1458e5c6720089dca43bc8fd1097de61e2904aef
[dragonfly.git] / sys / netgraph7 / ng_l2tp.c
1 /*-
2  * Copyright (c) 2001-2002 Packet Design, LLC.
3  * All rights reserved.
4  * 
5  * Subject to the following obligations and disclaimer of warranty,
6  * use and redistribution of this software, in source or object code
7  * forms, with or without modifications are expressly permitted by
8  * Packet Design; provided, however, that:
9  * 
10  *    (i)  Any and all reproductions of the source or object code
11  *         must include the copyright notice above and the following
12  *         disclaimer of warranties; and
13  *    (ii) No rights are granted, in any manner or form, to use
14  *         Packet Design trademarks, including the mark "PACKET DESIGN"
15  *         on advertising, endorsements, or otherwise except as such
16  *         appears in the above copyright notice or in the software.
17  * 
18  * THIS SOFTWARE IS BEING PROVIDED BY PACKET DESIGN "AS IS", AND
19  * TO THE MAXIMUM EXTENT PERMITTED BY LAW, PACKET DESIGN MAKES NO
20  * REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING
21  * THIS SOFTWARE, INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED
22  * WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE,
23  * OR NON-INFRINGEMENT.  PACKET DESIGN DOES NOT WARRANT, GUARANTEE,
24  * OR MAKE ANY REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS
25  * OF THE USE OF THIS SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY,
26  * RELIABILITY OR OTHERWISE.  IN NO EVENT SHALL PACKET DESIGN BE
27  * LIABLE FOR ANY DAMAGES RESULTING FROM OR ARISING OUT OF ANY USE
28  * OF THIS SOFTWARE, INCLUDING WITHOUT LIMITATION, ANY DIRECT,
29  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, PUNITIVE, OR CONSEQUENTIAL
30  * DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES, LOSS OF
31  * USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY THEORY OF
32  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
33  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
34  * THE USE OF THIS SOFTWARE, EVEN IF PACKET DESIGN IS ADVISED OF
35  * THE POSSIBILITY OF SUCH DAMAGE.
36  * 
37  * Author: Archie Cobbs <archie@freebsd.org>
38  *
39  * $FreeBSD: src/sys/netgraph/ng_l2tp.c,v 1.25 2008/03/16 21:33:12 mav Exp $
40  * $DragonFly: src/sys/netgraph7/ng_l2tp.c,v 1.2 2008/06/26 23:05:35 dillon Exp $
41  */
42
43 /*
44  * L2TP netgraph node type.
45  *
46  * This node type implements the lower layer of the
47  * L2TP protocol as specified in RFC 2661.
48  */
49
50 #include <sys/param.h>
51 #include <sys/systm.h>
52 #include <sys/kernel.h>
53 #include <sys/time.h>
54 #include <sys/conf.h>
55 #include <sys/mbuf.h>
56 #include <sys/malloc.h>
57 #include <sys/errno.h>
58 #include <sys/libkern.h>
59
60 #include "ng_message.h"
61 #include "netgraph.h"
62 #include "ng_parse.h"
63 #include "ng_l2tp.h"
64
65 #ifdef NG_SEPARATE_MALLOC
66 MALLOC_DEFINE(M_NETGRAPH_L2TP, "netgraph_l2tp", "netgraph l2tp node");
67 #else
68 #define M_NETGRAPH_L2TP M_NETGRAPH
69 #endif
70
71 /* L2TP header format (first 2 bytes only) */
72 #define L2TP_HDR_CTRL           0x8000                  /* control packet */
73 #define L2TP_HDR_LEN            0x4000                  /* has length field */
74 #define L2TP_HDR_SEQ            0x0800                  /* has ns, nr fields */
75 #define L2TP_HDR_OFF            0x0200                  /* has offset field */
76 #define L2TP_HDR_PRIO           0x0100                  /* give priority */
77 #define L2TP_HDR_VERS_MASK      0x000f                  /* version field mask */
78 #define L2TP_HDR_VERSION        0x0002                  /* version field */
79
80 /* Bits that must be zero or one in first two bytes of header */
81 #define L2TP_CTRL_0BITS         0x030d                  /* ctrl: must be 0 */
82 #define L2TP_CTRL_1BITS         0xc802                  /* ctrl: must be 1 */
83 #define L2TP_DATA_0BITS         0x800d                  /* data: must be 0 */
84 #define L2TP_DATA_1BITS         0x0002                  /* data: must be 1 */
85
86 /* Standard xmit ctrl and data header bits */
87 #define L2TP_CTRL_HDR           (L2TP_HDR_CTRL | L2TP_HDR_LEN \
88                                     | L2TP_HDR_SEQ | L2TP_HDR_VERSION)
89 #define L2TP_DATA_HDR           (L2TP_HDR_VERSION)      /* optional: len, seq */
90
91 /* Some hard coded values */
92 #define L2TP_MAX_XWIN           128                     /* my max xmit window */
93 #define L2TP_MAX_REXMIT         5                       /* default max rexmit */
94 #define L2TP_MAX_REXMIT_TO      30                      /* default rexmit to */
95 #define L2TP_DELAYED_ACK        ((hz + 19) / 20)        /* delayed ack: 50 ms */
96
97 /* Default data sequence number configuration for new sessions */
98 #define L2TP_CONTROL_DSEQ       1                       /* we are the lns */
99 #define L2TP_ENABLE_DSEQ        1                       /* enable data seq # */
100
101 /* Compare sequence numbers using circular math */
102 #define L2TP_SEQ_DIFF(x, y)     ((int)((int16_t)(x) - (int16_t)(y)))
103
104 #define SESSHASHSIZE            0x0020
105 #define SESSHASH(x)             (((x) ^ ((x) >> 8)) & (SESSHASHSIZE - 1))
106
107 /* Hook private data (data session hooks only) */
108 struct ng_l2tp_hook_private {
109         struct ng_l2tp_sess_config      conf;   /* hook/session config */
110         struct ng_l2tp_session_stats    stats;  /* per sessions statistics */
111         hook_p                          hook;   /* hook reference */
112         u_int16_t                       ns;     /* data ns sequence number */
113         u_int16_t                       nr;     /* data nr sequence number */
114         LIST_ENTRY(ng_l2tp_hook_private) sessions;
115 };
116 typedef struct ng_l2tp_hook_private *hookpriv_p;
117
118 /*
119  * Sequence number state
120  *
121  * Invariants:
122  *    - If cwnd < ssth, we're doing slow start, otherwise congestion avoidance
123  *    - The number of unacknowledged xmit packets is (ns - rack) <= seq->wmax
124  *    - The first (ns - rack) mbuf's in xwin[] array are copies of these
125  *      unacknowledged packets; the remainder of xwin[] consists first of
126  *      zero or more further untransmitted packets in the transmit queue
127  *    - We try to keep the peer's receive window as full as possible.
128  *      Therefore, (i < cwnd && xwin[i] != NULL) implies (ns - rack) > i.
