aboutsummaryrefslogtreecommitdiffstatshomepage
path: root/net/mptcp/protocol.c
blob: b22a63ba2348ae60e7f509ee7772faf19969660e (plain) (blame)
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
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
// SPDX-License-Identifier: GPL-2.0
/* Multipath TCP
 *
 * Copyright (c) 2017 - 2019, Intel Corporation.
 */

#define pr_fmt(fmt) "MPTCP: " fmt

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/sched/signal.h>
#include <linux/atomic.h>
#include <net/sock.h>
#include <net/inet_common.h>
#include <net/inet_hashtables.h>
#include <net/protocol.h>
#include <net/tcp.h>
#if IS_ENABLED(CONFIG_MPTCP_IPV6)
#include <net/transp_v6.h>
#endif
#include <net/mptcp.h>
#include "protocol.h"
#include "mib.h"

#define MPTCP_SAME_STATE TCP_MAX_STATES

#if IS_ENABLED(CONFIG_MPTCP_IPV6)
struct mptcp6_sock {
	struct mptcp_sock msk;
	struct ipv6_pinfo np;
};
#endif

struct mptcp_skb_cb {
	u32 offset;
};

#define MPTCP_SKB_CB(__skb)	((struct mptcp_skb_cb *)&((__skb)->cb[0]))

static struct percpu_counter mptcp_sockets_allocated;

/* If msk has an initial subflow socket, and the MP_CAPABLE handshake has not
 * completed yet or has failed, return the subflow socket.
 * Otherwise return NULL.
 */
static struct socket *__mptcp_nmpc_socket(const struct mptcp_sock *msk)
{
	if (!msk->subflow || READ_ONCE(msk->can_ack))
		return NULL;

	return msk->subflow;
}

static bool __mptcp_needs_tcp_fallback(const struct mptcp_sock *msk)
{
	return msk->first && !sk_is_mptcp(msk->first);
}

static struct socket *mptcp_is_tcpsk(struct sock *sk)
{
	struct socket *sock = sk->sk_socket;

	if (sock->sk != sk)
		return NULL;

	if (unlikely(sk->sk_prot == &tcp_prot)) {
		/* we are being invoked after mptcp_accept() has
		 * accepted a non-mp-capable flow: sk is a tcp_sk,
		 * not an mptcp one.
		 *
		 * Hand the socket over to tcp so all further socket ops
		 * bypass mptcp.
		 */
		sock->ops = &inet_stream_ops;
		return sock;
#if IS_ENABLED(CONFIG_MPTCP_IPV6)
	} else if (unlikely(sk->sk_prot == &tcpv6_prot)) {
		sock->ops = &inet6_stream_ops;
		return sock;
#endif
	}

	return NULL;
}

static struct socket *__mptcp_tcp_fallback(struct mptcp_sock *msk)
{
	struct socket *sock;

	sock_owned_by_me((const struct sock *)msk);

	sock = mptcp_is_tcpsk((struct sock *)msk);
	if (unlikely(sock))
		return sock;

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

	return msk->subflow;
}

static bool __mptcp_can_create_subflow(const struct mptcp_sock *msk)
{
	return !msk->first;
}

static struct socket *__mptcp_socket_create(struct mptcp_sock *msk, int state)
{
	struct mptcp_subflow_context *subflow;
	struct sock *sk = (struct sock *)msk;
	struct socket *ssock;
	int err;

	ssock = __mptcp_tcp_fallback(msk);
	if (unlikely(ssock))
		return ssock;

	ssock = __mptcp_nmpc_socket(msk);
	if (ssock)
		goto set_state;

	if (!__mptcp_can_create_subflow(msk))
		return ERR_PTR(-EINVAL);

	err = mptcp_subflow_create_socket(sk, &ssock);
	if (err)
		return ERR_PTR(err);

	msk->first = ssock->sk;
	msk->subflow = ssock;
	subflow = mptcp_subflow_ctx(ssock->sk);
	list_add(&subflow->node, &msk->conn_list);
	subflow->request_mptcp = 1;

set_state:
	if (state != MPTCP_SAME_STATE)
		inet_sk_state_store(sk, state);
	return ssock;
}

static void __mptcp_move_skb(struct mptcp_sock *msk, struct sock *ssk,
			     struct sk_buff *skb,
			     unsigned int offset, size_t copy_len)
{
	struct sock *sk = (struct sock *)msk;

	__skb_unlink(skb, &ssk->sk_receive_queue);
	skb_set_owner_r(skb, sk);
	__skb_queue_tail(&sk->sk_receive_queue, skb);

	msk->ack_seq += copy_len;
	MPTCP_SKB_CB(skb)->offset = offset;
}

/* both sockets must be locked */
static bool mptcp_subflow_dsn_valid(const struct mptcp_sock *msk,
				    struct sock *ssk)
{
	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
	u64 dsn = mptcp_subflow_get_mapped_dsn(subflow);

	/* revalidate data sequence number.
	 *
	 * mptcp_subflow_data_available() is usually called
	 * without msk lock.  Its unlikely (but possible)
	 * that msk->ack_seq has been advanced since the last
	 * call found in-sequence data.
	 */
	if (likely(dsn == msk->ack_seq))
		return true;

	subflow->data_avail = 0;
	return mptcp_subflow_data_available(ssk);
}

static bool __mptcp_move_skbs_from_subflow(struct mptcp_sock *msk,
					   struct sock *ssk,
					   unsigned int *bytes)
{
	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
	struct sock *sk = (struct sock *)msk;
	unsigned int moved = 0;
	bool more_data_avail;
	struct tcp_sock *tp;
	bool done = false;

	if (!mptcp_subflow_dsn_valid(msk, ssk)) {
		*bytes = 0;
		return false;
	}

	if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
		int rcvbuf = max(ssk->sk_rcvbuf, sk->sk_rcvbuf);

		if (rcvbuf > sk->sk_rcvbuf)
			sk->sk_rcvbuf = rcvbuf;
	}

	tp = tcp_sk(ssk);
	do {
		u32 map_remaining, offset;
		u32 seq = tp->copied_seq;
		struct sk_buff *skb;
		bool fin;

		/* try to move as much data as available */
		map_remaining = subflow->map_data_len -
				mptcp_subflow_get_map_offset(subflow);

		skb = skb_peek(&ssk->sk_receive_queue);
		if (!skb)
			break;

		offset = seq - TCP_SKB_CB(skb)->seq;
		fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN;
		if (fin) {
			done = true;
			seq++;
		}

		if (offset < skb->len) {
			size_t len = skb->len - offset;

			if (tp->urg_data)
				done = true;

			__mptcp_move_skb(msk, ssk, skb, offset, len);
			seq += len;
			moved += len;

			if (WARN_ON_ONCE(map_remaining < len))
				break;
		} else {
			WARN_ON_ONCE(!fin);
			sk_eat_skb(ssk, skb);
			done = true;
		}

		WRITE_ONCE(tp->copied_seq, seq);
		more_data_avail = mptcp_subflow_data_available(ssk);

		if (atomic_read(&sk->sk_rmem_alloc) > READ_ONCE(sk->sk_rcvbuf)) {
			done = true;
			break;
		}
	} while (more_data_avail);

	*bytes = moved;

	return done;
}

/* In most cases we will be able to lock the mptcp socket.  If its already
 * owned, we need to defer to the work queue to avoid ABBA deadlock.
 */
static bool move_skbs_to_msk(struct mptcp_sock *msk, struct sock *ssk)
{
	struct sock *sk = (struct sock *)msk;
	unsigned int moved = 0;

	if (READ_ONCE(sk->sk_lock.owned))
		return false;

	if (unlikely(!spin_trylock_bh(&sk->sk_lock.slock)))
		return false;

