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wireshark/wiretap/libpcap.c

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/* libpcap.c
*
* $Id: libpcap.c,v 1.26 1999/12/04 09:38:37 guy Exp $
*
* Wiretap Library
* Copyright (c) 1998 by Gilbert Ramirez <gram@verdict.uthscsa.edu>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <stdlib.h>
#include <errno.h>
#include "wtap.h"
#include "file.h"
#include "buffer.h"
#include "libpcap.h"
/* See source to the "libpcap" library for information on the "libpcap"
file format. */
/* Magic numbers in "libpcap" files.
"libpcap" file records are written in the byte order of the host that
writes them, and the reader is expected to fix this up.
PCAP_MAGIC is the magic number, in host byte order; PCAP_SWAPPED_MAGIC
is a byte-swapped version of that.
PCAP_MODIFIED_MAGIC is for Alexey Kuznetsov's modified "libpcap"
format, as generated on Linux systems that have a "libpcap" with
his patches, at
http://ftp.sunet.se/pub/os/Linux/ip-routing/lbl-tools/
applied; PCAP_SWAPPED_MODIFIED_MAGIC is the byte-swapped version. */
#define PCAP_MAGIC 0xa1b2c3d4
#define PCAP_SWAPPED_MAGIC 0xd4c3b2a1
#define PCAP_MODIFIED_MAGIC 0xa1b2cd34
#define PCAP_SWAPPED_MODIFIED_MAGIC 0x34cdb2a1
/* Macros to byte-swap 32-bit and 16-bit quantities. */
#define BSWAP32(x) \
((((x)&0xFF000000)>>24) | \
(((x)&0x00FF0000)>>8) | \
(((x)&0x0000FF00)<<8) | \
(((x)&0x000000FF)<<24))
#define BSWAP16(x) \
((((x)&0xFF00)>>8) | \
(((x)&0x00FF)<<8))
/* On some systems, the FDDI MAC addresses are bit-swapped. */
#if !defined(ultrix) && !defined(__alpha) && !defined(__bsdi__)
#define BIT_SWAPPED_MAC_ADDRS
#endif
/* "libpcap" file header (minus magic number). */
struct pcap_hdr {
guint16 version_major; /* major version number */
guint16 version_minor; /* minor version number */
gint32 thiszone; /* GMT to local correction */
guint32 sigfigs; /* accuracy of timestamps */
guint32 snaplen; /* max length of captured packets, in octets */
guint32 network; /* data link type */
};
/* "libpcap" record header. */
struct pcaprec_hdr {
guint32 ts_sec; /* timestamp seconds */
guint32 ts_usec; /* timestamp microseconds */
guint32 incl_len; /* number of octets of packet saved in file */
guint32 orig_len; /* actual length of packet */
};
/* "libpcap" record header for Alexey's patched version. */
struct pcaprec_modified_hdr {
struct pcaprec_hdr hdr; /* the regular header */
guint32 ifindex; /* index, in *capturing* machine's list of
interfaces, of the interface on which this
packet came in. */
guint16 protocol; /* Ethernet packet type */
guint8 pkt_type; /* broadcast/multicast/etc. indication */
};
static int libpcap_read(wtap *wth, int *err);
static void adjust_header(wtap *wth, struct pcaprec_hdr *hdr);
static gboolean libpcap_dump(wtap_dumper *wdh, const struct wtap_pkthdr *phdr,
const u_char *pd, int *err);
/*
* XXX - this is a bit of a mess. OpenBSD, and perhaps NetBSD, and
* BSD/OS have different DLT_ codes from FreeBSD (and from the LBL
* BPF code), and, at least in some cases, from each other.
* For now, we simply treat those type values with different
* meanings on different platforms, except for DLT_RAW, as "unknown";
* this means you won't be able to capture from a network using those
* types in Ethereal (and that capturing from the loopback interface
* won't necessarily work right on OpenBSD, either, as it uses
* DLT_LOOP, which is the same as DLT_RAW on other platforms).
*
* Does anybody know what BSD/OS uses as DLT_ types for SLIP and
* PPP? The LBL code, and the OpenBSD code, appear to disagree....
