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1// SPDX-License-Identifier: GPL-2.0
2#include <linux/kernel.h>
3#include <linux/tcp.h>
4#include <linux/rcupdate.h>
5#include <net/tcp.h>
6
7void tcp_fastopen_init_key_once(struct net *net)
8{
9 u8 key[TCP_FASTOPEN_KEY_LENGTH];
10 struct tcp_fastopen_context *ctxt;
11
12 rcu_read_lock();
13 ctxt = rcu_dereference(net->ipv4.tcp_fastopen_ctx);
14 if (ctxt) {
15 rcu_read_unlock();
16 return;
17 }
18 rcu_read_unlock();
19
20 /* tcp_fastopen_reset_cipher publishes the new context
21 * atomically, so we allow this race happening here.
22 *
23 * All call sites of tcp_fastopen_cookie_gen also check
24 * for a valid cookie, so this is an acceptable risk.
25 */
26 get_random_bytes(key, sizeof(key));
27 tcp_fastopen_reset_cipher(net, NULL, key, NULL);
28}
29
30static void tcp_fastopen_ctx_free(struct rcu_head *head)
31{
32 struct tcp_fastopen_context *ctx =
33 container_of(head, struct tcp_fastopen_context, rcu);
34
35 kfree_sensitive(ctx);
36}
37
38void tcp_fastopen_destroy_cipher(struct sock *sk)
39{
40 struct tcp_fastopen_context *ctx;
41
42 ctx = rcu_dereference_protected(
43 inet_csk(sk)->icsk_accept_queue.fastopenq.ctx, 1);
44 if (ctx)
45 call_rcu(&ctx->rcu, tcp_fastopen_ctx_free);
46}
47
48void tcp_fastopen_ctx_destroy(struct net *net)
49{
50 struct tcp_fastopen_context *ctxt;
51
52 ctxt = unrcu_pointer(xchg(&net->ipv4.tcp_fastopen_ctx, NULL));
53
54 if (ctxt)
55 call_rcu(&ctxt->rcu, tcp_fastopen_ctx_free);
56}
57
58int tcp_fastopen_reset_cipher(struct net *net, struct sock *sk,
59 void *primary_key, void *backup_key)
60{
61 struct tcp_fastopen_context *ctx, *octx;
62 struct fastopen_queue *q;
63 int err = 0;
64
65 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
66 if (!ctx) {
67 err = -ENOMEM;
68 goto out;
69 }
70
71 ctx->key[0].key[0] = get_unaligned_le64(primary_key);
72 ctx->key[0].key[1] = get_unaligned_le64(primary_key + 8);
73 if (backup_key) {
74 ctx->key[1].key[0] = get_unaligned_le64(backup_key);
75 ctx->key[1].key[1] = get_unaligned_le64(backup_key + 8);
76 ctx->num = 2;
77 } else {
78 ctx->num = 1;
79 }
80
81 if (sk) {
82 q = &inet_csk(sk)->icsk_accept_queue.fastopenq;
83 octx = unrcu_pointer(xchg(&q->ctx, RCU_INITIALIZER(ctx)));
84 } else {
85 octx = unrcu_pointer(xchg(&net->ipv4.tcp_fastopen_ctx,
86 RCU_INITIALIZER(ctx)));
87 }
88
89 if (octx)
90 call_rcu(&octx->rcu, tcp_fastopen_ctx_free);
91out:
92 return err;
93}
94
95int tcp_fastopen_get_cipher(struct net *net, struct inet_connection_sock *icsk,
96 u64 *key)
97{
98 struct tcp_fastopen_context *ctx;
99 int n_keys = 0, i;
100
101 rcu_read_lock();
102 if (icsk)
103 ctx = rcu_dereference(icsk->icsk_accept_queue.fastopenq.ctx);
104 else
105 ctx = rcu_dereference(net->ipv4.tcp_fastopen_ctx);
106 if (ctx) {
107 n_keys = tcp_fastopen_context_len(ctx);
108 for (i = 0; i < n_keys; i++) {
109 put_unaligned_le64(ctx->key[i].key[0], key + (i * 2));
110 put_unaligned_le64(ctx->key[i].key[1], key + (i * 2) + 1);
111 }
112 }
113 rcu_read_unlock();
114
115 return n_keys;
116}
117
118static bool __tcp_fastopen_cookie_gen_cipher(struct request_sock *req,
119 struct sk_buff *syn,
120 const siphash_key_t *key,
121 struct tcp_fastopen_cookie *foc)
122{
123 BUILD_BUG_ON(TCP_FASTOPEN_COOKIE_SIZE != sizeof(u64));
124
125 if (req->rsk_ops->family == AF_INET) {
126 const struct iphdr *iph = ip_hdr(syn);
127
128 foc->val[0] = cpu_to_le64(siphash(&iph->saddr,
129 sizeof(iph->saddr) +
130 sizeof(iph->daddr),
131 key));
132 foc->len = TCP_FASTOPEN_COOKIE_SIZE;
133 return true;
134 }
135#if IS_ENABLED(CONFIG_IPV6)
136 if (req->rsk_ops->family == AF_INET6) {
137 const struct ipv6hdr *ip6h = ipv6_hdr(syn);
138
139 foc->val[0] = cpu_to_le64(siphash(&ip6h->saddr,
140 sizeof(ip6h->saddr) +
141 sizeof(ip6h->daddr),
142 key));
143 foc->len = TCP_FASTOPEN_COOKIE_SIZE;
144 return true;
145 }
146#endif
147 return false;
148}
149
150/* Generate the fastopen cookie by applying SipHash to both the source and
151 * destination addresses.
