xref: /linux/net/mptcp/subflow.c (revision 1e15510b71c99c6e49134d756df91069f7d18141)
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\n", 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 	subflow_req->request_bkup = mptcp_pm_is_backup(msk, (struct sock_common *)req);
104 
105 	return msk;
106 }
107 
subflow_init_req(struct request_sock * req,const struct sock * sk_listener)108 static void subflow_init_req(struct request_sock *req, const struct sock *sk_listener)
109 {
110 	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
111 
112 	subflow_req->mp_capable = 0;
113 	subflow_req->mp_join = 0;
114 	subflow_req->csum_reqd = mptcp_is_checksum_enabled(sock_net(sk_listener));
115 	subflow_req->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk_listener));
116 	subflow_req->msk = NULL;
117 	mptcp_token_init_request(req);
118 }
119 
subflow_use_different_sport(struct mptcp_sock * msk,const struct sock * sk)120 static bool subflow_use_different_sport(struct mptcp_sock *msk, const struct sock *sk)
121 {
122 	return inet_sk(sk)->inet_sport != inet_sk((struct sock *)msk)->inet_sport;
123 }
124 
subflow_add_reset_reason(struct sk_buff * skb,u8 reason)125 static void subflow_add_reset_reason(struct sk_buff *skb, u8 reason)
126 {
127 	struct mptcp_ext *mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
128 
129 	if (mpext) {
130 		memset(mpext, 0, sizeof(*mpext));
131 		mpext->reset_reason = reason;
132 	}
133 }
134 
subflow_reset_req_endp(struct request_sock * req,struct sk_buff * skb)135 static int subflow_reset_req_endp(struct request_sock *req, struct sk_buff *skb)
136 {
137 	SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MPCAPABLEENDPATTEMPT);
138 	subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);
139 	return -EPERM;
140 }
141 
142 /* Init mptcp request socket.
143  *
144  * Returns an error code if a JOIN has failed and a TCP reset
145  * should be sent.
146  */
subflow_check_req(struct request_sock * req,const struct sock * sk_listener,struct sk_buff * skb)147 static int subflow_check_req(struct request_sock *req,
148 			     const struct sock *sk_listener,
149 			     struct sk_buff *skb)
150 {
151 	struct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk_listener);
152 	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
153 	struct mptcp_options_received mp_opt;
154 	bool opt_mp_capable, opt_mp_join;
155 
156 	pr_debug("subflow_req=%p, listener=%p\n", subflow_req, listener);
157 
158 #ifdef CONFIG_TCP_MD5SIG
159 	/* no MPTCP if MD5SIG is enabled on this socket or we may run out of
160 	 * TCP option space.
161 	 */
162 	if (rcu_access_pointer(tcp_sk(sk_listener)->md5sig_info)) {
163 		subflow_add_reset_reason(skb, MPTCP_RST_EMPTCP);
164 		return -EINVAL;
165 	}
166 #endif
167 
168 	mptcp_get_options(skb, &mp_opt);
169 
170 	opt_mp_capable = !!(mp_opt.suboptions & OPTION_MPTCP_MPC_SYN);
171 	opt_mp_join = !!(mp_opt.suboptions & OPTION_MPTCP_MPJ_SYN);
172 	if (opt_mp_capable) {
173 		SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MPCAPABLEPASSIVE);
174 
175 		if (unlikely(listener->pm_listener))
176 			return subflow_reset_req_endp(req, skb);
177 		if (opt_mp_join)
178 			return 0;
179 	} else if (opt_mp_join) {
180 		SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINSYNRX);
181 
182 		if (mp_opt.backup)
183 			SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINSYNBACKUPRX);
184 	} else if (unlikely(listener->pm_listener)) {
185 		return subflow_reset_req_endp(req, skb);
186 	}
187 
188 	if (opt_mp_capable && listener->request_mptcp) {
189 		int err, retries = MPTCP_TOKEN_MAX_RETRIES;
190 
191 		subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq;
192 again:
193 		do {
194 			get_random_bytes(&subflow_req->local_key, sizeof(subflow_req->local_key));
195 		} while (subflow_req->local_key == 0);
196 
197 		if (unlikely(req->syncookie)) {
198 			mptcp_crypto_key_sha(subflow_req->local_key,
199 					     &subflow_req->token,
200 					     &subflow_req->idsn);
201 			if (mptcp_token_exists(subflow_req->token)) {
202 				if (retries-- > 0)
203 					goto again;
204 				SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_TOKENFALLBACKINIT);
205 			} else {
206 				subflow_req->mp_capable = 1;
207 			}
208 			return 0;
209 		}
210 
211 		err = mptcp_token_new_request(req);
212 		if (err == 0)
213 			subflow_req->mp_capable = 1;
214 		else if (retries-- > 0)
215 			goto again;
216 		else
217 			SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_TOKENFALLBACKINIT);
218 
219 	} else if (opt_mp_join && listener->request_mptcp) {
220 		subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq;
221 		subflow_req->mp_join = 1;
222 		subflow_req->backup = mp_opt.backup;
223 		subflow_req->remote_id = mp_opt.join_id;
224 		subflow_req->token = mp_opt.token;
225 		subflow_req->remote_nonce = mp_opt.nonce;
226 		subflow_req->msk = subflow_token_join_request(req);
227 
228 		/* Can't fall back to TCP in this case. */
229 		if (!subflow_req->msk) {
230 			subflow_add_reset_reason(skb, MPTCP_RST_EMPTCP);
231 			return -EPERM;
232 		}
233 
234 		if (subflow_use_different_sport(subflow_req->msk, sk_listener)) {
235 			pr_debug("syn inet_sport=%d %d\n",
236 				 ntohs(inet_sk(sk_listener)->inet_sport),
237 				 ntohs(inet_sk((struct sock *)subflow_req->msk)->inet_sport));
238 			if (!mptcp_pm_sport_in_anno_list(subflow_req->msk, sk_listener)) {
239 				SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MISMATCHPORTSYNRX);
240 				subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);
241 				return -EPERM;
242 			}
243 			SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINPORTSYNRX);
244 		}
245 
246 		subflow_req_create_thmac(subflow_req);
247 
248 		if (unlikely(req->syncookie)) {
249 			if (!mptcp_can_accept_new_subflow(subflow_req->msk)) {
250 				subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);
251 				return -EPERM;
252 			}
253 
254 			subflow_init_req_cookie_join_save(subflow_req, skb);
255 		}
256 
257 		pr_debug("token=%u, remote_nonce=%u msk=%p\n", subflow_req->token,
258 			 subflow_req->remote_nonce, subflow_req->msk);
259 	}
260 
261 	return 0;
262 }
263 
mptcp_subflow_init_cookie_req(struct request_sock * req,const struct sock * sk_listener,struct sk_buff * skb)264 int mptcp_subflow_init_cookie_req(struct request_sock *req,
265 				  const struct sock *sk_listener,
266 				  struct sk_buff *skb)
267 {
268 	struct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk_listener);
269 	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
270 	struct mptcp_options_received mp_opt;
271 	bool opt_mp_capable, opt_mp_join;
272 	int err;
273 
274 	subflow_init_req(req, sk_listener);
275 	mptcp_get_options(skb, &mp_opt);
276 
277 	opt_mp_capable = !!(mp_opt.suboptions & OPTION_MPTCP_MPC_ACK);
278 	opt_mp_join = !!(mp_opt.suboptions & OPTION_MPTCP_MPJ_ACK);
279 	if (opt_mp_capable && opt_mp_join)
280 		return -EINVAL;
281 
282 	if (opt_mp_capable && listener->request_mptcp) {
283 		if (mp_opt.sndr_key == 0)
284 			return -EINVAL;
285 
286 		subflow_req->local_key = mp_opt.rcvr_key;
287 		err = mptcp_token_new_request(req);
288 		if (err)
289 			return err;
290 
291 		subflow_req->mp_capable = 1;
292 		subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq - 1;
293 	} else if (opt_mp_join && listener->request_mptcp) {
294 		if (!mptcp_token_join_cookie_init_state(subflow_req, skb))
295 			return -EINVAL;
296 
297 		subflow_req->mp_join = 1;
298 		subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq - 1;
299 	}
300 
301 	return 0;
302 }
303 EXPORT_SYMBOL_GPL(mptcp_subflow_init_cookie_req);
304 
mptcp_get_rst_reason(const struct sk_buff * skb)305 static enum sk_rst_reason mptcp_get_rst_reason(const struct sk_buff *skb)
306 {
307 	const struct mptcp_ext *mpext = mptcp_get_ext(skb);
308 
309 	if (!mpext)
310 		return SK_RST_REASON_NOT_SPECIFIED;
311 
312 	return sk_rst_convert_mptcp_reason(mpext->reset_reason);
313 }
314 
subflow_v4_route_req(const struct sock * sk,struct sk_buff * skb,struct flowi * fl,struct request_sock * req,u32 tw_isn)315 static struct dst_entry *subflow_v4_route_req(const struct sock *sk,
316 					      struct sk_buff *skb,
317 					      struct flowi *fl,
318 					      struct request_sock *req,
319 					      u32 tw_isn)
320 {
321 	struct dst_entry *dst;
322 	int err;
323 
324 	tcp_rsk(req)->is_mptcp = 1;
325 	subflow_init_req(req, sk);
326 
327 	dst = tcp_request_sock_ipv4_ops.route_req(sk, skb, fl, req, tw_isn);
328 	if (!dst)
329 		return NULL;
330 
331 	err = subflow_check_req(req, sk, skb);
332 	if (err == 0)
333 		return dst;
334 
335 	dst_release(dst);
336 	if (!req->syncookie)
337 		tcp_request_sock_ops.send_reset(sk, skb,
338 						mptcp_get_rst_reason(skb));
339 	return NULL;
340 }
341 
subflow_prep_synack(const struct sock * sk,struct request_sock * req,struct tcp_fastopen_cookie * foc,enum tcp_synack_type synack_type)342 static void subflow_prep_synack(const struct sock *sk, struct request_sock *req,
343 				struct tcp_fastopen_cookie *foc,
344 				enum tcp_synack_type synack_type)
345 {
346 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
347 	struct inet_request_sock *ireq = inet_rsk(req);
348 
349 	/* clear tstamp_ok, as needed depending on cookie */
350 	if (foc && foc->len > -1)
351 		ireq->tstamp_ok = 0;
352 
353 	if (synack_type == TCP_SYNACK_FASTOPEN)
