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_minisocks.c,v 1.5 2000/11/28 17:04:10 davem Exp $
9 *
10 * Authors: Ross Biro, <bir7@leland.Stanford.Edu>
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 #include <linux/config.h>
24 #include <linux/mm.h>
25 #include <linux/sysctl.h>
26 #include <net/tcp.h>
27 #include <net/inet_common.h>
28
29 #ifdef CONFIG_SYSCTL
30 #define SYNC_INIT 0 /* let the user enable it */
31 #else
32 #define SYNC_INIT 1
33 #endif
34
35 int sysctl_tcp_tw_recycle = 0;
36 int sysctl_tcp_max_tw_buckets = NR_FILE*2;
37
38 int sysctl_tcp_syncookies = SYNC_INIT;
39 int sysctl_tcp_abort_on_overflow = 0;
40
41 static __inline__ int tcp_in_window(u32 seq, u32 end_seq, u32 s_win, u32 e_win)
42 {
43 if (seq == s_win)
44 return 1;
45 if (after(end_seq, s_win) && before(seq, e_win))
46 return 1;
47 return (seq == e_win && seq == end_seq);
48 }
49
50 /* New-style handling of TIME_WAIT sockets. */
51
52 int tcp_tw_count = 0;
53
54
55 /* Must be called with locally disabled BHs. */
56 void tcp_timewait_kill(struct tcp_tw_bucket *tw)
57 {
58 struct tcp_ehash_bucket *ehead;
59 struct tcp_bind_hashbucket *bhead;
60 struct tcp_bind_bucket *tb;
61
62 /* Unlink from established hashes. */
63 ehead = &tcp_ehash[tw->hashent];
64 write_lock(&ehead->lock);
65 if (!tw->pprev) {
66 write_unlock(&ehead->lock);
67 return;
68 }
69 if(tw->next)
70 tw->next->pprev = tw->pprev;
71 *(tw->pprev) = tw->next;
72 tw->pprev = NULL;
73 write_unlock(&ehead->lock);
74
75 /* Disassociate with bind bucket. */
76 bhead = &tcp_bhash[tcp_bhashfn(tw->num)];
77 spin_lock(&bhead->lock);
78 if ((tb = tw->tb) != NULL) {
79 if(tw->bind_next)
80 tw->bind_next->bind_pprev = tw->bind_pprev;
81 *(tw->bind_pprev) = tw->bind_next;
82 tw->tb = NULL;
83 if (tb->owners == NULL) {
84 if (tb->next)
85 tb->next->pprev = tb->pprev;
86 *(tb->pprev) = tb->next;
87 kmem_cache_free(tcp_bucket_cachep, tb);
88 }
89 }
90 spin_unlock(&bhead->lock);
91
92 #ifdef INET_REFCNT_DEBUG
93 if (atomic_read(&tw->refcnt) != 1) {
94 printk(KERN_DEBUG "tw_bucket %p refcnt=%d\n", tw, atomic_read(&tw->refcnt));
95 }
96 #endif
97 tcp_tw_put(tw);
98 }
99
100 /*
101 * * Main purpose of TIME-WAIT state is to close connection gracefully,
102 * when one of ends sits in LAST-ACK or CLOSING retransmitting FIN
103 * (and, probably, tail of data) and one or more our ACKs are lost.
104 * * What is TIME-WAIT timeout? It is associated with maximal packet
105 * lifetime in the internet, which results in wrong conclusion, that
106 * it is set to catch "old duplicate segments" wandering out of their path.
107 * It is not quite correct. This timeout is calculated so that it exceeds
108 * maximal retransmision timeout enough to allow to lose one (or more)
109 * segments sent by peer and our ACKs. This time may be calculated from RTO.
110 * * When TIME-WAIT socket receives RST, it means that another end
111 * finally closed and we are allowed to kill TIME-WAIT too.
112 * * Second purpose of TIME-WAIT is catching old duplicate segments.
113 * Well, certainly it is pure paranoia, but if we load TIME-WAIT
114 * with this semantics, we MUST NOT kill TIME-WAIT state with RSTs.
115 * * If we invented some more clever way to catch duplicates
116 * (f.e. based on PAWS), we could truncate TIME-WAIT to several RTOs.
117 *
118 * The algorithm below is based on FORMAL INTERPRETATION of RFCs.
119 * When you compare it to RFCs, please, read section SEGMENT ARRIVES
120 * from the very beginning.
