Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0
2 : #include <linux/crypto.h>
3 : #include <linux/err.h>
4 : #include <linux/init.h>
5 : #include <linux/kernel.h>
6 : #include <linux/list.h>
7 : #include <linux/tcp.h>
8 : #include <linux/rcupdate.h>
9 : #include <linux/rculist.h>
10 : #include <net/inetpeer.h>
11 : #include <net/tcp.h>
12 :
13 1 : void tcp_fastopen_init_key_once(struct net *net)
14 : {
15 1 : u8 key[TCP_FASTOPEN_KEY_LENGTH];
16 1 : struct tcp_fastopen_context *ctxt;
17 :
18 1 : rcu_read_lock();
19 1 : ctxt = rcu_dereference(net->ipv4.tcp_fastopen_ctx);
20 1 : if (ctxt) {
21 0 : rcu_read_unlock();
22 0 : return;
23 : }
24 1 : rcu_read_unlock();
25 :
26 : /* tcp_fastopen_reset_cipher publishes the new context
27 : * atomically, so we allow this race happening here.
28 : *
29 : * All call sites of tcp_fastopen_cookie_gen also check
30 : * for a valid cookie, so this is an acceptable risk.
31 : */
32 1 : get_random_bytes(key, sizeof(key));
33 1 : tcp_fastopen_reset_cipher(net, NULL, key, NULL);
34 : }
35 :
36 0 : static void tcp_fastopen_ctx_free(struct rcu_head *head)
37 : {
38 0 : struct tcp_fastopen_context *ctx =
39 0 : container_of(head, struct tcp_fastopen_context, rcu);
40 :
41 0 : kfree_sensitive(ctx);
42 0 : }
43 :
44 4 : void tcp_fastopen_destroy_cipher(struct sock *sk)
45 : {
46 4 : struct tcp_fastopen_context *ctx;
47 :
48 4 : ctx = rcu_dereference_protected(
49 : inet_csk(sk)->icsk_accept_queue.fastopenq.ctx, 1);
50 4 : if (ctx)
51 0 : call_rcu(&ctx->rcu, tcp_fastopen_ctx_free);
52 4 : }
53 :
54 0 : void tcp_fastopen_ctx_destroy(struct net *net)
55 : {
56 0 : struct tcp_fastopen_context *ctxt;
57 :
58 0 : spin_lock(&net->ipv4.tcp_fastopen_ctx_lock);
59 :
60 0 : ctxt = rcu_dereference_protected(net->ipv4.tcp_fastopen_ctx,
61 : lockdep_is_held(&net->ipv4.tcp_fastopen_ctx_lock));
62 0 : rcu_assign_pointer(net->ipv4.tcp_fastopen_ctx, NULL);
63 0 : spin_unlock(&net->ipv4.tcp_fastopen_ctx_lock);
64 :
65 0 : if (ctxt)
66 0 : call_rcu(&ctxt->rcu, tcp_fastopen_ctx_free);
67 0 : }
68 :
69 1 : int tcp_fastopen_reset_cipher(struct net *net, struct sock *sk,
70 : void *primary_key, void *backup_key)
71 : {
72 1 : struct tcp_fastopen_context *ctx, *octx;
73 1 : struct fastopen_queue *q;
74 1 : int err = 0;
75 :
76 1 : ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
77 1 : if (!ctx) {
78 0 : err = -ENOMEM;
79 0 : goto out;
80 : }
81 :
82 1 : ctx->key[0].key[0] = get_unaligned_le64(primary_key);
83 1 : ctx->key[0].key[1] = get_unaligned_le64(primary_key + 8);
84 1 : if (backup_key) {
85 0 : ctx->key[1].key[0] = get_unaligned_le64(backup_key);
86 0 : ctx->key[1].key[1] = get_unaligned_le64(backup_key + 8);
87 0 : ctx->num = 2;
88 : } else {
89 1 : ctx->num = 1;
90 : }
91 :
92 1 : spin_lock(&net->ipv4.tcp_fastopen_ctx_lock);
93 1 : if (sk) {
94 0 : q = &inet_csk(sk)->icsk_accept_queue.fastopenq;
95 0 : octx = rcu_dereference_protected(q->ctx,
96 : lockdep_is_held(&net->ipv4.tcp_fastopen_ctx_lock));
97 0 : rcu_assign_pointer(q->ctx, ctx);
98 : } else {
