1 // SPDX-License-Identifier: GPL-2.0
2 /* Multipath TCP
3 *
4 * Copyright (c) 2017 - 2019, Intel Corporation.
5 */
6
7 #define pr_fmt(fmt) "MPTCP: " fmt
8
9 #include <linux/kernel.h>
10 #include <linux/module.h>
11 #include <linux/netdevice.h>
12 #include <crypto/sha2.h>
13 #include <crypto/utils.h>
14 #include <net/sock.h>
15 #include <net/inet_common.h>
16 #include <net/inet_hashtables.h>
17 #include <net/protocol.h>
18 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
19 #include <net/ip6_route.h>
20 #include <net/transp_v6.h>
21 #endif
22 #include <net/mptcp.h>
23
24 #include "protocol.h"
25 #include "mib.h"
26
27 #include <trace/events/mptcp.h>
28 #include <trace/events/sock.h>
29
30 static void mptcp_subflow_ops_undo_override(struct sock *ssk);
31
SUBFLOW_REQ_INC_STATS(struct request_sock * req,enum linux_mptcp_mib_field field)32 static void SUBFLOW_REQ_INC_STATS(struct request_sock *req,
33 enum linux_mptcp_mib_field field)
34 {
35 MPTCP_INC_STATS(sock_net(req_to_sk(req)), field);
36 }
37
subflow_req_destructor(struct request_sock * req)38 static void subflow_req_destructor(struct request_sock *req)
39 {
40 struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
41
42 pr_debug("subflow_req=%p", subflow_req);
43
44 if (subflow_req->msk)
45 sock_put((struct sock *)subflow_req->msk);
46
47 mptcp_token_destroy_request(req);
48 }
49
subflow_generate_hmac(u64 key1,u64 key2,u32 nonce1,u32 nonce2,void * hmac)50 static void subflow_generate_hmac(u64 key1, u64 key2, u32 nonce1, u32 nonce2,
51 void *hmac)
52 {
53 u8 msg[8];
54
55 put_unaligned_be32(nonce1, &msg[0]);
56 put_unaligned_be32(nonce2, &msg[4]);
57
58 mptcp_crypto_hmac_sha(key1, key2, msg, 8, hmac);
59 }
60
mptcp_can_accept_new_subflow(const struct mptcp_sock * msk)61 static bool mptcp_can_accept_new_subflow(const struct mptcp_sock *msk)
62 {
63 return mptcp_is_fully_established((void *)msk) &&
64 ((mptcp_pm_is_userspace(msk) &&
65 mptcp_userspace_pm_active(msk)) ||
66 READ_ONCE(msk->pm.accept_subflow));
67 }
68
69 /* validate received token and create truncated hmac and nonce for SYN-ACK */
subflow_req_create_thmac(struct mptcp_subflow_request_sock * subflow_req)70 static void subflow_req_create_thmac(struct mptcp_subflow_request_sock *subflow_req)
71 {
72 struct mptcp_sock *msk = subflow_req->msk;
73 u8 hmac[SHA256_DIGEST_SIZE];
74
75 get_random_bytes(&subflow_req->local_nonce, sizeof(u32));
76
77 subflow_generate_hmac(READ_ONCE(msk->local_key),
78 READ_ONCE(msk->remote_key),
79 subflow_req->local_nonce,
80 subflow_req->remote_nonce, hmac);
81
82 subflow_req->thmac = get_unaligned_be64(hmac);
83 }
84
subflow_token_join_request(struct request_sock * req)85 static struct mptcp_sock *subflow_token_join_request(struct request_sock *req)
86 {
87 struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
88 struct mptcp_sock *msk;
89 int local_id;
90
91 msk = mptcp_token_get_sock(sock_net(req_to_sk(req)), subflow_req->token);
92 if (!msk) {
93 SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINNOTOKEN);
94 return NULL;
95 }
96
97 local_id = mptcp_pm_get_local_id(msk, (struct sock_common *)req);
98 if (local_id < 0) {
99 sock_put((struct sock *)msk);
100 return NULL;
101 }
102 subflow_req->local_id = local_id;
103
104 return msk;
105 }
106
subflow_init_req(struct request_sock * req,const struct sock * sk_listener)107 static void subflow_init_req(struct request_sock *req, const struct sock *sk_listener)
108 {
109 struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
110
111 subflow_req->mp_capable = 0;
112 subflow_req->mp_join = 0;
113 subflow_req->csum_reqd = mptcp_is_checksum_enabled(sock_net(sk_listener));
114 subflow_req->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk_listener));
115 subflow_req->msk = NULL;
116 mptcp_token_init_request(req);
117 }
118
subflow_use_different_sport(struct mptcp_sock * msk,const struct sock * sk)119 static bool subflow_use_different_sport(struct mptcp_sock *msk, const struct sock *sk)
120 {
121 return inet_sk(sk)->inet_sport != inet_sk((struct sock *)msk)->inet_sport;
122 }
123
subflow_add_reset_reason(struct sk_buff * skb,u8 reason)124 static void subflow_add_reset_reason(struct sk_buff *skb, u8 reason)
125 {
126 struct mptcp_ext *mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
127
128 if (mpext) {
129 memset(mpext, 0, sizeof(*mpext));
130 mpext->reset_reason = reason;
131 }
132 }
133
134 /* Init mptcp request socket.
135 *
136 * Returns an error code if a JOIN has failed and a TCP reset
137 * should be sent.
138 */
subflow_check_req(struct request_sock * req,const struct sock * sk_listener,struct sk_buff * skb)139 static int subflow_check_req(struct request_sock *req,
140 const struct sock *sk_listener,
141 struct sk_buff *skb)
142 {
143 struct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk_listener);
144 struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
145 struct mptcp_options_received mp_opt;
146 bool opt_mp_capable, opt_mp_join;
147
148 pr_debug("subflow_req=%p, listener=%p", subflow_req, listener);
149
150 #ifdef CONFIG_TCP_MD5SIG
151 /* no MPTCP if MD5SIG is enabled on this socket or we may run out of
152 * TCP option space.
153 */
154 if (rcu_access_pointer(tcp_sk(sk_listener)->md5sig_info)) {
155 subflow_add_reset_reason(skb, MPTCP_RST_EMPTCP);
156 return -EINVAL;
157 }
158 #endif
159
160 mptcp_get_options(skb, &mp_opt);
161
162 opt_mp_capable = !!(mp_opt.suboptions & OPTION_MPTCP_MPC_SYN);
163 opt_mp_join = !!(mp_opt.suboptions & OPTION_MPTCP_MPJ_SYN);
164 if (opt_mp_capable) {
165 SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MPCAPABLEPASSIVE);
166
167 if (opt_mp_join)
168 return 0;
169 } else if (opt_mp_join) {
170 SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINSYNRX);
171 }
172
173 if (opt_mp_capable && listener->request_mptcp) {
174 int err, retries = MPTCP_TOKEN_MAX_RETRIES;
175
176 subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq;
177 again:
178 do {
179 get_random_bytes(&subflow_req->local_key, sizeof(subflow_req->local_key));
180 } while (subflow_req->local_key == 0);
181
182 if (unlikely(req->syncookie)) {
183 mptcp_crypto_key_sha(subflow_req->local_key,
184 &subflow_req->token,
185 &subflow_req->idsn);
186 if (mptcp_token_exists(subflow_req->token)) {
187 if (retries-- > 0)
188 goto again;
189 SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_TOKENFALLBACKINIT);
190 } else {
191 subflow_req->mp_capable = 1;
192 }
193 return 0;
194 }
195
196 err = mptcp_token_new_request(req);
197 if (err == 0)
198 subflow_req->mp_capable = 1;
199 else if (retries-- > 0)
200 goto again;
201 else
202 SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_TOKENFALLBACKINIT);
203
204 } else if (opt_mp_join && listener->request_mptcp) {
205 subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq;
206 subflow_req->mp_join = 1;
207 subflow_req->backup = mp_opt.backup;
208 subflow_req->remote_id = mp_opt.join_id;
209 subflow_req->token = mp_opt.token;
210 subflow_req->remote_nonce = mp_opt.nonce;
211 subflow_req->msk = subflow_token_join_request(req);
212
213 /* Can't fall back to TCP in this case. */
214 if (!subflow_req->msk) {
215 subflow_add_reset_reason(skb, MPTCP_RST_EMPTCP);
216 return -EPERM;
217 }
218
219 if (subflow_use_different_sport(subflow_req->msk, sk_listener)) {
220 pr_debug("syn inet_sport=%d %d",
221 ntohs(inet_sk(sk_listener)->inet_sport),
222 ntohs(inet_sk((struct sock *)subflow_req->msk)->inet_sport));
223 if (!mptcp_pm_sport_in_anno_list(subflow_req->msk, sk_listener)) {
224 SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MISMATCHPORTSYNRX);
225 subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);
226 return -EPERM;
227 }
228 SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINPORTSYNRX);
229 }
230
231 subflow_req_create_thmac(subflow_req);
232
233 if (unlikely(req->syncookie)) {
234 if (!mptcp_can_accept_new_subflow(subflow_req->msk)) {
235 subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);
236 return -EPERM;
237 }
238
239 subflow_init_req_cookie_join_save(subflow_req, skb);
240 }
241
242 pr_debug("token=%u, remote_nonce=%u msk=%p", subflow_req->token,
243 subflow_req->remote_nonce, subflow_req->msk);
244 }
245
246 return 0;
247 }
248
mptcp_subflow_init_cookie_req(struct request_sock * req,const struct sock * sk_listener,struct sk_buff * skb)249 int mptcp_subflow_init_cookie_req(struct request_sock *req,
250 const struct sock *sk_listener,
251 struct sk_buff *skb)
252 {
253 struct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk_listener);
254 struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
255 struct mptcp_options_received mp_opt;
256 bool opt_mp_capable, opt_mp_join;
257 int err;
258
259 subflow_init_req(req, sk_listener);
260 mptcp_get_options(skb, &mp_opt);
261
262 opt_mp_capable = !!(mp_opt.suboptions & OPTION_MPTCP_MPC_ACK);
263 opt_mp_join = !!(mp_opt.suboptions & OPTION_MPTCP_MPJ_ACK);
264 if (opt_mp_capable && opt_mp_join)
265 return -EINVAL;
266
267 if (opt_mp_capable && listener->request_mptcp) {
268 if (mp_opt.sndr_key == 0)
269 return -EINVAL;
270
271 subflow_req->local_key = mp_opt.rcvr_key;
272 err = mptcp_token_new_request(req);
273 if (err)
274 return err;
275
276 subflow_req->mp_capable = 1;
277 subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq - 1;
278 } else if (opt_mp_join && listener->request_mptcp) {
