sys/netgraph/ng_vjc.c

   1
   2 /*
   3  * ng_vjc.c
   4  */
   5
   6 /*-
   7  * Copyright (c) 1996-1999 Whistle Communications, Inc.
   8  * All rights reserved.
   9  *
  10  * Subject to the following obligations and disclaimer of warranty, use and
  11  * redistribution of this software, in source or object code forms, with or
  12  * without modifications are expressly permitted by Whistle Communications;
  13  * provided, however, that:
  14  * 1. Any and all reproductions of the source or object code must include the
  15  *    copyright notice above and the following disclaimer of warranties; and
  16  * 2. No rights are granted, in any manner or form, to use Whistle
  17  *    Communications, Inc. trademarks, including the mark "WHISTLE
  18  *    COMMUNICATIONS" on advertising, endorsements, or otherwise except as
  19  *    such appears in the above copyright notice or in the software.
  20  *
  21  * THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND
  22  * TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO
  23  * REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE,
  24  * INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF
  25  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT.
  26  * WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY
  27  * REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS
  28  * SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE.
  29  * IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES
  30  * RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING
  31  * WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
  32  * PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR
  33  * SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY
  34  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  35  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  36  * THIS SOFTWARE, EVEN IF WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY
  37  * OF SUCH DAMAGE.
  38  *
  39  * Author: Archie Cobbs <archie@freebsd.org>
  40  *
  41  * $FreeBSD$
  42  * $Whistle: ng_vjc.c,v 1.17 1999/11/01 09:24:52 julian Exp $
  43  */
  44
  45 /*
  46  * This node performs Van Jacobson IP header (de)compression.
  47  * You must have included net/slcompress.c in your kernel compilation.
  48  */
  49
  50 #include <sys/param.h>
  51 #include <sys/systm.h>
  52 #include <sys/errno.h>
  53 #include <sys/kernel.h>
  54 #include <sys/mbuf.h>
  55 #include <sys/malloc.h>
  56 #include <sys/errno.h>
  57
  58 #include <netgraph/ng_message.h>
  59 #include <netgraph/netgraph.h>
  60 #include <netgraph/ng_parse.h>
  61 #include <netgraph/ng_vjc.h>
  62
  63 #include <netinet/in.h>
  64 #include <netinet/in_systm.h>
  65 #include <netinet/ip.h>
  66 #include <netinet/tcp.h>
  67
  68 #include <net/slcompress.h>
  69
  70 /* Check agreement with slcompress.c */
  71 #if MAX_STATES != NG_VJC_MAX_CHANNELS
  72 #error NG_VJC_MAX_CHANNELS must be the same as MAX_STATES
  73 #endif
  74
  75 /* Maximum length of a compressed TCP VJ header */
  76 #define MAX_VJHEADER            19
  77
  78 /* Node private data */
  79 struct ng_vjc_private {
  80         struct  ngm_vjc_config conf;
  81         struct  slcompress slc;
  82         hook_p  ip;
  83         hook_p  vjcomp;
  84         hook_p  vjuncomp;
  85         hook_p  vjip;
  86 };
  87 typedef struct ng_vjc_private *priv_p;
  88
  89 #define ERROUT(x)       do { error = (x); goto done; } while (0)
  90
  91 /* Netgraph node methods */
  92 static ng_constructor_t ng_vjc_constructor;
  93 static ng_rcvmsg_t      ng_vjc_rcvmsg;
  94 static ng_shutdown_t    ng_vjc_shutdown;
  95 static ng_newhook_t     ng_vjc_newhook;
  96 static ng_rcvdata_t     ng_vjc_rcvdata;
  97 static ng_disconnect_t  ng_vjc_disconnect;
  98
  99 /* Helper stuff */
 100 static struct mbuf *ng_vjc_pulluphdrs(struct mbuf *m, int knownTCP);
 101
 102 /* Parse type for struct ngm_vjc_config */
 103 static const struct ng_parse_struct_field ng_vjc_config_type_fields[]
 104         = NG_VJC_CONFIG_TYPE_INFO;
