Commit | Line | Data |
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1da177e4 LT |
1 | /* |
2 | * INET An implementation of the TCP/IP protocol suite for the LINUX | |
3 | * operating system. INET is implemented using the BSD Socket | |
4 | * interface as the means of communication with the user level. | |
5 | * | |
6 | * Implementation of the Transmission Control Protocol(TCP). | |
7 | * | |
8 | * Version: $Id: tcp_minisocks.c,v 1.15 2002/02/01 22:01:04 davem Exp $ | |
9 | * | |
02c30a84 | 10 | * Authors: Ross Biro |
1da177e4 LT |
11 | * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> |
12 | * Mark Evans, <evansmp@uhura.aston.ac.uk> | |
13 | * Corey Minyard <wf-rch!minyard@relay.EU.net> | |
14 | * Florian La Roche, <flla@stud.uni-sb.de> | |
15 | * Charles Hedrick, <hedrick@klinzhai.rutgers.edu> | |
16 | * Linus Torvalds, <torvalds@cs.helsinki.fi> | |
17 | * Alan Cox, <gw4pts@gw4pts.ampr.org> | |
18 | * Matthew Dillon, <dillon@apollo.west.oic.com> | |
19 | * Arnt Gulbrandsen, <agulbra@nvg.unit.no> | |
20 | * Jorge Cwik, <jorge@laser.satlink.net> | |
21 | */ | |
22 | ||
23 | #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 | ||
38 | int sysctl_tcp_tw_recycle; | |
39 | int sysctl_tcp_max_tw_buckets = NR_FILE*2; | |
40 | ||
41 | int sysctl_tcp_syncookies = SYNC_INIT; | |
42 | int sysctl_tcp_abort_on_overflow; | |
43 | ||
8feaf0c0 | 44 | static void tcp_tw_schedule(struct inet_timewait_sock *tw, int timeo); |
1da177e4 LT |
45 | |
46 | static __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 | ||
57 | int tcp_tw_count; | |
58 | ||
1da177e4 LT |
59 | /* |
60 | * * Main purpose of TIME-WAIT state is to close connection gracefully, | |
61 | * when one of ends sits in LAST-ACK or CLOSING retransmitting FIN | |
62 | * (and, probably, tail of data) and one or more our ACKs are lost. | |
63 | * * What is TIME-WAIT timeout? It is associated with maximal packet | |
64 | * lifetime in the internet, which results in wrong conclusion, that | |
65 | * it is set to catch "old duplicate segments" wandering out of their path. | |
66 | * It is not quite correct. This timeout is calculated so that it exceeds | |
67 | * maximal retransmission timeout enough to allow to lose one (or more) | |
68 | * segments sent by peer and our ACKs. This time may be calculated from RTO. | |
69 | * * When TIME-WAIT socket receives RST, it means that another end | |
70 | * finally closed and we are allowed to kill TIME-WAIT too. | |
71 | * * Second purpose of TIME-WAIT is catching old duplicate segments. | |
72 | * Well, certainly it is pure paranoia, but if we load TIME-WAIT | |
73 | * with this semantics, we MUST NOT kill TIME-WAIT state with RSTs. | |
74 | * * If we invented some more clever way to catch duplicates | |
75 | * (f.e. based on PAWS), we could truncate TIME-WAIT to several RTOs. | |
76 | * | |
77 | * The algorithm below is based on FORMAL INTERPRETATION of RFCs. | |
78 | * When you compare it to RFCs, please, read section SEGMENT ARRIVES | |
79 | * from the very beginning. | |
80 | * | |
81 | * NOTE. With recycling (and later with fin-wait-2) TW bucket | |
82 | * is _not_ stateless. It means, that strictly speaking we must | |
83 | * spinlock it. I do not want! Well, probability of misbehaviour | |
84 | * is ridiculously low and, seems, we could use some mb() tricks | |
85 | * to avoid misread sequence numbers, states etc. --ANK | |
86 | */ | |
87 | enum tcp_tw_status | |
8feaf0c0 ACM |
88 | tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb, |
89 | const struct tcphdr *th) | |
1da177e4 | 90 | { |
8feaf0c0 | 91 | struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw); |
1da177e4 LT |
92 | struct tcp_options_received tmp_opt; |
93 | int paws_reject = 0; | |
94 | ||
95 | tmp_opt.saw_tstamp = 0; | |
8feaf0c0 | 96 | if (th->doff > (sizeof(*th) >> 2) && tcptw->tw_ts_recent_stamp) { |
1da177e4 LT |
97 | tcp_parse_options(skb, &tmp_opt, 0); |
98 | ||
99 | if (tmp_opt.saw_tstamp) { | |
8feaf0c0 ACM |
100 | tmp_opt.ts_recent = tcptw->tw_ts_recent; |
101 | tmp_opt.ts_recent_stamp = tcptw->tw_ts_recent_stamp; | |
1da177e4 LT |
102 | paws_reject = tcp_paws_check(&tmp_opt, th->rst); |
103 | } | |
104 | } | |
105 | ||
106 | if (tw->tw_substate == TCP_FIN_WAIT2) { | |
107 | /* Just repeat all the checks of tcp_rcv_state_process() */ | |
108 | ||
109 | /* Out of window, send ACK */ | |
110 | if (paws_reject || | |
111 | !tcp_in_window(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq, | |
8feaf0c0 ACM |
112 | tcptw->tw_rcv_nxt, |
113 | tcptw->tw_rcv_nxt + tcptw->tw_rcv_wnd)) | |
1da177e4 LT |
114 | return TCP_TW_ACK; |
115 | ||
116 | if (th->rst) | |
117 | goto kill; | |
118 | ||
8feaf0c0 | 119 | if (th->syn && !before(TCP_SKB_CB(skb)->seq, tcptw->tw_rcv_nxt)) |
1da177e4 LT |
120 | goto kill_with_rst; |
121 | ||
122 | /* Dup ACK? */ | |
8feaf0c0 | 123 | if (!after(TCP_SKB_CB(skb)->end_seq, tcptw->tw_rcv_nxt) || |
1da177e4 | 124 | TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq) { |
8feaf0c0 | 125 | inet_twsk_put(tw); |
