Use __func__ in some error messages in compress_savefile()

[tcpdump] / tcpdump.c

/*
 * Copyright (c) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 2000
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that: (1) source code distributions
 * retain the above copyright notice and this paragraph in its entirety, (2)
 * distributions including binary code include the above copyright notice and
 * this paragraph in its entirety in the documentation or other materials
 * provided with the distribution, and (3) all advertising materials mentioning
 * features or use of this software display the following acknowledgement:
 * ``This product includes software developed by the University of California,
 * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
 * the University nor the names of its contributors may be used to endorse
 * or promote products derived from this software without specific prior
 * written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 * Support for splitting captures into multiple files with a maximum
 * file size:
 *
 * Copyright (c) 2001
 *      Seth Webster <swebster@sst.ll.mit.edu>
 */

/*
 * tcpdump - dump traffic on a network
 *
 * First written in 1987 by Van Jacobson, Lawrence Berkeley Laboratory.
 * Mercilessly hacked and occasionally improved since then via the
 * combined efforts of Van, Steve McCanne and Craig Leres of LBL.
 */

#include <config.h>
#ifndef TCPDUMP_CONFIG_H_
#error "The included config.h header is not from the tcpdump build."
#endif

#include "netdissect-stdinc.h"

/*
 * This must appear after including netdissect-stdinc.h, so that _U_ is
 * defined.
 */
#ifndef lint
static const char copyright[] _U_ =
    "@(#) Copyright (c) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 2000\n\
The Regents of the University of California.  All rights reserved.\n";
#endif

#include <sys/stat.h>

#include <fcntl.h>

#ifdef HAVE_LIBCRYPTO
#include <openssl/crypto.h>
#endif

#ifdef HAVE_GETOPT_LONG
#include <getopt.h>
#else
#include "missing/getopt_long.h"
#endif
/* Capsicum-specific code requires macros from <net/bpf.h>, which will fail
 * to compile if <pcap.h> has already been included; including the headers
 * in the opposite order works fine. For the most part anyway, because in
 * FreeBSD <pcap/pcap.h> declares bpf_dump() instead of <net/bpf.h>. Thus
 * interface.h takes care of it later to avoid a compiler warning.
 */
#ifdef HAVE_CAPSICUM
#include <sys/capsicum.h>
#include <sys/ioccom.h>
#include <net/bpf.h>
#include <libgen.h>
#ifdef HAVE_CASPER
#include <libcasper.h>
#include <casper/cap_dns.h>
#include <sys/nv.h>
#endif  /* HAVE_CASPER */
#endif  /* HAVE_CAPSICUM */
#ifdef HAVE_PCAP_OPEN
/*
 * We found pcap_open() in the capture library, so we'll be using
 * the remote capture APIs; define PCAP_REMOTE before we include pcap.h,
 * so we get those APIs declared, and the types and #defines that they
 * use defined.
 *
 * WinPcap's headers require that PCAP_REMOTE be defined in order to get
 * remote-capture APIs declared and types and #defines that they use
 * defined.
 *
 * (Versions of libpcap with those APIs, and thus Npcap, which is based on
 * those versions of libpcap, don't require it.)
 */
#define HAVE_REMOTE
#endif
#include <pcap.h>
#include <signal.h>
#include <stdio.h>
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#ifdef _WIN32
#include <windows.h>
#else
#include <sys/time.h>
#include <sys/wait.h>
#include <sys/resource.h>
#include <pwd.h>
#include <grp.h>
#endif /* _WIN32 */

/*
 * Pathname separator.
 * Use this in pathnames, but do *not* use it in URLs.
 */
#ifdef _WIN32
#define PATH_SEPARATOR  '\\'
#else
#define PATH_SEPARATOR  '/'
#endif

/* capabilities convenience library */
/* If a code depends on HAVE_LIBCAP_NG, it depends also on HAVE_CAP_NG_H.
 * If HAVE_CAP_NG_H is not defined, undefine HAVE_LIBCAP_NG.
 * Thus, the later tests are done only on HAVE_LIBCAP_NG.
 */
#ifdef HAVE_LIBCAP_NG
#ifdef HAVE_CAP_NG_H
#include <cap-ng.h>
#else
#undef HAVE_LIBCAP_NG
#endif /* HAVE_CAP_NG_H */
#endif /* HAVE_LIBCAP_NG */

#ifdef __FreeBSD__
#include <sys/sysctl.h>
#endif /* __FreeBSD__ */

#include "netdissect-stdinc.h"
#include "netdissect.h"
#include "interface.h"
#include "addrtoname.h"
#include "ascii_strcasecmp.h"

#include "print.h"

#include "diag-control.h"

#include "fptype.h"

#ifndef PATH_MAX
#define PATH_MAX 1024
#endif

#if defined(SIGINFO)
#define SIGNAL_REQ_INFO SIGINFO
#elif defined(SIGUSR1)
#define SIGNAL_REQ_INFO SIGUSR1
#endif

#if defined(SIGUSR2)
#define SIGNAL_FLUSH_PCAP SIGUSR2
#endif

static int Bflag;                       /* buffer size */
static int64_t Cflag;                   /* rotate dump files after this many bytes */
static int Cflag_count;                 /* Keep track of which file number we're writing */
static int Dflag;                       /* list available devices and exit */
#ifdef HAVE_PCAP_FINDALLDEVS_EX
static char *remote_interfaces_source;  /* list available devices from this source and exit */
#endif

/*
 * This is exported because, in some versions of libpcap, if libpcap
 * is built with optimizer debugging code (which is *NOT* the default
 * configuration!), the library *imports*(!) a variable named dflag,
 * under the expectation that tcpdump is exporting it, to govern
 * how much debugging information to print when optimizing
 * the generated BPF code.
 *
 * This is a horrible hack; newer versions of libpcap don't import
 * dflag but, instead, *if* built with optimizer debugging code,
 * *export* a routine to set that flag.
 */
extern int dflag;
int dflag;                              /* print filter code */
static int Gflag;                       /* rotate dump files after this many seconds */
static int Gflag_count;                 /* number of files created with Gflag rotation */
static time_t Gflag_time;               /* The last time_t the dump file was rotated. */
static int Lflag;                       /* list available data link types and exit */
static int Iflag;                       /* rfmon (monitor) mode */
#ifdef HAVE_PCAP_SET_TSTAMP_TYPE
static int Jflag;                       /* list available time stamp types */
static int jflag = -1;                  /* packet time stamp source */
#endif
static int lflag;                       /* line-buffered output */
static int pflag;                       /* don't go promiscuous */
static int Qflag = -1;                  /* restrict captured packet by send/receive direction */
static int Uflag;                       /* "unbuffered" output of dump files */
static int Wflag;                       /* recycle output files after this number of files */
static int WflagChars;
static char *zflag = NULL;              /* compress each savefile using a specified command (like gzip or bzip2) */
static int timeout = 1000;              /* default timeout = 1000 ms = 1 s */
#ifdef HAVE_PCAP_SET_IMMEDIATE_MODE
static int immediate_mode;
#endif
static int count_mode;
static u_int packets_to_skip;

static int infodelay;
static int infoprint;

char *program_name;

/* Forwards */
static int parse_int(const char *argname, const char *string, char **endp,
    int minval, int maxval, int base);
static u_int parse_u_int(const char *argname, const char *string, char **endp,
    u_int minval, u_int maxval, int base);
static int64_t parse_int64(const char *argname, const char *string,
    char **endp, int64_t minval, int64_t maxval, int base);
static void (*setsignal (int sig, void (*func)(int)))(int);
static void cleanup(int);
#if defined(HAVE_FORK) || defined(HAVE_VFORK)
static void child_cleanup(int);
#endif
static void print_version(FILE *);
static void print_usage(FILE *);

static void print_packet(u_char *, const struct pcap_pkthdr *, const u_char *);
static void dump_packet_and_trunc(u_char *, const struct pcap_pkthdr *, const u_char *);
static void dump_packet(u_char *, const struct pcap_pkthdr *, const u_char *);

#ifdef SIGNAL_REQ_INFO
static void requestinfo(int);
#endif

#ifdef SIGNAL_FLUSH_PCAP
static void flushpcap(int);
#endif

#ifdef _WIN32
    static HANDLE timer_handle = INVALID_HANDLE_VALUE;
    static void CALLBACK verbose_stats_dump(PVOID param, BOOLEAN timer_fired);
#else /* _WIN32 */
  static void verbose_stats_dump(int sig);
#endif /* _WIN32 */

static void info(int);
static u_int packets_captured;

static const struct tok status_flags[] = {
#ifdef PCAP_IF_UP
        { PCAP_IF_UP,       "Up"       },
#endif
#ifdef PCAP_IF_RUNNING
        { PCAP_IF_RUNNING,  "Running"  },
#endif
        { PCAP_IF_LOOPBACK, "Loopback" },
#ifdef PCAP_IF_WIRELESS
        { PCAP_IF_WIRELESS, "Wireless" },
#endif
        { 0, NULL }
};

static pcap_t *pd;
static pcap_dumper_t *pdd = NULL;

static int supports_monitor_mode;

extern int optind;
extern int opterr;
extern char *optarg;

struct dump_info {
        char    *WFileName;
        char    *CurrentFileName;
        pcap_t  *pd;
        pcap_dumper_t *pdd;
        netdissect_options *ndo;
#ifdef HAVE_CAPSICUM
        int     dirfd;
#endif
};

#if defined(HAVE_PCAP_SET_PARSER_DEBUG)
/*
 * We have pcap_set_parser_debug() in libpcap; declare it (it's not declared
 * by any libpcap header, because it's a special hack, only available if
 * libpcap was configured to include it, and only intended for use by
 * libpcap developers trying to debug the parser for filter expressions).
 */
#ifdef _WIN32
__declspec(dllimport)
#else /* _WIN32 */
extern
#endif /* _WIN32 */
void pcap_set_parser_debug(int);
#elif defined(HAVE_PCAP_DEBUG) || defined(HAVE_YYDEBUG)
/*
 * We don't have pcap_set_parser_debug() in libpcap, but we do have
 * pcap_debug or yydebug.  Make a local version of pcap_set_parser_debug()
 * to set the flag, and define HAVE_PCAP_SET_PARSER_DEBUG.
 */
static void
pcap_set_parser_debug(int value)
{
#ifdef HAVE_PCAP_DEBUG
        extern int pcap_debug;

        pcap_debug = value;
#else /* HAVE_PCAP_DEBUG */
        extern int yydebug;

        yydebug = value;
#endif /* HAVE_PCAP_DEBUG */
}

#define HAVE_PCAP_SET_PARSER_DEBUG
#endif // HAVE_PCAP_SET_PARSER_DEBUG, HAVE_PCAP_DEBUG, HAVE_YYDEBUG

#if defined(HAVE_PCAP_SET_OPTIMIZER_DEBUG)
/*
 * We have pcap_set_optimizer_debug() in libpcap; declare it (it's not declared
 * by any libpcap header, because it's a special hack, only available if
 * libpcap was configured to include it, and only intended for use by
 * libpcap developers trying to debug the optimizer for filter expressions).
 */
#ifdef _WIN32
__declspec(dllimport)
#else /* _WIN32 */
extern
#endif /* _WIN32 */
void pcap_set_optimizer_debug(int);
#endif // HAVE_PCAP_SET_OPTIMIZER_DEBUG

static void NORETURN
exit_tcpdump(const int status)
{
        nd_cleanup();
        exit(status);
}

/* VARARGS */
static void NORETURN PRINTFLIKE(1, 2)
error(FORMAT_STRING(const char *fmt), ...)
{
        va_list ap;

        (void)fprintf(stderr, "%s: ", program_name);
        va_start(ap, fmt);
        (void)vfprintf(stderr, fmt, ap);
        va_end(ap);
        if (*fmt) {
                fmt += strlen(fmt);
                if (fmt[-1] != '\n')
                        (void)fputc('\n', stderr);
        }
        exit_tcpdump(S_ERR_HOST_PROGRAM);
        /* NOTREACHED */
}

/* VARARGS */
static void PRINTFLIKE(1, 2)
warning(FORMAT_STRING(const char *fmt), ...)
{
        va_list ap;

        (void)fprintf(stderr, "%s: WARNING: ", program_name);
        va_start(ap, fmt);
        (void)vfprintf(stderr, fmt, ap);
        va_end(ap);
        if (*fmt) {
                fmt += strlen(fmt);
                if (fmt[-1] != '\n')
                        (void)fputc('\n', stderr);
        }
}

#ifdef HAVE_PCAP_SET_TSTAMP_TYPE
static void NORETURN
show_tstamp_types_and_exit(pcap_t *pc, const char *device)
{
        int n_tstamp_types;
        int *tstamp_types = 0;
        const char *tstamp_type_name;
        int i;

        n_tstamp_types = pcap_list_tstamp_types(pc, &tstamp_types);
        if (n_tstamp_types < 0)
                error("%s", pcap_geterr(pc));

        if (n_tstamp_types == 0) {
                fprintf(stderr, "Time stamp type cannot be set for %s\n",
                    device);
                exit_tcpdump(S_SUCCESS);
        }
        fprintf(stdout, "Time stamp types for %s (use option -j to set):\n",
            device);
        for (i = 0; i < n_tstamp_types; i++) {
                tstamp_type_name = pcap_tstamp_type_val_to_name(tstamp_types[i]);
                if (tstamp_type_name != NULL) {
                        (void) fprintf(stdout, "  %s (%s)\n", tstamp_type_name,
                            pcap_tstamp_type_val_to_description(tstamp_types[i]));
                } else {
                        (void) fprintf(stdout, "  %d\n", tstamp_types[i]);
                }
        }
        pcap_free_tstamp_types(tstamp_types);
        exit_tcpdump(S_SUCCESS);
}
#endif // HAVE_PCAP_SET_TSTAMP_TYPE

static void NORETURN
show_dlts_and_exit(pcap_t *pc, const char *device)
{
        int n_dlts, i;
        int *dlts = 0;
        const char *dlt_name;

        n_dlts = pcap_list_datalinks(pc, &dlts);
        if (n_dlts < 0)
                error("%s", pcap_geterr(pc));
        else if (n_dlts == 0 || !dlts)
                error("No data link types.");