152 */
153static void tcp_fastopen_cookie_gen(struct sock *sk,
154 struct request_sock *req,
155 struct sk_buff *syn,
156 struct tcp_fastopen_cookie *foc)
157{
158 struct tcp_fastopen_context *ctx;
159
160 rcu_read_lock();
161 ctx = tcp_fastopen_get_ctx(sk);
162 if (ctx)
163 __tcp_fastopen_cookie_gen_cipher(req, syn, &ctx->key[0], foc);
164 rcu_read_unlock();
165}
166
167/* If an incoming SYN or SYNACK frame contains a payload and/or FIN,
168 * queue this additional data / FIN.
169 */
170void tcp_fastopen_add_skb(struct sock *sk, struct sk_buff *skb)
171{
172 struct tcp_sock *tp = tcp_sk(sk);
173
174 if (TCP_SKB_CB(skb)->end_seq == tp->rcv_nxt)
175 return;
176
177 skb = skb_clone(skb, GFP_ATOMIC);
178 if (!skb)
179 return;
180
181 tcp_cleanup_skb(skb);
182 /* segs_in has been initialized to 1 in tcp_create_openreq_child().
183 * Hence, reset segs_in to 0 before calling tcp_segs_in()
184 * to avoid double counting. Also, tcp_segs_in() expects
185 * skb->len to include the tcp_hdrlen. Hence, it should
186 * be called before __skb_pull().
187 */
188 tp->segs_in = 0;
189 tcp_segs_in(tp, skb);
190 __skb_pull(skb, tcp_hdrlen(skb));
191 sk_forced_mem_schedule(sk, skb->truesize);
192 skb_set_owner_r(skb, sk);
193
194 TCP_SKB_CB(skb)->seq++;
195 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_SYN;
196
197 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
198 tcp_add_receive_queue(sk, skb);
199 tp->syn_data_acked = 1;
200
201 /* u64_stats_update_begin(&tp->syncp) not needed here,
202 * as we certainly are not changing upper 32bit value (0)
203 */
204 tp->bytes_received = skb->len;
205
206 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
207 tcp_fin(sk);
208}
209
210/* returns 0 - no key match, 1 for primary, 2 for backup */
211static int tcp_fastopen_cookie_gen_check(struct sock *sk,
212 struct request_sock *req,
213 struct sk_buff *syn,
214 struct tcp_fastopen_cookie *orig,
215 struct tcp_fastopen_cookie *valid_foc)
216{
217 struct tcp_fastopen_cookie search_foc = { .len = -1 };
218 struct tcp_fastopen_cookie *foc = valid_foc;
219 struct tcp_fastopen_context *ctx;
220 int i, ret = 0;
221
222 rcu_read_lock();
223 ctx = tcp_fastopen_get_ctx(sk);
224 if (!ctx)
225 goto out;
226 for (i = 0; i < tcp_fastopen_context_len(ctx); i++) {
227 __tcp_fastopen_cookie_gen_cipher(req, syn, &ctx->key[i], foc);
228 if (tcp_fastopen_cookie_match(foc, orig)) {
229 ret = i + 1;
230 goto out;
231 }
232 foc = &search_foc;
233 }
234out:
235 rcu_read_unlock();
236 return ret;
237}
238
239static struct sock *tcp_fastopen_create_child(struct sock *sk,
240 struct sk_buff *skb,
241 struct request_sock *req)
242{
243 struct tcp_sock *tp;
244 struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
245 struct sock *child;
246 bool own_req;
247
248 child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL,
249 NULL, &own_req);
250 if (!child)
251 return NULL;
252
253 spin_lock(&queue->fastopenq.lock);
254 queue->fastopenq.qlen++;
255 spin_unlock(&queue->fastopenq.lock);
256
257 /* Initialize the child socket. Have to fix some values to take
258 * into account the child is a Fast Open socket and is created
259 * only out of the bits carried in the SYN packet.
260 */
261 tp = tcp_sk(child);
262
263 rcu_assign_pointer(tp->fastopen_rsk, req);
264 tcp_rsk(req)->tfo_listener = true;
265
266 /* RFC1323: The window in SYN & SYN/ACK segments is never
267 * scaled. So correct it appropriately.
268 */
269 tp->snd_wnd = ntohs(tcp_hdr(skb)->window);
270 tp->max_window = tp->snd_wnd;
271
272 /* Activate the retrans timer so that SYNACK can be retransmitted.
273 * The request socket is not added to the ehash
274 * because it's been added to the accept queue directly.
275 */
276 req->timeout = tcp_timeout_init(child);
277 inet_csk_reset_xmit_timer(child, ICSK_TIME_RETRANS,
278 req->timeout, TCP_RTO_MAX);
279
280 refcount_set(&req->rsk_refcnt, 2);
281
282 /* Now finish processing the fastopen child socket. */
283 tcp_init_transfer(child, BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB, skb);
284
285 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
286
287 tcp_fastopen_add_skb(child, skb);
288
289 tcp_rsk(req)->rcv_nxt = tp->rcv_nxt;
290 tp->rcv_wup = tp->rcv_nxt;
291 /* tcp_conn_request() is sending the SYNACK,
292 * and queues the child into listener accept queue.
293 */
294 return child;
295}
296
297static bool tcp_fastopen_queue_check(struct sock *sk)
298{
299 struct fastopen_queue *fastopenq;
300 int max_qlen;
301
302 /* Make sure the listener has enabled fastopen, and we don't
303 * exceed the max # of pending TFO requests allowed before trying
304 * to validating the cookie in order to avoid burning CPU cycles
305 * unnecessarily.