 105 static const struct ng_parse_type ng_vjc_config_type = {
 106         &ng_parse_struct_type,
 107         &ng_vjc_config_type_fields
 108 };
 109
 110 /* Parse type for the 'last_cs' and 'cs_next' fields in struct slcompress,
 111    which are pointers converted to integer indices, so parse them that way. */
 112 #ifndef __LP64__
 113 #define NG_VJC_TSTATE_PTR_TYPE  &ng_parse_uint32_type
 114 #else
 115 #define NG_VJC_TSTATE_PTR_TYPE  &ng_parse_uint64_type
 116 #endif
 117
 118 /* Parse type for the 'cs_hdr' field in a struct cstate. Ideally we would
 119    like to use a 'struct ip' type instead of a simple array of bytes. */
 120 static const struct ng_parse_fixedarray_info ng_vjc_cs_hdr_type_info = {
 121         &ng_parse_hint8_type,
 122         MAX_HDR
 123 };
 124 static const struct ng_parse_type ng_vjc_cs_hdr_type = {
 125         &ng_parse_fixedarray_type,
 126         &ng_vjc_cs_hdr_type_info
 127 };
 128
 129 /* Parse type for a struct cstate */
 130 static const struct ng_parse_struct_field ng_vjc_cstate_type_fields[] = {
 131         { "cs_next",            NG_VJC_TSTATE_PTR_TYPE          },
 132         { "cs_hlen",            &ng_parse_uint16_type           },
 133         { "cs_id",              &ng_parse_uint8_type            },
 134         { "cs_filler",          &ng_parse_uint8_type            },
 135         { "cs_hdr",             &ng_vjc_cs_hdr_type             },
 136         { NULL }
 137 };
 138 static const struct ng_parse_type ng_vjc_cstate_type = {
 139         &ng_parse_struct_type,
 140         &ng_vjc_cstate_type_fields
 141 };
 142
 143 /* Parse type for an array of MAX_STATES struct cstate's, ie, tstate & rstate */
 144 static const struct ng_parse_fixedarray_info ng_vjc_cstatearray_type_info = {
 145         &ng_vjc_cstate_type,
 146         MAX_STATES
 147 };
 148 static const struct ng_parse_type ng_vjc_cstatearray_type = {
 149         &ng_parse_fixedarray_type,
 150         &ng_vjc_cstatearray_type_info
 151 };
 152
 153 /* Parse type for struct slcompress. Keep this in sync with the
 154    definition of struct slcompress defined in <net/slcompress.h> */
 155 static const struct ng_parse_struct_field ng_vjc_slcompress_type_fields[] = {
 156         { "last_cs",            NG_VJC_TSTATE_PTR_TYPE          },
 157         { "last_recv",          &ng_parse_uint8_type            },
 158         { "last_xmit",          &ng_parse_uint8_type            },
 159         { "flags",              &ng_parse_hint16_type           },
 160 #ifndef SL_NO_STATS
 161         { "sls_packets",        &ng_parse_uint32_type           },
 162         { "sls_compressed",     &ng_parse_uint32_type           },
 163         { "sls_searches",       &ng_parse_uint32_type           },
 164         { "sls_misses",         &ng_parse_uint32_type           },
 165         { "sls_uncompressedin", &ng_parse_uint32_type           },
 166         { "sls_compressedin",   &ng_parse_uint32_type           },
 167         { "sls_errorin",        &ng_parse_uint32_type           },
 168         { "sls_tossed",         &ng_parse_uint32_type           },
 169 #endif
 170         { "tstate",             &ng_vjc_cstatearray_type        },
 171         { "rstate",             &ng_vjc_cstatearray_type        },
 172         { NULL }
 173 };
 174 static const struct ng_parse_type ng_vjc_slcompress_type = {
 175         &ng_parse_struct_type,
 176         &ng_vjc_slcompress_type_fields
 177 };
 178
 179 /* List of commands and how to convert arguments to/from ASCII */
 180 static const struct ng_cmdlist ng_vjc_cmds[] = {
 181         {
 182           NGM_VJC_COOKIE,
 183           NGM_VJC_SET_CONFIG,
 184           "setconfig",
 185           &ng_vjc_config_type,
 186           NULL
 187         },
 188         {
 189           NGM_VJC_COOKIE,
 190           NGM_VJC_GET_CONFIG,
 191           "getconfig",
 192           NULL,
 193           &ng_vjc_config_type,
 194         },
 195         {
 196           NGM_VJC_COOKIE,
 197           NGM_VJC_GET_STATE,
 198           "getstate",
 199           NULL,
 200           &ng_vjc_slcompress_type,
