416 lines
12 KiB
C
416 lines
12 KiB
C
/* libpcap.c
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*
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* $Id: libpcap.c,v 1.21 1999/10/05 07:06:06 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 "file.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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/* On some systems, the FDDI MAC addresses are bit-swapped. */
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#if !defined(ultrix) && !defined(__alpha) && !defined(__bsdi__)
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#define BIT_SWAPPED_MAC_ADDRS
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#endif
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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, int *err);
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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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/*
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* XXX - this is a bit of a mess. OpenBSD, and perhaps NetBSD, and
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* BSD/OS have different DLT_ codes from FreeBSD (and from the LBL
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* BPF code), and, at least in some cases, from each other.
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* For now, we simply treat those type values with different
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* meanings on different platforms, except for DLT_RAW, as "unknown";
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* this means you won't be able to capture from a network using those
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* types in Ethereal (and that capturing from the loopback interface
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* won't necessarily work right on OpenBSD, either, as it uses
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* DLT_LOOP, which is the same as DLT_RAW on other platforms).
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*
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* Does anybody know what BSD/OS uses as DLT_ types for SLIP and
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* PPP? The LBL code, and the OpenBSD code, appear to disagree....
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*
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* Nothing in FreeBSD appears to use DLT_RAW, so it's not clear what
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* link-layer header or fake header appears for DLT_RAW. If it's
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* completely unused, or if it behaves the same way OpenBSD DLT_LOOP
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* behaves, i.e. it puts an address family in *network* byte order
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* (as opposed to the *host* byte order that DLT_NULL uses on FreeBSD),
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* then we should just make it WTAP_ENCAP_NULL, which we treat in
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* such a fashion as to cause it to work with DLT_LOOP headers.
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*/
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static const int pcap_encap[] = {
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WTAP_ENCAP_NULL, /* null encapsulation */
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WTAP_ENCAP_ETHERNET,
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WTAP_ENCAP_UNKNOWN, /* 3Mb experimental Ethernet */
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WTAP_ENCAP_UNKNOWN, /* Amateur Radio AX.25 */
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WTAP_ENCAP_UNKNOWN, /* Proteon ProNET Token Ring */
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WTAP_ENCAP_UNKNOWN, /* 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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#ifdef BIT_SWAPPED_MAC_ADDRS
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WTAP_ENCAP_FDDI_BITSWAPPED,
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#else
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WTAP_ENCAP_FDDI,
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#endif
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WTAP_ENCAP_ATM_RFC1483, /* or, on BSD/OS, Frame Relay */
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WTAP_ENCAP_RAW_IP, /* or, on OpenBSD, DLT_LOOP, and on BSD/OS,
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Cisco HDLC */
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WTAP_ENCAP_UNKNOWN, /* In LBL BPF and FreeBSD, BSD/OS SLIP;
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on OpenBSD, DLT_ENC; on BSD/OS,
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DLT_ATM_RFC1483 */
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WTAP_ENCAP_UNKNOWN, /* In LBL BPF and FreeBSD, BSD/OS PPP;
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on OpenBSD and BSD/OS, DLT_RAW */
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WTAP_ENCAP_UNKNOWN, /* In OpenBSD and BSD/OS, BSD/OS SLIP,
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but the BSD/OS header says "internal
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to libpcap", whatever that means */
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WTAP_ENCAP_UNKNOWN, /* In OpenBSD and BSD/OS, BSD/OS PPP,
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but the BSD/OS header says "internal
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to libpcap", whatever that means */
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WTAP_ENCAP_UNKNOWN,
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WTAP_ENCAP_UNKNOWN,
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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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int libpcap_open(wtap *wth, int *err)
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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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file_seek(wth->fh, 0, SEEK_SET);
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wth->data_offset = 0;
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errno = WTAP_ERR_CANT_READ;
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bytes_read = file_read(&magic, 1, sizeof magic, wth->fh);
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if (bytes_read != sizeof magic) {
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*err = file_error(wth->fh);
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if (*err != 0)
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return -1;
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return 0;
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}
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wth->data_offset += sizeof magic;
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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 0;
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}
