blob: c701f6abbfc14a3ab05ba52c7469dc8cb5875df8 [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.
53 * Andi Kleen: Add tcp_measure_rcv_mss to make
54 * connections with MSS<min(MTU,ann. MSS)
55 * work without delayed acks.
56 * 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;
88int sysctl_tcp_frto __read_mostly;
89int sysctl_tcp_nometrics_save __read_mostly;
Linus Torvalds1da177e2005-04-16 15:20:36 -070090
Brian Haleyab32ea52006-09-22 14:15:41 -070091int sysctl_tcp_moderate_rcvbuf __read_mostly = 1;
92int sysctl_tcp_abc __read_mostly;
Linus Torvalds1da177e2005-04-16 15:20:36 -070093
Linus Torvalds1da177e2005-04-16 15:20:36 -070094#define FLAG_DATA 0x01 /* Incoming frame contained data. */
95#define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
96#define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
97#define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
98#define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
99#define FLAG_DATA_SACKED 0x20 /* New SACK. */
100#define FLAG_ECE 0x40 /* ECE in this ACK */
101#define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */
102#define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
103
104#define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
105#define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
106#define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
107#define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
108
109#define IsReno(tp) ((tp)->rx_opt.sack_ok == 0)
110#define IsFack(tp) ((tp)->rx_opt.sack_ok & 2)
111#define IsDSack(tp) ((tp)->rx_opt.sack_ok & 4)
112
113#define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
114
115/* Adapt the MSS value used to make delayed ack decision to the
116 * real world.
117 */
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800118static void tcp_measure_rcv_mss(struct sock *sk,
119 const struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700120{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700121 struct inet_connection_sock *icsk = inet_csk(sk);
122 const unsigned int lss = icsk->icsk_ack.last_seg_size;
123 unsigned int len;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700124
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700125 icsk->icsk_ack.last_seg_size = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700126
127 /* skb->len may jitter because of SACKs, even if peer
128 * sends good full-sized frames.
129 */
Herbert Xuff9b5e02006-08-31 15:11:02 -0700130 len = skb_shinfo(skb)->gso_size ?: skb->len;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700131 if (len >= icsk->icsk_ack.rcv_mss) {
132 icsk->icsk_ack.rcv_mss = len;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700133 } else {
134 /* Otherwise, we make more careful check taking into account,
135 * that SACKs block is variable.
136 *
137 * "len" is invariant segment length, including TCP header.
138 */
139 len += skb->data - skb->h.raw;
140 if (len >= TCP_MIN_RCVMSS + sizeof(struct tcphdr) ||
141 /* If PSH is not set, packet should be
142 * full sized, provided peer TCP is not badly broken.
143 * This observation (if it is correct 8)) allows
144 * to handle super-low mtu links fairly.
145 */
146 (len >= TCP_MIN_MSS + sizeof(struct tcphdr) &&
147 !(tcp_flag_word(skb->h.th)&TCP_REMNANT))) {
148 /* Subtract also invariant (if peer is RFC compliant),
149 * tcp header plus fixed timestamp option length.
150 * Resulting "len" is MSS free of SACK jitter.
151 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700152 len -= tcp_sk(sk)->tcp_header_len;
153 icsk->icsk_ack.last_seg_size = len;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700154 if (len == lss) {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700155 icsk->icsk_ack.rcv_mss = len;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700156 return;
157 }
158 }
Alexey Kuznetsov1ef96962006-09-19 12:52:50 -0700159 if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED)
160 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700161 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700162 }
163}
164
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700165static void tcp_incr_quickack(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700166{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700167 struct inet_connection_sock *icsk = inet_csk(sk);
168 unsigned quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700169
170 if (quickacks==0)
171 quickacks=2;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700172 if (quickacks > icsk->icsk_ack.quick)
173 icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700174}
175
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700176void tcp_enter_quickack_mode(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700177{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700178 struct inet_connection_sock *icsk = inet_csk(sk);
179 tcp_incr_quickack(sk);
180 icsk->icsk_ack.pingpong = 0;
181 icsk->icsk_ack.ato = TCP_ATO_MIN;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700182}
183
184/* Send ACKs quickly, if "quick" count is not exhausted
185 * and the session is not interactive.
186 */
187
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700188static inline int tcp_in_quickack_mode(const struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700189{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700190 const struct inet_connection_sock *icsk = inet_csk(sk);
191 return icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700192}
193
194/* Buffer size and advertised window tuning.
195 *
196 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
197 */
198
199static void tcp_fixup_sndbuf(struct sock *sk)
200{
201 int sndmem = tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER + 16 +
202 sizeof(struct sk_buff);
203
204 if (sk->sk_sndbuf < 3 * sndmem)
205 sk->sk_sndbuf = min(3 * sndmem, sysctl_tcp_wmem[2]);
206}
207
208/* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
209 *
210 * All tcp_full_space() is split to two parts: "network" buffer, allocated
211 * forward and advertised in receiver window (tp->rcv_wnd) and
212 * "application buffer", required to isolate scheduling/application
213 * latencies from network.
214 * window_clamp is maximal advertised window. It can be less than
215 * tcp_full_space(), in this case tcp_full_space() - window_clamp
216 * is reserved for "application" buffer. The less window_clamp is
217 * the smoother our behaviour from viewpoint of network, but the lower
218 * throughput and the higher sensitivity of the connection to losses. 8)
219 *
220 * rcv_ssthresh is more strict window_clamp used at "slow start"
221 * phase to predict further behaviour of this connection.
222 * It is used for two goals:
223 * - to enforce header prediction at sender, even when application
224 * requires some significant "application buffer". It is check #1.
225 * - to prevent pruning of receive queue because of misprediction
226 * of receiver window. Check #2.
227 *
228 * The scheme does not work when sender sends good segments opening
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800229 * window and then starts to feed us spaghetti. But it should work
Linus Torvalds1da177e2005-04-16 15:20:36 -0700230 * in common situations. Otherwise, we have to rely on queue collapsing.
231 */
232
233/* Slow part of check#2. */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700234static int __tcp_grow_window(const struct sock *sk, struct tcp_sock *tp,
235 const struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700236{
237 /* Optimize this! */
238 int truesize = tcp_win_from_space(skb->truesize)/2;
John Heffner326f36e2005-11-10 17:11:48 -0800239 int window = tcp_win_from_space(sysctl_tcp_rmem[2])/2;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700240
241 while (tp->rcv_ssthresh <= window) {
242 if (truesize <= skb->len)
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700243 return 2 * inet_csk(sk)->icsk_ack.rcv_mss;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700244
245 truesize >>= 1;
246 window >>= 1;
247 }
248 return 0;
249}
250
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800251static void tcp_grow_window(struct sock *sk, struct tcp_sock *tp,
252 struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700253{
254 /* Check #1 */
255 if (tp->rcv_ssthresh < tp->window_clamp &&
256 (int)tp->rcv_ssthresh < tcp_space(sk) &&
257 !tcp_memory_pressure) {
258 int incr;
259
260 /* Check #2. Increase window, if skb with such overhead
261 * will fit to rcvbuf in future.
262 */
263 if (tcp_win_from_space(skb->truesize) <= skb->len)
264 incr = 2*tp->advmss;
265 else
266 incr = __tcp_grow_window(sk, tp, skb);
267
268 if (incr) {
269 tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, tp->window_clamp);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700270 inet_csk(sk)->icsk_ack.quick |= 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700271 }
272 }
273}
274
275/* 3. Tuning rcvbuf, when connection enters established state. */
276
277static void tcp_fixup_rcvbuf(struct sock *sk)
278{
279 struct tcp_sock *tp = tcp_sk(sk);
280 int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff);
281
282 /* Try to select rcvbuf so that 4 mss-sized segments
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800283 * will fit to window and corresponding skbs will fit to our rcvbuf.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700284 * (was 3; 4 is minimum to allow fast retransmit to work.)
285 */
286 while (tcp_win_from_space(rcvmem) < tp->advmss)
287 rcvmem += 128;
288 if (sk->sk_rcvbuf < 4 * rcvmem)
289 sk->sk_rcvbuf = min(4 * rcvmem, sysctl_tcp_rmem[2]);
290}
291
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800292/* 4. Try to fixup all. It is made immediately after connection enters
Linus Torvalds1da177e2005-04-16 15:20:36 -0700293 * established state.
294 */
295static void tcp_init_buffer_space(struct sock *sk)
296{
297 struct tcp_sock *tp = tcp_sk(sk);
298 int maxwin;
299
300 if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK))
301 tcp_fixup_rcvbuf(sk);
302 if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK))
303 tcp_fixup_sndbuf(sk);
304
305 tp->rcvq_space.space = tp->rcv_wnd;
306
307 maxwin = tcp_full_space(sk);
308
309 if (tp->window_clamp >= maxwin) {
310 tp->window_clamp = maxwin;
311
312 if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss)
313 tp->window_clamp = max(maxwin -
314 (maxwin >> sysctl_tcp_app_win),
315 4 * tp->advmss);
316 }
317
318 /* Force reservation of one segment. */
319 if (sysctl_tcp_app_win &&
320 tp->window_clamp > 2 * tp->advmss &&
321 tp->window_clamp + tp->advmss > maxwin)
322 tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss);
323
324 tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp);
325 tp->snd_cwnd_stamp = tcp_time_stamp;
326}
327
Linus Torvalds1da177e2005-04-16 15:20:36 -0700328/* 5. Recalculate window clamp after socket hit its memory bounds. */
329static void tcp_clamp_window(struct sock *sk, struct tcp_sock *tp)
330{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300331 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700332
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300333 icsk->icsk_ack.quick = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700334
John Heffner326f36e2005-11-10 17:11:48 -0800335 if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] &&
336 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) &&
337 !tcp_memory_pressure &&
338 atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) {
339 sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc),
340 sysctl_tcp_rmem[2]);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700341 }
John Heffner326f36e2005-11-10 17:11:48 -0800342 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700343 tp->rcv_ssthresh = min(tp->window_clamp, 2U*tp->advmss);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700344}
345
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800346
347/* Initialize RCV_MSS value.
348 * RCV_MSS is an our guess about MSS used by the peer.
349 * We haven't any direct information about the MSS.
350 * It's better to underestimate the RCV_MSS rather than overestimate.
351 * Overestimations make us ACKing less frequently than needed.
352 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
353 */
354void tcp_initialize_rcv_mss(struct sock *sk)
355{
356 struct tcp_sock *tp = tcp_sk(sk);
357 unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache);
358
359 hint = min(hint, tp->rcv_wnd/2);
360 hint = min(hint, TCP_MIN_RCVMSS);
361 hint = max(hint, TCP_MIN_MSS);
362
363 inet_csk(sk)->icsk_ack.rcv_mss = hint;
364}
365
Linus Torvalds1da177e2005-04-16 15:20:36 -0700366/* Receiver "autotuning" code.
367 *
368 * The algorithm for RTT estimation w/o timestamps is based on
369 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
370 * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps>
371 *
372 * More detail on this code can be found at
373 * <http://www.psc.edu/~jheffner/senior_thesis.ps>,
374 * though this reference is out of date. A new paper
375 * is pending.
376 */
377static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep)
378{
379 u32 new_sample = tp->rcv_rtt_est.rtt;
380 long m = sample;
381
382 if (m == 0)
383 m = 1;
384
385 if (new_sample != 0) {
386 /* If we sample in larger samples in the non-timestamp
387 * case, we could grossly overestimate the RTT especially
388 * with chatty applications or bulk transfer apps which
389 * are stalled on filesystem I/O.
390 *
391 * Also, since we are only going for a minimum in the
Stephen Hemminger31f34262005-11-15 15:17:10 -0800392 * non-timestamp case, we do not smooth things out
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800393 * else with timestamps disabled convergence takes too
Linus Torvalds1da177e2005-04-16 15:20:36 -0700394 * long.
395 */
396 if (!win_dep) {
397 m -= (new_sample >> 3);
398 new_sample += m;
399 } else if (m < new_sample)
400 new_sample = m << 3;
401 } else {
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800402 /* No previous measure. */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700403 new_sample = m << 3;
404 }
405
406 if (tp->rcv_rtt_est.rtt != new_sample)
407 tp->rcv_rtt_est.rtt = new_sample;
408}
409
410static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp)
411{
412 if (tp->rcv_rtt_est.time == 0)
413 goto new_measure;
414 if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq))
415 return;
416 tcp_rcv_rtt_update(tp,
417 jiffies - tp->rcv_rtt_est.time,
418 1);
419
420new_measure:
421 tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd;
422 tp->rcv_rtt_est.time = tcp_time_stamp;
423}
424
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700425static inline void tcp_rcv_rtt_measure_ts(struct sock *sk, const struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700426{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700427 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700428 if (tp->rx_opt.rcv_tsecr &&
429 (TCP_SKB_CB(skb)->end_seq -
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700430 TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700431 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0);
432}
433
434/*
435 * This function should be called every time data is copied to user space.
436 * It calculates the appropriate TCP receive buffer space.
437 */
438void tcp_rcv_space_adjust(struct sock *sk)
439{
440 struct tcp_sock *tp = tcp_sk(sk);
441 int time;
442 int space;
443
444 if (tp->rcvq_space.time == 0)
445 goto new_measure;
446
447 time = tcp_time_stamp - tp->rcvq_space.time;
448 if (time < (tp->rcv_rtt_est.rtt >> 3) ||
449 tp->rcv_rtt_est.rtt == 0)
450 return;
451
452 space = 2 * (tp->copied_seq - tp->rcvq_space.seq);
453
454 space = max(tp->rcvq_space.space, space);
455
456 if (tp->rcvq_space.space != space) {
457 int rcvmem;
458
459 tp->rcvq_space.space = space;
460
John Heffner6fcf9412006-02-09 17:06:57 -0800461 if (sysctl_tcp_moderate_rcvbuf &&
462 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700463 int new_clamp = space;
464
465 /* Receive space grows, normalize in order to
466 * take into account packet headers and sk_buff
467 * structure overhead.
468 */
469 space /= tp->advmss;
470 if (!space)
471 space = 1;
472 rcvmem = (tp->advmss + MAX_TCP_HEADER +
473 16 + sizeof(struct sk_buff));
474 while (tcp_win_from_space(rcvmem) < tp->advmss)
475 rcvmem += 128;
476 space *= rcvmem;
477 space = min(space, sysctl_tcp_rmem[2]);
478 if (space > sk->sk_rcvbuf) {
479 sk->sk_rcvbuf = space;
480
481 /* Make the window clamp follow along. */
482 tp->window_clamp = new_clamp;
483 }
484 }
485 }
486
487new_measure:
488 tp->rcvq_space.seq = tp->copied_seq;
489 tp->rcvq_space.time = tcp_time_stamp;
490}
491
492/* There is something which you must keep in mind when you analyze the
493 * behavior of the tp->ato delayed ack timeout interval. When a
494 * connection starts up, we want to ack as quickly as possible. The
495 * problem is that "good" TCP's do slow start at the beginning of data
496 * transmission. The means that until we send the first few ACK's the
497 * sender will sit on his end and only queue most of his data, because
498 * he can only send snd_cwnd unacked packets at any given time. For
499 * each ACK we send, he increments snd_cwnd and transmits more of his
500 * queue. -DaveM
501 */
502static void tcp_event_data_recv(struct sock *sk, struct tcp_sock *tp, struct sk_buff *skb)
503{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700504 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700505 u32 now;
506
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700507 inet_csk_schedule_ack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700508
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700509 tcp_measure_rcv_mss(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700510
511 tcp_rcv_rtt_measure(tp);
512
513 now = tcp_time_stamp;
514
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700515 if (!icsk->icsk_ack.ato) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700516 /* The _first_ data packet received, initialize
517 * delayed ACK engine.
518 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700519 tcp_incr_quickack(sk);
520 icsk->icsk_ack.ato = TCP_ATO_MIN;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700521 } else {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700522 int m = now - icsk->icsk_ack.lrcvtime;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700523
524 if (m <= TCP_ATO_MIN/2) {
525 /* The fastest case is the first. */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700526 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2;
527 } else if (m < icsk->icsk_ack.ato) {
528 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m;
529 if (icsk->icsk_ack.ato > icsk->icsk_rto)
530 icsk->icsk_ack.ato = icsk->icsk_rto;
531 } else if (m > icsk->icsk_rto) {
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800532 /* Too long gap. Apparently sender failed to
Linus Torvalds1da177e2005-04-16 15:20:36 -0700533 * restart window, so that we send ACKs quickly.
534 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700535 tcp_incr_quickack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700536 sk_stream_mem_reclaim(sk);
537 }
538 }
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700539 icsk->icsk_ack.lrcvtime = now;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700540
541 TCP_ECN_check_ce(tp, skb);
542
543 if (skb->len >= 128)
544 tcp_grow_window(sk, tp, skb);
545}
546
Linus Torvalds1da177e2005-04-16 15:20:36 -0700547/* Called to compute a smoothed rtt estimate. The data fed to this
548 * routine either comes from timestamps, or from segments that were
549 * known _not_ to have been retransmitted [see Karn/Partridge
550 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
551 * piece by Van Jacobson.
552 * NOTE: the next three routines used to be one big routine.
553 * To save cycles in the RFC 1323 implementation it was better to break
554 * it up into three procedures. -- erics
555 */
Stephen Hemminger2d2abba2005-11-10 16:56:12 -0800556static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700557{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300558 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700559 long m = mrtt; /* RTT */
560
Linus Torvalds1da177e2005-04-16 15:20:36 -0700561 /* The following amusing code comes from Jacobson's
562 * article in SIGCOMM '88. Note that rtt and mdev
563 * are scaled versions of rtt and mean deviation.
564 * This is designed to be as fast as possible
565 * m stands for "measurement".
566 *
567 * On a 1990 paper the rto value is changed to:
568 * RTO = rtt + 4 * mdev
569 *
570 * Funny. This algorithm seems to be very broken.
571 * These formulae increase RTO, when it should be decreased, increase
Stephen Hemminger31f34262005-11-15 15:17:10 -0800572 * too slowly, when it should be increased quickly, decrease too quickly
Linus Torvalds1da177e2005-04-16 15:20:36 -0700573 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
574 * does not matter how to _calculate_ it. Seems, it was trap
575 * that VJ failed to avoid. 8)
576 */
577 if(m == 0)
578 m = 1;
579 if (tp->srtt != 0) {
580 m -= (tp->srtt >> 3); /* m is now error in rtt est */
581 tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */
582 if (m < 0) {
583 m = -m; /* m is now abs(error) */
584 m -= (tp->mdev >> 2); /* similar update on mdev */
585 /* This is similar to one of Eifel findings.
586 * Eifel blocks mdev updates when rtt decreases.
587 * This solution is a bit different: we use finer gain
588 * for mdev in this case (alpha*beta).
589 * Like Eifel it also prevents growth of rto,
590 * but also it limits too fast rto decreases,
591 * happening in pure Eifel.
592 */
593 if (m > 0)
594 m >>= 3;
595 } else {
596 m -= (tp->mdev >> 2); /* similar update on mdev */
597 }
598 tp->mdev += m; /* mdev = 3/4 mdev + 1/4 new */
599 if (tp->mdev > tp->mdev_max) {
600 tp->mdev_max = tp->mdev;
601 if (tp->mdev_max > tp->rttvar)
602 tp->rttvar = tp->mdev_max;
603 }
604 if (after(tp->snd_una, tp->rtt_seq)) {
605 if (tp->mdev_max < tp->rttvar)
606 tp->rttvar -= (tp->rttvar-tp->mdev_max)>>2;
607 tp->rtt_seq = tp->snd_nxt;
608 tp->mdev_max = TCP_RTO_MIN;
609 }
610 } else {
611 /* no previous measure. */
612 tp->srtt = m<<3; /* take the measured time to be rtt */
613 tp->mdev = m<<1; /* make sure rto = 3*rtt */
614 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
615 tp->rtt_seq = tp->snd_nxt;
616 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700617}
618
619/* Calculate rto without backoff. This is the second half of Van Jacobson's
620 * routine referred to above.
621 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700622static inline void tcp_set_rto(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700623{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700624 const struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700625 /* Old crap is replaced with new one. 8)
626 *
627 * More seriously:
628 * 1. If rtt variance happened to be less 50msec, it is hallucination.
629 * It cannot be less due to utterly erratic ACK generation made
630 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
631 * to do with delayed acks, because at cwnd>2 true delack timeout
632 * is invisible. Actually, Linux-2.4 also generates erratic
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800633 * ACKs in some circumstances.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700634 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700635 inet_csk(sk)->icsk_rto = (tp->srtt >> 3) + tp->rttvar;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700636
637 /* 2. Fixups made earlier cannot be right.
638 * If we do not estimate RTO correctly without them,
639 * all the algo is pure shit and should be replaced
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800640 * with correct one. It is exactly, which we pretend to do.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700641 */
642}
643
644/* NOTE: clamping at TCP_RTO_MIN is not required, current algo
645 * guarantees that rto is higher.
646 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700647static inline void tcp_bound_rto(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700648{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700649 if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
650 inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700651}
652
653/* Save metrics learned by this TCP session.
654 This function is called only, when TCP finishes successfully
655 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
656 */
657void tcp_update_metrics(struct sock *sk)
658{
659 struct tcp_sock *tp = tcp_sk(sk);
660 struct dst_entry *dst = __sk_dst_get(sk);
661
662 if (sysctl_tcp_nometrics_save)
663 return;
664
665 dst_confirm(dst);
666
667 if (dst && (dst->flags&DST_HOST)) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300668 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700669 int m;
670
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300671 if (icsk->icsk_backoff || !tp->srtt) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700672 /* This session failed to estimate rtt. Why?
