blob: a97ed5416c28ee14ecab0ac4483c079a0c3e4c1d [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 */
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800118static void tcp_measure_rcv_mss(struct sock *sk,
119 const struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700120{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700121 struct inet_connection_sock *icsk = inet_csk(sk);
122 const unsigned int lss = icsk->icsk_ack.last_seg_size;
123 unsigned int len;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700124
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700125 icsk->icsk_ack.last_seg_size = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700126
127 /* skb->len may jitter because of SACKs, even if peer
128 * sends good full-sized frames.
129 */
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
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800249static void tcp_grow_window(struct sock *sk, struct tcp_sock *tp,
250 struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700251{
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
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800344
345/* Initialize RCV_MSS value.
346 * RCV_MSS is an our guess about MSS used by the peer.
347 * We haven't any direct information about the MSS.
348 * It's better to underestimate the RCV_MSS rather than overestimate.
349 * Overestimations make us ACKing less frequently than needed.
350 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
351 */
352void tcp_initialize_rcv_mss(struct sock *sk)
353{
354 struct tcp_sock *tp = tcp_sk(sk);
355 unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache);
356
357 hint = min(hint, tp->rcv_wnd/2);
358 hint = min(hint, TCP_MIN_RCVMSS);
359 hint = max(hint, TCP_MIN_MSS);
360
361 inet_csk(sk)->icsk_ack.rcv_mss = hint;
362}
363
Linus Torvalds1da177e2005-04-16 15:20:36 -0700364/* Receiver "autotuning" code.
365 *
366 * The algorithm for RTT estimation w/o timestamps is based on
367 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
368 * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps>
369 *
370 * More detail on this code can be found at
371 * <http://www.psc.edu/~jheffner/senior_thesis.ps>,
372 * though this reference is out of date. A new paper
373 * is pending.
374 */
375static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep)
376{
377 u32 new_sample = tp->rcv_rtt_est.rtt;
378 long m = sample;
379
380 if (m == 0)
381 m = 1;
382
383 if (new_sample != 0) {
384 /* If we sample in larger samples in the non-timestamp
385 * case, we could grossly overestimate the RTT especially
386 * with chatty applications or bulk transfer apps which
387 * are stalled on filesystem I/O.
388 *
389 * Also, since we are only going for a minimum in the
Stephen Hemminger31f34262005-11-15 15:17:10 -0800390 * non-timestamp case, we do not smooth things out
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800391 * else with timestamps disabled convergence takes too
Linus Torvalds1da177e2005-04-16 15:20:36 -0700392 * long.
393 */
394 if (!win_dep) {
395 m -= (new_sample >> 3);
396 new_sample += m;
397 } else if (m < new_sample)
398 new_sample = m << 3;
399 } else {
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800400 /* No previous measure. */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700401 new_sample = m << 3;
402 }
403
404 if (tp->rcv_rtt_est.rtt != new_sample)
405 tp->rcv_rtt_est.rtt = new_sample;
406}
407
408static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp)
409{
410 if (tp->rcv_rtt_est.time == 0)
411 goto new_measure;
412 if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq))
413 return;
414 tcp_rcv_rtt_update(tp,
415 jiffies - tp->rcv_rtt_est.time,
416 1);
417
418new_measure:
419 tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd;
420 tp->rcv_rtt_est.time = tcp_time_stamp;
421}
422
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700423static inline void tcp_rcv_rtt_measure_ts(struct sock *sk, const struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700424{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700425 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700426 if (tp->rx_opt.rcv_tsecr &&
427 (TCP_SKB_CB(skb)->end_seq -
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700428 TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700429 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0);
430}
431
432/*
433 * This function should be called every time data is copied to user space.
434 * It calculates the appropriate TCP receive buffer space.
435 */
436void tcp_rcv_space_adjust(struct sock *sk)
437{
438 struct tcp_sock *tp = tcp_sk(sk);
439 int time;
440 int space;
441
442 if (tp->rcvq_space.time == 0)
443 goto new_measure;
444
445 time = tcp_time_stamp - tp->rcvq_space.time;
446 if (time < (tp->rcv_rtt_est.rtt >> 3) ||
447 tp->rcv_rtt_est.rtt == 0)
448 return;
449
450 space = 2 * (tp->copied_seq - tp->rcvq_space.seq);
451
452 space = max(tp->rcvq_space.space, space);
453
454 if (tp->rcvq_space.space != space) {
455 int rcvmem;
456
457 tp->rcvq_space.space = space;
458
459 if (sysctl_tcp_moderate_rcvbuf) {
460 int new_clamp = space;
461
462 /* Receive space grows, normalize in order to
463 * take into account packet headers and sk_buff
464 * structure overhead.
465 */
466 space /= tp->advmss;
467 if (!space)
468 space = 1;
469 rcvmem = (tp->advmss + MAX_TCP_HEADER +
470 16 + sizeof(struct sk_buff));
471 while (tcp_win_from_space(rcvmem) < tp->advmss)
472 rcvmem += 128;
473 space *= rcvmem;
474 space = min(space, sysctl_tcp_rmem[2]);
475 if (space > sk->sk_rcvbuf) {
476 sk->sk_rcvbuf = space;
477
478 /* Make the window clamp follow along. */
479 tp->window_clamp = new_clamp;
480 }
481 }
482 }
483
484new_measure:
485 tp->rcvq_space.seq = tp->copied_seq;
486 tp->rcvq_space.time = tcp_time_stamp;
487}
488
489/* There is something which you must keep in mind when you analyze the
490 * behavior of the tp->ato delayed ack timeout interval. When a
491 * connection starts up, we want to ack as quickly as possible. The
492 * problem is that "good" TCP's do slow start at the beginning of data
493 * transmission. The means that until we send the first few ACK's the
494 * sender will sit on his end and only queue most of his data, because
495 * he can only send snd_cwnd unacked packets at any given time. For
496 * each ACK we send, he increments snd_cwnd and transmits more of his
497 * queue. -DaveM
498 */
499static void tcp_event_data_recv(struct sock *sk, struct tcp_sock *tp, struct sk_buff *skb)
500{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700501 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700502 u32 now;
503
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700504 inet_csk_schedule_ack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700505
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700506 tcp_measure_rcv_mss(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700507
508 tcp_rcv_rtt_measure(tp);
509
510 now = tcp_time_stamp;
511
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700512 if (!icsk->icsk_ack.ato) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700513 /* The _first_ data packet received, initialize
514 * delayed ACK engine.
515 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700516 tcp_incr_quickack(sk);
517 icsk->icsk_ack.ato = TCP_ATO_MIN;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700518 } else {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700519 int m = now - icsk->icsk_ack.lrcvtime;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700520
521 if (m <= TCP_ATO_MIN/2) {
522 /* The fastest case is the first. */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700523 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2;
524 } else if (m < icsk->icsk_ack.ato) {
525 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m;
526 if (icsk->icsk_ack.ato > icsk->icsk_rto)
527 icsk->icsk_ack.ato = icsk->icsk_rto;
528 } else if (m > icsk->icsk_rto) {
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800529 /* Too long gap. Apparently sender failed to
Linus Torvalds1da177e2005-04-16 15:20:36 -0700530 * restart window, so that we send ACKs quickly.
531 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700532 tcp_incr_quickack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700533 sk_stream_mem_reclaim(sk);
534 }
535 }
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700536 icsk->icsk_ack.lrcvtime = now;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700537
538 TCP_ECN_check_ce(tp, skb);
539
540 if (skb->len >= 128)
541 tcp_grow_window(sk, tp, skb);
542}
543
Linus Torvalds1da177e2005-04-16 15:20:36 -0700544/* Called to compute a smoothed rtt estimate. The data fed to this
545 * routine either comes from timestamps, or from segments that were
546 * known _not_ to have been retransmitted [see Karn/Partridge
547 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
548 * piece by Van Jacobson.
549 * NOTE: the next three routines used to be one big routine.
550 * To save cycles in the RFC 1323 implementation it was better to break
551 * it up into three procedures. -- erics
552 */
Stephen Hemminger2d2abba2005-11-10 16:56:12 -0800553static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700554{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300555 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700556 long m = mrtt; /* RTT */
557
Linus Torvalds1da177e2005-04-16 15:20:36 -0700558 /* The following amusing code comes from Jacobson's
559 * article in SIGCOMM '88. Note that rtt and mdev
560 * are scaled versions of rtt and mean deviation.
561 * This is designed to be as fast as possible
562 * m stands for "measurement".
563 *
564 * On a 1990 paper the rto value is changed to:
565 * RTO = rtt + 4 * mdev
566 *
567 * Funny. This algorithm seems to be very broken.
568 * These formulae increase RTO, when it should be decreased, increase
Stephen Hemminger31f34262005-11-15 15:17:10 -0800569 * too slowly, when it should be increased quickly, decrease too quickly
Linus Torvalds1da177e2005-04-16 15:20:36 -0700570 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
571 * does not matter how to _calculate_ it. Seems, it was trap
572 * that VJ failed to avoid. 8)
573 */
574 if(m == 0)
575 m = 1;
576 if (tp->srtt != 0) {
577 m -= (tp->srtt >> 3); /* m is now error in rtt est */
578 tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */
579 if (m < 0) {
580 m = -m; /* m is now abs(error) */
581 m -= (tp->mdev >> 2); /* similar update on mdev */
582 /* This is similar to one of Eifel findings.
583 * Eifel blocks mdev updates when rtt decreases.
584 * This solution is a bit different: we use finer gain
585 * for mdev in this case (alpha*beta).
586 * Like Eifel it also prevents growth of rto,
587 * but also it limits too fast rto decreases,
588 * happening in pure Eifel.
589 */
590 if (m > 0)
591 m >>= 3;
592 } else {
593 m -= (tp->mdev >> 2); /* similar update on mdev */
594 }
595 tp->mdev += m; /* mdev = 3/4 mdev + 1/4 new */
596 if (tp->mdev > tp->mdev_max) {
597 tp->mdev_max = tp->mdev;
598 if (tp->mdev_max > tp->rttvar)
599 tp->rttvar = tp->mdev_max;
600 }
601 if (after(tp->snd_una, tp->rtt_seq)) {
602 if (tp->mdev_max < tp->rttvar)
603 tp->rttvar -= (tp->rttvar-tp->mdev_max)>>2;
604 tp->rtt_seq = tp->snd_nxt;
605 tp->mdev_max = TCP_RTO_MIN;
606 }
607 } else {
608 /* no previous measure. */
609 tp->srtt = m<<3; /* take the measured time to be rtt */
610 tp->mdev = m<<1; /* make sure rto = 3*rtt */
611 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
612 tp->rtt_seq = tp->snd_nxt;
613 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700614}
615
616/* Calculate rto without backoff. This is the second half of Van Jacobson's
617 * routine referred to above.
618 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700619static inline void tcp_set_rto(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700620{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700621 const struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700622 /* Old crap is replaced with new one. 8)
623 *
624 * More seriously:
625 * 1. If rtt variance happened to be less 50msec, it is hallucination.
626 * It cannot be less due to utterly erratic ACK generation made
627 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
628 * to do with delayed acks, because at cwnd>2 true delack timeout
629 * is invisible. Actually, Linux-2.4 also generates erratic
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800630 * ACKs in some circumstances.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700631 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700632 inet_csk(sk)->icsk_rto = (tp->srtt >> 3) + tp->rttvar;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700633
634 /* 2. Fixups made earlier cannot be right.
635 * If we do not estimate RTO correctly without them,
636 * all the algo is pure shit and should be replaced
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800637 * with correct one. It is exactly, which we pretend to do.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700638 */
639}
640
641/* NOTE: clamping at TCP_RTO_MIN is not required, current algo
642 * guarantees that rto is higher.
643 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700644static inline void tcp_bound_rto(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700645{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700646 if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
647 inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700648}
649
650/* Save metrics learned by this TCP session.
651 This function is called only, when TCP finishes successfully
652 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
653 */
654void tcp_update_metrics(struct sock *sk)
655{
656 struct tcp_sock *tp = tcp_sk(sk);
657 struct dst_entry *dst = __sk_dst_get(sk);
658
659 if (sysctl_tcp_nometrics_save)
660 return;
661
662 dst_confirm(dst);
663
664 if (dst && (dst->flags&DST_HOST)) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300665 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700666 int m;
667
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300668 if (icsk->icsk_backoff || !tp->srtt) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700669 /* This session failed to estimate rtt. Why?
670 * Probably, no packets returned in time.
671 * Reset our results.
672 */
673 if (!(dst_metric_locked(dst, RTAX_RTT)))
674 dst->metrics[RTAX_RTT-1] = 0;
675 return;
676 }
677
678 m = dst_metric(dst, RTAX_RTT) - tp->srtt;
679
680 /* If newly calculated rtt larger than stored one,
681 * store new one. Otherwise, use EWMA. Remember,
682 * rtt overestimation is always better than underestimation.
683 */
684 if (!(dst_metric_locked(dst, RTAX_RTT))) {
685 if (m <= 0)
686 dst->metrics[RTAX_RTT-1] = tp->srtt;
687 else
688 dst->metrics[RTAX_RTT-1] -= (m>>3);
689 }
690
691 if (!(dst_metric_locked(dst, RTAX_RTTVAR))) {
692 if (m < 0)
693 m = -m;
694
695 /* Scale deviation to rttvar fixed point */
696 m >>= 1;
697 if (m < tp->mdev)
698 m = tp->mdev;
699
700 if (m >= dst_metric(dst, RTAX_RTTVAR))
701 dst->metrics[RTAX_RTTVAR-1] = m;
702 else
703 dst->metrics[RTAX_RTTVAR-1] -=
704 (dst->metrics[RTAX_RTTVAR-1] - m)>>2;
705 }
706
707 if (tp->snd_ssthresh >= 0xFFFF) {
708 /* Slow start still did not finish. */
709 if (dst_metric(dst, RTAX_SSTHRESH) &&
710 !dst_metric_locked(dst, RTAX_SSTHRESH) &&
711 (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH))
712 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1;
713 if (!dst_metric_locked(dst, RTAX_CWND) &&
714 tp->snd_cwnd > dst_metric(dst, RTAX_CWND))
715 dst->metrics[RTAX_CWND-1] = tp->snd_cwnd;
716 } else if (tp->snd_cwnd > tp->snd_ssthresh &&
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300717 icsk->icsk_ca_state == TCP_CA_Open) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700718 /* Cong. avoidance phase, cwnd is reliable. */
719 if (!dst_metric_locked(dst, RTAX_SSTHRESH))
720 dst->metrics[RTAX_SSTHRESH-1] =
721 max(tp->snd_cwnd >> 1, tp->snd_ssthresh);
722 if (!dst_metric_locked(dst, RTAX_CWND))
723 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_cwnd) >> 1;
724 } else {
725 /* Else slow start did not finish, cwnd is non-sense,
726 ssthresh may be also invalid.
727 */
728 if (!dst_metric_locked(dst, RTAX_CWND))
729 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_ssthresh) >> 1;
730 if (dst->metrics[RTAX_SSTHRESH-1] &&
731 !dst_metric_locked(dst, RTAX_SSTHRESH) &&
732 tp->snd_ssthresh > dst->metrics[RTAX_SSTHRESH-1])
733 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh;
734 }
735
736 if (!dst_metric_locked(dst, RTAX_REORDERING)) {
737 if (dst->metrics[RTAX_REORDERING-1] < tp->reordering &&
738 tp->reordering != sysctl_tcp_reordering)
739 dst->metrics[RTAX_REORDERING-1] = tp->reordering;
740 }
741 }
742}
743
744/* Numbers are taken from RFC2414. */
745__u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst)
746{
747 __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0);
748
749 if (!cwnd) {
David S. Millerc1b4a7e2005-07-05 15:24:38 -0700750 if (tp->mss_cache > 1460)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700751 cwnd = 2;
752 else
David S. Millerc1b4a7e2005-07-05 15:24:38 -0700753 cwnd = (tp->mss_cache > 1095) ? 3 : 4;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700754 }
755 return min_t(__u32, cwnd, tp->snd_cwnd_clamp);
756}
757
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800758/* Set slow start threshold and cwnd not falling to slow start */
759void tcp_enter_cwr(struct sock *sk)
760{
761 struct tcp_sock *tp = tcp_sk(sk);
762
763 tp->prior_ssthresh = 0;
764 tp->bytes_acked = 0;
765 if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) {
766 tp->undo_marker = 0;
767 tp->snd_ssthresh = inet_csk(sk)->icsk_ca_ops->ssthresh(sk);
768 tp->snd_cwnd = min(tp->snd_cwnd,
769 tcp_packets_in_flight(tp) + 1U);
770 tp->snd_cwnd_cnt = 0;
771 tp->high_seq = tp->snd_nxt;
772 tp->snd_cwnd_stamp = tcp_time_stamp;
773 TCP_ECN_queue_cwr(tp);
774
775 tcp_set_ca_state(sk, TCP_CA_CWR);
776 }
777}
778
Linus Torvalds1da177e2005-04-16 15:20:36 -0700779/* Initialize metrics on socket. */
780
781static void tcp_init_metrics(struct sock *sk)
782{
783 struct tcp_sock *tp = tcp_sk(sk);
784 struct dst_entry *dst = __sk_dst_get(sk);
785
786 if (dst == NULL)
787 goto reset;
788
789 dst_confirm(dst);
790
791 if (dst_metric_locked(dst, RTAX_CWND))
792 tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND);
793 if (dst_metric(dst, RTAX_SSTHRESH)) {
794 tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH);
795 if (tp->snd_ssthresh > tp->snd_cwnd_clamp)
796 tp->snd_ssthresh = tp->snd_cwnd_clamp;
797 }
798 if (dst_metric(dst, RTAX_REORDERING) &&
799 tp->reordering != dst_metric(dst, RTAX_REORDERING)) {
800 tp->rx_opt.sack_ok &= ~2;
801 tp->reordering = dst_metric(dst, RTAX_REORDERING);
802 }
803
804 if (dst_metric(dst, RTAX_RTT) == 0)
805 goto reset;
806
807 if (!tp->srtt && dst_metric(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3))
808 goto reset;
809
810 /* Initial rtt is determined from SYN,SYN-ACK.
811 * The segment is small and rtt may appear much
812 * less than real one. Use per-dst memory
813 * to make it more realistic.
814 *
815 * A bit of theory. RTT is time passed after "normal" sized packet
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800816 * is sent until it is ACKed. In normal circumstances sending small
Linus Torvalds1da177e2005-04-16 15:20:36 -0700817 * packets force peer to delay ACKs and calculation is correct too.
818 * The algorithm is adaptive and, provided we follow specs, it
819 * NEVER underestimate RTT. BUT! If peer tries to make some clever
820 * tricks sort of "quick acks" for time long enough to decrease RTT
821 * to low value, and then abruptly stops to do it and starts to delay
822 * ACKs, wait for troubles.
823 */
824 if (dst_metric(dst, RTAX_RTT) > tp->srtt) {
825 tp->srtt = dst_metric(dst, RTAX_RTT);
826 tp->rtt_seq = tp->snd_nxt;
827 }
828 if (dst_metric(dst, RTAX_RTTVAR) > tp->mdev) {
829 tp->mdev = dst_metric(dst, RTAX_RTTVAR);
830 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
831 }
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700832 tcp_set_rto(sk);
833 tcp_bound_rto(sk);
834 if (inet_csk(sk)->icsk_rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700835 goto reset;
836 tp->snd_cwnd = tcp_init_cwnd(tp, dst);
837 tp->snd_cwnd_stamp = tcp_time_stamp;
838 return;
839
840reset:
841 /* Play conservative. If timestamps are not
842 * supported, TCP will fail to recalculate correct
843 * rtt, if initial rto is too small. FORGET ALL AND RESET!
