root/drivers/net/slhc.c

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DEFINITIONS

This source file includes following definitions.
  1. slhc_init
  2. slhc_free
  3. put16
  4. encode
  5. pull16
  6. decode
  7. slhc_compress
  8. slhc_uncompress
  9. slhc_remember
  10. slhc_toss
  11. slhc_i_status
  12. slhc_o_status

   1 /*
   2  * Routines to compress and uncompress tcp packets (for transmission
   3  * over low speed serial lines).
   4  *
   5  * Copyright (c) 1989 Regents of the University of California.
   6  * All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms are permitted
   9  * provided that the above copyright notice and this paragraph are
  10  * duplicated in all such forms and that any documentation,
  11  * advertising materials, and other materials related to such
  12  * distribution and use acknowledge that the software was developed
  13  * by the University of California, Berkeley.  The name of the
  14  * University may not be used to endorse or promote products derived
  15  * from this software without specific prior written permission.
  16  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
  17  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
  18  * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  19  *
  20  *      Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
  21  *      - Initial distribution.
  22  *
  23  *
  24  * modified for KA9Q Internet Software Package by
  25  * Katie Stevens (dkstevens@ucdavis.edu)
  26  * University of California, Davis
  27  * Computing Services
  28  *      - 01-31-90      initial adaptation (from 1.19)
  29  *      PPP.05  02-15-90 [ks]
  30  *      PPP.08  05-02-90 [ks]   use PPP protocol field to signal compression
  31  *      PPP.15  09-90    [ks]   improve mbuf handling
  32  *      PPP.16  11-02    [karn] substantially rewritten to use NOS facilities
  33  *
  34  *      - Feb 1991      Bill_Simpson@um.cc.umich.edu
  35  *                      variable number of conversation slots
  36  *                      allow zero or one slots
  37  *                      separate routines
  38  *                      status display
  39  */
  40 
  41 #include <linux/types.h>
  42 #include <linux/sched.h>
  43 #include <linux/mm.h>
  44 #include <linux/string.h>
  45 #include <linux/socket.h>
  46 #include <linux/sockios.h>
  47 #include <linux/termios.h>
  48 #include <linux/in.h>
  49 #include <linux/fcntl.h>
  50 #include "inet.h"
  51 #include "dev.h"
  52 #include "ip.h"
  53 #include "protocol.h"
  54 #include "icmp.h"
  55 #include "tcp.h"
  56 #include "skbuff.h"
  57 #include "sock.h"
  58 #include "arp.h"
  59 #include <linux/errno.h>
  60 #include <linux/timer.h>
  61 #include <asm/system.h>
  62 #include <asm/segment.h>
  63 #include <linux/mm.h>
  64 #include "slhc.h"
  65 
  66 #define DPRINT(x)
  67 
  68 int last_retran;
  69 
  70 static unsigned char *encode(unsigned char *cp,int n);
  71 static long decode(unsigned char **cpp);
  72 static unsigned char * put16(unsigned char *cp, unsigned short x);
  73 static unsigned short pull16(unsigned char **cpp);
  74 
  75 extern int ip_csum(struct iphdr *iph);
  76 
  77 
  78 /* Initialize compression data structure
  79  *      slots must be in range 0 to 255 (zero meaning no compression)
  80  */
  81 struct slcompress *
  82 slhc_init(int rslots, int tslots)
     /* [previous][next][first][last][top][bottom][index][help] */
  83 {
  84         register short i;
  85         register struct cstate *ts;
  86         struct slcompress *comp;
  87 
  88         comp = (struct slcompress *)kmalloc(sizeof(struct slcompress), 
  89                                             GFP_KERNEL);
  90         if (! comp)
  91                 return NULL;
  92 
  93         memset(comp, 0, sizeof(struct slcompress));
  94 
  95         if ( rslots > 0  &&  rslots < 256 ) {
  96                 comp->rstate =
