inline void TCP_ECN_rcv_synack(struct tcp_sock *tp, struct tcphdr *th)
230{
231 if ((tp->ecn_flags&TCP_ECN_OK) && (!th->ece || th->cwr))
232 tp->ecn_flags &= ~TCP_ECN_OK;
233}
234
235static inline void TCP_ECN_rcv_syn(struct tcp_sock *tp, struct tcphdr *th)
236{
237 if ((tp->ecn_flags&TCP_ECN_OK) && (!th->ece || !th->cwr))
238 tp->ecn_flags &= ~TCP_ECN_OK;
239}
240
241static inline int TCP_ECN_rcv_ecn_echo(struct tcp_sock *tp, struct tcphdr *th)
242{
243 if (th->ece && !th->syn && (tp->ecn_flags&TCP_ECN_OK))
244 return 1;
245 return 0;
246}
247
Linus Torvalds1da177e2005-04-16 15:20:36 -0700248/* Buffer size and advertised window tuning.
249 *
250 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
251 */
252
253static void tcp_fixup_sndbuf(struct sock *sk)
254{
255 int sndmem = tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER + 16 +
256 sizeof(struct sk_buff);
257
258 if (sk->sk_sndbuf < 3 * sndmem)
259 sk->sk_sndbuf = min(3 * sndmem, sysctl_tcp_wmem[2]);
260}
261
262/* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
263 *
264 * All tcp_full_space() is split to two parts: "network" buffer, allocated
265 * forward and advertised in receiver window (tp->rcv_wnd) and
266 * "application buffer", required to isolate scheduling/application
267 * latencies from network.
268 * window_clamp is maximal advertised window. It can be less than
269 * tcp_full_space(), in this case tcp_full_space() - window_clamp
270 * is reserved for "application" buffer. The less window_clamp is
271 * the smoother our behaviour from viewpoint of network, but the lower
272 * throughput and the higher sensitivity of the connection to losses. 8)
273 *
274 * rcv_ssthresh is more strict window_clamp used at "slow start"
275 * phase to predict further behaviour of this connection.
276 * It is used for two goals:
277 * - to enforce header prediction at sender, even when application
278 * requires some significant "application buffer". It is check #1.
279 * - to prevent pruning of receive queue because of misprediction
280 * of receiver window. Check #2.
281 *
282 * The scheme does not work when sender sends good segments opening
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800283 * window and then starts to feed us spaghetti. But it should work
Linus Torvalds1da177e2005-04-16 15:20:36 -0700284 * in common situations. Otherwise, we have to rely on queue collapsing.
285 */
286
287/* Slow part of check#2. */
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -0700288static int __tcp_grow_window(const struct sock *sk, const struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700289{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -0700290 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700291 /* Optimize this! */
292 int truesize = tcp_win_from_space(skb->truesize)/2;
John Heffner326f36e2005-11-10 17:11:48 -0800293 int window = tcp_win_from_space(sysctl_tcp_rmem[2])/2;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700294
295 while (tp->rcv_ssthresh <= window) {
296 if (truesize <= skb->len)
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700297 return 2 * inet_csk(sk)->icsk_ack.rcv_mss;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700298
299 truesize >>= 1;
300 window >>= 1;
301 }
302 return 0;
303}
304
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -0700305static void tcp_grow_window(struct sock *sk,
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800306 struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700307{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -0700308 struct tcp_sock *tp = tcp_sk(sk);
309
Linus Torvalds1da177e2005-04-16 15:20:36 -0700310 /* Check #1 */
311 if (tp->rcv_ssthresh < tp->window_clamp &&
312 (int)tp->rcv_ssthresh < tcp_space(sk) &&
313 !tcp_memory_pressure) {
314 int incr;
315
316 /* Check #2. Increase window, if skb with such overhead
317 * will fit to rcvbuf in future.
318 */
319 if (tcp_win_from_space(skb->truesize) <= skb->len)
320 incr = 2*tp->advmss;
321 else
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -0700322 incr = __tcp_grow_window(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700323
324 if (incr) {
325 tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, tp->window_clamp);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700326 inet_csk(sk)->icsk_ack.quick |= 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700327 }
328 }
329}
330
331/* 3. Tuning rcvbuf, when connection enters established state. */
332
333static void tcp_fixup_rcvbuf(struct sock *sk)
334{
335 struct tcp_sock *tp = tcp_sk(sk);
336 int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff);
337
338 /* Try to select rcvbuf so that 4 mss-sized segments
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800339 * will fit to window and corresponding skbs will fit to our rcvbuf.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700340 * (was 3; 4 is minimum to allow fast retransmit to work.)
341 */
342 while (tcp_win_from_space(rcvmem) < tp->advmss)
343 rcvmem += 128;
344 if (sk->sk_rcvbuf < 4 * rcvmem)
345 sk->sk_rcvbuf = min(4 * rcvmem, sysctl_tcp_rmem[2]);
346}
347
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800348/* 4. Try to fixup all. It is made immediately after connection enters
Linus Torvalds1da177e2005-04-16 15:20:36 -0700349 * established state.
350 */
351static void tcp_init_buffer_space(struct sock *sk)
352{
353 struct tcp_sock *tp = tcp_sk(sk);
354 int maxwin;
355
356 if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK))
357 tcp_fixup_rcvbuf(sk);
358 if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK))
359 tcp_fixup_sndbuf(sk);
360
361 tp->rcvq_space.space = tp->rcv_wnd;
362
363 maxwin = tcp_full_space(sk);
364
365 if (tp->window_clamp >= maxwin) {
366 tp->window_clamp = maxwin;
367
368 if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss)
369 tp->window_clamp = max(maxwin -
370 (maxwin >> sysctl_tcp_app_win),
371 4 * tp->advmss);
372 }
373
374 /* Force reservation of one segment. */
375 if (sysctl_tcp_app_win &&
376 tp->window_clamp > 2 * tp->advmss &&
377 tp->window_clamp + tp->advmss > maxwin)
378 tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss);
379
380 tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp);
381 tp->snd_cwnd_stamp = tcp_time_stamp;
382}
383
Linus Torvalds1da177e2005-04-16 15:20:36 -0700384/* 5. Recalculate window clamp after socket hit its memory bounds. */
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -0700385static void tcp_clamp_window(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700386{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -0700387 struct tcp_sock *tp = tcp_sk(sk);
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300388 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700389
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300390 icsk->icsk_ack.quick = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700391
John Heffner326f36e2005-11-10 17:11:48 -0800392 if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] &&
393 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) &&
394 !tcp_memory_pressure &&
395 atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) {
396 sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc),
397 sysctl_tcp_rmem[2]);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700398 }
John Heffner326f36e2005-11-10 17:11:48 -0800399 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700400 tp->rcv_ssthresh = min(tp->window_clamp, 2U*tp->advmss);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700401}
402
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800403
404/* Initialize RCV_MSS value.
405 * RCV_MSS is an our guess about MSS used by the peer.
406 * We haven't any direct information about the MSS.
407 * It's better to underestimate the RCV_MSS rather than overestimate.
408 * Overestimations make us ACKing less frequently than needed.
409 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
410 */
411void tcp_initialize_rcv_mss(struct sock *sk)
412{
413 struct tcp_sock *tp = tcp_sk(sk);
414 unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache);
415
416 hint = min(hint, tp->rcv_wnd/2);
417 hint = min(hint, TCP_MIN_RCVMSS);
418 hint = max(hint, TCP_MIN_MSS);
419
420 inet_csk(sk)->icsk_ack.rcv_mss = hint;
421}
422
Linus Torvalds1da177e2005-04-16 15:20:36 -0700423/* Receiver "autotuning" code.
424 *
425 * The algorithm for RTT estimation w/o timestamps is based on
426 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
427 * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps>
428 *
429 * More detail on this code can be found at
430 * <http://www.psc.edu/~jheffner/senior_thesis.ps>,
431 * though this reference is out of date. A new paper
432 * is pending.
433 */
434static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep)
435{
436 u32 new_sample = tp->rcv_rtt_est.rtt;
437 long m = sample;
438
439 if (m == 0)
440 m = 1;
441
442 if (new_sample != 0) {
443 /* If we sample in larger samples in the non-timestamp
444 * case, we could grossly overestimate the RTT especially
445 * with chatty applications or bulk transfer apps which
446 * are stalled on filesystem I/O.
447 *
448 * Also, since we are only going for a minimum in the
Stephen Hemminger31f34262005-11-15 15:17:10 -0800449 * non-timestamp case, we do not smooth things out
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800450 * else with timestamps disabled convergence takes too
Linus Torvalds1da177e2005-04-16 15:20:36 -0700451 * long.
452 */
453 if (!win_dep) {
454 m -= (new_sample >> 3);
455 new_sample += m;
456 } else if (m < new_sample)
457 new_sample = m << 3;
458 } else {
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800459 /* No previous measure. */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700460 new_sample = m << 3;
461 }
462
463 if (tp->rcv_rtt_est.rtt != new_sample)
464 tp->rcv_rtt_est.rtt = new_sample;
465}
466
467static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp)
468{
469 if (tp->rcv_rtt_est.time == 0)
470 goto new_measure;
471 if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq))
472 return;
473 tcp_rcv_rtt_update(tp,
474 jiffies - tp->rcv_rtt_est.time,
475 1);
476
477new_measure:
478 tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd;
479 tp->rcv_rtt_est.time = tcp_time_stamp;
480}
481
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700482static inline void tcp_rcv_rtt_measure_ts(struct sock *sk, const struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700483{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700484 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700485 if (tp->rx_opt.rcv_tsecr &&
486 (TCP_SKB_CB(skb)->end_seq -
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700487 TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700488 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0);
489}
490
491/*
492 * This function should be called every time data is copied to user space.
493 * It calculates the appropriate TCP receive buffer space.
494 */
495void tcp_rcv_space_adjust(struct sock *sk)
496{
497 struct tcp_sock *tp = tcp_sk(sk);
498 int time;
499 int space;
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900500
Linus Torvalds1da177e2005-04-16 15:20:36 -0700501 if (tp->rcvq_space.time == 0)
502 goto new_measure;
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900503
Linus Torvalds1da177e2005-04-16 15:20:36 -0700504 time = tcp_time_stamp - tp->rcvq_space.time;
505 if (time < (tp->rcv_rtt_est.rtt >> 3) ||
506 tp->rcv_rtt_est.rtt == 0)
507 return;
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900508
Linus Torvalds1da177e2005-04-16 15:20:36 -0700509 space = 2 * (tp->copied_seq - tp->rcvq_space.seq);
510
511 space = max(tp->rcvq_space.space, space);
512
513 if (tp->rcvq_space.space != space) {
514 int rcvmem;
515
516 tp->rcvq_space.space = space;
517
John Heffner6fcf9412006-02-09 17:06:57 -0800518 if (sysctl_tcp_moderate_rcvbuf &&
519 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700520 int new_clamp = space;
521
522 /* Receive space grows, normalize in order to
523 * take into account packet headers and sk_buff
524 * structure overhead.
525 */
526 space /= tp->advmss;
527 if (!space)
528 space = 1;
529 rcvmem = (tp->advmss + MAX_TCP_HEADER +
530 16 + sizeof(struct sk_buff));
531 while (tcp_win_from_space(rcvmem) < tp->advmss)
532 rcvmem += 128;
533 space *= rcvmem;
534 space = min(space, sysctl_tcp_rmem[2]);
535 if (space > sk->sk_rcvbuf) {
536 sk->sk_rcvbuf = space;
537
538 /* Make the window clamp follow along. */
539 tp->window_clamp = new_clamp;
540 }
541 }
542 }
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900543
Linus Torvalds1da177e2005-04-16 15:20:36 -0700544new_measure:
545 tp->rcvq_space.seq = tp->copied_seq;
546 tp->rcvq_space.time = tcp_time_stamp;
547}
548
549/* There is something which you must keep in mind when you analyze the
550 * behavior of the tp->ato delayed ack timeout interval. When a
551 * connection starts up, we want to ack as quickly as possible. The
552 * problem is that "good" TCP's do slow start at the beginning of data
553 * transmission. The means that until we send the first few ACK's the
554 * sender will sit on his end and only queue most of his data, because
555 * he can only send snd_cwnd unacked packets at any given time. For
556 * each ACK we send, he increments snd_cwnd and transmits more of his
557 * queue. -DaveM
558 */
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -0700559static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700560{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -0700561 struct tcp_sock *tp = tcp_sk(sk);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700562 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700563 u32 now;
564
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700565 inet_csk_schedule_ack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700566
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700567 tcp_measure_rcv_mss(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700568
569 tcp_rcv_rtt_measure(tp);
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900570
Linus Torvalds1da177e2005-04-16 15:20:36 -0700571 now = tcp_time_stamp;
572
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700573 if (!icsk->icsk_ack.ato) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700574 /* The _first_ data packet received, initialize
575 * delayed ACK engine.
576 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700577 tcp_incr_quickack(sk);
578 icsk->icsk_ack.ato = TCP_ATO_MIN;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700579 } else {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700580 int m = now - icsk->icsk_ack.lrcvtime;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700581
582 if (m <= TCP_ATO_MIN/2) {
583 /* The fastest case is the first. */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700584 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2;
585 } else if (m < icsk->icsk_ack.ato) {
586 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m;
587 if (icsk->icsk_ack.ato > icsk->icsk_rto)
588 icsk->icsk_ack.ato = icsk->icsk_rto;
589 } else if (m > icsk->icsk_rto) {
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800590 /* Too long gap. Apparently sender failed to
Linus Torvalds1da177e2005-04-16 15:20:36 -0700591 * restart window, so that we send ACKs quickly.
592 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700593 tcp_incr_quickack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700594 sk_stream_mem_reclaim(sk);
595 }
596 }
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700597 icsk->icsk_ack.lrcvtime = now;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700598
599 TCP_ECN_check_ce(tp, skb);
600
601 if (skb->len >= 128)
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -0700602 tcp_grow_window(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700603}
604
David S. Miller05bb1fa2007-08-30 22:10:28 -0700605static u32 tcp_rto_min(struct sock *sk)
606{
607 struct dst_entry *dst = __sk_dst_get(sk);
608 u32 rto_min = TCP_RTO_MIN;
609
David S. Miller5c127c52007-08-31 14:39:44 -0700610 if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
David S. Miller05bb1fa2007-08-30 22:10:28 -0700611 rto_min = dst->metrics[RTAX_RTO_MIN-1];
612 return rto_min;
613}
614
Linus Torvalds1da177e2005-04-16 15:20:36 -0700615/* Called to compute a smoothed rtt estimate. The data fed to this
616 * routine either comes from timestamps, or from segments that were
617 * known _not_ to have been retransmitted [see Karn/Partridge
618 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
619 * piece by Van Jacobson.
620 * NOTE: the next three routines used to be one big routine.
621 * To save cycles in the RFC 1323 implementation it was better to break
622 * it up into three procedures. -- erics
623 */
Stephen Hemminger2d2abba2005-11-10 16:56:12 -0800624static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700625{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300626 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700627 long m = mrtt; /* RTT */
628
Linus Torvalds1da177e2005-04-16 15:20:36 -0700629 /* The following amusing code comes from Jacobson's
630 * article in SIGCOMM '88. Note that rtt and mdev
631 * are scaled versions of rtt and mean deviation.
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900632 * This is designed to be as fast as possible
Linus Torvalds1da177e2005-04-16 15:20:36 -0700633 * m stands for "measurement".
634 *
635 * On a 1990 paper the rto value is changed to:
636 * RTO = rtt + 4 * mdev
637 *
638 * Funny. This algorithm seems to be very broken.
639 * These formulae increase RTO, when it should be decreased, increase
Stephen Hemminger31f34262005-11-15 15:17:10 -0800640 * too slowly, when it should be increased quickly, decrease too quickly
Linus Torvalds1da177e2005-04-16 15:20:36 -0700641 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
642 * does not matter how to _calculate_ it. Seems, it was trap
643 * that VJ failed to avoid. 8)
644 */
Stephen Hemminger2de979b2007-03-08 20:45:19 -0800645 if (m == 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700646 m = 1;
647 if (tp->srtt != 0) {
648 m -= (tp->srtt >> 3); /* m is now error in rtt est */
649 tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */
650 if (m < 0) {
651 m = -m; /* m is now abs(error) */
652 m -= (tp->mdev >> 2); /* similar update on mdev */
653 /* This is similar to one of Eifel findings.
654 * Eifel blocks mdev updates when rtt decreases.
655 * This solution is a bit different: we use finer gain
656 * for mdev in this case (alpha*beta).
657 * Like Eifel it also prevents growth of rto,
658 * but also it limits too fast rto decreases,
659 * happening in pure Eifel.
660 */
661 if (m > 0)
662 m >>= 3;
663 } else {
664 m -= (tp->mdev >> 2); /* similar update on mdev */
665 }
666 tp->mdev += m; /* mdev = 3/4 mdev + 1/4 new */
667 if (tp->mdev > tp->mdev_max) {
668 tp->mdev_max = tp->mdev;
669 if (tp->mdev_max > tp->rttvar)
670 tp->rttvar = tp->mdev_max;
671 }
672 if (after(tp->snd_una, tp->rtt_seq)) {
673 if (tp->mdev_max < tp->rttvar)
674 tp->rttvar -= (tp->rttvar-tp->mdev_max)>>2;
675 tp->rtt_seq = tp->snd_nxt;
David S. Miller05bb1fa2007-08-30 22:10:28 -0700676 tp->mdev_max = tcp_rto_min(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700677 }
678 } else {
679 /* no previous measure. */
680 tp->srtt = m<<3; /* take the measured time to be rtt */
681 tp->mdev = m<<1; /* make sure rto = 3*rtt */
David S. Miller05bb1fa2007-08-30 22:10:28 -0700682 tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700683 tp->rtt_seq = tp->snd_nxt;
684 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700685}
686
687/* Calculate rto without backoff. This is the second half of Van Jacobson's
688 * routine referred to above.
689 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700690static inline void tcp_set_rto(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700691{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700692 const struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700693 /* Old crap is replaced with new one. 8)
694 *
695 * More seriously:
696 * 1. If rtt variance happened to be less 50msec, it is hallucination.
697 * It cannot be less due to utterly erratic ACK generation made
698 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
699 * to do with delayed acks, because at cwnd>2 true delack timeout
700 * is invisible. Actually, Linux-2.4 also generates erratic
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800701 * ACKs in some circumstances.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700702 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700703 inet_csk(sk)->icsk_rto = (tp->srtt >> 3) + tp->rttvar;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700704
705 /* 2. Fixups made earlier cannot be right.
706 * If we do not estimate RTO correctly without them,
707 * all the algo is pure shit and should be replaced
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800708 * with correct one. It is exactly, which we pretend to do.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700709 */
710}
711
712/* NOTE: clamping at TCP_RTO_MIN is not required, current algo
713 * guarantees that rto is higher.
714 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700715static inline void tcp_bound_rto(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700716{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700717 if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
718 inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700719}
720
721/* Save metrics learned by this TCP session.
722 This function is called only, when TCP finishes successfully
723 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
724 */
725void tcp_update_metrics(struct sock *sk)
726{
727 struct tcp_sock *tp = tcp_sk(sk);
728 struct dst_entry *dst = __sk_dst_get(sk);
729
730 if (sysctl_tcp_nometrics_save)
731 return;
732
733 dst_confirm(dst);
734
735 if (dst && (dst->flags&DST_HOST)) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300736 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700737 int m;
738
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300739 if (icsk->icsk_backoff || !tp->srtt) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700740 /* This session failed to estimate rtt. Why?
741 * Probably, no packets returned in time.
742 * Reset our results.
743 */
744 if (!(dst_metric_locked(dst, RTAX_RTT)))
745 dst->metrics[RTAX_RTT-1] = 0;
746 return;
747 }
748
749 m = dst_metric(dst, RTAX_RTT) - tp->srtt;
750
751 /* If newly calculated rtt larger than stored one,
752 * store new one. Otherwise, use EWMA. Remember,
753 * rtt overestimation is always better than underestimation.
754 */
755 if (!(dst_metric_locked(dst, RTAX_RTT))) {
756 if (m <= 0)
757 dst->metrics[RTAX_RTT-1] = tp->srtt;
758 else
759 dst->metrics[RTAX_RTT-1] -= (m>>3);
760 }
761
762 if (!(dst_metric_locked(dst, RTAX_RTTVAR))) {
763 if (m < 0)
764 m = -m;
765
766 /* Scale deviation to rttvar fixed point */
767 m >>= 1;
768 if (m < tp->mdev)
769 m = tp->mdev;
770
771 if (m >= dst_metric(dst, RTAX_RTTVAR))
772 dst->metrics[RTAX_RTTVAR-1] = m;
773 else
774 dst->metrics[RTAX_RTTVAR-1] -=
775 (dst->metrics[RTAX_RTTVAR-1] - m)>>2;
776 }
777
778 if (tp->snd_ssthresh >= 0xFFFF) {
779 /* Slow start still did not finish. */
780 if (dst_metric(dst, RTAX_SSTHRESH) &&
781 !dst_metric_locked(dst, RTAX_SSTHRESH) &&
782 (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH))
783 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1;
784 if (!dst_metric_locked(dst, RTAX_CWND) &&
785 tp->snd_cwnd > dst_metric(dst, RTAX_CWND))
786 dst->metrics[RTAX_CWND-1] = tp->snd_cwnd;
787 } else if (tp->snd_cwnd > tp->snd_ssthresh &&
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300788 icsk->icsk_ca_state == TCP_CA_Open) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700789 /* Cong. avoidance phase, cwnd is reliable. */
790 if (!dst_metric_locked(dst, RTAX_SSTHRESH))
791 dst->metrics[RTAX_SSTHRESH-1] =
792 max(tp->snd_cwnd >> 1, tp->snd_ssthresh);
793 if (!dst_metric_locked(dst, RTAX_CWND))
794 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_cwnd) >> 1;
795 } else {
796 /* Else slow start did not finish, cwnd is non-sense,
797 ssthresh may be also invalid.
798 */
799 if (!dst_metric_locked(dst, RTAX_CWND))
800 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_ssthresh) >> 1;
801 if (dst->metrics[RTAX_SSTHRESH-1] &&
802 !dst_metric_locked(dst, RTAX_SSTHRESH) &&
803 tp->snd_ssthresh > dst->metrics[RTAX_SSTHRESH-1])
804 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh;
805 }
806
807 if (!dst_metric_locked(dst, RTAX_REORDERING)) {
808 if (dst->metrics[RTAX_REORDERING-1] < tp->reordering &&
809 tp->reordering != sysctl_tcp_reordering)
810 dst->metrics[RTAX_REORDERING-1] = tp->reordering;
811 }
812 }
813}
814
David S. Miller26722872007-08-24 22:21:50 -0700815/* Numbers are taken from RFC3390.
816 *
817 * John Heffner states:
818 *
819 * The RFC specifies a window of no more than 4380 bytes
820 * unless 2*MSS > 4380. Reading the pseudocode in the RFC
821 * is a bit misleading because they use a clamp at 4380 bytes
822 * rather than use a multiplier in the relevant range.
823 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700824__u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst)
825{
826 __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0);
827
828 if (!cwnd) {
David S. Millerc1b4a7e2005-07-05 15:24:38 -0700829 if (tp->mss_cache > 1460)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700830 cwnd = 2;
831 else
David S. Millerc1b4a7e2005-07-05 15:24:38 -0700832 cwnd = (tp->mss_cache > 1095) ? 3 : 4;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700833 }
834 return min_t(__u32, cwnd, tp->snd_cwnd_clamp);
835}
836
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800837/* Set slow start threshold and cwnd not falling to slow start */
Ilpo Järvinen3cfe3ba2007-02-27 10:09:49 -0800838void tcp_enter_cwr(struct sock *sk, const int set_ssthresh)
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800839{
840 struct tcp_sock *tp = tcp_sk(sk);
Ilpo Järvinen3cfe3ba2007-02-27 10:09:49 -0800841 const struct inet_connection_sock *icsk = inet_csk(sk);
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800842
843 tp->prior_ssthresh = 0;
844 tp->bytes_acked = 0;
Ilpo Järvinene01f9d72007-03-02 13:27:25 -0800845 if (icsk->icsk_ca_state < TCP_CA_CWR) {
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800846 tp->undo_marker = 0;
Ilpo Järvinen3cfe3ba2007-02-27 10:09:49 -0800847 if (set_ssthresh)
848 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800849 tp->snd_cwnd = min(tp->snd_cwnd,
850 tcp_packets_in_flight(tp) + 1U);
851 tp->snd_cwnd_cnt = 0;
852 tp->high_seq = tp->snd_nxt;
853 tp->snd_cwnd_stamp = tcp_time_stamp;
854 TCP_ECN_queue_cwr(tp);
855
856 tcp_set_ca_state(sk, TCP_CA_CWR);
857 }
858}
859
Ilpo Järvinene60402d2007-08-09 15:14:46 +0300860/*
861 * Packet counting of FACK is based on in-order assumptions, therefore TCP
862 * disables it when reordering is detected
863 */
864static void tcp_disable_fack(struct tcp_sock *tp)
865{
866 tp->rx_opt.sack_ok &= ~2;
867}
868
869/* Take a notice that peer is sending DSACKs */
870static void tcp_dsack_seen(struct tcp_sock *tp)
871{
872 tp->rx_opt.sack_ok |= 4;
873}
874
Linus Torvalds1da177e2005-04-16 15:20:36 -0700875/* Initialize metrics on socket. */
876
877static void tcp_init_metrics(struct sock *sk)
878{
879 struct tcp_sock *tp = tcp_sk(sk);
880 struct dst_entry *dst = __sk_dst_get(sk);
881
882 if (dst == NULL)
883 goto reset;
884
885 dst_confirm(dst);
886
887 if (dst_metric_locked(dst, RTAX_CWND))
888 tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND);
889 if (dst_metric(dst, RTAX_SSTHRESH)) {
890 tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH);
891 if (tp->snd_ssthresh > tp->snd_cwnd_clamp)
892 tp->snd_ssthresh = tp->snd_cwnd_clamp;
893 }
894 if (dst_metric(dst, RTAX_REORDERING) &&
895 tp->reordering != dst_metric(dst, RTAX_REORDERING)) {
Ilpo Järvinene60402d2007-08-09 15:14:46 +0300896 tcp_disable_fack(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700897 tp->reordering = dst_metric(dst, RTAX_REORDERING);
898 }
899
900 if (dst_metric(dst, RTAX_RTT) == 0)
901 goto reset;
902
903 if (!tp->srtt && dst_metric(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3))
904 goto reset;
905
906 /* Initial rtt is determined from SYN,SYN-ACK.
