blob: 7de6184d4bd8d578e49218d330cddb50091db45d [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
66#include <linux/config.h>
67#include <linux/mm.h>
68#include <linux/module.h>
69#include <linux/sysctl.h>
70#include <net/tcp.h>
71#include <net/inet_common.h>
72#include <linux/ipsec.h>
73#include <asm/unaligned.h>
74
75int sysctl_tcp_timestamps = 1;
76int sysctl_tcp_window_scaling = 1;
77int sysctl_tcp_sack = 1;
78int sysctl_tcp_fack = 1;
79int sysctl_tcp_reordering = TCP_FASTRETRANS_THRESH;
80int sysctl_tcp_ecn;
81int sysctl_tcp_dsack = 1;
82int sysctl_tcp_app_win = 31;
83int sysctl_tcp_adv_win_scale = 2;
84
85int sysctl_tcp_stdurg;
86int sysctl_tcp_rfc1337;
87int sysctl_tcp_max_orphans = NR_FILE;
88int sysctl_tcp_frto;
89int sysctl_tcp_nometrics_save;
Linus Torvalds1da177e2005-04-16 15:20:36 -070090
91int sysctl_tcp_moderate_rcvbuf = 1;
Stephen Hemminger9772efb2005-11-10 17:09:53 -080092int sysctl_tcp_abc = 1;
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 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700118static inline 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 */
130 len = 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 }
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700159 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700160 }
161}
162
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700163static void tcp_incr_quickack(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700164{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700165 struct inet_connection_sock *icsk = inet_csk(sk);
166 unsigned quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700167
168 if (quickacks==0)
169 quickacks=2;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700170 if (quickacks > icsk->icsk_ack.quick)
171 icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700172}
173
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700174void tcp_enter_quickack_mode(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700175{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700176 struct inet_connection_sock *icsk = inet_csk(sk);
177 tcp_incr_quickack(sk);
178 icsk->icsk_ack.pingpong = 0;
179 icsk->icsk_ack.ato = TCP_ATO_MIN;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700180}
181
182/* Send ACKs quickly, if "quick" count is not exhausted
183 * and the session is not interactive.
184 */
185
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700186static inline int tcp_in_quickack_mode(const struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700187{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700188 const struct inet_connection_sock *icsk = inet_csk(sk);
189 return icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700190}
191
192/* Buffer size and advertised window tuning.
193 *
194 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
195 */
196
197static void tcp_fixup_sndbuf(struct sock *sk)
198{
199 int sndmem = tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER + 16 +
200 sizeof(struct sk_buff);
201
202 if (sk->sk_sndbuf < 3 * sndmem)
203 sk->sk_sndbuf = min(3 * sndmem, sysctl_tcp_wmem[2]);
204}
205
206/* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
207 *
208 * All tcp_full_space() is split to two parts: "network" buffer, allocated
209 * forward and advertised in receiver window (tp->rcv_wnd) and
210 * "application buffer", required to isolate scheduling/application
211 * latencies from network.
212 * window_clamp is maximal advertised window. It can be less than
213 * tcp_full_space(), in this case tcp_full_space() - window_clamp
214 * is reserved for "application" buffer. The less window_clamp is
215 * the smoother our behaviour from viewpoint of network, but the lower
216 * throughput and the higher sensitivity of the connection to losses. 8)
217 *
218 * rcv_ssthresh is more strict window_clamp used at "slow start"
219 * phase to predict further behaviour of this connection.
220 * It is used for two goals:
221 * - to enforce header prediction at sender, even when application
222 * requires some significant "application buffer". It is check #1.
223 * - to prevent pruning of receive queue because of misprediction
224 * of receiver window. Check #2.
225 *
226 * The scheme does not work when sender sends good segments opening
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800227 * window and then starts to feed us spaghetti. But it should work
Linus Torvalds1da177e2005-04-16 15:20:36 -0700228 * in common situations. Otherwise, we have to rely on queue collapsing.
229 */
230
231/* Slow part of check#2. */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700232static int __tcp_grow_window(const struct sock *sk, struct tcp_sock *tp,
233 const struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700234{
235 /* Optimize this! */
236 int truesize = tcp_win_from_space(skb->truesize)/2;
John Heffner326f36e2005-11-10 17:11:48 -0800237 int window = tcp_win_from_space(sysctl_tcp_rmem[2])/2;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700238
239 while (tp->rcv_ssthresh <= window) {
240 if (truesize <= skb->len)
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700241 return 2 * inet_csk(sk)->icsk_ack.rcv_mss;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700242
243 truesize >>= 1;
244 window >>= 1;
245 }
246 return 0;
247}
248
249static inline void tcp_grow_window(struct sock *sk, struct tcp_sock *tp,
250 struct sk_buff *skb)
251{
252 /* Check #1 */
253 if (tp->rcv_ssthresh < tp->window_clamp &&
254 (int)tp->rcv_ssthresh < tcp_space(sk) &&
255 !tcp_memory_pressure) {
256 int incr;
257
258 /* Check #2. Increase window, if skb with such overhead
259 * will fit to rcvbuf in future.
260 */
261 if (tcp_win_from_space(skb->truesize) <= skb->len)
262 incr = 2*tp->advmss;
263 else
264 incr = __tcp_grow_window(sk, tp, skb);
265
266 if (incr) {
267 tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, tp->window_clamp);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700268 inet_csk(sk)->icsk_ack.quick |= 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700269 }
270 }
271}
272
273/* 3. Tuning rcvbuf, when connection enters established state. */
274
275static void tcp_fixup_rcvbuf(struct sock *sk)
276{
277 struct tcp_sock *tp = tcp_sk(sk);
278 int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff);
279
280 /* Try to select rcvbuf so that 4 mss-sized segments
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800281 * will fit to window and corresponding skbs will fit to our rcvbuf.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700282 * (was 3; 4 is minimum to allow fast retransmit to work.)
283 */
284 while (tcp_win_from_space(rcvmem) < tp->advmss)
285 rcvmem += 128;
286 if (sk->sk_rcvbuf < 4 * rcvmem)
287 sk->sk_rcvbuf = min(4 * rcvmem, sysctl_tcp_rmem[2]);
288}
289
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800290/* 4. Try to fixup all. It is made immediately after connection enters
Linus Torvalds1da177e2005-04-16 15:20:36 -0700291 * established state.
292 */
293static void tcp_init_buffer_space(struct sock *sk)
294{
295 struct tcp_sock *tp = tcp_sk(sk);
296 int maxwin;
297
298 if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK))
299 tcp_fixup_rcvbuf(sk);
300 if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK))
301 tcp_fixup_sndbuf(sk);
302
303 tp->rcvq_space.space = tp->rcv_wnd;
304
305 maxwin = tcp_full_space(sk);
306
307 if (tp->window_clamp >= maxwin) {
308 tp->window_clamp = maxwin;
309
310 if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss)
311 tp->window_clamp = max(maxwin -
312 (maxwin >> sysctl_tcp_app_win),
313 4 * tp->advmss);
314 }
315
316 /* Force reservation of one segment. */
317 if (sysctl_tcp_app_win &&
318 tp->window_clamp > 2 * tp->advmss &&
319 tp->window_clamp + tp->advmss > maxwin)
320 tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss);
321
322 tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp);
323 tp->snd_cwnd_stamp = tcp_time_stamp;
324}
325
Linus Torvalds1da177e2005-04-16 15:20:36 -0700326/* 5. Recalculate window clamp after socket hit its memory bounds. */
327static void tcp_clamp_window(struct sock *sk, struct tcp_sock *tp)
328{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300329 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700330
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300331 icsk->icsk_ack.quick = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700332
John Heffner326f36e2005-11-10 17:11:48 -0800333 if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] &&
334 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) &&
335 !tcp_memory_pressure &&
336 atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) {
337 sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc),
338 sysctl_tcp_rmem[2]);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700339 }
John Heffner326f36e2005-11-10 17:11:48 -0800340 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700341 tp->rcv_ssthresh = min(tp->window_clamp, 2U*tp->advmss);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700342}
343
344/* Receiver "autotuning" code.
345 *
346 * The algorithm for RTT estimation w/o timestamps is based on
347 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
348 * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps>
349 *
350 * More detail on this code can be found at
351 * <http://www.psc.edu/~jheffner/senior_thesis.ps>,
352 * though this reference is out of date. A new paper
353 * is pending.
354 */
355static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep)
356{
357 u32 new_sample = tp->rcv_rtt_est.rtt;
358 long m = sample;
359
360 if (m == 0)
361 m = 1;
362
363 if (new_sample != 0) {
364 /* If we sample in larger samples in the non-timestamp
365 * case, we could grossly overestimate the RTT especially
366 * with chatty applications or bulk transfer apps which
367 * are stalled on filesystem I/O.
368 *
369 * Also, since we are only going for a minimum in the
Stephen Hemminger31f34262005-11-15 15:17:10 -0800370 * non-timestamp case, we do not smooth things out
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800371 * else with timestamps disabled convergence takes too
Linus Torvalds1da177e2005-04-16 15:20:36 -0700372 * long.
373 */
374 if (!win_dep) {
375 m -= (new_sample >> 3);
376 new_sample += m;
377 } else if (m < new_sample)
378 new_sample = m << 3;
379 } else {
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800380 /* No previous measure. */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700381 new_sample = m << 3;
382 }
383
384 if (tp->rcv_rtt_est.rtt != new_sample)
385 tp->rcv_rtt_est.rtt = new_sample;
386}
387
388static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp)
389{
390 if (tp->rcv_rtt_est.time == 0)
391 goto new_measure;
392 if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq))
393 return;
394 tcp_rcv_rtt_update(tp,
395 jiffies - tp->rcv_rtt_est.time,
396 1);
397
398new_measure:
399 tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd;
400 tp->rcv_rtt_est.time = tcp_time_stamp;
401}
402
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700403static inline void tcp_rcv_rtt_measure_ts(struct sock *sk, const struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700404{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700405 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700406 if (tp->rx_opt.rcv_tsecr &&
407 (TCP_SKB_CB(skb)->end_seq -
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700408 TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700409 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0);
410}
411
412/*
413 * This function should be called every time data is copied to user space.
414 * It calculates the appropriate TCP receive buffer space.
415 */
416void tcp_rcv_space_adjust(struct sock *sk)
417{
418 struct tcp_sock *tp = tcp_sk(sk);
419 int time;
420 int space;
421
422 if (tp->rcvq_space.time == 0)
423 goto new_measure;
424
425 time = tcp_time_stamp - tp->rcvq_space.time;
426 if (time < (tp->rcv_rtt_est.rtt >> 3) ||
427 tp->rcv_rtt_est.rtt == 0)
428 return;
429
430 space = 2 * (tp->copied_seq - tp->rcvq_space.seq);
431
432 space = max(tp->rcvq_space.space, space);
433
434 if (tp->rcvq_space.space != space) {
435 int rcvmem;
436
437 tp->rcvq_space.space = space;
438
439 if (sysctl_tcp_moderate_rcvbuf) {
440 int new_clamp = space;
441
442 /* Receive space grows, normalize in order to
443 * take into account packet headers and sk_buff
444 * structure overhead.
445 */
446 space /= tp->advmss;
447 if (!space)
448 space = 1;
449 rcvmem = (tp->advmss + MAX_TCP_HEADER +
450 16 + sizeof(struct sk_buff));
451 while (tcp_win_from_space(rcvmem) < tp->advmss)
452 rcvmem += 128;
453 space *= rcvmem;
454 space = min(space, sysctl_tcp_rmem[2]);
455 if (space > sk->sk_rcvbuf) {
456 sk->sk_rcvbuf = space;
457
458 /* Make the window clamp follow along. */
459 tp->window_clamp = new_clamp;
460 }
461 }
462 }
463
464new_measure:
465 tp->rcvq_space.seq = tp->copied_seq;
466 tp->rcvq_space.time = tcp_time_stamp;
467}
468
469/* There is something which you must keep in mind when you analyze the
470 * behavior of the tp->ato delayed ack timeout interval. When a
471 * connection starts up, we want to ack as quickly as possible. The
472 * problem is that "good" TCP's do slow start at the beginning of data
473 * transmission. The means that until we send the first few ACK's the
474 * sender will sit on his end and only queue most of his data, because
475 * he can only send snd_cwnd unacked packets at any given time. For
476 * each ACK we send, he increments snd_cwnd and transmits more of his
477 * queue. -DaveM
478 */
479static void tcp_event_data_recv(struct sock *sk, struct tcp_sock *tp, struct sk_buff *skb)
480{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700481 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700482 u32 now;
483
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700484 inet_csk_schedule_ack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700485
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700486 tcp_measure_rcv_mss(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700487
488 tcp_rcv_rtt_measure(tp);
489
490 now = tcp_time_stamp;
491
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700492 if (!icsk->icsk_ack.ato) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700493 /* The _first_ data packet received, initialize
494 * delayed ACK engine.
495 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700496 tcp_incr_quickack(sk);
497 icsk->icsk_ack.ato = TCP_ATO_MIN;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700498 } else {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700499 int m = now - icsk->icsk_ack.lrcvtime;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700500
501 if (m <= TCP_ATO_MIN/2) {
502 /* The fastest case is the first. */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700503 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2;
504 } else if (m < icsk->icsk_ack.ato) {
505 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m;
506 if (icsk->icsk_ack.ato > icsk->icsk_rto)
507 icsk->icsk_ack.ato = icsk->icsk_rto;
508 } else if (m > icsk->icsk_rto) {
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800509 /* Too long gap. Apparently sender failed to
Linus Torvalds1da177e2005-04-16 15:20:36 -0700510 * restart window, so that we send ACKs quickly.
511 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700512 tcp_incr_quickack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700513 sk_stream_mem_reclaim(sk);
514 }
515 }
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700516 icsk->icsk_ack.lrcvtime = now;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700517
518 TCP_ECN_check_ce(tp, skb);
519
520 if (skb->len >= 128)
521 tcp_grow_window(sk, tp, skb);
522}
523
Linus Torvalds1da177e2005-04-16 15:20:36 -0700524/* Called to compute a smoothed rtt estimate. The data fed to this
525 * routine either comes from timestamps, or from segments that were
526 * known _not_ to have been retransmitted [see Karn/Partridge
527 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
528 * piece by Van Jacobson.
529 * NOTE: the next three routines used to be one big routine.
530 * To save cycles in the RFC 1323 implementation it was better to break
531 * it up into three procedures. -- erics
532 */
Stephen Hemminger2d2abba2005-11-10 16:56:12 -0800533static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700534{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300535 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700536 long m = mrtt; /* RTT */
537
Linus Torvalds1da177e2005-04-16 15:20:36 -0700538 /* The following amusing code comes from Jacobson's
539 * article in SIGCOMM '88. Note that rtt and mdev
540 * are scaled versions of rtt and mean deviation.
541 * This is designed to be as fast as possible
542 * m stands for "measurement".
543 *
544 * On a 1990 paper the rto value is changed to:
545 * RTO = rtt + 4 * mdev
546 *
547 * Funny. This algorithm seems to be very broken.
548 * These formulae increase RTO, when it should be decreased, increase
Stephen Hemminger31f34262005-11-15 15:17:10 -0800549 * too slowly, when it should be increased quickly, decrease too quickly
Linus Torvalds1da177e2005-04-16 15:20:36 -0700550 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
551 * does not matter how to _calculate_ it. Seems, it was trap
552 * that VJ failed to avoid. 8)
553 */
554 if(m == 0)
555 m = 1;
556 if (tp->srtt != 0) {
557 m -= (tp->srtt >> 3); /* m is now error in rtt est */
558 tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */
559 if (m < 0) {
560 m = -m; /* m is now abs(error) */
561 m -= (tp->mdev >> 2); /* similar update on mdev */
562 /* This is similar to one of Eifel findings.
563 * Eifel blocks mdev updates when rtt decreases.
564 * This solution is a bit different: we use finer gain
565 * for mdev in this case (alpha*beta).
566 * Like Eifel it also prevents growth of rto,
567 * but also it limits too fast rto decreases,
568 * happening in pure Eifel.
569 */
570 if (m > 0)
571 m >>= 3;
572 } else {
573 m -= (tp->mdev >> 2); /* similar update on mdev */
574 }
575 tp->mdev += m; /* mdev = 3/4 mdev + 1/4 new */
576 if (tp->mdev > tp->mdev_max) {
577 tp->mdev_max = tp->mdev;
578 if (tp->mdev_max > tp->rttvar)
579 tp->rttvar = tp->mdev_max;
580 }
581 if (after(tp->snd_una, tp->rtt_seq)) {
582 if (tp->mdev_max < tp->rttvar)
583 tp->rttvar -= (tp->rttvar-tp->mdev_max)>>2;
584 tp->rtt_seq = tp->snd_nxt;
585 tp->mdev_max = TCP_RTO_MIN;
586 }
587 } else {
588 /* no previous measure. */
589 tp->srtt = m<<3; /* take the measured time to be rtt */
590 tp->mdev = m<<1; /* make sure rto = 3*rtt */
591 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
592 tp->rtt_seq = tp->snd_nxt;
593 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700594}
595
596/* Calculate rto without backoff. This is the second half of Van Jacobson's
597 * routine referred to above.
598 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700599static inline void tcp_set_rto(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700600{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700601 const struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700602 /* Old crap is replaced with new one. 8)
603 *
604 * More seriously:
605 * 1. If rtt variance happened to be less 50msec, it is hallucination.
606 * It cannot be less due to utterly erratic ACK generation made
607 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
608 * to do with delayed acks, because at cwnd>2 true delack timeout
609 * is invisible. Actually, Linux-2.4 also generates erratic
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800610 * ACKs in some circumstances.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700611 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700612 inet_csk(sk)->icsk_rto = (tp->srtt >> 3) + tp->rttvar;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700613
614 /* 2. Fixups made earlier cannot be right.
615 * If we do not estimate RTO correctly without them,
616 * all the algo is pure shit and should be replaced
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800617 * with correct one. It is exactly, which we pretend to do.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700618 */
619}
620
621/* NOTE: clamping at TCP_RTO_MIN is not required, current algo
622 * guarantees that rto is higher.
623 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700624static inline void tcp_bound_rto(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700625{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700626 if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
627 inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700628}
629
630/* Save metrics learned by this TCP session.
631 This function is called only, when TCP finishes successfully
632 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
633 */
634void tcp_update_metrics(struct sock *sk)
635{
636 struct tcp_sock *tp = tcp_sk(sk);
637 struct dst_entry *dst = __sk_dst_get(sk);
638
639 if (sysctl_tcp_nometrics_save)
640 return;
641
642 dst_confirm(dst);
643
644 if (dst && (dst->flags&DST_HOST)) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300645 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700646 int m;
647
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300648 if (icsk->icsk_backoff || !tp->srtt) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700649 /* This session failed to estimate rtt. Why?
650 * Probably, no packets returned in time.
651 * Reset our results.
652 */
653 if (!(dst_metric_locked(dst, RTAX_RTT)))
654 dst->metrics[RTAX_RTT-1] = 0;
655 return;
656 }
657
658 m = dst_metric(dst, RTAX_RTT) - tp->srtt;
659
660 /* If newly calculated rtt larger than stored one,
661 * store new one. Otherwise, use EWMA. Remember,
662 * rtt overestimation is always better than underestimation.
