[MIPS] Delete duplicate definitions of break codes.
[linux-2.6/mini2440.git] / net / ipv4 / tcp_minisocks.c
blob1b66a2ac4321cb3dfe42326a03baa0897b016f37
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.
6 * Implementation of the Transmission Control Protocol(TCP).
8 * Version: $Id: tcp_minisocks.c,v 1.15 2002/02/01 22:01:04 davem Exp $
10 * Authors: Ross Biro
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>
23 #include <linux/config.h>
24 #include <linux/mm.h>
25 #include <linux/module.h>
26 #include <linux/sysctl.h>
27 #include <linux/workqueue.h>
28 #include <net/tcp.h>
29 #include <net/inet_common.h>
30 #include <net/xfrm.h>
32 #ifdef CONFIG_SYSCTL
33 #define SYNC_INIT 0 /* let the user enable it */
34 #else
35 #define SYNC_INIT 1
36 #endif
38 int sysctl_tcp_syncookies = SYNC_INIT;
39 int sysctl_tcp_abort_on_overflow;
41 struct inet_timewait_death_row tcp_death_row = {
42 .sysctl_max_tw_buckets = NR_FILE * 2,
43 .period = TCP_TIMEWAIT_LEN / INET_TWDR_TWKILL_SLOTS,
44 .death_lock = SPIN_LOCK_UNLOCKED,
45 .hashinfo = &tcp_hashinfo,
46 .tw_timer = TIMER_INITIALIZER(inet_twdr_hangman, 0,
47 (unsigned long)&tcp_death_row),
48 .twkill_work = __WORK_INITIALIZER(tcp_death_row.twkill_work,
49 inet_twdr_twkill_work,
50 &tcp_death_row),
51 /* Short-time timewait calendar */
53 .twcal_hand = -1,
54 .twcal_timer = TIMER_INITIALIZER(inet_twdr_twcal_tick, 0,
55 (unsigned long)&tcp_death_row),
58 EXPORT_SYMBOL_GPL(tcp_death_row);
60 static __inline__ int tcp_in_window(u32 seq, u32 end_seq, u32 s_win, u32 e_win)
62 if (seq == s_win)
63 return 1;
64 if (after(end_seq, s_win) && before(seq, e_win))
65 return 1;
66 return (seq == e_win && seq == end_seq);
69 /*
70 * * Main purpose of TIME-WAIT state is to close connection gracefully,
71 * when one of ends sits in LAST-ACK or CLOSING retransmitting FIN
72 * (and, probably, tail of data) and one or more our ACKs are lost.
73 * * What is TIME-WAIT timeout? It is associated with maximal packet
74 * lifetime in the internet, which results in wrong conclusion, that
75 * it is set to catch "old duplicate segments" wandering out of their path.
76 * It is not quite correct. This timeout is calculated so that it exceeds
77 * maximal retransmission timeout enough to allow to lose one (or more)
78 * segments sent by peer and our ACKs. This time may be calculated from RTO.
79 * * When TIME-WAIT socket receives RST, it means that another end
80 * finally closed and we are allowed to kill TIME-WAIT too.
81 * * Second purpose of TIME-WAIT is catching old duplicate segments.
82 * Well, certainly it is pure paranoia, but if we load TIME-WAIT
83 * with this semantics, we MUST NOT kill TIME-WAIT state with RSTs.
84 * * If we invented some more clever way to catch duplicates
85 * (f.e. based on PAWS), we could truncate TIME-WAIT to several RTOs.
87 * The algorithm below is based on FORMAL INTERPRETATION of RFCs.
88 * When you compare it to RFCs, please, read section SEGMENT ARRIVES
89 * from the very beginning.
