xref: /openbmc/linux/net/mptcp/protocol.c (revision 75020f2d)
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 <net/xfrm.h>
25 #include "protocol.h"
26 #include "mib.h"
27 
28 #define CREATE_TRACE_POINTS
29 #include <trace/events/mptcp.h>
30 
31 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
32 struct mptcp6_sock {
33 	struct mptcp_sock msk;
34 	struct ipv6_pinfo np;
35 };
36 #endif
37 
38 struct mptcp_skb_cb {
39 	u64 map_seq;
40 	u64 end_seq;
41 	u32 offset;
42 };
43 
44 #define MPTCP_SKB_CB(__skb)	((struct mptcp_skb_cb *)&((__skb)->cb[0]))
45 
46 static struct percpu_counter mptcp_sockets_allocated;
47 
48 static void __mptcp_destroy_sock(struct sock *sk);
49 static void __mptcp_check_send_data_fin(struct sock *sk);
50 
51 DEFINE_PER_CPU(struct mptcp_delegated_action, mptcp_delegated_actions);
52 static struct net_device mptcp_napi_dev;
53 
54 /* If msk has an initial subflow socket, and the MP_CAPABLE handshake has not
55  * completed yet or has failed, return the subflow socket.
56  * Otherwise return NULL.
57  */
58 struct socket *__mptcp_nmpc_socket(const struct mptcp_sock *msk)
59 {
60 	if (!msk->subflow || READ_ONCE(msk->can_ack))
61 		return NULL;
62 
63 	return msk->subflow;
64 }
65 
66 /* Returns end sequence number of the receiver's advertised window */
67 static u64 mptcp_wnd_end(const struct mptcp_sock *msk)
68 {
69 	return READ_ONCE(msk->wnd_end);
70 }
71 
72 static bool mptcp_is_tcpsk(struct sock *sk)
73 {
74 	struct socket *sock = sk->sk_socket;
75 
76 	if (unlikely(sk->sk_prot == &tcp_prot)) {
77 		/* we are being invoked after mptcp_accept() has
78 		 * accepted a non-mp-capable flow: sk is a tcp_sk,
79 		 * not an mptcp one.
80 		 *
81 		 * Hand the socket over to tcp so all further socket ops
82 		 * bypass mptcp.
83 		 */
84 		sock->ops = &inet_stream_ops;
85 		return true;
86 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
87 	} else if (unlikely(sk->sk_prot == &tcpv6_prot)) {
88 		sock->ops = &inet6_stream_ops;
89 		return true;
90 #endif
91 	}
92 
93 	return false;
94 }
95 
96 static int __mptcp_socket_create(struct mptcp_sock *msk)
97 {
98 	struct mptcp_subflow_context *subflow;
99 	struct sock *sk = (struct sock *)msk;
100 	struct socket *ssock;
101 	int err;
102 
103 	err = mptcp_subflow_create_socket(sk, &ssock);
104 	if (err)
105 		return err;
106 
107 	msk->first = ssock->sk;
108 	msk->subflow = ssock;
109 	subflow = mptcp_subflow_ctx(ssock->sk);
110 	list_add(&subflow->node, &msk->conn_list);
111 	sock_hold(ssock->sk);
112 	subflow->request_mptcp = 1;
113 	mptcp_sock_graft(msk->first, sk->sk_socket);
114 
115 	return 0;
116 }
117 
118 static void mptcp_drop(struct sock *sk, struct sk_buff *skb)
119 {
120 	sk_drops_add(sk, skb);
121 	__kfree_skb(skb);
122 }
123 
124 static bool mptcp_try_coalesce(struct sock *sk, struct sk_buff *to,
125 			       struct sk_buff *from)
126 {
127 	bool fragstolen;
128 	int delta;
129 
130 	if (MPTCP_SKB_CB(from)->offset ||
131 	    !skb_try_coalesce(to, from, &fragstolen, &delta))
132 		return false;
133 
134 	pr_debug("colesced seq %llx into %llx new len %d new end seq %llx",
135 		 MPTCP_SKB_CB(from)->map_seq, MPTCP_SKB_CB(to)->map_seq,
136 		 to->len, MPTCP_SKB_CB(from)->end_seq);
137 	MPTCP_SKB_CB(to)->end_seq = MPTCP_SKB_CB(from)->end_seq;
138 	kfree_skb_partial(from, fragstolen);
139 	atomic_add(delta, &sk->sk_rmem_alloc);
140 	sk_mem_charge(sk, delta);
141 	return true;
142 }
143 
144 static bool mptcp_ooo_try_coalesce(struct mptcp_sock *msk, struct sk_buff *to,
145 				   struct sk_buff *from)
146 {
147 	if (MPTCP_SKB_CB(from)->map_seq != MPTCP_SKB_CB(to)->end_seq)
148 		return false;
149 
150 	return mptcp_try_coalesce((struct sock *)msk, to, from);
151 }
152 
153 /* "inspired" by tcp_data_queue_ofo(), main differences:
154  * - use mptcp seqs
155  * - don't cope with sacks
156  */
157 static void mptcp_data_queue_ofo(struct mptcp_sock *msk, struct sk_buff *skb)
158 {
159 	struct sock *sk = (struct sock *)msk;
160 	struct rb_node **p, *parent;
161 	u64 seq, end_seq, max_seq;
162 	struct sk_buff *skb1;
163 
164 	seq = MPTCP_SKB_CB(skb)->map_seq;
165 	end_seq = MPTCP_SKB_CB(skb)->end_seq;
166 	max_seq = READ_ONCE(msk->rcv_wnd_sent);
167 
168 	pr_debug("msk=%p seq=%llx limit=%llx empty=%d", msk, seq, max_seq,
169 		 RB_EMPTY_ROOT(&msk->out_of_order_queue));
170 	if (after64(end_seq, max_seq)) {
171 		/* out of window */
172 		mptcp_drop(sk, skb);
173 		pr_debug("oow by %lld, rcv_wnd_sent %llu\n",
174 			 (unsigned long long)end_seq - (unsigned long)max_seq,
175 			 (unsigned long long)msk->rcv_wnd_sent);
176 		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_NODSSWINDOW);
177 		return;
178 	}
179 
180 	p = &msk->out_of_order_queue.rb_node;
181 	MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOQUEUE);
182 	if (RB_EMPTY_ROOT(&msk->out_of_order_queue)) {
183 		rb_link_node(&skb->rbnode, NULL, p);
184 		rb_insert_color(&skb->rbnode, &msk->out_of_order_queue);
185 		msk->ooo_last_skb = skb;
186 		goto end;
187 	}
188 
189 	/* with 2 subflows, adding at end of ooo queue is quite likely
190 	 * Use of ooo_last_skb avoids the O(Log(N)) rbtree lookup.
191 	 */
192 	if (mptcp_ooo_try_coalesce(msk, msk->ooo_last_skb, skb)) {
193 		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOMERGE);
194 		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOQUEUETAIL);
195 		return;
196 	}
197 
198 	/* Can avoid an rbtree lookup if we are adding skb after ooo_last_skb */
199 	if (!before64(seq, MPTCP_SKB_CB(msk->ooo_last_skb)->end_seq)) {
200 		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOQUEUETAIL);
201 		parent = &msk->ooo_last_skb->rbnode;
202 		p = &parent->rb_right;
203 		goto insert;
204 	}
205 
206 	/* Find place to insert this segment. Handle overlaps on the way. */
207 	parent = NULL;
208 	while (*p) {
209 		parent = *p;
210 		skb1 = rb_to_skb(parent);
211 		if (before64(seq, MPTCP_SKB_CB(skb1)->map_seq)) {
212 			p = &parent->rb_left;
213 			continue;
214 		}
215 		if (before64(seq, MPTCP_SKB_CB(skb1)->end_seq)) {
216 			if (!after64(end_seq, MPTCP_SKB_CB(skb1)->end_seq)) {
217 				/* All the bits are present. Drop. */
218 				mptcp_drop(sk, skb);
219 				MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA);
220 				return;
221 			}
222 			if (after64(seq, MPTCP_SKB_CB(skb1)->map_seq)) {
223 				/* partial overlap:
224 				 *     |     skb      |
225 				 *  |     skb1    |
226 				 * continue traversing
227 				 */
228 			} else {
229 				/* skb's seq == skb1's seq and skb covers skb1.
230 				 * Replace skb1 with skb.
231 				 */
232 				rb_replace_node(&skb1->rbnode, &skb->rbnode,
233 						&msk->out_of_order_queue);
234 				mptcp_drop(sk, skb1);
235 				MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA);
236 				goto merge_right;
237 			}
238 		} else if (mptcp_ooo_try_coalesce(msk, skb1, skb)) {
239 			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOMERGE);
240 			return;
241 		}
242 		p = &parent->rb_right;
243 	}
244 
245 insert:
246 	/* Insert segment into RB tree. */
247 	rb_link_node(&skb->rbnode, parent, p);
248 	rb_insert_color(&skb->rbnode, &msk->out_of_order_queue);
249 
250 merge_right:
251 	/* Remove other segments covered by skb. */
252 	while ((skb1 = skb_rb_next(skb)) != NULL) {
253 		if (before64(end_seq, MPTCP_SKB_CB(skb1)->end_seq))
254 			break;
255 		rb_erase(&skb1->rbnode, &msk->out_of_order_queue);
256 		mptcp_drop(sk, skb1);
257 		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA);
258 	}
259 	/* If there is no skb after us, we are the last_skb ! */
260 	if (!skb1)
261 		msk->ooo_last_skb = skb;
262 
263 end:
264 	skb_condense(skb);
265 	skb_set_owner_r(skb, sk);
266 }
267 
268 static bool __mptcp_move_skb(struct mptcp_sock *msk, struct sock *ssk,
269 			     struct sk_buff *skb, unsigned int offset,
270 			     size_t copy_len)
271 {
272 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
273 	struct sock *sk = (struct sock *)msk;
274 	struct sk_buff *tail;
275 
276 	__skb_unlink(skb, &ssk->sk_receive_queue);
277 
278 	skb_ext_reset(skb);
279 	skb_orphan(skb);
280 
281 	/* try to fetch required memory from subflow */
282 	if (!sk_rmem_schedule(sk, skb, skb->truesize)) {
283 		if (ssk->sk_forward_alloc < skb->truesize)
284 			goto drop;
285 		__sk_mem_reclaim(ssk, skb->truesize);
286 		if (!sk_rmem_schedule(sk, skb, skb->truesize))
287 			goto drop;
288 	}
289 
290 	/* the skb map_seq accounts for the skb offset:
291 	 * mptcp_subflow_get_mapped_dsn() is based on the current tp->copied_seq
292 	 * value
293 	 */
294 	MPTCP_SKB_CB(skb)->map_seq = mptcp_subflow_get_mapped_dsn(subflow);
295 	MPTCP_SKB_CB(skb)->end_seq = MPTCP_SKB_CB(skb)->map_seq + copy_len;
296 	MPTCP_SKB_CB(skb)->offset = offset;
297 
298 	if (MPTCP_SKB_CB(skb)->map_seq == msk->ack_seq) {
299 		/* in sequence */
300 		WRITE_ONCE(msk->ack_seq, msk->ack_seq + copy_len);
301 		tail = skb_peek_tail(&sk->sk_receive_queue);
302 		if (tail && mptcp_try_coalesce(sk, tail, skb))
303 			return true;
304 
305 		skb_set_owner_r(skb, sk);
306 		__skb_queue_tail(&sk->sk_receive_queue, skb);
307 		return true;
308 	} else if (after64(MPTCP_SKB_CB(skb)->map_seq, msk->ack_seq)) {
309 		mptcp_data_queue_ofo(msk, skb);
310 		return false;
311 	}
312 
313 	/* old data, keep it simple and drop the whole pkt, sender
314 	 * will retransmit as needed, if needed.
315 	 */
316 	MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA);
317 drop:
318 	mptcp_drop(sk, skb);
319 	return false;
320 }
321 
322 static void mptcp_stop_timer(struct sock *sk)
323 {
324 	struct inet_connection_sock *icsk = inet_csk(sk);
325 
326 	sk_stop_timer(sk, &icsk->icsk_retransmit_timer);
327 	mptcp_sk(sk)->timer_ival = 0;
328 }
329 
330 static void mptcp_close_wake_up(struct sock *sk)
331 {
332 	if (sock_flag(sk, SOCK_DEAD))
333 		return;
334 
335 	sk->sk_state_change(sk);
336 	if (sk->sk_shutdown == SHUTDOWN_MASK ||
337 	    sk->sk_state == TCP_CLOSE)
338 		sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
339 	else
340 		sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
341 }
342 
343 static bool mptcp_pending_data_fin_ack(struct sock *sk)
344 {
345 	struct mptcp_sock *msk = mptcp_sk(sk);
346 
347 	return !__mptcp_check_fallback(msk) &&
348 	       ((1 << sk->sk_state) &
349 		(TCPF_FIN_WAIT1 | TCPF_CLOSING | TCPF_LAST_ACK)) &&
350 	       msk->write_seq == READ_ONCE(msk->snd_una);
351 }
352 
353 static void mptcp_check_data_fin_ack(struct sock *sk)
354 {
355 	struct mptcp_sock *msk = mptcp_sk(sk);
356 
357 	/* Look for an acknowledged DATA_FIN */
358 	if (mptcp_pending_data_fin_ack(sk)) {
359 		WRITE_ONCE(msk->snd_data_fin_enable, 0);
360 
361 		switch (sk->sk_state) {
362 		case TCP_FIN_WAIT1:
363 			inet_sk_state_store(sk, TCP_FIN_WAIT2);
364 			break;
365 		case TCP_CLOSING:
366 		case TCP_LAST_ACK:
367 			inet_sk_state_store(sk, TCP_CLOSE);
368 			break;
369 		}
370 
371 		mptcp_close_wake_up(sk);
372 	}
373 }
374 
375 static bool mptcp_pending_data_fin(struct sock *sk, u64 *seq)
376 {
377 	struct mptcp_sock *msk = mptcp_sk(sk);
378 
379 	if (READ_ONCE(msk->rcv_data_fin) &&
380 	    ((1 << sk->sk_state) &
381 	     (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_FIN_WAIT2))) {
382 		u64 rcv_data_fin_seq = READ_ONCE(msk->rcv_data_fin_seq);
383 
384 		if (msk->ack_seq == rcv_data_fin_seq) {
385 			if (seq)
386 				*seq = rcv_data_fin_seq;
387 
388 			return true;
389 		}
390 	}
391 
392 	return false;
393 }
394 
395 static void mptcp_set_datafin_timeout(const struct sock *sk)
396 {
397 	struct inet_connection_sock *icsk = inet_csk(sk);
398 
399 	mptcp_sk(sk)->timer_ival = min(TCP_RTO_MAX,
400 				       TCP_RTO_MIN << icsk->icsk_retransmits);
401 }
402 
403 static void mptcp_set_timeout(const struct sock *sk, const struct sock *ssk)
404 {
405 	long tout = ssk && inet_csk(ssk)->icsk_pending ?
406 				      inet_csk(ssk)->icsk_timeout - jiffies : 0;
407 
408 	if (tout <= 0)
409 		tout = mptcp_sk(sk)->timer_ival;
410 	mptcp_sk(sk)->timer_ival = tout > 0 ? tout : TCP_RTO_MIN;
411 }
412 
413 static bool tcp_can_send_ack(const struct sock *ssk)
414 {
415 	return !((1 << inet_sk_state_load(ssk)) &
416 	       (TCPF_SYN_SENT | TCPF_SYN_RECV | TCPF_TIME_WAIT | TCPF_CLOSE | TCPF_LISTEN));
417 }
418 
419 static void mptcp_send_ack(struct mptcp_sock *msk)
420 {
421 	struct mptcp_subflow_context *subflow;
422 
423 	mptcp_for_each_subflow(msk, subflow) {
424 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
425 
426 		lock_sock(ssk);
427 		if (tcp_can_send_ack(ssk))
428 			tcp_send_ack(ssk);
429 		release_sock(ssk);
430 	}
431 }
432 
433 static bool mptcp_subflow_cleanup_rbuf(struct sock *ssk)
434 {
435 	int ret;
436 
437 	lock_sock(ssk);
438 	ret = tcp_can_send_ack(ssk);
439 	if (ret)
440 		tcp_cleanup_rbuf(ssk, 1);
441 	release_sock(ssk);
442 	return ret;
443 }
444 
445 static void mptcp_cleanup_rbuf(struct mptcp_sock *msk)
446 {
447 	struct sock *ack_hint = READ_ONCE(msk->ack_hint);
448 	int old_space = READ_ONCE(msk->old_wspace);
449 	struct mptcp_subflow_context *subflow;
450 	struct sock *sk = (struct sock *)msk;
451 	bool cleanup;
452 
453 	/* this is a simple superset of what tcp_cleanup_rbuf() implements
454 	 * so that we don't have to acquire the ssk socket lock most of the time
455 	 * to do actually nothing
456 	 */
457 	cleanup = __mptcp_space(sk) - old_space >= max(0, old_space);
458 	if (!cleanup)
459 		return;
460 
461 	/* if the hinted ssk is still active, try to use it */
462 	if (likely(ack_hint)) {
463 		mptcp_for_each_subflow(msk, subflow) {
464 			struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
465 
466 			if (ack_hint == ssk && mptcp_subflow_cleanup_rbuf(ssk))
467 				return;
468 		}
469 	}
470 
471 	/* otherwise pick the first active subflow */
472 	mptcp_for_each_subflow(msk, subflow)
473 		if (mptcp_subflow_cleanup_rbuf(mptcp_subflow_tcp_sock(subflow)))
474 			return;
475 }
476 
477 static bool mptcp_check_data_fin(struct sock *sk)
478 {
479 	struct mptcp_sock *msk = mptcp_sk(sk);
480 	u64 rcv_data_fin_seq;
481 	bool ret = false;
482 
483 	if (__mptcp_check_fallback(msk))
484 		return ret;
485 
486 	/* Need to ack a DATA_FIN received from a peer while this side
487 	 * of the connection is in ESTABLISHED, FIN_WAIT1, or FIN_WAIT2.
