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/* $Id: pcap_iface.c,v 1.16 2001/10/20 15:23:55 fygrave Exp $ */
/*
** Copyright (C) 2001 Fyodor Yarochkin <fygrave@tigerteam.net>,
** Ofir Arkin <ofir@sys-security.com>
**
** This program is free software; you can redistribute it and/or modify
** it under the terms of the GNU General Public License as published by
** the Free Software Foundation; either version 2 of the License, or
** (at your option) any later version.
**
** All material for nonprofit, educational use only.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
** GNU General Public License for more details.
**
** You should have received a copy of the GNU General Public License
** along with this program; if not, write to the Free Software
** Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
#include "xprobe.h"
/* heavily based on R.Stevens examples */
pcap_t *pd;
int datalink;
inter_t interf;
volatile unsigned char lpcap_done;
int init_pcap(char *iname, char *hostname, hstnet_t *targ) {
char cmd[BUFSIZ+1], errbuf[PCAP_ERRBUF_SIZE];
struct bpf_program fcode;
if (iname == NULL) {
if ((iname = pcap_lookupdev(errbuf)) == NULL) {
fprintf(stderr,"pcap_lookup: %s\n",errbuf);
return -1;
}
}
strncpy((void *)interf.iname, iname, sizeof(interf.iname));
interf.addr = get_iface_addr(interf.iname);
fprintf(stderr, "Interface: %s/%s\n\n",interf.iname, inet_ntoa(interf.addr));
if ((pd = pcap_open_live(iname, LPCAP_SNAPLEN, 0, LPCAP_TIMEOUT,
errbuf)) == NULL) {
fprintf(stderr,"pcap_open_live: %s\n",errbuf);
return -1;
}
if (pcap_lookupnet(iname, (bpf_u_int32 *)&(interf.net),
(bpf_u_int32 *)&(interf.netmask), errbuf) < 0) {
fprintf(stderr,"pcap_lookupnet: %s\n",errbuf);
return -1;
}
snprintf(cmd, sizeof(cmd),"icmp");
if (pcap_compile(pd, &fcode, cmd, 0,*((bpf_u_int32*)&interf.netmask)) < 0) {
fprintf(stderr,"failed to initalize pcap filter! (check "
"netmask/hostname!)\n");
return -1;
}
if (pcap_setfilter(pd, &fcode) < 0) {
fprintf(stderr,"pcap_setfilter: %s\n",errbuf);
return -1;
}
if ((datalink = pcap_datalink(pd)) < 0) {
fprintf(stderr,"pcap_datalink: %s\n",errbuf);
return -1;
}
return 1;
}
#ifdef __linux__
/* timeout handling on linux version of libpcap is bloody broken */
/* so we gotta fix it in such a dogdy way */
unsigned char *next_pack(ssize_t *len) {
unsigned char *ptr = NULL;
struct pcap_pkthdr hdr;
int sd;
fd_set fds;
struct timeval wait;
wait.tv_sec = receive_timeout;
wait.tv_usec = 0;
sd = pcap_fileno(pd);
while(!lpcap_done && ptr == NULL) {
FD_ZERO(&fds);
FD_SET(sd, &fds);
if (select(sd+1, &fds, (fd_set *)0, (fd_set *)0, &wait) <= 0)
return NULL;
ptr = (char *) pcap_next(pd, &hdr);
}
if (ptr != NULL) *len = hdr.caplen;
return(ptr);
}
#else /* everywhere esles timeout seems to be honored properly */
unsigned char *next_pack(ssize_t *len) {
unsigned char *ptr;
struct pcap_pkthdr hdr;
while((ptr = (unsigned char *) pcap_next(pd, &hdr)) == NULL) if (lpcap_done) return NULL;
*len = hdr.caplen;
return(ptr);
}
#endif
unsigned char *read_icmp(ssize_t *packlen, int type, int code) {
unsigned char *ptr;
struct ether_header *ehp;
struct ip *ip;
struct icmp *icmp;
lpcap_done = 0;
signal(SIGALRM, read_icmp_timeout);
alarm(receive_timeout);
while(!lpcap_done) {
if((ptr = next_pack(packlen)) == NULL) return NULL;
#ifdef DEBUG
hexdump(ptr, *packlen);
#endif
switch(datalink) {
case DLT_RAW:
break;
case DLT_NULL:
#ifdef DLT_LOOP
case DLT_LOOP:
#endif
*packlen -= 4;
ptr += 4;
break;
case DLT_EN10MB:
ehp = (struct ether_header *)ptr;
if (ntohs(ehp->ether_type) != ETHERTYPE_IP) {
fprintf(stderr,">>ERROR: datagram type %x is not IP\n",
ntohs(ehp->ether_type));
ptr = NULL;
break;
}
*packlen -= 14;
ptr += 14;
break;
case DLT_PPP:
*packlen -= 24;
ptr += 24;
break;
case DLT_SLIP:
*packlen -= 24;
ptr += 24;
break;
case DLT_FDDI:
*packlen -= 21;
ptr += 21;
break;
#ifdef DLT_LINUX_SLL
case DLT_LINUX_SLL:
*packlen -= 16;
ptr += 16;
break;
#endif
default:
fprintf(stderr,"Unknown datalink type: %d\nPlease report!\n",
datalink);
exit(1);
}
if (ptr != NULL && *packlen > (sizeof(ip) + 8)) {
ip = (struct ip *) ptr;
icmp =(struct icmp *)(ptr + (ip->ip_hl<<2));
#ifdef DEBUG
fprintf(stderr,"Received: icmp type: %d code: %d\n",
icmp->icmp_type, icmp->icmp_code);
#endif
if (((code == -1) || (code == icmp->icmp_code)) &&
((type == -1) || (type == icmp->icmp_type)))
return ptr;
}
} /* while(.. */
return NULL;
}
void read_icmp_timeout(int sig) {
lpcap_done = 1;
}
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