Program: CWE-119
Project: CVE-2017-6429
Buggy source:
/* $Id$ */

/*
 *   Copyright (c) 2001-2012 Aaron Turner <aturner at synfin dot net>
 *   Copyright (c) 2013-2016 Fred Klassen <tcpreplay at appneta dot com> - AppNeta
 *
 *   The Tcpreplay Suite of tools 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 3 of the 
 *   License, or with the authors permission any later version.
 *
 *   The Tcpreplay Suite 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 the Tcpreplay Suite.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "config.h"
#include "defines.h"
#include "common.h"

#include <fcntl.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <unistd.h>
#include <pcap.h>
#include <sys/stat.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <inttypes.h>

#define __STDC_FORMAT_MACROS 1
#include <inttypes.h>

#include "tcpcapinfo_opts.h"

static int do_checksum_math(u_int16_t *data, int len);

#ifdef DEBUG
int debug = 0;
#endif

#ifdef WORDS_BIGENDIAN
char is_swapped[] = "little-endian";
char is_not_swapped[] = "big-endian";
#else
char is_not_swapped[] = "little-endian";
char is_swapped[] = "big-endian";
#endif

int read_packet(int fd, uint32_t len, char *fname);

/*
 * Standard libpcap format.
 */
#define TCPDUMP_MAGIC           0xa1b2c3d4

/*
 * Alexey Kuznetzov's modified libpcap format.
 */
#define KUZNETZOV_TCPDUMP_MAGIC 0xa1b2cd34
struct pcap_timeval {
    bpf_int32 tv_sec;           /* seconds */
    bpf_int32 tv_usec;          /* microseconds */
};
struct pcap_sf_patched_pkthdr {
    struct pcap_timeval ts;     /* time stamp */
    bpf_u_int32 caplen;         /* length of portion present */
    bpf_u_int32 len;            /* length this packet (off wire) */
    int         index;
    unsigned short protocol;
    unsigned char pkt_type;
};

/*
 * Reserved for Francisco Mesquita <francisco.mesquita@radiomovel.pt>
 * for another modified format.
 */
#define FMESQUITA_TCPDUMP_MAGIC 0xa1b234cd

/*
 * Navtel Communcations' format, with nanosecond timestamps,
 * as per a request from Dumas Hwang <dumas.hwang@navtelcom.com>.
 */
#define NAVTEL_TCPDUMP_MAGIC    0xa12b3c4d

/*
 * Normal libpcap format, except for seconds/nanoseconds timestamps,
 * as per a request by Ulf Lamping <ulf.lamping@web.de>
 */
#define NSEC_TCPDUMP_MAGIC      0xa1b23c4d


int
main(int argc, char *argv[])
{
    int i, fd, swapped, pkthdrlen, ret, optct, backwards, caplentoobig;
    struct pcap_file_header pcap_fh;
    struct pcap_pkthdr pcap_ph;
    struct pcap_sf_patched_pkthdr pcap_patched_ph; /* Kuznetzov */
    char buf[10000];
    struct stat statinfo;
    uint64_t pktcnt;
    uint32_t readword;
    int32_t last_sec, last_usec, caplen;

    optct = optionProcess(&tcpcapinfoOptions, argc, argv);
    argc -= optct;
    argv += optct;

#ifdef DEBUG
    if (HAVE_OPT(DBUG))
        debug = OPT_VALUE_DBUG;
#endif

    for (i = 0; i < argc; i++) {
        dbgx(1, "processing:  %s\n", argv[i]);
        if ((fd = open(argv[i], O_RDONLY)) < 0)
            errx(-1, "Error opening file %s: %s", argv[i], strerror(errno));

        if (fstat(fd, &statinfo) < 0)
            errx(-1, "Error getting file stat info %s: %s", argv[i], strerror(errno));

        printf("file size   = %"PRIu64" bytes\n", (uint64_t)statinfo.st_size);

        if ((ret = read(fd, &buf, sizeof(pcap_fh))) != sizeof(pcap_fh))
            errx(-1, "File too small.  Unable to read pcap_file_header from %s", argv[i]);