488 	 * msk->rcv_data_fin was set when parsing the incoming options
489 	 * at the subflow level and the msk lock was not held, so this
490 	 * is the first opportunity to act on the DATA_FIN and change
491 	 * the msk state.
492 	 *
493 	 * If we are caught up to the sequence number of the incoming
494 	 * DATA_FIN, send the DATA_ACK now and do state transition.  If
495 	 * not caught up, do nothing and let the recv code send DATA_ACK
496 	 * when catching up.
497 	 */
498 
499 	if (mptcp_pending_data_fin(sk, &rcv_data_fin_seq)) {
500 		WRITE_ONCE(msk->ack_seq, msk->ack_seq + 1);
501 		WRITE_ONCE(msk->rcv_data_fin, 0);
502 
503 		sk->sk_shutdown |= RCV_SHUTDOWN;
504 		smp_mb__before_atomic(); /* SHUTDOWN must be visible first */
505 		set_bit(MPTCP_DATA_READY, &msk->flags);
506 
507 		switch (sk->sk_state) {
508 		case TCP_ESTABLISHED:
509 			inet_sk_state_store(sk, TCP_CLOSE_WAIT);
510 			break;
511 		case TCP_FIN_WAIT1:
512 			inet_sk_state_store(sk, TCP_CLOSING);
513 			break;
514 		case TCP_FIN_WAIT2:
515 			inet_sk_state_store(sk, TCP_CLOSE);
516 			break;
517 		default:
518 			/* Other states not expected */
519 			WARN_ON_ONCE(1);
520 			break;
521 		}
522 
523 		ret = true;
524 		mptcp_set_timeout(sk, NULL);
525 		mptcp_send_ack(msk);
526 		mptcp_close_wake_up(sk);
527 	}
528 	return ret;
529 }
530 
531 static bool __mptcp_move_skbs_from_subflow(struct mptcp_sock *msk,
532 					   struct sock *ssk,
533 					   unsigned int *bytes)
534 {
535 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
536 	struct sock *sk = (struct sock *)msk;
537 	unsigned int moved = 0;
538 	bool more_data_avail;
539 	struct tcp_sock *tp;
540 	bool done = false;
541 	int sk_rbuf;
542 
543 	sk_rbuf = READ_ONCE(sk->sk_rcvbuf);
544 
545 	if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
546 		int ssk_rbuf = READ_ONCE(ssk->sk_rcvbuf);
547 
548 		if (unlikely(ssk_rbuf > sk_rbuf)) {
549 			WRITE_ONCE(sk->sk_rcvbuf, ssk_rbuf);
550 			sk_rbuf = ssk_rbuf;
551 		}
552 	}
553 
554 	pr_debug("msk=%p ssk=%p", msk, ssk);
555 	tp = tcp_sk(ssk);
556 	do {
557 		u32 map_remaining, offset;
558 		u32 seq = tp->copied_seq;
559 		struct sk_buff *skb;
560 		bool fin;
561 
562 		/* try to move as much data as available */
563 		map_remaining = subflow->map_data_len -
564 				mptcp_subflow_get_map_offset(subflow);
565 
566 		skb = skb_peek(&ssk->sk_receive_queue);
567 		if (!skb) {
568 			/* if no data is found, a racing workqueue/recvmsg
569 			 * already processed the new data, stop here or we
570 			 * can enter an infinite loop
571 			 */
572 			if (!moved)
573 				done = true;
574 			break;
575 		}
576 
577 		if (__mptcp_check_fallback(msk)) {
578 			/* if we are running under the workqueue, TCP could have
579 			 * collapsed skbs between dummy map creation and now
580 			 * be sure to adjust the size
581 			 */
582 			map_remaining = skb->len;
583 			subflow->map_data_len = skb->len;
584 		}
585 
586 		offset = seq - TCP_SKB_CB(skb)->seq;
587 		fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN;
588 		if (fin) {
589 			done = true;
590 			seq++;
591 		}
592 
593 		if (offset < skb->len) {
594 			size_t len = skb->len - offset;
595 
596 			if (tp->urg_data)
597 				done = true;
598 
599 			if (__mptcp_move_skb(msk, ssk, skb, offset, len))
600 				moved += len;
601 			seq += len;
602 
603 			if (WARN_ON_ONCE(map_remaining < len))
604 				break;
605 		} else {
606 			WARN_ON_ONCE(!fin);
607 			sk_eat_skb(ssk, skb);
608 			done = true;
609 		}
610 
611 		WRITE_ONCE(tp->copied_seq, seq);
612 		more_data_avail = mptcp_subflow_data_available(ssk);
613 
614 		if (atomic_read(&sk->sk_rmem_alloc) > sk_rbuf) {
615 			done = true;
616 			break;
617 		}
618 	} while (more_data_avail);
619 	WRITE_ONCE(msk->ack_hint, ssk);
620 
621 	*bytes += moved;
622 	return done;
623 }
624 
625 static bool __mptcp_ofo_queue(struct mptcp_sock *msk)
626 {
627 	struct sock *sk = (struct sock *)msk;
628 	struct sk_buff *skb, *tail;
629 	bool moved = false;
630 	struct rb_node *p;
631 	u64 end_seq;
632 
633 	p = rb_first(&msk->out_of_order_queue);
634 	pr_debug("msk=%p empty=%d", msk, RB_EMPTY_ROOT(&msk->out_of_order_queue));
635 	while (p) {
636 		skb = rb_to_skb(p);
637 		if (after64(MPTCP_SKB_CB(skb)->map_seq, msk->ack_seq))
638 			break;
639 
640 		p = rb_next(p);
641 		rb_erase(&skb->rbnode, &msk->out_of_order_queue);
642 
643 		if (unlikely(!after64(MPTCP_SKB_CB(skb)->end_seq,
644 				      msk->ack_seq))) {
645 			mptcp_drop(sk, skb);
646 			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA);
647 			continue;
648 		}
649 
650 		end_seq = MPTCP_SKB_CB(skb)->end_seq;
651 		tail = skb_peek_tail(&sk->sk_receive_queue);
652 		if (!tail || !mptcp_ooo_try_coalesce(msk, tail, skb)) {
653 			int delta = msk->ack_seq - MPTCP_SKB_CB(skb)->map_seq;
654 
655 			/* skip overlapping data, if any */
656 			pr_debug("uncoalesced seq=%llx ack seq=%llx delta=%d",
657 				 MPTCP_SKB_CB(skb)->map_seq, msk->ack_seq,
658 				 delta);
659 			MPTCP_SKB_CB(skb)->offset += delta;
660 			__skb_queue_tail(&sk->sk_receive_queue, skb);
661 		}
662 		msk->ack_seq = end_seq;
663 		moved = true;
664 	}
665 	return moved;
666 }
667 
668 /* In most cases we will be able to lock the mptcp socket.  If its already
669  * owned, we need to defer to the work queue to avoid ABBA deadlock.
670  */
671 static void move_skbs_to_msk(struct mptcp_sock *msk, struct sock *ssk)
672 {
673 	struct sock *sk = (struct sock *)msk;
674 	unsigned int moved = 0;
675 
676 	if (inet_sk_state_load(sk) == TCP_CLOSE)
677 		return;
678 
679 	mptcp_data_lock(sk);
680 
681 	__mptcp_move_skbs_from_subflow(msk, ssk, &moved);
682 	__mptcp_ofo_queue(msk);
683 
684 	/* If the moves have caught up with the DATA_FIN sequence number
685 	 * it's time to ack the DATA_FIN and change socket state, but
686 	 * this is not a good place to change state. Let the workqueue
687 	 * do it.
688 	 */
689 	if (mptcp_pending_data_fin(sk, NULL))
690 		mptcp_schedule_work(sk);
691 	mptcp_data_unlock(sk);
692 }
693 
694 void mptcp_data_ready(struct sock *sk, struct sock *ssk)
695 {
696 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
697 	struct mptcp_sock *msk = mptcp_sk(sk);
698 	int sk_rbuf, ssk_rbuf;
699 	bool wake;
700 
701 	/* The peer can send data while we are shutting down this
702 	 * subflow at msk destruction time, but we must avoid enqueuing
703 	 * more data to the msk receive queue
704 	 */
705 	if (unlikely(subflow->disposable))
706 		return;
707 
708 	/* move_skbs_to_msk below can legitly clear the data_avail flag,
709 	 * but we will need later to properly woke the reader, cache its
710 	 * value
711 	 */
712 	wake = subflow->data_avail == MPTCP_SUBFLOW_DATA_AVAIL;
713 	if (wake)
714 		set_bit(MPTCP_DATA_READY, &msk->flags);
715 
716 	ssk_rbuf = READ_ONCE(ssk->sk_rcvbuf);
717 	sk_rbuf = READ_ONCE(sk->sk_rcvbuf);
718 	if (unlikely(ssk_rbuf > sk_rbuf))
719 		sk_rbuf = ssk_rbuf;
720 
721 	/* over limit? can't append more skbs to msk */
722 	if (atomic_read(&sk->sk_rmem_alloc) > sk_rbuf)
723 		goto wake;
724 
725 	move_skbs_to_msk(msk, ssk);
726 
727 wake:
728 	if (wake)
729 		sk->sk_data_ready(sk);
730 }
731 
732 static bool mptcp_do_flush_join_list(struct mptcp_sock *msk)
733 {
734 	struct mptcp_subflow_context *subflow;
735 	bool ret = false;
736 
737 	if (likely(list_empty(&msk->join_list)))
738 		return false;
739 
740 	spin_lock_bh(&msk->join_list_lock);
741 	list_for_each_entry(subflow, &msk->join_list, node) {
742 		u32 sseq = READ_ONCE(subflow->setsockopt_seq);
743 
744 		mptcp_propagate_sndbuf((struct sock *)msk, mptcp_subflow_tcp_sock(subflow));
745 		if (READ_ONCE(msk->setsockopt_seq) != sseq)
746 			ret = true;
747 	}
748 	list_splice_tail_init(&msk->join_list, &msk->conn_list);
749 	spin_unlock_bh(&msk->join_list_lock);
750 
751 	return ret;
752 }
753 
754 void __mptcp_flush_join_list(struct mptcp_sock *msk)
755 {
756 	if (likely(!mptcp_do_flush_join_list(msk)))
757 		return;
758 
759 	if (!test_and_set_bit(MPTCP_WORK_SYNC_SETSOCKOPT, &msk->flags))
760 		mptcp_schedule_work((struct sock *)msk);
761 }
762 
763 static void mptcp_flush_join_list(struct mptcp_sock *msk)
764 {
765 	bool sync_needed = test_and_clear_bit(MPTCP_WORK_SYNC_SETSOCKOPT, &msk->flags);
766 
767 	might_sleep();
768 
769 	if (!mptcp_do_flush_join_list(msk) && !sync_needed)
770 		return;
771 
772 	mptcp_sockopt_sync_all(msk);
773 }
774 
775 static bool mptcp_timer_pending(struct sock *sk)
776 {
777 	return timer_pending(&inet_csk(sk)->icsk_retransmit_timer);
778 }
779 
780 static void mptcp_reset_timer(struct sock *sk)
781 {
782 	struct inet_connection_sock *icsk = inet_csk(sk);
783 	unsigned long tout;
784 
785 	/* prevent rescheduling on close */
786 	if (unlikely(inet_sk_state_load(sk) == TCP_CLOSE))
787 		return;
788 
789 	/* should never be called with mptcp level timer cleared */
790 	tout = READ_ONCE(mptcp_sk(sk)->timer_ival);
791 	if (WARN_ON_ONCE(!tout))
792 		tout = TCP_RTO_MIN;
793 	sk_reset_timer(sk, &icsk->icsk_retransmit_timer, jiffies + tout);
794 }
795 
796 bool mptcp_schedule_work(struct sock *sk)
797 {
798 	if (inet_sk_state_load(sk) != TCP_CLOSE &&
799 	    schedule_work(&mptcp_sk(sk)->work)) {
800 		/* each subflow already holds a reference to the sk, and the
801 		 * workqueue is invoked by a subflow, so sk can't go away here.