  97                   (struct cstate *)kmalloc(rslots * sizeof(struct cstate),
  98                                            GFP_KERNEL);
  99                 if (! comp->rstate)
 100                         return NULL;
 101                 memset(comp->rstate, 0, rslots * sizeof(struct cstate));
 102                 comp->rslot_limit = rslots - 1;
 103         }
 104 
 105         if ( tslots > 0  &&  tslots < 256 ) {
 106                 comp->tstate = 
 107                   (struct cstate *)kmalloc(tslots * sizeof(struct cstate),
 108                                            GFP_KERNEL);
 109                 if (! comp->tstate)
 110                         return NULL;
 111                 memset(comp->tstate, 0, rslots * sizeof(struct cstate));
 112                 comp->tslot_limit = tslots - 1;
 113         }
 114 
 115         comp->xmit_oldest = 0;
 116         comp->xmit_current = 255;
 117         comp->recv_current = 255;
 118         /*
 119          * don't accept any packets with implicit index until we get
 120          * one with an explicit index.  Otherwise the uncompress code
 121          * will try to use connection 255, which is almost certainly
 122          * out of range
 123          */
 124         comp->flags |= SLF_TOSS;
 125 
 126         if ( tslots > 0 ) {
 127                 ts = comp->tstate;
 128                 for(i = comp->tslot_limit; i > 0; --i){
 129                         ts[i].cs_this = i;
 130                         ts[i].next = &(ts[i - 1]);
 131                 }
 132                 ts[0].next = &(ts[comp->tslot_limit]);
 133                 ts[0].cs_this = 0;
 134         }
 135         return comp;
 136 }
 137 
 138 
 139 /* Free a compression data structure */
 140 void
 141 slhc_free(struct slcompress *comp)
     /* [previous][next][first][last][top][bottom][index][help] */
 142 {
 143         if ( comp == NULLSLCOMPR )
 144                 return;
 145 
 146         if ( comp->rstate != NULLSLSTATE )
 147                 kfree( comp->rstate );
 148 
 149         if ( comp->tstate != NULLSLSTATE )
 150                 kfree( comp->tstate );
 151 
 152         kfree( comp );
 153 }
 154 
 155 
 156 /* Put a short in host order into a char array in network order */
 157 static unsigned char *
 158 put16(unsigned char *cp, unsigned short x)
     /* [previous][next][first][last][top][bottom][index][help] */
 159 {
 160         *cp++ = x >> 8;
 161         *cp++ = x;
 162 
 163         return cp;
 164 }
 165 
 166 
 167 /* Encode a number */
 168 unsigned char *
 169 encode(unsigned char *cp, int n)
     /* [previous][next][first][last][top][bottom][index][help] */
 170 {
 171         if(n >= 256 || n == 0){
 172                 *cp++ = 0;
 173                 cp = put16(cp,n);
 174         } else {
 175                 *cp++ = n;
 176         }
 177         return cp;
 178 }
 179 
 180 /* Pull a 16-bit integer in host order from buffer in network byte order */
 181 static unsigned short
 182 pull16(unsigned char **cpp)
     /* [previous][next][first][last][top][bottom][index][help] */
 183 {
 184         short rval;
 185 
 186         rval = *(*cpp)++;
 187         rval <<= 8;
 188         rval |= *(*cpp)++;
 189         return rval;
 190 }
 191 
 192 /* Decode a number */
 193 long
 194 decode(unsigned char **cpp)
     /* [previous][next][first][last][top][bottom][index][help] */
 195 {
 196         register int x;
 197 
 198         x = *(*cpp)++;
 199         if(x == 0){
 200                 return pull16(cpp) & 0xffff;    /* pull16 returns -1 on error */
 201         } else {
 202                 return x & 0xff;                /* -1 if PULLCHAR returned error */
 203         }
 204 }
 205 
 206 /* 
 207  * icp and isize are the original packet.
 208  * ocp is a place to put a copy if necessary.
 209  * cpp is initially a pointer to icp.  If the copy is used,
 210  *    change it to ocp.