        /*
         * If the interface is known to support monitor mode, indicate
         * whether these are the data link types available when not in
         * monitor mode, if -I wasn't specified, or when in monitor mode,
         * when -I was specified (the link-layer types available in
         * monitor mode might be different from the ones available when
         * not in monitor mode).
         */
        (void) fprintf(stdout, "Data link types for ");
        if (supports_monitor_mode)
                (void) fprintf(stdout, "%s %s",
                    device,
                    Iflag ? "when in monitor mode" : "when not in monitor mode");
        else
                (void) fprintf(stdout, "%s",
                    device);
        (void) fprintf(stdout, " (use option -y to set):\n");

        for (i = 0; i < n_dlts; i++) {
                dlt_name = pcap_datalink_val_to_name(dlts[i]);
                if (dlt_name != NULL) {
                        (void) fprintf(stdout, "  %s (%s)", dlt_name,
                            pcap_datalink_val_to_description(dlts[i]));

                        /*
                         * OK, does tcpdump handle that type?
                         */
                        if (!has_printer(dlts[i]))
                                (void) fprintf(stdout, " (printing not supported)");
                        fprintf(stdout, "\n");
                } else {
                        (void) fprintf(stdout, "  DLT %d (printing not supported)\n",
                            dlts[i]);
                }
        }
        pcap_free_datalinks(dlts);
        exit_tcpdump(S_SUCCESS);
}

static void NORETURN
show_devices_and_exit(void)
{
        pcap_if_t *dev, *devlist;
        char ebuf[PCAP_ERRBUF_SIZE];
        int i;

        if (pcap_findalldevs(&devlist, ebuf) < 0)
                error("%s", ebuf);
        for (i = 0, dev = devlist; dev != NULL; i++, dev = dev->next) {
                printf("%d.%s", i+1, dev->name);
                if (dev->description != NULL)
                        printf(" (%s)", dev->description);
                if (dev->flags != 0) {
                        printf(" [");
                        printf("%s", bittok2str(status_flags, "none", dev->flags));
#ifdef PCAP_IF_WIRELESS
                        if (dev->flags & PCAP_IF_WIRELESS) {
                                switch (dev->flags & PCAP_IF_CONNECTION_STATUS) {

                                case PCAP_IF_CONNECTION_STATUS_UNKNOWN:
                                        printf(", Association status unknown");
                                        break;

                                case PCAP_IF_CONNECTION_STATUS_CONNECTED:
                                        printf(", Associated");
                                        break;

                                case PCAP_IF_CONNECTION_STATUS_DISCONNECTED:
                                        printf(", Not associated");
                                        break;

                                case PCAP_IF_CONNECTION_STATUS_NOT_APPLICABLE:
                                        break;
                                }
                        } else {
                                switch (dev->flags & PCAP_IF_CONNECTION_STATUS) {

                                case PCAP_IF_CONNECTION_STATUS_UNKNOWN:
                                        printf(", Connection status unknown");
                                        break;

                                case PCAP_IF_CONNECTION_STATUS_CONNECTED:
                                        printf(", Connected");
                                        break;

                                case PCAP_IF_CONNECTION_STATUS_DISCONNECTED:
                                        printf(", Disconnected");
                                        break;

                                case PCAP_IF_CONNECTION_STATUS_NOT_APPLICABLE:
                                        break;
                                }
                        }
#endif // PCAP_IF_WIRELESS
                        printf("]");
                }
                printf("\n");
        }
        pcap_freealldevs(devlist);
        exit_tcpdump(S_SUCCESS);
}

#ifdef HAVE_PCAP_FINDALLDEVS_EX
static void NORETURN
show_remote_devices_and_exit(void)
{
        pcap_if_t *dev, *devlist;
        char ebuf[PCAP_ERRBUF_SIZE];
        int i;

        if (pcap_findalldevs_ex(remote_interfaces_source, NULL, &devlist,
            ebuf) < 0) {
                if (strcmp(ebuf, "not supported") == 0) {
                        /*
                         * macOS 14's pcap_findalldevs_ex(), which is a
                         * stub that always returns -1 with an error
                         * message of "not supported".
                         *
                         * In this case, as we passed it an rpcap://
                         * URL, treat that as meaning "remote capture
                         * not supported".
                         */
                        error("Remote capture not supported");
                }
                error("%s", ebuf);
        }
        for (i = 0, dev = devlist; dev != NULL; i++, dev = dev->next) {
                printf("%d.%s", i+1, dev->name);
                if (dev->description != NULL)
                        printf(" (%s)", dev->description);
                if (dev->flags != 0)
                        printf(" [%s]", bittok2str(status_flags, "none", dev->flags));
                printf("\n");
        }
        pcap_freealldevs(devlist);
        exit_tcpdump(S_SUCCESS);
}
#endif /* HAVE_PCAP_FINDALLDEVS_EX */

/*
 * Short options.
 *
 * Note that there we use all letters for short options except for g, k,
 * o, and P, and those are used by other versions of tcpdump, and we should
 * only use them for the same purposes that the other versions of tcpdump
 * use them:
 *
 * macOS tcpdump uses -g to force non--v output for IP to be on one
 * line, making it more "g"repable;
 *
 * macOS tcpdump uses -k to specify that packet comments in pcapng files
 * should be printed;
 *
 * OpenBSD tcpdump uses -o to indicate that OS fingerprinting should be done
 * for hosts sending TCP SYN packets;
 *
 * macOS tcpdump uses -P to indicate that -w should write pcapng rather
 * than pcap files.
 *
 * macOS tcpdump also uses -Q to specify expressions that match packet
 * metadata, including but not limited to the packet direction.
 * The expression syntax is different from a simple "in|out|inout",
 * and those expressions aren't accepted by macOS tcpdump, but the
 * equivalents would be "in" = "dir=in", "out" = "dir=out", and
 * "inout" = "dir=in or dir=out", and the parser could conceivably
 * special-case "in", "out", and "inout" as expressions for backwards
 * compatibility, so all is not (yet) lost.
 */

/*
 * Set up flags that might or might not be supported depending on the
 * version of libpcap we're using.
 */
#ifdef HAVE_PCAP_SET_TSTAMP_TYPE
#define j_FLAG          "j:"
#define j_FLAG_USAGE    " [ -j tstamptype ]"
#define J_FLAG          "J"
#else /* HAVE_PCAP_SET_TSTAMP_TYPE */
#define j_FLAG
#define j_FLAG_USAGE
#define J_FLAG
#endif /* HAVE_PCAP_SET_TSTAMP_TYPE */

#ifdef USE_LIBSMI
#define m_FLAG_USAGE "[ -m module ] ..."
#endif

#define SHORTOPTS "aAbB:c:C:dDeE:fF:G:hHi:I" j_FLAG J_FLAG "KlLm:M:nNOpqQ:r:s:StT:uUvV:w:W:xXy:Yz:Z:#"

/*
 * Long options.
 *
 * We do not currently have long options corresponding to all short
 * options; we should probably pick appropriate option names for them.
 *
 * However, the short options where the number of times the option is
 * specified matters, such as -v and -d and -t, should probably not
 * just map to a long option, as saying
 *
 *  tcpdump --verbose --verbose
 *
 * doesn't make sense; it should be --verbosity={N} or something such
 * as that.
 *
 * For long options with no corresponding short options, we define values
 * outside the range of ASCII graphic characters, make that the last
 * component of the entry for the long option, and have a case for that
 * option in the switch statement.
 */
#define OPTION_VERSION                  128
#define OPTION_TSTAMP_PRECISION         129
#define OPTION_IMMEDIATE_MODE           130
#define OPTION_PRINT                    131
#define OPTION_LIST_REMOTE_INTERFACES   132
#define OPTION_TSTAMP_MICRO             133
#define OPTION_TSTAMP_NANO              134
#define OPTION_FP_TYPE                  135
#define OPTION_COUNT                    136
#define OPTION_PRINT_SAMPLING           137
#define OPTION_LENGTHS                  138
#define OPTION_TIME_T_SIZE              139
#define OPTION_SKIP                     140

static const struct option longopts[] = {
        { "buffer-size", required_argument, NULL, 'B' },
        { "list-interfaces", no_argument, NULL, 'D' },
#ifdef HAVE_PCAP_FINDALLDEVS_EX
        { "list-remote-interfaces", required_argument, NULL, OPTION_LIST_REMOTE_INTERFACES },
#endif
        { "help", no_argument, NULL, 'h' },
        { "interface", required_argument, NULL, 'i' },
        { "monitor-mode", no_argument, NULL, 'I' },
#ifdef HAVE_PCAP_SET_TSTAMP_TYPE
        { "time-stamp-type", required_argument, NULL, 'j' },
        { "list-time-stamp-types", no_argument, NULL, 'J' },
#endif
#ifdef HAVE_PCAP_SET_TSTAMP_PRECISION
        { "micro", no_argument, NULL, OPTION_TSTAMP_MICRO},
        { "nano", no_argument, NULL, OPTION_TSTAMP_NANO},
        { "time-stamp-precision", required_argument, NULL, OPTION_TSTAMP_PRECISION},
#endif
        { "dont-verify-checksums", no_argument, NULL, 'K' },
        { "list-data-link-types", no_argument, NULL, 'L' },
        { "no-optimize", no_argument, NULL, 'O' },
        { "no-promiscuous-mode", no_argument, NULL, 'p' },
        { "direction", required_argument, NULL, 'Q' },
        { "snapshot-length", required_argument, NULL, 's' },
        { "absolute-tcp-sequence-numbers", no_argument, NULL, 'S' },
        { "packet-buffered", no_argument, NULL, 'U' },
        { "linktype", required_argument, NULL, 'y' },
#ifdef HAVE_PCAP_SET_IMMEDIATE_MODE
        { "immediate-mode", no_argument, NULL, OPTION_IMMEDIATE_MODE },
#endif
#ifdef HAVE_PCAP_SET_PARSER_DEBUG
        { "debug-filter-parser", no_argument, NULL, 'Y' },
#endif
        { "relinquish-privileges", required_argument, NULL, 'Z' },
        { "count", no_argument, NULL, OPTION_COUNT },
        { "fp-type", no_argument, NULL, OPTION_FP_TYPE },
        { "number", no_argument, NULL, '#' },
        { "print", no_argument, NULL, OPTION_PRINT },
        { "print-sampling", required_argument, NULL, OPTION_PRINT_SAMPLING },
        { "lengths", no_argument, NULL, OPTION_LENGTHS },
        { "time-t-size", no_argument, NULL, OPTION_TIME_T_SIZE },
        { "skip", required_argument, NULL, OPTION_SKIP },
        { "version", no_argument, NULL, OPTION_VERSION },
        { NULL, 0, NULL, 0 }
};

#ifdef HAVE_PCAP_FINDALLDEVS_EX
#define LIST_REMOTE_INTERFACES_USAGE " [ --list-remote-interfaces remote-source ]"
#else
#define LIST_REMOTE_INTERFACES_USAGE
#endif

#ifdef HAVE_PCAP_SET_IMMEDIATE_MODE
#define IMMEDIATE_MODE_USAGE " [ --immediate-mode ]"
#else
#define IMMEDIATE_MODE_USAGE ""
#endif

#ifndef _WIN32
/* Drop root privileges and chroot if necessary */
static void
droproot(const char *username, const char *chroot_dir)
{
        struct passwd *pw = NULL;

        if (chroot_dir && !username)
                error("Chroot without dropping root is insecure");

        pw = getpwnam(username);
        if (pw) {
                if (chroot_dir) {
                        if (chroot(chroot_dir) != 0 || chdir ("/") != 0)
                                error("Couldn't chroot/chdir to '%.64s': %s",
                                      chroot_dir, pcap_strerror(errno));
                }
#ifdef HAVE_LIBCAP_NG
                {
                        int ret = capng_change_id(pw->pw_uid, pw->pw_gid, CAPNG_NO_FLAG);
                        if (ret < 0)
                                error("capng_change_id(): return %d\n", ret);
                        else
                                fprintf(stderr, "dropped privs to %s\n", username);
                }
#else
                if (initgroups(pw->pw_name, pw->pw_gid) != 0 ||
                    setgid(pw->pw_gid) != 0 || setuid(pw->pw_uid) != 0)
                        error("Couldn't change to '%.32s' uid=%lu gid=%lu: %s",
                                username,
                                (unsigned long)pw->pw_uid,
                                (unsigned long)pw->pw_gid,
                                pcap_strerror(errno));
                else {
                        fprintf(stderr, "dropped privs to %s\n", username);
                }
#endif /* HAVE_LIBCAP_NG */
        } else
                error("Couldn't find user '%.32s'", username);
#ifdef HAVE_LIBCAP_NG
        /* We don't need CAP_SETUID, CAP_SETGID and CAP_SYS_CHROOT anymore. */
DIAG_OFF_ASSIGN_ENUM
        capng_updatev(
                CAPNG_DROP,
                CAPNG_EFFECTIVE | CAPNG_PERMITTED,
                CAP_SETUID,
                CAP_SETGID,
                CAP_SYS_CHROOT,
                -1);
DIAG_ON_ASSIGN_ENUM
        capng_apply(CAPNG_SELECT_BOTH);
#endif /* HAVE_LIBCAP_NG */

}
#endif /* _WIN32 */

static int
getWflagChars(int x)
{
        int c = 0;

        x -= 1;
        while (x > 0) {
                c += 1;
                x /= 10;
        }

        return c;
}


static void
MakeFilename(char *buffer, char *orig_name, int cnt, int max_chars)
{
        char *filename = malloc(PATH_MAX + 1);
        if (filename == NULL)
            error("%s: malloc", __func__);
        if (strlen(orig_name) == 0)
            error("an empty string is not a valid file name");

        /* Process with strftime if Gflag is set. */
        if (Gflag != 0) {
          struct tm *local_tm;

          /* Convert Gflag_time to a usable format */
          if ((local_tm = localtime(&Gflag_time)) == NULL) {
                  error("%s: localtime", __func__);
          }

