1 /* $NetBSD: slcompress.c,v 1.38 2009/04/18 15:20:06 tsutsui Exp $ */ 2 /* Id: slcompress.c,v 1.3 1996/05/24 07:04:47 paulus Exp */ 3 4 /* 5 * Copyright (c) 1989, 1993, 1994 6 * The Regents of the University of California. All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * @(#)slcompress.c 8.2 (Berkeley) 4/16/94 33 */ 34 35 /* 36 * Routines to compress and uncompess tcp packets (for transmission 37 * over low speed serial lines. 38 * 39 * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989: 40 * - Initial distribution. 41 */ 42 43 #include <sys/cdefs.h> 44 __KERNEL_RCSID(0, "$NetBSD: slcompress.c,v 1.38 2009/04/18 15:20:06 tsutsui Exp $"); 45 46 #include "opt_inet.h" 47 #ifdef INET 48 #include <sys/param.h> 49 #include <sys/mbuf.h> 50 #include <sys/systm.h> 51 52 #include <netinet/in.h> 53 #include <netinet/in_systm.h> 54 #include <netinet/ip.h> 55 #include <netinet/tcp.h> 56 57 #include <net/slcompress.h> 58 59 #ifndef SL_NO_STATS 60 #define INCR(counter) ++comp->counter; 61 #else 62 #define INCR(counter) 63 #endif 64 65 66 void 67 sl_compress_init(struct slcompress *comp) 68 { 69 u_int i; 70 struct cstate *tstate = comp->tstate; 71 72 memset(comp, 0, sizeof(*comp)); 73 for (i = MAX_STATES - 1; i > 0; --i) { 74 tstate[i].cs_id = i; 75 tstate[i].cs_next = &tstate[i - 1]; 76 } 77 tstate[0].cs_next = &tstate[MAX_STATES - 1]; 78 tstate[0].cs_id = 0; 79 comp->last_cs = &tstate[0]; 80 comp->last_recv = 255; 81 comp->last_xmit = 255; 82 comp->flags = SLF_TOSS; 83 } 84 85 86 /* 87 * Like sl_compress_init, but we get to specify the maximum connection 88 * ID to use on transmission. 89 */ 90 void 91 sl_compress_setup(struct slcompress *comp, int max_state) 92 { 93 u_int i; 94 struct cstate *tstate = comp->tstate; 95 96 if (max_state == -1) { 97 max_state = MAX_STATES - 1; 98 memset(comp, 0, sizeof(*comp)); 99 } else { 100 /* Don't reset statistics */ 101 memset(comp->tstate, 0, sizeof(comp->tstate)); 102 memset(comp->rstate, 0, sizeof(comp->rstate)); 103 } 104 for (i = max_state; i > 0; --i) { 105 tstate[i].cs_id = i; 106 tstate[i].cs_next = &tstate[i - 1]; 107 } 108 tstate[0].cs_next = &tstate[max_state]; 109 tstate[0].cs_id = 0; 110 comp->last_cs = &tstate[0]; 111 comp->last_recv = 255; 112 comp->last_xmit = 255; 113 comp->flags = SLF_TOSS; 114 } 115 116 117 /* ENCODE encodes a number that is known to be non-zero. ENCODEZ 118 * checks for zero (since zero has to be encoded in the long, 3 byte 119 * form). 120 */ 121 #define ENCODE(n) { \ 122 if ((uint16_t)(n) >= 256) { \ 123 *cp++ = 0; \ 124 cp[1] = (n); \ 125 cp[0] = (n) >> 8; \ 126 cp += 2; \ 127 } else { \ 128 *cp++ = (n); \ 129 } \ 130 } 131 #define ENCODEZ(n) { \ 132 if ((uint16_t)(n) >= 256 || (uint16_t)(n) == 0) { \ 133 *cp++ = 0; \ 134 cp[1] = (n); \ 135 cp[0] = (n) >> 8; \ 136 cp += 2; \ 137 } else { \ 138 *cp++ = (n); \ 139 } \ 140 } 141 142 #define DECODEL(f) { \ 143 if (*cp == 0) {\ 144 (f) = htonl(ntohl(f) + ((cp[1] << 8) | cp[2])); \ 145 cp += 3; \ 146 } else { \ 147 (f) = htonl(ntohl(f) + (uint32_t)*cp++); \ 148 } \ 149 } 150 151 #define DECODES(f) { \ 152 if (*cp == 0) {\ 153 (f) = htons(ntohs(f) + ((cp[1] << 8) | cp[2])); \ 154 cp += 3; \ 