release/src/router/pppd/modules/vjcompress.c

   1 /*
   2  * Routines to compress and uncompess 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  * Modified June 1993 by Paul Mackerras, paulus@cs.anu.edu.au,
  24  * so that the entire packet being decompressed doesn't have
  25  * to be in contiguous memory (just the compressed header).
  26  */
  27
  28 /*
  29  * This version is used under SunOS 4.x, Digital UNIX, AIX 4.x,
  30  * and SVR4 systems including Solaris 2.
  31  *
  32  * $Id: vjcompress.c,v 1.11 2004/01/17 05:47:55 carlsonj Exp $
  33  */
  34
  35 #include <sys/types.h>
  36 #include <sys/param.h>
  37
  38 #ifdef SVR4
  39 #ifndef __GNUC__
  40 #include <sys/byteorder.h>      /* for ntohl, etc. */
  41 #else
  42 /* make sure we don't get the gnu "fixed" one! */
  43 #include "/usr/include/sys/byteorder.h"
  44 #endif
  45 #endif
  46
  47 #ifdef __osf__
  48 #include <net/net_globals.h>
  49 #endif
  50 #include <netinet/in.h>
  51
  52 #ifdef AIX4
  53 #define _NETINET_IN_SYSTM_H_
  54 typedef u_long  n_long;
  55 #else
  56 #include <netinet/in_systm.h>
  57 #endif
  58
  59 #ifdef SOL2
  60 #include <sys/sunddi.h>
  61 #endif
  62
  63 #include <netinet/ip.h>
  64 #include <netinet/tcp.h>
  65
  66 #include <net/ppp_defs.h>
  67 #include <net/vjcompress.h>
  68
  69 #ifndef VJ_NO_STATS
  70 #define INCR(counter) ++comp->stats.counter
  71 #else
  72 #define INCR(counter)
  73 #endif
  74
  75 #define BCMP(p1, p2, n) bcmp((char *)(p1), (char *)(p2), (int)(n))
  76 #undef  BCOPY
  77 #define BCOPY(p1, p2, n) bcopy((char *)(p1), (char *)(p2), (int)(n))
  78 #ifndef KERNEL
  79 #define ovbcopy bcopy
  80 #endif
  81
  82 #ifdef __osf__
  83 #define getip_hl(base)  (((base).ip_vhl)&0xf)
  84 #define getth_off(base) ((((base).th_xoff)&0xf0)>>4)
  85
  86 #else
  87 #define getip_hl(base)  ((base).ip_hl)
  88 #define getth_off(base) ((base).th_off)
  89 #endif
  90
  91 void
  92 vj_compress_init(comp, max_state)
  93     struct vjcompress *comp;
  94     int max_state;
  95 {
  96     register u_int i;
  97     register struct cstate *tstate = comp->tstate;
  98
  99     if (max_state == -1)
 100         max_state = MAX_STATES - 1;
 101     bzero((char *)comp, sizeof(*comp));
 102     for (i = max_state; i > 0; --i) {
 103         tstate[i].cs_id = i;
 104         tstate[i].cs_next = &tstate[i - 1];
 105     }
 106     tstate[0].cs_next = &tstate[max_state];
 107     tstate[0].cs_id = 0;
 108     comp->last_cs = &tstate[0];
 109     comp->last_recv = 255;
 110     comp->last_xmit = 255;
 111     comp->flags = VJF_TOSS;
 112 }
 113
 114
 115 /* ENCODE encodes a number that is known to be non-zero.  ENCODEZ
 116  * checks for zero (since zero has to be encoded in the long, 3 byte
 117  * form).
