[obnox/wireshark/wip.git] / wiretap / libpcap.c

/* libpcap.c
 *
 * $Id: libpcap.c,v 1.81 2002/08/07 06:59:49 guy Exp $
 *
 * Wiretap Library
 * Copyright (c) 1998 by Gilbert Ramirez <gram@alumni.rice.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-int.h"
#include "file_wrappers.h"
#include "buffer.h"
#include "atm.h"
#include "libpcap.h"

#ifdef HAVE_PCAP_H
# ifdef HAVE_SYS_TYPES_H
#   include <sys/types.h>
# endif
#include <pcap.h>
#include "wtap-capture.h"
#endif

/*
 * The link-layer header on ATM packets.
 */
struct sunatm_hdr {
        guint8  flags;          /* destination and traffic type */
        guint8  vpi;            /* VPI */
        guint16 vci;            /* VCI */
};

/* See source to the "libpcap" library for information on the "libpcap"
   file format. */

/* On some systems, the FDDI MAC addresses are bit-swapped. */
#if !defined(ultrix) && !defined(__alpha) && !defined(__bsdi__)
#define BIT_SWAPPED_MAC_ADDRS
#endif

/* Try to read the first two records of the capture file. */
typedef enum {
        THIS_FORMAT,            /* the reads succeeded, assume it's this format */
        BAD_READ,               /* the file is probably not valid */
        OTHER_FORMAT            /* the file may be valid, but not in this format */
} libpcap_try_t;
static libpcap_try_t libpcap_try(wtap *wth, int *err);

static gboolean libpcap_read(wtap *wth, int *err, long *data_offset);
static gboolean libpcap_seek_read(wtap *wth, long seek_off,
    union wtap_pseudo_header *pseudo_header, guchar *pd, int length, int *err);
static int libpcap_read_header(wtap *wth, int *err,
    struct pcaprec_ss990915_hdr *hdr, gboolean silent);
static void adjust_header(wtap *wth, struct pcaprec_hdr *hdr);
static void libpcap_get_atm_pseudoheader(const struct sunatm_hdr *atm_phdr,
    union wtap_pseudo_header *pseudo_header);
static gboolean libpcap_read_atm_pseudoheader(FILE_T fh,
    union wtap_pseudo_header *pseudo_header, int *err);
static gboolean libpcap_read_rec_data(FILE_T fh, guchar *pd, int length,
    int *err);
static void libpcap_close(wtap *wth);
static gboolean libpcap_dump(wtap_dumper *wdh, const struct wtap_pkthdr *phdr,
    const union wtap_pseudo_header *pseudo_header, const guchar *pd, int *err);

/*
 * Either LBL NRG wasn't an adequate central registry (e.g., because of
 * the slow rate of releases from them), or nobody bothered using them
 * as a central registry, as many different groups have patched libpcap
 * (and BPF, on the BSDs) to add new encapsulation types, and have ended
 * up using the same DLT_ values for different encapsulation types.
 *
 * For those numerical encapsulation type values that everybody uses for
 * the same encapsulation type (which inclues those that some platforms
 * specify different DLT_ names for but don't appear to use), we map
 * those values to the appropriate Wiretap values.
 *
 * For those numerical encapsulation type values that different libpcap
 * variants use for different encapsulation types, we check what
 * <pcap.h> defined to determine how to interpret them, so that we
 * interpret them the way the libpcap with which we're building
 * Ethereal/Wiretap interprets them (which, if it doesn't support
 * them at all, means we don't support them either - any capture files
 * using them are foreign, and we don't hazard a guess as to which
 * platform they came from; we could, I guess, choose the most likely
 * platform).
 */

static const struct {
        int     dlt_value;
        int     wtap_encap_value;
} pcap_to_wtap_map[] = {
        /*
         * These are the values that are almost certainly the same
         * in all libpcaps (I've yet to find one where the values
         * in question are used for some purpose other than the
         * one below, but...), and that Wiretap and Ethereal
         * currently support.
         */
        { 0,            WTAP_ENCAP_NULL },      /* null encapsulation */
        { 1,            WTAP_ENCAP_ETHERNET },
        { 6,            WTAP_ENCAP_TOKEN_RING },        /* IEEE 802 Networks - assume token ring */
        { 7,            WTAP_ENCAP_ARCNET },
        { 8,            WTAP_ENCAP_SLIP },
        { 9,            WTAP_ENCAP_PPP },
#ifdef BIT_SWAPPED_MAC_ADDRS
        { 10,           WTAP_ENCAP_FDDI_BITSWAPPED },
#else
        { 10,           WTAP_ENCAP_FDDI },
#endif

        /*
         * 50 is DLT_PPP_SERIAL in NetBSD; it appears that DLT_PPP
         * on BSD (at least according to standard tcpdump) has, as
         * the first octet, an indication of whether the packet was
         * transmitted or received (rather than having the standard
         * PPP address value of 0xff), but that DLT_PPP_SERIAL puts
         * a real live PPP header there, or perhaps a Cisco PPP header
         * as per section 4.3.1 of RFC 1547 (implementations of this
         * exist in various BSDs in "sys/net/if_spppsubr.c", and
         * I think also exist either in standard Linux or in
         * various Linux patches; the implementations show how to handle
         * Cisco keepalive packets).
         *
         * However, I don't see any obvious place in FreeBSD "if_ppp.c"
         * where anything other than the standard PPP header would be
         * passed up.  I see some stuff that sets the first octet
         * to 0 for incoming and 1 for outgoing packets before applying
         * a BPF filter to see whether to drop packets whose protocol
         * field has the 0x8000 bit set, i.e. network control protocols -
         * those are handed up to userland - but that code puts the
         * address field back before passing the packet up.
         *
         * I also don't see anything immediately obvious that munges
         * the address field for sync PPP, either.
         *
         * Ethereal currently assumes that if the first octet of a
         * PPP frame is 0xFF, it's the address field and is followed
         * by a control field and a 2-byte protocol, otherwise the
         * address and control fields are absent and the frame begins
         * with a protocol field.  If we ever see a BSD/OS PPP
         * capture, we'll have to handle it differently, and we may
         * have to handle standard BSD captures differently if, in fact,
         * they don't have 0xff 0x03 as the first two bytes - but, as per
         * the two paragraphs preceding this, it's not clear that
         * the address field *is* munged into an incoming/outgoing
         * field when the packet is handed to the BPF device.
         *
         * For now, we just map DLT_PPP_SERIAL to WTAP_ENCAP_PPP, as
         * we treat WTAP_ENCAP_PPP packets as if those beginning with
         * 0xff have the standard RFC 1662 "PPP in HDLC-like Framing"
         * 0xff 0x03 address/control header, and DLT_PPP_SERIAL frames
         * appear to contain that unless they're Cisco frames (if we
         * ever see a capture with them, we'd need to implement the
         * RFC 1547 stuff, and the keepalive protocol stuff).
         *
         * We may have to distinguish between "PPP where if it doesn't
         * begin with 0xff there's no HDLC encapsulation and the frame
         * begins with the protocol field" (which is how we handle
         * WTAP_ENCAP_PPP now) and "PPP where there's either HDLC
         * encapsulation or Cisco PPP" (which is what DLT_PPP_SERIAL
         * is) at some point.
         *
         * XXX - NetBSD has DLT_HDLC, which appears to be used for
         * Cisco HDLC.  Ideally, they should use DLT_PPP_SERIAL
         * only for real live HDLC-encapsulated PPP, not for Cisco
         * HDLC.
         */
        { 50,           WTAP_ENCAP_PPP },

