Virgin import of tcpdump.org libpcap v0.6.2

1 files changed, 1290 insertions, 255 deletions

diff --git a/contrib/libpcap/pcap-linux.c b/contrib/libpcap/pcap-linux.c
index 17e0a3b..1199f8f 100644
--- a/contrib/libpcap/pcap-linux.c
+++ b/contrib/libpcap/pcap-linux.c
@@ -1,331 +1,1366 @@
 /*
- * Copyright (c) 1996, 1997
- *	The Regents of the University of California.  All rights reserved.
+ *  pcap-linux.c: Packet capture interface to the Linux kernel
  *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that: (1) source code distributions
- * retain the above copyright notice and this paragraph in its entirety, (2)
- * distributions including binary code include the above copyright notice and
- * this paragraph in its entirety in the documentation or other materials
- * provided with the distribution, and (3) all advertising materials mentioning
- * features or use of this software display the following acknowledgement:
- * ``This product includes software developed by the University of California,
- * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
- * the University nor the names of its contributors may 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.
+ *  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.
  */
 #ifndef lint
 static const char rcsid[] =
-    "@(#) $Header: /tcpdump/master/libpcap/pcap-linux.c,v 1.15.1.1 1999/10/07 23:46:40 mcr Exp $ (LBL)";
+    "@(#) $Header: /tcpdump/master/libpcap/pcap-linux.c,v 1.51.2.3 2001/01/18 03:59:56 guy Exp $ (LBL)";
 #endif
 
-#include <sys/param.h>
-#include <sys/ioctl.h>
-#include <sys/socket.h>
-#include <sys/time.h>
+/*
+ * 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.
+ */
 
-#include <net/if.h>
-#ifdef HAVE_NET_IF_ARP_H
-#include <net/if_arp.h>
-#else
-#include <linux/if_arp.h>
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
 #endif
-#include <linux/if_ether.h>
 
-#include <netinet/in.h>
+#include "pcap-int.h"
+#include "sll.h"
 
 #include <errno.h>
-#include <malloc.h>
-#include <stdio.h>
 #include <stdlib.h>
-#include <string.h>
 #include <unistd.h>
+#include <fcntl.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/ioctl.h>
+#include <sys/utsname.h>
+#include <net/if.h>
+#include <netinet/in.h>
+#include <linux/if_ether.h>
+#include <net/if_arp.h>
 
-static struct ifreq saved_ifr;
+#ifdef HAVE_NETPACKET_PACKET_H
+# include <netpacket/packet.h>
 
-#include "pcap-int.h"
+ /*
+  * We assume this means we really do have PF_PACKET sockets.
+  */
+# define HAVE_PF_PACKET_SOCKETS
+#else
+ /*
+  * Oh, joy.  Some Linux distributions have 2.2 or later kernels and
+  * libc5.  On at least one of those systems (Slackware 4.0), it
+  * appears that "/usr/include/sys/socket.h" includes <linux/socket.h>,
+  * which means it picks up all the AF_, PF_, and SO_ definitions
+  * appropriate for the current kernel; however, it also appears that
+  * they did not see fit to provide a "/usr/include/netpacket/packet.h"
+  * file.
+  *
+  * However, you should be able to get the right definitions by including
+  * <linux/if_packet.h>.
+  *
+  * So if this system has PF_PACKET defined but doesn't have the
+  * <netpacket/packet.h> header file, we include <linux/if_packet.h>
+  * instead.
+  */
+# ifdef PF_PACKET
+#  include <linux/if_packet.h>
 
-#include "gnuc.h"
-#ifdef HAVE_OS_PROTO_H
-#include "os-proto.h"
+ /*
+  * However, 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
+# endif /* PACKET_HOST */
+# endif /* PF_PACKET */
+#endif /* HAVE_NETPACKET_PACKET_H */
+
+#ifdef SO_ATTACH_FILTER
+#include <linux/types.h>
+#include <linux/filter.h>
 #endif
 
-void linux_restore_ifr(void);
+#ifndef __GLIBC__
+typedef int		socklen_t;
+#endif
 
-int
-pcap_stats(pcap_t *p, struct pcap_stat *ps)
+#ifndef MSG_TRUNC
+#define MSG_TRUNC	0
+#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
+ */
+static int map_arphrd_to_dlt(int arptype );
+static int live_open_old(pcap_t *, char *, int, int, char *);
+static int live_open_new(pcap_t *, char *, int, int, char *);
+static int pcap_read_packet(pcap_t *, pcap_handler, u_char *);
+
+/*
+ * Wrap some ioctl calls
+ */
+#ifdef HAVE_PF_PACKET_SOCKETS
+static int	iface_get_id(int fd, const char *device, char *ebuf);
+#endif
+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);
+#endif
+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);
+static int	fix_offset(struct bpf_insn *p);
+#endif
+
+/*
+ *  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).
+ *  
+ *  See also pcap(3).
+ */
+pcap_t *
+pcap_open_live(char *device, int snaplen, int promisc, int to_ms, char *ebuf)
 {
+        /* Allocate a handle for this session. */
+
+	pcap_t	*handle = malloc(sizeof(*handle));
+	if (handle == NULL) {
+		snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc: %s",
+			 pcap_strerror(errno));
+		return NULL;
+	}
+
+	/* Initialize some components of the pcap structure. */
+
+	memset(handle, 0, sizeof(*handle));
+	handle->snapshot	= snaplen;
+	handle->md.timeout	= to_ms;
+
+	/*
+	 * NULL and "any" are special devices which give us the hint to 
+	 * monitor all devices.
+	 */
+	if (!device || strcmp(device, "any") == 0) {
+		device			= NULL;
+		handle->md.device	= strdup("any");
+	} else
+		handle->md.device	= strdup(device);
+
+	if (handle->md.device == NULL) {
+		snprintf(ebuf, PCAP_ERRBUF_SIZE, "strdup: %s",
+			 pcap_strerror(errno) );
+		free(handle);
+		return NULL;
+	}
+
+	/* 
+	 * 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.
+	 */
+
+	if (! (live_open_new(handle, device, promisc, to_ms, ebuf) ||
+	       live_open_old(handle, device, promisc, to_ms, ebuf)) )
+	{
+		/* 
+		 * Both methods to open the packet socket failed. Tidy
+		 * up and report our failure (ebuf is expected to be
+		 * set by the functions above). 
+		 */
 