        dbgx(3, "Read %d bytes for file header", ret);

        swapped = 0;

        memcpy(&pcap_fh, &buf, sizeof(pcap_fh));

        pkthdrlen = 16; /* pcap_pkthdr isn't the actual on-disk format for 64bit systems! */

        switch (pcap_fh.magic) {
            case TCPDUMP_MAGIC:
            printf("magic       = 0x%08"PRIx32" (tcpdump) (%s)\n", pcap_fh.magic, is_not_swapped);
            break;

            case SWAPLONG(TCPDUMP_MAGIC):
            printf("magic       = 0x%08"PRIx32" (tcpdump/swapped) (%s)\n", pcap_fh.magic, is_swapped);
            swapped = 1;
            break;

            case KUZNETZOV_TCPDUMP_MAGIC:
            pkthdrlen = sizeof(pcap_patched_ph);
            printf("magic       = 0x%08"PRIx32" (Kuznetzov) (%s)\n", pcap_fh.magic, is_not_swapped);
            break;

            case SWAPLONG(KUZNETZOV_TCPDUMP_MAGIC):
            pkthdrlen = sizeof(pcap_patched_ph);
            printf("magic       = 0x%08"PRIx32" (Kuznetzov/swapped) (%s)\n", pcap_fh.magic, is_swapped);
            swapped = 1;
            break;

            case FMESQUITA_TCPDUMP_MAGIC:
            printf("magic       = 0x%08"PRIx32" (Fmesquita) (%s)\n", pcap_fh.magic, is_not_swapped);
            break;

            case SWAPLONG(FMESQUITA_TCPDUMP_MAGIC):
            printf("magic       = 0x%08"PRIx32" (Fmesquita) (%s)\n", pcap_fh.magic, is_swapped);
            swapped = 1;
            break;

            case NAVTEL_TCPDUMP_MAGIC:
            printf("magic       = 0x%08"PRIx32" (Navtel) (%s)\n", pcap_fh.magic, is_not_swapped);
            break;

            case SWAPLONG(NAVTEL_TCPDUMP_MAGIC):
            printf("magic       = 0x%08"PRIx32" (Navtel/swapped) (%s)\n", pcap_fh.magic, is_swapped);
            swapped = 1;
            break;

            case NSEC_TCPDUMP_MAGIC:
            printf("magic       = 0x%08"PRIx32" (Nsec) (%s)\n", pcap_fh.magic, is_not_swapped);
            break;

            case SWAPLONG(NSEC_TCPDUMP_MAGIC):
            printf("magic       = 0x%08"PRIx32" (Nsec/swapped) (%s)\n", pcap_fh.magic, is_swapped);
            swapped = 1;
            break;

            default:
            printf("magic       = 0x%08"PRIx32" (unknown)\n", pcap_fh.magic);
        }

        if (swapped == 1) {
            pcap_fh.version_major = SWAPSHORT(pcap_fh.version_major);
            pcap_fh.version_minor = SWAPSHORT(pcap_fh.version_minor);
            pcap_fh.thiszone = SWAPLONG(pcap_fh.thiszone);
            pcap_fh.sigfigs = SWAPLONG(pcap_fh.sigfigs);
            pcap_fh.snaplen = SWAPLONG(pcap_fh.snaplen);
            pcap_fh.linktype = SWAPLONG(pcap_fh.linktype);
        }

        printf("version     = %hu.%hu\n", pcap_fh.version_major, pcap_fh.version_minor);
        printf("thiszone    = 0x%08"PRIx32"\n", pcap_fh.thiszone);
        printf("sigfigs     = 0x%08"PRIx32"\n", pcap_fh.sigfigs);
        printf("snaplen     = %"PRIu32"\n", pcap_fh.snaplen);
        printf("linktype    = 0x%08"PRIx32"\n", pcap_fh.linktype);

        if (pcap_fh.version_major != 2 && pcap_fh.version_minor != 4) {
            printf("Sorry, we only support file format version 2.4\n");
            close(fd);
            continue;
        }

