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ngsniffer.c

/* ngsniffer.c
 *
 * $Id: ngsniffer.c 11995 2004-09-15 07:22:34Z guy $
 *
 * 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.
 */

/* The code in ngsniffer.c that decodes the time fields for each packet in the
 * Sniffer trace originally came from code from TCPVIEW:
 *
 * TCPVIEW
 *
 * Author:  Martin Hunt
 *          Networks and Distributed Computing
 *          Computing & Communications
 *          University of Washington
 *          Administration Building, AG-44
 *          Seattle, WA  98195
 *          Internet: martinh@cac.washington.edu
 *
 *
 * Copyright 1992 by the University of Washington
 *
 * Permission to use, copy, modify, and distribute this software and its
 * documentation for any purpose and without fee is hereby granted, provided
 * that the above copyright notice appears in all copies and that both the
 * above copyright notice and this permission notice appear in supporting
 * documentation, and that the name of the University of Washington not be
 * used in advertising or publicity pertaining to distribution of the software
 * without specific, written prior permission.  This software is made
 * available "as is", and
 * THE UNIVERSITY OF WASHINGTON DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED,
 * WITH REGARD TO THIS SOFTWARE, INCLUDING WITHOUT LIMITATION ALL IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, AND IN
 * NO EVENT SHALL THE UNIVERSITY OF WASHINGTON BE LIABLE FOR ANY SPECIAL,
 * INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, TORT
 * (INCLUDING NEGLIGENCE) OR STRICT LIABILITY, ARISING OUT OF OR IN CONNECTION
 * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include "wtap-int.h"
#include "file_wrappers.h"
#include "buffer.h"
#include "atm.h"
#include "ngsniffer.h"

/* Magic number in Sniffer files. */
static const char ngsniffer_magic[] = {
      'T', 'R', 'S', 'N', 'I', 'F', 'F', ' ', 'd', 'a', 't', 'a',
      ' ', ' ', ' ', ' ', 0x1a
};

/*
 * Sniffer record types.
 */
#define REC_VERS  1     /* Version record (f_vers) */
#define REC_FRAME2      4     /* Frame data (f_frame2) */
#define     REC_FRAME4  8     /* Frame data (f_frame4) */
#define REC_FRAME6      12    /* Frame data (f_frame6) (see below) */
#define REC_EOF         3     /* End-of-file record (no data follows) */
/*
 * and now for some unknown header types
 */
#define REC_HEADER1     6     /* Header containing serial numbers? */
#define REC_HEADER2     7     /* Header containing ??? */
#define REC_V2DESC      8     /* In version 2 sniffer traces contains
                         * infos about this capturing session.
                         * Collides with REC_FRAME4 */
#define REC_HEADER3     13    /* Retransmission counts? */
#define REC_HEADER4     14    /* ? */
#define REC_HEADER5     15    /* ? */
#define REC_HEADER6     16    /* More broadcast/retransmission counts? */
#define REC_HEADER7     17    /* ? */


/*
 * Sniffer version record format.
 */
struct vers_rec {
      gint16      maj_vers;   /* major version number */
      gint16      min_vers;   /* minor version number */
      gint16      time;       /* DOS-format time */
      gint16      date;       /* DOS-format date */
      gint8 type;       /* what type of records follow */
      guint8      network;    /* network type */
      gint8 format;           /* format version */
      guint8      timeunit;   /* timestamp units */
      gint8 cmprs_vers; /* compression version */
      gint8 cmprs_level;      /* compression level */
      gint16      rsvd[2];    /* reserved */
};

/*
 * Sniffer type 2 data record format - followed by frame data.
 *
 * The manual at
 *
 *    http://download.nai.com/products/media/sniffer/support/sdos/operation.pdf
 *
 * documents some of the values used in "fs" and "flags".  "flags" don't
 * look as if they'd be of much interest to us, as those are internal
 * flags for state used by the Sniffer, but "fs" gives various status
 * bits including error indications *and*:
 *
 *    ISDN channel information for ISDN;
 *
 *    PPP vs. SLIP information for Async.
 *
 * In that section it also refers to "FDDI analyzers using the NPI PCI
 * FDDI adapter" and "FDDI analyzers using the NPI ISA FDDI adapter",
 * referring to the first as "F1SNIFF" and the second as "FDSNIFF";
 * those sound as if they *could* be replacements for "TRSNIFF" in
 * the file header, but that manual says, earlier, that the header
 * starts with "TRSNIFF data, no matter where the frames were
 * collected".
 *
 * It also says that "time_high" is really "tstamp_high" and "tstamp_day";
 * did some older manual have it as a 16-bit "tstamp_high", so that perhaps
 * it depends on the version number in the file, or is it "tstamp_high"
 * plus "tstamp_day" in all versions?  (I forget whether this came purely
 * from tcpview, or if I saw any of it in an NAI document.)
 */
struct frame2_rec {
      guint16     time_low;   /* low part of time stamp */
      guint16     time_med;   /* middle part of time stamp */
      guint16     time_high;  /* high part of time stamp */
      gint16      size;       /* number of bytes of data */
      guint8      fs;         /* frame error status bits */
      guint8      flags;            /* buffer flags */
      gint16      true_size;  /* size of original frame, in bytes */
      gint16      rsvd;       /* reserved */
};

/*
 * Sniffer type 4 data record format - followed by frame data.
 *
 * The ATM Sniffer manual says that the "flags" field holds "buffer flags;
 * BF_xxxx", but doesn't say what the BF_xxxx flags are.  They may
 * be the same as they are in a type 2 record, in which case they're
 * probably not of much interest to us.
 *
 * XXX - the manual also says there's an 8-byte "ATMTimeStamp" driver
 * time stamp at the end of "ATMSaveInfo", but, from an ATM Sniffer capture
 * file I've looked at, that appears not to be the case.
 */

/*
 * Fields from the AAL5 trailer for the frame, if it's an AAL5 frame
 * rather than a cell.
 */
typedef struct _ATM_AAL5Trailer {
      guint16     aal5t_u2u;  /* user-to-user indicator */
      guint16     aal5t_len;  /* length of the packet */
      guint32     aal5t_chksum;     /* checksum for AAL5 packet */
} ATM_AAL5Trailer;

typedef struct _ATMTimeStamp {
      guint32     msw;  /* most significant word */
      guint32     lsw;  /* least significant word */
} ATMTimeStamp;

typedef struct _ATMSaveInfo {
      guint32 StatusWord;     /* status word from driver */
      ATM_AAL5Trailer Trailer; /* AAL5 trailer */
      guint8      AppTrafType;      /* traffic type */
      guint8      AppHLType;  /* protocol type */
      guint16     AppReserved;      /* reserved */
      guint16     Vpi;        /* virtual path identifier */
      guint16     Vci;        /* virtual circuit identifier */
      guint16     channel;    /* link: 0 for DCE, 1 for DTE */
      guint16     cells;            /* number of cells */
      guint32     AppVal1;    /* type-dependent */
      guint32     AppVal2;    /* type-dependent */
} ATMSaveInfo;

/*
 * Bits in StatusWord.
 */
#define     SW_ERRMASK        0x0F  /* Error mask: */
#define     SW_RX_FIFO_UNDERRUN     0x01  /* Receive FIFO underrun */
#define     SW_RX_FIFO_OVERRUN      0x02  /* Receive FIFO overrun */
#define     SW_RX_PKT_TOO_LONG      0x03  /* Received packet > max size */
#define     SW_CRC_ERROR            0x04  /* CRC error */
#define     SW_USER_ABORTED_RX      0x05  /* User aborted receive */
#define     SW_BUF_LEN_TOO_LONG     0x06  /* buffer len > max buf */
#define     SW_INTERNAL_T1_ERROR    0x07  /* Internal T1 error */
#define     SW_RX_CHANNEL_DEACTIV8  0x08  /* Rx channel deactivate */

#define     SW_ERROR          0x80  /* Error indicator */
#define     SW_CONGESTION           0x40  /* Congestion indicator */
#define     SW_CLP                  0x20  /* Cell loss priority indicator */
#define     SW_RAW_CELL       0x100 /* RAW cell indicator */
#define     SW_OAM_CELL       0x200 /* OAM cell indicator */

/*
 * Bits in AppTrafType.
 *
 * For AAL types other than AAL5, the packet data is presumably for a
 * single cell, not a reassembled frame, as the ATM Sniffer manual says
 * it dosn't reassemble cells other than AAL5 cells.
 */
#define     ATT_AALTYPE       0x0F  /* AAL type: */
#define     ATT_AAL_UNKNOWN         0x00  /* Unknown AAL */
#define     ATT_AAL1          0x01  /* AAL1 */
#define     ATT_AAL3_4        0x02  /* AAL3/4 */
#define     ATT_AAL5          0x03  /* AAL5 */
#define     ATT_AAL_USER            0x04  /* User AAL */
#define     ATT_AAL_SIGNALLING      0x05  /* Signaling AAL */
#define     ATT_OAMCELL       0x06  /* OAM cell */

#define     ATT_HLTYPE        0xF0  /* Higher-layer type: */
#define     ATT_HL_UNKNOWN          0x00  /* unknown */
#define     ATT_HL_LLCMX            0x10  /* LLC multiplexed (probably RFC 1483) */
#define     ATT_HL_VCMX       0x20  /* VC multiplexed (probably RFC 1483) */
#define     ATT_HL_LANE       0x30  /* LAN Emulation */
#define     ATT_HL_ILMI       0x40  /* ILMI */
#define     ATT_HL_FRMR       0x50  /* Frame Relay */
#define     ATT_HL_SPANS            0x60  /* FORE SPANS */
#define     ATT_HL_IPSILON          0x70  /* Ipsilon */

/*
 * Values for AppHLType; the interpretation depends on the ATT_HLTYPE
 * bits in AppTrafType.
 */
#define     AHLT_UNKNOWN            0x0
#define     AHLT_VCMX_802_3_FCS     0x1   /* VCMX: 802.3 FCS */
#define     AHLT_LANE_LE_CTRL 0x1   /* LANE: LE Ctrl */
#define     AHLT_IPSILON_FT0  0x1   /* Ipsilon: Flow Type 0 */
#define     AHLT_VCMX_802_4_FCS     0x2   /* VCMX: 802.4 FCS */
#define     AHLT_LANE_802_3         0x2   /* LANE: 802.3 */
#define     AHLT_IPSILON_FT1  0x2   /* Ipsilon: Flow Type 1 */
#define     AHLT_VCMX_802_5_FCS     0x3   /* VCMX: 802.5 FCS */
#define     AHLT_LANE_802_5         0x3   /* LANE: 802.5 */
#define     AHLT_IPSILON_FT2  0x3   /* Ipsilon: Flow Type 2 */
#define     AHLT_VCMX_FDDI_FCS      0x4   /* VCMX: FDDI FCS */
#define     AHLT_LANE_802_3_MC      0x4   /* LANE: 802.3 multicast */
#define     AHLT_VCMX_802_6_FCS     0x5   /* VCMX: 802.6 FCS */
#define     AHLT_LANE_802_5_MC      0x5   /* LANE: 802.5 multicast */
#define     AHLT_VCMX_802_3         0x7   /* VCMX: 802.3 */
#define     AHLT_VCMX_802_4         0x8   /* VCMX: 802.4 */
#define     AHLT_VCMX_802_5         0x9   /* VCMX: 802.5 */
#define     AHLT_VCMX_FDDI          0xa   /* VCMX: FDDI */
#define     AHLT_VCMX_802_6         0xb   /* VCMX: 802.6 */
#define     AHLT_VCMX_FRAGMENTS     0xc   /* VCMX: Fragments */
#define     AHLT_VCMX_BPDU          0xe   /* VCMX: BPDU */

struct frame4_rec {
      guint16     time_low;   /* low part of time stamp */
      guint16     time_med;   /* middle part of time stamp */
      gint8 time_high;  /* high part of time stamp */
      gint8 time_day;   /* time in days since start of capture */
      gint16      size;       /* number of bytes of data */
      gint8 fs;         /* frame error status bits */
      gint8 flags;            /* buffer flags */
      gint16      true_size;  /* size of original frame, in bytes */
      gint16      rsvd3;            /* reserved */
      gint16      atm_pad;    /* pad to 4-byte boundary */
      ATMSaveInfo atm_info;   /* ATM-specific stuff */
};