 211  */
 212 
 213 int
 214 slhc_compress(struct slcompress *comp, unsigned char *icp, int isize,
     /* [previous][next][first][last][top][bottom][index][help] */
 215         unsigned char *ocp, unsigned char **cpp, int compress_cid)
 216 {
 217         register struct cstate *ocs = &(comp->tstate[comp->xmit_oldest]);
 218         register struct cstate *lcs = ocs;
 219         register struct cstate *cs = lcs->next;
 220         register unsigned long deltaS, deltaA;
 221         register short changes = 0;
 222         int hlen;
 223         unsigned char new_seq[16];
 224         register unsigned char *cp = new_seq;
 225         struct iphdr *ip;
 226         struct tcphdr *th, *oth;
 227 
 228         ip = (struct iphdr *) icp;
 229 
 230         /* Bail if this packet isn't TCP, or is an IP fragment */
 231         if(ip->protocol != IPPROTO_TCP || (ntohs(ip->frag_off) & 0x1fff) || 
 232                                        (ip->frag_off & 32)){
 233                 DPRINT(("comp: noncomp 1 %d %d %d\n", ip->protocol, 
 234                       ntohs(ip->frag_off), ip->frag_off));
 235                 /* Send as regular IP */
 236                 if(ip->protocol != IPPROTO_TCP)
 237                         comp->sls_o_nontcp++;
 238                 else
 239                         comp->sls_o_tcp++;
 240                 return isize;
 241         }
 242         /* Extract TCP header */
 243 
 244         th = (struct tcphdr *)(((unsigned char *)ip) + ip->ihl*4);
 245         hlen = ip->ihl*4 + th->doff*4;
 246 
 247         /*  Bail if the TCP packet isn't `compressible' (i.e., ACK isn't set or
 248          *  some other control bit is set).
 249          */
 250         if(th->syn || th->fin || th->rst ||
 251             ! (th->ack)){
 252                 DPRINT(("comp: noncomp 2 %x %x %d %d %d %d\n", ip, th, 
 253                        th->syn, th->fin, th->rst, th->ack));
 254                 /* TCP connection stuff; send as regular IP */
 255                 comp->sls_o_tcp++;
 256                 return isize;
 257         }
 258         /*
 259          * Packet is compressible -- we're going to send either a
 260          * COMPRESSED_TCP or UNCOMPRESSED_TCP packet.  Either way,
 261          * we need to locate (or create) the connection state.
 262          *
 263          * States are kept in a circularly linked list with
 264          * xmit_oldest pointing to the end of the list.  The
 265          * list is kept in lru order by moving a state to the
 266          * head of the list whenever it is referenced.  Since
 267          * the list is short and, empirically, the connection
 268          * we want is almost always near the front, we locate
 269          * states via linear search.  If we don't find a state
 270          * for the datagram, the oldest state is (re-)used.
 271          */
 272         for ( ; ; ) {
 273                 if( ip->saddr == cs->cs_ip.saddr
 274                  && ip->daddr == cs->cs_ip.daddr
 275                  && th->source == cs->cs_tcp.source
 276                  && th->dest == cs->cs_tcp.dest)
 277                         goto found;
 278 
 279                 /* if current equal oldest, at end of list */
 280                 if ( cs == ocs )
 281                         break;
 282                 lcs = cs;
 283                 cs = cs->next;
 284                 comp->sls_o_searches++;
 285         };
 286         /*
 287          * Didn't find it -- re-use oldest cstate.  Send an
 288          * uncompressed packet that tells the other side what
 289          * connection number we're using for this conversation.
 290          *
 291          * Note that since the state list is circular, the oldest
 292          * state points to the newest and we only need to set
 293          * xmit_oldest to update the lru linkage.
 294          */
 295         comp->sls_o_misses++;
 296         comp->xmit_oldest = lcs->cs_this;
 297         DPRINT(("comp: not found\n"));
 298         goto uncompressed;
 299 
 300 found:
 301         /*
 302          * Found it -- move to the front on the connection list.
 303          */
 304         if(lcs == ocs) {
 305                 /* found at most recently used */
 306         } else if (cs == ocs) {
 307                 /* found at least recently used */
 308                 comp->xmit_oldest = lcs->cs_this;
 309         } else {
 310                 /* more than 2 elements */
 311                 lcs->next = cs->next;
 312                 cs->next = ocs->next;
 313                 ocs->next = cs;
 314         }
 315 
 316         /*
 317          * Make sure that only what we expect to change changed.
 318          * Check the following:
 319          * IP protocol version, header length & type of service.
 320          * The "Don't fragment" bit.
 321          * The time-to-live field.
 322          * The TCP header length.
 323          * IP options, if any.
 324          * TCP options, if any.
 325          * If any of these things are different between the previous &
 326          * current datagram, we send the current datagram `uncompressed'.