1da177e4 LT |
126 | return TCP_TW_SUCCESS; |
127 | } | |
128 | ||
129 | /* New data or FIN. If new data arrive after half-duplex close, | |
130 | * reset. | |
131 | */ | |
132 | if (!th->fin || | |
8feaf0c0 | 133 | TCP_SKB_CB(skb)->end_seq != tcptw->tw_rcv_nxt + 1) { |
1da177e4 LT |
134 | kill_with_rst: |
135 | tcp_tw_deschedule(tw); | |
8feaf0c0 | 136 | inet_twsk_put(tw); |
1da177e4 LT |
137 | return TCP_TW_RST; |
138 | } | |
139 | ||
140 | /* FIN arrived, enter true time-wait state. */ | |
8feaf0c0 ACM |
141 | tw->tw_substate = TCP_TIME_WAIT; |
142 | tcptw->tw_rcv_nxt = TCP_SKB_CB(skb)->end_seq; | |
1da177e4 | 143 | if (tmp_opt.saw_tstamp) { |
8feaf0c0 ACM |
144 | tcptw->tw_ts_recent_stamp = xtime.tv_sec; |
145 | tcptw->tw_ts_recent = tmp_opt.rcv_tsval; | |
1da177e4 LT |
146 | } |
147 | ||
148 | /* I am shamed, but failed to make it more elegant. | |
149 | * Yes, it is direct reference to IP, which is impossible | |
150 | * to generalize to IPv6. Taking into account that IPv6 | |
151 | * do not undertsnad recycling in any case, it not | |
152 | * a big problem in practice. --ANK */ | |
153 | if (tw->tw_family == AF_INET && | |
8feaf0c0 | 154 | sysctl_tcp_tw_recycle && tcptw->tw_ts_recent_stamp && |
1da177e4 LT |
155 | tcp_v4_tw_remember_stamp(tw)) |
156 | tcp_tw_schedule(tw, tw->tw_timeout); | |
157 | else | |
158 | tcp_tw_schedule(tw, TCP_TIMEWAIT_LEN); | |
159 | return TCP_TW_ACK; | |
160 | } | |
161 | ||
162 | /* | |
163 | * Now real TIME-WAIT state. | |
164 | * | |
165 | * RFC 1122: | |
166 | * "When a connection is [...] on TIME-WAIT state [...] | |
167 | * [a TCP] MAY accept a new SYN from the remote TCP to | |
168 | * reopen the connection directly, if it: | |
169 | * | |
170 | * (1) assigns its initial sequence number for the new | |
171 | * connection to be larger than the largest sequence | |
172 | * number it used on the previous connection incarnation, | |
173 | * and | |
174 | * | |
175 | * (2) returns to TIME-WAIT state if the SYN turns out | |
176 | * to be an old duplicate". | |
177 | */ | |
178 | ||
179 | if (!paws_reject && | |
8feaf0c0 | 180 | (TCP_SKB_CB(skb)->seq == tcptw->tw_rcv_nxt && |
1da177e4 LT |
181 | (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq || th->rst))) { |
182 | /* In window segment, it may be only reset or bare ack. */ | |
183 | ||
184 | if (th->rst) { | |
185 | /* This is TIME_WAIT assasination, in two flavors. | |
186 | * Oh well... nobody has a sufficient solution to this | |
187 | * protocol bug yet. | |
188 | */ | |
189 | if (sysctl_tcp_rfc1337 == 0) { | |
190 | kill: | |
191 | tcp_tw_deschedule(tw); | |
8feaf0c0 | 192 | inet_twsk_put(tw); |
1da177e4 LT |
193 | return TCP_TW_SUCCESS; |
194 | } | |
195 | } | |
196 | tcp_tw_schedule(tw, TCP_TIMEWAIT_LEN); | |
197 | ||
198 | if (tmp_opt.saw_tstamp) { | |
8feaf0c0 ACM |
199 | tcptw->tw_ts_recent = tmp_opt.rcv_tsval; |
200 | tcptw->tw_ts_recent_stamp = xtime.tv_sec; | |
1da177e4 LT |
201 | } |
202 | ||
8feaf0c0 | 203 | inet_twsk_put(tw); |
1da177e4 LT |
204 | return TCP_TW_SUCCESS; |
205 | } | |
206 | ||
207 | /* Out of window segment. | |
208 | ||
209 | All the segments are ACKed immediately. | |
210 | ||
211 | The only exception is new SYN. We accept it, if it is | |
212 | not old duplicate and we are not in danger to be killed | |
213 | by delayed old duplicates. RFC check is that it has | |
214 | newer sequence number works at rates <40Mbit/sec. | |
215 | However, if paws works, it is reliable AND even more, | |
216 | we even may relax silly seq space cutoff. | |
217 | ||
218 | RED-PEN: we violate main RFC requirement, if this SYN will appear | |
219 | old duplicate (i.e. we receive RST in reply to SYN-ACK), | |
220 | we must return socket to time-wait state. It is not good, | |
221 | but not fatal yet. | |
222 | */ | |
223 | ||
224 | if (th->syn && !th->rst && !th->ack && !paws_reject && | |
8feaf0c0 ACM |
225 | (after(TCP_SKB_CB(skb)->seq, tcptw->tw_rcv_nxt) || |
226 | (tmp_opt.saw_tstamp && | |
227 | (s32)(tcptw->tw_ts_recent - tmp_opt.rcv_tsval) < 0))) { | |
228 | u32 isn = tcptw->tw_snd_nxt + 65535 + 2; | |
1da177e4 LT |
229 | if (isn == 0) |
230 | isn++; | |
231 | TCP_SKB_CB(skb)->when = isn; | |
232 | return TCP_TW_SYN; | |
233 | } | |
234 | ||
235 | if (paws_reject) | |
236 | NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED); | |
237 | ||
238 | if(!th->rst) { | |
239 | /* In this case we must reset the TIMEWAIT timer. | |
240 | * | |
241 | * If it is ACKless SYN it may be both old duplicate | |
242 | * and new good SYN with random sequence number <rcv_nxt. | |
243 | * Do not reschedule in the last case. | |
244 | */ | |
245 | if (paws_reject || th->ack) | |
246 | tcp_tw_schedule(tw, TCP_TIMEWAIT_LEN); | |
247 | ||
248 | /* Send ACK. Note, we do not put the bucket, | |
249 | * it will be released by caller. | |
250 | */ | |
251 | return TCP_TW_ACK; | |
252 | } | |
8feaf0c0 | 253 | inet_twsk_put(tw); |
1da177e4 LT |
254 | return TCP_TW_SUCCESS; |
255 | } | |
256 | ||
1da177e4 LT |
257 | /* |