/*
 * XXX - I have a version 5.50 file with a bunch of token ring
 * records listed as type "12".  The record format below was
 * derived from frame4_rec and a bit of experimentation.
 * - Gerald
 */
struct frame6_rec {
      guint16     time_low;   /* low part of time stamp */
      guint16     time_med;   /* middle part of time stamp */
      gint8 time_high;  /* high part of time stamp */
      gint8 time_day;   /* time in days since start of capture */
      gint16      size;       /* number of bytes of data */
      guint8      fs;         /* frame error status bits */
      guint8      flags;            /* buffer flags */
      gint16      true_size;  /* size of original frame, in bytes */
      guint8      chemical_x[22];   /* ? */
};

/*
 * Network type values in some type 7 records.
 *
 * Captures with a major version number of 2 appear to have type 7
 * records with text in them (at least one I have does).
 *
 * Captures with a major version of 4, and at least some captures with
 * a major version of 5, have type 7 records with those values in the
 * 5th byte.
 *
 * However, some captures with a major version number of 5 appear not to
 * have type 7 records at all (at least one I have doesn't), but do appear
 * to put non-zero values in the "rsvd" field of the version header (at
 * least one I have does) - at least some other captures with smaller version
 * numbers appear to put 0 there, so *maybe* that's where the network
 * (sub)type is hidden in those captures.  The version 5 captures I've seen
 * that *do* have type 7 records put 0 there, so it's not as if *all* V5
 * captures have something in the "rsvd" field, however.
 *
 * The semantics of these network types is inferred from the Sniffer
 * documentation, as they correspond to types described in the UI;
 * in particular, see
 *
 *    http://download.nai.com/products/media/sniffer/support/sdos/operation.pdf
 *
 * starting at page 3-10 (56 of 496).
 *
 * XXX - I've seen X.25 captures with NET_ROUTER, and I've seen bridge/
 * router captures with NET_HDLC.  Sigh....
 */
#define NET_SDLC  0     /* Probably "SDLC then SNA" */
#define NET_HDLC  1     /* Used for X.25; is it used for other
                           things as well, or is it "HDLC then
                           X.25", as referred to by the document
                           cited above, and only used for X.25? */
#define NET_FRAME_RELAY 2
#define NET_ROUTER      3     /* Probably "Router/Bridge", for various
                           point-to-point protocols for use between
                           bridges and routers, including PPP as well
                           as various proprietary protocols; also
                           used for ISDN, for reasons not obvious
                           to me, given that a Sniffer knows
                           whether it's using a WAN or an ISDN pod */
#define NET_PPP         4     /* "Asynchronous", which includes SLIP too */
#define NET_SMDS  5     /* Not mentioned in the document, but
                           that's a document for version 5.50 of
                           the Sniffer, and that version might use
                           version 5 in the file format and thus
                           might not be using type 7 records */

/* values for V.timeunit */
#define NUM_NGSNIFF_TIMEUNITS 7
static double Usec[] = { 15.0, 0.838096, 15.0, 0.5, 2.0, 1.0, 0.1 };

static int process_header_records(wtap *wth, int *err, gchar **err_info,
    gint16 maj_vers);
static int process_rec_header2_v2(wtap *wth, unsigned char *buffer,
    guint16 length, int *err, gchar **err_info);
static int process_rec_header2_v145(wtap *wth, unsigned char *buffer,
    guint16 length, gint16 maj_vers, int *err, gchar **err_info);
static gboolean ngsniffer_read(wtap *wth, int *err, gchar **err_info,
    long *data_offset);
static gboolean ngsniffer_seek_read(wtap *wth, long seek_off,
    union wtap_pseudo_header *pseudo_header, guchar *pd, int packet_size,
    int *err, gchar **err_info);
static int ngsniffer_read_rec_header(wtap *wth, gboolean is_random,
    guint16 *typep, guint16 *lengthp, int *err);
static gboolean ngsniffer_read_frame2(wtap *wth, gboolean is_random,
    struct frame2_rec *frame2, int *err);
static void set_pseudo_header_frame2(wtap *wth,
    union wtap_pseudo_header *pseudo_header, struct frame2_rec *frame2);
static gboolean ngsniffer_read_frame4(wtap *wth, gboolean is_random,
    struct frame4_rec *frame4, int *err);
static void set_pseudo_header_frame4(union wtap_pseudo_header *pseudo_header,
    struct frame4_rec *frame4);
static gboolean ngsniffer_read_frame6(wtap *wth, gboolean is_random,
    struct frame6_rec *frame6, int *err);
static void set_pseudo_header_frame6(wtap *wth,
    union wtap_pseudo_header *pseudo_header, struct frame6_rec *frame6);
static gboolean ngsniffer_read_rec_data(wtap *wth, gboolean is_random,
    guchar *pd, int length, int *err);
static int infer_pkt_encap(const guint8 *pd, int len);
static int fix_pseudo_header(int encap, const guint8 *pd, int len,
    union wtap_pseudo_header *pseudo_header);
static void ngsniffer_sequential_close(wtap *wth);
static void ngsniffer_close(wtap *wth);
static gboolean ngsniffer_dump(wtap_dumper *wdh, const struct wtap_pkthdr *phdr,
      const union wtap_pseudo_header *pseudo_header, const guchar *pd, int *err);
static gboolean ngsniffer_dump_close(wtap_dumper *wdh, int *err);
static int SnifferDecompress( unsigned char * inbuf, size_t inlen,
        unsigned char * outbuf, size_t outlen, int *err );
static int ng_file_read(void *buffer, size_t elementsize, size_t numelements,
    wtap *wth, gboolean is_random, int *err);
static int read_blob(FILE_T infile, ngsniffer_comp_stream_t *comp_stream,
    int *err);
static long ng_file_seek_seq(wtap *wth, long offset, int whence, int *err);
static long ng_file_seek_rand(wtap *wth, long offset, int whence, int *err);

int ngsniffer_open(wtap *wth, int *err, gchar **err_info)
{
      int bytes_read;
      char magic[sizeof ngsniffer_magic];
      char record_type[2];
      char record_length[4]; /* only the first 2 bytes are length,
                          the last 2 are "reserved" and are thrown away */
      guint16 type, length;
      struct vers_rec version;
      guint16 maj_vers;
      guint16     start_date;
      guint16     start_time;
      static const int sniffer_encap[] = {
            WTAP_ENCAP_TOKEN_RING,
            WTAP_ENCAP_ETHERNET,
            WTAP_ENCAP_ARCNET,
            WTAP_ENCAP_UNKNOWN,     /* StarLAN */
            WTAP_ENCAP_UNKNOWN,     /* PC Network broadband */
            WTAP_ENCAP_UNKNOWN,     /* LocalTalk */
            WTAP_ENCAP_UNKNOWN,     /* Znet */
            WTAP_ENCAP_PER_PACKET,  /* Internetwork analyzer (synchronous) */
            WTAP_ENCAP_PER_PACKET,  /* Internetwork analyzer (asynchronous) */
            WTAP_ENCAP_FDDI_BITSWAPPED,
            WTAP_ENCAP_ATM_PDUS
      };
      #define NUM_NGSNIFF_ENCAPS (sizeof sniffer_encap / sizeof sniffer_encap[0])
      struct tm tm;

      /* Read in the string that should be at the start of a Sniffer 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;

      if (memcmp(magic, ngsniffer_magic, sizeof ngsniffer_magic)) {
            return 0;
      }

      /*
       * Read the first record, which the manual says is a version
       * record.
       */
      errno = WTAP_ERR_CANT_READ;
      bytes_read = file_read(record_type, 1, 2, wth->fh);
      bytes_read += file_read(record_length, 1, 4, wth->fh);
      if (bytes_read != 6) {
            *err = file_error(wth->fh);
            if (*err != 0)
                  return -1;
            return 0;
      }
      wth->data_offset += 6;

      type = pletohs(record_type);
      length = pletohs(record_length);

      if (type != REC_VERS) {
            *err = WTAP_ERR_BAD_RECORD;
            *err_info = g_strdup_printf("ngsniffer: Sniffer file doesn't start with a version record");
            return -1;
      }

      errno = WTAP_ERR_CANT_READ;
      bytes_read = file_read(&version, 1, sizeof version, wth->fh);
      if (bytes_read != sizeof version) {
            *err = file_error(wth->fh);
            if (*err != 0)
                  return -1;
            return 0;
      }
      wth->data_offset += sizeof version;

      /* Check the data link type. */
      if (version.network >= NUM_NGSNIFF_ENCAPS
          || sniffer_encap[version.network] == WTAP_ENCAP_UNKNOWN) {
            *err = WTAP_ERR_UNSUPPORTED_ENCAP;
            *err_info = g_strdup_printf("ngsniffer: network type %u unknown or unsupported",
                version.network);
            return -1;
      }

      /* Check the time unit */
      if (version.timeunit >= NUM_NGSNIFF_TIMEUNITS) {
            *err = WTAP_ERR_UNSUPPORTED;
            *err_info = g_strdup_printf("ngsniffer: Unknown timeunit %u", version.timeunit);
            return -1;
      }

      /* compressed or uncompressed Sniffer file? */
      if (version.format != 1) {
            wth->file_type = WTAP_FILE_NGSNIFFER_COMPRESSED;

      } else {
            wth->file_type = WTAP_FILE_NGSNIFFER_UNCOMPRESSED;
      }

      /* Set encap type before reading header records because the
       * header record may change encap type.
       */
      wth->file_encap = sniffer_encap[version.network];

      /*
       * We don't know how to handle the remaining header record types,
       * so we just skip them - except for REC_HEADER2 records, which
       * we look at, for "Internetwork analyzer" captures, to attempt to
       * determine what the link-layer encapsulation is.
       *
       * XXX - in some version 1.16 internetwork analyzer files
       * generated by the Windows Sniffer when saving Windows
       * Sniffer files as DOS Sniffer files, there's no REC_HEADER2
       * record, but the first "rsvd" word is 1 for PRI ISDN files, 2
       * for BRI ISDN files, and 0 for non-ISDN files; is that something
       * the DOS Sniffer understands?
       */
      maj_vers = pletohs(&version.maj_vers);
      if (process_header_records(wth, err, err_info, maj_vers) < 0)
            return -1;
      if (wth->file_encap == WTAP_ENCAP_PER_PACKET) {
            /*
             * Well, we haven't determined the internetwork analyzer
             * subtype yet...
             */
            switch (maj_vers) {

            case 1:
                  /*
                   * ... and this is a version 1 capture; look
                   * at the first "rsvd" word.
                   */
                  switch (pletohs(&version.rsvd[0])) {

                  case 1:
                  case 2:
                        wth->file_encap = WTAP_ENCAP_ISDN;
                        break;
                  }
                  break;

            case 3:
                  /*
                   * ...and this is a version 3 capture; we've
                   * seen nothing in those that obviously
                   * indicates the capture type, but the only
                   * one we've seen is a Frame Relay capture,
                   * so mark it as Frame Relay for now.
                   */
                  wth->file_encap = WTAP_ENCAP_FRELAY_WITH_PHDR;
                  break;
            }
      }

