Branch data Line data Source code
1 : : // SPDX-License-Identifier: GPL-2.0-only
2 : : /*
3 : : * INET An implementation of the TCP/IP protocol suite for the LINUX
4 : : * operating system. INET is implemented using the BSD Socket
5 : : * interface as the means of communication with the user level.
6 : : *
7 : : * Implementation of the Transmission Control Protocol(TCP).
8 : : *
9 : : * Authors: Ross Biro
10 : : * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
11 : : * Mark Evans, <evansmp@uhura.aston.ac.uk>
12 : : * Corey Minyard <wf-rch!minyard@relay.EU.net>
13 : : * Florian La Roche, <flla@stud.uni-sb.de>
14 : : * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
15 : : * Linus Torvalds, <torvalds@cs.helsinki.fi>
16 : : * Alan Cox, <gw4pts@gw4pts.ampr.org>
17 : : * Matthew Dillon, <dillon@apollo.west.oic.com>
18 : : * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
19 : : * Jorge Cwik, <jorge@laser.satlink.net>
20 : : */
21 : :
22 : : #include <linux/mm.h>
23 : : #include <linux/module.h>
24 : : #include <linux/slab.h>
25 : : #include <linux/sysctl.h>
26 : : #include <linux/workqueue.h>
27 : : #include <linux/static_key.h>
28 : : #include <net/tcp.h>
29 : : #include <net/inet_common.h>
30 : : #include <net/xfrm.h>
31 : : #include <net/busy_poll.h>
32 : :
33 : : static bool tcp_in_window(u32 seq, u32 end_seq, u32 s_win, u32 e_win)
34 : : {
35 [ # # # # ]: 0 : if (seq == s_win)
36 : : return true;
37 [ # # # # : 0 : if (after(end_seq, s_win) && before(seq, e_win))
# # # # ]
38 : : return true;
39 : 0 : return seq == e_win && seq == end_seq;
40 : : }
41 : :
42 : : static enum tcp_tw_status
43 : 0 : tcp_timewait_check_oow_rate_limit(struct inet_timewait_sock *tw,
44 : : const struct sk_buff *skb, int mib_idx)
45 : : {
46 : : struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
47 : :
48 [ # # ]: 0 : if (!tcp_oow_rate_limited(twsk_net(tw), skb, mib_idx,
49 : : &tcptw->tw_last_oow_ack_time)) {
50 : : /* Send ACK. Note, we do not put the bucket,
51 : : * it will be released by caller.
52 : : */
53 : : return TCP_TW_ACK;
54 : : }
55 : :
56 : : /* We are rate-limiting, so just release the tw sock and drop skb. */
57 : 0 : inet_twsk_put(tw);
58 : 0 : return TCP_TW_SUCCESS;
59 : : }
60 : :
61 : : /*
62 : : * * Main purpose of TIME-WAIT state is to close connection gracefully,
63 : : * when one of ends sits in LAST-ACK or CLOSING retransmitting FIN
64 : : * (and, probably, tail of data) and one or more our ACKs are lost.
65 : : * * What is TIME-WAIT timeout? It is associated with maximal packet
66 : : * lifetime in the internet, which results in wrong conclusion, that
67 : : * it is set to catch "old duplicate segments" wandering out of their path.
68 : : * It is not quite correct. This timeout is calculated so that it exceeds
69 : : * maximal retransmission timeout enough to allow to lose one (or more)
70 : : * segments sent by peer and our ACKs. This time may be calculated from RTO.
71 : : * * When TIME-WAIT socket receives RST, it means that another end
72 : : * finally closed and we are allowed to kill TIME-WAIT too.
73 : : * * Second purpose of TIME-WAIT is catching old duplicate segments.
74 : : * Well, certainly it is pure paranoia, but if we load TIME-WAIT
75 : : * with this semantics, we MUST NOT kill TIME-WAIT state with RSTs.
76 : : * * If we invented some more clever way to catch duplicates
77 : : * (f.e. based on PAWS), we could truncate TIME-WAIT to several RTOs.
78 : : *
79 : : * The algorithm below is based on FORMAL INTERPRETATION of RFCs.
80 : : * When you compare it to RFCs, please, read section SEGMENT ARRIVES
81 : : * from the very beginning.