129  *    - rack_timer is running iff (ns - rack) > 0 (unack'd xmit'd pkts)
130  *    - If xack != nr, there are unacknowledged recv packet(s) (delayed ack)
131  *    - xack_timer is running iff xack != nr (unack'd rec'd pkts)
132  */
133 struct l2tp_seq {
134         u_int16_t               ns;             /* next xmit seq we send */
135         u_int16_t               nr;             /* next recv seq we expect */
136         u_int16_t               inproc;         /* packet is in processing */
137         u_int16_t               rack;           /* last 'nr' we rec'd */
138         u_int16_t               xack;           /* last 'nr' we sent */
139         u_int16_t               wmax;           /* peer's max recv window */
140         u_int16_t               cwnd;           /* current congestion window */
141         u_int16_t               ssth;           /* slow start threshold */
142         u_int16_t               acks;           /* # consecutive acks rec'd */
143         u_int16_t               rexmits;        /* # retransmits sent */
144         struct callout          rack_timer;     /* retransmit timer */
145         struct callout          xack_timer;     /* delayed ack timer */
146         struct mbuf             *xwin[L2TP_MAX_XWIN];   /* transmit window */
147         struct mtx              mtx;                    /* seq mutex */
148 };
149
150 /* Node private data */
151 struct ng_l2tp_private {
152         node_p                  node;           /* back pointer to node */
153         hook_p                  ctrl;           /* hook to upper layers */
154         hook_p                  lower;          /* hook to lower layers */
155         struct ng_l2tp_config   conf;           /* node configuration */
156         struct ng_l2tp_stats    stats;          /* node statistics */
157         struct l2tp_seq         seq;            /* ctrl sequence number state */
158         ng_ID_t                 ftarget;        /* failure message target */
159         LIST_HEAD(, ng_l2tp_hook_private) sesshash[SESSHASHSIZE];
160 };
161 typedef struct ng_l2tp_private *priv_p;
162
163 /* Netgraph node methods */
164 static ng_constructor_t ng_l2tp_constructor;
165 static ng_rcvmsg_t      ng_l2tp_rcvmsg;
166 static ng_shutdown_t    ng_l2tp_shutdown;
167 static ng_newhook_t     ng_l2tp_newhook;
168 static ng_rcvdata_t     ng_l2tp_rcvdata;
169 static ng_rcvdata_t     ng_l2tp_rcvdata_lower;
170 static ng_rcvdata_t     ng_l2tp_rcvdata_ctrl;
171 static ng_disconnect_t  ng_l2tp_disconnect;
172
173 /* Internal functions */
174 static int      ng_l2tp_xmit_ctrl(priv_p priv, struct mbuf *m, u_int16_t ns);
175
176 static void     ng_l2tp_seq_init(priv_p priv);
177 static int      ng_l2tp_seq_set(priv_p priv,
178                         const struct ng_l2tp_seq_config *conf);
179 static int      ng_l2tp_seq_adjust(priv_p priv,
180                         const struct ng_l2tp_config *conf);
181 static void     ng_l2tp_seq_reset(priv_p priv);
182 static void     ng_l2tp_seq_failure(priv_p priv);
183 static void     ng_l2tp_seq_recv_nr(priv_p priv, u_int16_t nr);
184 static void     ng_l2tp_seq_xack_timeout(node_p node, hook_p hook,
185                     void *arg1, int arg2);
186 static void     ng_l2tp_seq_rack_timeout(node_p node, hook_p hook,
187                     void *arg1, int arg2);
188
189 static hookpriv_p       ng_l2tp_find_session(priv_p privp, u_int16_t sid);
190 static ng_fn_eachhook   ng_l2tp_reset_session;
191
192 #ifdef INVARIANTS
193 static void     ng_l2tp_seq_check(struct l2tp_seq *seq);
194 #endif
195
196 /* Parse type for struct ng_l2tp_seq_config. */
197 static const struct ng_parse_struct_field
198         ng_l2tp_seq_config_fields[] = NG_L2TP_SEQ_CONFIG_TYPE_INFO;
199 static const struct ng_parse_type ng_l2tp_seq_config_type = {
200         &ng_parse_struct_type,
201         &ng_l2tp_seq_config_fields
202 };
203
204 /* Parse type for struct ng_l2tp_config */
205 static const struct ng_parse_struct_field
206         ng_l2tp_config_type_fields[] = NG_L2TP_CONFIG_TYPE_INFO;
207 static const struct ng_parse_type ng_l2tp_config_type = {
208         &ng_parse_struct_type,
209         &ng_l2tp_config_type_fields,
210 };
211
212 /* Parse type for struct ng_l2tp_sess_config */
213 static const struct ng_parse_struct_field
214         ng_l2tp_sess_config_type_fields[] = NG_L2TP_SESS_CONFIG_TYPE_INFO;
215 static const struct ng_parse_type ng_l2tp_sess_config_type = {
216         &ng_parse_struct_type,
217         &ng_l2tp_sess_config_type_fields,
218 };
219
220 /* Parse type for struct ng_l2tp_stats */
221 static const struct ng_parse_struct_field
222         ng_l2tp_stats_type_fields[] = NG_L2TP_STATS_TYPE_INFO;
223 static const struct ng_parse_type ng_l2tp_stats_type = {
224         &ng_parse_struct_type,
225         &ng_l2tp_stats_type_fields
226 };
227
228 /* Parse type for struct ng_l2tp_session_stats. */
229 static const struct ng_parse_struct_field
230         ng_l2tp_session_stats_type_fields[] = NG_L2TP_SESSION_STATS_TYPE_INFO;
231 static const struct ng_parse_type ng_l2tp_session_stats_type = {
232         &ng_parse_struct_type,
233         &ng_l2tp_session_stats_type_fields
234 };
235
236 /* List of commands and how to convert arguments to/from ASCII */
237 static const struct ng_cmdlist ng_l2tp_cmdlist[] = {
238         {
239           NGM_L2TP_COOKIE,
240           NGM_L2TP_SET_CONFIG,
241           "setconfig",
242           &ng_l2tp_config_type,
243           NULL
244         },
245         {
246           NGM_L2TP_COOKIE,
247           NGM_L2TP_GET_CONFIG,
248           "getconfig",
249           NULL,
250           &ng_l2tp_config_type
251         },
252         {
253           NGM_L2TP_COOKIE,
254           NGM_L2TP_SET_SESS_CONFIG,
255           "setsessconfig",
256           &ng_l2tp_sess_config_type,
257           NULL
258         },
259         {
260           NGM_L2TP_COOKIE,
261           NGM_L2TP_GET_SESS_CONFIG,
262           "getsessconfig",
263           &ng_parse_hint16_type,
264           &ng_l2tp_sess_config_type
265         },
266         {
267           NGM_L2TP_COOKIE,
268           NGM_L2TP_GET_STATS,
269           "getstats",
270           NULL,
271           &ng_l2tp_stats_type
272         },
273         {
274           NGM_L2TP_COOKIE,
275           NGM_L2TP_CLR_STATS,
276           "clrstats",
277           NULL,
278           NULL
279         },
280         {
281           NGM_L2TP_COOKIE,
282           NGM_L2TP_GETCLR_STATS,
283           "getclrstats",
284           NULL,
285           &ng_l2tp_stats_type
286         },
287         {
288           NGM_L2TP_COOKIE,
289           NGM_L2TP_GET_SESSION_STATS,
290           "getsessstats",
291           &ng_parse_int16_type,
292           &ng_l2tp_session_stats_type
293         },
294         {
295           NGM_L2TP_COOKIE,
296           NGM_L2TP_CLR_SESSION_STATS,
297           "clrsessstats",
298           &ng_parse_int16_type,
299           NULL
300         },
301         {
302           NGM_L2TP_COOKIE,
303           NGM_L2TP_GETCLR_SESSION_STATS,
304           "getclrsessstats",
305           &ng_parse_int16_type,
306           &ng_l2tp_session_stats_type
307         },
308         {
309           NGM_L2TP_COOKIE,
310           NGM_L2TP_ACK_FAILURE,
311           "ackfailure",
312           NULL,
313           NULL
314         },
315         {
316           NGM_L2TP_COOKIE,
317           NGM_L2TP_SET_SEQ,
318           "setsequence",
319           &ng_l2tp_seq_config_type,
320           NULL
321         },
322         { 0 }
323 };
324
325 /* Node type descriptor */
326 static struct ng_type ng_l2tp_typestruct = {
327         .version =      NG_ABI_VERSION,
328         .name =         NG_L2TP_NODE_TYPE,
329         .constructor =  ng_l2tp_constructor,
330         .rcvmsg =       ng_l2tp_rcvmsg,
331         .shutdown =     ng_l2tp_shutdown,
332         .newhook =      ng_l2tp_newhook,
333         .rcvdata =      ng_l2tp_rcvdata,
334         .disconnect =   ng_l2tp_disconnect,
335         .cmdlist =      ng_l2tp_cmdlist,
336 };
337 NETGRAPH_INIT(l2tp, &ng_l2tp_typestruct);
338
339 /* Sequence number state sanity checking */
340 #ifdef INVARIANTS
341 #define L2TP_SEQ_CHECK(seq)     ng_l2tp_seq_check(seq)
342 #else
343 #define L2TP_SEQ_CHECK(x)       do { } while (0)
344 #endif
345
346 /* memmove macro */
347 #define memmove(d, s, l)        bcopy(s, d, l)
348
349 /* Whether to use m_copypacket() or m_dup() */
350 #define L2TP_COPY_MBUF          m_copypacket
351
352 #define ERROUT(x)       do { error = (x); goto done; } while (0)
353
354 /************************************************************************
355                         NETGRAPH NODE STUFF
356 ************************************************************************/
357
358 /*
359  * Node type constructor
360  */
361 static int
362 ng_l2tp_constructor(node_p node)
363 {
364         priv_p priv;
365         int     i;
366
367         /* Allocate private structure */
368         MALLOC(priv, priv_p, sizeof(*priv), M_NETGRAPH_L2TP, M_WAITOK | M_NULLOK | M_ZERO);
369         if (priv == NULL)
370                 return (ENOMEM);
371         NG_NODE_SET_PRIVATE(node, priv);
372         priv->node = node;
373
374         /* Apply a semi-reasonable default configuration */
375         priv->conf.peer_win = 1;
376         priv->conf.rexmit_max = L2TP_MAX_REXMIT;
377         priv->conf.rexmit_max_to = L2TP_MAX_REXMIT_TO;
378
379         /* Initialize sequence number state */
380         ng_l2tp_seq_init(priv);
381
382         for (i = 0; i < SESSHASHSIZE; i++)
383             LIST_INIT(&priv->sesshash[i]);
384
385         /* Done */
386         return (0);
387 }
388
389 /*
390  * Give our OK for a hook to be added.