844 */
845 if (!tp->rx_opt.saw_tstamp && tp->srtt) {
846 tp->srtt = 0;
847 tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700848 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700849 }
850}
851
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300852static void tcp_update_reordering(struct sock *sk, const int metric,
853 const int ts)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700854{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300855 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700856 if (metric > tp->reordering) {
857 tp->reordering = min(TCP_MAX_REORDERING, metric);
858
859 /* This exciting event is worth to be remembered. 8) */
860 if (ts)
861 NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER);
862 else if (IsReno(tp))
863 NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER);
864 else if (IsFack(tp))
865 NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER);
866 else
867 NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER);
868#if FASTRETRANS_DEBUG > 1
869 printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n",
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300870 tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700871 tp->reordering,
872 tp->fackets_out,
873 tp->sacked_out,
874 tp->undo_marker ? tp->undo_retrans : 0);
875#endif
876 /* Disable FACK yet. */
877 tp->rx_opt.sack_ok &= ~2;
878 }
879}
880
881/* This procedure tags the retransmission queue when SACKs arrive.
882 *
883 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
884 * Packets in queue with these bits set are counted in variables
885 * sacked_out, retrans_out and lost_out, correspondingly.
886 *
887 * Valid combinations are:
888 * Tag InFlight Description
889 * 0 1 - orig segment is in flight.
890 * S 0 - nothing flies, orig reached receiver.
891 * L 0 - nothing flies, orig lost by net.
892 * R 2 - both orig and retransmit are in flight.
893 * L|R 1 - orig is lost, retransmit is in flight.
894 * S|R 1 - orig reached receiver, retrans is still in flight.
895 * (L|S|R is logically valid, it could occur when L|R is sacked,
896 * but it is equivalent to plain S and code short-curcuits it to S.
897 * L|S is logically invalid, it would mean -1 packet in flight 8))
898 *
899 * These 6 states form finite state machine, controlled by the following events:
900 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
901 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
902 * 3. Loss detection event of one of three flavors:
903 * A. Scoreboard estimator decided the packet is lost.
904 * A'. Reno "three dupacks" marks head of queue lost.
905 * A''. Its FACK modfication, head until snd.fack is lost.
906 * B. SACK arrives sacking data transmitted after never retransmitted
907 * hole was sent out.
908 * C. SACK arrives sacking SND.NXT at the moment, when the
909 * segment was retransmitted.
910 * 4. D-SACK added new rule: D-SACK changes any tag to S.
911 *
912 * It is pleasant to note, that state diagram turns out to be commutative,
913 * so that we are allowed not to be bothered by order of our actions,
914 * when multiple events arrive simultaneously. (see the function below).
915 *
916 * Reordering detection.
917 * --------------------
918 * Reordering metric is maximal distance, which a packet can be displaced
919 * in packet stream. With SACKs we can estimate it:
920 *
921 * 1. SACK fills old hole and the corresponding segment was not
922 * ever retransmitted -> reordering. Alas, we cannot use it
923 * when segment was retransmitted.
924 * 2. The last flaw is solved with D-SACK. D-SACK arrives
925 * for retransmitted and already SACKed segment -> reordering..
926 * Both of these heuristics are not used in Loss state, when we cannot
927 * account for retransmits accurately.
928 */
929static int
930tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_una)
931{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300932 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700933 struct tcp_sock *tp = tcp_sk(sk);
934 unsigned char *ptr = ack_skb->h.raw + TCP_SKB_CB(ack_skb)->sacked;
935 struct tcp_sack_block *sp = (struct tcp_sack_block *)(ptr+2);
936 int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3;
937 int reord = tp->packets_out;
938 int prior_fackets;
939 u32 lost_retrans = 0;
940 int flag = 0;
Stephen Hemminger6a438bb2005-11-10 17:14:59 -0800941 int dup_sack = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700942 int i;
943
Linus Torvalds1da177e2005-04-16 15:20:36 -0700944 if (!tp->sacked_out)
945 tp->fackets_out = 0;
946 prior_fackets = tp->fackets_out;
947
Stephen Hemminger6a438bb2005-11-10 17:14:59 -0800948 /* SACK fastpath:
949 * if the only SACK change is the increase of the end_seq of
950 * the first block then only apply that SACK block
951 * and use retrans queue hinting otherwise slowpath */
952 flag = 1;
953 for (i = 0; i< num_sacks; i++) {
954 __u32 start_seq = ntohl(sp[i].start_seq);
955 __u32 end_seq = ntohl(sp[i].end_seq);
956
957 if (i == 0){
958 if (tp->recv_sack_cache[i].start_seq != start_seq)
959 flag = 0;
960 } else {
961 if ((tp->recv_sack_cache[i].start_seq != start_seq) ||
962 (tp->recv_sack_cache[i].end_seq != end_seq))
963 flag = 0;
964 }
965 tp->recv_sack_cache[i].start_seq = start_seq;
966 tp->recv_sack_cache[i].end_seq = end_seq;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700967
968 /* Check for D-SACK. */
969 if (i == 0) {
970 u32 ack = TCP_SKB_CB(ack_skb)->ack_seq;
971
972 if (before(start_seq, ack)) {
973 dup_sack = 1;
974 tp->rx_opt.sack_ok |= 4;
975 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV);
976 } else if (num_sacks > 1 &&
977 !after(end_seq, ntohl(sp[1].end_seq)) &&
978 !before(start_seq, ntohl(sp[1].start_seq))) {
979 dup_sack = 1;
980 tp->rx_opt.sack_ok |= 4;
981 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV);
982 }
983
984 /* D-SACK for already forgotten data...
985 * Do dumb counting. */
986 if (dup_sack &&
987 !after(end_seq, prior_snd_una) &&
988 after(end_seq, tp->undo_marker))
989 tp->undo_retrans--;
990
991 /* Eliminate too old ACKs, but take into
992 * account more or less fresh ones, they can
993 * contain valid SACK info.
994 */
995 if (before(ack, prior_snd_una - tp->max_window))
996 return 0;
997 }
Stephen Hemminger6a438bb2005-11-10 17:14:59 -0800998 }
999
1000 if (flag)
1001 num_sacks = 1;
1002 else {
1003 int j;
1004 tp->fastpath_skb_hint = NULL;
1005
1006 /* order SACK blocks to allow in order walk of the retrans queue */
1007 for (i = num_sacks-1; i > 0; i--) {
1008 for (j = 0; j < i; j++){
1009 if (after(ntohl(sp[j].start_seq),
1010 ntohl(sp[j+1].start_seq))){
1011 sp[j].start_seq = htonl(tp->recv_sack_cache[j+1].start_seq);
1012 sp[j].end_seq = htonl(tp->recv_sack_cache[j+1].end_seq);
1013 sp[j+1].start_seq = htonl(tp->recv_sack_cache[j].start_seq);
1014 sp[j+1].end_seq = htonl(tp->recv_sack_cache[j].end_seq);
1015 }
1016
1017 }
1018 }
1019 }
1020
1021 /* clear flag as used for different purpose in following code */
1022 flag = 0;
1023
1024 for (i=0; i<num_sacks; i++, sp++) {
1025 struct sk_buff *skb;
1026 __u32 start_seq = ntohl(sp->start_seq);
1027 __u32 end_seq = ntohl(sp->end_seq);
1028 int fack_count;
1029
1030 /* Use SACK fastpath hint if valid */
1031 if (tp->fastpath_skb_hint) {
1032 skb = tp->fastpath_skb_hint;
1033 fack_count = tp->fastpath_cnt_hint;
1034 } else {
1035 skb = sk->sk_write_queue.next;
1036 fack_count = 0;
1037 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001038
1039 /* Event "B" in the comment above. */
1040 if (after(end_seq, tp->high_seq))
1041 flag |= FLAG_DATA_LOST;
1042
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001043 sk_stream_for_retrans_queue_from(skb, sk) {
David S. Miller6475be12005-09-01 22:47:01 -07001044 int in_sack, pcount;
1045 u8 sacked;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001046
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001047 tp->fastpath_skb_hint = skb;
1048 tp->fastpath_cnt_hint = fack_count;
1049
Linus Torvalds1da177e2005-04-16 15:20:36 -07001050 /* The retransmission queue is always in order, so
1051 * we can short-circuit the walk early.
1052 */
David S. Miller6475be12005-09-01 22:47:01 -07001053 if (!before(TCP_SKB_CB(skb)->seq, end_seq))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001054 break;
1055
Herbert Xu3c05d922005-09-14 20:50:35 -07001056 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
1057 !before(end_seq, TCP_SKB_CB(skb)->end_seq);
1058
David S. Miller6475be12005-09-01 22:47:01 -07001059 pcount = tcp_skb_pcount(skb);
1060
Herbert Xu3c05d922005-09-14 20:50:35 -07001061 if (pcount > 1 && !in_sack &&
1062 after(TCP_SKB_CB(skb)->end_seq, start_seq)) {
David S. Miller6475be12005-09-01 22:47:01 -07001063 unsigned int pkt_len;
1064
Herbert Xu3c05d922005-09-14 20:50:35 -07001065 in_sack = !after(start_seq,
1066 TCP_SKB_CB(skb)->seq);
1067
1068 if (!in_sack)
David S. Miller6475be12005-09-01 22:47:01 -07001069 pkt_len = (start_seq -
1070 TCP_SKB_CB(skb)->seq);
1071 else
1072 pkt_len = (end_seq -
1073 TCP_SKB_CB(skb)->seq);
1074 if (tcp_fragment(sk, skb, pkt_len, skb_shinfo(skb)->tso_size))
1075 break;
1076 pcount = tcp_skb_pcount(skb);
1077 }
1078
1079 fack_count += pcount;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001080
David S. Miller6475be12005-09-01 22:47:01 -07001081 sacked = TCP_SKB_CB(skb)->sacked;
1082
Linus Torvalds1da177e2005-04-16 15:20:36 -07001083 /* Account D-SACK for retransmitted packet. */
1084 if ((dup_sack && in_sack) &&
1085 (sacked & TCPCB_RETRANS) &&
1086 after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
1087 tp->undo_retrans--;
1088
1089 /* The frame is ACKed. */
1090 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) {
1091 if (sacked&TCPCB_RETRANS) {
1092 if ((dup_sack && in_sack) &&
1093 (sacked&TCPCB_SACKED_ACKED))
1094 reord = min(fack_count, reord);
1095 } else {
1096 /* If it was in a hole, we detected reordering. */
1097 if (fack_count < prior_fackets &&
1098 !(sacked&TCPCB_SACKED_ACKED))
1099 reord = min(fack_count, reord);
1100 }
1101
1102 /* Nothing to do; acked frame is about to be dropped. */
1103 continue;
1104 }
1105
1106 if ((sacked&TCPCB_SACKED_RETRANS) &&
1107 after(end_seq, TCP_SKB_CB(skb)->ack_seq) &&
1108 (!lost_retrans || after(end_seq, lost_retrans)))
1109 lost_retrans = end_seq;
1110
1111 if (!in_sack)
1112 continue;
1113
1114 if (!(sacked&TCPCB_SACKED_ACKED)) {
1115 if (sacked & TCPCB_SACKED_RETRANS) {
1116 /* If the segment is not tagged as lost,
1117 * we do not clear RETRANS, believing
1118 * that retransmission is still in flight.
1119 */
1120 if (sacked & TCPCB_LOST) {
1121 TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
1122 tp->lost_out -= tcp_skb_pcount(skb);
1123 tp->retrans_out -= tcp_skb_pcount(skb);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001124
1125 /* clear lost hint */
1126 tp->retransmit_skb_hint = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001127 }
1128 } else {
1129 /* New sack for not retransmitted frame,
1130 * which was in hole. It is reordering.
1131 */
1132 if (!(sacked & TCPCB_RETRANS) &&
1133 fack_count < prior_fackets)
1134 reord = min(fack_count, reord);
1135
1136 if (sacked & TCPCB_LOST) {
1137 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1138 tp->lost_out -= tcp_skb_pcount(skb);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001139
1140 /* clear lost hint */
1141 tp->retransmit_skb_hint = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001142 }
1143 }
1144
1145 TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED;
1146 flag |= FLAG_DATA_SACKED;
1147 tp->sacked_out += tcp_skb_pcount(skb);
1148
1149 if (fack_count > tp->fackets_out)
1150 tp->fackets_out = fack_count;
1151 } else {
1152 if (dup_sack && (sacked&TCPCB_RETRANS))
1153 reord = min(fack_count, reord);
1154 }
1155
1156 /* D-SACK. We can detect redundant retransmission
1157 * in S|R and plain R frames and clear it.
1158 * undo_retrans is decreased above, L|R frames
1159 * are accounted above as well.
1160 */
1161 if (dup_sack &&
1162 (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS)) {
1163 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1164 tp->retrans_out -= tcp_skb_pcount(skb);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001165 tp->retransmit_skb_hint = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001166 }
1167 }
1168 }
1169
1170 /* Check for lost retransmit. This superb idea is
1171 * borrowed from "ratehalving". Event "C".
1172 * Later note: FACK people cheated me again 8),
1173 * we have to account for reordering! Ugly,
1174 * but should help.
1175 */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001176 if (lost_retrans && icsk->icsk_ca_state == TCP_CA_Recovery) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001177 struct sk_buff *skb;
1178
1179 sk_stream_for_retrans_queue(skb, sk) {
1180 if (after(TCP_SKB_CB(skb)->seq, lost_retrans))
1181 break;
1182 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
1183 continue;
1184 if ((TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) &&
1185 after(lost_retrans, TCP_SKB_CB(skb)->ack_seq) &&
1186 (IsFack(tp) ||
1187 !before(lost_retrans,
1188 TCP_SKB_CB(skb)->ack_seq + tp->reordering *
David S. Millerc1b4a7e2005-07-05 15:24:38 -07001189 tp->mss_cache))) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001190 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1191 tp->retrans_out -= tcp_skb_pcount(skb);
1192
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001193 /* clear lost hint */
1194 tp->retransmit_skb_hint = NULL;
1195
Linus Torvalds1da177e2005-04-16 15:20:36 -07001196 if (!(TCP_SKB_CB(skb)->sacked&(TCPCB_LOST|TCPCB_SACKED_ACKED))) {
1197 tp->lost_out += tcp_skb_pcount(skb);
1198 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1199 flag |= FLAG_DATA_SACKED;
1200 NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT);
1201 }
1202 }
1203 }
1204 }
1205
1206 tp->left_out = tp->sacked_out + tp->lost_out;
1207
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001208 if ((reord < tp->fackets_out) && icsk->icsk_ca_state != TCP_CA_Loss)
1209 tcp_update_reordering(sk, ((tp->fackets_out + 1) - reord), 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001210
1211#if FASTRETRANS_DEBUG > 0
1212 BUG_TRAP((int)tp->sacked_out >= 0);
1213 BUG_TRAP((int)tp->lost_out >= 0);
1214 BUG_TRAP((int)tp->retrans_out >= 0);
1215 BUG_TRAP((int)tcp_packets_in_flight(tp) >= 0);
1216#endif
1217 return flag;
1218}
1219
1220/* RTO occurred, but do not yet enter loss state. Instead, transmit two new
1221 * segments to see from the next ACKs whether any data was really missing.
1222 * If the RTO was spurious, new ACKs should arrive.
1223 */
1224void tcp_enter_frto(struct sock *sk)
1225{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001226 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001227 struct tcp_sock *tp = tcp_sk(sk);
1228 struct sk_buff *skb;
1229
1230 tp->frto_counter = 1;
1231
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001232 if (icsk->icsk_ca_state <= TCP_CA_Disorder ||
Linus Torvalds1da177e2005-04-16 15:20:36 -07001233 tp->snd_una == tp->high_seq ||
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001234 (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
1235 tp->prior_ssthresh = tcp_current_ssthresh(sk);
1236 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
1237 tcp_ca_event(sk, CA_EVENT_FRTO);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001238 }
1239
1240 /* Have to clear retransmission markers here to keep the bookkeeping
1241 * in shape, even though we are not yet in Loss state.
1242 * If something was really lost, it is eventually caught up
1243 * in tcp_enter_frto_loss.
1244 */
1245 tp->retrans_out = 0;
1246 tp->undo_marker = tp->snd_una;
1247 tp->undo_retrans = 0;
1248
1249 sk_stream_for_retrans_queue(skb, sk) {
1250 TCP_SKB_CB(skb)->sacked &= ~TCPCB_RETRANS;
1251 }
1252 tcp_sync_left_out(tp);
1253
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001254 tcp_set_ca_state(sk, TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001255 tp->frto_highmark = tp->snd_nxt;
1256}
1257
1258/* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
1259 * which indicates that we should follow the traditional RTO recovery,
1260 * i.e. mark everything lost and do go-back-N retransmission.
1261 */
1262static void tcp_enter_frto_loss(struct sock *sk)
1263{
1264 struct tcp_sock *tp = tcp_sk(sk);
1265 struct sk_buff *skb;
1266 int cnt = 0;
1267
1268 tp->sacked_out = 0;
1269 tp->lost_out = 0;
1270 tp->fackets_out = 0;
1271
1272 sk_stream_for_retrans_queue(skb, sk) {
1273 cnt += tcp_skb_pcount(skb);
1274 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1275 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) {
1276
1277 /* Do not mark those segments lost that were
1278 * forward transmitted after RTO
1279 */
1280 if (!after(TCP_SKB_CB(skb)->end_seq,
1281 tp->frto_highmark)) {
1282 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1283 tp->lost_out += tcp_skb_pcount(skb);
1284 }
1285 } else {
1286 tp->sacked_out += tcp_skb_pcount(skb);
1287 tp->fackets_out = cnt;
1288 }
1289 }
1290 tcp_sync_left_out(tp);
1291
1292 tp->snd_cwnd = tp->frto_counter + tcp_packets_in_flight(tp)+1;
1293 tp->snd_cwnd_cnt = 0;
1294 tp->snd_cwnd_stamp = tcp_time_stamp;
1295 tp->undo_marker = 0;
1296 tp->frto_counter = 0;
1297
1298 tp->reordering = min_t(unsigned int, tp->reordering,
1299 sysctl_tcp_reordering);
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001300 tcp_set_ca_state(sk, TCP_CA_Loss);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001301 tp->high_seq = tp->frto_highmark;
1302 TCP_ECN_queue_cwr(tp);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001303
1304 clear_all_retrans_hints(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001305}
1306
1307void tcp_clear_retrans(struct tcp_sock *tp)
1308{
1309 tp->left_out = 0;
1310 tp->retrans_out = 0;
1311
1312 tp->fackets_out = 0;
1313 tp->sacked_out = 0;
1314 tp->lost_out = 0;
1315
1316 tp->undo_marker = 0;
1317 tp->undo_retrans = 0;
1318}
1319
1320/* Enter Loss state. If "how" is not zero, forget all SACK information
1321 * and reset tags completely, otherwise preserve SACKs. If receiver
1322 * dropped its ofo queue, we will know this due to reneging detection.
