xref: /linux/net/mptcp/protocol.h (revision ed30aef3c864f99111e16d4ea5cf29488d99a278)
1 /* SPDX-License-Identifier: GPL-2.0 */
2 /* Multipath TCP
3  *
4  * Copyright (c) 2017 - 2019, Intel Corporation.
5  */
6 
7 #ifndef __MPTCP_PROTOCOL_H
8 #define __MPTCP_PROTOCOL_H
9 
10 #include <linux/random.h>
11 #include <net/tcp.h>
12 #include <net/inet_connection_sock.h>
13 
14 #define MPTCP_SUPPORTED_VERSION	1
15 
16 /* MPTCP option bits */
17 #define OPTION_MPTCP_MPC_SYN	BIT(0)
18 #define OPTION_MPTCP_MPC_SYNACK	BIT(1)
19 #define OPTION_MPTCP_MPC_ACK	BIT(2)
20 #define OPTION_MPTCP_MPJ_SYN	BIT(3)
21 #define OPTION_MPTCP_MPJ_SYNACK	BIT(4)
22 #define OPTION_MPTCP_MPJ_ACK	BIT(5)
23 #define OPTION_MPTCP_ADD_ADDR	BIT(6)
24 #define OPTION_MPTCP_ADD_ADDR6	BIT(7)
25 #define OPTION_MPTCP_RM_ADDR	BIT(8)
26 
27 /* MPTCP option subtypes */
28 #define MPTCPOPT_MP_CAPABLE	0
29 #define MPTCPOPT_MP_JOIN	1
30 #define MPTCPOPT_DSS		2
31 #define MPTCPOPT_ADD_ADDR	3
32 #define MPTCPOPT_RM_ADDR	4
33 #define MPTCPOPT_MP_PRIO	5
34 #define MPTCPOPT_MP_FAIL	6
35 #define MPTCPOPT_MP_FASTCLOSE	7
36 
37 /* MPTCP suboption lengths */
38 #define TCPOLEN_MPTCP_MPC_SYN		4
39 #define TCPOLEN_MPTCP_MPC_SYNACK	12
40 #define TCPOLEN_MPTCP_MPC_ACK		20
41 #define TCPOLEN_MPTCP_MPC_ACK_DATA	22
42 #define TCPOLEN_MPTCP_MPJ_SYN		12
43 #define TCPOLEN_MPTCP_MPJ_SYNACK	16
44 #define TCPOLEN_MPTCP_MPJ_ACK		24
45 #define TCPOLEN_MPTCP_DSS_BASE		4
46 #define TCPOLEN_MPTCP_DSS_ACK32		4
47 #define TCPOLEN_MPTCP_DSS_ACK64		8
48 #define TCPOLEN_MPTCP_DSS_MAP32		10
49 #define TCPOLEN_MPTCP_DSS_MAP64		14
50 #define TCPOLEN_MPTCP_DSS_CHECKSUM	2
51 #define TCPOLEN_MPTCP_ADD_ADDR		16
52 #define TCPOLEN_MPTCP_ADD_ADDR_PORT	18
53 #define TCPOLEN_MPTCP_ADD_ADDR_BASE	8
54 #define TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT	10
55 #define TCPOLEN_MPTCP_ADD_ADDR6		28
56 #define TCPOLEN_MPTCP_ADD_ADDR6_PORT	30
57 #define TCPOLEN_MPTCP_ADD_ADDR6_BASE	20
58 #define TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT	22
59 #define TCPOLEN_MPTCP_PORT_LEN		2
60 #define TCPOLEN_MPTCP_RM_ADDR_BASE	4
61 
62 /* MPTCP MP_JOIN flags */
63 #define MPTCPOPT_BACKUP		BIT(0)
64 #define MPTCPOPT_HMAC_LEN	20
65 #define MPTCPOPT_THMAC_LEN	8
66 
67 /* MPTCP MP_CAPABLE flags */
68 #define MPTCP_VERSION_MASK	(0x0F)
69 #define MPTCP_CAP_CHECKSUM_REQD	BIT(7)
70 #define MPTCP_CAP_EXTENSIBILITY	BIT(6)
71 #define MPTCP_CAP_HMAC_SHA256	BIT(0)
72 #define MPTCP_CAP_FLAG_MASK	(0x3F)
73 
74 /* MPTCP DSS flags */
75 #define MPTCP_DSS_DATA_FIN	BIT(4)
76 #define MPTCP_DSS_DSN64		BIT(3)
77 #define MPTCP_DSS_HAS_MAP	BIT(2)
78 #define MPTCP_DSS_ACK64		BIT(1)
79 #define MPTCP_DSS_HAS_ACK	BIT(0)
80 #define MPTCP_DSS_FLAG_MASK	(0x1F)
81 
82 /* MPTCP ADD_ADDR flags */
83 #define MPTCP_ADDR_ECHO		BIT(0)
84 #define MPTCP_ADDR_IPVERSION_4	4
85 #define MPTCP_ADDR_IPVERSION_6	6
86 
87 /* MPTCP socket flags */
88 #define MPTCP_DATA_READY	0
89 #define MPTCP_NOSPACE		1
90 #define MPTCP_WORK_RTX		2
91 #define MPTCP_WORK_EOF		3
92 #define MPTCP_FALLBACK_DONE	4
93 #define MPTCP_WORK_CLOSE_SUBFLOW 5
94 #define MPTCP_WORKER_RUNNING	6
95 
96 static inline bool before64(__u64 seq1, __u64 seq2)
97 {
98 	return (__s64)(seq1 - seq2) < 0;
99 }
100 
101 #define after64(seq2, seq1)	before64(seq1, seq2)
102 
103 struct mptcp_options_received {