155 } else { \ 156 (f) = htons(ntohs(f) + (uint32_t)*cp++); \ 157 } \ 158 } 159 160 #define DECODEU(f) { \ 161 if (*cp == 0) {\ 162 (f) = htons((cp[1] << 8) | cp[2]); \ 163 cp += 3; \ 164 } else { \ 165 (f) = htons((uint32_t)*cp++); \ 166 } \ 167 } 168 169 u_int 170 sl_compress_tcp(struct mbuf *m, struct ip *ip, struct slcompress *comp, 171 int compress_cid) 172 { 173 struct cstate *cs = comp->last_cs->cs_next; 174 u_int hlen = ip->ip_hl; 175 struct tcphdr *oth; 176 struct tcphdr *th; 177 u_int deltaS, deltaA; 178 u_int changes = 0; 179 u_char new_seq[16]; 180 u_char *cp = new_seq; 181 182 /* 183 * Bail if this is an IP fragment or if the TCP packet isn't 184 * `compressible' (i.e., ACK isn't set or some other control bit is 185 * set). (We assume that the caller has already made sure the 186 * packet is IP proto TCP). 187 */ 188 if ((ip->ip_off & htons(0x3fff)) || m->m_len < 40) 189 return (TYPE_IP); 190 191 th = (struct tcphdr *)&((int32_t *)ip)[hlen]; 192 if ((th->th_flags & (TH_SYN|TH_FIN|TH_RST|TH_ACK)) != TH_ACK) 193 return (TYPE_IP); 194 /* 195 * Packet is compressible -- we're going to send either a 196 * COMPRESSED_TCP or UNCOMPRESSED_TCP packet. Either way we need 197 * to locate (or create) the connection state. Special case the 198 * most recently used connection since it's most likely to be used 199 * again & we don't have to do any reordering if it's used. 200 */ 201 INCR(sls_packets) 202 if (ip->ip_src.s_addr != cs->cs_ip.ip_src.s_addr || 203 ip->ip_dst.s_addr != cs->cs_ip.ip_dst.s_addr || 204 *(int32_t *)th != ((int32_t *)&cs->cs_ip)[cs->cs_ip.ip_hl]) { 205 /* 206 * Wasn't the first -- search for it. 207 * 208 * States are kept in a circularly linked list with 209 * last_cs pointing to the end of the list. The 210 * list is kept in lru order by moving a state to the 211 * head of the list whenever it is referenced. Since 212 * the list is short and, empirically, the connection 213 * we want is almost always near the front, we locate 214 * states via linear search. If we don't find a state 215 * for the datagram, the oldest state is (re-)used. 216 */ 217 struct cstate *lcs; 218 struct cstate *lastcs = comp->last_cs; 219 220 do { 221 lcs = cs; cs = cs->cs_next; 222 INCR(sls_searches) 223 if (ip->ip_src.s_addr == cs->cs_ip.ip_src.s_addr 224 && ip->ip_dst.s_addr == cs->cs_ip.ip_dst.s_addr 225 && *(int32_t *)th == 226 ((int32_t *)&cs->cs_ip)[cs->cs_ip.ip_hl]) 227 goto found; 228 } while (cs != lastcs); 229 230 /* 231 * Didn't find it -- re-use oldest cstate. Send an 232 * uncompressed packet that tells the other side what 233 * connection number we're using for this conversation. 234 * Note that since the state list is circular, the oldest 235 * state points to the newest and we only need to set 236 * last_cs to update the lru linkage. 