1323 */
1324void tcp_enter_loss(struct sock *sk, int how)
1325{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001326 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001327 struct tcp_sock *tp = tcp_sk(sk);
1328 struct sk_buff *skb;
1329 int cnt = 0;
1330
1331 /* Reduce ssthresh if it has not yet been made inside this window. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001332 if (icsk->icsk_ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq ||
1333 (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
1334 tp->prior_ssthresh = tcp_current_ssthresh(sk);
1335 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
1336 tcp_ca_event(sk, CA_EVENT_LOSS);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001337 }
1338 tp->snd_cwnd = 1;
1339 tp->snd_cwnd_cnt = 0;
1340 tp->snd_cwnd_stamp = tcp_time_stamp;
1341
Stephen Hemminger9772efb2005-11-10 17:09:53 -08001342 tp->bytes_acked = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001343 tcp_clear_retrans(tp);
1344
1345 /* Push undo marker, if it was plain RTO and nothing
1346 * was retransmitted. */
1347 if (!how)
1348 tp->undo_marker = tp->snd_una;
1349
1350 sk_stream_for_retrans_queue(skb, sk) {
1351 cnt += tcp_skb_pcount(skb);
1352 if (TCP_SKB_CB(skb)->sacked&TCPCB_RETRANS)
1353 tp->undo_marker = 0;
1354 TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED;
1355 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) {
1356 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
1357 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1358 tp->lost_out += tcp_skb_pcount(skb);
1359 } else {
1360 tp->sacked_out += tcp_skb_pcount(skb);
1361 tp->fackets_out = cnt;
1362 }
1363 }
1364 tcp_sync_left_out(tp);
1365
1366 tp->reordering = min_t(unsigned int, tp->reordering,
1367 sysctl_tcp_reordering);
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001368 tcp_set_ca_state(sk, TCP_CA_Loss);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001369 tp->high_seq = tp->snd_nxt;
1370 TCP_ECN_queue_cwr(tp);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001371
1372 clear_all_retrans_hints(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001373}
1374
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001375static int tcp_check_sack_reneging(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001376{
1377 struct sk_buff *skb;
1378
1379 /* If ACK arrived pointing to a remembered SACK,
1380 * it means that our remembered SACKs do not reflect
1381 * real state of receiver i.e.
1382 * receiver _host_ is heavily congested (or buggy).
1383 * Do processing similar to RTO timeout.
1384 */
1385 if ((skb = skb_peek(&sk->sk_write_queue)) != NULL &&
1386 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001387 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001388 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING);
1389
1390 tcp_enter_loss(sk, 1);
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001391 icsk->icsk_retransmits++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001392 tcp_retransmit_skb(sk, skb_peek(&sk->sk_write_queue));
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001393 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001394 icsk->icsk_rto, TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001395 return 1;
1396 }
1397 return 0;
1398}
1399
1400static inline int tcp_fackets_out(struct tcp_sock *tp)
1401{
1402 return IsReno(tp) ? tp->sacked_out+1 : tp->fackets_out;
1403}
1404
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001405static inline int tcp_skb_timedout(struct sock *sk, struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001406{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001407 return (tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001408}
1409
1410static inline int tcp_head_timedout(struct sock *sk, struct tcp_sock *tp)
1411{
1412 return tp->packets_out &&
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001413 tcp_skb_timedout(sk, skb_peek(&sk->sk_write_queue));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001414}
1415
1416/* Linux NewReno/SACK/FACK/ECN state machine.
1417 * --------------------------------------
1418 *
1419 * "Open" Normal state, no dubious events, fast path.
1420 * "Disorder" In all the respects it is "Open",
1421 * but requires a bit more attention. It is entered when
1422 * we see some SACKs or dupacks. It is split of "Open"
1423 * mainly to move some processing from fast path to slow one.
1424 * "CWR" CWND was reduced due to some Congestion Notification event.
1425 * It can be ECN, ICMP source quench, local device congestion.
1426 * "Recovery" CWND was reduced, we are fast-retransmitting.
1427 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
1428 *
1429 * tcp_fastretrans_alert() is entered:
1430 * - each incoming ACK, if state is not "Open"
1431 * - when arrived ACK is unusual, namely:
1432 * * SACK
1433 * * Duplicate ACK.
1434 * * ECN ECE.
1435 *
1436 * Counting packets in flight is pretty simple.
1437 *
1438 * in_flight = packets_out - left_out + retrans_out
1439 *
1440 * packets_out is SND.NXT-SND.UNA counted in packets.
1441 *
1442 * retrans_out is number of retransmitted segments.
1443 *
1444 * left_out is number of segments left network, but not ACKed yet.
1445 *
1446 * left_out = sacked_out + lost_out
1447 *
1448 * sacked_out: Packets, which arrived to receiver out of order
1449 * and hence not ACKed. With SACKs this number is simply
1450 * amount of SACKed data. Even without SACKs
1451 * it is easy to give pretty reliable estimate of this number,
1452 * counting duplicate ACKs.
1453 *
1454 * lost_out: Packets lost by network. TCP has no explicit
1455 * "loss notification" feedback from network (for now).
1456 * It means that this number can be only _guessed_.
1457 * Actually, it is the heuristics to predict lossage that
1458 * distinguishes different algorithms.
1459 *
1460 * F.e. after RTO, when all the queue is considered as lost,
1461 * lost_out = packets_out and in_flight = retrans_out.
1462 *
1463 * Essentially, we have now two algorithms counting
1464 * lost packets.
1465 *
1466 * FACK: It is the simplest heuristics. As soon as we decided
1467 * that something is lost, we decide that _all_ not SACKed
1468 * packets until the most forward SACK are lost. I.e.
1469 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
1470 * It is absolutely correct estimate, if network does not reorder
1471 * packets. And it loses any connection to reality when reordering
1472 * takes place. We use FACK by default until reordering
1473 * is suspected on the path to this destination.
1474 *
1475 * NewReno: when Recovery is entered, we assume that one segment
1476 * is lost (classic Reno). While we are in Recovery and
1477 * a partial ACK arrives, we assume that one more packet
1478 * is lost (NewReno). This heuristics are the same in NewReno
1479 * and SACK.
1480 *
1481 * Imagine, that's all! Forget about all this shamanism about CWND inflation
1482 * deflation etc. CWND is real congestion window, never inflated, changes
1483 * only according to classic VJ rules.
1484 *
1485 * Really tricky (and requiring careful tuning) part of algorithm
1486 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
1487 * The first determines the moment _when_ we should reduce CWND and,
1488 * hence, slow down forward transmission. In fact, it determines the moment
1489 * when we decide that hole is caused by loss, rather than by a reorder.
1490 *
1491 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
1492 * holes, caused by lost packets.
1493 *
1494 * And the most logically complicated part of algorithm is undo
1495 * heuristics. We detect false retransmits due to both too early
1496 * fast retransmit (reordering) and underestimated RTO, analyzing
1497 * timestamps and D-SACKs. When we detect that some segments were
1498 * retransmitted by mistake and CWND reduction was wrong, we undo
1499 * window reduction and abort recovery phase. This logic is hidden
1500 * inside several functions named tcp_try_undo_<something>.
1501 */
1502
1503/* This function decides, when we should leave Disordered state
1504 * and enter Recovery phase, reducing congestion window.
1505 *
1506 * Main question: may we further continue forward transmission
1507 * with the same cwnd?
1508 */
1509static int tcp_time_to_recover(struct sock *sk, struct tcp_sock *tp)
1510{
1511 __u32 packets_out;
1512
1513 /* Trick#1: The loss is proven. */
1514 if (tp->lost_out)
1515 return 1;
1516
1517 /* Not-A-Trick#2 : Classic rule... */
1518 if (tcp_fackets_out(tp) > tp->reordering)
1519 return 1;
1520
1521 /* Trick#3 : when we use RFC2988 timer restart, fast
1522 * retransmit can be triggered by timeout of queue head.
1523 */
1524 if (tcp_head_timedout(sk, tp))
1525 return 1;
1526
1527 /* Trick#4: It is still not OK... But will it be useful to delay
1528 * recovery more?
1529 */
1530 packets_out = tp->packets_out;
1531 if (packets_out <= tp->reordering &&
1532 tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) &&
1533 !tcp_may_send_now(sk, tp)) {
1534 /* We have nothing to send. This connection is limited
1535 * either by receiver window or by application.
1536 */
1537 return 1;
1538 }
1539
1540 return 0;
1541}
1542
1543/* If we receive more dupacks than we expected counting segments
1544 * in assumption of absent reordering, interpret this as reordering.
1545 * The only another reason could be bug in receiver TCP.
1546 */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001547static void tcp_check_reno_reordering(struct sock *sk, const int addend)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001548{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001549 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001550 u32 holes;
1551
1552 holes = max(tp->lost_out, 1U);
1553 holes = min(holes, tp->packets_out);
1554
1555 if ((tp->sacked_out + holes) > tp->packets_out) {
1556 tp->sacked_out = tp->packets_out - holes;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001557 tcp_update_reordering(sk, tp->packets_out + addend, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001558 }
1559}
1560
1561/* Emulate SACKs for SACKless connection: account for a new dupack. */
1562
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001563static void tcp_add_reno_sack(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001564{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001565 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001566 tp->sacked_out++;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001567 tcp_check_reno_reordering(sk, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001568 tcp_sync_left_out(tp);
1569}
1570
1571/* Account for ACK, ACKing some data in Reno Recovery phase. */
1572
1573static void tcp_remove_reno_sacks(struct sock *sk, struct tcp_sock *tp, int acked)
1574{
1575 if (acked > 0) {
1576 /* One ACK acked hole. The rest eat duplicate ACKs. */
1577 if (acked-1 >= tp->sacked_out)
1578 tp->sacked_out = 0;
1579 else
1580 tp->sacked_out -= acked-1;
1581 }
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001582 tcp_check_reno_reordering(sk, acked);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001583 tcp_sync_left_out(tp);
1584}
1585
1586static inline void tcp_reset_reno_sack(struct tcp_sock *tp)
1587{
1588 tp->sacked_out = 0;
1589 tp->left_out = tp->lost_out;
1590}
1591
1592/* Mark head of queue up as lost. */
1593static void tcp_mark_head_lost(struct sock *sk, struct tcp_sock *tp,
1594 int packets, u32 high_seq)
1595{
1596 struct sk_buff *skb;
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001597 int cnt;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001598
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001599 BUG_TRAP(packets <= tp->packets_out);
1600 if (tp->lost_skb_hint) {
1601 skb = tp->lost_skb_hint;
1602 cnt = tp->lost_cnt_hint;
1603 } else {
1604 skb = sk->sk_write_queue.next;
1605 cnt = 0;
1606 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001607
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001608 sk_stream_for_retrans_queue_from(skb, sk) {
1609 /* TODO: do this better */
1610 /* this is not the most efficient way to do this... */
1611 tp->lost_skb_hint = skb;
1612 tp->lost_cnt_hint = cnt;
1613 cnt += tcp_skb_pcount(skb);
1614 if (cnt > packets || after(TCP_SKB_CB(skb)->end_seq, high_seq))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001615 break;
1616 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) {
1617 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1618 tp->lost_out += tcp_skb_pcount(skb);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001619
1620 /* clear xmit_retransmit_queue hints
1621 * if this is beyond hint */
1622 if(tp->retransmit_skb_hint != NULL &&
1623 before(TCP_SKB_CB(skb)->seq,
1624 TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) {
1625
1626 tp->retransmit_skb_hint = NULL;
1627 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001628 }
1629 }
1630 tcp_sync_left_out(tp);
1631}
1632
1633/* Account newly detected lost packet(s) */
1634
1635static void tcp_update_scoreboard(struct sock *sk, struct tcp_sock *tp)
1636{
1637 if (IsFack(tp)) {
1638 int lost = tp->fackets_out - tp->reordering;
1639 if (lost <= 0)
1640 lost = 1;
1641 tcp_mark_head_lost(sk, tp, lost, tp->high_seq);
1642 } else {
1643 tcp_mark_head_lost(sk, tp, 1, tp->high_seq);
1644 }
1645
1646 /* New heuristics: it is possible only after we switched
1647 * to restart timer each time when something is ACKed.
1648 * Hence, we can detect timed out packets during fast
1649 * retransmit without falling to slow start.
1650 */
1651 if (tcp_head_timedout(sk, tp)) {
1652 struct sk_buff *skb;
1653
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001654 skb = tp->scoreboard_skb_hint ? tp->scoreboard_skb_hint
1655 : sk->sk_write_queue.next;
1656
1657 sk_stream_for_retrans_queue_from(skb, sk) {
1658 if (!tcp_skb_timedout(sk, skb))
1659 break;
1660
1661 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001662 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1663 tp->lost_out += tcp_skb_pcount(skb);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001664
1665 /* clear xmit_retrans hint */
1666 if (tp->retransmit_skb_hint &&
1667 before(TCP_SKB_CB(skb)->seq,
1668 TCP_SKB_CB(tp->retransmit_skb_hint)->seq))
1669
1670 tp->retransmit_skb_hint = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001671 }
1672 }
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001673
1674 tp->scoreboard_skb_hint = skb;
1675
Linus Torvalds1da177e2005-04-16 15:20:36 -07001676 tcp_sync_left_out(tp);
1677 }
1678}
1679
1680/* CWND moderation, preventing bursts due to too big ACKs
1681 * in dubious situations.
1682 */
1683static inline void tcp_moderate_cwnd(struct tcp_sock *tp)
1684{
1685 tp->snd_cwnd = min(tp->snd_cwnd,
1686 tcp_packets_in_flight(tp)+tcp_max_burst(tp));
1687 tp->snd_cwnd_stamp = tcp_time_stamp;
1688}
1689
1690/* Decrease cwnd each second ack. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001691static void tcp_cwnd_down(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001692{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001693 const struct inet_connection_sock *icsk = inet_csk(sk);
1694 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001695 int decr = tp->snd_cwnd_cnt + 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001696
1697 tp->snd_cwnd_cnt = decr&1;
1698 decr >>= 1;
1699
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001700 if (decr && tp->snd_cwnd > icsk->icsk_ca_ops->min_cwnd(sk))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001701 tp->snd_cwnd -= decr;
1702
1703 tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp)+1);
1704 tp->snd_cwnd_stamp = tcp_time_stamp;
1705}
1706
1707/* Nothing was retransmitted or returned timestamp is less
1708 * than timestamp of the first retransmission.
1709 */
1710static inline int tcp_packet_delayed(struct tcp_sock *tp)
1711{
1712 return !tp->retrans_stamp ||
1713 (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
1714 (__s32)(tp->rx_opt.rcv_tsecr - tp->retrans_stamp) < 0);
1715}
1716
1717/* Undo procedures. */
1718
1719#if FASTRETRANS_DEBUG > 1
1720static void DBGUNDO(struct sock *sk, struct tcp_sock *tp, const char *msg)
1721{
1722 struct inet_sock *inet = inet_sk(sk);
1723 printk(KERN_DEBUG "Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n",
1724 msg,
1725 NIPQUAD(inet->daddr), ntohs(inet->dport),
1726 tp->snd_cwnd, tp->left_out,
1727 tp->snd_ssthresh, tp->prior_ssthresh,
1728 tp->packets_out);
1729}
1730#else
1731#define DBGUNDO(x...) do { } while (0)
1732#endif
1733
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001734static void tcp_undo_cwr(struct sock *sk, const int undo)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001735{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001736 struct tcp_sock *tp = tcp_sk(sk);
1737
Linus Torvalds1da177e2005-04-16 15:20:36 -07001738 if (tp->prior_ssthresh) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001739 const struct inet_connection_sock *icsk = inet_csk(sk);
1740
1741 if (icsk->icsk_ca_ops->undo_cwnd)
1742 tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001743 else
1744 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh<<1);
1745
1746 if (undo && tp->prior_ssthresh > tp->snd_ssthresh) {
1747 tp->snd_ssthresh = tp->prior_ssthresh;
1748 TCP_ECN_withdraw_cwr(tp);
1749 }
1750 } else {
1751 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh);
1752 }
1753 tcp_moderate_cwnd(tp);
1754 tp->snd_cwnd_stamp = tcp_time_stamp;
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001755
1756 /* There is something screwy going on with the retrans hints after
1757 an undo */
1758 clear_all_retrans_hints(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001759}
1760
1761static inline int tcp_may_undo(struct tcp_sock *tp)
1762{
1763 return tp->undo_marker &&
1764 (!tp->undo_retrans || tcp_packet_delayed(tp));
1765}
1766
1767/* People celebrate: "We love our President!" */
1768static int tcp_try_undo_recovery(struct sock *sk, struct tcp_sock *tp)
1769{
1770 if (tcp_may_undo(tp)) {
1771 /* Happy end! We did not retransmit anything
1772 * or our original transmission succeeded.
1773 */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001774 DBGUNDO(sk, tp, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans");
1775 tcp_undo_cwr(sk, 1);
1776 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001777 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO);
1778 else
1779 NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO);
1780 tp->undo_marker = 0;
1781 }
1782 if (tp->snd_una == tp->high_seq && IsReno(tp)) {
1783 /* Hold old state until something *above* high_seq
1784 * is ACKed. For Reno it is MUST to prevent false
1785 * fast retransmits (RFC2582). SACK TCP is safe. */
1786 tcp_moderate_cwnd(tp);
1787 return 1;
1788 }
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001789 tcp_set_ca_state(sk, TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001790 return 0;
1791}
1792
1793/* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
1794static void tcp_try_undo_dsack(struct sock *sk, struct tcp_sock *tp)
1795{
1796 if (tp->undo_marker && !tp->undo_retrans) {
1797 DBGUNDO(sk, tp, "D-SACK");
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001798 tcp_undo_cwr(sk, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001799 tp->undo_marker = 0;
1800 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO);
1801 }
1802}
1803
1804/* Undo during fast recovery after partial ACK. */
1805
1806static int tcp_try_undo_partial(struct sock *sk, struct tcp_sock *tp,
1807 int acked)
1808{
1809 /* Partial ACK arrived. Force Hoe's retransmit. */
1810 int failed = IsReno(tp) || tp->fackets_out>tp->reordering;
1811
1812 if (tcp_may_undo(tp)) {
1813 /* Plain luck! Hole if filled with delayed
1814 * packet, rather than with a retransmit.
1815 */
1816 if (tp->retrans_out == 0)
1817 tp->retrans_stamp = 0;
1818
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001819 tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001820
1821 DBGUNDO(sk, tp, "Hoe");
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001822 tcp_undo_cwr(sk, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001823 NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO);
1824
1825 /* So... Do not make Hoe's retransmit yet.
1826 * If the first packet was delayed, the rest
1827 * ones are most probably delayed as well.