          /* There's no good way to detect an error in strftime since a return
           * value of 0 isn't necessarily failure; if orig_name is an empty
           * string, the formatted string will be empty.
           *
           * However, the C90 standard says that, if there *is* a
           * buffer overflow, the content of the buffer is undefined,
           * so we must check for a buffer overflow.
           *
           * So we check above for an empty orig_name, and only call
           * strftime() if it's non-empty, in which case the return
           * value will only be 0 if the formatted date doesn't fit
           * in the buffer.
           *
           * (We check above because, even if we don't use -G, we
           * want a better error message than "tcpdump: : No such
           * file or directory" for this case.)
           */
          if (strftime(filename, PATH_MAX, orig_name, local_tm) == 0) {
            error("%s: strftime", __func__);
          }
        } else {
          strncpy(filename, orig_name, PATH_MAX);
        }

        if (cnt == 0 && max_chars == 0)
                strncpy(buffer, filename, PATH_MAX + 1);
        else
                if (snprintf(buffer, PATH_MAX + 1, "%s%0*d", filename, max_chars, cnt) > PATH_MAX)
                  /* Report an error if the filename is too large */
                  error("too many output files or filename is too long (> %d)", PATH_MAX);
        free(filename);
}

static char *
get_next_file(FILE *VFile, char *ptr)
{
        char *ret;
        size_t len;

        ret = fgets(ptr, PATH_MAX, VFile);
        if (!ret)
                return NULL;

        len = strlen (ptr);
        if (len > 0 && ptr[len - 1] == '\n')
                ptr[len - 1] = '\0';

        return ret;
}

#ifdef HAVE_CASPER
static cap_channel_t *
capdns_setup(void)
{
        cap_channel_t *capcas, *capdnsloc;
        const char *types[1];
        int families[2];

        capcas = cap_init();
        if (capcas == NULL)
                error("unable to create casper process");
        capdnsloc = cap_service_open(capcas, "system.dns");
        /* Casper capability no longer needed. */
        cap_close(capcas);
        if (capdnsloc == NULL)
                error("unable to open system.dns service");
        /* Limit system.dns to reverse DNS lookups. */
        types[0] = "ADDR";
        if (cap_dns_type_limit(capdnsloc, types, 1) < 0)
                error("unable to limit access to system.dns service");
        families[0] = AF_INET;
        /* Casper is a feature of FreeBSD, which defines AF_INET6. */
        families[1] = AF_INET6;
        if (cap_dns_family_limit(capdnsloc, families, 2) < 0)
                error("unable to limit access to system.dns service");

        return (capdnsloc);
}
#endif  /* HAVE_CASPER */

#ifdef HAVE_PCAP_SET_TSTAMP_PRECISION
static int
tstamp_precision_from_string(const char *precision)
{
        if (strncmp(precision, "nano", strlen("nano")) == 0)
                return PCAP_TSTAMP_PRECISION_NANO;

        if (strncmp(precision, "micro", strlen("micro")) == 0)
                return PCAP_TSTAMP_PRECISION_MICRO;

        return -EINVAL;
}

static const char *
tstamp_precision_to_string(int precision)
{
        switch (precision) {

        case PCAP_TSTAMP_PRECISION_MICRO:
                return "micro";

        case PCAP_TSTAMP_PRECISION_NANO:
                return "nano";

        default:
                return "unknown";
        }
}
#endif // HAVE_PCAP_SET_TSTAMP_PRECISION

#ifdef HAVE_CAPSICUM
/*
 * Ensure that, on a dump file's descriptor, we have all the rights
 * necessary to make the standard I/O library work with an fdopen()ed
 * FILE * from that descriptor.
 *
 * A long time ago in a galaxy far, far away, AT&T decided that, instead
 * of providing separate APIs for getting and setting the FD_ flags on a
 * descriptor, getting and setting the O_ flags on a descriptor, and
 * locking files, they'd throw them all into a kitchen-sink fcntl() call
 * along the lines of ioctl(), the fact that ioctl() operations are
 * largely specific to particular character devices but fcntl() operations
 * are either generic to all descriptors or generic to all descriptors for
 * regular files notwithstanding.
 *
 * The Capsicum people decided that fine-grained control of descriptor
 * operations was required, so that you need to grant permission for
 * reading, writing, seeking, and fcntl-ing.  The latter, courtesy of
 * AT&T's decision, means that "fcntl-ing" isn't a thing, but a motley
 * collection of things, so there are *individual* fcntls for which
 * permission needs to be granted.
 *
 * The FreeBSD standard I/O people implemented some optimizations that
 * requires that the standard I/O routines be able to determine whether
 * the descriptor for the FILE * is open append-only or not; as that
 * descriptor could have come from an open() rather than an fopen(),
 * that requires that it be able to do an F_GETFL fcntl() to read
 * the O_ flags.
 *
 * tcpdump uses ftell() to determine how much data has been written
 * to a file in order to, when used with -C, determine when it's time
 * to rotate capture files.  ftell() therefore needs to do an lseek()
 * to find out the file offset and must, thanks to the aforementioned
 * optimization, also know whether the descriptor is open append-only
 * or not.
 *
 * The net result of all the above is that we need to grant CAP_SEEK,
 * CAP_WRITE, and CAP_FCNTL with the CAP_FCNTL_GETFL subcapability.
 *
 * Perhaps this is the universe's way of saying that either
 *
 *      1) there needs to be an fopenat() call and a pcap_dump_openat() call
 *         using it, so that Capsicum-capable tcpdump wouldn't need to do
 *         an fdopen()
 *
 * or
 *
 *      2) there needs to be a cap_fdopen() call in the FreeBSD standard
 *         I/O library that knows what rights are needed by the standard
 *         I/O library, based on the open mode, and assigns them, perhaps
 *         with an additional argument indicating, for example, whether
 *         seeking should be allowed, so that tcpdump doesn't need to know
 *         what the standard I/O library happens to require this week.
 */
static void
set_dumper_capsicum_rights(pcap_dumper_t *p)
{
        int fd = fileno(pcap_dump_file(p));
        cap_rights_t rights;

        cap_rights_init(&rights, CAP_SEEK, CAP_WRITE, CAP_FCNTL);
        if (cap_rights_limit(fd, &rights) < 0 && errno != ENOSYS) {
                error("unable to limit dump descriptor");
        }
        if (cap_fcntls_limit(fd, CAP_FCNTL_GETFL) < 0 && errno != ENOSYS) {
                error("unable to limit dump descriptor fcntls");
        }
}
#endif // HAVE_CAPSICUM

/*
 * Copy arg vector into a new buffer, concatenating arguments with spaces.
 */
static char *
copy_argv(char **argv)
{
        char **p;
        size_t len = 0;
        char *buf;
        char *src, *dst;

        p = argv;
        if (*p == NULL)
                return 0;

        while (*p)
                len += strlen(*p++) + 1;

        buf = (char *)malloc(len);
        if (buf == NULL)
                error("%s: malloc", __func__);

        p = argv;
        dst = buf;
        while ((src = *p++) != NULL) {
                while ((*dst++ = *src++) != '\0')
                        ;
                dst[-1] = ' ';
        }
        dst[-1] = '\0';

        return buf;
}

/*
 * On Windows, we need to open the file in binary mode, so that
 * we get all the bytes specified by the size we get from "fstat()".
 * On UNIX, that's not necessary.  O_BINARY is defined on Windows;
 * we define it as 0 if it's not defined, so it does nothing.
 */
#ifndef O_BINARY
#define O_BINARY        0
#endif

static char *
read_infile(char *fname)
{
        int i, fd;
        ssize_t cc;
        char *cp;
        our_statb buf;

        fd = open(fname, O_RDONLY|O_BINARY);
        if (fd < 0)
                error("can't open %s: %s", fname, pcap_strerror(errno));

        if (our_fstat(fd, &buf) < 0)
                error("can't stat %s: %s", fname, pcap_strerror(errno));

        /*
         * Reject files whose size doesn't fit into an int; a filter
         * *that* large will probably be too big.
         */
        if (buf.st_size > INT_MAX)
                error("%s is too large", fname);

        cp = malloc((u_int)buf.st_size + 1);
        if (cp == NULL)
                error("malloc(%d) for %s: %s", (u_int)buf.st_size + 1,
                        fname, pcap_strerror(errno));
        cc = read(fd, cp, (u_int)buf.st_size);
        if (cc < 0)
                error("read %s: %s", fname, pcap_strerror(errno));
        if (cc != buf.st_size)
                error("short read %s (%d != %d)", fname, (int) cc,
                    (int)buf.st_size);

        close(fd);
        /* replace "# comment" with spaces */
        for (i = 0; i < cc; i++) {
                if (cp[i] == '#')
                        while (i < cc && cp[i] != '\n')
                                cp[i++] = ' ';
        }
        cp[cc] = '\0';
        return (cp);
}

static long
parse_interface_number(const char *device)
{
        const char *p;
        long devnum;
        char *end;

        /*
         * Search for a colon, terminating any scheme at the beginning
         * of the device.
         */
        p = strchr(device, ':');
        if (p != NULL) {
                /*
                 * We found it.  Is it followed by "//"?
                 */
                p++;    /* skip the : */
                if (strncmp(p, "//", 2) == 0) {
                        /*
                         * Yes.  Search for the next /, at the end of the
                         * authority part of the URL.
                         */
                        p += 2; /* skip the // */
                        p = strchr(p, '/');
                        if (p != NULL) {
                                /*
                                 * OK, past the / is the path.
                                 */
                                device = p + 1;
                        }
                }
        }
        devnum = strtol(device, &end, 10);
        if (device != end && *end == '\0') {
                /*
                 * It's all-numeric, but is it a valid number?
                 */
                if (devnum <= 0) {
                        /*
                         * No, it's not an ordinal.
                         */
                        error("Invalid adapter index %s", device);
                }
                return (devnum);
        } else {
                /*
                 * It's not all-numeric; return -1, so our caller
                 * knows that.
                 */
                return (-1);
        }
}

static char *
find_interface_by_number(const char *url
#ifndef HAVE_PCAP_FINDALLDEVS_EX
_U_
#endif
, long devnum)
{
        pcap_if_t *dev, *devlist;
        long i;
        char ebuf[PCAP_ERRBUF_SIZE];
        char *device;
#ifdef HAVE_PCAP_FINDALLDEVS_EX
        const char *endp;
        char *host_url;
#endif
        int status;

#ifdef HAVE_PCAP_FINDALLDEVS_EX
        /*
         * Search for a colon, terminating any scheme at the beginning
         * of the URL.
         */
        endp = strchr(url, ':');
        if (endp != NULL) {
                /*
                 * We found it.  Is it followed by "//"?
                 */
                endp++; /* skip the : */
                if (strncmp(endp, "//", 2) == 0) {
                        /*
                         * Yes.  Search for the next /, at the end of the
                         * authority part of the URL.
                         */
                        endp += 2;      /* skip the // */
                        endp = strchr(endp, '/');
                } else
                        endp = NULL;
        }
        if (endp != NULL) {
                /*
                 * OK, everything from device to endp is a URL to hand
                 * to pcap_findalldevs_ex().
                 */
                endp++; /* Include the trailing / in the URL; pcap_findalldevs_ex() requires it */
                host_url = malloc(endp - url + 1);
                if (host_url == NULL && (endp - url + 1) > 0)
                        error("Invalid allocation for host");

                memcpy(host_url, url, endp - url);
                host_url[endp - url] = '\0';
                status = pcap_findalldevs_ex(host_url, NULL, &devlist, ebuf);
                free(host_url);
        } else
#endif // HAVE_PCAP_FINDALLDEVS_EX
        status = pcap_findalldevs(&devlist, ebuf);
        if (status < 0)
                error("%s", ebuf);
        /*
         * Look for the devnum-th entry in the list of devices (1-based).
         */
        for (i = 0, dev = devlist; i < devnum-1 && dev != NULL;
            i++, dev = dev->next)
                ;
        if (dev == NULL) {
                pcap_freealldevs(devlist);
                error("Invalid adapter index %ld: only %ld interfaces found",
                    devnum, i);
        }
        device = strdup(dev->name);
        pcap_freealldevs(devlist);
        return (device);
}

#ifdef HAVE_PCAP_OPEN
/*
 * Prefixes for rpcap URLs.
 */
static char rpcap_prefix[] = "rpcap://";
static char rpcap_ssl_prefix[] = "rpcaps://";
#endif

static pcap_t *
open_interface(const char *device, netdissect_options *ndo, char *ebuf)
{
        pcap_t *pc;
        int status;
        char *cp;

#ifdef HAVE_PCAP_OPEN
        /*
         * Is this an rpcap URL?
         */
        if (strncmp(device, rpcap_prefix, sizeof(rpcap_prefix) - 1) == 0 ||
            strncmp(device, rpcap_ssl_prefix, sizeof(rpcap_ssl_prefix) - 1) == 0) {
                /*
                 * Yes.  Open it with pcap_open().
                 */
                *ebuf = '\0';
                pc = pcap_open(device, ndo->ndo_snaplen,
                    pflag ? 0 : PCAP_OPENFLAG_PROMISCUOUS, timeout, NULL,
                    ebuf);
                if (pc == NULL) {
                        /*
                         * macOS 14's pcap_pcap_open(), which is a
                         * stub that always returns NULL with an error
                         * message of "not supported".
                         *
                         * In this case, as we passed it an rpcap://
                         * URL, treat that as meaning "remote capture
                         * not supported".
                         */
                        if (strcmp(ebuf, "not supported") == 0)
                                error("Remote capture not supported");

                        /*
                         * If this failed with "No such device" or "The system
                         * cannot find the device specified", that means
                         * the interface doesn't exist; return NULL, so that
                         * the caller can see whether the device name is
                         * actually an interface index.
                         */
                        if (strstr(ebuf, "No such device") != NULL ||
                            strstr(ebuf, "The system cannot find the device specified") != NULL)
                                return (NULL);
                        error("%s", ebuf);
                }
                if (*ebuf)
                        warning("%s", ebuf);
                return (pc);
        }
#endif /* HAVE_PCAP_OPEN */

        pc = pcap_create(device, ebuf);
        if (pc == NULL) {
                /*
                 * If this failed with "No such device", that means
                 * the interface doesn't exist; return NULL, so that
                 * the caller can see whether the device name is
                 * actually an interface index.
                 */
                if (strstr(ebuf, "No such device") != NULL)
                        return (NULL);
                error("%s", ebuf);
        }
#ifdef HAVE_PCAP_SET_TSTAMP_TYPE
        if (Jflag)
                show_tstamp_types_and_exit(pc, device);
#endif
#ifdef HAVE_PCAP_SET_TSTAMP_PRECISION
        status = pcap_set_tstamp_precision(pc, ndo->ndo_tstamp_precision);
        if (status != 0)
                error("%s: Can't set %ssecond time stamp precision: %s",
                    device,
                    tstamp_precision_to_string(ndo->ndo_tstamp_precision),
                    pcap_statustostr(status));
#endif

