FreeBSD/Linux Kernel Cross Reference
sys/net/bpf.c

     /*-
      * Copyright (c) 1990, 1991, 1993
      *      The Regents of the University of California.  All rights reserved.
      *
      * This code is derived from the Stanford/CMU enet packet filter,
      * (net/enet.c) distributed as part of 4.3BSD, and code contributed
      * to Berkeley by Steven McCanne and Van Jacobson both of Lawrence
      * Berkeley Laboratory.
      *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 4. 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 BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      @(#)bpf.c       8.4 (Berkeley) 1/9/95
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include "opt_bpf.h"
    #include "opt_compat.h"
    #include "opt_netgraph.h"
    
    #include <sys/types.h>
    #include <sys/param.h>
    #include <sys/lock.h>
    #include <sys/rwlock.h>
    #include <sys/systm.h>
    #include <sys/conf.h>
    #include <sys/fcntl.h>
    #include <sys/jail.h>
    #include <sys/malloc.h>
    #include <sys/mbuf.h>
    #include <sys/time.h>
    #include <sys/priv.h>
    #include <sys/proc.h>
    #include <sys/signalvar.h>
    #include <sys/filio.h>
    #include <sys/sockio.h>
    #include <sys/ttycom.h>
    #include <sys/uio.h>
    
    #include <sys/event.h>
    #include <sys/file.h>
    #include <sys/poll.h>
    #include <sys/proc.h>
    
    #include <sys/socket.h>
    
    #include <net/if.h>
    #define BPF_INTERNAL
    #include <net/bpf.h>
    #include <net/bpf_buffer.h>
    #ifdef BPF_JITTER
    #include <net/bpf_jitter.h>
    #endif
    #include <net/bpf_zerocopy.h>
    #include <net/bpfdesc.h>
    #include <net/vnet.h>
    
    #include <netinet/in.h>
    #include <netinet/if_ether.h>
    #include <sys/kernel.h>
    #include <sys/sysctl.h>
    
    #include <net80211/ieee80211_freebsd.h>
    
    #include <security/mac/mac_framework.h>
    
    MALLOC_DEFINE(M_BPF, "BPF", "BPF data");
    
    #if defined(DEV_BPF) || defined(NETGRAPH_BPF)
    
    #define PRINET  26                      /* interruptible */
    
    #ifdef COMPAT_FREEBSD32
    #include <sys/mount.h>
    #include <compat/freebsd32/freebsd32.h>
    #define BPF_ALIGNMENT32 sizeof(int32_t)
   #define BPF_WORDALIGN32(x) (((x)+(BPF_ALIGNMENT32-1))&~(BPF_ALIGNMENT32-1))
   
   /*
    * 32-bit version of structure prepended to each packet.  We use this header
    * instead of the standard one for 32-bit streams.  We mark the a stream as
    * 32-bit the first time we see a 32-bit compat ioctl request.
    */
   struct bpf_hdr32 {
           struct timeval32 bh_tstamp;     /* time stamp */
           uint32_t        bh_caplen;      /* length of captured portion */
           uint32_t        bh_datalen;     /* original length of packet */
           uint16_t        bh_hdrlen;      /* length of bpf header (this struct
                                              plus alignment padding) */
   };
   
   struct bpf_program32 {
           u_int bf_len;
           uint32_t bf_insns;
   };
   
   struct bpf_dltlist32 {
           u_int   bfl_len;
           u_int   bfl_list;
   };
   
   #define BIOCSETF32      _IOW('B', 103, struct bpf_program32)
   #define BIOCSRTIMEOUT32 _IOW('B',109, struct timeval32)
   #define BIOCGRTIMEOUT32 _IOR('B',110, struct timeval32)
   #define BIOCGDLTLIST32  _IOWR('B',121, struct bpf_dltlist32)
   #define BIOCSETWF32     _IOW('B',123, struct bpf_program32)
   #define BIOCSETFNR32    _IOW('B',130, struct bpf_program32)
   #endif
   