279 if (!mptcp_token_join_cookie_init_state(subflow_req, skb))
280 return -EINVAL;
281
282 subflow_req->mp_join = 1;
283 subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq - 1;
284 }
285
286 return 0;
287 }
288 EXPORT_SYMBOL_GPL(mptcp_subflow_init_cookie_req);
289
mptcp_get_rst_reason(const struct sk_buff * skb)290 static enum sk_rst_reason mptcp_get_rst_reason(const struct sk_buff *skb)
291 {
292 const struct mptcp_ext *mpext = mptcp_get_ext(skb);
293
294 if (!mpext)
295 return SK_RST_REASON_NOT_SPECIFIED;
296
297 return sk_rst_convert_mptcp_reason(mpext->reset_reason);
298 }
299
subflow_v4_route_req(const struct sock * sk,struct sk_buff * skb,struct flowi * fl,struct request_sock * req,u32 tw_isn)300 static struct dst_entry *subflow_v4_route_req(const struct sock *sk,
301 struct sk_buff *skb,
302 struct flowi *fl,
303 struct request_sock *req,
304 u32 tw_isn)
305 {
306 struct dst_entry *dst;
307 int err;
308
309 tcp_rsk(req)->is_mptcp = 1;
310 subflow_init_req(req, sk);
311
312 dst = tcp_request_sock_ipv4_ops.route_req(sk, skb, fl, req, tw_isn);
313 if (!dst)
314 return NULL;
315
316 err = subflow_check_req(req, sk, skb);
317 if (err == 0)
318 return dst;
319
320 dst_release(dst);
321 if (!req->syncookie)
322 tcp_request_sock_ops.send_reset(sk, skb,
323 mptcp_get_rst_reason(skb));
324 return NULL;
325 }
326
subflow_prep_synack(const struct sock * sk,struct request_sock * req,struct tcp_fastopen_cookie * foc,enum tcp_synack_type synack_type)327 static void subflow_prep_synack(const struct sock *sk, struct request_sock *req,
328 struct tcp_fastopen_cookie *foc,
329 enum tcp_synack_type synack_type)
330 {
331 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
332 struct inet_request_sock *ireq = inet_rsk(req);
333
334 /* clear tstamp_ok, as needed depending on cookie */
335 if (foc && foc->len > -1)
336 ireq->tstamp_ok = 0;
337
338 if (synack_type == TCP_SYNACK_FASTOPEN)
339 mptcp_fastopen_subflow_synack_set_params(subflow, req);
340 }
341
subflow_v4_send_synack(const struct sock * sk,struct dst_entry * dst,struct flowi * fl,struct request_sock * req,struct tcp_fastopen_cookie * foc,enum tcp_synack_type synack_type,struct sk_buff * syn_skb)342 static int subflow_v4_send_synack(const struct sock *sk, struct dst_entry *dst,
343 struct flowi *fl,
344 struct request_sock *req,
345 struct tcp_fastopen_cookie *foc,
346 enum tcp_synack_type synack_type,
347 struct sk_buff *syn_skb)
348 {
349 subflow_prep_synack(sk, req, foc, synack_type);
350
351 return tcp_request_sock_ipv4_ops.send_synack(sk, dst, fl, req, foc,
352 synack_type, syn_skb);
353 }
354
355 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
subflow_v6_send_synack(const struct sock * sk,struct dst_entry * dst,struct flowi * fl,struct request_sock * req,struct tcp_fastopen_cookie * foc,enum tcp_synack_type synack_type,struct sk_buff * syn_skb)356 static int subflow_v6_send_synack(const struct sock *sk, struct dst_entry *dst,
357 struct flowi *fl,
358 struct request_sock *req,
359 struct tcp_fastopen_cookie *foc,
360 enum tcp_synack_type synack_type,
361 struct sk_buff *syn_skb)
362 {
363 subflow_prep_synack(sk, req, foc, synack_type);
364
365 return tcp_request_sock_ipv6_ops.send_synack(sk, dst, fl, req, foc,
366 synack_type, syn_skb);
367 }
368
subflow_v6_route_req(const struct sock * sk,struct sk_buff * skb,struct flowi * fl,struct request_sock * req,u32 tw_isn)369 static struct dst_entry *subflow_v6_route_req(const struct sock *sk,
370 struct sk_buff *skb,
371 struct flowi *fl,
372 struct request_sock *req,
373 u32 tw_isn)
374 {
375 struct dst_entry *dst;
376 int err;
377
378 tcp_rsk(req)->is_mptcp = 1;
379 subflow_init_req(req, sk);
380
381 dst = tcp_request_sock_ipv6_ops.route_req(sk, skb, fl, req, tw_isn);
382 if (!dst)
383 return NULL;
384
385 err = subflow_check_req(req, sk, skb);
386 if (err == 0)
387 return dst;
388
389 dst_release(dst);
390 if (!req->syncookie)
391 tcp6_request_sock_ops.send_reset(sk, skb,
392 mptcp_get_rst_reason(skb));
393 return NULL;
394 }
395 #endif
396
397 /* validate received truncated hmac and create hmac for third ACK */
subflow_thmac_valid(struct mptcp_subflow_context * subflow)398 static bool subflow_thmac_valid(struct mptcp_subflow_context *subflow)
399 {
400 u8 hmac[SHA256_DIGEST_SIZE];
401 u64 thmac;
402
403 subflow_generate_hmac(subflow->remote_key, subflow->local_key,
404 subflow->remote_nonce, subflow->local_nonce,
405 hmac);
406
407 thmac = get_unaligned_be64(hmac);
408 pr_debug("subflow=%p, token=%u, thmac=%llu, subflow->thmac=%llu\n",
409 subflow, subflow->token, thmac, subflow->thmac);
410
411 return thmac == subflow->thmac;
412 }
413
mptcp_subflow_reset(struct sock * ssk)414 void mptcp_subflow_reset(struct sock *ssk)
415 {
416 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
417 struct sock *sk = subflow->conn;
418
419 /* mptcp_mp_fail_no_response() can reach here on an already closed
420 * socket
421 */
422 if (ssk->sk_state == TCP_CLOSE)
423 return;
424
425 /* must hold: tcp_done() could drop last reference on parent */
426 sock_hold(sk);
427
428 mptcp_send_active_reset_reason(ssk);
429 tcp_done(ssk);
430 if (!test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &mptcp_sk(sk)->flags))
431 mptcp_schedule_work(sk);
432
433 sock_put(sk);
434 }
435
subflow_use_different_dport(struct mptcp_sock * msk,const struct sock * sk)436 static bool subflow_use_different_dport(struct mptcp_sock *msk, const struct sock *sk)
437 {
438 return inet_sk(sk)->inet_dport != inet_sk((struct sock *)msk)->inet_dport;
439 }
440
__mptcp_sync_state(struct sock * sk,int state)441 void __mptcp_sync_state(struct sock *sk, int state)
442 {
443 struct mptcp_subflow_context *subflow;
444 struct mptcp_sock *msk = mptcp_sk(sk);
445 struct sock *ssk = msk->first;
446
447 subflow = mptcp_subflow_ctx(ssk);
448 __mptcp_propagate_sndbuf(sk, ssk);
449 if (!msk->rcvspace_init)
450 mptcp_rcv_space_init(msk, ssk);
451
452 if (sk->sk_state == TCP_SYN_SENT) {
453 /* subflow->idsn is always available is TCP_SYN_SENT state,
454 * even for the FASTOPEN scenarios
455 */
456 WRITE_ONCE(msk->write_seq, subflow->idsn + 1);
457 WRITE_ONCE(msk->snd_nxt, msk->write_seq);
458 mptcp_set_state(sk, state);
459 sk->sk_state_change(sk);
460 }
461 }
462
subflow_set_remote_key(struct mptcp_sock * msk,struct mptcp_subflow_context * subflow,const struct mptcp_options_received * mp_opt)463 static void subflow_set_remote_key(struct mptcp_sock *msk,
464 struct mptcp_subflow_context *subflow,
465 const struct mptcp_options_received *mp_opt)
466 {
467 /* active MPC subflow will reach here multiple times:
468 * at subflow_finish_connect() time and at 4th ack time
469 */
470 if (subflow->remote_key_valid)
471 return;
472
473 subflow->remote_key_valid = 1;
474 subflow->remote_key = mp_opt->sndr_key;
475 mptcp_crypto_key_sha(subflow->remote_key, NULL, &subflow->iasn);
476 subflow->iasn++;
477
478 WRITE_ONCE(msk->remote_key, subflow->remote_key);
479 WRITE_ONCE(msk->ack_seq, subflow->iasn);
480 WRITE_ONCE(msk->can_ack, true);
481 atomic64_set(&msk->rcv_wnd_sent, subflow->iasn);
482 }
483
mptcp_propagate_state(struct sock * sk,struct sock * ssk,struct mptcp_subflow_context * subflow,const struct mptcp_options_received * mp_opt)484 static void mptcp_propagate_state(struct sock *sk, struct sock *ssk,
485 struct mptcp_subflow_context *subflow,
486 const struct mptcp_options_received *mp_opt)
487 {
488 struct mptcp_sock *msk = mptcp_sk(sk);
489
490 mptcp_data_lock(sk);
491 if (mp_opt) {
492 /* Options are available only in the non fallback cases
493 * avoid updating rx path fields otherwise
494 */
495 WRITE_ONCE(msk->snd_una, subflow->idsn + 1);
496 WRITE_ONCE(msk->wnd_end, subflow->idsn + 1 + tcp_sk(ssk)->snd_wnd);
497 subflow_set_remote_key(msk, subflow, mp_opt);
498 }
499
500 if (!sock_owned_by_user(sk)) {
501 __mptcp_sync_state(sk, ssk->sk_state);
502 } else {
503 msk->pending_state = ssk->sk_state;
504 __set_bit(MPTCP_SYNC_STATE, &msk->cb_flags);
505 }
506 mptcp_data_unlock(sk);
507 }
508
subflow_finish_connect(struct sock * sk,const struct sk_buff * skb)509 static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
510 {
511 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
512 struct mptcp_options_received mp_opt;
513 struct sock *parent = subflow->conn;
514 struct mptcp_sock *msk;
515
516 subflow->icsk_af_ops->sk_rx_dst_set(sk, skb);
517
518 /* be sure no special action on any packet other than syn-ack */
519 if (subflow->conn_finished)
520 return;
521
522 msk = mptcp_sk(parent);
523 subflow->rel_write_seq = 1;
524 subflow->conn_finished = 1;
525 subflow->ssn_offset = TCP_SKB_CB(skb)->seq;
526 pr_debug("subflow=%p synack seq=%x", subflow, subflow->ssn_offset);
527
528 mptcp_get_options(skb, &mp_opt);
529 if (subflow->request_mptcp) {
530 if (!(mp_opt.suboptions & OPTION_MPTCP_MPC_SYNACK)) {
531 MPTCP_INC_STATS(sock_net(sk),
532 MPTCP_MIB_MPCAPABLEACTIVEFALLBACK);
533 mptcp_do_fallback(sk);
534 pr_fallback(msk);
535 goto fallback;
536 }
537
538 if (mp_opt.suboptions & OPTION_MPTCP_CSUMREQD)
539 WRITE_ONCE(msk->csum_enabled, true);
540 if (mp_opt.deny_join_id0)
541 WRITE_ONCE(msk->pm.remote_deny_join_id0, true);
542 subflow->mp_capable = 1;
543 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPCAPABLEACTIVEACK);
544 mptcp_finish_connect(sk);
545 mptcp_propagate_state(parent, sk, subflow, &mp_opt);
546 } else if (subflow->request_join) {
