sys/netgraph/l2tp/ng_l2tp.c

   1
   2 /*
   3  * Copyright (c) 2001-2002 Packet Design, LLC.
   4  * All rights reserved.
   5  *
   6  * Subject to the following obligations and disclaimer of warranty,
   7  * use and redistribution of this software, in source or object code
   8  * forms, with or without modifications are expressly permitted by
   9  * Packet Design; provided, however, that:
  10  *
  11  *    (i)  Any and all reproductions of the source or object code
  12  *         must include the copyright notice above and the following
  13  *         disclaimer of warranties; and
  14  *    (ii) No rights are granted, in any manner or form, to use
  15  *         Packet Design trademarks, including the mark "PACKET DESIGN"
  16  *         on advertising, endorsements, or otherwise except as such
  17  *         appears in the above copyright notice or in the software.
  18  *
  19  * THIS SOFTWARE IS BEING PROVIDED BY PACKET DESIGN "AS IS", AND
  20  * TO THE MAXIMUM EXTENT PERMITTED BY LAW, PACKET DESIGN MAKES NO
  21  * REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING
  22  * THIS SOFTWARE, INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED
  23  * WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE,
  24  * OR NON-INFRINGEMENT.  PACKET DESIGN DOES NOT WARRANT, GUARANTEE,
  25  * OR MAKE ANY REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS
  26  * OF THE USE OF THIS SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY,
  27  * RELIABILITY OR OTHERWISE.  IN NO EVENT SHALL PACKET DESIGN BE
  28  * LIABLE FOR ANY DAMAGES RESULTING FROM OR ARISING OUT OF ANY USE
  29  * OF THIS SOFTWARE, INCLUDING WITHOUT LIMITATION, ANY DIRECT,
  30  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, PUNITIVE, OR CONSEQUENTIAL
  31  * DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES, LOSS OF
  32  * USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY THEORY OF
  33  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  34  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
  35  * THE USE OF THIS SOFTWARE, EVEN IF PACKET DESIGN IS ADVISED OF
  36  * THE POSSIBILITY OF SUCH DAMAGE.
  37  *
  38  * Author: Archie Cobbs <archie@freebsd.org>
  39  *
  40  * $FreeBSD: src/sys/netgraph/ng_l2tp.c,v 1.1.2.1 2002/08/20 23:48:15 archie Exp $
  41  * $DragonFly: src/sys/netgraph/l2tp/ng_l2tp.c,v 1.8 2006/01/14 11:10:47 swildner Exp $
  42  */
  43
  44 /*
  45  * L2TP netgraph node type.
  46  *
  47  * This node type implements the lower layer of the
  48  * L2TP protocol as specified in RFC 2661.
  49  */
  50
  51 #include <sys/param.h>
  52 #include <sys/systm.h>
  53 #include <sys/kernel.h>
  54 #include <sys/time.h>
  55 #include <sys/conf.h>
  56 #include <sys/mbuf.h>
  57 #include <sys/malloc.h>
  58 #include <sys/errno.h>
  59 #include <sys/libkern.h>
  60 #include <sys/thread2.h>
  61
  62 #include <netgraph/ng_message.h>
  63 #include <netgraph/netgraph.h>
  64 #include <netgraph/ng_parse.h>
  65 #include "ng_l2tp.h"
  66
  67 #ifdef NG_SEPARATE_MALLOC
  68 MALLOC_DEFINE(M_NETGRAPH_L2TP, "netgraph_l2tp", "netgraph l2tp node");
  69 #else
  70 #define M_NETGRAPH_L2TP M_NETGRAPH
  71 #endif
  72
  73 /* L2TP header format (first 2 bytes only) */
  74 #define L2TP_HDR_CTRL           0x8000                  /* control packet */
  75 #define L2TP_HDR_LEN            0x4000                  /* has length field */
  76 #define L2TP_HDR_SEQ            0x0800                  /* has ns, nr fields */
  77 #define L2TP_HDR_OFF            0x0200                  /* has offset field */
  78 #define L2TP_HDR_PRIO           0x0100                  /* give priority */
  79 #define L2TP_HDR_VERS_MASK      0x000f                  /* version field mask */
  80 #define L2TP_HDR_VERSION        0x0002                  /* version field */
  81
  82 /* Bits that must be zero or one in first two bytes of header */
  83 #define L2TP_CTRL_0BITS         0x030d                  /* ctrl: must be 0 */
  84 #define L2TP_CTRL_1BITS         0xc802                  /* ctrl: must be 1 */
  85 #define L2TP_DATA_0BITS         0x800d                  /* data: must be 0 */
  86 #define L2TP_DATA_1BITS         0x0002                  /* data: must be 1 */
  87
  88 /* Standard xmit ctrl and data header bits */
  89 #define L2TP_CTRL_HDR           (L2TP_HDR_CTRL | L2TP_HDR_LEN \
  90                                     | L2TP_HDR_SEQ | L2TP_HDR_VERSION)
  91 #define L2TP_DATA_HDR           (L2TP_HDR_VERSION)      /* optional: len, seq */
  92
  93 /* Some hard coded values */
  94 #define L2TP_MAX_XWIN           16                      /* my max xmit window */
  95 #define L2TP_MAX_REXMIT         5                       /* default max rexmit */
  96 #define L2TP_MAX_REXMIT_TO      30                      /* default rexmit to */
  97 #define L2TP_DELAYED_ACK        ((hz + 19) / 20)        /* delayed ack: 50 ms */
  98
  99 /* Default data sequence number configuration for new sessions */
 100 #define L2TP_CONTROL_DSEQ       1                       /* we are the lns */
 101 #define L2TP_ENABLE_DSEQ        1                       /* enable data seq # */
 102
 103 /* Compare sequence numbers using circular math */
 104 #define L2TP_SEQ_DIFF(x, y)     ((int)((int16_t)(x) - (int16_t)(y)))
 105
 106 /*
 107  * Sequence number state
 108  *
 109  * Invariants:
 110  *    - If cwnd < ssth, we're doing slow start, otherwise congestion avoidance
 111  *    - The number of unacknowledged xmit packets is (ns - rack) <= seq->wmax
 112  *    - The first (ns - rack) mbuf's in xwin[] array are copies of these
 113  *      unacknowledged packets; the remainder of xwin[] consists first of
 114  *      zero or more further untransmitted packets in the transmit queue
 115  *    - We try to keep the peer's receive window as full as possible.
 116  *      Therefore, (i < cwnd && xwin[i] != NULL) implies (ns - rack) > i.