907 * The segment is small and rtt may appear much
908 * less than real one. Use per-dst memory
909 * to make it more realistic.
910 *
911 * A bit of theory. RTT is time passed after "normal" sized packet
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800912 * is sent until it is ACKed. In normal circumstances sending small
Linus Torvalds1da177e2005-04-16 15:20:36 -0700913 * packets force peer to delay ACKs and calculation is correct too.
914 * The algorithm is adaptive and, provided we follow specs, it
915 * NEVER underestimate RTT. BUT! If peer tries to make some clever
916 * tricks sort of "quick acks" for time long enough to decrease RTT
917 * to low value, and then abruptly stops to do it and starts to delay
918 * ACKs, wait for troubles.
919 */
920 if (dst_metric(dst, RTAX_RTT) > tp->srtt) {
921 tp->srtt = dst_metric(dst, RTAX_RTT);
922 tp->rtt_seq = tp->snd_nxt;
923 }
924 if (dst_metric(dst, RTAX_RTTVAR) > tp->mdev) {
925 tp->mdev = dst_metric(dst, RTAX_RTTVAR);
926 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
927 }
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700928 tcp_set_rto(sk);
929 tcp_bound_rto(sk);
930 if (inet_csk(sk)->icsk_rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700931 goto reset;
932 tp->snd_cwnd = tcp_init_cwnd(tp, dst);
933 tp->snd_cwnd_stamp = tcp_time_stamp;
934 return;
935
936reset:
937 /* Play conservative. If timestamps are not
938 * supported, TCP will fail to recalculate correct
939 * rtt, if initial rto is too small. FORGET ALL AND RESET!
940 */
941 if (!tp->rx_opt.saw_tstamp && tp->srtt) {
942 tp->srtt = 0;
943 tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700944 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700945 }
946}
947
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300948static void tcp_update_reordering(struct sock *sk, const int metric,
949 const int ts)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700950{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300951 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700952 if (metric > tp->reordering) {
953 tp->reordering = min(TCP_MAX_REORDERING, metric);
954
955 /* This exciting event is worth to be remembered. 8) */
956 if (ts)
957 NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER);
Ilpo Järvinene60402d2007-08-09 15:14:46 +0300958 else if (tcp_is_reno(tp))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700959 NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER);
Ilpo Järvinene60402d2007-08-09 15:14:46 +0300960 else if (tcp_is_fack(tp))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700961 NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER);
962 else
963 NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER);
964#if FASTRETRANS_DEBUG > 1
965 printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n",
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300966 tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700967 tp->reordering,
968 tp->fackets_out,
969 tp->sacked_out,
970 tp->undo_marker ? tp->undo_retrans : 0);
971#endif
Ilpo Järvinene60402d2007-08-09 15:14:46 +0300972 tcp_disable_fack(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700973 }
974}
975
976/* This procedure tags the retransmission queue when SACKs arrive.
977 *
978 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
979 * Packets in queue with these bits set are counted in variables
980 * sacked_out, retrans_out and lost_out, correspondingly.
981 *
982 * Valid combinations are:
983 * Tag InFlight Description
984 * 0 1 - orig segment is in flight.
985 * S 0 - nothing flies, orig reached receiver.
986 * L 0 - nothing flies, orig lost by net.
987 * R 2 - both orig and retransmit are in flight.
988 * L|R 1 - orig is lost, retransmit is in flight.
989 * S|R 1 - orig reached receiver, retrans is still in flight.
990 * (L|S|R is logically valid, it could occur when L|R is sacked,
991 * but it is equivalent to plain S and code short-curcuits it to S.
992 * L|S is logically invalid, it would mean -1 packet in flight 8))
993 *
994 * These 6 states form finite state machine, controlled by the following events:
995 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
996 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
997 * 3. Loss detection event of one of three flavors:
998 * A. Scoreboard estimator decided the packet is lost.
999 * A'. Reno "three dupacks" marks head of queue lost.
1000 * A''. Its FACK modfication, head until snd.fack is lost.
1001 * B. SACK arrives sacking data transmitted after never retransmitted
1002 * hole was sent out.
1003 * C. SACK arrives sacking SND.NXT at the moment, when the
1004 * segment was retransmitted.
1005 * 4. D-SACK added new rule: D-SACK changes any tag to S.
1006 *
1007 * It is pleasant to note, that state diagram turns out to be commutative,
1008 * so that we are allowed not to be bothered by order of our actions,
1009 * when multiple events arrive simultaneously. (see the function below).
1010 *
1011 * Reordering detection.
1012 * --------------------
1013 * Reordering metric is maximal distance, which a packet can be displaced
1014 * in packet stream. With SACKs we can estimate it:
1015 *
1016 * 1. SACK fills old hole and the corresponding segment was not
1017 * ever retransmitted -> reordering. Alas, we cannot use it
1018 * when segment was retransmitted.
1019 * 2. The last flaw is solved with D-SACK. D-SACK arrives
1020 * for retransmitted and already SACKed segment -> reordering..
1021 * Both of these heuristics are not used in Loss state, when we cannot
1022 * account for retransmits accurately.
Ilpo Järvinen5b3c9882007-08-24 22:54:44 -07001023 *
1024 * SACK block validation.
1025 * ----------------------
1026 *
1027 * SACK block range validation checks that the received SACK block fits to
1028 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
1029 * Note that SND.UNA is not included to the range though being valid because
Ilpo Järvinen0e835332007-10-01 15:28:17 -07001030 * it means that the receiver is rather inconsistent with itself reporting
1031 * SACK reneging when it should advance SND.UNA. Such SACK block this is
1032 * perfectly valid, however, in light of RFC2018 which explicitly states
1033 * that "SACK block MUST reflect the newest segment. Even if the newest
1034 * segment is going to be discarded ...", not that it looks very clever
1035 * in case of head skb. Due to potentional receiver driven attacks, we
1036 * choose to avoid immediate execution of a walk in write queue due to
1037 * reneging and defer head skb's loss recovery to standard loss recovery
1038 * procedure that will eventually trigger (nothing forbids us doing this).
Ilpo Järvinen5b3c9882007-08-24 22:54:44 -07001039 *
1040 * Implements also blockage to start_seq wrap-around. Problem lies in the
1041 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
1042 * there's no guarantee that it will be before snd_nxt (n). The problem
1043 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
1044 * wrap (s_w):
1045 *
1046 * <- outs wnd -> <- wrapzone ->
1047 * u e n u_w e_w s n_w
1048 * | | | | | | |
1049 * |<------------+------+----- TCP seqno space --------------+---------->|
1050 * ...-- <2^31 ->| |<--------...
1051 * ...---- >2^31 ------>| |<--------...
1052 *
1053 * Current code wouldn't be vulnerable but it's better still to discard such
1054 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
1055 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
1056 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
1057 * equal to the ideal case (infinite seqno space without wrap caused issues).
1058 *
1059 * With D-SACK the lower bound is extended to cover sequence space below
1060 * SND.UNA down to undo_marker, which is the last point of interest. Yet
1061 * again, DSACK block must not to go across snd_una (for the same reason as
1062 * for the normal SACK blocks, explained above). But there all simplicity
1063 * ends, TCP might receive valid D-SACKs below that. As long as they reside
1064 * fully below undo_marker they do not affect behavior in anyway and can
1065 * therefore be safely ignored. In rare cases (which are more or less
1066 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
1067 * fragmentation and packet reordering past skb's retransmission. To consider
1068 * them correctly, the acceptable range must be extended even more though
1069 * the exact amount is rather hard to quantify. However, tp->max_window can
1070 * be used as an exaggerated estimate.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001071 */
Ilpo Järvinen5b3c9882007-08-24 22:54:44 -07001072static int tcp_is_sackblock_valid(struct tcp_sock *tp, int is_dsack,
1073 u32 start_seq, u32 end_seq)
1074{
1075 /* Too far in future, or reversed (interpretation is ambiguous) */
1076 if (after(end_seq, tp->snd_nxt) || !before(start_seq, end_seq))
1077 return 0;
1078
1079 /* Nasty start_seq wrap-around check (see comments above) */
1080 if (!before(start_seq, tp->snd_nxt))
1081 return 0;
1082
1083 /* In outstanding window? ...This is valid exit for DSACKs too.
1084 * start_seq == snd_una is non-sensical (see comments above)
1085 */
1086 if (after(start_seq, tp->snd_una))
1087 return 1;
1088
1089 if (!is_dsack || !tp->undo_marker)
1090 return 0;
1091
1092 /* ...Then it's D-SACK, and must reside below snd_una completely */
1093 if (!after(end_seq, tp->snd_una))
1094 return 0;
1095
1096 if (!before(start_seq, tp->undo_marker))
1097 return 1;
1098
1099 /* Too old */
1100 if (!after(end_seq, tp->undo_marker))
1101 return 0;
1102
1103 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1104 * start_seq < undo_marker and end_seq >= undo_marker.
1105 */
1106 return !before(start_seq, end_seq - tp->max_window);
1107}
1108
Ilpo Järvinen1c1e87e2007-10-10 02:45:32 -07001109/* Check for lost retransmit. This superb idea is borrowed from "ratehalving".
1110 * Event "C". Later note: FACK people cheated me again 8), we have to account
1111 * for reordering! Ugly, but should help.
Ilpo Järvinenf785a8e2007-10-11 17:35:41 -07001112 *
1113 * Search retransmitted skbs from write_queue that were sent when snd_nxt was
1114 * less than what is now known to be received by the other end (derived from
Ilpo Järvinenb08d6cb2007-10-11 17:36:13 -07001115 * SACK blocks by the caller). Also calculate the lowest snd_nxt among the
1116 * remaining retransmitted skbs to avoid some costly processing per ACKs.
Ilpo Järvinen1c1e87e2007-10-10 02:45:32 -07001117 */
Ilpo Järvinenf785a8e2007-10-11 17:35:41 -07001118static int tcp_mark_lost_retrans(struct sock *sk, u32 received_upto)
Ilpo Järvinen1c1e87e2007-10-10 02:45:32 -07001119{
1120 struct tcp_sock *tp = tcp_sk(sk);
1121 struct sk_buff *skb;
1122 int flag = 0;
Ilpo Järvinenf785a8e2007-10-11 17:35:41 -07001123 int cnt = 0;
Ilpo Järvinendf2e0142007-10-18 05:07:57 -07001124 u32 new_low_seq = tp->snd_nxt;
Ilpo Järvinen1c1e87e2007-10-10 02:45:32 -07001125
1126 tcp_for_write_queue(skb, sk) {
1127 u32 ack_seq = TCP_SKB_CB(skb)->ack_seq;
1128
1129 if (skb == tcp_send_head(sk))
1130 break;
Ilpo Järvinenf785a8e2007-10-11 17:35:41 -07001131 if (cnt == tp->retrans_out)
Ilpo Järvinen1c1e87e2007-10-10 02:45:32 -07001132 break;
1133 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
1134 continue;
1135
Ilpo Järvinenf785a8e2007-10-11 17:35:41 -07001136 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS))
1137 continue;
1138
1139 if (after(received_upto, ack_seq) &&
Ilpo Järvinen1c1e87e2007-10-10 02:45:32 -07001140 (tcp_is_fack(tp) ||
Ilpo Järvinenf785a8e2007-10-11 17:35:41 -07001141 !before(received_upto,
Ilpo Järvinen1c1e87e2007-10-10 02:45:32 -07001142 ack_seq + tp->reordering * tp->mss_cache))) {
1143 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1144 tp->retrans_out -= tcp_skb_pcount(skb);
1145
1146 /* clear lost hint */
1147 tp->retransmit_skb_hint = NULL;
1148
1149 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {
1150 tp->lost_out += tcp_skb_pcount(skb);
1151 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1152 flag |= FLAG_DATA_SACKED;
1153 NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT);
1154 }
Ilpo Järvinenf785a8e2007-10-11 17:35:41 -07001155 } else {
Ilpo Järvinendf2e0142007-10-18 05:07:57 -07001156 if (before(ack_seq, new_low_seq))
Ilpo Järvinenb08d6cb2007-10-11 17:36:13 -07001157 new_low_seq = ack_seq;
Ilpo Järvinenf785a8e2007-10-11 17:35:41 -07001158 cnt += tcp_skb_pcount(skb);
Ilpo Järvinen1c1e87e2007-10-10 02:45:32 -07001159 }
1160 }
Ilpo Järvinenb08d6cb2007-10-11 17:36:13 -07001161
1162 if (tp->retrans_out)
1163 tp->lost_retrans_low = new_low_seq;
1164
Ilpo Järvinen1c1e87e2007-10-10 02:45:32 -07001165 return flag;
1166}
Ilpo Järvinen5b3c9882007-08-24 22:54:44 -07001167
David S. Millerd06e0212007-06-18 22:43:06 -07001168static int tcp_check_dsack(struct tcp_sock *tp, struct sk_buff *ack_skb,
1169 struct tcp_sack_block_wire *sp, int num_sacks,
1170 u32 prior_snd_una)
1171{
1172 u32 start_seq_0 = ntohl(get_unaligned(&sp[0].start_seq));
1173 u32 end_seq_0 = ntohl(get_unaligned(&sp[0].end_seq));
1174 int dup_sack = 0;
1175
1176 if (before(start_seq_0, TCP_SKB_CB(ack_skb)->ack_seq)) {
1177 dup_sack = 1;
Ilpo Järvinene60402d2007-08-09 15:14:46 +03001178 tcp_dsack_seen(tp);
David S. Millerd06e0212007-06-18 22:43:06 -07001179 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV);
1180 } else if (num_sacks > 1) {
1181 u32 end_seq_1 = ntohl(get_unaligned(&sp[1].end_seq));
1182 u32 start_seq_1 = ntohl(get_unaligned(&sp[1].start_seq));
1183
1184 if (!after(end_seq_0, end_seq_1) &&
1185 !before(start_seq_0, start_seq_1)) {
1186 dup_sack = 1;
Ilpo Järvinene60402d2007-08-09 15:14:46 +03001187 tcp_dsack_seen(tp);
David S. Millerd06e0212007-06-18 22:43:06 -07001188 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV);
1189 }
1190 }
1191
1192 /* D-SACK for already forgotten data... Do dumb counting. */
1193 if (dup_sack &&
1194 !after(end_seq_0, prior_snd_una) &&
1195 after(end_seq_0, tp->undo_marker))
1196 tp->undo_retrans--;
1197
1198 return dup_sack;
1199}
1200
Ilpo Järvinend1935942007-10-11 17:34:25 -07001201/* Check if skb is fully within the SACK block. In presence of GSO skbs,
1202 * the incoming SACK may not exactly match but we can find smaller MSS
1203 * aligned portion of it that matches. Therefore we might need to fragment
1204 * which may fail and creates some hassle (caller must handle error case
1205 * returns).
1206 */
1207int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb,
1208 u32 start_seq, u32 end_seq)
1209{
1210 int in_sack, err;
1211 unsigned int pkt_len;
1212
1213 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
1214 !before(end_seq, TCP_SKB_CB(skb)->end_seq);
1215
1216 if (tcp_skb_pcount(skb) > 1 && !in_sack &&
1217 after(TCP_SKB_CB(skb)->end_seq, start_seq)) {
1218
1219 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq);
1220
1221 if (!in_sack)
1222 pkt_len = start_seq - TCP_SKB_CB(skb)->seq;
1223 else
1224 pkt_len = end_seq - TCP_SKB_CB(skb)->seq;
1225 err = tcp_fragment(sk, skb, pkt_len, skb_shinfo(skb)->gso_size);
1226 if (err < 0)
1227 return err;
1228 }
1229
1230 return in_sack;
1231}
1232
Linus Torvalds1da177e2005-04-16 15:20:36 -07001233static int
1234tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_una)
1235{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001236 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001237 struct tcp_sock *tp = tcp_sk(sk);
Arnaldo Carvalho de Melo9c702202007-04-25 18:04:18 -07001238 unsigned char *ptr = (skb_transport_header(ack_skb) +
1239 TCP_SKB_CB(ack_skb)->sacked);
Al Viro269bd272006-09-27 18:32:28 -07001240 struct tcp_sack_block_wire *sp = (struct tcp_sack_block_wire *)(ptr+2);
Baruch Evenfda03fb2007-02-04 23:35:57 -08001241 struct sk_buff *cached_skb;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001242 int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3;
1243 int reord = tp->packets_out;
1244 int prior_fackets;
Ilpo Järvinendf2e0142007-10-18 05:07:57 -07001245 u32 highest_sack_end_seq = tp->lost_retrans_low;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001246 int flag = 0;
Ilpo Järvinen7769f402007-06-15 15:14:04 -07001247 int found_dup_sack = 0;
Baruch Evenfda03fb2007-02-04 23:35:57 -08001248 int cached_fack_count;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001249 int i;
Baruch Evenfda03fb2007-02-04 23:35:57 -08001250 int first_sack_index;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001251
Ilpo Järvinend738cd82007-03-24 21:03:23 -07001252 if (!tp->sacked_out) {
Ilpo Järvinende83c052007-10-07 23:37:55 -07001253 if (WARN_ON(tp->fackets_out))
1254 tp->fackets_out = 0;
Ilpo Järvinend738cd82007-03-24 21:03:23 -07001255 tp->highest_sack = tp->snd_una;
1256 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001257 prior_fackets = tp->fackets_out;
1258
David S. Millerd06e0212007-06-18 22:43:06 -07001259 found_dup_sack = tcp_check_dsack(tp, ack_skb, sp,
1260 num_sacks, prior_snd_una);
1261 if (found_dup_sack)
Ilpo Järvinen49ff4bb2007-08-02 19:47:59 -07001262 flag |= FLAG_DSACKING_ACK;
Baruch Even6f746512007-02-04 23:36:42 -08001263
1264 /* Eliminate too old ACKs, but take into
1265 * account more or less fresh ones, they can
1266 * contain valid SACK info.
1267 */
1268 if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window))
1269 return 0;
1270
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001271 /* SACK fastpath:
1272 * if the only SACK change is the increase of the end_seq of
1273 * the first block then only apply that SACK block
1274 * and use retrans queue hinting otherwise slowpath */
1275 flag = 1;
Baruch Even6f746512007-02-04 23:36:42 -08001276 for (i = 0; i < num_sacks; i++) {
1277 __be32 start_seq = sp[i].start_seq;
1278 __be32 end_seq = sp[i].end_seq;
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001279
Baruch Even6f746512007-02-04 23:36:42 -08001280 if (i == 0) {
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001281 if (tp->recv_sack_cache[i].start_seq != start_seq)
1282 flag = 0;
1283 } else {
1284 if ((tp->recv_sack_cache[i].start_seq != start_seq) ||
1285 (tp->recv_sack_cache[i].end_seq != end_seq))
1286 flag = 0;
1287 }
1288 tp->recv_sack_cache[i].start_seq = start_seq;
1289 tp->recv_sack_cache[i].end_seq = end_seq;
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001290 }
Baruch Even8a3c3a92007-02-04 23:37:41 -08001291 /* Clear the rest of the cache sack blocks so they won't match mistakenly. */
1292 for (; i < ARRAY_SIZE(tp->recv_sack_cache); i++) {
1293 tp->recv_sack_cache[i].start_seq = 0;
1294 tp->recv_sack_cache[i].end_seq = 0;
1295 }
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001296
Baruch Evenfda03fb2007-02-04 23:35:57 -08001297 first_sack_index = 0;
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001298 if (flag)
1299 num_sacks = 1;
1300 else {
1301 int j;
1302 tp->fastpath_skb_hint = NULL;
1303
1304 /* order SACK blocks to allow in order walk of the retrans queue */
1305 for (i = num_sacks-1; i > 0; i--) {
1306 for (j = 0; j < i; j++){
1307 if (after(ntohl(sp[j].start_seq),
1308 ntohl(sp[j+1].start_seq))){
Baruch Evendb3ccda2007-01-25 13:35:06 -08001309 struct tcp_sack_block_wire tmp;
1310
1311 tmp = sp[j];
1312 sp[j] = sp[j+1];
1313 sp[j+1] = tmp;
Baruch Evenfda03fb2007-02-04 23:35:57 -08001314
1315 /* Track where the first SACK block goes to */
1316 if (j == first_sack_index)
1317 first_sack_index = j+1;
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001318 }
1319
1320 }
1321 }
1322 }
1323
1324 /* clear flag as used for different purpose in following code */
1325 flag = 0;
1326
Baruch Evenfda03fb2007-02-04 23:35:57 -08001327 /* Use SACK fastpath hint if valid */
1328 cached_skb = tp->fastpath_skb_hint;
1329 cached_fack_count = tp->fastpath_cnt_hint;
1330 if (!cached_skb) {
David S. Millerfe067e82007-03-07 12:12:44 -08001331 cached_skb = tcp_write_queue_head(sk);
Baruch Evenfda03fb2007-02-04 23:35:57 -08001332 cached_fack_count = 0;
1333 }
1334
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001335 for (i=0; i<num_sacks; i++, sp++) {
1336 struct sk_buff *skb;
1337 __u32 start_seq = ntohl(sp->start_seq);
1338 __u32 end_seq = ntohl(sp->end_seq);
1339 int fack_count;
Ilpo Järvinen7769f402007-06-15 15:14:04 -07001340 int dup_sack = (found_dup_sack && (i == first_sack_index));
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001341
Ilpo Järvinen18f02542007-08-24 22:55:52 -07001342 if (!tcp_is_sackblock_valid(tp, dup_sack, start_seq, end_seq)) {
1343 if (dup_sack) {
1344 if (!tp->undo_marker)
1345 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKIGNOREDNOUNDO);
1346 else
1347 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKIGNOREDOLD);
Ilpo Järvinen93e68022007-09-25 22:46:50 -07001348 } else {
1349 /* Don't count olds caused by ACK reordering */
1350 if ((TCP_SKB_CB(ack_skb)->ack_seq != tp->snd_una) &&
1351 !after(end_seq, tp->snd_una))
1352 continue;
Ilpo Järvinen18f02542007-08-24 22:55:52 -07001353 NET_INC_STATS_BH(LINUX_MIB_TCPSACKDISCARD);
Ilpo Järvinen93e68022007-09-25 22:46:50 -07001354 }
Ilpo Järvinen5b3c9882007-08-24 22:54:44 -07001355 continue;
Ilpo Järvinen18f02542007-08-24 22:55:52 -07001356 }
Ilpo Järvinen5b3c9882007-08-24 22:54:44 -07001357
Baruch Evenfda03fb2007-02-04 23:35:57 -08001358 skb = cached_skb;
1359 fack_count = cached_fack_count;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001360
1361 /* Event "B" in the comment above. */
1362 if (after(end_seq, tp->high_seq))
1363 flag |= FLAG_DATA_LOST;
1364
David S. Millerfe067e82007-03-07 12:12:44 -08001365 tcp_for_write_queue_from(skb, sk) {
Ilpo Järvinenf6fb1282007-10-11 17:33:55 -07001366 int in_sack;
David S. Miller6475be12005-09-01 22:47:01 -07001367 u8 sacked;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001368
David S. Millerfe067e82007-03-07 12:12:44 -08001369 if (skb == tcp_send_head(sk))
1370 break;
1371
Baruch Evenfda03fb2007-02-04 23:35:57 -08001372 cached_skb = skb;
1373 cached_fack_count = fack_count;
1374 if (i == first_sack_index) {
1375 tp->fastpath_skb_hint = skb;
1376 tp->fastpath_cnt_hint = fack_count;
1377 }
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001378
Linus Torvalds1da177e2005-04-16 15:20:36 -07001379 /* The retransmission queue is always in order, so
1380 * we can short-circuit the walk early.
1381 */
David S. Miller6475be12005-09-01 22:47:01 -07001382 if (!before(TCP_SKB_CB(skb)->seq, end_seq))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001383 break;
1384
Ilpo Järvinend1935942007-10-11 17:34:25 -07001385 in_sack = tcp_match_skb_to_sack(sk, skb, start_seq, end_seq);
1386 if (in_sack < 0)
1387 break;
David S. Miller6475be12005-09-01 22:47:01 -07001388
Ilpo Järvinenf6fb1282007-10-11 17:33:55 -07001389 fack_count += tcp_skb_pcount(skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001390
David S. Miller6475be12005-09-01 22:47:01 -07001391 sacked = TCP_SKB_CB(skb)->sacked;
1392
Linus Torvalds1da177e2005-04-16 15:20:36 -07001393 /* Account D-SACK for retransmitted packet. */
1394 if ((dup_sack && in_sack) &&
1395 (sacked & TCPCB_RETRANS) &&
1396 after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
1397 tp->undo_retrans--;
1398
1399 /* The frame is ACKed. */
1400 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) {
1401 if (sacked&TCPCB_RETRANS) {
1402 if ((dup_sack && in_sack) &&
1403 (sacked&TCPCB_SACKED_ACKED))
1404 reord = min(fack_count, reord);
1405 } else {
1406 /* If it was in a hole, we detected reordering. */
1407 if (fack_count < prior_fackets &&
1408 !(sacked&TCPCB_SACKED_ACKED))
1409 reord = min(fack_count, reord);
1410 }
1411
1412 /* Nothing to do; acked frame is about to be dropped. */
1413 continue;
1414 }
1415
Linus Torvalds1da177e2005-04-16 15:20:36 -07001416 if (!in_sack)
1417 continue;
1418
1419 if (!(sacked&TCPCB_SACKED_ACKED)) {
1420 if (sacked & TCPCB_SACKED_RETRANS) {
1421 /* If the segment is not tagged as lost,
1422 * we do not clear RETRANS, believing
1423 * that retransmission is still in flight.
1424 */
1425 if (sacked & TCPCB_LOST) {
1426 TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
1427 tp->lost_out -= tcp_skb_pcount(skb);
1428 tp->retrans_out -= tcp_skb_pcount(skb);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001429
1430 /* clear lost hint */
1431 tp->retransmit_skb_hint = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001432 }
1433 } else {
1434 /* New sack for not retransmitted frame,
1435 * which was in hole. It is reordering.
1436 */
1437 if (!(sacked & TCPCB_RETRANS) &&
1438 fack_count < prior_fackets)
1439 reord = min(fack_count, reord);
1440
1441 if (sacked & TCPCB_LOST) {
1442 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1443 tp->lost_out -= tcp_skb_pcount(skb);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001444
1445 /* clear lost hint */
1446 tp->retransmit_skb_hint = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001447 }
Ilpo Järvinen4dc26652007-02-21 23:16:11 -08001448 /* SACK enhanced F-RTO detection.
