xref: /openbmc/linux/net/mptcp/protocol.c (revision b79de57b)
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 <linux/sched/signal.h>
13 #include <linux/atomic.h>
14 #include <net/sock.h>
15 #include <net/inet_common.h>
16 #include <net/inet_hashtables.h>
17 #include <net/protocol.h>
18 #include <net/tcp.h>
19 #include <net/tcp_states.h>
20 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
21 #include <net/transp_v6.h>
22 #endif
23 #include <net/mptcp.h>
24 #include "protocol.h"
25 #include "mib.h"
26 
27 #define MPTCP_SAME_STATE TCP_MAX_STATES
28 
29 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
30 struct mptcp6_sock {
31 	struct mptcp_sock msk;
32 	struct ipv6_pinfo np;
33 };
34 #endif
35 
36 struct mptcp_skb_cb {
37 	u32 offset;
38 };
39 
40 #define MPTCP_SKB_CB(__skb)	((struct mptcp_skb_cb *)&((__skb)->cb[0]))
41 
42 static struct percpu_counter mptcp_sockets_allocated;
43 
44 /* If msk has an initial subflow socket, and the MP_CAPABLE handshake has not
45  * completed yet or has failed, return the subflow socket.
46  * Otherwise return NULL.
47  */
48 static struct socket *__mptcp_nmpc_socket(const struct mptcp_sock *msk)
49 {
50 	if (!msk->subflow || READ_ONCE(msk->can_ack))
51 		return NULL;
52 
53 	return msk->subflow;
54 }
55 
56 static bool mptcp_is_tcpsk(struct sock *sk)
57 {
58 	struct socket *sock = sk->sk_socket;
59 
60 	if (unlikely(sk->sk_prot == &tcp_prot)) {
61 		/* we are being invoked after mptcp_accept() has
62 		 * accepted a non-mp-capable flow: sk is a tcp_sk,
63 		 * not an mptcp one.
64 		 *
65 		 * Hand the socket over to tcp so all further socket ops
66 		 * bypass mptcp.
67 		 */
68 		sock->ops = &inet_stream_ops;
69 		return true;
70 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
71 	} else if (unlikely(sk->sk_prot == &tcpv6_prot)) {
72 		sock->ops = &inet6_stream_ops;
73 		return true;
74 #endif
75 	}
76 
77 	return false;
78 }
79 
80 static struct sock *__mptcp_tcp_fallback(struct mptcp_sock *msk)
81 {
82 	sock_owned_by_me((const struct sock *)msk);
83 
84 	if (likely(!__mptcp_check_fallback(msk)))
85 		return NULL;
86 
87 	return msk->first;
88 }
89 
90 static int __mptcp_socket_create(struct mptcp_sock *msk)
91 {
92 	struct mptcp_subflow_context *subflow;
93 	struct sock *sk = (struct sock *)msk;
94 	struct socket *ssock;
95 	int err;
96 
97 	err = mptcp_subflow_create_socket(sk, &ssock);
98 	if (err)
99 		return err;
100 
101 	msk->first = ssock->sk;
102 	msk->subflow = ssock;
103 	subflow = mptcp_subflow_ctx(ssock->sk);
104 	list_add(&subflow->node, &msk->conn_list);
105 	subflow->request_mptcp = 1;
106 
107 	/* accept() will wait on first subflow sk_wq, and we always wakes up
108 	 * via msk->sk_socket
109 	 */
110 	RCU_INIT_POINTER(msk->first->sk_wq, &sk->sk_socket->wq);
111 
112 	return 0;
113 }
114 
115 static void __mptcp_move_skb(struct mptcp_sock *msk, struct sock *ssk,
116 			     struct sk_buff *skb,
117 			     unsigned int offset, size_t copy_len)
118 {
119 	struct sock *sk = (struct sock *)msk;
120 	struct sk_buff *tail;
121 
122 	__skb_unlink(skb, &ssk->sk_receive_queue);
123 
124 	skb_ext_reset(skb);
125 	skb_orphan(skb);
126 	msk->ack_seq += copy_len;
127 
128 	tail = skb_peek_tail(&sk->sk_receive_queue);
129 	if (offset == 0 && tail) {
130 		bool fragstolen;
131 		int delta;
132 
133 		if (skb_try_coalesce(tail, skb, &fragstolen, &delta)) {
134 			kfree_skb_partial(skb, fragstolen);
135 			atomic_add(delta, &sk->sk_rmem_alloc);
136 			sk_mem_charge(sk, delta);
137 			return;
138 		}
139 	}
140 
141 	skb_set_owner_r(skb, sk);
142 	__skb_queue_tail(&sk->sk_receive_queue, skb);
143 	MPTCP_SKB_CB(skb)->offset = offset;
144 }
145 
146 static void mptcp_stop_timer(struct sock *sk)
147 {
148 	struct inet_connection_sock *icsk = inet_csk(sk);
149 
150 	sk_stop_timer(sk, &icsk->icsk_retransmit_timer);
151 	mptcp_sk(sk)->timer_ival = 0;
152 }
153 
154 /* both sockets must be locked */
155 static bool mptcp_subflow_dsn_valid(const struct mptcp_sock *msk,
156 				    struct sock *ssk)
157 {
158 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
159 	u64 dsn = mptcp_subflow_get_mapped_dsn(subflow);
160 
161 	/* revalidate data sequence number.
162 	 *
163 	 * mptcp_subflow_data_available() is usually called
164 	 * without msk lock.  Its unlikely (but possible)
165 	 * that msk->ack_seq has been advanced since the last
166 	 * call found in-sequence data.
167 	 */
168 	if (likely(dsn == msk->ack_seq))
169 		return true;
170 
171 	subflow->data_avail = 0;
172 	return mptcp_subflow_data_available(ssk);
173 }
174 
175 static void mptcp_check_data_fin_ack(struct sock *sk)
176 {
177 	struct mptcp_sock *msk = mptcp_sk(sk);
178 
179 	if (__mptcp_check_fallback(msk))
180 		return;
181 
182 	/* Look for an acknowledged DATA_FIN */
183 	if (((1 << sk->sk_state) &
184 	     (TCPF_FIN_WAIT1 | TCPF_CLOSING | TCPF_LAST_ACK)) &&
185 	    msk->write_seq == atomic64_read(&msk->snd_una)) {
186 		mptcp_stop_timer(sk);
187 
188 		WRITE_ONCE(msk->snd_data_fin_enable, 0);
189 
190 		switch (sk->sk_state) {
191 		case TCP_FIN_WAIT1:
192 			inet_sk_state_store(sk, TCP_FIN_WAIT2);
193 			sk->sk_state_change(sk);
194 			break;
195 		case TCP_CLOSING:
196 			fallthrough;
197 		case TCP_LAST_ACK:
198 			inet_sk_state_store(sk, TCP_CLOSE);
199 			sk->sk_state_change(sk);
200 			break;
201 		}
202 
203 		if (sk->sk_shutdown == SHUTDOWN_MASK ||
204 		    sk->sk_state == TCP_CLOSE)
205 			sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
206 		else
207 			sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
208 	}
209 }
210 
211 static bool mptcp_pending_data_fin(struct sock *sk, u64 *seq)
212 {
213 	struct mptcp_sock *msk = mptcp_sk(sk);
214 
215 	if (READ_ONCE(msk->rcv_data_fin) &&
216 	    ((1 << sk->sk_state) &
217 	     (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_FIN_WAIT2))) {
218 		u64 rcv_data_fin_seq = READ_ONCE(msk->rcv_data_fin_seq);
219 
220 		if (msk->ack_seq == rcv_data_fin_seq) {
221 			if (seq)
222 				*seq = rcv_data_fin_seq;
223 
224 			return true;
225 		}
226 	}
227 
228 	return false;
229 }
230 
231 static void mptcp_set_timeout(const struct sock *sk, const struct sock *ssk)
232 {
233 	long tout = ssk && inet_csk(ssk)->icsk_pending ?
234 				      inet_csk(ssk)->icsk_timeout - jiffies : 0;
235 
236 	if (tout <= 0)
237 		tout = mptcp_sk(sk)->timer_ival;
238 	mptcp_sk(sk)->timer_ival = tout > 0 ? tout : TCP_RTO_MIN;
239 }
240 
241 static void mptcp_check_data_fin(struct sock *sk)
242 {
243 	struct mptcp_sock *msk = mptcp_sk(sk);
244 	u64 rcv_data_fin_seq;
245 
246 	if (__mptcp_check_fallback(msk) || !msk->first)
247 		return;
248 
249 	/* Need to ack a DATA_FIN received from a peer while this side
250 	 * of the connection is in ESTABLISHED, FIN_WAIT1, or FIN_WAIT2.
251 	 * msk->rcv_data_fin was set when parsing the incoming options
252 	 * at the subflow level and the msk lock was not held, so this
253 	 * is the first opportunity to act on the DATA_FIN and change
254 	 * the msk state.
255 	 *
256 	 * If we are caught up to the sequence number of the incoming
257 	 * DATA_FIN, send the DATA_ACK now and do state transition.  If
258 	 * not caught up, do nothing and let the recv code send DATA_ACK
259 	 * when catching up.
260 	 */
261 
262 	if (mptcp_pending_data_fin(sk, &rcv_data_fin_seq)) {
263 		struct mptcp_subflow_context *subflow;
264 
265 		msk->ack_seq++;
266 		WRITE_ONCE(msk->rcv_data_fin, 0);
267 
268 		sk->sk_shutdown |= RCV_SHUTDOWN;
269 		smp_mb__before_atomic(); /* SHUTDOWN must be visible first */
270 		set_bit(MPTCP_DATA_READY, &msk->flags);
271 
272 		switch (sk->sk_state) {
273 		case TCP_ESTABLISHED:
274 			inet_sk_state_store(sk, TCP_CLOSE_WAIT);
275 			break;
276 		case TCP_FIN_WAIT1:
277 			inet_sk_state_store(sk, TCP_CLOSING);
278 			break;
279 		case TCP_FIN_WAIT2:
280 			inet_sk_state_store(sk, TCP_CLOSE);
281 			// @@ Close subflows now?
282 			break;
283 		default:
284 			/* Other states not expected */
285 			WARN_ON_ONCE(1);
286 			break;
287 		}
288 
289 		mptcp_set_timeout(sk, NULL);
290 		mptcp_for_each_subflow(msk, subflow) {
291 			struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
292 
293 			lock_sock(ssk);
294 			tcp_send_ack(ssk);
295 			release_sock(ssk);
296 		}
297 
298 		sk->sk_state_change(sk);
299 
300 		if (sk->sk_shutdown == SHUTDOWN_MASK ||
301 		    sk->sk_state == TCP_CLOSE)
302 			sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
303 		else
304 			sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
305 	}
306 }
307 
308 static bool __mptcp_move_skbs_from_subflow(struct mptcp_sock *msk,
309 					   struct sock *ssk,
310 					   unsigned int *bytes)
311 {
312 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
313 	struct sock *sk = (struct sock *)msk;
314 	unsigned int moved = 0;
315 	bool more_data_avail;
316 	struct tcp_sock *tp;
317 	bool done = false;
318 
319 	if (!mptcp_subflow_dsn_valid(msk, ssk)) {
320 		*bytes = 0;
321 		return false;
322 	}
323 
324 	tp = tcp_sk(ssk);
325 	do {
326 		u32 map_remaining, offset;
327 		u32 seq = tp->copied_seq;
328 		struct sk_buff *skb;
329 		bool fin;
330 
331 		/* try to move as much data as available */
332 		map_remaining = subflow->map_data_len -
333 				mptcp_subflow_get_map_offset(subflow);
334 
335 		skb = skb_peek(&ssk->sk_receive_queue);
336 		if (!skb)
337 			break;
338 
339 		if (__mptcp_check_fallback(msk)) {
340 			/* if we are running under the workqueue, TCP could have
341 			 * collapsed skbs between dummy map creation and now
342 			 * be sure to adjust the size
343 			 */
344 			map_remaining = skb->len;
345 			subflow->map_data_len = skb->len;
346 		}
347 
348 		offset = seq - TCP_SKB_CB(skb)->seq;
349 		fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN;
350 		if (fin) {
351 			done = true;
352 			seq++;
353 		}
354 
355 		if (offset < skb->len) {
356 			size_t len = skb->len - offset;
357 
358 			if (tp->urg_data)
359 				done = true;
360 
361 			__mptcp_move_skb(msk, ssk, skb, offset, len);
362 			seq += len;
363 			moved += len;
364 
365 			if (WARN_ON_ONCE(map_remaining < len))
366 				break;
367 		} else {
368 			WARN_ON_ONCE(!fin);
369 			sk_eat_skb(ssk, skb);
370 			done = true;
371 		}
372 
373 		WRITE_ONCE(tp->copied_seq, seq);
374 		more_data_avail = mptcp_subflow_data_available(ssk);
375 
376 		if (atomic_read(&sk->sk_rmem_alloc) > READ_ONCE(sk->sk_rcvbuf)) {
377 			done = true;
378 			break;
379 		}
380 	} while (more_data_avail);
381 
382 	*bytes = moved;
383 
384 	/* If the moves have caught up with the DATA_FIN sequence number
385 	 * it's time to ack the DATA_FIN and change socket state, but
386 	 * this is not a good place to change state. Let the workqueue
387 	 * do it.