 117  *    - rack_timer is running iff (ns - rack) > 0 (unack'd xmit'd pkts)
 118  *    - If xack != nr, there are unacknowledged recv packet(s) (delayed ack)
 119  *    - xack_timer is running iff xack != nr (unack'd rec'd pkts)
 120  */
 121 struct l2tp_seq {
 122         u_int16_t               ns;             /* next xmit seq we send */
 123         u_int16_t               nr;             /* next recv seq we expect */
 124         u_int16_t               rack;           /* last 'nr' we rec'd */
 125         u_int16_t               xack;           /* last 'nr' we sent */
 126         u_int16_t               wmax;           /* peer's max recv window */
 127         u_int16_t               cwnd;           /* current congestion window */
 128         u_int16_t               ssth;           /* slow start threshold */
 129         u_int16_t               acks;           /* # consecutive acks rec'd */
 130         u_int16_t               rexmits;        /* # retransmits sent */
 131         u_int16_t               max_rexmits;    /* max # retransmits sent */
 132         u_int16_t               max_rexmit_to;  /* max retransmit timeout */
 133         struct callout          rack_timer;     /* retransmit timer */
 134         struct callout          xack_timer;     /* delayed ack timer */
 135         u_char                  rack_timer_running;     /* xmit timer running */
 136         u_char                  xack_timer_running;     /* ack timer running */
 137         struct mbuf             *xwin[L2TP_MAX_XWIN];   /* transmit window */
 138 };
 139
 140 /* Node private data */
 141 struct ng_l2tp_private {
 142         node_p                  node;           /* back pointer to node */
 143         hook_p                  ctrl;           /* hook to upper layers */
 144         hook_p                  lower;          /* hook to lower layers */
 145         struct ng_l2tp_config   conf;           /* node configuration */
 146         struct ng_l2tp_stats    stats;          /* node statistics */
 147         struct l2tp_seq         seq;            /* ctrl sequence number state */
 148         char                    *ftarget;       /* failure message target */
 149 };
 150 typedef struct ng_l2tp_private *priv_p;
 151
 152 /* Hook private data (data session hooks only) */
 153 struct ng_l2tp_hook_private {
 154         struct ng_l2tp_sess_config      conf;   /* hook/session config */
 155         u_int16_t                       ns;     /* data ns sequence number */
 156         u_int16_t                       nr;     /* data nr sequence number */
 157 };
 158 typedef struct ng_l2tp_hook_private *hookpriv_p;
 159
 160 /* Netgraph node methods */
 161 static ng_constructor_t ng_l2tp_constructor;
 162 static ng_rcvmsg_t      ng_l2tp_rcvmsg;
 163 static ng_shutdown_t    ng_l2tp_shutdown;
 164 static ng_newhook_t     ng_l2tp_newhook;
 165 static ng_rcvdata_t     ng_l2tp_rcvdata;
 166 static ng_disconnect_t  ng_l2tp_disconnect;
 167
 168 /* Internal functions */
 169 static int      ng_l2tp_recv_lower(node_p node, struct mbuf *m, meta_p meta);
 170 static int      ng_l2tp_recv_ctrl(node_p node, struct mbuf *m, meta_p meta);
 171 static int      ng_l2tp_recv_data(node_p node,
 172                         struct mbuf *m, meta_p meta, hookpriv_p hpriv);
 173
 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_adjust(priv_p priv,
 178                         const struct ng_l2tp_config *conf);
 179 static void     ng_l2tp_seq_reset(priv_p priv);
 180 static void     ng_l2tp_seq_failure(priv_p priv);
 181 static void     ng_l2tp_seq_recv_nr(priv_p priv, u_int16_t nr);
 182 static int      ng_l2tp_seq_recv_ns(priv_p priv, u_int16_t ns);
 183 static void     ng_l2tp_seq_xack_timeout(void *arg);
 184 static void     ng_l2tp_seq_rack_timeout(void *arg);
 185
 186 #ifdef INVARIANTS
 187 static void     ng_l2tp_seq_check(struct l2tp_seq *seq);
 188 #endif
 189
 190 /* Parse type for struct ng_l2tp_config */
 191 static const struct ng_parse_struct_field
 192         ng_l2tp_config_type_fields[] = NG_L2TP_CONFIG_TYPE_INFO;
 193 static const struct ng_parse_type ng_l2tp_config_type = {
 194         &ng_parse_struct_type,
 195         &ng_l2tp_config_type_fields,
 196 };
 197
 198 /* Parse type for struct ng_l2tp_sess_config */
 199 static const struct ng_parse_struct_field
 200         ng_l2tp_sess_config_type_fields[] = NG_L2TP_SESS_CONFIG_TYPE_INFO;
 201 static const struct ng_parse_type ng_l2tp_sess_config_type = {
 202         &ng_parse_struct_type,
 203         &ng_l2tp_sess_config_type_fields,
 204 };
 205
 206 /* Parse type for struct ng_l2tp_stats */
 207 static const struct ng_parse_struct_field
 208         ng_l2tp_stats_type_fields[] = NG_L2TP_STATS_TYPE_INFO;
 209 static const struct ng_parse_type ng_pptp_stats_type = {
 210         &ng_parse_struct_type,
 211         &ng_l2tp_stats_type_fields
 212 };
 213
 214 /* List of commands and how to convert arguments to/from ASCII */
 215 static const struct ng_cmdlist ng_l2tp_cmdlist[] = {
 216         {
 217           NGM_L2TP_COOKIE,
 218           NGM_L2TP_SET_CONFIG,
 219           "setconfig",
 220           &ng_l2tp_config_type,
 221           NULL
 222         },
 223         {
 224           NGM_L2TP_COOKIE,
 225           NGM_L2TP_GET_CONFIG,
 226           "getconfig",
 227           NULL,
 228           &ng_l2tp_config_type
 229         },
 230         {
 231           NGM_L2TP_COOKIE,
 232           NGM_L2TP_SET_SESS_CONFIG,
 233           "setsessconfig",
 234           &ng_l2tp_sess_config_type,
 235           NULL
 236         },
 237         {
 238           NGM_L2TP_COOKIE,
 239           NGM_L2TP_GET_SESS_CONFIG,
 240           "getsessconfig",
 241           &ng_parse_hint16_type,
 242           &ng_l2tp_sess_config_type
 243         },
 244         {
 245           NGM_L2TP_COOKIE,
 246           NGM_L2TP_GET_STATS,
 247           "getstats",
 248           NULL,
 249           &ng_pptp_stats_type
 250         },
 251         {
 252           NGM_L2TP_COOKIE,
 253           NGM_L2TP_CLR_STATS,
 254           "clrstats",
 255           NULL,
 256           NULL
 257         },
 258         {
 259           NGM_L2TP_COOKIE,
 260           NGM_L2TP_GETCLR_STATS,
 261           "getclrstats",
 262           NULL,
 263           &ng_pptp_stats_type
 264         },
 265         {
 266           NGM_L2TP_COOKIE,
 267           NGM_L2TP_ACK_FAILURE,
 268           "ackfailure",
 269           NULL,
 270           NULL
 271         },
 272         { 0 }
 273 };
 274
 275 /* Node type descriptor */
 276 static struct ng_type ng_l2tp_typestruct = {
 277         NG_VERSION,
 278         NG_L2TP_NODE_TYPE,
 279         NULL,
 280         ng_l2tp_constructor,
 281         ng_l2tp_rcvmsg,
 282         ng_l2tp_shutdown,
 283         ng_l2tp_newhook,
 284         NULL,
 285         NULL,
 286         ng_l2tp_rcvdata,
 287         ng_l2tp_rcvdata,
 288         ng_l2tp_disconnect,
 289         ng_l2tp_cmdlist
 290 };
 291 NETGRAPH_INIT(l2tp, &ng_l2tp_typestruct);
 292
 293 /* Sequence number state sanity checking */
 294 #ifdef INVARIANTS
 295 #define L2TP_SEQ_CHECK(seq)     ng_l2tp_seq_check(seq)
 296 #else
 297 #define L2TP_SEQ_CHECK(x)       do { } while (0)
 298 #endif
 299
 300 /* memmove macro */
 301 #define memmove(d, s, l)        ovbcopy(s, d, l)
 302
 303 /* Whether to use m_copypacket() or m_dup() */
 304 #define L2TP_COPY_MBUF          m_copypacket
 305
 306 /************************************************************************
 307                         NETGRAPH NODE STUFF
 308 ************************************************************************/
 309
 310 /*
 311  * Node type constructor
 312  */
 313 static int
 314 ng_l2tp_constructor(node_p *nodep)
 315 {
 316         priv_p priv;
 317         int error;
 318
 319         /* Allocate private structure */
 320         MALLOC(priv, priv_p, sizeof(*priv), M_NETGRAPH_L2TP, M_NOWAIT | M_ZERO);
 321         if (priv == NULL)
 322                 return (ENOMEM);
 323
 324         /* Apply a semi-reasonable default configuration */
 325         priv->conf.peer_win = 1;
 326         priv->conf.rexmit_max = L2TP_MAX_REXMIT;
 327         priv->conf.rexmit_max_to = L2TP_MAX_REXMIT_TO;
 328
 329         /* Initialize sequence number state */
 330         ng_l2tp_seq_init(priv);
 331
 332         /* Call generic node constructor */
 333         if ((error = ng_make_node_common(&ng_l2tp_typestruct, nodep))) {
 334                 FREE(priv, M_NETGRAPH_L2TP);
 335                 return (error);
 336         }
 337         NG_NODE_SET_PRIVATE(*nodep, priv);
 338         priv->node = *nodep;
 339
 340         /* Done */
 341         return (0);
 342 }
 343
 344 /*
 345  * Give our OK for a hook to be added.
