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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
13void tcp_fastopen_init_key_once(struct net *net)
14{
15 u8 key[TCP_FASTOPEN_KEY_LENGTH];
16 struct tcp_fastopen_context *ctxt;
17
18 rcu_read_lock();
19 ctxt = rcu_dereference(net->ipv4.tcp_fastopen_ctx);
20 if (ctxt) {
21 rcu_read_unlock();
22 return;
23 }
24 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 get_random_bytes(key, sizeof(key));
33 tcp_fastopen_reset_cipher(net, NULL, key, NULL);
34}
35
36static void tcp_fastopen_ctx_free(struct rcu_head *head)
37{
38 struct tcp_fastopen_context *ctx =
39 container_of(head, struct tcp_fastopen_context, rcu);
40
41 kfree_sensitive(ctx);
42}
43
44void tcp_fastopen_destroy_cipher(struct sock *sk)
45{
46 struct tcp_fastopen_context *ctx;
47
48 ctx = rcu_dereference_protected(
49 inet_csk(sk)->icsk_accept_queue.fastopenq.ctx, 1);
50 if (ctx)
51 call_rcu(&ctx->rcu, tcp_fastopen_ctx_free);
52}
53
54void tcp_fastopen_ctx_destroy(struct net *net)
55{
56 struct tcp_fastopen_context *ctxt;
57
58 spin_lock(&net->ipv4.tcp_fastopen_ctx_lock);
59
60 ctxt = rcu_dereference_protected(net->ipv4.tcp_fastopen_ctx,
61 lockdep_is_held(&net->ipv4.tcp_fastopen_ctx_lock));
62 rcu_assign_pointer(net->ipv4.tcp_fastopen_ctx, NULL);
63 spin_unlock(&net->ipv4.tcp_fastopen_ctx_lock);
64
65 if (ctxt)
66 call_rcu(&ctxt->rcu, tcp_fastopen_ctx_free);
67}
68
69int tcp_fastopen_reset_cipher(struct net *net, struct sock *sk,
70 void *primary_key, void *backup_key)
71{
72 struct tcp_fastopen_context *ctx, *octx;
73 struct fastopen_queue *q;
74 int err = 0;
75
76 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
77 if (!ctx) {
78 err = -ENOMEM;
79 goto out;
80 }
81
82 ctx->key[0].key[0] = get_unaligned_le64(primary_key);
83 ctx->key[0].key[1] = get_unaligned_le64(primary_key + 8);
84 if (backup_key) {
85 ctx->key[1].key[0] = get_unaligned_le64(backup_key);
86 ctx->key[1].key[1] = get_unaligned_le64(backup_key + 8);
87 ctx->num = 2;
88 } else {
89 ctx->num = 1;
90 }
91
92 spin_lock(&net->ipv4.tcp_fastopen_ctx_lock);
93 if (sk) {
94 q = &inet_csk(sk)->icsk_accept_queue.fastopenq;
95 octx = rcu_dereference_protected(q->ctx,
96 lockdep_is_held(&net->ipv4.tcp_fastopen_ctx_lock));
97 rcu_assign_pointer(q->ctx, ctx);
98 } else {
99 octx = rcu_dereference_protected(net->ipv4.tcp_fastopen_ctx,
100 lockdep_is_held(&net->ipv4.tcp_fastopen_ctx_lock));
101 rcu_assign_pointer(net->ipv4.tcp_fastopen_ctx, ctx);
102 }
103 spin_unlock(&net->ipv4.tcp_fastopen_ctx_lock);
104
105 if (octx)
106 call_rcu(&octx->rcu, tcp_fastopen_ctx_free);
107out:
108 return err;
109}
110
111int tcp_fastopen_get_cipher(struct net *net, struct inet_connection_sock *icsk,
112 u64 *key)
113{
114 struct tcp_fastopen_context *ctx;
115 int n_keys = 0, i;
116
117 rcu_read_lock();
118 if (icsk)
119 ctx = rcu_dereference(icsk->icsk_accept_queue.fastopenq.ctx);
120 else
121 ctx = rcu_dereference(net->ipv4.tcp_fastopen_ctx);
122 if (ctx) {
123 n_keys = tcp_fastopen_context_len(ctx);
124 for (i = 0; i < n_keys; i++) {
125 put_unaligned_le64(ctx->key[i].key[0], key + (i * 2));
126 put_unaligned_le64(ctx->key[i].key[1], key + (i * 2) + 1);
127 }
128 }
129 rcu_read_unlock();
130
131 return n_keys;
