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1da177e4 LT |
1 | /* |
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 | * | |
02c30a84 | 10 | * Authors: Ross Biro |
1da177e4 LT |
11 | * 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. | |
caa20d9a | 45 | * Andrey Savochkin: Fix RTT measurements in the presence of |
1da177e4 LT |
46 | * 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. | |
e905a9ed | 53 | * Andi Kleen: Add tcp_measure_rcv_mss to make |
1da177e4 | 54 | * connections with MSS<min(MTU,ann. MSS) |
e905a9ed | 55 | * work without delayed acks. |
1da177e4 LT |
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 | |
1da177e4 LT |
64 | */ |
65 | ||
1da177e4 LT |
66 | #include <linux/mm.h> |
67 | #include <linux/module.h> | |
68 | #include <linux/sysctl.h> | |
69 | #include <net/tcp.h> | |
70 | #include <net/inet_common.h> | |
71 | #include <linux/ipsec.h> | |
72 | #include <asm/unaligned.h> | |
1a2449a8 | 73 | #include <net/netdma.h> |
1da177e4 | 74 | |
ab32ea5d BH |
75 | int sysctl_tcp_timestamps __read_mostly = 1; |
76 | int sysctl_tcp_window_scaling __read_mostly = 1; | |
77 | int sysctl_tcp_sack __read_mostly = 1; | |
78 | int sysctl_tcp_fack __read_mostly = 1; | |
79 | int sysctl_tcp_reordering __read_mostly = TCP_FASTRETRANS_THRESH; | |
80 | int sysctl_tcp_ecn __read_mostly; | |
81 | int sysctl_tcp_dsack __read_mostly = 1; | |
82 | int sysctl_tcp_app_win __read_mostly = 31; | |
83 | int sysctl_tcp_adv_win_scale __read_mostly = 2; | |
1da177e4 | 84 | |
ab32ea5d BH |
85 | int sysctl_tcp_stdurg __read_mostly; |
86 | int sysctl_tcp_rfc1337 __read_mostly; | |
87 | int sysctl_tcp_max_orphans __read_mostly = NR_FILE; | |
88 | int sysctl_tcp_frto __read_mostly; | |
3cfe3baa | 89 | int sysctl_tcp_frto_response __read_mostly; |
ab32ea5d | 90 | int sysctl_tcp_nometrics_save __read_mostly; |
1da177e4 | 91 | |
ab32ea5d BH |
92 | int sysctl_tcp_moderate_rcvbuf __read_mostly = 1; |
93 | int sysctl_tcp_abc __read_mostly; | |
1da177e4 | 94 | |
1da177e4 LT |
95 | #define FLAG_DATA 0x01 /* Incoming frame contained data. */ |
96 | #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */ | |
97 | #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */ | |
98 | #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */ | |
99 | #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */ | |
100 | #define FLAG_DATA_SACKED 0x20 /* New SACK. */ | |
101 | #define FLAG_ECE 0x40 /* ECE in this ACK */ | |
102 | #define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */ | |
103 | #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/ | |
4dc2665e | 104 | #define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */ |
1da177e4 LT |
105 | |
106 | #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED) | |
107 | #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED) | |
108 | #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE) | |
109 | #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED) | |
110 | ||
111 | #define IsReno(tp) ((tp)->rx_opt.sack_ok == 0) | |
112 | #define IsFack(tp) ((tp)->rx_opt.sack_ok & 2) | |
113 | #define IsDSack(tp) ((tp)->rx_opt.sack_ok & 4) | |
114 | ||
4dc2665e IJ |
115 | #define IsSackFrto() (sysctl_tcp_frto == 0x2) |
116 | ||
1da177e4 LT |
117 | #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH) |
118 | ||
e905a9ed | 119 | /* Adapt the MSS value used to make delayed ack decision to the |
1da177e4 | 120 | * real world. |
e905a9ed | 121 | */ |
40efc6fa SH |
122 | static void tcp_measure_rcv_mss(struct sock *sk, |
123 | const struct sk_buff *skb) | |
1da177e4 | 124 | { |
463c84b9 | 125 | struct inet_connection_sock *icsk = inet_csk(sk); |
e905a9ed | 126 | const unsigned int lss = icsk->icsk_ack.last_seg_size; |
463c84b9 | 127 | unsigned int len; |
1da177e4 | 128 | |
e905a9ed | 129 | icsk->icsk_ack.last_seg_size = 0; |
1da177e4 LT |
130 | |
131 | /* skb->len may jitter because of SACKs, even if peer | |
132 | * sends good full-sized frames. | |
133 | */ | |
ff9b5e0f | 134 | len = skb_shinfo(skb)->gso_size ?: skb->len; |
463c84b9 ACM |
135 | if (len >= icsk->icsk_ack.rcv_mss) { |
136 | icsk->icsk_ack.rcv_mss = len; | |
1da177e4 LT |
137 | } else { |
138 | /* Otherwise, we make more careful check taking into account, | |
139 | * that SACKs block is variable. | |
140 | * | |
141 | * "len" is invariant segment length, including TCP header. | |
142 | */ | |
9c70220b | 143 | len += skb->data - skb_transport_header(skb); |
1da177e4 LT |
144 | if (len >= TCP_MIN_RCVMSS + sizeof(struct tcphdr) || |
145 | /* If PSH is not set, packet should be | |
146 | * full sized, provided peer TCP is not badly broken. | |
147 | * This observation (if it is correct 8)) allows | |
148 | * to handle super-low mtu links fairly. | |
149 | */ | |
150 | (len >= TCP_MIN_MSS + sizeof(struct tcphdr) && | |
aa8223c7 | 151 | !(tcp_flag_word(tcp_hdr(skb)) & TCP_REMNANT))) { |
1da177e4 LT |
152 | /* Subtract also invariant (if peer is RFC compliant), |
153 | * tcp header plus fixed timestamp option length. | |
154 | * Resulting "len" is MSS free of SACK jitter. | |
155 | */ | |
463c84b9 ACM |
156 | len -= tcp_sk(sk)->tcp_header_len; |
157 | icsk->icsk_ack.last_seg_size = len; | |
1da177e4 | 158 | if (len == lss) { |
463c84b9 | 159 | icsk->icsk_ack.rcv_mss = len; |
1da177e4 LT |
160 | return; |
161 | } | |
162 | } | |
1ef9696c AK |
163 | if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED) |
164 | icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2; | |
463c84b9 | 165 | icsk->icsk_ack.pending |= ICSK_ACK_PUSHED; |
1da177e4 LT |
166 | } |
167 | } | |
168 | ||
463c84b9 | 169 | static void tcp_incr_quickack(struct sock *sk) |
1da177e4 | 170 | { |
463c84b9 ACM |
171 | struct inet_connection_sock *icsk = inet_csk(sk); |
172 | unsigned quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss); | |
1da177e4 LT |
173 | |
174 | if (quickacks==0) | |
175 | quickacks=2; | |
463c84b9 ACM |
176 | if (quickacks > icsk->icsk_ack.quick) |
177 | icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS); | |
1da177e4 LT |
178 | } |
179 | ||
463c84b9 | 180 | void tcp_enter_quickack_mode(struct sock *sk) |
1da177e4 | 181 | { |
463c84b9 ACM |
182 | struct inet_connection_sock *icsk = inet_csk(sk); |
183 | tcp_incr_quickack(sk); | |
184 | icsk->icsk_ack.pingpong = 0; | |
185 | icsk->icsk_ack.ato = TCP_ATO_MIN; | |
1da177e4 LT |
186 | } |
187 | ||
188 | /* Send ACKs quickly, if "quick" count is not exhausted | |
189 | * and the session is not interactive. | |
190 | */ | |
191 | ||
463c84b9 | 192 | static inline int tcp_in_quickack_mode(const struct sock *sk) |
1da177e4 | 193 | { |
463c84b9 ACM |
194 | const struct inet_connection_sock *icsk = inet_csk(sk); |
195 | return icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong; | |
1da177e4 LT |
196 | } |
197 | ||
198 | /* Buffer size and advertised window tuning. | |
199 | * | |
200 | * 1. Tuning sk->sk_sndbuf, when connection enters established state. | |
201 | */ | |
202 | ||
203 | static void tcp_fixup_sndbuf(struct sock *sk) | |
204 | { | |
205 | int sndmem = tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER + 16 + | |
206 | sizeof(struct sk_buff); | |
207 | ||
208 | if (sk->sk_sndbuf < 3 * sndmem) | |
209 | sk->sk_sndbuf = min(3 * sndmem, sysctl_tcp_wmem[2]); | |
210 | } | |
211 | ||
212 | /* 2. Tuning advertised window (window_clamp, rcv_ssthresh) | |
213 | * | |
214 | * All tcp_full_space() is split to two parts: "network" buffer, allocated | |
215 | * forward and advertised in receiver window (tp->rcv_wnd) and | |
216 | * "application buffer", required to isolate scheduling/application | |
217 | * latencies from network. | |
218 | * window_clamp is maximal advertised window. It can be less than | |
219 | * tcp_full_space(), in this case tcp_full_space() - window_clamp | |
220 | * is reserved for "application" buffer. The less window_clamp is | |
221 | * the smoother our behaviour from viewpoint of network, but the lower | |
222 | * throughput and the higher sensitivity of the connection to losses. 8) | |
223 | * | |
224 | * rcv_ssthresh is more strict window_clamp used at "slow start" | |
225 | * phase to predict further behaviour of this connection. | |
226 | * It is used for two goals: | |
227 | * - to enforce header prediction at sender, even when application | |
228 | * requires some significant "application buffer". It is check #1. | |
229 | * - to prevent pruning of receive queue because of misprediction | |
230 | * of receiver window. Check #2. | |
231 | * | |
232 | * The scheme does not work when sender sends good segments opening | |
caa20d9a | 233 | * window and then starts to feed us spaghetti. But it should work |
1da177e4 LT |
234 | * in common situations. Otherwise, we have to rely on queue collapsing. |
235 | */ | |
236 | ||
237 | /* Slow part of check#2. */ | |
463c84b9 ACM |
238 | static int __tcp_grow_window(const struct sock *sk, struct tcp_sock *tp, |
239 | const struct sk_buff *skb) | |
1da177e4 LT |
240 | { |
241 | /* Optimize this! */ | |
242 | int truesize = tcp_win_from_space(skb->truesize)/2; | |
326f36e9 | 243 | int window = tcp_win_from_space(sysctl_tcp_rmem[2])/2; |
1da177e4 LT |
244 | |
245 | while (tp->rcv_ssthresh <= window) { | |
246 | if (truesize <= skb->len) | |
463c84b9 | 247 | return 2 * inet_csk(sk)->icsk_ack.rcv_mss; |
1da177e4 LT |
248 | |
249 | truesize >>= 1; | |
250 | window >>= 1; | |
251 | } | |
252 | return 0; | |
253 | } | |
254 | ||
40efc6fa SH |
255 | static void tcp_grow_window(struct sock *sk, struct tcp_sock *tp, |
256 | struct sk_buff *skb) | |
1da177e4 LT |
257 | { |
258 | /* Check #1 */ | |
259 | if (tp->rcv_ssthresh < tp->window_clamp && | |
260 | (int)tp->rcv_ssthresh < tcp_space(sk) && | |
261 | !tcp_memory_pressure) { | |
262 | int incr; | |
263 | ||
264 | /* Check #2. Increase window, if skb with such overhead | |
265 | * will fit to rcvbuf in future. | |
266 | */ | |
267 | if (tcp_win_from_space(skb->truesize) <= skb->len) | |
268 | incr = 2*tp->advmss; | |
269 | else | |
270 | incr = __tcp_grow_window(sk, tp, skb); | |
271 | ||
272 | if (incr) { | |
273 | tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, tp->window_clamp); | |
463c84b9 | 274 | inet_csk(sk)->icsk_ack.quick |= 1; |
1da177e4 LT |
275 | } |
276 | } | |
277 | } | |
278 | ||
279 | /* 3. Tuning rcvbuf, when connection enters established state. */ | |
280 | ||
281 | static void tcp_fixup_rcvbuf(struct sock *sk) | |
282 | { | |
283 | struct tcp_sock *tp = tcp_sk(sk); | |
284 | int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff); | |
285 | ||
286 | /* Try to select rcvbuf so that 4 mss-sized segments | |
caa20d9a | 287 | * will fit to window and corresponding skbs will fit to our rcvbuf. |
1da177e4 LT |
288 | * (was 3; 4 is minimum to allow fast retransmit to work.) |
289 | */ | |
290 | while (tcp_win_from_space(rcvmem) < tp->advmss) | |
291 | rcvmem += 128; | |
292 | if (sk->sk_rcvbuf < 4 * rcvmem) | |
293 | sk->sk_rcvbuf = min(4 * rcvmem, sysctl_tcp_rmem[2]); | |
294 | } | |
295 | ||
caa20d9a | 296 | /* 4. Try to fixup all. It is made immediately after connection enters |
1da177e4 LT |
297 | * established state. |
298 | */ | |
299 | static void tcp_init_buffer_space(struct sock *sk) | |
300 | { | |
301 | struct tcp_sock *tp = tcp_sk(sk); | |
302 | int maxwin; | |
303 | ||
304 | if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) | |
305 | tcp_fixup_rcvbuf(sk); | |
306 | if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK)) | |
307 | tcp_fixup_sndbuf(sk); | |
308 | ||
309 | tp->rcvq_space.space = tp->rcv_wnd; | |
310 | ||
311 | maxwin = tcp_full_space(sk); | |
312 | ||
313 | if (tp->window_clamp >= maxwin) { | |
314 | tp->window_clamp = maxwin; | |
315 | ||
316 | if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss) | |
317 | tp->window_clamp = max(maxwin - | |
318 | (maxwin >> sysctl_tcp_app_win), | |
319 | 4 * tp->advmss); | |
320 | } | |
321 | ||
322 | /* Force reservation of one segment. */ | |
323 | if (sysctl_tcp_app_win && | |
324 | tp->window_clamp > 2 * tp->advmss && | |
325 | tp->window_clamp + tp->advmss > maxwin) | |
326 | tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss); | |
327 | ||
328 | tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp); | |
329 | tp->snd_cwnd_stamp = tcp_time_stamp; | |
330 | } | |
331 | ||
1da177e4 LT |
332 | /* 5. Recalculate window clamp after socket hit its memory bounds. */ |
333 | static void tcp_clamp_window(struct sock *sk, struct tcp_sock *tp) | |
334 | { | |
6687e988 | 335 | struct inet_connection_sock *icsk = inet_csk(sk); |
1da177e4 | 336 | |
6687e988 | 337 | icsk->icsk_ack.quick = 0; |
1da177e4 | 338 | |
326f36e9 JH |
339 | if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] && |
340 | !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) && | |
341 | !tcp_memory_pressure && | |
342 | atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) { | |
343 | sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc), | |
344 | sysctl_tcp_rmem[2]); | |
1da177e4 | 345 | } |
326f36e9 | 346 | if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf) |
1da177e4 | 347 | tp->rcv_ssthresh = min(tp->window_clamp, 2U*tp->advmss); |
1da177e4 LT |
348 | } |
349 | ||
40efc6fa SH |
350 | |
351 | /* Initialize RCV_MSS value. | |
352 | * RCV_MSS is an our guess about MSS used by the peer. | |
353 | * We haven't any direct information about the MSS. | |
354 | * It's better to underestimate the RCV_MSS rather than overestimate. | |
355 | * Overestimations make us ACKing less frequently than needed. | |
356 | * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss(). | |
357 | */ | |
358 | void tcp_initialize_rcv_mss(struct sock *sk) | |
359 | { | |
360 | struct tcp_sock *tp = tcp_sk(sk); | |
361 | unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache); | |
362 | ||
363 | hint = min(hint, tp->rcv_wnd/2); | |
364 | hint = min(hint, TCP_MIN_RCVMSS); | |
365 | hint = max(hint, TCP_MIN_MSS); | |
366 | ||
367 | inet_csk(sk)->icsk_ack.rcv_mss = hint; | |
368 | } | |
369 | ||
1da177e4 LT |
370 | /* Receiver "autotuning" code. |
371 | * | |
372 | * The algorithm for RTT estimation w/o timestamps is based on | |
373 | * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL. | |
374 | * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps> | |
375 | * | |
376 | * More detail on this code can be found at | |
377 | * <http://www.psc.edu/~jheffner/senior_thesis.ps>, | |
378 | * though this reference is out of date. A new paper | |
379 | * is pending. | |
380 | */ | |
381 | static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep) | |
382 | { | |
383 | u32 new_sample = tp->rcv_rtt_est.rtt; | |
384 | long m = sample; | |
385 | ||
386 | if (m == 0) | |
387 | m = 1; | |
388 | ||
389 | if (new_sample != 0) { | |
390 | /* If we sample in larger samples in the non-timestamp | |
391 | * case, we could grossly overestimate the RTT especially | |
392 | * with chatty applications or bulk transfer apps which | |
393 | * are stalled on filesystem I/O. | |
394 | * | |
395 | * Also, since we are only going for a minimum in the | |
31f34269 | 396 | * non-timestamp case, we do not smooth things out |
caa20d9a | 397 | * else with timestamps disabled convergence takes too |
1da177e4 LT |
398 | * long. |
399 | */ | |
400 | if (!win_dep) { | |
401 | m -= (new_sample >> 3); | |
402 | new_sample += m; | |
403 | } else if (m < new_sample) | |
404 | new_sample = m << 3; | |
405 | } else { | |
caa20d9a | 406 | /* No previous measure. */ |
1da177e4 LT |
407 | new_sample = m << 3; |
408 | } | |
409 | ||
410 | if (tp->rcv_rtt_est.rtt != new_sample) | |
411 | tp->rcv_rtt_est.rtt = new_sample; | |
412 | } | |
413 | ||
414 | static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp) | |
415 | { | |
416 | if (tp->rcv_rtt_est.time == 0) | |
417 | goto new_measure; | |
418 | if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq)) | |
419 | return; | |
420 | tcp_rcv_rtt_update(tp, | |
421 | jiffies - tp->rcv_rtt_est.time, | |
422 | 1); | |
423 | ||
424 | new_measure: | |
425 | tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd; | |
426 | tp->rcv_rtt_est.time = tcp_time_stamp; | |
427 | } | |
428 | ||
463c84b9 | 429 | static inline void tcp_rcv_rtt_measure_ts(struct sock *sk, const struct sk_buff *skb) |
1da177e4 | 430 | { |
463c84b9 | 431 | struct tcp_sock *tp = tcp_sk(sk); |
1da177e4 LT |
432 | if (tp->rx_opt.rcv_tsecr && |
433 | (TCP_SKB_CB(skb)->end_seq - | |
463c84b9 | 434 | TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss)) |
1da177e4 LT |
435 | tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0); |
436 | } | |
437 | ||
438 | /* | |
439 | * This function should be called every time data is copied to user space. | |
440 | * It calculates the appropriate TCP receive buffer space. | |
441 | */ | |
442 | void tcp_rcv_space_adjust(struct sock *sk) | |
443 | { | |
444 | struct tcp_sock *tp = tcp_sk(sk); | |
445 | int time; | |
446 | int space; | |
e905a9ed | 447 | |
1da177e4 LT |
448 | if (tp->rcvq_space.time == 0) |
449 | goto new_measure; | |
e905a9ed | 450 | |
1da177e4 LT |
451 | time = tcp_time_stamp - tp->rcvq_space.time; |
452 | if (time < (tp->rcv_rtt_est.rtt >> 3) || | |
453 | tp->rcv_rtt_est.rtt == 0) | |
454 | return; | |
e905a9ed | 455 | |
1da177e4 LT |
456 | space = 2 * (tp->copied_seq - tp->rcvq_space.seq); |
457 | ||
458 | space = max(tp->rcvq_space.space, space); | |
459 | ||
460 | if (tp->rcvq_space.space != space) { | |
461 | int rcvmem; | |
462 | ||
463 | tp->rcvq_space.space = space; | |
464 | ||
6fcf9412 JH |
465 | if (sysctl_tcp_moderate_rcvbuf && |
466 | !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) { | |
1da177e4 LT |
467 | int new_clamp = space; |
468 | ||
469 | /* Receive space grows, normalize in order to | |
470 | * take into account packet headers and sk_buff | |
471 | * structure overhead. | |
472 | */ | |
473 | space /= tp->advmss; | |
474 | if (!space) | |
475 | space = 1; | |
476 | rcvmem = (tp->advmss + MAX_TCP_HEADER + | |
477 | 16 + sizeof(struct sk_buff)); | |
478 | while (tcp_win_from_space(rcvmem) < tp->advmss) | |
479 | rcvmem += 128; | |
480 | space *= rcvmem; | |
481 | space = min(space, sysctl_tcp_rmem[2]); | |
482 | if (space > sk->sk_rcvbuf) { | |
483 | sk->sk_rcvbuf = space; | |
484 | ||
485 | /* Make the window clamp follow along. */ | |
486 | tp->window_clamp = new_clamp; | |
487 | } | |
488 | } | |
489 | } | |
e905a9ed | 490 | |
1da177e4 LT |
491 | new_measure: |
492 | tp->rcvq_space.seq = tp->copied_seq; | |
493 | tp->rcvq_space.time = tcp_time_stamp; | |
494 | } | |
495 | ||
496 | /* There is something which you must keep in mind when you analyze the | |
497 | * behavior of the tp->ato delayed ack timeout interval. When a | |
498 | * connection starts up, we want to ack as quickly as possible. The | |
499 | * problem is that "good" TCP's do slow start at the beginning of data | |
500 | * transmission. The means that until we send the first few ACK's the | |
501 | * sender will sit on his end and only queue most of his data, because | |
502 | * he can only send snd_cwnd unacked packets at any given time. For | |
503 | * each ACK we send, he increments snd_cwnd and transmits more of his | |
504 | * queue. -DaveM | |
505 | */ | |
506 | static void tcp_event_data_recv(struct sock *sk, struct tcp_sock *tp, struct sk_buff *skb) | |
507 | { | |
463c84b9 | 508 | struct inet_connection_sock *icsk = inet_csk(sk); |
1da177e4 LT |
509 | u32 now; |
510 | ||
463c84b9 | 511 | inet_csk_schedule_ack(sk); |
1da177e4 | 512 | |
463c84b9 | 513 | tcp_measure_rcv_mss(sk, skb); |
1da177e4 LT |
514 | |
515 | tcp_rcv_rtt_measure(tp); | |
e905a9ed | 516 | |
1da177e4 LT |
517 | now = tcp_time_stamp; |
518 | ||
463c84b9 | 519 | if (!icsk->icsk_ack.ato) { |
1da177e4 LT |
520 | /* The _first_ data packet received, initialize |
521 | * delayed ACK engine. | |
522 | */ | |
463c84b9 ACM |
523 | tcp_incr_quickack(sk); |
524 | icsk->icsk_ack.ato = TCP_ATO_MIN; | |
1da177e4 | 525 | } else { |
463c84b9 | 526 | int m = now - icsk->icsk_ack.lrcvtime; |
1da177e4 LT |
527 | |
528 | if (m <= TCP_ATO_MIN/2) { | |
529 | /* The fastest case is the first. */ | |
463c84b9 ACM |
530 | icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2; |
531 | } else if (m < icsk->icsk_ack.ato) { | |
532 | icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m; | |
533 | if (icsk->icsk_ack.ato > icsk->icsk_rto) | |
534 | icsk->icsk_ack.ato = icsk->icsk_rto; | |
535 | } else if (m > icsk->icsk_rto) { | |
caa20d9a | 536 | /* Too long gap. Apparently sender failed to |
1da177e4 LT |
537 | * restart window, so that we send ACKs quickly. |
538 | */ | |
463c84b9 | 539 | tcp_incr_quickack(sk); |
1da177e4 LT |
540 | sk_stream_mem_reclaim(sk); |
541 | } | |
542 | } | |
463c84b9 | 543 | icsk->icsk_ack.lrcvtime = now; |
1da177e4 LT |
544 | |
545 | TCP_ECN_check_ce(tp, skb); | |
546 | ||
547 | if (skb->len >= 128) | |
548 | tcp_grow_window(sk, tp, skb); | |
549 | } | |
550 | ||
1da177e4 LT |
551 | /* Called to compute a smoothed rtt estimate. The data fed to this |
552 | * routine either comes from timestamps, or from segments that were | |
553 | * known _not_ to have been retransmitted [see Karn/Partridge | |
554 | * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88 | |
555 | * piece by Van Jacobson. | |
556 | * NOTE: the next three routines used to be one big routine. | |
557 | * To save cycles in the RFC 1323 implementation it was better to break | |
558 | * it up into three procedures. -- erics | |
559 | */ | |
2d2abbab | 560 | static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt) |
1da177e4 | 561 | { |
6687e988 | 562 | struct tcp_sock *tp = tcp_sk(sk); |
1da177e4 LT |
563 | long m = mrtt; /* RTT */ |
564 | ||
1da177e4 LT |
565 | /* The following amusing code comes from Jacobson's |
566 | * article in SIGCOMM '88. Note that rtt and mdev | |
567 | * are scaled versions of rtt and mean deviation. | |
e905a9ed | 568 | * This is designed to be as fast as possible |
1da177e4 LT |
569 | * m stands for "measurement". |
570 | * | |
571 | * On a 1990 paper the rto value is changed to: | |
572 | * RTO = rtt + 4 * mdev | |
573 | * | |
574 | * Funny. This algorithm seems to be very broken. | |
575 | * These formulae increase RTO, when it should be decreased, increase | |
31f34269 | 576 | * too slowly, when it should be increased quickly, decrease too quickly |
1da177e4 LT |
577 | * etc. I guess in BSD RTO takes ONE value, so that it is absolutely |
578 | * does not matter how to _calculate_ it. Seems, it was trap | |
579 | * that VJ failed to avoid. 8) | |
580 | */ | |
2de979bd | 581 | if (m == 0) |
1da177e4 LT |
582 | m = 1; |
583 | if (tp->srtt != 0) { | |
584 | m -= (tp->srtt >> 3); /* m is now error in rtt est */ | |
585 | tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */ | |
586 | if (m < 0) { | |
587 | m = -m; /* m is now abs(error) */ | |
588 | m -= (tp->mdev >> 2); /* similar update on mdev */ | |
589 | /* This is similar to one of Eifel findings. | |
590 | * Eifel blocks mdev updates when rtt decreases. | |
591 | * This solution is a bit different: we use finer gain | |
592 | * for mdev in this case (alpha*beta). | |
593 | * Like Eifel it also prevents growth of rto, | |
594 | * but also it limits too fast rto decreases, | |
595 | * happening in pure Eifel. | |
596 | */ | |
597 | if (m > 0) | |
598 | m >>= 3; | |
599 | } else { | |
600 | m -= (tp->mdev >> 2); /* similar update on mdev */ | |
601 | } | |
602 | tp->mdev += m; /* mdev = 3/4 mdev + 1/4 new */ | |
603 | if (tp->mdev > tp->mdev_max) { | |
604 | tp->mdev_max = tp->mdev; | |
605 | if (tp->mdev_max > tp->rttvar) | |
606 | tp->rttvar = tp->mdev_max; | |
607 | } | |
608 | if (after(tp->snd_una, tp->rtt_seq)) { | |
609 | if (tp->mdev_max < tp->rttvar) | |
610 | tp->rttvar -= (tp->rttvar-tp->mdev_max)>>2; | |
611 | tp->rtt_seq = tp->snd_nxt; | |
612 | tp->mdev_max = TCP_RTO_MIN; | |
613 | } | |
614 | } else { | |
615 | /* no previous measure. */ | |
616 | tp->srtt = m<<3; /* take the measured time to be rtt */ | |
617 | tp->mdev = m<<1; /* make sure rto = 3*rtt */ | |
618 | tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN); | |
619 | tp->rtt_seq = tp->snd_nxt; | |
620 | } | |
1da177e4 LT |
621 | } |
622 | ||
