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/epoch.h>
  58 #include <sys/libkern.h>
  59
  60 #include <net/vnet.h>
  61
  62 #include <netgraph/ng_message.h>
  63 #include <netgraph/netgraph.h>
  64 #include <netgraph/ng_parse.h>
  65 #include <netgraph/ng_l2tp.h>
  66
  67 #ifdef NG_SEPARATE_MALLOC
  68 static 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           128                     /* 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)     ((int16_t)((x) - (y)))
 105
 106 #define SESSHASHSIZE            0x0020
 107 #define SESSHASH(x)             (((x) ^ ((x) >> 8)) & (SESSHASHSIZE - 1))
 108
 109 /* Hook private data (data session hooks only) */
 110 struct ng_l2tp_hook_private {
 111         struct ng_l2tp_sess_config      conf;   /* hook/session config */
 112         struct ng_l2tp_session_stats    stats;  /* per sessions statistics */
 113         hook_p                          hook;   /* hook reference */
 114         u_int16_t                       ns;     /* data ns sequence number */
 115         u_int16_t                       nr;     /* data nr sequence number */
 116         LIST_ENTRY(ng_l2tp_hook_private) sessions;
 117 };
 118 typedef struct ng_l2tp_hook_private *hookpriv_p;
 119
 120 /*
 121  * Sequence number state
 122  *
 123  * Invariants:
 124  *    - If cwnd < ssth, we're doing slow start, otherwise congestion avoidance
 125  *    - The number of unacknowledged xmit packets is (ns - rack) <= seq->wmax
 126  *    - The first (ns - rack) mbuf's in xwin[] array are copies of these
 127  *      unacknowledged packets; the remainder of xwin[] consists first of
 128  *      zero or more further untransmitted packets in the transmit queue
 129  *    - We try to keep the peer's receive window as full as possible.
 130  *      Therefore, (i < cwnd && xwin[i] != NULL) implies (ns - rack) > i.
 131  *    - rack_timer is running iff (ns - rack) > 0 (unack'd xmit'd pkts)
 132  *    - If xack != nr, there are unacknowledged recv packet(s) (delayed ack)
 133  *    - xack_timer is running iff xack != nr (unack'd rec'd pkts)
 134  */
 135 struct l2tp_seq {
 136         u_int16_t               ns;             /* next xmit seq we send */
 137         u_int16_t               nr;             /* next recv seq we expect */
 138         u_int16_t               inproc;         /* packet is in processing */
 139         u_int16_t               rack;           /* last 'nr' we rec'd */
 140         u_int16_t               xack;           /* last 'nr' we sent */
 141         u_int16_t               wmax;           /* peer's max recv window */
 142         u_int16_t               cwnd;           /* current congestion window */
 143         u_int16_t               ssth;           /* slow start threshold */
 144         u_int16_t               acks;           /* # consecutive acks rec'd */
 145         u_int16_t               rexmits;        /* # retransmits sent */
 146         struct callout          rack_timer;     /* retransmit timer */
 147         struct callout          xack_timer;     /* delayed ack timer */
 148         struct mbuf             *xwin[L2TP_MAX_XWIN];   /* transmit window */
 149         struct mtx              mtx;                    /* seq mutex */
 150 };
 151
 152 /* Node private data */
 153 struct ng_l2tp_private {
 154         node_p                  node;           /* back pointer to node */
 155         hook_p                  ctrl;           /* hook to upper layers */
 156         hook_p                  lower;          /* hook to lower layers */
 157         struct ng_l2tp_config   conf;           /* node configuration */
 158         struct ng_l2tp_stats    stats;          /* node statistics */
 159         struct l2tp_seq         seq;            /* ctrl sequence number state */
 160         ng_ID_t                 ftarget;        /* failure message target */
 161         LIST_HEAD(, ng_l2tp_hook_private) sesshash[SESSHASHSIZE];
 162 };
 163 typedef struct ng_l2tp_private *priv_p;
 164
 165 /* Netgraph node methods */
 166 static ng_constructor_t ng_l2tp_constructor;
 167 static ng_rcvmsg_t      ng_l2tp_rcvmsg;
 168 static ng_shutdown_t    ng_l2tp_shutdown;
 169 static ng_newhook_t     ng_l2tp_newhook;
 170 static ng_rcvdata_t     ng_l2tp_rcvdata;
 171 static ng_rcvdata_t     ng_l2tp_rcvdata_lower;
 172 static ng_rcvdata_t     ng_l2tp_rcvdata_ctrl;
 173 static ng_disconnect_t  ng_l2tp_disconnect;
 174
 175 /* Internal functions */
 176 static int      ng_l2tp_xmit_ctrl(priv_p priv, struct mbuf *m, u_int16_t ns);
 177
 178 static void     ng_l2tp_seq_init(priv_p priv);
 179 static int      ng_l2tp_seq_set(priv_p priv,
 180                         const struct ng_l2tp_seq_config *conf);
 181 static int      ng_l2tp_seq_adjust(priv_p priv,
 182                         const struct ng_l2tp_config *conf);
 183 static void     ng_l2tp_seq_reset(priv_p priv);
 184 static void     ng_l2tp_seq_failure(priv_p priv);
 185 static void     ng_l2tp_seq_recv_nr(priv_p priv, u_int16_t nr);
 186 static void     ng_l2tp_seq_xack_timeout(void *);
 187 static void     ng_l2tp_seq_rack_timeout(void *);
 188
 189 static hookpriv_p       ng_l2tp_find_session(priv_p privp, u_int16_t sid);
 190 static ng_fn_eachhook   ng_l2tp_reset_session;
 191
 192 /* 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 locking & sanity checking */
 336 #ifdef INVARIANTS
 337 static void     ng_l2tp_seq_check(struct l2tp_seq *seq);
 338 #define SEQ_LOCK(seq)   do {                                    \
 339                                 mtx_lock(&(seq)->mtx);          \
 340                                 ng_l2tp_seq_check(seq);         \
 341 } while (0)
 342 #define SEQ_UNLOCK(seq) do {                                    \
 343                                 ng_l2tp_seq_check(seq);         \
 344                                 mtx_unlock(&(seq)->mtx);        \
 345 } while (0)
 346 #else
 347 #define SEQ_LOCK(seq)           mtx_lock(&(seq)->mtx)
 348 #define SEQ_UNLOCK(seq)         mtx_unlock(&(seq)->mtx)
 349 #endif
 350 #define SEQ_LOCK_ASSERT(seq)    mtx_assert(&(seq)->mtx, MA_OWNED)
 351
 352 /* Whether to use m_copypacket() or m_dup() */
 353 #define L2TP_COPY_MBUF          m_copypacket
 354
 355 #define ERROUT(x)       do { error = (x); goto done; } while (0)
 356
 357 /************************************************************************
 358                         NETGRAPH NODE STUFF
 359 ************************************************************************/
 360
 361 /*
 362  * Node type constructor
 363  */
 364 static int
 365 ng_l2tp_constructor(node_p node)
 366 {
 367         priv_p priv;
 368         int     i;
 369
 370         /* Allocate private structure */
 371         priv = malloc(sizeof(*priv), M_NETGRAPH_L2TP, M_WAITOK | M_ZERO);
 372         NG_NODE_SET_PRIVATE(node, priv);
 373         priv->node = node;
 374
 375         /* Apply a semi-reasonable default configuration */
 376         priv->conf.peer_win = 1;
 377         priv->conf.rexmit_max = L2TP_MAX_REXMIT;
 378         priv->conf.rexmit_max_to = L2TP_MAX_REXMIT_TO;
 379
 380         /* Initialize sequence number state */
 381         ng_l2tp_seq_init(priv);
 382
 383         for (i = 0; i < SESSHASHSIZE; i++)
 384             LIST_INIT(&priv->sesshash[i]);
 385
 386         /* Done */
 387         return (0);
 388 }
 389
 390 /*
 391  * Give our OK for a hook to be added.