104 	u64	sndr_key;
105 	u64	rcvr_key;
106 	u64	data_ack;
107 	u64	data_seq;
108 	u32	subflow_seq;
109 	u16	data_len;
110 	u16	mp_capable : 1,
111 		mp_join : 1,
112 		dss : 1,
113 		add_addr : 1,
114 		rm_addr : 1,
115 		family : 4,
116 		echo : 1,
117 		backup : 1;
118 	u32	token;
119 	u32	nonce;
120 	u64	thmac;
121 	u8	hmac[20];
122 	u8	join_id;
123 	u8	use_map:1,
124 		dsn64:1,
125 		data_fin:1,
126 		use_ack:1,
127 		ack64:1,
128 		mpc_map:1,
129 		__unused:2;
130 	u8	addr_id;
131 	u8	rm_id;
132 	union {
133 		struct in_addr	addr;
134 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
135 		struct in6_addr	addr6;
136 #endif
137 	};
138 	u64	ahmac;
139 	u16	port;
140 };
141 
142 static inline __be32 mptcp_option(u8 subopt, u8 len, u8 nib, u8 field)
143 {
144 	return htonl((TCPOPT_MPTCP << 24) | (len << 16) | (subopt << 12) |
145 		     ((nib & 0xF) << 8) | field);
146 }
147 
148 struct mptcp_addr_info {
149 	sa_family_t		family;
150 	__be16			port;
151 	u8			id;
152 	u8			flags;
153 	int			ifindex;
154 	union {
155 		struct in_addr addr;
156 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
157 		struct in6_addr addr6;
158 #endif
159 	};
160 };
161 
162 enum mptcp_pm_status {
163 	MPTCP_PM_ADD_ADDR_RECEIVED,
164 	MPTCP_PM_RM_ADDR_RECEIVED,
165 	MPTCP_PM_ESTABLISHED,
166 	MPTCP_PM_SUBFLOW_ESTABLISHED,
167 };
168 
169 struct mptcp_pm_data {
170 	struct mptcp_addr_info local;
171 	struct mptcp_addr_info remote;
172 	struct list_head anno_list;
173 
174 	spinlock_t	lock;		/*protects the whole PM data */
175 
176 	bool		add_addr_signal;
177 	bool		rm_addr_signal;
178 	bool		server_side;
179 	bool		work_pending;
180 	bool		accept_addr;
181 	bool		accept_subflow;
182 	bool		add_addr_echo;
183 	u8		add_addr_signaled;
184 	u8		add_addr_accepted;
185 	u8		local_addr_used;
186 	u8		subflows;
187 	u8		add_addr_signal_max;
188 	u8		add_addr_accept_max;
189 	u8		local_addr_max;
190 	u8		subflows_max;
191 	u8		status;
192 	u8		rm_id;
193 };
194 
195 struct mptcp_data_frag {
196 	struct list_head list;
197 	u64 data_seq;
198 	u16 data_len;
199 	u16 offset;
200 	u16 overhead;
201 	u16 already_sent;
202 	struct page *page;
203 };
204 
205 /* MPTCP connection sock */
206 struct mptcp_sock {
207 	/* inet_connection_sock must be the first member */
208 	struct inet_connection_sock sk;
209 	u64		local_key;
210 	u64		remote_key;
211 	u64		write_seq;
212 	u64		snd_nxt;
213 	u64		ack_seq;
214 	u64		rcv_data_fin_seq;
215 	struct sock	*last_snd;
216 	int		snd_burst;
217 	atomic64_t	snd_una;
218 	atomic64_t	wnd_end;
219 	unsigned long	timer_ival;
220 	u32		token;
221 	unsigned long	flags;
222 	bool		can_ack;
223 	bool		fully_established;
224 	bool		rcv_data_fin;
225 	bool		snd_data_fin_enable;
226 	bool		use_64bit_ack; /* Set when we received a 64-bit DSN */
227 	spinlock_t	join_list_lock;
228 	struct work_struct work;
229 	struct sk_buff  *ooo_last_skb;
230 	struct rb_root  out_of_order_queue;
231 	struct list_head conn_list;
232 	struct list_head rtx_queue;
233 	struct mptcp_data_frag *first_pending;
234 	struct list_head join_list;
235 	struct skb_ext	*cached_ext;	/* for the next sendmsg */
236 	struct socket	*subflow; /* outgoing connect/listener/!mp_capable */
237 	struct sock	*first;
238 	struct mptcp_pm_data	pm;
239 	struct {