388 	 */
389 	if (mptcp_pending_data_fin(sk, NULL) &&
390 	    schedule_work(&msk->work))
391 		sock_hold(sk);
392 
393 	return done;
394 }
395 
396 /* In most cases we will be able to lock the mptcp socket.  If its already
397  * owned, we need to defer to the work queue to avoid ABBA deadlock.
398  */
399 static bool move_skbs_to_msk(struct mptcp_sock *msk, struct sock *ssk)
400 {
401 	struct sock *sk = (struct sock *)msk;
402 	unsigned int moved = 0;
403 
404 	if (READ_ONCE(sk->sk_lock.owned))
405 		return false;
406 
407 	if (unlikely(!spin_trylock_bh(&sk->sk_lock.slock)))
408 		return false;
409 
410 	/* must re-check after taking the lock */
411 	if (!READ_ONCE(sk->sk_lock.owned))
412 		__mptcp_move_skbs_from_subflow(msk, ssk, &moved);
413 
414 	spin_unlock_bh(&sk->sk_lock.slock);
415 
416 	return moved > 0;
417 }
418 
419 void mptcp_data_ready(struct sock *sk, struct sock *ssk)
420 {
421 	struct mptcp_sock *msk = mptcp_sk(sk);
422 
423 	set_bit(MPTCP_DATA_READY, &msk->flags);
424 
425 	if (atomic_read(&sk->sk_rmem_alloc) < READ_ONCE(sk->sk_rcvbuf) &&
426 	    move_skbs_to_msk(msk, ssk))
427 		goto wake;
428 
429 	/* don't schedule if mptcp sk is (still) over limit */
430 	if (atomic_read(&sk->sk_rmem_alloc) > READ_ONCE(sk->sk_rcvbuf))
431 		goto wake;
432 
433 	/* mptcp socket is owned, release_cb should retry */
434 	if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED,
435 			      &sk->sk_tsq_flags)) {
436 		sock_hold(sk);
437 
438 		/* need to try again, its possible release_cb() has already
439 		 * been called after the test_and_set_bit() above.
440 		 */
441 		move_skbs_to_msk(msk, ssk);
442 	}
443 wake:
444 	sk->sk_data_ready(sk);
445 }
446 
447 static void __mptcp_flush_join_list(struct mptcp_sock *msk)
448 {
449 	if (likely(list_empty(&msk->join_list)))
450 		return;
451 
452 	spin_lock_bh(&msk->join_list_lock);
453 	list_splice_tail_init(&msk->join_list, &msk->conn_list);
454 	spin_unlock_bh(&msk->join_list_lock);
455 }
456 
457 static bool mptcp_timer_pending(struct sock *sk)
458 {
459 	return timer_pending(&inet_csk(sk)->icsk_retransmit_timer);
460 }
461 
462 static void mptcp_reset_timer(struct sock *sk)
463 {
464 	struct inet_connection_sock *icsk = inet_csk(sk);
465 	unsigned long tout;
466 
467 	/* should never be called with mptcp level timer cleared */
468 	tout = READ_ONCE(mptcp_sk(sk)->timer_ival);
469 	if (WARN_ON_ONCE(!tout))
470 		tout = TCP_RTO_MIN;
471 	sk_reset_timer(sk, &icsk->icsk_retransmit_timer, jiffies + tout);
472 }
473 
474 void mptcp_data_acked(struct sock *sk)
475 {
476 	mptcp_reset_timer(sk);
477 
478 	if ((!sk_stream_is_writeable(sk) ||
479 	     (inet_sk_state_load(sk) != TCP_ESTABLISHED)) &&
480 	    schedule_work(&mptcp_sk(sk)->work))
481 		sock_hold(sk);
482 }
483 
484 void mptcp_subflow_eof(struct sock *sk)
485 {
486 	struct mptcp_sock *msk = mptcp_sk(sk);
487 
488 	if (!test_and_set_bit(MPTCP_WORK_EOF, &msk->flags) &&
489 	    schedule_work(&msk->work))
490 		sock_hold(sk);
491 }
492 
493 static void mptcp_check_for_eof(struct mptcp_sock *msk)
494 {
495 	struct mptcp_subflow_context *subflow;
496 	struct sock *sk = (struct sock *)msk;
497 	int receivers = 0;
498 
499 	mptcp_for_each_subflow(msk, subflow)
500 		receivers += !subflow->rx_eof;
501 
502 	if (!receivers && !(sk->sk_shutdown & RCV_SHUTDOWN)) {
503 		/* hopefully temporary hack: propagate shutdown status
504 		 * to msk, when all subflows agree on it
505 		 */
506 		sk->sk_shutdown |= RCV_SHUTDOWN;
507 
508 		smp_mb__before_atomic(); /* SHUTDOWN must be visible first */
509 		set_bit(MPTCP_DATA_READY, &msk->flags);
510 		sk->sk_data_ready(sk);
511 	}
512 }
513 
514 static bool mptcp_ext_cache_refill(struct mptcp_sock *msk)
515 {
516 	const struct sock *sk = (const struct sock *)msk;
517 
518 	if (!msk->cached_ext)
519 		msk->cached_ext = __skb_ext_alloc(sk->sk_allocation);
520 
521 	return !!msk->cached_ext;
522 }
523 
524 static struct sock *mptcp_subflow_recv_lookup(const struct mptcp_sock *msk)
525 {
526 	struct mptcp_subflow_context *subflow;
527 	struct sock *sk = (struct sock *)msk;
528 
529 	sock_owned_by_me(sk);
530 
531 	mptcp_for_each_subflow(msk, subflow) {
532 		if (subflow->data_avail)
533 			return mptcp_subflow_tcp_sock(subflow);
534 	}
535 
536 	return NULL;
537 }
538 
539 static bool mptcp_skb_can_collapse_to(u64 write_seq,
540 				      const struct sk_buff *skb,
541 				      const struct mptcp_ext *mpext)
542 {
543 	if (!tcp_skb_can_collapse_to(skb))
544 		return false;
545 
546 	/* can collapse only if MPTCP level sequence is in order */
547 	return mpext && mpext->data_seq + mpext->data_len == write_seq;
548 }
549 
550 static bool mptcp_frag_can_collapse_to(const struct mptcp_sock *msk,
551 				       const struct page_frag *pfrag,
552 				       const struct mptcp_data_frag *df)
553 {
554 	return df && pfrag->page == df->page &&
555 		df->data_seq + df->data_len == msk->write_seq;
556 }
557 
558 static void dfrag_uncharge(struct sock *sk, int len)
559 {
560 	sk_mem_uncharge(sk, len);
561 	sk_wmem_queued_add(sk, -len);
562 }
563 
564 static void dfrag_clear(struct sock *sk, struct mptcp_data_frag *dfrag)
565 {
566 	int len = dfrag->data_len + dfrag->overhead;
567 
568 	list_del(&dfrag->list);
569 	dfrag_uncharge(sk, len);
570 	put_page(dfrag->page);
571 }
572 
573 static void mptcp_clean_una(struct sock *sk)
574 {
575 	struct mptcp_sock *msk = mptcp_sk(sk);
576 	struct mptcp_data_frag *dtmp, *dfrag;
577 	bool cleaned = false;
578 	u64 snd_una;
579 
580 	/* on fallback we just need to ignore snd_una, as this is really
581 	 * plain TCP
582 	 */
583 	if (__mptcp_check_fallback(msk))
584 		atomic64_set(&msk->snd_una, msk->write_seq);
585 	snd_una = atomic64_read(&msk->snd_una);
586 
587 	list_for_each_entry_safe(dfrag, dtmp, &msk->rtx_queue, list) {
588 		if (after64(dfrag->data_seq + dfrag->data_len, snd_una))
589 			break;
590 
591 		dfrag_clear(sk, dfrag);
592 		cleaned = true;
593 	}
594 
595 	dfrag = mptcp_rtx_head(sk);
596 	if (dfrag && after64(snd_una, dfrag->data_seq)) {
597 		u64 delta = snd_una - dfrag->data_seq;
598 
599 		if (WARN_ON_ONCE(delta > dfrag->data_len))
600 			goto out;
601 
602 		dfrag->data_seq += delta;
603 		dfrag->offset += delta;
604 		dfrag->data_len -= delta;
605 
606 		dfrag_uncharge(sk, delta);
607 		cleaned = true;
608 	}
609 
610 out:
611 	if (cleaned) {
612 		sk_mem_reclaim_partial(sk);
613 
614 		/* Only wake up writers if a subflow is ready */
615 		if (test_bit(MPTCP_SEND_SPACE, &msk->flags))
616 			sk_stream_write_space(sk);
617 	}
618 }
619 
620 /* ensure we get enough memory for the frag hdr, beyond some minimal amount of
621  * data
622  */
623 static bool mptcp_page_frag_refill(struct sock *sk, struct page_frag *pfrag)
624 {
625 	if (likely(skb_page_frag_refill(32U + sizeof(struct mptcp_data_frag),
626 					pfrag, sk->sk_allocation)))
627 		return true;
628 
629 	sk->sk_prot->enter_memory_pressure(sk);
630 	sk_stream_moderate_sndbuf(sk);
631 	return false;
632 }
633 
634 static struct mptcp_data_frag *
635 mptcp_carve_data_frag(const struct mptcp_sock *msk, struct page_frag *pfrag,
636 		      int orig_offset)
637 {
638 	int offset = ALIGN(orig_offset, sizeof(long));
639 	struct mptcp_data_frag *dfrag;
640 
641 	dfrag = (struct mptcp_data_frag *)(page_to_virt(pfrag->page) + offset);
642 	dfrag->data_len = 0;
643 	dfrag->data_seq = msk->write_seq;
644 	dfrag->overhead = offset - orig_offset + sizeof(struct mptcp_data_frag);
645 	dfrag->offset = offset + sizeof(struct mptcp_data_frag);
646 	dfrag->page = pfrag->page;
647 
648 	return dfrag;
649 }
650 
651 static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
652 			      struct msghdr *msg, struct mptcp_data_frag *dfrag,
653 			      long *timeo, int *pmss_now,
654 			      int *ps_goal)
655 {
656 	int mss_now, avail_size, size_goal, offset, ret, frag_truesize = 0;
657 	bool dfrag_collapsed, can_collapse = false;
658 	struct mptcp_sock *msk = mptcp_sk(sk);
659 	struct mptcp_ext *mpext = NULL;
660 	bool retransmission = !!dfrag;
661 	struct sk_buff *skb, *tail;
662 	struct page_frag *pfrag;
663 	struct page *page;
664 	u64 *write_seq;
665 	size_t psize;
666 
667 	/* use the mptcp page cache so that we can easily move the data
668 	 * from one substream to another, but do per subflow memory accounting
669 	 * Note: pfrag is used only !retransmission, but the compiler if
670 	 * fooled into a warning if we don't init here
671 	 */
672 	pfrag = sk_page_frag(sk);
673 	if (!retransmission) {
674 		write_seq = &msk->write_seq;
675 		page = pfrag->page;
676 	} else {
677 		write_seq = &dfrag->data_seq;
678 		page = dfrag->page;
679 	}
680 
681 	/* compute copy limit */
682 	mss_now = tcp_send_mss(ssk, &size_goal, msg->msg_flags);
683 	*pmss_now = mss_now;
684 	*ps_goal = size_goal;
685 	avail_size = size_goal;
686 	skb = tcp_write_queue_tail(ssk);
687 	if (skb) {
688 		mpext = skb_ext_find(skb, SKB_EXT_MPTCP);
689 
690 		/* Limit the write to the size available in the
691 		 * current skb, if any, so that we create at most a new skb.
