freebsd-2.0/pppcompress.c

   1 /*-
   2  * Copyright (c) 1989 The Regents of the University of California.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  *      @(#)slcompress.c        7.7 (Berkeley) 5/7/91
  34  */
  35
  36 /*
  37  * Routines to compress and uncompess tcp packets (for transmission
  38  * over low speed serial lines.
  39  *
  40  * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
  41  *    - Initial distribution.
  42  *
  43  *      $Id: pppcompress.c,v 1.2 1996/05/24 07:04:14 paulus Exp $
  44  */
  45
  46 #include <sys/types.h>
  47 #include <sys/param.h>
  48 #include <sys/systm.h>
  49 #include <sys/mbuf.h>
  50 #include <sys/socket.h>
  51 #include <sys/socketvar.h>
  52
  53 #include <netinet/in.h>
  54 #include <netinet/in_systm.h>
  55 #include <netinet/ip.h>
  56 #include <netinet/tcp.h>
  57
  58 #include <net/pppcompress.h>
  59
  60 #ifndef SL_NO_STATS
  61 #define INCR(counter) ++comp->counter;
  62 #else
  63 #define INCR(counter)
  64 #endif
  65
  66 #define BCMP(p1, p2, n) bcmp((char *)(p1), (char *)(p2), (int)(n))
  67 #define BCOPY(p1, p2, n) bcopy((char *)(p1), (char *)(p2), (int)(n))
  68 #ifndef KERNEL
  69 #define ovbcopy bcopy
  70 #endif
  71
  72 void
  73 vj_compress_init(comp, max_state)
  74         struct vjcompress *comp;
  75         int max_state;
  76 {
  77         register u_int i;
  78         register struct cstate *tstate = comp->tstate;
  79
  80         if ((unsigned) max_state > MAX_STATES - 1)
  81                 max_state = MAX_STATES - 1;
  82         bzero((char *)comp, sizeof(*comp));
  83         for (i = max_state; i > 0; --i) {
  84                 tstate[i].cs_id = i;
  85                 tstate[i].cs_next = &tstate[i - 1];
  86         }
  87         tstate[0].cs_next = &tstate[max_state];
  88         tstate[0].cs_id = 0;
  89         comp->last_cs = &tstate[0];
  90         comp->last_recv = 255;
  91         comp->last_xmit = 255;
  92         comp->flags = SLF_TOSS;
  93 }
  94
  95
  96 /* ENCODE encodes a number that is known to be non-zero.  ENCODEZ
  97  * checks for zero (since zero has to be encoded in the long, 3 byte
  98  * form).
  99  */
 100 #define ENCODE(n) { \
 101         if ((u_short)(n) >= 256) { \
 102                 *cp++ = 0; \
 103                 cp[1] = (n); \
 104                 cp[0] = (n) >> 8; \
 105                 cp += 2; \
 106         } else { \
 107                 *cp++ = (n); \
 108         } \
 109 }
 110 #define ENCODEZ(n) { \
 111         if ((u_short)(n) >= 256 || (u_short)(n) == 0) { \
 112                 *cp++ = 0; \
 113                 cp[1] = (n); \
 114                 cp[0] = (n) >> 8; \
 115                 cp += 2; \
 116         } else { \
 117                 *cp++ = (n); \
 118         } \
 119 }
 120
 121 #define DECODEL(f) { \
 122         if (*cp == 0) {\
 123                 (f) = htonl(ntohl(f) + ((cp[1] << 8) | cp[2])); \
 124                 cp += 3; \
 125         } else { \
 126                 (f) = htonl(ntohl(f) + (u_long)*cp++); \
 127         } \
 128 }
 129
 130 #define DECODES(f) { \
 131         if (*cp == 0) {\
 132                 (f) = htons(ntohs(f) + ((cp[1] << 8) | cp[2])); \
 133                 cp += 3; \
 134         } else { \
 135                 (f) = htons(ntohs(f) + (u_long)*cp++); \
 136         } \
 137 }
 138
 139 #define DECODEU(f) { \
 140         if (*cp == 0) {\
 141                 (f) = htons((cp[1] << 8) | cp[2]); \
 142                 cp += 3; \
 143         } else { \
 144                 (f) = htons((u_long)*cp++); \
 145         } \
 146 }
 147
 148 u_int
 149 vj_compress_tcp(m, ip, comp, compress_cid)
 150         struct mbuf *m;
 151         register struct ip *ip;
 152         struct vjcompress *comp;
 153         int compress_cid;
 154 {
 155         register struct cstate *cs = comp->last_cs->cs_next;
 156         register u_int hlen = ip->ip_hl;
 157         register struct tcphdr *oth;
 158         register struct tcphdr *th;
 159         register u_int deltaS, deltaA;
 160         register u_int changes = 0;
 161         u_char new_seq[16];
 162         register u_char *cp = new_seq;
 163
 164         /*
 165          * Bail if this is an IP fragment or if the TCP packet isn't
 166          * `compressible' (i.e., ACK isn't set or some other control bit is
 167          * set).  (We assume that the caller has already made sure the
 168          * packet is IP proto TCP).