663 */
664 if (!(dst_metric_locked(dst, RTAX_RTT))) {
665 if (m <= 0)
666 dst->metrics[RTAX_RTT-1] = tp->srtt;
667 else
668 dst->metrics[RTAX_RTT-1] -= (m>>3);
669 }
670
671 if (!(dst_metric_locked(dst, RTAX_RTTVAR))) {
672 if (m < 0)
673 m = -m;
674
675 /* Scale deviation to rttvar fixed point */
676 m >>= 1;
677 if (m < tp->mdev)
678 m = tp->mdev;
679
680 if (m >= dst_metric(dst, RTAX_RTTVAR))
681 dst->metrics[RTAX_RTTVAR-1] = m;
682 else
683 dst->metrics[RTAX_RTTVAR-1] -=
684 (dst->metrics[RTAX_RTTVAR-1] - m)>>2;
685 }
686
687 if (tp->snd_ssthresh >= 0xFFFF) {
688 /* Slow start still did not finish. */
689 if (dst_metric(dst, RTAX_SSTHRESH) &&
690 !dst_metric_locked(dst, RTAX_SSTHRESH) &&
691 (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH))
692 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1;
693 if (!dst_metric_locked(dst, RTAX_CWND) &&
694 tp->snd_cwnd > dst_metric(dst, RTAX_CWND))
695 dst->metrics[RTAX_CWND-1] = tp->snd_cwnd;
696 } else if (tp->snd_cwnd > tp->snd_ssthresh &&
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300697 icsk->icsk_ca_state == TCP_CA_Open) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700698 /* Cong. avoidance phase, cwnd is reliable. */
699 if (!dst_metric_locked(dst, RTAX_SSTHRESH))
700 dst->metrics[RTAX_SSTHRESH-1] =
701 max(tp->snd_cwnd >> 1, tp->snd_ssthresh);
702 if (!dst_metric_locked(dst, RTAX_CWND))
703 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_cwnd) >> 1;
704 } else {
705 /* Else slow start did not finish, cwnd is non-sense,
706 ssthresh may be also invalid.
707 */
708 if (!dst_metric_locked(dst, RTAX_CWND))
709 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_ssthresh) >> 1;
710 if (dst->metrics[RTAX_SSTHRESH-1] &&
711 !dst_metric_locked(dst, RTAX_SSTHRESH) &&
712 tp->snd_ssthresh > dst->metrics[RTAX_SSTHRESH-1])
713 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh;
714 }
715
716 if (!dst_metric_locked(dst, RTAX_REORDERING)) {
717 if (dst->metrics[RTAX_REORDERING-1] < tp->reordering &&
718 tp->reordering != sysctl_tcp_reordering)
719 dst->metrics[RTAX_REORDERING-1] = tp->reordering;
720 }
721 }
722}
723
724/* Numbers are taken from RFC2414. */
725__u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst)
726{
727 __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0);
728
729 if (!cwnd) {
David S. Millerc1b4a7e2005-07-05 15:24:38 -0700730 if (tp->mss_cache > 1460)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700731 cwnd = 2;
732 else
David S. Millerc1b4a7e2005-07-05 15:24:38 -0700733 cwnd = (tp->mss_cache > 1095) ? 3 : 4;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700734 }
735 return min_t(__u32, cwnd, tp->snd_cwnd_clamp);
736}
737
738/* Initialize metrics on socket. */
739
740static void tcp_init_metrics(struct sock *sk)
741{
742 struct tcp_sock *tp = tcp_sk(sk);
743 struct dst_entry *dst = __sk_dst_get(sk);
744
745 if (dst == NULL)
746 goto reset;
747
748 dst_confirm(dst);
749
750 if (dst_metric_locked(dst, RTAX_CWND))
751 tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND);
752 if (dst_metric(dst, RTAX_SSTHRESH)) {
753 tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH);
754 if (tp->snd_ssthresh > tp->snd_cwnd_clamp)
755 tp->snd_ssthresh = tp->snd_cwnd_clamp;
756 }
757 if (dst_metric(dst, RTAX_REORDERING) &&
758 tp->reordering != dst_metric(dst, RTAX_REORDERING)) {
759 tp->rx_opt.sack_ok &= ~2;
760 tp->reordering = dst_metric(dst, RTAX_REORDERING);
761 }
762
763 if (dst_metric(dst, RTAX_RTT) == 0)
764 goto reset;
765
766 if (!tp->srtt && dst_metric(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3))
767 goto reset;
768
769 /* Initial rtt is determined from SYN,SYN-ACK.
770 * The segment is small and rtt may appear much
771 * less than real one. Use per-dst memory
772 * to make it more realistic.
773 *
774 * A bit of theory. RTT is time passed after "normal" sized packet
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800775 * is sent until it is ACKed. In normal circumstances sending small
Linus Torvalds1da177e2005-04-16 15:20:36 -0700776 * packets force peer to delay ACKs and calculation is correct too.
777 * The algorithm is adaptive and, provided we follow specs, it
778 * NEVER underestimate RTT. BUT! If peer tries to make some clever
779 * tricks sort of "quick acks" for time long enough to decrease RTT
780 * to low value, and then abruptly stops to do it and starts to delay
781 * ACKs, wait for troubles.
782 */
783 if (dst_metric(dst, RTAX_RTT) > tp->srtt) {
784 tp->srtt = dst_metric(dst, RTAX_RTT);
785 tp->rtt_seq = tp->snd_nxt;
786 }
787 if (dst_metric(dst, RTAX_RTTVAR) > tp->mdev) {
788 tp->mdev = dst_metric(dst, RTAX_RTTVAR);
789 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
790 }
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700791 tcp_set_rto(sk);
792 tcp_bound_rto(sk);
793 if (inet_csk(sk)->icsk_rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700794 goto reset;
795 tp->snd_cwnd = tcp_init_cwnd(tp, dst);
796 tp->snd_cwnd_stamp = tcp_time_stamp;
797 return;
798
799reset:
800 /* Play conservative. If timestamps are not
801 * supported, TCP will fail to recalculate correct
802 * rtt, if initial rto is too small. FORGET ALL AND RESET!
803 */
804 if (!tp->rx_opt.saw_tstamp && tp->srtt) {
805 tp->srtt = 0;
806 tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700807 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700808 }
809}
810
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300811static void tcp_update_reordering(struct sock *sk, const int metric,
812 const int ts)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700813{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300814 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700815 if (metric > tp->reordering) {
816 tp->reordering = min(TCP_MAX_REORDERING, metric);
817
818 /* This exciting event is worth to be remembered. 8) */
819 if (ts)
820 NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER);
821 else if (IsReno(tp))
822 NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER);
823 else if (IsFack(tp))
824 NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER);
825 else
826 NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER);
827#if FASTRETRANS_DEBUG > 1
828 printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n",
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300829 tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700830 tp->reordering,
831 tp->fackets_out,
832 tp->sacked_out,
833 tp->undo_marker ? tp->undo_retrans : 0);
834#endif
835 /* Disable FACK yet. */
836 tp->rx_opt.sack_ok &= ~2;
837 }
838}
839
840/* This procedure tags the retransmission queue when SACKs arrive.
841 *
842 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
843 * Packets in queue with these bits set are counted in variables
844 * sacked_out, retrans_out and lost_out, correspondingly.
845 *
846 * Valid combinations are:
847 * Tag InFlight Description
848 * 0 1 - orig segment is in flight.
849 * S 0 - nothing flies, orig reached receiver.
850 * L 0 - nothing flies, orig lost by net.
851 * R 2 - both orig and retransmit are in flight.
852 * L|R 1 - orig is lost, retransmit is in flight.
853 * S|R 1 - orig reached receiver, retrans is still in flight.
854 * (L|S|R is logically valid, it could occur when L|R is sacked,
855 * but it is equivalent to plain S and code short-curcuits it to S.
856 * L|S is logically invalid, it would mean -1 packet in flight 8))
857 *
858 * These 6 states form finite state machine, controlled by the following events:
859 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
860 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
861 * 3. Loss detection event of one of three flavors:
862 * A. Scoreboard estimator decided the packet is lost.
863 * A'. Reno "three dupacks" marks head of queue lost.
864 * A''. Its FACK modfication, head until snd.fack is lost.
865 * B. SACK arrives sacking data transmitted after never retransmitted
866 * hole was sent out.
867 * C. SACK arrives sacking SND.NXT at the moment, when the
868 * segment was retransmitted.
869 * 4. D-SACK added new rule: D-SACK changes any tag to S.
870 *
871 * It is pleasant to note, that state diagram turns out to be commutative,
872 * so that we are allowed not to be bothered by order of our actions,
873 * when multiple events arrive simultaneously. (see the function below).
874 *
875 * Reordering detection.
876 * --------------------
877 * Reordering metric is maximal distance, which a packet can be displaced
878 * in packet stream. With SACKs we can estimate it:
879 *
880 * 1. SACK fills old hole and the corresponding segment was not
881 * ever retransmitted -> reordering. Alas, we cannot use it
882 * when segment was retransmitted.
883 * 2. The last flaw is solved with D-SACK. D-SACK arrives
884 * for retransmitted and already SACKed segment -> reordering..
885 * Both of these heuristics are not used in Loss state, when we cannot
886 * account for retransmits accurately.
887 */
888static int
889tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_una)
890{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300891 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700892 struct tcp_sock *tp = tcp_sk(sk);
893 unsigned char *ptr = ack_skb->h.raw + TCP_SKB_CB(ack_skb)->sacked;
894 struct tcp_sack_block *sp = (struct tcp_sack_block *)(ptr+2);
895 int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3;
896 int reord = tp->packets_out;
897 int prior_fackets;
898 u32 lost_retrans = 0;
899 int flag = 0;
Stephen Hemminger6a438bb2005-11-10 17:14:59 -0800900 int dup_sack = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700901 int i;
902
Linus Torvalds1da177e2005-04-16 15:20:36 -0700903 if (!tp->sacked_out)
904 tp->fackets_out = 0;
905 prior_fackets = tp->fackets_out;
906
Stephen Hemminger6a438bb2005-11-10 17:14:59 -0800907 /* SACK fastpath:
908 * if the only SACK change is the increase of the end_seq of
909 * the first block then only apply that SACK block
910 * and use retrans queue hinting otherwise slowpath */
911 flag = 1;
912 for (i = 0; i< num_sacks; i++) {
913 __u32 start_seq = ntohl(sp[i].start_seq);
914 __u32 end_seq = ntohl(sp[i].end_seq);
915
916 if (i == 0){
917 if (tp->recv_sack_cache[i].start_seq != start_seq)
918 flag = 0;
919 } else {
920 if ((tp->recv_sack_cache[i].start_seq != start_seq) ||
921 (tp->recv_sack_cache[i].end_seq != end_seq))
922 flag = 0;
923 }
924 tp->recv_sack_cache[i].start_seq = start_seq;
925 tp->recv_sack_cache[i].end_seq = end_seq;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700926
927 /* Check for D-SACK. */
928 if (i == 0) {
929 u32 ack = TCP_SKB_CB(ack_skb)->ack_seq;
930
931 if (before(start_seq, ack)) {
932 dup_sack = 1;
933 tp->rx_opt.sack_ok |= 4;
934 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV);
935 } else if (num_sacks > 1 &&
936 !after(end_seq, ntohl(sp[1].end_seq)) &&
937 !before(start_seq, ntohl(sp[1].start_seq))) {
938 dup_sack = 1;
939 tp->rx_opt.sack_ok |= 4;
940 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV);
941 }
942
943 /* D-SACK for already forgotten data...
944 * Do dumb counting. */
945 if (dup_sack &&
946 !after(end_seq, prior_snd_una) &&
947 after(end_seq, tp->undo_marker))
948 tp->undo_retrans--;
949
950 /* Eliminate too old ACKs, but take into
951 * account more or less fresh ones, they can
952 * contain valid SACK info.
953 */
954 if (before(ack, prior_snd_una - tp->max_window))
955 return 0;
956 }
Stephen Hemminger6a438bb2005-11-10 17:14:59 -0800957 }
958
959 if (flag)
960 num_sacks = 1;
961 else {
962 int j;
963 tp->fastpath_skb_hint = NULL;
964
965 /* order SACK blocks to allow in order walk of the retrans queue */
966 for (i = num_sacks-1; i > 0; i--) {
967 for (j = 0; j < i; j++){
968 if (after(ntohl(sp[j].start_seq),
969 ntohl(sp[j+1].start_seq))){
970 sp[j].start_seq = htonl(tp->recv_sack_cache[j+1].start_seq);
971 sp[j].end_seq = htonl(tp->recv_sack_cache[j+1].end_seq);
972 sp[j+1].start_seq = htonl(tp->recv_sack_cache[j].start_seq);
973 sp[j+1].end_seq = htonl(tp->recv_sack_cache[j].end_seq);
974 }
975
976 }
977 }
978 }
979
980 /* clear flag as used for different purpose in following code */
981 flag = 0;
982
983 for (i=0; i<num_sacks; i++, sp++) {
984 struct sk_buff *skb;
985 __u32 start_seq = ntohl(sp->start_seq);
986 __u32 end_seq = ntohl(sp->end_seq);
987 int fack_count;
988
989 /* Use SACK fastpath hint if valid */
990 if (tp->fastpath_skb_hint) {
991 skb = tp->fastpath_skb_hint;
992 fack_count = tp->fastpath_cnt_hint;
993 } else {
994 skb = sk->sk_write_queue.next;
995 fack_count = 0;
996 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700997
998 /* Event "B" in the comment above. */
999 if (after(end_seq, tp->high_seq))
1000 flag |= FLAG_DATA_LOST;
1001
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001002 sk_stream_for_retrans_queue_from(skb, sk) {
David S. Miller6475be12005-09-01 22:47:01 -07001003 int in_sack, pcount;
1004 u8 sacked;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001005
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001006 tp->fastpath_skb_hint = skb;
1007 tp->fastpath_cnt_hint = fack_count;
1008
Linus Torvalds1da177e2005-04-16 15:20:36 -07001009 /* The retransmission queue is always in order, so
1010 * we can short-circuit the walk early.
1011 */
David S. Miller6475be12005-09-01 22:47:01 -07001012 if (!before(TCP_SKB_CB(skb)->seq, end_seq))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001013 break;
1014
Herbert Xu3c05d922005-09-14 20:50:35 -07001015 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
1016 !before(end_seq, TCP_SKB_CB(skb)->end_seq);
1017
David S. Miller6475be12005-09-01 22:47:01 -07001018 pcount = tcp_skb_pcount(skb);
1019
Herbert Xu3c05d922005-09-14 20:50:35 -07001020 if (pcount > 1 && !in_sack &&
1021 after(TCP_SKB_CB(skb)->end_seq, start_seq)) {
David S. Miller6475be12005-09-01 22:47:01 -07001022 unsigned int pkt_len;
1023
Herbert Xu3c05d922005-09-14 20:50:35 -07001024 in_sack = !after(start_seq,
1025 TCP_SKB_CB(skb)->seq);
1026
1027 if (!in_sack)
David S. Miller6475be12005-09-01 22:47:01 -07001028 pkt_len = (start_seq -
1029 TCP_SKB_CB(skb)->seq);
1030 else
1031 pkt_len = (end_seq -
1032 TCP_SKB_CB(skb)->seq);
1033 if (tcp_fragment(sk, skb, pkt_len, skb_shinfo(skb)->tso_size))
1034 break;
1035 pcount = tcp_skb_pcount(skb);
1036 }
1037
1038 fack_count += pcount;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001039
David S. Miller6475be12005-09-01 22:47:01 -07001040 sacked = TCP_SKB_CB(skb)->sacked;
1041
Linus Torvalds1da177e2005-04-16 15:20:36 -07001042 /* Account D-SACK for retransmitted packet. */
1043 if ((dup_sack && in_sack) &&
1044 (sacked & TCPCB_RETRANS) &&
1045 after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
1046 tp->undo_retrans--;
1047
1048 /* The frame is ACKed. */
1049 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) {
1050 if (sacked&TCPCB_RETRANS) {
1051 if ((dup_sack && in_sack) &&
1052 (sacked&TCPCB_SACKED_ACKED))
1053 reord = min(fack_count, reord);
1054 } else {
1055 /* If it was in a hole, we detected reordering. */
1056 if (fack_count < prior_fackets &&
1057 !(sacked&TCPCB_SACKED_ACKED))
1058 reord = min(fack_count, reord);
1059 }
1060
1061 /* Nothing to do; acked frame is about to be dropped. */
1062 continue;
1063 }
1064
1065 if ((sacked&TCPCB_SACKED_RETRANS) &&
1066 after(end_seq, TCP_SKB_CB(skb)->ack_seq) &&
1067 (!lost_retrans || after(end_seq, lost_retrans)))
1068 lost_retrans = end_seq;
1069
1070 if (!in_sack)
1071 continue;
1072
1073 if (!(sacked&TCPCB_SACKED_ACKED)) {
1074 if (sacked & TCPCB_SACKED_RETRANS) {
1075 /* If the segment is not tagged as lost,
1076 * we do not clear RETRANS, believing
1077 * that retransmission is still in flight.
1078 */
1079 if (sacked & TCPCB_LOST) {
1080 TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
1081 tp->lost_out -= tcp_skb_pcount(skb);
1082 tp->retrans_out -= tcp_skb_pcount(skb);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001083
1084 /* clear lost hint */
1085 tp->retransmit_skb_hint = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001086 }
1087 } else {
1088 /* New sack for not retransmitted frame,
1089 * which was in hole. It is reordering.
1090 */
1091 if (!(sacked & TCPCB_RETRANS) &&
1092 fack_count < prior_fackets)
1093 reord = min(fack_count, reord);
1094
1095 if (sacked & TCPCB_LOST) {
1096 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1097 tp->lost_out -= tcp_skb_pcount(skb);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001098
1099 /* clear lost hint */
1100 tp->retransmit_skb_hint = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001101 }
1102 }
1103
1104 TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED;
1105 flag |= FLAG_DATA_SACKED;
1106 tp->sacked_out += tcp_skb_pcount(skb);
1107
1108 if (fack_count > tp->fackets_out)
1109 tp->fackets_out = fack_count;
1110 } else {
1111 if (dup_sack && (sacked&TCPCB_RETRANS))
1112 reord = min(fack_count, reord);
1113 }
1114
1115 /* D-SACK. We can detect redundant retransmission
1116 * in S|R and plain R frames and clear it.
1117 * undo_retrans is decreased above, L|R frames
1118 * are accounted above as well.
1119 */
1120 if (dup_sack &&
1121 (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS)) {
1122 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1123 tp->retrans_out -= tcp_skb_pcount(skb);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001124 tp->retransmit_skb_hint = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001125 }
1126 }
1127 }
1128
1129 /* Check for lost retransmit. This superb idea is
1130 * borrowed from "ratehalving". Event "C".
1131 * Later note: FACK people cheated me again 8),
1132 * we have to account for reordering! Ugly,
1133 * but should help.
1134 */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001135 if (lost_retrans && icsk->icsk_ca_state == TCP_CA_Recovery) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001136 struct sk_buff *skb;
1137
1138 sk_stream_for_retrans_queue(skb, sk) {
1139 if (after(TCP_SKB_CB(skb)->seq, lost_retrans))
1140 break;
1141 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
1142 continue;
1143 if ((TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) &&
1144 after(lost_retrans, TCP_SKB_CB(skb)->ack_seq) &&
1145 (IsFack(tp) ||
1146 !before(lost_retrans,
1147 TCP_SKB_CB(skb)->ack_seq + tp->reordering *
David S. Millerc1b4a7e2005-07-05 15:24:38 -07001148 tp->mss_cache))) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001149 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1150 tp->retrans_out -= tcp_skb_pcount(skb);
1151
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001152 /* clear lost hint */
1153 tp->retransmit_skb_hint = NULL;
1154
Linus Torvalds1da177e2005-04-16 15:20:36 -07001155 if (!(TCP_SKB_CB(skb)->sacked&(TCPCB_LOST|TCPCB_SACKED_ACKED))) {
1156 tp->lost_out += tcp_skb_pcount(skb);
1157 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1158 flag |= FLAG_DATA_SACKED;
1159 NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT);
1160 }
1161 }
1162 }
1163 }
1164
1165 tp->left_out = tp->sacked_out + tp->lost_out;
1166
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001167 if ((reord < tp->fackets_out) && icsk->icsk_ca_state != TCP_CA_Loss)
1168 tcp_update_reordering(sk, ((tp->fackets_out + 1) - reord), 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001169
1170#if FASTRETRANS_DEBUG > 0
1171 BUG_TRAP((int)tp->sacked_out >= 0);
1172 BUG_TRAP((int)tp->lost_out >= 0);
1173 BUG_TRAP((int)tp->retrans_out >= 0);
1174 BUG_TRAP((int)tcp_packets_in_flight(tp) >= 0);
1175#endif
1176 return flag;
1177}
1178
1179/* RTO occurred, but do not yet enter loss state. Instead, transmit two new
1180 * segments to see from the next ACKs whether any data was really missing.
