*
- *
+ *
* 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
* 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 1.31 2000-10-12 03:53:59 guy Exp $ (LBL)";
+static const char rcsid[] _U_ =
+ "@(#) $Header: /tcpdump/master/libpcap/pcap-linux.c,v 1.110 2004-10-19 07:06:12 guy Exp $ (LBL)";
#endif
/*
- * Known bugs:
- * - setting promiscuous on loopback gives every packet twice
+ * 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.
*/
#endif
#include "pcap-int.h"
+#include "sll.h"
+#ifdef HAVE_DAG_API
+#include "pcap-dag.h"
+#endif /* HAVE_DAG_API */
+
#include <errno.h>
#include <stdlib.h>
#include <unistd.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 <netinet/if_ether.h>
+#include <net/if_arp.h>
+
+/*
+ * 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
+# endif /* PACKET_HOST */
+#endif /* PF_PACKET */
-#ifdef HAVE_NETPACKET_PACKET_H
-#include <netpacket/packet.h>
-#endif
#ifdef SO_ATTACH_FILTER
#include <linux/types.h>
#include <linux/filter.h>
#endif
#ifndef MSG_TRUNC
-#define MSG_TRUNC 0
+/*
+ * 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.
+/*
+ * 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.
*/
/*
* 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 void map_arphrd_to_dlt(pcap_t *, int, int);
+static int live_open_old(pcap_t *, const char *, int, int, char *);
+static int live_open_new(pcap_t *, const char *, int, int, char *);
+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 void pcap_close_linux(pcap_t *);
/*
* 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);
+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
+
/*
- * Get a handle for a live capture from the given device. You can
- * pass NULL as device to get all packages (without link level
+ * 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
+ * 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)
+pcap_open_live(const char *device, int snaplen, int promisc, int to_ms,
+ char *ebuf)
{
+ pcap_t *handle;
+ int mtu;
+ int err;
+ int live_open_ok = 0;
+ struct utsname utsname;
+
+#ifdef HAVE_DAG_API
+ if (strstr(device, "dag")) {
+ return dag_open_live(device, snaplen, promisc, to_ms, ebuf);
+ }
+#endif /* HAVE_DAG_API */
+
/* Allocate a handle for this session. */
-
- pcap_t *handle = malloc(sizeof(*handle));
+
+ handle = malloc(sizeof(*handle));
if (handle == NULL) {
snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc: %s",
pcap_strerror(errno));
memset(handle, 0, sizeof(*handle));
handle->snapshot = snaplen;
handle->md.timeout = to_ms;
- handle->md.promisc = promisc;
/*
- * NULL and "any" are special devices which give us the hint to
+ * 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");
+ if (promisc) {
+ promisc = 0;
+ /* Just a warning. */
+ snprintf(ebuf, PCAP_ERRBUF_SIZE,
+ "Promiscuous mode not supported on the \"any\" device");
+ }
+
} else
handle->md.device = strdup(device);
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
+ /*
+ * 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
+ * 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)) )
- {
- /*
+
+ if ((err = live_open_new(handle, device, promisc, to_ms, ebuf)) == 1)
+ live_open_ok = 1;
+ else if (err == 0) {
+ /* Non-fatal error; try old way */
+ if (live_open_old(handle, device, promisc, to_ms, ebuf))
+ live_open_ok = 1;
+ }
+ if (!live_open_ok) {
+ /*
* Both methods to open the packet socket failed. Tidy
* up and report our failure (ebuf is expected to be
- * set by the functions above).
+ * set by the functions above).
*/
- free(handle->md.device);
+ if (handle->md.device != NULL)
+ free(handle->md.device);
free(handle);
return NULL;
}
-
- /*
- * Okay, now we have a packet stream open. Maybe we need to handle
- * a timeout? In that case we set the filehandle to nonblocking
- * so pcap_read can try reading the fd and call select if no data
- * is available at first.
- */
- if (to_ms > 0) {
- int flags = fcntl(handle->fd, F_GETFL);
- if (flags != -1) {
- flags |= O_NONBLOCK;
- flags = fcntl(handle->fd, F_SETFL, flags);
- }
- if (flags == -1) {
- snprintf(ebuf, PCAP_ERRBUF_SIZE, "fcntl: %s",
- pcap_strerror(errno));
- pcap_close(handle);
+ /*
+ * Compute the buffer size.