 392  */
 393 static int
 394 ng_l2tp_newhook(node_p node, hook_p hook, const char *name)
 395 {
 396         const priv_p priv = NG_NODE_PRIVATE(node);
 397
 398         /* Check hook name */
 399         if (strcmp(name, NG_L2TP_HOOK_CTRL) == 0) {
 400                 if (priv->ctrl != NULL)
 401                         return (EISCONN);
 402                 priv->ctrl = hook;
 403                 NG_HOOK_SET_RCVDATA(hook, ng_l2tp_rcvdata_ctrl);
 404         } else if (strcmp(name, NG_L2TP_HOOK_LOWER) == 0) {
 405                 if (priv->lower != NULL)
 406                         return (EISCONN);
 407                 priv->lower = hook;
 408                 NG_HOOK_SET_RCVDATA(hook, ng_l2tp_rcvdata_lower);
 409         } else {
 410                 static const char hexdig[16] = "0123456789abcdef";
 411                 u_int16_t session_id;
 412                 hookpriv_p hpriv;
 413                 uint16_t hash;
 414                 const char *hex;
 415                 int i;
 416                 int j;
 417
 418                 /* Parse hook name to get session ID */
 419                 if (strncmp(name, NG_L2TP_HOOK_SESSION_P,
 420                     sizeof(NG_L2TP_HOOK_SESSION_P) - 1) != 0)
 421                         return (EINVAL);
 422                 hex = name + sizeof(NG_L2TP_HOOK_SESSION_P) - 1;
 423                 for (session_id = i = 0; i < 4; i++) {
 424                         for (j = 0; j < 16 && hex[i] != hexdig[j]; j++);
 425                         if (j == 16)
 426                                 return (EINVAL);
 427                         session_id = (session_id << 4) | j;
 428                 }
 429                 if (hex[i] != '\0')
 430                         return (EINVAL);
 431
 432                 /* Create hook private structure */
 433                 hpriv = malloc(sizeof(*hpriv),
 434                     M_NETGRAPH_L2TP, M_NOWAIT | M_ZERO);
 435                 if (hpriv == NULL)
 436                         return (ENOMEM);
 437                 hpriv->conf.session_id = session_id;
 438                 hpriv->conf.control_dseq = L2TP_CONTROL_DSEQ;
 439                 hpriv->conf.enable_dseq = L2TP_ENABLE_DSEQ;
 440                 hpriv->hook = hook;
 441                 NG_HOOK_SET_PRIVATE(hook, hpriv);
 442                 hash = SESSHASH(hpriv->conf.session_id);
 443                 LIST_INSERT_HEAD(&priv->sesshash[hash], hpriv, sessions);
 444         }
 445
 446         /* Done */
 447         return (0);
 448 }
 449
 450 /*
 451  * Receive a control message.
 452  */
 453 static int
 454 ng_l2tp_rcvmsg(node_p node, item_p item, hook_p lasthook)
 455 {
 456         const priv_p priv = NG_NODE_PRIVATE(node);
 457         struct ng_mesg *resp = NULL;
 458         struct ng_mesg *msg;
 459         int error = 0;
 460
 461         NGI_GET_MSG(item, msg);
 462         switch (msg->header.typecookie) {
 463         case NGM_L2TP_COOKIE:
 464                 switch (msg->header.cmd) {
 465                 case NGM_L2TP_SET_CONFIG:
 466                     {
 467                         struct ng_l2tp_config *const conf =
 468                                 (struct ng_l2tp_config *)msg->data;
 469
 470                         /* Check for invalid or illegal config */
 471                         if (msg->header.arglen != sizeof(*conf)) {
 472                                 error = EINVAL;
 473                                 break;
 474                         }
 475                         conf->enabled = !!conf->enabled;
 476                         conf->match_id = !!conf->match_id;
 477                         if (priv->conf.enabled
 478                             && ((priv->conf.tunnel_id != 0
 479                                && conf->tunnel_id != priv->conf.tunnel_id)
 480                               || ((priv->conf.peer_id != 0
 481                                && conf->peer_id != priv->conf.peer_id)))) {
 482                                 error = EBUSY;
 483                                 break;
 484                         }
 485
 486                         /* Save calling node as failure target */
 487                         priv->ftarget = NGI_RETADDR(item);
 488
 489                         /* Adjust sequence number state */
 490                         if ((error = ng_l2tp_seq_adjust(priv, conf)) != 0)
 491                                 break;
 492
 493                         /* Update node's config */
 494                         priv->conf = *conf;
 495                         break;
 496                     }
 497                 case NGM_L2TP_GET_CONFIG:
 498                     {
 499                         struct ng_l2tp_config *conf;
 500
 501                         NG_MKRESPONSE(resp, msg, sizeof(*conf), M_NOWAIT);
 502                         if (resp == NULL) {
 503                                 error = ENOMEM;
 504                                 break;
 505                         }
 506                         conf = (struct ng_l2tp_config *)resp->data;
 507                         *conf = priv->conf;
 508                         break;
 509                     }
 510                 case NGM_L2TP_SET_SESS_CONFIG:
 511                     {
 512                         struct ng_l2tp_sess_config *const conf =
 513                             (struct ng_l2tp_sess_config *)msg->data;
 514                         hookpriv_p hpriv;
 515
 516                         /* Check for invalid or illegal config. */
 517                         if (msg->header.arglen != sizeof(*conf)) {
 518                                 error = EINVAL;
 519                                 break;
 520                         }
 521
 522                         /* Find matching hook */
 523                         hpriv = ng_l2tp_find_session(priv, conf->session_id);
 524                         if (hpriv == NULL) {
 525                                 error = ENOENT;
 526                                 break;
 527                         }
 528
 529                         /* Update hook's config */
 530                         hpriv->conf = *conf;
 531                         break;
 532                     }
 533                 case NGM_L2TP_GET_SESS_CONFIG:
 534                     {
 535                         struct ng_l2tp_sess_config *conf;
 536                         u_int16_t session_id;
 537                         hookpriv_p hpriv;
 538
 539                         /* Get session ID */
 540                         if (msg->header.arglen != sizeof(session_id)) {
 541                                 error = EINVAL;
 542                                 break;
 543                         }
 544                         memcpy(&session_id, msg->data, 2);
 545
 546                         /* Find matching hook */
 547                         hpriv = ng_l2tp_find_session(priv, session_id);
 548                         if (hpriv == NULL) {
 549                                 error = ENOENT;
 550                                 break;
 551                         }