82 : : *
83 : : * NOTE. With recycling (and later with fin-wait-2) TW bucket
84 : : * is _not_ stateless. It means, that strictly speaking we must
85 : : * spinlock it. I do not want! Well, probability of misbehaviour
86 : : * is ridiculously low and, seems, we could use some mb() tricks
87 : : * to avoid misread sequence numbers, states etc. --ANK
88 : : *
89 : : * We don't need to initialize tmp_out.sack_ok as we don't use the results
90 : : */
91 : : enum tcp_tw_status
92 : 0 : tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
93 : : const struct tcphdr *th)
94 : : {
95 : : struct tcp_options_received tmp_opt;
96 : : struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
97 : : bool paws_reject = false;
98 : :
99 : 0 : tmp_opt.saw_tstamp = 0;
100 [ # # # # ]: 0 : if (th->doff > (sizeof(*th) >> 2) && tcptw->tw_ts_recent_stamp) {
101 : 0 : tcp_parse_options(twsk_net(tw), skb, &tmp_opt, 0, NULL);
102 : :
103 [ # # ]: 0 : if (tmp_opt.saw_tstamp) {
104 [ # # ]: 0 : if (tmp_opt.rcv_tsecr)
105 : 0 : tmp_opt.rcv_tsecr -= tcptw->tw_ts_offset;
106 : 0 : tmp_opt.ts_recent = tcptw->tw_ts_recent;
107 : 0 : tmp_opt.ts_recent_stamp = tcptw->tw_ts_recent_stamp;
108 : 0 : paws_reject = tcp_paws_reject(&tmp_opt, th->rst);
109 : : }
110 : : }
111 : :
112 [ # # ]: 0 : if (tw->tw_substate == TCP_FIN_WAIT2) {
113 : : /* Just repeat all the checks of tcp_rcv_state_process() */
114 : :
115 : : /* Out of window, send ACK */
116 [ # # # # ]: 0 : if (paws_reject ||
117 : 0 : !tcp_in_window(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq,
118 : : tcptw->tw_rcv_nxt,
119 : 0 : tcptw->tw_rcv_nxt + tcptw->tw_rcv_wnd))
120 : 0 : return tcp_timewait_check_oow_rate_limit(
121 : : tw, skb, LINUX_MIB_TCPACKSKIPPEDFINWAIT2);
122 : :
123 [ # # ]: 0 : if (th->rst)
124 : : goto kill;
125 : :
126 [ # # # # ]: 0 : if (th->syn && !before(TCP_SKB_CB(skb)->seq, tcptw->tw_rcv_nxt))
127 : : return TCP_TW_RST;
128 : :
129 : : /* Dup ACK? */
130 [ # # # # ]: 0 : if (!th->ack ||
131 [ # # ]: 0 : !after(TCP_SKB_CB(skb)->end_seq, tcptw->tw_rcv_nxt) ||
132 : : TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq) {
133 : 0 : inet_twsk_put(tw);
134 : 0 : return TCP_TW_SUCCESS;
135 : : }
136 : :
137 : : /* New data or FIN. If new data arrive after half-duplex close,
138 : : * reset.
139 : : */
140 [ # # # # ]: 0 : if (!th->fin ||
141 : 0 : TCP_SKB_CB(skb)->end_seq != tcptw->tw_rcv_nxt + 1)
142 : : return TCP_TW_RST;
143 : :
144 : : /* FIN arrived, enter true time-wait state. */
145 : 0 : tw->tw_substate = TCP_TIME_WAIT;
146 : 0 : tcptw->tw_rcv_nxt = TCP_SKB_CB(skb)->end_seq;
147 [ # # ]: 0 : if (tmp_opt.saw_tstamp) {
148 : 0 : tcptw->tw_ts_recent_stamp = ktime_get_seconds();
149 : 0 : tcptw->tw_ts_recent = tmp_opt.rcv_tsval;
150 : : }
151 : :
152 : : inet_twsk_reschedule(tw, TCP_TIMEWAIT_LEN);
153 : 0 : return TCP_TW_ACK;
154 : : }
155 : :
156 : : /*
157 : : * Now real TIME-WAIT state.
158 : : *
159 : : * RFC 1122:
160 : : * "When a connection is [...] on TIME-WAIT state [...]
161 : : * [a TCP] MAY accept a new SYN from the remote TCP to
162 : : * reopen the connection directly, if it:
163 : : *
164 : : * (1) assigns its initial sequence number for the new
165 : : * connection to be larger than the largest sequence
166 : : * number it used on the previous connection incarnation,
167 : : * and
168 : : *
169 : : * (2) returns to TIME-WAIT state if the SYN turns out
170 : : * to be an old duplicate".
171 : : */
172 : :
173 [ # # # # ]: 0 : if (!paws_reject &&
174 [ # # ]: 0 : (TCP_SKB_CB(skb)->seq == tcptw->tw_rcv_nxt &&
175 [ # # ]: 0 : (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq || th->rst))) {
176 : : /* In window segment, it may be only reset or bare ack. */
177 : :
178 [ # # ]: 0 : if (th->rst) {
179 : : /* This is TIME_WAIT assassination, in two flavors.
180 : : * Oh well... nobody has a sufficient solution to this
181 : : * protocol bug yet.
182 : : */
183 [ # # ]: 0 : if (twsk_net(tw)->ipv4.sysctl_tcp_rfc1337 == 0) {
184 : : kill:
185 : 0 : inet_twsk_deschedule_put(tw);
186 : 0 : return TCP_TW_SUCCESS;
187 : : }
188 : : } else {
189 : : inet_twsk_reschedule(tw, TCP_TIMEWAIT_LEN);
190 : : }
191 : :
192 [ # # ]: 0 : if (tmp_opt.saw_tstamp) {
193 : 0 : tcptw->tw_ts_recent = tmp_opt.rcv_tsval;
194 : 0 : tcptw->tw_ts_recent_stamp = ktime_get_seconds();
195 : : }
196 : :
197 : 0 : inet_twsk_put(tw);
198 : 0 : return TCP_TW_SUCCESS;
199 : : }
200 : :
201 : : /* Out of window segment.
202 : :
203 : : All the segments are ACKed immediately.
204 : :
205 : : The only exception is new SYN. We accept it, if it is
206 : : not old duplicate and we are not in danger to be killed
207 : : by delayed old duplicates. RFC check is that it has
208 : : newer sequence number works at rates <40Mbit/sec.
209 : : However, if paws works, it is reliable AND even more,
210 : : we even may relax silly seq space cutoff.
211 : :
212 : : RED-PEN: we violate main RFC requirement, if this SYN will appear
213 : : old duplicate (i.e. we receive RST in reply to SYN-ACK),
214 : : we must return socket to time-wait state. It is not good,
215 : : but not fatal yet.