121 *
122 * NOTE. With recycling (and later with fin-wait-2) TW bucket
123 * is _not_ stateless. It means, that strictly speaking we must
124 * spinlock it. I do not want! Well, probability of misbehaviour
125 * is ridiculously low and, seems, we could use some mb() tricks
126 * to avoid misread sequence numbers, states etc. --ANK
127 */
128 enum tcp_tw_status
129 tcp_timewait_state_process(struct tcp_tw_bucket *tw, struct sk_buff *skb,
130 struct tcphdr *th, unsigned len)
131 {
132 struct tcp_opt tp;
133 int paws_reject = 0;
134
135 tp.saw_tstamp = 0;
136 if (th->doff > (sizeof(struct tcphdr)>>2) && tw->ts_recent_stamp) {
137 tcp_parse_options(skb, &tp, 0);
138
139 if (tp.saw_tstamp) {
140 tp.ts_recent = tw->ts_recent;
141 tp.ts_recent_stamp = tw->ts_recent_stamp;
142 paws_reject = tcp_paws_check(&tp, th->rst);
143 }
144 }
145
146 if (tw->substate == TCP_FIN_WAIT2) {
147 /* Just repeat all the checks of tcp_rcv_state_process() */
148
149 /* Out of window, send ACK */
150 if (paws_reject ||
151 !tcp_in_window(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq,
152 tw->rcv_nxt, tw->rcv_nxt + tw->rcv_wnd))
153 return TCP_TW_ACK;
154
155 if (th->rst)
156 goto kill;
157
158 if (th->syn && TCP_SKB_CB(skb)->seq != tw->syn_seq)
159 goto kill_with_rst;
160
161 /* Dup ACK? */
162 if (!after(TCP_SKB_CB(skb)->end_seq, tw->rcv_nxt) ||
163 TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq) {
164 tcp_tw_put(tw);
165 return TCP_TW_SUCCESS;
166 }
167
168 /* New data or FIN. If new data arrive after half-duplex close,
169 * reset.
170 */
171 if (!th->fin || TCP_SKB_CB(skb)->end_seq != tw->rcv_nxt+1) {
172 kill_with_rst:
173 tcp_tw_deschedule(tw);
174 tcp_timewait_kill(tw);
175 tcp_tw_put(tw);
176 return TCP_TW_RST;
177 }
178
179 /* FIN arrived, enter true time-wait state. */
180 tw->substate = TCP_TIME_WAIT;
181 tw->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
182 if (tp.saw_tstamp) {
183 tw->ts_recent_stamp = xtime.tv_sec;
184 tw->ts_recent = tp.rcv_tsval;
185 }
186
187 /* I am shamed, but failed to make it more elegant.
188 * Yes, it is direct reference to IP, which is impossible
189 * to generalize to IPv6. Taking into account that IPv6
190 * do not undertsnad recycling in any case, it not
191 * a big problem in practice. --ANK */
192 if (tw->family == AF_INET &&
193 sysctl_tcp_tw_recycle && tw->ts_recent_stamp &&
194 tcp_v4_tw_remember_stamp(tw))
195 tcp_tw_schedule(tw, tw->timeout);
196 else
197 tcp_tw_schedule(tw, TCP_TIMEWAIT_LEN);
198 return TCP_TW_ACK;
199 }
200
201 /*
202 * Now real TIME-WAIT state.
203 *
204 * RFC 1122:
205 * "When a connection is [...] on TIME-WAIT state [...]
206 * [a TCP] MAY accept a new SYN from the remote TCP to
207 * reopen the connection directly, if it:
208 *
209 * (1) assigns its initial sequence number for the new
210 * connection to be larger than the largest sequence
211 * number it used on the previous connection incarnation,
212 * and
213 *
214 * (2) returns to TIME-WAIT state if the SYN turns out
215 * to be an old duplicate".
216 */
217
218 if (!paws_reject &&
219 (TCP_SKB_CB(skb)->seq == tw->rcv_nxt &&
220 (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq || th->rst))) {
221 /* In window segment, it may be only reset or bare ack. */
222
223 if (th->rst) {
224 /* This is TIME_WAIT assasination, in two flavors.
225 * Oh well... nobody has a sufficient solution to this
226 * protocol bug yet.
227 */
228 if (sysctl_tcp_rfc1337 == 0) {
229 kill:
230 tcp_tw_deschedule(tw);
231 tcp_timewait_kill(tw);
232 tcp_tw_put(tw);
233 return TCP_TW_SUCCESS;
234 }
235 }
236 tcp_tw_schedule(tw, TCP_TIMEWAIT_LEN);
237
238 if (tp.saw_tstamp) {
239 tw->ts_recent = tp.rcv_tsval;
240 tw->ts_recent_stamp = xtime.tv_sec;
241 }
242
243 tcp_tw_put(tw);
244 return TCP_TW_SUCCESS;
245 }
246
247 /* Out of window segment.
248
249 All the segments are ACKed immediately.
250
251 The only exception is new SYN. We accept it, if it is
252 not old duplicate and we are not in danger to be killed
253 by delayed old duplicates. RFC check is that it has
254 newer sequence number works at rates <40Mbit/sec.
255 However, if paws works, it is reliable AND even more,
256 we even may relax silly seq space cutoff.