*
* Nothing in FreeBSD appears to use DLT_RAW, so it's not clear what
* link-layer header or fake header appears for DLT_RAW. If it's
* completely unused, or if it behaves the same way OpenBSD DLT_LOOP
* behaves, i.e. it puts an address family in *network* byte order
* (as opposed to the *host* byte order that DLT_NULL uses on FreeBSD),
* then we should just make it WTAP_ENCAP_NULL, which we treat in
* such a fashion as to cause it to work with DLT_LOOP headers.
*/
static const int pcap_encap[] = {
WTAP_ENCAP_NULL, /* null encapsulation */
WTAP_ENCAP_ETHERNET,
WTAP_ENCAP_UNKNOWN, /* 3Mb experimental Ethernet */
WTAP_ENCAP_UNKNOWN, /* Amateur Radio AX.25 */
WTAP_ENCAP_UNKNOWN, /* Proteon ProNET Token Ring */
WTAP_ENCAP_UNKNOWN, /* Chaos */
WTAP_ENCAP_TR, /* IEEE 802 Networks - assume token ring */
WTAP_ENCAP_ARCNET,
WTAP_ENCAP_SLIP,
WTAP_ENCAP_PPP,
#ifdef BIT_SWAPPED_MAC_ADDRS
WTAP_ENCAP_FDDI_BITSWAPPED,
#else
WTAP_ENCAP_FDDI,
#endif
WTAP_ENCAP_ATM_RFC1483, /* or, on BSD/OS, Frame Relay */
WTAP_ENCAP_RAW_IP, /* or, on OpenBSD, DLT_LOOP, and on BSD/OS,
Cisco HDLC */
WTAP_ENCAP_UNKNOWN, /* In LBL BPF and FreeBSD, BSD/OS SLIP;
on OpenBSD, DLT_ENC; on BSD/OS,
DLT_ATM_RFC1483 */
WTAP_ENCAP_UNKNOWN, /* In LBL BPF and FreeBSD, BSD/OS PPP;
on OpenBSD and BSD/OS, DLT_RAW */
WTAP_ENCAP_UNKNOWN, /* In OpenBSD and BSD/OS, BSD/OS SLIP,
but the BSD/OS header says "internal
to libpcap", whatever that means */
WTAP_ENCAP_UNKNOWN, /* In OpenBSD and BSD/OS, BSD/OS PPP,
but the BSD/OS header says "internal
to libpcap", whatever that means */
WTAP_ENCAP_UNKNOWN,
WTAP_ENCAP_UNKNOWN,
WTAP_ENCAP_LINUX_ATM_CLIP
};
#define NUM_PCAP_ENCAPS (sizeof pcap_encap / sizeof pcap_encap[0])
int libpcap_open(wtap *wth, int *err)
{
int bytes_read;
guint32 magic;
struct pcap_hdr hdr;
gboolean byte_swapped;
gboolean modified;
struct pcaprec_hdr first_rec_hdr;
struct pcaprec_hdr second_rec_hdr;
/* Read in the number that should be at the start of a "libpcap" file */
file_seek(wth->fh, 0, SEEK_SET);
wth->data_offset = 0;
errno = WTAP_ERR_CANT_READ;
bytes_read = file_read(&magic, 1, sizeof magic, wth->fh);
if (bytes_read != sizeof magic) {
*err = file_error(wth->fh);
if (*err != 0)
return -1;
return 0;
}
wth->data_offset += sizeof magic;
switch (magic) {
case PCAP_MAGIC:
/* Host that wrote it has our byte order. */
byte_swapped = FALSE;
modified = FALSE;
break;
case PCAP_MODIFIED_MAGIC:
/* Host that wrote it has our byte order, but was running
a program using the patched "libpcap". */
byte_swapped = FALSE;
modified = TRUE;
break;
case PCAP_SWAPPED_MAGIC:
/* Host that wrote it has a byte order opposite to ours. */
byte_swapped = TRUE;
modified = FALSE;
break;
case PCAP_SWAPPED_MODIFIED_MAGIC:
/* Host that wrote it out has a byte order opposite to
ours, and was running a program using the patched
"libpcap". */
byte_swapped = TRUE;
modified = TRUE;
break;
default:
/* Not a "libpcap" type we know about. */
return 0;
}
/* Read the rest of the header. */
errno = WTAP_ERR_CANT_READ;
bytes_read = file_read(&hdr, 1, sizeof hdr, wth->fh);
if (bytes_read != sizeof hdr) {
*err = file_error(wth->fh);
if (*err != 0)
return -1;
return 0;
}
wth->data_offset += sizeof hdr;