216 : : */
217 : :
218 [ # # # # : 0 : if (th->syn && !th->rst && !th->ack && !paws_reject &&
# # ]
219 [ # # ]: 0 : (after(TCP_SKB_CB(skb)->seq, tcptw->tw_rcv_nxt) ||
220 [ # # ]: 0 : (tmp_opt.saw_tstamp &&
221 : 0 : (s32)(tcptw->tw_ts_recent - tmp_opt.rcv_tsval) < 0))) {
222 : 0 : u32 isn = tcptw->tw_snd_nxt + 65535 + 2;
223 [ # # ]: 0 : if (isn == 0)
224 : 0 : isn++;
225 : 0 : TCP_SKB_CB(skb)->tcp_tw_isn = isn;
226 : 0 : return TCP_TW_SYN;
227 : : }
228 : :
229 [ # # ]: 0 : if (paws_reject)
230 : 0 : __NET_INC_STATS(twsk_net(tw), LINUX_MIB_PAWSESTABREJECTED);
231 : :
232 [ # # ]: 0 : if (!th->rst) {
233 : : /* In this case we must reset the TIMEWAIT timer.
234 : : *
235 : : * If it is ACKless SYN it may be both old duplicate
236 : : * and new good SYN with random sequence number <rcv_nxt.
237 : : * Do not reschedule in the last case.
238 : : */
239 [ # # # # ]: 0 : if (paws_reject || th->ack)
240 : : inet_twsk_reschedule(tw, TCP_TIMEWAIT_LEN);
241 : :
242 : 0 : return tcp_timewait_check_oow_rate_limit(
243 : : tw, skb, LINUX_MIB_TCPACKSKIPPEDTIMEWAIT);
244 : : }
245 : 0 : inet_twsk_put(tw);
246 : 0 : return TCP_TW_SUCCESS;
247 : : }
248 : : EXPORT_SYMBOL(tcp_timewait_state_process);
249 : :
250 : : /*
251 : : * Move a socket to time-wait or dead fin-wait-2 state.
252 : : */
253 : 0 : void tcp_time_wait(struct sock *sk, int state, int timeo)
254 : : {
255 : : const struct inet_connection_sock *icsk = inet_csk(sk);
256 : : const struct tcp_sock *tp = tcp_sk(sk);
257 : : struct inet_timewait_sock *tw;
258 : 0 : struct inet_timewait_death_row *tcp_death_row = &sock_net(sk)->ipv4.tcp_death_row;
259 : :
260 : 0 : tw = inet_twsk_alloc(sk, tcp_death_row, state);
261 : :
262 [ # # ]: 0 : if (tw) {
263 : : struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
264 : 0 : const int rto = (icsk->icsk_rto << 2) - (icsk->icsk_rto >> 1);
265 : : struct inet_sock *inet = inet_sk(sk);
266 : :
267 : 0 : tw->tw_transparent = inet->transparent;
268 : 0 : tw->tw_mark = sk->sk_mark;
269 : 0 : tw->tw_priority = sk->sk_priority;
270 : 0 : tw->tw_rcv_wscale = tp->rx_opt.rcv_wscale;
271 : 0 : tcptw->tw_rcv_nxt = tp->rcv_nxt;
272 : 0 : tcptw->tw_snd_nxt = tp->snd_nxt;
273 : 0 : tcptw->tw_rcv_wnd = tcp_receive_window(tp);
274 : 0 : tcptw->tw_ts_recent = tp->rx_opt.ts_recent;
275 : 0 : tcptw->tw_ts_recent_stamp = tp->rx_opt.ts_recent_stamp;
276 : 0 : tcptw->tw_ts_offset = tp->tsoffset;
277 : 0 : tcptw->tw_last_oow_ack_time = 0;
278 : 0 : tcptw->tw_tx_delay = tp->tcp_tx_delay;
279 : : #if IS_ENABLED(CONFIG_IPV6)
280 [ # # ]: 0 : if (tw->tw_family == PF_INET6) {
281 : : struct ipv6_pinfo *np = inet6_sk(sk);
282 : :
283 : 0 : tw->tw_v6_daddr = sk->sk_v6_daddr;
284 : 0 : tw->tw_v6_rcv_saddr = sk->sk_v6_rcv_saddr;
285 : 0 : tw->tw_tclass = np->tclass;
286 : 0 : tw->tw_flowlabel = be32_to_cpu(np->flow_label & IPV6_FLOWLABEL_MASK);
287 : 0 : tw->tw_txhash = sk->sk_txhash;
288 : 0 : tw->tw_ipv6only = sk->sk_ipv6only;
289 : : }
290 : : #endif
291 : :
292 : : #ifdef CONFIG_TCP_MD5SIG
293 : : /*
294 : : * The timewait bucket does not have the key DB from the
295 : : * sock structure. We just make a quick copy of the
296 : : * md5 key being used (if indeed we are using one)
297 : : * so the timewait ack generating code has the key.
