blob: e0a4b56644aa0f8ccd384644fde7e4841da29d3f [file] [log] [blame]
Herbert Xucf80e0e2016-01-24 21:20:23 +08001#include <linux/crypto.h>
Jerry Chu10467162012-08-31 12:29:11 +00002#include <linux/err.h>
Yuchung Cheng2100c8d2012-07-19 06:43:05 +00003#include <linux/init.h>
4#include <linux/kernel.h>
Jerry Chu10467162012-08-31 12:29:11 +00005#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>
Yuchung Cheng2100c8d2012-07-19 06:43:05 +000011
Haishuang Yan43713842017-09-27 11:35:42 +080012void tcp_fastopen_init_key_once(struct net *net)
Hannes Frederic Sowa222e83d2013-10-19 21:48:58 +020013{
Haishuang Yan43713842017-09-27 11:35:42 +080014 u8 key[TCP_FASTOPEN_KEY_LENGTH];
15 struct tcp_fastopen_context *ctxt;
16
17 rcu_read_lock();
18 ctxt = rcu_dereference(net->ipv4.tcp_fastopen_ctx);
19 if (ctxt) {
20 rcu_read_unlock();
21 return;
22 }
23 rcu_read_unlock();
Hannes Frederic Sowa222e83d2013-10-19 21:48:58 +020024
25 /* tcp_fastopen_reset_cipher publishes the new context
26 * atomically, so we allow this race happening here.
27 *
28 * All call sites of tcp_fastopen_cookie_gen also check
29 * for a valid cookie, so this is an acceptable risk.
30 */
Haishuang Yan43713842017-09-27 11:35:42 +080031 get_random_bytes(key, sizeof(key));
Yuchung Cheng1fba70e2017-10-18 11:22:51 -070032 tcp_fastopen_reset_cipher(net, NULL, key, sizeof(key));
Hannes Frederic Sowa222e83d2013-10-19 21:48:58 +020033}
34
Jerry Chu10467162012-08-31 12:29:11 +000035static void tcp_fastopen_ctx_free(struct rcu_head *head)
36{
37 struct tcp_fastopen_context *ctx =
38 container_of(head, struct tcp_fastopen_context, rcu);
39 crypto_free_cipher(ctx->tfm);
40 kfree(ctx);
41}
42
Yuchung Cheng1fba70e2017-10-18 11:22:51 -070043void tcp_fastopen_destroy_cipher(struct sock *sk)
44{
45 struct tcp_fastopen_context *ctx;
46
47 ctx = rcu_dereference_protected(
48 inet_csk(sk)->icsk_accept_queue.fastopenq.ctx, 1);
49 if (ctx)
50 call_rcu(&ctx->rcu, tcp_fastopen_ctx_free);
51}
52
Haishuang Yan43713842017-09-27 11:35:42 +080053void tcp_fastopen_ctx_destroy(struct net *net)
54{
55 struct tcp_fastopen_context *ctxt;
56
57 spin_lock(&net->ipv4.tcp_fastopen_ctx_lock);
58
59 ctxt = rcu_dereference_protected(net->ipv4.tcp_fastopen_ctx,
60 lockdep_is_held(&net->ipv4.tcp_fastopen_ctx_lock));
61 rcu_assign_pointer(net->ipv4.tcp_fastopen_ctx, NULL);
62 spin_unlock(&net->ipv4.tcp_fastopen_ctx_lock);
63
64 if (ctxt)
65 call_rcu(&ctxt->rcu, tcp_fastopen_ctx_free);
66}
67
Yuchung Cheng1fba70e2017-10-18 11:22:51 -070068int tcp_fastopen_reset_cipher(struct net *net, struct sock *sk,
69 void *key, unsigned int len)
Jerry Chu10467162012-08-31 12:29:11 +000070{
Jerry Chu10467162012-08-31 12:29:11 +000071 struct tcp_fastopen_context *ctx, *octx;