 346  */
 347 static int
 348 ng_l2tp_newhook(node_p node, hook_p hook, const char *name)
 349 {
 350         const priv_p priv = NG_NODE_PRIVATE(node);
 351
 352         /* Check hook name */
 353         if (strcmp(name, NG_L2TP_HOOK_CTRL) == 0) {
 354                 if (priv->ctrl != NULL)
 355                         return (EISCONN);
 356                 priv->ctrl = hook;
 357         } else if (strcmp(name, NG_L2TP_HOOK_LOWER) == 0) {
 358                 if (priv->lower != NULL)
 359                         return (EISCONN);
 360                 priv->lower = hook;
 361         } else {
 362                 static const char hexdig[16] = "0123456789abcdef";
 363                 u_int16_t session_id;
 364                 hookpriv_p hpriv;
 365                 const char *hex;
 366                 int i;
 367                 int j;
 368
 369                 /* Parse hook name to get session ID */
 370                 if (strncmp(name, NG_L2TP_HOOK_SESSION_P,
 371                     sizeof(NG_L2TP_HOOK_SESSION_P) - 1) != 0)
 372                         return (EINVAL);
 373                 hex = name + sizeof(NG_L2TP_HOOK_SESSION_P) - 1;
 374                 for (session_id = i = 0; i < 4; i++) {
 375                         for (j = 0; j < 16 && hex[i] != hexdig[j]; j++);
 376                         if (j == 16)
 377                                 return (EINVAL);
 378                         session_id = (session_id << 4) | j;
 379                 }
 380                 if (hex[i] != '\0')
 381                         return (EINVAL);
 382
 383                 /* Create hook private structure */
 384                 MALLOC(hpriv, hookpriv_p,
 385                     sizeof(*hpriv), M_NETGRAPH_L2TP, M_NOWAIT | M_ZERO);
 386                 if (hpriv == NULL)
 387                         return (ENOMEM);
 388                 hpriv->conf.session_id = htons(session_id);
 389                 hpriv->conf.control_dseq = L2TP_CONTROL_DSEQ;
 390                 hpriv->conf.enable_dseq = L2TP_ENABLE_DSEQ;
 391                 NG_HOOK_SET_PRIVATE(hook, hpriv);
 392         }
 393
 394         /* Done */
 395         return (0);
 396 }
 397
 398 /*
 399  * Receive a control message.
 400  */
 401 static int
 402 ng_l2tp_rcvmsg(node_p node, struct ng_mesg *msg,
 403         const char *raddr, struct ng_mesg **rptr)
 404 {
 405         const priv_p priv = NG_NODE_PRIVATE(node);
 406         struct ng_mesg *resp = NULL;
 407         int error = 0;
 408
 409         switch (msg->header.typecookie) {
 410         case NGM_L2TP_COOKIE:
 411                 switch (msg->header.cmd) {
 412                 case NGM_L2TP_SET_CONFIG:
 413                     {
 414                         struct ng_l2tp_config *const conf =
 415                                 (struct ng_l2tp_config *)msg->data;
 416
 417                         /* Check for invalid or illegal config */
 418                         if (msg->header.arglen != sizeof(*conf)) {
 419                                 error = EINVAL;
 420                                 break;
 421                         }
 422                         conf->enabled = !!conf->enabled;
 423                         conf->match_id = !!conf->match_id;
 424                         conf->tunnel_id = htons(conf->tunnel_id);
 425                         conf->peer_id = htons(conf->peer_id);
 426                         if (priv->conf.enabled
 427                             && ((priv->conf.tunnel_id != 0
 428                                && conf->tunnel_id != priv->conf.tunnel_id)
 429                               || ((priv->conf.peer_id != 0
 430                                && conf->peer_id != priv->conf.peer_id)))) {
 431                                 error = EBUSY;
 432                                 break;
 433                         }
 434
 435                         /* Save calling node as failure target */
 436                         if (priv->ftarget != NULL)
 437                                 FREE(priv->ftarget, M_NETGRAPH_L2TP);
 438                         MALLOC(priv->ftarget, char *,
 439                             strlen(raddr) + 1, M_NETGRAPH_L2TP, M_NOWAIT);
 440                         if (priv->ftarget == NULL) {
 441                                 error = ENOMEM;
 442                                 break;
 443                         }
 444                         strcpy(priv->ftarget, raddr);
 445
 446                         /* Adjust sequence number state */
 447                         if ((error = ng_l2tp_seq_adjust(priv, conf)) != 0)
 448                                 break;
 449
 450                         /* Update node's config */
 451                         priv->conf = *conf;
 452                         break;
 453                     }
 454                 case NGM_L2TP_GET_CONFIG:
 455                     {
 456                         struct ng_l2tp_config *conf;
 457
 458                         NG_MKRESPONSE(resp, msg, sizeof(*conf), M_NOWAIT);
 459                         if (resp == NULL) {
 460                                 error = ENOMEM;
 461                                 break;
 462                         }
 463                         conf = (struct ng_l2tp_config *)resp->data;
 464                         *conf = priv->conf;
 465
 466                         /* Put ID's in host order */
 467                         conf->tunnel_id = ntohs(conf->tunnel_id);
 468                         conf->peer_id = ntohs(conf->peer_id);
 469                         break;
 470                     }
 471                 case NGM_L2TP_SET_SESS_CONFIG:
 472                     {
 473                         struct ng_l2tp_sess_config *const conf =
 474                             (struct ng_l2tp_sess_config *)msg->data;
 475                         hookpriv_p hpriv = NULL;
 476                         hook_p hook;
 477
 478                         /* Check for invalid or illegal config */
 479                         if (msg->header.arglen != sizeof(*conf)) {
 480                                 error = EINVAL;
 481                                 break;
 482                         }
 483
 484                         /* Put ID's in network order */
 485                         conf->session_id = htons(conf->session_id);
 486                         conf->peer_id = htons(conf->peer_id);
 487
 488                         /* Find matching hook */
 489                         LIST_FOREACH(hook, &node->hooks, hooks) {
 490                                 if ((hpriv = NG_HOOK_PRIVATE(hook)) == NULL)
 491                                         continue;
 492                                 if (hpriv->conf.session_id == conf->session_id)
 493                                         break;
 494                         }
 495                         if (hook == NULL) {