306 *
307 * XXX (TFO) - The implication of checking the max_qlen before
308 * processing a cookie request is that clients can't differentiate
309 * between qlen overflow causing Fast Open to be disabled
310 * temporarily vs a server not supporting Fast Open at all.
311 */
312 fastopenq = &inet_csk(sk)->icsk_accept_queue.fastopenq;
313 max_qlen = READ_ONCE(fastopenq->max_qlen);
314 if (max_qlen == 0)
315 return false;
316
317 if (fastopenq->qlen >= max_qlen) {
318 struct request_sock *req1;
319 spin_lock(&fastopenq->lock);
320 req1 = fastopenq->rskq_rst_head;
321 if (!req1 || time_after(req1->rsk_timer.expires, jiffies)) {
322 __NET_INC_STATS(sock_net(sk),
323 LINUX_MIB_TCPFASTOPENLISTENOVERFLOW);
324 spin_unlock(&fastopenq->lock);
325 return false;
326 }
327 fastopenq->rskq_rst_head = req1->dl_next;
328 fastopenq->qlen--;
329 spin_unlock(&fastopenq->lock);
330 reqsk_put(req1);
331 }
332 return true;
333}
334
335static bool tcp_fastopen_no_cookie(const struct sock *sk,
336 const struct dst_entry *dst,
337 int flag)
338{
339 return (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fastopen) & flag) ||
340 tcp_sk(sk)->fastopen_no_cookie ||
341 (dst && dst_metric(dst, RTAX_FASTOPEN_NO_COOKIE));
342}
343
344/* Returns true if we should perform Fast Open on the SYN. The cookie (foc)
345 * may be updated and return the client in the SYN-ACK later. E.g., Fast Open
346 * cookie request (foc->len == 0).
347 */
348struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
349 struct request_sock *req,
350 struct tcp_fastopen_cookie *foc,
351 const struct dst_entry *dst)
352{
353 bool syn_data = TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq + 1;
354 int tcp_fastopen = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fastopen);
355 struct tcp_fastopen_cookie valid_foc = { .len = -1 };
356 struct sock *child;
357 int ret = 0;
358
359 if (foc->len == 0) /* Client requests a cookie */
360 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENCOOKIEREQD);
361
362 if (!((tcp_fastopen & TFO_SERVER_ENABLE) &&
363 (syn_data || foc->len >= 0) &&
364 tcp_fastopen_queue_check(sk))) {
365 foc->len = -1;
366 return NULL;
367 }
368
369 if (tcp_fastopen_no_cookie(sk, dst, TFO_SERVER_COOKIE_NOT_REQD))
370 goto fastopen;
371
372 if (foc->len == 0) {
373 /* Client requests a cookie. */
374 tcp_fastopen_cookie_gen(sk, req, skb, &valid_foc);
375 } else if (foc->len > 0) {
376 ret = tcp_fastopen_cookie_gen_check(sk, req, skb, foc,
377 &valid_foc);
378 if (!ret) {
379 NET_INC_STATS(sock_net(sk),
380 LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
381 } else {
382 /* Cookie is valid. Create a (full) child socket to
383 * accept the data in SYN before returning a SYN-ACK to
384 * ack the data. If we fail to create the socket, fall
385 * back and ack the ISN only but includes the same
386 * cookie.
387 *
388 * Note: Data-less SYN with valid cookie is allowed to
389 * send data in SYN_RECV state.
390 */
391fastopen:
392 child = tcp_fastopen_create_child(sk, skb, req);
393 if (child) {
394 if (ret == 2) {
395 valid_foc.exp = foc->exp;
396 *foc = valid_foc;
397 NET_INC_STATS(sock_net(sk),
398 LINUX_MIB_TCPFASTOPENPASSIVEALTKEY);
399 } else {
400 foc->len = -1;
401 }
402 NET_INC_STATS(sock_net(sk),
403 LINUX_MIB_TCPFASTOPENPASSIVE);
404 return child;
405 }
406 NET_INC_STATS(sock_net(sk),
407 LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
408 }
409 }
410 valid_foc.exp = foc->exp;
411 *foc = valid_foc;
412 return NULL;
413}
414
415bool tcp_fastopen_cookie_check(struct sock *sk, u16 *mss,
416 struct tcp_fastopen_cookie *cookie)
417{
418 const struct dst_entry *dst;
419
420 tcp_fastopen_cache_get(sk, mss, cookie);
421
422 /* Firewall blackhole issue check */
423 if (tcp_fastopen_active_should_disable(sk)) {
424 cookie->len = -1;
425 return false;
426 }
427
428 dst = __sk_dst_get(sk);
429
430 if (tcp_fastopen_no_cookie(sk, dst, TFO_CLIENT_NO_COOKIE)) {
431 cookie->len = -1;
432 return true;
433 }
434 if (cookie->len > 0)
435 return true;
436 tcp_sk(sk)->fastopen_client_fail = TFO_COOKIE_UNAVAILABLE;
437 return false;
438}
439
440/* This function checks if we want to defer sending SYN until the first
441 * write(). We defer under the following conditions:
442 * 1. fastopen_connect sockopt is set
443 * 2. we have a valid cookie
444 * Return value: return true if we want to defer until application writes data
445 * return false if we want to send out SYN immediately
446 */
447bool tcp_fastopen_defer_connect(struct sock *sk, int *err)
448{
449 struct tcp_fastopen_cookie cookie = { .len = 0 };
450 struct tcp_sock *tp = tcp_sk(sk);
451 u16 mss;
452
453 if (tp->fastopen_connect && !tp->fastopen_req) {
454 if (tcp_fastopen_cookie_check(sk, &mss, &cookie)) {
455 inet_set_bit(DEFER_CONNECT, sk);
456 return true;
457 }
458
459 /* Alloc fastopen_req in order for FO option to be included
460 * in SYN
461 */
462 tp->fastopen_req = kzalloc(sizeof(*tp->fastopen_req),
463 sk->sk_allocation);
464 if (tp->fastopen_req)
465 tp->fastopen_req->cookie = cookie;
466 else
467 *err = -ENOBUFS;
468 }
469 return false;
470}
471EXPORT_SYMBOL(tcp_fastopen_defer_connect);
472
473/*
474 * The following code block is to deal with middle box issues with TFO:
475 * Middlebox firewall issues can potentially cause server's data being
476 * blackholed after a successful 3WHS using TFO.