1181 * If the RTO was spurious, new ACKs should arrive.
1182 */
1183void tcp_enter_frto(struct sock *sk)
1184{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001185 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001186 struct tcp_sock *tp = tcp_sk(sk);
1187 struct sk_buff *skb;
1188
1189 tp->frto_counter = 1;
1190
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001191 if (icsk->icsk_ca_state <= TCP_CA_Disorder ||
Linus Torvalds1da177e2005-04-16 15:20:36 -07001192 tp->snd_una == tp->high_seq ||
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001193 (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
1194 tp->prior_ssthresh = tcp_current_ssthresh(sk);
1195 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
1196 tcp_ca_event(sk, CA_EVENT_FRTO);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001197 }
1198
1199 /* Have to clear retransmission markers here to keep the bookkeeping
1200 * in shape, even though we are not yet in Loss state.
1201 * If something was really lost, it is eventually caught up
1202 * in tcp_enter_frto_loss.
1203 */
1204 tp->retrans_out = 0;
1205 tp->undo_marker = tp->snd_una;
1206 tp->undo_retrans = 0;
1207
1208 sk_stream_for_retrans_queue(skb, sk) {
1209 TCP_SKB_CB(skb)->sacked &= ~TCPCB_RETRANS;
1210 }
1211 tcp_sync_left_out(tp);
1212
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001213 tcp_set_ca_state(sk, TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001214 tp->frto_highmark = tp->snd_nxt;
1215}
1216
1217/* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
1218 * which indicates that we should follow the traditional RTO recovery,
1219 * i.e. mark everything lost and do go-back-N retransmission.
1220 */
1221static void tcp_enter_frto_loss(struct sock *sk)
1222{
1223 struct tcp_sock *tp = tcp_sk(sk);
1224 struct sk_buff *skb;
1225 int cnt = 0;
1226
1227 tp->sacked_out = 0;
1228 tp->lost_out = 0;
1229 tp->fackets_out = 0;
1230
1231 sk_stream_for_retrans_queue(skb, sk) {
1232 cnt += tcp_skb_pcount(skb);
1233 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1234 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) {
1235
1236 /* Do not mark those segments lost that were
1237 * forward transmitted after RTO
1238 */
1239 if (!after(TCP_SKB_CB(skb)->end_seq,
1240 tp->frto_highmark)) {
1241 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1242 tp->lost_out += tcp_skb_pcount(skb);
1243 }
1244 } else {
1245 tp->sacked_out += tcp_skb_pcount(skb);
1246 tp->fackets_out = cnt;
1247 }
1248 }
1249 tcp_sync_left_out(tp);
1250
1251 tp->snd_cwnd = tp->frto_counter + tcp_packets_in_flight(tp)+1;
1252 tp->snd_cwnd_cnt = 0;
1253 tp->snd_cwnd_stamp = tcp_time_stamp;
1254 tp->undo_marker = 0;
1255 tp->frto_counter = 0;
1256
1257 tp->reordering = min_t(unsigned int, tp->reordering,
1258 sysctl_tcp_reordering);
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001259 tcp_set_ca_state(sk, TCP_CA_Loss);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001260 tp->high_seq = tp->frto_highmark;
1261 TCP_ECN_queue_cwr(tp);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001262
1263 clear_all_retrans_hints(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001264}
1265
1266void tcp_clear_retrans(struct tcp_sock *tp)
1267{
1268 tp->left_out = 0;
1269 tp->retrans_out = 0;
1270
1271 tp->fackets_out = 0;
1272 tp->sacked_out = 0;
1273 tp->lost_out = 0;
1274
1275 tp->undo_marker = 0;
1276 tp->undo_retrans = 0;
1277}
1278
1279/* Enter Loss state. If "how" is not zero, forget all SACK information
1280 * and reset tags completely, otherwise preserve SACKs. If receiver
1281 * dropped its ofo queue, we will know this due to reneging detection.
1282 */
1283void tcp_enter_loss(struct sock *sk, int how)
1284{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001285 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001286 struct tcp_sock *tp = tcp_sk(sk);
1287 struct sk_buff *skb;
1288 int cnt = 0;
1289
1290 /* Reduce ssthresh if it has not yet been made inside this window. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001291 if (icsk->icsk_ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq ||
1292 (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
1293 tp->prior_ssthresh = tcp_current_ssthresh(sk);
1294 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
1295 tcp_ca_event(sk, CA_EVENT_LOSS);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001296 }
1297 tp->snd_cwnd = 1;
1298 tp->snd_cwnd_cnt = 0;
1299 tp->snd_cwnd_stamp = tcp_time_stamp;
1300
Stephen Hemminger9772efb2005-11-10 17:09:53 -08001301 tp->bytes_acked = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001302 tcp_clear_retrans(tp);
1303
1304 /* Push undo marker, if it was plain RTO and nothing
1305 * was retransmitted. */
1306 if (!how)
1307 tp->undo_marker = tp->snd_una;
1308
1309 sk_stream_for_retrans_queue(skb, sk) {
1310 cnt += tcp_skb_pcount(skb);
1311 if (TCP_SKB_CB(skb)->sacked&TCPCB_RETRANS)
1312 tp->undo_marker = 0;
1313 TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED;
1314 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) {
1315 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
1316 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1317 tp->lost_out += tcp_skb_pcount(skb);
1318 } else {
1319 tp->sacked_out += tcp_skb_pcount(skb);
1320 tp->fackets_out = cnt;
1321 }
1322 }
1323 tcp_sync_left_out(tp);
1324
1325 tp->reordering = min_t(unsigned int, tp->reordering,
1326 sysctl_tcp_reordering);
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001327 tcp_set_ca_state(sk, TCP_CA_Loss);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001328 tp->high_seq = tp->snd_nxt;
1329 TCP_ECN_queue_cwr(tp);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001330
1331 clear_all_retrans_hints(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001332}
1333
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001334static int tcp_check_sack_reneging(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001335{
1336 struct sk_buff *skb;
1337
1338 /* If ACK arrived pointing to a remembered SACK,
1339 * it means that our remembered SACKs do not reflect
1340 * real state of receiver i.e.
1341 * receiver _host_ is heavily congested (or buggy).
1342 * Do processing similar to RTO timeout.
1343 */
1344 if ((skb = skb_peek(&sk->sk_write_queue)) != NULL &&
1345 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001346 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001347 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING);
1348
1349 tcp_enter_loss(sk, 1);
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001350 icsk->icsk_retransmits++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001351 tcp_retransmit_skb(sk, skb_peek(&sk->sk_write_queue));
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001352 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001353 icsk->icsk_rto, TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001354 return 1;
1355 }
1356 return 0;
1357}
1358
1359static inline int tcp_fackets_out(struct tcp_sock *tp)
1360{
1361 return IsReno(tp) ? tp->sacked_out+1 : tp->fackets_out;
1362}
1363
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001364static inline int tcp_skb_timedout(struct sock *sk, struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001365{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001366 return (tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001367}
1368
1369static inline int tcp_head_timedout(struct sock *sk, struct tcp_sock *tp)
1370{
1371 return tp->packets_out &&
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001372 tcp_skb_timedout(sk, skb_peek(&sk->sk_write_queue));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001373}
1374
1375/* Linux NewReno/SACK/FACK/ECN state machine.
1376 * --------------------------------------
1377 *
1378 * "Open" Normal state, no dubious events, fast path.
1379 * "Disorder" In all the respects it is "Open",
1380 * but requires a bit more attention. It is entered when
1381 * we see some SACKs or dupacks. It is split of "Open"
1382 * mainly to move some processing from fast path to slow one.
1383 * "CWR" CWND was reduced due to some Congestion Notification event.
1384 * It can be ECN, ICMP source quench, local device congestion.
1385 * "Recovery" CWND was reduced, we are fast-retransmitting.
1386 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
1387 *
1388 * tcp_fastretrans_alert() is entered:
1389 * - each incoming ACK, if state is not "Open"
1390 * - when arrived ACK is unusual, namely:
1391 * * SACK
1392 * * Duplicate ACK.
1393 * * ECN ECE.
1394 *
1395 * Counting packets in flight is pretty simple.
1396 *
1397 * in_flight = packets_out - left_out + retrans_out
1398 *
1399 * packets_out is SND.NXT-SND.UNA counted in packets.
1400 *
1401 * retrans_out is number of retransmitted segments.
1402 *
1403 * left_out is number of segments left network, but not ACKed yet.
1404 *
1405 * left_out = sacked_out + lost_out
1406 *
1407 * sacked_out: Packets, which arrived to receiver out of order
1408 * and hence not ACKed. With SACKs this number is simply
1409 * amount of SACKed data. Even without SACKs
1410 * it is easy to give pretty reliable estimate of this number,
1411 * counting duplicate ACKs.
1412 *
1413 * lost_out: Packets lost by network. TCP has no explicit
1414 * "loss notification" feedback from network (for now).
1415 * It means that this number can be only _guessed_.
1416 * Actually, it is the heuristics to predict lossage that
1417 * distinguishes different algorithms.
1418 *
1419 * F.e. after RTO, when all the queue is considered as lost,
1420 * lost_out = packets_out and in_flight = retrans_out.
1421 *
1422 * Essentially, we have now two algorithms counting
1423 * lost packets.
1424 *
1425 * FACK: It is the simplest heuristics. As soon as we decided
1426 * that something is lost, we decide that _all_ not SACKed
1427 * packets until the most forward SACK are lost. I.e.
1428 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
1429 * It is absolutely correct estimate, if network does not reorder
1430 * packets. And it loses any connection to reality when reordering
1431 * takes place. We use FACK by default until reordering
1432 * is suspected on the path to this destination.
1433 *
1434 * NewReno: when Recovery is entered, we assume that one segment
1435 * is lost (classic Reno). While we are in Recovery and
1436 * a partial ACK arrives, we assume that one more packet
1437 * is lost (NewReno). This heuristics are the same in NewReno
1438 * and SACK.
1439 *
1440 * Imagine, that's all! Forget about all this shamanism about CWND inflation
1441 * deflation etc. CWND is real congestion window, never inflated, changes
1442 * only according to classic VJ rules.
1443 *
1444 * Really tricky (and requiring careful tuning) part of algorithm
1445 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
1446 * The first determines the moment _when_ we should reduce CWND and,
1447 * hence, slow down forward transmission. In fact, it determines the moment
1448 * when we decide that hole is caused by loss, rather than by a reorder.
1449 *
1450 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
1451 * holes, caused by lost packets.
1452 *
1453 * And the most logically complicated part of algorithm is undo
1454 * heuristics. We detect false retransmits due to both too early
1455 * fast retransmit (reordering) and underestimated RTO, analyzing
1456 * timestamps and D-SACKs. When we detect that some segments were
1457 * retransmitted by mistake and CWND reduction was wrong, we undo
1458 * window reduction and abort recovery phase. This logic is hidden
1459 * inside several functions named tcp_try_undo_<something>.
1460 */
1461
1462/* This function decides, when we should leave Disordered state
1463 * and enter Recovery phase, reducing congestion window.
1464 *
1465 * Main question: may we further continue forward transmission
1466 * with the same cwnd?
1467 */
1468static int tcp_time_to_recover(struct sock *sk, struct tcp_sock *tp)
1469{
1470 __u32 packets_out;
1471
1472 /* Trick#1: The loss is proven. */
1473 if (tp->lost_out)
1474 return 1;
1475
1476 /* Not-A-Trick#2 : Classic rule... */
1477 if (tcp_fackets_out(tp) > tp->reordering)
1478 return 1;
1479
1480 /* Trick#3 : when we use RFC2988 timer restart, fast
1481 * retransmit can be triggered by timeout of queue head.
1482 */
1483 if (tcp_head_timedout(sk, tp))
1484 return 1;
1485
1486 /* Trick#4: It is still not OK... But will it be useful to delay
1487 * recovery more?
1488 */
1489 packets_out = tp->packets_out;
1490 if (packets_out <= tp->reordering &&
1491 tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) &&
1492 !tcp_may_send_now(sk, tp)) {
1493 /* We have nothing to send. This connection is limited
1494 * either by receiver window or by application.
1495 */
1496 return 1;
1497 }
1498
1499 return 0;
1500}
1501
1502/* If we receive more dupacks than we expected counting segments
1503 * in assumption of absent reordering, interpret this as reordering.
1504 * The only another reason could be bug in receiver TCP.
1505 */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001506static void tcp_check_reno_reordering(struct sock *sk, const int addend)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001507{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001508 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001509 u32 holes;
1510
1511 holes = max(tp->lost_out, 1U);
1512 holes = min(holes, tp->packets_out);
1513
1514 if ((tp->sacked_out + holes) > tp->packets_out) {
1515 tp->sacked_out = tp->packets_out - holes;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001516 tcp_update_reordering(sk, tp->packets_out + addend, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001517 }
1518}
1519
1520/* Emulate SACKs for SACKless connection: account for a new dupack. */
1521
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001522static void tcp_add_reno_sack(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001523{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001524 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001525 tp->sacked_out++;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001526 tcp_check_reno_reordering(sk, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001527 tcp_sync_left_out(tp);
1528}
1529
1530/* Account for ACK, ACKing some data in Reno Recovery phase. */
1531
1532static void tcp_remove_reno_sacks(struct sock *sk, struct tcp_sock *tp, int acked)
1533{
1534 if (acked > 0) {
1535 /* One ACK acked hole. The rest eat duplicate ACKs. */
1536 if (acked-1 >= tp->sacked_out)
1537 tp->sacked_out = 0;
1538 else
1539 tp->sacked_out -= acked-1;
1540 }
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001541 tcp_check_reno_reordering(sk, acked);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001542 tcp_sync_left_out(tp);
1543}
1544
1545static inline void tcp_reset_reno_sack(struct tcp_sock *tp)
1546{
1547 tp->sacked_out = 0;
1548 tp->left_out = tp->lost_out;
1549}
1550
1551/* Mark head of queue up as lost. */
1552static void tcp_mark_head_lost(struct sock *sk, struct tcp_sock *tp,
1553 int packets, u32 high_seq)
1554{
1555 struct sk_buff *skb;
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001556 int cnt;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001557
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001558 BUG_TRAP(packets <= tp->packets_out);
1559 if (tp->lost_skb_hint) {
1560 skb = tp->lost_skb_hint;
1561 cnt = tp->lost_cnt_hint;
1562 } else {
1563 skb = sk->sk_write_queue.next;
1564 cnt = 0;
1565 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001566
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001567 sk_stream_for_retrans_queue_from(skb, sk) {
1568 /* TODO: do this better */
1569 /* this is not the most efficient way to do this... */
1570 tp->lost_skb_hint = skb;
1571 tp->lost_cnt_hint = cnt;
1572 cnt += tcp_skb_pcount(skb);
1573 if (cnt > packets || after(TCP_SKB_CB(skb)->end_seq, high_seq))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001574 break;
1575 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) {
1576 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1577 tp->lost_out += tcp_skb_pcount(skb);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001578
1579 /* clear xmit_retransmit_queue hints
1580 * if this is beyond hint */
1581 if(tp->retransmit_skb_hint != NULL &&
1582 before(TCP_SKB_CB(skb)->seq,
1583 TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) {
1584
1585 tp->retransmit_skb_hint = NULL;
1586 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001587 }
1588 }
1589 tcp_sync_left_out(tp);
1590}
1591
1592/* Account newly detected lost packet(s) */
1593
1594static void tcp_update_scoreboard(struct sock *sk, struct tcp_sock *tp)
1595{
1596 if (IsFack(tp)) {
1597 int lost = tp->fackets_out - tp->reordering;
1598 if (lost <= 0)
1599 lost = 1;
1600 tcp_mark_head_lost(sk, tp, lost, tp->high_seq);
1601 } else {
1602 tcp_mark_head_lost(sk, tp, 1, tp->high_seq);
1603 }
1604
1605 /* New heuristics: it is possible only after we switched
1606 * to restart timer each time when something is ACKed.
1607 * Hence, we can detect timed out packets during fast
1608 * retransmit without falling to slow start.
1609 */
1610 if (tcp_head_timedout(sk, tp)) {
1611 struct sk_buff *skb;
1612
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001613 skb = tp->scoreboard_skb_hint ? tp->scoreboard_skb_hint
1614 : sk->sk_write_queue.next;
1615
1616 sk_stream_for_retrans_queue_from(skb, sk) {
1617 if (!tcp_skb_timedout(sk, skb))
1618 break;
1619
1620 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001621 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1622 tp->lost_out += tcp_skb_pcount(skb);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001623
1624 /* clear xmit_retrans hint */
1625 if (tp->retransmit_skb_hint &&
1626 before(TCP_SKB_CB(skb)->seq,
1627 TCP_SKB_CB(tp->retransmit_skb_hint)->seq))
1628
1629 tp->retransmit_skb_hint = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001630 }
1631 }
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001632
1633 tp->scoreboard_skb_hint = skb;
1634
Linus Torvalds1da177e2005-04-16 15:20:36 -07001635 tcp_sync_left_out(tp);
1636 }
1637}
1638
1639/* CWND moderation, preventing bursts due to too big ACKs
1640 * in dubious situations.
1641 */
1642static inline void tcp_moderate_cwnd(struct tcp_sock *tp)
1643{
1644 tp->snd_cwnd = min(tp->snd_cwnd,
1645 tcp_packets_in_flight(tp)+tcp_max_burst(tp));
1646 tp->snd_cwnd_stamp = tcp_time_stamp;
1647}
1648
1649/* Decrease cwnd each second ack. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001650static void tcp_cwnd_down(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001651{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001652 const struct inet_connection_sock *icsk = inet_csk(sk);
1653 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001654 int decr = tp->snd_cwnd_cnt + 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001655
1656 tp->snd_cwnd_cnt = decr&1;
1657 decr >>= 1;
1658
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001659 if (decr && tp->snd_cwnd > icsk->icsk_ca_ops->min_cwnd(sk))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001660 tp->snd_cwnd -= decr;
1661
1662 tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp)+1);
1663 tp->snd_cwnd_stamp = tcp_time_stamp;
1664}
1665
1666/* Nothing was retransmitted or returned timestamp is less
1667 * than timestamp of the first retransmission.
1668 */
1669static inline int tcp_packet_delayed(struct tcp_sock *tp)
1670{
1671 return !tp->retrans_stamp ||
1672 (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
1673 (__s32)(tp->rx_opt.rcv_tsecr - tp->retrans_stamp) < 0);
1674}
1675
1676/* Undo procedures. */
1677
1678#if FASTRETRANS_DEBUG > 1
1679static void DBGUNDO(struct sock *sk, struct tcp_sock *tp, const char *msg)
1680{
1681 struct inet_sock *inet = inet_sk(sk);
1682 printk(KERN_DEBUG "Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n",
1683 msg,
1684 NIPQUAD(inet->daddr), ntohs(inet->dport),
1685 tp->snd_cwnd, tp->left_out,
1686 tp->snd_ssthresh, tp->prior_ssthresh,
1687 tp->packets_out);
1688}
1689#else
1690#define DBGUNDO(x...) do { } while (0)
1691#endif
1692
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001693static void tcp_undo_cwr(struct sock *sk, const int undo)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001694{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001695 struct tcp_sock *tp = tcp_sk(sk);
1696
Linus Torvalds1da177e2005-04-16 15:20:36 -07001697 if (tp->prior_ssthresh) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001698 const struct inet_connection_sock *icsk = inet_csk(sk);
1699
1700 if (icsk->icsk_ca_ops->undo_cwnd)
1701 tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001702 else
1703 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh<<1);
1704
1705 if (undo && tp->prior_ssthresh > tp->snd_ssthresh) {
1706 tp->snd_ssthresh = tp->prior_ssthresh;
1707 TCP_ECN_withdraw_cwr(tp);
1708 }
1709 } else {
1710 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh);
1711 }
1712 tcp_moderate_cwnd(tp);
1713 tp->snd_cwnd_stamp = tcp_time_stamp;
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001714
1715 /* There is something screwy going on with the retrans hints after
1716 an undo */
1717 clear_all_retrans_hints(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001718}
1719
1720static inline int tcp_may_undo(struct tcp_sock *tp)
1721{
1722 return tp->undo_marker &&
1723 (!tp->undo_retrans || tcp_packet_delayed(tp));
1724}
1725
1726/* People celebrate: "We love our President!" */
1727static int tcp_try_undo_recovery(struct sock *sk, struct tcp_sock *tp)
1728{
1729 if (tcp_may_undo(tp)) {
1730 /* Happy end! We did not retransmit anything
1731 * or our original transmission succeeded.