354 		mptcp_fastopen_subflow_synack_set_params(subflow, req);
355 }
356 
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)357 static int subflow_v4_send_synack(const struct sock *sk, struct dst_entry *dst,
358 				  struct flowi *fl,
359 				  struct request_sock *req,
360 				  struct tcp_fastopen_cookie *foc,
361 				  enum tcp_synack_type synack_type,
362 				  struct sk_buff *syn_skb)
363 {
364 	subflow_prep_synack(sk, req, foc, synack_type);
365 
366 	return tcp_request_sock_ipv4_ops.send_synack(sk, dst, fl, req, foc,
367 						     synack_type, syn_skb);
368 }
369 
370 #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)371 static int subflow_v6_send_synack(const struct sock *sk, struct dst_entry *dst,
372 				  struct flowi *fl,
373 				  struct request_sock *req,
374 				  struct tcp_fastopen_cookie *foc,
375 				  enum tcp_synack_type synack_type,
376 				  struct sk_buff *syn_skb)
377 {
378 	subflow_prep_synack(sk, req, foc, synack_type);
379 
380 	return tcp_request_sock_ipv6_ops.send_synack(sk, dst, fl, req, foc,
381 						     synack_type, syn_skb);
382 }
383 
subflow_v6_route_req(const struct sock * sk,struct sk_buff * skb,struct flowi * fl,struct request_sock * req,u32 tw_isn)384 static struct dst_entry *subflow_v6_route_req(const struct sock *sk,
385 					      struct sk_buff *skb,
386 					      struct flowi *fl,
387 					      struct request_sock *req,
388 					      u32 tw_isn)
389 {
390 	struct dst_entry *dst;
391 	int err;
392 
393 	tcp_rsk(req)->is_mptcp = 1;
394 	subflow_init_req(req, sk);
395 
396 	dst = tcp_request_sock_ipv6_ops.route_req(sk, skb, fl, req, tw_isn);
397 	if (!dst)
398 		return NULL;
399 
400 	err = subflow_check_req(req, sk, skb);
401 	if (err == 0)
402 		return dst;
403 
404 	dst_release(dst);
405 	if (!req->syncookie)
406 		tcp6_request_sock_ops.send_reset(sk, skb,
407 						 mptcp_get_rst_reason(skb));
408 	return NULL;
409 }
410 #endif
411 
412 /* validate received truncated hmac and create hmac for third ACK */
subflow_thmac_valid(struct mptcp_subflow_context * subflow)413 static bool subflow_thmac_valid(struct mptcp_subflow_context *subflow)
414 {
415 	u8 hmac[SHA256_DIGEST_SIZE];
416 	u64 thmac;
417 
418 	subflow_generate_hmac(subflow->remote_key, subflow->local_key,
419 			      subflow->remote_nonce, subflow->local_nonce,
420 			      hmac);
421 
422 	thmac = get_unaligned_be64(hmac);
423 	pr_debug("subflow=%p, token=%u, thmac=%llu, subflow->thmac=%llu\n",
424 		 subflow, subflow->token, thmac, subflow->thmac);
425 
426 	return thmac == subflow->thmac;
427 }
428 
mptcp_subflow_reset(struct sock * ssk)429 void mptcp_subflow_reset(struct sock *ssk)
430 {
431 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
432 	struct sock *sk = subflow->conn;
433 
434 	/* mptcp_mp_fail_no_response() can reach here on an already closed
435 	 * socket
436 	 */
437 	if (ssk->sk_state == TCP_CLOSE)
438 		return;
439 
440 	/* must hold: tcp_done() could drop last reference on parent */
441 	sock_hold(sk);
442 
443 	mptcp_send_active_reset_reason(ssk);
444 	tcp_done(ssk);
445 	if (!test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &mptcp_sk(sk)->flags))
446 		mptcp_schedule_work(sk);
447 
448 	sock_put(sk);
449 }
450 
subflow_use_different_dport(struct mptcp_sock * msk,const struct sock * sk)451 static bool subflow_use_different_dport(struct mptcp_sock *msk, const struct sock *sk)
452 {
453 	return inet_sk(sk)->inet_dport != inet_sk((struct sock *)msk)->inet_dport;
454 }
455 
__mptcp_sync_state(struct sock * sk,int state)456 void __mptcp_sync_state(struct sock *sk, int state)
457 {
458 	struct mptcp_subflow_context *subflow;
459 	struct mptcp_sock *msk = mptcp_sk(sk);
460 	struct sock *ssk = msk->first;
461 
462 	subflow = mptcp_subflow_ctx(ssk);
463 	__mptcp_propagate_sndbuf(sk, ssk);
464 	if (!msk->rcvspace_init)
465 		mptcp_rcv_space_init(msk, ssk);
466 
467 	if (sk->sk_state == TCP_SYN_SENT) {
468 		/* subflow->idsn is always available is TCP_SYN_SENT state,
469 		 * even for the FASTOPEN scenarios
470 		 */
471 		WRITE_ONCE(msk->write_seq, subflow->idsn + 1);
472 		WRITE_ONCE(msk->snd_nxt, msk->write_seq);
473 		mptcp_set_state(sk, state);
474 		sk->sk_state_change(sk);
475 	}
476 }
477 
subflow_set_remote_key(struct mptcp_sock * msk,struct mptcp_subflow_context * subflow,const struct mptcp_options_received * mp_opt)478 static void subflow_set_remote_key(struct mptcp_sock *msk,
479 				   struct mptcp_subflow_context *subflow,
480 				   const struct mptcp_options_received *mp_opt)
481 {
482 	/* active MPC subflow will reach here multiple times:
483 	 * at subflow_finish_connect() time and at 4th ack time
484 	 */
485 	if (subflow->remote_key_valid)
486 		return;
487 
488 	subflow->remote_key_valid = 1;
489 	subflow->remote_key = mp_opt->sndr_key;
490 	mptcp_crypto_key_sha(subflow->remote_key, NULL, &subflow->iasn);
491 	subflow->iasn++;
492 
493 	WRITE_ONCE(msk->remote_key, subflow->remote_key);
494 	WRITE_ONCE(msk->ack_seq, subflow->iasn);
495 	WRITE_ONCE(msk->can_ack, true);
496 	atomic64_set(&msk->rcv_wnd_sent, subflow->iasn);
497 }
498 
mptcp_propagate_state(struct sock * sk,struct sock * ssk,struct mptcp_subflow_context * subflow,const struct mptcp_options_received * mp_opt)499 static void mptcp_propagate_state(struct sock *sk, struct sock *ssk,
500 				  struct mptcp_subflow_context *subflow,
501 				  const struct mptcp_options_received *mp_opt)
502 {
503 	struct mptcp_sock *msk = mptcp_sk(sk);
504 
505 	mptcp_data_lock(sk);
506 	if (mp_opt) {
507 		/* Options are available only in the non fallback cases
508 		 * avoid updating rx path fields otherwise
509 		 */
510 		WRITE_ONCE(msk->snd_una, subflow->idsn + 1);
511 		WRITE_ONCE(msk->wnd_end, subflow->idsn + 1 + tcp_sk(ssk)->snd_wnd);
512 		subflow_set_remote_key(msk, subflow, mp_opt);
513 	}
514 
515 	if (!sock_owned_by_user(sk)) {
516 		__mptcp_sync_state(sk, ssk->sk_state);
517 	} else {
518 		msk->pending_state = ssk->sk_state;
519 		__set_bit(MPTCP_SYNC_STATE, &msk->cb_flags);
520 	}
521 	mptcp_data_unlock(sk);
522 }
523 
subflow_finish_connect(struct sock * sk,const struct sk_buff * skb)524 static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
525 {
526 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
527 	struct mptcp_options_received mp_opt;
528 	struct sock *parent = subflow->conn;
529 	struct mptcp_sock *msk;
530 
531 	subflow->icsk_af_ops->sk_rx_dst_set(sk, skb);
532 
533 	/* be sure no special action on any packet other than syn-ack */
534 	if (subflow->conn_finished)
535 		return;
536 
537 	msk = mptcp_sk(parent);
538 	subflow->rel_write_seq = 1;
539 	subflow->conn_finished = 1;
540 	subflow->ssn_offset = TCP_SKB_CB(skb)->seq;
541 	pr_debug("subflow=%p synack seq=%x\n", subflow, subflow->ssn_offset);
542 
543 	mptcp_get_options(skb, &mp_opt);
544 	if (subflow->request_mptcp) {
545 		if (!(mp_opt.suboptions & OPTION_MPTCP_MPC_SYNACK)) {
546 			MPTCP_INC_STATS(sock_net(sk),
547 					MPTCP_MIB_MPCAPABLEACTIVEFALLBACK);
548 			mptcp_do_fallback(sk);
549 			pr_fallback(msk);
550 			goto fallback;
551 		}
552 
553 		if (mp_opt.suboptions & OPTION_MPTCP_CSUMREQD)
554 			WRITE_ONCE(msk->csum_enabled, true);
555 		if (mp_opt.deny_join_id0)
556 			WRITE_ONCE(msk->pm.remote_deny_join_id0, true);
557 		subflow->mp_capable = 1;
558 		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPCAPABLEACTIVEACK);
559 		mptcp_finish_connect(sk);
560 		mptcp_active_enable(parent);
561 		mptcp_propagate_state(parent, sk, subflow, &mp_opt);
562 	} else if (subflow->request_join) {
563 		u8 hmac[SHA256_DIGEST_SIZE];
564 
565 		if (!(mp_opt.suboptions & OPTION_MPTCP_MPJ_SYNACK)) {
566 			subflow->reset_reason = MPTCP_RST_EMPTCP;
567 			goto do_reset;
568 		}
569 
570 		subflow->backup = mp_opt.backup;
571 		subflow->thmac = mp_opt.thmac;
572 		subflow->remote_nonce = mp_opt.nonce;
573 		WRITE_ONCE(subflow->remote_id, mp_opt.join_id);
574 		pr_debug("subflow=%p, thmac=%llu, remote_nonce=%u backup=%d\n",
575 			 subflow, subflow->thmac, subflow->remote_nonce,
576 			 subflow->backup);
577 
578 		if (!subflow_thmac_valid(subflow)) {
579 			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINACKMAC);
580 			subflow->reset_reason = MPTCP_RST_EMPTCP;
581 			goto do_reset;
582 		}
583 
584 		if (!mptcp_finish_join(sk))
585 			goto do_reset;
586 
587 		subflow_generate_hmac(subflow->local_key, subflow->remote_key,
588 				      subflow->local_nonce,
589 				      subflow->remote_nonce,
590 				      hmac);
591 		memcpy(subflow->hmac, hmac, MPTCPOPT_HMAC_LEN);
592 
593 		subflow->mp_join = 1;
594 		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNACKRX);
595 
596 		if (subflow->backup)
597 			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNACKBACKUPRX);
598 
599 		if (subflow_use_different_dport(msk, sk)) {
600 			pr_debug("synack inet_dport=%d %d\n",
601 				 ntohs(inet_sk(sk)->inet_dport),
602 				 ntohs(inet_sk(parent)->inet_dport));
603 			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINPORTSYNACKRX);
604 		}
605 	} else if (mptcp_check_fallback(sk)) {
606 		/* It looks like MPTCP is blocked, while TCP is not */
607 		if (subflow->mpc_drop)
608 			mptcp_active_disable(parent);
609 fallback:
610 		mptcp_propagate_state(parent, sk, subflow, NULL);
611 	}
612 	return;
613 
614 do_reset:
615 	subflow->reset_transient = 0;
616 	mptcp_subflow_reset(sk);