692 		 * Explicitly tells TCP internals to avoid collapsing on later
693 		 * queue management operation, to avoid breaking the ext <->
694 		 * SSN association set here
695 		 */
696 		can_collapse = (size_goal - skb->len > 0) &&
697 			      mptcp_skb_can_collapse_to(*write_seq, skb, mpext);
698 		if (!can_collapse)
699 			TCP_SKB_CB(skb)->eor = 1;
700 		else
701 			avail_size = size_goal - skb->len;
702 	}
703 
704 	if (!retransmission) {
705 		/* reuse tail pfrag, if possible, or carve a new one from the
706 		 * page allocator
707 		 */
708 		dfrag = mptcp_rtx_tail(sk);
709 		offset = pfrag->offset;
710 		dfrag_collapsed = mptcp_frag_can_collapse_to(msk, pfrag, dfrag);
711 		if (!dfrag_collapsed) {
712 			dfrag = mptcp_carve_data_frag(msk, pfrag, offset);
713 			offset = dfrag->offset;
714 			frag_truesize = dfrag->overhead;
715 		}
716 		psize = min_t(size_t, pfrag->size - offset, avail_size);
717 
718 		/* Copy to page */
719 		pr_debug("left=%zu", msg_data_left(msg));
720 		psize = copy_page_from_iter(pfrag->page, offset,
721 					    min_t(size_t, msg_data_left(msg),
722 						  psize),
723 					    &msg->msg_iter);
724 		pr_debug("left=%zu", msg_data_left(msg));
725 		if (!psize)
726 			return -EINVAL;
727 
728 		if (!sk_wmem_schedule(sk, psize + dfrag->overhead)) {
729 			iov_iter_revert(&msg->msg_iter, psize);
730 			return -ENOMEM;
731 		}
732 	} else {
733 		offset = dfrag->offset;
734 		psize = min_t(size_t, dfrag->data_len, avail_size);
735 	}
736 
737 	/* tell the TCP stack to delay the push so that we can safely
738 	 * access the skb after the sendpages call
739 	 */
740 	ret = do_tcp_sendpages(ssk, page, offset, psize,
741 			       msg->msg_flags | MSG_SENDPAGE_NOTLAST | MSG_DONTWAIT);
742 	if (ret <= 0) {
743 		if (!retransmission)
744 			iov_iter_revert(&msg->msg_iter, psize);
745 		return ret;
746 	}
747 
748 	frag_truesize += ret;
749 	if (!retransmission) {
750 		if (unlikely(ret < psize))
751 			iov_iter_revert(&msg->msg_iter, psize - ret);
752 
753 		/* send successful, keep track of sent data for mptcp-level
754 		 * retransmission
755 		 */
756 		dfrag->data_len += ret;
757 		if (!dfrag_collapsed) {
758 			get_page(dfrag->page);
759 			list_add_tail(&dfrag->list, &msk->rtx_queue);
760 			sk_wmem_queued_add(sk, frag_truesize);
761 		} else {
762 			sk_wmem_queued_add(sk, ret);
763 		}
764 
765 		/* charge data on mptcp rtx queue to the master socket
766 		 * Note: we charge such data both to sk and ssk
767 		 */
768 		sk->sk_forward_alloc -= frag_truesize;
769 	}
770 
771 	/* if the tail skb extension is still the cached one, collapsing
772 	 * really happened. Note: we can't check for 'same skb' as the sk_buff
773 	 * hdr on tail can be transmitted, freed and re-allocated by the
774 	 * do_tcp_sendpages() call
775 	 */
776 	tail = tcp_write_queue_tail(ssk);
777 	if (mpext && tail && mpext == skb_ext_find(tail, SKB_EXT_MPTCP)) {
778 		WARN_ON_ONCE(!can_collapse);
779 		mpext->data_len += ret;
780 		goto out;
781 	}
782 
783 	skb = tcp_write_queue_tail(ssk);
784 	mpext = __skb_ext_set(skb, SKB_EXT_MPTCP, msk->cached_ext);
785 	msk->cached_ext = NULL;
786 
787 	memset(mpext, 0, sizeof(*mpext));
788 	mpext->data_seq = *write_seq;
789 	mpext->subflow_seq = mptcp_subflow_ctx(ssk)->rel_write_seq;
790 	mpext->data_len = ret;
791 	mpext->use_map = 1;
792 	mpext->dsn64 = 1;
793 
794 	pr_debug("data_seq=%llu subflow_seq=%u data_len=%u dsn64=%d",
795 		 mpext->data_seq, mpext->subflow_seq, mpext->data_len,
796 		 mpext->dsn64);
797 
798 out:
799 	if (!retransmission)
800 		pfrag->offset += frag_truesize;
801 	WRITE_ONCE(*write_seq, *write_seq + ret);
802 	mptcp_subflow_ctx(ssk)->rel_write_seq += ret;
803 
804 	return ret;
805 }
806 
807 static void mptcp_nospace(struct mptcp_sock *msk, struct socket *sock)
808 {
809 	clear_bit(MPTCP_SEND_SPACE, &msk->flags);
810 	smp_mb__after_atomic(); /* msk->flags is changed by write_space cb */
811 
812 	/* enables sk->write_space() callbacks */
813 	set_bit(SOCK_NOSPACE, &sock->flags);
814 }
815 
816 static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
817 {
818 	struct mptcp_subflow_context *subflow;
819 	struct sock *backup = NULL;
820 
821 	sock_owned_by_me((const struct sock *)msk);
822 
823 	if (!mptcp_ext_cache_refill(msk))
824 		return NULL;
825 
826 	mptcp_for_each_subflow(msk, subflow) {
827 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
828 
829 		if (!sk_stream_memory_free(ssk)) {
830 			struct socket *sock = ssk->sk_socket;
831 
832 			if (sock)
833 				mptcp_nospace(msk, sock);
834 
835 			return NULL;
836 		}
837 
838 		if (subflow->backup) {
839 			if (!backup)
840 				backup = ssk;
841 
842 			continue;
843 		}
844 
845 		return ssk;
846 	}
847 
848 	return backup;
849 }
850 
851 static void ssk_check_wmem(struct mptcp_sock *msk, struct sock *ssk)
852 {
853 	struct socket *sock;
854 
855 	if (likely(sk_stream_is_writeable(ssk)))
856 		return;
857 
858 	sock = READ_ONCE(ssk->sk_socket);
859 	if (sock)
860 		mptcp_nospace(msk, sock);
861 }
862 
863 static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
864 {
865 	int mss_now = 0, size_goal = 0, ret = 0;
866 	struct mptcp_sock *msk = mptcp_sk(sk);
867 	struct page_frag *pfrag;
868 	size_t copied = 0;
869 	struct sock *ssk;
870 	bool tx_ok;
871 	long timeo;
872 
873 	if (msg->msg_flags & ~(MSG_MORE | MSG_DONTWAIT | MSG_NOSIGNAL))
874 		return -EOPNOTSUPP;
875 
876 	lock_sock(sk);
877 
878 	timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT);
879 
880 	if ((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) {
881 		ret = sk_stream_wait_connect(sk, &timeo);
882 		if (ret)
883 			goto out;
884 	}
885 
886 	pfrag = sk_page_frag(sk);
887 restart:
888 	mptcp_clean_una(sk);
889 
890 	if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN)) {
891 		ret = -EPIPE;
892 		goto out;
893 	}
894 
895 wait_for_sndbuf:
896 	__mptcp_flush_join_list(msk);
897 	ssk = mptcp_subflow_get_send(msk);
898 	while (!sk_stream_memory_free(sk) ||
899 	       !ssk ||
900 	       !mptcp_page_frag_refill(ssk, pfrag)) {
901 		if (ssk) {
902 			/* make sure retransmit timer is
903 			 * running before we wait for memory.
904 			 *
905 			 * The retransmit timer might be needed
906 			 * to make the peer send an up-to-date
907 			 * MPTCP Ack.
908 			 */
909 			mptcp_set_timeout(sk, ssk);
910 			if (!mptcp_timer_pending(sk))
911 				mptcp_reset_timer(sk);
912 		}
913 
914 		ret = sk_stream_wait_memory(sk, &timeo);
915 		if (ret)
916 			goto out;
917 
918 		mptcp_clean_una(sk);
919 
920 		ssk = mptcp_subflow_get_send(msk);
921 		if (list_empty(&msk->conn_list)) {
922 			ret = -ENOTCONN;
923 			goto out;
924 		}
925 	}
926 
927 	pr_debug("conn_list->subflow=%p", ssk);
928 
929 	lock_sock(ssk);
930 	tx_ok = msg_data_left(msg);
931 	while (tx_ok) {
932 		ret = mptcp_sendmsg_frag(sk, ssk, msg, NULL, &timeo, &mss_now,
933 					 &size_goal);
934 		if (ret < 0) {
935 			if (ret == -EAGAIN && timeo > 0) {
936 				mptcp_set_timeout(sk, ssk);
937 				release_sock(ssk);
938 				goto restart;
939 			}
940 			break;
941 		}
942 
943 		copied += ret;
944 
945 		tx_ok = msg_data_left(msg);
946 		if (!tx_ok)
947 			break;
948 
949 		if (!sk_stream_memory_free(ssk) ||
950 		    !mptcp_page_frag_refill(ssk, pfrag) ||
951 		    !mptcp_ext_cache_refill(msk)) {
952 			set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
953 			tcp_push(ssk, msg->msg_flags, mss_now,
954 				 tcp_sk(ssk)->nonagle, size_goal);
955 			mptcp_set_timeout(sk, ssk);
956 			release_sock(ssk);
957 			goto restart;
958 		}
959 
960 		/* memory is charged to mptcp level socket as well, i.e.
961 		 * if msg is very large, mptcp socket may run out of buffer
962 		 * space.  mptcp_clean_una() will release data that has
963 		 * been acked at mptcp level in the mean time, so there is
964 		 * a good chance we can continue sending data right away.
965 		 *
966 		 * Normally, when the tcp subflow can accept more data, then
967 		 * so can the MPTCP socket.  However, we need to cope with
968 		 * peers that might lag behind in their MPTCP-level
969 		 * acknowledgements, i.e.  data might have been acked at
970 		 * tcp level only.  So, we must also check the MPTCP socket
971 		 * limits before we send more data.
972 		 */
973 		if (unlikely(!sk_stream_memory_free(sk))) {
974 			tcp_push(ssk, msg->msg_flags, mss_now,
975 				 tcp_sk(ssk)->nonagle, size_goal);
976 			mptcp_clean_una(sk);
977 			if (!sk_stream_memory_free(sk)) {
978 				/* can't send more for now, need to wait for
979 				 * MPTCP-level ACKs from peer.
980 				 *
981 				 * Wakeup will happen via mptcp_clean_una().