 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                         break;
 562                     }
 563                 case NGM_L2TP_GET_STATS:
 564                 case NGM_L2TP_CLR_STATS:
 565                 case NGM_L2TP_GETCLR_STATS:
 566                     {
 567                         if (msg->header.cmd != NGM_L2TP_CLR_STATS) {
 568                                 NG_MKRESPONSE(resp, msg,
 569                                     sizeof(priv->stats), M_NOWAIT);
 570                                 if (resp == NULL) {
 571                                         error = ENOMEM;
 572                                         break;
 573                                 }
 574                                 memcpy(resp->data,
 575                                     &priv->stats, sizeof(priv->stats));
 576                         }
 577                         if (msg->header.cmd != NGM_L2TP_GET_STATS)
 578                                 memset(&priv->stats, 0, sizeof(priv->stats));
 579                         break;
 580                     }
 581                 case NGM_L2TP_GET_SESSION_STATS:
 582                 case NGM_L2TP_CLR_SESSION_STATS:
 583                 case NGM_L2TP_GETCLR_SESSION_STATS:
 584                     {
 585                         uint16_t session_id;
 586                         hookpriv_p hpriv;
 587
 588                         /* Get session ID. */
 589                         if (msg->header.arglen != sizeof(session_id)) {
 590                                 error = EINVAL;
 591                                 break;
 592                         }
 593                         bcopy(msg->data, &session_id, sizeof(uint16_t));
 594
 595                         /* Find matching hook. */
 596                         hpriv = ng_l2tp_find_session(priv, session_id);
 597                         if (hpriv == NULL) {
 598                                 error = ENOENT;
 599                                 break;
 600                         }
 601
 602                         if (msg->header.cmd != NGM_L2TP_CLR_SESSION_STATS) {
 603                                 NG_MKRESPONSE(resp, msg,
 604                                     sizeof(hpriv->stats), M_NOWAIT);
 605                                 if (resp == NULL) {
 606                                         error = ENOMEM;
 607                                         break;
 608                                 }
 609                                 bcopy(&hpriv->stats, resp->data,
 610                                         sizeof(hpriv->stats));
 611                         }
 612                         if (msg->header.cmd != NGM_L2TP_GET_SESSION_STATS)
 613                                 bzero(&hpriv->stats, sizeof(hpriv->stats));
 614                         break;
 615                     }
 616                 case NGM_L2TP_SET_SEQ:
 617                     {
 618                         struct ng_l2tp_seq_config *const conf =
 619                                 (struct ng_l2tp_seq_config *)msg->data;
 620
 621                         /* Check for invalid or illegal seq config. */
 622                         if (msg->header.arglen != sizeof(*conf)) {
 623                                 error = EINVAL;
 624                                 break;
 625                         }
 626                         conf->ns = htons(conf->ns);
 627                         conf->nr = htons(conf->nr);
 628                         conf->rack = htons(conf->rack);
 629                         conf->xack = htons(conf->xack);
 630
 631                         /* Set sequence numbers. */
 632                         error = ng_l2tp_seq_set(priv, conf);
 633                         break;
 634                     }
 635                 default:
 636                         error = EINVAL;
 637                         break;
 638                 }
 639                 break;
 640         default:
 641                 error = EINVAL;
 642                 break;
 643         }
 644
 645         /* Done */
 646         NG_RESPOND_MSG(error, node, item, resp);
 647         NG_FREE_MSG(msg);
 648         return (error);
 649 }
 650
 651 /*
 652  * Destroy node
 653  */
 654 static int
 655 ng_l2tp_shutdown(node_p node)
 656 {
 657         const priv_p priv = NG_NODE_PRIVATE(node);
 658         struct l2tp_seq *const seq = &priv->seq;
 659
 660         /* Reset sequence number state */
 661         SEQ_LOCK(seq);
 662         ng_l2tp_seq_reset(priv);
 663         SEQ_UNLOCK(seq);
 664
 665         /* Free private data if neither timer is running */
 666         callout_drain(&seq->rack_timer);
 667         callout_drain(&seq->xack_timer);
 668
 669         mtx_destroy(&seq->mtx);
 670
 671         free(priv, M_NETGRAPH_L2TP);
 672
 673         /* Unref node */
 674         NG_NODE_UNREF(node);
 675         return (0);
 676 }
 677
 678 /*
 679  * Hook disconnection
 680  */
 681 static int
 682 ng_l2tp_disconnect(hook_p hook)
 683 {
 684         const node_p node = NG_HOOK_NODE(hook);
 685         const priv_p priv = NG_NODE_PRIVATE(node);
 686
 687         /* Zero out hook pointer */
 688         if (hook == priv->ctrl)
 689                 priv->ctrl = NULL;
 690         else if (hook == priv->lower)
 691                 priv->lower = NULL;
 692         else {
 693                 const hookpriv_p hpriv = NG_HOOK_PRIVATE(hook);
 694                 LIST_REMOVE(hpriv, sessions);
 695                 free(hpriv, M_NETGRAPH_L2TP);
 696                 NG_HOOK_SET_PRIVATE(hook, NULL);
 697         }
 698
 699         /* Go away if no longer connected to anything */
 700         if (NG_NODE_NUMHOOKS(node) == 0 && NG_NODE_IS_VALID(node))
 701                 ng_rmnode_self(node);
 702         return (0);
 703 }
 704
 705 /*************************************************************************
 706                         INTERNAL FUNCTIONS
 707 *************************************************************************/
 708
 709 /*
 710  * Find the hook with a given session ID.
 711  */
 712 static hookpriv_p
 713 ng_l2tp_find_session(priv_p privp, u_int16_t sid)
 714 {
 715         uint16_t        hash = SESSHASH(sid);
 716         hookpriv_p      hpriv = NULL;
 717
 718         LIST_FOREACH(hpriv, &privp->sesshash[hash], sessions) {
 719                 if (hpriv->conf.session_id == sid)
 720                         break;
 721         }
 722
 723         return (hpriv);
 724 }
 725
 726 /*
 727  * Reset a hook's session state.
 728  */
 729 static int
 730 ng_l2tp_reset_session(hook_p hook, void *arg)
 731 {
 732         const hookpriv_p hpriv = NG_HOOK_PRIVATE(hook);
 733
 734         if (hpriv != NULL) {
 735                 hpriv->conf.control_dseq = 0;
 736                 hpriv->conf.enable_dseq = 0;
 737                 bzero(&hpriv->stats, sizeof(struct ng_l2tp_session_stats));
 738                 hpriv->nr = 0;
 739                 hpriv->ns = 0;
 740         }
 741         return (-1);
 742 }
 743
 744 /*
 745  * Handle an incoming frame from below.