1449 * Set flag if and only if non-rexmitted
1450 * segments below frto_highmark are
1451 * SACKed (RFC4138; Appendix B).
1452 * Clearing correct due to in-order walk
1453 */
1454 if (after(end_seq, tp->frto_highmark)) {
1455 flag &= ~FLAG_ONLY_ORIG_SACKED;
1456 } else {
1457 if (!(sacked & TCPCB_RETRANS))
1458 flag |= FLAG_ONLY_ORIG_SACKED;
1459 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001460 }
1461
1462 TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED;
1463 flag |= FLAG_DATA_SACKED;
1464 tp->sacked_out += tcp_skb_pcount(skb);
1465
1466 if (fack_count > tp->fackets_out)
1467 tp->fackets_out = fack_count;
Ilpo Järvinend738cd82007-03-24 21:03:23 -07001468
Ilpo Järvinenf785a8e2007-10-11 17:35:41 -07001469 if (after(TCP_SKB_CB(skb)->seq, tp->highest_sack)) {
Ilpo Järvinend738cd82007-03-24 21:03:23 -07001470 tp->highest_sack = TCP_SKB_CB(skb)->seq;
Ilpo Järvinenf785a8e2007-10-11 17:35:41 -07001471 highest_sack_end_seq = TCP_SKB_CB(skb)->end_seq;
1472 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001473 } else {
1474 if (dup_sack && (sacked&TCPCB_RETRANS))
1475 reord = min(fack_count, reord);
1476 }
1477
1478 /* D-SACK. We can detect redundant retransmission
1479 * in S|R and plain R frames and clear it.
1480 * undo_retrans is decreased above, L|R frames
1481 * are accounted above as well.
1482 */
1483 if (dup_sack &&
1484 (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS)) {
1485 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1486 tp->retrans_out -= tcp_skb_pcount(skb);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001487 tp->retransmit_skb_hint = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001488 }
1489 }
1490 }
1491
Ilpo Järvinenb08d6cb2007-10-11 17:36:13 -07001492 if (tp->retrans_out &&
1493 after(highest_sack_end_seq, tp->lost_retrans_low) &&
Ilpo Järvinenf785a8e2007-10-11 17:35:41 -07001494 icsk->icsk_ca_state == TCP_CA_Recovery)
1495 flag |= tcp_mark_lost_retrans(sk, highest_sack_end_seq);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001496
Ilpo Järvinen86426c22007-08-09 14:45:17 +03001497 tcp_verify_left_out(tp);
1498
Ilpo Järvinen288035f92007-02-21 23:14:42 -08001499 if ((reord < tp->fackets_out) && icsk->icsk_ca_state != TCP_CA_Loss &&
Ilpo Järvinenc5e7af02007-02-23 16:22:06 -08001500 (!tp->frto_highmark || after(tp->snd_una, tp->frto_highmark)))
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001501 tcp_update_reordering(sk, ((tp->fackets_out + 1) - reord), 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001502
1503#if FASTRETRANS_DEBUG > 0
1504 BUG_TRAP((int)tp->sacked_out >= 0);
1505 BUG_TRAP((int)tp->lost_out >= 0);
1506 BUG_TRAP((int)tp->retrans_out >= 0);
1507 BUG_TRAP((int)tcp_packets_in_flight(tp) >= 0);
1508#endif
1509 return flag;
1510}
1511
Ilpo Järvinen95eacd22007-10-01 15:27:42 -07001512/* If we receive more dupacks than we expected counting segments
1513 * in assumption of absent reordering, interpret this as reordering.
1514 * The only another reason could be bug in receiver TCP.
Ilpo Järvinen30935cf2007-02-21 23:01:36 -08001515 */
Ilpo Järvinen4ddf6672007-05-27 01:52:00 -07001516static void tcp_check_reno_reordering(struct sock *sk, const int addend)
1517{
1518 struct tcp_sock *tp = tcp_sk(sk);
1519 u32 holes;
1520
1521 holes = max(tp->lost_out, 1U);
1522 holes = min(holes, tp->packets_out);
1523
1524 if ((tp->sacked_out + holes) > tp->packets_out) {
1525 tp->sacked_out = tp->packets_out - holes;
1526 tcp_update_reordering(sk, tp->packets_out + addend, 0);
1527 }
1528}
1529
1530/* Emulate SACKs for SACKless connection: account for a new dupack. */
1531
1532static void tcp_add_reno_sack(struct sock *sk)
1533{
1534 struct tcp_sock *tp = tcp_sk(sk);
1535 tp->sacked_out++;
1536 tcp_check_reno_reordering(sk, 0);
Ilpo Järvinen005903b2007-08-09 14:44:16 +03001537 tcp_verify_left_out(tp);
Ilpo Järvinen4ddf6672007-05-27 01:52:00 -07001538}
1539
1540/* Account for ACK, ACKing some data in Reno Recovery phase. */
1541
1542static void tcp_remove_reno_sacks(struct sock *sk, int acked)
1543{
1544 struct tcp_sock *tp = tcp_sk(sk);
1545
1546 if (acked > 0) {
1547 /* One ACK acked hole. The rest eat duplicate ACKs. */
1548 if (acked-1 >= tp->sacked_out)
1549 tp->sacked_out = 0;
1550 else
1551 tp->sacked_out -= acked-1;
1552 }
1553 tcp_check_reno_reordering(sk, acked);
Ilpo Järvinen005903b2007-08-09 14:44:16 +03001554 tcp_verify_left_out(tp);
Ilpo Järvinen4ddf6672007-05-27 01:52:00 -07001555}
1556
1557static inline void tcp_reset_reno_sack(struct tcp_sock *tp)
1558{
1559 tp->sacked_out = 0;
Ilpo Järvinen4ddf6672007-05-27 01:52:00 -07001560}
1561
Ilpo Järvinen95eacd22007-10-01 15:27:42 -07001562/* F-RTO can only be used if TCP has never retransmitted anything other than
1563 * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here)
1564 */
Ilpo Järvinen46d0de42007-02-21 23:10:39 -08001565int tcp_use_frto(struct sock *sk)
Ilpo Järvinenbdaae172007-02-21 22:59:58 -08001566{
1567 const struct tcp_sock *tp = tcp_sk(sk);
Ilpo Järvinen46d0de42007-02-21 23:10:39 -08001568 struct sk_buff *skb;
Ilpo Järvinenbdaae172007-02-21 22:59:58 -08001569
Ilpo Järvinen575ee712007-04-30 00:39:55 -07001570 if (!sysctl_tcp_frto)
Ilpo Järvinen46d0de42007-02-21 23:10:39 -08001571 return 0;
1572
Ilpo Järvinen4dc26652007-02-21 23:16:11 -08001573 if (IsSackFrto())
1574 return 1;
1575
Ilpo Järvinen46d0de42007-02-21 23:10:39 -08001576 /* Avoid expensive walking of rexmit queue if possible */
1577 if (tp->retrans_out > 1)
1578 return 0;
1579
David S. Millerfe067e82007-03-07 12:12:44 -08001580 skb = tcp_write_queue_head(sk);
1581 skb = tcp_write_queue_next(sk, skb); /* Skips head */
1582 tcp_for_write_queue_from(skb, sk) {
1583 if (skb == tcp_send_head(sk))
1584 break;
Ilpo Järvinen46d0de42007-02-21 23:10:39 -08001585 if (TCP_SKB_CB(skb)->sacked&TCPCB_RETRANS)
1586 return 0;
1587 /* Short-circuit when first non-SACKed skb has been checked */
1588 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED))
1589 break;
1590 }
1591 return 1;
Ilpo Järvinenbdaae172007-02-21 22:59:58 -08001592}
1593
Ilpo Järvinen30935cf2007-02-21 23:01:36 -08001594/* RTO occurred, but do not yet enter Loss state. Instead, defer RTO
1595 * recovery a bit and use heuristics in tcp_process_frto() to detect if
Ilpo Järvinend1a54c62007-02-21 23:11:57 -08001596 * the RTO was spurious. Only clear SACKED_RETRANS of the head here to
1597 * keep retrans_out counting accurate (with SACK F-RTO, other than head
1598 * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS
1599 * bits are handled if the Loss state is really to be entered (in
1600 * tcp_enter_frto_loss).
Ilpo Järvinen7487c482007-02-21 23:02:30 -08001601 *
1602 * Do like tcp_enter_loss() would; when RTO expires the second time it
1603 * does:
1604 * "Reduce ssthresh if it has not yet been made inside this window."
Linus Torvalds1da177e2005-04-16 15:20:36 -07001605 */
1606void tcp_enter_frto(struct sock *sk)
1607{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001608 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001609 struct tcp_sock *tp = tcp_sk(sk);
1610 struct sk_buff *skb;
1611
Ilpo Järvinen7487c482007-02-21 23:02:30 -08001612 if ((!tp->frto_counter && icsk->icsk_ca_state <= TCP_CA_Disorder) ||
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09001613 tp->snd_una == tp->high_seq ||
Ilpo Järvinen7487c482007-02-21 23:02:30 -08001614 ((icsk->icsk_ca_state == TCP_CA_Loss || tp->frto_counter) &&
1615 !icsk->icsk_retransmits)) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001616 tp->prior_ssthresh = tcp_current_ssthresh(sk);
Ilpo Järvinen66e93e42007-02-21 23:13:47 -08001617 /* Our state is too optimistic in ssthresh() call because cwnd
1618 * is not reduced until tcp_enter_frto_loss() when previous FRTO
1619 * recovery has not yet completed. Pattern would be this: RTO,
1620 * Cumulative ACK, RTO (2xRTO for the same segment does not end
1621 * up here twice).
1622 * RFC4138 should be more specific on what to do, even though
1623 * RTO is quite unlikely to occur after the first Cumulative ACK
1624 * due to back-off and complexity of triggering events ...
1625 */
1626 if (tp->frto_counter) {
1627 u32 stored_cwnd;
1628 stored_cwnd = tp->snd_cwnd;
1629 tp->snd_cwnd = 2;
1630 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
1631 tp->snd_cwnd = stored_cwnd;
1632 } else {
1633 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
1634 }
1635 /* ... in theory, cong.control module could do "any tricks" in
1636 * ssthresh(), which means that ca_state, lost bits and lost_out
1637 * counter would have to be faked before the call occurs. We
1638 * consider that too expensive, unlikely and hacky, so modules
1639 * using these in ssthresh() must deal these incompatibility
1640 * issues if they receives CA_EVENT_FRTO and frto_counter != 0
1641 */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001642 tcp_ca_event(sk, CA_EVENT_FRTO);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001643 }
1644
Linus Torvalds1da177e2005-04-16 15:20:36 -07001645 tp->undo_marker = tp->snd_una;
1646 tp->undo_retrans = 0;
1647
David S. Millerfe067e82007-03-07 12:12:44 -08001648 skb = tcp_write_queue_head(sk);
Ilpo Järvinen009a2e32007-09-20 11:34:38 -07001649 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS)
1650 tp->undo_marker = 0;
Ilpo Järvinend1a54c62007-02-21 23:11:57 -08001651 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
Ilpo Järvinen522e7542007-02-21 22:54:52 -08001652 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
Ilpo Järvinend1a54c62007-02-21 23:11:57 -08001653 tp->retrans_out -= tcp_skb_pcount(skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001654 }
Ilpo Järvinen005903b2007-08-09 14:44:16 +03001655 tcp_verify_left_out(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001656
Ilpo Järvinen4dc26652007-02-21 23:16:11 -08001657 /* Earlier loss recovery underway (see RFC4138; Appendix B).
1658 * The last condition is necessary at least in tp->frto_counter case.
1659 */
1660 if (IsSackFrto() && (tp->frto_counter ||
1661 ((1 << icsk->icsk_ca_state) & (TCPF_CA_Recovery|TCPF_CA_Loss))) &&
1662 after(tp->high_seq, tp->snd_una)) {
1663 tp->frto_highmark = tp->high_seq;
1664 } else {
1665 tp->frto_highmark = tp->snd_nxt;
1666 }
Ilpo Järvinen7b0eb222007-02-21 23:03:35 -08001667 tcp_set_ca_state(sk, TCP_CA_Disorder);
1668 tp->high_seq = tp->snd_nxt;
Ilpo Järvinen7487c482007-02-21 23:02:30 -08001669 tp->frto_counter = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001670}
1671
1672/* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
1673 * which indicates that we should follow the traditional RTO recovery,
1674 * i.e. mark everything lost and do go-back-N retransmission.
1675 */
Ilpo Järvinend1a54c62007-02-21 23:11:57 -08001676static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001677{
1678 struct tcp_sock *tp = tcp_sk(sk);
1679 struct sk_buff *skb;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001680
Linus Torvalds1da177e2005-04-16 15:20:36 -07001681 tp->lost_out = 0;
Ilpo Järvinend1a54c62007-02-21 23:11:57 -08001682 tp->retrans_out = 0;
Ilpo Järvinene60402d2007-08-09 15:14:46 +03001683 if (tcp_is_reno(tp))
Ilpo Järvinen9bff40f2007-05-27 01:53:49 -07001684 tcp_reset_reno_sack(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001685
David S. Millerfe067e82007-03-07 12:12:44 -08001686 tcp_for_write_queue(skb, sk) {
1687 if (skb == tcp_send_head(sk))
1688 break;
Ilpo Järvinend1a54c62007-02-21 23:11:57 -08001689 /*
1690 * Count the retransmission made on RTO correctly (only when
1691 * waiting for the first ACK and did not get it)...
1692 */
1693 if ((tp->frto_counter == 1) && !(flag&FLAG_DATA_ACKED)) {
Ilpo Järvinen0a9f2a42007-07-15 00:19:29 -07001694 /* For some reason this R-bit might get cleared? */
1695 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
1696 tp->retrans_out += tcp_skb_pcount(skb);
Ilpo Järvinend1a54c62007-02-21 23:11:57 -08001697 /* ...enter this if branch just for the first segment */
1698 flag |= FLAG_DATA_ACKED;
1699 } else {
Ilpo Järvinen009a2e32007-09-20 11:34:38 -07001700 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS)
1701 tp->undo_marker = 0;
Ilpo Järvinend1a54c62007-02-21 23:11:57 -08001702 TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
1703 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001704
Ilpo Järvinen9bff40f2007-05-27 01:53:49 -07001705 /* Don't lost mark skbs that were fwd transmitted after RTO */
1706 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) &&
1707 !after(TCP_SKB_CB(skb)->end_seq, tp->frto_highmark)) {
1708 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1709 tp->lost_out += tcp_skb_pcount(skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001710 }
1711 }
Ilpo Järvinen005903b2007-08-09 14:44:16 +03001712 tcp_verify_left_out(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001713
Ilpo Järvinen95c49222007-02-21 23:05:18 -08001714 tp->snd_cwnd = tcp_packets_in_flight(tp) + allowed_segments;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001715 tp->snd_cwnd_cnt = 0;
1716 tp->snd_cwnd_stamp = tcp_time_stamp;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001717 tp->frto_counter = 0;
Ilpo Järvinen16e90682007-10-11 17:32:31 -07001718 tp->bytes_acked = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001719
1720 tp->reordering = min_t(unsigned int, tp->reordering,
1721 sysctl_tcp_reordering);
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001722 tcp_set_ca_state(sk, TCP_CA_Loss);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001723 tp->high_seq = tp->frto_highmark;
1724 TCP_ECN_queue_cwr(tp);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001725
Ilpo Järvinenb7689202007-09-20 11:37:19 -07001726 tcp_clear_retrans_hints_partial(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001727}
1728
Ilpo Järvinen4cd82992007-10-11 17:34:57 -07001729static void tcp_clear_retrans_partial(struct tcp_sock *tp)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001730{
Linus Torvalds1da177e2005-04-16 15:20:36 -07001731 tp->retrans_out = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001732 tp->lost_out = 0;
1733
1734 tp->undo_marker = 0;
1735 tp->undo_retrans = 0;
1736}
1737
Ilpo Järvinen4cd82992007-10-11 17:34:57 -07001738void tcp_clear_retrans(struct tcp_sock *tp)
1739{
1740 tcp_clear_retrans_partial(tp);
1741
1742 tp->fackets_out = 0;
1743 tp->sacked_out = 0;
1744}
1745
Linus Torvalds1da177e2005-04-16 15:20:36 -07001746/* Enter Loss state. If "how" is not zero, forget all SACK information
1747 * and reset tags completely, otherwise preserve SACKs. If receiver
1748 * dropped its ofo queue, we will know this due to reneging detection.
1749 */
1750void tcp_enter_loss(struct sock *sk, int how)
1751{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001752 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001753 struct tcp_sock *tp = tcp_sk(sk);
1754 struct sk_buff *skb;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001755
1756 /* Reduce ssthresh if it has not yet been made inside this window. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001757 if (icsk->icsk_ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq ||
1758 (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
1759 tp->prior_ssthresh = tcp_current_ssthresh(sk);
1760 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
1761 tcp_ca_event(sk, CA_EVENT_LOSS);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001762 }
1763 tp->snd_cwnd = 1;
1764 tp->snd_cwnd_cnt = 0;
1765 tp->snd_cwnd_stamp = tcp_time_stamp;
1766
Stephen Hemminger9772efb2005-11-10 17:09:53 -08001767 tp->bytes_acked = 0;
Ilpo Järvinen4cd82992007-10-11 17:34:57 -07001768 tcp_clear_retrans_partial(tp);
1769
1770 if (tcp_is_reno(tp))
1771 tcp_reset_reno_sack(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001772
Ilpo Järvinenb7689202007-09-20 11:37:19 -07001773 if (!how) {
1774 /* Push undo marker, if it was plain RTO and nothing
1775 * was retransmitted. */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001776 tp->undo_marker = tp->snd_una;
Ilpo Järvinenb7689202007-09-20 11:37:19 -07001777 tcp_clear_retrans_hints_partial(tp);
1778 } else {
Ilpo Järvinen4cd82992007-10-11 17:34:57 -07001779 tp->sacked_out = 0;
1780 tp->fackets_out = 0;
Ilpo Järvinenb7689202007-09-20 11:37:19 -07001781 tcp_clear_all_retrans_hints(tp);
1782 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001783
David S. Millerfe067e82007-03-07 12:12:44 -08001784 tcp_for_write_queue(skb, sk) {
1785 if (skb == tcp_send_head(sk))
1786 break;
Ilpo Järvinen4cd82992007-10-11 17:34:57 -07001787
Linus Torvalds1da177e2005-04-16 15:20:36 -07001788 if (TCP_SKB_CB(skb)->sacked&TCPCB_RETRANS)
1789 tp->undo_marker = 0;
1790 TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED;
1791 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) {
1792 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
1793 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1794 tp->lost_out += tcp_skb_pcount(skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001795 }
1796 }
Ilpo Järvinen005903b2007-08-09 14:44:16 +03001797 tcp_verify_left_out(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001798
1799 tp->reordering = min_t(unsigned int, tp->reordering,
1800 sysctl_tcp_reordering);
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001801 tcp_set_ca_state(sk, TCP_CA_Loss);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001802 tp->high_seq = tp->snd_nxt;
1803 TCP_ECN_queue_cwr(tp);
Ilpo Järvinen580e5722007-05-19 13:56:57 -07001804 /* Abort FRTO algorithm if one is in progress */
1805 tp->frto_counter = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001806}
1807
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001808static int tcp_check_sack_reneging(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001809{
1810 struct sk_buff *skb;
1811
1812 /* If ACK arrived pointing to a remembered SACK,
1813 * it means that our remembered SACKs do not reflect
1814 * real state of receiver i.e.
1815 * receiver _host_ is heavily congested (or buggy).
1816 * Do processing similar to RTO timeout.
1817 */
David S. Millerfe067e82007-03-07 12:12:44 -08001818 if ((skb = tcp_write_queue_head(sk)) != NULL &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07001819 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001820 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001821 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING);
1822
1823 tcp_enter_loss(sk, 1);
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001824 icsk->icsk_retransmits++;
David S. Millerfe067e82007-03-07 12:12:44 -08001825 tcp_retransmit_skb(sk, tcp_write_queue_head(sk));
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001826 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001827 icsk->icsk_rto, TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001828 return 1;
1829 }
1830 return 0;
1831}
1832
1833static inline int tcp_fackets_out(struct tcp_sock *tp)
1834{
Ilpo Järvinene60402d2007-08-09 15:14:46 +03001835 return tcp_is_reno(tp) ? tp->sacked_out+1 : tp->fackets_out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001836}
1837
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001838static inline int tcp_skb_timedout(struct sock *sk, struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001839{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001840 return (tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001841}
1842
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07001843static inline int tcp_head_timedout(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001844{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07001845 struct tcp_sock *tp = tcp_sk(sk);
1846
Linus Torvalds1da177e2005-04-16 15:20:36 -07001847 return tp->packets_out &&
David S. Millerfe067e82007-03-07 12:12:44 -08001848 tcp_skb_timedout(sk, tcp_write_queue_head(sk));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001849}
1850
1851/* Linux NewReno/SACK/FACK/ECN state machine.
1852 * --------------------------------------
1853 *
1854 * "Open" Normal state, no dubious events, fast path.
1855 * "Disorder" In all the respects it is "Open",
1856 * but requires a bit more attention. It is entered when
1857 * we see some SACKs or dupacks. It is split of "Open"
1858 * mainly to move some processing from fast path to slow one.
1859 * "CWR" CWND was reduced due to some Congestion Notification event.
1860 * It can be ECN, ICMP source quench, local device congestion.
1861 * "Recovery" CWND was reduced, we are fast-retransmitting.
1862 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
1863 *
1864 * tcp_fastretrans_alert() is entered:
1865 * - each incoming ACK, if state is not "Open"
1866 * - when arrived ACK is unusual, namely:
1867 * * SACK
1868 * * Duplicate ACK.
1869 * * ECN ECE.
1870 *
1871 * Counting packets in flight is pretty simple.
1872 *
1873 * in_flight = packets_out - left_out + retrans_out
1874 *
1875 * packets_out is SND.NXT-SND.UNA counted in packets.
1876 *
1877 * retrans_out is number of retransmitted segments.
1878 *
1879 * left_out is number of segments left network, but not ACKed yet.
1880 *
1881 * left_out = sacked_out + lost_out
1882 *
1883 * sacked_out: Packets, which arrived to receiver out of order
1884 * and hence not ACKed. With SACKs this number is simply
1885 * amount of SACKed data. Even without SACKs
1886 * it is easy to give pretty reliable estimate of this number,
1887 * counting duplicate ACKs.
1888 *
1889 * lost_out: Packets lost by network. TCP has no explicit
1890 * "loss notification" feedback from network (for now).
1891 * It means that this number can be only _guessed_.
1892 * Actually, it is the heuristics to predict lossage that
1893 * distinguishes different algorithms.
1894 *
1895 * F.e. after RTO, when all the queue is considered as lost,
1896 * lost_out = packets_out and in_flight = retrans_out.
1897 *
1898 * Essentially, we have now two algorithms counting
1899 * lost packets.
1900 *
1901 * FACK: It is the simplest heuristics. As soon as we decided
1902 * that something is lost, we decide that _all_ not SACKed
1903 * packets until the most forward SACK are lost. I.e.
1904 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
1905 * It is absolutely correct estimate, if network does not reorder
1906 * packets. And it loses any connection to reality when reordering
1907 * takes place. We use FACK by default until reordering
1908 * is suspected on the path to this destination.
1909 *
1910 * NewReno: when Recovery is entered, we assume that one segment
1911 * is lost (classic Reno). While we are in Recovery and
1912 * a partial ACK arrives, we assume that one more packet
1913 * is lost (NewReno). This heuristics are the same in NewReno
1914 * and SACK.
1915 *
1916 * Imagine, that's all! Forget about all this shamanism about CWND inflation
1917 * deflation etc. CWND is real congestion window, never inflated, changes
1918 * only according to classic VJ rules.
1919 *
1920 * Really tricky (and requiring careful tuning) part of algorithm
1921 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
1922 * The first determines the moment _when_ we should reduce CWND and,
1923 * hence, slow down forward transmission. In fact, it determines the moment
1924 * when we decide that hole is caused by loss, rather than by a reorder.
1925 *
1926 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
1927 * holes, caused by lost packets.
1928 *
1929 * And the most logically complicated part of algorithm is undo
1930 * heuristics. We detect false retransmits due to both too early
1931 * fast retransmit (reordering) and underestimated RTO, analyzing
1932 * timestamps and D-SACKs. When we detect that some segments were
1933 * retransmitted by mistake and CWND reduction was wrong, we undo
1934 * window reduction and abort recovery phase. This logic is hidden
1935 * inside several functions named tcp_try_undo_<something>.
1936 */
1937
1938/* This function decides, when we should leave Disordered state
1939 * and enter Recovery phase, reducing congestion window.
1940 *
1941 * Main question: may we further continue forward transmission
1942 * with the same cwnd?
1943 */
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07001944static int tcp_time_to_recover(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001945{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07001946 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001947 __u32 packets_out;
1948
Ilpo Järvinen52c63f12007-02-21 23:06:52 -08001949 /* Do not perform any recovery during FRTO algorithm */
1950 if (tp->frto_counter)
1951 return 0;
1952
Linus Torvalds1da177e2005-04-16 15:20:36 -07001953 /* Trick#1: The loss is proven. */
1954 if (tp->lost_out)
1955 return 1;
1956
1957 /* Not-A-Trick#2 : Classic rule... */
1958 if (tcp_fackets_out(tp) > tp->reordering)
1959 return 1;
1960
1961 /* Trick#3 : when we use RFC2988 timer restart, fast
1962 * retransmit can be triggered by timeout of queue head.
1963 */
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07001964 if (tcp_head_timedout(sk))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001965 return 1;
1966
1967 /* Trick#4: It is still not OK... But will it be useful to delay
1968 * recovery more?
1969 */
1970 packets_out = tp->packets_out;
1971 if (packets_out <= tp->reordering &&
1972 tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) &&
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07001973 !tcp_may_send_now(sk)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001974 /* We have nothing to send. This connection is limited
1975 * either by receiver window or by application.
1976 */
1977 return 1;
1978 }
1979
1980 return 0;
1981}
1982
Ilpo Järvinend8f4f222007-04-20 22:56:38 -07001983/* RFC: This is from the original, I doubt that this is necessary at all:
1984 * clear xmit_retrans hint if seq of this skb is beyond hint. How could we
1985 * retransmitted past LOST markings in the first place? I'm not fully sure
1986 * about undo and end of connection cases, which can cause R without L?