+ *
+ * If we're using SOCK_PACKET, this might be a 2.0[.x] kernel,
+ * and might require special handling - check.
+ */
+ if (handle->md.sock_packet && (uname(&utsname) < 0 ||
+ strncmp(utsname.release, "2.0", 3) == 0)) {
+ /*
+ * We're using a SOCK_PACKET structure, and 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.
+ *
+ * The buffer therefore needs to be big enough to
+ * hold the largest packet we can get from this
+ * device. Unfortunately, we can't get the MRU
+ * of the network; we can only get the MTU. The
+ * MTU may be too small, in which case a packet larger
+ * than the buffer size will be truncated *and* we
+ * won't get the actual packet size.
+ *
+ * However, if the snapshot length is larger than
+ * the buffer size based on the MTU, we use the
+ * snapshot length as the buffer size, instead;
+ * this means that with a sufficiently large snapshot
+ * length we won't artificially truncate packets
+ * to the MTU-based size.
+ *
+ * This mess 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.
+ */
+ mtu = iface_get_mtu(handle->fd, device, ebuf);
+ if (mtu == -1) {
+ pcap_close_linux(handle);
+ free(handle);
return NULL;
}
+ handle->bufsize = MAX_LINKHEADER_SIZE + mtu;
+ if (handle->bufsize < handle->snapshot)
+ handle->bufsize = handle->snapshot;
+ } else {
+ /*
+ * This is a 2.2[.x] or later kernel (we know that
+ * either because we're not using a SOCK_PACKET
+ * socket - PF_PACKET is supported only in 2.2
+ * and later kernels - or because we checked the
+ * kernel version).
+ *
+ * We can safely pass "recvfrom()" a byte count
+ * based on the snapshot length.
+ */
+ handle->bufsize = handle->snapshot;
}
+ /* Allocate the buffer */
+
+ handle->buffer = malloc(handle->bufsize + handle->offset);
+ if (!handle->buffer) {
+ snprintf(ebuf, PCAP_ERRBUF_SIZE,
+ "malloc: %s", pcap_strerror(errno));
+ pcap_close_linux(handle);
+ free(handle);
+ return NULL;
+ }
+
+ /*
+ * "handle->fd" is a socket, so "select()" and "poll()"
+ * should work on it.
+ */
+ handle->selectable_fd = handle->fd;
+
+ handle->read_op = pcap_read_linux;
+ handle->inject_op = pcap_inject_linux;
+ handle->setfilter_op = pcap_setfilter_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->stats_op = pcap_stats_linux;
+ handle->close_op = pcap_close_linux;
+
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.
- *
- * XXX: Can I rely on the Linux-specified behaviour of select (returning
- * the time left in the timeval structure)? I really don't want to query
- * the system time before each select call...
- *
- * pcap_read currently gets not only a packet from the kernel but also
- * the sockaddr_ll returned as source of the packet. This way we can at
- * some time extend tcpdump and libpcap to sniff on all devices at a time
- * and find the right printing routine by using the information in the
- * sockaddr_ll structure.
+ * error occured.
*/
-int
-pcap_read(pcap_t *handle, int max_packets, pcap_handler callback, u_char *user)
+static int
+pcap_read_linux(pcap_t *handle, int max_packets, pcap_handler callback, u_char *user)
{
- int status, packets;
- fd_set read_fds;
- struct timeval tv;
-
/*
- * Fill in a timeval structure for select if we need to obeye a
- * timeout.
+ * Currently, on Linux only one packet is delivered per read,
+ * so we don't loop.
*/
- if (handle->md.timeout > 0) {
- tv.tv_usec = (handle->md.timeout % 1000) * 1000;
- tv.tv_sec = (handle->md.timeout / 1000);
- }
-
- /*
- * Read packets until the packet limit has been reached or
- * an error occured while reading. Call the user function
- * for each received packet.
- */
- for (packets = 0; max_packets == -1 || packets < max_packets;)
- {
- status = pcap_read_packet(handle, callback, user);
-
- if (status > 0) {
- packets += status;
- continue;
- } else if (status == -1)
- return -1;
-
- /*
- * If no packet is available we go to sleep. FIXME: This
- * might be better implemented using poll(?)