        /*
         * These are the values that libpcap 0.5 and later use in
         * capture file headers, in an attempt to work around the
         * confusion decried above, and that Wiretap and Ethereal
         * currently support.
         */
        { 100,          WTAP_ENCAP_ATM_RFC1483 },
        { 101,          WTAP_ENCAP_RAW_IP },
#if 0
        /*
         * More values used by libpcap 0.5 as DLT_ values and used by the
         * current CVS version of libpcap in capture file headers.
         * They are not yet handled in Ethereal.
         * If we get a capture that contains them, we'll implement them.
         */
        { 102,          WTAP_ENCAP_SLIP_BSDOS },
        { 103,          WTAP_ENCAP_PPP_BSDOS },
#endif

        /*
         * These ones are handled in Ethereal, though.
         */
        { 104,          WTAP_ENCAP_CHDLC },     /* Cisco HDLC */
        { 105,          WTAP_ENCAP_IEEE_802_11 }, /* IEEE 802.11 */
        { 106,          WTAP_ENCAP_LINUX_ATM_CLIP },
        { 107,          WTAP_ENCAP_FRELAY },    /* Frame Relay */
        { 108,          WTAP_ENCAP_NULL },      /* OpenBSD loopback */
#if 0
        { 109,          WTAP_ENCAP_ENC },       /* OpenBSD IPSEC enc */
        { 110,          WTAP_ENCAP_LANE_802_3 },/* ATM LANE 802.3 */
        { 111,          WTAP_ENCAP_HIPPI },     /* NetBSD HIPPI */
#endif
        { 112,          WTAP_ENCAP_CHDLC },     /* NetBSD HDLC framing */

        /*
         * Linux "cooked mode" captures, used by the current CVS version
         * of libpcap.
         */
        { 113,          WTAP_ENCAP_SLL },       /* Linux cooked capture */

        { 114,          WTAP_ENCAP_LOCALTALK }, /* Localtalk */

        /*
         * The tcpdump.org version of libpcap uses 117, rather than 17,
         * for OpenBSD packet filter logging, so as to avoid conflicting
         * with DLT_LANE8023 in SuSE 6.3 libpcap.
         */
        { 117,          WTAP_ENCAP_PFLOG },

        { 118,          WTAP_ENCAP_CISCO_IOS },
        { 119,          WTAP_ENCAP_PRISM_HEADER }, /* Prism monitor mode hdr */
        { 121,          WTAP_ENCAP_HHDLC },     /* HiPath HDLC */
        { 123,          WTAP_ENCAP_ATM_SNIFFER }, /* SunATM */

        /*
         * The following are entries for libpcap type values that have
         * different meanings on different OSes.
         *
         * We put these *after* the entries for the platform-independent
         * libpcap type values for those Wiretap encapsulation types, so
         * that Ethereal chooses the platform-independent libpcap type
         * value for those encapsulatioin types, not the platform-dependent
         * one.
         */

        /*
         * 11 is DLT_ATM_RFC1483 on most platforms; the only libpcaps I've
         * seen that define anything other than DLT_ATM_RFC1483 as 11 are
         * the BSD/OS one, which defines DLT_FR as 11, and libpcap 0.5,
         * which define it as 100, mapping the kernel's value to 100, in
         * an attempt to hide the different values used on different
         * platforms.
         *
         * If this is a platform where DLT_FR is defined as 11, we
         * don't handle 11 at all; otherwise, we handle it as
         * DLT_ATM_RFC1483 (this means we'd misinterpret Frame Relay
         * captures from BSD/OS if running on platforms other than BSD/OS,
         * but
         *
         *      1) we don't yet support DLT_FR
         *
         * and
         *
         *      2) nothing short of a heuristic would let us interpret
         *         them correctly).
         */
#if defined(DLT_FR) && (DLT_FR == 11)
        { 11,           WTAP_ENCAP_FRELAY },
#else
        { 11,           WTAP_ENCAP_ATM_RFC1483 },
#endif

        /*
         * 12 is DLT_RAW on most platforms, but it's DLT_C_HDLC on
         * BSD/OS, and DLT_LOOP on OpenBSD.
         *
         * We don't yet handle DLT_C_HDLC, but we can handle DLT_LOOP
         * (it's just like DLT_NULL, only with the AF_ value in network
         * rather than host byte order - Ethereal figures out the
         * byte order from the data, so we don't care what byte order
         * it's in), so if DLT_LOOP is defined as 12, interpret 12
         * as WTAP_ENCAP_NULL, otherwise, unless DLT_C_HDLC is defined
         * as 12, interpret it as WTAP_ENCAP_RAW_IP.
         */
#if defined(DLT_LOOP) && (DLT_LOOP == 12)
        { 12,           WTAP_ENCAP_NULL },
#elif defined(DLT_C_HDLC) && (DLT_C_HDLC == 12)
        /*
         * Put entry for Cisco HDLC here.
         * XXX - is this just WTAP_ENCAP_CHDLC, i.e. does the frame
         * start with a 4-byte Cisco HDLC header?
         */
#else
        { 12,           WTAP_ENCAP_RAW_IP },
#endif