1987 */
1988static void tcp_verify_retransmit_hint(struct tcp_sock *tp,
1989 struct sk_buff *skb)
1990{
1991 if ((tp->retransmit_skb_hint != NULL) &&
1992 before(TCP_SKB_CB(skb)->seq,
1993 TCP_SKB_CB(tp->retransmit_skb_hint)->seq))
Ilpo Järvinen19b2b482007-03-28 12:06:37 -07001994 tp->retransmit_skb_hint = NULL;
Ilpo Järvinend8f4f222007-04-20 22:56:38 -07001995}
1996
Linus Torvalds1da177e2005-04-16 15:20:36 -07001997/* Mark head of queue up as lost. */
Ilpo Järvinenf885c5b2007-10-15 02:10:32 -07001998static void tcp_mark_head_lost(struct sock *sk, int packets)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001999{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002000 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002001 struct sk_buff *skb;
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08002002 int cnt;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002003
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08002004 BUG_TRAP(packets <= tp->packets_out);
2005 if (tp->lost_skb_hint) {
2006 skb = tp->lost_skb_hint;
2007 cnt = tp->lost_cnt_hint;
2008 } else {
David S. Millerfe067e82007-03-07 12:12:44 -08002009 skb = tcp_write_queue_head(sk);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08002010 cnt = 0;
2011 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002012
David S. Millerfe067e82007-03-07 12:12:44 -08002013 tcp_for_write_queue_from(skb, sk) {
2014 if (skb == tcp_send_head(sk))
2015 break;
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08002016 /* TODO: do this better */
2017 /* this is not the most efficient way to do this... */
2018 tp->lost_skb_hint = skb;
2019 tp->lost_cnt_hint = cnt;
2020 cnt += tcp_skb_pcount(skb);
Ilpo Järvinenf885c5b2007-10-15 02:10:32 -07002021 if (cnt > packets || after(TCP_SKB_CB(skb)->end_seq, tp->high_seq))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002022 break;
Ilpo Järvinen3eec0042007-10-11 17:33:11 -07002023 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_SACKED_ACKED|TCPCB_LOST))) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002024 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
2025 tp->lost_out += tcp_skb_pcount(skb);
Ilpo Järvinend8f4f222007-04-20 22:56:38 -07002026 tcp_verify_retransmit_hint(tp, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002027 }
2028 }
Ilpo Järvinen005903b2007-08-09 14:44:16 +03002029 tcp_verify_left_out(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002030}
2031
2032/* Account newly detected lost packet(s) */
2033
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002034static void tcp_update_scoreboard(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002035{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002036 struct tcp_sock *tp = tcp_sk(sk);
2037
Ilpo Järvinene60402d2007-08-09 15:14:46 +03002038 if (tcp_is_fack(tp)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002039 int lost = tp->fackets_out - tp->reordering;
2040 if (lost <= 0)
2041 lost = 1;
Ilpo Järvinenf885c5b2007-10-15 02:10:32 -07002042 tcp_mark_head_lost(sk, lost);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002043 } else {
Ilpo Järvinenf885c5b2007-10-15 02:10:32 -07002044 tcp_mark_head_lost(sk, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002045 }
2046
2047 /* New heuristics: it is possible only after we switched
2048 * to restart timer each time when something is ACKed.
2049 * Hence, we can detect timed out packets during fast
2050 * retransmit without falling to slow start.
2051 */
Ilpo Järvinene60402d2007-08-09 15:14:46 +03002052 if (!tcp_is_reno(tp) && tcp_head_timedout(sk)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002053 struct sk_buff *skb;
2054
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08002055 skb = tp->scoreboard_skb_hint ? tp->scoreboard_skb_hint
David S. Millerfe067e82007-03-07 12:12:44 -08002056 : tcp_write_queue_head(sk);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08002057
David S. Millerfe067e82007-03-07 12:12:44 -08002058 tcp_for_write_queue_from(skb, sk) {
2059 if (skb == tcp_send_head(sk))
2060 break;
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08002061 if (!tcp_skb_timedout(sk, skb))
2062 break;
2063
2064 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002065 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
2066 tp->lost_out += tcp_skb_pcount(skb);
Ilpo Järvinend8f4f222007-04-20 22:56:38 -07002067 tcp_verify_retransmit_hint(tp, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002068 }
2069 }
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08002070
2071 tp->scoreboard_skb_hint = skb;
2072
Ilpo Järvinen005903b2007-08-09 14:44:16 +03002073 tcp_verify_left_out(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002074 }
2075}
2076
2077/* CWND moderation, preventing bursts due to too big ACKs
2078 * in dubious situations.
2079 */
2080static inline void tcp_moderate_cwnd(struct tcp_sock *tp)
2081{
2082 tp->snd_cwnd = min(tp->snd_cwnd,
2083 tcp_packets_in_flight(tp)+tcp_max_burst(tp));
2084 tp->snd_cwnd_stamp = tcp_time_stamp;
2085}
2086
Stephen Hemminger72dc5b92006-06-05 17:30:08 -07002087/* Lower bound on congestion window is slow start threshold
2088 * unless congestion avoidance choice decides to overide it.
2089 */
2090static inline u32 tcp_cwnd_min(const struct sock *sk)
2091{
2092 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
2093
2094 return ca_ops->min_cwnd ? ca_ops->min_cwnd(sk) : tcp_sk(sk)->snd_ssthresh;
2095}
2096
Linus Torvalds1da177e2005-04-16 15:20:36 -07002097/* Decrease cwnd each second ack. */
Ilpo Järvinen1e757f92007-07-30 19:48:37 -07002098static void tcp_cwnd_down(struct sock *sk, int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002099{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002100 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002101 int decr = tp->snd_cwnd_cnt + 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002102
Ilpo Järvinen49ff4bb2007-08-02 19:47:59 -07002103 if ((flag&(FLAG_ANY_PROGRESS|FLAG_DSACKING_ACK)) ||
Ilpo Järvinene60402d2007-08-09 15:14:46 +03002104 (tcp_is_reno(tp) && !(flag&FLAG_NOT_DUP))) {
Ilpo Järvinen1e757f92007-07-30 19:48:37 -07002105 tp->snd_cwnd_cnt = decr&1;
2106 decr >>= 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002107
Ilpo Järvinen1e757f92007-07-30 19:48:37 -07002108 if (decr && tp->snd_cwnd > tcp_cwnd_min(sk))
2109 tp->snd_cwnd -= decr;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002110
Ilpo Järvinen1e757f92007-07-30 19:48:37 -07002111 tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp)+1);
2112 tp->snd_cwnd_stamp = tcp_time_stamp;
2113 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002114}
2115
2116/* Nothing was retransmitted or returned timestamp is less
2117 * than timestamp of the first retransmission.
2118 */
2119static inline int tcp_packet_delayed(struct tcp_sock *tp)
2120{
2121 return !tp->retrans_stamp ||
2122 (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
2123 (__s32)(tp->rx_opt.rcv_tsecr - tp->retrans_stamp) < 0);
2124}
2125
2126/* Undo procedures. */
2127
2128#if FASTRETRANS_DEBUG > 1
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002129static void DBGUNDO(struct sock *sk, const char *msg)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002130{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002131 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002132 struct inet_sock *inet = inet_sk(sk);
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002133
Linus Torvalds1da177e2005-04-16 15:20:36 -07002134 printk(KERN_DEBUG "Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n",
2135 msg,
2136 NIPQUAD(inet->daddr), ntohs(inet->dport),
Ilpo Järvinen83ae4082007-08-09 14:37:30 +03002137 tp->snd_cwnd, tcp_left_out(tp),
Linus Torvalds1da177e2005-04-16 15:20:36 -07002138 tp->snd_ssthresh, tp->prior_ssthresh,
2139 tp->packets_out);
2140}
2141#else
2142#define DBGUNDO(x...) do { } while (0)
2143#endif
2144
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002145static void tcp_undo_cwr(struct sock *sk, const int undo)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002146{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002147 struct tcp_sock *tp = tcp_sk(sk);
2148
Linus Torvalds1da177e2005-04-16 15:20:36 -07002149 if (tp->prior_ssthresh) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002150 const struct inet_connection_sock *icsk = inet_csk(sk);
2151
2152 if (icsk->icsk_ca_ops->undo_cwnd)
2153 tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002154 else
2155 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh<<1);
2156
2157 if (undo && tp->prior_ssthresh > tp->snd_ssthresh) {
2158 tp->snd_ssthresh = tp->prior_ssthresh;
2159 TCP_ECN_withdraw_cwr(tp);
2160 }
2161 } else {
2162 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh);
2163 }
2164 tcp_moderate_cwnd(tp);
2165 tp->snd_cwnd_stamp = tcp_time_stamp;
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08002166
2167 /* There is something screwy going on with the retrans hints after
2168 an undo */
Ilpo Järvinen5af4ec22007-09-20 11:30:48 -07002169 tcp_clear_all_retrans_hints(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002170}
2171
2172static inline int tcp_may_undo(struct tcp_sock *tp)
2173{
2174 return tp->undo_marker &&
2175 (!tp->undo_retrans || tcp_packet_delayed(tp));
2176}
2177
2178/* People celebrate: "We love our President!" */
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002179static int tcp_try_undo_recovery(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002180{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002181 struct tcp_sock *tp = tcp_sk(sk);
2182
Linus Torvalds1da177e2005-04-16 15:20:36 -07002183 if (tcp_may_undo(tp)) {
2184 /* Happy end! We did not retransmit anything
2185 * or our original transmission succeeded.
2186 */
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002187 DBGUNDO(sk, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans");
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002188 tcp_undo_cwr(sk, 1);
2189 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002190 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO);
2191 else
2192 NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO);
2193 tp->undo_marker = 0;
2194 }
Ilpo Järvinene60402d2007-08-09 15:14:46 +03002195 if (tp->snd_una == tp->high_seq && tcp_is_reno(tp)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002196 /* Hold old state until something *above* high_seq
2197 * is ACKed. For Reno it is MUST to prevent false
2198 * fast retransmits (RFC2582). SACK TCP is safe. */
2199 tcp_moderate_cwnd(tp);
2200 return 1;
2201 }
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002202 tcp_set_ca_state(sk, TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002203 return 0;
2204}
2205
2206/* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002207static void tcp_try_undo_dsack(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002208{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002209 struct tcp_sock *tp = tcp_sk(sk);
2210
Linus Torvalds1da177e2005-04-16 15:20:36 -07002211 if (tp->undo_marker && !tp->undo_retrans) {
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002212 DBGUNDO(sk, "D-SACK");
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002213 tcp_undo_cwr(sk, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002214 tp->undo_marker = 0;
2215 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO);
2216 }
2217}
2218
2219/* Undo during fast recovery after partial ACK. */
2220
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002221static int tcp_try_undo_partial(struct sock *sk, int acked)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002222{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002223 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002224 /* Partial ACK arrived. Force Hoe's retransmit. */
Ilpo Järvinene60402d2007-08-09 15:14:46 +03002225 int failed = tcp_is_reno(tp) || tp->fackets_out>tp->reordering;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002226
2227 if (tcp_may_undo(tp)) {
2228 /* Plain luck! Hole if filled with delayed
2229 * packet, rather than with a retransmit.
2230 */
2231 if (tp->retrans_out == 0)
2232 tp->retrans_stamp = 0;
2233
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002234 tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002235
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002236 DBGUNDO(sk, "Hoe");
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002237 tcp_undo_cwr(sk, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002238 NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO);
2239
2240 /* So... Do not make Hoe's retransmit yet.
2241 * If the first packet was delayed, the rest
2242 * ones are most probably delayed as well.
2243 */
2244 failed = 0;
2245 }
2246 return failed;
2247}
2248
2249/* Undo during loss recovery after partial ACK. */
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002250static int tcp_try_undo_loss(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002251{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002252 struct tcp_sock *tp = tcp_sk(sk);
2253
Linus Torvalds1da177e2005-04-16 15:20:36 -07002254 if (tcp_may_undo(tp)) {
2255 struct sk_buff *skb;
David S. Millerfe067e82007-03-07 12:12:44 -08002256 tcp_for_write_queue(skb, sk) {
2257 if (skb == tcp_send_head(sk))
2258 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002259 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
2260 }
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08002261
Ilpo Järvinen5af4ec22007-09-20 11:30:48 -07002262 tcp_clear_all_retrans_hints(tp);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08002263
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002264 DBGUNDO(sk, "partial loss");
Linus Torvalds1da177e2005-04-16 15:20:36 -07002265 tp->lost_out = 0;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002266 tcp_undo_cwr(sk, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002267 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002268 inet_csk(sk)->icsk_retransmits = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002269 tp->undo_marker = 0;
Ilpo Järvinene60402d2007-08-09 15:14:46 +03002270 if (tcp_is_sack(tp))
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002271 tcp_set_ca_state(sk, TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002272 return 1;
2273 }
2274 return 0;
2275}
2276
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002277static inline void tcp_complete_cwr(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002278{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002279 struct tcp_sock *tp = tcp_sk(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -07002280 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002281 tp->snd_cwnd_stamp = tcp_time_stamp;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002282 tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002283}
2284
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002285static void tcp_try_to_open(struct sock *sk, int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002286{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002287 struct tcp_sock *tp = tcp_sk(sk);
2288
Ilpo Järvinen86426c22007-08-09 14:45:17 +03002289 tcp_verify_left_out(tp);
2290
Linus Torvalds1da177e2005-04-16 15:20:36 -07002291 if (tp->retrans_out == 0)
2292 tp->retrans_stamp = 0;
2293
2294 if (flag&FLAG_ECE)
Ilpo Järvinen3cfe3ba2007-02-27 10:09:49 -08002295 tcp_enter_cwr(sk, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002296
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002297 if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002298 int state = TCP_CA_Open;
2299
Ilpo Järvinend02596e2007-07-07 13:39:02 +03002300 if (tcp_left_out(tp) || tp->retrans_out || tp->undo_marker)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002301 state = TCP_CA_Disorder;
2302
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002303 if (inet_csk(sk)->icsk_ca_state != state) {
2304 tcp_set_ca_state(sk, state);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002305 tp->high_seq = tp->snd_nxt;
2306 }
2307 tcp_moderate_cwnd(tp);
2308 } else {
Ilpo Järvinen1e757f92007-07-30 19:48:37 -07002309 tcp_cwnd_down(sk, flag);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002310 }
2311}
2312
John Heffner5d424d52006-03-20 17:53:41 -08002313static void tcp_mtup_probe_failed(struct sock *sk)
2314{
2315 struct inet_connection_sock *icsk = inet_csk(sk);
2316
2317 icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1;
2318 icsk->icsk_mtup.probe_size = 0;
2319}
2320
2321static void tcp_mtup_probe_success(struct sock *sk, struct sk_buff *skb)
2322{
2323 struct tcp_sock *tp = tcp_sk(sk);
2324 struct inet_connection_sock *icsk = inet_csk(sk);
2325
2326 /* FIXME: breaks with very large cwnd */
2327 tp->prior_ssthresh = tcp_current_ssthresh(sk);
2328 tp->snd_cwnd = tp->snd_cwnd *
2329 tcp_mss_to_mtu(sk, tp->mss_cache) /
2330 icsk->icsk_mtup.probe_size;
2331 tp->snd_cwnd_cnt = 0;
2332 tp->snd_cwnd_stamp = tcp_time_stamp;
2333 tp->rcv_ssthresh = tcp_current_ssthresh(sk);
2334
2335 icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size;
2336 icsk->icsk_mtup.probe_size = 0;
2337 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
2338}
2339
2340
Linus Torvalds1da177e2005-04-16 15:20:36 -07002341/* Process an event, which can update packets-in-flight not trivially.
2342 * Main goal of this function is to calculate new estimate for left_out,
2343 * taking into account both packets sitting in receiver's buffer and
2344 * packets lost by network.
2345 *
2346 * Besides that it does CWND reduction, when packet loss is detected
2347 * and changes state of machine.
2348 *
2349 * It does _not_ decide what to send, it is made in function
2350 * tcp_xmit_retransmit_queue().
2351 */
2352static void
Ilpo Järvinen1b6d427b2007-08-09 14:53:36 +03002353tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002354{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002355 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002356 struct tcp_sock *tp = tcp_sk(sk);
Ilpo Järvinen2e605292007-08-02 19:46:58 -07002357 int is_dupack = !(flag&(FLAG_SND_UNA_ADVANCED|FLAG_NOT_DUP));
2358 int do_lost = is_dupack || ((flag&FLAG_DATA_SACKED) &&
2359 (tp->fackets_out > tp->reordering));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002360
2361 /* Some technical things:
2362 * 1. Reno does not count dupacks (sacked_out) automatically. */
2363 if (!tp->packets_out)
2364 tp->sacked_out = 0;
Ilpo Järvinen91fed7a2007-10-09 01:24:15 -07002365
2366 if (WARN_ON(!tp->sacked_out && tp->fackets_out))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002367 tp->fackets_out = 0;
2368
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09002369 /* Now state machine starts.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002370 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
2371 if (flag&FLAG_ECE)
2372 tp->prior_ssthresh = 0;
2373
2374 /* B. In all the states check for reneging SACKs. */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002375 if (tp->sacked_out && tcp_check_sack_reneging(sk))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002376 return;
2377
2378 /* C. Process data loss notification, provided it is valid. */
2379 if ((flag&FLAG_DATA_LOST) &&
2380 before(tp->snd_una, tp->high_seq) &&
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002381 icsk->icsk_ca_state != TCP_CA_Open &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07002382 tp->fackets_out > tp->reordering) {
Ilpo Järvinenf885c5b2007-10-15 02:10:32 -07002383 tcp_mark_head_lost(sk, tp->fackets_out - tp->reordering);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002384 NET_INC_STATS_BH(LINUX_MIB_TCPLOSS);
2385 }
2386
Ilpo Järvinen005903b2007-08-09 14:44:16 +03002387 /* D. Check consistency of the current state. */
2388 tcp_verify_left_out(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002389
2390 /* E. Check state exit conditions. State can be terminated
2391 * when high_seq is ACKed. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002392 if (icsk->icsk_ca_state == TCP_CA_Open) {
Ilpo Järvinen7b0eb222007-02-21 23:03:35 -08002393 BUG_TRAP(tp->retrans_out == 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002394 tp->retrans_stamp = 0;
2395 } else if (!before(tp->snd_una, tp->high_seq)) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002396 switch (icsk->icsk_ca_state) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002397 case TCP_CA_Loss:
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002398 icsk->icsk_retransmits = 0;
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002399 if (tcp_try_undo_recovery(sk))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002400 return;
2401 break;
2402
2403 case TCP_CA_CWR:
2404 /* CWR is to be held something *above* high_seq
2405 * is ACKed for CWR bit to reach receiver. */
2406 if (tp->snd_una != tp->high_seq) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002407 tcp_complete_cwr(sk);
2408 tcp_set_ca_state(sk, TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002409 }
2410 break;
2411
2412 case TCP_CA_Disorder:
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002413 tcp_try_undo_dsack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002414 if (!tp->undo_marker ||
2415 /* For SACK case do not Open to allow to undo
2416 * catching for all duplicate ACKs. */
Ilpo Järvinene60402d2007-08-09 15:14:46 +03002417 tcp_is_reno(tp) || tp->snd_una != tp->high_seq) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002418 tp->undo_marker = 0;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002419 tcp_set_ca_state(sk, TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002420 }
2421 break;
2422
2423 case TCP_CA_Recovery:
Ilpo Järvinene60402d2007-08-09 15:14:46 +03002424 if (tcp_is_reno(tp))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002425 tcp_reset_reno_sack(tp);
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002426 if (tcp_try_undo_recovery(sk))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002427 return;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002428 tcp_complete_cwr(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002429 break;
2430 }
2431 }
2432
2433 /* F. Process state. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002434 switch (icsk->icsk_ca_state) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002435 case TCP_CA_Recovery:
Ilpo Järvinen2e605292007-08-02 19:46:58 -07002436 if (!(flag & FLAG_SND_UNA_ADVANCED)) {
Ilpo Järvinene60402d2007-08-09 15:14:46 +03002437 if (tcp_is_reno(tp) && is_dupack)
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002438 tcp_add_reno_sack(sk);
Ilpo Järvinen1b6d427b2007-08-09 14:53:36 +03002439 } else
2440 do_lost = tcp_try_undo_partial(sk, pkts_acked);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002441 break;
2442 case TCP_CA_Loss:
2443 if (flag&FLAG_DATA_ACKED)
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002444 icsk->icsk_retransmits = 0;
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002445 if (!tcp_try_undo_loss(sk)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002446 tcp_moderate_cwnd(tp);
2447 tcp_xmit_retransmit_queue(sk);
2448 return;
2449 }
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002450 if (icsk->icsk_ca_state != TCP_CA_Open)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002451 return;
2452 /* Loss is undone; fall through to processing in Open state. */
2453 default:
Ilpo Järvinene60402d2007-08-09 15:14:46 +03002454 if (tcp_is_reno(tp)) {
Ilpo Järvinen2e605292007-08-02 19:46:58 -07002455 if (flag & FLAG_SND_UNA_ADVANCED)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002456 tcp_reset_reno_sack(tp);
2457 if (is_dupack)
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002458 tcp_add_reno_sack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002459 }
2460
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002461 if (icsk->icsk_ca_state == TCP_CA_Disorder)
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002462 tcp_try_undo_dsack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002463
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002464 if (!tcp_time_to_recover(sk)) {
2465 tcp_try_to_open(sk, flag);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002466 return;
2467 }
2468
John Heffner5d424d52006-03-20 17:53:41 -08002469 /* MTU probe failure: don't reduce cwnd */
2470 if (icsk->icsk_ca_state < TCP_CA_CWR &&
2471 icsk->icsk_mtup.probe_size &&
John Heffner0e7b1362006-03-20 21:32:58 -08002472 tp->snd_una == tp->mtu_probe.probe_seq_start) {
John Heffner5d424d52006-03-20 17:53:41 -08002473 tcp_mtup_probe_failed(sk);
2474 /* Restores the reduction we did in tcp_mtup_probe() */
2475 tp->snd_cwnd++;
2476 tcp_simple_retransmit(sk);
2477 return;
2478 }
2479
Linus Torvalds1da177e2005-04-16 15:20:36 -07002480 /* Otherwise enter Recovery state */
2481
Ilpo Järvinene60402d2007-08-09 15:14:46 +03002482 if (tcp_is_reno(tp))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002483 NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY);
2484 else
2485 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY);
2486
2487 tp->high_seq = tp->snd_nxt;
2488 tp->prior_ssthresh = 0;
2489 tp->undo_marker = tp->snd_una;
2490 tp->undo_retrans = tp->retrans_out;
2491
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002492 if (icsk->icsk_ca_state < TCP_CA_CWR) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002493 if (!(flag&FLAG_ECE))
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002494 tp->prior_ssthresh = tcp_current_ssthresh(sk);
2495 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002496 TCP_ECN_queue_cwr(tp);
2497 }
2498
Stephen Hemminger9772efb2005-11-10 17:09:53 -08002499 tp->bytes_acked = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002500 tp->snd_cwnd_cnt = 0;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002501 tcp_set_ca_state(sk, TCP_CA_Recovery);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002502 }
2503
Ilpo Järvinen2e605292007-08-02 19:46:58 -07002504 if (do_lost || tcp_head_timedout(sk))
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002505 tcp_update_scoreboard(sk);
Ilpo Järvinen1e757f92007-07-30 19:48:37 -07002506 tcp_cwnd_down(sk, flag);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002507 tcp_xmit_retransmit_queue(sk);
2508}
2509
2510/* Read draft-ietf-tcplw-high-performance before mucking
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08002511 * with this code. (Supersedes RFC1323)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002512 */
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002513static void tcp_ack_saw_tstamp(struct sock *sk, int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002514{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002515 /* RTTM Rule: A TSecr value received in a segment is used to
2516 * update the averaged RTT measurement only if the segment
2517 * acknowledges some new data, i.e., only if it advances the
2518 * left edge of the send window.
2519 *
2520 * See draft-ietf-tcplw-high-performance-00, section 3.3.
2521 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
2522 *
2523 * Changed: reset backoff as soon as we see the first valid sample.
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08002524 * If we do not, we get strongly overestimated rto. With timestamps
Linus Torvalds1da177e2005-04-16 15:20:36 -07002525 * samples are accepted even from very old segments: f.e., when rtt=1
2526 * increases to 8, we retransmit 5 times and after 8 seconds delayed
2527 * answer arrives rto becomes 120 seconds! If at least one of segments
2528 * in window is lost... Voila. --ANK (010210)
2529 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002530 struct tcp_sock *tp = tcp_sk(sk);
2531 const __u32 seq_rtt = tcp_time_stamp - tp->rx_opt.rcv_tsecr;
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002532 tcp_rtt_estimator(sk, seq_rtt);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002533 tcp_set_rto(sk);
2534 inet_csk(sk)->icsk_backoff = 0;
2535 tcp_bound_rto(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002536}
2537
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002538static void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002539{
2540 /* We don't have a timestamp. Can only use
2541 * packets that are not retransmitted to determine
2542 * rtt estimates. Also, we must not reset the
2543 * backoff for rto until we get a non-retransmitted
2544 * packet. This allows us to deal with a situation
2545 * where the network delay has increased suddenly.
2546 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
2547 */
2548
2549 if (flag & FLAG_RETRANS_DATA_ACKED)
2550 return;
2551
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002552 tcp_rtt_estimator(sk, seq_rtt);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002553 tcp_set_rto(sk);
2554 inet_csk(sk)->icsk_backoff = 0;
2555 tcp_bound_rto(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002556}
2557
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002558static inline void tcp_ack_update_rtt(struct sock *sk, const int flag,
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002559 const s32 seq_rtt)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002560{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002561 const struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002562 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
2563 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002564 tcp_ack_saw_tstamp(sk, flag);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002565 else if (seq_rtt >= 0)
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002566 tcp_ack_no_tstamp(sk, seq_rtt, flag);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002567}
2568
Stephen Hemminger16751342007-07-16 18:35:52 -07002569static void tcp_cong_avoid(struct sock *sk, u32 ack,
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08002570 u32 in_flight, int good)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002571{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002572 const struct inet_connection_sock *icsk = inet_csk(sk);
Stephen Hemminger16751342007-07-16 18:35:52 -07002573 icsk->icsk_ca_ops->cong_avoid(sk, ack, in_flight, good);
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002574 tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002575}
2576
Linus Torvalds1da177e2005-04-16 15:20:36 -07002577/* Restart timer after forward progress on connection.
2578 * RFC2988 recommends to restart timer to now+rto.