982 				 */
983 				mptcp_set_timeout(sk, ssk);
984 				release_sock(ssk);
985 				goto wait_for_sndbuf;
986 			}
987 		}
988 	}
989 
990 	mptcp_set_timeout(sk, ssk);
991 	if (copied) {
992 		tcp_push(ssk, msg->msg_flags, mss_now, tcp_sk(ssk)->nonagle,
993 			 size_goal);
994 
995 		/* start the timer, if it's not pending */
996 		if (!mptcp_timer_pending(sk))
997 			mptcp_reset_timer(sk);
998 	}
999 
1000 	ssk_check_wmem(msk, ssk);
1001 	release_sock(ssk);
1002 out:
1003 	release_sock(sk);
1004 	return copied ? : ret;
1005 }
1006 
1007 static void mptcp_wait_data(struct sock *sk, long *timeo)
1008 {
1009 	DEFINE_WAIT_FUNC(wait, woken_wake_function);
1010 	struct mptcp_sock *msk = mptcp_sk(sk);
1011 
1012 	add_wait_queue(sk_sleep(sk), &wait);
1013 	sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);
1014 
1015 	sk_wait_event(sk, timeo,
1016 		      test_and_clear_bit(MPTCP_DATA_READY, &msk->flags), &wait);
1017 
1018 	sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);
1019 	remove_wait_queue(sk_sleep(sk), &wait);
1020 }
1021 
1022 static int __mptcp_recvmsg_mskq(struct mptcp_sock *msk,
1023 				struct msghdr *msg,
1024 				size_t len)
1025 {
1026 	struct sock *sk = (struct sock *)msk;
1027 	struct sk_buff *skb;
1028 	int copied = 0;
1029 
1030 	while ((skb = skb_peek(&sk->sk_receive_queue)) != NULL) {
1031 		u32 offset = MPTCP_SKB_CB(skb)->offset;
1032 		u32 data_len = skb->len - offset;
1033 		u32 count = min_t(size_t, len - copied, data_len);
1034 		int err;
1035 
1036 		err = skb_copy_datagram_msg(skb, offset, msg, count);
1037 		if (unlikely(err < 0)) {
1038 			if (!copied)
1039 				return err;
1040 			break;
1041 		}
1042 
1043 		copied += count;
1044 
1045 		if (count < data_len) {
1046 			MPTCP_SKB_CB(skb)->offset += count;
1047 			break;
1048 		}
1049 
1050 		__skb_unlink(skb, &sk->sk_receive_queue);
1051 		__kfree_skb(skb);
1052 
1053 		if (copied >= len)
1054 			break;
1055 	}
1056 
1057 	return copied;
1058 }
1059 
1060 /* receive buffer autotuning.  See tcp_rcv_space_adjust for more information.
1061  *
1062  * Only difference: Use highest rtt estimate of the subflows in use.
1063  */
1064 static void mptcp_rcv_space_adjust(struct mptcp_sock *msk, int copied)
1065 {
1066 	struct mptcp_subflow_context *subflow;
1067 	struct sock *sk = (struct sock *)msk;
1068 	u32 time, advmss = 1;
1069 	u64 rtt_us, mstamp;
1070 
1071 	sock_owned_by_me(sk);
1072 
1073 	if (copied <= 0)
1074 		return;
1075 
1076 	msk->rcvq_space.copied += copied;
1077 
1078 	mstamp = div_u64(tcp_clock_ns(), NSEC_PER_USEC);
1079 	time = tcp_stamp_us_delta(mstamp, msk->rcvq_space.time);
1080 
1081 	rtt_us = msk->rcvq_space.rtt_us;
1082 	if (rtt_us && time < (rtt_us >> 3))
1083 		return;
1084 
1085 	rtt_us = 0;
1086 	mptcp_for_each_subflow(msk, subflow) {
1087 		const struct tcp_sock *tp;
1088 		u64 sf_rtt_us;
1089 		u32 sf_advmss;
1090 
1091 		tp = tcp_sk(mptcp_subflow_tcp_sock(subflow));
1092 
1093 		sf_rtt_us = READ_ONCE(tp->rcv_rtt_est.rtt_us);
1094 		sf_advmss = READ_ONCE(tp->advmss);
1095 
1096 		rtt_us = max(sf_rtt_us, rtt_us);
1097 		advmss = max(sf_advmss, advmss);
1098 	}
1099 
1100 	msk->rcvq_space.rtt_us = rtt_us;
1101 	if (time < (rtt_us >> 3) || rtt_us == 0)
1102 		return;
1103 
1104 	if (msk->rcvq_space.copied <= msk->rcvq_space.space)
1105 		goto new_measure;
1106 
1107 	if (sock_net(sk)->ipv4.sysctl_tcp_moderate_rcvbuf &&
1108 	    !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
1109 		int rcvmem, rcvbuf;
1110 		u64 rcvwin, grow;
1111 
1112 		rcvwin = ((u64)msk->rcvq_space.copied << 1) + 16 * advmss;
1113 
1114 		grow = rcvwin * (msk->rcvq_space.copied - msk->rcvq_space.space);
1115 
1116 		do_div(grow, msk->rcvq_space.space);
1117 		rcvwin += (grow << 1);
1118 
1119 		rcvmem = SKB_TRUESIZE(advmss + MAX_TCP_HEADER);
1120 		while (tcp_win_from_space(sk, rcvmem) < advmss)
1121 			rcvmem += 128;
1122 
1123 		do_div(rcvwin, advmss);
1124 		rcvbuf = min_t(u64, rcvwin * rcvmem,
1125 			       sock_net(sk)->ipv4.sysctl_tcp_rmem[2]);
1126 
1127 		if (rcvbuf > sk->sk_rcvbuf) {
1128 			u32 window_clamp;
1129 
1130 			window_clamp = tcp_win_from_space(sk, rcvbuf);
1131 			WRITE_ONCE(sk->sk_rcvbuf, rcvbuf);
1132 
1133 			/* Make subflows follow along.  If we do not do this, we
1134 			 * get drops at subflow level if skbs can't be moved to
1135 			 * the mptcp rx queue fast enough (announced rcv_win can
1136 			 * exceed ssk->sk_rcvbuf).
1137 			 */
1138 			mptcp_for_each_subflow(msk, subflow) {
1139 				struct sock *ssk;
1140 
1141 				ssk = mptcp_subflow_tcp_sock(subflow);
1142 				WRITE_ONCE(ssk->sk_rcvbuf, rcvbuf);
1143 				tcp_sk(ssk)->window_clamp = window_clamp;
1144 			}
1145 		}
1146 	}
1147 
1148 	msk->rcvq_space.space = msk->rcvq_space.copied;
1149 new_measure:
1150 	msk->rcvq_space.copied = 0;
1151 	msk->rcvq_space.time = mstamp;
1152 }
1153 
1154 static bool __mptcp_move_skbs(struct mptcp_sock *msk)
1155 {
1156 	unsigned int moved = 0;
1157 	bool done;
1158 
1159 	do {
1160 		struct sock *ssk = mptcp_subflow_recv_lookup(msk);
1161 
1162 		if (!ssk)
1163 			break;
1164 
1165 		lock_sock(ssk);
1166 		done = __mptcp_move_skbs_from_subflow(msk, ssk, &moved);
1167 		release_sock(ssk);
1168 	} while (!done);
1169 
1170 	return moved > 0;
1171 }
1172 
1173 static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
1174 			 int nonblock, int flags, int *addr_len)
1175 {
1176 	struct mptcp_sock *msk = mptcp_sk(sk);
1177 	int copied = 0;
1178 	int target;
1179 	long timeo;
1180 
1181 	if (msg->msg_flags & ~(MSG_WAITALL | MSG_DONTWAIT))
1182 		return -EOPNOTSUPP;
1183 
1184 	lock_sock(sk);
1185 	timeo = sock_rcvtimeo(sk, nonblock);
1186 
1187 	len = min_t(size_t, len, INT_MAX);
1188 	target = sock_rcvlowat(sk, flags & MSG_WAITALL, len);
1189 	__mptcp_flush_join_list(msk);
1190 
1191 	while (len > (size_t)copied) {
1192 		int bytes_read;
1193 
1194 		bytes_read = __mptcp_recvmsg_mskq(msk, msg, len - copied);
1195 		if (unlikely(bytes_read < 0)) {
1196 			if (!copied)
1197 				copied = bytes_read;
1198 			goto out_err;
1199 		}
1200 
1201 		copied += bytes_read;
1202 
1203 		if (skb_queue_empty(&sk->sk_receive_queue) &&
1204 		    __mptcp_move_skbs(msk))
1205 			continue;
1206 
1207 		/* only the master socket status is relevant here. The exit
1208 		 * conditions mirror closely tcp_recvmsg()
1209 		 */
1210 		if (copied >= target)
1211 			break;
1212 
1213 		if (copied) {
1214 			if (sk->sk_err ||
1215 			    sk->sk_state == TCP_CLOSE ||
1216 			    (sk->sk_shutdown & RCV_SHUTDOWN) ||
1217 			    !timeo ||
1218 			    signal_pending(current))
1219 				break;
1220 		} else {
1221 			if (sk->sk_err) {
1222 				copied = sock_error(sk);
1223 				break;
1224 			}
1225 
1226 			if (test_and_clear_bit(MPTCP_WORK_EOF, &msk->flags))
1227 				mptcp_check_for_eof(msk);
1228 
1229 			if (sk->sk_shutdown & RCV_SHUTDOWN)
1230 				break;
1231 
1232 			if (sk->sk_state == TCP_CLOSE) {
1233 				copied = -ENOTCONN;
1234 				break;
1235 			}
1236 
1237 			if (!timeo) {
1238 				copied = -EAGAIN;
1239 				break;
1240 			}
1241 
1242 			if (signal_pending(current)) {
1243 				copied = sock_intr_errno(timeo);
1244 				break;
1245 			}
1246 		}
1247 
1248 		pr_debug("block timeout %ld", timeo);
1249 		mptcp_wait_data(sk, &timeo);
1250 	}
1251 
1252 	if (skb_queue_empty(&sk->sk_receive_queue)) {
1253 		/* entire backlog drained, clear DATA_READY. */
1254 		clear_bit(MPTCP_DATA_READY, &msk->flags);
1255 
1256 		/* .. race-breaker: ssk might have gotten new data
1257 		 * after last __mptcp_move_skbs() returned false.
1258 		 */
1259 		if (unlikely(__mptcp_move_skbs(msk)))
1260 			set_bit(MPTCP_DATA_READY, &msk->flags);
1261 	} else if (unlikely(!test_bit(MPTCP_DATA_READY, &msk->flags))) {
1262 		/* data to read but mptcp_wait_data() cleared DATA_READY */
1263 		set_bit(MPTCP_DATA_READY, &msk->flags);
1264 	}
1265 out_err:
1266 	mptcp_rcv_space_adjust(msk, copied);
1267 
1268 	release_sock(sk);
1269 	return copied;
1270 }
1271 
1272 static void mptcp_retransmit_handler(struct sock *sk)
1273 {
1274 	struct mptcp_sock *msk = mptcp_sk(sk);
1275 
1276 	if (atomic64_read(&msk->snd_una) == READ_ONCE(msk->write_seq)) {
1277 		mptcp_stop_timer(sk);
1278 	} else {
1279 		set_bit(MPTCP_WORK_RTX, &msk->flags);
1280 		if (schedule_work(&msk->work))
1281 			sock_hold(sk);
1282 	}
1283 }
1284 
1285 static void mptcp_retransmit_timer(struct timer_list *t)
1286 {
1287 	struct inet_connection_sock *icsk = from_timer(icsk, t,
1288 						       icsk_retransmit_timer);
1289 	struct sock *sk = &icsk->icsk_inet.sk;
1290 
1291 	bh_lock_sock(sk);
1292 	if (!sock_owned_by_user(sk)) {
1293 		mptcp_retransmit_handler(sk);
1294 	} else {
1295 		/* delegate our work to tcp_release_cb() */
1296 		if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED,
1297 				      &sk->sk_tsq_flags))
1298 			sock_hold(sk);
1299 	}
1300 	bh_unlock_sock(sk);
1301 	sock_put(sk);
1302 }
1303 
1304 /* Find an idle subflow.  Return NULL if there is unacked data at tcp
1305  * level.
1306  *
1307  * A backup subflow is returned only if that is the only kind available.