Yuchung Cheng1fba70e2017-10-18 11:22:51 -070072 struct fastopen_queue *q;
73 int err;
Jerry Chu10467162012-08-31 12:29:11 +000074
75 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
76 if (!ctx)
77 return -ENOMEM;
78 ctx->tfm = crypto_alloc_cipher("aes", 0, 0);
79
80 if (IS_ERR(ctx->tfm)) {
81 err = PTR_ERR(ctx->tfm);
82error: kfree(ctx);
83 pr_err("TCP: TFO aes cipher alloc error: %d\n", err);
84 return err;
85 }
86 err = crypto_cipher_setkey(ctx->tfm, key, len);
87 if (err) {
88 pr_err("TCP: TFO cipher key error: %d\n", err);
89 crypto_free_cipher(ctx->tfm);
90 goto error;
91 }
92 memcpy(ctx->key, key, len);
93
Jerry Chu10467162012-08-31 12:29:11 +000094
Yuchung Cheng1fba70e2017-10-18 11:22:51 -070095 if (sk) {
96 q = &inet_csk(sk)->icsk_accept_queue.fastopenq;
97 spin_lock_bh(&q->lock);
98 octx = rcu_dereference_protected(q->ctx,
99 lockdep_is_held(&q->lock));
100 rcu_assign_pointer(q->ctx, ctx);
101 spin_unlock_bh(&q->lock);
102 } else {
103 spin_lock(&net->ipv4.tcp_fastopen_ctx_lock);
104 octx = rcu_dereference_protected(net->ipv4.tcp_fastopen_ctx,
105 lockdep_is_held(&net->ipv4.tcp_fastopen_ctx_lock));
106 rcu_assign_pointer(net->ipv4.tcp_fastopen_ctx, ctx);
107 spin_unlock(&net->ipv4.tcp_fastopen_ctx_lock);
108 }
Jerry Chu10467162012-08-31 12:29:11 +0000109
110 if (octx)
111 call_rcu(&octx->rcu, tcp_fastopen_ctx_free);
112 return err;
113}
114
Yuchung Cheng1fba70e2017-10-18 11:22:51 -0700115static bool __tcp_fastopen_cookie_gen(struct sock *sk, const void *path,
Daniel Lee3a19ce02014-05-11 20:22:13 -0700116 struct tcp_fastopen_cookie *foc)
Jerry Chu10467162012-08-31 12:29:11 +0000117{
Jerry Chu10467162012-08-31 12:29:11 +0000118 struct tcp_fastopen_context *ctx;
Daniel Lee3a19ce02014-05-11 20:22:13 -0700119 bool ok = false;
Jerry Chu10467162012-08-31 12:29:11 +0000120
121 rcu_read_lock();
Yuchung Cheng1fba70e2017-10-18 11:22:51 -0700122
123 ctx = rcu_dereference(inet_csk(sk)->icsk_accept_queue.fastopenq.ctx);
124 if (!ctx)
125 ctx = rcu_dereference(sock_net(sk)->ipv4.tcp_fastopen_ctx);
126
Jerry Chu10467162012-08-31 12:29:11 +0000127 if (ctx) {
Daniel Lee3a19ce02014-05-11 20:22:13 -0700128 crypto_cipher_encrypt_one(ctx->tfm, foc->val, path);
Jerry Chu10467162012-08-31 12:29:11 +0000129 foc->len = TCP_FASTOPEN_COOKIE_SIZE;
Daniel Lee3a19ce02014-05-11 20:22:13 -0700130 ok = true;
Jerry Chu10467162012-08-31 12:29:11 +0000131 }
132 rcu_read_unlock();
Daniel Lee3a19ce02014-05-11 20:22:13 -0700133 return ok;
134}
135
136/* Generate the fastopen cookie by doing aes128 encryption on both
137 * the source and destination addresses. Pad 0s for IPv4 or IPv4-mapped-IPv6
138 * addresses. For the longer IPv6 addresses use CBC-MAC.
139 *
140 * XXX (TFO) - refactor when TCP_FASTOPEN_COOKIE_SIZE != AES_BLOCK_SIZE.