 496                                 error = ENOENT;
 497                                 break;
 498                         }
 499
 500                         /* Update hook's config */
 501                         hpriv->conf = *conf;
 502                         break;
 503                     }
 504                 case NGM_L2TP_GET_SESS_CONFIG:
 505                     {
 506                         struct ng_l2tp_sess_config *conf;
 507                         hookpriv_p hpriv = NULL;
 508                         u_int16_t session_id;
 509                         hook_p hook;
 510
 511                         /* Get session ID */
 512                         if (msg->header.arglen != sizeof(session_id)) {
 513                                 error = EINVAL;
 514                                 break;
 515                         }
 516                         memcpy(&session_id, msg->data, 2);
 517                         session_id = htons(session_id);
 518
 519                         /* Find matching hook */
 520                         LIST_FOREACH(hook, &node->hooks, hooks) {
 521                                 if ((hpriv = NG_HOOK_PRIVATE(hook)) == NULL)
 522                                         continue;
 523                                 if (hpriv->conf.session_id == session_id)
 524                                         break;
 525                         }
 526                         if (hook == NULL) {
 527                                 error = ENOENT;
 528                                 break;
 529                         }
 530
 531                         /* Send response */
 532                         NG_MKRESPONSE(resp, msg, sizeof(hpriv->conf), M_NOWAIT);
 533                         if (resp == NULL) {
 534                                 error = ENOMEM;
 535                                 break;
 536                         }
 537                         conf = (struct ng_l2tp_sess_config *)resp->data;
 538                         *conf = hpriv->conf;
 539
 540                         /* Put ID's in host order */
 541                         conf->session_id = ntohs(conf->session_id);
 542                         conf->peer_id = ntohs(conf->peer_id);
 543                         break;
 544                     }
 545                 case NGM_L2TP_GET_STATS:
 546                 case NGM_L2TP_CLR_STATS:
 547                 case NGM_L2TP_GETCLR_STATS:
 548                     {
 549                         if (msg->header.cmd != NGM_L2TP_CLR_STATS) {
 550                                 NG_MKRESPONSE(resp, msg,
 551                                     sizeof(priv->stats), M_NOWAIT);
 552                                 if (resp == NULL) {
 553                                         error = ENOMEM;
 554                                         break;
 555                                 }
 556                                 memcpy(resp->data,
 557                                     &priv->stats, sizeof(priv->stats));
 558                         }
 559                         if (msg->header.cmd != NGM_L2TP_GET_STATS)
 560                                 memset(&priv->stats, 0, sizeof(priv->stats));
 561                         break;
 562                     }
 563                 default:
 564                         error = EINVAL;
 565                         break;
 566                 }
 567                 break;
 568         default:
 569                 error = EINVAL;
 570                 break;
 571         }
 572         if (rptr)
 573                 *rptr = resp;
 574         else if (resp)
 575                 FREE(resp, M_NETGRAPH);
 576         FREE(msg, M_NETGRAPH);
 577         return (error);
 578 }
 579
 580 /*
 581  * Receive incoming data on a hook.
 582  */
 583 static int
 584 ng_l2tp_rcvdata(hook_p hook, struct mbuf *m, meta_p meta)
 585 {
 586         const node_p node = NG_HOOK_NODE(hook);
 587         const priv_p priv = NG_NODE_PRIVATE(node);
 588         int error;
 589
 590         /* Sanity check */
 591         L2TP_SEQ_CHECK(&priv->seq);
 592
 593         /* If not configured, reject */
 594         if (!priv->conf.enabled) {
 595                 NG_FREE_DATA(m, meta);
 596                 return (ENXIO);
 597         }
 598
 599         /* Handle incoming frame from below */
 600         if (hook == priv->lower) {
 601                 error = ng_l2tp_recv_lower(node, m, meta);
 602                 goto done;
 603         }
 604
 605         /* Handle outgoing control frame */
 606         if (hook == priv->ctrl) {
 607                 error = ng_l2tp_recv_ctrl(node, m, meta);
 608                 goto done;
 609         }
 610
 611         /* Handle outgoing data frame */
 612         error = ng_l2tp_recv_data(node, m, meta, NG_HOOK_PRIVATE(hook));
 613
 614 done:
 615         /* Done */
 616         L2TP_SEQ_CHECK(&priv->seq);
 617         return (error);
 618 }
 619
 620 /*
 621  * Destroy node
 622  */
 623 static int
 624 ng_l2tp_shutdown(node_p node)
 625 {
 626         const priv_p priv = NG_NODE_PRIVATE(node);
 627         struct l2tp_seq *const seq = &priv->seq;
 628
 629         /* Sanity check */
 630         L2TP_SEQ_CHECK(seq);
 631
 632         /* Reset sequence number state */
 633         node->flags |= NG_INVALID;
 634         ng_l2tp_seq_reset(priv);
 635         ng_cutlinks(node);
 636         ng_unname(node);
 637
 638         /* Free private data if neither timer is running */
 639         if (!seq->rack_timer_running && !seq->xack_timer_running) {
 640                 if (priv->ftarget != NULL)
 641                         FREE(priv->ftarget, M_NETGRAPH_L2TP);
 642                 FREE(priv, M_NETGRAPH_L2TP);
 643                 NG_NODE_SET_PRIVATE(node, NULL);
 644         }
 645
 646         /* Unref node */
 647         NG_NODE_UNREF(node);
 648         return (0);
 649 }
 650
 651 /*
 652  * Hook disconnection
 653  */
 654 static int
 655 ng_l2tp_disconnect(hook_p hook)
 656 {
 657         const node_p node = NG_HOOK_NODE(hook);
 658         const priv_p priv = NG_NODE_PRIVATE(node);
 659
 660         /* Zero out hook pointer */
 661         if (hook == priv->ctrl)
 662                 priv->ctrl = NULL;
 663         else if (hook == priv->lower)
 664                 priv->lower = NULL;
 665         else {
 666                 FREE(NG_HOOK_PRIVATE(hook), M_NETGRAPH_L2TP);
 667                 NG_HOOK_SET_PRIVATE(hook, NULL);
 668         }
 669
 670         /* Go away if no longer connected to anything */
 671         if (node->numhooks == 0)
 672                 ng_rmnode(node);
 673         return (0);
 674 }
 675
 676 /*************************************************************************
 677                         INTERNAL FUNCTIONS
 678 *************************************************************************/
 679
 680 /*
 681  * Handle an incoming frame from below.
