libpcap-1.3.0/pcap-linux.c

/*
 *  pcap-linux.c: Packet capture interface to the Linux kernel
 *
 *  Copyright (c) 2000 Torsten Landschoff <torsten@debian.org>
 *  		       Sebastian Krahmer  <krahmer@cs.uni-potsdam.de>
 *
 *  License: BSD
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions
 *  are met:
 *
 *  1. Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in
 *     the documentation and/or other materials provided with the
 *     distribution.
 *  3. The names of the authors may not be used to endorse or promote
 *     products derived from this software without specific prior
 *     written permission.
 *
 *  THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 *  IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 *  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 *  Modifications:     Added PACKET_MMAP support
 *                     Paolo Abeni <paolo.abeni@email.it> 
 *                     
 *                     based on previous works of:
 *                     Simon Patarin <patarin@cs.unibo.it>
 *                     Phil Wood <cpw@lanl.gov>
 *
 * Monitor-mode support for mac80211 includes code taken from the iw
 * command; the copyright notice for that code is
 *
 * Copyright (c) 2007, 2008	Johannes Berg
 * Copyright (c) 2007		Andy Lutomirski
 * Copyright (c) 2007		Mike Kershaw
 * Copyright (c) 2008		Gábor Stefanik
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifndef lint
static const char rcsid[] _U_ =
    "@(#) $Header: /tcpdump/master/libpcap/pcap-linux.c,v 1.164 2008-12-14 22:00:57 guy Exp $ (LBL)";
#endif

/*
 * Known problems with 2.0[.x] kernels:
 *
 *   - The loopback device gives every packet twice; on 2.2[.x] kernels,
 *     if we use PF_PACKET, we can filter out the transmitted version
 *     of the packet by using data in the "sockaddr_ll" returned by
 *     "recvfrom()", but, on 2.0[.x] kernels, we have to use
 *     PF_INET/SOCK_PACKET, which means "recvfrom()" supplies a
 *     "sockaddr_pkt" which doesn't give us enough information to let
 *     us do that.
 *
 *   - We have to set the interface's IFF_PROMISC flag ourselves, if
 *     we're to run in promiscuous mode, which means we have to turn
 *     it off ourselves when we're done; the kernel doesn't keep track
 *     of how many sockets are listening promiscuously, which means
 *     it won't get turned off automatically when no sockets are
 *     listening promiscuously.  We catch "pcap_close()" and, for
 *     interfaces we put into promiscuous mode, take them out of
 *     promiscuous mode - which isn't necessarily the right thing to
 *     do, if another socket also requested promiscuous mode between
 *     the time when we opened the socket and the time when we close
 *     the socket.
 *
 *   - MSG_TRUNC isn't supported, so you can't specify that "recvfrom()"
 *     return the amount of data that you could have read, rather than
 *     the amount that was returned, so we can't just allocate a buffer
 *     whose size is the snapshot length and pass the snapshot length
 *     as the byte count, and also pass MSG_TRUNC, so that the return
 *     value tells us how long the packet was on the wire.
 *
 *     This means that, if we want to get the actual size of the packet,
 *     so we can return it in the "len" field of the packet header,
 *     we have to read the entire packet, not just the part that fits
 *     within the snapshot length, and thus waste CPU time copying data
 *     from the kernel that our caller won't see.
 *
 *     We have to get the actual size, and supply it in "len", because
 *     otherwise, the IP dissector in tcpdump, for example, will complain
 *     about "truncated-ip", as the packet will appear to have been
 *     shorter, on the wire, than the IP header said it should have been.
 */


#define _GNU_SOURCE

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <limits.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <sys/utsname.h>
#include <sys/mman.h>
#include <linux/if.h>
#include <netinet/in.h>
#include <linux/if_ether.h>
#include <net/if_arp.h>
#include <poll.h>
#include <dirent.h>

#include "pcap-int.h"
#include "pcap/sll.h"
#include "pcap/vlan.h"

#ifdef HAVE_DAG_API
#include "pcap-dag.h"
#endif /* HAVE_DAG_API */

#ifdef HAVE_SEPTEL_API
#include "pcap-septel.h"
#endif /* HAVE_SEPTEL_API */

#ifdef HAVE_SNF_API
#include "pcap-snf.h"
#endif /* HAVE_SNF_API */

#ifdef PCAP_SUPPORT_USB
#include "pcap-usb-linux.h"
#endif

#ifdef PCAP_SUPPORT_BT
#include "pcap-bt-linux.h"
#endif

#ifdef PCAP_SUPPORT_CAN
#include "pcap-can-linux.h"
#endif

#if PCAP_SUPPORT_CANUSB
#include "pcap-canusb-linux.h"
#endif

#ifdef PCAP_SUPPORT_NETFILTER
#include "pcap-netfilter-linux.h"
#endif

/*
 * If PF_PACKET is defined, we can use {SOCK_RAW,SOCK_DGRAM}/PF_PACKET
 * sockets rather than SOCK_PACKET sockets.
 *
 * To use them, we include <linux/if_packet.h> rather than
 * <netpacket/packet.h>; we do so because
 *
 *	some Linux distributions (e.g., Slackware 4.0) have 2.2 or
 *	later kernels and libc5, and don't provide a <netpacket/packet.h>
 *	file;
 *
 *	not all versions of glibc2 have a <netpacket/packet.h> file
 *	that defines stuff needed for some of the 2.4-or-later-kernel
 *	features, so if the system has a 2.4 or later kernel, we
 *	still can't use those features.
 *
 * We're already including a number of other <linux/XXX.h> headers, and
 * this code is Linux-specific (no other OS has PF_PACKET sockets as
 * a raw packet capture mechanism), so it's not as if you gain any
 * useful portability by using <netpacket/packet.h>
 *
 * XXX - should we just include <linux/if_packet.h> even if PF_PACKET
 * isn't defined?  It only defines one data structure in 2.0.x, so
 * it shouldn't cause any problems.
 */
#ifdef PF_PACKET
# include <linux/if_packet.h>

 /*
  * On at least some Linux distributions (for example, Red Hat 5.2),
  * there's no <netpacket/packet.h> file, but PF_PACKET is defined if
  * you include <sys/socket.h>, but <linux/if_packet.h> doesn't define
  * any of the PF_PACKET stuff such as "struct sockaddr_ll" or any of
  * the PACKET_xxx stuff.
  *
  * So we check whether PACKET_HOST is defined, and assume that we have
  * PF_PACKET sockets only if it is defined.
  */
# ifdef PACKET_HOST
#  define HAVE_PF_PACKET_SOCKETS
#  ifdef PACKET_AUXDATA
#   define HAVE_PACKET_AUXDATA
#  endif /* PACKET_AUXDATA */
# endif /* PACKET_HOST */


 /* check for memory mapped access avaibility. We assume every needed 
  * struct is defined if the macro TPACKET_HDRLEN is defined, because it
  * uses many ring related structs and macros */
# ifdef TPACKET_HDRLEN
#  define HAVE_PACKET_RING
#  ifdef TPACKET2_HDRLEN
#   define HAVE_TPACKET2
#  else
#   define TPACKET_V1	0
#  endif /* TPACKET2_HDRLEN */
# endif /* TPACKET_HDRLEN */
#endif /* PF_PACKET */

#ifdef SO_ATTACH_FILTER
#include <linux/types.h>
#include <linux/filter.h>
#endif

/*
 * We need linux/sockios.h if we have linux/net_tstamp.h (for time stamp
 * specification) or linux/ethtool.h (for ethtool ioctls to get offloading
 * information).
 */
#if defined(HAVE_LINUX_NET_TSTAMP_H) || defined(HAVE_LINUX_ETHTOOL_H)
#include <linux/sockios.h>
#endif

#ifdef HAVE_LINUX_NET_TSTAMP_H
#include <linux/net_tstamp.h>
#endif

/*
 * Got Wireless Extensions?
 */
#ifdef HAVE_LINUX_WIRELESS_H
#include <linux/wireless.h>
#endif /* HAVE_LINUX_WIRELESS_H */

/*
 * Got libnl?
 */
#ifdef HAVE_LIBNL
#include <linux/nl80211.h>

#include <netlink/genl/genl.h>
#include <netlink/genl/family.h>
#include <netlink/genl/ctrl.h>
#include <netlink/msg.h>
#include <netlink/attr.h>
#endif /* HAVE_LIBNL */

/*
 * Got ethtool support?
 */
#ifdef HAVE_LINUX_ETHTOOL_H
#include <linux/ethtool.h>
#endif

#ifndef HAVE_SOCKLEN_T
typedef int		socklen_t;
#endif

#ifndef MSG_TRUNC
/*
 * This is being compiled on a system that lacks MSG_TRUNC; define it
 * with the value it has in the 2.2 and later kernels, so that, on
 * those kernels, when we pass it in the flags argument to "recvfrom()"
 * we're passing the right value and thus get the MSG_TRUNC behavior
 * we want.  (We don't get that behavior on 2.0[.x] kernels, because
 * they didn't support MSG_TRUNC.)
 */
#define MSG_TRUNC	0x20
#endif

#ifndef SOL_PACKET
/*
 * This is being compiled on a system that lacks SOL_PACKET; define it
 * with the value it has in the 2.2 and later kernels, so that we can
 * set promiscuous mode in the good modern way rather than the old
 * 2.0-kernel crappy way.
 */
#define SOL_PACKET	263
#endif

#define MAX_LINKHEADER_SIZE	256

/*
 * When capturing on all interfaces we use this as the buffer size.
 * Should be bigger then all MTUs that occur in real life.
 * 64kB should be enough for now.
 */
#define BIGGER_THAN_ALL_MTUS	(64*1024)

/*
 * Prototypes for internal functions and methods.
 */
static void map_arphrd_to_dlt(pcap_t *, int, int);
#ifdef HAVE_PF_PACKET_SOCKETS
static short int map_packet_type_to_sll_type(short int);
#endif
static int pcap_activate_linux(pcap_t *);
static int activate_old(pcap_t *);
static int activate_new(pcap_t *);
static int activate_mmap(pcap_t *, int *);
static int pcap_can_set_rfmon_linux(pcap_t *);
static int pcap_read_linux(pcap_t *, int, pcap_handler, u_char *);
static int pcap_read_packet(pcap_t *, pcap_handler, u_char *);
static int pcap_inject_linux(pcap_t *, const void *, size_t);
static int pcap_stats_linux(pcap_t *, struct pcap_stat *);
static int pcap_setfilter_linux(pcap_t *, struct bpf_program *);
static int pcap_setdirection_linux(pcap_t *, pcap_direction_t);
static void pcap_cleanup_linux(pcap_t *);

union thdr {
	struct tpacket_hdr	*h1;
	struct tpacket2_hdr	*h2;
	void			*raw;
};

#ifdef HAVE_PACKET_RING
#define RING_GET_FRAME(h) (((union thdr **)h->buffer)[h->offset])

static void destroy_ring(pcap_t *handle);
static int create_ring(pcap_t *handle, int *status);
static int prepare_tpacket_socket(pcap_t *handle);
static void pcap_cleanup_linux_mmap(pcap_t *);
static int pcap_read_linux_mmap(pcap_t *, int, pcap_handler , u_char *);
static int pcap_setfilter_linux_mmap(pcap_t *, struct bpf_program *);
static int pcap_setnonblock_mmap(pcap_t *p, int nonblock, char *errbuf);
static int pcap_getnonblock_mmap(pcap_t *p, char *errbuf);
static void pcap_oneshot_mmap(u_char *user, const struct pcap_pkthdr *h,
    const u_char *bytes);
#endif

/*
 * Wrap some ioctl calls
 */
#ifdef HAVE_PF_PACKET_SOCKETS
static int	iface_get_id(int fd, const char *device, char *ebuf);
#endif /* HAVE_PF_PACKET_SOCKETS */
static int	iface_get_mtu(int fd, const char *device, char *ebuf);
static int 	iface_get_arptype(int fd, const char *device, char *ebuf);
#ifdef HAVE_PF_PACKET_SOCKETS
static int 	iface_bind(int fd, int ifindex, char *ebuf);
#ifdef IW_MODE_MONITOR
static int	has_wext(int sock_fd, const char *device, char *ebuf);
#endif /* IW_MODE_MONITOR */
static int	enter_rfmon_mode(pcap_t *handle, int sock_fd,
    const char *device);
#endif /* HAVE_PF_PACKET_SOCKETS */
static int	iface_get_offload(pcap_t *handle);
static int 	iface_bind_old(int fd, const char *device, char *ebuf);

#ifdef SO_ATTACH_FILTER
static int	fix_program(pcap_t *handle, struct sock_fprog *fcode,
    int is_mapped);
static int	fix_offset(struct bpf_insn *p);
static int	set_kernel_filter(pcap_t *handle, struct sock_fprog *fcode);
static int	reset_kernel_filter(pcap_t *handle);

static struct sock_filter	total_insn
	= BPF_STMT(BPF_RET | BPF_K, 0);
static struct sock_fprog	total_fcode
	= { 1, &total_insn };
#endif /* SO_ATTACH_FILTER */

pcap_t *
pcap_create(const char *device, char *ebuf)
{
	pcap_t *handle;

	/*
	 * A null device name is equivalent to the "any" device.
	 */
	if (device == NULL)
		device = "any";

#ifdef HAVE_DAG_API
	if (strstr(device, "dag")) {
		return dag_create(device, ebuf);
	}
#endif /* HAVE_DAG_API */

