forked from osmocom/wireshark
213 lines
6.3 KiB
C
213 lines
6.3 KiB
C
/* libpcap.c
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*
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* $Id: libpcap.c,v 1.4 1999/03/01 18:57:05 gram 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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#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 captured in file */
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guint32 orig_len; /* actual length of packet */
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};
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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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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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};
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#define NUM_PCAP_ENCAPS (sizeof pcap_encap / sizeof pcap_encap[0])
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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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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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