802 		 */
803 		sock_hold(sk);
804 		return true;
805 	}
806 	return false;
807 }
808 
809 void mptcp_subflow_eof(struct sock *sk)
810 {
811 	if (!test_and_set_bit(MPTCP_WORK_EOF, &mptcp_sk(sk)->flags))
812 		mptcp_schedule_work(sk);
813 }
814 
815 static void mptcp_check_for_eof(struct mptcp_sock *msk)
816 {
817 	struct mptcp_subflow_context *subflow;
818 	struct sock *sk = (struct sock *)msk;
819 	int receivers = 0;
820 
821 	mptcp_for_each_subflow(msk, subflow)
822 		receivers += !subflow->rx_eof;
823 	if (receivers)
824 		return;
825 
826 	if (!(sk->sk_shutdown & RCV_SHUTDOWN)) {
827 		/* hopefully temporary hack: propagate shutdown status
828 		 * to msk, when all subflows agree on it
829 		 */
830 		sk->sk_shutdown |= RCV_SHUTDOWN;
831 
832 		smp_mb__before_atomic(); /* SHUTDOWN must be visible first */
833 		set_bit(MPTCP_DATA_READY, &msk->flags);
834 		sk->sk_data_ready(sk);
835 	}
836 
837 	switch (sk->sk_state) {
838 	case TCP_ESTABLISHED:
839 		inet_sk_state_store(sk, TCP_CLOSE_WAIT);
840 		break;
841 	case TCP_FIN_WAIT1:
842 		inet_sk_state_store(sk, TCP_CLOSING);
843 		break;
844 	case TCP_FIN_WAIT2:
845 		inet_sk_state_store(sk, TCP_CLOSE);
846 		break;
847 	default:
848 		return;
849 	}
850 	mptcp_close_wake_up(sk);
851 }
852 
853 static struct sock *mptcp_subflow_recv_lookup(const struct mptcp_sock *msk)
854 {
855 	struct mptcp_subflow_context *subflow;
856 	struct sock *sk = (struct sock *)msk;
857 
858 	sock_owned_by_me(sk);
859 
860 	mptcp_for_each_subflow(msk, subflow) {
861 		if (subflow->data_avail)
862 			return mptcp_subflow_tcp_sock(subflow);
863 	}
864 
865 	return NULL;
866 }
867 
868 static bool mptcp_skb_can_collapse_to(u64 write_seq,
869 				      const struct sk_buff *skb,
870 				      const struct mptcp_ext *mpext)
871 {
872 	if (!tcp_skb_can_collapse_to(skb))
873 		return false;
874 
875 	/* can collapse only if MPTCP level sequence is in order and this
876 	 * mapping has not been xmitted yet
877 	 */
878 	return mpext && mpext->data_seq + mpext->data_len == write_seq &&
879 	       !mpext->frozen;
880 }
881 
882 /* we can append data to the given data frag if:
883  * - there is space available in the backing page_frag
884  * - the data frag tail matches the current page_frag free offset
885  * - the data frag end sequence number matches the current write seq
886  */
887 static bool mptcp_frag_can_collapse_to(const struct mptcp_sock *msk,
888 				       const struct page_frag *pfrag,
889 				       const struct mptcp_data_frag *df)
890 {
891 	return df && pfrag->page == df->page &&
892 		pfrag->size - pfrag->offset > 0 &&
893 		pfrag->offset == (df->offset + df->data_len) &&
894 		df->data_seq + df->data_len == msk->write_seq;
895 }
896 
897 static int mptcp_wmem_with_overhead(struct sock *sk, int size)
898 {
899 	struct mptcp_sock *msk = mptcp_sk(sk);
900 	int ret, skbs;
901 
902 	ret = size + ((sizeof(struct mptcp_data_frag) * size) >> PAGE_SHIFT);
903 	skbs = (msk->tx_pending_data + size) / msk->size_goal_cache;
904 	if (skbs < msk->skb_tx_cache.qlen)
905 		return ret;
906 
907 	return ret + (skbs - msk->skb_tx_cache.qlen) * SKB_TRUESIZE(MAX_TCP_HEADER);
908 }
909 
910 static void __mptcp_wmem_reserve(struct sock *sk, int size)
911 {
912 	int amount = mptcp_wmem_with_overhead(sk, size);
913 	struct mptcp_sock *msk = mptcp_sk(sk);
914 
915 	WARN_ON_ONCE(msk->wmem_reserved);
916 	if (WARN_ON_ONCE(amount < 0))
917 		amount = 0;
918 
919 	if (amount <= sk->sk_forward_alloc)
920 		goto reserve;
921 
922 	/* under memory pressure try to reserve at most a single page
923 	 * otherwise try to reserve the full estimate and fallback
924 	 * to a single page before entering the error path
925 	 */
926 	if ((tcp_under_memory_pressure(sk) && amount > PAGE_SIZE) ||
927 	    !sk_wmem_schedule(sk, amount)) {
928 		if (amount <= PAGE_SIZE)
929 			goto nomem;
930 
931 		amount = PAGE_SIZE;
932 		if (!sk_wmem_schedule(sk, amount))
933 			goto nomem;
934 	}
935 
936 reserve:
937 	msk->wmem_reserved = amount;
938 	sk->sk_forward_alloc -= amount;
939 	return;
940 
941 nomem:
942 	/* we will wait for memory on next allocation */
943 	msk->wmem_reserved = -1;
944 }
945 
946 static void __mptcp_update_wmem(struct sock *sk)
947 {
948 	struct mptcp_sock *msk = mptcp_sk(sk);
949 
950 #ifdef CONFIG_LOCKDEP
951 	WARN_ON_ONCE(!lockdep_is_held(&sk->sk_lock.slock));
952 #endif
953 
954 	if (!msk->wmem_reserved)
955 		return;
956 
957 	if (msk->wmem_reserved < 0)
958 		msk->wmem_reserved = 0;
959 	if (msk->wmem_reserved > 0) {
960 		sk->sk_forward_alloc += msk->wmem_reserved;
961 		msk->wmem_reserved = 0;
962 	}
963 }
964 
965 static bool mptcp_wmem_alloc(struct sock *sk, int size)
966 {
967 	struct mptcp_sock *msk = mptcp_sk(sk);
968 
969 	/* check for pre-existing error condition */
970 	if (msk->wmem_reserved < 0)
971 		return false;
972 
973 	if (msk->wmem_reserved >= size)
974 		goto account;
975 
976 	mptcp_data_lock(sk);
977 	if (!sk_wmem_schedule(sk, size)) {
978 		mptcp_data_unlock(sk);
979 		return false;
980 	}
981 
982 	sk->sk_forward_alloc -= size;
983 	msk->wmem_reserved += size;
984 	mptcp_data_unlock(sk);
985 
986 account:
987 	msk->wmem_reserved -= size;
988 	return true;
989 }
990 
991 static void mptcp_wmem_uncharge(struct sock *sk, int size)
992 {
993 	struct mptcp_sock *msk = mptcp_sk(sk);
994 
995 	if (msk->wmem_reserved < 0)
996 		msk->wmem_reserved = 0;
997 	msk->wmem_reserved += size;
998 }
999 
1000 static void mptcp_mem_reclaim_partial(struct sock *sk)
1001 {
1002 	struct mptcp_sock *msk = mptcp_sk(sk);
1003 
1004 	/* if we are experiencing a transint allocation error,
1005 	 * the forward allocation memory has been already
1006 	 * released
1007 	 */
1008 	if (msk->wmem_reserved < 0)
1009 		return;
1010 
1011 	mptcp_data_lock(sk);
1012 	sk->sk_forward_alloc += msk->wmem_reserved;
1013 	sk_mem_reclaim_partial(sk);
1014 	msk->wmem_reserved = sk->sk_forward_alloc;
1015 	sk->sk_forward_alloc = 0;
1016 	mptcp_data_unlock(sk);
1017 }
1018 
1019 static void dfrag_uncharge(struct sock *sk, int len)
1020 {
1021 	sk_mem_uncharge(sk, len);
1022 	sk_wmem_queued_add(sk, -len);
1023 }
1024 
1025 static void dfrag_clear(struct sock *sk, struct mptcp_data_frag *dfrag)
1026 {
1027 	int len = dfrag->data_len + dfrag->overhead;
1028 
1029 	list_del(&dfrag->list);
1030 	dfrag_uncharge(sk, len);
1031 	put_page(dfrag->page);
1032 }
1033 
1034 static void __mptcp_clean_una(struct sock *sk)
1035 {
1036 	struct mptcp_sock *msk = mptcp_sk(sk);
1037 	struct mptcp_data_frag *dtmp, *dfrag;
1038 	bool cleaned = false;
1039 	u64 snd_una;
1040 
1041 	/* on fallback we just need to ignore snd_una, as this is really
1042 	 * plain TCP
1043 	 */
1044 	if (__mptcp_check_fallback(msk))
1045 		msk->snd_una = READ_ONCE(msk->snd_nxt);
1046 
1047 	snd_una = msk->snd_una;
1048 	list_for_each_entry_safe(dfrag, dtmp, &msk->rtx_queue, list) {
1049 		if (after64(dfrag->data_seq + dfrag->data_len, snd_una))
1050 			break;
1051 
1052 		if (WARN_ON_ONCE(dfrag == msk->first_pending))
1053 			break;
1054 		dfrag_clear(sk, dfrag);
1055 		cleaned = true;
1056 	}
1057 
1058 	dfrag = mptcp_rtx_head(sk);
1059 	if (dfrag && after64(snd_una, dfrag->data_seq)) {
1060 		u64 delta = snd_una - dfrag->data_seq;
1061 
1062 		if (WARN_ON_ONCE(delta > dfrag->already_sent))
1063 			goto out;
1064 
1065 		dfrag->data_seq += delta;
1066 		dfrag->offset += delta;
1067 		dfrag->data_len -= delta;
1068 		dfrag->already_sent -= delta;
1069 
1070 		dfrag_uncharge(sk, delta);
1071 		cleaned = true;
1072 	}
1073 
1074 out:
1075 	if (cleaned) {
1076 		if (tcp_under_memory_pressure(sk)) {
1077 			__mptcp_update_wmem(sk);
1078 			sk_mem_reclaim_partial(sk);
1079 		}
1080 	}
1081 
1082 	if (snd_una == READ_ONCE(msk->snd_nxt)) {
1083 		if (msk->timer_ival && !mptcp_data_fin_enabled(msk))
1084 			mptcp_stop_timer(sk);
1085 	} else {
1086 		mptcp_reset_timer(sk);
1087 	}
1088 }
1089 
1090 static void __mptcp_clean_una_wakeup(struct sock *sk)
1091 {
1092 #ifdef CONFIG_LOCKDEP
1093 	WARN_ON_ONCE(!lockdep_is_held(&sk->sk_lock.slock));
1094 #endif
1095 	__mptcp_clean_una(sk);
1096 	mptcp_write_space(sk);
1097 }
1098 
1099 static void mptcp_clean_una_wakeup(struct sock *sk)
1100 {
1101 	mptcp_data_lock(sk);
1102 	__mptcp_clean_una_wakeup(sk);
1103 	mptcp_data_unlock(sk);
1104 }
1105 
1106 static void mptcp_enter_memory_pressure(struct sock *sk)
1107 {
1108 	struct mptcp_subflow_context *subflow;
1109 	struct mptcp_sock *msk = mptcp_sk(sk);
1110 	bool first = true;
1111 
1112 	sk_stream_moderate_sndbuf(sk);
1113 	mptcp_for_each_subflow(msk, subflow) {
1114 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
1115 
1116 		if (first)
1117 			tcp_enter_memory_pressure(ssk);
1118 		sk_stream_moderate_sndbuf(ssk);
1119 		first = false;
1120 	}
1121 }
1122 
1123 /* ensure we get enough memory for the frag hdr, beyond some minimal amount of
1124  * data
1125  */
1126 static bool mptcp_page_frag_refill(struct sock *sk, struct page_frag *pfrag)
1127 {
1128 	if (likely(skb_page_frag_refill(32U + sizeof(struct mptcp_data_frag),
1129 					pfrag, sk->sk_allocation)))
1130 		return true;
1131 
1132 	mptcp_enter_memory_pressure(sk);
1133 	return false;
1134 }
1135 
1136 static struct mptcp_data_frag *
1137 mptcp_carve_data_frag(const struct mptcp_sock *msk, struct page_frag *pfrag,
1138 		      int orig_offset)
1139 {
1140 	int offset = ALIGN(orig_offset, sizeof(long));
1141 	struct mptcp_data_frag *dfrag;
1142 
1143 	dfrag = (struct mptcp_data_frag *)(page_to_virt(pfrag->page) + offset);
1144 	dfrag->data_len = 0;
1145 	dfrag->data_seq = msk->write_seq;
1146 	dfrag->overhead = offset - orig_offset + sizeof(struct mptcp_data_frag);
1147 	dfrag->offset = offset + sizeof(struct mptcp_data_frag);
1148 	dfrag->already_sent = 0;
1149 	dfrag->page = pfrag->page;
1150 
1151 	return dfrag;
1152 }
1153 
1154 struct mptcp_sendmsg_info {
1155 	int mss_now;
1156 	int size_goal;
1157 	u16 limit;
1158 	u16 sent;
1159 	unsigned int flags;
1160 };
1161 
1162 static int mptcp_check_allowed_size(struct mptcp_sock *msk, u64 data_seq,
1163 				    int avail_size)
1164 {
1165 	u64 window_end = mptcp_wnd_end(msk);
1166 
1167 	if (__mptcp_check_fallback(msk))
1168 		return avail_size;
1169 
1170 	if (!before64(data_seq + avail_size, window_end)) {
1171 		u64 allowed_size = window_end - data_seq;
1172 
1173 		return min_t(unsigned int, allowed_size, avail_size);
1174 	}
1175 
1176 	return avail_size;
1177 }
1178 
1179 static bool __mptcp_add_ext(struct sk_buff *skb, gfp_t gfp)
1180 {
1181 	struct skb_ext *mpext = __skb_ext_alloc(gfp);
1182 
1183 	if (!mpext)
1184 		return false;
1185 	__skb_ext_set(skb, SKB_EXT_MPTCP, mpext);
1186 	return true;
1187 }
1188 
1189 static struct sk_buff *__mptcp_do_alloc_tx_skb(struct sock *sk, gfp_t gfp)
1190 {
1191 	struct sk_buff *skb;
1192 
1193 	skb = alloc_skb_fclone(MAX_TCP_HEADER, gfp);
1194 	if (likely(skb)) {
1195 		if (likely(__mptcp_add_ext(skb, gfp))) {
1196 			skb_reserve(skb, MAX_TCP_HEADER);
1197 			skb->reserved_tailroom = skb->end - skb->tail;
1198 			return skb;
1199 		}
1200 		__kfree_skb(skb);
1201 	} else {
1202 		mptcp_enter_memory_pressure(sk);
1203 	}
1204 	return NULL;
1205 }
1206 
1207 static bool mptcp_tx_cache_refill(struct sock *sk, int size,
1208 				  struct sk_buff_head *skbs, int *total_ts)
1209 {
1210 	struct mptcp_sock *msk = mptcp_sk(sk);
1211 	struct sk_buff *skb;
1212 	int space_needed;
1213 
1214 	if (unlikely(tcp_under_memory_pressure(sk))) {
1215 		mptcp_mem_reclaim_partial(sk);
1216 
1217 		/* under pressure pre-allocate at most a single skb */
1218 		if (msk->skb_tx_cache.qlen)
1219 			return true;
1220 		space_needed = msk->size_goal_cache;
1221 	} else {
1222 		space_needed = msk->tx_pending_data + size -
1223 			       msk->skb_tx_cache.qlen * msk->size_goal_cache;
1224 	}
1225 
1226 	while (space_needed > 0) {
1227 		skb = __mptcp_do_alloc_tx_skb(sk, sk->sk_allocation);
1228 		if (unlikely(!skb)) {
1229 			/* under memory pressure, try to pass the caller a
1230 			 * single skb to allow forward progress
1231 			 */
1232 			while (skbs->qlen > 1) {
1233 				skb = __skb_dequeue_tail(skbs);
1234 				*total_ts -= skb->truesize;
1235 				__kfree_skb(skb);
1236 			}
1237 			return skbs->qlen > 0;
1238 		}
1239 
1240 		*total_ts += skb->truesize;
1241 		__skb_queue_tail(skbs, skb);
1242 		space_needed -= msk->size_goal_cache;
1243 	}
1244 	return true;
1245 }
1246 
1247 static bool __mptcp_alloc_tx_skb(struct sock *sk, struct sock *ssk, gfp_t gfp)
1248 {
1249 	struct mptcp_sock *msk = mptcp_sk(sk);
1250 	struct sk_buff *skb;
1251 
1252 	if (ssk->sk_tx_skb_cache) {
1253 		skb = ssk->sk_tx_skb_cache;
1254 		if (unlikely(!skb_ext_find(skb, SKB_EXT_MPTCP) &&
1255 			     !__mptcp_add_ext(skb, gfp)))
1256 			return false;
1257 		return true;
1258 	}
1259 
1260 	skb = skb_peek(&msk->skb_tx_cache);
1261 	if (skb) {
1262 		if (likely(sk_wmem_schedule(ssk, skb->truesize))) {
1263 			skb = __skb_dequeue(&msk->skb_tx_cache);
1264 			if (WARN_ON_ONCE(!skb))
1265 				return false;
1266 
1267 			mptcp_wmem_uncharge(sk, skb->truesize);
1268 			ssk->sk_tx_skb_cache = skb;
1269 			return true;
1270 		}
1271 
1272 		/* over memory limit, no point to try to allocate a new skb */
1273 		return false;
1274 	}
1275 
1276 	skb = __mptcp_do_alloc_tx_skb(sk, gfp);
1277 	if (!skb)
1278 		return false;
1279 
1280 	if (likely(sk_wmem_schedule(ssk, skb->truesize))) {
1281 		ssk->sk_tx_skb_cache = skb;
1282 		return true;
1283 	}
1284 	kfree_skb(skb);
1285 	return false;
1286 }
1287 
1288 static bool mptcp_must_reclaim_memory(struct sock *sk, struct sock *ssk)
1289 {
1290 	return !ssk->sk_tx_skb_cache &&
1291 	       !skb_peek(&mptcp_sk(sk)->skb_tx_cache) &&
1292 	       tcp_under_memory_pressure(sk);
1293 }
1294 
1295 static bool mptcp_alloc_tx_skb(struct sock *sk, struct sock *ssk)
1296 {
1297 	if (unlikely(mptcp_must_reclaim_memory(sk, ssk)))
1298 		mptcp_mem_reclaim_partial(sk);
1299 	return __mptcp_alloc_tx_skb(sk, ssk, sk->sk_allocation);
1300 }
1301 
1302 static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
1303 			      struct mptcp_data_frag *dfrag,
1304 			      struct mptcp_sendmsg_info *info)
1305 {
1306 	u64 data_seq = dfrag->data_seq + info->sent;
1307 	struct mptcp_sock *msk = mptcp_sk(sk);
1308 	bool zero_window_probe = false;
1309 	struct mptcp_ext *mpext = NULL;
1310 	struct sk_buff *skb, *tail;
1311 	bool can_collapse = false;
1312 	int size_bias = 0;
1313 	int avail_size;
1314 	size_t ret = 0;
1315 
1316 	pr_debug("msk=%p ssk=%p sending dfrag at seq=%llu len=%u already sent=%u",
1317 		 msk, ssk, dfrag->data_seq, dfrag->data_len, info->sent);
1318 
1319 	/* compute send limit */
1320 	info->mss_now = tcp_send_mss(ssk, &info->size_goal, info->flags);
1321 	avail_size = info->size_goal;
1322 	msk->size_goal_cache = info->size_goal;
1323 	skb = tcp_write_queue_tail(ssk);
1324 	if (skb) {
1325 		/* Limit the write to the size available in the
1326 		 * current skb, if any, so that we create at most a new skb.
1327 		 * Explicitly tells TCP internals to avoid collapsing on later
1328 		 * queue management operation, to avoid breaking the ext <->
1329 		 * SSN association set here
1330 		 */
1331 		mpext = skb_ext_find(skb, SKB_EXT_MPTCP);
1332 		can_collapse = (info->size_goal - skb->len > 0) &&
1333 			 mptcp_skb_can_collapse_to(data_seq, skb, mpext);
1334 		if (!can_collapse) {
1335 			TCP_SKB_CB(skb)->eor = 1;
1336 		} else {
1337 			size_bias = skb->len;
1338 			avail_size = info->size_goal - skb->len;
1339 		}
1340 	}
1341 
1342 	/* Zero window and all data acked? Probe. */
1343 	avail_size = mptcp_check_allowed_size(msk, data_seq, avail_size);
1344 	if (avail_size == 0) {
1345 		u64 snd_una = READ_ONCE(msk->snd_una);
1346 
1347 		if (skb || snd_una != msk->snd_nxt)
1348 			return 0;
1349 		zero_window_probe = true;
1350 		data_seq = snd_una - 1;
1351 		avail_size = 1;
1352 	}
1353 
1354 	if (WARN_ON_ONCE(info->sent > info->limit ||
1355 			 info->limit > dfrag->data_len))
1356 		return 0;
1357 
1358 	ret = info->limit - info->sent;
1359 	tail = tcp_build_frag(ssk, avail_size + size_bias, info->flags,
1360 			      dfrag->page, dfrag->offset + info->sent, &ret);
1361 	if (!tail) {
1362 		tcp_remove_empty_skb(sk, tcp_write_queue_tail(ssk));
1363 		return -ENOMEM;
1364 	}
1365 
1366 	/* if the tail skb is still the cached one, collapsing really happened.