257
258 RED-PEN: we violate main RFC requirement, if this SYN will appear
259 old duplicate (i.e. we receive RST in reply to SYN-ACK),
260 we must return socket to time-wait state. It is not good,
261 but not fatal yet.
262 */
263
264 if (th->syn && !th->rst && !th->ack && !paws_reject &&
265 (after(TCP_SKB_CB(skb)->seq, tw->rcv_nxt) ||
266 (tp.saw_tstamp && (s32)(tw->ts_recent - tp.rcv_tsval) < 0))) {
267 u32 isn = tw->snd_nxt+65535+2;
268 if (isn == 0)
269 isn++;
270 TCP_SKB_CB(skb)->when = isn;
271 return TCP_TW_SYN;
272 }
273
274 if (paws_reject)
275 NET_INC_STATS_BH(PAWSEstabRejected);
276
277 if(!th->rst) {
278 /* In this case we must reset the TIMEWAIT timer.
279 *
280 * If it is ACKless SYN it may be both old duplicate
281 * and new good SYN with random sequence number <rcv_nxt.
282 * Do not reschedule in the last case.
283 */
284 if (paws_reject || th->ack)
285 tcp_tw_schedule(tw, TCP_TIMEWAIT_LEN);
286
287 /* Send ACK. Note, we do not put the bucket,
288 * it will be released by caller.
289 */
290 return TCP_TW_ACK;
291 }
292 tcp_tw_put(tw);
293 return TCP_TW_SUCCESS;
294 }
295
296 /* Enter the time wait state. This is called with locally disabled BH.
297 * Essentially we whip up a timewait bucket, copy the
298 * relevant info into it from the SK, and mess with hash chains
299 * and list linkage.
300 */
301 static void __tcp_tw_hashdance(struct sock *sk, struct tcp_tw_bucket *tw)
302 {
303 struct tcp_ehash_bucket *ehead = &tcp_ehash[sk->hashent];
304 struct tcp_bind_hashbucket *bhead;
305 struct sock **head, *sktw;
306
307 write_lock(&ehead->lock);
308
309 /* Step 1: Remove SK from established hash. */
310 if (sk->pprev) {
311 if(sk->next)
312 sk->next->pprev = sk->pprev;
313 *sk->pprev = sk->next;
314 sk->pprev = NULL;
315 sock_prot_dec_use(sk->prot);
316 }
317
318 /* Step 2: Hash TW into TIMEWAIT half of established hash table. */
319 head = &(ehead + tcp_ehash_size)->chain;
320 sktw = (struct sock *)tw;
321 if((sktw->next = *head) != NULL)
322 (*head)->pprev = &sktw->next;
323 *head = sktw;
324 sktw->pprev = head;
325 atomic_inc(&tw->refcnt);
326
327 write_unlock(&ehead->lock);
328
329 /* Step 3: Put TW into bind hash. Original socket stays there too.
330 Note, that any socket with sk->num!=0 MUST be bound in binding
331 cache, even if it is closed.
332 */
333 bhead = &tcp_bhash[tcp_bhashfn(sk->num)];
334 spin_lock(&bhead->lock);
335 tw->tb = (struct tcp_bind_bucket *)sk->prev;
336 BUG_TRAP(sk->prev!=NULL);
337 if ((tw->bind_next = tw->tb->owners) != NULL)
338 tw->tb->owners->bind_pprev = &tw->bind_next;
339 tw->tb->owners = (struct sock*)tw;
340 tw->bind_pprev = &tw->tb->owners;
341 spin_unlock(&bhead->lock);
342 }
343
344 /*
345 * Move a socket to time-wait or dead fin-wait-2 state.