623 | /* Calculate rto without backoff. This is the second half of Van Jacobson's | |
624 | * routine referred to above. | |
625 | */ | |
463c84b9 | 626 | static inline void tcp_set_rto(struct sock *sk) |
1da177e4 | 627 | { |
463c84b9 | 628 | const struct tcp_sock *tp = tcp_sk(sk); |
1da177e4 LT |
629 | /* Old crap is replaced with new one. 8) |
630 | * | |
631 | * More seriously: | |
632 | * 1. If rtt variance happened to be less 50msec, it is hallucination. | |
633 | * It cannot be less due to utterly erratic ACK generation made | |
634 | * at least by solaris and freebsd. "Erratic ACKs" has _nothing_ | |
635 | * to do with delayed acks, because at cwnd>2 true delack timeout | |
636 | * is invisible. Actually, Linux-2.4 also generates erratic | |
caa20d9a | 637 | * ACKs in some circumstances. |
1da177e4 | 638 | */ |
463c84b9 | 639 | inet_csk(sk)->icsk_rto = (tp->srtt >> 3) + tp->rttvar; |
1da177e4 LT |
640 | |
641 | /* 2. Fixups made earlier cannot be right. | |
642 | * If we do not estimate RTO correctly without them, | |
643 | * all the algo is pure shit and should be replaced | |
caa20d9a | 644 | * with correct one. It is exactly, which we pretend to do. |
1da177e4 LT |
645 | */ |
646 | } | |
647 | ||
648 | /* NOTE: clamping at TCP_RTO_MIN is not required, current algo | |
649 | * guarantees that rto is higher. | |
650 | */ | |
463c84b9 | 651 | static inline void tcp_bound_rto(struct sock *sk) |
1da177e4 | 652 | { |
463c84b9 ACM |
653 | if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX) |
654 | inet_csk(sk)->icsk_rto = TCP_RTO_MAX; | |
1da177e4 LT |
655 | } |
656 | ||
657 | /* Save metrics learned by this TCP session. | |
658 | This function is called only, when TCP finishes successfully | |
659 | i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE. | |
660 | */ | |
661 | void tcp_update_metrics(struct sock *sk) | |
662 | { | |
663 | struct tcp_sock *tp = tcp_sk(sk); | |
664 | struct dst_entry *dst = __sk_dst_get(sk); | |
665 | ||
666 | if (sysctl_tcp_nometrics_save) | |
667 | return; | |
668 | ||
669 | dst_confirm(dst); | |
670 | ||
671 | if (dst && (dst->flags&DST_HOST)) { | |
6687e988 | 672 | const struct inet_connection_sock *icsk = inet_csk(sk); |
1da177e4 LT |
673 | int m; |
674 | ||
6687e988 | 675 | if (icsk->icsk_backoff || !tp->srtt) { |
1da177e4 LT |
676 | /* This session failed to estimate rtt. Why? |
677 | * Probably, no packets returned in time. | |
678 | * Reset our results. | |
679 | */ | |
680 | if (!(dst_metric_locked(dst, RTAX_RTT))) | |
681 | dst->metrics[RTAX_RTT-1] = 0; | |
682 | return; | |
683 | } | |
684 | ||
685 | m = dst_metric(dst, RTAX_RTT) - tp->srtt; | |
686 | ||
687 | /* If newly calculated rtt larger than stored one, | |
688 | * store new one. Otherwise, use EWMA. Remember, | |
689 | * rtt overestimation is always better than underestimation. | |
690 | */ | |
691 | if (!(dst_metric_locked(dst, RTAX_RTT))) { | |
692 | if (m <= 0) | |
693 | dst->metrics[RTAX_RTT-1] = tp->srtt; | |
694 | else | |
695 | dst->metrics[RTAX_RTT-1] -= (m>>3); | |
696 | } | |
697 | ||
698 | if (!(dst_metric_locked(dst, RTAX_RTTVAR))) { | |
699 | if (m < 0) | |
700 | m = -m; | |
701 | ||
702 | /* Scale deviation to rttvar fixed point */ | |
703 | m >>= 1; | |
704 | if (m < tp->mdev) | |
705 | m = tp->mdev; | |
706 | ||
707 | if (m >= dst_metric(dst, RTAX_RTTVAR)) | |
708 | dst->metrics[RTAX_RTTVAR-1] = m; | |
709 | else | |
710 | dst->metrics[RTAX_RTTVAR-1] -= | |
711 | (dst->metrics[RTAX_RTTVAR-1] - m)>>2; | |
712 | } | |
713 | ||
714 | if (tp->snd_ssthresh >= 0xFFFF) { | |
715 | /* Slow start still did not finish. */ | |
716 | if (dst_metric(dst, RTAX_SSTHRESH) && | |
717 | !dst_metric_locked(dst, RTAX_SSTHRESH) && | |
718 | (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH)) | |
719 | dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1; | |
720 | if (!dst_metric_locked(dst, RTAX_CWND) && | |
721 | tp->snd_cwnd > dst_metric(dst, RTAX_CWND)) | |
722 | dst->metrics[RTAX_CWND-1] = tp->snd_cwnd; | |
723 | } else if (tp->snd_cwnd > tp->snd_ssthresh && | |
6687e988 | 724 | icsk->icsk_ca_state == TCP_CA_Open) { |
1da177e4 LT |
725 | /* Cong. avoidance phase, cwnd is reliable. */ |
726 | if (!dst_metric_locked(dst, RTAX_SSTHRESH)) | |
727 | dst->metrics[RTAX_SSTHRESH-1] = | |
728 | max(tp->snd_cwnd >> 1, tp->snd_ssthresh); | |
729 | if (!dst_metric_locked(dst, RTAX_CWND)) | |
730 | dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_cwnd) >> 1; | |
731 | } else { | |
732 | /* Else slow start did not finish, cwnd is non-sense, | |
733 | ssthresh may be also invalid. | |
734 | */ | |
735 | if (!dst_metric_locked(dst, RTAX_CWND)) | |
736 | dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_ssthresh) >> 1; | |
737 | if (dst->metrics[RTAX_SSTHRESH-1] && | |
738 | !dst_metric_locked(dst, RTAX_SSTHRESH) && | |
739 | tp->snd_ssthresh > dst->metrics[RTAX_SSTHRESH-1]) | |
740 | dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh; | |
741 | } | |
742 | ||
743 | if (!dst_metric_locked(dst, RTAX_REORDERING)) { | |
744 | if (dst->metrics[RTAX_REORDERING-1] < tp->reordering && | |
745 | tp->reordering != sysctl_tcp_reordering) | |
746 | dst->metrics[RTAX_REORDERING-1] = tp->reordering; | |
747 | } | |
748 | } | |
749 | } | |
750 | ||
751 | /* Numbers are taken from RFC2414. */ | |
752 | __u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst) | |
753 | { | |
754 | __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0); | |
755 | ||
756 | if (!cwnd) { | |
c1b4a7e6 | 757 | if (tp->mss_cache > 1460) |
1da177e4 LT |
758 | cwnd = 2; |
759 | else | |
c1b4a7e6 | 760 | cwnd = (tp->mss_cache > 1095) ? 3 : 4; |
1da177e4 LT |
761 | } |
762 | return min_t(__u32, cwnd, tp->snd_cwnd_clamp); | |
763 | } | |
764 | ||
40efc6fa | 765 | /* Set slow start threshold and cwnd not falling to slow start */ |
3cfe3baa | 766 | void tcp_enter_cwr(struct sock *sk, const int set_ssthresh) |
40efc6fa SH |
767 | { |
768 | struct tcp_sock *tp = tcp_sk(sk); | |
3cfe3baa | 769 | const struct inet_connection_sock *icsk = inet_csk(sk); |
40efc6fa SH |
770 | |
771 | tp->prior_ssthresh = 0; | |
772 | tp->bytes_acked = 0; | |
e01f9d77 | 773 | if (icsk->icsk_ca_state < TCP_CA_CWR) { |
40efc6fa | 774 | tp->undo_marker = 0; |
3cfe3baa IJ |
775 | if (set_ssthresh) |
776 | tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); | |
40efc6fa SH |
777 | tp->snd_cwnd = min(tp->snd_cwnd, |
778 | tcp_packets_in_flight(tp) + 1U); | |
779 | tp->snd_cwnd_cnt = 0; | |
780 | tp->high_seq = tp->snd_nxt; | |
781 | tp->snd_cwnd_stamp = tcp_time_stamp; | |
782 | TCP_ECN_queue_cwr(tp); | |
783 | ||
784 | tcp_set_ca_state(sk, TCP_CA_CWR); | |
785 | } | |
786 | } | |
787 | ||
1da177e4 LT |
788 | /* Initialize metrics on socket. */ |
789 | ||
790 | static void tcp_init_metrics(struct sock *sk) | |
791 | { | |
792 | struct tcp_sock *tp = tcp_sk(sk); | |
793 | struct dst_entry *dst = __sk_dst_get(sk); | |
794 | ||
795 | if (dst == NULL) | |
796 | goto reset; | |
797 | ||
798 | dst_confirm(dst); | |
799 | ||
800 | if (dst_metric_locked(dst, RTAX_CWND)) | |
801 | tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND); | |
802 | if (dst_metric(dst, RTAX_SSTHRESH)) { | |
803 | tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH); | |
804 | if (tp->snd_ssthresh > tp->snd_cwnd_clamp) | |
805 | tp->snd_ssthresh = tp->snd_cwnd_clamp; | |
806 | } | |
807 | if (dst_metric(dst, RTAX_REORDERING) && | |
808 | tp->reordering != dst_metric(dst, RTAX_REORDERING)) { | |
809 | tp->rx_opt.sack_ok &= ~2; | |
810 | tp->reordering = dst_metric(dst, RTAX_REORDERING); | |
811 | } | |
812 | ||
813 | if (dst_metric(dst, RTAX_RTT) == 0) | |
814 | goto reset; | |
815 | ||
816 | if (!tp->srtt && dst_metric(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3)) | |
817 | goto reset; | |
818 | ||
819 | /* Initial rtt is determined from SYN,SYN-ACK. | |
820 | * The segment is small and rtt may appear much | |
821 | * less than real one. Use per-dst memory | |
822 | * to make it more realistic. | |
823 | * | |
824 | * A bit of theory. RTT is time passed after "normal" sized packet | |
caa20d9a | 825 | * is sent until it is ACKed. In normal circumstances sending small |
1da177e4 LT |
826 | * packets force peer to delay ACKs and calculation is correct too. |
827 | * The algorithm is adaptive and, provided we follow specs, it | |
828 | * NEVER underestimate RTT. BUT! If peer tries to make some clever | |
829 | * tricks sort of "quick acks" for time long enough to decrease RTT | |
830 | * to low value, and then abruptly stops to do it and starts to delay | |
831 | * ACKs, wait for troubles. | |
832 | */ | |
833 | if (dst_metric(dst, RTAX_RTT) > tp->srtt) { | |
834 | tp->srtt = dst_metric(dst, RTAX_RTT); | |
835 | tp->rtt_seq = tp->snd_nxt; | |
836 | } | |
837 | if (dst_metric(dst, RTAX_RTTVAR) > tp->mdev) { | |
838 | tp->mdev = dst_metric(dst, RTAX_RTTVAR); | |
839 | tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN); | |
840 | } | |
463c84b9 ACM |
841 | tcp_set_rto(sk); |
842 | tcp_bound_rto(sk); | |
843 | if (inet_csk(sk)->icsk_rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp) | |
1da177e4 LT |
844 | goto reset; |
845 | tp->snd_cwnd = tcp_init_cwnd(tp, dst); | |
846 | tp->snd_cwnd_stamp = tcp_time_stamp; | |
847 | return; | |
848 | ||
849 | reset: | |
850 | /* Play conservative. If timestamps are not | |
851 | * supported, TCP will fail to recalculate correct | |
852 | * rtt, if initial rto is too small. FORGET ALL AND RESET! | |
853 | */ | |
854 | if (!tp->rx_opt.saw_tstamp && tp->srtt) { | |
855 | tp->srtt = 0; | |
856 | tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT; | |
463c84b9 | 857 | inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT; |
1da177e4 LT |
858 | } |
859 | } | |
860 | ||
6687e988 ACM |
861 | static void tcp_update_reordering(struct sock *sk, const int metric, |
862 | const int ts) | |
1da177e4 | 863 | { |
6687e988 | 864 | struct tcp_sock *tp = tcp_sk(sk); |
1da177e4 LT |
865 | if (metric > tp->reordering) { |
866 | tp->reordering = min(TCP_MAX_REORDERING, metric); | |
867 | ||
868 | /* This exciting event is worth to be remembered. 8) */ | |
869 | if (ts) | |
870 | NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER); | |
871 | else if (IsReno(tp)) | |
872 | NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER); | |
873 | else if (IsFack(tp)) | |
874 | NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER); | |
875 | else | |
876 | NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER); | |
877 | #if FASTRETRANS_DEBUG > 1 | |
878 | printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n", | |
6687e988 | 879 | tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state, |
1da177e4 LT |
880 | tp->reordering, |
881 | tp->fackets_out, | |
882 | tp->sacked_out, | |
883 | tp->undo_marker ? tp->undo_retrans : 0); | |
884 | #endif | |
885 | /* Disable FACK yet. */ | |
886 | tp->rx_opt.sack_ok &= ~2; | |
887 | } | |
888 | } | |
889 | ||
890 | /* This procedure tags the retransmission queue when SACKs arrive. | |
891 | * | |
892 | * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L). | |
893 | * Packets in queue with these bits set are counted in variables | |
894 | * sacked_out, retrans_out and lost_out, correspondingly. | |
895 | * | |
896 | * Valid combinations are: | |
897 | * Tag InFlight Description | |
898 | * 0 1 - orig segment is in flight. | |
899 | * S 0 - nothing flies, orig reached receiver. | |
900 | * L 0 - nothing flies, orig lost by net. | |
901 | * R 2 - both orig and retransmit are in flight. | |
902 | * L|R 1 - orig is lost, retransmit is in flight. | |
903 | * S|R 1 - orig reached receiver, retrans is still in flight. | |
904 | * (L|S|R is logically valid, it could occur when L|R is sacked, | |
905 | * but it is equivalent to plain S and code short-curcuits it to S. | |
906 | * L|S is logically invalid, it would mean -1 packet in flight 8)) | |
907 | * | |
908 | * These 6 states form finite state machine, controlled by the following events: | |
909 | * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue()) | |
910 | * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue()) | |
911 | * 3. Loss detection event of one of three flavors: | |
912 | * A. Scoreboard estimator decided the packet is lost. | |
913 | * A'. Reno "three dupacks" marks head of queue lost. | |
914 | * A''. Its FACK modfication, head until snd.fack is lost. | |
915 | * B. SACK arrives sacking data transmitted after never retransmitted | |
916 | * hole was sent out. | |
917 | * C. SACK arrives sacking SND.NXT at the moment, when the | |
918 | * segment was retransmitted. | |
919 | * 4. D-SACK added new rule: D-SACK changes any tag to S. | |
920 | * | |
921 | * It is pleasant to note, that state diagram turns out to be commutative, | |
922 | * so that we are allowed not to be bothered by order of our actions, | |
923 | * when multiple events arrive simultaneously. (see the function below). | |
924 | * | |
925 | * Reordering detection. | |
926 | * -------------------- | |
927 | * Reordering metric is maximal distance, which a packet can be displaced | |
928 | * in packet stream. With SACKs we can estimate it: | |
929 | * | |
930 | * 1. SACK fills old hole and the corresponding segment was not | |
931 | * ever retransmitted -> reordering. Alas, we cannot use it | |
932 | * when segment was retransmitted. | |
933 | * 2. The last flaw is solved with D-SACK. D-SACK arrives | |
934 | * for retransmitted and already SACKed segment -> reordering.. | |
935 | * Both of these heuristics are not used in Loss state, when we cannot | |
936 | * account for retransmits accurately. | |
937 | */ | |
938 | static int | |
939 | tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_una) | |
940 | { | |
6687e988 | 941 | const struct inet_connection_sock *icsk = inet_csk(sk); |
1da177e4 | 942 | struct tcp_sock *tp = tcp_sk(sk); |
9c70220b ACM |
943 | unsigned char *ptr = (skb_transport_header(ack_skb) + |
944 | TCP_SKB_CB(ack_skb)->sacked); | |
269bd27e | 945 | struct tcp_sack_block_wire *sp = (struct tcp_sack_block_wire *)(ptr+2); |
fda03fbb | 946 | struct sk_buff *cached_skb; |
1da177e4 LT |
947 | int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3; |
948 | int reord = tp->packets_out; | |
949 | int prior_fackets; | |
950 | u32 lost_retrans = 0; | |
951 | int flag = 0; | |
6a438bbe | 952 | int dup_sack = 0; |
fda03fbb | 953 | int cached_fack_count; |
1da177e4 | 954 | int i; |
fda03fbb | 955 | int first_sack_index; |
1da177e4 | 956 | |
1da177e4 LT |
957 | if (!tp->sacked_out) |
958 | tp->fackets_out = 0; | |
959 | prior_fackets = tp->fackets_out; | |
960 | ||
6f74651a BE |
961 | /* Check for D-SACK. */ |
962 | if (before(ntohl(sp[0].start_seq), TCP_SKB_CB(ack_skb)->ack_seq)) { | |
963 | dup_sack = 1; | |
964 | tp->rx_opt.sack_ok |= 4; | |
965 | NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV); | |
966 | } else if (num_sacks > 1 && | |
967 | !after(ntohl(sp[0].end_seq), ntohl(sp[1].end_seq)) && | |
968 | !before(ntohl(sp[0].start_seq), ntohl(sp[1].start_seq))) { | |
969 | dup_sack = 1; | |
970 | tp->rx_opt.sack_ok |= 4; | |
971 | NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV); | |
972 | } | |
973 | ||
974 | /* D-SACK for already forgotten data... | |
975 | * Do dumb counting. */ | |
976 | if (dup_sack && | |
977 | !after(ntohl(sp[0].end_seq), prior_snd_una) && | |
978 | after(ntohl(sp[0].end_seq), tp->undo_marker)) | |
979 | tp->undo_retrans--; | |
980 | ||
981 | /* Eliminate too old ACKs, but take into | |
982 | * account more or less fresh ones, they can | |
983 | * contain valid SACK info. | |
984 | */ | |
985 | if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window)) | |
986 | return 0; | |
987 | ||
6a438bbe SH |
988 | /* SACK fastpath: |
989 | * if the only SACK change is the increase of the end_seq of | |
990 | * the first block then only apply that SACK block | |
991 | * and use retrans queue hinting otherwise slowpath */ | |
992 | flag = 1; | |
6f74651a BE |
993 | for (i = 0; i < num_sacks; i++) { |
994 | __be32 start_seq = sp[i].start_seq; | |
995 | __be32 end_seq = sp[i].end_seq; | |
6a438bbe | 996 | |
6f74651a | 997 | if (i == 0) { |
6a438bbe SH |
998 | if (tp->recv_sack_cache[i].start_seq != start_seq) |
999 | flag = 0; | |
1000 | } else { | |
1001 | if ((tp->recv_sack_cache[i].start_seq != start_seq) || | |
1002 | (tp->recv_sack_cache[i].end_seq != end_seq)) | |
1003 | flag = 0; | |
1004 | } | |
1005 | tp->recv_sack_cache[i].start_seq = start_seq; | |
1006 | tp->recv_sack_cache[i].end_seq = end_seq; | |
6a438bbe | 1007 | } |
8a3c3a97 BE |
1008 | /* Clear the rest of the cache sack blocks so they won't match mistakenly. */ |
1009 | for (; i < ARRAY_SIZE(tp->recv_sack_cache); i++) { | |
1010 | tp->recv_sack_cache[i].start_seq = 0; | |
1011 | tp->recv_sack_cache[i].end_seq = 0; | |
1012 | } | |
6a438bbe | 1013 | |
fda03fbb | 1014 | first_sack_index = 0; |
6a438bbe SH |
1015 | if (flag) |
1016 | num_sacks = 1; | |
1017 | else { | |
1018 | int j; | |
1019 | tp->fastpath_skb_hint = NULL; | |
1020 | ||
1021 | /* order SACK blocks to allow in order walk of the retrans queue */ | |
1022 | for (i = num_sacks-1; i > 0; i--) { | |
1023 | for (j = 0; j < i; j++){ | |
1024 | if (after(ntohl(sp[j].start_seq), | |
1025 | ntohl(sp[j+1].start_seq))){ | |
db3ccdac BE |
1026 | struct tcp_sack_block_wire tmp; |
1027 | ||
1028 | tmp = sp[j]; | |
1029 | sp[j] = sp[j+1]; | |
1030 | sp[j+1] = tmp; | |
fda03fbb BE |
1031 | |
1032 | /* Track where the first SACK block goes to */ | |
1033 | if (j == first_sack_index) | |
1034 | first_sack_index = j+1; | |
6a438bbe SH |
1035 | } |
1036 | ||
1037 | } | |
1038 | } | |
1039 | } | |
1040 | ||
1041 | /* clear flag as used for different purpose in following code */ | |
1042 | flag = 0; | |
1043 | ||
fda03fbb BE |
1044 | /* Use SACK fastpath hint if valid */ |
1045 | cached_skb = tp->fastpath_skb_hint; | |
1046 | cached_fack_count = tp->fastpath_cnt_hint; | |
1047 | if (!cached_skb) { | |
fe067e8a | 1048 | cached_skb = tcp_write_queue_head(sk); |
fda03fbb BE |
1049 | cached_fack_count = 0; |
1050 | } | |
1051 | ||
6a438bbe SH |
1052 | for (i=0; i<num_sacks; i++, sp++) { |
1053 | struct sk_buff *skb; | |
1054 | __u32 start_seq = ntohl(sp->start_seq); | |
1055 | __u32 end_seq = ntohl(sp->end_seq); | |
1056 | int fack_count; | |
1057 | ||
fda03fbb BE |
1058 | skb = cached_skb; |
1059 | fack_count = cached_fack_count; | |
1da177e4 LT |
1060 | |
1061 | /* Event "B" in the comment above. */ | |
1062 | if (after(end_seq, tp->high_seq)) | |
1063 | flag |= FLAG_DATA_LOST; | |
1064 | ||
fe067e8a | 1065 | tcp_for_write_queue_from(skb, sk) { |
6475be16 DM |
1066 | int in_sack, pcount; |
1067 | u8 sacked; | |
1da177e4 | 1068 | |
fe067e8a DM |
1069 | if (skb == tcp_send_head(sk)) |
1070 | break; | |
1071 | ||
fda03fbb BE |
1072 | cached_skb = skb; |
1073 | cached_fack_count = fack_count; | |
1074 | if (i == first_sack_index) { | |
1075 | tp->fastpath_skb_hint = skb; | |
1076 | tp->fastpath_cnt_hint = fack_count; | |
1077 | } | |
6a438bbe | 1078 | |
1da177e4 LT |
1079 | /* The retransmission queue is always in order, so |
1080 | * we can short-circuit the walk early. | |
1081 | */ | |
6475be16 | 1082 | if (!before(TCP_SKB_CB(skb)->seq, end_seq)) |
1da177e4 LT |
1083 | break; |
1084 | ||
3c05d92e HX |
1085 | in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && |
1086 | !before(end_seq, TCP_SKB_CB(skb)->end_seq); | |
1087 | ||
6475be16 DM |
1088 | pcount = tcp_skb_pcount(skb); |
1089 | ||
3c05d92e HX |
1090 | if (pcount > 1 && !in_sack && |
1091 | after(TCP_SKB_CB(skb)->end_seq, start_seq)) { | |
6475be16 DM |
1092 | unsigned int pkt_len; |
1093 | ||
3c05d92e HX |
1094 | in_sack = !after(start_seq, |
1095 | TCP_SKB_CB(skb)->seq); | |
1096 | ||
1097 | if (!in_sack) | |
6475be16 DM |
1098 | pkt_len = (start_seq - |
1099 | TCP_SKB_CB(skb)->seq); | |
1100 | else | |
1101 | pkt_len = (end_seq - | |
1102 | TCP_SKB_CB(skb)->seq); | |
7967168c | 1103 | if (tcp_fragment(sk, skb, pkt_len, skb_shinfo(skb)->gso_size)) |
6475be16 DM |
1104 | break; |
1105 | pcount = tcp_skb_pcount(skb); | |
1106 | } | |
1107 | ||
1108 | fack_count += pcount; | |
1da177e4 | 1109 | |
6475be16 DM |
1110 | sacked = TCP_SKB_CB(skb)->sacked; |
1111 | ||
1da177e4 LT |
1112 | /* Account D-SACK for retransmitted packet. */ |
1113 | if ((dup_sack && in_sack) && | |
1114 | (sacked & TCPCB_RETRANS) && | |
1115 | after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker)) | |
1116 | tp->undo_retrans--; | |
1117 | ||
1118 | /* The frame is ACKed. */ | |
1119 | if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) { | |
1120 | if (sacked&TCPCB_RETRANS) { | |
1121 | if ((dup_sack && in_sack) && | |
1122 | (sacked&TCPCB_SACKED_ACKED)) | |
1123 | reord = min(fack_count, reord); | |
1124 | } else { | |
1125 | /* If it was in a hole, we detected reordering. */ | |
1126 | if (fack_count < prior_fackets && | |
1127 | !(sacked&TCPCB_SACKED_ACKED)) | |
1128 | reord = min(fack_count, reord); | |
1129 | } | |
1130 | ||
1131 | /* Nothing to do; acked frame is about to be dropped. */ | |
1132 | continue; | |
1133 | } | |
1134 | ||
1135 | if ((sacked&TCPCB_SACKED_RETRANS) && | |
1136 | after(end_seq, TCP_SKB_CB(skb)->ack_seq) && | |
1137 | (!lost_retrans || after(end_seq, lost_retrans))) | |
1138 | lost_retrans = end_seq; | |
1139 | ||
1140 | if (!in_sack) | |
1141 | continue; | |
1142 | ||
1143 | if (!(sacked&TCPCB_SACKED_ACKED)) { | |
1144 | if (sacked & TCPCB_SACKED_RETRANS) { | |
1145 | /* If the segment is not tagged as lost, | |
1146 | * we do not clear RETRANS, believing | |
1147 | * that retransmission is still in flight. | |
1148 | */ | |
1149 | if (sacked & TCPCB_LOST) { | |
1150 | TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS); | |
1151 | tp->lost_out -= tcp_skb_pcount(skb); | |
1152 | tp->retrans_out -= tcp_skb_pcount(skb); | |
6a438bbe SH |
1153 | |
1154 | /* clear lost hint */ | |
1155 | tp->retransmit_skb_hint = NULL; | |
1da177e4 LT |
1156 | } |
1157 | } else { | |
1158 | /* New sack for not retransmitted frame, | |
1159 | * which was in hole. It is reordering. | |
1160 | */ | |
1161 | if (!(sacked & TCPCB_RETRANS) && | |
1162 | fack_count < prior_fackets) | |
1163 | reord = min(fack_count, reord); | |
1164 | ||
1165 | if (sacked & TCPCB_LOST) { | |
1166 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; | |
1167 | tp->lost_out -= tcp_skb_pcount(skb); | |
6a438bbe SH |
1168 | |
1169 | /* clear lost hint */ | |
1170 | tp->retransmit_skb_hint = NULL; | |
1da177e4 | 1171 | } |
4dc2665e IJ |
1172 | /* SACK enhanced F-RTO detection. |
1173 | * Set flag if and only if non-rexmitted | |
1174 | * segments below frto_highmark are | |
1175 | * SACKed (RFC4138; Appendix B). | |
1176 | * Clearing correct due to in-order walk | |
1177 | */ | |
1178 | if (after(end_seq, tp->frto_highmark)) { | |
1179 | flag &= ~FLAG_ONLY_ORIG_SACKED; | |
1180 | } else { | |
1181 | if (!(sacked & TCPCB_RETRANS)) | |
1182 | flag |= FLAG_ONLY_ORIG_SACKED; | |
1183 | } | |
1da177e4 LT |
1184 | } |
1185 | ||
1186 | TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED; | |
1187 | flag |= FLAG_DATA_SACKED; | |
1188 | tp->sacked_out += tcp_skb_pcount(skb); | |
1189 | ||
1190 | if (fack_count > tp->fackets_out) | |
1191 | tp->fackets_out = fack_count; | |
1192 | } else { | |
1193 | if (dup_sack && (sacked&TCPCB_RETRANS)) | |
1194 | reord = min(fack_count, reord); | |
1195 | } | |
1196 | ||
1197 | /* D-SACK. We can detect redundant retransmission | |
1198 | * in S|R and plain R frames and clear it. | |
1199 | * undo_retrans is decreased above, L|R frames | |
1200 | * are accounted above as well. | |
1201 | */ | |
1202 | if (dup_sack && | |
1203 | (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS)) { | |
1204 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; | |
1205 | tp->retrans_out -= tcp_skb_pcount(skb); | |
6a438bbe | 1206 | tp->retransmit_skb_hint = NULL; |
1da177e4 LT |
1207 | } |
1208 | } | |
1209 | } | |
1210 | ||
1211 | /* Check for lost retransmit. This superb idea is | |
1212 | * borrowed from "ratehalving". Event "C". | |
1213 | * Later note: FACK people cheated me again 8), | |
1214 | * we have to account for reordering! Ugly, | |