 201         },
 202         {
 203           NGM_VJC_COOKIE,
 204           NGM_VJC_CLR_STATS,
 205           "clrstats",
 206           NULL,
 207           NULL,
 208         },
 209         {
 210           NGM_VJC_COOKIE,
 211           NGM_VJC_RECV_ERROR,
 212           "recverror",
 213           NULL,
 214           NULL,
 215         },
 216         { 0 }
 217 };
 218
 219 /* Node type descriptor */
 220 static struct ng_type ng_vjc_typestruct = {
 221         .version =      NG_ABI_VERSION,
 222         .name =         NG_VJC_NODE_TYPE,
 223         .constructor =  ng_vjc_constructor,
 224         .rcvmsg =       ng_vjc_rcvmsg,
 225         .shutdown =     ng_vjc_shutdown,
 226         .newhook =      ng_vjc_newhook,
 227         .rcvdata =      ng_vjc_rcvdata,
 228         .disconnect =   ng_vjc_disconnect,
 229         .cmdlist =      ng_vjc_cmds,
 230 };
 231 NETGRAPH_INIT(vjc, &ng_vjc_typestruct);
 232
 233 /************************************************************************
 234                         NETGRAPH NODE METHODS
 235  ************************************************************************/
 236
 237 /*
 238  * Create a new node
 239  */
 240 static int
 241 ng_vjc_constructor(node_p node)
 242 {
 243         priv_p priv;
 244
 245         /* Allocate private structure */
 246         priv = malloc(sizeof(*priv), M_NETGRAPH, M_NOWAIT | M_ZERO);
 247         if (priv == NULL)
 248                 return (ENOMEM);
 249
 250         NG_NODE_SET_PRIVATE(node, priv);
 251
 252         /* slcompress is not thread-safe. Protect it's state here. */
 253         NG_NODE_FORCE_WRITER(node);
 254
 255         /* Done */
 256         return (0);
 257 }
 258
 259 /*
 260  * Add a new hook
 261  */
 262 static int
 263 ng_vjc_newhook(node_p node, hook_p hook, const char *name)
 264 {
 265         const priv_p priv = NG_NODE_PRIVATE(node);
 266         hook_p *hookp;
 267
 268         /* Get hook */
 269         if (strcmp(name, NG_VJC_HOOK_IP) == 0)
 270                 hookp = &priv->ip;
 271         else if (strcmp(name, NG_VJC_HOOK_VJCOMP) == 0)
 272                 hookp = &priv->vjcomp;
 273         else if (strcmp(name, NG_VJC_HOOK_VJUNCOMP) == 0)
 274                 hookp = &priv->vjuncomp;
 275         else if (strcmp(name, NG_VJC_HOOK_VJIP) == 0)
 276                 hookp = &priv->vjip;
 277         else
 278                 return (EINVAL);
 279
 280         /* See if already connected */
 281         if (*hookp)
 282                 return (EISCONN);
 283
 284         /* OK */
 285         *hookp = hook;
 286         return (0);
 287 }
 288
 289 /*
 290  * Receive a control message
 291  */
 292 static int
 293 ng_vjc_rcvmsg(node_p node, item_p item, hook_p lasthook)
 294 {
 295         const priv_p priv = NG_NODE_PRIVATE(node);
 296         struct ng_mesg *resp = NULL;
 297         int error = 0;
 298         struct ng_mesg *msg;
 299
 300         NGI_GET_MSG(item, msg);
 301         /* Check type cookie */
 302         switch (msg->header.typecookie) {
 303         case NGM_VJC_COOKIE:
 304                 switch (msg->header.cmd) {
 305                 case NGM_VJC_SET_CONFIG:
 306                     {
 307                         struct ngm_vjc_config *const c =
 308                                 (struct ngm_vjc_config *) msg->data;
 309
 310                         if (msg->header.arglen != sizeof(*c))
 311                                 ERROUT(EINVAL);
 312                         if ((priv->conf.enableComp || priv->conf.enableDecomp)
 313                             && (c->enableComp || c->enableDecomp))
 314                                 ERROUT(EALREADY);
 315                         if (c->enableComp) {
 316                                 if (c->maxChannel > NG_VJC_MAX_CHANNELS - 1
 317                                     || c->maxChannel < NG_VJC_MIN_CHANNELS - 1)
 318                                         ERROUT(EINVAL);
 319                         } else
 320                                 c->maxChannel = NG_VJC_MAX_CHANNELS - 1;