237 */ 238 INCR(sls_misses) 239 comp->last_cs = lcs; 240 hlen += th->th_off; 241 hlen <<= 2; 242 if (hlen > m->m_len) 243 return (TYPE_IP); 244 goto uncompressed; 245 246 found: 247 /* 248 * Found it -- move to the front on the connection list. 249 */ 250 if (cs == lastcs) 251 comp->last_cs = lcs; 252 else { 253 lcs->cs_next = cs->cs_next; 254 cs->cs_next = lastcs->cs_next; 255 lastcs->cs_next = cs; 256 } 257 } 258 259 /* 260 * Make sure that only what we expect to change changed. The first 261 * line of the `if' checks the IP protocol version, header length & 262 * type of service. The 2nd line checks the "Don't fragment" bit. 263 * The 3rd line checks the time-to-live and protocol (the protocol 264 * check is unnecessary but costless). The 4th line checks the TCP 265 * header length. The 5th line checks IP options, if any. The 6th 266 * line checks TCP options, if any. If any of these things are 267 * different between the previous & current datagram, we send the 268 * current datagram `uncompressed'. 269 */ 270 oth = (struct tcphdr *)&((int32_t *)&cs->cs_ip)[hlen]; 271 deltaS = hlen; 272 hlen += th->th_off; 273 hlen <<= 2; 274 if (hlen > m->m_len) 275 return (TYPE_IP); 276 277 if (((uint16_t *)ip)[0] != ((uint16_t *)&cs->cs_ip)[0] || 278 ((uint16_t *)ip)[3] != ((uint16_t *)&cs->cs_ip)[3] || 279 ((uint16_t *)ip)[4] != ((uint16_t *)&cs->cs_ip)[4] || 280 th->th_off != oth->th_off || 281 (deltaS > 5 && 282 memcmp(ip + 1, &cs->cs_ip + 1, (deltaS - 5) << 2)) || 283 (th->th_off > 5 && 284 memcmp(th + 1, oth + 1, (th->th_off - 5) << 2))) 285 goto uncompressed; 286 287 /* 288 * Figure out which of the changing fields changed. The 289 * receiver expects changes in the order: urgent, window, 290 * ack, seq (the order minimizes the number of temporaries 291 * needed in this section of code). 292 */ 293 if (th->th_flags & TH_URG) { 294 deltaS = ntohs(th->th_urp); 295 ENCODEZ(deltaS); 296 changes |= NEW_U; 297 } else if (th->th_urp != oth->th_urp) 298 /* argh! URG not set but urp changed -- a sensible 299 * implementation should never do this but RFC793 300 * doesn't prohibit the change so we have to deal 301 * with it. */ 302 goto uncompressed; 303 304 deltaS = (uint16_t)(ntohs(th->th_win) - ntohs(oth->th_win)); 305 if (deltaS) { 306 ENCODE(deltaS); 307 changes |= NEW_W; 308 } 309 310 deltaA = ntohl(th->th_ack) - ntohl(oth->th_ack); 311 if (deltaA) { 312 if (deltaA > 0xffff) 313 goto uncompressed; 314 ENCODE(deltaA); 315 changes |= NEW_A; 316 } 317 318 deltaS = ntohl(th->th_seq) - ntohl(oth->th_seq); 319 if (deltaS) { 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 && 353 deltaS == ntohs(cs->cs_ip.ip_len) - hlen) { 354 /* special case for echoed terminal traffic */ 355 changes = SPECIAL_I; 356 cp = new_seq; 357 } 358 break; 359 360 case NEW_S: 361 if (deltaS == ntohs(cs->cs_ip.ip_len) - hlen) { 362 /* special case for data xfer */ 363 changes = SPECIAL_D; 364 cp = new_seq; 365 } 366 break; 367 } 368 369 deltaS = ntohs(ip->ip_id) - ntohs(cs->cs_ip.ip_id); 370 if (deltaS != 1) { 371 ENCODEZ(deltaS); 372 changes |= NEW_I; 373 } 374 if (th->th_flags & TH_PUSH) 375 changes |= TCP_PUSH_BIT; 376 /* 377 * Grab the cksum before we overwrite it below. Then update our 378 * state with this packet's header. 379 */ 380 deltaA = ntohs(th->th_sum); 381 memcpy(&cs->cs_ip, ip, hlen); 382 383 /* 384 * We want to use the original packet as our compressed packet. 385 * (cp - new_seq) is the number of bytes we need for compressed 386 * sequence numbers. In addition we need one byte for the change 387 * mask, one for the connection id and two for the tcp checksum. 