 327          */
 328         oth = &cs->cs_tcp;
 329 
 330         if(last_retran
 331          || ip->version != cs->cs_ip.version || ip->ihl != cs->cs_ip.ihl
 332          || ip->tos != cs->cs_ip.tos
 333          || (ip->frag_off & 64) != (cs->cs_ip.frag_off & 64)
 334          || ip->ttl != cs->cs_ip.ttl
 335          || th->doff != cs->cs_tcp.doff
 336          || (ip->ihl > 5 && memcmp(ip+1,cs->cs_ipopt,((ip->ihl)-5)*4) != 0)
 337          || (th->doff > 5 && memcmp(th+1,cs->cs_tcpopt,((th->doff)-5)*4 != 0))){
 338                 DPRINT(("comp: incompat\n"));
 339                 goto uncompressed;
 340         }
 341         
 342         /*
 343          * Figure out which of the changing fields changed.  The
 344          * receiver expects changes in the order: urgent, window,
 345          * ack, seq (the order minimizes the number of temporaries
 346          * needed in this section of code).
 347          */
 348         if(th->urg){
 349                 deltaS = ntohs(th->urg_ptr);
 350                 cp = encode(cp,deltaS);
 351                 changes |= NEW_U;
 352         } else if(th->urg_ptr != oth->urg_ptr){
 353                 /* argh! URG not set but urp changed -- a sensible
 354                  * implementation should never do this but RFC793
 355                  * doesn't prohibit the change so we have to deal
 356                  * with it. */
 357                 DPRINT(("comp: urg incompat\n"));
 358                 goto uncompressed;
 359         }
 360         if((deltaS = ntohs(th->window) - ntohs(oth->window)) != 0){
 361                 cp = encode(cp,deltaS);
 362                 changes |= NEW_W;
 363         }
 364         if((deltaA = ntohl(th->ack_seq) - ntohl(oth->ack_seq)) != 0L){
 365                 if(deltaA > 0x0000ffff)
 366                         goto uncompressed;
 367                 cp = encode(cp,deltaA);
 368                 changes |= NEW_A;
 369         }
 370         if((deltaS = ntohl(th->seq) - ntohl(oth->seq)) != 0L){
 371                 if(deltaS > 0x0000ffff)
 372                         goto uncompressed;
 373                 cp = encode(cp,deltaS);
 374                 changes |= NEW_S;
 375         }
 376         
 377         switch(changes){
 378         case 0: /* Nothing changed. If this packet contains data and the
 379                  * last one didn't, this is probably a data packet following
 380                  * an ack (normal on an interactive connection) and we send
 381                  * it compressed.  Otherwise it's probably a retransmit,
 382                  * retransmitted ack or window probe.  Send it uncompressed
 383                  * in case the other side missed the compressed version.
 384                  */
 385                 if(ip->tot_len != cs->cs_ip.tot_len && 
 386                    ntohs(cs->cs_ip.tot_len) == hlen)
 387                         break;
 388                 DPRINT(("comp: retrans\n"));
 389                 goto uncompressed;
 390                 break;
 391         case SPECIAL_I:
 392         case SPECIAL_D:
 393                 /* actual changes match one of our special case encodings --
 394                  * send packet uncompressed.
 395                  */
 396                 DPRINT(("comp: special\n"));
 397                 goto uncompressed;
 398         case NEW_S|NEW_A:
 399                 if(deltaS == deltaA &&
 400                     deltaS == ntohs(cs->cs_ip.tot_len) - hlen){
 401                         /* special case for echoed terminal traffic */
 402                         changes = SPECIAL_I;
 403                         cp = new_seq;
 404                 }
 405                 break;
 406         case NEW_S:
 407                 if(deltaS == ntohs(cs->cs_ip.tot_len) - hlen){
 408                         /* special case for data xfer */
 409                         changes = SPECIAL_D;
 410                         cp = new_seq;
 411                 }
 412                 break;
 413         }
 414         deltaS = ntohs(ip->id) - ntohs(cs->cs_ip.id);
 415         if(deltaS != 1){
 416                 cp = encode(cp,deltaS);
 417                 changes |= NEW_I;
 418         }
 419         if(th->psh)
 420                 changes |= TCP_PUSH_BIT;
 421         /* Grab the cksum before we overwrite it below.  Then update our
 422          * state with this packet's header.
