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 $
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>
24 #include <linux/module.h>
25 #include <linux/sysctl.h>
26 #include <linux/workqueue.h>
28 #include <net/inet_common.h>
31 #include <linux/vs_limit.h>
32 #include <linux/vs_socket.h>
33 #include <linux/vs_context.h>
36 #define SYNC_INIT 0 /* let the user enable it */
41 int sysctl_tcp_syncookies __read_mostly = SYNC_INIT;
42 int sysctl_tcp_abort_on_overflow __read_mostly;
44 struct inet_timewait_death_row tcp_death_row = {
45 .sysctl_max_tw_buckets = NR_FILE * 2,
46 .period = TCP_TIMEWAIT_LEN / INET_TWDR_TWKILL_SLOTS,
47 .death_lock = __SPIN_LOCK_UNLOCKED(tcp_death_row.death_lock),
48 .hashinfo = &tcp_hashinfo,
49 .tw_timer = TIMER_INITIALIZER(inet_twdr_hangman, 0,
50 (unsigned long)&tcp_death_row),
51 .twkill_work = __WORK_INITIALIZER(tcp_death_row.twkill_work,
52 inet_twdr_twkill_work),
53 /* Short-time timewait calendar */
56 .twcal_timer = TIMER_INITIALIZER(inet_twdr_twcal_tick, 0,
57 (unsigned long)&tcp_death_row),
60 EXPORT_SYMBOL_GPL(tcp_death_row);
62 static __inline__ int tcp_in_window(u32 seq, u32 end_seq, u32 s_win, u32 e_win)
66 if (after(end_seq, s_win) && before(seq, e_win))
68 return (seq == e_win && seq == end_seq);
72 * * Main purpose of TIME-WAIT state is to close connection gracefully,
73 * when one of ends sits in LAST-ACK or CLOSING retransmitting FIN
74 * (and, probably, tail of data) and one or more our ACKs are lost.
75 * * What is TIME-WAIT timeout? It is associated with maximal packet
76 * lifetime in the internet, which results in wrong conclusion, that
77 * it is set to catch "old duplicate segments" wandering out of their path.
78 * It is not quite correct. This timeout is calculated so that it exceeds
79 * maximal retransmission timeout enough to allow to lose one (or more)
80 * segments sent by peer and our ACKs. This time may be calculated from RTO.
81 * * When TIME-WAIT socket receives RST, it means that another end
82 * finally closed and we are allowed to kill TIME-WAIT too.
83 * * Second purpose of TIME-WAIT is catching old duplicate segments.
84 * Well, certainly it is pure paranoia, but if we load TIME-WAIT
85 * with this semantics, we MUST NOT kill TIME-WAIT state with RSTs.
86 * * If we invented some more clever way to catch duplicates
87 * (f.e. based on PAWS), we could truncate TIME-WAIT to several RTOs.
89 * The algorithm below is based on FORMAL INTERPRETATION of RFCs.
90 * When you compare it to RFCs, please, read section SEGMENT ARRIVES
91 * from the very beginning.
93 * NOTE. With recycling (and later with fin-wait-2) TW bucket
94 * is _not_ stateless. It means, that strictly speaking we must
95 * spinlock it. I do not want! Well, probability of misbehaviour
96 * is ridiculously low and, seems, we could use some mb() tricks
97 * to avoid misread sequence numbers, states etc. --ANK
100 tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
101 const struct tcphdr *th)
103 struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
104 struct tcp_options_received tmp_opt;
107 tmp_opt.saw_tstamp = 0;
108 if (th->doff > (sizeof(*th) >> 2) && tcptw->tw_ts_recent_stamp) {
109 tcp_parse_options(skb, &tmp_opt, 0);
111 if (tmp_opt.saw_tstamp) {
112 tmp_opt.ts_recent = tcptw->tw_ts_recent;
113 tmp_opt.ts_recent_stamp = tcptw->tw_ts_recent_stamp;
114 paws_reject = tcp_paws_check(&tmp_opt, th->rst);
118 if (tw->tw_substate == TCP_FIN_WAIT2) {
119 /* Just repeat all the checks of tcp_rcv_state_process() */
121 /* Out of window, send ACK */
123 !tcp_in_window(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq,
125 tcptw->tw_rcv_nxt + tcptw->tw_rcv_wnd))
131 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tcptw->tw_rcv_nxt))
135 if (!after(TCP_SKB_CB(skb)->end_seq, tcptw->tw_rcv_nxt) ||
136 TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq) {
138 return TCP_TW_SUCCESS;
141 /* New data or FIN. If new data arrive after half-duplex close,
145 TCP_SKB_CB(skb)->end_seq != tcptw->tw_rcv_nxt + 1) {
147 inet_twsk_deschedule(tw, &tcp_death_row);
152 /* FIN arrived, enter true time-wait state. */
153 tw->tw_substate = TCP_TIME_WAIT;
154 tcptw->tw_rcv_nxt = TCP_SKB_CB(skb)->end_seq;
155 if (tmp_opt.saw_tstamp) {
156 tcptw->tw_ts_recent_stamp = xtime.tv_sec;
157 tcptw->tw_ts_recent = tmp_opt.rcv_tsval;
160 /* I am shamed, but failed to make it more elegant.