391  */
392 static int
393 ng_l2tp_newhook(node_p node, hook_p hook, const char *name)
394 {
395         const priv_p priv = NG_NODE_PRIVATE(node);
396
397         /* Check hook name */
398         if (strcmp(name, NG_L2TP_HOOK_CTRL) == 0) {
399                 if (priv->ctrl != NULL)
400                         return (EISCONN);
401                 priv->ctrl = hook;
402                 NG_HOOK_SET_RCVDATA(hook, ng_l2tp_rcvdata_ctrl);
403         } else if (strcmp(name, NG_L2TP_HOOK_LOWER) == 0) {
404                 if (priv->lower != NULL)
405                         return (EISCONN);
406                 priv->lower = hook;
407                 NG_HOOK_SET_RCVDATA(hook, ng_l2tp_rcvdata_lower);
408         } else {
409                 static const char hexdig[16] = "0123456789abcdef";
410                 u_int16_t session_id;
411                 hookpriv_p hpriv;
412                 uint16_t hash;
413                 const char *hex;
414                 int i;
415                 int j;
416
417                 /* Parse hook name to get session ID */
418                 if (strncmp(name, NG_L2TP_HOOK_SESSION_P,
419                     sizeof(NG_L2TP_HOOK_SESSION_P) - 1) != 0)
420                         return (EINVAL);
421                 hex = name + sizeof(NG_L2TP_HOOK_SESSION_P) - 1;
422                 for (session_id = i = 0; i < 4; i++) {
423                         for (j = 0; j < 16 && hex[i] != hexdig[j]; j++);
424                         if (j == 16)
425                                 return (EINVAL);
426                         session_id = (session_id << 4) | j;
427                 }
428                 if (hex[i] != '\0')
429                         return (EINVAL);
430
431                 /* Create hook private structure */
432                 MALLOC(hpriv, hookpriv_p,
433                     sizeof(*hpriv), M_NETGRAPH_L2TP, M_WAITOK | M_NULLOK | M_ZERO);
434                 if (hpriv == NULL)
435                         return (ENOMEM);
436                 hpriv->conf.session_id = htons(session_id);
437                 hpriv->conf.control_dseq = L2TP_CONTROL_DSEQ;
438                 hpriv->conf.enable_dseq = L2TP_ENABLE_DSEQ;
439                 hpriv->hook = hook;
440                 NG_HOOK_SET_PRIVATE(hook, hpriv);
441                 hash = SESSHASH(hpriv->conf.session_id);
442                 LIST_INSERT_HEAD(&priv->sesshash[hash], hpriv, sessions);
443         }
444
445         /* Done */
446         return (0);
447 }
448
449 /*
450  * Receive a control message.
451  */
452 static int
453 ng_l2tp_rcvmsg(node_p node, item_p item, hook_p lasthook)
454 {
455         const priv_p priv = NG_NODE_PRIVATE(node);
456         struct ng_mesg *resp = NULL;
457         struct ng_mesg *msg;
458         int error = 0;
459
460         NGI_GET_MSG(item, msg);
461         switch (msg->header.typecookie) {
462         case NGM_L2TP_COOKIE:
463                 switch (msg->header.cmd) {
464                 case NGM_L2TP_SET_CONFIG:
465                     {
466                         struct ng_l2tp_config *const conf =
467                                 (struct ng_l2tp_config *)msg->data;
468
469                         /* Check for invalid or illegal config */
470                         if (msg->header.arglen != sizeof(*conf)) {
471                                 error = EINVAL;
472                                 break;
473                         }
474                         conf->enabled = !!conf->enabled;
475                         conf->match_id = !!conf->match_id;
476                         conf->tunnel_id = htons(conf->tunnel_id);
477                         conf->peer_id = htons(conf->peer_id);
478                         if (priv->conf.enabled
479                             && ((priv->conf.tunnel_id != 0
480                                && conf->tunnel_id != priv->conf.tunnel_id)
481                               || ((priv->conf.peer_id != 0
482                                && conf->peer_id != priv->conf.peer_id)))) {
483                                 error = EBUSY;
484                                 break;
485                         }
486
487                         /* Save calling node as failure target */
488                         priv->ftarget = NGI_RETADDR(item);
489
490                         /* Adjust sequence number state */
491                         if ((error = ng_l2tp_seq_adjust(priv, conf)) != 0)
492                                 break;
493
494                         /* Update node's config */
495                         priv->conf = *conf;
496                         break;
497                     }
498                 case NGM_L2TP_GET_CONFIG:
499                     {
500                         struct ng_l2tp_config *conf;
501
502                         NG_MKRESPONSE(resp, msg, sizeof(*conf), M_WAITOK | M_NULLOK);
503                         if (resp == NULL) {
504                                 error = ENOMEM;
505                                 break;
506                         }
507                         conf = (struct ng_l2tp_config *)resp->data;
508                         *conf = priv->conf;
509
510                         /* Put ID's in host order */
511                         conf->tunnel_id = ntohs(conf->tunnel_id);
512                         conf->peer_id = ntohs(conf->peer_id);
513                         break;
514                     }
515                 case NGM_L2TP_SET_SESS_CONFIG:
516                     {
517                         struct ng_l2tp_sess_config *const conf =
518                             (struct ng_l2tp_sess_config *)msg->data;
519                         hookpriv_p hpriv;
520
521                         /* Check for invalid or illegal config. */
522                         if (msg->header.arglen != sizeof(*conf)) {
523                                 error = EINVAL;
524                                 break;
525                         }
526
527                         /* Put ID's in network order */
528                         conf->session_id = htons(conf->session_id);
529                         conf->peer_id = htons(conf->peer_id);
530
531                         /* Find matching hook */
532                         hpriv = ng_l2tp_find_session(priv, conf->session_id);
533                         if (hpriv == NULL) {
534                                 error = ENOENT;
535                                 break;
536                         }
537
538                         /* Update hook's config */
539                         hpriv->conf = *conf;
540                         break;
541                     }
542                 case NGM_L2TP_GET_SESS_CONFIG:
543                     {
544                         struct ng_l2tp_sess_config *conf;
545                         u_int16_t session_id;
546                         hookpriv_p hpriv;
547
548                         /* Get session ID */
549                         if (msg->header.arglen != sizeof(session_id)) {
550                                 error = EINVAL;
551                                 break;
552                         }
553                         memcpy(&session_id, msg->data, 2);
554                         session_id = htons(session_id);
555
556                         /* Find matching hook */
557                         hpriv = ng_l2tp_find_session(priv, session_id);
558                         if (hpriv == NULL) {
559                                 error = ENOENT;
560                                 break;
561                         }
562
563                         /* Send response */
