[libpcap] / pcap.c

/*
 * Copyright (c) 1993, 1994, 1995, 1996, 1997, 1998
 *      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 the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the Computer Systems
 *      Engineering Group at Lawrence Berkeley Laboratory.
 * 4. Neither the name of the University nor of the Laboratory may be used
 *    to endorse or promote products derived from this software without
 *    specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifndef lint
static const char rcsid[] _U_ =
    "@(#) $Header: /tcpdump/master/libpcap/pcap.c,v 1.83 2005-01-12 09:15:05 hannes Exp $ (LBL)";
#endif

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#ifdef WIN32
#include <pcap-stdinc.h>
#else /* WIN32 */
#include <sys/types.h>
#endif /* WIN32 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#if !defined(_MSC_VER) && !defined(__BORLANDC__)
#include <unistd.h>
#endif
#include <fcntl.h>
#include <errno.h>

#ifdef HAVE_OS_PROTO_H
#include "os-proto.h"
#endif

#ifdef MSDOS
#include "pcap-dos.h"
#endif

#include "pcap-int.h"

#ifdef HAVE_DAG_API
#include <dagnew.h>
#include <dagapi.h>
#endif

int
pcap_dispatch(pcap_t *p, int cnt, pcap_handler callback, u_char *user)
{

        return p->read_op(p, cnt, callback, user);
}

/*
 * XXX - is this necessary?
 */
int
pcap_read(pcap_t *p, int cnt, pcap_handler callback, u_char *user)
{

        return p->read_op(p, cnt, callback, user);
}

int
pcap_loop(pcap_t *p, int cnt, pcap_handler callback, u_char *user)
{
        register int n;

        for (;;) {
                if (p->sf.rfile != NULL) {
                        /*
                         * 0 means EOF, so don't loop if we get 0.
                         */
                        n = pcap_offline_read(p, cnt, callback, user);
                } else {
                        /*
                         * XXX keep reading until we get something
                         * (or an error occurs)
                         */
                        do {
                                n = p->read_op(p, cnt, callback, user);
                        } while (n == 0);
                }
                if (n <= 0)
                        return (n);
                if (cnt > 0) {
                        cnt -= n;
                        if (cnt <= 0)
                                return (0);
                }
        }
}

struct singleton {
        struct pcap_pkthdr *hdr;
        const u_char *pkt;
};


static void
pcap_oneshot(u_char *userData, const struct pcap_pkthdr *h, const u_char *pkt)
{
        struct singleton *sp = (struct singleton *)userData;
        *sp->hdr = *h;
        sp->pkt = pkt;
}

const u_char *
pcap_next(pcap_t *p, struct pcap_pkthdr *h)
{
        struct singleton s;

        s.hdr = h;
        if (pcap_dispatch(p, 1, pcap_oneshot, (u_char*)&s) <= 0)
                return (0);
        return (s.pkt);
}

struct pkt_for_fakecallback {
        struct pcap_pkthdr *hdr;
        const u_char **pkt;
};

static void
pcap_fakecallback(u_char *userData, const struct pcap_pkthdr *h,
    const u_char *pkt)
{
        struct pkt_for_fakecallback *sp = (struct pkt_for_fakecallback *)userData;

        *sp->hdr = *h;
        *sp->pkt = pkt;
}

int 
pcap_next_ex(pcap_t *p, struct pcap_pkthdr **pkt_header,
    const u_char **pkt_data)
{
        struct pkt_for_fakecallback s;

        s.hdr = &p->pcap_header;
        s.pkt = pkt_data;

        /* Saves a pointer to the packet headers */
        *pkt_header= &p->pcap_header;

        if (p->sf.rfile != NULL) {
                int status;

                /* We are on an offline capture */
                status = pcap_offline_read(p, 1, pcap_fakecallback,
                    (u_char *)&s);

                /*
                 * Return codes for pcap_offline_read() are:
                 *   -  0: EOF
                 *   - -1: error
                 *   - >1: OK
                 * The first one ('0') conflicts with the return code of
                 * 0 from pcap_read() meaning "no packets arrived before
                 * the timeout expired", so we map it to -2 so you can
                 * distinguish between an EOF from a savefile and a
                 * "no packets arrived before the timeout expired, try
                 * again" from a live capture.
                 */
                if (status == 0)
                        return (-2);
                else
                        return (status);
        }

