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pcap-linux.c
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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.
*
* Modifications: Added PACKET_MMAP support
* Paolo Abeni <paolo.abeni@email.it>
*
* based on previous works of:
* Simon Patarin <patarin@cs.unibo.it>
* Phil Wood <cpw@lanl.gov>
*/
#ifndef lint
static const char rcsid[] _U_ =
"@(#) $Header: /tcpdump/master/libpcap/pcap-linux.c,v 1.163 2008-12-14 20:30:11 guy Exp $ (LBL)";
#endif
/*
* Known problems with 2.0[.x] kernels:
*
* - The loopback device gives every packet twice; on 2.2[.x] kernels,
* if we use PF_PACKET, we can filter out the transmitted version
* of the packet by using data in the "sockaddr_ll" returned by
* "recvfrom()", but, on 2.0[.x] kernels, we have to use
* PF_INET/SOCK_PACKET, which means "recvfrom()" supplies a
* "sockaddr_pkt" which doesn't give us enough information to let
* us do that.
*
* - We have to set the interface's IFF_PROMISC flag ourselves, if
* we're to run in promiscuous mode, which means we have to turn
* it off ourselves when we're done; the kernel doesn't keep track
* of how many sockets are listening promiscuously, which means
* it won't get turned off automatically when no sockets are
* listening promiscuously. We catch "pcap_close()" and, for
* interfaces we put into promiscuous mode, take them out of
* promiscuous mode - which isn't necessarily the right thing to
* do, if another socket also requested promiscuous mode between
* the time when we opened the socket and the time when we close
* the socket.
*
* - MSG_TRUNC isn't supported, so you can't specify that "recvfrom()"
* return the amount of data that you could have read, rather than
* the amount that was returned, so we can't just allocate a buffer
* whose size is the snapshot length and pass the snapshot length
* as the byte count, and also pass MSG_TRUNC, so that the return
* value tells us how long the packet was on the wire.
*
* This means that, if we want to get the actual size of the packet,
* so we can return it in the "len" field of the packet header,
* we have to read the entire packet, not just the part that fits
* within the snapshot length, and thus waste CPU time copying data
* from the kernel that our caller won't see.
*
* We have to get the actual size, and supply it in "len", because
* otherwise, the IP dissector in tcpdump, for example, will complain
* about "truncated-ip", as the packet will appear to have been
* shorter, on the wire, than the IP header said it should have been.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#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 <sys/mman.h>
/*
* Got Wireless Extensions?
*/
#ifdef HAVE_LINUX_WIRELESS_H
#include <linux/wireless.h>
#else
#include <net/if.h>
#endif
#include <netinet/in.h>
#include <linux/if_ether.h>
#include <net/if_arp.h>
#include <poll.h>
#include "pcap-int.h"
#include "pcap/sll.h"
#include "pcap/vlan.h"
#ifdef HAVE_DAG_API
#include "pcap-dag.h"
#endif /* HAVE_DAG_API */
#ifdef HAVE_SEPTEL_API
#include "pcap-septel.h"
#endif /* HAVE_SEPTEL_API */
#ifdef PCAP_SUPPORT_USB
#include "pcap-usb-linux.h"
#endif
#ifdef PCAP_SUPPORT_BT
#include "pcap-bt-linux.h"
#endif
/*
* If PF_PACKET is defined, we can use {SOCK_RAW,SOCK_DGRAM}/PF_PACKET
* sockets rather than SOCK_PACKET sockets.
*
* To use them, we include <linux/if_packet.h> rather than
* <netpacket/packet.h>; we do so because
*
* some Linux distributions (e.g., Slackware 4.0) have 2.2 or
* later kernels and libc5, and don't provide a <netpacket/packet.h>
* file;
*
* not all versions of glibc2 have a <netpacket/packet.h> file
* that defines stuff needed for some of the 2.4-or-later-kernel
* features, so if the system has a 2.4 or later kernel, we
* still can't use those features.