346 */
347 void tcp_time_wait(struct sock *sk, int state, int timeo)
348 {
349 struct tcp_tw_bucket *tw = NULL;
350 struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
351 int recycle_ok = 0;
352
353 if (sysctl_tcp_tw_recycle && tp->ts_recent_stamp)
354 recycle_ok = tp->af_specific->remember_stamp(sk);
355
356 if (tcp_tw_count < sysctl_tcp_max_tw_buckets)
357 tw = kmem_cache_alloc(tcp_timewait_cachep, SLAB_ATOMIC);
358
359 if(tw != NULL) {
360 int rto = (tp->rto<<2) - (tp->rto>>1);
361
362 /* Give us an identity. */
363 tw->daddr = sk->daddr;
364 tw->rcv_saddr = sk->rcv_saddr;
365 tw->bound_dev_if= sk->bound_dev_if;
366 tw->num = sk->num;
367 tw->state = TCP_TIME_WAIT;
368 tw->substate = state;
369 tw->sport = sk->sport;
370 tw->dport = sk->dport;
371 tw->family = sk->family;
372 tw->reuse = sk->reuse;
373 tw->rcv_wscale = tp->rcv_wscale;
374 atomic_set(&tw->refcnt, 0);
375
376 tw->hashent = sk->hashent;
377 tw->rcv_nxt = tp->rcv_nxt;
378 tw->snd_nxt = tp->snd_nxt;
379 tw->rcv_wnd = tcp_receive_window(tp);
380 tw->syn_seq = tp->syn_seq;
381 tw->ts_recent = tp->ts_recent;
382 tw->ts_recent_stamp= tp->ts_recent_stamp;
383 tw->pprev_death = NULL;
384
385 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
386 if(tw->family == PF_INET6) {
387 memcpy(&tw->v6_daddr,
388 &sk->net_pinfo.af_inet6.daddr,
389 sizeof(struct in6_addr));
390 memcpy(&tw->v6_rcv_saddr,
391 &sk->net_pinfo.af_inet6.rcv_saddr,
392 sizeof(struct in6_addr));
393 }
394 #endif
395 /* Linkage updates. */
396 __tcp_tw_hashdance(sk, tw);
397
398 /* Get the TIME_WAIT timeout firing. */
399 if (timeo < rto)
400 timeo = rto;
401
402 if (recycle_ok) {
403 tw->timeout = rto;
404 } else {
405 tw->timeout = TCP_TIMEWAIT_LEN;
406 if (state == TCP_TIME_WAIT)
407 timeo = TCP_TIMEWAIT_LEN;
408 }
409
410 tcp_tw_schedule(tw, timeo);
411 } else {
412 /* Sorry, if we're out of memory, just CLOSE this
413 * socket up. We've got bigger problems than
414 * non-graceful socket closings.
415 */
416 if (net_ratelimit())
417 printk(KERN_INFO "TCP: time wait bucket table overflow\n");
418 }
419
420 tcp_update_metrics(sk);
421 tcp_done(sk);
422 }
423
424 /* Kill off TIME_WAIT sockets once their lifetime has expired. */
425 static int tcp_tw_death_row_slot = 0;
426
427 static void tcp_twkill(unsigned long);
428
429 static struct tcp_tw_bucket *tcp_tw_death_row[TCP_TWKILL_SLOTS];
430 static spinlock_t tw_death_lock = SPIN_LOCK_UNLOCKED;
431 static struct timer_list tcp_tw_timer = { function: tcp_twkill };
432
433 static void SMP_TIMER_NAME(tcp_twkill)(unsigned long dummy)
434 {
435 struct tcp_tw_bucket *tw;
436 int killed = 0;
437
438 /* NOTE: compare this to previous version where lock
439 * was released after detaching chain. It was racy,
440 * because tw buckets are scheduled in not serialized context
441 * in 2.3 (with netfilter), and with softnet it is common, because
442 * soft irqs are not sequenced.
443 */
444 spin_lock(&tw_death_lock);
445
446 if (tcp_tw_count == 0)
447 goto out;
448
449 while((tw = tcp_tw_death_row[tcp_tw_death_row_slot]) != NULL) {
450 tcp_tw_death_row[tcp_tw_death_row_slot] = tw->next_death;
451 tw->pprev_death = NULL;
452 spin_unlock(&tw_death_lock);
453
454 tcp_timewait_kill(tw);
455 tcp_tw_put(tw);
456
457 killed++;
458
459 spin_lock(&tw_death_lock);
460 }
461 tcp_tw_death_row_slot =
462 ((tcp_tw_death_row_slot + 1) & (TCP_TWKILL_SLOTS - 1));
463
464 if ((tcp_tw_count -= killed) != 0)
465 mod_timer(&tcp_tw_timer, jiffies+TCP_TWKILL_PERIOD);
466 net_statistics[smp_processor_id()*2].TimeWaited += killed;
467 out:
468 spin_unlock(&tw_death_lock);
469 }
470
471 SMP_TIMER_DEFINE(tcp_twkill, tcp_twkill_task);
472
473 /* These are always called from BH context. See callers in
474 * tcp_input.c to verify this.
475 */
476
477 /* This is for handling early-kills of TIME_WAIT sockets. */
478 void tcp_tw_deschedule(struct tcp_tw_bucket *tw)
479 {
480 spin_lock(&tw_death_lock);
481 if (tw->pprev_death) {
482 if(tw->next_death)
483 tw->next_death->pprev_death = tw->pprev_death;
484 *tw->pprev_death = tw->next_death;
485 tw->pprev_death = NULL;
486 tcp_tw_put(tw);
487 if (--tcp_tw_count == 0)
488 del_timer(&tcp_tw_timer);
489 }
490 spin_unlock(&tw_death_lock);
491 }
492
493 /* Short-time timewait calendar */
494
495 static int tcp_twcal_hand = -1;
496 static int tcp_twcal_jiffie;
497 static void tcp_twcal_tick(unsigned long);
498 static struct timer_list tcp_twcal_timer = {function: tcp_twcal_tick};
499 static struct tcp_tw_bucket *tcp_twcal_row[TCP_TW_RECYCLE_SLOTS];
500
501 void tcp_tw_schedule(struct tcp_tw_bucket *tw, int timeo)
502 {
503 struct tcp_tw_bucket **tpp;
504 int slot;
505
506 /* timeout := RTO * 3.5
507 *
508 * 3.5 = 1+2+0.5 to wait for two retransmits.
