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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 18:20:36 -0400
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 18:20:36 -0400
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /net/ipv4/tcp_minisocks.c
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
Diffstat (limited to 'net/ipv4/tcp_minisocks.c')
-rw-r--r--net/ipv4/tcp_minisocks.c1077
1 files changed, 1077 insertions, 0 deletions
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
new file mode 100644
index 000000000000..fd70509f0d53
--- /dev/null
+++ b/net/ipv4/tcp_minisocks.c
@@ -0,0 +1,1077 @@
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 1.15 2002/02/01 22:01:04 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/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>
31
32#ifdef CONFIG_SYSCTL
33#define SYNC_INIT 0 /* let the user enable it */
34#else
35#define SYNC_INIT 1
36#endif
37
38int sysctl_tcp_tw_recycle;
39int sysctl_tcp_max_tw_buckets = NR_FILE*2;
40
41int sysctl_tcp_syncookies = SYNC_INIT;
42int sysctl_tcp_abort_on_overflow;
43
44static void tcp_tw_schedule(struct tcp_tw_bucket *tw, int timeo);
45
46static __inline__ int tcp_in_window(u32 seq, u32 end_seq, u32 s_win, u32 e_win)
47{
48 if (seq == s_win)
49 return 1;
50 if (after(end_seq, s_win) && before(seq, e_win))
51 return 1;
52 return (seq == e_win && seq == end_seq);
53}
54
55/* New-style handling of TIME_WAIT sockets. */
56
57int tcp_tw_count;
58
59
60/* Must be called with locally disabled BHs. */
61static void tcp_timewait_kill(struct tcp_tw_bucket *tw)
62{
63 struct tcp_ehash_bucket *ehead;
64 struct tcp_bind_hashbucket *bhead;
65 struct tcp_bind_bucket *tb;
66
67 /* Unlink from established hashes. */
68 ehead = &tcp_ehash[tw->tw_hashent];
69 write_lock(&ehead->lock);
70 if (hlist_unhashed(&tw->tw_node)) {
71 write_unlock(&ehead->lock);
72 return;
73 }
74 __hlist_del(&tw->tw_node);
75 sk_node_init(&tw->tw_node);
76 write_unlock(&ehead->lock);
77
78 /* Disassociate with bind bucket. */
79 bhead = &tcp_bhash[tcp_bhashfn(tw->tw_num)];
80 spin_lock(&bhead->lock);
81 tb = tw->tw_tb;
82 __hlist_del(&tw->tw_bind_node);
83 tw->tw_tb = NULL;
84 tcp_bucket_destroy(tb);
85 spin_unlock(&bhead->lock);
86
87#ifdef INET_REFCNT_DEBUG
88 if (atomic_read(&tw->tw_refcnt) != 1) {
89 printk(KERN_DEBUG "tw_bucket %p refcnt=%d\n", tw,
90 atomic_read(&tw->tw_refcnt));
91 }
92#endif
93 tcp_tw_put(tw);
94}
95
96/*
97 * * Main purpose of TIME-WAIT state is to close connection gracefully,
98 * when one of ends sits in LAST-ACK or CLOSING retransmitting FIN
99 * (and, probably, tail of data) and one or more our ACKs are lost.
100 * * What is TIME-WAIT timeout? It is associated with maximal packet
101 * lifetime in the internet, which results in wrong conclusion, that
102 * it is set to catch "old duplicate segments" wandering out of their path.
103 * It is not quite correct. This timeout is calculated so that it exceeds
104 * maximal retransmission timeout enough to allow to lose one (or more)
105 * segments sent by peer and our ACKs. This time may be calculated from RTO.
106 * * When TIME-WAIT socket receives RST, it means that another end
107 * finally closed and we are allowed to kill TIME-WAIT too.
108 * * Second purpose of TIME-WAIT is catching old duplicate segments.
109 * Well, certainly it is pure paranoia, but if we load TIME-WAIT
110 * with this semantics, we MUST NOT kill TIME-WAIT state with RSTs.
111 * * If we invented some more clever way to catch duplicates
112 * (f.e. based on PAWS), we could truncate TIME-WAIT to several RTOs.
113 *
114 * The algorithm below is based on FORMAL INTERPRETATION of RFCs.
115 * When you compare it to RFCs, please, read section SEGMENT ARRIVES
116 * from the very beginning.
117 *
118 * NOTE. With recycling (and later with fin-wait-2) TW bucket
119 * is _not_ stateless. It means, that strictly speaking we must
120 * spinlock it. I do not want! Well, probability of misbehaviour
121 * is ridiculously low and, seems, we could use some mb() tricks
122 * to avoid misread sequence numbers, states etc. --ANK
123 */
124enum tcp_tw_status
125tcp_timewait_state_process(struct tcp_tw_bucket *tw, struct sk_buff *skb,
126 struct tcphdr *th, unsigned len)
127{
128 struct tcp_options_received tmp_opt;
129 int paws_reject = 0;
130
131 tmp_opt.saw_tstamp = 0;
132 if (th->doff > (sizeof(struct tcphdr) >> 2) && tw->tw_ts_recent_stamp) {
133 tcp_parse_options(skb, &tmp_opt, 0);
134
135 if (tmp_opt.saw_tstamp) {
136 tmp_opt.ts_recent = tw->tw_ts_recent;
137 tmp_opt.ts_recent_stamp = tw->tw_ts_recent_stamp;
138 paws_reject = tcp_paws_check(&tmp_opt, th->rst);
139 }
140 }
141
142 if (tw->tw_substate == TCP_FIN_WAIT2) {
143 /* Just repeat all the checks of tcp_rcv_state_process() */
144
145 /* Out of window, send ACK */
146 if (paws_reject ||
147 !tcp_in_window(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq,
148 tw->tw_rcv_nxt,
149 tw->tw_rcv_nxt + tw->tw_rcv_wnd))
150 return TCP_TW_ACK;
151
152 if (th->rst)
153 goto kill;
154
155 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tw->tw_rcv_nxt))
156 goto kill_with_rst;
157
158 /* Dup ACK? */
159 if (!after(TCP_SKB_CB(skb)->end_seq, tw->tw_rcv_nxt) ||
160 TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq) {
161 tcp_tw_put(tw);
162 return TCP_TW_SUCCESS;
163 }
164
165 /* New data or FIN. If new data arrive after half-duplex close,
166 * reset.