91 * NOTE. With recycling (and later with fin-wait-2) TW bucket
92 * is _not_ stateless. It means, that strictly speaking we must
93 * spinlock it. I do not want! Well, probability of misbehaviour
94 * is ridiculously low and, seems, we could use some mb() tricks
95 * to avoid misread sequence numbers, states etc. --ANK
97 enum tcp_tw_status
98 tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
99 const struct tcphdr *th)
101 struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
102 struct tcp_options_received tmp_opt;
103 int paws_reject = 0;
105 tmp_opt.saw_tstamp = 0;
106 if (th->doff > (sizeof(*th) >> 2) && tcptw->tw_ts_recent_stamp) {
107 tcp_parse_options(skb, &tmp_opt, 0);
109 if (tmp_opt.saw_tstamp) {
110 tmp_opt.ts_recent = tcptw->tw_ts_recent;
111 tmp_opt.ts_recent_stamp = tcptw->tw_ts_recent_stamp;
112 paws_reject = tcp_paws_check(&tmp_opt, th->rst);
116 if (tw->tw_substate == TCP_FIN_WAIT2) {
117 /* Just repeat all the checks of tcp_rcv_state_process() */
119 /* Out of window, send ACK */
120 if (paws_reject ||
121 !tcp_in_window(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq,
122 tcptw->tw_rcv_nxt,
123 tcptw->tw_rcv_nxt + tcptw->tw_rcv_wnd))
124 return TCP_TW_ACK;
126 if (th->rst)
127 goto kill;
129 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tcptw->tw_rcv_nxt))
130 goto kill_with_rst;
132 /* Dup ACK? */
133 if (!after(TCP_SKB_CB(skb)->end_seq, tcptw->tw_rcv_nxt) ||
134 TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq) {
135 inet_twsk_put(tw);
136 return TCP_TW_SUCCESS;
139 /* New data or FIN. If new data arrive after half-duplex close,
140 * reset.
142 if (!th->fin ||
143 TCP_SKB_CB(skb)->end_seq != tcptw->tw_rcv_nxt + 1) {
144 kill_with_rst:
145 inet_twsk_deschedule(tw, &tcp_death_row);
146 inet_twsk_put(tw);
147 return TCP_TW_RST;
150 /* FIN arrived, enter true time-wait state. */
151 tw->tw_substate = TCP_TIME_WAIT;
152 tcptw->tw_rcv_nxt = TCP_SKB_CB(skb)->end_seq;
153 if (tmp_opt.saw_tstamp) {
154 tcptw->tw_ts_recent_stamp = xtime.tv_sec;
155 tcptw->tw_ts_recent = tmp_opt.rcv_tsval;
158 /* I am shamed, but failed to make it more elegant.
159 * Yes, it is direct reference to IP, which is impossible
160 * to generalize to IPv6. Taking into account that IPv6
161 * do not understand recycling in any case, it not
162 * a big problem in practice. --ANK */
163 if (tw->tw_family == AF_INET &&
164 tcp_death_row.sysctl_tw_recycle && tcptw->tw_ts_recent_stamp &&
165 tcp_v4_tw_remember_stamp(tw))
166 inet_twsk_schedule(tw, &tcp_death_row, tw->tw_timeout,
167 TCP_TIMEWAIT_LEN);
168 else
169 inet_twsk_schedule(tw, &tcp_death_row, TCP_TIMEWAIT_LEN,
170 TCP_TIMEWAIT_LEN);
171 return TCP_TW_ACK;
175 * Now real TIME-WAIT state.
177 * RFC 1122:
178 * "When a connection is [...] on TIME-WAIT state [...]
179 * [a TCP] MAY accept a new SYN from the remote TCP to
180 * reopen the connection directly, if it:
182 * (1) assigns its initial sequence number for the new
183 * connection to be larger than the largest sequence
184 * number it used on the previous connection incarnation,
185 * and
187 * (2) returns to TIME-WAIT state if the SYN turns out
188 * to be an old duplicate".
