336 lines
9.3 KiB
C
336 lines
9.3 KiB
C
/* libpcap.c
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*
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* $Id: libpcap.c,v 1.9 1999/08/18 17:08:47 guy Exp $
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*
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* Wiretap Library
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* Copyright (c) 1998 by Gilbert Ramirez <gram@verdict.uthscsa.edu>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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*/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include <stdlib.h>
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#include <errno.h>
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#include "wtap.h"
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#include "buffer.h"
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#include "libpcap.h"
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/* See source to the "libpcap" library for information on the "libpcap"
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file format. */
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/* Magic numbers in "libpcap" files.
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"libpcap" file records are written in the byte order of the host that
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writes them, and the reader is expected to fix this up.
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PCAP_MAGIC is the magic number, in host byte order; PCAP_SWAPPED_MAGIC
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is a byte-swapped version of that. */
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#define PCAP_MAGIC 0xa1b2c3d4
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#define PCAP_SWAPPED_MAGIC 0xd4c3b2a1
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/* Macros to byte-swap 32-bit and 16-bit quantities. */
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#define BSWAP32(x) \
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((((x)&0xFF000000)>>24) | \
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(((x)&0x00FF0000)>>8) | \
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(((x)&0x0000FF00)<<8) | \
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(((x)&0x000000FF)<<24))
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#define BSWAP16(x) \
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((((x)&0xFF00)>>8) | \
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(((x)&0x00FF)<<8))
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/* "libpcap" file header (minus magic number). */
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struct pcap_hdr {
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guint16 version_major; /* major version number */
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guint16 version_minor; /* minor version number */
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gint32 thiszone; /* GMT to local correction */
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guint32 sigfigs; /* accuracy of timestamps */
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guint32 snaplen; /* max length of captured packets, in octets */
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guint32 network; /* data link type */
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};
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/* "libpcap" record header. */
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struct pcaprec_hdr {
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guint32 ts_sec; /* timestamp seconds */
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guint32 ts_usec; /* timestamp microseconds */
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guint32 incl_len; /* number of octets of packet saved in file */
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guint32 orig_len; /* actual length of packet */
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};
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static int libpcap_read(wtap *wth);
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static int libpcap_dump(wtap_dumper *wdh, const struct wtap_pkthdr *phdr,
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const u_char *pd, int *err);
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static int libpcap_dump_close(wtap_dumper *wdh, int *err);
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static const int pcap_encap[] = {
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WTAP_ENCAP_NONE, /* no encapsulation */
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WTAP_ENCAP_ETHERNET,
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WTAP_ENCAP_NONE, /* 3Mb experimental Ethernet */
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WTAP_ENCAP_NONE, /* Amateur Radio AX.25 */
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WTAP_ENCAP_NONE, /* Proteon ProNET Token Ring */
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WTAP_ENCAP_NONE, /* Chaos */
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WTAP_ENCAP_TR, /* IEEE 802 Networks - assume token ring */
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WTAP_ENCAP_ARCNET,
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WTAP_ENCAP_SLIP,
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WTAP_ENCAP_PPP,
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WTAP_ENCAP_FDDI,
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WTAP_ENCAP_ATM_RFC1483,
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WTAP_ENCAP_RAW_IP,
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WTAP_ENCAP_NONE,
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WTAP_ENCAP_NONE,
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WTAP_ENCAP_NONE,
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WTAP_ENCAP_NONE,
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WTAP_ENCAP_NONE,
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WTAP_ENCAP_NONE,
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WTAP_ENCAP_LINUX_ATM_CLIP
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};
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#define NUM_PCAP_ENCAPS (sizeof pcap_encap / sizeof pcap_encap[0])
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/* Returns WTAP_FILE_PCAP on success, WTAP_FILE_UNKNOWN on failure */
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int libpcap_open(wtap *wth)
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{
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int bytes_read;
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guint32 magic;
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struct pcap_hdr hdr;
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int byte_swapped = 0;
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/* Read in the number that should be at the start of a "libpcap" file */
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fseek(wth->fh, 0, SEEK_SET);
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bytes_read = fread(&magic, 1, sizeof magic, wth->fh);
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if (bytes_read != sizeof magic) {
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return WTAP_FILE_UNKNOWN;
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}
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if (magic == PCAP_SWAPPED_MAGIC) {
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/* Host that wrote it has a byte order opposite to ours. */
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magic = PCAP_MAGIC;
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byte_swapped = 1;