161 * Yes, it is direct reference to IP, which is impossible
162 * to generalize to IPv6. Taking into account that IPv6
163 * do not understand recycling in any case, it not
164 * a big problem in practice. --ANK */
165 if (tw->tw_family == AF_INET &&
166 tcp_death_row.sysctl_tw_recycle && tcptw->tw_ts_recent_stamp &&
167 tcp_v4_tw_remember_stamp(tw))
168 inet_twsk_schedule(tw, &tcp_death_row, tw->tw_timeout,
171 inet_twsk_schedule(tw, &tcp_death_row, TCP_TIMEWAIT_LEN,
177 * Now real TIME-WAIT state.
180 * "When a connection is [...] on TIME-WAIT state [...]
181 * [a TCP] MAY accept a new SYN from the remote TCP to
182 * reopen the connection directly, if it:
184 * (1) assigns its initial sequence number for the new
185 * connection to be larger than the largest sequence
186 * number it used on the previous connection incarnation,
189 * (2) returns to TIME-WAIT state if the SYN turns out
190 * to be an old duplicate".
194 (TCP_SKB_CB(skb)->seq == tcptw->tw_rcv_nxt &&
195 (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq || th->rst))) {
196 /* In window segment, it may be only reset or bare ack. */
199 /* This is TIME_WAIT assassination, in two flavors.
200 * Oh well... nobody has a sufficient solution to this
203 if (sysctl_tcp_rfc1337 == 0) {
205 inet_twsk_deschedule(tw, &tcp_death_row);
207 return TCP_TW_SUCCESS;
210 inet_twsk_schedule(tw, &tcp_death_row, TCP_TIMEWAIT_LEN,
213 if (tmp_opt.saw_tstamp) {
214 tcptw->tw_ts_recent = tmp_opt.rcv_tsval;
215 tcptw->tw_ts_recent_stamp = xtime.tv_sec;
219 return TCP_TW_SUCCESS;
222 /* Out of window segment.
224 All the segments are ACKed immediately.
226 The only exception is new SYN. We accept it, if it is
227 not old duplicate and we are not in danger to be killed
228 by delayed old duplicates. RFC check is that it has
229 newer sequence number works at rates <40Mbit/sec.
230 However, if paws works, it is reliable AND even more,
231 we even may relax silly seq space cutoff.
233 RED-PEN: we violate main RFC requirement, if this SYN will appear
234 old duplicate (i.e. we receive RST in reply to SYN-ACK),
235 we must return socket to time-wait state. It is not good,
239 if (th->syn && !th->rst && !th->ack && !paws_reject &&
240 (after(TCP_SKB_CB(skb)->seq, tcptw->tw_rcv_nxt) ||
241 (tmp_opt.saw_tstamp &&
242 (s32)(tcptw->tw_ts_recent - tmp_opt.rcv_tsval) < 0))) {
243 u32 isn = tcptw->tw_snd_nxt + 65535 + 2;
246 TCP_SKB_CB(skb)->when = isn;
251 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
254 /* In this case we must reset the TIMEWAIT timer.
256 * If it is ACKless SYN it may be both old duplicate
257 * and new good SYN with random sequence number <rcv_nxt.
258 * Do not reschedule in the last case.
260 if (paws_reject || th->ack)
261 inet_twsk_schedule(tw, &tcp_death_row, TCP_TIMEWAIT_LEN,
264 /* Send ACK. Note, we do not put the bucket,
265 * it will be released by caller.