2579 */
Ilpo Järvinen6728e7d2007-08-24 22:53:26 -07002580static void tcp_rearm_rto(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002581{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002582 struct tcp_sock *tp = tcp_sk(sk);
2583
Linus Torvalds1da177e2005-04-16 15:20:36 -07002584 if (!tp->packets_out) {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002585 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002586 } else {
Arnaldo Carvalho de Melo3f421ba2005-08-09 20:11:08 -07002587 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002588 }
2589}
2590
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07002591/* If we get here, the whole TSO packet has not been acked. */
Ilpo Järvinen13fcf852007-10-09 01:28:45 -07002592static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002593{
2594 struct tcp_sock *tp = tcp_sk(sk);
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07002595 u32 packets_acked;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002596
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07002597 BUG_ON(!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002598
2599 packets_acked = tcp_skb_pcount(skb);
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07002600 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002601 return 0;
2602 packets_acked -= tcp_skb_pcount(skb);
2603
2604 if (packets_acked) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002605 BUG_ON(tcp_skb_pcount(skb) == 0);
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07002606 BUG_ON(!before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002607 }
2608
Ilpo Järvinen13fcf852007-10-09 01:28:45 -07002609 return packets_acked;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002610}
2611
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07002612/* Remove acknowledged frames from the retransmission queue. If our packet
2613 * is before the ack sequence we can discard it as it's confirmed to have
2614 * arrived at the other end.
2615 */
2616static int tcp_clean_rtx_queue(struct sock *sk, s32 *seq_rtt_p)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002617{
2618 struct tcp_sock *tp = tcp_sk(sk);
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002619 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002620 struct sk_buff *skb;
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07002621 u32 now = tcp_time_stamp;
Ilpo Järvinen13fcf852007-10-09 01:28:45 -07002622 int fully_acked = 1;
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07002623 int flag = 0;
Ilpo Järvinen64182042007-05-31 21:37:55 -07002624 int prior_packets = tp->packets_out;
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07002625 s32 seq_rtt = -1;
Ilpo Järvinenb9ce2042007-06-15 15:08:43 -07002626 ktime_t last_ackt = net_invalid_timestamp();
Linus Torvalds1da177e2005-04-16 15:20:36 -07002627
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07002628 while ((skb = tcp_write_queue_head(sk)) && skb != tcp_send_head(sk)) {
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09002629 struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
Ilpo Järvinen13fcf852007-10-09 01:28:45 -07002630 u32 end_seq;
2631 u32 packets_acked;
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07002632 u8 sacked = scb->sacked;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002633
Linus Torvalds1da177e2005-04-16 15:20:36 -07002634 if (after(scb->end_seq, tp->snd_una)) {
Ilpo Järvinen13fcf852007-10-09 01:28:45 -07002635 if (tcp_skb_pcount(skb) == 1 ||
2636 !after(tp->snd_una, scb->seq))
2637 break;
2638
2639 packets_acked = tcp_tso_acked(sk, skb);
2640 if (!packets_acked)
2641 break;
2642
2643 fully_acked = 0;
2644 end_seq = tp->snd_una;
2645 } else {
2646 packets_acked = tcp_skb_pcount(skb);
2647 end_seq = scb->end_seq;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002648 }
2649
John Heffner5d424d52006-03-20 17:53:41 -08002650 /* MTU probing checks */
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07002651 if (fully_acked && icsk->icsk_mtup.probe_size &&
2652 !after(tp->mtu_probe.probe_seq_end, scb->end_seq)) {
2653 tcp_mtup_probe_success(sk, skb);
John Heffner5d424d52006-03-20 17:53:41 -08002654 }
2655
Linus Torvalds1da177e2005-04-16 15:20:36 -07002656 if (sacked) {
2657 if (sacked & TCPCB_RETRANS) {
Stephen Hemminger2de979b2007-03-08 20:45:19 -08002658 if (sacked & TCPCB_SACKED_RETRANS)
Ilpo Järvinen13fcf852007-10-09 01:28:45 -07002659 tp->retrans_out -= packets_acked;
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07002660 flag |= FLAG_RETRANS_DATA_ACKED;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002661 seq_rtt = -1;
Ilpo Järvinen009a2e32007-09-20 11:34:38 -07002662 if ((flag & FLAG_DATA_ACKED) ||
2663 (packets_acked > 1))
2664 flag |= FLAG_NONHEAD_RETRANS_ACKED;
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002665 } else if (seq_rtt < 0) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002666 seq_rtt = now - scb->when;
Ilpo Järvinen13fcf852007-10-09 01:28:45 -07002667 if (fully_acked)
2668 last_ackt = skb->tstamp;
Patrick McHardya61bbcf2005-08-14 17:24:31 -07002669 }
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07002670
Linus Torvalds1da177e2005-04-16 15:20:36 -07002671 if (sacked & TCPCB_SACKED_ACKED)
Ilpo Järvinen13fcf852007-10-09 01:28:45 -07002672 tp->sacked_out -= packets_acked;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002673 if (sacked & TCPCB_LOST)
Ilpo Järvinen13fcf852007-10-09 01:28:45 -07002674 tp->lost_out -= packets_acked;
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07002675
2676 if ((sacked & TCPCB_URG) && tp->urg_mode &&
2677 !before(end_seq, tp->snd_up))
2678 tp->urg_mode = 0;
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002679 } else if (seq_rtt < 0) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002680 seq_rtt = now - scb->when;
Ilpo Järvinen13fcf852007-10-09 01:28:45 -07002681 if (fully_acked)
2682 last_ackt = skb->tstamp;
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002683 }
Ilpo Järvinen13fcf852007-10-09 01:28:45 -07002684 tp->packets_out -= packets_acked;
2685
Ilpo Järvinen009a2e32007-09-20 11:34:38 -07002686 /* Initial outgoing SYN's get put onto the write_queue
2687 * just like anything else we transmit. It is not
2688 * true data, and if we misinform our callers that
2689 * this ACK acks real data, we will erroneously exit
2690 * connection startup slow start one packet too
2691 * quickly. This is severely frowned upon behavior.
2692 */
2693 if (!(scb->flags & TCPCB_FLAG_SYN)) {
2694 flag |= FLAG_DATA_ACKED;
2695 } else {
2696 flag |= FLAG_SYN_ACKED;
2697 tp->retrans_stamp = 0;
2698 }
2699
Ilpo Järvinen13fcf852007-10-09 01:28:45 -07002700 if (!fully_acked)
2701 break;
2702
David S. Millerfe067e82007-03-07 12:12:44 -08002703 tcp_unlink_write_queue(skb, sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002704 sk_stream_free_skb(sk, skb);
Ilpo Järvinen5af4ec22007-09-20 11:30:48 -07002705 tcp_clear_all_retrans_hints(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002706 }
2707
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07002708 if (flag & FLAG_ACKED) {
Ilpo Järvinen64182042007-05-31 21:37:55 -07002709 u32 pkts_acked = prior_packets - tp->packets_out;
Stephen Hemminger164891a2007-04-23 22:26:16 -07002710 const struct tcp_congestion_ops *ca_ops
2711 = inet_csk(sk)->icsk_ca_ops;
2712
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07002713 tcp_ack_update_rtt(sk, flag, seq_rtt);
Ilpo Järvinen6728e7d2007-08-24 22:53:26 -07002714 tcp_rearm_rto(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -07002715
Ilpo Järvinen91fed7a2007-10-09 01:24:15 -07002716 tp->fackets_out -= min(pkts_acked, tp->fackets_out);
Ilpo Järvinen13fcf852007-10-09 01:28:45 -07002717 /* hint's skb might be NULL but we don't need to care */
2718 tp->fastpath_cnt_hint -= min_t(u32, pkts_acked,
2719 tp->fastpath_cnt_hint);
Ilpo Järvinene60402d2007-08-09 15:14:46 +03002720 if (tcp_is_reno(tp))
Ilpo Järvinen1b6d427b2007-08-09 14:53:36 +03002721 tcp_remove_reno_sacks(sk, pkts_acked);
2722
Stephen Hemminger30cfd0b2007-07-25 23:49:34 -07002723 if (ca_ops->pkts_acked) {
2724 s32 rtt_us = -1;
Ilpo Järvinenb9ce2042007-06-15 15:08:43 -07002725
Stephen Hemminger30cfd0b2007-07-25 23:49:34 -07002726 /* Is the ACK triggering packet unambiguous? */
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07002727 if (!(flag & FLAG_RETRANS_DATA_ACKED)) {
Stephen Hemminger30cfd0b2007-07-25 23:49:34 -07002728 /* High resolution needed and available? */
2729 if (ca_ops->flags & TCP_CONG_RTT_STAMP &&
2730 !ktime_equal(last_ackt,
2731 net_invalid_timestamp()))
2732 rtt_us = ktime_us_delta(ktime_get_real(),
2733 last_ackt);
2734 else if (seq_rtt > 0)
2735 rtt_us = jiffies_to_usecs(seq_rtt);
2736 }
2737
2738 ca_ops->pkts_acked(sk, pkts_acked, rtt_us);
2739 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002740 }
2741
2742#if FASTRETRANS_DEBUG > 0
2743 BUG_TRAP((int)tp->sacked_out >= 0);
2744 BUG_TRAP((int)tp->lost_out >= 0);
2745 BUG_TRAP((int)tp->retrans_out >= 0);
Ilpo Järvinene60402d2007-08-09 15:14:46 +03002746 if (!tp->packets_out && tcp_is_sack(tp)) {
Stephen Hemmingercfcabdc2007-10-09 01:59:42 -07002747 icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002748 if (tp->lost_out) {
2749 printk(KERN_DEBUG "Leak l=%u %d\n",
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002750 tp->lost_out, icsk->icsk_ca_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002751 tp->lost_out = 0;
2752 }
2753 if (tp->sacked_out) {
2754 printk(KERN_DEBUG "Leak s=%u %d\n",
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002755 tp->sacked_out, icsk->icsk_ca_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002756 tp->sacked_out = 0;
2757 }
2758 if (tp->retrans_out) {
2759 printk(KERN_DEBUG "Leak r=%u %d\n",
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002760 tp->retrans_out, icsk->icsk_ca_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002761 tp->retrans_out = 0;
2762 }
2763 }
2764#endif
2765 *seq_rtt_p = seq_rtt;
Ilpo Järvinen7c46a032007-09-20 11:33:43 -07002766 return flag;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002767}
2768
2769static void tcp_ack_probe(struct sock *sk)
2770{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002771 const struct tcp_sock *tp = tcp_sk(sk);
2772 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002773
2774 /* Was it a usable window open? */
2775
David S. Millerfe067e82007-03-07 12:12:44 -08002776 if (!after(TCP_SKB_CB(tcp_send_head(sk))->end_seq,
Linus Torvalds1da177e2005-04-16 15:20:36 -07002777 tp->snd_una + tp->snd_wnd)) {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002778 icsk->icsk_backoff = 0;
2779 inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002780 /* Socket must be waked up by subsequent tcp_data_snd_check().
2781 * This function is not for random using!
2782 */
2783 } else {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002784 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
Arnaldo Carvalho de Melo3f421ba2005-08-09 20:11:08 -07002785 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
2786 TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002787 }
2788}
2789
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002790static inline int tcp_ack_is_dubious(const struct sock *sk, const int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002791{
2792 return (!(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) ||
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002793 inet_csk(sk)->icsk_ca_state != TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002794}
2795
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002796static inline int tcp_may_raise_cwnd(const struct sock *sk, const int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002797{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002798 const struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002799 return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) &&
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002800 !((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_Recovery | TCPF_CA_CWR));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002801}
2802
2803/* Check that window update is acceptable.
2804 * The function assumes that snd_una<=ack<=snd_next.
2805 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002806static inline int tcp_may_update_window(const struct tcp_sock *tp, const u32 ack,
2807 const u32 ack_seq, const u32 nwin)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002808{
2809 return (after(ack, tp->snd_una) ||
2810 after(ack_seq, tp->snd_wl1) ||
2811 (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd));
2812}
2813
2814/* Update our send window.
2815 *
2816 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
2817 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
2818 */
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002819static int tcp_ack_update_window(struct sock *sk, struct sk_buff *skb, u32 ack,
2820 u32 ack_seq)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002821{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002822 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002823 int flag = 0;
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -07002824 u32 nwin = ntohs(tcp_hdr(skb)->window);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002825
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -07002826 if (likely(!tcp_hdr(skb)->syn))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002827 nwin <<= tp->rx_opt.snd_wscale;
2828
2829 if (tcp_may_update_window(tp, ack, ack_seq, nwin)) {
2830 flag |= FLAG_WIN_UPDATE;
2831 tcp_update_wl(tp, ack, ack_seq);
2832
2833 if (tp->snd_wnd != nwin) {
2834 tp->snd_wnd = nwin;
2835
2836 /* Note, it is the only place, where
2837 * fast path is recovered for sending TCP.
2838 */
Herbert Xu2ad41062005-10-27 18:47:46 +10002839 tp->pred_flags = 0;
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07002840 tcp_fast_path_check(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002841
2842 if (nwin > tp->max_window) {
2843 tp->max_window = nwin;
Arnaldo Carvalho de Melod83d8462005-12-13 23:26:10 -08002844 tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002845 }
2846 }
2847 }
2848
2849 tp->snd_una = ack;
2850
2851 return flag;
2852}
2853
Ilpo Järvinen9ead9a12007-02-21 22:56:19 -08002854/* A very conservative spurious RTO response algorithm: reduce cwnd and
2855 * continue in congestion avoidance.
2856 */
2857static void tcp_conservative_spur_to_response(struct tcp_sock *tp)
2858{
2859 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
Ilpo Järvinenaa8b6a72007-02-21 23:06:03 -08002860 tp->snd_cwnd_cnt = 0;
Ilpo Järvinen16e90682007-10-11 17:32:31 -07002861 tp->bytes_acked = 0;
Ilpo Järvinen46323652007-05-19 13:56:23 -07002862 TCP_ECN_queue_cwr(tp);
Ilpo Järvinen9ead9a12007-02-21 22:56:19 -08002863 tcp_moderate_cwnd(tp);
2864}
2865
Ilpo Järvinen3cfe3ba2007-02-27 10:09:49 -08002866/* A conservative spurious RTO response algorithm: reduce cwnd using
2867 * rate halving and continue in congestion avoidance.
2868 */
2869static void tcp_ratehalving_spur_to_response(struct sock *sk)
2870{
Ilpo Järvinen3cfe3ba2007-02-27 10:09:49 -08002871 tcp_enter_cwr(sk, 0);
Ilpo Järvinen3cfe3ba2007-02-27 10:09:49 -08002872}
2873
Ilpo Järvinene317f6f2007-03-02 13:34:19 -08002874static void tcp_undo_spur_to_response(struct sock *sk, int flag)
Ilpo Järvinen3cfe3ba2007-02-27 10:09:49 -08002875{
Ilpo Järvinene317f6f2007-03-02 13:34:19 -08002876 if (flag&FLAG_ECE)
2877 tcp_ratehalving_spur_to_response(sk);
2878 else
2879 tcp_undo_cwr(sk, 1);
Ilpo Järvinen3cfe3ba2007-02-27 10:09:49 -08002880}
2881
Ilpo Järvinen30935cf2007-02-21 23:01:36 -08002882/* F-RTO spurious RTO detection algorithm (RFC4138)
2883 *
Ilpo Järvinen6408d202007-02-21 23:04:11 -08002884 * F-RTO affects during two new ACKs following RTO (well, almost, see inline
2885 * comments). State (ACK number) is kept in frto_counter. When ACK advances
2886 * window (but not to or beyond highest sequence sent before RTO):
Ilpo Järvinen30935cf2007-02-21 23:01:36 -08002887 * On First ACK, send two new segments out.
2888 * On Second ACK, RTO was likely spurious. Do spurious response (response
2889 * algorithm is not part of the F-RTO detection algorithm
2890 * given in RFC4138 but can be selected separately).
2891 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss
Ilpo Järvinend551e452007-04-30 00:42:20 -07002892 * and TCP falls back to conventional RTO recovery. F-RTO allows overriding
2893 * of Nagle, this is done using frto_counter states 2 and 3, when a new data
2894 * segment of any size sent during F-RTO, state 2 is upgraded to 3.
Ilpo Järvinen30935cf2007-02-21 23:01:36 -08002895 *
2896 * Rationale: if the RTO was spurious, new ACKs should arrive from the
2897 * original window even after we transmit two new data segments.
2898 *
Ilpo Järvinen4dc26652007-02-21 23:16:11 -08002899 * SACK version:
2900 * on first step, wait until first cumulative ACK arrives, then move to
2901 * the second step. In second step, the next ACK decides.
2902 *
Ilpo Järvinen30935cf2007-02-21 23:01:36 -08002903 * F-RTO is implemented (mainly) in four functions:
2904 * - tcp_use_frto() is used to determine if TCP is can use F-RTO
2905 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is
2906 * called when tcp_use_frto() showed green light
2907 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm
2908 * - tcp_enter_frto_loss() is called if there is not enough evidence
2909 * to prove that the RTO is indeed spurious. It transfers the control
2910 * from F-RTO to the conventional RTO recovery
2911 */
Ilpo Järvinen2e605292007-08-02 19:46:58 -07002912static int tcp_process_frto(struct sock *sk, int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002913{
2914 struct tcp_sock *tp = tcp_sk(sk);
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09002915
Ilpo Järvinen005903b2007-08-09 14:44:16 +03002916 tcp_verify_left_out(tp);
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09002917
Ilpo Järvinen7487c482007-02-21 23:02:30 -08002918 /* Duplicate the behavior from Loss state (fastretrans_alert) */
2919 if (flag&FLAG_DATA_ACKED)
2920 inet_csk(sk)->icsk_retransmits = 0;
2921
Ilpo Järvinen009a2e32007-09-20 11:34:38 -07002922 if ((flag & FLAG_NONHEAD_RETRANS_ACKED) ||
2923 ((tp->frto_counter >= 2) && (flag & FLAG_RETRANS_DATA_ACKED)))
2924 tp->undo_marker = 0;
2925
Ilpo Järvinen95c49222007-02-21 23:05:18 -08002926 if (!before(tp->snd_una, tp->frto_highmark)) {
Ilpo Järvinend551e452007-04-30 00:42:20 -07002927 tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 2 : 3), flag);
Ilpo Järvinen7c9a4a52007-02-21 23:08:34 -08002928 return 1;
Ilpo Järvinen95c49222007-02-21 23:05:18 -08002929 }
2930
Ilpo Järvinene60402d2007-08-09 15:14:46 +03002931 if (!IsSackFrto() || tcp_is_reno(tp)) {
Ilpo Järvinen4dc26652007-02-21 23:16:11 -08002932 /* RFC4138 shortcoming in step 2; should also have case c):
2933 * ACK isn't duplicate nor advances window, e.g., opposite dir
2934 * data, winupdate
2935 */
Ilpo Järvinen2e605292007-08-02 19:46:58 -07002936 if (!(flag&FLAG_ANY_PROGRESS) && (flag&FLAG_NOT_DUP))
Ilpo Järvinen4dc26652007-02-21 23:16:11 -08002937 return 1;
Ilpo Järvinen6408d202007-02-21 23:04:11 -08002938
Ilpo Järvinen4dc26652007-02-21 23:16:11 -08002939 if (!(flag&FLAG_DATA_ACKED)) {
2940 tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 0 : 3),
2941 flag);
2942 return 1;
2943 }
2944 } else {
2945 if (!(flag&FLAG_DATA_ACKED) && (tp->frto_counter == 1)) {
2946 /* Prevent sending of new data. */
2947 tp->snd_cwnd = min(tp->snd_cwnd,
2948 tcp_packets_in_flight(tp));
2949 return 1;
2950 }
2951
Ilpo Järvinend551e452007-04-30 00:42:20 -07002952 if ((tp->frto_counter >= 2) &&
Ilpo Järvinen4dc26652007-02-21 23:16:11 -08002953 (!(flag&FLAG_FORWARD_PROGRESS) ||
2954 ((flag&FLAG_DATA_SACKED) && !(flag&FLAG_ONLY_ORIG_SACKED)))) {
2955 /* RFC4138 shortcoming (see comment above) */
2956 if (!(flag&FLAG_FORWARD_PROGRESS) && (flag&FLAG_NOT_DUP))
2957 return 1;
2958
2959 tcp_enter_frto_loss(sk, 3, flag);
2960 return 1;
2961 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002962 }
2963
2964 if (tp->frto_counter == 1) {
Ilpo Järvinen575ee712007-04-30 00:39:55 -07002965 /* Sending of the next skb must be allowed or no FRTO */
2966 if (!tcp_send_head(sk) ||
2967 after(TCP_SKB_CB(tcp_send_head(sk))->end_seq,
2968 tp->snd_una + tp->snd_wnd)) {
Ilpo Järvinend551e452007-04-30 00:42:20 -07002969 tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 2 : 3),
2970 flag);
Ilpo Järvinen575ee712007-04-30 00:39:55 -07002971 return 1;
2972 }
2973
Linus Torvalds1da177e2005-04-16 15:20:36 -07002974 tp->snd_cwnd = tcp_packets_in_flight(tp) + 2;
Ilpo Järvinen94d0ea72007-02-21 23:07:27 -08002975 tp->frto_counter = 2;
Ilpo Järvinen7c9a4a52007-02-21 23:08:34 -08002976 return 1;
Ilpo Järvinend551e452007-04-30 00:42:20 -07002977 } else {
Ilpo Järvinen3cfe3ba2007-02-27 10:09:49 -08002978 switch (sysctl_tcp_frto_response) {
2979 case 2:
Ilpo Järvinene317f6f2007-03-02 13:34:19 -08002980 tcp_undo_spur_to_response(sk, flag);
Ilpo Järvinen3cfe3ba2007-02-27 10:09:49 -08002981 break;
2982 case 1:
2983 tcp_conservative_spur_to_response(tp);
2984 break;
2985 default:
2986 tcp_ratehalving_spur_to_response(sk);
2987 break;
Stephen Hemminger3ff50b72007-04-20 17:09:22 -07002988 }
Ilpo Järvinen94d0ea72007-02-21 23:07:27 -08002989 tp->frto_counter = 0;
Ilpo Järvinen009a2e32007-09-20 11:34:38 -07002990 tp->undo_marker = 0;
Ilpo Järvinen912d8f02007-09-25 22:47:31 -07002991 NET_INC_STATS_BH(LINUX_MIB_TCPSPURIOUSRTOS);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002992 }
Ilpo Järvinen7c9a4a52007-02-21 23:08:34 -08002993 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002994}
2995
Linus Torvalds1da177e2005-04-16 15:20:36 -07002996/* This routine deals with incoming acks, but not outgoing ones. */
2997static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
2998{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002999 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003000 struct tcp_sock *tp = tcp_sk(sk);
3001 u32 prior_snd_una = tp->snd_una;
3002 u32 ack_seq = TCP_SKB_CB(skb)->seq;
3003 u32 ack = TCP_SKB_CB(skb)->ack_seq;
3004 u32 prior_in_flight;
3005 s32 seq_rtt;
3006 int prior_packets;
Ilpo Järvinen7c9a4a52007-02-21 23:08:34 -08003007 int frto_cwnd = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003008
3009 /* If the ack is newer than sent or older than previous acks
3010 * then we can probably ignore it.
3011 */
3012 if (after(ack, tp->snd_nxt))
3013 goto uninteresting_ack;
3014
3015 if (before(ack, prior_snd_una))
3016 goto old_ack;
3017
Ilpo Järvinen2e605292007-08-02 19:46:58 -07003018 if (after(ack, prior_snd_una))
3019 flag |= FLAG_SND_UNA_ADVANCED;
3020
Daikichi Osuga3fdf3f02006-08-29 02:01:44 -07003021 if (sysctl_tcp_abc) {
3022 if (icsk->icsk_ca_state < TCP_CA_CWR)
3023 tp->bytes_acked += ack - prior_snd_una;
3024 else if (icsk->icsk_ca_state == TCP_CA_Loss)
3025 /* we assume just one segment left network */
3026 tp->bytes_acked += min(ack - prior_snd_una, tp->mss_cache);
3027 }
Stephen Hemminger9772efb2005-11-10 17:09:53 -08003028
Linus Torvalds1da177e2005-04-16 15:20:36 -07003029 if (!(flag&FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
3030 /* Window is constant, pure forward advance.
3031 * No more checks are required.
3032 * Note, we use the fact that SND.UNA>=SND.WL2.
3033 */
3034 tcp_update_wl(tp, ack, ack_seq);
3035 tp->snd_una = ack;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003036 flag |= FLAG_WIN_UPDATE;
3037
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003038 tcp_ca_event(sk, CA_EVENT_FAST_ACK);
Stephen Hemminger317a76f2005-06-23 12:19:55 -07003039
Linus Torvalds1da177e2005-04-16 15:20:36 -07003040 NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS);
3041 } else {
3042 if (ack_seq != TCP_SKB_CB(skb)->end_seq)
3043 flag |= FLAG_DATA;
3044 else
3045 NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS);
3046
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07003047 flag |= tcp_ack_update_window(sk, skb, ack, ack_seq);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003048
3049 if (TCP_SKB_CB(skb)->sacked)
3050 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una);
3051
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -07003052 if (TCP_ECN_rcv_ecn_echo(tp, tcp_hdr(skb)))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003053 flag |= FLAG_ECE;
3054
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003055 tcp_ca_event(sk, CA_EVENT_SLOW_ACK);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003056 }
3057
3058 /* We passed data and got it acked, remove any soft error
3059 * log. Something worked...
3060 */
3061 sk->sk_err_soft = 0;
3062 tp->rcv_tstamp = tcp_time_stamp;
3063 prior_packets = tp->packets_out;
3064 if (!prior_packets)
3065 goto no_queue;
3066
3067 prior_in_flight = tcp_packets_in_flight(tp);
3068
3069 /* See if we can take anything off of the retransmit queue. */
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08003070 flag |= tcp_clean_rtx_queue(sk, &seq_rtt);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003071
Ilpo Järvinen3de96472007-10-01 15:28:48 -07003072 /* Guarantee sacktag reordering detection against wrap-arounds */
3073 if (before(tp->frto_highmark, tp->snd_una))
3074 tp->frto_highmark = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003075 if (tp->frto_counter)
Ilpo Järvinen2e605292007-08-02 19:46:58 -07003076 frto_cwnd = tcp_process_frto(sk, flag);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003077
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003078 if (tcp_ack_is_dubious(sk, flag)) {
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08003079 /* Advance CWND, if state allows this. */
Ilpo Järvinen7c9a4a52007-02-21 23:08:34 -08003080 if ((flag & FLAG_DATA_ACKED) && !frto_cwnd &&
3081 tcp_may_raise_cwnd(sk, flag))
Stephen Hemminger16751342007-07-16 18:35:52 -07003082 tcp_cong_avoid(sk, ack, prior_in_flight, 0);
Ilpo Järvinen1b6d427b2007-08-09 14:53:36 +03003083 tcp_fastretrans_alert(sk, prior_packets - tp->packets_out, flag);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003084 } else {
Ilpo Järvinen7c9a4a52007-02-21 23:08:34 -08003085 if ((flag & FLAG_DATA_ACKED) && !frto_cwnd)
Stephen Hemminger16751342007-07-16 18:35:52 -07003086 tcp_cong_avoid(sk, ack, prior_in_flight, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003087 }
3088
3089 if ((flag & FLAG_FORWARD_PROGRESS) || !(flag&FLAG_NOT_DUP))
3090 dst_confirm(sk->sk_dst_cache);
3091
3092 return 1;
3093
3094no_queue:
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003095 icsk->icsk_probes_out = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003096
3097 /* If this ack opens up a zero window, clear backoff. It was
3098 * being used to time the probes, and is probably far higher than
3099 * it needs to be for normal retransmission.
