usr.sbin/ppp/slcompress.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 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  19  *
  20  * $FreeBSD: src/usr.sbin/ppp/slcompress.c,v 1.31.2.2 2002/09/01 02:12:32 brian Exp $
  21  *
  22  *      Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
  23  *      - Initial distribution.
  24  */
  25
  26 #include <sys/param.h>
  27 #include <netinet/in_systm.h>
  28 #include <netinet/in.h>
  29 #include <netinet/tcp.h>
  30 #include <netinet/ip.h>
  31 #include <sys/socket.h>
  32 #include <sys/un.h>
  33
  34 #include <stdarg.h>
  35 #include <stdio.h>
  36 #include <string.h>
  37 #include <termios.h>
  38
  39 #include "layer.h"
  40 #include "defs.h"
  41 #include "command.h"
  42 #include "mbuf.h"
  43 #include "log.h"
  44 #include "slcompress.h"
  45 #include "descriptor.h"
  46 #include "prompt.h"
  47 #include "timer.h"
  48 #include "fsm.h"
  49 #include "throughput.h"
  50 #include "iplist.h"
  51 #include "lqr.h"
  52 #include "hdlc.h"
  53 #include "ncpaddr.h"
  54 #include "ipcp.h"
  55 #include "filter.h"
  56 #include "lcp.h"
  57 #include "ccp.h"
  58 #include "link.h"
  59 #include "mp.h"
  60 #ifndef NORADIUS
  61 #include "radius.h"
  62 #endif
  63 #include "ipv6cp.h"
  64 #include "ncp.h"
  65 #include "bundle.h"
  66
  67 void
  68 sl_compress_init(struct slcompress *comp, int max_state)
  69 {
  70   u_int i;
  71   struct cstate *tstate = comp->tstate;
  72
  73   memset(comp, '\0', sizeof *comp);
  74   for (i = max_state; i > 0; --i) {
  75     tstate[i].cs_id = i;
  76     tstate[i].cs_next = &tstate[i - 1];
  77   }
  78   tstate[0].cs_next = &tstate[max_state];
  79   tstate[0].cs_id = 0;
  80   comp->last_cs = &tstate[0];
  81   comp->last_recv = 255;
  82   comp->last_xmit = 255;
  83   comp->flags = SLF_TOSS;
  84 }
  85
  86
  87 /* ENCODE encodes a number that is known to be non-zero.  ENCODEZ
  88  * checks for zero (since zero has to be encoded in the 32-bit, 3 byte
  89  * form).
  90  */
  91 #define ENCODE(n) { \
  92         if ((u_short)(n) >= 256) { \
  93                 *cp++ = 0; \
  94                 cp[1] = (n); \
  95                 cp[0] = (n) >> 8; \
  96                 cp += 2; \
  97         } else { \
  98                 *cp++ = (n); \
  99         } \
 100 }
 101 #define ENCODEZ(n) { \
 102         if ((u_short)(n) >= 256 || (u_short)(n) == 0) { \
 103                 *cp++ = 0; \
 104                 cp[1] = (n); \
 105                 cp[0] = (n) >> 8; \
 106                 cp += 2; \
 107         } else { \
 108                 *cp++ = (n); \
 109         } \
 110 }
 111
 112 #define DECODEL(f) { \
 113         if (*cp == 0) {\
 114                 (f) = htonl(ntohl(f) + ((cp[1] << 8) | cp[2])); \
 115                 cp += 3; \
 116         } else { \
 117                 (f) = htonl(ntohl(f) + (u_int32_t)*cp++); \
 118         } \
 119 }
 120
 121 #define DECODES(f) { \
 122         if (*cp == 0) {\
 123                 (f) = htons(ntohs(f) + ((cp[1] << 8) | cp[2])); \
 124                 cp += 3; \
 125         } else { \
 126                 (f) = htons(ntohs(f) + (u_int32_t)*cp++); \
 127         } \
 128 }
 129
 130 #define DECODEU(f) { \
 131         if (*cp == 0) {\
 132                 (f) = htons((cp[1] << 8) | cp[2]); \
 133                 cp += 3; \
 134         } else { \
 135                 (f) = htons((u_int32_t)*cp++); \
 136         } \
 137 }
 138
 139
 140 u_char
 141 sl_compress_tcp(struct mbuf * m,
 142                 struct ip * ip,
 143                 struct slcompress *comp,
 144                 struct slstat *slstat,
 145                 int compress_cid)
 146 {
 147   struct cstate *cs = comp->last_cs->cs_next;
 148   u_int hlen = ip->ip_hl;
 149   struct tcphdr *oth;
 150   struct tcphdr *th;
 151   u_int deltaS, deltaA;
 152   u_int changes = 0;
 153   u_char new_seq[16];
 154   u_char *cp = new_seq;
 155
 156   /*
 157    * Bail if this is an IP fragment or if the TCP packet isn't `compressible'
 158    * (i.e., ACK isn't set or some other control bit is set).  (We assume that
 159    * the caller has already made sure the packet is IP proto TCP).
