sys/netgraph/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  * $FreeBSD$
  40  */
  41
  42 /*
  43  * L2TP netgraph node type.
  44  *
  45  * This node type implements the lower layer of the
  46  * L2TP protocol as specified in RFC 2661.
  47  */
  48
  49 #include <sys/param.h>
  50 #include <sys/systm.h>
  51 #include <sys/kernel.h>
  52 #include <sys/time.h>
  53 #include <sys/conf.h>
  54 #include <sys/mbuf.h>
  55 #include <sys/malloc.h>
  56 #include <sys/errno.h>
  57 #include <sys/libkern.h>
  58
  59 #include <netgraph/ng_message.h>
  60 #include <netgraph/netgraph.h>
  61 #include <netgraph/ng_parse.h>
  62 #include <netgraph/ng_l2tp.h>
  63
  64 #ifdef NG_SEPARATE_MALLOC
  65 MALLOC_DEFINE(M_NETGRAPH_L2TP, "netgraph_l2tp", "netgraph l2tp node");
  66 #else
  67 #define M_NETGRAPH_L2TP M_NETGRAPH
  68 #endif
  69
  70 /* L2TP header format (first 2 bytes only) */
  71 #define L2TP_HDR_CTRL           0x8000                  /* control packet */
  72 #define L2TP_HDR_LEN            0x4000                  /* has length field */
  73 #define L2TP_HDR_SEQ            0x0800                  /* has ns, nr fields */
  74 #define L2TP_HDR_OFF            0x0200                  /* has offset field */
  75 #define L2TP_HDR_PRIO           0x0100                  /* give priority */
  76 #define L2TP_HDR_VERS_MASK      0x000f                  /* version field mask */
  77 #define L2TP_HDR_VERSION        0x0002                  /* version field */
  78
  79 /* Bits that must be zero or one in first two bytes of header */
  80 #define L2TP_CTRL_0BITS         0x030d                  /* ctrl: must be 0 */
  81 #define L2TP_CTRL_1BITS         0xc802                  /* ctrl: must be 1 */
  82 #define L2TP_DATA_0BITS         0x800d                  /* data: must be 0 */
  83 #define L2TP_DATA_1BITS         0x0002                  /* data: must be 1 */
  84
  85 /* Standard xmit ctrl and data header bits */
  86 #define L2TP_CTRL_HDR           (L2TP_HDR_CTRL | L2TP_HDR_LEN \
  87                                     | L2TP_HDR_SEQ | L2TP_HDR_VERSION)
  88 #define L2TP_DATA_HDR           (L2TP_HDR_VERSION)      /* optional: len, seq */
  89
  90 /* Some hard coded values */
  91 #define L2TP_MAX_XWIN           16                      /* my max xmit window */
  92 #define L2TP_MAX_REXMIT         5                       /* default max rexmit */
  93 #define L2TP_MAX_REXMIT_TO      30                      /* default rexmit to */
  94 #define L2TP_DELAYED_ACK        ((hz + 19) / 20)        /* delayed ack: 50 ms */
  95
  96 /* Default data sequence number configuration for new sessions */
  97 #define L2TP_CONTROL_DSEQ       1                       /* we are the lns */
  98 #define L2TP_ENABLE_DSEQ        1                       /* enable data seq # */
  99
 100 /* Compare sequence numbers using circular math */
 101 #define L2TP_SEQ_DIFF(x, y)     ((int)((int16_t)(x) - (int16_t)(y)))
 102
 103 /*
 104  * Sequence number state
 105  *
 106  * Invariants:
 107  *    - If cwnd < ssth, we're doing slow start, otherwise congestion avoidance
 108  *    - The number of unacknowledged xmit packets is (ns - rack) <= seq->wmax
 109  *    - The first (ns - rack) mbuf's in xwin[] array are copies of these
 110  *      unacknowledged packets; the remainder of xwin[] consists first of
 111  *      zero or more further untransmitted packets in the transmit queue
 112  *    - We try to keep the peer's receive window as full as possible.
 113  *      Therefore, (i < cwnd && xwin[i] != NULL) implies (ns - rack) > i.
 114  *    - rack_timer is running iff (ns - rack) > 0 (unack'd xmit'd pkts)
 115  *    - If xack != nr, there are unacknowledged recv packet(s) (delayed ack)
 116  *    - xack_timer is running iff xack != nr (unack'd rec'd pkts)
 117  */
 118 struct l2tp_seq {
 119         u_int16_t               ns;             /* next xmit seq we send */
 120         u_int16_t               nr;             /* next recv seq we expect */
 121         u_int16_t               rack;           /* last 'nr' we rec'd */
 122         u_int16_t               xack;           /* last 'nr' we sent */
 123         u_int16_t               wmax;           /* peer's max recv window */
 124         u_int16_t               cwnd;           /* current congestion window */
 125         u_int16_t               ssth;           /* slow start threshold */
 126         u_int16_t               acks;           /* # consecutive acks rec'd */
 127         u_int16_t               rexmits;        /* # retransmits sent */
 128         u_int16_t               max_rexmits;    /* max # retransmits sent */
 129         u_int16_t               max_rexmit_to;  /* max retransmit timeout */
 130         struct callout          rack_timer;     /* retransmit timer */
 131         struct callout          xack_timer;     /* delayed ack timer */
 132         struct mbuf             *xwin[L2TP_MAX_XWIN];   /* transmit window */
 133 };
 134
 135 /* Node private data */
 136 struct ng_l2tp_private {
 137         node_p                  node;           /* back pointer to node */
 138         hook_p                  ctrl;           /* hook to upper layers */
 139         hook_p                  lower;          /* hook to lower layers */
 140         struct ng_l2tp_config   conf;           /* node configuration */
 141         struct ng_l2tp_stats    stats;          /* node statistics */
 142         struct l2tp_seq         seq;            /* ctrl sequence number state */
 143         ng_ID_t                 ftarget;        /* failure message target */
 144 };
 145 typedef struct ng_l2tp_private *priv_p;
 146
 147 /* Hook private data (data session hooks only) */
 148 struct ng_l2tp_hook_private {
 149         struct ng_l2tp_sess_config      conf;   /* hook/session config */
 150         struct ng_l2tp_session_stats    stats;  /* per sessions statistics */
 151         u_int16_t                       ns;     /* data ns sequence number */
 152         u_int16_t                       nr;     /* data nr sequence number */
 153 };
 154 typedef struct ng_l2tp_hook_private *hookpriv_p;
 155
 156 /* Netgraph node methods */
 157 static ng_constructor_t ng_l2tp_constructor;
 158 static ng_rcvmsg_t      ng_l2tp_rcvmsg;
 159 static ng_shutdown_t    ng_l2tp_shutdown;
 160 static ng_newhook_t     ng_l2tp_newhook;
 161 static ng_rcvdata_t     ng_l2tp_rcvdata;
 162 static ng_disconnect_t  ng_l2tp_disconnect;
 163
 164 /* Internal functions */
 165 static int      ng_l2tp_recv_lower(node_p node, item_p item);
 166 static int      ng_l2tp_recv_ctrl(node_p node, item_p item);
 167 static int      ng_l2tp_recv_data(node_p node, item_p item, hookpriv_p hpriv);
 168
 169 static int      ng_l2tp_xmit_ctrl(priv_p priv, struct mbuf *m, u_int16_t ns);
 170
 171 static void     ng_l2tp_seq_init(priv_p priv);
 172 static int      ng_l2tp_seq_set(priv_p priv,
 173                         const struct ng_l2tp_seq_config *conf);