 321                         if (c->enableComp != 0 || c->enableDecomp != 0) {
 322                                 bzero(&priv->slc, sizeof(priv->slc));
 323                                 sl_compress_init(&priv->slc, c->maxChannel);
 324                         }
 325                         priv->conf = *c;
 326                         break;
 327                     }
 328                 case NGM_VJC_GET_CONFIG:
 329                     {
 330                         struct ngm_vjc_config *conf;
 331
 332                         NG_MKRESPONSE(resp, msg, sizeof(*conf), M_NOWAIT);
 333                         if (resp == NULL)
 334                                 ERROUT(ENOMEM);
 335                         conf = (struct ngm_vjc_config *)resp->data;
 336                         *conf = priv->conf;
 337                         break;
 338                     }
 339                 case NGM_VJC_GET_STATE:
 340                     {
 341                         const struct slcompress *const sl0 = &priv->slc;
 342                         struct slcompress *sl;
 343                         u_int16_t index;
 344                         int i;
 345
 346                         /* Get response structure */
 347                         NG_MKRESPONSE(resp, msg, sizeof(*sl), M_NOWAIT);
 348                         if (resp == NULL)
 349                                 ERROUT(ENOMEM);
 350                         sl = (struct slcompress *)resp->data;
 351                         *sl = *sl0;
 352
 353                         /* Replace pointers with integer indicies */
 354                         if (sl->last_cs != NULL) {
 355                                 index = sl0->last_cs - sl0->tstate;
 356                                 bzero(&sl->last_cs, sizeof(sl->last_cs));
 357                                 *((u_int16_t *)&sl->last_cs) = index;
 358                         }
 359                         for (i = 0; i < MAX_STATES; i++) {
 360                                 struct cstate *const cs = &sl->tstate[i];
 361
 362                                 index = sl0->tstate[i].cs_next - sl0->tstate;
 363                                 bzero(&cs->cs_next, sizeof(cs->cs_next));
 364                                 *((u_int16_t *)&cs->cs_next) = index;
 365                         }
 366                         break;
 367                     }
 368                 case NGM_VJC_CLR_STATS:
 369                         priv->slc.sls_packets = 0;
 370                         priv->slc.sls_compressed = 0;
 371                         priv->slc.sls_searches = 0;
 372                         priv->slc.sls_misses = 0;
 373                         priv->slc.sls_uncompressedin = 0;
 374                         priv->slc.sls_compressedin = 0;
 375                         priv->slc.sls_errorin = 0;
 376                         priv->slc.sls_tossed = 0;
 377                         break;
 378                 case NGM_VJC_RECV_ERROR:
 379                         sl_uncompress_tcp(NULL, 0, TYPE_ERROR, &priv->slc);
 380                         break;
 381                 default:
 382                         error = EINVAL;
 383                         break;
 384                 }
 385                 break;
 386         default:
 387                 error = EINVAL;
 388                 break;
 389         }
 390 done:
 391         NG_RESPOND_MSG(error, node, item, resp);
 392         NG_FREE_MSG(msg);
 393         return (error);
 394 }
 395
 396 /*
 397  * Receive data
 398  */
 399 static int
 400 ng_vjc_rcvdata(hook_p hook, item_p item)
 401 {
 402         const node_p node = NG_HOOK_NODE(hook);
 403         const priv_p priv = NG_NODE_PRIVATE(node);
 404         int error = 0;
 405         struct mbuf *m;
 406
 407         NGI_GET_M(item, m);
 408         if (hook == priv->ip) {                 /* outgoing packet */
 409                 u_int type = TYPE_IP;
 410
 411                 /* Compress packet if enabled and proto is TCP */
 412                 if (priv->conf.enableComp) {
 413                         struct ip *ip;
 414