 160    */
 161   if ((ip->ip_off & htons(0x3fff)) || m->m_len < 40) {
 162     log_Printf(LogDEBUG, "??? 1 ip_off = %x, m_len = %lu\n",
 163               ip->ip_off, (unsigned long)m->m_len);
 164     log_DumpBp(LogDEBUG, "", m);
 165     return (TYPE_IP);
 166   }
 167   th = (struct tcphdr *) & ((int *) ip)[hlen];
 168   if ((th->th_flags & (TH_SYN | TH_FIN | TH_RST | TH_ACK)) != TH_ACK) {
 169     log_Printf(LogDEBUG, "??? 2 th_flags = %x\n", th->th_flags);
 170     log_DumpBp(LogDEBUG, "", m);
 171     return (TYPE_IP);
 172   }
 173
 174   /*
 175    * Packet is compressible -- we're going to send either a COMPRESSED_TCP or
 176    * UNCOMPRESSED_TCP packet.  Either way we need to locate (or create) the
 177    * connection state.  Special case the most recently used connection since
 178    * it's most likely to be used again & we don't have to do any reordering
 179    * if it's used.
 180    */
 181   slstat->sls_packets++;
 182   if (ip->ip_src.s_addr != cs->cs_ip.ip_src.s_addr ||
 183       ip->ip_dst.s_addr != cs->cs_ip.ip_dst.s_addr ||
 184       *(int *) th != ((int *) &cs->cs_ip)[cs->cs_ip.ip_hl]) {
 185
 186     /*
 187      * Wasn't the first -- search for it.
 188      *
 189      * States are kept in a circularly linked list with last_cs pointing to the
 190      * end of the list.  The list is kept in lru order by moving a state to
 191      * the head of the list whenever it is referenced.  Since the list is
 192      * short and, empirically, the connection we want is almost always near
 193      * the front, we locate states via linear search.  If we don't find a
 194      * state for the datagram, the oldest state is (re-)used.
 195      */
 196     struct cstate *lcs;
 197     struct cstate *lastcs = comp->last_cs;
 198
 199     do {
 200       lcs = cs;
 201       cs = cs->cs_next;
 202       slstat->sls_searches++;
 203       if (ip->ip_src.s_addr == cs->cs_ip.ip_src.s_addr
 204           && ip->ip_dst.s_addr == cs->cs_ip.ip_dst.s_addr
 205           && *(int *) th == ((int *) &cs->cs_ip)[cs->cs_ip.ip_hl])
 206         goto found;
 207     } while (cs != lastcs);
 208
 209     /*
 210      * Didn't find it -- re-use oldest cstate.  Send an uncompressed packet
 211      * that tells the other side what connection number we're using for this
 212      * conversation. Note that since the state list is circular, the oldest
 213      * state points to the newest and we only need to set last_cs to update
 214      * the lru linkage.
 215      */
 216     slstat->sls_misses++;
 217       comp->last_cs = lcs;
 218 #define THOFFSET(th)    (th->th_off)
 219     hlen += th->th_off;
 220     hlen <<= 2;
 221     if (hlen > m->m_len)
 222       return (TYPE_IP);
 223     goto uncompressed;
 224
 225 found:
 226
 227     /*
 228      * Found it -- move to the front on the connection list.