        /*
         * 13 is DLT_SLIP_BSDOS on FreeBSD and NetBSD, but those OSes
         * don't actually generate it.  I infer that BSD/OS translates
         * DLT_SLIP from the kernel BPF code to DLT_SLIP_BSDOS in
         * libpcap, as the BSD/OS link-layer header is different;
         * however, in BSD/OS, DLT_SLIP_BSDOS is 15.
         *
         * From this, I infer that there's no point in handling 13
         * as DLT_SLIP_BSDOS.
         *
         * 13 is DLT_ATM_RFC1483 on BSD/OS.
         *
         * 13 is DLT_ENC in OpenBSD, which is, I suspect, some kind
         * of decrypted IPSEC traffic.
         */
#if defined(DLT_ATM_RFC1483) && (DLT_ATM_RFC1483 == 13)
        { 13,           WTAP_ENCAP_ATM_RFC1483 },
#elif defined(DLT_ENC) && (DLT_ENC == 13)
        /* Put entry for DLT_ENC here */
#endif

        /*
         * 14 is DLT_PPP_BSDOS on FreeBSD and NetBSD, but those OSes
         * don't actually generate it.  I infer that BSD/OS translates
         * DLT_PPP from the kernel BPF code to DLT_PPP_BSDOS in
         * libpcap, as the BSD/OS link-layer header is different;
         * however, in BSD/OS, DLT_PPP_BSDOS is 16.
         *
         * From this, I infer that there's no point in handling 14
         * as DLT_PPP_BSDOS.
         *
         * 14 is DLT_RAW on BSD/OS and OpenBSD.
         */
        { 14,           WTAP_ENCAP_RAW_IP },

        /*
         * 15 is:
         *
         *      DLT_SLIP_BSDOS on BSD/OS;
         *
         *      DLT_HIPPI on NetBSD;
         *
         *      DLT_LANE8023 with Alexey Kuznetzov's patches for
         *      Linux libpcap;
         *
         *      DLT_I4L_RAWIP with the ISDN4Linux patches for libpcap
         *      (and on SuSE 6.3);
         *
         * but we don't currently handle any of those.
         */

        /*
         * 16 is:
         *
         *      DLT_PPP_BSDOS on BSD/OS;
         *
         *      DLT_HDLC on NetBSD (Cisco HDLC);
         *
         *      DLT_CIP with Alexey Kuznetzov's patches for
         *      Linux libpcap - this is WTAP_ENCAP_LINUX_ATM_CLIP;
         *
         *      DLT_I4L_IP with the ISDN4Linux patches for libpcap
         *      (and on SuSE 6.3).
         */
#if defined(DLT_CIP) && (DLT_CIP == 16)
        { 16,           WTAP_ENCAP_LINUX_ATM_CLIP },
#endif
#if defined(DLT_HDLC) && (DLT_HDLC == 16)
        { 16,           WTAP_ENCAP_CHDLC },
#endif

        /*
         * 17 is DLT_LANE8023 in SuSE 6.3 libpcap; we don't currently
         * handle it.
         * It is also used as the PF (Packet Filter) logging format beginning
         * with OpenBSD 3.0; we use 17 for PF logs unless DLT_LANE8023 is
         * defined with the value 17.
         */
#if !defined(DLT_LANE8023) || (DLT_LANE8023 != 17)
        { 17,           WTAP_ENCAP_PFLOG },
#endif

        /*
         * 18 is DLT_CIP in SuSE 6.3 libpcap; if it's the same as the
         * DLT_CIP of 16 that the Alexey Kuznetzov patches for
         * libpcap/tcpdump define, it's WTAP_ENCAP_LINUX_ATM_CLIP.
         * I've not found any libpcap that uses it for any other purpose -
         * hopefully nobody will do so in the future.
         */
        { 18,           WTAP_ENCAP_LINUX_ATM_CLIP },

        /*
         * 19 is DLT_ATM_CLIP in the libpcap/tcpdump patches in the
         * recent versions I've seen of the Linux ATM distribution;
         * I've not yet found any libpcap that uses it for any other
         * purpose - hopefully nobody will do so in the future.
         */
        { 19,           WTAP_ENCAP_LINUX_ATM_CLIP },
};
#define NUM_PCAP_ENCAPS (sizeof pcap_to_wtap_map / sizeof pcap_to_wtap_map[0])

int wtap_pcap_encap_to_wtap_encap(int encap)
{
        unsigned int i;

        for (i = 0; i < NUM_PCAP_ENCAPS; i++) {
                if (pcap_to_wtap_map[i].dlt_value == encap)
                        return pcap_to_wtap_map[i].wtap_encap_value;
        }
        return WTAP_ENCAP_UNKNOWN;
}


int libpcap_open(wtap *wth, int *err)
{
        int bytes_read;
        guint32 magic;
        struct pcap_hdr hdr;
        gboolean byte_swapped;
        gboolean modified;
        gboolean aix;
        int file_encap;

        /* Read in the number that should be at the start of a "libpcap" file */
        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, and was running
                   a program using either standard or ss990417 libpcap. */
                byte_swapped = FALSE;
                modified = FALSE;
                break;

        case PCAP_MODIFIED_MAGIC:
                /* Host that wrote it has our byte order, and was running
                   a program using either ss990915 or ss991029 libpcap. */
                byte_swapped = FALSE;
                modified = TRUE;
                break;

        case PCAP_SWAPPED_MAGIC:
                /* Host that wrote it has a byte order opposite to ours,
                   and was running a program using either standard or
                   ss990417 libpcap. */
                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 either ss990915
                   or ss991029 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;
        }