1828 */
1829 failed = 0;
1830 }
1831 return failed;
1832}
1833
1834/* Undo during loss recovery after partial ACK. */
1835static int tcp_try_undo_loss(struct sock *sk, struct tcp_sock *tp)
1836{
1837 if (tcp_may_undo(tp)) {
1838 struct sk_buff *skb;
1839 sk_stream_for_retrans_queue(skb, sk) {
1840 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1841 }
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001842
1843 clear_all_retrans_hints(tp);
1844
Linus Torvalds1da177e2005-04-16 15:20:36 -07001845 DBGUNDO(sk, tp, "partial loss");
1846 tp->lost_out = 0;
1847 tp->left_out = tp->sacked_out;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001848 tcp_undo_cwr(sk, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001849 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001850 inet_csk(sk)->icsk_retransmits = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001851 tp->undo_marker = 0;
1852 if (!IsReno(tp))
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001853 tcp_set_ca_state(sk, TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001854 return 1;
1855 }
1856 return 0;
1857}
1858
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001859static inline void tcp_complete_cwr(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001860{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001861 struct tcp_sock *tp = tcp_sk(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -07001862 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001863 tp->snd_cwnd_stamp = tcp_time_stamp;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001864 tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001865}
1866
1867static void tcp_try_to_open(struct sock *sk, struct tcp_sock *tp, int flag)
1868{
1869 tp->left_out = tp->sacked_out;
1870
1871 if (tp->retrans_out == 0)
1872 tp->retrans_stamp = 0;
1873
1874 if (flag&FLAG_ECE)
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001875 tcp_enter_cwr(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001876
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001877 if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001878 int state = TCP_CA_Open;
1879
1880 if (tp->left_out || tp->retrans_out || tp->undo_marker)
1881 state = TCP_CA_Disorder;
1882
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001883 if (inet_csk(sk)->icsk_ca_state != state) {
1884 tcp_set_ca_state(sk, state);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001885 tp->high_seq = tp->snd_nxt;
1886 }
1887 tcp_moderate_cwnd(tp);
1888 } else {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001889 tcp_cwnd_down(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001890 }
1891}
1892
1893/* Process an event, which can update packets-in-flight not trivially.
1894 * Main goal of this function is to calculate new estimate for left_out,
1895 * taking into account both packets sitting in receiver's buffer and
1896 * packets lost by network.
1897 *
1898 * Besides that it does CWND reduction, when packet loss is detected
1899 * and changes state of machine.
1900 *
1901 * It does _not_ decide what to send, it is made in function
1902 * tcp_xmit_retransmit_queue().
1903 */
1904static void
1905tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una,
1906 int prior_packets, int flag)
1907{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001908 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001909 struct tcp_sock *tp = tcp_sk(sk);
1910 int is_dupack = (tp->snd_una == prior_snd_una && !(flag&FLAG_NOT_DUP));
1911
1912 /* Some technical things:
1913 * 1. Reno does not count dupacks (sacked_out) automatically. */
1914 if (!tp->packets_out)
1915 tp->sacked_out = 0;
1916 /* 2. SACK counts snd_fack in packets inaccurately. */
1917 if (tp->sacked_out == 0)
1918 tp->fackets_out = 0;
1919
1920 /* Now state machine starts.
1921 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
1922 if (flag&FLAG_ECE)
1923 tp->prior_ssthresh = 0;
1924
1925 /* B. In all the states check for reneging SACKs. */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001926 if (tp->sacked_out && tcp_check_sack_reneging(sk))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001927 return;
1928
1929 /* C. Process data loss notification, provided it is valid. */
1930 if ((flag&FLAG_DATA_LOST) &&
1931 before(tp->snd_una, tp->high_seq) &&
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001932 icsk->icsk_ca_state != TCP_CA_Open &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07001933 tp->fackets_out > tp->reordering) {
1934 tcp_mark_head_lost(sk, tp, tp->fackets_out-tp->reordering, tp->high_seq);
1935 NET_INC_STATS_BH(LINUX_MIB_TCPLOSS);
1936 }
1937
1938 /* D. Synchronize left_out to current state. */
1939 tcp_sync_left_out(tp);
1940
1941 /* E. Check state exit conditions. State can be terminated
1942 * when high_seq is ACKed. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001943 if (icsk->icsk_ca_state == TCP_CA_Open) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001944 if (!sysctl_tcp_frto)
1945 BUG_TRAP(tp->retrans_out == 0);
1946 tp->retrans_stamp = 0;
1947 } else if (!before(tp->snd_una, tp->high_seq)) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001948 switch (icsk->icsk_ca_state) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001949 case TCP_CA_Loss:
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001950 icsk->icsk_retransmits = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001951 if (tcp_try_undo_recovery(sk, tp))
1952 return;
1953 break;
1954
1955 case TCP_CA_CWR:
1956 /* CWR is to be held something *above* high_seq
1957 * is ACKed for CWR bit to reach receiver. */
1958 if (tp->snd_una != tp->high_seq) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001959 tcp_complete_cwr(sk);
1960 tcp_set_ca_state(sk, TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001961 }
1962 break;
1963
1964 case TCP_CA_Disorder:
1965 tcp_try_undo_dsack(sk, tp);
1966 if (!tp->undo_marker ||
1967 /* For SACK case do not Open to allow to undo
1968 * catching for all duplicate ACKs. */
1969 IsReno(tp) || tp->snd_una != tp->high_seq) {
1970 tp->undo_marker = 0;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001971 tcp_set_ca_state(sk, TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001972 }
1973 break;
1974
1975 case TCP_CA_Recovery:
1976 if (IsReno(tp))
1977 tcp_reset_reno_sack(tp);
1978 if (tcp_try_undo_recovery(sk, tp))
1979 return;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001980 tcp_complete_cwr(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001981 break;
1982 }
1983 }
1984
1985 /* F. Process state. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001986 switch (icsk->icsk_ca_state) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001987 case TCP_CA_Recovery:
1988 if (prior_snd_una == tp->snd_una) {
1989 if (IsReno(tp) && is_dupack)
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001990 tcp_add_reno_sack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001991 } else {
1992 int acked = prior_packets - tp->packets_out;
1993 if (IsReno(tp))
1994 tcp_remove_reno_sacks(sk, tp, acked);
1995 is_dupack = tcp_try_undo_partial(sk, tp, acked);
1996 }
1997 break;
1998 case TCP_CA_Loss:
1999 if (flag&FLAG_DATA_ACKED)
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002000 icsk->icsk_retransmits = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002001 if (!tcp_try_undo_loss(sk, tp)) {
2002 tcp_moderate_cwnd(tp);
2003 tcp_xmit_retransmit_queue(sk);
2004 return;
2005 }
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002006 if (icsk->icsk_ca_state != TCP_CA_Open)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002007 return;
2008 /* Loss is undone; fall through to processing in Open state. */
2009 default:
2010 if (IsReno(tp)) {
2011 if (tp->snd_una != prior_snd_una)
2012 tcp_reset_reno_sack(tp);
2013 if (is_dupack)
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002014 tcp_add_reno_sack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002015 }
2016
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002017 if (icsk->icsk_ca_state == TCP_CA_Disorder)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002018 tcp_try_undo_dsack(sk, tp);
2019
2020 if (!tcp_time_to_recover(sk, tp)) {
2021 tcp_try_to_open(sk, tp, flag);
2022 return;
2023 }
2024
2025 /* Otherwise enter Recovery state */
2026
2027 if (IsReno(tp))
2028 NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY);
2029 else
2030 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY);
2031
2032 tp->high_seq = tp->snd_nxt;
2033 tp->prior_ssthresh = 0;
2034 tp->undo_marker = tp->snd_una;
2035 tp->undo_retrans = tp->retrans_out;
2036
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002037 if (icsk->icsk_ca_state < TCP_CA_CWR) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002038 if (!(flag&FLAG_ECE))
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002039 tp->prior_ssthresh = tcp_current_ssthresh(sk);
2040 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002041 TCP_ECN_queue_cwr(tp);
2042 }
2043
Stephen Hemminger9772efb2005-11-10 17:09:53 -08002044 tp->bytes_acked = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002045 tp->snd_cwnd_cnt = 0;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002046 tcp_set_ca_state(sk, TCP_CA_Recovery);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002047 }
2048
2049 if (is_dupack || tcp_head_timedout(sk, tp))
2050 tcp_update_scoreboard(sk, tp);
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002051 tcp_cwnd_down(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002052 tcp_xmit_retransmit_queue(sk);
2053}
2054
2055/* Read draft-ietf-tcplw-high-performance before mucking
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08002056 * with this code. (Supersedes RFC1323)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002057 */
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002058static void tcp_ack_saw_tstamp(struct sock *sk, int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002059{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002060 /* RTTM Rule: A TSecr value received in a segment is used to
2061 * update the averaged RTT measurement only if the segment
2062 * acknowledges some new data, i.e., only if it advances the
2063 * left edge of the send window.
2064 *
2065 * See draft-ietf-tcplw-high-performance-00, section 3.3.
2066 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
2067 *
2068 * Changed: reset backoff as soon as we see the first valid sample.
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08002069 * If we do not, we get strongly overestimated rto. With timestamps
Linus Torvalds1da177e2005-04-16 15:20:36 -07002070 * samples are accepted even from very old segments: f.e., when rtt=1
2071 * increases to 8, we retransmit 5 times and after 8 seconds delayed
2072 * answer arrives rto becomes 120 seconds! If at least one of segments
2073 * in window is lost... Voila. --ANK (010210)
2074 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002075 struct tcp_sock *tp = tcp_sk(sk);
2076 const __u32 seq_rtt = tcp_time_stamp - tp->rx_opt.rcv_tsecr;
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002077 tcp_rtt_estimator(sk, seq_rtt);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002078 tcp_set_rto(sk);
2079 inet_csk(sk)->icsk_backoff = 0;
2080 tcp_bound_rto(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002081}
2082
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002083static void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002084{
2085 /* We don't have a timestamp. Can only use
2086 * packets that are not retransmitted to determine
2087 * rtt estimates. Also, we must not reset the
2088 * backoff for rto until we get a non-retransmitted
2089 * packet. This allows us to deal with a situation
2090 * where the network delay has increased suddenly.
2091 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
2092 */
2093
2094 if (flag & FLAG_RETRANS_DATA_ACKED)
2095 return;
2096
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002097 tcp_rtt_estimator(sk, seq_rtt);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002098 tcp_set_rto(sk);
2099 inet_csk(sk)->icsk_backoff = 0;
2100 tcp_bound_rto(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002101}
2102
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002103static inline void tcp_ack_update_rtt(struct sock *sk, const int flag,
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002104 const s32 seq_rtt)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002105{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002106 const struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002107 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
2108 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002109 tcp_ack_saw_tstamp(sk, flag);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002110 else if (seq_rtt >= 0)
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002111 tcp_ack_no_tstamp(sk, seq_rtt, flag);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002112}
2113
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08002114static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 rtt,
2115 u32 in_flight, int good)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002116{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002117 const struct inet_connection_sock *icsk = inet_csk(sk);
2118 icsk->icsk_ca_ops->cong_avoid(sk, ack, rtt, in_flight, good);
2119 tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002120}
2121
Linus Torvalds1da177e2005-04-16 15:20:36 -07002122/* Restart timer after forward progress on connection.
2123 * RFC2988 recommends to restart timer to now+rto.
2124 */
2125
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08002126static void tcp_ack_packets_out(struct sock *sk, struct tcp_sock *tp)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002127{
2128 if (!tp->packets_out) {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002129 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002130 } else {
Arnaldo Carvalho de Melo3f421ba2005-08-09 20:11:08 -07002131 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002132 }
2133}
2134
Linus Torvalds1da177e2005-04-16 15:20:36 -07002135static int tcp_tso_acked(struct sock *sk, struct sk_buff *skb,
2136 __u32 now, __s32 *seq_rtt)
2137{
2138 struct tcp_sock *tp = tcp_sk(sk);
2139 struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
2140 __u32 seq = tp->snd_una;
2141 __u32 packets_acked;
2142 int acked = 0;
2143
2144 /* If we get here, the whole TSO packet has not been
2145 * acked.
2146 */
2147 BUG_ON(!after(scb->end_seq, seq));
2148
2149 packets_acked = tcp_skb_pcount(skb);
2150 if (tcp_trim_head(sk, skb, seq - scb->seq))
2151 return 0;
2152 packets_acked -= tcp_skb_pcount(skb);
2153
2154 if (packets_acked) {
2155 __u8 sacked = scb->sacked;
2156
2157 acked |= FLAG_DATA_ACKED;
2158 if (sacked) {
2159 if (sacked & TCPCB_RETRANS) {
2160 if (sacked & TCPCB_SACKED_RETRANS)
2161 tp->retrans_out -= packets_acked;
2162 acked |= FLAG_RETRANS_DATA_ACKED;
2163 *seq_rtt = -1;
2164 } else if (*seq_rtt < 0)
2165 *seq_rtt = now - scb->when;
2166 if (sacked & TCPCB_SACKED_ACKED)
2167 tp->sacked_out -= packets_acked;
2168 if (sacked & TCPCB_LOST)
2169 tp->lost_out -= packets_acked;
2170 if (sacked & TCPCB_URG) {
2171 if (tp->urg_mode &&
2172 !before(seq, tp->snd_up))
2173 tp->urg_mode = 0;
2174 }
2175 } else if (*seq_rtt < 0)
2176 *seq_rtt = now - scb->when;
2177
2178 if (tp->fackets_out) {
2179 __u32 dval = min(tp->fackets_out, packets_acked);
2180 tp->fackets_out -= dval;
2181 }
2182 tp->packets_out -= packets_acked;
2183
2184 BUG_ON(tcp_skb_pcount(skb) == 0);
2185 BUG_ON(!before(scb->seq, scb->end_seq));
2186 }
2187
2188 return acked;
2189}
2190
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08002191static u32 tcp_usrtt(const struct sk_buff *skb)
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002192{
2193 struct timeval tv, now;
2194
2195 do_gettimeofday(&now);
2196 skb_get_timestamp(skb, &tv);
2197 return (now.tv_sec - tv.tv_sec) * 1000000 + (now.tv_usec - tv.tv_usec);
2198}
Linus Torvalds1da177e2005-04-16 15:20:36 -07002199
2200/* Remove acknowledged frames from the retransmission queue. */
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002201static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002202{
2203 struct tcp_sock *tp = tcp_sk(sk);
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002204 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002205 struct sk_buff *skb;
2206 __u32 now = tcp_time_stamp;
2207 int acked = 0;
2208 __s32 seq_rtt = -1;
Stephen Hemminger317a76f2005-06-23 12:19:55 -07002209 u32 pkts_acked = 0;
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002210 void (*rtt_sample)(struct sock *sk, u32 usrtt)
2211 = icsk->icsk_ca_ops->rtt_sample;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002212
2213 while ((skb = skb_peek(&sk->sk_write_queue)) &&
2214 skb != sk->sk_send_head) {
2215 struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
2216 __u8 sacked = scb->sacked;
2217
2218 /* If our packet is before the ack sequence we can
2219 * discard it as it's confirmed to have arrived at
2220 * the other end.
2221 */
2222 if (after(scb->end_seq, tp->snd_una)) {
David S. Millercb831992005-07-05 15:20:55 -07002223 if (tcp_skb_pcount(skb) > 1 &&
2224 after(tp->snd_una, scb->seq))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002225 acked |= tcp_tso_acked(sk, skb,
2226 now, &seq_rtt);
2227 break;
2228 }
2229
2230 /* Initial outgoing SYN's get put onto the write_queue
2231 * just like anything else we transmit. It is not
2232 * true data, and if we misinform our callers that
2233 * this ACK acks real data, we will erroneously exit
2234 * connection startup slow start one packet too
2235 * quickly. This is severely frowned upon behavior.
2236 */
2237 if (!(scb->flags & TCPCB_FLAG_SYN)) {
2238 acked |= FLAG_DATA_ACKED;
Stephen Hemminger317a76f2005-06-23 12:19:55 -07002239 ++pkts_acked;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002240 } else {
2241 acked |= FLAG_SYN_ACKED;
2242 tp->retrans_stamp = 0;
2243 }
2244
2245 if (sacked) {
2246 if (sacked & TCPCB_RETRANS) {
2247 if(sacked & TCPCB_SACKED_RETRANS)
2248 tp->retrans_out -= tcp_skb_pcount(skb);
2249 acked |= FLAG_RETRANS_DATA_ACKED;
2250 seq_rtt = -1;
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002251 } else if (seq_rtt < 0) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002252 seq_rtt = now - scb->when;
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002253 if (rtt_sample)
2254 (*rtt_sample)(sk, tcp_usrtt(skb));
Patrick McHardya61bbcf2005-08-14 17:24:31 -07002255 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002256 if (sacked & TCPCB_SACKED_ACKED)
2257 tp->sacked_out -= tcp_skb_pcount(skb);
2258 if (sacked & TCPCB_LOST)
2259 tp->lost_out -= tcp_skb_pcount(skb);
2260 if (sacked & TCPCB_URG) {
2261 if (tp->urg_mode &&
2262 !before(scb->end_seq, tp->snd_up))
2263 tp->urg_mode = 0;
2264 }
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002265 } else if (seq_rtt < 0) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002266 seq_rtt = now - scb->when;
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002267 if (rtt_sample)
2268 (*rtt_sample)(sk, tcp_usrtt(skb));
2269 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002270 tcp_dec_pcount_approx(&tp->fackets_out, skb);
2271 tcp_packets_out_dec(tp, skb);
David S. Miller8728b832005-08-09 19:25:21 -07002272 __skb_unlink(skb, &sk->sk_write_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002273 sk_stream_free_skb(sk, skb);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08002274 clear_all_retrans_hints(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002275 }
2276
2277 if (acked&FLAG_ACKED) {
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002278 tcp_ack_update_rtt(sk, acked, seq_rtt);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002279 tcp_ack_packets_out(sk, tp);
Stephen Hemminger317a76f2005-06-23 12:19:55 -07002280
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002281 if (icsk->icsk_ca_ops->pkts_acked)
2282 icsk->icsk_ca_ops->pkts_acked(sk, pkts_acked);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002283 }
2284
2285#if FASTRETRANS_DEBUG > 0
2286 BUG_TRAP((int)tp->sacked_out >= 0);
2287 BUG_TRAP((int)tp->lost_out >= 0);
2288 BUG_TRAP((int)tp->retrans_out >= 0);
2289 if (!tp->packets_out && tp->rx_opt.sack_ok) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002290 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002291 if (tp->lost_out) {
2292 printk(KERN_DEBUG "Leak l=%u %d\n",
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002293 tp->lost_out, icsk->icsk_ca_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002294 tp->lost_out = 0;
2295 }
2296 if (tp->sacked_out) {
2297 printk(KERN_DEBUG "Leak s=%u %d\n",
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002298 tp->sacked_out, icsk->icsk_ca_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002299 tp->sacked_out = 0;
2300 }
2301 if (tp->retrans_out) {
2302 printk(KERN_DEBUG "Leak r=%u %d\n",
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002303 tp->retrans_out, icsk->icsk_ca_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002304 tp->retrans_out = 0;
2305 }
2306 }
2307#endif
2308 *seq_rtt_p = seq_rtt;
2309 return acked;
2310}
2311
2312static void tcp_ack_probe(struct sock *sk)
2313{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002314 const struct tcp_sock *tp = tcp_sk(sk);
2315 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002316
2317 /* Was it a usable window open? */
2318
2319 if (!after(TCP_SKB_CB(sk->sk_send_head)->end_seq,
2320 tp->snd_una + tp->snd_wnd)) {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002321 icsk->icsk_backoff = 0;
2322 inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002323 /* Socket must be waked up by subsequent tcp_data_snd_check().
2324 * This function is not for random using!
2325 */
2326 } else {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002327 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
Arnaldo Carvalho de Melo3f421ba2005-08-09 20:11:08 -07002328 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
2329 TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002330 }
2331}
2332
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002333static inline int tcp_ack_is_dubious(const struct sock *sk, const int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002334{
2335 return (!(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) ||
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002336 inet_csk(sk)->icsk_ca_state != TCP_CA_Open);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002337}
2338
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002339static inline int tcp_may_raise_cwnd(const struct sock *sk, const int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002340{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002341 const struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002342 return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) &&
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002343 !((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_Recovery | TCPF_CA_CWR));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002344}
2345
2346/* Check that window update is acceptable.