547 u8 hmac[SHA256_DIGEST_SIZE];
548
549 if (!(mp_opt.suboptions & OPTION_MPTCP_MPJ_SYNACK)) {
550 subflow->reset_reason = MPTCP_RST_EMPTCP;
551 goto do_reset;
552 }
553
554 subflow->backup = mp_opt.backup;
555 subflow->thmac = mp_opt.thmac;
556 subflow->remote_nonce = mp_opt.nonce;
557 WRITE_ONCE(subflow->remote_id, mp_opt.join_id);
558 pr_debug("subflow=%p, thmac=%llu, remote_nonce=%u backup=%d",
559 subflow, subflow->thmac, subflow->remote_nonce,
560 subflow->backup);
561
562 if (!subflow_thmac_valid(subflow)) {
563 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINACKMAC);
564 subflow->reset_reason = MPTCP_RST_EMPTCP;
565 goto do_reset;
566 }
567
568 if (!mptcp_finish_join(sk))
569 goto do_reset;
570
571 subflow_generate_hmac(subflow->local_key, subflow->remote_key,
572 subflow->local_nonce,
573 subflow->remote_nonce,
574 hmac);
575 memcpy(subflow->hmac, hmac, MPTCPOPT_HMAC_LEN);
576
577 subflow->mp_join = 1;
578 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNACKRX);
579
580 if (subflow_use_different_dport(msk, sk)) {
581 pr_debug("synack inet_dport=%d %d",
582 ntohs(inet_sk(sk)->inet_dport),
583 ntohs(inet_sk(parent)->inet_dport));
584 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINPORTSYNACKRX);
585 }
586 } else if (mptcp_check_fallback(sk)) {
587 fallback:
588 mptcp_propagate_state(parent, sk, subflow, NULL);
589 }
590 return;
591
592 do_reset:
593 subflow->reset_transient = 0;
594 mptcp_subflow_reset(sk);
595 }
596
subflow_set_local_id(struct mptcp_subflow_context * subflow,int local_id)597 static void subflow_set_local_id(struct mptcp_subflow_context *subflow, int local_id)
598 {
599 WARN_ON_ONCE(local_id < 0 || local_id > 255);
600 WRITE_ONCE(subflow->local_id, local_id);
601 }
602
subflow_chk_local_id(struct sock * sk)603 static int subflow_chk_local_id(struct sock *sk)
604 {
605 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
606 struct mptcp_sock *msk = mptcp_sk(subflow->conn);
607 int err;
608
609 if (likely(subflow->local_id >= 0))
610 return 0;
611
612 err = mptcp_pm_get_local_id(msk, (struct sock_common *)sk);
613 if (err < 0)
614 return err;
615
616 subflow_set_local_id(subflow, err);
617 return 0;
618 }
619
subflow_rebuild_header(struct sock * sk)620 static int subflow_rebuild_header(struct sock *sk)
621 {
622 int err = subflow_chk_local_id(sk);
623
624 if (unlikely(err < 0))
625 return err;
626
627 return inet_sk_rebuild_header(sk);
628 }
629
630 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
subflow_v6_rebuild_header(struct sock * sk)631 static int subflow_v6_rebuild_header(struct sock *sk)
632 {
633 int err = subflow_chk_local_id(sk);
634
635 if (unlikely(err < 0))
636 return err;
637
638 return inet6_sk_rebuild_header(sk);
639 }
640 #endif
641
642 static struct request_sock_ops mptcp_subflow_v4_request_sock_ops __ro_after_init;
643 static struct tcp_request_sock_ops subflow_request_sock_ipv4_ops __ro_after_init;
644
subflow_v4_conn_request(struct sock * sk,struct sk_buff * skb)645 static int subflow_v4_conn_request(struct sock *sk, struct sk_buff *skb)
646 {
647 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
648
649 pr_debug("subflow=%p", subflow);
650
651 /* Never answer to SYNs sent to broadcast or multicast */
652 if (skb_rtable(skb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
653 goto drop;
654
655 return tcp_conn_request(&mptcp_subflow_v4_request_sock_ops,
656 &subflow_request_sock_ipv4_ops,
657 sk, skb);
658 drop:
659 tcp_listendrop(sk);
660 return 0;
661 }
662
subflow_v4_req_destructor(struct request_sock * req)663 static void subflow_v4_req_destructor(struct request_sock *req)
664 {
665 subflow_req_destructor(req);
666 tcp_request_sock_ops.destructor(req);
667 }
668
669 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
670 static struct request_sock_ops mptcp_subflow_v6_request_sock_ops __ro_after_init;
671 static struct tcp_request_sock_ops subflow_request_sock_ipv6_ops __ro_after_init;
672 static struct inet_connection_sock_af_ops subflow_v6_specific __ro_after_init;
673 static struct inet_connection_sock_af_ops subflow_v6m_specific __ro_after_init;
674 static struct proto tcpv6_prot_override __ro_after_init;
675
subflow_v6_conn_request(struct sock * sk,struct sk_buff * skb)676 static int subflow_v6_conn_request(struct sock *sk, struct sk_buff *skb)
677 {
678 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
679
680 pr_debug("subflow=%p", subflow);
681
682 if (skb->protocol == htons(ETH_P_IP))
683 return subflow_v4_conn_request(sk, skb);
684
685 if (!ipv6_unicast_destination(skb))
686 goto drop;
687
688 if (ipv6_addr_v4mapped(&ipv6_hdr(skb)->saddr)) {
689 __IP6_INC_STATS(sock_net(sk), NULL, IPSTATS_MIB_INHDRERRORS);
690 return 0;
691 }
692
693 return tcp_conn_request(&mptcp_subflow_v6_request_sock_ops,
694 &subflow_request_sock_ipv6_ops, sk, skb);
695
696 drop:
697 tcp_listendrop(sk);
698 return 0; /* don't send reset */
699 }
700
subflow_v6_req_destructor(struct request_sock * req)701 static void subflow_v6_req_destructor(struct request_sock *req)
702 {
703 subflow_req_destructor(req);
704 tcp6_request_sock_ops.destructor(req);
705 }
706 #endif
707
mptcp_subflow_reqsk_alloc(const struct request_sock_ops * ops,struct sock * sk_listener,bool attach_listener)708 struct request_sock *mptcp_subflow_reqsk_alloc(const struct request_sock_ops *ops,
709 struct sock *sk_listener,
710 bool attach_listener)
711 {
712 if (ops->family == AF_INET)
713 ops = &mptcp_subflow_v4_request_sock_ops;
714 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
715 else if (ops->family == AF_INET6)
716 ops = &mptcp_subflow_v6_request_sock_ops;
717 #endif
718
719 return inet_reqsk_alloc(ops, sk_listener, attach_listener);
720 }
721 EXPORT_SYMBOL(mptcp_subflow_reqsk_alloc);
722
723 /* validate hmac received in third ACK */
subflow_hmac_valid(const struct request_sock * req,const struct mptcp_options_received * mp_opt)724 static bool subflow_hmac_valid(const struct request_sock *req,
725 const struct mptcp_options_received *mp_opt)
726 {
727 const struct mptcp_subflow_request_sock *subflow_req;
728 u8 hmac[SHA256_DIGEST_SIZE];
729 struct mptcp_sock *msk;
730
731 subflow_req = mptcp_subflow_rsk(req);
732 msk = subflow_req->msk;
733 if (!msk)
734 return false;
735
736 subflow_generate_hmac(READ_ONCE(msk->remote_key),
737 READ_ONCE(msk->local_key),
738 subflow_req->remote_nonce,
739 subflow_req->local_nonce, hmac);
740
741 return !crypto_memneq(hmac, mp_opt->hmac, MPTCPOPT_HMAC_LEN);
742 }
743
subflow_ulp_fallback(struct sock * sk,struct mptcp_subflow_context * old_ctx)744 static void subflow_ulp_fallback(struct sock *sk,
745 struct mptcp_subflow_context *old_ctx)
746 {
747 struct inet_connection_sock *icsk = inet_csk(sk);
748
749 mptcp_subflow_tcp_fallback(sk, old_ctx);
750 icsk->icsk_ulp_ops = NULL;
751 rcu_assign_pointer(icsk->icsk_ulp_data, NULL);
752 tcp_sk(sk)->is_mptcp = 0;
753
754 mptcp_subflow_ops_undo_override(sk);
755 }
756
mptcp_subflow_drop_ctx(struct sock * ssk)757 void mptcp_subflow_drop_ctx(struct sock *ssk)
758 {
759 struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(ssk);
760
761 if (!ctx)
762 return;
763
764 list_del(&mptcp_subflow_ctx(ssk)->node);
765 if (inet_csk(ssk)->icsk_ulp_ops) {
766 subflow_ulp_fallback(ssk, ctx);
767 if (ctx->conn)
768 sock_put(ctx->conn);
769 }
770
771 kfree_rcu(ctx, rcu);
772 }
773
__mptcp_subflow_fully_established(struct mptcp_sock * msk,struct mptcp_subflow_context * subflow,const struct mptcp_options_received * mp_opt)774 void __mptcp_subflow_fully_established(struct mptcp_sock *msk,
775 struct mptcp_subflow_context *subflow,
776 const struct mptcp_options_received *mp_opt)
777 {
778 subflow_set_remote_key(msk, subflow, mp_opt);
779 subflow->fully_established = 1;
780 WRITE_ONCE(msk->fully_established, true);
781
782 if (subflow->is_mptfo)
783 __mptcp_fastopen_gen_msk_ackseq(msk, subflow, mp_opt);
784 }
785
subflow_syn_recv_sock(const struct sock * sk,struct sk_buff * skb,struct request_sock * req,struct dst_entry * dst,struct request_sock * req_unhash,bool * own_req)786 static struct sock *subflow_syn_recv_sock(const struct sock *sk,
787 struct sk_buff *skb,
788 struct request_sock *req,
789 struct dst_entry *dst,
790 struct request_sock *req_unhash,
791 bool *own_req)
792 {
793 struct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk);
794 struct mptcp_subflow_request_sock *subflow_req;
795 struct mptcp_options_received mp_opt;
796 bool fallback, fallback_is_fatal;
797 enum sk_rst_reason reason;
798 struct mptcp_sock *owner;
799 struct sock *child;
800
801 pr_debug("listener=%p, req=%p, conn=%p", listener, req, listener->conn);
802
803 /* After child creation we must look for MPC even when options
804 * are not parsed
805 */
806 mp_opt.suboptions = 0;
807
808 /* hopefully temporary handling for MP_JOIN+syncookie */
809 subflow_req = mptcp_subflow_rsk(req);
810 fallback_is_fatal = tcp_rsk(req)->is_mptcp && subflow_req->mp_join;
811 fallback = !tcp_rsk(req)->is_mptcp;
812 if (fallback)
813 goto create_child;
814
815 /* if the sk is MP_CAPABLE, we try to fetch the client key */
816 if (subflow_req->mp_capable) {
817 /* we can receive and accept an in-window, out-of-order pkt,
818 * which may not carry the MP_CAPABLE opt even on mptcp enabled
819 * paths: always try to extract the peer key, and fallback
820 * for packets missing it.