258 | * Move a socket to time-wait or dead fin-wait-2 state. | |
259 | */ | |
260 | void tcp_time_wait(struct sock *sk, int state, int timeo) | |
261 | { | |
8feaf0c0 ACM |
262 | struct inet_timewait_sock *tw = NULL; |
263 | const struct tcp_sock *tp = tcp_sk(sk); | |
1da177e4 LT |
264 | int recycle_ok = 0; |
265 | ||
266 | if (sysctl_tcp_tw_recycle && tp->rx_opt.ts_recent_stamp) | |
267 | recycle_ok = tp->af_specific->remember_stamp(sk); | |
268 | ||
269 | if (tcp_tw_count < sysctl_tcp_max_tw_buckets) | |
8feaf0c0 | 270 | tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_slab, SLAB_ATOMIC); |
1da177e4 | 271 | |
8feaf0c0 ACM |
272 | if (tw != NULL) { |
273 | struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw); | |
274 | const struct inet_sock *inet = inet_sk(sk); | |
275 | const int rto = (tp->rto << 2) - (tp->rto >> 1); | |
276 | ||
277 | /* Remember our protocol */ | |
278 | tw->tw_prot = sk->sk_prot_creator; | |
1da177e4 LT |
279 | |
280 | /* Give us an identity. */ | |
281 | tw->tw_daddr = inet->daddr; | |
282 | tw->tw_rcv_saddr = inet->rcv_saddr; | |
283 | tw->tw_bound_dev_if = sk->sk_bound_dev_if; | |
284 | tw->tw_num = inet->num; | |
285 | tw->tw_state = TCP_TIME_WAIT; | |
286 | tw->tw_substate = state; | |
287 | tw->tw_sport = inet->sport; | |
288 | tw->tw_dport = inet->dport; | |
289 | tw->tw_family = sk->sk_family; | |
290 | tw->tw_reuse = sk->sk_reuse; | |
291 | tw->tw_rcv_wscale = tp->rx_opt.rcv_wscale; | |
292 | atomic_set(&tw->tw_refcnt, 1); | |
293 | ||
294 | tw->tw_hashent = sk->sk_hashent; | |
8feaf0c0 ACM |
295 | tcptw->tw_rcv_nxt = tp->rcv_nxt; |
296 | tcptw->tw_snd_nxt = tp->snd_nxt; | |
297 | tcptw->tw_rcv_wnd = tcp_receive_window(tp); | |
298 | tcptw->tw_ts_recent = tp->rx_opt.ts_recent; | |
299 | tcptw->tw_ts_recent_stamp = tp->rx_opt.ts_recent_stamp; | |
300 | inet_twsk_dead_node_init(tw); | |
1da177e4 LT |
301 | |
302 | #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE) | |
303 | if (tw->tw_family == PF_INET6) { | |
304 | struct ipv6_pinfo *np = inet6_sk(sk); | |
8feaf0c0 | 305 | struct tcp6_timewait_sock *tcp6tw = tcp6_twsk((struct sock *)tw); |
1da177e4 | 306 | |
8feaf0c0 ACM |
307 | ipv6_addr_copy(&tcp6tw->tw_v6_daddr, &np->daddr); |
308 | ipv6_addr_copy(&tcp6tw->tw_v6_rcv_saddr, &np->rcv_saddr); | |
309 | tw->tw_ipv6only = np->ipv6only; | |
310 | } else | |
311 | tw->tw_ipv6only = 0; | |
1da177e4 LT |
312 | #endif |
313 | /* Linkage updates. */ | |
e48c414e | 314 | __inet_twsk_hashdance(tw, sk, &tcp_hashinfo); |
1da177e4 LT |
315 | |
316 | /* Get the TIME_WAIT timeout firing. */ | |
317 | if (timeo < rto) | |
318 | timeo = rto; | |
319 | ||
320 | if (recycle_ok) { | |
321 | tw->tw_timeout = rto; | |
322 | } else { | |
323 | tw->tw_timeout = TCP_TIMEWAIT_LEN; | |
324 | if (state == TCP_TIME_WAIT) | |
325 | timeo = TCP_TIMEWAIT_LEN; | |
326 | } | |
327 | ||
328 | tcp_tw_schedule(tw, timeo); | |
8feaf0c0 | 329 | inet_twsk_put(tw); |
1da177e4 LT |
330 | } else { |
331 | /* Sorry, if we're out of memory, just CLOSE this | |
332 | * socket up. We've got bigger problems than | |
333 | * non-graceful socket closings. | |
334 | */ | |
335 | if (net_ratelimit()) | |
336 | printk(KERN_INFO "TCP: time wait bucket table overflow\n"); | |
337 | } | |
338 | ||
339 | tcp_update_metrics(sk); | |
340 | tcp_done(sk); | |
341 | } | |
342 | ||
343 | /* Kill off TIME_WAIT sockets once their lifetime has expired. */ | |
344 | static int tcp_tw_death_row_slot; | |
345 | ||
346 | static void tcp_twkill(unsigned long); | |
347 | ||
348 | /* TIME_WAIT reaping mechanism. */ | |
349 | #define TCP_TWKILL_SLOTS 8 /* Please keep this a power of 2. */ | |
350 | #define TCP_TWKILL_PERIOD (TCP_TIMEWAIT_LEN/TCP_TWKILL_SLOTS) | |
351 | ||
352 | #define TCP_TWKILL_QUOTA 100 | |
353 | ||
354 | static struct hlist_head tcp_tw_death_row[TCP_TWKILL_SLOTS]; | |
355 | static DEFINE_SPINLOCK(tw_death_lock); | |
356 | static struct timer_list tcp_tw_timer = TIMER_INITIALIZER(tcp_twkill, 0, 0); | |
357 | static void twkill_work(void *); | |
358 | static DECLARE_WORK(tcp_twkill_work, twkill_work, NULL); | |
359 | static u32 twkill_thread_slots; | |
360 | ||
361 | /* Returns non-zero if quota exceeded. */ | |
362 | static int tcp_do_twkill_work(int slot, unsigned int quota) | |
363 | { | |
8feaf0c0 | 364 | struct inet_timewait_sock *tw; |
1da177e4 LT |
365 | struct hlist_node *node; |
366 | unsigned int killed; | |
367 | int ret; | |
368 | ||
369 | /* NOTE: compare this to previous version where lock | |
370 | * was released after detaching chain. It was racy, | |
371 | * because tw buckets are scheduled in not serialized context | |
372 | * in 2.3 (with netfilter), and with softnet it is common, because | |
373 | * soft irqs are not sequenced. | |
374 | */ | |
375 | killed = 0; | |
376 | ret = 0; | |
377 | rescan: | |
8feaf0c0 ACM |
378 | inet_twsk_for_each_inmate(tw, node, &tcp_tw_death_row[slot]) { |
379 | __inet_twsk_del_dead_node(tw); | |
1da177e4 | 380 | spin_unlock(&tw_death_lock); |
e48c414e | 381 | __inet_twsk_kill(tw, &tcp_hashinfo); |