99 1 : octx = rcu_dereference_protected(net->ipv4.tcp_fastopen_ctx,
100 : lockdep_is_held(&net->ipv4.tcp_fastopen_ctx_lock));
101 1 : rcu_assign_pointer(net->ipv4.tcp_fastopen_ctx, ctx);
102 : }
103 1 : spin_unlock(&net->ipv4.tcp_fastopen_ctx_lock);
104 :
105 1 : if (octx)
106 0 : call_rcu(&octx->rcu, tcp_fastopen_ctx_free);
107 1 : out:
108 1 : return err;
109 : }
110 :
111 0 : int tcp_fastopen_get_cipher(struct net *net, struct inet_connection_sock *icsk,
112 : u64 *key)
113 : {
114 0 : struct tcp_fastopen_context *ctx;
115 0 : int n_keys = 0, i;
116 :
117 0 : rcu_read_lock();
118 0 : if (icsk)
119 0 : ctx = rcu_dereference(icsk->icsk_accept_queue.fastopenq.ctx);
120 : else
121 0 : ctx = rcu_dereference(net->ipv4.tcp_fastopen_ctx);
122 0 : if (ctx) {
123 0 : n_keys = tcp_fastopen_context_len(ctx);
124 0 : for (i = 0; i < n_keys; i++) {
125 0 : put_unaligned_le64(ctx->key[i].key[0], key + (i * 2));
126 0 : put_unaligned_le64(ctx->key[i].key[1], key + (i * 2) + 1);
127 : }
128 : }
129 0 : rcu_read_unlock();
130 :
131 0 : return n_keys;
132 : }
133 :
134 0 : static bool __tcp_fastopen_cookie_gen_cipher(struct request_sock *req,
135 : struct sk_buff *syn,
136 : const siphash_key_t *key,
137 : struct tcp_fastopen_cookie *foc)
138 : {
139 0 : BUILD_BUG_ON(TCP_FASTOPEN_COOKIE_SIZE != sizeof(u64));
140 :
141 0 : if (req->rsk_ops->family == AF_INET) {
142 0 : const struct iphdr *iph = ip_hdr(syn);
143 :
144 0 : foc->val[0] = cpu_to_le64(siphash(&iph->saddr,
145 : sizeof(iph->saddr) +
146 : sizeof(iph->daddr),
147 : key));
148 0 : foc->len = TCP_FASTOPEN_COOKIE_SIZE;
149 0 : return true;
150 : }
151 : #if IS_ENABLED(CONFIG_IPV6)
152 : if (req->rsk_ops->family == AF_INET6) {
153 : const struct ipv6hdr *ip6h = ipv6_hdr(syn);
154 :
155 : foc->val[0] = cpu_to_le64(siphash(&ip6h->saddr,
156 : sizeof(ip6h->saddr) +
157 : sizeof(ip6h->daddr),
158 : key));
159 : foc->len = TCP_FASTOPEN_COOKIE_SIZE;
160 : return true;
161 : }
162 : #endif
163 : return false;
164 : }
165 :
166 : /* Generate the fastopen cookie by applying SipHash to both the source and
167 : * destination addresses.
168 : */
169 0 : static void tcp_fastopen_cookie_gen(struct sock *sk,
170 : struct request_sock *req,
171 : struct sk_buff *syn,
172 : struct tcp_fastopen_cookie *foc)
173 : {
174 0 : struct tcp_fastopen_context *ctx;
175 :
176 0 : rcu_read_lock();
177 0 : ctx = tcp_fastopen_get_ctx(sk);
178 0 : if (ctx)
179 0 : __tcp_fastopen_cookie_gen_cipher(req, syn, &ctx->key[0], foc);
180 0 : rcu_read_unlock();
181 0 : }
182 :
183 : /* If an incoming SYN or SYNACK frame contains a payload and/or FIN,
184 : * queue this additional data / FIN.
185 : */
186 0 : void tcp_fastopen_add_skb(struct sock *sk, struct sk_buff *skb)
187 : {
188 0 : struct tcp_sock *tp = tcp_sk(sk);
189 :
190 0 : if (TCP_SKB_CB(skb)->end_seq == tp->rcv_nxt)
191 : return;
192 :
193 0 : skb = skb_clone(skb, GFP_ATOMIC);
194 0 : if (!skb)
195 : return;
196 :
197 0 : skb_dst_drop(skb);
198 : /* segs_in has been initialized to 1 in tcp_create_openreq_child().