	/* must re-check after taking the lock */
	if (!READ_ONCE(sk->sk_lock.owned))
		__mptcp_move_skbs_from_subflow(msk, ssk, &moved);

	spin_unlock_bh(&sk->sk_lock.slock);

	return moved > 0;
}

void mptcp_data_ready(struct sock *sk, struct sock *ssk)
{
	struct mptcp_sock *msk = mptcp_sk(sk);

	set_bit(MPTCP_DATA_READY, &msk->flags);

	if (atomic_read(&sk->sk_rmem_alloc) < READ_ONCE(sk->sk_rcvbuf) &&
	    move_skbs_to_msk(msk, ssk))
		goto wake;

	/* don't schedule if mptcp sk is (still) over limit */
	if (atomic_read(&sk->sk_rmem_alloc) > READ_ONCE(sk->sk_rcvbuf))
		goto wake;

	/* mptcp socket is owned, release_cb should retry */
	if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED,
			      &sk->sk_tsq_flags)) {
		sock_hold(sk);

		/* need to try again, its possible release_cb() has already
		 * been called after the test_and_set_bit() above.
		 */
		move_skbs_to_msk(msk, ssk);
	}
wake:
	sk->sk_data_ready(sk);
}

static void __mptcp_flush_join_list(struct mptcp_sock *msk)
{
	if (likely(list_empty(&msk->join_list)))
		return;

	spin_lock_bh(&msk->join_list_lock);
	list_splice_tail_init(&msk->join_list, &msk->conn_list);
	spin_unlock_bh(&msk->join_list_lock);
}

static void mptcp_set_timeout(const struct sock *sk, const struct sock *ssk)
{
	long tout = ssk && inet_csk(ssk)->icsk_pending ?
				      inet_csk(ssk)->icsk_timeout - jiffies : 0;

	if (tout <= 0)
		tout = mptcp_sk(sk)->timer_ival;
	mptcp_sk(sk)->timer_ival = tout > 0 ? tout : TCP_RTO_MIN;
}

static bool mptcp_timer_pending(struct sock *sk)
{
	return timer_pending(&inet_csk(sk)->icsk_retransmit_timer);
}

static void mptcp_reset_timer(struct sock *sk)
{
	struct inet_connection_sock *icsk = inet_csk(sk);
	unsigned long tout;

	/* should never be called with mptcp level timer cleared */
	tout = READ_ONCE(mptcp_sk(sk)->timer_ival);
	if (WARN_ON_ONCE(!tout))
		tout = TCP_RTO_MIN;
	sk_reset_timer(sk, &icsk->icsk_retransmit_timer, jiffies + tout);
}

void mptcp_data_acked(struct sock *sk)
{
	mptcp_reset_timer(sk);

	if (!sk_stream_is_writeable(sk) &&
	    schedule_work(&mptcp_sk(sk)->work))
		sock_hold(sk);
}

void mptcp_subflow_eof(struct sock *sk)
{
	struct mptcp_sock *msk = mptcp_sk(sk);

	if (!test_and_set_bit(MPTCP_WORK_EOF, &msk->flags) &&
	    schedule_work(&msk->work))
		sock_hold(sk);
}

static void mptcp_stop_timer(struct sock *sk)
{
	struct inet_connection_sock *icsk = inet_csk(sk);

	sk_stop_timer(sk, &icsk->icsk_retransmit_timer);
	mptcp_sk(sk)->timer_ival = 0;
}

static bool mptcp_ext_cache_refill(struct mptcp_sock *msk)
{
	if (!msk->cached_ext)
		msk->cached_ext = __skb_ext_alloc();

	return !!msk->cached_ext;
}

static struct sock *mptcp_subflow_recv_lookup(const struct mptcp_sock *msk)
{
	struct mptcp_subflow_context *subflow;
	struct sock *sk = (struct sock *)msk;

	sock_owned_by_me(sk);

	mptcp_for_each_subflow(msk, subflow) {
		if (subflow->data_avail)
			return mptcp_subflow_tcp_sock(subflow);
	}

	return NULL;
}

static bool mptcp_skb_can_collapse_to(u64 write_seq,
				      const struct sk_buff *skb,
				      const struct mptcp_ext *mpext)
{
	if (!tcp_skb_can_collapse_to(skb))
		return false;

	/* can collapse only if MPTCP level sequence is in order */
	return mpext && mpext->data_seq + mpext->data_len == write_seq;
}

static bool mptcp_frag_can_collapse_to(const struct mptcp_sock *msk,
				       const struct page_frag *pfrag,
				       const struct mptcp_data_frag *df)
{
	return df && pfrag->page == df->page &&
		df->data_seq + df->data_len == msk->write_seq;
}

static void dfrag_uncharge(struct sock *sk, int len)
{
	sk_mem_uncharge(sk, len);
	sk_wmem_queued_add(sk, -len);
}

static void dfrag_clear(struct sock *sk, struct mptcp_data_frag *dfrag)
{
	int len = dfrag->data_len + dfrag->overhead;

	list_del(&dfrag->list);
	dfrag_uncharge(sk, len);
	put_page(dfrag->page);
}

static void mptcp_clean_una(struct sock *sk)
{
	struct mptcp_sock *msk = mptcp_sk(sk);
	struct mptcp_data_frag *dtmp, *dfrag;
	u64 snd_una = atomic64_read(&msk->snd_una);
	bool cleaned = false;

	list_for_each_entry_safe(dfrag, dtmp, &msk->rtx_queue, list) {
		if (after64(dfrag->data_seq + dfrag->data_len, snd_una))
			break;

		dfrag_clear(sk, dfrag);
		cleaned = true;
	}

	dfrag = mptcp_rtx_head(sk);
	if (dfrag && after64(snd_una, dfrag->data_seq)) {
		u64 delta = dfrag->data_seq + dfrag->data_len - snd_una;

		dfrag->data_seq += delta;
		dfrag->data_len -= delta;

		dfrag_uncharge(sk, delta);
		cleaned = true;
	}

	if (cleaned) {
		sk_mem_reclaim_partial(sk);

		/* Only wake up writers if a subflow is ready */
		if (test_bit(MPTCP_SEND_SPACE, &msk->flags))
			sk_stream_write_space(sk);
	}
}

/* ensure we get enough memory for the frag hdr, beyond some minimal amount of
 * data
 */
static bool mptcp_page_frag_refill(struct sock *sk, struct page_frag *pfrag)
{
	if (likely(skb_page_frag_refill(32U + sizeof(struct mptcp_data_frag),
					pfrag, sk->sk_allocation)))
		return true;

	sk->sk_prot->enter_memory_pressure(sk);
	sk_stream_moderate_sndbuf(sk);
	return false;
}

static struct mptcp_data_frag *
mptcp_carve_data_frag(const struct mptcp_sock *msk, struct page_frag *pfrag,
		      int orig_offset)
{
	int offset = ALIGN(orig_offset, sizeof(long));
	struct mptcp_data_frag *dfrag;

	dfrag = (struct mptcp_data_frag *)(page_to_virt(pfrag->page) + offset);
	dfrag->data_len = 0;
	dfrag->data_seq = msk->write_seq;
	dfrag->overhead = offset - orig_offset + sizeof(struct mptcp_data_frag);
	dfrag->offset = offset + sizeof(struct mptcp_data_frag);
	dfrag->page = pfrag->page;

	return dfrag;
}

static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
			      struct msghdr *msg, struct mptcp_data_frag *dfrag,
			      long *timeo, int *pmss_now,
			      int *ps_goal)
{
	int mss_now, avail_size, size_goal, offset, ret, frag_truesize = 0;
	bool dfrag_collapsed, can_collapse = false;
	struct mptcp_sock *msk = mptcp_sk(sk);
	struct mptcp_ext *mpext = NULL;
	bool retransmission = !!dfrag;
	struct sk_buff *skb, *tail;
	struct page_frag *pfrag;
	struct page *page;
	u64 *write_seq;
	size_t psize;

	/* use the mptcp page cache so that we can easily move the data
	 * from one substream to another, but do per subflow memory accounting
	 * Note: pfrag is used only !retransmission, but the compiler if
	 * fooled into a warning if we don't init here
	 */
	pfrag = sk_page_frag(sk);
	while ((!retransmission && !mptcp_page_frag_refill(ssk, pfrag)) ||
	       !mptcp_ext_cache_refill(msk)) {
		ret = sk_stream_wait_memory(ssk, timeo);
		if (ret)
			return ret;

