summaryrefslogtreecommitdiffstats
path: root/net/l2tp/l2tp_ppp.c
blob: 59f246d7b2906a1fcf53d76bc6f020dd9b2462b1 (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
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
/*****************************************************************************
 * Linux PPP over L2TP (PPPoX/PPPoL2TP) Sockets
 *
 * PPPoX    --- Generic PPP encapsulation socket family
 * PPPoL2TP --- PPP over L2TP (RFC 2661)
 *
 * Version:	2.0.0
 *
 * Authors:	James Chapman (jchapman@katalix.com)
 *
 * Based on original work by Martijn van Oosterhout <kleptog@svana.org>
 *
 * License:
 *		This program is free software; you can redistribute it and/or
 *		modify it under the terms of the GNU General Public License
 *		as published by the Free Software Foundation; either version
 *		2 of the License, or (at your option) any later version.
 *
 */

/* This driver handles only L2TP data frames; control frames are handled by a
 * userspace application.
 *
 * To send data in an L2TP session, userspace opens a PPPoL2TP socket and
 * attaches it to a bound UDP socket with local tunnel_id / session_id and
 * peer tunnel_id / session_id set. Data can then be sent or received using
 * regular socket sendmsg() / recvmsg() calls. Kernel parameters of the socket
 * can be read or modified using ioctl() or [gs]etsockopt() calls.
 *
 * When a PPPoL2TP socket is connected with local and peer session_id values
 * zero, the socket is treated as a special tunnel management socket.
 *
 * Here's example userspace code to create a socket for sending/receiving data
 * over an L2TP session:-
 *
 *	struct sockaddr_pppol2tp sax;
 *	int fd;
 *	int session_fd;
 *
 *	fd = socket(AF_PPPOX, SOCK_DGRAM, PX_PROTO_OL2TP);
 *
 *	sax.sa_family = AF_PPPOX;
 *	sax.sa_protocol = PX_PROTO_OL2TP;
 *	sax.pppol2tp.fd = tunnel_fd;	// bound UDP socket
 *	sax.pppol2tp.addr.sin_addr.s_addr = addr->sin_addr.s_addr;
 *	sax.pppol2tp.addr.sin_port = addr->sin_port;
 *	sax.pppol2tp.addr.sin_family = AF_INET;
 *	sax.pppol2tp.s_tunnel  = tunnel_id;
 *	sax.pppol2tp.s_session = session_id;
 *	sax.pppol2tp.d_tunnel  = peer_tunnel_id;
 *	sax.pppol2tp.d_session = peer_session_id;
 *
 *	session_fd = connect(fd, (struct sockaddr *)&sax, sizeof(sax));
 *
 * A pppd plugin that allows PPP traffic to be carried over L2TP using
 * this driver is available from the OpenL2TP project at
 * http://openl2tp.sourceforge.net.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/string.h>
#include <linux/list.h>
#include <linux/uaccess.h>

#include <linux/kernel.h>
#include <linux/spinlock.h>
#include <linux/kthread.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/jiffies.h>

#include <linux/netdevice.h>
#include <linux/net.h>
#include <linux/inetdevice.h>
#include <linux/skbuff.h>
#include <linux/init.h>
#include <linux/ip.h>
#include <linux/udp.h>
#include <linux/if_pppox.h>
#include <linux/if_pppol2tp.h>
#include <net/sock.h>
#include <linux/ppp_channel.h>
#include <linux/ppp_defs.h>
#include <linux/ppp-ioctl.h>
#include <linux/file.h>
#include <linux/hash.h>
#include <linux/sort.h>
#include <linux/proc_fs.h>
#include <linux/l2tp.h>
#include <linux/nsproxy.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>
#include <net/dst.h>
#include <net/ip.h>
#include <net/udp.h>
#include <net/xfrm.h>
#include <net/inet_common.h>

#include <asm/byteorder.h>
#include <linux/atomic.h>

#include "l2tp_core.h"

#define PPPOL2TP_DRV_VERSION	"V2.0"

/* Space for UDP, L2TP and PPP headers */
#define PPPOL2TP_HEADER_OVERHEAD	40

/* Number of bytes to build transmit L2TP headers.
 * Unfortunately the size is different depending on whether sequence numbers
 * are enabled.
 */
#define PPPOL2TP_L2TP_HDR_SIZE_SEQ		10
#define PPPOL2TP_L2TP_HDR_SIZE_NOSEQ		6

/* Private data of each session. This data lives at the end of struct
 * l2tp_session, referenced via session->priv[].
 */
struct pppol2tp_session {
	int			owner;		/* pid that opened the socket */

	struct mutex		sk_lock;	/* Protects .sk */
	struct sock __rcu	*sk;		/* Pointer to the session
						 * PPPoX socket */
	struct sock		*__sk;		/* Copy of .sk, for cleanup */
	struct rcu_head		rcu;		/* For asynchronous release */
	int			flags;		/* accessed by PPPIOCGFLAGS.
						 * Unused. */
};

static int pppol2tp_xmit(struct ppp_channel *chan, struct sk_buff *skb);

static const struct ppp_channel_ops pppol2tp_chan_ops = {
	.start_xmit =  pppol2tp_xmit,
};

static const struct proto_ops pppol2tp_ops;

/* Retrieves the pppol2tp socket associated to a session.
 * A reference is held on the returned socket, so this function must be paired
 * with sock_put().
 */
static struct sock *pppol2tp_session_get_sock(struct l2tp_session *session)
{
	struct pppol2tp_session *ps = l2tp_session_priv(session);
	struct sock *sk;

	rcu_read_lock();
	sk = rcu_dereference(ps->sk);
	if (sk)
		sock_hold(sk);
	rcu_read_unlock();

	return sk;
}

/* Helpers to obtain tunnel/session contexts from sockets.
 */
static inline struct l2tp_session *pppol2tp_sock_to_session(struct sock *sk)
{
	struct l2tp_session *session;

	if (sk == NULL)
		return NULL;

	sock_hold(sk);
	session = (struct l2tp_session *)(sk->sk_user_data);
	if (session == NULL) {
		sock_put(sk);
		goto out;
	}

	BUG_ON(session->magic != L2TP_SESSION_MAGIC);

out:
	return session;
}

/*****************************************************************************
 * Receive data handling
 *****************************************************************************/

static int pppol2tp_recv_payload_hook(struct sk_buff *skb)
{
	/* Skip PPP header, if present.	 In testing, Microsoft L2TP clients
	 * don't send the PPP header (PPP header compression enabled), but
	 * other clients can include the header. So we cope with both cases
	 * here. The PPP header is always FF03 when using L2TP.
	 *
	 * Note that skb->data[] isn't dereferenced from a u16 ptr here since
	 * the field may be unaligned.
	 */
	if (!pskb_may_pull(skb, 2))
		return 1;

	if ((skb->data[0] == PPP_ALLSTATIONS) && (skb->data[1] == PPP_UI))
		skb_pull(skb, 2);

	return 0;
}

/* Receive message. This is the recvmsg for the PPPoL2TP socket.
 */
static int pppol2tp_recvmsg(struct socket *sock, struct msghdr *msg,
			    size_t len, int flags)
{
	int err;
	struct sk_buff *skb;
	struct sock *sk = sock->sk;

	err = -EIO;
	if (sk->sk_state & PPPOX_BOUND)
		goto end;

	err = 0;
	skb = skb_recv_datagram(sk, flags & ~MSG_DONTWAIT,
				flags & MSG_DONTWAIT, &err);
	if (!skb)
		goto end;

	if (len > skb->len)
		len = skb->len;
	else if (len < skb->len)
		msg->msg_flags |= MSG_TRUNC;

	err = skb_copy_datagram_msg(skb, 0, msg, len);
	if (likely(err == 0))
		err = len;

	kfree_skb(skb);
end:
	return err;
}

static void pppol2tp_recv(struct l2tp_session *session, struct sk_buff *skb, int data_len)
{
	struct pppol2tp_session *ps = l2tp_session_priv(session);
	struct sock *sk = NULL;