        dbgx(5, "Packet header len: %d", pkthdrlen);

        if (pkthdrlen == 24) {
            printf("Packet\tOrigLen\t\tCaplen\t\tTimestamp\t\tIndex\tProto\tPktType\tPktCsum\tNote\n");
        } else {
            printf("Packet\tOrigLen\t\tCaplen\t\tTimestamp\tCsum\tNote\n");
        }

        pktcnt = 0;
        last_sec = 0;
        last_usec = 0;
        while ((ret = read(fd, &buf, pkthdrlen)) == pkthdrlen) {
            pktcnt ++;
            backwards = 0;
            caplentoobig = 0;
            dbgx(3, "Read %d bytes for packet %"PRIu64" header", ret, pktcnt);

            memset(&pcap_ph, 0, sizeof(pcap_ph));

            /* see what packet header we're using */
            if (pkthdrlen == sizeof(pcap_patched_ph)) {
                memcpy(&pcap_patched_ph, &buf, sizeof(pcap_patched_ph));

                if (swapped == 1) {
                    dbg(3, "Swapping packet header bytes...");
                    pcap_patched_ph.caplen = SWAPLONG(pcap_patched_ph.caplen);
                    pcap_patched_ph.len = SWAPLONG(pcap_patched_ph.len);
                    pcap_patched_ph.ts.tv_sec = SWAPLONG(pcap_patched_ph.ts.tv_sec);
                    pcap_patched_ph.ts.tv_usec = SWAPLONG(pcap_patched_ph.ts.tv_usec);
                    pcap_patched_ph.index = SWAPLONG(pcap_patched_ph.index);
                    pcap_patched_ph.protocol = SWAPSHORT(pcap_patched_ph.protocol);
                }
                printf("%"PRIu64"\t%4"PRIu32"\t\t%4"PRIu32"\t\t%"
                        PRIx32".%"PRIx32"\t\t%4"PRIu32"\t%4hu\t%4hhu", 
                        pktcnt, pcap_patched_ph.len, pcap_patched_ph.caplen, 
                        pcap_patched_ph.ts.tv_sec, pcap_patched_ph.ts.tv_usec,
                        pcap_patched_ph.index, pcap_patched_ph.protocol, pcap_patched_ph.pkt_type);

                if (pcap_fh.snaplen < pcap_patched_ph.caplen) {
                    caplentoobig = 1;
                }

                caplen = pcap_patched_ph.caplen;

            } else {
                /* manually map on-disk bytes to our memory structure */
                memcpy(&readword, buf, 4);
                pcap_ph.ts.tv_sec = readword;
                memcpy(&readword, &buf[4], 4);
                pcap_ph.ts.tv_usec = readword;
                memcpy(&pcap_ph.caplen, &buf[8], 4);
                memcpy(&pcap_ph.len, &buf[12], 4);

                if (swapped == 1) {
                    dbg(3, "Swapping packet header bytes...");
                    pcap_ph.caplen = SWAPLONG(pcap_ph.caplen);
                    pcap_ph.len = SWAPLONG(pcap_ph.len);
                    pcap_ph.ts.tv_sec = SWAPLONG(pcap_ph.ts.tv_sec);
                    pcap_ph.ts.tv_usec = SWAPLONG(pcap_ph.ts.tv_usec);
                }
                printf("%"PRIu64"\t%4"PRIu32"\t\t%4"PRIu32"\t\t%"
                        PRIx32".%"PRIx32,
                        pktcnt, pcap_ph.len, pcap_ph.caplen, 
                        (unsigned int)pcap_ph.ts.tv_sec, (unsigned int)pcap_ph.ts.tv_usec);
                if (pcap_fh.snaplen < pcap_ph.caplen) {
                    caplentoobig = 1;
                }
                caplen = pcap_ph.caplen;
            }