		/* if sk_stream_wait_memory() sleeps snd_una can change
		 * significantly, refresh the rtx queue
		 */
		mptcp_clean_una(sk);

		if (unlikely(__mptcp_needs_tcp_fallback(msk)))
			return 0;
	}
	if (!retransmission) {
		write_seq = &msk->write_seq;
		page = pfrag->page;
	} else {
		write_seq = &dfrag->data_seq;
		page = dfrag->page;
	}

	/* compute copy limit */
	mss_now = tcp_send_mss(ssk, &size_goal, msg->msg_flags);
	*pmss_now = mss_now;
	*ps_goal = size_goal;
	avail_size = size_goal;
	skb = tcp_write_queue_tail(ssk);
	if (skb) {
		mpext = skb_ext_find(skb, SKB_EXT_MPTCP);

		/* Limit the write to the size available in the
		 * current skb, if any, so that we create at most a new skb.
		 * Explicitly tells TCP internals to avoid collapsing on later
		 * queue management operation, to avoid breaking the ext <->
		 * SSN association set here
		 */
		can_collapse = (size_goal - skb->len > 0) &&
			      mptcp_skb_can_collapse_to(*write_seq, skb, mpext);
		if (!can_collapse)
			TCP_SKB_CB(skb)->eor = 1;
		else
			avail_size = size_goal - skb->len;
	}

	if (!retransmission) {
		/* reuse tail pfrag, if possible, or carve a new one from the
		 * page allocator
		 */
		dfrag = mptcp_rtx_tail(sk);
		offset = pfrag->offset;
		dfrag_collapsed = mptcp_frag_can_collapse_to(msk, pfrag, dfrag);
		if (!dfrag_collapsed) {
			dfrag = mptcp_carve_data_frag(msk, pfrag, offset);
			offset = dfrag->offset;
			frag_truesize = dfrag->overhead;
		}
		psize = min_t(size_t, pfrag->size - offset, avail_size);

		/* Copy to page */
		pr_debug("left=%zu", msg_data_left(msg));
		psize = copy_page_from_iter(pfrag->page, offset,
					    min_t(size_t, msg_data_left(msg),
						  psize),
					    &msg->msg_iter);
		pr_debug("left=%zu", msg_data_left(msg));
		if (!psize)
			return -EINVAL;

		if (!sk_wmem_schedule(sk, psize + dfrag->overhead))
			return -ENOMEM;
	} else {
		offset = dfrag->offset;
		psize = min_t(size_t, dfrag->data_len, avail_size);
	}

	/* tell the TCP stack to delay the push so that we can safely
	 * access the skb after the sendpages call
	 */
	ret = do_tcp_sendpages(ssk, page, offset, psize,
			       msg->msg_flags | MSG_SENDPAGE_NOTLAST);
	if (ret <= 0)
		return ret;

	frag_truesize += ret;
	if (!retransmission) {
		if (unlikely(ret < psize))
			iov_iter_revert(&msg->msg_iter, psize - ret);

		/* send successful, keep track of sent data for mptcp-level
		 * retransmission
		 */
		dfrag->data_len += ret;
		if (!dfrag_collapsed) {
			get_page(dfrag->page);
			list_add_tail(&dfrag->list, &msk->rtx_queue);
			sk_wmem_queued_add(sk, frag_truesize);
		} else {
			sk_wmem_queued_add(sk, ret);
		}

		/* charge data on mptcp rtx queue to the master socket
		 * Note: we charge such data both to sk and ssk
		 */
		sk->sk_forward_alloc -= frag_truesize;
	}

	/* if the tail skb extension is still the cached one, collapsing
	 * really happened. Note: we can't check for 'same skb' as the sk_buff
	 * hdr on tail can be transmitted, freed and re-allocated by the
	 * do_tcp_sendpages() call
	 */
	tail = tcp_write_queue_tail(ssk);
	if (mpext && tail && mpext == skb_ext_find(tail, SKB_EXT_MPTCP)) {
		WARN_ON_ONCE(!can_collapse);
		mpext->data_len += ret;
		goto out;
	}

	skb = tcp_write_queue_tail(ssk);
	mpext = __skb_ext_set(skb, SKB_EXT_MPTCP, msk->cached_ext);
	msk->cached_ext = NULL;

	memset(mpext, 0, sizeof(*mpext));
	mpext->data_seq = *write_seq;
	mpext->subflow_seq = mptcp_subflow_ctx(ssk)->rel_write_seq;
	mpext->data_len = ret;
	mpext->use_map = 1;
	mpext->dsn64 = 1;

	pr_debug("data_seq=%llu subflow_seq=%u data_len=%u dsn64=%d",
		 mpext->data_seq, mpext->subflow_seq, mpext->data_len,
		 mpext->dsn64);

out:
	if (!retransmission)
		pfrag->offset += frag_truesize;
	*write_seq += ret;
	mptcp_subflow_ctx(ssk)->rel_write_seq += ret;

	return ret;
}

static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
{
	struct mptcp_subflow_context *subflow;
	struct sock *backup = NULL;

	sock_owned_by_me((const struct sock *)msk);

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

		if (!sk_stream_memory_free(ssk)) {
			struct socket *sock = ssk->sk_socket;

			if (sock) {
				clear_bit(MPTCP_SEND_SPACE, &msk->flags);
				smp_mb__after_atomic();

				/* enables sk->write_space() callbacks */
				set_bit(SOCK_NOSPACE, &sock->flags);
			}

			return NULL;
		}

		if (subflow->backup) {
			if (!backup)
				backup = ssk;

			continue;
		}

		return ssk;
	}

	return backup;
}

static void ssk_check_wmem(struct mptcp_sock *msk, struct sock *ssk)
{
	struct socket *sock;

	if (likely(sk_stream_is_writeable(ssk)))
		return;

	sock = READ_ONCE(ssk->sk_socket);

	if (sock) {
		clear_bit(MPTCP_SEND_SPACE, &msk->flags);
		smp_mb__after_atomic();
		/* set NOSPACE only after clearing SEND_SPACE flag */
		set_bit(SOCK_NOSPACE, &sock->flags);
	}
}

static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
{
	int mss_now = 0, size_goal = 0, ret = 0;
	struct mptcp_sock *msk = mptcp_sk(sk);
	struct socket *ssock;
	size_t copied = 0;
	struct sock *ssk;
	long timeo;

	if (msg->msg_flags & ~(MSG_MORE | MSG_DONTWAIT | MSG_NOSIGNAL))
		return -EOPNOTSUPP;

	lock_sock(sk);

	timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT);

	if ((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) {
		ret = sk_stream_wait_connect(sk, &timeo);
		if (ret)
			goto out;
	}

fallback:
	ssock = __mptcp_tcp_fallback(msk);
	if (unlikely(ssock)) {
		release_sock(sk);
		pr_debug("fallback passthrough");
		ret = sock_sendmsg(ssock, msg);
		return ret >= 0 ? ret + copied : (copied ? copied : ret);
	}

	mptcp_clean_una(sk);

	__mptcp_flush_join_list(msk);
	ssk = mptcp_subflow_get_send(msk);
	while (!sk_stream_memory_free(sk) || !ssk) {
		ret = sk_stream_wait_memory(sk, &timeo);
		if (ret)
			goto out;

		mptcp_clean_una(sk);

		ssk = mptcp_subflow_get_send(msk);
		if (list_empty(&msk->conn_list)) {
			ret = -ENOTCONN;
			goto out;
		}
	}

	pr_debug("conn_list->subflow=%p", ssk);

	lock_sock(ssk);
	while (msg_data_left(msg)) {
		ret = mptcp_sendmsg_frag(sk, ssk, msg, NULL, &timeo, &mss_now,
					 &size_goal);
		if (ret < 0)
			break;
		if (ret == 0 && unlikely(__mptcp_needs_tcp_fallback(msk))) {
			/* Can happen for passive sockets:
			 * 3WHS negotiated MPTCP, but first packet after is
			 * plain TCP (e.g. due to middlebox filtering unknown
			 * options).
			 *
			 * Fall back to TCP.
			 */
			release_sock(ssk);
			goto fallback;
		}

		copied += ret;
	}

	mptcp_set_timeout(sk, ssk);
	if (copied) {
		ret = copied;
		tcp_push(ssk, msg->msg_flags, mss_now, tcp_sk(ssk)->nonagle,
			 size_goal);