	/* If the socket is bound, send it in to PPP's input queue. Otherwise
	 * queue it on the session socket.
	 */
	rcu_read_lock();
	sk = rcu_dereference(ps->sk);
	if (sk == NULL)
		goto no_sock;

	if (sk->sk_state & PPPOX_BOUND) {
		struct pppox_sock *po;

		l2tp_dbg(session, L2TP_MSG_DATA,
			 "%s: recv %d byte data frame, passing to ppp\n",
			 session->name, data_len);

		po = pppox_sk(sk);
		ppp_input(&po->chan, skb);
	} else {
		l2tp_dbg(session, L2TP_MSG_DATA,
			 "%s: recv %d byte data frame, passing to L2TP socket\n",
			 session->name, data_len);

		if (sock_queue_rcv_skb(sk, skb) < 0) {
			atomic_long_inc(&session->stats.rx_errors);
			kfree_skb(skb);
		}
	}
	rcu_read_unlock();

	return;

no_sock:
	rcu_read_unlock();
	l2tp_info(session, L2TP_MSG_DATA, "%s: no socket\n", session->name);
	kfree_skb(skb);
}

/************************************************************************
 * Transmit handling
 ***********************************************************************/

/* This is the sendmsg for the PPPoL2TP pppol2tp_session socket.  We come here
 * when a user application does a sendmsg() on the session socket. L2TP and
 * PPP headers must be inserted into the user's data.
 */
static int pppol2tp_sendmsg(struct socket *sock, struct msghdr *m,
			    size_t total_len)
{
	struct sock *sk = sock->sk;
	struct sk_buff *skb;
	int error;
	struct l2tp_session *session;
	struct l2tp_tunnel *tunnel;
	int uhlen;

	error = -ENOTCONN;
	if (sock_flag(sk, SOCK_DEAD) || !(sk->sk_state & PPPOX_CONNECTED))
		goto error;

	/* Get session and tunnel contexts */
	error = -EBADF;
	session = pppol2tp_sock_to_session(sk);
	if (session == NULL)
		goto error;

	tunnel = session->tunnel;

	uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;

	/* Allocate a socket buffer */
	error = -ENOMEM;
	skb = sock_wmalloc(sk, NET_SKB_PAD + sizeof(struct iphdr) +
			   uhlen + session->hdr_len +
			   2 + total_len, /* 2 bytes for PPP_ALLSTATIONS & PPP_UI */
			   0, GFP_KERNEL);
	if (!skb)
		goto error_put_sess;

	/* Reserve space for headers. */
	skb_reserve(skb, NET_SKB_PAD);
	skb_reset_network_header(skb);
	skb_reserve(skb, sizeof(struct iphdr));
	skb_reset_transport_header(skb);
	skb_reserve(skb, uhlen);

	/* Add PPP header */
	skb->data[0] = PPP_ALLSTATIONS;
	skb->data[1] = PPP_UI;
	skb_put(skb, 2);

	/* Copy user data into skb */
	error = memcpy_from_msg(skb_put(skb, total_len), m, total_len);
	if (error < 0) {
		kfree_skb(skb);
		goto error_put_sess;
	}

	local_bh_disable();
	l2tp_xmit_skb(session, skb, session->hdr_len);
	local_bh_enable();

	sock_put(sk);

	return total_len;

error_put_sess:
	sock_put(sk);
error:
	return error;
}

/* Transmit function called by generic PPP driver.  Sends PPP frame
 * over PPPoL2TP socket.
 *
 * This is almost the same as pppol2tp_sendmsg(), but rather than
 * being called with a msghdr from userspace, it is called with a skb
 * from the kernel.
 *
 * The supplied skb from ppp doesn't have enough headroom for the
 * insertion of L2TP, UDP and IP headers so we need to allocate more
 * headroom in the skb. This will create a cloned skb. But we must be
 * careful in the error case because the caller will expect to free
 * the skb it supplied, not our cloned skb. So we take care to always
 * leave the original skb unfreed if we return an error.
 */
static int pppol2tp_xmit(struct ppp_channel *chan, struct sk_buff *skb)
{
	struct sock *sk = (struct sock *) chan->private;
	struct l2tp_session *session;
	struct l2tp_tunnel *tunnel;
	int uhlen, headroom;

	if (sock_flag(sk, SOCK_DEAD) || !(sk->sk_state & PPPOX_CONNECTED))
		goto abort;

	/* Get session and tunnel contexts from the socket */
	session = pppol2tp_sock_to_session(sk);
	if (session == NULL)
		goto abort;

	tunnel = session->tunnel;

	uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
	headroom = NET_SKB_PAD +
		   sizeof(struct iphdr) + /* IP header */
		   uhlen +		/* UDP header (if L2TP_ENCAPTYPE_UDP) */
		   session->hdr_len +	/* L2TP header */
		   2;			/* 2 bytes for PPP_ALLSTATIONS & PPP_UI */
	if (skb_cow_head(skb, headroom))
		goto abort_put_sess;

	/* Setup PPP header */
	__skb_push(skb, 2);
	skb->data[0] = PPP_ALLSTATIONS;
	skb->data[1] = PPP_UI;

	local_bh_disable();
	l2tp_xmit_skb(session, skb, session->hdr_len);
	local_bh_enable();

	sock_put(sk);

	return 1;

abort_put_sess:
	sock_put(sk);
abort:
	/* Free the original skb */
	kfree_skb(skb);
	return 1;
}

/*****************************************************************************
 * Session (and tunnel control) socket create/destroy.
 *****************************************************************************/

/* Called by l2tp_core when a session socket is being closed.
 */
static void pppol2tp_session_close(struct l2tp_session *session)
{
	struct sock *sk;

	BUG_ON(session->magic != L2TP_SESSION_MAGIC);

	sk = pppol2tp_session_get_sock(session);
	if (sk) {
		if (sk->sk_socket)
			inet_shutdown(sk->sk_socket, SEND_SHUTDOWN);
		sock_put(sk);
	}
}

/* Really kill the session socket. (Called from sock_put() if
 * refcnt == 0.)
 */
static void pppol2tp_session_destruct(struct sock *sk)
{
	struct l2tp_session *session = sk->sk_user_data;

	skb_queue_purge(&sk->sk_receive_queue);
	skb_queue_purge(&sk->sk_write_queue);

	if (session) {
		sk->sk_user_data = NULL;
		BUG_ON(session->magic != L2TP_SESSION_MAGIC);
		l2tp_session_dec_refcount(session);
	}
}

static void pppol2tp_put_sk(struct rcu_head *head)
{
	struct pppol2tp_session *ps;

	ps = container_of(head, typeof(*ps), rcu);
	sock_put(ps->__sk);
}

/* Called when the PPPoX socket (session) is closed.
 */
static int pppol2tp_release(struct socket *sock)
{
	struct sock *sk = sock->sk;
	struct l2tp_session *session;
	int error;

	if (!sk)
		return 0;

	error = -EBADF;
	lock_sock(sk);
	if (sock_flag(sk, SOCK_DEAD) != 0)
		goto error;

	pppox_unbind_sock(sk);