673 * Probably, no packets returned in time.
674 * Reset our results.
675 */
676 if (!(dst_metric_locked(dst, RTAX_RTT)))
677 dst->metrics[RTAX_RTT-1] = 0;
678 return;
679 }
680
681 m = dst_metric(dst, RTAX_RTT) - tp->srtt;
682
683 /* If newly calculated rtt larger than stored one,
684 * store new one. Otherwise, use EWMA. Remember,
685 * rtt overestimation is always better than underestimation.
686 */
687 if (!(dst_metric_locked(dst, RTAX_RTT))) {
688 if (m <= 0)
689 dst->metrics[RTAX_RTT-1] = tp->srtt;
690 else
691 dst->metrics[RTAX_RTT-1] -= (m>>3);
692 }
693
694 if (!(dst_metric_locked(dst, RTAX_RTTVAR))) {
695 if (m < 0)
696 m = -m;
697
698 /* Scale deviation to rttvar fixed point */
699 m >>= 1;
700 if (m < tp->mdev)
701 m = tp->mdev;
702
703 if (m >= dst_metric(dst, RTAX_RTTVAR))
704 dst->metrics[RTAX_RTTVAR-1] = m;
705 else
706 dst->metrics[RTAX_RTTVAR-1] -=
707 (dst->metrics[RTAX_RTTVAR-1] - m)>>2;
708 }
709
710 if (tp->snd_ssthresh >= 0xFFFF) {
711 /* Slow start still did not finish. */
712 if (dst_metric(dst, RTAX_SSTHRESH) &&
713 !dst_metric_locked(dst, RTAX_SSTHRESH) &&
714 (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH))
715 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1;
716 if (!dst_metric_locked(dst, RTAX_CWND) &&
717 tp->snd_cwnd > dst_metric(dst, RTAX_CWND))
718 dst->metrics[RTAX_CWND-1] = tp->snd_cwnd;
719 } else if (tp->snd_cwnd > tp->snd_ssthresh &&
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300720 icsk->icsk_ca_state == TCP_CA_Open) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700721 /* Cong. avoidance phase, cwnd is reliable. */
722 if (!dst_metric_locked(dst, RTAX_SSTHRESH))
723 dst->metrics[RTAX_SSTHRESH-1] =
724 max(tp->snd_cwnd >> 1, tp->snd_ssthresh);
725 if (!dst_metric_locked(dst, RTAX_CWND))
726 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_cwnd) >> 1;
727 } else {
728 /* Else slow start did not finish, cwnd is non-sense,
729 ssthresh may be also invalid.
730 */
731 if (!dst_metric_locked(dst, RTAX_CWND))
732 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_ssthresh) >> 1;
733 if (dst->metrics[RTAX_SSTHRESH-1] &&
734 !dst_metric_locked(dst, RTAX_SSTHRESH) &&
735 tp->snd_ssthresh > dst->metrics[RTAX_SSTHRESH-1])
736 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh;
737 }
738
739 if (!dst_metric_locked(dst, RTAX_REORDERING)) {
740 if (dst->metrics[RTAX_REORDERING-1] < tp->reordering &&
741 tp->reordering != sysctl_tcp_reordering)
742 dst->metrics[RTAX_REORDERING-1] = tp->reordering;
743 }
744 }
745}
746
747/* Numbers are taken from RFC2414. */
748__u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst)
749{
750 __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0);
751
752 if (!cwnd) {
David S. Millerc1b4a7e2005-07-05 15:24:38 -0700753 if (tp->mss_cache > 1460)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700754 cwnd = 2;
755 else
David S. Millerc1b4a7e2005-07-05 15:24:38 -0700756 cwnd = (tp->mss_cache > 1095) ? 3 : 4;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700757 }
758 return min_t(__u32, cwnd, tp->snd_cwnd_clamp);
759}
760
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800761/* Set slow start threshold and cwnd not falling to slow start */
762void tcp_enter_cwr(struct sock *sk)
763{
764 struct tcp_sock *tp = tcp_sk(sk);
765
766 tp->prior_ssthresh = 0;
767 tp->bytes_acked = 0;
768 if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) {
769 tp->undo_marker = 0;
770 tp->snd_ssthresh = inet_csk(sk)->icsk_ca_ops->ssthresh(sk);
771 tp->snd_cwnd = min(tp->snd_cwnd,
772 tcp_packets_in_flight(tp) + 1U);
773 tp->snd_cwnd_cnt = 0;
774 tp->high_seq = tp->snd_nxt;
775 tp->snd_cwnd_stamp = tcp_time_stamp;
776 TCP_ECN_queue_cwr(tp);
777
778 tcp_set_ca_state(sk, TCP_CA_CWR);
779 }
780}
781
Linus Torvalds1da177e2005-04-16 15:20:36 -0700782/* Initialize metrics on socket. */
783
784static void tcp_init_metrics(struct sock *sk)
785{
786 struct tcp_sock *tp = tcp_sk(sk);
787 struct dst_entry *dst = __sk_dst_get(sk);
788
789 if (dst == NULL)
790 goto reset;
791
792 dst_confirm(dst);
793
794 if (dst_metric_locked(dst, RTAX_CWND))
795 tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND);
796 if (dst_metric(dst, RTAX_SSTHRESH)) {
797 tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH);
798 if (tp->snd_ssthresh > tp->snd_cwnd_clamp)
799 tp->snd_ssthresh = tp->snd_cwnd_clamp;
800 }
801 if (dst_metric(dst, RTAX_REORDERING) &&
802 tp->reordering != dst_metric(dst, RTAX_REORDERING)) {
803 tp->rx_opt.sack_ok &= ~2;
804 tp->reordering = dst_metric(dst, RTAX_REORDERING);
805 }
806
807 if (dst_metric(dst, RTAX_RTT) == 0)
808 goto reset;
809
810 if (!tp->srtt && dst_metric(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3))
811 goto reset;
812
813 /* Initial rtt is determined from SYN,SYN-ACK.
814 * The segment is small and rtt may appear much
815 * less than real one. Use per-dst memory
816 * to make it more realistic.
817 *
818 * A bit of theory. RTT is time passed after "normal" sized packet
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800819 * is sent until it is ACKed. In normal circumstances sending small
Linus Torvalds1da177e2005-04-16 15:20:36 -0700820 * packets force peer to delay ACKs and calculation is correct too.
821 * The algorithm is adaptive and, provided we follow specs, it
822 * NEVER underestimate RTT. BUT! If peer tries to make some clever
823 * tricks sort of "quick acks" for time long enough to decrease RTT
824 * to low value, and then abruptly stops to do it and starts to delay
825 * ACKs, wait for troubles.
826 */
827 if (dst_metric(dst, RTAX_RTT) > tp->srtt) {
828 tp->srtt = dst_metric(dst, RTAX_RTT);
829 tp->rtt_seq = tp->snd_nxt;
830 }
831 if (dst_metric(dst, RTAX_RTTVAR) > tp->mdev) {
832 tp->mdev = dst_metric(dst, RTAX_RTTVAR);
833 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
834 }
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700835 tcp_set_rto(sk);
836 tcp_bound_rto(sk);
837 if (inet_csk(sk)->icsk_rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700838 goto reset;
839 tp->snd_cwnd = tcp_init_cwnd(tp, dst);
840 tp->snd_cwnd_stamp = tcp_time_stamp;
841 return;
842
843reset:
844 /* Play conservative. If timestamps are not
845 * supported, TCP will fail to recalculate correct
846 * rtt, if initial rto is too small. FORGET ALL AND RESET!
847 */
848 if (!tp->rx_opt.saw_tstamp && tp->srtt) {
849 tp->srtt = 0;
850 tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700851 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700852 }
853}
854
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300855static void tcp_update_reordering(struct sock *sk, const int metric,
856 const int ts)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700857{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300858 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700859 if (metric > tp->reordering) {
860 tp->reordering = min(TCP_MAX_REORDERING, metric);
861
862 /* This exciting event is worth to be remembered. 8) */
863 if (ts)
864 NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER);
865 else if (IsReno(tp))
866 NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER);
867 else if (IsFack(tp))
868 NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER);
869 else
870 NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER);
871#if FASTRETRANS_DEBUG > 1
872 printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n",
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300873 tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700874 tp->reordering,
875 tp->fackets_out,
876 tp->sacked_out,
877 tp->undo_marker ? tp->undo_retrans : 0);
878#endif
879 /* Disable FACK yet. */
880 tp->rx_opt.sack_ok &= ~2;
881 }
882}
883
884/* This procedure tags the retransmission queue when SACKs arrive.
885 *
886 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
887 * Packets in queue with these bits set are counted in variables
888 * sacked_out, retrans_out and lost_out, correspondingly.
889 *
890 * Valid combinations are:
891 * Tag InFlight Description
892 * 0 1 - orig segment is in flight.
893 * S 0 - nothing flies, orig reached receiver.
894 * L 0 - nothing flies, orig lost by net.
895 * R 2 - both orig and retransmit are in flight.
896 * L|R 1 - orig is lost, retransmit is in flight.
897 * S|R 1 - orig reached receiver, retrans is still in flight.
898 * (L|S|R is logically valid, it could occur when L|R is sacked,
899 * but it is equivalent to plain S and code short-curcuits it to S.
900 * L|S is logically invalid, it would mean -1 packet in flight 8))
901 *
902 * These 6 states form finite state machine, controlled by the following events:
903 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
904 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
905 * 3. Loss detection event of one of three flavors:
906 * A. Scoreboard estimator decided the packet is lost.
907 * A'. Reno "three dupacks" marks head of queue lost.
908 * A''. Its FACK modfication, head until snd.fack is lost.
909 * B. SACK arrives sacking data transmitted after never retransmitted
910 * hole was sent out.
911 * C. SACK arrives sacking SND.NXT at the moment, when the
912 * segment was retransmitted.
913 * 4. D-SACK added new rule: D-SACK changes any tag to S.
914 *
915 * It is pleasant to note, that state diagram turns out to be commutative,
916 * so that we are allowed not to be bothered by order of our actions,
917 * when multiple events arrive simultaneously. (see the function below).
918 *
919 * Reordering detection.
920 * --------------------
921 * Reordering metric is maximal distance, which a packet can be displaced
922 * in packet stream. With SACKs we can estimate it:
923 *
924 * 1. SACK fills old hole and the corresponding segment was not
925 * ever retransmitted -> reordering. Alas, we cannot use it
926 * when segment was retransmitted.
927 * 2. The last flaw is solved with D-SACK. D-SACK arrives
928 * for retransmitted and already SACKed segment -> reordering..
929 * Both of these heuristics are not used in Loss state, when we cannot
930 * account for retransmits accurately.
931 */
932static int
933tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_una)
934{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300935 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700936 struct tcp_sock *tp = tcp_sk(sk);
937 unsigned char *ptr = ack_skb->h.raw + TCP_SKB_CB(ack_skb)->sacked;
Al Viro269bd272006-09-27 18:32:28 -0700938 struct tcp_sack_block_wire *sp = (struct tcp_sack_block_wire *)(ptr+2);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700939 int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3;
940 int reord = tp->packets_out;
941 int prior_fackets;
942 u32 lost_retrans = 0;
943 int flag = 0;
Stephen Hemminger6a438bb2005-11-10 17:14:59 -0800944 int dup_sack = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700945 int i;
946
Linus Torvalds1da177e2005-04-16 15:20:36 -0700947 if (!tp->sacked_out)
948 tp->fackets_out = 0;
949 prior_fackets = tp->fackets_out;
950
Stephen Hemminger6a438bb2005-11-10 17:14:59 -0800951 /* SACK fastpath:
952 * if the only SACK change is the increase of the end_seq of
953 * the first block then only apply that SACK block
954 * and use retrans queue hinting otherwise slowpath */
955 flag = 1;
956 for (i = 0; i< num_sacks; i++) {
957 __u32 start_seq = ntohl(sp[i].start_seq);
958 __u32 end_seq = ntohl(sp[i].end_seq);
959
960 if (i == 0){
961 if (tp->recv_sack_cache[i].start_seq != start_seq)
962 flag = 0;
963 } else {
964 if ((tp->recv_sack_cache[i].start_seq != start_seq) ||
965 (tp->recv_sack_cache[i].end_seq != end_seq))
966 flag = 0;
967 }
968 tp->recv_sack_cache[i].start_seq = start_seq;
969 tp->recv_sack_cache[i].end_seq = end_seq;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700970
971 /* Check for D-SACK. */
972 if (i == 0) {
973 u32 ack = TCP_SKB_CB(ack_skb)->ack_seq;
974
975 if (before(start_seq, ack)) {
976 dup_sack = 1;
977 tp->rx_opt.sack_ok |= 4;
978 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV);
979 } else if (num_sacks > 1 &&
980 !after(end_seq, ntohl(sp[1].end_seq)) &&
981 !before(start_seq, ntohl(sp[1].start_seq))) {
982 dup_sack = 1;
983 tp->rx_opt.sack_ok |= 4;
984 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV);
985 }
986
987 /* D-SACK for already forgotten data...
988 * Do dumb counting. */
989 if (dup_sack &&
990 !after(end_seq, prior_snd_una) &&
991 after(end_seq, tp->undo_marker))
992 tp->undo_retrans--;
993
994 /* Eliminate too old ACKs, but take into
995 * account more or less fresh ones, they can
996 * contain valid SACK info.
997 */
998 if (before(ack, prior_snd_una - tp->max_window))
999 return 0;
1000 }
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001001 }
1002
1003 if (flag)
1004 num_sacks = 1;
1005 else {
1006 int j;
1007 tp->fastpath_skb_hint = NULL;
1008
1009 /* order SACK blocks to allow in order walk of the retrans queue */
1010 for (i = num_sacks-1; i > 0; i--) {
1011 for (j = 0; j < i; j++){
1012 if (after(ntohl(sp[j].start_seq),
1013 ntohl(sp[j+1].start_seq))){
1014 sp[j].start_seq = htonl(tp->recv_sack_cache[j+1].start_seq);
1015 sp[j].end_seq = htonl(tp->recv_sack_cache[j+1].end_seq);
1016 sp[j+1].start_seq = htonl(tp->recv_sack_cache[j].start_seq);
1017 sp[j+1].end_seq = htonl(tp->recv_sack_cache[j].end_seq);
1018 }
1019
1020 }
1021 }
1022 }
1023
1024 /* clear flag as used for different purpose in following code */
1025 flag = 0;
1026
1027 for (i=0; i<num_sacks; i++, sp++) {
1028 struct sk_buff *skb;
1029 __u32 start_seq = ntohl(sp->start_seq);
1030 __u32 end_seq = ntohl(sp->end_seq);
1031 int fack_count;
1032
1033 /* Use SACK fastpath hint if valid */
1034 if (tp->fastpath_skb_hint) {
1035 skb = tp->fastpath_skb_hint;
1036 fack_count = tp->fastpath_cnt_hint;
1037 } else {
1038 skb = sk->sk_write_queue.next;
1039 fack_count = 0;
1040 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001041
1042 /* Event "B" in the comment above. */
1043 if (after(end_seq, tp->high_seq))
1044 flag |= FLAG_DATA_LOST;
1045
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001046 sk_stream_for_retrans_queue_from(skb, sk) {
David S. Miller6475be12005-09-01 22:47:01 -07001047 int in_sack, pcount;
1048 u8 sacked;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001049
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001050 tp->fastpath_skb_hint = skb;
1051 tp->fastpath_cnt_hint = fack_count;
1052
Linus Torvalds1da177e2005-04-16 15:20:36 -07001053 /* The retransmission queue is always in order, so
1054 * we can short-circuit the walk early.
1055 */
David S. Miller6475be12005-09-01 22:47:01 -07001056 if (!before(TCP_SKB_CB(skb)->seq, end_seq))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001057 break;
1058
Herbert Xu3c05d922005-09-14 20:50:35 -07001059 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
1060 !before(end_seq, TCP_SKB_CB(skb)->end_seq);
1061
David S. Miller6475be12005-09-01 22:47:01 -07001062 pcount = tcp_skb_pcount(skb);
1063
Herbert Xu3c05d922005-09-14 20:50:35 -07001064 if (pcount > 1 && !in_sack &&
1065 after(TCP_SKB_CB(skb)->end_seq, start_seq)) {
David S. Miller6475be12005-09-01 22:47:01 -07001066 unsigned int pkt_len;
1067
Herbert Xu3c05d922005-09-14 20:50:35 -07001068 in_sack = !after(start_seq,
1069 TCP_SKB_CB(skb)->seq);
1070
1071 if (!in_sack)
David S. Miller6475be12005-09-01 22:47:01 -07001072 pkt_len = (start_seq -
1073 TCP_SKB_CB(skb)->seq);
1074 else
1075 pkt_len = (end_seq -
1076 TCP_SKB_CB(skb)->seq);
Herbert Xu79671682006-06-22 02:40:14 -07001077 if (tcp_fragment(sk, skb, pkt_len, skb_shinfo(skb)->gso_size))
David S. Miller6475be12005-09-01 22:47:01 -07001078 break;
1079 pcount = tcp_skb_pcount(skb);
1080 }
1081
1082 fack_count += pcount;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001083
David S. Miller6475be12005-09-01 22:47:01 -07001084 sacked = TCP_SKB_CB(skb)->sacked;
1085
Linus Torvalds1da177e2005-04-16 15:20:36 -07001086 /* Account D-SACK for retransmitted packet. */
1087 if ((dup_sack && in_sack) &&
1088 (sacked & TCPCB_RETRANS) &&
1089 after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
1090 tp->undo_retrans--;
1091
1092 /* The frame is ACKed. */
1093 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) {
1094 if (sacked&TCPCB_RETRANS) {
1095 if ((dup_sack && in_sack) &&
1096 (sacked&TCPCB_SACKED_ACKED))
1097 reord = min(fack_count, reord);
1098 } else {
1099 /* If it was in a hole, we detected reordering. */
1100 if (fack_count < prior_fackets &&
1101 !(sacked&TCPCB_SACKED_ACKED))
1102 reord = min(fack_count, reord);
1103 }
1104
1105 /* Nothing to do; acked frame is about to be dropped. */
1106 continue;
1107 }
1108
1109 if ((sacked&TCPCB_SACKED_RETRANS) &&
1110 after(end_seq, TCP_SKB_CB(skb)->ack_seq) &&
1111 (!lost_retrans || after(end_seq, lost_retrans)))
1112 lost_retrans = end_seq;
1113
1114 if (!in_sack)
1115 continue;
1116
1117 if (!(sacked&TCPCB_SACKED_ACKED)) {
1118 if (sacked & TCPCB_SACKED_RETRANS) {
1119 /* If the segment is not tagged as lost,
1120 * we do not clear RETRANS, believing
1121 * that retransmission is still in flight.
1122 */
1123 if (sacked & TCPCB_LOST) {
1124 TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
1125 tp->lost_out -= tcp_skb_pcount(skb);
1126 tp->retrans_out -= tcp_skb_pcount(skb);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001127
1128 /* clear lost hint */
1129 tp->retransmit_skb_hint = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001130 }
1131 } else {
1132 /* New sack for not retransmitted frame,
1133 * which was in hole. It is reordering.
1134 */
1135 if (!(sacked & TCPCB_RETRANS) &&
1136 fack_count < prior_fackets)
1137 reord = min(fack_count, reord);
1138
1139 if (sacked & TCPCB_LOST) {
1140 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1141 tp->lost_out -= tcp_skb_pcount(skb);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001142
1143 /* clear lost hint */
1144 tp->retransmit_skb_hint = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001145 }
1146 }
1147
1148 TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED;
1149 flag |= FLAG_DATA_SACKED;
1150 tp->sacked_out += tcp_skb_pcount(skb);
1151
1152 if (fack_count > tp->fackets_out)
1153 tp->fackets_out = fack_count;
1154 } else {
1155 if (dup_sack && (sacked&TCPCB_RETRANS))
1156 reord = min(fack_count, reord);
1157 }
1158
1159 /* D-SACK. We can detect redundant retransmission
1160 * in S|R and plain R frames and clear it.
1161 * undo_retrans is decreased above, L|R frames
1162 * are accounted above as well.
1163 */
1164 if (dup_sack &&
1165 (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS)) {
1166 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1167 tp->retrans_out -= tcp_skb_pcount(skb);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001168 tp->retransmit_skb_hint = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001169 }
1170 }
1171 }
1172
1173 /* Check for lost retransmit. This superb idea is
1174 * borrowed from "ratehalving". Event "C".
1175 * Later note: FACK people cheated me again 8),
1176 * we have to account for reordering! Ugly,
1177 * but should help.