 169          */
 170         if ((ip->ip_off & htons(0x3fff)) || m->m_len < 40)
 171                 return (TYPE_IP);
 172
 173         th = (struct tcphdr *)&((int *)ip)[hlen];
 174         if ((th->th_flags & (TH_SYN|TH_FIN|TH_RST|TH_ACK)) != TH_ACK)
 175                 return (TYPE_IP);
 176         /*
 177          * Packet is compressible -- we're going to send either a
 178          * COMPRESSED_TCP or UNCOMPRESSED_TCP packet.  Either way we need
 179          * to locate (or create) the connection state.  Special case the
 180          * most recently used connection since it's most likely to be used
 181          * again & we don't have to do any reordering if it's used.
 182          */
 183         INCR(sls_packets)
 184         if (ip->ip_src.s_addr != cs->cs_ip.ip_src.s_addr ||
 185             ip->ip_dst.s_addr != cs->cs_ip.ip_dst.s_addr ||
 186             *(int *)th != ((int *)&cs->cs_ip)[cs->cs_ip.ip_hl]) {
 187                 /*
 188                  * Wasn't the first -- search for it.
 189                  *
 190                  * States are kept in a circularly linked list with
 191                  * last_cs pointing to the end of the list.  The
 192                  * list is kept in lru order by moving a state to the
 193                  * head of the list whenever it is referenced.  Since
 194                  * the list is short and, empirically, the connection
 195                  * we want is almost always near the front, we locate
 196                  * states via linear search.  If we don't find a state
 197                  * for the datagram, the oldest state is (re-)used.
 198                  */
 199                 register struct cstate *lcs;
 200                 register struct cstate *lastcs = comp->last_cs;
 201
 202                 do {
 203                         lcs = cs; cs = cs->cs_next;
 204                         INCR(sls_searches)
 205                         if (ip->ip_src.s_addr == cs->cs_ip.ip_src.s_addr
 206                             && ip->ip_dst.s_addr == cs->cs_ip.ip_dst.s_addr
 207                             && *(int *)th == ((int *)&cs->cs_ip)[cs->cs_ip.ip_hl])
 208                                 goto found;
 209                 } while (cs != lastcs);
 210
 211                 /*
 212                  * Didn't find it -- re-use oldest cstate.  Send an
 213                  * uncompressed packet that tells the other side what
 214                  * connection number we're using for this conversation.
 215                  * Note that since the state list is circular, the oldest
 216                  * state points to the newest and we only need to set
 217                  * last_cs to update the lru linkage.
 218                  */
 219                 INCR(sls_misses)
 220                 comp->last_cs = lcs;
 221                 hlen += th->th_off;
 222                 hlen <<= 2;
 223                 goto uncompressed;
 224
 225         found:
 226                 /*
 227                  * Found it -- move to the front on the connection list.
 228                  */
 229                 if (cs == lastcs)
 230                         comp->last_cs = lcs;
 231                 else {
 232                         lcs->cs_next = cs->cs_next;
 233                         cs->cs_next = lastcs->cs_next;
 234                         lastcs->cs_next = cs;
 235                 }
 236         }
 237
 238         /*
 239          * Make sure that only what we expect to change changed. The first
 240          * line of the `if' checks the IP protocol version, header length &
 241          * type of service.  The 2nd line checks the "Don't fragment" bit.
 242          * The 3rd line checks the time-to-live and protocol (the protocol
 243          * check is unnecessary but costless).  The 4th line checks the TCP
 244          * header length.  The 5th line checks IP options, if any.  The 6th
 245          * line checks TCP options, if any.  If any of these things are
 246          * different between the previous & current datagram, we send the
 247          * current datagram `uncompressed'.
