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_ 54typedef 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 91void 92vj_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 171u_int 172vj_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 */ 425void 426vj_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 */ 436int 437vj_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 */ 474int 475vj_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} 592