3100 */
David S. Millerfe067e82007-03-07 12:12:44 -08003101 if (tcp_send_head(sk))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003102 tcp_ack_probe(sk);
3103 return 1;
3104
3105old_ack:
3106 if (TCP_SKB_CB(skb)->sacked)
3107 tcp_sacktag_write_queue(sk, skb, prior_snd_una);
3108
3109uninteresting_ack:
3110 SOCK_DEBUG(sk, "Ack %u out of %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
3111 return 0;
3112}
3113
3114
3115/* Look for tcp options. Normally only called on SYN and SYNACK packets.
3116 * But, this can also be called on packets in the established flow when
3117 * the fast version below fails.
3118 */
3119void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx, int estab)
3120{
3121 unsigned char *ptr;
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -07003122 struct tcphdr *th = tcp_hdr(skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003123 int length=(th->doff*4)-sizeof(struct tcphdr);
3124
3125 ptr = (unsigned char *)(th + 1);
3126 opt_rx->saw_tstamp = 0;
3127
Stephen Hemminger2de979b2007-03-08 20:45:19 -08003128 while (length > 0) {
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09003129 int opcode=*ptr++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003130 int opsize;
3131
3132 switch (opcode) {
3133 case TCPOPT_EOL:
3134 return;
3135 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
3136 length--;
3137 continue;
3138 default:
3139 opsize=*ptr++;
3140 if (opsize < 2) /* "silly options" */
3141 return;
3142 if (opsize > length)
3143 return; /* don't parse partial options */
Stephen Hemminger2de979b2007-03-08 20:45:19 -08003144 switch (opcode) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003145 case TCPOPT_MSS:
Stephen Hemminger2de979b2007-03-08 20:45:19 -08003146 if (opsize==TCPOLEN_MSS && th->syn && !estab) {
Al Viro4f3608b2006-09-27 18:35:09 -07003147 u16 in_mss = ntohs(get_unaligned((__be16 *)ptr));
Linus Torvalds1da177e2005-04-16 15:20:36 -07003148 if (in_mss) {
3149 if (opt_rx->user_mss && opt_rx->user_mss < in_mss)
3150 in_mss = opt_rx->user_mss;
3151 opt_rx->mss_clamp = in_mss;
3152 }
3153 }
3154 break;
3155 case TCPOPT_WINDOW:
Stephen Hemminger2de979b2007-03-08 20:45:19 -08003156 if (opsize==TCPOLEN_WINDOW && th->syn && !estab)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003157 if (sysctl_tcp_window_scaling) {
3158 __u8 snd_wscale = *(__u8 *) ptr;
3159 opt_rx->wscale_ok = 1;
3160 if (snd_wscale > 14) {
Stephen Hemminger2de979b2007-03-08 20:45:19 -08003161 if (net_ratelimit())
Linus Torvalds1da177e2005-04-16 15:20:36 -07003162 printk(KERN_INFO "tcp_parse_options: Illegal window "
3163 "scaling value %d >14 received.\n",
3164 snd_wscale);
3165 snd_wscale = 14;
3166 }
3167 opt_rx->snd_wscale = snd_wscale;
3168 }
3169 break;
3170 case TCPOPT_TIMESTAMP:
Stephen Hemminger2de979b2007-03-08 20:45:19 -08003171 if (opsize==TCPOLEN_TIMESTAMP) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003172 if ((estab && opt_rx->tstamp_ok) ||
3173 (!estab && sysctl_tcp_timestamps)) {
3174 opt_rx->saw_tstamp = 1;
Al Viro4f3608b2006-09-27 18:35:09 -07003175 opt_rx->rcv_tsval = ntohl(get_unaligned((__be32 *)ptr));
3176 opt_rx->rcv_tsecr = ntohl(get_unaligned((__be32 *)(ptr+4)));
Linus Torvalds1da177e2005-04-16 15:20:36 -07003177 }
3178 }
3179 break;
3180 case TCPOPT_SACK_PERM:
Stephen Hemminger2de979b2007-03-08 20:45:19 -08003181 if (opsize==TCPOLEN_SACK_PERM && th->syn && !estab) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003182 if (sysctl_tcp_sack) {
3183 opt_rx->sack_ok = 1;
3184 tcp_sack_reset(opt_rx);
3185 }
3186 }
3187 break;
3188
3189 case TCPOPT_SACK:
Stephen Hemminger2de979b2007-03-08 20:45:19 -08003190 if ((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07003191 !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) &&
3192 opt_rx->sack_ok) {
3193 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th;
3194 }
Ilpo Järvinend7ea5b92007-06-14 12:58:26 -07003195 break;
YOSHIFUJI Hideakicfb6eeb2006-11-14 19:07:45 -08003196#ifdef CONFIG_TCP_MD5SIG
3197 case TCPOPT_MD5SIG:
3198 /*
3199 * The MD5 Hash has already been
3200 * checked (see tcp_v{4,6}_do_rcv()).
3201 */
3202 break;
3203#endif
Stephen Hemminger3ff50b72007-04-20 17:09:22 -07003204 }
3205
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09003206 ptr+=opsize-2;
3207 length-=opsize;
Stephen Hemminger3ff50b72007-04-20 17:09:22 -07003208 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07003209 }
3210}
3211
3212/* Fast parse options. This hopes to only see timestamps.
3213 * If it is wrong it falls back on tcp_parse_options().
3214 */
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08003215static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th,
3216 struct tcp_sock *tp)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003217{
3218 if (th->doff == sizeof(struct tcphdr)>>2) {
3219 tp->rx_opt.saw_tstamp = 0;
3220 return 0;
3221 } else if (tp->rx_opt.tstamp_ok &&
3222 th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) {
Al Viro4f3608b2006-09-27 18:35:09 -07003223 __be32 *ptr = (__be32 *)(th + 1);
3224 if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003225 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
3226 tp->rx_opt.saw_tstamp = 1;
3227 ++ptr;
3228 tp->rx_opt.rcv_tsval = ntohl(*ptr);
3229 ++ptr;
3230 tp->rx_opt.rcv_tsecr = ntohl(*ptr);
3231 return 1;
3232 }
3233 }
3234 tcp_parse_options(skb, &tp->rx_opt, 1);
3235 return 1;
3236}
3237
3238static inline void tcp_store_ts_recent(struct tcp_sock *tp)
3239{
3240 tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval;
James Morris9d729f72007-03-04 16:12:44 -08003241 tp->rx_opt.ts_recent_stamp = get_seconds();
Linus Torvalds1da177e2005-04-16 15:20:36 -07003242}
3243
3244static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)
3245{
3246 if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) {
3247 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3248 * extra check below makes sure this can only happen
3249 * for pure ACK frames. -DaveM
3250 *
3251 * Not only, also it occurs for expired timestamps.
3252 */
3253
Stephen Hemminger2de979b2007-03-08 20:45:19 -08003254 if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) >= 0 ||
James Morris9d729f72007-03-04 16:12:44 -08003255 get_seconds() >= tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003256 tcp_store_ts_recent(tp);
3257 }
3258}
3259
3260/* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3261 *
3262 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3263 * it can pass through stack. So, the following predicate verifies that
3264 * this segment is not used for anything but congestion avoidance or
3265 * fast retransmit. Moreover, we even are able to eliminate most of such
3266 * second order effects, if we apply some small "replay" window (~RTO)
3267 * to timestamp space.
3268 *
3269 * All these measures still do not guarantee that we reject wrapped ACKs
3270 * on networks with high bandwidth, when sequence space is recycled fastly,
3271 * but it guarantees that such events will be very rare and do not affect
3272 * connection seriously. This doesn't look nice, but alas, PAWS is really
3273 * buggy extension.
3274 *
3275 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3276 * states that events when retransmit arrives after original data are rare.
3277 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3278 * the biggest problem on large power networks even with minor reordering.
3279 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3280 * up to bandwidth of 18Gigabit/sec. 8) ]
3281 */
3282
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003283static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003284{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003285 struct tcp_sock *tp = tcp_sk(sk);
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -07003286 struct tcphdr *th = tcp_hdr(skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003287 u32 seq = TCP_SKB_CB(skb)->seq;
3288 u32 ack = TCP_SKB_CB(skb)->ack_seq;
3289
3290 return (/* 1. Pure ACK with correct sequence number. */
3291 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) &&
3292
3293 /* 2. ... and duplicate ACK. */
3294 ack == tp->snd_una &&
3295
3296 /* 3. ... and does not update window. */
3297 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) &&
3298
3299 /* 4. ... and sits in replay window. */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003300 (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 -07003301}
3302
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003303static inline int tcp_paws_discard(const struct sock *sk, const struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003304{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003305 const struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003306 return ((s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) > TCP_PAWS_WINDOW &&
James Morris9d729f72007-03-04 16:12:44 -08003307 get_seconds() < tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS &&
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003308 !tcp_disordered_ack(sk, skb));
Linus Torvalds1da177e2005-04-16 15:20:36 -07003309}
3310
3311/* Check segment sequence number for validity.
3312 *
3313 * Segment controls are considered valid, if the segment
3314 * fits to the window after truncation to the window. Acceptability
3315 * of data (and SYN, FIN, of course) is checked separately.
3316 * See tcp_data_queue(), for example.
3317 *
3318 * Also, controls (RST is main one) are accepted using RCV.WUP instead
3319 * of RCV.NXT. Peer still did not advance his SND.UNA when we
3320 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
3321 * (borrowed from freebsd)
3322 */
3323
3324static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq)
3325{
3326 return !before(end_seq, tp->rcv_wup) &&
3327 !after(seq, tp->rcv_nxt + tcp_receive_window(tp));
3328}
3329
3330/* When we get a reset we do this. */
3331static void tcp_reset(struct sock *sk)
3332{
3333 /* We want the right error as BSD sees it (and indeed as we do). */
3334 switch (sk->sk_state) {
3335 case TCP_SYN_SENT:
3336 sk->sk_err = ECONNREFUSED;
3337 break;
3338 case TCP_CLOSE_WAIT:
3339 sk->sk_err = EPIPE;
3340 break;
3341 case TCP_CLOSE:
3342 return;
3343 default:
3344 sk->sk_err = ECONNRESET;
3345 }
3346
3347 if (!sock_flag(sk, SOCK_DEAD))
3348 sk->sk_error_report(sk);
3349
3350 tcp_done(sk);
3351}
3352
3353/*
3354 * Process the FIN bit. This now behaves as it is supposed to work
3355 * and the FIN takes effect when it is validly part of sequence
3356 * space. Not before when we get holes.
3357 *
3358 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
3359 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
3360 * TIME-WAIT)
3361 *
3362 * If we are in FINWAIT-1, a received FIN indicates simultaneous
3363 * close and we go into CLOSING (and later onto TIME-WAIT)
3364 *
3365 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
3366 */
3367static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th)
3368{
3369 struct tcp_sock *tp = tcp_sk(sk);
3370
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003371 inet_csk_schedule_ack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003372
3373 sk->sk_shutdown |= RCV_SHUTDOWN;
3374 sock_set_flag(sk, SOCK_DONE);
3375
3376 switch (sk->sk_state) {
3377 case TCP_SYN_RECV:
3378 case TCP_ESTABLISHED:
3379 /* Move to CLOSE_WAIT */
3380 tcp_set_state(sk, TCP_CLOSE_WAIT);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003381 inet_csk(sk)->icsk_ack.pingpong = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003382 break;
3383
3384 case TCP_CLOSE_WAIT:
3385 case TCP_CLOSING:
3386 /* Received a retransmission of the FIN, do
3387 * nothing.
3388 */
3389 break;
3390 case TCP_LAST_ACK:
3391 /* RFC793: Remain in the LAST-ACK state. */
3392 break;
3393
3394 case TCP_FIN_WAIT1:
3395 /* This case occurs when a simultaneous close
3396 * happens, we must ack the received FIN and
3397 * enter the CLOSING state.
3398 */
3399 tcp_send_ack(sk);
3400 tcp_set_state(sk, TCP_CLOSING);
3401 break;
3402 case TCP_FIN_WAIT2:
3403 /* Received a FIN -- send ACK and enter TIME_WAIT. */
3404 tcp_send_ack(sk);
3405 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
3406 break;
3407 default:
3408 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
3409 * cases we should never reach this piece of code.
3410 */
3411 printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n",
3412 __FUNCTION__, sk->sk_state);
3413 break;
Stephen Hemminger3ff50b72007-04-20 17:09:22 -07003414 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07003415
3416 /* It _is_ possible, that we have something out-of-order _after_ FIN.
3417 * Probably, we should reset in this case. For now drop them.
3418 */
3419 __skb_queue_purge(&tp->out_of_order_queue);
Ilpo Järvinene60402d2007-08-09 15:14:46 +03003420 if (tcp_is_sack(tp))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003421 tcp_sack_reset(&tp->rx_opt);
3422 sk_stream_mem_reclaim(sk);
3423
3424 if (!sock_flag(sk, SOCK_DEAD)) {
3425 sk->sk_state_change(sk);
3426
3427 /* Do not send POLL_HUP for half duplex close. */
3428 if (sk->sk_shutdown == SHUTDOWN_MASK ||
3429 sk->sk_state == TCP_CLOSE)
3430 sk_wake_async(sk, 1, POLL_HUP);
3431 else
3432 sk_wake_async(sk, 1, POLL_IN);
3433 }
3434}
3435
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08003436static inline int tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, u32 end_seq)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003437{
3438 if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) {
3439 if (before(seq, sp->start_seq))
3440 sp->start_seq = seq;
3441 if (after(end_seq, sp->end_seq))
3442 sp->end_seq = end_seq;
3443 return 1;
3444 }
3445 return 0;
3446}
3447
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08003448static void tcp_dsack_set(struct tcp_sock *tp, u32 seq, u32 end_seq)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003449{
Ilpo Järvinene60402d2007-08-09 15:14:46 +03003450 if (tcp_is_sack(tp) && sysctl_tcp_dsack) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003451 if (before(seq, tp->rcv_nxt))
3452 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT);
3453 else
3454 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT);
3455
3456 tp->rx_opt.dsack = 1;
3457 tp->duplicate_sack[0].start_seq = seq;
3458 tp->duplicate_sack[0].end_seq = end_seq;
3459 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + 1, 4 - tp->rx_opt.tstamp_ok);
3460 }
3461}
3462
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08003463static void tcp_dsack_extend(struct tcp_sock *tp, u32 seq, u32 end_seq)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003464{
3465 if (!tp->rx_opt.dsack)
3466 tcp_dsack_set(tp, seq, end_seq);
3467 else
3468 tcp_sack_extend(tp->duplicate_sack, seq, end_seq);
3469}
3470
3471static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb)
3472{
3473 struct tcp_sock *tp = tcp_sk(sk);
3474
3475 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
3476 before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
3477 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003478 tcp_enter_quickack_mode(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003479
Ilpo Järvinene60402d2007-08-09 15:14:46 +03003480 if (tcp_is_sack(tp) && sysctl_tcp_dsack) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003481 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
3482
3483 if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))
3484 end_seq = tp->rcv_nxt;
3485 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, end_seq);
3486 }
3487 }
3488
3489 tcp_send_ack(sk);
3490}
3491
3492/* These routines update the SACK block as out-of-order packets arrive or
3493 * in-order packets close up the sequence space.
3494 */
3495static void tcp_sack_maybe_coalesce(struct tcp_sock *tp)
3496{
3497 int this_sack;
3498 struct tcp_sack_block *sp = &tp->selective_acks[0];
3499 struct tcp_sack_block *swalk = sp+1;
3500
3501 /* See if the recent change to the first SACK eats into
3502 * or hits the sequence space of other SACK blocks, if so coalesce.
3503 */
3504 for (this_sack = 1; this_sack < tp->rx_opt.num_sacks; ) {
3505 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) {
3506 int i;
3507
3508 /* Zap SWALK, by moving every further SACK up by one slot.
3509 * Decrease num_sacks.
3510 */
3511 tp->rx_opt.num_sacks--;
3512 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
Stephen Hemminger2de979b2007-03-08 20:45:19 -08003513 for (i=this_sack; i < tp->rx_opt.num_sacks; i++)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003514 sp[i] = sp[i+1];
3515 continue;
3516 }
3517 this_sack++, swalk++;
3518 }
3519}
3520
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08003521static inline void tcp_sack_swap(struct tcp_sack_block *sack1, struct tcp_sack_block *sack2)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003522{
3523 __u32 tmp;
3524
3525 tmp = sack1->start_seq;
3526 sack1->start_seq = sack2->start_seq;
3527 sack2->start_seq = tmp;
3528
3529 tmp = sack1->end_seq;
3530 sack1->end_seq = sack2->end_seq;
3531 sack2->end_seq = tmp;
3532}
3533
3534static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq)
3535{
3536 struct tcp_sock *tp = tcp_sk(sk);
3537 struct tcp_sack_block *sp = &tp->selective_acks[0];
3538 int cur_sacks = tp->rx_opt.num_sacks;
3539 int this_sack;
3540
3541 if (!cur_sacks)
3542 goto new_sack;
3543
3544 for (this_sack=0; this_sack<cur_sacks; this_sack++, sp++) {
3545 if (tcp_sack_extend(sp, seq, end_seq)) {
3546 /* Rotate this_sack to the first one. */
3547 for (; this_sack>0; this_sack--, sp--)
3548 tcp_sack_swap(sp, sp-1);
3549 if (cur_sacks > 1)
3550 tcp_sack_maybe_coalesce(tp);
3551 return;
3552 }
3553 }
3554
3555 /* Could not find an adjacent existing SACK, build a new one,
3556 * put it at the front, and shift everyone else down. We
3557 * always know there is at least one SACK present already here.
3558 *
3559 * If the sack array is full, forget about the last one.
3560 */
3561 if (this_sack >= 4) {
3562 this_sack--;
3563 tp->rx_opt.num_sacks--;
3564 sp--;
3565 }
Stephen Hemminger2de979b2007-03-08 20:45:19 -08003566 for (; this_sack > 0; this_sack--, sp--)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003567 *sp = *(sp-1);
3568
3569new_sack:
3570 /* Build the new head SACK, and we're done. */
3571 sp->start_seq = seq;
3572 sp->end_seq = end_seq;
3573 tp->rx_opt.num_sacks++;
3574 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
3575}
3576
3577/* RCV.NXT advances, some SACKs should be eaten. */
3578
3579static void tcp_sack_remove(struct tcp_sock *tp)
3580{
3581 struct tcp_sack_block *sp = &tp->selective_acks[0];
3582 int num_sacks = tp->rx_opt.num_sacks;
3583 int this_sack;
3584
3585 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
David S. Millerb03efcf2005-07-08 14:57:23 -07003586 if (skb_queue_empty(&tp->out_of_order_queue)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003587 tp->rx_opt.num_sacks = 0;
3588 tp->rx_opt.eff_sacks = tp->rx_opt.dsack;
3589 return;
3590 }
3591
Stephen Hemminger2de979b2007-03-08 20:45:19 -08003592 for (this_sack = 0; this_sack < num_sacks; ) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003593 /* Check if the start of the sack is covered by RCV.NXT. */
3594 if (!before(tp->rcv_nxt, sp->start_seq)) {
3595 int i;
3596
3597 /* RCV.NXT must cover all the block! */
3598 BUG_TRAP(!before(tp->rcv_nxt, sp->end_seq));
3599
3600 /* Zap this SACK, by moving forward any other SACKS. */
3601 for (i=this_sack+1; i < num_sacks; i++)
3602 tp->selective_acks[i-1] = tp->selective_acks[i];
3603 num_sacks--;
3604 continue;
3605 }
3606 this_sack++;
3607 sp++;
3608 }
3609 if (num_sacks != tp->rx_opt.num_sacks) {
3610 tp->rx_opt.num_sacks = num_sacks;
3611 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
3612 }
3613}
3614
3615/* This one checks to see if we can put data from the
3616 * out_of_order queue into the receive_queue.
3617 */
3618static void tcp_ofo_queue(struct sock *sk)
3619{
3620 struct tcp_sock *tp = tcp_sk(sk);
3621 __u32 dsack_high = tp->rcv_nxt;
3622 struct sk_buff *skb;
3623
3624 while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) {
3625 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
3626 break;
3627
3628 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) {
3629 __u32 dsack = dsack_high;
3630 if (before(TCP_SKB_CB(skb)->end_seq, dsack_high))
3631 dsack_high = TCP_SKB_CB(skb)->end_seq;
3632 tcp_dsack_extend(tp, TCP_SKB_CB(skb)->seq, dsack);
3633 }
3634
3635 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
3636 SOCK_DEBUG(sk, "ofo packet was already received \n");
David S. Miller8728b832005-08-09 19:25:21 -07003637 __skb_unlink(skb, &tp->out_of_order_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003638 __kfree_skb(skb);
3639 continue;
3640 }
3641 SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n",
3642 tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
3643 TCP_SKB_CB(skb)->end_seq);
3644
David S. Miller8728b832005-08-09 19:25:21 -07003645 __skb_unlink(skb, &tp->out_of_order_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003646 __skb_queue_tail(&sk->sk_receive_queue, skb);
3647 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -07003648 if (tcp_hdr(skb)->fin)
3649 tcp_fin(skb, sk, tcp_hdr(skb));
Linus Torvalds1da177e2005-04-16 15:20:36 -07003650 }
3651}
3652
3653static int tcp_prune_queue(struct sock *sk);
3654
3655static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
3656{
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -07003657 struct tcphdr *th = tcp_hdr(skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003658 struct tcp_sock *tp = tcp_sk(sk);
3659 int eaten = -1;
3660
3661 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq)
3662 goto drop;
3663
Linus Torvalds1da177e2005-04-16 15:20:36 -07003664 __skb_pull(skb, th->doff*4);
3665
3666 TCP_ECN_accept_cwr(tp, skb);
3667
3668 if (tp->rx_opt.dsack) {
3669 tp->rx_opt.dsack = 0;
3670 tp->rx_opt.eff_sacks = min_t(unsigned int, tp->rx_opt.num_sacks,
3671 4 - tp->rx_opt.tstamp_ok);
3672 }
3673
3674 /* Queue data for delivery to the user.
3675 * Packets in sequence go to the receive queue.
3676 * Out of sequence packets to the out_of_order_queue.
3677 */
3678 if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
3679 if (tcp_receive_window(tp) == 0)
3680 goto out_of_window;
3681
3682 /* Ok. In sequence. In window. */
3683 if (tp->ucopy.task == current &&
3684 tp->copied_seq == tp->rcv_nxt && tp->ucopy.len &&
3685 sock_owned_by_user(sk) && !tp->urg_data) {
3686 int chunk = min_t(unsigned int, skb->len,
3687 tp->ucopy.len);
3688
3689 __set_current_state(TASK_RUNNING);
3690
3691 local_bh_enable();
3692 if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) {
3693 tp->ucopy.len -= chunk;
3694 tp->copied_seq += chunk;
3695 eaten = (chunk == skb->len && !th->fin);
3696 tcp_rcv_space_adjust(sk);
3697 }
3698 local_bh_disable();
3699 }
3700
3701 if (eaten <= 0) {
3702queue_and_out:
3703 if (eaten < 0 &&
3704 (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
3705 !sk_stream_rmem_schedule(sk, skb))) {
3706 if (tcp_prune_queue(sk) < 0 ||
3707 !sk_stream_rmem_schedule(sk, skb))
3708 goto drop;
3709 }
3710 sk_stream_set_owner_r(skb, sk);
3711 __skb_queue_tail(&sk->sk_receive_queue, skb);
3712 }
3713 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
Stephen Hemminger2de979b2007-03-08 20:45:19 -08003714 if (skb->len)
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07003715 tcp_event_data_recv(sk, skb);
Stephen Hemminger2de979b2007-03-08 20:45:19 -08003716 if (th->fin)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003717 tcp_fin(skb, sk, th);
3718
David S. Millerb03efcf2005-07-08 14:57:23 -07003719 if (!skb_queue_empty(&tp->out_of_order_queue)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003720 tcp_ofo_queue(sk);
3721
3722 /* RFC2581. 4.2. SHOULD send immediate ACK, when
3723 * gap in queue is filled.
3724 */
David S. Millerb03efcf2005-07-08 14:57:23 -07003725 if (skb_queue_empty(&tp->out_of_order_queue))
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003726 inet_csk(sk)->icsk_ack.pingpong = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003727 }
3728
3729 if (tp->rx_opt.num_sacks)
3730 tcp_sack_remove(tp);
3731
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07003732 tcp_fast_path_check(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003733
3734 if (eaten > 0)
3735 __kfree_skb(skb);
3736 else if (!sock_flag(sk, SOCK_DEAD))
3737 sk->sk_data_ready(sk, 0);
3738 return;
3739 }
3740
3741 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
3742 /* A retransmit, 2nd most common case. Force an immediate ack. */
3743 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST);
3744 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
3745
3746out_of_window:
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003747 tcp_enter_quickack_mode(sk);
3748 inet_csk_schedule_ack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003749drop:
3750 __kfree_skb(skb);
3751 return;
3752 }
3753
3754 /* Out of window. F.e. zero window probe. */
3755 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp)))
3756 goto out_of_window;
3757
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003758 tcp_enter_quickack_mode(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003759
3760 if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
3761 /* Partial packet, seq < rcv_next < end_seq */
3762 SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n",
3763 tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
3764 TCP_SKB_CB(skb)->end_seq);
3765
3766 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, tp->rcv_nxt);
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09003767
Linus Torvalds1da177e2005-04-16 15:20:36 -07003768 /* If window is closed, drop tail of packet. But after
3769 * remembering D-SACK for its head made in previous line.