#ifdef HAVE_PCAP_SET_IMMEDIATE_MODE
        if (immediate_mode) {
                status = pcap_set_immediate_mode(pc, 1);
                if (status != 0)
                        error("%s: Can't set immediate mode: %s",
                            device, pcap_statustostr(status));
        }
#endif
        /*
         * Is this an interface that supports monitor mode?
         */
        if (pcap_can_set_rfmon(pc) == 1)
                supports_monitor_mode = 1;
        else
                supports_monitor_mode = 0;
        if (ndo->ndo_snaplen != 0) {
                /*
                 * A snapshot length was explicitly specified;
                 * use it.
                 */
                status = pcap_set_snaplen(pc, ndo->ndo_snaplen);
                if (status != 0)
                        error("%s: Can't set snapshot length: %s",
                            device, pcap_statustostr(status));
        }
        status = pcap_set_promisc(pc, !pflag);
        if (status != 0)
                error("%s: Can't set promiscuous mode: %s",
                    device, pcap_statustostr(status));
        if (Iflag) {
                status = pcap_set_rfmon(pc, 1);
                if (status != 0)
                        error("%s: Can't set monitor mode: %s",
                            device, pcap_statustostr(status));
        }
        status = pcap_set_timeout(pc, timeout);
        if (status != 0)
                error("%s: pcap_set_timeout failed: %s",
                    device, pcap_statustostr(status));
        if (Bflag != 0) {
                status = pcap_set_buffer_size(pc, Bflag);
                if (status != 0)
                        error("%s: Can't set buffer size: %s",
                            device, pcap_statustostr(status));
        }
#ifdef HAVE_PCAP_SET_TSTAMP_TYPE
        if (jflag != -1) {
                status = pcap_set_tstamp_type(pc, jflag);
                if (status < 0)
                        error("%s: Can't set time stamp type: %s",
                            device, pcap_statustostr(status));
                else if (status > 0)
                        warning("When trying to set timestamp type '%s' on %s: %s",
                            pcap_tstamp_type_val_to_name(jflag), device,
                            pcap_statustostr(status));
        }
#endif
        status = pcap_activate(pc);
        if (status < 0) {
                /*
                 * pcap_activate() failed.
                 */
                cp = pcap_geterr(pc);
                if (status == PCAP_ERROR)
                        error("%s", cp);
                else if (status == PCAP_ERROR_NO_SUCH_DEVICE) {
                        /*
                         * Return an error for our caller to handle.
                         */
                        snprintf(ebuf, PCAP_ERRBUF_SIZE, "%s: %s\n(%s)",
                            device, pcap_statustostr(status), cp);
                } else if (status == PCAP_ERROR_PERM_DENIED && *cp != '\0')
                        error("%s: %s\n(%s)", device,
                            pcap_statustostr(status), cp);
#ifdef PCAP_ERROR_CAPTURE_NOTSUP
                else if (status == PCAP_ERROR_CAPTURE_NOTSUP && *cp != '\0')
                        error("%s: %s\n(%s)", device,
                            pcap_statustostr(status), cp);
#endif
#ifdef __FreeBSD__
                else if (status == PCAP_ERROR_RFMON_NOTSUP &&
                    strncmp(device, "wlan", 4) == 0) {
                        char parent[8], newdev[8];
                        char sysctl[32];
                        size_t s = sizeof(parent);

                        snprintf(sysctl, sizeof(sysctl),
                            "net.wlan.%d.%%parent", atoi(device + 4));
                        sysctlbyname(sysctl, parent, &s, NULL, 0);
                        strlcpy(newdev, device, sizeof(newdev));
                        /* Suggest a new wlan device. */
                        /* FIXME: incrementing the index this way is not going to work well
                         * when the index is 9 or greater but the only consequence in this
                         * specific case would be an error message that looks a bit odd.
                         */
                        newdev[strlen(newdev)-1]++;
                        error("%s is not a monitor mode VAP\n"
                            "To create a new monitor mode VAP use:\n"
                            "  ifconfig %s create wlandev %s wlanmode monitor\n"
                            "and use %s as the tcpdump interface",
                            device, newdev, parent, newdev);
                }
#endif // __FreeBSD__
                else
                        error("%s: %s", device,
                            pcap_statustostr(status));
                pcap_close(pc);
                return (NULL);
        } else if (status > 0) {
                /*
                 * pcap_activate() succeeded, but it's warning us
                 * of a problem it had.
                 */
                cp = pcap_geterr(pc);
                if (status == PCAP_WARNING)
                        warning("%s", cp);
                else if (status == PCAP_WARNING_PROMISC_NOTSUP &&
                         *cp != '\0')
                        warning("%s: %s\n(%s)", device,
                            pcap_statustostr(status), cp);
                else
                        warning("%s: %s", device,
                            pcap_statustostr(status));
        }
        if (Qflag != -1) {
                status = pcap_setdirection(pc, Qflag);
                if (status != 0)
                        error("%s: pcap_setdirection() failed: %s",
                              device,  pcap_geterr(pc));
        }

        return (pc);
}

int
main(int argc, char **argv)
{
        int cnt, op, i;
        bpf_u_int32 localnet = 0, netmask = 0;
        char *cp, *infile, *cmdbuf, *device, *RFileName, *VFileName, *WFileName;
        char *endp;
        pcap_handler callback;
        int dlt;
        const char *dlt_name;
        struct bpf_program fcode;
#ifndef _WIN32
        void (*oldhandler)(int);
#endif
        struct dump_info dumpinfo;
        u_char *pcap_userdata;
        char ebuf[PCAP_ERRBUF_SIZE];
        char VFileLine[PATH_MAX + 1];
        const char *username = NULL;
#ifndef _WIN32
        const char *chroot_dir = NULL;
#endif
        char *ret = NULL;
        pcap_if_t *devlist;
        long devnum;
        int status;
        FILE *VFile;
#ifdef HAVE_CAPSICUM
        cap_rights_t rights;
        int cansandbox;
#endif  /* HAVE_CAPSICUM */
        int Oflag = 1;                  /* run filter code optimizer */
        int yflag_dlt = -1;
        const char *yflag_dlt_name = NULL;
        int print = 0;
        long Cflagmult;

        netdissect_options Ndo;
        netdissect_options *ndo = &Ndo;

#ifdef _WIN32
        /*
         * We need to look for wpcap.dll in \Windows\System32\Npcap first,
         * as either:
         *
         *  1) WinPcap isn't installed and Npcap isn't installed in "WinPcap
         *     API-compatible Mode", so there's no wpcap.dll in
         *     \Windows\System32, only in \Windows\System32\Npcap;
         *
         *  2) WinPcap is installed and Npcap isn't installed in "WinPcap
         *     API-compatible Mode", so the wpcap.dll in \Windows\System32
         *     is a WinPcap DLL, but we'd prefer an Npcap DLL (we should
         *     work with either one if we're configured against WinPcap,
         *     and we'll probably require Npcap if we're configured against
         *     it), and that's in \Windows\System32\Npcap;
         *
         *  3) Npcap is installed in "WinPcap API-compatible Mode", so both
         *     \Windows\System32 and \Windows\System32\Npcap have an Npcap
         *     wpcap.dll.
         *
         * Unfortunately, Windows has no notion of an rpath, so we can't
         * set the rpath to include \Windows\System32\Npcap at link time;
         * what we need to do is to link wpcap as a delay-load DLL and
         * add \Windows\System32\Npcap to the DLL search path early in
         * main() with a call to SetDllDirectory().
         *
         * The same applies to packet.dll.
         *
         * We add \Windows\System32\Npcap here.
         *
         * See https://npcap.com/guide/npcap-devguide.html#npcap-feature-native-dll-implicitly
         */
        WCHAR *dll_directory = NULL;
        size_t dll_directory_buf_len = 0;       /* units of bytes */
        UINT system_directory_buf_len = 0;      /* units of WCHARs */
        UINT system_directory_len;              /* units of WCHARs */
        static const WCHAR npcap[] = L"\\Npcap";

        /*
         * Get the system directory path, in UTF-16, into a buffer that's
         * large enough for that directory path plus "\Npcap".
         *
         * String manipulation in C, plus fetching a variable-length
         * string into a buffer whose size is fixed at the time of
         * the call, with an oddball return value (see below), is just
         * a huge bag of fun.
         *
         * And it's even more fun when dealing with UTF-16, so that the
         * buffer sizes used in GetSystemDirectoryW() are in different
         * units from the buffer sizes used in realloc()!   We maintain
         * all sizes/length in units of bytes, not WCHARs, so that our
         * heads don't explode.
         */
        for (;;) {
                /*
                 * Try to fetch the system directory.
                 *
                 * GetSystemDirectoryW() expects a buffer size in units
                 * of WCHARs, not bytes, and returns a directory path
                 * length in units of WCHARs, not bytes.
                 *
                 * For extra fun, if GetSystemDirectoryW() succeeds,
                 * the return value is the length of the directory
                 * path in units of WCHARs, *not* including the
                 * terminating '\0', but if it fails because the
                 * path string wouldn't fit, the return value is
                 * the length of the directory path in units of WCHARs,
                 * *including* the terminating '\0'.
                 */
                system_directory_len = GetSystemDirectoryW(dll_directory,
                    system_directory_buf_len);
                if (system_directory_len == 0)
                        error("GetSystemDirectoryW() failed");

                /*
                 * Did the directory path fit in the buffer?
                 *
                 * As per the above, this means that the return value
                 * *plus 1*, so that the terminating '\0' is counted,
                 * is <= the buffer size.
                 *
                 * (If the directory path, complete with the terminating
                 * '\0', fits *exactly*, the return value would be the
                 * size of the buffer minus 1, as it doesn't count the
                 * terminating '\0', so the test below would succeed.
                 *
                 * If everything *but* the terminating '\0' fits,
                 * the return value would be the size of the buffer + 1,
                 * i.e., the size that the string in question would
                 * have required.
                 *
                 * The astute reader will note that returning the
                 * size of the buffer is not one of the two cases
                 * above, and should never happen.)
                 */
                if ((system_directory_len + 1) <= system_directory_buf_len) {
                        /*
                         * No.  We have a buffer that's large enough
                         * for our purposes.
                         */
                        break;
                }

                /*
                 * Yes.  Grow the buffer.
                 *
                 * The space we'll need in the buffer for the system
                 * directory, in units of WCHARs, is system_directory_len,
                 * as that's the length of the system directory path
                 * including the terminating '\0'.
                 */
                system_directory_buf_len = system_directory_len;

                /*
                 * The size of the DLL directory buffer, in *bytes*, must
                 * be the number of WCHARs taken by the system directory,
                 * *minus* the terminating '\0' (as we'll overwrite that
                 * with the "\" of the "\Npcap" string), multiplied by
                 * sizeof(WCHAR) to convert it to the number of bytes,
                 * plus the size of the "\Npcap" string, in bytes (which
                 * will include the terminating '\0', as that will become
                 * the DLL path's terminating '\0').
                 */
                dll_directory_buf_len =
                    ((system_directory_len - 1)*sizeof(WCHAR)) + sizeof npcap;
                dll_directory = realloc(dll_directory, dll_directory_buf_len);
                if (dll_directory == NULL)
                        error("Can't allocate string for Npcap directory");
        }

        /*
         * OK, that worked.
         *
         * Now append \Npcap.  We add the length of the system directory path,
         * in WCHARs, *not* including the terminating '\0' (which, since
         * GetSystemDirectoryW() succeeded, is the return value of
         * GetSystemDirectoryW(), as per the above), to the pointer to the
         * beginning of the path, to go past the end of the system directory
         * to point to the terminating '\0'.
         */
        memcpy(dll_directory + system_directory_len, npcap, sizeof npcap);

        /*
         * Now add that as a system DLL directory.
         */
        if (!SetDllDirectoryW(dll_directory))
                error("SetDllDirectory failed");

        free(dll_directory);
#endif // _WIN32

        /*
         * Initialize the netdissect code.
         */
        if (nd_init(ebuf, sizeof(ebuf)) == -1)
                error("%s", ebuf);

        memset(ndo, 0, sizeof(*ndo));
        ndo_set_function_pointers(ndo);

        cnt = -1;
        device = NULL;
        infile = NULL;
        RFileName = NULL;
        VFileName = NULL;
        VFile = NULL;
        WFileName = NULL;
        dlt = -1;
        if ((cp = strrchr(argv[0], PATH_SEPARATOR)) != NULL)
                ndo->program_name = program_name = cp + 1;
        else
                ndo->program_name = program_name = argv[0];

#if defined(HAVE_PCAP_WSOCKINIT)
        if (pcap_wsockinit() != 0)
                error("Attempting to initialize Winsock failed");
#elif defined(HAVE_WSOCKINIT)
        if (wsockinit() != 0)
                error("Attempting to initialize Winsock failed");
#endif

        /*
         * An explicit tzset() call is usually not needed as it happens
         * implicitly the first time we call localtime() or mktime(),
         * but in some cases (sandboxing, chroot) this may be too late.
         */
        tzset();

        while (
            (op = getopt_long(argc, argv, SHORTOPTS, longopts, NULL)) != -1)
                switch (op) {

                case 'a':
                        /* compatibility for old -a */
                        break;

                case 'A':
                        ++ndo->ndo_Aflag;
                        break;

                case 'b':
                        ++ndo->ndo_bflag;
                        break;

                case 'B':
                        Bflag = parse_int("packet buffer size", optarg, NULL, 1,
                            INT_MAX, 10);
                        /*
                         * Will multiplying it by 1024 overflow?
                         */
                        if (Bflag > INT_MAX / 1024)
                                error("packet buffer size %s is too large", optarg);
                        Bflag *= 1024;
                        break;

                case 'c':
                        cnt = parse_int("packet count", optarg, NULL, 1,
                            INT_MAX, 10);
                        break;

                case 'C':
                        Cflag = parse_int64("file size", optarg, &endp, 1,
                            INT64_MAX, 10);

                        if (*endp == '\0') {
                                /*
                                 * There's nothing after the file size,
                                 * so the size is in units of 1 MB
                                 * (1,000,000 bytes).
                                 */
                                Cflagmult = 1000000;
                        } else {
                                /*
                                 * There's something after the file
                                 * size.
                                 *
                                 * If it's a single letter, then:
                                 *
                                 *   if the letter is k or K, the size
                                 *   is in units of 1 KiB (1024 bytes);
                                 *
                                 *   if the letter is m or M, the size
                                 *   is in units of 1 MiB (1,048,576 bytes);
                                 *
                                 *   if the letter is g or G, the size
                                 *   is in units of 1 GiB (1,073,741,824 bytes).
                                 *
                                 * Otherwise, it's an error.
                                 */
                                switch (*endp) {

                                case 'k':
                                case 'K':
                                        Cflagmult = 1024;
                                        break;

                                case 'm':
                                case 'M':
                                        Cflagmult = 1024*1024;
                                        break;

                                case 'g':
                                case 'G':
                                        Cflagmult = 1024*1024*1024;
                                        break;

                                default:
                                        error("invalid file size %s (invalid units)", optarg);
                                }