617 }
618 
subflow_set_local_id(struct mptcp_subflow_context * subflow,int local_id)619 static void subflow_set_local_id(struct mptcp_subflow_context *subflow, int local_id)
620 {
621 	WARN_ON_ONCE(local_id < 0 || local_id > 255);
622 	WRITE_ONCE(subflow->local_id, local_id);
623 }
624 
subflow_chk_local_id(struct sock * sk)625 static int subflow_chk_local_id(struct sock *sk)
626 {
627 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
628 	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
629 	int err;
630 
631 	if (likely(subflow->local_id >= 0))
632 		return 0;
633 
634 	err = mptcp_pm_get_local_id(msk, (struct sock_common *)sk);
635 	if (err < 0)
636 		return err;
637 
638 	subflow_set_local_id(subflow, err);
639 	subflow->request_bkup = mptcp_pm_is_backup(msk, (struct sock_common *)sk);
640 
641 	return 0;
642 }
643 
subflow_rebuild_header(struct sock * sk)644 static int subflow_rebuild_header(struct sock *sk)
645 {
646 	int err = subflow_chk_local_id(sk);
647 
648 	if (unlikely(err < 0))
649 		return err;
650 
651 	return inet_sk_rebuild_header(sk);
652 }
653 
654 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
subflow_v6_rebuild_header(struct sock * sk)655 static int subflow_v6_rebuild_header(struct sock *sk)
656 {
657 	int err = subflow_chk_local_id(sk);
658 
659 	if (unlikely(err < 0))
660 		return err;
661 
662 	return inet6_sk_rebuild_header(sk);
663 }
664 #endif
665 
666 static struct request_sock_ops mptcp_subflow_v4_request_sock_ops __ro_after_init;
667 static struct tcp_request_sock_ops subflow_request_sock_ipv4_ops __ro_after_init;
668 
subflow_v4_conn_request(struct sock * sk,struct sk_buff * skb)669 static int subflow_v4_conn_request(struct sock *sk, struct sk_buff *skb)
670 {
671 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
672 
673 	pr_debug("subflow=%p\n", subflow);
674 
675 	/* Never answer to SYNs sent to broadcast or multicast */
676 	if (skb_rtable(skb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
677 		goto drop;
678 
679 	return tcp_conn_request(&mptcp_subflow_v4_request_sock_ops,
680 				&subflow_request_sock_ipv4_ops,
681 				sk, skb);
682 drop:
683 	tcp_listendrop(sk);
684 	return 0;
685 }
686 
subflow_v4_req_destructor(struct request_sock * req)687 static void subflow_v4_req_destructor(struct request_sock *req)
688 {
689 	subflow_req_destructor(req);
690 	tcp_request_sock_ops.destructor(req);
691 }
692 
693 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
694 static struct request_sock_ops mptcp_subflow_v6_request_sock_ops __ro_after_init;
695 static struct tcp_request_sock_ops subflow_request_sock_ipv6_ops __ro_after_init;
696 static struct inet_connection_sock_af_ops subflow_v6_specific __ro_after_init;
697 static struct inet_connection_sock_af_ops subflow_v6m_specific __ro_after_init;
698 static struct proto tcpv6_prot_override __ro_after_init;
699 
subflow_v6_conn_request(struct sock * sk,struct sk_buff * skb)700 static int subflow_v6_conn_request(struct sock *sk, struct sk_buff *skb)
701 {
702 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
703 
704 	pr_debug("subflow=%p\n", subflow);
705 
706 	if (skb->protocol == htons(ETH_P_IP))
707 		return subflow_v4_conn_request(sk, skb);
708 
709 	if (!ipv6_unicast_destination(skb))
710 		goto drop;
711 
712 	if (ipv6_addr_v4mapped(&ipv6_hdr(skb)->saddr)) {
713 		__IP6_INC_STATS(sock_net(sk), NULL, IPSTATS_MIB_INHDRERRORS);
714 		return 0;
715 	}
716 
717 	return tcp_conn_request(&mptcp_subflow_v6_request_sock_ops,
718 				&subflow_request_sock_ipv6_ops, sk, skb);
719 
720 drop:
721 	tcp_listendrop(sk);
722 	return 0; /* don't send reset */
723 }
724 
subflow_v6_req_destructor(struct request_sock * req)725 static void subflow_v6_req_destructor(struct request_sock *req)
726 {
727 	subflow_req_destructor(req);
728 	tcp6_request_sock_ops.destructor(req);
729 }
730 #endif
731 
mptcp_subflow_reqsk_alloc(const struct request_sock_ops * ops,struct sock * sk_listener,bool attach_listener)732 struct request_sock *mptcp_subflow_reqsk_alloc(const struct request_sock_ops *ops,
733 					       struct sock *sk_listener,
734 					       bool attach_listener)
735 {
736 	if (ops->family == AF_INET)
737 		ops = &mptcp_subflow_v4_request_sock_ops;
738 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
739 	else if (ops->family == AF_INET6)
740 		ops = &mptcp_subflow_v6_request_sock_ops;
741 #endif
742 
743 	return inet_reqsk_alloc(ops, sk_listener, attach_listener);
744 }
745 EXPORT_SYMBOL(mptcp_subflow_reqsk_alloc);
746 
747 /* validate hmac received in third ACK */
subflow_hmac_valid(const struct request_sock * req,const struct mptcp_options_received * mp_opt)748 static bool subflow_hmac_valid(const struct request_sock *req,
749 			       const struct mptcp_options_received *mp_opt)
750 {
751 	const struct mptcp_subflow_request_sock *subflow_req;
752 	u8 hmac[SHA256_DIGEST_SIZE];
753 	struct mptcp_sock *msk;
754 
755 	subflow_req = mptcp_subflow_rsk(req);
756 	msk = subflow_req->msk;
757 	if (!msk)
758 		return false;
759 
760 	subflow_generate_hmac(READ_ONCE(msk->remote_key),
761 			      READ_ONCE(msk->local_key),
762 			      subflow_req->remote_nonce,
763 			      subflow_req->local_nonce, hmac);
764 
765 	return !crypto_memneq(hmac, mp_opt->hmac, MPTCPOPT_HMAC_LEN);
766 }
767 
subflow_ulp_fallback(struct sock * sk,struct mptcp_subflow_context * old_ctx)768 static void subflow_ulp_fallback(struct sock *sk,
769 				 struct mptcp_subflow_context *old_ctx)
770 {
771 	struct inet_connection_sock *icsk = inet_csk(sk);
772 
773 	mptcp_subflow_tcp_fallback(sk, old_ctx);
774 	icsk->icsk_ulp_ops = NULL;
775 	rcu_assign_pointer(icsk->icsk_ulp_data, NULL);
776 	tcp_sk(sk)->is_mptcp = 0;
777 
778 	mptcp_subflow_ops_undo_override(sk);
779 }
780 
mptcp_subflow_drop_ctx(struct sock * ssk)781 void mptcp_subflow_drop_ctx(struct sock *ssk)
782 {
783 	struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(ssk);
784 
785 	if (!ctx)
786 		return;
787 
788 	list_del(&mptcp_subflow_ctx(ssk)->node);
789 	if (inet_csk(ssk)->icsk_ulp_ops) {
790 		subflow_ulp_fallback(ssk, ctx);
791 		if (ctx->conn)
792 			sock_put(ctx->conn);
793 	}
794 
795 	kfree_rcu(ctx, rcu);
796 }
797 
__mptcp_subflow_fully_established(struct mptcp_sock * msk,struct mptcp_subflow_context * subflow,const struct mptcp_options_received * mp_opt)798 void __mptcp_subflow_fully_established(struct mptcp_sock *msk,
799 				       struct mptcp_subflow_context *subflow,
800 				       const struct mptcp_options_received *mp_opt)
801 {
802 	subflow_set_remote_key(msk, subflow, mp_opt);
803 	WRITE_ONCE(subflow->fully_established, true);
804 	WRITE_ONCE(msk->fully_established, true);
805 
806 	if (subflow->is_mptfo)
807 		__mptcp_fastopen_gen_msk_ackseq(msk, subflow, mp_opt);
808 }
809 
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)810 static struct sock *subflow_syn_recv_sock(const struct sock *sk,
811 					  struct sk_buff *skb,
812 					  struct request_sock *req,
813 					  struct dst_entry *dst,
814 					  struct request_sock *req_unhash,
815 					  bool *own_req)
816 {
817 	struct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk);
818 	struct mptcp_subflow_request_sock *subflow_req;
819 	struct mptcp_options_received mp_opt;
820 	bool fallback, fallback_is_fatal;
821 	enum sk_rst_reason reason;
822 	struct mptcp_sock *owner;
823 	struct sock *child;
824 
825 	pr_debug("listener=%p, req=%p, conn=%p\n", listener, req, listener->conn);
826 
827 	/* After child creation we must look for MPC even when options
828 	 * are not parsed
829 	 */
830 	mp_opt.suboptions = 0;
831 
832 	/* hopefully temporary handling for MP_JOIN+syncookie */
833 	subflow_req = mptcp_subflow_rsk(req);
834 	fallback_is_fatal = tcp_rsk(req)->is_mptcp && subflow_req->mp_join;
835 	fallback = !tcp_rsk(req)->is_mptcp;
836 	if (fallback)
837 		goto create_child;
838 
839 	/* if the sk is MP_CAPABLE, we try to fetch the client key */
840 	if (subflow_req->mp_capable) {
841 		/* we can receive and accept an in-window, out-of-order pkt,
842 		 * which may not carry the MP_CAPABLE opt even on mptcp enabled
843 		 * paths: always try to extract the peer key, and fallback
844 		 * for packets missing it.
845 		 * Even OoO DSS packets coming legitly after dropped or
846 		 * reordered MPC will cause fallback, but we don't have other
847 		 * options.
848 		 */
849 		mptcp_get_options(skb, &mp_opt);
850 		if (!(mp_opt.suboptions &
851 		      (OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_ACK)))
852 			fallback = true;
853 
854 	} else if (subflow_req->mp_join) {
855 		mptcp_get_options(skb, &mp_opt);
856 		if (!(mp_opt.suboptions & OPTION_MPTCP_MPJ_ACK) ||
857 		    !subflow_hmac_valid(req, &mp_opt) ||
858 		    !mptcp_can_accept_new_subflow(subflow_req->msk)) {
859 			SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINACKMAC);
860 			fallback = true;
861 		}
862 	}
863 
864 create_child:
865 	child = listener->icsk_af_ops->syn_recv_sock(sk, skb, req, dst,
866 						     req_unhash, own_req);
867 
868 	if (child && *own_req) {
869 		struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(child);
870 
871 		tcp_rsk(req)->drop_req = false;
872 
873 		/* we need to fallback on ctx allocation failure and on pre-reqs
874 		 * checking above. In the latter scenario we additionally need
875 		 * to reset the context to non MPTCP status.