298 : : */
299 : : do {
300 : : tcptw->tw_md5_key = NULL;
301 : : if (static_branch_unlikely(&tcp_md5_needed)) {
302 : : struct tcp_md5sig_key *key;
303 : :
304 : : key = tp->af_specific->md5_lookup(sk, sk);
305 : : if (key) {
306 : : tcptw->tw_md5_key = kmemdup(key, sizeof(*key), GFP_ATOMIC);
307 : : BUG_ON(tcptw->tw_md5_key && !tcp_alloc_md5sig_pool());
308 : : }
309 : : }
310 : : } while (0);
311 : : #endif
312 : :
313 : : /* Get the TIME_WAIT timeout firing. */
314 [ # # ]: 0 : if (timeo < rto)
315 : : timeo = rto;
316 : :
317 [ # # ]: 0 : if (state == TCP_TIME_WAIT)
318 : : timeo = TCP_TIMEWAIT_LEN;
319 : :
320 : : /* tw_timer is pinned, so we need to make sure BH are disabled
321 : : * in following section, otherwise timer handler could run before
322 : : * we complete the initialization.
323 : : */
324 : : local_bh_disable();
325 : : inet_twsk_schedule(tw, timeo);
326 : : /* Linkage updates.
327 : : * Note that access to tw after this point is illegal.
328 : : */
329 : 0 : inet_twsk_hashdance(tw, sk, &tcp_hashinfo);
330 : : local_bh_enable();
331 : : } else {
332 : : /* Sorry, if we're out of memory, just CLOSE this
333 : : * socket up. We've got bigger problems than
334 : : * non-graceful socket closings.
335 : : */
336 : 0 : NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEWAITOVERFLOW);
337 : : }
338 : :
339 : 0 : tcp_update_metrics(sk);
340 : 0 : tcp_done(sk);
341 : 0 : }
342 : : EXPORT_SYMBOL(tcp_time_wait);
343 : :
344 : 0 : void tcp_twsk_destructor(struct sock *sk)
345 : : {
346 : : #ifdef CONFIG_TCP_MD5SIG
347 : : if (static_branch_unlikely(&tcp_md5_needed)) {
348 : : struct tcp_timewait_sock *twsk = tcp_twsk(sk);
349 : :
350 : : if (twsk->tw_md5_key)
351 : : kfree_rcu(twsk->tw_md5_key, rcu);
352 : : }
353 : : #endif
354 : 0 : }
355 : : EXPORT_SYMBOL_GPL(tcp_twsk_destructor);
356 : :
357 : : /* Warning : This function is called without sk_listener being locked.
358 : : * Be sure to read socket fields once, as their value could change under us.
359 : : */
360 : 0 : void tcp_openreq_init_rwin(struct request_sock *req,
361 : : const struct sock *sk_listener,
362 : : const struct dst_entry *dst)
363 : : {
364 : : struct inet_request_sock *ireq = inet_rsk(req);
365 : : const struct tcp_sock *tp = tcp_sk(sk_listener);
366 : : int full_space = tcp_full_space(sk_listener);
367 : : u32 window_clamp;
368 : : __u8 rcv_wscale;
369 : : u32 rcv_wnd;
370 : : int mss;
371 : :
372 : 0 : mss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
373 : : window_clamp = READ_ONCE(tp->window_clamp);
374 : : /* Set this up on the first call only */
375 [ # # ]: 0 : req->rsk_window_clamp = window_clamp ? : dst_metric(dst, RTAX_WINDOW);
376 : :
377 : : /* limit the window selection if the user enforce a smaller rx buffer */
378 [ # # # # ]: 0 : if (sk_listener->sk_userlocks & SOCK_RCVBUF_LOCK &&
379 [ # # ]: 0 : (req->rsk_window_clamp > full_space || req->rsk_window_clamp == 0))
380 : 0 : req->rsk_window_clamp = full_space;
381 : :
382 : : rcv_wnd = tcp_rwnd_init_bpf((struct sock *)req);
383 [ # # ]: 0 : if (rcv_wnd == 0)
384 : 0 : rcv_wnd = dst_metric(dst, RTAX_INITRWND);
385 [ # # ]: 0 : else if (full_space < rcv_wnd * mss)
386 : 0 : full_space = rcv_wnd * mss;
387 : :
388 : : /* tcp_full_space because it is guaranteed to be the first packet */
389 : 0 : tcp_select_initial_window(sk_listener, full_space,
390 [ # # ]: 0 : mss - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
391 : 0 : &req->rsk_rcv_wnd,
392 : 0 : &req->rsk_window_clamp,
393 : 0 : ireq->wscale_ok,
394 : : &rcv_wscale,
395 : : rcv_wnd);
396 : 0 : ireq->rcv_wscale = rcv_wscale;
397 : 0 : }
398 : : EXPORT_SYMBOL(tcp_openreq_init_rwin);
399 : :
400 : : static void tcp_ecn_openreq_child(struct tcp_sock *tp,
401 : : const struct request_sock *req)
402 : : {
403 : 0 : tp->ecn_flags = inet_rsk(req)->ecn_ok ? TCP_ECN_OK : 0;
404 : : }
405 : :
406 : 0 : void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst)
407 : : {
408 : : struct inet_connection_sock *icsk = inet_csk(sk);
409 : 0 : u32 ca_key = dst_metric(dst, RTAX_CC_ALGO);
410 : : bool ca_got_dst = false;
411 : :
412 [ # # ]: 0 : if (ca_key != TCP_CA_UNSPEC) {
413 : : const struct tcp_congestion_ops *ca;
414 : :
415 : : rcu_read_lock();
416 : 0 : ca = tcp_ca_find_key(ca_key);
417 [ # # # # ]: 0 : if (likely(ca && try_module_get(ca->owner))) {
418 : 0 : icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst);
419 : 0 : icsk->icsk_ca_ops = ca;
420 : : ca_got_dst = true;
421 : : }
422 : : rcu_read_unlock();
423 : : }
424 : :
425 : : /* If no valid choice made yet, assign current system default ca. */
426 [ # # # # ]: 0 : if (!ca_got_dst &&
427 [ # # ]: 0 : (!icsk->icsk_ca_setsockopt ||
428 : 0 : !try_module_get(icsk->icsk_ca_ops->owner)))
429 : 0 : tcp_assign_congestion_control(sk);
430 : :
431 : : tcp_set_ca_state(sk, TCP_CA_Open);
432 : 0 : }
433 : : EXPORT_SYMBOL_GPL(tcp_ca_openreq_child);
434 : :
435 : : static void smc_check_reset_syn_req(struct tcp_sock *oldtp,
436 : : struct request_sock *req,
437 : : struct tcp_sock *newtp)
438 : : {
439 : : #if IS_ENABLED(CONFIG_SMC)
440 : : struct inet_request_sock *ireq;
441 : :
442 : : if (static_branch_unlikely(&tcp_have_smc)) {
443 : : ireq = inet_rsk(req);
444 : : if (oldtp->syn_smc && !ireq->smc_ok)
445 : : newtp->syn_smc = 0;
446 : : }
447 : : #endif
448 : : }
449 : :
450 : : /* This is not only more efficient than what we used to do, it eliminates
451 : : * a lot of code duplication between IPv4/IPv6 SYN recv processing. -DaveM
452 : : *
453 : : * Actually, we could lots of memory writes here. tp of listening
454 : : * socket contains all necessary default parameters.