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/* Read the rest of the header. */
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errno = WTAP_ERR_CANT_READ;
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bytes_read = file_read(&hdr, 1, sizeof hdr, wth->fh);
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if (bytes_read != sizeof hdr) {
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*err = file_error(wth->fh);
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if (*err != 0)
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return -1;
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return 0;
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}
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wth->data_offset += sizeof hdr;
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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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g_message("pcap: major version %u unsupported",
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hdr.version_major);
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*err = WTAP_ERR_UNSUPPORTED;
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return -1;
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}
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if (hdr.network >= NUM_PCAP_ENCAPS
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|| pcap_encap[hdr.network] == WTAP_ENCAP_UNKNOWN) {
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g_message("pcap: network type %u unknown or unsupported",
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hdr.network);
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*err = WTAP_ERR_UNSUPPORTED;
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return -1;
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}
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/* This is a libpcap file */
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wth->file_type = WTAP_FILE_PCAP;
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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 1;
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}
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/* Read the next packet */
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static int libpcap_read(wtap *wth, int *err)
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{
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guint 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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errno = WTAP_ERR_CANT_READ;
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bytes_read = file_read(&hdr, 1, sizeof hdr, wth->fh);
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if (bytes_read != sizeof hdr) {
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*err = file_error(wth->fh);
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if (*err != 0)
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return -1;
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if (bytes_read != 0) {
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*err = WTAP_ERR_SHORT_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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wth->data_offset += sizeof hdr;
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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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if (packet_size > WTAP_MAX_PACKET_SIZE) {
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/*
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* Probably a corrupt capture file; don't blow up trying
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* to allocate space for an immensely-large packet.
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*/
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g_message("pcap: File has %u-byte packet, bigger than maximum of %u",
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packet_size, WTAP_MAX_PACKET_SIZE);
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*err = WTAP_ERR_BAD_RECORD;
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return -1;
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}
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buffer_assure_space(wth->frame_buffer, packet_size);
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data_offset = wth->data_offset;
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errno = WTAP_ERR_CANT_READ;
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bytes_read = file_read(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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*err = file_error(wth->fh);
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if (*err == 0)
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*err = WTAP_ERR_SHORT_READ;
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return -1;
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}
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wth->data_offset += packet_size;
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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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-1, /* WTAP_ENCAP_UNKNOWN -> unsupported */
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1, /* WTAP_ENCAP_ETHERNET -> DLT_EN10MB */
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6, /* WTAP_ENCAP_TR -> DLT_IEEE802 */
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8, /* WTAP_ENCAP_SLIP -> DLT_SLIP */
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9, /* WTAP_ENCAP_PPP -> DLT_PPP */
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10, /* WTAP_ENCAP_FDDI -> DLT_FDDI */
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10, /* WTAP_ENCAP_FDDI_BITSWAPPED -> DLT_FDDI */
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12, /* WTAP_ENCAP_RAW_IP -> DLT_RAW */
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7, /* WTAP_ENCAP_ARCNET -> DLT_ARCNET */
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11, /* WTAP_ENCAP_ATM_RFC1483 -> DLT_ATM_RFC1483 */
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19, /* WTAP_ENCAP_LINUX_ATM_CLIP */
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-1, /* WTAP_ENCAP_LAPB -> unsupported*/
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-1, /* WTAP_ENCAP_ATM_SNIFFER -> unsupported */
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0 /* WTAP_ENCAP_NULL -> DLT_NULL */
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};
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#define NUM_WTAP_ENCAPS (sizeof wtap_encap / sizeof wtap_encap[0])
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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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if (wdh->encap < 0 || wdh->encap >= NUM_WTAP_ENCAPS
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|| wtap_encap[wdh->encap] == -1) {
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*err = WTAP_ERR_UNSUPPORTED_ENCAP;
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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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