Have a less nerdy error message for "output only isn't supported here".

[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.
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <sys/param.h>                  /* optionally get BSD define */
#include <sys/socket.h>
#include <time.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 macOS, 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>

#if defined(__FreeBSD__) && defined(SIOCIFCREATE2)
/*
 * Add support for capturing on FreeBSD usbusN interfaces.
 */
static const char usbus_prefix[] = "usbus";
#define USBUS_PREFIX_LEN        (sizeof(usbus_prefix) - 1)
#include <dirent.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

/*
 * If both BIOCROTZBUF and BPF_BUFMODE_ZBUF are defined, we have
 * zero-copy BPF.
 */
#if defined(BIOCROTZBUF) && defined(BPF_BUFMODE_ZBUF)
  #define HAVE_ZEROCOPY_BPF
  #include <sys/mman.h>
  #include <machine/atomic.h>
#endif

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

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

#include "pcap-int.h"

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

/*
 * Later versions of NetBSD stick padding in front of FDDI frames
 * to align the IP header on a 4-byte boundary.
 */
#if defined(__NetBSD__) && __NetBSD_Version__ > 106000000
#define       PCAP_FDDIPAD 3
#endif

/*
 * Private data for capturing on BPF devices.
 */
struct pcap_bpf {
#ifdef HAVE_ZEROCOPY_BPF
        /*
         * Zero-copy read buffer -- for zero-copy BPF.  'buffer' above will
         * alternative between these two actual mmap'd buffers as required.
         * As there is a header on the front size of the mmap'd buffer, only
         * some of the buffer is exposed to libpcap as a whole via bufsize;
         * zbufsize is the true size.  zbuffer tracks the current zbuf
         * assocated with buffer so that it can be used to decide which the
         * next buffer to read will be.
         */
        u_char *zbuf1, *zbuf2, *zbuffer;
        u_int zbufsize;
        u_int zerocopy;
        u_int interrupted;
        struct timespec firstsel;
        /*
         * If there's currently a buffer being actively processed, then it is
         * referenced here; 'buffer' is also pointed at it, but offset by the
         * size of the header.
         */
        struct bpf_zbuf_header *bzh;
        int nonblock;           /* true if in nonblocking mode */
#endif /* HAVE_ZEROCOPY_BPF */

        char *device;           /* device name */
        int filtering_in_kernel; /* using kernel filter */
        int must_do_on_close;   /* stuff we must do when we close */
};

/*
 * Stuff to do when we close.
 */
#define MUST_CLEAR_RFMON        0x00000001      /* clear rfmon (monitor) mode */
#define MUST_DESTROY_USBUS      0x00000002      /* destroy usbusN interface */

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

/*
 * The ifm_ulist member of a struct ifmediareq is an int * on most systems,
 * but it's a uint64_t on newer versions of OpenBSD.
 *
 * We check this by checking whether IFM_GMASK is defined and > 2^32-1.
 */
#  if defined(IFM_GMASK) && IFM_GMASK > 0xFFFFFFFF
#    define IFM_ULIST_TYPE      uint64_t
#  else
#    define IFM_ULIST_TYPE      int
#  endif
# 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_non_802_11(pcap_t *);
static void remove_802_11(pcap_t *);
#  endif

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

#endif /* BIOCGDLTLIST */

#if defined(sun) && defined(LIFNAMSIZ) && defined(lifr_zoneid)
#include <zone.h>
#endif

/*
 * 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

/*
 * In some versions of macOS, we might not even get any of the
 * 802.11-plus-radio-header DLT_'s defined, even though some
 * of them are used by various Airport drivers in those versions.
 */
#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);

/*
 * For zerocopy bpf, the setnonblock/getnonblock routines need to modify
 * pb->nonblock so we don't call select(2) if the pcap handle is in non-
 * blocking mode.
 */
static int
pcap_getnonblock_bpf(pcap_t *p)
{
#ifdef HAVE_ZEROCOPY_BPF
        struct pcap_bpf *pb = p->priv;

        if (pb->zerocopy)
                return (pb->nonblock);
#endif
        return (pcap_getnonblock_fd(p));
}

static int
pcap_setnonblock_bpf(pcap_t *p, int nonblock)
{
#ifdef HAVE_ZEROCOPY_BPF
        struct pcap_bpf *pb = p->priv;

        if (pb->zerocopy) {
                pb->nonblock = nonblock;
                return (0);
        }
#endif
        return (pcap_setnonblock_fd(p, nonblock));
}

#ifdef HAVE_ZEROCOPY_BPF
/*
 * 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 pcap_bpf *pb = p->priv;
        struct bpf_zbuf_header *bzh;

        if (pb->zbuffer == pb->zbuf2 || pb->zbuffer == NULL) {
                bzh = (struct bpf_zbuf_header *)pb->zbuf1;
                if (bzh->bzh_user_gen !=
                    atomic_load_acq_int(&bzh->bzh_kernel_gen)) {
                        pb->bzh = bzh;
                        pb->zbuffer = (u_char *)pb->zbuf1;
                        p->buffer = pb->zbuffer + sizeof(*bzh);
                        *cc = bzh->bzh_kernel_len;
                        return (1);
                }
        } else if (pb->zbuffer == pb->zbuf1) {
                bzh = (struct bpf_zbuf_header *)pb->zbuf2;
                if (bzh->bzh_user_gen !=
                    atomic_load_acq_int(&bzh->bzh_kernel_gen)) {
                        pb->bzh = bzh;
                        pb->zbuffer = (u_char *)pb->zbuf2;
                        p->buffer = pb->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 pcap_bpf *pb = p->priv;
        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->opt.timeout;
        if (tmout)
                (void) clock_gettime(CLOCK_MONOTONIC, &cur);
        if (pb->interrupted && p->opt.timeout) {
                expire = TSTOMILLI(&pb->firstsel) + p->opt.timeout;
                tmout = expire - TSTOMILLI(&cur);
#undef TSTOMILLI
                if (tmout <= 0) {
                        pb->interrupted = 0;
                        data = pcap_next_zbuf_shm(p, cc);
                        if (data)
                                return (data);
                        if (ioctl(p->fd, BIOCROTZBUF, &bz) < 0) {
                                pcap_fmt_errmsg_for_errno(p->errbuf,
                                    PCAP_ERRBUF_SIZE, errno, "BIOCROTZBUF");
                                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 (!pb->nonblock) {
                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->opt.timeout != 0 ? &tv : NULL);
                if (r < 0 && errno == EINTR) {
                        if (!pb->interrupted && p->opt.timeout) {
                                pb->interrupted = 1;
                                pb->firstsel = cur;
                        }
                        return (0);
                } else if (r < 0) {
                        pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                            errno, "select");
                        return (PCAP_ERROR);
                }
        }
        pb->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) {
                pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                    errno, "BIOCROTZBUF");
                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)
{
        struct pcap_bpf *pb = p->priv;

        atomic_store_rel_int(&pb->bzh->bzh_user_gen,
            pb->bzh->bzh_kernel_gen);
        pb->bzh = NULL;
        p->buffer = NULL;
        return (0);
}
#endif /* HAVE_ZEROCOPY_BPF */