1215 | * but should help. | |
1216 | */ | |
6687e988 | 1217 | if (lost_retrans && icsk->icsk_ca_state == TCP_CA_Recovery) { |
1da177e4 LT |
1218 | struct sk_buff *skb; |
1219 | ||
fe067e8a DM |
1220 | tcp_for_write_queue(skb, sk) { |
1221 | if (skb == tcp_send_head(sk)) | |
1222 | break; | |
1da177e4 LT |
1223 | if (after(TCP_SKB_CB(skb)->seq, lost_retrans)) |
1224 | break; | |
1225 | if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) | |
1226 | continue; | |
1227 | if ((TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) && | |
1228 | after(lost_retrans, TCP_SKB_CB(skb)->ack_seq) && | |
1229 | (IsFack(tp) || | |
1230 | !before(lost_retrans, | |
1231 | TCP_SKB_CB(skb)->ack_seq + tp->reordering * | |
c1b4a7e6 | 1232 | tp->mss_cache))) { |
1da177e4 LT |
1233 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; |
1234 | tp->retrans_out -= tcp_skb_pcount(skb); | |
1235 | ||
6a438bbe SH |
1236 | /* clear lost hint */ |
1237 | tp->retransmit_skb_hint = NULL; | |
1238 | ||
1da177e4 LT |
1239 | if (!(TCP_SKB_CB(skb)->sacked&(TCPCB_LOST|TCPCB_SACKED_ACKED))) { |
1240 | tp->lost_out += tcp_skb_pcount(skb); | |
1241 | TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; | |
1242 | flag |= FLAG_DATA_SACKED; | |
1243 | NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT); | |
1244 | } | |
1245 | } | |
1246 | } | |
1247 | } | |
1248 | ||
1249 | tp->left_out = tp->sacked_out + tp->lost_out; | |
1250 | ||
288035f9 | 1251 | if ((reord < tp->fackets_out) && icsk->icsk_ca_state != TCP_CA_Loss && |
c5e7af0d | 1252 | (!tp->frto_highmark || after(tp->snd_una, tp->frto_highmark))) |
6687e988 | 1253 | tcp_update_reordering(sk, ((tp->fackets_out + 1) - reord), 0); |
1da177e4 LT |
1254 | |
1255 | #if FASTRETRANS_DEBUG > 0 | |
1256 | BUG_TRAP((int)tp->sacked_out >= 0); | |
1257 | BUG_TRAP((int)tp->lost_out >= 0); | |
1258 | BUG_TRAP((int)tp->retrans_out >= 0); | |
1259 | BUG_TRAP((int)tcp_packets_in_flight(tp) >= 0); | |
1260 | #endif | |
1261 | return flag; | |
1262 | } | |
1263 | ||
30935cf4 IJ |
1264 | /* F-RTO can only be used if these conditions are satisfied: |
1265 | * - there must be some unsent new data | |
1266 | * - the advertised window should allow sending it | |
4dc2665e IJ |
1267 | * - TCP has never retransmitted anything other than head (SACK enhanced |
1268 | * variant from Appendix B of RFC4138 is more robust here) | |
30935cf4 | 1269 | */ |
46d0de4e | 1270 | int tcp_use_frto(struct sock *sk) |
bdaae17d IJ |
1271 | { |
1272 | const struct tcp_sock *tp = tcp_sk(sk); | |
46d0de4e IJ |
1273 | struct sk_buff *skb; |
1274 | ||
fe067e8a DM |
1275 | if (!sysctl_tcp_frto || !tcp_send_head(sk) || |
1276 | after(TCP_SKB_CB(tcp_send_head(sk))->end_seq, | |
46d0de4e IJ |
1277 | tp->snd_una + tp->snd_wnd)) |
1278 | return 0; | |
bdaae17d | 1279 | |
4dc2665e IJ |
1280 | if (IsSackFrto()) |
1281 | return 1; | |
1282 | ||
46d0de4e IJ |
1283 | /* Avoid expensive walking of rexmit queue if possible */ |
1284 | if (tp->retrans_out > 1) | |
1285 | return 0; | |
1286 | ||
fe067e8a DM |
1287 | skb = tcp_write_queue_head(sk); |
1288 | skb = tcp_write_queue_next(sk, skb); /* Skips head */ | |
1289 | tcp_for_write_queue_from(skb, sk) { | |
1290 | if (skb == tcp_send_head(sk)) | |
1291 | break; | |
46d0de4e IJ |
1292 | if (TCP_SKB_CB(skb)->sacked&TCPCB_RETRANS) |
1293 | return 0; | |
1294 | /* Short-circuit when first non-SACKed skb has been checked */ | |
1295 | if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) | |
1296 | break; | |
1297 | } | |
1298 | return 1; | |
bdaae17d IJ |
1299 | } |
1300 | ||
30935cf4 IJ |
1301 | /* RTO occurred, but do not yet enter Loss state. Instead, defer RTO |
1302 | * recovery a bit and use heuristics in tcp_process_frto() to detect if | |
d1a54c6a IJ |
1303 | * the RTO was spurious. Only clear SACKED_RETRANS of the head here to |
1304 | * keep retrans_out counting accurate (with SACK F-RTO, other than head | |
1305 | * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS | |
1306 | * bits are handled if the Loss state is really to be entered (in | |
1307 | * tcp_enter_frto_loss). | |
7487c48c IJ |
1308 | * |
1309 | * Do like tcp_enter_loss() would; when RTO expires the second time it | |
1310 | * does: | |
1311 | * "Reduce ssthresh if it has not yet been made inside this window." | |
1da177e4 LT |
1312 | */ |
1313 | void tcp_enter_frto(struct sock *sk) | |
1314 | { | |
6687e988 | 1315 | const struct inet_connection_sock *icsk = inet_csk(sk); |
1da177e4 LT |
1316 | struct tcp_sock *tp = tcp_sk(sk); |
1317 | struct sk_buff *skb; | |
1318 | ||
7487c48c | 1319 | if ((!tp->frto_counter && icsk->icsk_ca_state <= TCP_CA_Disorder) || |
e905a9ed | 1320 | tp->snd_una == tp->high_seq || |
7487c48c IJ |
1321 | ((icsk->icsk_ca_state == TCP_CA_Loss || tp->frto_counter) && |
1322 | !icsk->icsk_retransmits)) { | |
6687e988 | 1323 | tp->prior_ssthresh = tcp_current_ssthresh(sk); |
66e93e45 IJ |
1324 | /* Our state is too optimistic in ssthresh() call because cwnd |
1325 | * is not reduced until tcp_enter_frto_loss() when previous FRTO | |
1326 | * recovery has not yet completed. Pattern would be this: RTO, | |
1327 | * Cumulative ACK, RTO (2xRTO for the same segment does not end | |
1328 | * up here twice). | |
1329 | * RFC4138 should be more specific on what to do, even though | |
1330 | * RTO is quite unlikely to occur after the first Cumulative ACK | |
1331 | * due to back-off and complexity of triggering events ... | |
1332 | */ | |
1333 | if (tp->frto_counter) { | |
1334 | u32 stored_cwnd; | |
1335 | stored_cwnd = tp->snd_cwnd; | |
1336 | tp->snd_cwnd = 2; | |
1337 | tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); | |
1338 | tp->snd_cwnd = stored_cwnd; | |
1339 | } else { | |
1340 | tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); | |
1341 | } | |
1342 | /* ... in theory, cong.control module could do "any tricks" in | |
1343 | * ssthresh(), which means that ca_state, lost bits and lost_out | |
1344 | * counter would have to be faked before the call occurs. We | |
1345 | * consider that too expensive, unlikely and hacky, so modules | |
1346 | * using these in ssthresh() must deal these incompatibility | |
1347 | * issues if they receives CA_EVENT_FRTO and frto_counter != 0 | |
1348 | */ | |
6687e988 | 1349 | tcp_ca_event(sk, CA_EVENT_FRTO); |
1da177e4 LT |
1350 | } |
1351 | ||
1da177e4 LT |
1352 | tp->undo_marker = tp->snd_una; |
1353 | tp->undo_retrans = 0; | |
1354 | ||
fe067e8a | 1355 | skb = tcp_write_queue_head(sk); |
d1a54c6a | 1356 | if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) { |
522e7548 | 1357 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; |
d1a54c6a | 1358 | tp->retrans_out -= tcp_skb_pcount(skb); |
1da177e4 LT |
1359 | } |
1360 | tcp_sync_left_out(tp); | |
1361 | ||
4dc2665e IJ |
1362 | /* Earlier loss recovery underway (see RFC4138; Appendix B). |
1363 | * The last condition is necessary at least in tp->frto_counter case. | |
1364 | */ | |
1365 | if (IsSackFrto() && (tp->frto_counter || | |
1366 | ((1 << icsk->icsk_ca_state) & (TCPF_CA_Recovery|TCPF_CA_Loss))) && | |
1367 | after(tp->high_seq, tp->snd_una)) { | |
1368 | tp->frto_highmark = tp->high_seq; | |
1369 | } else { | |
1370 | tp->frto_highmark = tp->snd_nxt; | |
1371 | } | |
7b0eb22b IJ |
1372 | tcp_set_ca_state(sk, TCP_CA_Disorder); |
1373 | tp->high_seq = tp->snd_nxt; | |
7487c48c | 1374 | tp->frto_counter = 1; |
1da177e4 LT |
1375 | } |
1376 | ||
1377 | /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO, | |
1378 | * which indicates that we should follow the traditional RTO recovery, | |
1379 | * i.e. mark everything lost and do go-back-N retransmission. | |
1380 | */ | |
d1a54c6a | 1381 | static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag) |
1da177e4 LT |
1382 | { |
1383 | struct tcp_sock *tp = tcp_sk(sk); | |
1384 | struct sk_buff *skb; | |
1385 | int cnt = 0; | |
1386 | ||
1387 | tp->sacked_out = 0; | |
1388 | tp->lost_out = 0; | |
1389 | tp->fackets_out = 0; | |
d1a54c6a | 1390 | tp->retrans_out = 0; |
1da177e4 | 1391 | |
fe067e8a DM |
1392 | tcp_for_write_queue(skb, sk) { |
1393 | if (skb == tcp_send_head(sk)) | |
1394 | break; | |
1da177e4 | 1395 | cnt += tcp_skb_pcount(skb); |
d1a54c6a IJ |
1396 | /* |
1397 | * Count the retransmission made on RTO correctly (only when | |
1398 | * waiting for the first ACK and did not get it)... | |
1399 | */ | |
1400 | if ((tp->frto_counter == 1) && !(flag&FLAG_DATA_ACKED)) { | |
1401 | tp->retrans_out += tcp_skb_pcount(skb); | |
1402 | /* ...enter this if branch just for the first segment */ | |
1403 | flag |= FLAG_DATA_ACKED; | |
1404 | } else { | |
1405 | TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS); | |
1406 | } | |
1da177e4 LT |
1407 | if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) { |
1408 | ||
1409 | /* Do not mark those segments lost that were | |
1410 | * forward transmitted after RTO | |
1411 | */ | |
1412 | if (!after(TCP_SKB_CB(skb)->end_seq, | |
1413 | tp->frto_highmark)) { | |
1414 | TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; | |
1415 | tp->lost_out += tcp_skb_pcount(skb); | |
1416 | } | |
1417 | } else { | |
1418 | tp->sacked_out += tcp_skb_pcount(skb); | |
1419 | tp->fackets_out = cnt; | |
1420 | } | |
1421 | } | |
1422 | tcp_sync_left_out(tp); | |
1423 | ||
95c4922b | 1424 | tp->snd_cwnd = tcp_packets_in_flight(tp) + allowed_segments; |
1da177e4 LT |
1425 | tp->snd_cwnd_cnt = 0; |
1426 | tp->snd_cwnd_stamp = tcp_time_stamp; | |
1427 | tp->undo_marker = 0; | |
1428 | tp->frto_counter = 0; | |
1429 | ||
1430 | tp->reordering = min_t(unsigned int, tp->reordering, | |
1431 | sysctl_tcp_reordering); | |
6687e988 | 1432 | tcp_set_ca_state(sk, TCP_CA_Loss); |
1da177e4 LT |
1433 | tp->high_seq = tp->frto_highmark; |
1434 | TCP_ECN_queue_cwr(tp); | |
6a438bbe SH |
1435 | |
1436 | clear_all_retrans_hints(tp); | |
1da177e4 LT |
1437 | } |
1438 | ||
1439 | void tcp_clear_retrans(struct tcp_sock *tp) | |
1440 | { | |
1441 | tp->left_out = 0; | |
1442 | tp->retrans_out = 0; | |
1443 | ||
1444 | tp->fackets_out = 0; | |
1445 | tp->sacked_out = 0; | |
1446 | tp->lost_out = 0; | |
1447 | ||
1448 | tp->undo_marker = 0; | |
1449 | tp->undo_retrans = 0; | |
1450 | } | |
1451 | ||
1452 | /* Enter Loss state. If "how" is not zero, forget all SACK information | |
1453 | * and reset tags completely, otherwise preserve SACKs. If receiver | |
1454 | * dropped its ofo queue, we will know this due to reneging detection. | |
1455 | */ | |
1456 | void tcp_enter_loss(struct sock *sk, int how) | |
1457 | { | |
6687e988 | 1458 | const struct inet_connection_sock *icsk = inet_csk(sk); |
1da177e4 LT |
1459 | struct tcp_sock *tp = tcp_sk(sk); |
1460 | struct sk_buff *skb; | |
1461 | int cnt = 0; | |
1462 | ||
1463 | /* Reduce ssthresh if it has not yet been made inside this window. */ | |
6687e988 ACM |
1464 | if (icsk->icsk_ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq || |
1465 | (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) { | |
1466 | tp->prior_ssthresh = tcp_current_ssthresh(sk); | |
1467 | tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); | |
1468 | tcp_ca_event(sk, CA_EVENT_LOSS); | |
1da177e4 LT |
1469 | } |
1470 | tp->snd_cwnd = 1; | |
1471 | tp->snd_cwnd_cnt = 0; | |
1472 | tp->snd_cwnd_stamp = tcp_time_stamp; | |
1473 | ||
9772efb9 | 1474 | tp->bytes_acked = 0; |
1da177e4 LT |
1475 | tcp_clear_retrans(tp); |
1476 | ||
1477 | /* Push undo marker, if it was plain RTO and nothing | |
1478 | * was retransmitted. */ | |
1479 | if (!how) | |
1480 | tp->undo_marker = tp->snd_una; | |
1481 | ||
fe067e8a DM |
1482 | tcp_for_write_queue(skb, sk) { |
1483 | if (skb == tcp_send_head(sk)) | |
1484 | break; | |
1da177e4 LT |
1485 | cnt += tcp_skb_pcount(skb); |
1486 | if (TCP_SKB_CB(skb)->sacked&TCPCB_RETRANS) | |
1487 | tp->undo_marker = 0; | |
1488 | TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED; | |
1489 | if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) { | |
1490 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED; | |
1491 | TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; | |
1492 | tp->lost_out += tcp_skb_pcount(skb); | |
1493 | } else { | |
1494 | tp->sacked_out += tcp_skb_pcount(skb); | |
1495 | tp->fackets_out = cnt; | |
1496 | } | |
1497 | } | |
1498 | tcp_sync_left_out(tp); | |
1499 | ||
1500 | tp->reordering = min_t(unsigned int, tp->reordering, | |
1501 | sysctl_tcp_reordering); | |
6687e988 | 1502 | tcp_set_ca_state(sk, TCP_CA_Loss); |
1da177e4 LT |
1503 | tp->high_seq = tp->snd_nxt; |
1504 | TCP_ECN_queue_cwr(tp); | |
6a438bbe SH |
1505 | |
1506 | clear_all_retrans_hints(tp); | |
1da177e4 LT |
1507 | } |
1508 | ||
463c84b9 | 1509 | static int tcp_check_sack_reneging(struct sock *sk) |
1da177e4 LT |
1510 | { |
1511 | struct sk_buff *skb; | |
1512 | ||
1513 | /* If ACK arrived pointing to a remembered SACK, | |
1514 | * it means that our remembered SACKs do not reflect | |
1515 | * real state of receiver i.e. | |
1516 | * receiver _host_ is heavily congested (or buggy). | |
1517 | * Do processing similar to RTO timeout. | |
1518 | */ | |
fe067e8a | 1519 | if ((skb = tcp_write_queue_head(sk)) != NULL && |
1da177e4 | 1520 | (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) { |
6687e988 | 1521 | struct inet_connection_sock *icsk = inet_csk(sk); |
1da177e4 LT |
1522 | NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING); |
1523 | ||
1524 | tcp_enter_loss(sk, 1); | |
6687e988 | 1525 | icsk->icsk_retransmits++; |
fe067e8a | 1526 | tcp_retransmit_skb(sk, tcp_write_queue_head(sk)); |
463c84b9 | 1527 | inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, |
6687e988 | 1528 | icsk->icsk_rto, TCP_RTO_MAX); |
1da177e4 LT |
1529 | return 1; |
1530 | } | |
1531 | return 0; | |
1532 | } | |
1533 | ||
1534 | static inline int tcp_fackets_out(struct tcp_sock *tp) | |
1535 | { | |
1536 | return IsReno(tp) ? tp->sacked_out+1 : tp->fackets_out; | |
1537 | } | |
1538 | ||
463c84b9 | 1539 | static inline int tcp_skb_timedout(struct sock *sk, struct sk_buff *skb) |
1da177e4 | 1540 | { |
463c84b9 | 1541 | return (tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto); |
1da177e4 LT |
1542 | } |
1543 | ||
1544 | static inline int tcp_head_timedout(struct sock *sk, struct tcp_sock *tp) | |
1545 | { | |
1546 | return tp->packets_out && | |
fe067e8a | 1547 | tcp_skb_timedout(sk, tcp_write_queue_head(sk)); |
1da177e4 LT |
1548 | } |
1549 | ||
1550 | /* Linux NewReno/SACK/FACK/ECN state machine. | |
1551 | * -------------------------------------- | |
1552 | * | |
1553 | * "Open" Normal state, no dubious events, fast path. | |
1554 | * "Disorder" In all the respects it is "Open", | |
1555 | * but requires a bit more attention. It is entered when | |
1556 | * we see some SACKs or dupacks. It is split of "Open" | |
1557 | * mainly to move some processing from fast path to slow one. | |
1558 | * "CWR" CWND was reduced due to some Congestion Notification event. | |
1559 | * It can be ECN, ICMP source quench, local device congestion. | |
1560 | * "Recovery" CWND was reduced, we are fast-retransmitting. | |
1561 | * "Loss" CWND was reduced due to RTO timeout or SACK reneging. | |
1562 | * | |
1563 | * tcp_fastretrans_alert() is entered: | |
1564 | * - each incoming ACK, if state is not "Open" | |
1565 | * - when arrived ACK is unusual, namely: | |
1566 | * * SACK | |
1567 | * * Duplicate ACK. | |
1568 | * * ECN ECE. | |
1569 | * | |
1570 | * Counting packets in flight is pretty simple. | |
1571 | * | |
1572 | * in_flight = packets_out - left_out + retrans_out | |
1573 | * | |
1574 | * packets_out is SND.NXT-SND.UNA counted in packets. | |
1575 | * | |
1576 | * retrans_out is number of retransmitted segments. | |
1577 | * | |
1578 | * left_out is number of segments left network, but not ACKed yet. | |
1579 | * | |
1580 | * left_out = sacked_out + lost_out | |
1581 | * | |
1582 | * sacked_out: Packets, which arrived to receiver out of order | |
1583 | * and hence not ACKed. With SACKs this number is simply | |
1584 | * amount of SACKed data. Even without SACKs | |
1585 | * it is easy to give pretty reliable estimate of this number, | |
1586 | * counting duplicate ACKs. | |
1587 | * | |
1588 | * lost_out: Packets lost by network. TCP has no explicit | |
1589 | * "loss notification" feedback from network (for now). | |
1590 | * It means that this number can be only _guessed_. | |
1591 | * Actually, it is the heuristics to predict lossage that | |
1592 | * distinguishes different algorithms. | |
1593 | * | |
1594 | * F.e. after RTO, when all the queue is considered as lost, | |
1595 | * lost_out = packets_out and in_flight = retrans_out. | |
1596 | * | |
1597 | * Essentially, we have now two algorithms counting | |
1598 | * lost packets. | |
1599 | * | |
1600 | * FACK: It is the simplest heuristics. As soon as we decided | |
1601 | * that something is lost, we decide that _all_ not SACKed | |
1602 | * packets until the most forward SACK are lost. I.e. | |
1603 | * lost_out = fackets_out - sacked_out and left_out = fackets_out. | |
1604 | * It is absolutely correct estimate, if network does not reorder | |
1605 | * packets. And it loses any connection to reality when reordering | |
1606 | * takes place. We use FACK by default until reordering | |
1607 | * is suspected on the path to this destination. | |
1608 | * | |
1609 | * NewReno: when Recovery is entered, we assume that one segment | |
1610 | * is lost (classic Reno). While we are in Recovery and | |
1611 | * a partial ACK arrives, we assume that one more packet | |
1612 | * is lost (NewReno). This heuristics are the same in NewReno | |
1613 | * and SACK. | |
1614 | * | |
1615 | * Imagine, that's all! Forget about all this shamanism about CWND inflation | |
1616 | * deflation etc. CWND is real congestion window, never inflated, changes | |
1617 | * only according to classic VJ rules. | |
1618 | * | |
1619 | * Really tricky (and requiring careful tuning) part of algorithm | |
1620 | * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue(). | |
1621 | * The first determines the moment _when_ we should reduce CWND and, | |
1622 | * hence, slow down forward transmission. In fact, it determines the moment | |
1623 | * when we decide that hole is caused by loss, rather than by a reorder. | |
1624 | * | |
1625 | * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill | |
1626 | * holes, caused by lost packets. | |
1627 | * | |
1628 | * And the most logically complicated part of algorithm is undo | |
1629 | * heuristics. We detect false retransmits due to both too early | |
1630 | * fast retransmit (reordering) and underestimated RTO, analyzing | |
1631 | * timestamps and D-SACKs. When we detect that some segments were | |
1632 | * retransmitted by mistake and CWND reduction was wrong, we undo | |
1633 | * window reduction and abort recovery phase. This logic is hidden | |
1634 | * inside several functions named tcp_try_undo_<something>. | |
1635 | */ | |
1636 | ||
1637 | /* This function decides, when we should leave Disordered state | |
1638 | * and enter Recovery phase, reducing congestion window. | |
1639 | * | |
1640 | * Main question: may we further continue forward transmission | |
1641 | * with the same cwnd? | |
1642 | */ | |
1643 | static int tcp_time_to_recover(struct sock *sk, struct tcp_sock *tp) | |
1644 | { | |
1645 | __u32 packets_out; | |
1646 | ||
52c63f1e IJ |
1647 | /* Do not perform any recovery during FRTO algorithm */ |
1648 | if (tp->frto_counter) | |
1649 | return 0; | |
1650 | ||
1da177e4 LT |
1651 | /* Trick#1: The loss is proven. */ |
1652 | if (tp->lost_out) | |
1653 | return 1; | |
1654 | ||
1655 | /* Not-A-Trick#2 : Classic rule... */ | |
1656 | if (tcp_fackets_out(tp) > tp->reordering) | |
1657 | return 1; | |
1658 | ||
1659 | /* Trick#3 : when we use RFC2988 timer restart, fast | |
1660 | * retransmit can be triggered by timeout of queue head. | |
1661 | */ | |
1662 | if (tcp_head_timedout(sk, tp)) | |
1663 | return 1; | |
1664 | ||
1665 | /* Trick#4: It is still not OK... But will it be useful to delay | |
1666 | * recovery more? | |
1667 | */ | |
1668 | packets_out = tp->packets_out; | |
1669 | if (packets_out <= tp->reordering && | |
1670 | tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) && | |
1671 | !tcp_may_send_now(sk, tp)) { | |
1672 | /* We have nothing to send. This connection is limited | |
1673 | * either by receiver window or by application. | |
1674 | */ | |
1675 | return 1; | |
1676 | } | |
1677 | ||
1678 | return 0; | |
1679 | } | |
1680 | ||
1681 | /* If we receive more dupacks than we expected counting segments | |
1682 | * in assumption of absent reordering, interpret this as reordering. | |
1683 | * The only another reason could be bug in receiver TCP. | |
1684 | */ | |
6687e988 | 1685 | static void tcp_check_reno_reordering(struct sock *sk, const int addend) |
1da177e4 | 1686 | { |
6687e988 | 1687 | struct tcp_sock *tp = tcp_sk(sk); |
1da177e4 LT |
1688 | u32 holes; |
1689 | ||
1690 | holes = max(tp->lost_out, 1U); | |
1691 | holes = min(holes, tp->packets_out); | |
1692 | ||
1693 | if ((tp->sacked_out + holes) > tp->packets_out) { | |
1694 | tp->sacked_out = tp->packets_out - holes; | |
6687e988 | 1695 | tcp_update_reordering(sk, tp->packets_out + addend, 0); |
1da177e4 LT |
1696 | } |
1697 | } | |
1698 | ||
1699 | /* Emulate SACKs for SACKless connection: account for a new dupack. */ | |
1700 | ||
6687e988 | 1701 | static void tcp_add_reno_sack(struct sock *sk) |
1da177e4 | 1702 | { |
6687e988 | 1703 | struct tcp_sock *tp = tcp_sk(sk); |
1da177e4 | 1704 | tp->sacked_out++; |
6687e988 | 1705 | tcp_check_reno_reordering(sk, 0); |
1da177e4 LT |
1706 | tcp_sync_left_out(tp); |
1707 | } | |
1708 | ||
1709 | /* Account for ACK, ACKing some data in Reno Recovery phase. */ | |
1710 | ||
1711 | static void tcp_remove_reno_sacks(struct sock *sk, struct tcp_sock *tp, int acked) | |
1712 | { | |
1713 | if (acked > 0) { | |
1714 | /* One ACK acked hole. The rest eat duplicate ACKs. */ | |
1715 | if (acked-1 >= tp->sacked_out) | |
1716 | tp->sacked_out = 0; | |
1717 | else | |
1718 | tp->sacked_out -= acked-1; | |
1719 | } | |
6687e988 | 1720 | tcp_check_reno_reordering(sk, acked); |
1da177e4 LT |
1721 | tcp_sync_left_out(tp); |
1722 | } | |
1723 | ||
1724 | static inline void tcp_reset_reno_sack(struct tcp_sock *tp) | |
1725 | { | |
1726 | tp->sacked_out = 0; | |
1727 | tp->left_out = tp->lost_out; | |
1728 | } | |
1729 | ||
1730 | /* Mark head of queue up as lost. */ | |
1731 | static void tcp_mark_head_lost(struct sock *sk, struct tcp_sock *tp, | |
1732 | int packets, u32 high_seq) | |
1733 | { | |
1734 | struct sk_buff *skb; | |
6a438bbe | 1735 | int cnt; |
1da177e4 | 1736 | |
6a438bbe SH |
1737 | BUG_TRAP(packets <= tp->packets_out); |
1738 | if (tp->lost_skb_hint) { | |
1739 | skb = tp->lost_skb_hint; | |
1740 | cnt = tp->lost_cnt_hint; | |
1741 | } else { | |
fe067e8a | 1742 | skb = tcp_write_queue_head(sk); |
6a438bbe SH |
1743 | cnt = 0; |
1744 | } | |
1da177e4 | 1745 | |
fe067e8a DM |
1746 | tcp_for_write_queue_from(skb, sk) { |
1747 | if (skb == tcp_send_head(sk)) | |
1748 | break; | |
6a438bbe SH |
1749 | /* TODO: do this better */ |
1750 | /* this is not the most efficient way to do this... */ | |
1751 | tp->lost_skb_hint = skb; | |
1752 | tp->lost_cnt_hint = cnt; | |
1753 | cnt += tcp_skb_pcount(skb); | |
1754 | if (cnt > packets || after(TCP_SKB_CB(skb)->end_seq, high_seq)) | |
1da177e4 LT |
1755 | break; |
1756 | if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) { | |
1757 | TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; | |
1758 | tp->lost_out += tcp_skb_pcount(skb); | |
6a438bbe SH |
1759 | |
1760 | /* clear xmit_retransmit_queue hints | |
1761 | * if this is beyond hint */ | |
2de979bd SH |
1762 | if (tp->retransmit_skb_hint != NULL && |
1763 | before(TCP_SKB_CB(skb)->seq, | |
1764 | TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) | |
6a438bbe | 1765 | tp->retransmit_skb_hint = NULL; |
2de979bd | 1766 | |
1da177e4 LT |
1767 | } |
1768 | } | |
1769 | tcp_sync_left_out(tp); | |
1770 | } | |
1771 | ||
1772 | /* Account newly detected lost packet(s) */ | |
1773 | ||
1774 | static void tcp_update_scoreboard(struct sock *sk, struct tcp_sock *tp) | |
1775 | { | |