388 * So, (cp - new_seq) + 4 bytes of header are needed. hlen is how 389 * many bytes of the original packet to toss so subtract the two to 390 * get the new packet size. 391 */ 392 deltaS = cp - new_seq; 393 cp = (u_char *)ip; 394 if (compress_cid == 0 || comp->last_xmit != cs->cs_id) { 395 comp->last_xmit = cs->cs_id; 396 hlen -= deltaS + 4; 397 cp += hlen; 398 *cp++ = changes | NEW_C; 399 *cp++ = cs->cs_id; 400 } else { 401 hlen -= deltaS + 3; 402 cp += hlen; 403 *cp++ = changes; 404 } 405 m->m_len -= hlen; 406 m->m_data += hlen; 407 *cp++ = deltaA >> 8; 408 *cp++ = deltaA; 409 memcpy(cp, new_seq, deltaS); 410 INCR(sls_compressed) 411 return (TYPE_COMPRESSED_TCP); 412 413 /* 414 * Update connection state cs & send uncompressed packet ('uncompressed' 415 * means a regular ip/tcp packet but with the 'conversation id' we hope 416 * to use on future compressed packets in the protocol field). 417 */ 418 uncompressed: 419 memcpy(&cs->cs_ip, ip, hlen); 420 ip->ip_p = cs->cs_id; 421 comp->last_xmit = cs->cs_id; 422 return (TYPE_UNCOMPRESSED_TCP); 423 } 424 425 426 int 427 sl_uncompress_tcp(u_char **bufp, int len, u_int type, struct slcompress *comp) 428 { 429 u_char *hdr, *cp; 430 int vjlen; 431 u_int hlen; 432 433 cp = bufp ? *bufp : NULL; 434 vjlen = sl_uncompress_tcp_core(cp, len, len, type, comp, &hdr, &hlen); 435 if (vjlen < 0) 436 return (0); /* error */ 437 if (vjlen == 0) 438 return (len); /* was uncompressed already */ 439 440 cp += vjlen; 441 len -= vjlen; 442 443 /* 444 * At this point, cp points to the first byte of data in the 445 * packet. If we're not aligned on a 4-byte boundary, copy the 446 * data down so the ip & tcp headers will be aligned. Then back up 447 * cp by the tcp/ip header length to make room for the reconstructed 448 * header (we assume the packet we were handed has enough space to 449 * prepend 128 bytes of header). 450 */ 451 if ((long)cp & 3) { 452 if (len > 0) 453 memmove((void *)((long)cp &~ 3), cp, len); 454 cp = (u_char *)((long)cp &~ 3); 455 } 456 cp -= hlen; 457 len += hlen; 458 memcpy(cp, hdr, hlen); 459 460 *bufp = cp; 461 return (len); 462 } 463 464 /* 465 * Uncompress a packet of total length total_len. The first buflen 466 * bytes are at buf; this must include the entire (compressed or 467 * uncompressed) TCP/IP header. This procedure returns the length 468 * of the VJ header, with a pointer to the uncompressed IP header 469 * in *hdrp and its length in *hlenp. 470 */ 471 int 472 sl_uncompress_tcp_core(u_char *buf, int buflen, int total_len, u_int type, 473 struct slcompress *comp, u_char **hdrp, u_int *hlenp) 474 { 475 u_char *cp; 476 u_int hlen, changes; 477 struct tcphdr *th; 478 struct cstate *cs; 479 struct ip *ip; 480 uint16_t *bp; 481 u_int vjlen; 482 483 switch (type) { 484 485 case TYPE_UNCOMPRESSED_TCP: 486 if (buf == NULL) 487 goto bad; 488 ip = (struct ip *) buf; 489 if (ip->ip_p >= MAX_STATES) 490 goto bad; 491 cs = &comp->rstate[comp->last_recv = ip->ip_p]; 492 comp->flags &=~ SLF_TOSS; 493 ip->ip_p = IPPROTO_TCP; 494 /* 495 * Calculate the size of the TCP/IP header and make sure that 496 * we