564                         NG_MKRESPONSE(resp, msg, sizeof(hpriv->conf), M_WAITOK | M_NULLOK);
565                         if (resp == NULL) {
566                                 error = ENOMEM;
567                                 break;
568                         }
569                         conf = (struct ng_l2tp_sess_config *)resp->data;
570                         *conf = hpriv->conf;
571
572                         /* Put ID's in host order */
573                         conf->session_id = ntohs(conf->session_id);
574                         conf->peer_id = ntohs(conf->peer_id);
575                         break;
576                     }
577                 case NGM_L2TP_GET_STATS:
578                 case NGM_L2TP_CLR_STATS:
579                 case NGM_L2TP_GETCLR_STATS:
580                     {
581                         if (msg->header.cmd != NGM_L2TP_CLR_STATS) {
582                                 NG_MKRESPONSE(resp, msg,
583                                     sizeof(priv->stats), M_WAITOK | M_NULLOK);
584                                 if (resp == NULL) {
585                                         error = ENOMEM;
586                                         break;
587                                 }
588                                 memcpy(resp->data,
589                                     &priv->stats, sizeof(priv->stats));
590                         }
591                         if (msg->header.cmd != NGM_L2TP_GET_STATS)
592                                 memset(&priv->stats, 0, sizeof(priv->stats));
593                         break;
594                     }
595                 case NGM_L2TP_GET_SESSION_STATS:
596                 case NGM_L2TP_CLR_SESSION_STATS:
597                 case NGM_L2TP_GETCLR_SESSION_STATS:
598                     {
599                         uint16_t session_id;
600                         hookpriv_p hpriv;
601
602                         /* Get session ID. */
603                         if (msg->header.arglen != sizeof(session_id)) {
604                                 error = EINVAL;
605                                 break;
606                         }
607                         bcopy(msg->data, &session_id, sizeof(uint16_t));
608                         session_id = htons(session_id);
609
610                         /* Find matching hook. */
611                         hpriv = ng_l2tp_find_session(priv, session_id);
612                         if (hpriv == NULL) {
613                                 error = ENOENT;
614                                 break;
615                         }
616
617                         if (msg->header.cmd != NGM_L2TP_CLR_SESSION_STATS) {
618                                 NG_MKRESPONSE(resp, msg,
619                                     sizeof(hpriv->stats), M_WAITOK | M_NULLOK);
620                                 if (resp == NULL) {
621                                         error = ENOMEM;
622                                         break;
623                                 }
624                                 bcopy(&hpriv->stats, resp->data,
625                                         sizeof(hpriv->stats));
626                         }
627                         if (msg->header.cmd != NGM_L2TP_GET_SESSION_STATS)
628                                 bzero(&hpriv->stats, sizeof(hpriv->stats));
629                         break;
630                     }
631                 case NGM_L2TP_SET_SEQ:
632                     {
633                         struct ng_l2tp_seq_config *const conf =
634                                 (struct ng_l2tp_seq_config *)msg->data;
635
636                         /* Check for invalid or illegal seq config. */
637                         if (msg->header.arglen != sizeof(*conf)) {
638                                 error = EINVAL;
639                                 break;
640                         }
641                         conf->ns = htons(conf->ns);
642                         conf->nr = htons(conf->nr);
643                         conf->rack = htons(conf->rack);
644                         conf->xack = htons(conf->xack);
645
646                         /* Set sequence numbers. */
647                         error = ng_l2tp_seq_set(priv, conf);
648                         break;
649                     }
650                 default:
651                         error = EINVAL;
652                         break;
653                 }
654                 break;
655         default:
656                 error = EINVAL;
657                 break;
658         }
659
660         /* Done */
661         NG_RESPOND_MSG(error, node, item, resp);
662         NG_FREE_MSG(msg);
663         return (error);
664 }
665
666 /*
667  * Destroy node
668  */
669 static int
670 ng_l2tp_shutdown(node_p node)
671 {
672         const priv_p priv = NG_NODE_PRIVATE(node);
673         struct l2tp_seq *const seq = &priv->seq;
674
675         /* Sanity check */
676         L2TP_SEQ_CHECK(seq);
677
678         /* Reset sequence number state */
679         ng_l2tp_seq_reset(priv);
680
681         /* Free private data if neither timer is running */
682         ng_uncallout(&seq->rack_timer, node);
683         ng_uncallout(&seq->xack_timer, node);
684
685         mtx_destroy(&seq->mtx);
686
687         FREE(priv, M_NETGRAPH_L2TP);
688
689         /* Unref node */
690         NG_NODE_UNREF(node);
691         return (0);
692 }
693
694 /*
695  * Hook disconnection
696  */
697 static int
698 ng_l2tp_disconnect(hook_p hook)
699 {
700         const node_p node = NG_HOOK_NODE(hook);
701         const priv_p priv = NG_NODE_PRIVATE(node);
702
703         /* Zero out hook pointer */
704         if (hook == priv->ctrl)
705                 priv->ctrl = NULL;
706         else if (hook == priv->lower)
707                 priv->lower = NULL;
708         else {
709                 const hookpriv_p hpriv = NG_HOOK_PRIVATE(hook);
710                 LIST_REMOVE(hpriv, sessions);
711                 FREE(hpriv, M_NETGRAPH_L2TP);
712                 NG_HOOK_SET_PRIVATE(hook, NULL);
713         }
714
715         /* Go away if no longer connected to anything */
716         if (NG_NODE_NUMHOOKS(node) == 0 && NG_NODE_IS_VALID(node))
717                 ng_rmnode_self(node);
718         return (0);
719 }
720
721 /*************************************************************************
722                         INTERNAL FUNCTIONS
723 *************************************************************************/
724
725 /*
726  * Find the hook with a given session ID (in network order).
727  */
728 static hookpriv_p
729 ng_l2tp_find_session(priv_p privp, u_int16_t sid)
730 {
731         uint16_t        hash = SESSHASH(sid);
732         hookpriv_p      hpriv = NULL;
733
734         LIST_FOREACH(hpriv, &privp->sesshash[hash], sessions) {
735                 if (hpriv->conf.session_id == sid)
736                         break;
737         }
738
739         return (hpriv);
740 }
741
742 /*
743  * Reset a hook's session state.
744  */
745 static int
746 ng_l2tp_reset_session(hook_p hook, void *arg)
747 {
748         const hookpriv_p hpriv = NG_HOOK_PRIVATE(hook);
749
750         if (hpriv != NULL) {
751                 hpriv->conf.control_dseq = 0;
752                 hpriv->conf.enable_dseq = 0;
753                 bzero(&hpriv->conf, sizeof(struct ng_l2tp_session_stats));
754                 hpriv->nr = 0;
755                 hpriv->ns = 0;
756         }
757         return (-1);
758 }
759
760 /*
761  * Handle an incoming frame from below.