509 *
510 * RATIONALE: if FIN arrived and we entered TIME-WAIT state,
511 * our ACK acking that FIN can be lost. If N subsequent retransmitted
512 * FINs (or previous seqments) are lost (probability of such event
513 * is p^(N+1), where p is probability to lose single packet and
514 * time to detect the loss is about RTO*(2^N - 1) with exponential
515 * backoff). Normal timewait length is calculated so, that we
516 * waited at least for one retransmitted FIN (maximal RTO is 120sec).
517 * [ BTW Linux. following BSD, violates this requirement waiting
518 * only for 60sec, we should wait at least for 240 secs.
519 * Well, 240 consumes too much of resources 8)
520 * ]
521 * This interval is not reduced to catch old duplicate and
522 * responces to our wandering segments living for two MSLs.
523 * However, if we use PAWS to detect
524 * old duplicates, we can reduce the interval to bounds required
525 * by RTO, rather than MSL. So, if peer understands PAWS, we
526 * kill tw bucket after 3.5*RTO (it is important that this number
527 * is greater than TS tick!) and detect old duplicates with help
528 * of PAWS.
529 */
530 slot = (timeo + (1<<TCP_TW_RECYCLE_TICK) - 1) >> TCP_TW_RECYCLE_TICK;
531
532 spin_lock(&tw_death_lock);
533
534 /* Unlink it, if it was scheduled */
535 if (tw->pprev_death) {
536 if(tw->next_death)
537 tw->next_death->pprev_death = tw->pprev_death;
538 *tw->pprev_death = tw->next_death;
539 tw->pprev_death = NULL;
540 tcp_tw_count--;
541 } else
542 atomic_inc(&tw->refcnt);
543
544 if (slot >= TCP_TW_RECYCLE_SLOTS) {
545 /* Schedule to slow timer */
546 if (timeo >= TCP_TIMEWAIT_LEN) {
547 slot = TCP_TWKILL_SLOTS-1;
548 } else {
549 slot = (timeo + TCP_TWKILL_PERIOD-1) / TCP_TWKILL_PERIOD;
550 if (slot >= TCP_TWKILL_SLOTS)
551 slot = TCP_TWKILL_SLOTS-1;
552 }
553 tw->ttd = jiffies + timeo;
554 slot = (tcp_tw_death_row_slot + slot) & (TCP_TWKILL_SLOTS - 1);
555 tpp = &tcp_tw_death_row[slot];
556 } else {
557 tw->ttd = jiffies + (slot<<TCP_TW_RECYCLE_TICK);
558
559 if (tcp_twcal_hand < 0) {
560 tcp_twcal_hand = 0;
561 tcp_twcal_jiffie = jiffies;
562 tcp_twcal_timer.expires = tcp_twcal_jiffie + (slot<<TCP_TW_RECYCLE_TICK);
563 add_timer(&tcp_twcal_timer);
564 } else {
565 if ((long)(tcp_twcal_timer.expires - jiffies) > (slot<<TCP_TW_RECYCLE_TICK))
566 mod_timer(&tcp_twcal_timer, jiffies + (slot<<TCP_TW_RECYCLE_TICK));
567 slot = (tcp_twcal_hand + slot)&(TCP_TW_RECYCLE_SLOTS-1);
568 }
569 tpp = &tcp_twcal_row[slot];
570 }
571
572 if((tw->next_death = *tpp) != NULL)
573 (*tpp)->pprev_death = &tw->next_death;
574 *tpp = tw;
575 tw->pprev_death = tpp;
576
577 if (tcp_tw_count++ == 0)
578 mod_timer(&tcp_tw_timer, jiffies+TCP_TWKILL_PERIOD);
579 spin_unlock(&tw_death_lock);
580 }
581
582 void SMP_TIMER_NAME(tcp_twcal_tick)(unsigned long dummy)
583 {
584 int n, slot;
585 unsigned long j;
586 unsigned long now = jiffies;
587 int killed = 0;
588 int adv = 0;
589
590 spin_lock(&tw_death_lock);
591 if (tcp_twcal_hand < 0)
592 goto out;
593
594 slot = tcp_twcal_hand;
595 j = tcp_twcal_jiffie;
596
597 for (n=0; n<TCP_TW_RECYCLE_SLOTS; n++) {
598 if ((long)(j - now) <= 0) {
599 struct tcp_tw_bucket *tw;
600
601 while((tw = tcp_twcal_row[slot]) != NULL) {
602 tcp_twcal_row[slot] = tw->next_death;
603 tw->pprev_death = NULL;
604
605 tcp_timewait_kill(tw);
606 tcp_tw_put(tw);
607 killed++;
608 }
609 } else {
610 if (!adv) {
611 adv = 1;
612 tcp_twcal_jiffie = j;
613 tcp_twcal_hand = slot;
614 }
615
616 if (tcp_twcal_row[slot] != NULL) {
617 mod_timer(&tcp_twcal_timer, j);
618 goto out;
619 }
620 }
621 j += (1<<TCP_TW_RECYCLE_TICK);
622 slot = (slot+1)&(TCP_TW_RECYCLE_SLOTS-1);
623 }
624 tcp_twcal_hand = -1;
625
626 out:
627 if ((tcp_tw_count -= killed) == 0)
628 del_timer(&tcp_tw_timer);
629 net_statistics[smp_processor_id()*2].TimeWaitKilled += killed;
630 spin_unlock(&tw_death_lock);
631 }
632
633 SMP_TIMER_DEFINE(tcp_twcal_tick, tcp_twcal_tasklet);
634
635
636 /* This is not only more efficient than what we used to do, it eliminates
637 * a lot of code duplication between IPv4/IPv6 SYN recv processing. -DaveM
638 *
639 * Actually, we could lots of memory writes here. tp of listening
640 * socket contains all necessary default parameters.