        /*
         * AIX's non-standard tcpdump uses a minor version number of 2.
         * Unfortunately, older versions of libpcap might have used
         * that as well.
         *
         * The AIX libpcap uses RFC 1573 ifType values rather than
         * DLT_ values in the header; the ifType values for LAN devices
         * are:
         *
         *      Ethernet        6
         *      Token Ring      9
         *      FDDI            15
         *
         * which correspond to DLT_IEEE802 (used for Token Ring),
         * DLT_PPP, and DLT_SLIP_BSDOS, respectively.  We shall
         * assume that if the minor version number is 2, and
         * the network type is 6, 9, or 15, that it's AIX libpcap.
         *
         * I'm assuming those older versions of libpcap didn't
         * use DLT_IEEE802 for Token Ring, and didn't use DLT_SLIP_BSDOS
         * as that came later.  It may have used DLT_PPP, however, in
         * which case we're out of luck; we assume it's Token Ring
         * in AIX libpcap rather than PPP in standard libpcap, as
         * you're probably more likely to be handing an AIX libpcap
         * token-ring capture than an old (pre-libpcap 0.4) PPP capture
         * to Ethereal.
         */
        aix = FALSE;    /* assume it's not AIX */
        if (hdr.version_major == 2 && hdr.version_minor == 2) {
                switch (hdr.network) {

                case 6:
                        hdr.network = 1;        /* DLT_EN10MB, Ethernet */
                        aix = TRUE;
                        break;

                case 9:
                        hdr.network = 6;        /* DLT_IEEE802, Token Ring */
                        aix = TRUE;
                        break;

                case 15:
                        hdr.network = 10;       /* DLT_FDDI, FDDI */
                        aix = TRUE;
                        break;
                }
        }
        file_encap = wtap_pcap_encap_to_wtap_encap(hdr.network);
        if (file_encap == WTAP_ENCAP_UNKNOWN) {
                g_message("pcap: network type %u unknown or unsupported",
                    hdr.network);
                *err = WTAP_ERR_UNSUPPORTED_ENCAP;
                return -1;
        }

        /* This is a libpcap file */
        wth->capture.pcap = g_malloc(sizeof(libpcap_t));
        wth->capture.pcap->byte_swapped = byte_swapped;
        wth->capture.pcap->version_major = hdr.version_major;
        wth->capture.pcap->version_minor = hdr.version_minor;
        wth->subtype_read = libpcap_read;
        wth->subtype_seek_read = libpcap_seek_read;
        wth->subtype_close = libpcap_close;
        wth->file_encap = file_encap;
        wth->snapshot_length = hdr.snaplen;

        /*
         * Is this AIX format?
         */
        if (aix) {
                /*
                 * Yes.  Skip all the tests for other mutant formats.
                 */
                wth->file_type = WTAP_FILE_PCAP_AIX;
                return 1;
        }

        /*
         * No.  Let's look at the header for the first record,
         * and see if, interpreting it as a standard header (if the
         * magic number was standard) or a modified header (if the
         * magic number was modified), the position where it says the
         * header for the *second* record is contains a corrupted header.
         *
         * If so, then:
         *
         *      If this file had the standard magic number, it may be
         *      an ss990417 capture file - in that version of Alexey's
         *      patch, the packet header format was changed but the
         *      magic number wasn't, and, alas, Red Hat appear to have
         *      picked up that version of the patch 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).
         *
         *      If this file had the modified magic number, it may be
         *      an ss990915 capture file - in that version of Alexey's
         *      patch, the magic number was changed, but the record
         *      header had some extra fields, and, alas, SuSE appear
         *      to have picked up that version of the patch for SuSE
         *      6.3, meaning that programs expecting the standard per-
         *      packet header in captures with the modified magic number
         *      can't read dumps from its tcpdump.
         *
         * Oh, and if it has the standard magic number, it might, instead,
         * be a Nokia libpcap file, so we may need to try that if
         * neither normal nor ss990417 headers work.
         */
        if (modified) {
                /*
                 * Well, we have the magic number from Alexey's
                 * later two patches.
                 *
                 * Try ss991029, the last of his patches, first.
                 */
                wth->file_type = WTAP_FILE_PCAP_SS991029;
                switch (libpcap_try(wth, err)) {

                case BAD_READ:
                        /*
                         * Well, we couldn't even read it.
                         * Give up.
                         */
                        g_free(wth->capture.pcap);
                        return -1;

                case THIS_FORMAT:
                        /*
                         * Well, it looks as if it might be 991029.
                         * Put the seek pointer back, and return success.
                         */
                        if (file_seek(wth->fh, wth->data_offset, SEEK_SET, err) == -1) {
                                g_free(wth->capture.pcap);
                                return -1;
                        }
                        return 1;

                case OTHER_FORMAT:
                        /*
                         * Try the next format.
                         */
                        break;
                }

                /*
                 * Well, it's not completely unreadable,
                 * but it's not ss991029.  Try ss990915;
                 * there are no other types to try after that,
                 * so we put the seek pointer back and treat
                 * it as 990915.
                 */
                wth->file_type = WTAP_FILE_PCAP_SS990915;
                if (file_seek(wth->fh, wth->data_offset, SEEK_SET, err) == -1) {
                        g_free(wth->capture.pcap);
                        return -1;
                }
        } else {
                /*
                 * Well, we have the standard magic number.
                 *
                 * Try the standard format first.
                 */
                wth->file_type = WTAP_FILE_PCAP;
                switch (libpcap_try(wth, err)) {

                case BAD_READ:
                        /*
                         * Well, we couldn't even read it.
                         * Give up.
                         */
                        g_free(wth->capture.pcap);
                        return -1;

                case THIS_FORMAT:
                        /*
                         * Well, it looks as if it might be a standard
                         * libpcap file.
                         * Put the seek pointer back, and return success.
                         */
                        if (file_seek(wth->fh, wth->data_offset, SEEK_SET, err) == -1) {
                                g_free(wth->capture.pcap);
                                return -1;
                        }
                        return 1;

                case OTHER_FORMAT:
                        /*
                         * Try the next format.
                         */
                        break;
                }

                /*
                 * Well, it's not completely unreadable, but it's not
                 * a standard file.  Put the seek pointer back and try
                 * ss990417.
                 */
                wth->file_type = WTAP_FILE_PCAP_SS990417;
                if (file_seek(wth->fh, wth->data_offset, SEEK_SET, err) == -1) {
                        g_free(wth->capture.pcap);
                        return -1;
                }
                switch (libpcap_try(wth, err)) {

                case BAD_READ:
                        /*
                         * Well, we couldn't even read it.
                         * Give up.
                         */
                        g_free(wth->capture.pcap);
                        return -1;

                case THIS_FORMAT:
                        /*
                         * Well, it looks as if it might be ss990417.
                         * Put the seek pointer back, and return success.
                         */
                        if (file_seek(wth->fh, wth->data_offset, SEEK_SET, err) == -1) {
                                g_free(wth->capture.pcap);
                                return -1;
                        }
                        return 1;

                case OTHER_FORMAT:
                        /*
                         * Try the next format.
                         */
                        break;
                }