1732 */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001733 DBGUNDO(sk, tp, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans");
1734 tcp_undo_cwr(sk, 1);
1735 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001736 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO);
1737 else
1738 NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO);
1739 tp->undo_marker = 0;
1740 }
1741 if (tp->snd_una == tp->high_seq && IsReno(tp)) {
1742 /* Hold old state until something *above* high_seq
1743 * is ACKed. For Reno it is MUST to prevent false
1744 * fast retransmits (RFC2582). SACK TCP is safe. */
1745 tcp_moderate_cwnd(tp);
1746 return 1;
1747 }
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001748 tcp_set_ca_state(sk, TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001749 return 0;
1750}
1751
1752/* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
1753static void tcp_try_undo_dsack(struct sock *sk, struct tcp_sock *tp)
1754{
1755 if (tp->undo_marker && !tp->undo_retrans) {
1756 DBGUNDO(sk, tp, "D-SACK");
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001757 tcp_undo_cwr(sk, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001758 tp->undo_marker = 0;
1759 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO);
1760 }
1761}
1762
1763/* Undo during fast recovery after partial ACK. */
1764
1765static int tcp_try_undo_partial(struct sock *sk, struct tcp_sock *tp,
1766 int acked)
1767{
1768 /* Partial ACK arrived. Force Hoe's retransmit. */
1769 int failed = IsReno(tp) || tp->fackets_out>tp->reordering;
1770
1771 if (tcp_may_undo(tp)) {
1772 /* Plain luck! Hole if filled with delayed
1773 * packet, rather than with a retransmit.
1774 */
1775 if (tp->retrans_out == 0)
1776 tp->retrans_stamp = 0;
1777
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001778 tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001779
1780 DBGUNDO(sk, tp, "Hoe");
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001781 tcp_undo_cwr(sk, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001782 NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO);
1783
1784 /* So... Do not make Hoe's retransmit yet.
1785 * If the first packet was delayed, the rest
1786 * ones are most probably delayed as well.
1787 */
1788 failed = 0;
1789 }
1790 return failed;
1791}
1792
1793/* Undo during loss recovery after partial ACK. */
1794static int tcp_try_undo_loss(struct sock *sk, struct tcp_sock *tp)
1795{
1796 if (tcp_may_undo(tp)) {
1797 struct sk_buff *skb;
1798 sk_stream_for_retrans_queue(skb, sk) {
1799 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1800 }
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001801
1802 clear_all_retrans_hints(tp);
1803
Linus Torvalds1da177e2005-04-16 15:20:36 -07001804 DBGUNDO(sk, tp, "partial loss");
1805 tp->lost_out = 0;
1806 tp->left_out = tp->sacked_out;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001807 tcp_undo_cwr(sk, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001808 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001809 inet_csk(sk)->icsk_retransmits = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001810 tp->undo_marker = 0;
1811 if (!IsReno(tp))
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001812 tcp_set_ca_state(sk, TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001813 return 1;
1814 }
1815 return 0;
1816}
1817
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001818static inline void tcp_complete_cwr(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001819{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001820 struct tcp_sock *tp = tcp_sk(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -07001821 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001822 tp->snd_cwnd_stamp = tcp_time_stamp;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001823 tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001824}
1825
1826static void tcp_try_to_open(struct sock *sk, struct tcp_sock *tp, int flag)
1827{
1828 tp->left_out = tp->sacked_out;
1829
1830 if (tp->retrans_out == 0)
1831 tp->retrans_stamp = 0;
1832
1833 if (flag&FLAG_ECE)
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001834 tcp_enter_cwr(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001835
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001836 if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001837 int state = TCP_CA_Open;
1838
1839 if (tp->left_out || tp->retrans_out || tp->undo_marker)
1840 state = TCP_CA_Disorder;
1841
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001842 if (inet_csk(sk)->icsk_ca_state != state) {
1843 tcp_set_ca_state(sk, state);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001844 tp->high_seq = tp->snd_nxt;
1845 }
1846 tcp_moderate_cwnd(tp);
1847 } else {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001848 tcp_cwnd_down(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001849 }
1850}
1851
1852/* Process an event, which can update packets-in-flight not trivially.
1853 * Main goal of this function is to calculate new estimate for left_out,
1854 * taking into account both packets sitting in receiver's buffer and
1855 * packets lost by network.
1856 *
1857 * Besides that it does CWND reduction, when packet loss is detected
1858 * and changes state of machine.
1859 *
1860 * It does _not_ decide what to send, it is made in function
1861 * tcp_xmit_retransmit_queue().
1862 */
1863static void
1864tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una,
1865 int prior_packets, int flag)
1866{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001867 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001868 struct tcp_sock *tp = tcp_sk(sk);
1869 int is_dupack = (tp->snd_una == prior_snd_una && !(flag&FLAG_NOT_DUP));
1870
1871 /* Some technical things:
1872 * 1. Reno does not count dupacks (sacked_out) automatically. */
1873 if (!tp->packets_out)
1874 tp->sacked_out = 0;
1875 /* 2. SACK counts snd_fack in packets inaccurately. */
1876 if (tp->sacked_out == 0)
1877 tp->fackets_out = 0;
1878
1879 /* Now state machine starts.
1880 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
1881 if (flag&FLAG_ECE)
1882 tp->prior_ssthresh = 0;
1883
1884 /* B. In all the states check for reneging SACKs. */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001885 if (tp->sacked_out && tcp_check_sack_reneging(sk))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001886 return;
1887
1888 /* C. Process data loss notification, provided it is valid. */
1889 if ((flag&FLAG_DATA_LOST) &&
1890 before(tp->snd_una, tp->high_seq) &&
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001891 icsk->icsk_ca_state != TCP_CA_Open &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07001892 tp->fackets_out > tp->reordering) {
1893 tcp_mark_head_lost(sk, tp, tp->fackets_out-tp->reordering, tp->high_seq);
1894 NET_INC_STATS_BH(LINUX_MIB_TCPLOSS);
1895 }
1896
1897 /* D. Synchronize left_out to current state. */
1898 tcp_sync_left_out(tp);
1899
1900 /* E. Check state exit conditions. State can be terminated
1901 * when high_seq is ACKed. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001902 if (icsk->icsk_ca_state == TCP_CA_Open) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001903 if (!sysctl_tcp_frto)
1904 BUG_TRAP(tp->retrans_out == 0);
1905 tp->retrans_stamp = 0;
1906 } else if (!before(tp->snd_una, tp->high_seq)) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001907 switch (icsk->icsk_ca_state) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001908 case TCP_CA_Loss:
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001909 icsk->icsk_retransmits = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001910 if (tcp_try_undo_recovery(sk, tp))
1911 return;
1912 break;
1913
1914 case TCP_CA_CWR:
1915 /* CWR is to be held something *above* high_seq
1916 * is ACKed for CWR bit to reach receiver. */
1917 if (tp->snd_una != tp->high_seq) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001918 tcp_complete_cwr(sk);
1919 tcp_set_ca_state(sk, TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001920 }
1921 break;
1922
1923 case TCP_CA_Disorder:
1924 tcp_try_undo_dsack(sk, tp);
1925 if (!tp->undo_marker ||
1926 /* For SACK case do not Open to allow to undo
1927 * catching for all duplicate ACKs. */
1928 IsReno(tp) || tp->snd_una != tp->high_seq) {
1929 tp->undo_marker = 0;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001930 tcp_set_ca_state(sk, TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001931 }
1932 break;
1933
1934 case TCP_CA_Recovery:
1935 if (IsReno(tp))
1936 tcp_reset_reno_sack(tp);
1937 if (tcp_try_undo_recovery(sk, tp))
1938 return;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001939 tcp_complete_cwr(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001940 break;
1941 }
1942 }
1943
1944 /* F. Process state. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001945 switch (icsk->icsk_ca_state) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001946 case TCP_CA_Recovery:
1947 if (prior_snd_una == tp->snd_una) {
1948 if (IsReno(tp) && is_dupack)
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001949 tcp_add_reno_sack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001950 } else {
1951 int acked = prior_packets - tp->packets_out;
1952 if (IsReno(tp))
1953 tcp_remove_reno_sacks(sk, tp, acked);
1954 is_dupack = tcp_try_undo_partial(sk, tp, acked);
1955 }
1956 break;
1957 case TCP_CA_Loss:
1958 if (flag&FLAG_DATA_ACKED)
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001959 icsk->icsk_retransmits = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001960 if (!tcp_try_undo_loss(sk, tp)) {
1961 tcp_moderate_cwnd(tp);
1962 tcp_xmit_retransmit_queue(sk);
1963 return;
1964 }
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001965 if (icsk->icsk_ca_state != TCP_CA_Open)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001966 return;
1967 /* Loss is undone; fall through to processing in Open state. */
1968 default:
1969 if (IsReno(tp)) {
1970 if (tp->snd_una != prior_snd_una)
1971 tcp_reset_reno_sack(tp);
1972 if (is_dupack)
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001973 tcp_add_reno_sack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001974 }
1975
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001976 if (icsk->icsk_ca_state == TCP_CA_Disorder)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001977 tcp_try_undo_dsack(sk, tp);
1978
1979 if (!tcp_time_to_recover(sk, tp)) {
1980 tcp_try_to_open(sk, tp, flag);
1981 return;
1982 }
1983
1984 /* Otherwise enter Recovery state */
1985
1986 if (IsReno(tp))
1987 NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY);
1988 else
1989 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY);
1990
1991 tp->high_seq = tp->snd_nxt;
1992 tp->prior_ssthresh = 0;
1993 tp->undo_marker = tp->snd_una;
1994 tp->undo_retrans = tp->retrans_out;
1995
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001996 if (icsk->icsk_ca_state < TCP_CA_CWR) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001997 if (!(flag&FLAG_ECE))
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001998 tp->prior_ssthresh = tcp_current_ssthresh(sk);
1999 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002000 TCP_ECN_queue_cwr(tp);
2001 }
2002
Stephen Hemminger9772efb2005-11-10 17:09:53 -08002003 tp->bytes_acked = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002004 tp->snd_cwnd_cnt = 0;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002005 tcp_set_ca_state(sk, TCP_CA_Recovery);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002006 }
2007
2008 if (is_dupack || tcp_head_timedout(sk, tp))
2009 tcp_update_scoreboard(sk, tp);
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002010 tcp_cwnd_down(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002011 tcp_xmit_retransmit_queue(sk);
2012}
2013
2014/* Read draft-ietf-tcplw-high-performance before mucking
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08002015 * with this code. (Supersedes RFC1323)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002016 */
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002017static void tcp_ack_saw_tstamp(struct sock *sk, int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002018{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002019 /* RTTM Rule: A TSecr value received in a segment is used to
2020 * update the averaged RTT measurement only if the segment
2021 * acknowledges some new data, i.e., only if it advances the
2022 * left edge of the send window.
2023 *
2024 * See draft-ietf-tcplw-high-performance-00, section 3.3.
2025 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
2026 *
2027 * Changed: reset backoff as soon as we see the first valid sample.
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08002028 * If we do not, we get strongly overestimated rto. With timestamps
Linus Torvalds1da177e2005-04-16 15:20:36 -07002029 * samples are accepted even from very old segments: f.e., when rtt=1
2030 * increases to 8, we retransmit 5 times and after 8 seconds delayed
2031 * answer arrives rto becomes 120 seconds! If at least one of segments
2032 * in window is lost... Voila. --ANK (010210)
2033 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002034 struct tcp_sock *tp = tcp_sk(sk);
2035 const __u32 seq_rtt = tcp_time_stamp - tp->rx_opt.rcv_tsecr;
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002036 tcp_rtt_estimator(sk, seq_rtt);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002037 tcp_set_rto(sk);
2038 inet_csk(sk)->icsk_backoff = 0;
2039 tcp_bound_rto(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002040}
2041
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002042static void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002043{
2044 /* We don't have a timestamp. Can only use
2045 * packets that are not retransmitted to determine
2046 * rtt estimates. Also, we must not reset the
2047 * backoff for rto until we get a non-retransmitted
2048 * packet. This allows us to deal with a situation
2049 * where the network delay has increased suddenly.
2050 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
2051 */
2052
2053 if (flag & FLAG_RETRANS_DATA_ACKED)
2054 return;
2055
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002056 tcp_rtt_estimator(sk, seq_rtt);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002057 tcp_set_rto(sk);
2058 inet_csk(sk)->icsk_backoff = 0;
2059 tcp_bound_rto(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002060}
2061
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002062static inline void tcp_ack_update_rtt(struct sock *sk, const int flag,
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002063 const s32 seq_rtt)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002064{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002065 const struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002066 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
2067 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002068 tcp_ack_saw_tstamp(sk, flag);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002069 else if (seq_rtt >= 0)
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002070 tcp_ack_no_tstamp(sk, seq_rtt, flag);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002071}
2072
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002073static inline void tcp_cong_avoid(struct sock *sk, u32 ack, u32 rtt,
Stephen Hemminger317a76f2005-06-23 12:19:55 -07002074 u32 in_flight, int good)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002075{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002076 const struct inet_connection_sock *icsk = inet_csk(sk);
2077 icsk->icsk_ca_ops->cong_avoid(sk, ack, rtt, in_flight, good);
2078 tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002079}
2080
Linus Torvalds1da177e2005-04-16 15:20:36 -07002081/* Restart timer after forward progress on connection.
2082 * RFC2988 recommends to restart timer to now+rto.
2083 */
2084
2085static inline void tcp_ack_packets_out(struct sock *sk, struct tcp_sock *tp)
2086{
2087 if (!tp->packets_out) {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002088 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002089 } else {
Arnaldo Carvalho de Melo3f421ba2005-08-09 20:11:08 -07002090 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002091 }
2092}
2093
Linus Torvalds1da177e2005-04-16 15:20:36 -07002094static int tcp_tso_acked(struct sock *sk, struct sk_buff *skb,
2095 __u32 now, __s32 *seq_rtt)
2096{
2097 struct tcp_sock *tp = tcp_sk(sk);
2098 struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
2099 __u32 seq = tp->snd_una;
2100 __u32 packets_acked;
2101 int acked = 0;
2102
2103 /* If we get here, the whole TSO packet has not been
2104 * acked.
2105 */
2106 BUG_ON(!after(scb->end_seq, seq));
2107
2108 packets_acked = tcp_skb_pcount(skb);
2109 if (tcp_trim_head(sk, skb, seq - scb->seq))
2110 return 0;
2111 packets_acked -= tcp_skb_pcount(skb);
2112
2113 if (packets_acked) {
2114 __u8 sacked = scb->sacked;
2115
2116 acked |= FLAG_DATA_ACKED;
2117 if (sacked) {
2118 if (sacked & TCPCB_RETRANS) {
2119 if (sacked & TCPCB_SACKED_RETRANS)
2120 tp->retrans_out -= packets_acked;
2121 acked |= FLAG_RETRANS_DATA_ACKED;
2122 *seq_rtt = -1;
2123 } else if (*seq_rtt < 0)
2124 *seq_rtt = now - scb->when;
2125 if (sacked & TCPCB_SACKED_ACKED)
2126 tp->sacked_out -= packets_acked;
2127 if (sacked & TCPCB_LOST)
2128 tp->lost_out -= packets_acked;
2129 if (sacked & TCPCB_URG) {
2130 if (tp->urg_mode &&
2131 !before(seq, tp->snd_up))
2132 tp->urg_mode = 0;
2133 }
2134 } else if (*seq_rtt < 0)
2135 *seq_rtt = now - scb->when;
2136
2137 if (tp->fackets_out) {
2138 __u32 dval = min(tp->fackets_out, packets_acked);
2139 tp->fackets_out -= dval;
2140 }
2141 tp->packets_out -= packets_acked;
2142
2143 BUG_ON(tcp_skb_pcount(skb) == 0);
2144 BUG_ON(!before(scb->seq, scb->end_seq));
2145 }
2146
2147 return acked;
2148}
2149
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002150static inline u32 tcp_usrtt(const struct sk_buff *skb)
2151{
2152 struct timeval tv, now;
2153
2154 do_gettimeofday(&now);
2155 skb_get_timestamp(skb, &tv);
2156 return (now.tv_sec - tv.tv_sec) * 1000000 + (now.tv_usec - tv.tv_usec);
2157}
Linus Torvalds1da177e2005-04-16 15:20:36 -07002158
2159/* Remove acknowledged frames from the retransmission queue. */
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002160static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002161{
2162 struct tcp_sock *tp = tcp_sk(sk);
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002163 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002164 struct sk_buff *skb;
2165 __u32 now = tcp_time_stamp;
2166 int acked = 0;
2167 __s32 seq_rtt = -1;
Stephen Hemminger317a76f2005-06-23 12:19:55 -07002168 u32 pkts_acked = 0;
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002169 void (*rtt_sample)(struct sock *sk, u32 usrtt)
2170 = icsk->icsk_ca_ops->rtt_sample;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002171
2172 while ((skb = skb_peek(&sk->sk_write_queue)) &&
2173 skb != sk->sk_send_head) {
2174 struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
2175 __u8 sacked = scb->sacked;
2176
2177 /* If our packet is before the ack sequence we can
2178 * discard it as it's confirmed to have arrived at
2179 * the other end.
2180 */
2181 if (after(scb->end_seq, tp->snd_una)) {
David S. Millercb831992005-07-05 15:20:55 -07002182 if (tcp_skb_pcount(skb) > 1 &&
2183 after(tp->snd_una, scb->seq))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002184 acked |= tcp_tso_acked(sk, skb,
2185 now, &seq_rtt);
2186 break;
2187 }
2188
2189 /* Initial outgoing SYN's get put onto the write_queue
2190 * just like anything else we transmit. It is not
2191 * true data, and if we misinform our callers that
2192 * this ACK acks real data, we will erroneously exit
2193 * connection startup slow start one packet too
2194 * quickly. This is severely frowned upon behavior.
