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/****************************************************************************
**
** File: open_pcap()
**
** Author: Mike Borella
**
** Comments: Set up pcap to sniff the packets we want. Most of these
** commands are listed in the pcap(3) man page.
**
*****************************************************************************/
#include <stdio.h>
#include <pcap.h>
#include "config.h"
extern struct arg_t *my_args;
/*----------------------------------------------------------------------------
*
* pcap_open()
*
*----------------------------------------------------------------------------
*/
void open_pcap(void)
{
extern char *pcap_cmd;
extern pcap_t *pd;
extern int datalink;
bpf_u_int32 localnet, netmask;
struct bpf_program fcode;
char errorbuf[PCAP_ERRBUF_SIZE];
void ftlerr(char *, ...);
/*
* Look up the device and get a handle to it
*/
if (my_args->i == NULL)
{
my_args->i = pcap_lookupdev(errorbuf);
if (my_args->i == NULL)
ftlerr("open_pcap: pcap_lookupdev() failed for %s: %s", my_args->i,
errorbuf);
}
/*
* Get a file descriptor to the device
*/
pd = pcap_open_live(my_args->i, SNAPLEN, PROMISC, READ_TIMEOUT, errorbuf);
if (pd == NULL) ftlerr("open_pcap: pcap_open_live() failed for %s: %s",
my_args->i, errorbuf);
/*
* Determine local net and netmask
*/
if (pcap_lookupnet(my_args->i, &localnet, &netmask, errorbuf) < 0)
ftlerr("open_pcap: pcap_lookupnet() failed for %s: %s", my_args->i,
errorbuf);
/*
* Compile command line filter spec info fcode FSM
*/
if (pcap_compile(pd, &fcode, pcap_cmd, 0, netmask) < 0)
ftlerr("pcap_compile: %s", pcap_geterr(pd));
/*
* Set the pcap filter with our fcode FSM. That should do it...
*/
if (pcap_setfilter(pd, &fcode) < 0)
ftlerr("pcap_setfilter: %s", pcap_geterr(pd));
/*
* Get the data link type
*/
datalink = pcap_datalink(pd);
if (datalink < 0) ftlerr("pcap_datalink: %s", pcap_geterr(pd));
}
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