167 */
168 if (!th->fin ||
169 TCP_SKB_CB(skb)->end_seq != tw->tw_rcv_nxt + 1) {
170kill_with_rst:
171 tcp_tw_deschedule(tw);
172 tcp_tw_put(tw);
173 return TCP_TW_RST;
174 }
175
176 /* FIN arrived, enter true time-wait state. */
177 tw->tw_substate = TCP_TIME_WAIT;
178 tw->tw_rcv_nxt = TCP_SKB_CB(skb)->end_seq;
179 if (tmp_opt.saw_tstamp) {
180 tw->tw_ts_recent_stamp = xtime.tv_sec;
181 tw->tw_ts_recent = tmp_opt.rcv_tsval;
182 }
183
184 /* I am shamed, but failed to make it more elegant.
185 * Yes, it is direct reference to IP, which is impossible
186 * to generalize to IPv6. Taking into account that IPv6
187 * do not undertsnad recycling in any case, it not
188 * a big problem in practice. --ANK */
189 if (tw->tw_family == AF_INET &&
190 sysctl_tcp_tw_recycle && tw->tw_ts_recent_stamp &&
191 tcp_v4_tw_remember_stamp(tw))
192 tcp_tw_schedule(tw, tw->tw_timeout);
193 else
194 tcp_tw_schedule(tw, TCP_TIMEWAIT_LEN);
195 return TCP_TW_ACK;
196 }
197
198 /*
199 * Now real TIME-WAIT state.
200 *
201 * RFC 1122:
202 * "When a connection is [...] on TIME-WAIT state [...]
203 * [a TCP] MAY accept a new SYN from the remote TCP to
204 * reopen the connection directly, if it:
205 *
206 * (1) assigns its initial sequence number for the new
207 * connection to be larger than the largest sequence
208 * number it used on the previous connection incarnation,
209 * and
210 *
211 * (2) returns to TIME-WAIT state if the SYN turns out
212 * to be an old duplicate".
213 */
214
215 if (!paws_reject &&
216 (TCP_SKB_CB(skb)->seq == tw->tw_rcv_nxt &&
217 (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq || th->rst))) {
218 /* In window segment, it may be only reset or bare ack. */
219
220 if (th->rst) {
221 /* This is TIME_WAIT assasination, in two flavors.
222 * Oh well... nobody has a sufficient solution to this
223 * protocol bug yet.
224 */
225 if (sysctl_tcp_rfc1337 == 0) {
226kill:
227 tcp_tw_deschedule(tw);
228 tcp_tw_put(tw);
229 return TCP_TW_SUCCESS;
230 }
231 }
232 tcp_tw_schedule(tw, TCP_TIMEWAIT_LEN);
233
234 if (tmp_opt.saw_tstamp) {
235 tw->tw_ts_recent = tmp_opt.rcv_tsval;
236 tw->tw_ts_recent_stamp = xtime.tv_sec;
237 }
238
239 tcp_tw_put(tw);
240 return TCP_TW_SUCCESS;
241 }
242
243 /* Out of window segment.
244
245 All the segments are ACKed immediately.
246
247 The only exception is new SYN. We accept it, if it is
248 not old duplicate and we are not in danger to be killed
249 by delayed old duplicates. RFC check is that it has
250 newer sequence number works at rates <40Mbit/sec.
251 However, if paws works, it is reliable AND even more,
252 we even may relax silly seq space cutoff.
253
254 RED-PEN: we violate main RFC requirement, if this SYN will appear
255 old duplicate (i.e. we receive RST in reply to SYN-ACK),
256 we must return socket to time-wait state. It is not good,
257 but not fatal yet.
258 */
259
260 if (th->syn && !th->rst && !th->ack && !paws_reject &&
261 (after(TCP_SKB_CB(skb)->seq, tw->tw_rcv_nxt) ||
262 (tmp_opt.saw_tstamp && (s32)(tw->tw_ts_recent - tmp_opt.rcv_tsval) < 0))) {
263 u32 isn = tw->tw_snd_nxt + 65535 + 2;
264 if (isn == 0)
265 isn++;
266 TCP_SKB_CB(skb)->when = isn;
267 return TCP_TW_SYN;
268 }
269
270 if (paws_reject)
271 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
272
273 if(!th->rst) {
274 /* In this case we must reset the TIMEWAIT timer.
275 *
276 * If it is ACKless SYN it may be both old duplicate
277 * and new good SYN with random sequence number <rcv_nxt.
278 * Do not reschedule in the last case.
279 */
280 if (paws_reject || th->ack)
281 tcp_tw_schedule(tw, TCP_TIMEWAIT_LEN);
282
283 /* Send ACK. Note, we do not put the bucket,
284 * it will be released by caller.