270 return TCP_TW_SUCCESS;
274 * Move a socket to time-wait or dead fin-wait-2 state.
276 void tcp_time_wait(struct sock *sk, int state, int timeo)
278 struct inet_timewait_sock *tw = NULL;
279 const struct inet_connection_sock *icsk = inet_csk(sk);
280 const struct tcp_sock *tp = tcp_sk(sk);
283 if (tcp_death_row.sysctl_tw_recycle && tp->rx_opt.ts_recent_stamp)
284 recycle_ok = icsk->icsk_af_ops->remember_stamp(sk);
286 if (tcp_death_row.tw_count < tcp_death_row.sysctl_max_tw_buckets)
287 tw = inet_twsk_alloc(sk, state);
290 struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
291 const int rto = (icsk->icsk_rto << 2) - (icsk->icsk_rto >> 1);
293 tw->tw_rcv_wscale = tp->rx_opt.rcv_wscale;
294 tcptw->tw_rcv_nxt = tp->rcv_nxt;
295 tcptw->tw_snd_nxt = tp->snd_nxt;
296 tcptw->tw_rcv_wnd = tcp_receive_window(tp);
297 tcptw->tw_ts_recent = tp->rx_opt.ts_recent;
298 tcptw->tw_ts_recent_stamp = tp->rx_opt.ts_recent_stamp;
300 tw->tw_xid = sk->sk_xid;
301 tw->tw_vx_info = NULL;
302 tw->tw_nid = sk->sk_nid;
303 tw->tw_nx_info = NULL;
305 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
306 if (tw->tw_family == PF_INET6) {
307 struct ipv6_pinfo *np = inet6_sk(sk);
308 struct inet6_timewait_sock *tw6;
310 tw->tw_ipv6_offset = inet6_tw_offset(sk->sk_prot);
311 tw6 = inet6_twsk((struct sock *)tw);
312 ipv6_addr_copy(&tw6->tw_v6_daddr, &np->daddr);
313 ipv6_addr_copy(&tw6->tw_v6_rcv_saddr, &np->rcv_saddr);
314 tw->tw_ipv6only = np->ipv6only;
318 #ifdef CONFIG_TCP_MD5SIG
320 * The timewait bucket does not have the key DB from the
321 * sock structure. We just make a quick copy of the
322 * md5 key being used (if indeed we are using one)
323 * so the timewait ack generating code has the key.
326 struct tcp_md5sig_key *key;
327 memset(tcptw->tw_md5_key, 0, sizeof(tcptw->tw_md5_key));
328 tcptw->tw_md5_keylen = 0;
329 key = tp->af_specific->md5_lookup(sk, sk);
331 memcpy(&tcptw->tw_md5_key, key->key, key->keylen);
332 tcptw->tw_md5_keylen = key->keylen;
333 if (tcp_alloc_md5sig_pool() == NULL)
339 /* Linkage updates. */
340 __inet_twsk_hashdance(tw, sk, &tcp_hashinfo);
342 /* Get the TIME_WAIT timeout firing. */
347 tw->tw_timeout = rto;
349 tw->tw_timeout = TCP_TIMEWAIT_LEN;
350 if (state == TCP_TIME_WAIT)
351 timeo = TCP_TIMEWAIT_LEN;
354 inet_twsk_schedule(tw, &tcp_death_row, timeo,
358 /* Sorry, if we're out of memory, just CLOSE this
359 * socket up. We've got bigger problems than
360 * non-graceful socket closings.
362 LIMIT_NETDEBUG(KERN_INFO "TCP: time wait bucket table overflow\n");
365 tcp_update_metrics(sk);
369 void tcp_twsk_destructor(struct sock *sk)
371 #ifdef CONFIG_TCP_MD5SIG
372 struct tcp_timewait_sock *twsk = tcp_twsk(sk);
373 if (twsk->tw_md5_keylen)
374 tcp_put_md5sig_pool();
378 EXPORT_SYMBOL_GPL(tcp_twsk_destructor);
380 /* This is not only more efficient than what we used to do, it eliminates
381 * a lot of code duplication between IPv4/IPv6 SYN recv processing. -DaveM
383 * Actually, we could lots of memory writes here. tp of listening
384 * socket contains all necessary default parameters.