2347 * The function assumes that snd_una<=ack<=snd_next.
2348 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002349static inline int tcp_may_update_window(const struct tcp_sock *tp, const u32 ack,
2350 const u32 ack_seq, const u32 nwin)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002351{
2352 return (after(ack, tp->snd_una) ||
2353 after(ack_seq, tp->snd_wl1) ||
2354 (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd));
2355}
2356
2357/* Update our send window.
2358 *
2359 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
2360 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
2361 */
2362static int tcp_ack_update_window(struct sock *sk, struct tcp_sock *tp,
2363 struct sk_buff *skb, u32 ack, u32 ack_seq)
2364{
2365 int flag = 0;
2366 u32 nwin = ntohs(skb->h.th->window);
2367
2368 if (likely(!skb->h.th->syn))
2369 nwin <<= tp->rx_opt.snd_wscale;
2370
2371 if (tcp_may_update_window(tp, ack, ack_seq, nwin)) {
2372 flag |= FLAG_WIN_UPDATE;
2373 tcp_update_wl(tp, ack, ack_seq);
2374
2375 if (tp->snd_wnd != nwin) {
2376 tp->snd_wnd = nwin;
2377
2378 /* Note, it is the only place, where
2379 * fast path is recovered for sending TCP.
2380 */
Herbert Xu2ad41062005-10-27 18:47:46 +10002381 tp->pred_flags = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002382 tcp_fast_path_check(sk, tp);
2383
2384 if (nwin > tp->max_window) {
2385 tp->max_window = nwin;
Arnaldo Carvalho de Melod83d8462005-12-13 23:26:10 -08002386 tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002387 }
2388 }
2389 }
2390
2391 tp->snd_una = ack;
2392
2393 return flag;
2394}
2395
2396static void tcp_process_frto(struct sock *sk, u32 prior_snd_una)
2397{
2398 struct tcp_sock *tp = tcp_sk(sk);
2399
2400 tcp_sync_left_out(tp);
2401
2402 if (tp->snd_una == prior_snd_una ||
2403 !before(tp->snd_una, tp->frto_highmark)) {
2404 /* RTO was caused by loss, start retransmitting in
2405 * go-back-N slow start
2406 */
2407 tcp_enter_frto_loss(sk);
2408 return;
2409 }
2410
2411 if (tp->frto_counter == 1) {
2412 /* First ACK after RTO advances the window: allow two new
2413 * segments out.
2414 */
2415 tp->snd_cwnd = tcp_packets_in_flight(tp) + 2;
2416 } else {
2417 /* Also the second ACK after RTO advances the window.
2418 * The RTO was likely spurious. Reduce cwnd and continue
2419 * in congestion avoidance
2420 */
2421 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
2422 tcp_moderate_cwnd(tp);
2423 }
2424
2425 /* F-RTO affects on two new ACKs following RTO.
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08002426 * At latest on third ACK the TCP behavior is back to normal.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002427 */
2428 tp->frto_counter = (tp->frto_counter + 1) % 3;
2429}
2430
Linus Torvalds1da177e2005-04-16 15:20:36 -07002431/* This routine deals with incoming acks, but not outgoing ones. */
2432static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
2433{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002434 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002435 struct tcp_sock *tp = tcp_sk(sk);
2436 u32 prior_snd_una = tp->snd_una;
2437 u32 ack_seq = TCP_SKB_CB(skb)->seq;
2438 u32 ack = TCP_SKB_CB(skb)->ack_seq;
2439 u32 prior_in_flight;
2440 s32 seq_rtt;
2441 int prior_packets;
2442
2443 /* If the ack is newer than sent or older than previous acks
2444 * then we can probably ignore it.
2445 */
2446 if (after(ack, tp->snd_nxt))
2447 goto uninteresting_ack;
2448
2449 if (before(ack, prior_snd_una))
2450 goto old_ack;
2451
Stephen Hemminger9772efb2005-11-10 17:09:53 -08002452 if (sysctl_tcp_abc && icsk->icsk_ca_state < TCP_CA_CWR)
2453 tp->bytes_acked += ack - prior_snd_una;
2454
Linus Torvalds1da177e2005-04-16 15:20:36 -07002455 if (!(flag&FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
2456 /* Window is constant, pure forward advance.
2457 * No more checks are required.
2458 * Note, we use the fact that SND.UNA>=SND.WL2.
2459 */
2460 tcp_update_wl(tp, ack, ack_seq);
2461 tp->snd_una = ack;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002462 flag |= FLAG_WIN_UPDATE;
2463
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002464 tcp_ca_event(sk, CA_EVENT_FAST_ACK);
Stephen Hemminger317a76f2005-06-23 12:19:55 -07002465
Linus Torvalds1da177e2005-04-16 15:20:36 -07002466 NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS);
2467 } else {
2468 if (ack_seq != TCP_SKB_CB(skb)->end_seq)
2469 flag |= FLAG_DATA;
2470 else
2471 NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS);
2472
2473 flag |= tcp_ack_update_window(sk, tp, skb, ack, ack_seq);
2474
2475 if (TCP_SKB_CB(skb)->sacked)
2476 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una);
2477
2478 if (TCP_ECN_rcv_ecn_echo(tp, skb->h.th))
2479 flag |= FLAG_ECE;
2480
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002481 tcp_ca_event(sk, CA_EVENT_SLOW_ACK);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002482 }
2483
2484 /* We passed data and got it acked, remove any soft error
2485 * log. Something worked...
2486 */
2487 sk->sk_err_soft = 0;
2488 tp->rcv_tstamp = tcp_time_stamp;
2489 prior_packets = tp->packets_out;
2490 if (!prior_packets)
2491 goto no_queue;
2492
2493 prior_in_flight = tcp_packets_in_flight(tp);
2494
2495 /* See if we can take anything off of the retransmit queue. */
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08002496 flag |= tcp_clean_rtx_queue(sk, &seq_rtt);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002497
2498 if (tp->frto_counter)
2499 tcp_process_frto(sk, prior_snd_una);
2500
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002501 if (tcp_ack_is_dubious(sk, flag)) {
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08002502 /* Advance CWND, if state allows this. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002503 if ((flag & FLAG_DATA_ACKED) && tcp_may_raise_cwnd(sk, flag))
2504 tcp_cong_avoid(sk, ack, seq_rtt, prior_in_flight, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002505 tcp_fastretrans_alert(sk, prior_snd_una, prior_packets, flag);
2506 } else {
Stephen Hemminger317a76f2005-06-23 12:19:55 -07002507 if ((flag & FLAG_DATA_ACKED))
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002508 tcp_cong_avoid(sk, ack, seq_rtt, prior_in_flight, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002509 }
2510
2511 if ((flag & FLAG_FORWARD_PROGRESS) || !(flag&FLAG_NOT_DUP))
2512 dst_confirm(sk->sk_dst_cache);
2513
2514 return 1;
2515
2516no_queue:
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002517 icsk->icsk_probes_out = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002518
2519 /* If this ack opens up a zero window, clear backoff. It was
2520 * being used to time the probes, and is probably far higher than
2521 * it needs to be for normal retransmission.
2522 */
2523 if (sk->sk_send_head)
2524 tcp_ack_probe(sk);
2525 return 1;
2526
2527old_ack:
2528 if (TCP_SKB_CB(skb)->sacked)
2529 tcp_sacktag_write_queue(sk, skb, prior_snd_una);
2530
2531uninteresting_ack:
2532 SOCK_DEBUG(sk, "Ack %u out of %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
2533 return 0;
2534}
2535
2536
2537/* Look for tcp options. Normally only called on SYN and SYNACK packets.
2538 * But, this can also be called on packets in the established flow when
2539 * the fast version below fails.
2540 */
2541void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx, int estab)
2542{
2543 unsigned char *ptr;
2544 struct tcphdr *th = skb->h.th;
2545 int length=(th->doff*4)-sizeof(struct tcphdr);
2546
2547 ptr = (unsigned char *)(th + 1);
2548 opt_rx->saw_tstamp = 0;
2549
2550 while(length>0) {
2551 int opcode=*ptr++;
2552 int opsize;
2553
2554 switch (opcode) {
2555 case TCPOPT_EOL:
2556 return;
2557 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
2558 length--;
2559 continue;
2560 default:
2561 opsize=*ptr++;
2562 if (opsize < 2) /* "silly options" */
2563 return;
2564 if (opsize > length)
2565 return; /* don't parse partial options */
2566 switch(opcode) {
2567 case TCPOPT_MSS:
2568 if(opsize==TCPOLEN_MSS && th->syn && !estab) {
2569 u16 in_mss = ntohs(get_unaligned((__u16 *)ptr));
2570 if (in_mss) {
2571 if (opt_rx->user_mss && opt_rx->user_mss < in_mss)
2572 in_mss = opt_rx->user_mss;
2573 opt_rx->mss_clamp = in_mss;
2574 }
2575 }
2576 break;
2577 case TCPOPT_WINDOW:
2578 if(opsize==TCPOLEN_WINDOW && th->syn && !estab)
2579 if (sysctl_tcp_window_scaling) {
2580 __u8 snd_wscale = *(__u8 *) ptr;
2581 opt_rx->wscale_ok = 1;
2582 if (snd_wscale > 14) {
2583 if(net_ratelimit())
2584 printk(KERN_INFO "tcp_parse_options: Illegal window "
2585 "scaling value %d >14 received.\n",
2586 snd_wscale);
2587 snd_wscale = 14;
2588 }
2589 opt_rx->snd_wscale = snd_wscale;
2590 }
2591 break;
2592 case TCPOPT_TIMESTAMP:
2593 if(opsize==TCPOLEN_TIMESTAMP) {
2594 if ((estab && opt_rx->tstamp_ok) ||
2595 (!estab && sysctl_tcp_timestamps)) {
2596 opt_rx->saw_tstamp = 1;
2597 opt_rx->rcv_tsval = ntohl(get_unaligned((__u32 *)ptr));
2598 opt_rx->rcv_tsecr = ntohl(get_unaligned((__u32 *)(ptr+4)));
2599 }
2600 }
2601 break;
2602 case TCPOPT_SACK_PERM:
2603 if(opsize==TCPOLEN_SACK_PERM && th->syn && !estab) {
2604 if (sysctl_tcp_sack) {
2605 opt_rx->sack_ok = 1;
2606 tcp_sack_reset(opt_rx);
2607 }
2608 }
2609 break;
2610
2611 case TCPOPT_SACK:
2612 if((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) &&
2613 !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) &&
2614 opt_rx->sack_ok) {
2615 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th;
2616 }
2617 };
2618 ptr+=opsize-2;
2619 length-=opsize;
2620 };
2621 }
2622}
2623
2624/* Fast parse options. This hopes to only see timestamps.
2625 * If it is wrong it falls back on tcp_parse_options().
2626 */
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08002627static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th,
2628 struct tcp_sock *tp)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002629{
2630 if (th->doff == sizeof(struct tcphdr)>>2) {
2631 tp->rx_opt.saw_tstamp = 0;
2632 return 0;
2633 } else if (tp->rx_opt.tstamp_ok &&
2634 th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) {
2635 __u32 *ptr = (__u32 *)(th + 1);
2636 if (*ptr == ntohl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
2637 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
2638 tp->rx_opt.saw_tstamp = 1;
2639 ++ptr;
2640 tp->rx_opt.rcv_tsval = ntohl(*ptr);
2641 ++ptr;
2642 tp->rx_opt.rcv_tsecr = ntohl(*ptr);
2643 return 1;
2644 }
2645 }
2646 tcp_parse_options(skb, &tp->rx_opt, 1);
2647 return 1;
2648}
2649
2650static inline void tcp_store_ts_recent(struct tcp_sock *tp)
2651{
2652 tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval;
2653 tp->rx_opt.ts_recent_stamp = xtime.tv_sec;
2654}
2655
2656static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)
2657{
2658 if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) {
2659 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
2660 * extra check below makes sure this can only happen
2661 * for pure ACK frames. -DaveM
2662 *
2663 * Not only, also it occurs for expired timestamps.
2664 */
2665
2666 if((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) >= 0 ||
2667 xtime.tv_sec >= tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS)
2668 tcp_store_ts_recent(tp);
2669 }
2670}
2671
2672/* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
2673 *
2674 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
2675 * it can pass through stack. So, the following predicate verifies that
2676 * this segment is not used for anything but congestion avoidance or
2677 * fast retransmit. Moreover, we even are able to eliminate most of such
2678 * second order effects, if we apply some small "replay" window (~RTO)
2679 * to timestamp space.
2680 *
2681 * All these measures still do not guarantee that we reject wrapped ACKs
2682 * on networks with high bandwidth, when sequence space is recycled fastly,
2683 * but it guarantees that such events will be very rare and do not affect
2684 * connection seriously. This doesn't look nice, but alas, PAWS is really
2685 * buggy extension.
2686 *
2687 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
2688 * states that events when retransmit arrives after original data are rare.
2689 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
2690 * the biggest problem on large power networks even with minor reordering.
2691 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
2692 * up to bandwidth of 18Gigabit/sec. 8) ]
2693 */
2694
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002695static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002696{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002697 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002698 struct tcphdr *th = skb->h.th;
2699 u32 seq = TCP_SKB_CB(skb)->seq;
2700 u32 ack = TCP_SKB_CB(skb)->ack_seq;
2701
2702 return (/* 1. Pure ACK with correct sequence number. */
2703 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) &&
2704
2705 /* 2. ... and duplicate ACK. */
2706 ack == tp->snd_una &&
2707
2708 /* 3. ... and does not update window. */
2709 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) &&
2710
2711 /* 4. ... and sits in replay window. */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002712 (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 -07002713}
2714
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002715static inline int tcp_paws_discard(const struct sock *sk, const struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002716{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002717 const struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002718 return ((s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) > TCP_PAWS_WINDOW &&
2719 xtime.tv_sec < tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS &&
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002720 !tcp_disordered_ack(sk, skb));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002721}
2722
2723/* Check segment sequence number for validity.
2724 *
2725 * Segment controls are considered valid, if the segment
2726 * fits to the window after truncation to the window. Acceptability
2727 * of data (and SYN, FIN, of course) is checked separately.
2728 * See tcp_data_queue(), for example.
2729 *
2730 * Also, controls (RST is main one) are accepted using RCV.WUP instead
2731 * of RCV.NXT. Peer still did not advance his SND.UNA when we
2732 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
2733 * (borrowed from freebsd)
2734 */
2735
2736static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq)
2737{
2738 return !before(end_seq, tp->rcv_wup) &&
2739 !after(seq, tp->rcv_nxt + tcp_receive_window(tp));
2740}
2741
2742/* When we get a reset we do this. */
2743static void tcp_reset(struct sock *sk)
2744{
2745 /* We want the right error as BSD sees it (and indeed as we do). */
2746 switch (sk->sk_state) {
2747 case TCP_SYN_SENT:
2748 sk->sk_err = ECONNREFUSED;
2749 break;
2750 case TCP_CLOSE_WAIT:
2751 sk->sk_err = EPIPE;
2752 break;
2753 case TCP_CLOSE:
2754 return;
2755 default:
2756 sk->sk_err = ECONNRESET;
2757 }
2758
2759 if (!sock_flag(sk, SOCK_DEAD))
2760 sk->sk_error_report(sk);
2761
2762 tcp_done(sk);
2763}
2764
2765/*
2766 * Process the FIN bit. This now behaves as it is supposed to work
2767 * and the FIN takes effect when it is validly part of sequence
2768 * space. Not before when we get holes.
2769 *
2770 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
2771 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
2772 * TIME-WAIT)
2773 *
2774 * If we are in FINWAIT-1, a received FIN indicates simultaneous
2775 * close and we go into CLOSING (and later onto TIME-WAIT)
2776 *
2777 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
2778 */
2779static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th)
2780{
2781 struct tcp_sock *tp = tcp_sk(sk);
2782
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002783 inet_csk_schedule_ack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002784
2785 sk->sk_shutdown |= RCV_SHUTDOWN;
2786 sock_set_flag(sk, SOCK_DONE);
2787
2788 switch (sk->sk_state) {
2789 case TCP_SYN_RECV:
2790 case TCP_ESTABLISHED:
2791 /* Move to CLOSE_WAIT */
2792 tcp_set_state(sk, TCP_CLOSE_WAIT);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002793 inet_csk(sk)->icsk_ack.pingpong = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002794 break;
2795
2796 case TCP_CLOSE_WAIT:
2797 case TCP_CLOSING:
2798 /* Received a retransmission of the FIN, do
2799 * nothing.
2800 */
2801 break;
2802 case TCP_LAST_ACK:
2803 /* RFC793: Remain in the LAST-ACK state. */
2804 break;
2805
2806 case TCP_FIN_WAIT1:
2807 /* This case occurs when a simultaneous close
2808 * happens, we must ack the received FIN and
2809 * enter the CLOSING state.
2810 */
2811 tcp_send_ack(sk);
2812 tcp_set_state(sk, TCP_CLOSING);
2813 break;
2814 case TCP_FIN_WAIT2:
2815 /* Received a FIN -- send ACK and enter TIME_WAIT. */
2816 tcp_send_ack(sk);
2817 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
2818 break;
2819 default:
2820 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
2821 * cases we should never reach this piece of code.
2822 */
2823 printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n",
2824 __FUNCTION__, sk->sk_state);
2825 break;
2826 };
2827
2828 /* It _is_ possible, that we have something out-of-order _after_ FIN.
2829 * Probably, we should reset in this case. For now drop them.
2830 */
2831 __skb_queue_purge(&tp->out_of_order_queue);
2832 if (tp->rx_opt.sack_ok)
2833 tcp_sack_reset(&tp->rx_opt);
2834 sk_stream_mem_reclaim(sk);
2835
2836 if (!sock_flag(sk, SOCK_DEAD)) {
2837 sk->sk_state_change(sk);
2838
2839 /* Do not send POLL_HUP for half duplex close. */
2840 if (sk->sk_shutdown == SHUTDOWN_MASK ||
2841 sk->sk_state == TCP_CLOSE)
2842 sk_wake_async(sk, 1, POLL_HUP);
2843 else
2844 sk_wake_async(sk, 1, POLL_IN);
2845 }
2846}
2847
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08002848static inline int tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, u32 end_seq)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002849{
2850 if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) {
2851 if (before(seq, sp->start_seq))
2852 sp->start_seq = seq;
2853 if (after(end_seq, sp->end_seq))
2854 sp->end_seq = end_seq;
2855 return 1;
2856 }
2857 return 0;
2858}
2859
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08002860static void tcp_dsack_set(struct tcp_sock *tp, u32 seq, u32 end_seq)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002861{
2862 if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) {
2863 if (before(seq, tp->rcv_nxt))
2864 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT);
2865 else
2866 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT);
2867
2868 tp->rx_opt.dsack = 1;
2869 tp->duplicate_sack[0].start_seq = seq;
2870 tp->duplicate_sack[0].end_seq = end_seq;
2871 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + 1, 4 - tp->rx_opt.tstamp_ok);
2872 }
2873}
2874
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08002875static void tcp_dsack_extend(struct tcp_sock *tp, u32 seq, u32 end_seq)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002876{
2877 if (!tp->rx_opt.dsack)
2878 tcp_dsack_set(tp, seq, end_seq);
2879 else
2880 tcp_sack_extend(tp->duplicate_sack, seq, end_seq);
2881}
2882
2883static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb)
2884{
2885 struct tcp_sock *tp = tcp_sk(sk);
2886
2887 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
2888 before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
2889 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002890 tcp_enter_quickack_mode(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002891
2892 if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) {
2893 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
2894
2895 if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))
2896 end_seq = tp->rcv_nxt;
2897 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, end_seq);
2898 }
2899 }
2900
2901 tcp_send_ack(sk);
2902}
2903
2904/* These routines update the SACK block as out-of-order packets arrive or
2905 * in-order packets close up the sequence space.
