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link-bpf.c
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link-bpf.c
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/*
* The ARP Scanner (arp-scan) is Copyright (C) 2005-2019 Roy Hills,
* NTA Monitor Ltd.
*
* This file is part of arp-scan.
*
* arp-scan 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 3 of the License, or
* (at your option) any later version.
*
* arp-scan 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 arp-scan. If not, see <http://www.gnu.org/licenses/>.
*
* link-bpf.c -- BPF link layer functions for arp-scan
*
* Author: Roy Hills
* Date: 1 July 2006
*
* Description:
*
* This contains the link layer functions using the BPF (Berkeley
* Packet Filter) implementation. BPF is typically used on BSD systems such
* as FreeBSD See bpf(4) on a FreeBSD system for details.
*
*/
#include "arp-scan.h"
#ifdef HAVE_NET_IF_H
#include <net/if.h>
#endif
#ifdef HAVE_NET_ROUTE_H
#include <net/route.h>
#endif
/* OpenBSD needs sys/param.h */
#ifdef HAVE_SYS_PARAM_H
#include <sys/param.h>
#endif
#ifdef HAVE_SYS_SYSCTL_H
#include <sys/sysctl.h>
#endif
#ifdef HAVE_NET_IF_DL_H
#include <net/if_dl.h>
#endif
/*
* get_hardware_address -- Get the Ethernet MAC address associated
* with the given device.
* Inputs:
*
* if_name The name of the network interface
* hw_address (output) the Ethernet MAC address
*
* Returns:
*
* None
*/
void
get_hardware_address(const char *if_name, unsigned char hw_address[]) {
struct if_msghdr *ifm;
struct sockaddr_dl *sdl=NULL;
unsigned char *p;
unsigned char *buf;
size_t len;
int mib[] = { CTL_NET, PF_ROUTE, 0, AF_LINK, NET_RT_IFLIST, 0 };
/*
* Use sysctl to obtain interface list.
* We first call sysctl with the 3rd arg set to NULL to obtain the
* required length, then malloc the buffer and call sysctl again to get
* the data.
*/
if (sysctl(mib, 6, NULL, &len, NULL, 0) < 0)
err_sys("sysctl");
buf = Malloc(len);
if (sysctl(mib, 6, buf, &len, NULL, 0) < 0)
err_sys("sysctl");
/*
* Go through all the interfaces in the list until we find the one that
* corresponds to the device we are using.
*/
for (p = buf; p < buf + len; p += ifm->ifm_msglen) {
ifm = (struct if_msghdr *)p;
sdl = (struct sockaddr_dl *)(ifm + 1);
if (ifm->ifm_type != RTM_IFINFO || (ifm->ifm_addrs & RTA_IFP) == 0)
continue;
if (sdl->sdl_family != AF_LINK || sdl->sdl_nlen == 0)
continue;
if ((memcmp(sdl->sdl_data, if_name, sdl->sdl_nlen)) == 0)
break;
}
if (p >= buf + len)
err_msg("Could not get hardware address for interface %s",
if_name);
memcpy(hw_address, sdl->sdl_data + sdl->sdl_nlen, ETH_ALEN);
free(buf);
}