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ICMP.C
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1993-08-09
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258 lines
/* Internet Control Message Protocol (ICMP)
* Copyright 1991 Phil Karn, KA9Q
*/
#include <stdio.h>
#include "global.h"
#include "mbuf.h"
#include "timer.h"
#include "iface.h"
#include "ip.h"
#include "icmp.h"
#include "netuser.h"
struct mib_entry Icmp_mib[] = {
"", 0,
"InMsgs", 0,
"InErrors", 0,
"InDestUnreachs", 0,
"InTimeExcds", 0,
"InParmProbs", 0,
"InSrcQuenchs", 0,
"InRedirects", 0,
"InEchos", 0,
"InEchoReps", 0,
"InTimestamps", 0,
"InTimestampReps", 0,
"InAddrMasks", 0,
"InAddrMaskReps", 0,
"OutMsgs", 0,
"OutErrors", 0,
"OutDestUnreachs", 0,
"OutTimeExcds", 0,
"OutParmProbs", 0,
"OutSrcQuenchs", 0,
"OutRedirects", 0,
"OutEchos", 0,
"OutEchoReps", 0,
"OutTimestamps", 0,
"OutTimestampReps", 0,
"OutAddrMasks", 0,
"OutAddrMaskReps", 0,
};
/* 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 *bp, /* Pointer to ICMP message */
int rxbroadcast)
{
struct icmplink *ipp;
struct mbuf *tbp;
struct icmp icmp; /* ICMP header */
struct ip oip; /* Offending datagram header */
unsigned char type; /* Type of ICMP message */
int16 length;
icmpInMsgs++;
/* Broadcast ICMP packets are to be IGNORED !! */
if(rxbroadcast){
icmpInErrors++;
goto quit;
}
/* Bad ICMP checksum; discard */
if(cksum(NULLHEADER,bp,length = (ip->length - IPLEN - ip->optlen)) != 0) {
icmpInErrors++;
goto quit;
}
ntohicmp(&icmp,&bp);
/* Process the message. Some messages are passed up to the protocol
* module for handling, others are handled here.
*/
type = uchar(icmp.type);
switch(type){
case ICMP_TIME_EXCEED: /* Time-to-live Exceeded */
case ICMP_DEST_UNREACH: /* Destination Unreachable */
case ICMP_QUENCH: /* Source Quench */
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,&bp); /* Extract offending IP header */
if(Icmp_trace){
tprintf("ICMP from %s: ",inet_ntoa(ip->source));
tprintf("dest %s %s ",
inet_ntoa(oip.dest),Icmptypes[type]);
switch(type) {
case ICMP_TIME_EXCEED:
tprintf("%s\n",Exceed[uchar(icmp.code)]);
break;
case ICMP_DEST_UNREACH:
tprintf("%s\n",Unreach[uchar(icmp.code)]);
break;
default:
tprintf("%u\n",uchar(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,&bp);
}
break;
case ICMP_ECHO: /* Echo Request */
/* Change type to ECHO_REPLY, recompute checksum,
* and return datagram.
*/
icmpInEchos++;
icmpOutEchoReps++;
icmp.type = ICMP_ECHO_REPLY;
tbp = htonicmp(&icmp,bp);
ip_send(ip->dest,ip->source,ICMP_PTCL,ip->tos,0,tbp,length,0,0);
return;
case ICMP_REDIRECT: /* Redirect */
icmpInRedirects++;
break;
case ICMP_PARAM_PROB: /* Parameter Problem */
icmpInParmProbs++;
break;
case ICMP_ECHO_REPLY: /* Echo Reply */
icmpInEchoReps++;
echo_proc(ip->source,ip->dest,&icmp,bp);
bp = NULLBUF; /* so it won't get freed */
break;
case ICMP_TIMESTAMP: /* Timestamp */
icmpInTimestamps++;
break;
case ICMP_TIME_REPLY: /* Timestamp Reply */
icmpInTimestampReps++;
break;
case ICMP_INFO_RQST: /* Information Request */
case ICMP_INFO_REPLY: /* Information Reply */
break;
}
quit:
free_p(bp);
return;
}
/* Return an ICMP response to the sender of a datagram.
* Unlike most routines, the callER frees the mbuf.
*/
int
icmp_output(
struct ip *ip, /* Header of offending datagram */
struct mbuf *data, /* Data portion of datagram */
char type,char code, /* Codes to send */
union icmp_args *args)
{
struct mbuf *bp = NULLBUF;
struct icmp icmp; /* ICMP protocol header */
int16 dlen; /* Length of data portion of offending pkt */
int16 length; /* Total length of reply */
if(ip == NULLIP)
return -1;
if(uchar(ip->protocol) == ICMP_PTCL) {
/* Peek at type field of ICMP header to see if it's safe to
* return an ICMP message
*/
switch(uchar(data->data[0])){
case ICMP_ECHO_REPLY:
case ICMP_ECHO:
case ICMP_TIMESTAMP:
case ICMP_TIME_REPLY:
case ICMP_INFO_RQST:
case ICMP_INFO_REPLY:
break; /* These are all safe */
default:
/* Never send an ICMP error message about another
* ICMP error message!
*/
return -1;
}
}
/* Compute amount of original datagram to return.
* We return the original IP header, and up to 8 bytes past that.
*/
if((dlen = len_p(data)) > 8)
dlen = 8;
length = dlen + ICMPLEN + IPLEN + ip->optlen;
/* Take excerpt from data portion */
if(dup_p(&bp,data,0,dlen) == 0)
return -1; /* The caller will free data */
/* Recreate and tack on offending IP header */
data = htonip(ip,bp,0);
icmp.type = type;
icmp.code = code;
icmp.args.unused = 0;
switch(uchar(icmp.type)){
case ICMP_PARAM_PROB:
icmpOutParmProbs++;
icmp.args.pointer = args->pointer;
break;
case ICMP_REDIRECT:
icmpOutRedirects++;
icmp.args.address = args->address;
break;
case ICMP_ECHO:
icmpOutEchos++;
break;
case ICMP_ECHO_REPLY:
icmpOutEchoReps++;
break;
case ICMP_INFO_RQST:
case ICMP_INFO_REPLY:
break;
case ICMP_TIMESTAMP:
icmpOutTimestamps++;
break;
case ICMP_TIME_REPLY:
icmpOutTimestampReps++;
icmp.args.echo.id = args->echo.id;
icmp.args.echo.seq = args->echo.seq;
break;
case ICMP_ADDR_MASK:
icmpOutAddrMasks++;
break;
case ICMP_ADDR_MASK_REPLY:
icmpOutAddrMaskReps++;
break;
case ICMP_DEST_UNREACH:
if(icmp.code == ICMP_FRAG_NEEDED)
icmp.args.mtu = args->mtu;
icmpOutDestUnreachs++;
break;
case ICMP_TIME_EXCEED:
icmpOutTimeExcds++;
break;
case ICMP_QUENCH:
icmpOutSrcQuenchs++;
break;
}
icmpOutMsgs++;
/* Now stick on the ICMP header */
bp = htonicmp(&icmp,data);
return ip_send(INADDR_ANY,ip->source,ICMP_PTCL,ip->tos,0,bp,length,0,0);
}