        /*
         * Return codes for pcap_read() are:
         *   -  0: timeout
         *   - -1: error
         *   - -2: loop was broken out of with pcap_breakloop()
         *   - >1: OK
         * The first one ('0') conflicts with the return code of 0 from
         * pcap_offline_read() meaning "end of file".
        */
        return (p->read_op(p, 1, pcap_fakecallback, (u_char *)&s));
}

/*
 * Force the loop in "pcap_read()" or "pcap_read_offline()" to terminate.
 */
void
pcap_breakloop(pcap_t *p)
{
        p->break_loop = 1;
}

int
pcap_datalink(pcap_t *p)
{
        return (p->linktype);
}

int
pcap_list_datalinks(pcap_t *p, int **dlt_buffer)
{
        if (p->dlt_count == 0) {
                /*
                 * We couldn't fetch the list of DLTs, which means
                 * this platform doesn't support changing the
                 * DLT for an interface.  Return a list of DLTs
                 * containing only the DLT this device supports.
                 */
                *dlt_buffer = (int*)malloc(sizeof(**dlt_buffer));
                if (*dlt_buffer == NULL) {
                        (void)snprintf(p->errbuf, sizeof(p->errbuf),
                            "malloc: %s", pcap_strerror(errno));
                        return (-1);
                }
                **dlt_buffer = p->linktype;
                return (1);
        } else {
                *dlt_buffer = (int*)malloc(sizeof(**dlt_buffer) * p->dlt_count);
                if (*dlt_buffer == NULL) {
                        (void)snprintf(p->errbuf, sizeof(p->errbuf),
                            "malloc: %s", pcap_strerror(errno));
                        return (-1);
                }
                (void)memcpy(*dlt_buffer, p->dlt_list,
                    sizeof(**dlt_buffer) * p->dlt_count);
                return (p->dlt_count);
        }
}

int
pcap_set_datalink(pcap_t *p, int dlt)
{
        int i;
        const char *dlt_name;

        if (p->dlt_count == 0 || p->set_datalink_op == NULL) {
                /*
                 * We couldn't fetch the list of DLTs, or we don't
                 * have a "set datalink" operation, which means
                 * this platform doesn't support changing the
                 * DLT for an interface.  Check whether the new
                 * DLT is the one this interface supports.
                 */
                if (p->linktype != dlt)
                        goto unsupported;

                /*
                 * It is, so there's nothing we need to do here.
                 */
                return (0);
        }
        for (i = 0; i < p->dlt_count; i++)
                if (p->dlt_list[i] == dlt)
                        break;
        if (i >= p->dlt_count)
                goto unsupported;
        if (p->dlt_count == 2 && p->dlt_list[0] == DLT_EN10MB &&
            dlt == DLT_DOCSIS) {
                /*
                 * This is presumably an Ethernet device, as the first
                 * link-layer type it offers is DLT_EN10MB, and the only
                 * other type it offers is DLT_DOCSIS.  That means that
                 * we can't tell the driver to supply DOCSIS link-layer
                 * headers - we're just pretending that's what we're
                 * getting, as, presumably, we're capturing on a dedicated
                 * link to a Cisco Cable Modem Termination System, and
                 * it's putting raw DOCSIS frames on the wire inside low-level
                 * Ethernet framing.
                 */
                p->linktype = dlt;
                return (0);
        }
        if (p->set_datalink_op(p, dlt) == -1)
                return (-1);
        p->linktype = dlt;
        return (0);

unsupported:
        dlt_name = pcap_datalink_val_to_name(dlt);
        if (dlt_name != NULL) {
                (void) snprintf(p->errbuf, sizeof(p->errbuf),
                    "%s is not one of the DLTs supported by this device",
                    dlt_name);
        } else {
                (void) snprintf(p->errbuf, sizeof(p->errbuf),
                    "DLT %d is not one of the DLTs supported by this device",
                    dlt);
        }
        return (-1);
}

struct dlt_choice {
        const char *name;
        const char *description;
        int     dlt;
};

