sys/netgraph/vjc/ng_vjc.c

   1
   2 /*
   3  * ng_vjc.c
   4  *
   5  * Copyright (c) 1996-1999 Whistle Communications, Inc.
   6  * All rights reserved.
   7  *
   8  * Subject to the following obligations and disclaimer of warranty, use and
   9  * redistribution of this software, in source or object code forms, with or
  10  * without modifications are expressly permitted by Whistle Communications;
  11  * provided, however, that:
  12  * 1. Any and all reproductions of the source or object code must include the
  13  *    copyright notice above and the following disclaimer of warranties; and
  14  * 2. No rights are granted, in any manner or form, to use Whistle
  15  *    Communications, Inc. trademarks, including the mark "WHISTLE
  16  *    COMMUNICATIONS" on advertising, endorsements, or otherwise except as
  17  *    such appears in the above copyright notice or in the software.
  18  *
  19  * THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND
  20  * TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO
  21  * REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE,
  22  * INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF
  23  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT.
  24  * WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY
  25  * REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS
  26  * SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE.
  27  * IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES
  28  * RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING
  29  * WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
  30  * PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR
  31  * SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY
  32  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  33  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  34  * THIS SOFTWARE, EVEN IF WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY
  35  * OF SUCH DAMAGE.
  36  *
  37  * Author: Archie Cobbs <archie@freebsd.org>
  38  *
  39  * $FreeBSD: src/sys/netgraph/ng_vjc.c,v 1.9.2.5 2002/07/02 23:44:03 archie Exp $
  40  * $DragonFly: src/sys/netgraph/vjc/ng_vjc.c,v 1.5 2005/02/17 14:00:00 joerg Exp $
  41  * $Whistle: ng_vjc.c,v 1.17 1999/11/01 09:24:52 julian Exp $
  42  */
  43
  44 /*
  45  * This node performs Van Jacobson IP header (de)compression.
  46  * You must have included net/slcompress.c in your kernel compilation.
  47  */
  48
  49 #include <sys/param.h>
  50 #include <sys/systm.h>
  51 #include <sys/errno.h>
  52 #include <sys/kernel.h>
  53 #include <sys/mbuf.h>
  54 #include <sys/malloc.h>
  55 #include <sys/errno.h>
  56
  57 #include <netgraph/ng_message.h>
  58 #include <netgraph/netgraph.h>
  59 #include <netgraph/ng_parse.h>
  60 #include "ng_vjc.h"
  61
  62 #include <netinet/in.h>
  63 #include <netinet/in_systm.h>
  64 #include <netinet/ip.h>
  65 #include <netinet/tcp.h>
  66
  67 #include <net/slcompress.h>
  68
  69 /* Check agreement with slcompress.c */
  70 #if MAX_STATES != NG_VJC_MAX_CHANNELS
  71 #error NG_VJC_MAX_CHANNELS must be the same as MAX_STATES
  72 #endif
  73
  74 /* Maximum length of a compressed TCP VJ header */
  75 #define MAX_VJHEADER            19
  76
  77 /* Node private data */
  78 struct ng_vjc_private {
  79         struct  ngm_vjc_config conf;
  80         struct  slcompress slc;
  81         hook_p  ip;
  82         hook_p  vjcomp;
  83         hook_p  vjuncomp;
  84         hook_p  vjip;
  85 };
  86 typedef struct ng_vjc_private *priv_p;
  87
  88 #define ERROUT(x)       do { error = (x); goto done; } while (0)
  89
  90 /* Netgraph node methods */
  91 static ng_constructor_t ng_vjc_constructor;
  92 static ng_rcvmsg_t      ng_vjc_rcvmsg;
  93 static ng_shutdown_t    ng_vjc_rmnode;
  94 static ng_newhook_t     ng_vjc_newhook;
  95 static ng_rcvdata_t     ng_vjc_rcvdata;
  96 static ng_disconnect_t  ng_vjc_disconnect;
  97
  98 /* Helper stuff */
  99 static struct mbuf *ng_vjc_pulluphdrs(struct mbuf *m, int knownTCP);
 100
 101 /* Parse type for struct ngm_vjc_config */