1308  */
1309 static struct sock *mptcp_subflow_get_retrans(const struct mptcp_sock *msk)
1310 {
1311 	struct mptcp_subflow_context *subflow;
1312 	struct sock *backup = NULL;
1313 
1314 	sock_owned_by_me((const struct sock *)msk);
1315 
1316 	mptcp_for_each_subflow(msk, subflow) {
1317 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
1318 
1319 		/* still data outstanding at TCP level?  Don't retransmit. */
1320 		if (!tcp_write_queue_empty(ssk))
1321 			return NULL;
1322 
1323 		if (subflow->backup) {
1324 			if (!backup)
1325 				backup = ssk;
1326 			continue;
1327 		}
1328 
1329 		return ssk;
1330 	}
1331 
1332 	return backup;
1333 }
1334 
1335 /* subflow sockets can be either outgoing (connect) or incoming
1336  * (accept).
1337  *
1338  * Outgoing subflows use in-kernel sockets.
1339  * Incoming subflows do not have their own 'struct socket' allocated,
1340  * so we need to use tcp_close() after detaching them from the mptcp
1341  * parent socket.
1342  */
1343 static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
1344 			      struct mptcp_subflow_context *subflow,
1345 			      long timeout)
1346 {
1347 	struct socket *sock = READ_ONCE(ssk->sk_socket);
1348 
1349 	list_del(&subflow->node);
1350 
1351 	if (sock && sock != sk->sk_socket) {
1352 		/* outgoing subflow */
1353 		sock_release(sock);
1354 	} else {
1355 		/* incoming subflow */
1356 		tcp_close(ssk, timeout);
1357 	}
1358 }
1359 
1360 static unsigned int mptcp_sync_mss(struct sock *sk, u32 pmtu)
1361 {
1362 	return 0;
1363 }
1364 
1365 static void pm_work(struct mptcp_sock *msk)
1366 {
1367 	struct mptcp_pm_data *pm = &msk->pm;
1368 
1369 	spin_lock_bh(&msk->pm.lock);
1370 
1371 	pr_debug("msk=%p status=%x", msk, pm->status);
1372 	if (pm->status & BIT(MPTCP_PM_ADD_ADDR_RECEIVED)) {
1373 		pm->status &= ~BIT(MPTCP_PM_ADD_ADDR_RECEIVED);
1374 		mptcp_pm_nl_add_addr_received(msk);
1375 	}
1376 	if (pm->status & BIT(MPTCP_PM_ESTABLISHED)) {
1377 		pm->status &= ~BIT(MPTCP_PM_ESTABLISHED);
1378 		mptcp_pm_nl_fully_established(msk);
1379 	}
1380 	if (pm->status & BIT(MPTCP_PM_SUBFLOW_ESTABLISHED)) {
1381 		pm->status &= ~BIT(MPTCP_PM_SUBFLOW_ESTABLISHED);
1382 		mptcp_pm_nl_subflow_established(msk);
1383 	}
1384 
1385 	spin_unlock_bh(&msk->pm.lock);
1386 }
1387 
1388 static void mptcp_worker(struct work_struct *work)
1389 {
1390 	struct mptcp_sock *msk = container_of(work, struct mptcp_sock, work);
1391 	struct sock *ssk, *sk = &msk->sk.icsk_inet.sk;
1392 	int orig_len, orig_offset, mss_now = 0, size_goal = 0;
1393 	struct mptcp_data_frag *dfrag;
1394 	u64 orig_write_seq;
1395 	size_t copied = 0;
1396 	struct msghdr msg = {
1397 		.msg_flags = MSG_DONTWAIT,
1398 	};
1399 	long timeo = 0;
1400 
1401 	lock_sock(sk);
1402 	mptcp_clean_una(sk);
1403 	mptcp_check_data_fin_ack(sk);
1404 	__mptcp_flush_join_list(msk);
1405 	__mptcp_move_skbs(msk);
1406 
1407 	if (msk->pm.status)
1408 		pm_work(msk);
1409 
1410 	if (test_and_clear_bit(MPTCP_WORK_EOF, &msk->flags))
1411 		mptcp_check_for_eof(msk);
1412 
1413 	mptcp_check_data_fin(sk);
1414 
1415 	if (!test_and_clear_bit(MPTCP_WORK_RTX, &msk->flags))
1416 		goto unlock;
1417 
1418 	dfrag = mptcp_rtx_head(sk);
1419 	if (!dfrag)
1420 		goto unlock;
1421 
1422 	if (!mptcp_ext_cache_refill(msk))
1423 		goto reset_unlock;
1424 
1425 	ssk = mptcp_subflow_get_retrans(msk);
1426 	if (!ssk)
1427 		goto reset_unlock;
1428 
1429 	lock_sock(ssk);
1430 
1431 	orig_len = dfrag->data_len;
1432 	orig_offset = dfrag->offset;
1433 	orig_write_seq = dfrag->data_seq;
1434 	while (dfrag->data_len > 0) {
1435 		int ret = mptcp_sendmsg_frag(sk, ssk, &msg, dfrag, &timeo,
1436 					     &mss_now, &size_goal);
1437 		if (ret < 0)
1438 			break;
1439 
1440 		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_RETRANSSEGS);
1441 		copied += ret;
1442 		dfrag->data_len -= ret;
1443 		dfrag->offset += ret;
1444 
1445 		if (!mptcp_ext_cache_refill(msk))
1446 			break;
1447 	}
1448 	if (copied)
1449 		tcp_push(ssk, msg.msg_flags, mss_now, tcp_sk(ssk)->nonagle,
1450 			 size_goal);
1451 
1452 	dfrag->data_seq = orig_write_seq;
1453 	dfrag->offset = orig_offset;
1454 	dfrag->data_len = orig_len;
1455 
1456 	mptcp_set_timeout(sk, ssk);
1457 	release_sock(ssk);
1458 
1459 reset_unlock:
1460 	if (!mptcp_timer_pending(sk))
1461 		mptcp_reset_timer(sk);
1462 
1463 unlock:
1464 	release_sock(sk);
1465 	sock_put(sk);
1466 }
1467 
1468 static int __mptcp_init_sock(struct sock *sk)
1469 {
1470 	struct mptcp_sock *msk = mptcp_sk(sk);
1471 
1472 	spin_lock_init(&msk->join_list_lock);
1473 
1474 	INIT_LIST_HEAD(&msk->conn_list);
1475 	INIT_LIST_HEAD(&msk->join_list);
1476 	INIT_LIST_HEAD(&msk->rtx_queue);
1477 	__set_bit(MPTCP_SEND_SPACE, &msk->flags);
1478 	INIT_WORK(&msk->work, mptcp_worker);
1479 
1480 	msk->first = NULL;
1481 	inet_csk(sk)->icsk_sync_mss = mptcp_sync_mss;
1482 
1483 	mptcp_pm_data_init(msk);
1484 
1485 	/* re-use the csk retrans timer for MPTCP-level retrans */
1486 	timer_setup(&msk->sk.icsk_retransmit_timer, mptcp_retransmit_timer, 0);
1487 
1488 	return 0;
1489 }
1490 
1491 static int mptcp_init_sock(struct sock *sk)
1492 {
1493 	struct net *net = sock_net(sk);
1494 	int ret;
1495 
1496 	if (!mptcp_is_enabled(net))
1497 		return -ENOPROTOOPT;
1498 
1499 	if (unlikely(!net->mib.mptcp_statistics) && !mptcp_mib_alloc(net))
1500 		return -ENOMEM;
1501 
1502 	ret = __mptcp_init_sock(sk);
1503 	if (ret)
1504 		return ret;
1505 
1506 	ret = __mptcp_socket_create(mptcp_sk(sk));
1507 	if (ret)
1508 		return ret;
1509 
1510 	sk_sockets_allocated_inc(sk);
1511 	sk->sk_rcvbuf = sock_net(sk)->ipv4.sysctl_tcp_rmem[1];
1512 	sk->sk_sndbuf = sock_net(sk)->ipv4.sysctl_tcp_wmem[2];
1513 
1514 	return 0;
1515 }
1516 
1517 static void __mptcp_clear_xmit(struct sock *sk)
1518 {
1519 	struct mptcp_sock *msk = mptcp_sk(sk);
1520 	struct mptcp_data_frag *dtmp, *dfrag;
1521 
1522 	sk_stop_timer(sk, &msk->sk.icsk_retransmit_timer);
1523 
1524 	list_for_each_entry_safe(dfrag, dtmp, &msk->rtx_queue, list)
1525 		dfrag_clear(sk, dfrag);
1526 }
1527 
1528 static void mptcp_cancel_work(struct sock *sk)
1529 {
1530 	struct mptcp_sock *msk = mptcp_sk(sk);
1531 
1532 	if (cancel_work_sync(&msk->work))
1533 		sock_put(sk);
1534 }
1535 
1536 static void mptcp_subflow_shutdown(struct sock *sk, struct sock *ssk, int how)
1537 {
1538 	lock_sock(ssk);
1539 
1540 	switch (ssk->sk_state) {
1541 	case TCP_LISTEN:
1542 		if (!(how & RCV_SHUTDOWN))
1543 			break;
1544 		/* fall through */
1545 	case TCP_SYN_SENT:
1546 		tcp_disconnect(ssk, O_NONBLOCK);
1547 		break;
1548 	default:
1549 		if (__mptcp_check_fallback(mptcp_sk(sk))) {
1550 			pr_debug("Fallback");
1551 			ssk->sk_shutdown |= how;
1552 			tcp_shutdown(ssk, how);
1553 		} else {
1554 			pr_debug("Sending DATA_FIN on subflow %p", ssk);
1555 			mptcp_set_timeout(sk, ssk);
1556 			tcp_send_ack(ssk);
1557 		}
1558 		break;
1559 	}
1560 
1561 	release_sock(ssk);
1562 }
1563 
1564 static const unsigned char new_state[16] = {
1565 	/* current state:     new state:      action:	*/
1566 	[0 /* (Invalid) */] = TCP_CLOSE,
1567 	[TCP_ESTABLISHED]   = TCP_FIN_WAIT1 | TCP_ACTION_FIN,
1568 	[TCP_SYN_SENT]      = TCP_CLOSE,
1569 	[TCP_SYN_RECV]      = TCP_FIN_WAIT1 | TCP_ACTION_FIN,
1570 	[TCP_FIN_WAIT1]     = TCP_FIN_WAIT1,
1571 	[TCP_FIN_WAIT2]     = TCP_FIN_WAIT2,
1572 	[TCP_TIME_WAIT]     = TCP_CLOSE,	/* should not happen ! */
1573 	[TCP_CLOSE]         = TCP_CLOSE,
1574 	[TCP_CLOSE_WAIT]    = TCP_LAST_ACK  | TCP_ACTION_FIN,
1575 	[TCP_LAST_ACK]      = TCP_LAST_ACK,
1576 	[TCP_LISTEN]        = TCP_CLOSE,
1577 	[TCP_CLOSING]       = TCP_CLOSING,
1578 	[TCP_NEW_SYN_RECV]  = TCP_CLOSE,	/* should not happen ! */
1579 };
1580 
1581 static int mptcp_close_state(struct sock *sk)
1582 {
1583 	int next = (int)new_state[sk->sk_state];
1584 	int ns = next & TCP_STATE_MASK;
1585 
1586 	inet_sk_state_store(sk, ns);
1587 
1588 	return next & TCP_ACTION_FIN;
1589 }
1590 
1591 static void mptcp_close(struct sock *sk, long timeout)
1592 {
1593 	struct mptcp_subflow_context *subflow, *tmp;
1594 	struct mptcp_sock *msk = mptcp_sk(sk);
1595 	LIST_HEAD(conn_list);
1596 
1597 	lock_sock(sk);
1598 	sk->sk_shutdown = SHUTDOWN_MASK;
1599 
1600 	if (sk->sk_state == TCP_LISTEN) {
1601 		inet_sk_state_store(sk, TCP_CLOSE);
1602 		goto cleanup;
1603 	} else if (sk->sk_state == TCP_CLOSE) {
1604 		goto cleanup;
1605 	}
1606 
1607 	if (__mptcp_check_fallback(msk)) {
1608 		goto update_state;
1609 	} else if (mptcp_close_state(sk)) {
1610 		pr_debug("Sending DATA_FIN sk=%p", sk);
1611 		WRITE_ONCE(msk->write_seq, msk->write_seq + 1);
1612 		WRITE_ONCE(msk->snd_data_fin_enable, 1);
1613 
1614 		mptcp_for_each_subflow(msk, subflow) {
1615 			struct sock *tcp_sk = mptcp_subflow_tcp_sock(subflow);
1616 
1617 			mptcp_subflow_shutdown(sk, tcp_sk, SHUTDOWN_MASK);
1618 		}
1619 	}
1620 
1621 	sk_stream_wait_close(sk, timeout);
1622 
1623 update_state:
1624 	inet_sk_state_store(sk, TCP_CLOSE);
1625 
1626 cleanup:
1627 	/* be sure to always acquire the join list lock, to sync vs
1628 	 * mptcp_finish_join().