199 : * Hence, reset segs_in to 0 before calling tcp_segs_in()
200 : * to avoid double counting. Also, tcp_segs_in() expects
201 : * skb->len to include the tcp_hdrlen. Hence, it should
202 : * be called before __skb_pull().
203 : */
204 0 : tp->segs_in = 0;
205 0 : tcp_segs_in(tp, skb);
206 0 : __skb_pull(skb, tcp_hdrlen(skb));
207 0 : sk_forced_mem_schedule(sk, skb->truesize);
208 0 : skb_set_owner_r(skb, sk);
209 :
210 0 : TCP_SKB_CB(skb)->seq++;
211 0 : TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_SYN;
212 :
213 0 : tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
214 0 : __skb_queue_tail(&sk->sk_receive_queue, skb);
215 0 : tp->syn_data_acked = 1;
216 :
217 : /* u64_stats_update_begin(&tp->syncp) not needed here,
218 : * as we certainly are not changing upper 32bit value (0)
219 : */
220 0 : tp->bytes_received = skb->len;
221 :
222 0 : if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
223 0 : tcp_fin(sk);
224 : }
225 :
226 : /* returns 0 - no key match, 1 for primary, 2 for backup */
227 0 : static int tcp_fastopen_cookie_gen_check(struct sock *sk,
228 : struct request_sock *req,
229 : struct sk_buff *syn,
230 : struct tcp_fastopen_cookie *orig,
231 : struct tcp_fastopen_cookie *valid_foc)
232 : {
233 0 : struct tcp_fastopen_cookie search_foc = { .len = -1 };
234 0 : struct tcp_fastopen_cookie *foc = valid_foc;
235 0 : struct tcp_fastopen_context *ctx;
236 0 : int i, ret = 0;
237 :
238 0 : rcu_read_lock();
239 0 : ctx = tcp_fastopen_get_ctx(sk);
240 0 : if (!ctx)
241 0 : goto out;
242 0 : for (i = 0; i < tcp_fastopen_context_len(ctx); i++) {
243 0 : __tcp_fastopen_cookie_gen_cipher(req, syn, &ctx->key[i], foc);
244 0 : if (tcp_fastopen_cookie_match(foc, orig)) {
245 0 : ret = i + 1;
246 0 : goto out;
247 : }
248 0 : foc = &search_foc;
249 : }
250 0 : out:
251 0 : rcu_read_unlock();
252 0 : return ret;
253 : }
254 :
255 0 : static struct sock *tcp_fastopen_create_child(struct sock *sk,
256 : struct sk_buff *skb,
257 : struct request_sock *req)
258 : {
259 0 : struct tcp_sock *tp;
260 0 : struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
261 0 : struct sock *child;
262 0 : bool own_req;
263 :
264 0 : child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL,
265 : NULL, &own_req);
266 0 : if (!child)
267 : return NULL;
268 :
269 0 : spin_lock(&queue->fastopenq.lock);
270 0 : queue->fastopenq.qlen++;
271 0 : spin_unlock(&queue->fastopenq.lock);
272 :
273 : /* Initialize the child socket. Have to fix some values to take
274 : * into account the child is a Fast Open socket and is created
275 : * only out of the bits carried in the SYN packet.
276 : */
277 0 : tp = tcp_sk(child);
278 :
279 0 : rcu_assign_pointer(tp->fastopen_rsk, req);
280 0 : tcp_rsk(req)->tfo_listener = true;
281 :
282 : /* RFC1323: The window in SYN & SYN/ACK segments is never
283 : * scaled. So correct it appropriately.
284 : */
285 0 : tp->snd_wnd = ntohs(tcp_hdr(skb)->window);
286 0 : tp->max_window = tp->snd_wnd;
287 :
288 : /* Activate the retrans timer so that SYNACK can be retransmitted.
289 : * The request socket is not added to the ehash
290 : * because it's been added to the accept queue directly.