#define DLT_CHOICE(code, description) { #code, description, code }
#define DLT_CHOICE_SENTINEL { NULL, NULL, 0 }

static struct dlt_choice dlt_choices[] = {
        DLT_CHOICE(DLT_NULL, "BSD loopback"),
        DLT_CHOICE(DLT_EN10MB, "Ethernet"),
        DLT_CHOICE(DLT_IEEE802, "Token ring"),
        DLT_CHOICE(DLT_ARCNET, "ARCNET"),
        DLT_CHOICE(DLT_SLIP, "SLIP"),
        DLT_CHOICE(DLT_PPP, "PPP"),
        DLT_CHOICE(DLT_FDDI, "FDDI"),
        DLT_CHOICE(DLT_ATM_RFC1483, "RFC 1483 IP-over-ATM"),
        DLT_CHOICE(DLT_RAW, "Raw IP"),
        DLT_CHOICE(DLT_SLIP_BSDOS, "BSD/OS SLIP"),
        DLT_CHOICE(DLT_PPP_BSDOS, "BSD/OS PPP"),
        DLT_CHOICE(DLT_ATM_CLIP, "Linux Classical IP-over-ATM"),
        DLT_CHOICE(DLT_PPP_SERIAL, "PPP over serial"),
        DLT_CHOICE(DLT_PPP_ETHER, "PPPoE"),
        DLT_CHOICE(DLT_C_HDLC, "Cisco HDLC"),
        DLT_CHOICE(DLT_IEEE802_11, "802.11"),
        DLT_CHOICE(DLT_FRELAY, "Frame Relay"),
        DLT_CHOICE(DLT_LOOP, "OpenBSD loopback"),
        DLT_CHOICE(DLT_ENC, "OpenBSD encapsulated IP"),
        DLT_CHOICE(DLT_LINUX_SLL, "Linux cooked"),
        DLT_CHOICE(DLT_LTALK, "Localtalk"),
        DLT_CHOICE(DLT_PFLOG, "OpenBSD pflog file"),
        DLT_CHOICE(DLT_PRISM_HEADER, "802.11 plus Prism header"),
        DLT_CHOICE(DLT_IP_OVER_FC, "RFC 2625 IP-over-Fibre Channel"),
        DLT_CHOICE(DLT_SUNATM, "Sun raw ATM"),
        DLT_CHOICE(DLT_IEEE802_11_RADIO, "802.11 plus BSD radio information header"),
        DLT_CHOICE(DLT_APPLE_IP_OVER_IEEE1394, "Apple IP-over-IEEE 1394"),
        DLT_CHOICE(DLT_ARCNET_LINUX, "Linux ARCNET"),
        DLT_CHOICE(DLT_DOCSIS, "DOCSIS"),
        DLT_CHOICE(DLT_LINUX_IRDA, "Linux IrDA"),
        DLT_CHOICE(DLT_IEEE802_11_RADIO_AVS, "802.11 plus AVS radio information header"),
        DLT_CHOICE(DLT_SYMANTEC_FIREWALL, "Symantec Firewall"),
        DLT_CHOICE(DLT_JUNIPER_ATM1, "Juniper ATM1 PIC"),
        DLT_CHOICE(DLT_JUNIPER_ATM2, "Juniper ATM2 PIC"),
        DLT_CHOICE(DLT_JUNIPER_MLPPP, "Juniper ML/LS PIC"),
        DLT_CHOICE(DLT_PPP_WITHDIRECTION, "PPP with direction"),
        DLT_CHOICE(DLT_JUNIPER_PPPOE, "Juniper PPPoE"),
        DLT_CHOICE(DLT_JUNIPER_PPPOE_ATM, "Juniper PPPoE/ATM"),
        DLT_CHOICE(DLT_GPRS_LLC, "GPRS LLC"),
        DLT_CHOICE(DLT_GPF_T, "GPF-T"),
        DLT_CHOICE(DLT_GPF_F, "GPF-F"),
        DLT_CHOICE(DLT_JUNIPER_PIC_PEER, "Juniper PIC Peer"),
        DLT_CHOICE_SENTINEL
};