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

        p = pcap_create_common(ebuf, sizeof (struct pcap_bpf));
        if (p == NULL)
                return (NULL);

        p->activate_op = pcap_activate_bpf;
        p->can_set_rfmon_op = pcap_can_set_rfmon_bpf;
#ifdef BIOCSTSTAMP
        /*
         * We claim that we support microsecond and nanosecond time
         * stamps.
         */
        p->tstamp_precision_count = 2;
        p->tstamp_precision_list = malloc(2 * sizeof(u_int));
        if (p->tstamp_precision_list == NULL) {
                pcap_fmt_errmsg_for_errno(ebuf, PCAP_ERRBUF_SIZE, errno,
                    "malloc");
                free(p);
                return (NULL);
        }
        p->tstamp_precision_list[0] = PCAP_TSTAMP_PRECISION_MICRO;
        p->tstamp_precision_list[1] = PCAP_TSTAMP_PRECISION_NANO;
#endif /* BIOCSTSTAMP */
        return (p);
}

/*
 * On success, returns a file descriptor for a BPF device.
 * On failure, returns a PCAP_ERROR_ value, and sets p->errbuf.
 */
static int
bpf_open(char *errbuf)
{
        int fd = -1;
        static const char cloning_device[] = "/dev/bpf";
        int n = 0;
        char device[sizeof "/dev/bpf0000000000"];
        static int no_cloning_bpf = 0;

#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(errbuf) == PCAP_ERROR)
                return (PCAP_ERROR);
#endif

        /*
         * First, unless we've already tried opening /dev/bpf and
         * gotten ENOENT, try opening /dev/bpf.
         * If it fails with ENOENT, remember that, so we don't try
         * again, and try /dev/bpfN.
         */
        if (!no_cloning_bpf &&
            (fd = open(cloning_device, O_RDWR)) == -1 &&
            ((errno != EACCES && errno != ENOENT) ||
             (fd = open(cloning_device, O_RDONLY)) == -1)) {
                if (errno != ENOENT) {
                        if (errno == EACCES)
                                fd = PCAP_ERROR_PERM_DENIED;
                        else
                                fd = PCAP_ERROR;
                        pcap_fmt_errmsg_for_errno(errbuf, PCAP_ERRBUF_SIZE,
                            errno, "(cannot open device) %s", cloning_device);
                        return (fd);
                }
                no_cloning_bpf = 1;
        }

        if (no_cloning_bpf) {
                /*
                 * We don't have /dev/bpf.
                 * Go through all the /dev/bpfN 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) {
                switch (errno) {

                case ENOENT:
                        fd = PCAP_ERROR;
                        if (n == 1) {
                                /*
                                 * /dev/bpf0 doesn't exist, which
                                 * means we probably have no BPF
                                 * devices.
                                 */
                                snprintf(errbuf, PCAP_ERRBUF_SIZE,
                                    "(there are no BPF devices)");
                        } else {
                                /*
                                 * We got EBUSY on at least one
                                 * BPF device, so we have BPF
                                 * devices, but all the ones
                                 * that exist are busy.
                                 */
                                snprintf(errbuf, PCAP_ERRBUF_SIZE,
                                    "(all BPF devices are busy)");
                        }
                        break;

                case EACCES:
                        /*
                         * Got EACCES on the last device we tried,
                         * and EBUSY on all devices before that,
                         * if any.
                         */
                        fd = PCAP_ERROR_PERM_DENIED;
                        pcap_fmt_errmsg_for_errno(errbuf, PCAP_ERRBUF_SIZE,
                            errno, "(cannot open BPF device) %s", device);
                        break;

                default:
                        /*
                         * Some other problem.
                         */
                        fd = PCAP_ERROR;
                        pcap_fmt_errmsg_for_errno(errbuf, PCAP_ERRBUF_SIZE,
                            errno, "(cannot open BPF device) %s", device);
                        break;
                }
        }

        return (fd);
}

/*
 * Open and bind to a device; used if we're not actually going to use
 * the device, but are just testing whether it can be opened, or opening
 * it to get information about it.
 *
 * Returns an error code on failure (always negative), and an FD for
 * the now-bound BPF device on success (always non-negative).
 */
static int
bpf_open_and_bind(const char *name, char *errbuf)
{
        int fd;
        struct ifreq ifr;

        /*
         * First, open a BPF device.
         */
        fd = bpf_open(errbuf);
        if (fd < 0)
                return (fd);    /* fd is the appropriate error code */

        /*
         * Now bind to the device.
         */
        (void)strncpy(ifr.ifr_name, name, sizeof(ifr.ifr_name));
        if (ioctl(fd, BIOCSETIF, (caddr_t)&ifr) < 0) {
                switch (errno) {

                case ENXIO:
                        /*
                         * There's no such device.
                         */
                        close(fd);
                        return (PCAP_ERROR_NO_SUCH_DEVICE);

                case 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);

                default:
                        pcap_fmt_errmsg_for_errno(errbuf, PCAP_ERRBUF_SIZE,
                            errno, "BIOCSETIF: %s", name);
                        close(fd);
                        return (PCAP_ERROR);
                }
        }

        /*
         * Success.
         */
        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) {
                        pcap_fmt_errmsg_for_errno(ebuf, PCAP_ERRBUF_SIZE,
                            errno, "malloc");
                        return (PCAP_ERROR);
                }

                if (ioctl(fd, BIOCGDLTLIST, (caddr_t)bdlp) < 0) {
                        pcap_fmt_errmsg_for_errno(ebuf, PCAP_ERRBUF_SIZE,
                            errno, "BIOCGDLTLIST");
                        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).
                 *
                 * On Solaris with BPF, Ethernet devices also offer
                 * DLT_IPNET, so we, if DLT_IPNET is defined, we don't
                 * treat it as an indication that the device isn't an
                 * Ethernet.
                 */
                if (v == DLT_EN10MB) {
                        is_ethernet = 1;
                        for (i = 0; i < bdlp->bfl_len; i++) {
                                if (bdlp->bfl_list[i] != DLT_EN10MB
#ifdef DLT_IPNET
                                    && bdlp->bfl_list[i] != DLT_IPNET
#endif
                                    ) {
                                        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) {
                        pcap_fmt_errmsg_for_errno(ebuf, PCAP_ERRBUF_SIZE,
                            errno, "BIOCGDLTLIST");
                        return (PCAP_ERROR);
                }
        }
        return (0);
}
#endif