      /*
       * Now, if we have a random stream open, position it to the same
       * location, which should be the beginning of the real data, and
       * should be the beginning of the compressed data.
       *
       * XXX - will we see any records other than REC_FRAME2, REC_FRAME4,
       * or REC_EOF after this?  If not, we can get rid of the loop in
       * "ngsniffer_read()".
       */
      if (wth->random_fh != NULL) {
            if (file_seek(wth->random_fh, wth->data_offset, SEEK_SET, err) == -1)
                  return -1;
      }

      /* This is a ngsniffer file */
      wth->capture.ngsniffer = g_malloc(sizeof(ngsniffer_t));
      wth->capture.ngsniffer->maj_vers = maj_vers;
      wth->capture.ngsniffer->min_vers = pletohs(&version.min_vers);

      /* We haven't allocated any uncompression buffers yet. */
      wth->capture.ngsniffer->seq.buf = NULL;
      wth->capture.ngsniffer->rand.buf = NULL;

      /* Set the current file offset; the offset in the compressed file
         and in the uncompressed data stream currently the same. */
      wth->capture.ngsniffer->seq.uncomp_offset = wth->data_offset;
      wth->capture.ngsniffer->seq.comp_offset = wth->data_offset;
      wth->capture.ngsniffer->rand.uncomp_offset = wth->data_offset;
      wth->capture.ngsniffer->rand.comp_offset = wth->data_offset;

      /* We don't yet have any list of compressed blobs. */
      wth->capture.ngsniffer->first_blob = NULL;
      wth->capture.ngsniffer->last_blob = NULL;
      wth->capture.ngsniffer->current_blob = NULL;

      wth->subtype_read = ngsniffer_read;
      wth->subtype_seek_read = ngsniffer_seek_read;
      wth->subtype_sequential_close = ngsniffer_sequential_close;
      wth->subtype_close = ngsniffer_close;
      wth->snapshot_length = 0;     /* not available in header, only in frame */
      wth->capture.ngsniffer->timeunit = Usec[version.timeunit];
      wth->capture.ngsniffer->is_atm =
          (wth->file_encap == WTAP_ENCAP_ATM_PDUS);

      /* Get capture start time */
      start_time = pletohs(&version.time);
      start_date = pletohs(&version.date);
      tm.tm_year = ((start_date&0xfe00)>>9) + 1980 - 1900;
      tm.tm_mon = ((start_date&0x1e0)>>5) - 1;
      tm.tm_mday = (start_date&0x1f);
      /* The time does not appear to act as an offset; only the date
      tm.tm_hour = (start_time&0xf800)>>11;
      tm.tm_min = (start_time&0x7e0)>>5;
      tm.tm_sec = (start_time&0x1f)<<1;*/
      tm.tm_hour = 0;
      tm.tm_min = 0;
      tm.tm_sec = 0;
      tm.tm_isdst = -1;
      wth->capture.ngsniffer->start = mktime(&tm);
      /*
       * XXX - what if "secs" is -1?  Unlikely,
       * but if the capture was done in a time
       * zone that switches between standard and
       * summer time sometime other than when we
       * do, and thus the time was one that doesn't
       * exist here because a switch from standard
       * to summer time zips over it, it could
       * happen.
       *
       * On the other hand, if the capture was done
       * in a different time zone, this won't work
       * right anyway; unfortunately, the time zone
       * isn't stored in the capture file.
       */

      return 1;
}

static int
process_header_records(wtap *wth, int *err, gchar **err_info, gint16 maj_vers)
{
      int bytes_read;
      char record_type[2];
      char record_length[4]; /* only the first 2 bytes are length,
                          the last 2 are "reserved" and are thrown away */
      guint16 type, length;
      int bytes_to_read;
      unsigned char buffer[256];

      for (;;) {
            errno = WTAP_ERR_CANT_READ;
            bytes_read = file_read(record_type, 1, 2, wth->fh);
            if (bytes_read != 2) {
                  *err = file_error(wth->fh);
                  if (*err != 0)
                        return -1;
                  if (bytes_read != 0) {
                        *err = WTAP_ERR_SHORT_READ;
                        return -1;
                  }
                  return 0;   /* EOF */
            }

            type = pletohs(record_type);
            if ((type != REC_HEADER1) && (type != REC_HEADER2)
                  && (type != REC_HEADER3) && (type != REC_HEADER4)
                  && (type != REC_HEADER5) && (type != REC_HEADER6)
                  && (type != REC_HEADER7)
                  && ((type != REC_V2DESC) || (maj_vers > 2)) ) {
                  /*
                   * Well, this is either some unknown header type
                   * (we ignore this case), an uncompressed data
                   * frame or the length of a compressed blob
                   * which implies data. Seek backwards over the
                   * two bytes we read, and return.
                   */
                  if (file_seek(wth->fh, -2, SEEK_CUR, err) == -1)
                        return -1;
                  return 0;
            }

            errno = WTAP_ERR_CANT_READ;
            bytes_read = file_read(record_length, 1, 4, wth->fh);
            if (bytes_read != 4) {
                  *err = file_error(wth->fh);
                  if (*err == 0)
                        *err = WTAP_ERR_SHORT_READ;
                  return -1;
            }
            wth->data_offset += 6;

            length = pletohs(record_length);

            /*
             * Do we not yet know the encapsulation type (i.e., is
             * this is an "Internetwork analyzer" capture?), and
             * is this a REC_HEADER2 record?
             *
             * If so, it appears to specify the particular type
             * of network we're on.
             */
            if (wth->file_encap == WTAP_ENCAP_PER_PACKET &&
                type == REC_HEADER2) {
                  /*
                   * Yes, get the first up-to-256 bytes of the
                   * record data.
                   */
                  bytes_to_read = MIN(length, sizeof buffer);
                  bytes_read = file_read(buffer, 1, bytes_to_read,
                        wth->fh);
                  if (bytes_read != bytes_to_read) {
                        *err = file_error(wth->fh);
                        if (*err == 0) {
                              *err = WTAP_ERR_SHORT_READ;
                              return -1;
                        }
                  }

                  switch (maj_vers) {

                  case 2:
                        if (process_rec_header2_v2(wth, buffer,
                            length, err, err_info) < 0)
                              return -1;
                        break;

                  case 1:
                  case 4:
                  case 5:
                        if (process_rec_header2_v145(wth, buffer,
                            length, maj_vers, err, err_info) < 0)
                              return -1;
                        break;
                  }

                  /*
                   * Skip the rest of the record.
                   */
                  if (length > sizeof buffer) {
                        if (file_seek(wth->fh, length - sizeof buffer,
                            SEEK_CUR, err) == -1)
                              return -1;
                  }
            } else {
                  /* Nope, just skip over the data. */
                  if (file_seek(wth->fh, length, SEEK_CUR, err) == -1)
                        return -1;
            }
            wth->data_offset += length;
      }
}

static int
process_rec_header2_v2(wtap *wth, unsigned char *buffer, guint16 length,
    int *err, gchar **err_info)
{
      static const char x_25_str[] = "HDLC\nX.25\n";

      /*
       * There appears to be a string in a REC_HEADER2 record, with
       * a list of protocols.  In one X.25 capture I've seen, the
       * string was "HDLC\nX.25\nCLNP\nISO_TP\nSESS\nPRES\nVTP\nACSE".
       * Presumably CLNP and everything else is per-packet, but
       * we assume "HDLC\nX.25\n" indicates that it's an X.25 capture.
       */
      if (length < sizeof x_25_str - 1) {
            /*
             * There's not enough data to compare.
             */
            *err = WTAP_ERR_UNSUPPORTED_ENCAP;
            *err_info = g_strdup_printf("ngsniffer: WAN capture has too-short protocol list");
            return -1;
      }

      if (strncmp((char *)buffer, x_25_str, sizeof x_25_str - 1) == 0) {
            /*
             * X.25.
             */
            wth->file_encap = WTAP_ENCAP_LAPB;
      } else {
            *err = WTAP_ERR_UNSUPPORTED_ENCAP;
            *err_info = g_strdup_printf("ngsniffer: WAN capture protocol string %.*s unknown",
                length, buffer);
            return -1;
      }
      return 0;
}

static int
process_rec_header2_v145(wtap *wth, unsigned char *buffer, guint16 length,
    gint16 maj_vers, int *err, gchar **err_info)
{
      /*
       * The 5th byte of the REC_HEADER2 record appears to be a
       * network type.
       */
      if (length < 5) {
            /*
             * There is no 5th byte; give up.
             */
            *err = WTAP_ERR_UNSUPPORTED_ENCAP;
            *err_info = g_strdup("ngsniffer: WAN capture has no network subtype");
            return -1;
      }

      /*
       * The X.25 captures I've seen have a type of NET_HDLC, and the
       * Sniffer documentation seems to imply that it's used for
       * X.25, although it could be used for other purposes as well.
       *
       * NET_ROUTER is used for all sorts of point-to-point protocols,
       * including ISDN.  It appears, from the documentation, that the
       * Sniffer attempts to infer the particular protocol by looking
       * at the traffic; it's not clear whether it stores in the file
       * an indication of the protocol it inferred was being used.
       *
       * Unfortunately, it also appears that NET_HDLC is used for
       * stuff other than X.25 as well, so we can't just interpret
       * it unconditionally as X.25.
       *
       * For now, we interpret both NET_HDLC and NET_ROUTER as "per-packet
       * encapsulation".  We remember that we saw NET_ROUTER, though,
       * as it appears that we can infer whether a packet is PPP or
       * ISDN based on the channel number subfield of the frame error
       * status bits - if it's 0, it's PPP, otherwise it's ISDN and
       * the channel number indicates which channel it is.  We assume
       * NET_HDLC isn't used for ISDN.
       */
      switch (buffer[4]) {

      case NET_SDLC:
            wth->file_encap = WTAP_ENCAP_SDLC;
            break;

      case NET_HDLC:
            wth->file_encap = WTAP_ENCAP_PER_PACKET;
            break;

      case NET_FRAME_RELAY:
            wth->file_encap = WTAP_ENCAP_FRELAY_WITH_PHDR;
            break;

      case NET_ROUTER:
            /*
             * For most of the version 4 capture files I've seen,
             * 0xfa in buffer[1] means the file is an ISDN capture,
             * but there's one PPP file with 0xfa there; does that
             * mean that the 0xfa has nothing to do with ISDN,
             * or is that just an ISDN file with no D channel
             * packets?  (The channel number is not 0 in any
             * of the packets, so perhaps it is.)
             *
             * For one version 5 ISDN capture I've seen, there's
             * a 0x01 in buffer[6]; none of the non-ISDN version
             * 5 captures have it.
             */
            wth->file_encap = WTAP_ENCAP_PER_PACKET;
            switch (maj_vers) {

            case 4:
                  if (buffer[1] == 0xfa)
                        wth->file_encap = WTAP_ENCAP_ISDN;
                  break;

            case 5:
                  if (length < 7) {
                        /*
                         * There is no 5th byte; give up.
                         */
                        *err = WTAP_ERR_UNSUPPORTED_ENCAP;
                        *err_info = g_strdup("ngsniffer: WAN bridge/router capture has no ISDN flag");
                        return -1;
                  }
                  if (buffer[6] == 0x01)
                        wth->file_encap = WTAP_ENCAP_ISDN;
                  break;
            }
            break;

      case NET_PPP:
            wth->file_encap = WTAP_ENCAP_PPP_WITH_PHDR;
            break;

      default:
            /*
             * Reject these until we can figure them out.
             */
            *err = WTAP_ERR_UNSUPPORTED_ENCAP;
            *err_info = g_strdup_printf("ngsniffer: WAN network subtype %u unknown or unsupported",
                buffer[4]);
            return -1;
      }
      return 0;
}