2906 */
2907static void tcp_sack_maybe_coalesce(struct tcp_sock *tp)
2908{
2909 int this_sack;
2910 struct tcp_sack_block *sp = &tp->selective_acks[0];
2911 struct tcp_sack_block *swalk = sp+1;
2912
2913 /* See if the recent change to the first SACK eats into
2914 * or hits the sequence space of other SACK blocks, if so coalesce.
2915 */
2916 for (this_sack = 1; this_sack < tp->rx_opt.num_sacks; ) {
2917 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) {
2918 int i;
2919
2920 /* Zap SWALK, by moving every further SACK up by one slot.
2921 * Decrease num_sacks.
2922 */
2923 tp->rx_opt.num_sacks--;
2924 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
2925 for(i=this_sack; i < tp->rx_opt.num_sacks; i++)
2926 sp[i] = sp[i+1];
2927 continue;
2928 }
2929 this_sack++, swalk++;
2930 }
2931}
2932
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08002933static inline void tcp_sack_swap(struct tcp_sack_block *sack1, struct tcp_sack_block *sack2)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002934{
2935 __u32 tmp;
2936
2937 tmp = sack1->start_seq;
2938 sack1->start_seq = sack2->start_seq;
2939 sack2->start_seq = tmp;
2940
2941 tmp = sack1->end_seq;
2942 sack1->end_seq = sack2->end_seq;
2943 sack2->end_seq = tmp;
2944}
2945
2946static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq)
2947{
2948 struct tcp_sock *tp = tcp_sk(sk);
2949 struct tcp_sack_block *sp = &tp->selective_acks[0];
2950 int cur_sacks = tp->rx_opt.num_sacks;
2951 int this_sack;
2952
2953 if (!cur_sacks)
2954 goto new_sack;
2955
2956 for (this_sack=0; this_sack<cur_sacks; this_sack++, sp++) {
2957 if (tcp_sack_extend(sp, seq, end_seq)) {
2958 /* Rotate this_sack to the first one. */
2959 for (; this_sack>0; this_sack--, sp--)
2960 tcp_sack_swap(sp, sp-1);
2961 if (cur_sacks > 1)
2962 tcp_sack_maybe_coalesce(tp);
2963 return;
2964 }
2965 }
2966
2967 /* Could not find an adjacent existing SACK, build a new one,
2968 * put it at the front, and shift everyone else down. We
2969 * always know there is at least one SACK present already here.
2970 *
2971 * If the sack array is full, forget about the last one.
2972 */
2973 if (this_sack >= 4) {
2974 this_sack--;
2975 tp->rx_opt.num_sacks--;
2976 sp--;
2977 }
2978 for(; this_sack > 0; this_sack--, sp--)
2979 *sp = *(sp-1);
2980
2981new_sack:
2982 /* Build the new head SACK, and we're done. */
2983 sp->start_seq = seq;
2984 sp->end_seq = end_seq;
2985 tp->rx_opt.num_sacks++;
2986 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
2987}
2988
2989/* RCV.NXT advances, some SACKs should be eaten. */
2990
2991static void tcp_sack_remove(struct tcp_sock *tp)
2992{
2993 struct tcp_sack_block *sp = &tp->selective_acks[0];
2994 int num_sacks = tp->rx_opt.num_sacks;
2995 int this_sack;
2996
2997 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
David S. Millerb03efcf2005-07-08 14:57:23 -07002998 if (skb_queue_empty(&tp->out_of_order_queue)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002999 tp->rx_opt.num_sacks = 0;
3000 tp->rx_opt.eff_sacks = tp->rx_opt.dsack;
3001 return;
3002 }
3003
3004 for(this_sack = 0; this_sack < num_sacks; ) {
3005 /* Check if the start of the sack is covered by RCV.NXT. */
3006 if (!before(tp->rcv_nxt, sp->start_seq)) {
3007 int i;
3008
3009 /* RCV.NXT must cover all the block! */
3010 BUG_TRAP(!before(tp->rcv_nxt, sp->end_seq));
3011
3012 /* Zap this SACK, by moving forward any other SACKS. */
3013 for (i=this_sack+1; i < num_sacks; i++)
3014 tp->selective_acks[i-1] = tp->selective_acks[i];
3015 num_sacks--;
3016 continue;
3017 }
3018 this_sack++;
3019 sp++;
3020 }
3021 if (num_sacks != tp->rx_opt.num_sacks) {
3022 tp->rx_opt.num_sacks = num_sacks;
3023 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
3024 }
3025}
3026
3027/* This one checks to see if we can put data from the
3028 * out_of_order queue into the receive_queue.
3029 */
3030static void tcp_ofo_queue(struct sock *sk)
3031{
3032 struct tcp_sock *tp = tcp_sk(sk);
3033 __u32 dsack_high = tp->rcv_nxt;
3034 struct sk_buff *skb;
3035
3036 while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) {
3037 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
3038 break;
3039
3040 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) {
3041 __u32 dsack = dsack_high;
3042 if (before(TCP_SKB_CB(skb)->end_seq, dsack_high))
3043 dsack_high = TCP_SKB_CB(skb)->end_seq;
3044 tcp_dsack_extend(tp, TCP_SKB_CB(skb)->seq, dsack);
3045 }
3046
3047 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
3048 SOCK_DEBUG(sk, "ofo packet was already received \n");
David S. Miller8728b832005-08-09 19:25:21 -07003049 __skb_unlink(skb, &tp->out_of_order_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003050 __kfree_skb(skb);
3051 continue;
3052 }
3053 SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n",
3054 tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
3055 TCP_SKB_CB(skb)->end_seq);
3056
David S. Miller8728b832005-08-09 19:25:21 -07003057 __skb_unlink(skb, &tp->out_of_order_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003058 __skb_queue_tail(&sk->sk_receive_queue, skb);
3059 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3060 if(skb->h.th->fin)
3061 tcp_fin(skb, sk, skb->h.th);
3062 }
3063}
3064
3065static int tcp_prune_queue(struct sock *sk);
3066
3067static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
3068{
3069 struct tcphdr *th = skb->h.th;
3070 struct tcp_sock *tp = tcp_sk(sk);
3071 int eaten = -1;
3072
3073 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq)
3074 goto drop;
3075
Linus Torvalds1da177e2005-04-16 15:20:36 -07003076 __skb_pull(skb, th->doff*4);
3077
3078 TCP_ECN_accept_cwr(tp, skb);
3079
3080 if (tp->rx_opt.dsack) {
3081 tp->rx_opt.dsack = 0;
3082 tp->rx_opt.eff_sacks = min_t(unsigned int, tp->rx_opt.num_sacks,
3083 4 - tp->rx_opt.tstamp_ok);
3084 }
3085
3086 /* Queue data for delivery to the user.
3087 * Packets in sequence go to the receive queue.
3088 * Out of sequence packets to the out_of_order_queue.
3089 */
3090 if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
3091 if (tcp_receive_window(tp) == 0)
3092 goto out_of_window;
3093
3094 /* Ok. In sequence. In window. */
3095 if (tp->ucopy.task == current &&
3096 tp->copied_seq == tp->rcv_nxt && tp->ucopy.len &&
3097 sock_owned_by_user(sk) && !tp->urg_data) {
3098 int chunk = min_t(unsigned int, skb->len,
3099 tp->ucopy.len);
3100
3101 __set_current_state(TASK_RUNNING);
3102
3103 local_bh_enable();
3104 if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) {
3105 tp->ucopy.len -= chunk;
3106 tp->copied_seq += chunk;
3107 eaten = (chunk == skb->len && !th->fin);
3108 tcp_rcv_space_adjust(sk);
3109 }
3110 local_bh_disable();
3111 }
3112
3113 if (eaten <= 0) {
3114queue_and_out:
3115 if (eaten < 0 &&
3116 (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
3117 !sk_stream_rmem_schedule(sk, skb))) {
3118 if (tcp_prune_queue(sk) < 0 ||
3119 !sk_stream_rmem_schedule(sk, skb))
3120 goto drop;
3121 }
3122 sk_stream_set_owner_r(skb, sk);
3123 __skb_queue_tail(&sk->sk_receive_queue, skb);
3124 }
3125 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3126 if(skb->len)
3127 tcp_event_data_recv(sk, tp, skb);
3128 if(th->fin)
3129 tcp_fin(skb, sk, th);
3130
David S. Millerb03efcf2005-07-08 14:57:23 -07003131 if (!skb_queue_empty(&tp->out_of_order_queue)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003132 tcp_ofo_queue(sk);
3133
3134 /* RFC2581. 4.2. SHOULD send immediate ACK, when
3135 * gap in queue is filled.
3136 */
David S. Millerb03efcf2005-07-08 14:57:23 -07003137 if (skb_queue_empty(&tp->out_of_order_queue))
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003138 inet_csk(sk)->icsk_ack.pingpong = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003139 }
3140
3141 if (tp->rx_opt.num_sacks)
3142 tcp_sack_remove(tp);
3143
3144 tcp_fast_path_check(sk, tp);
3145
3146 if (eaten > 0)
3147 __kfree_skb(skb);
3148 else if (!sock_flag(sk, SOCK_DEAD))
3149 sk->sk_data_ready(sk, 0);
3150 return;
3151 }
3152
3153 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
3154 /* A retransmit, 2nd most common case. Force an immediate ack. */
3155 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST);
3156 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
3157
3158out_of_window:
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003159 tcp_enter_quickack_mode(sk);
3160 inet_csk_schedule_ack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003161drop:
3162 __kfree_skb(skb);
3163 return;
3164 }
3165
3166 /* Out of window. F.e. zero window probe. */
3167 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp)))
3168 goto out_of_window;
3169
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003170 tcp_enter_quickack_mode(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003171
3172 if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
3173 /* Partial packet, seq < rcv_next < end_seq */
3174 SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n",
3175 tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
3176 TCP_SKB_CB(skb)->end_seq);
3177
3178 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, tp->rcv_nxt);
3179
3180 /* If window is closed, drop tail of packet. But after
3181 * remembering D-SACK for its head made in previous line.
3182 */
3183 if (!tcp_receive_window(tp))
3184 goto out_of_window;
3185 goto queue_and_out;
3186 }
3187
3188 TCP_ECN_check_ce(tp, skb);
3189
3190 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
3191 !sk_stream_rmem_schedule(sk, skb)) {
3192 if (tcp_prune_queue(sk) < 0 ||
3193 !sk_stream_rmem_schedule(sk, skb))
3194 goto drop;
3195 }
3196
3197 /* Disable header prediction. */
3198 tp->pred_flags = 0;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003199 inet_csk_schedule_ack(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003200
3201 SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n",
3202 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
3203
3204 sk_stream_set_owner_r(skb, sk);
3205
3206 if (!skb_peek(&tp->out_of_order_queue)) {
3207 /* Initial out of order segment, build 1 SACK. */
3208 if (tp->rx_opt.sack_ok) {
3209 tp->rx_opt.num_sacks = 1;
3210 tp->rx_opt.dsack = 0;
3211 tp->rx_opt.eff_sacks = 1;
3212 tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
3213 tp->selective_acks[0].end_seq =
3214 TCP_SKB_CB(skb)->end_seq;
3215 }
3216 __skb_queue_head(&tp->out_of_order_queue,skb);
3217 } else {
3218 struct sk_buff *skb1 = tp->out_of_order_queue.prev;
3219 u32 seq = TCP_SKB_CB(skb)->seq;
3220 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
3221
3222 if (seq == TCP_SKB_CB(skb1)->end_seq) {
David S. Miller8728b832005-08-09 19:25:21 -07003223 __skb_append(skb1, skb, &tp->out_of_order_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003224
3225 if (!tp->rx_opt.num_sacks ||
3226 tp->selective_acks[0].end_seq != seq)
3227 goto add_sack;
3228
3229 /* Common case: data arrive in order after hole. */
3230 tp->selective_acks[0].end_seq = end_seq;
3231 return;
3232 }
3233
3234 /* Find place to insert this segment. */
3235 do {
3236 if (!after(TCP_SKB_CB(skb1)->seq, seq))
3237 break;
3238 } while ((skb1 = skb1->prev) !=
3239 (struct sk_buff*)&tp->out_of_order_queue);
3240
3241 /* Do skb overlap to previous one? */
3242 if (skb1 != (struct sk_buff*)&tp->out_of_order_queue &&
3243 before(seq, TCP_SKB_CB(skb1)->end_seq)) {
3244 if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
3245 /* All the bits are present. Drop. */
3246 __kfree_skb(skb);
3247 tcp_dsack_set(tp, seq, end_seq);
3248 goto add_sack;
3249 }
3250 if (after(seq, TCP_SKB_CB(skb1)->seq)) {
3251 /* Partial overlap. */
3252 tcp_dsack_set(tp, seq, TCP_SKB_CB(skb1)->end_seq);
3253 } else {
3254 skb1 = skb1->prev;
3255 }
3256 }
3257 __skb_insert(skb, skb1, skb1->next, &tp->out_of_order_queue);
3258
3259 /* And clean segments covered by new one as whole. */
3260 while ((skb1 = skb->next) !=
3261 (struct sk_buff*)&tp->out_of_order_queue &&
3262 after(end_seq, TCP_SKB_CB(skb1)->seq)) {
3263 if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
3264 tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, end_seq);
3265 break;
3266 }
David S. Miller8728b832005-08-09 19:25:21 -07003267 __skb_unlink(skb1, &tp->out_of_order_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003268 tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, TCP_SKB_CB(skb1)->end_seq);
3269 __kfree_skb(skb1);
3270 }
3271
3272add_sack:
3273 if (tp->rx_opt.sack_ok)
3274 tcp_sack_new_ofo_skb(sk, seq, end_seq);
3275 }
3276}
3277
3278/* Collapse contiguous sequence of skbs head..tail with
3279 * sequence numbers start..end.
3280 * Segments with FIN/SYN are not collapsed (only because this
3281 * simplifies code)
3282 */
3283static void
David S. Miller8728b832005-08-09 19:25:21 -07003284tcp_collapse(struct sock *sk, struct sk_buff_head *list,
3285 struct sk_buff *head, struct sk_buff *tail,
3286 u32 start, u32 end)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003287{
3288 struct sk_buff *skb;
3289
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08003290 /* First, check that queue is collapsible and find
Linus Torvalds1da177e2005-04-16 15:20:36 -07003291 * the point where collapsing can be useful. */
3292 for (skb = head; skb != tail; ) {
3293 /* No new bits? It is possible on ofo queue. */
3294 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
3295 struct sk_buff *next = skb->next;
David S. Miller8728b832005-08-09 19:25:21 -07003296 __skb_unlink(skb, list);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003297 __kfree_skb(skb);
3298 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED);
3299 skb = next;
3300 continue;
3301 }
3302
3303 /* The first skb to collapse is:
3304 * - not SYN/FIN and
3305 * - bloated or contains data before "start" or
3306 * overlaps to the next one.
3307 */
3308 if (!skb->h.th->syn && !skb->h.th->fin &&
3309 (tcp_win_from_space(skb->truesize) > skb->len ||
3310 before(TCP_SKB_CB(skb)->seq, start) ||
3311 (skb->next != tail &&
3312 TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb->next)->seq)))
3313 break;
3314
3315 /* Decided to skip this, advance start seq. */
3316 start = TCP_SKB_CB(skb)->end_seq;
3317 skb = skb->next;
3318 }
3319 if (skb == tail || skb->h.th->syn || skb->h.th->fin)
3320 return;
3321
3322 while (before(start, end)) {
3323 struct sk_buff *nskb;
3324 int header = skb_headroom(skb);
3325 int copy = SKB_MAX_ORDER(header, 0);
3326
3327 /* Too big header? This can happen with IPv6. */
3328 if (copy < 0)
3329 return;
3330 if (end-start < copy)
3331 copy = end-start;
3332 nskb = alloc_skb(copy+header, GFP_ATOMIC);
3333 if (!nskb)
3334 return;
3335 skb_reserve(nskb, header);
3336 memcpy(nskb->head, skb->head, header);
3337 nskb->nh.raw = nskb->head + (skb->nh.raw-skb->head);
3338 nskb->h.raw = nskb->head + (skb->h.raw-skb->head);
3339 nskb->mac.raw = nskb->head + (skb->mac.raw-skb->head);
3340 memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
3341 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start;
David S. Miller8728b832005-08-09 19:25:21 -07003342 __skb_insert(nskb, skb->prev, skb, list);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003343 sk_stream_set_owner_r(nskb, sk);
3344
3345 /* Copy data, releasing collapsed skbs. */
3346 while (copy > 0) {
3347 int offset = start - TCP_SKB_CB(skb)->seq;
3348 int size = TCP_SKB_CB(skb)->end_seq - start;
3349
Kris Katterjohn09a62662006-01-08 22:24:28 -08003350 BUG_ON(offset < 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003351 if (size > 0) {
3352 size = min(copy, size);
3353 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size))
3354 BUG();
3355 TCP_SKB_CB(nskb)->end_seq += size;
3356 copy -= size;
3357 start += size;
3358 }
3359 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
3360 struct sk_buff *next = skb->next;
David S. Miller8728b832005-08-09 19:25:21 -07003361 __skb_unlink(skb, list);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003362 __kfree_skb(skb);
3363 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED);
3364 skb = next;
3365 if (skb == tail || skb->h.th->syn || skb->h.th->fin)
3366 return;
3367 }
3368 }
3369 }
3370}
3371
3372/* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
3373 * and tcp_collapse() them until all the queue is collapsed.
3374 */
3375static void tcp_collapse_ofo_queue(struct sock *sk)
3376{
3377 struct tcp_sock *tp = tcp_sk(sk);
3378 struct sk_buff *skb = skb_peek(&tp->out_of_order_queue);
3379 struct sk_buff *head;
3380 u32 start, end;
3381
3382 if (skb == NULL)
3383 return;
3384
3385 start = TCP_SKB_CB(skb)->seq;
3386 end = TCP_SKB_CB(skb)->end_seq;
3387 head = skb;
3388
3389 for (;;) {
3390 skb = skb->next;
3391
3392 /* Segment is terminated when we see gap or when
3393 * we are at the end of all the queue. */
3394 if (skb == (struct sk_buff *)&tp->out_of_order_queue ||
3395 after(TCP_SKB_CB(skb)->seq, end) ||
3396 before(TCP_SKB_CB(skb)->end_seq, start)) {
David S. Miller8728b832005-08-09 19:25:21 -07003397 tcp_collapse(sk, &tp->out_of_order_queue,
3398 head, skb, start, end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003399 head = skb;
3400 if (skb == (struct sk_buff *)&tp->out_of_order_queue)
3401 break;
3402 /* Start new segment */
3403 start = TCP_SKB_CB(skb)->seq;
3404 end = TCP_SKB_CB(skb)->end_seq;
3405 } else {
3406 if (before(TCP_SKB_CB(skb)->seq, start))
3407 start = TCP_SKB_CB(skb)->seq;
3408 if (after(TCP_SKB_CB(skb)->end_seq, end))
3409 end = TCP_SKB_CB(skb)->end_seq;
3410 }
3411 }
3412}
3413
3414/* Reduce allocated memory if we can, trying to get
3415 * the socket within its memory limits again.
