/* * 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. * * $Id: slcompress.c,v 1.15.2.11 1998/05/01 19:25:59 brian Exp $ * * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989: * - Initial distribution. */ #include #include #include #include #include #include #include #include #include #include "command.h" #include "mbuf.h" #include "log.h" #include "defs.h" #include "slcompress.h" #include "descriptor.h" #include "prompt.h" #include "timer.h" #include "fsm.h" #include "throughput.h" #include "iplist.h" #include "ipcp.h" #include "filter.h" #include "lqr.h" #include "hdlc.h" #include "lcp.h" #include "ccp.h" #include "link.h" #include "mp.h" #include "bundle.h" void sl_compress_init(struct slcompress * comp, int max_state) { register u_int i; register struct cstate *tstate = comp->tstate; memset(comp, '\0', sizeof *comp); for (i = max_state; i > 0; --i) { tstate[i].cs_id = i; tstate[i].cs_next = &tstate[i - 1]; } tstate[0].cs_next = &tstate[max_state]; tstate[0].cs_id = 0; comp->last_cs = &tstate[0]; comp->last_recv = 255; comp->last_xmit = 255; comp->flags = SLF_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) {\ (f) = htonl(ntohl(f) + ((cp[1] << 8) | cp[2])); \ cp += 3; \ } else { \ (f) = htonl(ntohl(f) + (u_long)*cp++); \ } \ } #define DECODES(f) { \ if (*cp == 0) {\ (f) = htons(ntohs(f) + ((cp[1] << 8) | cp[2])); \ cp += 3; \ } else { \ (f) = htons(ntohs(f) + (u_long)*cp++); \ } \ } #define DECODEU(f) { \ if (*cp == 0) {\ (f) = htons((cp[1] << 8) | cp[2]); \ cp += 3; \ } else { \ (f) = htons((u_long)*cp++); \ } \ } u_char sl_compress_tcp(struct mbuf * m, struct ip * ip, struct slcompress *comp, struct slstat *slstat, int compress_cid) { register struct cstate *cs = comp->last_cs->cs_next; register u_int hlen = ip->ip_hl; register struct tcphdr *oth; register struct tcphdr *th; register u_int deltaS, deltaA; register u_int changes = 0; u_char new_seq[16]; register u_char *cp = new_seq; /* * 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). (We assume that * the caller has already made sure the packet is IP proto TCP). */ if ((ip->ip_off & htons(0x3fff)) || m->cnt < 40) { log_Printf(LogDEBUG, "??? 1 ip_off = %x, cnt = %d\n", ip->ip_off, m->cnt); log_DumpBp(LogDEBUG, "", m); return (TYPE_IP); } th = (struct tcphdr *) & ((int *) ip)[hlen]; if ((th->th_flags & (TH_SYN | TH_FIN | TH_RST | TH_ACK)) != TH_ACK) { log_Printf(LogDEBUG, "??? 2 th_flags = %x\n", th->th_flags); log_DumpBp(LogDEBUG, "", m); 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. */ slstat->sls_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 || *(int *) th != ((int *) &cs->cs_ip)[cs->cs_ip.ip_hl]) { /* * 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; slstat->sls_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 && *(int *) th == ((int *) &cs->cs_ip)[cs->cs_ip.ip_hl]) 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. */ slstat->sls_misses++; comp->last_cs = lcs; #define THOFFSET(th) (th->th_off) hlen += th->th_off; hlen <<= 2; if (hlen > m->cnt) 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; } } /* * 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'. */ oth = (struct tcphdr *) & ((int *) &cs->cs_ip)[hlen]; deltaS = hlen; hlen += th->th_off; hlen <<= 2; if (hlen > m->cnt) return (TYPE_IP); 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] || THOFFSET(th) != THOFFSET(oth) || (deltaS > 5 && memcmp(ip + 1, &cs->cs_ip + 1, (deltaS - 5) << 2)) || (THOFFSET(th) > 5 && memcmp(th + 1, oth + 1, (THOFFSET(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 & TH_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; } deltaS = (u_short) (ntohs(th->th_win) - ntohs(oth->th_win)); if (deltaS) { ENCODE(deltaS); changes |= NEW_W; } deltaA = ntohl(th->th_ack) - ntohl(oth->th_ack); if (deltaA) { if (deltaA > 0xffff) { goto uncompressed; } ENCODE(deltaA); changes |= NEW_A; } deltaS = ntohl(th->th_seq) - ntohl(oth->th_seq); if (deltaS) { if (deltaS > 0xffff) { goto uncompressed; } 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 = ntohs(ip->ip_id) - ntohs(cs->cs_ip.ip_id); if (deltaS != 1) { ENCODEZ(deltaS); changes |= NEW_I; } if (th->th_flags & TH_PUSH) 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); memcpy(&cs->cs_ip, 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 = cp - new_seq; cp = (u_char *) ip; /* * Since fastq traffic can jump ahead of the background traffic, we don't * know what order packets will go on the line. In this case, we always * send a "new" connection id so the receiver state stays synchronized. */ if (comp->last_xmit == cs->cs_id && compress_cid) { hlen -= deltaS + 3; cp += hlen; *cp++ = changes; } else { comp->last_xmit = cs->cs_id; hlen -= deltaS + 4; cp += hlen; *cp++ = changes | NEW_C; *cp++ = cs->cs_id; } m->cnt -= hlen; m->offset += hlen; *cp++ = deltaA >> 8; *cp++ = deltaA; memcpy(cp, new_seq, deltaS); slstat->sls_compressed++; return (TYPE_COMPRESSED_TCP); /* * Update connection state cs & send uncompressed packet ('uncompressed' * means a regular ip/tcp packet but with the 'conversation id' we hope to * use on future compressed packets in the protocol field). */ uncompressed: memcpy(&cs->cs_ip, ip, hlen); ip->ip_p = cs->cs_id; comp->last_xmit = cs->cs_id; return (TYPE_UNCOMPRESSED_TCP); } int sl_uncompress_tcp(u_char ** bufp, int len, u_int type, struct slcompress *comp, struct slstat *slstat) { register u_char *cp; register u_int hlen, changes; register struct tcphdr *th; register struct cstate *cs; register struct ip *ip; switch (type) { case TYPE_UNCOMPRESSED_TCP: ip = (struct ip *) * bufp; if (ip->ip_p >= MAX_VJ_STATES) goto bad; cs = &comp->rstate[comp->last_recv = ip->ip_p]; comp->flags &= ~SLF_TOSS; ip->ip_p = IPPROTO_TCP; /* * Calculate the size of the TCP/IP header and make sure that we don't * overflow the space we have available for it. */ hlen = ip->ip_hl << 2; if (hlen + sizeof(struct tcphdr) > len) goto bad; th = (struct tcphdr *) & ((char *) ip)[hlen]; hlen += THOFFSET(th) << 2; if (hlen > MAX_HDR) goto bad; memcpy(&cs->cs_ip, ip, hlen); cs->cs_ip.ip_sum = 0; cs->cs_hlen = hlen; slstat->sls_uncompressedin++; return (len); default: goto bad; case TYPE_COMPRESSED_TCP: break; } /* We've got a compressed packet. */ slstat->sls_compressedin++; cp = *bufp; changes = *cp++; log_Printf(LogDEBUG, "compressed: changes = %02x\n", changes); 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_VJ_STATES || comp->last_recv == 255) goto bad; comp->flags &= ~SLF_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 & SLF_TOSS) { slstat->sls_tossed++; return (0); } } cs = &comp->rstate[comp->last_recv]; hlen = cs->cs_ip.ip_hl << 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 |= TH_PUSH; else th->th_flags &= ~TH_PUSH; switch (changes & SPECIALS_MASK) { case SPECIAL_I: { register u_int i = ntohs(cs->cs_ip.ip_len) - cs->cs_hlen; th->th_ack = htonl(ntohl(th->th_ack) + i); th->th_seq = htonl(ntohl(th->th_seq) + i); } break; case SPECIAL_D: th->th_seq = htonl(ntohl(th->th_seq) + ntohs(cs->cs_ip.ip_len) - cs->cs_hlen); break; default: if (changes & NEW_U) { th->th_flags |= TH_URG; DECODEU(th->th_urp) } else th->th_flags &= ~TH_URG; if (changes & NEW_W) DECODES(th->th_win) if (changes & NEW_A) DECODEL(th->th_ack) if (changes & NEW_S) { log_Printf(LogDEBUG, "NEW_S: %02x, %02x, %02x\n", *cp, cp[1], cp[2]); DECODEL(th->th_seq) } break; } if (changes & NEW_I) { DECODES(cs->cs_ip.ip_id) } else cs->cs_ip.ip_id = htons(ntohs(cs->cs_ip.ip_id) + 1); log_Printf(LogDEBUG, "Uncompress: id = %04x, seq = %08lx\n", cs->cs_ip.ip_id, (u_long)ntohl(th->th_seq)); /* * At this point, cp points to the first byte of data in the packet. If * we're not aligned on a 4-byte boundary, copy the data down so the ip & * tcp headers will be aligned. Then back up cp by the tcp/ip header * length to make room for the reconstructed header (we assume the packet * we were handed has enough space to prepend 128 bytes of header). Adjust * the length to account for the new header & fill in the IP total length. */ len -= (cp - *bufp); if (len < 0) /* * we must have dropped some characters (crc should detect this but the * old slip framing won't) */ goto bad; #ifdef notdef if ((int) cp & 3) { if (len > 0) (void) bcopy(cp, (caddr_t) ((int) cp & ~3), len); cp = (u_char *) ((int) cp & ~3); } #endif cp -= cs->cs_hlen; len += cs->cs_hlen; cs->cs_ip.ip_len = htons(len); memcpy(cp, &cs->cs_ip, cs->cs_hlen); *bufp = cp; /* recompute the ip header checksum */ { register u_short *bp = (u_short *) cp; for (changes = 0; hlen > 0; hlen -= 2) changes += *bp++; changes = (changes & 0xffff) + (changes >> 16); changes = (changes & 0xffff) + (changes >> 16); ((struct ip *) cp)->ip_sum = ~changes; } return (len); bad: comp->flags |= SLF_TOSS; slstat->sls_errorin++; return (0); } int sl_Show(struct cmdargs const *arg) { prompt_Printf(arg->prompt, "VJ compression statistics:\n"); prompt_Printf(arg->prompt, " Out: %d (compress) / %d (total)", arg->bundle->ncp.ipcp.vj.slstat.sls_compressed, arg->bundle->ncp.ipcp.vj.slstat.sls_packets); prompt_Printf(arg->prompt, " %d (miss) / %d (search)\n", arg->bundle->ncp.ipcp.vj.slstat.sls_misses, arg->bundle->ncp.ipcp.vj.slstat.sls_searches); prompt_Printf(arg->prompt, " In: %d (compress), %d (uncompress)", arg->bundle->ncp.ipcp.vj.slstat.sls_compressedin, arg->bundle->ncp.ipcp.vj.slstat.sls_uncompressedin); prompt_Printf(arg->prompt, " %d (error), %d (tossed)\n", arg->bundle->ncp.ipcp.vj.slstat.sls_errorin, arg->bundle->ncp.ipcp.vj.slstat.sls_tossed); return 0; }