/* * Routines to compress and uncompess tcp packets (for transmission * over low speed serial lines. * * Copyright (c) 1989 Regents of the University of California. * All rights reserved. * * Redistribution and use in source and binary forms are permitted * provided that the above copyright notice and this paragraph are * duplicated in all such forms and that any documentation, * advertising materials, and other materials related to such * distribution and use acknowledge that the software was developed * by the University of California, Berkeley. The name of the * University may not be used to endorse or promote products derived * from this software without specific prior written permission. * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE. * * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989: * - Initial distribution. * * Modified June 1993 by Paul Mackerras, paulus@cs.anu.edu.au, * so that the entire packet being decompressed doesn't have * to be in contiguous memory (just the compressed header). * * Modified March 1998 by Guy Lancaster, glanca@gesn.com, * for a 16 bit processor. */ #include "ppp.h" #include "vj.h" #include "pppdebug.h" #if VJ_SUPPORT > 0 #ifdef LINK_STATS #define INCR(counter) ++comp->stats.counter #else #define INCR(counter) #endif #if defined(NO_CHAR_BITFIELDS) #define getip_hl(base) ((base).ip_hl_v&0xf) #define getth_off(base) (((base).th_x2_off&0xf0)>>4) #else #define getip_hl(base) ((base).ip_hl) #define getth_off(base) ((base).th_off) #endif void vj_compress_init(struct vjcompress *comp) { register u_int i; register struct cstate *tstate = comp->tstate; #if MAX_SLOTS == 0 memset((char *)comp, 0, sizeof(*comp)); #endif comp->maxSlotIndex = MAX_SLOTS - 1; comp->compressSlot = 0; /* Disable slot ID compression by default. */ for (i = MAX_SLOTS - 1; i > 0; --i) { tstate[i].cs_id = i; tstate[i].cs_next = &tstate[i - 1]; } tstate[0].cs_next = &tstate[MAX_SLOTS - 1]; tstate[0].cs_id = 0; comp->last_cs = &tstate[0]; comp->last_recv = 255; comp->last_xmit = 255; comp->flags = VJF_TOSS; } /* ENCODE encodes a number that is known to be non-zero. ENCODEZ * checks for zero (since zero has to be encoded in the long, 3 byte * form). */ #define ENCODE(n) { \ if ((u_short)(n) >= 256) { \ *cp++ = 0; \ cp[1] = (n); \ cp[0] = (n) >> 8; \ cp += 2; \ } else { \ *cp++ = (n); \ } \ } #define ENCODEZ(n) { \ if ((u_short)(n) >= 256 || (u_short)(n) == 0) { \ *cp++ = 0; \ cp[1] = (n); \ cp[0] = (n) >> 8; \ cp += 2; \ } else { \ *cp++ = (n); \ } \ } #define DECODEL(f) { \ if (*cp == 0) {\ u32_t tmp = ntohl(f) + ((cp[1] << 8) | cp[2]); \ (f) = htonl(tmp); \ cp += 3; \ } else { \ u32_t tmp = ntohl(f) + (u32_t)*cp++; \ (f) = htonl(tmp); \ } \ } #define DECODES(f) { \ if (*cp == 0) {\ u_short tmp = ntohs(f) + (((u_short)cp[1] << 8) | cp[2]); \ (f) = htons(tmp); \ cp += 3; \ } else { \ u_short tmp = ntohs(f) + (u_short)*cp++; \ (f) = htons(tmp); \ } \ } #define DECODEU(f) { \ if (*cp == 0) {\ (f) = htons(((u_short)cp[1] << 8) | cp[2]); \ cp += 3; \ } else { \ (f) = htons((u_short)*cp++); \ } \ } /* * vj_compress_tcp - Attempt to do Van Jacobsen header compression on a * packet. This assumes that nb and comp are not null and that the first * buffer of the chain contains a valid IP header. * Return the VJ type code indicating whether or not the packet was * compressed. */ u_int vj_compress_tcp( struct vjcompress *comp, struct pbuf *pb ) { register struct ip *ip = (struct ip *)pb->payload; register struct cstate *cs = comp->last_cs->cs_next; register u_short hlen = getip_hl(*ip); register struct tcphdr *oth; register struct tcphdr *th; register u_short deltaS, deltaA; register u_long deltaL; register u_int changes = 0; u_char new_seq[16]; register u_char *cp = new_seq; /* * Check that the packet is IP proto TCP. */ if (ip->ip_p != IPPROTO_TCP) return (TYPE_IP); /* * Bail if this is an IP fragment