 102 static const struct ng_parse_struct_field ng_vjc_config_type_fields[]
 103         = NG_VJC_CONFIG_TYPE_INFO;
 104 static const struct ng_parse_type ng_vjc_config_type = {
 105         &ng_parse_struct_type,
 106         &ng_vjc_config_type_fields
 107 };
 108
 109 /* Parse type for the 'last_cs' and 'cs_next' fields in struct slcompress,
 110    which are pointers converted to integer indices, so parse them that way. */
 111 #if _MACHINE_ARCH == i386
 112 #define NG_VJC_TSTATE_PTR_TYPE  &ng_parse_uint32_type
 113 #elif _MACHINE_ARCH == alpha
 114 #define NG_VJC_TSTATE_PTR_TYPE  &ng_parse_uint64_type
 115 #else
 116 #error Unspported _MACHINE_ARCH
 117 #endif
 118
 119 /* Parse type for the 'cs_hdr' field in a struct cstate. Ideally we would
 120    like to use a 'struct ip' type instead of a simple array of bytes. */
 121 static const struct ng_parse_fixedarray_info ng_vjc_cs_hdr_type_info = {
 122         &ng_parse_hint8_type,
 123         MAX_HDR
 124 };
 125 static const struct ng_parse_type ng_vjc_cs_hdr_type = {
 126         &ng_parse_fixedarray_type,
 127         &ng_vjc_cs_hdr_type_info
 128 };
 129
 130 /* Parse type for a struct cstate */
 131 static const struct ng_parse_struct_field ng_vjc_cstate_type_fields[] = {
 132         { "cs_next",            NG_VJC_TSTATE_PTR_TYPE          },
 133         { "cs_hlen",            &ng_parse_uint16_type           },
 134         { "cs_id",              &ng_parse_uint8_type            },
 135         { "cs_filler",          &ng_parse_uint8_type            },
 136         { "cs_hdr",             &ng_vjc_cs_hdr_type             },
 137         { NULL }
 138 };
 139 static const struct ng_parse_type ng_vjc_cstate_type = {
 140         &ng_parse_struct_type,
 141         &ng_vjc_cstate_type_fields
 142 };
 143
 144 /* Parse type for an array of MAX_STATES struct cstate's, ie, tstate & rstate */
 145 static const struct ng_parse_fixedarray_info ng_vjc_cstatearray_type_info = {
 146         &ng_vjc_cstate_type,
 147         MAX_STATES
 148 };
 149 static const struct ng_parse_type ng_vjc_cstatearray_type = {
 150         &ng_parse_fixedarray_type,
 151         &ng_vjc_cstatearray_type_info
 152 };
 153
 154 /* Parse type for struct slcompress. Keep this in sync with the
 155    definition of struct slcompress defined in <net/slcompress.h> */
 156 static const struct ng_parse_struct_field ng_vjc_slcompress_type_fields[] = {
 157         { "last_cs",            NG_VJC_TSTATE_PTR_TYPE          },
 158         { "last_recv",          &ng_parse_uint8_type            },
 159         { "last_xmit",          &ng_parse_uint8_type            },
 160         { "flags",              &ng_parse_hint16_type           },
 161 #ifndef SL_NO_STATS
 162         { "sls_packets",        &ng_parse_uint32_type           },
 163         { "sls_compressed",     &ng_parse_uint32_type           },
 164         { "sls_searches",       &ng_parse_uint32_type           },
 165         { "sls_misses",         &ng_parse_uint32_type           },
 166         { "sls_uncompressedin", &ng_parse_uint32_type           },
 167         { "sls_compressedin",   &ng_parse_uint32_type           },
 168         { "sls_errorin",        &ng_parse_uint32_type           },
 169         { "sls_tossed",         &ng_parse_uint32_type           },
 170 #endif
 171         { "tstate",             &ng_vjc_cstatearray_type        },
 172         { "rstate",             &ng_vjc_cstatearray_type        },
 173         { NULL }
 174 };
 175 static const struct ng_parse_type ng_vjc_slcompress_type = {
 176         &ng_parse_struct_type,
 177         &ng_vjc_slcompress_type_fields
 178 };
 179
 180 /* List of commands and how to convert arguments to/from ASCII */
 181 static const struct ng_cmdlist ng_vjc_cmds[] = {
 182         {
 183           NGM_VJC_COOKIE,
 184           NGM_VJC_SET_CONFIG,
 185           "setconfig",
 186           &ng_vjc_config_type,
 187           NULL
 188         },
 189         {
 190           NGM_VJC_COOKIE,
 191           NGM_VJC_GET_CONFIG,
 192           "getconfig",
 193           NULL,
 194           &ng_vjc_config_type,