386 struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req, struct sk_buff *skb)
388 struct sock *newsk = inet_csk_clone(sk, req, GFP_ATOMIC);
391 const struct inet_request_sock *ireq = inet_rsk(req);
392 struct tcp_request_sock *treq = tcp_rsk(req);
393 struct inet_connection_sock *newicsk = inet_csk(newsk);
394 struct tcp_sock *newtp;
396 /* Now setup tcp_sock */
397 newtp = tcp_sk(newsk);
398 newtp->pred_flags = 0;
399 newtp->rcv_nxt = treq->rcv_isn + 1;
400 newtp->snd_nxt = newtp->snd_una = newtp->snd_sml = treq->snt_isn + 1;
402 tcp_prequeue_init(newtp);
404 tcp_init_wl(newtp, treq->snt_isn, treq->rcv_isn);
407 newtp->mdev = TCP_TIMEOUT_INIT;
408 newicsk->icsk_rto = TCP_TIMEOUT_INIT;
410 newtp->packets_out = 0;
412 newtp->retrans_out = 0;
413 newtp->sacked_out = 0;
414 newtp->fackets_out = 0;
415 newtp->snd_ssthresh = 0x7fffffff;
417 /* So many TCP implementations out there (incorrectly) count the
418 * initial SYN frame in their delayed-ACK and congestion control
419 * algorithms that we must have the following bandaid to talk
420 * efficiently to them. -DaveM
423 newtp->snd_cwnd_cnt = 0;
424 newtp->bytes_acked = 0;
426 newtp->frto_counter = 0;
427 newtp->frto_highmark = 0;
429 newicsk->icsk_ca_ops = &tcp_init_congestion_ops;
431 tcp_set_ca_state(newsk, TCP_CA_Open);
432 tcp_init_xmit_timers(newsk);
433 skb_queue_head_init(&newtp->out_of_order_queue);
434 newtp->rcv_wup = treq->rcv_isn + 1;
435 newtp->write_seq = treq->snt_isn + 1;
436 newtp->pushed_seq = newtp->write_seq;
437 newtp->copied_seq = treq->rcv_isn + 1;
439 newtp->rx_opt.saw_tstamp = 0;
441 newtp->rx_opt.dsack = 0;
442 newtp->rx_opt.eff_sacks = 0;
444 newtp->rx_opt.num_sacks = 0;
447 if (sock_flag(newsk, SOCK_KEEPOPEN))
448 inet_csk_reset_keepalive_timer(newsk,
449 keepalive_time_when(newtp));
451 newtp->rx_opt.tstamp_ok = ireq->tstamp_ok;
452 if((newtp->rx_opt.sack_ok = ireq->sack_ok) != 0) {
454 newtp->rx_opt.sack_ok |= 2;
456 newtp->window_clamp = req->window_clamp;
457 newtp->rcv_ssthresh = req->rcv_wnd;
458 newtp->rcv_wnd = req->rcv_wnd;
459 newtp->rx_opt.wscale_ok = ireq->wscale_ok;
460 if (newtp->rx_opt.wscale_ok) {
461 newtp->rx_opt.snd_wscale = ireq->snd_wscale;
462 newtp->rx_opt.rcv_wscale = ireq->rcv_wscale;
464 newtp->rx_opt.snd_wscale = newtp->rx_opt.rcv_wscale = 0;
465 newtp->window_clamp = min(newtp->window_clamp, 65535U);
467 newtp->snd_wnd = ntohs(skb->h.th->window) << newtp->rx_opt.snd_wscale;
468 newtp->max_window = newtp->snd_wnd;
470 if (newtp->rx_opt.tstamp_ok) {
471 newtp->rx_opt.ts_recent = req->ts_recent;
472 newtp->rx_opt.ts_recent_stamp = xtime.tv_sec;
473 newtp->tcp_header_len = sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
475 newtp->rx_opt.ts_recent_stamp = 0;
476 newtp->tcp_header_len = sizeof(struct tcphdr);
478 #ifdef CONFIG_TCP_MD5SIG
479 newtp->md5sig_info = NULL; /*XXX*/
480 if (newtp->af_specific->md5_lookup(sk, newsk))
481 newtp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
483 if (skb->len >= TCP_MIN_RCVMSS+newtp->tcp_header_len)
484 newicsk->icsk_ack.last_seg_size = skb->len - newtp->tcp_header_len;
485 newtp->rx_opt.mss_clamp = req->mss;
486 TCP_ECN_openreq_child(newtp, req);
488 TCP_INC_STATS_BH(TCP_MIB_PASSIVEOPENS);
494 * Process an incoming packet for SYN_RECV sockets represented
498 struct sock *tcp_check_req(struct sock *sk,struct sk_buff *skb,
499 struct request_sock *req,
500 struct request_sock **prev)
502 struct tcphdr *th = skb->h.th;
503 __be32 flg = tcp_flag_word(th) & (TCP_FLAG_RST|TCP_FLAG_SYN|TCP_FLAG_ACK);
505 struct tcp_options_received tmp_opt;