 746  */
 747 static int
 748 ng_l2tp_rcvdata_lower(hook_p h, item_p item)
 749 {
 750         static const u_int16_t req_bits[2][2] = {
 751                 { L2TP_DATA_0BITS, L2TP_DATA_1BITS },
 752                 { L2TP_CTRL_0BITS, L2TP_CTRL_1BITS },
 753         };
 754         const node_p node = NG_HOOK_NODE(h);
 755         const priv_p priv = NG_NODE_PRIVATE(node);
 756         hookpriv_p hpriv = NULL;
 757         hook_p hook = NULL;
 758         struct mbuf *m;
 759         u_int16_t tid, sid;
 760         u_int16_t hdr;
 761         u_int16_t ns, nr;
 762         int is_ctrl;
 763         int error;
 764         int len, plen;
 765
 766         /* If not configured, reject */
 767         if (!priv->conf.enabled) {
 768                 NG_FREE_ITEM(item);
 769                 ERROUT(ENXIO);
 770         }
 771
 772         /* Grab mbuf */
 773         NGI_GET_M(item, m);
 774
 775         /* Remember full packet length; needed for per session accounting. */
 776         plen = m->m_pkthdr.len;
 777
 778         /* Update stats */
 779         priv->stats.recvPackets++;
 780         priv->stats.recvOctets += plen;
 781
 782         /* Get initial header */
 783         if (m->m_pkthdr.len < 6) {
 784                 priv->stats.recvRunts++;
 785                 NG_FREE_ITEM(item);
 786                 NG_FREE_M(m);
 787                 ERROUT(EINVAL);
 788         }
 789         if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
 790                 priv->stats.memoryFailures++;
 791                 NG_FREE_ITEM(item);
 792                 ERROUT(EINVAL);
 793         }
 794         hdr = (mtod(m, uint8_t *)[0] << 8) + mtod(m, uint8_t *)[1];
 795         m_adj(m, 2);
 796
 797         /* Check required header bits and minimum length */
 798         is_ctrl = (hdr & L2TP_HDR_CTRL) != 0;
 799         if ((hdr & req_bits[is_ctrl][0]) != 0
 800             || (~hdr & req_bits[is_ctrl][1]) != 0) {
 801                 priv->stats.recvInvalid++;
 802                 NG_FREE_ITEM(item);
 803                 NG_FREE_M(m);
 804                 ERROUT(EINVAL);
 805         }
 806         if (m->m_pkthdr.len < 4                         /* tunnel, session id */
 807             + (2 * ((hdr & L2TP_HDR_LEN) != 0))         /* length field */
 808             + (4 * ((hdr & L2TP_HDR_SEQ) != 0))         /* seq # fields */
 809             + (2 * ((hdr & L2TP_HDR_OFF) != 0))) {      /* offset field */
 810                 priv->stats.recvRunts++;
 811                 NG_FREE_ITEM(item);
 812                 NG_FREE_M(m);
 813                 ERROUT(EINVAL);
 814         }
 815
 816         /* Get and validate length field if present */
 817         if ((hdr & L2TP_HDR_LEN) != 0) {
 818                 if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
 819                         priv->stats.memoryFailures++;
 820                         NG_FREE_ITEM(item);
 821                         ERROUT(EINVAL);
 822                 }
 823                 len = (mtod(m, uint8_t *)[0] << 8) + mtod(m, uint8_t *)[1] - 4;
 824                 m_adj(m, 2);
 825                 if (len < 0 || len > m->m_pkthdr.len) {
 826                         priv->stats.recvInvalid++;
 827                         NG_FREE_ITEM(item);
 828                         NG_FREE_M(m);
 829                         ERROUT(EINVAL);
 830                 }
 831                 if (len < m->m_pkthdr.len)              /* trim extra bytes */
 832                         m_adj(m, -(m->m_pkthdr.len - len));
 833         }
 834
 835         /* Get tunnel ID and session ID */
 836         if (m->m_len < 4 && (m = m_pullup(m, 4)) == NULL) {
 837                 priv->stats.memoryFailures++;
 838                 NG_FREE_ITEM(item);
 839                 ERROUT(EINVAL);
 840         }
 841         tid = (mtod(m, u_int8_t *)[0] << 8) + mtod(m, u_int8_t *)[1];
 842         sid = (mtod(m, u_int8_t *)[2] << 8) + mtod(m, u_int8_t *)[3];
 843         m_adj(m, 4);
 844
 845         /* Check tunnel ID */
 846         if (tid != priv->conf.tunnel_id &&
 847             (priv->conf.match_id || tid != 0)) {
 848                 priv->stats.recvWrongTunnel++;
 849                 NG_FREE_ITEM(item);
 850                 NG_FREE_M(m);
 851                 ERROUT(EADDRNOTAVAIL);
 852         }
 853
 854         /* Check session ID (for data packets only) */
 855         if ((hdr & L2TP_HDR_CTRL) == 0) {
 856                 hpriv = ng_l2tp_find_session(priv, sid);
 857                 if (hpriv == NULL) {
 858                         priv->stats.recvUnknownSID++;
 859                         NG_FREE_ITEM(item);
 860                         NG_FREE_M(m);
 861                         ERROUT(ENOTCONN);
 862                 }
 863                 hook = hpriv->hook;
 864         }
 865
 866         /* Get Ns, Nr fields if present */
 867         if ((hdr & L2TP_HDR_SEQ) != 0) {
 868                 if (m->m_len < 4 && (m = m_pullup(m, 4)) == NULL) {
 869                         priv->stats.memoryFailures++;
 870                         NG_FREE_ITEM(item);
 871                         ERROUT(EINVAL);
 872                 }
 873                 ns = (mtod(m, u_int8_t *)[0] << 8) + mtod(m, u_int8_t *)[1];
 874                 nr = (mtod(m, u_int8_t *)[2] << 8) + mtod(m, u_int8_t *)[3];
 875                 m_adj(m, 4);
 876         } else
 877                 ns = nr = 0;
 878
 879         /* Strip offset padding if present */
 880         if ((hdr & L2TP_HDR_OFF) != 0) {
 881                 u_int16_t offset;
 882
 883                 /* Get length of offset padding */
 884                 if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
 885                         priv->stats.memoryFailures++;
 886                         NG_FREE_ITEM(item);
 887                         ERROUT(EINVAL);
 888                 }
 889                 offset = (mtod(m, u_int8_t *)[0] << 8) + mtod(m, u_int8_t *)[1];
 890
 891                 /* Trim offset padding */
 892                 if ((2+offset) > m->m_pkthdr.len) {
 893                         priv->stats.recvInvalid++;
 894                         NG_FREE_ITEM(item);
 895                         NG_FREE_M(m);
 896                         ERROUT(EINVAL);
 897                 }
 898                 m_adj(m, 2+offset);
 899         }
 900
 901         /* Handle control packets */
 902         if ((hdr & L2TP_HDR_CTRL) != 0) {
 903                 struct l2tp_seq *const seq = &priv->seq;
 904
 905                 SEQ_LOCK(seq);
 906
 907                 /* Handle receive ack sequence number Nr */
 908                 ng_l2tp_seq_recv_nr(priv, nr);
 909
 910                 /* Discard ZLB packets */
 911                 if (m->m_pkthdr.len == 0) {
 912                         SEQ_UNLOCK(seq);
 913                         priv->stats.recvZLBs++;
 914                         NG_FREE_ITEM(item);
 915                         NG_FREE_M(m);
 916                         ERROUT(0);
 917                 }
 918
 919                 /*
 920                  * If not what we expect or we are busy, drop packet and
 921                  * send an immediate ZLB ack.