 195         },
 196         {
 197           NGM_VJC_COOKIE,
 198           NGM_VJC_GET_STATE,
 199           "getstate",
 200           NULL,
 201           &ng_vjc_slcompress_type,
 202         },
 203         {
 204           NGM_VJC_COOKIE,
 205           NGM_VJC_CLR_STATS,
 206           "clrstats",
 207           NULL,
 208           NULL,
 209         },
 210         {
 211           NGM_VJC_COOKIE,
 212           NGM_VJC_RECV_ERROR,
 213           "recverror",
 214           NULL,
 215           NULL,
 216         },
 217         { 0 }
 218 };
 219
 220 /* Node type descriptor */
 221 static struct ng_type ng_vjc_typestruct = {
 222         NG_VERSION,
 223         NG_VJC_NODE_TYPE,
 224         NULL,
 225         ng_vjc_constructor,
 226         ng_vjc_rcvmsg,
 227         ng_vjc_rmnode,
 228         ng_vjc_newhook,
 229         NULL,
 230         NULL,
 231         ng_vjc_rcvdata,
 232         ng_vjc_rcvdata,
 233         ng_vjc_disconnect,
 234         ng_vjc_cmds
 235 };
 236 NETGRAPH_INIT(vjc, &ng_vjc_typestruct);
 237
 238 /************************************************************************
 239                         NETGRAPH NODE METHODS
 240  ************************************************************************/
 241
 242 /*
 243  * Create a new node
 244  */
 245 static int
 246 ng_vjc_constructor(node_p *nodep)
 247 {
 248         priv_p priv;
 249         int error;
 250
 251         /* Allocate private structure */
 252         MALLOC(priv, priv_p, sizeof(*priv), M_NETGRAPH, M_NOWAIT);
 253         if (priv == NULL)
 254                 return (ENOMEM);
 255         bzero(priv, sizeof(*priv));
 256
 257         /* Call generic node constructor */
 258         if ((error = ng_make_node_common(&ng_vjc_typestruct, nodep))) {
 259                 FREE(priv, M_NETGRAPH);
 260                 return (error);
 261         }
 262         (*nodep)->private = priv;
 263
 264         /* Done */
 265         return (0);
 266 }
 267
 268 /*
 269  * Add a new hook
 270  */
 271 static int
 272 ng_vjc_newhook(node_p node, hook_p hook, const char *name)
 273 {
 274         const priv_p priv = (priv_p) node->private;
 275         hook_p *hookp;
 276
 277         /* Get hook */
 278         if (strcmp(name, NG_VJC_HOOK_IP) == 0)
 279                 hookp = &priv->ip;
 280         else if (strcmp(name, NG_VJC_HOOK_VJCOMP) == 0)
 281                 hookp = &priv->vjcomp;
 282         else if (strcmp(name, NG_VJC_HOOK_VJUNCOMP) == 0)
 283                 hookp = &priv->vjuncomp;
 284         else if (strcmp(name, NG_VJC_HOOK_VJIP) == 0)
 285                 hookp = &priv->vjip;
 286         else
 287                 return (EINVAL);
 288
 289         /* See if already connected */
 290         if (*hookp)
 291                 return (EISCONN);
 292
 293         /* OK */
 294         *hookp = hook;
 295         return (0);
 296 }
 297
 298 /*
 299  * Receive a control message
 300  */
 301 static int
 302 ng_vjc_rcvmsg(node_p node, struct ng_mesg *msg,
 303               const char *raddr, struct ng_mesg **rptr)
 304 {
 305         const priv_p priv = (priv_p) node->private;
 306         struct ng_mesg *resp = NULL;
 307         int error = 0;
 308
 309         /* Check type cookie */
 310         switch (msg->header.typecookie) {
 311         case NGM_VJC_COOKIE:
 312                 switch (msg->header.cmd) {
 313                 case NGM_VJC_SET_CONFIG:
 314                     {
 315                         struct ngm_vjc_config *const c =
 316                                 (struct ngm_vjc_config *) msg->data;
 317
 318                         if (msg->header.arglen != sizeof(*c))
 319                                 ERROUT(EINVAL);
 320                         if ((priv->conf.enableComp || priv->conf.enableDecomp)
 321                             && (c->enableComp || c->enableDecomp))
 322                                 ERROUT(EALREADY);
 323                         if (c->enableComp) {
 324                                 if (c->maxChannel > NG_VJC_MAX_CHANNELS - 1