1629 	 */
1630 	spin_lock_bh(&msk->join_list_lock);
1631 	list_splice_tail_init(&msk->join_list, &msk->conn_list);
1632 	spin_unlock_bh(&msk->join_list_lock);
1633 	list_splice_init(&msk->conn_list, &conn_list);
1634 
1635 	__mptcp_clear_xmit(sk);
1636 
1637 	release_sock(sk);
1638 
1639 	list_for_each_entry_safe(subflow, tmp, &conn_list, node) {
1640 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
1641 		__mptcp_close_ssk(sk, ssk, subflow, timeout);
1642 	}
1643 
1644 	mptcp_cancel_work(sk);
1645 
1646 	__skb_queue_purge(&sk->sk_receive_queue);
1647 
1648 	sk_common_release(sk);
1649 }
1650 
1651 static void mptcp_copy_inaddrs(struct sock *msk, const struct sock *ssk)
1652 {
1653 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1654 	const struct ipv6_pinfo *ssk6 = inet6_sk(ssk);
1655 	struct ipv6_pinfo *msk6 = inet6_sk(msk);
1656 
1657 	msk->sk_v6_daddr = ssk->sk_v6_daddr;
1658 	msk->sk_v6_rcv_saddr = ssk->sk_v6_rcv_saddr;
1659 
1660 	if (msk6 && ssk6) {
1661 		msk6->saddr = ssk6->saddr;
1662 		msk6->flow_label = ssk6->flow_label;
1663 	}
1664 #endif
1665 
1666 	inet_sk(msk)->inet_num = inet_sk(ssk)->inet_num;
1667 	inet_sk(msk)->inet_dport = inet_sk(ssk)->inet_dport;
1668 	inet_sk(msk)->inet_sport = inet_sk(ssk)->inet_sport;
1669 	inet_sk(msk)->inet_daddr = inet_sk(ssk)->inet_daddr;
1670 	inet_sk(msk)->inet_saddr = inet_sk(ssk)->inet_saddr;
1671 	inet_sk(msk)->inet_rcv_saddr = inet_sk(ssk)->inet_rcv_saddr;
1672 }
1673 
1674 static int mptcp_disconnect(struct sock *sk, int flags)
1675 {
1676 	/* Should never be called.
1677 	 * inet_stream_connect() calls ->disconnect, but that
1678 	 * refers to the subflow socket, not the mptcp one.
1679 	 */
1680 	WARN_ON_ONCE(1);
1681 	return 0;
1682 }
1683 
1684 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1685 static struct ipv6_pinfo *mptcp_inet6_sk(const struct sock *sk)
1686 {
1687 	unsigned int offset = sizeof(struct mptcp6_sock) - sizeof(struct ipv6_pinfo);
1688 
1689 	return (struct ipv6_pinfo *)(((u8 *)sk) + offset);
1690 }
1691 #endif
1692 
1693 struct sock *mptcp_sk_clone(const struct sock *sk,
1694 			    const struct mptcp_options_received *mp_opt,
1695 			    struct request_sock *req)
1696 {
1697 	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
1698 	struct sock *nsk = sk_clone_lock(sk, GFP_ATOMIC);
1699 	struct mptcp_sock *msk;
1700 	u64 ack_seq;
1701 
1702 	if (!nsk)
1703 		return NULL;
1704 
1705 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1706 	if (nsk->sk_family == AF_INET6)
1707 		inet_sk(nsk)->pinet6 = mptcp_inet6_sk(nsk);
1708 #endif
1709 
1710 	__mptcp_init_sock(nsk);
1711 
1712 	msk = mptcp_sk(nsk);
1713 	msk->local_key = subflow_req->local_key;
1714 	msk->token = subflow_req->token;
1715 	msk->subflow = NULL;
1716 	WRITE_ONCE(msk->fully_established, false);
1717 
1718 	msk->write_seq = subflow_req->idsn + 1;
1719 	atomic64_set(&msk->snd_una, msk->write_seq);
1720 	if (mp_opt->mp_capable) {
1721 		msk->can_ack = true;
1722 		msk->remote_key = mp_opt->sndr_key;
1723 		mptcp_crypto_key_sha(msk->remote_key, NULL, &ack_seq);
1724 		ack_seq++;
1725 		msk->ack_seq = ack_seq;
1726 	}
1727 
1728 	sock_reset_flag(nsk, SOCK_RCU_FREE);
1729 	/* will be fully established after successful MPC subflow creation */
1730 	inet_sk_state_store(nsk, TCP_SYN_RECV);
1731 	bh_unlock_sock(nsk);
1732 
1733 	/* keep a single reference */
1734 	__sock_put(nsk);
1735 	return nsk;
1736 }
1737 
1738 void mptcp_rcv_space_init(struct mptcp_sock *msk, const struct sock *ssk)
1739 {
1740 	const struct tcp_sock *tp = tcp_sk(ssk);
1741 
1742 	msk->rcvq_space.copied = 0;
1743 	msk->rcvq_space.rtt_us = 0;
1744 
1745 	msk->rcvq_space.time = tp->tcp_mstamp;
1746 
1747 	/* initial rcv_space offering made to peer */
1748 	msk->rcvq_space.space = min_t(u32, tp->rcv_wnd,
1749 				      TCP_INIT_CWND * tp->advmss);
1750 	if (msk->rcvq_space.space == 0)
1751 		msk->rcvq_space.space = TCP_INIT_CWND * TCP_MSS_DEFAULT;
1752 }
1753 
1754 static struct sock *mptcp_accept(struct sock *sk, int flags, int *err,
1755 				 bool kern)
1756 {
1757 	struct mptcp_sock *msk = mptcp_sk(sk);
1758 	struct socket *listener;
1759 	struct sock *newsk;
1760 
1761 	listener = __mptcp_nmpc_socket(msk);
1762 	if (WARN_ON_ONCE(!listener)) {
1763 		*err = -EINVAL;
1764 		return NULL;
1765 	}
1766 
1767 	pr_debug("msk=%p, listener=%p", msk, mptcp_subflow_ctx(listener->sk));
1768 	newsk = inet_csk_accept(listener->sk, flags, err, kern);
1769 	if (!newsk)
1770 		return NULL;
1771 
1772 	pr_debug("msk=%p, subflow is mptcp=%d", msk, sk_is_mptcp(newsk));
1773 	if (sk_is_mptcp(newsk)) {
1774 		struct mptcp_subflow_context *subflow;
1775 		struct sock *new_mptcp_sock;
1776 		struct sock *ssk = newsk;
1777 
1778 		subflow = mptcp_subflow_ctx(newsk);
1779 		new_mptcp_sock = subflow->conn;
1780 
1781 		/* is_mptcp should be false if subflow->conn is missing, see
1782 		 * subflow_syn_recv_sock()
1783 		 */
1784 		if (WARN_ON_ONCE(!new_mptcp_sock)) {
1785 			tcp_sk(newsk)->is_mptcp = 0;
1786 			return newsk;
1787 		}
1788 
1789 		/* acquire the 2nd reference for the owning socket */
1790 		sock_hold(new_mptcp_sock);
1791 
1792 		local_bh_disable();
1793 		bh_lock_sock(new_mptcp_sock);
1794 		msk = mptcp_sk(new_mptcp_sock);
1795 		msk->first = newsk;
1796 
1797 		newsk = new_mptcp_sock;
1798 		mptcp_copy_inaddrs(newsk, ssk);
1799 		list_add(&subflow->node, &msk->conn_list);
1800 
1801 		mptcp_rcv_space_init(msk, ssk);
1802 		bh_unlock_sock(new_mptcp_sock);
1803 
1804 		__MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPCAPABLEPASSIVEACK);
1805 		local_bh_enable();
1806 	} else {
1807 		MPTCP_INC_STATS(sock_net(sk),
1808 				MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK);
1809 	}
1810 
1811 	return newsk;
1812 }
1813 
1814 static void mptcp_destroy(struct sock *sk)
1815 {
1816 	struct mptcp_sock *msk = mptcp_sk(sk);
1817 
1818 	mptcp_token_destroy(msk);
1819 	if (msk->cached_ext)
1820 		__skb_ext_put(msk->cached_ext);
1821 
1822 	sk_sockets_allocated_dec(sk);
1823 }
1824 
1825 static int mptcp_setsockopt_sol_socket(struct mptcp_sock *msk, int optname,
1826 				       sockptr_t optval, unsigned int optlen)
1827 {
1828 	struct sock *sk = (struct sock *)msk;
1829 	struct socket *ssock;
1830 	int ret;
1831 
1832 	switch (optname) {
1833 	case SO_REUSEPORT:
1834 	case SO_REUSEADDR:
1835 		lock_sock(sk);
1836 		ssock = __mptcp_nmpc_socket(msk);
1837 		if (!ssock) {
1838 			release_sock(sk);
1839 			return -EINVAL;
1840 		}
1841 
1842 		ret = sock_setsockopt(ssock, SOL_SOCKET, optname, optval, optlen);
1843 		if (ret == 0) {
1844 			if (optname == SO_REUSEPORT)
1845 				sk->sk_reuseport = ssock->sk->sk_reuseport;
1846 			else if (optname == SO_REUSEADDR)
1847 				sk->sk_reuse = ssock->sk->sk_reuse;
1848 		}
1849 		release_sock(sk);
1850 		return ret;
1851 	}
1852 
1853 	return sock_setsockopt(sk->sk_socket, SOL_SOCKET, optname, optval, optlen);
1854 }
1855 
1856 static int mptcp_setsockopt_v6(struct mptcp_sock *msk, int optname,
1857 			       sockptr_t optval, unsigned int optlen)
1858 {
1859 	struct sock *sk = (struct sock *)msk;
1860 	int ret = -EOPNOTSUPP;
1861 	struct socket *ssock;
1862 
1863 	switch (optname) {
1864 	case IPV6_V6ONLY:
1865 		lock_sock(sk);
1866 		ssock = __mptcp_nmpc_socket(msk);
1867 		if (!ssock) {
1868 			release_sock(sk);
1869 			return -EINVAL;
1870 		}
1871 
1872 		ret = tcp_setsockopt(ssock->sk, SOL_IPV6, optname, optval, optlen);
1873 		if (ret == 0)
1874 			sk->sk_ipv6only = ssock->sk->sk_ipv6only;
1875 
1876 		release_sock(sk);
1877 		break;
1878 	}
1879 
1880 	return ret;
1881 }
1882 
1883 static int mptcp_setsockopt(struct sock *sk, int level, int optname,
1884 			    sockptr_t optval, unsigned int optlen)
1885 {
1886 	struct mptcp_sock *msk = mptcp_sk(sk);
1887 	struct sock *ssk;
1888 
1889 	pr_debug("msk=%p", msk);
1890 
1891 	if (level == SOL_SOCKET)
1892 		return mptcp_setsockopt_sol_socket(msk, optname, optval, optlen);
1893 
1894 	/* @@ the meaning of setsockopt() when the socket is connected and
1895 	 * there are multiple subflows is not yet defined. It is up to the
1896 	 * MPTCP-level socket to configure the subflows until the subflow
1897 	 * is in TCP fallback, when TCP socket options are passed through
1898 	 * to the one remaining subflow.