876 		 */
877 		if (!ctx || fallback) {
878 			if (fallback_is_fatal) {
879 				subflow_add_reset_reason(skb, MPTCP_RST_EMPTCP);
880 				goto dispose_child;
881 			}
882 			goto fallback;
883 		}
884 
885 		/* ssk inherits options of listener sk */
886 		ctx->setsockopt_seq = listener->setsockopt_seq;
887 
888 		if (ctx->mp_capable) {
889 			ctx->conn = mptcp_sk_clone_init(listener->conn, &mp_opt, child, req);
890 			if (!ctx->conn)
891 				goto fallback;
892 
893 			ctx->subflow_id = 1;
894 			owner = mptcp_sk(ctx->conn);
895 			mptcp_pm_new_connection(owner, child, 1);
896 
897 			/* with OoO packets we can reach here without ingress
898 			 * mpc option
899 			 */
900 			if (mp_opt.suboptions & OPTION_MPTCP_MPC_ACK) {
901 				mptcp_pm_fully_established(owner, child);
902 				ctx->pm_notified = 1;
903 			}
904 		} else if (ctx->mp_join) {
905 			owner = subflow_req->msk;
906 			if (!owner) {
907 				subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);
908 				goto dispose_child;
909 			}
910 
911 			/* move the msk reference ownership to the subflow */
912 			subflow_req->msk = NULL;
913 			ctx->conn = (struct sock *)owner;
914 
915 			if (subflow_use_different_sport(owner, sk)) {
916 				pr_debug("ack inet_sport=%d %d\n",
917 					 ntohs(inet_sk(sk)->inet_sport),
918 					 ntohs(inet_sk((struct sock *)owner)->inet_sport));
919 				if (!mptcp_pm_sport_in_anno_list(owner, sk)) {
920 					SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MISMATCHPORTACKRX);
921 					subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);
922 					goto dispose_child;
923 				}
924 				SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINPORTACKRX);
925 			}
926 
927 			if (!mptcp_finish_join(child)) {
928 				struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(child);
929 
930 				subflow_add_reset_reason(skb, subflow->reset_reason);
931 				goto dispose_child;
932 			}
933 
934 			SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINACKRX);
935 			tcp_rsk(req)->drop_req = true;
936 		}
937 	}
938 
939 	/* check for expected invariant - should never trigger, just help
940 	 * catching earlier subtle bugs
941 	 */
942 	WARN_ON_ONCE(child && *own_req && tcp_sk(child)->is_mptcp &&
943 		     (!mptcp_subflow_ctx(child) ||
944 		      !mptcp_subflow_ctx(child)->conn));
945 	return child;
946 
947 dispose_child:
948 	mptcp_subflow_drop_ctx(child);
949 	tcp_rsk(req)->drop_req = true;
950 	inet_csk_prepare_for_destroy_sock(child);
951 	tcp_done(child);
952 	reason = mptcp_get_rst_reason(skb);
953 	req->rsk_ops->send_reset(sk, skb, reason);
954 
955 	/* The last child reference will be released by the caller */
956 	return child;
957 
958 fallback:
959 	if (fallback)
960 		SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK);
961 	mptcp_subflow_drop_ctx(child);
962 	return child;
963 }
964 
965 static struct inet_connection_sock_af_ops subflow_specific __ro_after_init;
966 static struct proto tcp_prot_override __ro_after_init;
967 
968 enum mapping_status {
969 	MAPPING_OK,
970 	MAPPING_INVALID,
971 	MAPPING_EMPTY,
972 	MAPPING_DATA_FIN,
973 	MAPPING_DUMMY,
974 	MAPPING_BAD_CSUM,
975 	MAPPING_NODSS
976 };
977 
dbg_bad_map(struct mptcp_subflow_context * subflow,u32 ssn)978 static void dbg_bad_map(struct mptcp_subflow_context *subflow, u32 ssn)
979 {
980 	pr_debug("Bad mapping: ssn=%d map_seq=%d map_data_len=%d\n",
981 		 ssn, subflow->map_subflow_seq, subflow->map_data_len);
982 }
983 
skb_is_fully_mapped(struct sock * ssk,struct sk_buff * skb)984 static bool skb_is_fully_mapped(struct sock *ssk, struct sk_buff *skb)
985 {
986 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
987 	unsigned int skb_consumed;
988 
989 	skb_consumed = tcp_sk(ssk)->copied_seq - TCP_SKB_CB(skb)->seq;
990 	if (unlikely(skb_consumed >= skb->len)) {
991 		DEBUG_NET_WARN_ON_ONCE(1);
992 		return true;
993 	}
994 
995 	return skb->len - skb_consumed <= subflow->map_data_len -
996 					  mptcp_subflow_get_map_offset(subflow);
997 }
998 
validate_mapping(struct sock * ssk,struct sk_buff * skb)999 static bool validate_mapping(struct sock *ssk, struct sk_buff *skb)
1000 {
1001 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
1002 	u32 ssn = tcp_sk(ssk)->copied_seq - subflow->ssn_offset;
1003 
1004 	if (unlikely(before(ssn, subflow->map_subflow_seq))) {
1005 		/* Mapping covers data later in the subflow stream,
1006 		 * currently unsupported.
1007 		 */
1008 		dbg_bad_map(subflow, ssn);
1009 		return false;
1010 	}
1011 	if (unlikely(!before(ssn, subflow->map_subflow_seq +
1012 				  subflow->map_data_len))) {
1013 		/* Mapping does covers past subflow data, invalid */
1014 		dbg_bad_map(subflow, ssn);
1015 		return false;
1016 	}
1017 	return true;
1018 }
1019 
validate_data_csum(struct sock * ssk,struct sk_buff * skb,bool csum_reqd)1020 static enum mapping_status validate_data_csum(struct sock *ssk, struct sk_buff *skb,
1021 					      bool csum_reqd)
1022 {
1023 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
1024 	u32 offset, seq, delta;
1025 	__sum16 csum;
1026 	int len;
1027 
1028 	if (!csum_reqd)
1029 		return MAPPING_OK;
1030 
1031 	/* mapping already validated on previous traversal */
1032 	if (subflow->map_csum_len == subflow->map_data_len)
1033 		return MAPPING_OK;
1034 
1035 	/* traverse the receive queue, ensuring it contains a full
1036 	 * DSS mapping and accumulating the related csum.
1037 	 * Preserve the accoumlate csum across multiple calls, to compute
1038 	 * the csum only once
1039 	 */
1040 	delta = subflow->map_data_len - subflow->map_csum_len;
1041 	for (;;) {
1042 		seq = tcp_sk(ssk)->copied_seq + subflow->map_csum_len;
1043 		offset = seq - TCP_SKB_CB(skb)->seq;
1044 
1045 		/* if the current skb has not been accounted yet, csum its contents
1046 		 * up to the amount covered by the current DSS
1047 		 */
1048 		if (offset < skb->len) {
1049 			__wsum csum;
1050 
1051 			len = min(skb->len - offset, delta);
1052 			csum = skb_checksum(skb, offset, len, 0);
1053 			subflow->map_data_csum = csum_block_add(subflow->map_data_csum, csum,
1054 								subflow->map_csum_len);
1055 
1056 			delta -= len;
1057 			subflow->map_csum_len += len;
1058 		}
1059 		if (delta == 0)
1060 			break;
1061 
1062 		if (skb_queue_is_last(&ssk->sk_receive_queue, skb)) {
1063 			/* if this subflow is closed, the partial mapping
1064 			 * will be never completed; flush the pending skbs, so
1065 			 * that subflow_sched_work_if_closed() can kick in
1066 			 */
1067 			if (unlikely(ssk->sk_state == TCP_CLOSE))
1068 				while ((skb = skb_peek(&ssk->sk_receive_queue)))
1069 					sk_eat_skb(ssk, skb);
1070 
1071 			/* not enough data to validate the csum */
1072 			return MAPPING_EMPTY;
1073 		}
1074 
1075 		/* the DSS mapping for next skbs will be validated later,
1076 		 * when a get_mapping_status call will process such skb
1077 		 */
1078 		skb = skb->next;
1079 	}
1080 
1081 	/* note that 'map_data_len' accounts only for the carried data, does
1082 	 * not include the eventual seq increment due to the data fin,
1083 	 * while the pseudo header requires the original DSS data len,
1084 	 * including that
1085 	 */
1086 	csum = __mptcp_make_csum(subflow->map_seq,
1087 				 subflow->map_subflow_seq,
1088 				 subflow->map_data_len + subflow->map_data_fin,
1089 				 subflow->map_data_csum);
1090 	if (unlikely(csum)) {
1091 		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DATACSUMERR);
1092 		return MAPPING_BAD_CSUM;
1093 	}
1094 
1095 	subflow->valid_csum_seen = 1;
1096 	return MAPPING_OK;
1097 }
1098 
get_mapping_status(struct sock * ssk,struct mptcp_sock * msk)1099 static enum mapping_status get_mapping_status(struct sock *ssk,
1100 					      struct mptcp_sock *msk)
1101 {
1102 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
1103 	bool csum_reqd = READ_ONCE(msk->csum_enabled);
1104 	struct mptcp_ext *mpext;
1105 	struct sk_buff *skb;
1106 	u16 data_len;
1107 	u64 map_seq;
1108 
1109 	skb = skb_peek(&ssk->sk_receive_queue);
1110 	if (!skb)
1111 		return MAPPING_EMPTY;
1112 
1113 	if (mptcp_check_fallback(ssk))
1114 		return MAPPING_DUMMY;
1115 
1116 	mpext = mptcp_get_ext(skb);
1117 	if (!mpext || !mpext->use_map) {
1118 		if (!subflow->map_valid && !skb->len) {
1119 			/* the TCP stack deliver 0 len FIN pkt to the receive
1120 			 * queue, that is the only 0len pkts ever expected here,
1121 			 * and we can admit no mapping only for 0 len pkts
1122 			 */
1123 			if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN))
1124 				WARN_ONCE(1, "0len seq %d:%d flags %x",
1125 					  TCP_SKB_CB(skb)->seq,
1126 					  TCP_SKB_CB(skb)->end_seq,
1127 					  TCP_SKB_CB(skb)->tcp_flags);
1128 			sk_eat_skb(ssk, skb);
1129 			return MAPPING_EMPTY;
1130 		}
1131 
1132 		/* If the required DSS has likely been dropped by a middlebox */
1133 		if (!subflow->map_valid)
1134 			return MAPPING_NODSS;
1135 
1136 		goto validate_seq;
1137 	}
1138 
1139 	trace_get_mapping_status(mpext);
1140 
1141 	data_len = mpext->data_len;
1142 	if (data_len == 0) {
1143 		pr_debug("infinite mapping received\n");
1144 		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_INFINITEMAPRX);
1145 		return MAPPING_INVALID;
1146 	}
1147 
1148 	if (mpext->data_fin == 1) {
1149 		u64 data_fin_seq;
1150 
1151 		if (data_len == 1) {
1152 			bool updated = mptcp_update_rcv_data_fin(msk, mpext->data_seq,
1153 								 mpext->dsn64);
1154 			pr_debug("DATA_FIN with no payload seq=%llu\n", mpext->data_seq);
1155 			if (subflow->map_valid) {
1156 				/* A DATA_FIN might arrive in a DSS
1157 				 * option before the previous mapping
1158 				 * has been fully consumed. Continue
1159 				 * handling the existing mapping.
1160 				 */
1161 				skb_ext_del(skb, SKB_EXT_MPTCP);
1162 				return MAPPING_OK;
1163 			}
1164 
1165 			if (updated)
1166 				mptcp_schedule_work((struct sock *)msk);
1167 
1168 			return MAPPING_DATA_FIN;
1169 		}
1170 
1171 		data_fin_seq = mpext->data_seq + data_len - 1;
1172 
1173 		/* If mpext->data_seq is a 32-bit value, data_fin_seq must also
1174 		 * be limited to 32 bits.