641 */
642 struct sock *tcp_create_openreq_child(struct sock *sk, struct open_request *req, struct sk_buff *skb)
643 {
644 struct sock *newsk = sk_alloc(PF_INET, GFP_ATOMIC, 0);
645
646 if(newsk != NULL) {
647 struct tcp_opt *newtp;
648 #ifdef CONFIG_FILTER
649 struct sk_filter *filter;
650 #endif
651
652 memcpy(newsk, sk, sizeof(*newsk));
653 newsk->state = TCP_SYN_RECV;
654
655 /* SANITY */
656 newsk->pprev = NULL;
657 newsk->prev = NULL;
658
659 /* Clone the TCP header template */
660 newsk->dport = req->rmt_port;
661
662 sock_lock_init(newsk);
663 bh_lock_sock(newsk);
664
665 newsk->dst_lock = RW_LOCK_UNLOCKED;
666 atomic_set(&newsk->rmem_alloc, 0);
667 skb_queue_head_init(&newsk->receive_queue);
668 atomic_set(&newsk->wmem_alloc, 0);
669 skb_queue_head_init(&newsk->write_queue);
670 atomic_set(&newsk->omem_alloc, 0);
671 newsk->wmem_queued = 0;
672 newsk->forward_alloc = 0;
673
674 newsk->done = 0;
675 newsk->userlocks = sk->userlocks & ~SOCK_BINDPORT_LOCK;
676 newsk->proc = 0;
677 newsk->backlog.head = newsk->backlog.tail = NULL;
678 newsk->callback_lock = RW_LOCK_UNLOCKED;
679 skb_queue_head_init(&newsk->error_queue);
680 newsk->write_space = tcp_write_space;
681 #ifdef CONFIG_FILTER
682 if ((filter = newsk->filter) != NULL)
683 sk_filter_charge(newsk, filter);
684 #endif
685
686 /* Now setup tcp_opt */
687 newtp = &(newsk->tp_pinfo.af_tcp);
688 newtp->pred_flags = 0;
689 newtp->rcv_nxt = req->rcv_isn + 1;
690 newtp->snd_nxt = req->snt_isn + 1;
691 newtp->snd_una = req->snt_isn + 1;
692 newtp->snd_sml = req->snt_isn + 1;
693
694 tcp_delack_init(newtp);
695
696 tcp_prequeue_init(newtp);
697
698 tcp_init_wl(newtp, req->snt_isn, req->rcv_isn);
699
700 newtp->retransmits = 0;
701 newtp->backoff = 0;
702 newtp->srtt = 0;
703 newtp->mdev = TCP_TIMEOUT_INIT;
704 newtp->rto = TCP_TIMEOUT_INIT;
705
706 newtp->packets_out = 0;
707 newtp->left_out = 0;
708 newtp->retrans_out = 0;
709 newtp->sacked_out = 0;
710 newtp->fackets_out = 0;
711 newtp->snd_ssthresh = 0x7fffffff;
712
713 /* So many TCP implementations out there (incorrectly) count the
714 * initial SYN frame in their delayed-ACK and congestion control
715 * algorithms that we must have the following bandaid to talk
716 * efficiently to them. -DaveM
717 */
718 newtp->snd_cwnd = 2;
719 newtp->snd_cwnd_cnt = 0;
720
721 newtp->ca_state = TCP_CA_Open;
722 tcp_init_xmit_timers(newsk);
723 skb_queue_head_init(&newtp->out_of_order_queue);
724 newtp->send_head = NULL;
725 newtp->rcv_wup = req->rcv_isn + 1;
726 newtp->write_seq = req->snt_isn + 1;
727 newtp->pushed_seq = newtp->write_seq;
728 newtp->copied_seq = req->rcv_isn + 1;
729
730 newtp->saw_tstamp = 0;
731
732 newtp->dsack = 0;
733 newtp->eff_sacks = 0;
734
735 newtp->probes_out = 0;
736 newtp->num_sacks = 0;
737 newtp->syn_seq = req->rcv_isn;
738 newtp->fin_seq = req->rcv_isn;
739 newtp->urg_data = 0;
740 newtp->listen_opt = NULL;
741 newtp->accept_queue = newtp->accept_queue_tail = NULL;
742 /* Deinitialize syn_wait_lock to trap illegal accesses. */