1178 */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001179 if (lost_retrans && icsk->icsk_ca_state == TCP_CA_Recovery) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001180 struct sk_buff *skb;
1181
1182 sk_stream_for_retrans_queue(skb, sk) {
1183 if (after(TCP_SKB_CB(skb)->seq, lost_retrans))
1184 break;
1185 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
1186 continue;
1187 if ((TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) &&
1188 after(lost_retrans, TCP_SKB_CB(skb)->ack_seq) &&
1189 (IsFack(tp) ||
1190 !before(lost_retrans,
1191 TCP_SKB_CB(skb)->ack_seq + tp->reordering *
David S. Millerc1b4a7e2005-07-05 15:24:38 -07001192 tp->mss_cache))) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001193 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1194 tp->retrans_out -= tcp_skb_pcount(skb);
1195
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001196 /* clear lost hint */
1197 tp->retransmit_skb_hint = NULL;
1198
Linus Torvalds1da177e2005-04-16 15:20:36 -07001199 if (!(TCP_SKB_CB(skb)->sacked&(TCPCB_LOST|TCPCB_SACKED_ACKED))) {
1200 tp->lost_out += tcp_skb_pcount(skb);
1201 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1202 flag |= FLAG_DATA_SACKED;
1203 NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT);
1204 }
1205 }
1206 }
1207 }
1208
1209 tp->left_out = tp->sacked_out + tp->lost_out;
1210
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001211 if ((reord < tp->fackets_out) && icsk->icsk_ca_state != TCP_CA_Loss)
1212 tcp_update_reordering(sk, ((tp->fackets_out + 1) - reord), 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001213
1214#if FASTRETRANS_DEBUG > 0
1215 BUG_TRAP((int)tp->sacked_out >= 0);
1216 BUG_TRAP((int)tp->lost_out >= 0);
1217 BUG_TRAP((int)tp->retrans_out >= 0);
1218 BUG_TRAP((int)tcp_packets_in_flight(tp) >= 0);
1219#endif
1220 return flag;
1221}
1222
1223/* RTO occurred, but do not yet enter loss state. Instead, transmit two new
1224 * segments to see from the next ACKs whether any data was really missing.
1225 * If the RTO was spurious, new ACKs should arrive.
1226 */
1227void tcp_enter_frto(struct sock *sk)
1228{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001229 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001230 struct tcp_sock *tp = tcp_sk(sk);
1231 struct sk_buff *skb;
1232
1233 tp->frto_counter = 1;
1234
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001235 if (icsk->icsk_ca_state <= TCP_CA_Disorder ||
Linus Torvalds1da177e2005-04-16 15:20:36 -07001236 tp->snd_una == tp->high_seq ||
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001237 (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
1238 tp->prior_ssthresh = tcp_current_ssthresh(sk);
1239 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
1240 tcp_ca_event(sk, CA_EVENT_FRTO);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001241 }
1242
1243 /* Have to clear retransmission markers here to keep the bookkeeping
1244 * in shape, even though we are not yet in Loss state.
1245 * If something was really lost, it is eventually caught up
1246 * in tcp_enter_frto_loss.
1247 */
1248 tp->retrans_out = 0;
1249 tp->undo_marker = tp->snd_una;
1250 tp->undo_retrans = 0;
1251
1252 sk_stream_for_retrans_queue(skb, sk) {
1253 TCP_SKB_CB(skb)->sacked &= ~TCPCB_RETRANS;
1254 }
1255 tcp_sync_left_out(tp);
1256
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001257 tcp_set_ca_state(sk, TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001258 tp->frto_highmark = tp->snd_nxt;
1259}
1260
1261/* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
1262 * which indicates that we should follow the traditional RTO recovery,
1263 * i.e. mark everything lost and do go-back-N retransmission.
1264 */
1265static void tcp_enter_frto_loss(struct sock *sk)
1266{
1267 struct tcp_sock *tp = tcp_sk(sk);
1268 struct sk_buff *skb;
1269 int cnt = 0;
1270
1271 tp->sacked_out = 0;
1272 tp->lost_out = 0;
1273 tp->fackets_out = 0;
1274
1275 sk_stream_for_retrans_queue(skb, sk) {
1276 cnt += tcp_skb_pcount(skb);
1277 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1278 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) {
1279
1280 /* Do not mark those segments lost that were
1281 * forward transmitted after RTO
1282 */
1283 if (!after(TCP_SKB_CB(skb)->end_seq,
1284 tp->frto_highmark)) {
1285 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1286 tp->lost_out += tcp_skb_pcount(skb);
1287 }
1288 } else {
1289 tp->sacked_out += tcp_skb_pcount(skb);
1290 tp->fackets_out = cnt;
1291 }
1292 }
1293 tcp_sync_left_out(tp);
1294
1295 tp->snd_cwnd = tp->frto_counter + tcp_packets_in_flight(tp)+1;
1296 tp->snd_cwnd_cnt = 0;
1297 tp->snd_cwnd_stamp = tcp_time_stamp;
1298 tp->undo_marker = 0;
1299 tp->frto_counter = 0;
1300
1301 tp->reordering = min_t(unsigned int, tp->reordering,
1302 sysctl_tcp_reordering);
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001303 tcp_set_ca_state(sk, TCP_CA_Loss);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001304 tp->high_seq = tp->frto_highmark;
1305 TCP_ECN_queue_cwr(tp);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001306
1307 clear_all_retrans_hints(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001308}
1309
1310void tcp_clear_retrans(struct tcp_sock *tp)
1311{
1312 tp->left_out = 0;
1313 tp->retrans_out = 0;
1314
1315 tp->fackets_out = 0;
1316 tp->sacked_out = 0;
1317 tp->lost_out = 0;
1318
1319 tp->undo_marker = 0;
1320 tp->undo_retrans = 0;
1321}
1322
1323/* Enter Loss state. If "how" is not zero, forget all SACK information
1324 * and reset tags completely, otherwise preserve SACKs. If receiver
1325 * dropped its ofo queue, we will know this due to reneging detection.
1326 */
1327void tcp_enter_loss(struct sock *sk, int how)
1328{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001329 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001330 struct tcp_sock *tp = tcp_sk(sk);
1331 struct sk_buff *skb;
1332 int cnt = 0;
1333
1334 /* Reduce ssthresh if it has not yet been made inside this window. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001335 if (icsk->icsk_ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq ||
1336 (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
1337 tp->prior_ssthresh = tcp_current_ssthresh(sk);
1338 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
1339 tcp_ca_event(sk, CA_EVENT_LOSS);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001340 }
1341 tp->snd_cwnd = 1;
1342 tp->snd_cwnd_cnt = 0;
1343 tp->snd_cwnd_stamp = tcp_time_stamp;
1344
Stephen Hemminger9772efb2005-11-10 17:09:53 -08001345 tp->bytes_acked = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001346 tcp_clear_retrans(tp);
1347
1348 /* Push undo marker, if it was plain RTO and nothing
1349 * was retransmitted. */
1350 if (!how)
1351 tp->undo_marker = tp->snd_una;
1352
1353 sk_stream_for_retrans_queue(skb, sk) {
1354 cnt += tcp_skb_pcount(skb);
1355 if (TCP_SKB_CB(skb)->sacked&TCPCB_RETRANS)
1356 tp->undo_marker = 0;
1357 TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED;
1358 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) {
1359 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
1360 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1361 tp->lost_out += tcp_skb_pcount(skb);
1362 } else {
1363 tp->sacked_out += tcp_skb_pcount(skb);
1364 tp->fackets_out = cnt;
1365 }
1366 }
1367 tcp_sync_left_out(tp);
1368
1369 tp->reordering = min_t(unsigned int, tp->reordering,
1370 sysctl_tcp_reordering);
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001371 tcp_set_ca_state(sk, TCP_CA_Loss);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001372 tp->high_seq = tp->snd_nxt;
1373 TCP_ECN_queue_cwr(tp);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001374
1375 clear_all_retrans_hints(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001376}
1377
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001378static int tcp_check_sack_reneging(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001379{
1380 struct sk_buff *skb;
1381
1382 /* If ACK arrived pointing to a remembered SACK,
1383 * it means that our remembered SACKs do not reflect
1384 * real state of receiver i.e.
1385 * receiver _host_ is heavily congested (or buggy).
1386 * Do processing similar to RTO timeout.
1387 */
1388 if ((skb = skb_peek(&sk->sk_write_queue)) != NULL &&
1389 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001390 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001391 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING);
1392
1393 tcp_enter_loss(sk, 1);
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001394 icsk->icsk_retransmits++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001395 tcp_retransmit_skb(sk, skb_peek(&sk->sk_write_queue));
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001396 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001397 icsk->icsk_rto, TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001398 return 1;
1399 }
1400 return 0;
1401}
1402
1403static inline int tcp_fackets_out(struct tcp_sock *tp)
1404{
1405 return IsReno(tp) ? tp->sacked_out+1 : tp->fackets_out;
1406}
1407
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001408static inline int tcp_skb_timedout(struct sock *sk, struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001409{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001410 return (tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001411}
1412
1413static inline int tcp_head_timedout(struct sock *sk, struct tcp_sock *tp)
1414{
1415 return tp->packets_out &&
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001416 tcp_skb_timedout(sk, skb_peek(&sk->sk_write_queue));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001417}
1418
1419/* Linux NewReno/SACK/FACK/ECN state machine.
1420 * --------------------------------------
1421 *
1422 * "Open" Normal state, no dubious events, fast path.
1423 * "Disorder" In all the respects it is "Open",
1424 * but requires a bit more attention. It is entered when
1425 * we see some SACKs or dupacks. It is split of "Open"
1426 * mainly to move some processing from fast path to slow one.
1427 * "CWR" CWND was reduced due to some Congestion Notification event.
1428 * It can be ECN, ICMP source quench, local device congestion.
1429 * "Recovery" CWND was reduced, we are fast-retransmitting.
1430 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
1431 *
1432 * tcp_fastretrans_alert() is entered:
1433 * - each incoming ACK, if state is not "Open"
1434 * - when arrived ACK is unusual, namely:
1435 * * SACK
1436 * * Duplicate ACK.
1437 * * ECN ECE.
1438 *
1439 * Counting packets in flight is pretty simple.
1440 *
1441 * in_flight = packets_out - left_out + retrans_out
1442 *
1443 * packets_out is SND.NXT-SND.UNA counted in packets.
1444 *
1445 * retrans_out is number of retransmitted segments.
1446 *
1447 * left_out is number of segments left network, but not ACKed yet.
1448 *
1449 * left_out = sacked_out + lost_out
1450 *
1451 * sacked_out: Packets, which arrived to receiver out of order
1452 * and hence not ACKed. With SACKs this number is simply
1453 * amount of SACKed data. Even without SACKs
1454 * it is easy to give pretty reliable estimate of this number,
1455 * counting duplicate ACKs.
1456 *
1457 * lost_out: Packets lost by network. TCP has no explicit
1458 * "loss notification" feedback from network (for now).
1459 * It means that this number can be only _guessed_.
1460 * Actually, it is the heuristics to predict lossage that
1461 * distinguishes different algorithms.
1462 *
1463 * F.e. after RTO, when all the queue is considered as lost,
1464 * lost_out = packets_out and in_flight = retrans_out.
1465 *
1466 * Essentially, we have now two algorithms counting
1467 * lost packets.
1468 *
1469 * FACK: It is the simplest heuristics. As soon as we decided
1470 * that something is lost, we decide that _all_ not SACKed
1471 * packets until the most forward SACK are lost. I.e.
1472 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
1473 * It is absolutely correct estimate, if network does not reorder
1474 * packets. And it loses any connection to reality when reordering
1475 * takes place. We use FACK by default until reordering
1476 * is suspected on the path to this destination.
1477 *
1478 * NewReno: when Recovery is entered, we assume that one segment
1479 * is lost (classic Reno). While we are in Recovery and
1480 * a partial ACK arrives, we assume that one more packet
1481 * is lost (NewReno). This heuristics are the same in NewReno
1482 * and SACK.
1483 *
1484 * Imagine, that's all! Forget about all this shamanism about CWND inflation
1485 * deflation etc. CWND is real congestion window, never inflated, changes
1486 * only according to classic VJ rules.
1487 *
1488 * Really tricky (and requiring careful tuning) part of algorithm
1489 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
1490 * The first determines the moment _when_ we should reduce CWND and,
1491 * hence, slow down forward transmission. In fact, it determines the moment
1492 * when we decide that hole is caused by loss, rather than by a reorder.
1493 *
1494 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
1495 * holes, caused by lost packets.
1496 *
1497 * And the most logically complicated part of algorithm is undo
1498 * heuristics. We detect false retransmits due to both too early
1499 * fast retransmit (reordering) and underestimated RTO, analyzing
1500 * timestamps and D-SACKs. When we detect that some segments were
1501 * retransmitted by mistake and CWND reduction was wrong, we undo
1502 * window reduction and abort recovery phase. This logic is hidden
1503 * inside several functions named tcp_try_undo_<something>.
1504 */
1505
1506/* This function decides, when we should leave Disordered state
1507 * and enter Recovery phase, reducing congestion window.
1508 *
1509 * Main question: may we further continue forward transmission
1510 * with the same cwnd?
1511 */
1512static int tcp_time_to_recover(struct sock *sk, struct tcp_sock *tp)
1513{
1514 __u32 packets_out;
1515
1516 /* Trick#1: The loss is proven. */
1517 if (tp->lost_out)
1518 return 1;
1519
1520 /* Not-A-Trick#2 : Classic rule... */
1521 if (tcp_fackets_out(tp) > tp->reordering)
1522 return 1;
1523
1524 /* Trick#3 : when we use RFC2988 timer restart, fast
1525 * retransmit can be triggered by timeout of queue head.
1526 */
1527 if (tcp_head_timedout(sk, tp))
1528 return 1;
1529
1530 /* Trick#4: It is still not OK... But will it be useful to delay
1531 * recovery more?
1532 */
1533 packets_out = tp->packets_out;
1534 if (packets_out <= tp->reordering &&
1535 tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) &&
1536 !tcp_may_send_now(sk, tp)) {
1537 /* We have nothing to send. This connection is limited
1538 * either by receiver window or by application.
1539 */
1540 return 1;
1541 }
1542
1543 return 0;
1544}
1545
1546/* If we receive more dupacks than we expected counting segments
1547 * in assumption of absent reordering, interpret this as reordering.
1548 * The only another reason could be bug in receiver TCP.
1549 */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001550static void tcp_check_reno_reordering(struct sock *sk, const int addend)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001551{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001552 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001553 u32 holes;
1554
1555 holes = max(tp->lost_out, 1U);
1556 holes = min(holes, tp->packets_out);
1557
1558 if ((tp->sacked_out + holes) > tp->packets_out) {
1559 tp->sacked_out = tp->packets_out - holes;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001560 tcp_update_reordering(sk, tp->packets_out + addend, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001561 }
1562}
1563
1564/* Emulate SACKs for SACKless connection: account for a new dupack. */
1565
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001566static void tcp_add_reno_sack(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001567{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001568 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001569 tp->sacked_out++;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001570 tcp_check_reno_reordering(sk, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001571 tcp_sync_left_out(tp);
1572}
1573
1574/* Account for ACK, ACKing some data in Reno Recovery phase. */
1575
1576static void tcp_remove_reno_sacks(struct sock *sk, struct tcp_sock *tp, int acked)
1577{
1578 if (acked > 0) {
1579 /* One ACK acked hole. The rest eat duplicate ACKs. */
1580 if (acked-1 >= tp->sacked_out)
1581 tp->sacked_out = 0;
1582 else
1583 tp->sacked_out -= acked-1;
1584 }
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001585 tcp_check_reno_reordering(sk, acked);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001586 tcp_sync_left_out(tp);
1587}
1588
1589static inline void tcp_reset_reno_sack(struct tcp_sock *tp)
1590{
1591 tp->sacked_out = 0;
1592 tp->left_out = tp->lost_out;
1593}
1594
1595/* Mark head of queue up as lost. */
1596static void tcp_mark_head_lost(struct sock *sk, struct tcp_sock *tp,
1597 int packets, u32 high_seq)
1598{
1599 struct sk_buff *skb;
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001600 int cnt;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001601
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001602 BUG_TRAP(packets <= tp->packets_out);
1603 if (tp->lost_skb_hint) {
1604 skb = tp->lost_skb_hint;
1605 cnt = tp->lost_cnt_hint;
1606 } else {
1607 skb = sk->sk_write_queue.next;
1608 cnt = 0;
1609 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001610
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001611 sk_stream_for_retrans_queue_from(skb, sk) {
1612 /* TODO: do this better */
1613 /* this is not the most efficient way to do this... */
1614 tp->lost_skb_hint = skb;
1615 tp->lost_cnt_hint = cnt;
1616 cnt += tcp_skb_pcount(skb);
1617 if (cnt > packets || after(TCP_SKB_CB(skb)->end_seq, high_seq))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001618 break;
1619 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) {
1620 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1621 tp->lost_out += tcp_skb_pcount(skb);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001622
1623 /* clear xmit_retransmit_queue hints
1624 * if this is beyond hint */
1625 if(tp->retransmit_skb_hint != NULL &&
1626 before(TCP_SKB_CB(skb)->seq,
1627 TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) {
1628
1629 tp->retransmit_skb_hint = NULL;
1630 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001631 }
1632 }
1633 tcp_sync_left_out(tp);
1634}
1635
1636/* Account newly detected lost packet(s) */
1637
1638static void tcp_update_scoreboard(struct sock *sk, struct tcp_sock *tp)
1639{
1640 if (IsFack(tp)) {
1641 int lost = tp->fackets_out - tp->reordering;
1642 if (lost <= 0)
1643 lost = 1;
1644 tcp_mark_head_lost(sk, tp, lost, tp->high_seq);
1645 } else {
1646 tcp_mark_head_lost(sk, tp, 1, tp->high_seq);
1647 }
1648
1649 /* New heuristics: it is possible only after we switched
1650 * to restart timer each time when something is ACKed.
1651 * Hence, we can detect timed out packets during fast
1652 * retransmit without falling to slow start.
1653 */
Aki M Nyrhinen79320d72006-06-11 21:18:56 -07001654 if (!IsReno(tp) && tcp_head_timedout(sk, tp)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001655 struct sk_buff *skb;
1656
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001657 skb = tp->scoreboard_skb_hint ? tp->scoreboard_skb_hint
1658 : sk->sk_write_queue.next;
1659
1660 sk_stream_for_retrans_queue_from(skb, sk) {
1661 if (!tcp_skb_timedout(sk, skb))
1662 break;
1663
1664 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001665 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1666 tp->lost_out += tcp_skb_pcount(skb);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001667
1668 /* clear xmit_retrans hint */
1669 if (tp->retransmit_skb_hint &&
1670 before(TCP_SKB_CB(skb)->seq,
1671 TCP_SKB_CB(tp->retransmit_skb_hint)->seq))
1672
1673 tp->retransmit_skb_hint = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001674 }
1675 }
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001676
1677 tp->scoreboard_skb_hint = skb;
1678
Linus Torvalds1da177e2005-04-16 15:20:36 -07001679 tcp_sync_left_out(tp);
1680 }
1681}
1682
1683/* CWND moderation, preventing bursts due to too big ACKs
1684 * in dubious situations.
1685 */
1686static inline void tcp_moderate_cwnd(struct tcp_sock *tp)
1687{
1688 tp->snd_cwnd = min(tp->snd_cwnd,
1689 tcp_packets_in_flight(tp)+tcp_max_burst(tp));
1690 tp->snd_cwnd_stamp = tcp_time_stamp;
1691}
1692
Stephen Hemminger72dc5b92006-06-05 17:30:08 -07001693/* Lower bound on congestion window is slow start threshold
1694 * unless congestion avoidance choice decides to overide it.
1695 */
1696static inline u32 tcp_cwnd_min(const struct sock *sk)
1697{
1698 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1699
1700 return ca_ops->min_cwnd ? ca_ops->min_cwnd(sk) : tcp_sk(sk)->snd_ssthresh;
1701}
1702
Linus Torvalds1da177e2005-04-16 15:20:36 -07001703/* Decrease cwnd each second ack. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001704static void tcp_cwnd_down(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001705{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001706 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001707 int decr = tp->snd_cwnd_cnt + 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001708
1709 tp->snd_cwnd_cnt = decr&1;
1710 decr >>= 1;
1711
Stephen Hemminger72dc5b92006-06-05 17:30:08 -07001712 if (decr && tp->snd_cwnd > tcp_cwnd_min(sk))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001713 tp->snd_cwnd -= decr;
1714
1715 tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp)+1);
1716 tp->snd_cwnd_stamp = tcp_time_stamp;
1717}
1718
1719/* Nothing was retransmitted or returned timestamp is less
1720 * than timestamp of the first retransmission.
1721 */
1722static inline int tcp_packet_delayed(struct tcp_sock *tp)
1723{
1724 return !tp->retrans_stamp ||
1725 (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
1726 (__s32)(tp->rx_opt.rcv_tsecr - tp->retrans_stamp) < 0);
1727}
1728
1729/* Undo procedures. */
1730
1731#if FASTRETRANS_DEBUG > 1
1732static void DBGUNDO(struct sock *sk, struct tcp_sock *tp, const char *msg)
1733{
1734 struct inet_sock *inet = inet_sk(sk);
1735 printk(KERN_DEBUG "Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n",
1736 msg,
1737 NIPQUAD(inet->daddr), ntohs(inet->dport),
1738 tp->snd_cwnd, tp->left_out,
1739 tp->snd_ssthresh, tp->prior_ssthresh,
1740 tp->packets_out);
1741}
1742#else
1743#define DBGUNDO(x...) do { } while (0)
1744#endif
1745
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001746static void tcp_undo_cwr(struct sock *sk, const int undo)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001747{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001748 struct tcp_sock *tp = tcp_sk(sk);
1749
Linus Torvalds1da177e2005-04-16 15:20:36 -07001750 if (tp->prior_ssthresh) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001751 const struct inet_connection_sock *icsk = inet_csk(sk);
1752
1753 if (icsk->icsk_ca_ops->undo_cwnd)
1754 tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001755 else
1756 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh<<1);
1757
1758 if (undo && tp->prior_ssthresh > tp->snd_ssthresh) {
1759 tp->snd_ssthresh = tp->prior_ssthresh;
1760 TCP_ECN_withdraw_cwr(tp);
1761 }
1762 } else {
1763 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh);
1764 }
1765 tcp_moderate_cwnd(tp);
1766 tp->snd_cwnd_stamp = tcp_time_stamp;
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001767
1768 /* There is something screwy going on with the retrans hints after
1769 an undo */
1770 clear_all_retrans_hints(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001771}
1772
1773static inline int tcp_may_undo(struct tcp_sock *tp)
1774{
1775 return tp->undo_marker &&
1776 (!tp->undo_retrans || tcp_packet_delayed(tp));
1777}
1778
1779/* People celebrate: "We love our President!" */
1780static int tcp_try_undo_recovery(struct sock *sk, struct tcp_sock *tp)
1781{
1782 if (tcp_may_undo(tp)) {
1783 /* Happy end! We did not retransmit anything
1784 * or our original transmission succeeded.