1776 | if (IsFack(tp)) { | |
1777 | int lost = tp->fackets_out - tp->reordering; | |
1778 | if (lost <= 0) | |
1779 | lost = 1; | |
1780 | tcp_mark_head_lost(sk, tp, lost, tp->high_seq); | |
1781 | } else { | |
1782 | tcp_mark_head_lost(sk, tp, 1, tp->high_seq); | |
1783 | } | |
1784 | ||
1785 | /* New heuristics: it is possible only after we switched | |
1786 | * to restart timer each time when something is ACKed. | |
1787 | * Hence, we can detect timed out packets during fast | |
1788 | * retransmit without falling to slow start. | |
1789 | */ | |
79320d7e | 1790 | if (!IsReno(tp) && tcp_head_timedout(sk, tp)) { |
1da177e4 LT |
1791 | struct sk_buff *skb; |
1792 | ||
6a438bbe | 1793 | skb = tp->scoreboard_skb_hint ? tp->scoreboard_skb_hint |
fe067e8a | 1794 | : tcp_write_queue_head(sk); |
6a438bbe | 1795 | |
fe067e8a DM |
1796 | tcp_for_write_queue_from(skb, sk) { |
1797 | if (skb == tcp_send_head(sk)) | |
1798 | break; | |
6a438bbe SH |
1799 | if (!tcp_skb_timedout(sk, skb)) |
1800 | break; | |
1801 | ||
1802 | if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) { | |
1da177e4 LT |
1803 | TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; |
1804 | tp->lost_out += tcp_skb_pcount(skb); | |
6a438bbe SH |
1805 | |
1806 | /* clear xmit_retrans hint */ | |
1807 | if (tp->retransmit_skb_hint && | |
1808 | before(TCP_SKB_CB(skb)->seq, | |
1809 | TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) | |
1810 | ||
1811 | tp->retransmit_skb_hint = NULL; | |
1da177e4 LT |
1812 | } |
1813 | } | |
6a438bbe SH |
1814 | |
1815 | tp->scoreboard_skb_hint = skb; | |
1816 | ||
1da177e4 LT |
1817 | tcp_sync_left_out(tp); |
1818 | } | |
1819 | } | |
1820 | ||
1821 | /* CWND moderation, preventing bursts due to too big ACKs | |
1822 | * in dubious situations. | |
1823 | */ | |
1824 | static inline void tcp_moderate_cwnd(struct tcp_sock *tp) | |
1825 | { | |
1826 | tp->snd_cwnd = min(tp->snd_cwnd, | |
1827 | tcp_packets_in_flight(tp)+tcp_max_burst(tp)); | |
1828 | tp->snd_cwnd_stamp = tcp_time_stamp; | |
1829 | } | |
1830 | ||
72dc5b92 SH |
1831 | /* Lower bound on congestion window is slow start threshold |
1832 | * unless congestion avoidance choice decides to overide it. | |
1833 | */ | |
1834 | static inline u32 tcp_cwnd_min(const struct sock *sk) | |
1835 | { | |
1836 | const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; | |
1837 | ||
1838 | return ca_ops->min_cwnd ? ca_ops->min_cwnd(sk) : tcp_sk(sk)->snd_ssthresh; | |
1839 | } | |
1840 | ||
1da177e4 | 1841 | /* Decrease cwnd each second ack. */ |
6687e988 | 1842 | static void tcp_cwnd_down(struct sock *sk) |
1da177e4 | 1843 | { |
6687e988 | 1844 | struct tcp_sock *tp = tcp_sk(sk); |
1da177e4 | 1845 | int decr = tp->snd_cwnd_cnt + 1; |
1da177e4 LT |
1846 | |
1847 | tp->snd_cwnd_cnt = decr&1; | |
1848 | decr >>= 1; | |
1849 | ||
72dc5b92 | 1850 | if (decr && tp->snd_cwnd > tcp_cwnd_min(sk)) |
1da177e4 LT |
1851 | tp->snd_cwnd -= decr; |
1852 | ||
1853 | tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp)+1); | |
1854 | tp->snd_cwnd_stamp = tcp_time_stamp; | |
1855 | } | |
1856 | ||
1857 | /* Nothing was retransmitted or returned timestamp is less | |
1858 | * than timestamp of the first retransmission. | |
1859 | */ | |
1860 | static inline int tcp_packet_delayed(struct tcp_sock *tp) | |
1861 | { | |
1862 | return !tp->retrans_stamp || | |
1863 | (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && | |
1864 | (__s32)(tp->rx_opt.rcv_tsecr - tp->retrans_stamp) < 0); | |
1865 | } | |
1866 | ||
1867 | /* Undo procedures. */ | |
1868 | ||
1869 | #if FASTRETRANS_DEBUG > 1 | |
1870 | static void DBGUNDO(struct sock *sk, struct tcp_sock *tp, const char *msg) | |
1871 | { | |
1872 | struct inet_sock *inet = inet_sk(sk); | |
1873 | printk(KERN_DEBUG "Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n", | |
1874 | msg, | |
1875 | NIPQUAD(inet->daddr), ntohs(inet->dport), | |
1876 | tp->snd_cwnd, tp->left_out, | |
1877 | tp->snd_ssthresh, tp->prior_ssthresh, | |
1878 | tp->packets_out); | |
1879 | } | |
1880 | #else | |
1881 | #define DBGUNDO(x...) do { } while (0) | |
1882 | #endif | |
1883 | ||
6687e988 | 1884 | static void tcp_undo_cwr(struct sock *sk, const int undo) |
1da177e4 | 1885 | { |
6687e988 ACM |
1886 | struct tcp_sock *tp = tcp_sk(sk); |
1887 | ||
1da177e4 | 1888 | if (tp->prior_ssthresh) { |
6687e988 ACM |
1889 | const struct inet_connection_sock *icsk = inet_csk(sk); |
1890 | ||
1891 | if (icsk->icsk_ca_ops->undo_cwnd) | |
1892 | tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk); | |
1da177e4 LT |
1893 | else |
1894 | tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh<<1); | |
1895 | ||
1896 | if (undo && tp->prior_ssthresh > tp->snd_ssthresh) { | |
1897 | tp->snd_ssthresh = tp->prior_ssthresh; | |
1898 | TCP_ECN_withdraw_cwr(tp); | |
1899 | } | |
1900 | } else { | |
1901 | tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh); | |
1902 | } | |
1903 | tcp_moderate_cwnd(tp); | |
1904 | tp->snd_cwnd_stamp = tcp_time_stamp; | |
6a438bbe SH |
1905 | |
1906 | /* There is something screwy going on with the retrans hints after | |
1907 | an undo */ | |
1908 | clear_all_retrans_hints(tp); | |
1da177e4 LT |
1909 | } |
1910 | ||
1911 | static inline int tcp_may_undo(struct tcp_sock *tp) | |
1912 | { | |
1913 | return tp->undo_marker && | |
1914 | (!tp->undo_retrans || tcp_packet_delayed(tp)); | |
1915 | } | |
1916 | ||
1917 | /* People celebrate: "We love our President!" */ | |
1918 | static int tcp_try_undo_recovery(struct sock *sk, struct tcp_sock *tp) | |
1919 | { | |
1920 | if (tcp_may_undo(tp)) { | |
1921 | /* Happy end! We did not retransmit anything | |
1922 | * or our original transmission succeeded. | |
1923 | */ | |
6687e988 ACM |
1924 | DBGUNDO(sk, tp, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans"); |
1925 | tcp_undo_cwr(sk, 1); | |
1926 | if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss) | |
1da177e4 LT |
1927 | NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO); |
1928 | else | |
1929 | NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO); | |
1930 | tp->undo_marker = 0; | |
1931 | } | |
1932 | if (tp->snd_una == tp->high_seq && IsReno(tp)) { | |
1933 | /* Hold old state until something *above* high_seq | |
1934 | * is ACKed. For Reno it is MUST to prevent false | |
1935 | * fast retransmits (RFC2582). SACK TCP is safe. */ | |
1936 | tcp_moderate_cwnd(tp); | |
1937 | return 1; | |
1938 | } | |
6687e988 | 1939 | tcp_set_ca_state(sk, TCP_CA_Open); |
1da177e4 LT |
1940 | return 0; |
1941 | } | |
1942 | ||
1943 | /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */ | |
1944 | static void tcp_try_undo_dsack(struct sock *sk, struct tcp_sock *tp) | |
1945 | { | |
1946 | if (tp->undo_marker && !tp->undo_retrans) { | |
1947 | DBGUNDO(sk, tp, "D-SACK"); | |
6687e988 | 1948 | tcp_undo_cwr(sk, 1); |
1da177e4 LT |
1949 | tp->undo_marker = 0; |
1950 | NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO); | |
1951 | } | |
1952 | } | |
1953 | ||
1954 | /* Undo during fast recovery after partial ACK. */ | |
1955 | ||
1956 | static int tcp_try_undo_partial(struct sock *sk, struct tcp_sock *tp, | |
1957 | int acked) | |
1958 | { | |
1959 | /* Partial ACK arrived. Force Hoe's retransmit. */ | |
1960 | int failed = IsReno(tp) || tp->fackets_out>tp->reordering; | |
1961 | ||
1962 | if (tcp_may_undo(tp)) { | |
1963 | /* Plain luck! Hole if filled with delayed | |
1964 | * packet, rather than with a retransmit. | |
1965 | */ | |
1966 | if (tp->retrans_out == 0) | |
1967 | tp->retrans_stamp = 0; | |
1968 | ||
6687e988 | 1969 | tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1); |
1da177e4 LT |
1970 | |
1971 | DBGUNDO(sk, tp, "Hoe"); | |
6687e988 | 1972 | tcp_undo_cwr(sk, 0); |
1da177e4 LT |
1973 | NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO); |
1974 | ||
1975 | /* So... Do not make Hoe's retransmit yet. | |
1976 | * If the first packet was delayed, the rest | |
1977 | * ones are most probably delayed as well. | |
1978 | */ | |
1979 | failed = 0; | |
1980 | } | |
1981 | return failed; | |
1982 | } | |
1983 | ||
1984 | /* Undo during loss recovery after partial ACK. */ | |
1985 | static int tcp_try_undo_loss(struct sock *sk, struct tcp_sock *tp) | |
1986 | { | |
1987 | if (tcp_may_undo(tp)) { | |
1988 | struct sk_buff *skb; | |
fe067e8a DM |
1989 | tcp_for_write_queue(skb, sk) { |
1990 | if (skb == tcp_send_head(sk)) | |
1991 | break; | |
1da177e4 LT |
1992 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; |
1993 | } | |
6a438bbe SH |
1994 | |
1995 | clear_all_retrans_hints(tp); | |
1996 | ||
1da177e4 LT |
1997 | DBGUNDO(sk, tp, "partial loss"); |
1998 | tp->lost_out = 0; | |
1999 | tp->left_out = tp->sacked_out; | |
6687e988 | 2000 | tcp_undo_cwr(sk, 1); |
1da177e4 | 2001 | NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO); |
463c84b9 | 2002 | inet_csk(sk)->icsk_retransmits = 0; |
1da177e4 LT |
2003 | tp->undo_marker = 0; |
2004 | if (!IsReno(tp)) | |
6687e988 | 2005 | tcp_set_ca_state(sk, TCP_CA_Open); |
1da177e4 LT |
2006 | return 1; |
2007 | } | |
2008 | return 0; | |
2009 | } | |
2010 | ||
6687e988 | 2011 | static inline void tcp_complete_cwr(struct sock *sk) |
1da177e4 | 2012 | { |
6687e988 | 2013 | struct tcp_sock *tp = tcp_sk(sk); |
317a76f9 | 2014 | tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); |
1da177e4 | 2015 | tp->snd_cwnd_stamp = tcp_time_stamp; |
6687e988 | 2016 | tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR); |
1da177e4 LT |
2017 | } |
2018 | ||
2019 | static void tcp_try_to_open(struct sock *sk, struct tcp_sock *tp, int flag) | |
2020 | { | |
2021 | tp->left_out = tp->sacked_out; | |
2022 | ||
2023 | if (tp->retrans_out == 0) | |
2024 | tp->retrans_stamp = 0; | |
2025 | ||
2026 | if (flag&FLAG_ECE) | |
3cfe3baa | 2027 | tcp_enter_cwr(sk, 1); |
1da177e4 | 2028 | |
6687e988 | 2029 | if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) { |
1da177e4 LT |
2030 | int state = TCP_CA_Open; |
2031 | ||
2032 | if (tp->left_out || tp->retrans_out || tp->undo_marker) | |
2033 | state = TCP_CA_Disorder; | |
2034 | ||
6687e988 ACM |
2035 | if (inet_csk(sk)->icsk_ca_state != state) { |
2036 | tcp_set_ca_state(sk, state); | |
1da177e4 LT |
2037 | tp->high_seq = tp->snd_nxt; |
2038 | } | |
2039 | tcp_moderate_cwnd(tp); | |
2040 | } else { | |
6687e988 | 2041 | tcp_cwnd_down(sk); |
1da177e4 LT |
2042 | } |
2043 | } | |
2044 | ||
5d424d5a JH |
2045 | static void tcp_mtup_probe_failed(struct sock *sk) |
2046 | { | |
2047 | struct inet_connection_sock *icsk = inet_csk(sk); | |
2048 | ||
2049 | icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1; | |
2050 | icsk->icsk_mtup.probe_size = 0; | |
2051 | } | |
2052 | ||
2053 | static void tcp_mtup_probe_success(struct sock *sk, struct sk_buff *skb) | |
2054 | { | |
2055 | struct tcp_sock *tp = tcp_sk(sk); | |
2056 | struct inet_connection_sock *icsk = inet_csk(sk); | |
2057 | ||
2058 | /* FIXME: breaks with very large cwnd */ | |
2059 | tp->prior_ssthresh = tcp_current_ssthresh(sk); | |
2060 | tp->snd_cwnd = tp->snd_cwnd * | |
2061 | tcp_mss_to_mtu(sk, tp->mss_cache) / | |
2062 | icsk->icsk_mtup.probe_size; | |
2063 | tp->snd_cwnd_cnt = 0; | |
2064 | tp->snd_cwnd_stamp = tcp_time_stamp; | |
2065 | tp->rcv_ssthresh = tcp_current_ssthresh(sk); | |
2066 | ||
2067 | icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size; | |
2068 | icsk->icsk_mtup.probe_size = 0; | |
2069 | tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); | |
2070 | } | |
2071 | ||
2072 | ||
1da177e4 LT |
2073 | /* Process an event, which can update packets-in-flight not trivially. |
2074 | * Main goal of this function is to calculate new estimate for left_out, | |
2075 | * taking into account both packets sitting in receiver's buffer and | |
2076 | * packets lost by network. | |
2077 | * | |
2078 | * Besides that it does CWND reduction, when packet loss is detected | |
2079 | * and changes state of machine. | |
2080 | * | |
2081 | * It does _not_ decide what to send, it is made in function | |
2082 | * tcp_xmit_retransmit_queue(). | |
2083 | */ | |
2084 | static void | |
2085 | tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una, | |
2086 | int prior_packets, int flag) | |
2087 | { | |
6687e988 | 2088 | struct inet_connection_sock *icsk = inet_csk(sk); |
1da177e4 LT |
2089 | struct tcp_sock *tp = tcp_sk(sk); |
2090 | int is_dupack = (tp->snd_una == prior_snd_una && !(flag&FLAG_NOT_DUP)); | |
2091 | ||
2092 | /* Some technical things: | |
2093 | * 1. Reno does not count dupacks (sacked_out) automatically. */ | |
2094 | if (!tp->packets_out) | |
2095 | tp->sacked_out = 0; | |
e905a9ed | 2096 | /* 2. SACK counts snd_fack in packets inaccurately. */ |
1da177e4 LT |
2097 | if (tp->sacked_out == 0) |
2098 | tp->fackets_out = 0; | |
2099 | ||
e905a9ed | 2100 | /* Now state machine starts. |
1da177e4 LT |
2101 | * A. ECE, hence prohibit cwnd undoing, the reduction is required. */ |
2102 | if (flag&FLAG_ECE) | |
2103 | tp->prior_ssthresh = 0; | |
2104 | ||
2105 | /* B. In all the states check for reneging SACKs. */ | |
463c84b9 | 2106 | if (tp->sacked_out && tcp_check_sack_reneging(sk)) |
1da177e4 LT |
2107 | return; |
2108 | ||
2109 | /* C. Process data loss notification, provided it is valid. */ | |
2110 | if ((flag&FLAG_DATA_LOST) && | |
2111 | before(tp->snd_una, tp->high_seq) && | |
6687e988 | 2112 | icsk->icsk_ca_state != TCP_CA_Open && |
1da177e4 LT |
2113 | tp->fackets_out > tp->reordering) { |
2114 | tcp_mark_head_lost(sk, tp, tp->fackets_out-tp->reordering, tp->high_seq); | |
2115 | NET_INC_STATS_BH(LINUX_MIB_TCPLOSS); | |
2116 | } | |
2117 | ||
2118 | /* D. Synchronize left_out to current state. */ | |
2119 | tcp_sync_left_out(tp); | |
2120 | ||
2121 | /* E. Check state exit conditions. State can be terminated | |
2122 | * when high_seq is ACKed. */ | |
6687e988 | 2123 | if (icsk->icsk_ca_state == TCP_CA_Open) { |
7b0eb22b | 2124 | BUG_TRAP(tp->retrans_out == 0); |
1da177e4 LT |
2125 | tp->retrans_stamp = 0; |
2126 | } else if (!before(tp->snd_una, tp->high_seq)) { | |
6687e988 | 2127 | switch (icsk->icsk_ca_state) { |
1da177e4 | 2128 | case TCP_CA_Loss: |
6687e988 | 2129 | icsk->icsk_retransmits = 0; |
1da177e4 LT |
2130 | if (tcp_try_undo_recovery(sk, tp)) |
2131 | return; | |
2132 | break; | |
2133 | ||
2134 | case TCP_CA_CWR: | |
2135 | /* CWR is to be held something *above* high_seq | |
2136 | * is ACKed for CWR bit to reach receiver. */ | |
2137 | if (tp->snd_una != tp->high_seq) { | |
6687e988 ACM |
2138 | tcp_complete_cwr(sk); |
2139 | tcp_set_ca_state(sk, TCP_CA_Open); | |
1da177e4 LT |
2140 | } |
2141 | break; | |
2142 | ||
2143 | case TCP_CA_Disorder: | |
2144 | tcp_try_undo_dsack(sk, tp); | |
2145 | if (!tp->undo_marker || | |
2146 | /* For SACK case do not Open to allow to undo | |
2147 | * catching for all duplicate ACKs. */ | |
2148 | IsReno(tp) || tp->snd_una != tp->high_seq) { | |
2149 | tp->undo_marker = 0; | |
6687e988 | 2150 | tcp_set_ca_state(sk, TCP_CA_Open); |
1da177e4 LT |
2151 | } |
2152 | break; | |
2153 | ||
2154 | case TCP_CA_Recovery: | |
2155 | if (IsReno(tp)) | |
2156 | tcp_reset_reno_sack(tp); | |
2157 | if (tcp_try_undo_recovery(sk, tp)) | |
2158 | return; | |
6687e988 | 2159 | tcp_complete_cwr(sk); |
1da177e4 LT |
2160 | break; |
2161 | } | |
2162 | } | |
2163 | ||
2164 | /* F. Process state. */ | |
6687e988 | 2165 | switch (icsk->icsk_ca_state) { |
1da177e4 LT |
2166 | case TCP_CA_Recovery: |
2167 | if (prior_snd_una == tp->snd_una) { | |
2168 | if (IsReno(tp) && is_dupack) | |
6687e988 | 2169 | tcp_add_reno_sack(sk); |
1da177e4 LT |
2170 | } else { |
2171 | int acked = prior_packets - tp->packets_out; | |
2172 | if (IsReno(tp)) | |
2173 | tcp_remove_reno_sacks(sk, tp, acked); | |
2174 | is_dupack = tcp_try_undo_partial(sk, tp, acked); | |
2175 | } | |
2176 | break; | |
2177 | case TCP_CA_Loss: | |
2178 | if (flag&FLAG_DATA_ACKED) | |
6687e988 | 2179 | icsk->icsk_retransmits = 0; |
1da177e4 LT |
2180 | if (!tcp_try_undo_loss(sk, tp)) { |
2181 | tcp_moderate_cwnd(tp); | |
2182 | tcp_xmit_retransmit_queue(sk); | |
2183 | return; | |
2184 | } | |
6687e988 | 2185 | if (icsk->icsk_ca_state != TCP_CA_Open) |
1da177e4 LT |
2186 | return; |
2187 | /* Loss is undone; fall through to processing in Open state. */ | |
2188 | default: | |
2189 | if (IsReno(tp)) { | |
2190 | if (tp->snd_una != prior_snd_una) | |
2191 | tcp_reset_reno_sack(tp); | |
2192 | if (is_dupack) | |
6687e988 | 2193 | tcp_add_reno_sack(sk); |
1da177e4 LT |
2194 | } |
2195 | ||
6687e988 | 2196 | if (icsk->icsk_ca_state == TCP_CA_Disorder) |
1da177e4 LT |
2197 | tcp_try_undo_dsack(sk, tp); |
2198 | ||
2199 | if (!tcp_time_to_recover(sk, tp)) { | |
2200 | tcp_try_to_open(sk, tp, flag); | |
2201 | return; | |
2202 | } | |
2203 | ||
5d424d5a JH |
2204 | /* MTU probe failure: don't reduce cwnd */ |
2205 | if (icsk->icsk_ca_state < TCP_CA_CWR && | |
2206 | icsk->icsk_mtup.probe_size && | |
0e7b1368 | 2207 | tp->snd_una == tp->mtu_probe.probe_seq_start) { |
5d424d5a JH |
2208 | tcp_mtup_probe_failed(sk); |
2209 | /* Restores the reduction we did in tcp_mtup_probe() */ | |
2210 | tp->snd_cwnd++; | |
2211 | tcp_simple_retransmit(sk); | |
2212 | return; | |
2213 | } | |
2214 | ||
1da177e4 LT |
2215 | /* Otherwise enter Recovery state */ |
2216 | ||
2217 | if (IsReno(tp)) | |
2218 | NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY); | |
2219 | else | |
2220 | NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY); | |
2221 | ||
2222 | tp->high_seq = tp->snd_nxt; | |
2223 | tp->prior_ssthresh = 0; | |
2224 | tp->undo_marker = tp->snd_una; | |
2225 | tp->undo_retrans = tp->retrans_out; | |
2226 | ||
6687e988 | 2227 | if (icsk->icsk_ca_state < TCP_CA_CWR) { |
1da177e4 | 2228 | if (!(flag&FLAG_ECE)) |
6687e988 ACM |
2229 | tp->prior_ssthresh = tcp_current_ssthresh(sk); |
2230 | tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); | |
1da177e4 LT |
2231 | TCP_ECN_queue_cwr(tp); |
2232 | } | |
2233 | ||
9772efb9 | 2234 | tp->bytes_acked = 0; |
1da177e4 | 2235 | tp->snd_cwnd_cnt = 0; |
6687e988 | 2236 | tcp_set_ca_state(sk, TCP_CA_Recovery); |
1da177e4 LT |
2237 | } |
2238 | ||
2239 | if (is_dupack || tcp_head_timedout(sk, tp)) | |
2240 | tcp_update_scoreboard(sk, tp); | |
6687e988 | 2241 | tcp_cwnd_down(sk); |
1da177e4 LT |
2242 | tcp_xmit_retransmit_queue(sk); |
2243 | } | |
2244 | ||
2245 | /* Read draft-ietf-tcplw-high-performance before mucking | |
caa20d9a | 2246 | * with this code. (Supersedes RFC1323) |
1da177e4 | 2247 | */ |
2d2abbab | 2248 | static void tcp_ack_saw_tstamp(struct sock *sk, int flag) |
1da177e4 | 2249 | { |
1da177e4 LT |
2250 | /* RTTM Rule: A TSecr value received in a segment is used to |
2251 | * update the averaged RTT measurement only if the segment | |
2252 | * acknowledges some new data, i.e., only if it advances the | |
2253 | * left edge of the send window. | |
2254 | * | |
2255 | * See draft-ietf-tcplw-high-performance-00, section 3.3. | |
2256 | * 1998/04/10 Andrey V. Savochkin <saw@msu.ru> | |
2257 | * | |
2258 | * Changed: reset backoff as soon as we see the first valid sample. | |
caa20d9a | 2259 | * If we do not, we get strongly overestimated rto. With timestamps |
1da177e4 LT |
2260 | * samples are accepted even from very old segments: f.e., when rtt=1 |
2261 | * increases to 8, we retransmit 5 times and after 8 seconds delayed | |
2262 | * answer arrives rto becomes 120 seconds! If at least one of segments | |
2263 | * in window is lost... Voila. --ANK (010210) | |
2264 | */ | |
463c84b9 ACM |
2265 | struct tcp_sock *tp = tcp_sk(sk); |
2266 | const __u32 seq_rtt = tcp_time_stamp - tp->rx_opt.rcv_tsecr; | |
2d2abbab | 2267 | tcp_rtt_estimator(sk, seq_rtt); |
463c84b9 ACM |
2268 | tcp_set_rto(sk); |
2269 | inet_csk(sk)->icsk_backoff = 0; | |
2270 | tcp_bound_rto(sk); | |
1da177e4 LT |
2271 | } |
2272 | ||
2d2abbab | 2273 | static void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag) |
1da177e4 LT |
2274 | { |
2275 | /* We don't have a timestamp. Can only use | |
2276 | * packets that are not retransmitted to determine | |
2277 | * rtt estimates. Also, we must not reset the | |
2278 | * backoff for rto until we get a non-retransmitted | |
2279 | * packet. This allows us to deal with a situation | |
2280 | * where the network delay has increased suddenly. | |
2281 | * I.e. Karn's algorithm. (SIGCOMM '87, p5.) | |
2282 | */ | |
2283 | ||
2284 | if (flag & FLAG_RETRANS_DATA_ACKED) | |
2285 | return; | |
2286 | ||
2d2abbab | 2287 | tcp_rtt_estimator(sk, seq_rtt); |
463c84b9 ACM |
2288 | tcp_set_rto(sk); |
2289 | inet_csk(sk)->icsk_backoff = 0; | |
2290 | tcp_bound_rto(sk); | |
1da177e4 LT |
2291 | } |
2292 | ||
463c84b9 | 2293 | static inline void tcp_ack_update_rtt(struct sock *sk, const int flag, |
2d2abbab | 2294 | const s32 seq_rtt) |
1da177e4 | 2295 | { |
463c84b9 | 2296 | const struct tcp_sock *tp = tcp_sk(sk); |
1da177e4 LT |
2297 | /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */ |
2298 | if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr) | |
2d2abbab | 2299 | tcp_ack_saw_tstamp(sk, flag); |
1da177e4 | 2300 | else if (seq_rtt >= 0) |
2d2abbab | 2301 | tcp_ack_no_tstamp(sk, seq_rtt, flag); |
1da177e4 LT |
2302 | } |
2303 | ||
40efc6fa SH |
2304 | static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 rtt, |
2305 | u32 in_flight, int good) | |
1da177e4 | 2306 | { |
6687e988 ACM |
2307 | const struct inet_connection_sock *icsk = inet_csk(sk); |
2308 | icsk->icsk_ca_ops->cong_avoid(sk, ack, rtt, in_flight, good); | |
2309 | tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp; | |
1da177e4 LT |
2310 | } |
2311 | ||
1da177e4 LT |
2312 | /* Restart timer after forward progress on connection. |
2313 | * RFC2988 recommends to restart timer to now+rto. | |
2314 | */ | |
2315 | ||
40efc6fa | 2316 | static void tcp_ack_packets_out(struct sock *sk, struct tcp_sock *tp) |
1da177e4 LT |
2317 | { |
2318 | if (!tp->packets_out) { | |
463c84b9 | 2319 | inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS); |
1da177e4 | 2320 | } else { |
3f421baa | 2321 | inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, inet_csk(sk)->icsk_rto, TCP_RTO_MAX); |
1da177e4 LT |
2322 | } |
2323 | } | |
2324 | ||
1da177e4 LT |
2325 | static int tcp_tso_acked(struct sock *sk, struct sk_buff *skb, |
2326 | __u32 now, __s32 *seq_rtt) | |
2327 | { | |
2328 | struct tcp_sock *tp = tcp_sk(sk); | |
e905a9ed | 2329 | struct tcp_skb_cb *scb = TCP_SKB_CB(skb); |
1da177e4 LT |
2330 | __u32 seq = tp->snd_una; |
2331 | __u32 packets_acked; | |
2332 | int acked = 0; | |
2333 | ||
2334 | /* If we get here, the whole TSO packet has not been | |
2335 | * acked. | |
2336 | */ | |
2337 | BUG_ON(!after(scb->end_seq, seq)); | |
2338 | ||
2339 | packets_acked = tcp_skb_pcount(skb); | |
2340 | if (tcp_trim_head(sk, skb, seq - scb->seq)) | |
2341 | return 0; | |
2342 | packets_acked -= tcp_skb_pcount(skb); | |
2343 | ||
2344 | if (packets_acked) { | |
2345 | __u8 sacked = scb->sacked; | |
2346 | ||
2347 | acked |= FLAG_DATA_ACKED; | |
2348 | if (sacked) { | |
2349 | if (sacked & TCPCB_RETRANS) { | |
2350 | if (sacked & TCPCB_SACKED_RETRANS) | |
2351 | tp->retrans_out -= packets_acked; | |
2352 | acked |= FLAG_RETRANS_DATA_ACKED; | |
2353 | *seq_rtt = -1; | |
2354 | } else if (*seq_rtt < 0) | |
2355 | *seq_rtt = now - scb->when; | |
2356 | if (sacked & TCPCB_SACKED_ACKED) | |
2357 | tp->sacked_out -= packets_acked; | |
2358 | if (sacked & TCPCB_LOST) | |
2359 | tp->lost_out -= packets_acked; | |
2360 | if (sacked & TCPCB_URG) { | |
2361 | if (tp->urg_mode && | |
2362 | !before(seq, tp->snd_up)) | |
2363 | tp->urg_mode = 0; | |
2364 | } | |
2365 | } else if (*seq_rtt < 0) | |
2366 | *seq_rtt = now - scb->when; | |
2367 | ||
2368 | if (tp->fackets_out) { | |
2369 | __u32 dval = min(tp->fackets_out, packets_acked); | |
2370 | tp->fackets_out -= dval; | |
2371 | } | |
2372 | tp->packets_out -= packets_acked; | |
2373 | ||
2374 | BUG_ON(tcp_skb_pcount(skb) == 0); | |
2375 | BUG_ON(!before(scb->seq, scb->end_seq)); | |
2376 | } | |
2377 | ||
2378 | return acked; | |
2379 | } | |
2380 | ||
8ea333eb | 2381 | static u32 tcp_usrtt(struct timeval *tv) |
2d2abbab | 2382 | { |
8ea333eb | 2383 | struct timeval now; |
2d2abbab SH |
2384 | |
