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freebsd/usr.sbin/ppp/slcompress.c
Brian Somers 3f06c5995f Don't assume ``sizeof(u_long) == 4'' 
Submitted by: Theo
1998-06-27 12:03:50 +00:00

594 lines
16 KiB
C
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/*
* 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 1.18 1998/06/15 19:06:24 brian Exp $
*
* Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
* - Initial distribution.
*/
#include <sys/types.h>
#include <netinet/in_systm.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <netinet/ip.h>
#include <sys/un.h>
#include <stdio.h>
#include <string.h>
#include <termios.h>
#include "defs.h"
#include "command.h"
#include "mbuf.h"
#include "log.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 32-bit, 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_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++); \
} \
}
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, int max_state)
{
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_state)
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_state || 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;
if (hlen == 0)
goto bad; /* We've been pointed at a not-yet-used slot ! */
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;
}
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