743 memset(&newtp->syn_wait_lock, 0, sizeof(newtp->syn_wait_lock));
744
745 /* Back to base struct sock members. */
746 newsk->err = 0;
747 newsk->priority = 0;
748 atomic_set(&newsk->refcnt, 2);
749 #ifdef INET_REFCNT_DEBUG
750 atomic_inc(&inet_sock_nr);
751 #endif
752 atomic_inc(&tcp_sockets_allocated);
753
754 if (newsk->keepopen)
755 tcp_reset_keepalive_timer(newsk, keepalive_time_when(newtp));
756 newsk->socket = NULL;
757 newsk->sleep = NULL;
758
759 newtp->tstamp_ok = req->tstamp_ok;
760 if((newtp->sack_ok = req->sack_ok) != 0) {
761 if (sysctl_tcp_fack)
762 newtp->sack_ok |= 2;
763 }
764 newtp->window_clamp = req->window_clamp;
765 newtp->rcv_ssthresh = req->rcv_wnd;
766 newtp->rcv_wnd = req->rcv_wnd;
767 newtp->wscale_ok = req->wscale_ok;
768 if (newtp->wscale_ok) {
769 newtp->snd_wscale = req->snd_wscale;
770 newtp->rcv_wscale = req->rcv_wscale;
771 } else {
772 newtp->snd_wscale = newtp->rcv_wscale = 0;
773 newtp->window_clamp = min(newtp->window_clamp,65535);
774 }
775 newtp->snd_wnd = ntohs(skb->h.th->window) << newtp->snd_wscale;
776 newtp->max_window = newtp->snd_wnd;
777
778 if (newtp->tstamp_ok) {
779 newtp->ts_recent = req->ts_recent;
780 newtp->ts_recent_stamp = xtime.tv_sec;
781 newtp->tcp_header_len = sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
782 } else {
783 newtp->ts_recent_stamp = 0;
784 newtp->tcp_header_len = sizeof(struct tcphdr);
785 }
786 if (skb->len >= TCP_MIN_RCVMSS+newtp->tcp_header_len)
787 newtp->ack.last_seg_size = skb->len-newtp->tcp_header_len;
788 newtp->mss_clamp = req->mss;
789 TCP_ECN_openreq_child(newtp, req);
790 }
791 return newsk;
792 }
793
794 /*
795 * Process an incoming packet for SYN_RECV sockets represented
796 * as an open_request.
797 */
798
799 struct sock *tcp_check_req(struct sock *sk,struct sk_buff *skb,
800 struct open_request *req,
801 struct open_request **prev)
802 {
803 struct tcphdr *th = skb->h.th;
804 struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
805 u32 flg = tcp_flag_word(th) & (TCP_FLAG_RST|TCP_FLAG_SYN|TCP_FLAG_ACK);
806 int paws_reject = 0;
807 struct tcp_opt ttp;
808 struct sock *child;
809
810 ttp.saw_tstamp = 0;
811 if (th->doff > (sizeof(struct tcphdr)>>2)) {
812 tcp_parse_options(skb, &ttp, 0);
813
814 if (ttp.saw_tstamp) {
815 ttp.ts_recent = req->ts_recent;
816 /* We do not store true stamp, but it is not required,
817 * it can be estimated (approximately)
818 * from another data.
819 */
820 ttp.ts_recent_stamp = xtime.tv_sec - ((TCP_TIMEOUT_INIT/HZ)<<req->retrans);
821 paws_reject = tcp_paws_check(&ttp, th->rst);
822 }
823 }
824
825 /* Check for pure retransmited SYN. */
826 if (TCP_SKB_CB(skb)->seq == req->rcv_isn &&
827 flg == TCP_FLAG_SYN &&
828 !paws_reject) {
829 /*
830 * RFC793 draws (Incorrectly! It was fixed in RFC1122)
831 * this case on figure 6 and figure 8, but formal
832 * protocol description says NOTHING.
833 * To be more exact, it says that we should send ACK,
834 * because this segment (at least, if it has no data)
835 * is out of window.