*
* We're already including a number of other <linux/XXX.h> headers, and
* this code is Linux-specific (no other OS has PF_PACKET sockets as
* a raw packet capture mechanism), so it's not as if you gain any
* useful portability by using <netpacket/packet.h>
*
* XXX - should we just include <linux/if_packet.h> even if PF_PACKET
* isn't defined? It only defines one data structure in 2.0.x, so
* it shouldn't cause any problems.
*/
#ifdef PF_PACKET
# include <linux/if_packet.h>
/*
* On at least some Linux distributions (for example, Red Hat 5.2),
* there's no <netpacket/packet.h> file, but PF_PACKET is defined if
* you include <sys/socket.h>, but <linux/if_packet.h> doesn't define
* any of the PF_PACKET stuff such as "struct sockaddr_ll" or any of
* the PACKET_xxx stuff.
*
* So we check whether PACKET_HOST is defined, and assume that we have
* PF_PACKET sockets only if it is defined.
*/
# ifdef PACKET_HOST
# define HAVE_PF_PACKET_SOCKETS
# ifdef PACKET_AUXDATA
# define HAVE_PACKET_AUXDATA
# endif /* PACKET_AUXDATA */
# endif /* PACKET_HOST */
/* check for memory mapped access avaibility. We assume every needed
* struct is defined if the macro TPACKET_HDRLEN is defined, because it
* uses many ring related structs and macros */
# ifdef TPACKET_HDRLEN
# define HAVE_PACKET_RING
# ifdef TPACKET2_HDRLEN
# define HAVE_TPACKET2
# else
# define TPACKET_V1 0
# endif /* TPACKET2_HDRLEN */
# endif /* TPACKET_HDRLEN */
#endif /* PF_PACKET */
#ifdef SO_ATTACH_FILTER
#include <linux/types.h>
#include <linux/filter.h>
#endif
#ifndef HAVE_SOCKLEN_T
typedef int socklen_t;
#endif
#ifndef MSG_TRUNC
/*
* This is being compiled on a system that lacks MSG_TRUNC; define it
* with the value it has in the 2.2 and later kernels, so that, on
* those kernels, when we pass it in the flags argument to "recvfrom()"
* we're passing the right value and thus get the MSG_TRUNC behavior
* we want. (We don't get that behavior on 2.0[.x] kernels, because
* they didn't support MSG_TRUNC.)
*/
#define MSG_TRUNC 0x20
#endif
#ifndef SOL_PACKET
/*
* This is being compiled on a system that lacks SOL_PACKET; define it
* with the value it has in the 2.2 and later kernels, so that we can
* set promiscuous mode in the good modern way rather than the old
* 2.0-kernel crappy way.
*/
#define SOL_PACKET 263
#endif
#define MAX_LINKHEADER_SIZE 256
/*
* When capturing on all interfaces we use this as the buffer size.
* Should be bigger then all MTUs that occur in real life.
* 64kB should be enough for now.
*/
#define BIGGER_THAN_ALL_MTUS (64*1024)
/*
* Prototypes for internal functions and methods.
*/
static void map_arphrd_to_dlt(pcap_t *, int, int);
#ifdef HAVE_PF_PACKET_SOCKETS
static short int map_packet_type_to_sll_type(short int);
#endif
static int pcap_activate_linux(pcap_t *);
static int activate_old(pcap_t *);
static int activate_new(pcap_t *);
static int activate_mmap(pcap_t *);
static int pcap_can_set_rfmon_linux(pcap_t *);
static int pcap_read_linux(pcap_t *, int, pcap_handler, u_char *);
static int pcap_read_packet(pcap_t *, pcap_handler, u_char *);
static int pcap_inject_linux(pcap_t *, const void *, size_t);
static int pcap_stats_linux(pcap_t *, struct pcap_stat *);
static int pcap_setfilter_linux(pcap_t *, struct bpf_program *);
static int pcap_setdirection_linux(pcap_t *, pcap_direction_t);
static void pcap_cleanup_linux(pcap_t *);
union thdr {
struct tpacket_hdr *h1;
struct tpacket2_hdr *h2;
void *raw;
};
#ifdef HAVE_PACKET_RING
#define RING_GET_FRAME(h) (((union thdr **)h->buffer)[h->offset])
static void destroy_ring(pcap_t *handle);
static int create_ring(pcap_t *handle);
static int prepare_tpacket_socket(pcap_t *handle);
static void pcap_cleanup_linux_mmap(pcap_t *);
static int pcap_read_linux_mmap(pcap_t *, int, pcap_handler , u_char *);
static int pcap_setfilter_linux_mmap(pcap_t *, struct bpf_program *);
static int pcap_setnonblock_mmap(pcap_t *p, int nonblock, char *errbuf);
static int pcap_getnonblock_mmap(pcap_t *p, char *errbuf);
#endif
/*
* 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);
#ifdef IW_MODE_MONITOR
static int has_wext(int sock_fd, const char *device, char *ebuf);
#endif /* IW_MODE_MONITOR */
static int enter_rfmon_mode_wext(pcap_t *handle, int sock_fd,
const char *device);
#endif /* HAVE_PF_PACKET_SOCKETS */
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
pcap_t *
pcap_create(const char *device, char *ebuf)
{
pcap_t *handle;
/*
* A null device name is equivalent to the "any" device.