-	*ps = p->md.stat;
-	return (0);
+		free(handle->md.device);
+		free(handle);
+		return NULL;
+	}
+
+	return handle;
 }
 
+/*
+ *  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. 
+ */
 int
-pcap_read(pcap_t *p, int cnt, pcap_handler callback, u_char *user)
+pcap_read(pcap_t *handle, int max_packets, pcap_handler callback, u_char *user)
 {
-	register int cc;
-	register int bufsize;
-	register int caplen;
-	register u_char *bp;
-	struct sockaddr from;
-	int fromlen;
-
-	bp = p->buffer + p->offset;
-	bufsize = p->bufsize;
-	if (p->md.pad > 0) {
-		memset(bp, 0, p->md.pad);
-		bp += p->md.pad;
-		bufsize -= p->md.pad;
-	}
+	/*
+	 * 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)
+{
+	int			offset;
+#ifdef HAVE_PF_PACKET_SOCKETS
+	struct sockaddr_ll	from;
+	struct sll_header	*hdrp;
+#else
+	struct sockaddr		from;
+#endif
+	socklen_t		fromlen;
+	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 */
 
-again:
 	do {
 		fromlen = sizeof(from);
-		cc = recvfrom(p->fd, bp, bufsize, 0, &from, &fromlen);
-		if (cc < 0) {
-			/* Don't choke when we get ptraced */
-			switch (errno) {
+		packet_len = recvfrom( 
+			handle->fd, handle->buffer + offset + handle->offset,
+			handle->md.readlen - offset, MSG_TRUNC, 
+			(struct sockaddr *) &from, &fromlen);
+	} while (packet_len == -1 && errno == EINTR);
 
-			case EINTR:
-					goto again;
+	/* Check if an error occured */
 
-			case EWOULDBLOCK:
-				return (0);		/* XXX */
-			}
-			sprintf(p->errbuf, "read: %s", pcap_strerror(errno));
-			return (-1);
+	if (packet_len == -1) {
+		if (errno == EAGAIN)
+			return 0;	/* no packet there */
+		else {
+			snprintf(handle->errbuf, sizeof(handle->errbuf),
+				 "recvfrom: %s", pcap_strerror(errno));
+			return -1;
 		}
-	} while (strcmp(p->md.device, from.sa_data));
-
-	/* If we need have leading zero bytes, adjust count */
-	cc += p->md.pad;
-	bp = p->buffer + p->offset;
-
-	/* If we need to step over leading junk, adjust count and pointer */
-	cc -= p->md.skip;
-	bp += p->md.skip;
-
-	/* Captured length can't exceed our read buffer size */
-	caplen = cc;
-	if (caplen > bufsize)
-		caplen = bufsize;
-
-	/* Captured length can't exceed the snapshot length */
-	if (caplen > p->snapshot)
-		caplen = p->snapshot;
-
-	if (p->fcode.bf_insns == NULL ||
-	    bpf_filter(p->fcode.bf_insns, bp, cc, caplen)) {
-		struct pcap_pkthdr h;
-
-		++p->md.stat.ps_recv;
-		/* Get timestamp */
-		if (ioctl(p->fd, SIOCGSTAMP, &h.ts) < 0) {
-			sprintf(p->errbuf, "SIOCGSTAMP: %s",
-			    pcap_strerror(errno));
-			return (-1);
+	}
+
+#ifdef HAVE_PF_PACKET_SOCKETS
+	/*
+	 * If this is from the loopback device, reject outgoing packets;
+	 * we'll see the packet as an incoming packet as well, and
+	 * we don't want to see it twice.
+	 *
+	 * 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 (!handle->md.sock_packet &&
+	    from.sll_ifindex == handle->md.lo_ifindex &&
+	    from.sll_pkttype == PACKET_OUTGOING)
+		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 *)handle->buffer;
+
+		/*
+		 * 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.
+		 */
+		switch (from.sll_pkttype) {
+
+		case PACKET_HOST:
+			hdrp->sll_pkttype = htons(LINUX_SLL_HOST);
+			break;
+
+		case PACKET_BROADCAST:
+			hdrp->sll_pkttype = htons(LINUX_SLL_BROADCAST);
+			break;
+
+		case PACKET_MULTICAST:
+			hdrp->sll_pkttype = htons(LINUX_SLL_MULTICAST);
+			break;
+
+		case PACKET_OTHERHOST:
+			hdrp->sll_pkttype = htons(LINUX_SLL_OTHERHOST);
+			break;
+
+		case PACKET_OUTGOING:
+			hdrp->sll_pkttype = htons(LINUX_SLL_OUTGOING);
+			break;
+
+		default:
+			hdrp->sll_pkttype = -1;
+			break;
+		}
+
+		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;
+	}
+#endif
+
+	/*
+	 * 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, handle->buffer, 
+		                packet_len, caplen) == 0)
+		{
+			/* rejected by filter */
+			return 0;
 		}
-		h.len = cc;
-		h.caplen = caplen;
-		(*callback)(user, &h, bp);
-		return (1);
 	}
-	return (0);
+
+	/* Fill in our own header data */
+
+	if (ioctl(handle->fd, SIOCGSTAMP, &pcap_header.ts) == -1) {
+		snprintf(handle->errbuf, sizeof(handle->errbuf),
+			 "ioctl: %s", pcap_strerror(errno));
+		return -1;
+	}
+	pcap_header.caplen	= caplen;
+	pcap_header.len		= packet_len;
+
+	/* Call the user supplied callback function */
+	handle->md.stat.ps_recv++;
+	callback(userdata, &pcap_header, handle->buffer + handle->offset);
+
+	return 1;
 }
 
