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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#include <linux/crypto.h>
2#include <linux/err.h>
3#include <linux/init.h>
4#include <linux/kernel.h>
5#include <linux/list.h>
6#include <linux/tcp.h>
7#include <linux/rcupdate.h>
8#include <linux/rculist.h>
9#include <net/inetpeer.h>
10#include <net/tcp.h>
11
12int sysctl_tcp_fastopen __read_mostly = TFO_CLIENT_ENABLE;
13
14struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
15
16static DEFINE_SPINLOCK(tcp_fastopen_ctx_lock);
17
18void tcp_fastopen_init_key_once(bool publish)
19{
20 static u8 key[TCP_FASTOPEN_KEY_LENGTH];
21
22 /* tcp_fastopen_reset_cipher publishes the new context
23 * atomically, so we allow this race happening here.
24 *
25 * All call sites of tcp_fastopen_cookie_gen also check
26 * for a valid cookie, so this is an acceptable risk.
27 */
28 if (net_get_random_once(key, sizeof(key)) && publish)
29 tcp_fastopen_reset_cipher(key, sizeof(key));
30}
31
32static void tcp_fastopen_ctx_free(struct rcu_head *head)
33{
34 struct tcp_fastopen_context *ctx =
35 container_of(head, struct tcp_fastopen_context, rcu);
36 crypto_free_cipher(ctx->tfm);
37 kfree(ctx);
38}
39
40int tcp_fastopen_reset_cipher(void *key, unsigned int len)
41{
42 int err;
43 struct tcp_fastopen_context *ctx, *octx;
44
45 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
46 if (!ctx)
47 return -ENOMEM;
48 ctx->tfm = crypto_alloc_cipher("aes", 0, 0);
49
50 if (IS_ERR(ctx->tfm)) {
51 err = PTR_ERR(ctx->tfm);
52error: kfree(ctx);
53 pr_err("TCP: TFO aes cipher alloc error: %d\n", err);
54 return err;
55 }
56 err = crypto_cipher_setkey(ctx->tfm, key, len);
57 if (err) {
58 pr_err("TCP: TFO cipher key error: %d\n", err);
59 crypto_free_cipher(ctx->tfm);
60 goto error;
61 }
62 memcpy(ctx->key, key, len);
63
64 spin_lock(&tcp_fastopen_ctx_lock);
65
66 octx = rcu_dereference_protected(tcp_fastopen_ctx,
67 lockdep_is_held(&tcp_fastopen_ctx_lock));
68 rcu_assign_pointer(tcp_fastopen_ctx, ctx);
69 spin_unlock(&tcp_fastopen_ctx_lock);
70
71 if (octx)
72 call_rcu(&octx->rcu, tcp_fastopen_ctx_free);
73 return err;
74}
75
76static bool __tcp_fastopen_cookie_gen(const void *path,
77 struct tcp_fastopen_cookie *foc)
78{
79 struct tcp_fastopen_context *ctx;
80 bool ok = false;
81
82 rcu_read_lock();
83 ctx = rcu_dereference(tcp_fastopen_ctx);
84 if (ctx) {
85 crypto_cipher_encrypt_one(ctx->tfm, foc->val, path);
86 foc->len = TCP_FASTOPEN_COOKIE_SIZE;
87 ok = true;
88 }
89 rcu_read_unlock();
90 return ok;
91}
92
93/* Generate the fastopen cookie by doing aes128 encryption on both
94 * the source and destination addresses. Pad 0s for IPv4 or IPv4-mapped-IPv6
95 * addresses. For the longer IPv6 addresses use CBC-MAC.
96 *
97 * XXX (TFO) - refactor when TCP_FASTOPEN_COOKIE_SIZE != AES_BLOCK_SIZE.