 325                                     || c->maxChannel < NG_VJC_MIN_CHANNELS - 1)
 326                                         ERROUT(EINVAL);
 327                         } else
 328                                 c->maxChannel = NG_VJC_MAX_CHANNELS - 1;
 329                         if (c->enableComp != 0 || c->enableDecomp != 0) {
 330                                 bzero(&priv->slc, sizeof(priv->slc));
 331                                 sl_compress_init(&priv->slc, c->maxChannel);
 332                         }
 333                         priv->conf = *c;
 334                         break;
 335                     }
 336                 case NGM_VJC_GET_CONFIG:
 337                     {
 338                         struct ngm_vjc_config *conf;
 339
 340                         NG_MKRESPONSE(resp, msg, sizeof(*conf), M_NOWAIT);
 341                         if (resp == NULL)
 342                                 ERROUT(ENOMEM);
 343                         conf = (struct ngm_vjc_config *)resp->data;
 344                         *conf = priv->conf;
 345                         break;
 346                     }
 347                 case NGM_VJC_GET_STATE:
 348                     {
 349                         const struct slcompress *const sl0 = &priv->slc;
 350                         struct slcompress *sl;
 351                         u_int16_t index;
 352                         int i;
 353
 354                         /* Get response structure */
 355                         NG_MKRESPONSE(resp, msg, sizeof(*sl), M_NOWAIT);
 356                         if (resp == NULL)
 357                                 ERROUT(ENOMEM);
 358                         sl = (struct slcompress *)resp->data;
 359                         *sl = *sl0;
 360
 361                         /* Replace pointers with integer indicies */
 362                         if (sl->last_cs != NULL) {
 363                                 index = sl0->last_cs - sl0->tstate;
 364                                 bzero(&sl->last_cs, sizeof(sl->last_cs));
 365                                 *((u_int16_t *)&sl->last_cs) = index;
 366                         }
 367                         for (i = 0; i < MAX_STATES; i++) {
 368                                 struct cstate *const cs = &sl->tstate[i];
 369
 370                                 index = sl0->tstate[i].cs_next - sl0->tstate;
 371                                 bzero(&cs->cs_next, sizeof(cs->cs_next));
 372                                 *((u_int16_t *)&cs->cs_next) = index;
 373                         }
 374                         break;
 375                     }
 376                 case NGM_VJC_CLR_STATS:
 377                         priv->slc.sls_packets = 0;
 378                         priv->slc.sls_compressed = 0;
 379                         priv->slc.sls_searches = 0;
 380                         priv->slc.sls_misses = 0;
 381                         priv->slc.sls_uncompressedin = 0;
 382                         priv->slc.sls_compressedin = 0;
 383                         priv->slc.sls_errorin = 0;
 384                         priv->slc.sls_tossed = 0;
 385                         break;
 386                 case NGM_VJC_RECV_ERROR:
 387                         sl_uncompress_tcp(NULL, 0, TYPE_ERROR, &priv->slc);
 388                         break;
 389                 default:
 390                         error = EINVAL;
 391                         break;
 392                 }
 393                 break;
 394         default:
 395                 error = EINVAL;
 396                 break;
 397         }
 398         if (rptr)
 399                 *rptr = resp;
 400         else if (resp)
 401                 FREE(resp, M_NETGRAPH);
 402
 403 done:
 404         FREE(msg, M_NETGRAPH);
 405         return (error);
 406 }
 407
 408 /*
 409  * Receive data
 410  */
 411 static int
 412 ng_vjc_rcvdata(hook_p hook, struct mbuf *m, meta_p meta)
 413 {
 414         const node_p node = hook->node;
 415         const priv_p priv = (priv_p) node->private;
 416         int error = 0;
 417
