Fix typo.

[libpcap] / pcap-bpf.c

/*
 * Copyright (c) 1993, 1994, 1995, 1996, 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: (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.
 */
#ifndef lint
static const char rcsid[] _U_ =
    "@(#) $Header: /tcpdump/master/libpcap/pcap-bpf.c,v 1.116 2008-09-16 18:42:29 guy Exp $ (LBL)";
#endif

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

#include <sys/param.h>                  /* optionally get BSD define */
#ifdef HAVE_ZEROCOPY_BPF
#include <sys/mman.h>
#endif
#include <sys/time.h>
#include <sys/socket.h>
/*
 * <net/bpf.h> defines ioctls, but doesn't include <sys/ioccom.h>.
 *
 * We include <sys/ioctl.h> as it might be necessary to declare ioctl();
 * at least on *BSD and Mac OS X, it also defines various SIOC ioctls -
 * we could include <sys/sockio.h>, but if we're already including
 * <sys/ioctl.h>, which includes <sys/sockio.h> on those platforms,
 * there's not much point in doing so.
 *
 * If we have <sys/ioccom.h>, we include it as well, to handle systems
 * such as Solaris which don't arrange to include <sys/ioccom.h> if you
 * include <sys/ioctl.h>
 */
#include <sys/ioctl.h>
#ifdef HAVE_SYS_IOCCOM_H
#include <sys/ioccom.h>
#endif
#include <sys/utsname.h>

#ifdef HAVE_ZEROCOPY_BPF
#include <machine/atomic.h>
#endif

#include <net/if.h>

#ifdef _AIX

/*
 * Make "pcap.h" not include "pcap/bpf.h"; we are going to include the
 * native OS version, as we need "struct bpf_config" from it.
 */
#define PCAP_DONT_INCLUDE_PCAP_BPF_H

#include <sys/types.h>

/*
 * Prevent bpf.h from redefining the DLT_ values to their
 * IFT_ values, as we're going to return the standard libpcap
 * values, not IBM's non-standard IFT_ values.
 */
#undef _AIX
#include <net/bpf.h>
#define _AIX

#include <net/if_types.h>               /* for IFT_ values */
#include <sys/sysconfig.h>
#include <sys/device.h>
#include <sys/cfgodm.h>
#include <cf.h>

#ifdef __64BIT__
#define domakedev makedev64
#define getmajor major64
#define bpf_hdr bpf_hdr32
#else /* __64BIT__ */
#define domakedev makedev
#define getmajor major
#endif /* __64BIT__ */

#define BPF_NAME "bpf"
#define BPF_MINORS 4
#define DRIVER_PATH "/usr/lib/drivers"
#define BPF_NODE "/dev/bpf"
static int bpfloadedflag = 0;
static int odmlockid = 0;

static int bpf_load(char *errbuf);

#else /* _AIX */

#include <net/bpf.h>

#endif /* _AIX */

#include <ctype.h>
#include <fcntl.h>
#include <errno.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#ifdef HAVE_NET_IF_MEDIA_H
# include <net/if_media.h>
#endif

#include "pcap-int.h"

#ifdef HAVE_DAG_API
#include "pcap-dag.h"
#endif /* HAVE_DAG_API */

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

#ifdef BIOCGDLTLIST
# if (defined(HAVE_NET_IF_MEDIA_H) && defined(IFM_IEEE80211)) && !defined(__APPLE__)
#define HAVE_BSD_IEEE80211
# endif

# if defined(__APPLE__) || defined(HAVE_BSD_IEEE80211)
static int find_802_11(struct bpf_dltlist *);

#  ifdef HAVE_BSD_IEEE80211
static int monitor_mode(pcap_t *, int);
#  endif

#  if defined(__APPLE__)
static void remove_en(pcap_t *);
static void remove_802_11(pcap_t *);
#  endif

# endif /* defined(__APPLE__) || defined(HAVE_BSD_IEEE80211) */

#endif /* BIOCGDLTLIST */

/*
 * We include the OS's <net/bpf.h>, not our "pcap/bpf.h", so we probably
 * don't get DLT_DOCSIS defined.
 */
#ifndef DLT_DOCSIS
#define DLT_DOCSIS      143
#endif

/*
 * On OS X, we don't even get any of the 802.11-plus-radio-header DLT_'s
 * defined, even though some of them are used by various Airport drivers.
 */
#ifndef DLT_PRISM_HEADER
#define DLT_PRISM_HEADER        119
#endif
#ifndef DLT_AIRONET_HEADER
#define DLT_AIRONET_HEADER      120
#endif
#ifndef DLT_IEEE802_11_RADIO
#define DLT_IEEE802_11_RADIO    127
#endif
#ifndef DLT_IEEE802_11_RADIO_AVS
#define DLT_IEEE802_11_RADIO_AVS 163
#endif

static int pcap_can_set_rfmon_bpf(pcap_t *p);
static int pcap_activate_bpf(pcap_t *p);
static int pcap_setfilter_bpf(pcap_t *p, struct bpf_program *fp);
static int pcap_setdirection_bpf(pcap_t *, pcap_direction_t);
static int pcap_set_datalink_bpf(pcap_t *p, int dlt);

#ifdef HAVE_ZEROCOPY_BPF
/*
 * For zerocopy bpf, we need to override the setnonblock/getnonblock routines
 * so we don't call select(2) if the pcap handle is in non-blocking mode.  We
 * preserve the timeout supplied by pcap_open functions to make sure it
 * does not get clobbered if the pcap handle moves between blocking and non-
 * blocking mode.
 */
static int
pcap_getnonblock_zbuf(pcap_t *p, char *errbuf)
{ 
        /*
         * Use a negative value for the timeout to represent that the
         * pcap handle is in non-blocking mode.
         */
        return (p->md.timeout < 0);
}

static int
pcap_setnonblock_zbuf(pcap_t *p, int nonblock, char *errbuf)
{   
        /*
         * Map each value to the corresponding 2's complement, to
         * preserve the timeout value provided with pcap_set_timeout.
         * (from pcap-linux.c).
         */
        if (nonblock) {
                if (p->md.timeout >= 0) {
                        /*
                         * Timeout is non-negative, so we're not already
                         * in non-blocking mode; set it to the 2's
                         * complement, to make it negative, as an
                         * indication that we're in non-blocking mode.
                         */
                        p->md.timeout = p->md.timeout * -1 - 1;
                }
        } else {
                if (p->md.timeout < 0) {
                        /*
                         * Timeout is negative, so we're not already
                         * in blocking mode; reverse the previous
                         * operation, to make the timeout non-negative
                         * again.
                         */
                        p->md.timeout = (p->md.timeout + 1) * -1;
                }
        }
        return (0);
}

/*
 * Zero-copy specific close method.  Un-map the shared buffers then call
 * pcap_cleanup_live_common.
 */
static void
pcap_cleanup_zbuf(pcap_t *p)
{
        /*
         * Delete the mappings.  Note that p->buffer gets initialized to one
         * of the mmapped regions in this case, so do not try and free it
         * directly; null it out so that pcap_cleanup_live_common() doesn't
         * try to free it.
         */
        if (p->md.zbuf1 != MAP_FAILED && p->md.zbuf1 != NULL)
                (void) munmap(p->md.zbuf1, p->md.zbufsize);
        if (p->md.zbuf2 != MAP_FAILED && p->md.zbuf2 != NULL)
                (void) munmap(p->md.zbuf2, p->md.zbufsize);
        p->buffer = NULL;
        pcap_cleanup_live_common(p);
}

/*
 * Zero-copy BPF buffer routines to check for and acknowledge BPF data in
 * shared memory buffers.
 *
 * pcap_next_zbuf_shm(): Check for a newly available shared memory buffer,
 * and set up p->buffer and cc to reflect one if available.  Notice that if
 * there was no prior buffer, we select zbuf1 as this will be the first
 * buffer filled for a fresh BPF session.
 */
static int
pcap_next_zbuf_shm(pcap_t *p, int *cc)
{
        struct bpf_zbuf_header *bzh;

        if (p->md.zbuffer == p->md.zbuf2 || p->md.zbuffer == NULL) {
                bzh = (struct bpf_zbuf_header *)p->md.zbuf1;
                if (bzh->bzh_user_gen !=
                    atomic_load_acq_int(&bzh->bzh_kernel_gen)) {
                        p->md.bzh = bzh;
                        p->md.zbuffer = (u_char *)p->md.zbuf1;
                        p->buffer = p->md.zbuffer + sizeof(*bzh);
                        *cc = bzh->bzh_kernel_len;
                        return (1);
                }
        } else if (p->md.zbuffer == p->md.zbuf1) {
                bzh = (struct bpf_zbuf_header *)p->md.zbuf2;
                if (bzh->bzh_user_gen !=
                    atomic_load_acq_int(&bzh->bzh_kernel_gen)) {
                        p->md.bzh = bzh;
                        p->md.zbuffer = (u_char *)p->md.zbuf2;
                        p->buffer = p->md.zbuffer + sizeof(*bzh);
                        *cc = bzh->bzh_kernel_len;
                        return (1);
                }
        }
        *cc = 0;
        return (0);
}

/*
 * pcap_next_zbuf() -- Similar to pcap_next_zbuf_shm(), except wait using
 * select() for data or a timeout, and possibly force rotation of the buffer
 * in the event we time out or are in immediate mode.  Invoke the shared
 * memory check before doing system calls in order to avoid doing avoidable
 * work.
 */
static int
pcap_next_zbuf(pcap_t *p, int *cc)
{
        struct bpf_zbuf bz;
        struct timeval tv;
        struct timespec cur;
        fd_set r_set;
        int data, r;
        int expire, tmout;