821 * Even OoO DSS packets coming legitly after dropped or
822 * reordered MPC will cause fallback, but we don't have other
823 * options.
824 */
825 mptcp_get_options(skb, &mp_opt);
826 if (!(mp_opt.suboptions &
827 (OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_ACK)))
828 fallback = true;
829
830 } else if (subflow_req->mp_join) {
831 mptcp_get_options(skb, &mp_opt);
832 if (!(mp_opt.suboptions & OPTION_MPTCP_MPJ_ACK) ||
833 !subflow_hmac_valid(req, &mp_opt) ||
834 !mptcp_can_accept_new_subflow(subflow_req->msk)) {
835 SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINACKMAC);
836 fallback = true;
837 }
838 }
839
840 create_child:
841 child = listener->icsk_af_ops->syn_recv_sock(sk, skb, req, dst,
842 req_unhash, own_req);
843
844 if (child && *own_req) {
845 struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(child);
846
847 tcp_rsk(req)->drop_req = false;
848
849 /* we need to fallback on ctx allocation failure and on pre-reqs
850 * checking above. In the latter scenario we additionally need
851 * to reset the context to non MPTCP status.
852 */
853 if (!ctx || fallback) {
854 if (fallback_is_fatal) {
855 subflow_add_reset_reason(skb, MPTCP_RST_EMPTCP);
856 goto dispose_child;
857 }
858 goto fallback;
859 }
860
861 /* ssk inherits options of listener sk */
862 ctx->setsockopt_seq = listener->setsockopt_seq;
863
864 if (ctx->mp_capable) {
865 ctx->conn = mptcp_sk_clone_init(listener->conn, &mp_opt, child, req);
866 if (!ctx->conn)
867 goto fallback;
868
869 ctx->subflow_id = 1;
870 owner = mptcp_sk(ctx->conn);
871 mptcp_pm_new_connection(owner, child, 1);
872
873 /* with OoO packets we can reach here without ingress
874 * mpc option
875 */
876 if (mp_opt.suboptions & OPTION_MPTCP_MPC_ACK) {
877 mptcp_pm_fully_established(owner, child);
878 ctx->pm_notified = 1;
879 }
880 } else if (ctx->mp_join) {
881 owner = subflow_req->msk;
882 if (!owner) {
883 subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);
884 goto dispose_child;
885 }
886
887 /* move the msk reference ownership to the subflow */
888 subflow_req->msk = NULL;
889 ctx->conn = (struct sock *)owner;
890
891 if (subflow_use_different_sport(owner, sk)) {
892 pr_debug("ack inet_sport=%d %d",
893 ntohs(inet_sk(sk)->inet_sport),
894 ntohs(inet_sk((struct sock *)owner)->inet_sport));
895 if (!mptcp_pm_sport_in_anno_list(owner, sk)) {
896 SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MISMATCHPORTACKRX);
897 subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);
898 goto dispose_child;
899 }
900 SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINPORTACKRX);
901 }
902
903 if (!mptcp_finish_join(child)) {
904 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(child);
905
906 subflow_add_reset_reason(skb, subflow->reset_reason);
907 goto dispose_child;
908 }
909
910 SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINACKRX);
911 tcp_rsk(req)->drop_req = true;
912 }
913 }
914
915 /* check for expected invariant - should never trigger, just help
916 * catching earlier subtle bugs
917 */
918 WARN_ON_ONCE(child && *own_req && tcp_sk(child)->is_mptcp &&
919 (!mptcp_subflow_ctx(child) ||
920 !mptcp_subflow_ctx(child)->conn));
921 return child;
922
923 dispose_child:
924 mptcp_subflow_drop_ctx(child);
925 tcp_rsk(req)->drop_req = true;
926 inet_csk_prepare_for_destroy_sock(child);
927 tcp_done(child);
928 reason = mptcp_get_rst_reason(skb);
929 req->rsk_ops->send_reset(sk, skb, reason);
930
931 /* The last child reference will be released by the caller */
932 return child;
933
934 fallback:
935 if (fallback)
936 SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK);
937 mptcp_subflow_drop_ctx(child);
938 return child;
939 }
940
941 static struct inet_connection_sock_af_ops subflow_specific __ro_after_init;
942 static struct proto tcp_prot_override __ro_after_init;
943
944 enum mapping_status {
945 MAPPING_OK,
946 MAPPING_INVALID,
947 MAPPING_EMPTY,
948 MAPPING_DATA_FIN,
949 MAPPING_DUMMY,
950 MAPPING_BAD_CSUM
951 };
952
dbg_bad_map(struct mptcp_subflow_context * subflow,u32 ssn)953 static void dbg_bad_map(struct mptcp_subflow_context *subflow, u32 ssn)
954 {
955 pr_debug("Bad mapping: ssn=%d map_seq=%d map_data_len=%d",
956 ssn, subflow->map_subflow_seq, subflow->map_data_len);
957 }
958
skb_is_fully_mapped(struct sock * ssk,struct sk_buff * skb)959 static bool skb_is_fully_mapped(struct sock *ssk, struct sk_buff *skb)
960 {
961 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
962 unsigned int skb_consumed;
963
964 skb_consumed = tcp_sk(ssk)->copied_seq - TCP_SKB_CB(skb)->seq;
965 if (WARN_ON_ONCE(skb_consumed >= skb->len))
966 return true;
967
968 return skb->len - skb_consumed <= subflow->map_data_len -
969 mptcp_subflow_get_map_offset(subflow);
970 }
971
validate_mapping(struct sock * ssk,struct sk_buff * skb)972 static bool validate_mapping(struct sock *ssk, struct sk_buff *skb)
973 {
974 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
975 u32 ssn = tcp_sk(ssk)->copied_seq - subflow->ssn_offset;
976
977 if (unlikely(before(ssn, subflow->map_subflow_seq))) {
978 /* Mapping covers data later in the subflow stream,
979 * currently unsupported.
980 */
981 dbg_bad_map(subflow, ssn);
982 return false;
983 }
984 if (unlikely(!before(ssn, subflow->map_subflow_seq +
985 subflow->map_data_len))) {
986 /* Mapping does covers past subflow data, invalid */
987 dbg_bad_map(subflow, ssn);
988 return false;
989 }
990 return true;
991 }
992
validate_data_csum(struct sock * ssk,struct sk_buff * skb,bool csum_reqd)993 static enum mapping_status validate_data_csum(struct sock *ssk, struct sk_buff *skb,
994 bool csum_reqd)
995 {
996 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
997 u32 offset, seq, delta;
998 __sum16 csum;
999 int len;
1000
1001 if (!csum_reqd)
1002 return MAPPING_OK;
1003
1004 /* mapping already validated on previous traversal */
1005 if (subflow->map_csum_len == subflow->map_data_len)
1006 return MAPPING_OK;
1007
1008 /* traverse the receive queue, ensuring it contains a full
1009 * DSS mapping and accumulating the related csum.
1010 * Preserve the accoumlate csum across multiple calls, to compute
1011 * the csum only once
1012 */
1013 delta = subflow->map_data_len - subflow->map_csum_len;
1014 for (;;) {
1015 seq = tcp_sk(ssk)->copied_seq + subflow->map_csum_len;
1016 offset = seq - TCP_SKB_CB(skb)->seq;
1017
1018 /* if the current skb has not been accounted yet, csum its contents
1019 * up to the amount covered by the current DSS
1020 */
1021 if (offset < skb->len) {
1022 __wsum csum;
1023
1024 len = min(skb->len - offset, delta);
1025 csum = skb_checksum(skb, offset, len, 0);
1026 subflow->map_data_csum = csum_block_add(subflow->map_data_csum, csum,
1027 subflow->map_csum_len);
1028
1029 delta -= len;
1030 subflow->map_csum_len += len;
1031 }
1032 if (delta == 0)
1033 break;
1034
1035 if (skb_queue_is_last(&ssk->sk_receive_queue, skb)) {
1036 /* if this subflow is closed, the partial mapping
1037 * will be never completed; flush the pending skbs, so
1038 * that subflow_sched_work_if_closed() can kick in
1039 */
1040 if (unlikely(ssk->sk_state == TCP_CLOSE))
1041 while ((skb = skb_peek(&ssk->sk_receive_queue)))
1042 sk_eat_skb(ssk, skb);
1043
1044 /* not enough data to validate the csum */
1045 return MAPPING_EMPTY;
1046 }
1047
1048 /* the DSS mapping for next skbs will be validated later,
1049 * when a get_mapping_status call will process such skb
1050 */
1051 skb = skb->next;
1052 }
1053
1054 /* note that 'map_data_len' accounts only for the carried data, does
1055 * not include the eventual seq increment due to the data fin,
1056 * while the pseudo header requires the original DSS data len,
1057 * including that
1058 */
1059 csum = __mptcp_make_csum(subflow->map_seq,
1060 subflow->map_subflow_seq,
1061 subflow->map_data_len + subflow->map_data_fin,
1062 subflow->map_data_csum);
1063 if (unlikely(csum)) {
1064 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DATACSUMERR);
1065 return MAPPING_BAD_CSUM;
1066 }
1067
1068 subflow->valid_csum_seen = 1;
1069 return MAPPING_OK;
1070 }
1071
get_mapping_status(struct sock * ssk,struct mptcp_sock * msk)1072 static enum mapping_status get_mapping_status(struct sock *ssk,
1073 struct mptcp_sock *msk)
1074 {
1075 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
1076 bool csum_reqd = READ_ONCE(msk->csum_enabled);
1077 struct mptcp_ext *mpext;
1078 struct sk_buff *skb;
1079 u16 data_len;
1080 u64 map_seq;
1081
1082 skb = skb_peek(&ssk->sk_receive_queue);
1083 if (!skb)
1084 return MAPPING_EMPTY;
1085
1086 if (mptcp_check_fallback(ssk))
1087 return MAPPING_DUMMY;
1088
1089 mpext = mptcp_get_ext(skb);
1090 if (!mpext || !mpext->use_map) {
1091 if (!subflow->map_valid && !skb->len) {
1092 /* the TCP stack deliver 0 len FIN pkt to the receive
1093 * queue, that is the only 0len pkts ever expected here,
1094 * and we can admit no mapping only for 0 len pkts
1095 */
1096 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN))
1097 WARN_ONCE(1, "0len seq %d:%d flags %x",
1098 TCP_SKB_CB(skb)->seq,
1099 TCP_SKB_CB(skb)->end_seq,
1100 TCP_SKB_CB(skb)->tcp_flags);
1101 sk_eat_skb(ssk, skb);
1102 return MAPPING_EMPTY;
1103 }
1104
1105 if (!subflow->map_valid)
1106 return MAPPING_INVALID;
1107
1108 goto validate_seq;
1109 }
1110
1111 trace_get_mapping_status(mpext);
1112
1113 data_len = mpext->data_len;
1114 if (data_len == 0) {
1115 pr_debug("infinite mapping received");
1116 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_INFINITEMAPRX);
1117 subflow->map_data_len = 0;
1118 return MAPPING_INVALID;
1119 }
1120
1121 if (mpext->data_fin == 1) {
1122 u64 data_fin_seq;
1123
1124 if (data_len == 1) {
1125 bool updated = mptcp_update_rcv_data_fin(msk, mpext->data_seq,
1126 mpext->dsn64);
1127 pr_debug("DATA_FIN with no payload seq=%llu", mpext->data_seq);
1128 if (subflow->map_valid) {
1129 /* A DATA_FIN might arrive in a DSS
1130 * option before the previous mapping
1131 * has been fully consumed. Continue
1132 * handling the existing mapping.