 682  */
 683 static int
 684 ng_l2tp_recv_lower(node_p node, struct mbuf *m, meta_p meta)
 685 {
 686         static const u_int16_t req_bits[2][2] = {
 687                 { L2TP_DATA_0BITS, L2TP_DATA_1BITS },
 688                 { L2TP_CTRL_0BITS, L2TP_CTRL_1BITS },
 689         };
 690         const priv_p priv = NG_NODE_PRIVATE(node);
 691         hookpriv_p hpriv = NULL;
 692         hook_p hook = NULL;
 693         u_int16_t ids[2];
 694         u_int16_t hdr;
 695         u_int16_t ns;
 696         u_int16_t nr;
 697         int is_ctrl;
 698         int error;
 699         int len;
 700
 701         /* Update stats */
 702         priv->stats.recvPackets++;
 703         priv->stats.recvOctets += m->m_pkthdr.len;
 704
 705         /* Get initial header */
 706         if (m->m_pkthdr.len < 6) {
 707                 priv->stats.recvRunts++;
 708                 NG_FREE_DATA(m, meta);
 709                 return (EINVAL);
 710         }
 711         if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
 712                 priv->stats.memoryFailures++;
 713                 NG_FREE_META(meta);
 714                 return (EINVAL);
 715         }
 716         hdr = ntohs(*mtod(m, u_int16_t *));
 717         m_adj(m, 2);
 718
 719         /* Check required header bits and minimum length */
 720         is_ctrl = (hdr & L2TP_HDR_CTRL) != 0;
 721         if ((hdr & req_bits[is_ctrl][0]) != 0
 722             || (~hdr & req_bits[is_ctrl][1]) != 0) {
 723                 priv->stats.recvInvalid++;
 724                 NG_FREE_DATA(m, meta);
 725                 return (EINVAL);
 726         }
 727         if (m->m_pkthdr.len < 4                         /* tunnel, session id */
 728             + (2 * ((hdr & L2TP_HDR_LEN) != 0))         /* length field */
 729             + (4 * ((hdr & L2TP_HDR_SEQ) != 0))         /* seq # fields */
 730             + (2 * ((hdr & L2TP_HDR_OFF) != 0))) {      /* offset field */
 731                 priv->stats.recvRunts++;
 732                 NG_FREE_DATA(m, meta);
 733                 return (EINVAL);
 734         }
 735
 736         /* Get and validate length field if present */
 737         if ((hdr & L2TP_HDR_LEN) != 0) {
 738                 if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
 739                         priv->stats.memoryFailures++;
 740                         NG_FREE_META(meta);
 741                         return (EINVAL);
 742                 }
 743                 len = (u_int16_t)ntohs(*mtod(m, u_int16_t *)) - 4;
 744                 m_adj(m, 2);
 745                 if (len < 0 || len > m->m_pkthdr.len) {
 746                         priv->stats.recvInvalid++;
 747                         NG_FREE_DATA(m, meta);
 748                         return (EINVAL);
 749                 }
 750                 if (len < m->m_pkthdr.len)              /* trim extra bytes */
 751                         m_adj(m, -(m->m_pkthdr.len - len));
 752         }
 753
 754         /* Get tunnel ID and session ID */
 755         if (m->m_len < 4 && (m = m_pullup(m, 4)) == NULL) {
 756                 priv->stats.memoryFailures++;
 757                 NG_FREE_META(meta);
 758                 return (EINVAL);
 759         }
 760         memcpy(ids, mtod(m, u_int16_t *), 4);
 761         m_adj(m, 4);
 762
 763         /* Check tunnel ID */
 764         if (ids[0] != priv->conf.tunnel_id
 765             && (priv->conf.match_id || ids[0] != 0)) {
 766                 priv->stats.recvWrongTunnel++;
 767                 NG_FREE_DATA(m, meta);
 768                 return (EADDRNOTAVAIL);
 769         }
 770
 771         /* Check session ID (for data packets only) */
 772         if ((hdr & L2TP_HDR_CTRL) == 0) {
 773                 LIST_FOREACH(hook, &node->hooks, hooks) {
 774                         if ((hpriv = NG_HOOK_PRIVATE(hook)) == NULL)
 775                                 continue;
 776                         if (hpriv->conf.session_id == ids[1])
 777                                 break;
 778                 }
 779                 if (hook == NULL) {
 780                         priv->stats.recvUnknownSID++;
 781                         NG_FREE_DATA(m, meta);
 782                         return (ENOTCONN);
 783                 }
 784                 hpriv = NG_HOOK_PRIVATE(hook);
 785         }
 786
 787         /* Get Ns, Nr fields if present */
 788         if ((hdr & L2TP_HDR_SEQ) != 0) {
 789                 if (m->m_len < 4 && (m = m_pullup(m, 4)) == NULL) {
 790                         priv->stats.memoryFailures++;
 791                         NG_FREE_META(meta);
 792                         return (EINVAL);
 793                 }
 794                 memcpy(&ns, &mtod(m, u_int16_t *)[0], 2);
 795                 ns = ntohs(ns);
 796                 memcpy(&nr, &mtod(m, u_int16_t *)[1], 2);
 797                 nr = ntohs(nr);
 798                 m_adj(m, 4);
 799         }
 800
 801         /* Strip offset padding if present */
 802         if ((hdr & L2TP_HDR_OFF) != 0) {
 803                 u_int16_t offset;
 804
 805                 /* Get length of offset padding */
 806                 if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
 807                         priv->stats.memoryFailures++;
 808                         NG_FREE_META(meta);
 809                         return (EINVAL);
 810                 }
 811                 memcpy(&offset, mtod(m, u_int16_t *), 2);
 812                 offset = ntohs(offset);
 813
 814                 /* Trim offset padding */
 815                 if (offset <= 2 || offset > m->m_pkthdr.len) {
 816                         priv->stats.recvInvalid++;
 817                         NG_FREE_DATA(m, meta);
 818                         return (EINVAL);
 819                 }
 820                 m_adj(m, offset);
 821         }
 822
 823         /* Handle control packets */
 824         if ((hdr & L2TP_HDR_CTRL) != 0) {
 825
 826                 /* Handle receive ack sequence number Nr */
 827                 ng_l2tp_seq_recv_nr(priv, nr);
 828
 829                 /* Discard ZLB packets */
 830                 if (m->m_pkthdr.len == 0) {
 831                         priv->stats.recvZLBs++;
 832                         NG_FREE_DATA(m, meta);
 833                         return (0);
 834                 }
 835
 836                 /*
 837                  * Prepend session ID to packet here: we don't want to accept
 838                  * the send sequence number Ns if we have to drop the packet
 839                  * later because of a memory error, because then the upper
 840                  * layer would never get the packet.
 841                  */
 842                 M_PREPEND(m, 2, MB_DONTWAIT);
 843                 if (m == NULL) {
 844                         priv->stats.memoryFailures++;
 845                         NG_FREE_META(meta);
 846                         return (ENOBUFS);
 847                 }
 848                 memcpy(mtod(m, u_int16_t *), &ids[1], 2);
 849
 850                 /* Now handle send sequence number */
 851                 if (ng_l2tp_seq_recv_ns(priv, ns) == -1) {
 852                         NG_FREE_DATA(m, meta);
 853                         return (0);
 854                 }
 855
 856                 /* Deliver packet to upper layers */
 857                 NG_SEND_DATA(error, priv->ctrl, m, meta);
 858                 return (error);
 859         }
 860
 861         /* Follow peer's lead in data sequencing, if configured to do so */
 862         if (!hpriv->conf.control_dseq)
 863                 hpriv->conf.enable_dseq = ((hdr & L2TP_HDR_SEQ) != 0);
 864
 865         /* Handle data sequence numbers if present and enabled */
 866         if ((hdr & L2TP_HDR_SEQ) != 0) {
 867                 if (hpriv->conf.enable_dseq
 868                     && L2TP_SEQ_DIFF(ns, hpriv->nr) < 0) {
 869                         NG_FREE_DATA(m, meta);  /* duplicate or out of order */
 870                         priv->stats.recvDataDrops++;
 871                         return (0);
 872                 }
 873                 hpriv->nr = ns + 1;
 874         }
 875
 876         /* Drop empty data packets */
 877         if (m->m_pkthdr.len == 0) {
 878                 NG_FREE_DATA(m, meta);
 879                 return (0);
 880         }
 881
 882         /* Deliver data */
 883         NG_SEND_DATA(error, hook, m, meta);
 884         return (error);
 885 }
 886
 887 /*
 888  * Handle an outgoing control frame.