	/* Signal the death of the socket. */
	sk->sk_state = PPPOX_DEAD;
	sock_orphan(sk);
	sock->sk = NULL;

	session = pppol2tp_sock_to_session(sk);

	if (session != NULL) {
		struct pppol2tp_session *ps;

		l2tp_session_delete(session);

		ps = l2tp_session_priv(session);
		mutex_lock(&ps->sk_lock);
		ps->__sk = rcu_dereference_protected(ps->sk,
						     lockdep_is_held(&ps->sk_lock));
		RCU_INIT_POINTER(ps->sk, NULL);
		mutex_unlock(&ps->sk_lock);
		call_rcu(&ps->rcu, pppol2tp_put_sk);

		/* Rely on the sock_put() call at the end of the function for
		 * dropping the reference held by pppol2tp_sock_to_session().
		 * The last reference will be dropped by pppol2tp_put_sk().
		 */
	}
	release_sock(sk);

	/* This will delete the session context via
	 * pppol2tp_session_destruct() if the socket's refcnt drops to
	 * zero.
	 */
	sock_put(sk);

	return 0;

error:
	release_sock(sk);
	return error;
}

static struct proto pppol2tp_sk_proto = {
	.name	  = "PPPOL2TP",
	.owner	  = THIS_MODULE,
	.obj_size = sizeof(struct pppox_sock),
};

static int pppol2tp_backlog_recv(struct sock *sk, struct sk_buff *skb)
{
	int rc;

	rc = l2tp_udp_encap_recv(sk, skb);
	if (rc)
		kfree_skb(skb);

	return NET_RX_SUCCESS;
}

/* socket() handler. Initialize a new struct sock.
 */
static int pppol2tp_create(struct net *net, struct socket *sock, int kern)
{
	int error = -ENOMEM;
	struct sock *sk;

	sk = sk_alloc(net, PF_PPPOX, GFP_KERNEL, &pppol2tp_sk_proto, kern);
	if (!sk)
		goto out;

	sock_init_data(sock, sk);

	sock->state  = SS_UNCONNECTED;
	sock->ops    = &pppol2tp_ops;

	sk->sk_backlog_rcv = pppol2tp_backlog_recv;
	sk->sk_protocol	   = PX_PROTO_OL2TP;
	sk->sk_family	   = PF_PPPOX;
	sk->sk_state	   = PPPOX_NONE;
	sk->sk_type	   = SOCK_STREAM;
	sk->sk_destruct	   = pppol2tp_session_destruct;

	error = 0;

out:
	return error;
}

#if IS_ENABLED(CONFIG_L2TP_DEBUGFS)
static void pppol2tp_show(struct seq_file *m, void *arg)
{
	struct l2tp_session *session = arg;
	struct sock *sk;

	sk = pppol2tp_session_get_sock(session);
	if (sk) {
		struct pppox_sock *po = pppox_sk(sk);

		seq_printf(m, "   interface %s\n", ppp_dev_name(&po->chan));
		sock_put(sk);
	}
}
#endif

static void pppol2tp_session_init(struct l2tp_session *session)
{
	struct pppol2tp_session *ps;
	struct dst_entry *dst;

	session->recv_skb = pppol2tp_recv;
	session->session_close = pppol2tp_session_close;
#if IS_ENABLED(CONFIG_L2TP_DEBUGFS)
	session->show = pppol2tp_show;
#endif

	ps = l2tp_session_priv(session);
	mutex_init(&ps->sk_lock);
	ps->owner = current->pid;

	/* If PMTU discovery was enabled, use the MTU that was discovered */
	dst = sk_dst_get(session->tunnel->sock);
	if (dst) {
		u32 pmtu = dst_mtu(dst);

		if (pmtu) {
			session->mtu = pmtu - PPPOL2TP_HEADER_OVERHEAD;
			session->mru = pmtu - PPPOL2TP_HEADER_OVERHEAD;
		}
		dst_release(dst);
	}
}

/* connect() handler. Attach a PPPoX socket to a tunnel UDP socket
 */
static int pppol2tp_connect(struct socket *sock, struct sockaddr *uservaddr,
			    int sockaddr_len, int flags)
{
	struct sock *sk = sock->sk;
	struct sockaddr_pppol2tp *sp = (struct sockaddr_pppol2tp *) uservaddr;
	struct pppox_sock *po = pppox_sk(sk);
	struct l2tp_session *session = NULL;
	struct l2tp_tunnel *tunnel;
	struct pppol2tp_session *ps;
	struct l2tp_session_cfg cfg = { 0, };
	int error = 0;
	u32 tunnel_id, peer_tunnel_id;
	u32 session_id, peer_session_id;
	bool drop_refcnt = false;
	bool drop_tunnel = false;
	int ver = 2;
	int fd;

	lock_sock(sk);

	error = -EINVAL;
	if (sp->sa_protocol != PX_PROTO_OL2TP)
		goto end;

	/* Check for already bound sockets */
	error = -EBUSY;
	if (sk->sk_state & PPPOX_CONNECTED)
		goto end;

	/* We don't supporting rebinding anyway */
	error = -EALREADY;
	if (sk->sk_user_data)
		goto end; /* socket is already attached */

	/* Get params from socket address. Handle L2TPv2 and L2TPv3.
	 * This is nasty because there are different sockaddr_pppol2tp
	 * structs for L2TPv2, L2TPv3, over IPv4 and IPv6. We use
	 * the sockaddr size to determine which structure the caller
	 * is using.
	 */
	peer_tunnel_id = 0;
	if (sockaddr_len == sizeof(struct sockaddr_pppol2tp)) {
		fd = sp->pppol2tp.fd;
		tunnel_id = sp->pppol2tp.s_tunnel;
		peer_tunnel_id = sp->pppol2tp.d_tunnel;
		session_id = sp->pppol2tp.s_session;
		peer_session_id = sp->pppol2tp.d_session;
	} else if (sockaddr_len == sizeof(struct sockaddr_pppol2tpv3)) {
		struct sockaddr_pppol2tpv3 *sp3 =
			(struct sockaddr_pppol2tpv3 *) sp;
		ver = 3;
		fd = sp3->pppol2tp.fd;
		tunnel_id = sp3->pppol2tp.s_tunnel;
		peer_tunnel_id = sp3->pppol2tp.d_tunnel;
		session_id = sp3->pppol2tp.s_session;
		peer_session_id = sp3->pppol2tp.d_session;
	} else if (sockaddr_len == sizeof(struct sockaddr_pppol2tpin6)) {
		struct sockaddr_pppol2tpin6 *sp6 =
			(struct sockaddr_pppol2tpin6 *) sp;
		fd = sp6->pppol2tp.fd;
		tunnel_id = sp6->pppol2tp.s_tunnel;
		peer_tunnel_id = sp6->pppol2tp.d_tunnel;
		session_id = sp6->pppol2tp.s_session;
		peer_session_id = sp6->pppol2tp.d_session;
	} else if (sockaddr_len == sizeof(struct sockaddr_pppol2tpv3in6)) {
		struct sockaddr_pppol2tpv3in6 *sp6 =
			(struct sockaddr_pppol2tpv3in6 *) sp;
		ver = 3;
		fd = sp6->pppol2tp.fd;
		tunnel_id = sp6->pppol2tp.s_tunnel;
		peer_tunnel_id = sp6->pppol2tp.d_tunnel;
		session_id = sp6->pppol2tp.s_session;
		peer_session_id = sp6->pppol2tp.d_session;
	} else {
		error = -EINVAL;
		goto end; /* bad socket address */
	}

	/* Don't bind if tunnel_id is 0 */
	error = -EINVAL;
	if (tunnel_id == 0)
		goto end;

	tunnel = l2tp_tunnel_get(sock_net(sk), tunnel_id);
	if (tunnel)
		drop_tunnel = true;