or if the TCP packet isn't * `compressible' (i.e., ACK isn't set or some other control bit is * set). */ if ((ip->ip_off & htons(0x3fff)) || pb->tot_len < 40) return (TYPE_IP); th = (struct tcphdr *)&((long *)ip)[hlen]; if ((th->th_flags & (TCP_SYN|TCP_FIN|TCP_RST|TCP_ACK)) != TCP_ACK) return (TYPE_IP); /* * Packet is compressible -- we're going to send either a * COMPRESSED_TCP or UNCOMPRESSED_TCP packet. Either way we need * to locate (or create) the connection state. Special case the * most recently used connection since it's most likely to be used * again & we don't have to do any reordering if it's used. */ INCR(vjs_packets); if (ip->ip_src.s_addr != cs->cs_ip.ip_src.s_addr || ip->ip_dst.s_addr != cs->cs_ip.ip_dst.s_addr || *(long *)th != ((long *)&cs->cs_ip)[getip_hl(cs->cs_ip)]) { /* * Wasn't the first -- search for it. * * States are kept in a circularly linked list with * last_cs pointing to the end of the list. The * list is kept in lru order by moving a state to the * head of the list whenever it is referenced. Since * the list is short and, empirically, the connection * we want is almost always near the front, we locate * states via linear search. If we don't find a state * for the datagram, the oldest state is (re-)used. */ register struct cstate *lcs; register struct cstate *lastcs = comp->last_cs; do { lcs = cs; cs = cs->cs_next; INCR(vjs_searches); if (ip->ip_src.s_addr == cs->cs_ip.ip_src.s_addr && ip->ip_dst.s_addr == cs->cs_ip.ip_dst.s_addr && *(long *)th == ((long *)&cs->cs_ip)[getip_hl(cs->cs_ip)]) goto found; } while (cs != lastcs); /* * Didn't find it -- re-use oldest cstate. Send an * uncompressed packet that tells the other side what * connection number we're using for this conversation. * Note that since the state list is circular, the oldest * state points to the newest and we only need to set * last_cs to update the lru linkage. */ INCR(vjs_misses); comp->last_cs = lcs; hlen += getth_off(*th); hlen <<= 2; /* Check that the IP/TCP headers are contained in the first buffer. */ if (hlen > pb->len) return (TYPE_IP); goto uncompressed; found: /* * Found it -- move to the front on the connection list. */ if (cs == lastcs) comp->last_cs = lcs; else { lcs->cs_next = cs->cs_next; cs->cs_next = lastcs->cs_next; lastcs->cs_next = cs; } } oth = (struct tcphdr *)&((long *)&cs->cs_ip)[hlen]; deltaS = hlen; hlen += getth_off(*th); hlen <<= 2; /* Check that the IP/TCP headers are contained in the first buffer. */ if (hlen > pb->len) { PPPDEBUG((LOG_INFO, "vj_compress_tcp: header len %d spans buffers\n", hlen)); return (TYPE_IP); } /* * Make sure that only what we expect to change changed. The first * line of the `if' checks the IP protocol version, header length & * type of service. The 2nd line checks the "Don't fragment" bit. * The 3rd line checks the time-to-live and protocol (the protocol * check is unnecessary but costless). The 4th line checks the TCP * header length. The 5th line checks IP options, if any. The 6th * line checks TCP options, if any. If any of these things are * different between the previous & current datagram, we send the * current datagram `uncompressed'. */ if (((u_short *)ip)[0] != ((u_short *)&cs->cs_ip)[0] || ((u_short *)ip)[3] != ((u_short *)&cs->cs_ip)[3] || ((u_short *)ip)[4] != ((u_short *)&cs->cs_ip)[4] || getth_off(*th) != getth_off(*oth) || (deltaS > 5 && BCMP(ip + 1, &cs->cs_ip + 1, (deltaS - 5) << 2)) || (getth_off(*th) > 5 && BCMP(th + 1, oth + 1, (getth_off(*th) - 5) << 2))) goto uncompressed; /* * Figure out which of the changing fields changed. The * receiver expects changes in the order: urgent, window, * ack, seq (the order minimizes the number of temporaries * needed in this section of code). */ if (th->th_flags & TCP_URG) { deltaS = ntohs(th->th_urp); ENCODEZ(deltaS); changes |= NEW_U; } else if (th->th_urp != oth->th_urp) /* argh! URG