1899 	 */
1900 	lock_sock(sk);
1901 	ssk = __mptcp_tcp_fallback(msk);
1902 	release_sock(sk);
1903 	if (ssk)
1904 		return tcp_setsockopt(ssk, level, optname, optval, optlen);
1905 
1906 	if (level == SOL_IPV6)
1907 		return mptcp_setsockopt_v6(msk, optname, optval, optlen);
1908 
1909 	return -EOPNOTSUPP;
1910 }
1911 
1912 static int mptcp_getsockopt(struct sock *sk, int level, int optname,
1913 			    char __user *optval, int __user *option)
1914 {
1915 	struct mptcp_sock *msk = mptcp_sk(sk);
1916 	struct sock *ssk;
1917 
1918 	pr_debug("msk=%p", msk);
1919 
1920 	/* @@ the meaning of setsockopt() when the socket is connected and
1921 	 * there are multiple subflows is not yet defined. It is up to the
1922 	 * MPTCP-level socket to configure the subflows until the subflow
1923 	 * is in TCP fallback, when socket options are passed through
1924 	 * to the one remaining subflow.
1925 	 */
1926 	lock_sock(sk);
1927 	ssk = __mptcp_tcp_fallback(msk);
1928 	release_sock(sk);
1929 	if (ssk)
1930 		return tcp_getsockopt(ssk, level, optname, optval, option);
1931 
1932 	return -EOPNOTSUPP;
1933 }
1934 
1935 #define MPTCP_DEFERRED_ALL (TCPF_DELACK_TIMER_DEFERRED | \
1936 			    TCPF_WRITE_TIMER_DEFERRED)
1937 
1938 /* this is very alike tcp_release_cb() but we must handle differently a
1939  * different set of events
1940  */
1941 static void mptcp_release_cb(struct sock *sk)
1942 {
1943 	unsigned long flags, nflags;
1944 
1945 	do {
1946 		flags = sk->sk_tsq_flags;
1947 		if (!(flags & MPTCP_DEFERRED_ALL))
1948 			return;
1949 		nflags = flags & ~MPTCP_DEFERRED_ALL;
1950 	} while (cmpxchg(&sk->sk_tsq_flags, flags, nflags) != flags);
1951 
1952 	sock_release_ownership(sk);
1953 
1954 	if (flags & TCPF_DELACK_TIMER_DEFERRED) {
1955 		struct mptcp_sock *msk = mptcp_sk(sk);
1956 		struct sock *ssk;
1957 
1958 		ssk = mptcp_subflow_recv_lookup(msk);
1959 		if (!ssk || !schedule_work(&msk->work))
1960 			__sock_put(sk);
1961 	}
1962 
1963 	if (flags & TCPF_WRITE_TIMER_DEFERRED) {
1964 		mptcp_retransmit_handler(sk);
1965 		__sock_put(sk);
1966 	}
1967 }
1968 
1969 static int mptcp_hash(struct sock *sk)
1970 {
1971 	/* should never be called,
1972 	 * we hash the TCP subflows not the master socket
1973 	 */
1974 	WARN_ON_ONCE(1);
1975 	return 0;
1976 }
1977 
1978 static void mptcp_unhash(struct sock *sk)
1979 {
1980 	/* called from sk_common_release(), but nothing to do here */
1981 }
1982 
1983 static int mptcp_get_port(struct sock *sk, unsigned short snum)
1984 {
1985 	struct mptcp_sock *msk = mptcp_sk(sk);
1986 	struct socket *ssock;
1987 
1988 	ssock = __mptcp_nmpc_socket(msk);
1989 	pr_debug("msk=%p, subflow=%p", msk, ssock);
1990 	if (WARN_ON_ONCE(!ssock))
1991 		return -EINVAL;
1992 
1993 	return inet_csk_get_port(ssock->sk, snum);
1994 }
1995 
1996 void mptcp_finish_connect(struct sock *ssk)
1997 {
1998 	struct mptcp_subflow_context *subflow;
1999 	struct mptcp_sock *msk;
2000 	struct sock *sk;
2001 	u64 ack_seq;
2002 
2003 	subflow = mptcp_subflow_ctx(ssk);
2004 	sk = subflow->conn;
2005 	msk = mptcp_sk(sk);
2006 
2007 	pr_debug("msk=%p, token=%u", sk, subflow->token);
2008 
2009 	mptcp_crypto_key_sha(subflow->remote_key, NULL, &ack_seq);
2010 	ack_seq++;
2011 	subflow->map_seq = ack_seq;
2012 	subflow->map_subflow_seq = 1;
2013 
2014 	/* the socket is not connected yet, no msk/subflow ops can access/race
2015 	 * accessing the field below
2016 	 */
2017 	WRITE_ONCE(msk->remote_key, subflow->remote_key);
2018 	WRITE_ONCE(msk->local_key, subflow->local_key);
2019 	WRITE_ONCE(msk->write_seq, subflow->idsn + 1);
2020 	WRITE_ONCE(msk->ack_seq, ack_seq);
2021 	WRITE_ONCE(msk->can_ack, 1);
2022 	atomic64_set(&msk->snd_una, msk->write_seq);
2023 
2024 	mptcp_pm_new_connection(msk, 0);
2025 
2026 	mptcp_rcv_space_init(msk, ssk);
2027 }
2028 
2029 static void mptcp_sock_graft(struct sock *sk, struct socket *parent)
2030 {
2031 	write_lock_bh(&sk->sk_callback_lock);
2032 	rcu_assign_pointer(sk->sk_wq, &parent->wq);
2033 	sk_set_socket(sk, parent);
2034 	sk->sk_uid = SOCK_INODE(parent)->i_uid;
2035 	write_unlock_bh(&sk->sk_callback_lock);
2036 }
2037 
2038 bool mptcp_finish_join(struct sock *sk)
2039 {
2040 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
2041 	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
2042 	struct sock *parent = (void *)msk;
2043 	struct socket *parent_sock;
2044 	bool ret;
2045 
2046 	pr_debug("msk=%p, subflow=%p", msk, subflow);
2047 
2048 	/* mptcp socket already closing? */
2049 	if (!mptcp_is_fully_established(parent))
2050 		return false;
2051 
2052 	if (!msk->pm.server_side)
2053 		return true;
2054 
2055 	if (!mptcp_pm_allow_new_subflow(msk))
2056 		return false;
2057 
2058 	/* active connections are already on conn_list, and we can't acquire
2059 	 * msk lock here.
2060 	 * use the join list lock as synchronization point and double-check
2061 	 * msk status to avoid racing with mptcp_close()
2062 	 */
2063 	spin_lock_bh(&msk->join_list_lock);
2064 	ret = inet_sk_state_load(parent) == TCP_ESTABLISHED;
2065 	if (ret && !WARN_ON_ONCE(!list_empty(&subflow->node)))
2066 		list_add_tail(&subflow->node, &msk->join_list);
2067 	spin_unlock_bh(&msk->join_list_lock);
2068 	if (!ret)
2069 		return false;
2070 
2071 	/* attach to msk socket only after we are sure he will deal with us
2072 	 * at close time
2073 	 */
2074 	parent_sock = READ_ONCE(parent->sk_socket);
2075 	if (parent_sock && !sk->sk_socket)
2076 		mptcp_sock_graft(sk, parent_sock);
2077 	subflow->map_seq = msk->ack_seq;
2078 	return true;
2079 }
2080 
2081 static bool mptcp_memory_free(const struct sock *sk, int wake)
2082 {
2083 	struct mptcp_sock *msk = mptcp_sk(sk);
2084 
2085 	return wake ? test_bit(MPTCP_SEND_SPACE, &msk->flags) : true;
2086 }
2087 
2088 static struct proto mptcp_prot = {
2089 	.name		= "MPTCP",
2090 	.owner		= THIS_MODULE,
2091 	.init		= mptcp_init_sock,
2092 	.disconnect	= mptcp_disconnect,
2093 	.close		= mptcp_close,
2094 	.accept		= mptcp_accept,
2095 	.setsockopt	= mptcp_setsockopt,
2096 	.getsockopt	= mptcp_getsockopt,
2097 	.shutdown	= tcp_shutdown,
2098 	.destroy	= mptcp_destroy,
2099 	.sendmsg	= mptcp_sendmsg,
2100 	.recvmsg	= mptcp_recvmsg,
2101 	.release_cb	= mptcp_release_cb,
2102 	.hash		= mptcp_hash,
2103 	.unhash		= mptcp_unhash,
2104 	.get_port	= mptcp_get_port,
2105 	.sockets_allocated	= &mptcp_sockets_allocated,
2106 	.memory_allocated	= &tcp_memory_allocated,
2107 	.memory_pressure	= &tcp_memory_pressure,
2108 	.stream_memory_free	= mptcp_memory_free,
2109 	.sysctl_wmem_offset	= offsetof(struct net, ipv4.sysctl_tcp_wmem),
2110 	.sysctl_mem	= sysctl_tcp_mem,
2111 	.obj_size	= sizeof(struct mptcp_sock),
2112 	.slab_flags	= SLAB_TYPESAFE_BY_RCU,
2113 	.no_autobind	= true,
2114 };
2115 
2116 static int mptcp_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
2117 {
2118 	struct mptcp_sock *msk = mptcp_sk(sock->sk);
2119 	struct socket *ssock;
2120 	int err;
2121 
2122 	lock_sock(sock->sk);
2123 	ssock = __mptcp_nmpc_socket(msk);
2124 	if (!ssock) {
2125 		err = -EINVAL;
2126 		goto unlock;
2127 	}
2128 
2129 	err = ssock->ops->bind(ssock, uaddr, addr_len);
2130 	if (!err)
2131 		mptcp_copy_inaddrs(sock->sk, ssock->sk);
2132 
2133 unlock:
2134 	release_sock(sock->sk);
2135 	return err;
2136 }
2137 
2138 static void mptcp_subflow_early_fallback(struct mptcp_sock *msk,
2139 					 struct mptcp_subflow_context *subflow)
2140 {
2141 	subflow->request_mptcp = 0;
2142 	__mptcp_do_fallback(msk);
2143 }
2144 
2145 static int mptcp_stream_connect(struct socket *sock, struct sockaddr *uaddr,
2146 				int addr_len, int flags)
2147 {
2148 	struct mptcp_sock *msk = mptcp_sk(sock->sk);
2149 	struct mptcp_subflow_context *subflow;
2150 	struct socket *ssock;
2151 	int err;
2152 
2153 	lock_sock(sock->sk);
2154 	if (sock->state != SS_UNCONNECTED && msk->subflow) {
2155 		/* pending connection or invalid state, let existing subflow
2156 		 * cope with that
2157 		 */
2158 		ssock = msk->subflow;
2159 		goto do_connect;
2160 	}
2161 
2162 	ssock = __mptcp_nmpc_socket(msk);
2163 	if (!ssock) {
2164 		err = -EINVAL;
2165 		goto unlock;
2166 	}
2167 
2168 	mptcp_token_destroy(msk);
2169 	inet_sk_state_store(sock->sk, TCP_SYN_SENT);
2170 	subflow = mptcp_subflow_ctx(ssock->sk);
2171 #ifdef CONFIG_TCP_MD5SIG
2172 	/* no MPTCP if MD5SIG is enabled on this socket or we may run out of
2173 	 * TCP option space.
