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-rw-r--r--src/gprs/slhc.c813
1 files changed, 813 insertions, 0 deletions
diff --git a/src/gprs/slhc.c b/src/gprs/slhc.c
new file mode 100644
index 000000000..cbdf8dbd8
--- /dev/null
+++ b/src/gprs/slhc.c
@@ -0,0 +1,813 @@
+/*
+ * 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 <string.h>
+#include <stdio.h>
+#include <errno.h>
+#include <stdint.h>
+#include <arpa/inet.h>
+#include <osmocom/core/utils.h>
+#include <osmocom/core/talloc.h>
+#include <openbsc/slhc.h>
+#include <openbsc/debug.h>
+
+#define ERR_PTR(x) x
+
+
+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);
+
+/* Replacement for kernel space function ip_fast_csum() */
+static uint16_t ip_fast_csum(uint8_t *iph, int ihl)
+{
+ int i;
+ uint16_t temp;
+ uint32_t accumulator = 0xFFFF;
+
+ for(i=0;i<ihl*2;i++)
+ {
+ temp = ((*iph) << 8)&0xFF00;
+ iph++;
+ temp |= (*iph)&0xFF;
+ iph++;
+
+ accumulator+=temp;
+ if(accumulator>0xFFFF)
+ {
+ accumulator++;
+ accumulator&=0xFFFF;
+ }
+ }
+
+ return (uint16_t)(htons(~accumulator)&0xFFFF);
+}
+
+/* Replacement for kernel space function put_unaligned() */
+static void put_unaligned(uint16_t val, void *ptr)
+{
+ memcpy(ptr,&val,sizeof(val));
+}
+
+
+/* Allocate compression data structure
+ * slots must be in range 0 to 255 (zero meaning no compression)
+ * Returns pointer to structure or ERR_PTR() on error.
+ */
+struct slcompress *
+slhc_init(const void *ctx, int rslots, int tslots)
+{
+ register short i;
+ register struct cstate *ts;
+ struct slcompress *comp;
+
+ if (rslots < 0 || rslots > 255 || tslots < 0 || tslots > 255)
+ return NULL;
+
+ comp = (struct slcompress *)talloc_zero_size(ctx,sizeof(struct slcompress));
+ if (! comp)
+ goto out_fail;
+
+ if (rslots > 0) {
+ size_t rsize = rslots * sizeof(struct cstate);
+ comp->rstate = (struct cstate *) talloc_zero_size(ctx, rsize);
+ if (! comp->rstate)
+ goto out_free;
+ comp->rslot_limit = rslots - 1;
+ }
+
+ if (tslots > 0) {
+ size_t tsize = tslots * sizeof(struct cstate);
+ comp->tstate = (struct cstate *) talloc_zero_size(ctx, tsize);
+ 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:
+ talloc_free(comp->rstate);
+out_free:
+ talloc_free(comp);
+out_fail:
+ return NULL;
+}
+
+
+/* Free a compression data structure */
+void
+slhc_free(struct slcompress *comp)
+{
+ DEBUGP(DSLHC, "slhc_free(): Freeing compression states...\n");
+
+ if ( comp == NULLSLCOMPR )
+ return;
+
+ if ( comp->tstate != NULLSLSTATE )
+ talloc_free(comp->tstate );
+
+ if ( comp->rstate != NULLSLSTATE )
+ talloc_free( comp->rstate );
+
+ talloc_free( 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;
+ }
+
+ DEBUGP(DSLHC, "encode(): n=%04x\n",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++;
+ DEBUGP(DSLHC, "slhc_compress(): Not a TCP packat, will not touch...\n");
+ 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++;
+ DEBUGP(DSLHC, "slhc_compress(): Packet is part of a TCP connection, will not touch...\n");
+ 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.
+ */
+
+ DEBUGP(DSLHC, "slhc_compress(): Compressible packet detected!\n");
+
+ 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.