                                /*
                                 * OK, there was a letter that we treat
                                 * as a units indication; was there
                                 * anything after it?
                                 */
                                endp++;
                                if (*endp != '\0') {
                                        /* Yes - error */
                                        error("invalid file size %s (invalid units)", optarg);
                                }
                        }

                        /*
                         * Will multiplying it by multiplier overflow?
                         */
#ifdef HAVE_PCAP_DUMP_FTELL64
                        if (Cflag > INT64_MAX / Cflagmult)
#else
                        if (Cflag > LONG_MAX / Cflagmult)
#endif
                                error("file size %s is too large", optarg);
                        Cflag *= Cflagmult;
                        break;

                case 'd':
                        ++dflag;
                        break;

                case 'D':
                        Dflag++;
                        break;

#ifdef HAVE_PCAP_FINDALLDEVS_EX
                case OPTION_LIST_REMOTE_INTERFACES:
                        remote_interfaces_source = optarg;
                        break;
#endif

                case 'L':
                        Lflag++;
                        break;

                case 'e':
                        ++ndo->ndo_eflag;
                        break;

                case 'E':
#ifndef HAVE_LIBCRYPTO
                        warning("crypto code not compiled in");
#endif
                        ndo->ndo_espsecret = optarg;
                        break;

                case 'f':
                        ++ndo->ndo_fflag;
                        break;

                case 'F':
                        infile = optarg;
                        break;

                case 'G':
                        Gflag = parse_int("number of seconds", optarg, NULL, 0,
                            INT_MAX, 10);

                        /* We will create one file initially. */
                        Gflag_count = 0;

                        /* Grab the current time for rotation use. */
                        if ((Gflag_time = time(NULL)) == (time_t)-1) {
                                error("%s: can't get current time: %s",
                                    __func__, pcap_strerror(errno));
                        }
                        break;

                case 'h':
                        print_usage(stdout);
                        exit_tcpdump(S_SUCCESS);
                        /* NOTREACHED */

                case 'H':
                        ++ndo->ndo_Hflag;
                        break;

                case 'i':
                        device = optarg;
                        break;

                case 'I':
                        ++Iflag;
                        break;

#ifdef HAVE_PCAP_SET_TSTAMP_TYPE
                case 'j':
                        jflag = pcap_tstamp_type_name_to_val(optarg);
                        if (jflag < 0)
                                error("invalid time stamp type %s", optarg);
                        break;

                case 'J':
                        Jflag++;
                        break;
#endif

                case 'l':
#ifdef _WIN32
                        /*
                         * _IOLBF is the same as _IOFBF in Microsoft's C
                         * libraries; the only alternative they offer
                         * is _IONBF.
                         *
                         * XXX - this should really be checking for MSVC++,
                         * not _WIN32, if, for example, MinGW has its own
                         * C library that is more UNIX-compatible.
                         */
                        setvbuf(stdout, NULL, _IONBF, 0);
#else /* _WIN32 */
                        setvbuf(stdout, NULL, _IOLBF, 0);
#endif /* _WIN32 */
                        lflag = 1;
                        break;

                case 'K':
                        ++ndo->ndo_Kflag;
                        break;

                case 'm':
                        if (nd_have_smi_support()) {
                                if (nd_load_smi_module(optarg, ebuf, sizeof(ebuf)) == -1)
                                        error("%s", ebuf);
                        } else {
                                (void)fprintf(stderr, "%s: ignoring option '-m %s' ",
                                              program_name, optarg);
                                (void)fprintf(stderr, "(no libsmi support)\n");
                        }
                        break;

                case 'M':
                        /* TCP-MD5 shared secret */
#ifndef HAVE_LIBCRYPTO
                        warning("crypto code not compiled in");
#endif
                        ndo->ndo_sigsecret = optarg;
                        break;

                case 'n':
                        ++ndo->ndo_nflag;
                        break;

                case 'N':
                        ++ndo->ndo_Nflag;
                        break;

                case 'O':
                        Oflag = 0;
                        break;

                case 'p':
                        ++pflag;
                        break;

                case 'q':
                        ++ndo->ndo_qflag;
                        ++ndo->ndo_suppress_default_print;
                        break;

                case 'Q':
                        if (ascii_strcasecmp(optarg, "in") == 0)
                                Qflag = PCAP_D_IN;
                        else if (ascii_strcasecmp(optarg, "out") == 0)
                                Qflag = PCAP_D_OUT;
                        else if (ascii_strcasecmp(optarg, "inout") == 0)
                                Qflag = PCAP_D_INOUT;
                        else
                                error("unknown capture direction '%s'", optarg);
                        break;

                case 'r':
                        RFileName = optarg;
                        break;

                case 's':
                        ndo->ndo_snaplen = parse_int("snaplen", optarg, NULL,
                            0, MAXIMUM_SNAPLEN, 0);
                        break;

                case 'S':
                        ++ndo->ndo_Sflag;
                        break;

                case 't':
                        ++ndo->ndo_tflag;
                        break;

                case 'T':
                        if (ascii_strcasecmp(optarg, "vat") == 0)
                                ndo->ndo_packettype = PT_VAT;
                        else if (ascii_strcasecmp(optarg, "wb") == 0)
                                ndo->ndo_packettype = PT_WB;
                        else if (ascii_strcasecmp(optarg, "rpc") == 0)
                                ndo->ndo_packettype = PT_RPC;
                        else if (ascii_strcasecmp(optarg, "rtp") == 0)
                                ndo->ndo_packettype = PT_RTP;
                        else if (ascii_strcasecmp(optarg, "rtcp") == 0)
                                ndo->ndo_packettype = PT_RTCP;
                        else if (ascii_strcasecmp(optarg, "snmp") == 0)
                                ndo->ndo_packettype = PT_SNMP;
                        else if (ascii_strcasecmp(optarg, "cnfp") == 0)
                                ndo->ndo_packettype = PT_CNFP;
                        else if (ascii_strcasecmp(optarg, "tftp") == 0)
                                ndo->ndo_packettype = PT_TFTP;
                        else if (ascii_strcasecmp(optarg, "aodv") == 0)
                                ndo->ndo_packettype = PT_AODV;
                        else if (ascii_strcasecmp(optarg, "carp") == 0)
                                ndo->ndo_packettype = PT_CARP;
                        else if (ascii_strcasecmp(optarg, "radius") == 0)
                                ndo->ndo_packettype = PT_RADIUS;
                        else if (ascii_strcasecmp(optarg, "zmtp1") == 0)
                                ndo->ndo_packettype = PT_ZMTP1;
                        else if (ascii_strcasecmp(optarg, "vxlan") == 0)
                                ndo->ndo_packettype = PT_VXLAN;
                        else if (ascii_strcasecmp(optarg, "pgm") == 0)
                                ndo->ndo_packettype = PT_PGM;
                        else if (ascii_strcasecmp(optarg, "pgm_zmtp1") == 0)
                                ndo->ndo_packettype = PT_PGM_ZMTP1;
                        else if (ascii_strcasecmp(optarg, "lmp") == 0)
                                ndo->ndo_packettype = PT_LMP;
                        else if (ascii_strcasecmp(optarg, "resp") == 0)
                                ndo->ndo_packettype = PT_RESP;
                        else if (ascii_strcasecmp(optarg, "ptp") == 0)
                                ndo->ndo_packettype = PT_PTP;
                        else if (ascii_strcasecmp(optarg, "someip") == 0)
                                ndo->ndo_packettype = PT_SOMEIP;
                        else if (ascii_strcasecmp(optarg, "domain") == 0)
                                ndo->ndo_packettype = PT_DOMAIN;
                        else if (ascii_strcasecmp(optarg, "quic") == 0)
                                ndo->ndo_packettype = PT_QUIC;
                        else
                                error("unknown packet type '%s'", optarg);
                        break;

                case 'u':
                        ++ndo->ndo_uflag;
                        break;

                case 'U':
                        ++Uflag;
                        break;

                case 'v':
                        ++ndo->ndo_vflag;
                        break;

                case 'V':
                        VFileName = optarg;
                        break;

                case 'w':
                        WFileName = optarg;
                        break;

                case 'W':
                        Wflag = parse_int("number of output files", optarg,
                            NULL, 1, INT_MAX, 10);
                        WflagChars = getWflagChars(Wflag);
                        break;

                case 'x':
                        ++ndo->ndo_xflag;
                        ++ndo->ndo_suppress_default_print;
                        break;

                case 'X':
                        ++ndo->ndo_Xflag;
                        ++ndo->ndo_suppress_default_print;
                        break;

                case 'y':
                        yflag_dlt_name = optarg;
                        yflag_dlt =
                                pcap_datalink_name_to_val(yflag_dlt_name);
                        if (yflag_dlt < 0)
                                error("invalid data link type %s", yflag_dlt_name);
                        break;

#ifdef HAVE_PCAP_SET_PARSER_DEBUG
                case 'Y':
                        {
                        /* Undocumented flag */
                        pcap_set_parser_debug(1);
                        }
                        break;
#endif
                case 'z':
                        zflag = optarg;
                        break;

                case 'Z':
                        username = optarg;
                        break;

                case '#':
                        ndo->ndo_packet_number = 1;
                        break;

                case OPTION_LENGTHS:
                        ndo->ndo_lengths = 1;
                        break;

                case OPTION_TIME_T_SIZE:
                        printf("%zu\n", sizeof(time_t) * 8);
                        return 0;

                case OPTION_VERSION:
                        print_version(stdout);
                        exit_tcpdump(S_SUCCESS);
                        /* NOTREACHED */

#ifdef HAVE_PCAP_SET_TSTAMP_PRECISION
                case OPTION_TSTAMP_PRECISION:
                        ndo->ndo_tstamp_precision = tstamp_precision_from_string(optarg);
                        if (ndo->ndo_tstamp_precision < 0)
                                error("unsupported time stamp precision");
                        break;
#endif

#ifdef HAVE_PCAP_SET_IMMEDIATE_MODE
                case OPTION_IMMEDIATE_MODE:
                        immediate_mode = 1;
                        break;
#endif

                case OPTION_PRINT:
                        print = 1;
                        break;

                case OPTION_PRINT_SAMPLING:
                        print = 1;
                        ++ndo->ndo_Sflag;
                        ndo->ndo_print_sampling = parse_int("print sampling",
                            optarg, NULL, 1, INT_MAX, 10);
                        break;

                case OPTION_SKIP:
                        packets_to_skip = parse_u_int("packet skip count",
                            optarg, NULL, 0, INT_MAX, 0);
                        break;

#ifdef HAVE_PCAP_SET_TSTAMP_PRECISION
                case OPTION_TSTAMP_MICRO:
                        ndo->ndo_tstamp_precision = PCAP_TSTAMP_PRECISION_MICRO;
                        break;

                case OPTION_TSTAMP_NANO:
                        ndo->ndo_tstamp_precision = PCAP_TSTAMP_PRECISION_NANO;
                        break;
#endif

                case OPTION_FP_TYPE:
                        /*
                         * Print out the type of floating-point arithmetic
                         * we're doing; it's probably IEEE, unless somebody
                         * tries to run this on a VAX, but the precision
                         * may differ (e.g., it might be 32-bit, 64-bit,
                         * or 80-bit).
                         */
                        float_type_check(0x4e93312d);
                        return 0;

                case OPTION_COUNT:
                        count_mode = 1;
                        break;

                default:
                        print_usage(stderr);
                        exit_tcpdump(S_ERR_HOST_PROGRAM);
                        /* NOTREACHED */
                }

        if (ndo->ndo_Aflag && ndo->ndo_xflag)
                warning("-A and -x[x] are mutually exclusive. -A ignored.");
        if (ndo->ndo_Aflag && ndo->ndo_Xflag)
                warning("-A and -X[X] are mutually exclusive. -A ignored.");
        if (ndo->ndo_xflag && ndo->ndo_Xflag)
                warning("-x[x] and -X[X] are mutually exclusive. -x[x] ignored.");

        if (cnt != -1)
                if ((int)packets_to_skip > (INT_MAX - cnt))
                        // cnt + (int)packets_to_skip used in pcap_loop() call
                        error("Overflow (-c count) %d + (--skip count) %d", cnt,
                              (int)packets_to_skip);

        if (Dflag)
                show_devices_and_exit();
#ifdef HAVE_PCAP_FINDALLDEVS_EX
        if (remote_interfaces_source != NULL)
                show_remote_devices_and_exit();
#endif

        switch (ndo->ndo_tflag) {

        case 0: /* Default */
        case 1: /* No time stamp */
        case 2: /* Unix timeval style */
        case 3: /* Microseconds/nanoseconds since previous packet */
        case 4: /* Date + Default */
        case 5: /* Microseconds/nanoseconds since first packet */
                break;

        default: /* Not supported */
                error("only -t, -tt, -ttt, -tttt and -ttttt are supported");
                /* NOTREACHED */
        }

        if (ndo->ndo_fflag != 0 && (VFileName != NULL || RFileName != NULL))
                error("-f can not be used with -V or -r");

        if (VFileName != NULL && RFileName != NULL)
                error("-V and -r are mutually exclusive.");

        /*
         * If we're printing dissected packets to the standard output,
         * and either the standard output is a terminal or we're doing
         * "line" buffering, set the capture timeout to .1 second rather
         * than 1 second, as the user's probably expecting to see packets
         * pop up immediately shortly after they arrive.
         *
         * XXX - would there be some value appropriate for all cases,
         * based on, say, the buffer size and packet input rate?
         */
        if ((WFileName == NULL || print) && (isatty(1) || lflag))
                timeout = 100;

#ifdef WITH_CHROOT
        /* if run as root, prepare for chrooting */
        if (getuid() == 0 || geteuid() == 0) {
                /* future extensibility for cmd-line arguments */
                if (!chroot_dir)
                        chroot_dir = WITH_CHROOT;
        }
#endif

#ifdef WITH_USER
        /* if run as root, prepare for dropping root privileges */
        if (getuid() == 0 || geteuid() == 0) {
                /* Run with '-Z root' to restore old behaviour */
                if (!username)
                        username = WITH_USER;
                else if (strcmp(username, "root") == 0)
                        username = NULL;
        }
#endif

        if (RFileName != NULL || VFileName != NULL) {
                /*
                 * If RFileName is non-null, it's the pathname of a
                 * savefile to read.  If VFileName is non-null, it's
                 * the pathname of a file containing a list of pathnames
                 * (one per line) of savefiles to read.
                 *
                 * In either case, we're reading a savefile, not doing
                 * a live capture.
                 */
#ifndef _WIN32
                /*
                 * We don't need network access, so relinquish any set-UID
                 * or set-GID privileges we have (if any).
                 *
                 * We do *not* want set-UID privileges when opening a
                 * trace file, as that might let the user read other
                 * people's trace files (especially if we're set-UID
                 * root).
                 */
                if (setgid(getgid()) != 0 || setuid(getuid()) != 0 )
                        fprintf(stderr, "Warning: setgid/setuid failed !\n");
#endif /* _WIN32 */
                if (VFileName != NULL) {
                        if (VFileName[0] == '-' && VFileName[1] == '\0')
                                VFile = stdin;
                        else
                                VFile = fopen(VFileName, "r");