 118  */
 119 #define ENCODE(n) { \
 120         if ((u_short)(n) >= 256) { \
 121                 *cp++ = 0; \
 122                 cp[1] = (n); \
 123                 cp[0] = (n) >> 8; \
 124                 cp += 2; \
 125         } else { \
 126                 *cp++ = (n); \
 127         } \
 128 }
 129 #define ENCODEZ(n) { \
 130         if ((u_short)(n) >= 256 || (u_short)(n) == 0) { \
 131                 *cp++ = 0; \
 132                 cp[1] = (n); \
 133                 cp[0] = (n) >> 8; \
 134                 cp += 2; \
 135         } else { \
 136                 *cp++ = (n); \
 137         } \
 138 }
 139
 140 #define DECODEL(f) { \
 141         if (*cp == 0) {\
 142                 u_int32_t tmp = ntohl(f) + ((cp[1] << 8) | cp[2]); \
 143                 (f) = htonl(tmp); \
 144                 cp += 3; \
 145         } else { \
 146                 u_int32_t tmp = ntohl(f) + (u_int32_t)*cp++; \
 147                 (f) = htonl(tmp); \
 148         } \
 149 }
 150
 151 #define DECODES(f) { \
 152         if (*cp == 0) {\
 153                 u_short tmp = ntohs(f) + ((cp[1] << 8) | cp[2]); \
 154                 (f) = htons(tmp); \
 155                 cp += 3; \
 156         } else { \
 157                 u_short tmp = ntohs(f) + (u_int32_t)*cp++; \
 158                 (f) = htons(tmp); \
 159         } \
 160 }
 161
 162 #define DECODEU(f) { \
 163         if (*cp == 0) {\
 164                 (f) = htons((cp[1] << 8) | cp[2]); \
 165                 cp += 3; \
 166         } else { \
 167                 (f) = htons((u_int32_t)*cp++); \
 168         } \
 169 }
 170
 171 u_int
 172 vj_compress_tcp(ip, mlen, comp, compress_cid, vjhdrp)
 173     register struct ip *ip;
 174     u_int mlen;
 175     struct vjcompress *comp;
 176     int compress_cid;
 177     u_char **vjhdrp;
 178 {
 179     register struct cstate *cs = comp->last_cs->cs_next;
 180     register u_int hlen = getip_hl(*ip);
 181     register struct tcphdr *oth;
 182     register struct tcphdr *th;
 183     register u_int deltaS, deltaA;
 184     register u_int changes = 0;
 185     u_char new_seq[16];
 186     register u_char *cp = new_seq;
 187
 188     /*
 189      * Bail if this is an IP fragment or if the TCP packet isn't
 190      * `compressible' (i.e., ACK isn't set or some other control bit is
 191      * set).  (We assume that the caller has already made sure the
 192      * packet is IP proto TCP).
 193      */
 194     if ((ip->ip_off & htons(0x3fff)) || mlen < 40)
 195         return (TYPE_IP);
 196
 197     th = (struct tcphdr *)&((int *)ip)[hlen];
 198     if ((th->th_flags & (TH_SYN|TH_FIN|TH_RST|TH_ACK)) != TH_ACK)
 199         return (TYPE_IP);
 200     /*
 201      * Packet is compressible -- we're going to send either a
 202      * COMPRESSED_TCP or UNCOMPRESSED_TCP packet.  Either way we need
 203      * to locate (or create) the connection state.  Special case the
 204      * most recently used connection since it's most likely to be used
 205      * again & we don't have to do any reordering if it's used.
 206      */
 207     INCR(vjs_packets);
 208     if (ip->ip_src.s_addr != cs->cs_ip.ip_src.s_addr ||
 209         ip->ip_dst.s_addr != cs->cs_ip.ip_dst.s_addr ||
 210         *(int *)th != ((int *)&cs->cs_ip)[getip_hl(cs->cs_ip)]) {
 211         /*
 212          * Wasn't the first -- search for it.
 213          *
 214          * States are kept in a circularly linked list with
 215          * last_cs pointing to the end of the list.  The
 216          * list is kept in lru order by moving a state to the
 217          * head of the list whenever it is referenced.  Since
 218          * the list is short and, empirically, the connection
 219          * we want is almost always near the front, we locate
 220          * states via linear search.  If we don't find a state
 221          * for the datagram, the oldest state is (re-)used.
 222          */
 223         register struct cstate *lcs;
 224         register struct cstate *lastcs = comp->last_cs;
 225
 226         do {
 227             lcs = cs; cs = cs->cs_next;
 228             INCR(vjs_searches);
 229             if (ip->ip_src.s_addr == cs->cs_ip.ip_src.s_addr
 230                 && ip->ip_dst.s_addr == cs->cs_ip.ip_dst.s_addr
 231                 && *(int *)th == ((int *)&cs->cs_ip)[getip_hl(cs->cs_ip)])
 232                 goto found;
 233         } while (cs != lastcs);
 234
 235         /*
 236          * Didn't find it -- re-use oldest cstate.  Send an
 237          * uncompressed packet that tells the other side what
 238          * connection number we're using for this conversation.
 239          * Note that since the state list is circular, the oldest
 240          * state points to the newest and we only need to set
 241          * last_cs to update the lru linkage.
 242          */
 243         INCR(vjs_misses);
 244         comp->last_cs = lcs;
 245         hlen += getth_off(*th);
 246         hlen <<= 2;
 247         if (hlen > mlen)
 248             return (TYPE_IP);
 249         goto uncompressed;
 250
 251     found:
 252         /*
 253          * Found it -- move to the front on the connection list.