                /*
                 * Well, it's not completely unreadable,
                 * but it's not a standard file *nor* is it ss990417.
                 * Try it as a Nokia file; there are no other types
                 * to try after that, so we put the seek pointer back
                 * and treat it as a Nokia file.
                 */
                wth->file_type = WTAP_FILE_PCAP_NOKIA;
                if (file_seek(wth->fh, wth->data_offset, SEEK_SET, err) == -1) {
                        g_free(wth->capture.pcap);
                        return -1;
                }
        }

        return 1;
}

/* Try to read the first two records of the capture file. */
static libpcap_try_t libpcap_try(wtap *wth, int *err)
{
        /*
         * pcaprec_ss990915_hdr is the largest header type.
         */
        struct pcaprec_ss990915_hdr first_rec_hdr, second_rec_hdr;

        /*
         * Attempt to read the first record's header.
         */
        if (libpcap_read_header(wth, err, &first_rec_hdr, TRUE) == -1) {
                if (*err == 0 || *err == WTAP_ERR_SHORT_READ) {
                        /*
                         * EOF or short read - assume the file is in this
                         * format.
                         * When our client tries to read the first packet
                         * they will presumably get the same EOF or short
                         * read.
                         */
                        return THIS_FORMAT;
                }

                if (*err == WTAP_ERR_BAD_RECORD) {
                        /*
                         * The first record is bogus, so this is probably
                         * a corrupt file.  Assume the file is in this
                         * format.  When our client tries to read the
                         * first packet they will presumably get the
                         * same bogus record.
                         */
                        return THIS_FORMAT;
                }

                /*
                 * Some other error, e.g. an I/O error; just give up.
                 */
                return BAD_READ;
        }

        /*
         * Now skip over the first record's data, under the assumption
         * that the header is sane.
         */
        if (file_seek(wth->fh, first_rec_hdr.hdr.incl_len, SEEK_CUR, err) == -1)
                return BAD_READ;

        /*
         * Now attempt to read the second record's header.
         */
        if (libpcap_read_header(wth, err, &second_rec_hdr, TRUE) == -1) {
                if (*err == 0 || *err == WTAP_ERR_SHORT_READ) {
                        /*
                         * EOF or short read - assume the file is in this
                         * format.
                         * When our client tries to read the second packet
                         * they will presumably get the same EOF or short
                         * read.
                         */
                        return THIS_FORMAT;
                }

                if (*err == WTAP_ERR_BAD_RECORD) {
                        /*
                         * The second record is bogus; 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 the next format; if we run out of formats,
                         * it probably *is* a corrupt file.
                         */
                        return OTHER_FORMAT;
                }

                /*
                 * Some other error, e.g. an I/O error; just give up.
                 */
                return BAD_READ;
        }

        /*
         * OK, the first two records look OK; assume this is the
         * right format.
         */
        return THIS_FORMAT;
}

/* Read the next packet */
static gboolean libpcap_read(wtap *wth, int *err, long *data_offset)
{
        struct pcaprec_ss990915_hdr hdr;
        guint packet_size;
        guint orig_size;
        int bytes_read;

        bytes_read = libpcap_read_header(wth, err, &hdr, FALSE);
        if (bytes_read == -1) {
                /*
                 * We failed to read the header.
                 */
                return FALSE;
        }

        wth->data_offset += bytes_read;
        packet_size = hdr.hdr.incl_len;
        orig_size = hdr.hdr.orig_len;

        *data_offset = wth->data_offset;

        /*
         * If this is an ATM packet, the first four bytes are the
         * direction of the packet (transmit/receive), the VPI, and
         * the VCI; read them and generate the pseudo-header from
         * them.
         */
        if (wth->file_encap == WTAP_ENCAP_ATM_SNIFFER) {
                if (packet_size < sizeof (struct sunatm_hdr)) {
                        /*
                         * Uh-oh, the packet isn't big enough to even
                         * have a pseudo-header.
                         */
                        g_message("libpcap: SunATM file has a %u-byte packet, too small to have even an ATM pseudo-header\n",
                            packet_size);
                        *err = WTAP_ERR_BAD_RECORD;
                        return FALSE;
                }
                if (!libpcap_read_atm_pseudoheader(wth->fh, &wth->pseudo_header,
                    err))
                        return FALSE;   /* Read error */

                /*
                 * Don't count the pseudo-header as part of the packet.
                 */
                orig_size -= sizeof (struct sunatm_hdr);
                packet_size -= sizeof (struct sunatm_hdr);
                wth->data_offset += sizeof (struct sunatm_hdr);
        }

        buffer_assure_space(wth->frame_buffer, packet_size);
        if (!libpcap_read_rec_data(wth->fh, buffer_start_ptr(wth->frame_buffer),
            packet_size, err))
                return FALSE;   /* Read error */
        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 = orig_size;
        wth->phdr.pkt_encap = wth->file_encap;

        /*
         * If this is ATM LANE traffic, try to guess what type of LANE
         * traffic it is based on the packet contents.
         */
        if (wth->file_encap == WTAP_ENCAP_ATM_SNIFFER &&
            wth->pseudo_header.atm.type == TRAF_LANE) {
                atm_guess_lane_type(buffer_start_ptr(wth->frame_buffer),
                    wth->phdr.caplen, &wth->pseudo_header);
        }

        return TRUE;
}

static gboolean
libpcap_seek_read(wtap *wth, long seek_off,
    union wtap_pseudo_header *pseudo_header, guchar *pd, int length, int *err)
{
        if (file_seek(wth->random_fh, seek_off, SEEK_SET, err) == -1)
                return FALSE;

        if (wth->file_encap == WTAP_ENCAP_ATM_SNIFFER) {
                if (!libpcap_read_atm_pseudoheader(wth->random_fh, pseudo_header,
                    err)) {
                        /* Read error */
                        return FALSE;
                }
        }

        /*
         * Read the packet data.
         */
        if (!libpcap_read_rec_data(wth->random_fh, pd, length, err))
                return FALSE;   /* failed */

        /*
         * If this is ATM LANE traffic, try to guess what type of LANE
         * traffic it is based on the packet contents.
         */
        if (wth->file_encap == WTAP_ENCAP_ATM_SNIFFER &&
            pseudo_header->atm.type == TRAF_LANE)
                atm_guess_lane_type(pd, length, pseudo_header);
        return TRUE;
}

/* Read the header of the next packet; if "silent" is TRUE, don't complain
   to the console, as we're testing to see if the file appears to be of a
   particular type.