 248          */
 249         oth = (struct tcphdr *)&((int *)&cs->cs_ip)[hlen];
 250         deltaS = hlen;
 251         hlen += th->th_off;
 252         hlen <<= 2;
 253
 254         if (((u_short *)ip)[0] != ((u_short *)&cs->cs_ip)[0] ||
 255             ((u_short *)ip)[3] != ((u_short *)&cs->cs_ip)[3] ||
 256             ((u_short *)ip)[4] != ((u_short *)&cs->cs_ip)[4] ||
 257             th->th_off != oth->th_off ||
 258             (deltaS > 5 &&
 259              BCMP(ip + 1, &cs->cs_ip + 1, (deltaS - 5) << 2)) ||
 260             (th->th_off > 5 &&
 261              BCMP(th + 1, oth + 1, (th->th_off - 5) << 2)))
 262                 goto uncompressed;
 263
 264         /*
 265          * Figure out which of the changing fields changed.  The
 266          * receiver expects changes in the order: urgent, window,
 267          * ack, seq (the order minimizes the number of temporaries
 268          * needed in this section of code).
 269          */
 270         if (th->th_flags & TH_URG) {
 271                 deltaS = ntohs(th->th_urp);
 272                 ENCODEZ(deltaS);
 273                 changes |= NEW_U;
 274         } else if (th->th_urp != oth->th_urp)
 275                 /* argh! URG not set but urp changed -- a sensible
 276                  * implementation should never do this but RFC793
 277                  * doesn't prohibit the change so we have to deal
 278                  * with it. */
 279                  goto uncompressed;
 280
 281         if (deltaS = (u_short)(ntohs(th->th_win) - ntohs(oth->th_win))) {
 282                 ENCODE(deltaS);
 283                 changes |= NEW_W;
 284         }
 285
 286         if (deltaA = ntohl(th->th_ack) - ntohl(oth->th_ack)) {
 287                 if (deltaA > 0xffff)
 288                         goto uncompressed;
 289                 ENCODE(deltaA);
 290                 changes |= NEW_A;
 291         }
 292
 293         if (deltaS = ntohl(th->th_seq) - ntohl(oth->th_seq)) {
 294                 if (deltaS > 0xffff)
 295                         goto uncompressed;
 296                 ENCODE(deltaS);
 297                 changes |= NEW_S;
 298         }
 299
 300         switch(changes) {
 301
 302         case 0:
 303                 /*
 304                  * Nothing changed. If this packet contains data and the
 305                  * last one didn't, this is probably a data packet following
 306                  * an ack (normal on an interactive connection) and we send
 307                  * it compressed.  Otherwise it's probably a retransmit,
 308                  * retransmitted ack or window probe.  Send it uncompressed
 309                  * in case the other side missed the compressed version.
 310                  */
 311                 if (ip->ip_len != cs->cs_ip.ip_len &&
 312                     ntohs(cs->cs_ip.ip_len) == hlen)
 313                         break;
 314
 315                 /* (fall through) */
 316
 317         case SPECIAL_I:
 318         case SPECIAL_D:
 319                 /*
 320                  * actual changes match one of our special case encodings --
 321                  * send packet uncompressed.
 322                  */
 323                 goto uncompressed;
 324
 325         case NEW_S|NEW_A:
 326                 if (deltaS == deltaA &&
 327                     deltaS == ntohs(cs->cs_ip.ip_len) - hlen) {
 328                         /* special case for echoed terminal traffic */
 329                         changes = SPECIAL_I;
 330                         cp = new_seq;
 331                 }
 332                 break;
 333
 334         case NEW_S:
 335                 if (deltaS == ntohs(cs->cs_ip.ip_len) - hlen) {
 336                         /* special case for data xfer */
 337                         changes = SPECIAL_D;
 338                         cp = new_seq;
 339                 }
 340                 break;
 341         }
 342
 343         deltaS = ntohs(ip->ip_id) - ntohs(cs->cs_ip.ip_id);
 344         if (deltaS != 1) {
 345                 ENCODEZ(deltaS);
 346                 changes |= NEW_I;
 347         }
 348         if (th->th_flags & TH_PUSH)
 349                 changes |= TCP_PUSH_BIT;
 350         /*
 351          * Grab the cksum before we overwrite it below.  Then update our
 352          * state with this packet's header.
 353          */
 354         deltaA = ntohs(th->th_sum);
 355         BCOPY(ip, &cs->cs_ip, hlen);
 356
 357         /*
 358          * We want to use the original packet as our compressed packet.
 359          * (cp - new_seq) is the number of bytes we need for compressed
 360          * sequence numbers.  In addition we need one byte for the change
 361          * mask, one for the connection id and two for the tcp checksum.
 362          * So, (cp - new_seq) + 4 bytes of header are needed.  hlen is how
 363          * many bytes of the original packet to toss so subtract the two to
 364          * get the new packet size.
