+++ /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).
- *
- * $Id: slcompress.c,v 1.4 1997/03/04 03:45:18 paulus Exp $
- */
-
-#include "../h/types.h"
-#include "../h/param.h"
-#include "../h/mbuf.h"
-#include "../net/netinet/in.h"
-#include "../net/netinet/in_systm.h"
-#include "../net/netinet/ip.h"
-#include "../net/netinet/tcp.h"
-
-#include "ppp_defs.h"
-#include "slcompress.h"
-
-#ifndef SL_NO_STATS
-#define INCR(counter) ++comp->counter;
-#else
-#define INCR(counter)
-#endif
-
-#define BCMP(p1, p2, n) bcmp((char *)(p1), (char *)(p2), (int)(n))
-#define BCOPY(p1, p2, n) bcopy((char *)(p1), (char *)(p2), (int)(n))
-#ifndef KERNEL
-#define ovbcopy bcopy
-#endif
-
-
-void
-sl_compress_init(comp)
- struct slcompress *comp;
-{
- register u_int i;
- register struct cstate *tstate = comp->tstate;
-
- bzero((char *)comp, sizeof(*comp));
- for (i = MAX_STATES - 1; i > 0; --i) {
- tstate[i].cs_id = i;
- tstate[i].cs_next = &tstate[i - 1];
- }
- tstate[0].cs_next = &tstate[MAX_STATES - 1];
- tstate[0].cs_id = 0;
- comp->last_cs = &tstate[0];
- comp->last_recv = 255;
- comp->last_xmit = 255;
- comp->flags = SLF_TOSS;
-}
-
-
-/*
- * Like sl_compress_init, but we get to specify the maximum connection
- * ID to use on transmission.
- */
-void
-sl_compress_setup(comp, max_state)
- struct slcompress *comp;
- int max_state;
-{
- register u_int i;
- register struct cstate *tstate = comp->tstate;
-
- if ((unsigned) max_state > MAX_STATES - 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 = 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_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 *)&((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(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;
- 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
- && *(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.
- */
- 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 *)&((int *)&cs->cs_ip)[hlen];
- deltaS = hlen;
- hlen += th->th_off;
- hlen <<= 2;
- if (hlen > m->m_len)
- 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] ||
- 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;
-
- 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;
- cp += hlen;
- *cp++ = changes | NEW_C;
- *cp++ = cs->cs_id;
- } else {
- hlen -= deltaS + 3;
- cp += hlen;
- *cp++ = changes;
- }
- m->m_len -= hlen;
- m->m_off += 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 vjlen;
- u_int hlen;
-
- 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 ((int)cp & 3) {
- if (len > 0)
- (void) ovbcopy(cp, (caddr_t)((int)cp &~ 3), len);
- cp = (u_char *)((int)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_short *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_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 |= SLF_TOSS;
- INCR(sls_errorin)
- return (-1);
-}
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