/* Read the next packet */
static gboolean ngsniffer_read(wtap *wth, int *err, gchar **err_info,
    long *data_offset)
{
      int   ret;
      guint16     type, length;
      struct frame2_rec frame2;
      struct frame4_rec frame4;
      struct frame6_rec frame6;
      double      t;
      guint16     time_low, time_med, time_high, true_size, size;
      guchar      *pd;

      for (;;) {
            /*
             * Read the record header.
             */
            *data_offset = wth->data_offset;
            ret = ngsniffer_read_rec_header(wth, FALSE, &type, &length,
                err);
            if (ret <= 0) {
                  /* Read error or EOF */
                  return FALSE;
            }
            wth->data_offset += 6;

            switch (type) {

            case REC_FRAME2:
                  if (wth->capture.ngsniffer->is_atm) {
                        /*
                         * We shouldn't get a frame2 record in
                         * an ATM capture.
                         */
                        *err = WTAP_ERR_BAD_RECORD;
                        *err_info = g_strdup("ngsniffer: REC_FRAME2 record in an ATM Sniffer file");
                        return FALSE;
                  }

                  /* Read the f_frame2_struct */
                  if (!ngsniffer_read_frame2(wth, FALSE, &frame2, err)) {
                        /* Read error */
                        return FALSE;
                  }
                  wth->data_offset += sizeof frame2;
                  time_low = pletohs(&frame2.time_low);
                  time_med = pletohs(&frame2.time_med);
                  time_high = pletohs(&frame2.time_high);
                  size = pletohs(&frame2.size);
                  true_size = pletohs(&frame2.true_size);

                  length -= sizeof frame2;      /* we already read that much */

                  t = (double)time_low+(double)(time_med)*65536.0 +
                      (double)time_high*4294967296.0;

                  set_pseudo_header_frame2(wth, &wth->pseudo_header,
                      &frame2);
                  goto found;

            case REC_FRAME4:
                  if (!wth->capture.ngsniffer->is_atm) {
                        /*
                         * We shouldn't get a frame2 record in
                         * a non-ATM capture.
                         */
                        *err = WTAP_ERR_BAD_RECORD;
                        *err_info = g_strdup("ngsniffer: REC_FRAME4 record in a non-ATM Sniffer file");
                        return FALSE;
                  }

                  /* Read the f_frame4_struct */
                  if (!ngsniffer_read_frame4(wth, FALSE, &frame4, err)) {
                        /* Read error */
                        return FALSE;
                  }
                  wth->data_offset += sizeof frame4;
                  time_low = pletohs(&frame4.time_low);
                  time_med = pletohs(&frame4.time_med);
                  time_high = frame4.time_high;
                  size = pletohs(&frame4.size);
                  true_size = pletohs(&frame4.true_size);

                  /*
                   * XXX - it looks as if version 4 captures have
                   * a bogus record length, based on the assumption
                   * that the record is a frame2 record.
                   */
                  if (wth->capture.ngsniffer->maj_vers >= 5)
                        length -= sizeof frame4;      /* we already read that much */
                  else {
                        if (wth->capture.ngsniffer->min_vers >= 95)
                              length -= sizeof frame2;
                        else
                              length -= sizeof frame4;
                  }

                  /*
                   * XXX - use the "time_day" field?  Is that for captures
                   * that take a *really* long time?
                   */
                  t = (double)time_low+(double)(time_med)*65536.0 +
                      (double)time_high*4294967296.0;

                  set_pseudo_header_frame4(&wth->pseudo_header, &frame4);
                  goto found;

            case REC_FRAME6:
                  /* Read the f_frame6_struct */
                  if (!ngsniffer_read_frame6(wth, FALSE, &frame6, err)) {
                        /* Read error */
                        return FALSE;
                  }
                  wth->data_offset += sizeof frame6;
                  time_low = pletohs(&frame6.time_low);
                  time_med = pletohs(&frame6.time_med);
                  time_high = frame6.time_high;
                  size = pletohs(&frame6.size);
                  true_size = pletohs(&frame6.true_size);

                  length -= sizeof frame6;      /* we already read that much */

                  /*
                   * XXX - use the "time_day" field?  Is that for captures
                   * that take a *really* long time?
                   */
                  t = (double)time_low+(double)(time_med)*65536.0 +
                      (double)time_high*4294967296.0;

                  set_pseudo_header_frame6(wth, &wth->pseudo_header,
                      &frame6);
                  goto found;

            case REC_EOF:
                  /*
                   * End of file.  Return an EOF indication.
                   */
                  *err = 0;   /* EOF, not error */
                  return FALSE;

            default:
                  break;      /* unknown type, skip it */
            }

            /*
             * Well, we don't know what it is, or we know what
             * it is but can't handle it.  Skip past the data
             * portion, and keep looping.
             */
            if (ng_file_seek_seq(wth, length, SEEK_CUR, err) == -1)
                  return FALSE;
            wth->data_offset += length;
      }

found:
      /*
       * OK, is the frame data size greater than than what's left of the
       * record?
       */
      if (size > length) {
            /*
             * Yes - treat this as an error.
             */
            *err = WTAP_ERR_BAD_RECORD;
            *err_info = g_strdup("ngsniffer: Record length is less than packet size");
            return FALSE;
      }

      wth->phdr.len = true_size ? true_size : size;
      wth->phdr.caplen = size;

      /*
       * Read the packet data.
       */
      buffer_assure_space(wth->frame_buffer, length);
      pd = buffer_start_ptr(wth->frame_buffer);
      if (!ngsniffer_read_rec_data(wth, FALSE, pd, length, err))
            return FALSE;     /* Read error */
      wth->data_offset += length;

      wth->phdr.pkt_encap = fix_pseudo_header(wth->file_encap, pd, length,
          &wth->pseudo_header);

      t = t/1000000.0 * wth->capture.ngsniffer->timeunit; /* t = # of secs */
      t += wth->capture.ngsniffer->start;
      wth->phdr.ts.tv_sec = (long)t;
      wth->phdr.ts.tv_usec = (unsigned long)((t-(double)(wth->phdr.ts.tv_sec))
                  *1.0e6);
      return TRUE;
}

static gboolean ngsniffer_seek_read(wtap *wth, long seek_off,
    union wtap_pseudo_header *pseudo_header, guchar *pd, int packet_size,
    int *err, gchar **err_info _U_)
{
      int   ret;
      guint16     type, length;
      struct frame2_rec frame2;
      struct frame4_rec frame4;
      struct frame6_rec frame6;

      if (ng_file_seek_rand(wth, seek_off, SEEK_SET, err) == -1)
            return FALSE;

      ret = ngsniffer_read_rec_header(wth, TRUE, &type, &length, err);
      if (ret <= 0) {
            /* Read error or EOF */
            if (ret == 0) {
                  /* EOF means "short read" in random-access mode */
                  *err = WTAP_ERR_SHORT_READ;
            }
            return FALSE;
      }

      switch (type) {

      case REC_FRAME2:
            /* Read the f_frame2_struct */
            if (!ngsniffer_read_frame2(wth, TRUE, &frame2, err)) {
                  /* Read error */
                  return FALSE;
            }

            length -= sizeof frame2;      /* we already read that much */

            set_pseudo_header_frame2(wth, pseudo_header, &frame2);
            break;

      case REC_FRAME4:
            /* Read the f_frame4_struct */
            if (!ngsniffer_read_frame4(wth, TRUE, &frame4, err)) {
                  /* Read error */
                  return FALSE;
            }

            length -= sizeof frame4;      /* we already read that much */

            set_pseudo_header_frame4(pseudo_header, &frame4);
            break;

      case REC_FRAME6:
            /* Read the f_frame6_struct */
            if (!ngsniffer_read_frame6(wth, TRUE, &frame6, err)) {
                  /* Read error */
                  return FALSE;
            }

            length -= sizeof frame6;      /* we already read that much */

            set_pseudo_header_frame6(wth, pseudo_header, &frame6);
            break;

      default:
            /*
             * "Can't happen".
             */
            g_assert_not_reached();
            return FALSE;
      }

      /*
       * Got the pseudo-header (if any), now get the data.
       */
      if (!ngsniffer_read_rec_data(wth, TRUE, pd, packet_size, err))
            return FALSE;

      fix_pseudo_header(wth->file_encap, pd, packet_size, pseudo_header);

      return TRUE;
}

static int ngsniffer_read_rec_header(wtap *wth, gboolean is_random,
    guint16 *typep, guint16 *lengthp, int *err)
{
      int   bytes_read;
      char  record_type[2];
      char  record_length[4]; /* only 1st 2 bytes are length */

      /*
       * Read the record header.
       */
      bytes_read = ng_file_read(record_type, 1, 2, wth, is_random, err);
      if (bytes_read != 2) {
            if (*err != 0)
                  return -1;
            if (bytes_read != 0) {
                  *err = WTAP_ERR_SHORT_READ;
                  return -1;
            }
            return 0;
      }
      bytes_read = ng_file_read(record_length, 1, 4, wth, is_random, err);
      if (bytes_read != 4) {
            if (*err == 0)
                  *err = WTAP_ERR_SHORT_READ;
            return -1;
      }

      *typep = pletohs(record_type);
      *lengthp = pletohs(record_length);
      return 1;   /* success */
}

static gboolean ngsniffer_read_frame2(wtap *wth, gboolean is_random,
    struct frame2_rec *frame2, int *err)
{
      int bytes_read;

      /* Read the f_frame2_struct */
      bytes_read = ng_file_read(frame2, 1, sizeof *frame2, wth, is_random,
          err);
      if (bytes_read != sizeof *frame2) {
            if (*err == 0)
                  *err = WTAP_ERR_SHORT_READ;
            return FALSE;
      }
      return TRUE;
}

static void set_pseudo_header_frame2(wtap *wth,
    union wtap_pseudo_header *pseudo_header, struct frame2_rec *frame2)
{
      /*
       * In one PPP "Internetwork analyzer" capture:
       *
       *    The only bit seen in "frame2.fs" is the 0x80 bit, which
       *    probably indicates the packet's direction; all other
       *    bits were zero.  The Expert Sniffer Network Analyzer
       *    5.50 Operations manual says that bit is the FS_DTE bit
       *    for async/PPP data.  The other bits are error bits
       *    plus bits indicating whether the frame is PPP or SLIP,
       *    but the PPP bit isn't set.
       *
       *    All bits in "frame2.flags" were zero.
       *
       * In one X.25 "Internetwork analyzer" capture:
       *
       *    The only bit seen in "frame2.fs" is the 0x80 bit, which
       *    probably indicates the packet's direction; all other
       *    bits were zero.
       *
       *    "frame2.flags" was always 0x18; however, the Sniffer
       *    manual says that just means that a display filter was
       *    calculated for the frame, and it should be displayed,
       *    so perhaps that's just a quirk of that particular capture.
       *
       * In one Ethernet capture:
       *
       *    "frame2.fs" was always 0; the Sniffer manual says they're
       *    error bits of various sorts.
       *
       *    "frame2.flags" was either 0 or 0x18, with no obvious
       *    correlation with anything.  See previous comment
       *    about display filters.
       *
       * In one Token Ring capture:
       *
       *    "frame2.fs" was either 0 or 0xcc; the Sniffer manual says
       *    nothing about those bits for Token Ring captures.
       *
       *    "frame2.flags" was either 0 or 0x18, with no obvious
       *    correlation with anything.  See previous comment
       *    about display filters.
       */
      switch (wth->file_encap) {