455 : : */
456 : 0 : struct sock *tcp_create_openreq_child(const struct sock *sk,
457 : : struct request_sock *req,
458 : : struct sk_buff *skb)
459 : : {
460 : 0 : struct sock *newsk = inet_csk_clone_lock(sk, req, GFP_ATOMIC);
461 : : const struct inet_request_sock *ireq = inet_rsk(req);
462 : : struct tcp_request_sock *treq = tcp_rsk(req);
463 : : struct inet_connection_sock *newicsk;
464 : : struct tcp_sock *oldtp, *newtp;
465 : : u32 seq;
466 : :
467 [ # # ]: 0 : if (!newsk)
468 : : return NULL;
469 : :
470 : : newicsk = inet_csk(newsk);
471 : : newtp = tcp_sk(newsk);
472 : : oldtp = tcp_sk(sk);
473 : :
474 : : smc_check_reset_syn_req(oldtp, req, newtp);
475 : :
476 : : /* Now setup tcp_sock */
477 : 0 : newtp->pred_flags = 0;
478 : :
479 : 0 : seq = treq->rcv_isn + 1;
480 : 0 : newtp->rcv_wup = seq;
481 : : WRITE_ONCE(newtp->copied_seq, seq);
482 : : WRITE_ONCE(newtp->rcv_nxt, seq);
483 : 0 : newtp->segs_in = 1;
484 : :
485 : 0 : seq = treq->snt_isn + 1;
486 : 0 : newtp->snd_sml = newtp->snd_una = seq;
487 : : WRITE_ONCE(newtp->snd_nxt, seq);
488 : 0 : newtp->snd_up = seq;
489 : :
490 : 0 : INIT_LIST_HEAD(&newtp->tsq_node);
491 : 0 : INIT_LIST_HEAD(&newtp->tsorted_sent_queue);
492 : :
493 : 0 : tcp_init_wl(newtp, treq->rcv_isn);
494 : :
495 : 0 : minmax_reset(&newtp->rtt_min, tcp_jiffies32, ~0U);
496 : 0 : newicsk->icsk_ack.lrcvtime = tcp_jiffies32;
497 : :
498 : 0 : newtp->lsndtime = tcp_jiffies32;
499 : 0 : newsk->sk_txhash = treq->txhash;
500 : 0 : newtp->total_retrans = req->num_retrans;
501 : :
502 : 0 : tcp_init_xmit_timers(newsk);
503 : 0 : WRITE_ONCE(newtp->write_seq, newtp->pushed_seq = treq->snt_isn + 1);
504 : :
505 [ # # ]: 0 : if (sock_flag(newsk, SOCK_KEEPOPEN))
506 : 0 : inet_csk_reset_keepalive_timer(newsk,
507 : : keepalive_time_when(newtp));
508 : :
509 : 0 : newtp->rx_opt.tstamp_ok = ireq->tstamp_ok;
510 : 0 : newtp->rx_opt.sack_ok = ireq->sack_ok;
511 : 0 : newtp->window_clamp = req->rsk_window_clamp;
512 : 0 : newtp->rcv_ssthresh = req->rsk_rcv_wnd;
513 : 0 : newtp->rcv_wnd = req->rsk_rcv_wnd;
514 : 0 : newtp->rx_opt.wscale_ok = ireq->wscale_ok;
515 [ # # ]: 0 : if (newtp->rx_opt.wscale_ok) {
516 : 0 : newtp->rx_opt.snd_wscale = ireq->snd_wscale;
517 : 0 : newtp->rx_opt.rcv_wscale = ireq->rcv_wscale;
518 : : } else {
519 : 0 : newtp->rx_opt.snd_wscale = newtp->rx_opt.rcv_wscale = 0;
520 : 0 : newtp->window_clamp = min(newtp->window_clamp, 65535U);
521 : : }
522 : 0 : newtp->snd_wnd = ntohs(tcp_hdr(skb)->window) << newtp->rx_opt.snd_wscale;
523 : 0 : newtp->max_window = newtp->snd_wnd;
524 : :
525 [ # # ]: 0 : if (newtp->rx_opt.tstamp_ok) {
526 : 0 : newtp->rx_opt.ts_recent = req->ts_recent;
527 : 0 : newtp->rx_opt.ts_recent_stamp = ktime_get_seconds();
528 : 0 : newtp->tcp_header_len = sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
529 : : } else {
530 : 0 : newtp->rx_opt.ts_recent_stamp = 0;
531 : 0 : newtp->tcp_header_len = sizeof(struct tcphdr);
532 : : }
533 [ # # ]: 0 : if (req->num_timeout) {
534 : 0 : newtp->undo_marker = treq->snt_isn;
535 : 0 : newtp->retrans_stamp = div_u64(treq->snt_synack,
536 : : USEC_PER_SEC / TCP_TS_HZ);
537 : : }
538 : 0 : newtp->tsoffset = treq->ts_off;
539 : : #ifdef CONFIG_TCP_MD5SIG
540 : : newtp->md5sig_info = NULL; /*XXX*/
541 : : if (newtp->af_specific->md5_lookup(sk, newsk))