/*
 * This array is designed for mapping upper and lower case letter
 * together for a case independent comparison.  The mappings are
 * based upon ascii character sequences.
 */
static const u_char charmap[] = {
        (u_char)'\000', (u_char)'\001', (u_char)'\002', (u_char)'\003',
        (u_char)'\004', (u_char)'\005', (u_char)'\006', (u_char)'\007',
        (u_char)'\010', (u_char)'\011', (u_char)'\012', (u_char)'\013',
        (u_char)'\014', (u_char)'\015', (u_char)'\016', (u_char)'\017',
        (u_char)'\020', (u_char)'\021', (u_char)'\022', (u_char)'\023',
        (u_char)'\024', (u_char)'\025', (u_char)'\026', (u_char)'\027',
        (u_char)'\030', (u_char)'\031', (u_char)'\032', (u_char)'\033',
        (u_char)'\034', (u_char)'\035', (u_char)'\036', (u_char)'\037',
        (u_char)'\040', (u_char)'\041', (u_char)'\042', (u_char)'\043',
        (u_char)'\044', (u_char)'\045', (u_char)'\046', (u_char)'\047',
        (u_char)'\050', (u_char)'\051', (u_char)'\052', (u_char)'\053',
        (u_char)'\054', (u_char)'\055', (u_char)'\056', (u_char)'\057',
        (u_char)'\060', (u_char)'\061', (u_char)'\062', (u_char)'\063',
        (u_char)'\064', (u_char)'\065', (u_char)'\066', (u_char)'\067',
        (u_char)'\070', (u_char)'\071', (u_char)'\072', (u_char)'\073',
        (u_char)'\074', (u_char)'\075', (u_char)'\076', (u_char)'\077',
        (u_char)'\100', (u_char)'\141', (u_char)'\142', (u_char)'\143',
        (u_char)'\144', (u_char)'\145', (u_char)'\146', (u_char)'\147',
        (u_char)'\150', (u_char)'\151', (u_char)'\152', (u_char)'\153',
        (u_char)'\154', (u_char)'\155', (u_char)'\156', (u_char)'\157',
        (u_char)'\160', (u_char)'\161', (u_char)'\162', (u_char)'\163',
        (u_char)'\164', (u_char)'\165', (u_char)'\166', (u_char)'\167',
        (u_char)'\170', (u_char)'\171', (u_char)'\172', (u_char)'\133',
        (u_char)'\134', (u_char)'\135', (u_char)'\136', (u_char)'\137',
        (u_char)'\140', (u_char)'\141', (u_char)'\142', (u_char)'\143',
        (u_char)'\144', (u_char)'\145', (u_char)'\146', (u_char)'\147',
        (u_char)'\150', (u_char)'\151', (u_char)'\152', (u_char)'\153',
        (u_char)'\154', (u_char)'\155', (u_char)'\156', (u_char)'\157',
        (u_char)'\160', (u_char)'\161', (u_char)'\162', (u_char)'\163',
        (u_char)'\164', (u_char)'\165', (u_char)'\166', (u_char)'\167',
        (u_char)'\170', (u_char)'\171', (u_char)'\172', (u_char)'\173',
        (u_char)'\174', (u_char)'\175', (u_char)'\176', (u_char)'\177',
        (u_char)'\200', (u_char)'\201', (u_char)'\202', (u_char)'\203',
        (u_char)'\204', (u_char)'\205', (u_char)'\206', (u_char)'\207',
        (u_char)'\210', (u_char)'\211', (u_char)'\212', (u_char)'\213',
        (u_char)'\214', (u_char)'\215', (u_char)'\216', (u_char)'\217',
        (u_char)'\220', (u_char)'\221', (u_char)'\222', (u_char)'\223',
        (u_char)'\224', (u_char)'\225', (u_char)'\226', (u_char)'\227',
        (u_char)'\230', (u_char)'\231', (u_char)'\232', (u_char)'\233',
        (u_char)'\234', (u_char)'\235', (u_char)'\236', (u_char)'\237',
        (u_char)'\240', (u_char)'\241', (u_char)'\242', (u_char)'\243',
        (u_char)'\244', (u_char)'\245', (u_char)'\246', (u_char)'\247',
        (u_char)'\250', (u_char)'\251', (u_char)'\252', (u_char)'\253',
        (u_char)'\254', (u_char)'\255', (u_char)'\256', (u_char)'\257',
        (u_char)'\260', (u_char)'\261', (u_char)'\262', (u_char)'\263',
        (u_char)'\264', (u_char)'\265', (u_char)'\266', (u_char)'\267',
        (u_char)'\270', (u_char)'\271', (u_char)'\272', (u_char)'\273',
        (u_char)'\274', (u_char)'\275', (u_char)'\276', (u_char)'\277',
        (u_char)'\300', (u_char)'\341', (u_char)'\342', (u_char)'\343',
        (u_char)'\344', (u_char)'\345', (u_char)'\346', (u_char)'\347',
        (u_char)'\350', (u_char)'\351', (u_char)'\352', (u_char)'\353',
        (u_char)'\354', (u_char)'\355', (u_char)'\356', (u_char)'\357',
        (u_char)'\360', (u_char)'\361', (u_char)'\362', (u_char)'\363',
        (u_char)'\364', (u_char)'\365', (u_char)'\366', (u_char)'\367',
        (u_char)'\370', (u_char)'\371', (u_char)'\372', (u_char)'\333',
        (u_char)'\334', (u_char)'\335', (u_char)'\336', (u_char)'\337',
        (u_char)'\340', (u_char)'\341', (u_char)'\342', (u_char)'\343',
        (u_char)'\344', (u_char)'\345', (u_char)'\346', (u_char)'\347',
        (u_char)'\350', (u_char)'\351', (u_char)'\352', (u_char)'\353',
        (u_char)'\354', (u_char)'\355', (u_char)'\356', (u_char)'\357',
        (u_char)'\360', (u_char)'\361', (u_char)'\362', (u_char)'\363',
        (u_char)'\364', (u_char)'\365', (u_char)'\366', (u_char)'\367',
        (u_char)'\370', (u_char)'\371', (u_char)'\372', (u_char)'\373',
        (u_char)'\374', (u_char)'\375', (u_char)'\376', (u_char)'\377',
};