                        if (VFile == NULL)
                                error("Unable to open file: %s\n", pcap_strerror(errno));

                        ret = get_next_file(VFile, VFileLine);
                        if (!ret)
                                error("Nothing in %s\n", VFileName);
                        RFileName = VFileLine;
                }

#ifdef HAVE_PCAP_SET_TSTAMP_PRECISION
                pd = pcap_open_offline_with_tstamp_precision(RFileName,
                    ndo->ndo_tstamp_precision, ebuf);
#else
                pd = pcap_open_offline(RFileName, ebuf);
#endif

                if (pd == NULL)
                        error("%s", ebuf);
#ifdef HAVE_CAPSICUM
                cap_rights_init(&rights, CAP_READ);
                if (cap_rights_limit(fileno(pcap_file(pd)), &rights) < 0 &&
                    errno != ENOSYS) {
                        error("unable to limit pcap descriptor");
                }
#endif
                dlt = pcap_datalink(pd);
                dlt_name = pcap_datalink_val_to_name(dlt);
                fprintf(stderr, "reading from file %s", RFileName);
                if (dlt_name == NULL) {
                        fprintf(stderr, ", link-type %u", dlt);
                } else {
                        fprintf(stderr, ", link-type %s (%s)", dlt_name,
                                pcap_datalink_val_to_description(dlt));
                }
                fprintf(stderr, ", snapshot length %d\n", pcap_snapshot(pd));
#if defined(DLT_LINUX_SLL2) && defined(__linux__)
                if (dlt == DLT_LINUX_SLL2)
                        fprintf(stderr, "Warning: interface names might be incorrect\n");
#endif
        } else if (dflag && !device) {
                int dump_dlt = DLT_EN10MB;
                /*
                 * We're dumping the compiled code without an explicit
                 * device specification.  (If a device is specified, we
                 * definitely want to open it to use the DLT of that device.)
                 * Either default to DLT_EN10MB with a warning, or use
                 * the user-specified value if supplied.
                 */
                /*
                 * If no snapshot length was specified, or a length of 0 was
                 * specified, default to 256KB.
                 */
                if (ndo->ndo_snaplen == 0)
                        ndo->ndo_snaplen = MAXIMUM_SNAPLEN;
                /*
                 * If a DLT was specified with the -y flag, use that instead.
                 */
                if (yflag_dlt != -1)
                        dump_dlt = yflag_dlt;
                else
                        fprintf(stderr, "Warning: assuming Ethernet\n");
                pd = pcap_open_dead(dump_dlt, ndo->ndo_snaplen);
        } else {
                /*
                 * We're doing a live capture.
                 */
                if (device == NULL) {
                        /*
                         * No interface was specified.  Pick one.
                         */
                        /*
                         * Find the list of interfaces, and pick
                         * the first interface.
                         */
                        if (pcap_findalldevs(&devlist, ebuf) == -1)
                                error("%s", ebuf);
                        if (devlist == NULL)
                                error("no interfaces available for capture");
                        device = strdup(devlist->name);
                        pcap_freealldevs(devlist);
                }

                /*
                 * Try to open the interface with the specified name.
                 */
                pd = open_interface(device, ndo, ebuf);
                if (pd == NULL) {
                        /*
                         * That failed.  If we can get a list of
                         * interfaces, and the interface name
                         * is purely numeric, try to use it as
                         * a 1-based index in the list of
                         * interfaces.
                         */
                        devnum = parse_interface_number(device);
                        if (devnum == -1) {
                                /*
                                 * It's not a number; just report
                                 * the open error and fail.
                                 */
                                error("%s", ebuf);
                        }

                        /*
                         * OK, it's a number; try to find the
                         * interface with that index, and try
                         * to open it.
                         *
                         * find_interface_by_number() exits if it
                         * couldn't be found.
                         */
                        device = find_interface_by_number(device, devnum);
                        pd = open_interface(device, ndo, ebuf);
                        if (pd == NULL)
                                error("%s", ebuf);
                }

                /*
                 * Let user own process after capture device has
                 * been opened.
                 */
#ifndef _WIN32
                if (setgid(getgid()) != 0 || setuid(getuid()) != 0)
                        fprintf(stderr, "Warning: setgid/setuid failed !\n");
#endif /* _WIN32 */
                if (Lflag)
                        show_dlts_and_exit(pd, device);
                if (yflag_dlt >= 0) {
                        if (pcap_set_datalink(pd, yflag_dlt) < 0)
                                error("%s", pcap_geterr(pd));
                        (void)fprintf(stderr, "%s: data link type %s\n",
                                      program_name,
                                      pcap_datalink_val_to_name(yflag_dlt));
                        (void)fflush(stderr);
                }
#if defined(DLT_LINUX_SLL2)
                else {
                        /*
                         * Attempt to set default linktype to
                         * DLT_LINUX_SLL2 when capturing on the
                         * "any" device.
                         *
                         * If the attempt fails, just quietly drive
                         * on; this may be a non-Linux "any" device
                         * that doesn't support DLT_LINUX_SLL2.
                         */
                        if (strcmp(device, "any") == 0) {
DIAG_OFF_WARN_UNUSED_RESULT
                                (void) pcap_set_datalink(pd, DLT_LINUX_SLL2);
DIAG_ON_WARN_UNUSED_RESULT
                        }
                }
#endif
                i = pcap_snapshot(pd);
                if (ndo->ndo_snaplen < i) {
                        if (ndo->ndo_snaplen != 0)
                                warning("snaplen raised from %d to %d", ndo->ndo_snaplen, i);
                        ndo->ndo_snaplen = i;
                } else if (ndo->ndo_snaplen > i) {
                        warning("snaplen lowered from %d to %d", ndo->ndo_snaplen, i);
                        ndo->ndo_snaplen = i;
                }
                if(ndo->ndo_fflag != 0) {
                        if (pcap_lookupnet(device, &localnet, &netmask, ebuf) < 0) {
                                warning("foreign (-f) flag used but: %s", ebuf);
                        }
                }

        }
        if (infile)
                cmdbuf = read_infile(infile);
        else
                cmdbuf = copy_argv(&argv[optind]);

#ifdef HAVE_PCAP_SET_OPTIMIZER_DEBUG
        pcap_set_optimizer_debug(dflag);
#endif
        /*
         * netmask is in network byte order, pcap_compile() takes it
         * in host byte order.
         */
        if (pcap_compile(pd, &fcode, cmdbuf, Oflag, ntohl(netmask)) < 0)
                error("%s", pcap_geterr(pd));
        if (dflag) {
                bpf_dump(&fcode, dflag);
                pcap_close(pd);
                free(cmdbuf);
                pcap_freecode(&fcode);
                exit_tcpdump(S_SUCCESS);
        }

#ifdef HAVE_CASPER
        if (!ndo->ndo_nflag)
                capdns = capdns_setup();
#endif  /* HAVE_CASPER */

        // Both localnet and netmask are in network byte order.
        init_print(ndo, localnet, netmask);

#ifndef _WIN32
        (void)setsignal(SIGPIPE, cleanup);
        (void)setsignal(SIGTERM, cleanup);
#endif /* _WIN32 */
        (void)setsignal(SIGINT, cleanup);
#if defined(HAVE_FORK) || defined(HAVE_VFORK)
        (void)setsignal(SIGCHLD, child_cleanup);
#endif
        /* Cooperate with nohup(1) */
#ifndef _WIN32
        /*
         * In illumos /usr/include/sys/iso/signal_iso.h causes Clang to
         * generate a -Wstrict-prototypes warning here, see [1].  The
         * __illumos__ macro is available since at least GCC 11 and Clang 13,
         * see [2].
         * 1: https://www.illumos.org/issues/16344
         * 2: https://www.illumos.org/issues/13726
         */
#ifdef __illumos__
        DIAG_OFF_STRICT_PROTOTYPES
#endif /* __illumos__ */
        if ((oldhandler = setsignal(SIGHUP, cleanup)) != SIG_DFL)
#ifdef __illumos__
        DIAG_ON_STRICT_PROTOTYPES
#endif /* __illumos__ */
                (void)setsignal(SIGHUP, oldhandler);
#endif /* _WIN32 */

#ifndef _WIN32
        /*
         * If a user name was specified with "-Z", attempt to switch to
         * that user's UID.  This would probably be used with sudo,
         * to allow tcpdump to be run in a special restricted
         * account (if you just want to allow users to open capture
         * devices, and can't just give users that permission,
         * you'd make tcpdump set-UID or set-GID).
         *
         * tcpdump doesn't necessarily write only to one savefile;
         * the general only way to allow a -Z instance to write to
         * savefiles as the user under whose UID it's run, rather
         * than as the user specified with -Z, would thus be to switch
         * to the original user ID before opening a capture file and
         * then switch back to the -Z user ID after opening the savefile.
         * Switching to the -Z user ID only after opening the first
         * savefile doesn't handle the general case.
         */

        if (getuid() == 0 || geteuid() == 0) {
#ifdef HAVE_LIBCAP_NG
                /* Initialize capng */
                capng_clear(CAPNG_SELECT_BOTH);
                if (username) {
DIAG_OFF_ASSIGN_ENUM
                        capng_updatev(
                                CAPNG_ADD,
                                CAPNG_PERMITTED | CAPNG_EFFECTIVE,
                                CAP_SETUID,
                                CAP_SETGID,
                                -1);
DIAG_ON_ASSIGN_ENUM
                }
                if (chroot_dir) {
DIAG_OFF_ASSIGN_ENUM
                        capng_update(
                                CAPNG_ADD,
                                CAPNG_PERMITTED | CAPNG_EFFECTIVE,
                                CAP_SYS_CHROOT
                                );
DIAG_ON_ASSIGN_ENUM
                }

                if (WFileName) {
DIAG_OFF_ASSIGN_ENUM
                        capng_update(
                                CAPNG_ADD,
                                CAPNG_PERMITTED | CAPNG_EFFECTIVE,
                                CAP_DAC_OVERRIDE
                                );
DIAG_ON_ASSIGN_ENUM
                }
                capng_apply(CAPNG_SELECT_BOTH);
#endif /* HAVE_LIBCAP_NG */
                if (username || chroot_dir)
                        droproot(username, chroot_dir);

        }
#endif /* _WIN32 */

        if (pcap_setfilter(pd, &fcode) < 0)
                error("%s", pcap_geterr(pd));
#ifdef HAVE_CAPSICUM
        if (RFileName == NULL && VFileName == NULL && pcap_fileno(pd) != -1) {
                static const unsigned long cmds[] = { BIOCGSTATS, BIOCROTZBUF };

                /*
                 * The various libpcap devices use a combination of
                 * read (bpf), ioctl (bpf, netmap), poll (netmap)
                 * so we add the relevant access rights.
                 */
                cap_rights_init(&rights, CAP_IOCTL, CAP_READ, CAP_EVENT);
                if (cap_rights_limit(pcap_fileno(pd), &rights) < 0 &&
                    errno != ENOSYS) {
                        error("unable to limit pcap descriptor");
                }
                if (cap_ioctls_limit(pcap_fileno(pd), cmds,
                    sizeof(cmds) / sizeof(cmds[0])) < 0 && errno != ENOSYS) {
                        error("unable to limit ioctls on pcap descriptor");
                }
        }
#endif
        if (WFileName) {
                /* Do not exceed the default PATH_MAX for files. */
                dumpinfo.CurrentFileName = (char *)malloc(PATH_MAX + 1);

                if (dumpinfo.CurrentFileName == NULL)
                        error("malloc of dumpinfo.CurrentFileName");

                /* We do not need numbering for dumpfiles if Cflag isn't set. */
                if (Cflag != 0)
                  MakeFilename(dumpinfo.CurrentFileName, WFileName, 0, WflagChars);
                else
                  MakeFilename(dumpinfo.CurrentFileName, WFileName, 0, 0);

                pdd = pcap_dump_open(pd, dumpinfo.CurrentFileName);
#ifdef HAVE_LIBCAP_NG
                /* Give up CAP_DAC_OVERRIDE capability.
                 * Only allow it to be restored if the -C or -G flag have been
                 * set since we may need to create more files later on.
                 */
                capng_update(
                        CAPNG_DROP,
                        (Cflag || Gflag ? 0 : CAPNG_PERMITTED)
                                | CAPNG_EFFECTIVE,
                        CAP_DAC_OVERRIDE
                        );
                capng_apply(CAPNG_SELECT_BOTH);
#endif /* HAVE_LIBCAP_NG */
                if (pdd == NULL)
                        error("%s", pcap_geterr(pd));
#ifdef HAVE_CAPSICUM
                set_dumper_capsicum_rights(pdd);
#endif
                if (Cflag != 0 || Gflag != 0) {
#ifdef HAVE_CAPSICUM
                        /*
                         * basename() and dirname() may modify their input buffer
                         * and they do since FreeBSD 12.0, but they didn't before.
                         * Hence use the return value only, but always assume the
                         * input buffer has been modified and would need to be
                         * reset before the next use.
                         */
                        char *WFileName_copy;

                        if ((WFileName_copy = strdup(WFileName)) == NULL) {
                                error("Unable to allocate memory for file %s",
                                    WFileName);
                        }
                        DIAG_OFF_C11_EXTENSIONS
                        dumpinfo.WFileName = strdup(basename(WFileName_copy));
                        DIAG_ON_C11_EXTENSIONS
                        if (dumpinfo.WFileName == NULL) {
                                error("Unable to allocate memory for file %s",
                                    WFileName);
                        }
                        free(WFileName_copy);

                        if ((WFileName_copy = strdup(WFileName)) == NULL) {
                                error("Unable to allocate memory for file %s",
                                    WFileName);
                        }
                        DIAG_OFF_C11_EXTENSIONS
                        char *WFileName_dirname = dirname(WFileName_copy);
                        DIAG_ON_C11_EXTENSIONS
                        dumpinfo.dirfd = open(WFileName_dirname,
                            O_DIRECTORY | O_RDONLY);
                        if (dumpinfo.dirfd < 0) {
                                error("unable to open directory %s",
                                    WFileName_dirname);
                        }
                        free(WFileName_dirname);
                        free(WFileName_copy);

