summaryrefslogtreecommitdiff
path: root/net/mptcp/sockopt.c
blob: a797981895995edae37ba612fdd120ac07d20e01 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
// SPDX-License-Identifier: GPL-2.0
/* Multipath TCP
 *
 * Copyright (c) 2021, Red Hat.
 */

#define pr_fmt(fmt) "MPTCP: " fmt

#include <linux/kernel.h>
#include <linux/module.h>
#include <net/sock.h>
#include <net/protocol.h>
#include <net/tcp.h>
#include <net/mptcp.h>
#include "protocol.h"

static struct sock *__mptcp_tcp_fallback(struct mptcp_sock *msk)
{
	sock_owned_by_me((const struct sock *)msk);

	if (likely(!__mptcp_check_fallback(msk)))
		return NULL;

	return msk->first;
}

static u32 sockopt_seq_reset(const struct sock *sk)
{
	sock_owned_by_me(sk);

	/* Highbits contain state.  Allows to distinguish sockopt_seq
	 * of listener and established:
	 * s0 = new_listener()
	 * sockopt(s0) - seq is 1
	 * s1 = accept(s0) - s1 inherits seq 1 if listener sk (s0)
	 * sockopt(s0) - seq increments to 2 on s0
	 * sockopt(s1) // seq increments to 2 on s1 (different option)
	 * new ssk completes join, inherits options from s0 // seq 2
	 * Needs sync from mptcp join logic, but ssk->seq == msk->seq
	 *
	 * Set High order bits to sk_state so ssk->seq == msk->seq test
	 * will fail.
	 */

	return (u32)sk->sk_state << 24u;
}

static void sockopt_seq_inc(struct mptcp_sock *msk)
{
	u32 seq = (msk->setsockopt_seq + 1) & 0x00ffffff;

	msk->setsockopt_seq = sockopt_seq_reset((struct sock *)msk) + seq;
}

static int mptcp_get_int_option(struct mptcp_sock *msk, sockptr_t optval,
				unsigned int optlen, int *val)
{
	if (optlen < sizeof(int))
		return -EINVAL;

	if (copy_from_sockptr(val, optval, sizeof(*val)))
		return -EFAULT;

	return 0;
}

static void mptcp_sol_socket_sync_intval(struct mptcp_sock *msk, int optname, int val)
{
	struct mptcp_subflow_context *subflow;
	struct sock *sk = (struct sock *)msk;

	lock_sock(sk);
	sockopt_seq_inc(msk);

	mptcp_for_each_subflow(msk, subflow) {
		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
		bool slow = lock_sock_fast(ssk);

		switch (optname) {
		case SO_DEBUG:
			sock_valbool_flag(ssk, SOCK_DBG, !!val);
			break;
		case SO_KEEPALIVE:
			if (ssk->sk_prot->keepalive)
				ssk->sk_prot->keepalive(ssk, !!val);
			sock_valbool_flag(ssk, SOCK_KEEPOPEN, !!val);
			break;
		case SO_PRIORITY:
			ssk->sk_priority = val;
			break;
		case SO_SNDBUF:
		case SO_SNDBUFFORCE:
			ssk->sk_userlocks |= SOCK_SNDBUF_LOCK;
			WRITE_ONCE(ssk->sk_sndbuf, sk->sk_sndbuf);
			break;
		case SO_RCVBUF:
		case SO_RCVBUFFORCE:
			ssk->sk_userlocks |= SOCK_RCVBUF_LOCK;
			WRITE_ONCE(ssk->sk_rcvbuf, sk->sk_rcvbuf);
			break;
		case SO_MARK:
			if (READ_ONCE(ssk->sk_mark) != sk->sk_mark) {
				ssk->sk_mark = sk->sk_mark;
				sk_dst_reset(ssk);
			}
			break;
		case SO_INCOMING_CPU:
			WRITE_ONCE(ssk->sk_incoming_cpu, val);
			break;
		}

