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 01:39:13 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 } 592