1175 		 */
1176 		if (!mpext->dsn64)
1177 			data_fin_seq &= GENMASK_ULL(31, 0);
1178 
1179 		mptcp_update_rcv_data_fin(msk, data_fin_seq, mpext->dsn64);
1180 		pr_debug("DATA_FIN with mapping seq=%llu dsn64=%d\n",
1181 			 data_fin_seq, mpext->dsn64);
1182 
1183 		/* Adjust for DATA_FIN using 1 byte of sequence space */
1184 		data_len--;
1185 	}
1186 
1187 	map_seq = mptcp_expand_seq(READ_ONCE(msk->ack_seq), mpext->data_seq, mpext->dsn64);
1188 	WRITE_ONCE(mptcp_sk(subflow->conn)->use_64bit_ack, !!mpext->dsn64);
1189 
1190 	if (subflow->map_valid) {
1191 		/* Allow replacing only with an identical map */
1192 		if (subflow->map_seq == map_seq &&
1193 		    subflow->map_subflow_seq == mpext->subflow_seq &&
1194 		    subflow->map_data_len == data_len &&
1195 		    subflow->map_csum_reqd == mpext->csum_reqd) {
1196 			skb_ext_del(skb, SKB_EXT_MPTCP);
1197 			goto validate_csum;
1198 		}
1199 
1200 		/* If this skb data are fully covered by the current mapping,
1201 		 * the new map would need caching, which is not supported
1202 		 */
1203 		if (skb_is_fully_mapped(ssk, skb)) {
1204 			MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DSSNOMATCH);
1205 			return MAPPING_INVALID;
1206 		}
1207 
1208 		/* will validate the next map after consuming the current one */
1209 		goto validate_csum;
1210 	}
1211 
1212 	subflow->map_seq = map_seq;
1213 	subflow->map_subflow_seq = mpext->subflow_seq;
1214 	subflow->map_data_len = data_len;
1215 	subflow->map_valid = 1;
1216 	subflow->map_data_fin = mpext->data_fin;
1217 	subflow->mpc_map = mpext->mpc_map;
1218 	subflow->map_csum_reqd = mpext->csum_reqd;
1219 	subflow->map_csum_len = 0;
1220 	subflow->map_data_csum = csum_unfold(mpext->csum);
1221 
1222 	/* Cfr RFC 8684 Section 3.3.0 */
1223 	if (unlikely(subflow->map_csum_reqd != csum_reqd))
1224 		return MAPPING_INVALID;
1225 
1226 	pr_debug("new map seq=%llu subflow_seq=%u data_len=%u csum=%d:%u\n",
1227 		 subflow->map_seq, subflow->map_subflow_seq,
1228 		 subflow->map_data_len, subflow->map_csum_reqd,
1229 		 subflow->map_data_csum);
1230 
1231 validate_seq:
1232 	/* we revalidate valid mapping on new skb, because we must ensure
1233 	 * the current skb is completely covered by the available mapping
1234 	 */
1235 	if (!validate_mapping(ssk, skb)) {
1236 		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DSSTCPMISMATCH);
1237 		return MAPPING_INVALID;
1238 	}
1239 
1240 	skb_ext_del(skb, SKB_EXT_MPTCP);
1241 
1242 validate_csum:
1243 	return validate_data_csum(ssk, skb, csum_reqd);
1244 }
1245 
mptcp_subflow_discard_data(struct sock * ssk,struct sk_buff * skb,u64 limit)1246 static void mptcp_subflow_discard_data(struct sock *ssk, struct sk_buff *skb,
1247 				       u64 limit)
1248 {
1249 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
1250 	bool fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN;
1251 	struct tcp_sock *tp = tcp_sk(ssk);
1252 	u32 offset, incr, avail_len;
1253 
1254 	offset = tp->copied_seq - TCP_SKB_CB(skb)->seq;
1255 	if (WARN_ON_ONCE(offset > skb->len))
1256 		goto out;
1257 
1258 	avail_len = skb->len - offset;
1259 	incr = limit >= avail_len ? avail_len + fin : limit;
1260 
1261 	pr_debug("discarding=%d len=%d offset=%d seq=%d\n", incr, skb->len,
1262 		 offset, subflow->map_subflow_seq);
1263 	MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DUPDATA);
1264 	tcp_sk(ssk)->copied_seq += incr;
1265 
1266 out:
1267 	if (!before(tcp_sk(ssk)->copied_seq, TCP_SKB_CB(skb)->end_seq))
1268 		sk_eat_skb(ssk, skb);
1269 	if (mptcp_subflow_get_map_offset(subflow) >= subflow->map_data_len)
1270 		subflow->map_valid = 0;
1271 }
1272 
1273 /* 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)1274 static void subflow_sched_work_if_closed(struct mptcp_sock *msk, struct sock *ssk)
1275 {
1276 	struct sock *sk = (struct sock *)msk;
1277 
1278 	if (likely(ssk->sk_state != TCP_CLOSE &&
1279 		   (ssk->sk_state != TCP_CLOSE_WAIT ||
1280 		    inet_sk_state_load(sk) != TCP_ESTABLISHED)))
1281 		return;
1282 
1283 	if (skb_queue_empty(&ssk->sk_receive_queue) &&
1284 	    !test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &msk->flags))
1285 		mptcp_schedule_work(sk);
1286 }
1287 
mptcp_subflow_fail(struct mptcp_sock * msk,struct sock * ssk)1288 static void mptcp_subflow_fail(struct mptcp_sock *msk, struct sock *ssk)
1289 {
1290 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
1291 	unsigned long fail_tout;
1292 
1293 	/* graceful failure can happen only on the MPC subflow */
1294 	if (WARN_ON_ONCE(ssk != READ_ONCE(msk->first)))
1295 		return;
1296 
1297 	/* since the close timeout take precedence on the fail one,
1298 	 * no need to start the latter when the first is already set
1299 	 */
1300 	if (sock_flag((struct sock *)msk, SOCK_DEAD))
1301 		return;
1302 
1303 	/* we don't need extreme accuracy here, use a zero fail_tout as special
1304 	 * value meaning no fail timeout at all;
1305 	 */
1306 	fail_tout = jiffies + TCP_RTO_MAX;
1307 	if (!fail_tout)
1308 		fail_tout = 1;
1309 	WRITE_ONCE(subflow->fail_tout, fail_tout);
1310 	tcp_send_ack(ssk);
1311 
1312 	mptcp_reset_tout_timer(msk, subflow->fail_tout);
1313 }
1314 
subflow_check_data_avail(struct sock * ssk)1315 static bool subflow_check_data_avail(struct sock *ssk)
1316 {
1317 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
1318 	enum mapping_status status;
1319 	struct mptcp_sock *msk;
1320 	struct sk_buff *skb;
1321 
1322 	if (!skb_peek(&ssk->sk_receive_queue))
1323 		WRITE_ONCE(subflow->data_avail, false);
1324 	if (subflow->data_avail)
1325 		return true;
1326 
1327 	msk = mptcp_sk(subflow->conn);
1328 	for (;;) {
1329 		u64 ack_seq;
1330 		u64 old_ack;
1331 
1332 		status = get_mapping_status(ssk, msk);
1333 		trace_subflow_check_data_avail(status, skb_peek(&ssk->sk_receive_queue));
1334 		if (unlikely(status == MAPPING_INVALID || status == MAPPING_DUMMY ||
1335 			     status == MAPPING_BAD_CSUM || status == MAPPING_NODSS))
1336 			goto fallback;
1337 
1338 		if (status != MAPPING_OK)
1339 			goto no_data;
1340 
1341 		skb = skb_peek(&ssk->sk_receive_queue);
1342 		if (WARN_ON_ONCE(!skb))
1343 			goto no_data;
1344 
1345 		if (unlikely(!READ_ONCE(msk->can_ack)))
1346 			goto fallback;
1347 
1348 		old_ack = READ_ONCE(msk->ack_seq);
1349 		ack_seq = mptcp_subflow_get_mapped_dsn(subflow);
1350 		pr_debug("msk ack_seq=%llx subflow ack_seq=%llx\n", old_ack,
1351 			 ack_seq);
1352 		if (unlikely(before64(ack_seq, old_ack))) {
1353 			mptcp_subflow_discard_data(ssk, skb, old_ack - ack_seq);
1354 			continue;
1355 		}
1356 
1357 		WRITE_ONCE(subflow->data_avail, true);
1358 		break;
1359 	}
1360 	return true;
1361 
1362 no_data:
1363 	subflow_sched_work_if_closed(msk, ssk);
1364 	return false;
1365 
1366 fallback:
1367 	if (!__mptcp_check_fallback(msk)) {
1368 		/* RFC 8684 section 3.7. */
1369 		if (status == MAPPING_BAD_CSUM &&
1370 		    (subflow->mp_join || subflow->valid_csum_seen)) {
1371 			subflow->send_mp_fail = 1;
1372 
1373 			if (!READ_ONCE(msk->allow_infinite_fallback)) {
1374 				subflow->reset_transient = 0;
1375 				subflow->reset_reason = MPTCP_RST_EMIDDLEBOX;
1376 				goto reset;
1377 			}
1378 			mptcp_subflow_fail(msk, ssk);
1379 			WRITE_ONCE(subflow->data_avail, true);
1380 			return true;
1381 		}
1382 
1383 		if (!READ_ONCE(msk->allow_infinite_fallback)) {
1384 			/* fatal protocol error, close the socket.
1385 			 * subflow_error_report() will introduce the appropriate barriers
1386 			 */
1387 			subflow->reset_transient = 0;
1388 			subflow->reset_reason = status == MAPPING_NODSS ?
1389 						MPTCP_RST_EMIDDLEBOX :
1390 						MPTCP_RST_EMPTCP;
1391 
1392 reset:
1393 			WRITE_ONCE(ssk->sk_err, EBADMSG);
1394 			tcp_set_state(ssk, TCP_CLOSE);
1395 			while ((skb = skb_peek(&ssk->sk_receive_queue)))
1396 				sk_eat_skb(ssk, skb);
1397 			mptcp_send_active_reset_reason(ssk);
1398 			WRITE_ONCE(subflow->data_avail, false);
1399 			return false;
1400 		}
1401 
1402 		mptcp_do_fallback(ssk);
1403 	}
1404 
1405 	skb = skb_peek(&ssk->sk_receive_queue);
1406 	subflow->map_valid = 1;
1407 	subflow->map_seq = READ_ONCE(msk->ack_seq);
1408 	subflow->map_data_len = skb->len;
1409 	subflow->map_subflow_seq = tcp_sk(ssk)->copied_seq - subflow->ssn_offset;
1410 	WRITE_ONCE(subflow->data_avail, true);
1411 	return true;
1412 }
1413 
mptcp_subflow_data_available(struct sock * sk)1414 bool mptcp_subflow_data_available(struct sock *sk)
1415 {
1416 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1417 
1418 	/* check if current mapping is still valid */
1419 	if (subflow->map_valid &&
1420 	    mptcp_subflow_get_map_offset(subflow) >= subflow->map_data_len) {
1421 		subflow->map_valid = 0;
1422 		WRITE_ONCE(subflow->data_avail, false);
1423 
1424 		pr_debug("Done with mapping: seq=%u data_len=%u\n",
1425 			 subflow->map_subflow_seq,
1426 			 subflow->map_data_len);
1427 	}
1428 
1429 	return subflow_check_data_avail(sk);
1430 }
1431 
1432 /* If ssk has an mptcp parent socket, use the mptcp rcvbuf occupancy,
1433  * not the ssk one.
1434  *
1435  * In mptcp, rwin is about the mptcp-level connection data.
1436  *
1437  * Data that is still on the ssk rx queue can thus be ignored,
1438  * as far as mptcp peer is concerned that data is still inflight.