		subflow->setsockopt_seq = msk->setsockopt_seq;
		unlock_sock_fast(ssk, slow);
	}

	release_sock(sk);
}

static int mptcp_sol_socket_intval(struct mptcp_sock *msk, int optname, int val)
{
	sockptr_t optval = KERNEL_SOCKPTR(&val);
	struct sock *sk = (struct sock *)msk;
	int ret;

	ret = sock_setsockopt(sk->sk_socket, SOL_SOCKET, optname,
			      optval, sizeof(val));
	if (ret)
		return ret;

	mptcp_sol_socket_sync_intval(msk, optname, val);
	return 0;
}

static void mptcp_so_incoming_cpu(struct mptcp_sock *msk, int val)
{
	struct sock *sk = (struct sock *)msk;

	WRITE_ONCE(sk->sk_incoming_cpu, val);

	mptcp_sol_socket_sync_intval(msk, SO_INCOMING_CPU, val);
}

static int mptcp_setsockopt_sol_socket_int(struct mptcp_sock *msk, int optname,
					   sockptr_t optval, unsigned int optlen)
{
	int val, ret;

	ret = mptcp_get_int_option(msk, optval, optlen, &val);
	if (ret)
		return ret;

	switch (optname) {
	case SO_KEEPALIVE:
		mptcp_sol_socket_sync_intval(msk, optname, val);
		return 0;
	case SO_DEBUG:
	case SO_MARK:
	case SO_PRIORITY:
	case SO_SNDBUF:
	case SO_SNDBUFFORCE:
	case SO_RCVBUF:
	case SO_RCVBUFFORCE:
		return mptcp_sol_socket_intval(msk, optname, val);
	case SO_INCOMING_CPU:
		mptcp_so_incoming_cpu(msk, val);
		return 0;
	}

	return -ENOPROTOOPT;
}

static int mptcp_setsockopt_sol_socket_linger(struct mptcp_sock *msk, sockptr_t optval,
					      unsigned int optlen)
{
	struct mptcp_subflow_context *subflow;
	struct sock *sk = (struct sock *)msk;
	struct linger ling;
	sockptr_t kopt;
	int ret;

	if (optlen < sizeof(ling))
		return -EINVAL;

	if (copy_from_sockptr(&ling, optval, sizeof(ling)))
		return -EFAULT;

	kopt = KERNEL_SOCKPTR(&ling);
	ret = sock_setsockopt(sk->sk_socket, SOL_SOCKET, SO_LINGER, kopt, sizeof(ling));
	if (ret)
		return ret;

	lock_sock(sk);
	sockopt_seq_inc(msk);
	mptcp_for_each_subflow(msk, subflow) {
		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
		bool slow = lock_sock_fast(ssk);

		if (!ling.l_onoff) {
			sock_reset_flag(ssk, SOCK_LINGER);
		} else {
			ssk->sk_lingertime = sk->sk_lingertime;
			sock_set_flag(ssk, SOCK_LINGER);
		}

		subflow->setsockopt_seq = msk->setsockopt_seq;
		unlock_sock_fast(ssk, slow);
	}

	release_sock(sk);
	return 0;
}

static int mptcp_setsockopt_sol_socket(struct mptcp_sock *msk, int optname,
				       sockptr_t optval, unsigned int optlen)
{
	struct sock *sk = (struct sock *)msk;
	struct socket *ssock;
	int ret;

	switch (optname) {
	case SO_REUSEPORT:
	case SO_REUSEADDR:
	case SO_BINDTODEVICE:
	case SO_BINDTOIFINDEX:
		lock_sock(sk);
		ssock = __mptcp_nmpc_socket(msk);
		if (!ssock) {
			release_sock(sk);
			return -EINVAL;
		}