291 : */
292 0 : inet_csk_reset_xmit_timer(child, ICSK_TIME_RETRANS,
293 : TCP_TIMEOUT_INIT, TCP_RTO_MAX);
294 :
295 0 : refcount_set(&req->rsk_refcnt, 2);
296 :
297 : /* Now finish processing the fastopen child socket. */
298 0 : tcp_init_transfer(child, BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB, skb);
299 :
300 0 : tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
301 :
302 0 : tcp_fastopen_add_skb(child, skb);
303 :
304 0 : tcp_rsk(req)->rcv_nxt = tp->rcv_nxt;
305 0 : tp->rcv_wup = tp->rcv_nxt;
306 : /* tcp_conn_request() is sending the SYNACK,
307 : * and queues the child into listener accept queue.
308 : */
309 0 : return child;
310 : }
311 :
312 0 : static bool tcp_fastopen_queue_check(struct sock *sk)
313 : {
314 0 : struct fastopen_queue *fastopenq;
315 :
316 : /* Make sure the listener has enabled fastopen, and we don't
317 : * exceed the max # of pending TFO requests allowed before trying
318 : * to validating the cookie in order to avoid burning CPU cycles
319 : * unnecessarily.
320 : *
321 : * XXX (TFO) - The implication of checking the max_qlen before
322 : * processing a cookie request is that clients can't differentiate
323 : * between qlen overflow causing Fast Open to be disabled
324 : * temporarily vs a server not supporting Fast Open at all.
325 : */
326 0 : fastopenq = &inet_csk(sk)->icsk_accept_queue.fastopenq;
327 0 : if (fastopenq->max_qlen == 0)
328 : return false;
329 :
330 0 : if (fastopenq->qlen >= fastopenq->max_qlen) {
331 0 : struct request_sock *req1;
332 0 : spin_lock(&fastopenq->lock);
333 0 : req1 = fastopenq->rskq_rst_head;
334 0 : if (!req1 || time_after(req1->rsk_timer.expires, jiffies)) {
335 0 : __NET_INC_STATS(sock_net(sk),
336 : LINUX_MIB_TCPFASTOPENLISTENOVERFLOW);
337 0 : spin_unlock(&fastopenq->lock);
338 0 : return false;
339 : }
340 0 : fastopenq->rskq_rst_head = req1->dl_next;
341 0 : fastopenq->qlen--;
342 0 : spin_unlock(&fastopenq->lock);
343 0 : reqsk_put(req1);
344 : }
345 : return true;
346 : }
347 :
348 0 : static bool tcp_fastopen_no_cookie(const struct sock *sk,
349 : const struct dst_entry *dst,
350 : int flag)
351 : {
352 0 : return (sock_net(sk)->ipv4.sysctl_tcp_fastopen & flag) ||
353 0 : tcp_sk(sk)->fastopen_no_cookie ||
354 0 : (dst && dst_metric(dst, RTAX_FASTOPEN_NO_COOKIE));
355 : }
356 :
357 : /* Returns true if we should perform Fast Open on the SYN. The cookie (foc)
358 : * may be updated and return the client in the SYN-ACK later. E.g., Fast Open
359 : * cookie request (foc->len == 0).
360 : */
361 4 : struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
362 : struct request_sock *req,
363 : struct tcp_fastopen_cookie *foc,
364 : const struct dst_entry *dst)
365 : {
366 4 : bool syn_data = TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq + 1;
367 4 : int tcp_fastopen = sock_net(sk)->ipv4.sysctl_tcp_fastopen;
368 4 : struct tcp_fastopen_cookie valid_foc = { .len = -1 };
369 4 : struct sock *child;
370 4 : int ret = 0;
371 :
372 4 : if (foc->len == 0) /* Client requests a cookie */
373 4 : NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENCOOKIEREQD);
374 :
375 4 : if (!((tcp_fastopen & TFO_SERVER_ENABLE) &&
376 0 : (syn_data || foc->len >= 0) &&
377 0 : tcp_fastopen_queue_check(sk))) {
378 4 : foc->len = -1;
379 4 : return NULL;
380 : }
381 :
382 0 : if (syn_data &&
383 0 : tcp_fastopen_no_cookie(sk, dst, TFO_SERVER_COOKIE_NOT_REQD))
384 0 : goto fastopen;
385 :
386 0 : if (foc->len == 0) {
387 : /* Client requests a cookie. */
388 0 : tcp_fastopen_cookie_gen(sk, req, skb, &valid_foc);
389 0 : } else if (foc->len > 0) {
390 0 : ret = tcp_fastopen_cookie_gen_check(sk, req, skb, foc,
391 : &valid_foc);
392 0 : if (!ret) {
393 0 : NET_INC_STATS(sock_net(sk),
394 : LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
395 : } else {
396 : /* Cookie is valid. Create a (full) child socket to
397 : * accept the data in SYN before returning a SYN-ACK to
398 : * ack the data. If we fail to create the socket, fall
399 : * back and ack the ISN only but includes the same
400 : * cookie.