	/* Special case: create tunnel context if session_id and
	 * peer_session_id is 0. Otherwise look up tunnel using supplied
	 * tunnel id.
	 */
	if ((session_id == 0) && (peer_session_id == 0)) {
		if (tunnel == NULL) {
			struct l2tp_tunnel_cfg tcfg = {
				.encap = L2TP_ENCAPTYPE_UDP,
				.debug = 0,
			};
			error = l2tp_tunnel_create(sock_net(sk), fd, ver, tunnel_id, peer_tunnel_id, &tcfg, &tunnel);
			if (error < 0)
				goto end;
		}
	} else {
		/* Error if we can't find the tunnel */
		error = -ENOENT;
		if (tunnel == NULL)
			goto end;

		/* Error if socket is not prepped */
		if (tunnel->sock == NULL)
			goto end;
	}

	if (tunnel->recv_payload_hook == NULL)
		tunnel->recv_payload_hook = pppol2tp_recv_payload_hook;

	if (tunnel->peer_tunnel_id == 0)
		tunnel->peer_tunnel_id = peer_tunnel_id;

	session = l2tp_session_get(sock_net(sk), tunnel, session_id);
	if (session) {
		drop_refcnt = true;
		ps = l2tp_session_priv(session);

		/* Using a pre-existing session is fine as long as it hasn't
		 * been connected yet.
		 */
		mutex_lock(&ps->sk_lock);
		if (rcu_dereference_protected(ps->sk,
					      lockdep_is_held(&ps->sk_lock))) {
			mutex_unlock(&ps->sk_lock);
			error = -EEXIST;
			goto end;
		}
	} else {
		/* Default MTU must allow space for UDP/L2TP/PPP headers */
		cfg.mtu = 1500 - PPPOL2TP_HEADER_OVERHEAD;
		cfg.mru = cfg.mtu;

		session = l2tp_session_create(sizeof(struct pppol2tp_session),
					      tunnel, session_id,
					      peer_session_id, &cfg);
		if (IS_ERR(session)) {
			error = PTR_ERR(session);
			goto end;
		}

		pppol2tp_session_init(session);
		ps = l2tp_session_priv(session);
		l2tp_session_inc_refcount(session);

		mutex_lock(&ps->sk_lock);
		error = l2tp_session_register(session, tunnel);
		if (error < 0) {
			mutex_unlock(&ps->sk_lock);
			kfree(session);
			goto end;
		}
		drop_refcnt = true;
	}

	/* Special case: if source & dest session_id == 0x0000, this
	 * socket is being created to manage the tunnel. Just set up
	 * the internal context for use by ioctl() and sockopt()
	 * handlers.
	 */
	if ((session->session_id == 0) &&
	    (session->peer_session_id == 0)) {
		error = 0;
		goto out_no_ppp;
	}

	/* The only header we need to worry about is the L2TP
	 * header. This size is different depending on whether
	 * sequence numbers are enabled for the data channel.
	 */
	po->chan.hdrlen = PPPOL2TP_L2TP_HDR_SIZE_NOSEQ;

	po->chan.private = sk;
	po->chan.ops	 = &pppol2tp_chan_ops;
	po->chan.mtu	 = session->mtu;

	error = ppp_register_net_channel(sock_net(sk), &po->chan);
	if (error) {
		mutex_unlock(&ps->sk_lock);
		goto end;
	}

out_no_ppp:
	/* This is how we get the session context from the socket. */
	sk->sk_user_data = session;
	rcu_assign_pointer(ps->sk, sk);
	mutex_unlock(&ps->sk_lock);

	/* Keep the reference we've grabbed on the session: sk doesn't expect
	 * the session to disappear. pppol2tp_session_destruct() is responsible
	 * for dropping it.
	 */
	drop_refcnt = false;

	sk->sk_state = PPPOX_CONNECTED;
	l2tp_info(session, L2TP_MSG_CONTROL, "%s: created\n",
		  session->name);

end:
	if (drop_refcnt)
		l2tp_session_dec_refcount(session);
	if (drop_tunnel)
		l2tp_tunnel_dec_refcount(tunnel);
	release_sock(sk);

	return error;
}

#ifdef CONFIG_L2TP_V3

/* Called when creating sessions via the netlink interface. */
static int pppol2tp_session_create(struct net *net, struct l2tp_tunnel *tunnel,
				   u32 session_id, u32 peer_session_id,
				   struct l2tp_session_cfg *cfg)
{
	int error;
	struct l2tp_session *session;

	/* Error if tunnel socket is not prepped */
	if (!tunnel->sock) {
		error = -ENOENT;
		goto err;
	}

	/* Default MTU values. */
	if (cfg->mtu == 0)
		cfg->mtu = 1500 - PPPOL2TP_HEADER_OVERHEAD;
	if (cfg->mru == 0)
		cfg->mru = cfg->mtu;

	/* Allocate and initialize a new session context. */
	session = l2tp_session_create(sizeof(struct pppol2tp_session),
				      tunnel, session_id,
				      peer_session_id, cfg);
	if (IS_ERR(session)) {
		error = PTR_ERR(session);
		goto err;
	}

	pppol2tp_session_init(session);

	error = l2tp_session_register(session, tunnel);
	if (error < 0)
		goto err_sess;

	return 0;

err_sess:
	kfree(session);
err:
	return error;
}

#endif /* CONFIG_L2TP_V3 */

/* getname() support.
 */
static int pppol2tp_getname(struct socket *sock, struct sockaddr *uaddr,
			    int *usockaddr_len, int peer)
{
	int len = 0;
	int error = 0;
	struct l2tp_session *session;
	struct l2tp_tunnel *tunnel;
	struct sock *sk = sock->sk;
	struct inet_sock *inet;
	struct pppol2tp_session *pls;

	error = -ENOTCONN;
	if (sk == NULL)
		goto end;
	if (!(sk->sk_state & PPPOX_CONNECTED))
		goto end;

	error = -EBADF;
	session = pppol2tp_sock_to_session(sk);
	if (session == NULL)
		goto end;

	pls = l2tp_session_priv(session);
	tunnel = session->tunnel;

	inet = inet_sk(tunnel->sock);
	if ((tunnel->version == 2) && (tunnel->sock->sk_family == AF_INET)) {
		struct sockaddr_pppol2tp sp;
		len = sizeof(sp);
		memset(&sp, 0, len);
		sp.sa_family	= AF_PPPOX;
		sp.sa_protocol	= PX_PROTO_OL2TP;
		sp.pppol2tp.fd  = tunnel->fd;
		sp.pppol2tp.pid = pls->owner;
		sp.pppol2tp.s_tunnel = tunnel->tunnel_id;
		sp.pppol2tp.d_tunnel = tunnel->peer_tunnel_id;
		sp.pppol2tp.s_session = session->session_id;
		sp.pppol2tp.d_session = session->peer_session_id;
		sp.pppol2tp.addr.sin_family = AF_INET;
		sp.pppol2tp.addr.sin_port = inet->inet_dport;
		sp.pppol2tp.addr.sin_addr.s_addr = inet->inet_daddr;
		memcpy(uaddr, &sp, len);
#if IS_ENABLED(CONFIG_IPV6)
	} else if ((tunnel->version == 2) &&
		   (tunnel->sock->sk_family == AF_INET6)) {
		struct sockaddr_pppol2tpin6 sp;