		ret = sock_setsockopt(ssock, SOL_SOCKET, optname, optval, optlen);
		if (ret == 0) {
			if (optname == SO_REUSEPORT)
				sk->sk_reuseport = ssock->sk->sk_reuseport;
			else if (optname == SO_REUSEADDR)
				sk->sk_reuse = ssock->sk->sk_reuse;
			else if (optname == SO_BINDTODEVICE)
				sk->sk_bound_dev_if = ssock->sk->sk_bound_dev_if;
			else if (optname == SO_BINDTOIFINDEX)
				sk->sk_bound_dev_if = ssock->sk->sk_bound_dev_if;
		}
		release_sock(sk);
		return ret;
	case SO_KEEPALIVE:
	case SO_PRIORITY:
	case SO_SNDBUF:
	case SO_SNDBUFFORCE:
	case SO_RCVBUF:
	case SO_RCVBUFFORCE:
	case SO_MARK:
	case SO_INCOMING_CPU:
	case SO_DEBUG:
		return mptcp_setsockopt_sol_socket_int(msk, optname, optval, optlen);
	case SO_LINGER:
		return mptcp_setsockopt_sol_socket_linger(msk, optval, optlen);
	case SO_NO_CHECK:
	case SO_DONTROUTE:
	case SO_BROADCAST:
	case SO_BSDCOMPAT:
	case SO_PASSCRED:
	case SO_PASSSEC:
	case SO_RXQ_OVFL:
	case SO_WIFI_STATUS:
	case SO_NOFCS:
	case SO_SELECT_ERR_QUEUE:
		return 0;
	}

	return sock_setsockopt(sk->sk_socket, SOL_SOCKET, optname, optval, optlen);
}

static int mptcp_setsockopt_v6(struct mptcp_sock *msk, int optname,
			       sockptr_t optval, unsigned int optlen)
{
	struct sock *sk = (struct sock *)msk;
	int ret = -EOPNOTSUPP;
	struct socket *ssock;

	switch (optname) {
	case IPV6_V6ONLY:
		lock_sock(sk);
		ssock = __mptcp_nmpc_socket(msk);
		if (!ssock) {
			release_sock(sk);
			return -EINVAL;
		}

		ret = tcp_setsockopt(ssock->sk, SOL_IPV6, optname, optval, optlen);
		if (ret == 0)
			sk->sk_ipv6only = ssock->sk->sk_ipv6only;

		release_sock(sk);
		break;
	}

	return ret;
}

static bool mptcp_supported_sockopt(int level, int optname)
{
	if (level == SOL_SOCKET) {
		switch (optname) {
		case SO_DEBUG:
		case SO_REUSEPORT:
		case SO_REUSEADDR:

		/* the following ones need a better implementation,
		 * but are quite common we want to preserve them
		 */
		case SO_BINDTODEVICE:
		case SO_SNDBUF:
		case SO_SNDBUFFORCE:
		case SO_RCVBUF:
		case SO_RCVBUFFORCE:
		case SO_KEEPALIVE:
		case SO_PRIORITY:
		case SO_LINGER:
		case SO_TIMESTAMP_OLD:
		case SO_TIMESTAMP_NEW:
		case SO_TIMESTAMPNS_OLD:
		case SO_TIMESTAMPNS_NEW:
		case SO_TIMESTAMPING_OLD:
		case SO_TIMESTAMPING_NEW:
		case SO_RCVLOWAT:
		case SO_RCVTIMEO_OLD:
		case SO_RCVTIMEO_NEW:
		case SO_SNDTIMEO_OLD:
		case SO_SNDTIMEO_NEW:
		case SO_MARK:
		case SO_INCOMING_CPU:
		case SO_BINDTOIFINDEX:
		case SO_BUSY_POLL:
		case SO_PREFER_BUSY_POLL:
		case SO_BUSY_POLL_BUDGET:

		/* next ones are no-op for plain TCP */
		case SO_NO_CHECK:
		case SO_DONTROUTE:
		case SO_BROADCAST:
		case SO_BSDCOMPAT:
		case SO_PASSCRED:
		case SO_PASSSEC:
		case SO_RXQ_OVFL:
		case SO_WIFI_STATUS:
		case SO_NOFCS:
		case SO_SELECT_ERR_QUEUE:
			return true;
		}