                        cap_rights_init(&rights, CAP_CREATE, CAP_FCNTL,
                            CAP_FTRUNCATE, CAP_LOOKUP, CAP_SEEK, CAP_WRITE);
                        if (cap_rights_limit(dumpinfo.dirfd, &rights) < 0 &&
                            errno != ENOSYS) {
                                error("unable to limit directory rights");
                        }
                        if (cap_fcntls_limit(dumpinfo.dirfd, CAP_FCNTL_GETFL) < 0 &&
                            errno != ENOSYS) {
                                error("unable to limit dump descriptor fcntls");
                        }
#else   /* !HAVE_CAPSICUM */
                        dumpinfo.WFileName = WFileName;
#endif
                        callback = dump_packet_and_trunc;
                        dumpinfo.pd = pd;
                        dumpinfo.pdd = pdd;
                        pcap_userdata = (u_char *)&dumpinfo;
                } else {
                        callback = dump_packet;
                        dumpinfo.WFileName = WFileName;
                        dumpinfo.pd = pd;
                        dumpinfo.pdd = pdd;
                        pcap_userdata = (u_char *)&dumpinfo;
                }
                if (print) {
                        dlt = pcap_datalink(pd);
                        ndo->ndo_if_printer = get_if_printer(dlt);
                        dumpinfo.ndo = ndo;
                } else
                        dumpinfo.ndo = NULL;

                if (Uflag)
                        pcap_dump_flush(pdd);
        } else {
                dlt = pcap_datalink(pd);
                ndo->ndo_if_printer = get_if_printer(dlt);
                callback = print_packet;
                pcap_userdata = (u_char *)ndo;
        }

#ifdef SIGNAL_REQ_INFO
        /*
         * We can't get statistics when reading from a file rather
         * than capturing from a device.
         */
        if (RFileName == NULL)
                (void)setsignal(SIGNAL_REQ_INFO, requestinfo);
#endif
#ifdef SIGNAL_FLUSH_PCAP
        (void)setsignal(SIGNAL_FLUSH_PCAP, flushpcap);
#endif

        if (ndo->ndo_vflag > 0 && WFileName && RFileName == NULL && !print) {
                /*
                 * When capturing to a file, if "--print" wasn't specified,
                 *"-v" means tcpdump should, once per second,
                 * "v"erbosely report the number of packets captured.
                 * Except when reading from a file, because -r, -w and -v
                 * together used to make a corner case, in which pcap_loop()
                 * errored due to EINTR (see GH #155 for details).
                 */
#ifdef _WIN32
                /*
                 * https://blogs.msdn.microsoft.com/oldnewthing/20151230-00/?p=92741
                 *
                 * suggests that this dates back to W2K.
                 *
                 * I don't know what a "long wait" is, but we'll assume
                 * that printing the stats could be a "long wait".
                 */
                CreateTimerQueueTimer(&timer_handle, NULL,
                    verbose_stats_dump, NULL, 1000, 1000,
                    WT_EXECUTEDEFAULT|WT_EXECUTELONGFUNCTION);
                setvbuf(stderr, NULL, _IONBF, 0);
#else /* _WIN32 */
                /*
                 * Assume this is UN*X, and that it has setitimer(); that
                 * dates back to UNIX 95.
                 */
                struct itimerval timer;
                (void)setsignal(SIGALRM, verbose_stats_dump);
                timer.it_interval.tv_sec = 1;
                timer.it_interval.tv_usec = 0;
                timer.it_value.tv_sec = 1;
                timer.it_value.tv_usec = 1;
                setitimer(ITIMER_REAL, &timer, NULL);
#endif /* _WIN32 */
        }

        if (RFileName == NULL) {
                /*
                 * Live capture (if -V was specified, we set RFileName
                 * to a file from the -V file).  Print a message to
                 * the standard error on UN*X.
                 */
                if (!ndo->ndo_vflag && !WFileName) {
                        (void)fprintf(stderr,
                            "%s: verbose output suppressed, use -v[v]... for full protocol decode\n",
                            program_name);
                } else
                        (void)fprintf(stderr, "%s: ", program_name);
                dlt = pcap_datalink(pd);
                dlt_name = pcap_datalink_val_to_name(dlt);
                (void)fprintf(stderr, "listening on %s", device);
                if (dlt_name == NULL) {
                        (void)fprintf(stderr, ", link-type %u", dlt);
                } else {
                        (void)fprintf(stderr, ", link-type %s (%s)", dlt_name,
                                      pcap_datalink_val_to_description(dlt));
                }
                (void)fprintf(stderr, ", snapshot length %d bytes\n", ndo->ndo_snaplen);
                (void)fflush(stderr);
        }

#ifdef HAVE_CAPSICUM
        cansandbox = (VFileName == NULL && zflag == NULL);
#ifdef HAVE_CASPER
        cansandbox = (cansandbox && (ndo->ndo_nflag || capdns != NULL));
#else
        cansandbox = (cansandbox && ndo->ndo_nflag);
#endif /* HAVE_CASPER */
        cansandbox = (cansandbox && (pcap_fileno(pd) != -1 ||
            RFileName != NULL));

        if (cansandbox && cap_enter() < 0 && errno != ENOSYS)
                error("unable to enter the capability mode");
#endif  /* HAVE_CAPSICUM */

        do {
                status = pcap_loop(pd,
                                   (cnt == -1 ? -1 : cnt + (int)packets_to_skip),
                                   callback, pcap_userdata);
                if (WFileName == NULL) {
                        /*
                         * We're printing packets.  Flush the printed output,
                         * so it doesn't get intermingled with error output.
                         */
                        if (status == -2) {
                                /*
                                 * We got interrupted, so perhaps we didn't
                                 * manage to finish a line we were printing.
                                 * Print an extra newline, just in case.
                                 */
                                putchar('\n');
                        }
                        (void)fflush(stdout);
                }
                if (status == -2) {
                        /*
                         * We got interrupted. If we are reading multiple
                         * files (via -V) set these so that we stop.
                         */
                        VFileName = NULL;
                        ret = NULL;
                }
                if (status == -1) {
                        /*
                         * Error.  Report it.
                         */
                        (void)fprintf(stderr, "%s: pcap_loop: %s\n",
                            program_name, pcap_geterr(pd));
                }
                if (RFileName == NULL) {
                        /*
                         * We're doing a live capture.  Report the capture
                         * statistics.
                         */
                        info(1);
                }
                pcap_close(pd);
                if (VFileName != NULL) {
                        ret = get_next_file(VFile, VFileLine);
                        if (ret) {
                                int new_dlt;

                                RFileName = VFileLine;
                                pd = pcap_open_offline(RFileName, ebuf);
                                if (pd == NULL)
                                        error("%s", ebuf);
#ifdef HAVE_CAPSICUM
                                cap_rights_init(&rights, CAP_READ);
                                if (cap_rights_limit(fileno(pcap_file(pd)),
                                    &rights) < 0 && errno != ENOSYS) {
                                        error("unable to limit pcap descriptor");
                                }
#endif
                                new_dlt = pcap_datalink(pd);
                                if (new_dlt != dlt) {
                                        /*
                                         * The new file has a different
                                         * link-layer header type from the
                                         * previous one.
                                         */
                                        if (WFileName != NULL) {
                                                /*
                                                 * We're writing raw packets
                                                 * that match the filter to
                                                 * a pcap file.  pcap files
                                                 * don't support multiple
                                                 * different link-layer
                                                 * header types, so we fail
                                                 * here.
                                                 */
                                                error("%s: new dlt does not match original", RFileName);
                                        }

                                        /*
                                         * We're printing the decoded packets;
                                         * switch to the new DLT.
                                         *
                                         * To do that, we need to change
                                         * the printer, change the DLT name,
                                         * and recompile the filter with
                                         * the new DLT.
                                         */
                                        dlt = new_dlt;
                                        ndo->ndo_if_printer = get_if_printer(dlt);
                                        /* Free the old filter */
                                        pcap_freecode(&fcode);
                                        /*
                                         * netmask is in network byte order, pcap_compile() takes it
                                         * in host byte order.
                                         */
                                        if (pcap_compile(pd, &fcode, cmdbuf, Oflag, ntohl(netmask)) < 0)
                                                error("%s", pcap_geterr(pd));
                                }

                                /*
                                 * Set the filter on the new file.
                                 */
                                if (pcap_setfilter(pd, &fcode) < 0)
                                        error("%s", pcap_geterr(pd));

                                /*
                                 * Report the new file.
                                 */
                                dlt_name = pcap_datalink_val_to_name(dlt);
                                fprintf(stderr, "reading from file %s", RFileName);
                                if (dlt_name == NULL) {
                                        fprintf(stderr, ", link-type %u", dlt);
                                } else {
                                        fprintf(stderr, ", link-type %s (%s)",
                                                dlt_name,
                                                pcap_datalink_val_to_description(dlt));
                                }
                                fprintf(stderr, ", snapshot length %d\n", pcap_snapshot(pd));
                        }
                }
        }
        while (ret != NULL);

        if (count_mode && RFileName != NULL)
                fprintf(stdout, "%u packet%s\n", packets_captured,
                        PLURAL_SUFFIX(packets_captured));

        free(cmdbuf);
        pcap_freecode(&fcode);
        exit_tcpdump(status == -1 ? S_ERR_HOST_PROGRAM : S_SUCCESS);
}

/*
 * Routines to parse numerical command-line arguments and check for
 * errors, including "too large for that type".
 */
static int
parse_int(const char *argname, const char *string, char **endpp,
    int minval, int maxval, int base)
{
        long val;
        char *endp;

        errno = 0;
        val = strtol(string, &endp, base);

        /*
         * Did it either not parse any of the string, find extra stuff
         * at the end that the caller isn't interested in, or get
         * another parsing error?
         */
        if (string == endp || (endpp == NULL && *endp != '\0') ||
            (val == 0 && errno == EINVAL)) {
                error("invalid %s \"%s\" (not a valid number)", argname,
                    string);
        }

        /*
         * Did it get a value that's out of range?
         */
        if (((val == LONG_MAX || val == LONG_MIN) && errno == ERANGE) ||
            val < minval || val > maxval) {
                error("invalid %s %s (must be >= %d and <= %d)",
                    argname, string, minval, maxval);
        }

        /*
         * OK, it passes all the tests.
         */
        if (endpp != NULL)
                *endpp = endp;
        return ((int)val);
}

static u_int
parse_u_int(const char *argname, const char *string, char **endpp,
    u_int minval, u_int maxval, int base)
{
        unsigned long val;
        char *endp;

        errno = 0;

        /*
         * strtoul() does *NOT* report an error if the string
         * begins with a minus sign. We do.
         */
        if (*string == '-') {
                error("invalid %s \"%s\" (not a valid unsigned number)",
                    argname, string);
        }

        val = strtoul(string, &endp, base);

        /*
         * Did it either not parse any of the string, find extra stuff
         * at the end that the caller isn't interested in, or get
         * another parsing error?
         */
        if (string == endp || (endpp == NULL && *endp != '\0') ||
            (val == 0 && errno == EINVAL)) {
                error("invalid %s \"%s\" (not a valid unsigned number)",
                    argname, string);
        }

        /*
         * Did it get a value that's out of range?
         */
        if ((val == ULONG_MAX && errno == ERANGE) ||
            val < minval || val > maxval) {
                error("invalid %s %s (must be >= %u and <= %u)",
                    argname, string, minval, maxval);
        }

        /*
         * OK, it passes all the tests.
         */
        if (endpp != NULL)
                *endpp = endp;
        return ((u_int)val);
}

static int64_t
parse_int64(const char *argname, const char *string, char **endpp,
    int64_t minval, int64_t maxval, int base)
{
        intmax_t val;
        char *endp;

        errno = 0;
        val = strtoimax(string, &endp, base);

        /*
         * Did it either not parse any of the string, find extra stuff
         * at the end that the caller isn't interested in, or get
         * another parsing error?
         */
        if (string == endp || (endpp == NULL && *endp != '\0') ||
            (val == 0 && errno == EINVAL)) {
                error("invalid %s \"%s\" (not a valid number)", argname,
                    string);
        }

        /*
         * Did it get a value that's out of range?
         */
        if (((val == INTMAX_MAX || val == INTMAX_MIN) && errno == ERANGE) ||
            val < minval || val > maxval) {
                error("invalid %s %s (must be >= %" PRId64 " and <= %" PRId64 ")",
                    argname, string, minval, maxval);
        }

        /*
         * OK, it passes all the tests.
         */
        if (endpp != NULL)
                *endpp = endp;
        return ((int64_t)val);
}

/*
 * Catch a signal.
 */
static void
(*setsignal (int sig, void (*func)(int)))(int)
{
#ifdef _WIN32
        return (signal(sig, func));
#else
        struct sigaction old, new;

        memset(&new, 0, sizeof(new));
        new.sa_handler = func;
        if ((sig == SIGCHLD)
# ifdef SIGNAL_REQ_INFO
                || (sig == SIGNAL_REQ_INFO)
# endif
# ifdef SIGNAL_FLUSH_PCAP
                || (sig == SIGNAL_FLUSH_PCAP)
# endif
                )
                new.sa_flags = SA_RESTART;
        if (sigaction(sig, &new, &old) < 0)
                /* The same workaround as for SIG_DFL above. */
#ifdef __illumos__
                DIAG_OFF_STRICT_PROTOTYPES
#endif /* __illumos__ */
                return (SIG_ERR);
#ifdef __illumos__
                DIAG_ON_STRICT_PROTOTYPES
#endif /* __illumos__ */
        return (old.sa_handler);
#endif
}

/* make a clean exit on interrupts */
static void
cleanup(int signo _U_)
{
#ifdef _WIN32
        if (timer_handle != INVALID_HANDLE_VALUE) {
                DeleteTimerQueueTimer(NULL, timer_handle, NULL);
                CloseHandle(timer_handle);
                timer_handle = INVALID_HANDLE_VALUE;
        }
#else /* _WIN32 */
        struct itimerval timer;

        timer.it_interval.tv_sec = 0;
        timer.it_interval.tv_usec = 0;
        timer.it_value.tv_sec = 0;
        timer.it_value.tv_usec = 0;
        setitimer(ITIMER_REAL, &timer, NULL);
#endif /* _WIN32 */