98 */
99static bool tcp_fastopen_cookie_gen(struct request_sock *req,
100 struct sk_buff *syn,
101 struct tcp_fastopen_cookie *foc)
102{
103 if (req->rsk_ops->family == AF_INET) {
104 const struct iphdr *iph = ip_hdr(syn);
105
106 __be32 path[4] = { iph->saddr, iph->daddr, 0, 0 };
107 return __tcp_fastopen_cookie_gen(path, foc);
108 }
109
110#if IS_ENABLED(CONFIG_IPV6)
111 if (req->rsk_ops->family == AF_INET6) {
112 const struct ipv6hdr *ip6h = ipv6_hdr(syn);
113 struct tcp_fastopen_cookie tmp;
114
115 if (__tcp_fastopen_cookie_gen(&ip6h->saddr, &tmp)) {
116 struct in6_addr *buf = (struct in6_addr *) tmp.val;
117 int i;
118
119 for (i = 0; i < 4; i++)
120 buf->s6_addr32[i] ^= ip6h->daddr.s6_addr32[i];
121 return __tcp_fastopen_cookie_gen(buf, foc);
122 }
123 }
124#endif
125 return false;
126}
127
128
129/* If an incoming SYN or SYNACK frame contains a payload and/or FIN,
130 * queue this additional data / FIN.
131 */
132void tcp_fastopen_add_skb(struct sock *sk, struct sk_buff *skb)
133{
134 struct tcp_sock *tp = tcp_sk(sk);
135
136 if (TCP_SKB_CB(skb)->end_seq == tp->rcv_nxt)
137 return;
138
139 skb = skb_clone(skb, GFP_ATOMIC);
140 if (!skb)
141 return;
142
143 skb_dst_drop(skb);
144 /* segs_in has been initialized to 1 in tcp_create_openreq_child().
145 * Hence, reset segs_in to 0 before calling tcp_segs_in()
146 * to avoid double counting. Also, tcp_segs_in() expects
147 * skb->len to include the tcp_hdrlen. Hence, it should
148 * be called before __skb_pull().
149 */
150 tp->segs_in = 0;
151 tcp_segs_in(tp, skb);
152 __skb_pull(skb, tcp_hdrlen(skb));
153 skb_set_owner_r(skb, sk);
154
155 TCP_SKB_CB(skb)->seq++;
156 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_SYN;
157
158 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
159 __skb_queue_tail(&sk->sk_receive_queue, skb);
160 tp->syn_data_acked = 1;
161
162 /* u64_stats_update_begin(&tp->syncp) not needed here,
163 * as we certainly are not changing upper 32bit value (0)
164 */
165 tp->bytes_received = skb->len;
166
167 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
168 tcp_fin(sk);
169}
170
171static struct sock *tcp_fastopen_create_child(struct sock *sk,
172 struct sk_buff *skb,
173 struct dst_entry *dst,
174 struct request_sock *req)
175{
176 struct tcp_sock *tp;
177 struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
178 struct sock *child;
179 bool own_req;
180
181 req->num_retrans = 0;
182 req->num_timeout = 0;
183 req->sk = NULL;
184
185 child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL,
186 NULL, &own_req);
187 if (!child)
188 return NULL;
189
190 spin_lock(&queue->fastopenq.lock);
191 queue->fastopenq.qlen++;
192 spin_unlock(&queue->fastopenq.lock);
193
194 /* Initialize the child socket. Have to fix some values to take
195 * into account the child is a Fast Open socket and is created
196 * only out of the bits carried in the SYN packet.
197 */
198 tp = tcp_sk(child);
199
200 tp->fastopen_rsk = req;
201 tcp_rsk(req)->tfo_listener = true;
202
203 /* RFC1323: The window in SYN & SYN/ACK segments is never
204 * scaled. So correct it appropriately.
205 */
206 tp->snd_wnd = ntohs(tcp_hdr(skb)->window);
207
208 /* Activate the retrans timer so that SYNACK can be retransmitted.
209 * The request socket is not added to the ehash
210 * because it's been added to the accept queue directly.
211 */
212 inet_csk_reset_xmit_timer(child, ICSK_TIME_RETRANS,
213 TCP_TIMEOUT_INIT, TCP_RTO_MAX);
214
215 atomic_set(&req->rsk_refcnt, 2);
216
217 /* Now finish processing the fastopen child socket. */
218 inet_csk(child)->icsk_af_ops->rebuild_header(child);
219 tcp_init_congestion_control(child);
220 tcp_mtup_init(child);
221 tcp_init_metrics(child);
222 tcp_init_buffer_space(child);
223
224 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
225
226 tcp_fastopen_add_skb(child, skb);
227
228 tcp_rsk(req)->rcv_nxt = tp->rcv_nxt;
229 /* tcp_conn_request() is sending the SYNACK,
230 * and queues the child into listener accept queue.