2195 */
2196 if (!(scb->flags & TCPCB_FLAG_SYN)) {
2197 acked |= FLAG_DATA_ACKED;
Stephen Hemminger317a76f2005-06-23 12:19:55 -07002198 ++pkts_acked;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002199 } else {
2200 acked |= FLAG_SYN_ACKED;
2201 tp->retrans_stamp = 0;
2202 }
2203
2204 if (sacked) {
2205 if (sacked & TCPCB_RETRANS) {
2206 if(sacked & TCPCB_SACKED_RETRANS)
2207 tp->retrans_out -= tcp_skb_pcount(skb);
2208 acked |= FLAG_RETRANS_DATA_ACKED;
2209 seq_rtt = -1;
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002210 } else if (seq_rtt < 0) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002211 seq_rtt = now - scb->when;
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002212 if (rtt_sample)
2213 (*rtt_sample)(sk, tcp_usrtt(skb));
Patrick McHardya61bbcf2005-08-14 17:24:31 -07002214 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002215 if (sacked & TCPCB_SACKED_ACKED)
2216 tp->sacked_out -= tcp_skb_pcount(skb);
2217 if (sacked & TCPCB_LOST)
2218 tp->lost_out -= tcp_skb_pcount(skb);
2219 if (sacked & TCPCB_URG) {
2220 if (tp->urg_mode &&
2221 !before(scb->end_seq, tp->snd_up))
2222 tp->urg_mode = 0;
2223 }
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002224 } else if (seq_rtt < 0) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002225 seq_rtt = now - scb->when;
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002226 if (rtt_sample)
2227 (*rtt_sample)(sk, tcp_usrtt(skb));
2228 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002229 tcp_dec_pcount_approx(&tp->fackets_out, skb);
2230 tcp_packets_out_dec(tp, skb);
David S. Miller8728b832005-08-09 19:25:21 -07002231 __skb_unlink(skb, &sk->sk_write_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002232 sk_stream_free_skb(sk, skb);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08002233 clear_all_retrans_hints(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002234 }
2235
2236 if (acked&FLAG_ACKED) {
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002237 tcp_ack_update_rtt(sk, acked, seq_rtt);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002238 tcp_ack_packets_out(sk, tp);
Stephen Hemminger317a76f2005-06-23 12:19:55 -07002239
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002240 if (icsk->icsk_ca_ops->pkts_acked)
2241 icsk->icsk_ca_ops->pkts_acked(sk, pkts_acked);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002242 }
2243
2244#if FASTRETRANS_DEBUG > 0
2245 BUG_TRAP((int)tp->sacked_out >= 0);
2246 BUG_TRAP((int)tp->lost_out >= 0);
2247 BUG_TRAP((int)tp->retrans_out >= 0);
2248 if (!tp->packets_out && tp->rx_opt.sack_ok) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002249 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002250 if (tp->lost_out) {
2251 printk(KERN_DEBUG "Leak l=%u %d\n",
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002252 tp->lost_out, icsk->icsk_ca_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002253 tp->lost_out = 0;
2254 }
2255 if (tp->sacked_out) {
2256 printk(KERN_DEBUG "Leak s=%u %d\n",
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002257 tp->sacked_out, icsk->icsk_ca_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002258 tp->sacked_out = 0;
2259 }
2260 if (tp->retrans_out) {
2261 printk(KERN_DEBUG "Leak r=%u %d\n",
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002262 tp->retrans_out, icsk->icsk_ca_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002263 tp->retrans_out = 0;
2264 }
2265 }
2266#endif
2267 *seq_rtt_p = seq_rtt;
2268 return acked;
2269}
2270
2271static void tcp_ack_probe(struct sock *sk)
2272{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002273 const struct tcp_sock *tp = tcp_sk(sk);
2274 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002275
2276 /* Was it a usable window open? */
2277
2278 if (!after(TCP_SKB_CB(sk->sk_send_head)->end_seq,
2279 tp->snd_una + tp->snd_wnd)) {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002280 icsk->icsk_backoff = 0;
2281 inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002282 /* Socket must be waked up by subsequent tcp_data_snd_check().
2283 * This function is not for random using!
2284 */
2285 } else {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002286 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
Arnaldo Carvalho de Melo3f421ba2005-08-09 20:11:08 -07002287 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
2288 TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002289 }
2290}
2291
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002292static inline int tcp_ack_is_dubious(const struct sock *sk, const int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002293{
2294 return (!(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) ||
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002295 inet_csk(sk)->icsk_ca_state != TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002296}
2297
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002298static inline int tcp_may_raise_cwnd(const struct sock *sk, const int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002299{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002300 const struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002301 return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) &&
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002302 !((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_Recovery | TCPF_CA_CWR));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002303}
2304
2305/* Check that window update is acceptable.
2306 * The function assumes that snd_una<=ack<=snd_next.
2307 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002308static inline int tcp_may_update_window(const struct tcp_sock *tp, const u32 ack,
2309 const u32 ack_seq, const u32 nwin)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002310{
2311 return (after(ack, tp->snd_una) ||
2312 after(ack_seq, tp->snd_wl1) ||
2313 (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd));
2314}
2315
2316/* Update our send window.
2317 *
2318 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
2319 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
2320 */
2321static int tcp_ack_update_window(struct sock *sk, struct tcp_sock *tp,
2322 struct sk_buff *skb, u32 ack, u32 ack_seq)
2323{
2324 int flag = 0;
2325 u32 nwin = ntohs(skb->h.th->window);
2326
2327 if (likely(!skb->h.th->syn))
2328 nwin <<= tp->rx_opt.snd_wscale;
2329
2330 if (tcp_may_update_window(tp, ack, ack_seq, nwin)) {
2331 flag |= FLAG_WIN_UPDATE;
2332 tcp_update_wl(tp, ack, ack_seq);
2333
2334 if (tp->snd_wnd != nwin) {
2335 tp->snd_wnd = nwin;
2336
2337 /* Note, it is the only place, where
2338 * fast path is recovered for sending TCP.
2339 */
Herbert Xu2ad41062005-10-27 18:47:46 +10002340 tp->pred_flags = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002341 tcp_fast_path_check(sk, tp);
2342
2343 if (nwin > tp->max_window) {
2344 tp->max_window = nwin;
2345 tcp_sync_mss(sk, tp->pmtu_cookie);
2346 }
2347 }
2348 }
2349
2350 tp->snd_una = ack;
2351
2352 return flag;
2353}
2354
2355static void tcp_process_frto(struct sock *sk, u32 prior_snd_una)
2356{
2357 struct tcp_sock *tp = tcp_sk(sk);
2358
2359 tcp_sync_left_out(tp);
2360
2361 if (tp->snd_una == prior_snd_una ||
2362 !before(tp->snd_una, tp->frto_highmark)) {
2363 /* RTO was caused by loss, start retransmitting in
2364 * go-back-N slow start
2365 */
2366 tcp_enter_frto_loss(sk);
2367 return;
2368 }
2369
2370 if (tp->frto_counter == 1) {
2371 /* First ACK after RTO advances the window: allow two new
2372 * segments out.
2373 */
2374 tp->snd_cwnd = tcp_packets_in_flight(tp) + 2;
2375 } else {
2376 /* Also the second ACK after RTO advances the window.
2377 * The RTO was likely spurious. Reduce cwnd and continue
2378 * in congestion avoidance
2379 */
2380 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
2381 tcp_moderate_cwnd(tp);
2382 }
2383
2384 /* F-RTO affects on two new ACKs following RTO.
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08002385 * At latest on third ACK the TCP behavior is back to normal.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002386 */
2387 tp->frto_counter = (tp->frto_counter + 1) % 3;
2388}
2389
Linus Torvalds1da177e2005-04-16 15:20:36 -07002390/* This routine deals with incoming acks, but not outgoing ones. */
2391static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
2392{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002393 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002394 struct tcp_sock *tp = tcp_sk(sk);
2395 u32 prior_snd_una = tp->snd_una;
2396 u32 ack_seq = TCP_SKB_CB(skb)->seq;
2397 u32 ack = TCP_SKB_CB(skb)->ack_seq;
2398 u32 prior_in_flight;
2399 s32 seq_rtt;
2400 int prior_packets;
2401
2402 /* If the ack is newer than sent or older than previous acks
2403 * then we can probably ignore it.
2404 */
2405 if (after(ack, tp->snd_nxt))
2406 goto uninteresting_ack;
2407
2408 if (before(ack, prior_snd_una))
2409 goto old_ack;
2410
Stephen Hemminger9772efb2005-11-10 17:09:53 -08002411 if (sysctl_tcp_abc && icsk->icsk_ca_state < TCP_CA_CWR)
2412 tp->bytes_acked += ack - prior_snd_una;
2413
Linus Torvalds1da177e2005-04-16 15:20:36 -07002414 if (!(flag&FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
2415 /* Window is constant, pure forward advance.
2416 * No more checks are required.
2417 * Note, we use the fact that SND.UNA>=SND.WL2.
2418 */
2419 tcp_update_wl(tp, ack, ack_seq);
2420 tp->snd_una = ack;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002421 flag |= FLAG_WIN_UPDATE;
2422
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002423 tcp_ca_event(sk, CA_EVENT_FAST_ACK);
Stephen Hemminger317a76f2005-06-23 12:19:55 -07002424
Linus Torvalds1da177e2005-04-16 15:20:36 -07002425 NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS);
2426 } else {
2427 if (ack_seq != TCP_SKB_CB(skb)->end_seq)
2428 flag |= FLAG_DATA;
2429 else
2430 NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS);
2431
2432 flag |= tcp_ack_update_window(sk, tp, skb, ack, ack_seq);
2433
2434 if (TCP_SKB_CB(skb)->sacked)
2435 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una);
2436
2437 if (TCP_ECN_rcv_ecn_echo(tp, skb->h.th))
2438 flag |= FLAG_ECE;
2439
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002440 tcp_ca_event(sk, CA_EVENT_SLOW_ACK);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002441 }
2442
2443 /* We passed data and got it acked, remove any soft error
2444 * log. Something worked...
2445 */
2446 sk->sk_err_soft = 0;
2447 tp->rcv_tstamp = tcp_time_stamp;
2448 prior_packets = tp->packets_out;
2449 if (!prior_packets)
2450 goto no_queue;
2451
2452 prior_in_flight = tcp_packets_in_flight(tp);
2453
2454 /* See if we can take anything off of the retransmit queue. */
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002455 flag |= tcp_clean_rtx_queue(sk, &seq_rtt);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002456
2457 if (tp->frto_counter)
2458 tcp_process_frto(sk, prior_snd_una);
2459
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002460 if (tcp_ack_is_dubious(sk, flag)) {
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08002461 /* Advance CWND, if state allows this. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002462 if ((flag & FLAG_DATA_ACKED) && tcp_may_raise_cwnd(sk, flag))
2463 tcp_cong_avoid(sk, ack, seq_rtt, prior_in_flight, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002464 tcp_fastretrans_alert(sk, prior_snd_una, prior_packets, flag);
2465 } else {
Stephen Hemminger317a76f2005-06-23 12:19:55 -07002466 if ((flag & FLAG_DATA_ACKED))
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002467 tcp_cong_avoid(sk, ack, seq_rtt, prior_in_flight, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002468 }
2469
2470 if ((flag & FLAG_FORWARD_PROGRESS) || !(flag&FLAG_NOT_DUP))
2471 dst_confirm(sk->sk_dst_cache);
2472
2473 return 1;
2474
2475no_queue:
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002476 icsk->icsk_probes_out = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002477
2478 /* If this ack opens up a zero window, clear backoff. It was
2479 * being used to time the probes, and is probably far higher than
2480 * it needs to be for normal retransmission.
2481 */
2482 if (sk->sk_send_head)
2483 tcp_ack_probe(sk);
2484 return 1;
2485
2486old_ack:
2487 if (TCP_SKB_CB(skb)->sacked)
2488 tcp_sacktag_write_queue(sk, skb, prior_snd_una);
2489
2490uninteresting_ack:
2491 SOCK_DEBUG(sk, "Ack %u out of %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
2492 return 0;
2493}
2494
2495
2496/* Look for tcp options. Normally only called on SYN and SYNACK packets.
2497 * But, this can also be called on packets in the established flow when
2498 * the fast version below fails.
2499 */
2500void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx, int estab)
2501{
2502 unsigned char *ptr;
2503 struct tcphdr *th = skb->h.th;
2504 int length=(th->doff*4)-sizeof(struct tcphdr);
2505
2506 ptr = (unsigned char *)(th + 1);
2507 opt_rx->saw_tstamp = 0;
2508
2509 while(length>0) {
2510 int opcode=*ptr++;
2511 int opsize;
2512
2513 switch (opcode) {
2514 case TCPOPT_EOL:
2515 return;
2516 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
2517 length--;
2518 continue;
2519 default:
2520 opsize=*ptr++;
2521 if (opsize < 2) /* "silly options" */
2522 return;
2523 if (opsize > length)
2524 return; /* don't parse partial options */
2525 switch(opcode) {
2526 case TCPOPT_MSS:
2527 if(opsize==TCPOLEN_MSS && th->syn && !estab) {
2528 u16 in_mss = ntohs(get_unaligned((__u16 *)ptr));
2529 if (in_mss) {
2530 if (opt_rx->user_mss && opt_rx->user_mss < in_mss)
2531 in_mss = opt_rx->user_mss;
2532 opt_rx->mss_clamp = in_mss;
2533 }
2534 }
2535 break;
2536 case TCPOPT_WINDOW:
2537 if(opsize==TCPOLEN_WINDOW && th->syn && !estab)
2538 if (sysctl_tcp_window_scaling) {
2539 __u8 snd_wscale = *(__u8 *) ptr;
2540 opt_rx->wscale_ok = 1;
2541 if (snd_wscale > 14) {
2542 if(net_ratelimit())
2543 printk(KERN_INFO "tcp_parse_options: Illegal window "
2544 "scaling value %d >14 received.\n",
2545 snd_wscale);
2546 snd_wscale = 14;
2547 }
2548 opt_rx->snd_wscale = snd_wscale;
2549 }
2550 break;
2551 case TCPOPT_TIMESTAMP:
2552 if(opsize==TCPOLEN_TIMESTAMP) {
2553 if ((estab && opt_rx->tstamp_ok) ||
2554 (!estab && sysctl_tcp_timestamps)) {
2555 opt_rx->saw_tstamp = 1;
2556 opt_rx->rcv_tsval = ntohl(get_unaligned((__u32 *)ptr));
2557 opt_rx->rcv_tsecr = ntohl(get_unaligned((__u32 *)(ptr+4)));
2558 }
2559 }
2560 break;
2561 case TCPOPT_SACK_PERM:
2562 if(opsize==TCPOLEN_SACK_PERM && th->syn && !estab) {
2563 if (sysctl_tcp_sack) {
2564 opt_rx->sack_ok = 1;
2565 tcp_sack_reset(opt_rx);
2566 }
2567 }
2568 break;
2569
2570 case TCPOPT_SACK:
2571 if((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) &&
2572 !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) &&
2573 opt_rx->sack_ok) {
2574 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th;
2575 }
2576 };
2577 ptr+=opsize-2;
2578 length-=opsize;
2579 };
2580 }
2581}
2582
2583/* Fast parse options. This hopes to only see timestamps.
2584 * If it is wrong it falls back on tcp_parse_options().
2585 */
2586static inline int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th,
2587 struct tcp_sock *tp)
2588{
2589 if (th->doff == sizeof(struct tcphdr)>>2) {
2590 tp->rx_opt.saw_tstamp = 0;
2591 return 0;
2592 } else if (tp->rx_opt.tstamp_ok &&
2593 th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) {
2594 __u32 *ptr = (__u32 *)(th + 1);
2595 if (*ptr == ntohl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
2596 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
2597 tp->rx_opt.saw_tstamp = 1;
2598 ++ptr;
2599 tp->rx_opt.rcv_tsval = ntohl(*ptr);
2600 ++ptr;
2601 tp->rx_opt.rcv_tsecr = ntohl(*ptr);
2602 return 1;
2603 }
2604 }
2605 tcp_parse_options(skb, &tp->rx_opt, 1);
2606 return 1;
2607}
2608
2609static inline void tcp_store_ts_recent(struct tcp_sock *tp)
2610{
2611 tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval;
2612 tp->rx_opt.ts_recent_stamp = xtime.tv_sec;
2613}
2614
2615static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)
2616{
2617 if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) {
2618 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
2619 * extra check below makes sure this can only happen
2620 * for pure ACK frames. -DaveM
2621 *
2622 * Not only, also it occurs for expired timestamps.
2623 */
2624
2625 if((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) >= 0 ||
2626 xtime.tv_sec >= tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS)
2627 tcp_store_ts_recent(tp);
2628 }
2629}
2630
2631/* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
2632 *
2633 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
2634 * it can pass through stack. So, the following predicate verifies that
2635 * this segment is not used for anything but congestion avoidance or
2636 * fast retransmit. Moreover, we even are able to eliminate most of such
2637 * second order effects, if we apply some small "replay" window (~RTO)
2638 * to timestamp space.
2639 *
2640 * All these measures still do not guarantee that we reject wrapped ACKs
2641 * on networks with high bandwidth, when sequence space is recycled fastly,
2642 * but it guarantees that such events will be very rare and do not affect
2643 * connection seriously. This doesn't look nice, but alas, PAWS is really
2644 * buggy extension.
2645 *
2646 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
2647 * states that events when retransmit arrives after original data are rare.
2648 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
2649 * the biggest problem on large power networks even with minor reordering.
2650 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
2651 * up to bandwidth of 18Gigabit/sec. 8) ]
2652 */
2653
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002654static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002655{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002656 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002657 struct tcphdr *th = skb->h.th;
2658 u32 seq = TCP_SKB_CB(skb)->seq;
2659 u32 ack = TCP_SKB_CB(skb)->ack_seq;
2660
2661 return (/* 1. Pure ACK with correct sequence number. */
2662 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) &&
2663
2664 /* 2. ... and duplicate ACK. */
2665 ack == tp->snd_una &&
2666
2667 /* 3. ... and does not update window. */
2668 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) &&
2669
2670 /* 4. ... and sits in replay window. */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002671 (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 -07002672}
2673
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002674static inline int tcp_paws_discard(const struct sock *sk, const struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002675{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002676 const struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002677 return ((s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) > TCP_PAWS_WINDOW &&
2678 xtime.tv_sec < tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS &&
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002679 !tcp_disordered_ack(sk, skb));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002680}
2681
2682/* Check segment sequence number for validity.
2683 *
2684 * Segment controls are considered valid, if the segment
2685 * fits to the window after truncation to the window. Acceptability
2686 * of data (and SYN, FIN, of course) is checked separately.
2687 * See tcp_data_queue(), for example.
2688 *
2689 * Also, controls (RST is main one) are accepted using RCV.WUP instead
2690 * of RCV.NXT. Peer still did not advance his SND.UNA when we
2691 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
2692 * (borrowed from freebsd)
2693 */
2694
2695static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq)
2696{
2697 return !before(end_seq, tp->rcv_wup) &&
2698 !after(seq, tp->rcv_nxt + tcp_receive_window(tp));
2699}
2700
2701/* When we get a reset we do this. */
2702static void tcp_reset(struct sock *sk)
2703{
2704 /* We want the right error as BSD sees it (and indeed as we do). */
2705 switch (sk->sk_state) {
2706 case TCP_SYN_SENT:
2707 sk->sk_err = ECONNREFUSED;
2708 break;
2709 case TCP_CLOSE_WAIT:
2710 sk->sk_err = EPIPE;
2711 break;
2712 case TCP_CLOSE:
2713 return;
2714 default:
2715 sk->sk_err = ECONNRESET;
2716 }
2717
2718 if (!sock_flag(sk, SOCK_DEAD))
2719 sk->sk_error_report(sk);
2720
2721 tcp_done(sk);
2722}
2723
2724/*
2725 * Process the FIN bit. This now behaves as it is supposed to work
2726 * and the FIN takes effect when it is validly part of sequence
2727 * space. Not before when we get holes.
2728 *
2729 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
2730 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
2731 * TIME-WAIT)
2732 *
2733 * If we are in FINWAIT-1, a received FIN indicates simultaneous
2734 * close and we go into CLOSING (and later onto TIME-WAIT)
2735 *
2736 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
2737 */
2738static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th)
2739{
2740 struct tcp_sock *tp = tcp_sk(sk);
2741
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002742 inet_csk_schedule_ack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002743
2744 sk->sk_shutdown |= RCV_SHUTDOWN;
2745 sock_set_flag(sk, SOCK_DONE);
2746
2747 switch (sk->sk_state) {
2748 case TCP_SYN_RECV:
2749 case TCP_ESTABLISHED:
2750 /* Move to CLOSE_WAIT */
2751 tcp_set_state(sk, TCP_CLOSE_WAIT);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002752 inet_csk(sk)->icsk_ack.pingpong = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002753 break;
2754
2755 case TCP_CLOSE_WAIT:
2756 case TCP_CLOSING:
2757 /* Received a retransmission of the FIN, do
2758 * nothing.
2759 */
2760 break;
2761 case TCP_LAST_ACK:
2762 /* RFC793: Remain in the LAST-ACK state. */
2763 break;
2764
2765 case TCP_FIN_WAIT1:
2766 /* This case occurs when a simultaneous close
2767 * happens, we must ack the received FIN and
2768 * enter the CLOSING state.