#ifdef HAVE_SEPTEL_API
	if (strstr(device, "septel")) {
		return septel_create(device, ebuf);
	}
#endif /* HAVE_SEPTEL_API */

#ifdef HAVE_SNF_API
        handle = snf_create(device, ebuf);
        if (strstr(device, "snf") || handle != NULL)
		return handle;

#endif /* HAVE_SNF_API */

#ifdef PCAP_SUPPORT_BT
	if (strstr(device, "bluetooth")) {
		return bt_create(device, ebuf);
	}
#endif

#if PCAP_SUPPORT_CANUSB
  if (strstr(device, "canusb")) {
    return canusb_create(device, ebuf);
  }
#endif

#ifdef PCAP_SUPPORT_CAN
	if ((strncmp(device, "can", 3) == 0 && isdigit(device[3])) ||
	    (strncmp(device, "vcan", 4) == 0 && isdigit(device[4]))) {
		return can_create(device, ebuf);
	}
#endif

#ifdef PCAP_SUPPORT_USB
	if (strstr(device, "usbmon")) {
		return usb_create(device, ebuf);
	}
#endif

#ifdef PCAP_SUPPORT_NETFILTER
	if (strncmp(device, "nflog", strlen("nflog")) == 0) {
		return nflog_create(device, ebuf);
	}
#endif

	handle = pcap_create_common(device, ebuf);
	if (handle == NULL)
		return NULL;

	handle->activate_op = pcap_activate_linux;
	handle->can_set_rfmon_op = pcap_can_set_rfmon_linux;
#if defined(HAVE_LINUX_NET_TSTAMP_H) && defined(PACKET_TIMESTAMP)
	/*
	 * We claim that we support:
	 *
	 *	software time stamps, with no details about their precision;
	 *	hardware time stamps, synced to the host time;
	 *	hardware time stamps, not synced to the host time.
	 *
	 * XXX - we can't ask a device whether it supports
	 * hardware time stamps, so we just claim all devices do.
	 */
	handle->tstamp_type_count = 3;
	handle->tstamp_type_list = malloc(3 * sizeof(u_int));
	if (handle->tstamp_type_list == NULL) {
		free(handle);
		return NULL;
	}
	handle->tstamp_type_list[0] = PCAP_TSTAMP_HOST;
	handle->tstamp_type_list[1] = PCAP_TSTAMP_ADAPTER;
	handle->tstamp_type_list[2] = PCAP_TSTAMP_ADAPTER_UNSYNCED;
#endif

	return handle;
}

#ifdef HAVE_LIBNL
/*
 * If interface {if} is a mac80211 driver, the file
 * /sys/class/net/{if}/phy80211 is a symlink to
 * /sys/class/ieee80211/{phydev}, for some {phydev}.
 *
 * On Fedora 9, with a 2.6.26.3-29 kernel, my Zydas stick, at
 * least, has a "wmaster0" device and a "wlan0" device; the
 * latter is the one with the IP address.  Both show up in
 * "tcpdump -D" output.  Capturing on the wmaster0 device
 * captures with 802.11 headers.
 *
 * airmon-ng searches through /sys/class/net for devices named
 * monN, starting with mon0; as soon as one *doesn't* exist,
 * it chooses that as the monitor device name.  If the "iw"
 * command exists, it does "iw dev {if} interface add {monif}
 * type monitor", where {monif} is the monitor device.  It
 * then (sigh) sleeps .1 second, and then configures the
 * device up.  Otherwise, if /sys/class/ieee80211/{phydev}/add_iface
 * is a file, it writes {mondev}, without a newline, to that file,
 * and again (sigh) sleeps .1 second, and then iwconfig's that
 * device into monitor mode and configures it up.  Otherwise,
 * you can't do monitor mode.
 *
 * All these devices are "glued" together by having the
 * /sys/class/net/{device}/phy80211 links pointing to the same
 * place, so, given a wmaster, wlan, or mon device, you can
 * find the other devices by looking for devices with
 * the same phy80211 link.
 *
 * To turn monitor mode off, delete the monitor interface,
 * either with "iw dev {monif} interface del" or by sending
 * {monif}, with no NL, down /sys/class/ieee80211/{phydev}/remove_iface
 *
 * Note: if you try to create a monitor device named "monN", and
 * there's already a "monN" device, it fails, as least with
 * the netlink interface (which is what iw uses), with a return
 * value of -ENFILE.  (Return values are negative errnos.)  We
 * could probably use that to find an unused device.
 *
 * Yes, you can have multiple monitor devices for a given
 * physical device.
*/

/*
 * Is this a mac80211 device?  If so, fill in the physical device path and
 * return 1; if not, return 0.  On an error, fill in handle->errbuf and
 * return PCAP_ERROR.
 */
static int
get_mac80211_phydev(pcap_t *handle, const char *device, char *phydev_path,
    size_t phydev_max_pathlen)
{
	char *pathstr;
	ssize_t bytes_read;

	/*
	 * Generate the path string for the symlink to the physical device.
	 */
	if (asprintf(&pathstr, "/sys/class/net/%s/phy80211", device) == -1) {
		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
		    "%s: Can't generate path name string for /sys/class/net device",
		    device);
		return PCAP_ERROR;
	}
	bytes_read = readlink(pathstr, phydev_path, phydev_max_pathlen);
	if (bytes_read == -1) {
		if (errno == ENOENT || errno == EINVAL) {
			/*
			 * Doesn't exist, or not a symlink; assume that
			 * means it's not a mac80211 device.
			 */
			free(pathstr);
			return 0;
		}
		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
		    "%s: Can't readlink %s: %s", device, pathstr,
		    strerror(errno));
		free(pathstr);
		return PCAP_ERROR;
	}
	free(pathstr);
	phydev_path[bytes_read] = '\0';
	return 1;
}

#ifdef HAVE_LIBNL_2_x
#define get_nl_errmsg	nl_geterror
#else
/* libnl 2.x compatibility code */

#define nl_sock nl_handle

static inline struct nl_handle *
nl_socket_alloc(void)
{
	return nl_handle_alloc();
}

static inline void
nl_socket_free(struct nl_handle *h)
{
	nl_handle_destroy(h);
}

#define get_nl_errmsg	strerror

static inline int
__genl_ctrl_alloc_cache(struct nl_handle *h, struct nl_cache **cache)
{
	struct nl_cache *tmp = genl_ctrl_alloc_cache(h);
	if (!tmp)
		return -ENOMEM;
	*cache = tmp;
	return 0;
}
#define genl_ctrl_alloc_cache __genl_ctrl_alloc_cache
#endif /* !HAVE_LIBNL_2_x */

struct nl80211_state {
	struct nl_sock *nl_sock;
	struct nl_cache *nl_cache;
	struct genl_family *nl80211;
};

static int
nl80211_init(pcap_t *handle, struct nl80211_state *state, const char *device)
{
	int err;

	state->nl_sock = nl_socket_alloc();
	if (!state->nl_sock) {
		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
		    "%s: failed to allocate netlink handle", device);
		return PCAP_ERROR;
	}

	if (genl_connect(state->nl_sock)) {
		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
		    "%s: failed to connect to generic netlink", device);
		goto out_handle_destroy;
	}

	err = genl_ctrl_alloc_cache(state->nl_sock, &state->nl_cache);
	if (err < 0) {
		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
		    "%s: failed to allocate generic netlink cache: %s",
		    device, get_nl_errmsg(-err));
		goto out_handle_destroy;
	}

	state->nl80211 = genl_ctrl_search_by_name(state->nl_cache, "nl80211");
	if (!state->nl80211) {
		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
		    "%s: nl80211 not found", device);
		goto out_cache_free;
	}

	return 0;

out_cache_free:
	nl_cache_free(state->nl_cache);
out_handle_destroy:
	nl_socket_free(state->nl_sock);
	return PCAP_ERROR;
}

static void
nl80211_cleanup(struct nl80211_state *state)
{
	genl_family_put(state->nl80211);
	nl_cache_free(state->nl_cache);
	nl_socket_free(state->nl_sock);
}

static int
add_mon_if(pcap_t *handle, int sock_fd, struct nl80211_state *state,
    const char *device, const char *mondevice)
{
	int ifindex;
	struct nl_msg *msg;
	int err;

	ifindex = iface_get_id(sock_fd, device, handle->errbuf);
	if (ifindex == -1)
		return PCAP_ERROR;

	msg = nlmsg_alloc();
	if (!msg) {
		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
		    "%s: failed to allocate netlink msg", device);
		return PCAP_ERROR;
	}

	genlmsg_put(msg, 0, 0, genl_family_get_id(state->nl80211), 0,
		    0, NL80211_CMD_NEW_INTERFACE, 0);
	NLA_PUT_U32(msg, NL80211_ATTR_IFINDEX, ifindex);
	NLA_PUT_STRING(msg, NL80211_ATTR_IFNAME, mondevice);
	NLA_PUT_U32(msg, NL80211_ATTR_IFTYPE, NL80211_IFTYPE_MONITOR);

	err = nl_send_auto_complete(state->nl_sock, msg);
	if (err < 0) {
#ifdef HAVE_LIBNL_2_x
		if (err == -NLE_FAILURE) {
#else
		if (err == -ENFILE) {
#endif
			/*
			 * Device not available; our caller should just
			 * keep trying.  (libnl 2.x maps ENFILE to
			 * NLE_FAILURE; it can also map other errors
			 * to that, but there's not much we can do
			 * about that.)
			 */
			nlmsg_free(msg);
			return 0;
		} else {
			/*
			 * Real failure, not just "that device is not
			 * available.
			 */
			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
			    "%s: nl_send_auto_complete failed adding %s interface: %s",
			    device, mondevice, get_nl_errmsg(-err));
			nlmsg_free(msg);
			return PCAP_ERROR;
		}
	}
	err = nl_wait_for_ack(state->nl_sock);
	if (err < 0) {
#ifdef HAVE_LIBNL_2_x
		if (err == -NLE_FAILURE) {
#else
		if (err == -ENFILE) {
#endif
			/*
			 * Device not available; our caller should just
			 * keep trying.  (libnl 2.x maps ENFILE to
			 * NLE_FAILURE; it can also map other errors
			 * to that, but there's not much we can do
			 * about that.)
			 */
			nlmsg_free(msg);
			return 0;
		} else {
			/*
			 * Real failure, not just "that device is not
			 * available.
			 */
			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
			    "%s: nl_wait_for_ack failed adding %s interface: %s",
			    device, mondevice, get_nl_errmsg(-err));
			nlmsg_free(msg);
			return PCAP_ERROR;
		}
	}

	/*
	 * Success.
	 */
	nlmsg_free(msg);
	return 1;

nla_put_failure:
	snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
	    "%s: nl_put failed adding %s interface",
	    device, mondevice);
	nlmsg_free(msg);
	return PCAP_ERROR;
}

static int
del_mon_if(pcap_t *handle, int sock_fd, struct nl80211_state *state,
    const char *device, const char *mondevice)
{
	int ifindex;
	struct nl_msg *msg;
	int err;

	ifindex = iface_get_id(sock_fd, mondevice, handle->errbuf);
	if (ifindex == -1)
		return PCAP_ERROR;

	msg = nlmsg_alloc();
	if (!msg) {
		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
		    "%s: failed to allocate netlink msg", device);
		return PCAP_ERROR;
	}

	genlmsg_put(msg, 0, 0, genl_family_get_id(state->nl80211), 0,
		    0, NL80211_CMD_DEL_INTERFACE, 0);
	NLA_PUT_U32(msg, NL80211_ATTR_IFINDEX, ifindex);

	err = nl_send_auto_complete(state->nl_sock, msg);
	if (err < 0) {
		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
		    "%s: nl_send_auto_complete failed deleting %s interface: %s",
		    device, mondevice, get_nl_errmsg(-err));
		nlmsg_free(msg);
		return PCAP_ERROR;
	}
	err = nl_wait_for_ack(state->nl_sock);
	if (err < 0) {
		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
		    "%s: nl_wait_for_ack failed adding %s interface: %s",
		    device, mondevice, get_nl_errmsg(-err));
		nlmsg_free(msg);
		return PCAP_ERROR;
	}

	/*
	 * Success.
	 */
	nlmsg_free(msg);
	return 1;

nla_put_failure:
	snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
	    "%s: nl_put failed deleting %s interface",
	    device, mondevice);
	nlmsg_free(msg);
	return PCAP_ERROR;
}

static int
enter_rfmon_mode_mac80211(pcap_t *handle, int sock_fd, const char *device)
{
	int ret;
	char phydev_path[PATH_MAX+1];
	struct nl80211_state nlstate;
	struct ifreq ifr;
	u_int n;

	/*
	 * Is this a mac80211 device?
	 */
	ret = get_mac80211_phydev(handle, device, phydev_path, PATH_MAX);
	if (ret < 0)
		return ret;	/* error */
	if (ret == 0)
		return 0;	/* no error, but not mac80211 device */

	/*
	 * XXX - is this already a monN device?
	 * If so, we're done.
	 * Is that determined by old Wireless Extensions ioctls?
	 */