#define TSTOMILLI(ts) (((ts)->tv_sec * 1000) + ((ts)->tv_nsec / 1000000))
        /*
         * Start out by seeing whether anything is waiting by checking the
         * next shared memory buffer for data.
         */
        data = pcap_next_zbuf_shm(p, cc);
        if (data)
                return (data);
        /*
         * If a previous sleep was interrupted due to signal delivery, make
         * sure that the timeout gets adjusted accordingly.  This requires
         * that we analyze when the timeout should be been expired, and
         * subtract the current time from that.  If after this operation,
         * our timeout is less then or equal to zero, handle it like a
         * regular timeout.
         */
        tmout = p->md.timeout;
        if (tmout)
                (void) clock_gettime(CLOCK_MONOTONIC, &cur);
        if (p->md.interrupted && p->md.timeout) {
                expire = TSTOMILLI(&p->md.firstsel) + p->md.timeout;
                tmout = expire - TSTOMILLI(&cur);
#undef TSTOMILLI
                if (tmout <= 0) {
                        p->md.interrupted = 0;
                        data = pcap_next_zbuf_shm(p, cc);
                        if (data)
                                return (data);
                        if (ioctl(p->fd, BIOCROTZBUF, &bz) < 0) {
                                (void) snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                                    "BIOCROTZBUF: %s", strerror(errno));
                                return (PCAP_ERROR);
                        }
                        return (pcap_next_zbuf_shm(p, cc));
                }
        }
        /*
         * No data in the buffer, so must use select() to wait for data or
         * the next timeout.  Note that we only call select if the handle
         * is in blocking mode.
         */
        if (p->md.timeout >= 0) {
                FD_ZERO(&r_set);
                FD_SET(p->fd, &r_set);
                if (tmout != 0) {
                        tv.tv_sec = tmout / 1000;
                        tv.tv_usec = (tmout * 1000) % 1000000;
                }
                r = select(p->fd + 1, &r_set, NULL, NULL,
                    p->md.timeout != 0 ? &tv : NULL);
                if (r < 0 && errno == EINTR) {
                        if (!p->md.interrupted && p->md.timeout) {
                                p->md.interrupted = 1;
                                p->md.firstsel = cur;
                        }
                        return (0);
                } else if (r < 0) {
                        (void) snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                            "select: %s", strerror(errno));
                        return (PCAP_ERROR);
                }
        }
        p->md.interrupted = 0;
        /*
         * Check again for data, which may exist now that we've either been
         * woken up as a result of data or timed out.  Try the "there's data"
         * case first since it doesn't require a system call.
         */
        data = pcap_next_zbuf_shm(p, cc);
        if (data)
                return (data);
        /*
         * Try forcing a buffer rotation to dislodge timed out or immediate
         * data.
         */
        if (ioctl(p->fd, BIOCROTZBUF, &bz) < 0) {
                (void) snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                    "BIOCROTZBUF: %s", strerror(errno));
                return (PCAP_ERROR);
        }
        return (pcap_next_zbuf_shm(p, cc));
}

/*
 * Notify kernel that we are done with the buffer.  We don't reset zbuffer so
 * that we know which buffer to use next time around.
 */
static int
pcap_ack_zbuf(pcap_t *p)
{

        atomic_store_rel_int(&p->md.bzh->bzh_user_gen,
            p->md.bzh->bzh_kernel_gen);
        p->md.bzh = NULL;
        p->buffer = NULL;
        return (0);
}
#endif

pcap_t *
pcap_create(const char *device, char *ebuf)
{
        pcap_t *p;

#ifdef HAVE_DAG_API
        if (strstr(device, "dag"))
                return (dag_create(device, ebuf));
#endif /* HAVE_DAG_API */

        p = pcap_create_common(device, ebuf);
        if (p == NULL)
                return (NULL);

        p->activate_op = pcap_activate_bpf;
        p->can_set_rfmon_op = pcap_can_set_rfmon_bpf;
        return (p);
}

static int
bpf_open(pcap_t *p)
{
        int fd;
#ifdef HAVE_CLONING_BPF
        static const char device[] = "/dev/bpf";
#else
        int n = 0;
        char device[sizeof "/dev/bpf0000000000"];
#endif

#ifdef _AIX
        /*
         * Load the bpf driver, if it isn't already loaded,
         * and create the BPF device entries, if they don't
         * already exist.
         */
        if (bpf_load(p->errbuf) == PCAP_ERROR)
                return (PCAP_ERROR);
#endif

#ifdef HAVE_CLONING_BPF
        if ((fd = open(device, O_RDWR)) == -1 &&
            (errno != EACCES || (fd = open(device, O_RDONLY)) == -1)) {
                if (errno == EACCES)
                        fd = PCAP_ERROR_PERM_DENIED;
                else
                        fd = PCAP_ERROR;
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                  "(cannot open device) %s: %s", device, pcap_strerror(errno));
        }
#else
        /*
         * Go through all the minors and find one that isn't in use.
         */
        do {
                (void)snprintf(device, sizeof(device), "/dev/bpf%d", n++);
                /*
                 * Initially try a read/write open (to allow the inject
                 * method to work).  If that fails due to permission
                 * issues, fall back to read-only.  This allows a
                 * non-root user to be granted specific access to pcap
                 * capabilities via file permissions.
                 *
                 * XXX - we should have an API that has a flag that
                 * controls whether to open read-only or read-write,
                 * so that denial of permission to send (or inability
                 * to send, if sending packets isn't supported on
                 * the device in question) can be indicated at open
                 * time.
                 */
                fd = open(device, O_RDWR);
                if (fd == -1 && errno == EACCES)
                        fd = open(device, O_RDONLY);
        } while (fd < 0 && errno == EBUSY);

        /*
         * XXX better message for all minors used
         */
        if (fd < 0) {
                if (errno == EACCES)
                        fd = PCAP_ERROR_PERM_DENIED;
                else
                        fd = PCAP_ERROR;
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "(no devices found) %s: %s",
                    device, pcap_strerror(errno));
        }
#endif

        return (fd);
}

#ifdef BIOCGDLTLIST
static int
get_dlt_list(int fd, int v, struct bpf_dltlist *bdlp, char *ebuf)
{
        memset(bdlp, 0, sizeof(*bdlp));
        if (ioctl(fd, BIOCGDLTLIST, (caddr_t)bdlp) == 0) {
                u_int i;
                int is_ethernet;

                bdlp->bfl_list = (u_int *) malloc(sizeof(u_int) * (bdlp->bfl_len + 1));
                if (bdlp->bfl_list == NULL) {
                        (void)snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc: %s",
                            pcap_strerror(errno));
                        return (PCAP_ERROR);
                }

                if (ioctl(fd, BIOCGDLTLIST, (caddr_t)bdlp) < 0) {
                        (void)snprintf(ebuf, PCAP_ERRBUF_SIZE,
                            "BIOCGDLTLIST: %s", pcap_strerror(errno));
                        free(bdlp->bfl_list);
                        return (PCAP_ERROR);
                }

                /*
                 * OK, for real Ethernet devices, add DLT_DOCSIS to the
                 * list, so that an application can let you choose it,
                 * in case you're capturing DOCSIS traffic that a Cisco
                 * Cable Modem Termination System is putting out onto
                 * an Ethernet (it doesn't put an Ethernet header onto
                 * the wire, it puts raw DOCSIS frames out on the wire
                 * inside the low-level Ethernet framing).
                 *
                 * A "real Ethernet device" is defined here as a device
                 * that has a link-layer type of DLT_EN10MB and that has
                 * no alternate link-layer types; that's done to exclude
                 * 802.11 interfaces (which might or might not be the
                 * right thing to do, but I suspect it is - Ethernet <->
                 * 802.11 bridges would probably badly mishandle frames
                 * that don't have Ethernet headers).
                 */
                if (v == DLT_EN10MB) {
                        is_ethernet = 1;
                        for (i = 0; i < bdlp->bfl_len; i++) {
                                if (bdlp->bfl_list[i] != DLT_EN10MB) {
                                        is_ethernet = 0;
                                        break;
                                }
                        }
                        if (is_ethernet) {
                                /*
                                 * We reserved one more slot at the end of
                                 * the list.
                                 */
                                bdlp->bfl_list[bdlp->bfl_len] = DLT_DOCSIS;
                                bdlp->bfl_len++;
                        }
                }
        } else {
                /*
                 * EINVAL just means "we don't support this ioctl on
                 * this device"; don't treat it as an error.
                 */
                if (errno != EINVAL) {
                        (void)snprintf(ebuf, PCAP_ERRBUF_SIZE,
                            "BIOCGDLTLIST: %s", pcap_strerror(errno));
                        return (PCAP_ERROR);
                }
        }
        return (0);
}
#endif

static int
pcap_can_set_rfmon_bpf(pcap_t *p)
{
#if defined(__APPLE__)
        struct utsname osinfo;
        struct ifreq ifr;
        int fd;
#ifdef BIOCGDLTLIST
        struct bpf_dltlist bdl;
#endif

        /*
         * The joys of monitor mode on OS X.
         *
         * Prior to 10.4, it's not supported at all.
         *
         * In 10.4, if adapter enN supports monitor mode, there's a
         * wltN adapter corresponding to it; you open it, instead of
         * enN, to get monitor mode.  You get whatever link-layer
         * headers it supplies.
         *
         * In 10.5, and, we assume, later releases, if adapter enN
         * supports monitor mode, it offers, among its selectable
         * DLT_ values, values that let you get the 802.11 header;
         * selecting one of those values puts the adapter into monitor
         * mode (i.e., you can't get 802.11 headers except in monitor
         * mode, and you can't get Ethernet headers in monitor mode).
         */
        if (uname(&osinfo) == -1) {
                /*
                 * Can't get the OS version; just say "no".
                 */
                return (0);
        }
        /*
         * We assume osinfo.sysname is "Darwin", because
         * __APPLE__ is defined.  We just check the version.
         */
        if (osinfo.release[0] < '8' && osinfo.release[1] == '.') {
                /*
                 * 10.3 (Darwin 7.x) or earlier.
                 * Monitor mode not supported.
                 */
                return (0);
        }
        if (osinfo.release[0] == '8' && osinfo.release[1] == '.') {
                /*
                 * 10.4 (Darwin 8.x).  s/en/wlt/, and check
                 * whether the device exists.
                 */
                if (strncmp(p->opt.source, "en", 2) != 0) {
                        /*
                         * Not an enN device; no monitor mode.
                         */
                        return (0);
                }
                fd = socket(AF_INET, SOCK_DGRAM, 0);
                if (fd == -1) {
                        (void)snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                            "socket: %s", pcap_strerror(errno));
                        return (PCAP_ERROR);
                }
                strlcpy(ifr.ifr_name, "wlt", sizeof(ifr.ifr_name));
                strlcat(ifr.ifr_name, p->opt.source + 2, sizeof(ifr.ifr_name));
                if (ioctl(fd, SIOCGIFFLAGS, (char *)&ifr) < 0) {
                        /*
                         * No such device?
                         */
                        close(fd);
                        return (0);
                }
                close(fd);
                return (1);
        }