2174 	 */
2175 	if (rcu_access_pointer(tcp_sk(ssock->sk)->md5sig_info))
2176 		mptcp_subflow_early_fallback(msk, subflow);
2177 #endif
2178 	if (subflow->request_mptcp && mptcp_token_new_connect(ssock->sk))
2179 		mptcp_subflow_early_fallback(msk, subflow);
2180 
2181 do_connect:
2182 	err = ssock->ops->connect(ssock, uaddr, addr_len, flags);
2183 	sock->state = ssock->state;
2184 
2185 	/* on successful connect, the msk state will be moved to established by
2186 	 * subflow_finish_connect()
2187 	 */
2188 	if (!err || err == -EINPROGRESS)
2189 		mptcp_copy_inaddrs(sock->sk, ssock->sk);
2190 	else
2191 		inet_sk_state_store(sock->sk, inet_sk_state_load(ssock->sk));
2192 
2193 unlock:
2194 	release_sock(sock->sk);
2195 	return err;
2196 }
2197 
2198 static int mptcp_listen(struct socket *sock, int backlog)
2199 {
2200 	struct mptcp_sock *msk = mptcp_sk(sock->sk);
2201 	struct socket *ssock;
2202 	int err;
2203 
2204 	pr_debug("msk=%p", msk);
2205 
2206 	lock_sock(sock->sk);
2207 	ssock = __mptcp_nmpc_socket(msk);
2208 	if (!ssock) {
2209 		err = -EINVAL;
2210 		goto unlock;
2211 	}
2212 
2213 	mptcp_token_destroy(msk);
2214 	inet_sk_state_store(sock->sk, TCP_LISTEN);
2215 	sock_set_flag(sock->sk, SOCK_RCU_FREE);
2216 
2217 	err = ssock->ops->listen(ssock, backlog);
2218 	inet_sk_state_store(sock->sk, inet_sk_state_load(ssock->sk));
2219 	if (!err)
2220 		mptcp_copy_inaddrs(sock->sk, ssock->sk);
2221 
2222 unlock:
2223 	release_sock(sock->sk);
2224 	return err;
2225 }
2226 
2227 static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
2228 			       int flags, bool kern)
2229 {
2230 	struct mptcp_sock *msk = mptcp_sk(sock->sk);
2231 	struct socket *ssock;
2232 	int err;
2233 
2234 	pr_debug("msk=%p", msk);
2235 
2236 	lock_sock(sock->sk);
2237 	if (sock->sk->sk_state != TCP_LISTEN)
2238 		goto unlock_fail;
2239 
2240 	ssock = __mptcp_nmpc_socket(msk);
2241 	if (!ssock)
2242 		goto unlock_fail;
2243 
2244 	clear_bit(MPTCP_DATA_READY, &msk->flags);
2245 	sock_hold(ssock->sk);
2246 	release_sock(sock->sk);
2247 
2248 	err = ssock->ops->accept(sock, newsock, flags, kern);
2249 	if (err == 0 && !mptcp_is_tcpsk(newsock->sk)) {
2250 		struct mptcp_sock *msk = mptcp_sk(newsock->sk);
2251 		struct mptcp_subflow_context *subflow;
2252 
2253 		/* set ssk->sk_socket of accept()ed flows to mptcp socket.
2254 		 * This is needed so NOSPACE flag can be set from tcp stack.
2255 		 */
2256 		__mptcp_flush_join_list(msk);
2257 		mptcp_for_each_subflow(msk, subflow) {
2258 			struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
2259 
2260 			if (!ssk->sk_socket)
2261 				mptcp_sock_graft(ssk, newsock);
2262 		}
2263 	}
2264 
2265 	if (inet_csk_listen_poll(ssock->sk))
2266 		set_bit(MPTCP_DATA_READY, &msk->flags);
2267 	sock_put(ssock->sk);
2268 	return err;
2269 
2270 unlock_fail:
2271 	release_sock(sock->sk);
2272 	return -EINVAL;
2273 }
2274 
2275 static __poll_t mptcp_check_readable(struct mptcp_sock *msk)
2276 {
2277 	return test_bit(MPTCP_DATA_READY, &msk->flags) ? EPOLLIN | EPOLLRDNORM :
2278 	       0;
2279 }
2280 
2281 static __poll_t mptcp_poll(struct file *file, struct socket *sock,
2282 			   struct poll_table_struct *wait)
2283 {
2284 	struct sock *sk = sock->sk;
2285 	struct mptcp_sock *msk;
2286 	__poll_t mask = 0;
2287 	int state;
2288 
2289 	msk = mptcp_sk(sk);
2290 	sock_poll_wait(file, sock, wait);
2291 
2292 	state = inet_sk_state_load(sk);
2293 	if (state == TCP_LISTEN)
2294 		return mptcp_check_readable(msk);
2295 
2296 	if (state != TCP_SYN_SENT && state != TCP_SYN_RECV) {
2297 		mask |= mptcp_check_readable(msk);
2298 		if (sk_stream_is_writeable(sk) &&
2299 		    test_bit(MPTCP_SEND_SPACE, &msk->flags))
2300 			mask |= EPOLLOUT | EPOLLWRNORM;
2301 	}
2302 	if (sk->sk_shutdown & RCV_SHUTDOWN)
2303 		mask |= EPOLLIN | EPOLLRDNORM | EPOLLRDHUP;
2304 
2305 	return mask;
2306 }
2307 
2308 static int mptcp_shutdown(struct socket *sock, int how)
2309 {
2310 	struct mptcp_sock *msk = mptcp_sk(sock->sk);
2311 	struct mptcp_subflow_context *subflow;
2312 	int ret = 0;
2313 
2314 	pr_debug("sk=%p, how=%d", msk, how);
2315 
2316 	lock_sock(sock->sk);
2317 
2318 	how++;
2319 	if ((how & ~SHUTDOWN_MASK) || !how) {
2320 		ret = -EINVAL;
2321 		goto out_unlock;
2322 	}
2323 
2324 	if (sock->state == SS_CONNECTING) {
2325 		if ((1 << sock->sk->sk_state) &
2326 		    (TCPF_SYN_SENT | TCPF_SYN_RECV | TCPF_CLOSE))
2327 			sock->state = SS_DISCONNECTING;
2328 		else
2329 			sock->state = SS_CONNECTED;
2330 	}
2331 
2332 	/* If we've already sent a FIN, or it's a closed state, skip this. */
2333 	if (__mptcp_check_fallback(msk)) {
2334 		if (how == SHUT_WR || how == SHUT_RDWR)
2335 			inet_sk_state_store(sock->sk, TCP_FIN_WAIT1);
2336 
2337 		mptcp_for_each_subflow(msk, subflow) {
2338 			struct sock *tcp_sk = mptcp_subflow_tcp_sock(subflow);
2339 
2340 			mptcp_subflow_shutdown(sock->sk, tcp_sk, how);
2341 		}
2342 	} else if ((how & SEND_SHUTDOWN) &&
2343 		   ((1 << sock->sk->sk_state) &
2344 		    (TCPF_ESTABLISHED | TCPF_SYN_SENT |
2345 		     TCPF_SYN_RECV | TCPF_CLOSE_WAIT)) &&
2346 		   mptcp_close_state(sock->sk)) {
2347 		__mptcp_flush_join_list(msk);
2348 
2349 		WRITE_ONCE(msk->write_seq, msk->write_seq + 1);
2350 		WRITE_ONCE(msk->snd_data_fin_enable, 1);
2351 
2352 		mptcp_for_each_subflow(msk, subflow) {
2353 			struct sock *tcp_sk = mptcp_subflow_tcp_sock(subflow);
2354 
2355 			mptcp_subflow_shutdown(sock->sk, tcp_sk, how);
2356 		}
2357 	}
2358 
2359 	/* Wake up anyone sleeping in poll. */
2360 	sock->sk->sk_state_change(sock->sk);
2361 
2362 out_unlock:
2363 	release_sock(sock->sk);
2364 
2365 	return ret;
2366 }
2367 
2368 static const struct proto_ops mptcp_stream_ops = {
2369 	.family		   = PF_INET,
2370 	.owner		   = THIS_MODULE,
2371 	.release	   = inet_release,
2372 	.bind		   = mptcp_bind,
2373 	.connect	   = mptcp_stream_connect,
2374 	.socketpair	   = sock_no_socketpair,
2375 	.accept		   = mptcp_stream_accept,
2376 	.getname	   = inet_getname,
2377 	.poll		   = mptcp_poll,
2378 	.ioctl		   = inet_ioctl,
2379 	.gettstamp	   = sock_gettstamp,
2380 	.listen		   = mptcp_listen,
2381 	.shutdown	   = mptcp_shutdown,
2382 	.setsockopt	   = sock_common_setsockopt,
2383 	.getsockopt	   = sock_common_getsockopt,
2384 	.sendmsg	   = inet_sendmsg,
2385 	.recvmsg	   = inet_recvmsg,
2386 	.mmap		   = sock_no_mmap,
2387 	.sendpage	   = inet_sendpage,
2388 };
2389 
2390 static struct inet_protosw mptcp_protosw = {
2391 	.type		= SOCK_STREAM,
2392 	.protocol	= IPPROTO_MPTCP,
2393 	.prot		= &mptcp_prot,
2394 	.ops		= &mptcp_stream_ops,
2395 	.flags		= INET_PROTOSW_ICSK,
2396 };
2397 
2398 void __init mptcp_proto_init(void)
2399 {
2400 	mptcp_prot.h.hashinfo = tcp_prot.h.hashinfo;
2401 
2402 	if (percpu_counter_init(&mptcp_sockets_allocated, 0, GFP_KERNEL))
2403 		panic("Failed to allocate MPTCP pcpu counter\n");
2404 
2405 	mptcp_subflow_init();
2406 	mptcp_pm_init();
2407 	mptcp_token_init();
2408 
2409 	if (proto_register(&mptcp_prot, 1) != 0)
2410 		panic("Failed to register MPTCP proto.\n");
2411 
2412 	inet_register_protosw(&mptcp_protosw);
2413 
2414 	BUILD_BUG_ON(sizeof(struct mptcp_skb_cb) > sizeof_field(struct sk_buff, cb));
2415 }
2416 
2417 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
2418 static const struct proto_ops mptcp_v6_stream_ops = {
2419 	.family		   = PF_INET6,
2420 	.owner		   = THIS_MODULE,
2421 	.release	   = inet6_release,
2422 	.bind		   = mptcp_bind,
2423 	.connect	   = mptcp_stream_connect,
2424 	.socketpair	   = sock_no_socketpair,
2425 	.accept		   = mptcp_stream_accept,
2426 	.getname	   = inet6_getname,
2427 	.poll		   = mptcp_poll,
2428 	.ioctl		   = inet6_ioctl,
2429 	.gettstamp	   = sock_gettstamp,
2430 	.listen		   = mptcp_listen,
2431 	.shutdown	   = mptcp_shutdown,
2432 	.setsockopt	   = sock_common_setsockopt,
2433 	.getsockopt	   = sock_common_getsockopt,
2434 	.sendmsg	   = inet6_sendmsg,
2435 	.recvmsg	   = inet6_recvmsg,
2436 	.mmap		   = sock_no_mmap,
2437 	.sendpage	   = inet_sendpage,
2438 #ifdef CONFIG_COMPAT
2439 	.compat_ioctl	   = inet6_compat_ioctl,
2440 #endif
2441 };
2442 
2443 static struct proto mptcp_v6_prot;
2444 
2445 static void mptcp_v6_destroy(struct sock *sk)
2446 {
2447 	mptcp_destroy(sk);
2448 	inet6_destroy_sock(sk);
2449 }
2450 
2451 static struct inet_protosw mptcp_v6_protosw = {
2452 	.type		= SOCK_STREAM,
2453 	.protocol	= IPPROTO_MPTCP,
2454 	.prot		= &mptcp_v6_prot,
2455 	.ops		= &mptcp_v6_stream_ops,
2456 	.flags		= INET_PROTOSW_ICSK,
2457 };
2458 
2459 int __init mptcp_proto_v6_init(void)
2460 {
2461 	int err;
2462 
2463 	mptcp_v6_prot = mptcp_prot;
2464 	strcpy(mptcp_v6_prot.name, "MPTCPv6");
2465 	mptcp_v6_prot.slab = NULL;
2466 	mptcp_v6_prot.destroy = mptcp_v6_destroy;
2467 	mptcp_v6_prot.obj_size = sizeof(struct mptcp6_sock);
2468 
2469 	err = proto_register(&mptcp_v6_prot, 1);
2470 	if (err)
2471 		return err;
2472 
2473 	err = inet6_register_protosw(&mptcp_v6_protosw);
2474 	if (err)
2475 		proto_unregister(&mptcp_v6_prot);
2476 
2477 	return err;
2478 }
2479 #endif
2480