int
pcap_strcasecmp(const char *s1, const char *s2)
{
        register const u_char   *cm = charmap,
                                *us1 = (u_char *)s1,
                                *us2 = (u_char *)s2;

        while (cm[*us1] == cm[*us2++])
                if (*us1++ == '\0')
                        return(0);
        return (cm[*us1] - cm[*--us2]);
}

int
pcap_datalink_name_to_val(const char *name)
{
        int i;

        for (i = 0; dlt_choices[i].name != NULL; i++) {
                if (pcap_strcasecmp(dlt_choices[i].name + sizeof("DLT_") - 1,
                    name) == 0)
                        return (dlt_choices[i].dlt);
        }
        return (-1);
}

const char *
pcap_datalink_val_to_name(int dlt)
{
        int i;

        for (i = 0; dlt_choices[i].name != NULL; i++) {
                if (dlt_choices[i].dlt == dlt)
                        return (dlt_choices[i].name + sizeof("DLT_") - 1);
        }
        return (NULL);
}

const char *
pcap_datalink_val_to_description(int dlt)
{
        int i;

        for (i = 0; dlt_choices[i].name != NULL; i++) {
                if (dlt_choices[i].dlt == dlt)
                        return (dlt_choices[i].description);
        }
        return (NULL);
}

int
pcap_snapshot(pcap_t *p)
{
        return (p->snapshot);
}

int
pcap_is_swapped(pcap_t *p)
{
        return (p->sf.swapped);
}

int
pcap_major_version(pcap_t *p)
{
        return (p->sf.version_major);
}

int
pcap_minor_version(pcap_t *p)
{
        return (p->sf.version_minor);
}

FILE *
pcap_file(pcap_t *p)
{
        return (p->sf.rfile);
}

int
pcap_fileno(pcap_t *p)
{
#ifndef WIN32
        return (p->fd);
#else
        if (p->adapter != NULL)
                return ((int)(DWORD)p->adapter->hFile);
        else
                return (-1);
#endif
}

#if !defined(WIN32) && !defined(MSDOS)
int
pcap_get_selectable_fd(pcap_t *p)
{
        return (p->selectable_fd);
}
#endif

void
pcap_perror(pcap_t *p, char *prefix)
{
        fprintf(stderr, "%s: %s\n", prefix, p->errbuf);
}

char *
pcap_geterr(pcap_t *p)
{
        return (p->errbuf);
}

int
pcap_getnonblock(pcap_t *p, char *errbuf)
{
        return p->getnonblock_op(p, errbuf);
}