-pcap_t *
-pcap_open_live(char *device, int snaplen, int promisc, int to_ms, char *ebuf)
+/*
+ *  Get the statistics for the given packet capture handle.
+ *  FIXME: Currently does not report the number of dropped packets.
+ */
+int
+pcap_stats(pcap_t *handle, struct pcap_stat *stats)
 {
-	register int fd, broadcast;
-	register pcap_t *p;
-	struct ifreq ifr;
-	struct sockaddr sa;
-
-	p = (pcap_t *)malloc(sizeof(*p));
-	if (p == NULL) {
-		sprintf(ebuf, "malloc: %s", pcap_strerror(errno));
-		return (NULL);
+	*stats = handle->md.stat;
+	return 0;
+}
+
+/*
+ *  Attach the given BPF code to the packet capture device. 
+ */
+int
+pcap_setfilter(pcap_t *handle, struct bpf_program *filter)
+{
+#ifdef SO_ATTACH_FILTER
+	struct sock_fprog	fcode;
+	int			can_filter_in_kernel;
+#endif
+
+	if (!handle)
+		return -1;
+	if (!filter) {
+	        strncpy(handle->errbuf, "setfilter: No filter specified",
+			sizeof(handle->errbuf));
+		return -1;
 	}
-	memset(p, 0, sizeof(*p));
-	fd = -1;
 
-	fd = socket(PF_INET, SOCK_PACKET, htons(ETH_P_ALL));
-	if (fd < 0) {
-		sprintf(ebuf, "socket: %s", pcap_strerror(errno));
-		goto bad;
+	/* Make our private copy of the filter */
+
+	if (install_bpf_program(handle, filter) < 0) {
+		snprintf(handle->errbuf, sizeof(handle->errbuf),
+			 "malloc: %s", pcap_strerror(errno));
+		return -1;
 	}
-	p->fd = fd;
-
-	/* Bind to the interface name */
-	memset(&sa, 0, sizeof(sa));
-	sa.sa_family = AF_INET;
-	(void)strncpy(sa.sa_data, device, sizeof(sa.sa_data));
-	if (bind(p->fd, &sa, sizeof(sa))) {
-		sprintf(ebuf, "bind: %s: %s", device, pcap_strerror(errno));
-		goto bad;
+
+	/* 
+	 * Run user level packet filter by default. Will be overriden if 
+	 * installing a kernel filter succeeds. 
+	 */
+	handle->md.use_bpf = 0;
+
+	/*
+	 * If we're reading from a savefile, don't try to install
+	 * a kernel filter.
+	 */
+	if (handle->sf.rfile != NULL)
+		return 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.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, 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)) {
+
+		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;
+		}
 	}
 
-	memset(&ifr, 0, sizeof(ifr));
-	strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
-	if (ioctl(p->fd, SIOCGIFHWADDR, &ifr) < 0 ) {
-		sprintf(ebuf, "SIOCGIFHWADDR: %s", pcap_strerror(errno));
-		goto bad;
+	if (can_filter_in_kernel) {
+		if (setsockopt(handle->fd, SOL_SOCKET, SO_ATTACH_FILTER, 
+			       &fcode, sizeof(fcode)) == 0)
+		{
+			/* Installation succeded - using kernel filter. */
+			handle->md.use_bpf = 1;
+		}
+		else
+		{
+			/* 
+			 * 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));
+			}
+		}
 	}
-	broadcast = 0;
-	switch (ifr.ifr_hwaddr.sa_family) {
 
