netvj.c

基于东南大学开发的SEP3203的ARM7中的所有驱动

/*

 * 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 ([e-mail]), Dec 31, 1989:

 *	- Initial distribution.

 *

 * Modified June 1993 by Paul Mackerras, [e-mail],

 * so that the entire packet being decompressed doesn't have

 * to be in contiguous memory (just the compressed header).

 *

 * Modified March 1998 by Guy Lancaster, [e-mail],

 * for a 16 bit processor.

 */



#include "netconf.h"

#include <string.h>

#include "net.h"

#include "netbuf.h"

#include "netip.h"

#include "netiphdr.h"

#include "nettcp.h"

#include "nettcphd.h"

#include "netvj.h"



#include <stdio.h>

#include "netdebug.h"



/*#pragma warning (push)

#pragma warning (disable: 4761) // integral size mismatch in argument; conversion supplied

#pragma warning (disable: 4244) // 'function' : conversion from 'short ' to 'unsigned char ', possible loss of data*/

////////////////////////////////////////////////////////////////////////////////





#if VJ_SUPPORT > 0



#ifndef VJ_NO_STATS

#define INCR(counter) ++comp->stats.counter

#else

#define INCR(counter)

#endif



#define getip_hl(base)	((base).ip_hl)

#define getth_off(base)	((base).th_off)



void vj_compress_init(struct vjcompress *comp)

{

	register u_int i;

	register struct cstate *tstate = comp->tstate;

	

#if MAX_SLOTS == 0

	bzero((char *)comp, sizeof(*comp));

#endif

	comp->maxSlotIndex = MAX_SLOTS - 1;

	comp->compressSlot = 0;		/* Disable slot ID compression by default. */

	for (i = MAX_SLOTS - 1; i > 0; --i) {

		tstate[i].cs_id = i;

		tstate[i].cs_next = &tstate[i - 1];

	}

	tstate[0].cs_next = &tstate[MAX_SLOTS - 1];

	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] = (unsigned char)(n); \
		cp[0] = (unsigned char)((n) >> 8); \
		cp += 2; \
	} else { \
		*cp++ = (unsigned char)(n); \
	} \
}

#define ENCODEZ(n) { \
	if ((u_short)(n) >= 256 || (u_short)(n) == 0) { \
		*cp++ = 0; \
		cp[1] = (unsigned char)(n); \
		cp[0] = (unsigned char)((n) >> 8); \
		cp += 2; \
	} else { \
		*cp++ = (unsigned char)(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) + (((u_short)cp[1] << 8) | cp[2]); \
		(f) = htons(tmp); \
		cp += 3; \
	} else { \
		u_short tmp = ntohs(f) + (u_short)*cp++; \
		(f) = htons(tmp); \
	} \
}



#define DECODEU(f) { \
	if (*cp == 0) {\
		(f) = htons(((u_short)cp[1] << 8) | cp[2]); \
		cp += 3; \
	} else { \
		(f) = htons((u_short)*cp++); \
	} \
}



/*

 * vj_compress_tcp - Attempt to do Van Jacobsen header compression on a

 * packet.  This assumes that nb and comp are not null and that the first

 * buffer of the chain contains a valid IP header.

 * Return the VJ type code indicating whether or not the packet was

 * compressed.

 */

u_int vj_compress_tcp(

	struct vjcompress *comp,

	NBuf *nb

)

{

	register struct ip *ip = nBUFTOPTR(nb, IPHdr *);

	register struct cstate *cs = comp->last_cs->cs_next;

	register u_short hlen = getip_hl(*ip);

	register struct tcphdr *oth;

	register struct tcphdr *th;

	register u_short deltaS, deltaA;

	register u_long deltaL;

	register u_int changes = 0;

	u_char new_seq[16];

	register u_char *cp = new_seq;



	/*	

	 * Check that the packet is IP proto TCP.

	 */

	if (ip->ip_p != IPPROTO_TCP)

		return (TYPE_IP);

		

	/*

	 * 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).  

	 */

	if ((ip->ip_off & htons(0x3fff)) || nb->chainLen < 40)

		return (TYPE_IP);

	th = (struct tcphdr *)&((long *)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 

			|| *(long *)th != ((long *)&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

					&& *(long *)th == ((long *)&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;

		/* Check that the IP/TCP headers are contained in the first buffer. */

		if (hlen > nb->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;

		}

	}

	

	oth = (struct tcphdr *)&((long *)&cs->cs_ip)[hlen];

	deltaS = hlen;

	hlen += getth_off(*th);

	hlen <<= 2;

	/* Check that the IP/TCP headers are contained in the first buffer. */

	if (hlen > nb->len) {

		PPPDEBUG((LOG_INFO, TL_PPP, "vj_compress_tcp: header len %d spans buffers", 

					hlen));

		return (TYPE_IP);

	}

	

	/*
	 * 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'.
	 */

	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))) != 0) {
		ENCODE(deltaS);
		changes |= NEW_W;
	}

	

	if ((deltaL = ntohl(th->th_ack) - ntohl(oth->th_ack)) != 0) {

		if (deltaL > 0xffff)

			goto uncompressed;

		deltaA = (u_short)deltaL;

		ENCODE(deltaA);

		changes |= NEW_A;

	}

	

	if ((deltaL = ntohl(th->th_seq) - ntohl(oth->th_seq)) != 0) {

		if (deltaL > 0xffff)

			goto uncompressed;

		deltaS = (u_short)deltaL;

		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.

		 */