477 * The proposed solution is to disable active TFO globally under the
478 * following circumstances:
479 * 1. client side TFO socket receives out of order FIN
480 * 2. client side TFO socket receives out of order RST
481 * 3. client side TFO socket has timed out three times consecutively during
482 * or after handshake
483 * We disable active side TFO globally for 1hr at first. Then if it
484 * happens again, we disable it for 2h, then 4h, 8h, ...
485 * And we reset the timeout back to 1hr when we see a successful active
486 * TFO connection with data exchanges.
487 */
488
489/* Disable active TFO and record current jiffies and
490 * tfo_active_disable_times
491 */
492void tcp_fastopen_active_disable(struct sock *sk)
493{
494 struct net *net = sock_net(sk);
495
496 if (!READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fastopen_blackhole_timeout))
497 return;
498
499 /* Paired with READ_ONCE() in tcp_fastopen_active_should_disable() */
500 WRITE_ONCE(net->ipv4.tfo_active_disable_stamp, jiffies);
501
502 /* Paired with smp_rmb() in tcp_fastopen_active_should_disable().
503 * We want net->ipv4.tfo_active_disable_stamp to be updated first.
504 */
505 smp_mb__before_atomic();
506 atomic_inc(&net->ipv4.tfo_active_disable_times);
507
508 NET_INC_STATS(net, LINUX_MIB_TCPFASTOPENBLACKHOLE);
509}
510
511/* Calculate timeout for tfo active disable
512 * Return true if we are still in the active TFO disable period
513 * Return false if timeout already expired and we should use active TFO
514 */
515bool tcp_fastopen_active_should_disable(struct sock *sk)
516{
517 unsigned int tfo_bh_timeout =
518 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fastopen_blackhole_timeout);
519 unsigned long timeout;
520 int tfo_da_times;
521 int multiplier;
522
523 if (!tfo_bh_timeout)
524 return false;
525
526 tfo_da_times = atomic_read(&sock_net(sk)->ipv4.tfo_active_disable_times);
527 if (!tfo_da_times)
528 return false;
529
530 /* Paired with smp_mb__before_atomic() in tcp_fastopen_active_disable() */
531 smp_rmb();
532
533 /* Limit timeout to max: 2^6 * initial timeout */
534 multiplier = 1 << min(tfo_da_times - 1, 6);
535
536 /* Paired with the WRITE_ONCE() in tcp_fastopen_active_disable(). */
537 timeout = READ_ONCE(sock_net(sk)->ipv4.tfo_active_disable_stamp) +
538 multiplier * tfo_bh_timeout * HZ;
539 if (time_before(jiffies, timeout))
540 return true;
541
542 /* Mark check bit so we can check for successful active TFO
543 * condition and reset tfo_active_disable_times
544 */
545 tcp_sk(sk)->syn_fastopen_ch = 1;
546 return false;
547}
548
549/* Disable active TFO if FIN is the only packet in the ofo queue
550 * and no data is received.
551 * Also check if we can reset tfo_active_disable_times if data is
552 * received successfully on a marked active TFO sockets opened on
553 * a non-loopback interface
554 */
555void tcp_fastopen_active_disable_ofo_check(struct sock *sk)
556{
557 struct tcp_sock *tp = tcp_sk(sk);
558 struct dst_entry *dst;
559 struct sk_buff *skb;
560
561 if (!tp->syn_fastopen)
562 return;
563
564 if (!tp->data_segs_in) {
565 skb = skb_rb_first(&tp->out_of_order_queue);
566 if (skb && !skb_rb_next(skb)) {
567 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) {
568 tcp_fastopen_active_disable(sk);
569 return;
570 }
571 }
572 } else if (tp->syn_fastopen_ch &&
573 atomic_read(&sock_net(sk)->ipv4.tfo_active_disable_times)) {
574 dst = sk_dst_get(sk);
575 if (!(dst && dst->dev && (dst->dev->flags & IFF_LOOPBACK)))
576 atomic_set(&sock_net(sk)->ipv4.tfo_active_disable_times, 0);
577 dst_release(dst);
578 }
579}
580
581void tcp_fastopen_active_detect_blackhole(struct sock *sk, bool expired)
582{
583 u32 timeouts = inet_csk(sk)->icsk_retransmits;
584 struct tcp_sock *tp = tcp_sk(sk);
585
586 /* Broken middle-boxes may black-hole Fast Open connection during or
587 * even after the handshake. Be extremely conservative and pause
588 * Fast Open globally after hitting the third consecutive timeout or
589 * exceeding the configured timeout limit.
