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 MERCHANTIBILITY 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  * $DragonFly: src/usr.sbin/ppp/slcompress.c,v 1.3 2004/03/27 02:39:13 cpressey Exp $
  22  *
  23  *      Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
  24  *      - Initial distribution.
  25  */
  26
  27 #include <sys/param.h>
  28 #include <netinet/in_systm.h>
  29 #include <netinet/in.h>
  30 #include <netinet/tcp.h>
  31 #include <netinet/ip.h>
  32 #include <sys/socket.h>
  33 #include <sys/un.h>
  34
  35 #include <stdarg.h>
  36 #include <stdio.h>
  37 #include <string.h>
  38 #include <termios.h>
  39
  40 #include "layer.h"
  41 #include "defs.h"
  42 #include "command.h"
  43 #include "mbuf.h"
  44 #include "log.h"
  45 #include "slcompress.h"
  46 #include "descriptor.h"
  47 #include "prompt.h"
  48 #include "timer.h"
  49 #include "fsm.h"
  50 #include "throughput.h"
  51 #include "iplist.h"
  52 #include "lqr.h"
  53 #include "hdlc.h"
  54 #include "ncpaddr.h"
  55 #include "ipcp.h"
  56 #include "filter.h"
  57 #include "lcp.h"
  58 #include "ccp.h"
  59 #include "link.h"
  60 #include "mp.h"
  61 #ifndef NORADIUS
  62 #include "radius.h"
  63 #endif
  64 #include "ipv6cp.h"
  65 #include "ncp.h"
  66 #include "bundle.h"
  67
  68 void
  69 sl_compress_init(struct slcompress *comp, int max_state)
  70 {
  71   u_int i;
  72   struct cstate *tstate = comp->tstate;
  73
  74   memset(comp, '\0', sizeof *comp);
  75   for (i = max_state; i > 0; --i) {
  76     tstate[i].cs_id = i;
  77     tstate[i].cs_next = &tstate[i - 1];
  78   }
  79   tstate[0].cs_next = &tstate[max_state];
  80   tstate[0].cs_id = 0;
  81   comp->last_cs = &tstate[0];
  82   comp->last_recv = 255;
  83   comp->last_xmit = 255;
  84   comp->flags = SLF_TOSS;
  85 }
  86
  87
  88 /* ENCODE encodes a number that is known to be non-zero.  ENCODEZ
  89  * checks for zero (since zero has to be encoded in the 32-bit, 3 byte
  90  * form).
  91  */
  92 #define ENCODE(n) { \
  93         if ((u_short)(n) >= 256) { \
  94                 *cp++ = 0; \
  95                 cp[1] = (n); \
  96                 cp[0] = (n) >> 8; \
  97                 cp += 2; \
  98         } else { \
  99                 *cp++ = (n); \
 100         } \
 101 }
 102 #define ENCODEZ(n) { \
 103         if ((u_short)(n) >= 256 || (u_short)(n) == 0) { \
 104                 *cp++ = 0; \
 105                 cp[1] = (n); \
 106                 cp[0] = (n) >> 8; \
 107                 cp += 2; \
 108         } else { \
 109                 *cp++ = (n); \
 110         } \
 111 }
 112
 113 #define DECODEL(f) { \
 114         if (*cp == 0) {\
 115                 (f) = htonl(ntohl(f) + ((cp[1] << 8) | cp[2])); \
 116                 cp += 3; \
 117         } else { \
 118                 (f) = htonl(ntohl(f) + (u_int32_t)*cp++); \
 119         } \
 120 }
 121
 122 #define DECODES(f) { \
 123         if (*cp == 0) {\
 124                 (f) = htons(ntohs(f) + ((cp[1] << 8) | cp[2])); \
 125                 cp += 3; \
 126         } else { \
 127                 (f) = htons(ntohs(f) + (u_int32_t)*cp++); \
 128         } \
 129 }
 130
 131 #define DECODEU(f) { \
 132         if (*cp == 0) {\
 133                 (f) = htons((cp[1] << 8) | cp[2]); \
 134                 cp += 3; \
 135         } else { \
 136                 (f) = htons((u_int32_t)*cp++); \
 137         } \
 138 }
 139
 140
 141 u_char
 142 sl_compress_tcp(struct mbuf * m,
 143                 struct ip * ip,
 144                 struct slcompress *comp,
 145                 struct slstat *slstat,
 146                 int compress_cid)
 147 {
 148   struct cstate *cs = comp->last_cs->cs_next;
 149   u_int hlen = ip->ip_hl;
 150   struct tcphdr *oth;
 151   struct tcphdr *th;
 152   u_int deltaS, deltaA;
 153   u_int changes = 0;
 154   u_char new_seq[16];
 155   u_char *cp = new_seq;
 156
 157   /*
 158    * Bail if this is an IP fragment or if the TCP packet isn't `compressible'
 159    * (i.e., ACK isn't set or some other control bit is set).  (We assume that
 160    * the caller has already made sure the packet is IP proto TCP).