 889  */
 890 static int
 891 ng_l2tp_recv_ctrl(node_p node, struct mbuf *m, meta_p meta)
 892 {
 893         const priv_p priv = NG_NODE_PRIVATE(node);
 894         struct l2tp_seq *const seq = &priv->seq;
 895         int i;
 896
 897         /* Discard meta XXX should queue meta's along with packet */
 898         NG_FREE_META(meta);
 899
 900         /* Packet should have session ID prepended */
 901         if (m->m_pkthdr.len < 2) {
 902                 priv->stats.xmitInvalid++;
 903                 m_freem(m);
 904                 return (EINVAL);
 905         }
 906
 907         /* Check max length */
 908         if (m->m_pkthdr.len >= 0x10000 - 14) {
 909                 priv->stats.xmitTooBig++;
 910                 m_freem(m);
 911                 return (EOVERFLOW);
 912         }
 913
 914         /* Find next empty slot in transmit queue */
 915         for (i = 0; i < L2TP_MAX_XWIN && seq->xwin[i] != NULL; i++);
 916         if (i == L2TP_MAX_XWIN) {
 917                 priv->stats.xmitDrops++;
 918                 m_freem(m);
 919                 return (ENOBUFS);
 920         }
 921         seq->xwin[i] = m;
 922
 923         /* Sanity check receive ack timer state */
 924         KASSERT((i == 0) ^ seq->rack_timer_running,
 925             ("%s: xwin %d full but rack timer %srunning",
 926             __func__, i, seq->rack_timer_running ? "" : "not "));
 927
 928         /* If peer's receive window is already full, nothing else to do */
 929         if (i >= seq->cwnd)
 930                 return (0);
 931
 932         /* Start retransmit timer if not already running */
 933         if (!seq->rack_timer_running) {
 934                 callout_reset(&seq->rack_timer,
 935                     hz, ng_l2tp_seq_rack_timeout, node);
 936                 seq->rack_timer_running = 1;
 937                 NG_NODE_REF(node);
 938         }
 939
 940         /* Copy packet */
 941         if ((m = L2TP_COPY_MBUF(seq->xwin[i], MB_DONTWAIT)) == NULL) {
 942                 priv->stats.memoryFailures++;
 943                 return (ENOBUFS);
 944         }
 945
 946         /* Send packet and increment xmit sequence number */
 947         return (ng_l2tp_xmit_ctrl(priv, m, seq->ns++));
 948 }
 949
 950 /*
 951  * Handle an outgoing data frame.
 952  */
 953 static int
 954 ng_l2tp_recv_data(node_p node, struct mbuf *m, meta_p meta, hookpriv_p hpriv)
 955 {
 956         const priv_p priv = NG_NODE_PRIVATE(node);
 957         u_int16_t hdr;
 958         int error;
 959         int i = 1;
 960
 961         /* Check max length */
 962         if (m->m_pkthdr.len >= 0x10000 - 12) {
 963                 priv->stats.xmitDataTooBig++;
 964                 NG_FREE_META(meta);
 965                 m_freem(m);
 966                 return (EOVERFLOW);
 967         }
 968
 969         /* Prepend L2TP header */
 970         M_PREPEND(m, 6
 971             + (2 * (hpriv->conf.include_length != 0))
 972             + (4 * (hpriv->conf.enable_dseq != 0)),
 973             MB_DONTWAIT);
 974         if (m == NULL) {
 975                 priv->stats.memoryFailures++;
 976                 NG_FREE_META(meta);
 977                 return (ENOBUFS);
 978         }
 979         hdr = L2TP_DATA_HDR;
 980         if (hpriv->conf.include_length) {
 981                 hdr |= L2TP_HDR_LEN;
 982                 mtod(m, u_int16_t *)[i++] = htons(m->m_pkthdr.len);
 983         }
 984         mtod(m, u_int16_t *)[i++] = priv->conf.peer_id;
 985         mtod(m, u_int16_t *)[i++] = hpriv->conf.peer_id;
 986         if (hpriv->conf.enable_dseq) {
 987                 hdr |= L2TP_HDR_SEQ;
 988                 mtod(m, u_int16_t *)[i++] = htons(hpriv->ns);
 989                 mtod(m, u_int16_t *)[i++] = htons(hpriv->nr);
 990                 hpriv->ns++;
 991         }
 992         mtod(m, u_int16_t *)[0] = htons(hdr);
 993
 994         /* Send packet */
 995         NG_SEND_DATA(error, priv->lower, m, meta);
 996         return (error);
 997 }
 998
 999 /*
1000  * Send a message to our controlling node that we've failed.
1001  */
1002 static void
1003 ng_l2tp_seq_failure(priv_p priv)
1004 {
1005         struct ng_mesg *msg;
1006
1007         NG_MKMESSAGE(msg, NGM_L2TP_COOKIE, NGM_L2TP_ACK_FAILURE, 0, M_NOWAIT);
1008         if (msg == NULL)
1009                 return;
1010         ng_send_msg(priv->node, msg, priv->ftarget, NULL);
1011 }
1012
1013 /************************************************************************
1014                         SEQUENCE NUMBER HANDLING
1015 ************************************************************************/
1016
1017 /*
1018  * Initialize sequence number state.
1019  */
1020 static void
1021 ng_l2tp_seq_init(priv_p priv)
1022 {
1023         struct l2tp_seq *const seq = &priv->seq;
1024
1025         KASSERT(priv->conf.peer_win >= 1,
1026             ("%s: peer_win is zero", __func__));
1027         memset(seq, 0, sizeof(*seq));
1028         seq->cwnd = 1;
1029         seq->wmax = priv->conf.peer_win;
1030         if (seq->wmax > L2TP_MAX_XWIN)
1031                 seq->wmax = L2TP_MAX_XWIN;
1032         seq->ssth = seq->wmax;
1033         seq->max_rexmits = priv->conf.rexmit_max;
1034         seq->max_rexmit_to = priv->conf.rexmit_max_to;
1035         callout_init(&seq->rack_timer);
1036         callout_init(&seq->xack_timer);
1037         L2TP_SEQ_CHECK(seq);
1038 }
1039
1040 /*
1041  * Adjust sequence number state accordingly after reconfiguration.
1042  */
1043 static int
1044 ng_l2tp_seq_adjust(priv_p priv, const struct ng_l2tp_config *conf)
1045 {
1046         struct l2tp_seq *const seq = &priv->seq;
1047         u_int16_t new_wmax;
1048
1049         /* If disabling node, reset state sequence number */
1050         if (!conf->enabled) {
1051                 ng_l2tp_seq_reset(priv);
1052                 return (0);
1053         }
1054
1055         /* Adjust peer's max recv window; it can only increase */
1056         new_wmax = conf->peer_win;
1057         if (new_wmax > L2TP_MAX_XWIN)
1058                 new_wmax = L2TP_MAX_XWIN;
1059         if (new_wmax == 0)
1060                 return (EINVAL);
1061         if (new_wmax < seq->wmax)
1062                 return (EBUSY);
1063         seq->wmax = new_wmax;
1064
1065         /* Update retransmit parameters */
1066         seq->max_rexmits = conf->rexmit_max;
1067         seq->max_rexmit_to = conf->rexmit_max_to;
1068
1069         /* Done */
1070         return (0);
1071 }
1072
1073 /*
1074  * Reset sequence number state.