 365          */
 366         deltaS = cp - new_seq;
 367         cp = (u_char *)ip;
 368         if (compress_cid == 0 || comp->last_xmit != cs->cs_id) {
 369                 comp->last_xmit = cs->cs_id;
 370                 hlen -= deltaS + 4;
 371                 cp += hlen;
 372                 *cp++ = changes | NEW_C;
 373                 *cp++ = cs->cs_id;
 374         } else {
 375                 hlen -= deltaS + 3;
 376                 cp += hlen;
 377                 *cp++ = changes;
 378         }
 379         m->m_len -= hlen;
 380         m->m_data += hlen;
 381         *cp++ = deltaA >> 8;
 382         *cp++ = deltaA;
 383         BCOPY(new_seq, cp, deltaS);
 384         INCR(sls_compressed)
 385         return (TYPE_COMPRESSED_TCP);
 386
 387         /*
 388          * Update connection state cs & send uncompressed packet ('uncompressed'
 389          * means a regular ip/tcp packet but with the 'conversation id' we hope
 390          * to use on future compressed packets in the protocol field).
 391          */
 392 uncompressed:
 393         BCOPY(ip, &cs->cs_ip, hlen);
 394         ip->ip_p = cs->cs_id;
 395         comp->last_xmit = cs->cs_id;
 396         return (TYPE_UNCOMPRESSED_TCP);
 397 }
 398
 399
 400 int
 401 vj_uncompress_tcp(bufp, len, type, comp)
 402         u_char **bufp;
 403         int len;
 404         u_int type;
 405         struct vjcompress *comp;
 406 {
 407         u_char *hdr, *cp;
 408         int hlen, vjlen;
 409
 410         cp = bufp? *bufp: NULL;
 411         vjlen = vj_uncompress_tcp_core(cp, len, len, type, comp, &hdr, &hlen);
 412         if (vjlen < 0)
 413                 return (0);     /* error */
 414         if (vjlen == 0)
 415                 return (len);   /* was uncompressed already */
 416
 417         cp += vjlen;
 418         len -= vjlen;
 419
 420         /*
 421          * At this point, cp points to the first byte of data in the
 422          * packet.  If we're not aligned on a 4-byte boundary, copy the
 423          * data down so the ip & tcp headers will be aligned.  Then back up
 424          * cp by the tcp/ip header length to make room for the reconstructed
 425          * header (we assume the packet we were handed has enough space to
 426          * prepend 128 bytes of header).
 427          */
 428         if ((int)cp & 3) {
 429                 if (len > 0)
 430                         (void) ovbcopy(cp, (caddr_t)((int)cp &~ 3), len);
 431                 cp = (u_char *)((int)cp &~ 3);
 432         }
 433         cp -= hlen;
 434         len += hlen;
 435         BCOPY(hdr, cp, hlen);
 436
 437         *bufp = cp;
 438         return (len);
 439 }
 440
 441 /*
 442  * Uncompress a packet of total length total_len.  The first buflen
 443  * bytes are at buf; this must include the entire (compressed or
 444  * uncompressed) TCP/IP header.  This procedure returns the length
 445  * of the VJ header, with a pointer to the uncompressed IP header
 446  * in *hdrp and its length in *hlenp.
 447  */
 448 int
 449 vj_uncompress_tcp_core(buf, buflen, total_len, type, comp, hdrp, hlenp)
 450         u_char *buf;
 451         int buflen, total_len;
 452         u_int type;
 453         struct vjcompress *comp;
 454         u_char **hdrp;
 455         u_int *hlenp;
 456 {
 457         register u_char *cp;
 458         register u_int hlen, changes;
 459         register struct tcphdr *th;
 460         register struct cstate *cs;
 461         register struct ip *ip;
 462         register u_short *bp;
 463         register u_int vjlen;
 464
 465         switch (type) {
 466
 467         case TYPE_UNCOMPRESSED_TCP:
 468                 ip = (struct ip *) buf;
 469                 if (ip->ip_p >= MAX_STATES)
 470                         goto bad;
 471                 cs = &comp->rstate[comp->last_recv = ip->ip_p];
 472                 comp->flags &=~ SLF_TOSS;
 473                 ip->ip_p = IPPROTO_TCP;
 474                 /*
 475                  * Calculate the size of the TCP/IP header and make sure that
 476                  * we don't overflow the space we have available for it.