      case WTAP_ENCAP_ETHERNET:
            /*
             * XXX - do we ever have an FCS?  If not, why do we often
             * have 4 extra bytes of stuff at the end?  Do some
             * PC Ethernet interfaces report the length including the
             * FCS but not store the FCS in the packet, or do some
             * Ethernet drivers work that way?
             */
            pseudo_header->eth.fcs_len = 0;
            break;

      case WTAP_ENCAP_PPP_WITH_PHDR:
      case WTAP_ENCAP_SDLC:
            pseudo_header->p2p.sent = (frame2->fs & 0x80) ? TRUE : FALSE;
            break;

      case WTAP_ENCAP_LAPB:
      case WTAP_ENCAP_FRELAY_WITH_PHDR:
      case WTAP_ENCAP_PER_PACKET:
            pseudo_header->x25.flags = (frame2->fs & 0x80) ? 0x00 : FROM_DCE;
            break;

      case WTAP_ENCAP_ISDN:
            pseudo_header->isdn.uton = (frame2->fs & 0x80) ? FALSE : TRUE;
            switch (frame2->fs & 0x18) {

            case 0x18:
                  pseudo_header->isdn.channel = 0;    /* D-channel */
                  break;

            case 0x08:
                  pseudo_header->isdn.channel = 1;    /* B1-channel */
                  break;

            case 0x10:
                  pseudo_header->isdn.channel = 2;    /* B1-channel */
                  break;

            default:
                  pseudo_header->isdn.channel = 30;   /* XXX */
                  break;
            }
      }
}

static gboolean ngsniffer_read_frame4(wtap *wth, gboolean is_random,
    struct frame4_rec *frame4, int *err)
{
      int bytes_read;

      /* Read the f_frame4_struct */
      bytes_read = ng_file_read(frame4, 1, sizeof *frame4, wth, is_random,
          err);
      if (bytes_read != sizeof *frame4) {
            if (*err == 0)
                  *err = WTAP_ERR_SHORT_READ;
            return FALSE;
      }
      return TRUE;
}

static void set_pseudo_header_frame4(union wtap_pseudo_header *pseudo_header,
    struct frame4_rec *frame4)
{
      guint32 StatusWord;
      guint8 aal_type, hl_type;
      guint16 vpi, vci;

      /*
       * Map flags from frame4.atm_info.StatusWord.
       */
      pseudo_header->atm.flags = 0;
      StatusWord = pletohl(&frame4->atm_info.StatusWord);
      if (StatusWord & SW_RAW_CELL)
            pseudo_header->atm.flags |= ATM_RAW_CELL;

      aal_type = frame4->atm_info.AppTrafType & ATT_AALTYPE;
      hl_type = frame4->atm_info.AppTrafType & ATT_HLTYPE;
      vpi = pletohs(&frame4->atm_info.Vpi);
      vci = pletohs(&frame4->atm_info.Vci);

      switch (aal_type) {

      case ATT_AAL_UNKNOWN:
            /*
             * Map ATT_AAL_UNKNOWN on VPI 0, VCI 5 to ATT_AAL_SIGNALLING,
             * as that's the VPCI used for signalling.
             *
             * XXX - is this necessary, or will frames to 0/5 always
             * have ATT_AAL_SIGNALLING?
             */
            if (vpi == 0 && vci == 5)
                  pseudo_header->atm.aal = AAL_SIGNALLING;
            else
                  pseudo_header->atm.aal = AAL_UNKNOWN;
            pseudo_header->atm.type = TRAF_UNKNOWN;
            pseudo_header->atm.subtype = TRAF_ST_UNKNOWN;
            break;

      case ATT_AAL1:
            pseudo_header->atm.aal = AAL_1;
            pseudo_header->atm.type = TRAF_UNKNOWN;
            pseudo_header->atm.subtype = TRAF_ST_UNKNOWN;
            break;

      case ATT_AAL3_4:
            pseudo_header->atm.aal = AAL_3_4;
            pseudo_header->atm.type = TRAF_UNKNOWN;
            pseudo_header->atm.subtype = TRAF_ST_UNKNOWN;
            break;

      case ATT_AAL5:
            pseudo_header->atm.aal = AAL_5;
            switch (hl_type) {

            case ATT_HL_UNKNOWN:
                  pseudo_header->atm.type = TRAF_UNKNOWN;
                  pseudo_header->atm.subtype = TRAF_ST_UNKNOWN;
                  break;

            case ATT_HL_LLCMX:
                  pseudo_header->atm.type = TRAF_LLCMX;
                  pseudo_header->atm.subtype = TRAF_ST_UNKNOWN;
                  break;

            case ATT_HL_VCMX:
                  pseudo_header->atm.type = TRAF_VCMX;
                  switch (frame4->atm_info.AppHLType) {

                  case AHLT_UNKNOWN:
                        pseudo_header->atm.subtype = TRAF_ST_UNKNOWN;
                        break;

                  case AHLT_VCMX_802_3_FCS:
                        pseudo_header->atm.subtype =
                            TRAF_ST_VCMX_802_3_FCS;
                        break;

                  case AHLT_VCMX_802_4_FCS:
                        pseudo_header->atm.subtype =
                            TRAF_ST_VCMX_802_4_FCS;
                        break;

                  case AHLT_VCMX_802_5_FCS:
                        pseudo_header->atm.subtype =
                            TRAF_ST_VCMX_802_5_FCS;
                        break;

                  case AHLT_VCMX_FDDI_FCS:
                        pseudo_header->atm.subtype =
                            TRAF_ST_VCMX_FDDI_FCS;
                        break;

                  case AHLT_VCMX_802_6_FCS:
                        pseudo_header->atm.subtype =
                            TRAF_ST_VCMX_802_6_FCS;
                        break;

                  case AHLT_VCMX_802_3:
                        pseudo_header->atm.subtype = TRAF_ST_VCMX_802_3;
                        break;

                  case AHLT_VCMX_802_4:
                        pseudo_header->atm.subtype = TRAF_ST_VCMX_802_4;
                        break;

                  case AHLT_VCMX_802_5:
                        pseudo_header->atm.subtype = TRAF_ST_VCMX_802_5;
                        break;

                  case AHLT_VCMX_FDDI:
                        pseudo_header->atm.subtype = TRAF_ST_VCMX_FDDI;
                        break;

                  case AHLT_VCMX_802_6:
                        pseudo_header->atm.subtype = TRAF_ST_VCMX_802_6;
                        break;

                  case AHLT_VCMX_FRAGMENTS:
                        pseudo_header->atm.subtype =
                            TRAF_ST_VCMX_FRAGMENTS;
                        break;

                  case AHLT_VCMX_BPDU:
                        pseudo_header->atm.subtype = TRAF_ST_VCMX_BPDU;
                        break;

                  default:
                        pseudo_header->atm.subtype = TRAF_ST_UNKNOWN;
                        break;
                  }
                  break;

            case ATT_HL_LANE:
                  pseudo_header->atm.type = TRAF_LANE;
                  switch (frame4->atm_info.AppHLType) {

                  case AHLT_UNKNOWN:
                        pseudo_header->atm.subtype = TRAF_ST_UNKNOWN;
                        break;

                  case AHLT_LANE_LE_CTRL:
                        pseudo_header->atm.subtype =
                            TRAF_ST_LANE_LE_CTRL;
                        break;

                  case AHLT_LANE_802_3:
                        pseudo_header->atm.subtype = TRAF_ST_LANE_802_3;
                        break;

                  case AHLT_LANE_802_5:
                        pseudo_header->atm.subtype = TRAF_ST_LANE_802_5;
                        break;

                  case AHLT_LANE_802_3_MC:
                        pseudo_header->atm.subtype =
                            TRAF_ST_LANE_802_3_MC;
                        break;

                  case AHLT_LANE_802_5_MC:
                        pseudo_header->atm.subtype =
                            TRAF_ST_LANE_802_5_MC;
                        break;

                  default:
                        pseudo_header->atm.subtype = TRAF_ST_UNKNOWN;
                        break;
                  }
                  break;

            case ATT_HL_ILMI:
                  pseudo_header->atm.type = TRAF_ILMI;
                  pseudo_header->atm.subtype = TRAF_ST_UNKNOWN;
                  break;

            case ATT_HL_FRMR:
                  pseudo_header->atm.type = TRAF_FR;
                  pseudo_header->atm.subtype = TRAF_ST_UNKNOWN;
                  break;

            case ATT_HL_SPANS:
                  pseudo_header->atm.type = TRAF_SPANS;
                  pseudo_header->atm.subtype = TRAF_ST_UNKNOWN;
                  break;

            case ATT_HL_IPSILON:
                  pseudo_header->atm.type = TRAF_IPSILON;
                  switch (frame4->atm_info.AppHLType) {

                  case AHLT_UNKNOWN:
                        pseudo_header->atm.subtype = TRAF_ST_UNKNOWN;
                        break;

                  case AHLT_IPSILON_FT0:
                        pseudo_header->atm.subtype =
                            TRAF_ST_IPSILON_FT0;
                        break;

                  case AHLT_IPSILON_FT1:
                        pseudo_header->atm.subtype =
                            TRAF_ST_IPSILON_FT1;
                        break;

                  case AHLT_IPSILON_FT2:
                        pseudo_header->atm.subtype =
                            TRAF_ST_IPSILON_FT2;
                        break;

                  default:
                        pseudo_header->atm.subtype = TRAF_ST_UNKNOWN;
                        break;
                  }
                  break;

            default:
                  pseudo_header->atm.type = TRAF_UNKNOWN;
                  pseudo_header->atm.subtype = TRAF_ST_UNKNOWN;
                  break;
            }
            break;

      case ATT_AAL_USER:
            pseudo_header->atm.aal = AAL_USER;
            pseudo_header->atm.type = TRAF_UNKNOWN;
            pseudo_header->atm.subtype = TRAF_ST_UNKNOWN;
            break;

      case ATT_AAL_SIGNALLING:
            pseudo_header->atm.aal = AAL_SIGNALLING;
            pseudo_header->atm.type = TRAF_UNKNOWN;
            pseudo_header->atm.subtype = TRAF_ST_UNKNOWN;
            break;

      case ATT_OAMCELL:
            pseudo_header->atm.aal = AAL_OAMCELL;
            pseudo_header->atm.type = TRAF_UNKNOWN;
            pseudo_header->atm.subtype = TRAF_ST_UNKNOWN;
            break;

      default:
            pseudo_header->atm.aal = AAL_UNKNOWN;
            pseudo_header->atm.type = TRAF_UNKNOWN;
            pseudo_header->atm.subtype = TRAF_ST_UNKNOWN;
            break;
      }
      pseudo_header->atm.vpi = vpi;
      pseudo_header->atm.vci = vci;
      pseudo_header->atm.channel = pletohs(&frame4->atm_info.channel);
      pseudo_header->atm.cells = pletohs(&frame4->atm_info.cells);
      pseudo_header->atm.aal5t_u2u = pletohs(&frame4->atm_info.Trailer.aal5t_u2u);
      pseudo_header->atm.aal5t_len = pletohs(&frame4->atm_info.Trailer.aal5t_len);
      pseudo_header->atm.aal5t_chksum = pntohl(&frame4->atm_info.Trailer.aal5t_chksum);
}

static gboolean ngsniffer_read_frame6(wtap *wth, gboolean is_random,
    struct frame6_rec *frame6, int *err)
{
      int bytes_read;