231 */
232 return child;
233}
234
235static bool tcp_fastopen_queue_check(struct sock *sk)
236{
237 struct fastopen_queue *fastopenq;
238
239 /* Make sure the listener has enabled fastopen, and we don't
240 * exceed the max # of pending TFO requests allowed before trying
241 * to validating the cookie in order to avoid burning CPU cycles
242 * unnecessarily.
243 *
244 * XXX (TFO) - The implication of checking the max_qlen before
245 * processing a cookie request is that clients can't differentiate
246 * between qlen overflow causing Fast Open to be disabled
247 * temporarily vs a server not supporting Fast Open at all.
248 */
249 fastopenq = &inet_csk(sk)->icsk_accept_queue.fastopenq;
250 if (fastopenq->max_qlen == 0)
251 return false;
252
253 if (fastopenq->qlen >= fastopenq->max_qlen) {
254 struct request_sock *req1;
255 spin_lock(&fastopenq->lock);
256 req1 = fastopenq->rskq_rst_head;
257 if (!req1 || time_after(req1->rsk_timer.expires, jiffies)) {
258 spin_unlock(&fastopenq->lock);
259 NET_INC_STATS_BH(sock_net(sk),
260 LINUX_MIB_TCPFASTOPENLISTENOVERFLOW);
261 return false;
262 }
263 fastopenq->rskq_rst_head = req1->dl_next;
264 fastopenq->qlen--;
265 spin_unlock(&fastopenq->lock);
266 reqsk_put(req1);
267 }
268 return true;
269}
270
271/* Returns true if we should perform Fast Open on the SYN. The cookie (foc)
272 * may be updated and return the client in the SYN-ACK later. E.g., Fast Open
273 * cookie request (foc->len == 0).
274 */
275struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
276 struct request_sock *req,
277 struct tcp_fastopen_cookie *foc,
278 struct dst_entry *dst)
279{
280 struct tcp_fastopen_cookie valid_foc = { .len = -1 };
281 bool syn_data = TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq + 1;
282 struct sock *child;
283
284 if (foc->len == 0) /* Client requests a cookie */
285 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENCOOKIEREQD);
286
287 if (!((sysctl_tcp_fastopen & TFO_SERVER_ENABLE) &&
288 (syn_data || foc->len >= 0) &&
289 tcp_fastopen_queue_check(sk))) {
290 foc->len = -1;
291 return NULL;
292 }
293
294 if (syn_data && (sysctl_tcp_fastopen & TFO_SERVER_COOKIE_NOT_REQD))
295 goto fastopen;
296
297 if (foc->len >= 0 && /* Client presents or requests a cookie */
298 tcp_fastopen_cookie_gen(req, skb, &valid_foc) &&
299 foc->len == TCP_FASTOPEN_COOKIE_SIZE &&
300 foc->len == valid_foc.len &&
301 !memcmp(foc->val, valid_foc.val, foc->len)) {
302 /* Cookie is valid. Create a (full) child socket to accept
303 * the data in SYN before returning a SYN-ACK to ack the
304 * data. If we fail to create the socket, fall back and
305 * ack the ISN only but includes the same cookie.
306 *
307 * Note: Data-less SYN with valid cookie is allowed to send
308 * data in SYN_RECV state.
309 */
310fastopen:
311 child = tcp_fastopen_create_child(sk, skb, dst, req);
312 if (child) {
313 foc->len = -1;
314 NET_INC_STATS_BH(sock_net(sk),
315 LINUX_MIB_TCPFASTOPENPASSIVE);
316 return child;
317 }
318 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
319 } else if (foc->len > 0) /* Client presents an invalid cookie */
320 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
321
322 valid_foc.exp = foc->exp;
323 *foc = valid_foc;
324 return NULL;
325}