*/
if (device == NULL)
device = "any";
#ifdef HAVE_DAG_API
if (strstr(device, "dag")) {
return dag_create(device, ebuf);
}
#endif /* HAVE_DAG_API */
#ifdef HAVE_SEPTEL_API
if (strstr(device, "septel")) {
return septel_create(device, ebuf);
}
#endif /* HAVE_SEPTEL_API */
#ifdef PCAP_SUPPORT_BT
if (strstr(device, "bluetooth")) {
return bt_create(device, ebuf);
}
#endif
#ifdef PCAP_SUPPORT_USB
if (strstr(device, "usb")) {
return usb_create(device, ebuf);
}
#endif
handle = pcap_create_common(device, ebuf);
if (handle == NULL)
return NULL;
handle->activate_op = pcap_activate_linux;
handle->can_set_rfmon_op = pcap_can_set_rfmon_linux;
return handle;
}
static int
pcap_can_set_rfmon_linux(pcap_t *p)
{
#ifdef IW_MODE_MONITOR
int sock_fd;
struct iwreq ireq;
#endif
if (strcmp(p->opt.source, "any") == 0) {
/*
* Monitor mode makes no sense on the "any" device.
*/
return 0;
}
#ifdef IW_MODE_MONITOR
/*
* Bleah. There doesn't appear to be an ioctl to use to ask
* whether a device supports monitor mode; we'll just do
* SIOCGIWMODE and, if it succeeds, assume the device supports
* monitor mode.
*
* Open a socket on which to attempt to get the mode.
* (We assume that if we have Wireless Extensions support
* we also have PF_PACKET support.)
*/
sock_fd = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
if (sock_fd == -1) {
(void)snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
"socket: %s", pcap_strerror(errno));
return PCAP_ERROR;
}
/*
* Attempt to get the current mode.
*/
strncpy(ireq.ifr_ifrn.ifrn_name, p->opt.source,
sizeof ireq.ifr_ifrn.ifrn_name);
ireq.ifr_ifrn.ifrn_name[sizeof ireq.ifr_ifrn.ifrn_name - 1] = 0;
if (ioctl(sock_fd, SIOCGIWMODE, &ireq) != -1) {
/*
* Well, we got the mode; assume we can set it.
*/
close(sock_fd);
return 1;
}
if (errno == ENODEV) {
/* The device doesn't even exist. */
close(sock_fd);
return PCAP_ERROR_NO_SUCH_DEVICE;
}
close(sock_fd);
#endif
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.
* If we put the interface into promiscuous mode, we set a flag indicating
* that we must take it out of that mode when the interface is closed,
* and, when closing the interface, if that flag is set we take it out
* of promiscuous mode.
*
* Even with newer kernels, we have the same issue with rfmon mode.
*/
static void pcap_cleanup_linux( pcap_t *handle )
{
struct ifreq ifr;
#ifdef IW_MODE_MONITOR
struct iwreq ireq;
#endif
if (handle->md.must_clear != 0) {
/*
* There's something we have to do when closing this
* pcap_t.
