/* Decrement the IP TTL field in each packet on the send queue. If
* a TTL goes to zero, discard the packet.
*/
void
ttldec(
struct iface *ifp
){
struct mbuf *bp,*bpprev,*bpnext;
struct qhdr qhdr;
struct ip ip;
bpprev = NULL;
for(bp = ifp->outq; bp != NULL;bpprev = bp,bp = bpnext){
bpnext = bp->anext;
pullup(&bp,&qhdr,sizeof(qhdr));
ntohip(&ip,&bp);
if(--ip.ttl == 0){
/* Drop packet */
icmp_output(&ip,bp,ICMP_TIME_EXCEED,0,NULL);
if(bpprev == NULL) /* First on queue */
ifp->outq = bpnext;
else
bpprev->anext = bpnext;
free_p(&bp);
bp = bpprev;
continue;
}
/* Put IP and queue headers back, restore to queue */
htonip(&ip,&bp,0);
pushdown(&bp,&qhdr,sizeof(qhdr));
if(bpprev == NULL) /* First on queue */
ifp->outq = bp;
else
bpprev->anext = bp;
bp->anext = bpnext;
}
}
void
ip_dump(
FILE *fp,
struct mbuf **bpp,
int check
){
struct ip ip;
uint16 ip_len;
uint16 csum;
if(bpp == NULL || *bpp == NULL)
return;
/* Sneak peek at IP header and find length */
ip_len = ((*bpp)->data[0] & 0xf) << 2;
if(ip_len < IPLEN){
fprintf(fp,"IP: bad header\n");
return;
}
if(check && cksum(NULL,*bpp,ip_len) != 0)
fprintf(fp,"IP: CHECKSUM ERROR (%u)",csum);
ntohip(&ip,bpp); /* Can't fail, we've already checked ihl */
ipldump(fp,&ip,bpp,check);
}
void
keep_things_going()
{
void check_time(), ip_recv();
struct interface *ifp;
struct mbuf *bp;
/* Service the loopback queue */
if((bp = dequeue(&loopq)) != NULLBUF){
struct ip ip;
#ifdef TRACE
dump(&loopback,IF_TRACE_IN,TRACE_IP,bp);
#endif
/* Extract IP header */
ntohip(&ip,&bp);
ip_recv(&ip,bp,0);
}
/* Service the interfaces */
#ifdef SYS5
do {
io_active = 0;
#endif
for(ifp = ifaces; ifp != NULLIF; ifp = ifp->next){
if(ifp->recv != NULLVFP)
(*ifp->recv)(ifp);
}
#ifdef SYS5
} while(io_active);
#endif
#ifdef XOBBS
/* service the W2XO PBBS code */
axchk();
#endif
/* Service the clock if it has ticked */
check_time();
#ifdef MSDOS
/* Tell DoubleDos to let the other task run for awhile.
* If DoubleDos isn't active, this is a no-op
*/
#ifndef PLUS
giveup();
#endif
#else
/* Wait until interrupt, then do it all over again */
eihalt();
#endif
}
/* Execute random quench algorithm on an interface's output queue */
void
rquench(
struct iface *ifp,
int drop
){
struct mbuf *bp,*bplast;
int i;
struct qhdr qhdr;
struct ip ip;
struct mbuf *bpdup;
if((i = len_q(ifp->outq)) == 0)
return; /* Queue is empty */
i = urandom(i); /* Select a victim */
/* Search for i-th message on queue */
bplast = NULL;
for(bp = ifp->outq;bp != NULL && i>0;i--,bplast=bp,bp=bp->anext)
;
if(bp == NULL)
return; /* "Can't happen" */
/* Send a source quench */
dup_p(&bpdup,bp,0,len_p(bp));
pullup(&bpdup,&qhdr,sizeof(qhdr));
ntohip(&ip,&bpdup);
icmp_output(&ip,bpdup,ICMP_QUENCH,0,NULL);
free_p(&bpdup);
if(!drop)
return; /* All done */
/* Drop the packet */
if(bplast != NULL)
bplast->anext = bp->anext;
else
ifp->outq = bp->anext; /* First on list */
free_p(&bp);
}
/* Process an incoming ICMP packet */
void
icmp_input(
struct iface *iface, /* Incoming interface (ignored) */
struct ip *ip, /* Pointer to decoded IP header structure */
struct mbuf **bpp, /* Pointer to ICMP message */
int rxbroadcast,
int32 said
){
struct icmplink *ipp;
struct icmp icmp; /* ICMP header */
struct ip oip; /* Offending datagram header */
uint type; /* Type of ICMP message */
uint length;
icmpInMsgs++;
if(rxbroadcast){
/* Broadcast ICMP packets are to be IGNORED !! */
icmpInErrors++;
free_p(bpp);
return;
}
length = ip->length - IPLEN - ip->optlen;
if(cksum(NULL,*bpp,length) != 0){
/* Bad ICMP checksum; discard */
icmpInErrors++;
free_p(bpp);
return;
}
ntohicmp(&icmp,bpp);
/* Process the message. Some messages are passed up to the protocol
* module for handling, others are handled here.