762  */
763 static int
764 ng_l2tp_rcvdata_lower(hook_p h, item_p item)
765 {
766         static const u_int16_t req_bits[2][2] = {
767                 { L2TP_DATA_0BITS, L2TP_DATA_1BITS },
768                 { L2TP_CTRL_0BITS, L2TP_CTRL_1BITS },
769         };
770         const node_p node = NG_HOOK_NODE(h);
771         const priv_p priv = NG_NODE_PRIVATE(node);
772         hookpriv_p hpriv = NULL;
773         hook_p hook = NULL;
774         u_int16_t ids[2];
775         struct mbuf *m;
776         u_int16_t hdr;
777         u_int16_t ns;
778         u_int16_t nr;
779         int is_ctrl;
780         int error;
781         int len, plen;
782
783         /* Sanity check */
784         L2TP_SEQ_CHECK(&priv->seq);
785
786         /* If not configured, reject */
787         if (!priv->conf.enabled) {
788                 NG_FREE_ITEM(item);
789                 ERROUT(ENXIO);
790         }
791
792         /* Grab mbuf */
793         NGI_GET_M(item, m);
794
795         /* Remember full packet length; needed for per session accounting. */
796         plen = m->m_pkthdr.len;
797
798         /* Update stats */
799         priv->stats.recvPackets++;
800         priv->stats.recvOctets += plen;
801
802         /* Get initial header */
803         if (m->m_pkthdr.len < 6) {
804                 priv->stats.recvRunts++;
805                 NG_FREE_ITEM(item);
806                 NG_FREE_M(m);
807                 ERROUT(EINVAL);
808         }
809         if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
810                 priv->stats.memoryFailures++;
811                 NG_FREE_ITEM(item);
812                 ERROUT(EINVAL);
813         }
814         hdr = ntohs(*mtod(m, u_int16_t *));
815         m_adj(m, 2);
816
817         /* Check required header bits and minimum length */
818         is_ctrl = (hdr & L2TP_HDR_CTRL) != 0;
819         if ((hdr & req_bits[is_ctrl][0]) != 0
820             || (~hdr & req_bits[is_ctrl][1]) != 0) {
821                 priv->stats.recvInvalid++;
822                 NG_FREE_ITEM(item);
823                 NG_FREE_M(m);
824                 ERROUT(EINVAL);
825         }
826         if (m->m_pkthdr.len < 4                         /* tunnel, session id */
827             + (2 * ((hdr & L2TP_HDR_LEN) != 0))         /* length field */
828             + (4 * ((hdr & L2TP_HDR_SEQ) != 0))         /* seq # fields */
829             + (2 * ((hdr & L2TP_HDR_OFF) != 0))) {      /* offset field */
830                 priv->stats.recvRunts++;
831                 NG_FREE_ITEM(item);
832                 NG_FREE_M(m);
833                 ERROUT(EINVAL);
834         }
835
836         /* Get and validate length field if present */
837         if ((hdr & L2TP_HDR_LEN) != 0) {
838                 if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
839                         priv->stats.memoryFailures++;
840                         NG_FREE_ITEM(item);
841                         ERROUT(EINVAL);
842                 }
843                 len = (u_int16_t)ntohs(*mtod(m, u_int16_t *)) - 4;
844                 m_adj(m, 2);
845                 if (len < 0 || len > m->m_pkthdr.len) {
846                         priv->stats.recvInvalid++;
847                         NG_FREE_ITEM(item);
848                         NG_FREE_M(m);
849                         ERROUT(EINVAL);
850                 }
851                 if (len < m->m_pkthdr.len)              /* trim extra bytes */
852                         m_adj(m, -(m->m_pkthdr.len - len));
853         }
854
855         /* Get tunnel ID and session ID */
856         if (m->m_len < 4 && (m = m_pullup(m, 4)) == NULL) {
857                 priv->stats.memoryFailures++;
858                 NG_FREE_ITEM(item);
859                 ERROUT(EINVAL);
860         }
861         memcpy(ids, mtod(m, u_int16_t *), 4);
862         m_adj(m, 4);
863
864         /* Check tunnel ID */
865         if (ids[0] != priv->conf.tunnel_id
866             && (priv->conf.match_id || ids[0] != 0)) {
867                 priv->stats.recvWrongTunnel++;
868                 NG_FREE_ITEM(item);
869                 NG_FREE_M(m);
870                 ERROUT(EADDRNOTAVAIL);
871         }
872
873         /* Check session ID (for data packets only) */
874         if ((hdr & L2TP_HDR_CTRL) == 0) {
875                 hpriv = ng_l2tp_find_session(priv, ids[1]);
876                 if (hpriv == NULL) {
877                         priv->stats.recvUnknownSID++;
878                         NG_FREE_ITEM(item);
879                         NG_FREE_M(m);
880                         ERROUT(ENOTCONN);
881                 }
882                 hook = hpriv->hook;
883         }
884
885         /* Get Ns, Nr fields if present */
886         if ((hdr & L2TP_HDR_SEQ) != 0) {
887                 if (m->m_len < 4 && (m = m_pullup(m, 4)) == NULL) {
888                         priv->stats.memoryFailures++;
889                         NG_FREE_ITEM(item);
890                         ERROUT(EINVAL);
891                 }
892                 memcpy(&ns, &mtod(m, u_int16_t *)[0], 2);
893                 ns = ntohs(ns);
894                 memcpy(&nr, &mtod(m, u_int16_t *)[1], 2);
895                 nr = ntohs(nr);
896                 m_adj(m, 4);
897         }
898
899         /* Strip offset padding if present */
900         if ((hdr & L2TP_HDR_OFF) != 0) {
901                 u_int16_t offset;
902
903                 /* Get length of offset padding */
904                 if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
905                         priv->stats.memoryFailures++;
906                         NG_FREE_ITEM(item);
907                         ERROUT(EINVAL);
908                 }
909                 memcpy(&offset, mtod(m, u_int16_t *), 2);
910                 offset = ntohs(offset);
911
912                 /* Trim offset padding */
913                 if ((2+offset) > m->m_pkthdr.len) {
914                         priv->stats.recvInvalid++;
915                         NG_FREE_ITEM(item);
916                         NG_FREE_M(m);
917                         ERROUT(EINVAL);
918                 }
919                 m_adj(m, 2+offset);
920         }
921
922         /* Handle control packets */
923         if ((hdr & L2TP_HDR_CTRL) != 0) {
924                 struct l2tp_seq *const seq = &priv->seq;
925
926                 /* Handle receive ack sequence number Nr */
927                 ng_l2tp_seq_recv_nr(priv, nr);
928
929                 /* Discard ZLB packets */
930                 if (m->m_pkthdr.len == 0) {
931                         priv->stats.recvZLBs++;
932                         NG_FREE_ITEM(item);
933                         NG_FREE_M(m);
934                         ERROUT(0);
935                 }
936
937                 mtx_lock(&seq->mtx);
938                 /*
939                  * If not what we expect or we are busy, drop packet and
940                  * send an immediate ZLB ack.
941                  */
942                 if (ns != seq->nr || seq->inproc) {
943                         if (L2TP_SEQ_DIFF(ns, seq->nr) <= 0)
944                                 priv->stats.recvDuplicates++;
945                         else
946                                 priv->stats.recvOutOfOrder++;
947                         mtx_unlock(&seq->mtx);
948                         ng_l2tp_xmit_ctrl(priv, NULL, seq->ns);
949                         NG_FREE_ITEM(item);
950                         NG_FREE_M(m);
951                         ERROUT(0);
952                 }
953                 /*
954                  * Until we deliver this packet we can't receive next one as
955                  * we have no information for sending ack.
956                  */
957                 seq->inproc = 1;
958                 mtx_unlock(&seq->mtx);
959
960                 /* Prepend session ID to packet. */
961                 M_PREPEND(m, 2, MB_DONTWAIT);
962                 if (m == NULL) {
963                         seq->inproc = 0;
964                         priv->stats.memoryFailures++;
965                         NG_FREE_ITEM(item);
966                         ERROUT(ENOBUFS);
967                 }
968                 memcpy(mtod(m, u_int16_t *), &ids[1], 2);
969
970                 /* Deliver packet to upper layers */
971                 NG_FWD_NEW_DATA(error, item, priv->ctrl, m);
972                 
973                 mtx_lock(&seq->mtx);
974                 /* Ready to process next packet. */
975                 seq->inproc = 0;
976
977                 /* If packet was successfully delivered send ack. */
978                 if (error == 0) {
979                         /* Update recv sequence number */
980                         seq->nr++;
981                         /* Start receive ack timer, if not already running */
982                         if (!callout_active(&seq->xack_timer)) {
983                                 ng_callout(&seq->xack_timer, priv->node, NULL,
984                                     L2TP_DELAYED_ACK, ng_l2tp_seq_xack_timeout,
985                                     NULL, 0);
986                         }
987                 }
988                 mtx_unlock(&seq->mtx);
989
990                 ERROUT(error);
991         }
992
993         /* Per session packet, account it. */
994         hpriv->stats.recvPackets++;
995         hpriv->stats.recvOctets += plen;
996
997         /* Follow peer's lead in data sequencing, if configured to do so */
998         if (!hpriv->conf.control_dseq)
999                 hpriv->conf.enable_dseq = ((hdr & L2TP_HDR_SEQ) != 0);
1000
1001         /* Handle data sequence numbers if present and enabled */
1002         if ((hdr & L2TP_HDR_SEQ) != 0) {
1003                 if (hpriv->conf.enable_dseq
1004                     && L2TP_SEQ_DIFF(ns, hpriv->nr) < 0) {
1005                         NG_FREE_ITEM(item);     /* duplicate or out of order */
1006                         NG_FREE_M(m);
1007                         priv->stats.recvDataDrops++;
1008                         ERROUT(0);
1009                 }
1010                 hpriv->nr = ns + 1;
1011         }
1012
1013         /* Drop empty data packets */
1014         if (m->m_pkthdr.len == 0) {
1015                 NG_FREE_ITEM(item);
1016                 NG_FREE_M(m);
1017                 ERROUT(0);
1018         }
1019
1020         /* Deliver data */
1021         NG_FWD_NEW_DATA(error, item, hook, m);
1022 done:
1023         /* Done */
1024         L2TP_SEQ_CHECK(&priv->seq);
1025         return (error);
1026 }
1027
1028 /*
1029  * Handle an outgoing control frame.