 423          */
 424         deltaA = ntohs(th->check);
 425         memcpy(&cs->cs_ip,ip,20);
 426         memcpy(&cs->cs_tcp,th,20);
 427         /* We want to use the original packet as our compressed packet.
 428          * (cp - new_seq) is the number of bytes we need for compressed
 429          * sequence numbers.  In addition we need one byte for the change
 430          * mask, one for the connection id and two for the tcp checksum.
 431          * So, (cp - new_seq) + 4 bytes of header are needed.
 432          */
 433         deltaS = cp - new_seq;
 434         if(compress_cid == 0 || comp->xmit_current != cs->cs_this){
 435                 cp = ocp;
 436                 *cpp = ocp;
 437                 *cp++ = changes | NEW_C;
 438                 *cp++ = cs->cs_this;
 439                 comp->xmit_current = cs->cs_this;
 440         } else {
 441                 cp = ocp;
 442                 *cpp = ocp;
 443                 *cp++ = changes;
 444         }
 445         cp = put16(cp,(short)deltaA);   /* Write TCP checksum */
 446 /* deltaS is now the size of the change section of the compressed header */
 447         DPRINT(("comp: %x %x %x %d %d\n", icp, cp, new_seq, hlen, deltaS));
 448         memcpy(cp,new_seq,deltaS);      /* Write list of deltas */
 449         memcpy(cp+deltaS,icp+hlen,isize-hlen);
 450         comp->sls_o_compressed++;
 451         ocp[0] |= SL_TYPE_COMPRESSED_TCP;
 452         return isize - hlen + deltaS + (cp - ocp);
 453 
 454         /* Update connection state cs & send uncompressed packet (i.e.,
 455          * a regular ip/tcp packet but with the 'conversation id' we hope
 456          * to use on future compressed packets in the protocol field).
 457          */
 458 uncompressed:
 459         memcpy(&cs->cs_ip,ip,20);
 460         memcpy(&cs->cs_tcp,th,20);
 461         if (ip->ihl > 5)
 462           memcpy(cs->cs_ipopt, ip+1, ((ip->ihl) - 5) * 4);
 463         if (th->doff > 5)
 464           memcpy(cs->cs_tcpopt, th+1, ((th->doff) - 5) * 4);
 465         comp->xmit_current = cs->cs_this;
 466         comp->sls_o_uncompressed++;
 467         memcpy(ocp, icp, isize);
 468         *cpp = ocp;
 469         ocp[9] = cs->cs_this;
 470         ocp[0] |= SL_TYPE_UNCOMPRESSED_TCP;
 471         return isize;
 472 }
 473 
 474 
 475 int
 476 slhc_uncompress(struct slcompress *comp, unsigned char *icp, int isize)
     /* [previous][next][first][last][top][bottom][index][help] */
 477 {
 478         register int changes;
 479         long x;
 480         register struct tcphdr *thp;
 481         register struct iphdr *ip;
 482         register struct cstate *cs;
 483         int len, hdrlen;
 484         unsigned char *cp = icp;
 485 
 486         /* We've got a compressed packet; read the change byte */
 487         comp->sls_i_compressed++;
 488         if(isize < 3){
 489                 comp->sls_i_error++;
 490                 DPRINT(("uncomp: runt\n"));
 491                 return 0;
 492         }
 493         changes = *cp++;
 494         if(changes & NEW_C){
 495                 /* Make sure the state index is in range, then grab the state.
 496                  * If we have a good state index, clear the 'discard' flag.