	/*
	 * OK, it's apparently a mac80211 device.
	 * Try to find an unused monN device for it.
	 */
	ret = nl80211_init(handle, &nlstate, device);
	if (ret != 0)
		return ret;
	for (n = 0; n < UINT_MAX; n++) {
		/*
		 * Try mon{n}.
		 */
		char mondevice[3+10+1];	/* mon{UINT_MAX}\0 */

		snprintf(mondevice, sizeof mondevice, "mon%u", n);
		ret = add_mon_if(handle, sock_fd, &nlstate, device, mondevice);
		if (ret == 1) {
			handle->md.mondevice = strdup(mondevice);
			goto added;
		}
		if (ret < 0) {
			/*
			 * Hard failure.  Just return ret; handle->errbuf
			 * has already been set.
			 */
			nl80211_cleanup(&nlstate);
			return ret;
		}
	}

	snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
	    "%s: No free monN interfaces", device);
	nl80211_cleanup(&nlstate);
	return PCAP_ERROR;

added:

#if 0
	/*
	 * Sleep for .1 seconds.
	 */
	delay.tv_sec = 0;
	delay.tv_nsec = 500000000;
	nanosleep(&delay, NULL);
#endif

	/*
	 * If we haven't already done so, arrange to have
	 * "pcap_close_all()" called when we exit.
	 */
	if (!pcap_do_addexit(handle)) {
		/*
		 * "atexit()" failed; don't put the interface
		 * in rfmon mode, just give up.
		 */
		return PCAP_ERROR_RFMON_NOTSUP;
	}

	/*
	 * Now configure the monitor interface up.
	 */
	memset(&ifr, 0, sizeof(ifr));
	strncpy(ifr.ifr_name, handle->md.mondevice, sizeof(ifr.ifr_name));
	if (ioctl(sock_fd, SIOCGIFFLAGS, &ifr) == -1) {
		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
		    "%s: Can't get flags for %s: %s", device,
		    handle->md.mondevice, strerror(errno));
		del_mon_if(handle, sock_fd, &nlstate, device,
		    handle->md.mondevice);
		nl80211_cleanup(&nlstate);
		return PCAP_ERROR;
	}
	ifr.ifr_flags |= IFF_UP|IFF_RUNNING;
	if (ioctl(sock_fd, SIOCSIFFLAGS, &ifr) == -1) {
		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
		    "%s: Can't set flags for %s: %s", device,
		    handle->md.mondevice, strerror(errno));
		del_mon_if(handle, sock_fd, &nlstate, device,
		    handle->md.mondevice);
		nl80211_cleanup(&nlstate);
		return PCAP_ERROR;
	}

	/*
	 * Success.  Clean up the libnl state.
	 */
	nl80211_cleanup(&nlstate);

	/*
	 * Note that we have to delete the monitor device when we close
	 * the handle.
	 */
	handle->md.must_do_on_close |= MUST_DELETE_MONIF;

	/*
	 * Add this to the list of pcaps to close when we exit.
	 */
	pcap_add_to_pcaps_to_close(handle);

	return 1;
}
#endif /* HAVE_LIBNL */

static int
pcap_can_set_rfmon_linux(pcap_t *handle)
{
#ifdef HAVE_LIBNL
	char phydev_path[PATH_MAX+1];
	int ret;
#endif
#ifdef IW_MODE_MONITOR
	int sock_fd;
	struct iwreq ireq;
#endif

	if (strcmp(handle->opt.source, "any") == 0) {
		/*
		 * Monitor mode makes no sense on the "any" device.
		 */
		return 0;
	}

#ifdef HAVE_LIBNL
	/*
	 * Bleah.  There doesn't seem to be a way to ask a mac80211
	 * device, through libnl, whether it supports monitor mode;
	 * we'll just check whether the device appears to be a
	 * mac80211 device and, if so, assume the device supports
	 * monitor mode.
	 *
	 * wmaster devices don't appear to support the Wireless
	 * Extensions, but we can create a mon device for a
	 * wmaster device, so we don't bother checking whether
	 * a mac80211 device supports the Wireless Extensions.
	 */
	ret = get_mac80211_phydev(handle, handle->opt.source, phydev_path,
	    PATH_MAX);
	if (ret < 0)
		return ret;	/* error */
	if (ret == 1)
		return 1;	/* mac80211 device */
#endif

#ifdef IW_MODE_MONITOR
	/*
	 * Bleah.  There doesn't appear to be an ioctl to use to ask
	 * whether a device supports monitor mode; we'll just do
	 * SIOCGIWMODE and, if it succeeds, assume the device supports
	 * monitor mode.
	 *
	 * Open a socket on which to attempt to get the mode.
	 * (We assume that if we have Wireless Extensions support
	 * we also have PF_PACKET support.)
	 */
	sock_fd = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
	if (sock_fd == -1) {
		(void)snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
		    "socket: %s", pcap_strerror(errno));
		return PCAP_ERROR;
	}

	/*
	 * Attempt to get the current mode.
	 */
	strncpy(ireq.ifr_ifrn.ifrn_name, handle->opt.source,
	    sizeof ireq.ifr_ifrn.ifrn_name);
	ireq.ifr_ifrn.ifrn_name[sizeof ireq.ifr_ifrn.ifrn_name - 1] = 0;
	if (ioctl(sock_fd, SIOCGIWMODE, &ireq) != -1) {
		/*
		 * Well, we got the mode; assume we can set it.
		 */
		close(sock_fd);
		return 1;
	}
	if (errno == ENODEV) {
		/* The device doesn't even exist. */
		(void)snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
		    "SIOCGIWMODE failed: %s", pcap_strerror(errno));
		close(sock_fd);
		return PCAP_ERROR_NO_SUCH_DEVICE;
	}
	close(sock_fd);
#endif
	return 0;
}

/*
 * Grabs the number of dropped packets by the interface from /proc/net/dev.
 *
 * XXX - what about /sys/class/net/{interface name}/rx_*?  There are
 * individual devices giving, in ASCII, various rx_ and tx_ statistics.
 *
 * Or can we get them in binary form from netlink?
 */
static long int
linux_if_drops(const char * if_name)
{
	char buffer[512];
	char * bufptr;
	FILE * file;
	int field_to_convert = 3, if_name_sz = strlen(if_name);
	long int dropped_pkts = 0;
	
	file = fopen("/proc/net/dev", "r");
	if (!file)
		return 0;

	while (!dropped_pkts && fgets( buffer, sizeof(buffer), file ))
	{
		/* 	search for 'bytes' -- if its in there, then
			that means we need to grab the fourth field. otherwise
			grab the third field. */
		if (field_to_convert != 4 && strstr(buffer, "bytes"))
		{
			field_to_convert = 4;
			continue;
		}
	
		/* find iface and make sure it actually matches -- space before the name and : after it */
		if ((bufptr = strstr(buffer, if_name)) &&
			(bufptr == buffer || *(bufptr-1) == ' ') &&
			*(bufptr + if_name_sz) == ':')
		{
			bufptr = bufptr + if_name_sz + 1;

			/* grab the nth field from it */
			while( --field_to_convert && *bufptr != '\0')
			{
				while (*bufptr != '\0' && *(bufptr++) == ' ');
				while (*bufptr != '\0' && *(bufptr++) != ' ');
			}
			
			/* get rid of any final spaces */
			while (*bufptr != '\0' && *bufptr == ' ') bufptr++;
			
			if (*bufptr != '\0')
				dropped_pkts = strtol(bufptr, NULL, 10);

			break;
		}
	}
	
	fclose(file);
	return dropped_pkts;
} 


/*
 * With older kernels promiscuous mode is kind of interesting because we
 * have to reset the interface before exiting. The problem can't really
 * be solved without some daemon taking care of managing usage counts.
 * If we put the interface into promiscuous mode, we set a flag indicating
 * that we must take it out of that mode when the interface is closed,
 * and, when closing the interface, if that flag is set we take it out
 * of promiscuous mode.
 *
 * Even with newer kernels, we have the same issue with rfmon mode.
 */

static void	pcap_cleanup_linux( pcap_t *handle )
{
	struct ifreq	ifr;
#ifdef HAVE_LIBNL
	struct nl80211_state nlstate;
	int ret;
#endif /* HAVE_LIBNL */
#ifdef IW_MODE_MONITOR
	int oldflags;
	struct iwreq ireq;
#endif /* IW_MODE_MONITOR */

	if (handle->md.must_do_on_close != 0) {
		/*
		 * There's something we have to do when closing this
		 * pcap_t.
		 */
		if (handle->md.must_do_on_close & MUST_CLEAR_PROMISC) {
			/*
			 * We put the interface into promiscuous mode;
			 * take it out of promiscuous mode.
			 *
			 * XXX - if somebody else wants it in promiscuous
			 * mode, this code cannot know that, so it'll take
			 * it out of promiscuous mode.  That's not fixable
			 * in 2.0[.x] kernels.
			 */
			memset(&ifr, 0, sizeof(ifr));
			strncpy(ifr.ifr_name, handle->md.device,
			    sizeof(ifr.ifr_name));
			if (ioctl(handle->fd, SIOCGIFFLAGS, &ifr) == -1) {
				fprintf(stderr,
				    "Can't restore interface %s flags (SIOCGIFFLAGS failed: %s).\n"
				    "Please adjust manually.\n"
				    "Hint: This can't happen with Linux >= 2.2.0.\n",
				    handle->md.device, strerror(errno));
			} else {
				if (ifr.ifr_flags & IFF_PROMISC) {
					/*
					 * Promiscuous mode is currently on;
					 * turn it off.
					 */
					ifr.ifr_flags &= ~IFF_PROMISC;
					if (ioctl(handle->fd, SIOCSIFFLAGS,
					    &ifr) == -1) {
						fprintf(stderr,
						    "Can't restore interface %s flags (SIOCSIFFLAGS failed: %s).\n"
						    "Please adjust manually.\n"
						    "Hint: This can't happen with Linux >= 2.2.0.\n",
						    handle->md.device,
						    strerror(errno));
					}
				}
			}
		}

#ifdef HAVE_LIBNL
		if (handle->md.must_do_on_close & MUST_DELETE_MONIF) {
			ret = nl80211_init(handle, &nlstate, handle->md.device);
			if (ret >= 0) {
				ret = del_mon_if(handle, handle->fd, &nlstate,
				    handle->md.device, handle->md.mondevice);
				nl80211_cleanup(&nlstate);
			}
			if (ret < 0) {
				fprintf(stderr,
				    "Can't delete monitor interface %s (%s).\n"
				    "Please delete manually.\n",
				    handle->md.mondevice, handle->errbuf);
			}
		}
#endif /* HAVE_LIBNL */

#ifdef IW_MODE_MONITOR
		if (handle->md.must_do_on_close & MUST_CLEAR_RFMON) {
			/*
			 * We put the interface into rfmon mode;
			 * take it out of rfmon mode.
			 *
			 * XXX - if somebody else wants it in rfmon
			 * mode, this code cannot know that, so it'll take
			 * it out of rfmon mode.
			 */

			/*
			 * First, take the interface down if it's up;
			 * otherwise, we might get EBUSY.
			 * If we get errors, just drive on and print
			 * a warning if we can't restore the mode.
			 */
			oldflags = 0;
			memset(&ifr, 0, sizeof(ifr));
			strncpy(ifr.ifr_name, handle->md.device,
			    sizeof(ifr.ifr_name));
			if (ioctl(handle->fd, SIOCGIFFLAGS, &ifr) != -1) {
				if (ifr.ifr_flags & IFF_UP) {
					oldflags = ifr.ifr_flags;
					ifr.ifr_flags &= ~IFF_UP;
					if (ioctl(handle->fd, SIOCSIFFLAGS, &ifr) == -1)
						oldflags = 0;	/* didn't set, don't restore */
				}
			}

			/*
			 * Now restore the mode.
			 */
			strncpy(ireq.ifr_ifrn.ifrn_name, handle->md.device,
			    sizeof ireq.ifr_ifrn.ifrn_name);
			ireq.ifr_ifrn.ifrn_name[sizeof ireq.ifr_ifrn.ifrn_name - 1]
			    = 0;
			ireq.u.mode = handle->md.oldmode;
			if (ioctl(handle->fd, SIOCSIWMODE, &ireq) == -1) {
				/*
				 * Scientist, you've failed.
				 */
				fprintf(stderr,
				    "Can't restore interface %s wireless mode (SIOCSIWMODE failed: %s).\n"
				    "Please adjust manually.\n",
				    handle->md.device, strerror(errno));
			}

			/*
			 * Now bring the interface back up if we brought
			 * it down.
			 */
			if (oldflags != 0) {
				ifr.ifr_flags = oldflags;
				if (ioctl(handle->fd, SIOCSIFFLAGS, &ifr) == -1) {
					fprintf(stderr,
					    "Can't bring interface %s back up (SIOCSIFFLAGS failed: %s).\n"
					    "Please adjust manually.\n",
					    handle->md.device, strerror(errno));
				}
			}
		}
#endif /* IW_MODE_MONITOR */

		/*
		 * Take this pcap out of the list of pcaps for which we
		 * have to take the interface out of some mode.
		 */
		pcap_remove_from_pcaps_to_close(handle);
	}

	if (handle->md.mondevice != NULL) {
		free(handle->md.mondevice);
		handle->md.mondevice = NULL;
	}
	if (handle->md.device != NULL) {
		free(handle->md.device);
		handle->md.device = NULL;
	}
	pcap_cleanup_live_common(handle);
}