 922                  */
 923                 if (ns != seq->nr || seq->inproc) {
 924                         if (L2TP_SEQ_DIFF(ns, seq->nr) <= 0)
 925                                 priv->stats.recvDuplicates++;
 926                         else
 927                                 priv->stats.recvOutOfOrder++;
 928                         ng_l2tp_xmit_ctrl(priv, NULL, seq->ns);
 929                         NG_FREE_ITEM(item);
 930                         NG_FREE_M(m);
 931                         ERROUT(0);
 932                 }
 933
 934                 /* Prepend session ID to packet. */
 935                 M_PREPEND(m, 2, M_NOWAIT);
 936                 if (m == NULL) {
 937                         SEQ_UNLOCK(seq);
 938                         priv->stats.memoryFailures++;
 939                         NG_FREE_ITEM(item);
 940                         ERROUT(ENOBUFS);
 941                 }
 942                 mtod(m, u_int8_t *)[0] = sid >> 8;
 943                 mtod(m, u_int8_t *)[1] = sid & 0xff;
 944
 945                 /*
 946                  * Until we deliver this packet we can't receive next one as
 947                  * we have no information for sending ack.
 948                  */
 949                 seq->inproc = 1;
 950                 SEQ_UNLOCK(seq);
 951
 952                 /* Deliver packet to upper layers */
 953                 NG_FWD_NEW_DATA(error, item, priv->ctrl, m);
 954
 955                 SEQ_LOCK(seq);
 956                 /* Ready to process next packet. */
 957                 seq->inproc = 0;
 958
 959                 /* If packet was successfully delivered send ack. */
 960                 if (error == 0) {
 961                         /* Update recv sequence number */
 962                         seq->nr++;
 963                         /* Start receive ack timer, if not already running */
 964                         if (!callout_active(&seq->xack_timer)) {
 965                                 callout_reset(&seq->xack_timer,
 966                                     L2TP_DELAYED_ACK, ng_l2tp_seq_xack_timeout,
 967                                     node);
 968                         }
 969                 }
 970                 SEQ_UNLOCK(seq);
 971
 972                 ERROUT(error);
 973         }
 974
 975         /* Per session packet, account it. */
 976         hpriv->stats.recvPackets++;
 977         hpriv->stats.recvOctets += plen;
 978
 979         /* Follow peer's lead in data sequencing, if configured to do so */
 980         if (!hpriv->conf.control_dseq)
 981                 hpriv->conf.enable_dseq = ((hdr & L2TP_HDR_SEQ) != 0);
 982
 983         /* Handle data sequence numbers if present and enabled */
 984         if ((hdr & L2TP_HDR_SEQ) != 0) {
 985                 if (hpriv->conf.enable_dseq
 986                     && L2TP_SEQ_DIFF(ns, hpriv->nr) < 0) {
 987                         NG_FREE_ITEM(item);     /* duplicate or out of order */
 988                         NG_FREE_M(m);
 989                         priv->stats.recvDataDrops++;
 990                         ERROUT(0);
 991                 }
 992                 hpriv->nr = ns + 1;
 993         }
 994
 995         /* Drop empty data packets */
 996         if (m->m_pkthdr.len == 0) {
 997                 NG_FREE_ITEM(item);
 998                 NG_FREE_M(m);
 999                 ERROUT(0);
1000         }
1001
1002         /* Deliver data */
1003         NG_FWD_NEW_DATA(error, item, hook, m);
1004 done:
1005         return (error);
1006 }
1007
1008 /*
1009  * Handle an outgoing control frame.
1010  */
1011 static int
1012 ng_l2tp_rcvdata_ctrl(hook_p hook, item_p item)
1013 {
1014         const node_p node = NG_HOOK_NODE(hook);
1015         const priv_p priv = NG_NODE_PRIVATE(node);
1016         struct l2tp_seq *const seq = &priv->seq;
1017         struct mbuf *m;
1018         int error;
1019         int i;
1020         u_int16_t       ns;
1021
1022         /* If not configured, reject */
1023         if (!priv->conf.enabled) {
1024                 NG_FREE_ITEM(item);
1025                 ERROUT(ENXIO);
1026         }
1027
1028         /* Grab mbuf and discard other stuff XXX */
1029         NGI_GET_M(item, m);
1030         NG_FREE_ITEM(item);
1031
1032         /* Packet should have session ID prepended */
1033         if (m->m_pkthdr.len < 2) {
1034                 priv->stats.xmitInvalid++;
1035                 m_freem(m);
1036                 ERROUT(EINVAL);
1037         }
1038
1039         /* Check max length */
1040         if (m->m_pkthdr.len >= 0x10000 - 14) {
1041                 priv->stats.xmitTooBig++;
1042                 m_freem(m);
1043                 ERROUT(EOVERFLOW);
1044         }
1045
1046         SEQ_LOCK(seq);
1047
1048         /* Find next empty slot in transmit queue */
1049         for (i = 0; i < L2TP_MAX_XWIN && seq->xwin[i] != NULL; i++);
1050         if (i == L2TP_MAX_XWIN) {
1051                 SEQ_UNLOCK(seq);
1052                 priv->stats.xmitDrops++;
1053                 m_freem(m);
1054                 ERROUT(ENOBUFS);
1055         }
1056         seq->xwin[i] = m;
1057
1058         /* If peer's receive window is already full, nothing else to do */
1059         if (i >= seq->cwnd) {
1060                 SEQ_UNLOCK(seq);
1061                 ERROUT(0);
1062         }
1063
1064         /* Start retransmit timer if not already running */
1065         if (!callout_active(&seq->rack_timer))
1066                 callout_reset(&seq->rack_timer, hz, ng_l2tp_seq_rack_timeout,
1067                     node);
1068
1069         ns = seq->ns++;
1070
1071         /* Copy packet */
1072         if ((m = L2TP_COPY_MBUF(m, M_NOWAIT)) == NULL) {
1073                 SEQ_UNLOCK(seq);
1074                 priv->stats.memoryFailures++;
1075                 ERROUT(ENOBUFS);
1076         }
1077
1078         /* Send packet and increment xmit sequence number */
1079         error = ng_l2tp_xmit_ctrl(priv, m, ns);
1080 done:
1081         return (error);
1082 }
1083
1084 /*
1085  * Handle an outgoing data frame.