8feaf0c0 | 382 | inet_twsk_put(tw); |
1da177e4 LT |
383 | killed++; |
384 | spin_lock(&tw_death_lock); | |
385 | if (killed > quota) { | |
386 | ret = 1; | |
387 | break; | |
388 | } | |
389 | ||
390 | /* While we dropped tw_death_lock, another cpu may have | |
391 | * killed off the next TW bucket in the list, therefore | |
392 | * do a fresh re-read of the hlist head node with the | |
393 | * lock reacquired. We still use the hlist traversal | |
394 | * macro in order to get the prefetches. | |
395 | */ | |
396 | goto rescan; | |
397 | } | |
398 | ||
399 | tcp_tw_count -= killed; | |
400 | NET_ADD_STATS_BH(LINUX_MIB_TIMEWAITED, killed); | |
401 | ||
402 | return ret; | |
403 | } | |
404 | ||
405 | static void tcp_twkill(unsigned long dummy) | |
406 | { | |
407 | int need_timer, ret; | |
408 | ||
409 | spin_lock(&tw_death_lock); | |
410 | ||
411 | if (tcp_tw_count == 0) | |
412 | goto out; | |
413 | ||
414 | need_timer = 0; | |
415 | ret = tcp_do_twkill_work(tcp_tw_death_row_slot, TCP_TWKILL_QUOTA); | |
416 | if (ret) { | |
417 | twkill_thread_slots |= (1 << tcp_tw_death_row_slot); | |
418 | mb(); | |
419 | schedule_work(&tcp_twkill_work); | |
420 | need_timer = 1; | |
421 | } else { | |
422 | /* We purged the entire slot, anything left? */ | |
423 | if (tcp_tw_count) | |
424 | need_timer = 1; | |
425 | } | |
426 | tcp_tw_death_row_slot = | |
427 | ((tcp_tw_death_row_slot + 1) & (TCP_TWKILL_SLOTS - 1)); | |
428 | if (need_timer) | |
429 | mod_timer(&tcp_tw_timer, jiffies + TCP_TWKILL_PERIOD); | |
430 | out: | |
431 | spin_unlock(&tw_death_lock); | |
432 | } | |
433 | ||
434 | extern void twkill_slots_invalid(void); | |
435 | ||
436 | static void twkill_work(void *dummy) | |
437 | { | |
438 | int i; | |
439 | ||
440 | if ((TCP_TWKILL_SLOTS - 1) > (sizeof(twkill_thread_slots) * 8)) | |
441 | twkill_slots_invalid(); | |
442 | ||
443 | while (twkill_thread_slots) { | |
444 | spin_lock_bh(&tw_death_lock); | |
445 | for (i = 0; i < TCP_TWKILL_SLOTS; i++) { | |
446 | if (!(twkill_thread_slots & (1 << i))) | |
447 | continue; | |
448 | ||
449 | while (tcp_do_twkill_work(i, TCP_TWKILL_QUOTA) != 0) { | |
450 | if (need_resched()) { | |
451 | spin_unlock_bh(&tw_death_lock); | |
452 | schedule(); | |
453 | spin_lock_bh(&tw_death_lock); | |
454 | } | |
455 | } | |
456 | ||
457 | twkill_thread_slots &= ~(1 << i); | |
458 | } | |
459 | spin_unlock_bh(&tw_death_lock); | |
460 | } | |
461 | } | |
462 | ||
463 | /* These are always called from BH context. See callers in | |
464 | * tcp_input.c to verify this. | |
465 | */ | |
466 | ||
467 | /* This is for handling early-kills of TIME_WAIT sockets. */ | |
8feaf0c0 | 468 | void tcp_tw_deschedule(struct inet_timewait_sock *tw) |
1da177e4 LT |
469 | { |
470 | spin_lock(&tw_death_lock); | |
8feaf0c0 ACM |
471 | if (inet_twsk_del_dead_node(tw)) { |
472 | inet_twsk_put(tw); | |
1da177e4 LT |
473 | if (--tcp_tw_count == 0) |
474 | del_timer(&tcp_tw_timer); | |
475 | } | |
476 | spin_unlock(&tw_death_lock); | |
e48c414e | 477 | __inet_twsk_kill(tw, &tcp_hashinfo); |
1da177e4 LT |
478 | } |
479 | ||
480 | /* Short-time timewait calendar */ | |
481 | ||
482 | static int tcp_twcal_hand = -1; | |
483 | static int tcp_twcal_jiffie; | |
484 | static void tcp_twcal_tick(unsigned long); | |
485 | static struct timer_list tcp_twcal_timer = | |
486 | TIMER_INITIALIZER(tcp_twcal_tick, 0, 0); | |
487 | static struct hlist_head tcp_twcal_row[TCP_TW_RECYCLE_SLOTS]; | |
488 | ||
8feaf0c0 | 489 | static void tcp_tw_schedule(struct inet_timewait_sock *tw, const int timeo) |
1da177e4 LT |
490 | { |
491 | struct hlist_head *list; | |
492 | int slot; | |
493 | ||
494 | /* timeout := RTO * 3.5 | |
495 | * | |
496 | * 3.5 = 1+2+0.5 to wait for two retransmits. | |
497 | * | |
498 | * RATIONALE: if FIN arrived and we entered TIME-WAIT state, | |
499 | * our ACK acking that FIN can be lost. If N subsequent retransmitted | |
500 | * FINs (or previous seqments) are lost (probability of such event | |
501 | * is p^(N+1), where p is probability to lose single packet and | |
502 | * time to detect the loss is about RTO*(2^N - 1) with exponential | |
503 | * backoff). Normal timewait length is calculated so, that we | |
504 | * waited at least for one retransmitted FIN (maximal RTO is 120sec). | |
505 | * [ BTW Linux. following BSD, violates this requirement waiting | |
506 | * only for 60sec, we should wait at least for 240 secs. | |
507 | * Well, 240 consumes too much of resources 8) | |
508 | * ] | |
509 | * This interval is not reduced to catch old duplicate and | |
510 | * responces to our wandering segments living for two MSLs. | |
511 | * However, if we use PAWS to detect | |
512 | * old duplicates, we can reduce the interval to bounds required | |
513 | * by RTO, rather than MSL. So, if peer understands PAWS, we | |
514 | * kill tw bucket after 3.5*RTO (it is important that this number | |
515 | * is greater than TS tick!) and detect old duplicates with help | |
516 | * of PAWS. | |
517 | */ | |