 174 static int      ng_l2tp_seq_adjust(priv_p priv,
 175                         const struct ng_l2tp_config *conf);
 176 static void     ng_l2tp_seq_reset(priv_p priv);
 177 static void     ng_l2tp_seq_failure(priv_p priv);
 178 static void     ng_l2tp_seq_recv_nr(priv_p priv, u_int16_t nr);
 179 static int      ng_l2tp_seq_recv_ns(priv_p priv, u_int16_t ns);
 180 static void     ng_l2tp_seq_xack_timeout(node_p node, hook_p hook,
 181                     void *arg1, int arg2);
 182 static void     ng_l2tp_seq_rack_timeout(node_p node, hook_p hook,
 183                     void *arg1, int arg2);
 184
 185 static ng_fn_eachhook   ng_l2tp_find_session;
 186 static ng_fn_eachhook   ng_l2tp_reset_session;
 187
 188 #ifdef INVARIANTS
 189 static void     ng_l2tp_seq_check(struct l2tp_seq *seq);
 190 #endif
 191
 192 /* Parse type for struct ng_l2tp_seq_config. */
 193 static const struct ng_parse_struct_field
 194         ng_l2tp_seq_config_fields[] = NG_L2TP_SEQ_CONFIG_TYPE_INFO;
 195 static const struct ng_parse_type ng_l2tp_seq_config_type = {
 196         &ng_parse_struct_type,
 197         &ng_l2tp_seq_config_fields
 198 };
 199
 200 /* Parse type for struct ng_l2tp_config */
 201 static const struct ng_parse_struct_field
 202         ng_l2tp_config_type_fields[] = NG_L2TP_CONFIG_TYPE_INFO;
 203 static const struct ng_parse_type ng_l2tp_config_type = {
 204         &ng_parse_struct_type,
 205         &ng_l2tp_config_type_fields,
 206 };
 207
 208 /* Parse type for struct ng_l2tp_sess_config */
 209 static const struct ng_parse_struct_field
 210         ng_l2tp_sess_config_type_fields[] = NG_L2TP_SESS_CONFIG_TYPE_INFO;
 211 static const struct ng_parse_type ng_l2tp_sess_config_type = {
 212         &ng_parse_struct_type,
 213         &ng_l2tp_sess_config_type_fields,
 214 };
 215
 216 /* Parse type for struct ng_l2tp_stats */
 217 static const struct ng_parse_struct_field
 218         ng_l2tp_stats_type_fields[] = NG_L2TP_STATS_TYPE_INFO;
 219 static const struct ng_parse_type ng_l2tp_stats_type = {
 220         &ng_parse_struct_type,
 221         &ng_l2tp_stats_type_fields
 222 };
 223
 224 /* Parse type for struct ng_l2tp_session_stats. */
 225 static const struct ng_parse_struct_field
 226         ng_l2tp_session_stats_type_fields[] = NG_L2TP_SESSION_STATS_TYPE_INFO;
 227 static const struct ng_parse_type ng_l2tp_session_stats_type = {
 228         &ng_parse_struct_type,
 229         &ng_l2tp_session_stats_type_fields
 230 };
 231
 232 /* List of commands and how to convert arguments to/from ASCII */
 233 static const struct ng_cmdlist ng_l2tp_cmdlist[] = {
 234         {
 235           NGM_L2TP_COOKIE,
 236           NGM_L2TP_SET_CONFIG,
 237           "setconfig",
 238           &ng_l2tp_config_type,
 239           NULL
 240         },
 241         {
 242           NGM_L2TP_COOKIE,
 243           NGM_L2TP_GET_CONFIG,
 244           "getconfig",
 245           NULL,
 246           &ng_l2tp_config_type
 247         },
 248         {
 249           NGM_L2TP_COOKIE,
 250           NGM_L2TP_SET_SESS_CONFIG,
 251           "setsessconfig",
 252           &ng_l2tp_sess_config_type,
 253           NULL
 254         },
 255         {
 256           NGM_L2TP_COOKIE,
 257           NGM_L2TP_GET_SESS_CONFIG,
 258           "getsessconfig",
 259           &ng_parse_hint16_type,
 260           &ng_l2tp_sess_config_type
 261         },
 262         {
 263           NGM_L2TP_COOKIE,
 264           NGM_L2TP_GET_STATS,
 265           "getstats",
 266           NULL,
 267           &ng_l2tp_stats_type
 268         },
 269         {
 270           NGM_L2TP_COOKIE,
 271           NGM_L2TP_CLR_STATS,
 272           "clrstats",
 273           NULL,
 274           NULL
 275         },
 276         {
 277           NGM_L2TP_COOKIE,
 278           NGM_L2TP_GETCLR_STATS,
 279           "getclrstats",
 280           NULL,
 281           &ng_l2tp_stats_type
 282         },
 283         {
 284           NGM_L2TP_COOKIE,
 285           NGM_L2TP_GET_SESSION_STATS,
 286           "getsessstats",
 287           &ng_parse_int16_type,
 288           &ng_l2tp_session_stats_type
 289         },
 290         {
 291           NGM_L2TP_COOKIE,
 292           NGM_L2TP_CLR_SESSION_STATS,
 293           "clrsessstats",
 294           &ng_parse_int16_type,
 295           NULL
 296         },
 297         {
 298           NGM_L2TP_COOKIE,
 299           NGM_L2TP_GETCLR_SESSION_STATS,
 300           "getclrsessstats",
 301           &ng_parse_int16_type,
 302           &ng_l2tp_session_stats_type
 303         },
 304         {
 305           NGM_L2TP_COOKIE,
 306           NGM_L2TP_ACK_FAILURE,
 307           "ackfailure",
 308           NULL,
 309           NULL
 310         },
 311         {
 312           NGM_L2TP_COOKIE,
 313           NGM_L2TP_SET_SEQ,
 314           "setsequence",
 315           &ng_l2tp_seq_config_type,
 316           NULL
 317         },
 318         { 0 }
 319 };
 320
 321 /* Node type descriptor */
 322 static struct ng_type ng_l2tp_typestruct = {
 323         .version =      NG_ABI_VERSION,
 324         .name =         NG_L2TP_NODE_TYPE,
 325         .constructor =  ng_l2tp_constructor,
 326         .rcvmsg =       ng_l2tp_rcvmsg,
 327         .shutdown =     ng_l2tp_shutdown,
 328         .newhook =      ng_l2tp_newhook,
 329         .rcvdata =      ng_l2tp_rcvdata,
 330         .disconnect =   ng_l2tp_disconnect,
 331         .cmdlist =      ng_l2tp_cmdlist,
 332 };
 333 NETGRAPH_INIT(l2tp, &ng_l2tp_typestruct);
 334
 335 /* Sequence number state sanity checking */
 336 #ifdef INVARIANTS
 337 #define L2TP_SEQ_CHECK(seq)     ng_l2tp_seq_check(seq)
 338 #else
 339 #define L2TP_SEQ_CHECK(x)       do { } while (0)
 340 #endif
 341
 342 /* memmove macro */
 343 #define memmove(d, s, l)        bcopy(s, d, l)
 344
 345 /* Whether to use m_copypacket() or m_dup() */
 346 #define L2TP_COPY_MBUF          m_copypacket
 347
 348 /************************************************************************
 349                         NETGRAPH NODE STUFF
 350 ************************************************************************/
 351
 352 /*
 353  * Node type constructor
 354  */
 355 static int
 356 ng_l2tp_constructor(node_p node)
 357 {
 358         priv_p priv;
 359
 360         /* Allocate private structure */
 361         MALLOC(priv, priv_p, sizeof(*priv), M_NETGRAPH_L2TP, M_NOWAIT | M_ZERO);
 362         if (priv == NULL)
 363                 return (ENOMEM);
 364         NG_NODE_SET_PRIVATE(node, priv);
 365         priv->node = node;
 366
 367         /* Apply a semi-reasonable default configuration */
 368         priv->conf.peer_win = 1;
 369         priv->conf.rexmit_max = L2TP_MAX_REXMIT;
 370         priv->conf.rexmit_max_to = L2TP_MAX_REXMIT_TO;
 371
 372         /* Initialize sequence number state */
 373         ng_l2tp_seq_init(priv);
 374
 375         /* Done */
 376         return (0);
 377 }
 378
 379 /*
 380  * Give our OK for a hook to be added.