542 : : newtp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
543 : : #endif
544 [ # # ]: 0 : if (skb->len >= TCP_MSS_DEFAULT + newtp->tcp_header_len)
545 : 0 : newicsk->icsk_ack.last_seg_size = skb->len - newtp->tcp_header_len;
546 : 0 : newtp->rx_opt.mss_clamp = req->mss;
547 : : tcp_ecn_openreq_child(newtp, req);
548 : 0 : newtp->fastopen_req = NULL;
549 : : RCU_INIT_POINTER(newtp->fastopen_rsk, NULL);
550 : :
551 : 0 : __TCP_INC_STATS(sock_net(sk), TCP_MIB_PASSIVEOPENS);
552 : :
553 : 0 : return newsk;
554 : : }
555 : : EXPORT_SYMBOL(tcp_create_openreq_child);
556 : :
557 : : /*
558 : : * Process an incoming packet for SYN_RECV sockets represented as a
559 : : * request_sock. Normally sk is the listener socket but for TFO it
560 : : * points to the child socket.
561 : : *
562 : : * XXX (TFO) - The current impl contains a special check for ack
563 : : * validation and inside tcp_v4_reqsk_send_ack(). Can we do better?
564 : : *
565 : : * We don't need to initialize tmp_opt.sack_ok as we don't use the results
566 : : */
567 : :
568 : 0 : struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
569 : : struct request_sock *req,
570 : : bool fastopen, bool *req_stolen)
571 : : {
572 : : struct tcp_options_received tmp_opt;
573 : : struct sock *child;
574 : : const struct tcphdr *th = tcp_hdr(skb);
575 : 0 : __be32 flg = tcp_flag_word(th) & (TCP_FLAG_RST|TCP_FLAG_SYN|TCP_FLAG_ACK);
576 : : bool paws_reject = false;
577 : : bool own_req;
578 : :
579 : 0 : tmp_opt.saw_tstamp = 0;
580 [ # # ]: 0 : if (th->doff > (sizeof(struct tcphdr)>>2)) {
581 : 0 : tcp_parse_options(sock_net(sk), skb, &tmp_opt, 0, NULL);
582 : :
583 [ # # ]: 0 : if (tmp_opt.saw_tstamp) {
584 : 0 : tmp_opt.ts_recent = req->ts_recent;
585 [ # # ]: 0 : if (tmp_opt.rcv_tsecr)
586 : 0 : tmp_opt.rcv_tsecr -= tcp_rsk(req)->ts_off;
587 : : /* We do not store true stamp, but it is not required,
588 : : * it can be estimated (approximately)
589 : : * from another data.
590 : : */
591 : 0 : tmp_opt.ts_recent_stamp = ktime_get_seconds() - ((TCP_TIMEOUT_INIT/HZ)<<req->num_timeout);
592 : 0 : paws_reject = tcp_paws_reject(&tmp_opt, th->rst);
593 : : }
594 : : }
595 : :
596 : : /* Check for pure retransmitted SYN. */
597 [ # # ]: 0 : if (TCP_SKB_CB(skb)->seq == tcp_rsk(req)->rcv_isn &&
598 [ # # ]: 0 : flg == TCP_FLAG_SYN &&
599 : : !paws_reject) {
600 : : /*
601 : : * RFC793 draws (Incorrectly! It was fixed in RFC1122)
602 : : * this case on figure 6 and figure 8, but formal
603 : : * protocol description says NOTHING.
604 : : * To be more exact, it says that we should send ACK,
605 : : * because this segment (at least, if it has no data)
606 : : * is out of window.
607 : : *
608 : : * CONCLUSION: RFC793 (even with RFC1122) DOES NOT
609 : : * describe SYN-RECV state. All the description
610 : : * is wrong, we cannot believe to it and should
611 : : * rely only on common sense and implementation
612 : : * experience.
613 : : *
614 : : * Enforce "SYN-ACK" according to figure 8, figure 6
615 : : * of RFC793, fixed by RFC1122.
616 : : *
617 : : * Note that even if there is new data in the SYN packet
618 : : * they will be thrown away too.
619 : : *
620 : : * Reset timer after retransmitting SYNACK, similar to
621 : : * the idea of fast retransmit in recovery.