/*
 *  Get a handle for a live capture from the given device. You can
 *  pass NULL as device to get all packages (without link level
 *  information of course). If you pass 1 as promisc the interface
 *  will be set to promiscous mode (XXX: I think this usage should
 *  be deprecated and functions be added to select that later allow
 *  modification of that values -- Torsten).
 */
static int
pcap_activate_linux(pcap_t *handle)
{
	const char	*device;
	int		status = 0;

	device = handle->opt.source;

	handle->inject_op = pcap_inject_linux;
	handle->setfilter_op = pcap_setfilter_linux;
	handle->setdirection_op = pcap_setdirection_linux;
	handle->set_datalink_op = NULL;	/* can't change data link type */
	handle->getnonblock_op = pcap_getnonblock_fd;
	handle->setnonblock_op = pcap_setnonblock_fd;
	handle->cleanup_op = pcap_cleanup_linux;
	handle->read_op = pcap_read_linux;
	handle->stats_op = pcap_stats_linux;

	/*
	 * The "any" device is a special device which causes us not
	 * to bind to a particular device and thus to look at all
	 * devices.
	 */
	if (strcmp(device, "any") == 0) {
		if (handle->opt.promisc) {
			handle->opt.promisc = 0;
			/* Just a warning. */
			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
			    "Promiscuous mode not supported on the \"any\" device");
			status = PCAP_WARNING_PROMISC_NOTSUP;
		}
	}

	handle->md.device	= strdup(device);
	if (handle->md.device == NULL) {
		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "strdup: %s",
			 pcap_strerror(errno) );
		return PCAP_ERROR;
	}
	
	/*
	 * If we're in promiscuous mode, then we probably want 
	 * to see when the interface drops packets too, so get an
	 * initial count from /proc/net/dev
	 */
	if (handle->opt.promisc)
		handle->md.proc_dropped = linux_if_drops(handle->md.device);

	/*
	 * Current Linux kernels use the protocol family PF_PACKET to
	 * allow direct access to all packets on the network while
	 * older kernels had a special socket type SOCK_PACKET to
	 * implement this feature.
	 * While this old implementation is kind of obsolete we need
	 * to be compatible with older kernels for a while so we are
	 * trying both methods with the newer method preferred.
	 */
	status = activate_new(handle);
	if (status < 0) {
		/*
		 * Fatal error with the new way; just fail.
		 * status has the error return; if it's PCAP_ERROR,
		 * handle->errbuf has been set appropriately.
		 */
		goto fail;
	}
	if (status == 1) {
		/*
		 * Success.
		 * Try to use memory-mapped access.
		 */
		switch (activate_mmap(handle, &status)) {

		case 1:
			/*
			 * We succeeded.  status has been
			 * set to the status to return,
			 * which might be 0, or might be
			 * a PCAP_WARNING_ value.
			 */
			return status;

		case 0:
			/*
			 * Kernel doesn't support it - just continue
			 * with non-memory-mapped access.
			 */
			break;

		case -1:
			/*
			 * We failed to set up to use it, or the kernel
			 * supports it, but we failed to enable it.
			 * status has been set to the error status to
			 * return and, if it's PCAP_ERROR, handle->errbuf
			 * contains the error message.
			 */
			goto fail;
		}
	}
	else if (status == 0) {
		/* Non-fatal error; try old way */
		if ((status = activate_old(handle)) != 1) {
			/*
			 * Both methods to open the packet socket failed.
			 * Tidy up and report our failure (handle->errbuf
			 * is expected to be set by the functions above).
			 */
			goto fail;
		}
	}

	/*
	 * We set up the socket, but not with memory-mapped access.
	 */
	status = 0;
	if (handle->opt.buffer_size != 0) {
		/*
		 * Set the socket buffer size to the specified value.
		 */
		if (setsockopt(handle->fd, SOL_SOCKET, SO_RCVBUF,
		    &handle->opt.buffer_size,
		    sizeof(handle->opt.buffer_size)) == -1) {
			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
				 "SO_RCVBUF: %s", pcap_strerror(errno));
			status = PCAP_ERROR;
			goto fail;
		}
	}

	/* Allocate the buffer */

	handle->buffer	 = malloc(handle->bufsize + handle->offset);
	if (!handle->buffer) {
		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
			 "malloc: %s", pcap_strerror(errno));
		status = PCAP_ERROR;
		goto fail;
	}

	/*
	 * "handle->fd" is a socket, so "select()" and "poll()"
	 * should work on it.
	 */
	handle->selectable_fd = handle->fd;

	return status;

fail:
	pcap_cleanup_linux(handle);
	return status;
}

/*
 *  Read at most max_packets from the capture stream and call the callback
 *  for each of them. Returns the number of packets handled or -1 if an
 *  error occured.
 */
static int
pcap_read_linux(pcap_t *handle, int max_packets, pcap_handler callback, u_char *user)
{
	/*
	 * Currently, on Linux only one packet is delivered per read,
	 * so we don't loop.
	 */
	return pcap_read_packet(handle, callback, user);
}

/*
 *  Read a packet from the socket calling the handler provided by
 *  the user. Returns the number of packets received or -1 if an
 *  error occured.
 */
static int
pcap_read_packet(pcap_t *handle, pcap_handler callback, u_char *userdata)
{
	u_char			*bp;
	int			offset;
#ifdef HAVE_PF_PACKET_SOCKETS
	struct sockaddr_ll	from;
	struct sll_header	*hdrp;
#else
	struct sockaddr		from;
#endif
#if defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI)
	struct iovec		iov;
	struct msghdr		msg;
	struct cmsghdr		*cmsg;
	union {
		struct cmsghdr	cmsg;
		char		buf[CMSG_SPACE(sizeof(struct tpacket_auxdata))];
	} cmsg_buf;
#else /* defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI) */
	socklen_t		fromlen;
#endif /* defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI) */
	int			packet_len, caplen;
	struct pcap_pkthdr	pcap_header;

#ifdef HAVE_PF_PACKET_SOCKETS
	/*
	 * If this is a cooked device, leave extra room for a
	 * fake packet header.
	 */
	if (handle->md.cooked)
		offset = SLL_HDR_LEN;
	else
		offset = 0;
#else
	/*
	 * This system doesn't have PF_PACKET sockets, so it doesn't
	 * support cooked devices.
	 */
	offset = 0;
#endif

	/*
	 * Receive a single packet from the kernel.
	 * We ignore EINTR, as that might just be due to a signal
	 * being delivered - if the signal should interrupt the
	 * loop, the signal handler should call pcap_breakloop()
	 * to set handle->break_loop (we ignore it on other
	 * platforms as well).
	 * We also ignore ENETDOWN, so that we can continue to
	 * capture traffic if the interface goes down and comes
	 * back up again; comments in the kernel indicate that
	 * we'll just block waiting for packets if we try to
	 * receive from a socket that delivered ENETDOWN, and,
	 * if we're using a memory-mapped buffer, we won't even
	 * get notified of "network down" events.
	 */
	bp = handle->buffer + handle->offset;

#if defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI)
	msg.msg_name		= &from;
	msg.msg_namelen		= sizeof(from);
	msg.msg_iov		= &iov;
	msg.msg_iovlen		= 1;
	msg.msg_control		= &cmsg_buf;
	msg.msg_controllen	= sizeof(cmsg_buf);
	msg.msg_flags		= 0;

	iov.iov_len		= handle->bufsize - offset;
	iov.iov_base		= bp + offset;
#endif /* defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI) */

	do {
		/*
		 * Has "pcap_breakloop()" been called?
		 */
		if (handle->break_loop) {
			/*
			 * Yes - clear the flag that indicates that it has,
			 * and return PCAP_ERROR_BREAK as an indication that
			 * we were told to break out of the loop.
			 */
			handle->break_loop = 0;
			return PCAP_ERROR_BREAK;
		}

#if defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI)
		packet_len = recvmsg(handle->fd, &msg, MSG_TRUNC);
#else /* defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI) */
		fromlen = sizeof(from);
		packet_len = recvfrom(
			handle->fd, bp + offset,
			handle->bufsize - offset, MSG_TRUNC,
			(struct sockaddr *) &from, &fromlen);
#endif /* defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI) */
	} while (packet_len == -1 && errno == EINTR);

	/* Check if an error occured */

	if (packet_len == -1) {
		switch (errno) {

		case EAGAIN:
			return 0;	/* no packet there */

		case ENETDOWN:
			/*
			 * The device on which we're capturing went away.
			 *
			 * XXX - we should really return
			 * PCAP_ERROR_IFACE_NOT_UP, but pcap_dispatch()
			 * etc. aren't defined to return that.
			 */
			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
				"The interface went down");
			return PCAP_ERROR;

		default:
			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
				 "recvfrom: %s", pcap_strerror(errno));
			return PCAP_ERROR;
		}
	}

#ifdef HAVE_PF_PACKET_SOCKETS
	if (!handle->md.sock_packet) {
		/*
		 * Unfortunately, there is a window between socket() and
		 * bind() where the kernel may queue packets from any
		 * interface.  If we're bound to a particular interface,
		 * discard packets not from that interface.
		 *
		 * (If socket filters are supported, we could do the
		 * same thing we do when changing the filter; however,
		 * that won't handle packet sockets without socket
		 * filter support, and it's a bit more complicated.
		 * It would save some instructions per packet, however.)
		 */
		if (handle->md.ifindex != -1 &&
		    from.sll_ifindex != handle->md.ifindex)
			return 0;

		/*
		 * Do checks based on packet direction.
		 * We can only do this if we're using PF_PACKET; the
		 * address returned for SOCK_PACKET is a "sockaddr_pkt"
		 * which lacks the relevant packet type information.
		 */
		if (from.sll_pkttype == PACKET_OUTGOING) {
			/*
			 * Outgoing packet.
			 * If this is from the loopback device, reject it;
			 * we'll see the packet as an incoming packet as well,
			 * and we don't want to see it twice.
			 */
			if (from.sll_ifindex == handle->md.lo_ifindex)
				return 0;

			/*
			 * If the user only wants incoming packets, reject it.
			 */
			if (handle->direction == PCAP_D_IN)
				return 0;
		} else {
			/*
			 * Incoming packet.
			 * If the user only wants outgoing packets, reject it.
			 */
			if (handle->direction == PCAP_D_OUT)
				return 0;
		}
	}
#endif

#ifdef HAVE_PF_PACKET_SOCKETS
	/*
	 * If this is a cooked device, fill in the fake packet header.
	 */
	if (handle->md.cooked) {
		/*
		 * Add the length of the fake header to the length
		 * of packet data we read.
		 */
		packet_len += SLL_HDR_LEN;

		hdrp = (struct sll_header *)bp;
		hdrp->sll_pkttype = map_packet_type_to_sll_type(from.sll_pkttype);
		hdrp->sll_hatype = htons(from.sll_hatype);
		hdrp->sll_halen = htons(from.sll_halen);
		memcpy(hdrp->sll_addr, from.sll_addr,
		    (from.sll_halen > SLL_ADDRLEN) ?
		      SLL_ADDRLEN :
		      from.sll_halen);
		hdrp->sll_protocol = from.sll_protocol;
	}

#if defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI)
	for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
		struct tpacket_auxdata *aux;
		unsigned int len;
		struct vlan_tag *tag;

		if (cmsg->cmsg_len < CMSG_LEN(sizeof(struct tpacket_auxdata)) ||
		    cmsg->cmsg_level != SOL_PACKET ||
		    cmsg->cmsg_type != PACKET_AUXDATA)
			continue;

		aux = (struct tpacket_auxdata *)CMSG_DATA(cmsg);
		if (aux->tp_vlan_tci == 0)
			continue;

		len = packet_len > iov.iov_len ? iov.iov_len : packet_len;
		if (len < 2 * ETH_ALEN)
			break;

		bp -= VLAN_TAG_LEN;
		memmove(bp, bp + VLAN_TAG_LEN, 2 * ETH_ALEN);

		tag = (struct vlan_tag *)(bp + 2 * ETH_ALEN);
		tag->vlan_tpid = htons(ETH_P_8021Q);
		tag->vlan_tci = htons(aux->tp_vlan_tci);

		packet_len += VLAN_TAG_LEN;
	}
#endif /* defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI) */
#endif /* HAVE_PF_PACKET_SOCKETS */

	/*
	 * XXX: According to the kernel source we should get the real
	 * packet len if calling recvfrom with MSG_TRUNC set. It does
	 * not seem to work here :(, but it is supported by this code
	 * anyway.
	 * To be honest the code RELIES on that feature so this is really
	 * broken with 2.2.x kernels.
	 * I spend a day to figure out what's going on and I found out
	 * that the following is happening:
	 *
	 * The packet comes from a random interface and the packet_rcv
	 * hook is called with a clone of the packet. That code inserts
	 * the packet into the receive queue of the packet socket.
	 * If a filter is attached to that socket that filter is run
	 * first - and there lies the problem. The default filter always
	 * cuts the packet at the snaplen:
	 *
	 * # tcpdump -d
	 * (000) ret      #68
	 *
	 * So the packet filter cuts down the packet. The recvfrom call
	 * says "hey, it's only 68 bytes, it fits into the buffer" with
	 * the result that we don't get the real packet length. This
	 * is valid at least until kernel 2.2.17pre6.
	 *
	 * We currently handle this by making a copy of the filter
	 * program, fixing all "ret" instructions with non-zero
	 * operands to have an operand of 65535 so that the filter
	 * doesn't truncate the packet, and supplying that modified
	 * filter to the kernel.
	 */

	caplen = packet_len;
	if (caplen > handle->snapshot)
		caplen = handle->snapshot;

	/* Run the packet filter if not using kernel filter */
	if (!handle->md.use_bpf && handle->fcode.bf_insns) {
		if (bpf_filter(handle->fcode.bf_insns, bp,
		                packet_len, caplen) == 0)
		{
			/* rejected by filter */
			return 0;
		}
	}