		len = sizeof(sp);
		memset(&sp, 0, len);
		sp.sa_family	= AF_PPPOX;
		sp.sa_protocol	= PX_PROTO_OL2TP;
		sp.pppol2tp.fd  = tunnel->fd;
		sp.pppol2tp.pid = pls->owner;
		sp.pppol2tp.s_tunnel = tunnel->tunnel_id;
		sp.pppol2tp.d_tunnel = tunnel->peer_tunnel_id;
		sp.pppol2tp.s_session = session->session_id;
		sp.pppol2tp.d_session = session->peer_session_id;
		sp.pppol2tp.addr.sin6_family = AF_INET6;
		sp.pppol2tp.addr.sin6_port = inet->inet_dport;
		memcpy(&sp.pppol2tp.addr.sin6_addr, &tunnel->sock->sk_v6_daddr,
		       sizeof(tunnel->sock->sk_v6_daddr));
		memcpy(uaddr, &sp, len);
	} else if ((tunnel->version == 3) &&
		   (tunnel->sock->sk_family == AF_INET6)) {
		struct sockaddr_pppol2tpv3in6 sp;

		len = sizeof(sp);
		memset(&sp, 0, len);
		sp.sa_family	= AF_PPPOX;
		sp.sa_protocol	= PX_PROTO_OL2TP;
		sp.pppol2tp.fd  = tunnel->fd;
		sp.pppol2tp.pid = pls->owner;
		sp.pppol2tp.s_tunnel = tunnel->tunnel_id;
		sp.pppol2tp.d_tunnel = tunnel->peer_tunnel_id;
		sp.pppol2tp.s_session = session->session_id;
		sp.pppol2tp.d_session = session->peer_session_id;
		sp.pppol2tp.addr.sin6_family = AF_INET6;
		sp.pppol2tp.addr.sin6_port = inet->inet_dport;
		memcpy(&sp.pppol2tp.addr.sin6_addr, &tunnel->sock->sk_v6_daddr,
		       sizeof(tunnel->sock->sk_v6_daddr));
		memcpy(uaddr, &sp, len);
#endif
	} else if (tunnel->version == 3) {
		struct sockaddr_pppol2tpv3 sp;
		len = sizeof(sp);
		memset(&sp, 0, len);
		sp.sa_family	= AF_PPPOX;
		sp.sa_protocol	= PX_PROTO_OL2TP;
		sp.pppol2tp.fd  = tunnel->fd;
		sp.pppol2tp.pid = pls->owner;
		sp.pppol2tp.s_tunnel = tunnel->tunnel_id;
		sp.pppol2tp.d_tunnel = tunnel->peer_tunnel_id;
		sp.pppol2tp.s_session = session->session_id;
		sp.pppol2tp.d_session = session->peer_session_id;
		sp.pppol2tp.addr.sin_family = AF_INET;
		sp.pppol2tp.addr.sin_port = inet->inet_dport;
		sp.pppol2tp.addr.sin_addr.s_addr = inet->inet_daddr;
		memcpy(uaddr, &sp, len);
	}

	*usockaddr_len = len;
	error = 0;

	sock_put(sk);
end:
	return error;
}

/****************************************************************************
 * ioctl() handlers.
 *
 * The PPPoX socket is created for L2TP sessions: tunnels have their own UDP
 * sockets. However, in order to control kernel tunnel features, we allow
 * userspace to create a special "tunnel" PPPoX socket which is used for
 * control only.  Tunnel PPPoX sockets have session_id == 0 and simply allow
 * the user application to issue L2TP setsockopt(), getsockopt() and ioctl()
 * calls.
 ****************************************************************************/

static void pppol2tp_copy_stats(struct pppol2tp_ioc_stats *dest,
				struct l2tp_stats *stats)
{
	dest->tx_packets = atomic_long_read(&stats->tx_packets);
	dest->tx_bytes = atomic_long_read(&stats->tx_bytes);
	dest->tx_errors = atomic_long_read(&stats->tx_errors);
	dest->rx_packets = atomic_long_read(&stats->rx_packets);
	dest->rx_bytes = atomic_long_read(&stats->rx_bytes);
	dest->rx_seq_discards = atomic_long_read(&stats->rx_seq_discards);
	dest->rx_oos_packets = atomic_long_read(&stats->rx_oos_packets);
	dest->rx_errors = atomic_long_read(&stats->rx_errors);
}

/* Session ioctl helper.
 */
static int pppol2tp_session_ioctl(struct l2tp_session *session,
				  unsigned int cmd, unsigned long arg)
{
	struct ifreq ifr;
	int err = 0;
	struct sock *sk;
	int val = (int) arg;
	struct pppol2tp_session *ps = l2tp_session_priv(session);
	struct l2tp_tunnel *tunnel = session->tunnel;
	struct pppol2tp_ioc_stats stats;

	l2tp_dbg(session, L2TP_MSG_CONTROL,
		 "%s: pppol2tp_session_ioctl(cmd=%#x, arg=%#lx)\n",
		 session->name, cmd, arg);

	sk = pppol2tp_session_get_sock(session);
	if (!sk)
		return -EBADR;

	switch (cmd) {
	case SIOCGIFMTU:
		err = -ENXIO;
		if (!(sk->sk_state & PPPOX_CONNECTED))
			break;

		err = -EFAULT;
		if (copy_from_user(&ifr, (void __user *) arg, sizeof(struct ifreq)))
			break;
		ifr.ifr_mtu = session->mtu;
		if (copy_to_user((void __user *) arg, &ifr, sizeof(struct ifreq)))
			break;

		l2tp_info(session, L2TP_MSG_CONTROL, "%s: get mtu=%d\n",
			  session->name, session->mtu);
		err = 0;
		break;

	case SIOCSIFMTU:
		err = -ENXIO;
		if (!(sk->sk_state & PPPOX_CONNECTED))
			break;

		err = -EFAULT;
		if (copy_from_user(&ifr, (void __user *) arg, sizeof(struct ifreq)))
			break;

		session->mtu = ifr.ifr_mtu;

		l2tp_info(session, L2TP_MSG_CONTROL, "%s: set mtu=%d\n",
			  session->name, session->mtu);
		err = 0;
		break;

	case PPPIOCGMRU:
		err = -ENXIO;
		if (!(sk->sk_state & PPPOX_CONNECTED))
			break;

		err = -EFAULT;
		if (put_user(session->mru, (int __user *) arg))
			break;

		l2tp_info(session, L2TP_MSG_CONTROL, "%s: get mru=%d\n",
			  session->name, session->mru);
		err = 0;
		break;

	case PPPIOCSMRU:
		err = -ENXIO;
		if (!(sk->sk_state & PPPOX_CONNECTED))
			break;

		err = -EFAULT;
		if (get_user(val, (int __user *) arg))
			break;

		session->mru = val;
		l2tp_info(session, L2TP_MSG_CONTROL, "%s: set mru=%d\n",
			  session->name, session->mru);
		err = 0;
		break;

	case PPPIOCGFLAGS:
		err = -EFAULT;
		if (put_user(ps->flags, (int __user *) arg))
			break;

		l2tp_info(session, L2TP_MSG_CONTROL, "%s: get flags=%d\n",
			  session->name, ps->flags);
		err = 0;
		break;

	case PPPIOCSFLAGS:
		err = -EFAULT;
		if (get_user(val, (int __user *) arg))
			break;
		ps->flags = val;
		l2tp_info(session, L2TP_MSG_CONTROL, "%s: set flags=%d\n",
			  session->name, ps->flags);
		err = 0;
		break;

	case PPPIOCGL2TPSTATS:
		err = -ENXIO;
		if (!(sk->sk_state & PPPOX_CONNECTED))
			break;

		memset(&stats, 0, sizeof(stats));
		stats.tunnel_id = tunnel->tunnel_id;
		stats.session_id = session->session_id;
		pppol2tp_copy_stats(&stats, &session->stats);
		if (copy_to_user((void __user *) arg, &stats,
				 sizeof(stats)))
			break;
		l2tp_info(session, L2TP_MSG_CONTROL, "%s: get L2TP stats\n",
			  session->name);
		err = 0;
		break;