 477                  */
 478                 hlen = ip->ip_hl << 2;
 479                 if (hlen + sizeof(struct tcphdr) > buflen)
 480                         goto bad;
 481                 hlen += ((struct tcphdr *)&((char *)ip)[hlen])->th_off << 2;
 482                 if (hlen > MAX_HDR || hlen > buflen)
 483                         goto bad;
 484                 BCOPY(ip, &cs->cs_ip, hlen);
 485                 cs->cs_hlen = hlen;
 486                 INCR(sls_uncompressedin)
 487                 *hdrp = (u_char *) &cs->cs_ip;
 488                 *hlenp = hlen;
 489                 return (0);
 490
 491         default:
 492                 goto bad;
 493
 494         case TYPE_COMPRESSED_TCP:
 495                 break;
 496         }
 497         /* We've got a compressed packet. */
 498         INCR(sls_compressedin)
 499         cp = buf;
 500         changes = *cp++;
 501         if (changes & NEW_C) {
 502                 /* Make sure the state index is in range, then grab the state.
 503                  * If we have a good state index, clear the 'discard' flag. */
 504                 if (*cp >= MAX_STATES)
 505                         goto bad;
 506
 507                 comp->flags &=~ SLF_TOSS;
 508                 comp->last_recv = *cp++;
 509         } else {
 510                 /* this packet has an implicit state index.  If we've
 511                  * had a line error since the last time we got an
 512                  * explicit state index, we have to toss the packet. */
 513                 if (comp->flags & SLF_TOSS) {
 514                         INCR(sls_tossed)
 515                         return (-1);
 516                 }
 517         }
 518         cs = &comp->rstate[comp->last_recv];
 519         hlen = cs->cs_ip.ip_hl << 2;
 520         th = (struct tcphdr *)&((u_char *)&cs->cs_ip)[hlen];
 521         th->th_sum = htons((*cp << 8) | cp[1]);
 522         cp += 2;
 523         if (changes & TCP_PUSH_BIT)
 524                 th->th_flags |= TH_PUSH;
 525         else
 526                 th->th_flags &=~ TH_PUSH;
 527
 528         switch (changes & SPECIALS_MASK) {
 529         case SPECIAL_I:
 530                 {
 531                 register u_int i = ntohs(cs->cs_ip.ip_len) - cs->cs_hlen;
 532                 th->th_ack = htonl(ntohl(th->th_ack) + i);
 533                 th->th_seq = htonl(ntohl(th->th_seq) + i);
 534                 }
 535                 break;
 536
 537         case SPECIAL_D:
 538                 th->th_seq = htonl(ntohl(th->th_seq) + ntohs(cs->cs_ip.ip_len)
 539                                    - cs->cs_hlen);
 540                 break;
 541
 542         default:
 543                 if (changes & NEW_U) {
 544                         th->th_flags |= TH_URG;
 545                         DECODEU(th->th_urp)
 546                 } else
 547                         th->th_flags &=~ TH_URG;
 548                 if (changes & NEW_W)
 549                         DECODES(th->th_win)
 550                 if (changes & NEW_A)
 551                         DECODEL(th->th_ack)
 552                 if (changes & NEW_S)
 553                         DECODEL(th->th_seq)
 554                 break;
 555         }
 556         if (changes & NEW_I) {
 557                 DECODES(cs->cs_ip.ip_id)
 558         } else
 559                 cs->cs_ip.ip_id = htons(ntohs(cs->cs_ip.ip_id) + 1);
 560
 561         /*
 562          * At this point, cp points to the first byte of data in the
 563          * packet.  Fill in the IP total length and update the IP
 564          * header checksum.
 565          */
 566         vjlen = cp - buf;
 567         buflen -= vjlen;
 568         if (buflen < 0)
 569                 /* we must have dropped some characters (crc should detect
 570                  * this but the old slip framing won't) */
 571                 goto bad;
 572
 573         total_len += cs->cs_hlen - vjlen;
 574         cs->cs_ip.ip_len = htons(total_len);
 575
 576         /* recompute the ip header checksum */
 577         bp = (u_short *) &cs->cs_ip;
 578         cs->cs_ip.ip_sum = 0;
 579         for (changes = 0; hlen > 0; hlen -= 2)
 580                 changes += *bp++;
 581         changes = (changes & 0xffff) + (changes >> 16);
 582         changes = (changes & 0xffff) + (changes >> 16);
 583         cs->cs_ip.ip_sum = ~ changes;
 584
 585         *hdrp = (u_char *) &cs->cs_ip;
 586         *hlenp = cs->cs_hlen;
 587         return vjlen;
 588
 589 bad:
 590         comp->flags |= SLF_TOSS;
 591         INCR(sls_errorin)
 592         return (-1);
 593 }