 381  */
 382 static int
 383 ng_l2tp_newhook(node_p node, hook_p hook, const char *name)
 384 {
 385         const priv_p priv = NG_NODE_PRIVATE(node);
 386
 387         /* Check hook name */
 388         if (strcmp(name, NG_L2TP_HOOK_CTRL) == 0) {
 389                 if (priv->ctrl != NULL)
 390                         return (EISCONN);
 391                 priv->ctrl = hook;
 392         } else if (strcmp(name, NG_L2TP_HOOK_LOWER) == 0) {
 393                 if (priv->lower != NULL)
 394                         return (EISCONN);
 395                 priv->lower = hook;
 396         } else {
 397                 static const char hexdig[16] = "0123456789abcdef";
 398                 u_int16_t session_id;
 399                 hookpriv_p hpriv;
 400                 const char *hex;
 401                 int i;
 402                 int j;
 403
 404                 /* Parse hook name to get session ID */
 405                 if (strncmp(name, NG_L2TP_HOOK_SESSION_P,
 406                     sizeof(NG_L2TP_HOOK_SESSION_P) - 1) != 0)
 407                         return (EINVAL);
 408                 hex = name + sizeof(NG_L2TP_HOOK_SESSION_P) - 1;
 409                 for (session_id = i = 0; i < 4; i++) {
 410                         for (j = 0; j < 16 && hex[i] != hexdig[j]; j++);
 411                         if (j == 16)
 412                                 return (EINVAL);
 413                         session_id = (session_id << 4) | j;
 414                 }
 415                 if (hex[i] != '\0')
 416                         return (EINVAL);
 417
 418                 /* Create hook private structure */
 419                 MALLOC(hpriv, hookpriv_p,
 420                     sizeof(*hpriv), M_NETGRAPH_L2TP, M_NOWAIT | M_ZERO);
 421                 if (hpriv == NULL)
 422                         return (ENOMEM);
 423                 hpriv->conf.session_id = htons(session_id);
 424                 hpriv->conf.control_dseq = L2TP_CONTROL_DSEQ;
 425                 hpriv->conf.enable_dseq = L2TP_ENABLE_DSEQ;
 426                 NG_HOOK_SET_PRIVATE(hook, hpriv);
 427         }
 428
 429         /* Done */
 430         return (0);
 431 }
 432
 433 /*
 434  * Receive a control message.
 435  */
 436 static int
 437 ng_l2tp_rcvmsg(node_p node, item_p item, hook_p lasthook)
 438 {
 439         const priv_p priv = NG_NODE_PRIVATE(node);
 440         struct ng_mesg *resp = NULL;
 441         struct ng_mesg *msg;
 442         int error = 0;
 443
 444         NGI_GET_MSG(item, msg);
 445         switch (msg->header.typecookie) {
 446         case NGM_L2TP_COOKIE:
 447                 switch (msg->header.cmd) {
 448                 case NGM_L2TP_SET_CONFIG:
 449                     {
 450                         struct ng_l2tp_config *const conf =
 451                                 (struct ng_l2tp_config *)msg->data;
 452
 453                         /* Check for invalid or illegal config */
 454                         if (msg->header.arglen != sizeof(*conf)) {
 455                                 error = EINVAL;
 456                                 break;
 457                         }
 458                         conf->enabled = !!conf->enabled;
 459                         conf->match_id = !!conf->match_id;
 460                         conf->tunnel_id = htons(conf->tunnel_id);
 461                         conf->peer_id = htons(conf->peer_id);
 462                         if (priv->conf.enabled
 463                             && ((priv->conf.tunnel_id != 0
 464                                && conf->tunnel_id != priv->conf.tunnel_id)
 465                               || ((priv->conf.peer_id != 0
 466                                && conf->peer_id != priv->conf.peer_id)))) {
 467                                 error = EBUSY;
 468                                 break;
 469                         }
 470
 471                         /* Save calling node as failure target */
 472                         priv->ftarget = NGI_RETADDR(item);
 473
 474                         /* Adjust sequence number state */
 475                         if ((error = ng_l2tp_seq_adjust(priv, conf)) != 0)
 476                                 break;
 477
 478                         /* Update node's config */
 479                         priv->conf = *conf;
 480                         break;
 481                     }
 482                 case NGM_L2TP_GET_CONFIG:
 483                     {
 484                         struct ng_l2tp_config *conf;
 485
 486                         NG_MKRESPONSE(resp, msg, sizeof(*conf), M_NOWAIT);
 487                         if (resp == NULL) {
 488                                 error = ENOMEM;
 489                                 break;
 490                         }
 491                         conf = (struct ng_l2tp_config *)resp->data;
 492                         *conf = priv->conf;
 493
 494                         /* Put ID's in host order */
 495                         conf->tunnel_id = ntohs(conf->tunnel_id);
 496                         conf->peer_id = ntohs(conf->peer_id);
 497                         break;
 498                     }
 499                 case NGM_L2TP_SET_SESS_CONFIG:
 500                     {
 501                         struct ng_l2tp_sess_config *const conf =
 502                             (struct ng_l2tp_sess_config *)msg->data;
 503                         hookpriv_p hpriv;
 504                         hook_p hook;
 505
 506                         /* Check for invalid or illegal config. */
 507                         if (msg->header.arglen != sizeof(*conf)) {
 508                                 error = EINVAL;
 509                                 break;
 510                         }
 511
 512                         /* Put ID's in network order */
 513                         conf->session_id = htons(conf->session_id);
 514                         conf->peer_id = htons(conf->peer_id);
 515
 516                         /* Find matching hook */
 517                         NG_NODE_FOREACH_HOOK(node, ng_l2tp_find_session,
 518                             (void *)(uintptr_t)conf->session_id, hook);
 519                         if (hook == NULL) {
 520                                 error = ENOENT;
 521                                 break;
 522                         }
 523                         hpriv = NG_HOOK_PRIVATE(hook);
 524
 525                         /* Update hook's config */
 526                         hpriv->conf = *conf;
 527                         break;
 528                     }
 529                 case NGM_L2TP_GET_SESS_CONFIG:
 530                     {
 531                         struct ng_l2tp_sess_config *conf;
 532                         u_int16_t session_id;
 533                         hookpriv_p hpriv;
 534                         hook_p hook;
 535
 536                         /* Get session ID */
 537                         if (msg->header.arglen != sizeof(session_id)) {
 538                                 error = EINVAL;
 539                                 break;
 540                         }
 541                         memcpy(&session_id, msg->data, 2);
 542                         session_id = htons(session_id);
 543
 544                         /* Find matching hook */
 545                         NG_NODE_FOREACH_HOOK(node, ng_l2tp_find_session,
 546                             (void *)(uintptr_t)session_id, hook);
 547                         if (hook == NULL) {
 548                                 error = ENOENT;
 549                                 break;
 550                         }
 551                         hpriv = NG_HOOK_PRIVATE(hook);
 552
 553                         /* Send response */
 554                         NG_MKRESPONSE(resp, msg, sizeof(hpriv->conf), M_NOWAIT);
 555                         if (resp == NULL) {
 556                                 error = ENOMEM;
 557                                 break;
 558                         }
 559                         conf = (struct ng_l2tp_sess_config *)resp->data;
 560                         *conf = hpriv->conf;
 561
 562                         /* Put ID's in host order */
 563                         conf->session_id = ntohs(conf->session_id);