191 if (!paws_reject &&
192 (TCP_SKB_CB(skb)->seq == tcptw->tw_rcv_nxt &&
193 (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq || th->rst))) {
194 /* In window segment, it may be only reset or bare ack. */
196 if (th->rst) {
197 /* This is TIME_WAIT assassination, in two flavors.
198 * Oh well... nobody has a sufficient solution to this
199 * protocol bug yet.
201 if (sysctl_tcp_rfc1337 == 0) {
202 kill:
203 inet_twsk_deschedule(tw, &tcp_death_row);
204 inet_twsk_put(tw);
205 return TCP_TW_SUCCESS;
208 inet_twsk_schedule(tw, &tcp_death_row, TCP_TIMEWAIT_LEN,
209 TCP_TIMEWAIT_LEN);
211 if (tmp_opt.saw_tstamp) {
212 tcptw->tw_ts_recent = tmp_opt.rcv_tsval;
213 tcptw->tw_ts_recent_stamp = xtime.tv_sec;
216 inet_twsk_put(tw);
217 return TCP_TW_SUCCESS;
220 /* Out of window segment.
222 All the segments are ACKed immediately.
224 The only exception is new SYN. We accept it, if it is
225 not old duplicate and we are not in danger to be killed
226 by delayed old duplicates. RFC check is that it has
227 newer sequence number works at rates <40Mbit/sec.
228 However, if paws works, it is reliable AND even more,
229 we even may relax silly seq space cutoff.
231 RED-PEN: we violate main RFC requirement, if this SYN will appear
232 old duplicate (i.e. we receive RST in reply to SYN-ACK),
233 we must return socket to time-wait state. It is not good,
234 but not fatal yet.
237 if (th->syn && !th->rst && !th->ack && !paws_reject &&
238 (after(TCP_SKB_CB(skb)->seq, tcptw->tw_rcv_nxt) ||
239 (tmp_opt.saw_tstamp &&
240 (s32)(tcptw->tw_ts_recent - tmp_opt.rcv_tsval) < 0))) {
241 u32 isn = tcptw->tw_snd_nxt + 65535 + 2;
242 if (isn == 0)
243 isn++;
244 TCP_SKB_CB(skb)->when = isn;
245 return TCP_TW_SYN;
248 if (paws_reject)
249 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
251 if(!th->rst) {
252 /* In this case we must reset the TIMEWAIT timer.
254 * If it is ACKless SYN it may be both old duplicate
255 * and new good SYN with random sequence number <rcv_nxt.
256 * Do not reschedule in the last case.
258 if (paws_reject || th->ack)
259 inet_twsk_schedule(tw, &tcp_death_row, TCP_TIMEWAIT_LEN,
260 TCP_TIMEWAIT_LEN);
262 /* Send ACK. Note, we do not put the bucket,
263 * it will be released by caller.
265 return TCP_TW_ACK;
267 inet_twsk_put(tw);
268 return TCP_TW_SUCCESS;
272 * Move a socket to time-wait or dead fin-wait-2 state.