1086  */
1087 static int
1088 ng_l2tp_rcvdata(hook_p hook, item_p item)
1089 {
1090         const priv_p priv = NG_NODE_PRIVATE(NG_HOOK_NODE(hook));
1091         const hookpriv_p hpriv = NG_HOOK_PRIVATE(hook);
1092         struct mbuf *m;
1093         uint8_t *p;
1094         u_int16_t hdr;
1095         int error;
1096         int i = 2;
1097
1098         /* If not configured, reject */
1099         if (!priv->conf.enabled) {
1100                 NG_FREE_ITEM(item);
1101                 ERROUT(ENXIO);
1102         }
1103
1104         /* Get mbuf */
1105         NGI_GET_M(item, m);
1106
1107         /* Check max length */
1108         if (m->m_pkthdr.len >= 0x10000 - 12) {
1109                 priv->stats.xmitDataTooBig++;
1110                 NG_FREE_ITEM(item);
1111                 NG_FREE_M(m);
1112                 ERROUT(EOVERFLOW);
1113         }
1114
1115         /* Prepend L2TP header */
1116         M_PREPEND(m, 6
1117             + (2 * (hpriv->conf.include_length != 0))
1118             + (4 * (hpriv->conf.enable_dseq != 0)),
1119             M_NOWAIT);
1120         if (m == NULL) {
1121                 priv->stats.memoryFailures++;
1122                 NG_FREE_ITEM(item);
1123                 ERROUT(ENOBUFS);
1124         }
1125         p = mtod(m, uint8_t *);
1126         hdr = L2TP_DATA_HDR;
1127         if (hpriv->conf.include_length) {
1128                 hdr |= L2TP_HDR_LEN;
1129                 p[i++] = m->m_pkthdr.len >> 8;
1130                 p[i++] = m->m_pkthdr.len & 0xff;
1131         }
1132         p[i++] = priv->conf.peer_id >> 8;
1133         p[i++] = priv->conf.peer_id & 0xff;
1134         p[i++] = hpriv->conf.peer_id >> 8;
1135         p[i++] = hpriv->conf.peer_id & 0xff;
1136         if (hpriv->conf.enable_dseq) {
1137                 hdr |= L2TP_HDR_SEQ;
1138                 p[i++] = hpriv->ns >> 8;
1139                 p[i++] = hpriv->ns & 0xff;
1140                 p[i++] = hpriv->nr >> 8;
1141                 p[i++] = hpriv->nr & 0xff;
1142                 hpriv->ns++;
1143         }
1144         p[0] = hdr >> 8;
1145         p[1] = hdr & 0xff;
1146
1147         /* Update per session stats. */
1148         hpriv->stats.xmitPackets++;
1149         hpriv->stats.xmitOctets += m->m_pkthdr.len;
1150
1151         /* And the global one. */
1152         priv->stats.xmitPackets++;
1153         priv->stats.xmitOctets += m->m_pkthdr.len;
1154
1155         /* Send packet */
1156         NG_FWD_NEW_DATA(error, item, priv->lower, m);
1157 done:
1158         return (error);
1159 }
1160
1161 /*
1162  * Send a message to our controlling node that we've failed.
1163  */
1164 static void
1165 ng_l2tp_seq_failure(priv_p priv)
1166 {
1167         struct ng_mesg *msg;
1168         int error;
1169
1170         NG_MKMESSAGE(msg, NGM_L2TP_COOKIE, NGM_L2TP_ACK_FAILURE, 0, M_NOWAIT);
1171         if (msg == NULL)
1172                 return;
1173         NG_SEND_MSG_ID(error, priv->node, msg, priv->ftarget, 0);
1174 }
1175
1176 /************************************************************************
1177                         SEQUENCE NUMBER HANDLING
1178 ************************************************************************/
1179
1180 /*
1181  * Initialize sequence number state.
1182  */
1183 static void
1184 ng_l2tp_seq_init(priv_p priv)
1185 {
1186         struct l2tp_seq *const seq = &priv->seq;
1187
1188         KASSERT(priv->conf.peer_win >= 1,
1189             ("%s: peer_win is zero", __func__));
1190         memset(seq, 0, sizeof(*seq));
1191         seq->cwnd = 1;
1192         seq->wmax = priv->conf.peer_win;
1193         if (seq->wmax > L2TP_MAX_XWIN)
1194                 seq->wmax = L2TP_MAX_XWIN;
1195         seq->ssth = seq->wmax;
1196         mtx_init(&seq->mtx, "ng_l2tp", NULL, MTX_DEF);
1197         callout_init_mtx(&seq->rack_timer, &seq->mtx, CALLOUT_RETURNUNLOCKED);
1198         callout_init_mtx(&seq->xack_timer, &seq->mtx, CALLOUT_RETURNUNLOCKED);
1199 }
1200
1201 /*
1202  * Set sequence number state as given from user.
1203  */
1204 static int
1205 ng_l2tp_seq_set(priv_p priv, const struct ng_l2tp_seq_config *conf)
1206 {
1207         struct l2tp_seq *const seq = &priv->seq;
1208
1209         /* If node is enabled, deny update to sequence numbers. */
1210         if (priv->conf.enabled)
1211                 return (EBUSY);
1212
1213         /* We only can handle the simple cases. */
1214         if (conf->xack != conf->nr || conf->ns != conf->rack)
1215                 return (EINVAL);
1216
1217         /* Set ns,nr,rack,xack parameters. */
1218         seq->ns = conf->ns;
1219         seq->nr = conf->nr;
1220         seq->rack = conf->rack;
1221         seq->xack = conf->xack;
1222
1223         return (0);
1224 }
1225
1226 /*
1227  * Adjust sequence number state accordingly after reconfiguration.
1228  */
1229 static int
1230 ng_l2tp_seq_adjust(priv_p priv, const struct ng_l2tp_config *conf)
1231 {
1232         struct l2tp_seq *const seq = &priv->seq;
1233         u_int16_t new_wmax;
1234         int error = 0;
1235
1236         SEQ_LOCK(seq);
1237         /* If disabling node, reset state sequence number */
1238         if (!conf->enabled) {
1239                 ng_l2tp_seq_reset(priv);
1240                 SEQ_UNLOCK(seq);
1241                 return (0);
1242         }
1243
1244         /* Adjust peer's max recv window; it can only increase */
1245         new_wmax = conf->peer_win;
1246         if (new_wmax > L2TP_MAX_XWIN)
1247                 new_wmax = L2TP_MAX_XWIN;
1248         if (new_wmax == 0)
1249                 ERROUT(EINVAL);
1250         if (new_wmax < seq->wmax)
1251                 ERROUT(EBUSY);
1252         seq->wmax = new_wmax;
1253
1254 done:
1255         SEQ_UNLOCK(seq);
1256         return (error);
1257 }
1258
1259 /*
1260  * Reset sequence number state.