	default:
		err = -ENOSYS;
		break;
	}

	sock_put(sk);

	return err;
}

/* Tunnel ioctl helper.
 *
 * Note the special handling for PPPIOCGL2TPSTATS below. If the ioctl data
 * specifies a session_id, the session ioctl handler is called. This allows an
 * application to retrieve session stats via a tunnel socket.
 */
static int pppol2tp_tunnel_ioctl(struct l2tp_tunnel *tunnel,
				 unsigned int cmd, unsigned long arg)
{
	int err = 0;
	struct sock *sk;
	struct pppol2tp_ioc_stats stats;

	l2tp_dbg(tunnel, L2TP_MSG_CONTROL,
		 "%s: pppol2tp_tunnel_ioctl(cmd=%#x, arg=%#lx)\n",
		 tunnel->name, cmd, arg);

	sk = tunnel->sock;
	sock_hold(sk);

	switch (cmd) {
	case PPPIOCGL2TPSTATS:
		err = -ENXIO;
		if (!(sk->sk_state & PPPOX_CONNECTED))
			break;

		if (copy_from_user(&stats, (void __user *) arg,
				   sizeof(stats))) {
			err = -EFAULT;
			break;
		}
		if (stats.session_id != 0) {
			/* resend to session ioctl handler */
			struct l2tp_session *session =
				l2tp_session_get(sock_net(sk), tunnel,
						 stats.session_id);

			if (session) {
				err = pppol2tp_session_ioctl(session, cmd,
							     arg);
				l2tp_session_dec_refcount(session);
			} else {
				err = -EBADR;
			}
			break;
		}
#ifdef CONFIG_XFRM
		stats.using_ipsec = (sk->sk_policy[0] || sk->sk_policy[1]) ? 1 : 0;
#endif
		pppol2tp_copy_stats(&stats, &tunnel->stats);
		if (copy_to_user((void __user *) arg, &stats, sizeof(stats))) {
			err = -EFAULT;
			break;
		}
		l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: get L2TP stats\n",
			  tunnel->name);
		err = 0;
		break;

	default:
		err = -ENOSYS;
		break;
	}

	sock_put(sk);

	return err;
}

/* Main ioctl() handler.
 * Dispatch to tunnel or session helpers depending on the socket.
 */
static int pppol2tp_ioctl(struct socket *sock, unsigned int cmd,
			  unsigned long arg)
{
	struct sock *sk = sock->sk;
	struct l2tp_session *session;
	struct l2tp_tunnel *tunnel;
	int err;

	if (!sk)
		return 0;

	err = -EBADF;
	if (sock_flag(sk, SOCK_DEAD) != 0)
		goto end;

	err = -ENOTCONN;
	if ((sk->sk_user_data == NULL) ||
	    (!(sk->sk_state & (PPPOX_CONNECTED | PPPOX_BOUND))))
		goto end;

	/* Get session context from the socket */
	err = -EBADF;
	session = pppol2tp_sock_to_session(sk);
	if (session == NULL)
		goto end;

	/* Special case: if session's session_id is zero, treat ioctl as a
	 * tunnel ioctl
	 */
	if ((session->session_id == 0) &&
	    (session->peer_session_id == 0)) {
		tunnel = session->tunnel;
		err = pppol2tp_tunnel_ioctl(tunnel, cmd, arg);
		goto end_put_sess;
	}

	err = pppol2tp_session_ioctl(session, cmd, arg);

end_put_sess:
	sock_put(sk);
end:
	return err;
}

/*****************************************************************************
 * setsockopt() / getsockopt() support.
 *
 * The PPPoX socket is created for L2TP sessions: tunnels have their own UDP
 * sockets. In order to control kernel tunnel features, we allow userspace to
 * create a special "tunnel" PPPoX socket which is used for control only.
 * Tunnel PPPoX sockets have session_id == 0 and simply allow the user
 * application to issue L2TP setsockopt(), getsockopt() and ioctl() calls.
 *****************************************************************************/

/* Tunnel setsockopt() helper.
 */
static int pppol2tp_tunnel_setsockopt(struct sock *sk,
				      struct l2tp_tunnel *tunnel,
				      int optname, int val)
{
	int err = 0;

	switch (optname) {
	case PPPOL2TP_SO_DEBUG:
		tunnel->debug = val;
		l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: set debug=%x\n",
			  tunnel->name, tunnel->debug);
		break;

	default:
		err = -ENOPROTOOPT;
		break;
	}

	return err;
}

/* Session setsockopt helper.
 */
static int pppol2tp_session_setsockopt(struct sock *sk,
				       struct l2tp_session *session,
				       int optname, int val)
{
	int err = 0;

	switch (optname) {
	case PPPOL2TP_SO_RECVSEQ:
		if ((val != 0) && (val != 1)) {
			err = -EINVAL;
			break;
		}
		session->recv_seq = !!val;
		l2tp_info(session, L2TP_MSG_CONTROL,
			  "%s: set recv_seq=%d\n",
			  session->name, session->recv_seq);
		break;

	case PPPOL2TP_SO_SENDSEQ:
		if ((val != 0) && (val != 1)) {
			err = -EINVAL;
			break;
		}
		session->send_seq = !!val;
		{
			struct pppox_sock *po = pppox_sk(sk);

			po->chan.hdrlen = val ? PPPOL2TP_L2TP_HDR_SIZE_SEQ :
				PPPOL2TP_L2TP_HDR_SIZE_NOSEQ;
		}
		l2tp_session_set_header_len(session, session->tunnel->version);
		l2tp_info(session, L2TP_MSG_CONTROL,
			  "%s: set send_seq=%d\n",
			  session->name, session->send_seq);
		break;

	case PPPOL2TP_SO_LNSMODE:
		if ((val != 0) && (val != 1)) {
			err = -EINVAL;
			break;
		}
		session->lns_mode = !!val;
		l2tp_info(session, L2TP_MSG_CONTROL,
			  "%s: set lns_mode=%d\n",
			  session->name, session->lns_mode);
		break;

	case PPPOL2TP_SO_DEBUG:
		session->debug = val;
		l2tp_info(session, L2TP_MSG_CONTROL, "%s: set debug=%x\n",
			  session->name, session->debug);
		break;

	case PPPOL2TP_SO_REORDERTO:
		session->reorder_timeout = msecs_to_jiffies(val);
		l2tp_info(session, L2TP_MSG_CONTROL,
			  "%s: set reorder_timeout=%d\n",
			  session->name, session->reorder_timeout);
		break;

	default:
		err = -ENOPROTOOPT;
		break;
	}

	return err;
}

/* Main setsockopt() entry point.
 * Does API checks, then calls either the tunnel or session setsockopt
 * handler, according to whether the PPPoL2TP socket is a for a regular
 * session or the special tunnel type.
 */
static int pppol2tp_setsockopt(struct socket *sock, int level, int optname,
			       char __user *optval, unsigned int optlen)
{
	struct sock *sk = sock->sk;
	struct l2tp_session *session;
	struct l2tp_tunnel *tunnel;
	int val;
	int err;

	if (level != SOL_PPPOL2TP)
		return -EINVAL;

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

	if (get_user(val, (int __user *)optval))
		return -EFAULT;

	err = -ENOTCONN;
	if (sk->sk_user_data == NULL)
		goto end;

	/* Get session context from the socket */
	err = -EBADF;
	session = pppol2tp_sock_to_session(sk);
	if (session == NULL)
		goto end;