240 		u32	space;	/* bytes copied in last measurement window */
241 		u32	copied; /* bytes copied in this measurement window */
242 		u64	time;	/* start time of measurement window */
243 		u64	rtt_us; /* last maximum rtt of subflows */
244 	} rcvq_space;
245 };
246 
247 #define mptcp_for_each_subflow(__msk, __subflow)			\
248 	list_for_each_entry(__subflow, &((__msk)->conn_list), node)
249 
250 static inline struct mptcp_sock *mptcp_sk(const struct sock *sk)
251 {
252 	return (struct mptcp_sock *)sk;
253 }
254 
255 static inline struct mptcp_data_frag *mptcp_send_head(const struct sock *sk)
256 {
257 	const struct mptcp_sock *msk = mptcp_sk(sk);
258 
259 	return READ_ONCE(msk->first_pending);
260 }
261 
262 static inline struct mptcp_data_frag *mptcp_send_next(struct sock *sk)
263 {
264 	struct mptcp_sock *msk = mptcp_sk(sk);
265 	struct mptcp_data_frag *cur;
266 
267 	cur = msk->first_pending;
268 	return list_is_last(&cur->list, &msk->rtx_queue) ? NULL :
269 						     list_next_entry(cur, list);
270 }
271 
272 static inline struct mptcp_data_frag *mptcp_pending_tail(const struct sock *sk)
273 {
274 	struct mptcp_sock *msk = mptcp_sk(sk);
275 
276 	if (!msk->first_pending)
277 		return NULL;
278 
279 	if (WARN_ON_ONCE(list_empty(&msk->rtx_queue)))
280 		return NULL;
281 
282 	return list_last_entry(&msk->rtx_queue, struct mptcp_data_frag, list);
283 }
284 
285 static inline struct mptcp_data_frag *mptcp_rtx_tail(const struct sock *sk)
286 {
287 	struct mptcp_sock *msk = mptcp_sk(sk);
288 
289 	if (!before64(msk->snd_nxt, atomic64_read(&msk->snd_una)))
290 		return NULL;
291 
292 	return list_last_entry(&msk->rtx_queue, struct mptcp_data_frag, list);
293 }
294 
295 static inline struct mptcp_data_frag *mptcp_rtx_head(const struct sock *sk)
296 {
297 	struct mptcp_sock *msk = mptcp_sk(sk);
298 
299 	return list_first_entry_or_null(&msk->rtx_queue, struct mptcp_data_frag, list);
300 }
301 
302 struct mptcp_subflow_request_sock {
303 	struct	tcp_request_sock sk;
304 	u16	mp_capable : 1,
305 		mp_join : 1,
306 		backup : 1;
307 	u8	local_id;
308 	u8	remote_id;
309 	u64	local_key;
310 	u64	idsn;
311 	u32	token;
312 	u32	ssn_offset;
313 	u64	thmac;
314 	u32	local_nonce;
315 	u32	remote_nonce;
316 	struct mptcp_sock	*msk;
317 	struct hlist_nulls_node token_node;
318 };
319 
320 static inline struct mptcp_subflow_request_sock *
321 mptcp_subflow_rsk(const struct request_sock *rsk)
322 {
323 	return (struct mptcp_subflow_request_sock *)rsk;
324 }
325 
326 enum mptcp_data_avail {
327 	MPTCP_SUBFLOW_NODATA,
328 	MPTCP_SUBFLOW_DATA_AVAIL,
329 	MPTCP_SUBFLOW_OOO_DATA
330 };
331 
332 /* MPTCP subflow context */
333 struct mptcp_subflow_context {
334 	struct	list_head node;/* conn_list of subflows */
335 	u64	local_key;
336 	u64	remote_key;
337 	u64	idsn;
338 	u64	map_seq;
339 	u32	snd_isn;
340 	u32	token;
341 	u32	rel_write_seq;
342 	u32	map_subflow_seq;
343 	u32	ssn_offset;
344 	u32	map_data_len;
345 	u32	request_mptcp : 1,  /* send MP_CAPABLE */
346 		request_join : 1,   /* send MP_JOIN */
347 		request_bkup : 1,
348 		mp_capable : 1,	    /* remote is MPTCP capable */
349 		mp_join : 1,	    /* remote is JOINing */
350 		fully_established : 1,	    /* path validated */
351 		pm_notified : 1,    /* PM hook called for established status */
352 		conn_finished : 1,