      /* Read the f_frame6_struct */
      bytes_read = ng_file_read(frame6, 1, sizeof *frame6, wth, is_random,
          err);
      if (bytes_read != sizeof *frame6) {
            if (*err == 0)
                  *err = WTAP_ERR_SHORT_READ;
            return FALSE;
      }
      return TRUE;
}

static void set_pseudo_header_frame6(wtap *wth,
      union wtap_pseudo_header *pseudo_header,
      struct frame6_rec *frame6 _U_)
{
      /* XXX - Once the frame format is divined, something will most likely go here */

      switch (wth->file_encap) {

      case WTAP_ENCAP_ETHERNET:
            /* XXX - is there an FCS? */
            pseudo_header->eth.fcs_len = -1;
            break;
      }
}

static gboolean ngsniffer_read_rec_data(wtap *wth, gboolean is_random,
    guchar *pd, int length, int *err)
{
      int   bytes_read;

      bytes_read = ng_file_read(pd, 1, length, wth, is_random, err);

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

/*
 * OK, this capture is from an "Internetwork analyzer", and we either
 * didn't see a type 7 record or it had a network type such as NET_HDLC
 * that doesn't tell us which *particular* HDLC derivative this is;
 * let's look at the first few bytes of the packet, a pointer to which
 * was passed to us as an argument, and see whether it looks like PPP,
 * Frame Relay, Wellfleet HDLC, Cisco HDLC, or LAPB - or, if it's none
 * of those, assume it's LAPD.
 *
 * (XXX - are there any "Internetwork analyzer" captures that don't
 * have type 7 records?  If so, is there some other field that will
 * tell us what type of capture it is?)
 */
static int infer_pkt_encap(const guint8 *pd, int len)
{
      int i;

      if (len <= 0) {
            /*
             * Nothing to infer, but it doesn't matter how you
             * dissect an empty packet.  Let's just say PPP.
             */
            return WTAP_ENCAP_PPP_WITH_PHDR;
      }

      if (pd[0] == 0xFF) {
            /*
             * PPP.  (XXX - check for 0xFF 0x03?)
             */
            return WTAP_ENCAP_PPP_WITH_PHDR;
      }

      if (len >= 2) {
            if (pd[0] == 0x07 && pd[1] == 0x03) {
                  /*
                   * Wellfleet HDLC.
                   */
                  return WTAP_ENCAP_WFLEET_HDLC;
            } else if ((pd[0] == 0x0F && pd[1] == 0x00) ||
                     (pd[0] == 0x8F && pd[1] == 0x00)) {
                  /*
                   * Cisco HDLC.
                   */
                  return WTAP_ENCAP_CHDLC_WITH_PHDR;
            }

            /*
             * Check for Frame Relay.  Look for packets with at least
             * 3 bytes of header - 2 bytes of DLCI followed by 1 byte
             * of control, which, for now, we require to be 0x03 (UI),
             * although there might be other frame types as well.
             * Scan forward until we see the last DLCI byte, with
             * the low-order bit being 1, and then check the next
             * byte to see if it's a control byte.
             *
             * XXX - in version 4 and 5 captures, wouldn't this just
             * have a capture subtype of NET_FRAME_RELAY?  Or is this
             * here only to handle other versions of the capture
             * file, where we might just not yet have found where
             * the subtype is specified in the capture?
             *
             * Bay^H^H^HNortel Networks has a mechanism in the Optivity
             * software for some of their routers to save captures
             * in Sniffer format; they use a version number of 4.9, but
             * don't put out any header records before the first FRAME2
             * record.  That means we have to use heuristics to guess
             * what type of packet we have.
             */
            for (i = 0; i < len && (pd[i] & 0x01) == 0; i++)
                  ;
            i++;  /* advance to the byte after the last DLCI byte */
            if (i == len) {
                  /*
                   * No control byte.
                   */
                  return WTAP_ENCAP_LAPB;
            }
            if (pd[i] == 0x03)
                  return WTAP_ENCAP_FRELAY_WITH_PHDR;
      }

      /*
       * Assume LAPB, for now.  If we support other HDLC encapsulations,
       * we can check whether the low-order bit of the first byte is
       * set (as it should be for LAPB) if no other checks pass.
       *
       * Or, if it's truly impossible to distinguish ISDN from non-ISDN
       * captures, we could assume it's ISDN if it's not anything
       * else.
       */
      return WTAP_ENCAP_LAPB;
}

static int fix_pseudo_header(int encap, const guint8 *pd, int len,
    union wtap_pseudo_header *pseudo_header)
{
      switch (encap) {

      case WTAP_ENCAP_PER_PACKET:
            /*
             * Infer the packet type from the first two bytes.
             */
            encap = infer_pkt_encap(pd, len);

            /*
             * Fix up the pseudo-header to match the new
             * encapsulation type.
             */
            switch (encap) {

            case WTAP_ENCAP_WFLEET_HDLC:
            case WTAP_ENCAP_CHDLC_WITH_PHDR:
            case WTAP_ENCAP_PPP_WITH_PHDR:
                  if (pseudo_header->x25.flags == 0)
                        pseudo_header->p2p.sent = TRUE;
                  else
                        pseudo_header->p2p.sent = FALSE;
                  break;

            case WTAP_ENCAP_ISDN:
                  if (pseudo_header->x25.flags == 0x00)
                        pseudo_header->isdn.uton = FALSE;
                  else
                        pseudo_header->isdn.uton = TRUE;

                  /*
                   * XXX - this is currently a per-packet
                   * encapsulation type, and we can't determine
                   * whether a capture is an ISDN capture before
                   * seeing any packets, and B-channel PPP packets
                   * look like PPP packets and are given
                   * WTAP_ENCAP_PPP_WITH_PHDR, not WTAP_ENCAP_ISDN,
                   * so we assume this is a D-channel packet and
                   * thus give it a channel number of 0.
                   */
                  pseudo_header->isdn.channel = 0;
                  break;
            }
            break;

      case WTAP_ENCAP_ATM_PDUS:
            /*
             * If the Windows Sniffer writes out one of its ATM
             * capture files in DOS Sniffer format, it doesn't
             * distinguish between LE Control and LANE encapsulated
             * LAN frames, it just marks them as LAN frames,
             * so we fix that up here.
             *
             * I've also seen DOS Sniffer captures claiming that
             * LANE packets that *don't* start with FF 00 are
             * marked as LE Control frames, so we fix that up
             * as well.
             */
            if (pseudo_header->atm.type == TRAF_LANE && len >= 2) {
                  if (pd[0] == 0xff && pd[1] == 0x00) {
                        /*
                         * This must be LE Control.
                         */
                        pseudo_header->atm.subtype =
                            TRAF_ST_LANE_LE_CTRL;
                  } else {
                        /*
                         * This can't be LE Control.
                         */
                        if (pseudo_header->atm.subtype ==
                            TRAF_ST_LANE_LE_CTRL) {
                              /*
                               * XXX - Ethernet or Token Ring?
                               */
                              pseudo_header->atm.subtype =
                                  TRAF_ST_LANE_802_3;
                        }
                  }
            }
            break;
      }
      return encap;
}

/* Throw away the buffers used by the sequential I/O stream, but not
   those used by the random I/O stream. */
static void ngsniffer_sequential_close(wtap *wth)
{
      if (wth->capture.ngsniffer->seq.buf != NULL) {
            g_free(wth->capture.ngsniffer->seq.buf);
            wth->capture.ngsniffer->seq.buf = NULL;
      }
}

static void free_blob(gpointer data, gpointer user_data _U_)
{
      g_free(data);
}

/* Close stuff used by the random I/O stream, if any, and free up any
   private data structures.  (If there's a "sequential_close" routine
   for a capture file type, it'll be called before the "close" routine
   is called, so we don't have to free the sequential buffer here.) */
static void ngsniffer_close(wtap *wth)
{
      if (wth->capture.ngsniffer->rand.buf != NULL)
            g_free(wth->capture.ngsniffer->rand.buf);
      if (wth->capture.ngsniffer->first_blob != NULL) {
            g_list_foreach(wth->capture.ngsniffer->first_blob, free_blob, NULL);
            g_list_free(wth->capture.ngsniffer->first_blob);
      }
      g_free(wth->capture.ngsniffer);
}

static const int wtap_encap[] = {
    -1,           /* WTAP_ENCAP_UNKNOWN -> unsupported */
    1,            /* WTAP_ENCAP_ETHERNET */
    0,            /* WTAP_ENCAP_TOKEN_RING */
    -1,           /* WTAP_ENCAP_SLIP -> unsupported */
    7,            /* WTAP_ENCAP_PPP -> Internetwork analyzer (synchronous) FIXME ! */
    9,            /* WTAP_ENCAP_FDDI */
    9,            /* WTAP_ENCAP_FDDI_BITSWAPPED */
    -1,           /* WTAP_ENCAP_RAW_IP -> unsupported */
    2,            /* WTAP_ENCAP_ARCNET */
    -1,           /* WTAP_ENCAP_ATM_RFC1483 */
    -1,           /* WTAP_ENCAP_LINUX_ATM_CLIP */
    7,            /* WTAP_ENCAP_LAPB -> Internetwork analyzer (synchronous) */
    -1,           /* WTAP_ENCAP_ATM_PDUS */
    -1,           /* WTAP_ENCAP_NULL -> unsupported */
    -1,           /* WTAP_ENCAP_ASCEND -> unsupported */
    -1,           /* WTAP_ENCAP_ISDN -> unsupported */
    -1,           /* WTAP_ENCAP_IP_OVER_FC -> unsupported */
    7,            /* WTAP_ENCAP_PPP_WITH_PHDR -> Internetwork analyzer (synchronous) FIXME ! */
};
#define NUM_WTAP_ENCAPS (sizeof wtap_encap / sizeof wtap_encap[0])

/* Returns 0 if we could write the specified encapsulation type,
   an error indication otherwise. */
int ngsniffer_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 (encap < 0 || (unsigned)encap >= NUM_WTAP_ENCAPS || wtap_encap[encap] == -1)
      return WTAP_ERR_UNSUPPORTED_ENCAP;

    return 0;
}

/* Returns TRUE on success, FALSE on failure; sets "*err" to an error code on
   failure */
gboolean ngsniffer_dump_open(wtap_dumper *wdh, gboolean cant_seek _U_, int *err)
{
    size_t nwritten;
    char buf[6] = {REC_VERS, 0x00, 0x12, 0x00, 0x00, 0x00}; /* version record */

    /* This is a sniffer file */
    wdh->subtype_write = ngsniffer_dump;
    wdh->subtype_close = ngsniffer_dump_close;

    wdh->dump.ngsniffer = g_malloc(sizeof(ngsniffer_dump_t));
    wdh->dump.ngsniffer->first_frame = TRUE;
    wdh->dump.ngsniffer->start = 0;

    /* Write the file header. */
    nwritten = fwrite(ngsniffer_magic, 1, sizeof ngsniffer_magic, wdh->fh);
    if (nwritten != sizeof ngsniffer_magic) {
      if (nwritten == 0 && ferror(wdh->fh))
          *err = errno;
      else
          *err = WTAP_ERR_SHORT_WRITE;
      return FALSE;
    }
    nwritten = fwrite(buf, 1, 6, wdh->fh);
    if (nwritten != 6) {
      if (nwritten == 0 && ferror(wdh->fh))
          *err = errno;
      else
          *err = WTAP_ERR_SHORT_WRITE;
      return FALSE;
    }

    return TRUE;
}

/* Write a record for a packet to a dump file.
   Returns TRUE on success, FALSE on failure. */
static gboolean ngsniffer_dump(wtap_dumper *wdh, const struct wtap_pkthdr *phdr,
    const union wtap_pseudo_header *pseudo_header, const guchar *pd, int *err)
{
    ngsniffer_dump_t *priv = wdh->dump.ngsniffer;
    struct frame2_rec rec_hdr;
    size_t nwritten;
    char buf[6];
    double t;
    guint16 t_low, t_med, t_high;
    struct vers_rec version;
    gint16 maj_vers, min_vers;
    guint16 start_date;
    struct tm *tm;