- */
- FD_ZERO(&read_fds);
- FD_SET(handle->fd, &read_fds);
- status = select(handle->fd + 1,
- &read_fds, NULL, NULL, &tv);
- if (status == -1) {
- snprintf(handle->errbuf, sizeof(handle->errbuf),
- "select: %s", pcap_strerror(errno));
- return -1;
- } else if (status == 0 ||
- (tv.tv_usec == 0 && tv.tv_sec == 0))
- return packets;
- }
-
- return packets;
+ return pcap_read_packet(handle, callback, user);
}
-
+
/*
- * Read a packet from the socket calling the handler provided by
+ * 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
socklen_t fromlen;
int packet_len, caplen;
struct pcap_pkthdr pcap_header;
+#ifdef HAVE_PF_PACKET_SOCKETS
/*
- * We don't currently use the from return value of recvfrom but
- * this will probably be implemented in the future.
+ * 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 */
+ bp = handle->buffer + handle->offset;
do {
+ /*
+ * Has "pcap_breakloop()" been called?
+ */
+ if (handle->break_loop) {
+ /*
+ * Yes - clear the flag that indicates that it
+ * has, and return -2 as an indication that we
+ * were told to break out of the loop.
+ */
+ handle->break_loop = 0;
+ return -2;
+ }
fromlen = sizeof(from);
- packet_len = recvfrom(
- handle->fd, handle->buffer + handle->offset,
- handle->snapshot, MSG_TRUNC,
+ packet_len = recvfrom(
+ handle->fd, bp + offset,
+ handle->bufsize - offset, MSG_TRUNC,
(struct sockaddr *) &from, &fromlen);
} while (packet_len == -1 && errno == EINTR);
}
}
+#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
/*
- * XXX: According to the kernel source we should get the real
- * packet len if calling recvfrom with MSG_TRUNC set. It does
+ * 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;
+
+ /*
+ * 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.
+ * 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:
+ * that the following is happening:
*
- * The packet comes from a random interface and the packet_rcv
+ * 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
* # tcpdump -d
* (000) ret #68
*
- * So the packet filter cuts down the packet. The recvfrom call
+ * 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.
+ * the result that we don't get the real packet length. This
+ * is valid at least until kernel 2.2.17pre6.
*
- * tcpdump is currently fixed by changing the BPF code generator
- * to not truncate the received packet.
+ * 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,
+ 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, sizeof(handle->errbuf),
"ioctl: %s", pcap_strerror(errno));
}
pcap_header.caplen = caplen;
pcap_header.len = packet_len;
-
- /* Call the user supplied callback function */
+
+ /*
+ * 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.
+ */
handle->md.stat.ps_recv++;
- callback(userdata, &pcap_header, handle->buffer + handle->offset);
+
+ /* 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.
- * FIXME: Currently does not report the number of dropped packets.
+ * 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.
*/
-int
-pcap_stats(pcap_t *handle, struct pcap_stat *stats)
+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
+
+#ifdef HAVE_TPACKET_STATS
+ /*
+ * Try to get the packet counts from the kernel.
+ */
+ if (getsockopt(handle->fd, SOL_PACKET, PACKET_STATISTICS,
+ &kstats, &len) > -1) {
+ /*
+ * 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;
+ }
+ 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 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.
+ *
+ * Both statistics include packets not yet read from the
+ * kernel by libpcap, and thus not yet seen by the application.
+ *
+ * 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_recv" doesn't include packets not yet read from
+ * the kernel by libpcap.
+ */
*stats = handle->md.stat;
return 0;
}
/*
- * Attach the given BPF code to the packet capture device.
+ * Description string for the "any" device.
*/
+static const char any_descr[] = "Pseudo-device that captures on all interfaces";
+
int
-pcap_setfilter(pcap_t *handle, struct bpf_program *filter)
+pcap_platform_finddevs(pcap_if_t **alldevsp, char *errbuf)
+{
+ if (pcap_add_if(alldevsp, "any", 0, any_descr, errbuf) < 0)
+ return (-1);
+
+#ifdef HAVE_DAG_API
+ if (dag_platform_finddevs(alldevsp, errbuf) < 0)
+ return (-1);
+#endif /* HAVE_DAG_API */
+
+ return (0);
+}
+
+/*
+ * Attach the given BPF code to the packet capture device.