1439  * DSS ACK is updated when skb is moved to the mptcp rx queue.
1440  */
mptcp_space(const struct sock * ssk,int * space,int * full_space)1441 void mptcp_space(const struct sock *ssk, int *space, int *full_space)
1442 {
1443 	const struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
1444 	const struct sock *sk = subflow->conn;
1445 
1446 	*space = __mptcp_space(sk);
1447 	*full_space = mptcp_win_from_space(sk, READ_ONCE(sk->sk_rcvbuf));
1448 }
1449 
subflow_error_report(struct sock * ssk)1450 static void subflow_error_report(struct sock *ssk)
1451 {
1452 	struct sock *sk = mptcp_subflow_ctx(ssk)->conn;
1453 
1454 	/* bail early if this is a no-op, so that we avoid introducing a
1455 	 * problematic lockdep dependency between TCP accept queue lock
1456 	 * and msk socket spinlock
1457 	 */
1458 	if (!sk->sk_socket)
1459 		return;
1460 
1461 	mptcp_data_lock(sk);
1462 	if (!sock_owned_by_user(sk))
1463 		__mptcp_error_report(sk);
1464 	else
1465 		__set_bit(MPTCP_ERROR_REPORT,  &mptcp_sk(sk)->cb_flags);
1466 	mptcp_data_unlock(sk);
1467 }
1468 
subflow_data_ready(struct sock * sk)1469 static void subflow_data_ready(struct sock *sk)
1470 {
1471 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1472 	u16 state = 1 << inet_sk_state_load(sk);
1473 	struct sock *parent = subflow->conn;
1474 	struct mptcp_sock *msk;
1475 
1476 	trace_sk_data_ready(sk);
1477 
1478 	msk = mptcp_sk(parent);
1479 	if (state & TCPF_LISTEN) {
1480 		/* MPJ subflow are removed from accept queue before reaching here,
1481 		 * avoid stray wakeups
1482 		 */
1483 		if (reqsk_queue_empty(&inet_csk(sk)->icsk_accept_queue))
1484 			return;
1485 
1486 		parent->sk_data_ready(parent);
1487 		return;
1488 	}
1489 
1490 	WARN_ON_ONCE(!__mptcp_check_fallback(msk) && !subflow->mp_capable &&
1491 		     !subflow->mp_join && !(state & TCPF_CLOSE));
1492 
1493 	if (mptcp_subflow_data_available(sk)) {
1494 		mptcp_data_ready(parent, sk);
1495 
1496 		/* subflow-level lowat test are not relevant.
1497 		 * respect the msk-level threshold eventually mandating an immediate ack
1498 		 */
1499 		if (mptcp_data_avail(msk) < parent->sk_rcvlowat &&
1500 		    (tcp_sk(sk)->rcv_nxt - tcp_sk(sk)->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss)
1501 			inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_NOW;
1502 	} else if (unlikely(sk->sk_err)) {
1503 		subflow_error_report(sk);
1504 	}
1505 }
1506 
subflow_write_space(struct sock * ssk)1507 static void subflow_write_space(struct sock *ssk)
1508 {
1509 	struct sock *sk = mptcp_subflow_ctx(ssk)->conn;
1510 
1511 	mptcp_propagate_sndbuf(sk, ssk);
1512 	mptcp_write_space(sk);
1513 }
1514 
1515 static const struct inet_connection_sock_af_ops *
subflow_default_af_ops(struct sock * sk)1516 subflow_default_af_ops(struct sock *sk)
1517 {
1518 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1519 	if (sk->sk_family == AF_INET6)
1520 		return &subflow_v6_specific;
1521 #endif
1522 	return &subflow_specific;
1523 }
1524 
1525 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
mptcpv6_handle_mapped(struct sock * sk,bool mapped)1526 void mptcpv6_handle_mapped(struct sock *sk, bool mapped)
1527 {
1528 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1529 	struct inet_connection_sock *icsk = inet_csk(sk);
1530 	const struct inet_connection_sock_af_ops *target;
1531 
1532 	target = mapped ? &subflow_v6m_specific : subflow_default_af_ops(sk);
1533 
1534 	pr_debug("subflow=%p family=%d ops=%p target=%p mapped=%d\n",
1535 		 subflow, sk->sk_family, icsk->icsk_af_ops, target, mapped);
1536 
1537 	if (likely(icsk->icsk_af_ops == target))
1538 		return;
1539 
1540 	subflow->icsk_af_ops = icsk->icsk_af_ops;
1541 	icsk->icsk_af_ops = target;
1542 }
1543 #endif
1544 
mptcp_info2sockaddr(const struct mptcp_addr_info * info,struct sockaddr_storage * addr,unsigned short family)1545 void mptcp_info2sockaddr(const struct mptcp_addr_info *info,
1546 			 struct sockaddr_storage *addr,
1547 			 unsigned short family)
1548 {
1549 	memset(addr, 0, sizeof(*addr));
1550 	addr->ss_family = family;
1551 	if (addr->ss_family == AF_INET) {
1552 		struct sockaddr_in *in_addr = (struct sockaddr_in *)addr;
1553 
1554 		if (info->family == AF_INET)
1555 			in_addr->sin_addr = info->addr;
1556 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1557 		else if (ipv6_addr_v4mapped(&info->addr6))
1558 			in_addr->sin_addr.s_addr = info->addr6.s6_addr32[3];
1559 #endif
1560 		in_addr->sin_port = info->port;
1561 	}
1562 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1563 	else if (addr->ss_family == AF_INET6) {
1564 		struct sockaddr_in6 *in6_addr = (struct sockaddr_in6 *)addr;
1565 
1566 		if (info->family == AF_INET)
1567 			ipv6_addr_set_v4mapped(info->addr.s_addr,
1568 					       &in6_addr->sin6_addr);
1569 		else
1570 			in6_addr->sin6_addr = info->addr6;
1571 		in6_addr->sin6_port = info->port;
1572 	}
1573 #endif
1574 }
1575 
__mptcp_subflow_connect(struct sock * sk,const struct mptcp_pm_local * local,const struct mptcp_addr_info * remote)1576 int __mptcp_subflow_connect(struct sock *sk, const struct mptcp_pm_local *local,
1577 			    const struct mptcp_addr_info *remote)
1578 {
1579 	struct mptcp_sock *msk = mptcp_sk(sk);
1580 	struct mptcp_subflow_context *subflow;
1581 	int local_id = local->addr.id;
1582 	struct sockaddr_storage addr;
1583 	int remote_id = remote->id;
1584 	int err = -ENOTCONN;
1585 	struct socket *sf;
1586 	struct sock *ssk;
1587 	u32 remote_token;
1588 	int addrlen;
1589 
1590 	/* The userspace PM sent the request too early? */
1591 	if (!mptcp_is_fully_established(sk))
1592 		goto err_out;
1593 
1594 	err = mptcp_subflow_create_socket(sk, local->addr.family, &sf);
1595 	if (err) {
1596 		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNTXCREATSKERR);
1597 		pr_debug("msk=%p local=%d remote=%d create sock error: %d\n",
1598 			 msk, local_id, remote_id, err);
1599 		goto err_out;
1600 	}
1601 
1602 	ssk = sf->sk;
1603 	subflow = mptcp_subflow_ctx(ssk);
1604 	do {
1605 		get_random_bytes(&subflow->local_nonce, sizeof(u32));
1606 	} while (!subflow->local_nonce);
1607 
1608 	/* if 'IPADDRANY', the ID will be set later, after the routing */
1609 	if (local->addr.family == AF_INET) {
1610 		if (!local->addr.addr.s_addr)
1611 			local_id = -1;
1612 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1613 	} else if (sk->sk_family == AF_INET6) {
1614 		if (ipv6_addr_any(&local->addr.addr6))
1615 			local_id = -1;
1616 #endif
1617 	}
1618 
1619 	if (local_id >= 0)
1620 		subflow_set_local_id(subflow, local_id);
1621 
1622 	subflow->remote_key_valid = 1;
1623 	subflow->remote_key = READ_ONCE(msk->remote_key);
1624 	subflow->local_key = READ_ONCE(msk->local_key);
1625 	subflow->token = msk->token;
1626 	mptcp_info2sockaddr(&local->addr, &addr, ssk->sk_family);
1627 
1628 	addrlen = sizeof(struct sockaddr_in);
1629 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1630 	if (addr.ss_family == AF_INET6)
1631 		addrlen = sizeof(struct sockaddr_in6);
1632 #endif
1633 	ssk->sk_bound_dev_if = local->ifindex;
1634 	err = kernel_bind(sf, (struct sockaddr *)&addr, addrlen);
1635 	if (err) {
1636 		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNTXBINDERR);
1637 		pr_debug("msk=%p local=%d remote=%d bind error: %d\n",
1638 			 msk, local_id, remote_id, err);
1639 		goto failed;
1640 	}
1641 
1642 	mptcp_crypto_key_sha(subflow->remote_key, &remote_token, NULL);
1643 	pr_debug("msk=%p remote_token=%u local_id=%d remote_id=%d\n", msk,
1644 		 remote_token, local_id, remote_id);
1645 	subflow->remote_token = remote_token;
1646 	WRITE_ONCE(subflow->remote_id, remote_id);
1647 	subflow->request_join = 1;
1648 	subflow->request_bkup = !!(local->flags & MPTCP_PM_ADDR_FLAG_BACKUP);
1649 	subflow->subflow_id = msk->subflow_id++;
1650 	mptcp_info2sockaddr(remote, &addr, ssk->sk_family);
1651 
1652 	sock_hold(ssk);
1653 	list_add_tail(&subflow->node, &msk->conn_list);
1654 	err = kernel_connect(sf, (struct sockaddr *)&addr, addrlen, O_NONBLOCK);
1655 	if (err && err != -EINPROGRESS) {
1656 		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNTXCONNECTERR);
1657 		pr_debug("msk=%p local=%d remote=%d connect error: %d\n",
1658 			 msk, local_id, remote_id, err);
1659 		goto failed_unlink;
1660 	}
1661 
1662 	MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNTX);
1663 
1664 	/* discard the subflow socket */
1665 	mptcp_sock_graft(ssk, sk->sk_socket);
1666 	iput(SOCK_INODE(sf));
1667 	WRITE_ONCE(msk->allow_infinite_fallback, false);
1668 	mptcp_stop_tout_timer(sk);
1669 	return 0;
1670 
1671 failed_unlink:
1672 	list_del(&subflow->node);
1673 	sock_put(mptcp_subflow_tcp_sock(subflow));
1674 
1675 failed:
1676 	subflow->disposable = 1;
1677 	sock_release(sf);
1678 
1679 err_out:
1680 	/* we account subflows before the creation, and this failures will not
1681 	 * be caught by sk_state_change()
1682 	 */
1683 	mptcp_pm_close_subflow(msk);
1684 	return err;
1685 }
1686 
mptcp_attach_cgroup(struct sock * parent,struct sock * child)1687 static void mptcp_attach_cgroup(struct sock *parent, struct sock *child)
1688 {
1689 #ifdef CONFIG_SOCK_CGROUP_DATA
1690 	struct sock_cgroup_data *parent_skcd = &parent->sk_cgrp_data,
1691 				*child_skcd = &child->sk_cgrp_data;
1692 
1693 	/* only the additional subflows created by kworkers have to be modified */
1694 	if (cgroup_id(sock_cgroup_ptr(parent_skcd)) !=
1695 	    cgroup_id(sock_cgroup_ptr(child_skcd))) {
1696 #ifdef CONFIG_MEMCG
1697 		struct mem_cgroup *memcg = parent->sk_memcg;
1698 
1699 		mem_cgroup_sk_free(child);
1700 		if (memcg && css_tryget(&memcg->css))
1701 			child->sk_memcg = memcg;
1702 #endif /* CONFIG_MEMCG */
1703 
1704 		cgroup_sk_free(child_skcd);
1705 		*child_skcd = *parent_skcd;
1706 		cgroup_sk_clone(child_skcd);
1707 	}
1708 #endif /* CONFIG_SOCK_CGROUP_DATA */
1709 }
1710 
mptcp_subflow_ops_override(struct sock * ssk)1711 static void mptcp_subflow_ops_override(struct sock *ssk)
1712 {
1713 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1714 	if (ssk->sk_prot == &tcpv6_prot)
1715 		ssk->sk_prot = &tcpv6_prot_override;
1716 	else
1717 #endif
1718 		ssk->sk_prot = &tcp_prot_override;
1719 }
1720 
mptcp_subflow_ops_undo_override(struct sock * ssk)1721 static void mptcp_subflow_ops_undo_override(struct sock *ssk)
1722 {
1723 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1724 	if (ssk->sk_prot == &tcpv6_prot_override)
1725 		ssk->sk_prot = &tcpv6_prot;
1726 	else
1727 #endif
1728 		ssk->sk_prot = &tcp_prot;
1729 }
1730 
mptcp_subflow_create_socket(struct sock * sk,unsigned short family,struct socket ** new_sock)1731 int mptcp_subflow_create_socket(struct sock *sk, unsigned short family,
1732 				struct socket **new_sock)
1733 {
1734 	struct mptcp_subflow_context *subflow;
1735 	struct net *net = sock_net(sk);
1736 	struct socket *sf;
1737 	int err;
1738 
1739 	/* un-accepted server sockets can reach here - on bad configuration
1740 	 * bail early to avoid greater trouble later
1741 	 */
1742 	if (unlikely(!sk->sk_socket))
1743 		return -EINVAL;
1744 
1745 	err = sock_create_kern(net, family, SOCK_STREAM, IPPROTO_TCP, &sf);
1746 	if (err)
1747 		return err;
1748 
1749 	lock_sock_nested(sf->sk, SINGLE_DEPTH_NESTING);
1750 
1751 	err = security_mptcp_add_subflow(sk, sf->sk);
1752 	if (err)
1753 		goto err_free;
1754 
1755 	/* the newly created socket has to be in the same cgroup as its parent */
1756 	mptcp_attach_cgroup(sk, sf->sk);
1757 
1758 	/* kernel sockets do not by default acquire net ref, but TCP timer
1759 	 * needs it.