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

        /*
         * The joys of monitor mode on Mac OS X/OS X/macOS.
         *
         * 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.device, "en", 2) != 0) {
                        /*
                         * Not an enN device; no monitor mode.
                         */
                        return (0);
                }
                fd = socket(AF_INET, SOCK_DGRAM, 0);
                if (fd == -1) {
                        pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                            errno, "socket");
                        return (PCAP_ERROR);
                }
                pcap_strlcpy(ifr.ifr_name, "wlt", sizeof(ifr.ifr_name));
                pcap_strlcat(ifr.ifr_name, p->opt.device + 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->errbuf);
        if (fd < 0)
                return (fd);    /* fd is the appropriate error code */

        /*
         * Now bind to the device.
         */
        (void)strncpy(ifr.ifr_name, p->opt.device, sizeof(ifr.ifr_name));
        if (ioctl(fd, BIOCSETIF, (caddr_t)&ifr) < 0) {
                switch (errno) {

                case ENXIO:
                        /*
                         * There's no such device.
                         */
                        close(fd);
                        return (PCAP_ERROR_NO_SUCH_DEVICE);

                case 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);

                default:
                        pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                            errno, "BIOCSETIF: %s", p->opt.device);
                        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);
        close(fd);
#endif /* BIOCGDLTLIST */
        return (0);
}
#elif defined(HAVE_BSD_IEEE80211)
static int
pcap_can_set_rfmon_bpf(pcap_t *p)
{
        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
static int
pcap_can_set_rfmon_bpf(pcap_t *p _U_)
{
        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) {
                pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                    errno, "BIOCGSTATS");
                return (PCAP_ERROR);
        }

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

static int
pcap_read_bpf(pcap_t *p, int cnt, pcap_handler callback, u_char *user)
{
        struct pcap_bpf *pb = p->priv;
        int cc;
        int n = 0;
        register u_char *bp, *ep;
        u_char *datap;
#ifdef PCAP_FDDIPAD
        register u_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 (pb->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 = (int)read(p->fd, 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);

                        case ENXIO:     /* FreeBSD, DragonFly BSD, and Darwin */
                        case EIO:       /* OpenBSD */
                                        /* NetBSD appears not to return an error in this case */
                                /*
                                 * The device on which we're capturing
                                 * went away.
                                 *
                                 * XXX - we should really return
                                 * an appropriate error for that,
                                 * but pcap_dispatch() etc. aren't
                                 * documented as having error returns
                                 * other than PCAP_ERROR or PCAP_ERROR_BREAK.
                                 */
                                snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                                    "The interface disappeared");
                                return (PCAP_ERROR);

#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
                        }
                        pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                            errno, "read");
                        return (PCAP_ERROR);
                }
                bp = (u_char *)p->buffer;
        } else
                bp = p->bp;

        /*
         * Loop through each packet.
         */
#ifdef BIOCSTSTAMP
#define bhp ((struct bpf_xhdr *)bp)
#else
#define bhp ((struct bpf_hdr *)bp)
#endif
        ep = bp + cc;
#ifdef PCAP_FDDIPAD
        pad = p->fddipad;
#endif
        while (bp < ep) {
                register u_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) {
                        p->bp = bp;
                        p->cc = (int)(ep - bp);
                        /*
                         * ep is set based on the return value of read(),
                         * but read() from a BPF device doesn't necessarily
                         * return a value that's a multiple of the alignment
                         * value for BPF_WORDALIGN().  However, whenever we
                         * increment bp, we round up the increment value by
                         * a value rounded up by BPF_WORDALIGN(), so we
                         * could increment bp past ep after processing the
                         * last packet in the buffer.
                         *
                         * We treat ep < bp as an indication that this
                         * happened, and just set p->cc to 0.
                         */
                        if (p->cc < 0)
                                p->cc = 0;
                        if (n == 0) {
                                p->break_loop = 0;
                                return (PCAP_ERROR_BREAK);
                        } else
                                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 (pb->filtering_in_kernel ||
                    pcap_filter(p->fcode.bf_insns, datap, bhp->bh_datalen, caplen)) {
                        struct pcap_pkthdr pkthdr;
#ifdef BIOCSTSTAMP
                        struct bintime bt;

                        bt.sec = bhp->bh_tstamp.bt_sec;
                        bt.frac = bhp->bh_tstamp.bt_frac;
                        if (p->opt.tstamp_precision == PCAP_TSTAMP_PRECISION_NANO) {
                                struct timespec ts;

                                bintime2timespec(&bt, &ts);
                                pkthdr.ts.tv_sec = ts.tv_sec;
                                pkthdr.ts.tv_usec = ts.tv_nsec;
                        } else {
                                struct timeval tv;

                                bintime2timeval(&bt, &tv);
                                pkthdr.ts.tv_sec = tv.tv_sec;
                                pkthdr.ts.tv_usec = tv.tv_usec;
                        }
#else
                        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
#endif /* BIOCSTSTAMP */
#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 && !PACKET_COUNT_IS_UNLIMITED(cnt)) {
                                p->bp = bp;
                                p->cc = (int)(ep - bp);
                                /*
                                 * See comment above about p->cc < 0.
                                 */
                                if (p->cc < 0)
                                        p->cc = 0;
                                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, int size)
{
        int ret;

        ret = (int)write(p->fd, buf, size);
#ifdef __APPLE__
        if (ret == -1 && errno == EAFNOSUPPORT) {
                /*
                 * In some versions of macOS, 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 macOS, 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 macOS release.
                 */
                u_int spoof_eth_src = 0;

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

                /*
                 * Now try the write again.
                 */
                ret = (int)write(p->fd, buf, size);
        }
#endif /* __APPLE__ */
        if (ret == -1) {
                pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                    errno, "send");
                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);
                (void)odm_terminate();
                return (PCAP_ERROR);
        }

        return (0);
}

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

        if (odm_unlock(odmlockid) == -1) {
                if (errbuf != NULL) {
                        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 (errbuf != NULL) {
                        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) {
                pcap_fmt_errmsg_for_errno(errbuf, PCAP_ERRBUF_SIZE,
                    errno, "bpf_load: genmajor failed");
                (void)bpf_odmcleanup(NULL);
                return (PCAP_ERROR);
        }

        minors = getminor(major, &numminors, BPF_NAME);
        if (!minors) {
                minors = genminor("bpf", major, 0, BPF_MINORS, 1, 1);
                if (!minors) {
                        pcap_fmt_errmsg_for_errno(errbuf, PCAP_ERRBUF_SIZE,
                            errno, "bpf_load: genminor failed");
                        (void)bpf_odmcleanup(NULL);
                        return (PCAP_ERROR);
                }
        }