*/
type = icmp.type;
switch(type){
case ICMP_TIME_EXCEED: /* Time-to-live Exceeded */
case ICMP_DEST_UNREACH: /* Destination Unreachable */
case ICMP_QUENCH: /* Source Quench */
case ICMP_IPSP: /* Bad security packet */
switch(type){
case ICMP_TIME_EXCEED: /* Time-to-live Exceeded */
icmpInTimeExcds++;
break;
case ICMP_DEST_UNREACH: /* Destination Unreachable */
icmpInDestUnreachs++;
break;
case ICMP_QUENCH: /* Source Quench */
icmpInSrcQuenchs++;
break;
}
ntohip(&oip,bpp); /* Extract offending IP header */
if(Icmp_trace){
printf("ICMP from %s:",inet_ntoa(ip->source));
printf(" dest %s %s",inet_ntoa(oip.dest),
smsg(Icmptypes,ICMP_TYPES,type));
switch(type){
case ICMP_TIME_EXCEED:
printf(" %s\n",
smsg(Exceed,NEXCEED,icmp.code));
break;
case ICMP_DEST_UNREACH:
printf(" %s\n",
smsg(Unreach,NUNREACH,icmp.code));
break;
case ICMP_IPSP:
printf(" %s\n",smsg(Said_icmp,NIPSP,icmp.code));
break;
default:
printf(" %u\n",icmp.code);
break;
}
}
for(ipp = Icmplink;ipp->funct != NULL;ipp++)
if(ipp->proto == oip.protocol)
break;
if(ipp->funct != NULL){
(*ipp->funct)(ip->source,oip.source,oip.dest,icmp.type,
icmp.code,bpp);
}
break;
case ICMP_ECHO: /* Echo Request */
/* Change type to ECHO_REPLY, recompute checksum,
* and return datagram.
*/
icmpInEchos++;
icmp.type = ICMP_ECHO_REPLY;
htonicmp(&icmp,bpp);
icmpOutEchoReps++;
{
int32 tmp = ip->source;
ip->source = ip->dest;
ip->dest = tmp;
ip->ttl = (char) ipDefaultTTL;
htonip(ip,bpp,IP_CS_NEW);
icmpOutMsgs++;
net_route(NULL,bpp);
}
return;
case ICMP_REDIRECT: /* Redirect */
icmpInRedirects++;
ntohip(&oip,bpp); /* Extract offending IP header */
if(Icmp_trace){
printf("ICMP from %s:",inet_ntoa(ip->source));
printf(" dest %s %s",inet_ntoa(oip.dest),
smsg(Icmptypes,ICMP_TYPES,type));
printf(" new gateway %s\n",inet_ntoa(icmp.args.address));
}
break;
case ICMP_PARAM_PROB: /* Parameter Problem */
icmpInParmProbs++;
break;
case ICMP_ECHO_REPLY: /* Echo Reply */
icmpInEchoReps++;
echo_proc(ip->source,ip->dest,&icmp,bpp);
break;
case ICMP_TIMESTAMP: /* Timestamp */
icmpInTimestamps++;
{
int32 tmp;
uint8 buf[12];
struct timeval tv;
if(pullup(bpp,buf,sizeof(buf)) != sizeof(buf)){
free_p(bpp);
return;
}
gettimeofday(&tv,0);
tmp = (tv.tv_sec % 86400) * 1000 + tv.tv_usec / 1000;
put32(&buf[4],tmp); /* Receive Timestamp */
put32(&buf[8],tmp); /* Transmit Timestamp */
pushdown(bpp,buf,sizeof(buf));
icmp.type = ICMP_TIME_REPLY;
htonicmp(&icmp,bpp);
icmpOutTimestampReps++;
tmp = ip->source;
ip->source = ip->dest;
ip->dest = tmp;
ip->ttl = (char) ipDefaultTTL;
htonip(ip,bpp,IP_CS_NEW);
icmpOutMsgs++;
net_route(NULL,bpp);
return;
}
case ICMP_TIME_REPLY: /* Timestamp Reply */
icmpInTimestampReps++;
break;
case ICMP_INFO_RQST: /* Information Request */
break;
case ICMP_INFO_REPLY: /* Information Reply */
break;
}
free_p(bpp);
}