   Return -1 on an error, or the number of bytes of header read on success. */
static int libpcap_read_header(wtap *wth, int *err,
    struct pcaprec_ss990915_hdr *hdr, gboolean silent)
{
        int     bytes_to_read, bytes_read;

        /* Read record header. */
        errno = WTAP_ERR_CANT_READ;
        switch (wth->file_type) {

        case WTAP_FILE_PCAP:
        case WTAP_FILE_PCAP_AIX:
                bytes_to_read = sizeof (struct pcaprec_hdr);
                break;

        case WTAP_FILE_PCAP_SS990417:
        case WTAP_FILE_PCAP_SS991029:
                bytes_to_read = sizeof (struct pcaprec_modified_hdr);
                break;

        case WTAP_FILE_PCAP_SS990915:
                bytes_to_read = sizeof (struct pcaprec_ss990915_hdr);
                break;

        case WTAP_FILE_PCAP_NOKIA:
                bytes_to_read = sizeof (struct pcaprec_nokia_hdr);
                break;

        default:
                g_assert_not_reached();
                bytes_to_read = 0;
        }
        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 && bytes_read != 0) {
                        *err = WTAP_ERR_SHORT_READ;
                }
                return -1;
        }

        adjust_header(wth, &hdr->hdr);

        if (hdr->hdr.incl_len > WTAP_MAX_PACKET_SIZE) {
                /*
                 * Probably a corrupt capture file; return an error,
                 * so that our caller doesn't blow up trying to allocate
                 * space for an immensely-large packet, and so that
                 * the code to try to guess what type of libpcap file
                 * this is can tell when it's not the type we're guessing
                 * it is.
                 */
                if (!silent) {
                        g_message("pcap: File has %u-byte packet, bigger than maximum of %u",
                            hdr->hdr.incl_len, WTAP_MAX_PACKET_SIZE);
                }
                *err = WTAP_ERR_BAD_RECORD;
                return -1;
        }

        if (hdr->hdr.orig_len > WTAP_MAX_PACKET_SIZE) {
                /*
                 * Probably a corrupt capture file; return an error,
                 * so that our caller doesn't blow up trying to
                 * cope with a huge "real" packet length, and so that
                 * the code to try to guess what type of libpcap file
                 * this is can tell when it's not the type we're guessing
                 * it is.
                 */
                if (!silent) {
                        g_message("pcap: File has %u-byte packet, bigger than maximum of %u",
                            hdr->hdr.orig_len, WTAP_MAX_PACKET_SIZE);
                }
                *err = WTAP_ERR_BAD_RECORD;
                return -1;
        }

        return bytes_read;
}

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);
        }

        /* If this is AIX, convert the time stamp from seconds/nanoseconds
           to seconds/microseconds.  */
        if (wth->file_type == WTAP_FILE_PCAP_AIX)
                hdr->ts_usec = hdr->ts_usec/1000;

        /* 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;
        }
}

static void
libpcap_get_atm_pseudoheader(const struct sunatm_hdr *atm_phdr,
    union wtap_pseudo_header *pseudo_header)
{
        guint8  vpi;
        guint16 vci;

        vpi = atm_phdr->vpi;
        vci = pntohs(&atm_phdr->vci);

        /*
         * The lower 4 bits of the first byte of the header indicate
         * the type of traffic, as per the "atmioctl.h" header in
         * SunATM.
         */
        switch (atm_phdr->flags & 0x0F) {

        case 0x01:      /* LANE */
                pseudo_header->atm.aal = AAL_5;
                pseudo_header->atm.type = TRAF_LANE;
                break;

        case 0x02:      /* RFC 1483 LLC multiplexed traffic */
                pseudo_header->atm.aal = AAL_5;
                pseudo_header->atm.type = TRAF_LLCMX;
                break;

        case 0x05:      /* ILMI */
                pseudo_header->atm.aal = AAL_5;
                pseudo_header->atm.type = TRAF_ILMI;
                break;

        case 0x06:      /* Q.2931 */
                pseudo_header->atm.aal = AAL_SIGNALLING;
                pseudo_header->atm.type = TRAF_UNKNOWN;
                break;

        case 0x03:      /* MARS (RFC 2022) */
                pseudo_header->atm.aal = AAL_5;
                pseudo_header->atm.type = TRAF_UNKNOWN;
                break;

        case 0x04:      /* IFMP (Ipsilon Flow Management Protocol; see RFC 1954) */
                pseudo_header->atm.aal = AAL_5;
                pseudo_header->atm.type = TRAF_UNKNOWN; /* XXX - TRAF_IPSILON? */
                break;

        default:
                /*
                 * Assume it's AAL5, unless it's VPI 0 and VCI 5, in which
                 * case assume it's AAL_SIGNALLING; we know nothing more
                 * about it.
                 *
                 * XXX - is this necessary?  Or are we guaranteed that
                 * all signalling traffic has a type of 0x06?
                 *
                 * XXX - is this guaranteed to be AAL5?  Or, if the type is
                 * 0x00 ("raw"), might it be non-AAL5 traffic?
                 */
                if (vpi == 0 && vci == 5)
                        pseudo_header->atm.aal = AAL_SIGNALLING;
                else
                        pseudo_header->atm.aal = AAL_5;
                pseudo_header->atm.type = TRAF_UNKNOWN;
                break;
        }
        pseudo_header->atm.subtype = TRAF_ST_UNKNOWN;

        pseudo_header->atm.vpi = vpi;
        pseudo_header->atm.vci = vci;
        pseudo_header->atm.channel = (atm_phdr->flags & 0x80) ? 1 : 0;