518 | slot = (timeo + (1<<TCP_TW_RECYCLE_TICK) - 1) >> TCP_TW_RECYCLE_TICK; | |
519 | ||
520 | spin_lock(&tw_death_lock); | |
521 | ||
522 | /* Unlink it, if it was scheduled */ | |
8feaf0c0 | 523 | if (inet_twsk_del_dead_node(tw)) |
1da177e4 LT |
524 | tcp_tw_count--; |
525 | else | |
526 | atomic_inc(&tw->tw_refcnt); | |
527 | ||
528 | if (slot >= TCP_TW_RECYCLE_SLOTS) { | |
529 | /* Schedule to slow timer */ | |
530 | if (timeo >= TCP_TIMEWAIT_LEN) { | |
531 | slot = TCP_TWKILL_SLOTS-1; | |
532 | } else { | |
533 | slot = (timeo + TCP_TWKILL_PERIOD-1) / TCP_TWKILL_PERIOD; | |
534 | if (slot >= TCP_TWKILL_SLOTS) | |
535 | slot = TCP_TWKILL_SLOTS-1; | |
536 | } | |
537 | tw->tw_ttd = jiffies + timeo; | |
538 | slot = (tcp_tw_death_row_slot + slot) & (TCP_TWKILL_SLOTS - 1); | |
539 | list = &tcp_tw_death_row[slot]; | |
540 | } else { | |
541 | tw->tw_ttd = jiffies + (slot << TCP_TW_RECYCLE_TICK); | |
542 | ||
543 | if (tcp_twcal_hand < 0) { | |
544 | tcp_twcal_hand = 0; | |
545 | tcp_twcal_jiffie = jiffies; | |
546 | tcp_twcal_timer.expires = tcp_twcal_jiffie + (slot<<TCP_TW_RECYCLE_TICK); | |
547 | add_timer(&tcp_twcal_timer); | |
548 | } else { | |
549 | if (time_after(tcp_twcal_timer.expires, jiffies + (slot<<TCP_TW_RECYCLE_TICK))) | |
550 | mod_timer(&tcp_twcal_timer, jiffies + (slot<<TCP_TW_RECYCLE_TICK)); | |
551 | slot = (tcp_twcal_hand + slot)&(TCP_TW_RECYCLE_SLOTS-1); | |
552 | } | |
553 | list = &tcp_twcal_row[slot]; | |
554 | } | |
555 | ||
556 | hlist_add_head(&tw->tw_death_node, list); | |
557 | ||
558 | if (tcp_tw_count++ == 0) | |
559 | mod_timer(&tcp_tw_timer, jiffies+TCP_TWKILL_PERIOD); | |
560 | spin_unlock(&tw_death_lock); | |
561 | } | |
562 | ||
563 | void tcp_twcal_tick(unsigned long dummy) | |
564 | { | |
565 | int n, slot; | |
566 | unsigned long j; | |
567 | unsigned long now = jiffies; | |
568 | int killed = 0; | |
569 | int adv = 0; | |
570 | ||
571 | spin_lock(&tw_death_lock); | |
572 | if (tcp_twcal_hand < 0) | |
573 | goto out; | |
574 | ||
575 | slot = tcp_twcal_hand; | |
576 | j = tcp_twcal_jiffie; | |
577 | ||
578 | for (n=0; n<TCP_TW_RECYCLE_SLOTS; n++) { | |
579 | if (time_before_eq(j, now)) { | |
580 | struct hlist_node *node, *safe; | |
8feaf0c0 | 581 | struct inet_timewait_sock *tw; |
1da177e4 | 582 | |
8feaf0c0 ACM |
583 | inet_twsk_for_each_inmate_safe(tw, node, safe, |
584 | &tcp_twcal_row[slot]) { | |
585 | __inet_twsk_del_dead_node(tw); | |
e48c414e | 586 | __inet_twsk_kill(tw, &tcp_hashinfo); |
8feaf0c0 | 587 | inet_twsk_put(tw); |
1da177e4 LT |
588 | killed++; |
589 | } | |
590 | } else { | |
591 | if (!adv) { | |
592 | adv = 1; | |
593 | tcp_twcal_jiffie = j; | |
594 | tcp_twcal_hand = slot; | |
595 | } | |
596 | ||
597 | if (!hlist_empty(&tcp_twcal_row[slot])) { | |
598 | mod_timer(&tcp_twcal_timer, j); | |
599 | goto out; | |
600 | } | |
601 | } | |
602 | j += (1<<TCP_TW_RECYCLE_TICK); | |
603 | slot = (slot+1)&(TCP_TW_RECYCLE_SLOTS-1); | |
604 | } | |
605 | tcp_twcal_hand = -1; | |
606 | ||
607 | out: | |
608 | if ((tcp_tw_count -= killed) == 0) | |
609 | del_timer(&tcp_tw_timer); | |
610 | NET_ADD_STATS_BH(LINUX_MIB_TIMEWAITKILLED, killed); | |
611 | spin_unlock(&tw_death_lock); | |
612 | } | |
613 | ||
614 | /* This is not only more efficient than what we used to do, it eliminates | |
615 | * a lot of code duplication between IPv4/IPv6 SYN recv processing. -DaveM | |
616 | * | |
617 | * Actually, we could lots of memory writes here. tp of listening | |
618 | * socket contains all necessary default parameters. | |
619 | */ | |
60236fdd | 620 | struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req, struct sk_buff *skb) |
1da177e4 LT |
621 | { |
622 | /* allocate the newsk from the same slab of the master sock, | |
623 | * if not, at sk_free time we'll try to free it from the wrong | |
624 | * slabcache (i.e. is it TCPv4 or v6?), this is handled thru sk->sk_prot -acme */ | |
625 | struct sock *newsk = sk_alloc(PF_INET, GFP_ATOMIC, sk->sk_prot, 0); | |
626 | ||
627 | if(newsk != NULL) { | |
2e6599cb ACM |
628 | struct inet_request_sock *ireq = inet_rsk(req); |
629 | struct tcp_request_sock *treq = tcp_rsk(req); | |
a55ebcc4 | 630 | struct inet_sock *newinet = inet_sk(newsk); |
1da177e4 LT |
631 | struct tcp_sock *newtp; |
632 | struct sk_filter *filter; | |
633 | ||
634 | memcpy(newsk, sk, sizeof(struct tcp_sock)); | |
635 | newsk->sk_state = TCP_SYN_RECV; | |
636 | ||
637 | /* SANITY */ | |
638 | sk_node_init(&newsk->sk_node); | |
a55ebcc4 | 639 | newinet->bind_hash = NULL; |
1da177e4 LT |
640 | |
641 | /* Clone the TCP header template */ | |
a55ebcc4 | 642 | newinet->dport = ireq->rmt_port; |
1da177e4 LT |
643 | |
644 | sock_lock_init(newsk); | |
645 | bh_lock_sock(newsk); | |
646 | ||
647 | rwlock_init(&newsk->sk_dst_lock); | |
6cbb0df7 | 648 | newsk->sk_dst_cache = NULL; |
1da177e4 LT |
649 | atomic_set(&newsk->sk_rmem_alloc, 0); |
650 | skb_queue_head_init(&newsk->sk_receive_queue); | |
651 | atomic_set(&newsk->sk_wmem_alloc, 0); | |
652 | skb_queue_head_init(&newsk->sk_write_queue); | |