 564                         conf->peer_id = ntohs(conf->peer_id);
 565                         break;
 566                     }
 567                 case NGM_L2TP_GET_STATS:
 568                 case NGM_L2TP_CLR_STATS:
 569                 case NGM_L2TP_GETCLR_STATS:
 570                     {
 571                         if (msg->header.cmd != NGM_L2TP_CLR_STATS) {
 572                                 NG_MKRESPONSE(resp, msg,
 573                                     sizeof(priv->stats), M_NOWAIT);
 574                                 if (resp == NULL) {
 575                                         error = ENOMEM;
 576                                         break;
 577                                 }
 578                                 memcpy(resp->data,
 579                                     &priv->stats, sizeof(priv->stats));
 580                         }
 581                         if (msg->header.cmd != NGM_L2TP_GET_STATS)
 582                                 memset(&priv->stats, 0, sizeof(priv->stats));
 583                         break;
 584                     }
 585                 case NGM_L2TP_GET_SESSION_STATS:
 586                 case NGM_L2TP_CLR_SESSION_STATS:
 587                 case NGM_L2TP_GETCLR_SESSION_STATS:
 588                     {
 589                         uint16_t session_id;
 590                         hookpriv_p hpriv;
 591                         hook_p hook;
 592
 593                         /* Get session ID. */
 594                         if (msg->header.arglen != sizeof(session_id)) {
 595                                 error = EINVAL;
 596                                 break;
 597                         }
 598                         bcopy(msg->data, &session_id, sizeof(uint16_t));
 599                         session_id = htons(session_id);
 600
 601                         /* Find matching hook. */
 602                         NG_NODE_FOREACH_HOOK(node, ng_l2tp_find_session,
 603                             (void *)(uintptr_t)session_id, hook);
 604                         if (hook == NULL) {
 605                                 error = ENOENT;
 606                                 break;
 607                         }
 608                         hpriv = NG_HOOK_PRIVATE(hook);
 609
 610                         if (msg->header.cmd != NGM_L2TP_CLR_SESSION_STATS) {
 611                                 NG_MKRESPONSE(resp, msg,
 612                                     sizeof(hpriv->stats), M_NOWAIT);
 613                                 if (resp == NULL) {
 614                                         error = ENOMEM;
 615                                         break;
 616                                 }
 617                                 bcopy(&hpriv->stats, resp->data,
 618                                         sizeof(hpriv->stats));
 619                         }
 620                         if (msg->header.cmd != NGM_L2TP_GET_SESSION_STATS)
 621                                 bzero(&hpriv->stats, sizeof(hpriv->stats));
 622                         break;
 623                     }
 624                 case NGM_L2TP_SET_SEQ:
 625                     {
 626                         struct ng_l2tp_seq_config *const conf =
 627                                 (struct ng_l2tp_seq_config *)msg->data;
 628
 629                         /* Check for invalid or illegal seq config. */
 630                         if (msg->header.arglen != sizeof(*conf)) {
 631                                 error = EINVAL;
 632                                 break;
 633                         }
 634                         conf->ns = htons(conf->ns);
 635                         conf->nr = htons(conf->nr);
 636                         conf->rack = htons(conf->rack);
 637                         conf->xack = htons(conf->xack);
 638
 639                         /* Set sequence numbers. */
 640                         error = ng_l2tp_seq_set(priv, conf);
 641                         break;
 642                     }
 643                 default:
 644                         error = EINVAL;
 645                         break;
 646                 }
 647                 break;
 648         default:
 649                 error = EINVAL;
 650                 break;
 651         }
 652
 653         /* Done */
 654         NG_RESPOND_MSG(error, node, item, resp);
 655         NG_FREE_MSG(msg);
 656         return (error);
 657 }
 658
 659 /*
 660  * Receive incoming data on a hook.
 661  */
 662 static int
 663 ng_l2tp_rcvdata(hook_p hook, item_p item)
 664 {
 665         const node_p node = NG_HOOK_NODE(hook);
 666         const priv_p priv = NG_NODE_PRIVATE(node);
 667         int error;
 668
 669         /* Sanity check */
 670         L2TP_SEQ_CHECK(&priv->seq);
 671
 672         /* If not configured, reject */
 673         if (!priv->conf.enabled) {
 674                 NG_FREE_ITEM(item);
 675                 return (ENXIO);
 676         }
 677
 678         /* Handle incoming frame from below */
 679         if (hook == priv->lower) {
 680                 error = ng_l2tp_recv_lower(node, item);
 681                 goto done;
 682         }
 683
 684         /* Handle outgoing control frame */
 685         if (hook == priv->ctrl) {
 686                 error = ng_l2tp_recv_ctrl(node, item);
 687                 goto done;
 688         }
 689
 690         /* Handle outgoing data frame */
 691         error = ng_l2tp_recv_data(node, item, NG_HOOK_PRIVATE(hook));
 692
 693 done:
 694         /* Done */
 695         L2TP_SEQ_CHECK(&priv->seq);
 696         return (error);
 697 }
 698
 699 /*
 700  * Destroy node
 701  */
 702 static int
 703 ng_l2tp_shutdown(node_p node)
 704 {
 705         const priv_p priv = NG_NODE_PRIVATE(node);
 706         struct l2tp_seq *const seq = &priv->seq;
 707
 708         /* Sanity check */
 709         L2TP_SEQ_CHECK(seq);
 710
 711         /* Reset sequence number state */
 712         ng_l2tp_seq_reset(priv);
 713
 714         /* Free private data if neither timer is running */
 715         ng_uncallout(&seq->rack_timer, node);
 716         ng_uncallout(&seq->xack_timer, node);
 717
 718         FREE(priv, M_NETGRAPH_L2TP);
 719
 720         /* Unref node */
 721         NG_NODE_UNREF(node);
 722         return (0);
 723 }
 724
 725 /*
 726  * Hook disconnection
 727  */
 728 static int
 729 ng_l2tp_disconnect(hook_p hook)
 730 {
 731         const node_p node = NG_HOOK_NODE(hook);
 732         const priv_p priv = NG_NODE_PRIVATE(node);
 733
 734         /* Zero out hook pointer */
 735         if (hook == priv->ctrl)
 736                 priv->ctrl = NULL;
 737         else if (hook == priv->lower)
 738                 priv->lower = NULL;
 739         else {
 740                 FREE(NG_HOOK_PRIVATE(hook), M_NETGRAPH_L2TP);
 741                 NG_HOOK_SET_PRIVATE(hook, NULL);
 742         }
 743
 744         /* Go away if no longer connected to anything */
 745         if (NG_NODE_NUMHOOKS(node) == 0 && NG_NODE_IS_VALID(node))
 746                 ng_rmnode_self(node);
 747         return (0);
 748 }
 749
 750 /*************************************************************************
 751                         INTERNAL FUNCTIONS
 752 *************************************************************************/
 753
 754 /*
 755  * Find the hook with a given session ID.
 756  */
 757 static int
 758 ng_l2tp_find_session(hook_p hook, void *arg)
 759 {
 760         const hookpriv_p hpriv = NG_HOOK_PRIVATE(hook);
 761         const u_int16_t sid = (u_int16_t)(uintptr_t)arg;
 762
 763         if (hpriv == NULL || hpriv->conf.session_id != sid)
 764                 return (-1);
 765         return (0);
 766 }
 767
 768 /*
 769  * Reset a hook's session state.
 770  */
 771 static int
 772 ng_l2tp_reset_session(hook_p hook, void *arg)
 773 {
 774         const hookpriv_p hpriv = NG_HOOK_PRIVATE(hook);
 775
 776         if (hpriv != NULL) {
 777                 hpriv->conf.control_dseq = 0;
 778                 hpriv->conf.enable_dseq = 0;
 779                 bzero(&hpriv->conf, sizeof(struct ng_l2tp_session_stats));
 780                 hpriv->nr = 0;
 781                 hpriv->ns = 0;
 782         }
 783         return (-1);
 784 }
 785
 786 /*
 787  * Handle an incoming frame from below.