#ifdef BIOCGDLTLIST
        /*
         * Everything else is 10.5 or later; for those,
         * we just open the enN device, and check whether
         * we have any 802.11 devices.
         *
         * First, open a BPF device.
         */
        fd = bpf_open(p);
        if (fd < 0)
                return (fd);

        /*
         * Now bind to the device.
         */
        (void)strncpy(ifr.ifr_name, p->opt.source, sizeof(ifr.ifr_name));
        if (ioctl(fd, BIOCSETIF, (caddr_t)&ifr) < 0) {
                if (errno == ENETDOWN) {
                        /*
                         * Return a "network down" indication, so that
                         * the application can report that rather than
                         * saying we had a mysterious failure and
                         * suggest that they report a problem to the
                         * libpcap developers.
                         */
                        close(fd);
                        return (PCAP_ERROR_IFACE_NOT_UP);
                } else {
                        snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                            "BIOCSETIF: %s: %s",
                            p->opt.source, pcap_strerror(errno));
                        close(fd);
                        return (PCAP_ERROR);
                }
        }

        /*
         * We know the default link type -- now determine all the DLTs
         * this interface supports.  If this fails with EINVAL, it's
         * not fatal; we just don't get to use the feature later.
         * (We don't care about DLT_DOCSIS, so we pass DLT_NULL
         * as the default DLT for this adapter.)
         */
        if (get_dlt_list(fd, DLT_NULL, &bdl, p->errbuf) == PCAP_ERROR) {
                close(fd);
                return (PCAP_ERROR);
        }
        if (find_802_11(&bdl) != -1) {
                /*
                 * We have an 802.11 DLT, so we can set monitor mode.
                 */
                free(bdl.bfl_list);
                close(fd);
                return (1);
        }
        free(bdl.bfl_list);
#endif /* BIOCGDLTLIST */
        return (0);
#elif defined(HAVE_BSD_IEEE80211)
        int ret;

        ret = monitor_mode(p, 0);
        if (ret == PCAP_ERROR_RFMON_NOTSUP)
                return (0);     /* not an error, just a "can't do" */
        if (ret == 0)
                return (1);     /* success */
        return (ret);
#else
        return (0);
#endif
}

static int
pcap_stats_bpf(pcap_t *p, struct pcap_stat *ps)
{
        struct bpf_stat s;

        /*
         * "ps_recv" counts packets handed to the filter, not packets
         * that passed the filter.  This includes packets later dropped
         * because we ran out of buffer space.
         *
         * "ps_drop" counts packets dropped inside the BPF device
         * because we ran out of buffer space.  It doesn't count
         * packets dropped by the interface driver.  It counts
         * only packets that passed the filter.
         *
         * Both statistics include packets not yet read from the kernel
         * by libpcap, and thus not yet seen by the application.
         */
        if (ioctl(p->fd, BIOCGSTATS, (caddr_t)&s) < 0) {
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCGSTATS: %s",
                    pcap_strerror(errno));
                return (PCAP_ERROR);
        }

        ps->ps_recv = s.bs_recv;
        ps->ps_drop = s.bs_drop;
        return (0);
}

static int
pcap_read_bpf(pcap_t *p, int cnt, pcap_handler callback, u_char *user)
{
        int cc;
        int n = 0;
        register u_char *bp, *ep;
        u_char *datap;
#ifdef PCAP_FDDIPAD
        register int pad;
#endif
#ifdef HAVE_ZEROCOPY_BPF
        int i;
#endif

 again:
        /*
         * Has "pcap_breakloop()" been called?
         */
        if (p->break_loop) {
                /*
                 * Yes - clear the flag that indicates that it
                 * has, and return PCAP_ERROR_BREAK to indicate
                 * that we were told to break out of the loop.
                 */
                p->break_loop = 0;
                return (PCAP_ERROR_BREAK);
        }
        cc = p->cc;
        if (p->cc == 0) {
                /*
                 * When reading without zero-copy from a file descriptor, we
                 * use a single buffer and return a length of data in the
                 * buffer.  With zero-copy, we update the p->buffer pointer
                 * to point at whatever underlying buffer contains the next
                 * data and update cc to reflect the data found in the
                 * buffer.
                 */
#ifdef HAVE_ZEROCOPY_BPF
                if (p->md.zerocopy) {
                        if (p->buffer != NULL)
                                pcap_ack_zbuf(p);
                        i = pcap_next_zbuf(p, &cc);
                        if (i == 0)
                                goto again;
                        if (i < 0)
                                return (PCAP_ERROR);
                } else
#endif
                {
                        cc = read(p->fd, (char *)p->buffer, p->bufsize);
                }
                if (cc < 0) {
                        /* Don't choke when we get ptraced */
                        switch (errno) {

                        case EINTR:
                                goto again;

#ifdef _AIX
                        case EFAULT:
                                /*
                                 * Sigh.  More AIX wonderfulness.
                                 *
                                 * For some unknown reason the uiomove()
                                 * operation in the bpf kernel extension
                                 * used to copy the buffer into user
                                 * space sometimes returns EFAULT. I have
                                 * no idea why this is the case given that
                                 * a kernel debugger shows the user buffer
                                 * is correct. This problem appears to
                                 * be mostly mitigated by the memset of
                                 * the buffer before it is first used.
                                 * Very strange.... Shaun Clowes
                                 *
                                 * In any case this means that we shouldn't
                                 * treat EFAULT as a fatal error; as we
                                 * don't have an API for returning
                                 * a "some packets were dropped since
                                 * the last packet you saw" indication,
                                 * we just ignore EFAULT and keep reading.
                                 */
                                goto again;
#endif

                        case EWOULDBLOCK:
                                return (0);
#if defined(sun) && !defined(BSD) && !defined(__svr4__) && !defined(__SVR4)
                        /*
                         * Due to a SunOS bug, after 2^31 bytes, the kernel
                         * file offset overflows and read fails with EINVAL.
                         * The lseek() to 0 will fix things.
                         */
                        case EINVAL:
                                if (lseek(p->fd, 0L, SEEK_CUR) +
                                    p->bufsize < 0) {
                                        (void)lseek(p->fd, 0L, SEEK_SET);
                                        goto again;
                                }
                                /* fall through */
#endif
                        }
                        snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "read: %s",
                            pcap_strerror(errno));
                        return (PCAP_ERROR);
                }
                bp = p->buffer;
        } else
                bp = p->bp;

        /*
         * Loop through each packet.
         */
#define bhp ((struct bpf_hdr *)bp)
        ep = bp + cc;
#ifdef PCAP_FDDIPAD
        pad = p->fddipad;
#endif
        while (bp < ep) {
                register int caplen, hdrlen;

                /*
                 * Has "pcap_breakloop()" been called?
                 * If so, return immediately - if we haven't read any
                 * packets, clear the flag and return PCAP_ERROR_BREAK
                 * to indicate that we were told to break out of the loop,
                 * otherwise leave the flag set, so that the *next* call
                 * will break out of the loop without having read any
                 * packets, and return the number of packets we've
                 * processed so far.
                 */
                if (p->break_loop) {
                        if (n == 0) {
                                p->break_loop = 0;
                                return (PCAP_ERROR_BREAK);
                        } else {
                                p->bp = bp;
                                p->cc = ep - bp;
                                return (n);
                        }
                }

                caplen = bhp->bh_caplen;
                hdrlen = bhp->bh_hdrlen;
                datap = bp + hdrlen;
                /*
                 * Short-circuit evaluation: if using BPF filter
                 * in kernel, no need to do it now - we already know
                 * the packet passed the filter.
                 *
#ifdef PCAP_FDDIPAD
                 * Note: the filter code was generated assuming
                 * that p->fddipad was the amount of padding
                 * before the header, as that's what's required
                 * in the kernel, so we run the filter before
                 * skipping that padding.
#endif
                 */
                if (p->md.use_bpf ||
                    bpf_filter(p->fcode.bf_insns, datap, bhp->bh_datalen, caplen)) {
                        struct pcap_pkthdr pkthdr;

                        pkthdr.ts.tv_sec = bhp->bh_tstamp.tv_sec;
#ifdef _AIX
                        /*
                         * AIX's BPF returns seconds/nanoseconds time
                         * stamps, not seconds/microseconds time stamps.
                         */
                        pkthdr.ts.tv_usec = bhp->bh_tstamp.tv_usec/1000;
#else
                        pkthdr.ts.tv_usec = bhp->bh_tstamp.tv_usec;
#endif
#ifdef PCAP_FDDIPAD
                        if (caplen > pad)
                                pkthdr.caplen = caplen - pad;
                        else
                                pkthdr.caplen = 0;
                        if (bhp->bh_datalen > pad)
                                pkthdr.len = bhp->bh_datalen - pad;
                        else
                                pkthdr.len = 0;
                        datap += pad;
#else
                        pkthdr.caplen = caplen;
                        pkthdr.len = bhp->bh_datalen;
#endif
                        (*callback)(user, &pkthdr, datap);
                        bp += BPF_WORDALIGN(caplen + hdrlen);
                        if (++n >= cnt && cnt > 0) {
                                p->bp = bp;
                                p->cc = ep - bp;
                                return (n);
                        }
                } else {
                        /*
                         * Skip this packet.
                         */
                        bp += BPF_WORDALIGN(caplen + hdrlen);
                }
        }
#undef bhp
        p->cc = 0;
        return (n);
}

static int
pcap_inject_bpf(pcap_t *p, const void *buf, size_t size)
{
        int ret;

        ret = write(p->fd, buf, size);
#ifdef __APPLE__
        if (ret == -1 && errno == EAFNOSUPPORT) {
                /*
                 * In Mac OS X, there's a bug wherein setting the
                 * BIOCSHDRCMPLT flag causes writes to fail; see,
                 * for example:
                 *
                 *      http://cerberus.sourcefire.com/~jeff/archives/patches/macosx/BIOCSHDRCMPLT-10.3.3.patch
                 *
                 * So, if, on OS X, we get EAFNOSUPPORT from the write, we
                 * assume it's due to that bug, and turn off that flag
                 * and try again.  If we succeed, it either means that
                 * somebody applied the fix from that URL, or other patches
                 * for that bug from
                 *
                 *      http://cerberus.sourcefire.com/~jeff/archives/patches/macosx/
                 *
                 * and are running a Darwin kernel with those fixes, or
                 * that Apple fixed the problem in some OS X release.
                 */
                u_int spoof_eth_src = 0;

                if (ioctl(p->fd, BIOCSHDRCMPLT, &spoof_eth_src) == -1) {
                        (void)snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                            "send: can't turn off BIOCSHDRCMPLT: %s",
                            pcap_strerror(errno));
                        return (PCAP_ERROR);
                }