 415                         if ((m = ng_vjc_pulluphdrs(m, 0)) == NULL) {
 416                                 NG_FREE_ITEM(item);
 417                                 return (ENOBUFS);
 418                         }
 419                         ip = mtod(m, struct ip *);
 420                         if (ip->ip_p == IPPROTO_TCP) {
 421                                 const int origLen = m->m_len;
 422
 423                                 type = sl_compress_tcp(m, ip,
 424                                     &priv->slc, priv->conf.compressCID);
 425                                 m->m_pkthdr.len += m->m_len - origLen;
 426                         }
 427                 }
 428
 429                 /* Dispatch to the appropriate outgoing hook */
 430                 switch (type) {
 431                 case TYPE_IP:
 432                         hook = priv->vjip;
 433                         break;
 434                 case TYPE_UNCOMPRESSED_TCP:
 435                         hook = priv->vjuncomp;
 436                         break;
 437                 case TYPE_COMPRESSED_TCP:
 438                         hook = priv->vjcomp;
 439                         break;
 440                 default:
 441                         panic("%s: type=%d", __func__, type);
 442                 }
 443         } else if (hook == priv->vjcomp) {      /* incoming compressed packet */
 444                 int vjlen, need2pullup;
 445                 struct mbuf *hm;
 446                 u_char *hdr;
 447                 u_int hlen;
 448
 449                 /* Are we decompressing? */
 450                 if (!priv->conf.enableDecomp) {
 451                         NG_FREE_M(m);
 452                         NG_FREE_ITEM(item);
 453                         return (ENXIO);
 454                 }
 455
 456                 /* Pull up the necessary amount from the mbuf */
 457                 need2pullup = MAX_VJHEADER;
 458                 if (need2pullup > m->m_pkthdr.len)
 459                         need2pullup = m->m_pkthdr.len;
 460                 if (m->m_len < need2pullup
 461                     && (m = m_pullup(m, need2pullup)) == NULL) {
 462                         priv->slc.sls_errorin++;
 463                         NG_FREE_ITEM(item);
 464                         return (ENOBUFS);
 465                 }
 466
 467                 /* Uncompress packet to reconstruct TCP/IP header */
 468                 vjlen = sl_uncompress_tcp_core(mtod(m, u_char *),
 469                     m->m_len, m->m_pkthdr.len, TYPE_COMPRESSED_TCP,
 470                     &priv->slc, &hdr, &hlen);
 471                 if (vjlen <= 0) {
 472                         NG_FREE_M(m);
 473                         NG_FREE_ITEM(item);
 474                         return (EINVAL);
 475                 }
 476                 m_adj(m, vjlen);
 477
 478                 /* Copy the reconstructed TCP/IP headers into a new mbuf */
 479                 MGETHDR(hm, M_DONTWAIT, MT_DATA);
 480                 if (hm == NULL) {
 481                         priv->slc.sls_errorin++;
 482                         NG_FREE_M(m);
 483                         NG_FREE_ITEM(item);
 484                         return (ENOBUFS);
 485                 }
 486                 hm->m_len = 0;
 487                 hm->m_pkthdr.rcvif = NULL;
 488                 if (hlen > MHLEN) {             /* unlikely, but can happen */
 489                         MCLGET(hm, M_DONTWAIT);
 490                         if ((hm->m_flags & M_EXT) == 0) {
 491                                 m_freem(hm);
 492                                 priv->slc.sls_errorin++;
 493                                 NG_FREE_M(m);
 494                                 NG_FREE_ITEM(item);
 495                                 return (ENOBUFS);
 496                         }
 497                 }
 498                 bcopy(hdr, mtod(hm, u_char *), hlen);
 499                 hm->m_len = hlen;
 500
 501                 /* Glue TCP/IP headers and rest of packet together */
 502                 hm->m_next = m;