1030  */
1031 static int
1032 ng_l2tp_rcvdata_ctrl(hook_p hook, item_p item)
1033 {
1034         const node_p node = NG_HOOK_NODE(hook);
1035         const priv_p priv = NG_NODE_PRIVATE(node);
1036         struct l2tp_seq *const seq = &priv->seq;
1037         struct mbuf *m;
1038         int error;
1039         int i;
1040         u_int16_t       ns;
1041
1042         /* Sanity check */
1043         L2TP_SEQ_CHECK(&priv->seq);
1044
1045         /* If not configured, reject */
1046         if (!priv->conf.enabled) {
1047                 NG_FREE_ITEM(item);
1048                 ERROUT(ENXIO);
1049         }
1050
1051         /* Grab mbuf and discard other stuff XXX */
1052         NGI_GET_M(item, m);
1053         NG_FREE_ITEM(item);
1054
1055         /* Packet should have session ID prepended */
1056         if (m->m_pkthdr.len < 2) {
1057                 priv->stats.xmitInvalid++;
1058                 m_freem(m);
1059                 ERROUT(EINVAL);
1060         }
1061
1062         /* Check max length */
1063         if (m->m_pkthdr.len >= 0x10000 - 14) {
1064                 priv->stats.xmitTooBig++;
1065                 m_freem(m);
1066                 ERROUT(EOVERFLOW);
1067         }
1068
1069         mtx_lock(&seq->mtx);
1070
1071         /* Find next empty slot in transmit queue */
1072         for (i = 0; i < L2TP_MAX_XWIN && seq->xwin[i] != NULL; i++);
1073         if (i == L2TP_MAX_XWIN) {
1074                 mtx_unlock(&seq->mtx);
1075                 priv->stats.xmitDrops++;
1076                 m_freem(m);
1077                 ERROUT(ENOBUFS);
1078         }
1079         seq->xwin[i] = m;
1080
1081         /* If peer's receive window is already full, nothing else to do */
1082         if (i >= seq->cwnd) {
1083                 mtx_unlock(&seq->mtx);
1084                 ERROUT(0);
1085         }
1086
1087         /* Start retransmit timer if not already running */
1088         if (!callout_active(&seq->rack_timer))
1089                 ng_callout(&seq->rack_timer, node, NULL,
1090                     hz, ng_l2tp_seq_rack_timeout, NULL, 0);
1091         
1092         ns = seq->ns++;
1093         
1094         mtx_unlock(&seq->mtx);
1095
1096         /* Copy packet */
1097         if ((m = L2TP_COPY_MBUF(m, MB_DONTWAIT)) == NULL) {
1098                 priv->stats.memoryFailures++;
1099                 ERROUT(ENOBUFS);
1100         }
1101
1102         /* Send packet and increment xmit sequence number */
1103         error = ng_l2tp_xmit_ctrl(priv, m, ns);
1104 done:
1105         /* Done */
1106         L2TP_SEQ_CHECK(&priv->seq);
1107         return (error);
1108 }
1109
1110 /*
1111  * Handle an outgoing data frame.
1112  */
1113 static int
1114 ng_l2tp_rcvdata(hook_p hook, item_p item)
1115 {
1116         const priv_p priv = NG_NODE_PRIVATE(NG_HOOK_NODE(hook));
1117         const hookpriv_p hpriv = NG_HOOK_PRIVATE(hook);
1118         struct mbuf *m;
1119         u_int16_t hdr;
1120         int error;
1121         int i = 1;
1122
1123         /* Sanity check */
1124         L2TP_SEQ_CHECK(&priv->seq);
1125
1126         /* If not configured, reject */
1127         if (!priv->conf.enabled) {
1128                 NG_FREE_ITEM(item);
1129                 ERROUT(ENXIO);
1130         }
1131
1132         /* Get mbuf */
1133         NGI_GET_M(item, m);
1134
1135         /* Check max length */
1136         if (m->m_pkthdr.len >= 0x10000 - 12) {
1137                 priv->stats.xmitDataTooBig++;
1138                 NG_FREE_ITEM(item);
1139                 NG_FREE_M(m);
1140                 ERROUT(EOVERFLOW);
1141         }
1142
1143         /* Prepend L2TP header */
1144         M_PREPEND(m, 6
1145             + (2 * (hpriv->conf.include_length != 0))
1146             + (4 * (hpriv->conf.enable_dseq != 0)),
1147             MB_DONTWAIT);
1148         if (m == NULL) {
1149                 priv->stats.memoryFailures++;
1150                 NG_FREE_ITEM(item);
1151                 ERROUT(ENOBUFS);
1152         }
1153         hdr = L2TP_DATA_HDR;
1154         if (hpriv->conf.include_length) {
1155                 hdr |= L2TP_HDR_LEN;
1156                 mtod(m, u_int16_t *)[i++] = htons(m->m_pkthdr.len);
1157         }
1158         mtod(m, u_int16_t *)[i++] = priv->conf.peer_id;
1159         mtod(m, u_int16_t *)[i++] = hpriv->conf.peer_id;
1160         if (hpriv->conf.enable_dseq) {
1161                 hdr |= L2TP_HDR_SEQ;
1162                 mtod(m, u_int16_t *)[i++] = htons(hpriv->ns);
1163                 mtod(m, u_int16_t *)[i++] = htons(hpriv->nr);
1164                 hpriv->ns++;
1165         }
1166         mtod(m, u_int16_t *)[0] = htons(hdr);
1167
1168         /* Update per session stats. */
1169         hpriv->stats.xmitPackets++;
1170         hpriv->stats.xmitOctets += m->m_pkthdr.len;
1171
1172         /* And the global one. */
1173         priv->stats.xmitPackets++;
1174         priv->stats.xmitOctets += m->m_pkthdr.len;
1175
1176         /* Send packet */
1177         NG_FWD_NEW_DATA(error, item, priv->lower, m);
1178 done:
1179         /* Done */
1180         L2TP_SEQ_CHECK(&priv->seq);
1181         return (error);
1182 }
1183
1184 /*
1185  * Send a message to our controlling node that we've failed.
1186  */
1187 static void
1188 ng_l2tp_seq_failure(priv_p priv)
1189 {
1190         struct ng_mesg *msg;
1191         int error;
1192
1193         NG_MKMESSAGE(msg, NGM_L2TP_COOKIE, NGM_L2TP_ACK_FAILURE, 0, M_WAITOK | M_NULLOK);
1194         if (msg == NULL)
1195                 return;
1196         NG_SEND_MSG_ID(error, priv->node, msg, priv->ftarget, 0);
1197 }
1198
1199 /************************************************************************
1200                         SEQUENCE NUMBER HANDLING
1201 ************************************************************************/
1202
1203 /*
1204  * Initialize sequence number state.