285 */
286 return TCP_TW_ACK;
287 }
288 tcp_tw_put(tw);
289 return TCP_TW_SUCCESS;
290}
291
292/* Enter the time wait state. This is called with locally disabled BH.
293 * Essentially we whip up a timewait bucket, copy the
294 * relevant info into it from the SK, and mess with hash chains
295 * and list linkage.
296 */
297static void __tcp_tw_hashdance(struct sock *sk, struct tcp_tw_bucket *tw)
298{
299 struct tcp_ehash_bucket *ehead = &tcp_ehash[sk->sk_hashent];
300 struct tcp_bind_hashbucket *bhead;
301
302 /* Step 1: Put TW into bind hash. Original socket stays there too.
303 Note, that any socket with inet_sk(sk)->num != 0 MUST be bound in
304 binding cache, even if it is closed.
305 */
306 bhead = &tcp_bhash[tcp_bhashfn(inet_sk(sk)->num)];
307 spin_lock(&bhead->lock);
308 tw->tw_tb = tcp_sk(sk)->bind_hash;
309 BUG_TRAP(tcp_sk(sk)->bind_hash);
310 tw_add_bind_node(tw, &tw->tw_tb->owners);
311 spin_unlock(&bhead->lock);
312
313 write_lock(&ehead->lock);
314
315 /* Step 2: Remove SK from established hash. */
316 if (__sk_del_node_init(sk))
317 sock_prot_dec_use(sk->sk_prot);
318
319 /* Step 3: Hash TW into TIMEWAIT half of established hash table. */
320 tw_add_node(tw, &(ehead + tcp_ehash_size)->chain);
321 atomic_inc(&tw->tw_refcnt);
322
323 write_unlock(&ehead->lock);
324}
325
326/*
327 * Move a socket to time-wait or dead fin-wait-2 state.
328 */
329void tcp_time_wait(struct sock *sk, int state, int timeo)
330{
331 struct tcp_tw_bucket *tw = NULL;
332 struct tcp_sock *tp = tcp_sk(sk);
333 int recycle_ok = 0;
334
335 if (sysctl_tcp_tw_recycle && tp->rx_opt.ts_recent_stamp)
336 recycle_ok = tp->af_specific->remember_stamp(sk);
337
338 if (tcp_tw_count < sysctl_tcp_max_tw_buckets)
339 tw = kmem_cache_alloc(tcp_timewait_cachep, SLAB_ATOMIC);
340
341 if(tw != NULL) {
342 struct inet_sock *inet = inet_sk(sk);
343 int rto = (tp->rto<<2) - (tp->rto>>1);
344
345 /* Give us an identity. */
346 tw->tw_daddr = inet->daddr;
347 tw->tw_rcv_saddr = inet->rcv_saddr;
348 tw->tw_bound_dev_if = sk->sk_bound_dev_if;
349 tw->tw_num = inet->num;
350 tw->tw_state = TCP_TIME_WAIT;
351 tw->tw_substate = state;
352 tw->tw_sport = inet->sport;
353 tw->tw_dport = inet->dport;
354 tw->tw_family = sk->sk_family;
355 tw->tw_reuse = sk->sk_reuse;
356 tw->tw_rcv_wscale = tp->rx_opt.rcv_wscale;
357 atomic_set(&tw->tw_refcnt, 1);
358
359 tw->tw_hashent = sk->sk_hashent;
360 tw->tw_rcv_nxt = tp->rcv_nxt;
361 tw->tw_snd_nxt = tp->snd_nxt;
362 tw->tw_rcv_wnd = tcp_receive_window(tp);
363 tw->tw_ts_recent = tp->rx_opt.ts_recent;
364 tw->tw_ts_recent_stamp = tp->rx_opt.ts_recent_stamp;
365 tw_dead_node_init(tw);
366
367#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
368 if (tw->tw_family == PF_INET6) {
369 struct ipv6_pinfo *np = inet6_sk(sk);
370
371 ipv6_addr_copy(&tw->tw_v6_daddr, &np->daddr);
372 ipv6_addr_copy(&tw->tw_v6_rcv_saddr, &np->rcv_saddr);
373 tw->tw_v6_ipv6only = np->ipv6only;
374 } else {
375 memset(&tw->tw_v6_daddr, 0, sizeof(tw->tw_v6_daddr));
376 memset(&tw->tw_v6_rcv_saddr, 0, sizeof(tw->tw_v6_rcv_saddr));
377 tw->tw_v6_ipv6only = 0;
378 }
379#endif
380 /* Linkage updates. */
381 __tcp_tw_hashdance(sk, tw);
382
383 /* Get the TIME_WAIT timeout firing. */
384 if (timeo < rto)
385 timeo = rto;
386
387 if (recycle_ok) {
388 tw->tw_timeout = rto;
389 } else {
390 tw->tw_timeout = TCP_TIMEWAIT_LEN;
391 if (state == TCP_TIME_WAIT)
392 timeo = TCP_TIMEWAIT_LEN;
393 }
394
395 tcp_tw_schedule(tw, timeo);
396 tcp_tw_put(tw);
397 } else {
398 /* Sorry, if we're out of memory, just CLOSE this
399 * socket up. We've got bigger problems than
400 * non-graceful socket closings.
