- 根目录:
- drivers
- net
- slip
- slhc.c
/*
* Routines to compress and uncompress 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 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*
* Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
* - Initial distribution.
*
*
* modified for KA9Q Internet Software Package by
* Katie Stevens (dkstevens@ucdavis.edu)
* University of California, Davis
* Computing Services
* - 01-31-90 initial adaptation (from 1.19)
* PPP.05 02-15-90 [ks]
* PPP.08 05-02-90 [ks] use PPP protocol field to signal compression
* PPP.15 09-90 [ks] improve mbuf handling
* PPP.16 11-02 [karn] substantially rewritten to use NOS facilities
*
* - Feb 1991 Bill_Simpson@um.cc.umich.edu
* variable number of conversation slots
* allow zero or one slots
* separate routines
* status display
* - Jul 1994 Dmitry Gorodchanin
* Fixes for memory leaks.
* - Oct 1994 Dmitry Gorodchanin
* Modularization.
* - Jan 1995 Bjorn Ekwall
* Use ip_fast_csum from ip.h
* - July 1995 Christos A. Polyzols
* Spotted bug in tcp option checking
*
*
* This module is a difficult issue. It's clearly inet code but it's also clearly
* driver code belonging close to PPP and SLIP
*/
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <net/slhc_vj.h>
#ifdef CONFIG_INET
/* Entire module is for IP only */
#include <linux/mm.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/termios.h>
#include <linux/in.h>
#include <linux/fcntl.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <net/ip.h>
#include <net/protocol.h>
#include <net/icmp.h>
#include <net/tcp.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <linux/timer.h>
#include <asm/uaccess.h>
#include <net/checksum.h>
#include <asm/unaligned.h>
static unsigned char *encode(unsigned char *cp, unsigned short n);
static long decode(unsigned char **cpp);
static unsigned char * put16(unsigned char *cp, unsigned short x);
static unsigned short pull16(unsigned char **cpp);
/* Initialize compression data structure
* slots must be in range 0 to 255 (zero meaning no compression)
*/
struct slcompress *
slhc_init(int rslots, int tslots)
{
register short i;
register struct cstate *ts;
struct slcompress *comp;
comp = kzalloc(sizeof(struct slcompress), GFP_KERNEL);
if (! comp)
goto out_fail;
if ( rslots > 0 && rslots < 256 ) {
size_t rsize = rslots * sizeof(struct cstate);
comp->rstate = kzalloc(rsize, GFP_KERNEL);
if (! comp->rstate)
goto out_free;
comp->rslot_limit = rslots - 1;
}
if ( tslots > 0 && tslots < 256 ) {
size_t tsize = tslots * sizeof(struct cstate);
comp->tstate = kzalloc(tsize, GFP_KERNEL);
if (! comp->tstate)
goto out_free2;
comp->tslot_limit = tslots - 1;
}
comp->xmit_oldest = 0;
comp->xmit_current = 255;
comp->recv_current = 255;
/*
* don't accept any packets with implicit index until we get
* one with an explicit index. Otherwise the uncompress code
* will try to use connection 255, which is almost certainly
* out of range
*/
comp->flags |= SLF_TOSS;
if ( tslots > 0 ) {
ts = comp->tstate;
for(i = comp->tslot_limit; i > 0; --i){
ts[i].cs_this = i;
ts[i].next = &(ts[i - 1]);
}
ts[0].next = &(ts[comp->tslot_limit]);
ts[0].cs_this = 0;
}
return comp;
out_free2:
kfree(comp->rstate);
out_free:
kfree(comp);
out_fail:
return NULL;
}
/* Free a compression data structure */
void
slhc_free(struct slcompress *comp)
{
if ( comp == NULLSLCOMPR )
return;
if ( comp->tstate != NULLSLSTATE )
kfree( comp->tstate );
if ( comp->rstate != NULLSLSTATE )
kfree( comp->rstate );
kfree( comp );
}
/* Put a short in host order into a char array in network order */
static inline unsigned char *
put16(unsigned char *cp, unsigned short x)
{
*cp++ = x >> 8;
*cp++ = x;
return cp;
}
/* Encode a number */
static unsigned char *
encode(unsigned char *cp, unsigned short n)
{
if(n >= 256 || n == 0){
*cp++ = 0;
cp = put16(cp,n);
} else {
*cp++ = n;
}
return cp;
}
/* Pull a 16-bit integer in host order from buffer in network byte order */
static unsigned short
pull16(unsigned char **cpp)
{
short rval;
rval = *(*cpp)++;
rval <<= 8;
rval |= *(*cpp)++;
return rval;
}
/* Decode a number */
static long
decode(unsigned char **cpp)
{
register int x;
x = *(*cpp)++;
if(x == 0){
return pull16(cpp) & 0xffff; /* pull16 returns -1 on error */
} else {
return x & 0xff; /* -1 if PULLCHAR returned error */
}
}
/*
* icp and isize are the original packet.