2385 | do_gettimeofday(&now); | |
8ea333eb | 2386 | return (now.tv_sec - tv->tv_sec) * 1000000 + (now.tv_usec - tv->tv_usec); |
2d2abbab | 2387 | } |
1da177e4 LT |
2388 | |
2389 | /* Remove acknowledged frames from the retransmission queue. */ | |
2d2abbab | 2390 | static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p) |
1da177e4 LT |
2391 | { |
2392 | struct tcp_sock *tp = tcp_sk(sk); | |
2d2abbab | 2393 | const struct inet_connection_sock *icsk = inet_csk(sk); |
1da177e4 LT |
2394 | struct sk_buff *skb; |
2395 | __u32 now = tcp_time_stamp; | |
2396 | int acked = 0; | |
2397 | __s32 seq_rtt = -1; | |
317a76f9 | 2398 | u32 pkts_acked = 0; |
2d2abbab SH |
2399 | void (*rtt_sample)(struct sock *sk, u32 usrtt) |
2400 | = icsk->icsk_ca_ops->rtt_sample; | |
80246ab3 | 2401 | struct timeval tv = { .tv_sec = 0, .tv_usec = 0 }; |
1da177e4 | 2402 | |
fe067e8a DM |
2403 | while ((skb = tcp_write_queue_head(sk)) && |
2404 | skb != tcp_send_head(sk)) { | |
e905a9ed | 2405 | struct tcp_skb_cb *scb = TCP_SKB_CB(skb); |
1da177e4 LT |
2406 | __u8 sacked = scb->sacked; |
2407 | ||
2408 | /* If our packet is before the ack sequence we can | |
2409 | * discard it as it's confirmed to have arrived at | |
2410 | * the other end. | |
2411 | */ | |
2412 | if (after(scb->end_seq, tp->snd_una)) { | |
cb83199a DM |
2413 | if (tcp_skb_pcount(skb) > 1 && |
2414 | after(tp->snd_una, scb->seq)) | |
1da177e4 LT |
2415 | acked |= tcp_tso_acked(sk, skb, |
2416 | now, &seq_rtt); | |
2417 | break; | |
2418 | } | |
2419 | ||
2420 | /* Initial outgoing SYN's get put onto the write_queue | |
2421 | * just like anything else we transmit. It is not | |
2422 | * true data, and if we misinform our callers that | |
2423 | * this ACK acks real data, we will erroneously exit | |
2424 | * connection startup slow start one packet too | |
2425 | * quickly. This is severely frowned upon behavior. | |
2426 | */ | |
2427 | if (!(scb->flags & TCPCB_FLAG_SYN)) { | |
2428 | acked |= FLAG_DATA_ACKED; | |
317a76f9 | 2429 | ++pkts_acked; |
1da177e4 LT |
2430 | } else { |
2431 | acked |= FLAG_SYN_ACKED; | |
2432 | tp->retrans_stamp = 0; | |
2433 | } | |
2434 | ||
5d424d5a JH |
2435 | /* MTU probing checks */ |
2436 | if (icsk->icsk_mtup.probe_size) { | |
0e7b1368 | 2437 | if (!after(tp->mtu_probe.probe_seq_end, TCP_SKB_CB(skb)->end_seq)) { |
5d424d5a JH |
2438 | tcp_mtup_probe_success(sk, skb); |
2439 | } | |
2440 | } | |
2441 | ||
1da177e4 LT |
2442 | if (sacked) { |
2443 | if (sacked & TCPCB_RETRANS) { | |
2de979bd | 2444 | if (sacked & TCPCB_SACKED_RETRANS) |
1da177e4 LT |
2445 | tp->retrans_out -= tcp_skb_pcount(skb); |
2446 | acked |= FLAG_RETRANS_DATA_ACKED; | |
2447 | seq_rtt = -1; | |
2d2abbab | 2448 | } else if (seq_rtt < 0) { |
1da177e4 | 2449 | seq_rtt = now - scb->when; |
8ea333eb | 2450 | skb_get_timestamp(skb, &tv); |
a61bbcf2 | 2451 | } |
1da177e4 LT |
2452 | if (sacked & TCPCB_SACKED_ACKED) |
2453 | tp->sacked_out -= tcp_skb_pcount(skb); | |
2454 | if (sacked & TCPCB_LOST) | |
2455 | tp->lost_out -= tcp_skb_pcount(skb); | |
2456 | if (sacked & TCPCB_URG) { | |
2457 | if (tp->urg_mode && | |
2458 | !before(scb->end_seq, tp->snd_up)) | |
2459 | tp->urg_mode = 0; | |
2460 | } | |
2d2abbab | 2461 | } else if (seq_rtt < 0) { |
1da177e4 | 2462 | seq_rtt = now - scb->when; |
8ea333eb | 2463 | skb_get_timestamp(skb, &tv); |
2d2abbab | 2464 | } |
1da177e4 LT |
2465 | tcp_dec_pcount_approx(&tp->fackets_out, skb); |
2466 | tcp_packets_out_dec(tp, skb); | |
fe067e8a | 2467 | tcp_unlink_write_queue(skb, sk); |
1da177e4 | 2468 | sk_stream_free_skb(sk, skb); |
6a438bbe | 2469 | clear_all_retrans_hints(tp); |
1da177e4 LT |
2470 | } |
2471 | ||
2472 | if (acked&FLAG_ACKED) { | |
2d2abbab | 2473 | tcp_ack_update_rtt(sk, acked, seq_rtt); |
1da177e4 | 2474 | tcp_ack_packets_out(sk, tp); |
8ea333eb JH |
2475 | if (rtt_sample && !(acked & FLAG_RETRANS_DATA_ACKED)) |
2476 | (*rtt_sample)(sk, tcp_usrtt(&tv)); | |
317a76f9 | 2477 | |
6687e988 ACM |
2478 | if (icsk->icsk_ca_ops->pkts_acked) |
2479 | icsk->icsk_ca_ops->pkts_acked(sk, pkts_acked); | |
1da177e4 LT |
2480 | } |
2481 | ||
2482 | #if FASTRETRANS_DEBUG > 0 | |
2483 | BUG_TRAP((int)tp->sacked_out >= 0); | |
2484 | BUG_TRAP((int)tp->lost_out >= 0); | |
2485 | BUG_TRAP((int)tp->retrans_out >= 0); | |
2486 | if (!tp->packets_out && tp->rx_opt.sack_ok) { | |
6687e988 | 2487 | const struct inet_connection_sock *icsk = inet_csk(sk); |
1da177e4 LT |
2488 | if (tp->lost_out) { |
2489 | printk(KERN_DEBUG "Leak l=%u %d\n", | |
6687e988 | 2490 | tp->lost_out, icsk->icsk_ca_state); |
1da177e4 LT |
2491 | tp->lost_out = 0; |
2492 | } | |
2493 | if (tp->sacked_out) { | |
2494 | printk(KERN_DEBUG "Leak s=%u %d\n", | |
6687e988 | 2495 | tp->sacked_out, icsk->icsk_ca_state); |
1da177e4 LT |
2496 | tp->sacked_out = 0; |
2497 | } | |
2498 | if (tp->retrans_out) { | |
2499 | printk(KERN_DEBUG "Leak r=%u %d\n", | |
6687e988 | 2500 | tp->retrans_out, icsk->icsk_ca_state); |
1da177e4 LT |
2501 | tp->retrans_out = 0; |
2502 | } | |
2503 | } | |
2504 | #endif | |
2505 | *seq_rtt_p = seq_rtt; | |
2506 | return acked; | |
2507 | } | |
2508 | ||
2509 | static void tcp_ack_probe(struct sock *sk) | |
2510 | { | |
463c84b9 ACM |
2511 | const struct tcp_sock *tp = tcp_sk(sk); |
2512 | struct inet_connection_sock *icsk = inet_csk(sk); | |
1da177e4 LT |
2513 | |
2514 | /* Was it a usable window open? */ | |
2515 | ||
fe067e8a | 2516 | if (!after(TCP_SKB_CB(tcp_send_head(sk))->end_seq, |
1da177e4 | 2517 | tp->snd_una + tp->snd_wnd)) { |
463c84b9 ACM |
2518 | icsk->icsk_backoff = 0; |
2519 | inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0); | |
1da177e4 LT |
2520 | /* Socket must be waked up by subsequent tcp_data_snd_check(). |
2521 | * This function is not for random using! | |
2522 | */ | |
2523 | } else { | |
463c84b9 | 2524 | inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, |
3f421baa ACM |
2525 | min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX), |
2526 | TCP_RTO_MAX); | |
1da177e4 LT |
2527 | } |
2528 | } | |
2529 | ||
6687e988 | 2530 | static inline int tcp_ack_is_dubious(const struct sock *sk, const int flag) |
1da177e4 LT |
2531 | { |
2532 | return (!(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) || | |
6687e988 | 2533 | inet_csk(sk)->icsk_ca_state != TCP_CA_Open); |
1da177e4 LT |
2534 | } |
2535 | ||
6687e988 | 2536 | static inline int tcp_may_raise_cwnd(const struct sock *sk, const int flag) |
1da177e4 | 2537 | { |
6687e988 | 2538 | const struct tcp_sock *tp = tcp_sk(sk); |
1da177e4 | 2539 | return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) && |
6687e988 | 2540 | !((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_Recovery | TCPF_CA_CWR)); |
1da177e4 LT |
2541 | } |
2542 | ||
2543 | /* Check that window update is acceptable. | |
2544 | * The function assumes that snd_una<=ack<=snd_next. | |
2545 | */ | |
463c84b9 ACM |
2546 | static inline int tcp_may_update_window(const struct tcp_sock *tp, const u32 ack, |
2547 | const u32 ack_seq, const u32 nwin) | |
1da177e4 LT |
2548 | { |
2549 | return (after(ack, tp->snd_una) || | |
2550 | after(ack_seq, tp->snd_wl1) || | |
2551 | (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd)); | |
2552 | } | |
2553 | ||
2554 | /* Update our send window. | |
2555 | * | |
2556 | * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2 | |
2557 | * and in FreeBSD. NetBSD's one is even worse.) is wrong. | |
2558 | */ | |
2559 | static int tcp_ack_update_window(struct sock *sk, struct tcp_sock *tp, | |
2560 | struct sk_buff *skb, u32 ack, u32 ack_seq) | |
2561 | { | |
2562 | int flag = 0; | |
aa8223c7 | 2563 | u32 nwin = ntohs(tcp_hdr(skb)->window); |
1da177e4 | 2564 | |
aa8223c7 | 2565 | if (likely(!tcp_hdr(skb)->syn)) |
1da177e4 LT |
2566 | nwin <<= tp->rx_opt.snd_wscale; |
2567 | ||
2568 | if (tcp_may_update_window(tp, ack, ack_seq, nwin)) { | |
2569 | flag |= FLAG_WIN_UPDATE; | |
2570 | tcp_update_wl(tp, ack, ack_seq); | |
2571 | ||
2572 | if (tp->snd_wnd != nwin) { | |
2573 | tp->snd_wnd = nwin; | |
2574 | ||
2575 | /* Note, it is the only place, where | |
2576 | * fast path is recovered for sending TCP. | |
2577 | */ | |
2ad41065 | 2578 | tp->pred_flags = 0; |
1da177e4 LT |
2579 | tcp_fast_path_check(sk, tp); |
2580 | ||
2581 | if (nwin > tp->max_window) { | |
2582 | tp->max_window = nwin; | |
d83d8461 | 2583 | tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie); |
1da177e4 LT |
2584 | } |
2585 | } | |
2586 | } | |
2587 | ||
2588 | tp->snd_una = ack; | |
2589 | ||
2590 | return flag; | |
2591 | } | |
2592 | ||
9ead9a1d IJ |
2593 | /* A very conservative spurious RTO response algorithm: reduce cwnd and |
2594 | * continue in congestion avoidance. | |
2595 | */ | |
2596 | static void tcp_conservative_spur_to_response(struct tcp_sock *tp) | |
2597 | { | |
2598 | tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); | |
aa8b6a7a | 2599 | tp->snd_cwnd_cnt = 0; |
9ead9a1d IJ |
2600 | tcp_moderate_cwnd(tp); |
2601 | } | |
2602 | ||
3cfe3baa IJ |
2603 | /* A conservative spurious RTO response algorithm: reduce cwnd using |
2604 | * rate halving and continue in congestion avoidance. | |
2605 | */ | |
2606 | static void tcp_ratehalving_spur_to_response(struct sock *sk) | |
2607 | { | |
3cfe3baa | 2608 | tcp_enter_cwr(sk, 0); |
3cfe3baa IJ |
2609 | } |
2610 | ||
e317f6f6 | 2611 | static void tcp_undo_spur_to_response(struct sock *sk, int flag) |
3cfe3baa | 2612 | { |
e317f6f6 IJ |
2613 | if (flag&FLAG_ECE) |
2614 | tcp_ratehalving_spur_to_response(sk); | |
2615 | else | |
2616 | tcp_undo_cwr(sk, 1); | |
3cfe3baa IJ |
2617 | } |
2618 | ||
30935cf4 IJ |
2619 | /* F-RTO spurious RTO detection algorithm (RFC4138) |
2620 | * | |
6408d206 IJ |
2621 | * F-RTO affects during two new ACKs following RTO (well, almost, see inline |
2622 | * comments). State (ACK number) is kept in frto_counter. When ACK advances | |
2623 | * window (but not to or beyond highest sequence sent before RTO): | |
30935cf4 IJ |
2624 | * On First ACK, send two new segments out. |
2625 | * On Second ACK, RTO was likely spurious. Do spurious response (response | |
2626 | * algorithm is not part of the F-RTO detection algorithm | |
2627 | * given in RFC4138 but can be selected separately). | |
2628 | * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss | |
2629 | * and TCP falls back to conventional RTO recovery. | |
2630 | * | |
2631 | * Rationale: if the RTO was spurious, new ACKs should arrive from the | |
2632 | * original window even after we transmit two new data segments. | |
2633 | * | |
4dc2665e IJ |
2634 | * SACK version: |
2635 | * on first step, wait until first cumulative ACK arrives, then move to | |
2636 | * the second step. In second step, the next ACK decides. | |
2637 | * | |
30935cf4 IJ |
2638 | * F-RTO is implemented (mainly) in four functions: |
2639 | * - tcp_use_frto() is used to determine if TCP is can use F-RTO | |
2640 | * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is | |
2641 | * called when tcp_use_frto() showed green light | |
2642 | * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm | |
2643 | * - tcp_enter_frto_loss() is called if there is not enough evidence | |
2644 | * to prove that the RTO is indeed spurious. It transfers the control | |
2645 | * from F-RTO to the conventional RTO recovery | |
2646 | */ | |
7c9a4a5b | 2647 | static int tcp_process_frto(struct sock *sk, u32 prior_snd_una, int flag) |
1da177e4 LT |
2648 | { |
2649 | struct tcp_sock *tp = tcp_sk(sk); | |
e905a9ed | 2650 | |
1da177e4 | 2651 | tcp_sync_left_out(tp); |
e905a9ed | 2652 | |
7487c48c IJ |
2653 | /* Duplicate the behavior from Loss state (fastretrans_alert) */ |
2654 | if (flag&FLAG_DATA_ACKED) | |
2655 | inet_csk(sk)->icsk_retransmits = 0; | |
2656 | ||
95c4922b | 2657 | if (!before(tp->snd_una, tp->frto_highmark)) { |
d1a54c6a | 2658 | tcp_enter_frto_loss(sk, tp->frto_counter + 1, flag); |
7c9a4a5b | 2659 | return 1; |
95c4922b IJ |
2660 | } |
2661 | ||
4dc2665e IJ |
2662 | if (!IsSackFrto() || IsReno(tp)) { |
2663 | /* RFC4138 shortcoming in step 2; should also have case c): | |
2664 | * ACK isn't duplicate nor advances window, e.g., opposite dir | |
2665 | * data, winupdate | |
2666 | */ | |
2667 | if ((tp->snd_una == prior_snd_una) && (flag&FLAG_NOT_DUP) && | |
2668 | !(flag&FLAG_FORWARD_PROGRESS)) | |
2669 | return 1; | |
2670 | ||
2671 | if (!(flag&FLAG_DATA_ACKED)) { | |
2672 | tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 0 : 3), | |
2673 | flag); | |
2674 | return 1; | |
2675 | } | |
2676 | } else { | |
2677 | if (!(flag&FLAG_DATA_ACKED) && (tp->frto_counter == 1)) { | |
2678 | /* Prevent sending of new data. */ | |
2679 | tp->snd_cwnd = min(tp->snd_cwnd, | |
2680 | tcp_packets_in_flight(tp)); | |
2681 | return 1; | |
2682 | } | |
6408d206 | 2683 | |
4dc2665e IJ |
2684 | if ((tp->frto_counter == 2) && |
2685 | (!(flag&FLAG_FORWARD_PROGRESS) || | |
2686 | ((flag&FLAG_DATA_SACKED) && !(flag&FLAG_ONLY_ORIG_SACKED)))) { | |
2687 | /* RFC4138 shortcoming (see comment above) */ | |
2688 | if (!(flag&FLAG_FORWARD_PROGRESS) && (flag&FLAG_NOT_DUP)) | |
2689 | return 1; | |
2690 | ||
2691 | tcp_enter_frto_loss(sk, 3, flag); | |
2692 | return 1; | |
2693 | } | |
1da177e4 LT |
2694 | } |
2695 | ||
2696 | if (tp->frto_counter == 1) { | |
1da177e4 | 2697 | tp->snd_cwnd = tcp_packets_in_flight(tp) + 2; |
94d0ea77 | 2698 | tp->frto_counter = 2; |
7c9a4a5b | 2699 | return 1; |
30935cf4 | 2700 | } else /* frto_counter == 2 */ { |
3cfe3baa IJ |
2701 | switch (sysctl_tcp_frto_response) { |
2702 | case 2: | |
e317f6f6 | 2703 | tcp_undo_spur_to_response(sk, flag); |
3cfe3baa IJ |
2704 | break; |
2705 | case 1: | |
2706 | tcp_conservative_spur_to_response(tp); | |
2707 | break; | |
2708 | default: | |
2709 | tcp_ratehalving_spur_to_response(sk); | |
2710 | break; | |
3ff50b79 | 2711 | } |
94d0ea77 | 2712 | tp->frto_counter = 0; |
1da177e4 | 2713 | } |
7c9a4a5b | 2714 | return 0; |
1da177e4 LT |
2715 | } |
2716 | ||
1da177e4 LT |
2717 | /* This routine deals with incoming acks, but not outgoing ones. */ |
2718 | static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag) | |
2719 | { | |
6687e988 | 2720 | struct inet_connection_sock *icsk = inet_csk(sk); |
1da177e4 LT |
2721 | struct tcp_sock *tp = tcp_sk(sk); |
2722 | u32 prior_snd_una = tp->snd_una; | |
2723 | u32 ack_seq = TCP_SKB_CB(skb)->seq; | |
2724 | u32 ack = TCP_SKB_CB(skb)->ack_seq; | |
2725 | u32 prior_in_flight; | |
2726 | s32 seq_rtt; | |
2727 | int prior_packets; | |
7c9a4a5b | 2728 | int frto_cwnd = 0; |
1da177e4 LT |
2729 | |
2730 | /* If the ack is newer than sent or older than previous acks | |
2731 | * then we can probably ignore it. | |
2732 | */ | |
2733 | if (after(ack, tp->snd_nxt)) | |
2734 | goto uninteresting_ack; | |
2735 | ||
2736 | if (before(ack, prior_snd_una)) | |
2737 | goto old_ack; | |
2738 | ||
3fdf3f0c DO |
2739 | if (sysctl_tcp_abc) { |
2740 | if (icsk->icsk_ca_state < TCP_CA_CWR) | |
2741 | tp->bytes_acked += ack - prior_snd_una; | |
2742 | else if (icsk->icsk_ca_state == TCP_CA_Loss) | |
2743 | /* we assume just one segment left network */ | |
2744 | tp->bytes_acked += min(ack - prior_snd_una, tp->mss_cache); | |
2745 | } | |
9772efb9 | 2746 | |
1da177e4 LT |
2747 | if (!(flag&FLAG_SLOWPATH) && after(ack, prior_snd_una)) { |
2748 | /* Window is constant, pure forward advance. | |
2749 | * No more checks are required. | |
2750 | * Note, we use the fact that SND.UNA>=SND.WL2. | |
2751 | */ | |
2752 | tcp_update_wl(tp, ack, ack_seq); | |
2753 | tp->snd_una = ack; | |
1da177e4 LT |
2754 | flag |= FLAG_WIN_UPDATE; |
2755 | ||
6687e988 | 2756 | tcp_ca_event(sk, CA_EVENT_FAST_ACK); |
317a76f9 | 2757 | |
1da177e4 LT |
2758 | NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS); |
2759 | } else { | |
2760 | if (ack_seq != TCP_SKB_CB(skb)->end_seq) | |
2761 | flag |= FLAG_DATA; | |
2762 | else | |
2763 | NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS); | |
2764 | ||
2765 | flag |= tcp_ack_update_window(sk, tp, skb, ack, ack_seq); | |
2766 | ||
2767 | if (TCP_SKB_CB(skb)->sacked) | |
2768 | flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una); | |
2769 | ||
aa8223c7 | 2770 | if (TCP_ECN_rcv_ecn_echo(tp, tcp_hdr(skb))) |
1da177e4 LT |
2771 | flag |= FLAG_ECE; |
2772 | ||
6687e988 | 2773 | tcp_ca_event(sk, CA_EVENT_SLOW_ACK); |
1da177e4 LT |
2774 | } |
2775 | ||
2776 | /* We passed data and got it acked, remove any soft error | |
2777 | * log. Something worked... | |
2778 | */ | |
2779 | sk->sk_err_soft = 0; | |
2780 | tp->rcv_tstamp = tcp_time_stamp; | |
2781 | prior_packets = tp->packets_out; | |
2782 | if (!prior_packets) | |
2783 | goto no_queue; | |
2784 | ||
2785 | prior_in_flight = tcp_packets_in_flight(tp); | |
2786 | ||
2787 | /* See if we can take anything off of the retransmit queue. */ | |
2d2abbab | 2788 | flag |= tcp_clean_rtx_queue(sk, &seq_rtt); |
1da177e4 LT |
2789 | |
2790 | if (tp->frto_counter) | |
7c9a4a5b | 2791 | frto_cwnd = tcp_process_frto(sk, prior_snd_una, flag); |
1da177e4 | 2792 | |
6687e988 | 2793 | if (tcp_ack_is_dubious(sk, flag)) { |
caa20d9a | 2794 | /* Advance CWND, if state allows this. */ |
7c9a4a5b IJ |
2795 | if ((flag & FLAG_DATA_ACKED) && !frto_cwnd && |
2796 | tcp_may_raise_cwnd(sk, flag)) | |
6687e988 | 2797 | tcp_cong_avoid(sk, ack, seq_rtt, prior_in_flight, 0); |
1da177e4 LT |
2798 | tcp_fastretrans_alert(sk, prior_snd_una, prior_packets, flag); |
2799 | } else { | |
7c9a4a5b | 2800 | if ((flag & FLAG_DATA_ACKED) && !frto_cwnd) |
6687e988 | 2801 | tcp_cong_avoid(sk, ack, seq_rtt, prior_in_flight, 1); |
1da177e4 LT |
2802 | } |
2803 | ||
2804 | if ((flag & FLAG_FORWARD_PROGRESS) || !(flag&FLAG_NOT_DUP)) | |
2805 | dst_confirm(sk->sk_dst_cache); | |
2806 | ||
2807 | return 1; | |
2808 | ||
2809 | no_queue: | |
6687e988 | 2810 | icsk->icsk_probes_out = 0; |
1da177e4 LT |
2811 | |
2812 | /* If this ack opens up a zero window, clear backoff. It was | |
2813 | * being used to time the probes, and is probably far higher than | |
2814 | * it needs to be for normal retransmission. | |
2815 | */ | |
fe067e8a | 2816 | if (tcp_send_head(sk)) |
1da177e4 LT |
2817 | tcp_ack_probe(sk); |
2818 | return 1; | |
2819 | ||
2820 | old_ack: | |
2821 | if (TCP_SKB_CB(skb)->sacked) | |
2822 | tcp_sacktag_write_queue(sk, skb, prior_snd_una); | |
2823 | ||
2824 | uninteresting_ack: | |
2825 | SOCK_DEBUG(sk, "Ack %u out of %u:%u\n", ack, tp->snd_una, tp->snd_nxt); | |
2826 | return 0; | |
2827 | } | |
2828 | ||
2829 | ||
2830 | /* Look for tcp options. Normally only called on SYN and SYNACK packets. | |
2831 | * But, this can also be called on packets in the established flow when | |
2832 | * the fast version below fails. | |
2833 | */ | |
2834 | void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx, int estab) | |
2835 | { | |
2836 | unsigned char *ptr; | |
aa8223c7 | 2837 | struct tcphdr *th = tcp_hdr(skb); |
1da177e4 LT |
2838 | int length=(th->doff*4)-sizeof(struct tcphdr); |
2839 | ||
2840 | ptr = (unsigned char *)(th + 1); | |
2841 | opt_rx->saw_tstamp = 0; | |
2842 | ||
2de979bd | 2843 | while (length > 0) { |
e905a9ed | 2844 | int opcode=*ptr++; |
1da177e4 LT |
2845 | int opsize; |
2846 | ||
2847 | switch (opcode) { | |
2848 | case TCPOPT_EOL: | |
2849 | return; | |
2850 | case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */ | |
2851 | length--; | |
2852 | continue; | |
2853 | default: | |
2854 | opsize=*ptr++; | |
2855 | if (opsize < 2) /* "silly options" */ | |
2856 | return; | |
2857 | if (opsize > length) | |
2858 | return; /* don't parse partial options */ | |
2de979bd | 2859 | switch (opcode) { |
1da177e4 | 2860 | case TCPOPT_MSS: |
2de979bd | 2861 | if (opsize==TCPOLEN_MSS && th->syn && !estab) { |
4f3608b7 | 2862 | u16 in_mss = ntohs(get_unaligned((__be16 *)ptr)); |
1da177e4 LT |
2863 | if (in_mss) { |
2864 | if (opt_rx->user_mss && opt_rx->user_mss < in_mss) | |
2865 | in_mss = opt_rx->user_mss; | |
2866 | opt_rx->mss_clamp = in_mss; | |
2867 | } | |
2868 | } | |
2869 | break; | |
2870 | case TCPOPT_WINDOW: | |
2de979bd | 2871 | if (opsize==TCPOLEN_WINDOW && th->syn && !estab) |
1da177e4 LT |
2872 | if (sysctl_tcp_window_scaling) { |
2873 | __u8 snd_wscale = *(__u8 *) ptr; | |
2874 | opt_rx->wscale_ok = 1; | |
2875 | if (snd_wscale > 14) { | |
2de979bd | 2876 | if (net_ratelimit()) |
1da177e4 LT |
2877 | printk(KERN_INFO "tcp_parse_options: Illegal window " |
2878 | "scaling value %d >14 received.\n", | |
2879 | snd_wscale); | |
2880 | snd_wscale = 14; | |
2881 | } | |
2882 | opt_rx->snd_wscale = snd_wscale; | |
2883 | } | |
2884 | break; | |
2885 | case TCPOPT_TIMESTAMP: | |
2de979bd | 2886 | if (opsize==TCPOLEN_TIMESTAMP) { |
1da177e4 LT |
2887 | if ((estab && opt_rx->tstamp_ok) || |
2888 | (!estab && sysctl_tcp_timestamps)) { | |
2889 | opt_rx->saw_tstamp = 1; | |
4f3608b7 AV |
2890 | opt_rx->rcv_tsval = ntohl(get_unaligned((__be32 *)ptr)); |
2891 | opt_rx->rcv_tsecr = ntohl(get_unaligned((__be32 *)(ptr+4))); | |
1da177e4 LT |
2892 | } |
2893 | } | |
2894 | break; | |
2895 | case TCPOPT_SACK_PERM: | |
2de979bd | 2896 | if (opsize==TCPOLEN_SACK_PERM && th->syn && !estab) { |
1da177e4 LT |
2897 | if (sysctl_tcp_sack) { |
2898 | opt_rx->sack_ok = 1; | |
2899 | tcp_sack_reset(opt_rx); | |
2900 | } | |
2901 | } | |
2902 | break; | |
2903 | ||
2904 | case TCPOPT_SACK: | |
2de979bd | 2905 | if ((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) && |
1da177e4 LT |
2906 | !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) && |
2907 | opt_rx->sack_ok) { | |
2908 | TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th; | |
2909 | } | |
cfb6eeb4 YH |
2910 | #ifdef CONFIG_TCP_MD5SIG |
2911 | case TCPOPT_MD5SIG: | |
2912 | /* | |
2913 | * The MD5 Hash has already been | |
2914 | * checked (see tcp_v{4,6}_do_rcv()). | |
2915 | */ | |
2916 | break; | |
2917 | #endif | |
3ff50b79 SH |
2918 | } |
2919 | ||
e905a9ed YH |
2920 | ptr+=opsize-2; |
2921 | length-=opsize; | |
3ff50b79 | 2922 | } |
1da177e4 LT |
2923 | } |
2924 | } | |
2925 | ||
2926 | /* Fast parse options. This hopes to only see timestamps. | |
2927 | * If it is wrong it falls back on tcp_parse_options(). | |
2928 | */ | |
40efc6fa SH |
2929 | static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th, |
2930 | struct tcp_sock *tp) | |
1da177e4 LT |
2931 | { |
2932 | if (th->doff == sizeof(struct tcphdr)>>2) { | |
2933 | tp->rx_opt.saw_tstamp = 0; | |
2934 | return 0; | |
2935 | } else if (tp->rx_opt.tstamp_ok && | |
2936 | th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) { | |
4f3608b7 AV |
2937 | __be32 *ptr = (__be32 *)(th + 1); |
2938 | if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) | |
1da177e4 LT |
2939 | | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) { |
2940 | tp->rx_opt.saw_tstamp = 1; | |
2941 | ++ptr; | |
2942 | tp->rx_opt.rcv_tsval = ntohl(*ptr); | |
2943 | ++ptr; | |
2944 | tp->rx_opt.rcv_tsecr = ntohl(*ptr); | |
2945 | return 1; | |
2946 | } | |
2947 | } | |
2948 | tcp_parse_options(skb, &tp->rx_opt, 1); | |
2949 | return 1; | |
2950 | } | |
2951 | ||
2952 | static inline void tcp_store_ts_recent(struct tcp_sock *tp) | |
2953 | { | |
2954 | tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval; | |
9d729f72 | 2955 | tp->rx_opt.ts_recent_stamp = get_seconds(); |
1da177e4 LT |
2956 | } |
2957 | ||
2958 | static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq) | |
2959 | { | |
2960 | if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) { | |
2961 | /* PAWS bug workaround wrt. ACK frames, the PAWS discard | |
2962 | * extra check below makes sure this can only happen | |
2963 | * for pure ACK frames. -DaveM | |
2964 | * | |
2965 | * Not only, also it occurs for expired timestamps. | |
2966 | */ | |
2967 | ||
2de979bd | 2968 | if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) >= 0 || |
9d729f72 | 2969 | get_seconds() >= tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS) |
1da177e4 LT |
2970 | tcp_store_ts_recent(tp); |
2971 | } | |
2972 | } | |
2973 | ||
2974 | /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM | |
2975 | * | |
2976 | * It is not fatal. If this ACK does _not_ change critical state (seqs, window) | |
2977 | * it can pass through stack. So, the following predicate verifies that | |