274 void tcp_time_wait(struct sock *sk, int state, int timeo)
276 struct inet_timewait_sock *tw = NULL;
277 const struct tcp_sock *tp = tcp_sk(sk);
278 int recycle_ok = 0;
280 if (tcp_death_row.sysctl_tw_recycle && tp->rx_opt.ts_recent_stamp)
281 recycle_ok = tp->af_specific->remember_stamp(sk);
283 if (tcp_death_row.tw_count < tcp_death_row.sysctl_max_tw_buckets)
284 tw = inet_twsk_alloc(sk, state);
286 if (tw != NULL) {
287 struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
288 const struct inet_connection_sock *icsk = inet_csk(sk);
289 const int rto = (icsk->icsk_rto << 2) - (icsk->icsk_rto >> 1);
291 tw->tw_rcv_wscale = tp->rx_opt.rcv_wscale;
292 tcptw->tw_rcv_nxt = tp->rcv_nxt;
293 tcptw->tw_snd_nxt = tp->snd_nxt;
294 tcptw->tw_rcv_wnd = tcp_receive_window(tp);
295 tcptw->tw_ts_recent = tp->rx_opt.ts_recent;
296 tcptw->tw_ts_recent_stamp = tp->rx_opt.ts_recent_stamp;
298 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
299 if (tw->tw_family == PF_INET6) {
300 struct ipv6_pinfo *np = inet6_sk(sk);
301 struct tcp6_timewait_sock *tcp6tw = tcp6_twsk((struct sock *)tw);
303 ipv6_addr_copy(&tcp6tw->tw_v6_daddr, &np->daddr);
304 ipv6_addr_copy(&tcp6tw->tw_v6_rcv_saddr, &np->rcv_saddr);
305 tw->tw_ipv6only = np->ipv6only;
307 #endif
308 /* Linkage updates. */
309 __inet_twsk_hashdance(tw, sk, &tcp_hashinfo);
311 /* Get the TIME_WAIT timeout firing. */
312 if (timeo < rto)
313 timeo = rto;
315 if (recycle_ok) {
316 tw->tw_timeout = rto;
317 } else {
318 tw->tw_timeout = TCP_TIMEWAIT_LEN;
319 if (state == TCP_TIME_WAIT)
320 timeo = TCP_TIMEWAIT_LEN;
323 inet_twsk_schedule(tw, &tcp_death_row, timeo,
324 TCP_TIMEWAIT_LEN);
325 inet_twsk_put(tw);
326 } else {
327 /* Sorry, if we're out of memory, just CLOSE this
328 * socket up. We've got bigger problems than
329 * non-graceful socket closings.
331 if (net_ratelimit())
332 printk(KERN_INFO "TCP: time wait bucket table overflow\n");
335 tcp_update_metrics(sk);
336 tcp_done(sk);
339 /* This is not only more efficient than what we used to do, it eliminates
340 * a lot of code duplication between IPv4/IPv6 SYN recv processing. -DaveM
342 * Actually, we could lots of memory writes here. tp of listening
343 * socket contains all necessary default parameters.
345 struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req, struct sk_buff *skb)
347 struct sock *newsk = inet_csk_clone(sk, req, GFP_ATOMIC);
349 if (newsk != NULL) {
350 const struct inet_request_sock *ireq = inet_rsk(req);
351 struct tcp_request_sock *treq = tcp_rsk(req);
352 struct inet_connection_sock *newicsk = inet_csk(sk);
353 struct tcp_sock *newtp;
355 /* Now setup tcp_sock */
356 newtp = tcp_sk(newsk);
357 newtp->pred_flags = 0;
358 newtp->rcv_nxt = treq->rcv_isn + 1;
359 newtp->snd_nxt = newtp->snd_una = newtp->snd_sml = treq->snt_isn + 1;
361 tcp_prequeue_init(newtp);
363 tcp_init_wl(newtp, treq->snt_isn, treq->rcv_isn);
365 newtp->srtt = 0;
366 newtp->mdev = TCP_TIMEOUT_INIT;
367 newicsk->icsk_rto = TCP_TIMEOUT_INIT;
369 newtp->packets_out = 0;
370 newtp->left_out = 0;
371 newtp->retrans_out = 0;
372 newtp->sacked_out = 0;
373 newtp->fackets_out = 0;
374 newtp->snd_ssthresh = 0x7fffffff;