141 */
Yuchung Cheng1fba70e2017-10-18 11:22:51 -0700142static bool tcp_fastopen_cookie_gen(struct sock *sk,
Haishuang Yan43713842017-09-27 11:35:42 +0800143 struct request_sock *req,
Daniel Lee3a19ce02014-05-11 20:22:13 -0700144 struct sk_buff *syn,
145 struct tcp_fastopen_cookie *foc)
146{
147 if (req->rsk_ops->family == AF_INET) {
148 const struct iphdr *iph = ip_hdr(syn);
149
150 __be32 path[4] = { iph->saddr, iph->daddr, 0, 0 };
Yuchung Cheng1fba70e2017-10-18 11:22:51 -0700151 return __tcp_fastopen_cookie_gen(sk, path, foc);
Daniel Lee3a19ce02014-05-11 20:22:13 -0700152 }
153
154#if IS_ENABLED(CONFIG_IPV6)
155 if (req->rsk_ops->family == AF_INET6) {
156 const struct ipv6hdr *ip6h = ipv6_hdr(syn);
157 struct tcp_fastopen_cookie tmp;
158
Yuchung Cheng1fba70e2017-10-18 11:22:51 -0700159 if (__tcp_fastopen_cookie_gen(sk, &ip6h->saddr, &tmp)) {
Shannon Nelson003c9412017-01-12 14:24:58 -0800160 struct in6_addr *buf = &tmp.addr;
Li RongQing41c91992014-09-29 15:04:37 +0800161 int i;
Daniel Lee3a19ce02014-05-11 20:22:13 -0700162
163 for (i = 0; i < 4; i++)
164 buf->s6_addr32[i] ^= ip6h->daddr.s6_addr32[i];
Yuchung Cheng1fba70e2017-10-18 11:22:51 -0700165 return __tcp_fastopen_cookie_gen(sk, buf, foc);
Daniel Lee3a19ce02014-05-11 20:22:13 -0700166 }
167 }
168#endif
169 return false;
Jerry Chu10467162012-08-31 12:29:11 +0000170}
Yuchung Cheng5b7ed082014-05-11 20:22:09 -0700171
Eric Dumazet61d2bca2016-02-01 21:03:07 -0800172
173/* If an incoming SYN or SYNACK frame contains a payload and/or FIN,
174 * queue this additional data / FIN.
175 */
176void tcp_fastopen_add_skb(struct sock *sk, struct sk_buff *skb)
177{
178 struct tcp_sock *tp = tcp_sk(sk);
179
180 if (TCP_SKB_CB(skb)->end_seq == tp->rcv_nxt)
181 return;
182
183 skb = skb_clone(skb, GFP_ATOMIC);
184 if (!skb)
185 return;
186
187 skb_dst_drop(skb);
Martin KaFai Laua44d6ea2016-03-14 10:52:15 -0700188 /* segs_in has been initialized to 1 in tcp_create_openreq_child().
189 * Hence, reset segs_in to 0 before calling tcp_segs_in()
190 * to avoid double counting. Also, tcp_segs_in() expects
191 * skb->len to include the tcp_hdrlen. Hence, it should
192 * be called before __skb_pull().