401 : *
402 : * Note: Data-less SYN with valid cookie is allowed to
403 : * send data in SYN_RECV state.
404 : */
405 0 : fastopen:
406 0 : child = tcp_fastopen_create_child(sk, skb, req);
407 0 : if (child) {
408 0 : if (ret == 2) {
409 0 : valid_foc.exp = foc->exp;
410 0 : *foc = valid_foc;
411 0 : NET_INC_STATS(sock_net(sk),
412 : LINUX_MIB_TCPFASTOPENPASSIVEALTKEY);
413 : } else {
414 0 : foc->len = -1;
415 : }
416 0 : NET_INC_STATS(sock_net(sk),
417 : LINUX_MIB_TCPFASTOPENPASSIVE);
418 0 : return child;
419 : }
420 0 : NET_INC_STATS(sock_net(sk),
421 : LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
422 : }
423 : }
424 0 : valid_foc.exp = foc->exp;
425 0 : *foc = valid_foc;
426 0 : return NULL;
427 : }
428 :
429 0 : bool tcp_fastopen_cookie_check(struct sock *sk, u16 *mss,
430 : struct tcp_fastopen_cookie *cookie)
431 : {
432 0 : const struct dst_entry *dst;
433 :
434 0 : tcp_fastopen_cache_get(sk, mss, cookie);
435 :
436 : /* Firewall blackhole issue check */
437 0 : if (tcp_fastopen_active_should_disable(sk)) {
438 0 : cookie->len = -1;
439 0 : return false;
440 : }
441 :
442 0 : dst = __sk_dst_get(sk);
443 :
444 0 : if (tcp_fastopen_no_cookie(sk, dst, TFO_CLIENT_NO_COOKIE)) {
445 0 : cookie->len = -1;
446 0 : return true;
447 : }
448 0 : if (cookie->len > 0)
449 : return true;
450 0 : tcp_sk(sk)->fastopen_client_fail = TFO_COOKIE_UNAVAILABLE;
451 0 : return false;
452 : }
453 :
454 : /* This function checks if we want to defer sending SYN until the first
455 : * write(). We defer under the following conditions:
456 : * 1. fastopen_connect sockopt is set
457 : * 2. we have a valid cookie
458 : * Return value: return true if we want to defer until application writes data
459 : * return false if we want to send out SYN immediately
460 : */
461 0 : bool tcp_fastopen_defer_connect(struct sock *sk, int *err)
462 : {
463 0 : struct tcp_fastopen_cookie cookie = { .len = 0 };
464 0 : struct tcp_sock *tp = tcp_sk(sk);
465 0 : u16 mss;
466 :
467 0 : if (tp->fastopen_connect && !tp->fastopen_req) {
468 0 : if (tcp_fastopen_cookie_check(sk, &mss, &cookie)) {
469 0 : inet_sk(sk)->defer_connect = 1;
470 0 : return true;
471 : }
472 :
473 : /* Alloc fastopen_req in order for FO option to be included
474 : * in SYN
475 : */
476 0 : tp->fastopen_req = kzalloc(sizeof(*tp->fastopen_req),
477 : sk->sk_allocation);
478 0 : if (tp->fastopen_req)
479 0 : tp->fastopen_req->cookie = cookie;
480 : else
481 0 : *err = -ENOBUFS;
482 : }
483 : return false;
484 : }
485 : EXPORT_SYMBOL(tcp_fastopen_defer_connect);
486 :
487 : /*
488 : * The following code block is to deal with middle box issues with TFO:
489 : * Middlebox firewall issues can potentially cause server's data being
490 : * blackholed after a successful 3WHS using TFO.
491 : * The proposed solution is to disable active TFO globally under the
492 : * following circumstances:
493 : * 1. client side TFO socket receives out of order FIN
494 : * 2. client side TFO socket receives out of order RST
495 : * 3. client side TFO socket has timed out three times consecutively during
496 : * or after handshake
497 : * We disable active side TFO globally for 1hr at first. Then if it
498 : * happens again, we disable it for 2h, then 4h, 8h, ...