1133 */
1134 skb_ext_del(skb, SKB_EXT_MPTCP);
1135 return MAPPING_OK;
1136 }
1137
1138 if (updated)
1139 mptcp_schedule_work((struct sock *)msk);
1140
1141 return MAPPING_DATA_FIN;
1142 }
1143
1144 data_fin_seq = mpext->data_seq + data_len - 1;
1145
1146 /* If mpext->data_seq is a 32-bit value, data_fin_seq must also
1147 * be limited to 32 bits.
1148 */
1149 if (!mpext->dsn64)
1150 data_fin_seq &= GENMASK_ULL(31, 0);
1151
1152 mptcp_update_rcv_data_fin(msk, data_fin_seq, mpext->dsn64);
1153 pr_debug("DATA_FIN with mapping seq=%llu dsn64=%d",
1154 data_fin_seq, mpext->dsn64);
1155
1156 /* Adjust for DATA_FIN using 1 byte of sequence space */
1157 data_len--;
1158 }
1159
1160 map_seq = mptcp_expand_seq(READ_ONCE(msk->ack_seq), mpext->data_seq, mpext->dsn64);
1161 WRITE_ONCE(mptcp_sk(subflow->conn)->use_64bit_ack, !!mpext->dsn64);
1162
1163 if (subflow->map_valid) {
1164 /* Allow replacing only with an identical map */
1165 if (subflow->map_seq == map_seq &&
1166 subflow->map_subflow_seq == mpext->subflow_seq &&
1167 subflow->map_data_len == data_len &&
1168 subflow->map_csum_reqd == mpext->csum_reqd) {
1169 skb_ext_del(skb, SKB_EXT_MPTCP);
1170 goto validate_csum;
1171 }
1172
1173 /* If this skb data are fully covered by the current mapping,
1174 * the new map would need caching, which is not supported
1175 */
1176 if (skb_is_fully_mapped(ssk, skb)) {
1177 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DSSNOMATCH);
1178 return MAPPING_INVALID;
1179 }
1180
1181 /* will validate the next map after consuming the current one */
1182 goto validate_csum;
1183 }
1184
1185 subflow->map_seq = map_seq;
1186 subflow->map_subflow_seq = mpext->subflow_seq;
1187 subflow->map_data_len = data_len;
1188 subflow->map_valid = 1;
1189 subflow->map_data_fin = mpext->data_fin;
1190 subflow->mpc_map = mpext->mpc_map;
1191 subflow->map_csum_reqd = mpext->csum_reqd;
1192 subflow->map_csum_len = 0;
1193 subflow->map_data_csum = csum_unfold(mpext->csum);
1194
1195 /* Cfr RFC 8684 Section 3.3.0 */
1196 if (unlikely(subflow->map_csum_reqd != csum_reqd))
1197 return MAPPING_INVALID;
1198
1199 pr_debug("new map seq=%llu subflow_seq=%u data_len=%u csum=%d:%u",
1200 subflow->map_seq, subflow->map_subflow_seq,
1201 subflow->map_data_len, subflow->map_csum_reqd,
1202 subflow->map_data_csum);
1203
1204 validate_seq:
1205 /* we revalidate valid mapping on new skb, because we must ensure
1206 * the current skb is completely covered by the available mapping
1207 */
1208 if (!validate_mapping(ssk, skb)) {
1209 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DSSTCPMISMATCH);
1210 return MAPPING_INVALID;
1211 }
1212
1213 skb_ext_del(skb, SKB_EXT_MPTCP);
1214
1215 validate_csum:
1216 return validate_data_csum(ssk, skb, csum_reqd);
1217 }
1218
mptcp_subflow_discard_data(struct sock * ssk,struct sk_buff * skb,u64 limit)1219 static void mptcp_subflow_discard_data(struct sock *ssk, struct sk_buff *skb,
1220 u64 limit)
1221 {
1222 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
1223 bool fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN;
1224 u32 incr;
1225
1226 incr = limit >= skb->len ? skb->len + fin : limit;
1227
1228 pr_debug("discarding=%d len=%d seq=%d", incr, skb->len,
1229 subflow->map_subflow_seq);
1230 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DUPDATA);
1231 tcp_sk(ssk)->copied_seq += incr;
1232 if (!before(tcp_sk(ssk)->copied_seq, TCP_SKB_CB(skb)->end_seq))
1233 sk_eat_skb(ssk, skb);
1234 if (mptcp_subflow_get_map_offset(subflow) >= subflow->map_data_len)
1235 subflow->map_valid = 0;
1236 }
1237
1238 /* sched mptcp worker to remove the subflow if no more data is pending */
subflow_sched_work_if_closed(struct mptcp_sock * msk,struct sock * ssk)1239 static void subflow_sched_work_if_closed(struct mptcp_sock *msk, struct sock *ssk)
1240 {
1241 if (likely(ssk->sk_state != TCP_CLOSE))
1242 return;
1243
1244 if (skb_queue_empty(&ssk->sk_receive_queue) &&
1245 !test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &msk->flags))
1246 mptcp_schedule_work((struct sock *)msk);
1247 }
1248
subflow_can_fallback(struct mptcp_subflow_context * subflow)1249 static bool subflow_can_fallback(struct mptcp_subflow_context *subflow)
1250 {
1251 struct mptcp_sock *msk = mptcp_sk(subflow->conn);
1252
1253 if (subflow->mp_join)
1254 return false;
1255 else if (READ_ONCE(msk->csum_enabled))
1256 return !subflow->valid_csum_seen;
1257 else
1258 return !subflow->fully_established;
1259 }
1260
mptcp_subflow_fail(struct mptcp_sock * msk,struct sock * ssk)1261 static void mptcp_subflow_fail(struct mptcp_sock *msk, struct sock *ssk)
1262 {
1263 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
1264 unsigned long fail_tout;
1265
1266 /* graceful failure can happen only on the MPC subflow */
1267 if (WARN_ON_ONCE(ssk != READ_ONCE(msk->first)))
1268 return;
1269
1270 /* since the close timeout take precedence on the fail one,
1271 * no need to start the latter when the first is already set
1272 */
1273 if (sock_flag((struct sock *)msk, SOCK_DEAD))
1274 return;
1275
1276 /* we don't need extreme accuracy here, use a zero fail_tout as special
1277 * value meaning no fail timeout at all;
1278 */
1279 fail_tout = jiffies + TCP_RTO_MAX;
1280 if (!fail_tout)
1281 fail_tout = 1;
1282 WRITE_ONCE(subflow->fail_tout, fail_tout);
1283 tcp_send_ack(ssk);
1284
1285 mptcp_reset_tout_timer(msk, subflow->fail_tout);
1286 }
1287
subflow_check_data_avail(struct sock * ssk)1288 static bool subflow_check_data_avail(struct sock *ssk)
1289 {
1290 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
1291 enum mapping_status status;
1292 struct mptcp_sock *msk;
1293 struct sk_buff *skb;
1294
1295 if (!skb_peek(&ssk->sk_receive_queue))
1296 WRITE_ONCE(subflow->data_avail, false);
1297 if (subflow->data_avail)
1298 return true;
1299
1300 msk = mptcp_sk(subflow->conn);
1301 for (;;) {
1302 u64 ack_seq;
1303 u64 old_ack;
1304
1305 status = get_mapping_status(ssk, msk);
1306 trace_subflow_check_data_avail(status, skb_peek(&ssk->sk_receive_queue));
1307 if (unlikely(status == MAPPING_INVALID || status == MAPPING_DUMMY ||
1308 status == MAPPING_BAD_CSUM))
1309 goto fallback;
1310
1311 if (status != MAPPING_OK)
1312 goto no_data;
1313
1314 skb = skb_peek(&ssk->sk_receive_queue);
1315 if (WARN_ON_ONCE(!skb))
1316 goto no_data;
1317
1318 if (unlikely(!READ_ONCE(msk->can_ack)))
1319 goto fallback;
1320
1321 old_ack = READ_ONCE(msk->ack_seq);
1322 ack_seq = mptcp_subflow_get_mapped_dsn(subflow);
1323 pr_debug("msk ack_seq=%llx subflow ack_seq=%llx", old_ack,
1324 ack_seq);
1325 if (unlikely(before64(ack_seq, old_ack))) {
1326 mptcp_subflow_discard_data(ssk, skb, old_ack - ack_seq);
1327 continue;
1328 }
1329
1330 WRITE_ONCE(subflow->data_avail, true);
1331 break;
1332 }
1333 return true;
1334
1335 no_data:
1336 subflow_sched_work_if_closed(msk, ssk);
1337 return false;
1338
1339 fallback:
1340 if (!__mptcp_check_fallback(msk)) {
1341 /* RFC 8684 section 3.7. */
1342 if (status == MAPPING_BAD_CSUM &&
1343 (subflow->mp_join || subflow->valid_csum_seen)) {
1344 subflow->send_mp_fail = 1;
1345
1346 if (!READ_ONCE(msk->allow_infinite_fallback)) {
1347 subflow->reset_transient = 0;
1348 subflow->reset_reason = MPTCP_RST_EMIDDLEBOX;
1349 goto reset;
1350 }
1351 mptcp_subflow_fail(msk, ssk);
1352 WRITE_ONCE(subflow->data_avail, true);
1353 return true;
1354 }
1355
1356 if (!subflow_can_fallback(subflow) && subflow->map_data_len) {
1357 /* fatal protocol error, close the socket.