                /*
                 * Now try the write again.
                 */
                ret = write(p->fd, buf, size);
        }
#endif /* __APPLE__ */
        if (ret == -1) {
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "send: %s",
                    pcap_strerror(errno));
                return (PCAP_ERROR);
        }
        return (ret);
}

#ifdef _AIX
static int
bpf_odminit(char *errbuf)
{
        char *errstr;

        if (odm_initialize() == -1) {
                if (odm_err_msg(odmerrno, &errstr) == -1)
                        errstr = "Unknown error";
                snprintf(errbuf, PCAP_ERRBUF_SIZE,
                    "bpf_load: odm_initialize failed: %s",
                    errstr);
                return (PCAP_ERROR);
        }

        if ((odmlockid = odm_lock("/etc/objrepos/config_lock", ODM_WAIT)) == -1) {
                if (odm_err_msg(odmerrno, &errstr) == -1)
                        errstr = "Unknown error";
                snprintf(errbuf, PCAP_ERRBUF_SIZE,
                    "bpf_load: odm_lock of /etc/objrepos/config_lock failed: %s",
                    errstr);
                return (PCAP_ERROR);
        }

        return (0);
}

static int
bpf_odmcleanup(char *errbuf)
{
        char *errstr;

        if (odm_unlock(odmlockid) == -1) {
                if (odm_err_msg(odmerrno, &errstr) == -1)
                        errstr = "Unknown error";
                snprintf(errbuf, PCAP_ERRBUF_SIZE,
                    "bpf_load: odm_unlock failed: %s",
                    errstr);
                return (PCAP_ERROR);
        }

        if (odm_terminate() == -1) {
                if (odm_err_msg(odmerrno, &errstr) == -1)
                        errstr = "Unknown error";
                snprintf(errbuf, PCAP_ERRBUF_SIZE,
                    "bpf_load: odm_terminate failed: %s",
                    errstr);
                return (PCAP_ERROR);
        }

        return (0);
}

static int
bpf_load(char *errbuf)
{
        long major;
        int *minors;
        int numminors, i, rc;
        char buf[1024];
        struct stat sbuf;
        struct bpf_config cfg_bpf;
        struct cfg_load cfg_ld;
        struct cfg_kmod cfg_km;

        /*
         * This is very very close to what happens in the real implementation
         * but I've fixed some (unlikely) bug situations.
         */
        if (bpfloadedflag)
                return (0);

        if (bpf_odminit(errbuf) == PCAP_ERROR)
                return (PCAP_ERROR);

        major = genmajor(BPF_NAME);
        if (major == -1) {
                snprintf(errbuf, PCAP_ERRBUF_SIZE,
                    "bpf_load: genmajor failed: %s", pcap_strerror(errno));
                return (PCAP_ERROR);
        }

        minors = getminor(major, &numminors, BPF_NAME);
        if (!minors) {
                minors = genminor("bpf", major, 0, BPF_MINORS, 1, 1);
                if (!minors) {
                        snprintf(errbuf, PCAP_ERRBUF_SIZE,
                            "bpf_load: genminor failed: %s",
                            pcap_strerror(errno));
                        return (PCAP_ERROR);
                }
        }

        if (bpf_odmcleanup(errbuf) == PCAP_ERROR)
                return (PCAP_ERROR);

        rc = stat(BPF_NODE "0", &sbuf);
        if (rc == -1 && errno != ENOENT) {
                snprintf(errbuf, PCAP_ERRBUF_SIZE,
                    "bpf_load: can't stat %s: %s",
                    BPF_NODE "0", pcap_strerror(errno));
                return (PCAP_ERROR);
        }

        if (rc == -1 || getmajor(sbuf.st_rdev) != major) {
                for (i = 0; i < BPF_MINORS; i++) {
                        sprintf(buf, "%s%d", BPF_NODE, i);
                        unlink(buf);
                        if (mknod(buf, S_IRUSR | S_IFCHR, domakedev(major, i)) == -1) {
                                snprintf(errbuf, PCAP_ERRBUF_SIZE,
                                    "bpf_load: can't mknod %s: %s",
                                    buf, pcap_strerror(errno));
                                return (PCAP_ERROR);
                        }
                }
        }

        /* Check if the driver is loaded */
        memset(&cfg_ld, 0x0, sizeof(cfg_ld));
        cfg_ld.path = buf;
        sprintf(cfg_ld.path, "%s/%s", DRIVER_PATH, BPF_NAME);
        if ((sysconfig(SYS_QUERYLOAD, (void *)&cfg_ld, sizeof(cfg_ld)) == -1) ||
            (cfg_ld.kmid == 0)) {
                /* Driver isn't loaded, load it now */
                if (sysconfig(SYS_SINGLELOAD, (void *)&cfg_ld, sizeof(cfg_ld)) == -1) {
                        snprintf(errbuf, PCAP_ERRBUF_SIZE,
                            "bpf_load: could not load driver: %s",
                            strerror(errno));
                        return (PCAP_ERROR);
                }
        }

        /* Configure the driver */
        cfg_km.cmd = CFG_INIT;
        cfg_km.kmid = cfg_ld.kmid;
        cfg_km.mdilen = sizeof(cfg_bpf);
        cfg_km.mdiptr = (void *)&cfg_bpf;
        for (i = 0; i < BPF_MINORS; i++) {
                cfg_bpf.devno = domakedev(major, i);
                if (sysconfig(SYS_CFGKMOD, (void *)&cfg_km, sizeof(cfg_km)) == -1) {
                        snprintf(errbuf, PCAP_ERRBUF_SIZE,
                            "bpf_load: could not configure driver: %s",
                            strerror(errno));
                        return (PCAP_ERROR);
                }
        }

        bpfloadedflag = 1;

        return (0);
}
#endif

/*
 * Turn off rfmon mode if necessary.
 */
static void
pcap_cleanup_bpf(pcap_t *p)
{
#ifdef HAVE_BSD_IEEE80211
        int sock;
        struct ifmediareq req;
        struct ifreq ifr;
#endif

        if (p->md.must_do_on_close != 0) {
                /*
                 * There's something we have to do when closing this
                 * pcap_t.
                 */
#ifdef HAVE_BSD_IEEE80211
                if (p->md.must_do_on_close & MUST_CLEAR_RFMON) {
                        /*
                         * We put the interface into rfmon mode;
                         * take it out of rfmon mode.
                         *
                         * XXX - if somebody else wants it in rfmon
                         * mode, this code cannot know that, so it'll take
                         * it out of rfmon mode.
                         */
                        sock = socket(AF_INET, SOCK_DGRAM, 0);
                        if (sock == -1) {
                                fprintf(stderr,
                                    "Can't restore interface flags (socket() failed: %s).\n"
                                    "Please adjust manually.\n",
                                    strerror(errno));
                        } else {
                                memset(&req, 0, sizeof(req));
                                strncpy(req.ifm_name, p->md.device,
                                    sizeof(req.ifm_name));
                                if (ioctl(sock, SIOCGIFMEDIA, &req) < 0) {
                                        fprintf(stderr,
                                            "Can't restore interface flags (SIOCGIFMEDIA failed: %s).\n"
                                            "Please adjust manually.\n",
                                            strerror(errno));
                                } else {
                                        if (req.ifm_current & IFM_IEEE80211_MONITOR) {
                                                /*
                                                 * Rfmon mode is currently on;
                                                 * turn it off.
                                                 */
                                                memset(&ifr, 0, sizeof(ifr));
                                                (void)strncpy(ifr.ifr_name,
                                                    p->md.device,
                                                    sizeof(ifr.ifr_name));
                                                ifr.ifr_media =
                                                    req.ifm_current & ~IFM_IEEE80211_MONITOR;
                                                if (ioctl(sock, SIOCSIFMEDIA,
                                                    &ifr) == -1) {
                                                        fprintf(stderr,
                                                            "Can't restore interface flags (SIOCSIFMEDIA failed: %s).\n"
                                                            "Please adjust manually.\n",
                                                            strerror(errno));
                                                }
                                        }
                                }
                                close(sock);
                        }
                }
#endif /* HAVE_BSD_IEEE80211 */

                /*
                 * Take this pcap out of the list of pcaps for which we
                 * have to take the interface out of some mode.
                 */
                pcap_remove_from_pcaps_to_close(p);
                p->md.must_do_on_close = 0;
        }