1367 	 */
1368 	if (skb == tail) {
1369 		TCP_SKB_CB(tail)->tcp_flags &= ~TCPHDR_PSH;
1370 		mpext->data_len += ret;
1371 		WARN_ON_ONCE(!can_collapse);
1372 		WARN_ON_ONCE(zero_window_probe);
1373 		goto out;
1374 	}
1375 
1376 	mpext = skb_ext_find(tail, SKB_EXT_MPTCP);
1377 	if (WARN_ON_ONCE(!mpext)) {
1378 		/* should never reach here, stream corrupted */
1379 		return -EINVAL;
1380 	}
1381 
1382 	memset(mpext, 0, sizeof(*mpext));
1383 	mpext->data_seq = data_seq;
1384 	mpext->subflow_seq = mptcp_subflow_ctx(ssk)->rel_write_seq;
1385 	mpext->data_len = ret;
1386 	mpext->use_map = 1;
1387 	mpext->dsn64 = 1;
1388 
1389 	pr_debug("data_seq=%llu subflow_seq=%u data_len=%u dsn64=%d",
1390 		 mpext->data_seq, mpext->subflow_seq, mpext->data_len,
1391 		 mpext->dsn64);
1392 
1393 	if (zero_window_probe) {
1394 		mptcp_subflow_ctx(ssk)->rel_write_seq += ret;
1395 		mpext->frozen = 1;
1396 		ret = 0;
1397 		tcp_push_pending_frames(ssk);
1398 	}
1399 out:
1400 	mptcp_subflow_ctx(ssk)->rel_write_seq += ret;
1401 	return ret;
1402 }
1403 
1404 #define MPTCP_SEND_BURST_SIZE		((1 << 16) - \
1405 					 sizeof(struct tcphdr) - \
1406 					 MAX_TCP_OPTION_SPACE - \
1407 					 sizeof(struct ipv6hdr) - \
1408 					 sizeof(struct frag_hdr))
1409 
1410 struct subflow_send_info {
1411 	struct sock *ssk;
1412 	u64 ratio;
1413 };
1414 
1415 static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
1416 {
1417 	struct subflow_send_info send_info[2];
1418 	struct mptcp_subflow_context *subflow;
1419 	int i, nr_active = 0;
1420 	struct sock *ssk;
1421 	u64 ratio;
1422 	u32 pace;
1423 
1424 	sock_owned_by_me((struct sock *)msk);
1425 
1426 	if (__mptcp_check_fallback(msk)) {
1427 		if (!msk->first)
1428 			return NULL;
1429 		return sk_stream_memory_free(msk->first) ? msk->first : NULL;
1430 	}
1431 
1432 	/* re-use last subflow, if the burst allow that */
1433 	if (msk->last_snd && msk->snd_burst > 0 &&
1434 	    sk_stream_memory_free(msk->last_snd) &&
1435 	    mptcp_subflow_active(mptcp_subflow_ctx(msk->last_snd)))
1436 		return msk->last_snd;
1437 
1438 	/* pick the subflow with the lower wmem/wspace ratio */
1439 	for (i = 0; i < 2; ++i) {
1440 		send_info[i].ssk = NULL;
1441 		send_info[i].ratio = -1;
1442 	}
1443 	mptcp_for_each_subflow(msk, subflow) {
1444 		trace_mptcp_subflow_get_send(subflow);
1445 		ssk =  mptcp_subflow_tcp_sock(subflow);
1446 		if (!mptcp_subflow_active(subflow))
1447 			continue;
1448 
1449 		nr_active += !subflow->backup;
1450 		if (!sk_stream_memory_free(subflow->tcp_sock) || !tcp_sk(ssk)->snd_wnd)
1451 			continue;
1452 
1453 		pace = READ_ONCE(ssk->sk_pacing_rate);
1454 		if (!pace)
1455 			continue;
1456 
1457 		ratio = div_u64((u64)READ_ONCE(ssk->sk_wmem_queued) << 32,
1458 				pace);
1459 		if (ratio < send_info[subflow->backup].ratio) {
1460 			send_info[subflow->backup].ssk = ssk;
1461 			send_info[subflow->backup].ratio = ratio;
1462 		}
1463 	}
1464 
1465 	/* pick the best backup if no other subflow is active */
1466 	if (!nr_active)
1467 		send_info[0].ssk = send_info[1].ssk;
1468 
1469 	if (send_info[0].ssk) {
1470 		msk->last_snd = send_info[0].ssk;
1471 		msk->snd_burst = min_t(int, MPTCP_SEND_BURST_SIZE,
1472 				       tcp_sk(msk->last_snd)->snd_wnd);
1473 		return msk->last_snd;
1474 	}
1475 
1476 	return NULL;
1477 }
1478 
1479 static void mptcp_push_release(struct sock *sk, struct sock *ssk,
1480 			       struct mptcp_sendmsg_info *info)
1481 {
1482 	mptcp_set_timeout(sk, ssk);
1483 	tcp_push(ssk, 0, info->mss_now, tcp_sk(ssk)->nonagle, info->size_goal);
1484 	release_sock(ssk);
1485 }
1486 
1487 static void __mptcp_push_pending(struct sock *sk, unsigned int flags)
1488 {
1489 	struct sock *prev_ssk = NULL, *ssk = NULL;
1490 	struct mptcp_sock *msk = mptcp_sk(sk);
1491 	struct mptcp_sendmsg_info info = {
1492 				.flags = flags,
1493 	};
1494 	struct mptcp_data_frag *dfrag;
1495 	int len, copied = 0;
1496 
1497 	while ((dfrag = mptcp_send_head(sk))) {
1498 		info.sent = dfrag->already_sent;
1499 		info.limit = dfrag->data_len;
1500 		len = dfrag->data_len - dfrag->already_sent;
1501 		while (len > 0) {
1502 			int ret = 0;
1503 
1504 			prev_ssk = ssk;
1505 			mptcp_flush_join_list(msk);
1506 			ssk = mptcp_subflow_get_send(msk);
1507 
1508 			/* try to keep the subflow socket lock across
1509 			 * consecutive xmit on the same socket
1510 			 */
1511 			if (ssk != prev_ssk && prev_ssk)
1512 				mptcp_push_release(sk, prev_ssk, &info);
1513 			if (!ssk)
1514 				goto out;
1515 
1516 			if (ssk != prev_ssk || !prev_ssk)
1517 				lock_sock(ssk);
1518 
1519 			/* keep it simple and always provide a new skb for the
1520 			 * subflow, even if we will not use it when collapsing
1521 			 * on the pending one
1522 			 */
1523 			if (!mptcp_alloc_tx_skb(sk, ssk)) {
1524 				mptcp_push_release(sk, ssk, &info);
1525 				goto out;
1526 			}
1527 
1528 			ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
1529 			if (ret <= 0) {
1530 				mptcp_push_release(sk, ssk, &info);
1531 				goto out;
1532 			}
1533 
1534 			info.sent += ret;
1535 			dfrag->already_sent += ret;
1536 			msk->snd_nxt += ret;
1537 			msk->snd_burst -= ret;
1538 			msk->tx_pending_data -= ret;
1539 			copied += ret;
1540 			len -= ret;
1541 		}
1542 		WRITE_ONCE(msk->first_pending, mptcp_send_next(sk));
1543 	}
1544 
1545 	/* at this point we held the socket lock for the last subflow we used */
1546 	if (ssk)
1547 		mptcp_push_release(sk, ssk, &info);
1548 
1549 out:
1550 	if (copied) {
1551 		/* start the timer, if it's not pending */
1552 		if (!mptcp_timer_pending(sk))
1553 			mptcp_reset_timer(sk);
1554 		__mptcp_check_send_data_fin(sk);
1555 	}
1556 }
1557 
1558 static void __mptcp_subflow_push_pending(struct sock *sk, struct sock *ssk)
1559 {
1560 	struct mptcp_sock *msk = mptcp_sk(sk);
1561 	struct mptcp_sendmsg_info info;
1562 	struct mptcp_data_frag *dfrag;
1563 	struct sock *xmit_ssk;
1564 	int len, copied = 0;
1565 	bool first = true;
1566 
1567 	info.flags = 0;
1568 	while ((dfrag = mptcp_send_head(sk))) {
1569 		info.sent = dfrag->already_sent;
1570 		info.limit = dfrag->data_len;
1571 		len = dfrag->data_len - dfrag->already_sent;
1572 		while (len > 0) {
1573 			int ret = 0;
1574 
1575 			/* the caller already invoked the packet scheduler,
1576 			 * check for a different subflow usage only after
1577 			 * spooling the first chunk of data
1578 			 */
1579 			xmit_ssk = first ? ssk : mptcp_subflow_get_send(mptcp_sk(sk));
1580 			if (!xmit_ssk)
1581 				goto out;
1582 			if (xmit_ssk != ssk) {
1583 				mptcp_subflow_delegate(mptcp_subflow_ctx(xmit_ssk));
1584 				goto out;
1585 			}
1586 
1587 			if (unlikely(mptcp_must_reclaim_memory(sk, ssk))) {
1588 				__mptcp_update_wmem(sk);
1589 				sk_mem_reclaim_partial(sk);
1590 			}
1591 			if (!__mptcp_alloc_tx_skb(sk, ssk, GFP_ATOMIC))
1592 				goto out;
1593 
1594 			ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
1595 			if (ret <= 0)
1596 				goto out;
1597 
1598 			info.sent += ret;
1599 			dfrag->already_sent += ret;
1600 			msk->snd_nxt += ret;
1601 			msk->snd_burst -= ret;
1602 			msk->tx_pending_data -= ret;
1603 			copied += ret;
1604 			len -= ret;
1605 			first = false;
1606 		}
1607 		WRITE_ONCE(msk->first_pending, mptcp_send_next(sk));
1608 	}
1609 
1610 out:
1611 	/* __mptcp_alloc_tx_skb could have released some wmem and we are
1612 	 * not going to flush it via release_sock()
1613 	 */
1614 	__mptcp_update_wmem(sk);
1615 	if (copied) {
1616 		mptcp_set_timeout(sk, ssk);
1617 		tcp_push(ssk, 0, info.mss_now, tcp_sk(ssk)->nonagle,
1618 			 info.size_goal);
1619 		if (!mptcp_timer_pending(sk))
1620 			mptcp_reset_timer(sk);
1621 
1622 		if (msk->snd_data_fin_enable &&
1623 		    msk->snd_nxt + 1 == msk->write_seq)
1624 			mptcp_schedule_work(sk);
1625 	}
1626 }
1627 
1628 static void mptcp_set_nospace(struct sock *sk)
1629 {
1630 	/* enable autotune */
1631 	set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
1632 
1633 	/* will be cleared on avail space */
1634 	set_bit(MPTCP_NOSPACE, &mptcp_sk(sk)->flags);
1635 }
1636 
1637 static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
1638 {
1639 	struct mptcp_sock *msk = mptcp_sk(sk);
1640 	struct page_frag *pfrag;
1641 	size_t copied = 0;
1642 	int ret = 0;
1643 	long timeo;
1644 
1645 	/* we don't support FASTOPEN yet */
1646 	if (msg->msg_flags & MSG_FASTOPEN)
1647 		return -EOPNOTSUPP;
1648 
1649 	/* silently ignore everything else */
1650 	msg->msg_flags &= MSG_MORE | MSG_DONTWAIT | MSG_NOSIGNAL;
1651 
1652 	mptcp_lock_sock(sk, __mptcp_wmem_reserve(sk, min_t(size_t, 1 << 20, len)));
1653 
1654 	timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT);
1655 
1656 	if ((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) {
1657 		ret = sk_stream_wait_connect(sk, &timeo);
1658 		if (ret)
1659 			goto out;
1660 	}
1661 
1662 	pfrag = sk_page_frag(sk);
1663 
1664 	while (msg_data_left(msg)) {
1665 		int total_ts, frag_truesize = 0;
1666 		struct mptcp_data_frag *dfrag;
1667 		struct sk_buff_head skbs;
1668 		bool dfrag_collapsed;
1669 		size_t psize, offset;
1670 
1671 		if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN)) {
1672 			ret = -EPIPE;
1673 			goto out;
1674 		}
1675 
1676 		/* reuse tail pfrag, if possible, or carve a new one from the
1677 		 * page allocator
1678 		 */
1679 		dfrag = mptcp_pending_tail(sk);
1680 		dfrag_collapsed = mptcp_frag_can_collapse_to(msk, pfrag, dfrag);
1681 		if (!dfrag_collapsed) {
1682 			if (!sk_stream_memory_free(sk))
1683 				goto wait_for_memory;
1684 
1685 			if (!mptcp_page_frag_refill(sk, pfrag))
1686 				goto wait_for_memory;
1687 
1688 			dfrag = mptcp_carve_data_frag(msk, pfrag, pfrag->offset);
1689 			frag_truesize = dfrag->overhead;
1690 		}
1691 
1692 		/* we do not bound vs wspace, to allow a single packet.
1693 		 * memory accounting will prevent execessive memory usage
1694 		 * anyway
1695 		 */
1696 		offset = dfrag->offset + dfrag->data_len;
1697 		psize = pfrag->size - offset;
1698 		psize = min_t(size_t, psize, msg_data_left(msg));
1699 		total_ts = psize + frag_truesize;
1700 		__skb_queue_head_init(&skbs);
1701 		if (!mptcp_tx_cache_refill(sk, psize, &skbs, &total_ts))
1702 			goto wait_for_memory;
1703 
1704 		if (!mptcp_wmem_alloc(sk, total_ts)) {
1705 			__skb_queue_purge(&skbs);
1706 			goto wait_for_memory;
1707 		}
1708 
1709 		skb_queue_splice_tail(&skbs, &msk->skb_tx_cache);
1710 		if (copy_page_from_iter(dfrag->page, offset, psize,
1711 					&msg->msg_iter) != psize) {
1712 			mptcp_wmem_uncharge(sk, psize + frag_truesize);
1713 			ret = -EFAULT;
1714 			goto out;
1715 		}
1716 
1717 		/* data successfully copied into the write queue */
1718 		copied += psize;
1719 		dfrag->data_len += psize;
1720 		frag_truesize += psize;
1721 		pfrag->offset += frag_truesize;
1722 		WRITE_ONCE(msk->write_seq, msk->write_seq + psize);
1723 		msk->tx_pending_data += psize;
1724 
1725 		/* charge data on mptcp pending queue to the msk socket
1726 		 * Note: we charge such data both to sk and ssk
1727 		 */
1728 		sk_wmem_queued_add(sk, frag_truesize);
1729 		if (!dfrag_collapsed) {
1730 			get_page(dfrag->page);
1731 			list_add_tail(&dfrag->list, &msk->rtx_queue);
1732 			if (!msk->first_pending)
1733 				WRITE_ONCE(msk->first_pending, dfrag);
1734 		}
1735 		pr_debug("msk=%p dfrag at seq=%llu len=%u sent=%u new=%d", msk,
1736 			 dfrag->data_seq, dfrag->data_len, dfrag->already_sent,
1737 			 !dfrag_collapsed);
1738 
1739 		continue;
1740 
1741 wait_for_memory:
1742 		mptcp_set_nospace(sk);
1743 		__mptcp_push_pending(sk, msg->msg_flags);
1744 		ret = sk_stream_wait_memory(sk, &timeo);
1745 		if (ret)
1746 			goto out;
1747 	}
1748 
1749 	if (copied)
1750 		__mptcp_push_pending(sk, msg->msg_flags);
1751 
1752 out:
1753 	release_sock(sk);
1754 	return copied ? : ret;
1755 }
1756 
1757 static void mptcp_wait_data(struct sock *sk, long *timeo)
1758 {
1759 	DEFINE_WAIT_FUNC(wait, woken_wake_function);
1760 	struct mptcp_sock *msk = mptcp_sk(sk);
1761 
1762 	add_wait_queue(sk_sleep(sk), &wait);
1763 	sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);
1764 
1765 	sk_wait_event(sk, timeo,
1766 		      test_and_clear_bit(MPTCP_DATA_READY, &msk->flags), &wait);
1767 
1768 	sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);
1769 	remove_wait_queue(sk_sleep(sk), &wait);
1770 }
1771 
1772 static int __mptcp_recvmsg_mskq(struct mptcp_sock *msk,
1773 				struct msghdr *msg,
1774 				size_t len, int flags)
1775 {
1776 	struct sk_buff *skb, *tmp;
1777 	int copied = 0;
1778 
1779 	skb_queue_walk_safe(&msk->receive_queue, skb, tmp) {
1780 		u32 offset = MPTCP_SKB_CB(skb)->offset;
1781 		u32 data_len = skb->len - offset;
1782 		u32 count = min_t(size_t, len - copied, data_len);
1783 		int err;
1784 
1785 		if (!(flags & MSG_TRUNC)) {
1786 			err = skb_copy_datagram_msg(skb, offset, msg, count);
1787 			if (unlikely(err < 0)) {
1788 				if (!copied)
1789 					return err;
1790 				break;
1791 			}
1792 		}
1793 
1794 		copied += count;
1795 
1796 		if (count < data_len) {
1797 			if (!(flags & MSG_PEEK))
1798 				MPTCP_SKB_CB(skb)->offset += count;
1799 			break;
1800 		}
1801 
1802 		if (!(flags & MSG_PEEK)) {
1803 			/* we will bulk release the skb memory later */
1804 			skb->destructor = NULL;
1805 			msk->rmem_released += skb->truesize;
1806 			__skb_unlink(skb, &msk->receive_queue);
1807 			__kfree_skb(skb);
1808 		}
1809 
1810 		if (copied >= len)
1811 			break;
1812 	}
1813 
1814 	return copied;
1815 }
1816 
1817 /* receive buffer autotuning.  See tcp_rcv_space_adjust for more information.
1818  *
1819  * Only difference: Use highest rtt estimate of the subflows in use.