+ */
+static int
+pcap_setfilter_linux(pcap_t *handle, struct bpf_program *filter)
{
#ifdef SO_ATTACH_FILTER
struct sock_fprog fcode;
+ int can_filter_in_kernel;
+ int err = 0;
#endif
if (!handle)
return -1;
}
- /* Free old filter code if existing */
-
- handle->fcode.bf_len = 0;
- if (handle->fcode.bf_insns) {
- free(handle->fcode.bf_insns);
- handle->fcode.bf_insns = NULL;
- }
-
-
/* Make our private copy of the filter */
- handle->fcode.bf_len = filter->bf_len;
- handle->fcode.bf_insns =
- malloc(filter->bf_len * sizeof(*filter->bf_insns));
- if (handle->fcode.bf_insns == NULL) {
- snprintf(handle->errbuf, sizeof(handle->errbuf),
- "malloc: %s", pcap_strerror(errno));
+ if (install_bpf_program(handle, filter) < 0)
+ /* install_bpf_program() filled in errbuf */
return -1;
- }
- memcpy(handle->fcode.bf_insns, filter->bf_insns,
- filter->bf_len * sizeof(*filter->bf_insns));
- /*
- * Run user level packet filter by default. Will be overriden if
- * installing a kernel filter succeeds.
+ /*
+ * 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
- /*
- * 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
- */
- fcode.filter = (struct sock_filter *) handle->fcode.bf_insns;
- fcode.len = filter->bf_len;
+#ifdef SO_ATTACH_FILTER
#ifdef USHRT_MAX
- if (filter->bf_len > 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.
+ * 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 to complex for kernel\n");
- }
- else
-#endif
- if (setsockopt(handle->fd, SOL_SOCKET, SO_ATTACH_FILTER,
- &fcode, sizeof(fcode)) == 0)
- {
- /* Installation succeded - using kernel filter. */
- handle->md.use_bpf = 1;
- }
- else
+ fprintf(stderr, "Warning: Filter too complex for kernel\n");
+ fcode.filter = NULL;
+ can_filter_in_kernel = 0;
+ } else
+#endif /* USHRT_MAX */
{
- /*
- * Print a warning if kernel filter available but a problem
- * occured using it.
+ /*
+ * 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.
*/
- if (errno != ENOPROTOOPT && errno != EOPNOTSUPP) {
- fprintf(stderr, "Warning: Kernel filter failed: %s\n",
- pcap_strerror(errno));
+ 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;
}
}
-#endif
+
+ 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;
}
/*
- * 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.
+ * 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 int map_arphrd_to_dlt(int arptype)
+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 "live_open_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: 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;
- case ARPHRD_IEEE802: return DLT_IEEE802;
- case ARPHRD_ARCNET: return DLT_ARCNET;
- case ARPHRD_FDDI: return DLT_FDDI;
+ 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;
+ break;
+
+ case ARPHRD_PRONET:
+ handle->linktype = DLT_PRONET;
+ break;
+
+ case ARPHRD_CHAOS:
+ handle->linktype = DLT_CHAOS;
+ 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: return DLT_ATM_CLIP;
+ 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;
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_SLIP: return DLT_RAW;
- }
+ 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;
- return -1;
+#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;
+
+ default:
+ handle->linktype = -1;
+ break;
+ }
}
/* ===== Functions to interface to the newer kernels ================== */
* FIXME: 0 uses to mean success (Sebastian)
*/
static int
-live_open_new(pcap_t *handle, char *device, int promisc,
+live_open_new(pcap_t *handle, const char *device, int promisc,
int to_ms, char *ebuf)
{
-#ifdef HAVE_NETPACKET_PACKET_H
- int sock_fd = -1, device_id, mtu, arptype;
+#ifdef HAVE_PF_PACKET_SOCKETS
+ int sock_fd = -1, arptype;
+ int err;
+ int fatal_err = 0;
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.
+ * given we try to open it in raw mode otherwise we use
+ * the cooked interface.
*/
- sock_fd = device ?
+ sock_fd = device ?
socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL))
: socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_ALL));
handle->md.sock_packet = 0;
/*
- * What kind of frames do we have to deal with? Fall back
- * to cooked mode if we have an unknown interface type.
+ * 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);
+
+ /*
+ * 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.