#ifdef HAVE_ZEROCOPY_BPF
        /*
         * In zero-copy mode, p->buffer is just a pointer into one of the two
         * memory-mapped buffers, so no need to free it.
         */
        if (p->md.zerocopy) {
                if (p->md.zbuf1 != MAP_FAILED && p->md.zbuf1 != NULL)
                        munmap(p->md.zbuf1, p->md.zbufsize);
                if (p->md.zbuf2 != MAP_FAILED && p->md.zbuf2 != NULL)
                        munmap(p->md.zbuf2, p->md.zbufsize);
        }
#endif
        if (p->md.device != NULL) {
                free(p->md.device);
                p->md.device = NULL;
        }
        pcap_cleanup_live_common(p);
}

static int
check_setif_failure(pcap_t *p, int error)
{
#ifdef __APPLE__
        int fd;
        struct ifreq ifr;
        int err;
#endif

        if (error == ENXIO) {
                /*
                 * No such device exists.
                 */
#ifdef __APPLE__
                if (p->opt.rfmon && strncmp(p->opt.source, "wlt", 3) == 0) {
                        /*
                         * Monitor mode was requested, and we're trying
                         * to open a "wltN" device.  Assume that this
                         * is 10.4 and that we were asked to open an
                         * "enN" device; if that device exists, return
                         * "monitor mode not supported on the device".
                         */
                        fd = socket(AF_INET, SOCK_DGRAM, 0);
                        if (fd != -1) {
                                strlcpy(ifr.ifr_name, "en",
                                    sizeof(ifr.ifr_name));
                                strlcat(ifr.ifr_name, p->opt.source + 3,
                                    sizeof(ifr.ifr_name));
                                if (ioctl(fd, SIOCGIFFLAGS, (char *)&ifr) < 0) {
                                        /*
                                         * We assume this failed because
                                         * the underlying device doesn't
                                         * exist.
                                         */
                                        err = PCAP_ERROR_NO_SUCH_DEVICE;
                                        strcpy(p->errbuf, "");
                                } else {
                                        /*
                                         * The underlying "enN" device
                                         * exists, but there's no
                                         * corresponding "wltN" device;
                                         * that means that the "enN"
                                         * device doesn't support
                                         * monitor mode, probably because
                                         * it's an Ethernet device rather
                                         * than a wireless device.
                                         */
                                        err = PCAP_ERROR_RFMON_NOTSUP;
                                }
                                close(fd);
                        } else {
                                /*
                                 * We can't find out whether there's
                                 * an underlying "enN" device, so
                                 * just report "no such device".
                                 */
                                err = PCAP_ERROR_NO_SUCH_DEVICE;
                                strcpy(p->errbuf, "");
                        }
                        return (err);
                }
#endif
                /*
                 * No such device.
                 */
                strcpy(p->errbuf, "");
                return (PCAP_ERROR_NO_SUCH_DEVICE);
        } else if (errno == ENETDOWN) {
                /*
                 * Return a "network down" indication, so that
                 * the application can report that rather than
                 * saying we had a mysterious failure and
                 * suggest that they report a problem to the
                 * libpcap developers.
                 */
                return (PCAP_ERROR_IFACE_NOT_UP);
        } else {
                /*
                 * Some other error; fill in the error string, and
                 * return PCAP_ERROR.
                 */
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCSETIF: %s: %s",
                    p->opt.source, pcap_strerror(errno));
                return (PCAP_ERROR);
        }
}

static int
pcap_activate_bpf(pcap_t *p)
{
        int status = 0;
        int fd;
        struct ifreq ifr;
        struct bpf_version bv;
#ifdef __APPLE__
        int sockfd;
        char *wltdev = NULL;
#endif
#ifdef BIOCGDLTLIST
        struct bpf_dltlist bdl;
#if defined(__APPLE__) || defined(HAVE_BSD_IEEE80211)
        int new_dlt;
#endif
#endif /* BIOCGDLTLIST */
#if defined(BIOCGHDRCMPLT) && defined(BIOCSHDRCMPLT)
        u_int spoof_eth_src = 1;
#endif
        u_int v;
        struct bpf_insn total_insn;
        struct bpf_program total_prog;
        struct utsname osinfo;
        int have_osinfo = 0;
#ifdef HAVE_ZEROCOPY_BPF
        struct bpf_zbuf bz;
        u_int bufmode, zbufmax;
#endif

        fd = bpf_open(p);
        if (fd < 0) {
                status = fd;
                goto bad;
        }

        p->fd = fd;

        if (ioctl(fd, BIOCVERSION, (caddr_t)&bv) < 0) {
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCVERSION: %s",
                    pcap_strerror(errno));
                status = PCAP_ERROR;
                goto bad;
        }
        if (bv.bv_major != BPF_MAJOR_VERSION ||
            bv.bv_minor < BPF_MINOR_VERSION) {
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                    "kernel bpf filter out of date");
                status = PCAP_ERROR;
                goto bad;
        }

        p->md.device = strdup(p->opt.source);
        if (p->md.device == NULL) {
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "strdup: %s",
                     pcap_strerror(errno));
                status = PCAP_ERROR;
                goto bad;
        }

        /*
         * Attempt to find out the version of the OS on which we're running.
         */
        if (uname(&osinfo) == 0)
                have_osinfo = 1;

#ifdef __APPLE__
        /*
         * See comment in pcap_can_set_rfmon_bpf() for an explanation
         * of why we check the version number.
         */
        if (p->opt.rfmon) {
                if (have_osinfo) {
                        /*
                         * We assume osinfo.sysname is "Darwin", because
                         * __APPLE__ is defined.  We just check the version.
                         */
                        if (osinfo.release[0] < '8' &&
                            osinfo.release[1] == '.') {
                                /*
                                 * 10.3 (Darwin 7.x) or earlier.
                                 */
                                status = PCAP_ERROR_RFMON_NOTSUP;
                                goto bad;
                        }
                        if (osinfo.release[0] == '8' &&
                            osinfo.release[1] == '.') {
                                /*
                                 * 10.4 (Darwin 8.x).  s/en/wlt/
                                 */
                                if (strncmp(p->opt.source, "en", 2) != 0) {
                                        /*
                                         * Not an enN device; check
                                         * whether the device even exists.
                                         */
                                        sockfd = socket(AF_INET, SOCK_DGRAM, 0);
                                        if (sockfd != -1) {
                                                strlcpy(ifr.ifr_name,
                                                    p->opt.source,
                                                    sizeof(ifr.ifr_name));
                                                if (ioctl(sockfd, SIOCGIFFLAGS,
                                                    (char *)&ifr) < 0) {
                                                        /*
                                                         * We assume this
                                                         * failed because
                                                         * the underlying
                                                         * device doesn't
                                                         * exist.
                                                         */
                                                        status = PCAP_ERROR_NO_SUCH_DEVICE;
                                                        strcpy(p->errbuf, "");
                                                } else
                                                        status = PCAP_ERROR_RFMON_NOTSUP;
                                                close(sockfd);
                                        } else {
                                                /*
                                                 * We can't find out whether
                                                 * the device exists, so just
                                                 * report "no such device".
                                                 */
                                                status = PCAP_ERROR_NO_SUCH_DEVICE;
                                                strcpy(p->errbuf, "");
                                        }
                                        goto bad;
                                }
                                wltdev = malloc(strlen(p->opt.source) + 2);
                                if (wltdev == NULL) {
                                        (void)snprintf(p->errbuf,
                                            PCAP_ERRBUF_SIZE, "malloc: %s",
                                            pcap_strerror(errno));
                                        status = PCAP_ERROR;
                                        goto bad;
                                }
                                strcpy(wltdev, "wlt");
                                strcat(wltdev, p->opt.source + 2);
                                free(p->opt.source);
                                p->opt.source = wltdev;
                        }
                        /*
                         * Everything else is 10.5 or later; for those,
                         * we just open the enN device, and set the DLT.
                         */
                }
        }
#endif /* __APPLE__ */
#ifdef HAVE_ZEROCOPY_BPF
        /*
         * If the BPF extension to set buffer mode is present, try setting
         * the mode to zero-copy.  If that fails, use regular buffering.  If
         * it succeeds but other setup fails, return an error to the user.
         */
        bufmode = BPF_BUFMODE_ZBUF;
        if (ioctl(fd, BIOCSETBUFMODE, (caddr_t)&bufmode) == 0) {
                /*
                 * We have zerocopy BPF; use it.
                 */
                p->md.zerocopy = 1;

                /*
                 * Set the cleanup and set/get nonblocking mode ops
                 * as appropriate for zero-copy mode.
                 */
                p->cleanup_op = pcap_cleanup_zbuf;
                p->setnonblock_op = pcap_setnonblock_zbuf;
                p->getnonblock_op = pcap_getnonblock_zbuf;

                /*
                 * How to pick a buffer size: first, query the maximum buffer
                 * size supported by zero-copy.  This also lets us quickly
                 * determine whether the kernel generally supports zero-copy.
                 * Then, if a buffer size was specified, use that, otherwise
                 * query the default buffer size, which reflects kernel
                 * policy for a desired default.  Round to the nearest page
                 * size.
                 */
                if (ioctl(fd, BIOCGETZMAX, (caddr_t)&zbufmax) < 0) {
                        snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCGETZMAX: %s",
                            pcap_strerror(errno));
                        goto bad;
                }

                if (p->opt.buffer_size != 0) {
                        /*
                         * A buffer size was explicitly specified; use it.
                         */
                        v = p->opt.buffer_size;
                } else {
                        if ((ioctl(fd, BIOCGBLEN, (caddr_t)&v) < 0) ||
                            v < 32768)
                                v = 32768;
                }
#ifndef roundup
#define roundup(x, y)   ((((x)+((y)-1))/(y))*(y))  /* to any y */
#endif
                p->md.zbufsize = roundup(v, getpagesize());
                if (p->md.zbufsize > zbufmax)
                        p->md.zbufsize = zbufmax;
                p->md.zbuf1 = mmap(NULL, p->md.zbufsize, PROT_READ | PROT_WRITE,
                    MAP_ANON, -1, 0);
                p->md.zbuf2 = mmap(NULL, p->md.zbufsize, PROT_READ | PROT_WRITE,
                    MAP_ANON, -1, 0);
                if (p->md.zbuf1 == MAP_FAILED || p->md.zbuf2 == MAP_FAILED) {
                        snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "mmap: %s",
                            pcap_strerror(errno));
                        goto bad;
                }
                bzero(&bz, sizeof(bz));
                bz.bz_bufa = p->md.zbuf1;
                bz.bz_bufb = p->md.zbuf2;
                bz.bz_buflen = p->md.zbufsize;
                if (ioctl(fd, BIOCSETZBUF, (caddr_t)&bz) < 0) {
                        snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCSETZBUF: %s",
                            pcap_strerror(errno));
                        goto bad;
                }
                (void)strncpy(ifr.ifr_name, p->opt.source, sizeof(ifr.ifr_name));
                if (ioctl(fd, BIOCSETIF, (caddr_t)&ifr) < 0) {
                        snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCSETIF: %s: %s",
                            p->opt.source, pcap_strerror(errno));
                        goto bad;
                }
                v = p->md.zbufsize - sizeof(struct bpf_zbuf_header);
        } else
#endif
        {
                /*
                 * We don't have zerocopy BPF.
                 * Set the buffer size.
                 */
                if (p->opt.buffer_size != 0) {
                        /*
                         * A buffer size was explicitly specified; use it.
                         */
                        if (ioctl(fd, BIOCSBLEN,
                            (caddr_t)&p->opt.buffer_size) < 0) {
                                snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                                    "BIOCSBLEN: %s: %s", p->opt.source,
                                    pcap_strerror(errno));
                                status = PCAP_ERROR;
                                goto bad;
                        }