            /* check to make sure timestamps don't go backwards */
            if (last_sec > 0 && last_usec > 0) {
                if ((pcap_ph.ts.tv_sec == last_sec) ? 
                        (pcap_ph.ts.tv_usec < last_usec) : 
                        (pcap_ph.ts.tv_sec < last_sec)) {
                    backwards = 1;
                }
            }
            if (pkthdrlen == sizeof(pcap_patched_ph)) {
                last_sec = pcap_patched_ph.ts.tv_sec;
                last_usec = pcap_patched_ph.ts.tv_usec;
            } else {
                last_sec = pcap_ph.ts.tv_sec;
                last_usec = pcap_ph.ts.tv_usec;
            }

            /* read the frame */
            if ((ret = read(fd, &buf, caplen)) != caplen) {
                if (ret < 0) {
                    printf("Error reading file: %s: %s\n", argv[i], strerror(errno));
                } else {
                    printf("File truncated!  Unable to jump to next packet.\n");
                }

                close(fd);
                continue;
            }

            /* print the frame checksum */
            printf("\t%x\t", do_checksum_math((u_int16_t *)buf, caplen));

            /* print the Note */
            if (! backwards && ! caplentoobig) {
                printf("OK\n");
            } else if (backwards && ! caplentoobig) {
                printf("BAD_TS\n");
            } else if (caplentoobig && ! backwards) {
                printf("TOOBIG\n");
            } else if (backwards && caplentoobig) {
                printf("BAD_TS|TOOBIG");
            } 

        }

    }

    exit(0);

}

/**
 * code to do a ones-compliment checksum
 */
static int
do_checksum_math(u_int16_t *data, int len)
{
    int sum = 0;
    union {
        u_int16_t s;
        u_int8_t b[2];
    } pad;

    while (len > 1) {
        sum += *data++;
        len -= 2;
    }

    if (len == 1) {
        pad.b[0] = *(u_int8_t *)data;
        pad.b[1] = 0;
        sum += pad.s;
    }

    return (sum);
}



Fixed version (ground truth):
/* $Id$ */

/*
 *   Copyright (c) 2001-2012 Aaron Turner <aturner at synfin dot net>
 *   Copyright (c) 2013-2016 Fred Klassen <tcpreplay at appneta dot com> - AppNeta
 *
 *   The Tcpreplay Suite of tools 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 3 of the 
 *   License, or with the authors permission any later version.
 *
 *   The Tcpreplay Suite 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 the Tcpreplay Suite.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "config.h"
#include "defines.h"
#include "common.h"

#include <fcntl.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <unistd.h>
#include <pcap.h>
#include <sys/stat.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <inttypes.h>

#define __STDC_FORMAT_MACROS 1
#include <inttypes.h>

#include "tcpcapinfo_opts.h"

static int do_checksum_math(u_int16_t *data, int len);

#ifdef DEBUG
int debug = 0;
#endif

#ifdef WORDS_BIGENDIAN
char is_swapped[] = "little-endian";
char is_not_swapped[] = "big-endian";
#else
char is_not_swapped[] = "little-endian";
char is_swapped[] = "big-endian";
#endif

int read_packet(int fd, uint32_t len, char *fname);

/*
 * Standard libpcap format.
 */
#define TCPDUMP_MAGIC           0xa1b2c3d4

/*
 * Alexey Kuznetzov's modified libpcap format.
 */
#define KUZNETZOV_TCPDUMP_MAGIC 0xa1b2cd34
struct pcap_timeval {
    bpf_int32 tv_sec;           /* seconds */
    bpf_int32 tv_usec;          /* microseconds */
};
struct pcap_sf_patched_pkthdr {
    struct pcap_timeval ts;     /* time stamp */
    bpf_u_int32 caplen;         /* length of portion present */
    bpf_u_int32 len;            /* length this packet (off wire) */
    int         index;
    unsigned short protocol;
    unsigned char pkt_type;
};

/*
 * Reserved for Francisco Mesquita <francisco.mesquita@radiomovel.pt>
 * for another modified format.
 */
#define FMESQUITA_TCPDUMP_MAGIC 0xa1b234cd