353 		map_valid : 1,
354 		mpc_map : 1,
355 		backup : 1,
356 		rx_eof : 1,
357 		can_ack : 1,        /* only after processing the remote a key */
358 		disposable : 1;	    /* ctx can be free at ulp release time */
359 	enum mptcp_data_avail data_avail;
360 	u32	remote_nonce;
361 	u64	thmac;
362 	u32	local_nonce;
363 	u32	remote_token;
364 	u8	hmac[MPTCPOPT_HMAC_LEN];
365 	u8	local_id;
366 	u8	remote_id;
367 
368 	struct	sock *tcp_sock;	    /* tcp sk backpointer */
369 	struct	sock *conn;	    /* parent mptcp_sock */
370 	const	struct inet_connection_sock_af_ops *icsk_af_ops;
371 	void	(*tcp_data_ready)(struct sock *sk);
372 	void	(*tcp_state_change)(struct sock *sk);
373 	void	(*tcp_write_space)(struct sock *sk);
374 
375 	struct	rcu_head rcu;
376 };
377 
378 static inline struct mptcp_subflow_context *
379 mptcp_subflow_ctx(const struct sock *sk)
380 {
381 	struct inet_connection_sock *icsk = inet_csk(sk);
382 
383 	/* Use RCU on icsk_ulp_data only for sock diag code */
384 	return (__force struct mptcp_subflow_context *)icsk->icsk_ulp_data;
385 }
386 
387 static inline struct sock *
388 mptcp_subflow_tcp_sock(const struct mptcp_subflow_context *subflow)
389 {
390 	return subflow->tcp_sock;
391 }
392 
393 static inline u64
394 mptcp_subflow_get_map_offset(const struct mptcp_subflow_context *subflow)
395 {
396 	return tcp_sk(mptcp_subflow_tcp_sock(subflow))->copied_seq -
397 		      subflow->ssn_offset -
398 		      subflow->map_subflow_seq;
399 }
400 
401 static inline u64
402 mptcp_subflow_get_mapped_dsn(const struct mptcp_subflow_context *subflow)
403 {
404 	return subflow->map_seq + mptcp_subflow_get_map_offset(subflow);
405 }
406 
407 int mptcp_is_enabled(struct net *net);
408 unsigned int mptcp_get_add_addr_timeout(struct net *net);
409 void mptcp_subflow_fully_established(struct mptcp_subflow_context *subflow,
410 				     struct mptcp_options_received *mp_opt);
411 bool mptcp_subflow_data_available(struct sock *sk);
412 void __init mptcp_subflow_init(void);
413 void mptcp_subflow_shutdown(struct sock *sk, struct sock *ssk, int how);
414 void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
415 		       struct mptcp_subflow_context *subflow);
416 void mptcp_subflow_reset(struct sock *ssk);
417 
418 /* called with sk socket lock held */
419 int __mptcp_subflow_connect(struct sock *sk, const struct mptcp_addr_info *loc,
420 			    const struct mptcp_addr_info *remote);
421 int mptcp_subflow_create_socket(struct sock *sk, struct socket **new_sock);
422 
423 static inline void mptcp_subflow_tcp_fallback(struct sock *sk,
424 					      struct mptcp_subflow_context *ctx)
425 {
426 	sk->sk_data_ready = ctx->tcp_data_ready;
427 	sk->sk_state_change = ctx->tcp_state_change;
428 	sk->sk_write_space = ctx->tcp_write_space;
429 
430 	inet_csk(sk)->icsk_af_ops = ctx->icsk_af_ops;
431 }
432 
433 void __init mptcp_proto_init(void);
434 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
435 int __init mptcp_proto_v6_init(void);
436 #endif
437 
438 struct sock *mptcp_sk_clone(const struct sock *sk,
439 			    const struct mptcp_options_received *mp_opt,
440 			    struct request_sock *req);
441 void mptcp_get_options(const struct sk_buff *skb,
442 		       struct mptcp_options_received *mp_opt);
443 