401 */
402 if (net_ratelimit())
403 printk(KERN_INFO "TCP: time wait bucket table overflow\n");
404 }
405
406 tcp_update_metrics(sk);
407 tcp_done(sk);
408}
409
410/* Kill off TIME_WAIT sockets once their lifetime has expired. */
411static int tcp_tw_death_row_slot;
412
413static void tcp_twkill(unsigned long);
414
415/* TIME_WAIT reaping mechanism. */
416#define TCP_TWKILL_SLOTS 8 /* Please keep this a power of 2. */
417#define TCP_TWKILL_PERIOD (TCP_TIMEWAIT_LEN/TCP_TWKILL_SLOTS)
418
419#define TCP_TWKILL_QUOTA 100
420
421static struct hlist_head tcp_tw_death_row[TCP_TWKILL_SLOTS];
422static DEFINE_SPINLOCK(tw_death_lock);
423static struct timer_list tcp_tw_timer = TIMER_INITIALIZER(tcp_twkill, 0, 0);
424static void twkill_work(void *);
425static DECLARE_WORK(tcp_twkill_work, twkill_work, NULL);
426static u32 twkill_thread_slots;
427
428/* Returns non-zero if quota exceeded. */
429static int tcp_do_twkill_work(int slot, unsigned int quota)
430{
431 struct tcp_tw_bucket *tw;
432 struct hlist_node *node;
433 unsigned int killed;
434 int ret;
435
436 /* NOTE: compare this to previous version where lock
437 * was released after detaching chain. It was racy,
438 * because tw buckets are scheduled in not serialized context
439 * in 2.3 (with netfilter), and with softnet it is common, because
440 * soft irqs are not sequenced.
441 */
442 killed = 0;
443 ret = 0;
444rescan:
445 tw_for_each_inmate(tw, node, &tcp_tw_death_row[slot]) {
446 __tw_del_dead_node(tw);
447 spin_unlock(&tw_death_lock);
448 tcp_timewait_kill(tw);
449 tcp_tw_put(tw);
450 killed++;
451 spin_lock(&tw_death_lock);
452 if (killed > quota) {
453 ret = 1;
454 break;
455 }
456
457 /* While we dropped tw_death_lock, another cpu may have
458 * killed off the next TW bucket in the list, therefore
459 * do a fresh re-read of the hlist head node with the
460 * lock reacquired. We still use the hlist traversal
461 * macro in order to get the prefetches.
462 */
463 goto rescan;
464 }
465
466 tcp_tw_count -= killed;
467 NET_ADD_STATS_BH(LINUX_MIB_TIMEWAITED, killed);
468
469 return ret;
470}
471
472static void tcp_twkill(unsigned long dummy)
473{
474 int need_timer, ret;
475
476 spin_lock(&tw_death_lock);
477
478 if (tcp_tw_count == 0)
479 goto out;
480
481 need_timer = 0;
482 ret = tcp_do_twkill_work(tcp_tw_death_row_slot, TCP_TWKILL_QUOTA);
483 if (ret) {
484 twkill_thread_slots |= (1 << tcp_tw_death_row_slot);
485 mb();
486 schedule_work(&tcp_twkill_work);
487 need_timer = 1;
488 } else {
489 /* We purged the entire slot, anything left? */
490 if (tcp_tw_count)
491 need_timer = 1;
492 }
493 tcp_tw_death_row_slot =
494 ((tcp_tw_death_row_slot + 1) & (TCP_TWKILL_SLOTS - 1));
495 if (need_timer)
496 mod_timer(&tcp_tw_timer, jiffies + TCP_TWKILL_PERIOD);
497out:
498 spin_unlock(&tw_death_lock);
499}
500
501extern void twkill_slots_invalid(void);
502
503static void twkill_work(void *dummy)
504{
505 int i;
506
507 if ((TCP_TWKILL_SLOTS - 1) > (sizeof(twkill_thread_slots) * 8))
508 twkill_slots_invalid();
509
510 while (twkill_thread_slots) {
511 spin_lock_bh(&tw_death_lock);
512 for (i = 0; i < TCP_TWKILL_SLOTS; i++) {
513 if (!(twkill_thread_slots & (1 << i)))
514 continue;
515
516 while (tcp_do_twkill_work(i, TCP_TWKILL_QUOTA) != 0) {
517 if (need_resched()) {
518 spin_unlock_bh(&tw_death_lock);
519 schedule();
520 spin_lock_bh(&tw_death_lock);
521 }
522 }
523
524 twkill_thread_slots &= ~(1 << i);
525 }
526 spin_unlock_bh(&tw_death_lock);
527 }
528}
529
530/* These are always called from BH context. See callers in
531 * tcp_input.c to verify this.
532 */
533
534/* This is for handling early-kills of TIME_WAIT sockets. */
535void tcp_tw_deschedule(struct tcp_tw_bucket *tw)
536{
537 spin_lock(&tw_death_lock);
538 if (tw_del_dead_node(tw)) {
539 tcp_tw_put(tw);
540 if (--tcp_tw_count == 0)
541 del_timer(&tcp_tw_timer);
542 }
543 spin_unlock(&tw_death_lock);
544 tcp_timewait_kill(tw);
545}
546
547/* Short-time timewait calendar */
548
549static int tcp_twcal_hand = -1;
550static int tcp_twcal_jiffie;
551static void tcp_twcal_tick(unsigned long);
552static struct timer_list tcp_twcal_timer =
553 TIMER_INITIALIZER(tcp_twcal_tick, 0, 0);
554static struct hlist_head tcp_twcal_row[TCP_TW_RECYCLE_SLOTS];
555
556static void tcp_tw_schedule(struct tcp_tw_bucket *tw, int timeo)
557{
558 struct hlist_head *list;
559 int slot;
560
561 /* timeout := RTO * 3.5
562 *
563 * 3.5 = 1+2+0.5 to wait for two retransmits.