*/
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);
- } else
- handle->linktype = PCAP_ENCAP_RAW;
-
- if (handle->linktype == -1) {
- /* Unknown interface type - reopen in cooked mode */
-
- if (close(sock_fd) == -1) {
- snprintf(ebuf, PCAP_ERRBUF_SIZE,
- "close: %s", pcap_strerror(errno));
+ if (arptype == -1) {
+ fatal_err = 1;
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;
- }
-
- fprintf(stderr,
- "Warning: Falling back to cooked socket\n");
- handle->linktype = DLT_RAW;
- }
+ map_arphrd_to_dlt(handle, arptype, 1);
+ if (handle->linktype == -1 ||
+ handle->linktype == DLT_LINUX_SLL ||
+ handle->linktype == DLT_LINUX_IRDA ||
+ (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(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;
+
+ /*
+ * 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(ebuf, 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. */
+ if (handle->linktype != DLT_LINUX_IRDA)
+ handle->linktype = DLT_LINUX_SLL;
+ }
- if (device) {
- device_id = iface_get_id(sock_fd, device, ebuf);
- if (device_id == -1)
+ handle->md.ifindex = iface_get_id(sock_fd, device, ebuf);
+ if (handle->md.ifindex == -1)
break;
- if (iface_bind(sock_fd, device_id, ebuf) == -1)
+ if ((err = iface_bind(sock_fd, handle->md.ifindex,
+ ebuf)) < 0) {
+ if (err == -2)
+ fatal_err = 1;
break;
+ }
+ } else {
+ /*
+ * This is cooked mode.
+ */
+ handle->md.cooked = 1;
+ handle->linktype = DLT_LINUX_SLL;
+
+ /*
+ * We're not bound to a device.
+ * XXX - true? Or true only if we're using
+ * the "any" 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 promiscous mode on/off */
+ /*
+ * 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.
+ */
-#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) {
+ if (device && promisc) {
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,
+ 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(ebuf, PCAP_ERRBUF_SIZE,
+ snprintf(ebuf, PCAP_ERRBUF_SIZE,
"setsockopt: %s", pcap_strerror(errno));
break;
}
}
-#endif
-
- /* 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 */
+ /* Save the socket FD 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;
- }
return 1;
if (sock_fd != -1)
close(sock_fd);
- return 0;
+
+ if (fatal_err) {
+ /*
+ * Get rid of any link-layer type list we allocated.
+ */
+ if (handle->dlt_list != NULL)
+ free(handle->dlt_list);
+ return -2;
+ } else
+ return 0;
#else
- strncpy(ebuf,
- "New packet capturing interface not supported by build "
+ strncpy(ebuf,
+ "New packet capturing interface not supported by build "
"environment", PCAP_ERRBUF_SIZE);
return 0;
#endif
}
-#ifdef HAVE_NETPACKET_PACKET_H
+#ifdef HAVE_PF_PACKET_SOCKETS
/*
- * Return the index of the given device name. Fill ebuf and return
+ * Return the index of the given device name. Fill ebuf and return
* -1 on failure.
*/
static int
}
/*
- * Bind the socket associated with FD to the given device.
+ * Bind the socket associated with FD to the given device.
*/
static int
iface_bind(int fd, int ifindex, char *ebuf)
{
struct sockaddr_ll sll;
+ int err;
+ socklen_t errlen = sizeof(err);
memset(&sll, 0, sizeof(sll));
sll.sll_family = AF_PACKET;
return -1;
}
+ /* Any pending errors, e.g., network is down? */
+
+ if (getsockopt(fd, SOL_SOCKET, SO_ERROR, &err, &errlen) == -1) {
+ snprintf(ebuf, PCAP_ERRBUF_SIZE,
+ "getsockopt: %s", pcap_strerror(errno));
+ return -2;
+ }
+
+ if (err > 0) {
+ snprintf(ebuf, PCAP_ERRBUF_SIZE,
+ "bind: %s", pcap_strerror(err));
+ return -2;
+ }
+
return 0;
}
/*
* 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.
- * We save the promiscuous state of the device when opening the capture
- * stream and arrange for it to be reset on process exit.
- *
- * XXX: This solution is still not correct even for this case. The
- * devices stay in promiscuous mode until the process exits. I need to
- * modify pcap_close to solve this.
+ * 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.
*/
-/*
- * The device name and the interface flags to be restored at exit
+/*
+ * 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.