1785 */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001786 DBGUNDO(sk, tp, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans");
1787 tcp_undo_cwr(sk, 1);
1788 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001789 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO);
1790 else
1791 NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO);
1792 tp->undo_marker = 0;
1793 }
1794 if (tp->snd_una == tp->high_seq && IsReno(tp)) {
1795 /* Hold old state until something *above* high_seq
1796 * is ACKed. For Reno it is MUST to prevent false
1797 * fast retransmits (RFC2582). SACK TCP is safe. */
1798 tcp_moderate_cwnd(tp);
1799 return 1;
1800 }
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001801 tcp_set_ca_state(sk, TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001802 return 0;
1803}
1804
1805/* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
1806static void tcp_try_undo_dsack(struct sock *sk, struct tcp_sock *tp)
1807{
1808 if (tp->undo_marker && !tp->undo_retrans) {
1809 DBGUNDO(sk, tp, "D-SACK");
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001810 tcp_undo_cwr(sk, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001811 tp->undo_marker = 0;
1812 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO);
1813 }
1814}
1815
1816/* Undo during fast recovery after partial ACK. */
1817
1818static int tcp_try_undo_partial(struct sock *sk, struct tcp_sock *tp,
1819 int acked)
1820{
1821 /* Partial ACK arrived. Force Hoe's retransmit. */
1822 int failed = IsReno(tp) || tp->fackets_out>tp->reordering;
1823
1824 if (tcp_may_undo(tp)) {
1825 /* Plain luck! Hole if filled with delayed
1826 * packet, rather than with a retransmit.
1827 */
1828 if (tp->retrans_out == 0)
1829 tp->retrans_stamp = 0;
1830
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001831 tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001832
1833 DBGUNDO(sk, tp, "Hoe");
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001834 tcp_undo_cwr(sk, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001835 NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO);
1836
1837 /* So... Do not make Hoe's retransmit yet.
1838 * If the first packet was delayed, the rest
1839 * ones are most probably delayed as well.
1840 */
1841 failed = 0;
1842 }
1843 return failed;
1844}
1845
1846/* Undo during loss recovery after partial ACK. */
1847static int tcp_try_undo_loss(struct sock *sk, struct tcp_sock *tp)
1848{
1849 if (tcp_may_undo(tp)) {
1850 struct sk_buff *skb;
1851 sk_stream_for_retrans_queue(skb, sk) {
1852 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1853 }
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001854
1855 clear_all_retrans_hints(tp);
1856
Linus Torvalds1da177e2005-04-16 15:20:36 -07001857 DBGUNDO(sk, tp, "partial loss");
1858 tp->lost_out = 0;
1859 tp->left_out = tp->sacked_out;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001860 tcp_undo_cwr(sk, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001861 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001862 inet_csk(sk)->icsk_retransmits = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001863 tp->undo_marker = 0;
1864 if (!IsReno(tp))
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001865 tcp_set_ca_state(sk, TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001866 return 1;
1867 }
1868 return 0;
1869}
1870
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001871static inline void tcp_complete_cwr(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001872{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001873 struct tcp_sock *tp = tcp_sk(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -07001874 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001875 tp->snd_cwnd_stamp = tcp_time_stamp;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001876 tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001877}
1878
1879static void tcp_try_to_open(struct sock *sk, struct tcp_sock *tp, int flag)
1880{
1881 tp->left_out = tp->sacked_out;
1882
1883 if (tp->retrans_out == 0)
1884 tp->retrans_stamp = 0;
1885
1886 if (flag&FLAG_ECE)
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001887 tcp_enter_cwr(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001888
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001889 if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001890 int state = TCP_CA_Open;
1891
1892 if (tp->left_out || tp->retrans_out || tp->undo_marker)
1893 state = TCP_CA_Disorder;
1894
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001895 if (inet_csk(sk)->icsk_ca_state != state) {
1896 tcp_set_ca_state(sk, state);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001897 tp->high_seq = tp->snd_nxt;
1898 }
1899 tcp_moderate_cwnd(tp);
1900 } else {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001901 tcp_cwnd_down(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001902 }
1903}
1904
John Heffner5d424d52006-03-20 17:53:41 -08001905static void tcp_mtup_probe_failed(struct sock *sk)
1906{
1907 struct inet_connection_sock *icsk = inet_csk(sk);
1908
1909 icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1;
1910 icsk->icsk_mtup.probe_size = 0;
1911}
1912
1913static void tcp_mtup_probe_success(struct sock *sk, struct sk_buff *skb)
1914{
1915 struct tcp_sock *tp = tcp_sk(sk);
1916 struct inet_connection_sock *icsk = inet_csk(sk);
1917
1918 /* FIXME: breaks with very large cwnd */
1919 tp->prior_ssthresh = tcp_current_ssthresh(sk);
1920 tp->snd_cwnd = tp->snd_cwnd *
1921 tcp_mss_to_mtu(sk, tp->mss_cache) /
1922 icsk->icsk_mtup.probe_size;
1923 tp->snd_cwnd_cnt = 0;
1924 tp->snd_cwnd_stamp = tcp_time_stamp;
1925 tp->rcv_ssthresh = tcp_current_ssthresh(sk);
1926
1927 icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size;
1928 icsk->icsk_mtup.probe_size = 0;
1929 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
1930}
1931
1932
Linus Torvalds1da177e2005-04-16 15:20:36 -07001933/* Process an event, which can update packets-in-flight not trivially.
1934 * Main goal of this function is to calculate new estimate for left_out,
1935 * taking into account both packets sitting in receiver's buffer and
1936 * packets lost by network.
1937 *
1938 * Besides that it does CWND reduction, when packet loss is detected
1939 * and changes state of machine.
1940 *
1941 * It does _not_ decide what to send, it is made in function
1942 * tcp_xmit_retransmit_queue().
1943 */
1944static void
1945tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una,
1946 int prior_packets, int flag)
1947{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001948 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001949 struct tcp_sock *tp = tcp_sk(sk);
1950 int is_dupack = (tp->snd_una == prior_snd_una && !(flag&FLAG_NOT_DUP));
1951
1952 /* Some technical things:
1953 * 1. Reno does not count dupacks (sacked_out) automatically. */
1954 if (!tp->packets_out)
1955 tp->sacked_out = 0;
1956 /* 2. SACK counts snd_fack in packets inaccurately. */
1957 if (tp->sacked_out == 0)
1958 tp->fackets_out = 0;
1959
1960 /* Now state machine starts.
1961 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
1962 if (flag&FLAG_ECE)
1963 tp->prior_ssthresh = 0;
1964
1965 /* B. In all the states check for reneging SACKs. */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001966 if (tp->sacked_out && tcp_check_sack_reneging(sk))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001967 return;
1968
1969 /* C. Process data loss notification, provided it is valid. */
1970 if ((flag&FLAG_DATA_LOST) &&
1971 before(tp->snd_una, tp->high_seq) &&
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001972 icsk->icsk_ca_state != TCP_CA_Open &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07001973 tp->fackets_out > tp->reordering) {
1974 tcp_mark_head_lost(sk, tp, tp->fackets_out-tp->reordering, tp->high_seq);
1975 NET_INC_STATS_BH(LINUX_MIB_TCPLOSS);
1976 }
1977
1978 /* D. Synchronize left_out to current state. */
1979 tcp_sync_left_out(tp);
1980
1981 /* E. Check state exit conditions. State can be terminated
1982 * when high_seq is ACKed. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001983 if (icsk->icsk_ca_state == TCP_CA_Open) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001984 if (!sysctl_tcp_frto)
1985 BUG_TRAP(tp->retrans_out == 0);
1986 tp->retrans_stamp = 0;
1987 } else if (!before(tp->snd_una, tp->high_seq)) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001988 switch (icsk->icsk_ca_state) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001989 case TCP_CA_Loss:
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001990 icsk->icsk_retransmits = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001991 if (tcp_try_undo_recovery(sk, tp))
1992 return;
1993 break;
1994
1995 case TCP_CA_CWR:
1996 /* CWR is to be held something *above* high_seq
1997 * is ACKed for CWR bit to reach receiver. */
1998 if (tp->snd_una != tp->high_seq) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001999 tcp_complete_cwr(sk);
2000 tcp_set_ca_state(sk, TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002001 }
2002 break;
2003
2004 case TCP_CA_Disorder:
2005 tcp_try_undo_dsack(sk, tp);
2006 if (!tp->undo_marker ||
2007 /* For SACK case do not Open to allow to undo
2008 * catching for all duplicate ACKs. */
2009 IsReno(tp) || tp->snd_una != tp->high_seq) {
2010 tp->undo_marker = 0;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002011 tcp_set_ca_state(sk, TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002012 }
2013 break;
2014
2015 case TCP_CA_Recovery:
2016 if (IsReno(tp))
2017 tcp_reset_reno_sack(tp);
2018 if (tcp_try_undo_recovery(sk, tp))
2019 return;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002020 tcp_complete_cwr(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002021 break;
2022 }
2023 }
2024
2025 /* F. Process state. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002026 switch (icsk->icsk_ca_state) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002027 case TCP_CA_Recovery:
2028 if (prior_snd_una == tp->snd_una) {
2029 if (IsReno(tp) && is_dupack)
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002030 tcp_add_reno_sack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002031 } else {
2032 int acked = prior_packets - tp->packets_out;
2033 if (IsReno(tp))
2034 tcp_remove_reno_sacks(sk, tp, acked);
2035 is_dupack = tcp_try_undo_partial(sk, tp, acked);
2036 }
2037 break;
2038 case TCP_CA_Loss:
2039 if (flag&FLAG_DATA_ACKED)
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002040 icsk->icsk_retransmits = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002041 if (!tcp_try_undo_loss(sk, tp)) {
2042 tcp_moderate_cwnd(tp);
2043 tcp_xmit_retransmit_queue(sk);
2044 return;
2045 }
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002046 if (icsk->icsk_ca_state != TCP_CA_Open)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002047 return;
2048 /* Loss is undone; fall through to processing in Open state. */
2049 default:
2050 if (IsReno(tp)) {
2051 if (tp->snd_una != prior_snd_una)
2052 tcp_reset_reno_sack(tp);
2053 if (is_dupack)
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002054 tcp_add_reno_sack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002055 }
2056
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002057 if (icsk->icsk_ca_state == TCP_CA_Disorder)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002058 tcp_try_undo_dsack(sk, tp);
2059
2060 if (!tcp_time_to_recover(sk, tp)) {
2061 tcp_try_to_open(sk, tp, flag);
2062 return;
2063 }
2064
John Heffner5d424d52006-03-20 17:53:41 -08002065 /* MTU probe failure: don't reduce cwnd */
2066 if (icsk->icsk_ca_state < TCP_CA_CWR &&
2067 icsk->icsk_mtup.probe_size &&
John Heffner0e7b1362006-03-20 21:32:58 -08002068 tp->snd_una == tp->mtu_probe.probe_seq_start) {
John Heffner5d424d52006-03-20 17:53:41 -08002069 tcp_mtup_probe_failed(sk);
2070 /* Restores the reduction we did in tcp_mtup_probe() */
2071 tp->snd_cwnd++;
2072 tcp_simple_retransmit(sk);
2073 return;
2074 }
2075
Linus Torvalds1da177e2005-04-16 15:20:36 -07002076 /* Otherwise enter Recovery state */
2077
2078 if (IsReno(tp))
2079 NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY);
2080 else
2081 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY);
2082
2083 tp->high_seq = tp->snd_nxt;
2084 tp->prior_ssthresh = 0;
2085 tp->undo_marker = tp->snd_una;
2086 tp->undo_retrans = tp->retrans_out;
2087
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002088 if (icsk->icsk_ca_state < TCP_CA_CWR) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002089 if (!(flag&FLAG_ECE))
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002090 tp->prior_ssthresh = tcp_current_ssthresh(sk);
2091 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002092 TCP_ECN_queue_cwr(tp);
2093 }
2094
Stephen Hemminger9772efb2005-11-10 17:09:53 -08002095 tp->bytes_acked = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002096 tp->snd_cwnd_cnt = 0;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002097 tcp_set_ca_state(sk, TCP_CA_Recovery);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002098 }
2099
2100 if (is_dupack || tcp_head_timedout(sk, tp))
2101 tcp_update_scoreboard(sk, tp);
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002102 tcp_cwnd_down(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002103 tcp_xmit_retransmit_queue(sk);
2104}
2105
2106/* Read draft-ietf-tcplw-high-performance before mucking
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08002107 * with this code. (Supersedes RFC1323)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002108 */
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002109static void tcp_ack_saw_tstamp(struct sock *sk, int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002110{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002111 /* RTTM Rule: A TSecr value received in a segment is used to
2112 * update the averaged RTT measurement only if the segment
2113 * acknowledges some new data, i.e., only if it advances the
2114 * left edge of the send window.
2115 *
2116 * See draft-ietf-tcplw-high-performance-00, section 3.3.
2117 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
2118 *
2119 * Changed: reset backoff as soon as we see the first valid sample.
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08002120 * If we do not, we get strongly overestimated rto. With timestamps
Linus Torvalds1da177e2005-04-16 15:20:36 -07002121 * samples are accepted even from very old segments: f.e., when rtt=1
2122 * increases to 8, we retransmit 5 times and after 8 seconds delayed
2123 * answer arrives rto becomes 120 seconds! If at least one of segments
2124 * in window is lost... Voila. --ANK (010210)
2125 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002126 struct tcp_sock *tp = tcp_sk(sk);
2127 const __u32 seq_rtt = tcp_time_stamp - tp->rx_opt.rcv_tsecr;
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002128 tcp_rtt_estimator(sk, seq_rtt);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002129 tcp_set_rto(sk);
2130 inet_csk(sk)->icsk_backoff = 0;
2131 tcp_bound_rto(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002132}
2133
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002134static void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002135{
2136 /* We don't have a timestamp. Can only use
2137 * packets that are not retransmitted to determine
2138 * rtt estimates. Also, we must not reset the
2139 * backoff for rto until we get a non-retransmitted
2140 * packet. This allows us to deal with a situation
2141 * where the network delay has increased suddenly.
2142 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
2143 */
2144
2145 if (flag & FLAG_RETRANS_DATA_ACKED)
2146 return;
2147
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002148 tcp_rtt_estimator(sk, seq_rtt);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002149 tcp_set_rto(sk);
2150 inet_csk(sk)->icsk_backoff = 0;
2151 tcp_bound_rto(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002152}
2153
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002154static inline void tcp_ack_update_rtt(struct sock *sk, const int flag,
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002155 const s32 seq_rtt)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002156{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002157 const struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002158 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
2159 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002160 tcp_ack_saw_tstamp(sk, flag);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002161 else if (seq_rtt >= 0)
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002162 tcp_ack_no_tstamp(sk, seq_rtt, flag);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002163}
2164
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08002165static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 rtt,
2166 u32 in_flight, int good)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002167{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002168 const struct inet_connection_sock *icsk = inet_csk(sk);
2169 icsk->icsk_ca_ops->cong_avoid(sk, ack, rtt, in_flight, good);
2170 tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002171}
2172
Linus Torvalds1da177e2005-04-16 15:20:36 -07002173/* Restart timer after forward progress on connection.
2174 * RFC2988 recommends to restart timer to now+rto.
2175 */
2176
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08002177static void tcp_ack_packets_out(struct sock *sk, struct tcp_sock *tp)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002178{
2179 if (!tp->packets_out) {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002180 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002181 } else {
Arnaldo Carvalho de Melo3f421ba2005-08-09 20:11:08 -07002182 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002183 }
2184}
2185
Linus Torvalds1da177e2005-04-16 15:20:36 -07002186static int tcp_tso_acked(struct sock *sk, struct sk_buff *skb,
2187 __u32 now, __s32 *seq_rtt)
2188{
2189 struct tcp_sock *tp = tcp_sk(sk);
2190 struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
2191 __u32 seq = tp->snd_una;
2192 __u32 packets_acked;
2193 int acked = 0;
2194
2195 /* If we get here, the whole TSO packet has not been
2196 * acked.
2197 */
2198 BUG_ON(!after(scb->end_seq, seq));
2199
2200 packets_acked = tcp_skb_pcount(skb);
2201 if (tcp_trim_head(sk, skb, seq - scb->seq))
2202 return 0;
2203 packets_acked -= tcp_skb_pcount(skb);
2204
2205 if (packets_acked) {
2206 __u8 sacked = scb->sacked;
2207
2208 acked |= FLAG_DATA_ACKED;
2209 if (sacked) {
2210 if (sacked & TCPCB_RETRANS) {
2211 if (sacked & TCPCB_SACKED_RETRANS)
2212 tp->retrans_out -= packets_acked;
2213 acked |= FLAG_RETRANS_DATA_ACKED;
2214 *seq_rtt = -1;
2215 } else if (*seq_rtt < 0)
2216 *seq_rtt = now - scb->when;
2217 if (sacked & TCPCB_SACKED_ACKED)
2218 tp->sacked_out -= packets_acked;
2219 if (sacked & TCPCB_LOST)
2220 tp->lost_out -= packets_acked;
2221 if (sacked & TCPCB_URG) {
2222 if (tp->urg_mode &&
2223 !before(seq, tp->snd_up))
2224 tp->urg_mode = 0;
2225 }
2226 } else if (*seq_rtt < 0)
2227 *seq_rtt = now - scb->when;
2228
2229 if (tp->fackets_out) {
2230 __u32 dval = min(tp->fackets_out, packets_acked);
2231 tp->fackets_out -= dval;
2232 }
2233 tp->packets_out -= packets_acked;
2234
2235 BUG_ON(tcp_skb_pcount(skb) == 0);
2236 BUG_ON(!before(scb->seq, scb->end_seq));
2237 }
2238
2239 return acked;
2240}
2241
John Heffner8ea333e2006-09-28 14:47:38 -07002242static u32 tcp_usrtt(struct timeval *tv)
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002243{
John Heffner8ea333e2006-09-28 14:47:38 -07002244 struct timeval now;
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002245
2246 do_gettimeofday(&now);
John Heffner8ea333e2006-09-28 14:47:38 -07002247 return (now.tv_sec - tv->tv_sec) * 1000000 + (now.tv_usec - tv->tv_usec);
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002248}
Linus Torvalds1da177e2005-04-16 15:20:36 -07002249
2250/* Remove acknowledged frames from the retransmission queue. */
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002251static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002252{
2253 struct tcp_sock *tp = tcp_sk(sk);
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002254 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002255 struct sk_buff *skb;
2256 __u32 now = tcp_time_stamp;
2257 int acked = 0;
2258 __s32 seq_rtt = -1;
Stephen Hemminger317a76f2005-06-23 12:19:55 -07002259 u32 pkts_acked = 0;
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002260 void (*rtt_sample)(struct sock *sk, u32 usrtt)
2261 = icsk->icsk_ca_ops->rtt_sample;
David S. Miller80246ab2006-10-03 16:49:53 -07002262 struct timeval tv = { .tv_sec = 0, .tv_usec = 0 };
Linus Torvalds1da177e2005-04-16 15:20:36 -07002263
2264 while ((skb = skb_peek(&sk->sk_write_queue)) &&
2265 skb != sk->sk_send_head) {
2266 struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
2267 __u8 sacked = scb->sacked;
2268
2269 /* If our packet is before the ack sequence we can
2270 * discard it as it's confirmed to have arrived at
2271 * the other end.
2272 */
2273 if (after(scb->end_seq, tp->snd_una)) {
David S. Millercb831992005-07-05 15:20:55 -07002274 if (tcp_skb_pcount(skb) > 1 &&
2275 after(tp->snd_una, scb->seq))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002276 acked |= tcp_tso_acked(sk, skb,
2277 now, &seq_rtt);
2278 break;
2279 }
2280
2281 /* Initial outgoing SYN's get put onto the write_queue
2282 * just like anything else we transmit. It is not
2283 * true data, and if we misinform our callers that
2284 * this ACK acks real data, we will erroneously exit
2285 * connection startup slow start one packet too
2286 * quickly. This is severely frowned upon behavior.
