588 lines
16 KiB
C
588 lines
16 KiB
C
/*
|
|
* 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 1.5 1996/04/11 08:14:44 davidg Exp $
|
|
*
|
|
* Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
|
|
* - Initial distribution.
|
|
*/
|
|
#ifndef lint
|
|
static char const rcsid[] = "$Id: slcompress.c,v 1.5 1996/04/11 08:14:44 davidg Exp $";
|
|
#endif
|
|
|
|
#include "defs.h"
|
|
#include <netinet/in_systm.h>
|
|
#include <netinet/in.h>
|
|
#include <netinet/tcp.h>
|
|
#include <netinet/ip.h>
|
|
#include "slcompress.h"
|
|
|
|
struct slstat slstat;
|
|
|
|
#define INCR(counter) slstat.counter++;
|
|
|
|
#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;
|
|
}
|
|
|
|
|
|
/* 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(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).
|
|
*/
|
|
#ifdef DEBUG
|
|
if ((ip->ip_off & htons(0x3fff)) || m->cnt < 40) {
|
|
logprintf("??? 1 ip_off = %x, cnt = %d\n", ip->ip_off, m->cnt);
|
|
DumpBp(m);
|
|
return (TYPE_IP);
|
|
}
|
|
#else
|
|
if ((ip->ip_off & htons(0x3fff)) || m->cnt < 40)
|
|
return (TYPE_IP);
|
|
#endif
|
|
|
|
th = (struct tcphdr *)&((int *)ip)[hlen];
|
|
#ifdef DEBUG
|
|
if ((th->th_flags & (TH_SYN|TH_FIN|TH_RST|TH_ACK)) != TH_ACK) {
|
|
logprintf("??? 2 th_flags = %x\n", th->th_flags);
|
|
DumpBp(m);
|
|
return (TYPE_IP);
|
|
}
|
|
#else
|
|
if ((th->th_flags & (TH_SYN|TH_FIN|TH_RST|TH_ACK)) != TH_ACK)
|
|
return (TYPE_IP);
|
|
#endif
|
|
|
|
/*
|
|
* 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;
|
|
#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 &&
|
|
BCMP(ip + 1, &cs->cs_ip + 1, (deltaS - 5) << 2)) ||
|
|
(THOFFSET(th) > 5 &&
|
|
BCMP(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);
|
|
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;
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
#ifdef SL_NOFASTQ
|
|
if (comp->last_xmit == cs->cs_id) {
|
|
hlen -= deltaS + 3;
|
|
cp += hlen;
|
|
*cp++ = changes;
|
|
} else
|
|
#endif
|
|
{
|
|
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;
|
|
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;
|
|
{
|
|
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_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;
|
|
BCOPY(ip, &cs->cs_ip, hlen);
|
|
cs->cs_ip.ip_sum = 0;
|
|
cs->cs_hlen = hlen;
|
|
INCR(sls_uncompressedin)
|
|
return (len);
|
|
|
|
default:
|
|
goto bad;
|
|
|
|
case TYPE_COMPRESSED_TCP:
|
|
break;
|
|
}
|
|
/* We've got a compressed packet. */
|
|
INCR(sls_compressedin)
|
|
cp = *bufp;
|
|
changes = *cp++;
|
|
#ifdef DEBUG
|
|
logprintf("compressed: changes = %02x\n", changes);
|
|
#endif
|
|
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 || 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) {
|
|
INCR(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) {
|
|
#ifdef DEBUG
|
|
logprintf("NEW_S: %02x, %02x, %02x\r\n", *cp, cp[1], cp[2]);
|
|
#endif
|
|
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);
|
|
#ifdef DEBUG
|
|
logprintf("id = %04x, seq = %08x\r\n", cs->cs_ip.ip_id, ntohl(th->th_seq));
|
|
#endif
|
|
|
|
/*
|
|
* 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) ovbcopy(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);
|
|
BCOPY(&cs->cs_ip, cp, 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;
|
|
INCR(sls_errorin)
|
|
return (0);
|
|
}
|
|
|
|
int
|
|
ReportCompress()
|
|
{
|
|
printf("Out: %d (compress) / %d (total)",
|
|
slstat.sls_compressed, slstat.sls_packets);
|
|
printf(" %d (miss) / %d (search)\n",
|
|
slstat.sls_misses, slstat.sls_searches);
|
|
printf("In: %d (compress), %d (uncompress)",
|
|
slstat.sls_compressedin, slstat.sls_uncompressedin);
|
|
printf(" %d (error), %d (tossed)\n",
|
|
slstat.sls_errorin, slstat.sls_tossed);
|
|
return(1);
|
|
}
|