3770 */
3771 if (!tcp_receive_window(tp))
3772 goto out_of_window;
3773 goto queue_and_out;
3774 }
3775
3776 TCP_ECN_check_ce(tp, skb);
3777
3778 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
3779 !sk_stream_rmem_schedule(sk, skb)) {
3780 if (tcp_prune_queue(sk) < 0 ||
3781 !sk_stream_rmem_schedule(sk, skb))
3782 goto drop;
3783 }
3784
3785 /* Disable header prediction. */
3786 tp->pred_flags = 0;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003787 inet_csk_schedule_ack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003788
3789 SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n",
3790 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
3791
3792 sk_stream_set_owner_r(skb, sk);
3793
3794 if (!skb_peek(&tp->out_of_order_queue)) {
3795 /* Initial out of order segment, build 1 SACK. */
Ilpo Järvinene60402d2007-08-09 15:14:46 +03003796 if (tcp_is_sack(tp)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003797 tp->rx_opt.num_sacks = 1;
3798 tp->rx_opt.dsack = 0;
3799 tp->rx_opt.eff_sacks = 1;
3800 tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
3801 tp->selective_acks[0].end_seq =
3802 TCP_SKB_CB(skb)->end_seq;
3803 }
3804 __skb_queue_head(&tp->out_of_order_queue,skb);
3805 } else {
3806 struct sk_buff *skb1 = tp->out_of_order_queue.prev;
3807 u32 seq = TCP_SKB_CB(skb)->seq;
3808 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
3809
3810 if (seq == TCP_SKB_CB(skb1)->end_seq) {
David S. Miller8728b832005-08-09 19:25:21 -07003811 __skb_append(skb1, skb, &tp->out_of_order_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003812
3813 if (!tp->rx_opt.num_sacks ||
3814 tp->selective_acks[0].end_seq != seq)
3815 goto add_sack;
3816
3817 /* Common case: data arrive in order after hole. */
3818 tp->selective_acks[0].end_seq = end_seq;
3819 return;
3820 }
3821
3822 /* Find place to insert this segment. */
3823 do {
3824 if (!after(TCP_SKB_CB(skb1)->seq, seq))
3825 break;
3826 } while ((skb1 = skb1->prev) !=
3827 (struct sk_buff*)&tp->out_of_order_queue);
3828
3829 /* Do skb overlap to previous one? */
3830 if (skb1 != (struct sk_buff*)&tp->out_of_order_queue &&
3831 before(seq, TCP_SKB_CB(skb1)->end_seq)) {
3832 if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
3833 /* All the bits are present. Drop. */
3834 __kfree_skb(skb);
3835 tcp_dsack_set(tp, seq, end_seq);
3836 goto add_sack;
3837 }
3838 if (after(seq, TCP_SKB_CB(skb1)->seq)) {
3839 /* Partial overlap. */
3840 tcp_dsack_set(tp, seq, TCP_SKB_CB(skb1)->end_seq);
3841 } else {
3842 skb1 = skb1->prev;
3843 }
3844 }
3845 __skb_insert(skb, skb1, skb1->next, &tp->out_of_order_queue);
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09003846
Linus Torvalds1da177e2005-04-16 15:20:36 -07003847 /* And clean segments covered by new one as whole. */
3848 while ((skb1 = skb->next) !=
3849 (struct sk_buff*)&tp->out_of_order_queue &&
3850 after(end_seq, TCP_SKB_CB(skb1)->seq)) {
3851 if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
3852 tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, end_seq);
3853 break;
3854 }
David S. Miller8728b832005-08-09 19:25:21 -07003855 __skb_unlink(skb1, &tp->out_of_order_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003856 tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, TCP_SKB_CB(skb1)->end_seq);
3857 __kfree_skb(skb1);
3858 }
3859
3860add_sack:
Ilpo Järvinene60402d2007-08-09 15:14:46 +03003861 if (tcp_is_sack(tp))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003862 tcp_sack_new_ofo_skb(sk, seq, end_seq);
3863 }
3864}
3865
3866/* Collapse contiguous sequence of skbs head..tail with
3867 * sequence numbers start..end.
3868 * Segments with FIN/SYN are not collapsed (only because this
3869 * simplifies code)
3870 */
3871static void
David S. Miller8728b832005-08-09 19:25:21 -07003872tcp_collapse(struct sock *sk, struct sk_buff_head *list,
3873 struct sk_buff *head, struct sk_buff *tail,
3874 u32 start, u32 end)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003875{
3876 struct sk_buff *skb;
3877
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08003878 /* First, check that queue is collapsible and find
Linus Torvalds1da177e2005-04-16 15:20:36 -07003879 * the point where collapsing can be useful. */
3880 for (skb = head; skb != tail; ) {
3881 /* No new bits? It is possible on ofo queue. */
3882 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
3883 struct sk_buff *next = skb->next;
David S. Miller8728b832005-08-09 19:25:21 -07003884 __skb_unlink(skb, list);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003885 __kfree_skb(skb);
3886 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED);
3887 skb = next;
3888 continue;
3889 }
3890
3891 /* The first skb to collapse is:
3892 * - not SYN/FIN and
3893 * - bloated or contains data before "start" or
3894 * overlaps to the next one.
3895 */
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -07003896 if (!tcp_hdr(skb)->syn && !tcp_hdr(skb)->fin &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07003897 (tcp_win_from_space(skb->truesize) > skb->len ||
3898 before(TCP_SKB_CB(skb)->seq, start) ||
3899 (skb->next != tail &&
3900 TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb->next)->seq)))
3901 break;
3902
3903 /* Decided to skip this, advance start seq. */
3904 start = TCP_SKB_CB(skb)->end_seq;
3905 skb = skb->next;
3906 }
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -07003907 if (skb == tail || tcp_hdr(skb)->syn || tcp_hdr(skb)->fin)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003908 return;
3909
3910 while (before(start, end)) {
3911 struct sk_buff *nskb;
3912 int header = skb_headroom(skb);
3913 int copy = SKB_MAX_ORDER(header, 0);
3914
3915 /* Too big header? This can happen with IPv6. */
3916 if (copy < 0)
3917 return;
3918 if (end-start < copy)
3919 copy = end-start;
3920 nskb = alloc_skb(copy+header, GFP_ATOMIC);
3921 if (!nskb)
3922 return;
Arnaldo Carvalho de Meloc51957d2007-03-10 12:47:22 -03003923
Arnaldo Carvalho de Melo98e399f2007-03-19 15:33:04 -07003924 skb_set_mac_header(nskb, skb_mac_header(skb) - skb->head);
Arnaldo Carvalho de Melo9c702202007-04-25 18:04:18 -07003925 skb_set_network_header(nskb, (skb_network_header(skb) -
3926 skb->head));
3927 skb_set_transport_header(nskb, (skb_transport_header(skb) -
3928 skb->head));
Linus Torvalds1da177e2005-04-16 15:20:36 -07003929 skb_reserve(nskb, header);
3930 memcpy(nskb->head, skb->head, header);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003931 memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
3932 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start;
David S. Miller8728b832005-08-09 19:25:21 -07003933 __skb_insert(nskb, skb->prev, skb, list);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003934 sk_stream_set_owner_r(nskb, sk);
3935
3936 /* Copy data, releasing collapsed skbs. */
3937 while (copy > 0) {
3938 int offset = start - TCP_SKB_CB(skb)->seq;
3939 int size = TCP_SKB_CB(skb)->end_seq - start;
3940
Kris Katterjohn09a62662006-01-08 22:24:28 -08003941 BUG_ON(offset < 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003942 if (size > 0) {
3943 size = min(copy, size);
3944 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size))
3945 BUG();
3946 TCP_SKB_CB(nskb)->end_seq += size;
3947 copy -= size;
3948 start += size;
3949 }
3950 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
3951 struct sk_buff *next = skb->next;
David S. Miller8728b832005-08-09 19:25:21 -07003952 __skb_unlink(skb, list);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003953 __kfree_skb(skb);
3954 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED);
3955 skb = next;
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -07003956 if (skb == tail ||
3957 tcp_hdr(skb)->syn ||
3958 tcp_hdr(skb)->fin)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003959 return;
3960 }
3961 }
3962 }
3963}
3964
3965/* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
3966 * and tcp_collapse() them until all the queue is collapsed.
3967 */
3968static void tcp_collapse_ofo_queue(struct sock *sk)
3969{
3970 struct tcp_sock *tp = tcp_sk(sk);
3971 struct sk_buff *skb = skb_peek(&tp->out_of_order_queue);
3972 struct sk_buff *head;
3973 u32 start, end;
3974
3975 if (skb == NULL)
3976 return;
3977
3978 start = TCP_SKB_CB(skb)->seq;
3979 end = TCP_SKB_CB(skb)->end_seq;
3980 head = skb;
3981
3982 for (;;) {
3983 skb = skb->next;
3984
3985 /* Segment is terminated when we see gap or when
3986 * we are at the end of all the queue. */
3987 if (skb == (struct sk_buff *)&tp->out_of_order_queue ||
3988 after(TCP_SKB_CB(skb)->seq, end) ||
3989 before(TCP_SKB_CB(skb)->end_seq, start)) {
David S. Miller8728b832005-08-09 19:25:21 -07003990 tcp_collapse(sk, &tp->out_of_order_queue,
3991 head, skb, start, end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003992 head = skb;
3993 if (skb == (struct sk_buff *)&tp->out_of_order_queue)
3994 break;
3995 /* Start new segment */
3996 start = TCP_SKB_CB(skb)->seq;
3997 end = TCP_SKB_CB(skb)->end_seq;
3998 } else {
3999 if (before(TCP_SKB_CB(skb)->seq, start))
4000 start = TCP_SKB_CB(skb)->seq;
4001 if (after(TCP_SKB_CB(skb)->end_seq, end))
4002 end = TCP_SKB_CB(skb)->end_seq;
4003 }
4004 }
4005}
4006
4007/* Reduce allocated memory if we can, trying to get
4008 * the socket within its memory limits again.
4009 *
4010 * Return less than zero if we should start dropping frames
4011 * until the socket owning process reads some of the data
4012 * to stabilize the situation.
4013 */
4014static int tcp_prune_queue(struct sock *sk)
4015{
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004016 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004017
4018 SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq);
4019
4020 NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED);
4021
4022 if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07004023 tcp_clamp_window(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004024 else if (tcp_memory_pressure)
4025 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss);
4026
4027 tcp_collapse_ofo_queue(sk);
David S. Miller8728b832005-08-09 19:25:21 -07004028 tcp_collapse(sk, &sk->sk_receive_queue,
4029 sk->sk_receive_queue.next,
Linus Torvalds1da177e2005-04-16 15:20:36 -07004030 (struct sk_buff*)&sk->sk_receive_queue,
4031 tp->copied_seq, tp->rcv_nxt);
4032 sk_stream_mem_reclaim(sk);
4033
4034 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
4035 return 0;
4036
4037 /* Collapsing did not help, destructive actions follow.
4038 * This must not ever occur. */
4039
4040 /* First, purge the out_of_order queue. */
David S. Millerb03efcf2005-07-08 14:57:23 -07004041 if (!skb_queue_empty(&tp->out_of_order_queue)) {
4042 NET_INC_STATS_BH(LINUX_MIB_OFOPRUNED);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004043 __skb_queue_purge(&tp->out_of_order_queue);
4044
4045 /* Reset SACK state. A conforming SACK implementation will
4046 * do the same at a timeout based retransmit. When a connection
4047 * is in a sad state like this, we care only about integrity
4048 * of the connection not performance.
4049 */
Ilpo Järvinene60402d2007-08-09 15:14:46 +03004050 if (tcp_is_sack(tp))
Linus Torvalds1da177e2005-04-16 15:20:36 -07004051 tcp_sack_reset(&tp->rx_opt);
4052 sk_stream_mem_reclaim(sk);
4053 }
4054
4055 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
4056 return 0;
4057
4058 /* If we are really being abused, tell the caller to silently
4059 * drop receive data on the floor. It will get retransmitted
4060 * and hopefully then we'll have sufficient space.
4061 */
4062 NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED);
4063
4064 /* Massive buffer overcommit. */
4065 tp->pred_flags = 0;
4066 return -1;
4067}
4068
4069
4070/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
4071 * As additional protections, we do not touch cwnd in retransmission phases,
4072 * and if application hit its sndbuf limit recently.
4073 */
4074void tcp_cwnd_application_limited(struct sock *sk)
4075{
4076 struct tcp_sock *tp = tcp_sk(sk);
4077
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03004078 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07004079 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
4080 /* Limited by application or receiver window. */
Ilpo Järvinend254bcd2006-08-04 16:57:42 -07004081 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk));
4082 u32 win_used = max(tp->snd_cwnd_used, init_win);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004083 if (win_used < tp->snd_cwnd) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03004084 tp->snd_ssthresh = tcp_current_ssthresh(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004085 tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
4086 }
4087 tp->snd_cwnd_used = 0;
4088 }
4089 tp->snd_cwnd_stamp = tcp_time_stamp;
4090}
4091
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07004092static int tcp_should_expand_sndbuf(struct sock *sk)
David S. Miller0d9901d2005-07-05 15:21:10 -07004093{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07004094 struct tcp_sock *tp = tcp_sk(sk);
4095
David S. Miller0d9901d2005-07-05 15:21:10 -07004096 /* If the user specified a specific send buffer setting, do
4097 * not modify it.
4098 */
4099 if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
4100 return 0;
4101
4102 /* If we are under global TCP memory pressure, do not expand. */
4103 if (tcp_memory_pressure)
4104 return 0;
4105
4106 /* If we are under soft global TCP memory pressure, do not expand. */
4107 if (atomic_read(&tcp_memory_allocated) >= sysctl_tcp_mem[0])
4108 return 0;
4109
4110 /* If we filled the congestion window, do not expand. */
4111 if (tp->packets_out >= tp->snd_cwnd)
4112 return 0;
4113
4114 return 1;
4115}
Linus Torvalds1da177e2005-04-16 15:20:36 -07004116
4117/* When incoming ACK allowed to free some skb from write_queue,
4118 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
4119 * on the exit from tcp input handler.
4120 *
4121 * PROBLEM: sndbuf expansion does not work well with largesend.
4122 */
4123static void tcp_new_space(struct sock *sk)
4124{
4125 struct tcp_sock *tp = tcp_sk(sk);
4126
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07004127 if (tcp_should_expand_sndbuf(sk)) {
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004128 int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) +
Linus Torvalds1da177e2005-04-16 15:20:36 -07004129 MAX_TCP_HEADER + 16 + sizeof(struct sk_buff),
4130 demanded = max_t(unsigned int, tp->snd_cwnd,
4131 tp->reordering + 1);
4132 sndmem *= 2*demanded;
4133 if (sndmem > sk->sk_sndbuf)
4134 sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]);
4135 tp->snd_cwnd_stamp = tcp_time_stamp;
4136 }
4137
4138 sk->sk_write_space(sk);
4139}
4140
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08004141static void tcp_check_space(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004142{
4143 if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
4144 sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
4145 if (sk->sk_socket &&
4146 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
4147 tcp_new_space(sk);
4148 }
4149}
4150
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07004151static inline void tcp_data_snd_check(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004152{
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07004153 tcp_push_pending_frames(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004154 tcp_check_space(sk);
4155}
4156
4157/*
4158 * Check if sending an ack is needed.
4159 */
4160static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
4161{
4162 struct tcp_sock *tp = tcp_sk(sk);
4163
4164 /* More than one full frame received... */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004165 if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss
Linus Torvalds1da177e2005-04-16 15:20:36 -07004166 /* ... and right edge of window advances far enough.
4167 * (tcp_recvmsg() will send ACK otherwise). Or...
4168 */
4169 && __tcp_select_window(sk) >= tp->rcv_wnd) ||
4170 /* We ACK each frame or... */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004171 tcp_in_quickack_mode(sk) ||
Linus Torvalds1da177e2005-04-16 15:20:36 -07004172 /* We have out of order data. */
4173 (ofo_possible &&
4174 skb_peek(&tp->out_of_order_queue))) {
4175 /* Then ack it now */
4176 tcp_send_ack(sk);
4177 } else {
4178 /* Else, send delayed ack. */
4179 tcp_send_delayed_ack(sk);
4180 }
4181}
4182
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08004183static inline void tcp_ack_snd_check(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004184{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004185 if (!inet_csk_ack_scheduled(sk)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004186 /* We sent a data segment already. */
4187 return;
4188 }
4189 __tcp_ack_snd_check(sk, 1);
4190}
4191
4192/*
4193 * This routine is only called when we have urgent data
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08004194 * signaled. Its the 'slow' part of tcp_urg. It could be
Linus Torvalds1da177e2005-04-16 15:20:36 -07004195 * moved inline now as tcp_urg is only called from one
4196 * place. We handle URGent data wrong. We have to - as
4197 * BSD still doesn't use the correction from RFC961.
4198 * For 1003.1g we should support a new option TCP_STDURG to permit
4199 * either form (or just set the sysctl tcp_stdurg).
4200 */
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004201
Linus Torvalds1da177e2005-04-16 15:20:36 -07004202static void tcp_check_urg(struct sock * sk, struct tcphdr * th)
4203{
4204 struct tcp_sock *tp = tcp_sk(sk);
4205 u32 ptr = ntohs(th->urg_ptr);
4206
4207 if (ptr && !sysctl_tcp_stdurg)
4208 ptr--;
4209 ptr += ntohl(th->seq);
4210
4211 /* Ignore urgent data that we've already seen and read. */
4212 if (after(tp->copied_seq, ptr))
4213 return;
4214
4215 /* Do not replay urg ptr.
4216 *
4217 * NOTE: interesting situation not covered by specs.
4218 * Misbehaving sender may send urg ptr, pointing to segment,
4219 * which we already have in ofo queue. We are not able to fetch
4220 * such data and will stay in TCP_URG_NOTYET until will be eaten
4221 * by recvmsg(). Seems, we are not obliged to handle such wicked
4222 * situations. But it is worth to think about possibility of some
4223 * DoSes using some hypothetical application level deadlock.
4224 */
4225 if (before(ptr, tp->rcv_nxt))
4226 return;
4227
4228 /* Do we already have a newer (or duplicate) urgent pointer? */
4229 if (tp->urg_data && !after(ptr, tp->urg_seq))
4230 return;
4231
4232 /* Tell the world about our new urgent pointer. */
4233 sk_send_sigurg(sk);
4234
4235 /* We may be adding urgent data when the last byte read was
4236 * urgent. To do this requires some care. We cannot just ignore
4237 * tp->copied_seq since we would read the last urgent byte again
4238 * as data, nor can we alter copied_seq until this data arrives
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08004239 * or we break the semantics of SIOCATMARK (and thus sockatmark())
Linus Torvalds1da177e2005-04-16 15:20:36 -07004240 *
4241 * NOTE. Double Dutch. Rendering to plain English: author of comment
4242 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
4243 * and expect that both A and B disappear from stream. This is _wrong_.
4244 * Though this happens in BSD with high probability, this is occasional.
4245 * Any application relying on this is buggy. Note also, that fix "works"
4246 * only in this artificial test. Insert some normal data between A and B and we will
4247 * decline of BSD again. Verdict: it is better to remove to trap
4248 * buggy users.
4249 */
4250 if (tp->urg_seq == tp->copied_seq && tp->urg_data &&
4251 !sock_flag(sk, SOCK_URGINLINE) &&
4252 tp->copied_seq != tp->rcv_nxt) {
4253 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
4254 tp->copied_seq++;
4255 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) {
David S. Miller8728b832005-08-09 19:25:21 -07004256 __skb_unlink(skb, &sk->sk_receive_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004257 __kfree_skb(skb);
4258 }
4259 }
4260
4261 tp->urg_data = TCP_URG_NOTYET;
4262 tp->urg_seq = ptr;
4263
4264 /* Disable header prediction. */
4265 tp->pred_flags = 0;
4266}
4267
4268/* This is the 'fast' part of urgent handling. */
4269static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th)
4270{
4271 struct tcp_sock *tp = tcp_sk(sk);
4272
4273 /* Check if we get a new urgent pointer - normally not. */
4274 if (th->urg)
4275 tcp_check_urg(sk,th);
4276
4277 /* Do we wait for any urgent data? - normally not... */
4278 if (tp->urg_data == TCP_URG_NOTYET) {
4279 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) -
4280 th->syn;
4281
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004282 /* Is the urgent pointer pointing into this packet? */
Linus Torvalds1da177e2005-04-16 15:20:36 -07004283 if (ptr < skb->len) {
4284 u8 tmp;
4285 if (skb_copy_bits(skb, ptr, &tmp, 1))
4286 BUG();
4287 tp->urg_data = TCP_URG_VALID | tmp;
4288 if (!sock_flag(sk, SOCK_DEAD))
4289 sk->sk_data_ready(sk, 0);
4290 }
4291 }
4292}
4293
4294static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen)
4295{
4296 struct tcp_sock *tp = tcp_sk(sk);
4297 int chunk = skb->len - hlen;
4298 int err;
4299
4300 local_bh_enable();
Herbert Xu60476372007-04-09 11:59:39 -07004301 if (skb_csum_unnecessary(skb))
Linus Torvalds1da177e2005-04-16 15:20:36 -07004302 err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk);
4303 else
4304 err = skb_copy_and_csum_datagram_iovec(skb, hlen,
4305 tp->ucopy.iov);
4306
4307 if (!err) {
4308 tp->ucopy.len -= chunk;
4309 tp->copied_seq += chunk;
4310 tcp_rcv_space_adjust(sk);
4311 }
4312
4313 local_bh_disable();
4314 return err;
4315}
4316
Al Virob51655b2006-11-14 21:40:42 -08004317static __sum16 __tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004318{
Al Virob51655b2006-11-14 21:40:42 -08004319 __sum16 result;
Linus Torvalds1da177e2005-04-16 15:20:36 -07004320
4321 if (sock_owned_by_user(sk)) {
4322 local_bh_enable();
4323 result = __tcp_checksum_complete(skb);
4324 local_bh_disable();
4325 } else {
4326 result = __tcp_checksum_complete(skb);
4327 }
4328 return result;
4329}
4330
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08004331static inline int tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004332{
Herbert Xu60476372007-04-09 11:59:39 -07004333 return !skb_csum_unnecessary(skb) &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07004334 __tcp_checksum_complete_user(sk, skb);
4335}
4336
Chris Leech1a2449a2006-05-23 18:05:53 -07004337#ifdef CONFIG_NET_DMA
4338static int tcp_dma_try_early_copy(struct sock *sk, struct sk_buff *skb, int hlen)
4339{
4340 struct tcp_sock *tp = tcp_sk(sk);
4341 int chunk = skb->len - hlen;
4342 int dma_cookie;
4343 int copied_early = 0;
4344
4345 if (tp->ucopy.wakeup)
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004346 return 0;
Chris Leech1a2449a2006-05-23 18:05:53 -07004347
4348 if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list)
4349 tp->ucopy.dma_chan = get_softnet_dma();
4350
Herbert Xu60476372007-04-09 11:59:39 -07004351 if (tp->ucopy.dma_chan && skb_csum_unnecessary(skb)) {
Chris Leech1a2449a2006-05-23 18:05:53 -07004352
4353 dma_cookie = dma_skb_copy_datagram_iovec(tp->ucopy.dma_chan,
4354 skb, hlen, tp->ucopy.iov, chunk, tp->ucopy.pinned_list);
4355
4356 if (dma_cookie < 0)
4357 goto out;
4358
4359 tp->ucopy.dma_cookie = dma_cookie;
4360 copied_early = 1;
4361
4362 tp->ucopy.len -= chunk;
4363 tp->copied_seq += chunk;
4364 tcp_rcv_space_adjust(sk);
4365
4366 if ((tp->ucopy.len == 0) ||
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -07004367 (tcp_flag_word(tcp_hdr(skb)) & TCP_FLAG_PSH) ||
Chris Leech1a2449a2006-05-23 18:05:53 -07004368 (atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1))) {
4369 tp->ucopy.wakeup = 1;
4370 sk->sk_data_ready(sk, 0);
4371 }
4372 } else if (chunk > 0) {
4373 tp->ucopy.wakeup = 1;
4374 sk->sk_data_ready(sk, 0);
4375 }
4376out:
4377 return copied_early;
4378}
4379#endif /* CONFIG_NET_DMA */
4380
Linus Torvalds1da177e2005-04-16 15:20:36 -07004381/*
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004382 * TCP receive function for the ESTABLISHED state.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004383 *
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004384 * It is split into a fast path and a slow path. The fast path is
Linus Torvalds1da177e2005-04-16 15:20:36 -07004385 * disabled when:
4386 * - A zero window was announced from us - zero window probing
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004387 * is only handled properly in the slow path.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004388 * - Out of order segments arrived.
4389 * - Urgent data is expected.
4390 * - There is no buffer space left
4391 * - Unexpected TCP flags/window values/header lengths are received
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004392 * (detected by checking the TCP header against pred_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004393 * - Data is sent in both directions. Fast path only supports pure senders
4394 * or pure receivers (this means either the sequence number or the ack
4395 * value must stay constant)
4396 * - Unexpected TCP option.
4397 *
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004398 * When these conditions are not satisfied it drops into a standard
Linus Torvalds1da177e2005-04-16 15:20:36 -07004399 * receive procedure patterned after RFC793 to handle all cases.
4400 * The first three cases are guaranteed by proper pred_flags setting,
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004401 * the rest is checked inline. Fast processing is turned on in
Linus Torvalds1da177e2005-04-16 15:20:36 -07004402 * tcp_data_queue when everything is OK.
4403 */
4404int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
4405 struct tcphdr *th, unsigned len)
4406{
4407 struct tcp_sock *tp = tcp_sk(sk);
4408
4409 /*
4410 * Header prediction.
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004411 * The code loosely follows the one in the famous
Linus Torvalds1da177e2005-04-16 15:20:36 -07004412 * "30 instruction TCP receive" Van Jacobson mail.
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004413 *
4414 * Van's trick is to deposit buffers into socket queue
Linus Torvalds1da177e2005-04-16 15:20:36 -07004415 * on a device interrupt, to call tcp_recv function
4416 * on the receive process context and checksum and copy
4417 * the buffer to user space. smart...
4418 *
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004419 * Our current scheme is not silly either but we take the
Linus Torvalds1da177e2005-04-16 15:20:36 -07004420 * extra cost of the net_bh soft interrupt processing...
4421 * We do checksum and copy also but from device to kernel.