2287 */
2288 if (!(scb->flags & TCPCB_FLAG_SYN)) {
2289 acked |= FLAG_DATA_ACKED;
Stephen Hemminger317a76f2005-06-23 12:19:55 -07002290 ++pkts_acked;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002291 } else {
2292 acked |= FLAG_SYN_ACKED;
2293 tp->retrans_stamp = 0;
2294 }
2295
John Heffner5d424d52006-03-20 17:53:41 -08002296 /* MTU probing checks */
2297 if (icsk->icsk_mtup.probe_size) {
John Heffner0e7b1362006-03-20 21:32:58 -08002298 if (!after(tp->mtu_probe.probe_seq_end, TCP_SKB_CB(skb)->end_seq)) {
John Heffner5d424d52006-03-20 17:53:41 -08002299 tcp_mtup_probe_success(sk, skb);
2300 }
2301 }
2302
Linus Torvalds1da177e2005-04-16 15:20:36 -07002303 if (sacked) {
2304 if (sacked & TCPCB_RETRANS) {
2305 if(sacked & TCPCB_SACKED_RETRANS)
2306 tp->retrans_out -= tcp_skb_pcount(skb);
2307 acked |= FLAG_RETRANS_DATA_ACKED;
2308 seq_rtt = -1;
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002309 } else if (seq_rtt < 0) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002310 seq_rtt = now - scb->when;
John Heffner8ea333e2006-09-28 14:47:38 -07002311 skb_get_timestamp(skb, &tv);
Patrick McHardya61bbcf2005-08-14 17:24:31 -07002312 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002313 if (sacked & TCPCB_SACKED_ACKED)
2314 tp->sacked_out -= tcp_skb_pcount(skb);
2315 if (sacked & TCPCB_LOST)
2316 tp->lost_out -= tcp_skb_pcount(skb);
2317 if (sacked & TCPCB_URG) {
2318 if (tp->urg_mode &&
2319 !before(scb->end_seq, tp->snd_up))
2320 tp->urg_mode = 0;
2321 }
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002322 } else if (seq_rtt < 0) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002323 seq_rtt = now - scb->when;
John Heffner8ea333e2006-09-28 14:47:38 -07002324 skb_get_timestamp(skb, &tv);
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002325 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002326 tcp_dec_pcount_approx(&tp->fackets_out, skb);
2327 tcp_packets_out_dec(tp, skb);
David S. Miller8728b832005-08-09 19:25:21 -07002328 __skb_unlink(skb, &sk->sk_write_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002329 sk_stream_free_skb(sk, skb);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08002330 clear_all_retrans_hints(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002331 }
2332
2333 if (acked&FLAG_ACKED) {
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002334 tcp_ack_update_rtt(sk, acked, seq_rtt);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002335 tcp_ack_packets_out(sk, tp);
John Heffner8ea333e2006-09-28 14:47:38 -07002336 if (rtt_sample && !(acked & FLAG_RETRANS_DATA_ACKED))
2337 (*rtt_sample)(sk, tcp_usrtt(&tv));
Stephen Hemminger317a76f2005-06-23 12:19:55 -07002338
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002339 if (icsk->icsk_ca_ops->pkts_acked)
2340 icsk->icsk_ca_ops->pkts_acked(sk, pkts_acked);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002341 }
2342
2343#if FASTRETRANS_DEBUG > 0
2344 BUG_TRAP((int)tp->sacked_out >= 0);
2345 BUG_TRAP((int)tp->lost_out >= 0);
2346 BUG_TRAP((int)tp->retrans_out >= 0);
2347 if (!tp->packets_out && tp->rx_opt.sack_ok) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002348 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002349 if (tp->lost_out) {
2350 printk(KERN_DEBUG "Leak l=%u %d\n",
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002351 tp->lost_out, icsk->icsk_ca_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002352 tp->lost_out = 0;
2353 }
2354 if (tp->sacked_out) {
2355 printk(KERN_DEBUG "Leak s=%u %d\n",
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002356 tp->sacked_out, icsk->icsk_ca_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002357 tp->sacked_out = 0;
2358 }
2359 if (tp->retrans_out) {
2360 printk(KERN_DEBUG "Leak r=%u %d\n",
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002361 tp->retrans_out, icsk->icsk_ca_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002362 tp->retrans_out = 0;
2363 }
2364 }
2365#endif
2366 *seq_rtt_p = seq_rtt;
2367 return acked;
2368}
2369
2370static void tcp_ack_probe(struct sock *sk)
2371{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002372 const struct tcp_sock *tp = tcp_sk(sk);
2373 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002374
2375 /* Was it a usable window open? */
2376
2377 if (!after(TCP_SKB_CB(sk->sk_send_head)->end_seq,
2378 tp->snd_una + tp->snd_wnd)) {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002379 icsk->icsk_backoff = 0;
2380 inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002381 /* Socket must be waked up by subsequent tcp_data_snd_check().
2382 * This function is not for random using!
2383 */
2384 } else {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002385 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
Arnaldo Carvalho de Melo3f421ba2005-08-09 20:11:08 -07002386 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
2387 TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002388 }
2389}
2390
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002391static inline int tcp_ack_is_dubious(const struct sock *sk, const int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002392{
2393 return (!(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) ||
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002394 inet_csk(sk)->icsk_ca_state != TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002395}
2396
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002397static inline int tcp_may_raise_cwnd(const struct sock *sk, const int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002398{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002399 const struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002400 return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) &&
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002401 !((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_Recovery | TCPF_CA_CWR));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002402}
2403
2404/* Check that window update is acceptable.
2405 * The function assumes that snd_una<=ack<=snd_next.
2406 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002407static inline int tcp_may_update_window(const struct tcp_sock *tp, const u32 ack,
2408 const u32 ack_seq, const u32 nwin)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002409{
2410 return (after(ack, tp->snd_una) ||
2411 after(ack_seq, tp->snd_wl1) ||
2412 (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd));
2413}
2414
2415/* Update our send window.
2416 *
2417 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
2418 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
2419 */
2420static int tcp_ack_update_window(struct sock *sk, struct tcp_sock *tp,
2421 struct sk_buff *skb, u32 ack, u32 ack_seq)
2422{
2423 int flag = 0;
2424 u32 nwin = ntohs(skb->h.th->window);
2425
2426 if (likely(!skb->h.th->syn))
2427 nwin <<= tp->rx_opt.snd_wscale;
2428
2429 if (tcp_may_update_window(tp, ack, ack_seq, nwin)) {
2430 flag |= FLAG_WIN_UPDATE;
2431 tcp_update_wl(tp, ack, ack_seq);
2432
2433 if (tp->snd_wnd != nwin) {
2434 tp->snd_wnd = nwin;
2435
2436 /* Note, it is the only place, where
2437 * fast path is recovered for sending TCP.
2438 */
Herbert Xu2ad41062005-10-27 18:47:46 +10002439 tp->pred_flags = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002440 tcp_fast_path_check(sk, tp);
2441
2442 if (nwin > tp->max_window) {
2443 tp->max_window = nwin;
Arnaldo Carvalho de Melod83d8462005-12-13 23:26:10 -08002444 tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002445 }
2446 }
2447 }
2448
2449 tp->snd_una = ack;
2450
2451 return flag;
2452}
2453
2454static void tcp_process_frto(struct sock *sk, u32 prior_snd_una)
2455{
2456 struct tcp_sock *tp = tcp_sk(sk);
2457
2458 tcp_sync_left_out(tp);
2459
2460 if (tp->snd_una == prior_snd_una ||
2461 !before(tp->snd_una, tp->frto_highmark)) {
2462 /* RTO was caused by loss, start retransmitting in
2463 * go-back-N slow start
2464 */
2465 tcp_enter_frto_loss(sk);
2466 return;
2467 }
2468
2469 if (tp->frto_counter == 1) {
2470 /* First ACK after RTO advances the window: allow two new
2471 * segments out.
2472 */
2473 tp->snd_cwnd = tcp_packets_in_flight(tp) + 2;
2474 } else {
2475 /* Also the second ACK after RTO advances the window.
2476 * The RTO was likely spurious. Reduce cwnd and continue
2477 * in congestion avoidance
2478 */
2479 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
2480 tcp_moderate_cwnd(tp);
2481 }
2482
2483 /* F-RTO affects on two new ACKs following RTO.
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08002484 * At latest on third ACK the TCP behavior is back to normal.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002485 */
2486 tp->frto_counter = (tp->frto_counter + 1) % 3;
2487}
2488
Linus Torvalds1da177e2005-04-16 15:20:36 -07002489/* This routine deals with incoming acks, but not outgoing ones. */
2490static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
2491{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002492 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002493 struct tcp_sock *tp = tcp_sk(sk);
2494 u32 prior_snd_una = tp->snd_una;
2495 u32 ack_seq = TCP_SKB_CB(skb)->seq;
2496 u32 ack = TCP_SKB_CB(skb)->ack_seq;
2497 u32 prior_in_flight;
2498 s32 seq_rtt;
2499 int prior_packets;
2500
2501 /* If the ack is newer than sent or older than previous acks
2502 * then we can probably ignore it.
2503 */
2504 if (after(ack, tp->snd_nxt))
2505 goto uninteresting_ack;
2506
2507 if (before(ack, prior_snd_una))
2508 goto old_ack;
2509
Daikichi Osuga3fdf3f02006-08-29 02:01:44 -07002510 if (sysctl_tcp_abc) {
2511 if (icsk->icsk_ca_state < TCP_CA_CWR)
2512 tp->bytes_acked += ack - prior_snd_una;
2513 else if (icsk->icsk_ca_state == TCP_CA_Loss)
2514 /* we assume just one segment left network */
2515 tp->bytes_acked += min(ack - prior_snd_una, tp->mss_cache);
2516 }
Stephen Hemminger9772efb2005-11-10 17:09:53 -08002517
Linus Torvalds1da177e2005-04-16 15:20:36 -07002518 if (!(flag&FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
2519 /* Window is constant, pure forward advance.
2520 * No more checks are required.
2521 * Note, we use the fact that SND.UNA>=SND.WL2.
2522 */
2523 tcp_update_wl(tp, ack, ack_seq);
2524 tp->snd_una = ack;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002525 flag |= FLAG_WIN_UPDATE;
2526
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002527 tcp_ca_event(sk, CA_EVENT_FAST_ACK);
Stephen Hemminger317a76f2005-06-23 12:19:55 -07002528
Linus Torvalds1da177e2005-04-16 15:20:36 -07002529 NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS);
2530 } else {
2531 if (ack_seq != TCP_SKB_CB(skb)->end_seq)
2532 flag |= FLAG_DATA;
2533 else
2534 NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS);
2535
2536 flag |= tcp_ack_update_window(sk, tp, skb, ack, ack_seq);
2537
2538 if (TCP_SKB_CB(skb)->sacked)
2539 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una);
2540
2541 if (TCP_ECN_rcv_ecn_echo(tp, skb->h.th))
2542 flag |= FLAG_ECE;
2543
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002544 tcp_ca_event(sk, CA_EVENT_SLOW_ACK);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002545 }
2546
2547 /* We passed data and got it acked, remove any soft error
2548 * log. Something worked...
2549 */
2550 sk->sk_err_soft = 0;
2551 tp->rcv_tstamp = tcp_time_stamp;
2552 prior_packets = tp->packets_out;
2553 if (!prior_packets)
2554 goto no_queue;
2555
2556 prior_in_flight = tcp_packets_in_flight(tp);
2557
2558 /* See if we can take anything off of the retransmit queue. */
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002559 flag |= tcp_clean_rtx_queue(sk, &seq_rtt);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002560
2561 if (tp->frto_counter)
2562 tcp_process_frto(sk, prior_snd_una);
2563
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002564 if (tcp_ack_is_dubious(sk, flag)) {
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08002565 /* Advance CWND, if state allows this. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002566 if ((flag & FLAG_DATA_ACKED) && tcp_may_raise_cwnd(sk, flag))
2567 tcp_cong_avoid(sk, ack, seq_rtt, prior_in_flight, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002568 tcp_fastretrans_alert(sk, prior_snd_una, prior_packets, flag);
2569 } else {
Stephen Hemminger317a76f2005-06-23 12:19:55 -07002570 if ((flag & FLAG_DATA_ACKED))
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002571 tcp_cong_avoid(sk, ack, seq_rtt, prior_in_flight, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002572 }
2573
2574 if ((flag & FLAG_FORWARD_PROGRESS) || !(flag&FLAG_NOT_DUP))
2575 dst_confirm(sk->sk_dst_cache);
2576
2577 return 1;
2578
2579no_queue:
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002580 icsk->icsk_probes_out = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002581
2582 /* If this ack opens up a zero window, clear backoff. It was
2583 * being used to time the probes, and is probably far higher than
2584 * it needs to be for normal retransmission.
2585 */
2586 if (sk->sk_send_head)
2587 tcp_ack_probe(sk);
2588 return 1;
2589
2590old_ack:
2591 if (TCP_SKB_CB(skb)->sacked)
2592 tcp_sacktag_write_queue(sk, skb, prior_snd_una);
2593
2594uninteresting_ack:
2595 SOCK_DEBUG(sk, "Ack %u out of %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
2596 return 0;
2597}
2598
2599
2600/* Look for tcp options. Normally only called on SYN and SYNACK packets.
2601 * But, this can also be called on packets in the established flow when
2602 * the fast version below fails.
2603 */
2604void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx, int estab)
2605{
2606 unsigned char *ptr;
2607 struct tcphdr *th = skb->h.th;
2608 int length=(th->doff*4)-sizeof(struct tcphdr);
2609
2610 ptr = (unsigned char *)(th + 1);
2611 opt_rx->saw_tstamp = 0;
2612
2613 while(length>0) {
2614 int opcode=*ptr++;
2615 int opsize;
2616
2617 switch (opcode) {
2618 case TCPOPT_EOL:
2619 return;
2620 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
2621 length--;
2622 continue;
2623 default:
2624 opsize=*ptr++;
2625 if (opsize < 2) /* "silly options" */
2626 return;
2627 if (opsize > length)
2628 return; /* don't parse partial options */
2629 switch(opcode) {
2630 case TCPOPT_MSS:
2631 if(opsize==TCPOLEN_MSS && th->syn && !estab) {
Al Viro4f3608b2006-09-27 18:35:09 -07002632 u16 in_mss = ntohs(get_unaligned((__be16 *)ptr));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002633 if (in_mss) {
2634 if (opt_rx->user_mss && opt_rx->user_mss < in_mss)
2635 in_mss = opt_rx->user_mss;
2636 opt_rx->mss_clamp = in_mss;
2637 }
2638 }
2639 break;
2640 case TCPOPT_WINDOW:
2641 if(opsize==TCPOLEN_WINDOW && th->syn && !estab)
2642 if (sysctl_tcp_window_scaling) {
2643 __u8 snd_wscale = *(__u8 *) ptr;
2644 opt_rx->wscale_ok = 1;
2645 if (snd_wscale > 14) {
2646 if(net_ratelimit())
2647 printk(KERN_INFO "tcp_parse_options: Illegal window "
2648 "scaling value %d >14 received.\n",
2649 snd_wscale);
2650 snd_wscale = 14;
2651 }
2652 opt_rx->snd_wscale = snd_wscale;
2653 }
2654 break;
2655 case TCPOPT_TIMESTAMP:
2656 if(opsize==TCPOLEN_TIMESTAMP) {
2657 if ((estab && opt_rx->tstamp_ok) ||
2658 (!estab && sysctl_tcp_timestamps)) {
2659 opt_rx->saw_tstamp = 1;
Al Viro4f3608b2006-09-27 18:35:09 -07002660 opt_rx->rcv_tsval = ntohl(get_unaligned((__be32 *)ptr));
2661 opt_rx->rcv_tsecr = ntohl(get_unaligned((__be32 *)(ptr+4)));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002662 }
2663 }
2664 break;
2665 case TCPOPT_SACK_PERM:
2666 if(opsize==TCPOLEN_SACK_PERM && th->syn && !estab) {
2667 if (sysctl_tcp_sack) {
2668 opt_rx->sack_ok = 1;
2669 tcp_sack_reset(opt_rx);
2670 }
2671 }
2672 break;
2673
2674 case TCPOPT_SACK:
2675 if((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) &&
2676 !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) &&
2677 opt_rx->sack_ok) {
2678 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th;
2679 }
YOSHIFUJI Hideakicfb6eeb2006-11-14 19:07:45 -08002680#ifdef CONFIG_TCP_MD5SIG
2681 case TCPOPT_MD5SIG:
2682 /*
2683 * The MD5 Hash has already been
2684 * checked (see tcp_v{4,6}_do_rcv()).
2685 */
2686 break;
2687#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -07002688 };
2689 ptr+=opsize-2;
2690 length-=opsize;
2691 };
2692 }
2693}
2694
2695/* Fast parse options. This hopes to only see timestamps.
2696 * If it is wrong it falls back on tcp_parse_options().
2697 */
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08002698static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th,
2699 struct tcp_sock *tp)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002700{
2701 if (th->doff == sizeof(struct tcphdr)>>2) {
2702 tp->rx_opt.saw_tstamp = 0;
2703 return 0;
2704 } else if (tp->rx_opt.tstamp_ok &&
2705 th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) {
Al Viro4f3608b2006-09-27 18:35:09 -07002706 __be32 *ptr = (__be32 *)(th + 1);
2707 if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002708 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
2709 tp->rx_opt.saw_tstamp = 1;
2710 ++ptr;
2711 tp->rx_opt.rcv_tsval = ntohl(*ptr);
2712 ++ptr;
2713 tp->rx_opt.rcv_tsecr = ntohl(*ptr);
2714 return 1;
2715 }
2716 }
2717 tcp_parse_options(skb, &tp->rx_opt, 1);
2718 return 1;
2719}
2720
2721static inline void tcp_store_ts_recent(struct tcp_sock *tp)
2722{
2723 tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval;
2724 tp->rx_opt.ts_recent_stamp = xtime.tv_sec;
2725}
2726
2727static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)
2728{
2729 if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) {
2730 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
2731 * extra check below makes sure this can only happen
2732 * for pure ACK frames. -DaveM
2733 *
2734 * Not only, also it occurs for expired timestamps.
2735 */
2736
2737 if((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) >= 0 ||
2738 xtime.tv_sec >= tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS)
2739 tcp_store_ts_recent(tp);
2740 }
2741}
2742
2743/* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
2744 *
2745 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
2746 * it can pass through stack. So, the following predicate verifies that
2747 * this segment is not used for anything but congestion avoidance or
2748 * fast retransmit. Moreover, we even are able to eliminate most of such
2749 * second order effects, if we apply some small "replay" window (~RTO)
2750 * to timestamp space.
2751 *
2752 * All these measures still do not guarantee that we reject wrapped ACKs
2753 * on networks with high bandwidth, when sequence space is recycled fastly,
2754 * but it guarantees that such events will be very rare and do not affect
2755 * connection seriously. This doesn't look nice, but alas, PAWS is really
2756 * buggy extension.
2757 *
2758 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
2759 * states that events when retransmit arrives after original data are rare.
2760 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
2761 * the biggest problem on large power networks even with minor reordering.
2762 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
2763 * up to bandwidth of 18Gigabit/sec. 8) ]
2764 */
2765
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002766static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002767{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002768 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002769 struct tcphdr *th = skb->h.th;
2770 u32 seq = TCP_SKB_CB(skb)->seq;
2771 u32 ack = TCP_SKB_CB(skb)->ack_seq;
2772
2773 return (/* 1. Pure ACK with correct sequence number. */
2774 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) &&
2775
2776 /* 2. ... and duplicate ACK. */
2777 ack == tp->snd_una &&
2778
2779 /* 3. ... and does not update window. */
2780 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) &&
2781
2782 /* 4. ... and sits in replay window. */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002783 (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 -07002784}
2785
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002786static inline int tcp_paws_discard(const struct sock *sk, const struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002787{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002788 const struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002789 return ((s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) > TCP_PAWS_WINDOW &&
2790 xtime.tv_sec < tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS &&
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002791 !tcp_disordered_ack(sk, skb));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002792}
2793
2794/* Check segment sequence number for validity.
2795 *
2796 * Segment controls are considered valid, if the segment
2797 * fits to the window after truncation to the window. Acceptability
2798 * of data (and SYN, FIN, of course) is checked separately.
2799 * See tcp_data_queue(), for example.
2800 *
2801 * Also, controls (RST is main one) are accepted using RCV.WUP instead
2802 * of RCV.NXT. Peer still did not advance his SND.UNA when we
2803 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
2804 * (borrowed from freebsd)
2805 */
2806
2807static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq)
2808{
2809 return !before(end_seq, tp->rcv_wup) &&
2810 !after(seq, tp->rcv_nxt + tcp_receive_window(tp));
2811}
2812
2813/* When we get a reset we do this. */
2814static void tcp_reset(struct sock *sk)
2815{
2816 /* We want the right error as BSD sees it (and indeed as we do). */
2817 switch (sk->sk_state) {
2818 case TCP_SYN_SENT:
2819 sk->sk_err = ECONNREFUSED;
2820 break;
2821 case TCP_CLOSE_WAIT:
2822 sk->sk_err = EPIPE;
2823 break;
2824 case TCP_CLOSE:
2825 return;
2826 default:
2827 sk->sk_err = ECONNRESET;
2828 }
2829
2830 if (!sock_flag(sk, SOCK_DEAD))
2831 sk->sk_error_report(sk);
2832
2833 tcp_done(sk);
2834}
2835
2836/*
2837 * Process the FIN bit. This now behaves as it is supposed to work
2838 * and the FIN takes effect when it is validly part of sequence
2839 * space. Not before when we get holes.