		/* start the timer, if it's not pending */
		if (!mptcp_timer_pending(sk))
			mptcp_reset_timer(sk);
	}

	ssk_check_wmem(msk, ssk);
	release_sock(ssk);
out:
	release_sock(sk);
	return ret;
}

static void mptcp_wait_data(struct sock *sk, long *timeo)
{
	DEFINE_WAIT_FUNC(wait, woken_wake_function);
	struct mptcp_sock *msk = mptcp_sk(sk);

	add_wait_queue(sk_sleep(sk), &wait);
	sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);

	sk_wait_event(sk, timeo,
		      test_and_clear_bit(MPTCP_DATA_READY, &msk->flags), &wait);

	sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);
	remove_wait_queue(sk_sleep(sk), &wait);
}

static int __mptcp_recvmsg_mskq(struct mptcp_sock *msk,
				struct msghdr *msg,
				size_t len)
{
	struct sock *sk = (struct sock *)msk;
	struct sk_buff *skb;
	int copied = 0;

	while ((skb = skb_peek(&sk->sk_receive_queue)) != NULL) {
		u32 offset = MPTCP_SKB_CB(skb)->offset;
		u32 data_len = skb->len - offset;
		u32 count = min_t(size_t, len - copied, data_len);
		int err;

		err = skb_copy_datagram_msg(skb, offset, msg, count);
		if (unlikely(err < 0)) {
			if (!copied)
				return err;
			break;
		}

		copied += count;

		if (count < data_len) {
			MPTCP_SKB_CB(skb)->offset += count;
			break;
		}

		__skb_unlink(skb, &sk->sk_receive_queue);
		__kfree_skb(skb);

		if (copied >= len)
			break;
	}

	return copied;
}

static bool __mptcp_move_skbs(struct mptcp_sock *msk)
{
	unsigned int moved = 0;
	bool done;

	do {
		struct sock *ssk = mptcp_subflow_recv_lookup(msk);

		if (!ssk)
			break;

		lock_sock(ssk);
		done = __mptcp_move_skbs_from_subflow(msk, ssk, &moved);
		release_sock(ssk);
	} while (!done);

	return moved > 0;
}

static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
			 int nonblock, int flags, int *addr_len)
{
	struct mptcp_sock *msk = mptcp_sk(sk);
	struct socket *ssock;
	int copied = 0;
	int target;
	long timeo;

	if (msg->msg_flags & ~(MSG_WAITALL | MSG_DONTWAIT))
		return -EOPNOTSUPP;

	lock_sock(sk);
	ssock = __mptcp_tcp_fallback(msk);
	if (unlikely(ssock)) {
fallback:
		release_sock(sk);
		pr_debug("fallback-read subflow=%p",
			 mptcp_subflow_ctx(ssock->sk));
		copied = sock_recvmsg(ssock, msg, flags);
		return copied;
	}

	timeo = sock_rcvtimeo(sk, nonblock);

	len = min_t(size_t, len, INT_MAX);
	target = sock_rcvlowat(sk, flags & MSG_WAITALL, len);
	__mptcp_flush_join_list(msk);

	while (len > (size_t)copied) {
		int bytes_read;

		bytes_read = __mptcp_recvmsg_mskq(msk, msg, len - copied);
		if (unlikely(bytes_read < 0)) {
			if (!copied)
				copied = bytes_read;
			goto out_err;
		}

		copied += bytes_read;

		if (skb_queue_empty(&sk->sk_receive_queue) &&
		    __mptcp_move_skbs(msk))
			continue;

		/* only the master socket status is relevant here. The exit
		 * conditions mirror closely tcp_recvmsg()
		 */
		if (copied >= target)
			break;

		if (copied) {
			if (sk->sk_err ||
			    sk->sk_state == TCP_CLOSE ||
			    (sk->sk_shutdown & RCV_SHUTDOWN) ||
			    !timeo ||
			    signal_pending(current))
				break;
		} else {
			if (sk->sk_err) {
				copied = sock_error(sk);
				break;
			}

			if (sk->sk_shutdown & RCV_SHUTDOWN)
				break;

			if (sk->sk_state == TCP_CLOSE) {
				copied = -ENOTCONN;
				break;
			}

			if (!timeo) {
				copied = -EAGAIN;
				break;
			}

			if (signal_pending(current)) {
				copied = sock_intr_errno(timeo);
				break;
			}
		}

		pr_debug("block timeout %ld", timeo);
		mptcp_wait_data(sk, &timeo);
		if (unlikely(__mptcp_tcp_fallback(msk)))
			goto fallback;
	}

	if (skb_queue_empty(&sk->sk_receive_queue)) {
		/* entire backlog drained, clear DATA_READY. */
		clear_bit(MPTCP_DATA_READY, &msk->flags);

		/* .. race-breaker: ssk might have gotten new data
		 * after last __mptcp_move_skbs() returned false.
		 */
		if (unlikely(__mptcp_move_skbs(msk)))
			set_bit(MPTCP_DATA_READY, &msk->flags);
	} else if (unlikely(!test_bit(MPTCP_DATA_READY, &msk->flags))) {
		/* data to read but mptcp_wait_data() cleared DATA_READY */
		set_bit(MPTCP_DATA_READY, &msk->flags);
	}
out_err:
	release_sock(sk);
	return copied;
}

static void mptcp_retransmit_handler(struct sock *sk)
{
	struct mptcp_sock *msk = mptcp_sk(sk);

	if (atomic64_read(&msk->snd_una) == msk->write_seq) {
		mptcp_stop_timer(sk);
	} else {
		set_bit(MPTCP_WORK_RTX, &msk->flags);
		if (schedule_work(&msk->work))
			sock_hold(sk);
	}
}

static void mptcp_retransmit_timer(struct timer_list *t)
{
	struct inet_connection_sock *icsk = from_timer(icsk, t,
						       icsk_retransmit_timer);
	struct sock *sk = &icsk->icsk_inet.sk;

	bh_lock_sock(sk);
	if (!sock_owned_by_user(sk)) {
		mptcp_retransmit_handler(sk);
	} else {
		/* delegate our work to tcp_release_cb() */
		if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED,
				      &sk->sk_tsq_flags))
			sock_hold(sk);
	}
	bh_unlock_sock(sk);
	sock_put(sk);
}

/* Find an idle subflow.  Return NULL if there is unacked data at tcp
 * level.
 *
 * A backup subflow is returned only if that is the only kind available.
 */
static struct sock *mptcp_subflow_get_retrans(const struct mptcp_sock *msk)
{
	struct mptcp_subflow_context *subflow;
	struct sock *backup = NULL;

	sock_owned_by_me((const struct sock *)msk);