653 | atomic_set(&newsk->sk_omem_alloc, 0); | |
654 | newsk->sk_wmem_queued = 0; | |
655 | newsk->sk_forward_alloc = 0; | |
656 | ||
657 | sock_reset_flag(newsk, SOCK_DONE); | |
658 | newsk->sk_userlocks = sk->sk_userlocks & ~SOCK_BINDPORT_LOCK; | |
659 | newsk->sk_backlog.head = newsk->sk_backlog.tail = NULL; | |
660 | newsk->sk_send_head = NULL; | |
661 | rwlock_init(&newsk->sk_callback_lock); | |
662 | skb_queue_head_init(&newsk->sk_error_queue); | |
663 | newsk->sk_write_space = sk_stream_write_space; | |
664 | ||
665 | if ((filter = newsk->sk_filter) != NULL) | |
666 | sk_filter_charge(newsk, filter); | |
667 | ||
668 | if (unlikely(xfrm_sk_clone_policy(newsk))) { | |
669 | /* It is still raw copy of parent, so invalidate | |
670 | * destructor and make plain sk_free() */ | |
671 | newsk->sk_destruct = NULL; | |
672 | sk_free(newsk); | |
673 | return NULL; | |
674 | } | |
675 | ||
676 | /* Now setup tcp_sock */ | |
677 | newtp = tcp_sk(newsk); | |
678 | newtp->pred_flags = 0; | |
2e6599cb ACM |
679 | newtp->rcv_nxt = treq->rcv_isn + 1; |
680 | newtp->snd_nxt = treq->snt_isn + 1; | |
681 | newtp->snd_una = treq->snt_isn + 1; | |
682 | newtp->snd_sml = treq->snt_isn + 1; | |
1da177e4 LT |
683 | |
684 | tcp_prequeue_init(newtp); | |
685 | ||
2e6599cb | 686 | tcp_init_wl(newtp, treq->snt_isn, treq->rcv_isn); |
1da177e4 LT |
687 | |
688 | newtp->retransmits = 0; | |
689 | newtp->backoff = 0; | |
690 | newtp->srtt = 0; | |
691 | newtp->mdev = TCP_TIMEOUT_INIT; | |
692 | newtp->rto = TCP_TIMEOUT_INIT; | |
693 | ||
694 | newtp->packets_out = 0; | |
695 | newtp->left_out = 0; | |
696 | newtp->retrans_out = 0; | |
697 | newtp->sacked_out = 0; | |
698 | newtp->fackets_out = 0; | |
699 | newtp->snd_ssthresh = 0x7fffffff; | |
700 | ||
701 | /* So many TCP implementations out there (incorrectly) count the | |
702 | * initial SYN frame in their delayed-ACK and congestion control | |
703 | * algorithms that we must have the following bandaid to talk | |
704 | * efficiently to them. -DaveM | |
705 | */ | |
706 | newtp->snd_cwnd = 2; | |
707 | newtp->snd_cwnd_cnt = 0; | |
708 | ||
709 | newtp->frto_counter = 0; | |
710 | newtp->frto_highmark = 0; | |
711 | ||
317a76f9 SH |
712 | newtp->ca_ops = &tcp_reno; |
713 | ||
1da177e4 LT |
714 | tcp_set_ca_state(newtp, TCP_CA_Open); |
715 | tcp_init_xmit_timers(newsk); | |
716 | skb_queue_head_init(&newtp->out_of_order_queue); | |
2e6599cb ACM |
717 | newtp->rcv_wup = treq->rcv_isn + 1; |
718 | newtp->write_seq = treq->snt_isn + 1; | |
1da177e4 | 719 | newtp->pushed_seq = newtp->write_seq; |
2e6599cb | 720 | newtp->copied_seq = treq->rcv_isn + 1; |
1da177e4 LT |
721 | |
722 | newtp->rx_opt.saw_tstamp = 0; | |
723 | ||
724 | newtp->rx_opt.dsack = 0; | |
725 | newtp->rx_opt.eff_sacks = 0; | |
726 | ||
727 | newtp->probes_out = 0; | |
728 | newtp->rx_opt.num_sacks = 0; | |
729 | newtp->urg_data = 0; | |
0e87506f ACM |
730 | /* Deinitialize accept_queue to trap illegal accesses. */ |
731 | memset(&newtp->accept_queue, 0, sizeof(newtp->accept_queue)); | |
1da177e4 LT |
732 | |
733 | /* Back to base struct sock members. */ | |
734 | newsk->sk_err = 0; | |
735 | newsk->sk_priority = 0; | |
736 | atomic_set(&newsk->sk_refcnt, 2); | |
e6848976 ACM |
737 | |
738 | /* | |
739 | * Increment the counter in the same struct proto as the master | |
740 | * sock (sk_refcnt_debug_inc uses newsk->sk_prot->socks, that | |
741 | * is the same as sk->sk_prot->socks, as this field was copied | |
742 | * with memcpy), same rationale as the first comment in this | |
743 | * function. | |
744 | * | |
745 | * This _changes_ the previous behaviour, where | |
746 | * tcp_create_openreq_child always was incrementing the | |
747 | * equivalent to tcp_prot->socks (inet_sock_nr), so this have | |
748 | * to be taken into account in all callers. -acme | |
749 | */ | |
750 | sk_refcnt_debug_inc(newsk); | |
751 | ||
1da177e4 LT |
752 | atomic_inc(&tcp_sockets_allocated); |
753 | ||
754 | if (sock_flag(newsk, SOCK_KEEPOPEN)) | |
755 | tcp_reset_keepalive_timer(newsk, | |
756 | keepalive_time_when(newtp)); | |
757 | newsk->sk_socket = NULL; | |
758 | newsk->sk_sleep = NULL; | |
759 | ||
2e6599cb ACM |
760 | newtp->rx_opt.tstamp_ok = ireq->tstamp_ok; |
761 | if((newtp->rx_opt.sack_ok = ireq->sack_ok) != 0) { | |
1da177e4 LT |
762 | if (sysctl_tcp_fack) |
763 | newtp->rx_opt.sack_ok |= 2; | |
764 | } | |
765 | newtp->window_clamp = req->window_clamp; | |
766 | newtp->rcv_ssthresh = req->rcv_wnd; | |
767 | newtp->rcv_wnd = req->rcv_wnd; | |
2e6599cb | 768 | newtp->rx_opt.wscale_ok = ireq->wscale_ok; |
1da177e4 | 769 | if (newtp->rx_opt.wscale_ok) { |
2e6599cb ACM |
770 | newtp->rx_opt.snd_wscale = ireq->snd_wscale; |
771 | newtp->rx_opt.rcv_wscale = ireq->rcv_wscale; | |
1da177e4 LT |
772 | } else { |
773 | newtp->rx_opt.snd_wscale = newtp->rx_opt.rcv_wscale = 0; | |
774 | newtp->window_clamp = min(newtp->window_clamp, 65535U); | |
775 | } | |
776 | newtp->snd_wnd = ntohs(skb->h.th->window) << newtp->rx_opt.snd_wscale; | |