    /* Sniffer files have a capture start date in the file header, and
       have times relative to the beginning of that day in the packet
       headers; pick the date of the first packet as the capture start
       date. */
    if (priv->first_frame) {
      priv->first_frame=FALSE;
      tm = localtime(&phdr->ts.tv_sec);
      if (tm != NULL) {
        start_date = (tm->tm_year - (1980 - 1900)) << 9;
        start_date |= (tm->tm_mon + 1) << 5;
        start_date |= tm->tm_mday;
        /* record the start date, not the start time */
        priv->start = phdr->ts.tv_sec - (3600*tm->tm_hour + 60*tm->tm_min + tm->tm_sec);
      } else {
        start_date = 0;
        priv->start = 0;
      }

      /* "sniffer" version ? */
      maj_vers = 4;
      min_vers = 0;
      version.maj_vers = htoles(maj_vers);
      version.min_vers = htoles(min_vers);
      version.time = 0;
      version.date = htoles(start_date);
      version.type = 4;
      version.network = wtap_encap[wdh->encap];
      version.format = 1;
      version.timeunit = 1; /* 0.838096 */
      version.cmprs_vers = 0;
      version.cmprs_level = 0;
      version.rsvd[0] = 0;
      version.rsvd[1] = 0;
      nwritten = fwrite(&version, 1, sizeof version, wdh->fh);
      if (nwritten != sizeof version) {
          if (nwritten == 0 && ferror(wdh->fh))
            *err = errno;
          else
            *err = WTAP_ERR_SHORT_WRITE;
          return FALSE;
      }
    }

    buf[0] = REC_FRAME2;
    buf[1] = 0x00;
    buf[2] = (char)((phdr->caplen + sizeof(struct frame2_rec))%256);
    buf[3] = (char)((phdr->caplen + sizeof(struct frame2_rec))/256);
    buf[4] = 0x00;
    buf[5] = 0x00;
    nwritten = fwrite(buf, 1, 6, wdh->fh);
    if (nwritten != 6) {
      if (nwritten == 0 && ferror(wdh->fh))
          *err = errno;
      else
          *err = WTAP_ERR_SHORT_WRITE;
      return FALSE;
    }
    t = (double)phdr->ts.tv_sec + (double)phdr->ts.tv_usec/1.0e6; /* # of secs */
    t = (t - priv->start)*1.0e6 / Usec[1]; /* timeunit = 1 */
    t_low = (guint16)(t-(double)((guint32)(t/65536.0))*65536.0);
    t_med = (guint16)((guint32)(t/65536.0) % 65536);
    t_high = (guint16)(t/4294967296.0);
    rec_hdr.time_low = htoles(t_low);
    rec_hdr.time_med = htoles(t_med);
    rec_hdr.time_high = htoles(t_high);
    rec_hdr.size = htoles(phdr->caplen);
    if (wdh->encap == WTAP_ENCAP_LAPB || wdh->encap == WTAP_ENCAP_PPP_WITH_PHDR)
      rec_hdr.fs = (pseudo_header->x25.flags & FROM_DCE) ? 0x00 : 0x80;
    else
      rec_hdr.fs = 0;
    rec_hdr.flags = 0;
    rec_hdr.true_size = phdr->len != phdr->caplen ? htoles(phdr->len) : 0;
    rec_hdr.rsvd = 0;
    nwritten = fwrite(&rec_hdr, 1, sizeof rec_hdr, wdh->fh);
    if (nwritten != sizeof rec_hdr) {
      if (nwritten == 0 && ferror(wdh->fh))
          *err = errno;
      else
          *err = WTAP_ERR_SHORT_WRITE;
      return FALSE;
    }
    nwritten = fwrite(pd, 1, phdr->caplen, wdh->fh);
    if (nwritten != phdr->caplen) {
      if (nwritten == 0 && ferror(wdh->fh))
          *err = errno;
      else
          *err = WTAP_ERR_SHORT_WRITE;
      return FALSE;
    }
    return TRUE;
}

/* Finish writing to a dump file.
   Returns TRUE on success, FALSE on failure. */
static gboolean ngsniffer_dump_close(wtap_dumper *wdh, int *err)
{
    /* EOF record */
    char buf[6] = {REC_EOF, 0x00, 0x00, 0x00, 0x00, 0x00};
    size_t nwritten;

    nwritten = fwrite(buf, 1, 6, wdh->fh);
    if (nwritten != 6) {
      if (err != NULL) {
          if (nwritten == 0 && ferror(wdh->fh))
            *err = errno;
          else
            *err = WTAP_ERR_SHORT_WRITE;
      }
      return FALSE;
    }
    return TRUE;
}

/*
   SnifferDecompress() decompresses a blob of compressed data from a
         Sniffer(R) capture file.

   This function is Copyright (c) 1999-2999 Tim Farley

   Parameters
      inbuf - buffer of compressed bytes from file, not including
         the preceding length word
      inlen - length of inbuf in bytes
      outbuf - decompressed contents, could contain a partial Sniffer
         record at the end.
      outlen - length of outbuf.

   Return value is the number of bytes in outbuf on return.
*/
static int
SnifferDecompress( unsigned char * inbuf, size_t inlen,
                       unsigned char * outbuf, size_t outlen, int *err )
{
   unsigned char * pin = inbuf;
   unsigned char * pout = outbuf;
   unsigned char * pin_end = pin + inlen;
   unsigned char * pout_end = pout + outlen;
   unsigned int bit_mask;  /* one bit is set in this, to mask with bit_value */
   unsigned int bit_value = 0; /* cache the last 16 coding bits we retrieved */
   unsigned int code_type; /* encoding type, from high 4 bits of byte */
   unsigned int code_low;  /* other 4 bits from encoding byte */
   int length;             /* length of RLE sequence or repeated string */
   int offset;             /* offset of string to repeat */

   bit_mask  = 0;  /* don't have any bits yet */
   while (1)
   {
      /* Shift down the bit mask we use to see whats encoded */
      bit_mask = bit_mask >> 1;

      /* If there are no bits left, time to get another 16 bits */
      if ( 0 == bit_mask )
      {
         bit_mask  = 0x8000;  /* start with the high bit */
         bit_value = pletohs(pin);   /* get the next 16 bits */
         pin += 2;          /* skip over what we just grabbed */
         if ( pin >= pin_end )
         {
            *err = WTAP_ERR_UNC_TRUNCATED;       /* data was oddly truncated */
            return ( -1 );
         }
      }

      /* Use the bits in bit_value to see what's encoded and what is raw data */
      if ( !(bit_mask & bit_value) )
      {
         /* bit not set - raw byte we just copy */
         *(pout++) = *(pin++);
      }
      else
      {
         /* bit set - next item is encoded.  Peel off high nybble
            of next byte to see the encoding type.  Set aside low
            nybble while we are at it */
         code_type = (unsigned int) ((*pin) >> 4 ) & 0xF;
         code_low  = (unsigned int) ((*pin) & 0xF );
         pin++;   /* increment over the code byte we just retrieved */
         if ( pin >= pin_end )
         {
            *err = WTAP_ERR_UNC_TRUNCATED;       /* data was oddly truncated */
            return ( -1 );
         }

         /* Based on the code type, decode the compressed string */
         switch ( code_type )
         {
            case 0  :   /* RLE short runs */
                /*
                    Run length is the low nybble of the first code byte.
                    Byte to repeat immediately follows.
                    Total code size: 2 bytes.
                */
                length = code_low + 3;
                /* If length would put us past end of output, avoid overflow */
                if ( pout + length > pout_end )
                {
                    *err = WTAP_ERR_UNC_OVERFLOW;
                    return ( -1 );
                }

                /* generate the repeated series of bytes */
                memset( pout, *pin++, length );
                pout += length;
                break;
            case 1  :   /* RLE long runs */
                /*
                    Low 4 bits of run length is the low nybble of the
                    first code byte, upper 8 bits of run length is in
                    the next byte.
                    Byte to repeat immediately follows.
                    Total code size: 3 bytes.
                */
                length = code_low + ((unsigned int)(*pin++) << 4) + 19;
                /* If we are already at end of input, there is no byte
                   to repeat */
                if ( pin >= pin_end )
                {
                    *err = WTAP_ERR_UNC_TRUNCATED;     /* data was oddly truncated */
                    return ( -1 );
                }
                /* If length would put us past end of output, avoid overflow */
                if ( pout + length > pout_end )
                {
                    *err = WTAP_ERR_UNC_OVERFLOW;
                    return ( -1 );
                }

                /* generate the repeated series of bytes */
                memset( pout, *pin++, length );
                pout += length;
                break;
            case 2  :   /* LZ77 long strings */
                /*
                    Low 4 bits of offset to string is the low nybble of the
                    first code byte, upper 8 bits of offset is in
                    the next byte.
                    Length of string immediately follows.
                    Total code size: 3 bytes.
                */
                offset = code_low + ((unsigned int)(*pin++) << 4) + 3;
                /* If we are already at end of input, there is no byte
                   to repeat */
                if ( pin >= pin_end )
                {
                    *err = WTAP_ERR_UNC_TRUNCATED;     /* data was oddly truncated */
                    return ( -1 );
                }
                /* Check if offset would put us back past begin of buffer */
                if ( pout - offset < outbuf )
                {
                    *err = WTAP_ERR_UNC_BAD_OFFSET;
                    return ( -1 );
                }

                /* get length from next byte, make sure it won't overrun buf */
                length = (unsigned int)(*pin++) + 16;
                if ( pout + length > pout_end )
                {
                    *err = WTAP_ERR_UNC_OVERFLOW;
                    return ( -1 );
                }

                /* Copy the string from previous text to output position,
                   advance output pointer */
                memcpy( pout, pout - offset, length );
                pout += length;
                break;
            default :   /* (3 to 15): LZ77 short strings */
                /*
                    Low 4 bits of offset to string is the low nybble of the
                    first code byte, upper 8 bits of offset is in
                    the next byte.
                    Length of string to repeat is overloaded into code_type.
                    Total code size: 2 bytes.
                */
                offset = code_low + ((unsigned int)(*pin++) << 4) + 3;
                /* Check if offset would put us back past begin of buffer */
                if ( pout - offset < outbuf )
                {
                    *err = WTAP_ERR_UNC_BAD_OFFSET;
                    return ( -1 );
                }

                /* get length from code_type, make sure it won't overrun buf */
                length = code_type;
                if ( pout + length > pout_end )
                {
                    *err = WTAP_ERR_UNC_OVERFLOW;
                    return ( -1 );
                }

                /* Copy the string from previous text to output position,
                   advance output pointer */
                memcpy( pout, pout - offset, length );
                pout += length;
                break;
         }
      }

      /* If we've consumed all the input, we are done */
      if ( pin >= pin_end )
         break;
   }

   return ( pout - outbuf );  /* return length of expanded text */
}

/*
 * XXX - is there any guarantee that this is big enough to hold the
 * uncompressed data from any blob?
 */
#define     OUTBUF_SIZE 65536