376 /* So many TCP implementations out there (incorrectly) count the
377 * initial SYN frame in their delayed-ACK and congestion control
378 * algorithms that we must have the following bandaid to talk
379 * efficiently to them. -DaveM
381 newtp->snd_cwnd = 2;
382 newtp->snd_cwnd_cnt = 0;
383 newtp->bytes_acked = 0;
385 newtp->frto_counter = 0;
386 newtp->frto_highmark = 0;
388 newicsk->icsk_ca_ops = &tcp_init_congestion_ops;
390 tcp_set_ca_state(newsk, TCP_CA_Open);
391 tcp_init_xmit_timers(newsk);
392 skb_queue_head_init(&newtp->out_of_order_queue);
393 newtp->rcv_wup = treq->rcv_isn + 1;
394 newtp->write_seq = treq->snt_isn + 1;
395 newtp->pushed_seq = newtp->write_seq;
396 newtp->copied_seq = treq->rcv_isn + 1;
398 newtp->rx_opt.saw_tstamp = 0;
400 newtp->rx_opt.dsack = 0;
401 newtp->rx_opt.eff_sacks = 0;
403 newtp->rx_opt.num_sacks = 0;
404 newtp->urg_data = 0;
406 if (sock_flag(newsk, SOCK_KEEPOPEN))
407 inet_csk_reset_keepalive_timer(newsk,
408 keepalive_time_when(newtp));
410 newtp->rx_opt.tstamp_ok = ireq->tstamp_ok;
411 if((newtp->rx_opt.sack_ok = ireq->sack_ok) != 0) {
412 if (sysctl_tcp_fack)
413 newtp->rx_opt.sack_ok |= 2;
415 newtp->window_clamp = req->window_clamp;
416 newtp->rcv_ssthresh = req->rcv_wnd;
417 newtp->rcv_wnd = req->rcv_wnd;
418 newtp->rx_opt.wscale_ok = ireq->wscale_ok;
419 if (newtp->rx_opt.wscale_ok) {
420 newtp->rx_opt.snd_wscale = ireq->snd_wscale;
421 newtp->rx_opt.rcv_wscale = ireq->rcv_wscale;
422 } else {
423 newtp->rx_opt.snd_wscale = newtp->rx_opt.rcv_wscale = 0;
424 newtp->window_clamp = min(newtp->window_clamp, 65535U);
426 newtp->snd_wnd = ntohs(skb->h.th->window) << newtp->rx_opt.snd_wscale;
427 newtp->max_window = newtp->snd_wnd;
429 if (newtp->rx_opt.tstamp_ok) {
430 newtp->rx_opt.ts_recent = req->ts_recent;
431 newtp->rx_opt.ts_recent_stamp = xtime.tv_sec;
432 newtp->tcp_header_len = sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
433 } else {
434 newtp->rx_opt.ts_recent_stamp = 0;
435 newtp->tcp_header_len = sizeof(struct tcphdr);
437 if (skb->len >= TCP_MIN_RCVMSS+newtp->tcp_header_len)
438 newicsk->icsk_ack.last_seg_size = skb->len - newtp->tcp_header_len;
439 newtp->rx_opt.mss_clamp = req->mss;
440 TCP_ECN_openreq_child(newtp, req);
441 if (newtp->ecn_flags&TCP_ECN_OK)
442 sock_set_flag(newsk, SOCK_NO_LARGESEND);
444 TCP_INC_STATS_BH(TCP_MIB_PASSIVEOPENS);
446 return newsk;
450 * Process an incoming packet for SYN_RECV sockets represented
451 * as a request_sock.
454 struct sock *tcp_check_req(struct sock *sk,struct sk_buff *skb,
455 struct request_sock *req,
456 struct request_sock **prev)
458 struct tcphdr *th = skb->h.th;
459 struct tcp_sock *tp = tcp_sk(sk);
460 u32 flg = tcp_flag_word(th) & (TCP_FLAG_RST|TCP_FLAG_SYN|TCP_FLAG_ACK);
461 int paws_reject = 0;
462 struct tcp_options_received tmp_opt;
463 struct sock *child;
465 tmp_opt.saw_tstamp = 0;
466 if (th->doff > (sizeof(struct tcphdr)>>2)) {
467 tcp_parse_options(skb, &tmp_opt, 0);
469 if (tmp_opt.saw_tstamp) {
470 tmp_opt.ts_recent = req->ts_recent;
471 /* We do not store true stamp, but it is not required,
472 * it can be estimated (approximately)
473 * from another data.