2978 | * this segment is not used for anything but congestion avoidance or | |
2979 | * fast retransmit. Moreover, we even are able to eliminate most of such | |
2980 | * second order effects, if we apply some small "replay" window (~RTO) | |
2981 | * to timestamp space. | |
2982 | * | |
2983 | * All these measures still do not guarantee that we reject wrapped ACKs | |
2984 | * on networks with high bandwidth, when sequence space is recycled fastly, | |
2985 | * but it guarantees that such events will be very rare and do not affect | |
2986 | * connection seriously. This doesn't look nice, but alas, PAWS is really | |
2987 | * buggy extension. | |
2988 | * | |
2989 | * [ Later note. Even worse! It is buggy for segments _with_ data. RFC | |
2990 | * states that events when retransmit arrives after original data are rare. | |
2991 | * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is | |
2992 | * the biggest problem on large power networks even with minor reordering. | |
2993 | * OK, let's give it small replay window. If peer clock is even 1hz, it is safe | |
2994 | * up to bandwidth of 18Gigabit/sec. 8) ] | |
2995 | */ | |
2996 | ||
463c84b9 | 2997 | static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb) |
1da177e4 | 2998 | { |
463c84b9 | 2999 | struct tcp_sock *tp = tcp_sk(sk); |
aa8223c7 | 3000 | struct tcphdr *th = tcp_hdr(skb); |
1da177e4 LT |
3001 | u32 seq = TCP_SKB_CB(skb)->seq; |
3002 | u32 ack = TCP_SKB_CB(skb)->ack_seq; | |
3003 | ||
3004 | return (/* 1. Pure ACK with correct sequence number. */ | |
3005 | (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) && | |
3006 | ||
3007 | /* 2. ... and duplicate ACK. */ | |
3008 | ack == tp->snd_una && | |
3009 | ||
3010 | /* 3. ... and does not update window. */ | |
3011 | !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) && | |
3012 | ||
3013 | /* 4. ... and sits in replay window. */ | |
463c84b9 | 3014 | (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ); |
1da177e4 LT |
3015 | } |
3016 | ||
463c84b9 | 3017 | static inline int tcp_paws_discard(const struct sock *sk, const struct sk_buff *skb) |
1da177e4 | 3018 | { |
463c84b9 | 3019 | const struct tcp_sock *tp = tcp_sk(sk); |
1da177e4 | 3020 | return ((s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) > TCP_PAWS_WINDOW && |
9d729f72 | 3021 | get_seconds() < tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS && |
463c84b9 | 3022 | !tcp_disordered_ack(sk, skb)); |
1da177e4 LT |
3023 | } |
3024 | ||
3025 | /* Check segment sequence number for validity. | |
3026 | * | |
3027 | * Segment controls are considered valid, if the segment | |
3028 | * fits to the window after truncation to the window. Acceptability | |
3029 | * of data (and SYN, FIN, of course) is checked separately. | |
3030 | * See tcp_data_queue(), for example. | |
3031 | * | |
3032 | * Also, controls (RST is main one) are accepted using RCV.WUP instead | |
3033 | * of RCV.NXT. Peer still did not advance his SND.UNA when we | |
3034 | * delayed ACK, so that hisSND.UNA<=ourRCV.WUP. | |
3035 | * (borrowed from freebsd) | |
3036 | */ | |
3037 | ||
3038 | static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq) | |
3039 | { | |
3040 | return !before(end_seq, tp->rcv_wup) && | |
3041 | !after(seq, tp->rcv_nxt + tcp_receive_window(tp)); | |
3042 | } | |
3043 | ||
3044 | /* When we get a reset we do this. */ | |
3045 | static void tcp_reset(struct sock *sk) | |
3046 | { | |
3047 | /* We want the right error as BSD sees it (and indeed as we do). */ | |
3048 | switch (sk->sk_state) { | |
3049 | case TCP_SYN_SENT: | |
3050 | sk->sk_err = ECONNREFUSED; | |
3051 | break; | |
3052 | case TCP_CLOSE_WAIT: | |
3053 | sk->sk_err = EPIPE; | |
3054 | break; | |
3055 | case TCP_CLOSE: | |
3056 | return; | |
3057 | default: | |
3058 | sk->sk_err = ECONNRESET; | |
3059 | } | |
3060 | ||
3061 | if (!sock_flag(sk, SOCK_DEAD)) | |
3062 | sk->sk_error_report(sk); | |
3063 | ||
3064 | tcp_done(sk); | |
3065 | } | |
3066 | ||
3067 | /* | |
3068 | * Process the FIN bit. This now behaves as it is supposed to work | |
3069 | * and the FIN takes effect when it is validly part of sequence | |
3070 | * space. Not before when we get holes. | |
3071 | * | |
3072 | * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT | |
3073 | * (and thence onto LAST-ACK and finally, CLOSE, we never enter | |
3074 | * TIME-WAIT) | |
3075 | * | |
3076 | * If we are in FINWAIT-1, a received FIN indicates simultaneous | |
3077 | * close and we go into CLOSING (and later onto TIME-WAIT) | |
3078 | * | |
3079 | * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT. | |
3080 | */ | |
3081 | static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th) | |
3082 | { | |
3083 | struct tcp_sock *tp = tcp_sk(sk); | |
3084 | ||
463c84b9 | 3085 | inet_csk_schedule_ack(sk); |
1da177e4 LT |
3086 | |
3087 | sk->sk_shutdown |= RCV_SHUTDOWN; | |
3088 | sock_set_flag(sk, SOCK_DONE); | |
3089 | ||
3090 | switch (sk->sk_state) { | |
3091 | case TCP_SYN_RECV: | |
3092 | case TCP_ESTABLISHED: | |
3093 | /* Move to CLOSE_WAIT */ | |
3094 | tcp_set_state(sk, TCP_CLOSE_WAIT); | |
463c84b9 | 3095 | inet_csk(sk)->icsk_ack.pingpong = 1; |
1da177e4 LT |
3096 | break; |
3097 | ||
3098 | case TCP_CLOSE_WAIT: | |
3099 | case TCP_CLOSING: | |
3100 | /* Received a retransmission of the FIN, do | |
3101 | * nothing. | |
3102 | */ | |
3103 | break; | |
3104 | case TCP_LAST_ACK: | |
3105 | /* RFC793: Remain in the LAST-ACK state. */ | |
3106 | break; | |
3107 | ||
3108 | case TCP_FIN_WAIT1: | |
3109 | /* This case occurs when a simultaneous close | |
3110 | * happens, we must ack the received FIN and | |
3111 | * enter the CLOSING state. | |
3112 | */ | |
3113 | tcp_send_ack(sk); | |
3114 | tcp_set_state(sk, TCP_CLOSING); | |
3115 | break; | |
3116 | case TCP_FIN_WAIT2: | |
3117 | /* Received a FIN -- send ACK and enter TIME_WAIT. */ | |
3118 | tcp_send_ack(sk); | |
3119 | tcp_time_wait(sk, TCP_TIME_WAIT, 0); | |
3120 | break; | |
3121 | default: | |
3122 | /* Only TCP_LISTEN and TCP_CLOSE are left, in these | |
3123 | * cases we should never reach this piece of code. | |
3124 | */ | |
3125 | printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n", | |
3126 | __FUNCTION__, sk->sk_state); | |
3127 | break; | |
3ff50b79 | 3128 | } |
1da177e4 LT |
3129 | |
3130 | /* It _is_ possible, that we have something out-of-order _after_ FIN. | |
3131 | * Probably, we should reset in this case. For now drop them. | |
3132 | */ | |
3133 | __skb_queue_purge(&tp->out_of_order_queue); | |
3134 | if (tp->rx_opt.sack_ok) | |
3135 | tcp_sack_reset(&tp->rx_opt); | |
3136 | sk_stream_mem_reclaim(sk); | |
3137 | ||
3138 | if (!sock_flag(sk, SOCK_DEAD)) { | |
3139 | sk->sk_state_change(sk); | |
3140 | ||
3141 | /* Do not send POLL_HUP for half duplex close. */ | |
3142 | if (sk->sk_shutdown == SHUTDOWN_MASK || | |
3143 | sk->sk_state == TCP_CLOSE) | |
3144 | sk_wake_async(sk, 1, POLL_HUP); | |
3145 | else | |
3146 | sk_wake_async(sk, 1, POLL_IN); | |
3147 | } | |
3148 | } | |
3149 | ||
40efc6fa | 3150 | static inline int tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, u32 end_seq) |
1da177e4 LT |
3151 | { |
3152 | if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) { | |
3153 | if (before(seq, sp->start_seq)) | |
3154 | sp->start_seq = seq; | |
3155 | if (after(end_seq, sp->end_seq)) | |
3156 | sp->end_seq = end_seq; | |
3157 | return 1; | |
3158 | } | |
3159 | return 0; | |
3160 | } | |
3161 | ||
40efc6fa | 3162 | static void tcp_dsack_set(struct tcp_sock *tp, u32 seq, u32 end_seq) |
1da177e4 LT |
3163 | { |
3164 | if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) { | |
3165 | if (before(seq, tp->rcv_nxt)) | |
3166 | NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT); | |
3167 | else | |
3168 | NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT); | |
3169 | ||
3170 | tp->rx_opt.dsack = 1; | |
3171 | tp->duplicate_sack[0].start_seq = seq; | |
3172 | tp->duplicate_sack[0].end_seq = end_seq; | |
3173 | tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + 1, 4 - tp->rx_opt.tstamp_ok); | |
3174 | } | |
3175 | } | |
3176 | ||
40efc6fa | 3177 | static void tcp_dsack_extend(struct tcp_sock *tp, u32 seq, u32 end_seq) |
1da177e4 LT |
3178 | { |
3179 | if (!tp->rx_opt.dsack) | |
3180 | tcp_dsack_set(tp, seq, end_seq); | |
3181 | else | |
3182 | tcp_sack_extend(tp->duplicate_sack, seq, end_seq); | |
3183 | } | |
3184 | ||
3185 | static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb) | |
3186 | { | |
3187 | struct tcp_sock *tp = tcp_sk(sk); | |
3188 | ||
3189 | if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && | |
3190 | before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { | |
3191 | NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST); | |
463c84b9 | 3192 | tcp_enter_quickack_mode(sk); |
1da177e4 LT |
3193 | |
3194 | if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) { | |
3195 | u32 end_seq = TCP_SKB_CB(skb)->end_seq; | |
3196 | ||
3197 | if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) | |
3198 | end_seq = tp->rcv_nxt; | |
3199 | tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, end_seq); | |
3200 | } | |
3201 | } | |
3202 | ||
3203 | tcp_send_ack(sk); | |
3204 | } | |
3205 | ||
3206 | /* These routines update the SACK block as out-of-order packets arrive or | |
3207 | * in-order packets close up the sequence space. | |
3208 | */ | |
3209 | static void tcp_sack_maybe_coalesce(struct tcp_sock *tp) | |
3210 | { | |
3211 | int this_sack; | |
3212 | struct tcp_sack_block *sp = &tp->selective_acks[0]; | |
3213 | struct tcp_sack_block *swalk = sp+1; | |
3214 | ||
3215 | /* See if the recent change to the first SACK eats into | |
3216 | * or hits the sequence space of other SACK blocks, if so coalesce. | |
3217 | */ | |
3218 | for (this_sack = 1; this_sack < tp->rx_opt.num_sacks; ) { | |
3219 | if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) { | |
3220 | int i; | |
3221 | ||
3222 | /* Zap SWALK, by moving every further SACK up by one slot. | |
3223 | * Decrease num_sacks. | |
3224 | */ | |
3225 | tp->rx_opt.num_sacks--; | |
3226 | tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok); | |
2de979bd | 3227 | for (i=this_sack; i < tp->rx_opt.num_sacks; i++) |
1da177e4 LT |
3228 | sp[i] = sp[i+1]; |
3229 | continue; | |
3230 | } | |
3231 | this_sack++, swalk++; | |
3232 | } | |
3233 | } | |
3234 | ||
40efc6fa | 3235 | static inline void tcp_sack_swap(struct tcp_sack_block *sack1, struct tcp_sack_block *sack2) |
1da177e4 LT |
3236 | { |
3237 | __u32 tmp; | |
3238 | ||
3239 | tmp = sack1->start_seq; | |
3240 | sack1->start_seq = sack2->start_seq; | |
3241 | sack2->start_seq = tmp; | |
3242 | ||
3243 | tmp = sack1->end_seq; | |
3244 | sack1->end_seq = sack2->end_seq; | |
3245 | sack2->end_seq = tmp; | |
3246 | } | |
3247 | ||
3248 | static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq) | |
3249 | { | |
3250 | struct tcp_sock *tp = tcp_sk(sk); | |
3251 | struct tcp_sack_block *sp = &tp->selective_acks[0]; | |
3252 | int cur_sacks = tp->rx_opt.num_sacks; | |
3253 | int this_sack; | |
3254 | ||
3255 | if (!cur_sacks) | |
3256 | goto new_sack; | |
3257 | ||
3258 | for (this_sack=0; this_sack<cur_sacks; this_sack++, sp++) { | |
3259 | if (tcp_sack_extend(sp, seq, end_seq)) { | |
3260 | /* Rotate this_sack to the first one. */ | |
3261 | for (; this_sack>0; this_sack--, sp--) | |
3262 | tcp_sack_swap(sp, sp-1); | |
3263 | if (cur_sacks > 1) | |
3264 | tcp_sack_maybe_coalesce(tp); | |
3265 | return; | |
3266 | } | |
3267 | } | |
3268 | ||
3269 | /* Could not find an adjacent existing SACK, build a new one, | |
3270 | * put it at the front, and shift everyone else down. We | |
3271 | * always know there is at least one SACK present already here. | |
3272 | * | |
3273 | * If the sack array is full, forget about the last one. | |
3274 | */ | |
3275 | if (this_sack >= 4) { | |
3276 | this_sack--; | |
3277 | tp->rx_opt.num_sacks--; | |
3278 | sp--; | |
3279 | } | |
2de979bd | 3280 | for (; this_sack > 0; this_sack--, sp--) |
1da177e4 LT |
3281 | *sp = *(sp-1); |
3282 | ||
3283 | new_sack: | |
3284 | /* Build the new head SACK, and we're done. */ | |
3285 | sp->start_seq = seq; | |
3286 | sp->end_seq = end_seq; | |
3287 | tp->rx_opt.num_sacks++; | |
3288 | tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok); | |
3289 | } | |
3290 | ||
3291 | /* RCV.NXT advances, some SACKs should be eaten. */ | |
3292 | ||
3293 | static void tcp_sack_remove(struct tcp_sock *tp) | |
3294 | { | |
3295 | struct tcp_sack_block *sp = &tp->selective_acks[0]; | |
3296 | int num_sacks = tp->rx_opt.num_sacks; | |
3297 | int this_sack; | |
3298 | ||
3299 | /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */ | |
b03efcfb | 3300 | if (skb_queue_empty(&tp->out_of_order_queue)) { |
1da177e4 LT |
3301 | tp->rx_opt.num_sacks = 0; |
3302 | tp->rx_opt.eff_sacks = tp->rx_opt.dsack; | |
3303 | return; | |
3304 | } | |
3305 | ||
2de979bd | 3306 | for (this_sack = 0; this_sack < num_sacks; ) { |
1da177e4 LT |
3307 | /* Check if the start of the sack is covered by RCV.NXT. */ |
3308 | if (!before(tp->rcv_nxt, sp->start_seq)) { | |
3309 | int i; | |
3310 | ||
3311 | /* RCV.NXT must cover all the block! */ | |
3312 | BUG_TRAP(!before(tp->rcv_nxt, sp->end_seq)); | |
3313 | ||
3314 | /* Zap this SACK, by moving forward any other SACKS. */ | |
3315 | for (i=this_sack+1; i < num_sacks; i++) | |
3316 | tp->selective_acks[i-1] = tp->selective_acks[i]; | |
3317 | num_sacks--; | |
3318 | continue; | |
3319 | } | |
3320 | this_sack++; | |
3321 | sp++; | |
3322 | } | |
3323 | if (num_sacks != tp->rx_opt.num_sacks) { | |
3324 | tp->rx_opt.num_sacks = num_sacks; | |
3325 | tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok); | |
3326 | } | |
3327 | } | |
3328 | ||
3329 | /* This one checks to see if we can put data from the | |
3330 | * out_of_order queue into the receive_queue. | |
3331 | */ | |
3332 | static void tcp_ofo_queue(struct sock *sk) | |
3333 | { | |
3334 | struct tcp_sock *tp = tcp_sk(sk); | |
3335 | __u32 dsack_high = tp->rcv_nxt; | |
3336 | struct sk_buff *skb; | |
3337 | ||
3338 | while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) { | |
3339 | if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) | |
3340 | break; | |
3341 | ||
3342 | if (before(TCP_SKB_CB(skb)->seq, dsack_high)) { | |
3343 | __u32 dsack = dsack_high; | |
3344 | if (before(TCP_SKB_CB(skb)->end_seq, dsack_high)) | |
3345 | dsack_high = TCP_SKB_CB(skb)->end_seq; | |
3346 | tcp_dsack_extend(tp, TCP_SKB_CB(skb)->seq, dsack); | |
3347 | } | |
3348 | ||
3349 | if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { | |
3350 | SOCK_DEBUG(sk, "ofo packet was already received \n"); | |
8728b834 | 3351 | __skb_unlink(skb, &tp->out_of_order_queue); |
1da177e4 LT |
3352 | __kfree_skb(skb); |
3353 | continue; | |
3354 | } | |
3355 | SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n", | |
3356 | tp->rcv_nxt, TCP_SKB_CB(skb)->seq, | |
3357 | TCP_SKB_CB(skb)->end_seq); | |
3358 | ||
8728b834 | 3359 | __skb_unlink(skb, &tp->out_of_order_queue); |
1da177e4 LT |
3360 | __skb_queue_tail(&sk->sk_receive_queue, skb); |
3361 | tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; | |
aa8223c7 ACM |
3362 | if (tcp_hdr(skb)->fin) |
3363 | tcp_fin(skb, sk, tcp_hdr(skb)); | |
1da177e4 LT |
3364 | } |
3365 | } | |
3366 | ||
3367 | static int tcp_prune_queue(struct sock *sk); | |
3368 | ||
3369 | static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) | |
3370 | { | |
aa8223c7 | 3371 | struct tcphdr *th = tcp_hdr(skb); |
1da177e4 LT |
3372 | struct tcp_sock *tp = tcp_sk(sk); |
3373 | int eaten = -1; | |
3374 | ||
3375 | if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) | |
3376 | goto drop; | |
3377 | ||
1da177e4 LT |
3378 | __skb_pull(skb, th->doff*4); |
3379 | ||
3380 | TCP_ECN_accept_cwr(tp, skb); | |
3381 | ||
3382 | if (tp->rx_opt.dsack) { | |
3383 | tp->rx_opt.dsack = 0; | |
3384 | tp->rx_opt.eff_sacks = min_t(unsigned int, tp->rx_opt.num_sacks, | |
3385 | 4 - tp->rx_opt.tstamp_ok); | |
3386 | } | |
3387 | ||
3388 | /* Queue data for delivery to the user. | |
3389 | * Packets in sequence go to the receive queue. | |
3390 | * Out of sequence packets to the out_of_order_queue. | |
3391 | */ | |
3392 | if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) { | |
3393 | if (tcp_receive_window(tp) == 0) | |
3394 | goto out_of_window; | |
3395 | ||
3396 | /* Ok. In sequence. In window. */ | |
3397 | if (tp->ucopy.task == current && | |
3398 | tp->copied_seq == tp->rcv_nxt && tp->ucopy.len && | |
3399 | sock_owned_by_user(sk) && !tp->urg_data) { | |
3400 | int chunk = min_t(unsigned int, skb->len, | |
3401 | tp->ucopy.len); | |
3402 | ||
3403 | __set_current_state(TASK_RUNNING); | |
3404 | ||
3405 | local_bh_enable(); | |
3406 | if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) { | |
3407 | tp->ucopy.len -= chunk; | |
3408 | tp->copied_seq += chunk; | |
3409 | eaten = (chunk == skb->len && !th->fin); | |
3410 | tcp_rcv_space_adjust(sk); | |
3411 | } | |
3412 | local_bh_disable(); | |
3413 | } | |
3414 | ||
3415 | if (eaten <= 0) { | |
3416 | queue_and_out: | |
3417 | if (eaten < 0 && | |
3418 | (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf || | |
3419 | !sk_stream_rmem_schedule(sk, skb))) { | |
3420 | if (tcp_prune_queue(sk) < 0 || | |
3421 | !sk_stream_rmem_schedule(sk, skb)) | |
3422 | goto drop; | |
3423 | } | |
3424 | sk_stream_set_owner_r(skb, sk); | |
3425 | __skb_queue_tail(&sk->sk_receive_queue, skb); | |
3426 | } | |
3427 | tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; | |
2de979bd | 3428 | if (skb->len) |
1da177e4 | 3429 | tcp_event_data_recv(sk, tp, skb); |
2de979bd | 3430 | if (th->fin) |
1da177e4 LT |
3431 | tcp_fin(skb, sk, th); |
3432 | ||
b03efcfb | 3433 | if (!skb_queue_empty(&tp->out_of_order_queue)) { |
1da177e4 LT |
3434 | tcp_ofo_queue(sk); |
3435 | ||
3436 | /* RFC2581. 4.2. SHOULD send immediate ACK, when | |
3437 | * gap in queue is filled. | |
3438 | */ | |
b03efcfb | 3439 | if (skb_queue_empty(&tp->out_of_order_queue)) |
463c84b9 | 3440 | inet_csk(sk)->icsk_ack.pingpong = 0; |
1da177e4 LT |
3441 | } |
3442 | ||
3443 | if (tp->rx_opt.num_sacks) | |
3444 | tcp_sack_remove(tp); | |
3445 | ||
3446 | tcp_fast_path_check(sk, tp); | |
3447 | ||
3448 | if (eaten > 0) | |
3449 | __kfree_skb(skb); | |
3450 | else if (!sock_flag(sk, SOCK_DEAD)) | |
3451 | sk->sk_data_ready(sk, 0); | |
3452 | return; | |
3453 | } | |
3454 | ||
3455 | if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { | |
3456 | /* A retransmit, 2nd most common case. Force an immediate ack. */ | |
3457 | NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST); | |
3458 | tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); | |
3459 | ||
3460 | out_of_window: | |
463c84b9 ACM |
3461 | tcp_enter_quickack_mode(sk); |
3462 | inet_csk_schedule_ack(sk); | |
1da177e4 LT |
3463 | drop: |
3464 | __kfree_skb(skb); | |
3465 | return; | |
3466 | } | |
3467 | ||
3468 | /* Out of window. F.e. zero window probe. */ | |
3469 | if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp))) | |
3470 | goto out_of_window; | |
3471 | ||
463c84b9 | 3472 | tcp_enter_quickack_mode(sk); |
1da177e4 LT |
3473 | |
3474 | if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { | |
3475 | /* Partial packet, seq < rcv_next < end_seq */ | |
3476 | SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n", | |
3477 | tp->rcv_nxt, TCP_SKB_CB(skb)->seq, | |
3478 | TCP_SKB_CB(skb)->end_seq); | |
3479 | ||
3480 | tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, tp->rcv_nxt); | |
e905a9ed | 3481 | |
1da177e4 LT |
3482 | /* If window is closed, drop tail of packet. But after |
3483 | * remembering D-SACK for its head made in previous line. | |
3484 | */ | |
3485 | if (!tcp_receive_window(tp)) | |
3486 | goto out_of_window; | |
3487 | goto queue_and_out; | |
3488 | } | |
3489 | ||
3490 | TCP_ECN_check_ce(tp, skb); | |
3491 | ||
3492 | if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf || | |
3493 | !sk_stream_rmem_schedule(sk, skb)) { | |
3494 | if (tcp_prune_queue(sk) < 0 || | |
3495 | !sk_stream_rmem_schedule(sk, skb)) | |
3496 | goto drop; | |
3497 | } | |
3498 | ||
3499 | /* Disable header prediction. */ | |
3500 | tp->pred_flags = 0; | |
463c84b9 | 3501 | inet_csk_schedule_ack(sk); |
1da177e4 LT |
3502 | |
3503 | SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n", | |
3504 | tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); | |
3505 | ||
3506 | sk_stream_set_owner_r(skb, sk); | |
3507 | ||
3508 | if (!skb_peek(&tp->out_of_order_queue)) { | |
3509 | /* Initial out of order segment, build 1 SACK. */ | |
3510 | if (tp->rx_opt.sack_ok) { | |
3511 | tp->rx_opt.num_sacks = 1; | |
3512 | tp->rx_opt.dsack = 0; | |
3513 | tp->rx_opt.eff_sacks = 1; | |
3514 | tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq; | |
3515 | tp->selective_acks[0].end_seq = | |
3516 | TCP_SKB_CB(skb)->end_seq; | |
3517 | } | |
3518 | __skb_queue_head(&tp->out_of_order_queue,skb); | |
3519 | } else { | |
3520 | struct sk_buff *skb1 = tp->out_of_order_queue.prev; | |
3521 | u32 seq = TCP_SKB_CB(skb)->seq; | |
3522 | u32 end_seq = TCP_SKB_CB(skb)->end_seq; | |
3523 | ||
3524 | if (seq == TCP_SKB_CB(skb1)->end_seq) { | |
8728b834 | 3525 | __skb_append(skb1, skb, &tp->out_of_order_queue); |
1da177e4 LT |
3526 | |
3527 | if (!tp->rx_opt.num_sacks || | |
3528 | tp->selective_acks[0].end_seq != seq) | |
3529 | goto add_sack; | |
3530 | ||
3531 | /* Common case: data arrive in order after hole. */ | |
3532 | tp->selective_acks[0].end_seq = end_seq; | |
3533 | return; | |
3534 | } | |
3535 | ||
3536 | /* Find place to insert this segment. */ | |
3537 | do { | |
3538 | if (!after(TCP_SKB_CB(skb1)->seq, seq)) | |
3539 | break; | |
3540 | } while ((skb1 = skb1->prev) != | |
3541 | (struct sk_buff*)&tp->out_of_order_queue); | |
3542 | ||
3543 | /* Do skb overlap to previous one? */ | |
3544 | if (skb1 != (struct sk_buff*)&tp->out_of_order_queue && | |
3545 | before(seq, TCP_SKB_CB(skb1)->end_seq)) { | |
3546 | if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) { | |
3547 | /* All the bits are present. Drop. */ | |
3548 | __kfree_skb(skb); | |
3549 | tcp_dsack_set(tp, seq, end_seq); | |
3550 | goto add_sack; | |
3551 | } | |
3552 | if (after(seq, TCP_SKB_CB(skb1)->seq)) { | |
3553 | /* Partial overlap. */ | |
3554 | tcp_dsack_set(tp, seq, TCP_SKB_CB(skb1)->end_seq); | |
3555 | } else { | |
3556 | skb1 = skb1->prev; | |
3557 | } | |
3558 | } | |
3559 | __skb_insert(skb, skb1, skb1->next, &tp->out_of_order_queue); | |
e905a9ed | 3560 | |
1da177e4 LT |
3561 | /* And clean segments covered by new one as whole. */ |
3562 | while ((skb1 = skb->next) != | |
3563 | (struct sk_buff*)&tp->out_of_order_queue && | |
3564 | after(end_seq, TCP_SKB_CB(skb1)->seq)) { | |
3565 | if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) { | |
3566 | tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, end_seq); | |
3567 | break; | |
3568 | } | |
8728b834 | 3569 | __skb_unlink(skb1, &tp->out_of_order_queue); |
1da177e4 LT |
3570 | tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, TCP_SKB_CB(skb1)->end_seq); |
3571 | __kfree_skb(skb1); | |
3572 | } | |
3573 | ||
3574 | add_sack: | |
3575 | if (tp->rx_opt.sack_ok) | |
3576 | tcp_sack_new_ofo_skb(sk, seq, end_seq); | |
3577 | } | |
3578 | } | |
3579 | ||
3580 | /* Collapse contiguous sequence of skbs head..tail with | |
3581 | * sequence numbers start..end. | |
3582 | * Segments with FIN/SYN are not collapsed (only because this | |
3583 | * simplifies code) | |
3584 | */ | |
3585 | static void | |
8728b834 DM |
3586 | tcp_collapse(struct sock *sk, struct sk_buff_head *list, |
3587 | struct sk_buff *head, struct sk_buff *tail, | |
3588 | u32 start, u32 end) | |
1da177e4 LT |
3589 | { |
3590 | struct sk_buff *skb; | |
3591 | ||
caa20d9a | 3592 | /* First, check that queue is collapsible and find |
1da177e4 LT |
3593 | * the point where collapsing can be useful. */ |
3594 | for (skb = head; skb != tail; ) { | |
3595 | /* No new bits? It is possible on ofo queue. */ | |
3596 | if (!before(start, TCP_SKB_CB(skb)->end_seq)) { | |
3597 | struct sk_buff *next = skb->next; | |
8728b834 | 3598 | __skb_unlink(skb, list); |
1da177e4 LT |