1820  */
1821 static void mptcp_rcv_space_adjust(struct mptcp_sock *msk, int copied)
1822 {
1823 	struct mptcp_subflow_context *subflow;
1824 	struct sock *sk = (struct sock *)msk;
1825 	u32 time, advmss = 1;
1826 	u64 rtt_us, mstamp;
1827 
1828 	sock_owned_by_me(sk);
1829 
1830 	if (copied <= 0)
1831 		return;
1832 
1833 	msk->rcvq_space.copied += copied;
1834 
1835 	mstamp = div_u64(tcp_clock_ns(), NSEC_PER_USEC);
1836 	time = tcp_stamp_us_delta(mstamp, msk->rcvq_space.time);
1837 
1838 	rtt_us = msk->rcvq_space.rtt_us;
1839 	if (rtt_us && time < (rtt_us >> 3))
1840 		return;
1841 
1842 	rtt_us = 0;
1843 	mptcp_for_each_subflow(msk, subflow) {
1844 		const struct tcp_sock *tp;
1845 		u64 sf_rtt_us;
1846 		u32 sf_advmss;
1847 
1848 		tp = tcp_sk(mptcp_subflow_tcp_sock(subflow));
1849 
1850 		sf_rtt_us = READ_ONCE(tp->rcv_rtt_est.rtt_us);
1851 		sf_advmss = READ_ONCE(tp->advmss);
1852 
1853 		rtt_us = max(sf_rtt_us, rtt_us);
1854 		advmss = max(sf_advmss, advmss);
1855 	}
1856 
1857 	msk->rcvq_space.rtt_us = rtt_us;
1858 	if (time < (rtt_us >> 3) || rtt_us == 0)
1859 		return;
1860 
1861 	if (msk->rcvq_space.copied <= msk->rcvq_space.space)
1862 		goto new_measure;
1863 
1864 	if (sock_net(sk)->ipv4.sysctl_tcp_moderate_rcvbuf &&
1865 	    !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
1866 		int rcvmem, rcvbuf;
1867 		u64 rcvwin, grow;
1868 
1869 		rcvwin = ((u64)msk->rcvq_space.copied << 1) + 16 * advmss;
1870 
1871 		grow = rcvwin * (msk->rcvq_space.copied - msk->rcvq_space.space);
1872 
1873 		do_div(grow, msk->rcvq_space.space);
1874 		rcvwin += (grow << 1);
1875 
1876 		rcvmem = SKB_TRUESIZE(advmss + MAX_TCP_HEADER);
1877 		while (tcp_win_from_space(sk, rcvmem) < advmss)
1878 			rcvmem += 128;
1879 
1880 		do_div(rcvwin, advmss);
1881 		rcvbuf = min_t(u64, rcvwin * rcvmem,
1882 			       sock_net(sk)->ipv4.sysctl_tcp_rmem[2]);
1883 
1884 		if (rcvbuf > sk->sk_rcvbuf) {
1885 			u32 window_clamp;
1886 
1887 			window_clamp = tcp_win_from_space(sk, rcvbuf);
1888 			WRITE_ONCE(sk->sk_rcvbuf, rcvbuf);
1889 
1890 			/* Make subflows follow along.  If we do not do this, we
1891 			 * get drops at subflow level if skbs can't be moved to
1892 			 * the mptcp rx queue fast enough (announced rcv_win can
1893 			 * exceed ssk->sk_rcvbuf).
1894 			 */
1895 			mptcp_for_each_subflow(msk, subflow) {
1896 				struct sock *ssk;
1897 				bool slow;
1898 
1899 				ssk = mptcp_subflow_tcp_sock(subflow);
1900 				slow = lock_sock_fast(ssk);
1901 				WRITE_ONCE(ssk->sk_rcvbuf, rcvbuf);
1902 				tcp_sk(ssk)->window_clamp = window_clamp;
1903 				tcp_cleanup_rbuf(ssk, 1);
1904 				unlock_sock_fast(ssk, slow);
1905 			}
1906 		}
1907 	}
1908 
1909 	msk->rcvq_space.space = msk->rcvq_space.copied;
1910 new_measure:
1911 	msk->rcvq_space.copied = 0;
1912 	msk->rcvq_space.time = mstamp;
1913 }
1914 
1915 static void __mptcp_update_rmem(struct sock *sk)
1916 {
1917 	struct mptcp_sock *msk = mptcp_sk(sk);
1918 
1919 	if (!msk->rmem_released)
1920 		return;
1921 
1922 	atomic_sub(msk->rmem_released, &sk->sk_rmem_alloc);
1923 	sk_mem_uncharge(sk, msk->rmem_released);
1924 	msk->rmem_released = 0;
1925 }
1926 
1927 static void __mptcp_splice_receive_queue(struct sock *sk)
1928 {
1929 	struct mptcp_sock *msk = mptcp_sk(sk);
1930 
1931 	skb_queue_splice_tail_init(&sk->sk_receive_queue, &msk->receive_queue);
1932 }
1933 
1934 static bool __mptcp_move_skbs(struct mptcp_sock *msk)
1935 {
1936 	struct sock *sk = (struct sock *)msk;
1937 	unsigned int moved = 0;
1938 	bool ret, done;
1939 
1940 	mptcp_flush_join_list(msk);
1941 	do {
1942 		struct sock *ssk = mptcp_subflow_recv_lookup(msk);
1943 		bool slowpath;
1944 
1945 		/* we can have data pending in the subflows only if the msk
1946 		 * receive buffer was full at subflow_data_ready() time,
1947 		 * that is an unlikely slow path.
1948 		 */
1949 		if (likely(!ssk))
1950 			break;
1951 
1952 		slowpath = lock_sock_fast(ssk);
1953 		mptcp_data_lock(sk);
1954 		__mptcp_update_rmem(sk);
1955 		done = __mptcp_move_skbs_from_subflow(msk, ssk, &moved);
1956 		mptcp_data_unlock(sk);
1957 		tcp_cleanup_rbuf(ssk, moved);
1958 		unlock_sock_fast(ssk, slowpath);
1959 	} while (!done);
1960 
1961 	/* acquire the data lock only if some input data is pending */
1962 	ret = moved > 0;
1963 	if (!RB_EMPTY_ROOT(&msk->out_of_order_queue) ||
1964 	    !skb_queue_empty_lockless(&sk->sk_receive_queue)) {
1965 		mptcp_data_lock(sk);
1966 		__mptcp_update_rmem(sk);
1967 		ret |= __mptcp_ofo_queue(msk);
1968 		__mptcp_splice_receive_queue(sk);
1969 		mptcp_data_unlock(sk);
1970 		mptcp_cleanup_rbuf(msk);
1971 	}
1972 	if (ret)
1973 		mptcp_check_data_fin((struct sock *)msk);
1974 	return !skb_queue_empty(&msk->receive_queue);
1975 }
1976 
1977 static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
1978 			 int nonblock, int flags, int *addr_len)
1979 {
1980 	struct mptcp_sock *msk = mptcp_sk(sk);
1981 	int copied = 0;
1982 	int target;
1983 	long timeo;
1984 
1985 	/* MSG_ERRQUEUE is really a no-op till we support IP_RECVERR */
1986 	if (unlikely(flags & MSG_ERRQUEUE))
1987 		return inet_recv_error(sk, msg, len, addr_len);
1988 
1989 	mptcp_lock_sock(sk, __mptcp_splice_receive_queue(sk));
1990 	if (unlikely(sk->sk_state == TCP_LISTEN)) {
1991 		copied = -ENOTCONN;
1992 		goto out_err;
1993 	}
1994 
1995 	timeo = sock_rcvtimeo(sk, nonblock);
1996 
1997 	len = min_t(size_t, len, INT_MAX);
1998 	target = sock_rcvlowat(sk, flags & MSG_WAITALL, len);
1999 
2000 	while (copied < len) {
2001 		int bytes_read;
2002 
2003 		bytes_read = __mptcp_recvmsg_mskq(msk, msg, len - copied, flags);
2004 		if (unlikely(bytes_read < 0)) {
2005 			if (!copied)
2006 				copied = bytes_read;
2007 			goto out_err;
2008 		}
2009 
2010 		copied += bytes_read;
2011 
2012 		/* be sure to advertise window change */
2013 		mptcp_cleanup_rbuf(msk);
2014 
2015 		if (skb_queue_empty(&msk->receive_queue) && __mptcp_move_skbs(msk))
2016 			continue;
2017 
2018 		/* only the master socket status is relevant here. The exit
2019 		 * conditions mirror closely tcp_recvmsg()
2020 		 */
2021 		if (copied >= target)
2022 			break;
2023 
2024 		if (copied) {
2025 			if (sk->sk_err ||
2026 			    sk->sk_state == TCP_CLOSE ||
2027 			    (sk->sk_shutdown & RCV_SHUTDOWN) ||
2028 			    !timeo ||
2029 			    signal_pending(current))
2030 				break;
2031 		} else {
2032 			if (sk->sk_err) {
2033 				copied = sock_error(sk);
2034 				break;
2035 			}
2036 
2037 			if (test_and_clear_bit(MPTCP_WORK_EOF, &msk->flags))
2038 				mptcp_check_for_eof(msk);
2039 
2040 			if (sk->sk_shutdown & RCV_SHUTDOWN) {
2041 				/* race breaker: the shutdown could be after the
2042 				 * previous receive queue check
2043 				 */
2044 				if (__mptcp_move_skbs(msk))
2045 					continue;
2046 				break;
2047 			}
2048 
2049 			if (sk->sk_state == TCP_CLOSE) {
2050 				copied = -ENOTCONN;
2051 				break;
2052 			}
2053 
2054 			if (!timeo) {
2055 				copied = -EAGAIN;
2056 				break;
2057 			}
2058 
2059 			if (signal_pending(current)) {
2060 				copied = sock_intr_errno(timeo);
2061 				break;
2062 			}
2063 		}
2064 
2065 		pr_debug("block timeout %ld", timeo);
2066 		mptcp_wait_data(sk, &timeo);
2067 	}
2068 
2069 	if (skb_queue_empty_lockless(&sk->sk_receive_queue) &&
2070 	    skb_queue_empty(&msk->receive_queue)) {
2071 		/* entire backlog drained, clear DATA_READY. */
2072 		clear_bit(MPTCP_DATA_READY, &msk->flags);
2073 
2074 		/* .. race-breaker: ssk might have gotten new data
2075 		 * after last __mptcp_move_skbs() returned false.
2076 		 */
2077 		if (unlikely(__mptcp_move_skbs(msk)))
2078 			set_bit(MPTCP_DATA_READY, &msk->flags);
2079 	} else if (unlikely(!test_bit(MPTCP_DATA_READY, &msk->flags))) {
2080 		/* data to read but mptcp_wait_data() cleared DATA_READY */
2081 		set_bit(MPTCP_DATA_READY, &msk->flags);
2082 	}
2083 out_err:
2084 	pr_debug("msk=%p data_ready=%d rx queue empty=%d copied=%d",
2085 		 msk, test_bit(MPTCP_DATA_READY, &msk->flags),
2086 		 skb_queue_empty_lockless(&sk->sk_receive_queue), copied);
2087 	if (!(flags & MSG_PEEK))
2088 		mptcp_rcv_space_adjust(msk, copied);
2089 
2090 	release_sock(sk);
2091 	return copied;
2092 }
2093 
2094 static void mptcp_retransmit_timer(struct timer_list *t)
2095 {
2096 	struct inet_connection_sock *icsk = from_timer(icsk, t,
2097 						       icsk_retransmit_timer);
2098 	struct sock *sk = &icsk->icsk_inet.sk;
2099 	struct mptcp_sock *msk = mptcp_sk(sk);
2100 
2101 	bh_lock_sock(sk);
2102 	if (!sock_owned_by_user(sk)) {
2103 		/* we need a process context to retransmit */
2104 		if (!test_and_set_bit(MPTCP_WORK_RTX, &msk->flags))
2105 			mptcp_schedule_work(sk);
2106 	} else {
2107 		/* delegate our work to tcp_release_cb() */
2108 		set_bit(MPTCP_RETRANSMIT, &msk->flags);
2109 	}
2110 	bh_unlock_sock(sk);
2111 	sock_put(sk);
2112 }
2113 
2114 static void mptcp_timeout_timer(struct timer_list *t)
2115 {
2116 	struct sock *sk = from_timer(sk, t, sk_timer);
2117 
2118 	mptcp_schedule_work(sk);
2119 	sock_put(sk);
2120 }
2121 
2122 /* Find an idle subflow.  Return NULL if there is unacked data at tcp
2123  * level.
2124  *
2125  * A backup subflow is returned only if that is the only kind available.
2126  */
2127 static struct sock *mptcp_subflow_get_retrans(const struct mptcp_sock *msk)
2128 {
2129 	struct mptcp_subflow_context *subflow;
2130 	struct sock *backup = NULL;
2131 
2132 	sock_owned_by_me((const struct sock *)msk);
2133 
2134 	if (__mptcp_check_fallback(msk))
2135 		return NULL;
2136 
2137 	mptcp_for_each_subflow(msk, subflow) {
2138 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
2139 
2140 		if (!mptcp_subflow_active(subflow))
2141 			continue;
2142 
2143 		/* still data outstanding at TCP level?  Don't retransmit. */
2144 		if (!tcp_write_queue_empty(ssk)) {
2145 			if (inet_csk(ssk)->icsk_ca_state >= TCP_CA_Loss)
2146 				continue;
2147 			return NULL;
2148 		}
2149 
2150 		if (subflow->backup) {
2151 			if (!backup)
2152 				backup = ssk;
2153 			continue;
2154 		}
2155 
2156 		return ssk;
2157 	}
2158 
2159 	return backup;
2160 }
2161 
2162 static void mptcp_dispose_initial_subflow(struct mptcp_sock *msk)
2163 {
2164 	if (msk->subflow) {
2165 		iput(SOCK_INODE(msk->subflow));
2166 		msk->subflow = NULL;
2167 	}
2168 }
2169 
2170 /* subflow sockets can be either outgoing (connect) or incoming
2171  * (accept).
2172  *
2173  * Outgoing subflows use in-kernel sockets.
2174  * Incoming subflows do not have their own 'struct socket' allocated,
2175  * so we need to use tcp_close() after detaching them from the mptcp
2176  * parent socket.
