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