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

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

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

        /* Check if the driver is loaded */
        memset(&cfg_ld, 0x0, sizeof(cfg_ld));
        snprintf(buf, sizeof(buf), "%s/%s", DRIVER_PATH, BPF_NAME);
        cfg_ld.path = buf;
        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) {
                        pcap_fmt_errmsg_for_errno(errbuf, PCAP_ERRBUF_SIZE,
                            errno, "bpf_load: could not load driver");
                        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) {
                        pcap_fmt_errmsg_for_errno(errbuf, PCAP_ERRBUF_SIZE,
                            errno, "bpf_load: could not configure driver");
                        return (PCAP_ERROR);
                }
        }

        bpfloadedflag = 1;

        return (0);
}
#endif

/*
 * Undo any operations done when opening the device when necessary.
 */
static void
pcap_cleanup_bpf(pcap_t *p)
{
        struct pcap_bpf *pb = p->priv;
#ifdef HAVE_BSD_IEEE80211
        int sock;
        struct ifmediareq req;
        struct ifreq ifr;
#endif

        if (pb->must_do_on_close != 0) {
                /*
                 * There's something we have to do when closing this
                 * pcap_t.
                 */
#ifdef HAVE_BSD_IEEE80211
                if (pb->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, pb->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,
                                                    pb->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 */

#if defined(__FreeBSD__) && defined(SIOCIFCREATE2)
                /*
                 * Attempt to destroy the usbusN interface that we created.
                 */
                if (pb->must_do_on_close & MUST_DESTROY_USBUS) {
                        if (if_nametoindex(pb->device) > 0) {
                                int s;

                                s = socket(AF_LOCAL, SOCK_DGRAM, 0);
                                if (s >= 0) {
                                        pcap_strlcpy(ifr.ifr_name, pb->device,
                                            sizeof(ifr.ifr_name));
                                        ioctl(s, SIOCIFDESTROY, &ifr);
                                        close(s);
                                }
                        }
                }
#endif /* defined(__FreeBSD__) && defined(SIOCIFCREATE2) */
                /*
                 * 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);
                pb->must_do_on_close = 0;
        }

#ifdef HAVE_ZEROCOPY_BPF
        if (pb->zerocopy) {
                /*
                 * 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 (pb->zbuf1 != MAP_FAILED && pb->zbuf1 != NULL)
                        (void) munmap(pb->zbuf1, pb->zbufsize);
                if (pb->zbuf2 != MAP_FAILED && pb->zbuf2 != NULL)
                        (void) munmap(pb->zbuf2, pb->zbufsize);
                p->buffer = NULL;
        }
#endif
        if (pb->device != NULL) {
                free(pb->device);
                pb->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.device, "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) {
                                pcap_strlcpy(ifr.ifr_name, "en",
                                    sizeof(ifr.ifr_name));
                                pcap_strlcat(ifr.ifr_name, p->opt.device + 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;
                                        pcap_fmt_errmsg_for_errno(p->errbuf,
                                            PCAP_ERRBUF_SIZE, errno,
                                            "SIOCGIFFLAGS on %s failed",
                                            ifr.ifr_name);
                                } 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;
                                pcap_fmt_errmsg_for_errno(p->errbuf,
                                    errno, PCAP_ERRBUF_SIZE,
                                    "socket() failed");
                        }
                        return (err);
                }
#endif
                /*
                 * No such device.
                 */
                pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                    errno, "BIOCSETIF failed");
                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.
                 */
                pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                    errno, "BIOCSETIF: %s", p->opt.device);
                return (PCAP_ERROR);
        }
}

/*
 * Default capture buffer size.
 * 32K isn't very much for modern machines with fast networks; we
 * pick .5M, as that's the maximum on at least some systems with BPF.
 *
 * However, on AIX 3.5, the larger buffer sized caused unrecoverable
 * read failures under stress, so we leave it as 32K; yet another
 * place where AIX's BPF is broken.
 */
#ifdef _AIX
#define DEFAULT_BUFSIZE 32768
#else
#define DEFAULT_BUFSIZE 524288
#endif

static int
pcap_activate_bpf(pcap_t *p)
{
        struct pcap_bpf *pb = p->priv;
        int status = 0;
#ifdef HAVE_BSD_IEEE80211
        int retv;
#endif
        int fd;
#ifdef LIFNAMSIZ
        char *zonesep;
        struct lifreq ifr;
        char *ifrname = ifr.lifr_name;
        const size_t ifnamsiz = sizeof(ifr.lifr_name);
#else
        struct ifreq ifr;
        char *ifrname = ifr.ifr_name;
        const size_t ifnamsiz = sizeof(ifr.ifr_name);
#endif
        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->errbuf);
        if (fd < 0) {
                status = fd;
                goto bad;
        }

        p->fd = fd;

        if (ioctl(fd, BIOCVERSION, (caddr_t)&bv) < 0) {
                pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                    errno, "BIOCVERSION");
                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;
        }

        /*
         * Turn a negative snapshot value (invalid), a snapshot value of
         * 0 (unspecified), or a value bigger than the normal maximum
         * value, into the maximum allowed value.
         *
         * If some application really *needs* a bigger snapshot
         * length, we should just increase MAXIMUM_SNAPLEN.
         */
        if (p->snapshot <= 0 || p->snapshot > MAXIMUM_SNAPLEN)
                p->snapshot = MAXIMUM_SNAPLEN;

#if defined(LIFNAMSIZ) && defined(ZONENAME_MAX) && defined(lifr_zoneid)
        /*
         * Retrieve the zoneid of the zone we are currently executing in.
         */
        if ((ifr.lifr_zoneid = getzoneid()) == -1) {
                pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                    errno, "getzoneid()");
                status = PCAP_ERROR;
                goto bad;
        }
        /*
         * Check if the given source datalink name has a '/' separated
         * zonename prefix string.  The zonename prefixed source datalink can
         * be used by pcap consumers in the Solaris global zone to capture
         * traffic on datalinks in non-global zones.  Non-global zones
         * do not have access to datalinks outside of their own namespace.
         */
        if ((zonesep = strchr(p->opt.device, '/')) != NULL) {
                char path_zname[ZONENAME_MAX];
                int  znamelen;
                char *lnamep;

                if (ifr.lifr_zoneid != GLOBAL_ZONEID) {
                        snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                            "zonename/linkname only valid in global zone.");
                        status = PCAP_ERROR;
                        goto bad;
                }
                znamelen = zonesep - p->opt.device;
                (void) pcap_strlcpy(path_zname, p->opt.device, znamelen + 1);
                ifr.lifr_zoneid = getzoneidbyname(path_zname);
                if (ifr.lifr_zoneid == -1) {
                        pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                            errno, "getzoneidbyname(%s)", path_zname);
                        status = PCAP_ERROR;
                        goto bad;
                }
                lnamep = strdup(zonesep + 1);
                if (lnamep == NULL) {
                        pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                            errno, "strdup");
                        status = PCAP_ERROR;
                        goto bad;
                }
                free(p->opt.device);
                p->opt.device = lnamep;
        }
#endif