2840 *
2841 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
2842 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
2843 * TIME-WAIT)
2844 *
2845 * If we are in FINWAIT-1, a received FIN indicates simultaneous
2846 * close and we go into CLOSING (and later onto TIME-WAIT)
2847 *
2848 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
2849 */
2850static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th)
2851{
2852 struct tcp_sock *tp = tcp_sk(sk);
2853
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002854 inet_csk_schedule_ack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002855
2856 sk->sk_shutdown |= RCV_SHUTDOWN;
2857 sock_set_flag(sk, SOCK_DONE);
2858
2859 switch (sk->sk_state) {
2860 case TCP_SYN_RECV:
2861 case TCP_ESTABLISHED:
2862 /* Move to CLOSE_WAIT */
2863 tcp_set_state(sk, TCP_CLOSE_WAIT);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002864 inet_csk(sk)->icsk_ack.pingpong = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002865 break;
2866
2867 case TCP_CLOSE_WAIT:
2868 case TCP_CLOSING:
2869 /* Received a retransmission of the FIN, do
2870 * nothing.
2871 */
2872 break;
2873 case TCP_LAST_ACK:
2874 /* RFC793: Remain in the LAST-ACK state. */
2875 break;
2876
2877 case TCP_FIN_WAIT1:
2878 /* This case occurs when a simultaneous close
2879 * happens, we must ack the received FIN and
2880 * enter the CLOSING state.
2881 */
2882 tcp_send_ack(sk);
2883 tcp_set_state(sk, TCP_CLOSING);
2884 break;
2885 case TCP_FIN_WAIT2:
2886 /* Received a FIN -- send ACK and enter TIME_WAIT. */
2887 tcp_send_ack(sk);
2888 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
2889 break;
2890 default:
2891 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
2892 * cases we should never reach this piece of code.
2893 */
2894 printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n",
2895 __FUNCTION__, sk->sk_state);
2896 break;
2897 };
2898
2899 /* It _is_ possible, that we have something out-of-order _after_ FIN.
2900 * Probably, we should reset in this case. For now drop them.
2901 */
2902 __skb_queue_purge(&tp->out_of_order_queue);
2903 if (tp->rx_opt.sack_ok)
2904 tcp_sack_reset(&tp->rx_opt);
2905 sk_stream_mem_reclaim(sk);
2906
2907 if (!sock_flag(sk, SOCK_DEAD)) {
2908 sk->sk_state_change(sk);
2909
2910 /* Do not send POLL_HUP for half duplex close. */
2911 if (sk->sk_shutdown == SHUTDOWN_MASK ||
2912 sk->sk_state == TCP_CLOSE)
2913 sk_wake_async(sk, 1, POLL_HUP);
2914 else
2915 sk_wake_async(sk, 1, POLL_IN);
2916 }
2917}
2918
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08002919static inline int tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, u32 end_seq)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002920{
2921 if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) {
2922 if (before(seq, sp->start_seq))
2923 sp->start_seq = seq;
2924 if (after(end_seq, sp->end_seq))
2925 sp->end_seq = end_seq;
2926 return 1;
2927 }
2928 return 0;
2929}
2930
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08002931static void tcp_dsack_set(struct tcp_sock *tp, u32 seq, u32 end_seq)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002932{
2933 if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) {
2934 if (before(seq, tp->rcv_nxt))
2935 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT);
2936 else
2937 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT);
2938
2939 tp->rx_opt.dsack = 1;
2940 tp->duplicate_sack[0].start_seq = seq;
2941 tp->duplicate_sack[0].end_seq = end_seq;
2942 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + 1, 4 - tp->rx_opt.tstamp_ok);
2943 }
2944}
2945
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08002946static void tcp_dsack_extend(struct tcp_sock *tp, u32 seq, u32 end_seq)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002947{
2948 if (!tp->rx_opt.dsack)
2949 tcp_dsack_set(tp, seq, end_seq);
2950 else
2951 tcp_sack_extend(tp->duplicate_sack, seq, end_seq);
2952}
2953
2954static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb)
2955{
2956 struct tcp_sock *tp = tcp_sk(sk);
2957
2958 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
2959 before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
2960 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002961 tcp_enter_quickack_mode(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002962
2963 if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) {
2964 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
2965
2966 if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))
2967 end_seq = tp->rcv_nxt;
2968 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, end_seq);
2969 }
2970 }
2971
2972 tcp_send_ack(sk);
2973}
2974
2975/* These routines update the SACK block as out-of-order packets arrive or
2976 * in-order packets close up the sequence space.
2977 */
2978static void tcp_sack_maybe_coalesce(struct tcp_sock *tp)
2979{
2980 int this_sack;
2981 struct tcp_sack_block *sp = &tp->selective_acks[0];
2982 struct tcp_sack_block *swalk = sp+1;
2983
2984 /* See if the recent change to the first SACK eats into
2985 * or hits the sequence space of other SACK blocks, if so coalesce.
2986 */
2987 for (this_sack = 1; this_sack < tp->rx_opt.num_sacks; ) {
2988 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) {
2989 int i;
2990
2991 /* Zap SWALK, by moving every further SACK up by one slot.
2992 * Decrease num_sacks.
2993 */
2994 tp->rx_opt.num_sacks--;
2995 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
2996 for(i=this_sack; i < tp->rx_opt.num_sacks; i++)
2997 sp[i] = sp[i+1];
2998 continue;
2999 }
3000 this_sack++, swalk++;
3001 }
3002}
3003
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08003004static inline void tcp_sack_swap(struct tcp_sack_block *sack1, struct tcp_sack_block *sack2)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003005{
3006 __u32 tmp;
3007
3008 tmp = sack1->start_seq;
3009 sack1->start_seq = sack2->start_seq;
3010 sack2->start_seq = tmp;
3011
3012 tmp = sack1->end_seq;
3013 sack1->end_seq = sack2->end_seq;
3014 sack2->end_seq = tmp;
3015}
3016
3017static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq)
3018{
3019 struct tcp_sock *tp = tcp_sk(sk);
3020 struct tcp_sack_block *sp = &tp->selective_acks[0];
3021 int cur_sacks = tp->rx_opt.num_sacks;
3022 int this_sack;
3023
3024 if (!cur_sacks)
3025 goto new_sack;
3026
3027 for (this_sack=0; this_sack<cur_sacks; this_sack++, sp++) {
3028 if (tcp_sack_extend(sp, seq, end_seq)) {
3029 /* Rotate this_sack to the first one. */
3030 for (; this_sack>0; this_sack--, sp--)
3031 tcp_sack_swap(sp, sp-1);
3032 if (cur_sacks > 1)
3033 tcp_sack_maybe_coalesce(tp);
3034 return;
3035 }
3036 }
3037
3038 /* Could not find an adjacent existing SACK, build a new one,
3039 * put it at the front, and shift everyone else down. We
3040 * always know there is at least one SACK present already here.
3041 *
3042 * If the sack array is full, forget about the last one.
3043 */
3044 if (this_sack >= 4) {
3045 this_sack--;
3046 tp->rx_opt.num_sacks--;
3047 sp--;
3048 }
3049 for(; this_sack > 0; this_sack--, sp--)
3050 *sp = *(sp-1);
3051
3052new_sack:
3053 /* Build the new head SACK, and we're done. */
3054 sp->start_seq = seq;
3055 sp->end_seq = end_seq;
3056 tp->rx_opt.num_sacks++;
3057 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
3058}
3059
3060/* RCV.NXT advances, some SACKs should be eaten. */
3061
3062static void tcp_sack_remove(struct tcp_sock *tp)
3063{
3064 struct tcp_sack_block *sp = &tp->selective_acks[0];
3065 int num_sacks = tp->rx_opt.num_sacks;
3066 int this_sack;
3067
3068 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
David S. Millerb03efcf2005-07-08 14:57:23 -07003069 if (skb_queue_empty(&tp->out_of_order_queue)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003070 tp->rx_opt.num_sacks = 0;
3071 tp->rx_opt.eff_sacks = tp->rx_opt.dsack;
3072 return;
3073 }
3074
3075 for(this_sack = 0; this_sack < num_sacks; ) {
3076 /* Check if the start of the sack is covered by RCV.NXT. */
3077 if (!before(tp->rcv_nxt, sp->start_seq)) {
3078 int i;
3079
3080 /* RCV.NXT must cover all the block! */
3081 BUG_TRAP(!before(tp->rcv_nxt, sp->end_seq));
3082
3083 /* Zap this SACK, by moving forward any other SACKS. */
3084 for (i=this_sack+1; i < num_sacks; i++)
3085 tp->selective_acks[i-1] = tp->selective_acks[i];
3086 num_sacks--;
3087 continue;
3088 }
3089 this_sack++;
3090 sp++;
3091 }
3092 if (num_sacks != tp->rx_opt.num_sacks) {
3093 tp->rx_opt.num_sacks = num_sacks;
3094 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
3095 }
3096}
3097
3098/* This one checks to see if we can put data from the
3099 * out_of_order queue into the receive_queue.
3100 */
3101static void tcp_ofo_queue(struct sock *sk)
3102{
3103 struct tcp_sock *tp = tcp_sk(sk);
3104 __u32 dsack_high = tp->rcv_nxt;
3105 struct sk_buff *skb;
3106
3107 while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) {
3108 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
3109 break;
3110
3111 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) {
3112 __u32 dsack = dsack_high;
3113 if (before(TCP_SKB_CB(skb)->end_seq, dsack_high))
3114 dsack_high = TCP_SKB_CB(skb)->end_seq;
3115 tcp_dsack_extend(tp, TCP_SKB_CB(skb)->seq, dsack);
3116 }
3117
3118 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
3119 SOCK_DEBUG(sk, "ofo packet was already received \n");
David S. Miller8728b832005-08-09 19:25:21 -07003120 __skb_unlink(skb, &tp->out_of_order_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003121 __kfree_skb(skb);
3122 continue;
3123 }
3124 SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n",
3125 tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
3126 TCP_SKB_CB(skb)->end_seq);
3127
David S. Miller8728b832005-08-09 19:25:21 -07003128 __skb_unlink(skb, &tp->out_of_order_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003129 __skb_queue_tail(&sk->sk_receive_queue, skb);
3130 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3131 if(skb->h.th->fin)
3132 tcp_fin(skb, sk, skb->h.th);
3133 }
3134}
3135
3136static int tcp_prune_queue(struct sock *sk);
3137
3138static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
3139{
3140 struct tcphdr *th = skb->h.th;
3141 struct tcp_sock *tp = tcp_sk(sk);
3142 int eaten = -1;
3143
3144 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq)
3145 goto drop;
3146
Linus Torvalds1da177e2005-04-16 15:20:36 -07003147 __skb_pull(skb, th->doff*4);
3148
3149 TCP_ECN_accept_cwr(tp, skb);
3150
3151 if (tp->rx_opt.dsack) {
3152 tp->rx_opt.dsack = 0;
3153 tp->rx_opt.eff_sacks = min_t(unsigned int, tp->rx_opt.num_sacks,
3154 4 - tp->rx_opt.tstamp_ok);
3155 }
3156
3157 /* Queue data for delivery to the user.
3158 * Packets in sequence go to the receive queue.
3159 * Out of sequence packets to the out_of_order_queue.
3160 */
3161 if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
3162 if (tcp_receive_window(tp) == 0)
3163 goto out_of_window;
3164
3165 /* Ok. In sequence. In window. */
3166 if (tp->ucopy.task == current &&
3167 tp->copied_seq == tp->rcv_nxt && tp->ucopy.len &&
3168 sock_owned_by_user(sk) && !tp->urg_data) {
3169 int chunk = min_t(unsigned int, skb->len,
3170 tp->ucopy.len);
3171
3172 __set_current_state(TASK_RUNNING);
3173
3174 local_bh_enable();
3175 if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) {
3176 tp->ucopy.len -= chunk;
3177 tp->copied_seq += chunk;
3178 eaten = (chunk == skb->len && !th->fin);
3179 tcp_rcv_space_adjust(sk);
3180 }
3181 local_bh_disable();
3182 }
3183
3184 if (eaten <= 0) {
3185queue_and_out:
3186 if (eaten < 0 &&
3187 (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
3188 !sk_stream_rmem_schedule(sk, skb))) {
3189 if (tcp_prune_queue(sk) < 0 ||
3190 !sk_stream_rmem_schedule(sk, skb))
3191 goto drop;
3192 }
3193 sk_stream_set_owner_r(skb, sk);
3194 __skb_queue_tail(&sk->sk_receive_queue, skb);
3195 }
3196 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3197 if(skb->len)
3198 tcp_event_data_recv(sk, tp, skb);
3199 if(th->fin)
3200 tcp_fin(skb, sk, th);
3201
David S. Millerb03efcf2005-07-08 14:57:23 -07003202 if (!skb_queue_empty(&tp->out_of_order_queue)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003203 tcp_ofo_queue(sk);
3204
3205 /* RFC2581. 4.2. SHOULD send immediate ACK, when
3206 * gap in queue is filled.
3207 */
David S. Millerb03efcf2005-07-08 14:57:23 -07003208 if (skb_queue_empty(&tp->out_of_order_queue))
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003209 inet_csk(sk)->icsk_ack.pingpong = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003210 }
3211
3212 if (tp->rx_opt.num_sacks)
3213 tcp_sack_remove(tp);
3214
3215 tcp_fast_path_check(sk, tp);
3216
3217 if (eaten > 0)
3218 __kfree_skb(skb);
3219 else if (!sock_flag(sk, SOCK_DEAD))
3220 sk->sk_data_ready(sk, 0);
3221 return;
3222 }
3223
3224 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
3225 /* A retransmit, 2nd most common case. Force an immediate ack. */
3226 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST);
3227 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
3228
3229out_of_window:
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003230 tcp_enter_quickack_mode(sk);
3231 inet_csk_schedule_ack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003232drop:
3233 __kfree_skb(skb);
3234 return;
3235 }
3236
3237 /* Out of window. F.e. zero window probe. */
3238 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp)))
3239 goto out_of_window;
3240
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003241 tcp_enter_quickack_mode(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003242
3243 if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
3244 /* Partial packet, seq < rcv_next < end_seq */
3245 SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n",
3246 tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
3247 TCP_SKB_CB(skb)->end_seq);
3248
3249 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, tp->rcv_nxt);
3250
3251 /* If window is closed, drop tail of packet. But after
3252 * remembering D-SACK for its head made in previous line.
3253 */
3254 if (!tcp_receive_window(tp))
3255 goto out_of_window;
3256 goto queue_and_out;
3257 }
3258
3259 TCP_ECN_check_ce(tp, skb);
3260
3261 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
3262 !sk_stream_rmem_schedule(sk, skb)) {
3263 if (tcp_prune_queue(sk) < 0 ||
3264 !sk_stream_rmem_schedule(sk, skb))
3265 goto drop;
3266 }
3267
3268 /* Disable header prediction. */
3269 tp->pred_flags = 0;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003270 inet_csk_schedule_ack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003271
3272 SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n",
3273 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
3274
3275 sk_stream_set_owner_r(skb, sk);
3276
3277 if (!skb_peek(&tp->out_of_order_queue)) {
3278 /* Initial out of order segment, build 1 SACK. */
3279 if (tp->rx_opt.sack_ok) {
3280 tp->rx_opt.num_sacks = 1;
3281 tp->rx_opt.dsack = 0;
3282 tp->rx_opt.eff_sacks = 1;
3283 tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
3284 tp->selective_acks[0].end_seq =
3285 TCP_SKB_CB(skb)->end_seq;
3286 }
3287 __skb_queue_head(&tp->out_of_order_queue,skb);
3288 } else {
3289 struct sk_buff *skb1 = tp->out_of_order_queue.prev;
3290 u32 seq = TCP_SKB_CB(skb)->seq;
3291 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
3292
3293 if (seq == TCP_SKB_CB(skb1)->end_seq) {
David S. Miller8728b832005-08-09 19:25:21 -07003294 __skb_append(skb1, skb, &tp->out_of_order_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003295
3296 if (!tp->rx_opt.num_sacks ||
3297 tp->selective_acks[0].end_seq != seq)
3298 goto add_sack;
3299
3300 /* Common case: data arrive in order after hole. */
3301 tp->selective_acks[0].end_seq = end_seq;
3302 return;
3303 }
3304
3305 /* Find place to insert this segment. */
3306 do {
3307 if (!after(TCP_SKB_CB(skb1)->seq, seq))
3308 break;
3309 } while ((skb1 = skb1->prev) !=
3310 (struct sk_buff*)&tp->out_of_order_queue);
3311
3312 /* Do skb overlap to previous one? */
3313 if (skb1 != (struct sk_buff*)&tp->out_of_order_queue &&
3314 before(seq, TCP_SKB_CB(skb1)->end_seq)) {
3315 if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
3316 /* All the bits are present. Drop. */
3317 __kfree_skb(skb);
3318 tcp_dsack_set(tp, seq, end_seq);
3319 goto add_sack;
3320 }
3321 if (after(seq, TCP_SKB_CB(skb1)->seq)) {
3322 /* Partial overlap. */
3323 tcp_dsack_set(tp, seq, TCP_SKB_CB(skb1)->end_seq);
3324 } else {
3325 skb1 = skb1->prev;
3326 }
3327 }
3328 __skb_insert(skb, skb1, skb1->next, &tp->out_of_order_queue);
3329
3330 /* And clean segments covered by new one as whole. */
3331 while ((skb1 = skb->next) !=
3332 (struct sk_buff*)&tp->out_of_order_queue &&
3333 after(end_seq, TCP_SKB_CB(skb1)->seq)) {
3334 if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
3335 tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, end_seq);
3336 break;
3337 }
David S. Miller8728b832005-08-09 19:25:21 -07003338 __skb_unlink(skb1, &tp->out_of_order_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003339 tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, TCP_SKB_CB(skb1)->end_seq);
3340 __kfree_skb(skb1);
3341 }
3342
3343add_sack:
3344 if (tp->rx_opt.sack_ok)
3345 tcp_sack_new_ofo_skb(sk, seq, end_seq);
3346 }
3347}
3348
3349/* Collapse contiguous sequence of skbs head..tail with
3350 * sequence numbers start..end.
3351 * Segments with FIN/SYN are not collapsed (only because this
3352 * simplifies code)
3353 */
3354static void
David S. Miller8728b832005-08-09 19:25:21 -07003355tcp_collapse(struct sock *sk, struct sk_buff_head *list,
3356 struct sk_buff *head, struct sk_buff *tail,
3357 u32 start, u32 end)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003358{
3359 struct sk_buff *skb;
3360
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08003361 /* First, check that queue is collapsible and find
Linus Torvalds1da177e2005-04-16 15:20:36 -07003362 * the point where collapsing can be useful. */
3363 for (skb = head; skb != tail; ) {
3364 /* No new bits? It is possible on ofo queue. */
3365 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
3366 struct sk_buff *next = skb->next;
David S. Miller8728b832005-08-09 19:25:21 -07003367 __skb_unlink(skb, list);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003368 __kfree_skb(skb);
3369 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED);
3370 skb = next;
3371 continue;
3372 }
3373
3374 /* The first skb to collapse is:
3375 * - not SYN/FIN and
3376 * - bloated or contains data before "start" or
3377 * overlaps to the next one.
3378 */
3379 if (!skb->h.th->syn && !skb->h.th->fin &&
3380 (tcp_win_from_space(skb->truesize) > skb->len ||
3381 before(TCP_SKB_CB(skb)->seq, start) ||
3382 (skb->next != tail &&
3383 TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb->next)->seq)))
3384 break;
3385
3386 /* Decided to skip this, advance start seq. */
3387 start = TCP_SKB_CB(skb)->end_seq;
3388 skb = skb->next;
3389 }
3390 if (skb == tail || skb->h.th->syn || skb->h.th->fin)
3391 return;
3392
3393 while (before(start, end)) {
3394 struct sk_buff *nskb;
3395 int header = skb_headroom(skb);
3396 int copy = SKB_MAX_ORDER(header, 0);
3397
3398 /* Too big header? This can happen with IPv6. */
3399 if (copy < 0)
3400 return;
3401 if (end-start < copy)
3402 copy = end-start;
3403 nskb = alloc_skb(copy+header, GFP_ATOMIC);
3404 if (!nskb)
3405 return;
3406 skb_reserve(nskb, header);
3407 memcpy(nskb->head, skb->head, header);
3408 nskb->nh.raw = nskb->head + (skb->nh.raw-skb->head);
3409 nskb->h.raw = nskb->head + (skb->h.raw-skb->head);
3410 nskb->mac.raw = nskb->head + (skb->mac.raw-skb->head);
3411 memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
3412 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start;
David S. Miller8728b832005-08-09 19:25:21 -07003413 __skb_insert(nskb, skb->prev, skb, list);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003414 sk_stream_set_owner_r(nskb, sk);
3415
3416 /* Copy data, releasing collapsed skbs. */
3417 while (copy > 0) {
3418 int offset = start - TCP_SKB_CB(skb)->seq;
3419 int size = TCP_SKB_CB(skb)->end_seq - start;
3420
Kris Katterjohn09a62662006-01-08 22:24:28 -08003421 BUG_ON(offset < 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003422 if (size > 0) {
3423 size = min(copy, size);
3424 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size))
3425 BUG();
3426 TCP_SKB_CB(nskb)->end_seq += size;
3427 copy -= size;
3428 start += size;
3429 }
3430 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
3431 struct sk_buff *next = skb->next;
David S. Miller8728b832005-08-09 19:25:21 -07003432 __skb_unlink(skb, list);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003433 __kfree_skb(skb);
3434 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED);
3435 skb = next;
3436 if (skb == tail || skb->h.th->syn || skb->h.th->fin)
3437 return;
3438 }
3439 }
3440 }
3441}
3442
3443/* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
3444 * and tcp_collapse() them until all the queue is collapsed.