2177  */
2178 static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
2179 			      struct mptcp_subflow_context *subflow)
2180 {
2181 	struct mptcp_sock *msk = mptcp_sk(sk);
2182 
2183 	list_del(&subflow->node);
2184 
2185 	lock_sock_nested(ssk, SINGLE_DEPTH_NESTING);
2186 
2187 	/* if we are invoked by the msk cleanup code, the subflow is
2188 	 * already orphaned
2189 	 */
2190 	if (ssk->sk_socket)
2191 		sock_orphan(ssk);
2192 
2193 	subflow->disposable = 1;
2194 
2195 	/* if ssk hit tcp_done(), tcp_cleanup_ulp() cleared the related ops
2196 	 * the ssk has been already destroyed, we just need to release the
2197 	 * reference owned by msk;
2198 	 */
2199 	if (!inet_csk(ssk)->icsk_ulp_ops) {
2200 		kfree_rcu(subflow, rcu);
2201 	} else {
2202 		/* otherwise tcp will dispose of the ssk and subflow ctx */
2203 		__tcp_close(ssk, 0);
2204 
2205 		/* close acquired an extra ref */
2206 		__sock_put(ssk);
2207 	}
2208 	release_sock(ssk);
2209 
2210 	sock_put(ssk);
2211 
2212 	if (ssk == msk->last_snd)
2213 		msk->last_snd = NULL;
2214 
2215 	if (ssk == msk->ack_hint)
2216 		msk->ack_hint = NULL;
2217 
2218 	if (ssk == msk->first)
2219 		msk->first = NULL;
2220 
2221 	if (msk->subflow && ssk == msk->subflow->sk)
2222 		mptcp_dispose_initial_subflow(msk);
2223 }
2224 
2225 void mptcp_close_ssk(struct sock *sk, struct sock *ssk,
2226 		     struct mptcp_subflow_context *subflow)
2227 {
2228 	if (sk->sk_state == TCP_ESTABLISHED)
2229 		mptcp_event(MPTCP_EVENT_SUB_CLOSED, mptcp_sk(sk), ssk, GFP_KERNEL);
2230 	__mptcp_close_ssk(sk, ssk, subflow);
2231 }
2232 
2233 static unsigned int mptcp_sync_mss(struct sock *sk, u32 pmtu)
2234 {
2235 	return 0;
2236 }
2237 
2238 static void __mptcp_close_subflow(struct mptcp_sock *msk)
2239 {
2240 	struct mptcp_subflow_context *subflow, *tmp;
2241 
2242 	might_sleep();
2243 
2244 	list_for_each_entry_safe(subflow, tmp, &msk->conn_list, node) {
2245 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
2246 
2247 		if (inet_sk_state_load(ssk) != TCP_CLOSE)
2248 			continue;
2249 
2250 		/* 'subflow_data_ready' will re-sched once rx queue is empty */
2251 		if (!skb_queue_empty_lockless(&ssk->sk_receive_queue))
2252 			continue;
2253 
2254 		mptcp_close_ssk((struct sock *)msk, ssk, subflow);
2255 	}
2256 }
2257 
2258 static bool mptcp_check_close_timeout(const struct sock *sk)
2259 {
2260 	s32 delta = tcp_jiffies32 - inet_csk(sk)->icsk_mtup.probe_timestamp;
2261 	struct mptcp_subflow_context *subflow;
2262 
2263 	if (delta >= TCP_TIMEWAIT_LEN)
2264 		return true;
2265 
2266 	/* if all subflows are in closed status don't bother with additional
2267 	 * timeout
2268 	 */
2269 	mptcp_for_each_subflow(mptcp_sk(sk), subflow) {
2270 		if (inet_sk_state_load(mptcp_subflow_tcp_sock(subflow)) !=
2271 		    TCP_CLOSE)
2272 			return false;
2273 	}
2274 	return true;
2275 }
2276 
2277 static void mptcp_check_fastclose(struct mptcp_sock *msk)
2278 {
2279 	struct mptcp_subflow_context *subflow, *tmp;
2280 	struct sock *sk = &msk->sk.icsk_inet.sk;
2281 
2282 	if (likely(!READ_ONCE(msk->rcv_fastclose)))
2283 		return;
2284 
2285 	mptcp_token_destroy(msk);
2286 
2287 	list_for_each_entry_safe(subflow, tmp, &msk->conn_list, node) {
2288 		struct sock *tcp_sk = mptcp_subflow_tcp_sock(subflow);
2289 
2290 		lock_sock(tcp_sk);
2291 		if (tcp_sk->sk_state != TCP_CLOSE) {
2292 			tcp_send_active_reset(tcp_sk, GFP_ATOMIC);
2293 			tcp_set_state(tcp_sk, TCP_CLOSE);
2294 		}
2295 		release_sock(tcp_sk);
2296 	}
2297 
2298 	inet_sk_state_store(sk, TCP_CLOSE);
2299 	sk->sk_shutdown = SHUTDOWN_MASK;
2300 	smp_mb__before_atomic(); /* SHUTDOWN must be visible first */
2301 	set_bit(MPTCP_DATA_READY, &msk->flags);
2302 	set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &msk->flags);
2303 
2304 	mptcp_close_wake_up(sk);
2305 }
2306 
2307 static void __mptcp_retrans(struct sock *sk)
2308 {
2309 	struct mptcp_sock *msk = mptcp_sk(sk);
2310 	struct mptcp_sendmsg_info info = {};
2311 	struct mptcp_data_frag *dfrag;
2312 	size_t copied = 0;
2313 	struct sock *ssk;
2314 	int ret;
2315 
2316 	mptcp_clean_una_wakeup(sk);
2317 	dfrag = mptcp_rtx_head(sk);
2318 	if (!dfrag) {
2319 		if (mptcp_data_fin_enabled(msk)) {
2320 			struct inet_connection_sock *icsk = inet_csk(sk);
2321 
2322 			icsk->icsk_retransmits++;
2323 			mptcp_set_datafin_timeout(sk);
2324 			mptcp_send_ack(msk);
2325 
2326 			goto reset_timer;
2327 		}
2328 
2329 		return;
2330 	}
2331 
2332 	ssk = mptcp_subflow_get_retrans(msk);
2333 	if (!ssk)
2334 		goto reset_timer;
2335 
2336 	lock_sock(ssk);
2337 
2338 	/* limit retransmission to the bytes already sent on some subflows */
2339 	info.sent = 0;
2340 	info.limit = dfrag->already_sent;
2341 	while (info.sent < dfrag->already_sent) {
2342 		if (!mptcp_alloc_tx_skb(sk, ssk))
2343 			break;
2344 
2345 		ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
2346 		if (ret <= 0)
2347 			break;
2348 
2349 		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_RETRANSSEGS);
2350 		copied += ret;
2351 		info.sent += ret;
2352 	}
2353 	if (copied)
2354 		tcp_push(ssk, 0, info.mss_now, tcp_sk(ssk)->nonagle,
2355 			 info.size_goal);
2356 
2357 	mptcp_set_timeout(sk, ssk);
2358 	release_sock(ssk);
2359 
2360 reset_timer:
2361 	if (!mptcp_timer_pending(sk))
2362 		mptcp_reset_timer(sk);
2363 }
2364 
2365 static void mptcp_worker(struct work_struct *work)
2366 {
2367 	struct mptcp_sock *msk = container_of(work, struct mptcp_sock, work);
2368 	struct sock *sk = &msk->sk.icsk_inet.sk;
2369 	int state;
2370 
2371 	lock_sock(sk);
2372 	state = sk->sk_state;
2373 	if (unlikely(state == TCP_CLOSE))
2374 		goto unlock;
2375 
2376 	mptcp_check_data_fin_ack(sk);
2377 	mptcp_flush_join_list(msk);
2378 
2379 	mptcp_check_fastclose(msk);
2380 
2381 	if (msk->pm.status)
2382 		mptcp_pm_nl_work(msk);
2383 
2384 	if (test_and_clear_bit(MPTCP_WORK_EOF, &msk->flags))
2385 		mptcp_check_for_eof(msk);
2386 
2387 	__mptcp_check_send_data_fin(sk);
2388 	mptcp_check_data_fin(sk);
2389 
2390 	/* There is no point in keeping around an orphaned sk timedout or
2391 	 * closed, but we need the msk around to reply to incoming DATA_FIN,
2392 	 * even if it is orphaned and in FIN_WAIT2 state
2393 	 */
2394 	if (sock_flag(sk, SOCK_DEAD) &&
2395 	    (mptcp_check_close_timeout(sk) || sk->sk_state == TCP_CLOSE)) {
2396 		inet_sk_state_store(sk, TCP_CLOSE);
2397 		__mptcp_destroy_sock(sk);
2398 		goto unlock;
2399 	}
2400 
2401 	if (test_and_clear_bit(MPTCP_WORK_CLOSE_SUBFLOW, &msk->flags))
2402 		__mptcp_close_subflow(msk);
2403 
2404 	if (test_and_clear_bit(MPTCP_WORK_RTX, &msk->flags))
2405 		__mptcp_retrans(sk);
2406 
2407 unlock:
2408 	release_sock(sk);
2409 	sock_put(sk);
2410 }
2411 
2412 static int __mptcp_init_sock(struct sock *sk)
2413 {
2414 	struct mptcp_sock *msk = mptcp_sk(sk);
2415 
2416 	spin_lock_init(&msk->join_list_lock);
2417 
2418 	INIT_LIST_HEAD(&msk->conn_list);
2419 	INIT_LIST_HEAD(&msk->join_list);
2420 	INIT_LIST_HEAD(&msk->rtx_queue);
2421 	INIT_WORK(&msk->work, mptcp_worker);
2422 	__skb_queue_head_init(&msk->receive_queue);
2423 	__skb_queue_head_init(&msk->skb_tx_cache);
2424 	msk->out_of_order_queue = RB_ROOT;
2425 	msk->first_pending = NULL;
2426 	msk->wmem_reserved = 0;
2427 	msk->rmem_released = 0;
2428 	msk->tx_pending_data = 0;
2429 	msk->size_goal_cache = TCP_BASE_MSS;
2430 
2431 	msk->ack_hint = NULL;
2432 	msk->first = NULL;
2433 	inet_csk(sk)->icsk_sync_mss = mptcp_sync_mss;
2434 
2435 	mptcp_pm_data_init(msk);
2436 
2437 	/* re-use the csk retrans timer for MPTCP-level retrans */
2438 	timer_setup(&msk->sk.icsk_retransmit_timer, mptcp_retransmit_timer, 0);
2439 	timer_setup(&sk->sk_timer, mptcp_timeout_timer, 0);
2440 
2441 	return 0;
2442 }
2443 
2444 static int mptcp_init_sock(struct sock *sk)
2445 {
2446 	struct inet_connection_sock *icsk = inet_csk(sk);
2447 	struct net *net = sock_net(sk);
2448 	int ret;
2449 
2450 	ret = __mptcp_init_sock(sk);
2451 	if (ret)
2452 		return ret;
2453 
2454 	if (!mptcp_is_enabled(net))
2455 		return -ENOPROTOOPT;
2456 
2457 	if (unlikely(!net->mib.mptcp_statistics) && !mptcp_mib_alloc(net))
2458 		return -ENOMEM;
2459 
2460 	ret = __mptcp_socket_create(mptcp_sk(sk));
2461 	if (ret)
2462 		return ret;
2463 
2464 	/* fetch the ca name; do it outside __mptcp_init_sock(), so that clone will
2465 	 * propagate the correct value
2466 	 */
2467 	tcp_assign_congestion_control(sk);
2468 	strcpy(mptcp_sk(sk)->ca_name, icsk->icsk_ca_ops->name);
2469 
2470 	/* no need to keep a reference to the ops, the name will suffice */
2471 	tcp_cleanup_congestion_control(sk);
2472 	icsk->icsk_ca_ops = NULL;
2473 
2474 	sk_sockets_allocated_inc(sk);
2475 	sk->sk_rcvbuf = sock_net(sk)->ipv4.sysctl_tcp_rmem[1];
2476 	sk->sk_sndbuf = sock_net(sk)->ipv4.sysctl_tcp_wmem[1];
2477 
2478 	return 0;
2479 }
2480 
2481 static void __mptcp_clear_xmit(struct sock *sk)
2482 {
2483 	struct mptcp_sock *msk = mptcp_sk(sk);
2484 	struct mptcp_data_frag *dtmp, *dfrag;
2485 	struct sk_buff *skb;
2486 
2487 	WRITE_ONCE(msk->first_pending, NULL);
2488 	list_for_each_entry_safe(dfrag, dtmp, &msk->rtx_queue, list)
2489 		dfrag_clear(sk, dfrag);
2490 	while ((skb = __skb_dequeue(&msk->skb_tx_cache)) != NULL) {
2491 		sk->sk_forward_alloc += skb->truesize;
2492 		kfree_skb(skb);
2493 	}
2494 }
2495 
2496 static void mptcp_cancel_work(struct sock *sk)
2497 {
2498 	struct mptcp_sock *msk = mptcp_sk(sk);
2499 
2500 	if (cancel_work_sync(&msk->work))
2501 		__sock_put(sk);
2502 }
2503 
2504 void mptcp_subflow_shutdown(struct sock *sk, struct sock *ssk, int how)
2505 {
2506 	lock_sock(ssk);
2507 
2508 	switch (ssk->sk_state) {
2509 	case TCP_LISTEN:
2510 		if (!(how & RCV_SHUTDOWN))
2511 			break;
2512 		fallthrough;
2513 	case TCP_SYN_SENT:
2514 		tcp_disconnect(ssk, O_NONBLOCK);
2515 		break;
2516 	default:
2517 		if (__mptcp_check_fallback(mptcp_sk(sk))) {
2518 			pr_debug("Fallback");
2519 			ssk->sk_shutdown |= how;
2520 			tcp_shutdown(ssk, how);
2521 		} else {
2522 			pr_debug("Sending DATA_FIN on subflow %p", ssk);
2523 			mptcp_set_timeout(sk, ssk);
2524 			tcp_send_ack(ssk);
2525 			if (!mptcp_timer_pending(sk))
2526 				mptcp_reset_timer(sk);
2527 		}
2528 		break;
2529 	}
2530 
2531 	release_sock(ssk);
2532 }
2533 
2534 static const unsigned char new_state[16] = {
2535 	/* current state:     new state:      action:	*/
2536 	[0 /* (Invalid) */] = TCP_CLOSE,
2537 	[TCP_ESTABLISHED]   = TCP_FIN_WAIT1 | TCP_ACTION_FIN,
2538 	[TCP_SYN_SENT]      = TCP_CLOSE,
2539 	[TCP_SYN_RECV]      = TCP_FIN_WAIT1 | TCP_ACTION_FIN,
2540 	[TCP_FIN_WAIT1]     = TCP_FIN_WAIT1,
2541 	[TCP_FIN_WAIT2]     = TCP_FIN_WAIT2,
2542 	[TCP_TIME_WAIT]     = TCP_CLOSE,	/* should not happen ! */
2543 	[TCP_CLOSE]         = TCP_CLOSE,
2544 	[TCP_CLOSE_WAIT]    = TCP_LAST_ACK  | TCP_ACTION_FIN,
2545 	[TCP_LAST_ACK]      = TCP_LAST_ACK,
2546 	[TCP_LISTEN]        = TCP_CLOSE,
2547 	[TCP_CLOSING]       = TCP_CLOSING,
2548 	[TCP_NEW_SYN_RECV]  = TCP_CLOSE,	/* should not happen ! */
2549 };
2550 
2551 static int mptcp_close_state(struct sock *sk)
2552 {
2553 	int next = (int)new_state[sk->sk_state];
2554 	int ns = next & TCP_STATE_MASK;
2555 
2556 	inet_sk_state_store(sk, ns);
2557 
2558 	return next & TCP_ACTION_FIN;
2559 }
2560 
2561 static void __mptcp_check_send_data_fin(struct sock *sk)
2562 {
2563 	struct mptcp_subflow_context *subflow;
2564 	struct mptcp_sock *msk = mptcp_sk(sk);
2565 
2566 	pr_debug("msk=%p snd_data_fin_enable=%d pending=%d snd_nxt=%llu write_seq=%llu",
2567 		 msk, msk->snd_data_fin_enable, !!mptcp_send_head(sk),
2568 		 msk->snd_nxt, msk->write_seq);
2569 
2570 	/* we still need to enqueue subflows or not really shutting down,
2571 	 * skip this
2572 	 */
2573 	if (!msk->snd_data_fin_enable || msk->snd_nxt + 1 != msk->write_seq ||
2574 	    mptcp_send_head(sk))
2575 		return;
2576 
2577 	WRITE_ONCE(msk->snd_nxt, msk->write_seq);
2578 
2579 	/* fallback socket will not get data_fin/ack, can move to the next
2580 	 * state now
2581 	 */
2582 	if (__mptcp_check_fallback(msk)) {
2583 		if ((1 << sk->sk_state) & (TCPF_CLOSING | TCPF_LAST_ACK)) {
2584 			inet_sk_state_store(sk, TCP_CLOSE);
2585 			mptcp_close_wake_up(sk);
2586 		} else if (sk->sk_state == TCP_FIN_WAIT1) {
2587 			inet_sk_state_store(sk, TCP_FIN_WAIT2);
2588 		}
2589 	}
2590 
2591 	mptcp_flush_join_list(msk);
2592 	mptcp_for_each_subflow(msk, subflow) {
2593 		struct sock *tcp_sk = mptcp_subflow_tcp_sock(subflow);
2594 
2595 		mptcp_subflow_shutdown(sk, tcp_sk, SEND_SHUTDOWN);
2596 	}
2597 }
2598 
2599 static void __mptcp_wr_shutdown(struct sock *sk)
2600 {
2601 	struct mptcp_sock *msk = mptcp_sk(sk);
2602 
2603 	pr_debug("msk=%p snd_data_fin_enable=%d shutdown=%x state=%d pending=%d",
2604 		 msk, msk->snd_data_fin_enable, sk->sk_shutdown, sk->sk_state,
2605 		 !!mptcp_send_head(sk));
2606 
2607 	/* will be ignored by fallback sockets */
2608 	WRITE_ONCE(msk->write_seq, msk->write_seq + 1);
2609 	WRITE_ONCE(msk->snd_data_fin_enable, 1);
2610 
2611 	__mptcp_check_send_data_fin(sk);
2612 }
2613 
2614 static void __mptcp_destroy_sock(struct sock *sk)
2615 {
2616 	struct mptcp_subflow_context *subflow, *tmp;
2617 	struct mptcp_sock *msk = mptcp_sk(sk);
2618 	LIST_HEAD(conn_list);
2619 
2620 	pr_debug("msk=%p", msk);
2621 
2622 	might_sleep();
2623 
2624 	/* be sure to always acquire the join list lock, to sync vs
2625 	 * mptcp_finish_join().