1205  */
1206 static void
1207 ng_l2tp_seq_init(priv_p priv)
1208 {
1209         struct l2tp_seq *const seq = &priv->seq;
1210
1211         KASSERT(priv->conf.peer_win >= 1,
1212             ("%s: peer_win is zero", __func__));
1213         memset(seq, 0, sizeof(*seq));
1214         seq->cwnd = 1;
1215         seq->wmax = priv->conf.peer_win;
1216         if (seq->wmax > L2TP_MAX_XWIN)
1217                 seq->wmax = L2TP_MAX_XWIN;
1218         seq->ssth = seq->wmax;
1219         ng_callout_init(&seq->rack_timer);
1220         ng_callout_init(&seq->xack_timer);
1221         mtx_init(&seq->mtx, "ng_l2tp", NULL, MTX_DEF);
1222         L2TP_SEQ_CHECK(seq);
1223 }
1224
1225 /*
1226  * Set sequence number state as given from user.
1227  */
1228 static int
1229 ng_l2tp_seq_set(priv_p priv, const struct ng_l2tp_seq_config *conf)
1230 {
1231         struct l2tp_seq *const seq = &priv->seq;
1232
1233         /* If node is enabled, deny update to sequence numbers. */
1234         if (priv->conf.enabled)
1235                 return (EBUSY);
1236
1237         /* We only can handle the simple cases. */
1238         if (conf->xack != conf->nr || conf->ns != conf->rack)
1239                 return (EINVAL);
1240
1241         /* Set ns,nr,rack,xack parameters. */
1242         seq->ns = conf->ns;
1243         seq->nr = conf->nr;
1244         seq->rack = conf->rack;
1245         seq->xack = conf->xack;
1246
1247         return (0);
1248 }
1249
1250 /*
1251  * Adjust sequence number state accordingly after reconfiguration.
1252  */
1253 static int
1254 ng_l2tp_seq_adjust(priv_p priv, const struct ng_l2tp_config *conf)
1255 {
1256         struct l2tp_seq *const seq = &priv->seq;
1257         u_int16_t new_wmax;
1258
1259         /* If disabling node, reset state sequence number */
1260         if (!conf->enabled) {
1261                 ng_l2tp_seq_reset(priv);
1262                 return (0);
1263         }
1264
1265         /* Adjust peer's max recv window; it can only increase */
1266         new_wmax = conf->peer_win;
1267         if (new_wmax > L2TP_MAX_XWIN)
1268                 new_wmax = L2TP_MAX_XWIN;
1269         if (new_wmax == 0)
1270                 return (EINVAL);
1271         if (new_wmax < seq->wmax)
1272                 return (EBUSY);
1273         seq->wmax = new_wmax;
1274
1275         /* Done */
1276         return (0);
1277 }
1278
1279 /*
1280  * Reset sequence number state.
1281  */
1282 static void
1283 ng_l2tp_seq_reset(priv_p priv)
1284 {
1285         struct l2tp_seq *const seq = &priv->seq;
1286         hook_p hook;
1287         int i;
1288
1289         /* Sanity check */
1290         L2TP_SEQ_CHECK(seq);
1291
1292         /* Stop timers */
1293         ng_uncallout(&seq->rack_timer, priv->node);
1294         ng_uncallout(&seq->xack_timer, priv->node);
1295
1296         /* Free retransmit queue */
1297         for (i = 0; i < L2TP_MAX_XWIN; i++) {
1298                 if (seq->xwin[i] == NULL)
1299                         break;
1300                 m_freem(seq->xwin[i]);
1301         }
1302
1303         /* Reset session hooks' sequence number states */
1304         NG_NODE_FOREACH_HOOK(priv->node, ng_l2tp_reset_session, NULL, hook);
1305
1306         /* Reset node's sequence number state */
1307         seq->ns = 0;
1308         seq->nr = 0;
1309         seq->rack = 0;
1310         seq->xack = 0;
1311         seq->wmax = L2TP_MAX_XWIN;
1312         seq->cwnd = 1;
1313         seq->ssth = seq->wmax;
1314         seq->acks = 0;
1315         seq->rexmits = 0;
1316         bzero(seq->xwin, sizeof(seq->xwin));
1317
1318         /* Done */
1319         L2TP_SEQ_CHECK(seq);
1320 }
1321
1322 /*
1323  * Handle receipt of an acknowledgement value (Nr) from peer.
1324  */
1325 static void
1326 ng_l2tp_seq_recv_nr(priv_p priv, u_int16_t nr)
1327 {
1328         struct l2tp_seq *const seq = &priv->seq;
1329         struct mbuf     *xwin[L2TP_MAX_XWIN];   /* partial local copy */
1330         int             nack;
1331         int             i, j;
1332         uint16_t        ns;
1333
1334         mtx_lock(&seq->mtx);
1335
1336         /* Verify peer's ACK is in range */
1337         if ((nack = L2TP_SEQ_DIFF(nr, seq->rack)) <= 0) {
1338                 mtx_unlock(&seq->mtx);
1339                 return;                         /* duplicate ack */
1340         }
1341         if (L2TP_SEQ_DIFF(nr, seq->ns) > 0) {
1342                 mtx_unlock(&seq->mtx);
1343                 priv->stats.recvBadAcks++;      /* ack for packet not sent */
1344                 return;
1345         }
1346         KASSERT(nack <= L2TP_MAX_XWIN,
1347             ("%s: nack=%d > %d", __func__, nack, L2TP_MAX_XWIN));
1348
1349         /* Update receive ack stats */
1350         seq->rack = nr;
1351         seq->rexmits = 0;
1352
1353         /* Free acknowledged packets and shift up packets in the xmit queue */
1354         for (i = 0; i < nack; i++)
1355                 m_freem(seq->xwin[i]);
1356         memmove(seq->xwin, seq->xwin + nack,
1357             (L2TP_MAX_XWIN - nack) * sizeof(*seq->xwin));
1358         memset(seq->xwin + (L2TP_MAX_XWIN - nack), 0,
1359             nack * sizeof(*seq->xwin));
1360
1361         /*
1362          * Do slow-start/congestion avoidance windowing algorithm described
1363          * in RFC 2661, Appendix A. Here we handle a multiple ACK as if each
1364          * ACK had arrived separately.
1365          */
1366         if (seq->cwnd < seq->wmax) {
1367
1368                 /* Handle slow start phase */
1369                 if (seq->cwnd < seq->ssth) {
1370                         seq->cwnd += nack;
1371                         nack = 0;
1372                         if (seq->cwnd > seq->ssth) {    /* into cg.av. phase */
1373                                 nack = seq->cwnd - seq->ssth;
1374                                 seq->cwnd = seq->ssth;
1375                         }
1376                 }
1377
1378                 /* Handle congestion avoidance phase */
1379                 if (seq->cwnd >= seq->ssth) {
1380                         seq->acks += nack;
1381                         while (seq->acks >= seq->cwnd) {
1382                                 seq->acks -= seq->cwnd;
1383                                 if (seq->cwnd < seq->wmax)
1384                                         seq->cwnd++;
1385                         }
1386                 }
1387         }
1388
1389         /* Stop xmit timer */
1390         if (callout_active(&seq->rack_timer))
1391                 ng_uncallout(&seq->rack_timer, priv->node);
1392
1393         /* If transmit queue is empty, we're done for now */
1394         if (seq->xwin[0] == NULL) {
1395                 mtx_unlock(&seq->mtx);
1396                 return;
1397         }
1398
1399         /* Start restransmit timer again */
1400         ng_callout(&seq->rack_timer, priv->node, NULL,
1401             hz, ng_l2tp_seq_rack_timeout, NULL, 0);
1402
1403         /*
1404          * Send more packets, trying to keep peer's receive window full.
1405          * Make copy of everything we need before lock release.
1406          */
1407         ns = seq->ns;
1408         j = 0;
1409         while ((i = L2TP_SEQ_DIFF(seq->ns, seq->rack)) < seq->cwnd
1410             && seq->xwin[i] != NULL) {
1411                 xwin[j++] = seq->xwin[i];
1412                 seq->ns++;
1413         }
1414
1415         mtx_unlock(&seq->mtx);
1416
1417         /*
1418          * Send prepared.
1419          * If there is a memory error, pretend packet was sent, as it
1420          * will get retransmitted later anyway.