 229      */
 230     if (cs == lastcs)
 231       comp->last_cs = lcs;
 232     else {
 233       lcs->cs_next = cs->cs_next;
 234       cs->cs_next = lastcs->cs_next;
 235       lastcs->cs_next = cs;
 236     }
 237   }
 238
 239   /*
 240    * Make sure that only what we expect to change changed. The first line of
 241    * the `if' checks the IP protocol version, header length & type of
 242    * service.  The 2nd line checks the "Don't fragment" bit. The 3rd line
 243    * checks the time-to-live and protocol (the protocol check is unnecessary
 244    * but costless).  The 4th line checks the TCP header length.  The 5th line
 245    * checks IP options, if any.  The 6th line checks TCP options, if any.  If
 246    * any of these things are different between the previous & current
 247    * datagram, we send the 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   if (hlen > m->m_len)
 254     return (TYPE_IP);
 255
 256   if (((u_short *) ip)[0] != ((u_short *) & cs->cs_ip)[0] ||
 257       ((u_short *) ip)[3] != ((u_short *) & cs->cs_ip)[3] ||
 258       ((u_short *) ip)[4] != ((u_short *) & cs->cs_ip)[4] ||
 259       THOFFSET(th) != THOFFSET(oth) ||
 260       (deltaS > 5 &&
 261        memcmp(ip + 1, &cs->cs_ip + 1, (deltaS - 5) << 2)) ||
 262       (THOFFSET(th) > 5 &&
 263        memcmp(th + 1, oth + 1, (THOFFSET(th) - 5) << 2))) {
 264     goto uncompressed;
 265   }
 266
 267   /*
 268    * Figure out which of the changing fields changed.  The receiver expects
 269    * changes in the order: urgent, window, ack, seq (the order minimizes the
 270    * number of temporaries needed in this section of code).
 271    */
 272   if (th->th_flags & TH_URG) {
 273     deltaS = ntohs(th->th_urp);
 274     ENCODEZ(deltaS);
 275     changes |= NEW_U;
 276   } else if (th->th_urp != oth->th_urp) {
 277
 278     /*
 279      * argh! URG not set but urp changed -- a sensible implementation should
 280      * never do this but RFC793 doesn't prohibit the change so we have to
 281      * deal with it.
 282      */
 283     goto uncompressed;
 284   }
 285   deltaS = (u_short) (ntohs(th->th_win) - ntohs(oth->th_win));
 286   if (deltaS) {
 287     ENCODE(deltaS);
 288     changes |= NEW_W;
 289   }
 290   deltaA = ntohl(th->th_ack) - ntohl(oth->th_ack);
 291   if (deltaA) {
 292     if (deltaA > 0xffff) {
 293       goto uncompressed;
 294     }
 295     ENCODE(deltaA);
 296     changes |= NEW_A;
 297   }
 298   deltaS = ntohl(th->th_seq) - ntohl(oth->th_seq);
 299   if (deltaS) {
 300     if (deltaS > 0xffff) {
 301       goto uncompressed;
 302     }
 303     ENCODE(deltaS);
 304     changes |= NEW_S;
 305   }
 306   switch (changes) {
 307
 308   case 0:
 309
 310     /*
 311      * Nothing changed. If this packet contains data and the last one didn't,
 312      * this is probably a data packet following an ack (normal on an
 313      * interactive connection) and we send it compressed.  Otherwise it's
 314      * probably a retransmit, retransmitted ack or window probe.  Send it
 315      * uncompressed in case the other side missed the compressed version.
 316      */
 317     if (ip->ip_len != cs->cs_ip.ip_len &&
 318         ntohs(cs->cs_ip.ip_len) == hlen)
 319       break;
 320
 321     /* FALLTHROUGH */
 322
 323   case SPECIAL_I:
 324   case SPECIAL_D:
 325
 326     /*
 327      * actual changes match one of our special case encodings -- send packet
 328      * uncompressed.
 329      */
 330     goto uncompressed;
 331
 332   case NEW_S | NEW_A:
 333     if (deltaS == deltaA &&
 334         deltaS == ntohs(cs->cs_ip.ip_len) - hlen) {
 335       /* special case for echoed terminal traffic */
 336       changes = SPECIAL_I;
 337       cp = new_seq;
 338     }
 339     break;
 340
 341   case NEW_S:
 342     if (deltaS == ntohs(cs->cs_ip.ip_len) - hlen) {
 343       /* special case for data xfer */
 344       changes = SPECIAL_D;
 345       cp = new_seq;
 346     }
 347     break;
 348   }
 349
 350   deltaS = ntohs(ip->ip_id) - ntohs(cs->cs_ip.ip_id);
 351   if (deltaS != 1) {
 352     ENCODEZ(deltaS);
 353     changes |= NEW_I;
 354   }
 355   if (th->th_flags & TH_PUSH)
 356     changes |= TCP_PUSH_BIT;
 357
 358   /*
 359    * Grab the cksum before we overwrite it below.  Then update our state with
 360    * this packet's header.
 361    */
 362   deltaA = ntohs(th->th_sum);
 363   memcpy(&cs->cs_ip, ip, hlen);
 364
 365   /*
 366    * We want to use the original packet as our compressed packet. (cp -
 367    * new_seq) is the number of bytes we need for compressed sequence numbers.
 368    * In addition we need one byte for the change mask, one for the connection
 369    * id and two for the tcp checksum. So, (cp - new_seq) + 4 bytes of header
 370    * are needed.  hlen is how many bytes of the original packet to toss so
 371    * subtract the two to get the new packet size.