        /* We don't have this information */
        pseudo_header->atm.cells = 0;
        pseudo_header->atm.aal5t_u2u = 0;
        pseudo_header->atm.aal5t_len = 0;
        pseudo_header->atm.aal5t_chksum = 0;
}

static gboolean
libpcap_read_atm_pseudoheader(FILE_T fh, union wtap_pseudo_header *pseudo_header,
    int *err)
{
        struct sunatm_hdr atm_phdr;
        int     bytes_read;

        errno = WTAP_ERR_CANT_READ;
        bytes_read = file_read(&atm_phdr, 1, sizeof (struct sunatm_hdr), fh);
        if (bytes_read != sizeof (struct sunatm_hdr)) {
                *err = file_error(fh);
                if (*err == 0)
                        *err = WTAP_ERR_SHORT_READ;
                return FALSE;
        }

        libpcap_get_atm_pseudoheader(&atm_phdr, pseudo_header);

        return TRUE;
}

static gboolean
libpcap_read_rec_data(FILE_T fh, guchar *pd, int length, int *err)
{
        int     bytes_read;

        errno = WTAP_ERR_CANT_READ;
        bytes_read = file_read(pd, 1, length, fh);

        if (bytes_read != length) {
                *err = file_error(fh);
                if (*err == 0)
                        *err = WTAP_ERR_SHORT_READ;
                return FALSE;
        }
        return TRUE;
}

static void
libpcap_close(wtap *wth)
{
        g_free(wth->capture.pcap);
}

static int wtap_wtap_encap_to_pcap_encap(int encap)
{
        unsigned int i;

        /*
         * Special-case WTAP_ENCAP_FDDI and WTAP_ENCAP_FDDI_BITSWAPPED;
         * both of them get mapped to DLT_FDDI (even though that may
         * mean that the bit order in the FDDI MAC addresses is wrong;
         * so it goes - libpcap format doesn't record the byte order,
         * so that's not fixable).
         */
        if (encap == WTAP_ENCAP_FDDI || encap == WTAP_ENCAP_FDDI_BITSWAPPED)
                return 10;      /* that's DLT_FDDI */
        for (i = 0; i < NUM_PCAP_ENCAPS; i++) {
                if (pcap_to_wtap_map[i].wtap_encap_value == encap)
                        return pcap_to_wtap_map[i].dlt_value;
        }
        return -1;
}

#ifdef HAVE_PCAP_H
/*
 * Given a Wiretap encapsulation type, and raw packet data and the packet
 * header from libpcap, process any pseudo-header in the packet,
 * fill in the Wiretap packet header, and return a pointer to the
 * beginning of the non-pseudo-header data in the packet.
 */
const guchar *
wtap_process_pcap_packet(gint linktype, const struct pcap_pkthdr *phdr,
    const guchar *pd, union wtap_pseudo_header *pseudo_header,
    struct wtap_pkthdr *whdr, int *err)
{
        /* "phdr->ts" may not necessarily be a "struct timeval" - it may
           be a "struct bpf_timeval", with member sizes wired to 32
           bits - and we may go that way ourselves in the future, so
           copy the members individually. */
        whdr->ts.tv_sec = phdr->ts.tv_sec;
        whdr->ts.tv_usec = phdr->ts.tv_usec;
        whdr->caplen = phdr->caplen;
        whdr->len = phdr->len;
        whdr->pkt_encap = linktype;

        /*
         * If this is an ATM packet, the first four bytes are the
         * direction of the packet (transmit/receive), the VPI, and
         * the VCI; read them and generate the pseudo-header from
         * them.
         */
        if (linktype == WTAP_ENCAP_ATM_SNIFFER) {
                if (whdr->caplen < sizeof (struct sunatm_hdr)) {
                        /*
                         * Uh-oh, the packet isn't big enough to even
                         * have a pseudo-header.
                         */
                        g_message("libpcap: SunATM capture has a %u-byte packet, too small to have even an ATM pseudo-header\n",
                            whdr->caplen);
                        *err = WTAP_ERR_BAD_RECORD;
                        return NULL;
                }
                libpcap_get_atm_pseudoheader((struct sunatm_hdr *)pd,
                    pseudo_header);

                /*
                 * Don't count the pseudo-header as part of the packet.
                 */
                whdr->len -= sizeof (struct sunatm_hdr);
                whdr->caplen -= sizeof (struct sunatm_hdr);
                pd += sizeof (struct sunatm_hdr);

                /*
                 * If this is ATM LANE traffic, try to guess what type of
                 * LANE traffic it is based on the packet contents.
                 */
                if (pseudo_header->atm.type == TRAF_LANE)
                        atm_guess_lane_type(pd, whdr->caplen, pseudo_header);
        }
        return pd;
}
#endif

/* Returns 0 if we could write the specified encapsulation type,
   an error indication otherwise. */
int libpcap_dump_can_write_encap(int encap)
{
        /* Per-packet encapsulations aren't supported. */
        if (encap == WTAP_ENCAP_PER_PACKET)
                return WTAP_ERR_ENCAP_PER_PACKET_UNSUPPORTED;

        if (wtap_wtap_encap_to_pcap_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, gboolean cant_seek _U_, int *err)
{
        guint32 magic;
        struct pcap_hdr file_hdr;
        size_t nwritten;

        /* This is a libpcap file */
        wdh->subtype_write = libpcap_dump;
        wdh->subtype_close = NULL;

        /* Write the file header. */
        switch (wdh->file_type) {

        case WTAP_FILE_PCAP:
        case WTAP_FILE_PCAP_SS990417:   /* modified, but with the old magic, sigh */
        case WTAP_FILE_PCAP_NOKIA:      /* Nokia libpcap of some sort */
                magic = PCAP_MAGIC;
                break;

        case WTAP_FILE_PCAP_SS990915:   /* new magic, extra crap */
        case WTAP_FILE_PCAP_SS991029:
                magic = PCAP_MODIFIED_MAGIC;
                break;

        default:
                /* We should never get here - our open routine
                   should only get called for the types above. */
                *err = WTAP_ERR_UNSUPPORTED_FILE_TYPE;
                return FALSE;
        }

        nwritten = fwrite(&magic, 1, sizeof magic, wdh->fh);
        if (nwritten != sizeof magic) {
                if (nwritten == 0 && ferror(wdh->fh))
                        *err = errno;
                else
                        *err = WTAP_ERR_SHORT_WRITE;
                return FALSE;
        }
        wdh->bytes_dumped += sizeof magic;