777 | newtp->max_window = newtp->snd_wnd; | |
778 | ||
779 | if (newtp->rx_opt.tstamp_ok) { | |
780 | newtp->rx_opt.ts_recent = req->ts_recent; | |
781 | newtp->rx_opt.ts_recent_stamp = xtime.tv_sec; | |
782 | newtp->tcp_header_len = sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; | |
783 | } else { | |
784 | newtp->rx_opt.ts_recent_stamp = 0; | |
785 | newtp->tcp_header_len = sizeof(struct tcphdr); | |
786 | } | |
787 | if (skb->len >= TCP_MIN_RCVMSS+newtp->tcp_header_len) | |
788 | newtp->ack.last_seg_size = skb->len-newtp->tcp_header_len; | |
789 | newtp->rx_opt.mss_clamp = req->mss; | |
790 | TCP_ECN_openreq_child(newtp, req); | |
791 | if (newtp->ecn_flags&TCP_ECN_OK) | |
792 | sock_set_flag(newsk, SOCK_NO_LARGESEND); | |
793 | ||
1da177e4 LT |
794 | TCP_INC_STATS_BH(TCP_MIB_PASSIVEOPENS); |
795 | } | |
796 | return newsk; | |
797 | } | |
798 | ||
799 | /* | |
800 | * Process an incoming packet for SYN_RECV sockets represented | |
60236fdd | 801 | * as a request_sock. |
1da177e4 LT |
802 | */ |
803 | ||
804 | struct sock *tcp_check_req(struct sock *sk,struct sk_buff *skb, | |
60236fdd ACM |
805 | struct request_sock *req, |
806 | struct request_sock **prev) | |
1da177e4 LT |
807 | { |
808 | struct tcphdr *th = skb->h.th; | |
809 | struct tcp_sock *tp = tcp_sk(sk); | |
810 | u32 flg = tcp_flag_word(th) & (TCP_FLAG_RST|TCP_FLAG_SYN|TCP_FLAG_ACK); | |
811 | int paws_reject = 0; | |
812 | struct tcp_options_received tmp_opt; | |
813 | struct sock *child; | |
814 | ||
815 | tmp_opt.saw_tstamp = 0; | |
816 | if (th->doff > (sizeof(struct tcphdr)>>2)) { | |
817 | tcp_parse_options(skb, &tmp_opt, 0); | |
818 | ||
819 | if (tmp_opt.saw_tstamp) { | |
820 | tmp_opt.ts_recent = req->ts_recent; | |
821 | /* We do not store true stamp, but it is not required, | |
822 | * it can be estimated (approximately) | |
823 | * from another data. | |
824 | */ | |
825 | tmp_opt.ts_recent_stamp = xtime.tv_sec - ((TCP_TIMEOUT_INIT/HZ)<<req->retrans); | |
826 | paws_reject = tcp_paws_check(&tmp_opt, th->rst); | |
827 | } | |
828 | } | |
829 | ||
830 | /* Check for pure retransmitted SYN. */ | |
2e6599cb | 831 | if (TCP_SKB_CB(skb)->seq == tcp_rsk(req)->rcv_isn && |
1da177e4 LT |
832 | flg == TCP_FLAG_SYN && |
833 | !paws_reject) { | |
834 | /* | |
835 | * RFC793 draws (Incorrectly! It was fixed in RFC1122) | |
836 | * this case on figure 6 and figure 8, but formal | |
837 | * protocol description says NOTHING. | |
838 | * To be more exact, it says that we should send ACK, | |
839 | * because this segment (at least, if it has no data) | |
840 | * is out of window. | |
841 | * | |
842 | * CONCLUSION: RFC793 (even with RFC1122) DOES NOT | |
843 | * describe SYN-RECV state. All the description | |
844 | * is wrong, we cannot believe to it and should | |
845 | * rely only on common sense and implementation | |
846 | * experience. | |
847 | * | |
848 | * Enforce "SYN-ACK" according to figure 8, figure 6 | |
849 | * of RFC793, fixed by RFC1122. | |
850 | */ | |
60236fdd | 851 | req->rsk_ops->rtx_syn_ack(sk, req, NULL); |
1da177e4 LT |
852 | return NULL; |
853 | } | |
854 | ||
855 | /* Further reproduces section "SEGMENT ARRIVES" | |
856 | for state SYN-RECEIVED of RFC793. | |
857 | It is broken, however, it does not work only | |
858 | when SYNs are crossed. | |
859 | ||
860 | You would think that SYN crossing is impossible here, since | |
861 | we should have a SYN_SENT socket (from connect()) on our end, | |
862 | but this is not true if the crossed SYNs were sent to both | |
863 | ends by a malicious third party. We must defend against this, | |
864 | and to do that we first verify the ACK (as per RFC793, page | |
865 | 36) and reset if it is invalid. Is this a true full defense? | |
866 | To convince ourselves, let us consider a way in which the ACK | |
867 | test can still pass in this 'malicious crossed SYNs' case. | |
868 | Malicious sender sends identical SYNs (and thus identical sequence | |
869 | numbers) to both A and B: | |
870 | ||
871 | A: gets SYN, seq=7 | |
872 | B: gets SYN, seq=7 | |
873 | ||
874 | By our good fortune, both A and B select the same initial | |
875 | send sequence number of seven :-) | |
876 | ||
877 | A: sends SYN|ACK, seq=7, ack_seq=8 | |
878 | B: sends SYN|ACK, seq=7, ack_seq=8 | |
879 | ||
880 | So we are now A eating this SYN|ACK, ACK test passes. So | |
881 | does sequence test, SYN is truncated, and thus we consider | |
882 | it a bare ACK. | |
883 | ||
884 | If tp->defer_accept, we silently drop this bare ACK. Otherwise, | |
885 | we create an established connection. Both ends (listening sockets) | |
886 | accept the new incoming connection and try to talk to each other. 8-) | |
887 | ||
888 | Note: This case is both harmless, and rare. Possibility is about the | |
889 | same as us discovering intelligent life on another plant tomorrow. | |
890 | ||
891 | But generally, we should (RFC lies!) to accept ACK | |
892 | from SYNACK both here and in tcp_rcv_state_process(). | |