 418         if (hook == priv->ip) {                 /* outgoing packet */
 419                 u_int type = TYPE_IP;
 420
 421                 /* Compress packet if enabled and proto is TCP */
 422                 if (priv->conf.enableComp) {
 423                         struct ip *ip;
 424
 425                         if ((m = ng_vjc_pulluphdrs(m, 0)) == NULL) {
 426                                 NG_FREE_META(meta);
 427                                 return (ENOBUFS);
 428                         }
 429                         ip = mtod(m, struct ip *);
 430                         if (ip->ip_p == IPPROTO_TCP) {
 431                                 const int origLen = m->m_len;
 432
 433                                 type = sl_compress_tcp(m, ip,
 434                                     &priv->slc, priv->conf.compressCID);
 435                                 m->m_pkthdr.len += m->m_len - origLen;
 436                         }
 437                 }
 438
 439                 /* Dispatch to the appropriate outgoing hook */
 440                 switch (type) {
 441                 case TYPE_IP:
 442                         hook = priv->vjip;
 443                         break;
 444                 case TYPE_UNCOMPRESSED_TCP:
 445                         hook = priv->vjuncomp;
 446                         break;
 447                 case TYPE_COMPRESSED_TCP:
 448                         hook = priv->vjcomp;
 449                         break;
 450                 default:
 451                         panic("%s: type=%d", __func__, type);
 452                 }
 453         } else if (hook == priv->vjcomp) {      /* incoming compressed packet */
 454                 int vjlen, need2pullup;
 455                 struct mbuf *hm;
 456                 u_char *hdr;
 457                 u_int hlen;
 458
 459                 /* Are we decompressing? */
 460                 if (!priv->conf.enableDecomp) {
 461                         NG_FREE_DATA(m, meta);
 462                         return (ENXIO);
 463                 }
 464
 465                 /* Pull up the necessary amount from the mbuf */
 466                 need2pullup = MAX_VJHEADER;
 467                 if (need2pullup > m->m_pkthdr.len)
 468                         need2pullup = m->m_pkthdr.len;
 469                 if (m->m_len < need2pullup
 470                     && (m = m_pullup(m, need2pullup)) == NULL) {
 471                         priv->slc.sls_errorin++;
 472                         NG_FREE_META(meta);
 473                         return (ENOBUFS);
 474                 }
 475
 476                 /* Uncompress packet to reconstruct TCP/IP header */
 477                 vjlen = sl_uncompress_tcp_core(mtod(m, u_char *),
 478                     m->m_len, m->m_pkthdr.len, TYPE_COMPRESSED_TCP,
 479                     &priv->slc, &hdr, &hlen);
 480                 if (vjlen <= 0) {
 481                         NG_FREE_DATA(m, meta);
 482                         return (EINVAL);
 483                 }
 484                 m_adj(m, vjlen);
 485
 486                 /* Copy the reconstructed TCP/IP headers into a new mbuf */
 487                 MGETHDR(hm, MB_DONTWAIT, MT_DATA);
 488                 if (hm == NULL) {
 489                         priv->slc.sls_errorin++;
 490                         NG_FREE_DATA(m, meta);
 491                         return (ENOBUFS);
 492                 }
 493                 hm->m_len = 0;
 494                 hm->m_pkthdr.rcvif = NULL;
 495                 if (hlen > MHLEN) {             /* unlikely, but can happen */
 496                         MCLGET(hm, MB_DONTWAIT);
 497                         if ((hm->m_flags & M_EXT) == 0) {
 498                                 m_freem(hm);
 499                                 priv->slc.sls_errorin++;
 500                                 NG_FREE_DATA(m, meta);
 501                                 return (ENOBUFS);
 502                         }
 503                 }
 504                 bcopy(hdr, mtod(hm, u_char *), hlen);
 505                 hm->m_len = hlen;
 506
 507                 /* Glue TCP/IP headers and rest of packet together */