*/
if (handle->md.must_clear & MUST_CLEAR_PROMISC) {
/*
* We put the interface into promiscuous mode;
* take it out of promiscuous mode.
*
* XXX - if somebody else wants it in promiscuous
* mode, this code cannot know that, so it'll take
* it out of promiscuous mode. That's not fixable
* in 2.0[.x] kernels.
*/
memset(&ifr, 0, sizeof(ifr));
strncpy(ifr.ifr_name, handle->md.device,
sizeof(ifr.ifr_name));
if (ioctl(handle->fd, SIOCGIFFLAGS, &ifr) == -1) {
fprintf(stderr,
"Can't restore interface 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));
}
}
}
}
#ifdef IW_MODE_MONITOR
if (handle->md.must_clear & MUST_CLEAR_RFMON) {
/*
* We put the interface into rfmon mode;
* take it out of rfmon mode.
*
* XXX - if somebody else wants it in rfmon
* mode, this code cannot know that, so it'll take
* it out of rfmon mode.
*/
strncpy(ireq.ifr_ifrn.ifrn_name, handle->md.device,
sizeof ireq.ifr_ifrn.ifrn_name);
ireq.ifr_ifrn.ifrn_name[sizeof ireq.ifr_ifrn.ifrn_name - 1]
= 0;
ireq.u.mode = handle->md.oldmode;
if (ioctl(handle->fd, SIOCSIWMODE, &ireq) == -1) {
/*
* Scientist, you've failed.
*/
fprintf(stderr,
"Can't restore interface wireless mode (SIOCSIWMODE failed: %s).\n"
"Please adjust manually.\n",
strerror(errno));
}
}
#endif
/*
* Take this pcap out of the list of pcaps for which we
* have to take the interface out of some mode.
*/
pcap_remove_from_pcaps_to_close(handle);
}
if (handle->md.device != NULL) {
free(handle->md.device);
handle->md.device = NULL;
}
pcap_cleanup_live_common(handle);
}
/*
* Get a handle for a live capture from the given device. You can
* pass NULL as device to get all packages (without link level
* information of course). If you pass 1 as promisc the interface
* will be set to promiscous mode (XXX: I think this usage should
* be deprecated and functions be added to select that later allow
* modification of that values -- Torsten).
*/
static int
pcap_activate_linux(pcap_t *handle)
{
const char *device;
int status = 0;
device = handle->opt.source;
handle->inject_op = pcap_inject_linux;
handle->setfilter_op = pcap_setfilter_linux;
handle->setdirection_op = pcap_setdirection_linux;
handle->set_datalink_op = NULL; /* can't change data link type */
handle->getnonblock_op = pcap_getnonblock_fd;
handle->setnonblock_op = pcap_setnonblock_fd;
handle->cleanup_op = pcap_cleanup_linux;
handle->read_op = pcap_read_linux;
handle->stats_op = pcap_stats_linux;
/*
* The "any" device is a special device which causes us not
* to bind to a particular device and thus to look at all
* devices.
*/
if (strcmp(device, "any") == 0) {
if (handle->opt.promisc) {
handle->opt.promisc = 0;
/* Just a warning. */
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
"Promiscuous mode not supported on the \"any\" device");
status = PCAP_WARNING_PROMISC_NOTSUP;
}
}
handle->md.device = strdup(device);
if (handle->md.device == NULL) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "strdup: %s",
pcap_strerror(errno) );
return PCAP_ERROR;
}
/*
* 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 ((status = activate_new(handle)) == 1) {
/*
* Success.
* Try to use memory-mapped access.
*/
switch (activate_mmap(handle)) {
case 1:
/* we succeeded; nothing more to do */
return 0;
case 0:
/*
* Kernel doesn't support it - just continue
* with non-memory-mapped access.
*/
break;
case -1:
/*
* We failed to set up to use it, or kernel
* supports it, but we failed to enable it;
* return an error. handle->errbuf contains
* an error message.