4422 */
4423
4424 tp->rx_opt.saw_tstamp = 0;
4425
4426 /* pred_flags is 0xS?10 << 16 + snd_wnd
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08004427 * if header_prediction is to be made
Linus Torvalds1da177e2005-04-16 15:20:36 -07004428 * 'S' will always be tp->tcp_header_len >> 2
4429 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004430 * turn it off (when there are holes in the receive
Linus Torvalds1da177e2005-04-16 15:20:36 -07004431 * space for instance)
4432 * PSH flag is ignored.
4433 */
4434
4435 if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags &&
4436 TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
4437 int tcp_header_len = tp->tcp_header_len;
4438
4439 /* Timestamp header prediction: tcp_header_len
4440 * is automatically equal to th->doff*4 due to pred_flags
4441 * match.
4442 */
4443
4444 /* Check timestamp */
4445 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) {
Al Viro4f3608b2006-09-27 18:35:09 -07004446 __be32 *ptr = (__be32 *)(th + 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004447
4448 /* No? Slow path! */
Al Viro4f3608b2006-09-27 18:35:09 -07004449 if (*ptr != htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004450 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP))
4451 goto slow_path;
4452
4453 tp->rx_opt.saw_tstamp = 1;
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004454 ++ptr;
Linus Torvalds1da177e2005-04-16 15:20:36 -07004455 tp->rx_opt.rcv_tsval = ntohl(*ptr);
4456 ++ptr;
4457 tp->rx_opt.rcv_tsecr = ntohl(*ptr);
4458
4459 /* If PAWS failed, check it more carefully in slow path */
4460 if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0)
4461 goto slow_path;
4462
4463 /* DO NOT update ts_recent here, if checksum fails
4464 * and timestamp was corrupted part, it will result
4465 * in a hung connection since we will drop all
4466 * future packets due to the PAWS test.
4467 */
4468 }
4469
4470 if (len <= tcp_header_len) {
4471 /* Bulk data transfer: sender */
4472 if (len == tcp_header_len) {
4473 /* Predicted packet is in window by definition.
4474 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4475 * Hence, check seq<=rcv_wup reduces to:
4476 */
4477 if (tcp_header_len ==
4478 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
4479 tp->rcv_nxt == tp->rcv_wup)
4480 tcp_store_ts_recent(tp);
4481
Linus Torvalds1da177e2005-04-16 15:20:36 -07004482 /* We know that such packets are checksummed
4483 * on entry.
4484 */
4485 tcp_ack(sk, skb, 0);
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004486 __kfree_skb(skb);
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07004487 tcp_data_snd_check(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004488 return 0;
4489 } else { /* Header too small */
4490 TCP_INC_STATS_BH(TCP_MIB_INERRS);
4491 goto discard;
4492 }
4493 } else {
4494 int eaten = 0;
Chris Leech1a2449a2006-05-23 18:05:53 -07004495 int copied_early = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07004496
Chris Leech1a2449a2006-05-23 18:05:53 -07004497 if (tp->copied_seq == tp->rcv_nxt &&
4498 len - tcp_header_len <= tp->ucopy.len) {
4499#ifdef CONFIG_NET_DMA
4500 if (tcp_dma_try_early_copy(sk, skb, tcp_header_len)) {
4501 copied_early = 1;
4502 eaten = 1;
4503 }
4504#endif
4505 if (tp->ucopy.task == current && sock_owned_by_user(sk) && !copied_early) {
4506 __set_current_state(TASK_RUNNING);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004507
Chris Leech1a2449a2006-05-23 18:05:53 -07004508 if (!tcp_copy_to_iovec(sk, skb, tcp_header_len))
4509 eaten = 1;
4510 }
4511 if (eaten) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004512 /* Predicted packet is in window by definition.
4513 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4514 * Hence, check seq<=rcv_wup reduces to:
4515 */
4516 if (tcp_header_len ==
4517 (sizeof(struct tcphdr) +
4518 TCPOLEN_TSTAMP_ALIGNED) &&
4519 tp->rcv_nxt == tp->rcv_wup)
4520 tcp_store_ts_recent(tp);
4521
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004522 tcp_rcv_rtt_measure_ts(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004523
4524 __skb_pull(skb, tcp_header_len);
4525 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
4526 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004527 }
Chris Leech1a2449a2006-05-23 18:05:53 -07004528 if (copied_early)
4529 tcp_cleanup_rbuf(sk, skb->len);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004530 }
4531 if (!eaten) {
4532 if (tcp_checksum_complete_user(sk, skb))
4533 goto csum_error;
4534
4535 /* Predicted packet is in window by definition.
4536 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4537 * Hence, check seq<=rcv_wup reduces to:
4538 */
4539 if (tcp_header_len ==
4540 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
4541 tp->rcv_nxt == tp->rcv_wup)
4542 tcp_store_ts_recent(tp);
4543
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004544 tcp_rcv_rtt_measure_ts(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004545
4546 if ((int)skb->truesize > sk->sk_forward_alloc)
4547 goto step5;
4548
4549 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS);
4550
4551 /* Bulk data transfer: receiver */
4552 __skb_pull(skb,tcp_header_len);
4553 __skb_queue_tail(&sk->sk_receive_queue, skb);
4554 sk_stream_set_owner_r(skb, sk);
4555 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
4556 }
4557
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07004558 tcp_event_data_recv(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004559
4560 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) {
4561 /* Well, only one small jumplet in fast path... */
4562 tcp_ack(sk, skb, FLAG_DATA);
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07004563 tcp_data_snd_check(sk);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004564 if (!inet_csk_ack_scheduled(sk))
Linus Torvalds1da177e2005-04-16 15:20:36 -07004565 goto no_ack;
4566 }
4567
David S. Miller31432412005-05-23 12:03:06 -07004568 __tcp_ack_snd_check(sk, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004569no_ack:
Chris Leech1a2449a2006-05-23 18:05:53 -07004570#ifdef CONFIG_NET_DMA
4571 if (copied_early)
4572 __skb_queue_tail(&sk->sk_async_wait_queue, skb);
4573 else
4574#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -07004575 if (eaten)
4576 __kfree_skb(skb);
4577 else
4578 sk->sk_data_ready(sk, 0);
4579 return 0;
4580 }
4581 }
4582
4583slow_path:
4584 if (len < (th->doff<<2) || tcp_checksum_complete_user(sk, skb))
4585 goto csum_error;
4586
4587 /*
4588 * RFC1323: H1. Apply PAWS check first.
4589 */
4590 if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004591 tcp_paws_discard(sk, skb)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004592 if (!th->rst) {
4593 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
4594 tcp_send_dupack(sk, skb);
4595 goto discard;
4596 }
4597 /* Resets are accepted even if PAWS failed.
4598
4599 ts_recent update must be made after we are sure
4600 that the packet is in window.
4601 */
4602 }
4603
4604 /*
4605 * Standard slow path.
4606 */
4607
4608 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
4609 /* RFC793, page 37: "In all states except SYN-SENT, all reset
4610 * (RST) segments are validated by checking their SEQ-fields."
4611 * And page 69: "If an incoming segment is not acceptable,
4612 * an acknowledgment should be sent in reply (unless the RST bit
4613 * is set, if so drop the segment and return)".
4614 */
4615 if (!th->rst)
4616 tcp_send_dupack(sk, skb);
4617 goto discard;
4618 }
4619
Stephen Hemminger2de979b2007-03-08 20:45:19 -08004620 if (th->rst) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004621 tcp_reset(sk);
4622 goto discard;
4623 }
4624
4625 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
4626
4627 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4628 TCP_INC_STATS_BH(TCP_MIB_INERRS);
4629 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN);
4630 tcp_reset(sk);
4631 return 1;
4632 }
4633
4634step5:
Stephen Hemminger2de979b2007-03-08 20:45:19 -08004635 if (th->ack)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004636 tcp_ack(sk, skb, FLAG_SLOWPATH);
4637
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004638 tcp_rcv_rtt_measure_ts(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004639
4640 /* Process urgent data. */
4641 tcp_urg(sk, skb, th);
4642
4643 /* step 7: process the segment text */
4644 tcp_data_queue(sk, skb);
4645
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07004646 tcp_data_snd_check(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004647 tcp_ack_snd_check(sk);
4648 return 0;
4649
4650csum_error:
4651 TCP_INC_STATS_BH(TCP_MIB_INERRS);
4652
4653discard:
4654 __kfree_skb(skb);
4655 return 0;
4656}
4657
4658static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
4659 struct tcphdr *th, unsigned len)
4660{
4661 struct tcp_sock *tp = tcp_sk(sk);
Arnaldo Carvalho de Melod83d8462005-12-13 23:26:10 -08004662 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004663 int saved_clamp = tp->rx_opt.mss_clamp;
4664
4665 tcp_parse_options(skb, &tp->rx_opt, 0);
4666
4667 if (th->ack) {
4668 /* rfc793:
4669 * "If the state is SYN-SENT then
4670 * first check the ACK bit
4671 * If the ACK bit is set
4672 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
4673 * a reset (unless the RST bit is set, if so drop
4674 * the segment and return)"
4675 *
4676 * We do not send data with SYN, so that RFC-correct
4677 * test reduces to:
4678 */
4679 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt)
4680 goto reset_and_undo;
4681
4682 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
4683 !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp,
4684 tcp_time_stamp)) {
4685 NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED);
4686 goto reset_and_undo;
4687 }
4688
4689 /* Now ACK is acceptable.
4690 *
4691 * "If the RST bit is set
4692 * If the ACK was acceptable then signal the user "error:
4693 * connection reset", drop the segment, enter CLOSED state,
4694 * delete TCB, and return."
4695 */
4696
4697 if (th->rst) {
4698 tcp_reset(sk);
4699 goto discard;
4700 }
4701
4702 /* rfc793:
4703 * "fifth, if neither of the SYN or RST bits is set then
4704 * drop the segment and return."
4705 *
4706 * See note below!
4707 * --ANK(990513)
4708 */
4709 if (!th->syn)
4710 goto discard_and_undo;
4711
4712 /* rfc793:
4713 * "If the SYN bit is on ...
4714 * are acceptable then ...
4715 * (our SYN has been ACKed), change the connection
4716 * state to ESTABLISHED..."
4717 */
4718
4719 TCP_ECN_rcv_synack(tp, th);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004720
4721 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
4722 tcp_ack(sk, skb, FLAG_SLOWPATH);
4723
4724 /* Ok.. it's good. Set up sequence numbers and
4725 * move to established.
4726 */
4727 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
4728 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
4729
4730 /* RFC1323: The window in SYN & SYN/ACK segments is
4731 * never scaled.
4732 */
4733 tp->snd_wnd = ntohs(th->window);
4734 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, TCP_SKB_CB(skb)->seq);
4735
4736 if (!tp->rx_opt.wscale_ok) {
4737 tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0;
4738 tp->window_clamp = min(tp->window_clamp, 65535U);
4739 }
4740
4741 if (tp->rx_opt.saw_tstamp) {
4742 tp->rx_opt.tstamp_ok = 1;
4743 tp->tcp_header_len =
4744 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
4745 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
4746 tcp_store_ts_recent(tp);
4747 } else {
4748 tp->tcp_header_len = sizeof(struct tcphdr);
4749 }
4750
Ilpo Järvinene60402d2007-08-09 15:14:46 +03004751 if (tcp_is_sack(tp) && sysctl_tcp_fack)
4752 tcp_enable_fack(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004753
John Heffner5d424d52006-03-20 17:53:41 -08004754 tcp_mtup_init(sk);
Arnaldo Carvalho de Melod83d8462005-12-13 23:26:10 -08004755 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004756 tcp_initialize_rcv_mss(sk);
4757
4758 /* Remember, tcp_poll() does not lock socket!
4759 * Change state from SYN-SENT only after copied_seq
4760 * is initialized. */
4761 tp->copied_seq = tp->rcv_nxt;
Ralf Baechlee16aa202006-12-07 00:11:33 -08004762 smp_mb();
Linus Torvalds1da177e2005-04-16 15:20:36 -07004763 tcp_set_state(sk, TCP_ESTABLISHED);
4764
Venkat Yekkirala6b877692006-11-08 17:04:09 -06004765 security_inet_conn_established(sk, skb);
4766
Linus Torvalds1da177e2005-04-16 15:20:36 -07004767 /* Make sure socket is routed, for correct metrics. */
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -08004768 icsk->icsk_af_ops->rebuild_header(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004769
4770 tcp_init_metrics(sk);
4771
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03004772 tcp_init_congestion_control(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -07004773
Linus Torvalds1da177e2005-04-16 15:20:36 -07004774 /* Prevent spurious tcp_cwnd_restart() on first data
4775 * packet.
4776 */
4777 tp->lsndtime = tcp_time_stamp;
4778
4779 tcp_init_buffer_space(sk);
4780
4781 if (sock_flag(sk, SOCK_KEEPOPEN))
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004782 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp));
Linus Torvalds1da177e2005-04-16 15:20:36 -07004783
4784 if (!tp->rx_opt.snd_wscale)
4785 __tcp_fast_path_on(tp, tp->snd_wnd);
4786 else
4787 tp->pred_flags = 0;
4788
4789 if (!sock_flag(sk, SOCK_DEAD)) {
4790 sk->sk_state_change(sk);
4791 sk_wake_async(sk, 0, POLL_OUT);
4792 }
4793
Arnaldo Carvalho de Melo295f7322005-08-09 20:11:56 -07004794 if (sk->sk_write_pending ||
4795 icsk->icsk_accept_queue.rskq_defer_accept ||
4796 icsk->icsk_ack.pingpong) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004797 /* Save one ACK. Data will be ready after
4798 * several ticks, if write_pending is set.
4799 *
4800 * It may be deleted, but with this feature tcpdumps
4801 * look so _wonderfully_ clever, that I was not able
4802 * to stand against the temptation 8) --ANK
4803 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004804 inet_csk_schedule_ack(sk);
Arnaldo Carvalho de Melo295f7322005-08-09 20:11:56 -07004805 icsk->icsk_ack.lrcvtime = tcp_time_stamp;
4806 icsk->icsk_ack.ato = TCP_ATO_MIN;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004807 tcp_incr_quickack(sk);
4808 tcp_enter_quickack_mode(sk);
Arnaldo Carvalho de Melo3f421ba2005-08-09 20:11:08 -07004809 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
4810 TCP_DELACK_MAX, TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004811
4812discard:
4813 __kfree_skb(skb);
4814 return 0;
4815 } else {
4816 tcp_send_ack(sk);
4817 }
4818 return -1;
4819 }
4820
4821 /* No ACK in the segment */
4822
4823 if (th->rst) {
4824 /* rfc793:
4825 * "If the RST bit is set
4826 *
4827 * Otherwise (no ACK) drop the segment and return."
4828 */
4829
4830 goto discard_and_undo;
4831 }
4832
4833 /* PAWS check. */
4834 if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && tcp_paws_check(&tp->rx_opt, 0))
4835 goto discard_and_undo;
4836
4837 if (th->syn) {
4838 /* We see SYN without ACK. It is attempt of
4839 * simultaneous connect with crossed SYNs.
4840 * Particularly, it can be connect to self.
4841 */
4842 tcp_set_state(sk, TCP_SYN_RECV);
4843
4844 if (tp->rx_opt.saw_tstamp) {
4845 tp->rx_opt.tstamp_ok = 1;
4846 tcp_store_ts_recent(tp);
4847 tp->tcp_header_len =
4848 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
4849 } else {
4850 tp->tcp_header_len = sizeof(struct tcphdr);
4851 }
4852
4853 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
4854 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
4855
4856 /* RFC1323: The window in SYN & SYN/ACK segments is
4857 * never scaled.
4858 */
4859 tp->snd_wnd = ntohs(th->window);
4860 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
4861 tp->max_window = tp->snd_wnd;
4862
4863 TCP_ECN_rcv_syn(tp, th);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004864
John Heffner5d424d52006-03-20 17:53:41 -08004865 tcp_mtup_init(sk);
Arnaldo Carvalho de Melod83d8462005-12-13 23:26:10 -08004866 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004867 tcp_initialize_rcv_mss(sk);
4868
4869
4870 tcp_send_synack(sk);
4871#if 0
4872 /* Note, we could accept data and URG from this segment.
4873 * There are no obstacles to make this.
4874 *
4875 * However, if we ignore data in ACKless segments sometimes,
4876 * we have no reasons to accept it sometimes.
4877 * Also, seems the code doing it in step6 of tcp_rcv_state_process
4878 * is not flawless. So, discard packet for sanity.
4879 * Uncomment this return to process the data.
4880 */
4881 return -1;
4882#else
4883 goto discard;
4884#endif
4885 }
4886 /* "fifth, if neither of the SYN or RST bits is set then
4887 * drop the segment and return."
4888 */
4889
4890discard_and_undo:
4891 tcp_clear_options(&tp->rx_opt);
4892 tp->rx_opt.mss_clamp = saved_clamp;
4893 goto discard;
4894
4895reset_and_undo:
4896 tcp_clear_options(&tp->rx_opt);
4897 tp->rx_opt.mss_clamp = saved_clamp;
4898 return 1;
4899}
4900
4901
4902/*
4903 * This function implements the receiving procedure of RFC 793 for
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004904 * all states except ESTABLISHED and TIME_WAIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004905 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
4906 * address independent.
4907 */
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004908
Linus Torvalds1da177e2005-04-16 15:20:36 -07004909int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
4910 struct tcphdr *th, unsigned len)
4911{
4912 struct tcp_sock *tp = tcp_sk(sk);
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -08004913 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004914 int queued = 0;
4915
4916 tp->rx_opt.saw_tstamp = 0;
4917
4918 switch (sk->sk_state) {
4919 case TCP_CLOSE:
4920 goto discard;
4921
4922 case TCP_LISTEN:
Stephen Hemminger2de979b2007-03-08 20:45:19 -08004923 if (th->ack)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004924 return 1;
4925
Stephen Hemminger2de979b2007-03-08 20:45:19 -08004926 if (th->rst)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004927 goto discard;
4928
Stephen Hemminger2de979b2007-03-08 20:45:19 -08004929 if (th->syn) {
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -08004930 if (icsk->icsk_af_ops->conn_request(sk, skb) < 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004931 return 1;
4932
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004933 /* Now we have several options: In theory there is
4934 * nothing else in the frame. KA9Q has an option to
Linus Torvalds1da177e2005-04-16 15:20:36 -07004935 * send data with the syn, BSD accepts data with the
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004936 * syn up to the [to be] advertised window and
4937 * Solaris 2.1 gives you a protocol error. For now
4938 * we just ignore it, that fits the spec precisely
Linus Torvalds1da177e2005-04-16 15:20:36 -07004939 * and avoids incompatibilities. It would be nice in
4940 * future to drop through and process the data.
4941 *
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004942 * Now that TTCP is starting to be used we ought to
Linus Torvalds1da177e2005-04-16 15:20:36 -07004943 * queue this data.
4944 * But, this leaves one open to an easy denial of
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09004945 * service attack, and SYN cookies can't defend
Linus Torvalds1da177e2005-04-16 15:20:36 -07004946 * against this problem. So, we drop the data
Masayuki Nakagawafb7e2392007-01-23 20:15:06 -08004947 * in the interest of security over speed unless
4948 * it's still in use.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004949 */
Masayuki Nakagawafb7e2392007-01-23 20:15:06 -08004950 kfree_skb(skb);
4951 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07004952 }
4953 goto discard;
4954
4955 case TCP_SYN_SENT:
Linus Torvalds1da177e2005-04-16 15:20:36 -07004956 queued = tcp_rcv_synsent_state_process(sk, skb, th, len);
4957 if (queued >= 0)
4958 return queued;
4959
4960 /* Do step6 onward by hand. */
4961 tcp_urg(sk, skb, th);
4962 __kfree_skb(skb);
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07004963 tcp_data_snd_check(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004964 return 0;
4965 }
4966
4967 if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004968 tcp_paws_discard(sk, skb)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004969 if (!th->rst) {
4970 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
4971 tcp_send_dupack(sk, skb);
4972 goto discard;
4973 }
4974 /* Reset is accepted even if it did not pass PAWS. */
4975 }
4976
4977 /* step 1: check sequence number */
4978 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
4979 if (!th->rst)
4980 tcp_send_dupack(sk, skb);
4981 goto discard;
4982 }
4983
4984 /* step 2: check RST bit */
Stephen Hemminger2de979b2007-03-08 20:45:19 -08004985 if (th->rst) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004986 tcp_reset(sk);
4987 goto discard;
4988 }
4989
4990 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
4991
4992 /* step 3: check security and precedence [ignored] */
4993
4994 /* step 4:
4995 *
4996 * Check for a SYN in window.
4997 */
4998 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4999 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN);
5000 tcp_reset(sk);
5001 return 1;
5002 }
5003
5004 /* step 5: check the ACK field */
5005 if (th->ack) {
5006 int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH);
5007
Stephen Hemminger2de979b2007-03-08 20:45:19 -08005008 switch (sk->sk_state) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07005009 case TCP_SYN_RECV:
5010 if (acceptable) {
5011 tp->copied_seq = tp->rcv_nxt;
Ralf Baechlee16aa202006-12-07 00:11:33 -08005012 smp_mb();
Linus Torvalds1da177e2005-04-16 15:20:36 -07005013 tcp_set_state(sk, TCP_ESTABLISHED);
5014 sk->sk_state_change(sk);
5015
5016 /* Note, that this wakeup is only for marginal
5017 * crossed SYN case. Passively open sockets
5018 * are not waked up, because sk->sk_sleep ==
5019 * NULL and sk->sk_socket == NULL.
5020 */
5021 if (sk->sk_socket) {
5022 sk_wake_async(sk,0,POLL_OUT);
5023 }
5024
5025 tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
5026 tp->snd_wnd = ntohs(th->window) <<
5027 tp->rx_opt.snd_wscale;
5028 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq,
5029 TCP_SKB_CB(skb)->seq);
5030
5031 /* tcp_ack considers this ACK as duplicate
5032 * and does not calculate rtt.
5033 * Fix it at least with timestamps.
5034 */
5035 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
5036 !tp->srtt)
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08005037 tcp_ack_saw_tstamp(sk, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005038
5039 if (tp->rx_opt.tstamp_ok)
5040 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
5041
5042 /* Make sure socket is routed, for
5043 * correct metrics.
5044 */
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -08005045 icsk->icsk_af_ops->rebuild_header(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005046
5047 tcp_init_metrics(sk);
5048
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03005049 tcp_init_congestion_control(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -07005050
Linus Torvalds1da177e2005-04-16 15:20:36 -07005051 /* Prevent spurious tcp_cwnd_restart() on
5052 * first data packet.
5053 */
5054 tp->lsndtime = tcp_time_stamp;
5055
John Heffner5d424d52006-03-20 17:53:41 -08005056 tcp_mtup_init(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005057 tcp_initialize_rcv_mss(sk);
5058 tcp_init_buffer_space(sk);
5059 tcp_fast_path_on(tp);
5060 } else {
5061 return 1;
5062 }
5063 break;
5064
5065 case TCP_FIN_WAIT1:
5066 if (tp->snd_una == tp->write_seq) {
5067 tcp_set_state(sk, TCP_FIN_WAIT2);
5068 sk->sk_shutdown |= SEND_SHUTDOWN;
5069 dst_confirm(sk->sk_dst_cache);
5070
5071 if (!sock_flag(sk, SOCK_DEAD))
5072 /* Wake up lingering close() */
5073 sk->sk_state_change(sk);
5074 else {
5075 int tmo;
5076
5077 if (tp->linger2 < 0 ||
5078 (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
5079 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) {
5080 tcp_done(sk);
5081 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA);
5082 return 1;
5083 }
5084
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07005085 tmo = tcp_fin_time(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005086 if (tmo > TCP_TIMEWAIT_LEN) {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07005087 inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005088 } else if (th->fin || sock_owned_by_user(sk)) {
5089 /* Bad case. We could lose such FIN otherwise.
5090 * It is not a big problem, but it looks confusing
5091 * and not so rare event. We still can lose it now,
5092 * if it spins in bh_lock_sock(), but it is really
5093 * marginal case.
5094 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07005095 inet_csk_reset_keepalive_timer(sk, tmo);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005096 } else {
5097 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
5098 goto discard;
5099 }
5100 }
5101 }
5102 break;
5103
5104 case TCP_CLOSING:
5105 if (tp->snd_una == tp->write_seq) {
5106 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
5107 goto discard;
5108 }
5109 break;
5110
5111 case TCP_LAST_ACK:
5112 if (tp->snd_una == tp->write_seq) {
5113 tcp_update_metrics(sk);
5114 tcp_done(sk);
5115 goto discard;
5116 }
5117 break;
5118 }
5119 } else
5120 goto discard;
5121
5122 /* step 6: check the URG bit */
5123 tcp_urg(sk, skb, th);
5124
5125 /* step 7: process the segment text */
5126 switch (sk->sk_state) {
5127 case TCP_CLOSE_WAIT:
5128 case TCP_CLOSING:
5129 case TCP_LAST_ACK:
5130 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
5131 break;
5132 case TCP_FIN_WAIT1:
5133 case TCP_FIN_WAIT2:
5134 /* RFC 793 says to queue data in these states,
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09005135 * RFC 1122 says we MUST send a reset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07005136 * BSD 4.4 also does reset.
5137 */
5138 if (sk->sk_shutdown & RCV_SHUTDOWN) {
5139 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
5140 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
5141 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA);
5142 tcp_reset(sk);
5143 return 1;
5144 }
5145 }
5146 /* Fall through */
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09005147 case TCP_ESTABLISHED:
Linus Torvalds1da177e2005-04-16 15:20:36 -07005148 tcp_data_queue(sk, skb);
5149 queued = 1;
5150 break;
5151 }
5152
5153 /* tcp_data could move socket to TIME-WAIT */
5154 if (sk->sk_state != TCP_CLOSE) {
Ilpo Järvinen9e412ba2007-04-20 22:18:02 -07005155 tcp_data_snd_check(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005156 tcp_ack_snd_check(sk);
5157 }
5158
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09005159 if (!queued) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07005160discard:
5161 __kfree_skb(skb);
5162 }
5163 return 0;
5164}
5165
5166EXPORT_SYMBOL(sysctl_tcp_ecn);
5167EXPORT_SYMBOL(sysctl_tcp_reordering);
Linus Torvalds1da177e2005-04-16 15:20:36 -07005168EXPORT_SYMBOL(tcp_parse_options);
5169EXPORT_SYMBOL(tcp_rcv_established);
5170EXPORT_SYMBOL(tcp_rcv_state_process);
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08005171EXPORT_SYMBOL(tcp_initialize_rcv_mss);