* ocp is a place to put a copy if necessary.
* cpp is initially a pointer to icp. If the copy is used,
* change it to ocp.
*/
int
slhc_compress(struct slcompress *comp, unsigned char *icp, int isize,
unsigned char *ocp, unsigned char **cpp, int compress_cid)
{
register struct cstate *ocs = &(comp->tstate[comp->xmit_oldest]);
register struct cstate *lcs = ocs;
register struct cstate *cs = lcs->next;
register unsigned long deltaS, deltaA;
register short changes = 0;
int hlen;
unsigned char new_seq[16];
register unsigned char *cp = new_seq;
struct iphdr *ip;
struct tcphdr *th, *oth;
__sum16 csum;
/*
* Don't play with runt packets.
*/
if(isize<sizeof(struct iphdr))
return isize;
ip = (struct iphdr *) icp;
/* Bail if this packet isn't TCP, or is an IP fragment */
if (ip->protocol != IPPROTO_TCP || (ntohs(ip->frag_off) & 0x3fff)) {
/* Send as regular IP */
if(ip->protocol != IPPROTO_TCP)
comp->sls_o_nontcp++;
else
comp->sls_o_tcp++;
return isize;
}
/* Extract TCP header */
th = (struct tcphdr *)(((unsigned char *)ip) + ip->ihl*4);
hlen = ip->ihl*4 + th->doff*4;
/* Bail if the TCP packet isn't `compressible' (i.e., ACK isn't set or
* some other control bit is set). Also uncompressible if
* it's a runt.
*/
if(hlen > isize || th->syn || th->fin || th->rst ||
! (th->ack)){
/* TCP connection stuff; send as regular IP */
comp->sls_o_tcp++;
return isize;
}
/*
* 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.
*
* States are kept in a circularly linked list with
* xmit_oldest 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.
*/
for ( ; ; ) {
if( ip->saddr == cs->cs_ip.saddr
&& ip->daddr == cs->cs_ip.daddr
&& th->source == cs->cs_tcp.source
&& th->dest == cs->cs_tcp.dest)
goto found;
/* if current equal oldest, at end of list */
if ( cs == ocs )
break;
lcs = cs;
cs = cs->next;
comp->sls_o_searches++;
}
/*
* 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
* xmit_oldest to update the lru linkage.
*/
comp->sls_o_misses++;
comp->xmit_oldest = lcs->cs_this;
goto uncompressed;
found:
/*
* Found it -- move to the front on the connection list.
*/
if(lcs == ocs) {
/* found at most recently used */
} else if (cs == ocs) {
/* found at least recently used */
comp->xmit_oldest = lcs->cs_this;
} else {
/* more than 2 elements */
lcs->next = cs->next;
cs->next = ocs->next;
ocs->next = cs;
}
/*
* Make sure that only what we expect to change changed.
* Check the following:
* IP protocol version, header length & type of service.
* The "Don't fragment" bit.
* The time-to-live field.
* The TCP header length.
* IP options, if any.
* TCP options, if any.
* If any of these things are different between the previous &
* current datagram, we send the current datagram `uncompressed'.
*/
oth = &cs->cs_tcp;
if(ip->version != cs->cs_ip.version || ip->ihl != cs->cs_ip.ihl
|| ip->tos != cs->cs_ip.tos
|| (ip->frag_off & htons(0x4000)) != (cs->cs_ip.frag_off & htons(0x4000))
|| ip->ttl != cs->cs_ip.ttl
|| th->doff != cs->cs_tcp.doff
|| (ip->ihl > 5 && memcmp(ip+1,cs->cs_ipopt,((ip->ihl)-5)*4) != 0)
|| (th->doff > 5 && memcmp(th+1,cs->cs_tcpopt,((th->doff)-5)*4) != 0)){
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->urg){
deltaS = ntohs(th->urg_ptr);
cp = encode(cp,deltaS);
changes |= NEW_U;
} else if(th->urg_ptr != oth->urg_ptr){
/* 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 = ntohs(th->window) - ntohs(oth->window)) != 0){
cp = encode(cp,deltaS);
changes |= NEW_W;
}
if((deltaA = ntohl(th->ack_seq) - ntohl(oth->ack_seq)) != 0L){
if(deltaA > 0x0000ffff)
goto uncompressed;
cp = encode(cp,deltaA);
changes |= NEW_A;
}
if((deltaS = ntohl(th->seq) - ntohl(oth->seq)) != 0L){
if(deltaS > 0x0000ffff)
goto uncompressed;
cp = encode(cp,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->tot_len != cs->cs_ip.tot_len &&
ntohs(cs->cs_ip.tot_len) == hlen)
break;
goto uncompressed;
break;
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.tot_len) - hlen){
/* special case for echoed terminal traffic */
changes = SPECIAL_I;
cp = new_seq;
}
break;
case NEW_S:
if(deltaS == ntohs(cs->cs_ip.tot_len) - hlen){
/* special case for data xfer */
changes = SPECIAL_D;
cp = new_seq;
}
break;
}
deltaS = ntohs(ip->id) - ntohs(cs->cs_ip.id);
if(deltaS != 1){
cp = encode(cp,deltaS);
changes |= NEW_I;
}
if(th->psh)
changes |= TCP_PUSH_BIT;
/* Grab the cksum before we overwrite it below. Then update our
* state with this packet's header.