if (byte_swapped) {
/* Byte-swap the header fields about which we care. */
hdr.version_major = BSWAP16(hdr.version_major);
hdr.version_minor = BSWAP16(hdr.version_minor);
hdr.snaplen = BSWAP32(hdr.snaplen);
hdr.network = BSWAP32(hdr.network);
}
if (hdr.version_major < 2) {
/* We only support version 2.0 and later. */
g_message("pcap: major version %u unsupported",
hdr.version_major);
*err = WTAP_ERR_UNSUPPORTED;
return -1;
}
if (hdr.network >= NUM_PCAP_ENCAPS
|| pcap_encap[hdr.network] == WTAP_ENCAP_UNKNOWN) {
g_message("pcap: network type %u unknown or unsupported",
hdr.network);
*err = WTAP_ERR_UNSUPPORTED;
return -1;
}
/* This is a libpcap file */
wth->file_type = modified ? WTAP_FILE_PCAP_MODIFIED : WTAP_FILE_PCAP;
wth->capture.pcap = g_malloc(sizeof(libpcap_t));
wth->capture.pcap->byte_swapped = byte_swapped;
wth->capture.pcap->modified = modified;
wth->capture.pcap->version_major = hdr.version_major;
wth->capture.pcap->version_minor = hdr.version_minor;
wth->subtype_read = libpcap_read;
wth->file_encap = pcap_encap[hdr.network];
wth->snapshot_length = hdr.snaplen;
/*
* Is this a capture file with the non-modified magic number?
*/
if (!wth->capture.pcap->modified) {
/*
* Yes. Let's look at the header for the first record,
* and see if, interpreting it as a non-modified header,
* the position where it says the header for the
* *second* record is contains a corrupted header.
*
* If so, this may be a modified capture file with a
* non-modified magic number - in some versions of
* Alexey's patches, the packet header format was
* changed but the magic number wasn't, and, alas,
* Red Hat appear to have picked up one of those
* patches for RH 6.1, meaning RH 6.1 has a "tcpdump"
* that writes out files that can't be read by any software
* that expects non-modified headers if the magic number isn't
* the modified magic number (e.g., any normal version of
* "tcpdump", and Ethereal if we don't do this gross
* heuristic).
*/
bytes_read = file_read(&first_rec_hdr, 1,
sizeof first_rec_hdr, wth->fh);
if (bytes_read != sizeof first_rec_hdr) {
*err = file_error(wth->fh);
if (*err != 0)
return -1; /* failed to read it */
/*
* Short read - assume the file isn't modified,
* and put the seek pointer back. The attempt
* to read the first packet will presumably get
* the same short read.
*/
goto give_up;
}
adjust_header(wth, &first_rec_hdr);
if (first_rec_hdr.incl_len > WTAP_MAX_PACKET_SIZE) {
/*
* The first record is bogus, so this is probably
* a corrupt file. Assume the file isn't modified,
* and put the seek pointer back. The attempt
* to read the first packet will probably get
* the same bogus length.
*/
goto give_up;
}
file_seek(wth->fh,
wth->data_offset + sizeof first_rec_hdr + first_rec_hdr.incl_len,
SEEK_SET);
bytes_read = file_read(&second_rec_hdr, 1,
sizeof second_rec_hdr, wth->fh);
/*
* OK, does the next packet's header look sane?
*/
if (bytes_read != sizeof second_rec_hdr) {
*err = file_error(wth->fh);
if (*err != 0)
return -1; /* failed to read it */
/*
* Short read - assume the file isn't modified,
* and put the seek pointer back. The attempt
* to read the second packet will presumably get
* the same short read error.