1075  */
1076 static void
1077 ng_l2tp_seq_reset(priv_p priv)
1078 {
1079         struct l2tp_seq *const seq = &priv->seq;
1080         hookpriv_p hpriv = NULL;
1081         hook_p hook;
1082         int i;
1083
1084         /* Sanity check */
1085         L2TP_SEQ_CHECK(seq);
1086
1087         /* Stop timers */
1088         if (seq->rack_timer_running && callout_stop(&seq->rack_timer) == 1) {
1089                 seq->rack_timer_running = 0;
1090                 NG_NODE_UNREF(priv->node);
1091         }
1092         if (seq->xack_timer_running && callout_stop(&seq->xack_timer) == 1) {
1093                 seq->xack_timer_running = 0;
1094                 NG_NODE_UNREF(priv->node);
1095         }
1096
1097         /* Free retransmit queue */
1098         for (i = 0; i < L2TP_MAX_XWIN; i++) {
1099                 if (seq->xwin[i] == NULL)
1100                         break;
1101                 m_freem(seq->xwin[i]);
1102         }
1103
1104         /* Reset session hooks' sequence number states */
1105         LIST_FOREACH(hook, &priv->node->hooks, hooks) {
1106                 if ((hpriv = NG_HOOK_PRIVATE(hook)) == NULL)
1107                         continue;
1108                 hpriv->conf.control_dseq = 0;
1109                 hpriv->conf.enable_dseq = 0;
1110                 hpriv->nr = 0;
1111                 hpriv->ns = 0;
1112         }
1113
1114         /* Reset node's sequence number state */
1115         memset(seq, 0, sizeof(*seq));
1116         seq->cwnd = 1;
1117         seq->wmax = L2TP_MAX_XWIN;
1118         seq->ssth = seq->wmax;
1119
1120         /* Done */
1121         L2TP_SEQ_CHECK(seq);
1122 }
1123
1124 /*
1125  * Handle receipt of an acknowledgement value (Nr) from peer.
1126  */
1127 static void
1128 ng_l2tp_seq_recv_nr(priv_p priv, u_int16_t nr)
1129 {
1130         struct l2tp_seq *const seq = &priv->seq;
1131         struct mbuf *m;
1132         int nack;
1133         int i;
1134
1135         /* Verify peer's ACK is in range */
1136         if ((nack = L2TP_SEQ_DIFF(nr, seq->rack)) <= 0)
1137                 return;                         /* duplicate ack */
1138         if (L2TP_SEQ_DIFF(nr, seq->ns) > 0) {
1139                 priv->stats.recvBadAcks++;      /* ack for packet not sent */
1140                 return;
1141         }
1142         KASSERT(nack <= L2TP_MAX_XWIN,
1143             ("%s: nack=%d > %d", __func__, nack, L2TP_MAX_XWIN));
1144
1145         /* Update receive ack stats */
1146         seq->rack = nr;
1147         seq->rexmits = 0;
1148
1149         /* Free acknowledged packets and shift up packets in the xmit queue */
1150         for (i = 0; i < nack; i++)
1151                 m_freem(seq->xwin[i]);
1152         memmove(seq->xwin, seq->xwin + nack,
1153             (L2TP_MAX_XWIN - nack) * sizeof(*seq->xwin));
1154         memset(seq->xwin + (L2TP_MAX_XWIN - nack), 0,
1155             nack * sizeof(*seq->xwin));
1156
1157         /*
1158          * Do slow-start/congestion avoidance windowing algorithm described
1159          * in RFC 2661, Appendix A. Here we handle a multiple ACK as if each
1160          * ACK had arrived separately.
1161          */
1162         if (seq->cwnd < seq->wmax) {
1163
1164                 /* Handle slow start phase */
1165                 if (seq->cwnd < seq->ssth) {
1166                         seq->cwnd += nack;
1167                         nack = 0;
1168                         if (seq->cwnd > seq->ssth) {    /* into cg.av. phase */
1169                                 nack = seq->cwnd - seq->ssth;
1170                                 seq->cwnd = seq->ssth;
1171                         }
1172                 }
1173
1174                 /* Handle congestion avoidance phase */
1175                 if (seq->cwnd >= seq->ssth) {
1176                         seq->acks += nack;
1177                         while (seq->acks >= seq->cwnd) {
1178                                 seq->acks -= seq->cwnd;
1179                                 if (seq->cwnd < seq->wmax)
1180                                         seq->cwnd++;
1181                         }
1182                 }
1183         }
1184
1185         /* Stop xmit timer */
1186         if (seq->rack_timer_running && callout_stop(&seq->rack_timer) == 1) {
1187                 seq->rack_timer_running = 0;
1188                 NG_NODE_UNREF(priv->node);
1189         }
1190
1191         /* If transmit queue is empty, we're done for now */
1192         if (seq->xwin[0] == NULL)
1193                 return;
1194
1195         /* Start restransmit timer again */
1196         callout_reset(&seq->rack_timer,
1197             hz, ng_l2tp_seq_rack_timeout, priv->node);
1198         seq->rack_timer_running = 1;
1199         NG_NODE_REF(priv->node);
1200
1201         /*
1202          * Send more packets, trying to keep peer's receive window full.
1203          * If there is a memory error, pretend packet was sent, as it
1204          * will get retransmitted later anyway.
1205          */
1206         while ((i = L2TP_SEQ_DIFF(seq->ns, seq->rack)) < seq->cwnd
1207             && seq->xwin[i] != NULL) {
1208                 if ((m = L2TP_COPY_MBUF(seq->xwin[i], MB_DONTWAIT)) == NULL)
1209                         priv->stats.memoryFailures++;
1210                 else
1211                         ng_l2tp_xmit_ctrl(priv, m, seq->ns);
1212                 seq->ns++;
1213         }
1214 }
1215
1216 /*
1217  * Handle receipt of a sequence number value (Ns) from peer.
1218  * We make no attempt to re-order out of order packets.
1219  *
1220  * This function should only be called for non-ZLB packets.
1221  *
1222  * Returns:
1223  *       0      Accept packet
1224  *      -1      Drop packet
1225  */
1226 static int
1227 ng_l2tp_seq_recv_ns(priv_p priv, u_int16_t ns)
1228 {
1229         struct l2tp_seq *const seq = &priv->seq;
1230
1231         /* If not what we expect, drop packet and send an immediate ZLB ack */
1232         if (ns != seq->nr) {
1233                 if (L2TP_SEQ_DIFF(ns, seq->nr) < 0)
1234                         priv->stats.recvDuplicates++;
1235                 else
1236                         priv->stats.recvOutOfOrder++;
1237                 ng_l2tp_xmit_ctrl(priv, NULL, seq->ns);
1238                 return (-1);
1239         }
1240
1241         /* Update recv sequence number */
1242         seq->nr++;
1243
1244         /* Start receive ack timer, if not already running */
1245         if (!seq->xack_timer_running) {
1246                 callout_reset(&seq->xack_timer,
1247                     L2TP_DELAYED_ACK, ng_l2tp_seq_xack_timeout, priv->node);
1248                 seq->xack_timer_running = 1;
1249                 NG_NODE_REF(priv->node);
1250         }
1251
1252         /* Accept packet */
1253         return (0);
1254 }
1255
1256 /*
1257  * Handle an ack timeout. We have an outstanding ack that we
1258  * were hoping to piggy-back, but haven't, so send a ZLB.
1259  */
1260 static void
1261 ng_l2tp_seq_xack_timeout(void *arg)
1262 {
1263         const node_p node = arg;
1264         const priv_p priv = NG_NODE_PRIVATE(node);
1265         struct l2tp_seq *const seq = &priv->seq;
1266
1267         /* Check if node is going away */
1268         crit_enter();
1269         if (NG_NODE_NOT_VALID(node)) {
1270                 seq->xack_timer_running = 0;
1271                 if (!seq->rack_timer_running) {
1272                         if (priv->ftarget != NULL)
1273                                 FREE(priv->ftarget, M_NETGRAPH_L2TP);
1274                         FREE(priv, M_NETGRAPH_L2TP);
1275                         NG_NODE_SET_PRIVATE(node, NULL);
1276                 }
1277                 NG_NODE_UNREF(node);
1278                 crit_exit();
1279                 return;
1280         }
1281
1282         /* Sanity check */
1283         L2TP_SEQ_CHECK(seq);
1284
1285         /* If ack is still outstanding, send a ZLB */
1286         if (seq->xack != seq->nr)
1287                 ng_l2tp_xmit_ctrl(priv, NULL, seq->ns);
1288
1289         /* Done */
1290         seq->xack_timer_running = 0;
1291         NG_NODE_UNREF(node);
1292         L2TP_SEQ_CHECK(seq);
1293         crit_exit();
1294 }
1295
1296 /*
1297  * Handle a transmit timeout. The peer has failed to respond
1298  * with an ack for our packet, so retransmit it.