2626 	 */
2627 	spin_lock_bh(&msk->join_list_lock);
2628 	list_splice_tail_init(&msk->join_list, &msk->conn_list);
2629 	spin_unlock_bh(&msk->join_list_lock);
2630 	list_splice_init(&msk->conn_list, &conn_list);
2631 
2632 	sk_stop_timer(sk, &msk->sk.icsk_retransmit_timer);
2633 	sk_stop_timer(sk, &sk->sk_timer);
2634 	msk->pm.status = 0;
2635 
2636 	list_for_each_entry_safe(subflow, tmp, &conn_list, node) {
2637 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
2638 		__mptcp_close_ssk(sk, ssk, subflow);
2639 	}
2640 
2641 	sk->sk_prot->destroy(sk);
2642 
2643 	WARN_ON_ONCE(msk->wmem_reserved);
2644 	WARN_ON_ONCE(msk->rmem_released);
2645 	sk_stream_kill_queues(sk);
2646 	xfrm_sk_free_policy(sk);
2647 
2648 	sk_refcnt_debug_release(sk);
2649 	mptcp_dispose_initial_subflow(msk);
2650 	sock_put(sk);
2651 }
2652 
2653 static void mptcp_close(struct sock *sk, long timeout)
2654 {
2655 	struct mptcp_subflow_context *subflow;
2656 	bool do_cancel_work = false;
2657 
2658 	lock_sock(sk);
2659 	sk->sk_shutdown = SHUTDOWN_MASK;
2660 
2661 	if ((1 << sk->sk_state) & (TCPF_LISTEN | TCPF_CLOSE)) {
2662 		inet_sk_state_store(sk, TCP_CLOSE);
2663 		goto cleanup;
2664 	}
2665 
2666 	if (mptcp_close_state(sk))
2667 		__mptcp_wr_shutdown(sk);
2668 
2669 	sk_stream_wait_close(sk, timeout);
2670 
2671 cleanup:
2672 	/* orphan all the subflows */
2673 	inet_csk(sk)->icsk_mtup.probe_timestamp = tcp_jiffies32;
2674 	mptcp_for_each_subflow(mptcp_sk(sk), subflow) {
2675 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
2676 		bool slow = lock_sock_fast(ssk);
2677 
2678 		sock_orphan(ssk);
2679 		unlock_sock_fast(ssk, slow);
2680 	}
2681 	sock_orphan(sk);
2682 
2683 	sock_hold(sk);
2684 	pr_debug("msk=%p state=%d", sk, sk->sk_state);
2685 	if (sk->sk_state == TCP_CLOSE) {
2686 		__mptcp_destroy_sock(sk);
2687 		do_cancel_work = true;
2688 	} else {
2689 		sk_reset_timer(sk, &sk->sk_timer, jiffies + TCP_TIMEWAIT_LEN);
2690 	}
2691 	release_sock(sk);
2692 	if (do_cancel_work)
2693 		mptcp_cancel_work(sk);
2694 
2695 	if (mptcp_sk(sk)->token)
2696 		mptcp_event(MPTCP_EVENT_CLOSED, mptcp_sk(sk), NULL, GFP_KERNEL);
2697 
2698 	sock_put(sk);
2699 }
2700 
2701 static void mptcp_copy_inaddrs(struct sock *msk, const struct sock *ssk)
2702 {
2703 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
2704 	const struct ipv6_pinfo *ssk6 = inet6_sk(ssk);
2705 	struct ipv6_pinfo *msk6 = inet6_sk(msk);
2706 
2707 	msk->sk_v6_daddr = ssk->sk_v6_daddr;
2708 	msk->sk_v6_rcv_saddr = ssk->sk_v6_rcv_saddr;
2709 
2710 	if (msk6 && ssk6) {
2711 		msk6->saddr = ssk6->saddr;
2712 		msk6->flow_label = ssk6->flow_label;
2713 	}
2714 #endif
2715 
2716 	inet_sk(msk)->inet_num = inet_sk(ssk)->inet_num;
2717 	inet_sk(msk)->inet_dport = inet_sk(ssk)->inet_dport;
2718 	inet_sk(msk)->inet_sport = inet_sk(ssk)->inet_sport;
2719 	inet_sk(msk)->inet_daddr = inet_sk(ssk)->inet_daddr;
2720 	inet_sk(msk)->inet_saddr = inet_sk(ssk)->inet_saddr;
2721 	inet_sk(msk)->inet_rcv_saddr = inet_sk(ssk)->inet_rcv_saddr;
2722 }
2723 
2724 static int mptcp_disconnect(struct sock *sk, int flags)
2725 {
2726 	struct mptcp_subflow_context *subflow;
2727 	struct mptcp_sock *msk = mptcp_sk(sk);
2728 
2729 	mptcp_do_flush_join_list(msk);
2730 
2731 	mptcp_for_each_subflow(msk, subflow) {
2732 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
2733 
2734 		lock_sock(ssk);
2735 		tcp_disconnect(ssk, flags);
2736 		release_sock(ssk);
2737 	}
2738 	return 0;
2739 }
2740 
2741 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
2742 static struct ipv6_pinfo *mptcp_inet6_sk(const struct sock *sk)
2743 {
2744 	unsigned int offset = sizeof(struct mptcp6_sock) - sizeof(struct ipv6_pinfo);
2745 
2746 	return (struct ipv6_pinfo *)(((u8 *)sk) + offset);
2747 }
2748 #endif
2749 
2750 struct sock *mptcp_sk_clone(const struct sock *sk,
2751 			    const struct mptcp_options_received *mp_opt,
2752 			    struct request_sock *req)
2753 {
2754 	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
2755 	struct sock *nsk = sk_clone_lock(sk, GFP_ATOMIC);
2756 	struct mptcp_sock *msk;
2757 	u64 ack_seq;
2758 
2759 	if (!nsk)
2760 		return NULL;
2761 
2762 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
2763 	if (nsk->sk_family == AF_INET6)
2764 		inet_sk(nsk)->pinet6 = mptcp_inet6_sk(nsk);
2765 #endif
2766 
2767 	__mptcp_init_sock(nsk);
2768 
2769 	msk = mptcp_sk(nsk);
2770 	msk->local_key = subflow_req->local_key;
2771 	msk->token = subflow_req->token;
2772 	msk->subflow = NULL;
2773 	WRITE_ONCE(msk->fully_established, false);
2774 
2775 	msk->write_seq = subflow_req->idsn + 1;
2776 	msk->snd_nxt = msk->write_seq;
2777 	msk->snd_una = msk->write_seq;
2778 	msk->wnd_end = msk->snd_nxt + req->rsk_rcv_wnd;
2779 	msk->setsockopt_seq = mptcp_sk(sk)->setsockopt_seq;
2780 
2781 	if (mp_opt->mp_capable) {
2782 		msk->can_ack = true;
2783 		msk->remote_key = mp_opt->sndr_key;
2784 		mptcp_crypto_key_sha(msk->remote_key, NULL, &ack_seq);
2785 		ack_seq++;
2786 		WRITE_ONCE(msk->ack_seq, ack_seq);
2787 		WRITE_ONCE(msk->rcv_wnd_sent, ack_seq);
2788 	}
2789 
2790 	sock_reset_flag(nsk, SOCK_RCU_FREE);
2791 	/* will be fully established after successful MPC subflow creation */
2792 	inet_sk_state_store(nsk, TCP_SYN_RECV);
2793 
2794 	security_inet_csk_clone(nsk, req);
2795 	bh_unlock_sock(nsk);
2796 
2797 	/* keep a single reference */
2798 	__sock_put(nsk);
2799 	return nsk;
2800 }
2801 
2802 void mptcp_rcv_space_init(struct mptcp_sock *msk, const struct sock *ssk)
2803 {
2804 	const struct tcp_sock *tp = tcp_sk(ssk);
2805 
2806 	msk->rcvq_space.copied = 0;
2807 	msk->rcvq_space.rtt_us = 0;
2808 
2809 	msk->rcvq_space.time = tp->tcp_mstamp;
2810 
2811 	/* initial rcv_space offering made to peer */
2812 	msk->rcvq_space.space = min_t(u32, tp->rcv_wnd,
2813 				      TCP_INIT_CWND * tp->advmss);
2814 	if (msk->rcvq_space.space == 0)
2815 		msk->rcvq_space.space = TCP_INIT_CWND * TCP_MSS_DEFAULT;
2816 
2817 	WRITE_ONCE(msk->wnd_end, msk->snd_nxt + tcp_sk(ssk)->snd_wnd);
2818 }
2819 
2820 static struct sock *mptcp_accept(struct sock *sk, int flags, int *err,
2821 				 bool kern)
2822 {
2823 	struct mptcp_sock *msk = mptcp_sk(sk);
2824 	struct socket *listener;
2825 	struct sock *newsk;
2826 
2827 	listener = __mptcp_nmpc_socket(msk);
2828 	if (WARN_ON_ONCE(!listener)) {
2829 		*err = -EINVAL;
2830 		return NULL;
2831 	}
2832 
2833 	pr_debug("msk=%p, listener=%p", msk, mptcp_subflow_ctx(listener->sk));
2834 	newsk = inet_csk_accept(listener->sk, flags, err, kern);
2835 	if (!newsk)
2836 		return NULL;
2837 
2838 	pr_debug("msk=%p, subflow is mptcp=%d", msk, sk_is_mptcp(newsk));
2839 	if (sk_is_mptcp(newsk)) {
2840 		struct mptcp_subflow_context *subflow;
2841 		struct sock *new_mptcp_sock;
2842 
2843 		subflow = mptcp_subflow_ctx(newsk);
2844 		new_mptcp_sock = subflow->conn;
2845 
2846 		/* is_mptcp should be false if subflow->conn is missing, see
2847 		 * subflow_syn_recv_sock()
2848 		 */
2849 		if (WARN_ON_ONCE(!new_mptcp_sock)) {
2850 			tcp_sk(newsk)->is_mptcp = 0;
2851 			return newsk;
2852 		}
2853 
2854 		/* acquire the 2nd reference for the owning socket */
2855 		sock_hold(new_mptcp_sock);
2856 		newsk = new_mptcp_sock;
2857 		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPCAPABLEPASSIVEACK);
2858 	} else {
2859 		MPTCP_INC_STATS(sock_net(sk),
2860 				MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK);
2861 	}
2862 
2863 	return newsk;
2864 }
2865 
2866 void mptcp_destroy_common(struct mptcp_sock *msk)
2867 {
2868 	struct sock *sk = (struct sock *)msk;
2869 
2870 	__mptcp_clear_xmit(sk);
2871 
2872 	/* move to sk_receive_queue, sk_stream_kill_queues will purge it */
2873 	skb_queue_splice_tail_init(&msk->receive_queue, &sk->sk_receive_queue);
2874 
2875 	skb_rbtree_purge(&msk->out_of_order_queue);
2876 	mptcp_token_destroy(msk);
2877 	mptcp_pm_free_anno_list(msk);
2878 }
2879 
2880 static void mptcp_destroy(struct sock *sk)
2881 {
2882 	struct mptcp_sock *msk = mptcp_sk(sk);
2883 
2884 	mptcp_destroy_common(msk);
2885 	sk_sockets_allocated_dec(sk);
2886 }
2887 
2888 void __mptcp_data_acked(struct sock *sk)
2889 {
2890 	if (!sock_owned_by_user(sk))
2891 		__mptcp_clean_una(sk);
2892 	else
2893 		set_bit(MPTCP_CLEAN_UNA, &mptcp_sk(sk)->flags);
2894 
2895 	if (mptcp_pending_data_fin_ack(sk))
2896 		mptcp_schedule_work(sk);
2897 }
2898 
2899 void __mptcp_check_push(struct sock *sk, struct sock *ssk)
2900 {
2901 	if (!mptcp_send_head(sk))
2902 		return;
2903 
2904 	if (!sock_owned_by_user(sk)) {
2905 		struct sock *xmit_ssk = mptcp_subflow_get_send(mptcp_sk(sk));
2906 
2907 		if (xmit_ssk == ssk)
2908 			__mptcp_subflow_push_pending(sk, ssk);
2909 		else if (xmit_ssk)
2910 			mptcp_subflow_delegate(mptcp_subflow_ctx(xmit_ssk));
2911 	} else {
2912 		set_bit(MPTCP_PUSH_PENDING, &mptcp_sk(sk)->flags);
2913 	}
2914 }
2915 
2916 /* processes deferred events and flush wmem */
2917 static void mptcp_release_cb(struct sock *sk)
2918 {
2919 	for (;;) {
2920 		unsigned long flags = 0;
2921 
2922 		if (test_and_clear_bit(MPTCP_PUSH_PENDING, &mptcp_sk(sk)->flags))
2923 			flags |= BIT(MPTCP_PUSH_PENDING);
2924 		if (test_and_clear_bit(MPTCP_RETRANSMIT, &mptcp_sk(sk)->flags))
2925 			flags |= BIT(MPTCP_RETRANSMIT);
2926 		if (!flags)
2927 			break;
2928 
2929 		/* the following actions acquire the subflow socket lock
2930 		 *
2931 		 * 1) can't be invoked in atomic scope
2932 		 * 2) must avoid ABBA deadlock with msk socket spinlock: the RX
2933 		 *    datapath acquires the msk socket spinlock while helding
2934 		 *    the subflow socket lock
2935 		 */
2936 
2937 		spin_unlock_bh(&sk->sk_lock.slock);
2938 		if (flags & BIT(MPTCP_PUSH_PENDING))
2939 			__mptcp_push_pending(sk, 0);
2940 		if (flags & BIT(MPTCP_RETRANSMIT))
2941 			__mptcp_retrans(sk);
2942 
2943 		cond_resched();
2944 		spin_lock_bh(&sk->sk_lock.slock);
2945 	}
2946 
2947 	if (test_and_clear_bit(MPTCP_CLEAN_UNA, &mptcp_sk(sk)->flags))
2948 		__mptcp_clean_una_wakeup(sk);
2949 	if (test_and_clear_bit(MPTCP_ERROR_REPORT, &mptcp_sk(sk)->flags))
2950 		__mptcp_error_report(sk);
2951 
2952 	/* push_pending may touch wmem_reserved, ensure we do the cleanup
2953 	 * later
2954 	 */
2955 	__mptcp_update_wmem(sk);
2956 	__mptcp_update_rmem(sk);
2957 }
2958 
2959 void mptcp_subflow_process_delegated(struct sock *ssk)
2960 {
2961 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
2962 	struct sock *sk = subflow->conn;
2963 
2964 	mptcp_data_lock(sk);
2965 	if (!sock_owned_by_user(sk))
2966 		__mptcp_subflow_push_pending(sk, ssk);
2967 	else
2968 		set_bit(MPTCP_PUSH_PENDING, &mptcp_sk(sk)->flags);
2969 	mptcp_data_unlock(sk);
2970 	mptcp_subflow_delegated_done(subflow);
2971 }
2972 
2973 static int mptcp_hash(struct sock *sk)
2974 {
2975 	/* should never be called,
2976 	 * we hash the TCP subflows not the master socket
2977 	 */
2978 	WARN_ON_ONCE(1);
2979 	return 0;
2980 }
2981 
2982 static void mptcp_unhash(struct sock *sk)
2983 {
2984 	/* called from sk_common_release(), but nothing to do here */
2985 }
2986 
2987 static int mptcp_get_port(struct sock *sk, unsigned short snum)
2988 {
2989 	struct mptcp_sock *msk = mptcp_sk(sk);
2990 	struct socket *ssock;
2991 
2992 	ssock = __mptcp_nmpc_socket(msk);
2993 	pr_debug("msk=%p, subflow=%p", msk, ssock);
2994 	if (WARN_ON_ONCE(!ssock))
2995 		return -EINVAL;
2996 
2997 	return inet_csk_get_port(ssock->sk, snum);
2998 }
2999 
3000 void mptcp_finish_connect(struct sock *ssk)
3001 {
3002 	struct mptcp_subflow_context *subflow;
3003 	struct mptcp_sock *msk;
3004 	struct sock *sk;
3005 	u64 ack_seq;
3006 
3007 	subflow = mptcp_subflow_ctx(ssk);
3008 	sk = subflow->conn;
3009 	msk = mptcp_sk(sk);
3010 
3011 	pr_debug("msk=%p, token=%u", sk, subflow->token);
3012 
3013 	mptcp_crypto_key_sha(subflow->remote_key, NULL, &ack_seq);
3014 	ack_seq++;
3015 	subflow->map_seq = ack_seq;
3016 	subflow->map_subflow_seq = 1;
3017 
3018 	/* the socket is not connected yet, no msk/subflow ops can access/race
3019 	 * accessing the field below
3020 	 */
3021 	WRITE_ONCE(msk->remote_key, subflow->remote_key);
3022 	WRITE_ONCE(msk->local_key, subflow->local_key);
3023 	WRITE_ONCE(msk->write_seq, subflow->idsn + 1);
3024 	WRITE_ONCE(msk->snd_nxt, msk->write_seq);
3025 	WRITE_ONCE(msk->ack_seq, ack_seq);
3026 	WRITE_ONCE(msk->rcv_wnd_sent, ack_seq);
3027 	WRITE_ONCE(msk->can_ack, 1);
3028 	WRITE_ONCE(msk->snd_una, msk->write_seq);
3029 
3030 	mptcp_pm_new_connection(msk, ssk, 0);
3031 
3032 	mptcp_rcv_space_init(msk, ssk);
3033 }
3034 
3035 void mptcp_sock_graft(struct sock *sk, struct socket *parent)
3036 {
3037 	write_lock_bh(&sk->sk_callback_lock);
3038 	rcu_assign_pointer(sk->sk_wq, &parent->wq);
3039 	sk_set_socket(sk, parent);
3040 	sk->sk_uid = SOCK_INODE(parent)->i_uid;
3041 	write_unlock_bh(&sk->sk_callback_lock);
3042 }
3043 
3044 bool mptcp_finish_join(struct sock *ssk)
3045 {
3046 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
3047 	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
3048 	struct sock *parent = (void *)msk;
3049 	struct socket *parent_sock;
3050 	bool ret;
3051 
3052 	pr_debug("msk=%p, subflow=%p", msk, subflow);
3053 
3054 	/* mptcp socket already closing? */
3055 	if (!mptcp_is_fully_established(parent)) {
3056 		subflow->reset_reason = MPTCP_RST_EMPTCP;
3057 		return false;
3058 	}
3059 
3060 	if (!msk->pm.server_side)
3061 		goto out;
3062 
3063 	if (!mptcp_pm_allow_new_subflow(msk)) {
3064 		subflow->reset_reason = MPTCP_RST_EPROHIBIT;
3065 		return false;
3066 	}
3067 
3068 	/* active connections are already on conn_list, and we can't acquire
3069 	 * msk lock here.