193 */
194 tp->segs_in = 0;
195 tcp_segs_in(tp, skb);
Eric Dumazet61d2bca2016-02-01 21:03:07 -0800196 __skb_pull(skb, tcp_hdrlen(skb));
Eric Dumazet76061f62016-09-07 08:34:11 -0700197 sk_forced_mem_schedule(sk, skb->truesize);
Eric Dumazet61d2bca2016-02-01 21:03:07 -0800198 skb_set_owner_r(skb, sk);
199
Eric Dumazet9d691532016-02-01 21:03:08 -0800200 TCP_SKB_CB(skb)->seq++;
201 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_SYN;
202
Eric Dumazet61d2bca2016-02-01 21:03:07 -0800203 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
204 __skb_queue_tail(&sk->sk_receive_queue, skb);
205 tp->syn_data_acked = 1;
206
207 /* u64_stats_update_begin(&tp->syncp) not needed here,
208 * as we certainly are not changing upper 32bit value (0)
209 */
210 tp->bytes_received = skb->len;
Eric Dumazete3e17b72016-02-06 11:16:28 -0800211
212 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
213 tcp_fin(sk);
Eric Dumazet61d2bca2016-02-01 21:03:07 -0800214}
215
Eric Dumazet7c85af82015-09-24 17:16:05 -0700216static struct sock *tcp_fastopen_create_child(struct sock *sk,
217 struct sk_buff *skb,
Eric Dumazet7c85af82015-09-24 17:16:05 -0700218 struct request_sock *req)
Yuchung Cheng5b7ed082014-05-11 20:22:09 -0700219{
Dave Jones17846372014-06-16 16:30:36 -0400220 struct tcp_sock *tp;
Yuchung Cheng5b7ed082014-05-11 20:22:09 -0700221 struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
Yuchung Cheng5b7ed082014-05-11 20:22:09 -0700222 struct sock *child;
Eric Dumazet5e0724d2015-10-22 08:20:46 -0700223 bool own_req;
Yuchung Cheng5b7ed082014-05-11 20:22:09 -0700224
225 req->num_retrans = 0;
226 req->num_timeout = 0;
227 req->sk = NULL;
228
Eric Dumazet5e0724d2015-10-22 08:20:46 -0700229 child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL,
230 NULL, &own_req);
Ian Morris51456b22015-04-03 09:17:26 +0100231 if (!child)
Eric Dumazet7c85af82015-09-24 17:16:05 -0700232 return NULL;
Yuchung Cheng5b7ed082014-05-11 20:22:09 -0700233
Eric Dumazet0536fcc2015-09-29 07:42:52 -0700234 spin_lock(&queue->fastopenq.lock);
235 queue->fastopenq.qlen++;
236 spin_unlock(&queue->fastopenq.lock);
Yuchung Cheng5b7ed082014-05-11 20:22:09 -0700237
238 /* Initialize the child socket. Have to fix some values to take
239 * into account the child is a Fast Open socket and is created
240 * only out of the bits carried in the SYN packet.
241 */
242 tp = tcp_sk(child);
243
244 tp->fastopen_rsk = req;
Eric Dumazet9439ce02015-03-17 18:32:29 -0700245 tcp_rsk(req)->tfo_listener = true;
Yuchung Cheng5b7ed082014-05-11 20:22:09 -0700246
247 /* RFC1323: The window in SYN & SYN/ACK segments is never
248 * scaled. So correct it appropriately.
249 */
250 tp->snd_wnd = ntohs(tcp_hdr(skb)->window);
Alexey Kodanev0dbd7ff2017-01-19 16:36:39 +0300251 tp->max_window = tp->snd_wnd;
Yuchung Cheng5b7ed082014-05-11 20:22:09 -0700252
253 /* Activate the retrans timer so that SYNACK can be retransmitted.
Eric Dumazetca6fb062015-10-02 11:43:35 -0700254 * The request socket is not added to the ehash
Yuchung Cheng5b7ed082014-05-11 20:22:09 -0700255 * because it's been added to the accept queue directly.
256 */
257 inet_csk_reset_xmit_timer(child, ICSK_TIME_RETRANS,
258 TCP_TIMEOUT_INIT, TCP_RTO_MAX);
259
Reshetova, Elena41c6d652017-06-30 13:08:01 +0300260 refcount_set(&req->rsk_refcnt, 2);
Yuchung Cheng5b7ed082014-05-11 20:22:09 -0700261
262 /* Now finish processing the fastopen child socket. */
Wei Wang27204aa2017-10-04 10:03:44 -0700263 tcp_init_transfer(child, BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB);
Yuchung Cheng5b7ed082014-05-11 20:22:09 -0700264
Eric Dumazet61d2bca2016-02-01 21:03:07 -0800265 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
Eric Dumazetba34e6d2015-02-13 04:47:12 -0800266
Eric Dumazet61d2bca2016-02-01 21:03:07 -0800267 tcp_fastopen_add_skb(child, skb);
Eric Dumazetd6549762015-05-21 21:51:19 -0700268
Eric Dumazet61d2bca2016-02-01 21:03:07 -0800269 tcp_rsk(req)->rcv_nxt = tp->rcv_nxt;
Neal Cardwell28b346c2016-08-30 11:55:23 -0400270 tp->rcv_wup = tp->rcv_nxt;
Eric Dumazet7656d842015-10-04 21:08:07 -0700271 /* tcp_conn_request() is sending the SYNACK,
272 * and queues the child into listener accept queue.