	/* Special case: if session_id == 0x0000, treat as operation on tunnel
	 */
	if ((session->session_id == 0) &&
	    (session->peer_session_id == 0)) {
		tunnel = session->tunnel;
		err = pppol2tp_tunnel_setsockopt(sk, tunnel, optname, val);
	} else {
		err = pppol2tp_session_setsockopt(sk, session, optname, val);
	}

	sock_put(sk);
end:
	return err;
}

/* Tunnel getsockopt helper. Called with sock locked.
 */
static int pppol2tp_tunnel_getsockopt(struct sock *sk,
				      struct l2tp_tunnel *tunnel,
				      int optname, int *val)
{
	int err = 0;

	switch (optname) {
	case PPPOL2TP_SO_DEBUG:
		*val = tunnel->debug;
		l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: get debug=%x\n",
			  tunnel->name, tunnel->debug);
		break;

	default:
		err = -ENOPROTOOPT;
		break;
	}

	return err;
}

/* Session getsockopt helper. Called with sock locked.
 */
static int pppol2tp_session_getsockopt(struct sock *sk,
				       struct l2tp_session *session,
				       int optname, int *val)
{
	int err = 0;

	switch (optname) {
	case PPPOL2TP_SO_RECVSEQ:
		*val = session->recv_seq;
		l2tp_info(session, L2TP_MSG_CONTROL,
			  "%s: get recv_seq=%d\n", session->name, *val);
		break;

	case PPPOL2TP_SO_SENDSEQ:
		*val = session->send_seq;
		l2tp_info(session, L2TP_MSG_CONTROL,
			  "%s: get send_seq=%d\n", session->name, *val);
		break;

	case PPPOL2TP_SO_LNSMODE:
		*val = session->lns_mode;
		l2tp_info(session, L2TP_MSG_CONTROL,
			  "%s: get lns_mode=%d\n", session->name, *val);
		break;

	case PPPOL2TP_SO_DEBUG:
		*val = session->debug;
		l2tp_info(session, L2TP_MSG_CONTROL, "%s: get debug=%d\n",
			  session->name, *val);
		break;

	case PPPOL2TP_SO_REORDERTO:
		*val = (int) jiffies_to_msecs(session->reorder_timeout);
		l2tp_info(session, L2TP_MSG_CONTROL,
			  "%s: get reorder_timeout=%d\n", session->name, *val);
		break;

	default:
		err = -ENOPROTOOPT;
	}

	return err;
}

/* Main getsockopt() entry point.
 * Does API checks, then calls either the tunnel or session getsockopt
 * handler, according to whether the PPPoX socket is a for a regular session
 * or the special tunnel type.
 */
static int pppol2tp_getsockopt(struct socket *sock, int level, int optname,
			       char __user *optval, int __user *optlen)
{
	struct sock *sk = sock->sk;
	struct l2tp_session *session;
	struct l2tp_tunnel *tunnel;
	int val, len;
	int err;

	if (level != SOL_PPPOL2TP)
		return -EINVAL;

	if (get_user(len, optlen))
		return -EFAULT;

	len = min_t(unsigned int, len, sizeof(int));

	if (len < 0)
		return -EINVAL;

	err = -ENOTCONN;
	if (sk->sk_user_data == NULL)
		goto end;

	/* Get the session context */
	err = -EBADF;
	session = pppol2tp_sock_to_session(sk);
	if (session == NULL)
		goto end;

	/* Special case: if session_id == 0x0000, treat as operation on tunnel */
	if ((session->session_id == 0) &&
	    (session->peer_session_id == 0)) {
		tunnel = session->tunnel;
		err = pppol2tp_tunnel_getsockopt(sk, tunnel, optname, &val);
		if (err)
			goto end_put_sess;
	} else {
		err = pppol2tp_session_getsockopt(sk, session, optname, &val);
		if (err)
			goto end_put_sess;
	}

	err = -EFAULT;
	if (put_user(len, optlen))
		goto end_put_sess;

	if (copy_to_user((void __user *) optval, &val, len))
		goto end_put_sess;

	err = 0;

end_put_sess:
	sock_put(sk);
end:
	return err;
}

/*****************************************************************************
 * /proc filesystem for debug
 * Since the original pppol2tp driver provided /proc/net/pppol2tp for
 * L2TPv2, we dump only L2TPv2 tunnels and sessions here.
 *****************************************************************************/

static unsigned int pppol2tp_net_id;

#ifdef CONFIG_PROC_FS

struct pppol2tp_seq_data {
	struct seq_net_private p;
	int tunnel_idx;			/* current tunnel */
	int session_idx;		/* index of session within current tunnel */
	struct l2tp_tunnel *tunnel;
	struct l2tp_session *session;	/* NULL means get next tunnel */
};

static void pppol2tp_next_tunnel(struct net *net, struct pppol2tp_seq_data *pd)
{
	for (;;) {
		pd->tunnel = l2tp_tunnel_find_nth(net, pd->tunnel_idx);
		pd->tunnel_idx++;

		if (pd->tunnel == NULL)
			break;

		/* Ignore L2TPv3 tunnels */
		if (pd->tunnel->version < 3)
			break;
	}
}

static void pppol2tp_next_session(struct net *net, struct pppol2tp_seq_data *pd)
{
	pd->session = l2tp_session_get_nth(pd->tunnel, pd->session_idx);
	pd->session_idx++;

	if (pd->session == NULL) {
		pd->session_idx = 0;
		pppol2tp_next_tunnel(net, pd);
	}
}

static void *pppol2tp_seq_start(struct seq_file *m, loff_t *offs)
{
	struct pppol2tp_seq_data *pd = SEQ_START_TOKEN;
	loff_t pos = *offs;
	struct net *net;

	if (!pos)
		goto out;

	BUG_ON(m->private == NULL);
	pd = m->private;
	net = seq_file_net(m);

	if (pd->tunnel == NULL)
		pppol2tp_next_tunnel(net, pd);
	else
		pppol2tp_next_session(net, pd);

	/* NULL tunnel and session indicates end of list */
	if ((pd->tunnel == NULL) && (pd->session == NULL))
		pd = NULL;

out:
	return pd;
}

static void *pppol2tp_seq_next(struct seq_file *m, void *v, loff_t *pos)
{
	(*pos)++;
	return NULL;
}

static void pppol2tp_seq_stop(struct seq_file *p, void *v)
{
	/* nothing to do */
}

static void pppol2tp_seq_tunnel_show(struct seq_file *m, void *v)
{
	struct l2tp_tunnel *tunnel = v;

	seq_printf(m, "\nTUNNEL '%s', %c %d\n",
		   tunnel->name,
		   (tunnel == tunnel->sock->sk_user_data) ? 'Y' : 'N',
		   refcount_read(&tunnel->ref_count) - 1);
	seq_printf(m, " %08x %ld/%ld/%ld %ld/%ld/%ld\n",
		   tunnel->debug,
		   atomic_long_read(&tunnel->stats.tx_packets),
		   atomic_long_read(&tunnel->stats.tx_bytes),
		   atomic_long_read(&tunnel->stats.tx_errors),
		   atomic_long_read(&tunnel->stats.rx_packets),
		   atomic_long_read(&tunnel->stats.rx_bytes),
		   atomic_long_read(&tunnel->stats.rx_errors));
}

static void pppol2tp_seq_session_show(struct seq_file *m, void *v)
{
	struct l2tp_session *session = v;
	struct l2tp_tunnel *tunnel = session->tunnel;
	unsigned char state;
	char user_data_ok;
	struct sock *sk;
	u32 ip = 0;
	u16 port = 0;

	if (tunnel->sock) {
		struct inet_sock *inet = inet_sk(tunnel->sock);
		ip = ntohl(inet->inet_saddr);
		port = ntohs(inet->inet_sport);
	}