+	/*
+	 * Free up the copy of the filter that was made by "fix_program()".
+	 */
+	if (fcode.filter != NULL)
+		free(fcode.filter);
+#endif /* SO_ATTACH_FILTER */
+
+	return 0;
+}
+
+/*
+ *  Linux uses the ARP hardware type to identify the type of an 
+ *  interface. pcap uses the DLT_xxx constants for this. This 
+ *  function maps the ARPHRD_xxx constant to an appropriate
+ *  DLT_xxx constant.
+ *  
+ *  Returns -1 if unable to map the type; we print a message and,
+ *  if we're using PF_PACKET/SOCK_RAW rather than PF_INET/SOCK_PACKET,
+ *  we fall back on using PF_PACKET/SOCK_DGRAM.
+ */
+static int map_arphrd_to_dlt(int arptype)
+{
+	switch (arptype) {
 	case ARPHRD_ETHER:
 	case ARPHRD_METRICOM:
-		p->linktype = DLT_EN10MB;
-		p->offset = 2;
-		++broadcast;
-		break;
-
-	case ARPHRD_EETHER:
-		p->linktype = DLT_EN3MB;
-		++broadcast;
-		break;
-
-	case ARPHRD_AX25:
-		p->linktype = DLT_AX25;
-		++broadcast;
-		break;
-
-	case ARPHRD_PRONET:
-		p->linktype = DLT_PRONET;
-		break;
-
-	case ARPHRD_CHAOS:
-		p->linktype = DLT_CHAOS;
-		break;
-
-	case ARPHRD_IEEE802:
-		p->linktype = DLT_IEEE802;
-		++broadcast;
-		break;
-
-	case ARPHRD_ARCNET:
-		p->linktype = DLT_ARCNET;
-		++broadcast;
-		break;
-
-	case ARPHRD_SLIP:
+	case ARPHRD_LOOPBACK:	return DLT_EN10MB;
+	case ARPHRD_EETHER:	return DLT_EN3MB;
+	case ARPHRD_AX25:	return DLT_AX25;
+	case ARPHRD_PRONET:	return DLT_PRONET;
+	case ARPHRD_CHAOS:	return DLT_CHAOS;
+#ifndef ARPHRD_IEEE802_TR
+#define ARPHRD_IEEE802_TR 800	/* From Linux 2.4 */
+#endif
+	case ARPHRD_IEEE802_TR:
+	case ARPHRD_IEEE802:	return DLT_IEEE802;
+	case ARPHRD_ARCNET:	return DLT_ARCNET;
+	case ARPHRD_FDDI:	return DLT_FDDI;
+
+#ifndef ARPHRD_ATM  /* FIXME: How to #include this? */
+#define ARPHRD_ATM 19
+#endif
+	case ARPHRD_ATM:	return DLT_ATM_CLIP;
+
+	case ARPHRD_PPP:
+	/* 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 2.2.14 */
+#endif
+	case ARPHRD_SIT:
 	case ARPHRD_CSLIP:
 	case ARPHRD_SLIP6:
 	case ARPHRD_CSLIP6:
-	case ARPHRD_PPP:
-		p->linktype = DLT_RAW;
-		break;
-
-	case ARPHRD_LOOPBACK:
-		p->linktype = DLT_NULL;
-		p->md.pad = 2;
-		p->md.skip = 12;
-		break;
-
-#ifdef ARPHRD_FDDI
-	/* Not all versions of the kernel has this define */
-	case ARPHRD_FDDI:
-		p->linktype = DLT_FDDI;
-		++broadcast;
-		break;
+	case ARPHRD_SLIP:	return DLT_RAW;
+	}
+
+	return -1;
+}
+
+/* ===== Functions to interface to the newer kernels ================== */
+
+/*
+ *  Try to open a packet socket using the new kernel interface.
+ *  Returns 0 on failure.
+ *  FIXME: 0 uses to mean success (Sebastian)
+ */
+static int
+live_open_new(pcap_t *handle, char *device, int promisc, 
+	      int to_ms, char *ebuf)
+{
+#ifdef HAVE_PF_PACKET_SOCKETS
+	int			sock_fd = -1, device_id, mtu, arptype;
+	struct packet_mreq	mr;
+
+	/* One shot loop used for error handling - bail out with break */
+
+	do {
+		/*
+		 * Open a socket with protocol family packet. If a device is
+		 * given we try to open it in raw mode otherwise we use 
+		 * the cooked interface. 
+		 */
+		sock_fd = device ? 
+			socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL))
+		      : socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_ALL));
+
+		if (sock_fd == -1) {
+			snprintf(ebuf, PCAP_ERRBUF_SIZE, "socket: %s",
+				 pcap_strerror(errno) );
+			break;
+		}
+
+		/* 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", ebuf);
+
+		/*
+		 * What kind of frames do we have to deal with? Fall back 
+		 * to cooked mode if we have an unknown interface type. 
+		 */
+
+		if (device) {
+			/* Assume for now we don't need cooked mode. */
+			handle->md.cooked = 0;
+
+			arptype	= iface_get_arptype(sock_fd, device, ebuf);
+			if (arptype == -1) 
+				break;
+			handle->linktype = map_arphrd_to_dlt(arptype);
+			if (handle->linktype == -1 ||
+			    (handle->linktype == DLT_EN10MB &&
+			     (strncmp("isdn", device, 4) == 0 ||
+			      strncmp("isdY", device, 4) == 0)) ||
+			    (handle->linktype == DLT_RAW &&
+			     (strncmp("ippp", device, 4) == 0))) {
+				/*
+				 * Unknown interface type (-1), 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.
+				 *
+				 * XXX - do that with DLT_RAW as well?
+				 */
+				if (close(sock_fd) == -1) {
+					snprintf(ebuf, PCAP_ERRBUF_SIZE,
+						 "close: %s", pcap_strerror(errno));
+					break;
+				}
+				sock_fd = socket(PF_PACKET, SOCK_DGRAM, 
+						 htons(ETH_P_ALL));
+				if (sock_fd == -1) {
+					snprintf(ebuf, PCAP_ERRBUF_SIZE,
+						 "socket: %s", pcap_strerror(errno));
+					break;
+				}
+				handle->md.cooked = 1;
+
+				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.
+					 */
+					fprintf(stderr, 
+						"Warning: arptype %d not "
+						"supported by libpcap - "
+						"falling back to cooked "
+						"socket\n",
+						arptype);
+				}
+				handle->linktype = DLT_LINUX_SLL;
+			}
+
+			device_id = iface_get_id(sock_fd, device, ebuf);
+			if (device_id == -1)
+				break;
+
+			if (iface_bind(sock_fd, device_id, ebuf) == -1)
+				break;
+		} else {
+			/*
+			 * This is cooked mode.
+			 */
+			handle->md.cooked = 1;
+			handle->linktype = DLT_LINUX_SLL;
+
+			/*
+			 * XXX - squelch GCC complaints about
+			 * uninitialized variables; if we can't
+			 * select promiscuous mode on all interfaces,
+			 * we should move the code below into the
+			 * "if (device)" branch of the "if" and
+			 * get rid of the next statement.
+			 */
+			device_id = -1;
+		}
+
+		/* Select promiscuous mode on/off */
+
+#ifdef SOL_PACKET
+		/* 
+		 * Hmm, how can we set promiscuous mode on all interfaces?
+		 * I am not sure if that is possible at all.
+		 */
+
+		if (device) {
+			memset(&mr, 0, sizeof(mr));
+			mr.mr_ifindex = device_id;
+			mr.mr_type    = promisc ? 
+				PACKET_MR_PROMISC : PACKET_MR_ALLMULTI;
+			if (setsockopt(sock_fd, SOL_PACKET, 
+				PACKET_ADD_MEMBERSHIP, &mr, sizeof(mr)) == -1)
+			{
+				snprintf(ebuf, PCAP_ERRBUF_SIZE, 
+					"setsockopt: %s", pcap_strerror(errno));
+				break;
+			}
+		}
 #endif
 
