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pcap-bpf.c

/*
 * Copyright (c) 1993, 1994, 1995, 1996, 1998
 *    The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that: (1) source code distributions
 * retain the above copyright notice and this paragraph in its entirety, (2)
 * distributions including binary code include the above copyright notice and
 * this paragraph in its entirety in the documentation or other materials
 * provided with the distribution, and (3) all advertising materials mentioning
 * features or use of this software display the following acknowledgement:
 * ``This product includes software developed by the University of California,
 * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
 * the University nor the names of its contributors may be used to endorse
 * or promote products derived from this software without specific prior
 * written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */
#ifndef lint
static const char rcsid[] _U_ =
    "@(#) $Header: /tcpdump/master/libpcap/pcap-bpf.c,v 1.99.2.17 2008-09-16 18:43:02 guy Exp $ (LBL)";
#endif

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

#include <sys/param.h>              /* optionally get BSD define */
#ifdef HAVE_ZEROCOPY_BPF
#include <sys/mman.h>
#endif
#include <sys/time.h>
#include <sys/timeb.h>
#include <sys/socket.h>
#include <sys/file.h>
#include <sys/ioctl.h>
#include <sys/utsname.h>

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

#include <net/if.h>

#ifdef _AIX

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

#include <sys/types.h>

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

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

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

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

#else /* _AIX */

#include <net/bpf.h>

#endif /* _AIX */

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

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

#include "pcap-int.h"

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

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

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

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

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

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

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

#endif /* BIOCGDLTLIST */

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

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

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

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

static int
pcap_setnonblock_zbuf(pcap_t *p, int nonblock, char *errbuf)
{   
      /*
       * Map each value to the corresponding 2's complement, to
       * preserve the timeout value provided with pcap_set_timeout.
       * (from pcap-linux.c).
       */
      if (nonblock) {
            if (p->md.timeout > 0)
                  p->md.timeout = p->md.timeout * -1 - 1;
      } else
            if (p->md.timeout < 0)
                  p->md.timeout = (p->md.timeout + 1) * -1;
      return (0);
}

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

      return (fd);
}

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

                  case EINTR:
                        goto again;

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

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

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

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

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

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

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

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

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

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

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

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

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

      return (0);
}

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

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

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

      return (0);
}

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

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

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

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

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

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

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

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

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

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

      bpfloadedflag = 1;

      return (0);
}
#endif

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

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

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

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

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

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

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

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

      p->fd = fd;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

      case IFT_FDDI:
            v = DLT_FDDI;
            break;

      case IFT_ISO88025:
            v = DLT_IEEE802;
            break;

      case IFT_LOOP:
            v = DLT_NULL;
            break;

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

      case DLT_SLIP:
            v = DLT_SLIP_BSDOS;
            break;

      case DLT_PPP:
            v = DLT_PPP_BSDOS;
            break;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

      return (0);
}

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

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

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

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

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

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

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

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

                  p->md.must_clear |= MUST_CLEAR_RFMON;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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