590 */
591 if ((tp->syn_fastopen || tp->syn_data || tp->syn_data_acked) &&
592 (timeouts == 2 || (timeouts < 2 && expired))) {
593 tcp_fastopen_active_disable(sk);
594 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVEFAIL);
595 }
596}
1// SPDX-License-Identifier: GPL-2.0
2#include <linux/kernel.h>
3#include <linux/tcp.h>
4#include <linux/rcupdate.h>
5#include <net/tcp.h>
6
7void tcp_fastopen_init_key_once(struct net *net)
8{
9 u8 key[TCP_FASTOPEN_KEY_LENGTH];
10 struct tcp_fastopen_context *ctxt;
11
12 rcu_read_lock();
13 ctxt = rcu_dereference(net->ipv4.tcp_fastopen_ctx);
14 if (ctxt) {
15 rcu_read_unlock();
16 return;
17 }
18 rcu_read_unlock();
19
20 /* tcp_fastopen_reset_cipher publishes the new context
21 * atomically, so we allow this race happening here.
22 *
23 * All call sites of tcp_fastopen_cookie_gen also check
24 * for a valid cookie, so this is an acceptable risk.
25 */
26 get_random_bytes(key, sizeof(key));
27 tcp_fastopen_reset_cipher(net, NULL, key, NULL);
28}
29
30static void tcp_fastopen_ctx_free(struct rcu_head *head)
31{
32 struct tcp_fastopen_context *ctx =
33 container_of(head, struct tcp_fastopen_context, rcu);
34
35 kfree_sensitive(ctx);
36}
37
38void tcp_fastopen_destroy_cipher(struct sock *sk)
39{
40 struct tcp_fastopen_context *ctx;
41
42 ctx = rcu_dereference_protected(
43 inet_csk(sk)->icsk_accept_queue.fastopenq.ctx, 1);
44 if (ctx)
45 call_rcu(&ctx->rcu, tcp_fastopen_ctx_free);
46}
47
48void tcp_fastopen_ctx_destroy(struct net *net)
49{
50 struct tcp_fastopen_context *ctxt;
51
52 ctxt = xchg((__force struct tcp_fastopen_context **)&net->ipv4.tcp_fastopen_ctx, NULL);
53
54 if (ctxt)
55 call_rcu(&ctxt->rcu, tcp_fastopen_ctx_free);
56}
57
58int tcp_fastopen_reset_cipher(struct net *net, struct sock *sk,
59 void *primary_key, void *backup_key)
60{
61 struct tcp_fastopen_context *ctx, *octx;
62 struct fastopen_queue *q;
63 int err = 0;
64
65 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
66 if (!ctx) {
67 err = -ENOMEM;
68 goto out;
69 }
70
71 ctx->key[0].key[0] = get_unaligned_le64(primary_key);
72 ctx->key[0].key[1] = get_unaligned_le64(primary_key + 8);
73 if (backup_key) {
74 ctx->key[1].key[0] = get_unaligned_le64(backup_key);
75 ctx->key[1].key[1] = get_unaligned_le64(backup_key + 8);
76 ctx->num = 2;
77 } else {
78 ctx->num = 1;
79 }
80
81 if (sk) {
82 q = &inet_csk(sk)->icsk_accept_queue.fastopenq;
83 octx = xchg((__force struct tcp_fastopen_context **)&q->ctx, ctx);
84 } else {
85 octx = xchg((__force struct tcp_fastopen_context **)&net->ipv4.tcp_fastopen_ctx, ctx);
86 }
87
88 if (octx)
89 call_rcu(&octx->rcu, tcp_fastopen_ctx_free);
90out:
91 return err;
92}
93
94int tcp_fastopen_get_cipher(struct net *net, struct inet_connection_sock *icsk,
95 u64 *key)
96{
97 struct tcp_fastopen_context *ctx;
98 int n_keys = 0, i;
99
100 rcu_read_lock();
101 if (icsk)
102 ctx = rcu_dereference(icsk->icsk_accept_queue.fastopenq.ctx);
103 else
104 ctx = rcu_dereference(net->ipv4.tcp_fastopen_ctx);
105 if (ctx) {
106 n_keys = tcp_fastopen_context_len(ctx);
107 for (i = 0; i < n_keys; i++) {
108 put_unaligned_le64(ctx->key[i].key[0], key + (i * 2));
109 put_unaligned_le64(ctx->key[i].key[1], key + (i * 2) + 1);
110 }
111 }
112 rcu_read_unlock();
113
114 return n_keys;
115}
116
117static bool __tcp_fastopen_cookie_gen_cipher(struct request_sock *req,
118 struct sk_buff *syn,
119 const siphash_key_t *key,
120 struct tcp_fastopen_cookie *foc)
121{
122 BUILD_BUG_ON(TCP_FASTOPEN_COOKIE_SIZE != sizeof(u64));
123
124 if (req->rsk_ops->family == AF_INET) {
125 const struct iphdr *iph = ip_hdr(syn);
126
127 foc->val[0] = cpu_to_le64(siphash(&iph->saddr,
128 sizeof(iph->saddr) +
129 sizeof(iph->daddr),
130 key));
131 foc->len = TCP_FASTOPEN_COOKIE_SIZE;
132 return true;
133 }
134#if IS_ENABLED(CONFIG_IPV6)
135 if (req->rsk_ops->family == AF_INET6) {
136 const struct ipv6hdr *ip6h = ipv6_hdr(syn);
137
138 foc->val[0] = cpu_to_le64(siphash(&ip6h->saddr,
139 sizeof(ip6h->saddr) +
140 sizeof(ip6h->daddr),
141 key));
142 foc->len = TCP_FASTOPEN_COOKIE_SIZE;
143 return true;
144 }
145#endif
146 return false;
147}
148
149/* Generate the fastopen cookie by applying SipHash to both the source and
150 * destination addresses.