		/* SO_OOBINLINE is not supported, let's avoid the related mess */
		/* SO_ATTACH_FILTER, SO_ATTACH_BPF, SO_ATTACH_REUSEPORT_CBPF,
		 * SO_DETACH_REUSEPORT_BPF, SO_DETACH_FILTER, SO_LOCK_FILTER,
		 * we must be careful with subflows
		 */
		/* SO_ATTACH_REUSEPORT_EBPF is not supported, at it checks
		 * explicitly the sk_protocol field
		 */
		/* SO_PEEK_OFF is unsupported, as it is for plain TCP */
		/* SO_MAX_PACING_RATE is unsupported, we must be careful with subflows */
		/* SO_CNX_ADVICE is currently unsupported, could possibly be relevant,
		 * but likely needs careful design
		 */
		/* SO_ZEROCOPY is currently unsupported, TODO in sndmsg */
		/* SO_TXTIME is currently unsupported */
		return false;
	}
	if (level == SOL_IP) {
		switch (optname) {
		/* should work fine */
		case IP_FREEBIND:
		case IP_TRANSPARENT:

		/* the following are control cmsg related */
		case IP_PKTINFO:
		case IP_RECVTTL:
		case IP_RECVTOS:
		case IP_RECVOPTS:
		case IP_RETOPTS:
		case IP_PASSSEC:
		case IP_RECVORIGDSTADDR:
		case IP_CHECKSUM:
		case IP_RECVFRAGSIZE:

		/* common stuff that need some love */
		case IP_TOS:
		case IP_TTL:
		case IP_BIND_ADDRESS_NO_PORT:
		case IP_MTU_DISCOVER:
		case IP_RECVERR:

		/* possibly less common may deserve some love */
		case IP_MINTTL:

		/* the following is apparently a no-op for plain TCP */
		case IP_RECVERR_RFC4884:
			return true;
		}

		/* IP_OPTIONS is not supported, needs subflow care */
		/* IP_HDRINCL, IP_NODEFRAG are not supported, RAW specific */
		/* IP_MULTICAST_TTL, IP_MULTICAST_LOOP, IP_UNICAST_IF,
		 * IP_ADD_MEMBERSHIP, IP_ADD_SOURCE_MEMBERSHIP, IP_DROP_MEMBERSHIP,
		 * IP_DROP_SOURCE_MEMBERSHIP, IP_BLOCK_SOURCE, IP_UNBLOCK_SOURCE,
		 * MCAST_JOIN_GROUP, MCAST_LEAVE_GROUP MCAST_JOIN_SOURCE_GROUP,
		 * MCAST_LEAVE_SOURCE_GROUP, MCAST_BLOCK_SOURCE, MCAST_UNBLOCK_SOURCE,
		 * MCAST_MSFILTER, IP_MULTICAST_ALL are not supported, better not deal
		 * with mcast stuff
		 */
		/* IP_IPSEC_POLICY, IP_XFRM_POLICY are nut supported, unrelated here */
		return false;
	}
	if (level == SOL_IPV6) {
		switch (optname) {
		case IPV6_V6ONLY:

		/* the following are control cmsg related */
		case IPV6_RECVPKTINFO:
		case IPV6_2292PKTINFO:
		case IPV6_RECVHOPLIMIT:
		case IPV6_2292HOPLIMIT:
		case IPV6_RECVRTHDR:
		case IPV6_2292RTHDR:
		case IPV6_RECVHOPOPTS:
		case IPV6_2292HOPOPTS:
		case IPV6_RECVDSTOPTS:
		case IPV6_2292DSTOPTS:
		case IPV6_RECVTCLASS:
		case IPV6_FLOWINFO:
		case IPV6_RECVPATHMTU:
		case IPV6_RECVORIGDSTADDR:
		case IPV6_RECVFRAGSIZE:

		/* the following ones need some love but are quite common */
		case IPV6_TCLASS:
		case IPV6_TRANSPARENT:
		case IPV6_FREEBIND:
		case IPV6_PKTINFO:
		case IPV6_2292PKTOPTIONS:
		case IPV6_UNICAST_HOPS:
		case IPV6_MTU_DISCOVER:
		case IPV6_MTU:
		case IPV6_RECVERR:
		case IPV6_FLOWINFO_SEND:
		case IPV6_FLOWLABEL_MGR:
		case IPV6_MINHOPCOUNT:
		case IPV6_DONTFRAG:
		case IPV6_AUTOFLOWLABEL:

		/* the following one is a no-op for plain TCP */
		case IPV6_RECVERR_RFC4884:
			return true;
		}

		/* IPV6_HOPOPTS, IPV6_RTHDRDSTOPTS, IPV6_RTHDR, IPV6_DSTOPTS are
		 * not supported
		 */
		/* IPV6_MULTICAST_HOPS, IPV6_MULTICAST_LOOP, IPV6_UNICAST_IF,
		 * IPV6_MULTICAST_IF, IPV6_ADDRFORM,
		 * IPV6_ADD_MEMBERSHIP, IPV6_DROP_MEMBERSHIP, IPV6_JOIN_ANYCAST,
		 * IPV6_LEAVE_ANYCAST, IPV6_MULTICAST_ALL, MCAST_JOIN_GROUP, MCAST_LEAVE_GROUP,
		 * MCAST_JOIN_SOURCE_GROUP, MCAST_LEAVE_SOURCE_GROUP,
		 * MCAST_BLOCK_SOURCE, MCAST_UNBLOCK_SOURCE, MCAST_MSFILTER
		 * are not supported better not deal with mcast
		 */
		/* IPV6_ROUTER_ALERT, IPV6_ROUTER_ALERT_ISOLATE are not supported, since are evil */

		/* IPV6_IPSEC_POLICY, IPV6_XFRM_POLICY are not supported */
		/* IPV6_ADDR_PREFERENCES is not supported, we must be careful with subflows */
		return false;
	}
	if (level == SOL_TCP) {
		switch (optname) {
		/* the following are no-op or should work just fine */
		case TCP_THIN_DUPACK:
		case TCP_DEFER_ACCEPT:

		/* the following need some love */
		case TCP_MAXSEG:
		case TCP_NODELAY:
		case TCP_THIN_LINEAR_TIMEOUTS:
		case TCP_CONGESTION:
		case TCP_ULP:
		case TCP_CORK:
		case TCP_KEEPIDLE:
		case TCP_KEEPINTVL:
		case TCP_KEEPCNT:
		case TCP_SYNCNT:
		case TCP_SAVE_SYN:
		case TCP_LINGER2:
		case TCP_WINDOW_CLAMP:
		case TCP_QUICKACK:
		case TCP_USER_TIMEOUT:
		case TCP_TIMESTAMP:
		case TCP_NOTSENT_LOWAT:
		case TCP_TX_DELAY:
			return true;
		}

		/* TCP_MD5SIG, TCP_MD5SIG_EXT are not supported, MD5 is not compatible with MPTCP */

		/* TCP_REPAIR, TCP_REPAIR_QUEUE, TCP_QUEUE_SEQ, TCP_REPAIR_OPTIONS,
		 * TCP_REPAIR_WINDOW are not supported, better avoid this mess
		 */
		/* TCP_FASTOPEN_KEY, TCP_FASTOPEN TCP_FASTOPEN_CONNECT, TCP_FASTOPEN_NO_COOKIE,
		 * are not supported fastopen is currently unsupported
		 */
		/* TCP_INQ is currently unsupported, needs some recvmsg work */
	}
	return false;
}

static int mptcp_setsockopt_sol_tcp_congestion(struct mptcp_sock *msk, sockptr_t optval,
					       unsigned int optlen)
{
	struct mptcp_subflow_context *subflow;
	struct sock *sk = (struct sock *)msk;
	char name[TCP_CA_NAME_MAX];
	bool cap_net_admin;
	int ret;