622 : : */
623 [ # # ]: 0 : if (!tcp_oow_rate_limited(sock_net(sk), skb,
624 : : LINUX_MIB_TCPACKSKIPPEDSYNRECV,
625 [ # # ]: 0 : &tcp_rsk(req)->last_oow_ack_time) &&
626 : :
627 : 0 : !inet_rtx_syn_ack(sk, req)) {
628 : 0 : unsigned long expires = jiffies;
629 : :
630 : 0 : expires += min(TCP_TIMEOUT_INIT << req->num_timeout,
631 : : TCP_RTO_MAX);
632 [ # # ]: 0 : if (!fastopen)
633 : 0 : mod_timer_pending(&req->rsk_timer, expires);
634 : : else
635 : 0 : req->rsk_timer.expires = expires;
636 : : }
637 : : return NULL;
638 : : }
639 : :
640 : : /* Further reproduces section "SEGMENT ARRIVES"
641 : : for state SYN-RECEIVED of RFC793.
642 : : It is broken, however, it does not work only
643 : : when SYNs are crossed.
644 : :
645 : : You would think that SYN crossing is impossible here, since
646 : : we should have a SYN_SENT socket (from connect()) on our end,
647 : : but this is not true if the crossed SYNs were sent to both
648 : : ends by a malicious third party. We must defend against this,
649 : : and to do that we first verify the ACK (as per RFC793, page
650 : : 36) and reset if it is invalid. Is this a true full defense?
651 : : To convince ourselves, let us consider a way in which the ACK
652 : : test can still pass in this 'malicious crossed SYNs' case.
653 : : Malicious sender sends identical SYNs (and thus identical sequence
654 : : numbers) to both A and B:
655 : :
656 : : A: gets SYN, seq=7
657 : : B: gets SYN, seq=7
658 : :
659 : : By our good fortune, both A and B select the same initial
660 : : send sequence number of seven :-)
661 : :
662 : : A: sends SYN|ACK, seq=7, ack_seq=8
663 : : B: sends SYN|ACK, seq=7, ack_seq=8
664 : :
665 : : So we are now A eating this SYN|ACK, ACK test passes. So
666 : : does sequence test, SYN is truncated, and thus we consider
667 : : it a bare ACK.
668 : :
669 : : If icsk->icsk_accept_queue.rskq_defer_accept, we silently drop this
670 : : bare ACK. Otherwise, we create an established connection. Both
671 : : ends (listening sockets) accept the new incoming connection and try
672 : : to talk to each other. 8-)
673 : :
674 : : Note: This case is both harmless, and rare. Possibility is about the
675 : : same as us discovering intelligent life on another plant tomorrow.
676 : :
677 : : But generally, we should (RFC lies!) to accept ACK
678 : : from SYNACK both here and in tcp_rcv_state_process().
679 : : tcp_rcv_state_process() does not, hence, we do not too.
680 : :
681 : : Note that the case is absolutely generic:
682 : : we cannot optimize anything here without
683 : : violating protocol. All the checks must be made
684 : : before attempt to create socket.
685 : : */
686 : :
687 : : /* RFC793 page 36: "If the connection is in any non-synchronized state ...
688 : : * and the incoming segment acknowledges something not yet
689 : : * sent (the segment carries an unacceptable ACK) ...
690 : : * a reset is sent."
691 : : *
692 : : * Invalid ACK: reset will be sent by listening socket.
693 : : * Note that the ACK validity check for a Fast Open socket is done
694 : : * elsewhere and is checked directly against the child socket rather
695 : : * than req because user data may have been sent out.
696 : : */
697 [ # # # # : 0 : if ((flg & TCP_FLAG_ACK) && !fastopen &&
# # ]
698 : 0 : (TCP_SKB_CB(skb)->ack_seq !=
699 : 0 : tcp_rsk(req)->snt_isn + 1))
700 : : return sk;
701 : :
702 : : /* Also, it would be not so bad idea to check rcv_tsecr, which
703 : : * is essentially ACK extension and too early or too late values
704 : : * should cause reset in unsynchronized states.
705 : : */
706 : :
707 : : /* RFC793: "first check sequence number". */
708 : :
709 [ # # # # ]: 0 : if (paws_reject || !tcp_in_window(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq,
710 : 0 : tcp_rsk(req)->rcv_nxt, tcp_rsk(req)->rcv_nxt + req->rsk_rcv_wnd)) {
711 : : /* Out of window: send ACK and drop. */
712 [ # # # # ]: 0 : if (!(flg & TCP_FLAG_RST) &&
713 : 0 : !tcp_oow_rate_limited(sock_net(sk), skb,
714 : : LINUX_MIB_TCPACKSKIPPEDSYNRECV,
715 : : &tcp_rsk(req)->last_oow_ack_time))
716 : 0 : req->rsk_ops->send_ack(sk, skb, req);
717 [ # # ]: 0 : if (paws_reject)
718 : 0 : __NET_INC_STATS(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
719 : : return NULL;
720 : : }
721 : :
722 : : /* In sequence, PAWS is OK. */
723 : :
724 [ # # # # ]: 0 : if (tmp_opt.saw_tstamp && !after(TCP_SKB_CB(skb)->seq, tcp_rsk(req)->rcv_nxt))
725 : 0 : req->ts_recent = tmp_opt.rcv_tsval;
726 : :
727 [ # # ]: 0 : if (TCP_SKB_CB(skb)->seq == tcp_rsk(req)->rcv_isn) {
728 : : /* Truncate SYN, it is out of window starting
729 : : at tcp_rsk(req)->rcv_isn + 1. */
730 : 0 : flg &= ~TCP_FLAG_SYN;
731 : : }
732 : :
733 : : /* RFC793: "second check the RST bit" and
734 : : * "fourth, check the SYN bit"
735 : : */
736 [ # # ]: 0 : if (flg & (TCP_FLAG_RST|TCP_FLAG_SYN)) {
737 : 0 : __TCP_INC_STATS(sock_net(sk), TCP_MIB_ATTEMPTFAILS);
738 : : goto embryonic_reset;
739 : : }
740 : :
741 : : /* ACK sequence verified above, just make sure ACK is
742 : : * set. If ACK not set, just silently drop the packet.