*/
csum = th->check;
memcpy(&cs->cs_ip,ip,20);
memcpy(&cs->cs_tcp,th,20);
/* 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.
*/
deltaS = cp - new_seq;
if(compress_cid == 0 || comp->xmit_current != cs->cs_this){
cp = ocp;
*cpp = ocp;
*cp++ = changes | NEW_C;
*cp++ = cs->cs_this;
comp->xmit_current = cs->cs_this;
} else {
cp = ocp;
*cpp = ocp;
*cp++ = changes;
}
*(__sum16 *)cp = csum;
cp += 2;
/* deltaS is now the size of the change section of the compressed header */
memcpy(cp,new_seq,deltaS); /* Write list of deltas */
memcpy(cp+deltaS,icp+hlen,isize-hlen);
comp->sls_o_compressed++;
ocp[0] |= SL_TYPE_COMPRESSED_TCP;
return isize - hlen + deltaS + (cp - ocp);
/* Update connection state cs & send uncompressed packet (i.e.,
* 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,20);
memcpy(&cs->cs_tcp,th,20);
if (ip->ihl > 5)
memcpy(cs->cs_ipopt, ip+1, ((ip->ihl) - 5) * 4);
if (th->doff > 5)
memcpy(cs->cs_tcpopt, th+1, ((th->doff) - 5) * 4);
comp->xmit_current = cs->cs_this;
comp->sls_o_uncompressed++;
memcpy(ocp, icp, isize);
*cpp = ocp;
ocp[9] = cs->cs_this;
ocp[0] |= SL_TYPE_UNCOMPRESSED_TCP;
return isize;
}
int
slhc_uncompress(struct slcompress *comp, unsigned char *icp, int isize)
{
register int changes;
long x;
register struct tcphdr *thp;
register struct iphdr *ip;
register struct cstate *cs;
int len, hdrlen;
unsigned char *cp = icp;
/* We've got a compressed packet; read the change byte */
comp->sls_i_compressed++;
if(isize < 3){
comp->sls_i_error++;
return 0;
}
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.
*/
x = *cp++; /* Read conn index */
if(x < 0 || x > comp->rslot_limit)
goto bad;
comp->flags &=~ SLF_TOSS;
comp->recv_current = x;
} 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){
comp->sls_i_tossed++;
return 0;
}
}
cs = &comp->rstate[comp->recv_current];
thp = &cs->cs_tcp;
ip = &cs->cs_ip;
thp->check = *(__sum16 *)cp;
cp += 2;
thp->psh = (changes & TCP_PUSH_BIT) ? 1 : 0;
/*
* we can use the same number for the length of the saved header and
* the current one, because the packet wouldn't have been sent
* as compressed unless the options were the same as the previous one
*/
hdrlen = ip->ihl * 4 + thp->doff * 4;
switch(changes & SPECIALS_MASK){
case SPECIAL_I: /* Echoed terminal traffic */
{
register short i;
i = ntohs(ip->tot_len) - hdrlen;
thp->ack_seq = htonl( ntohl(thp->ack_seq) + i);
thp->seq = htonl( ntohl(thp->seq) + i);
}
break;
case SPECIAL_D: /* Unidirectional data */
thp->seq = htonl( ntohl(thp->seq) +
ntohs(ip->tot_len) - hdrlen);
break;
default:
if(changes & NEW_U){
thp->urg = 1;
if((x = decode(&cp)) == -1) {
goto bad;
}
thp->urg_ptr = htons(x);
} else
thp->urg = 0;
if(changes & NEW_W){
if((x = decode(&cp)) == -1) {
goto bad;
}
thp->window = htons( ntohs(thp->window) + x);
}
if(changes & NEW_A){
if((x = decode(&cp)) == -1) {
goto bad;
}
thp->ack_seq = htonl( ntohl(thp->ack_seq) + x);
}
if(changes & NEW_S){
if((x = decode(&cp)) == -1) {
goto bad;
}
thp->seq = htonl( ntohl(thp->seq) + x);
}
break;
}
if(changes & NEW_I){
if((x = decode(&cp)) == -1) {
goto bad;
}
ip->id = htons (ntohs (ip->id) + x);
} else
ip->id = htons (ntohs (ip->id) + 1);
/*
* At this point, cp points to the first byte of data in the
* packet. Put the reconstructed TCP and IP headers back on the
* packet. Recalculate IP checksum (but not TCP checksum).