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}
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if (magic != PCAP_MAGIC) {
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return WTAP_FILE_UNKNOWN;
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}
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/* Read the rest of the header. */
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bytes_read = fread(&hdr, 1, sizeof hdr, wth->fh);
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if (bytes_read != sizeof hdr) {
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return WTAP_FILE_UNKNOWN;
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}
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if (byte_swapped) {
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/* Byte-swap the header fields about which we care. */
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hdr.version_major = BSWAP16(hdr.version_major);
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hdr.version_minor = BSWAP16(hdr.version_minor);
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hdr.snaplen = BSWAP32(hdr.snaplen);
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hdr.network = BSWAP32(hdr.network);
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}
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if (hdr.version_major < 2) {
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/* We only support version 2.0 and later. */
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return WTAP_FILE_UNKNOWN;
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}
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if (hdr.network >= NUM_PCAP_ENCAPS) {
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g_error("pcap: network type %d unknown", hdr.network);
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return WTAP_FILE_UNKNOWN;
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}
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/* This is a libpcap file */
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wth->capture.pcap = g_malloc(sizeof(libpcap_t));
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wth->capture.pcap->byte_swapped = byte_swapped;
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wth->capture.pcap->version_major = hdr.version_major;
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wth->capture.pcap->version_minor = hdr.version_minor;
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wth->subtype_read = libpcap_read;
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wth->file_encap = pcap_encap[hdr.network];
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wth->snapshot_length = hdr.snaplen;
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return WTAP_FILE_PCAP;
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}
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/* Read the next packet */
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static int libpcap_read(wtap *wth)
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{
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int packet_size;
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int bytes_read;
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struct pcaprec_hdr hdr;
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int data_offset;
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/* Read record header. */
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bytes_read = fread(&hdr, 1, sizeof hdr, wth->fh);
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if (bytes_read != sizeof hdr) {
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if (bytes_read != 0) {
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g_error("pcap_read: not enough packet header data (%d bytes)",
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bytes_read);
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return -1;
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}
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return 0;
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}
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if (wth->capture.pcap->byte_swapped) {
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/* Byte-swap the record header fields. */
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hdr.ts_sec = BSWAP32(hdr.ts_sec);
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hdr.ts_usec = BSWAP32(hdr.ts_usec);
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hdr.incl_len = BSWAP32(hdr.incl_len);
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hdr.orig_len = BSWAP32(hdr.orig_len);
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}
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/* In file format version 2.3, the "incl_len" and "orig_len" fields
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were swapped, in order to match the BPF header layout.
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Unfortunately, some files were, according to a comment in the
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"libpcap" source, written with version 2.3 in their headers
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but without the interchanged fields, so if "incl_len" is
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greater than "orig_len" - which would make no sense - we
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assume that we need to swap them. */
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if (wth->capture.pcap->version_major == 2 &&
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(wth->capture.pcap->version_minor < 3 ||
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(wth->capture.pcap->version_minor == 3 &&
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hdr.incl_len > hdr.orig_len))) {
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guint32 temp;
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temp = hdr.orig_len;
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hdr.orig_len = hdr.incl_len;
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hdr.incl_len = temp;
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}
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packet_size = hdr.incl_len;
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buffer_assure_space(wth->frame_buffer, packet_size);
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data_offset = ftell(wth->fh);
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bytes_read = fread(buffer_start_ptr(wth->frame_buffer), 1,
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packet_size, wth->fh);
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if (bytes_read != packet_size) {
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if (ferror(wth->fh)) {
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g_error("pcap_read: fread for data: read error\n");
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} else {
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g_error("pcap_read: fread for data: %d bytes out of %d",
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bytes_read, packet_size);
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}
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return -1;
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}
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wth->phdr.ts.tv_sec = hdr.ts_sec;
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wth->phdr.ts.tv_usec = hdr.ts_usec;
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wth->phdr.caplen = packet_size;
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wth->phdr.len = hdr.orig_len;
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wth->phdr.pkt_encap = wth->file_encap;