	/* Fill in our own header data */

	if (ioctl(handle->fd, SIOCGSTAMP, &pcap_header.ts) == -1) {
		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
			 "SIOCGSTAMP: %s", pcap_strerror(errno));
		return PCAP_ERROR;
	}
	pcap_header.caplen	= caplen;
	pcap_header.len		= packet_len;

	/*
	 * Count the packet.
	 *
	 * Arguably, we should count them before we check the filter,
	 * as on many other platforms "ps_recv" counts packets
	 * handed to the filter rather than packets that passed
	 * the filter, but if filtering is done in the kernel, we
	 * can't get a count of packets that passed the filter,
	 * and that would mean the meaning of "ps_recv" wouldn't
	 * be the same on all Linux systems.
	 *
	 * XXX - it's not the same on all systems in any case;
	 * ideally, we should have a "get the statistics" call
	 * that supplies more counts and indicates which of them
	 * it supplies, so that we supply a count of packets
	 * handed to the filter only on platforms where that
	 * information is available.
	 *
	 * We count them here even if we can get the packet count
	 * from the kernel, as we can only determine at run time
	 * whether we'll be able to get it from the kernel (if
	 * HAVE_TPACKET_STATS isn't defined, we can't get it from
	 * the kernel, but if it is defined, the library might
	 * have been built with a 2.4 or later kernel, but we
	 * might be running on a 2.2[.x] kernel without Alexey
	 * Kuznetzov's turbopacket patches, and thus the kernel
	 * might not be able to supply those statistics).  We
	 * could, I guess, try, when opening the socket, to get
	 * the statistics, and if we can not increment the count
	 * here, but it's not clear that always incrementing
	 * the count is more expensive than always testing a flag
	 * in memory.
	 *
	 * We keep the count in "md.packets_read", and use that for
	 * "ps_recv" if we can't get the statistics from the kernel.
	 * We do that because, if we *can* get the statistics from
	 * the kernel, we use "md.stat.ps_recv" and "md.stat.ps_drop"
	 * as running counts, as reading the statistics from the
	 * kernel resets the kernel statistics, and if we directly
	 * increment "md.stat.ps_recv" here, that means it will
	 * count packets *twice* on systems where we can get kernel
	 * statistics - once here, and once in pcap_stats_linux().
	 */
	handle->md.packets_read++;

	/* Call the user supplied callback function */
	callback(userdata, &pcap_header, bp);

	return 1;
}

static int
pcap_inject_linux(pcap_t *handle, const void *buf, size_t size)
{
	int ret;

#ifdef HAVE_PF_PACKET_SOCKETS
	if (!handle->md.sock_packet) {
		/* PF_PACKET socket */
		if (handle->md.ifindex == -1) {
			/*
			 * We don't support sending on the "any" device.
			 */
			strlcpy(handle->errbuf,
			    "Sending packets isn't supported on the \"any\" device",
			    PCAP_ERRBUF_SIZE);
			return (-1);
		}

		if (handle->md.cooked) {
			/*
			 * We don't support sending on the "any" device.
			 *
			 * XXX - how do you send on a bound cooked-mode
			 * socket?
			 * Is a "sendto()" required there?
			 */
			strlcpy(handle->errbuf,
			    "Sending packets isn't supported in cooked mode",
			    PCAP_ERRBUF_SIZE);
			return (-1);
		}
	}
#endif

	ret = send(handle->fd, buf, size, 0);
	if (ret == -1) {
		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "send: %s",
		    pcap_strerror(errno));
		return (-1);
	}
	return (ret);
}                           

/*
 *  Get the statistics for the given packet capture handle.
 *  Reports the number of dropped packets iff the kernel supports
 *  the PACKET_STATISTICS "getsockopt()" argument (2.4 and later
 *  kernels, and 2.2[.x] kernels with Alexey Kuznetzov's turbopacket
 *  patches); otherwise, that information isn't available, and we lie
 *  and report 0 as the count of dropped packets.
 */
static int
pcap_stats_linux(pcap_t *handle, struct pcap_stat *stats)
{
#ifdef HAVE_TPACKET_STATS
	struct tpacket_stats kstats;
	socklen_t len = sizeof (struct tpacket_stats);
#endif

	long if_dropped = 0;
	
	/* 
	 *	To fill in ps_ifdrop, we parse /proc/net/dev for the number
	 */
	if (handle->opt.promisc)
	{
		if_dropped = handle->md.proc_dropped;
		handle->md.proc_dropped = linux_if_drops(handle->md.device);
		handle->md.stat.ps_ifdrop += (handle->md.proc_dropped - if_dropped);
	}

#ifdef HAVE_TPACKET_STATS
	/*
	 * Try to get the packet counts from the kernel.
	 */
	if (getsockopt(handle->fd, SOL_PACKET, PACKET_STATISTICS,
			&kstats, &len) > -1) {
		/*
		 * On systems where the PACKET_STATISTICS "getsockopt()"
		 * argument is supported on PF_PACKET sockets:
		 *
		 *	"ps_recv" counts only packets that *passed* the
		 *	filter, not packets that didn't pass the filter.
		 *	This includes packets later dropped because we
		 *	ran out of buffer space.
		 *
		 *	"ps_drop" counts packets dropped because we ran
		 *	out of buffer space.  It doesn't count packets
		 *	dropped by the interface driver.  It counts only
		 *	packets that passed the filter.
		 *
		 *	See above for ps_ifdrop. 
		 *
		 *	Both statistics include packets not yet read from
		 *	the kernel by libpcap, and thus not yet seen by
		 *	the application.
		 *
		 * In "linux/net/packet/af_packet.c", at least in the
		 * 2.4.9 kernel, "tp_packets" is incremented for every
		 * packet that passes the packet filter *and* is
		 * successfully queued on the socket; "tp_drops" is
		 * incremented for every packet dropped because there's
		 * not enough free space in the socket buffer.
		 *
		 * When the statistics are returned for a PACKET_STATISTICS
		 * "getsockopt()" call, "tp_drops" is added to "tp_packets",
		 * so that "tp_packets" counts all packets handed to
		 * the PF_PACKET socket, including packets dropped because
		 * there wasn't room on the socket buffer - but not
		 * including packets that didn't pass the filter.
		 *
		 * In the BSD BPF, the count of received packets is
		 * incremented for every packet handed to BPF, regardless
		 * of whether it passed the filter.
		 *
		 * We can't make "pcap_stats()" work the same on both
		 * platforms, but the best approximation is to return
		 * "tp_packets" as the count of packets and "tp_drops"
		 * as the count of drops.
		 *
		 * Keep a running total because each call to 
		 *    getsockopt(handle->fd, SOL_PACKET, PACKET_STATISTICS, ....
		 * resets the counters to zero.
		 */
		handle->md.stat.ps_recv += kstats.tp_packets;
		handle->md.stat.ps_drop += kstats.tp_drops;
		*stats = handle->md.stat;
		return 0;
	}
	else
	{
		/*
		 * If the error was EOPNOTSUPP, fall through, so that
		 * if you build the library on a system with
		 * "struct tpacket_stats" and run it on a system
		 * that doesn't, it works as it does if the library
		 * is built on a system without "struct tpacket_stats".
		 */
		if (errno != EOPNOTSUPP) {
			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
			    "pcap_stats: %s", pcap_strerror(errno));
			return -1;
		}
	}
#endif
	/*
	 * On systems where the PACKET_STATISTICS "getsockopt()" argument
	 * is not supported on PF_PACKET sockets:
	 *
	 *	"ps_recv" counts only packets that *passed* the filter,
	 *	not packets that didn't pass the filter.  It does not
	 *	count packets dropped because we ran out of buffer
	 *	space.
	 *
	 *	"ps_drop" is not supported.
	 *
	 *	"ps_ifdrop" is supported. It will return the number
	 *	of drops the interface reports in /proc/net/dev,
	 *	if that is available.
	 *
	 *	"ps_recv" doesn't include packets not yet read from
	 *	the kernel by libpcap.
	 *
	 * We maintain the count of packets processed by libpcap in
	 * "md.packets_read", for reasons described in the comment
	 * at the end of pcap_read_packet().  We have no idea how many
	 * packets were dropped by the kernel buffers -- but we know 
	 * how many the interface dropped, so we can return that.
	 */
	 
	stats->ps_recv = handle->md.packets_read;
	stats->ps_drop = 0;
	stats->ps_ifdrop = handle->md.stat.ps_ifdrop;
	return 0;
}

/*
 * Get from "/sys/class/net" all interfaces listed there; if they're
 * already in the list of interfaces we have, that won't add another
 * instance, but if they're not, that'll add them.
 *
 * We don't bother getting any addresses for them; it appears you can't
 * use SIOCGIFADDR on Linux to get IPv6 addresses for interfaces, and,
 * although some other types of addresses can be fetched with SIOCGIFADDR,
 * we don't bother with them for now.
 *
 * We also don't fail if we couldn't open "/sys/class/net"; we just leave
 * the list of interfaces as is, and return 0, so that we can try
 * scanning /proc/net/dev.
 */
static int
scan_sys_class_net(pcap_if_t **devlistp, char *errbuf)
{
	DIR *sys_class_net_d;
	int fd;
	struct dirent *ent;
	char *p;
	char name[512];	/* XXX - pick a size */
	char *q, *saveq;
	struct ifreq ifrflags;
	int ret = 1;

	sys_class_net_d = opendir("/sys/class/net");
	if (sys_class_net_d == NULL) {
		/*
		 * Don't fail if it doesn't exist at all.
		 */
		if (errno == ENOENT)
			return (0);

		/*
		 * Fail if we got some other error.
		 */
		(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
		    "Can't open /sys/class/net: %s", pcap_strerror(errno));
		return (-1);
	}

	/*
	 * Create a socket from which to fetch interface information.
	 */
	fd = socket(AF_INET, SOCK_DGRAM, 0);
	if (fd < 0) {
		(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
		    "socket: %s", pcap_strerror(errno));
		(void)closedir(sys_class_net_d);
		return (-1);
	}

	for (;;) {
		errno = 0;
		ent = readdir(sys_class_net_d);
		if (ent == NULL) {
			/*
			 * Error or EOF; if errno != 0, it's an error.
			 */
			break;
		}

		/*
		 * Ignore directories (".", "..", and any subdirectories).
		 */
		if (ent->d_type == DT_DIR)
			continue;

		/*
		 * Get the interface name.
		 */
		p = &ent->d_name[0];
		q = &name[0];
		while (*p != '\0' && isascii(*p) && !isspace(*p)) {
			if (*p == ':') {
				/*
				 * This could be the separator between a
				 * name and an alias number, or it could be
				 * the separator between a name with no
				 * alias number and the next field.
				 *
				 * If there's a colon after digits, it
				 * separates the name and the alias number,
				 * otherwise it separates the name and the
				 * next field.
				 */
				saveq = q;
				while (isascii(*p) && isdigit(*p))
					*q++ = *p++;
				if (*p != ':') {
					/*
					 * That was the next field,
					 * not the alias number.
					 */
					q = saveq;
				}
				break;
			} else
				*q++ = *p++;
		}
		*q = '\0';

		/*
		 * Get the flags for this interface, and skip it if
		 * it's not up.
		 */
		strncpy(ifrflags.ifr_name, name, sizeof(ifrflags.ifr_name));
		if (ioctl(fd, SIOCGIFFLAGS, (char *)&ifrflags) < 0) {
			if (errno == ENXIO || errno == ENODEV)
				continue;
			(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
			    "SIOCGIFFLAGS: %.*s: %s",
			    (int)sizeof(ifrflags.ifr_name),
			    ifrflags.ifr_name,
			    pcap_strerror(errno));
			ret = -1;
			break;
		}
		if (!(ifrflags.ifr_flags & IFF_UP))
			continue;

		/*
		 * Add an entry for this interface, with no addresses.
		 */
		if (pcap_add_if(devlistp, name, ifrflags.ifr_flags, NULL,
		    errbuf) == -1) {
			/*
			 * Failure.
			 */
			ret = -1;
			break;
		}
	}
	if (ret != -1) {
		/*
		 * Well, we didn't fail for any other reason; did we
		 * fail due to an error reading the directory?
		 */
		if (errno != 0) {
			(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
			    "Error reading /sys/class/net: %s",
			    pcap_strerror(errno));
			ret = -1;
		}
	}

	(void)close(fd);
	(void)closedir(sys_class_net_d);
	return (ret);
}

/*
 * Get from "/proc/net/dev" all interfaces listed there; if they're
 * already in the list of interfaces we have, that won't add another
 * instance, but if they're not, that'll add them.
 *
 * See comments from scan_sys_class_net().
 */
static int
scan_proc_net_dev(pcap_if_t **devlistp, char *errbuf)
{
	FILE *proc_net_f;
	int fd;
	char linebuf[512];
	int linenum;
	char *p;
	char name[512];	/* XXX - pick a size */
	char *q, *saveq;
	struct ifreq ifrflags;
	int ret = 0;

	proc_net_f = fopen("/proc/net/dev", "r");
	if (proc_net_f == NULL) {
		/*
		 * Don't fail if it doesn't exist at all.
		 */
		if (errno == ENOENT)
			return (0);

		/*
		 * Fail if we got some other error.
		 */
		(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
		    "Can't open /proc/net/dev: %s", pcap_strerror(errno));
		return (-1);
	}