2769 */
2770 tcp_send_ack(sk);
2771 tcp_set_state(sk, TCP_CLOSING);
2772 break;
2773 case TCP_FIN_WAIT2:
2774 /* Received a FIN -- send ACK and enter TIME_WAIT. */
2775 tcp_send_ack(sk);
2776 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
2777 break;
2778 default:
2779 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
2780 * cases we should never reach this piece of code.
2781 */
2782 printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n",
2783 __FUNCTION__, sk->sk_state);
2784 break;
2785 };
2786
2787 /* It _is_ possible, that we have something out-of-order _after_ FIN.
2788 * Probably, we should reset in this case. For now drop them.
2789 */
2790 __skb_queue_purge(&tp->out_of_order_queue);
2791 if (tp->rx_opt.sack_ok)
2792 tcp_sack_reset(&tp->rx_opt);
2793 sk_stream_mem_reclaim(sk);
2794
2795 if (!sock_flag(sk, SOCK_DEAD)) {
2796 sk->sk_state_change(sk);
2797
2798 /* Do not send POLL_HUP for half duplex close. */
2799 if (sk->sk_shutdown == SHUTDOWN_MASK ||
2800 sk->sk_state == TCP_CLOSE)
2801 sk_wake_async(sk, 1, POLL_HUP);
2802 else
2803 sk_wake_async(sk, 1, POLL_IN);
2804 }
2805}
2806
2807static __inline__ int
2808tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, u32 end_seq)
2809{
2810 if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) {
2811 if (before(seq, sp->start_seq))
2812 sp->start_seq = seq;
2813 if (after(end_seq, sp->end_seq))
2814 sp->end_seq = end_seq;
2815 return 1;
2816 }
2817 return 0;
2818}
2819
2820static inline void tcp_dsack_set(struct tcp_sock *tp, u32 seq, u32 end_seq)
2821{
2822 if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) {
2823 if (before(seq, tp->rcv_nxt))
2824 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT);
2825 else
2826 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT);
2827
2828 tp->rx_opt.dsack = 1;
2829 tp->duplicate_sack[0].start_seq = seq;
2830 tp->duplicate_sack[0].end_seq = end_seq;
2831 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + 1, 4 - tp->rx_opt.tstamp_ok);
2832 }
2833}
2834
2835static inline void tcp_dsack_extend(struct tcp_sock *tp, u32 seq, u32 end_seq)
2836{
2837 if (!tp->rx_opt.dsack)
2838 tcp_dsack_set(tp, seq, end_seq);
2839 else
2840 tcp_sack_extend(tp->duplicate_sack, seq, end_seq);
2841}
2842
2843static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb)
2844{
2845 struct tcp_sock *tp = tcp_sk(sk);
2846
2847 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
2848 before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
2849 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002850 tcp_enter_quickack_mode(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002851
2852 if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) {
2853 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
2854
2855 if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))
2856 end_seq = tp->rcv_nxt;
2857 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, end_seq);
2858 }
2859 }
2860
2861 tcp_send_ack(sk);
2862}
2863
2864/* These routines update the SACK block as out-of-order packets arrive or
2865 * in-order packets close up the sequence space.
2866 */
2867static void tcp_sack_maybe_coalesce(struct tcp_sock *tp)
2868{
2869 int this_sack;
2870 struct tcp_sack_block *sp = &tp->selective_acks[0];
2871 struct tcp_sack_block *swalk = sp+1;
2872
2873 /* See if the recent change to the first SACK eats into
2874 * or hits the sequence space of other SACK blocks, if so coalesce.
2875 */
2876 for (this_sack = 1; this_sack < tp->rx_opt.num_sacks; ) {
2877 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) {
2878 int i;
2879
2880 /* Zap SWALK, by moving every further SACK up by one slot.
2881 * Decrease num_sacks.
2882 */
2883 tp->rx_opt.num_sacks--;
2884 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
2885 for(i=this_sack; i < tp->rx_opt.num_sacks; i++)
2886 sp[i] = sp[i+1];
2887 continue;
2888 }
2889 this_sack++, swalk++;
2890 }
2891}
2892
2893static __inline__ void tcp_sack_swap(struct tcp_sack_block *sack1, struct tcp_sack_block *sack2)
2894{
2895 __u32 tmp;
2896
2897 tmp = sack1->start_seq;
2898 sack1->start_seq = sack2->start_seq;
2899 sack2->start_seq = tmp;
2900
2901 tmp = sack1->end_seq;
2902 sack1->end_seq = sack2->end_seq;
2903 sack2->end_seq = tmp;
2904}
2905
2906static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq)
2907{
2908 struct tcp_sock *tp = tcp_sk(sk);
2909 struct tcp_sack_block *sp = &tp->selective_acks[0];
2910 int cur_sacks = tp->rx_opt.num_sacks;
2911 int this_sack;
2912
2913 if (!cur_sacks)
2914 goto new_sack;
2915
2916 for (this_sack=0; this_sack<cur_sacks; this_sack++, sp++) {
2917 if (tcp_sack_extend(sp, seq, end_seq)) {
2918 /* Rotate this_sack to the first one. */
2919 for (; this_sack>0; this_sack--, sp--)
2920 tcp_sack_swap(sp, sp-1);
2921 if (cur_sacks > 1)
2922 tcp_sack_maybe_coalesce(tp);
2923 return;
2924 }
2925 }
2926
2927 /* Could not find an adjacent existing SACK, build a new one,
2928 * put it at the front, and shift everyone else down. We
2929 * always know there is at least one SACK present already here.
2930 *
2931 * If the sack array is full, forget about the last one.
2932 */
2933 if (this_sack >= 4) {
2934 this_sack--;
2935 tp->rx_opt.num_sacks--;
2936 sp--;
2937 }
2938 for(; this_sack > 0; this_sack--, sp--)
2939 *sp = *(sp-1);
2940
2941new_sack:
2942 /* Build the new head SACK, and we're done. */
2943 sp->start_seq = seq;
2944 sp->end_seq = end_seq;
2945 tp->rx_opt.num_sacks++;
2946 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
2947}
2948
2949/* RCV.NXT advances, some SACKs should be eaten. */
2950
2951static void tcp_sack_remove(struct tcp_sock *tp)
2952{
2953 struct tcp_sack_block *sp = &tp->selective_acks[0];
2954 int num_sacks = tp->rx_opt.num_sacks;
2955 int this_sack;
2956
2957 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
David S. Millerb03efcf2005-07-08 14:57:23 -07002958 if (skb_queue_empty(&tp->out_of_order_queue)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002959 tp->rx_opt.num_sacks = 0;
2960 tp->rx_opt.eff_sacks = tp->rx_opt.dsack;
2961 return;
2962 }
2963
2964 for(this_sack = 0; this_sack < num_sacks; ) {
2965 /* Check if the start of the sack is covered by RCV.NXT. */
2966 if (!before(tp->rcv_nxt, sp->start_seq)) {
2967 int i;
2968
2969 /* RCV.NXT must cover all the block! */
2970 BUG_TRAP(!before(tp->rcv_nxt, sp->end_seq));
2971
2972 /* Zap this SACK, by moving forward any other SACKS. */
2973 for (i=this_sack+1; i < num_sacks; i++)
2974 tp->selective_acks[i-1] = tp->selective_acks[i];
2975 num_sacks--;
2976 continue;
2977 }
2978 this_sack++;
2979 sp++;
2980 }
2981 if (num_sacks != tp->rx_opt.num_sacks) {
2982 tp->rx_opt.num_sacks = num_sacks;
2983 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
2984 }
2985}
2986
2987/* This one checks to see if we can put data from the
2988 * out_of_order queue into the receive_queue.
2989 */
2990static void tcp_ofo_queue(struct sock *sk)
2991{
2992 struct tcp_sock *tp = tcp_sk(sk);
2993 __u32 dsack_high = tp->rcv_nxt;
2994 struct sk_buff *skb;
2995
2996 while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) {
2997 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
2998 break;
2999
3000 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) {
3001 __u32 dsack = dsack_high;
3002 if (before(TCP_SKB_CB(skb)->end_seq, dsack_high))
3003 dsack_high = TCP_SKB_CB(skb)->end_seq;
3004 tcp_dsack_extend(tp, TCP_SKB_CB(skb)->seq, dsack);
3005 }
3006
3007 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
3008 SOCK_DEBUG(sk, "ofo packet was already received \n");
David S. Miller8728b832005-08-09 19:25:21 -07003009 __skb_unlink(skb, &tp->out_of_order_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003010 __kfree_skb(skb);
3011 continue;
3012 }
3013 SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n",
3014 tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
3015 TCP_SKB_CB(skb)->end_seq);
3016
David S. Miller8728b832005-08-09 19:25:21 -07003017 __skb_unlink(skb, &tp->out_of_order_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003018 __skb_queue_tail(&sk->sk_receive_queue, skb);
3019 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3020 if(skb->h.th->fin)
3021 tcp_fin(skb, sk, skb->h.th);
3022 }
3023}
3024
3025static int tcp_prune_queue(struct sock *sk);
3026
3027static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
3028{
3029 struct tcphdr *th = skb->h.th;
3030 struct tcp_sock *tp = tcp_sk(sk);
3031 int eaten = -1;
3032
3033 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq)
3034 goto drop;
3035
Linus Torvalds1da177e2005-04-16 15:20:36 -07003036 __skb_pull(skb, th->doff*4);
3037
3038 TCP_ECN_accept_cwr(tp, skb);
3039
3040 if (tp->rx_opt.dsack) {
3041 tp->rx_opt.dsack = 0;
3042 tp->rx_opt.eff_sacks = min_t(unsigned int, tp->rx_opt.num_sacks,
3043 4 - tp->rx_opt.tstamp_ok);
3044 }
3045
3046 /* Queue data for delivery to the user.
3047 * Packets in sequence go to the receive queue.
3048 * Out of sequence packets to the out_of_order_queue.
3049 */
3050 if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
3051 if (tcp_receive_window(tp) == 0)
3052 goto out_of_window;
3053
3054 /* Ok. In sequence. In window. */
3055 if (tp->ucopy.task == current &&
3056 tp->copied_seq == tp->rcv_nxt && tp->ucopy.len &&
3057 sock_owned_by_user(sk) && !tp->urg_data) {
3058 int chunk = min_t(unsigned int, skb->len,
3059 tp->ucopy.len);
3060
3061 __set_current_state(TASK_RUNNING);
3062
3063 local_bh_enable();
3064 if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) {
3065 tp->ucopy.len -= chunk;
3066 tp->copied_seq += chunk;
3067 eaten = (chunk == skb->len && !th->fin);
3068 tcp_rcv_space_adjust(sk);
3069 }
3070 local_bh_disable();
3071 }
3072
3073 if (eaten <= 0) {
3074queue_and_out:
3075 if (eaten < 0 &&
3076 (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
3077 !sk_stream_rmem_schedule(sk, skb))) {
3078 if (tcp_prune_queue(sk) < 0 ||
3079 !sk_stream_rmem_schedule(sk, skb))
3080 goto drop;
3081 }
3082 sk_stream_set_owner_r(skb, sk);
3083 __skb_queue_tail(&sk->sk_receive_queue, skb);
3084 }
3085 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3086 if(skb->len)
3087 tcp_event_data_recv(sk, tp, skb);
3088 if(th->fin)
3089 tcp_fin(skb, sk, th);
3090
David S. Millerb03efcf2005-07-08 14:57:23 -07003091 if (!skb_queue_empty(&tp->out_of_order_queue)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003092 tcp_ofo_queue(sk);
3093
3094 /* RFC2581. 4.2. SHOULD send immediate ACK, when
3095 * gap in queue is filled.
3096 */
David S. Millerb03efcf2005-07-08 14:57:23 -07003097 if (skb_queue_empty(&tp->out_of_order_queue))
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003098 inet_csk(sk)->icsk_ack.pingpong = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003099 }
3100
3101 if (tp->rx_opt.num_sacks)
3102 tcp_sack_remove(tp);
3103
3104 tcp_fast_path_check(sk, tp);
3105
3106 if (eaten > 0)
3107 __kfree_skb(skb);
3108 else if (!sock_flag(sk, SOCK_DEAD))
3109 sk->sk_data_ready(sk, 0);
3110 return;
3111 }
3112
3113 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
3114 /* A retransmit, 2nd most common case. Force an immediate ack. */
3115 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST);
3116 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
3117
3118out_of_window:
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003119 tcp_enter_quickack_mode(sk);
3120 inet_csk_schedule_ack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003121drop:
3122 __kfree_skb(skb);
3123 return;
3124 }
3125
3126 /* Out of window. F.e. zero window probe. */
3127 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp)))
3128 goto out_of_window;
3129
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003130 tcp_enter_quickack_mode(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003131
3132 if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
3133 /* Partial packet, seq < rcv_next < end_seq */
3134 SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n",
3135 tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
3136 TCP_SKB_CB(skb)->end_seq);
3137
3138 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, tp->rcv_nxt);
3139
3140 /* If window is closed, drop tail of packet. But after
3141 * remembering D-SACK for its head made in previous line.
3142 */
3143 if (!tcp_receive_window(tp))
3144 goto out_of_window;
3145 goto queue_and_out;
3146 }
3147
3148 TCP_ECN_check_ce(tp, skb);
3149
3150 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
3151 !sk_stream_rmem_schedule(sk, skb)) {
3152 if (tcp_prune_queue(sk) < 0 ||
3153 !sk_stream_rmem_schedule(sk, skb))
3154 goto drop;
3155 }
3156
3157 /* Disable header prediction. */
3158 tp->pred_flags = 0;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003159 inet_csk_schedule_ack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003160
3161 SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n",
3162 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
3163
3164 sk_stream_set_owner_r(skb, sk);
3165
3166 if (!skb_peek(&tp->out_of_order_queue)) {
3167 /* Initial out of order segment, build 1 SACK. */
3168 if (tp->rx_opt.sack_ok) {
3169 tp->rx_opt.num_sacks = 1;
3170 tp->rx_opt.dsack = 0;
3171 tp->rx_opt.eff_sacks = 1;
3172 tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
3173 tp->selective_acks[0].end_seq =
3174 TCP_SKB_CB(skb)->end_seq;
3175 }
3176 __skb_queue_head(&tp->out_of_order_queue,skb);
3177 } else {
3178 struct sk_buff *skb1 = tp->out_of_order_queue.prev;
3179 u32 seq = TCP_SKB_CB(skb)->seq;
3180 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
3181
3182 if (seq == TCP_SKB_CB(skb1)->end_seq) {
David S. Miller8728b832005-08-09 19:25:21 -07003183 __skb_append(skb1, skb, &tp->out_of_order_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003184
3185 if (!tp->rx_opt.num_sacks ||
3186 tp->selective_acks[0].end_seq != seq)
3187 goto add_sack;
3188
3189 /* Common case: data arrive in order after hole. */
3190 tp->selective_acks[0].end_seq = end_seq;
3191 return;
3192 }
3193
3194 /* Find place to insert this segment. */
3195 do {
3196 if (!after(TCP_SKB_CB(skb1)->seq, seq))
3197 break;
3198 } while ((skb1 = skb1->prev) !=
3199 (struct sk_buff*)&tp->out_of_order_queue);
3200
3201 /* Do skb overlap to previous one? */
3202 if (skb1 != (struct sk_buff*)&tp->out_of_order_queue &&
3203 before(seq, TCP_SKB_CB(skb1)->end_seq)) {
3204 if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
3205 /* All the bits are present. Drop. */
3206 __kfree_skb(skb);
3207 tcp_dsack_set(tp, seq, end_seq);
3208 goto add_sack;
3209 }
3210 if (after(seq, TCP_SKB_CB(skb1)->seq)) {
3211 /* Partial overlap. */
3212 tcp_dsack_set(tp, seq, TCP_SKB_CB(skb1)->end_seq);
3213 } else {
3214 skb1 = skb1->prev;
3215 }
3216 }
3217 __skb_insert(skb, skb1, skb1->next, &tp->out_of_order_queue);
3218
3219 /* And clean segments covered by new one as whole. */
3220 while ((skb1 = skb->next) !=
3221 (struct sk_buff*)&tp->out_of_order_queue &&
3222 after(end_seq, TCP_SKB_CB(skb1)->seq)) {
3223 if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
3224 tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, end_seq);
3225 break;
3226 }
David S. Miller8728b832005-08-09 19:25:21 -07003227 __skb_unlink(skb1, &tp->out_of_order_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003228 tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, TCP_SKB_CB(skb1)->end_seq);
3229 __kfree_skb(skb1);
3230 }
3231
3232add_sack:
3233 if (tp->rx_opt.sack_ok)
3234 tcp_sack_new_ofo_skb(sk, seq, end_seq);
3235 }
3236}
3237
3238/* Collapse contiguous sequence of skbs head..tail with
3239 * sequence numbers start..end.
3240 * Segments with FIN/SYN are not collapsed (only because this
3241 * simplifies code)
3242 */
3243static void
David S. Miller8728b832005-08-09 19:25:21 -07003244tcp_collapse(struct sock *sk, struct sk_buff_head *list,
3245 struct sk_buff *head, struct sk_buff *tail,
3246 u32 start, u32 end)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003247{
3248 struct sk_buff *skb;
3249
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08003250 /* First, check that queue is collapsible and find
Linus Torvalds1da177e2005-04-16 15:20:36 -07003251 * the point where collapsing can be useful. */
3252 for (skb = head; skb != tail; ) {
3253 /* No new bits? It is possible on ofo queue. */
3254 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
3255 struct sk_buff *next = skb->next;
David S. Miller8728b832005-08-09 19:25:21 -07003256 __skb_unlink(skb, list);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003257 __kfree_skb(skb);
3258 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED);
3259 skb = next;
3260 continue;
3261 }
3262
3263 /* The first skb to collapse is:
3264 * - not SYN/FIN and
3265 * - bloated or contains data before "start" or
3266 * overlaps to the next one.
3267 */
3268 if (!skb->h.th->syn && !skb->h.th->fin &&
3269 (tcp_win_from_space(skb->truesize) > skb->len ||
3270 before(TCP_SKB_CB(skb)->seq, start) ||
3271 (skb->next != tail &&
3272 TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb->next)->seq)))
3273 break;
3274
3275 /* Decided to skip this, advance start seq. */
3276 start = TCP_SKB_CB(skb)->end_seq;
3277 skb = skb->next;
3278 }
3279 if (skb == tail || skb->h.th->syn || skb->h.th->fin)
3280 return;
3281
3282 while (before(start, end)) {
3283 struct sk_buff *nskb;
3284 int header = skb_headroom(skb);
3285 int copy = SKB_MAX_ORDER(header, 0);
3286
3287 /* Too big header? This can happen with IPv6. */
3288 if (copy < 0)
3289 return;
3290 if (end-start < copy)
3291 copy = end-start;
3292 nskb = alloc_skb(copy+header, GFP_ATOMIC);
3293 if (!nskb)
3294 return;
3295 skb_reserve(nskb, header);
3296 memcpy(nskb->head, skb->head, header);
3297 nskb->nh.raw = nskb->head + (skb->nh.raw-skb->head);
3298 nskb->h.raw = nskb->head + (skb->h.raw-skb->head);
3299 nskb->mac.raw = nskb->head + (skb->mac.raw-skb->head);
3300 memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
3301 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start;
David S. Miller8728b832005-08-09 19:25:21 -07003302 __skb_insert(nskb, skb->prev, skb, list);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003303 sk_stream_set_owner_r(nskb, sk);
3304
3305 /* Copy data, releasing collapsed skbs. */
3306 while (copy > 0) {
3307 int offset = start - TCP_SKB_CB(skb)->seq;
3308 int size = TCP_SKB_CB(skb)->end_seq - start;
3309
3310 if (offset < 0) BUG();
3311 if (size > 0) {
3312 size = min(copy, size);
3313 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size))
3314 BUG();
3315 TCP_SKB_CB(nskb)->end_seq += size;
3316 copy -= size;
3317 start += size;
3318 }
3319 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
3320 struct sk_buff *next = skb->next;
David S. Miller8728b832005-08-09 19:25:21 -07003321 __skb_unlink(skb, list);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003322 __kfree_skb(skb);
3323 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED);
3324 skb = next;
3325 if (skb == tail || skb->h.th->syn || skb->h.th->fin)
3326 return;
3327 }
3328 }
3329 }
3330}
3331
3332/* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
3333 * and tcp_collapse() them until all the queue is collapsed.