475 tmp_opt.ts_recent_stamp = xtime.tv_sec - ((TCP_TIMEOUT_INIT/HZ)<<req->retrans);
476 paws_reject = tcp_paws_check(&tmp_opt, th->rst);
480 /* Check for pure retransmitted SYN. */
481 if (TCP_SKB_CB(skb)->seq == tcp_rsk(req)->rcv_isn &&
482 flg == TCP_FLAG_SYN &&
483 !paws_reject) {
485 * RFC793 draws (Incorrectly! It was fixed in RFC1122)
486 * this case on figure 6 and figure 8, but formal
487 * protocol description says NOTHING.
488 * To be more exact, it says that we should send ACK,
489 * because this segment (at least, if it has no data)
490 * is out of window.
492 * CONCLUSION: RFC793 (even with RFC1122) DOES NOT
493 * describe SYN-RECV state. All the description
494 * is wrong, we cannot believe to it and should
495 * rely only on common sense and implementation
496 * experience.
498 * Enforce "SYN-ACK" according to figure 8, figure 6
499 * of RFC793, fixed by RFC1122.
501 req->rsk_ops->rtx_syn_ack(sk, req, NULL);
502 return NULL;
505 /* Further reproduces section "SEGMENT ARRIVES"
506 for state SYN-RECEIVED of RFC793.
507 It is broken, however, it does not work only
508 when SYNs are crossed.
510 You would think that SYN crossing is impossible here, since
511 we should have a SYN_SENT socket (from connect()) on our end,
512 but this is not true if the crossed SYNs were sent to both
513 ends by a malicious third party. We must defend against this,
514 and to do that we first verify the ACK (as per RFC793, page
515 36) and reset if it is invalid. Is this a true full defense?
516 To convince ourselves, let us consider a way in which the ACK
517 test can still pass in this 'malicious crossed SYNs' case.
518 Malicious sender sends identical SYNs (and thus identical sequence
519 numbers) to both A and B:
521 A: gets SYN, seq=7
522 B: gets SYN, seq=7
524 By our good fortune, both A and B select the same initial
525 send sequence number of seven :-)
527 A: sends SYN|ACK, seq=7, ack_seq=8
528 B: sends SYN|ACK, seq=7, ack_seq=8
530 So we are now A eating this SYN|ACK, ACK test passes. So
531 does sequence test, SYN is truncated, and thus we consider
532 it a bare ACK.
534 If icsk->icsk_accept_queue.rskq_defer_accept, we silently drop this
535 bare ACK. Otherwise, we create an established connection. Both
536 ends (listening sockets) accept the new incoming connection and try
537 to talk to each other. 8-)
539 Note: This case is both harmless, and rare. Possibility is about the
540 same as us discovering intelligent life on another plant tomorrow.
542 But generally, we should (RFC lies!) to accept ACK
543 from SYNACK both here and in tcp_rcv_state_process().
544 tcp_rcv_state_process() does not, hence, we do not too.
546 Note that the case is absolutely generic:
547 we cannot optimize anything here without
548 violating protocol. All the checks must be made
549 before attempt to create socket.
552 /* RFC793 page 36: "If the connection is in any non-synchronized state ...
553 * and the incoming segment acknowledges something not yet
554 * sent (the segment carries an unacceptable ACK) ...
555 * a reset is sent."
557 * Invalid ACK: reset will be sent by listening socket
559 if ((flg & TCP_FLAG_ACK) &&
560 (TCP_SKB_CB(skb)->ack_seq != tcp_rsk(req)->snt_isn + 1))
561 return sk;
563 /* Also, it would be not so bad idea to check rcv_tsecr, which
564 * is essentially ACK extension and too early or too late values
565 * should cause reset in unsynchronized states.
