--- /dev/null
+/*
+ * 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).
+ */
+
+/*
+ * This version is used under SunOS 4.x, DEC Alpha OSF/1, AIX 4.x,
+ * and SVR4 systems including Solaris 2.
+ *
+ * $Id: vjcompress.c,v 1.1 1995/12/18 03:30:20 paulus Exp $
+ */
+
+#include <sys/types.h>
+#include <sys/param.h>
+
+#ifdef __svr4__
+#ifndef __GNUC__
+#include <sys/byteorder.h> /* for ntohl, etc. */
+#else
+/* make sure we don't get the gnu "fixed" one! */
+#include "/usr/include/sys/byteorder.h"
+#endif
+#endif
+
+#ifdef __osf__
+#include <net/net_globals.h>
+#endif
+#include <netinet/in.h>
+
+#ifdef __aix4__
+#define _NETINET_IN_SYSTM_H_
+typedef u_long n_long;
+#else
+#include <netinet/in_systm.h>
+#endif
+
+#include <netinet/ip.h>
+#include <netinet/tcp.h>
+
+#include <net/ppp_defs.h>
+#include <net/vjcompress.h>
+
+#ifndef VJ_NO_STATS
+#define INCR(counter) ++comp->stats.counter
+#else
+#define INCR(counter)
+#endif
+
+#define BCMP(p1, p2, n) bcmp((char *)(p1), (char *)(p2), (int)(n))
+#undef BCOPY
+#define BCOPY(p1, p2, n) bcopy((char *)(p1), (char *)(p2), (int)(n))
+#ifndef KERNEL
+#define ovbcopy bcopy
+#endif
+
+#ifdef __osf__
+#define getip_hl(base) (((base).ip_vhl)&0xf)
+#define getth_off(base) ((((base).th_xoff)&0xf0)>>4)
+
+#else
+#define getip_hl(base) ((base).ip_hl)
+#define getth_off(base) ((base).th_off)
+#endif
+
+void
+vj_compress_init(comp, max_state)
+ struct vjcompress *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));
+ 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 = 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) {\
+ u_int32_t tmp = ntohl(f) + ((cp[1] << 8) | cp[2]); \
+ (f) = htonl(tmp); \
+ cp += 3; \
+ } else { \
+ u_int32_t tmp = ntohl(f) + (u_int32_t)*cp++; \
+ (f) = htonl(tmp); \
+ } \
+}
+
+#define DECODES(f) { \
+ if (*cp == 0) {\
+ u_short tmp = ntohs(f) + ((cp[1] << 8) | cp[2]); \
+ (f) = htons(tmp); \
+ cp += 3; \
+ } else { \
+ u_short tmp = ntohs(f) + (u_int32_t)*cp++; \
+ (f) = htons(tmp); \
+ } \
+}
+
+#define DECODEU(f) { \
+ if (*cp == 0) {\
+ (f) = htons((cp[1] << 8) | cp[2]); \
+ cp += 3; \
+ } else { \
+ (f) = htons((u_int32_t)*cp++); \
+ } \
+}
+
+u_int
+vj_compress_tcp(ip, mlen, comp, compress_cid, vjhdrp)
+ register struct ip *ip;
+ u_int mlen;
+ struct vjcompress *comp;
+ int compress_cid;
+ u_char **vjhdrp;
+{
+ register struct cstate *cs = comp->last_cs->cs_next;
+ register u_int hlen = getip_hl(*ip);
+ 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)) || mlen < 40)
+ return (TYPE_IP);
+
+ th = (struct tcphdr *)&((int *)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(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 ||
+ *(int *)th != ((int *)&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
+ && *(int *)th == ((int *)&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;
+ if (hlen > mlen)
+ 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 += getth_off(*th);
+ hlen <<= 2;
+ if (hlen > mlen)
+ 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] ||
+ 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 & 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;
+
+ if (deltaS = (u_short)(ntohs(th->th_win) - ntohs(oth->th_win))) {
+ ENCODE(deltaS);
+ changes |= NEW_W;
+ }
+
+ if (deltaA = ntohl(th->th_ack) - ntohl(oth->th_ack)) {
+ if (deltaA > 0xffff)
+ goto uncompressed;
+ ENCODE(deltaA);
+ changes |= NEW_A;
+ }
+
+ if (deltaS = ntohl(th->th_seq) - ntohl(oth->th_seq)) {
+ 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);
+ 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;
+ *vjhdrp = (cp += hlen);
+ *cp++ = changes | NEW_C;
+ *cp++ = cs->cs_id;
+ } else {
+ hlen -= deltaS + 3;
+ *vjhdrp = (cp += hlen);
+ *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(comp)
+ struct vjcompress *comp;
+{
+ comp->flags |= VJF_TOSS;
+ INCR(vjs_errorin);
+}
+
+/*
+ * "Uncompress" a packet of type TYPE_UNCOMPRESSED_TCP.
+ */
+int
+vj_uncompress_uncomp(buf, comp)
+ u_char *buf;
+ struct vjcompress *comp;
+{
+ register u_int hlen;
+ register struct cstate *cs;
+ register struct ip *ip;
+
+ ip = (struct ip *) buf;
+ if (ip->ip_p >= MAX_STATES) {
+ comp->flags |= VJF_TOSS;
+ INCR(vjs_errorin);
+ return (0);
+ }
+ cs = &comp->rstate[comp->last_recv = ip->ip_p];
+ comp->flags &=~ VJF_TOSS;
+ ip->ip_p = IPPROTO_TCP;
+ hlen = getip_hl(*ip);
+ hlen += getth_off(*((struct tcphdr *)&((int *)ip)[hlen]));
+ hlen <<= 2;
+ BCOPY(ip, &cs->cs_ip, hlen);
+ cs->cs_hlen = hlen;
+ INCR(vjs_uncompressedin);
+ return (1);
+}
+
+/*
+ * Uncompress a packet of type TYPE_COMPRESSED_TCP.
+ * The packet starts at buf and is of total length total_len.
+ * The first buflen bytes are at buf; this must include the entire
+ * compressed 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
+vj_uncompress_tcp(buf, buflen, total_len, comp, hdrp, hlenp)
+ u_char *buf;
+ int buflen, total_len;
+ struct vjcompress *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 u_short *bp;
+ register u_int vjlen;
+ register u_int32_t tmp;
+
+ INCR(vjs_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 &=~ 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) {
+ 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 |= TH_PUSH;
+ else
+ th->th_flags &=~ TH_PUSH;
+
+ switch (changes & SPECIALS_MASK) {
+ case SPECIAL_I:
+ {
+ register u_int32_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 |= 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 = 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 = 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_short *) &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 |= VJF_TOSS;
+ INCR(vjs_errorin);
+ return (-1);
+}
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