*/
status = PCAP_ERROR;
goto fail;
}
}
else if (status == 0) {
/* Non-fatal error; try old way */
if ((status = activate_old(handle)) != 1) {
/*
* Both methods to open the packet socket failed.
* Tidy up and report our failure (handle->errbuf
* is expected to be set by the functions above).
*/
goto fail;
}
} else {
/*
* Fatal error with the new way; just fail.
* status has the error return; if it's PCAP_ERROR,
* handle->errbuf has been set appropriately.
*/
goto fail;
}
/*
* We set up the socket, but not with memory-mapped access.
*/
if (handle->opt.buffer_size != 0) {
/*
* Set the socket buffer size to the specified value.
*/
if (setsockopt(handle->fd, SOL_SOCKET, SO_RCVBUF,
&handle->opt.buffer_size,
sizeof(handle->opt.buffer_size)) == -1) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
"SO_RCVBUF: %s", pcap_strerror(errno));
status = PCAP_ERROR;
goto fail;
}
}
/* Allocate the buffer */
handle->buffer = malloc(handle->bufsize + handle->offset);
if (!handle->buffer) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
"malloc: %s", pcap_strerror(errno));
status = PCAP_ERROR;
goto fail;
}
/*
* "handle->fd" is a socket, so "select()" and "poll()"
* should work on it.
*/
handle->selectable_fd = handle->fd;
return status;
fail:
pcap_cleanup_linux(handle);
return status;
}
/*
* Read at most max_packets from the capture stream and call the callback
* for each of them. Returns the number of packets handled or -1 if an
* error occured.
*/
static int
pcap_read_linux(pcap_t *handle, int max_packets, pcap_handler callback, u_char *user)
{
/*
* Currently, on Linux only one packet is delivered per read,
* so we don't loop.
*/
return pcap_read_packet(handle, callback, user);
}
/*
* Read a packet from the socket calling the handler provided by
* the user. Returns the number of packets received or -1 if an
* error occured.
*/
static int
pcap_read_packet(pcap_t *handle, pcap_handler callback, u_char *userdata)
{
u_char *bp;
int offset;
#ifdef HAVE_PF_PACKET_SOCKETS
struct sockaddr_ll from;
struct sll_header *hdrp;
#else
struct sockaddr from;
#endif
#if defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI)
struct iovec iov;
struct msghdr msg;
struct cmsghdr *cmsg;
union {
struct cmsghdr cmsg;
char buf[CMSG_SPACE(sizeof(struct tpacket_auxdata))];
} cmsg_buf;
#else /* defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI) */
socklen_t fromlen;
#endif /* defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI) */
int packet_len, caplen;
struct pcap_pkthdr pcap_header;
#ifdef HAVE_PF_PACKET_SOCKETS
/*
* If this is a cooked device, leave extra room for a
* fake packet header.
*/
if (handle->md.cooked)
offset = SLL_HDR_LEN;
else
offset = 0;
#else
/*
* This system doesn't have PF_PACKET sockets, so it doesn't
* support cooked devices.
*/
offset = 0;
#endif
/*
* Receive a single packet from the kernel.
* We ignore EINTR, as that might just be due to a signal
* being delivered - if the signal should interrupt the
* loop, the signal handler should call pcap_breakloop()
* to set handle->break_loop (we ignore it on other
* platforms as well).
* We also ignore ENETDOWN, so that we can continue to
* capture traffic if the interface goes down and comes
* back up again; comments in the kernel indicate that
* we'll just block waiting for packets if we try to
* receive from a socket that delivered ENETDOWN, and,
* if we're using a memory-mapped buffer, we won't even
* get notified of "network down" events.
*/
bp = handle->buffer + handle->offset;
#if defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI)
msg.msg_name = &from;
msg.msg_namelen = sizeof(from);
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
msg.msg_control = &cmsg_buf;
msg.msg_controllen = sizeof(cmsg_buf);
msg.msg_flags = 0;
iov.iov_len = handle->bufsize - offset;
iov.iov_base = bp + offset;
#endif /* defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI) */
do {
/*
* Has "pcap_breakloop()" been called?