/*
 * Get the current non-blocking mode setting, under the assumption that
 * it's just the standard POSIX non-blocking flag.
 *
 * We don't look at "p->nonblock", in case somebody tweaked the FD
 * directly.
 */
#if !defined(WIN32) && !defined(MSDOS)
int
pcap_getnonblock_fd(pcap_t *p, char *errbuf)
{
        int fdflags;

        fdflags = fcntl(p->fd, F_GETFL, 0);
        if (fdflags == -1) {
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "F_GETFL: %s",
                    pcap_strerror(errno));
                return (-1);
        }
        if (fdflags & O_NONBLOCK)
                return (1);
        else
                return (0);
}
#endif

int
pcap_setnonblock(pcap_t *p, int nonblock, char *errbuf)
{
        return p->setnonblock_op(p, nonblock, errbuf);
}

#if !defined(WIN32) && !defined(MSDOS)
/*
 * Set non-blocking mode, under the assumption that it's just the
 * standard POSIX non-blocking flag.  (This can be called by the
 * per-platform non-blocking-mode routine if that routine also
 * needs to do some additional work.)
 */
int
pcap_setnonblock_fd(pcap_t *p, int nonblock, char *errbuf)
{
        int fdflags;

        fdflags = fcntl(p->fd, F_GETFL, 0);
        if (fdflags == -1) {
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "F_GETFL: %s",
                    pcap_strerror(errno));
                return (-1);
        }
        if (nonblock)
                fdflags |= O_NONBLOCK;
        else
                fdflags &= ~O_NONBLOCK;
        if (fcntl(p->fd, F_SETFL, fdflags) == -1) {
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "F_SETFL: %s",
                    pcap_strerror(errno));
                return (-1);
        }
        return (0);
}
#endif

#ifdef WIN32
/*
 * Generate a string for the last Win32-specific error (i.e. an error generated when 
 * calling a Win32 API).
 * For errors occurred during standard C calls, we still use pcap_strerror()
 */
char *
pcap_win32strerror(void)
{
        DWORD error;
        static char errbuf[PCAP_ERRBUF_SIZE+1];
        int errlen;
        char *p;

        error = GetLastError();
        FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM, NULL, error, 0, errbuf,
            PCAP_ERRBUF_SIZE, NULL);

        /*
         * "FormatMessage()" "helpfully" sticks CR/LF at the end of the
         * message.  Get rid of it.
         */
        errlen = strlen(errbuf);
        if (errlen >= 2) {
                errbuf[errlen - 1] = '\0';
                errbuf[errlen - 2] = '\0';
        }
        p = strchr(errbuf, '\0');
        snprintf (p, sizeof(errbuf)-(p-errbuf), " (%lu)", error);
        return (errbuf);
}
#endif

/*
 * Not all systems have strerror().
 */
char *
pcap_strerror(int errnum)
{
#ifdef HAVE_STRERROR
        return (strerror(errnum));
#else
        extern int sys_nerr;
        extern const char *const sys_errlist[];
        static char ebuf[20];

        if ((unsigned int)errnum < sys_nerr)
                return ((char *)sys_errlist[errnum]);
        (void)snprintf(ebuf, sizeof ebuf, "Unknown error: %d", errnum);
        return(ebuf);
#endif
}

int
pcap_setfilter(pcap_t *p, struct bpf_program *fp)
{
        return p->setfilter_op(p, fp);
}

int
pcap_stats(pcap_t *p, struct pcap_stat *ps)
{
        return p->stats_op(p, ps);
}

static int
pcap_stats_dead(pcap_t *p, struct pcap_stat *ps _U_)
{
        snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
            "Statistics aren't available from a pcap_open_dead pcap_t");
        return (-1);
}

void
pcap_close_common(pcap_t *p)
{
        if (p->buffer != NULL)
                free(p->buffer);
#if !defined(WIN32) && !defined(MSDOS)
        if (p->fd >= 0)
                close(p->fd);
#endif
}

static void
pcap_close_dead(pcap_t *p _U_)
{
        /* Nothing to do. */
}

pcap_t *
pcap_open_dead(int linktype, int snaplen)
{
        pcap_t *p;

        p = malloc(sizeof(*p));
        if (p == NULL)
                return NULL;
        memset (p, 0, sizeof(*p));
        p->snapshot = snaplen;
        p->linktype = linktype;
        p->stats_op = pcap_stats_dead;
        p->close_op = pcap_close_dead;
        return p;
}