                        /*
                         * Now bind to the device.
                         */
                        (void)strncpy(ifr.ifr_name, p->opt.source,
                            sizeof(ifr.ifr_name));
                        if (ioctl(fd, BIOCSETIF, (caddr_t)&ifr) < 0) {
                                status = check_setif_failure(p, errno);
                                goto bad;
                        }
                } else {
                        /*
                         * No buffer size was explicitly specified.
                         *
                         * Try finding a good size for the buffer; 32768 may
                         * be too big, so keep cutting it in half until we
                         * find a size that works, or run out of sizes to try.
                         * If the default is larger, don't make it smaller.
                         */
                        if ((ioctl(fd, BIOCGBLEN, (caddr_t)&v) < 0) ||
                            v < 32768)
                                v = 32768;
                        for ( ; v != 0; v >>= 1) {
                                /*
                                 * Ignore the return value - this is because the
                                 * call fails on BPF systems that don't have
                                 * kernel malloc.  And if the call fails, it's
                                 * no big deal, we just continue to use the
                                 * standard buffer size.
                                 */
                                (void) ioctl(fd, BIOCSBLEN, (caddr_t)&v);

                                (void)strncpy(ifr.ifr_name, p->opt.source,
                                    sizeof(ifr.ifr_name));
                                if (ioctl(fd, BIOCSETIF, (caddr_t)&ifr) >= 0)
                                        break;  /* that size worked; we're done */

                                if (errno != ENOBUFS) {
                                        status = check_setif_failure(p, errno);
                                        goto bad;
                                }
                        }

                        if (v == 0) {
                                snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                                    "BIOCSBLEN: %s: No buffer size worked",
                                    p->opt.source);
                                status = PCAP_ERROR;
                                goto bad;
                        }
                }
        }

        /* Get the data link layer type. */
        if (ioctl(fd, BIOCGDLT, (caddr_t)&v) < 0) {
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCGDLT: %s",
                    pcap_strerror(errno));
                status = PCAP_ERROR;
                goto bad;
        }

#ifdef _AIX
        /*
         * AIX's BPF returns IFF_ types, not DLT_ types, in BIOCGDLT.
         */
        switch (v) {

        case IFT_ETHER:
        case IFT_ISO88023:
                v = DLT_EN10MB;
                break;

        case IFT_FDDI:
                v = DLT_FDDI;
                break;

        case IFT_ISO88025:
                v = DLT_IEEE802;
                break;

        case IFT_LOOP:
                v = DLT_NULL;
                break;

        default:
                /*
                 * We don't know what to map this to yet.
                 */
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "unknown interface type %u",
                    v);
                status = PCAP_ERROR;
                goto bad;
        }
#endif
#if _BSDI_VERSION - 0 >= 199510
        /* The SLIP and PPP link layer header changed in BSD/OS 2.1 */
        switch (v) {

        case DLT_SLIP:
                v = DLT_SLIP_BSDOS;
                break;

        case DLT_PPP:
                v = DLT_PPP_BSDOS;
                break;

        case 11:        /*DLT_FR*/
                v = DLT_FRELAY;
                break;

        case 12:        /*DLT_C_HDLC*/
                v = DLT_CHDLC;
                break;
        }
#endif

#ifdef BIOCGDLTLIST
        /*
         * We know the default link type -- now determine all the DLTs
         * this interface supports.  If this fails with EINVAL, it's
         * not fatal; we just don't get to use the feature later.
         */
        if (get_dlt_list(fd, v, &bdl, p->errbuf) == -1) {
                status = PCAP_ERROR;
                goto bad;
        }
        p->dlt_count = bdl.bfl_len;
        p->dlt_list = bdl.bfl_list;

#ifdef __APPLE__
        /*
         * Monitor mode fun, continued.
         *
         * For 10.5 and, we're assuming, later releases, as noted above,
         * 802.1 adapters that support monitor mode offer both DLT_EN10MB,
         * DLT_IEEE802_11, and possibly some 802.11-plus-radio-information
         * DLT_ value.  Choosing one of the 802.11 DLT_ values will turn
         * monitor mode on.
         *
         * Therefore, if the user asked for monitor mode, we filter out
         * the DLT_EN10MB value, as you can't get that in monitor mode,
         * and, if the user didn't ask for monitor mode, we filter out
         * the 802.11 DLT_ values, because selecting those will turn
         * monitor mode on.  Then, for monitor mode, if an 802.11-plus-
         * radio DLT_ value is offered, we try to select that, otherwise
         * we try to select DLT_IEEE802_11.
         */
        if (have_osinfo) {
                if (isdigit((unsigned)osinfo.release[0]) &&
                     (osinfo.release[0] == '9' ||
                     isdigit((unsigned)osinfo.release[1]))) {
                        /*
                         * 10.5 (Darwin 9.x), or later.
                         */
                        new_dlt = find_802_11(&bdl);
                        if (new_dlt != -1) {
                                /*
                                 * We have at least one 802.11 DLT_ value,
                                 * so this is an 802.11 interface.
                                 * new_dlt is the best of the 802.11
                                 * DLT_ values in the list.
                                 */
                                if (p->opt.rfmon) {
                                        /*
                                         * Our caller wants monitor mode.
                                         * Purge DLT_EN10MB from the list
                                         * of link-layer types, as selecting
                                         * it will keep monitor mode off.
                                         */
                                        remove_en(p);

                                        /*
                                         * If the new mode we want isn't
                                         * the default mode, attempt to
                                         * select the new mode.
                                         */
                                        if (new_dlt != v) {
                                                if (ioctl(p->fd, BIOCSDLT,
                                                    &new_dlt) != -1) {
                                                        /*
                                                         * We succeeded;
                                                         * make this the
                                                         * new DLT_ value.
                                                         */
                                                        v = new_dlt;
                                                }
                                        }
                                } else {
                                        /*
                                         * Our caller doesn't want
                                         * monitor mode.  Unless this
                                         * is being done by pcap_open_live(),
                                         * purge the 802.11 link-layer types
                                         * from the list, as selecting
                                         * one of them will turn monitor
                                         * mode on.
                                         */
                                        if (!p->oldstyle)
                                                remove_802_11(p);
                                }
                        } else {
                                if (p->opt.rfmon) {
                                        /*
                                         * The caller requested monitor
                                         * mode, but we have no 802.11
                                         * link-layer types, so they
                                         * can't have it.
                                         */
                                        status = PCAP_ERROR_RFMON_NOTSUP;
                                        goto bad;
                                }
                        }
                }
        }
#elif defined(HAVE_BSD_IEEE80211)
        /*
         * *BSD with the new 802.11 ioctls.
         * Do we want monitor mode?
         */
        if (p->opt.rfmon) {
                /*
                 * Try to put the interface into monitor mode.
                 */
                status = monitor_mode(p, 1);
                if (status != 0) {
                        /*
                         * We failed.
                         */
                        goto bad;
                }

                /*
                 * We're in monitor mode.
                 * Try to find the best 802.11 DLT_ value and, if we
                 * succeed, try to switch to that mode if we're not
                 * already in that mode.
                 */
                new_dlt = find_802_11(&bdl);
                if (new_dlt != -1) {
                        /*
                         * We have at least one 802.11 DLT_ value.
                         * new_dlt is the best of the 802.11
                         * DLT_ values in the list.
                         *
                         * If the new mode we want isn't the default mode,
                         * attempt to select the new mode.
                         */
                        if (new_dlt != v) {
                                if (ioctl(p->fd, BIOCSDLT, &new_dlt) != -1) {
                                        /*
                                         * We succeeded; make this the
                                         * new DLT_ value.
                                         */
                                        v = new_dlt;
                                }
                        }
                }
        }
#endif /* various platforms */
#endif /* BIOCGDLTLIST */

        /*
         * If this is an Ethernet device, and we don't have a DLT_ list,
         * give it a list with DLT_EN10MB and DLT_DOCSIS.  (That'd give
         * 802.11 interfaces DLT_DOCSIS, which isn't the right thing to
         * do, but there's not much we can do about that without finding
         * some other way of determining whether it's an Ethernet or 802.11
         * device.)
         */
        if (v == DLT_EN10MB && p->dlt_count == 0) {
                p->dlt_list = (u_int *) malloc(sizeof(u_int) * 2);
                /*
                 * If that fails, just leave the list empty.
                 */
                if (p->dlt_list != NULL) {
                        p->dlt_list[0] = DLT_EN10MB;
                        p->dlt_list[1] = DLT_DOCSIS;
                        p->dlt_count = 2;
                }
        }
#ifdef PCAP_FDDIPAD
        if (v == DLT_FDDI)
                p->fddipad = PCAP_FDDIPAD;
        else
                p->fddipad = 0;
#endif
        p->linktype = v;