 254          */
 255         if (cs == lastcs)
 256             comp->last_cs = lcs;
 257         else {
 258             lcs->cs_next = cs->cs_next;
 259             cs->cs_next = lastcs->cs_next;
 260             lastcs->cs_next = cs;
 261         }
 262     }
 263
 264     /*
 265      * Make sure that only what we expect to change changed. The first
 266      * line of the `if' checks the IP protocol version, header length &
 267      * type of service.  The 2nd line checks the "Don't fragment" bit.
 268      * The 3rd line checks the time-to-live and protocol (the protocol
 269      * check is unnecessary but costless).  The 4th line checks the TCP
 270      * header length.  The 5th line checks IP options, if any.  The 6th
 271      * line checks TCP options, if any.  If any of these things are
 272      * different between the previous & current datagram, we send the
 273      * current datagram `uncompressed'.
 274      */
 275     oth = (struct tcphdr *)&((int *)&cs->cs_ip)[hlen];
 276     deltaS = hlen;
 277     hlen += getth_off(*th);
 278     hlen <<= 2;
 279     if (hlen > mlen)
 280         return (TYPE_IP);
 281
 282     if (((u_short *)ip)[0] != ((u_short *)&cs->cs_ip)[0] ||
 283         ((u_short *)ip)[3] != ((u_short *)&cs->cs_ip)[3] ||
 284         ((u_short *)ip)[4] != ((u_short *)&cs->cs_ip)[4] ||
 285         getth_off(*th) != getth_off(*oth) ||
 286         (deltaS > 5 && BCMP(ip + 1, &cs->cs_ip + 1, (deltaS - 5) << 2)) ||
 287         (getth_off(*th) > 5 && BCMP(th + 1, oth + 1, (getth_off(*th) - 5) << 2)))
 288         goto uncompressed;
 289
 290     /*
 291      * Figure out which of the changing fields changed.  The
 292      * receiver expects changes in the order: urgent, window,
 293      * ack, seq (the order minimizes the number of temporaries
 294      * needed in this section of code).
 295      */
 296     if (th->th_flags & TH_URG) {
 297         deltaS = ntohs(th->th_urp);
 298         ENCODEZ(deltaS);
 299         changes |= NEW_U;
 300     } else if (th->th_urp != oth->th_urp)
 301         /* argh! URG not set but urp changed -- a sensible
 302          * implementation should never do this but RFC793
 303          * doesn't prohibit the change so we have to deal
 304          * with it. */
 305         goto uncompressed;
 306
 307     if ((deltaS = (u_short)(ntohs(th->th_win) - ntohs(oth->th_win))) > 0) {
 308         ENCODE(deltaS);
 309         changes |= NEW_W;
 310     }
 311
 312     if ((deltaA = ntohl(th->th_ack) - ntohl(oth->th_ack)) > 0) {
 313         if (deltaA > 0xffff)
 314             goto uncompressed;
 315         ENCODE(deltaA);
 316         changes |= NEW_A;
 317     }
 318
 319     if ((deltaS = ntohl(th->th_seq) - ntohl(oth->th_seq)) > 0) {
 320         if (deltaS > 0xffff)
 321             goto uncompressed;
 322         ENCODE(deltaS);
 323         changes |= NEW_S;
 324     }
 325
 326     switch(changes) {
 327
 328     case 0:
 329         /*
 330          * Nothing changed. If this packet contains data and the
 331          * last one didn't, this is probably a data packet following
 332          * an ack (normal on an interactive connection) and we send
 333          * it compressed.  Otherwise it's probably a retransmit,
 334          * retransmitted ack or window probe.  Send it uncompressed
 335          * in case the other side missed the compressed version.
 336          */
 337         if (ip->ip_len != cs->cs_ip.ip_len &&
 338             ntohs(cs->cs_ip.ip_len) == hlen)
 339             break;
 340
 341         /* (fall through) */
 342
 343     case SPECIAL_I:
 344     case SPECIAL_D:
 345         /*
 346          * actual changes match one of our special case encodings --
 347          * send packet uncompressed.