508 tmp_opt.saw_tstamp = 0;
509 if (th->doff > (sizeof(struct tcphdr)>>2)) {
510 tcp_parse_options(skb, &tmp_opt, 0);
512 if (tmp_opt.saw_tstamp) {
513 tmp_opt.ts_recent = req->ts_recent;
514 /* We do not store true stamp, but it is not required,
515 * it can be estimated (approximately)
518 tmp_opt.ts_recent_stamp = xtime.tv_sec - ((TCP_TIMEOUT_INIT/HZ)<<req->retrans);
519 paws_reject = tcp_paws_check(&tmp_opt, th->rst);
523 /* Check for pure retransmitted SYN. */
524 if (TCP_SKB_CB(skb)->seq == tcp_rsk(req)->rcv_isn &&
525 flg == TCP_FLAG_SYN &&
528 * RFC793 draws (Incorrectly! It was fixed in RFC1122)
529 * this case on figure 6 and figure 8, but formal
530 * protocol description says NOTHING.
531 * To be more exact, it says that we should send ACK,
532 * because this segment (at least, if it has no data)
535 * CONCLUSION: RFC793 (even with RFC1122) DOES NOT
536 * describe SYN-RECV state. All the description
537 * is wrong, we cannot believe to it and should
538 * rely only on common sense and implementation
541 * Enforce "SYN-ACK" according to figure 8, figure 6
542 * of RFC793, fixed by RFC1122.
544 req->rsk_ops->rtx_syn_ack(sk, req, NULL);
548 /* Further reproduces section "SEGMENT ARRIVES"
549 for state SYN-RECEIVED of RFC793.
550 It is broken, however, it does not work only
551 when SYNs are crossed.
553 You would think that SYN crossing is impossible here, since
554 we should have a SYN_SENT socket (from connect()) on our end,
555 but this is not true if the crossed SYNs were sent to both
556 ends by a malicious third party. We must defend against this,
557 and to do that we first verify the ACK (as per RFC793, page
558 36) and reset if it is invalid. Is this a true full defense?
559 To convince ourselves, let us consider a way in which the ACK
560 test can still pass in this 'malicious crossed SYNs' case.
561 Malicious sender sends identical SYNs (and thus identical sequence
562 numbers) to both A and B:
567 By our good fortune, both A and B select the same initial
568 send sequence number of seven :-)
570 A: sends SYN|ACK, seq=7, ack_seq=8
571 B: sends SYN|ACK, seq=7, ack_seq=8
573 So we are now A eating this SYN|ACK, ACK test passes. So
574 does sequence test, SYN is truncated, and thus we consider
577 If icsk->icsk_accept_queue.rskq_defer_accept, we silently drop this
578 bare ACK. Otherwise, we create an established connection. Both
579 ends (listening sockets) accept the new incoming connection and try
580 to talk to each other. 8-)
582 Note: This case is both harmless, and rare. Possibility is about the
583 same as us discovering intelligent life on another plant tomorrow.
585 But generally, we should (RFC lies!) to accept ACK
586 from SYNACK both here and in tcp_rcv_state_process().
587 tcp_rcv_state_process() does not, hence, we do not too.
589 Note that the case is absolutely generic:
590 we cannot optimize anything here without
591 violating protocol. All the checks must be made
592 before attempt to create socket.
595 /* RFC793 page 36: "If the connection is in any non-synchronized state ...
596 * and the incoming segment acknowledges something not yet
597 * sent (the segment carries an unacceptable ACK) ...
600 * Invalid ACK: reset will be sent by listening socket
602 if ((flg & TCP_FLAG_ACK) &&
603 (TCP_SKB_CB(skb)->ack_seq != tcp_rsk(req)->snt_isn + 1))
606 /* Also, it would be not so bad idea to check rcv_tsecr, which
607 * is essentially ACK extension and too early or too late values
608 * should cause reset in unsynchronized states.