564 *
565 * RATIONALE: if FIN arrived and we entered TIME-WAIT state,
566 * our ACK acking that FIN can be lost. If N subsequent retransmitted
567 * FINs (or previous seqments) are lost (probability of such event
568 * is p^(N+1), where p is probability to lose single packet and
569 * time to detect the loss is about RTO*(2^N - 1) with exponential
570 * backoff). Normal timewait length is calculated so, that we
571 * waited at least for one retransmitted FIN (maximal RTO is 120sec).
572 * [ BTW Linux. following BSD, violates this requirement waiting
573 * only for 60sec, we should wait at least for 240 secs.
574 * Well, 240 consumes too much of resources 8)
575 * ]
576 * This interval is not reduced to catch old duplicate and
577 * responces to our wandering segments living for two MSLs.
578 * However, if we use PAWS to detect
579 * old duplicates, we can reduce the interval to bounds required
580 * by RTO, rather than MSL. So, if peer understands PAWS, we
581 * kill tw bucket after 3.5*RTO (it is important that this number
582 * is greater than TS tick!) and detect old duplicates with help
583 * of PAWS.
584 */
585 slot = (timeo + (1<<TCP_TW_RECYCLE_TICK) - 1) >> TCP_TW_RECYCLE_TICK;
586
587 spin_lock(&tw_death_lock);
588
589 /* Unlink it, if it was scheduled */
590 if (tw_del_dead_node(tw))
591 tcp_tw_count--;
592 else
593 atomic_inc(&tw->tw_refcnt);
594
595 if (slot >= TCP_TW_RECYCLE_SLOTS) {
596 /* Schedule to slow timer */
597 if (timeo >= TCP_TIMEWAIT_LEN) {
598 slot = TCP_TWKILL_SLOTS-1;
599 } else {
600 slot = (timeo + TCP_TWKILL_PERIOD-1) / TCP_TWKILL_PERIOD;
601 if (slot >= TCP_TWKILL_SLOTS)
602 slot = TCP_TWKILL_SLOTS-1;
603 }
604 tw->tw_ttd = jiffies + timeo;
605 slot = (tcp_tw_death_row_slot + slot) & (TCP_TWKILL_SLOTS - 1);
606 list = &tcp_tw_death_row[slot];
607 } else {
608 tw->tw_ttd = jiffies + (slot << TCP_TW_RECYCLE_TICK);
609
610 if (tcp_twcal_hand < 0) {
611 tcp_twcal_hand = 0;
612 tcp_twcal_jiffie = jiffies;
613 tcp_twcal_timer.expires = tcp_twcal_jiffie + (slot<<TCP_TW_RECYCLE_TICK);
614 add_timer(&tcp_twcal_timer);
615 } else {
616 if (time_after(tcp_twcal_timer.expires, jiffies + (slot<<TCP_TW_RECYCLE_TICK)))
617 mod_timer(&tcp_twcal_timer, jiffies + (slot<<TCP_TW_RECYCLE_TICK));
618 slot = (tcp_twcal_hand + slot)&(TCP_TW_RECYCLE_SLOTS-1);
619 }
620 list = &tcp_twcal_row[slot];
621 }
622
623 hlist_add_head(&tw->tw_death_node, list);
624
625 if (tcp_tw_count++ == 0)
626 mod_timer(&tcp_tw_timer, jiffies+TCP_TWKILL_PERIOD);
627 spin_unlock(&tw_death_lock);
628}
629
630void tcp_twcal_tick(unsigned long dummy)
631{
632 int n, slot;
633 unsigned long j;
634 unsigned long now = jiffies;
635 int killed = 0;
636 int adv = 0;
637
638 spin_lock(&tw_death_lock);
639 if (tcp_twcal_hand < 0)
640 goto out;
641
642 slot = tcp_twcal_hand;
643 j = tcp_twcal_jiffie;
644
645 for (n=0; n<TCP_TW_RECYCLE_SLOTS; n++) {
646 if (time_before_eq(j, now)) {
647 struct hlist_node *node, *safe;
648 struct tcp_tw_bucket *tw;
649
650 tw_for_each_inmate_safe(tw, node, safe,
651 &tcp_twcal_row[slot]) {
652 __tw_del_dead_node(tw);
653 tcp_timewait_kill(tw);
654 tcp_tw_put(tw);
655 killed++;
656 }
657 } else {
658 if (!adv) {
659 adv = 1;
660 tcp_twcal_jiffie = j;
661 tcp_twcal_hand = slot;
662 }
663
664 if (!hlist_empty(&tcp_twcal_row[slot])) {
665 mod_timer(&tcp_twcal_timer, j);
666 goto out;
667 }
668 }
669 j += (1<<TCP_TW_RECYCLE_TICK);
670 slot = (slot+1)&(TCP_TW_RECYCLE_SLOTS-1);
671 }
672 tcp_twcal_hand = -1;
673
674out:
675 if ((tcp_tw_count -= killed) == 0)
676 del_timer(&tcp_tw_timer);
677 NET_ADD_STATS_BH(LINUX_MIB_TIMEWAITKILLED, killed);
678 spin_unlock(&tw_death_lock);
679}
680
681/* This is not only more efficient than what we used to do, it eliminates
682 * a lot of code duplication between IPv4/IPv6 SYN recv processing. -DaveM
683 *
684 * Actually, we could lots of memory writes here. tp of listening
685 * socket contains all necessary default parameters.