not set but urp changed -- a sensible * implementation should never do this but RFC793 * doesn't prohibit the change so we have to deal * with it. */ goto uncompressed; if ((deltaS = (u_short)(ntohs(th->th_win) - ntohs(oth->th_win))) != 0) { ENCODE(deltaS); changes |= NEW_W; } if ((deltaL = ntohl(th->th_ack) - ntohl(oth->th_ack)) != 0) { if (deltaL > 0xffff) goto uncompressed; deltaA = (u_short)deltaL; ENCODE(deltaA); changes |= NEW_A; } if ((deltaL = ntohl(th->th_seq) - ntohl(oth->th_seq)) != 0) { if (deltaL > 0xffff) goto uncompressed; deltaS = (u_short)deltaL; ENCODE(deltaS); changes |= NEW_S; } switch(changes) { case 0: /* * Nothing changed. If this packet contains data and the * last one didn't, this is probably a data packet following * an ack (normal on an interactive connection) and we send * it compressed. Otherwise it's probably a retransmit, * retransmitted ack or window probe. Send it uncompressed * in case the other side missed the compressed version. */ if (ip->ip_len != cs->cs_ip.ip_len && ntohs(cs->cs_ip.ip_len) == hlen) break; /* (fall through) */ case SPECIAL_I: case SPECIAL_D: /* * actual changes match one of our special case encodings -- * send packet uncompressed. */ goto uncompressed; case NEW_S|NEW_A: if (deltaS == deltaA && deltaS == ntohs(cs->cs_ip.ip_len) - hlen) { /* special case for echoed terminal traffic */ changes = SPECIAL_I; cp = new_seq; } break; case NEW_S: if (deltaS == ntohs(cs->cs_ip.ip_len) - hlen) { /* special case for data xfer */ changes = SPECIAL_D; cp = new_seq; } break; } deltaS = (u_short)(ntohs(ip->ip_id) - ntohs(cs->cs_ip.ip_id)); if (deltaS != 1) { ENCODEZ(deltaS); changes |= NEW_I; } if (th->th_flags & TCP_PSH) changes |= TCP_PUSH_BIT; /* * Grab the cksum before we overwrite it below. Then update our * state with this packet's header. */ deltaA = ntohs(th->th_sum); BCOPY(ip, &cs->cs_ip, hlen); /* * We want to use the original packet as our compressed packet. * (cp - new_seq) is the number of bytes we need for compressed * sequence numbers. In addition we need one byte for the change * mask, one for the connection id and two for the tcp checksum. * So, (cp - new_seq) + 4 bytes of header are needed. hlen is how * many bytes of the original packet to toss so subtract the two to * get the new packet size. */ deltaS = (u_short)(cp - new_seq); if (!comp->compressSlot || comp->last_xmit != cs->cs_id) { comp->last_xmit = cs->cs_id; hlen -= deltaS + 4; pbuf_header(pb, -hlen); cp = (u_char *)pb->payload; *cp++ = changes | NEW_C; *cp++ = cs->cs_id; } else { hlen -= deltaS + 3; pbuf_header(pb, -hlen); cp = (u_char *)pb->payload; *cp++ = changes; } *cp++ = deltaA >> 8; *cp++ = deltaA; BCOPY(new_seq, cp, deltaS); INCR(vjs_compressed); return (TYPE_COMPRESSED_TCP); /* * Update connection state cs & send uncompressed packet (that is, * a regular ip/tcp packet but with the 'conversation id' we hope * to use on future compressed packets in the protocol field). */ uncompressed: BCOPY(ip, &cs->cs_ip, hlen); ip->ip_p = cs->cs_id; comp->last_xmit = cs->cs_id; return (TYPE_UNCOMPRESSED_TCP); } /* * Called when we may have missed a packet. */ void vj_uncompress_err(struct vjcompress *comp) { comp->flags |= VJF_TOSS; INCR(vjs_errorin); } /* * "Uncompress" a packet of type TYPE_UNCOMPRESSED_TCP. * Return 0 on success, -1 on failure. */ int vj_uncompress_uncomp( struct pbuf *nb, struct vjcompress *comp ) { register u_int hlen; register struct cstate *cs; register struct ip *ip; ip = (struct ip *)nb->payload; hlen = getip_hl(*ip) << 2; if (ip->ip_p >= MAX_SLOTS || hlen + sizeof(struct tcphdr) > nb->len || (hlen += getth_off(*((struct tcphdr *)&((char *)ip)[hlen])) << 2) > nb->len || hlen > MAX_HDR) { PPPDEBUG((LOG_INFO, "vj_uncompress_uncomp: bad cid=%d, hlen=%d buflen=%d\n", ip->ip_p, hlen, nb->len)); comp->flags |= VJF_TOSS; INCR(vjs_errorin); return -1; } cs = &comp->rstate[comp->last_recv = ip->ip_p]; comp->flags &=~ VJF_TOSS; ip->ip_p = IPPROTO_TCP; BCOPY(ip, &cs->cs_ip, hlen); cs->cs_hlen = hlen; INCR(vjs_uncompressedin); return 0; } /* * Uncompress a packet of type TYPE_COMPRESSED_TCP. * The packet is composed of a buffer chain and the first buffer * must contain an accurate chain length. * The first buffer must include the entire compressed TCP/IP header. * This procedure replaces the compressed header with the uncompressed * header and returns the length of the VJ header. */ int vj_uncompress_tcp( struct pbuf **nb, struct vjcompress *comp ) { u_char *cp; struct tcphdr *th; struct cstate *cs; u_short *bp; struct pbuf *n0 = *nb; u32_t tmp; u_int vjlen, hlen, changes; INCR(vjs_compressedin); cp = (u_char *)n0->payload; changes = *cp++; if (changes & NEW_C) { /* * Make sure the state index is in range, then grab the state. * If we have a good state index, clear the 'discard' flag. */ if (*cp >= MAX_SLOTS) { PPPDEBUG((LOG_INFO, "vj_uncompress_tcp: bad cid=%d\n", *cp)); goto bad; } comp->flags &=~ VJF_TOSS; comp->last_recv = *cp++; } else { /* * this packet has an implicit state index. If we've * had a line error since the last time we got an * explicit state index, we have to toss the packet. */ if (comp->flags & VJF_TOSS) { PPPDEBUG((LOG_INFO, "vj_uncompress_tcp: tossing\n")); INCR(vjs_tossed); return (-1); } } cs = &comp->rstate[comp->last_recv]; hlen = getip_hl(cs->cs_ip) << 2; th = (struct tcphdr *)&((u_char *)&cs->cs_ip)[hlen]; th->th_sum = htons((*cp << 8) | cp[1]); cp += 2; if (changes & TCP_PUSH_BIT) th->th_flags |= TCP_PSH; else th->th_flags &=~ TCP_PSH; switch (changes & SPECIALS_MASK) { case SPECIAL_I: { register u32_t i = ntohs(cs->cs_ip.ip_len) - cs->cs_hlen; /* some compilers can't nest inline assembler.. */ tmp = ntohl(th->th_ack) + i; th->th_ack = htonl(tmp); tmp = ntohl(th->th_seq) + i; th->th_seq = htonl(tmp); } break; case SPECIAL_D: /* some compilers can't nest inline assembler.. */ tmp = ntohl(th->th_seq) + ntohs(cs->cs_ip.ip_len) - cs->cs_hlen; th->th_seq = htonl(tmp); break; default: if (changes & NEW_U) { th->th_flags |= TCP_URG; DECODEU(th->th_urp); } else th->th_flags &=~ TCP_URG; if (changes & NEW_W) DECODES(th->th_win); if (changes & NEW_A) DECODEL(th->th_ack); if (changes & NEW_S) DECODEL(th->th_seq); break; } if (changes & NEW_I) { DECODES(cs->cs_ip.ip_id); } else { cs->cs_ip.ip_id = ntohs(cs->cs_ip.ip_id) + 1; cs->cs_ip.ip_id = htons(cs->cs_ip.ip_id); } /* * At this point, cp points to the first byte of data in the * packet. Fill in the IP total length and update the IP * header checksum. */ vjlen = (u_short)(cp - (u_char*)n0->payload); if (n0->len < vjlen) { /* * We must have dropped some characters (crc should detect * this but the old slip framing won't) */ PPPDEBUG((LOG_INFO, "vj_uncompress_tcp: head buffer %d too short %d\n", n0->len, vjlen)); goto bad; } #if BYTE_ORDER == LITTLE_ENDIAN tmp = n0->tot_len - vjlen + cs->cs_hlen; cs->cs_ip.ip_len = htons(tmp); #else cs->cs_ip.ip_len = htons(n0->tot_len - vjlen + cs->cs_hlen); #endif /* recompute the ip header checksum */ bp = (u_short *) &cs->cs_ip; cs->cs_ip.ip_sum = 0; for (tmp = 0; hlen > 0; hlen -= 2) tmp += *bp++; tmp = (tmp & 0xffff) + (tmp >> 16); tmp = (tmp & 0xffff) + (tmp >> 16); cs->cs_ip.ip_sum = (u_short)(~tmp); /* Remove the compressed header and prepend the uncompressed header. */ pbuf_header(n0, -vjlen); if(pbuf_header(n0, cs->cs_hlen)) { struct pbuf *np; LWIP_ASSERT("vj_uncompress_tcp: cs->cs_hlen <= PBUF_POOL_BUFSIZE", cs->cs_hlen <= PBUF_POOL_BUFSIZE); np = pbuf_alloc(PBUF_RAW, cs->cs_hlen, PBUF_POOL); if(!np) { PPPDEBUG((LOG_WARNING, "vj_uncompress_tcp: prepend failed\n")); *nb = NULL; goto bad; } pbuf_chain(np, n0); n0 = np; } memcpy(n0->payload, &cs->cs_ip, cs->cs_hlen); *nb = n0; return vjlen; bad: comp->flags |= VJF_TOSS; INCR(vjs_errorin); return (-1); } #endif