568 /* RFC793: "first check sequence number". */
570 if (paws_reject || !tcp_in_window(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq,
571 tcp_rsk(req)->rcv_isn + 1, tcp_rsk(req)->rcv_isn + 1 + req->rcv_wnd)) {
572 /* Out of window: send ACK and drop. */
573 if (!(flg & TCP_FLAG_RST))
574 req->rsk_ops->send_ack(skb, req);
575 if (paws_reject)
576 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
577 return NULL;
580 /* In sequence, PAWS is OK. */
582 if (tmp_opt.saw_tstamp && !after(TCP_SKB_CB(skb)->seq, tcp_rsk(req)->rcv_isn + 1))
583 req->ts_recent = tmp_opt.rcv_tsval;
585 if (TCP_SKB_CB(skb)->seq == tcp_rsk(req)->rcv_isn) {
586 /* Truncate SYN, it is out of window starting
587 at tcp_rsk(req)->rcv_isn + 1. */
588 flg &= ~TCP_FLAG_SYN;
591 /* RFC793: "second check the RST bit" and
592 * "fourth, check the SYN bit"
594 if (flg & (TCP_FLAG_RST|TCP_FLAG_SYN))
595 goto embryonic_reset;
597 /* ACK sequence verified above, just make sure ACK is
598 * set. If ACK not set, just silently drop the packet.
600 if (!(flg & TCP_FLAG_ACK))
601 return NULL;
603 /* If TCP_DEFER_ACCEPT is set, drop bare ACK. */
604 if (inet_csk(sk)->icsk_accept_queue.rskq_defer_accept &&
605 TCP_SKB_CB(skb)->end_seq == tcp_rsk(req)->rcv_isn + 1) {
606 inet_rsk(req)->acked = 1;
607 return NULL;
610 /* OK, ACK is valid, create big socket and
611 * feed this segment to it. It will repeat all
612 * the tests. THIS SEGMENT MUST MOVE SOCKET TO
613 * ESTABLISHED STATE. If it will be dropped after
614 * socket is created, wait for troubles.
616 child = tp->af_specific->syn_recv_sock(sk, skb, req, NULL);
617 if (child == NULL)
618 goto listen_overflow;
620 inet_csk_reqsk_queue_unlink(sk, req, prev);
621 inet_csk_reqsk_queue_removed(sk, req);
623 inet_csk_reqsk_queue_add(sk, req, child);
624 return child;
626 listen_overflow:
627 if (!sysctl_tcp_abort_on_overflow) {
628 inet_rsk(req)->acked = 1;
629 return NULL;
632 embryonic_reset:
633 NET_INC_STATS_BH(LINUX_MIB_EMBRYONICRSTS);
634 if (!(flg & TCP_FLAG_RST))
635 req->rsk_ops->send_reset(skb);
637 inet_csk_reqsk_queue_drop(sk, req, prev);
638 return NULL;
642 * Queue segment on the new socket if the new socket is active,
643 * otherwise we just shortcircuit this and continue with
644 * the new socket.
647 int tcp_child_process(struct sock *parent, struct sock *child,
648 struct sk_buff *skb)
650 int ret = 0;
651 int state = child->sk_state;
653 if (!sock_owned_by_user(child)) {
654 ret = tcp_rcv_state_process(child, skb, skb->h.th, skb->len);
656 /* Wakeup parent, send SIGIO */
657 if (state == TCP_SYN_RECV && child->sk_state != state)
658 parent->sk_data_ready(parent, 0);
659 } else {
660 /* Alas, it is possible again, because we do lookup
661 * in main socket hash table and lock on listening
662 * socket does not protect us more.
664 sk_add_backlog(child, skb);
667 bh_unlock_sock(child);
668 sock_put(child);
669 return ret;
672 EXPORT_SYMBOL(tcp_check_req);
673 EXPORT_SYMBOL(tcp_child_process);
674 EXPORT_SYMBOL(tcp_create_openreq_child);
675 EXPORT_SYMBOL(tcp_timewait_state_process);