$NetBSD: patch-at,v 1.1.1.1 1999/10/08 04:34:43 dbj Exp $

--- /dev/null	Sat Sep 18 04:00:15 1999
+++ netbsd-1.4/slcompress.c	Sat Sep 18 04:06:38 1999
@@ -0,0 +1,628 @@
+/*	NetBSD: slcompress.c,v 1.20 1999/03/13 14:09:46 drochner Exp    */
+/*	Id: slcompress.c,v 1.3 1996/05/24 07:04:47 paulus Exp 	*/
+
+/*
+ * 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.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *	This product includes software developed by the University of
+ *	California, Berkeley and its contributors.
+ * 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
+ */
+
+/*
+ * 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((char *)(p1), (char *)(p2), (int)(n))
+#define BCOPY(p1, p2, n) bcopy((char *)(p1), (char *)(p2), (int)(n))
+
+
+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 (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++); \
+	} \
+}
+
+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;
+
+		/* (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_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 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 ((long)cp & 3) {
+		if (len > 0)
+			memmove((caddr_t)((long)cp &~ 3), cp, len);
+		cp = (u_char *)((long)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);
+}