+ */
+
+ DEBUGP(DSLHC, "slhc_compress(): Header not yet seen, will memorize header for the next turn...\n");
+ comp->sls_o_misses++;
+ comp->xmit_oldest = lcs->cs_this;
+ goto uncompressed;
+
+found:
+ DEBUGP(DSLHC, "slhc_compress(): Header already seen, trying to compress...\n");
+ /*
+ * 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;
+
+ /* Display a little more debug information about which of the
+ * header fields changed unexpectedly */
+ if(ip->version != cs->cs_ip.version)
+ DEBUGP(DSLHC, "slhc_compress(): Unexpected change: ip->version != cs->cs_ip.version\n");
+ if(ip->ihl != cs->cs_ip.ihl)
+ DEBUGP(DSLHC, "slhc_compress(): Unexpected change: ip->ihl != cs->cs_ip.ihl\n");
+ if(ip->tos != cs->cs_ip.tos)
+ DEBUGP(DSLHC, "slhc_compress(): Unexpected change: ip->tos != cs->cs_ip.tos\n");
+ if((ip->frag_off & htons(0x4000)) != (cs->cs_ip.frag_off & htons(0x4000)))
+ DEBUGP(DSLHC, "slhc_compress(): Unexpected change: (ip->frag_off & htons(0x4000)) != (cs->cs_ip.frag_off & htons(0x4000))\n");
+ if(ip->ttl != cs->cs_ip.ttl)
+ DEBUGP(DSLHC, "slhc_compress(): Unexpected change: ip->ttl != cs->cs_ip.ttl\n");
+ if(th->doff != cs->cs_tcp.doff)
+ DEBUGP(DSLHC, "slhc_compress(): Unexpected change: th->doff != cs->cs_tcp.doff\n");
+ if(ip->ihl > 5 && memcmp(ip+1,cs->cs_ipopt,((ip->ihl)-5)*4) != 0) {
+ DEBUGP(DSLHC, "slhc_compress(): Unexpected change: (ip->ihl > 5 && memcmp(ip+1,cs->cs_ipopt,((ip->ihl)-5)*4) != 0)\n");
+ DEBUGP(DSLHC, "slhc_compress(): ip->ihl = %i\n", ip->ihl);
+ DEBUGP(DSLHC, "slhc_compress(): ip+1 = %s\n",
+ osmo_hexdump_nospc((uint8_t*)(ip+1),((ip->ihl)-5)*4));
+ DEBUGP(DSLHC, "slhc_compress(): Unexpected change: cs->cs_ipopt = %s\n",
+ osmo_hexdump_nospc((uint8_t*)(cs->cs_ipopt),((ip->ihl)-5)*4));
+ }
+ if(th->doff > 5 && memcmp(th+1,cs->cs_tcpopt,((th->doff)-5)*4) != 0) {
+ DEBUGP(DSLHC, "slhc_compress(): Unexpected change: (th->doff > 5 && memcmp(th+1,cs->cs_tcpopt,((th->doff)-5)*4) != 0)\n");
+ DEBUGP(DSLHC, "slhc_compress(): th->doff = %i\n", th->doff);
+ DEBUGP(DSLHC, "slhc_compress(): th+1 = %s\n",
+ osmo_hexdump_nospc((uint8_t*)(th+1),((th->doff)-5)*4));
+ DEBUGP(DSLHC, "slhc_compress(): cs->cs_tcpopt = %s\n",
+ osmo_hexdump_nospc((uint8_t*)cs->cs_tcpopt,
+ ((th->doff)-5)*4));
+ }
+
+
+ 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)){
+ DEBUGP(DSLHC, "slhc_compress(): The header contains unexpected changes, can't compress...\n");
+ 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);
+ DEBUGP(DSLHC, "slhc_compress(): flag: Urgent Pointer (U) = 1\n");
+ 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. */
+ DEBUGP(DSLHC, "slhc_compress(): URG not set but urp changed, can't compress...\n");
+ goto uncompressed;
+ }
+ if((deltaS = ntohs(th->window) - ntohs(oth->window)) != 0){
+ DEBUGP(DSLHC, "slhc_compress(): flag: Delta Window (W) = 1\n");
+ cp = encode(cp,deltaS);
+ changes |= NEW_W;
+ }
+ if((deltaA = ntohl(th->ack_seq) - ntohl(oth->ack_seq)) != 0L){
+ if(deltaA > 0x0000ffff) {
+ DEBUGP(DSLHC, "slhc_compress(): (deltaA = ntohl(th->ack_seq) - ntohl(oth->ack_seq)) != 0L, can't compress...\n");
+ goto uncompressed;
+ }
+ DEBUGP(DSLHC, "slhc_compress(): flag: Delta Ack (A) = 1\n");
+ cp = encode(cp,deltaA);
+ changes |= NEW_A;
+ }
+ if((deltaS = ntohl(th->seq) - ntohl(oth->seq)) != 0L){
+ if(deltaS > 0x0000ffff) {
+ DEBUGP(DSLHC, "slhc_compress(): (deltaS = ntohl(th->seq) - ntohl(oth->seq)) != 0L, can't compress...\n");
+ goto uncompressed;
+ }
+ DEBUGP(DSLHC, "slhc_compress(): flag: Delta Sequence (S) = 1\n");
+ 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;
+ DEBUGP(DSLHC, "slhc_compress(): Retransmitted packet detected, can't compress...\n");
+ goto uncompressed;
+ case SPECIAL_I:
+ case SPECIAL_D:
+ /* actual changes match one of our special case encodings --
+ * send packet uncompressed.