-#ifdef notdef
-	case ARPHRD_LOCALTLK:
-	case ARPHRD_NETROM:
-	case ARPHRD_APPLETLK:
-	case ARPHRD_DLCI:
-	case ARPHRD_RSRVD:
-	case ARPHRD_ADAPT:
-	case ARPHRD_TUNNEL:
-	case ARPHRD_TUNNEL6:
-	case ARPHRD_FRAD:
-	case ARPHRD_SKIP:
-		/* XXX currently do not know what to do with these... */
-		abort();
+		/* Compute the buffersize */
+
+		mtu	= iface_get_mtu(sock_fd, device, ebuf);
+		if (mtu == -1)
+			break;
+		handle->bufsize	 = MAX_LINKHEADER_SIZE + mtu;
+
+		/* Fill in the pcap structure */
+
+		handle->fd 	 = sock_fd;
+		handle->offset	 = 0;
+
+		handle->buffer	 = malloc(handle->bufsize);
+		if (!handle->buffer) {
+			snprintf(ebuf, PCAP_ERRBUF_SIZE,
+				 "malloc: %s", pcap_strerror(errno));
+			break;
+		}
+
+		/*
+		 * This is a 2.2 or later kernel, as it has PF_PACKET;
+		 * "recvfrom()", when passed the MSG_TRUNC flag, will
+		 * return the actual length of the packet, not the
+		 * number of bytes from the packet copied to userland,
+		 * so we can safely pass it a byte count based on the
+		 * snapshot length.
+		 */
+		handle->md.readlen = handle->snapshot;
+		return 1;
+
+	} while(0);
+
+	if (sock_fd != -1)
+		close(sock_fd);
+	return 0;
+#else
+	strncpy(ebuf, 
+		"New packet capturing interface not supported by build " 
+		"environment", PCAP_ERRBUF_SIZE);
+	return 0;
 #endif
+}
 
-	default:
-		sprintf(ebuf, "unknown physical layer type 0x%x",
-		    ifr.ifr_hwaddr.sa_family);
-		goto bad;
-	}
+#ifdef HAVE_PF_PACKET_SOCKETS
+/*
+ *  Return the index of the given device name. Fill ebuf and return 
+ *  -1 on failure.
+ */
+static int
+iface_get_id(int fd, const char *device, char *ebuf)
+{
+	struct ifreq	ifr;
 
-	/* Base the buffer size on the interface MTU */
 	memset(&ifr, 0, sizeof(ifr));
 	strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
-	if (ioctl(p->fd, SIOCGIFMTU, &ifr) < 0 ) {
-		sprintf(ebuf, "SIOCGIFMTU: %s", pcap_strerror(errno));
-		goto bad;
+
+	if (ioctl(fd, SIOCGIFINDEX, &ifr) == -1) {
+		snprintf(ebuf, PCAP_ERRBUF_SIZE,
+			 "ioctl: %s", pcap_strerror(errno));
+		return -1;
 	}
 
-	/* Leave room for link header (which is never large under linux...) */
-	p->bufsize = ifr.ifr_mtu + 64;
+	return ifr.ifr_ifindex;
+}
 
-	p->buffer = (u_char *)malloc(p->bufsize + p->offset);
-	if (p->buffer == NULL) {
-		sprintf(ebuf, "malloc: %s", pcap_strerror(errno));
-		goto bad;
+/*
+ *  Bind the socket associated with FD to the given device. 
+ */
+static int
+iface_bind(int fd, int ifindex, char *ebuf)
+{
+	struct sockaddr_ll	sll;
+
+	memset(&sll, 0, sizeof(sll));
+	sll.sll_family		= AF_PACKET;
+	sll.sll_ifindex		= ifindex;
+	sll.sll_protocol	= htons(ETH_P_ALL);
+
+	if (bind(fd, (struct sockaddr *) &sll, sizeof(sll)) == -1) {
+		snprintf(ebuf, PCAP_ERRBUF_SIZE,
+			 "bind: %s", pcap_strerror(errno));
+		return -1;
 	}
 