	/*
	 * Create a socket from which to fetch interface information.
	 */
	fd = socket(AF_INET, SOCK_DGRAM, 0);
	if (fd < 0) {
		(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
		    "socket: %s", pcap_strerror(errno));
		(void)fclose(proc_net_f);
		return (-1);
	}

	for (linenum = 1;
	    fgets(linebuf, sizeof linebuf, proc_net_f) != NULL; linenum++) {
		/*
		 * Skip the first two lines - they're headers.
		 */
		if (linenum <= 2)
			continue;

		p = &linebuf[0];

		/*
		 * Skip leading white space.
		 */
		while (*p != '\0' && isascii(*p) && isspace(*p))
			p++;
		if (*p == '\0' || *p == '\n')
			continue;	/* blank line */

		/*
		 * Get the interface name.
		 */
		q = &name[0];
		while (*p != '\0' && isascii(*p) && !isspace(*p)) {
			if (*p == ':') {
				/*
				 * This could be the separator between a
				 * name and an alias number, or it could be
				 * the separator between a name with no
				 * alias number and the next field.
				 *
				 * If there's a colon after digits, it
				 * separates the name and the alias number,
				 * otherwise it separates the name and the
				 * next field.
				 */
				saveq = q;
				while (isascii(*p) && isdigit(*p))
					*q++ = *p++;
				if (*p != ':') {
					/*
					 * That was the next field,
					 * not the alias number.
					 */
					q = saveq;
				}
				break;
			} else
				*q++ = *p++;
		}
		*q = '\0';

		/*
		 * Get the flags for this interface, and skip it if
		 * it's not up.
		 */
		strncpy(ifrflags.ifr_name, name, sizeof(ifrflags.ifr_name));
		if (ioctl(fd, SIOCGIFFLAGS, (char *)&ifrflags) < 0) {
			if (errno == ENXIO)
				continue;
			(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
			    "SIOCGIFFLAGS: %.*s: %s",
			    (int)sizeof(ifrflags.ifr_name),
			    ifrflags.ifr_name,
			    pcap_strerror(errno));
			ret = -1;
			break;
		}
		if (!(ifrflags.ifr_flags & IFF_UP))
			continue;

		/*
		 * Add an entry for this interface, with no addresses.
		 */
		if (pcap_add_if(devlistp, name, ifrflags.ifr_flags, NULL,
		    errbuf) == -1) {
			/*
			 * Failure.
			 */
			ret = -1;
			break;
		}
	}
	if (ret != -1) {
		/*
		 * Well, we didn't fail for any other reason; did we
		 * fail due to an error reading the file?
		 */
		if (ferror(proc_net_f)) {
			(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
			    "Error reading /proc/net/dev: %s",
			    pcap_strerror(errno));
			ret = -1;
		}
	}

	(void)close(fd);
	(void)fclose(proc_net_f);
	return (ret);
}

/*
 * Description string for the "any" device.
 */
static const char any_descr[] = "Pseudo-device that captures on all interfaces";

int
pcap_platform_finddevs(pcap_if_t **alldevsp, char *errbuf)
{
	int ret;

	/*
	 * Read "/sys/class/net", and add to the list of interfaces all
	 * interfaces listed there that we don't already have, because,
	 * on Linux, SIOCGIFCONF reports only interfaces with IPv4 addresses,
	 * and even getifaddrs() won't return information about
	 * interfaces with no addresses, so you need to read "/sys/class/net"
	 * to get the names of the rest of the interfaces.
	 */
	ret = scan_sys_class_net(alldevsp, errbuf);
	if (ret == -1)
		return (-1);	/* failed */
	if (ret == 0) {
		/*
		 * No /sys/class/net; try reading /proc/net/dev instead.
		 */
		if (scan_proc_net_dev(alldevsp, errbuf) == -1)
			return (-1);
	}

	/*
	 * Add the "any" device.
	 */
	if (pcap_add_if(alldevsp, "any", 0, any_descr, errbuf) < 0)
		return (-1);

#ifdef HAVE_DAG_API
	/*
	 * Add DAG devices.
	 */
	if (dag_platform_finddevs(alldevsp, errbuf) < 0)
		return (-1);
#endif /* HAVE_DAG_API */

#ifdef HAVE_SEPTEL_API
	/*
	 * Add Septel devices.
	 */
	if (septel_platform_finddevs(alldevsp, errbuf) < 0)
		return (-1);
#endif /* HAVE_SEPTEL_API */

#ifdef HAVE_SNF_API
	if (snf_platform_finddevs(alldevsp, errbuf) < 0)
		return (-1);
#endif /* HAVE_SNF_API */

#ifdef PCAP_SUPPORT_BT
	/*
	 * Add Bluetooth devices.
	 */
	if (bt_platform_finddevs(alldevsp, errbuf) < 0)
		return (-1);
#endif

#ifdef PCAP_SUPPORT_USB
	/*
	 * Add USB devices.
	 */
	if (usb_platform_finddevs(alldevsp, errbuf) < 0)
		return (-1);
#endif

#ifdef PCAP_SUPPORT_NETFILTER
	/*
	 * Add netfilter devices.
	 */
	if (netfilter_platform_finddevs(alldevsp, errbuf) < 0)
		return (-1);
#endif

#if PCAP_SUPPORT_CANUSB
  if (canusb_platform_finddevs(alldevsp, errbuf) < 0)
    return (-1);
#endif

	return (0);
}

/*
 *  Attach the given BPF code to the packet capture device.
 */
static int
pcap_setfilter_linux_common(pcap_t *handle, struct bpf_program *filter,
    int is_mmapped)
{
#ifdef SO_ATTACH_FILTER
	struct sock_fprog	fcode;
	int			can_filter_in_kernel;
	int			err = 0;
#endif

	if (!handle)
		return -1;
	if (!filter) {
	        strncpy(handle->errbuf, "setfilter: No filter specified",
			PCAP_ERRBUF_SIZE);
		return -1;
	}

	/* Make our private copy of the filter */

	if (install_bpf_program(handle, filter) < 0)
		/* install_bpf_program() filled in errbuf */
		return -1;

	/*
	 * Run user level packet filter by default. Will be overriden if
	 * installing a kernel filter succeeds.
	 */
	handle->md.use_bpf = 0;

	/* Install kernel level filter if possible */

#ifdef SO_ATTACH_FILTER
#ifdef USHRT_MAX
	if (handle->fcode.bf_len > USHRT_MAX) {
		/*
		 * fcode.len is an unsigned short for current kernel.
		 * I have yet to see BPF-Code with that much
		 * instructions but still it is possible. So for the
		 * sake of correctness I added this check.
		 */
		fprintf(stderr, "Warning: Filter too complex for kernel\n");
		fcode.len = 0;
		fcode.filter = NULL;
		can_filter_in_kernel = 0;
	} else
#endif /* USHRT_MAX */
	{
		/*
		 * Oh joy, the Linux kernel uses struct sock_fprog instead
		 * of struct bpf_program and of course the length field is
		 * of different size. Pointed out by Sebastian
		 *
		 * Oh, and we also need to fix it up so that all "ret"
		 * instructions with non-zero operands have 65535 as the
		 * operand if we're not capturing in memory-mapped modee,
		 * and so that, if we're in cooked mode, all memory-reference
		 * instructions use special magic offsets in references to
		 * the link-layer header and assume that the link-layer
		 * payload begins at 0; "fix_program()" will do that.
		 */
		switch (fix_program(handle, &fcode, is_mmapped)) {

		case -1:
		default:
			/*
			 * Fatal error; just quit.
			 * (The "default" case shouldn't happen; we
			 * return -1 for that reason.)
			 */
			return -1;

		case 0:
			/*
			 * The program performed checks that we can't make
			 * work in the kernel.
			 */
			can_filter_in_kernel = 0;
			break;

		case 1:
			/*
			 * We have a filter that'll work in the kernel.
			 */
			can_filter_in_kernel = 1;
			break;
		}
	}

	/*
	 * NOTE: at this point, we've set both the "len" and "filter"
	 * fields of "fcode".  As of the 2.6.32.4 kernel, at least,
	 * those are the only members of the "sock_fprog" structure,
	 * so we initialize every member of that structure.
	 *
	 * If there is anything in "fcode" that is not initialized,
	 * it is either a field added in a later kernel, or it's
	 * padding.
	 *
	 * If a new field is added, this code needs to be updated
	 * to set it correctly.
	 *
	 * If there are no other fields, then:
	 *
	 *	if the Linux kernel looks at the padding, it's
	 *	buggy;
	 *
	 *	if the Linux kernel doesn't look at the padding,
	 *	then if some tool complains that we're passing
	 *	uninitialized data to the kernel, then the tool
	 *	is buggy and needs to understand that it's just
	 *	padding.
	 */
	if (can_filter_in_kernel) {
		if ((err = set_kernel_filter(handle, &fcode)) == 0)
		{
			/* Installation succeded - using kernel filter. */
			handle->md.use_bpf = 1;
		}
		else if (err == -1)	/* Non-fatal error */
		{
			/*
			 * Print a warning if we weren't able to install
			 * the filter for a reason other than "this kernel
			 * isn't configured to support socket filters.
			 */
			if (errno != ENOPROTOOPT && errno != EOPNOTSUPP) {
				fprintf(stderr,
				    "Warning: Kernel filter failed: %s\n",
					pcap_strerror(errno));
			}
		}
	}

	/*
	 * If we're not using the kernel filter, get rid of any kernel
	 * filter that might've been there before, e.g. because the
	 * previous filter could work in the kernel, or because some other
	 * code attached a filter to the socket by some means other than
	 * calling "pcap_setfilter()".  Otherwise, the kernel filter may
	 * filter out packets that would pass the new userland filter.
	 */
	if (!handle->md.use_bpf)
		reset_kernel_filter(handle);

	/*
	 * Free up the copy of the filter that was made by "fix_program()".
	 */
	if (fcode.filter != NULL)
		free(fcode.filter);

	if (err == -2)
		/* Fatal error */
		return -1;
#endif /* SO_ATTACH_FILTER */

	return 0;
}

static int
pcap_setfilter_linux(pcap_t *handle, struct bpf_program *filter)
{
	return pcap_setfilter_linux_common(handle, filter, 0);
}


/*
 * Set direction flag: Which packets do we accept on a forwarding
 * single device? IN, OUT or both?
 */
static int
pcap_setdirection_linux(pcap_t *handle, pcap_direction_t d)
{
#ifdef HAVE_PF_PACKET_SOCKETS
	if (!handle->md.sock_packet) {
		handle->direction = d;
		return 0;
	}
#endif
	/*
	 * We're not using PF_PACKET sockets, so we can't determine
	 * the direction of the packet.
	 */
	snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
	    "Setting direction is not supported on SOCK_PACKET sockets");
	return -1;
}

#ifdef HAVE_PF_PACKET_SOCKETS
/*
 * Map the PACKET_ value to a LINUX_SLL_ value; we
 * want the same numerical value to be used in
 * the link-layer header even if the numerical values
 * for the PACKET_ #defines change, so that programs
 * that look at the packet type field will always be
 * able to handle DLT_LINUX_SLL captures.
 */
static short int
map_packet_type_to_sll_type(short int sll_pkttype)
{
	switch (sll_pkttype) {

	case PACKET_HOST:
		return htons(LINUX_SLL_HOST);

	case PACKET_BROADCAST:
		return htons(LINUX_SLL_BROADCAST);

	case PACKET_MULTICAST:
		return  htons(LINUX_SLL_MULTICAST);

	case PACKET_OTHERHOST:
		return htons(LINUX_SLL_OTHERHOST);

	case PACKET_OUTGOING:
		return htons(LINUX_SLL_OUTGOING);

	default:
		return -1;
	}
}
#endif

/*
 *  Linux uses the ARP hardware type to identify the type of an
 *  interface. pcap uses the DLT_xxx constants for this. This
 *  function takes a pointer to a "pcap_t", and an ARPHRD_xxx
 *  constant, as arguments, and sets "handle->linktype" to the
 *  appropriate DLT_XXX constant and sets "handle->offset" to
 *  the appropriate value (to make "handle->offset" plus link-layer
 *  header length be a multiple of 4, so that the link-layer payload
 *  will be aligned on a 4-byte boundary when capturing packets).
 *  (If the offset isn't set here, it'll be 0; add code as appropriate
 *  for cases where it shouldn't be 0.)
 *
 *  If "cooked_ok" is non-zero, we can use DLT_LINUX_SLL and capture
 *  in cooked mode; otherwise, we can't use cooked mode, so we have
 *  to pick some type that works in raw mode, or fail.
 *
 *  Sets the link type to -1 if unable to map the type.
 */
static void map_arphrd_to_dlt(pcap_t *handle, int arptype, int cooked_ok)
{
	switch (arptype) {

	case ARPHRD_ETHER:
		/*
		 * This is (presumably) a real Ethernet capture; give it a
		 * link-layer-type list with DLT_EN10MB and DLT_DOCSIS, so
		 * that an application can let you choose it, in case you're
		 * capturing DOCSIS traffic that a Cisco Cable Modem
		 * Termination System is putting out onto an Ethernet (it
		 * doesn't put an Ethernet header onto the wire, it puts raw
		 * DOCSIS frames out on the wire inside the low-level
		 * Ethernet framing).
		 *
		 * XXX - are there any sorts of "fake Ethernet" that have
		 * ARPHRD_ETHER but that *shouldn't offer DLT_DOCSIS as
		 * a Cisco CMTS won't put traffic onto it or get traffic
		 * bridged onto it?  ISDN is handled in "activate_new()",
		 * as we fall back on cooked mode there; are there any
		 * others?
		 */
		handle->dlt_list = (u_int *) malloc(sizeof(u_int) * 2);
		/*
		 * If that fails, just leave the list empty.
		 */
		if (handle->dlt_list != NULL) {
			handle->dlt_list[0] = DLT_EN10MB;
			handle->dlt_list[1] = DLT_DOCSIS;
			handle->dlt_count = 2;
		}
		/* FALLTHROUGH */

	case ARPHRD_METRICOM:
	case ARPHRD_LOOPBACK:
		handle->linktype = DLT_EN10MB;
		handle->offset = 2;
		break;

	case ARPHRD_EETHER:
		handle->linktype = DLT_EN3MB;
		break;

	case ARPHRD_AX25:
		handle->linktype = DLT_AX25_KISS;
		break;

	case ARPHRD_PRONET:
		handle->linktype = DLT_PRONET;
		break;

	case ARPHRD_CHAOS:
		handle->linktype = DLT_CHAOS;
		break;
#ifndef ARPHRD_CAN
#define ARPHRD_CAN 280
#endif
	case ARPHRD_CAN:
		handle->linktype = DLT_CAN_SOCKETCAN;
		break;