151 */
152static void tcp_fastopen_cookie_gen(struct sock *sk,
153 struct request_sock *req,
154 struct sk_buff *syn,
155 struct tcp_fastopen_cookie *foc)
156{
157 struct tcp_fastopen_context *ctx;
158
159 rcu_read_lock();
160 ctx = tcp_fastopen_get_ctx(sk);
161 if (ctx)
162 __tcp_fastopen_cookie_gen_cipher(req, syn, &ctx->key[0], foc);
163 rcu_read_unlock();
164}
165
166/* If an incoming SYN or SYNACK frame contains a payload and/or FIN,
167 * queue this additional data / FIN.
168 */
169void tcp_fastopen_add_skb(struct sock *sk, struct sk_buff *skb)
170{
171 struct tcp_sock *tp = tcp_sk(sk);
172
173 if (TCP_SKB_CB(skb)->end_seq == tp->rcv_nxt)
174 return;
175
176 skb = skb_clone(skb, GFP_ATOMIC);
177 if (!skb)
178 return;
179
180 skb_dst_drop(skb);
181 /* segs_in has been initialized to 1 in tcp_create_openreq_child().
182 * Hence, reset segs_in to 0 before calling tcp_segs_in()
183 * to avoid double counting. Also, tcp_segs_in() expects
184 * skb->len to include the tcp_hdrlen. Hence, it should
185 * be called before __skb_pull().
186 */
187 tp->segs_in = 0;
188 tcp_segs_in(tp, skb);
189 __skb_pull(skb, tcp_hdrlen(skb));
190 sk_forced_mem_schedule(sk, skb->truesize);
191 skb_set_owner_r(skb, sk);
192
193 TCP_SKB_CB(skb)->seq++;
194 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_SYN;
195
196 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
197 __skb_queue_tail(&sk->sk_receive_queue, skb);
198 tp->syn_data_acked = 1;
199
200 /* u64_stats_update_begin(&tp->syncp) not needed here,
201 * as we certainly are not changing upper 32bit value (0)
202 */
203 tp->bytes_received = skb->len;
204
205 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
206 tcp_fin(sk);
207}
208
209/* returns 0 - no key match, 1 for primary, 2 for backup */
210static int tcp_fastopen_cookie_gen_check(struct sock *sk,
211 struct request_sock *req,
212 struct sk_buff *syn,
213 struct tcp_fastopen_cookie *orig,
214 struct tcp_fastopen_cookie *valid_foc)
215{
216 struct tcp_fastopen_cookie search_foc = { .len = -1 };
217 struct tcp_fastopen_cookie *foc = valid_foc;
218 struct tcp_fastopen_context *ctx;
219 int i, ret = 0;
220
221 rcu_read_lock();
222 ctx = tcp_fastopen_get_ctx(sk);
223 if (!ctx)
224 goto out;
225 for (i = 0; i < tcp_fastopen_context_len(ctx); i++) {
226 __tcp_fastopen_cookie_gen_cipher(req, syn, &ctx->key[i], foc);
227 if (tcp_fastopen_cookie_match(foc, orig)) {
228 ret = i + 1;
229 goto out;
230 }
231 foc = &search_foc;
232 }
233out:
234 rcu_read_unlock();
235 return ret;
236}
237
238static struct sock *tcp_fastopen_create_child(struct sock *sk,
239 struct sk_buff *skb,
240 struct request_sock *req)
241{
242 struct tcp_sock *tp;
243 struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
244 struct sock *child;
245 bool own_req;
246
247 child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL,
248 NULL, &own_req);
249 if (!child)
250 return NULL;
251
252 spin_lock(&queue->fastopenq.lock);
253 queue->fastopenq.qlen++;
254 spin_unlock(&queue->fastopenq.lock);
255
256 /* Initialize the child socket. Have to fix some values to take
257 * into account the child is a Fast Open socket and is created
258 * only out of the bits carried in the SYN packet.
259 */
260 tp = tcp_sk(child);
261
262 rcu_assign_pointer(tp->fastopen_rsk, req);
263 tcp_rsk(req)->tfo_listener = true;
264
265 /* RFC1323: The window in SYN & SYN/ACK segments is never
266 * scaled. So correct it appropriately.
267 */
268 tp->snd_wnd = ntohs(tcp_hdr(skb)->window);
269 tp->max_window = tp->snd_wnd;
270
271 /* Activate the retrans timer so that SYNACK can be retransmitted.
272 * The request socket is not added to the ehash
273 * because it's been added to the accept queue directly.
274 */
275 req->timeout = tcp_timeout_init(child);
276 inet_csk_reset_xmit_timer(child, ICSK_TIME_RETRANS,
277 req->timeout, TCP_RTO_MAX);
278
279 refcount_set(&req->rsk_refcnt, 2);
280
281 /* Now finish processing the fastopen child socket. */
282 tcp_init_transfer(child, BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB, skb);
283
284 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
285
286 tcp_fastopen_add_skb(child, skb);
287
288 tcp_rsk(req)->rcv_nxt = tp->rcv_nxt;
289 tp->rcv_wup = tp->rcv_nxt;
290 /* tcp_conn_request() is sending the SYNACK,
291 * and queues the child into listener accept queue.
292 */
293 return child;
294}
295
296static bool tcp_fastopen_queue_check(struct sock *sk)
297{
298 struct fastopen_queue *fastopenq;
299 int max_qlen;
300
301 /* Make sure the listener has enabled fastopen, and we don't
302 * exceed the max # of pending TFO requests allowed before trying
303 * to validating the cookie in order to avoid burning CPU cycles
304 * unnecessarily.