 161    */
 162   if ((ip->ip_off & htons(0x3fff)) || m->m_len < 40) {
 163     log_Printf(LogDEBUG, "??? 1 ip_off = %x, m_len = %lu\n",
 164               ip->ip_off, (unsigned long)m->m_len);
 165     log_DumpBp(LogDEBUG, "", m);
 166     return (TYPE_IP);
 167   }
 168   th = (struct tcphdr *) & ((int *) ip)[hlen];
 169   if ((th->th_flags & (TH_SYN | TH_FIN | TH_RST | TH_ACK)) != TH_ACK) {
 170     log_Printf(LogDEBUG, "??? 2 th_flags = %x\n", th->th_flags);
 171     log_DumpBp(LogDEBUG, "", m);
 172     return (TYPE_IP);
 173   }
 174
 175   /*
 176    * Packet is compressible -- we're going to send either a COMPRESSED_TCP or
 177    * UNCOMPRESSED_TCP packet.  Either way we need to locate (or create) the
 178    * connection state.  Special case the most recently used connection since
 179    * it's most likely to be used again & we don't have to do any reordering
 180    * if it's used.
 181    */
 182   slstat->sls_packets++;
 183   if (ip->ip_src.s_addr != cs->cs_ip.ip_src.s_addr ||
 184       ip->ip_dst.s_addr != cs->cs_ip.ip_dst.s_addr ||
 185       *(int *) th != ((int *) &cs->cs_ip)[cs->cs_ip.ip_hl]) {
 186
 187     /*
 188      * Wasn't the first -- search for it.
 189      *
 190      * States are kept in a circularly linked list with last_cs pointing to the
 191      * end of the list.  The list is kept in lru order by moving a state to
 192      * the head of the list whenever it is referenced.  Since the list is
 193      * short and, empirically, the connection we want is almost always near
 194      * the front, we locate states via linear search.  If we don't find a
 195      * state for the datagram, the oldest state is (re-)used.
 196      */
 197     struct cstate *lcs;
 198     struct cstate *lastcs = comp->last_cs;
 199
 200     do {
 201       lcs = cs;
 202       cs = cs->cs_next;
 203       slstat->sls_searches++;
 204       if (ip->ip_src.s_addr == cs->cs_ip.ip_src.s_addr
 205           && ip->ip_dst.s_addr == cs->cs_ip.ip_dst.s_addr
 206           && *(int *) th == ((int *) &cs->cs_ip)[cs->cs_ip.ip_hl])
 207         goto found;
 208     } while (cs != lastcs);
 209
 210     /*
 211      * Didn't find it -- re-use oldest cstate.  Send an uncompressed packet
 212      * that tells the other side what connection number we're using for this
 213      * conversation. Note that since the state list is circular, the oldest
 214      * state points to the newest and we only need to set last_cs to update
 215      * the lru linkage.
 216      */
 217     slstat->sls_misses++;
 218       comp->last_cs = lcs;
 219 #define THOFFSET(th)    (th->th_off)
 220     hlen += th->th_off;
 221     hlen <<= 2;
 222     if (hlen > m->m_len)
 223       return (TYPE_IP);
 224     goto uncompressed;
 225
 226 found:
 227
 228     /*
 229      * Found it -- move to the front on the connection list.
 230      */
 231     if (cs == lastcs)
 232       comp->last_cs = lcs;
 233     else {
 234       lcs->cs_next = cs->cs_next;
 235       cs->cs_next = lastcs->cs_next;
 236       lastcs->cs_next = cs;
 237     }
 238   }
 239
 240   /*
 241    * Make sure that only what we expect to change changed. The first line of
 242    * the `if' checks the IP protocol version, header length & type of
 243    * service.  The 2nd line checks the "Don't fragment" bit. The 3rd line
 244    * checks the time-to-live and protocol (the protocol check is unnecessary
 245    * but costless).  The 4th line checks the TCP header length.  The 5th line
 246    * checks IP options, if any.  The 6th line checks TCP options, if any.  If
 247    * any of these things are different between the previous & current
 248    * datagram, we send the current datagram `uncompressed'.