686 */
687struct sock *tcp_create_openreq_child(struct sock *sk, struct open_request *req, struct sk_buff *skb)
688{
689 /* allocate the newsk from the same slab of the master sock,
690 * if not, at sk_free time we'll try to free it from the wrong
691 * slabcache (i.e. is it TCPv4 or v6?), this is handled thru sk->sk_prot -acme */
692 struct sock *newsk = sk_alloc(PF_INET, GFP_ATOMIC, sk->sk_prot, 0);
693
694 if(newsk != NULL) {
695 struct tcp_sock *newtp;
696 struct sk_filter *filter;
697
698 memcpy(newsk, sk, sizeof(struct tcp_sock));
699 newsk->sk_state = TCP_SYN_RECV;
700
701 /* SANITY */
702 sk_node_init(&newsk->sk_node);
703 tcp_sk(newsk)->bind_hash = NULL;
704
705 /* Clone the TCP header template */
706 inet_sk(newsk)->dport = req->rmt_port;
707
708 sock_lock_init(newsk);
709 bh_lock_sock(newsk);
710
711 rwlock_init(&newsk->sk_dst_lock);
712 atomic_set(&newsk->sk_rmem_alloc, 0);
713 skb_queue_head_init(&newsk->sk_receive_queue);
714 atomic_set(&newsk->sk_wmem_alloc, 0);
715 skb_queue_head_init(&newsk->sk_write_queue);
716 atomic_set(&newsk->sk_omem_alloc, 0);
717 newsk->sk_wmem_queued = 0;
718 newsk->sk_forward_alloc = 0;
719
720 sock_reset_flag(newsk, SOCK_DONE);
721 newsk->sk_userlocks = sk->sk_userlocks & ~SOCK_BINDPORT_LOCK;
722 newsk->sk_backlog.head = newsk->sk_backlog.tail = NULL;
723 newsk->sk_send_head = NULL;
724 rwlock_init(&newsk->sk_callback_lock);
725 skb_queue_head_init(&newsk->sk_error_queue);
726 newsk->sk_write_space = sk_stream_write_space;
727
728 if ((filter = newsk->sk_filter) != NULL)
729 sk_filter_charge(newsk, filter);
730
731 if (unlikely(xfrm_sk_clone_policy(newsk))) {
732 /* It is still raw copy of parent, so invalidate
733 * destructor and make plain sk_free() */
734 newsk->sk_destruct = NULL;
735 sk_free(newsk);
736 return NULL;
737 }
738
739 /* Now setup tcp_sock */
740 newtp = tcp_sk(newsk);
741 newtp->pred_flags = 0;
742 newtp->rcv_nxt = req->rcv_isn + 1;
743 newtp->snd_nxt = req->snt_isn + 1;
744 newtp->snd_una = req->snt_isn + 1;
745 newtp->snd_sml = req->snt_isn + 1;
746
747 tcp_prequeue_init(newtp);
748
749 tcp_init_wl(newtp, req->snt_isn, req->rcv_isn);
750
751 newtp->retransmits = 0;
752 newtp->backoff = 0;
753 newtp->srtt = 0;
754 newtp->mdev = TCP_TIMEOUT_INIT;
755 newtp->rto = TCP_TIMEOUT_INIT;
756
757 newtp->packets_out = 0;
758 newtp->left_out = 0;
759 newtp->retrans_out = 0;
760 newtp->sacked_out = 0;
761 newtp->fackets_out = 0;
762 newtp->snd_ssthresh = 0x7fffffff;
763
764 /* So many TCP implementations out there (incorrectly) count the
765 * initial SYN frame in their delayed-ACK and congestion control
766 * algorithms that we must have the following bandaid to talk
767 * efficiently to them. -DaveM
768 */
769 newtp->snd_cwnd = 2;
770 newtp->snd_cwnd_cnt = 0;
771
772 newtp->frto_counter = 0;
773 newtp->frto_highmark = 0;
774
775 tcp_set_ca_state(newtp, TCP_CA_Open);
776 tcp_init_xmit_timers(newsk);
777 skb_queue_head_init(&newtp->out_of_order_queue);
778 newtp->rcv_wup = req->rcv_isn + 1;
779 newtp->write_seq = req->snt_isn + 1;
780 newtp->pushed_seq = newtp->write_seq;
781 newtp->copied_seq = req->rcv_isn + 1;
782
783 newtp->rx_opt.saw_tstamp = 0;
784
785 newtp->rx_opt.dsack = 0;
786 newtp->rx_opt.eff_sacks = 0;
787
788 newtp->probes_out = 0;
789 newtp->rx_opt.num_sacks = 0;
790 newtp->urg_data = 0;
791 newtp->listen_opt = NULL;
792 newtp->accept_queue = newtp->accept_queue_tail = NULL;
793 /* Deinitialize syn_wait_lock to trap illegal accesses. */
794 memset(&newtp->syn_wait_lock, 0, sizeof(newtp->syn_wait_lock));
795
796 /* Back to base struct sock members. */
797 newsk->sk_err = 0;
798 newsk->sk_priority = 0;
799 atomic_set(&newsk->sk_refcnt, 2);
800#ifdef INET_REFCNT_DEBUG
801 atomic_inc(&inet_sock_nr);
802#endif
803 atomic_inc(&tcp_sockets_allocated);
804
805 if (sock_flag(newsk, SOCK_KEEPOPEN))
806 tcp_reset_keepalive_timer(newsk,
807 keepalive_time_when(newtp));
808 newsk->sk_socket = NULL;
809 newsk->sk_sleep = NULL;
810
811 newtp->rx_opt.tstamp_ok = req->tstamp_ok;
812 if((newtp->rx_opt.sack_ok = req->sack_ok) != 0) {
813 if (sysctl_tcp_fack)
814 newtp->rx_opt.sack_ok |= 2;
815 }
816 newtp->window_clamp = req->window_clamp;