1261  */
1262 static void
1263 ng_l2tp_seq_reset(priv_p priv)
1264 {
1265         struct l2tp_seq *const seq = &priv->seq;
1266         int i;
1267
1268         SEQ_LOCK_ASSERT(seq);
1269
1270         /* Stop timers */
1271         (void )callout_stop(&seq->rack_timer);
1272         (void )callout_stop(&seq->xack_timer);
1273
1274         /* Free retransmit queue */
1275         for (i = 0; i < L2TP_MAX_XWIN; i++) {
1276                 if (seq->xwin[i] == NULL)
1277                         break;
1278                 m_freem(seq->xwin[i]);
1279         }
1280
1281         /* Reset session hooks' sequence number states */
1282         NG_NODE_FOREACH_HOOK(priv->node, ng_l2tp_reset_session, NULL);
1283
1284         /* Reset node's sequence number state */
1285         seq->ns = 0;
1286         seq->nr = 0;
1287         seq->rack = 0;
1288         seq->xack = 0;
1289         seq->wmax = L2TP_MAX_XWIN;
1290         seq->cwnd = 1;
1291         seq->ssth = seq->wmax;
1292         seq->acks = 0;
1293         seq->rexmits = 0;
1294         bzero(seq->xwin, sizeof(seq->xwin));
1295 }
1296
1297 /*
1298  * Handle receipt of an acknowledgement value (Nr) from peer.
1299  */
1300 static void
1301 ng_l2tp_seq_recv_nr(priv_p priv, u_int16_t nr)
1302 {
1303         struct l2tp_seq *const seq = &priv->seq;
1304         struct mbuf     *xwin[L2TP_MAX_XWIN];   /* partial local copy */
1305         int             nack;
1306         int             i, j;
1307         uint16_t        ns;
1308
1309         SEQ_LOCK_ASSERT(seq);
1310
1311         /* Verify peer's ACK is in range */
1312         if ((nack = L2TP_SEQ_DIFF(nr, seq->rack)) <= 0)
1313                 return;                         /* duplicate ack */
1314         if (L2TP_SEQ_DIFF(nr, seq->ns) > 0) {
1315                 priv->stats.recvBadAcks++;      /* ack for packet not sent */
1316                 return;
1317         }
1318         KASSERT(nack <= L2TP_MAX_XWIN,
1319             ("%s: nack=%d > %d", __func__, nack, L2TP_MAX_XWIN));
1320
1321         /* Update receive ack stats */
1322         seq->rack = nr;
1323         seq->rexmits = 0;
1324
1325         /* Free acknowledged packets and shift up packets in the xmit queue */
1326         for (i = 0; i < nack; i++)
1327                 m_freem(seq->xwin[i]);
1328         memmove(seq->xwin, seq->xwin + nack,
1329             (L2TP_MAX_XWIN - nack) * sizeof(*seq->xwin));
1330         memset(seq->xwin + (L2TP_MAX_XWIN - nack), 0,
1331             nack * sizeof(*seq->xwin));
1332
1333         /*
1334          * Do slow-start/congestion avoidance windowing algorithm described
1335          * in RFC 2661, Appendix A. Here we handle a multiple ACK as if each
1336          * ACK had arrived separately.
1337          */
1338         if (seq->cwnd < seq->wmax) {
1339                 /* Handle slow start phase */
1340                 if (seq->cwnd < seq->ssth) {
1341                         seq->cwnd += nack;
1342                         nack = 0;
1343                         if (seq->cwnd > seq->ssth) {    /* into cg.av. phase */
1344                                 nack = seq->cwnd - seq->ssth;
1345                                 seq->cwnd = seq->ssth;
1346                         }
1347                 }
1348
1349                 /* Handle congestion avoidance phase */
1350                 if (seq->cwnd >= seq->ssth) {
1351                         seq->acks += nack;
1352                         while (seq->acks >= seq->cwnd) {
1353                                 seq->acks -= seq->cwnd;
1354                                 if (seq->cwnd < seq->wmax)
1355                                         seq->cwnd++;
1356                         }
1357                 }
1358         }
1359
1360         /* Stop xmit timer */
1361         if (callout_active(&seq->rack_timer))
1362                 (void )callout_stop(&seq->rack_timer);
1363
1364         /* If transmit queue is empty, we're done for now */
1365         if (seq->xwin[0] == NULL)
1366                 return;
1367
1368         /* Start restransmit timer again */
1369         callout_reset(&seq->rack_timer, hz, ng_l2tp_seq_rack_timeout,
1370             priv->node);
1371
1372         /*
1373          * Send more packets, trying to keep peer's receive window full.
1374          * Make copy of everything we need before lock release.
1375          */
1376         ns = seq->ns;
1377         j = 0;
1378         while ((i = L2TP_SEQ_DIFF(seq->ns, seq->rack)) < seq->cwnd
1379             && seq->xwin[i] != NULL) {
1380                 xwin[j++] = seq->xwin[i];
1381                 seq->ns++;
1382         }
1383
1384         /*
1385          * Send prepared.
1386          * If there is a memory error, pretend packet was sent, as it
1387          * will get retransmitted later anyway.
1388          */
1389         for (i = 0; i < j; i++) {
1390                 struct mbuf     *m;
1391                 if ((m = L2TP_COPY_MBUF(xwin[i], M_NOWAIT)) == NULL)
1392                         priv->stats.memoryFailures++;
1393                 else {
1394                         ng_l2tp_xmit_ctrl(priv, m, ns);
1395                         SEQ_LOCK(seq);
1396                 }
1397                 ns++;
1398         }
1399 }
1400
1401 /*
1402  * Handle an ack timeout. We have an outstanding ack that we
1403  * were hoping to piggy-back, but haven't, so send a ZLB.
1404  */
1405 static void
1406 ng_l2tp_seq_xack_timeout(void *arg)
1407 {
1408         const node_p node = arg;
1409         const priv_p priv = NG_NODE_PRIVATE(node);
1410         struct epoch_tracker et;
1411         struct l2tp_seq *const seq = &priv->seq;
1412
1413         SEQ_LOCK_ASSERT(seq);
1414         MPASS(!callout_pending(&seq->xack_timer));
1415         MPASS(callout_active(&seq->xack_timer));
1416
1417         NET_EPOCH_ENTER(et);
1418         CURVNET_SET(node->nd_vnet);
1419         /* Send a ZLB */
1420         ng_l2tp_xmit_ctrl(priv, NULL, seq->ns);
1421         CURVNET_RESTORE();
1422         NET_EPOCH_EXIT(et);
1423
1424         /* callout_deactivate() is not needed here
1425             as callout_stop() was called by ng_l2tp_xmit_ctrl() */
1426 }
1427
1428 /*
1429  * Handle a transmit timeout. The peer has failed to respond
1430  * with an ack for our packet, so retransmit it.