/*
 * API compatible with WinPcap's "send a packet" routine - returns -1
 * on error, 0 otherwise.
 *
 * XXX - what if we get a short write?
 */
int
pcap_sendpacket(pcap_t *p, const u_char *buf, int size)
{
        if (p->inject_op(p, buf, size) == -1)
                return (-1);
        return (0);
}

/*
 * API compatible with OpenBSD's "send a packet" routine - returns -1 on
 * error, number of bytes written otherwise.
 */
int
pcap_inject(pcap_t *p, const void *buf, size_t size)
{
        return (p->inject_op(p, buf, size));
}

void
pcap_close(pcap_t *p)
{
        p->close_op(p);
        if (p->dlt_list != NULL)
                free(p->dlt_list);
        pcap_freecode(&p->fcode);
        free(p);
}

/*
 * We make the version string static, and return a pointer to it, rather
 * than exporting the version string directly.  On at least some UNIXes,
 * if you import data from a shared library into an program, the data is
 * bound into the program binary, so if the string in the version of the
 * library with which the program was linked isn't the same as the
 * string in the version of the library with which the program is being
 * run, various undesirable things may happen (warnings, the string
 * being the one from the version of the library with which the program
 * was linked, or even weirder things, such as the string being the one
 * from the library but being truncated).
 */
#ifdef HAVE_VERSION_H
#include "version.h"
#else
static const char pcap_version_string[] = "libpcap version 0.9[.x]";
#endif

#ifdef WIN32
/*
 * XXX - it'd be nice if we could somehow generate the WinPcap and libpcap
 * version numbers when building WinPcap.  (It'd be nice to do so for
 * the packet.dll version number as well.)
 */
static const char wpcap_version_string[] = "3.1";
static const char pcap_version_string_fmt[] =
    "WinPcap version %s, based on %s";
static const char pcap_version_string_packet_dll_fmt[] =
    "WinPcap version %s (packet.dll version %s), based on %s";
static char *full_pcap_version_string;

const char *
pcap_lib_version(void)
{
        char *packet_version_string;
        size_t full_pcap_version_string_len;

        if (full_pcap_version_string == NULL) {
                /*
                 * Generate the version string.
                 */
                packet_version_string = PacketGetVersion();
                if (strcmp(wpcap_version_string, packet_version_string) == 0) {
                        /*
                         * WinPcap version string and packet.dll version
                         * string are the same; just report the WinPcap
                         * version.
                         */
                        full_pcap_version_string_len =
                            (sizeof pcap_version_string_fmt - 4) +
                            strlen(wpcap_version_string) +
                            strlen(pcap_version_string);
                        full_pcap_version_string =
                            malloc(full_pcap_version_string_len);
                        sprintf(full_pcap_version_string,
                            pcap_version_string_fmt, wpcap_version_string,
                            pcap_version_string);
                } else {
                        /*
                         * WinPcap version string and packet.dll version
                         * string are different; that shouldn't be the
                         * case (the two libraries should come from the
                         * same version of WinPcap), so we report both
                         * versions.
                         */
                        full_pcap_version_string_len =
                            (sizeof pcap_version_string_packet_dll_fmt - 6) +
                            strlen(wpcap_version_string) +
                            strlen(packet_version_string) +
                            strlen(pcap_version_string);
                        full_pcap_version_string = malloc(full_pcap_version_string_len);

                        sprintf(full_pcap_version_string,
                            pcap_version_string_packet_dll_fmt,
                            wpcap_version_string, packet_version_string,
                            pcap_version_string);
                }
        }
        return (full_pcap_version_string);
}

#elif defined(MSDOS)

static char *full_pcap_version_string;

const char *
pcap_lib_version (void)
{
        char *packet_version_string;
        size_t full_pcap_version_string_len;
        static char dospfx[] = "DOS-";

        if (full_pcap_version_string == NULL) {
                /*
                 * Generate the version string.
                 */
                full_pcap_version_string_len =
                    sizeof dospfx + strlen(pcap_version_string);
                full_pcap_version_string =
                    malloc(full_pcap_version_string_len);
                strcpy(full_pcap_version_string, dospfx);
                strcat(full_pcap_version_string, pcap_version_string);
        }
        return (full_pcap_version_string);
}

#else /* UN*X */

const char *
pcap_lib_version(void)
{
        return (pcap_version_string);
}
#endif