*/
len = isize - (cp - icp);
if (len < 0)
goto bad;
len += hdrlen;
ip->tot_len = htons(len);
ip->check = 0;
memmove(icp + hdrlen, cp, len - hdrlen);
cp = icp;
memcpy(cp, ip, 20);
cp += 20;
if (ip->ihl > 5) {
memcpy(cp, cs->cs_ipopt, (ip->ihl - 5) * 4);
cp += (ip->ihl - 5) * 4;
}
put_unaligned(ip_fast_csum(icp, ip->ihl),
&((struct iphdr *)icp)->check);
memcpy(cp, thp, 20);
cp += 20;
if (thp->doff > 5) {
memcpy(cp, cs->cs_tcpopt, ((thp->doff) - 5) * 4);
cp += ((thp->doff) - 5) * 4;
}
return len;
bad:
comp->sls_i_error++;
return slhc_toss( comp );
}
int
slhc_remember(struct slcompress *comp, unsigned char *icp, int isize)
{
register struct cstate *cs;
unsigned ihl;
unsigned char index;
if(isize < 20) {
/* The packet is shorter than a legal IP header */
comp->sls_i_runt++;
return slhc_toss( comp );
}
/* Peek at the IP header's IHL field to find its length */
ihl = icp[0] & 0xf;
if(ihl < 20 / 4){
/* The IP header length field is too small */
comp->sls_i_runt++;
return slhc_toss( comp );
}
index = icp[9];
icp[9] = IPPROTO_TCP;
if (ip_fast_csum(icp, ihl)) {
/* Bad IP header checksum; discard */
comp->sls_i_badcheck++;
return slhc_toss( comp );
}
if(index > comp->rslot_limit) {
comp->sls_i_error++;
return slhc_toss(comp);
}
/* Update local state */
cs = &comp->rstate[comp->recv_current = index];
comp->flags &=~ SLF_TOSS;
memcpy(&cs->cs_ip,icp,20);
memcpy(&cs->cs_tcp,icp + ihl*4,20);
if (ihl > 5)
memcpy(cs->cs_ipopt, icp + sizeof(struct iphdr), (ihl - 5) * 4);
if (cs->cs_tcp.doff > 5)
memcpy(cs->cs_tcpopt, icp + ihl*4 + sizeof(struct tcphdr), (cs->cs_tcp.doff - 5) * 4);
cs->cs_hsize = ihl*2 + cs->cs_tcp.doff*2;
/* Put headers back on packet
* Neither header checksum is recalculated
*/
comp->sls_i_uncompressed++;
return isize;
}
int
slhc_toss(struct slcompress *comp)
{
if ( comp == NULLSLCOMPR )
return 0;
comp->flags |= SLF_TOSS;
return 0;
}
#else /* CONFIG_INET */
int
slhc_toss(struct slcompress *comp)
{
printk(KERN_DEBUG "Called IP function on non IP-system: slhc_toss");
return -EINVAL;
}
int
slhc_uncompress(struct slcompress *comp, unsigned char *icp, int isize)
{
printk(KERN_DEBUG "Called IP function on non IP-system: slhc_uncompress");
return -EINVAL;
}
int
slhc_compress(struct slcompress *comp, unsigned char *icp, int isize,
unsigned char *ocp, unsigned char **cpp, int compress_cid)
{
printk(KERN_DEBUG "Called IP function on non IP-system: slhc_compress");
return -EINVAL;
}
int
slhc_remember(struct slcompress *comp, unsigned char *icp, int isize)
{
printk(KERN_DEBUG "Called IP function on non IP-system: slhc_remember");
return -EINVAL;
}
void
slhc_free(struct slcompress *comp)
{
printk(KERN_DEBUG "Called IP function on non IP-system: slhc_free");
}
struct slcompress *
slhc_init(int rslots, int tslots)
{
printk(KERN_DEBUG "Called IP function on non IP-system: slhc_init");
return NULL;
}
#endif /* CONFIG_INET */
/* VJ header compression */
EXPORT_SYMBOL(slhc_init);
EXPORT_SYMBOL(slhc_free);
EXPORT_SYMBOL(slhc_remember);
EXPORT_SYMBOL(slhc_compress);
EXPORT_SYMBOL(slhc_uncompress);
EXPORT_SYMBOL(slhc_toss);
MODULE_LICENSE("Dual BSD/GPL");