444 void mptcp_finish_connect(struct sock *sk);
445 static inline bool mptcp_is_fully_established(struct sock *sk)
446 {
447 	return inet_sk_state_load(sk) == TCP_ESTABLISHED &&
448 	       READ_ONCE(mptcp_sk(sk)->fully_established);
449 }
450 void mptcp_rcv_space_init(struct mptcp_sock *msk, const struct sock *ssk);
451 void mptcp_data_ready(struct sock *sk, struct sock *ssk);
452 bool mptcp_finish_join(struct sock *sk);
453 bool mptcp_schedule_work(struct sock *sk);
454 void mptcp_data_acked(struct sock *sk);
455 void mptcp_subflow_eof(struct sock *sk);
456 bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit);
457 static inline bool mptcp_data_fin_enabled(const struct mptcp_sock *msk)
458 {
459 	return READ_ONCE(msk->snd_data_fin_enable) &&
460 	       READ_ONCE(msk->write_seq) == READ_ONCE(msk->snd_nxt);
461 }
462 
463 void mptcp_destroy_common(struct mptcp_sock *msk);
464 
465 void __init mptcp_token_init(void);
466 static inline void mptcp_token_init_request(struct request_sock *req)
467 {
468 	mptcp_subflow_rsk(req)->token_node.pprev = NULL;
469 }
470 
471 int mptcp_token_new_request(struct request_sock *req);
472 void mptcp_token_destroy_request(struct request_sock *req);
473 int mptcp_token_new_connect(struct sock *sk);
474 void mptcp_token_accept(struct mptcp_subflow_request_sock *r,
475 			struct mptcp_sock *msk);
476 bool mptcp_token_exists(u32 token);
477 struct mptcp_sock *mptcp_token_get_sock(u32 token);
478 struct mptcp_sock *mptcp_token_iter_next(const struct net *net, long *s_slot,
479 					 long *s_num);
480 void mptcp_token_destroy(struct mptcp_sock *msk);
481 
482 void mptcp_crypto_key_sha(u64 key, u32 *token, u64 *idsn);
483 
484 void mptcp_crypto_hmac_sha(u64 key1, u64 key2, u8 *msg, int len, void *hmac);
485 
486 void __init mptcp_pm_init(void);
487 void mptcp_pm_data_init(struct mptcp_sock *msk);
488 void mptcp_pm_new_connection(struct mptcp_sock *msk, int server_side);
489 void mptcp_pm_fully_established(struct mptcp_sock *msk);
490 bool mptcp_pm_allow_new_subflow(struct mptcp_sock *msk);
491 void mptcp_pm_connection_closed(struct mptcp_sock *msk);
492 void mptcp_pm_subflow_established(struct mptcp_sock *msk,
493 				  struct mptcp_subflow_context *subflow);
494 void mptcp_pm_subflow_closed(struct mptcp_sock *msk, u8 id);
495 void mptcp_pm_add_addr_received(struct mptcp_sock *msk,
496 				const struct mptcp_addr_info *addr);
497 void mptcp_pm_rm_addr_received(struct mptcp_sock *msk, u8 rm_id);
498 void mptcp_pm_free_anno_list(struct mptcp_sock *msk);
499 struct mptcp_pm_add_entry *
500 mptcp_pm_del_add_timer(struct mptcp_sock *msk,
501 		       struct mptcp_addr_info *addr);
502 
503 int mptcp_pm_announce_addr(struct mptcp_sock *msk,
504 			   const struct mptcp_addr_info *addr,
505 			   bool echo);
506 int mptcp_pm_remove_addr(struct mptcp_sock *msk, u8 local_id);
507 int mptcp_pm_remove_subflow(struct mptcp_sock *msk, u8 local_id);
508 
509 static inline bool mptcp_pm_should_add_signal(struct mptcp_sock *msk)
510 {
511 	return READ_ONCE(msk->pm.add_addr_signal);
512 }
513 
514 static inline bool mptcp_pm_should_rm_signal(struct mptcp_sock *msk)
515 {
516 	return READ_ONCE(msk->pm.rm_addr_signal);
517 }
518 
519 static inline unsigned int mptcp_add_addr_len(int family, bool echo)
520 {
521 	if (family == AF_INET)