*/
if (handle->break_loop) {
/*
* Yes - clear the flag that indicates that it
* has, and return -2 as an indication that we
* were told to break out of the loop.
*/
handle->break_loop = 0;
return -2;
}
#if defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI)
packet_len = recvmsg(handle->fd, &msg, MSG_TRUNC);
#else /* defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI) */
fromlen = sizeof(from);
packet_len = recvfrom(
handle->fd, bp + offset,
handle->bufsize - offset, MSG_TRUNC,
(struct sockaddr *) &from, &fromlen);
#endif /* defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI) */
} while (packet_len == -1 && (errno == EINTR || errno == ENETDOWN));
/* Check if an error occured */
if (packet_len == -1) {
if (errno == EAGAIN)
return 0; /* no packet there */
else {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
"recvfrom: %s", pcap_strerror(errno));
return -1;
}
}
#ifdef HAVE_PF_PACKET_SOCKETS
if (!handle->md.sock_packet) {
/*
* Unfortunately, there is a window between socket() and
* bind() where the kernel may queue packets from any
* interface. If we're bound to a particular interface,
* discard packets not from that interface.
*
* (If socket filters are supported, we could do the
* same thing we do when changing the filter; however,
* that won't handle packet sockets without socket
* filter support, and it's a bit more complicated.
* It would save some instructions per packet, however.)
*/
if (handle->md.ifindex != -1 &&
from.sll_ifindex != handle->md.ifindex)
return 0;
/*
* Do checks based on packet direction.
* We can only do this if we're using PF_PACKET; the
* address returned for SOCK_PACKET is a "sockaddr_pkt"
* which lacks the relevant packet type information.
*/
if (from.sll_pkttype == PACKET_OUTGOING) {
/*
* Outgoing packet.
* If this is from the loopback device, reject it;
* we'll see the packet as an incoming packet as well,
* and we don't want to see it twice.
*/
if (from.sll_ifindex == handle->md.lo_ifindex)
return 0;
/*
* If the user only wants incoming packets, reject it.
*/
if (handle->direction == PCAP_D_IN)
return 0;
} else {
/*
* Incoming packet.
* If the user only wants outgoing packets, reject it.
*/
if (handle->direction == PCAP_D_OUT)
return 0;
}
}
#endif
#ifdef HAVE_PF_PACKET_SOCKETS
/*
* If this is a cooked device, fill in the fake packet header.
*/
if (handle->md.cooked) {
/*
* Add the length of the fake header to the length
* of packet data we read.
*/
packet_len += SLL_HDR_LEN;
hdrp = (struct sll_header *)bp;
hdrp->sll_pkttype = map_packet_type_to_sll_type(from.sll_pkttype);
hdrp->sll_hatype = htons(from.sll_hatype);
hdrp->sll_halen = htons(from.sll_halen);
memcpy(hdrp->sll_addr, from.sll_addr,
(from.sll_halen > SLL_ADDRLEN) ?
SLL_ADDRLEN :
from.sll_halen);
hdrp->sll_protocol = from.sll_protocol;
}
#if defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI)
for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
struct tpacket_auxdata *aux;
unsigned int len;
struct vlan_tag *tag;
if (cmsg->cmsg_len < CMSG_LEN(sizeof(struct tpacket_auxdata)) ||
cmsg->cmsg_level != SOL_PACKET ||
cmsg->cmsg_type != PACKET_AUXDATA)
continue;
aux = (struct tpacket_auxdata *)CMSG_DATA(cmsg);
if (aux->tp_vlan_tci == 0)
continue;
len = packet_len > iov.iov_len ? iov.iov_len : packet_len;
if (len < 2 * ETH_ALEN)
break;
bp -= VLAN_TAG_LEN;
memmove(bp, bp + VLAN_TAG_LEN, 2 * ETH_ALEN);
tag = (struct vlan_tag *)(bp + 2 * ETH_ALEN);
tag->vlan_tpid = htons(ETH_P_8021Q);
tag->vlan_tci = htons(aux->tp_vlan_tci);
packet_len += VLAN_TAG_LEN;
}
#endif /* defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI) */
#endif /* HAVE_PF_PACKET_SOCKETS */
/*
* XXX: According to the kernel source we should get the real
* packet len if calling recvfrom with MSG_TRUNC set. It does
* not seem to work here :(, but it is supported by this code
* anyway.