1358 * subflow_error_report() will introduce the appropriate barriers
1359 */
1360 subflow->reset_transient = 0;
1361 subflow->reset_reason = MPTCP_RST_EMPTCP;
1362
1363 reset:
1364 WRITE_ONCE(ssk->sk_err, EBADMSG);
1365 tcp_set_state(ssk, TCP_CLOSE);
1366 while ((skb = skb_peek(&ssk->sk_receive_queue)))
1367 sk_eat_skb(ssk, skb);
1368 mptcp_send_active_reset_reason(ssk);
1369 WRITE_ONCE(subflow->data_avail, false);
1370 return false;
1371 }
1372
1373 mptcp_do_fallback(ssk);
1374 }
1375
1376 skb = skb_peek(&ssk->sk_receive_queue);
1377 subflow->map_valid = 1;
1378 subflow->map_seq = READ_ONCE(msk->ack_seq);
1379 subflow->map_data_len = skb->len;
1380 subflow->map_subflow_seq = tcp_sk(ssk)->copied_seq - subflow->ssn_offset;
1381 WRITE_ONCE(subflow->data_avail, true);
1382 return true;
1383 }
1384
mptcp_subflow_data_available(struct sock * sk)1385 bool mptcp_subflow_data_available(struct sock *sk)
1386 {
1387 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1388
1389 /* check if current mapping is still valid */
1390 if (subflow->map_valid &&
1391 mptcp_subflow_get_map_offset(subflow) >= subflow->map_data_len) {
1392 subflow->map_valid = 0;
1393 WRITE_ONCE(subflow->data_avail, false);
1394
1395 pr_debug("Done with mapping: seq=%u data_len=%u",
1396 subflow->map_subflow_seq,
1397 subflow->map_data_len);
1398 }
1399
1400 return subflow_check_data_avail(sk);
1401 }
1402
1403 /* If ssk has an mptcp parent socket, use the mptcp rcvbuf occupancy,
1404 * not the ssk one.
1405 *
1406 * In mptcp, rwin is about the mptcp-level connection data.
1407 *
1408 * Data that is still on the ssk rx queue can thus be ignored,
1409 * as far as mptcp peer is concerned that data is still inflight.
1410 * DSS ACK is updated when skb is moved to the mptcp rx queue.
1411 */
mptcp_space(const struct sock * ssk,int * space,int * full_space)1412 void mptcp_space(const struct sock *ssk, int *space, int *full_space)
1413 {
1414 const struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
1415 const struct sock *sk = subflow->conn;
1416
1417 *space = __mptcp_space(sk);
1418 *full_space = mptcp_win_from_space(sk, READ_ONCE(sk->sk_rcvbuf));
1419 }
1420
subflow_error_report(struct sock * ssk)1421 static void subflow_error_report(struct sock *ssk)
1422 {
1423 struct sock *sk = mptcp_subflow_ctx(ssk)->conn;
1424
1425 /* bail early if this is a no-op, so that we avoid introducing a
1426 * problematic lockdep dependency between TCP accept queue lock
1427 * and msk socket spinlock
1428 */
1429 if (!sk->sk_socket)
1430 return;
1431
1432 mptcp_data_lock(sk);
1433 if (!sock_owned_by_user(sk))
1434 __mptcp_error_report(sk);
1435 else
1436 __set_bit(MPTCP_ERROR_REPORT, &mptcp_sk(sk)->cb_flags);
1437 mptcp_data_unlock(sk);
1438 }
1439
subflow_data_ready(struct sock * sk)1440 static void subflow_data_ready(struct sock *sk)
1441 {
1442 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1443 u16 state = 1 << inet_sk_state_load(sk);
1444 struct sock *parent = subflow->conn;
1445 struct mptcp_sock *msk;
1446
1447 trace_sk_data_ready(sk);
1448
1449 msk = mptcp_sk(parent);
1450 if (state & TCPF_LISTEN) {
1451 /* MPJ subflow are removed from accept queue before reaching here,
1452 * avoid stray wakeups
1453 */
1454 if (reqsk_queue_empty(&inet_csk(sk)->icsk_accept_queue))
1455 return;
1456
1457 parent->sk_data_ready(parent);
1458 return;
1459 }
1460
1461 WARN_ON_ONCE(!__mptcp_check_fallback(msk) && !subflow->mp_capable &&
1462 !subflow->mp_join && !(state & TCPF_CLOSE));
1463
1464 if (mptcp_subflow_data_available(sk)) {
1465 mptcp_data_ready(parent, sk);
1466
1467 /* subflow-level lowat test are not relevant.
1468 * respect the msk-level threshold eventually mandating an immediate ack
1469 */
1470 if (mptcp_data_avail(msk) < parent->sk_rcvlowat &&
1471 (tcp_sk(sk)->rcv_nxt - tcp_sk(sk)->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss)
1472 inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_NOW;
1473 } else if (unlikely(sk->sk_err)) {
1474 subflow_error_report(sk);
1475 }
1476 }
1477
subflow_write_space(struct sock * ssk)1478 static void subflow_write_space(struct sock *ssk)
1479 {
1480 struct sock *sk = mptcp_subflow_ctx(ssk)->conn;
1481
1482 mptcp_propagate_sndbuf(sk, ssk);
1483 mptcp_write_space(sk);
1484 }
1485
1486 static const struct inet_connection_sock_af_ops *
subflow_default_af_ops(struct sock * sk)1487 subflow_default_af_ops(struct sock *sk)
1488 {
1489 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1490 if (sk->sk_family == AF_INET6)
1491 return &subflow_v6_specific;
1492 #endif
1493 return &subflow_specific;
1494 }
1495
1496 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
mptcpv6_handle_mapped(struct sock * sk,bool mapped)1497 void mptcpv6_handle_mapped(struct sock *sk, bool mapped)
1498 {
1499 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1500 struct inet_connection_sock *icsk = inet_csk(sk);
1501 const struct inet_connection_sock_af_ops *target;
1502
1503 target = mapped ? &subflow_v6m_specific : subflow_default_af_ops(sk);
1504
1505 pr_debug("subflow=%p family=%d ops=%p target=%p mapped=%d",
1506 subflow, sk->sk_family, icsk->icsk_af_ops, target, mapped);
1507
1508 if (likely(icsk->icsk_af_ops == target))
1509 return;
1510
1511 subflow->icsk_af_ops = icsk->icsk_af_ops;
1512 icsk->icsk_af_ops = target;
1513 }
1514 #endif
1515
mptcp_info2sockaddr(const struct mptcp_addr_info * info,struct sockaddr_storage * addr,unsigned short family)1516 void mptcp_info2sockaddr(const struct mptcp_addr_info *info,
1517 struct sockaddr_storage *addr,
1518 unsigned short family)
1519 {
1520 memset(addr, 0, sizeof(*addr));
1521 addr->ss_family = family;
1522 if (addr->ss_family == AF_INET) {
1523 struct sockaddr_in *in_addr = (struct sockaddr_in *)addr;
1524
1525 if (info->family == AF_INET)
1526 in_addr->sin_addr = info->addr;
1527 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1528 else if (ipv6_addr_v4mapped(&info->addr6))
1529 in_addr->sin_addr.s_addr = info->addr6.s6_addr32[3];
1530 #endif
1531 in_addr->sin_port = info->port;
1532 }
1533 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1534 else if (addr->ss_family == AF_INET6) {
1535 struct sockaddr_in6 *in6_addr = (struct sockaddr_in6 *)addr;
1536
1537 if (info->family == AF_INET)
1538 ipv6_addr_set_v4mapped(info->addr.s_addr,
1539 &in6_addr->sin6_addr);
1540 else
1541 in6_addr->sin6_addr = info->addr6;
1542 in6_addr->sin6_port = info->port;
1543 }
1544 #endif
1545 }
1546
__mptcp_subflow_connect(struct sock * sk,const struct mptcp_addr_info * loc,const struct mptcp_addr_info * remote)1547 int __mptcp_subflow_connect(struct sock *sk, const struct mptcp_addr_info *loc,
1548 const struct mptcp_addr_info *remote)
1549 {
1550 struct mptcp_sock *msk = mptcp_sk(sk);
1551 struct mptcp_subflow_context *subflow;
1552 struct sockaddr_storage addr;
1553 int remote_id = remote->id;
1554 int local_id = loc->id;
1555 int err = -ENOTCONN;
1556 struct socket *sf;
1557 struct sock *ssk;
1558 u32 remote_token;
1559 int addrlen;
1560 int ifindex;
1561 u8 flags;
1562
1563 if (!mptcp_is_fully_established(sk))
1564 goto err_out;
1565
1566 err = mptcp_subflow_create_socket(sk, loc->family, &sf);
1567 if (err)
1568 goto err_out;
1569
1570 ssk = sf->sk;
1571 subflow = mptcp_subflow_ctx(ssk);
1572 do {
1573 get_random_bytes(&subflow->local_nonce, sizeof(u32));
1574 } while (!subflow->local_nonce);
1575
1576 if (local_id)
1577 subflow_set_local_id(subflow, local_id);
1578
1579 mptcp_pm_get_flags_and_ifindex_by_id(msk, local_id,
1580 &flags, &ifindex);
1581 subflow->remote_key_valid = 1;
1582 subflow->remote_key = READ_ONCE(msk->remote_key);
1583 subflow->local_key = READ_ONCE(msk->local_key);
1584 subflow->token = msk->token;
1585 mptcp_info2sockaddr(loc, &addr, ssk->sk_family);
1586
1587 addrlen = sizeof(struct sockaddr_in);
1588 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1589 if (addr.ss_family == AF_INET6)
1590 addrlen = sizeof(struct sockaddr_in6);
1591 #endif
1592 ssk->sk_bound_dev_if = ifindex;
1593 err = kernel_bind(sf, (struct sockaddr *)&addr, addrlen);
1594 if (err)
1595 goto failed;
1596
1597 mptcp_crypto_key_sha(subflow->remote_key, &remote_token, NULL);
1598 pr_debug("msk=%p remote_token=%u local_id=%d remote_id=%d", msk,
1599 remote_token, local_id, remote_id);
1600 subflow->remote_token = remote_token;
1601 WRITE_ONCE(subflow->remote_id, remote_id);
1602 subflow->request_join = 1;
1603 subflow->request_bkup = !!(flags & MPTCP_PM_ADDR_FLAG_BACKUP);
1604 subflow->subflow_id = msk->subflow_id++;
1605 mptcp_info2sockaddr(remote, &addr, ssk->sk_family);
1606
1607 sock_hold(ssk);
1608 list_add_tail(&subflow->node, &msk->conn_list);
1609 err = kernel_connect(sf, (struct sockaddr *)&addr, addrlen, O_NONBLOCK);
1610 if (err && err != -EINPROGRESS)
1611 goto failed_unlink;
1612
1613 /* discard the subflow socket */
1614 mptcp_sock_graft(ssk, sk->sk_socket);
1615 iput(SOCK_INODE(sf));
1616 WRITE_ONCE(msk->allow_infinite_fallback, false);
1617 mptcp_stop_tout_timer(sk);
1618 return 0;
1619
1620 failed_unlink:
1621 list_del(&subflow->node);
1622 sock_put(mptcp_subflow_tcp_sock(subflow));
1623
1624 failed:
1625 subflow->disposable = 1;
1626 sock_release(sf);
1627
1628 err_out:
1629 /* we account subflows before the creation, and this failures will not
1630 * be caught by sk_state_change()
1631 */
1632 mptcp_pm_close_subflow(msk);
1633 return err;
1634 }
1635
mptcp_attach_cgroup(struct sock * parent,struct sock * child)1636 static void mptcp_attach_cgroup(struct sock *parent, struct sock *child)
1637 {
1638 #ifdef CONFIG_SOCK_CGROUP_DATA
1639 struct sock_cgroup_data *parent_skcd = &parent->sk_cgrp_data,
1640 *child_skcd = &child->sk_cgrp_data;
1641
1642 /* only the additional subflows created by kworkers have to be modified */
1643 if (cgroup_id(sock_cgroup_ptr(parent_skcd)) !=
1644 cgroup_id(sock_cgroup_ptr(child_skcd))) {
1645 #ifdef CONFIG_MEMCG
1646 struct mem_cgroup *memcg = parent->sk_memcg;
1647
1648 mem_cgroup_sk_free(child);
1649 if (memcg && css_tryget(&memcg->css))
1650 child->sk_memcg = memcg;
1651 #endif /* CONFIG_MEMCG */
1652
1653 cgroup_sk_free(child_skcd);
1654 *child_skcd = *parent_skcd;
1655 cgroup_sk_clone(child_skcd);
1656 }
1657 #endif /* CONFIG_SOCK_CGROUP_DATA */
1658 }
1659
mptcp_subflow_ops_override(struct sock * ssk)1660 static void mptcp_subflow_ops_override(struct sock *ssk)
1661 {
1662 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1663 if (ssk->sk_prot == &tcpv6_prot)
1664 ssk->sk_prot = &tcpv6_prot_override;
1665 else
1666 #endif
1667 ssk->sk_prot = &tcp_prot_override;
1668 }
1669
mptcp_subflow_ops_undo_override(struct sock * ssk)1670 static void mptcp_subflow_ops_undo_override(struct sock *ssk)
1671 {
1672 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1673 if (ssk->sk_prot == &tcpv6_prot_override)
1674 ssk->sk_prot = &tcpv6_prot;
1675 else
1676 #endif
1677 ssk->sk_prot = &tcp_prot;
1678 }
1679
mptcp_subflow_create_socket(struct sock * sk,unsigned short family,struct socket ** new_sock)1680 int mptcp_subflow_create_socket(struct sock *sk, unsigned short family,
1681 struct socket **new_sock)
1682 {
1683 struct mptcp_subflow_context *subflow;
1684 struct net *net = sock_net(sk);
1685 struct socket *sf;
1686 int err;
1687
1688 /* un-accepted server sockets can reach here - on bad configuration
1689 * bail early to avoid greater trouble later
1690 */
1691 if (unlikely(!sk->sk_socket))
1692 return -EINVAL;
1693
1694 err = sock_create_kern(net, family, SOCK_STREAM, IPPROTO_TCP, &sf);
1695 if (err)
1696 return err;
1697
1698 lock_sock_nested(sf->sk, SINGLE_DEPTH_NESTING);
1699
1700 err = security_mptcp_add_subflow(sk, sf->sk);
1701 if (err)
1702 goto err_free;
1703
1704 /* the newly created socket has to be in the same cgroup as its parent */
1705 mptcp_attach_cgroup(sk, sf->sk);
1706
1707 /* kernel sockets do not by default acquire net ref, but TCP timer
1708 * needs it.