3599 | __kfree_skb(skb); |
3600 | NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED); | |
3601 | skb = next; | |
3602 | continue; | |
3603 | } | |
3604 | ||
3605 | /* The first skb to collapse is: | |
3606 | * - not SYN/FIN and | |
3607 | * - bloated or contains data before "start" or | |
3608 | * overlaps to the next one. | |
3609 | */ | |
aa8223c7 | 3610 | if (!tcp_hdr(skb)->syn && !tcp_hdr(skb)->fin && |
1da177e4 LT |
3611 | (tcp_win_from_space(skb->truesize) > skb->len || |
3612 | before(TCP_SKB_CB(skb)->seq, start) || | |
3613 | (skb->next != tail && | |
3614 | TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb->next)->seq))) | |
3615 | break; | |
3616 | ||
3617 | /* Decided to skip this, advance start seq. */ | |
3618 | start = TCP_SKB_CB(skb)->end_seq; | |
3619 | skb = skb->next; | |
3620 | } | |
aa8223c7 | 3621 | if (skb == tail || tcp_hdr(skb)->syn || tcp_hdr(skb)->fin) |
1da177e4 LT |
3622 | return; |
3623 | ||
3624 | while (before(start, end)) { | |
3625 | struct sk_buff *nskb; | |
3626 | int header = skb_headroom(skb); | |
3627 | int copy = SKB_MAX_ORDER(header, 0); | |
3628 | ||
3629 | /* Too big header? This can happen with IPv6. */ | |
3630 | if (copy < 0) | |
3631 | return; | |
3632 | if (end-start < copy) | |
3633 | copy = end-start; | |
3634 | nskb = alloc_skb(copy+header, GFP_ATOMIC); | |
3635 | if (!nskb) | |
3636 | return; | |
c51957da | 3637 | |
98e399f8 | 3638 | skb_set_mac_header(nskb, skb_mac_header(skb) - skb->head); |
9c70220b ACM |
3639 | skb_set_network_header(nskb, (skb_network_header(skb) - |
3640 | skb->head)); | |
3641 | skb_set_transport_header(nskb, (skb_transport_header(skb) - | |
3642 | skb->head)); | |
1da177e4 LT |
3643 | skb_reserve(nskb, header); |
3644 | memcpy(nskb->head, skb->head, header); | |
1da177e4 LT |
3645 | memcpy(nskb->cb, skb->cb, sizeof(skb->cb)); |
3646 | TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start; | |
8728b834 | 3647 | __skb_insert(nskb, skb->prev, skb, list); |
1da177e4 LT |
3648 | sk_stream_set_owner_r(nskb, sk); |
3649 | ||
3650 | /* Copy data, releasing collapsed skbs. */ | |
3651 | while (copy > 0) { | |
3652 | int offset = start - TCP_SKB_CB(skb)->seq; | |
3653 | int size = TCP_SKB_CB(skb)->end_seq - start; | |
3654 | ||
09a62660 | 3655 | BUG_ON(offset < 0); |
1da177e4 LT |
3656 | if (size > 0) { |
3657 | size = min(copy, size); | |
3658 | if (skb_copy_bits(skb, offset, skb_put(nskb, size), size)) | |
3659 | BUG(); | |
3660 | TCP_SKB_CB(nskb)->end_seq += size; | |
3661 | copy -= size; | |
3662 | start += size; | |
3663 | } | |
3664 | if (!before(start, TCP_SKB_CB(skb)->end_seq)) { | |
3665 | struct sk_buff *next = skb->next; | |
8728b834 | 3666 | __skb_unlink(skb, list); |
1da177e4 LT |
3667 | __kfree_skb(skb); |
3668 | NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED); | |
3669 | skb = next; | |
aa8223c7 ACM |
3670 | if (skb == tail || |
3671 | tcp_hdr(skb)->syn || | |
3672 | tcp_hdr(skb)->fin) | |
1da177e4 LT |
3673 | return; |
3674 | } | |
3675 | } | |
3676 | } | |
3677 | } | |
3678 | ||
3679 | /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs | |
3680 | * and tcp_collapse() them until all the queue is collapsed. | |
3681 | */ | |
3682 | static void tcp_collapse_ofo_queue(struct sock *sk) | |
3683 | { | |
3684 | struct tcp_sock *tp = tcp_sk(sk); | |
3685 | struct sk_buff *skb = skb_peek(&tp->out_of_order_queue); | |
3686 | struct sk_buff *head; | |
3687 | u32 start, end; | |
3688 | ||
3689 | if (skb == NULL) | |
3690 | return; | |
3691 | ||
3692 | start = TCP_SKB_CB(skb)->seq; | |
3693 | end = TCP_SKB_CB(skb)->end_seq; | |
3694 | head = skb; | |
3695 | ||
3696 | for (;;) { | |
3697 | skb = skb->next; | |
3698 | ||
3699 | /* Segment is terminated when we see gap or when | |
3700 | * we are at the end of all the queue. */ | |
3701 | if (skb == (struct sk_buff *)&tp->out_of_order_queue || | |
3702 | after(TCP_SKB_CB(skb)->seq, end) || | |
3703 | before(TCP_SKB_CB(skb)->end_seq, start)) { | |
8728b834 DM |
3704 | tcp_collapse(sk, &tp->out_of_order_queue, |
3705 | head, skb, start, end); | |
1da177e4 LT |
3706 | head = skb; |
3707 | if (skb == (struct sk_buff *)&tp->out_of_order_queue) | |
3708 | break; | |
3709 | /* Start new segment */ | |
3710 | start = TCP_SKB_CB(skb)->seq; | |
3711 | end = TCP_SKB_CB(skb)->end_seq; | |
3712 | } else { | |
3713 | if (before(TCP_SKB_CB(skb)->seq, start)) | |
3714 | start = TCP_SKB_CB(skb)->seq; | |
3715 | if (after(TCP_SKB_CB(skb)->end_seq, end)) | |
3716 | end = TCP_SKB_CB(skb)->end_seq; | |
3717 | } | |
3718 | } | |
3719 | } | |
3720 | ||
3721 | /* Reduce allocated memory if we can, trying to get | |
3722 | * the socket within its memory limits again. | |
3723 | * | |
3724 | * Return less than zero if we should start dropping frames | |
3725 | * until the socket owning process reads some of the data | |
3726 | * to stabilize the situation. | |
3727 | */ | |
3728 | static int tcp_prune_queue(struct sock *sk) | |
3729 | { | |
e905a9ed | 3730 | struct tcp_sock *tp = tcp_sk(sk); |
1da177e4 LT |
3731 | |
3732 | SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq); | |
3733 | ||
3734 | NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED); | |
3735 | ||
3736 | if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf) | |
3737 | tcp_clamp_window(sk, tp); | |
3738 | else if (tcp_memory_pressure) | |
3739 | tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss); | |
3740 | ||
3741 | tcp_collapse_ofo_queue(sk); | |
8728b834 DM |
3742 | tcp_collapse(sk, &sk->sk_receive_queue, |
3743 | sk->sk_receive_queue.next, | |
1da177e4 LT |
3744 | (struct sk_buff*)&sk->sk_receive_queue, |
3745 | tp->copied_seq, tp->rcv_nxt); | |
3746 | sk_stream_mem_reclaim(sk); | |
3747 | ||
3748 | if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) | |
3749 | return 0; | |
3750 | ||
3751 | /* Collapsing did not help, destructive actions follow. | |
3752 | * This must not ever occur. */ | |
3753 | ||
3754 | /* First, purge the out_of_order queue. */ | |
b03efcfb DM |
3755 | if (!skb_queue_empty(&tp->out_of_order_queue)) { |
3756 | NET_INC_STATS_BH(LINUX_MIB_OFOPRUNED); | |
1da177e4 LT |
3757 | __skb_queue_purge(&tp->out_of_order_queue); |
3758 | ||
3759 | /* Reset SACK state. A conforming SACK implementation will | |
3760 | * do the same at a timeout based retransmit. When a connection | |
3761 | * is in a sad state like this, we care only about integrity | |
3762 | * of the connection not performance. | |
3763 | */ | |
3764 | if (tp->rx_opt.sack_ok) | |
3765 | tcp_sack_reset(&tp->rx_opt); | |
3766 | sk_stream_mem_reclaim(sk); | |
3767 | } | |
3768 | ||
3769 | if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) | |
3770 | return 0; | |
3771 | ||
3772 | /* If we are really being abused, tell the caller to silently | |
3773 | * drop receive data on the floor. It will get retransmitted | |
3774 | * and hopefully then we'll have sufficient space. | |
3775 | */ | |
3776 | NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED); | |
3777 | ||
3778 | /* Massive buffer overcommit. */ | |
3779 | tp->pred_flags = 0; | |
3780 | return -1; | |
3781 | } | |
3782 | ||
3783 | ||
3784 | /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto. | |
3785 | * As additional protections, we do not touch cwnd in retransmission phases, | |
3786 | * and if application hit its sndbuf limit recently. | |
3787 | */ | |
3788 | void tcp_cwnd_application_limited(struct sock *sk) | |
3789 | { | |
3790 | struct tcp_sock *tp = tcp_sk(sk); | |
3791 | ||
6687e988 | 3792 | if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open && |
1da177e4 LT |
3793 | sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) { |
3794 | /* Limited by application or receiver window. */ | |
d254bcdb IJ |
3795 | u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk)); |
3796 | u32 win_used = max(tp->snd_cwnd_used, init_win); | |
1da177e4 | 3797 | if (win_used < tp->snd_cwnd) { |
6687e988 | 3798 | tp->snd_ssthresh = tcp_current_ssthresh(sk); |
1da177e4 LT |
3799 | tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1; |
3800 | } | |
3801 | tp->snd_cwnd_used = 0; | |
3802 | } | |
3803 | tp->snd_cwnd_stamp = tcp_time_stamp; | |
3804 | } | |
3805 | ||
40efc6fa | 3806 | static int tcp_should_expand_sndbuf(struct sock *sk, struct tcp_sock *tp) |
0d9901df DM |
3807 | { |
3808 | /* If the user specified a specific send buffer setting, do | |
3809 | * not modify it. | |
3810 | */ | |
3811 | if (sk->sk_userlocks & SOCK_SNDBUF_LOCK) | |
3812 | return 0; | |
3813 | ||
3814 | /* If we are under global TCP memory pressure, do not expand. */ | |
3815 | if (tcp_memory_pressure) | |
3816 | return 0; | |
3817 | ||
3818 | /* If we are under soft global TCP memory pressure, do not expand. */ | |
3819 | if (atomic_read(&tcp_memory_allocated) >= sysctl_tcp_mem[0]) | |
3820 | return 0; | |
3821 | ||
3822 | /* If we filled the congestion window, do not expand. */ | |
3823 | if (tp->packets_out >= tp->snd_cwnd) | |
3824 | return 0; | |
3825 | ||
3826 | return 1; | |
3827 | } | |
1da177e4 LT |
3828 | |
3829 | /* When incoming ACK allowed to free some skb from write_queue, | |
3830 | * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket | |
3831 | * on the exit from tcp input handler. | |
3832 | * | |
3833 | * PROBLEM: sndbuf expansion does not work well with largesend. | |
3834 | */ | |
3835 | static void tcp_new_space(struct sock *sk) | |
3836 | { | |
3837 | struct tcp_sock *tp = tcp_sk(sk); | |
3838 | ||
0d9901df | 3839 | if (tcp_should_expand_sndbuf(sk, tp)) { |
e905a9ed | 3840 | int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) + |
1da177e4 LT |
3841 | MAX_TCP_HEADER + 16 + sizeof(struct sk_buff), |
3842 | demanded = max_t(unsigned int, tp->snd_cwnd, | |
3843 | tp->reordering + 1); | |
3844 | sndmem *= 2*demanded; | |
3845 | if (sndmem > sk->sk_sndbuf) | |
3846 | sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]); | |
3847 | tp->snd_cwnd_stamp = tcp_time_stamp; | |
3848 | } | |
3849 | ||
3850 | sk->sk_write_space(sk); | |
3851 | } | |
3852 | ||
40efc6fa | 3853 | static void tcp_check_space(struct sock *sk) |
1da177e4 LT |
3854 | { |
3855 | if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) { | |
3856 | sock_reset_flag(sk, SOCK_QUEUE_SHRUNK); | |
3857 | if (sk->sk_socket && | |
3858 | test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) | |
3859 | tcp_new_space(sk); | |
3860 | } | |
3861 | } | |
3862 | ||
40efc6fa | 3863 | static inline void tcp_data_snd_check(struct sock *sk, struct tcp_sock *tp) |
1da177e4 | 3864 | { |
55c97f3e | 3865 | tcp_push_pending_frames(sk, tp); |
1da177e4 LT |
3866 | tcp_check_space(sk); |
3867 | } | |
3868 | ||
3869 | /* | |
3870 | * Check if sending an ack is needed. | |
3871 | */ | |
3872 | static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible) | |
3873 | { | |
3874 | struct tcp_sock *tp = tcp_sk(sk); | |
3875 | ||
3876 | /* More than one full frame received... */ | |
463c84b9 | 3877 | if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss |
1da177e4 LT |
3878 | /* ... and right edge of window advances far enough. |
3879 | * (tcp_recvmsg() will send ACK otherwise). Or... | |
3880 | */ | |
3881 | && __tcp_select_window(sk) >= tp->rcv_wnd) || | |
3882 | /* We ACK each frame or... */ | |
463c84b9 | 3883 | tcp_in_quickack_mode(sk) || |
1da177e4 LT |
3884 | /* We have out of order data. */ |
3885 | (ofo_possible && | |
3886 | skb_peek(&tp->out_of_order_queue))) { | |
3887 | /* Then ack it now */ | |
3888 | tcp_send_ack(sk); | |
3889 | } else { | |
3890 | /* Else, send delayed ack. */ | |
3891 | tcp_send_delayed_ack(sk); | |
3892 | } | |
3893 | } | |
3894 | ||
40efc6fa | 3895 | static inline void tcp_ack_snd_check(struct sock *sk) |
1da177e4 | 3896 | { |
463c84b9 | 3897 | if (!inet_csk_ack_scheduled(sk)) { |
1da177e4 LT |
3898 | /* We sent a data segment already. */ |
3899 | return; | |
3900 | } | |
3901 | __tcp_ack_snd_check(sk, 1); | |
3902 | } | |
3903 | ||
3904 | /* | |
3905 | * This routine is only called when we have urgent data | |
caa20d9a | 3906 | * signaled. Its the 'slow' part of tcp_urg. It could be |
1da177e4 LT |
3907 | * moved inline now as tcp_urg is only called from one |
3908 | * place. We handle URGent data wrong. We have to - as | |
3909 | * BSD still doesn't use the correction from RFC961. | |
3910 | * For 1003.1g we should support a new option TCP_STDURG to permit | |
3911 | * either form (or just set the sysctl tcp_stdurg). | |
3912 | */ | |
e905a9ed | 3913 | |
1da177e4 LT |
3914 | static void tcp_check_urg(struct sock * sk, struct tcphdr * th) |
3915 | { | |
3916 | struct tcp_sock *tp = tcp_sk(sk); | |
3917 | u32 ptr = ntohs(th->urg_ptr); | |
3918 | ||
3919 | if (ptr && !sysctl_tcp_stdurg) | |
3920 | ptr--; | |
3921 | ptr += ntohl(th->seq); | |
3922 | ||
3923 | /* Ignore urgent data that we've already seen and read. */ | |
3924 | if (after(tp->copied_seq, ptr)) | |
3925 | return; | |
3926 | ||
3927 | /* Do not replay urg ptr. | |
3928 | * | |
3929 | * NOTE: interesting situation not covered by specs. | |
3930 | * Misbehaving sender may send urg ptr, pointing to segment, | |
3931 | * which we already have in ofo queue. We are not able to fetch | |
3932 | * such data and will stay in TCP_URG_NOTYET until will be eaten | |
3933 | * by recvmsg(). Seems, we are not obliged to handle such wicked | |
3934 | * situations. But it is worth to think about possibility of some | |
3935 | * DoSes using some hypothetical application level deadlock. | |
3936 | */ | |
3937 | if (before(ptr, tp->rcv_nxt)) | |
3938 | return; | |
3939 | ||
3940 | /* Do we already have a newer (or duplicate) urgent pointer? */ | |
3941 | if (tp->urg_data && !after(ptr, tp->urg_seq)) | |
3942 | return; | |
3943 | ||
3944 | /* Tell the world about our new urgent pointer. */ | |
3945 | sk_send_sigurg(sk); | |
3946 | ||
3947 | /* We may be adding urgent data when the last byte read was | |
3948 | * urgent. To do this requires some care. We cannot just ignore | |
3949 | * tp->copied_seq since we would read the last urgent byte again | |
3950 | * as data, nor can we alter copied_seq until this data arrives | |
caa20d9a | 3951 | * or we break the semantics of SIOCATMARK (and thus sockatmark()) |
1da177e4 LT |
3952 | * |
3953 | * NOTE. Double Dutch. Rendering to plain English: author of comment | |
3954 | * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB); | |
3955 | * and expect that both A and B disappear from stream. This is _wrong_. | |
3956 | * Though this happens in BSD with high probability, this is occasional. | |
3957 | * Any application relying on this is buggy. Note also, that fix "works" | |
3958 | * only in this artificial test. Insert some normal data between A and B and we will | |
3959 | * decline of BSD again. Verdict: it is better to remove to trap | |
3960 | * buggy users. | |
3961 | */ | |
3962 | if (tp->urg_seq == tp->copied_seq && tp->urg_data && | |
3963 | !sock_flag(sk, SOCK_URGINLINE) && | |
3964 | tp->copied_seq != tp->rcv_nxt) { | |
3965 | struct sk_buff *skb = skb_peek(&sk->sk_receive_queue); | |
3966 | tp->copied_seq++; | |
3967 | if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) { | |
8728b834 | 3968 | __skb_unlink(skb, &sk->sk_receive_queue); |
1da177e4 LT |
3969 | __kfree_skb(skb); |
3970 | } | |
3971 | } | |
3972 | ||
3973 | tp->urg_data = TCP_URG_NOTYET; | |
3974 | tp->urg_seq = ptr; | |
3975 | ||
3976 | /* Disable header prediction. */ | |
3977 | tp->pred_flags = 0; | |
3978 | } | |
3979 | ||
3980 | /* This is the 'fast' part of urgent handling. */ | |
3981 | static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th) | |
3982 | { | |
3983 | struct tcp_sock *tp = tcp_sk(sk); | |
3984 | ||
3985 | /* Check if we get a new urgent pointer - normally not. */ | |
3986 | if (th->urg) | |
3987 | tcp_check_urg(sk,th); | |
3988 | ||
3989 | /* Do we wait for any urgent data? - normally not... */ | |
3990 | if (tp->urg_data == TCP_URG_NOTYET) { | |
3991 | u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) - | |
3992 | th->syn; | |
3993 | ||
e905a9ed | 3994 | /* Is the urgent pointer pointing into this packet? */ |
1da177e4 LT |
3995 | if (ptr < skb->len) { |
3996 | u8 tmp; | |
3997 | if (skb_copy_bits(skb, ptr, &tmp, 1)) | |
3998 | BUG(); | |
3999 | tp->urg_data = TCP_URG_VALID | tmp; | |
4000 | if (!sock_flag(sk, SOCK_DEAD)) | |
4001 | sk->sk_data_ready(sk, 0); | |
4002 | } | |
4003 | } | |
4004 | } | |
4005 | ||
4006 | static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen) | |
4007 | { | |
4008 | struct tcp_sock *tp = tcp_sk(sk); | |
4009 | int chunk = skb->len - hlen; | |
4010 | int err; | |
4011 | ||
4012 | local_bh_enable(); | |
60476372 | 4013 | if (skb_csum_unnecessary(skb)) |
1da177e4 LT |
4014 | err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk); |
4015 | else | |
4016 | err = skb_copy_and_csum_datagram_iovec(skb, hlen, | |
4017 | tp->ucopy.iov); | |
4018 | ||
4019 | if (!err) { | |
4020 | tp->ucopy.len -= chunk; | |
4021 | tp->copied_seq += chunk; | |
4022 | tcp_rcv_space_adjust(sk); | |
4023 | } | |
4024 | ||
4025 | local_bh_disable(); | |
4026 | return err; | |
4027 | } | |
4028 | ||
b51655b9 | 4029 | static __sum16 __tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb) |
1da177e4 | 4030 | { |
b51655b9 | 4031 | __sum16 result; |
1da177e4 LT |
4032 | |
4033 | if (sock_owned_by_user(sk)) { | |
4034 | local_bh_enable(); | |
4035 | result = __tcp_checksum_complete(skb); | |
4036 | local_bh_disable(); | |
4037 | } else { | |
4038 | result = __tcp_checksum_complete(skb); | |
4039 | } | |
4040 | return result; | |
4041 | } | |
4042 | ||
40efc6fa | 4043 | static inline int tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb) |
1da177e4 | 4044 | { |
60476372 | 4045 | return !skb_csum_unnecessary(skb) && |
1da177e4 LT |
4046 | __tcp_checksum_complete_user(sk, skb); |
4047 | } | |
4048 | ||
1a2449a8 CL |
4049 | #ifdef CONFIG_NET_DMA |
4050 | static int tcp_dma_try_early_copy(struct sock *sk, struct sk_buff *skb, int hlen) | |
4051 | { | |
4052 | struct tcp_sock *tp = tcp_sk(sk); | |
4053 | int chunk = skb->len - hlen; | |
4054 | int dma_cookie; | |
4055 | int copied_early = 0; | |
4056 | ||
4057 | if (tp->ucopy.wakeup) | |
e905a9ed | 4058 | return 0; |
1a2449a8 CL |
4059 | |
4060 | if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list) | |
4061 | tp->ucopy.dma_chan = get_softnet_dma(); | |
4062 | ||
60476372 | 4063 | if (tp->ucopy.dma_chan && skb_csum_unnecessary(skb)) { |
1a2449a8 CL |
4064 | |
4065 | dma_cookie = dma_skb_copy_datagram_iovec(tp->ucopy.dma_chan, | |
4066 | skb, hlen, tp->ucopy.iov, chunk, tp->ucopy.pinned_list); | |
4067 | ||
4068 | if (dma_cookie < 0) | |
4069 | goto out; | |
4070 | ||
4071 | tp->ucopy.dma_cookie = dma_cookie; | |
4072 | copied_early = 1; | |
4073 | ||
4074 | tp->ucopy.len -= chunk; | |
4075 | tp->copied_seq += chunk; | |
4076 | tcp_rcv_space_adjust(sk); | |
4077 | ||
4078 | if ((tp->ucopy.len == 0) || | |
aa8223c7 | 4079 | (tcp_flag_word(tcp_hdr(skb)) & TCP_FLAG_PSH) || |
1a2449a8 CL |
4080 | (atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1))) { |
4081 | tp->ucopy.wakeup = 1; | |
4082 | sk->sk_data_ready(sk, 0); | |
4083 | } | |
4084 | } else if (chunk > 0) { | |
4085 | tp->ucopy.wakeup = 1; | |
4086 | sk->sk_data_ready(sk, 0); | |
4087 | } | |
4088 | out: | |
4089 | return copied_early; | |
4090 | } | |
4091 | #endif /* CONFIG_NET_DMA */ | |
4092 | ||
1da177e4 | 4093 | /* |
e905a9ed | 4094 | * TCP receive function for the ESTABLISHED state. |
1da177e4 | 4095 | * |
e905a9ed | 4096 | * It is split into a fast path and a slow path. The fast path is |
1da177e4 LT |
4097 | * disabled when: |
4098 | * - A zero window was announced from us - zero window probing | |
e905a9ed | 4099 | * is only handled properly in the slow path. |
1da177e4 LT |
4100 | * - Out of order segments arrived. |
4101 | * - Urgent data is expected. | |
4102 | * - There is no buffer space left | |
4103 | * - Unexpected TCP flags/window values/header lengths are received | |
e905a9ed | 4104 | * (detected by checking the TCP header against pred_flags) |
1da177e4 LT |
4105 | * - Data is sent in both directions. Fast path only supports pure senders |
4106 | * or pure receivers (this means either the sequence number or the ack | |
4107 | * value must stay constant) | |
4108 | * - Unexpected TCP option. | |
4109 | * | |
e905a9ed | 4110 | * When these conditions are not satisfied it drops into a standard |
1da177e4 LT |
4111 | * receive procedure patterned after RFC793 to handle all cases. |
4112 | * The first three cases are guaranteed by proper pred_flags setting, | |
e905a9ed | 4113 | * the rest is checked inline. Fast processing is turned on in |
1da177e4 LT |
4114 | * tcp_data_queue when everything is OK. |
4115 | */ | |
4116 | int tcp_rcv_established(struct sock *sk, struct sk_buff *skb, | |
4117 | struct tcphdr *th, unsigned len) | |
4118 | { | |
4119 | struct tcp_sock *tp = tcp_sk(sk); | |
4120 | ||
4121 | /* | |
4122 | * Header prediction. | |
e905a9ed | 4123 | * The code loosely follows the one in the famous |
1da177e4 | 4124 | * "30 instruction TCP receive" Van Jacobson mail. |
e905a9ed YH |
4125 | * |
4126 | * Van's trick is to deposit buffers into socket queue | |
1da177e4 LT |
4127 | * on a device interrupt, to call tcp_recv function |
4128 | * on the receive process context and checksum and copy | |
4129 | * the buffer to user space. smart... | |
4130 | * | |
e905a9ed | 4131 | * Our current scheme is not silly either but we take the |
1da177e4 LT |
4132 | * extra cost of the net_bh soft interrupt processing... |
4133 | * We do checksum and copy also but from device to kernel. | |
4134 | */ | |
4135 | ||
4136 | tp->rx_opt.saw_tstamp = 0; | |
4137 | ||
4138 | /* pred_flags is 0xS?10 << 16 + snd_wnd | |
caa20d9a | 4139 | * if header_prediction is to be made |
1da177e4 LT |
4140 | * 'S' will always be tp->tcp_header_len >> 2 |
4141 | * '?' will be 0 for the fast path, otherwise pred_flags is 0 to | |
e905a9ed | 4142 | * turn it off (when there are holes in the receive |
1da177e4 LT |
4143 | * space for instance) |
4144 | * PSH flag is ignored. | |
4145 | */ | |
4146 | ||
4147 | if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags && | |
4148 | TCP_SKB_CB(skb)->seq == tp->rcv_nxt) { | |
4149 | int tcp_header_len = tp->tcp_header_len; | |
4150 | ||
4151 | /* Timestamp header prediction: tcp_header_len | |
4152 | * is automatically equal to th->doff*4 due to pred_flags | |
4153 | * match. | |
4154 | */ | |
4155 | ||
4156 | /* Check timestamp */ | |
4157 | if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) { | |
4f3608b7 | 4158 | __be32 *ptr = (__be32 *)(th + 1); |
1da177e4 LT |
4159 | |
4160 | /* No? Slow path! */ | |
4f3608b7 | 4161 | if (*ptr != htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
1da177e4 LT |
4162 | | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) |
4163 | goto slow_path; | |
4164 | ||
4165 | tp->rx_opt.saw_tstamp = 1; | |
e905a9ed | 4166 | ++ptr; |
1da177e4 LT |
4167 | tp->rx_opt.rcv_tsval = ntohl(*ptr); |
4168 | ++ptr; | |
4169 | tp->rx_opt.rcv_tsecr = ntohl(*ptr); | |
4170 | ||
4171 | /* If PAWS failed, check it more carefully in slow path */ | |
4172 | if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0) | |
4173 | goto slow_path; | |
4174 | ||
4175 | /* DO NOT update ts_recent here, if checksum fails | |
4176 | * and timestamp was corrupted part, it will result | |
4177 | * in a hung connection since we will drop all | |
4178 | * future packets due to the PAWS test. | |
4179 | */ | |
4180 | } | |
4181 | ||
4182 | if (len <= tcp_header_len) { | |
4183 | /* Bulk data transfer: sender */ | |
4184 | if (len == tcp_header_len) { | |
4185 | /* Predicted packet is in window by definition. | |
4186 | * seq == rcv_nxt and rcv_wup <= rcv_nxt. | |
4187 | * Hence, check seq<=rcv_wup reduces to: | |
4188 | */ | |
4189 | if (tcp_header_len == | |
4190 | (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && | |
4191 | tp->rcv_nxt == tp->rcv_wup) | |
4192 | tcp_store_ts_recent(tp); | |
4193 | ||
1da177e4 LT |
4194 | /* We know that such packets are checksummed |
4195 | * on entry. | |
4196 | */ | |
4197 | tcp_ack(sk, skb, 0); | |
e905a9ed | 4198 | __kfree_skb(skb); |
55c97f3e | 4199 | tcp_data_snd_check(sk, tp); |