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

		/* still data outstanding at TCP level?  Don't retransmit. */
		if (!tcp_write_queue_empty(ssk))
			return NULL;

		if (subflow->backup) {
			if (!backup)
				backup = ssk;
			continue;
		}

		return ssk;
	}

	return backup;
}

/* subflow sockets can be either outgoing (connect) or incoming
 * (accept).
 *
 * Outgoing subflows use in-kernel sockets.
 * Incoming subflows do not have their own 'struct socket' allocated,
 * so we need to use tcp_close() after detaching them from the mptcp
 * parent socket.
 */
static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
			      struct mptcp_subflow_context *subflow,
			      long timeout)
{
	struct socket *sock = READ_ONCE(ssk->sk_socket);

	list_del(&subflow->node);

	if (sock && sock != sk->sk_socket) {
		/* outgoing subflow */
		sock_release(sock);
	} else {
		/* incoming subflow */
		tcp_close(ssk, timeout);
	}
}

static unsigned int mptcp_sync_mss(struct sock *sk, u32 pmtu)
{
	return 0;
}

static void mptcp_check_for_eof(struct mptcp_sock *msk)
{
	struct mptcp_subflow_context *subflow;
	struct sock *sk = (struct sock *)msk;
	int receivers = 0;

	mptcp_for_each_subflow(msk, subflow)
		receivers += !subflow->rx_eof;

	if (!receivers && !(sk->sk_shutdown & RCV_SHUTDOWN)) {
		/* hopefully temporary hack: propagate shutdown status
		 * to msk, when all subflows agree on it
		 */
		sk->sk_shutdown |= RCV_SHUTDOWN;

		smp_mb__before_atomic(); /* SHUTDOWN must be visible first */
		set_bit(MPTCP_DATA_READY, &msk->flags);
		sk->sk_data_ready(sk);
	}
}

static void mptcp_worker(struct work_struct *work)
{
	struct mptcp_sock *msk = container_of(work, struct mptcp_sock, work);
	struct sock *ssk, *sk = &msk->sk.icsk_inet.sk;
	int orig_len, orig_offset, ret, mss_now = 0, size_goal = 0;
	struct mptcp_data_frag *dfrag;
	u64 orig_write_seq;
	size_t copied = 0;
	struct msghdr msg;
	long timeo = 0;

	lock_sock(sk);
	mptcp_clean_una(sk);
	__mptcp_flush_join_list(msk);
	__mptcp_move_skbs(msk);

	if (test_and_clear_bit(MPTCP_WORK_EOF, &msk->flags))
		mptcp_check_for_eof(msk);

	if (!test_and_clear_bit(MPTCP_WORK_RTX, &msk->flags))
		goto unlock;

	dfrag = mptcp_rtx_head(sk);
	if (!dfrag)
		goto unlock;

	ssk = mptcp_subflow_get_retrans(msk);
	if (!ssk)
		goto reset_unlock;

	lock_sock(ssk);

	msg.msg_flags = MSG_DONTWAIT;
	orig_len = dfrag->data_len;
	orig_offset = dfrag->offset;
	orig_write_seq = dfrag->data_seq;
	while (dfrag->data_len > 0) {
		ret = mptcp_sendmsg_frag(sk, ssk, &msg, dfrag, &timeo, &mss_now,
					 &size_goal);
		if (ret < 0)
			break;

		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_RETRANSSEGS);
		copied += ret;
		dfrag->data_len -= ret;
		dfrag->offset += ret;
	}
	if (copied)
		tcp_push(ssk, msg.msg_flags, mss_now, tcp_sk(ssk)->nonagle,
			 size_goal);

	dfrag->data_seq = orig_write_seq;
	dfrag->offset = orig_offset;
	dfrag->data_len = orig_len;

	mptcp_set_timeout(sk, ssk);
	release_sock(ssk);

reset_unlock:
	if (!mptcp_timer_pending(sk))
		mptcp_reset_timer(sk);

unlock:
	release_sock(sk);
	sock_put(sk);
}

static int __mptcp_init_sock(struct sock *sk)
{
	struct mptcp_sock *msk = mptcp_sk(sk);

	spin_lock_init(&msk->join_list_lock);

	INIT_LIST_HEAD(&msk->conn_list);
	INIT_LIST_HEAD(&msk->join_list);
	INIT_LIST_HEAD(&msk->rtx_queue);
	__set_bit(MPTCP_SEND_SPACE, &msk->flags);
	INIT_WORK(&msk->work, mptcp_worker);

	msk->first = NULL;
	inet_csk(sk)->icsk_sync_mss = mptcp_sync_mss;

	mptcp_pm_data_init(msk);

	/* re-use the csk retrans timer for MPTCP-level retrans */
	timer_setup(&msk->sk.icsk_retransmit_timer, mptcp_retransmit_timer, 0);

	return 0;
}

static int mptcp_init_sock(struct sock *sk)
{
	struct net *net = sock_net(sk);
	int ret;

	if (!mptcp_is_enabled(net))
		return -ENOPROTOOPT;

	if (unlikely(!net->mib.mptcp_statistics) && !mptcp_mib_alloc(net))
		return -ENOMEM;

	ret = __mptcp_init_sock(sk);
	if (ret)
		return ret;

	sk_sockets_allocated_inc(sk);
	sk->sk_sndbuf = sock_net(sk)->ipv4.sysctl_tcp_wmem[2];

	return 0;
}

static void __mptcp_clear_xmit(struct sock *sk)
{
	struct mptcp_sock *msk = mptcp_sk(sk);
	struct mptcp_data_frag *dtmp, *dfrag;

	sk_stop_timer(sk, &msk->sk.icsk_retransmit_timer);

	list_for_each_entry_safe(dfrag, dtmp, &msk->rtx_queue, list)
		dfrag_clear(sk, dfrag);
}

static void mptcp_cancel_work(struct sock *sk)
{
	struct mptcp_sock *msk = mptcp_sk(sk);

	if (cancel_work_sync(&msk->work))
		sock_put(sk);
}

static void mptcp_subflow_shutdown(struct sock *ssk, int how,
				   bool data_fin_tx_enable, u64 data_fin_tx_seq)
{
	lock_sock(ssk);

	switch (ssk->sk_state) {
	case TCP_LISTEN:
		if (!(how & RCV_SHUTDOWN))
			break;
		/* fall through */
	case TCP_SYN_SENT:
		tcp_disconnect(ssk, O_NONBLOCK);
		break;
	default:
		if (data_fin_tx_enable) {
			struct mptcp_subflow_context *subflow;

			subflow = mptcp_subflow_ctx(ssk);
			subflow->data_fin_tx_seq = data_fin_tx_seq;
			subflow->data_fin_tx_enable = 1;
		}

		ssk->sk_shutdown |= how;
		tcp_shutdown(ssk, how);
		break;
	}

	/* Wake up anyone sleeping in poll. */
	ssk->sk_state_change(ssk);
	release_sock(ssk);
}

/* Called with msk lock held, releases such lock before returning */
static void mptcp_close(struct sock *sk, long timeout)
{
	struct mptcp_subflow_context *subflow, *tmp;
	struct mptcp_sock *msk = mptcp_sk(sk);
	LIST_HEAD(conn_list);
	u64 data_fin_tx_seq;

	lock_sock(sk);

	mptcp_token_destroy(msk->token);
	inet_sk_state_store(sk, TCP_CLOSE);

	__mptcp_flush_join_list(msk);

	list_splice_init(&msk->conn_list, &conn_list);

	data_fin_tx_seq = msk->write_seq;

	__mptcp_clear_xmit(sk);

	release_sock(sk);

	list_for_each_entry_safe(subflow, tmp, &conn_list, node) {
		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);

		subflow->data_fin_tx_seq = data_fin_tx_seq;
		subflow->data_fin_tx_enable = 1;
		__mptcp_close_ssk(sk, ssk, subflow, timeout);
	}

	mptcp_cancel_work(sk);
	mptcp_pm_close(msk);

	__skb_queue_purge(&sk->sk_receive_queue);

	sk_common_release(sk);
}

static void mptcp_copy_inaddrs(struct sock *msk, const struct sock *ssk)
{
#if IS_ENABLED(CONFIG_MPTCP_IPV6)
	const struct ipv6_pinfo *ssk6 = inet6_sk(ssk);
	struct ipv6_pinfo *msk6 = inet6_sk(msk);

	msk->sk_v6_daddr = ssk->sk_v6_daddr;
	msk->sk_v6_rcv_saddr = ssk->sk_v6_rcv_saddr;

	if (msk6 && ssk6) {
		msk6->saddr = ssk6->saddr;
		msk6->flow_label = ssk6->flow_label;
	}
#endif

	inet_sk(msk)->inet_num = inet_sk(ssk)->inet_num;
	inet_sk(msk)->inet_dport = inet_sk(ssk)->inet_dport;
	inet_sk(msk)->inet_sport = inet_sk(ssk)->inet_sport;
	inet_sk(msk)->inet_daddr = inet_sk(ssk)->inet_daddr;
	inet_sk(msk)->inet_saddr = inet_sk(ssk)->inet_saddr;
	inet_sk(msk)->inet_rcv_saddr = inet_sk(ssk)->inet_rcv_saddr;
}

static int mptcp_disconnect(struct sock *sk, int flags)
{
	lock_sock(sk);
	__mptcp_clear_xmit(sk);
	release_sock(sk);
	mptcp_cancel_work(sk);
	return tcp_disconnect(sk, flags);
}