/* Information about a compressed blob; we save the offset in the
   underlying compressed file, and the offset in the uncompressed data
   stream, of the blob. */
typedef struct {
      long  blob_comp_offset;
      long  blob_uncomp_offset;
} blob_info_t;

static int
ng_file_read(void *buffer, size_t elementsize, size_t numelements, wtap *wth,
    gboolean is_random, int *err)
{
    FILE_T infile;
    ngsniffer_comp_stream_t *comp_stream;
    int copybytes = elementsize * numelements; /* bytes left to be copied */
    int copied_bytes = 0; /* bytes already copied */
    unsigned char *outbuffer = buffer; /* where to write next decompressed data */
    blob_info_t *blob;
    int bytes_to_copy;
    int bytes_left;

    if (is_random) {
      infile = wth->random_fh;
      comp_stream = &wth->capture.ngsniffer->rand;
    } else {
      infile = wth->fh;
      comp_stream = &wth->capture.ngsniffer->seq;
    }

    if (wth->file_type == WTAP_FILE_NGSNIFFER_UNCOMPRESSED) {
      errno = WTAP_ERR_CANT_READ;
      copied_bytes = file_read(buffer, 1, copybytes, infile);
      if (copied_bytes != copybytes)
          *err = file_error(infile);
      return copied_bytes;
    }

    /* Allocate the stream buffer if it hasn't already been allocated. */
    if (comp_stream->buf == NULL) {
      comp_stream->buf = g_malloc(OUTBUF_SIZE);

      if (is_random) {
          /* This is the first read of the random file, so we're at
             the beginning of the sequence of blobs in the file
             (as we've not done any random reads yet to move the
             current position in the random stream); set the
             current blob to be the first blob. */
          wth->capture.ngsniffer->current_blob =
            wth->capture.ngsniffer->first_blob;
      } else {
          /* This is the first sequential read; if we also have a
             random stream open, allocate the first element for the
             list of blobs, and make it the last element as well. */
          if (wth->random_fh != NULL) {
            g_assert(wth->capture.ngsniffer->first_blob == NULL);
            blob = g_malloc(sizeof (blob_info_t));
            blob->blob_comp_offset = comp_stream->comp_offset;
            blob->blob_uncomp_offset = comp_stream->uncomp_offset;
            wth->capture.ngsniffer->first_blob =
                  g_list_append(wth->capture.ngsniffer->first_blob, blob);
            wth->capture.ngsniffer->last_blob =
                  wth->capture.ngsniffer->first_blob;
          }
      }

      /* Now read the first blob into the buffer. */
      if (read_blob(infile, comp_stream, err) < 0)
          return -1;
    }
    while (copybytes > 0) {
      bytes_left = comp_stream->nbytes - comp_stream->nextout;
      if (bytes_left == 0) {
          /* There's no decompressed stuff left to copy from the current
             blob; get the next blob. */

          if (is_random) {
            /* Move to the next blob in the list. */
            wth->capture.ngsniffer->current_blob =
                  g_list_next(wth->capture.ngsniffer->current_blob);
            blob = wth->capture.ngsniffer->current_blob->data;
          } else {
            /* If we also have a random stream open, add a new element,
               for this blob, to the list of blobs; we know the list is
               non-empty, as we initialized it on the first sequential
               read, so we just add the new element at the end, and
               adjust the pointer to the last element to refer to it. */
            if (wth->random_fh != NULL) {
                blob = g_malloc(sizeof (blob_info_t));
                blob->blob_comp_offset = comp_stream->comp_offset;
                blob->blob_uncomp_offset = comp_stream->uncomp_offset;
                wth->capture.ngsniffer->last_blob =
                  g_list_append(wth->capture.ngsniffer->last_blob, blob);
            }
          }

          if (read_blob(infile, comp_stream, err) < 0)
            return -1;
          bytes_left = comp_stream->nbytes - comp_stream->nextout;
      }

      bytes_to_copy = copybytes;
      if (bytes_to_copy > bytes_left)
          bytes_to_copy = bytes_left;
      memcpy(outbuffer, &comp_stream->buf[comp_stream->nextout],
            bytes_to_copy);
      copybytes -= bytes_to_copy;
      copied_bytes += bytes_to_copy;
      outbuffer += bytes_to_copy;
      comp_stream->nextout += bytes_to_copy;
      comp_stream->uncomp_offset += bytes_to_copy;
    }
    return copied_bytes;
}

/* Read a blob from a compressed stream.
   Return -1 and set "*err" on error, otherwise return 0. */
static int
read_blob(FILE_T infile, ngsniffer_comp_stream_t *comp_stream, int *err)
{
    size_t in_len;
    size_t read_len;
    unsigned short blob_len;
    gint16 blob_len_host;
    gboolean uncompressed;
    unsigned char file_inbuf[65536];
    int out_len;

    /* Read one 16-bit word which is length of next compressed blob */
    errno = WTAP_ERR_CANT_READ;
    read_len = file_read(&blob_len, 1, 2, infile);
    if (2 != read_len) {
      *err = file_error(infile);
      return -1;
    }
    comp_stream->comp_offset += 2;
    blob_len_host = pletohs(&blob_len);

    /* Compressed or uncompressed? */
    if (blob_len_host < 0) {
      /* Uncompressed blob; blob length is absolute value of the number. */
      in_len = -blob_len_host;
      uncompressed = TRUE;
    } else {
      in_len = blob_len_host;
      uncompressed = FALSE;
    }

    /* Read the blob */
    errno = WTAP_ERR_CANT_READ;
    read_len = file_read(file_inbuf, 1, in_len, infile);
    if (in_len != read_len) {
      *err = file_error(infile);
      return -1;
    }
    comp_stream->comp_offset += in_len;

    if (uncompressed) {
      memcpy(comp_stream->buf, file_inbuf, in_len);
      out_len = in_len;
    } else {
      /* Decompress the blob */
      out_len = SnifferDecompress(file_inbuf, in_len,
                        comp_stream->buf, OUTBUF_SIZE, err);
      if (out_len < 0)
          return -1;
    }
    comp_stream->nextout = 0;
    comp_stream->nbytes = out_len;
    return 0;
}

/* Seek in the sequential data stream; we can only seek forward, and we
   do it on compressed files by skipping forward. */
static long
ng_file_seek_seq(wtap *wth, long offset, int whence, int *err)
{
    long delta;
    char buf[65536];
    long amount_to_read;

    if (wth->file_type == WTAP_FILE_NGSNIFFER_UNCOMPRESSED)
      return file_seek(wth->fh, offset, whence, err);

    switch (whence) {

    case SEEK_SET:
      break;            /* "offset" is the target offset */

    case SEEK_CUR:
      offset += wth->capture.ngsniffer->seq.uncomp_offset;
      break;            /* "offset" is relative to the current offset */

    case SEEK_END:
      g_assert_not_reached(); /* "offset" is relative to the end of the file... */
      break;            /* ...but we don't know where that is. */
    }

    delta = offset - wth->capture.ngsniffer->seq.uncomp_offset;
    g_assert(delta >= 0);

    /* Ok, now read and discard "delta" bytes. */
    while (delta != 0) {
      amount_to_read = delta;
      if ((unsigned long)amount_to_read > sizeof buf)
          amount_to_read = sizeof buf;
      if (ng_file_read(buf, 1, amount_to_read, wth, FALSE, err) < 0)
          return -1;    /* error */
      delta -= amount_to_read;
    }
    return offset;
}

/* Seek in the random data stream.

   On compressed files, we see whether we're seeking to a position within
   the blob we currently have in memory and, if not, we find in the list
   of blobs the last blob that starts at or before the position to which
   we're seeking, and read that blob in.  We can then move to the appropriate
   position within the blob we have in memory (whether it's the blob we
   already had in memory or, if necessary, the one we read in). */
static long
ng_file_seek_rand(wtap *wth, long offset, int whence, int *err)
{
    ngsniffer_t *ngsniffer;
    long delta;
    GList *new, *next;
    blob_info_t *next_blob, *new_blob;

    if (wth->file_type == WTAP_FILE_NGSNIFFER_UNCOMPRESSED)
      return file_seek(wth->random_fh, offset, whence, err);

    ngsniffer = wth->capture.ngsniffer;

    switch (whence) {

    case SEEK_SET:
      break;            /* "offset" is the target offset */

    case SEEK_CUR:
      offset += ngsniffer->rand.uncomp_offset;
      break;            /* "offset" is relative to the current offset */

    case SEEK_END:
      g_assert_not_reached(); /* "offset" is relative to the end of the file... */
      break;            /* ...but we don't know where that is. */
    }

    delta = offset - ngsniffer->rand.uncomp_offset;

    /* Is the place to which we're seeking within the current buffer, or
       will we have to read a different blob into the buffer? */
    new = NULL;
    if (delta > 0) {
      /* We're going forwards.
         Is the place to which we're seeking within the current buffer? */
      if ((size_t)(ngsniffer->rand.nextout + delta) >= ngsniffer->rand.nbytes) {
          /* No.  Search for a blob that contains the target offset in
             the uncompressed byte stream, starting with the blob
             following the current blob. */
          new = g_list_next(ngsniffer->current_blob);
          for (;;) {
            next = g_list_next(new);
            if (next == NULL) {
                /* No more blobs; the current one is it. */
                break;
            }

            next_blob = next->data;
            /* Does the next blob start after the target offset?
               If so, the current blob is the one we want. */
            if (next_blob->blob_uncomp_offset > offset)
                break;

            new = next;
          }
      }
    } else if (delta < 0) {
      /* We're going backwards.
         Is the place to which we're seeking within the current buffer? */
      if (ngsniffer->rand.nextout + delta < 0) {
          /* No.  Search for a blob that contains the target offset in
             the uncompressed byte stream, starting with the blob
             preceding the current blob. */
          new = g_list_previous(ngsniffer->current_blob);
          for (;;) {
            /* Does this blob start at or before the target offset?
               If so, the current blob is the one we want. */
            new_blob = new->data;
            if (new_blob->blob_uncomp_offset <= offset)
                break;

            /* It doesn't - skip to the previous blob. */
            new = g_list_previous(new);
          }
      }
    }

    if (new != NULL) {
      /* The place to which we're seeking isn't in the current buffer;
         move to a new blob. */
      new_blob = new->data;

      /* Seek in the compressed file to the offset in the compressed file
         of the beginning of that blob. */
      if (file_seek(wth->random_fh, new_blob->blob_comp_offset, SEEK_SET, err) == -1)
          return -1;

      /* Make the blob we found the current one. */
      ngsniffer->current_blob = new;

      /* Now set the current offsets to the offsets of the beginning
         of the blob. */
      ngsniffer->rand.uncomp_offset = new_blob->blob_uncomp_offset;
      ngsniffer->rand.comp_offset = new_blob->blob_comp_offset;

      /* Now fill the buffer. */
      if (read_blob(wth->random_fh, &ngsniffer->rand, err) < 0)
          return -1;

      /* Set "delta" to the amount to move within this blob; it had
         better be >= 0, and < the amount of uncompressed data in
         the blob, as otherwise it'd mean we need to seek before
         the beginning or after the end of this blob. */
      delta = offset - ngsniffer->rand.uncomp_offset;
      g_assert(delta >= 0 && (unsigned long)delta < ngsniffer->rand.nbytes);
    }

    /* OK, the place to which we're seeking is in the buffer; adjust
       "ngsniffer->rand.nextout" to point to the place to which
       we're seeking, and adjust "ngsniffer->rand.uncomp_offset" to be
       the destination offset. */
    ngsniffer->rand.nextout += delta;
    ngsniffer->rand.uncomp_offset += delta;

    return offset;
}

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