836 *
837 * CONCLUSION: RFC793 (even with RFC1122) DOES NOT
838 * describe SYN-RECV state. All the description
839 * is wrong, we cannot believe to it and should
840 * rely only on common sense and implementation
841 * experience.
842 *
843 * Enforce "SYN-ACK" according to figure 8, figure 6
844 * of RFC793, fixed by RFC1122.
845 */
846 req->class->rtx_syn_ack(sk, req, NULL);
847 return NULL;
848 }
849
850 /* Further reproduces section "SEGMENT ARRIVES"
851 for state SYN-RECEIVED of RFC793.
852 It is broken, however, it does not work only
853 when SYNs are crossed, which is impossible in our
854 case.
855
856 But generally, we should (RFC lies!) to accept ACK
857 from SYNACK both here and in tcp_rcv_state_process().
858 tcp_rcv_state_process() does not, hence, we do not too.
859
860 Note that the case is absolutely generic:
861 we cannot optimize anything here without
862 violating protocol. All the checks must be made
863 before attempt to create socket.
864 */
865
866 /* RFC793: "first check sequence number". */
867
868 if (paws_reject || !tcp_in_window(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq,
869 req->rcv_isn+1, req->rcv_isn+1+req->rcv_wnd)) {
870 /* Out of window: send ACK and drop. */
871 if (!(flg & TCP_FLAG_RST))
872 req->class->send_ack(skb, req);
873 if (paws_reject)
874 NET_INC_STATS_BH(PAWSEstabRejected);
875 return NULL;
876 }
877
878 /* In sequence, PAWS is OK. */
879
880 if (ttp.saw_tstamp && !after(TCP_SKB_CB(skb)->seq, req->rcv_isn+1))
881 req->ts_recent = ttp.rcv_tsval;
882
883 if (TCP_SKB_CB(skb)->seq == req->rcv_isn) {
884 /* Truncate SYN, it is out of window starting
885 at req->rcv_isn+1. */
886 flg &= ~TCP_FLAG_SYN;
887 }
888
889 /* RFC793: "second check the RST bit" and
890 * "fourth, check the SYN bit"
891 */
892 if (flg & (TCP_FLAG_RST|TCP_FLAG_SYN))
893 goto embryonic_reset;
894
895 /* RFC793: "fifth check the ACK field" */
896
897 if (!(flg & TCP_FLAG_ACK))
898 return NULL;
899
900 /* Invalid ACK: reset will be sent by listening socket */
901 if (TCP_SKB_CB(skb)->ack_seq != req->snt_isn+1)
902 return sk;
903 /* Also, it would be not so bad idea to check rcv_tsecr, which
904 * is essentially ACK extension and too early or too late values
905 * should cause reset in unsynchronized states.
906 */
907
908 /* If TCP_DEFER_ACCEPT is set, drop bare ACK. */
909 if (tp->defer_accept && TCP_SKB_CB(skb)->end_seq == req->rcv_isn+1) {
910 req->acked = 1;
911 return NULL;
912 }
913
914 /* OK, ACK is valid, create big socket and
915 * feed this segment to it. It will repeat all
916 * the tests. THIS SEGMENT MUST MOVE SOCKET TO
917 * ESTABLISHED STATE. If it will be dropped after
918 * socket is created, wait for troubles.
919 */
920 child = tp->af_specific->syn_recv_sock(sk, skb, req, NULL);
921 if (child == NULL)
922 goto listen_overflow;
923
924 tcp_synq_unlink(tp, req, prev);
925 tcp_synq_removed(sk, req);
926
927 tcp_acceptq_queue(sk, req, child);
928 return child;
929
930 listen_overflow:
931 if (!sysctl_tcp_abort_on_overflow) {
932 req->acked = 1;
933 return NULL;
934 }
935
936 embryonic_reset:
937 NET_INC_STATS_BH(EmbryonicRsts);
938 if (!(flg & TCP_FLAG_RST))
939 req->class->send_reset(skb);
940
941 tcp_synq_drop(sk, req, prev);
942 return NULL;
943 }
944
945 /*
946 * Queue segment on the new socket if the new socket is active,
947 * otherwise we just shortcircuit this and continue with
948 * the new socket.
949 */
950
951 int tcp_child_process(struct sock *parent, struct sock *child,
952 struct sk_buff *skb)
953 {
954 int ret = 0;
955 int state = child->state;
956
957 if (child->lock.users == 0) {
958 ret = tcp_rcv_state_process(child, skb, skb->h.th, skb->len);
959
960 /* Wakeup parent, send SIGIO */
961 if (state == TCP_SYN_RECV && child->state != state)
962 parent->data_ready(parent, 0);
963 } else {
964 /* Alas, it is possible again, because we do lookup
965 * in main socket hash table and lock on listening
966 * socket does not protect us more.
967 */
968 sk_add_backlog(child, skb);
969 }
970
971 bh_unlock_sock(child);
972 sock_put(child);
973 return ret;
974 }
975
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