3445 */
3446static void tcp_collapse_ofo_queue(struct sock *sk)
3447{
3448 struct tcp_sock *tp = tcp_sk(sk);
3449 struct sk_buff *skb = skb_peek(&tp->out_of_order_queue);
3450 struct sk_buff *head;
3451 u32 start, end;
3452
3453 if (skb == NULL)
3454 return;
3455
3456 start = TCP_SKB_CB(skb)->seq;
3457 end = TCP_SKB_CB(skb)->end_seq;
3458 head = skb;
3459
3460 for (;;) {
3461 skb = skb->next;
3462
3463 /* Segment is terminated when we see gap or when
3464 * we are at the end of all the queue. */
3465 if (skb == (struct sk_buff *)&tp->out_of_order_queue ||
3466 after(TCP_SKB_CB(skb)->seq, end) ||
3467 before(TCP_SKB_CB(skb)->end_seq, start)) {
David S. Miller8728b832005-08-09 19:25:21 -07003468 tcp_collapse(sk, &tp->out_of_order_queue,
3469 head, skb, start, end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003470 head = skb;
3471 if (skb == (struct sk_buff *)&tp->out_of_order_queue)
3472 break;
3473 /* Start new segment */
3474 start = TCP_SKB_CB(skb)->seq;
3475 end = TCP_SKB_CB(skb)->end_seq;
3476 } else {
3477 if (before(TCP_SKB_CB(skb)->seq, start))
3478 start = TCP_SKB_CB(skb)->seq;
3479 if (after(TCP_SKB_CB(skb)->end_seq, end))
3480 end = TCP_SKB_CB(skb)->end_seq;
3481 }
3482 }
3483}
3484
3485/* Reduce allocated memory if we can, trying to get
3486 * the socket within its memory limits again.
3487 *
3488 * Return less than zero if we should start dropping frames
3489 * until the socket owning process reads some of the data
3490 * to stabilize the situation.
3491 */
3492static int tcp_prune_queue(struct sock *sk)
3493{
3494 struct tcp_sock *tp = tcp_sk(sk);
3495
3496 SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq);
3497
3498 NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED);
3499
3500 if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
3501 tcp_clamp_window(sk, tp);
3502 else if (tcp_memory_pressure)
3503 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss);
3504
3505 tcp_collapse_ofo_queue(sk);
David S. Miller8728b832005-08-09 19:25:21 -07003506 tcp_collapse(sk, &sk->sk_receive_queue,
3507 sk->sk_receive_queue.next,
Linus Torvalds1da177e2005-04-16 15:20:36 -07003508 (struct sk_buff*)&sk->sk_receive_queue,
3509 tp->copied_seq, tp->rcv_nxt);
3510 sk_stream_mem_reclaim(sk);
3511
3512 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
3513 return 0;
3514
3515 /* Collapsing did not help, destructive actions follow.
3516 * This must not ever occur. */
3517
3518 /* First, purge the out_of_order queue. */
David S. Millerb03efcf2005-07-08 14:57:23 -07003519 if (!skb_queue_empty(&tp->out_of_order_queue)) {
3520 NET_INC_STATS_BH(LINUX_MIB_OFOPRUNED);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003521 __skb_queue_purge(&tp->out_of_order_queue);
3522
3523 /* Reset SACK state. A conforming SACK implementation will
3524 * do the same at a timeout based retransmit. When a connection
3525 * is in a sad state like this, we care only about integrity
3526 * of the connection not performance.
3527 */
3528 if (tp->rx_opt.sack_ok)
3529 tcp_sack_reset(&tp->rx_opt);
3530 sk_stream_mem_reclaim(sk);
3531 }
3532
3533 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
3534 return 0;
3535
3536 /* If we are really being abused, tell the caller to silently
3537 * drop receive data on the floor. It will get retransmitted
3538 * and hopefully then we'll have sufficient space.
3539 */
3540 NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED);
3541
3542 /* Massive buffer overcommit. */
3543 tp->pred_flags = 0;
3544 return -1;
3545}
3546
3547
3548/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
3549 * As additional protections, we do not touch cwnd in retransmission phases,
3550 * and if application hit its sndbuf limit recently.
3551 */
3552void tcp_cwnd_application_limited(struct sock *sk)
3553{
3554 struct tcp_sock *tp = tcp_sk(sk);
3555
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003556 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07003557 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
3558 /* Limited by application or receiver window. */
Ilpo Järvinend254bcd2006-08-04 16:57:42 -07003559 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk));
3560 u32 win_used = max(tp->snd_cwnd_used, init_win);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003561 if (win_used < tp->snd_cwnd) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003562 tp->snd_ssthresh = tcp_current_ssthresh(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003563 tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
3564 }
3565 tp->snd_cwnd_used = 0;
3566 }
3567 tp->snd_cwnd_stamp = tcp_time_stamp;
3568}
3569
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08003570static int tcp_should_expand_sndbuf(struct sock *sk, struct tcp_sock *tp)
David S. Miller0d9901d2005-07-05 15:21:10 -07003571{
3572 /* If the user specified a specific send buffer setting, do
3573 * not modify it.
3574 */
3575 if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
3576 return 0;
3577
3578 /* If we are under global TCP memory pressure, do not expand. */
3579 if (tcp_memory_pressure)
3580 return 0;
3581
3582 /* If we are under soft global TCP memory pressure, do not expand. */
3583 if (atomic_read(&tcp_memory_allocated) >= sysctl_tcp_mem[0])
3584 return 0;
3585
3586 /* If we filled the congestion window, do not expand. */
3587 if (tp->packets_out >= tp->snd_cwnd)
3588 return 0;
3589
3590 return 1;
3591}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003592
3593/* When incoming ACK allowed to free some skb from write_queue,
3594 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
3595 * on the exit from tcp input handler.
3596 *
3597 * PROBLEM: sndbuf expansion does not work well with largesend.
3598 */
3599static void tcp_new_space(struct sock *sk)
3600{
3601 struct tcp_sock *tp = tcp_sk(sk);
3602
David S. Miller0d9901d2005-07-05 15:21:10 -07003603 if (tcp_should_expand_sndbuf(sk, tp)) {
David S. Millerc1b4a7e2005-07-05 15:24:38 -07003604 int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) +
Linus Torvalds1da177e2005-04-16 15:20:36 -07003605 MAX_TCP_HEADER + 16 + sizeof(struct sk_buff),
3606 demanded = max_t(unsigned int, tp->snd_cwnd,
3607 tp->reordering + 1);
3608 sndmem *= 2*demanded;
3609 if (sndmem > sk->sk_sndbuf)
3610 sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]);
3611 tp->snd_cwnd_stamp = tcp_time_stamp;
3612 }
3613
3614 sk->sk_write_space(sk);
3615}
3616
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08003617static void tcp_check_space(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003618{
3619 if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
3620 sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
3621 if (sk->sk_socket &&
3622 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
3623 tcp_new_space(sk);
3624 }
3625}
3626
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08003627static inline void tcp_data_snd_check(struct sock *sk, struct tcp_sock *tp)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003628{
David S. Miller55c97f32005-07-05 15:19:38 -07003629 tcp_push_pending_frames(sk, tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003630 tcp_check_space(sk);
3631}
3632
3633/*
3634 * Check if sending an ack is needed.
3635 */
3636static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
3637{
3638 struct tcp_sock *tp = tcp_sk(sk);
3639
3640 /* More than one full frame received... */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003641 if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss
Linus Torvalds1da177e2005-04-16 15:20:36 -07003642 /* ... and right edge of window advances far enough.
3643 * (tcp_recvmsg() will send ACK otherwise). Or...
3644 */
3645 && __tcp_select_window(sk) >= tp->rcv_wnd) ||
3646 /* We ACK each frame or... */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003647 tcp_in_quickack_mode(sk) ||
Linus Torvalds1da177e2005-04-16 15:20:36 -07003648 /* We have out of order data. */
3649 (ofo_possible &&
3650 skb_peek(&tp->out_of_order_queue))) {
3651 /* Then ack it now */
3652 tcp_send_ack(sk);
3653 } else {
3654 /* Else, send delayed ack. */
3655 tcp_send_delayed_ack(sk);
3656 }
3657}
3658
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08003659static inline void tcp_ack_snd_check(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003660{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003661 if (!inet_csk_ack_scheduled(sk)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003662 /* We sent a data segment already. */
3663 return;
3664 }
3665 __tcp_ack_snd_check(sk, 1);
3666}
3667
3668/*
3669 * This routine is only called when we have urgent data
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08003670 * signaled. Its the 'slow' part of tcp_urg. It could be
Linus Torvalds1da177e2005-04-16 15:20:36 -07003671 * moved inline now as tcp_urg is only called from one
3672 * place. We handle URGent data wrong. We have to - as
3673 * BSD still doesn't use the correction from RFC961.
3674 * For 1003.1g we should support a new option TCP_STDURG to permit
3675 * either form (or just set the sysctl tcp_stdurg).
3676 */
3677
3678static void tcp_check_urg(struct sock * sk, struct tcphdr * th)
3679{
3680 struct tcp_sock *tp = tcp_sk(sk);
3681 u32 ptr = ntohs(th->urg_ptr);
3682
3683 if (ptr && !sysctl_tcp_stdurg)
3684 ptr--;
3685 ptr += ntohl(th->seq);
3686
3687 /* Ignore urgent data that we've already seen and read. */
3688 if (after(tp->copied_seq, ptr))
3689 return;
3690
3691 /* Do not replay urg ptr.
3692 *
3693 * NOTE: interesting situation not covered by specs.
3694 * Misbehaving sender may send urg ptr, pointing to segment,
3695 * which we already have in ofo queue. We are not able to fetch
3696 * such data and will stay in TCP_URG_NOTYET until will be eaten
3697 * by recvmsg(). Seems, we are not obliged to handle such wicked
3698 * situations. But it is worth to think about possibility of some
3699 * DoSes using some hypothetical application level deadlock.
3700 */
3701 if (before(ptr, tp->rcv_nxt))
3702 return;
3703
3704 /* Do we already have a newer (or duplicate) urgent pointer? */
3705 if (tp->urg_data && !after(ptr, tp->urg_seq))
3706 return;
3707
3708 /* Tell the world about our new urgent pointer. */
3709 sk_send_sigurg(sk);
3710
3711 /* We may be adding urgent data when the last byte read was
3712 * urgent. To do this requires some care. We cannot just ignore
3713 * tp->copied_seq since we would read the last urgent byte again
3714 * as data, nor can we alter copied_seq until this data arrives
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08003715 * or we break the semantics of SIOCATMARK (and thus sockatmark())
Linus Torvalds1da177e2005-04-16 15:20:36 -07003716 *
3717 * NOTE. Double Dutch. Rendering to plain English: author of comment
3718 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
3719 * and expect that both A and B disappear from stream. This is _wrong_.
3720 * Though this happens in BSD with high probability, this is occasional.
3721 * Any application relying on this is buggy. Note also, that fix "works"
3722 * only in this artificial test. Insert some normal data between A and B and we will
3723 * decline of BSD again. Verdict: it is better to remove to trap
3724 * buggy users.
3725 */
3726 if (tp->urg_seq == tp->copied_seq && tp->urg_data &&
3727 !sock_flag(sk, SOCK_URGINLINE) &&
3728 tp->copied_seq != tp->rcv_nxt) {
3729 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
3730 tp->copied_seq++;
3731 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) {
David S. Miller8728b832005-08-09 19:25:21 -07003732 __skb_unlink(skb, &sk->sk_receive_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003733 __kfree_skb(skb);
3734 }
3735 }
3736
3737 tp->urg_data = TCP_URG_NOTYET;
3738 tp->urg_seq = ptr;
3739
3740 /* Disable header prediction. */
3741 tp->pred_flags = 0;
3742}
3743
3744/* This is the 'fast' part of urgent handling. */
3745static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th)
3746{
3747 struct tcp_sock *tp = tcp_sk(sk);
3748
3749 /* Check if we get a new urgent pointer - normally not. */
3750 if (th->urg)
3751 tcp_check_urg(sk,th);
3752
3753 /* Do we wait for any urgent data? - normally not... */
3754 if (tp->urg_data == TCP_URG_NOTYET) {
3755 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) -
3756 th->syn;
3757
3758 /* Is the urgent pointer pointing into this packet? */
3759 if (ptr < skb->len) {
3760 u8 tmp;
3761 if (skb_copy_bits(skb, ptr, &tmp, 1))
3762 BUG();
3763 tp->urg_data = TCP_URG_VALID | tmp;
3764 if (!sock_flag(sk, SOCK_DEAD))
3765 sk->sk_data_ready(sk, 0);
3766 }
3767 }
3768}
3769
3770static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen)
3771{
3772 struct tcp_sock *tp = tcp_sk(sk);
3773 int chunk = skb->len - hlen;
3774 int err;
3775
3776 local_bh_enable();
3777 if (skb->ip_summed==CHECKSUM_UNNECESSARY)
3778 err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk);
3779 else
3780 err = skb_copy_and_csum_datagram_iovec(skb, hlen,
3781 tp->ucopy.iov);
3782
3783 if (!err) {
3784 tp->ucopy.len -= chunk;
3785 tp->copied_seq += chunk;
3786 tcp_rcv_space_adjust(sk);
3787 }
3788
3789 local_bh_disable();
3790 return err;
3791}
3792
Al Virob51655b2006-11-14 21:40:42 -08003793static __sum16 __tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003794{
Al Virob51655b2006-11-14 21:40:42 -08003795 __sum16 result;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003796
3797 if (sock_owned_by_user(sk)) {
3798 local_bh_enable();
3799 result = __tcp_checksum_complete(skb);
3800 local_bh_disable();
3801 } else {
3802 result = __tcp_checksum_complete(skb);
3803 }
3804 return result;
3805}
3806
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08003807static inline int tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003808{
3809 return skb->ip_summed != CHECKSUM_UNNECESSARY &&
3810 __tcp_checksum_complete_user(sk, skb);
3811}
3812
Chris Leech1a2449a2006-05-23 18:05:53 -07003813#ifdef CONFIG_NET_DMA
3814static int tcp_dma_try_early_copy(struct sock *sk, struct sk_buff *skb, int hlen)
3815{
3816 struct tcp_sock *tp = tcp_sk(sk);
3817 int chunk = skb->len - hlen;
3818 int dma_cookie;
3819 int copied_early = 0;
3820
3821 if (tp->ucopy.wakeup)
3822 return 0;
3823
3824 if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list)
3825 tp->ucopy.dma_chan = get_softnet_dma();
3826
3827 if (tp->ucopy.dma_chan && skb->ip_summed == CHECKSUM_UNNECESSARY) {
3828
3829 dma_cookie = dma_skb_copy_datagram_iovec(tp->ucopy.dma_chan,
3830 skb, hlen, tp->ucopy.iov, chunk, tp->ucopy.pinned_list);
3831
3832 if (dma_cookie < 0)
3833 goto out;
3834
3835 tp->ucopy.dma_cookie = dma_cookie;
3836 copied_early = 1;
3837
3838 tp->ucopy.len -= chunk;
3839 tp->copied_seq += chunk;
3840 tcp_rcv_space_adjust(sk);
3841
3842 if ((tp->ucopy.len == 0) ||
3843 (tcp_flag_word(skb->h.th) & TCP_FLAG_PSH) ||
3844 (atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1))) {
3845 tp->ucopy.wakeup = 1;
3846 sk->sk_data_ready(sk, 0);
3847 }
3848 } else if (chunk > 0) {
3849 tp->ucopy.wakeup = 1;
3850 sk->sk_data_ready(sk, 0);
3851 }
3852out:
3853 return copied_early;
3854}
3855#endif /* CONFIG_NET_DMA */
3856
Linus Torvalds1da177e2005-04-16 15:20:36 -07003857/*
3858 * TCP receive function for the ESTABLISHED state.
3859 *
3860 * It is split into a fast path and a slow path. The fast path is
3861 * disabled when:
3862 * - A zero window was announced from us - zero window probing
3863 * is only handled properly in the slow path.
3864 * - Out of order segments arrived.
3865 * - Urgent data is expected.
3866 * - There is no buffer space left
3867 * - Unexpected TCP flags/window values/header lengths are received
3868 * (detected by checking the TCP header against pred_flags)
3869 * - Data is sent in both directions. Fast path only supports pure senders
3870 * or pure receivers (this means either the sequence number or the ack
3871 * value must stay constant)
3872 * - Unexpected TCP option.
3873 *
3874 * When these conditions are not satisfied it drops into a standard
3875 * receive procedure patterned after RFC793 to handle all cases.
3876 * The first three cases are guaranteed by proper pred_flags setting,
3877 * the rest is checked inline. Fast processing is turned on in
3878 * tcp_data_queue when everything is OK.
3879 */
3880int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
3881 struct tcphdr *th, unsigned len)
3882{
3883 struct tcp_sock *tp = tcp_sk(sk);
3884
3885 /*
3886 * Header prediction.
3887 * The code loosely follows the one in the famous
3888 * "30 instruction TCP receive" Van Jacobson mail.
3889 *
3890 * Van's trick is to deposit buffers into socket queue
3891 * on a device interrupt, to call tcp_recv function
3892 * on the receive process context and checksum and copy
3893 * the buffer to user space. smart...
3894 *
3895 * Our current scheme is not silly either but we take the
3896 * extra cost of the net_bh soft interrupt processing...
3897 * We do checksum and copy also but from device to kernel.
3898 */
3899
3900 tp->rx_opt.saw_tstamp = 0;
3901
3902 /* pred_flags is 0xS?10 << 16 + snd_wnd
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08003903 * if header_prediction is to be made
Linus Torvalds1da177e2005-04-16 15:20:36 -07003904 * 'S' will always be tp->tcp_header_len >> 2
3905 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
3906 * turn it off (when there are holes in the receive
3907 * space for instance)
3908 * PSH flag is ignored.
3909 */
3910
3911 if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags &&
3912 TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
3913 int tcp_header_len = tp->tcp_header_len;
3914
3915 /* Timestamp header prediction: tcp_header_len
3916 * is automatically equal to th->doff*4 due to pred_flags
3917 * match.
3918 */
3919
3920 /* Check timestamp */
3921 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) {
Al Viro4f3608b2006-09-27 18:35:09 -07003922 __be32 *ptr = (__be32 *)(th + 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003923
3924 /* No? Slow path! */
Al Viro4f3608b2006-09-27 18:35:09 -07003925 if (*ptr != htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003926 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP))
3927 goto slow_path;
3928
3929 tp->rx_opt.saw_tstamp = 1;
3930 ++ptr;
3931 tp->rx_opt.rcv_tsval = ntohl(*ptr);
3932 ++ptr;
3933 tp->rx_opt.rcv_tsecr = ntohl(*ptr);
3934
3935 /* If PAWS failed, check it more carefully in slow path */
3936 if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0)
3937 goto slow_path;
3938
3939 /* DO NOT update ts_recent here, if checksum fails
3940 * and timestamp was corrupted part, it will result
3941 * in a hung connection since we will drop all
3942 * future packets due to the PAWS test.
3943 */
3944 }
3945
3946 if (len <= tcp_header_len) {
3947 /* Bulk data transfer: sender */
3948 if (len == tcp_header_len) {
3949 /* Predicted packet is in window by definition.
3950 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
3951 * Hence, check seq<=rcv_wup reduces to:
3952 */
3953 if (tcp_header_len ==
3954 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
3955 tp->rcv_nxt == tp->rcv_wup)
3956 tcp_store_ts_recent(tp);
3957
Linus Torvalds1da177e2005-04-16 15:20:36 -07003958 /* We know that such packets are checksummed
3959 * on entry.
3960 */
3961 tcp_ack(sk, skb, 0);
3962 __kfree_skb(skb);
David S. Miller55c97f32005-07-05 15:19:38 -07003963 tcp_data_snd_check(sk, tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003964 return 0;
3965 } else { /* Header too small */
3966 TCP_INC_STATS_BH(TCP_MIB_INERRS);
3967 goto discard;
3968 }
3969 } else {
3970 int eaten = 0;
Chris Leech1a2449a2006-05-23 18:05:53 -07003971 int copied_early = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003972
Chris Leech1a2449a2006-05-23 18:05:53 -07003973 if (tp->copied_seq == tp->rcv_nxt &&
3974 len - tcp_header_len <= tp->ucopy.len) {
3975#ifdef CONFIG_NET_DMA
3976 if (tcp_dma_try_early_copy(sk, skb, tcp_header_len)) {
3977 copied_early = 1;
3978 eaten = 1;
3979 }
3980#endif
3981 if (tp->ucopy.task == current && sock_owned_by_user(sk) && !copied_early) {
3982 __set_current_state(TASK_RUNNING);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003983
Chris Leech1a2449a2006-05-23 18:05:53 -07003984 if (!tcp_copy_to_iovec(sk, skb, tcp_header_len))
3985 eaten = 1;
3986 }
3987 if (eaten) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003988 /* Predicted packet is in window by definition.
3989 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
3990 * Hence, check seq<=rcv_wup reduces to:
3991 */
3992 if (tcp_header_len ==
3993 (sizeof(struct tcphdr) +
3994 TCPOLEN_TSTAMP_ALIGNED) &&
3995 tp->rcv_nxt == tp->rcv_wup)
3996 tcp_store_ts_recent(tp);
3997
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003998 tcp_rcv_rtt_measure_ts(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003999
4000 __skb_pull(skb, tcp_header_len);
4001 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
4002 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004003 }
Chris Leech1a2449a2006-05-23 18:05:53 -07004004 if (copied_early)
4005 tcp_cleanup_rbuf(sk, skb->len);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004006 }
4007 if (!eaten) {
4008 if (tcp_checksum_complete_user(sk, skb))
4009 goto csum_error;
4010
4011 /* Predicted packet is in window by definition.