#if defined(BIOCGHDRCMPLT) && defined(BIOCSHDRCMPLT)
        /*
         * Do a BIOCSHDRCMPLT, if defined, to turn that flag on, so
         * the link-layer source address isn't forcibly overwritten.
         * (Should we ignore errors?  Should we do this only if
         * we're open for writing?)
         *
         * XXX - I seem to remember some packet-sending bug in some
         * BSDs - check CVS log for "bpf.c"?
         */
        if (ioctl(fd, BIOCSHDRCMPLT, &spoof_eth_src) == -1) {
                (void)snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                    "BIOCSHDRCMPLT: %s", pcap_strerror(errno));
                status = PCAP_ERROR;
                goto bad;
        }
#endif
        /* set timeout */
#ifdef HAVE_ZEROCOPY_BPF
        if (p->md.timeout != 0 && !p->md.zerocopy) {
#else
        if (p->md.timeout) {
#endif
                /*
                 * XXX - is this seconds/nanoseconds in AIX?
                 * (Treating it as such doesn't fix the timeout
                 * problem described below.)
                 */
                struct timeval to;
                to.tv_sec = p->md.timeout / 1000;
                to.tv_usec = (p->md.timeout * 1000) % 1000000;
                if (ioctl(p->fd, BIOCSRTIMEOUT, (caddr_t)&to) < 0) {
                        snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCSRTIMEOUT: %s",
                            pcap_strerror(errno));
                        status = PCAP_ERROR;
                        goto bad;
                }
        }

#ifdef _AIX
#ifdef  BIOCIMMEDIATE
        /*
         * Darren Reed notes that
         *
         *      On AIX (4.2 at least), if BIOCIMMEDIATE is not set, the
         *      timeout appears to be ignored and it waits until the buffer
         *      is filled before returning.  The result of not having it
         *      set is almost worse than useless if your BPF filter
         *      is reducing things to only a few packets (i.e. one every
         *      second or so).
         *
         * so we turn BIOCIMMEDIATE mode on if this is AIX.
         *
         * We don't turn it on for other platforms, as that means we
         * get woken up for every packet, which may not be what we want;
         * in the Winter 1993 USENIX paper on BPF, they say:
         *
         *      Since a process might want to look at every packet on a
         *      network and the time between packets can be only a few
         *      microseconds, it is not possible to do a read system call
         *      per packet and BPF must collect the data from several
         *      packets and return it as a unit when the monitoring
         *      application does a read.
         *
         * which I infer is the reason for the timeout - it means we
         * wait that amount of time, in the hopes that more packets
         * will arrive and we'll get them all with one read.
         *
         * Setting BIOCIMMEDIATE mode on FreeBSD (and probably other
         * BSDs) causes the timeout to be ignored.
         *
         * On the other hand, some platforms (e.g., Linux) don't support
         * timeouts, they just hand stuff to you as soon as it arrives;
         * if that doesn't cause a problem on those platforms, it may
         * be OK to have BIOCIMMEDIATE mode on BSD as well.
         *
         * (Note, though, that applications may depend on the read
         * completing, even if no packets have arrived, when the timeout
         * expires, e.g. GUI applications that have to check for input
         * while waiting for packets to arrive; a non-zero timeout
         * prevents "select()" from working right on FreeBSD and
         * possibly other BSDs, as the timer doesn't start until a
         * "read()" is done, so the timer isn't in effect if the
         * application is blocked on a "select()", and the "select()"
         * doesn't get woken up for a BPF device until the buffer
         * fills up.)
         */
        v = 1;
        if (ioctl(p->fd, BIOCIMMEDIATE, &v) < 0) {
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCIMMEDIATE: %s",
                    pcap_strerror(errno));
                status = PCAP_ERROR;
                goto bad;
        }
#endif  /* BIOCIMMEDIATE */
#endif  /* _AIX */

        if (p->opt.promisc) {
                /* set promiscuous mode, just warn if it fails */
                if (ioctl(p->fd, BIOCPROMISC, NULL) < 0) {
                        snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCPROMISC: %s",
                            pcap_strerror(errno));
                        status = PCAP_WARNING_PROMISC_NOTSUP;
                }
        }

        if (ioctl(fd, BIOCGBLEN, (caddr_t)&v) < 0) {
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCGBLEN: %s",
                    pcap_strerror(errno));
                status = PCAP_ERROR;
                goto bad;
        }
        p->bufsize = v;
#ifdef HAVE_ZEROCOPY_BPF
        if (!p->md.zerocopy) {
#endif
        p->buffer = (u_char *)malloc(p->bufsize);
        if (p->buffer == NULL) {
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "malloc: %s",
                    pcap_strerror(errno));
                status = PCAP_ERROR;
                goto bad;
        }
#ifdef _AIX
        /* For some strange reason this seems to prevent the EFAULT
         * problems we have experienced from AIX BPF. */
        memset(p->buffer, 0x0, p->bufsize);
#endif
#ifdef HAVE_ZEROCOPY_BPF
        }
#endif

        /*
         * If there's no filter program installed, there's
         * no indication to the kernel of what the snapshot
         * length should be, so no snapshotting is done.
         *
         * Therefore, when we open the device, we install
         * an "accept everything" filter with the specified
         * snapshot length.
         */
        total_insn.code = (u_short)(BPF_RET | BPF_K);
        total_insn.jt = 0;
        total_insn.jf = 0;
        total_insn.k = p->snapshot;

        total_prog.bf_len = 1;
        total_prog.bf_insns = &total_insn;
        if (ioctl(p->fd, BIOCSETF, (caddr_t)&total_prog) < 0) {
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCSETF: %s",
                    pcap_strerror(errno));
                status = PCAP_ERROR;
                goto bad;
        }

        /*
         * On most BPF platforms, either you can do a "select()" or
         * "poll()" on a BPF file descriptor and it works correctly,
         * or you can do it and it will return "readable" if the
         * hold buffer is full but not if the timeout expires *and*
         * a non-blocking read will, if the hold buffer is empty
         * but the store buffer isn't empty, rotate the buffers
         * and return what packets are available.
         *
         * In the latter case, the fact that a non-blocking read
         * will give you the available packets means you can work
         * around the failure of "select()" and "poll()" to wake up
         * and return "readable" when the timeout expires by using
         * the timeout as the "select()" or "poll()" timeout, putting
         * the BPF descriptor into non-blocking mode, and read from
         * it regardless of whether "select()" reports it as readable
         * or not.
         *
         * However, in FreeBSD 4.3 and 4.4, "select()" and "poll()"
         * won't wake up and return "readable" if the timer expires
         * and non-blocking reads return EWOULDBLOCK if the hold
         * buffer is empty, even if the store buffer is non-empty.
         *
         * This means the workaround in question won't work.
         *
         * Therefore, on FreeBSD 4.3 and 4.4, we set "p->selectable_fd"
         * to -1, which means "sorry, you can't use 'select()' or 'poll()'
         * here".  On all other BPF platforms, we set it to the FD for
         * the BPF device; in NetBSD, OpenBSD, and Darwin, a non-blocking
         * read will, if the hold buffer is empty and the store buffer
         * isn't empty, rotate the buffers and return what packets are
         * there (and in sufficiently recent versions of OpenBSD
         * "select()" and "poll()" should work correctly).
         *
         * XXX - what about AIX?
         */
        p->selectable_fd = p->fd;       /* assume select() works until we know otherwise */
        if (have_osinfo) {
                /*
                 * We can check what OS this is.
                 */
                if (strcmp(osinfo.sysname, "FreeBSD") == 0) {
                        if (strncmp(osinfo.release, "4.3-", 4) == 0 ||
                             strncmp(osinfo.release, "4.4-", 4) == 0)
                                p->selectable_fd = -1;
                }
        }

        p->read_op = pcap_read_bpf;
        p->inject_op = pcap_inject_bpf;
        p->setfilter_op = pcap_setfilter_bpf;
        p->setdirection_op = pcap_setdirection_bpf;
        p->set_datalink_op = pcap_set_datalink_bpf;
        p->getnonblock_op = pcap_getnonblock_fd;
        p->setnonblock_op = pcap_setnonblock_fd;
        p->stats_op = pcap_stats_bpf;
        p->cleanup_op = pcap_cleanup_bpf;

        return (status);
 bad:
        pcap_cleanup_bpf(p);
        return (status);
}

int
pcap_platform_finddevs(pcap_if_t **alldevsp, char *errbuf)
{
#ifdef HAVE_DAG_API
        if (dag_platform_finddevs(alldevsp, errbuf) < 0)
                return (-1);
#endif /* HAVE_DAG_API */

        return (0);
}

#ifdef HAVE_BSD_IEEE80211
static int
monitor_mode(pcap_t *p, int set)
{
        int sock;
        struct ifmediareq req;
        int *media_list;
        int i;
        int can_do;
        struct ifreq ifr;

        sock = socket(AF_INET, SOCK_DGRAM, 0);
        if (sock == -1) {
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "can't open socket: %s",
                    pcap_strerror(errno));
                return (PCAP_ERROR);
        }

        memset(&req, 0, sizeof req);
        strncpy(req.ifm_name, p->opt.source, sizeof req.ifm_name);

        /*
         * Find out how many media types we have.
         */
        if (ioctl(sock, SIOCGIFMEDIA, &req) < 0) {
                /*
                 * Can't get the media types.
                 */
                if (errno == EINVAL) {
                        /*
                         * Interface doesn't support SIOC{G,S}IFMEDIA.
                         */
                        close(sock);
                        return (PCAP_ERROR_RFMON_NOTSUP);
                }
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "SIOCGIFMEDIA 1: %s",
                    pcap_strerror(errno));
                close(sock);
                return (PCAP_ERROR);
        }
        if (req.ifm_count == 0) {
                /*
                 * No media types.
                 */
                close(sock);
                return (PCAP_ERROR_RFMON_NOTSUP);
        }

        /*
         * Allocate a buffer to hold all the media types, and
         * get the media types.
         */
        media_list = malloc(req.ifm_count * sizeof(int));
        if (media_list == NULL) {
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "malloc: %s",
                    pcap_strerror(errno));
                close(sock);
                return (PCAP_ERROR);
        }
        req.ifm_ulist = media_list;
        if (ioctl(sock, SIOCGIFMEDIA, &req) < 0) {
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "SIOCGIFMEDIA: %s",
                    pcap_strerror(errno));
                free(media_list);
                close(sock);
                return (PCAP_ERROR);
        }

