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Current File : //sys/net/slcompress.c |
/*- * Copyright (c) 1989, 1993, 1994 * The Regents of the University of California. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * @(#)slcompress.c 8.2 (Berkeley) 4/16/94 * $FreeBSD: release/9.1.0/sys/net/slcompress.c 128019 2004-04-07 20:46:16Z imp $ */ /* * Routines to compress and uncompess tcp packets (for transmission * over low speed serial lines. * * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989: * - Initial distribution. * */ #include <sys/param.h> #include <sys/mbuf.h> #include <sys/systm.h> #include <netinet/in.h> #include <netinet/in_systm.h> #include <netinet/ip.h> #include <netinet/tcp.h> #include <net/slcompress.h> #ifndef SL_NO_STATS #define INCR(counter) ++comp->counter; #else #define INCR(counter) #endif #define BCMP(p1, p2, n) bcmp((void *)(p1), (void *)(p2), (int)(n)) #define BCOPY(p1, p2, n) bcopy((void *)(p1), (void *)(p2), (int)(n)) void sl_compress_init(comp, max_state) struct slcompress *comp; int max_state; { register u_int i; register struct cstate *tstate = comp->tstate; if (max_state == -1) { max_state = MAX_STATES - 1; bzero((char *)comp, sizeof(*comp)); } else { /* Don't reset statistics */ bzero((char *)comp->tstate, sizeof(comp->tstate)); bzero((char *)comp->rstate, sizeof(comp->rstate)); } 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_int16_t)(n) >= 256) { \ *cp++ = 0; \ cp[1] = (n); \ cp[0] = (n) >> 8; \ cp += 2; \ } else { \ *cp++ = (n); \ } \ } #define ENCODEZ(n) { \ if ((u_int16_t)(n) >= 256 || (u_int16_t)(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_int32_t)*cp++); \ } \ } #define DECODES(f) { \ if (*cp == 0) {\ (f) = htons(ntohs(f) + ((cp[1] << 8) | cp[2])); \ cp += 3; \ } else { \ (f) = htons(ntohs(f) + (u_int32_t)*cp++); \ } \ } #define DECODEU(f) { \ if (*cp == 0) {\ (f) = htons((cp[1] << 8) | cp[2]); \ cp += 3; \ } else { \ (f) = htons((u_int32_t)*cp++); \ } \ } /* * Attempt to compress an outgoing TCP packet and return the type of * the result. The caller must have already verified that the protocol * is TCP. The first mbuf must contain the complete IP and TCP headers, * and "ip" must be == mtod(m, struct ip *). "comp" supplies the * compression state, and "compress_cid" tells us whether it is OK * to leave out the CID field when feasible. * * The caller is responsible for adjusting m->m_pkthdr.len upon return, * if m is an M_PKTHDR mbuf. */ u_int sl_compress_tcp(m, ip, comp, compress_cid) struct mbuf *m; register struct ip *ip; struct slcompress *comp; 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->m_len < 40) return (TYPE_IP); th = (struct tcphdr *)&((int32_t *)ip)[hlen]; if ((th->th_flags & (TH_SYN|TH_FIN|TH_RST|TH_ACK)) != TH_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(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 || *(int32_t *)th != ((int32_t *)&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; INCR(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 && *(int32_t *)th == ((int32_t *)&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. */ INCR(sls_misses) comp->last_cs = lcs; hlen += th->th_off; hlen <<= 2; if (hlen > m->m_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; } } /* * 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 *)&((int32_t *)&cs->cs_ip)[hlen]; deltaS = hlen; hlen += th->th_off; hlen <<= 2; if (hlen > m->m_len) return TYPE_IP; if (((u_int16_t *)ip)[0] != ((u_int16_t *)&cs->cs_ip)[0] || ((u_int16_t *)ip)[3] != ((u_int16_t *)&cs->cs_ip)[3] || ((u_int16_t *)ip)[4] != ((u_int16_t *)&cs->cs_ip)[4] || th->th_off != oth->th_off || (deltaS > 5 && BCMP(ip + 1, &cs->cs_ip + 1, (deltaS - 5) << 2)) || (th->th_off > 5 && BCMP(th + 1, oth + 1, (th->th_off - 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_int16_t)(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; /* FALLTHROUGH */ 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); 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 = cp - new_seq; cp = (u_char *)ip; if (compress_cid == 0 || comp->last_xmit != cs->cs_id) { comp->last_xmit = cs->cs_id; hlen -= deltaS + 4; cp += hlen; *cp++ = changes | NEW_C; *cp++ = cs->cs_id; } else { hlen -= deltaS + 3; cp += hlen; *cp++ = changes; } m->m_len -= hlen; m->m_data += hlen; *cp++ = deltaA >> 8; *cp++ = deltaA; BCOPY(new_seq, cp, deltaS); INCR(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: BCOPY(ip, &cs->cs_ip, hlen); ip->ip_p = cs->cs_id; comp->last_xmit = cs->cs_id; return (TYPE_UNCOMPRESSED_TCP); } int sl_uncompress_tcp(bufp, len, type, comp) u_char **bufp; int len; u_int type; struct slcompress *comp; { u_char *hdr, *cp; int hlen, vjlen; cp = bufp? *bufp: NULL; vjlen = sl_uncompress_tcp_core(cp, len, len, type, comp, &hdr, &hlen); if (vjlen < 0) return (0); /* error */ if (vjlen == 0) return (len); /* was uncompressed already */ cp += vjlen; len -= vjlen; /* * 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). */ if ((intptr_t)cp & 3) { if (len > 0) BCOPY(cp, ((intptr_t)cp &~ 3), len); cp = (u_char *)((intptr_t)cp &~ 3); } cp -= hlen; len += hlen; BCOPY(hdr, cp, hlen); *bufp = cp; return (len); } /* * Uncompress a packet of total length total_len. The first buflen * bytes are at buf; this must include the entire (compressed or * uncompressed) TCP/IP header. This procedure returns the length * of the VJ header, with a pointer to the uncompressed IP header * in *hdrp and its length in *hlenp. */ int sl_uncompress_tcp_core(buf, buflen, total_len, type, comp, hdrp, hlenp) u_char *buf; int buflen, total_len; u_int type; struct slcompress *comp; u_char **hdrp; u_int *hlenp; { register u_char *cp; register u_int hlen, changes; register struct tcphdr *th; register struct cstate *cs; register struct ip *ip; register u_int16_t *bp; register u_int vjlen; switch (type) { case TYPE_UNCOMPRESSED_TCP: ip = (struct ip *) buf; if (ip->ip_p >= MAX_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) > buflen) goto bad; hlen += ((struct tcphdr *)&((char *)ip)[hlen])->th_off << 2; if (hlen > MAX_HDR || hlen > buflen) goto bad; BCOPY(ip, &cs->cs_ip, hlen); cs->cs_hlen = hlen; INCR(sls_uncompressedin) *hdrp = (u_char *) &cs->cs_ip; *hlenp = hlen; return (0); default: goto bad; case TYPE_COMPRESSED_TCP: break; } /* We've got a compressed packet. */ INCR(sls_compressedin) cp = buf; 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_STATES) 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) { INCR(sls_tossed) return (-1); } } 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) 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); /* * 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 = cp - buf; buflen -= vjlen; if (buflen < 0) /* we must have dropped some characters (crc should detect * this but the old slip framing won't) */ goto bad; total_len += cs->cs_hlen - vjlen; cs->cs_ip.ip_len = htons(total_len); /* recompute the ip header checksum */ bp = (u_int16_t *) &cs->cs_ip; cs->cs_ip.ip_sum = 0; for (changes = 0; hlen > 0; hlen -= 2) changes += *bp++; changes = (changes & 0xffff) + (changes >> 16); changes = (changes & 0xffff) + (changes >> 16); cs->cs_ip.ip_sum = ~ changes; *hdrp = (u_char *) &cs->cs_ip; *hlenp = cs->cs_hlen; return vjlen; bad: comp->flags |= SLF_TOSS; INCR(sls_errorin) return (-1); }