-	/* XXX */
-	if (promisc && broadcast) {
+	return 0;
+}
+
+#endif
+
+
+/* ===== Functions to interface to the older kernels ================== */
+
+/*
+ * 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.
+ */
+
+/*
+ * List of pcaps for which we turned promiscuous mode on by hand.
+ * If there are any such pcaps, we arrange to call "pcap_close_all()"
+ * when we exit, and have it close all of them to turn promiscuous mode
+ * off.
+ */
+static struct pcap *pcaps_to_close;
+
+/*
+ * TRUE if we've already called "atexit()" to cause "pcap_close_all()" to
+ * be called on exit.
+ */
+static int did_atexit;
+
+static void	pcap_close_all(void)
+{
+	struct pcap *handle;
+
+	while ((handle = pcaps_to_close) != NULL)
+		pcap_close(handle);
+}
+
+void	pcap_close_linux( pcap_t *handle )
+{
+	struct pcap	*p, *prevp;
+	struct ifreq	ifr;
+
+	if (handle->md.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));
-		strcpy(ifr.ifr_name, device);
-		if (ioctl(p->fd, SIOCGIFFLAGS, &ifr) < 0 ) {
-			sprintf(ebuf, "SIOCGIFFLAGS: %s", pcap_strerror(errno));
-			goto bad;
+		strncpy(ifr.ifr_name, handle->md.device, sizeof(ifr.ifr_name));
+		if (ioctl(handle->fd, SIOCGIFFLAGS, &ifr) == -1) {
+			fprintf(stderr, 
+			    "Can't restore interface flags (SIOCGIFFLAGS failed: %s).\n"
+			    "Please adjust manually.\n"
+			    "Hint: This can't happen with Linux >= 2.2.0.\n",
+			    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 flags (SIOCSIFFLAGS failed: %s).\n"
+					    "Please adjust manually.\n"
+					    "Hint: This can't happen with Linux >= 2.2.0.\n",
+					    strerror(errno));
+				}
+			}
+		}
+
+		/*
+		 * Take this pcap out of the list of pcaps for which we
+		 * have to take the interface out of promiscuous mode.
+		 */
+		for (p = pcaps_to_close, prevp = NULL; p != NULL;
+		    prevp = p, p = p->md.next) {
+			if (p == handle) {
+				/*
+				 * Found it.  Remove it from the list.
+				 */
+				if (prevp == NULL) {
+					/*
+					 * It was at the head of the list.
+					 */
+					pcaps_to_close = p->md.next;
+				} else {
+					/*
+					 * It was in the middle of the list.
+					 */
+					prevp->md.next = p->md.next;
+				}
+				break;
+			}
+		}
+	}
+	if (handle->md.device != NULL)
+		free(handle->md.device);
+}
+
+/*
+ *  Try to open a packet socket using the old kernel interface.
+ *  Returns 0 on failure.
+ *  FIXME: 0 uses to mean success (Sebastian)
+ */
+static int
+live_open_old(pcap_t *handle, char *device, int promisc, 
+	      int to_ms, char *ebuf)
+{
+	int		sock_fd = -1, mtu, arptype;
+	struct utsname	utsname;
+	struct ifreq	ifr;
+
+	do {
+		/* Open the socket */
+
+		sock_fd = socket(PF_INET, SOCK_PACKET, htons(ETH_P_ALL));
+		if (sock_fd == -1) {
+			snprintf(ebuf, PCAP_ERRBUF_SIZE,
+				 "socket: %s", pcap_strerror(errno));
+			break;
+		}
+
+		/* It worked - we are using the old interface */
+		handle->md.sock_packet = 1;
+
+		/* ...which means we get the link-layer header. */
+		handle->md.cooked = 0;
+
+		/* Bind to the given device */
+
+		if (!device) {
+		        strncpy(ebuf, "pcap_open_live: The \"any\" device isn't supported on 2.0[.x]-kernel systems",
+				PCAP_ERRBUF_SIZE);
+			break;
+		}
+		if (iface_bind_old(sock_fd, device, ebuf) == -1)
+			break;
+
+		/* Go to promisc mode */
+		if (promisc) {
+			memset(&ifr, 0, sizeof(ifr));
+			strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
+			if (ioctl(sock_fd, SIOCGIFFLAGS, &ifr) == -1) {
+				snprintf(ebuf, PCAP_ERRBUF_SIZE,
+					 "ioctl: %s", pcap_strerror(errno));
+				break;
+			}
+			if ((ifr.ifr_flags & IFF_PROMISC) == 0) {
+				/*
+				 * Promiscuous mode isn't currently on,
+				 * so turn it on, and remember that
+				 * we should turn it off when the
+				 * pcap_t is closed.
+				 */
+
+				/*
+				 * If we haven't already done so, arrange
+				 * to have "pcap_close_all()" called when
+				 * we exit.
+				 */