3334 */
3335static void tcp_collapse_ofo_queue(struct sock *sk)
3336{
3337 struct tcp_sock *tp = tcp_sk(sk);
3338 struct sk_buff *skb = skb_peek(&tp->out_of_order_queue);
3339 struct sk_buff *head;
3340 u32 start, end;
3341
3342 if (skb == NULL)
3343 return;
3344
3345 start = TCP_SKB_CB(skb)->seq;
3346 end = TCP_SKB_CB(skb)->end_seq;
3347 head = skb;
3348
3349 for (;;) {
3350 skb = skb->next;
3351
3352 /* Segment is terminated when we see gap or when
3353 * we are at the end of all the queue. */
3354 if (skb == (struct sk_buff *)&tp->out_of_order_queue ||
3355 after(TCP_SKB_CB(skb)->seq, end) ||
3356 before(TCP_SKB_CB(skb)->end_seq, start)) {
David S. Miller8728b832005-08-09 19:25:21 -07003357 tcp_collapse(sk, &tp->out_of_order_queue,
3358 head, skb, start, end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003359 head = skb;
3360 if (skb == (struct sk_buff *)&tp->out_of_order_queue)
3361 break;
3362 /* Start new segment */
3363 start = TCP_SKB_CB(skb)->seq;
3364 end = TCP_SKB_CB(skb)->end_seq;
3365 } else {
3366 if (before(TCP_SKB_CB(skb)->seq, start))
3367 start = TCP_SKB_CB(skb)->seq;
3368 if (after(TCP_SKB_CB(skb)->end_seq, end))
3369 end = TCP_SKB_CB(skb)->end_seq;
3370 }
3371 }
3372}
3373
3374/* Reduce allocated memory if we can, trying to get
3375 * the socket within its memory limits again.
3376 *
3377 * Return less than zero if we should start dropping frames
3378 * until the socket owning process reads some of the data
3379 * to stabilize the situation.
3380 */
3381static int tcp_prune_queue(struct sock *sk)
3382{
3383 struct tcp_sock *tp = tcp_sk(sk);
3384
3385 SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq);
3386
3387 NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED);
3388
3389 if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
3390 tcp_clamp_window(sk, tp);
3391 else if (tcp_memory_pressure)
3392 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss);
3393
3394 tcp_collapse_ofo_queue(sk);
David S. Miller8728b832005-08-09 19:25:21 -07003395 tcp_collapse(sk, &sk->sk_receive_queue,
3396 sk->sk_receive_queue.next,
Linus Torvalds1da177e2005-04-16 15:20:36 -07003397 (struct sk_buff*)&sk->sk_receive_queue,
3398 tp->copied_seq, tp->rcv_nxt);
3399 sk_stream_mem_reclaim(sk);
3400
3401 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
3402 return 0;
3403
3404 /* Collapsing did not help, destructive actions follow.
3405 * This must not ever occur. */
3406
3407 /* First, purge the out_of_order queue. */
David S. Millerb03efcf2005-07-08 14:57:23 -07003408 if (!skb_queue_empty(&tp->out_of_order_queue)) {
3409 NET_INC_STATS_BH(LINUX_MIB_OFOPRUNED);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003410 __skb_queue_purge(&tp->out_of_order_queue);
3411
3412 /* Reset SACK state. A conforming SACK implementation will
3413 * do the same at a timeout based retransmit. When a connection
3414 * is in a sad state like this, we care only about integrity
3415 * of the connection not performance.
3416 */
3417 if (tp->rx_opt.sack_ok)
3418 tcp_sack_reset(&tp->rx_opt);
3419 sk_stream_mem_reclaim(sk);
3420 }
3421
3422 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
3423 return 0;
3424
3425 /* If we are really being abused, tell the caller to silently
3426 * drop receive data on the floor. It will get retransmitted
3427 * and hopefully then we'll have sufficient space.
3428 */
3429 NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED);
3430
3431 /* Massive buffer overcommit. */
3432 tp->pred_flags = 0;
3433 return -1;
3434}
3435
3436
3437/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
3438 * As additional protections, we do not touch cwnd in retransmission phases,
3439 * and if application hit its sndbuf limit recently.
3440 */
3441void tcp_cwnd_application_limited(struct sock *sk)
3442{
3443 struct tcp_sock *tp = tcp_sk(sk);
3444
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003445 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07003446 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
3447 /* Limited by application or receiver window. */
3448 u32 win_used = max(tp->snd_cwnd_used, 2U);
3449 if (win_used < tp->snd_cwnd) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003450 tp->snd_ssthresh = tcp_current_ssthresh(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003451 tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
3452 }
3453 tp->snd_cwnd_used = 0;
3454 }
3455 tp->snd_cwnd_stamp = tcp_time_stamp;
3456}
3457
David S. Miller0d9901d2005-07-05 15:21:10 -07003458static inline int tcp_should_expand_sndbuf(struct sock *sk, struct tcp_sock *tp)
3459{
3460 /* If the user specified a specific send buffer setting, do
3461 * not modify it.
3462 */
3463 if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
3464 return 0;
3465
3466 /* If we are under global TCP memory pressure, do not expand. */
3467 if (tcp_memory_pressure)
3468 return 0;
3469
3470 /* If we are under soft global TCP memory pressure, do not expand. */
3471 if (atomic_read(&tcp_memory_allocated) >= sysctl_tcp_mem[0])
3472 return 0;
3473
3474 /* If we filled the congestion window, do not expand. */
3475 if (tp->packets_out >= tp->snd_cwnd)
3476 return 0;
3477
3478 return 1;
3479}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003480
3481/* When incoming ACK allowed to free some skb from write_queue,
3482 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
3483 * on the exit from tcp input handler.
3484 *
3485 * PROBLEM: sndbuf expansion does not work well with largesend.
3486 */
3487static void tcp_new_space(struct sock *sk)
3488{
3489 struct tcp_sock *tp = tcp_sk(sk);
3490
David S. Miller0d9901d2005-07-05 15:21:10 -07003491 if (tcp_should_expand_sndbuf(sk, tp)) {
David S. Millerc1b4a7e2005-07-05 15:24:38 -07003492 int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) +
Linus Torvalds1da177e2005-04-16 15:20:36 -07003493 MAX_TCP_HEADER + 16 + sizeof(struct sk_buff),
3494 demanded = max_t(unsigned int, tp->snd_cwnd,
3495 tp->reordering + 1);
3496 sndmem *= 2*demanded;
3497 if (sndmem > sk->sk_sndbuf)
3498 sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]);
3499 tp->snd_cwnd_stamp = tcp_time_stamp;
3500 }
3501
3502 sk->sk_write_space(sk);
3503}
3504
3505static inline void tcp_check_space(struct sock *sk)
3506{
3507 if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
3508 sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
3509 if (sk->sk_socket &&
3510 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
3511 tcp_new_space(sk);
3512 }
3513}
3514
David S. Miller55c97f32005-07-05 15:19:38 -07003515static __inline__ void tcp_data_snd_check(struct sock *sk, struct tcp_sock *tp)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003516{
David S. Miller55c97f32005-07-05 15:19:38 -07003517 tcp_push_pending_frames(sk, tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003518 tcp_check_space(sk);
3519}
3520
3521/*
3522 * Check if sending an ack is needed.
3523 */
3524static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
3525{
3526 struct tcp_sock *tp = tcp_sk(sk);
3527
3528 /* More than one full frame received... */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003529 if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss
Linus Torvalds1da177e2005-04-16 15:20:36 -07003530 /* ... and right edge of window advances far enough.
3531 * (tcp_recvmsg() will send ACK otherwise). Or...
3532 */
3533 && __tcp_select_window(sk) >= tp->rcv_wnd) ||
3534 /* We ACK each frame or... */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003535 tcp_in_quickack_mode(sk) ||
Linus Torvalds1da177e2005-04-16 15:20:36 -07003536 /* We have out of order data. */
3537 (ofo_possible &&
3538 skb_peek(&tp->out_of_order_queue))) {
3539 /* Then ack it now */
3540 tcp_send_ack(sk);
3541 } else {
3542 /* Else, send delayed ack. */
3543 tcp_send_delayed_ack(sk);
3544 }
3545}
3546
3547static __inline__ void tcp_ack_snd_check(struct sock *sk)
3548{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003549 if (!inet_csk_ack_scheduled(sk)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003550 /* We sent a data segment already. */
3551 return;
3552 }
3553 __tcp_ack_snd_check(sk, 1);
3554}
3555
3556/*
3557 * This routine is only called when we have urgent data
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08003558 * signaled. Its the 'slow' part of tcp_urg. It could be
Linus Torvalds1da177e2005-04-16 15:20:36 -07003559 * moved inline now as tcp_urg is only called from one
3560 * place. We handle URGent data wrong. We have to - as
3561 * BSD still doesn't use the correction from RFC961.
3562 * For 1003.1g we should support a new option TCP_STDURG to permit
3563 * either form (or just set the sysctl tcp_stdurg).
3564 */
3565
3566static void tcp_check_urg(struct sock * sk, struct tcphdr * th)
3567{
3568 struct tcp_sock *tp = tcp_sk(sk);
3569 u32 ptr = ntohs(th->urg_ptr);
3570
3571 if (ptr && !sysctl_tcp_stdurg)
3572 ptr--;
3573 ptr += ntohl(th->seq);
3574
3575 /* Ignore urgent data that we've already seen and read. */
3576 if (after(tp->copied_seq, ptr))
3577 return;
3578
3579 /* Do not replay urg ptr.
3580 *
3581 * NOTE: interesting situation not covered by specs.
3582 * Misbehaving sender may send urg ptr, pointing to segment,
3583 * which we already have in ofo queue. We are not able to fetch
3584 * such data and will stay in TCP_URG_NOTYET until will be eaten
3585 * by recvmsg(). Seems, we are not obliged to handle such wicked
3586 * situations. But it is worth to think about possibility of some
3587 * DoSes using some hypothetical application level deadlock.
3588 */
3589 if (before(ptr, tp->rcv_nxt))
3590 return;
3591
3592 /* Do we already have a newer (or duplicate) urgent pointer? */
3593 if (tp->urg_data && !after(ptr, tp->urg_seq))
3594 return;
3595
3596 /* Tell the world about our new urgent pointer. */
3597 sk_send_sigurg(sk);
3598
3599 /* We may be adding urgent data when the last byte read was
3600 * urgent. To do this requires some care. We cannot just ignore
3601 * tp->copied_seq since we would read the last urgent byte again
3602 * as data, nor can we alter copied_seq until this data arrives
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08003603 * or we break the semantics of SIOCATMARK (and thus sockatmark())
Linus Torvalds1da177e2005-04-16 15:20:36 -07003604 *
3605 * NOTE. Double Dutch. Rendering to plain English: author of comment
3606 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
3607 * and expect that both A and B disappear from stream. This is _wrong_.
3608 * Though this happens in BSD with high probability, this is occasional.
3609 * Any application relying on this is buggy. Note also, that fix "works"
3610 * only in this artificial test. Insert some normal data between A and B and we will
3611 * decline of BSD again. Verdict: it is better to remove to trap
3612 * buggy users.
3613 */
3614 if (tp->urg_seq == tp->copied_seq && tp->urg_data &&
3615 !sock_flag(sk, SOCK_URGINLINE) &&
3616 tp->copied_seq != tp->rcv_nxt) {
3617 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
3618 tp->copied_seq++;
3619 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) {
David S. Miller8728b832005-08-09 19:25:21 -07003620 __skb_unlink(skb, &sk->sk_receive_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003621 __kfree_skb(skb);
3622 }
3623 }
3624
3625 tp->urg_data = TCP_URG_NOTYET;
3626 tp->urg_seq = ptr;
3627
3628 /* Disable header prediction. */
3629 tp->pred_flags = 0;
3630}
3631
3632/* This is the 'fast' part of urgent handling. */
3633static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th)
3634{
3635 struct tcp_sock *tp = tcp_sk(sk);
3636
3637 /* Check if we get a new urgent pointer - normally not. */
3638 if (th->urg)
3639 tcp_check_urg(sk,th);
3640
3641 /* Do we wait for any urgent data? - normally not... */
3642 if (tp->urg_data == TCP_URG_NOTYET) {
3643 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) -
3644 th->syn;
3645
3646 /* Is the urgent pointer pointing into this packet? */
3647 if (ptr < skb->len) {
3648 u8 tmp;
3649 if (skb_copy_bits(skb, ptr, &tmp, 1))
3650 BUG();
3651 tp->urg_data = TCP_URG_VALID | tmp;
3652 if (!sock_flag(sk, SOCK_DEAD))
3653 sk->sk_data_ready(sk, 0);
3654 }
3655 }
3656}
3657
3658static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen)
3659{
3660 struct tcp_sock *tp = tcp_sk(sk);
3661 int chunk = skb->len - hlen;
3662 int err;
3663
3664 local_bh_enable();
3665 if (skb->ip_summed==CHECKSUM_UNNECESSARY)
3666 err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk);
3667 else
3668 err = skb_copy_and_csum_datagram_iovec(skb, hlen,
3669 tp->ucopy.iov);
3670
3671 if (!err) {
3672 tp->ucopy.len -= chunk;
3673 tp->copied_seq += chunk;
3674 tcp_rcv_space_adjust(sk);
3675 }
3676
3677 local_bh_disable();
3678 return err;
3679}
3680
3681static int __tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb)
3682{
3683 int result;
3684
3685 if (sock_owned_by_user(sk)) {
3686 local_bh_enable();
3687 result = __tcp_checksum_complete(skb);
3688 local_bh_disable();
3689 } else {
3690 result = __tcp_checksum_complete(skb);
3691 }
3692 return result;
3693}
3694
3695static __inline__ int
3696tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb)
3697{
3698 return skb->ip_summed != CHECKSUM_UNNECESSARY &&
3699 __tcp_checksum_complete_user(sk, skb);
3700}
3701
3702/*
3703 * TCP receive function for the ESTABLISHED state.
3704 *
3705 * It is split into a fast path and a slow path. The fast path is
3706 * disabled when:
3707 * - A zero window was announced from us - zero window probing
3708 * is only handled properly in the slow path.
3709 * - Out of order segments arrived.
3710 * - Urgent data is expected.
3711 * - There is no buffer space left
3712 * - Unexpected TCP flags/window values/header lengths are received
3713 * (detected by checking the TCP header against pred_flags)
3714 * - Data is sent in both directions. Fast path only supports pure senders
3715 * or pure receivers (this means either the sequence number or the ack
3716 * value must stay constant)
3717 * - Unexpected TCP option.
3718 *
3719 * When these conditions are not satisfied it drops into a standard
3720 * receive procedure patterned after RFC793 to handle all cases.
3721 * The first three cases are guaranteed by proper pred_flags setting,
3722 * the rest is checked inline. Fast processing is turned on in
3723 * tcp_data_queue when everything is OK.
3724 */
3725int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
3726 struct tcphdr *th, unsigned len)
3727{
3728 struct tcp_sock *tp = tcp_sk(sk);
3729
3730 /*
3731 * Header prediction.
3732 * The code loosely follows the one in the famous
3733 * "30 instruction TCP receive" Van Jacobson mail.
3734 *
3735 * Van's trick is to deposit buffers into socket queue
3736 * on a device interrupt, to call tcp_recv function
3737 * on the receive process context and checksum and copy
3738 * the buffer to user space. smart...
3739 *
3740 * Our current scheme is not silly either but we take the
3741 * extra cost of the net_bh soft interrupt processing...
3742 * We do checksum and copy also but from device to kernel.
3743 */
3744
3745 tp->rx_opt.saw_tstamp = 0;
3746
3747 /* pred_flags is 0xS?10 << 16 + snd_wnd
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08003748 * if header_prediction is to be made
Linus Torvalds1da177e2005-04-16 15:20:36 -07003749 * 'S' will always be tp->tcp_header_len >> 2
3750 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
3751 * turn it off (when there are holes in the receive
3752 * space for instance)
3753 * PSH flag is ignored.
3754 */
3755
3756 if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags &&
3757 TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
3758 int tcp_header_len = tp->tcp_header_len;
3759
3760 /* Timestamp header prediction: tcp_header_len
3761 * is automatically equal to th->doff*4 due to pred_flags
3762 * match.
3763 */
3764
3765 /* Check timestamp */
3766 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) {
3767 __u32 *ptr = (__u32 *)(th + 1);
3768
3769 /* No? Slow path! */
3770 if (*ptr != ntohl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
3771 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP))
3772 goto slow_path;
3773
3774 tp->rx_opt.saw_tstamp = 1;
3775 ++ptr;
3776 tp->rx_opt.rcv_tsval = ntohl(*ptr);
3777 ++ptr;
3778 tp->rx_opt.rcv_tsecr = ntohl(*ptr);
3779
3780 /* If PAWS failed, check it more carefully in slow path */
3781 if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0)
3782 goto slow_path;
3783
3784 /* DO NOT update ts_recent here, if checksum fails
3785 * and timestamp was corrupted part, it will result
3786 * in a hung connection since we will drop all
3787 * future packets due to the PAWS test.
3788 */
3789 }
3790
3791 if (len <= tcp_header_len) {
3792 /* Bulk data transfer: sender */
3793 if (len == tcp_header_len) {
3794 /* Predicted packet is in window by definition.
3795 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
3796 * Hence, check seq<=rcv_wup reduces to:
3797 */
3798 if (tcp_header_len ==
3799 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
3800 tp->rcv_nxt == tp->rcv_wup)
3801 tcp_store_ts_recent(tp);
3802
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003803 tcp_rcv_rtt_measure_ts(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003804
3805 /* We know that such packets are checksummed
3806 * on entry.
3807 */
3808 tcp_ack(sk, skb, 0);
3809 __kfree_skb(skb);
David S. Miller55c97f32005-07-05 15:19:38 -07003810 tcp_data_snd_check(sk, tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003811 return 0;
3812 } else { /* Header too small */
3813 TCP_INC_STATS_BH(TCP_MIB_INERRS);
3814 goto discard;
3815 }
3816 } else {
3817 int eaten = 0;
3818
3819 if (tp->ucopy.task == current &&
3820 tp->copied_seq == tp->rcv_nxt &&
3821 len - tcp_header_len <= tp->ucopy.len &&
3822 sock_owned_by_user(sk)) {
3823 __set_current_state(TASK_RUNNING);
3824
3825 if (!tcp_copy_to_iovec(sk, skb, tcp_header_len)) {
3826 /* Predicted packet is in window by definition.
3827 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
3828 * Hence, check seq<=rcv_wup reduces to:
3829 */
3830 if (tcp_header_len ==
3831 (sizeof(struct tcphdr) +
3832 TCPOLEN_TSTAMP_ALIGNED) &&
3833 tp->rcv_nxt == tp->rcv_wup)
3834 tcp_store_ts_recent(tp);
3835
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003836 tcp_rcv_rtt_measure_ts(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003837
3838 __skb_pull(skb, tcp_header_len);
3839 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3840 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER);
3841 eaten = 1;
3842 }
3843 }
3844 if (!eaten) {
3845 if (tcp_checksum_complete_user(sk, skb))
3846 goto csum_error;
3847
3848 /* Predicted packet is in window by definition.