305 *
306 * XXX (TFO) - The implication of checking the max_qlen before
307 * processing a cookie request is that clients can't differentiate
308 * between qlen overflow causing Fast Open to be disabled
309 * temporarily vs a server not supporting Fast Open at all.
310 */
311 fastopenq = &inet_csk(sk)->icsk_accept_queue.fastopenq;
312 max_qlen = READ_ONCE(fastopenq->max_qlen);
313 if (max_qlen == 0)
314 return false;
315
316 if (fastopenq->qlen >= max_qlen) {
317 struct request_sock *req1;
318 spin_lock(&fastopenq->lock);
319 req1 = fastopenq->rskq_rst_head;
320 if (!req1 || time_after(req1->rsk_timer.expires, jiffies)) {
321 __NET_INC_STATS(sock_net(sk),
322 LINUX_MIB_TCPFASTOPENLISTENOVERFLOW);
323 spin_unlock(&fastopenq->lock);
324 return false;
325 }
326 fastopenq->rskq_rst_head = req1->dl_next;
327 fastopenq->qlen--;
328 spin_unlock(&fastopenq->lock);
329 reqsk_put(req1);
330 }
331 return true;
332}
333
334static bool tcp_fastopen_no_cookie(const struct sock *sk,
335 const struct dst_entry *dst,
336 int flag)
337{
338 return (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fastopen) & flag) ||
339 tcp_sk(sk)->fastopen_no_cookie ||
340 (dst && dst_metric(dst, RTAX_FASTOPEN_NO_COOKIE));
341}
342
343/* Returns true if we should perform Fast Open on the SYN. The cookie (foc)
344 * may be updated and return the client in the SYN-ACK later. E.g., Fast Open
345 * cookie request (foc->len == 0).
346 */
347struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
348 struct request_sock *req,
349 struct tcp_fastopen_cookie *foc,
350 const struct dst_entry *dst)
351{
352 bool syn_data = TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq + 1;
353 int tcp_fastopen = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fastopen);
354 struct tcp_fastopen_cookie valid_foc = { .len = -1 };
355 struct sock *child;
356 int ret = 0;
357
358 if (foc->len == 0) /* Client requests a cookie */
359 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENCOOKIEREQD);
360
361 if (!((tcp_fastopen & TFO_SERVER_ENABLE) &&
362 (syn_data || foc->len >= 0) &&
363 tcp_fastopen_queue_check(sk))) {
364 foc->len = -1;
365 return NULL;
366 }
367
368 if (tcp_fastopen_no_cookie(sk, dst, TFO_SERVER_COOKIE_NOT_REQD))
369 goto fastopen;
370
371 if (foc->len == 0) {
372 /* Client requests a cookie. */
373 tcp_fastopen_cookie_gen(sk, req, skb, &valid_foc);
374 } else if (foc->len > 0) {
375 ret = tcp_fastopen_cookie_gen_check(sk, req, skb, foc,
376 &valid_foc);
377 if (!ret) {
378 NET_INC_STATS(sock_net(sk),
379 LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
380 } else {
381 /* Cookie is valid. Create a (full) child socket to
382 * accept the data in SYN before returning a SYN-ACK to
383 * ack the data. If we fail to create the socket, fall
384 * back and ack the ISN only but includes the same
385 * cookie.
386 *
387 * Note: Data-less SYN with valid cookie is allowed to
388 * send data in SYN_RECV state.
389 */
390fastopen:
391 child = tcp_fastopen_create_child(sk, skb, req);
392 if (child) {
393 if (ret == 2) {
394 valid_foc.exp = foc->exp;
395 *foc = valid_foc;
396 NET_INC_STATS(sock_net(sk),
397 LINUX_MIB_TCPFASTOPENPASSIVEALTKEY);
398 } else {
399 foc->len = -1;
400 }
401 NET_INC_STATS(sock_net(sk),
402 LINUX_MIB_TCPFASTOPENPASSIVE);
403 return child;
404 }
405 NET_INC_STATS(sock_net(sk),
406 LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
407 }
408 }
409 valid_foc.exp = foc->exp;
410 *foc = valid_foc;
411 return NULL;
412}
413
414bool tcp_fastopen_cookie_check(struct sock *sk, u16 *mss,
415 struct tcp_fastopen_cookie *cookie)
416{
417 const struct dst_entry *dst;
418
419 tcp_fastopen_cache_get(sk, mss, cookie);
420
421 /* Firewall blackhole issue check */
422 if (tcp_fastopen_active_should_disable(sk)) {
423 cookie->len = -1;
424 return false;
425 }
426
427 dst = __sk_dst_get(sk);
428
429 if (tcp_fastopen_no_cookie(sk, dst, TFO_CLIENT_NO_COOKIE)) {
430 cookie->len = -1;
431 return true;
432 }
433 if (cookie->len > 0)
434 return true;
435 tcp_sk(sk)->fastopen_client_fail = TFO_COOKIE_UNAVAILABLE;
436 return false;
437}
438
439/* This function checks if we want to defer sending SYN until the first
440 * write(). We defer under the following conditions:
441 * 1. fastopen_connect sockopt is set
442 * 2. we have a valid cookie
443 * Return value: return true if we want to defer until application writes data
444 * return false if we want to send out SYN immediately
445 */
446bool tcp_fastopen_defer_connect(struct sock *sk, int *err)
447{
448 struct tcp_fastopen_cookie cookie = { .len = 0 };
449 struct tcp_sock *tp = tcp_sk(sk);
450 u16 mss;
451
452 if (tp->fastopen_connect && !tp->fastopen_req) {
453 if (tcp_fastopen_cookie_check(sk, &mss, &cookie)) {
454 inet_set_bit(DEFER_CONNECT, sk);
455 return true;
456 }
457
458 /* Alloc fastopen_req in order for FO option to be included
459 * in SYN
460 */
461 tp->fastopen_req = kzalloc(sizeof(*tp->fastopen_req),
462 sk->sk_allocation);
463 if (tp->fastopen_req)
464 tp->fastopen_req->cookie = cookie;
465 else
466 *err = -ENOBUFS;
467 }
468 return false;
469}
470EXPORT_SYMBOL(tcp_fastopen_defer_connect);
471
472/*
473 * The following code block is to deal with middle box issues with TFO:
474 * Middlebox firewall issues can potentially cause server's data being
475 * blackholed after a successful 3WHS using TFO.