 788  */
 789 static int
 790 ng_l2tp_recv_lower(node_p node, item_p item)
 791 {
 792         static const u_int16_t req_bits[2][2] = {
 793                 { L2TP_DATA_0BITS, L2TP_DATA_1BITS },
 794                 { L2TP_CTRL_0BITS, L2TP_CTRL_1BITS },
 795         };
 796         const priv_p priv = NG_NODE_PRIVATE(node);
 797         hookpriv_p hpriv = NULL;
 798         hook_p hook = NULL;
 799         u_int16_t ids[2];
 800         struct mbuf *m;
 801         u_int16_t hdr;
 802         u_int16_t ns;
 803         u_int16_t nr;
 804         int is_ctrl;
 805         int error;
 806         int len, plen;
 807
 808         /* Grab mbuf */
 809         NGI_GET_M(item, m);
 810
 811         /* Remember full packet length; needed for per session accounting. */
 812         plen = m->m_pkthdr.len;
 813
 814         /* Update stats */
 815         priv->stats.recvPackets++;
 816         priv->stats.recvOctets += plen;
 817
 818         /* Get initial header */
 819         if (m->m_pkthdr.len < 6) {
 820                 priv->stats.recvRunts++;
 821                 NG_FREE_ITEM(item);
 822                 NG_FREE_M(m);
 823                 return (EINVAL);
 824         }
 825         if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
 826                 priv->stats.memoryFailures++;
 827                 NG_FREE_ITEM(item);
 828                 return (EINVAL);
 829         }
 830         hdr = ntohs(*mtod(m, u_int16_t *));
 831         m_adj(m, 2);
 832
 833         /* Check required header bits and minimum length */
 834         is_ctrl = (hdr & L2TP_HDR_CTRL) != 0;
 835         if ((hdr & req_bits[is_ctrl][0]) != 0
 836             || (~hdr & req_bits[is_ctrl][1]) != 0) {
 837                 priv->stats.recvInvalid++;
 838                 NG_FREE_ITEM(item);
 839                 NG_FREE_M(m);
 840                 return (EINVAL);
 841         }
 842         if (m->m_pkthdr.len < 4                         /* tunnel, session id */
 843             + (2 * ((hdr & L2TP_HDR_LEN) != 0))         /* length field */
 844             + (4 * ((hdr & L2TP_HDR_SEQ) != 0))         /* seq # fields */
 845             + (2 * ((hdr & L2TP_HDR_OFF) != 0))) {      /* offset field */
 846                 priv->stats.recvRunts++;
 847                 NG_FREE_ITEM(item);
 848                 NG_FREE_M(m);
 849                 return (EINVAL);
 850         }
 851
 852         /* Get and validate length field if present */
 853         if ((hdr & L2TP_HDR_LEN) != 0) {
 854                 if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
 855                         priv->stats.memoryFailures++;
 856                         NG_FREE_ITEM(item);
 857                         return (EINVAL);
 858                 }
 859                 len = (u_int16_t)ntohs(*mtod(m, u_int16_t *)) - 4;
 860                 m_adj(m, 2);
 861                 if (len < 0 || len > m->m_pkthdr.len) {
 862                         priv->stats.recvInvalid++;
 863                         NG_FREE_ITEM(item);
 864                         NG_FREE_M(m);
 865                         return (EINVAL);
 866                 }
 867                 if (len < m->m_pkthdr.len)              /* trim extra bytes */
 868                         m_adj(m, -(m->m_pkthdr.len - len));
 869         }
 870
 871         /* Get tunnel ID and session ID */
 872         if (m->m_len < 4 && (m = m_pullup(m, 4)) == NULL) {
 873                 priv->stats.memoryFailures++;
 874                 NG_FREE_ITEM(item);
 875                 return (EINVAL);
 876         }
 877         memcpy(ids, mtod(m, u_int16_t *), 4);
 878         m_adj(m, 4);
 879
 880         /* Check tunnel ID */
 881         if (ids[0] != priv->conf.tunnel_id
 882             && (priv->conf.match_id || ids[0] != 0)) {
 883                 priv->stats.recvWrongTunnel++;
 884                 NG_FREE_ITEM(item);
 885                 NG_FREE_M(m);
 886                 return (EADDRNOTAVAIL);
 887         }
 888
 889         /* Check session ID (for data packets only) */
 890         if ((hdr & L2TP_HDR_CTRL) == 0) {
 891                 NG_NODE_FOREACH_HOOK(node, ng_l2tp_find_session,
 892                     (void *)(uintptr_t)ids[1], hook);
 893                 if (hook == NULL) {
 894                         priv->stats.recvUnknownSID++;
 895                         NG_FREE_ITEM(item);
 896                         NG_FREE_M(m);
 897                         return (ENOTCONN);
 898                 }
 899                 hpriv = NG_HOOK_PRIVATE(hook);
 900         }
 901
 902         /* Get Ns, Nr fields if present */
 903         if ((hdr & L2TP_HDR_SEQ) != 0) {
 904                 if (m->m_len < 4 && (m = m_pullup(m, 4)) == NULL) {
 905                         priv->stats.memoryFailures++;
 906                         NG_FREE_ITEM(item);
 907                         return (EINVAL);
 908                 }
 909                 memcpy(&ns, &mtod(m, u_int16_t *)[0], 2);
 910                 ns = ntohs(ns);
 911                 memcpy(&nr, &mtod(m, u_int16_t *)[1], 2);
 912                 nr = ntohs(nr);
 913                 m_adj(m, 4);
 914         }
 915
 916         /* Strip offset padding if present */
 917         if ((hdr & L2TP_HDR_OFF) != 0) {
 918                 u_int16_t offset;
 919
 920                 /* Get length of offset padding */
 921                 if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
 922                         priv->stats.memoryFailures++;
 923                         NG_FREE_ITEM(item);
 924                         return (EINVAL);
 925                 }
 926                 memcpy(&offset, mtod(m, u_int16_t *), 2);
 927                 offset = ntohs(offset);
 928
 929                 /* Trim offset padding */
 930                 if ((2+offset) > m->m_pkthdr.len) {
 931                         priv->stats.recvInvalid++;
 932                         NG_FREE_ITEM(item);
 933                         NG_FREE_M(m);
 934                         return (EINVAL);
 935                 }
 936                 m_adj(m, 2+offset);
 937         }
 938
 939         /* Handle control packets */
 940         if ((hdr & L2TP_HDR_CTRL) != 0) {
 941
 942                 /* Handle receive ack sequence number Nr */
 943                 ng_l2tp_seq_recv_nr(priv, nr);
 944
 945                 /* Discard ZLB packets */
 946                 if (m->m_pkthdr.len == 0) {
 947                         priv->stats.recvZLBs++;
 948                         NG_FREE_ITEM(item);
 949                         NG_FREE_M(m);
 950                         return (0);
 951                 }
 952
 953                 /*
 954                  * Prepend session ID to packet here: we don't want to accept
 955                  * the send sequence number Ns if we have to drop the packet
 956                  * later because of a memory error, because then the upper
 957                  * layer would never get the packet.