Eric Dumazet7c85af82015-09-24 17:16:05 -0700273 */
Eric Dumazet7c85af82015-09-24 17:16:05 -0700274 return child;
Yuchung Cheng5b7ed082014-05-11 20:22:09 -0700275}
Yuchung Cheng5b7ed082014-05-11 20:22:09 -0700276
277static bool tcp_fastopen_queue_check(struct sock *sk)
278{
279 struct fastopen_queue *fastopenq;
280
281 /* Make sure the listener has enabled fastopen, and we don't
282 * exceed the max # of pending TFO requests allowed before trying
283 * to validating the cookie in order to avoid burning CPU cycles
284 * unnecessarily.
285 *
286 * XXX (TFO) - The implication of checking the max_qlen before
287 * processing a cookie request is that clients can't differentiate
288 * between qlen overflow causing Fast Open to be disabled
289 * temporarily vs a server not supporting Fast Open at all.
290 */
Eric Dumazet0536fcc2015-09-29 07:42:52 -0700291 fastopenq = &inet_csk(sk)->icsk_accept_queue.fastopenq;
292 if (fastopenq->max_qlen == 0)
Yuchung Cheng5b7ed082014-05-11 20:22:09 -0700293 return false;
294
295 if (fastopenq->qlen >= fastopenq->max_qlen) {
296 struct request_sock *req1;
297 spin_lock(&fastopenq->lock);
298 req1 = fastopenq->rskq_rst_head;
Eric Dumazetfa76ce732015-03-19 19:04:20 -0700299 if (!req1 || time_after(req1->rsk_timer.expires, jiffies)) {
Eric Dumazet02a1d6e2016-04-27 16:44:39 -0700300 __NET_INC_STATS(sock_net(sk),
301 LINUX_MIB_TCPFASTOPENLISTENOVERFLOW);
Eric Dumazetc10d9312016-04-29 14:16:47 -0700302 spin_unlock(&fastopenq->lock);
Yuchung Cheng5b7ed082014-05-11 20:22:09 -0700303 return false;
304 }
305 fastopenq->rskq_rst_head = req1->dl_next;
306 fastopenq->qlen--;
307 spin_unlock(&fastopenq->lock);
Eric Dumazet13854e52015-03-15 21:12:16 -0700308 reqsk_put(req1);
Yuchung Cheng5b7ed082014-05-11 20:22:09 -0700309 }
310 return true;
311}
312
Christoph Paasch71c02372017-10-23 13:22:23 -0700313static bool tcp_fastopen_no_cookie(const struct sock *sk,
314 const struct dst_entry *dst,
315 int flag)
316{
317 return (sock_net(sk)->ipv4.sysctl_tcp_fastopen & flag) ||
318 tcp_sk(sk)->fastopen_no_cookie ||
319 (dst && dst_metric(dst, RTAX_FASTOPEN_NO_COOKIE));
320}
321
Yuchung Cheng89278c92014-05-11 20:22:10 -0700322/* Returns true if we should perform Fast Open on the SYN. The cookie (foc)
323 * may be updated and return the client in the SYN-ACK later. E.g., Fast Open
324 * cookie request (foc->len == 0).