743 : : *
744 : : * XXX (TFO) - if we ever allow "data after SYN", the
745 : : * following check needs to be removed.
746 : : */
747 [ # # ]: 0 : if (!(flg & TCP_FLAG_ACK))
748 : : return NULL;
749 : :
750 : : /* For Fast Open no more processing is needed (sk is the
751 : : * child socket).
752 : : */
753 [ # # ]: 0 : if (fastopen)
754 : : return sk;
755 : :
756 : : /* While TCP_DEFER_ACCEPT is active, drop bare ACK. */
757 [ # # # # ]: 0 : if (req->num_timeout < inet_csk(sk)->icsk_accept_queue.rskq_defer_accept &&
758 : 0 : TCP_SKB_CB(skb)->end_seq == tcp_rsk(req)->rcv_isn + 1) {
759 : 0 : inet_rsk(req)->acked = 1;
760 : 0 : __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPDEFERACCEPTDROP);
761 : 0 : return NULL;
762 : : }
763 : :
764 : : /* OK, ACK is valid, create big socket and
765 : : * feed this segment to it. It will repeat all
766 : : * the tests. THIS SEGMENT MUST MOVE SOCKET TO
767 : : * ESTABLISHED STATE. If it will be dropped after
768 : : * socket is created, wait for troubles.
769 : : */
770 : 0 : child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL,
771 : : req, &own_req);
772 [ # # ]: 0 : if (!child)
773 : : goto listen_overflow;
774 : :
775 : : sock_rps_save_rxhash(child, skb);
776 : 0 : tcp_synack_rtt_meas(child, req);
777 : 0 : *req_stolen = !own_req;
778 : 0 : return inet_csk_complete_hashdance(sk, child, req, own_req);
779 : :
780 : : listen_overflow:
781 [ # # ]: 0 : if (!sock_net(sk)->ipv4.sysctl_tcp_abort_on_overflow) {
782 : 0 : inet_rsk(req)->acked = 1;
783 : 0 : return NULL;
784 : : }
785 : :
786 : : embryonic_reset:
787 [ # # ]: 0 : if (!(flg & TCP_FLAG_RST)) {
788 : : /* Received a bad SYN pkt - for TFO We try not to reset
789 : : * the local connection unless it's really necessary to
790 : : * avoid becoming vulnerable to outside attack aiming at
791 : : * resetting legit local connections.
792 : : */
793 : 0 : req->rsk_ops->send_reset(sk, skb);
794 [ # # ]: 0 : } else if (fastopen) { /* received a valid RST pkt */
795 : 0 : reqsk_fastopen_remove(sk, req, true);
796 : 0 : tcp_reset(sk);
797 : : }
798 [ # # ]: 0 : if (!fastopen) {
799 : 0 : inet_csk_reqsk_queue_drop(sk, req);
800 : 0 : __NET_INC_STATS(sock_net(sk), LINUX_MIB_EMBRYONICRSTS);
801 : : }
802 : : return NULL;
803 : : }
804 : : EXPORT_SYMBOL(tcp_check_req);
805 : :
806 : : /*
807 : : * Queue segment on the new socket if the new socket is active,
808 : : * otherwise we just shortcircuit this and continue with
809 : : * the new socket.
810 : : *
811 : : * For the vast majority of cases child->sk_state will be TCP_SYN_RECV
812 : : * when entering. But other states are possible due to a race condition
813 : : * where after __inet_lookup_established() fails but before the listener
814 : : * locked is obtained, other packets cause the same connection to
815 : : * be created.
816 : : */
817 : :
818 : 0 : int tcp_child_process(struct sock *parent, struct sock *child,
819 : : struct sk_buff *skb)
820 : : {
821 : : int ret = 0;
822 : 0 : int state = child->sk_state;
823 : :
824 : : /* record NAPI ID of child */
825 : : sk_mark_napi_id(child, skb);
826 : :
827 : 0 : tcp_segs_in(tcp_sk(child), skb);
828 [ # # ]: 0 : if (!sock_owned_by_user(child)) {
829 : 0 : ret = tcp_rcv_state_process(child, skb);
830 : : /* Wakeup parent, send SIGIO */
831 [ # # # # ]: 0 : if (state == TCP_SYN_RECV && child->sk_state != state)
832 : 0 : parent->sk_data_ready(parent);
833 : : } else {
834 : : /* Alas, it is possible again, because we do lookup
835 : : * in main socket hash table and lock on listening
836 : : * socket does not protect us more.
837 : : */
838 : : __sk_add_backlog(child, skb);
839 : : }
840 : :
841 : : bh_unlock_sock(child);
842 : 0 : sock_put(child);
843 : 0 : return ret;
844 : : }
845 : : EXPORT_SYMBOL(tcp_child_process);
|