 503                 hm->m_pkthdr.len = hlen + m->m_pkthdr.len;
 504                 m = hm;
 505                 hook = priv->ip;
 506         } else if (hook == priv->vjuncomp) {    /* incoming uncompressed pkt */
 507                 u_char *hdr;
 508                 u_int hlen;
 509
 510                 /* Are we decompressing? */
 511                 if (!priv->conf.enableDecomp) {
 512                         NG_FREE_M(m);
 513                         NG_FREE_ITEM(item);
 514                         return (ENXIO);
 515                 }
 516
 517                 /* Pull up IP+TCP headers */
 518                 if ((m = ng_vjc_pulluphdrs(m, 1)) == NULL) {
 519                         NG_FREE_ITEM(item);
 520                         return (ENOBUFS);
 521                 }
 522
 523                 /* Run packet through uncompressor */
 524                 if (sl_uncompress_tcp_core(mtod(m, u_char *),
 525                     m->m_len, m->m_pkthdr.len, TYPE_UNCOMPRESSED_TCP,
 526                     &priv->slc, &hdr, &hlen) < 0) {
 527                         NG_FREE_M(m);
 528                         NG_FREE_ITEM(item);
 529                         return (EINVAL);
 530                 }
 531                 hook = priv->ip;
 532         } else if (hook == priv->vjip)  /* incoming regular packet (bypass) */
 533                 hook = priv->ip;
 534         else
 535                 panic("%s: unknown hook", __func__);
 536
 537         /* Send result back out */
 538         NG_FWD_NEW_DATA(error, item, hook, m);
 539         return (error);
 540 }
 541
 542 /*
 543  * Shutdown node
 544  */
 545 static int
 546 ng_vjc_shutdown(node_p node)
 547 {
 548         const priv_p priv = NG_NODE_PRIVATE(node);
 549
 550         bzero(priv, sizeof(*priv));
 551         free(priv, M_NETGRAPH);
 552         NG_NODE_SET_PRIVATE(node, NULL);
 553         NG_NODE_UNREF(node);
 554         return (0);
 555 }
 556
 557 /*
 558  * Hook disconnection
 559  */
 560 static int
 561 ng_vjc_disconnect(hook_p hook)
 562 {
 563         const node_p node = NG_HOOK_NODE(hook);
 564         const priv_p priv = NG_NODE_PRIVATE(node);
 565
 566         /* Zero out hook pointer */
 567         if (hook == priv->ip)
 568                 priv->ip = NULL;
 569         else if (hook == priv->vjcomp)
 570                 priv->vjcomp = NULL;
 571         else if (hook == priv->vjuncomp)
 572                 priv->vjuncomp = NULL;
 573         else if (hook == priv->vjip)
 574                 priv->vjip = NULL;
 575         else
 576                 panic("%s: unknown hook", __func__);
 577
 578         /* Go away if no hooks left */
 579         if ((NG_NODE_NUMHOOKS(node) == 0)
 580         && (NG_NODE_IS_VALID(node)))
 581                 ng_rmnode_self(node);
 582         return (0);
 583 }
 584
 585 /************************************************************************
 586                         HELPER STUFF
 587  ************************************************************************/
 588
 589 /*
 590  * Pull up the full IP and TCP headers of a packet. If packet is not
 591  * a TCP packet, just pull up the IP header.
 592  */
 593 static struct mbuf *
 594 ng_vjc_pulluphdrs(struct mbuf *m, int knownTCP)
 595 {
 596         struct ip *ip;
 597         struct tcphdr *tcp;
 598         int ihlen, thlen;
 599
 600         if (m->m_len < sizeof(*ip) && (m = m_pullup(m, sizeof(*ip))) == NULL)
 601                 return (NULL);
 602         ip = mtod(m, struct ip *);
 603         if (!knownTCP && ip->ip_p != IPPROTO_TCP)
 604                 return (m);
 605         ihlen = ip->ip_hl << 2;
 606         if (m->m_len < ihlen + sizeof(*tcp)) {
 607                 if ((m = m_pullup(m, ihlen + sizeof(*tcp))) == NULL)
 608                         return (NULL);
 609                 ip = mtod(m, struct ip *);
 610         }
 611         tcp = (struct tcphdr *)((u_char *)ip + ihlen);
 612         thlen = tcp->th_off << 2;
 613         if (m->m_len < ihlen + thlen)
 614                 m = m_pullup(m, ihlen + thlen);
 615         return (m);
 616 }
 617