1431  */
1432 static void
1433 ng_l2tp_seq_rack_timeout(void *arg)
1434 {
1435         const node_p node = arg;
1436         const priv_p priv = NG_NODE_PRIVATE(node);
1437         struct epoch_tracker et;
1438         struct l2tp_seq *const seq = &priv->seq;
1439         struct mbuf *m;
1440         u_int delay;
1441
1442         SEQ_LOCK_ASSERT(seq);
1443         MPASS(seq->xwin[0]);
1444         MPASS(!callout_pending(&seq->rack_timer));
1445         MPASS(callout_active(&seq->rack_timer));
1446
1447         NET_EPOCH_ENTER(et);
1448         CURVNET_SET(node->nd_vnet);
1449
1450         priv->stats.xmitRetransmits++;
1451
1452         /* Have we reached the retransmit limit? If so, notify owner. */
1453         if (seq->rexmits++ >= priv->conf.rexmit_max)
1454                 ng_l2tp_seq_failure(priv);
1455
1456         /* Restart timer, this time with an increased delay */
1457         delay = (seq->rexmits > 12) ? (1 << 12) : (1 << seq->rexmits);
1458         if (delay > priv->conf.rexmit_max_to)
1459                 delay = priv->conf.rexmit_max_to;
1460         callout_reset(&seq->rack_timer, hz * delay, ng_l2tp_seq_rack_timeout,
1461             node);
1462
1463         /* Do slow-start/congestion algorithm windowing algorithm */
1464         seq->ns = seq->rack;
1465         seq->ssth = (seq->cwnd + 1) / 2;
1466         seq->cwnd = 1;
1467         seq->acks = 0;
1468
1469         /* Retransmit oldest unack'd packet */
1470         m = L2TP_COPY_MBUF(seq->xwin[0], M_NOWAIT);
1471         if (m == NULL) {
1472                 SEQ_UNLOCK(seq);
1473                 priv->stats.memoryFailures++;
1474         } else
1475                 ng_l2tp_xmit_ctrl(priv, m, seq->ns++);
1476
1477         CURVNET_RESTORE();
1478         NET_EPOCH_EXIT(et);
1479
1480         /* callout_deactivate() is not needed here
1481             as ng_callout() is getting called each time */
1482 }
1483
1484 /*
1485  * Transmit a control stream packet, payload optional.
1486  * The transmit sequence number is not incremented.
1487  * Requires seq lock, returns unlocked.
1488  */
1489 static int
1490 ng_l2tp_xmit_ctrl(priv_p priv, struct mbuf *m, u_int16_t ns)
1491 {
1492         struct l2tp_seq *const seq = &priv->seq;
1493         uint8_t *p;
1494         uint16_t nr, session_id = 0;
1495         int error;
1496
1497         SEQ_LOCK_ASSERT(seq);
1498
1499         /* Stop ack timer: we're sending an ack with this packet.
1500            Doing this before to keep state predictable after error. */
1501         if (callout_active(&seq->xack_timer))
1502                 (void )callout_stop(&seq->xack_timer);
1503
1504         nr = seq->xack = seq->nr;
1505
1506         SEQ_UNLOCK(seq);
1507
1508         /* If no mbuf passed, send an empty packet (ZLB) */
1509         if (m == NULL) {
1510                 /* Create a new mbuf for ZLB packet */
1511                 MGETHDR(m, M_NOWAIT, MT_DATA);
1512                 if (m == NULL) {
1513                         priv->stats.memoryFailures++;
1514                         return (ENOBUFS);
1515                 }
1516                 m->m_len = m->m_pkthdr.len = 12;
1517                 m->m_pkthdr.rcvif = NULL;
1518                 priv->stats.xmitZLBs++;
1519         } else {
1520                 /* Strip off session ID */
1521                 if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
1522                         priv->stats.memoryFailures++;
1523                         return (ENOBUFS);
1524                 }
1525                 session_id = (mtod(m, u_int8_t *)[0] << 8) + mtod(m, u_int8_t *)[1];
1526
1527                 /* Make room for L2TP header */
1528                 M_PREPEND(m, 10, M_NOWAIT);     /* - 2 + 12 = 10 */
1529                 if (m == NULL) {
1530                         priv->stats.memoryFailures++;
1531                         return (ENOBUFS);
1532                 }
1533
1534                 /*
1535                  * The below requires 12 contiguous bytes for the L2TP header
1536                  * to be written into.
1537                  */
1538                 m = m_pullup(m, 12);
1539                 if (m == NULL) {
1540                         priv->stats.memoryFailures++;
1541                         return (ENOBUFS);
1542                 }
1543         }
1544
1545         /* Fill in L2TP header */
1546         p = mtod(m, u_int8_t *);
1547         p[0] = L2TP_CTRL_HDR >> 8;
1548         p[1] = L2TP_CTRL_HDR & 0xff;
1549         p[2] = m->m_pkthdr.len >> 8;
1550         p[3] = m->m_pkthdr.len & 0xff;
1551         p[4] = priv->conf.peer_id >> 8;
1552         p[5] = priv->conf.peer_id & 0xff;
1553         p[6] = session_id >> 8;
1554         p[7] = session_id & 0xff;
1555         p[8] = ns >> 8;
1556         p[9] = ns & 0xff;
1557         p[10] = nr >> 8;
1558         p[11] = nr & 0xff;
1559
1560         /* Update sequence number info and stats */
1561         priv->stats.xmitPackets++;
1562         priv->stats.xmitOctets += m->m_pkthdr.len;
1563
1564         /* Send packet */
1565         NG_SEND_DATA_ONLY(error, priv->lower, m);
1566         return (error);
1567 }
1568
1569 #ifdef INVARIANTS
1570 /*
1571  * Sanity check sequence number state.
1572  */
1573 static void
1574 ng_l2tp_seq_check(struct l2tp_seq *seq)
1575 {
1576         int self_unack, peer_unack;
1577         int i;
1578
1579 #define CHECK(p)        KASSERT((p), ("%s: not: %s", __func__, #p))
1580
1581         SEQ_LOCK_ASSERT(seq);
1582
1583         self_unack = L2TP_SEQ_DIFF(seq->nr, seq->xack);
1584         peer_unack = L2TP_SEQ_DIFF(seq->ns, seq->rack);
1585         CHECK(seq->wmax <= L2TP_MAX_XWIN);
1586         CHECK(seq->cwnd >= 1);
1587         CHECK(seq->cwnd <= seq->wmax);
1588         CHECK(seq->ssth >= 1);
1589         CHECK(seq->ssth <= seq->wmax);
1590         if (seq->cwnd < seq->ssth)
1591                 CHECK(seq->acks == 0);
1592         else
1593                 CHECK(seq->acks <= seq->cwnd);
1594         CHECK(self_unack >= 0);
1595         CHECK(peer_unack >= 0);
1596         CHECK(peer_unack <= seq->wmax);
1597         CHECK((self_unack == 0) ^ callout_active(&seq->xack_timer));
1598         CHECK((peer_unack == 0) ^ callout_active(&seq->rack_timer));
1599         for (i = 0; i < peer_unack; i++)
1600                 CHECK(seq->xwin[i] != NULL);
1601         for ( ; i < seq->cwnd; i++)         /* verify peer's recv window full */
1602                 CHECK(seq->xwin[i] == NULL);
1603
1604 #undef CHECK
1605 }
1606 #endif  /* INVARIANTS */