        /* 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 */
        /*
         * Tcpdump cannot handle capture files with a snapshot length of 0,
         * as BPF filters return either 0 if they fail or the snapshot length
         * if they succeed, and a snapshot length of 0 means success is
         * indistinguishable from failure and the filter expression would
         * reject all packets.
         *
         * A snapshot length of 0, inside Wiretap, means "snapshot length
         * unknown"; if the snapshot length supplied to us is 0, we make
         * the snapshot length in the header file WTAP_MAX_PACKET_SIZE.
         */
        file_hdr.snaplen = (wdh->snaplen != 0) ? wdh->snaplen :
                                                 WTAP_MAX_PACKET_SIZE;
        file_hdr.network = wtap_wtap_encap_to_pcap_encap(wdh->encap);
        nwritten = fwrite(&file_hdr, 1, sizeof file_hdr, wdh->fh);
        if (nwritten != sizeof file_hdr) {
                if (nwritten == 0 && ferror(wdh->fh))
                        *err = errno;
                else
                        *err = WTAP_ERR_SHORT_WRITE;
                return FALSE;
        }
        wdh->bytes_dumped += sizeof file_hdr;

        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 union wtap_pseudo_header *pseudo_header _U_,
        const guchar *pd, int *err)
{
        struct pcaprec_ss990915_hdr rec_hdr;
        size_t hdr_size;
        size_t nwritten;
        struct sunatm_hdr atm_hdr;
        int atm_hdrsize;

        if (wdh->encap == WTAP_ENCAP_ATM_SNIFFER)
                atm_hdrsize = sizeof (struct sunatm_hdr);
        else
                atm_hdrsize = 0;

        rec_hdr.hdr.ts_sec = phdr->ts.tv_sec;
        rec_hdr.hdr.ts_usec = phdr->ts.tv_usec;
        rec_hdr.hdr.incl_len = phdr->caplen + atm_hdrsize;
        rec_hdr.hdr.orig_len = phdr->len + atm_hdrsize;
        switch (wdh->file_type) {

        case WTAP_FILE_PCAP:
                hdr_size = sizeof (struct pcaprec_hdr);
                break;

        case WTAP_FILE_PCAP_SS990417:   /* modified, but with the old magic, sigh */
        case WTAP_FILE_PCAP_SS991029:
                /* XXX - what should we supply here?

                   Alexey's "libpcap" looks up the interface in the system's
                   interface list if "ifindex" is non-zero, and prints
                   the interface name.  It ignores "protocol", and uses
                   "pkt_type" to tag the packet as "host", "broadcast",
                   "multicast", "other host", "outgoing", or "none of the
                   above", but that's it.

                   If the capture we're writing isn't a modified or
                   RH 6.1 capture, we'd have to do some work to
                   generate the packet type and interface index - and
                   we can't generate the interface index unless we
                   just did the capture ourselves in any case.

                   I'm inclined to continue to punt; systems other than
                   those with the older patch can read standard "libpcap"
                   files, and systems with the older patch, e.g. RH 6.1,
                   will just have to live with this. */
                rec_hdr.ifindex = 0;
                rec_hdr.protocol = 0;
                rec_hdr.pkt_type = 0;
                hdr_size = sizeof (struct pcaprec_modified_hdr);
                break;

        case WTAP_FILE_PCAP_SS990915:   /* new magic, extra crap at the end */
                rec_hdr.ifindex = 0;
                rec_hdr.protocol = 0;
                rec_hdr.pkt_type = 0;
                rec_hdr.cpu1 = 0;
                rec_hdr.cpu2 = 0;
                hdr_size = sizeof (struct pcaprec_ss990915_hdr);
                break;

        case WTAP_FILE_PCAP_NOKIA:      /* old magic, extra crap at the end */
                rec_hdr.ifindex = 0;
                rec_hdr.protocol = 0;
                rec_hdr.pkt_type = 0;
                rec_hdr.cpu1 = 0;
                rec_hdr.cpu2 = 0;
                hdr_size = sizeof (struct pcaprec_nokia_hdr);
                break;

        default:
                /* We should never get here - our open routine
                   should only get called for the types above. */
                g_assert_not_reached();
                *err = WTAP_ERR_UNSUPPORTED_FILE_TYPE;
                return FALSE;
        }

        nwritten = fwrite(&rec_hdr, 1, hdr_size, wdh->fh);
        if (nwritten != hdr_size) {
                if (nwritten == 0 && ferror(wdh->fh))
                        *err = errno;
                else
                        *err = WTAP_ERR_SHORT_WRITE;
                return FALSE;
        }
        wdh->bytes_dumped += hdr_size;

        if (wdh->encap == WTAP_ENCAP_ATM_SNIFFER) {
                /*
                 * Write the ATM header.
                 */
                atm_hdr.flags =
                    (pseudo_header->atm.channel != 0) ? 0x80 : 0x00;
                switch (pseudo_header->atm.aal) {

                case AAL_SIGNALLING:
                        /* Q.2931 */
                        atm_hdr.flags |= 0x06;
                        break;

                case AAL_5:
                        switch (pseudo_header->atm.type) {

                        case TRAF_LANE:
                                /* LANE */
                                atm_hdr.flags |= 0x01;
                                break;

                        case TRAF_LLCMX:
                                /* RFC 1483 LLC multiplexed traffic */
                                atm_hdr.flags |= 0x02;
                                break;

                        case TRAF_ILMI:
                                /* ILMI */
                                atm_hdr.flags |= 0x05;
                                break;
                        }
                        break;
                }
                atm_hdr.vpi = pseudo_header->atm.vpi;
                atm_hdr.vci = phtons(&pseudo_header->atm.vci);
                nwritten = fwrite(&atm_hdr, 1, sizeof atm_hdr, wdh->fh);
                if (nwritten != sizeof atm_hdr) {
                        if (nwritten == 0 && ferror(wdh->fh))
                                *err = errno;
                        else
                                *err = WTAP_ERR_SHORT_WRITE;
                        return FALSE;
                }
                wdh->bytes_dumped += sizeof atm_hdr;
        }

        nwritten = fwrite(pd, 1, phdr->caplen, wdh->fh);
        if (nwritten != phdr->caplen) {
                if (nwritten == 0 && ferror(wdh->fh))
                        *err = errno;
                else
                        *err = WTAP_ERR_SHORT_WRITE;
                return FALSE;
        }
        wdh->bytes_dumped += phdr->caplen;
        return TRUE;
}