	sk = pppol2tp_session_get_sock(session);
	if (sk) {
		state = sk->sk_state;
		user_data_ok = (session == sk->sk_user_data) ? 'Y' : 'N';
	} else {
		state = 0;
		user_data_ok = 'N';
	}

	seq_printf(m, "  SESSION '%s' %08X/%d %04X/%04X -> "
		   "%04X/%04X %d %c\n",
		   session->name, ip, port,
		   tunnel->tunnel_id,
		   session->session_id,
		   tunnel->peer_tunnel_id,
		   session->peer_session_id,
		   state, user_data_ok);
	seq_printf(m, "   %d/%d/%c/%c/%s %08x %u\n",
		   session->mtu, session->mru,
		   session->recv_seq ? 'R' : '-',
		   session->send_seq ? 'S' : '-',
		   session->lns_mode ? "LNS" : "LAC",
		   session->debug,
		   jiffies_to_msecs(session->reorder_timeout));
	seq_printf(m, "   %hu/%hu %ld/%ld/%ld %ld/%ld/%ld\n",
		   session->nr, session->ns,
		   atomic_long_read(&session->stats.tx_packets),
		   atomic_long_read(&session->stats.tx_bytes),
		   atomic_long_read(&session->stats.tx_errors),
		   atomic_long_read(&session->stats.rx_packets),
		   atomic_long_read(&session->stats.rx_bytes),
		   atomic_long_read(&session->stats.rx_errors));

	if (sk) {
		struct pppox_sock *po = pppox_sk(sk);

		seq_printf(m, "   interface %s\n", ppp_dev_name(&po->chan));
		sock_put(sk);
	}
}

static int pppol2tp_seq_show(struct seq_file *m, void *v)
{
	struct pppol2tp_seq_data *pd = v;

	/* display header on line 1 */
	if (v == SEQ_START_TOKEN) {
		seq_puts(m, "PPPoL2TP driver info, " PPPOL2TP_DRV_VERSION "\n");
		seq_puts(m, "TUNNEL name, user-data-ok session-count\n");
		seq_puts(m, " debug tx-pkts/bytes/errs rx-pkts/bytes/errs\n");
		seq_puts(m, "  SESSION name, addr/port src-tid/sid "
			 "dest-tid/sid state user-data-ok\n");
		seq_puts(m, "   mtu/mru/rcvseq/sendseq/lns debug reorderto\n");
		seq_puts(m, "   nr/ns tx-pkts/bytes/errs rx-pkts/bytes/errs\n");
		goto out;
	}

	/* Show the tunnel or session context.
	 */
	if (!pd->session) {
		pppol2tp_seq_tunnel_show(m, pd->tunnel);
	} else {
		pppol2tp_seq_session_show(m, pd->session);
		l2tp_session_dec_refcount(pd->session);
	}

out:
	return 0;
}

static const struct seq_operations pppol2tp_seq_ops = {
	.start		= pppol2tp_seq_start,
	.next		= pppol2tp_seq_next,
	.stop		= pppol2tp_seq_stop,
	.show		= pppol2tp_seq_show,
};

/* Called when our /proc file is opened. We allocate data for use when
 * iterating our tunnel / session contexts and store it in the private
 * data of the seq_file.
 */
static int pppol2tp_proc_open(struct inode *inode, struct file *file)
{
	return seq_open_net(inode, file, &pppol2tp_seq_ops,
			    sizeof(struct pppol2tp_seq_data));
}

static const struct file_operations pppol2tp_proc_fops = {
	.open		= pppol2tp_proc_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= seq_release_net,
};

#endif /* CONFIG_PROC_FS */

/*****************************************************************************
 * Network namespace
 *****************************************************************************/

static __net_init int pppol2tp_init_net(struct net *net)
{
	struct proc_dir_entry *pde;
	int err = 0;

	pde = proc_create("pppol2tp", S_IRUGO, net->proc_net,
			  &pppol2tp_proc_fops);
	if (!pde) {
		err = -ENOMEM;
		goto out;
	}

out:
	return err;
}

static __net_exit void pppol2tp_exit_net(struct net *net)
{
	remove_proc_entry("pppol2tp", net->proc_net);
}

static struct pernet_operations pppol2tp_net_ops = {
	.init = pppol2tp_init_net,
	.exit = pppol2tp_exit_net,
	.id   = &pppol2tp_net_id,
};

/*****************************************************************************
 * Init and cleanup
 *****************************************************************************/

static const struct proto_ops pppol2tp_ops = {
	.family		= AF_PPPOX,
	.owner		= THIS_MODULE,
	.release	= pppol2tp_release,
	.bind		= sock_no_bind,
	.connect	= pppol2tp_connect,
	.socketpair	= sock_no_socketpair,
	.accept		= sock_no_accept,
	.getname	= pppol2tp_getname,
	.poll		= datagram_poll,
	.listen		= sock_no_listen,
	.shutdown	= sock_no_shutdown,
	.setsockopt	= pppol2tp_setsockopt,
	.getsockopt	= pppol2tp_getsockopt,
	.sendmsg	= pppol2tp_sendmsg,
	.recvmsg	= pppol2tp_recvmsg,
	.mmap		= sock_no_mmap,
	.ioctl		= pppox_ioctl,
};

static const struct pppox_proto pppol2tp_proto = {
	.create		= pppol2tp_create,
	.ioctl		= pppol2tp_ioctl,
	.owner		= THIS_MODULE,
};

#ifdef CONFIG_L2TP_V3

static const struct l2tp_nl_cmd_ops pppol2tp_nl_cmd_ops = {
	.session_create	= pppol2tp_session_create,
	.session_delete	= l2tp_session_delete,
};

#endif /* CONFIG_L2TP_V3 */

static int __init pppol2tp_init(void)
{
	int err;

	err = register_pernet_device(&pppol2tp_net_ops);
	if (err)
		goto out;

	err = proto_register(&pppol2tp_sk_proto, 0);
	if (err)
		goto out_unregister_pppol2tp_pernet;

	err = register_pppox_proto(PX_PROTO_OL2TP, &pppol2tp_proto);
	if (err)
		goto out_unregister_pppol2tp_proto;

#ifdef CONFIG_L2TP_V3
	err = l2tp_nl_register_ops(L2TP_PWTYPE_PPP, &pppol2tp_nl_cmd_ops);
	if (err)
		goto out_unregister_pppox;
#endif

	pr_info("PPPoL2TP kernel driver, %s\n", PPPOL2TP_DRV_VERSION);

out:
	return err;

#ifdef CONFIG_L2TP_V3
out_unregister_pppox:
	unregister_pppox_proto(PX_PROTO_OL2TP);
#endif
out_unregister_pppol2tp_proto:
	proto_unregister(&pppol2tp_sk_proto);
out_unregister_pppol2tp_pernet:
	unregister_pernet_device(&pppol2tp_net_ops);
	goto out;
}

static void __exit pppol2tp_exit(void)
{
#ifdef CONFIG_L2TP_V3
	l2tp_nl_unregister_ops(L2TP_PWTYPE_PPP);
#endif
	unregister_pppox_proto(PX_PROTO_OL2TP);
	proto_unregister(&pppol2tp_sk_proto);
	unregister_pernet_device(&pppol2tp_net_ops);
}

module_init(pppol2tp_init);
module_exit(pppol2tp_exit);

MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
MODULE_DESCRIPTION("PPP over L2TP over UDP");
MODULE_LICENSE("GPL");
MODULE_VERSION(PPPOL2TP_DRV_VERSION);
MODULE_ALIAS_NET_PF_PROTO(PF_PPPOX, PX_PROTO_OL2TP);
MODULE_ALIAS_L2TP_PWTYPE(7);