1299  */
1300 static void
1301 ng_l2tp_seq_rack_timeout(void *arg)
1302 {
1303         const node_p node = arg;
1304         const priv_p priv = NG_NODE_PRIVATE(node);
1305         struct l2tp_seq *const seq = &priv->seq;
1306         struct mbuf *m;
1307         u_int delay;
1308
1309         /* Check if node is going away */
1310         crit_enter();
1311         if (NG_NODE_NOT_VALID(node)) {
1312                 seq->rack_timer_running = 0;
1313                 if (!seq->xack_timer_running) {
1314                         if (priv->ftarget != NULL)
1315                                 FREE(priv->ftarget, M_NETGRAPH_L2TP);
1316                         FREE(priv, M_NETGRAPH_L2TP);
1317                         NG_NODE_SET_PRIVATE(node, NULL);
1318                 }
1319                 NG_NODE_UNREF(node);
1320                 crit_exit();
1321                 return;
1322         }
1323
1324         /* Sanity check */
1325         L2TP_SEQ_CHECK(seq);
1326
1327         /* Make sure peer's ack is still outstanding before doing anything */
1328         if (seq->rack == seq->ns) {
1329                 seq->rack_timer_running = 0;
1330                 NG_NODE_UNREF(node);
1331                 goto done;
1332         }
1333         priv->stats.xmitRetransmits++;
1334
1335         /* Have we reached the retransmit limit? If so, notify owner. */
1336         if (seq->rexmits++ >= seq->max_rexmits)
1337                 ng_l2tp_seq_failure(priv);
1338
1339         /* Restart timer, this time with an increased delay */
1340         delay = (seq->rexmits > 12) ? (1 << 12) : (1 << seq->rexmits);
1341         if (delay > seq->max_rexmit_to)
1342                 delay = seq->max_rexmit_to;
1343         callout_reset(&seq->rack_timer,
1344             hz * delay, ng_l2tp_seq_rack_timeout, node);
1345
1346         /* Do slow-start/congestion algorithm windowing algorithm */
1347         seq->ssth = (seq->cwnd + 1) / 2;
1348         seq->cwnd = 1;
1349         seq->acks = 0;
1350
1351         /* Retransmit oldest unack'd packet */
1352         if ((m = L2TP_COPY_MBUF(seq->xwin[0], MB_DONTWAIT)) == NULL)
1353                 priv->stats.memoryFailures++;
1354         else
1355                 ng_l2tp_xmit_ctrl(priv, m, seq->rack);
1356
1357 done:
1358         /* Done */
1359         L2TP_SEQ_CHECK(seq);
1360         crit_exit();
1361 }
1362
1363 /*
1364  * Transmit a control stream packet, payload optional.
1365  * The transmit sequence number is not incremented.
1366  */
1367 static int
1368 ng_l2tp_xmit_ctrl(priv_p priv, struct mbuf *m, u_int16_t ns)
1369 {
1370         struct l2tp_seq *const seq = &priv->seq;
1371         u_int16_t session_id = 0;
1372         meta_p meta = NULL;
1373         int error;
1374
1375         /* If no mbuf passed, send an empty packet (ZLB) */
1376         if (m == NULL) {
1377
1378                 /* Create a new mbuf for ZLB packet */
1379                 MGETHDR(m, MB_DONTWAIT, MT_DATA);
1380                 if (m == NULL) {
1381                         priv->stats.memoryFailures++;
1382                         return (ENOBUFS);
1383                 }
1384                 m->m_len = m->m_pkthdr.len = 12;
1385                 m->m_pkthdr.rcvif = NULL;
1386                 priv->stats.xmitZLBs++;
1387         } else {
1388
1389                 /* Strip off session ID */
1390                 if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
1391                         priv->stats.memoryFailures++;
1392                         return (ENOBUFS);
1393                 }
1394                 memcpy(&session_id, mtod(m, u_int16_t *), 2);
1395                 m_adj(m, 2);
1396
1397                 /* Make room for L2TP header */
1398                 M_PREPEND(m, 12, MB_DONTWAIT);
1399                 if (m == NULL) {
1400                         priv->stats.memoryFailures++;
1401                         return (ENOBUFS);
1402                 }
1403         }
1404
1405         /* Fill in L2TP header */
1406         mtod(m, u_int16_t *)[0] = htons(L2TP_CTRL_HDR);
1407         mtod(m, u_int16_t *)[1] = htons(m->m_pkthdr.len);
1408         mtod(m, u_int16_t *)[2] = priv->conf.peer_id;
1409         mtod(m, u_int16_t *)[3] = session_id;
1410         mtod(m, u_int16_t *)[4] = htons(ns);
1411         mtod(m, u_int16_t *)[5] = htons(seq->nr);
1412
1413         /* Update sequence number info and stats */
1414         priv->stats.xmitPackets++;
1415         priv->stats.xmitOctets += m->m_pkthdr.len;
1416
1417         /* Stop ack timer: we're sending an ack with this packet */
1418         if (seq->xack_timer_running && callout_stop(&seq->xack_timer) == 1) {
1419                 seq->xack_timer_running = 0;
1420                 NG_NODE_UNREF(priv->node);
1421         }
1422         seq->xack = seq->nr;
1423
1424         /* Send packet */
1425         NG_SEND_DATA(error, priv->lower, m, meta);
1426         return (error);
1427 }
1428
1429 #ifdef INVARIANTS
1430 /*
1431  * Sanity check sequence number state.
1432  */
1433 static void
1434 ng_l2tp_seq_check(struct l2tp_seq *seq)
1435 {
1436         const int self_unack = L2TP_SEQ_DIFF(seq->nr, seq->xack);
1437         const int peer_unack = L2TP_SEQ_DIFF(seq->ns, seq->rack);
1438         int i;
1439
1440 #define CHECK(p)        KASSERT((p), ("%s: not: %s", __func__, #p))
1441
1442         CHECK(seq->wmax <= L2TP_MAX_XWIN);
1443         CHECK(seq->cwnd >= 1);
1444         CHECK(seq->cwnd <= seq->wmax);
1445         CHECK(seq->ssth >= 1);
1446         CHECK(seq->ssth <= seq->wmax);
1447         if (seq->cwnd < seq->ssth)
1448                 CHECK(seq->acks == 0);
1449         else
1450                 CHECK(seq->acks <= seq->cwnd);
1451         CHECK(self_unack >= 0);
1452         CHECK(peer_unack >= 0);
1453         CHECK(peer_unack <= seq->wmax);
1454         CHECK((self_unack == 0) ^ seq->xack_timer_running);
1455         CHECK((peer_unack == 0) ^ seq->rack_timer_running);
1456         CHECK(seq->rack_timer_running || !callout_pending(&seq->rack_timer));
1457         CHECK(seq->xack_timer_running || !callout_pending(&seq->xack_timer));
1458         for (i = 0; i < peer_unack; i++)
1459                 CHECK(seq->xwin[i] != NULL);
1460         for ( ; i < seq->cwnd; i++)         /* verify peer's recv window full */
1461                 CHECK(seq->xwin[i] == NULL);
1462
1463 #undef CHECK
1464 }
1465 #endif  /* INVARIANTS */
1466
1467