893 | tcp_rcv_state_process() does not, hence, we do not too. | |
894 | ||
895 | Note that the case is absolutely generic: | |
896 | we cannot optimize anything here without | |
897 | violating protocol. All the checks must be made | |
898 | before attempt to create socket. | |
899 | */ | |
900 | ||
901 | /* RFC793 page 36: "If the connection is in any non-synchronized state ... | |
902 | * and the incoming segment acknowledges something not yet | |
903 | * sent (the segment carries an unaccaptable ACK) ... | |
904 | * a reset is sent." | |
905 | * | |
906 | * Invalid ACK: reset will be sent by listening socket | |
907 | */ | |
908 | if ((flg & TCP_FLAG_ACK) && | |
2e6599cb | 909 | (TCP_SKB_CB(skb)->ack_seq != tcp_rsk(req)->snt_isn + 1)) |
1da177e4 LT |
910 | return sk; |
911 | ||
912 | /* Also, it would be not so bad idea to check rcv_tsecr, which | |
913 | * is essentially ACK extension and too early or too late values | |
914 | * should cause reset in unsynchronized states. | |
915 | */ | |
916 | ||
917 | /* RFC793: "first check sequence number". */ | |
918 | ||
919 | if (paws_reject || !tcp_in_window(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq, | |
2e6599cb | 920 | tcp_rsk(req)->rcv_isn + 1, tcp_rsk(req)->rcv_isn + 1 + req->rcv_wnd)) { |
1da177e4 LT |
921 | /* Out of window: send ACK and drop. */ |
922 | if (!(flg & TCP_FLAG_RST)) | |
60236fdd | 923 | req->rsk_ops->send_ack(skb, req); |
1da177e4 LT |
924 | if (paws_reject) |
925 | NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED); | |
926 | return NULL; | |
927 | } | |
928 | ||
929 | /* In sequence, PAWS is OK. */ | |
930 | ||
2e6599cb | 931 | if (tmp_opt.saw_tstamp && !after(TCP_SKB_CB(skb)->seq, tcp_rsk(req)->rcv_isn + 1)) |
1da177e4 LT |
932 | req->ts_recent = tmp_opt.rcv_tsval; |
933 | ||
2e6599cb | 934 | if (TCP_SKB_CB(skb)->seq == tcp_rsk(req)->rcv_isn) { |
1da177e4 | 935 | /* Truncate SYN, it is out of window starting |
2e6599cb | 936 | at tcp_rsk(req)->rcv_isn + 1. */ |
1da177e4 LT |
937 | flg &= ~TCP_FLAG_SYN; |
938 | } | |
939 | ||
940 | /* RFC793: "second check the RST bit" and | |
941 | * "fourth, check the SYN bit" | |
942 | */ | |
943 | if (flg & (TCP_FLAG_RST|TCP_FLAG_SYN)) | |
944 | goto embryonic_reset; | |
945 | ||
946 | /* ACK sequence verified above, just make sure ACK is | |
947 | * set. If ACK not set, just silently drop the packet. | |
948 | */ | |
949 | if (!(flg & TCP_FLAG_ACK)) | |
950 | return NULL; | |
951 | ||
952 | /* If TCP_DEFER_ACCEPT is set, drop bare ACK. */ | |
2e6599cb ACM |
953 | if (tp->defer_accept && TCP_SKB_CB(skb)->end_seq == tcp_rsk(req)->rcv_isn + 1) { |
954 | inet_rsk(req)->acked = 1; | |
1da177e4 LT |
955 | return NULL; |
956 | } | |
957 | ||
958 | /* OK, ACK is valid, create big socket and | |
959 | * feed this segment to it. It will repeat all | |
960 | * the tests. THIS SEGMENT MUST MOVE SOCKET TO | |
961 | * ESTABLISHED STATE. If it will be dropped after | |
962 | * socket is created, wait for troubles. | |
963 | */ | |
964 | child = tp->af_specific->syn_recv_sock(sk, skb, req, NULL); | |
965 | if (child == NULL) | |
966 | goto listen_overflow; | |
967 | ||
968 | tcp_synq_unlink(tp, req, prev); | |
969 | tcp_synq_removed(sk, req); | |
970 | ||
971 | tcp_acceptq_queue(sk, req, child); | |
972 | return child; | |
973 | ||
974 | listen_overflow: | |
975 | if (!sysctl_tcp_abort_on_overflow) { | |
2e6599cb | 976 | inet_rsk(req)->acked = 1; |
1da177e4 LT |
977 | return NULL; |
978 | } | |
979 | ||
980 | embryonic_reset: | |
981 | NET_INC_STATS_BH(LINUX_MIB_EMBRYONICRSTS); | |
982 | if (!(flg & TCP_FLAG_RST)) | |
60236fdd | 983 | req->rsk_ops->send_reset(skb); |
1da177e4 LT |
984 | |
985 | tcp_synq_drop(sk, req, prev); | |
986 | return NULL; | |
987 | } | |
988 | ||
989 | /* | |
990 | * Queue segment on the new socket if the new socket is active, | |
991 | * otherwise we just shortcircuit this and continue with | |
992 | * the new socket. | |
993 | */ | |
994 | ||
995 | int tcp_child_process(struct sock *parent, struct sock *child, | |
996 | struct sk_buff *skb) | |
997 | { | |
998 | int ret = 0; | |
999 | int state = child->sk_state; | |
1000 | ||
1001 | if (!sock_owned_by_user(child)) { | |
1002 | ret = tcp_rcv_state_process(child, skb, skb->h.th, skb->len); | |
1003 | ||
1004 | /* Wakeup parent, send SIGIO */ | |
1005 | if (state == TCP_SYN_RECV && child->sk_state != state) | |
1006 | parent->sk_data_ready(parent, 0); | |
1007 | } else { | |
1008 | /* Alas, it is possible again, because we do lookup | |
1009 | * in main socket hash table and lock on listening | |
1010 | * socket does not protect us more. | |
1011 | */ | |
1012 | sk_add_backlog(child, skb); | |
1013 | } | |
1014 | ||
1015 | bh_unlock_sock(child); | |
1016 | sock_put(child); | |
1017 | return ret; | |
1018 | } | |
1019 | ||
1020 | EXPORT_SYMBOL(tcp_check_req); | |
1021 | EXPORT_SYMBOL(tcp_child_process); | |
1022 | EXPORT_SYMBOL(tcp_create_openreq_child); | |
1023 | EXPORT_SYMBOL(tcp_timewait_state_process); | |
1024 | EXPORT_SYMBOL(tcp_tw_deschedule); |