        pb->device = strdup(p->opt.device);
        if (pb->device == NULL) {
                pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                    errno, "strdup");
                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.device, "en", 2) != 0) {
                                        /*
                                         * Not an enN device; check
                                         * whether the device even exists.
                                         */
                                        sockfd = socket(AF_INET, SOCK_DGRAM, 0);
                                        if (sockfd != -1) {
                                                pcap_strlcpy(ifrname,
                                                    p->opt.device, ifnamsiz);
                                                if (ioctl(sockfd, SIOCGIFFLAGS,
                                                    (char *)&ifr) < 0) {
                                                        /*
                                                         * We assume this
                                                         * failed because
                                                         * the underlying
                                                         * device doesn't
                                                         * exist.
                                                         */
                                                        status = PCAP_ERROR_NO_SUCH_DEVICE;
                                                        pcap_fmt_errmsg_for_errno(p->errbuf,
                                                            PCAP_ERRBUF_SIZE,
                                                            errno,
                                                            "SIOCGIFFLAGS failed");
                                                } 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;
                                                pcap_fmt_errmsg_for_errno(p->errbuf,
                                                    PCAP_ERRBUF_SIZE, errno,
                                                    "socket() failed");
                                        }
                                        goto bad;
                                }
                                wltdev = malloc(strlen(p->opt.device) + 2);
                                if (wltdev == NULL) {
                                        pcap_fmt_errmsg_for_errno(p->errbuf,
                                            PCAP_ERRBUF_SIZE, errno,
                                            "malloc");
                                        status = PCAP_ERROR;
                                        goto bad;
                                }
                                strcpy(wltdev, "wlt");
                                strcat(wltdev, p->opt.device + 2);
                                free(p->opt.device);
                                p->opt.device = wltdev;
                        }
                        /*
                         * Everything else is 10.5 or later; for those,
                         * we just open the enN device, and set the DLT.
                         */
                }
        }
#endif /* __APPLE__ */

        /*
         * If this is FreeBSD, and the device name begins with "usbus",
         * try to create the interface if it's not available.
         */
#if defined(__FreeBSD__) && defined(SIOCIFCREATE2)
        if (strncmp(p->opt.device, usbus_prefix, USBUS_PREFIX_LEN) == 0) {
                /*
                 * Do we already have an interface with that name?
                 */
                if (if_nametoindex(p->opt.device) == 0) {
                        /*
                         * No.  We need to create it, and, if we
                         * succeed, remember that we should destroy
                         * it when the pcap_t is closed.
                         */
                        int s;

                        /*
                         * Open a socket to use for ioctls to
                         * create the interface.
                         */
                        s = socket(AF_LOCAL, SOCK_DGRAM, 0);
                        if (s < 0) {
                                pcap_fmt_errmsg_for_errno(p->errbuf,
                                    PCAP_ERRBUF_SIZE, errno,
                                    "Can't open socket");
                                status = PCAP_ERROR;
                                goto bad;
                        }

                        /*
                         * 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 create the
                                 * interface, just give up.
                                 */
                                snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                                     "atexit failed");
                                close(s);
                                status = PCAP_ERROR;
                                goto bad;
                        }

                        /*
                         * Create the interface.
                         */
                        pcap_strlcpy(ifr.ifr_name, p->opt.device, sizeof(ifr.ifr_name));
                        if (ioctl(s, SIOCIFCREATE2, &ifr) < 0) {
                                if (errno == EINVAL) {
                                        snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                                            "Invalid USB bus interface %s",
                                            p->opt.device);
                                } else {
                                        pcap_fmt_errmsg_for_errno(p->errbuf,
                                            PCAP_ERRBUF_SIZE, errno,
                                            "Can't create interface for %s",
                                            p->opt.device);
                                }
                                close(s);
                                status = PCAP_ERROR;
                                goto bad;
                        }

                        /*
                         * Make sure we clean this up when we close.
                         */
                        pb->must_do_on_close |= MUST_DESTROY_USBUS;

                        /*
                         * Add this to the list of pcaps to close when we exit.
                         */
                        pcap_add_to_pcaps_to_close(p);
                }
        }
#endif /* defined(__FreeBSD__) && defined(SIOCIFCREATE2) */

#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.
                 */
                pb->zerocopy = 1;

                /*
                 * 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) {
                        pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                            errno, "BIOCGETZMAX");
                        status = PCAP_ERROR;
                        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 < DEFAULT_BUFSIZE)
                                v = DEFAULT_BUFSIZE;
                }
#ifndef roundup
#define roundup(x, y)   ((((x)+((y)-1))/(y))*(y))  /* to any y */
#endif
                pb->zbufsize = roundup(v, getpagesize());
                if (pb->zbufsize > zbufmax)
                        pb->zbufsize = zbufmax;
                pb->zbuf1 = mmap(NULL, pb->zbufsize, PROT_READ | PROT_WRITE,
                    MAP_ANON, -1, 0);
                pb->zbuf2 = mmap(NULL, pb->zbufsize, PROT_READ | PROT_WRITE,
                    MAP_ANON, -1, 0);
                if (pb->zbuf1 == MAP_FAILED || pb->zbuf2 == MAP_FAILED) {
                        pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                            errno, "mmap");
                        status = PCAP_ERROR;
                        goto bad;
                }
                memset(&bz, 0, sizeof(bz)); /* bzero() deprecated, replaced with memset() */
                bz.bz_bufa = pb->zbuf1;
                bz.bz_bufb = pb->zbuf2;
                bz.bz_buflen = pb->zbufsize;
                if (ioctl(fd, BIOCSETZBUF, (caddr_t)&bz) < 0) {
                        pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                            errno, "BIOCSETZBUF");
                        status = PCAP_ERROR;
                        goto bad;
                }
                (void)strncpy(ifrname, p->opt.device, ifnamsiz);
                if (ioctl(fd, BIOCSETIF, (caddr_t)&ifr) < 0) {
                        pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                            errno, "BIOCSETIF: %s", p->opt.device);
                        status = PCAP_ERROR;
                        goto bad;
                }
                v = pb->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) {
                                pcap_fmt_errmsg_for_errno(p->errbuf,
                                    PCAP_ERRBUF_SIZE, errno,
                                    "BIOCSBLEN: %s", p->opt.device);
                                status = PCAP_ERROR;
                                goto bad;
                        }

                        /*
                         * Now bind to the device.
                         */
                        (void)strncpy(ifrname, p->opt.device, ifnamsiz);
#ifdef BIOCSETLIF
                        if (ioctl(fd, BIOCSETLIF, (caddr_t)&ifr) < 0)
#else
                        if (ioctl(fd, BIOCSETIF, (caddr_t)&ifr) < 0)
#endif
                        {
                                status = check_setif_failure(p, errno);
                                goto bad;
                        }
                } else {
                        /*
                         * No buffer size was explicitly specified.
                         *
                         * Try finding a good size for the buffer;
                         * DEFAULT_BUFSIZE 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 < DEFAULT_BUFSIZE)
                                v = DEFAULT_BUFSIZE;
                        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(ifrname, p->opt.device, ifnamsiz);
#ifdef BIOCSETLIF
                                if (ioctl(fd, BIOCSETLIF, (caddr_t)&ifr) >= 0)
#else
                                if (ioctl(fd, BIOCSETIF, (caddr_t)&ifr) >= 0)
#endif
                                        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.device);
                                status = PCAP_ERROR;
                                goto bad;
                        }
                }
        }

