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freebsd-dev/contrib/libpcap/pcap-linux.c

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/*
* pcap-linux.c: Packet capture interface to the Linux kernel
*
* Copyright (c) 2000 Torsten Landschoff <torsten@debian.org>
* Sebastian Krahmer <krahmer@cs.uni-potsdam.de>
*
* License: BSD
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. The names of the authors may not be used to endorse or promote
* products derived from this software without specific prior
* written permission.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/
#ifndef lint
static const char rcsid[] =
"@(#) $Header: /tcpdump/master/libpcap/pcap-linux.c,v 1.51.2.3 2001/01/18 03:59:56 guy Exp $ (LBL)";
#endif
/*
* Known problems with 2.0[.x] kernels:
*
* - The loopback device gives every packet twice; on 2.2[.x] kernels,
* if we use PF_PACKET, we can filter out the transmitted version
* of the packet by using data in the "sockaddr_ll" returned by
* "recvfrom()", but, on 2.0[.x] kernels, we have to use
* PF_INET/SOCK_PACKET, which means "recvfrom()" supplies a
* "sockaddr_pkt" which doesn't give us enough information to let
* us do that.
*
* - We have to set the interface's IFF_PROMISC flag ourselves, if
* we're to run in promiscuous mode, which means we have to turn
* it off ourselves when we're done; the kernel doesn't keep track
* of how many sockets are listening promiscuously, which means
* it won't get turned off automatically when no sockets are
* listening promiscuously. We catch "pcap_close()" and, for
* interfaces we put into promiscuous mode, take them out of
* promiscuous mode - which isn't necessarily the right thing to
* do, if another socket also requested promiscuous mode between
* the time when we opened the socket and the time when we close
* the socket.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "pcap-int.h"
#include "sll.h"
#include <errno.h>
#include <stdlib.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>
#ifdef HAVE_NETPACKET_PACKET_H
# include <netpacket/packet.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>
/*
* 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
#ifndef __GLIBC__
typedef int socklen_t;
#endif
#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).
*/
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 *handle, int max_packets, pcap_handler callback, u_char *user)
{
/*
* Currently, on Linux only one packet is delivered per read,
* so we don't loop.
*/
return pcap_read_packet(handle, callback, user);
}
/*
* Read a packet from the socket calling the handler provided by
* the user. Returns the number of packets received or -1 if an
* error occured.
*/
static int
pcap_read_packet(pcap_t *handle, pcap_handler callback, u_char *userdata)
{
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 */
do {
fromlen = sizeof(from);
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);
/* Check if an error occured */
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;
}
}
#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;
}
}
/* 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;
}
/*
* 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)
{
*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;
}
/* 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;
}
/*
* 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;
}
}
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));
}
}
}
/*
* 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:
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_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
/* 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
}
#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;
memset(&ifr, 0, sizeof(ifr));
strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
if (ioctl(fd, SIOCGIFINDEX, &ifr) == -1) {
snprintf(ebuf, PCAP_ERRBUF_SIZE,
"ioctl: %s", pcap_strerror(errno));
return -1;
}
return ifr.ifr_ifindex;
}
/*
* 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;
}
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));
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;
}
/*
* 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;
}
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;
}
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;
}
return ifr.ifr_mtu;
}
/*
* 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;
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;
}
#ifdef HAVE_PF_PACKET_SOCKETS
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;
}
#endif
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