132}
133
134static 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 BUILD_BUG_ON(TCP_FASTOPEN_COOKIE_SIZE != sizeof(u64));
140
141 if (req->rsk_ops->family == AF_INET) {
142 const struct iphdr *iph = ip_hdr(syn);
143
144 foc->val[0] = cpu_to_le64(siphash(&iph->saddr,
145 sizeof(iph->saddr) +
146 sizeof(iph->daddr),
147 key));
148 foc->len = TCP_FASTOPEN_COOKIE_SIZE;
149 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 */
169static 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 struct tcp_fastopen_context *ctx;
175
176 rcu_read_lock();
177 ctx = tcp_fastopen_get_ctx(sk);
178 if (ctx)
179 __tcp_fastopen_cookie_gen_cipher(req, syn, &ctx->key[0], foc);
180 rcu_read_unlock();
181}
182
183/* If an incoming SYN or SYNACK frame contains a payload and/or FIN,
184 * queue this additional data / FIN.
185 */
186void tcp_fastopen_add_skb(struct sock *sk, struct sk_buff *skb)
187{
188 struct tcp_sock *tp = tcp_sk(sk);
189
190 if (TCP_SKB_CB(skb)->end_seq == tp->rcv_nxt)
191 return;
192
193 skb = skb_clone(skb, GFP_ATOMIC);
194 if (!skb)
195 return;
196
197 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 tp->segs_in = 0;
205 tcp_segs_in(tp, skb);
206 __skb_pull(skb, tcp_hdrlen(skb));
207 sk_forced_mem_schedule(sk, skb->truesize);
208 skb_set_owner_r(skb, sk);
209
210 TCP_SKB_CB(skb)->seq++;
211 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_SYN;
212
213 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
214 __skb_queue_tail(&sk->sk_receive_queue, skb);
215 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 tp->bytes_received = skb->len;
221
222 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
223 tcp_fin(sk);
224}
225
226/* returns 0 - no key match, 1 for primary, 2 for backup */
227static 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 struct tcp_fastopen_cookie search_foc = { .len = -1 };
234 struct tcp_fastopen_cookie *foc = valid_foc;
235 struct tcp_fastopen_context *ctx;
236 int i, ret = 0;
237
238 rcu_read_lock();
239 ctx = tcp_fastopen_get_ctx(sk);
240 if (!ctx)
241 goto out;
242 for (i = 0; i < tcp_fastopen_context_len(ctx); i++) {
243 __tcp_fastopen_cookie_gen_cipher(req, syn, &ctx->key[i], foc);
244 if (tcp_fastopen_cookie_match(foc, orig)) {
245 ret = i + 1;
246 goto out;
247 }
248 foc = &search_foc;
249 }
250out:
251 rcu_read_unlock();
252 return ret;
253}
254
255static struct sock *tcp_fastopen_create_child(struct sock *sk,
256 struct sk_buff *skb,
257 struct request_sock *req)
258{
259 struct tcp_sock *tp;
260 struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
261 struct sock *child;
262 bool own_req;
263
264 child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL,
265 NULL, &own_req);
266 if (!child)
267 return NULL;
268
269 spin_lock(&queue->fastopenq.lock);
270 queue->fastopenq.qlen++;
271 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 tp = tcp_sk(child);
278
279 rcu_assign_pointer(tp->fastopen_rsk, req);
280 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 tp->snd_wnd = ntohs(tcp_hdr(skb)->window);
286 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 inet_csk_reset_xmit_timer(child, ICSK_TIME_RETRANS,
293 TCP_TIMEOUT_INIT, TCP_RTO_MAX);
294
295 refcount_set(&req->rsk_refcnt, 2);
296