        /* Get the data link layer type. */
        if (ioctl(fd, BIOCGDLT, (caddr_t)&v) < 0) {
                pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                    errno, "BIOCGDLT");
                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 (PCAP_ISDIGIT((unsigned)osinfo.release[0]) &&
                     (osinfo.release[0] == '9' ||
                     PCAP_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_non_802_11(p);

                                        /*
                                         * If the new mode we want isn't
                                         * the default mode, attempt to
                                         * select the new mode.
                                         */
                                        if ((u_int)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.
                 */
                retv = monitor_mode(p, 1);
                if (retv != 0) {
                        /*
                         * We failed.
                         */
                        status = retv;
                        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 ((u_int)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
#endif
                p->fddipad = 0;
        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) {
                pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                    errno, "BIOCSHDRCMPLT");
                status = PCAP_ERROR;
                goto bad;
        }
#endif
        /* set timeout */
#ifdef HAVE_ZEROCOPY_BPF
        /*
         * In zero-copy mode, we just use the timeout in select().
         * XXX - what if we're in non-blocking mode and the *application*
         * is using select() or poll() or kqueues or....?
         */
        if (p->opt.timeout && !pb->zerocopy) {
#else
        if (p->opt.timeout) {
#endif
                /*
                 * XXX - is this seconds/nanoseconds in AIX?
                 * (Treating it as such doesn't fix the timeout
                 * problem described below.)
                 *
                 * XXX - Mac OS X 10.6 mishandles BIOCSRTIMEOUT in
                 * 64-bit userland - it takes, as an argument, a
                 * "struct BPF_TIMEVAL", which has 32-bit tv_sec
                 * and tv_usec, rather than a "struct timeval".
                 *
                 * If this platform defines "struct BPF_TIMEVAL",
                 * we check whether the structure size in BIOCSRTIMEOUT
                 * is that of a "struct timeval" and, if not, we use
                 * a "struct BPF_TIMEVAL" rather than a "struct timeval".
                 * (That way, if the bug is fixed in a future release,
                 * we will still do the right thing.)
                 */
                struct timeval to;
#ifdef HAVE_STRUCT_BPF_TIMEVAL
                struct BPF_TIMEVAL bpf_to;

                if (IOCPARM_LEN(BIOCSRTIMEOUT) != sizeof(struct timeval)) {
                        bpf_to.tv_sec = p->opt.timeout / 1000;
                        bpf_to.tv_usec = (p->opt.timeout * 1000) % 1000000;
                        if (ioctl(p->fd, BIOCSRTIMEOUT, (caddr_t)&bpf_to) < 0) {
                                pcap_fmt_errmsg_for_errno(p->errbuf,
                                    errno, PCAP_ERRBUF_SIZE, "BIOCSRTIMEOUT");
                                status = PCAP_ERROR;
                                goto bad;
                        }
                } else {
#endif
                        to.tv_sec = p->opt.timeout / 1000;
                        to.tv_usec = (p->opt.timeout * 1000) % 1000000;
                        if (ioctl(p->fd, BIOCSRTIMEOUT, (caddr_t)&to) < 0) {
                                pcap_fmt_errmsg_for_errno(p->errbuf,
                                    errno, PCAP_ERRBUF_SIZE, "BIOCSRTIMEOUT");
                                status = PCAP_ERROR;
                                goto bad;
                        }
#ifdef HAVE_STRUCT_BPF_TIMEVAL
                }
#endif
        }

#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 always turn BIOCIMMEDIATE mode on if this is AIX.
         *
         * For other platforms, we don't turn immediate mode on by default,
         * as that would mean we get woken up for every packet, which
         * probably isn't what you want for a packet sniffer.
         *
         * We set immediate mode if the caller requested it by calling
         * pcap_set_immediate() before calling pcap_activate().
         */
#ifndef _AIX
        if (p->opt.immediate) {
#endif /* _AIX */
                v = 1;
                if (ioctl(p->fd, BIOCIMMEDIATE, &v) < 0) {
                        pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                            errno, "BIOCIMMEDIATE");
                        status = PCAP_ERROR;
                        goto bad;
                }
#ifndef _AIX
        }
#endif /* _AIX */
#else /* BIOCIMMEDIATE */
        if (p->opt.immediate) {
                /*
                 * We don't support immediate mode.  Fail.
                 */
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "Immediate mode not supported");
                status = PCAP_ERROR;
                goto bad;
        }
#endif /* BIOCIMMEDIATE */

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

#ifdef BIOCSTSTAMP
        v = BPF_T_BINTIME;
        if (ioctl(p->fd, BIOCSTSTAMP, &v) < 0) {
                pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                    errno, "BIOCSTSTAMP");
                status = PCAP_ERROR;
                goto bad;
        }
#endif /* BIOCSTSTAMP */

        if (ioctl(fd, BIOCGBLEN, (caddr_t)&v) < 0) {
                pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                    errno, "BIOCGBLEN");
                status = PCAP_ERROR;
                goto bad;
        }
        p->bufsize = v;
#ifdef HAVE_ZEROCOPY_BPF
        if (!pb->zerocopy) {
#endif
        p->buffer = malloc(p->bufsize);
        if (p->buffer == NULL) {
                pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                    errno, "malloc");
                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) {
                pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                    errno, "BIOCSETF");
                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_bpf;
        p->setnonblock_op = pcap_setnonblock_bpf;
        p->stats_op = pcap_stats_bpf;
        p->cleanup_op = pcap_cleanup_bpf;

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

/*
 * Not all interfaces can be bound to by BPF, so try to bind to
 * the specified interface; return 0 if we fail with
 * PCAP_ERROR_NO_SUCH_DEVICE (which means we got an ENXIO when we tried
 * to bind, which means this interface isn't in the list of interfaces
 * attached to BPF) and 1 otherwise.
 */
static int
check_bpf_bindable(const char *name)
{
        int fd;
        char errbuf[PCAP_ERRBUF_SIZE];

        /*
         * On macOS, we don't do this check if the device name begins
         * with "wlt"; at least some versions of macOS (actually, it
         * was called "Mac OS X" then...) offer monitor mode capturing
         * by having a separate "monitor mode" device for each wireless
         * adapter, rather than by implementing the ioctls that
         * {Free,Net,Open,DragonFly}BSD provide. Opening that device
         * puts the adapter into monitor mode, which, at least for
         * some adapters, causes them to deassociate from the network
         * with which they're associated.
         *
         * Instead, we try to open the corresponding "en" device (so
         * that we don't end up with, for users without sufficient
         * privilege to open capture devices, a list of adapters that
         * only includes the wlt devices).
         */
#ifdef __APPLE__
        if (strncmp(name, "wlt", 3) == 0) {
                char *en_name;
                size_t en_name_len;

