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 <netgraph/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 #elif _MACHINE_ARCH == alpha
 113 #define NG_VJC_TSTATE_PTR_TYPE  &ng_parse_uint64_type
 114 #else
 115 #error Unspported _MACHINE_ARCH
 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         NG_VERSION,
 222         NG_VJC_NODE_TYPE,
 223         NULL,
 224         ng_vjc_constructor,
 225         ng_vjc_rcvmsg,
 226         ng_vjc_rmnode,
 227         ng_vjc_newhook,
 228         NULL,
 229         NULL,
 230         ng_vjc_rcvdata,
 231         ng_vjc_rcvdata,
 232         ng_vjc_disconnect,
 233         ng_vjc_cmds
 234 };
 235 NETGRAPH_INIT(vjc, &ng_vjc_typestruct);
 236
 237 /************************************************************************
 238                         NETGRAPH NODE METHODS
 239  ************************************************************************/
 240
 241 /*
 242  * Create a new node
 243  */
 244 static int
 245 ng_vjc_constructor(node_p *nodep)
 246 {
 247         priv_p priv;
 248         int error;
 249
 250         /* Allocate private structure */
 251         MALLOC(priv, priv_p, sizeof(*priv), M_NETGRAPH, M_NOWAIT);
 252         if (priv == NULL)
 253                 return (ENOMEM);
 254         bzero(priv, sizeof(*priv));
 255
 256         /* Call generic node constructor */
 257         if ((error = ng_make_node_common(&ng_vjc_typestruct, nodep))) {
 258                 FREE(priv, M_NETGRAPH);
 259                 return (error);
 260         }
 261         (*nodep)->private = priv;
 262
 263         /* Done */
 264         return (0);
 265 }
 266
 267 /*
 268  * Add a new hook
 269  */
 270 static int
 271 ng_vjc_newhook(node_p node, hook_p hook, const char *name)
 272 {
 273         const priv_p priv = (priv_p) node->private;
 274         hook_p *hookp;
 275
 276         /* Get hook */
 277         if (strcmp(name, NG_VJC_HOOK_IP) == 0)
 278                 hookp = &priv->ip;
 279         else if (strcmp(name, NG_VJC_HOOK_VJCOMP) == 0)
 280                 hookp = &priv->vjcomp;
 281         else if (strcmp(name, NG_VJC_HOOK_VJUNCOMP) == 0)
 282                 hookp = &priv->vjuncomp;
 283         else if (strcmp(name, NG_VJC_HOOK_VJIP) == 0)
 284                 hookp = &priv->vjip;
 285         else
 286                 return (EINVAL);
 287
 288         /* See if already connected */
 289         if (*hookp)
 290                 return (EISCONN);
 291
 292         /* OK */
 293         *hookp = hook;
 294         return (0);
 295 }
 296
 297 /*
 298  * Receive a control message
 299  */
 300 static int
 301 ng_vjc_rcvmsg(node_p node, struct ng_mesg *msg,
 302               const char *raddr, struct ng_mesg **rptr)
 303 {
 304         const priv_p priv = (priv_p) node->private;
 305         struct ng_mesg *resp = NULL;
 306         int error = 0;
 307
 308         /* Check type cookie */
 309         switch (msg->header.typecookie) {
 310         case NGM_VJC_COOKIE:
 311                 switch (msg->header.cmd) {
 312                 case NGM_VJC_SET_CONFIG:
 313                     {
 314                         struct ngm_vjc_config *const c =
 315                                 (struct ngm_vjc_config *) msg->data;
 316
 317                         if (msg->header.arglen != sizeof(*c))
 318                                 ERROUT(EINVAL);
 319                         if ((priv->conf.enableComp || priv->conf.enableDecomp)
 320                             && (c->enableComp || c->enableDecomp))
 321                                 ERROUT(EALREADY);
 322                         if (c->enableComp) {
 323                                 if (c->maxChannel > NG_VJC_MAX_CHANNELS - 1
 324                                     || c->maxChannel < NG_VJC_MIN_CHANNELS - 1)
 325                                         ERROUT(EINVAL);
 326                         } else
 327                                 c->maxChannel = NG_VJC_MAX_CHANNELS - 1;