 958                  */
 959                 M_PREPEND(m, 2, M_DONTWAIT);
 960                 if (m == NULL) {
 961                         priv->stats.memoryFailures++;
 962                         NG_FREE_ITEM(item);
 963                         return (ENOBUFS);
 964                 }
 965                 memcpy(mtod(m, u_int16_t *), &ids[1], 2);
 966
 967                 /* Now handle send sequence number */
 968                 if (ng_l2tp_seq_recv_ns(priv, ns) == -1) {
 969                         NG_FREE_ITEM(item);
 970                         NG_FREE_M(m);
 971                         return (0);
 972                 }
 973
 974                 /* Deliver packet to upper layers */
 975                 NG_FWD_NEW_DATA(error, item, priv->ctrl, m);
 976                 return (error);
 977         }
 978
 979         /* Per session packet, account it. */
 980         hpriv->stats.recvPackets++;
 981         hpriv->stats.recvOctets += plen;
 982
 983         /* Follow peer's lead in data sequencing, if configured to do so */
 984         if (!hpriv->conf.control_dseq)
 985                 hpriv->conf.enable_dseq = ((hdr & L2TP_HDR_SEQ) != 0);
 986
 987         /* Handle data sequence numbers if present and enabled */
 988         if ((hdr & L2TP_HDR_SEQ) != 0) {
 989                 if (hpriv->conf.enable_dseq
 990                     && L2TP_SEQ_DIFF(ns, hpriv->nr) < 0) {
 991                         NG_FREE_ITEM(item);     /* duplicate or out of order */
 992                         NG_FREE_M(m);
 993                         priv->stats.recvDataDrops++;
 994                         return (0);
 995                 }
 996                 hpriv->nr = ns + 1;
 997         }
 998
 999         /* Drop empty data packets */
1000         if (m->m_pkthdr.len == 0) {
1001                 NG_FREE_ITEM(item);
1002                 NG_FREE_M(m);
1003                 return (0);
1004         }
1005
1006         /* Deliver data */
1007         NG_FWD_NEW_DATA(error, item, hook, m);
1008         return (error);
1009 }
1010
1011 /*
1012  * Handle an outgoing control frame.
1013  */
1014 static int
1015 ng_l2tp_recv_ctrl(node_p node, item_p item)
1016 {
1017         const priv_p priv = NG_NODE_PRIVATE(node);
1018         struct l2tp_seq *const seq = &priv->seq;
1019         struct mbuf *m;
1020         int i;
1021
1022         /* Grab mbuf and discard other stuff XXX */
1023         NGI_GET_M(item, m);
1024         NG_FREE_ITEM(item);
1025
1026         /* Packet should have session ID prepended */
1027         if (m->m_pkthdr.len < 2) {
1028                 priv->stats.xmitInvalid++;
1029                 m_freem(m);
1030                 return (EINVAL);
1031         }
1032
1033         /* Check max length */
1034         if (m->m_pkthdr.len >= 0x10000 - 14) {
1035                 priv->stats.xmitTooBig++;
1036                 m_freem(m);
1037                 return (EOVERFLOW);
1038         }
1039
1040         /* Find next empty slot in transmit queue */
1041         for (i = 0; i < L2TP_MAX_XWIN && seq->xwin[i] != NULL; i++);
1042         if (i == L2TP_MAX_XWIN) {
1043                 priv->stats.xmitDrops++;
1044                 m_freem(m);
1045                 return (ENOBUFS);
1046         }
1047         seq->xwin[i] = m;
1048
1049         /* Sanity check receive ack timer state */
1050         KASSERT((i == 0) ^ callout_pending(&seq->rack_timer),
1051             ("%s: xwin %d full but rack timer %s running",
1052             __func__, i, callout_pending(&seq->rack_timer) ? "" : "not "));
1053
1054         /* If peer's receive window is already full, nothing else to do */
1055         if (i >= seq->cwnd)
1056                 return (0);
1057
1058         /* Start retransmit timer if not already running */
1059         if (!callout_pending(&seq->rack_timer))
1060                 ng_callout(&seq->rack_timer, node, NULL,
1061                     hz, ng_l2tp_seq_rack_timeout, NULL, 0);
1062
1063         /* Copy packet */
1064         if ((m = L2TP_COPY_MBUF(seq->xwin[i], M_DONTWAIT)) == NULL) {
1065                 priv->stats.memoryFailures++;
1066                 return (ENOBUFS);
1067         }
1068
1069         /* Send packet and increment xmit sequence number */
1070         return (ng_l2tp_xmit_ctrl(priv, m, seq->ns++));
1071 }
1072
1073 /*
1074  * Handle an outgoing data frame.
1075  */
1076 static int
1077 ng_l2tp_recv_data(node_p node, item_p item, hookpriv_p hpriv)
1078 {
1079         const priv_p priv = NG_NODE_PRIVATE(node);
1080         struct mbuf *m;
1081         u_int16_t hdr;
1082         int error;
1083         int i = 1;
1084
1085         /* Get mbuf */
1086         NGI_GET_M(item, m);
1087
1088         /* Check max length */
1089         if (m->m_pkthdr.len >= 0x10000 - 12) {
1090                 priv->stats.xmitDataTooBig++;
1091                 NG_FREE_ITEM(item);
1092                 NG_FREE_M(m);
1093                 return (EOVERFLOW);
1094         }
1095
1096         /* Prepend L2TP header */
1097         M_PREPEND(m, 6
1098             + (2 * (hpriv->conf.include_length != 0))
1099             + (4 * (hpriv->conf.enable_dseq != 0)),
1100             M_DONTWAIT);
1101         if (m == NULL) {
1102                 priv->stats.memoryFailures++;
1103                 NG_FREE_ITEM(item);
1104                 return (ENOBUFS);
1105         }
1106         hdr = L2TP_DATA_HDR;
1107         if (hpriv->conf.include_length) {
1108                 hdr |= L2TP_HDR_LEN;
1109                 mtod(m, u_int16_t *)[i++] = htons(m->m_pkthdr.len);
1110         }
1111         mtod(m, u_int16_t *)[i++] = priv->conf.peer_id;
1112         mtod(m, u_int16_t *)[i++] = hpriv->conf.peer_id;
1113         if (hpriv->conf.enable_dseq) {
1114                 hdr |= L2TP_HDR_SEQ;
1115                 mtod(m, u_int16_t *)[i++] = htons(hpriv->ns);
1116                 mtod(m, u_int16_t *)[i++] = htons(hpriv->nr);
1117                 hpriv->ns++;
1118         }
1119         mtod(m, u_int16_t *)[0] = htons(hdr);
1120
1121         /* Update per session stats. */
1122         hpriv->stats.xmitPackets++;
1123         hpriv->stats.xmitOctets += m->m_pkthdr.len;
1124
1125         /* Send packet */
1126         NG_FWD_NEW_DATA(error, item, priv->lower, m);
1127         return (error);
1128 }
1129
1130 /*
1131  * Send a message to our controlling node that we've failed.
1132  */
1133 static void
1134 ng_l2tp_seq_failure(priv_p priv)
1135 {
1136         struct ng_mesg *msg;
1137         int error;
1138
1139         NG_MKMESSAGE(msg, NGM_L2TP_COOKIE, NGM_L2TP_ACK_FAILURE, 0, M_NOWAIT);
1140         if (msg == NULL)
1141                 return;
1142         NG_SEND_MSG_ID(error, priv->node, msg, priv->ftarget, 0);
1143 }
1144
1145 /************************************************************************
1146                         SEQUENCE NUMBER HANDLING
1147 ************************************************************************/
1148
1149 /*
1150  * Initialize sequence number state.
1151  */
1152 static void
1153 ng_l2tp_seq_init(priv_p priv)
1154 {
1155         struct l2tp_seq *const seq = &priv->seq;
1156
1157         KASSERT(priv->conf.peer_win >= 1,
1158             ("%s: peer_win is zero", __func__));
1159         memset(seq, 0, sizeof(*seq));
1160         seq->cwnd = 1;
1161         seq->wmax = priv->conf.peer_win;
1162         if (seq->wmax > L2TP_MAX_XWIN)
1163                 seq->wmax = L2TP_MAX_XWIN;
1164         seq->ssth = seq->wmax;
1165         seq->max_rexmits = priv->conf.rexmit_max;
1166         seq->max_rexmit_to = priv->conf.rexmit_max_to;
1167         ng_callout_init(&seq->rack_timer);
1168         ng_callout_init(&seq->xack_timer);
1169         L2TP_SEQ_CHECK(seq);
1170 }
1171
1172 /*
1173  * Set sequence number state as given from user.