3070 	 * use the join list lock as synchronization point and double-check
3071 	 * msk status to avoid racing with __mptcp_destroy_sock()
3072 	 */
3073 	spin_lock_bh(&msk->join_list_lock);
3074 	ret = inet_sk_state_load(parent) == TCP_ESTABLISHED;
3075 	if (ret && !WARN_ON_ONCE(!list_empty(&subflow->node))) {
3076 		list_add_tail(&subflow->node, &msk->join_list);
3077 		sock_hold(ssk);
3078 	}
3079 	spin_unlock_bh(&msk->join_list_lock);
3080 	if (!ret) {
3081 		subflow->reset_reason = MPTCP_RST_EPROHIBIT;
3082 		return false;
3083 	}
3084 
3085 	/* attach to msk socket only after we are sure he will deal with us
3086 	 * at close time
3087 	 */
3088 	parent_sock = READ_ONCE(parent->sk_socket);
3089 	if (parent_sock && !ssk->sk_socket)
3090 		mptcp_sock_graft(ssk, parent_sock);
3091 	subflow->map_seq = READ_ONCE(msk->ack_seq);
3092 out:
3093 	mptcp_event(MPTCP_EVENT_SUB_ESTABLISHED, msk, ssk, GFP_ATOMIC);
3094 	return true;
3095 }
3096 
3097 static void mptcp_shutdown(struct sock *sk, int how)
3098 {
3099 	pr_debug("sk=%p, how=%d", sk, how);
3100 
3101 	if ((how & SEND_SHUTDOWN) && mptcp_close_state(sk))
3102 		__mptcp_wr_shutdown(sk);
3103 }
3104 
3105 static struct proto mptcp_prot = {
3106 	.name		= "MPTCP",
3107 	.owner		= THIS_MODULE,
3108 	.init		= mptcp_init_sock,
3109 	.disconnect	= mptcp_disconnect,
3110 	.close		= mptcp_close,
3111 	.accept		= mptcp_accept,
3112 	.setsockopt	= mptcp_setsockopt,
3113 	.getsockopt	= mptcp_getsockopt,
3114 	.shutdown	= mptcp_shutdown,
3115 	.destroy	= mptcp_destroy,
3116 	.sendmsg	= mptcp_sendmsg,
3117 	.recvmsg	= mptcp_recvmsg,
3118 	.release_cb	= mptcp_release_cb,
3119 	.hash		= mptcp_hash,
3120 	.unhash		= mptcp_unhash,
3121 	.get_port	= mptcp_get_port,
3122 	.sockets_allocated	= &mptcp_sockets_allocated,
3123 	.memory_allocated	= &tcp_memory_allocated,
3124 	.memory_pressure	= &tcp_memory_pressure,
3125 	.sysctl_wmem_offset	= offsetof(struct net, ipv4.sysctl_tcp_wmem),
3126 	.sysctl_rmem_offset	= offsetof(struct net, ipv4.sysctl_tcp_rmem),
3127 	.sysctl_mem	= sysctl_tcp_mem,
3128 	.obj_size	= sizeof(struct mptcp_sock),
3129 	.slab_flags	= SLAB_TYPESAFE_BY_RCU,
3130 	.no_autobind	= true,
3131 };
3132 
3133 static int mptcp_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
3134 {
3135 	struct mptcp_sock *msk = mptcp_sk(sock->sk);
3136 	struct socket *ssock;
3137 	int err;
3138 
3139 	lock_sock(sock->sk);
3140 	ssock = __mptcp_nmpc_socket(msk);
3141 	if (!ssock) {
3142 		err = -EINVAL;
3143 		goto unlock;
3144 	}
3145 
3146 	err = ssock->ops->bind(ssock, uaddr, addr_len);
3147 	if (!err)
3148 		mptcp_copy_inaddrs(sock->sk, ssock->sk);
3149 
3150 unlock:
3151 	release_sock(sock->sk);
3152 	return err;
3153 }
3154 
3155 static void mptcp_subflow_early_fallback(struct mptcp_sock *msk,
3156 					 struct mptcp_subflow_context *subflow)
3157 {
3158 	subflow->request_mptcp = 0;
3159 	__mptcp_do_fallback(msk);
3160 }
3161 
3162 static int mptcp_stream_connect(struct socket *sock, struct sockaddr *uaddr,
3163 				int addr_len, int flags)
3164 {
3165 	struct mptcp_sock *msk = mptcp_sk(sock->sk);
3166 	struct mptcp_subflow_context *subflow;
3167 	struct socket *ssock;
3168 	int err;
3169 
3170 	lock_sock(sock->sk);
3171 	if (sock->state != SS_UNCONNECTED && msk->subflow) {
3172 		/* pending connection or invalid state, let existing subflow
3173 		 * cope with that
3174 		 */
3175 		ssock = msk->subflow;
3176 		goto do_connect;
3177 	}
3178 
3179 	ssock = __mptcp_nmpc_socket(msk);
3180 	if (!ssock) {
3181 		err = -EINVAL;
3182 		goto unlock;
3183 	}
3184 
3185 	mptcp_token_destroy(msk);
3186 	inet_sk_state_store(sock->sk, TCP_SYN_SENT);
3187 	subflow = mptcp_subflow_ctx(ssock->sk);
3188 #ifdef CONFIG_TCP_MD5SIG
3189 	/* no MPTCP if MD5SIG is enabled on this socket or we may run out of
3190 	 * TCP option space.
3191 	 */
3192 	if (rcu_access_pointer(tcp_sk(ssock->sk)->md5sig_info))
3193 		mptcp_subflow_early_fallback(msk, subflow);
3194 #endif
3195 	if (subflow->request_mptcp && mptcp_token_new_connect(ssock->sk)) {
3196 		MPTCP_INC_STATS(sock_net(ssock->sk), MPTCP_MIB_TOKENFALLBACKINIT);
3197 		mptcp_subflow_early_fallback(msk, subflow);
3198 	}
3199 	if (likely(!__mptcp_check_fallback(msk)))
3200 		MPTCP_INC_STATS(sock_net(sock->sk), MPTCP_MIB_MPCAPABLEACTIVE);
3201 
3202 do_connect:
3203 	err = ssock->ops->connect(ssock, uaddr, addr_len, flags);
3204 	sock->state = ssock->state;
3205 
3206 	/* on successful connect, the msk state will be moved to established by
3207 	 * subflow_finish_connect()
3208 	 */
3209 	if (!err || err == -EINPROGRESS)
3210 		mptcp_copy_inaddrs(sock->sk, ssock->sk);
3211 	else
3212 		inet_sk_state_store(sock->sk, inet_sk_state_load(ssock->sk));
3213 
3214 unlock:
3215 	release_sock(sock->sk);
3216 	return err;
3217 }
3218 
3219 static int mptcp_listen(struct socket *sock, int backlog)
3220 {
3221 	struct mptcp_sock *msk = mptcp_sk(sock->sk);
3222 	struct socket *ssock;
3223 	int err;
3224 
3225 	pr_debug("msk=%p", msk);
3226 
3227 	lock_sock(sock->sk);
3228 	ssock = __mptcp_nmpc_socket(msk);
3229 	if (!ssock) {
3230 		err = -EINVAL;
3231 		goto unlock;
3232 	}
3233 
3234 	mptcp_token_destroy(msk);
3235 	inet_sk_state_store(sock->sk, TCP_LISTEN);
3236 	sock_set_flag(sock->sk, SOCK_RCU_FREE);
3237 
3238 	err = ssock->ops->listen(ssock, backlog);
3239 	inet_sk_state_store(sock->sk, inet_sk_state_load(ssock->sk));
3240 	if (!err)
3241 		mptcp_copy_inaddrs(sock->sk, ssock->sk);
3242 
3243 unlock:
3244 	release_sock(sock->sk);
3245 	return err;
3246 }
3247 
3248 static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
3249 			       int flags, bool kern)
3250 {
3251 	struct mptcp_sock *msk = mptcp_sk(sock->sk);
3252 	struct socket *ssock;
3253 	int err;
3254 
3255 	pr_debug("msk=%p", msk);
3256 
3257 	lock_sock(sock->sk);
3258 	if (sock->sk->sk_state != TCP_LISTEN)
3259 		goto unlock_fail;
3260 
3261 	ssock = __mptcp_nmpc_socket(msk);
3262 	if (!ssock)
3263 		goto unlock_fail;
3264 
3265 	clear_bit(MPTCP_DATA_READY, &msk->flags);
3266 	sock_hold(ssock->sk);
3267 	release_sock(sock->sk);
3268 
3269 	err = ssock->ops->accept(sock, newsock, flags, kern);
3270 	if (err == 0 && !mptcp_is_tcpsk(newsock->sk)) {
3271 		struct mptcp_sock *msk = mptcp_sk(newsock->sk);
3272 		struct mptcp_subflow_context *subflow;
3273 		struct sock *newsk = newsock->sk;
3274 
3275 		lock_sock(newsk);
3276 
3277 		/* PM/worker can now acquire the first subflow socket
3278 		 * lock without racing with listener queue cleanup,
3279 		 * we can notify it, if needed.
3280 		 *
3281 		 * Even if remote has reset the initial subflow by now
3282 		 * the refcnt is still at least one.
3283 		 */
3284 		subflow = mptcp_subflow_ctx(msk->first);
3285 		list_add(&subflow->node, &msk->conn_list);
3286 		sock_hold(msk->first);
3287 		if (mptcp_is_fully_established(newsk))
3288 			mptcp_pm_fully_established(msk, msk->first, GFP_KERNEL);
3289 
3290 		mptcp_copy_inaddrs(newsk, msk->first);
3291 		mptcp_rcv_space_init(msk, msk->first);
3292 		mptcp_propagate_sndbuf(newsk, msk->first);
3293 
3294 		/* set ssk->sk_socket of accept()ed flows to mptcp socket.
3295 		 * This is needed so NOSPACE flag can be set from tcp stack.
3296 		 */
3297 		mptcp_flush_join_list(msk);
3298 		mptcp_for_each_subflow(msk, subflow) {
3299 			struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
3300 
3301 			if (!ssk->sk_socket)
3302 				mptcp_sock_graft(ssk, newsock);
3303 		}
3304 		release_sock(newsk);
3305 	}
3306 
3307 	if (inet_csk_listen_poll(ssock->sk))
3308 		set_bit(MPTCP_DATA_READY, &msk->flags);
3309 	sock_put(ssock->sk);
3310 	return err;
3311 
3312 unlock_fail:
3313 	release_sock(sock->sk);
3314 	return -EINVAL;
3315 }
3316 
3317 static __poll_t mptcp_check_readable(struct mptcp_sock *msk)
3318 {
3319 	return test_bit(MPTCP_DATA_READY, &msk->flags) ? EPOLLIN | EPOLLRDNORM :
3320 	       0;
3321 }
3322 
3323 static __poll_t mptcp_check_writeable(struct mptcp_sock *msk)
3324 {
3325 	struct sock *sk = (struct sock *)msk;
3326 
3327 	if (unlikely(sk->sk_shutdown & SEND_SHUTDOWN))
3328 		return EPOLLOUT | EPOLLWRNORM;
3329 
3330 	if (sk_stream_is_writeable(sk))
3331 		return EPOLLOUT | EPOLLWRNORM;
3332 
3333 	mptcp_set_nospace(sk);
3334 	smp_mb__after_atomic(); /* msk->flags is changed by write_space cb */
3335 	if (sk_stream_is_writeable(sk))
3336 		return EPOLLOUT | EPOLLWRNORM;
3337 
3338 	return 0;
3339 }
3340 
3341 static __poll_t mptcp_poll(struct file *file, struct socket *sock,
3342 			   struct poll_table_struct *wait)
3343 {
3344 	struct sock *sk = sock->sk;
3345 	struct mptcp_sock *msk;
3346 	__poll_t mask = 0;
3347 	int state;
3348 
3349 	msk = mptcp_sk(sk);
3350 	sock_poll_wait(file, sock, wait);
3351 
3352 	state = inet_sk_state_load(sk);
3353 	pr_debug("msk=%p state=%d flags=%lx", msk, state, msk->flags);
3354 	if (state == TCP_LISTEN)
3355 		return mptcp_check_readable(msk);
3356 
3357 	if (state != TCP_SYN_SENT && state != TCP_SYN_RECV) {
3358 		mask |= mptcp_check_readable(msk);
3359 		mask |= mptcp_check_writeable(msk);
3360 	}
3361 	if (sk->sk_shutdown == SHUTDOWN_MASK || state == TCP_CLOSE)
3362 		mask |= EPOLLHUP;
3363 	if (sk->sk_shutdown & RCV_SHUTDOWN)
3364 		mask |= EPOLLIN | EPOLLRDNORM | EPOLLRDHUP;
3365 
3366 	/* This barrier is coupled with smp_wmb() in tcp_reset() */
3367 	smp_rmb();
3368 	if (sk->sk_err)
3369 		mask |= EPOLLERR;
3370 
3371 	return mask;
3372 }
3373 
3374 static const struct proto_ops mptcp_stream_ops = {
3375 	.family		   = PF_INET,
3376 	.owner		   = THIS_MODULE,
3377 	.release	   = inet_release,
3378 	.bind		   = mptcp_bind,
3379 	.connect	   = mptcp_stream_connect,
3380 	.socketpair	   = sock_no_socketpair,
3381 	.accept		   = mptcp_stream_accept,
3382 	.getname	   = inet_getname,
3383 	.poll		   = mptcp_poll,
3384 	.ioctl		   = inet_ioctl,
3385 	.gettstamp	   = sock_gettstamp,
3386 	.listen		   = mptcp_listen,
3387 	.shutdown	   = inet_shutdown,
3388 	.setsockopt	   = sock_common_setsockopt,
3389 	.getsockopt	   = sock_common_getsockopt,
3390 	.sendmsg	   = inet_sendmsg,
3391 	.recvmsg	   = inet_recvmsg,
3392 	.mmap		   = sock_no_mmap,
3393 	.sendpage	   = inet_sendpage,
3394 };
3395 
3396 static struct inet_protosw mptcp_protosw = {
3397 	.type		= SOCK_STREAM,
3398 	.protocol	= IPPROTO_MPTCP,
3399 	.prot		= &mptcp_prot,
3400 	.ops		= &mptcp_stream_ops,
3401 	.flags		= INET_PROTOSW_ICSK,
3402 };
3403 
3404 static int mptcp_napi_poll(struct napi_struct *napi, int budget)
3405 {
3406 	struct mptcp_delegated_action *delegated;
3407 	struct mptcp_subflow_context *subflow;
3408 	int work_done = 0;
3409 
3410 	delegated = container_of(napi, struct mptcp_delegated_action, napi);
3411 	while ((subflow = mptcp_subflow_delegated_next(delegated)) != NULL) {
3412 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
3413 
3414 		bh_lock_sock_nested(ssk);
3415 		if (!sock_owned_by_user(ssk) &&
3416 		    mptcp_subflow_has_delegated_action(subflow))
3417 			mptcp_subflow_process_delegated(ssk);
3418 		/* ... elsewhere tcp_release_cb_override already processed
3419 		 * the action or will do at next release_sock().
3420 		 * In both case must dequeue the subflow here - on the same
3421 		 * CPU that scheduled it.
3422 		 */
3423 		bh_unlock_sock(ssk);
3424 		sock_put(ssk);
3425 
3426 		if (++work_done == budget)
3427 			return budget;
3428 	}
3429 
3430 	/* always provide a 0 'work_done' argument, so that napi_complete_done
3431 	 * will not try accessing the NULL napi->dev ptr
3432 	 */
3433 	napi_complete_done(napi, 0);
3434 	return work_done;
3435 }
3436 
3437 void __init mptcp_proto_init(void)
3438 {
3439 	struct mptcp_delegated_action *delegated;
3440 	int cpu;
3441 
3442 	mptcp_prot.h.hashinfo = tcp_prot.h.hashinfo;
3443 
3444 	if (percpu_counter_init(&mptcp_sockets_allocated, 0, GFP_KERNEL))
3445 		panic("Failed to allocate MPTCP pcpu counter\n");
3446 
3447 	init_dummy_netdev(&mptcp_napi_dev);
3448 	for_each_possible_cpu(cpu) {
3449 		delegated = per_cpu_ptr(&mptcp_delegated_actions, cpu);
3450 		INIT_LIST_HEAD(&delegated->head);
3451 		netif_tx_napi_add(&mptcp_napi_dev, &delegated->napi, mptcp_napi_poll,
3452 				  NAPI_POLL_WEIGHT);
3453 		napi_enable(&delegated->napi);
3454 	}
3455 
3456 	mptcp_subflow_init();
3457 	mptcp_pm_init();
3458 	mptcp_token_init();
3459 
3460 	if (proto_register(&mptcp_prot, 1) != 0)
3461 		panic("Failed to register MPTCP proto.\n");
3462 
3463 	inet_register_protosw(&mptcp_protosw);
3464 
3465 	BUILD_BUG_ON(sizeof(struct mptcp_skb_cb) > sizeof_field(struct sk_buff, cb));
3466 }
3467 
3468 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
3469 static const struct proto_ops mptcp_v6_stream_ops = {
3470 	.family		   = PF_INET6,
3471 	.owner		   = THIS_MODULE,
3472 	.release	   = inet6_release,
3473 	.bind		   = mptcp_bind,
3474 	.connect	   = mptcp_stream_connect,
3475 	.socketpair	   = sock_no_socketpair,
3476 	.accept		   = mptcp_stream_accept,
3477 	.getname	   = inet6_getname,
3478 	.poll		   = mptcp_poll,
3479 	.ioctl		   = inet6_ioctl,
3480 	.gettstamp	   = sock_gettstamp,
3481 	.listen		   = mptcp_listen,
3482 	.shutdown	   = inet_shutdown,
3483 	.setsockopt	   = sock_common_setsockopt,
3484 	.getsockopt	   = sock_common_getsockopt,
3485 	.sendmsg	   = inet6_sendmsg,
3486 	.recvmsg	   = inet6_recvmsg,
3487 	.mmap		   = sock_no_mmap,
3488 	.sendpage	   = inet_sendpage,
3489 #ifdef CONFIG_COMPAT
3490 	.compat_ioctl	   = inet6_compat_ioctl,
3491 #endif
3492 };
3493 
3494 static struct proto mptcp_v6_prot;
3495 
3496 static void mptcp_v6_destroy(struct sock *sk)
3497 {
3498 	mptcp_destroy(sk);
3499 	inet6_destroy_sock(sk);
3500 }
3501 
3502 static struct inet_protosw mptcp_v6_protosw = {
3503 	.type		= SOCK_STREAM,
3504 	.protocol	= IPPROTO_MPTCP,
3505 	.prot		= &mptcp_v6_prot,
3506 	.ops		= &mptcp_v6_stream_ops,
3507 	.flags		= INET_PROTOSW_ICSK,
3508 };
3509 
3510 int __init mptcp_proto_v6_init(void)
3511 {
3512 	int err;
3513 
3514 	mptcp_v6_prot = mptcp_prot;
3515 	strcpy(mptcp_v6_prot.name, "MPTCPv6");
3516 	mptcp_v6_prot.slab = NULL;
3517 	mptcp_v6_prot.destroy = mptcp_v6_destroy;
3518 	mptcp_v6_prot.obj_size = sizeof(struct mptcp6_sock);
3519 
3520 	err = proto_register(&mptcp_v6_prot, 1);
3521 	if (err)
3522 		return err;
3523 
3524 	err = inet6_register_protosw(&mptcp_v6_protosw);
3525 	if (err)
3526 		proto_unregister(&mptcp_v6_prot);
3527 
3528 	return err;
3529 }
3530 #endif
3531