 348          */
 349         goto uncompressed;
 350
 351     case NEW_S|NEW_A:
 352         if (deltaS == deltaA && deltaS == ntohs(cs->cs_ip.ip_len) - hlen) {
 353             /* special case for echoed terminal traffic */
 354             changes = SPECIAL_I;
 355             cp = new_seq;
 356         }
 357         break;
 358
 359     case NEW_S:
 360         if (deltaS == ntohs(cs->cs_ip.ip_len) - hlen) {
 361             /* special case for data xfer */
 362             changes = SPECIAL_D;
 363             cp = new_seq;
 364         }
 365         break;
 366     }
 367
 368     deltaS = ntohs(ip->ip_id) - ntohs(cs->cs_ip.ip_id);
 369     if (deltaS != 1) {
 370         ENCODEZ(deltaS);
 371         changes |= NEW_I;
 372     }
 373     if (th->th_flags & TH_PUSH)
 374         changes |= TCP_PUSH_BIT;
 375     /*
 376      * Grab the cksum before we overwrite it below.  Then update our
 377      * state with this packet's header.
 378      */
 379     deltaA = ntohs(th->th_sum);
 380     BCOPY(ip, &cs->cs_ip, hlen);
 381
 382     /*
 383      * We want to use the original packet as our compressed packet.
 384      * (cp - new_seq) is the number of bytes we need for compressed
 385      * sequence numbers.  In addition we need one byte for the change
 386      * mask, one for the connection id and two for the tcp checksum.
 387      * So, (cp - new_seq) + 4 bytes of header are needed.  hlen is how
 388      * many bytes of the original packet to toss so subtract the two to
 389      * get the new packet size.
 390      */
 391     deltaS = cp - new_seq;
 392     cp = (u_char *)ip;
 393     if (compress_cid == 0 || comp->last_xmit != cs->cs_id) {
 394         comp->last_xmit = cs->cs_id;
 395         hlen -= deltaS + 4;
 396         *vjhdrp = (cp += hlen);
 397         *cp++ = changes | NEW_C;
 398         *cp++ = cs->cs_id;
 399     } else {
 400         hlen -= deltaS + 3;
 401         *vjhdrp = (cp += hlen);
 402         *cp++ = changes;
 403     }
 404     *cp++ = deltaA >> 8;
 405     *cp++ = deltaA;
 406     BCOPY(new_seq, cp, deltaS);
 407     INCR(vjs_compressed);
 408     return (TYPE_COMPRESSED_TCP);
 409
 410     /*
 411      * Update connection state cs & send uncompressed packet (that is,
 412      * a regular ip/tcp packet but with the 'conversation id' we hope
 413      * to use on future compressed packets in the protocol field).
 414      */
 415  uncompressed:
 416     BCOPY(ip, &cs->cs_ip, hlen);
 417     ip->ip_p = cs->cs_id;
 418     comp->last_xmit = cs->cs_id;
 419     return (TYPE_UNCOMPRESSED_TCP);
 420 }
 421
 422 /*
 423  * Called when we may have missed a packet.
 424  */
 425 void
 426 vj_uncompress_err(comp)
 427     struct vjcompress *comp;
 428 {
 429     comp->flags |= VJF_TOSS;
 430     INCR(vjs_errorin);
 431 }
 432
 433 /*
 434  * "Uncompress" a packet of type TYPE_UNCOMPRESSED_TCP.
 435  */
 436 int
 437 vj_uncompress_uncomp(buf, buflen, comp)
 438     u_char *buf;
 439     int buflen;
 440     struct vjcompress *comp;
 441 {
 442     register u_int hlen;
 443     register struct cstate *cs;
 444     register struct ip *ip;
 445
 446     ip = (struct ip *) buf;
 447     hlen = getip_hl(*ip) << 2;
 448     if (ip->ip_p >= MAX_STATES
 449         || hlen + sizeof(struct tcphdr) > buflen
 450         || (hlen += getth_off(*((struct tcphdr *)&((char *)ip)[hlen])) << 2)
 451             > buflen
 452         || hlen > MAX_HDR) {
 453         comp->flags |= VJF_TOSS;
 454         INCR(vjs_errorin);
 455         return (0);
 456     }
 457     cs = &comp->rstate[comp->last_recv = ip->ip_p];
 458     comp->flags &=~ VJF_TOSS;
 459     ip->ip_p = IPPROTO_TCP;
 460     BCOPY(ip, &cs->cs_ip, hlen);
 461     cs->cs_hlen = hlen;
 462     INCR(vjs_uncompressedin);
 463     return (1);
 464 }
 465
 466 /*
 467  * Uncompress a packet of type TYPE_COMPRESSED_TCP.
 468  * The packet starts at buf and is of total length total_len.
 469  * The first buflen bytes are at buf; this must include the entire
 470  * compressed TCP/IP header.  This procedure returns the length
 471  * of the VJ header, with a pointer to the uncompressed IP header
 472  * in *hdrp and its length in *hlenp.