1da177e4 LT |
4200 | return 0; |
4201 | } else { /* Header too small */ | |
4202 | TCP_INC_STATS_BH(TCP_MIB_INERRS); | |
4203 | goto discard; | |
4204 | } | |
4205 | } else { | |
4206 | int eaten = 0; | |
1a2449a8 | 4207 | int copied_early = 0; |
1da177e4 | 4208 | |
1a2449a8 CL |
4209 | if (tp->copied_seq == tp->rcv_nxt && |
4210 | len - tcp_header_len <= tp->ucopy.len) { | |
4211 | #ifdef CONFIG_NET_DMA | |
4212 | if (tcp_dma_try_early_copy(sk, skb, tcp_header_len)) { | |
4213 | copied_early = 1; | |
4214 | eaten = 1; | |
4215 | } | |
4216 | #endif | |
4217 | if (tp->ucopy.task == current && sock_owned_by_user(sk) && !copied_early) { | |
4218 | __set_current_state(TASK_RUNNING); | |
1da177e4 | 4219 | |
1a2449a8 CL |
4220 | if (!tcp_copy_to_iovec(sk, skb, tcp_header_len)) |
4221 | eaten = 1; | |
4222 | } | |
4223 | if (eaten) { | |
1da177e4 LT |
4224 | /* Predicted packet is in window by definition. |
4225 | * seq == rcv_nxt and rcv_wup <= rcv_nxt. | |
4226 | * Hence, check seq<=rcv_wup reduces to: | |
4227 | */ | |
4228 | if (tcp_header_len == | |
4229 | (sizeof(struct tcphdr) + | |
4230 | TCPOLEN_TSTAMP_ALIGNED) && | |
4231 | tp->rcv_nxt == tp->rcv_wup) | |
4232 | tcp_store_ts_recent(tp); | |
4233 | ||
463c84b9 | 4234 | tcp_rcv_rtt_measure_ts(sk, skb); |
1da177e4 LT |
4235 | |
4236 | __skb_pull(skb, tcp_header_len); | |
4237 | tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; | |
4238 | NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER); | |
1da177e4 | 4239 | } |
1a2449a8 CL |
4240 | if (copied_early) |
4241 | tcp_cleanup_rbuf(sk, skb->len); | |
1da177e4 LT |
4242 | } |
4243 | if (!eaten) { | |
4244 | if (tcp_checksum_complete_user(sk, skb)) | |
4245 | goto csum_error; | |
4246 | ||
4247 | /* Predicted packet is in window by definition. | |
4248 | * seq == rcv_nxt and rcv_wup <= rcv_nxt. | |
4249 | * Hence, check seq<=rcv_wup reduces to: | |
4250 | */ | |
4251 | if (tcp_header_len == | |
4252 | (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && | |
4253 | tp->rcv_nxt == tp->rcv_wup) | |
4254 | tcp_store_ts_recent(tp); | |
4255 | ||
463c84b9 | 4256 | tcp_rcv_rtt_measure_ts(sk, skb); |
1da177e4 LT |
4257 | |
4258 | if ((int)skb->truesize > sk->sk_forward_alloc) | |
4259 | goto step5; | |
4260 | ||
4261 | NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS); | |
4262 | ||
4263 | /* Bulk data transfer: receiver */ | |
4264 | __skb_pull(skb,tcp_header_len); | |
4265 | __skb_queue_tail(&sk->sk_receive_queue, skb); | |
4266 | sk_stream_set_owner_r(skb, sk); | |
4267 | tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; | |
4268 | } | |
4269 | ||
4270 | tcp_event_data_recv(sk, tp, skb); | |
4271 | ||
4272 | if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) { | |
4273 | /* Well, only one small jumplet in fast path... */ | |
4274 | tcp_ack(sk, skb, FLAG_DATA); | |
55c97f3e | 4275 | tcp_data_snd_check(sk, tp); |
463c84b9 | 4276 | if (!inet_csk_ack_scheduled(sk)) |
1da177e4 LT |
4277 | goto no_ack; |
4278 | } | |
4279 | ||
31432412 | 4280 | __tcp_ack_snd_check(sk, 0); |
1da177e4 | 4281 | no_ack: |
1a2449a8 CL |
4282 | #ifdef CONFIG_NET_DMA |
4283 | if (copied_early) | |
4284 | __skb_queue_tail(&sk->sk_async_wait_queue, skb); | |
4285 | else | |
4286 | #endif | |
1da177e4 LT |
4287 | if (eaten) |
4288 | __kfree_skb(skb); | |
4289 | else | |
4290 | sk->sk_data_ready(sk, 0); | |
4291 | return 0; | |
4292 | } | |
4293 | } | |
4294 | ||
4295 | slow_path: | |
4296 | if (len < (th->doff<<2) || tcp_checksum_complete_user(sk, skb)) | |
4297 | goto csum_error; | |
4298 | ||
4299 | /* | |
4300 | * RFC1323: H1. Apply PAWS check first. | |
4301 | */ | |
4302 | if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp && | |
463c84b9 | 4303 | tcp_paws_discard(sk, skb)) { |
1da177e4 LT |
4304 | if (!th->rst) { |
4305 | NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED); | |
4306 | tcp_send_dupack(sk, skb); | |
4307 | goto discard; | |
4308 | } | |
4309 | /* Resets are accepted even if PAWS failed. | |
4310 | ||
4311 | ts_recent update must be made after we are sure | |
4312 | that the packet is in window. | |
4313 | */ | |
4314 | } | |
4315 | ||
4316 | /* | |
4317 | * Standard slow path. | |
4318 | */ | |
4319 | ||
4320 | if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) { | |
4321 | /* RFC793, page 37: "In all states except SYN-SENT, all reset | |
4322 | * (RST) segments are validated by checking their SEQ-fields." | |
4323 | * And page 69: "If an incoming segment is not acceptable, | |
4324 | * an acknowledgment should be sent in reply (unless the RST bit | |
4325 | * is set, if so drop the segment and return)". | |
4326 | */ | |
4327 | if (!th->rst) | |
4328 | tcp_send_dupack(sk, skb); | |
4329 | goto discard; | |
4330 | } | |
4331 | ||
2de979bd | 4332 | if (th->rst) { |
1da177e4 LT |
4333 | tcp_reset(sk); |
4334 | goto discard; | |
4335 | } | |
4336 | ||
4337 | tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); | |
4338 | ||
4339 | if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { | |
4340 | TCP_INC_STATS_BH(TCP_MIB_INERRS); | |
4341 | NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN); | |
4342 | tcp_reset(sk); | |
4343 | return 1; | |
4344 | } | |
4345 | ||
4346 | step5: | |
2de979bd | 4347 | if (th->ack) |
1da177e4 LT |
4348 | tcp_ack(sk, skb, FLAG_SLOWPATH); |
4349 | ||
463c84b9 | 4350 | tcp_rcv_rtt_measure_ts(sk, skb); |
1da177e4 LT |
4351 | |
4352 | /* Process urgent data. */ | |
4353 | tcp_urg(sk, skb, th); | |
4354 | ||
4355 | /* step 7: process the segment text */ | |
4356 | tcp_data_queue(sk, skb); | |
4357 | ||
55c97f3e | 4358 | tcp_data_snd_check(sk, tp); |
1da177e4 LT |
4359 | tcp_ack_snd_check(sk); |
4360 | return 0; | |
4361 | ||
4362 | csum_error: | |
4363 | TCP_INC_STATS_BH(TCP_MIB_INERRS); | |
4364 | ||
4365 | discard: | |
4366 | __kfree_skb(skb); | |
4367 | return 0; | |
4368 | } | |
4369 | ||
4370 | static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, | |
4371 | struct tcphdr *th, unsigned len) | |
4372 | { | |
4373 | struct tcp_sock *tp = tcp_sk(sk); | |
d83d8461 | 4374 | struct inet_connection_sock *icsk = inet_csk(sk); |
1da177e4 LT |
4375 | int saved_clamp = tp->rx_opt.mss_clamp; |
4376 | ||
4377 | tcp_parse_options(skb, &tp->rx_opt, 0); | |
4378 | ||
4379 | if (th->ack) { | |
4380 | /* rfc793: | |
4381 | * "If the state is SYN-SENT then | |
4382 | * first check the ACK bit | |
4383 | * If the ACK bit is set | |
4384 | * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send | |
4385 | * a reset (unless the RST bit is set, if so drop | |
4386 | * the segment and return)" | |
4387 | * | |
4388 | * We do not send data with SYN, so that RFC-correct | |
4389 | * test reduces to: | |
4390 | */ | |
4391 | if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt) | |
4392 | goto reset_and_undo; | |
4393 | ||
4394 | if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && | |
4395 | !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp, | |
4396 | tcp_time_stamp)) { | |
4397 | NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED); | |
4398 | goto reset_and_undo; | |
4399 | } | |
4400 | ||
4401 | /* Now ACK is acceptable. | |
4402 | * | |
4403 | * "If the RST bit is set | |
4404 | * If the ACK was acceptable then signal the user "error: | |
4405 | * connection reset", drop the segment, enter CLOSED state, | |
4406 | * delete TCB, and return." | |
4407 | */ | |
4408 | ||
4409 | if (th->rst) { | |
4410 | tcp_reset(sk); | |
4411 | goto discard; | |
4412 | } | |
4413 | ||
4414 | /* rfc793: | |
4415 | * "fifth, if neither of the SYN or RST bits is set then | |
4416 | * drop the segment and return." | |
4417 | * | |
4418 | * See note below! | |
4419 | * --ANK(990513) | |
4420 | */ | |
4421 | if (!th->syn) | |
4422 | goto discard_and_undo; | |
4423 | ||
4424 | /* rfc793: | |
4425 | * "If the SYN bit is on ... | |
4426 | * are acceptable then ... | |
4427 | * (our SYN has been ACKed), change the connection | |
4428 | * state to ESTABLISHED..." | |
4429 | */ | |
4430 | ||
4431 | TCP_ECN_rcv_synack(tp, th); | |
1da177e4 LT |
4432 | |
4433 | tp->snd_wl1 = TCP_SKB_CB(skb)->seq; | |
4434 | tcp_ack(sk, skb, FLAG_SLOWPATH); | |
4435 | ||
4436 | /* Ok.. it's good. Set up sequence numbers and | |
4437 | * move to established. | |
4438 | */ | |
4439 | tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; | |
4440 | tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; | |
4441 | ||
4442 | /* RFC1323: The window in SYN & SYN/ACK segments is | |
4443 | * never scaled. | |
4444 | */ | |
4445 | tp->snd_wnd = ntohs(th->window); | |
4446 | tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, TCP_SKB_CB(skb)->seq); | |
4447 | ||
4448 | if (!tp->rx_opt.wscale_ok) { | |
4449 | tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0; | |
4450 | tp->window_clamp = min(tp->window_clamp, 65535U); | |
4451 | } | |
4452 | ||
4453 | if (tp->rx_opt.saw_tstamp) { | |
4454 | tp->rx_opt.tstamp_ok = 1; | |
4455 | tp->tcp_header_len = | |
4456 | sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; | |
4457 | tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; | |
4458 | tcp_store_ts_recent(tp); | |
4459 | } else { | |
4460 | tp->tcp_header_len = sizeof(struct tcphdr); | |
4461 | } | |
4462 | ||
4463 | if (tp->rx_opt.sack_ok && sysctl_tcp_fack) | |
4464 | tp->rx_opt.sack_ok |= 2; | |
4465 | ||
5d424d5a | 4466 | tcp_mtup_init(sk); |
d83d8461 | 4467 | tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); |
1da177e4 LT |
4468 | tcp_initialize_rcv_mss(sk); |
4469 | ||
4470 | /* Remember, tcp_poll() does not lock socket! | |
4471 | * Change state from SYN-SENT only after copied_seq | |
4472 | * is initialized. */ | |
4473 | tp->copied_seq = tp->rcv_nxt; | |
e16aa207 | 4474 | smp_mb(); |
1da177e4 LT |
4475 | tcp_set_state(sk, TCP_ESTABLISHED); |
4476 | ||
6b877699 VY |
4477 | security_inet_conn_established(sk, skb); |
4478 | ||
1da177e4 | 4479 | /* Make sure socket is routed, for correct metrics. */ |
8292a17a | 4480 | icsk->icsk_af_ops->rebuild_header(sk); |
1da177e4 LT |
4481 | |
4482 | tcp_init_metrics(sk); | |
4483 | ||
6687e988 | 4484 | tcp_init_congestion_control(sk); |
317a76f9 | 4485 | |
1da177e4 LT |
4486 | /* Prevent spurious tcp_cwnd_restart() on first data |
4487 | * packet. | |
4488 | */ | |
4489 | tp->lsndtime = tcp_time_stamp; | |
4490 | ||
4491 | tcp_init_buffer_space(sk); | |
4492 | ||
4493 | if (sock_flag(sk, SOCK_KEEPOPEN)) | |
463c84b9 | 4494 | inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp)); |
1da177e4 LT |
4495 | |
4496 | if (!tp->rx_opt.snd_wscale) | |
4497 | __tcp_fast_path_on(tp, tp->snd_wnd); | |
4498 | else | |
4499 | tp->pred_flags = 0; | |
4500 | ||
4501 | if (!sock_flag(sk, SOCK_DEAD)) { | |
4502 | sk->sk_state_change(sk); | |
4503 | sk_wake_async(sk, 0, POLL_OUT); | |
4504 | } | |
4505 | ||
295f7324 ACM |
4506 | if (sk->sk_write_pending || |
4507 | icsk->icsk_accept_queue.rskq_defer_accept || | |
4508 | icsk->icsk_ack.pingpong) { | |
1da177e4 LT |
4509 | /* Save one ACK. Data will be ready after |
4510 | * several ticks, if write_pending is set. | |
4511 | * | |
4512 | * It may be deleted, but with this feature tcpdumps | |
4513 | * look so _wonderfully_ clever, that I was not able | |
4514 | * to stand against the temptation 8) --ANK | |
4515 | */ | |
463c84b9 | 4516 | inet_csk_schedule_ack(sk); |
295f7324 ACM |
4517 | icsk->icsk_ack.lrcvtime = tcp_time_stamp; |
4518 | icsk->icsk_ack.ato = TCP_ATO_MIN; | |
463c84b9 ACM |
4519 | tcp_incr_quickack(sk); |
4520 | tcp_enter_quickack_mode(sk); | |
3f421baa ACM |
4521 | inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, |
4522 | TCP_DELACK_MAX, TCP_RTO_MAX); | |
1da177e4 LT |
4523 | |
4524 | discard: | |
4525 | __kfree_skb(skb); | |
4526 | return 0; | |
4527 | } else { | |
4528 | tcp_send_ack(sk); | |
4529 | } | |
4530 | return -1; | |
4531 | } | |
4532 | ||
4533 | /* No ACK in the segment */ | |
4534 | ||
4535 | if (th->rst) { | |
4536 | /* rfc793: | |
4537 | * "If the RST bit is set | |
4538 | * | |
4539 | * Otherwise (no ACK) drop the segment and return." | |
4540 | */ | |
4541 | ||
4542 | goto discard_and_undo; | |
4543 | } | |
4544 | ||
4545 | /* PAWS check. */ | |
4546 | if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && tcp_paws_check(&tp->rx_opt, 0)) | |
4547 | goto discard_and_undo; | |
4548 | ||
4549 | if (th->syn) { | |
4550 | /* We see SYN without ACK. It is attempt of | |
4551 | * simultaneous connect with crossed SYNs. | |
4552 | * Particularly, it can be connect to self. | |
4553 | */ | |
4554 | tcp_set_state(sk, TCP_SYN_RECV); | |
4555 | ||
4556 | if (tp->rx_opt.saw_tstamp) { | |
4557 | tp->rx_opt.tstamp_ok = 1; | |
4558 | tcp_store_ts_recent(tp); | |
4559 | tp->tcp_header_len = | |
4560 | sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; | |
4561 | } else { | |
4562 | tp->tcp_header_len = sizeof(struct tcphdr); | |
4563 | } | |
4564 | ||
4565 | tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; | |
4566 | tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; | |
4567 | ||
4568 | /* RFC1323: The window in SYN & SYN/ACK segments is | |
4569 | * never scaled. | |
4570 | */ | |
4571 | tp->snd_wnd = ntohs(th->window); | |
4572 | tp->snd_wl1 = TCP_SKB_CB(skb)->seq; | |
4573 | tp->max_window = tp->snd_wnd; | |
4574 | ||
4575 | TCP_ECN_rcv_syn(tp, th); | |
1da177e4 | 4576 | |
5d424d5a | 4577 | tcp_mtup_init(sk); |
d83d8461 | 4578 | tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); |
1da177e4 LT |
4579 | tcp_initialize_rcv_mss(sk); |
4580 | ||
4581 | ||
4582 | tcp_send_synack(sk); | |
4583 | #if 0 | |
4584 | /* Note, we could accept data and URG from this segment. | |
4585 | * There are no obstacles to make this. | |
4586 | * | |
4587 | * However, if we ignore data in ACKless segments sometimes, | |
4588 | * we have no reasons to accept it sometimes. | |
4589 | * Also, seems the code doing it in step6 of tcp_rcv_state_process | |
4590 | * is not flawless. So, discard packet for sanity. | |
4591 | * Uncomment this return to process the data. | |
4592 | */ | |
4593 | return -1; | |
4594 | #else | |
4595 | goto discard; | |
4596 | #endif | |
4597 | } | |
4598 | /* "fifth, if neither of the SYN or RST bits is set then | |
4599 | * drop the segment and return." | |
4600 | */ | |
4601 | ||
4602 | discard_and_undo: | |
4603 | tcp_clear_options(&tp->rx_opt); | |
4604 | tp->rx_opt.mss_clamp = saved_clamp; | |
4605 | goto discard; | |
4606 | ||
4607 | reset_and_undo: | |
4608 | tcp_clear_options(&tp->rx_opt); | |
4609 | tp->rx_opt.mss_clamp = saved_clamp; | |
4610 | return 1; | |
4611 | } | |
4612 | ||
4613 | ||
4614 | /* | |
4615 | * This function implements the receiving procedure of RFC 793 for | |
e905a9ed | 4616 | * all states except ESTABLISHED and TIME_WAIT. |
1da177e4 LT |
4617 | * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be |
4618 | * address independent. | |
4619 | */ | |
e905a9ed | 4620 | |
1da177e4 LT |
4621 | int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb, |
4622 | struct tcphdr *th, unsigned len) | |
4623 | { | |
4624 | struct tcp_sock *tp = tcp_sk(sk); | |
8292a17a | 4625 | struct inet_connection_sock *icsk = inet_csk(sk); |
1da177e4 LT |
4626 | int queued = 0; |
4627 | ||
4628 | tp->rx_opt.saw_tstamp = 0; | |
4629 | ||
4630 | switch (sk->sk_state) { | |
4631 | case TCP_CLOSE: | |
4632 | goto discard; | |
4633 | ||
4634 | case TCP_LISTEN: | |
2de979bd | 4635 | if (th->ack) |
1da177e4 LT |
4636 | return 1; |
4637 | ||
2de979bd | 4638 | if (th->rst) |
1da177e4 LT |
4639 | goto discard; |
4640 | ||
2de979bd | 4641 | if (th->syn) { |
8292a17a | 4642 | if (icsk->icsk_af_ops->conn_request(sk, skb) < 0) |
1da177e4 LT |
4643 | return 1; |
4644 | ||
e905a9ed YH |
4645 | /* Now we have several options: In theory there is |
4646 | * nothing else in the frame. KA9Q has an option to | |
1da177e4 | 4647 | * send data with the syn, BSD accepts data with the |
e905a9ed YH |
4648 | * syn up to the [to be] advertised window and |
4649 | * Solaris 2.1 gives you a protocol error. For now | |
4650 | * we just ignore it, that fits the spec precisely | |
1da177e4 LT |
4651 | * and avoids incompatibilities. It would be nice in |
4652 | * future to drop through and process the data. | |
4653 | * | |
e905a9ed | 4654 | * Now that TTCP is starting to be used we ought to |
1da177e4 LT |
4655 | * queue this data. |
4656 | * But, this leaves one open to an easy denial of | |
e905a9ed | 4657 | * service attack, and SYN cookies can't defend |
1da177e4 | 4658 | * against this problem. So, we drop the data |
fb7e2399 MN |
4659 | * in the interest of security over speed unless |
4660 | * it's still in use. | |
1da177e4 | 4661 | */ |
fb7e2399 MN |
4662 | kfree_skb(skb); |
4663 | return 0; | |
1da177e4 LT |
4664 | } |
4665 | goto discard; | |
4666 | ||
4667 | case TCP_SYN_SENT: | |
1da177e4 LT |
4668 | queued = tcp_rcv_synsent_state_process(sk, skb, th, len); |
4669 | if (queued >= 0) | |
4670 | return queued; | |
4671 | ||
4672 | /* Do step6 onward by hand. */ | |
4673 | tcp_urg(sk, skb, th); | |
4674 | __kfree_skb(skb); | |
55c97f3e | 4675 | tcp_data_snd_check(sk, tp); |
1da177e4 LT |
4676 | return 0; |
4677 | } | |
4678 | ||
4679 | if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp && | |
463c84b9 | 4680 | tcp_paws_discard(sk, skb)) { |
1da177e4 LT |
4681 | if (!th->rst) { |
4682 | NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED); | |
4683 | tcp_send_dupack(sk, skb); | |
4684 | goto discard; | |
4685 | } | |
4686 | /* Reset is accepted even if it did not pass PAWS. */ | |
4687 | } | |
4688 | ||
4689 | /* step 1: check sequence number */ | |
4690 | if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) { | |
4691 | if (!th->rst) | |
4692 | tcp_send_dupack(sk, skb); | |
4693 | goto discard; | |
4694 | } | |
4695 | ||
4696 | /* step 2: check RST bit */ | |
2de979bd | 4697 | if (th->rst) { |
1da177e4 LT |
4698 | tcp_reset(sk); |
4699 | goto discard; | |
4700 | } | |
4701 | ||
4702 | tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); | |
4703 | ||
4704 | /* step 3: check security and precedence [ignored] */ | |
4705 | ||
4706 | /* step 4: | |
4707 | * | |
4708 | * Check for a SYN in window. | |
4709 | */ | |
4710 | if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { | |
4711 | NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN); | |
4712 | tcp_reset(sk); | |
4713 | return 1; | |
4714 | } | |
4715 | ||
4716 | /* step 5: check the ACK field */ | |
4717 | if (th->ack) { | |
4718 | int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH); | |
4719 | ||
2de979bd | 4720 | switch (sk->sk_state) { |
1da177e4 LT |
4721 | case TCP_SYN_RECV: |
4722 | if (acceptable) { | |
4723 | tp->copied_seq = tp->rcv_nxt; | |
e16aa207 | 4724 | smp_mb(); |
1da177e4 LT |
4725 | tcp_set_state(sk, TCP_ESTABLISHED); |
4726 | sk->sk_state_change(sk); | |
4727 | ||
4728 | /* Note, that this wakeup is only for marginal | |
4729 | * crossed SYN case. Passively open sockets | |
4730 | * are not waked up, because sk->sk_sleep == | |
4731 | * NULL and sk->sk_socket == NULL. | |
4732 | */ | |
4733 | if (sk->sk_socket) { | |
4734 | sk_wake_async(sk,0,POLL_OUT); | |
4735 | } | |
4736 | ||
4737 | tp->snd_una = TCP_SKB_CB(skb)->ack_seq; | |
4738 | tp->snd_wnd = ntohs(th->window) << | |
4739 | tp->rx_opt.snd_wscale; | |
4740 | tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, | |
4741 | TCP_SKB_CB(skb)->seq); | |
4742 | ||
4743 | /* tcp_ack considers this ACK as duplicate | |
4744 | * and does not calculate rtt. | |
4745 | * Fix it at least with timestamps. | |
4746 | */ | |
4747 | if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && | |
4748 | !tp->srtt) | |
2d2abbab | 4749 | tcp_ack_saw_tstamp(sk, 0); |
1da177e4 LT |
4750 | |
4751 | if (tp->rx_opt.tstamp_ok) | |
4752 | tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; | |
4753 | ||
4754 | /* Make sure socket is routed, for | |
4755 | * correct metrics. | |
4756 | */ | |
8292a17a | 4757 | icsk->icsk_af_ops->rebuild_header(sk); |
1da177e4 LT |
4758 | |
4759 | tcp_init_metrics(sk); | |
4760 | ||
6687e988 | 4761 | tcp_init_congestion_control(sk); |
317a76f9 | 4762 | |
1da177e4 LT |
4763 | /* Prevent spurious tcp_cwnd_restart() on |
4764 | * first data packet. | |
4765 | */ | |
4766 | tp->lsndtime = tcp_time_stamp; | |
4767 | ||
5d424d5a | 4768 | tcp_mtup_init(sk); |
1da177e4 LT |
4769 | tcp_initialize_rcv_mss(sk); |
4770 | tcp_init_buffer_space(sk); | |
4771 | tcp_fast_path_on(tp); | |
4772 | } else { | |
4773 | return 1; | |
4774 | } | |
4775 | break; | |
4776 | ||
4777 | case TCP_FIN_WAIT1: | |
4778 | if (tp->snd_una == tp->write_seq) { | |
4779 | tcp_set_state(sk, TCP_FIN_WAIT2); | |
4780 | sk->sk_shutdown |= SEND_SHUTDOWN; | |
4781 | dst_confirm(sk->sk_dst_cache); | |
4782 | ||
4783 | if (!sock_flag(sk, SOCK_DEAD)) | |
4784 | /* Wake up lingering close() */ | |
4785 | sk->sk_state_change(sk); | |
4786 | else { | |
4787 | int tmo; | |
4788 | ||
4789 | if (tp->linger2 < 0 || | |
4790 | (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && | |
4791 | after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) { | |
4792 | tcp_done(sk); | |
4793 | NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA); | |
4794 | return 1; | |
4795 | } | |
4796 | ||
463c84b9 | 4797 | tmo = tcp_fin_time(sk); |
1da177e4 | 4798 | if (tmo > TCP_TIMEWAIT_LEN) { |
463c84b9 | 4799 | inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN); |
1da177e4 LT |
4800 | } else if (th->fin || sock_owned_by_user(sk)) { |
4801 | /* Bad case. We could lose such FIN otherwise. | |
4802 | * It is not a big problem, but it looks confusing | |
4803 | * and not so rare event. We still can lose it now, | |
4804 | * if it spins in bh_lock_sock(), but it is really | |
4805 | * marginal case. | |
4806 | */ | |
463c84b9 | 4807 | inet_csk_reset_keepalive_timer(sk, tmo); |
1da177e4 LT |
4808 | } else { |
4809 | tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); | |
4810 | goto discard; | |
4811 | } | |
4812 | } | |
4813 | } | |
4814 | break; | |
4815 | ||
4816 | case TCP_CLOSING: | |
4817 | if (tp->snd_una == tp->write_seq) { | |
4818 | tcp_time_wait(sk, TCP_TIME_WAIT, 0); | |
4819 | goto discard; | |
4820 | } | |
4821 | break; | |
4822 | ||
4823 | case TCP_LAST_ACK: | |
4824 | if (tp->snd_una == tp->write_seq) { | |
4825 | tcp_update_metrics(sk); | |
4826 | tcp_done(sk); | |
4827 | goto discard; | |
4828 | } | |
4829 | break; | |
4830 | } | |
4831 | } else | |
4832 | goto discard; | |
4833 | ||
4834 | /* step 6: check the URG bit */ | |
4835 | tcp_urg(sk, skb, th); | |
4836 | ||
4837 | /* step 7: process the segment text */ | |
4838 | switch (sk->sk_state) { | |
4839 | case TCP_CLOSE_WAIT: | |
4840 | case TCP_CLOSING: | |
4841 | case TCP_LAST_ACK: | |
4842 | if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) | |
4843 | break; | |
4844 | case TCP_FIN_WAIT1: | |
4845 | case TCP_FIN_WAIT2: | |
4846 | /* RFC 793 says to queue data in these states, | |
e905a9ed | 4847 | * RFC 1122 says we MUST send a reset. |
1da177e4 LT |
4848 | * BSD 4.4 also does reset. |
4849 | */ | |
4850 | if (sk->sk_shutdown & RCV_SHUTDOWN) { | |
4851 | if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && | |
4852 | after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) { | |
4853 | NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA); | |
4854 | tcp_reset(sk); | |
4855 | return 1; | |
4856 | } | |
4857 | } | |
4858 | /* Fall through */ | |
e905a9ed | 4859 | case TCP_ESTABLISHED: |
1da177e4 LT |
4860 | tcp_data_queue(sk, skb); |
4861 | queued = 1; | |
4862 | break; | |
4863 | } | |
4864 | ||
4865 | /* tcp_data could move socket to TIME-WAIT */ | |
4866 | if (sk->sk_state != TCP_CLOSE) { | |
55c97f3e | 4867 | tcp_data_snd_check(sk, tp); |
1da177e4 LT |
4868 | tcp_ack_snd_check(sk); |
4869 | } | |
4870 | ||
e905a9ed | 4871 | if (!queued) { |
1da177e4 LT |
4872 | discard: |
4873 | __kfree_skb(skb); | |
4874 | } | |
4875 | return 0; | |
4876 | } | |
4877 | ||
4878 | EXPORT_SYMBOL(sysctl_tcp_ecn); | |
4879 | EXPORT_SYMBOL(sysctl_tcp_reordering); | |
4880 | EXPORT_SYMBOL(tcp_parse_options); | |
4881 | EXPORT_SYMBOL(tcp_rcv_established); | |
4882 | EXPORT_SYMBOL(tcp_rcv_state_process); | |
40efc6fa | 4883 | EXPORT_SYMBOL(tcp_initialize_rcv_mss); |