#if IS_ENABLED(CONFIG_MPTCP_IPV6)
static struct ipv6_pinfo *mptcp_inet6_sk(const struct sock *sk)
{
	unsigned int offset = sizeof(struct mptcp6_sock) - sizeof(struct ipv6_pinfo);

	return (struct ipv6_pinfo *)(((u8 *)sk) + offset);
}
#endif

struct sock *mptcp_sk_clone(const struct sock *sk,
			    const struct tcp_options_received *opt_rx,
			    struct request_sock *req)
{
	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
	struct sock *nsk = sk_clone_lock(sk, GFP_ATOMIC);
	struct mptcp_sock *msk;
	u64 ack_seq;

	if (!nsk)
		return NULL;

#if IS_ENABLED(CONFIG_MPTCP_IPV6)
	if (nsk->sk_family == AF_INET6)
		inet_sk(nsk)->pinet6 = mptcp_inet6_sk(nsk);
#endif

	__mptcp_init_sock(nsk);

	msk = mptcp_sk(nsk);
	msk->local_key = subflow_req->local_key;
	msk->token = subflow_req->token;
	msk->subflow = NULL;

	if (unlikely(mptcp_token_new_accept(subflow_req->token, nsk))) {
		nsk->sk_state = TCP_CLOSE;
		bh_unlock_sock(nsk);

		/* we can't call into mptcp_close() here - possible BH context
		 * free the sock directly.
		 * sk_clone_lock() sets nsk refcnt to two, hence call sk_free()
		 * too.
		 */
		sk_common_release(nsk);
		sk_free(nsk);
		return NULL;
	}

	msk->write_seq = subflow_req->idsn + 1;
	atomic64_set(&msk->snd_una, msk->write_seq);
	if (opt_rx->mptcp.mp_capable) {
		msk->can_ack = true;
		msk->remote_key = opt_rx->mptcp.sndr_key;
		mptcp_crypto_key_sha(msk->remote_key, NULL, &ack_seq);
		ack_seq++;
		msk->ack_seq = ack_seq;
	}

	sock_reset_flag(nsk, SOCK_RCU_FREE);
	/* will be fully established after successful MPC subflow creation */
	inet_sk_state_store(nsk, TCP_SYN_RECV);
	bh_unlock_sock(nsk);

	/* keep a single reference */
	__sock_put(nsk);
	return nsk;
}

static struct sock *mptcp_accept(struct sock *sk, int flags, int *err,
				 bool kern)
{
	struct mptcp_sock *msk = mptcp_sk(sk);
	struct socket *listener;
	struct sock *newsk;

	listener = __mptcp_nmpc_socket(msk);
	if (WARN_ON_ONCE(!listener)) {
		*err = -EINVAL;
		return NULL;
	}

	pr_debug("msk=%p, listener=%p", msk, mptcp_subflow_ctx(listener->sk));
	newsk = inet_csk_accept(listener->sk, flags, err, kern);
	if (!newsk)
		return NULL;

	pr_debug("msk=%p, subflow is mptcp=%d", msk, sk_is_mptcp(newsk));

	if (sk_is_mptcp(newsk)) {
		struct mptcp_subflow_context *subflow;
		struct sock *new_mptcp_sock;
		struct sock *ssk = newsk;

		subflow = mptcp_subflow_ctx(newsk);
		new_mptcp_sock = subflow->conn;

		/* is_mptcp should be false if subflow->conn is missing, see
		 * subflow_syn_recv_sock()
		 */
		if (WARN_ON_ONCE(!new_mptcp_sock)) {
			tcp_sk(newsk)->is_mptcp = 0;
			return newsk;
		}

		/* acquire the 2nd reference for the owning socket */
		sock_hold(new_mptcp_sock);

		local_bh_disable();
		bh_lock_sock(new_mptcp_sock);
		msk = mptcp_sk(new_mptcp_sock);
		msk->first = newsk;

		newsk = new_mptcp_sock;
		mptcp_copy_inaddrs(newsk, ssk);
		list_add(&subflow->node, &msk->conn_list);
		inet_sk_state_store(newsk, TCP_ESTABLISHED);

		bh_unlock_sock(new_mptcp_sock);

		__MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPCAPABLEPASSIVEACK);
		local_bh_enable();
	} else {
		MPTCP_INC_STATS(sock_net(sk),
				MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK);
	}

	return newsk;
}

static void mptcp_destroy(struct sock *sk)
{
	struct mptcp_sock *msk = mptcp_sk(sk);

	if (msk->cached_ext)
		__skb_ext_put(msk->cached_ext);

	sk_sockets_allocated_dec(sk);
}

static int mptcp_setsockopt(struct sock *sk, int level, int optname,
			    char __user *optval, unsigned int optlen)
{
	struct mptcp_sock *msk = mptcp_sk(sk);
	struct socket *ssock;

	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 TCP socket options are passed through
	 * to the one remaining subflow.
	 */
	lock_sock(sk);
	ssock = __mptcp_tcp_fallback(msk);
	release_sock(sk);
	if (ssock)
		return tcp_setsockopt(ssock->sk, level, optname, optval,
				      optlen);

	return -EOPNOTSUPP;
}

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

	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);
	ssock = __mptcp_tcp_fallback(msk);
	release_sock(sk);
	if (ssock)
		return tcp_getsockopt(ssock->sk, level, optname, optval,
				      option);

	return -EOPNOTSUPP;
}

#define MPTCP_DEFERRED_ALL (TCPF_DELACK_TIMER_DEFERRED | \
			    TCPF_WRITE_TIMER_DEFERRED)

/* this is very alike tcp_release_cb() but we must handle differently a
 * different set of events
 */
static void mptcp_release_cb(struct sock *sk)
{
	unsigned long flags, nflags;

	do {
		flags = sk->sk_tsq_flags;
		if (!(flags & MPTCP_DEFERRED_ALL))
			return;
		nflags = flags & ~MPTCP_DEFERRED_ALL;
	} while (cmpxchg(&sk->sk_tsq_flags, flags, nflags) != flags);

	sock_release_ownership(sk);

	if (flags & TCPF_DELACK_TIMER_DEFERRED) {
		struct mptcp_sock *msk = mptcp_sk(sk);
		struct sock *ssk;

		ssk = mptcp_subflow_recv_lookup(msk);
		if (!ssk || !schedule_work(&msk->work))
			__sock_put(sk);
	}

	if (flags & TCPF_WRITE_TIMER_DEFERRED) {
		mptcp_retransmit_handler(sk);
		__sock_put(sk);
	}
}

static int mptcp_get_port(struct sock *sk, unsigned short snum)
{
	struct mptcp_sock *msk = mptcp_sk(sk);
	struct socket *ssock;

	ssock = __mptcp_nmpc_socket(msk);
	pr_debug("msk=%p, subflow=%p", msk, ssock);
	if (WARN_ON_ONCE(!ssock))
		return -EINVAL;

	return inet_csk_get_port(ssock->sk, snum);
}

void mptcp_finish_connect(struct sock *ssk)
{
	struct mptcp_subflow_context *subflow;
	struct mptcp_sock *msk;
	struct sock *sk;
	u64 ack_seq;

	subflow = mptcp_subflow_ctx(ssk);
	sk = subflow->conn;
	msk = mptcp_sk(sk);

	if (!subflow->mp_capable) {
		MPTCP_INC_STATS(sock_net(sk),
				MPTCP_MIB_MPCAPABLEACTIVEFALLBACK);
		return;
	}

	pr_debug("msk=%p, token=%u", sk, subflow->token);

	mptcp_crypto_key_sha(subflow->remote_key, NULL, &ack_seq);
	ack_seq++;
	subflow->map_seq = ack_seq;
	subflow->map_subflow_seq = 1;
	subflow->rel_write_seq = 1;