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return data_offset;
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}
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int wtap_pcap_encap_to_wtap_encap(int encap)
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{
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if (encap < 0 || encap >= NUM_PCAP_ENCAPS)
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return WTAP_ENCAP_UNKNOWN;
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return pcap_encap[encap];
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}
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/* Returns 1 on success, 0 on failure; sets "*err" to an error code on
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failure */
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int libpcap_dump_open(wtap_dumper *wdh, int *err)
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{
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static const guint32 pcap_magic = PCAP_MAGIC;
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struct pcap_hdr file_hdr;
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static const int wtap_encap[] = {
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0, /* WTAP_ENCAP_NONE */
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1, /* WTAP_ENCAP_ETHERNET */
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6, /* WTAP_ENCAP_TR */
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8, /* WTAP_ENCAP_SLIP */
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9, /* WTAP_ENCAP_PPP */
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10, /* WTAP_ENCAP_FDDI */
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12, /* WTAP_ENCAP_RAW_IP */
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7, /* WTAP_ENCAP_ARCNET */
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11, /* WTAP_ENCAP_ATM_RFC1483 */
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19 /* WTAP_ENCAP_LINUX_ATM_CLIP */
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};
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int nwritten;
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/* Per-packet encapsulations aren't supported. */
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if (wdh->encap == WTAP_ENCAP_PER_PACKET) {
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*err = WTAP_ERR_ENCAP_PER_PACKET_UNSUPPORTED;
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return 0;
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}
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/* This is a libpcap file */
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wdh->subtype_write = libpcap_dump;
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wdh->subtype_close = libpcap_dump_close;
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/* Write the file header. */
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nwritten = fwrite(&pcap_magic, 1, sizeof pcap_magic, wdh->fh);
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if (nwritten != sizeof pcap_magic) {
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if (nwritten < 0)
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*err = errno;
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else
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*err = WTAP_ERR_SHORT_WRITE;
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return 0;
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}
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/* current "libpcap" format is 2.4 */
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file_hdr.version_major = 2;
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file_hdr.version_minor = 4;
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file_hdr.thiszone = 0; /* XXX - current offset? */
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file_hdr.sigfigs = 0; /* unknown, but also apparently unused */
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file_hdr.snaplen = wdh->snaplen;
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file_hdr.network = wtap_encap[wdh->encap];
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nwritten = fwrite(&file_hdr, 1, sizeof file_hdr, wdh->fh);
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if (nwritten != sizeof file_hdr) {
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if (nwritten < 0)
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*err = errno;
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else
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*err = WTAP_ERR_SHORT_WRITE;
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return 0;
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}
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return 1;
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}
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/* Write a record for a packet to a dump file.
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Returns 1 on success, 0 on failure. */
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static int libpcap_dump(wtap_dumper *wdh, const struct wtap_pkthdr *phdr,
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const u_char *pd, int *err)
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{
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struct pcaprec_hdr rec_hdr;
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int nwritten;
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rec_hdr.ts_sec = phdr->ts.tv_sec;
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rec_hdr.ts_usec = phdr->ts.tv_usec;
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rec_hdr.incl_len = phdr->caplen;
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rec_hdr.orig_len = phdr->len;
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nwritten = fwrite(&rec_hdr, 1, sizeof rec_hdr, wdh->fh);
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if (nwritten != sizeof rec_hdr) {
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if (nwritten < 0)
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*err = errno;
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else
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*err = WTAP_ERR_SHORT_WRITE;
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return 0;
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}
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nwritten = fwrite(pd, 1, phdr->caplen, wdh->fh);
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if (nwritten != phdr->caplen) {
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if (nwritten < 0)
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*err = errno;
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else
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*err = WTAP_ERR_SHORT_WRITE;
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return 0;
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}
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return 1;
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}
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/* Finish writing to a dump file.
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Returns 1 on success, 0 on failure. */
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static int libpcap_dump_close(wtap_dumper *wdh, int *err)
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{
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/* Nothing to do here. */
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return 1;
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}
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