 497                  */
 498                 x = *cp++;      /* Read conn index */
 499                 if(x < 0 || x > comp->rslot_limit)
 500                         goto bad;
 501 
 502                 comp->flags &=~ SLF_TOSS;
 503                 comp->recv_current = x;
 504         } else {
 505                 /* this packet has an implicit state index.  If we've
 506                  * had a line error since the last time we got an
 507                  * explicit state index, we have to toss the packet. */
 508                 if(comp->flags & SLF_TOSS){
 509                         comp->sls_i_tossed++;
 510                         DPRINT(("uncomp: toss\n"));
 511                         return 0;
 512                 }
 513         }
 514         cs = &comp->rstate[comp->recv_current];
 515         thp = &cs->cs_tcp;
 516         ip = &cs->cs_ip;
 517 
 518         if((x = pull16(&cp)) == -1) {   /* Read the TCP checksum */
 519                 DPRINT(("uncomp: bad tcp chk\n"));
 520                 goto bad;
 521         }
 522         thp->check = htons(x);
 523 
 524         thp->psh = (changes & TCP_PUSH_BIT) ? 1 : 0;
 525 /* 
 526  * we can use the same number for the length of the saved header and
 527  * the current one, because the packet wouldn't have been sent
 528  * as compressed unless the options were the same as the previous one
 529  */
 530 
 531         hdrlen = ip->ihl * 4 + thp->doff * 4;
 532 
 533         switch(changes & SPECIALS_MASK){
 534         case SPECIAL_I:         /* Echoed terminal traffic */
 535                 {
 536                 register short i;
 537                 i = ntohs(ip->tot_len) - hdrlen;
 538                 thp->ack_seq = htonl( ntohl(thp->ack_seq) + i);
 539                 thp->seq = htonl( ntohl(thp->seq) + i);
 540                 }
 541                 break;
 542 
 543         case SPECIAL_D:                 /* Unidirectional data */
 544                 thp->seq = htonl( ntohl(thp->seq) +
 545                                   ntohs(ip->tot_len) - hdrlen);
 546                 break;
 547 
 548         default:
 549                 if(changes & NEW_U){
 550                         thp->urg = 1;
 551                         if((x = decode(&cp)) == -1) {
 552                                 DPRINT(("uncomp: bad U\n"));
 553                                 goto bad;
 554                         }
 555                         thp->urg_ptr = htons(x);
 556                 } else
 557                         thp->urg = 0;
 558                 if(changes & NEW_W){
 559                         if((x = decode(&cp)) == -1) {
 560                                 DPRINT(("uncomp: bad W\n"));
 561                                 goto bad;
 562                         }       
 563                         thp->window = htons( ntohs(thp->window) + x);
 564                 }
 565                 if(changes & NEW_A){
 566                         if((x = decode(&cp)) == -1) {
 567                                 DPRINT(("uncomp: bad A\n"));
 568                                 goto bad;
 569                         }
 570                         thp->ack_seq = htonl( ntohl(thp->ack_seq) + x);
 571                 }
 572                 if(changes & NEW_S){
 573                         if((x = decode(&cp)) == -1) {
 574                                 DPRINT(("uncomp: bad S\n"));
 575                                 goto bad;
 576                         }
 577                         thp->seq = htonl( ntohl(thp->seq) + x);
 578                 }
 579                 break;
 580         }
 581         if(changes & NEW_I){
 582                 if((x = decode(&cp)) == -1) {
 583                         DPRINT(("uncomp: bad I\n"));
 584                         goto bad;
 585                 }
 586                 ip->id = htons (ntohs (ip->id) + x);
 587         } else
 588                 ip->id = htons (ntohs (ip->id) + 1);
 589 
 590         /*
 591          * At this point, cp points to the first byte of data in the
 592          * packet.  Put the reconstructed TCP and IP headers back on the
 593          * packet.  Recalculate IP checksum (but not TCP checksum).