 328                         if (c->enableComp != 0 || c->enableDecomp != 0) {
 329                                 bzero(&priv->slc, sizeof(priv->slc));
 330                                 sl_compress_init(&priv->slc, c->maxChannel);
 331                         }
 332                         priv->conf = *c;
 333                         break;
 334                     }
 335                 case NGM_VJC_GET_CONFIG:
 336                     {
 337                         struct ngm_vjc_config *conf;
 338
 339                         NG_MKRESPONSE(resp, msg, sizeof(*conf), M_NOWAIT);
 340                         if (resp == NULL)
 341                                 ERROUT(ENOMEM);
 342                         conf = (struct ngm_vjc_config *)resp->data;
 343                         *conf = priv->conf;
 344                         break;
 345                     }
 346                 case NGM_VJC_GET_STATE:
 347                     {
 348                         const struct slcompress *const sl0 = &priv->slc;
 349                         struct slcompress *sl;
 350                         u_int16_t index;
 351                         int i;
 352
 353                         /* Get response structure */
 354                         NG_MKRESPONSE(resp, msg, sizeof(*sl), M_NOWAIT);
 355                         if (resp == NULL)
 356                                 ERROUT(ENOMEM);
 357                         sl = (struct slcompress *)resp->data;
 358                         *sl = *sl0;
 359
 360                         /* Replace pointers with integer indicies */
 361                         if (sl->last_cs != NULL) {
 362                                 index = sl0->last_cs - sl0->tstate;
 363                                 bzero(&sl->last_cs, sizeof(sl->last_cs));
 364                                 *((u_int16_t *)&sl->last_cs) = index;
 365                         }
 366                         for (i = 0; i < MAX_STATES; i++) {
 367                                 struct cstate *const cs = &sl->tstate[i];
 368
 369                                 index = sl0->tstate[i].cs_next - sl0->tstate;
 370                                 bzero(&cs->cs_next, sizeof(cs->cs_next));
 371                                 *((u_int16_t *)&cs->cs_next) = index;
 372                         }
 373                         break;
 374                     }
 375                 case NGM_VJC_CLR_STATS:
 376                         priv->slc.sls_packets = 0;
 377                         priv->slc.sls_compressed = 0;
 378                         priv->slc.sls_searches = 0;
 379                         priv->slc.sls_misses = 0;
 380                         priv->slc.sls_uncompressedin = 0;
 381                         priv->slc.sls_compressedin = 0;
 382                         priv->slc.sls_errorin = 0;
 383                         priv->slc.sls_tossed = 0;
 384                         break;
 385                 case NGM_VJC_RECV_ERROR:
 386                         sl_uncompress_tcp(NULL, 0, TYPE_ERROR, &priv->slc);
 387                         break;
 388                 default:
 389                         error = EINVAL;
 390                         break;
 391                 }
 392                 break;
 393         default:
 394                 error = EINVAL;
 395                 break;
 396         }
 397         if (rptr)
 398                 *rptr = resp;
 399         else if (resp)
 400                 FREE(resp, M_NETGRAPH);
 401
 402 done:
 403         FREE(msg, M_NETGRAPH);
 404         return (error);
 405 }
 406
 407 /*
 408  * Receive data
 409  */
 410 static int
 411 ng_vjc_rcvdata(hook_p hook, struct mbuf *m, meta_p meta)
 412 {
 413         const node_p node = hook->node;
 414         const priv_p priv = (priv_p) node->private;
 415         int error = 0;
 416
 417         if (hook == priv->ip) {                 /* outgoing packet */
 418                 u_int type = TYPE_IP;
 419
 420                 /* Compress packet if enabled and proto is TCP */