/*
 * Navtel Communcations' format, with nanosecond timestamps,
 * as per a request from Dumas Hwang <dumas.hwang@navtelcom.com>.
 */
#define NAVTEL_TCPDUMP_MAGIC    0xa12b3c4d

/*
 * Normal libpcap format, except for seconds/nanoseconds timestamps,
 * as per a request by Ulf Lamping <ulf.lamping@web.de>
 */
#define NSEC_TCPDUMP_MAGIC      0xa1b23c4d


int
main(int argc, char *argv[])
{
    int i, fd, swapped, pkthdrlen, ret, optct, backwards, caplentoobig;
    struct pcap_file_header pcap_fh;
    struct pcap_pkthdr pcap_ph;
    struct pcap_sf_patched_pkthdr pcap_patched_ph; /* Kuznetzov */
    char buf[10000];
    struct stat statinfo;
    uint64_t pktcnt;
    uint32_t readword;
    int32_t last_sec, last_usec, caplen;

    optct = optionProcess(&tcpcapinfoOptions, argc, argv);
    argc -= optct;
    argv += optct;

#ifdef DEBUG
    if (HAVE_OPT(DBUG))
        debug = OPT_VALUE_DBUG;
#endif

    for (i = 0; i < argc; i++) {
        dbgx(1, "processing:  %s\n", argv[i]);
        if ((fd = open(argv[i], O_RDONLY)) < 0)
            errx(-1, "Error opening file %s: %s", argv[i], strerror(errno));

        if (fstat(fd, &statinfo) < 0)
            errx(-1, "Error getting file stat info %s: %s", argv[i], strerror(errno));

        printf("file size   = %"PRIu64" bytes\n", (uint64_t)statinfo.st_size);

        if ((ret = read(fd, &buf, sizeof(pcap_fh))) != sizeof(pcap_fh))
            errx(-1, "File too small.  Unable to read pcap_file_header from %s", argv[i]);

        dbgx(3, "Read %d bytes for file header", ret);

        swapped = 0;

        memcpy(&pcap_fh, &buf, sizeof(pcap_fh));

        pkthdrlen = 16; /* pcap_pkthdr isn't the actual on-disk format for 64bit systems! */

        switch (pcap_fh.magic) {
            case TCPDUMP_MAGIC:
            printf("magic       = 0x%08"PRIx32" (tcpdump) (%s)\n", pcap_fh.magic, is_not_swapped);
            break;

            case SWAPLONG(TCPDUMP_MAGIC):
            printf("magic       = 0x%08"PRIx32" (tcpdump/swapped) (%s)\n", pcap_fh.magic, is_swapped);
            swapped = 1;
            break;

            case KUZNETZOV_TCPDUMP_MAGIC:
            pkthdrlen = sizeof(pcap_patched_ph);
            printf("magic       = 0x%08"PRIx32" (Kuznetzov) (%s)\n", pcap_fh.magic, is_not_swapped);
            break;

            case SWAPLONG(KUZNETZOV_TCPDUMP_MAGIC):
            pkthdrlen = sizeof(pcap_patched_ph);
            printf("magic       = 0x%08"PRIx32" (Kuznetzov/swapped) (%s)\n", pcap_fh.magic, is_swapped);
            swapped = 1;
            break;

            case FMESQUITA_TCPDUMP_MAGIC:
            printf("magic       = 0x%08"PRIx32" (Fmesquita) (%s)\n", pcap_fh.magic, is_not_swapped);
            break;

            case SWAPLONG(FMESQUITA_TCPDUMP_MAGIC):
            printf("magic       = 0x%08"PRIx32" (Fmesquita) (%s)\n", pcap_fh.magic, is_swapped);
            swapped = 1;
            break;

            case NAVTEL_TCPDUMP_MAGIC:
            printf("magic       = 0x%08"PRIx32" (Navtel) (%s)\n", pcap_fh.magic, is_not_swapped);
            break;