4012 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4013 * Hence, check seq<=rcv_wup reduces to:
4014 */
4015 if (tcp_header_len ==
4016 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
4017 tp->rcv_nxt == tp->rcv_wup)
4018 tcp_store_ts_recent(tp);
4019
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004020 tcp_rcv_rtt_measure_ts(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004021
4022 if ((int)skb->truesize > sk->sk_forward_alloc)
4023 goto step5;
4024
4025 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS);
4026
4027 /* Bulk data transfer: receiver */
4028 __skb_pull(skb,tcp_header_len);
4029 __skb_queue_tail(&sk->sk_receive_queue, skb);
4030 sk_stream_set_owner_r(skb, sk);
4031 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
4032 }
4033
4034 tcp_event_data_recv(sk, tp, skb);
4035
4036 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) {
4037 /* Well, only one small jumplet in fast path... */
4038 tcp_ack(sk, skb, FLAG_DATA);
David S. Miller55c97f32005-07-05 15:19:38 -07004039 tcp_data_snd_check(sk, tp);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004040 if (!inet_csk_ack_scheduled(sk))
Linus Torvalds1da177e2005-04-16 15:20:36 -07004041 goto no_ack;
4042 }
4043
David S. Miller31432412005-05-23 12:03:06 -07004044 __tcp_ack_snd_check(sk, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004045no_ack:
Chris Leech1a2449a2006-05-23 18:05:53 -07004046#ifdef CONFIG_NET_DMA
4047 if (copied_early)
4048 __skb_queue_tail(&sk->sk_async_wait_queue, skb);
4049 else
4050#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -07004051 if (eaten)
4052 __kfree_skb(skb);
4053 else
4054 sk->sk_data_ready(sk, 0);
4055 return 0;
4056 }
4057 }
4058
4059slow_path:
4060 if (len < (th->doff<<2) || tcp_checksum_complete_user(sk, skb))
4061 goto csum_error;
4062
4063 /*
4064 * RFC1323: H1. Apply PAWS check first.
4065 */
4066 if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004067 tcp_paws_discard(sk, skb)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004068 if (!th->rst) {
4069 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
4070 tcp_send_dupack(sk, skb);
4071 goto discard;
4072 }
4073 /* Resets are accepted even if PAWS failed.
4074
4075 ts_recent update must be made after we are sure
4076 that the packet is in window.
4077 */
4078 }
4079
4080 /*
4081 * Standard slow path.
4082 */
4083
4084 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
4085 /* RFC793, page 37: "In all states except SYN-SENT, all reset
4086 * (RST) segments are validated by checking their SEQ-fields."
4087 * And page 69: "If an incoming segment is not acceptable,
4088 * an acknowledgment should be sent in reply (unless the RST bit
4089 * is set, if so drop the segment and return)".
4090 */
4091 if (!th->rst)
4092 tcp_send_dupack(sk, skb);
4093 goto discard;
4094 }
4095
4096 if(th->rst) {
4097 tcp_reset(sk);
4098 goto discard;
4099 }
4100
4101 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
4102
4103 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4104 TCP_INC_STATS_BH(TCP_MIB_INERRS);
4105 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN);
4106 tcp_reset(sk);
4107 return 1;
4108 }
4109
4110step5:
4111 if(th->ack)
4112 tcp_ack(sk, skb, FLAG_SLOWPATH);
4113
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004114 tcp_rcv_rtt_measure_ts(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004115
4116 /* Process urgent data. */
4117 tcp_urg(sk, skb, th);
4118
4119 /* step 7: process the segment text */
4120 tcp_data_queue(sk, skb);
4121
David S. Miller55c97f32005-07-05 15:19:38 -07004122 tcp_data_snd_check(sk, tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004123 tcp_ack_snd_check(sk);
4124 return 0;
4125
4126csum_error:
4127 TCP_INC_STATS_BH(TCP_MIB_INERRS);
4128
4129discard:
4130 __kfree_skb(skb);
4131 return 0;
4132}
4133
4134static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
4135 struct tcphdr *th, unsigned len)
4136{
4137 struct tcp_sock *tp = tcp_sk(sk);
Arnaldo Carvalho de Melod83d8462005-12-13 23:26:10 -08004138 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004139 int saved_clamp = tp->rx_opt.mss_clamp;
4140
4141 tcp_parse_options(skb, &tp->rx_opt, 0);
4142
4143 if (th->ack) {
4144 /* rfc793:
4145 * "If the state is SYN-SENT then
4146 * first check the ACK bit
4147 * If the ACK bit is set
4148 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
4149 * a reset (unless the RST bit is set, if so drop
4150 * the segment and return)"
4151 *
4152 * We do not send data with SYN, so that RFC-correct
4153 * test reduces to:
4154 */
4155 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt)
4156 goto reset_and_undo;
4157
4158 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
4159 !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp,
4160 tcp_time_stamp)) {
4161 NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED);
4162 goto reset_and_undo;
4163 }
4164
4165 /* Now ACK is acceptable.
4166 *
4167 * "If the RST bit is set
4168 * If the ACK was acceptable then signal the user "error:
4169 * connection reset", drop the segment, enter CLOSED state,
4170 * delete TCB, and return."
4171 */
4172
4173 if (th->rst) {
4174 tcp_reset(sk);
4175 goto discard;
4176 }
4177
4178 /* rfc793:
4179 * "fifth, if neither of the SYN or RST bits is set then
4180 * drop the segment and return."
4181 *
4182 * See note below!
4183 * --ANK(990513)
4184 */
4185 if (!th->syn)
4186 goto discard_and_undo;
4187
4188 /* rfc793:
4189 * "If the SYN bit is on ...
4190 * are acceptable then ...
4191 * (our SYN has been ACKed), change the connection
4192 * state to ESTABLISHED..."
4193 */
4194
4195 TCP_ECN_rcv_synack(tp, th);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004196
4197 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
4198 tcp_ack(sk, skb, FLAG_SLOWPATH);
4199
4200 /* Ok.. it's good. Set up sequence numbers and
4201 * move to established.
4202 */
4203 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
4204 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
4205
4206 /* RFC1323: The window in SYN & SYN/ACK segments is
4207 * never scaled.
4208 */
4209 tp->snd_wnd = ntohs(th->window);
4210 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, TCP_SKB_CB(skb)->seq);
4211
4212 if (!tp->rx_opt.wscale_ok) {
4213 tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0;
4214 tp->window_clamp = min(tp->window_clamp, 65535U);
4215 }
4216
4217 if (tp->rx_opt.saw_tstamp) {
4218 tp->rx_opt.tstamp_ok = 1;
4219 tp->tcp_header_len =
4220 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
4221 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
4222 tcp_store_ts_recent(tp);
4223 } else {
4224 tp->tcp_header_len = sizeof(struct tcphdr);
4225 }
4226
4227 if (tp->rx_opt.sack_ok && sysctl_tcp_fack)
4228 tp->rx_opt.sack_ok |= 2;
4229
John Heffner5d424d52006-03-20 17:53:41 -08004230 tcp_mtup_init(sk);
Arnaldo Carvalho de Melod83d8462005-12-13 23:26:10 -08004231 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004232 tcp_initialize_rcv_mss(sk);
4233
4234 /* Remember, tcp_poll() does not lock socket!
4235 * Change state from SYN-SENT only after copied_seq
4236 * is initialized. */
4237 tp->copied_seq = tp->rcv_nxt;
Ralf Baechlee16aa202006-12-07 00:11:33 -08004238 smp_mb();
Linus Torvalds1da177e2005-04-16 15:20:36 -07004239 tcp_set_state(sk, TCP_ESTABLISHED);
4240
Venkat Yekkirala6b877692006-11-08 17:04:09 -06004241 security_inet_conn_established(sk, skb);
4242
Linus Torvalds1da177e2005-04-16 15:20:36 -07004243 /* Make sure socket is routed, for correct metrics. */
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -08004244 icsk->icsk_af_ops->rebuild_header(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004245
4246 tcp_init_metrics(sk);
4247
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03004248 tcp_init_congestion_control(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -07004249
Linus Torvalds1da177e2005-04-16 15:20:36 -07004250 /* Prevent spurious tcp_cwnd_restart() on first data
4251 * packet.
4252 */
4253 tp->lsndtime = tcp_time_stamp;
4254
4255 tcp_init_buffer_space(sk);
4256
4257 if (sock_flag(sk, SOCK_KEEPOPEN))
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004258 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp));
Linus Torvalds1da177e2005-04-16 15:20:36 -07004259
4260 if (!tp->rx_opt.snd_wscale)
4261 __tcp_fast_path_on(tp, tp->snd_wnd);
4262 else
4263 tp->pred_flags = 0;
4264
4265 if (!sock_flag(sk, SOCK_DEAD)) {
4266 sk->sk_state_change(sk);
4267 sk_wake_async(sk, 0, POLL_OUT);
4268 }
4269
Arnaldo Carvalho de Melo295f7322005-08-09 20:11:56 -07004270 if (sk->sk_write_pending ||
4271 icsk->icsk_accept_queue.rskq_defer_accept ||
4272 icsk->icsk_ack.pingpong) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004273 /* Save one ACK. Data will be ready after
4274 * several ticks, if write_pending is set.
4275 *
4276 * It may be deleted, but with this feature tcpdumps
4277 * look so _wonderfully_ clever, that I was not able
4278 * to stand against the temptation 8) --ANK
4279 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004280 inet_csk_schedule_ack(sk);
Arnaldo Carvalho de Melo295f7322005-08-09 20:11:56 -07004281 icsk->icsk_ack.lrcvtime = tcp_time_stamp;
4282 icsk->icsk_ack.ato = TCP_ATO_MIN;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004283 tcp_incr_quickack(sk);
4284 tcp_enter_quickack_mode(sk);
Arnaldo Carvalho de Melo3f421ba2005-08-09 20:11:08 -07004285 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
4286 TCP_DELACK_MAX, TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004287
4288discard:
4289 __kfree_skb(skb);
4290 return 0;
4291 } else {
4292 tcp_send_ack(sk);
4293 }
4294 return -1;
4295 }
4296
4297 /* No ACK in the segment */
4298
4299 if (th->rst) {
4300 /* rfc793:
4301 * "If the RST bit is set
4302 *
4303 * Otherwise (no ACK) drop the segment and return."
4304 */
4305
4306 goto discard_and_undo;
4307 }
4308
4309 /* PAWS check. */
4310 if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && tcp_paws_check(&tp->rx_opt, 0))
4311 goto discard_and_undo;
4312
4313 if (th->syn) {
4314 /* We see SYN without ACK. It is attempt of
4315 * simultaneous connect with crossed SYNs.
4316 * Particularly, it can be connect to self.
4317 */
4318 tcp_set_state(sk, TCP_SYN_RECV);
4319
4320 if (tp->rx_opt.saw_tstamp) {
4321 tp->rx_opt.tstamp_ok = 1;
4322 tcp_store_ts_recent(tp);
4323 tp->tcp_header_len =
4324 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
4325 } else {
4326 tp->tcp_header_len = sizeof(struct tcphdr);
4327 }
4328
4329 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
4330 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
4331
4332 /* RFC1323: The window in SYN & SYN/ACK segments is
4333 * never scaled.
4334 */
4335 tp->snd_wnd = ntohs(th->window);
4336 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
4337 tp->max_window = tp->snd_wnd;
4338
4339 TCP_ECN_rcv_syn(tp, th);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004340
John Heffner5d424d52006-03-20 17:53:41 -08004341 tcp_mtup_init(sk);
Arnaldo Carvalho de Melod83d8462005-12-13 23:26:10 -08004342 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004343 tcp_initialize_rcv_mss(sk);
4344
4345
4346 tcp_send_synack(sk);
4347#if 0
4348 /* Note, we could accept data and URG from this segment.
4349 * There are no obstacles to make this.
4350 *
4351 * However, if we ignore data in ACKless segments sometimes,
4352 * we have no reasons to accept it sometimes.
4353 * Also, seems the code doing it in step6 of tcp_rcv_state_process
4354 * is not flawless. So, discard packet for sanity.
4355 * Uncomment this return to process the data.
4356 */
4357 return -1;
4358#else
4359 goto discard;
4360#endif
4361 }
4362 /* "fifth, if neither of the SYN or RST bits is set then
4363 * drop the segment and return."
4364 */
4365
4366discard_and_undo:
4367 tcp_clear_options(&tp->rx_opt);
4368 tp->rx_opt.mss_clamp = saved_clamp;
4369 goto discard;
4370
4371reset_and_undo:
4372 tcp_clear_options(&tp->rx_opt);
4373 tp->rx_opt.mss_clamp = saved_clamp;
4374 return 1;
4375}
4376
4377
4378/*
4379 * This function implements the receiving procedure of RFC 793 for
4380 * all states except ESTABLISHED and TIME_WAIT.
4381 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
4382 * address independent.
4383 */
4384
4385int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
4386 struct tcphdr *th, unsigned len)
4387{
4388 struct tcp_sock *tp = tcp_sk(sk);
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -08004389 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004390 int queued = 0;
4391
4392 tp->rx_opt.saw_tstamp = 0;
4393
4394 switch (sk->sk_state) {
4395 case TCP_CLOSE:
4396 goto discard;
4397
4398 case TCP_LISTEN:
4399 if(th->ack)
4400 return 1;
4401
4402 if(th->rst)
4403 goto discard;
4404
4405 if(th->syn) {
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -08004406 if (icsk->icsk_af_ops->conn_request(sk, skb) < 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004407 return 1;
4408
Linus Torvalds1da177e2005-04-16 15:20:36 -07004409 /* Now we have several options: In theory there is
4410 * nothing else in the frame. KA9Q has an option to
4411 * send data with the syn, BSD accepts data with the
4412 * syn up to the [to be] advertised window and
4413 * Solaris 2.1 gives you a protocol error. For now
4414 * we just ignore it, that fits the spec precisely
4415 * and avoids incompatibilities. It would be nice in
4416 * future to drop through and process the data.
4417 *
4418 * Now that TTCP is starting to be used we ought to
4419 * queue this data.
4420 * But, this leaves one open to an easy denial of
4421 * service attack, and SYN cookies can't defend
4422 * against this problem. So, we drop the data
4423 * in the interest of security over speed.
4424 */
4425 goto discard;
4426 }
4427 goto discard;
4428
4429 case TCP_SYN_SENT:
Linus Torvalds1da177e2005-04-16 15:20:36 -07004430 queued = tcp_rcv_synsent_state_process(sk, skb, th, len);
4431 if (queued >= 0)
4432 return queued;
4433
4434 /* Do step6 onward by hand. */
4435 tcp_urg(sk, skb, th);
4436 __kfree_skb(skb);
David S. Miller55c97f32005-07-05 15:19:38 -07004437 tcp_data_snd_check(sk, tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004438 return 0;
4439 }
4440
4441 if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004442 tcp_paws_discard(sk, skb)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004443 if (!th->rst) {
4444 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
4445 tcp_send_dupack(sk, skb);
4446 goto discard;
4447 }
4448 /* Reset is accepted even if it did not pass PAWS. */
4449 }
4450
4451 /* step 1: check sequence number */
4452 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
4453 if (!th->rst)
4454 tcp_send_dupack(sk, skb);
4455 goto discard;
4456 }
4457
4458 /* step 2: check RST bit */
4459 if(th->rst) {
4460 tcp_reset(sk);
4461 goto discard;
4462 }
4463
4464 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
4465
4466 /* step 3: check security and precedence [ignored] */
4467
4468 /* step 4:
4469 *
4470 * Check for a SYN in window.
4471 */
4472 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4473 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN);
4474 tcp_reset(sk);
4475 return 1;
4476 }
4477
4478 /* step 5: check the ACK field */
4479 if (th->ack) {
4480 int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH);
4481
4482 switch(sk->sk_state) {
4483 case TCP_SYN_RECV:
4484 if (acceptable) {
4485 tp->copied_seq = tp->rcv_nxt;
Ralf Baechlee16aa202006-12-07 00:11:33 -08004486 smp_mb();
Linus Torvalds1da177e2005-04-16 15:20:36 -07004487 tcp_set_state(sk, TCP_ESTABLISHED);
4488 sk->sk_state_change(sk);
4489
4490 /* Note, that this wakeup is only for marginal
4491 * crossed SYN case. Passively open sockets
4492 * are not waked up, because sk->sk_sleep ==
4493 * NULL and sk->sk_socket == NULL.
4494 */
4495 if (sk->sk_socket) {
4496 sk_wake_async(sk,0,POLL_OUT);
4497 }
4498
4499 tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
4500 tp->snd_wnd = ntohs(th->window) <<
4501 tp->rx_opt.snd_wscale;
4502 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq,
4503 TCP_SKB_CB(skb)->seq);
4504
4505 /* tcp_ack considers this ACK as duplicate
4506 * and does not calculate rtt.
4507 * Fix it at least with timestamps.
4508 */
4509 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
4510 !tp->srtt)
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08004511 tcp_ack_saw_tstamp(sk, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004512
4513 if (tp->rx_opt.tstamp_ok)
4514 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
4515
4516 /* Make sure socket is routed, for
4517 * correct metrics.
4518 */
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -08004519 icsk->icsk_af_ops->rebuild_header(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004520
4521 tcp_init_metrics(sk);
4522
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03004523 tcp_init_congestion_control(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -07004524
Linus Torvalds1da177e2005-04-16 15:20:36 -07004525 /* Prevent spurious tcp_cwnd_restart() on
4526 * first data packet.
4527 */
4528 tp->lsndtime = tcp_time_stamp;
4529
John Heffner5d424d52006-03-20 17:53:41 -08004530 tcp_mtup_init(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004531 tcp_initialize_rcv_mss(sk);
4532 tcp_init_buffer_space(sk);
4533 tcp_fast_path_on(tp);
4534 } else {
4535 return 1;
4536 }
4537 break;
4538
4539 case TCP_FIN_WAIT1:
4540 if (tp->snd_una == tp->write_seq) {
4541 tcp_set_state(sk, TCP_FIN_WAIT2);
4542 sk->sk_shutdown |= SEND_SHUTDOWN;
4543 dst_confirm(sk->sk_dst_cache);
4544
4545 if (!sock_flag(sk, SOCK_DEAD))
4546 /* Wake up lingering close() */
4547 sk->sk_state_change(sk);
4548 else {
4549 int tmo;
4550
4551 if (tp->linger2 < 0 ||
4552 (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
4553 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) {
4554 tcp_done(sk);
4555 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA);
4556 return 1;
4557 }
4558
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004559 tmo = tcp_fin_time(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004560 if (tmo > TCP_TIMEWAIT_LEN) {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004561 inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004562 } else if (th->fin || sock_owned_by_user(sk)) {
4563 /* Bad case. We could lose such FIN otherwise.
4564 * It is not a big problem, but it looks confusing
4565 * and not so rare event. We still can lose it now,
4566 * if it spins in bh_lock_sock(), but it is really
4567 * marginal case.
4568 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004569 inet_csk_reset_keepalive_timer(sk, tmo);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004570 } else {
4571 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
4572 goto discard;
4573 }
4574 }
4575 }
4576 break;
4577
4578 case TCP_CLOSING:
4579 if (tp->snd_una == tp->write_seq) {
4580 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
4581 goto discard;
4582 }
4583 break;
4584
4585 case TCP_LAST_ACK:
4586 if (tp->snd_una == tp->write_seq) {
4587 tcp_update_metrics(sk);
4588 tcp_done(sk);
4589 goto discard;
4590 }
4591 break;
4592 }
4593 } else
4594 goto discard;
4595
4596 /* step 6: check the URG bit */
4597 tcp_urg(sk, skb, th);
4598
4599 /* step 7: process the segment text */
4600 switch (sk->sk_state) {
4601 case TCP_CLOSE_WAIT:
4602 case TCP_CLOSING:
4603 case TCP_LAST_ACK:
4604 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
4605 break;
4606 case TCP_FIN_WAIT1:
4607 case TCP_FIN_WAIT2:
4608 /* RFC 793 says to queue data in these states,
4609 * RFC 1122 says we MUST send a reset.
4610 * BSD 4.4 also does reset.
4611 */
4612 if (sk->sk_shutdown & RCV_SHUTDOWN) {
4613 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
4614 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
4615 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA);
4616 tcp_reset(sk);
4617 return 1;
4618 }
4619 }
4620 /* Fall through */
4621 case TCP_ESTABLISHED:
4622 tcp_data_queue(sk, skb);
4623 queued = 1;
4624 break;
4625 }
4626
4627 /* tcp_data could move socket to TIME-WAIT */
4628 if (sk->sk_state != TCP_CLOSE) {
David S. Miller55c97f32005-07-05 15:19:38 -07004629 tcp_data_snd_check(sk, tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004630 tcp_ack_snd_check(sk);
4631 }
4632
4633 if (!queued) {
4634discard:
4635 __kfree_skb(skb);
4636 }
4637 return 0;
4638}
4639
4640EXPORT_SYMBOL(sysctl_tcp_ecn);
4641EXPORT_SYMBOL(sysctl_tcp_reordering);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004642EXPORT_SYMBOL(tcp_parse_options);
4643EXPORT_SYMBOL(tcp_rcv_established);
4644EXPORT_SYMBOL(tcp_rcv_state_process);
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08004645EXPORT_SYMBOL(tcp_initialize_rcv_mss);