3416 *
3417 * Return less than zero if we should start dropping frames
3418 * until the socket owning process reads some of the data
3419 * to stabilize the situation.
3420 */
3421static int tcp_prune_queue(struct sock *sk)
3422{
3423 struct tcp_sock *tp = tcp_sk(sk);
3424
3425 SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq);
3426
3427 NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED);
3428
3429 if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
3430 tcp_clamp_window(sk, tp);
3431 else if (tcp_memory_pressure)
3432 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss);
3433
3434 tcp_collapse_ofo_queue(sk);
David S. Miller8728b832005-08-09 19:25:21 -07003435 tcp_collapse(sk, &sk->sk_receive_queue,
3436 sk->sk_receive_queue.next,
Linus Torvalds1da177e2005-04-16 15:20:36 -07003437 (struct sk_buff*)&sk->sk_receive_queue,
3438 tp->copied_seq, tp->rcv_nxt);
3439 sk_stream_mem_reclaim(sk);
3440
3441 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
3442 return 0;
3443
3444 /* Collapsing did not help, destructive actions follow.
3445 * This must not ever occur. */
3446
3447 /* First, purge the out_of_order queue. */
David S. Millerb03efcf2005-07-08 14:57:23 -07003448 if (!skb_queue_empty(&tp->out_of_order_queue)) {
3449 NET_INC_STATS_BH(LINUX_MIB_OFOPRUNED);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003450 __skb_queue_purge(&tp->out_of_order_queue);
3451
3452 /* Reset SACK state. A conforming SACK implementation will
3453 * do the same at a timeout based retransmit. When a connection
3454 * is in a sad state like this, we care only about integrity
3455 * of the connection not performance.
3456 */
3457 if (tp->rx_opt.sack_ok)
3458 tcp_sack_reset(&tp->rx_opt);
3459 sk_stream_mem_reclaim(sk);
3460 }
3461
3462 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
3463 return 0;
3464
3465 /* If we are really being abused, tell the caller to silently
3466 * drop receive data on the floor. It will get retransmitted
3467 * and hopefully then we'll have sufficient space.
3468 */
3469 NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED);
3470
3471 /* Massive buffer overcommit. */
3472 tp->pred_flags = 0;
3473 return -1;
3474}
3475
3476
3477/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
3478 * As additional protections, we do not touch cwnd in retransmission phases,
3479 * and if application hit its sndbuf limit recently.
3480 */
3481void tcp_cwnd_application_limited(struct sock *sk)
3482{
3483 struct tcp_sock *tp = tcp_sk(sk);
3484
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003485 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07003486 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
3487 /* Limited by application or receiver window. */
3488 u32 win_used = max(tp->snd_cwnd_used, 2U);
3489 if (win_used < tp->snd_cwnd) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03003490 tp->snd_ssthresh = tcp_current_ssthresh(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003491 tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
3492 }
3493 tp->snd_cwnd_used = 0;
3494 }
3495 tp->snd_cwnd_stamp = tcp_time_stamp;
3496}
3497
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08003498static int tcp_should_expand_sndbuf(struct sock *sk, struct tcp_sock *tp)
David S. Miller0d9901d2005-07-05 15:21:10 -07003499{
3500 /* If the user specified a specific send buffer setting, do
3501 * not modify it.
3502 */
3503 if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
3504 return 0;
3505
3506 /* If we are under global TCP memory pressure, do not expand. */
3507 if (tcp_memory_pressure)
3508 return 0;
3509
3510 /* If we are under soft global TCP memory pressure, do not expand. */
3511 if (atomic_read(&tcp_memory_allocated) >= sysctl_tcp_mem[0])
3512 return 0;
3513
3514 /* If we filled the congestion window, do not expand. */
3515 if (tp->packets_out >= tp->snd_cwnd)
3516 return 0;
3517
3518 return 1;
3519}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003520
3521/* When incoming ACK allowed to free some skb from write_queue,
3522 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
3523 * on the exit from tcp input handler.
3524 *
3525 * PROBLEM: sndbuf expansion does not work well with largesend.
3526 */
3527static void tcp_new_space(struct sock *sk)
3528{
3529 struct tcp_sock *tp = tcp_sk(sk);
3530
David S. Miller0d9901d2005-07-05 15:21:10 -07003531 if (tcp_should_expand_sndbuf(sk, tp)) {
David S. Millerc1b4a7e2005-07-05 15:24:38 -07003532 int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) +
Linus Torvalds1da177e2005-04-16 15:20:36 -07003533 MAX_TCP_HEADER + 16 + sizeof(struct sk_buff),
3534 demanded = max_t(unsigned int, tp->snd_cwnd,
3535 tp->reordering + 1);
3536 sndmem *= 2*demanded;
3537 if (sndmem > sk->sk_sndbuf)
3538 sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]);
3539 tp->snd_cwnd_stamp = tcp_time_stamp;
3540 }
3541
3542 sk->sk_write_space(sk);
3543}
3544
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08003545static void tcp_check_space(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003546{
3547 if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
3548 sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
3549 if (sk->sk_socket &&
3550 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
3551 tcp_new_space(sk);
3552 }
3553}
3554
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08003555static inline void tcp_data_snd_check(struct sock *sk, struct tcp_sock *tp)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003556{
David S. Miller55c97f32005-07-05 15:19:38 -07003557 tcp_push_pending_frames(sk, tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003558 tcp_check_space(sk);
3559}
3560
3561/*
3562 * Check if sending an ack is needed.
3563 */
3564static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
3565{
3566 struct tcp_sock *tp = tcp_sk(sk);
3567
3568 /* More than one full frame received... */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003569 if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss
Linus Torvalds1da177e2005-04-16 15:20:36 -07003570 /* ... and right edge of window advances far enough.
3571 * (tcp_recvmsg() will send ACK otherwise). Or...
3572 */
3573 && __tcp_select_window(sk) >= tp->rcv_wnd) ||
3574 /* We ACK each frame or... */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003575 tcp_in_quickack_mode(sk) ||
Linus Torvalds1da177e2005-04-16 15:20:36 -07003576 /* We have out of order data. */
3577 (ofo_possible &&
3578 skb_peek(&tp->out_of_order_queue))) {
3579 /* Then ack it now */
3580 tcp_send_ack(sk);
3581 } else {
3582 /* Else, send delayed ack. */
3583 tcp_send_delayed_ack(sk);
3584 }
3585}
3586
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08003587static inline void tcp_ack_snd_check(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003588{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003589 if (!inet_csk_ack_scheduled(sk)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003590 /* We sent a data segment already. */
3591 return;
3592 }
3593 __tcp_ack_snd_check(sk, 1);
3594}
3595
3596/*
3597 * This routine is only called when we have urgent data
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08003598 * signaled. Its the 'slow' part of tcp_urg. It could be
Linus Torvalds1da177e2005-04-16 15:20:36 -07003599 * moved inline now as tcp_urg is only called from one
3600 * place. We handle URGent data wrong. We have to - as
3601 * BSD still doesn't use the correction from RFC961.
3602 * For 1003.1g we should support a new option TCP_STDURG to permit
3603 * either form (or just set the sysctl tcp_stdurg).
3604 */
3605
3606static void tcp_check_urg(struct sock * sk, struct tcphdr * th)
3607{
3608 struct tcp_sock *tp = tcp_sk(sk);
3609 u32 ptr = ntohs(th->urg_ptr);
3610
3611 if (ptr && !sysctl_tcp_stdurg)
3612 ptr--;
3613 ptr += ntohl(th->seq);
3614
3615 /* Ignore urgent data that we've already seen and read. */
3616 if (after(tp->copied_seq, ptr))
3617 return;
3618
3619 /* Do not replay urg ptr.
3620 *
3621 * NOTE: interesting situation not covered by specs.
3622 * Misbehaving sender may send urg ptr, pointing to segment,
3623 * which we already have in ofo queue. We are not able to fetch
3624 * such data and will stay in TCP_URG_NOTYET until will be eaten
3625 * by recvmsg(). Seems, we are not obliged to handle such wicked
3626 * situations. But it is worth to think about possibility of some
3627 * DoSes using some hypothetical application level deadlock.
3628 */
3629 if (before(ptr, tp->rcv_nxt))
3630 return;
3631
3632 /* Do we already have a newer (or duplicate) urgent pointer? */
3633 if (tp->urg_data && !after(ptr, tp->urg_seq))
3634 return;
3635
3636 /* Tell the world about our new urgent pointer. */
3637 sk_send_sigurg(sk);
3638
3639 /* We may be adding urgent data when the last byte read was
3640 * urgent. To do this requires some care. We cannot just ignore
3641 * tp->copied_seq since we would read the last urgent byte again
3642 * as data, nor can we alter copied_seq until this data arrives
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08003643 * or we break the semantics of SIOCATMARK (and thus sockatmark())
Linus Torvalds1da177e2005-04-16 15:20:36 -07003644 *
3645 * NOTE. Double Dutch. Rendering to plain English: author of comment
3646 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
3647 * and expect that both A and B disappear from stream. This is _wrong_.
3648 * Though this happens in BSD with high probability, this is occasional.
3649 * Any application relying on this is buggy. Note also, that fix "works"
3650 * only in this artificial test. Insert some normal data between A and B and we will
3651 * decline of BSD again. Verdict: it is better to remove to trap
3652 * buggy users.
3653 */
3654 if (tp->urg_seq == tp->copied_seq && tp->urg_data &&
3655 !sock_flag(sk, SOCK_URGINLINE) &&
3656 tp->copied_seq != tp->rcv_nxt) {
3657 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
3658 tp->copied_seq++;
3659 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) {
David S. Miller8728b832005-08-09 19:25:21 -07003660 __skb_unlink(skb, &sk->sk_receive_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003661 __kfree_skb(skb);
3662 }
3663 }
3664
3665 tp->urg_data = TCP_URG_NOTYET;
3666 tp->urg_seq = ptr;
3667
3668 /* Disable header prediction. */
3669 tp->pred_flags = 0;
3670}
3671
3672/* This is the 'fast' part of urgent handling. */
3673static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th)
3674{
3675 struct tcp_sock *tp = tcp_sk(sk);
3676
3677 /* Check if we get a new urgent pointer - normally not. */
3678 if (th->urg)
3679 tcp_check_urg(sk,th);
3680
3681 /* Do we wait for any urgent data? - normally not... */
3682 if (tp->urg_data == TCP_URG_NOTYET) {
3683 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) -
3684 th->syn;
3685
3686 /* Is the urgent pointer pointing into this packet? */
3687 if (ptr < skb->len) {
3688 u8 tmp;
3689 if (skb_copy_bits(skb, ptr, &tmp, 1))
3690 BUG();
3691 tp->urg_data = TCP_URG_VALID | tmp;
3692 if (!sock_flag(sk, SOCK_DEAD))
3693 sk->sk_data_ready(sk, 0);
3694 }
3695 }
3696}
3697
3698static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen)
3699{
3700 struct tcp_sock *tp = tcp_sk(sk);
3701 int chunk = skb->len - hlen;
3702 int err;
3703
3704 local_bh_enable();
3705 if (skb->ip_summed==CHECKSUM_UNNECESSARY)
3706 err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk);
3707 else
3708 err = skb_copy_and_csum_datagram_iovec(skb, hlen,
3709 tp->ucopy.iov);
3710
3711 if (!err) {
3712 tp->ucopy.len -= chunk;
3713 tp->copied_seq += chunk;
3714 tcp_rcv_space_adjust(sk);
3715 }
3716
3717 local_bh_disable();
3718 return err;
3719}
3720
3721static int __tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb)
3722{
3723 int result;
3724
3725 if (sock_owned_by_user(sk)) {
3726 local_bh_enable();
3727 result = __tcp_checksum_complete(skb);
3728 local_bh_disable();
3729 } else {
3730 result = __tcp_checksum_complete(skb);
3731 }
3732 return result;
3733}
3734
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08003735static inline int tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003736{
3737 return skb->ip_summed != CHECKSUM_UNNECESSARY &&
3738 __tcp_checksum_complete_user(sk, skb);
3739}
3740
3741/*
3742 * TCP receive function for the ESTABLISHED state.
3743 *
3744 * It is split into a fast path and a slow path. The fast path is
3745 * disabled when:
3746 * - A zero window was announced from us - zero window probing
3747 * is only handled properly in the slow path.
3748 * - Out of order segments arrived.
3749 * - Urgent data is expected.
3750 * - There is no buffer space left
3751 * - Unexpected TCP flags/window values/header lengths are received
3752 * (detected by checking the TCP header against pred_flags)
3753 * - Data is sent in both directions. Fast path only supports pure senders
3754 * or pure receivers (this means either the sequence number or the ack
3755 * value must stay constant)
3756 * - Unexpected TCP option.
3757 *
3758 * When these conditions are not satisfied it drops into a standard
3759 * receive procedure patterned after RFC793 to handle all cases.
3760 * The first three cases are guaranteed by proper pred_flags setting,
3761 * the rest is checked inline. Fast processing is turned on in
3762 * tcp_data_queue when everything is OK.
3763 */
3764int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
3765 struct tcphdr *th, unsigned len)
3766{
3767 struct tcp_sock *tp = tcp_sk(sk);
3768
3769 /*
3770 * Header prediction.
3771 * The code loosely follows the one in the famous
3772 * "30 instruction TCP receive" Van Jacobson mail.
3773 *
3774 * Van's trick is to deposit buffers into socket queue
3775 * on a device interrupt, to call tcp_recv function
3776 * on the receive process context and checksum and copy
3777 * the buffer to user space. smart...
3778 *
3779 * Our current scheme is not silly either but we take the
3780 * extra cost of the net_bh soft interrupt processing...
3781 * We do checksum and copy also but from device to kernel.
3782 */
3783
3784 tp->rx_opt.saw_tstamp = 0;
3785
3786 /* pred_flags is 0xS?10 << 16 + snd_wnd
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08003787 * if header_prediction is to be made
Linus Torvalds1da177e2005-04-16 15:20:36 -07003788 * 'S' will always be tp->tcp_header_len >> 2
3789 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
3790 * turn it off (when there are holes in the receive
3791 * space for instance)
3792 * PSH flag is ignored.
3793 */
3794
3795 if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags &&
3796 TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
3797 int tcp_header_len = tp->tcp_header_len;
3798
3799 /* Timestamp header prediction: tcp_header_len
3800 * is automatically equal to th->doff*4 due to pred_flags
3801 * match.
3802 */
3803
3804 /* Check timestamp */
3805 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) {
3806 __u32 *ptr = (__u32 *)(th + 1);
3807
3808 /* No? Slow path! */
3809 if (*ptr != ntohl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
3810 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP))
3811 goto slow_path;
3812
3813 tp->rx_opt.saw_tstamp = 1;
3814 ++ptr;
3815 tp->rx_opt.rcv_tsval = ntohl(*ptr);
3816 ++ptr;
3817 tp->rx_opt.rcv_tsecr = ntohl(*ptr);
3818
3819 /* If PAWS failed, check it more carefully in slow path */
3820 if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0)
3821 goto slow_path;
3822
3823 /* DO NOT update ts_recent here, if checksum fails
3824 * and timestamp was corrupted part, it will result
3825 * in a hung connection since we will drop all
3826 * future packets due to the PAWS test.
3827 */
3828 }
3829
3830 if (len <= tcp_header_len) {
3831 /* Bulk data transfer: sender */
3832 if (len == tcp_header_len) {
3833 /* Predicted packet is in window by definition.
3834 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
3835 * Hence, check seq<=rcv_wup reduces to:
3836 */
3837 if (tcp_header_len ==
3838 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
3839 tp->rcv_nxt == tp->rcv_wup)
3840 tcp_store_ts_recent(tp);
3841
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003842 tcp_rcv_rtt_measure_ts(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003843
3844 /* We know that such packets are checksummed
3845 * on entry.
3846 */
3847 tcp_ack(sk, skb, 0);
3848 __kfree_skb(skb);
David S. Miller55c97f32005-07-05 15:19:38 -07003849 tcp_data_snd_check(sk, tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003850 return 0;
3851 } else { /* Header too small */
3852 TCP_INC_STATS_BH(TCP_MIB_INERRS);
3853 goto discard;
3854 }
3855 } else {
3856 int eaten = 0;
3857
3858 if (tp->ucopy.task == current &&
3859 tp->copied_seq == tp->rcv_nxt &&
3860 len - tcp_header_len <= tp->ucopy.len &&
3861 sock_owned_by_user(sk)) {
3862 __set_current_state(TASK_RUNNING);
3863
3864 if (!tcp_copy_to_iovec(sk, skb, tcp_header_len)) {
3865 /* Predicted packet is in window by definition.
3866 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
3867 * Hence, check seq<=rcv_wup reduces to:
3868 */
3869 if (tcp_header_len ==
3870 (sizeof(struct tcphdr) +
3871 TCPOLEN_TSTAMP_ALIGNED) &&
3872 tp->rcv_nxt == tp->rcv_wup)
3873 tcp_store_ts_recent(tp);
3874
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003875 tcp_rcv_rtt_measure_ts(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003876
3877 __skb_pull(skb, tcp_header_len);
3878 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3879 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER);
3880 eaten = 1;
3881 }
3882 }
3883 if (!eaten) {
3884 if (tcp_checksum_complete_user(sk, skb))
3885 goto csum_error;
3886
3887 /* Predicted packet is in window by definition.
3888 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
3889 * Hence, check seq<=rcv_wup reduces to:
3890 */
3891 if (tcp_header_len ==
3892 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
3893 tp->rcv_nxt == tp->rcv_wup)
3894 tcp_store_ts_recent(tp);
3895
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003896 tcp_rcv_rtt_measure_ts(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003897
3898 if ((int)skb->truesize > sk->sk_forward_alloc)
3899 goto step5;
3900
3901 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS);
3902
3903 /* Bulk data transfer: receiver */
3904 __skb_pull(skb,tcp_header_len);
3905 __skb_queue_tail(&sk->sk_receive_queue, skb);
3906 sk_stream_set_owner_r(skb, sk);
3907 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3908 }
3909
3910 tcp_event_data_recv(sk, tp, skb);
3911
3912 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) {
3913 /* Well, only one small jumplet in fast path... */
3914 tcp_ack(sk, skb, FLAG_DATA);
David S. Miller55c97f32005-07-05 15:19:38 -07003915 tcp_data_snd_check(sk, tp);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003916 if (!inet_csk_ack_scheduled(sk))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003917 goto no_ack;
3918 }
3919
David S. Miller31432412005-05-23 12:03:06 -07003920 __tcp_ack_snd_check(sk, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003921no_ack:
3922 if (eaten)
3923 __kfree_skb(skb);
3924 else
3925 sk->sk_data_ready(sk, 0);
3926 return 0;
3927 }
3928 }
3929
3930slow_path:
3931 if (len < (th->doff<<2) || tcp_checksum_complete_user(sk, skb))
3932 goto csum_error;
3933
3934 /*
3935 * RFC1323: H1. Apply PAWS check first.