* To be honest the code RELIES on that feature so this is really
* broken with 2.2.x kernels.
* I spend a day to figure out what's going on and I found out
* that the following is happening:
*
* The packet comes from a random interface and the packet_rcv
* hook is called with a clone of the packet. That code inserts
* the packet into the receive queue of the packet socket.
* If a filter is attached to that socket that filter is run
* first - and there lies the problem. The default filter always
* cuts the packet at the snaplen:
*
* # tcpdump -d
* (000) ret #68
*
* So the packet filter cuts down the packet. The recvfrom call
* says "hey, it's only 68 bytes, it fits into the buffer" with
* the result that we don't get the real packet length. This
* is valid at least until kernel 2.2.17pre6.
*
* We currently handle this by making a copy of the filter
* program, fixing all "ret" instructions with non-zero
* operands to have an operand of 65535 so that the filter
* doesn't truncate the packet, and supplying that modified
* filter to the kernel.
*/
caplen = packet_len;
if (caplen > handle->snapshot)
caplen = handle->snapshot;
/* Run the packet filter if not using kernel filter */
if (!handle->md.use_bpf && handle->fcode.bf_insns) {
if (bpf_filter(handle->fcode.bf_insns, bp,
packet_len, caplen) == 0)
{
/* rejected by filter */
return 0;
}
}
/* Fill in our own header data */
if (ioctl(handle->fd, SIOCGSTAMP, &pcap_header.ts) == -1) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
"SIOCGSTAMP: %s", pcap_strerror(errno));
return -1;
}
pcap_header.caplen = caplen;
pcap_header.len = packet_len;
/*
* Count the packet.
*
* Arguably, we should count them before we check the filter,
* as on many other platforms "ps_recv" counts packets
* handed to the filter rather than packets that passed
* the filter, but if filtering is done in the kernel, we
* can't get a count of packets that passed the filter,
* and that would mean the meaning of "ps_recv" wouldn't
* be the same on all Linux systems.
*
* XXX - it's not the same on all systems in any case;
* ideally, we should have a "get the statistics" call
* that supplies more counts and indicates which of them
* it supplies, so that we supply a count of packets
* handed to the filter only on platforms where that
* information is available.
*
* We count them here even if we can get the packet count
* from the kernel, as we can only determine at run time
* whether we'll be able to get it from the kernel (if
* HAVE_TPACKET_STATS isn't defined, we can't get it from
* the kernel, but if it is defined, the library might
* have been built with a 2.4 or later kernel, but we
* might be running on a 2.2[.x] kernel without Alexey
* Kuznetzov's turbopacket patches, and thus the kernel
* might not be able to supply those statistics). We
* could, I guess, try, when opening the socket, to get
* the statistics, and if we can not increment the count
* here, but it's not clear that always incrementing
* the count is more expensive than always testing a flag
* in memory.
*
* We keep the count in "md.packets_read", and use that for
* "ps_recv" if we can't get the statistics from the kernel.
* We do that because, if we *can* get the statistics from
* the kernel, we use "md.stat.ps_recv" and "md.stat.ps_drop"
* as running counts, as reading the statistics from the
* kernel resets the kernel statistics, and if we directly
* increment "md.stat.ps_recv" here, that means it will
* count packets *twice* on systems where we can get kernel
* statistics - once here, and once in pcap_stats_linux().
*/
handle->md.packets_read++;
/* Call the user supplied callback function */
callback(userdata, &pcap_header, bp);
return 1;
}
static int
pcap_inject_linux(pcap_t *handle, const void *buf, size_t size)
{
int ret;
#ifdef HAVE_PF_PACKET_SOCKETS
if (!handle->md.sock_packet) {
/* PF_PACKET socket */
if (handle->md.ifindex == -1) {
/*
* We don't support sending on the "any" device.
*/
strlcpy(handle->errbuf,
"Sending packets isn't supported on the \"any\" device",