 508                 hm->m_next = m;
 509                 hm->m_pkthdr.len = hlen + m->m_pkthdr.len;
 510                 m = hm;
 511                 hook = priv->ip;
 512         } else if (hook == priv->vjuncomp) {    /* incoming uncompressed pkt */
 513                 u_char *hdr;
 514                 u_int hlen;
 515
 516                 /* Are we decompressing? */
 517                 if (!priv->conf.enableDecomp) {
 518                         NG_FREE_DATA(m, meta);
 519                         return (ENXIO);
 520                 }
 521
 522                 /* Pull up IP+TCP headers */
 523                 if ((m = ng_vjc_pulluphdrs(m, 1)) == NULL) {
 524                         NG_FREE_META(meta);
 525                         return (ENOBUFS);
 526                 }
 527
 528                 /* Run packet through uncompressor */
 529                 if (sl_uncompress_tcp_core(mtod(m, u_char *),
 530                     m->m_len, m->m_pkthdr.len, TYPE_UNCOMPRESSED_TCP,
 531                     &priv->slc, &hdr, &hlen) < 0) {
 532                         NG_FREE_DATA(m, meta);
 533                         return (EINVAL);
 534                 }
 535                 hook = priv->ip;
 536         } else if (hook == priv->vjip)  /* incoming regular packet (bypass) */
 537                 hook = priv->ip;
 538         else
 539                 panic("%s: unknown hook", __func__);
 540
 541         /* Send result back out */
 542         NG_SEND_DATA(error, hook, m, meta);
 543         return (error);
 544 }
 545
 546 /*
 547  * Shutdown node
 548  */
 549 static int
 550 ng_vjc_rmnode(node_p node)
 551 {
 552         const priv_p priv = (priv_p) node->private;
 553
 554         node->flags |= NG_INVALID;
 555         ng_cutlinks(node);
 556         ng_unname(node);
 557         bzero(priv, sizeof(*priv));
 558         FREE(priv, M_NETGRAPH);
 559         node->private = NULL;
 560         ng_unref(node);
 561         return (0);
 562 }
 563
 564 /*
 565  * Hook disconnection
 566  */
 567 static int
 568 ng_vjc_disconnect(hook_p hook)
 569 {
 570         const node_p node = hook->node;
 571         const priv_p priv = node->private;
 572
 573         /* Zero out hook pointer */
 574         if (hook == priv->ip)
 575                 priv->ip = NULL;
 576         else if (hook == priv->vjcomp)
 577                 priv->vjcomp = NULL;
 578         else if (hook == priv->vjuncomp)
 579                 priv->vjuncomp = NULL;
 580         else if (hook == priv->vjip)
 581                 priv->vjip = NULL;
 582         else
 583                 panic("%s: unknown hook", __func__);
 584
 585         /* Go away if no hooks left */
 586         if (node->numhooks == 0)
 587                 ng_rmnode(node);
 588         return (0);
 589 }
 590
 591 /************************************************************************
 592                         HELPER STUFF
 593  ************************************************************************/
 594
 595 /*
 596  * Pull up the full IP and TCP headers of a packet. If packet is not
 597  * a TCP packet, just pull up the IP header.
 598  */
 599 static struct mbuf *
 600 ng_vjc_pulluphdrs(struct mbuf *m, int knownTCP)
 601 {
 602         struct ip *ip;
 603         struct tcphdr *tcp;
 604         int ihlen, thlen;
 605
 606         if (m->m_len < sizeof(*ip) && (m = m_pullup(m, sizeof(*ip))) == NULL)
 607                 return (NULL);
 608         ip = mtod(m, struct ip *);
 609         if (!knownTCP && ip->ip_p != IPPROTO_TCP)
 610                 return (m);
 611         ihlen = ip->ip_hl << 2;
 612         if (m->m_len < ihlen + sizeof(*tcp)) {
 613                 if ((m = m_pullup(m, ihlen + sizeof(*tcp))) == NULL)
 614                         return (NULL);
 615                 ip = mtod(m, struct ip *);
 616         }
 617         tcp = (struct tcphdr *)((u_char *)ip + ihlen);
 618         thlen = tcp->th_off << 2;
 619         if (m->m_len < ihlen + thlen)
 620                 m = m_pullup(m, ihlen + thlen);
 621         return (m);
 622 }
 623