499 : * And we reset the timeout back to 1hr when we see a successful active
500 : * TFO connection with data exchanges.
501 : */
502 :
503 : /* Disable active TFO and record current jiffies and
504 : * tfo_active_disable_times
505 : */
506 0 : void tcp_fastopen_active_disable(struct sock *sk)
507 : {
508 0 : struct net *net = sock_net(sk);
509 :
510 0 : atomic_inc(&net->ipv4.tfo_active_disable_times);
511 0 : net->ipv4.tfo_active_disable_stamp = jiffies;
512 0 : NET_INC_STATS(net, LINUX_MIB_TCPFASTOPENBLACKHOLE);
513 0 : }
514 :
515 : /* Calculate timeout for tfo active disable
516 : * Return true if we are still in the active TFO disable period
517 : * Return false if timeout already expired and we should use active TFO
518 : */
519 0 : bool tcp_fastopen_active_should_disable(struct sock *sk)
520 : {
521 0 : unsigned int tfo_bh_timeout = sock_net(sk)->ipv4.sysctl_tcp_fastopen_blackhole_timeout;
522 0 : int tfo_da_times = atomic_read(&sock_net(sk)->ipv4.tfo_active_disable_times);
523 0 : unsigned long timeout;
524 0 : int multiplier;
525 :
526 0 : if (!tfo_da_times)
527 : return false;
528 :
529 : /* Limit timout to max: 2^6 * initial timeout */
530 0 : multiplier = 1 << min(tfo_da_times - 1, 6);
531 0 : timeout = multiplier * tfo_bh_timeout * HZ;
532 0 : if (time_before(jiffies, sock_net(sk)->ipv4.tfo_active_disable_stamp + timeout))
533 : return true;
534 :
535 : /* Mark check bit so we can check for successful active TFO
536 : * condition and reset tfo_active_disable_times
537 : */
538 0 : tcp_sk(sk)->syn_fastopen_ch = 1;
539 0 : return false;
540 : }
541 :
542 : /* Disable active TFO if FIN is the only packet in the ofo queue
543 : * and no data is received.
544 : * Also check if we can reset tfo_active_disable_times if data is
545 : * received successfully on a marked active TFO sockets opened on
546 : * a non-loopback interface
547 : */
548 4 : void tcp_fastopen_active_disable_ofo_check(struct sock *sk)
549 : {
550 4 : struct tcp_sock *tp = tcp_sk(sk);
551 4 : struct dst_entry *dst;
552 4 : struct sk_buff *skb;
553 :
554 4 : if (!tp->syn_fastopen)
555 : return;
556 :
557 0 : if (!tp->data_segs_in) {
558 0 : skb = skb_rb_first(&tp->out_of_order_queue);
559 0 : if (skb && !skb_rb_next(skb)) {
560 0 : if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) {
561 0 : tcp_fastopen_active_disable(sk);
562 0 : return;
563 : }
564 : }
565 0 : } else if (tp->syn_fastopen_ch &&
566 0 : atomic_read(&sock_net(sk)->ipv4.tfo_active_disable_times)) {
567 0 : dst = sk_dst_get(sk);
568 0 : if (!(dst && dst->dev && (dst->dev->flags & IFF_LOOPBACK)))
569 0 : atomic_set(&sock_net(sk)->ipv4.tfo_active_disable_times, 0);
570 0 : dst_release(dst);
571 : }
572 : }
573 :
574 0 : void tcp_fastopen_active_detect_blackhole(struct sock *sk, bool expired)
575 : {
576 0 : u32 timeouts = inet_csk(sk)->icsk_retransmits;
577 0 : struct tcp_sock *tp = tcp_sk(sk);
578 :
579 : /* Broken middle-boxes may black-hole Fast Open connection during or
580 : * even after the handshake. Be extremely conservative and pause
581 : * Fast Open globally after hitting the third consecutive timeout or
582 : * exceeding the configured timeout limit.
583 : */
584 0 : if ((tp->syn_fastopen || tp->syn_data || tp->syn_data_acked) &&
585 0 : (timeouts == 2 || (timeouts < 2 && expired))) {
586 0 : tcp_fastopen_active_disable(sk);
587 0 : NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVEFAIL);
588 : }
589 0 : }
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