*/
-struct ifreq restore_ifr;
+static int did_atexit;
-static void restore_interface( void )
+static void pcap_close_all(void)
{
- int status = socket(PF_INET, SOCK_PACKET, 0);
+ struct pcap *handle;
- if (status != -1)
- status = ioctl(status, SIOCSIFFLAGS, &restore_ifr);
+ while ((handle = pcaps_to_close) != NULL)
+ pcap_close(handle);
+}
+
+static 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));
+ 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));
+ }
+ }
+ }
- if (status == -1) {
- fprintf(stderr,
- "Can't restore interface flags. Please adjust manually. \n"
- "Hint: This can't happen with Linux >= 2.2.0.\n");
+ /*
+ * 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);
+ handle->md.device = NULL;
+ pcap_close_common(handle);
}
/*
* FIXME: 0 uses to mean success (Sebastian)
*/
static int
-live_open_old(pcap_t *handle, char *device, int promisc,
+live_open_old(pcap_t *handle, const char *device, int promisc,
int to_ms, char *ebuf)
{
- int sock_fd = -1, mtu, arptype;
+ int arptype;
struct ifreq ifr;
do {
/* Open the socket */
-
- sock_fd = socket(PF_INET, SOCK_PACKET, htons(ETH_P_ALL));
- if (sock_fd == -1) {
+
+ handle->fd = socket(PF_INET, SOCK_PACKET, htons(ETH_P_ALL));
+ if (handle->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: No interface given",
+ 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)
+ if (iface_bind_old(handle->fd, device, ebuf) == -1)
break;
- /* Go to promisc mode */
+ /*
+ * Try to get the link-layer type.
+ */
+ arptype = iface_get_arptype(handle->fd, device, ebuf);
+ if (arptype == -1)
+ break;
+
+ /*
+ * Try to find the DLT_ type corresponding to that
+ * link-layer type.
+ */
+ map_arphrd_to_dlt(handle, arptype, 0);
+ if (handle->linktype == -1) {
+ snprintf(ebuf, PCAP_ERRBUF_SIZE,
+ "unknown arptype %d", arptype);
+ break;
+ }
+
+ /* Go to promisc mode if requested */
+
if (promisc) {
memset(&ifr, 0, sizeof(ifr));
strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
- if (ioctl(sock_fd, SIOCGIFFLAGS, &ifr) == -1) {
+ if (ioctl(handle->fd, SIOCGIFFLAGS, &ifr) == -1) {
snprintf(ebuf, PCAP_ERRBUF_SIZE,
"ioctl: %s", pcap_strerror(errno));
break;
}
if ((ifr.ifr_flags & IFF_PROMISC) == 0) {
- restore_ifr = ifr;
+ /*
+ * 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;
+ }
+ did_atexit = 1;
+ }
+
ifr.ifr_flags |= IFF_PROMISC;
- if (ioctl(sock_fd, SIOCSIFFLAGS, &ifr) == -1) {
+ if (ioctl(handle->fd, SIOCSIFFLAGS, &ifr) == -1) {
snprintf(ebuf, PCAP_ERRBUF_SIZE,
"ioctl: %s",
pcap_strerror(errno));
break;
}
- if (atexit(restore_interface) == -1) {
- restore_interface();
- strncpy(ebuf, "atexit failed",
- PCAP_ERRBUF_SIZE);
- 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;
-
- /* All done - fill in the pcap handle */
-
- arptype = iface_get_arptype(sock_fd, device, ebuf);
- if (arptype == -1)
- break;
-
- handle->fd = sock_fd;
+ /*
+ * Default value for offset to align link-layer payload
+ * on a 4-byte boundary.
+ */
handle->offset = 0;
- handle->linktype = map_arphrd_to_dlt(arptype);
- 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;
- }
return 1;
-
+
} while (0);
-
- if (sock_fd != -1)
- close(sock_fd);
+
+ pcap_close_linux(handle);
return 0;
}
/*
- * Bind the socket associated with FD to the given device using the
+ * 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;
+ int err;
+ socklen_t errlen = sizeof(err);
memset(&saddr, 0, sizeof(saddr));
strncpy(saddr.sa_data, device, sizeof(saddr.sa_data));
return -1;
}
+ /* Any pending errors, e.g., network is down? */
+
+ if (getsockopt(fd, SOL_SOCKET, SO_ERROR, &err, &errlen) == -1) {
+ snprintf(ebuf, PCAP_ERRBUF_SIZE,
+ "getsockopt: %s", pcap_strerror(errno));
+ return -1;
+ }
+
+ if (err > 0) {
+ snprintf(ebuf, PCAP_ERRBUF_SIZE,
+ "bind: %s", pcap_strerror(err));
+ return -1;
+ }
+
return 0;
}
/* ===== System calls available on all supported kernels ============== */
/*
- * Query the kernel for the MTU of the given interface.