 249    */
 250   oth = (struct tcphdr *) & ((int *) &cs->cs_ip)[hlen];
 251   deltaS = hlen;
 252   hlen += th->th_off;
 253   hlen <<= 2;
 254   if (hlen > m->m_len)
 255     return (TYPE_IP);
 256
 257   if (((u_short *) ip)[0] != ((u_short *) & cs->cs_ip)[0] ||
 258       ((u_short *) ip)[3] != ((u_short *) & cs->cs_ip)[3] ||
 259       ((u_short *) ip)[4] != ((u_short *) & cs->cs_ip)[4] ||
 260       THOFFSET(th) != THOFFSET(oth) ||
 261       (deltaS > 5 &&
 262        memcmp(ip + 1, &cs->cs_ip + 1, (deltaS - 5) << 2)) ||
 263       (THOFFSET(th) > 5 &&
 264        memcmp(th + 1, oth + 1, (THOFFSET(th) - 5) << 2))) {
 265     goto uncompressed;
 266   }
 267
 268   /*
 269    * Figure out which of the changing fields changed.  The receiver expects
 270    * changes in the order: urgent, window, ack, seq (the order minimizes the
 271    * number of temporaries needed in this section of code).
 272    */
 273   if (th->th_flags & TH_URG) {
 274     deltaS = ntohs(th->th_urp);
 275     ENCODEZ(deltaS);
 276     changes |= NEW_U;
 277   } else if (th->th_urp != oth->th_urp) {
 278
 279     /*
 280      * argh! URG not set but urp changed -- a sensible implementation should
 281      * never do this but RFC793 doesn't prohibit the change so we have to
 282      * deal with it.
 283      */
 284     goto uncompressed;
 285   }
 286   deltaS = (u_short) (ntohs(th->th_win) - ntohs(oth->th_win));
 287   if (deltaS) {
 288     ENCODE(deltaS);
 289     changes |= NEW_W;
 290   }
 291   deltaA = ntohl(th->th_ack) - ntohl(oth->th_ack);
 292   if (deltaA) {
 293     if (deltaA > 0xffff) {
 294       goto uncompressed;
 295     }
 296     ENCODE(deltaA);
 297     changes |= NEW_A;
 298   }
 299   deltaS = ntohl(th->th_seq) - ntohl(oth->th_seq);
 300   if (deltaS) {
 301     if (deltaS > 0xffff) {
 302       goto uncompressed;
 303     }
 304     ENCODE(deltaS);
 305     changes |= NEW_S;
 306   }
 307   switch (changes) {
 308
 309   case 0:
 310
 311     /*
 312      * Nothing changed. If this packet contains data and the last one didn't,
 313      * this is probably a data packet following an ack (normal on an
 314      * interactive connection) and we send it compressed.  Otherwise it's
 315      * probably a retransmit, retransmitted ack or window probe.  Send it
 316      * uncompressed in case the other side missed the compressed version.
 317      */
 318     if (ip->ip_len != cs->cs_ip.ip_len &&
 319         ntohs(cs->cs_ip.ip_len) == hlen)
 320       break;
 321
 322     /* FALLTHROUGH */
 323
 324   case SPECIAL_I:
 325   case SPECIAL_D:
 326
 327     /*
 328      * actual changes match one of our special case encodings -- send packet
 329      * uncompressed.
 330      */
 331     goto uncompressed;
 332
 333   case NEW_S | NEW_A:
 334     if (deltaS == deltaA &&
 335         deltaS == ntohs(cs->cs_ip.ip_len) - hlen) {
 336       /* special case for echoed terminal traffic */
 337       changes = SPECIAL_I;
 338       cp = new_seq;
 339     }
 340     break;
 341
 342   case NEW_S:
 343     if (deltaS == ntohs(cs->cs_ip.ip_len) - hlen) {
 344       /* special case for data xfer */
 345       changes = SPECIAL_D;
 346       cp = new_seq;
 347     }
 348     break;
 349   }
 350
 351   deltaS = ntohs(ip->ip_id) - ntohs(cs->cs_ip.ip_id);
 352   if (deltaS != 1) {
 353     ENCODEZ(deltaS);
 354     changes |= NEW_I;
 355   }
 356   if (th->th_flags & TH_PUSH)
 357     changes |= TCP_PUSH_BIT;
 358
 359   /*
 360    * Grab the cksum before we overwrite it below.  Then update our state with
 361    * this packet's header.
 362    */
 363   deltaA = ntohs(th->th_sum);
 364   memcpy(&cs->cs_ip, ip, hlen);
 365
 366   /*
 367    * We want to use the original packet as our compressed packet. (cp -
 368    * new_seq) is the number of bytes we need for compressed sequence numbers.