3849 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
3850 * Hence, check seq<=rcv_wup reduces to:
3851 */
3852 if (tcp_header_len ==
3853 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
3854 tp->rcv_nxt == tp->rcv_wup)
3855 tcp_store_ts_recent(tp);
3856
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003857 tcp_rcv_rtt_measure_ts(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003858
3859 if ((int)skb->truesize > sk->sk_forward_alloc)
3860 goto step5;
3861
3862 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS);
3863
3864 /* Bulk data transfer: receiver */
3865 __skb_pull(skb,tcp_header_len);
3866 __skb_queue_tail(&sk->sk_receive_queue, skb);
3867 sk_stream_set_owner_r(skb, sk);
3868 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3869 }
3870
3871 tcp_event_data_recv(sk, tp, skb);
3872
3873 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) {
3874 /* Well, only one small jumplet in fast path... */
3875 tcp_ack(sk, skb, FLAG_DATA);
David S. Miller55c97f32005-07-05 15:19:38 -07003876 tcp_data_snd_check(sk, tp);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003877 if (!inet_csk_ack_scheduled(sk))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003878 goto no_ack;
3879 }
3880
David S. Miller31432412005-05-23 12:03:06 -07003881 __tcp_ack_snd_check(sk, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003882no_ack:
3883 if (eaten)
3884 __kfree_skb(skb);
3885 else
3886 sk->sk_data_ready(sk, 0);
3887 return 0;
3888 }
3889 }
3890
3891slow_path:
3892 if (len < (th->doff<<2) || tcp_checksum_complete_user(sk, skb))
3893 goto csum_error;
3894
3895 /*
3896 * RFC1323: H1. Apply PAWS check first.
3897 */
3898 if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003899 tcp_paws_discard(sk, skb)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003900 if (!th->rst) {
3901 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
3902 tcp_send_dupack(sk, skb);
3903 goto discard;
3904 }
3905 /* Resets are accepted even if PAWS failed.
3906
3907 ts_recent update must be made after we are sure
3908 that the packet is in window.
3909 */
3910 }
3911
3912 /*
3913 * Standard slow path.
3914 */
3915
3916 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
3917 /* RFC793, page 37: "In all states except SYN-SENT, all reset
3918 * (RST) segments are validated by checking their SEQ-fields."
3919 * And page 69: "If an incoming segment is not acceptable,
3920 * an acknowledgment should be sent in reply (unless the RST bit
3921 * is set, if so drop the segment and return)".
3922 */
3923 if (!th->rst)
3924 tcp_send_dupack(sk, skb);
3925 goto discard;
3926 }
3927
3928 if(th->rst) {
3929 tcp_reset(sk);
3930 goto discard;
3931 }
3932
3933 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
3934
3935 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
3936 TCP_INC_STATS_BH(TCP_MIB_INERRS);
3937 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN);
3938 tcp_reset(sk);
3939 return 1;
3940 }
3941
3942step5:
3943 if(th->ack)
3944 tcp_ack(sk, skb, FLAG_SLOWPATH);
3945
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003946 tcp_rcv_rtt_measure_ts(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003947
3948 /* Process urgent data. */
3949 tcp_urg(sk, skb, th);
3950
3951 /* step 7: process the segment text */
3952 tcp_data_queue(sk, skb);
3953
David S. Miller55c97f32005-07-05 15:19:38 -07003954 tcp_data_snd_check(sk, tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003955 tcp_ack_snd_check(sk);
3956 return 0;
3957
3958csum_error:
3959 TCP_INC_STATS_BH(TCP_MIB_INERRS);
3960
3961discard:
3962 __kfree_skb(skb);
3963 return 0;
3964}
3965
3966static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
3967 struct tcphdr *th, unsigned len)
3968{
3969 struct tcp_sock *tp = tcp_sk(sk);
3970 int saved_clamp = tp->rx_opt.mss_clamp;
3971
3972 tcp_parse_options(skb, &tp->rx_opt, 0);
3973
3974 if (th->ack) {
Arnaldo Carvalho de Melo295f7322005-08-09 20:11:56 -07003975 struct inet_connection_sock *icsk;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003976 /* rfc793:
3977 * "If the state is SYN-SENT then
3978 * first check the ACK bit
3979 * If the ACK bit is set
3980 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
3981 * a reset (unless the RST bit is set, if so drop
3982 * the segment and return)"
3983 *
3984 * We do not send data with SYN, so that RFC-correct
3985 * test reduces to:
3986 */
3987 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt)
3988 goto reset_and_undo;
3989
3990 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
3991 !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp,
3992 tcp_time_stamp)) {
3993 NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED);
3994 goto reset_and_undo;
3995 }
3996
3997 /* Now ACK is acceptable.
3998 *
3999 * "If the RST bit is set
4000 * If the ACK was acceptable then signal the user "error:
4001 * connection reset", drop the segment, enter CLOSED state,
4002 * delete TCB, and return."
4003 */
4004
4005 if (th->rst) {
4006 tcp_reset(sk);
4007 goto discard;
4008 }
4009
4010 /* rfc793:
4011 * "fifth, if neither of the SYN or RST bits is set then
4012 * drop the segment and return."
4013 *
4014 * See note below!
4015 * --ANK(990513)
4016 */
4017 if (!th->syn)
4018 goto discard_and_undo;
4019
4020 /* rfc793:
4021 * "If the SYN bit is on ...
4022 * are acceptable then ...
4023 * (our SYN has been ACKed), change the connection
4024 * state to ESTABLISHED..."
4025 */
4026
4027 TCP_ECN_rcv_synack(tp, th);
4028 if (tp->ecn_flags&TCP_ECN_OK)
4029 sock_set_flag(sk, SOCK_NO_LARGESEND);
4030
4031 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
4032 tcp_ack(sk, skb, FLAG_SLOWPATH);
4033
4034 /* Ok.. it's good. Set up sequence numbers and
4035 * move to established.
4036 */
4037 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
4038 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
4039
4040 /* RFC1323: The window in SYN & SYN/ACK segments is
4041 * never scaled.
4042 */
4043 tp->snd_wnd = ntohs(th->window);
4044 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, TCP_SKB_CB(skb)->seq);
4045
4046 if (!tp->rx_opt.wscale_ok) {
4047 tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0;
4048 tp->window_clamp = min(tp->window_clamp, 65535U);
4049 }
4050
4051 if (tp->rx_opt.saw_tstamp) {
4052 tp->rx_opt.tstamp_ok = 1;
4053 tp->tcp_header_len =
4054 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
4055 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
4056 tcp_store_ts_recent(tp);
4057 } else {
4058 tp->tcp_header_len = sizeof(struct tcphdr);
4059 }
4060
4061 if (tp->rx_opt.sack_ok && sysctl_tcp_fack)
4062 tp->rx_opt.sack_ok |= 2;
4063
4064 tcp_sync_mss(sk, tp->pmtu_cookie);
4065 tcp_initialize_rcv_mss(sk);
4066
4067 /* Remember, tcp_poll() does not lock socket!
4068 * Change state from SYN-SENT only after copied_seq
4069 * is initialized. */
4070 tp->copied_seq = tp->rcv_nxt;
4071 mb();
4072 tcp_set_state(sk, TCP_ESTABLISHED);
4073
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -08004074 icsk = inet_csk(sk);
4075
Linus Torvalds1da177e2005-04-16 15:20:36 -07004076 /* Make sure socket is routed, for correct metrics. */
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -08004077 icsk->icsk_af_ops->rebuild_header(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004078
4079 tcp_init_metrics(sk);
4080
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03004081 tcp_init_congestion_control(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -07004082
Linus Torvalds1da177e2005-04-16 15:20:36 -07004083 /* Prevent spurious tcp_cwnd_restart() on first data
4084 * packet.
4085 */
4086 tp->lsndtime = tcp_time_stamp;
4087
4088 tcp_init_buffer_space(sk);
4089
4090 if (sock_flag(sk, SOCK_KEEPOPEN))
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004091 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp));
Linus Torvalds1da177e2005-04-16 15:20:36 -07004092
4093 if (!tp->rx_opt.snd_wscale)
4094 __tcp_fast_path_on(tp, tp->snd_wnd);
4095 else
4096 tp->pred_flags = 0;
4097
4098 if (!sock_flag(sk, SOCK_DEAD)) {
4099 sk->sk_state_change(sk);
4100 sk_wake_async(sk, 0, POLL_OUT);
4101 }
4102
Arnaldo Carvalho de Melo295f7322005-08-09 20:11:56 -07004103 if (sk->sk_write_pending ||
4104 icsk->icsk_accept_queue.rskq_defer_accept ||
4105 icsk->icsk_ack.pingpong) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004106 /* Save one ACK. Data will be ready after
4107 * several ticks, if write_pending is set.
4108 *
4109 * It may be deleted, but with this feature tcpdumps
4110 * look so _wonderfully_ clever, that I was not able
4111 * to stand against the temptation 8) --ANK
4112 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004113 inet_csk_schedule_ack(sk);
Arnaldo Carvalho de Melo295f7322005-08-09 20:11:56 -07004114 icsk->icsk_ack.lrcvtime = tcp_time_stamp;
4115 icsk->icsk_ack.ato = TCP_ATO_MIN;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004116 tcp_incr_quickack(sk);
4117 tcp_enter_quickack_mode(sk);
Arnaldo Carvalho de Melo3f421ba2005-08-09 20:11:08 -07004118 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
4119 TCP_DELACK_MAX, TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004120
4121discard:
4122 __kfree_skb(skb);
4123 return 0;
4124 } else {
4125 tcp_send_ack(sk);
4126 }
4127 return -1;
4128 }
4129
4130 /* No ACK in the segment */
4131
4132 if (th->rst) {
4133 /* rfc793:
4134 * "If the RST bit is set
4135 *
4136 * Otherwise (no ACK) drop the segment and return."
4137 */
4138
4139 goto discard_and_undo;
4140 }
4141
4142 /* PAWS check. */
4143 if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && tcp_paws_check(&tp->rx_opt, 0))
4144 goto discard_and_undo;
4145
4146 if (th->syn) {
4147 /* We see SYN without ACK. It is attempt of
4148 * simultaneous connect with crossed SYNs.
4149 * Particularly, it can be connect to self.
4150 */
4151 tcp_set_state(sk, TCP_SYN_RECV);
4152
4153 if (tp->rx_opt.saw_tstamp) {
4154 tp->rx_opt.tstamp_ok = 1;
4155 tcp_store_ts_recent(tp);
4156 tp->tcp_header_len =
4157 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
4158 } else {
4159 tp->tcp_header_len = sizeof(struct tcphdr);
4160 }
4161
4162 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
4163 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
4164
4165 /* RFC1323: The window in SYN & SYN/ACK segments is
4166 * never scaled.
4167 */
4168 tp->snd_wnd = ntohs(th->window);
4169 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
4170 tp->max_window = tp->snd_wnd;
4171
4172 TCP_ECN_rcv_syn(tp, th);
4173 if (tp->ecn_flags&TCP_ECN_OK)
4174 sock_set_flag(sk, SOCK_NO_LARGESEND);
4175
4176 tcp_sync_mss(sk, tp->pmtu_cookie);
4177 tcp_initialize_rcv_mss(sk);
4178
4179
4180 tcp_send_synack(sk);
4181#if 0
4182 /* Note, we could accept data and URG from this segment.
4183 * There are no obstacles to make this.
4184 *
4185 * However, if we ignore data in ACKless segments sometimes,
4186 * we have no reasons to accept it sometimes.
4187 * Also, seems the code doing it in step6 of tcp_rcv_state_process
4188 * is not flawless. So, discard packet for sanity.
4189 * Uncomment this return to process the data.
4190 */
4191 return -1;
4192#else
4193 goto discard;
4194#endif
4195 }
4196 /* "fifth, if neither of the SYN or RST bits is set then
4197 * drop the segment and return."
4198 */
4199
4200discard_and_undo:
4201 tcp_clear_options(&tp->rx_opt);
4202 tp->rx_opt.mss_clamp = saved_clamp;
4203 goto discard;
4204
4205reset_and_undo:
4206 tcp_clear_options(&tp->rx_opt);
4207 tp->rx_opt.mss_clamp = saved_clamp;
4208 return 1;
4209}
4210
4211
4212/*
4213 * This function implements the receiving procedure of RFC 793 for
4214 * all states except ESTABLISHED and TIME_WAIT.
4215 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
4216 * address independent.
4217 */
4218
4219int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
4220 struct tcphdr *th, unsigned len)
4221{
4222 struct tcp_sock *tp = tcp_sk(sk);
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -08004223 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004224 int queued = 0;
4225
4226 tp->rx_opt.saw_tstamp = 0;
4227
4228 switch (sk->sk_state) {
4229 case TCP_CLOSE:
4230 goto discard;
4231
4232 case TCP_LISTEN:
4233 if(th->ack)
4234 return 1;
4235
4236 if(th->rst)
4237 goto discard;
4238
4239 if(th->syn) {
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -08004240 if (icsk->icsk_af_ops->conn_request(sk, skb) < 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004241 return 1;
4242
Linus Torvalds1da177e2005-04-16 15:20:36 -07004243 /* Now we have several options: In theory there is
4244 * nothing else in the frame. KA9Q has an option to
4245 * send data with the syn, BSD accepts data with the
4246 * syn up to the [to be] advertised window and
4247 * Solaris 2.1 gives you a protocol error. For now
4248 * we just ignore it, that fits the spec precisely
4249 * and avoids incompatibilities. It would be nice in
4250 * future to drop through and process the data.
4251 *
4252 * Now that TTCP is starting to be used we ought to
4253 * queue this data.
4254 * But, this leaves one open to an easy denial of
4255 * service attack, and SYN cookies can't defend
4256 * against this problem. So, we drop the data
4257 * in the interest of security over speed.
4258 */
4259 goto discard;
4260 }
4261 goto discard;
4262
4263 case TCP_SYN_SENT:
Linus Torvalds1da177e2005-04-16 15:20:36 -07004264 queued = tcp_rcv_synsent_state_process(sk, skb, th, len);
4265 if (queued >= 0)
4266 return queued;
4267
4268 /* Do step6 onward by hand. */
4269 tcp_urg(sk, skb, th);
4270 __kfree_skb(skb);
David S. Miller55c97f32005-07-05 15:19:38 -07004271 tcp_data_snd_check(sk, tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004272 return 0;
4273 }
4274
4275 if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004276 tcp_paws_discard(sk, skb)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004277 if (!th->rst) {
4278 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
4279 tcp_send_dupack(sk, skb);
4280 goto discard;
4281 }
4282 /* Reset is accepted even if it did not pass PAWS. */
4283 }
4284
4285 /* step 1: check sequence number */
4286 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
4287 if (!th->rst)
4288 tcp_send_dupack(sk, skb);
4289 goto discard;
4290 }
4291
4292 /* step 2: check RST bit */
4293 if(th->rst) {
4294 tcp_reset(sk);
4295 goto discard;
4296 }
4297
4298 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
4299
4300 /* step 3: check security and precedence [ignored] */
4301
4302 /* step 4:
4303 *
4304 * Check for a SYN in window.
4305 */
4306 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4307 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN);
4308 tcp_reset(sk);
4309 return 1;
4310 }
4311
4312 /* step 5: check the ACK field */
4313 if (th->ack) {
4314 int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH);
4315
4316 switch(sk->sk_state) {
4317 case TCP_SYN_RECV:
4318 if (acceptable) {
4319 tp->copied_seq = tp->rcv_nxt;
4320 mb();
4321 tcp_set_state(sk, TCP_ESTABLISHED);
4322 sk->sk_state_change(sk);
4323
4324 /* Note, that this wakeup is only for marginal
4325 * crossed SYN case. Passively open sockets
4326 * are not waked up, because sk->sk_sleep ==
4327 * NULL and sk->sk_socket == NULL.
4328 */
4329 if (sk->sk_socket) {
4330 sk_wake_async(sk,0,POLL_OUT);
4331 }
4332
4333 tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
4334 tp->snd_wnd = ntohs(th->window) <<
4335 tp->rx_opt.snd_wscale;
4336 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq,
4337 TCP_SKB_CB(skb)->seq);
4338
4339 /* tcp_ack considers this ACK as duplicate
4340 * and does not calculate rtt.
4341 * Fix it at least with timestamps.
4342 */
4343 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
4344 !tp->srtt)
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08004345 tcp_ack_saw_tstamp(sk, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004346
4347 if (tp->rx_opt.tstamp_ok)
4348 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
4349
4350 /* Make sure socket is routed, for
4351 * correct metrics.
4352 */
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -08004353 icsk->icsk_af_ops->rebuild_header(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004354
4355 tcp_init_metrics(sk);
4356
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03004357 tcp_init_congestion_control(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -07004358
Linus Torvalds1da177e2005-04-16 15:20:36 -07004359 /* Prevent spurious tcp_cwnd_restart() on
4360 * first data packet.
4361 */
4362 tp->lsndtime = tcp_time_stamp;
4363
4364 tcp_initialize_rcv_mss(sk);
4365 tcp_init_buffer_space(sk);
4366 tcp_fast_path_on(tp);
4367 } else {
4368 return 1;
4369 }
4370 break;
4371
4372 case TCP_FIN_WAIT1:
4373 if (tp->snd_una == tp->write_seq) {
4374 tcp_set_state(sk, TCP_FIN_WAIT2);
4375 sk->sk_shutdown |= SEND_SHUTDOWN;
4376 dst_confirm(sk->sk_dst_cache);
4377
4378 if (!sock_flag(sk, SOCK_DEAD))
4379 /* Wake up lingering close() */
4380 sk->sk_state_change(sk);
4381 else {
4382 int tmo;
4383
4384 if (tp->linger2 < 0 ||
4385 (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
4386 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) {
4387 tcp_done(sk);
4388 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA);
4389 return 1;
4390 }
4391
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004392 tmo = tcp_fin_time(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004393 if (tmo > TCP_TIMEWAIT_LEN) {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004394 inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004395 } else if (th->fin || sock_owned_by_user(sk)) {
4396 /* Bad case. We could lose such FIN otherwise.
4397 * It is not a big problem, but it looks confusing
4398 * and not so rare event. We still can lose it now,
4399 * if it spins in bh_lock_sock(), but it is really
4400 * marginal case.
4401 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004402 inet_csk_reset_keepalive_timer(sk, tmo);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004403 } else {
4404 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
4405 goto discard;
4406 }
4407 }
4408 }
4409 break;
4410
4411 case TCP_CLOSING:
4412 if (tp->snd_una == tp->write_seq) {
4413 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
4414 goto discard;
4415 }
4416 break;
4417
4418 case TCP_LAST_ACK:
4419 if (tp->snd_una == tp->write_seq) {
4420 tcp_update_metrics(sk);
4421 tcp_done(sk);
4422 goto discard;
4423 }
4424 break;
4425 }
4426 } else
4427 goto discard;
4428
4429 /* step 6: check the URG bit */
4430 tcp_urg(sk, skb, th);
4431
4432 /* step 7: process the segment text */
4433 switch (sk->sk_state) {
4434 case TCP_CLOSE_WAIT:
4435 case TCP_CLOSING:
4436 case TCP_LAST_ACK:
4437 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
4438 break;
4439 case TCP_FIN_WAIT1:
4440 case TCP_FIN_WAIT2:
4441 /* RFC 793 says to queue data in these states,
4442 * RFC 1122 says we MUST send a reset.
4443 * BSD 4.4 also does reset.
4444 */
4445 if (sk->sk_shutdown & RCV_SHUTDOWN) {
4446 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
4447 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
4448 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA);
4449 tcp_reset(sk);
4450 return 1;
4451 }
4452 }
4453 /* Fall through */
4454 case TCP_ESTABLISHED:
4455 tcp_data_queue(sk, skb);
4456 queued = 1;
4457 break;
4458 }
4459
4460 /* tcp_data could move socket to TIME-WAIT */
4461 if (sk->sk_state != TCP_CLOSE) {
David S. Miller55c97f32005-07-05 15:19:38 -07004462 tcp_data_snd_check(sk, tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004463 tcp_ack_snd_check(sk);
4464 }
4465
4466 if (!queued) {
4467discard:
4468 __kfree_skb(skb);
4469 }
4470 return 0;
4471}
4472
4473EXPORT_SYMBOL(sysctl_tcp_ecn);
4474EXPORT_SYMBOL(sysctl_tcp_reordering);
Stephen Hemminger9772efb2005-11-10 17:09:53 -08004475EXPORT_SYMBOL(sysctl_tcp_abc);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004476EXPORT_SYMBOL(tcp_parse_options);
4477EXPORT_SYMBOL(tcp_rcv_established);
4478EXPORT_SYMBOL(tcp_rcv_state_process);