	/* the socket is not connected yet, no msk/subflow ops can access/race
	 * accessing the field below
	 */
	WRITE_ONCE(msk->remote_key, subflow->remote_key);
	WRITE_ONCE(msk->local_key, subflow->local_key);
	WRITE_ONCE(msk->token, subflow->token);
	WRITE_ONCE(msk->write_seq, subflow->idsn + 1);
	WRITE_ONCE(msk->ack_seq, ack_seq);
	WRITE_ONCE(msk->can_ack, 1);
	atomic64_set(&msk->snd_una, msk->write_seq);

	mptcp_pm_new_connection(msk, 0);
}

static void mptcp_sock_graft(struct sock *sk, struct socket *parent)
{
	write_lock_bh(&sk->sk_callback_lock);
	rcu_assign_pointer(sk->sk_wq, &parent->wq);
	sk_set_socket(sk, parent);
	sk->sk_uid = SOCK_INODE(parent)->i_uid;
	write_unlock_bh(&sk->sk_callback_lock);
}

bool mptcp_finish_join(struct sock *sk)
{
	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
	struct sock *parent = (void *)msk;
	struct socket *parent_sock;
	bool ret;

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

	/* mptcp socket already closing? */
	if (inet_sk_state_load(parent) != TCP_ESTABLISHED)
		return false;

	if (!msk->pm.server_side)
		return true;

	/* passive connection, attach to msk socket */
	parent_sock = READ_ONCE(parent->sk_socket);
	if (parent_sock && !sk->sk_socket)
		mptcp_sock_graft(sk, parent_sock);

	ret = mptcp_pm_allow_new_subflow(msk);
	if (ret) {
		/* active connections are already on conn_list */
		spin_lock_bh(&msk->join_list_lock);
		if (!WARN_ON_ONCE(!list_empty(&subflow->node)))
			list_add_tail(&subflow->node, &msk->join_list);
		spin_unlock_bh(&msk->join_list_lock);
	}
	return ret;
}

bool mptcp_sk_is_subflow(const struct sock *sk)
{
	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);

	return subflow->mp_join == 1;
}

static bool mptcp_memory_free(const struct sock *sk, int wake)
{
	struct mptcp_sock *msk = mptcp_sk(sk);

	return wake ? test_bit(MPTCP_SEND_SPACE, &msk->flags) : true;
}

static struct proto mptcp_prot = {
	.name		= "MPTCP",
	.owner		= THIS_MODULE,
	.init		= mptcp_init_sock,
	.disconnect	= mptcp_disconnect,
	.close		= mptcp_close,
	.accept		= mptcp_accept,
	.setsockopt	= mptcp_setsockopt,
	.getsockopt	= mptcp_getsockopt,
	.shutdown	= tcp_shutdown,
	.destroy	= mptcp_destroy,
	.sendmsg	= mptcp_sendmsg,
	.recvmsg	= mptcp_recvmsg,
	.release_cb	= mptcp_release_cb,
	.hash		= inet_hash,
	.unhash		= inet_unhash,
	.get_port	= mptcp_get_port,
	.sockets_allocated	= &mptcp_sockets_allocated,
	.memory_allocated	= &tcp_memory_allocated,
	.memory_pressure	= &tcp_memory_pressure,
	.stream_memory_free	= mptcp_memory_free,
	.sysctl_wmem_offset	= offsetof(struct net, ipv4.sysctl_tcp_wmem),
	.sysctl_mem	= sysctl_tcp_mem,
	.obj_size	= sizeof(struct mptcp_sock),
	.no_autobind	= true,
};

static int mptcp_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
{
	struct mptcp_sock *msk = mptcp_sk(sock->sk);
	struct socket *ssock;
	int err;

	lock_sock(sock->sk);
	ssock = __mptcp_socket_create(msk, MPTCP_SAME_STATE);
	if (IS_ERR(ssock)) {
		err = PTR_ERR(ssock);
		goto unlock;
	}

	err = ssock->ops->bind(ssock, uaddr, addr_len);
	if (!err)
		mptcp_copy_inaddrs(sock->sk, ssock->sk);

unlock:
	release_sock(sock->sk);
	return err;
}

static int mptcp_stream_connect(struct socket *sock, struct sockaddr *uaddr,
				int addr_len, int flags)
{
	struct mptcp_sock *msk = mptcp_sk(sock->sk);
	struct socket *ssock;
	int err;

	lock_sock(sock->sk);
	ssock = __mptcp_socket_create(msk, TCP_SYN_SENT);
	if (IS_ERR(ssock)) {
		err = PTR_ERR(ssock);
		goto unlock;
	}

#ifdef CONFIG_TCP_MD5SIG
	/* no MPTCP if MD5SIG is enabled on this socket or we may run out of
	 * TCP option space.
	 */
	if (rcu_access_pointer(tcp_sk(ssock->sk)->md5sig_info))
		mptcp_subflow_ctx(ssock->sk)->request_mptcp = 0;
#endif

	err = ssock->ops->connect(ssock, uaddr, addr_len, flags);
	inet_sk_state_store(sock->sk, inet_sk_state_load(ssock->sk));
	mptcp_copy_inaddrs(sock->sk, ssock->sk);

unlock:
	release_sock(sock->sk);
	return err;
}

static int mptcp_v4_getname(struct socket *sock, struct sockaddr *uaddr,
			    int peer)
{
	if (sock->sk->sk_prot == &tcp_prot) {
		/* we are being invoked from __sys_accept4, after
		 * mptcp_accept() has just accepted a non-mp-capable
		 * flow: sk is a tcp_sk, not an mptcp one.
		 *
		 * Hand the socket over to tcp so all further socket ops
		 * bypass mptcp.
		 */
		sock->ops = &inet_stream_ops;
	}

	return inet_getname(sock, uaddr, peer);
}

#if IS_ENABLED(CONFIG_MPTCP_IPV6)
static int mptcp_v6_getname(struct socket *sock, struct sockaddr *uaddr,
			    int peer)
{
	if (sock->sk->sk_prot == &tcpv6_prot) {
		/* we are being invoked from __sys_accept4 after
		 * mptcp_accept() has accepted a non-mp-capable
		 * subflow: sk is a tcp_sk, not mptcp.
		 *
		 * Hand the socket over to tcp so all further
		 * socket ops bypass mptcp.
		 */
		sock->ops = &inet6_stream_ops;
	}

	return inet6_getname(sock, uaddr, peer);
}
#endif

static int mptcp_listen(struct socket *sock, int backlog)
{
	struct mptcp_sock *msk = mptcp_sk(sock->sk);
	struct socket *ssock;
	int err;

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

	lock_sock(sock->sk);
	ssock = __mptcp_socket_create(msk, TCP_LISTEN);
	if (IS_ERR(ssock)) {
		err = PTR_ERR(ssock);
		goto unlock;
	}

	sock_set_flag(sock->sk, SOCK_RCU_FREE);

	err = ssock->ops->listen(ssock, backlog);
	inet_sk_state_store(sock->sk, inet_sk_state_load(ssock->sk));
	if (!err)
		mptcp_copy_inaddrs(sock->sk, ssock->sk);

unlock:
	release_sock(sock->sk);
	return err;
}

static bool is_tcp_proto(const struct proto *p)
{
#if IS_ENABLED(CONFIG_MPTCP_IPV6)
	return p == &tcp_prot || p == &tcpv6_prot;
#else
	return p == &tcp_prot;
#endif
}

static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
			       int flags, bool kern)
{
	struct mptcp_sock *msk = mptcp_sk(sock->sk);
	struct socket *ssock;
	int err;