*/
goto give_up;
}
adjust_header(wth, &second_rec_hdr);
if (second_rec_hdr.incl_len > WTAP_MAX_PACKET_SIZE) {
/*
* Oh, dear. Maybe it's a Capture File
* From Hell, and what looks like the
* "header" of the next packet is actually
* random junk from the middle of a packet.
* Try treating it as a modified file;
* if that doesn't work, it probably *is*
* a corrupt file.
*/
wth->file_type = WTAP_FILE_PCAP_MODIFIED;
wth->capture.pcap->modified = TRUE;
}
give_up:
/*
* Restore the seek pointer.
*/
file_seek(wth->fh, wth->data_offset, SEEK_SET);
}
return 1;
}
/* Read the next packet */
static int libpcap_read(wtap *wth, int *err)
{
guint packet_size;
int bytes_to_read, bytes_read;
struct pcaprec_modified_hdr hdr;
int data_offset;
/* Read record header. */
errno = WTAP_ERR_CANT_READ;
bytes_to_read = wth->capture.pcap->modified ?
sizeof hdr : sizeof hdr.hdr;
bytes_read = file_read(&hdr, 1, bytes_to_read, wth->fh);
if (bytes_read != bytes_to_read) {
*err = file_error(wth->fh);
if (*err != 0)
return -1;
if (bytes_read != 0) {
*err = WTAP_ERR_SHORT_READ;
return -1;
}
return 0;
}
wth->data_offset += bytes_read;
adjust_header(wth, &hdr.hdr);
packet_size = hdr.hdr.incl_len;
if (packet_size > WTAP_MAX_PACKET_SIZE) {
/*
* Probably a corrupt capture file; don't blow up trying
* to allocate space for an immensely-large packet.
*/
g_message("pcap: File has %u-byte packet, bigger than maximum of %u",
packet_size, WTAP_MAX_PACKET_SIZE);
*err = WTAP_ERR_BAD_RECORD;
return -1;
}
buffer_assure_space(wth->frame_buffer, packet_size);
data_offset = wth->data_offset;
errno = WTAP_ERR_CANT_READ;
bytes_read = file_read(buffer_start_ptr(wth->frame_buffer), 1,
packet_size, wth->fh);
if (bytes_read != packet_size) {
*err = file_error(wth->fh);
if (*err == 0)
*err = WTAP_ERR_SHORT_READ;
return -1;
}
wth->data_offset += packet_size;
wth->phdr.ts.tv_sec = hdr.hdr.ts_sec;
wth->phdr.ts.tv_usec = hdr.hdr.ts_usec;
wth->phdr.caplen = packet_size;
wth->phdr.len = hdr.hdr.orig_len;
wth->phdr.pkt_encap = wth->file_encap;
return data_offset;
}
static void
adjust_header(wtap *wth, struct pcaprec_hdr *hdr)
{
if (wth->capture.pcap->byte_swapped) {
/* Byte-swap the record header fields. */
hdr->ts_sec = BSWAP32(hdr->ts_sec);
hdr->ts_usec = BSWAP32(hdr->ts_usec);
hdr->incl_len = BSWAP32(hdr->incl_len);
hdr->orig_len = BSWAP32(hdr->orig_len);
}
/* In file format version 2.3, the "incl_len" and "orig_len" fields
were swapped, in order to match the BPF header layout.