 372    */
 373   deltaS = cp - new_seq;
 374   cp = (u_char *) ip;
 375
 376   /*
 377    * Since fastq traffic can jump ahead of the background traffic, we don't
 378    * know what order packets will go on the line.  In this case, we always
 379    * send a "new" connection id so the receiver state stays synchronized.
 380    */
 381   if (comp->last_xmit == cs->cs_id && compress_cid) {
 382     hlen -= deltaS + 3;
 383     cp += hlen;
 384     *cp++ = changes;
 385   } else {
 386     comp->last_xmit = cs->cs_id;
 387     hlen -= deltaS + 4;
 388     cp += hlen;
 389     *cp++ = changes | NEW_C;
 390     *cp++ = cs->cs_id;
 391   }
 392   m->m_len -= hlen;
 393   m->m_offset += hlen;
 394   *cp++ = deltaA >> 8;
 395   *cp++ = deltaA;
 396   memcpy(cp, new_seq, deltaS);
 397   slstat->sls_compressed++;
 398   return (TYPE_COMPRESSED_TCP);
 399
 400   /*
 401    * Update connection state cs & send uncompressed packet ('uncompressed'
 402    * means a regular ip/tcp packet but with the 'conversation id' we hope to
 403    * use on future compressed packets in the protocol field).
 404    */
 405 uncompressed:
 406   memcpy(&cs->cs_ip, ip, hlen);
 407   ip->ip_p = cs->cs_id;
 408   comp->last_xmit = cs->cs_id;
 409   return (TYPE_UNCOMPRESSED_TCP);
 410 }
 411
 412
 413 int
 414 sl_uncompress_tcp(u_char ** bufp, int len, u_int type, struct slcompress *comp,
 415                   struct slstat *slstat, int max_state)
 416 {
 417   u_char *cp;
 418   u_int hlen, changes;
 419   struct tcphdr *th;
 420   struct cstate *cs;
 421   struct ip *ip;
 422   u_short *bp;
 423
 424   switch (type) {
 425
 426   case TYPE_UNCOMPRESSED_TCP:
 427     ip = (struct ip *) * bufp;
 428     if (ip->ip_p > max_state)
 429       goto bad;
 430     cs = &comp->rstate[comp->last_recv = ip->ip_p];
 431     comp->flags &= ~SLF_TOSS;
 432     ip->ip_p = IPPROTO_TCP;
 433
 434     /*
 435      * Calculate the size of the TCP/IP header and make sure that we don't
 436      * overflow the space we have available for it.
 437      */
 438     hlen = ip->ip_hl << 2;
 439     if ((int)(hlen + sizeof(struct tcphdr)) > len)
 440       goto bad;
 441     th = (struct tcphdr *) & ((char *) ip)[hlen];
 442     hlen += THOFFSET(th) << 2;
 443     if (hlen > MAX_HDR)
 444       goto bad;
 445     memcpy(&cs->cs_ip, ip, hlen);
 446     cs->cs_hlen = hlen;
 447     slstat->sls_uncompressedin++;
 448     return (len);
 449
 450   default:
 451     goto bad;
 452
 453   case TYPE_COMPRESSED_TCP:
 454     break;
 455   }
 456
 457   /* We've got a compressed packet. */
 458   slstat->sls_compressedin++;
 459   cp = *bufp;
 460   changes = *cp++;
 461   log_Printf(LogDEBUG, "compressed: changes = %02x\n", changes);
 462
 463   if (changes & NEW_C) {
 464     /*
 465      * Make sure the state index is in range, then grab the state. If we have
 466      * a good state index, clear the 'discard' flag.
 467      */
 468     if (*cp > max_state || comp->last_recv == 255)
 469       goto bad;
 470
 471     comp->flags &= ~SLF_TOSS;
 472     comp->last_recv = *cp++;
 473   } else {
 474     /*
 475      * this packet has an implicit state index.  If we've had a line error
 476      * since the last time we got an explicit state index, we have to toss
 477      * the packet.