#ifndef ARPHRD_IEEE802_TR
#define ARPHRD_IEEE802_TR 800	/* From Linux 2.4 */
#endif
	case ARPHRD_IEEE802_TR:
	case ARPHRD_IEEE802:
		handle->linktype = DLT_IEEE802;
		handle->offset = 2;
		break;

	case ARPHRD_ARCNET:
		handle->linktype = DLT_ARCNET_LINUX;
		break;

#ifndef ARPHRD_FDDI	/* From Linux 2.2.13 */
#define ARPHRD_FDDI	774
#endif
	case ARPHRD_FDDI:
		handle->linktype = DLT_FDDI;
		handle->offset = 3;
		break;

#ifndef ARPHRD_ATM  /* FIXME: How to #include this? */
#define ARPHRD_ATM 19
#endif
	case ARPHRD_ATM:
		/*
		 * The Classical IP implementation in ATM for Linux
		 * supports both what RFC 1483 calls "LLC Encapsulation",
		 * in which each packet has an LLC header, possibly
		 * with a SNAP header as well, prepended to it, and
		 * what RFC 1483 calls "VC Based Multiplexing", in which
		 * different virtual circuits carry different network
		 * layer protocols, and no header is prepended to packets.
		 *
		 * They both have an ARPHRD_ type of ARPHRD_ATM, so
		 * you can't use the ARPHRD_ type to find out whether
		 * captured packets will have an LLC header, and,
		 * while there's a socket ioctl to *set* the encapsulation
		 * type, there's no ioctl to *get* the encapsulation type.
		 *
		 * This means that
		 *
		 *	programs that dissect Linux Classical IP frames
		 *	would have to check for an LLC header and,
		 *	depending on whether they see one or not, dissect
		 *	the frame as LLC-encapsulated or as raw IP (I
		 *	don't know whether there's any traffic other than
		 *	IP that would show up on the socket, or whether
		 *	there's any support for IPv6 in the Linux
		 *	Classical IP code);
		 *
		 *	filter expressions would have to compile into
		 *	code that checks for an LLC header and does
		 *	the right thing.
		 *
		 * Both of those are a nuisance - and, at least on systems
		 * that support PF_PACKET sockets, we don't have to put
		 * up with those nuisances; instead, we can just capture
		 * in cooked mode.  That's what we'll do, if we can.
		 * Otherwise, we'll just fail.
		 */
		if (cooked_ok)
			handle->linktype = DLT_LINUX_SLL;
		else
			handle->linktype = -1;
		break;

#ifndef ARPHRD_IEEE80211  /* From Linux 2.4.6 */
#define ARPHRD_IEEE80211 801
#endif
	case ARPHRD_IEEE80211:
		handle->linktype = DLT_IEEE802_11;
		break;

#ifndef ARPHRD_IEEE80211_PRISM  /* From Linux 2.4.18 */
#define ARPHRD_IEEE80211_PRISM 802
#endif
	case ARPHRD_IEEE80211_PRISM:
		handle->linktype = DLT_PRISM_HEADER;
		break;

#ifndef ARPHRD_IEEE80211_RADIOTAP /* new */
#define ARPHRD_IEEE80211_RADIOTAP 803
#endif
	case ARPHRD_IEEE80211_RADIOTAP:
		handle->linktype = DLT_IEEE802_11_RADIO;
		break;

	case ARPHRD_PPP:
		/*
		 * Some PPP code in the kernel supplies no link-layer
		 * header whatsoever to PF_PACKET sockets; other PPP
		 * code supplies PPP link-layer headers ("syncppp.c");
		 * some PPP code might supply random link-layer
		 * headers (PPP over ISDN - there's code in Ethereal,
		 * for example, to cope with PPP-over-ISDN captures
		 * with which the Ethereal developers have had to cope,
		 * heuristically trying to determine which of the
		 * oddball link-layer headers particular packets have).
		 *
		 * As such, we just punt, and run all PPP interfaces
		 * in cooked mode, if we can; otherwise, we just treat
		 * it as DLT_RAW, for now - if somebody needs to capture,
		 * on a 2.0[.x] kernel, on PPP devices that supply a
		 * link-layer header, they'll have to add code here to
		 * map to the appropriate DLT_ type (possibly adding a
		 * new DLT_ type, if necessary).
		 */
		if (cooked_ok)
			handle->linktype = DLT_LINUX_SLL;
		else {
			/*
			 * XXX - handle ISDN types here?  We can't fall
			 * back on cooked sockets, so we'd have to
			 * figure out from the device name what type of
			 * link-layer encapsulation it's using, and map
			 * that to an appropriate DLT_ value, meaning
			 * we'd map "isdnN" devices to DLT_RAW (they
			 * supply raw IP packets with no link-layer
			 * header) and "isdY" devices to a new DLT_I4L_IP
			 * type that has only an Ethernet packet type as
			 * a link-layer header.
			 *
			 * But sometimes we seem to get random crap
			 * in the link-layer header when capturing on
			 * ISDN devices....
			 */
			handle->linktype = DLT_RAW;
		}
		break;

#ifndef ARPHRD_CISCO
#define ARPHRD_CISCO 513 /* previously ARPHRD_HDLC */
#endif
	case ARPHRD_CISCO:
		handle->linktype = DLT_C_HDLC;
		break;

	/* Not sure if this is correct for all tunnels, but it
	 * works for CIPE */
	case ARPHRD_TUNNEL:
#ifndef ARPHRD_SIT
#define ARPHRD_SIT 776	/* From Linux 2.2.13 */
#endif
	case ARPHRD_SIT:
	case ARPHRD_CSLIP:
	case ARPHRD_SLIP6:
	case ARPHRD_CSLIP6:
	case ARPHRD_ADAPT:
	case ARPHRD_SLIP:
#ifndef ARPHRD_RAWHDLC
#define ARPHRD_RAWHDLC 518
#endif
	case ARPHRD_RAWHDLC:
#ifndef ARPHRD_DLCI
#define ARPHRD_DLCI 15
#endif
	case ARPHRD_DLCI:
		/*
		 * XXX - should some of those be mapped to DLT_LINUX_SLL
		 * instead?  Should we just map all of them to DLT_LINUX_SLL?
		 */
		handle->linktype = DLT_RAW;
		break;

#ifndef ARPHRD_FRAD
#define ARPHRD_FRAD 770
#endif
	case ARPHRD_FRAD:
		handle->linktype = DLT_FRELAY;
		break;

	case ARPHRD_LOCALTLK:
		handle->linktype = DLT_LTALK;
		break;

#ifndef ARPHRD_FCPP
#define ARPHRD_FCPP	784
#endif
	case ARPHRD_FCPP:
#ifndef ARPHRD_FCAL
#define ARPHRD_FCAL	785
#endif
	case ARPHRD_FCAL:
#ifndef ARPHRD_FCPL
#define ARPHRD_FCPL	786
#endif
	case ARPHRD_FCPL:
#ifndef ARPHRD_FCFABRIC
#define ARPHRD_FCFABRIC	787
#endif
	case ARPHRD_FCFABRIC:
		/*
		 * We assume that those all mean RFC 2625 IP-over-
		 * Fibre Channel, with the RFC 2625 header at
		 * the beginning of the packet.
		 */
		handle->linktype = DLT_IP_OVER_FC;
		break;

#ifndef ARPHRD_IRDA
#define ARPHRD_IRDA	783
#endif
	case ARPHRD_IRDA:
		/* Don't expect IP packet out of this interfaces... */
		handle->linktype = DLT_LINUX_IRDA;
		/* We need to save packet direction for IrDA decoding,
		 * so let's use "Linux-cooked" mode. Jean II */
		//handle->md.cooked = 1;
		break;

	/* ARPHRD_LAPD is unofficial and randomly allocated, if reallocation
	 * is needed, please report it to <daniele@orlandi.com> */
#ifndef ARPHRD_LAPD
#define ARPHRD_LAPD	8445
#endif
	case ARPHRD_LAPD:
		/* Don't expect IP packet out of this interfaces... */
		handle->linktype = DLT_LINUX_LAPD;
		break;

#ifndef ARPHRD_NONE
#define ARPHRD_NONE	0xFFFE
#endif
	case ARPHRD_NONE:
		/*
		 * No link-layer header; packets are just IP
		 * packets, so use DLT_RAW.
		 */
		handle->linktype = DLT_RAW;
		break;

#ifndef ARPHRD_IEEE802154
#define ARPHRD_IEEE802154      804
#endif
       case ARPHRD_IEEE802154:
               handle->linktype =  DLT_IEEE802_15_4_NOFCS;
               break;

	default:
		handle->linktype = -1;
		break;
	}
}

/* ===== Functions to interface to the newer kernels ================== */

/*
 * Try to open a packet socket using the new kernel PF_PACKET interface.
 * Returns 1 on success, 0 on an error that means the new interface isn't
 * present (so the old SOCK_PACKET interface should be tried), and a
 * PCAP_ERROR_ value on an error that means that the old mechanism won't
 * work either (so it shouldn't be tried).
 */
static int
activate_new(pcap_t *handle)
{
#ifdef HAVE_PF_PACKET_SOCKETS
	const char		*device = handle->opt.source;
	int			is_any_device = (strcmp(device, "any") == 0);
	int			sock_fd = -1, arptype;
#ifdef HAVE_PACKET_AUXDATA
	int			val;
#endif
	int			err = 0;
	struct packet_mreq	mr;

	/*
	 * Open a socket with protocol family packet. If the
	 * "any" device was specified, we open a SOCK_DGRAM
	 * socket for the cooked interface, otherwise we first
	 * try a SOCK_RAW socket for the raw interface.
	 */
	sock_fd = is_any_device ?
		socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_ALL)) :
		socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));

	if (sock_fd == -1) {
		if (errno == EINVAL || errno == EAFNOSUPPORT) {
			/*
			 * We don't support PF_PACKET/SOCK_whatever
			 * sockets; try the old mechanism.
			 */
			return 0;
		}

		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "socket: %s",
			 pcap_strerror(errno) );
		if (errno == EPERM || errno == EACCES) {
			/*
			 * You don't have permission to open the
			 * socket.
			 */
			return PCAP_ERROR_PERM_DENIED;
		} else {
			/*
			 * Other error.
			 */
			return PCAP_ERROR;
		}
	}

	/* It seems the kernel supports the new interface. */
	handle->md.sock_packet = 0;

	/*
	 * Get the interface index of the loopback device.
	 * If the attempt fails, don't fail, just set the
	 * "md.lo_ifindex" to -1.
	 *
	 * XXX - can there be more than one device that loops
	 * packets back, i.e. devices other than "lo"?  If so,
	 * we'd need to find them all, and have an array of
	 * indices for them, and check all of them in
	 * "pcap_read_packet()".
	 */
	handle->md.lo_ifindex = iface_get_id(sock_fd, "lo", handle->errbuf);

	/*
	 * Default value for offset to align link-layer payload
	 * on a 4-byte boundary.
	 */
	handle->offset	 = 0;

	/*
	 * What kind of frames do we have to deal with? Fall back
	 * to cooked mode if we have an unknown interface type
	 * or a type we know doesn't work well in raw mode.
	 */
	if (!is_any_device) {
		/* Assume for now we don't need cooked mode. */
		handle->md.cooked = 0;

		if (handle->opt.rfmon) {
			/*
			 * We were asked to turn on monitor mode.
			 * Do so before we get the link-layer type,
			 * because entering monitor mode could change
			 * the link-layer type.
			 */
			err = enter_rfmon_mode(handle, sock_fd, device);
			if (err < 0) {
				/* Hard failure */
				close(sock_fd);
				return err;
			}
			if (err == 0) {
				/*
				 * Nothing worked for turning monitor mode
				 * on.
				 */
				close(sock_fd);
				return PCAP_ERROR_RFMON_NOTSUP;
			}