297 /* Now finish processing the fastopen child socket. */
298 tcp_init_transfer(child, BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB);
299
300 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
301
302 tcp_fastopen_add_skb(child, skb);
303
304 tcp_rsk(req)->rcv_nxt = tp->rcv_nxt;
305 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 return child;
310}
311
312static bool tcp_fastopen_queue_check(struct sock *sk)
313{
314 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 fastopenq = &inet_csk(sk)->icsk_accept_queue.fastopenq;
327 if (fastopenq->max_qlen == 0)
328 return false;
329
330 if (fastopenq->qlen >= fastopenq->max_qlen) {
331 struct request_sock *req1;
332 spin_lock(&fastopenq->lock);
333 req1 = fastopenq->rskq_rst_head;
334 if (!req1 || time_after(req1->rsk_timer.expires, jiffies)) {
335 __NET_INC_STATS(sock_net(sk),
336 LINUX_MIB_TCPFASTOPENLISTENOVERFLOW);
337 spin_unlock(&fastopenq->lock);
338 return false;
339 }
340 fastopenq->rskq_rst_head = req1->dl_next;
341 fastopenq->qlen--;
342 spin_unlock(&fastopenq->lock);
343 reqsk_put(req1);
344 }
345 return true;
346}
347
348static bool tcp_fastopen_no_cookie(const struct sock *sk,
349 const struct dst_entry *dst,
350 int flag)
351{
352 return (sock_net(sk)->ipv4.sysctl_tcp_fastopen & flag) ||
353 tcp_sk(sk)->fastopen_no_cookie ||
354 (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 */
361struct 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 bool syn_data = TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq + 1;
367 int tcp_fastopen = sock_net(sk)->ipv4.sysctl_tcp_fastopen;
368 struct tcp_fastopen_cookie valid_foc = { .len = -1 };
369 struct sock *child;
370 int ret = 0;
371
372 if (foc->len == 0) /* Client requests a cookie */
373 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENCOOKIEREQD);
374
375 if (!((tcp_fastopen & TFO_SERVER_ENABLE) &&
376 (syn_data || foc->len >= 0) &&
377 tcp_fastopen_queue_check(sk))) {
378 foc->len = -1;
379 return NULL;
380 }
381
382 if (syn_data &&
383 tcp_fastopen_no_cookie(sk, dst, TFO_SERVER_COOKIE_NOT_REQD))
384 goto fastopen;
385
386 if (foc->len == 0) {
387 /* Client requests a cookie. */
388 tcp_fastopen_cookie_gen(sk, req, skb, &valid_foc);
389 } else if (foc->len > 0) {
390 ret = tcp_fastopen_cookie_gen_check(sk, req, skb, foc,
391 &valid_foc);
392 if (!ret) {
393 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 */
405fastopen:
406 child = tcp_fastopen_create_child(sk, skb, req);
407 if (child) {
408 if (ret == 2) {
409 valid_foc.exp = foc->exp;
410 *foc = valid_foc;
411 NET_INC_STATS(sock_net(sk),
412 LINUX_MIB_TCPFASTOPENPASSIVEALTKEY);
413 } else {
414 foc->len = -1;
415 }
416 NET_INC_STATS(sock_net(sk),
417 LINUX_MIB_TCPFASTOPENPASSIVE);
418 return child;
419 }
420 NET_INC_STATS(sock_net(sk),
421 LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
422 }
423 }
424 valid_foc.exp = foc->exp;
425 *foc = valid_foc;
426 return NULL;
427}
428
429bool tcp_fastopen_cookie_check(struct sock *sk, u16 *mss,
430 struct tcp_fastopen_cookie *cookie)
431{
432 const struct dst_entry *dst;
433
434 tcp_fastopen_cache_get(sk, mss, cookie);
435
436 /* Firewall blackhole issue check */
437 if (tcp_fastopen_active_should_disable(sk)) {