+				if (!did_atexit) {
+					if (atexit(pcap_close_all) == -1) {
+						/*
+						 * "atexit()" failed; don't
+						 * put the interface in
+						 * promiscuous mode, just
+						 * give up.
+						 */
+						strncpy(ebuf, "atexit failed",
+							PCAP_ERRBUF_SIZE);
+						break;
+					}
+				}
+
+				ifr.ifr_flags |= IFF_PROMISC;
+				if (ioctl(sock_fd, SIOCSIFFLAGS, &ifr) == -1) {
+				        snprintf(ebuf, PCAP_ERRBUF_SIZE,
+						 "ioctl: %s",
+						 pcap_strerror(errno));
+					break;
+				}
+				handle->md.clear_promisc = 1;
+
+				/*
+				 * Add this to the list of pcaps
+				 * to close when we exit.
+				 */
+				handle->md.next = pcaps_to_close;
+				pcaps_to_close = handle;
+			}
+		}
+
+		/* Compute the buffersize */
+
+		mtu	= iface_get_mtu(sock_fd, device, ebuf);
+		if (mtu == -1)
+			break;
+		handle->bufsize	 = MAX_LINKHEADER_SIZE + mtu;
+		if (handle->bufsize < handle->snapshot)
+			handle->bufsize = handle->snapshot;
+
+		/* All done - fill in the pcap handle */
+
+		arptype = iface_get_arptype(sock_fd, device, ebuf);
+		if (arptype == -1)
+			break;
+
+		handle->fd 	 = sock_fd;
+		handle->offset	 = 0;
+		handle->linktype = map_arphrd_to_dlt(arptype);
+		/*
+		 * 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.
+		 */
+		if (handle->linktype == -1) {
+			snprintf(ebuf, PCAP_ERRBUF_SIZE,
+				 "interface type of %s not supported", device);
+			break;
+		}
+		handle->buffer	 = malloc(handle->bufsize);
+		if (!handle->buffer) {
+		        snprintf(ebuf, PCAP_ERRBUF_SIZE,
+				 "malloc: %s", pcap_strerror(errno));
+			break;
 		}
-		saved_ifr = ifr;
-		ifr.ifr_flags |= IFF_PROMISC;
-		if (ioctl(p->fd, SIOCSIFFLAGS, &ifr) < 0 ) {
-			sprintf(ebuf, "SIOCSIFFLAGS: %s", pcap_strerror(errno));
-			goto bad;
+
+		/*
+		 * This might be a 2.0[.x] kernel - check.
+		 */
+		if (uname(&utsname) < 0 ||
+		    strncmp(utsname.release, "2.0", 3) == 0) {
+			/*
+			 * Either we couldn't find out what kernel release
+			 * this is, or it's a 2.0[.x] kernel.
+			 *
+			 * In the 2.0[.x] kernel, a "recvfrom()" on
+			 * a SOCK_PACKET socket, with MSG_TRUNC set, will
+			 * return the number of bytes read, so if we pass
+			 * a length based on the snapshot length, it'll
+			 * return the number of bytes from the packet
+			 * copied to userland, not the actual length
+			 * of the packet.
+			 *
+			 * This means that, for example, the IP dissector
+			 * in tcpdump will get handed a packet length less
+			 * than the length in the IP header, and will
+			 * complain about "truncated-ip".
+			 *
+			 * So we don't bother trying to copy from the
+			 * kernel only the bytes in which we're interested,
+			 * but instead copy them all, just as the older
+			 * versions of libpcap for Linux did.
+			 *
+			 * Just one of many problems with packet capture
+			 * on 2.0[.x] kernels; you really want a 2.2[.x]
+			 * or later kernel if you want packet capture to
+			 * work well.
+			 */
+			handle->md.readlen = handle->bufsize;
+		} else {
+			/*
+			 * This is a 2.2[.x] or later kernel (although
+			 * why we're using SOCK_PACKET on such a system
+			 * is unknown to me).
+			 *
+			 * We can safely pass "recvfrom()" a byte count
+			 * based on the snapshot length.
+			 */
+			handle->md.readlen = handle->snapshot;
 		}
-		ifr.ifr_flags &= ~IFF_PROMISC;
-		atexit(linux_restore_ifr);
+		return 1;
+
+	} while (0);
+
+	if (sock_fd != -1)
+		close(sock_fd);
+	return 0;
+}
+
+/*
+ *  Bind the socket associated with FD to the given device using the 
+ *  interface of the old kernels.
+ */
+static int
+iface_bind_old(int fd, const char *device, char *ebuf)
+{
+	struct sockaddr	saddr;
+
+	memset(&saddr, 0, sizeof(saddr));
+	strncpy(saddr.sa_data, device, sizeof(saddr.sa_data));
+	if (bind(fd, &saddr, sizeof(saddr)) == -1) {
+		snprintf(ebuf, PCAP_ERRBUF_SIZE,
+			 "bind: %s", pcap_strerror(errno));
+		return -1;
 	}
 