        /*
         * Look for an 802.11 "automatic" media type.
         * We assume that all 802.11 adapters have that media type,
         * and that it will carry the monitor mode supported flag.
         */
        can_do = 0;
        for (i = 0; i < req.ifm_count; i++) {
                if (IFM_TYPE(media_list[i]) == IFM_IEEE80211
                    && IFM_SUBTYPE(media_list[i]) == IFM_AUTO) {
                        /* OK, does it do monitor mode? */
                        if (media_list[i] & IFM_IEEE80211_MONITOR) {
                                can_do = 1;
                                break;
                        }
                }
        }
        free(media_list);
        if (!can_do) {
                /*
                 * This adapter doesn't support monitor mode.
                 */
                close(sock);
                return (PCAP_ERROR_RFMON_NOTSUP);
        }

        if (set) {
                /*
                 * Don't just check whether we can enable monitor mode,
                 * do so, if it's not already enabled.
                 */
                if ((req.ifm_current & IFM_IEEE80211_MONITOR) == 0) {
                        /*
                         * Monitor mode isn't currently on, so turn it on,
                         * and remember that we should turn it off when the
                         * pcap_t is closed.
                         */

                        /*
                         * If we haven't already done so, arrange to have
                         * "pcap_close_all()" called when we exit.
                         */
                        if (!pcap_do_addexit(p)) {
                                /*
                                 * "atexit()" failed; don't put the interface
                                 * in monitor mode, just give up.
                                 */
                                snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                                     "atexit failed");
                                close(sock);
                                return (PCAP_ERROR);
                        }
                        memset(&ifr, 0, sizeof(ifr));
                        (void)strncpy(ifr.ifr_name, p->opt.source,
                            sizeof(ifr.ifr_name));
                        ifr.ifr_media = req.ifm_current | IFM_IEEE80211_MONITOR;
                        if (ioctl(sock, SIOCSIFMEDIA, &ifr) == -1) {
                                snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                                     "SIOCSIFMEDIA: %s", pcap_strerror(errno));
                                close(sock);
                                return (PCAP_ERROR);
                        }

                        p->md.must_do_on_close |= MUST_CLEAR_RFMON;

                        /*
                         * Add this to the list of pcaps to close when we exit.
                         */
                        pcap_add_to_pcaps_to_close(p);
                }
        }
        return (0);
}
#endif /* HAVE_BSD_IEEE80211 */

#if defined(BIOCGDLTLIST) && (defined(__APPLE__) || defined(HAVE_BSD_IEEE80211))
/*
 * Check whether we have any 802.11 link-layer types; return the best
 * of the 802.11 link-layer types if we find one, and return -1
 * otherwise.
 *
 * DLT_IEEE802_11_RADIO, with the radiotap header, is considered the
 * best 802.11 link-layer type; any of the other 802.11-plus-radio
 * headers are second-best; 802.11 with no radio information is
 * the least good.
 */
static int
find_802_11(struct bpf_dltlist *bdlp)
{
        int new_dlt;
        int i;

        /*
         * Scan the list of DLT_ values, looking for 802.11 values,
         * and, if we find any, choose the best of them.
         */
        new_dlt = -1;
        for (i = 0; i < bdlp->bfl_len; i++) {
                switch (bdlp->bfl_list[i]) {

                case DLT_IEEE802_11:
                        /*
                         * 802.11, but no radio.
                         *
                         * Offer this, and select it as the new mode
                         * unless we've already found an 802.11
                         * header with radio information.
                         */
                        if (new_dlt == -1)
                                new_dlt = bdlp->bfl_list[i];
                        break;

                case DLT_PRISM_HEADER:
                case DLT_AIRONET_HEADER:
                case DLT_IEEE802_11_RADIO_AVS:
                        /*
                         * 802.11 with radio, but not radiotap.
                         *
                         * Offer this, and select it as the new mode
                         * unless we've already found the radiotap DLT_.
                         */
                        if (new_dlt != DLT_IEEE802_11_RADIO)
                                new_dlt = bdlp->bfl_list[i];
                        break;

                case DLT_IEEE802_11_RADIO:
                        /*
                         * 802.11 with radiotap.
                         *
                         * Offer this, and select it as the new mode.
                         */
                        new_dlt = bdlp->bfl_list[i];
                        break;

                default:
                        /*
                         * Not 802.11.
                         */
                        break;
                }
        }

        return (new_dlt);
}
#endif /* defined(BIOCGDLTLIST) && (defined(__APPLE__) || defined(HAVE_BSD_IEEE80211)) */

#if defined(__APPLE__) && defined(BIOCGDLTLIST)
/*
 * Remove DLT_EN10MB from the list of DLT_ values.
 */
static void
remove_en(pcap_t *p)
{
        int i, j;

        /*
         * Scan the list of DLT_ values and discard DLT_EN10MB.
         */
        j = 0;
        for (i = 0; i < p->dlt_count; i++) {
                switch (p->dlt_list[i]) {

                case DLT_EN10MB:
                        /*
                         * Don't offer this one.
                         */
                        continue;

                default:
                        /*
                         * Just copy this mode over.
                         */
                        break;
                }

                /*
                 * Copy this DLT_ value to its new position.
                 */
                p->dlt_list[j] = p->dlt_list[i];
                j++;
        }

        /*
         * Set the DLT_ count to the number of entries we copied.
         */
        p->dlt_count = j;
}

/*
 * Remove DLT_EN10MB from the list of DLT_ values, and look for the
 * best 802.11 link-layer type in that list and return it.
 * Radiotap is better than anything else; 802.11 with any other radio
 * header is better than 802.11 with no radio header.
 */
static void
remove_802_11(pcap_t *p)
{
        int i, j;

        /*
         * Scan the list of DLT_ values and discard 802.11 values.
         */
        j = 0;
        for (i = 0; i < p->dlt_count; i++) {
                switch (p->dlt_list[i]) {

                case DLT_IEEE802_11:
                case DLT_PRISM_HEADER:
                case DLT_AIRONET_HEADER:
                case DLT_IEEE802_11_RADIO:
                case DLT_IEEE802_11_RADIO_AVS:
                        /*
                         * 802.11.  Don't offer this one.
                         */
                        continue;

                default:
                        /*
                         * Just copy this mode over.
                         */
                        break;
                }

                /*
                 * Copy this DLT_ value to its new position.
                 */
                p->dlt_list[j] = p->dlt_list[i];
                j++;
        }

        /*
         * Set the DLT_ count to the number of entries we copied.
         */
        p->dlt_count = j;
}
#endif /* defined(__APPLE__) && defined(BIOCGDLTLIST) */

static int
pcap_setfilter_bpf(pcap_t *p, struct bpf_program *fp)
{
        /*
         * Free any user-mode filter we might happen to have installed.
         */
        pcap_freecode(&p->fcode);

        /*
         * Try to install the kernel filter.
         */
        if (ioctl(p->fd, BIOCSETF, (caddr_t)fp) == 0) {
                /*
                 * It worked.
                 */
                p->md.use_bpf = 1;      /* filtering in the kernel */

                /*
                 * Discard any previously-received packets, as they might
                 * have passed whatever filter was formerly in effect, but
                 * might not pass this filter (BIOCSETF discards packets
                 * buffered in the kernel, so you can lose packets in any
                 * case).
                 */
                p->cc = 0;
                return (0);
        }

        /*
         * We failed.
         *
         * If it failed with EINVAL, that's probably because the program
         * is invalid or too big.  Validate it ourselves; if we like it
         * (we currently allow backward branches, to support protochain),
         * run it in userland.  (There's no notion of "too big" for
         * userland.)
         *
         * Otherwise, just give up.
         * XXX - if the copy of the program into the kernel failed,
         * we will get EINVAL rather than, say, EFAULT on at least
         * some kernels.
         */
        if (errno != EINVAL) {
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCSETF: %s",
                    pcap_strerror(errno));
                return (-1);
        }

        /*
         * install_bpf_program() validates the program.
         *
         * XXX - what if we already have a filter in the kernel?
         */
        if (install_bpf_program(p, fp) < 0)
                return (-1);
        p->md.use_bpf = 0;      /* filtering in userland */
        return (0);
}

/*
 * Set direction flag: Which packets do we accept on a forwarding
 * single device? IN, OUT or both?
 */
static int
pcap_setdirection_bpf(pcap_t *p, pcap_direction_t d)
{
#if defined(BIOCSDIRECTION)
        u_int direction;

        direction = (d == PCAP_D_IN) ? BPF_D_IN :
            ((d == PCAP_D_OUT) ? BPF_D_OUT : BPF_D_INOUT);
        if (ioctl(p->fd, BIOCSDIRECTION, &direction) == -1) {
                (void) snprintf(p->errbuf, sizeof(p->errbuf),
                    "Cannot set direction to %s: %s",
                        (d == PCAP_D_IN) ? "PCAP_D_IN" :
                        ((d == PCAP_D_OUT) ? "PCAP_D_OUT" : "PCAP_D_INOUT"),
                        strerror(errno));
                return (-1);
        }
        return (0);
#elif defined(BIOCSSEESENT)
        u_int seesent;

        /*
         * We don't support PCAP_D_OUT.
         */
        if (d == PCAP_D_OUT) {
                snprintf(p->errbuf, sizeof(p->errbuf),
                    "Setting direction to PCAP_D_OUT is not supported on BPF");
                return -1;
        }

        seesent = (d == PCAP_D_INOUT);
        if (ioctl(p->fd, BIOCSSEESENT, &seesent) == -1) {
                (void) snprintf(p->errbuf, sizeof(p->errbuf),
                    "Cannot set direction to %s: %s",
                        (d == PCAP_D_INOUT) ? "PCAP_D_INOUT" : "PCAP_D_IN",
                        strerror(errno));
                return (-1);
        }
        return (0);
#else
        (void) snprintf(p->errbuf, sizeof(p->errbuf),
            "This system doesn't support BIOCSSEESENT, so the direction can't be set");
        return (-1);
#endif
}

static int
pcap_set_datalink_bpf(pcap_t *p, int dlt)
{
#ifdef BIOCSDLT
        if (ioctl(p->fd, BIOCSDLT, &dlt) == -1) {
                (void) snprintf(p->errbuf, sizeof(p->errbuf),
                    "Cannot set DLT %d: %s", dlt, strerror(errno));
                return (-1);
        }
#endif
        return (0);
}