 421                 if (priv->conf.enableComp) {
 422                         struct ip *ip;
 423
 424                         if ((m = ng_vjc_pulluphdrs(m, 0)) == NULL) {
 425                                 NG_FREE_META(meta);
 426                                 return (ENOBUFS);
 427                         }
 428                         ip = mtod(m, struct ip *);
 429                         if (ip->ip_p == IPPROTO_TCP) {
 430                                 const int origLen = m->m_len;
 431
 432                                 type = sl_compress_tcp(m, ip,
 433                                     &priv->slc, priv->conf.compressCID);
 434                                 m->m_pkthdr.len += m->m_len - origLen;
 435                         }
 436                 }
 437
 438                 /* Dispatch to the appropriate outgoing hook */
 439                 switch (type) {
 440                 case TYPE_IP:
 441                         hook = priv->vjip;
 442                         break;
 443                 case TYPE_UNCOMPRESSED_TCP:
 444                         hook = priv->vjuncomp;
 445                         break;
 446                 case TYPE_COMPRESSED_TCP:
 447                         hook = priv->vjcomp;
 448                         break;
 449                 default:
 450                         panic("%s: type=%d", __FUNCTION__, type);
 451                 }
 452         } else if (hook == priv->vjcomp) {      /* incoming compressed packet */
 453                 int vjlen, need2pullup;
 454                 struct mbuf *hm;
 455                 u_char *hdr;
 456                 u_int hlen;
 457
 458                 /* Are we decompressing? */
 459                 if (!priv->conf.enableDecomp) {
 460                         NG_FREE_DATA(m, meta);
 461                         return (ENXIO);
 462                 }
 463
 464                 /* Pull up the necessary amount from the mbuf */
 465                 need2pullup = MAX_VJHEADER;
 466                 if (need2pullup > m->m_pkthdr.len)
 467                         need2pullup = m->m_pkthdr.len;
 468                 if (m->m_len < need2pullup
 469                     && (m = m_pullup(m, need2pullup)) == NULL) {
 470                         priv->slc.sls_errorin++;
 471                         NG_FREE_META(meta);
 472                         return (ENOBUFS);
 473                 }
 474
 475                 /* Uncompress packet to reconstruct TCP/IP header */
 476                 vjlen = sl_uncompress_tcp_core(mtod(m, u_char *),
 477                     m->m_len, m->m_pkthdr.len, TYPE_COMPRESSED_TCP,
 478                     &priv->slc, &hdr, &hlen);
 479                 if (vjlen <= 0) {
 480                         NG_FREE_DATA(m, meta);
 481                         return (EINVAL);
 482                 }
 483                 m_adj(m, vjlen);
 484
 485                 /* Copy the reconstructed TCP/IP headers into a new mbuf */
 486                 MGETHDR(hm, M_DONTWAIT, MT_DATA);
 487                 if (hm == NULL) {
 488                         priv->slc.sls_errorin++;
 489                         NG_FREE_DATA(m, meta);
 490                         return (ENOBUFS);
 491                 }
 492                 hm->m_len = 0;
 493                 hm->m_pkthdr.rcvif = NULL;
 494                 if (hlen > MHLEN) {             /* unlikely, but can happen */
 495                         MCLGET(hm, M_DONTWAIT);
 496                         if ((hm->m_flags & M_EXT) == 0) {
 497                                 m_freem(hm);
 498                                 priv->slc.sls_errorin++;
 499                                 NG_FREE_DATA(m, meta);
 500                                 return (ENOBUFS);
 501                         }
 502                 }
 503                 bcopy(hdr, mtod(hm, u_char *), hlen);
 504                 hm->m_len = hlen;
 505
 506                 /* Glue TCP/IP headers and rest of packet together */
 507                 hm->m_next = m;