Unfortunately, some files were, according to a comment in the
"libpcap" source, written with version 2.3 in their headers
but without the interchanged fields, so if "incl_len" is
greater than "orig_len" - which would make no sense - we
assume that we need to swap them. */
if (wth->capture.pcap->version_major == 2 &&
(wth->capture.pcap->version_minor < 3 ||
(wth->capture.pcap->version_minor == 3 &&
hdr->incl_len > hdr->orig_len))) {
guint32 temp;
temp = hdr->orig_len;
hdr->orig_len = hdr->incl_len;
hdr->incl_len = temp;
}
}
int wtap_pcap_encap_to_wtap_encap(int encap)
{
if (encap < 0 || encap >= NUM_PCAP_ENCAPS)
return WTAP_ENCAP_UNKNOWN;
return pcap_encap[encap];
}
static const int wtap_encap[] = {
-1, /* WTAP_ENCAP_UNKNOWN -> unsupported */
1, /* WTAP_ENCAP_ETHERNET -> DLT_EN10MB */
6, /* WTAP_ENCAP_TR -> DLT_IEEE802 */
8, /* WTAP_ENCAP_SLIP -> DLT_SLIP */
9, /* WTAP_ENCAP_PPP -> DLT_PPP */
10, /* WTAP_ENCAP_FDDI -> DLT_FDDI */
10, /* WTAP_ENCAP_FDDI_BITSWAPPED -> DLT_FDDI */
12, /* WTAP_ENCAP_RAW_IP -> DLT_RAW */
7, /* WTAP_ENCAP_ARCNET -> DLT_ARCNET */
11, /* WTAP_ENCAP_ATM_RFC1483 -> DLT_ATM_RFC1483 */
19, /* WTAP_ENCAP_LINUX_ATM_CLIP */
-1, /* WTAP_ENCAP_LAPB -> unsupported*/
-1, /* WTAP_ENCAP_ATM_SNIFFER -> unsupported */
0 /* WTAP_ENCAP_NULL -> DLT_NULL */
};
#define NUM_WTAP_ENCAPS (sizeof wtap_encap / sizeof wtap_encap[0])
/* Returns 0 if we could write the specified encapsulation type,
an error indication otherwise. */
int libpcap_dump_can_write_encap(int filetype, int encap)
{
/* Per-packet encapsulations aren't supported. */
if (encap == WTAP_ENCAP_PER_PACKET)
return WTAP_ERR_ENCAP_PER_PACKET_UNSUPPORTED;
if (encap < 0 || encap >= NUM_WTAP_ENCAPS || wtap_encap[encap] == -1)
return WTAP_ERR_UNSUPPORTED_ENCAP;
return 0;
}
/* Returns TRUE on success, FALSE on failure; sets "*err" to an error code on
failure */
gboolean libpcap_dump_open(wtap_dumper *wdh, int *err)
{
static const guint32 pcap_magic = PCAP_MAGIC;
struct pcap_hdr file_hdr;
int nwritten;
/* This is a libpcap file */
wdh->subtype_write = libpcap_dump;
wdh->subtype_close = NULL;
/* Write the file header. */
nwritten = fwrite(&pcap_magic, 1, sizeof pcap_magic, wdh->fh);
if (nwritten != sizeof pcap_magic) {
if (nwritten < 0)
*err = errno;
else
*err = WTAP_ERR_SHORT_WRITE;
return FALSE;
}
/* current "libpcap" format is 2.4 */
file_hdr.version_major = 2;
file_hdr.version_minor = 4;
file_hdr.thiszone = 0; /* XXX - current offset? */
file_hdr.sigfigs = 0; /* unknown, but also apparently unused */
file_hdr.snaplen = wdh->snaplen;
file_hdr.network = wtap_encap[wdh->encap];
nwritten = fwrite(&file_hdr, 1, sizeof file_hdr, wdh->fh);
if (nwritten != sizeof file_hdr) {
if (nwritten < 0)
*err = errno;
else
*err = WTAP_ERR_SHORT_WRITE;
return FALSE;
}
return TRUE;
}
/* Write a record for a packet to a dump file.
Returns TRUE on success, FALSE on failure. */
static gboolean libpcap_dump(wtap_dumper *wdh, const struct wtap_pkthdr *phdr,
const u_char *pd, int *err)
{
struct pcaprec_hdr rec_hdr;
int nwritten;
rec_hdr.ts_sec = phdr->ts.tv_sec;
rec_hdr.ts_usec = phdr->ts.tv_usec;
rec_hdr.incl_len = phdr->caplen;
rec_hdr.orig_len = phdr->len;
nwritten = fwrite(&rec_hdr, 1, sizeof rec_hdr, wdh->fh);
if (nwritten != sizeof rec_hdr) {
if (nwritten < 0)
*err = errno;
else
*err = WTAP_ERR_SHORT_WRITE;
return FALSE;
}
nwritten = fwrite(pd, 1, phdr->caplen, wdh->fh);
if (nwritten != phdr->caplen) {
if (nwritten < 0)
*err = errno;
else
*err = WTAP_ERR_SHORT_WRITE;
return FALSE;
}
return TRUE;
}
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