817 newtp->rcv_ssthresh = req->rcv_wnd;
818 newtp->rcv_wnd = req->rcv_wnd;
819 newtp->rx_opt.wscale_ok = req->wscale_ok;
820 if (newtp->rx_opt.wscale_ok) {
821 newtp->rx_opt.snd_wscale = req->snd_wscale;
822 newtp->rx_opt.rcv_wscale = req->rcv_wscale;
823 } else {
824 newtp->rx_opt.snd_wscale = newtp->rx_opt.rcv_wscale = 0;
825 newtp->window_clamp = min(newtp->window_clamp, 65535U);
826 }
827 newtp->snd_wnd = ntohs(skb->h.th->window) << newtp->rx_opt.snd_wscale;
828 newtp->max_window = newtp->snd_wnd;
829
830 if (newtp->rx_opt.tstamp_ok) {
831 newtp->rx_opt.ts_recent = req->ts_recent;
832 newtp->rx_opt.ts_recent_stamp = xtime.tv_sec;
833 newtp->tcp_header_len = sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
834 } else {
835 newtp->rx_opt.ts_recent_stamp = 0;
836 newtp->tcp_header_len = sizeof(struct tcphdr);
837 }
838 if (skb->len >= TCP_MIN_RCVMSS+newtp->tcp_header_len)
839 newtp->ack.last_seg_size = skb->len-newtp->tcp_header_len;
840 newtp->rx_opt.mss_clamp = req->mss;
841 TCP_ECN_openreq_child(newtp, req);
842 if (newtp->ecn_flags&TCP_ECN_OK)
843 sock_set_flag(newsk, SOCK_NO_LARGESEND);
844
845 tcp_ca_init(newtp);
846
847 TCP_INC_STATS_BH(TCP_MIB_PASSIVEOPENS);
848 }
849 return newsk;
850}
851
852/*
853 * Process an incoming packet for SYN_RECV sockets represented
854 * as an open_request.
855 */
856
857struct sock *tcp_check_req(struct sock *sk,struct sk_buff *skb,
858 struct open_request *req,
859 struct open_request **prev)
860{
861 struct tcphdr *th = skb->h.th;
862 struct tcp_sock *tp = tcp_sk(sk);
863 u32 flg = tcp_flag_word(th) & (TCP_FLAG_RST|TCP_FLAG_SYN|TCP_FLAG_ACK);
864 int paws_reject = 0;
865 struct tcp_options_received tmp_opt;
866 struct sock *child;
867
868 tmp_opt.saw_tstamp = 0;
869 if (th->doff > (sizeof(struct tcphdr)>>2)) {
870 tcp_parse_options(skb, &tmp_opt, 0);
871
872 if (tmp_opt.saw_tstamp) {
873 tmp_opt.ts_recent = req->ts_recent;
874 /* We do not store true stamp, but it is not required,
875 * it can be estimated (approximately)
876 * from another data.
877 */
878 tmp_opt.ts_recent_stamp = xtime.tv_sec - ((TCP_TIMEOUT_INIT/HZ)<<req->retrans);
879 paws_reject = tcp_paws_check(&tmp_opt, th->rst);
880 }
881 }
882
883 /* Check for pure retransmitted SYN. */
884 if (TCP_SKB_CB(skb)->seq == req->rcv_isn &&
885 flg == TCP_FLAG_SYN &&
886 !paws_reject) {
887 /*
888 * RFC793 draws (Incorrectly! It was fixed in RFC1122)
889 * this case on figure 6 and figure 8, but formal
890 * protocol description says NOTHING.
891 * To be more exact, it says that we should send ACK,
892 * because this segment (at least, if it has no data)
893 * is out of window.
894 *
895 * CONCLUSION: RFC793 (even with RFC1122) DOES NOT
896 * describe SYN-RECV state. All the description
897 * is wrong, we cannot believe to it and should
898 * rely only on common sense and implementation
899 * experience.
900 *
901 * Enforce "SYN-ACK" according to figure 8, figure 6
902 * of RFC793, fixed by RFC1122.
903 */
904 req->class->rtx_syn_ack(sk, req, NULL);
905 return NULL;
906 }
907
908 /* Further reproduces section "SEGMENT ARRIVES"
909 for state SYN-RECEIVED of RFC793.
910 It is broken, however, it does not work only
911 when SYNs are crossed.
912
913 You would think that SYN crossing is impossible here, since
914 we should have a SYN_SENT socket (from connect()) on our end,
915 but this is not true if the crossed SYNs were sent to both
916 ends by a malicious third party. We must defend against this,
917 and to do that we first verify the ACK (as per RFC793, page
918 36) and reset if it is invalid. Is this a true full defense?
919 To convince ourselves, let us consider a way in which the ACK
920 test can still pass in this 'malicious crossed SYNs' case.
921 Malicious sender sends identical SYNs (and thus identical sequence
922 numbers) to both A and B:
923
924 A: gets SYN, seq=7
925 B: gets SYN, seq=7
926
927 By our good fortune, both A and B select the same initial
928 send sequence number of seven :-)
929
930 A: sends SYN|ACK, seq=7, ack_seq=8
931 B: sends SYN|ACK, seq=7, ack_seq=8
932
933 So we are now A eating this SYN|ACK, ACK test passes. So
934 does sequence test, SYN is truncated, and thus we consider
935 it a bare ACK.