1709 * Update ns_tracker to current stack trace and refcounted tracker.
1710 */
1711 __netns_tracker_free(net, &sf->sk->ns_tracker, false);
1712 sf->sk->sk_net_refcnt = 1;
1713 get_net_track(net, &sf->sk->ns_tracker, GFP_KERNEL);
1714 sock_inuse_add(net, 1);
1715 err = tcp_set_ulp(sf->sk, "mptcp");
1716 if (err)
1717 goto err_free;
1718
1719 mptcp_sockopt_sync_locked(mptcp_sk(sk), sf->sk);
1720 release_sock(sf->sk);
1721
1722 /* the newly created socket really belongs to the owning MPTCP master
1723 * socket, even if for additional subflows the allocation is performed
1724 * by a kernel workqueue. Adjust inode references, so that the
1725 * procfs/diag interfaces really show this one belonging to the correct
1726 * user.
1727 */
1728 SOCK_INODE(sf)->i_ino = SOCK_INODE(sk->sk_socket)->i_ino;
1729 SOCK_INODE(sf)->i_uid = SOCK_INODE(sk->sk_socket)->i_uid;
1730 SOCK_INODE(sf)->i_gid = SOCK_INODE(sk->sk_socket)->i_gid;
1731
1732 subflow = mptcp_subflow_ctx(sf->sk);
1733 pr_debug("subflow=%p", subflow);
1734
1735 *new_sock = sf;
1736 sock_hold(sk);
1737 subflow->conn = sk;
1738 mptcp_subflow_ops_override(sf->sk);
1739
1740 return 0;
1741
1742 err_free:
1743 release_sock(sf->sk);
1744 sock_release(sf);
1745 return err;
1746 }
1747
subflow_create_ctx(struct sock * sk,gfp_t priority)1748 static struct mptcp_subflow_context *subflow_create_ctx(struct sock *sk,
1749 gfp_t priority)
1750 {
1751 struct inet_connection_sock *icsk = inet_csk(sk);
1752 struct mptcp_subflow_context *ctx;
1753
1754 ctx = kzalloc(sizeof(*ctx), priority);
1755 if (!ctx)
1756 return NULL;
1757
1758 rcu_assign_pointer(icsk->icsk_ulp_data, ctx);
1759 INIT_LIST_HEAD(&ctx->node);
1760 INIT_LIST_HEAD(&ctx->delegated_node);
1761
1762 pr_debug("subflow=%p", ctx);
1763
1764 ctx->tcp_sock = sk;
1765 WRITE_ONCE(ctx->local_id, -1);
1766
1767 return ctx;
1768 }
1769
__subflow_state_change(struct sock * sk)1770 static void __subflow_state_change(struct sock *sk)
1771 {
1772 struct socket_wq *wq;
1773
1774 rcu_read_lock();
1775 wq = rcu_dereference(sk->sk_wq);
1776 if (skwq_has_sleeper(wq))
1777 wake_up_interruptible_all(&wq->wait);
1778 rcu_read_unlock();
1779 }
1780
subflow_is_done(const struct sock * sk)1781 static bool subflow_is_done(const struct sock *sk)
1782 {
1783 return sk->sk_shutdown & RCV_SHUTDOWN || sk->sk_state == TCP_CLOSE;
1784 }
1785
subflow_state_change(struct sock * sk)1786 static void subflow_state_change(struct sock *sk)
1787 {
1788 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1789 struct sock *parent = subflow->conn;
1790 struct mptcp_sock *msk;
1791
1792 __subflow_state_change(sk);
1793
1794 msk = mptcp_sk(parent);
1795 if (subflow_simultaneous_connect(sk)) {
1796 mptcp_do_fallback(sk);
1797 pr_fallback(msk);
1798 subflow->conn_finished = 1;
1799 mptcp_propagate_state(parent, sk, subflow, NULL);
1800 }
1801
1802 /* as recvmsg() does not acquire the subflow socket for ssk selection
1803 * a fin packet carrying a DSS can be unnoticed if we don't trigger
1804 * the data available machinery here.
1805 */
1806 if (mptcp_subflow_data_available(sk))
1807 mptcp_data_ready(parent, sk);
1808 else if (unlikely(sk->sk_err))
1809 subflow_error_report(sk);
1810
1811 subflow_sched_work_if_closed(mptcp_sk(parent), sk);
1812
1813 /* when the fallback subflow closes the rx side, trigger a 'dummy'
1814 * ingress data fin, so that the msk state will follow along
1815 */
1816 if (__mptcp_check_fallback(msk) && subflow_is_done(sk) && msk->first == sk &&
1817 mptcp_update_rcv_data_fin(msk, READ_ONCE(msk->ack_seq), true))
1818 mptcp_schedule_work(parent);
1819 }
1820
mptcp_subflow_queue_clean(struct sock * listener_sk,struct sock * listener_ssk)1821 void mptcp_subflow_queue_clean(struct sock *listener_sk, struct sock *listener_ssk)
1822 {
1823 struct request_sock_queue *queue = &inet_csk(listener_ssk)->icsk_accept_queue;
1824 struct request_sock *req, *head, *tail;
1825 struct mptcp_subflow_context *subflow;
1826 struct sock *sk, *ssk;
1827
1828 /* Due to lock dependencies no relevant lock can be acquired under rskq_lock.
1829 * Splice the req list, so that accept() can not reach the pending ssk after
1830 * the listener socket is released below.
1831 */
1832 spin_lock_bh(&queue->rskq_lock);
1833 head = queue->rskq_accept_head;
1834 tail = queue->rskq_accept_tail;
1835 queue->rskq_accept_head = NULL;
1836 queue->rskq_accept_tail = NULL;
1837 spin_unlock_bh(&queue->rskq_lock);
1838
1839 if (!head)
1840 return;
1841
1842 /* can't acquire the msk socket lock under the subflow one,
1843 * or will cause ABBA deadlock
1844 */
1845 release_sock(listener_ssk);
1846
1847 for (req = head; req; req = req->dl_next) {
1848 ssk = req->sk;
1849 if (!sk_is_mptcp(ssk))
1850 continue;
1851
1852 subflow = mptcp_subflow_ctx(ssk);
1853 if (!subflow || !subflow->conn)
1854 continue;
1855
1856 sk = subflow->conn;
1857 sock_hold(sk);
1858
1859 lock_sock_nested(sk, SINGLE_DEPTH_NESTING);
1860 __mptcp_unaccepted_force_close(sk);
1861 release_sock(sk);
1862
1863 /* lockdep will report a false positive ABBA deadlock
1864 * between cancel_work_sync and the listener socket.
1865 * The involved locks belong to different sockets WRT
1866 * the existing AB chain.
1867 * Using a per socket key is problematic as key
1868 * deregistration requires process context and must be
1869 * performed at socket disposal time, in atomic
1870 * context.
1871 * Just tell lockdep to consider the listener socket
1872 * released here.