 508                 hm->m_pkthdr.len = hlen + m->m_pkthdr.len;
 509                 m = hm;
 510                 hook = priv->ip;
 511         } else if (hook == priv->vjuncomp) {    /* incoming uncompressed pkt */
 512                 u_char *hdr;
 513                 u_int hlen;
 514
 515                 /* Are we decompressing? */
 516                 if (!priv->conf.enableDecomp) {
 517                         NG_FREE_DATA(m, meta);
 518                         return (ENXIO);
 519                 }
 520
 521                 /* Pull up IP+TCP headers */
 522                 if ((m = ng_vjc_pulluphdrs(m, 1)) == NULL) {
 523                         NG_FREE_META(meta);
 524                         return (ENOBUFS);
 525                 }
 526
 527                 /* Run packet through uncompressor */
 528                 if (sl_uncompress_tcp_core(mtod(m, u_char *),
 529                     m->m_len, m->m_pkthdr.len, TYPE_UNCOMPRESSED_TCP,
 530                     &priv->slc, &hdr, &hlen) < 0) {
 531                         NG_FREE_DATA(m, meta);
 532                         return (EINVAL);
 533                 }
 534                 hook = priv->ip;
 535         } else if (hook == priv->vjip)  /* incoming regular packet (bypass) */
 536                 hook = priv->ip;
 537         else
 538                 panic("%s: unknown hook", __FUNCTION__);
 539
 540         /* Send result back out */
 541         NG_SEND_DATA(error, hook, m, meta);
 542         return (error);
 543 }
 544
 545 /*
 546  * Shutdown node
 547  */
 548 static int
 549 ng_vjc_rmnode(node_p node)
 550 {
 551         const priv_p priv = (priv_p) node->private;
 552
 553         node->flags |= NG_INVALID;
 554         ng_cutlinks(node);
 555         ng_unname(node);
 556         bzero(priv, sizeof(*priv));
 557         FREE(priv, M_NETGRAPH);
 558         node->private = NULL;
 559         ng_unref(node);
 560         return (0);
 561 }
 562
 563 /*
 564  * Hook disconnection
 565  */
 566 static int
 567 ng_vjc_disconnect(hook_p hook)
 568 {
 569         const node_p node = hook->node;
 570         const priv_p priv = node->private;
 571
 572         /* Zero out hook pointer */
 573         if (hook == priv->ip)
 574                 priv->ip = NULL;
 575         else if (hook == priv->vjcomp)
 576                 priv->vjcomp = NULL;
 577         else if (hook == priv->vjuncomp)
 578                 priv->vjuncomp = NULL;
 579         else if (hook == priv->vjip)
 580                 priv->vjip = NULL;
 581         else
 582                 panic("%s: unknown hook", __FUNCTION__);
 583
 584         /* Go away if no hooks left */
 585         if (node->numhooks == 0)
 586                 ng_rmnode(node);
 587         return (0);
 588 }
 589
 590 /************************************************************************
 591                         HELPER STUFF
 592  ************************************************************************/
 593
 594 /*
 595  * Pull up the full IP and TCP headers of a packet. If packet is not
 596  * a TCP packet, just pull up the IP header.
 597  */
 598 static struct mbuf *
 599 ng_vjc_pulluphdrs(struct mbuf *m, int knownTCP)
 600 {
 601         struct ip *ip;
 602         struct tcphdr *tcp;
 603         int ihlen, thlen;
 604
 605         if (m->m_len < sizeof(*ip) && (m = m_pullup(m, sizeof(*ip))) == NULL)
 606                 return (NULL);
 607         ip = mtod(m, struct ip *);
 608         if (!knownTCP && ip->ip_p != IPPROTO_TCP)
 609                 return (m);
 610         ihlen = ip->ip_hl << 2;
 611         if (m->m_len < ihlen + sizeof(*tcp)) {
 612                 if ((m = m_pullup(m, ihlen + sizeof(*tcp))) == NULL)
 613                         return (NULL);
 614                 ip = mtod(m, struct ip *);
 615         }
 616         tcp = (struct tcphdr *)((u_char *)ip + ihlen);
 617         thlen = tcp->th_off << 2;
 618         if (m->m_len < ihlen + thlen)
 619                 m = m_pullup(m, ihlen + thlen);
 620         return (m);
 621 }
 622