438 cookie->len = -1;
439 return false;
440 }
441
442 dst = __sk_dst_get(sk);
443
444 if (tcp_fastopen_no_cookie(sk, dst, TFO_CLIENT_NO_COOKIE)) {
445 cookie->len = -1;
446 return true;
447 }
448 if (cookie->len > 0)
449 return true;
450 tcp_sk(sk)->fastopen_client_fail = TFO_COOKIE_UNAVAILABLE;
451 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 */
461bool tcp_fastopen_defer_connect(struct sock *sk, int *err)
462{
463 struct tcp_fastopen_cookie cookie = { .len = 0 };
464 struct tcp_sock *tp = tcp_sk(sk);
465 u16 mss;
466
467 if (tp->fastopen_connect && !tp->fastopen_req) {
468 if (tcp_fastopen_cookie_check(sk, &mss, &cookie)) {
469 inet_sk(sk)->defer_connect = 1;
470 return true;
471 }
472
473 /* Alloc fastopen_req in order for FO option to be included
474 * in SYN
475 */
476 tp->fastopen_req = kzalloc(sizeof(*tp->fastopen_req),
477 sk->sk_allocation);
478 if (tp->fastopen_req)
479 tp->fastopen_req->cookie = cookie;
480 else
481 *err = -ENOBUFS;
482 }
483 return false;
484}
485EXPORT_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 */
506void tcp_fastopen_active_disable(struct sock *sk)
507{
508 struct net *net = sock_net(sk);
509
510 atomic_inc(&net->ipv4.tfo_active_disable_times);
511 net->ipv4.tfo_active_disable_stamp = jiffies;
512 NET_INC_STATS(net, LINUX_MIB_TCPFASTOPENBLACKHOLE);
513}
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 */
519bool tcp_fastopen_active_should_disable(struct sock *sk)
520{
521 unsigned int tfo_bh_timeout = sock_net(sk)->ipv4.sysctl_tcp_fastopen_blackhole_timeout;
522 int tfo_da_times = atomic_read(&sock_net(sk)->ipv4.tfo_active_disable_times);
523 unsigned long timeout;
524 int multiplier;
525
526 if (!tfo_da_times)
527 return false;
528
529 /* Limit timout to max: 2^6 * initial timeout */
530 multiplier = 1 << min(tfo_da_times - 1, 6);
531 timeout = multiplier * tfo_bh_timeout * HZ;
532 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 tcp_sk(sk)->syn_fastopen_ch = 1;
539 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 */
548void tcp_fastopen_active_disable_ofo_check(struct sock *sk)
549{
550 struct tcp_sock *tp = tcp_sk(sk);
551 struct dst_entry *dst;
552 struct sk_buff *skb;
553
554 if (!tp->syn_fastopen)
555 return;
556
557 if (!tp->data_segs_in) {
558 skb = skb_rb_first(&tp->out_of_order_queue);
559 if (skb && !skb_rb_next(skb)) {
560 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) {
561 tcp_fastopen_active_disable(sk);
562 return;
563 }
564 }
565 } else if (tp->syn_fastopen_ch &&
566 atomic_read(&sock_net(sk)->ipv4.tfo_active_disable_times)) {
567 dst = sk_dst_get(sk);
568 if (!(dst && dst->dev && (dst->dev->flags & IFF_LOOPBACK)))
569 atomic_set(&sock_net(sk)->ipv4.tfo_active_disable_times, 0);
570 dst_release(dst);
571 }
572}
573
574void tcp_fastopen_active_detect_blackhole(struct sock *sk, bool expired)
575{
576 u32 timeouts = inet_csk(sk)->icsk_retransmits;
577 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 if ((tp->syn_fastopen || tp->syn_data || tp->syn_data_acked) &&
585 (timeouts == 2 || (timeouts < 2 && expired))) {
586 tcp_fastopen_active_disable(sk);
587 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVEFAIL);
588 }
589}
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}