don't overflow the space we have available for it. 497 */ 498 hlen = ip->ip_hl << 2; 499 if (hlen + sizeof(struct tcphdr) > buflen) 500 goto bad; 501 hlen += ((struct tcphdr *)&((char *)ip)[hlen])->th_off << 2; 502 if (hlen > MAX_HDR || hlen > buflen) 503 goto bad; 504 memcpy(&cs->cs_ip, ip, hlen); 505 cs->cs_hlen = hlen; 506 INCR(sls_uncompressedin) 507 *hdrp = (u_char *) &cs->cs_ip; 508 *hlenp = hlen; 509 return (0); 510 511 default: 512 goto bad; 513 514 case TYPE_COMPRESSED_TCP: 515 break; 516 } 517 /* We've got a compressed packet. */ 518 INCR(sls_compressedin) 519 if (buf == NULL) 520 goto bad; 521 cp = buf; 522 changes = *cp++; 523 if (changes & NEW_C) { 524 /* Make sure the state index is in range, then grab the state. 525 * If we have a good state index, clear the 'discard' flag. */ 526 if (*cp >= MAX_STATES) 527 goto bad; 528 529 comp->flags &=~ SLF_TOSS; 530 comp->last_recv = *cp++; 531 } else { 532 /* this packet has an implicit state index. If we've 533 * had a line error since the last time we got an 534 * explicit state index, we have to toss the packet. */ 535 if (comp->flags & SLF_TOSS) { 536 INCR(sls_tossed) 537 return (-1); 538 } 539 } 540 cs = &comp->rstate[comp->last_recv]; 541 hlen = cs->cs_ip.ip_hl << 2; 542 th = (struct tcphdr *)&((u_char *)&cs->cs_ip)[hlen]; 543 th->th_sum = htons((*cp << 8) | cp[1]); 544 cp += 2; 545 if (changes & TCP_PUSH_BIT) 546 th->th_flags |= TH_PUSH; 547 else 548 th->th_flags &=~ TH_PUSH; 549 550 switch (changes & SPECIALS_MASK) { 551 case SPECIAL_I: 552 { 553 u_int i = ntohs(cs->cs_ip.ip_len) - cs->cs_hlen; 554 th->th_ack = htonl(ntohl(th->th_ack) + i); 555 th->th_seq = htonl(ntohl(th->th_seq) + i); 556 } 557 break; 558 559 case SPECIAL_D: 560 th->th_seq = htonl(ntohl(th->th_seq) + ntohs(cs->cs_ip.ip_len) 561 - cs->cs_hlen); 562 break; 563 564 default: 565 if (changes & NEW_U) { 566 th->th_flags |= TH_URG; 567 DECODEU(th->th_urp) 568 } else 569 th->th_flags &=~ TH_URG; 570 if (changes & NEW_W) 571 DECODES(th->th_win) 572 if (changes & NEW_A) 573 DECODEL(th->th_ack) 574 if (changes & NEW_S) 575 DECODEL(th->th_seq) 576 break; 577 } 578 if (changes & NEW_I) { 579 DECODES(cs->cs_ip.ip_id) 580 } else 581 cs->cs_ip.ip_id = htons(ntohs(cs->cs_ip.ip_id) + 1); 582 583 /* 584 * At this point, cp points to the first byte of data in the 585 * packet. Fill in the IP total length and update the IP 586 * header checksum. 587 */ 588 vjlen = cp - buf; 589 buflen -= vjlen; 590 if (buflen < 0) 591 /* we must have dropped some characters (crc should detect 592 * this but the old slip framing won't) */ 593 goto bad; 594 595 total_len += cs->cs_hlen - vjlen; 596 cs->cs_ip.ip_len = htons(total_len); 597 598 /* recompute the ip header checksum */ 599 bp = (uint16_t *) &cs->cs_ip; 600 cs->cs_ip.ip_sum = 0; 601 for (changes = 0; hlen > 0; hlen -= 2) 602 changes += *bp++; 603 changes = (changes & 0xffff) + (changes >> 16); 604 changes = (changes & 0xffff) + (changes >> 16); 605 cs->cs_ip.ip_sum = ~ changes; 606 607 *hdrp = (u_char *) &cs->cs_ip; 608 *hlenp = cs->cs_hlen; 609 return vjlen; 610 611 bad: 612 comp->flags |= SLF_TOSS; 613 INCR(sls_errorin) 614 return (-1); 615 } 616 #endif 617