        /*
         * We have "pcap_breakloop()"; use it, so that we do as little
         * as possible in the signal handler (it's probably not safe
         * to do anything with standard I/O streams in a signal handler -
         * the ANSI C standard doesn't say it is).
         */
        pcap_breakloop(pd);
}

/*
  On windows, we do not use a fork, so we do not care less about
  waiting a child processes to die
 */
#if defined(HAVE_FORK) || defined(HAVE_VFORK)
static void
child_cleanup(int signo _U_)
{
  while (waitpid(-1, NULL, WNOHANG) >= 0);
}
#endif /* HAVE_FORK && HAVE_VFORK */

static void
info(int verbose)
{
        struct pcap_stat stats;

        /*
         * Older versions of libpcap didn't set ps_ifdrop on some
         * platforms; initialize it to 0 to handle that.
         */
        stats.ps_ifdrop = 0;
        if (pcap_stats(pd, &stats) < 0) {
                (void)fprintf(stderr, "pcap_stats: %s\n", pcap_geterr(pd));
                infoprint = 0;
                return;
        }

        if (!verbose)
                fprintf(stderr, "%s: ", program_name);

        (void)fprintf(stderr, "%u packet%s captured", packets_captured,
            PLURAL_SUFFIX(packets_captured));
        if (!verbose)
                fputs(", ", stderr);
        else
                putc('\n', stderr);
        (void)fprintf(stderr, "%u packet%s received by filter", stats.ps_recv,
            PLURAL_SUFFIX(stats.ps_recv));
        if (!verbose)
                fputs(", ", stderr);
        else
                putc('\n', stderr);
        (void)fprintf(stderr, "%u packet%s dropped by kernel", stats.ps_drop,
            PLURAL_SUFFIX(stats.ps_drop));
        if (stats.ps_ifdrop != 0) {
                if (!verbose)
                        fputs(", ", stderr);
                else
                        putc('\n', stderr);
                (void)fprintf(stderr, "%u packet%s dropped by interface\n",
                    stats.ps_ifdrop, PLURAL_SUFFIX(stats.ps_ifdrop));
        } else
                putc('\n', stderr);
        infoprint = 0;
}

#if defined(HAVE_FORK) || defined(HAVE_VFORK)
#ifdef HAVE_FORK
#define fork_subprocess() fork()
#else
#define fork_subprocess() vfork()
#endif
static void
compress_savefile(const char *filename)
{
        pid_t child;

        child = fork_subprocess();
        if (child == -1) {
                fprintf(stderr,
                        "%s: fork failed: %s\n",
                        __func__, pcap_strerror(errno));
                return;
        }
        if (child != 0) {
                /* Parent process. */
                return;
        }

        /*
         * Child process.
         * Set to lowest priority so that this doesn't disturb the capture.
         */
#ifdef NZERO
        setpriority(PRIO_PROCESS, 0, NZERO - 1);
#else
        setpriority(PRIO_PROCESS, 0, 19);
#endif
        if (execlp(zflag, zflag, filename, (char *)NULL) == -1)
                fprintf(stderr,
                        "%s: execlp(%s, %s) failed: %s\n",
                        __func__, zflag, filename, pcap_strerror(errno));
#ifdef HAVE_FORK
        exit(S_ERR_HOST_PROGRAM);
#else
        _exit(S_ERR_HOST_PROGRAM);
#endif
}
#else  /* HAVE_FORK && HAVE_VFORK */
static void
compress_savefile(const char *filename)
{
        fprintf(stderr,
                "%s failed. Functionality not implemented under your system\n",
                __func__);
}
#endif /* HAVE_FORK && HAVE_VFORK */

static void
close_old_dump_file(struct dump_info *dump_info)
{
        /*
         * Close the current file and open a new one.
         */
        pcap_dump_close(dump_info->pdd);

        /*
         * Compress the file we just closed, if the user asked for it.
         */
        if (zflag != NULL)
                compress_savefile(dump_info->CurrentFileName);
}

static void
open_new_dump_file(struct dump_info *dump_info)
{
#ifdef HAVE_CAPSICUM
        FILE *fp;
        int fd;
#endif

#ifdef HAVE_LIBCAP_NG
        capng_update(CAPNG_ADD, CAPNG_EFFECTIVE, CAP_DAC_OVERRIDE);
        capng_apply(CAPNG_SELECT_BOTH);
#endif /* HAVE_LIBCAP_NG */
#ifdef HAVE_CAPSICUM
        fd = openat(dump_info->dirfd, dump_info->CurrentFileName,
            O_CREAT | O_WRONLY | O_TRUNC, 0644);
        if (fd < 0) {
                error("unable to open file %s", dump_info->CurrentFileName);
        }
        fp = fdopen(fd, "w");
        if (fp == NULL) {
                error("unable to fdopen file %s", dump_info->CurrentFileName);
        }
        dump_info->pdd = pcap_dump_fopen(dump_info->pd, fp);
#else   /* !HAVE_CAPSICUM */
        dump_info->pdd = pcap_dump_open(dump_info->pd, dump_info->CurrentFileName);
#endif
#ifdef HAVE_LIBCAP_NG
        capng_update(CAPNG_DROP, CAPNG_EFFECTIVE, CAP_DAC_OVERRIDE);
        capng_apply(CAPNG_SELECT_BOTH);
#endif /* HAVE_LIBCAP_NG */
        if (dump_info->pdd == NULL)
                error("%s", pcap_geterr(pd));
#ifdef HAVE_CAPSICUM
        set_dumper_capsicum_rights(dump_info->pdd);
#endif
}

static void
dump_packet_and_trunc(u_char *user, const struct pcap_pkthdr *h, const u_char *sp)
{
        struct dump_info *dump_info;

        ++packets_captured;

        ++infodelay;

        dump_info = (struct dump_info *)user;

        if (packets_captured <= packets_to_skip)
                return;

        /*
         * XXX - this won't force the file to rotate on the specified time
         * boundary, but it will rotate on the first packet received after the
         * specified Gflag number of seconds. Note: if a Gflag time boundary
         * and a Cflag size boundary coincide, the time rotation will occur
         * first thereby cancelling the Cflag boundary (since the file should
         * be 0).
         */
        if (Gflag != 0) {
                /* Check if it is time to rotate */
                time_t t;

                /* Get the current time */
                if ((t = time(NULL)) == (time_t)-1) {
                        error("%s: can't get current_time: %s",
                            __func__, pcap_strerror(errno));
                }


                /* If the time is greater than the specified window, rotate */
                if (t - Gflag_time >= Gflag) {
                        /* Update the Gflag_time */
                        Gflag_time = t;
                        /* Update Gflag_count */
                        Gflag_count++;

                        close_old_dump_file(dump_info);

                        /*
                         * Check to see if we've exceeded the Wflag (when
                         * not using Cflag).
                         */
                        if (Cflag == 0 && Wflag > 0 && Gflag_count >= Wflag) {
                                (void)fprintf(stderr, "Maximum file limit reached: %d\n",
                                    Wflag);
                                info(1);
                                exit_tcpdump(S_SUCCESS);
                                /* NOTREACHED */
                        }
                        if (dump_info->CurrentFileName != NULL)
                                free(dump_info->CurrentFileName);
                        /* Allocate space for max filename + \0. */
                        dump_info->CurrentFileName = (char *)malloc(PATH_MAX + 1);
                        if (dump_info->CurrentFileName == NULL)
                                error("dump_packet_and_trunc: malloc");
                        /*
                         * Gflag was set otherwise we wouldn't be here. Reset the count
                         * so multiple files would end with 1,2,3 in the filename.
                         * The counting is handled with the -C flow after this.
                         */
                        Cflag_count = 0;

                        /*
                         * This is always the first file in the Cflag
                         * rotation: e.g. 0
                         * We also don't need numbering if Cflag is not set.
                         */
                        if (Cflag != 0)
                                MakeFilename(dump_info->CurrentFileName, dump_info->WFileName, 0,
                                    WflagChars);
                        else
                                MakeFilename(dump_info->CurrentFileName, dump_info->WFileName, 0, 0);

                        open_new_dump_file(dump_info);
                }
        }

        /*
         * XXX - this won't prevent capture files from getting
         * larger than Cflag - the last packet written to the
         * file could put it over Cflag.
         */
        if (Cflag != 0) {
#ifdef HAVE_PCAP_DUMP_FTELL64
                int64_t size = pcap_dump_ftell64(dump_info->pdd);
#else
                /*
                 * XXX - this only handles a Cflag value > 2^31-1 on
                 * LP64 platforms; to handle ILP32 (32-bit UN*X and
                 * Windows) or LLP64 (64-bit Windows) would require
                 * a version of libpcap with pcap_dump_ftell64().
                 */
                long size = pcap_dump_ftell(dump_info->pdd);
#endif

                if (size == -1)
                        error("ftell fails on output file");
                if (size > Cflag) {
                        close_old_dump_file(dump_info);

                        Cflag_count++;
                        if (Wflag > 0) {
                                if (Cflag_count >= Wflag)
                                        Cflag_count = 0;
                        }
                        if (dump_info->CurrentFileName != NULL)
                                free(dump_info->CurrentFileName);
                        dump_info->CurrentFileName = (char *)malloc(PATH_MAX + 1);
                        if (dump_info->CurrentFileName == NULL)
                                error("%s: malloc", __func__);
                        MakeFilename(dump_info->CurrentFileName, dump_info->WFileName, Cflag_count, WflagChars);

                        open_new_dump_file(dump_info);
                }
        }

        pcap_dump((u_char *)dump_info->pdd, h, sp);
        if (Uflag)
                pcap_dump_flush(dump_info->pdd);

        if (dump_info->ndo != NULL)
                pretty_print_packet(dump_info->ndo, h, sp, packets_captured);

        --infodelay;
        if (infoprint)
                info(0);
}

static void
dump_packet(u_char *user, const struct pcap_pkthdr *h, const u_char *sp)
{
        struct dump_info *dump_info;

        ++packets_captured;

        ++infodelay;

        dump_info = (struct dump_info *)user;

        if (packets_captured <= packets_to_skip)
                return;

        pcap_dump((u_char *)dump_info->pdd, h, sp);
        if (Uflag)
                pcap_dump_flush(dump_info->pdd);

        if (dump_info->ndo != NULL)
                pretty_print_packet(dump_info->ndo, h, sp, packets_captured);

        --infodelay;
        if (infoprint)
                info(0);
}

static void
print_packet(u_char *user, const struct pcap_pkthdr *h, const u_char *sp)
{
        ++packets_captured;

        ++infodelay;

        if (!count_mode && packets_captured > packets_to_skip)
                pretty_print_packet((netdissect_options *)user, h, sp, packets_captured);

        --infodelay;
        if (infoprint)
                info(0);
}

#ifdef SIGNAL_REQ_INFO
static void
requestinfo(int signo _U_)
{
        if (infodelay)
                ++infoprint;
        else
                info(0);
}
#endif

#ifdef SIGNAL_FLUSH_PCAP
static void
flushpcap(int signo _U_)
{
        if (pdd != NULL)
                pcap_dump_flush(pdd);
}
#endif

static void
print_packets_captured (void)
{
        static u_int prev_packets_captured, first = 1;

        if (infodelay == 0 && (first || packets_captured != prev_packets_captured)) {
                fprintf(stderr, "Got %u\r", packets_captured);
                first = 0;
                prev_packets_captured = packets_captured;
        }
}

/*
 * Called once each second in verbose mode while dumping to file
 */
#ifdef _WIN32
static void CALLBACK verbose_stats_dump(PVOID param _U_,
    BOOLEAN timer_fired _U_)
{
        print_packets_captured();
}
#else /* _WIN32 */
static void verbose_stats_dump(int sig _U_)
{
        print_packets_captured();
}
#endif /* _WIN32 */

DIAG_OFF_DEPRECATION
static void
print_version(FILE *f)
{
        const char *smi_version_string;

        (void)fprintf(f, "%s version " PACKAGE_VERSION "\n", program_name);
        (void)fprintf(f, "%s\n", pcap_lib_version());

#if defined(HAVE_LIBCRYPTO) && defined(SSLEAY_VERSION)
        (void)fprintf (f, "%s\n", SSLeay_version(SSLEAY_VERSION));
#endif

        smi_version_string = nd_smi_version_string();
        if (smi_version_string != NULL)
                (void)fprintf (f, "SMI-library: %s\n", smi_version_string);

#if defined(__SANITIZE_ADDRESS__)
        (void)fprintf (f, "Compiled with AddressSanitizer/GCC.\n");
#elif defined(__has_feature)
#  if __has_feature(address_sanitizer)
        (void)fprintf (f, "Compiled with AddressSanitizer/Clang.\n");
#  elif __has_feature(memory_sanitizer)
        (void)fprintf (f, "Compiled with MemorySanitizer/Clang.\n");
#  endif
#endif /* __SANITIZE_ADDRESS__ or __has_feature */
        (void)fprintf (f, "%zu-bit build, %zu-bit time_t\n",
                       sizeof(void *) * 8, sizeof(time_t) * 8);
}
DIAG_ON_DEPRECATION

static void
print_usage(FILE *f)
{
        print_version(f);
        (void)fprintf(f,
"Usage: %s [-AbdDefhHI" J_FLAG "KlLnNOpqStuUvxX#] [ -B size ] [ -c count ] [--count]\n", program_name);
        (void)fprintf(f,
"\t\t[ -C file_size ] [ -E algo:secret ] [ -F file ] [ -G seconds ]\n");
        (void)fprintf(f,
"\t\t[ -i interface ]" IMMEDIATE_MODE_USAGE j_FLAG_USAGE "\n");
        (void)fprintf(f,
"\t\t[ --lengths ]" LIST_REMOTE_INTERFACES_USAGE "\n");
#ifdef USE_LIBSMI
        (void)fprintf(f,
"\t\t" m_FLAG_USAGE "\n");
#endif
        (void)fprintf(f,
"\t\t[ -M secret ] [ --number ] [ --print ]\n");
        (void)fprintf(f,
"\t\t[ --print-sampling nth ] [ -Q in|out|inout ] [ -r file ]\n");
        (void)fprintf(f,
"\t\t[ -s snaplen ] [ --skip count ] [ -T type ] [ --version ]\n");
        (void)fprintf(f,
"\t\t[ -V file ] [ -w file ] [ -W filecount ] [ -y datalinktype ]\n");
#ifdef HAVE_PCAP_SET_TSTAMP_PRECISION
        (void)fprintf(f,
"\t\t[ --time-stamp-precision precision ] [ --micro ] [ --nano ]\n");
#endif
        (void)fprintf(f,
"\t\t[ -z postrotate-command ] [ -Z user ] [ expression ]\n");
}