 369    * In addition we need one byte for the change mask, one for the connection
 370    * id and two for the tcp checksum. So, (cp - new_seq) + 4 bytes of header
 371    * are needed.  hlen is how many bytes of the original packet to toss so
 372    * subtract the two to get the new packet size.
 373    */
 374   deltaS = cp - new_seq;
 375   cp = (u_char *) ip;
 376
 377   /*
 378    * Since fastq traffic can jump ahead of the background traffic, we don't
 379    * know what order packets will go on the line.  In this case, we always
 380    * send a "new" connection id so the receiver state stays synchronized.
 381    */
 382   if (comp->last_xmit == cs->cs_id && compress_cid) {
 383     hlen -= deltaS + 3;
 384     cp += hlen;
 385     *cp++ = changes;
 386   } else {
 387     comp->last_xmit = cs->cs_id;
 388     hlen -= deltaS + 4;
 389     cp += hlen;
 390     *cp++ = changes | NEW_C;
 391     *cp++ = cs->cs_id;
 392   }
 393   m->m_len -= hlen;
 394   m->m_offset += hlen;
 395   *cp++ = deltaA >> 8;
 396   *cp++ = deltaA;
 397   memcpy(cp, new_seq, deltaS);
 398   slstat->sls_compressed++;
 399   return (TYPE_COMPRESSED_TCP);
 400
 401   /*
 402    * Update connection state cs & send uncompressed packet ('uncompressed'
 403    * means a regular ip/tcp packet but with the 'conversation id' we hope to
 404    * use on future compressed packets in the protocol field).
 405    */
 406 uncompressed:
 407   memcpy(&cs->cs_ip, ip, hlen);
 408   ip->ip_p = cs->cs_id;
 409   comp->last_xmit = cs->cs_id;
 410   return (TYPE_UNCOMPRESSED_TCP);
 411 }
 412
 413
 414 int
 415 sl_uncompress_tcp(u_char ** bufp, int len, u_int type, struct slcompress *comp,
 416                   struct slstat *slstat, int max_state)
 417 {
 418   u_char *cp;
 419   u_int hlen, changes;
 420   struct tcphdr *th;
 421   struct cstate *cs;
 422   struct ip *ip;
 423   u_short *bp;
 424
 425   switch (type) {
 426
 427   case TYPE_UNCOMPRESSED_TCP:
 428     ip = (struct ip *) * bufp;
 429     if (ip->ip_p > max_state)
 430       goto bad;
 431     cs = &comp->rstate[comp->last_recv = ip->ip_p];
 432     comp->flags &= ~SLF_TOSS;
 433     ip->ip_p = IPPROTO_TCP;
 434
 435     /*
 436      * Calculate the size of the TCP/IP header and make sure that we don't
 437      * overflow the space we have available for it.
 438      */
 439     hlen = ip->ip_hl << 2;
 440     if (hlen + sizeof(struct tcphdr) > len)
 441       goto bad;
 442     th = (struct tcphdr *) & ((char *) ip)[hlen];
 443     hlen += THOFFSET(th) << 2;
 444     if (hlen > MAX_HDR)
 445       goto bad;
 446     memcpy(&cs->cs_ip, ip, hlen);
 447     cs->cs_hlen = hlen;
 448     slstat->sls_uncompressedin++;
 449     return (len);
 450
 451   default:
 452     goto bad;
 453
 454   case TYPE_COMPRESSED_TCP:
 455     break;
 456   }
 457
 458   /* We've got a compressed packet. */
 459   slstat->sls_compressedin++;
 460   cp = *bufp;
 461   changes = *cp++;
 462   log_Printf(LogDEBUG, "compressed: changes = %02x\n", changes);
 463
 464   if (changes & NEW_C) {
 465     /*
 466      * Make sure the state index is in range, then grab the state. If we have
 467      * a good state index, clear the 'discard' flag.
 468      */
 469     if (*cp > max_state || comp->last_recv == 255)
 470       goto bad;
 471
 472     comp->flags &= ~SLF_TOSS;
 473     comp->last_recv = *cp++;
 474   } else {
 475     /*
 476      * this packet has an implicit state index.  If we've had a line error
 477      * since the last time we got an explicit state index, we have to toss
 478      * the packet.