611 /* RFC793: "first check sequence number". */
613 if (paws_reject || !tcp_in_window(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq,
614 tcp_rsk(req)->rcv_isn + 1, tcp_rsk(req)->rcv_isn + 1 + req->rcv_wnd)) {
615 /* Out of window: send ACK and drop. */
616 if (!(flg & TCP_FLAG_RST))
617 req->rsk_ops->send_ack(skb, req);
619 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
623 /* In sequence, PAWS is OK. */
625 if (tmp_opt.saw_tstamp && !after(TCP_SKB_CB(skb)->seq, tcp_rsk(req)->rcv_isn + 1))
626 req->ts_recent = tmp_opt.rcv_tsval;
628 if (TCP_SKB_CB(skb)->seq == tcp_rsk(req)->rcv_isn) {
629 /* Truncate SYN, it is out of window starting
630 at tcp_rsk(req)->rcv_isn + 1. */
631 flg &= ~TCP_FLAG_SYN;
634 /* RFC793: "second check the RST bit" and
635 * "fourth, check the SYN bit"
637 if (flg & (TCP_FLAG_RST|TCP_FLAG_SYN)) {
638 TCP_INC_STATS_BH(TCP_MIB_ATTEMPTFAILS);
639 goto embryonic_reset;
642 /* ACK sequence verified above, just make sure ACK is
643 * set. If ACK not set, just silently drop the packet.
645 if (!(flg & TCP_FLAG_ACK))
648 /* If TCP_DEFER_ACCEPT is set, drop bare ACK. */
649 if (inet_csk(sk)->icsk_accept_queue.rskq_defer_accept &&
650 TCP_SKB_CB(skb)->end_seq == tcp_rsk(req)->rcv_isn + 1) {
651 inet_rsk(req)->acked = 1;
655 /* OK, ACK is valid, create big socket and
656 * feed this segment to it. It will repeat all
657 * the tests. THIS SEGMENT MUST MOVE SOCKET TO
658 * ESTABLISHED STATE. If it will be dropped after
659 * socket is created, wait for troubles.
661 child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb,
664 goto listen_overflow;
665 #ifdef CONFIG_TCP_MD5SIG
667 /* Copy over the MD5 key from the original socket */
668 struct tcp_md5sig_key *key;
669 struct tcp_sock *tp = tcp_sk(sk);
670 key = tp->af_specific->md5_lookup(sk, child);
673 * We're using one, so create a matching key on the
674 * newsk structure. If we fail to get memory then we
675 * end up not copying the key across. Shucks.
677 char *newkey = kmemdup(key->key, key->keylen,
680 if (!tcp_alloc_md5sig_pool())
682 tp->af_specific->md5_add(child, child,
690 inet_csk_reqsk_queue_unlink(sk, req, prev);
691 inet_csk_reqsk_queue_removed(sk, req);
693 inet_csk_reqsk_queue_add(sk, req, child);
697 if (!sysctl_tcp_abort_on_overflow) {
698 inet_rsk(req)->acked = 1;
703 NET_INC_STATS_BH(LINUX_MIB_EMBRYONICRSTS);
704 if (!(flg & TCP_FLAG_RST))
705 req->rsk_ops->send_reset(sk, skb);
707 inet_csk_reqsk_queue_drop(sk, req, prev);
712 * Queue segment on the new socket if the new socket is active,
713 * otherwise we just shortcircuit this and continue with
717 int tcp_child_process(struct sock *parent, struct sock *child,
721 int state = child->sk_state;
723 if (!sock_owned_by_user(child)) {
724 ret = tcp_rcv_state_process(child, skb, skb->h.th, skb->len);
726 /* Wakeup parent, send SIGIO */
727 if (state == TCP_SYN_RECV && child->sk_state != state)
728 parent->sk_data_ready(parent, 0);
730 /* Alas, it is possible again, because we do lookup
731 * in main socket hash table and lock on listening
732 * socket does not protect us more.
734 sk_add_backlog(child, skb);
737 bh_unlock_sock(child);
742 EXPORT_SYMBOL(tcp_check_req);
743 EXPORT_SYMBOL(tcp_child_process);
744 EXPORT_SYMBOL(tcp_create_openreq_child);
745 EXPORT_SYMBOL(tcp_timewait_state_process);