476 * The proposed solution is to disable active TFO globally under the
477 * following circumstances:
478 * 1. client side TFO socket receives out of order FIN
479 * 2. client side TFO socket receives out of order RST
480 * 3. client side TFO socket has timed out three times consecutively during
481 * or after handshake
482 * We disable active side TFO globally for 1hr at first. Then if it
483 * happens again, we disable it for 2h, then 4h, 8h, ...
484 * And we reset the timeout back to 1hr when we see a successful active
485 * TFO connection with data exchanges.
486 */
487
488/* Disable active TFO and record current jiffies and
489 * tfo_active_disable_times
490 */
491void tcp_fastopen_active_disable(struct sock *sk)
492{
493 struct net *net = sock_net(sk);
494
495 if (!READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fastopen_blackhole_timeout))
496 return;
497
498 /* Paired with READ_ONCE() in tcp_fastopen_active_should_disable() */
499 WRITE_ONCE(net->ipv4.tfo_active_disable_stamp, jiffies);
500
501 /* Paired with smp_rmb() in tcp_fastopen_active_should_disable().
502 * We want net->ipv4.tfo_active_disable_stamp to be updated first.
503 */
504 smp_mb__before_atomic();
505 atomic_inc(&net->ipv4.tfo_active_disable_times);
506
507 NET_INC_STATS(net, LINUX_MIB_TCPFASTOPENBLACKHOLE);
508}
509
510/* Calculate timeout for tfo active disable
511 * Return true if we are still in the active TFO disable period
512 * Return false if timeout already expired and we should use active TFO
513 */
514bool tcp_fastopen_active_should_disable(struct sock *sk)
515{
516 unsigned int tfo_bh_timeout =
517 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fastopen_blackhole_timeout);
518 unsigned long timeout;
519 int tfo_da_times;
520 int multiplier;
521
522 if (!tfo_bh_timeout)
523 return false;
524
525 tfo_da_times = atomic_read(&sock_net(sk)->ipv4.tfo_active_disable_times);
526 if (!tfo_da_times)
527 return false;
528
529 /* Paired with smp_mb__before_atomic() in tcp_fastopen_active_disable() */
530 smp_rmb();
531
532 /* Limit timeout to max: 2^6 * initial timeout */
533 multiplier = 1 << min(tfo_da_times - 1, 6);
534
535 /* Paired with the WRITE_ONCE() in tcp_fastopen_active_disable(). */
536 timeout = READ_ONCE(sock_net(sk)->ipv4.tfo_active_disable_stamp) +
537 multiplier * tfo_bh_timeout * HZ;
538 if (time_before(jiffies, timeout))
539 return true;
540
541 /* Mark check bit so we can check for successful active TFO
542 * condition and reset tfo_active_disable_times
543 */
544 tcp_sk(sk)->syn_fastopen_ch = 1;
545 return false;
546}
547
548/* Disable active TFO if FIN is the only packet in the ofo queue
549 * and no data is received.
550 * Also check if we can reset tfo_active_disable_times if data is
551 * received successfully on a marked active TFO sockets opened on
552 * a non-loopback interface
553 */
554void tcp_fastopen_active_disable_ofo_check(struct sock *sk)
555{
556 struct tcp_sock *tp = tcp_sk(sk);
557 struct dst_entry *dst;
558 struct sk_buff *skb;
559
560 if (!tp->syn_fastopen)
561 return;
562
563 if (!tp->data_segs_in) {
564 skb = skb_rb_first(&tp->out_of_order_queue);
565 if (skb && !skb_rb_next(skb)) {
566 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) {
567 tcp_fastopen_active_disable(sk);
568 return;
569 }
570 }
571 } else if (tp->syn_fastopen_ch &&
572 atomic_read(&sock_net(sk)->ipv4.tfo_active_disable_times)) {
573 dst = sk_dst_get(sk);
574 if (!(dst && dst->dev && (dst->dev->flags & IFF_LOOPBACK)))
575 atomic_set(&sock_net(sk)->ipv4.tfo_active_disable_times, 0);
576 dst_release(dst);
577 }
578}
579
580void tcp_fastopen_active_detect_blackhole(struct sock *sk, bool expired)
581{
582 u32 timeouts = inet_csk(sk)->icsk_retransmits;
583 struct tcp_sock *tp = tcp_sk(sk);
584
585 /* Broken middle-boxes may black-hole Fast Open connection during or
586 * even after the handshake. Be extremely conservative and pause
587 * Fast Open globally after hitting the third consecutive timeout or
588 * exceeding the configured timeout limit.
589 */
590 if ((tp->syn_fastopen || tp->syn_data || tp->syn_data_acked) &&
591 (timeouts == 2 || (timeouts < 2 && expired))) {
592 tcp_fastopen_active_disable(sk);
593 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVEFAIL);
594 }
595}