+ */
+ DEBUGP(DSLHC, "slhc_compress(): Special case detected, can't compress...\n");
+ goto uncompressed;
+ case NEW_S|NEW_A:
+ if(deltaS == deltaA &&
+ deltaS == ntohs(cs->cs_ip.tot_len) - hlen){
+ /* special case for echoed terminal traffic */
+ DEBUGP(DSLHC, "slhc_compress(): Special case for echoed terminal traffic detected...\n");
+ DEBUGP(DSLHC, "slhc_compress(): flag: Delta Sequence (S) = 1, Delta Window (W) = 1, Urgent Pointer (U) = 1\n");
+ changes = SPECIAL_I;
+ cp = new_seq;
+ }
+ break;
+ case NEW_S:
+ if(deltaS == ntohs(cs->cs_ip.tot_len) - hlen){
+ /* special case for data xfer */
+ DEBUGP(DSLHC, "slhc_compress(): Special case for data xfer detected...\n");
+ DEBUGP(DSLHC, "slhc_compress(): flag: Delta Sequence (S) = 1, Delta Ack (A) = 1, Delta Window (W) = 1, Urgent Pointer (U) = 1\n");
+ changes = SPECIAL_D;
+ cp = new_seq;
+ }
+ break;
+ }
+ deltaS = ntohs(ip->id) - ntohs(cs->cs_ip.id);
+ if(deltaS != 1){
+ DEBUGP(DSLHC, "slhc_compress(): flag: Delta IP ID (I) = 1\n");
+ cp = encode(cp,deltaS);
+ changes |= NEW_I;
+ }
+ if(th->psh) {
+ DEBUGP(DSLHC, "slhc_compress(): flag: Push (P) = 1\n");
+ 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;
+ DEBUGP(DSLHC, "slhc_compress(): flag: Connection number (C) = 1\n");
+ *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 */
+
+ DEBUGP(DSLHC, "slhc_compress(): Delta-list length (deltaS) = %li\n",deltaS);
+ DEBUGP(DSLHC, "slhc_compress(): Original header len (hlen) = %i\n",hlen);
+
+ 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:
+ DEBUGP(DSLHC, "slhc_compress(): Packet will be sent uncompressed...\n");
+ 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 */
+ DEBUGP(DSLHC, "slhc_uncompress(): Echoed terminal traffic detected\n");
+
+ {
+ 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 */
+ DEBUGP(DSLHC, "slhc_uncompress(): Unidirectional data detected\n");
+ thp->seq = htonl( ntohl(thp->seq) +
+ ntohs(ip->tot_len) - hdrlen);
+ break;
+
+ default:
+ DEBUGP(DSLHC, "slhc_uncompress(): default packet type detected\n");
+ 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;
+
+ DEBUGP(DSLHC, "slhc_uncompress(): making space for the reconstructed header...\n");
+ 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:
+ DEBUGP(DSLHC, "slhc_uncompress(): bad packet detected!\n");
+ 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++;
+ DEBUGP(DSLHC, "slhc_remember(): The packet is shorter than a legal IP header ==> slhc_toss()\n");
+ 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++;
+ DEBUGP(DSLHC, "slhc_remember(): The IP header length field is too small ==> slhc_toss()\n");
+ 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++;
+ DEBUGP(DSLHC, "slhc_remember(): Bad IP header checksum; discard ==> slhc_toss()\n");
+ return slhc_toss( comp );
+ }
+ if(index > comp->rslot_limit) {
+ comp->sls_i_error++;
+ DEBUGP(DSLHC, "slhc_remember(): index > comp->rslot_limit ==> slhc_toss()\n");
+ 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)
+{
+ DEBUGP(DSLHC, "slhc_toss(): Reset compression state...\n");
+ if ( comp == NULLSLCOMPR )
+ return 0;
+
+ comp->flags |= SLF_TOSS;
+ return 0;
+}
+
+void slhc_i_status(struct slcompress *comp)
+{
+ if (comp != NULLSLCOMPR) {
+ DEBUGP(DSLHC, "slhc_i_status(): %d Cmp, %d Uncmp, %d Bad, %d Tossed\n",
+ comp->sls_i_compressed,
+ comp->sls_i_uncompressed,
+ comp->sls_i_error,
+ comp->sls_i_tossed);
+ }
+}
+
+void slhc_o_status(struct slcompress *comp)
+{
+ if (comp != NULLSLCOMPR) {
+ DEBUGP(DSLHC, "slhc_o_status(): %d Cmp, %d Uncmp, %d AsIs, %d NotTCP %d Searches, %d Misses\n",
+ comp->sls_o_compressed,
+ comp->sls_o_uncompressed,
+ comp->sls_o_tcp,
+ comp->sls_o_nontcp,
+ comp->sls_o_searches,
+ comp->sls_o_misses);
+ }
+}
+
generated by cgit v1.2.3 (git 2.25.1) at 2024-04-16 19:05:48 +0000