3936 */
3937 if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003938 tcp_paws_discard(sk, skb)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003939 if (!th->rst) {
3940 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
3941 tcp_send_dupack(sk, skb);
3942 goto discard;
3943 }
3944 /* Resets are accepted even if PAWS failed.
3945
3946 ts_recent update must be made after we are sure
3947 that the packet is in window.
3948 */
3949 }
3950
3951 /*
3952 * Standard slow path.
3953 */
3954
3955 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
3956 /* RFC793, page 37: "In all states except SYN-SENT, all reset
3957 * (RST) segments are validated by checking their SEQ-fields."
3958 * And page 69: "If an incoming segment is not acceptable,
3959 * an acknowledgment should be sent in reply (unless the RST bit
3960 * is set, if so drop the segment and return)".
3961 */
3962 if (!th->rst)
3963 tcp_send_dupack(sk, skb);
3964 goto discard;
3965 }
3966
3967 if(th->rst) {
3968 tcp_reset(sk);
3969 goto discard;
3970 }
3971
3972 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
3973
3974 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
3975 TCP_INC_STATS_BH(TCP_MIB_INERRS);
3976 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN);
3977 tcp_reset(sk);
3978 return 1;
3979 }
3980
3981step5:
3982 if(th->ack)
3983 tcp_ack(sk, skb, FLAG_SLOWPATH);
3984
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07003985 tcp_rcv_rtt_measure_ts(sk, skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003986
3987 /* Process urgent data. */
3988 tcp_urg(sk, skb, th);
3989
3990 /* step 7: process the segment text */
3991 tcp_data_queue(sk, skb);
3992
David S. Miller55c97f32005-07-05 15:19:38 -07003993 tcp_data_snd_check(sk, tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003994 tcp_ack_snd_check(sk);
3995 return 0;
3996
3997csum_error:
3998 TCP_INC_STATS_BH(TCP_MIB_INERRS);
3999
4000discard:
4001 __kfree_skb(skb);
4002 return 0;
4003}
4004
4005static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
4006 struct tcphdr *th, unsigned len)
4007{
4008 struct tcp_sock *tp = tcp_sk(sk);
Arnaldo Carvalho de Melod83d8462005-12-13 23:26:10 -08004009 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004010 int saved_clamp = tp->rx_opt.mss_clamp;
4011
4012 tcp_parse_options(skb, &tp->rx_opt, 0);
4013
4014 if (th->ack) {
4015 /* rfc793:
4016 * "If the state is SYN-SENT then
4017 * first check the ACK bit
4018 * If the ACK bit is set
4019 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
4020 * a reset (unless the RST bit is set, if so drop
4021 * the segment and return)"
4022 *
4023 * We do not send data with SYN, so that RFC-correct
4024 * test reduces to:
4025 */
4026 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt)
4027 goto reset_and_undo;
4028
4029 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
4030 !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp,
4031 tcp_time_stamp)) {
4032 NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED);
4033 goto reset_and_undo;
4034 }
4035
4036 /* Now ACK is acceptable.
4037 *
4038 * "If the RST bit is set
4039 * If the ACK was acceptable then signal the user "error:
4040 * connection reset", drop the segment, enter CLOSED state,
4041 * delete TCB, and return."
4042 */
4043
4044 if (th->rst) {
4045 tcp_reset(sk);
4046 goto discard;
4047 }
4048
4049 /* rfc793:
4050 * "fifth, if neither of the SYN or RST bits is set then
4051 * drop the segment and return."
4052 *
4053 * See note below!
4054 * --ANK(990513)
4055 */
4056 if (!th->syn)
4057 goto discard_and_undo;
4058
4059 /* rfc793:
4060 * "If the SYN bit is on ...
4061 * are acceptable then ...
4062 * (our SYN has been ACKed), change the connection
4063 * state to ESTABLISHED..."
4064 */
4065
4066 TCP_ECN_rcv_synack(tp, th);
4067 if (tp->ecn_flags&TCP_ECN_OK)
4068 sock_set_flag(sk, SOCK_NO_LARGESEND);
4069
4070 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
4071 tcp_ack(sk, skb, FLAG_SLOWPATH);
4072
4073 /* Ok.. it's good. Set up sequence numbers and
4074 * move to established.
4075 */
4076 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
4077 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
4078
4079 /* RFC1323: The window in SYN & SYN/ACK segments is
4080 * never scaled.
4081 */
4082 tp->snd_wnd = ntohs(th->window);
4083 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, TCP_SKB_CB(skb)->seq);
4084
4085 if (!tp->rx_opt.wscale_ok) {
4086 tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0;
4087 tp->window_clamp = min(tp->window_clamp, 65535U);
4088 }
4089
4090 if (tp->rx_opt.saw_tstamp) {
4091 tp->rx_opt.tstamp_ok = 1;
4092 tp->tcp_header_len =
4093 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
4094 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
4095 tcp_store_ts_recent(tp);
4096 } else {
4097 tp->tcp_header_len = sizeof(struct tcphdr);
4098 }
4099
4100 if (tp->rx_opt.sack_ok && sysctl_tcp_fack)
4101 tp->rx_opt.sack_ok |= 2;
4102
Arnaldo Carvalho de Melod83d8462005-12-13 23:26:10 -08004103 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004104 tcp_initialize_rcv_mss(sk);
4105
4106 /* Remember, tcp_poll() does not lock socket!
4107 * Change state from SYN-SENT only after copied_seq
4108 * is initialized. */
4109 tp->copied_seq = tp->rcv_nxt;
4110 mb();
4111 tcp_set_state(sk, TCP_ESTABLISHED);
4112
4113 /* Make sure socket is routed, for correct metrics. */
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -08004114 icsk->icsk_af_ops->rebuild_header(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004115
4116 tcp_init_metrics(sk);
4117
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03004118 tcp_init_congestion_control(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -07004119
Linus Torvalds1da177e2005-04-16 15:20:36 -07004120 /* Prevent spurious tcp_cwnd_restart() on first data
4121 * packet.
4122 */
4123 tp->lsndtime = tcp_time_stamp;
4124
4125 tcp_init_buffer_space(sk);
4126
4127 if (sock_flag(sk, SOCK_KEEPOPEN))
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004128 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp));
Linus Torvalds1da177e2005-04-16 15:20:36 -07004129
4130 if (!tp->rx_opt.snd_wscale)
4131 __tcp_fast_path_on(tp, tp->snd_wnd);
4132 else
4133 tp->pred_flags = 0;
4134
4135 if (!sock_flag(sk, SOCK_DEAD)) {
4136 sk->sk_state_change(sk);
4137 sk_wake_async(sk, 0, POLL_OUT);
4138 }
4139
Arnaldo Carvalho de Melo295f7322005-08-09 20:11:56 -07004140 if (sk->sk_write_pending ||
4141 icsk->icsk_accept_queue.rskq_defer_accept ||
4142 icsk->icsk_ack.pingpong) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004143 /* Save one ACK. Data will be ready after
4144 * several ticks, if write_pending is set.
4145 *
4146 * It may be deleted, but with this feature tcpdumps
4147 * look so _wonderfully_ clever, that I was not able
4148 * to stand against the temptation 8) --ANK
4149 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004150 inet_csk_schedule_ack(sk);
Arnaldo Carvalho de Melo295f7322005-08-09 20:11:56 -07004151 icsk->icsk_ack.lrcvtime = tcp_time_stamp;
4152 icsk->icsk_ack.ato = TCP_ATO_MIN;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004153 tcp_incr_quickack(sk);
4154 tcp_enter_quickack_mode(sk);
Arnaldo Carvalho de Melo3f421ba2005-08-09 20:11:08 -07004155 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
4156 TCP_DELACK_MAX, TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004157
4158discard:
4159 __kfree_skb(skb);
4160 return 0;
4161 } else {
4162 tcp_send_ack(sk);
4163 }
4164 return -1;
4165 }
4166
4167 /* No ACK in the segment */
4168
4169 if (th->rst) {
4170 /* rfc793:
4171 * "If the RST bit is set
4172 *
4173 * Otherwise (no ACK) drop the segment and return."
4174 */
4175
4176 goto discard_and_undo;
4177 }
4178
4179 /* PAWS check. */
4180 if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && tcp_paws_check(&tp->rx_opt, 0))
4181 goto discard_and_undo;
4182
4183 if (th->syn) {
4184 /* We see SYN without ACK. It is attempt of
4185 * simultaneous connect with crossed SYNs.
4186 * Particularly, it can be connect to self.
4187 */
4188 tcp_set_state(sk, TCP_SYN_RECV);
4189
4190 if (tp->rx_opt.saw_tstamp) {
4191 tp->rx_opt.tstamp_ok = 1;
4192 tcp_store_ts_recent(tp);
4193 tp->tcp_header_len =
4194 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
4195 } else {
4196 tp->tcp_header_len = sizeof(struct tcphdr);
4197 }
4198
4199 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
4200 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
4201
4202 /* RFC1323: The window in SYN & SYN/ACK segments is
4203 * never scaled.
4204 */
4205 tp->snd_wnd = ntohs(th->window);
4206 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
4207 tp->max_window = tp->snd_wnd;
4208
4209 TCP_ECN_rcv_syn(tp, th);
4210 if (tp->ecn_flags&TCP_ECN_OK)
4211 sock_set_flag(sk, SOCK_NO_LARGESEND);
4212
Arnaldo Carvalho de Melod83d8462005-12-13 23:26:10 -08004213 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004214 tcp_initialize_rcv_mss(sk);
4215
4216
4217 tcp_send_synack(sk);
4218#if 0
4219 /* Note, we could accept data and URG from this segment.
4220 * There are no obstacles to make this.
4221 *
4222 * However, if we ignore data in ACKless segments sometimes,
4223 * we have no reasons to accept it sometimes.
4224 * Also, seems the code doing it in step6 of tcp_rcv_state_process
4225 * is not flawless. So, discard packet for sanity.
4226 * Uncomment this return to process the data.
4227 */
4228 return -1;
4229#else
4230 goto discard;
4231#endif
4232 }
4233 /* "fifth, if neither of the SYN or RST bits is set then
4234 * drop the segment and return."
4235 */
4236
4237discard_and_undo:
4238 tcp_clear_options(&tp->rx_opt);
4239 tp->rx_opt.mss_clamp = saved_clamp;
4240 goto discard;
4241
4242reset_and_undo:
4243 tcp_clear_options(&tp->rx_opt);
4244 tp->rx_opt.mss_clamp = saved_clamp;
4245 return 1;
4246}
4247
4248
4249/*
4250 * This function implements the receiving procedure of RFC 793 for
4251 * all states except ESTABLISHED and TIME_WAIT.
4252 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
4253 * address independent.
4254 */
4255
4256int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
4257 struct tcphdr *th, unsigned len)
4258{
4259 struct tcp_sock *tp = tcp_sk(sk);
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -08004260 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004261 int queued = 0;
4262
4263 tp->rx_opt.saw_tstamp = 0;
4264
4265 switch (sk->sk_state) {
4266 case TCP_CLOSE:
4267 goto discard;
4268
4269 case TCP_LISTEN:
4270 if(th->ack)
4271 return 1;
4272
4273 if(th->rst)
4274 goto discard;
4275
4276 if(th->syn) {
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -08004277 if (icsk->icsk_af_ops->conn_request(sk, skb) < 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07004278 return 1;
4279
Linus Torvalds1da177e2005-04-16 15:20:36 -07004280 /* Now we have several options: In theory there is
4281 * nothing else in the frame. KA9Q has an option to
4282 * send data with the syn, BSD accepts data with the
4283 * syn up to the [to be] advertised window and
4284 * Solaris 2.1 gives you a protocol error. For now
4285 * we just ignore it, that fits the spec precisely
4286 * and avoids incompatibilities. It would be nice in
4287 * future to drop through and process the data.
4288 *
4289 * Now that TTCP is starting to be used we ought to
4290 * queue this data.
4291 * But, this leaves one open to an easy denial of
4292 * service attack, and SYN cookies can't defend
4293 * against this problem. So, we drop the data
4294 * in the interest of security over speed.
4295 */
4296 goto discard;
4297 }
4298 goto discard;
4299
4300 case TCP_SYN_SENT:
Linus Torvalds1da177e2005-04-16 15:20:36 -07004301 queued = tcp_rcv_synsent_state_process(sk, skb, th, len);
4302 if (queued >= 0)
4303 return queued;
4304
4305 /* Do step6 onward by hand. */
4306 tcp_urg(sk, skb, th);
4307 __kfree_skb(skb);
David S. Miller55c97f32005-07-05 15:19:38 -07004308 tcp_data_snd_check(sk, tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004309 return 0;
4310 }
4311
4312 if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004313 tcp_paws_discard(sk, skb)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07004314 if (!th->rst) {
4315 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
4316 tcp_send_dupack(sk, skb);
4317 goto discard;
4318 }
4319 /* Reset is accepted even if it did not pass PAWS. */
4320 }
4321
4322 /* step 1: check sequence number */
4323 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
4324 if (!th->rst)
4325 tcp_send_dupack(sk, skb);
4326 goto discard;
4327 }
4328
4329 /* step 2: check RST bit */
4330 if(th->rst) {
4331 tcp_reset(sk);
4332 goto discard;
4333 }
4334
4335 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
4336
4337 /* step 3: check security and precedence [ignored] */
4338
4339 /* step 4:
4340 *
4341 * Check for a SYN in window.
4342 */
4343 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4344 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN);
4345 tcp_reset(sk);
4346 return 1;
4347 }
4348
4349 /* step 5: check the ACK field */
4350 if (th->ack) {
4351 int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH);
4352
4353 switch(sk->sk_state) {
4354 case TCP_SYN_RECV:
4355 if (acceptable) {
4356 tp->copied_seq = tp->rcv_nxt;
4357 mb();
4358 tcp_set_state(sk, TCP_ESTABLISHED);
4359 sk->sk_state_change(sk);
4360
4361 /* Note, that this wakeup is only for marginal
4362 * crossed SYN case. Passively open sockets
4363 * are not waked up, because sk->sk_sleep ==
4364 * NULL and sk->sk_socket == NULL.
4365 */
4366 if (sk->sk_socket) {
4367 sk_wake_async(sk,0,POLL_OUT);
4368 }
4369
4370 tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
4371 tp->snd_wnd = ntohs(th->window) <<
4372 tp->rx_opt.snd_wscale;
4373 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq,
4374 TCP_SKB_CB(skb)->seq);
4375
4376 /* tcp_ack considers this ACK as duplicate
4377 * and does not calculate rtt.
4378 * Fix it at least with timestamps.
4379 */
4380 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
4381 !tp->srtt)
Stephen Hemminger2d2abba2005-11-10 16:56:12 -08004382 tcp_ack_saw_tstamp(sk, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004383
4384 if (tp->rx_opt.tstamp_ok)
4385 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
4386
4387 /* Make sure socket is routed, for
4388 * correct metrics.
4389 */
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -08004390 icsk->icsk_af_ops->rebuild_header(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004391
4392 tcp_init_metrics(sk);
4393
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03004394 tcp_init_congestion_control(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -07004395
Linus Torvalds1da177e2005-04-16 15:20:36 -07004396 /* Prevent spurious tcp_cwnd_restart() on
4397 * first data packet.
4398 */
4399 tp->lsndtime = tcp_time_stamp;
4400
4401 tcp_initialize_rcv_mss(sk);
4402 tcp_init_buffer_space(sk);
4403 tcp_fast_path_on(tp);
4404 } else {
4405 return 1;
4406 }
4407 break;
4408
4409 case TCP_FIN_WAIT1:
4410 if (tp->snd_una == tp->write_seq) {
4411 tcp_set_state(sk, TCP_FIN_WAIT2);
4412 sk->sk_shutdown |= SEND_SHUTDOWN;
4413 dst_confirm(sk->sk_dst_cache);
4414
4415 if (!sock_flag(sk, SOCK_DEAD))
4416 /* Wake up lingering close() */
4417 sk->sk_state_change(sk);
4418 else {
4419 int tmo;
4420
4421 if (tp->linger2 < 0 ||
4422 (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
4423 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) {
4424 tcp_done(sk);
4425 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA);
4426 return 1;
4427 }
4428
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004429 tmo = tcp_fin_time(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004430 if (tmo > TCP_TIMEWAIT_LEN) {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004431 inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004432 } else if (th->fin || sock_owned_by_user(sk)) {
4433 /* Bad case. We could lose such FIN otherwise.
4434 * It is not a big problem, but it looks confusing
4435 * and not so rare event. We still can lose it now,
4436 * if it spins in bh_lock_sock(), but it is really
4437 * marginal case.
4438 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07004439 inet_csk_reset_keepalive_timer(sk, tmo);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004440 } else {
4441 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
4442 goto discard;
4443 }
4444 }
4445 }
4446 break;
4447
4448 case TCP_CLOSING:
4449 if (tp->snd_una == tp->write_seq) {
4450 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
4451 goto discard;
4452 }
4453 break;
4454
4455 case TCP_LAST_ACK:
4456 if (tp->snd_una == tp->write_seq) {
4457 tcp_update_metrics(sk);
4458 tcp_done(sk);
4459 goto discard;
4460 }
4461 break;
4462 }
4463 } else
4464 goto discard;
4465
4466 /* step 6: check the URG bit */
4467 tcp_urg(sk, skb, th);
4468
4469 /* step 7: process the segment text */
4470 switch (sk->sk_state) {
4471 case TCP_CLOSE_WAIT:
4472 case TCP_CLOSING:
4473 case TCP_LAST_ACK:
4474 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
4475 break;
4476 case TCP_FIN_WAIT1:
4477 case TCP_FIN_WAIT2:
4478 /* RFC 793 says to queue data in these states,
4479 * RFC 1122 says we MUST send a reset.
4480 * BSD 4.4 also does reset.
4481 */
4482 if (sk->sk_shutdown & RCV_SHUTDOWN) {
4483 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
4484 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
4485 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA);
4486 tcp_reset(sk);
4487 return 1;
4488 }
4489 }
4490 /* Fall through */
4491 case TCP_ESTABLISHED:
4492 tcp_data_queue(sk, skb);
4493 queued = 1;
4494 break;
4495 }
4496
4497 /* tcp_data could move socket to TIME-WAIT */
4498 if (sk->sk_state != TCP_CLOSE) {
David S. Miller55c97f32005-07-05 15:19:38 -07004499 tcp_data_snd_check(sk, tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004500 tcp_ack_snd_check(sk);
4501 }
4502
4503 if (!queued) {
4504discard:
4505 __kfree_skb(skb);
4506 }
4507 return 0;
4508}
4509
4510EXPORT_SYMBOL(sysctl_tcp_ecn);
4511EXPORT_SYMBOL(sysctl_tcp_reordering);
Stephen Hemminger9772efb2005-11-10 17:09:53 -08004512EXPORT_SYMBOL(sysctl_tcp_abc);
Linus Torvalds1da177e2005-04-16 15:20:36 -07004513EXPORT_SYMBOL(tcp_parse_options);
4514EXPORT_SYMBOL(tcp_rcv_established);
4515EXPORT_SYMBOL(tcp_rcv_state_process);
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08004516EXPORT_SYMBOL(tcp_initialize_rcv_mss);