                /*
                 * Try to allocate a buffer for the "en"
                 * device's name.
                 */
                en_name_len = strlen(name) - 1;
                en_name = malloc(en_name_len + 1);
                if (en_name == NULL) {
                        pcap_fmt_errmsg_for_errno(errbuf, PCAP_ERRBUF_SIZE,
                            errno, "malloc");
                        return (-1);
                }
                strcpy(en_name, "en");
                strcat(en_name, name + 3);
                fd = bpf_open_and_bind(en_name, errbuf);
                free(en_name);
        } else
#endif /* __APPLE */
        fd = bpf_open_and_bind(name, errbuf);
        if (fd < 0) {
                /*
                 * Error - was it PCAP_ERROR_NO_SUCH_DEVICE?
                 */
                if (fd == PCAP_ERROR_NO_SUCH_DEVICE) {
                        /*
                         * Yes, so we can't bind to this because it's
                         * not something supported by BPF.
                         */
                        return (0);
                }
                /*
                 * No, so we don't know whether it's supported or not;
                 * say it is, so that the user can at least try to
                 * open it and report the error (which is probably
                 * "you don't have permission to open BPF devices";
                 * reporting those interfaces means users will ask
                 * "why am I getting a permissions error when I try
                 * to capture" rather than "why am I not seeing any
                 * interfaces", making the underlying problem clearer).
                 */
                return (1);
        }

        /*
         * Success.
         */
        close(fd);
        return (1);
}

#if defined(__FreeBSD__) && defined(SIOCIFCREATE2)
static int
get_usb_if_flags(const char *name _U_, bpf_u_int32 *flags _U_, char *errbuf _U_)
{
        /*
         * XXX - if there's a way to determine whether there's something
         * plugged into a given USB bus, use that to determine whether
         * this device is "connected" or not.
         */
        return (0);
}

static int
finddevs_usb(pcap_if_list_t *devlistp, char *errbuf)
{
        DIR *usbdir;
        struct dirent *usbitem;
        size_t name_max;
        char *name;

        /*
         * We might have USB sniffing support, so try looking for USB
         * interfaces.
         *
         * We want to report a usbusN device for each USB bus, but
         * usbusN interfaces might, or might not, exist for them -
         * we create one if there isn't already one.
         *
         * So, instead, we look in /dev/usb for all buses and create
         * a "usbusN" device for each one.
         */
        usbdir = opendir("/dev/usb");
        if (usbdir == NULL) {
                /*
                 * Just punt.
                 */
                return (0);
        }

        /*
         * Leave enough room for a 32-bit (10-digit) bus number.
         * Yes, that's overkill, but we won't be using
         * the buffer very long.
         */
        name_max = USBUS_PREFIX_LEN + 10 + 1;
        name = malloc(name_max);
        if (name == NULL) {
                closedir(usbdir);
                return (0);
        }
        while ((usbitem = readdir(usbdir)) != NULL) {
                char *p;
                size_t busnumlen;

                if (strcmp(usbitem->d_name, ".") == 0 ||
                    strcmp(usbitem->d_name, "..") == 0) {
                        /*
                         * Ignore these.
                         */
                        continue;
                }
                p = strchr(usbitem->d_name, '.');
                if (p == NULL)
                        continue;
                busnumlen = p - usbitem->d_name;
                memcpy(name, usbus_prefix, USBUS_PREFIX_LEN);
                memcpy(name + USBUS_PREFIX_LEN, usbitem->d_name, busnumlen);
                *(name + USBUS_PREFIX_LEN + busnumlen) = '\0';
                /*
                 * There's an entry in this directory for every USB device,
                 * not for every bus; if there's more than one device on
                 * the bus, there'll be more than one entry for that bus,
                 * so we need to avoid adding multiple capture devices
                 * for each bus.
                 */
                if (find_or_add_dev(devlistp, name, PCAP_IF_UP,
                    get_usb_if_flags, NULL, errbuf) == NULL) {
                        free(name);
                        closedir(usbdir);
                        return (PCAP_ERROR);
                }
        }
        free(name);
        closedir(usbdir);
        return (0);
}
#endif

/*
 * Get additional flags for a device, using SIOCGIFMEDIA.
 */
#ifdef SIOCGIFMEDIA
static int
get_if_flags(const char *name, bpf_u_int32 *flags, char *errbuf)
{
        int sock;
        struct ifmediareq req;

        sock = socket(AF_INET, SOCK_DGRAM, 0);
        if (sock == -1) {
                pcap_fmt_errmsg_for_errno(errbuf, PCAP_ERRBUF_SIZE, errno,
                    "Can't create socket to get media information for %s",
                    name);
                return (-1);
        }
        memset(&req, 0, sizeof(req));
        strncpy(req.ifm_name, name, sizeof(req.ifm_name));
        if (ioctl(sock, SIOCGIFMEDIA, &req) < 0) {
                if (errno == EOPNOTSUPP || errno == EINVAL || errno == ENOTTY ||
                    errno == ENODEV || errno == EPERM) {
                        /*
                         * Not supported, so we can't provide any
                         * additional information.  Assume that
                         * this means that "connected" vs.
                         * "disconnected" doesn't apply.
                         *
                         * The ioctl routine for Apple's pktap devices,
                         * annoyingly, checks for "are you root?" before
                         * checking whether the ioctl is valid, so it
                         * returns EPERM, rather than ENOTSUP, for the
                         * invalid SIOCGIFMEDIA, unless you're root.
                         * So, just as we do for some ethtool ioctls
                         * on Linux, which makes the same mistake, we
                         * also treat EPERM as meaning "not supported".
                         */
                        *flags |= PCAP_IF_CONNECTION_STATUS_NOT_APPLICABLE;
                        close(sock);
                        return (0);
                }
                pcap_fmt_errmsg_for_errno(errbuf, PCAP_ERRBUF_SIZE, errno,
                    "SIOCGIFMEDIA on %s failed", name);
                close(sock);
                return (-1);
        }
        close(sock);

        /*
         * OK, what type of network is this?
         */
        switch (IFM_TYPE(req.ifm_active)) {

        case IFM_IEEE80211:
                /*
                 * Wireless.
                 */
                *flags |= PCAP_IF_WIRELESS;
                break;
        }