1760 	 * Update ns_tracker to current stack trace and refcounted tracker.
1761 	 */
1762 	sk_net_refcnt_upgrade(sf->sk);
1763 	err = tcp_set_ulp(sf->sk, "mptcp");
1764 	if (err)
1765 		goto err_free;
1766 
1767 	mptcp_sockopt_sync_locked(mptcp_sk(sk), sf->sk);
1768 	release_sock(sf->sk);
1769 
1770 	/* the newly created socket really belongs to the owning MPTCP
1771 	 * socket, even if for additional subflows the allocation is performed
1772 	 * by a kernel workqueue. Adjust inode references, so that the
1773 	 * procfs/diag interfaces really show this one belonging to the correct
1774 	 * user.
1775 	 */
1776 	SOCK_INODE(sf)->i_ino = SOCK_INODE(sk->sk_socket)->i_ino;
1777 	SOCK_INODE(sf)->i_uid = SOCK_INODE(sk->sk_socket)->i_uid;
1778 	SOCK_INODE(sf)->i_gid = SOCK_INODE(sk->sk_socket)->i_gid;
1779 
1780 	subflow = mptcp_subflow_ctx(sf->sk);
1781 	pr_debug("subflow=%p\n", subflow);
1782 
1783 	*new_sock = sf;
1784 	sock_hold(sk);
1785 	subflow->conn = sk;
1786 	mptcp_subflow_ops_override(sf->sk);
1787 
1788 	return 0;
1789 
1790 err_free:
1791 	release_sock(sf->sk);
1792 	sock_release(sf);
1793 	return err;
1794 }
1795 
subflow_create_ctx(struct sock * sk,gfp_t priority)1796 static struct mptcp_subflow_context *subflow_create_ctx(struct sock *sk,
1797 							gfp_t priority)
1798 {
1799 	struct inet_connection_sock *icsk = inet_csk(sk);
1800 	struct mptcp_subflow_context *ctx;
1801 
1802 	ctx = kzalloc(sizeof(*ctx), priority);
1803 	if (!ctx)
1804 		return NULL;
1805 
1806 	rcu_assign_pointer(icsk->icsk_ulp_data, ctx);
1807 	INIT_LIST_HEAD(&ctx->node);
1808 	INIT_LIST_HEAD(&ctx->delegated_node);
1809 
1810 	pr_debug("subflow=%p\n", ctx);
1811 
1812 	ctx->tcp_sock = sk;
1813 	WRITE_ONCE(ctx->local_id, -1);
1814 
1815 	return ctx;
1816 }
1817 
__subflow_state_change(struct sock * sk)1818 static void __subflow_state_change(struct sock *sk)
1819 {
1820 	struct socket_wq *wq;
1821 
1822 	rcu_read_lock();
1823 	wq = rcu_dereference(sk->sk_wq);
1824 	if (skwq_has_sleeper(wq))
1825 		wake_up_interruptible_all(&wq->wait);
1826 	rcu_read_unlock();
1827 }
1828 
subflow_is_done(const struct sock * sk)1829 static bool subflow_is_done(const struct sock *sk)
1830 {
1831 	return sk->sk_shutdown & RCV_SHUTDOWN || sk->sk_state == TCP_CLOSE;
1832 }
1833 
subflow_state_change(struct sock * sk)1834 static void subflow_state_change(struct sock *sk)
1835 {
1836 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1837 	struct sock *parent = subflow->conn;
1838 	struct mptcp_sock *msk;
1839 
1840 	__subflow_state_change(sk);
1841 
1842 	msk = mptcp_sk(parent);
1843 	if (subflow_simultaneous_connect(sk)) {
1844 		mptcp_do_fallback(sk);
1845 		pr_fallback(msk);
1846 		subflow->conn_finished = 1;
1847 		mptcp_propagate_state(parent, sk, subflow, NULL);
1848 	}
1849 
1850 	/* as recvmsg() does not acquire the subflow socket for ssk selection
1851 	 * a fin packet carrying a DSS can be unnoticed if we don't trigger
1852 	 * the data available machinery here.
1853 	 */
1854 	if (mptcp_subflow_data_available(sk))
1855 		mptcp_data_ready(parent, sk);
1856 	else if (unlikely(sk->sk_err))
1857 		subflow_error_report(sk);
1858 
1859 	subflow_sched_work_if_closed(mptcp_sk(parent), sk);
1860 
1861 	/* when the fallback subflow closes the rx side, trigger a 'dummy'
1862 	 * ingress data fin, so that the msk state will follow along
1863 	 */
1864 	if (__mptcp_check_fallback(msk) && subflow_is_done(sk) && msk->first == sk &&
1865 	    mptcp_update_rcv_data_fin(msk, READ_ONCE(msk->ack_seq), true))
1866 		mptcp_schedule_work(parent);
1867 }
1868 
mptcp_subflow_queue_clean(struct sock * listener_sk,struct sock * listener_ssk)1869 void mptcp_subflow_queue_clean(struct sock *listener_sk, struct sock *listener_ssk)
1870 {
1871 	struct request_sock_queue *queue = &inet_csk(listener_ssk)->icsk_accept_queue;
1872 	struct request_sock *req, *head, *tail;
1873 	struct mptcp_subflow_context *subflow;
1874 	struct sock *sk, *ssk;
1875 
1876 	/* Due to lock dependencies no relevant lock can be acquired under rskq_lock.
1877 	 * Splice the req list, so that accept() can not reach the pending ssk after
1878 	 * the listener socket is released below.
1879 	 */
1880 	spin_lock_bh(&queue->rskq_lock);
1881 	head = queue->rskq_accept_head;
1882 	tail = queue->rskq_accept_tail;
1883 	queue->rskq_accept_head = NULL;
1884 	queue->rskq_accept_tail = NULL;
1885 	spin_unlock_bh(&queue->rskq_lock);
1886 
1887 	if (!head)
1888 		return;
1889 
1890 	/* can't acquire the msk socket lock under the subflow one,
1891 	 * or will cause ABBA deadlock
1892 	 */
1893 	release_sock(listener_ssk);
1894 
1895 	for (req = head; req; req = req->dl_next) {
1896 		ssk = req->sk;
1897 		if (!sk_is_mptcp(ssk))
1898 			continue;
1899 
1900 		subflow = mptcp_subflow_ctx(ssk);
1901 		if (!subflow || !subflow->conn)
1902 			continue;
1903 
1904 		sk = subflow->conn;
1905 		sock_hold(sk);
1906 
1907 		lock_sock_nested(sk, SINGLE_DEPTH_NESTING);
1908 		__mptcp_unaccepted_force_close(sk);
1909 		release_sock(sk);
1910 
1911 		/* lockdep will report a false positive ABBA deadlock
1912 		 * between cancel_work_sync and the listener socket.
1913 		 * The involved locks belong to different sockets WRT
1914 		 * the existing AB chain.
1915 		 * Using a per socket key is problematic as key
1916 		 * deregistration requires process context and must be
1917 		 * performed at socket disposal time, in atomic
1918 		 * context.
1919 		 * Just tell lockdep to consider the listener socket
1920 		 * released here.