            case SWAPLONG(NAVTEL_TCPDUMP_MAGIC):
            printf("magic       = 0x%08"PRIx32" (Navtel/swapped) (%s)\n", pcap_fh.magic, is_swapped);
            swapped = 1;
            break;

            case NSEC_TCPDUMP_MAGIC:
            printf("magic       = 0x%08"PRIx32" (Nsec) (%s)\n", pcap_fh.magic, is_not_swapped);
            break;

            case SWAPLONG(NSEC_TCPDUMP_MAGIC):
            printf("magic       = 0x%08"PRIx32" (Nsec/swapped) (%s)\n", pcap_fh.magic, is_swapped);
            swapped = 1;
            break;

            default:
            printf("magic       = 0x%08"PRIx32" (unknown)\n", pcap_fh.magic);
        }

        if (swapped == 1) {
            pcap_fh.version_major = SWAPSHORT(pcap_fh.version_major);
            pcap_fh.version_minor = SWAPSHORT(pcap_fh.version_minor);
            pcap_fh.thiszone = SWAPLONG(pcap_fh.thiszone);
            pcap_fh.sigfigs = SWAPLONG(pcap_fh.sigfigs);
            pcap_fh.snaplen = SWAPLONG(pcap_fh.snaplen);
            pcap_fh.linktype = SWAPLONG(pcap_fh.linktype);
        }

        printf("version     = %hu.%hu\n", pcap_fh.version_major, pcap_fh.version_minor);
        printf("thiszone    = 0x%08"PRIx32"\n", pcap_fh.thiszone);
        printf("sigfigs     = 0x%08"PRIx32"\n", pcap_fh.sigfigs);
        printf("snaplen     = %"PRIu32"\n", pcap_fh.snaplen);
        printf("linktype    = 0x%08"PRIx32"\n", pcap_fh.linktype);

        if (pcap_fh.version_major != 2 && pcap_fh.version_minor != 4) {
            printf("Sorry, we only support file format version 2.4\n");
            close(fd);
            continue;
        }

        dbgx(5, "Packet header len: %d", pkthdrlen);

        if (pkthdrlen == 24) {
            printf("Packet\tOrigLen\t\tCaplen\t\tTimestamp\t\tIndex\tProto\tPktType\tPktCsum\tNote\n");
        } else {
            printf("Packet\tOrigLen\t\tCaplen\t\tTimestamp\tCsum\tNote\n");
        }

        pktcnt = 0;
        last_sec = 0;
        last_usec = 0;
        while ((ret = read(fd, &buf, pkthdrlen)) == pkthdrlen) {
            pktcnt ++;
            backwards = 0;
            caplentoobig = 0;
            dbgx(3, "Read %d bytes for packet %"PRIu64" header", ret, pktcnt);

            memset(&pcap_ph, 0, sizeof(pcap_ph));

            /* see what packet header we're using */
            if (pkthdrlen == sizeof(pcap_patched_ph)) {
                memcpy(&pcap_patched_ph, &buf, sizeof(pcap_patched_ph));

                if (swapped == 1) {
                    dbg(3, "Swapping packet header bytes...");
                    pcap_patched_ph.caplen = SWAPLONG(pcap_patched_ph.caplen);
                    pcap_patched_ph.len = SWAPLONG(pcap_patched_ph.len);
                    pcap_patched_ph.ts.tv_sec = SWAPLONG(pcap_patched_ph.ts.tv_sec);
                    pcap_patched_ph.ts.tv_usec = SWAPLONG(pcap_patched_ph.ts.tv_usec);
                    pcap_patched_ph.index = SWAPLONG(pcap_patched_ph.index);
                    pcap_patched_ph.protocol = SWAPSHORT(pcap_patched_ph.protocol);
                }
                printf("%"PRIu64"\t%4"PRIu32"\t\t%4"PRIu32"\t\t%"
                        PRIx32".%"PRIx32"\t\t%4"PRIu32"\t%4hu\t%4hhu", 
                        pktcnt, pcap_patched_ph.len, pcap_patched_ph.caplen, 
                        pcap_patched_ph.ts.tv_sec, pcap_patched_ph.ts.tv_usec,
                        pcap_patched_ph.index, pcap_patched_ph.protocol, pcap_patched_ph.pkt_type);

                if (pcap_fh.snaplen < pcap_patched_ph.caplen) {
                    caplentoobig = 1;
                }

                caplen = pcap_patched_ph.caplen;