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

	lock_sock(sock->sk);
	if (sock->sk->sk_state != TCP_LISTEN)
		goto unlock_fail;

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

	sock_hold(ssock->sk);
	release_sock(sock->sk);

	err = ssock->ops->accept(sock, newsock, flags, kern);
	if (err == 0 && !is_tcp_proto(newsock->sk->sk_prot)) {
		struct mptcp_sock *msk = mptcp_sk(newsock->sk);
		struct mptcp_subflow_context *subflow;

		/* set ssk->sk_socket of accept()ed flows to mptcp socket.
		 * This is needed so NOSPACE flag can be set from tcp stack.
		 */
		__mptcp_flush_join_list(msk);
		list_for_each_entry(subflow, &msk->conn_list, node) {
			struct sock *ssk = mptcp_subflow_tcp_sock(subflow);

			if (!ssk->sk_socket)
				mptcp_sock_graft(ssk, newsock);
		}
	}

	sock_put(ssock->sk);
	return err;

unlock_fail:
	release_sock(sock->sk);
	return -EINVAL;
}

static __poll_t mptcp_poll(struct file *file, struct socket *sock,
			   struct poll_table_struct *wait)
{
	struct sock *sk = sock->sk;
	struct mptcp_sock *msk;
	struct socket *ssock;
	__poll_t mask = 0;

	msk = mptcp_sk(sk);
	lock_sock(sk);
	ssock = __mptcp_tcp_fallback(msk);
	if (!ssock)
		ssock = __mptcp_nmpc_socket(msk);
	if (ssock) {
		mask = ssock->ops->poll(file, ssock, wait);
		release_sock(sk);
		return mask;
	}

	release_sock(sk);
	sock_poll_wait(file, sock, wait);
	lock_sock(sk);

	if (test_bit(MPTCP_DATA_READY, &msk->flags))
		mask = EPOLLIN | EPOLLRDNORM;
	if (sk_stream_is_writeable(sk) &&
	    test_bit(MPTCP_SEND_SPACE, &msk->flags))
		mask |= EPOLLOUT | EPOLLWRNORM;
	if (sk->sk_shutdown & RCV_SHUTDOWN)
		mask |= EPOLLIN | EPOLLRDNORM | EPOLLRDHUP;

	release_sock(sk);

	return mask;
}

static int mptcp_shutdown(struct socket *sock, int how)
{
	struct mptcp_sock *msk = mptcp_sk(sock->sk);
	struct mptcp_subflow_context *subflow;
	struct socket *ssock;
	int ret = 0;

	pr_debug("sk=%p, how=%d", msk, how);

	lock_sock(sock->sk);
	ssock = __mptcp_tcp_fallback(msk);
	if (ssock) {
		release_sock(sock->sk);
		return inet_shutdown(ssock, how);
	}

	if (how == SHUT_WR || how == SHUT_RDWR)
		inet_sk_state_store(sock->sk, TCP_FIN_WAIT1);

	how++;

	if ((how & ~SHUTDOWN_MASK) || !how) {
		ret = -EINVAL;
		goto out_unlock;
	}

	if (sock->state == SS_CONNECTING) {
		if ((1 << sock->sk->sk_state) &
		    (TCPF_SYN_SENT | TCPF_SYN_RECV | TCPF_CLOSE))
			sock->state = SS_DISCONNECTING;
		else
			sock->state = SS_CONNECTED;
	}

	__mptcp_flush_join_list(msk);
	mptcp_for_each_subflow(msk, subflow) {
		struct sock *tcp_sk = mptcp_subflow_tcp_sock(subflow);

		mptcp_subflow_shutdown(tcp_sk, how, 1, msk->write_seq);
	}

out_unlock:
	release_sock(sock->sk);

	return ret;
}

static const struct proto_ops mptcp_stream_ops = {
	.family		   = PF_INET,
	.owner		   = THIS_MODULE,
	.release	   = inet_release,
	.bind		   = mptcp_bind,
	.connect	   = mptcp_stream_connect,
	.socketpair	   = sock_no_socketpair,
	.accept		   = mptcp_stream_accept,
	.getname	   = mptcp_v4_getname,
	.poll		   = mptcp_poll,
	.ioctl		   = inet_ioctl,
	.gettstamp	   = sock_gettstamp,
	.listen		   = mptcp_listen,
	.shutdown	   = mptcp_shutdown,
	.setsockopt	   = sock_common_setsockopt,
	.getsockopt	   = sock_common_getsockopt,
	.sendmsg	   = inet_sendmsg,
	.recvmsg	   = inet_recvmsg,
	.mmap		   = sock_no_mmap,
	.sendpage	   = inet_sendpage,
#ifdef CONFIG_COMPAT
	.compat_setsockopt = compat_sock_common_setsockopt,
	.compat_getsockopt = compat_sock_common_getsockopt,
#endif
};

static struct inet_protosw mptcp_protosw = {
	.type		= SOCK_STREAM,
	.protocol	= IPPROTO_MPTCP,
	.prot		= &mptcp_prot,
	.ops		= &mptcp_stream_ops,
	.flags		= INET_PROTOSW_ICSK,
};

void mptcp_proto_init(void)
{
	mptcp_prot.h.hashinfo = tcp_prot.h.hashinfo;

	if (percpu_counter_init(&mptcp_sockets_allocated, 0, GFP_KERNEL))
		panic("Failed to allocate MPTCP pcpu counter\n");

	mptcp_subflow_init();
	mptcp_pm_init();

	if (proto_register(&mptcp_prot, 1) != 0)
		panic("Failed to register MPTCP proto.\n");

	inet_register_protosw(&mptcp_protosw);

	BUILD_BUG_ON(sizeof(struct mptcp_skb_cb) > sizeof_field(struct sk_buff, cb));
}

#if IS_ENABLED(CONFIG_MPTCP_IPV6)
static const struct proto_ops mptcp_v6_stream_ops = {
	.family		   = PF_INET6,
	.owner		   = THIS_MODULE,
	.release	   = inet6_release,
	.bind		   = mptcp_bind,
	.connect	   = mptcp_stream_connect,
	.socketpair	   = sock_no_socketpair,
	.accept		   = mptcp_stream_accept,
	.getname	   = mptcp_v6_getname,
	.poll		   = mptcp_poll,
	.ioctl		   = inet6_ioctl,
	.gettstamp	   = sock_gettstamp,
	.listen		   = mptcp_listen,
	.shutdown	   = mptcp_shutdown,
	.setsockopt	   = sock_common_setsockopt,
	.getsockopt	   = sock_common_getsockopt,
	.sendmsg	   = inet6_sendmsg,
	.recvmsg	   = inet6_recvmsg,
	.mmap		   = sock_no_mmap,
	.sendpage	   = inet_sendpage,
#ifdef CONFIG_COMPAT
	.compat_setsockopt = compat_sock_common_setsockopt,
	.compat_getsockopt = compat_sock_common_getsockopt,
#endif
};

static struct proto mptcp_v6_prot;

static void mptcp_v6_destroy(struct sock *sk)
{
	mptcp_destroy(sk);
	inet6_destroy_sock(sk);
}

static struct inet_protosw mptcp_v6_protosw = {
	.type		= SOCK_STREAM,
	.protocol	= IPPROTO_MPTCP,
	.prot		= &mptcp_v6_prot,
	.ops		= &mptcp_v6_stream_ops,
	.flags		= INET_PROTOSW_ICSK,
};

int mptcp_proto_v6_init(void)
{
	int err;

	mptcp_v6_prot = mptcp_prot;
	strcpy(mptcp_v6_prot.name, "MPTCPv6");
	mptcp_v6_prot.slab = NULL;
	mptcp_v6_prot.destroy = mptcp_v6_destroy;
	mptcp_v6_prot.obj_size = sizeof(struct mptcp6_sock);

	err = proto_register(&mptcp_v6_prot, 1);
	if (err)
		return err;

	err = inet6_register_protosw(&mptcp_v6_protosw);
	if (err)
		proto_unregister(&mptcp_v6_prot);

	return err;
}
#endif