1873 */
1874 mutex_release(&listener_sk->sk_lock.dep_map, _RET_IP_);
1875 mptcp_cancel_work(sk);
1876 mutex_acquire(&listener_sk->sk_lock.dep_map, 0, 0, _RET_IP_);
1877
1878 sock_put(sk);
1879 }
1880
1881 /* we are still under the listener msk socket lock */
1882 lock_sock_nested(listener_ssk, SINGLE_DEPTH_NESTING);
1883
1884 /* restore the listener queue, to let the TCP code clean it up */
1885 spin_lock_bh(&queue->rskq_lock);
1886 WARN_ON_ONCE(queue->rskq_accept_head);
1887 queue->rskq_accept_head = head;
1888 queue->rskq_accept_tail = tail;
1889 spin_unlock_bh(&queue->rskq_lock);
1890 }
1891
subflow_ulp_init(struct sock * sk)1892 static int subflow_ulp_init(struct sock *sk)
1893 {
1894 struct inet_connection_sock *icsk = inet_csk(sk);
1895 struct mptcp_subflow_context *ctx;
1896 struct tcp_sock *tp = tcp_sk(sk);
1897 int err = 0;
1898
1899 /* disallow attaching ULP to a socket unless it has been
1900 * created with sock_create_kern()
1901 */
1902 if (!sk->sk_kern_sock) {
1903 err = -EOPNOTSUPP;
1904 goto out;
1905 }
1906
1907 ctx = subflow_create_ctx(sk, GFP_KERNEL);
1908 if (!ctx) {
1909 err = -ENOMEM;
1910 goto out;
1911 }
1912
1913 pr_debug("subflow=%p, family=%d", ctx, sk->sk_family);
1914
1915 tp->is_mptcp = 1;
1916 ctx->icsk_af_ops = icsk->icsk_af_ops;
1917 icsk->icsk_af_ops = subflow_default_af_ops(sk);
1918 ctx->tcp_state_change = sk->sk_state_change;
1919 ctx->tcp_error_report = sk->sk_error_report;
1920
1921 WARN_ON_ONCE(sk->sk_data_ready != sock_def_readable);
1922 WARN_ON_ONCE(sk->sk_write_space != sk_stream_write_space);
1923
1924 sk->sk_data_ready = subflow_data_ready;
1925 sk->sk_write_space = subflow_write_space;
1926 sk->sk_state_change = subflow_state_change;
1927 sk->sk_error_report = subflow_error_report;
1928 out:
1929 return err;
1930 }
1931
subflow_ulp_release(struct sock * ssk)1932 static void subflow_ulp_release(struct sock *ssk)
1933 {
1934 struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(ssk);
1935 bool release = true;
1936 struct sock *sk;
1937
1938 if (!ctx)
1939 return;
1940
1941 sk = ctx->conn;
1942 if (sk) {
1943 /* if the msk has been orphaned, keep the ctx
1944 * alive, will be freed by __mptcp_close_ssk(),
1945 * when the subflow is still unaccepted
1946 */
1947 release = ctx->disposable || list_empty(&ctx->node);
1948
1949 /* inet_child_forget() does not call sk_state_change(),
1950 * explicitly trigger the socket close machinery
1951 */
1952 if (!release && !test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW,
1953 &mptcp_sk(sk)->flags))
1954 mptcp_schedule_work(sk);
1955 sock_put(sk);
1956 }
1957
1958 mptcp_subflow_ops_undo_override(ssk);
1959 if (release)
1960 kfree_rcu(ctx, rcu);
1961 }
1962
subflow_ulp_clone(const struct request_sock * req,struct sock * newsk,const gfp_t priority)1963 static void subflow_ulp_clone(const struct request_sock *req,
1964 struct sock *newsk,
1965 const gfp_t priority)
1966 {
1967 struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
1968 struct mptcp_subflow_context *old_ctx = mptcp_subflow_ctx(newsk);
1969 struct mptcp_subflow_context *new_ctx;
1970
1971 if (!tcp_rsk(req)->is_mptcp ||
1972 (!subflow_req->mp_capable && !subflow_req->mp_join)) {
1973 subflow_ulp_fallback(newsk, old_ctx);
1974 return;
1975 }
1976
1977 new_ctx = subflow_create_ctx(newsk, priority);
1978 if (!new_ctx) {
1979 subflow_ulp_fallback(newsk, old_ctx);
1980 return;
1981 }
1982
1983 new_ctx->conn_finished = 1;
1984 new_ctx->icsk_af_ops = old_ctx->icsk_af_ops;
1985 new_ctx->tcp_state_change = old_ctx->tcp_state_change;
1986 new_ctx->tcp_error_report = old_ctx->tcp_error_report;
1987 new_ctx->rel_write_seq = 1;
1988 new_ctx->tcp_sock = newsk;
1989
1990 if (subflow_req->mp_capable) {
1991 /* see comments in subflow_syn_recv_sock(), MPTCP connection
1992 * is fully established only after we receive the remote key
1993 */
1994 new_ctx->mp_capable = 1;
1995 new_ctx->local_key = subflow_req->local_key;
1996 new_ctx->token = subflow_req->token;
1997 new_ctx->ssn_offset = subflow_req->ssn_offset;
1998 new_ctx->idsn = subflow_req->idsn;
1999
2000 /* this is the first subflow, id is always 0 */
2001 subflow_set_local_id(new_ctx, 0);
2002 } else if (subflow_req->mp_join) {
2003 new_ctx->ssn_offset = subflow_req->ssn_offset;
2004 new_ctx->mp_join = 1;
2005 new_ctx->fully_established = 1;
2006 new_ctx->remote_key_valid = 1;
2007 new_ctx->backup = subflow_req->backup;
2008 WRITE_ONCE(new_ctx->remote_id, subflow_req->remote_id);
2009 new_ctx->token = subflow_req->token;
2010 new_ctx->thmac = subflow_req->thmac;
2011
2012 /* the subflow req id is valid, fetched via subflow_check_req()
2013 * and subflow_token_join_request()
2014 */
2015 subflow_set_local_id(new_ctx, subflow_req->local_id);
2016 }
2017 }
2018
tcp_release_cb_override(struct sock * ssk)2019 static void tcp_release_cb_override(struct sock *ssk)
2020 {
2021 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
2022 long status;
2023
2024 /* process and clear all the pending actions, but leave the subflow into
2025 * the napi queue. To respect locking, only the same CPU that originated
2026 * the action can touch the list. mptcp_napi_poll will take care of it.
2027 */
2028 status = set_mask_bits(&subflow->delegated_status, MPTCP_DELEGATE_ACTIONS_MASK, 0);
2029 if (status)
2030 mptcp_subflow_process_delegated(ssk, status);
2031
2032 tcp_release_cb(ssk);
2033 }
2034
tcp_abort_override(struct sock * ssk,int err)2035 static int tcp_abort_override(struct sock *ssk, int err)
2036 {
2037 /* closing a listener subflow requires a great deal of care.
2038 * keep it simple and just prevent such operation
2039 */
2040 if (inet_sk_state_load(ssk) == TCP_LISTEN)
2041 return -EINVAL;
2042
2043 return tcp_abort(ssk, err);
2044 }
2045
2046 static struct tcp_ulp_ops subflow_ulp_ops __read_mostly = {
2047 .name = "mptcp",
2048 .owner = THIS_MODULE,
2049 .init = subflow_ulp_init,
2050 .release = subflow_ulp_release,
2051 .clone = subflow_ulp_clone,
2052 };
2053
subflow_ops_init(struct request_sock_ops * subflow_ops)2054 static int subflow_ops_init(struct request_sock_ops *subflow_ops)
2055 {
2056 subflow_ops->obj_size = sizeof(struct mptcp_subflow_request_sock);
2057
2058 subflow_ops->slab = kmem_cache_create(subflow_ops->slab_name,
2059 subflow_ops->obj_size, 0,
2060 SLAB_ACCOUNT |
2061 SLAB_TYPESAFE_BY_RCU,
2062 NULL);
2063 if (!subflow_ops->slab)
2064 return -ENOMEM;
2065
2066 return 0;
2067 }
2068
mptcp_subflow_init(void)2069 void __init mptcp_subflow_init(void)
2070 {
2071 mptcp_subflow_v4_request_sock_ops = tcp_request_sock_ops;
2072 mptcp_subflow_v4_request_sock_ops.slab_name = "request_sock_subflow_v4";
2073 mptcp_subflow_v4_request_sock_ops.destructor = subflow_v4_req_destructor;
2074
2075 if (subflow_ops_init(&mptcp_subflow_v4_request_sock_ops) != 0)
2076 panic("MPTCP: failed to init subflow v4 request sock ops\n");
2077
2078 subflow_request_sock_ipv4_ops = tcp_request_sock_ipv4_ops;
2079 subflow_request_sock_ipv4_ops.route_req = subflow_v4_route_req;
2080 subflow_request_sock_ipv4_ops.send_synack = subflow_v4_send_synack;
2081
2082 subflow_specific = ipv4_specific;
2083 subflow_specific.conn_request = subflow_v4_conn_request;
2084 subflow_specific.syn_recv_sock = subflow_syn_recv_sock;
2085 subflow_specific.sk_rx_dst_set = subflow_finish_connect;
2086 subflow_specific.rebuild_header = subflow_rebuild_header;
2087
2088 tcp_prot_override = tcp_prot;
2089 tcp_prot_override.release_cb = tcp_release_cb_override;
2090 tcp_prot_override.diag_destroy = tcp_abort_override;
2091
2092 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
2093 /* In struct mptcp_subflow_request_sock, we assume the TCP request sock
2094 * structures for v4 and v6 have the same size. It should not changed in
2095 * the future but better to make sure to be warned if it is no longer
2096 * the case.
2097 */
2098 BUILD_BUG_ON(sizeof(struct tcp_request_sock) != sizeof(struct tcp6_request_sock));
2099
2100 mptcp_subflow_v6_request_sock_ops = tcp6_request_sock_ops;
2101 mptcp_subflow_v6_request_sock_ops.slab_name = "request_sock_subflow_v6";
2102 mptcp_subflow_v6_request_sock_ops.destructor = subflow_v6_req_destructor;
2103
2104 if (subflow_ops_init(&mptcp_subflow_v6_request_sock_ops) != 0)
2105 panic("MPTCP: failed to init subflow v6 request sock ops\n");
2106
2107 subflow_request_sock_ipv6_ops = tcp_request_sock_ipv6_ops;
2108 subflow_request_sock_ipv6_ops.route_req = subflow_v6_route_req;
2109 subflow_request_sock_ipv6_ops.send_synack = subflow_v6_send_synack;
2110
2111 subflow_v6_specific = ipv6_specific;
2112 subflow_v6_specific.conn_request = subflow_v6_conn_request;
2113 subflow_v6_specific.syn_recv_sock = subflow_syn_recv_sock;
2114 subflow_v6_specific.sk_rx_dst_set = subflow_finish_connect;
2115 subflow_v6_specific.rebuild_header = subflow_v6_rebuild_header;
2116
2117 subflow_v6m_specific = subflow_v6_specific;
2118 subflow_v6m_specific.queue_xmit = ipv4_specific.queue_xmit;
2119 subflow_v6m_specific.send_check = ipv4_specific.send_check;
2120 subflow_v6m_specific.net_header_len = ipv4_specific.net_header_len;
2121 subflow_v6m_specific.mtu_reduced = ipv4_specific.mtu_reduced;
2122 subflow_v6m_specific.rebuild_header = subflow_rebuild_header;
2123
2124 tcpv6_prot_override = tcpv6_prot;
2125 tcpv6_prot_override.release_cb = tcp_release_cb_override;
2126 tcpv6_prot_override.diag_destroy = tcp_abort_override;
2127 #endif
2128
2129 mptcp_diag_subflow_init(&subflow_ulp_ops);
2130
2131 if (tcp_register_ulp(&subflow_ulp_ops) != 0)
2132 panic("MPTCP: failed to register subflows to ULP\n");
2133 }
2134