            } else {
                /* manually map on-disk bytes to our memory structure */
                memcpy(&readword, buf, 4);
                pcap_ph.ts.tv_sec = readword;
                memcpy(&readword, &buf[4], 4);
                pcap_ph.ts.tv_usec = readword;
                memcpy(&pcap_ph.caplen, &buf[8], 4);
                memcpy(&pcap_ph.len, &buf[12], 4);

                if (swapped == 1) {
                    dbg(3, "Swapping packet header bytes...");
                    pcap_ph.caplen = SWAPLONG(pcap_ph.caplen);
                    pcap_ph.len = SWAPLONG(pcap_ph.len);
                    pcap_ph.ts.tv_sec = SWAPLONG(pcap_ph.ts.tv_sec);
                    pcap_ph.ts.tv_usec = SWAPLONG(pcap_ph.ts.tv_usec);
                }
                printf("%"PRIu64"\t%4"PRIu32"\t\t%4"PRIu32"\t\t%"
                        PRIx32".%"PRIx32,
                        pktcnt, pcap_ph.len, pcap_ph.caplen, 
                        (unsigned int)pcap_ph.ts.tv_sec, (unsigned int)pcap_ph.ts.tv_usec);
                if (pcap_fh.snaplen < pcap_ph.caplen) {
                    caplentoobig = 1;
                }
                caplen = pcap_ph.caplen;
            }

            if (caplentoobig) {
                printf("\n\nCapture file appears to be damaged or corrupt.\n"
                        "Contains packet of size %u, bigger than snap length %u\n",
                        caplen, pcap_fh.snaplen);

                close(fd);
                break;
            }

            /* check to make sure timestamps don't go backwards */
            if (last_sec > 0 && last_usec > 0) {
                if ((pcap_ph.ts.tv_sec == last_sec) ? 
                        (pcap_ph.ts.tv_usec < last_usec) : 
                        (pcap_ph.ts.tv_sec < last_sec)) {
                    backwards = 1;
                }
            }
            if (pkthdrlen == sizeof(pcap_patched_ph)) {
                last_sec = pcap_patched_ph.ts.tv_sec;
                last_usec = pcap_patched_ph.ts.tv_usec;
            } else {
                last_sec = pcap_ph.ts.tv_sec;
                last_usec = pcap_ph.ts.tv_usec;
            }

            /* read the frame */
            if ((ret = read(fd, &buf, caplen)) != caplen) {
                if (ret < 0) {
                    printf("Error reading file: %s: %s\n", argv[i], strerror(errno));
                } else {
                    printf("File truncated!  Unable to jump to next packet.\n");
                }

                close(fd);
                break;
            }

            /* print the frame checksum */
            printf("\t%x\t", do_checksum_math((u_int16_t *)buf, caplen));

            /* print the Note */
            if (! backwards && ! caplentoobig) {
                printf("OK\n");
            } else if (backwards && ! caplentoobig) {
                printf("BAD_TS\n");
            } else if (caplentoobig && ! backwards) {
                printf("TOOBIG\n");
            } else if (backwards && caplentoobig) {
                printf("BAD_TS|TOOBIG");
            } 

        }

    }

    exit(0);

}

/**
 * code to do a ones-compliment checksum
 */
static int
do_checksum_math(u_int16_t *data, int len)
{
    int sum = 0;
    union {
        u_int16_t s;
        u_int8_t b[2];
    } pad;

    while (len > 1) {
        sum += *data++;
        len -= 2;
    }

    if (len == 1) {
        pad.b[0] = *(u_int8_t *)data;
        pad.b[1] = 0;
        sum += pad.s;
    }

    return (sum);
}