1174  */
1175 static int
1176 ng_l2tp_seq_set(priv_p priv, const struct ng_l2tp_seq_config *conf)
1177 {
1178         struct l2tp_seq *const seq = &priv->seq;
1179
1180         /* If node is enabled, deny update to sequence numbers. */
1181         if (priv->conf.enabled)
1182                 return (EBUSY);
1183
1184         /* We only can handle the simple cases. */
1185         if (conf->xack != conf->nr || conf->ns != conf->rack)
1186                 return (EINVAL);
1187
1188         /* Set ns,nr,rack,xack parameters. */
1189         seq->ns = conf->ns;
1190         seq->nr = conf->nr;
1191         seq->rack = conf->rack;
1192         seq->xack = conf->xack;
1193
1194         return (0);
1195 }
1196
1197 /*
1198  * Adjust sequence number state accordingly after reconfiguration.
1199  */
1200 static int
1201 ng_l2tp_seq_adjust(priv_p priv, const struct ng_l2tp_config *conf)
1202 {
1203         struct l2tp_seq *const seq = &priv->seq;
1204         u_int16_t new_wmax;
1205
1206         /* If disabling node, reset state sequence number */
1207         if (!conf->enabled) {
1208                 ng_l2tp_seq_reset(priv);
1209                 return (0);
1210         }
1211
1212         /* Adjust peer's max recv window; it can only increase */
1213         new_wmax = conf->peer_win;
1214         if (new_wmax > L2TP_MAX_XWIN)
1215                 new_wmax = L2TP_MAX_XWIN;
1216         if (new_wmax == 0)
1217                 return (EINVAL);
1218         if (new_wmax < seq->wmax)
1219                 return (EBUSY);
1220         seq->wmax = new_wmax;
1221
1222         /* Update retransmit parameters */
1223         seq->max_rexmits = conf->rexmit_max;
1224         seq->max_rexmit_to = conf->rexmit_max_to;
1225
1226         /* Done */
1227         return (0);
1228 }
1229
1230 /*
1231  * Reset sequence number state.
1232  */
1233 static void
1234 ng_l2tp_seq_reset(priv_p priv)
1235 {
1236         struct l2tp_seq *const seq = &priv->seq;
1237         hook_p hook;
1238         int i;
1239
1240         /* Sanity check */
1241         L2TP_SEQ_CHECK(seq);
1242
1243         /* Stop timers */
1244         ng_uncallout(&seq->rack_timer, priv->node);
1245         ng_uncallout(&seq->xack_timer, priv->node);
1246
1247         /* Free retransmit queue */
1248         for (i = 0; i < L2TP_MAX_XWIN; i++) {
1249                 if (seq->xwin[i] == NULL)
1250                         break;
1251                 m_freem(seq->xwin[i]);
1252         }
1253
1254         /* Reset session hooks' sequence number states */
1255         NG_NODE_FOREACH_HOOK(priv->node, ng_l2tp_reset_session, NULL, hook);
1256
1257         /* Reset node's sequence number state */
1258         memset(seq, 0, sizeof(*seq));
1259         seq->cwnd = 1;
1260         seq->wmax = L2TP_MAX_XWIN;
1261         seq->ssth = seq->wmax;
1262
1263         /* Done */
1264         L2TP_SEQ_CHECK(seq);
1265 }
1266
1267 /*
1268  * Handle receipt of an acknowledgement value (Nr) from peer.
1269  */
1270 static void
1271 ng_l2tp_seq_recv_nr(priv_p priv, u_int16_t nr)
1272 {
1273         struct l2tp_seq *const seq = &priv->seq;
1274         struct mbuf *m;
1275         int nack;
1276         int i;
1277
1278         /* Verify peer's ACK is in range */
1279         if ((nack = L2TP_SEQ_DIFF(nr, seq->rack)) <= 0)
1280                 return;                         /* duplicate ack */
1281         if (L2TP_SEQ_DIFF(nr, seq->ns) > 0) {
1282                 priv->stats.recvBadAcks++;      /* ack for packet not sent */
1283                 return;
1284         }
1285         KASSERT(nack <= L2TP_MAX_XWIN,
1286             ("%s: nack=%d > %d", __func__, nack, L2TP_MAX_XWIN));
1287
1288         /* Update receive ack stats */
1289         seq->rack = nr;
1290         seq->rexmits = 0;
1291
1292         /* Free acknowledged packets and shift up packets in the xmit queue */
1293         for (i = 0; i < nack; i++)
1294                 m_freem(seq->xwin[i]);
1295         memmove(seq->xwin, seq->xwin + nack,
1296             (L2TP_MAX_XWIN - nack) * sizeof(*seq->xwin));
1297         memset(seq->xwin + (L2TP_MAX_XWIN - nack), 0,
1298             nack * sizeof(*seq->xwin));
1299
1300         /*
1301          * Do slow-start/congestion avoidance windowing algorithm described
1302          * in RFC 2661, Appendix A. Here we handle a multiple ACK as if each
1303          * ACK had arrived separately.
1304          */
1305         if (seq->cwnd < seq->wmax) {
1306
1307                 /* Handle slow start phase */
1308                 if (seq->cwnd < seq->ssth) {
1309                         seq->cwnd += nack;
1310                         nack = 0;
1311                         if (seq->cwnd > seq->ssth) {    /* into cg.av. phase */
1312                                 nack = seq->cwnd - seq->ssth;
1313                                 seq->cwnd = seq->ssth;
1314                         }
1315                 }
1316
1317                 /* Handle congestion avoidance phase */
1318                 if (seq->cwnd >= seq->ssth) {
1319                         seq->acks += nack;
1320                         while (seq->acks >= seq->cwnd) {
1321                                 seq->acks -= seq->cwnd;
1322                                 if (seq->cwnd < seq->wmax)
1323                                         seq->cwnd++;
1324                         }
1325                 }
1326         }
1327
1328         /* Stop xmit timer */
1329         if (callout_pending(&seq->rack_timer))
1330                 ng_uncallout(&seq->rack_timer, priv->node);
1331
1332         /* If transmit queue is empty, we're done for now */
1333         if (seq->xwin[0] == NULL)
1334                 return;
1335
1336         /* Start restransmit timer again */
1337         ng_callout(&seq->rack_timer, priv->node, NULL,
1338             hz, ng_l2tp_seq_rack_timeout, NULL, 0);
1339
1340         /*
1341          * Send more packets, trying to keep peer's receive window full.
1342          * If there is a memory error, pretend packet was sent, as it
1343          * will get retransmitted later anyway.
1344          */
1345         while ((i = L2TP_SEQ_DIFF(seq->ns, seq->rack)) < seq->cwnd
1346             && seq->xwin[i] != NULL) {
1347                 if ((m = L2TP_COPY_MBUF(seq->xwin[i], M_DONTWAIT)) == NULL)
1348                         priv->stats.memoryFailures++;
1349                 else
1350                         ng_l2tp_xmit_ctrl(priv, m, seq->ns);
1351                 seq->ns++;
1352         }
1353 }
1354
1355 /*
1356  * Handle receipt of a sequence number value (Ns) from peer.
1357  * We make no attempt to re-order out of order packets.
1358  *
1359  * This function should only be called for non-ZLB packets.