 478      */
 479     if (comp->flags & SLF_TOSS) {
 480       slstat->sls_tossed++;
 481       return (0);
 482     }
 483   }
 484   cs = &comp->rstate[comp->last_recv];
 485   hlen = cs->cs_ip.ip_hl << 2;
 486   th = (struct tcphdr *) & ((u_char *) & cs->cs_ip)[hlen];
 487   th->th_sum = htons((*cp << 8) | cp[1]);
 488   cp += 2;
 489   if (changes & TCP_PUSH_BIT)
 490     th->th_flags |= TH_PUSH;
 491   else
 492     th->th_flags &= ~TH_PUSH;
 493
 494   switch (changes & SPECIALS_MASK) {
 495   case SPECIAL_I:
 496     {
 497       u_int i;
 498
 499       i = ntohs(cs->cs_ip.ip_len) - cs->cs_hlen;
 500       th->th_ack = htonl(ntohl(th->th_ack) + i);
 501       th->th_seq = htonl(ntohl(th->th_seq) + i);
 502     }
 503     break;
 504
 505   case SPECIAL_D:
 506     th->th_seq = htonl(ntohl(th->th_seq) + ntohs(cs->cs_ip.ip_len)
 507                        - cs->cs_hlen);
 508     break;
 509
 510   default:
 511     if (changes & NEW_U) {
 512       th->th_flags |= TH_URG;
 513       DECODEU(th->th_urp)
 514     } else
 515       th->th_flags &= ~TH_URG;
 516     if (changes & NEW_W)
 517       DECODES(th->th_win)
 518         if (changes & NEW_A)
 519         DECODEL(th->th_ack)
 520           if (changes & NEW_S) {
 521           log_Printf(LogDEBUG, "NEW_S: %02x, %02x, %02x\n",
 522                     *cp, cp[1], cp[2]);
 523           DECODEL(th->th_seq)
 524         }
 525     break;
 526   }
 527   if (changes & NEW_I) {
 528     DECODES(cs->cs_ip.ip_id)
 529   } else
 530     cs->cs_ip.ip_id = htons(ntohs(cs->cs_ip.ip_id) + 1);
 531
 532   log_Printf(LogDEBUG, "Uncompress: id = %04x, seq = %08lx\n",
 533             cs->cs_ip.ip_id, (u_long)ntohl(th->th_seq));
 534
 535   /*
 536    * At this point, cp points to the first byte of data in the packet.
 537    * Back up cp by the tcp/ip header length to make room for the
 538    * reconstructed header (we assume the packet we were handed has enough
 539    * space to prepend 128 bytes of header).  Adjust the length to account
 540    * for the new header & fill in the IP total length.
 541    */
 542   len -= (cp - *bufp);
 543   if (len < 0)
 544     /*
 545      * we must have dropped some characters (crc should detect this but the
 546      * old slip framing won't)
 547      */
 548     goto bad;
 549
 550   *bufp = cp - cs->cs_hlen;
 551   len += cs->cs_hlen;
 552   cs->cs_ip.ip_len = htons(len);
 553
 554   /* recompute the ip header checksum */
 555   cs->cs_ip.ip_sum = 0;
 556   bp = (u_short *)&cs->cs_ip;
 557   for (changes = 0; hlen > 0; hlen -= 2)
 558     changes += *bp++;
 559   changes = (changes & 0xffff) + (changes >> 16);
 560   changes = (changes & 0xffff) + (changes >> 16);
 561   cs->cs_ip.ip_sum = ~changes;
 562
 563   /* And copy the result into our buffer */
 564   memcpy(*bufp, &cs->cs_ip, cs->cs_hlen);
 565
 566   return (len);
 567 bad:
 568   comp->flags |= SLF_TOSS;
 569   slstat->sls_errorin++;
 570   return (0);
 571 }
 572
 573 int
 574 sl_Show(struct cmdargs const *arg)
 575 {
 576   prompt_Printf(arg->prompt, "VJ compression statistics:\n");
 577   prompt_Printf(arg->prompt, "  Out:  %d (compress) / %d (total)",
 578                 arg->bundle->ncp.ipcp.vj.slstat.sls_compressed,
 579                 arg->bundle->ncp.ipcp.vj.slstat.sls_packets);
 580   prompt_Printf(arg->prompt, "  %d (miss) / %d (search)\n",
 581                 arg->bundle->ncp.ipcp.vj.slstat.sls_misses,
 582                 arg->bundle->ncp.ipcp.vj.slstat.sls_searches);
 583   prompt_Printf(arg->prompt, "  In:  %d (compress), %d (uncompress)",
 584                 arg->bundle->ncp.ipcp.vj.slstat.sls_compressedin,
 585                 arg->bundle->ncp.ipcp.vj.slstat.sls_uncompressedin);
 586   prompt_Printf(arg->prompt, "  %d (error),  %d (tossed)\n",
 587                 arg->bundle->ncp.ipcp.vj.slstat.sls_errorin,
 588                 arg->bundle->ncp.ipcp.vj.slstat.sls_tossed);
 589   return 0;
 590 }