325 */
Eric Dumazet7c85af82015-09-24 17:16:05 -0700326struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
327 struct request_sock *req,
Christoph Paasch71c02372017-10-23 13:22:23 -0700328 struct tcp_fastopen_cookie *foc,
329 const struct dst_entry *dst)
Yuchung Cheng5b7ed082014-05-11 20:22:09 -0700330{
Yuchung Cheng89278c92014-05-11 20:22:10 -0700331 bool syn_data = TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq + 1;
Haishuang Yane1cfcbe2017-09-27 11:35:40 +0800332 int tcp_fastopen = sock_net(sk)->ipv4.sysctl_tcp_fastopen;
333 struct tcp_fastopen_cookie valid_foc = { .len = -1 };
Eric Dumazet7c85af82015-09-24 17:16:05 -0700334 struct sock *child;
Yuchung Cheng5b7ed082014-05-11 20:22:09 -0700335
Yuchung Cheng531c94a2015-02-09 12:35:23 -0800336 if (foc->len == 0) /* Client requests a cookie */
Eric Dumazetc10d9312016-04-29 14:16:47 -0700337 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENCOOKIEREQD);
Yuchung Cheng531c94a2015-02-09 12:35:23 -0800338
Haishuang Yane1cfcbe2017-09-27 11:35:40 +0800339 if (!((tcp_fastopen & TFO_SERVER_ENABLE) &&
Yuchung Cheng89278c92014-05-11 20:22:10 -0700340 (syn_data || foc->len >= 0) &&
341 tcp_fastopen_queue_check(sk))) {
342 foc->len = -1;
Eric Dumazet7c85af82015-09-24 17:16:05 -0700343 return NULL;
Yuchung Cheng89278c92014-05-11 20:22:10 -0700344 }
Yuchung Cheng5b7ed082014-05-11 20:22:09 -0700345
Christoph Paasch71c02372017-10-23 13:22:23 -0700346 if (syn_data &&
347 tcp_fastopen_no_cookie(sk, dst, TFO_SERVER_COOKIE_NOT_REQD))
Yuchung Cheng89278c92014-05-11 20:22:10 -0700348 goto fastopen;
349
Yuchung Cheng531c94a2015-02-09 12:35:23 -0800350 if (foc->len >= 0 && /* Client presents or requests a cookie */
Yuchung Cheng1fba70e2017-10-18 11:22:51 -0700351 tcp_fastopen_cookie_gen(sk, req, skb, &valid_foc) &&
Daniel Lee3a19ce02014-05-11 20:22:13 -0700352 foc->len == TCP_FASTOPEN_COOKIE_SIZE &&
Yuchung Cheng89278c92014-05-11 20:22:10 -0700353 foc->len == valid_foc.len &&
354 !memcmp(foc->val, valid_foc.val, foc->len)) {
Yuchung Cheng843f4a52014-05-11 20:22:11 -0700355 /* Cookie is valid. Create a (full) child socket to accept
356 * the data in SYN before returning a SYN-ACK to ack the
357 * data. If we fail to create the socket, fall back and
358 * ack the ISN only but includes the same cookie.
359 *
360 * Note: Data-less SYN with valid cookie is allowed to send
361 * data in SYN_RECV state.
362 */
Yuchung Cheng89278c92014-05-11 20:22:10 -0700363fastopen:
Tonghao Zhang11199362017-08-21 23:33:49 -0700364 child = tcp_fastopen_create_child(sk, skb, req);
Eric Dumazet7c85af82015-09-24 17:16:05 -0700365 if (child) {
Yuchung Cheng843f4a52014-05-11 20:22:11 -0700366 foc->len = -1;
Eric Dumazetc10d9312016-04-29 14:16:47 -0700367 NET_INC_STATS(sock_net(sk),
368 LINUX_MIB_TCPFASTOPENPASSIVE);
Eric Dumazet7c85af82015-09-24 17:16:05 -0700369 return child;
Yuchung Cheng843f4a52014-05-11 20:22:11 -0700370 }
Eric Dumazetc10d9312016-04-29 14:16:47 -0700371 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
Yuchung Cheng531c94a2015-02-09 12:35:23 -0800372 } else if (foc->len > 0) /* Client presents an invalid cookie */
Eric Dumazetc10d9312016-04-29 14:16:47 -0700373 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