			/*
			 * Either monitor mode has been turned on for
			 * the device, or we've been given a different
			 * device to open for monitor mode.  If we've
			 * been given a different device, use it.
			 */
			if (handle->md.mondevice != NULL)
				device = handle->md.mondevice;
		}
		arptype	= iface_get_arptype(sock_fd, device, handle->errbuf);
		if (arptype < 0) {
			close(sock_fd);
			return arptype;
		}
		map_arphrd_to_dlt(handle, arptype, 1);
		if (handle->linktype == -1 ||
		    handle->linktype == DLT_LINUX_SLL ||
		    handle->linktype == DLT_LINUX_IRDA ||
		    handle->linktype == DLT_LINUX_LAPD ||
		    (handle->linktype == DLT_EN10MB &&
		     (strncmp("isdn", device, 4) == 0 ||
		      strncmp("isdY", device, 4) == 0))) {
			/*
			 * Unknown interface type (-1), or a
			 * device we explicitly chose to run
			 * in cooked mode (e.g., PPP devices),
			 * or an ISDN device (whose link-layer
			 * type we can only determine by using
			 * APIs that may be different on different
			 * kernels) - reopen in cooked mode.
			 */
			if (close(sock_fd) == -1) {
				snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
					 "close: %s", pcap_strerror(errno));
				return PCAP_ERROR;
			}
			sock_fd = socket(PF_PACKET, SOCK_DGRAM,
			    htons(ETH_P_ALL));
			if (sock_fd == -1) {
				snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
				    "socket: %s", pcap_strerror(errno));
				if (errno == EPERM || errno == EACCES) {
					/*
					 * You don't have permission to
					 * open the socket.
					 */
					return PCAP_ERROR_PERM_DENIED;
				} else {
					/*
					 * Other error.
					 */
					return PCAP_ERROR;
				}
			}
			handle->md.cooked = 1;

			/*
			 * Get rid of any link-layer type list
			 * we allocated - this only supports cooked
			 * capture.
			 */
			if (handle->dlt_list != NULL) {
				free(handle->dlt_list);
				handle->dlt_list = NULL;
				handle->dlt_count = 0;
			}

			if (handle->linktype == -1) {
				/*
				 * Warn that we're falling back on
				 * cooked mode; we may want to
				 * update "map_arphrd_to_dlt()"
				 * to handle the new type.
				 */
				snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
					"arptype %d not "
					"supported by libpcap - "
					"falling back to cooked "
					"socket",
					arptype);
			}

			/*
			 * IrDA capture is not a real "cooked" capture,
			 * it's IrLAP frames, not IP packets.  The
			 * same applies to LAPD capture.
			 */
			if (handle->linktype != DLT_LINUX_IRDA &&
			    handle->linktype != DLT_LINUX_LAPD)
				handle->linktype = DLT_LINUX_SLL;
		}

		handle->md.ifindex = iface_get_id(sock_fd, device,
		    handle->errbuf);
		if (handle->md.ifindex == -1) {
			close(sock_fd);
			return PCAP_ERROR;
		}

		if ((err = iface_bind(sock_fd, handle->md.ifindex,
		    handle->errbuf)) != 1) {
		    	close(sock_fd);
			if (err < 0)
				return err;
			else
				return 0;	/* try old mechanism */
		}
	} else {
		/*
		 * The "any" device.
		 */
		if (handle->opt.rfmon) {
			/*
			 * It doesn't support monitor mode.
			 */
			return PCAP_ERROR_RFMON_NOTSUP;
		}

		/*
		 * It uses cooked mode.
		 */
		handle->md.cooked = 1;
		handle->linktype = DLT_LINUX_SLL;

		/*
		 * We're not bound to a device.
		 * For now, we're using this as an indication
		 * that we can't transmit; stop doing that only
		 * if we figure out how to transmit in cooked
		 * mode.
		 */
		handle->md.ifindex = -1;
	}

	/*
	 * Select promiscuous mode on if "promisc" is set.
	 *
	 * Do not turn allmulti mode on if we don't select
	 * promiscuous mode - on some devices (e.g., Orinoco
	 * wireless interfaces), allmulti mode isn't supported
	 * and the driver implements it by turning promiscuous
	 * mode on, and that screws up the operation of the
	 * card as a normal networking interface, and on no
	 * other platform I know of does starting a non-
	 * promiscuous capture affect which multicast packets
	 * are received by the interface.
	 */

	/*
	 * Hmm, how can we set promiscuous mode on all interfaces?
	 * I am not sure if that is possible at all.  For now, we
	 * silently ignore attempts to turn promiscuous mode on
	 * for the "any" device (so you don't have to explicitly
	 * disable it in programs such as tcpdump).
	 */

	if (!is_any_device && handle->opt.promisc) {
		memset(&mr, 0, sizeof(mr));
		mr.mr_ifindex = handle->md.ifindex;
		mr.mr_type    = PACKET_MR_PROMISC;
		if (setsockopt(sock_fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP,
		    &mr, sizeof(mr)) == -1) {
			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
				"setsockopt: %s", pcap_strerror(errno));
			close(sock_fd);
			return PCAP_ERROR;
		}
	}

	/* Enable auxillary data if supported and reserve room for
	 * reconstructing VLAN headers. */
#ifdef HAVE_PACKET_AUXDATA
	val = 1;
	if (setsockopt(sock_fd, SOL_PACKET, PACKET_AUXDATA, &val,
		       sizeof(val)) == -1 && errno != ENOPROTOOPT) {
		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
			 "setsockopt: %s", pcap_strerror(errno));
		close(sock_fd);
		return PCAP_ERROR;
	}
	handle->offset += VLAN_TAG_LEN;
#endif /* HAVE_PACKET_AUXDATA */

	/*
	 * This is a 2.2[.x] or later kernel (we know that
	 * because we're not using a SOCK_PACKET socket -
	 * PF_PACKET is supported only in 2.2 and later
	 * kernels).
	 *
	 * We can safely pass "recvfrom()" a byte count
	 * based on the snapshot length.
	 *
	 * If we're in cooked mode, make the snapshot length
	 * large enough to hold a "cooked mode" header plus
	 * 1 byte of packet data (so we don't pass a byte
	 * count of 0 to "recvfrom()").
	 */
	if (handle->md.cooked) {
		if (handle->snapshot < SLL_HDR_LEN + 1)
			handle->snapshot = SLL_HDR_LEN + 1;
	}
	handle->bufsize = handle->snapshot;

	/* Save the socket FD in the pcap structure */
	handle->fd = sock_fd;

	return 1;
#else
	strncpy(ebuf,
		"New packet capturing interface not supported by build "
		"environment", PCAP_ERRBUF_SIZE);
	return 0;
#endif
}

#ifdef HAVE_PACKET_RING
/*
 * Attempt to activate with memory-mapped access.
 *
 * On success, returns 1, and sets *status to 0 if there are no warnings
 * or to a PCAP_WARNING_ code if there is a warning.
 *
 * On failure due to lack of support for memory-mapped capture, returns
 * 0.
 *
 * On error, returns -1, and sets *status to the appropriate error code;
 * if that is PCAP_ERROR, sets handle->errbuf to the appropriate message.
 */
static int 
activate_mmap(pcap_t *handle, int *status)
{
	int ret;

	/*
	 * Attempt to allocate a buffer to hold the contents of one
	 * packet, for use by the oneshot callback.
	 */
	handle->md.oneshot_buffer = malloc(handle->snapshot);
	if (handle->md.oneshot_buffer == NULL) {
		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
			 "can't allocate oneshot buffer: %s",
			 pcap_strerror(errno));
		*status = PCAP_ERROR;
		return -1;
	}

	if (handle->opt.buffer_size == 0) {
		/* by default request 2M for the ring buffer */
		handle->opt.buffer_size = 2*1024*1024;
	}
	ret = prepare_tpacket_socket(handle);
	if (ret == -1) {
		free(handle->md.oneshot_buffer);
		*status = PCAP_ERROR;
		return ret;
	}
	ret = create_ring(handle, status);
	if (ret == 0) {
		/*
		 * We don't support memory-mapped capture; our caller
		 * will fall back on reading from the socket.
		 */
		free(handle->md.oneshot_buffer);
		return 0;
	}
	if (ret == -1) {
		/*
		 * Error attempting to enable memory-mapped capture;
		 * fail.  create_ring() has set *status.
		 */
		free(handle->md.oneshot_buffer);
		return -1;
	}

	/*
	 * Success.  *status has been set either to 0 if there are no
	 * warnings or to a PCAP_WARNING_ value if there is a warning.
	 *
	 * Override some defaults and inherit the other fields from
	 * activate_new.
	 * handle->offset is used to get the current position into the rx ring.
	 * handle->cc is used to store the ring size.
	 */
	handle->read_op = pcap_read_linux_mmap;
	handle->cleanup_op = pcap_cleanup_linux_mmap;
	handle->setfilter_op = pcap_setfilter_linux_mmap;
	handle->setnonblock_op = pcap_setnonblock_mmap;
	handle->getnonblock_op = pcap_getnonblock_mmap;
	handle->oneshot_callback = pcap_oneshot_mmap;
	handle->selectable_fd = handle->fd;
	return 1;
}
#else /* HAVE_PACKET_RING */
static int 
activate_mmap(pcap_t *handle _U_, int *status _U_)
{
	return 0;
}
#endif /* HAVE_PACKET_RING */

#ifdef HAVE_PACKET_RING
/*
 * Attempt to set the socket to version 2 of the memory-mapped header.
 * Return 1 if we succeed or if we fail because version 2 isn't
 * supported; return -1 on any other error, and set handle->errbuf.
 */
static int
prepare_tpacket_socket(pcap_t *handle)
{
#ifdef HAVE_TPACKET2
	socklen_t len;
	int val;
#endif

	handle->md.tp_version = TPACKET_V1;
	handle->md.tp_hdrlen = sizeof(struct tpacket_hdr);

#ifdef HAVE_TPACKET2
	/* Probe whether kernel supports TPACKET_V2 */
	val = TPACKET_V2;
	len = sizeof(val);
	if (getsockopt(handle->fd, SOL_PACKET, PACKET_HDRLEN, &val, &len) < 0) {
		if (errno == ENOPROTOOPT)
			return 1;	/* no - just drive on */

		/* Yes - treat as a failure. */
		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
		    "can't get TPACKET_V2 header len on packet socket: %s",
		    pcap_strerror(errno));
		return -1;
	}
	handle->md.tp_hdrlen = val;

	val = TPACKET_V2;
	if (setsockopt(handle->fd, SOL_PACKET, PACKET_VERSION, &val,
		       sizeof(val)) < 0) {
		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
		    "can't activate TPACKET_V2 on packet socket: %s",
		    pcap_strerror(errno));
		return -1;
	}
	handle->md.tp_version = TPACKET_V2;

	/* Reserve space for VLAN tag reconstruction */
	val = VLAN_TAG_LEN;
	if (setsockopt(handle->fd, SOL_PACKET, PACKET_RESERVE, &val,
		       sizeof(val)) < 0) {
		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
		    "can't set up reserve on packet socket: %s",
		    pcap_strerror(errno));
		return -1;
	}

#endif /* HAVE_TPACKET2 */
	return 1;
}

/*
 * Attempt to set up memory-mapped access.
 *
 * On success, returns 1, and sets *status to 0 if there are no warnings
 * or to a PCAP_WARNING_ code if there is a warning.
 *
 * On failure due to lack of support for memory-mapped capture, returns
 * 0.
 *
 * On error, returns -1, and sets *status to the appropriate error code;
 * if that is PCAP_ERROR, sets handle->errbuf to the appropriate message.
 */
static int
create_ring(pcap_t *handle, int *status)
{
	unsigned i, j, frames_per_block;
	struct tpacket_req req;
	socklen_t len;
	unsigned int sk_type, tp_reserve, maclen, tp_hdrlen, netoff, macoff;
	unsigned int frame_size;

	/*
	 * Start out assuming no warnings or errors.
	 */
	*status = 0;

	/* Note that with large snapshot length (say 64K, which is the default
	 * for recent versions of tcpdump, the value that "-s 0" has given
	 * for a long time with tcpdump, and the default in Wireshark/TShark),
	 * if we use the snapshot length to calculate the frame length,
	 * only a few frames will be available in the ring even with pretty
	 * large ring size (and a lot of memory will be unused).
	 *
	 * Ideally, we should choose a frame length based on the
	 * minimum of the specified snapshot length and the maximum
	 * packet size.  That's not as easy as it sounds; consider, for
	 * example, an 802.11 interface in monitor mode, where the
	 * frame would include a radiotap header, where the maximum
	 * radiotap header length is device-dependent.
	 *
	 * So, for now, we just do this for Ethernet devices, where
	 * there's no metadata header, and the link-layer header is
	 * fixed length.  We can get the maximum packet size by
	 * adding 18, the Ethernet header length plus the CRC length
	 * (just in case we happen to get the CRC in the packet), to
	 * the MTU of the interface; we fetch the MTU in the hopes
	 * that it reflects support for jumbo frames.  (Even if the
	 * interface is just being used for passive snooping, the driver
	 * might set the size of buffers in the receive ring based on
	 * the MTU, so that the MTU limits the maximum size of packets
	 * that we can receive.)
	 *
	 * We don't do that if segmentation/fragmentation or receive
	 * offload are enabled, so we don't get rudely surprised by
	 * "packets" bigger than the MTU. */
	frame_size = handle->snapshot;
	if (handle->linktype == DLT_EN10MB) {
		int mtu;
		int offload;

		offload = iface_get_offload(handle);
		if (offload == -1) {
			*status = PCAP_ERROR;
			return -1;
		}
		if (!offload) {
			mtu = iface_get_mtu(handle->fd, handle->opt.source,
			    handle->errbuf);
			if (mtu == -1) {
				*status = PCAP_ERROR;
				return -1;
			}
			if (frame_size > mtu + 18)
				frame_size = mtu + 18;
		}
	}
	
	/* NOTE: calculus matching those in tpacket_rcv()
	 * in linux-2.6/net/packet/af_packet.c
	 */
	len = sizeof(sk_type);