 594          */
 595 
 596         len = isize - (cp - icp);
 597         if (len < 0)
 598                 goto bad;
 599         len += hdrlen;
 600         ip->tot_len = htons(len);
 601         ip->check = 0;
 602 
 603         DPRINT(("uncomp: %d %d %d %d\n", cp - icp, hdrlen, isize, len));
 604 
 605         memmove(icp + hdrlen, cp, len - hdrlen);
 606 
 607         cp = icp;
 608         memcpy(cp, ip, 20);
 609         cp += 20;
 610 
 611         if (ip->ihl > 5) {
 612           memcpy(cp, cs->cs_ipopt, ((ip->ihl) - 5) * 4);
 613           cp += ((ip->ihl) - 5) * 4;
 614         }
 615 
 616         ((struct iphdr *)icp)->check = ip_csum((struct iphdr*)icp);
 617 
 618         memcpy(cp, thp, 20);
 619         cp += 20;
 620 
 621         if (thp->doff > 5) {
 622           memcpy(cp, cs->cs_tcpopt, ((thp->doff) - 5) * 4);
 623           cp += ((thp->doff) - 5) * 4;
 624         }
 625 
 626 if (inet_debug == DBG_SLIP) printk("\runcomp: change %x len %d\n", changes, len);
 627         return len;
 628 bad:
 629         comp->sls_i_error++;
 630         return slhc_toss( comp );
 631 }
 632 
 633 
 634 int
 635 slhc_remember(struct slcompress *comp, unsigned char *icp, int isize)
     /* [previous][next][first][last][top][bottom][index][help] */
 636 {
 637         register struct cstate *cs;
 638         short ip_len;
 639         struct iphdr *ip;
 640         struct tcphdr *thp;
 641 
 642         unsigned char index;
 643 
 644         if(isize < 20) {
 645                 /* The packet is shorter than a legal IP header */
 646                 comp->sls_i_runt++;
 647                 return slhc_toss( comp );
 648         }
 649         /* Sneak a peek at the IP header's IHL field to find its length */
 650         ip_len = (icp[0] & 0xf) << 2;
 651         if(ip_len < 20){
 652                 /* The IP header length field is too small */
 653                 comp->sls_i_runt++;
 654                 return slhc_toss( comp );
 655         }
 656         index = icp[9];
 657         icp[9] = IPPROTO_TCP;
 658         ip = (struct iphdr *) icp;
 659 
 660         if (ip_csum(ip)) {
 661                 /* Bad IP header checksum; discard */
 662                 comp->sls_i_badcheck++;
 663                 return slhc_toss( comp );
 664         }
 665         thp = (struct tcphdr *)(((unsigned char *)ip) + ip->ihl*4);
 666         if(index > comp->rslot_limit) {
 667                 comp->sls_i_error++;
 668                 return slhc_toss(comp);
 669         }
 670 
 671         /* Update local state */
 672         cs = &comp->rstate[comp->recv_current = index];
 673         comp->flags &=~ SLF_TOSS;
 674         memcpy(&cs->cs_ip,ip,20);
 675         memcpy(&cs->cs_tcp,thp,20);
 676         if (ip->ihl > 5)
 677           memcpy(cs->cs_ipopt, ip+1, ((ip->ihl) - 5) * 4);
 678         if (thp->doff > 5)
 679           memcpy(cs->cs_tcpopt, thp+1, ((thp->doff) - 5) * 4);
 680         cs->cs_hsize = ip->ihl*2 + thp->doff*2;
 681         /* Put headers back on packet
 682          * Neither header checksum is recalculated
 683          */
 684         comp->sls_i_uncompressed++;
 685         return isize;
 686 }
 687 
 688 
 689 int
 690 slhc_toss(struct slcompress *comp)
     /* [previous][next][first][last][top][bottom][index][help] */
 691 {
 692         if ( comp == NULLSLCOMPR )
 693                 return 0;
 694 
 695         comp->flags |= SLF_TOSS;
 696         return 0;
 697 }
 698 
 699 
 700 void slhc_i_status(struct slcompress *comp)
     /* [previous][next][first][last][top][bottom][index][help] */
 701 {
 702         if (comp != NULLSLCOMPR) {
 703                 printk("\t%ld Cmp, %ld Uncmp, %ld Bad, %ld Tossed\n",
 704                         comp->sls_i_compressed,
 705                         comp->sls_i_uncompressed,
 706                         comp->sls_i_error,
 707                         comp->sls_i_tossed);
 708         }
 709 }
 710 
 711 
 712 void slhc_o_status(struct slcompress *comp)
     /* [previous][next][first][last][top][bottom][index][help] */
 713 {
 714         if (comp != NULLSLCOMPR) {
 715                 printk("\t%ld Cmp, %ld Uncmp, %ld AsIs, %ld NotTCP\n",
 716                         comp->sls_o_compressed,
 717                         comp->sls_o_uncompressed,
 718                         comp->sls_o_tcp,
 719                         comp->sls_o_nontcp);
 720                 printk("\t%10ld Searches, %10ld Misses\n",
 721                         comp->sls_o_searches,
 722                         comp->sls_o_misses);
 723         }
 724 }
 725 

/* [previous][next][first][last][top][bottom][index][help] */