1421          */
1422         for (i = 0; i < j; i++) {
1423                 struct mbuf     *m;
1424                 if ((m = L2TP_COPY_MBUF(xwin[i], MB_DONTWAIT)) == NULL)
1425                         priv->stats.memoryFailures++;
1426                 else
1427                         ng_l2tp_xmit_ctrl(priv, m, ns);
1428                 ns++;
1429         }
1430 }
1431
1432 /*
1433  * Handle an ack timeout. We have an outstanding ack that we
1434  * were hoping to piggy-back, but haven't, so send a ZLB.
1435  */
1436 static void
1437 ng_l2tp_seq_xack_timeout(node_p node, hook_p hook, void *arg1, int arg2)
1438 {
1439         const priv_p priv = NG_NODE_PRIVATE(node);
1440         struct l2tp_seq *const seq = &priv->seq;
1441
1442         /* Make sure callout is still active before doing anything */
1443         if (callout_pending(&seq->xack_timer) ||
1444             (!callout_active(&seq->xack_timer)))
1445                 return;
1446
1447         /* Sanity check */
1448         L2TP_SEQ_CHECK(seq);
1449
1450         /* Send a ZLB */
1451         ng_l2tp_xmit_ctrl(priv, NULL, seq->ns);
1452
1453         /* callout_deactivate() is not needed here 
1454             as ng_uncallout() was called by ng_l2tp_xmit_ctrl() */
1455
1456         /* Sanity check */
1457         L2TP_SEQ_CHECK(seq);
1458 }
1459
1460 /* 
1461  * Handle a transmit timeout. The peer has failed to respond
1462  * with an ack for our packet, so retransmit it.
1463  */
1464 static void
1465 ng_l2tp_seq_rack_timeout(node_p node, hook_p hook, void *arg1, int arg2)
1466 {
1467         const priv_p priv = NG_NODE_PRIVATE(node);
1468         struct l2tp_seq *const seq = &priv->seq;
1469         struct mbuf *m;
1470         u_int delay;
1471
1472         /* Make sure callout is still active before doing anything */
1473         if (callout_pending(&seq->rack_timer) ||
1474             (!callout_active(&seq->rack_timer)))
1475                 return;
1476
1477         /* Sanity check */
1478         L2TP_SEQ_CHECK(seq);
1479
1480         priv->stats.xmitRetransmits++;
1481
1482         /* Have we reached the retransmit limit? If so, notify owner. */
1483         if (seq->rexmits++ >= priv->conf.rexmit_max)
1484                 ng_l2tp_seq_failure(priv);
1485
1486         /* Restart timer, this time with an increased delay */
1487         delay = (seq->rexmits > 12) ? (1 << 12) : (1 << seq->rexmits);
1488         if (delay > priv->conf.rexmit_max_to)
1489                 delay = priv->conf.rexmit_max_to;
1490         ng_callout(&seq->rack_timer, node, NULL,
1491             hz * delay, ng_l2tp_seq_rack_timeout, NULL, 0);
1492
1493         /* Do slow-start/congestion algorithm windowing algorithm */
1494         seq->ns = seq->rack;
1495         seq->ssth = (seq->cwnd + 1) / 2;
1496         seq->cwnd = 1;
1497         seq->acks = 0;
1498
1499         /* Retransmit oldest unack'd packet */
1500         if ((m = L2TP_COPY_MBUF(seq->xwin[0], MB_DONTWAIT)) == NULL)
1501                 priv->stats.memoryFailures++;
1502         else
1503                 ng_l2tp_xmit_ctrl(priv, m, seq->ns++);
1504
1505         /* callout_deactivate() is not needed here 
1506             as ng_callout() is getting called each time */
1507
1508         /* Sanity check */
1509         L2TP_SEQ_CHECK(seq);
1510 }
1511
1512 /*
1513  * Transmit a control stream packet, payload optional.
1514  * The transmit sequence number is not incremented.
1515  */
1516 static int
1517 ng_l2tp_xmit_ctrl(priv_p priv, struct mbuf *m, u_int16_t ns)
1518 {
1519         struct l2tp_seq *const seq = &priv->seq;
1520         u_int16_t session_id = 0;
1521         int error;
1522
1523         mtx_lock(&seq->mtx);
1524
1525         /* Stop ack timer: we're sending an ack with this packet.
1526            Doing this before to keep state predictable after error. */
1527         if (callout_active(&seq->xack_timer))
1528                 ng_uncallout(&seq->xack_timer, priv->node);
1529
1530         seq->xack = seq->nr;
1531
1532         mtx_unlock(&seq->mtx);
1533
1534         /* If no mbuf passed, send an empty packet (ZLB) */
1535         if (m == NULL) {
1536
1537                 /* Create a new mbuf for ZLB packet */
1538                 MGETHDR(m, MB_DONTWAIT, MT_DATA);
1539                 if (m == NULL) {
1540                         priv->stats.memoryFailures++;
1541                         return (ENOBUFS);
1542                 }
1543                 m->m_len = m->m_pkthdr.len = 12;
1544                 m->m_pkthdr.rcvif = NULL;
1545                 priv->stats.xmitZLBs++;
1546         } else {
1547
1548                 /* Strip off session ID */
1549                 if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
1550                         priv->stats.memoryFailures++;
1551                         return (ENOBUFS);
1552                 }
1553                 memcpy(&session_id, mtod(m, u_int16_t *), 2);
1554                 m_adj(m, 2);
1555
1556                 /* Make room for L2TP header */
1557                 M_PREPEND(m, 12, MB_DONTWAIT);
1558                 if (m == NULL) {
1559                         priv->stats.memoryFailures++;
1560                         return (ENOBUFS);
1561                 }
1562         }
1563
1564         /* Fill in L2TP header */
1565         mtod(m, u_int16_t *)[0] = htons(L2TP_CTRL_HDR);
1566         mtod(m, u_int16_t *)[1] = htons(m->m_pkthdr.len);
1567         mtod(m, u_int16_t *)[2] = priv->conf.peer_id;
1568         mtod(m, u_int16_t *)[3] = session_id;
1569         mtod(m, u_int16_t *)[4] = htons(ns);
1570         mtod(m, u_int16_t *)[5] = htons(seq->nr);
1571
1572         /* Update sequence number info and stats */
1573         priv->stats.xmitPackets++;
1574         priv->stats.xmitOctets += m->m_pkthdr.len;
1575
1576         /* Send packet */
1577         NG_SEND_DATA_ONLY(error, priv->lower, m);
1578         return (error);
1579 }
1580
1581 #ifdef INVARIANTS
1582 /*
1583  * Sanity check sequence number state.
1584  */
1585 static void
1586 ng_l2tp_seq_check(struct l2tp_seq *seq)
1587 {
1588         int self_unack, peer_unack;
1589         int i;
1590
1591 #define CHECK(p)        KASSERT((p), ("%s: not: %s", __func__, #p))
1592
1593         mtx_lock(&seq->mtx);
1594
1595         self_unack = L2TP_SEQ_DIFF(seq->nr, seq->xack);
1596         peer_unack = L2TP_SEQ_DIFF(seq->ns, seq->rack);
1597         CHECK(seq->wmax <= L2TP_MAX_XWIN);
1598         CHECK(seq->cwnd >= 1);
1599         CHECK(seq->cwnd <= seq->wmax);
1600         CHECK(seq->ssth >= 1);
1601         CHECK(seq->ssth <= seq->wmax);
1602         if (seq->cwnd < seq->ssth)
1603                 CHECK(seq->acks == 0);
1604         else
1605                 CHECK(seq->acks <= seq->cwnd);
1606         CHECK(self_unack >= 0);
1607         CHECK(peer_unack >= 0);
1608         CHECK(peer_unack <= seq->wmax);
1609         CHECK((self_unack == 0) ^ callout_active(&seq->xack_timer));
1610         CHECK((peer_unack == 0) ^ callout_active(&seq->rack_timer));
1611         for (i = 0; i < peer_unack; i++)
1612                 CHECK(seq->xwin[i] != NULL);
1613         for ( ; i < seq->cwnd; i++)         /* verify peer's recv window full */
1614                 CHECK(seq->xwin[i] == NULL);
1615
1616         mtx_unlock(&seq->mtx);
1617
1618 #undef CHECK
1619 }
1620 #endif  /* INVARIANTS */