+ * Query the kernel for the MTU of the given interface.
*/
static int
iface_get_mtu(int fd, const char *device, char *ebuf)
return ifr.ifr_hwaddr.sa_family;
}
+
+#ifdef SO_ATTACH_FILTER
+static int
+fix_program(pcap_t *handle, struct sock_fprog *fcode)
+{
+ 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)) {
+
+ 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;
+}
+
+static int
+set_kernel_filter(pcap_t *handle, struct sock_fprog *fcode)
+{
+ int total_filter_on = 0;
+ int save_mode;
+ int ret;
+ int save_errno;
+
+ /*
+ * The socket filter code doesn't discard all packets queued
+ * up on the socket when the filter is changed; this means
+ * that packets that don't match the new filter may show up
+ * after the new filter is put onto the socket, if those
+ * packets haven't yet been read.
+ *
+ * This means, for example, that if you do a tcpdump capture
+ * with a filter, the first few packets in the capture might
+ * be packets that wouldn't have passed the filter.
+ *
+ * We therefore discard all packets queued up on the socket
+ * when setting a kernel filter. (This isn't an issue for
+ * userland filters, as the userland filtering is done after
+ * packets are queued up.)
+ *
+ * To flush those packets, we put the socket in read-only mode,
+ * and read packets from the socket until there are no more to
+ * read.
+ *
+ * In order to keep that from being an infinite loop - i.e.,
+ * to keep more packets from arriving while we're draining
+ * the queue - we put the "total filter", which is a filter
+ * that rejects all packets, onto the socket before draining
+ * the queue.
+ *
+ * This code deliberately ignores any errors, so that you may
+ * get bogus packets if an error occurs, rather than having
+ * the filtering done in userland even if it could have been
+ * done in the kernel.
+ */
+ if (setsockopt(handle->fd, SOL_SOCKET, SO_ATTACH_FILTER,
+ &total_fcode, sizeof(total_fcode)) == 0) {
+ char drain[1];
+
+ /*
+ * Note that we've put the total filter onto the socket.
+ */
+ total_filter_on = 1;
+
+ /*
+ * Save the socket's current mode, and put it in
+ * non-blocking mode; we drain it by reading packets
+ * until we get an error (which is normally a
+ * "nothing more to be read" error).
+ */
+ save_mode = fcntl(handle->fd, F_GETFL, 0);
+ if (save_mode != -1 &&
+ fcntl(handle->fd, F_SETFL, save_mode | O_NONBLOCK) >= 0) {
+ while (recv(handle->fd, &drain, sizeof drain,
+ MSG_TRUNC) >= 0)
+ ;
+ save_errno = errno;
+ fcntl(handle->fd, F_SETFL, save_mode);
+ if (save_errno != EAGAIN) {
+ /* Fatal error */
+ reset_kernel_filter(handle);
+ snprintf(handle->errbuf, sizeof(handle->errbuf),
+ "recv: %s", pcap_strerror(save_errno));
+ return -2;
+ }
+ }
+ }
+
+ /*
+ * Now attach the new filter.
+ */
+ ret = setsockopt(handle->fd, SOL_SOCKET, SO_ATTACH_FILTER,
+ fcode, sizeof(*fcode));
+ if (ret == -1 && total_filter_on) {
+ /*
+ * Well, we couldn't set that filter on the socket,
+ * but we could set the total filter on the socket.
+ *
+ * This could, for example, mean that the filter was
+ * too big to put into the kernel, so we'll have to
+ * filter in userland; in any case, we'll be doing
+ * filtering in userland, so we need to remove the
+ * total filter so we see packets.
+ */
+ save_errno = errno;
+
+ /*
+ * XXX - if this fails, we're really screwed;
+ * we have the total filter on the socket,
+ * and it won't come off. What do we do then?
+ */
+ reset_kernel_filter(handle);
+
+ errno = save_errno;
+ }
+ return ret;
+}
+
+static int
+reset_kernel_filter(pcap_t *handle)
+{
+ /* setsockopt() barfs unless it get a dummy parameter */
+ int dummy;
+
+ return setsockopt(handle->fd, SOL_SOCKET, SO_DETACH_FILTER,
+ &dummy, sizeof(dummy));
+}
+#endif
projects / libpcap / blobdiff