 479      */
 480     if (comp->flags & SLF_TOSS) {
 481       slstat->sls_tossed++;
 482       return (0);
 483     }
 484   }
 485   cs = &comp->rstate[comp->last_recv];
 486   hlen = cs->cs_ip.ip_hl << 2;
 487   th = (struct tcphdr *) & ((u_char *) & cs->cs_ip)[hlen];
 488   th->th_sum = htons((*cp << 8) | cp[1]);
 489   cp += 2;
 490   if (changes & TCP_PUSH_BIT)
 491     th->th_flags |= TH_PUSH;
 492   else
 493     th->th_flags &= ~TH_PUSH;
 494
 495   switch (changes & SPECIALS_MASK) {
 496   case SPECIAL_I:
 497     {
 498       u_int i;
 499
 500       i = ntohs(cs->cs_ip.ip_len) - cs->cs_hlen;
 501       th->th_ack = htonl(ntohl(th->th_ack) + i);
 502       th->th_seq = htonl(ntohl(th->th_seq) + i);
 503     }
 504     break;
 505
 506   case SPECIAL_D:
 507     th->th_seq = htonl(ntohl(th->th_seq) + ntohs(cs->cs_ip.ip_len)
 508                        - cs->cs_hlen);
 509     break;
 510
 511   default:
 512     if (changes & NEW_U) {
 513       th->th_flags |= TH_URG;
 514       DECODEU(th->th_urp)
 515     } else
 516       th->th_flags &= ~TH_URG;
 517     if (changes & NEW_W)
 518       DECODES(th->th_win)
 519         if (changes & NEW_A)
 520         DECODEL(th->th_ack)
 521           if (changes & NEW_S) {
 522           log_Printf(LogDEBUG, "NEW_S: %02x, %02x, %02x\n",
 523                     *cp, cp[1], cp[2]);
 524           DECODEL(th->th_seq)
 525         }
 526     break;
 527   }
 528   if (changes & NEW_I) {
 529     DECODES(cs->cs_ip.ip_id)
 530   } else
 531     cs->cs_ip.ip_id = htons(ntohs(cs->cs_ip.ip_id) + 1);
 532
 533   log_Printf(LogDEBUG, "Uncompress: id = %04x, seq = %08lx\n",
 534             cs->cs_ip.ip_id, (u_long)ntohl(th->th_seq));
 535
 536   /*
 537    * At this point, cp points to the first byte of data in the packet.
 538    * Back up cp by the tcp/ip header length to make room for the
 539    * reconstructed header (we assume the packet we were handed has enough
 540    * space to prepend 128 bytes of header).  Adjust the length to account
 541    * for the new header & fill in the IP total length.
 542    */
 543   len -= (cp - *bufp);
 544   if (len < 0)
 545     /*
 546      * we must have dropped some characters (crc should detect this but the
 547      * old slip framing won't)
 548      */
 549     goto bad;
 550
 551   *bufp = cp - cs->cs_hlen;
 552   len += cs->cs_hlen;
 553   cs->cs_ip.ip_len = htons(len);
 554
 555   /* recompute the ip header checksum */
 556   cs->cs_ip.ip_sum = 0;
 557   bp = (u_short *)&cs->cs_ip;
 558   for (changes = 0; hlen > 0; hlen -= 2)
 559     changes += *bp++;
 560   changes = (changes & 0xffff) + (changes >> 16);
 561   changes = (changes & 0xffff) + (changes >> 16);
 562   cs->cs_ip.ip_sum = ~changes;
 563
 564   /* And copy the result into our buffer */
 565   memcpy(*bufp, &cs->cs_ip, cs->cs_hlen);
 566
 567   return (len);
 568 bad:
 569   comp->flags |= SLF_TOSS;
 570   slstat->sls_errorin++;
 571   return (0);
 572 }
 573
 574 int
 575 sl_Show(struct cmdargs const *arg)
 576 {
 577   prompt_Printf(arg->prompt, "VJ compression statistics:\n");
 578   prompt_Printf(arg->prompt, "  Out:  %d (compress) / %d (total)",
 579                 arg->bundle->ncp.ipcp.vj.slstat.sls_compressed,
 580                 arg->bundle->ncp.ipcp.vj.slstat.sls_packets);
 581   prompt_Printf(arg->prompt, "  %d (miss) / %d (search)\n",
 582                 arg->bundle->ncp.ipcp.vj.slstat.sls_misses,
 583                 arg->bundle->ncp.ipcp.vj.slstat.sls_searches);
 584   prompt_Printf(arg->prompt, "  In:  %d (compress), %d (uncompress)",
 585                 arg->bundle->ncp.ipcp.vj.slstat.sls_compressedin,
 586                 arg->bundle->ncp.ipcp.vj.slstat.sls_uncompressedin);
 587   prompt_Printf(arg->prompt, "  %d (error),  %d (tossed)\n",
 588                 arg->bundle->ncp.ipcp.vj.slstat.sls_errorin,
 589                 arg->bundle->ncp.ipcp.vj.slstat.sls_tossed);
 590   return 0;
 591 }