Yuchung Cheng5b7ed082014-05-11 20:22:09 -0700374
Daniel Lee7f9b8382015-04-06 14:37:26 -0700375 valid_foc.exp = foc->exp;
Yuchung Cheng89278c92014-05-11 20:22:10 -0700376 *foc = valid_foc;
Eric Dumazet7c85af82015-09-24 17:16:05 -0700377 return NULL;
Yuchung Cheng5b7ed082014-05-11 20:22:09 -0700378}
Wei Wang065263f2017-01-23 10:59:20 -0800379
380bool tcp_fastopen_cookie_check(struct sock *sk, u16 *mss,
381 struct tcp_fastopen_cookie *cookie)
382{
383 unsigned long last_syn_loss = 0;
Christoph Paasch71c02372017-10-23 13:22:23 -0700384 const struct dst_entry *dst;
Wei Wang065263f2017-01-23 10:59:20 -0800385 int syn_loss = 0;
386
387 tcp_fastopen_cache_get(sk, mss, cookie, &syn_loss, &last_syn_loss);
388
389 /* Recurring FO SYN losses: no cookie or data in SYN */
390 if (syn_loss > 1 &&
391 time_before(jiffies, last_syn_loss + (60*HZ << syn_loss))) {
392 cookie->len = -1;
393 return false;
394 }
Wei Wangcf1ef3f2017-04-20 14:45:46 -0700395
396 /* Firewall blackhole issue check */
397 if (tcp_fastopen_active_should_disable(sk)) {
398 cookie->len = -1;
399 return false;
400 }
401
Christoph Paasch71c02372017-10-23 13:22:23 -0700402 dst = __sk_dst_get(sk);
403
404 if (tcp_fastopen_no_cookie(sk, dst, TFO_CLIENT_NO_COOKIE)) {
Wei Wang065263f2017-01-23 10:59:20 -0800405 cookie->len = -1;
406 return true;
407 }
408 return cookie->len > 0;
409}
Wei Wang19f6d3f2017-01-23 10:59:22 -0800410
411/* This function checks if we want to defer sending SYN until the first
412 * write(). We defer under the following conditions:
413 * 1. fastopen_connect sockopt is set
414 * 2. we have a valid cookie
415 * Return value: return true if we want to defer until application writes data
416 * return false if we want to send out SYN immediately
417 */
418bool tcp_fastopen_defer_connect(struct sock *sk, int *err)
419{
420 struct tcp_fastopen_cookie cookie = { .len = 0 };
421 struct tcp_sock *tp = tcp_sk(sk);
422 u16 mss;
423
424 if (tp->fastopen_connect && !tp->fastopen_req) {
425 if (tcp_fastopen_cookie_check(sk, &mss, &cookie)) {
426 inet_sk(sk)->defer_connect = 1;
427 return true;
428 }
429
430 /* Alloc fastopen_req in order for FO option to be included
431 * in SYN
432 */
433 tp->fastopen_req = kzalloc(sizeof(*tp->fastopen_req),
434 sk->sk_allocation);
435 if (tp->fastopen_req)
436 tp->fastopen_req->cookie = cookie;
437 else
438 *err = -ENOBUFS;
439 }
440 return false;
441}
442EXPORT_SYMBOL(tcp_fastopen_defer_connect);
Wei Wangcf1ef3f2017-04-20 14:45:46 -0700443
444/*
445 * The following code block is to deal with middle box issues with TFO:
446 * Middlebox firewall issues can potentially cause server's data being
447 * blackholed after a successful 3WHS using TFO.
448 * The proposed solution is to disable active TFO globally under the
449 * following circumstances:
450 * 1. client side TFO socket receives out of order FIN
451 * 2. client side TFO socket receives out of order RST
452 * We disable active side TFO globally for 1hr at first. Then if it
453 * happens again, we disable it for 2h, then 4h, 8h, ...
454 * And we reset the timeout back to 1hr when we see a successful active
455 * TFO connection with data exchanges.