        /*
         * Do we know whether it's connected?
         */
        if (req.ifm_status & IFM_AVALID) {
                /*
                 * Yes.
                 */
                if (req.ifm_status & IFM_ACTIVE) {
                        /*
                         * It's connected.
                         */
                        *flags |= PCAP_IF_CONNECTION_STATUS_CONNECTED;
                } else {
                        /*
                         * It's disconnected.
                         */
                        *flags |= PCAP_IF_CONNECTION_STATUS_DISCONNECTED;
                }
        }
        return (0);
}
#else
static int
get_if_flags(const char *name _U_, bpf_u_int32 *flags _U_, char *errbuf _U_)
{
        /*
         * Nothing we can do other than mark loopback devices as "the
         * connected/disconnected status doesn't apply".
         *
         * XXX - on Solaris, can we do what the dladm command does,
         * i.e. get a connected/disconnected indication from a kstat?
         * (Note that you can also get the link speed, and possibly
         * other information, from a kstat as well.)
         */
        if (*flags & PCAP_IF_LOOPBACK) {
                /*
                 * Loopback devices aren't wireless, and "connected"/
                 * "disconnected" doesn't apply to them.
                 */
                *flags |= PCAP_IF_CONNECTION_STATUS_NOT_APPLICABLE;
                return (0);
        }
        return (0);
}
#endif

int
pcap_platform_finddevs(pcap_if_list_t *devlistp, char *errbuf)
{
        /*
         * Get the list of regular interfaces first.
         */
        if (pcap_findalldevs_interfaces(devlistp, errbuf, check_bpf_bindable,
            get_if_flags) == -1)
                return (-1);    /* failure */

#if defined(__FreeBSD__) && defined(SIOCIFCREATE2)
        if (finddevs_usb(devlistp, errbuf) == -1)
                return (-1);
#endif

        return (0);
}

#ifdef HAVE_BSD_IEEE80211
static int
monitor_mode(pcap_t *p, int set)
{
        struct pcap_bpf *pb = p->priv;
        int sock;
        struct ifmediareq req;
        IFM_ULIST_TYPE *media_list;
        int i;
        int can_do;
        struct ifreq ifr;

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

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

        /*
         * Find out how many media types we have.
         */
        if (ioctl(sock, SIOCGIFMEDIA, &req) < 0) {
                /*
                 * Can't get the media types.
                 */
                switch (errno) {

                case ENXIO:
                        /*
                         * There's no such device.
                         */
                        close(sock);
                        return (PCAP_ERROR_NO_SUCH_DEVICE);

                case EINVAL:
                        /*
                         * Interface doesn't support SIOC{G,S}IFMEDIA.
                         */
                        close(sock);
                        return (PCAP_ERROR_RFMON_NOTSUP);

                default:
                        pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                            errno, "SIOCGIFMEDIA");
                        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(*media_list));
        if (media_list == NULL) {
                pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                    errno, "malloc");
                close(sock);
                return (PCAP_ERROR);
        }
        req.ifm_ulist = media_list;
        if (ioctl(sock, SIOCGIFMEDIA, &req) < 0) {
                pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                    errno, "SIOCGIFMEDIA");
                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.
                                 */
                                close(sock);
                                return (PCAP_ERROR);
                        }
                        memset(&ifr, 0, sizeof(ifr));
                        (void)strncpy(ifr.ifr_name, p->opt.device,
                            sizeof(ifr.ifr_name));
                        ifr.ifr_media = req.ifm_current | IFM_IEEE80211_MONITOR;
                        if (ioctl(sock, SIOCSIFMEDIA, &ifr) == -1) {
                                pcap_fmt_errmsg_for_errno(p->errbuf,
                                    PCAP_ERRBUF_SIZE, errno, "SIOCSIFMEDIA");
                                close(sock);
                                return (PCAP_ERROR);
                        }

                        pb->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;
        u_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;

#ifdef DLT_PRISM_HEADER
                case DLT_PRISM_HEADER:
#endif
#ifdef DLT_AIRONET_HEADER
                case DLT_AIRONET_HEADER:
#endif
                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 non-802.11 header types from the list of DLT_ values, as we're in
 * monitor mode, and those header types aren't supported in monitor mode.
 */
static void
remove_non_802_11(pcap_t *p)
{
        int i, j;

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

                case DLT_EN10MB:
                case DLT_RAW:
                        /*
                         * Not 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;
}

/*
 * Remove 802.11 link-layer types from the list of DLT_ values, as
 * we're not in monitor mode, and those DLT_ values will switch us
 * to monitor mode.
 */
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:
#ifdef DLT_PRISM_HEADER
                case DLT_PRISM_HEADER:
#endif
#ifdef DLT_AIRONET_HEADER
                case DLT_AIRONET_HEADER:
#endif
                case DLT_IEEE802_11_RADIO:
                case DLT_IEEE802_11_RADIO_AVS:
#ifdef DLT_PPI
                case DLT_PPI:
#endif
                        /*
                         * 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)
{
        struct pcap_bpf *pb = p->priv;

        /*
         * 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.
                 */
                pb->filtering_in_kernel = 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) {
                pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
                    errno, "BIOCSETF");
                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);
        pb->filtering_in_kernel = 0;    /* filtering in userland */
        return (0);
}

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

        /*
         * FreeBSD and NetBSD.
         */
        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) {
                pcap_fmt_errmsg_for_errno(p->errbuf, sizeof(p->errbuf),
                    errno, "Cannot set direction to %s",
                        (d == PCAP_D_IN) ? "PCAP_D_IN" :
                        ((d == PCAP_D_OUT) ? "PCAP_D_OUT" : "PCAP_D_INOUT"));
                return (-1);
        }
        return (0);
}
#elif defined(BIOCSDIRFILT)
static int
pcap_setdirection_bpf(pcap_t *p, pcap_direction_t d)
{
        u_int direction;

        /*
         * OpenBSD; same functionality, different names, different
         * semantics (the flags mean "*don't* capture packets in
         * that direction", not "*capture only* packets in that
         * direction").
         */
        direction = (d == PCAP_D_IN) ? BPF_DIRECTION_OUT :
            ((d == PCAP_D_OUT) ? BPF_DIRECTION_IN : 0);
        if (ioctl(p->fd, BIOCSDIRFILT, &direction) == -1) {
                pcap_fmt_errmsg_for_errno(p->errbuf, sizeof(p->errbuf),
                    errno, "Cannot set direction to %s",
                        (d == PCAP_D_IN) ? "PCAP_D_IN" :
                        ((d == PCAP_D_OUT) ? "PCAP_D_OUT" : "PCAP_D_INOUT"));
                return (-1);
        }
        return (0);
}
#elif defined(BIOCSSEESENT)
static int
pcap_setdirection_bpf(pcap_t *p, pcap_direction_t d)
{
        u_int seesent;

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

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

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

/*
 * Platform-specific information.
 */
const char *
pcap_lib_version(void)
{
#ifdef HAVE_ZEROCOPY_BPF
        return (PCAP_VERSION_STRING " (with zerocopy support)");
#else
        return (PCAP_VERSION_STRING);
#endif
}