	if (optlen < 1)
		return -EINVAL;

	ret = strncpy_from_sockptr(name, optval,
				   min_t(long, TCP_CA_NAME_MAX - 1, optlen));
	if (ret < 0)
		return -EFAULT;

	name[ret] = 0;

	cap_net_admin = ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN);

	ret = 0;
	lock_sock(sk);
	sockopt_seq_inc(msk);
	mptcp_for_each_subflow(msk, subflow) {
		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
		int err;

		lock_sock(ssk);
		err = tcp_set_congestion_control(ssk, name, true, cap_net_admin);
		if (err < 0 && ret == 0)
			ret = err;
		subflow->setsockopt_seq = msk->setsockopt_seq;
		release_sock(ssk);
	}

	if (ret == 0)
		strcpy(msk->ca_name, name);

	release_sock(sk);
	return ret;
}

static int mptcp_setsockopt_sol_tcp(struct mptcp_sock *msk, int optname,
				    sockptr_t optval, unsigned int optlen)
{
	switch (optname) {
	case TCP_ULP:
		return -EOPNOTSUPP;
	case TCP_CONGESTION:
		return mptcp_setsockopt_sol_tcp_congestion(msk, optval, optlen);
	}

	return -EOPNOTSUPP;
}

int mptcp_setsockopt(struct sock *sk, int level, int optname,
		     sockptr_t optval, unsigned int optlen)
{
	struct mptcp_sock *msk = mptcp_sk(sk);
	struct sock *ssk;

	pr_debug("msk=%p", msk);

	if (!mptcp_supported_sockopt(level, optname))
		return -ENOPROTOOPT;

	if (level == SOL_SOCKET)
		return mptcp_setsockopt_sol_socket(msk, optname, optval, optlen);

	/* @@ the meaning of setsockopt() when the socket is connected and
	 * there are multiple subflows is not yet defined. It is up to the
	 * MPTCP-level socket to configure the subflows until the subflow
	 * is in TCP fallback, when TCP socket options are passed through
	 * to the one remaining subflow.
	 */
	lock_sock(sk);
	ssk = __mptcp_tcp_fallback(msk);
	release_sock(sk);
	if (ssk)
		return tcp_setsockopt(ssk, level, optname, optval, optlen);

	if (level == SOL_IPV6)
		return mptcp_setsockopt_v6(msk, optname, optval, optlen);

	if (level == SOL_TCP)
		return mptcp_setsockopt_sol_tcp(msk, optname, optval, optlen);

	return -EOPNOTSUPP;
}

static int mptcp_getsockopt_first_sf_only(struct mptcp_sock *msk, int level, int optname,
					  char __user *optval, int __user *optlen)
{
	struct sock *sk = (struct sock *)msk;
	struct socket *ssock;
	int ret = -EINVAL;
	struct sock *ssk;

	lock_sock(sk);
	ssk = msk->first;
	if (ssk) {
		ret = tcp_getsockopt(ssk, level, optname, optval, optlen);
		goto out;
	}

	ssock = __mptcp_nmpc_socket(msk);
	if (!ssock)
		goto out;

	ret = tcp_getsockopt(ssock->sk, level, optname, optval, optlen);

out:
	release_sock(sk);
	return ret;
}

static int mptcp_getsockopt_sol_tcp(struct mptcp_sock *msk, int optname,
				    char __user *optval, int __user *optlen)
{
	switch (optname) {
	case TCP_ULP:
	case TCP_CONGESTION:
	case TCP_INFO:
	case TCP_CC_INFO:
		return mptcp_getsockopt_first_sf_only(msk, SOL_TCP, optname,
						      optval, optlen);
	}
	return -EOPNOTSUPP;
}

int mptcp_getsockopt(struct sock *sk, int level, int optname,
		     char __user *optval, int __user *option)
{
	struct mptcp_sock *msk = mptcp_sk(sk);
	struct sock *ssk;

	pr_debug("msk=%p", msk);