936
937 If tp->defer_accept, we silently drop this bare ACK. Otherwise,
938 we create an established connection. Both ends (listening sockets)
939 accept the new incoming connection and try to talk to each other. 8-)
940
941 Note: This case is both harmless, and rare. Possibility is about the
942 same as us discovering intelligent life on another plant tomorrow.
943
944 But generally, we should (RFC lies!) to accept ACK
945 from SYNACK both here and in tcp_rcv_state_process().
946 tcp_rcv_state_process() does not, hence, we do not too.
947
948 Note that the case is absolutely generic:
949 we cannot optimize anything here without
950 violating protocol. All the checks must be made
951 before attempt to create socket.
952 */
953
954 /* RFC793 page 36: "If the connection is in any non-synchronized state ...
955 * and the incoming segment acknowledges something not yet
956 * sent (the segment carries an unaccaptable ACK) ...
957 * a reset is sent."
958 *
959 * Invalid ACK: reset will be sent by listening socket
960 */
961 if ((flg & TCP_FLAG_ACK) &&
962 (TCP_SKB_CB(skb)->ack_seq != req->snt_isn+1))
963 return sk;
964
965 /* Also, it would be not so bad idea to check rcv_tsecr, which
966 * is essentially ACK extension and too early or too late values
967 * should cause reset in unsynchronized states.
968 */
969
970 /* RFC793: "first check sequence number". */
971
972 if (paws_reject || !tcp_in_window(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq,
973 req->rcv_isn+1, req->rcv_isn+1+req->rcv_wnd)) {
974 /* Out of window: send ACK and drop. */
975 if (!(flg & TCP_FLAG_RST))
976 req->class->send_ack(skb, req);
977 if (paws_reject)
978 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
979 return NULL;
980 }
981
982 /* In sequence, PAWS is OK. */
983
984 if (tmp_opt.saw_tstamp && !after(TCP_SKB_CB(skb)->seq, req->rcv_isn+1))
985 req->ts_recent = tmp_opt.rcv_tsval;
986
987 if (TCP_SKB_CB(skb)->seq == req->rcv_isn) {
988 /* Truncate SYN, it is out of window starting
989 at req->rcv_isn+1. */
990 flg &= ~TCP_FLAG_SYN;
991 }
992
993 /* RFC793: "second check the RST bit" and
994 * "fourth, check the SYN bit"
995 */
996 if (flg & (TCP_FLAG_RST|TCP_FLAG_SYN))
997 goto embryonic_reset;
998
999 /* ACK sequence verified above, just make sure ACK is
1000 * set. If ACK not set, just silently drop the packet.
1001 */
1002 if (!(flg & TCP_FLAG_ACK))
1003 return NULL;
1004
1005 /* If TCP_DEFER_ACCEPT is set, drop bare ACK. */
1006 if (tp->defer_accept && TCP_SKB_CB(skb)->end_seq == req->rcv_isn+1) {
1007 req->acked = 1;
1008 return NULL;
1009 }
1010
1011 /* OK, ACK is valid, create big socket and
1012 * feed this segment to it. It will repeat all
1013 * the tests. THIS SEGMENT MUST MOVE SOCKET TO
1014 * ESTABLISHED STATE. If it will be dropped after
1015 * socket is created, wait for troubles.
1016 */
1017 child = tp->af_specific->syn_recv_sock(sk, skb, req, NULL);
1018 if (child == NULL)
1019 goto listen_overflow;
1020
1021 tcp_synq_unlink(tp, req, prev);
1022 tcp_synq_removed(sk, req);
1023
1024 tcp_acceptq_queue(sk, req, child);
1025 return child;
1026
1027 listen_overflow:
1028 if (!sysctl_tcp_abort_on_overflow) {
1029 req->acked = 1;
1030 return NULL;
1031 }
1032
1033 embryonic_reset:
1034 NET_INC_STATS_BH(LINUX_MIB_EMBRYONICRSTS);
1035 if (!(flg & TCP_FLAG_RST))
1036 req->class->send_reset(skb);
1037
1038 tcp_synq_drop(sk, req, prev);
1039 return NULL;
1040}
1041
1042/*
1043 * Queue segment on the new socket if the new socket is active,
1044 * otherwise we just shortcircuit this and continue with
1045 * the new socket.
1046 */
1047
1048int tcp_child_process(struct sock *parent, struct sock *child,
1049 struct sk_buff *skb)
1050{
1051 int ret = 0;
1052 int state = child->sk_state;
1053
1054 if (!sock_owned_by_user(child)) {
1055 ret = tcp_rcv_state_process(child, skb, skb->h.th, skb->len);
1056
1057 /* Wakeup parent, send SIGIO */
1058 if (state == TCP_SYN_RECV && child->sk_state != state)
1059 parent->sk_data_ready(parent, 0);
1060 } else {
1061 /* Alas, it is possible again, because we do lookup
1062 * in main socket hash table and lock on listening
1063 * socket does not protect us more.
1064 */
1065 sk_add_backlog(child, skb);
1066 }
1067
1068 bh_unlock_sock(child);
1069 sock_put(child);
1070 return ret;
1071}
1072
1073EXPORT_SYMBOL(tcp_check_req);
1074EXPORT_SYMBOL(tcp_child_process);
1075EXPORT_SYMBOL(tcp_create_openreq_child);
1076EXPORT_SYMBOL(tcp_timewait_state_process);
1077EXPORT_SYMBOL(tcp_tw_deschedule);
generated by cgit v1.2.2 (git 2.25.0) at 2024-11-12 11:12:46 -0500