456 */
457
Wei Wangcf1ef3f2017-04-20 14:45:46 -0700458/* Disable active TFO and record current jiffies and
459 * tfo_active_disable_times
460 */
Wei Wang46c2fa32017-04-20 14:45:47 -0700461void tcp_fastopen_active_disable(struct sock *sk)
Wei Wangcf1ef3f2017-04-20 14:45:46 -0700462{
Haishuang Yan3733be12017-09-27 11:35:43 +0800463 struct net *net = sock_net(sk);
Wei Wangcf1ef3f2017-04-20 14:45:46 -0700464
Haishuang Yan3733be12017-09-27 11:35:43 +0800465 atomic_inc(&net->ipv4.tfo_active_disable_times);
466 net->ipv4.tfo_active_disable_stamp = jiffies;
467 NET_INC_STATS(net, LINUX_MIB_TCPFASTOPENBLACKHOLE);
Wei Wangcf1ef3f2017-04-20 14:45:46 -0700468}
469
470/* Calculate timeout for tfo active disable
471 * Return true if we are still in the active TFO disable period
472 * Return false if timeout already expired and we should use active TFO
473 */
474bool tcp_fastopen_active_should_disable(struct sock *sk)
475{
Haishuang Yan3733be12017-09-27 11:35:43 +0800476 unsigned int tfo_bh_timeout = sock_net(sk)->ipv4.sysctl_tcp_fastopen_blackhole_timeout;
477 int tfo_da_times = atomic_read(&sock_net(sk)->ipv4.tfo_active_disable_times);
Wei Wangcf1ef3f2017-04-20 14:45:46 -0700478 unsigned long timeout;
Haishuang Yan3733be12017-09-27 11:35:43 +0800479 int multiplier;
Wei Wangcf1ef3f2017-04-20 14:45:46 -0700480
481 if (!tfo_da_times)
482 return false;
483
484 /* Limit timout to max: 2^6 * initial timeout */
485 multiplier = 1 << min(tfo_da_times - 1, 6);
Haishuang Yan3733be12017-09-27 11:35:43 +0800486 timeout = multiplier * tfo_bh_timeout * HZ;
487 if (time_before(jiffies, sock_net(sk)->ipv4.tfo_active_disable_stamp + timeout))
Wei Wangcf1ef3f2017-04-20 14:45:46 -0700488 return true;
489
490 /* Mark check bit so we can check for successful active TFO
491 * condition and reset tfo_active_disable_times
492 */
493 tcp_sk(sk)->syn_fastopen_ch = 1;
494 return false;
495}
496
497/* Disable active TFO if FIN is the only packet in the ofo queue
498 * and no data is received.
499 * Also check if we can reset tfo_active_disable_times if data is
500 * received successfully on a marked active TFO sockets opened on
501 * a non-loopback interface
502 */
503void tcp_fastopen_active_disable_ofo_check(struct sock *sk)
504{
505 struct tcp_sock *tp = tcp_sk(sk);
Wei Wangcf1ef3f2017-04-20 14:45:46 -0700506 struct dst_entry *dst;
Eric Dumazet18a4c0e2017-10-05 22:21:21 -0700507 struct sk_buff *skb;
Wei Wangcf1ef3f2017-04-20 14:45:46 -0700508
509 if (!tp->syn_fastopen)
510 return;
511
512 if (!tp->data_segs_in) {
Eric Dumazet18a4c0e2017-10-05 22:21:21 -0700513 skb = skb_rb_first(&tp->out_of_order_queue);
514 if (skb && !skb_rb_next(skb)) {
Wei Wangcf1ef3f2017-04-20 14:45:46 -0700515 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) {
Wei Wang46c2fa32017-04-20 14:45:47 -0700516 tcp_fastopen_active_disable(sk);
Wei Wangcf1ef3f2017-04-20 14:45:46 -0700517 return;
518 }
519 }
520 } else if (tp->syn_fastopen_ch &&
Haishuang Yan3733be12017-09-27 11:35:43 +0800521 atomic_read(&sock_net(sk)->ipv4.tfo_active_disable_times)) {
Wei Wangcf1ef3f2017-04-20 14:45:46 -0700522 dst = sk_dst_get(sk);
523 if (!(dst && dst->dev && (dst->dev->flags & IFF_LOOPBACK)))
Haishuang Yan3733be12017-09-27 11:35:43 +0800524 atomic_set(&sock_net(sk)->ipv4.tfo_active_disable_times, 0);
Wei Wangcf1ef3f2017-04-20 14:45:46 -0700525 dst_release(dst);
526 }
527}