1360  *
1361  * Returns:
1362  *       0      Accept packet
1363  *      -1      Drop packet
1364  */
1365 static int
1366 ng_l2tp_seq_recv_ns(priv_p priv, u_int16_t ns)
1367 {
1368         struct l2tp_seq *const seq = &priv->seq;
1369
1370         /* If not what we expect, drop packet and send an immediate ZLB ack */
1371         if (ns != seq->nr) {
1372                 if (L2TP_SEQ_DIFF(ns, seq->nr) < 0)
1373                         priv->stats.recvDuplicates++;
1374                 else
1375                         priv->stats.recvOutOfOrder++;
1376                 ng_l2tp_xmit_ctrl(priv, NULL, seq->ns);
1377                 return (-1);
1378         }
1379
1380         /* Update recv sequence number */
1381         seq->nr++;
1382
1383         /* Start receive ack timer, if not already running */
1384         if (!callout_pending(&seq->xack_timer))
1385                 ng_callout(&seq->xack_timer, priv->node, NULL,
1386                     L2TP_DELAYED_ACK, ng_l2tp_seq_xack_timeout, NULL, 0);
1387
1388         /* Accept packet */
1389         return (0);
1390 }
1391
1392 /*
1393  * Handle an ack timeout. We have an outstanding ack that we
1394  * were hoping to piggy-back, but haven't, so send a ZLB.
1395  */
1396 static void
1397 ng_l2tp_seq_xack_timeout(node_p node, hook_p hook, void *arg1, int arg2)
1398 {
1399         const priv_p priv = NG_NODE_PRIVATE(node);
1400         struct l2tp_seq *const seq = &priv->seq;
1401
1402         /* Sanity check */
1403         L2TP_SEQ_CHECK(seq);
1404
1405         /* If ack is still outstanding, send a ZLB */
1406         if (seq->xack != seq->nr)
1407                 ng_l2tp_xmit_ctrl(priv, NULL, seq->ns);
1408
1409         /* Done */
1410         L2TP_SEQ_CHECK(seq);
1411 }
1412
1413 /*
1414  * Handle a transmit timeout. The peer has failed to respond
1415  * with an ack for our packet, so retransmit it.
1416  */
1417 static void
1418 ng_l2tp_seq_rack_timeout(node_p node, hook_p hook, void *arg1, int arg2)
1419 {
1420         const priv_p priv = NG_NODE_PRIVATE(node);
1421         struct l2tp_seq *const seq = &priv->seq;
1422         struct mbuf *m;
1423         u_int delay;
1424
1425         /* Sanity check */
1426         L2TP_SEQ_CHECK(seq);
1427
1428         /* Make sure peer's ack is still outstanding before doing anything */
1429         if (seq->rack == seq->ns)
1430                 goto done;
1431
1432         priv->stats.xmitRetransmits++;
1433
1434         /* Have we reached the retransmit limit? If so, notify owner. */
1435         if (seq->rexmits++ >= seq->max_rexmits)
1436                 ng_l2tp_seq_failure(priv);
1437
1438         /* Restart timer, this time with an increased delay */
1439         delay = (seq->rexmits > 12) ? (1 << 12) : (1 << seq->rexmits);
1440         if (delay > seq->max_rexmit_to)
1441                 delay = seq->max_rexmit_to;
1442         ng_callout(&seq->rack_timer, node, NULL,
1443             hz * delay, ng_l2tp_seq_rack_timeout, NULL, 0);
1444
1445         /* Do slow-start/congestion algorithm windowing algorithm */
1446         seq->ssth = (seq->cwnd + 1) / 2;
1447         seq->cwnd = 1;
1448         seq->acks = 0;
1449
1450         /* Retransmit oldest unack'd packet */
1451         if ((m = L2TP_COPY_MBUF(seq->xwin[0], M_DONTWAIT)) == NULL)
1452                 priv->stats.memoryFailures++;
1453         else
1454                 ng_l2tp_xmit_ctrl(priv, m, seq->rack);
1455
1456 done:
1457         /* Done */
1458         L2TP_SEQ_CHECK(seq);
1459 }
1460
1461 /*
1462  * Transmit a control stream packet, payload optional.
1463  * The transmit sequence number is not incremented.
1464  */
1465 static int
1466 ng_l2tp_xmit_ctrl(priv_p priv, struct mbuf *m, u_int16_t ns)
1467 {
1468         struct l2tp_seq *const seq = &priv->seq;
1469         u_int16_t session_id = 0;
1470         int error;
1471
1472         /* If no mbuf passed, send an empty packet (ZLB) */
1473         if (m == NULL) {
1474
1475                 /* Create a new mbuf for ZLB packet */
1476                 MGETHDR(m, M_DONTWAIT, MT_DATA);
1477                 if (m == NULL) {
1478                         priv->stats.memoryFailures++;
1479                         return (ENOBUFS);
1480                 }
1481                 m->m_len = m->m_pkthdr.len = 12;
1482                 m->m_pkthdr.rcvif = NULL;
1483                 priv->stats.xmitZLBs++;
1484         } else {
1485
1486                 /* Strip off session ID */
1487                 if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
1488                         priv->stats.memoryFailures++;
1489                         return (ENOBUFS);
1490                 }
1491                 memcpy(&session_id, mtod(m, u_int16_t *), 2);
1492                 m_adj(m, 2);
1493
1494                 /* Make room for L2TP header */
1495                 M_PREPEND(m, 12, M_DONTWAIT);
1496                 if (m == NULL) {
1497                         priv->stats.memoryFailures++;
1498                         return (ENOBUFS);
1499                 }
1500         }
1501
1502         /* Fill in L2TP header */
1503         mtod(m, u_int16_t *)[0] = htons(L2TP_CTRL_HDR);
1504         mtod(m, u_int16_t *)[1] = htons(m->m_pkthdr.len);
1505         mtod(m, u_int16_t *)[2] = priv->conf.peer_id;
1506         mtod(m, u_int16_t *)[3] = session_id;
1507         mtod(m, u_int16_t *)[4] = htons(ns);
1508         mtod(m, u_int16_t *)[5] = htons(seq->nr);
1509
1510         /* Update sequence number info and stats */
1511         priv->stats.xmitPackets++;
1512         priv->stats.xmitOctets += m->m_pkthdr.len;
1513
1514         /* Stop ack timer: we're sending an ack with this packet */
1515         if (callout_pending(&seq->xack_timer))
1516                 ng_uncallout(&seq->xack_timer, priv->node);
1517
1518         seq->xack = seq->nr;
1519
1520         /* Send packet */
1521         NG_SEND_DATA_ONLY(error, priv->lower, m);
1522         return (error);
1523 }
1524
1525 #ifdef INVARIANTS
1526 /*
1527  * Sanity check sequence number state.
1528  */
1529 static void
1530 ng_l2tp_seq_check(struct l2tp_seq *seq)
1531 {
1532         const int self_unack = L2TP_SEQ_DIFF(seq->nr, seq->xack);
1533         const int peer_unack = L2TP_SEQ_DIFF(seq->ns, seq->rack);
1534         int i;
1535
1536 #define CHECK(p)        KASSERT((p), ("%s: not: %s", __func__, #p))
1537
1538         CHECK(seq->wmax <= L2TP_MAX_XWIN);
1539         CHECK(seq->cwnd >= 1);
1540         CHECK(seq->cwnd <= seq->wmax);
1541         CHECK(seq->ssth >= 1);
1542         CHECK(seq->ssth <= seq->wmax);
1543         if (seq->cwnd < seq->ssth)
1544                 CHECK(seq->acks == 0);
1545         else
1546                 CHECK(seq->acks <= seq->cwnd);
1547         CHECK(self_unack >= 0);
1548         CHECK(peer_unack >= 0);
1549         CHECK(peer_unack <= seq->wmax);
1550         CHECK((self_unack == 0) ^ callout_pending(&seq->xack_timer));
1551         CHECK((peer_unack == 0) ^ callout_pending(&seq->rack_timer));
1552         for (i = 0; i < peer_unack; i++)
1553                 CHECK(seq->xwin[i] != NULL);
1554         for ( ; i < seq->cwnd; i++)         /* verify peer's recv window full */
1555                 CHECK(seq->xwin[i] == NULL);
1556
1557 #undef CHECK
1558 }
1559 #endif  /* INVARIANTS */