	/* @@ the meaning of setsockopt() when the socket is connected and
	 * there are multiple subflows is not yet defined. It is up to the
	 * MPTCP-level socket to configure the subflows until the subflow
	 * is in TCP fallback, when socket options are passed through
	 * to the one remaining subflow.
	 */
	lock_sock(sk);
	ssk = __mptcp_tcp_fallback(msk);
	release_sock(sk);
	if (ssk)
		return tcp_getsockopt(ssk, level, optname, optval, option);

	if (level == SOL_TCP)
		return mptcp_getsockopt_sol_tcp(msk, optname, optval, option);
	return -EOPNOTSUPP;
}

static void sync_socket_options(struct mptcp_sock *msk, struct sock *ssk)
{
	static const unsigned int tx_rx_locks = SOCK_RCVBUF_LOCK | SOCK_SNDBUF_LOCK;
	struct sock *sk = (struct sock *)msk;

	if (ssk->sk_prot->keepalive) {
		if (sock_flag(sk, SOCK_KEEPOPEN))
			ssk->sk_prot->keepalive(ssk, 1);
		else
			ssk->sk_prot->keepalive(ssk, 0);
	}

	ssk->sk_priority = sk->sk_priority;
	ssk->sk_bound_dev_if = sk->sk_bound_dev_if;
	ssk->sk_incoming_cpu = sk->sk_incoming_cpu;

	if (sk->sk_userlocks & tx_rx_locks) {
		ssk->sk_userlocks |= sk->sk_userlocks & tx_rx_locks;
		if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
			WRITE_ONCE(ssk->sk_sndbuf, sk->sk_sndbuf);
		if (sk->sk_userlocks & SOCK_RCVBUF_LOCK)
			WRITE_ONCE(ssk->sk_rcvbuf, sk->sk_rcvbuf);
	}

	if (sock_flag(sk, SOCK_LINGER)) {
		ssk->sk_lingertime = sk->sk_lingertime;
		sock_set_flag(ssk, SOCK_LINGER);
	} else {
		sock_reset_flag(ssk, SOCK_LINGER);
	}

	if (sk->sk_mark != ssk->sk_mark) {
		ssk->sk_mark = sk->sk_mark;
		sk_dst_reset(ssk);
	}

	sock_valbool_flag(ssk, SOCK_DBG, sock_flag(sk, SOCK_DBG));

	if (inet_csk(sk)->icsk_ca_ops != inet_csk(ssk)->icsk_ca_ops)
		tcp_set_congestion_control(ssk, msk->ca_name, false, true);
}

static void __mptcp_sockopt_sync(struct mptcp_sock *msk, struct sock *ssk)
{
	bool slow = lock_sock_fast(ssk);

	sync_socket_options(msk, ssk);

	unlock_sock_fast(ssk, slow);
}

void mptcp_sockopt_sync(struct mptcp_sock *msk, struct sock *ssk)
{
	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);

	msk_owned_by_me(msk);

	if (READ_ONCE(subflow->setsockopt_seq) != msk->setsockopt_seq) {
		__mptcp_sockopt_sync(msk, ssk);

		subflow->setsockopt_seq = msk->setsockopt_seq;
	}
}

void mptcp_sockopt_sync_all(struct mptcp_sock *msk)
{
	struct mptcp_subflow_context *subflow;
	struct sock *sk = (struct sock *)msk;
	u32 seq;

	seq = sockopt_seq_reset(sk);

	mptcp_for_each_subflow(msk, subflow) {
		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
		u32 sseq = READ_ONCE(subflow->setsockopt_seq);

		if (sseq != msk->setsockopt_seq) {
			__mptcp_sockopt_sync(msk, ssk);
			WRITE_ONCE(subflow->setsockopt_seq, seq);
		} else if (sseq != seq) {
			WRITE_ONCE(subflow->setsockopt_seq, seq);
		}

		cond_resched();
	}

	msk->setsockopt_seq = seq;
}