1921 		 */
1922 		mutex_release(&listener_sk->sk_lock.dep_map, _RET_IP_);
1923 		mptcp_cancel_work(sk);
1924 		mutex_acquire(&listener_sk->sk_lock.dep_map, 0, 0, _RET_IP_);
1925 
1926 		sock_put(sk);
1927 	}
1928 
1929 	/* we are still under the listener msk socket lock */
1930 	lock_sock_nested(listener_ssk, SINGLE_DEPTH_NESTING);
1931 
1932 	/* restore the listener queue, to let the TCP code clean it up */
1933 	spin_lock_bh(&queue->rskq_lock);
1934 	WARN_ON_ONCE(queue->rskq_accept_head);
1935 	queue->rskq_accept_head = head;
1936 	queue->rskq_accept_tail = tail;
1937 	spin_unlock_bh(&queue->rskq_lock);
1938 }
1939 
subflow_ulp_init(struct sock * sk)1940 static int subflow_ulp_init(struct sock *sk)
1941 {
1942 	struct inet_connection_sock *icsk = inet_csk(sk);
1943 	struct mptcp_subflow_context *ctx;
1944 	struct tcp_sock *tp = tcp_sk(sk);
1945 	int err = 0;
1946 
1947 	/* disallow attaching ULP to a socket unless it has been
1948 	 * created with sock_create_kern()
1949 	 */
1950 	if (!sk->sk_kern_sock) {
1951 		err = -EOPNOTSUPP;
1952 		goto out;
1953 	}
1954 
1955 	ctx = subflow_create_ctx(sk, GFP_KERNEL);
1956 	if (!ctx) {
1957 		err = -ENOMEM;
1958 		goto out;
1959 	}
1960 
1961 	pr_debug("subflow=%p, family=%d\n", ctx, sk->sk_family);
1962 
1963 	tp->is_mptcp = 1;
1964 	ctx->icsk_af_ops = icsk->icsk_af_ops;
1965 	icsk->icsk_af_ops = subflow_default_af_ops(sk);
1966 	ctx->tcp_state_change = sk->sk_state_change;
1967 	ctx->tcp_error_report = sk->sk_error_report;
1968 
1969 	WARN_ON_ONCE(sk->sk_data_ready != sock_def_readable);
1970 	WARN_ON_ONCE(sk->sk_write_space != sk_stream_write_space);
1971 
1972 	sk->sk_data_ready = subflow_data_ready;
1973 	sk->sk_write_space = subflow_write_space;
1974 	sk->sk_state_change = subflow_state_change;
1975 	sk->sk_error_report = subflow_error_report;
1976 out:
1977 	return err;
1978 }
1979 
subflow_ulp_release(struct sock * ssk)1980 static void subflow_ulp_release(struct sock *ssk)
1981 {
1982 	struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(ssk);
1983 	bool release = true;
1984 	struct sock *sk;
1985 
1986 	if (!ctx)
1987 		return;
1988 
1989 	sk = ctx->conn;
1990 	if (sk) {
1991 		/* if the msk has been orphaned, keep the ctx
1992 		 * alive, will be freed by __mptcp_close_ssk(),
1993 		 * when the subflow is still unaccepted
1994 		 */
1995 		release = ctx->disposable || list_empty(&ctx->node);
1996 
1997 		/* inet_child_forget() does not call sk_state_change(),
1998 		 * explicitly trigger the socket close machinery
1999 		 */
2000 		if (!release && !test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW,
2001 						  &mptcp_sk(sk)->flags))
2002 			mptcp_schedule_work(sk);
2003 		sock_put(sk);
2004 	}
2005 
2006 	mptcp_subflow_ops_undo_override(ssk);
2007 	if (release)
2008 		kfree_rcu(ctx, rcu);
2009 }
2010 
subflow_ulp_clone(const struct request_sock * req,struct sock * newsk,const gfp_t priority)2011 static void subflow_ulp_clone(const struct request_sock *req,
2012 			      struct sock *newsk,
2013 			      const gfp_t priority)
2014 {
2015 	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
2016 	struct mptcp_subflow_context *old_ctx = mptcp_subflow_ctx(newsk);
2017 	struct mptcp_subflow_context *new_ctx;
2018 
2019 	if (!tcp_rsk(req)->is_mptcp ||
2020 	    (!subflow_req->mp_capable && !subflow_req->mp_join)) {
2021 		subflow_ulp_fallback(newsk, old_ctx);
2022 		return;
2023 	}
2024 
2025 	new_ctx = subflow_create_ctx(newsk, priority);
2026 	if (!new_ctx) {
2027 		subflow_ulp_fallback(newsk, old_ctx);
2028 		return;
2029 	}
2030 
2031 	new_ctx->conn_finished = 1;
2032 	new_ctx->icsk_af_ops = old_ctx->icsk_af_ops;
2033 	new_ctx->tcp_state_change = old_ctx->tcp_state_change;
2034 	new_ctx->tcp_error_report = old_ctx->tcp_error_report;
2035 	new_ctx->rel_write_seq = 1;
2036 
2037 	if (subflow_req->mp_capable) {
2038 		/* see comments in subflow_syn_recv_sock(), MPTCP connection
2039 		 * is fully established only after we receive the remote key
2040 		 */
2041 		new_ctx->mp_capable = 1;
2042 		new_ctx->local_key = subflow_req->local_key;
2043 		new_ctx->token = subflow_req->token;
2044 		new_ctx->ssn_offset = subflow_req->ssn_offset;
2045 		new_ctx->idsn = subflow_req->idsn;
2046 
2047 		/* this is the first subflow, id is always 0 */
2048 		subflow_set_local_id(new_ctx, 0);
2049 	} else if (subflow_req->mp_join) {
2050 		new_ctx->ssn_offset = subflow_req->ssn_offset;
2051 		new_ctx->mp_join = 1;
2052 		WRITE_ONCE(new_ctx->fully_established, true);
2053 		new_ctx->remote_key_valid = 1;
2054 		new_ctx->backup = subflow_req->backup;
2055 		new_ctx->request_bkup = subflow_req->request_bkup;
2056 		WRITE_ONCE(new_ctx->remote_id, subflow_req->remote_id);
2057 		new_ctx->token = subflow_req->token;
2058 		new_ctx->thmac = subflow_req->thmac;
2059 
2060 		/* the subflow req id is valid, fetched via subflow_check_req()
2061 		 * and subflow_token_join_request()
2062 		 */
2063 		subflow_set_local_id(new_ctx, subflow_req->local_id);
2064 	}
2065 }
2066 
tcp_release_cb_override(struct sock * ssk)2067 static void tcp_release_cb_override(struct sock *ssk)
2068 {
2069 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
2070 	long status;
2071 
2072 	/* process and clear all the pending actions, but leave the subflow into
2073 	 * the napi queue. To respect locking, only the same CPU that originated
2074 	 * the action can touch the list. mptcp_napi_poll will take care of it.
2075 	 */
2076 	status = set_mask_bits(&subflow->delegated_status, MPTCP_DELEGATE_ACTIONS_MASK, 0);
2077 	if (status)
2078 		mptcp_subflow_process_delegated(ssk, status);
2079 
2080 	tcp_release_cb(ssk);
2081 }
2082 
tcp_abort_override(struct sock * ssk,int err)2083 static int tcp_abort_override(struct sock *ssk, int err)
2084 {
2085 	/* closing a listener subflow requires a great deal of care.
2086 	 * keep it simple and just prevent such operation
2087 	 */
2088 	if (inet_sk_state_load(ssk) == TCP_LISTEN)
2089 		return -EINVAL;
2090 
2091 	return tcp_abort(ssk, err);
2092 }
2093 
2094 static struct tcp_ulp_ops subflow_ulp_ops __read_mostly = {
2095 	.name		= "mptcp",
2096 	.owner		= THIS_MODULE,
2097 	.init		= subflow_ulp_init,
2098 	.release	= subflow_ulp_release,
2099 	.clone		= subflow_ulp_clone,
2100 };
2101 
subflow_ops_init(struct request_sock_ops * subflow_ops)2102 static int subflow_ops_init(struct request_sock_ops *subflow_ops)
2103 {
2104 	subflow_ops->obj_size = sizeof(struct mptcp_subflow_request_sock);
2105 
2106 	subflow_ops->slab = kmem_cache_create(subflow_ops->slab_name,
2107 					      subflow_ops->obj_size, 0,
2108 					      SLAB_ACCOUNT |
2109 					      SLAB_TYPESAFE_BY_RCU,
2110 					      NULL);
2111 	if (!subflow_ops->slab)
2112 		return -ENOMEM;
2113 
2114 	return 0;
2115 }
2116 
mptcp_subflow_init(void)2117 void __init mptcp_subflow_init(void)
2118 {
2119 	mptcp_subflow_v4_request_sock_ops = tcp_request_sock_ops;
2120 	mptcp_subflow_v4_request_sock_ops.slab_name = "request_sock_subflow_v4";
2121 	mptcp_subflow_v4_request_sock_ops.destructor = subflow_v4_req_destructor;
2122 
2123 	if (subflow_ops_init(&mptcp_subflow_v4_request_sock_ops) != 0)
2124 		panic("MPTCP: failed to init subflow v4 request sock ops\n");
2125 
2126 	subflow_request_sock_ipv4_ops = tcp_request_sock_ipv4_ops;
2127 	subflow_request_sock_ipv4_ops.route_req = subflow_v4_route_req;
2128 	subflow_request_sock_ipv4_ops.send_synack = subflow_v4_send_synack;
2129 
2130 	subflow_specific = ipv4_specific;
2131 	subflow_specific.conn_request = subflow_v4_conn_request;
2132 	subflow_specific.syn_recv_sock = subflow_syn_recv_sock;
2133 	subflow_specific.sk_rx_dst_set = subflow_finish_connect;
2134 	subflow_specific.rebuild_header = subflow_rebuild_header;
2135 
2136 	tcp_prot_override = tcp_prot;
2137 	tcp_prot_override.release_cb = tcp_release_cb_override;
2138 	tcp_prot_override.diag_destroy = tcp_abort_override;
2139 
2140 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
2141 	/* In struct mptcp_subflow_request_sock, we assume the TCP request sock
2142 	 * structures for v4 and v6 have the same size. It should not changed in
2143 	 * the future but better to make sure to be warned if it is no longer
2144 	 * the case.
2145 	 */
2146 	BUILD_BUG_ON(sizeof(struct tcp_request_sock) != sizeof(struct tcp6_request_sock));
2147 
2148 	mptcp_subflow_v6_request_sock_ops = tcp6_request_sock_ops;
2149 	mptcp_subflow_v6_request_sock_ops.slab_name = "request_sock_subflow_v6";
2150 	mptcp_subflow_v6_request_sock_ops.destructor = subflow_v6_req_destructor;
2151 
2152 	if (subflow_ops_init(&mptcp_subflow_v6_request_sock_ops) != 0)
2153 		panic("MPTCP: failed to init subflow v6 request sock ops\n");
2154 
2155 	subflow_request_sock_ipv6_ops = tcp_request_sock_ipv6_ops;
2156 	subflow_request_sock_ipv6_ops.route_req = subflow_v6_route_req;
2157 	subflow_request_sock_ipv6_ops.send_synack = subflow_v6_send_synack;
2158 
2159 	subflow_v6_specific = ipv6_specific;
2160 	subflow_v6_specific.conn_request = subflow_v6_conn_request;
2161 	subflow_v6_specific.syn_recv_sock = subflow_syn_recv_sock;
2162 	subflow_v6_specific.sk_rx_dst_set = subflow_finish_connect;
2163 	subflow_v6_specific.rebuild_header = subflow_v6_rebuild_header;
2164 
2165 	subflow_v6m_specific = subflow_v6_specific;
2166 	subflow_v6m_specific.queue_xmit = ipv4_specific.queue_xmit;
2167 	subflow_v6m_specific.send_check = ipv4_specific.send_check;
2168 	subflow_v6m_specific.net_header_len = ipv4_specific.net_header_len;
2169 	subflow_v6m_specific.mtu_reduced = ipv4_specific.mtu_reduced;
2170 	subflow_v6m_specific.rebuild_header = subflow_rebuild_header;
2171 
2172 	tcpv6_prot_override = tcpv6_prot;
2173 	tcpv6_prot_override.release_cb = tcp_release_cb_override;
2174 	tcpv6_prot_override.diag_destroy = tcp_abort_override;
2175 #endif
2176 
2177 	mptcp_diag_subflow_init(&subflow_ulp_ops);
2178 
2179 	if (tcp_register_ulp(&subflow_ulp_ops) != 0)
2180 		panic("MPTCP: failed to register subflows to ULP\n");
2181 }
2182