 473  */
 474 int
 475 vj_uncompress_tcp(buf, buflen, total_len, comp, hdrp, hlenp)
 476     u_char *buf;
 477     int buflen, total_len;
 478     struct vjcompress *comp;
 479     u_char **hdrp;
 480     u_int *hlenp;
 481 {
 482     register u_char *cp;
 483     register u_int hlen, changes;
 484     register struct tcphdr *th;
 485     register struct cstate *cs;
 486     register u_short *bp;
 487     register u_int vjlen;
 488     register u_int32_t tmp;
 489
 490     INCR(vjs_compressedin);
 491     cp = buf;
 492     changes = *cp++;
 493     if (changes & NEW_C) {
 494         /* Make sure the state index is in range, then grab the state.
 495          * If we have a good state index, clear the 'discard' flag. */
 496         if (*cp >= MAX_STATES)
 497             goto bad;
 498
 499         comp->flags &=~ VJF_TOSS;
 500         comp->last_recv = *cp++;
 501     } else {
 502         /* this packet has an implicit state index.  If we've
 503          * had a line error since the last time we got an
 504          * explicit state index, we have to toss the packet. */
 505         if (comp->flags & VJF_TOSS) {
 506             INCR(vjs_tossed);
 507             return (-1);
 508         }
 509     }
 510     cs = &comp->rstate[comp->last_recv];
 511     hlen = getip_hl(cs->cs_ip) << 2;
 512     th = (struct tcphdr *)&((u_char *)&cs->cs_ip)[hlen];
 513     th->th_sum = htons((*cp << 8) | cp[1]);
 514     cp += 2;
 515     if (changes & TCP_PUSH_BIT)
 516         th->th_flags |= TH_PUSH;
 517     else
 518         th->th_flags &=~ TH_PUSH;
 519
 520     switch (changes & SPECIALS_MASK) {
 521     case SPECIAL_I:
 522         {
 523             register u_int32_t i = ntohs(cs->cs_ip.ip_len) - cs->cs_hlen;
 524             /* some compilers can't nest inline assembler.. */
 525             tmp = ntohl(th->th_ack) + i;
 526             th->th_ack = htonl(tmp);
 527             tmp = ntohl(th->th_seq) + i;
 528             th->th_seq = htonl(tmp);
 529         }
 530         break;
 531
 532     case SPECIAL_D:
 533         /* some compilers can't nest inline assembler.. */
 534         tmp = ntohl(th->th_seq) + ntohs(cs->cs_ip.ip_len) - cs->cs_hlen;
 535         th->th_seq = htonl(tmp);
 536         break;
 537
 538     default:
 539         if (changes & NEW_U) {
 540             th->th_flags |= TH_URG;
 541             DECODEU(th->th_urp);
 542         } else
 543             th->th_flags &=~ TH_URG;
 544         if (changes & NEW_W)
 545             DECODES(th->th_win);
 546         if (changes & NEW_A)
 547             DECODEL(th->th_ack);
 548         if (changes & NEW_S)
 549             DECODEL(th->th_seq);
 550         break;
 551     }
 552     if (changes & NEW_I) {
 553         DECODES(cs->cs_ip.ip_id);
 554     } else {
 555         cs->cs_ip.ip_id = ntohs(cs->cs_ip.ip_id) + 1;
 556         cs->cs_ip.ip_id = htons(cs->cs_ip.ip_id);
 557     }
 558
 559     /*
 560      * At this point, cp points to the first byte of data in the
 561      * packet.  Fill in the IP total length and update the IP
 562      * header checksum.
 563      */
 564     vjlen = cp - buf;
 565     buflen -= vjlen;
 566     if (buflen < 0)
 567         /* we must have dropped some characters (crc should detect
 568          * this but the old slip framing won't) */
 569         goto bad;
 570
 571     total_len += cs->cs_hlen - vjlen;
 572     cs->cs_ip.ip_len = htons(total_len);
 573
 574     /* recompute the ip header checksum */
 575     bp = (u_short *) &cs->cs_ip;
 576     cs->cs_ip.ip_sum = 0;
 577     for (changes = 0; hlen > 0; hlen -= 2)
 578         changes += *bp++;
 579     changes = (changes & 0xffff) + (changes >> 16);
 580     changes = (changes & 0xffff) + (changes >> 16);
 581     cs->cs_ip.ip_sum = ~ changes;
 582
 583     *hdrp = (u_char *) &cs->cs_ip;
 584     *hlenp = cs->cs_hlen;
 585     return vjlen;
 586
 587  bad:
 588     comp->flags |= VJF_TOSS;
 589     INCR(vjs_errorin);
 590     return (-1);
 591 }