522 		return echo ? TCPOLEN_MPTCP_ADD_ADDR_BASE
523 			    : TCPOLEN_MPTCP_ADD_ADDR;
524 	return echo ? TCPOLEN_MPTCP_ADD_ADDR6_BASE : TCPOLEN_MPTCP_ADD_ADDR6;
525 }
526 
527 bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
528 			      struct mptcp_addr_info *saddr, bool *echo);
529 bool mptcp_pm_rm_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
530 			     u8 *rm_id);
531 int mptcp_pm_get_local_id(struct mptcp_sock *msk, struct sock_common *skc);
532 
533 void __init mptcp_pm_nl_init(void);
534 void mptcp_pm_nl_data_init(struct mptcp_sock *msk);
535 void mptcp_pm_nl_fully_established(struct mptcp_sock *msk);
536 void mptcp_pm_nl_subflow_established(struct mptcp_sock *msk);
537 void mptcp_pm_nl_add_addr_received(struct mptcp_sock *msk);
538 void mptcp_pm_nl_rm_addr_received(struct mptcp_sock *msk);
539 void mptcp_pm_nl_rm_subflow_received(struct mptcp_sock *msk, u8 rm_id);
540 int mptcp_pm_nl_get_local_id(struct mptcp_sock *msk, struct sock_common *skc);
541 
542 static inline struct mptcp_ext *mptcp_get_ext(struct sk_buff *skb)
543 {
544 	return (struct mptcp_ext *)skb_ext_find(skb, SKB_EXT_MPTCP);
545 }
546 
547 void mptcp_diag_subflow_init(struct tcp_ulp_ops *ops);
548 
549 static inline bool __mptcp_check_fallback(const struct mptcp_sock *msk)
550 {
551 	return test_bit(MPTCP_FALLBACK_DONE, &msk->flags);
552 }
553 
554 static inline bool mptcp_check_fallback(const struct sock *sk)
555 {
556 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
557 	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
558 
559 	return __mptcp_check_fallback(msk);
560 }
561 
562 static inline void __mptcp_do_fallback(struct mptcp_sock *msk)
563 {
564 	if (test_bit(MPTCP_FALLBACK_DONE, &msk->flags)) {
565 		pr_debug("TCP fallback already done (msk=%p)", msk);
566 		return;
567 	}
568 	set_bit(MPTCP_FALLBACK_DONE, &msk->flags);
569 }
570 
571 static inline void mptcp_do_fallback(struct sock *sk)
572 {
573 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
574 	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
575 
576 	__mptcp_do_fallback(msk);
577 }
578 
579 #define pr_fallback(a) pr_debug("%s:fallback to TCP (msk=%p)", __func__, a)
580 
581 static inline bool subflow_simultaneous_connect(struct sock *sk)
582 {
583 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
584 	struct sock *parent = subflow->conn;
585 
586 	return sk->sk_state == TCP_ESTABLISHED &&
587 	       !mptcp_sk(parent)->pm.server_side &&
588 	       !subflow->conn_finished;
589 }
590 
591 #ifdef CONFIG_SYN_COOKIES
592 void subflow_init_req_cookie_join_save(const struct mptcp_subflow_request_sock *subflow_req,
593 				       struct sk_buff *skb);
594 bool mptcp_token_join_cookie_init_state(struct mptcp_subflow_request_sock *subflow_req,
595 					struct sk_buff *skb);
596 void __init mptcp_join_cookie_init(void);
597 #else
598 static inline void
599 subflow_init_req_cookie_join_save(const struct mptcp_subflow_request_sock *subflow_req,
600 				  struct sk_buff *skb) {}
601 static inline bool
602 mptcp_token_join_cookie_init_state(struct mptcp_subflow_request_sock *subflow_req,
603 				   struct sk_buff *skb)
604 {
605 	return false;
606 }
607 
608 static inline void mptcp_join_cookie_init(void) {}
609 #endif
610 
611 #endif /* __MPTCP_PROTOCOL_H */
612