-	p->md.device = strdup(device);
-	if (p->md.device == NULL) {
-		sprintf(ebuf, "malloc: %s", pcap_strerror(errno));
-		goto bad;
+	return 0;
+}
+
+
+/* ===== System calls available on all supported kernels ============== */
+
+/*
+ *  Query the kernel for the MTU of the given interface. 
+ */
+static int
+iface_get_mtu(int fd, const char *device, char *ebuf)
+{
+	struct ifreq	ifr;
+
+	if (!device)
+		return BIGGER_THAN_ALL_MTUS;
+
+	memset(&ifr, 0, sizeof(ifr));
+	strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
+
+	if (ioctl(fd, SIOCGIFMTU, &ifr) == -1) {
+		snprintf(ebuf, PCAP_ERRBUF_SIZE,
+			 "ioctl: %s", pcap_strerror(errno));
+		return -1;
 	}
-	p->snapshot = snaplen;
-
-	return (p);
-bad:
-	if (fd >= 0)
-		(void)close(fd);
-	if (p->buffer != NULL)
-		free(p->buffer);
-	if (p->md.device != NULL)
-		free(p->md.device);
-	free(p);
-	return (NULL);
+
+	return ifr.ifr_mtu;
 }
 
-int
-pcap_setfilter(pcap_t *p, struct bpf_program *fp)
+/*
+ *  Get the hardware type of the given interface as ARPHRD_xxx constant.
+ */
+static int
+iface_get_arptype(int fd, const char *device, char *ebuf)
 {
+	struct ifreq	ifr;
 
-	p->fcode = *fp;
-	return (0);
+	memset(&ifr, 0, sizeof(ifr));
+	strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
+
+	if (ioctl(fd, SIOCGIFHWADDR, &ifr) == -1) {
+		snprintf(ebuf, PCAP_ERRBUF_SIZE,
+			 "ioctl: %s", pcap_strerror(errno));
+		return -1;
+	}
+
+	return ifr.ifr_hwaddr.sa_family;
 }
 
-void
-linux_restore_ifr(void)
+#ifdef HAVE_PF_PACKET_SOCKETS
+static int
+fix_program(pcap_t *handle, struct sock_fprog *fcode)
 {
-	register int fd;
+	size_t prog_size;
+	register int i;
+	register struct bpf_insn *p;
+	struct bpf_insn *f;
+	int len;
+
+	/*
+	 * Make a copy of the filter, and modify that copy if
+	 * necessary.
+	 */
+	prog_size = sizeof(*handle->fcode.bf_insns) * handle->fcode.bf_len;
+	len = handle->fcode.bf_len;
+	f = (struct bpf_insn *)malloc(prog_size);
+	if (f == NULL) {
+		snprintf(handle->errbuf, sizeof(handle->errbuf),
+			 "malloc: %s", pcap_strerror(errno));
+		return -1;
+	}
+	memcpy(f, handle->fcode.bf_insns, prog_size);
+	fcode->len = len;
+	fcode->filter = (struct sock_filter *) f;
+
+	for (i = 0; i < len; ++i) {
+		p = &f[i];
+		/*
+		 * What type of instruction is this?
+		 */
+		switch (BPF_CLASS(p->code)) {
+
+		case BPF_RET:
+			/*
+			 * It's a return instruction; is the snapshot
+			 * length a constant, rather than the contents
+			 * of the accumulator?
+			 */
+			if (BPF_MODE(p->code) == BPF_K) {
+				/*
+				 * Yes - if the value to be returned,
+				 * i.e. the snapshot length, is anything
+				 * other than 0, make it 65535, so that
+				 * the packet is truncated by "recvfrom()",
+				 * not by the filter.
+				 *
+				 * XXX - there's nothing we can easily do
+				 * if it's getting the value from the
+				 * accumulator; we'd have to insert
+				 * code to force non-zero values to be
+				 * 65535.
+				 */
+				if (p->k != 0)
+					p->k = 65535;
+			}
+			break;
+
+		case BPF_LD:
+		case BPF_LDX:
+			/*
+			 * It's a load instruction; is it loading
+			 * from the packet?
+			 */
+			switch (BPF_MODE(p->code)) {
 
-	fd = socket(PF_INET, SOCK_PACKET, htons(0x0003));
-	if (fd < 0)
-		fprintf(stderr, "linux socket: %s", pcap_strerror(errno));
-	else if (ioctl(fd, SIOCSIFFLAGS, &saved_ifr) < 0)
-		fprintf(stderr, "linux SIOCSIFFLAGS: %s", pcap_strerror(errno));
+			case BPF_ABS:
+			case BPF_IND:
+			case BPF_MSH:
+				/*
+				 * Yes; are we in cooked mode?
+				 */
+				if (handle->md.cooked) {
+					/*
+					 * Yes, so we need to fix this
+					 * instruction.
+					 */
+					if (fix_offset(p) < 0) {
+						/*
+						 * We failed to do so.
+						 * Return 0, so our caller
+						 * knows to punt to userland.
+						 */
+						return 0;
+					}
+				}
+				break;
+			}
+			break;
+		}
+	}
+	return 1;	/* we succeeded */
+}
+
+static int
+fix_offset(struct bpf_insn *p)
+{
+	/*
+	 * What's the offset?
+	 */
+	if (p->k >= SLL_HDR_LEN) {
+		/*
+		 * It's within the link-layer payload; that starts at an
+		 * offset of 0, as far as the kernel packet filter is
+		 * concerned, so subtract the length of the link-layer
+		 * header.
+		 */
+		p->k -= SLL_HDR_LEN;
+	} else if (p->k == 14) {
+		/*
+		 * It's the protocol field; map it to the special magic
+		 * kernel offset for that field.
+		 */
+		p->k = SKF_AD_OFF + SKF_AD_PROTOCOL;
+	} else {
+		/*
+		 * It's within the header, but it's not one of those
+		 * fields; we can't do that in the kernel, so punt
+		 * to userland.
+		 */
+		return -1;
+	}
+	return 0;
 }
+#endif