   /*
    * bpf_iflist is a list of BPF interface structures, each corresponding to a
    * specific DLT.  The same network interface might have several BPF interface
    * structures registered by different layers in the stack (i.e., 802.11
    * frames, ethernet frames, etc).
    */
   static LIST_HEAD(, bpf_if)      bpf_iflist;
   static struct mtx       bpf_mtx;                /* bpf global lock */
   static int              bpf_bpfd_cnt;
   
   static void     bpf_attachd(struct bpf_d *, struct bpf_if *);
   static void     bpf_detachd(struct bpf_d *);
   static void     bpf_detachd_locked(struct bpf_d *);
   static void     bpf_freed(struct bpf_d *);
   static int      bpf_movein(struct uio *, int, struct ifnet *, struct mbuf **,
                       struct sockaddr *, int *, struct bpf_insn *);
   static int      bpf_setif(struct bpf_d *, struct ifreq *);
   static void     bpf_timed_out(void *);
   static __inline void
                   bpf_wakeup(struct bpf_d *);
   static void     catchpacket(struct bpf_d *, u_char *, u_int, u_int,
                       void (*)(struct bpf_d *, caddr_t, u_int, void *, u_int),
                       struct timeval *);
   static void     reset_d(struct bpf_d *);
   static int      bpf_setf(struct bpf_d *, struct bpf_program *, u_long cmd);
   static int      bpf_getdltlist(struct bpf_d *, struct bpf_dltlist *);
   static int      bpf_setdlt(struct bpf_d *, u_int);
   static void     filt_bpfdetach(struct knote *);
   static int      filt_bpfread(struct knote *, long);
   static void     bpf_drvinit(void *);
   static int      bpf_stats_sysctl(SYSCTL_HANDLER_ARGS);
   
   SYSCTL_NODE(_net, OID_AUTO, bpf, CTLFLAG_RW, 0, "bpf sysctl");
   int bpf_maxinsns = BPF_MAXINSNS;
   SYSCTL_INT(_net_bpf, OID_AUTO, maxinsns, CTLFLAG_RW,
       &bpf_maxinsns, 0, "Maximum bpf program instructions");
   static int bpf_zerocopy_enable = 0;
   SYSCTL_INT(_net_bpf, OID_AUTO, zerocopy_enable, CTLFLAG_RW,
       &bpf_zerocopy_enable, 0, "Enable new zero-copy BPF buffer sessions");
   SYSCTL_NODE(_net_bpf, OID_AUTO, stats, CTLFLAG_MPSAFE | CTLFLAG_RW,
       bpf_stats_sysctl, "bpf statistics portal");
   
   static VNET_DEFINE(int, bpf_optimize_writers) = 0;
   #define V_bpf_optimize_writers VNET(bpf_optimize_writers)
   SYSCTL_VNET_INT(_net_bpf, OID_AUTO, optimize_writers,
       CTLFLAG_RW, &VNET_NAME(bpf_optimize_writers), 0,
       "Do not send packets until BPF program is set");
   
   static  d_open_t        bpfopen;
   static  d_read_t        bpfread;
   static  d_write_t       bpfwrite;
   static  d_ioctl_t       bpfioctl;
   static  d_poll_t        bpfpoll;
   static  d_kqfilter_t    bpfkqfilter;
   
   static struct cdevsw bpf_cdevsw = {
           .d_version =    D_VERSION,
           .d_open =       bpfopen,
           .d_read =       bpfread,
           .d_write =      bpfwrite,
           .d_ioctl =      bpfioctl,
           .d_poll =       bpfpoll,
           .d_name =       "bpf",
           .d_kqfilter =   bpfkqfilter,
   };
   
   static struct filterops bpfread_filtops =
           { 1, NULL, filt_bpfdetach, filt_bpfread };
   
   eventhandler_tag        bpf_ifdetach_cookie = NULL;
   
   /*
    * LOCKING MODEL USED BY BPF:
    * Locks:
    * 1) global lock (BPF_LOCK). Mutex, used to protect interface addition/removal,
    * some global counters and every bpf_if reference.
    * 2) Interface lock. Rwlock, used to protect list of BPF descriptors and their filters.
    * 3) Descriptor lock. Mutex, used to protect BPF buffers and various structure fields
    *   used by bpf_mtap code.
    *
    * Lock order:
    *
    * Global lock, interface lock, descriptor lock
    *
    * We have to acquire interface lock before descriptor main lock due to BPF_MTAP[2]
    * working model. In many places (like bpf_detachd) we start with BPF descriptor
    * (and we need to at least rlock it to get reliable interface pointer). This
    * gives us potential LOR. As a result, we use global lock to protect from bpf_if
    * change in every such place.
    *
    * Changing d->bd_bif is protected by 1) global lock, 2) interface lock and
    * 3) descriptor main wlock.
    * Reading bd_bif can be protected by any of these locks, typically global lock.
    *
    * Changing read/write BPF filter is protected by the same three locks,
    * the same applies for reading.
    *
    * Sleeping in global lock is not allowed due to bpfdetach() using it.
    */
   
   /*
    * Wrapper functions for various buffering methods.  If the set of buffer
    * modes expands, we will probably want to introduce a switch data structure
    * similar to protosw, et.
    */
   static void
   bpf_append_bytes(struct bpf_d *d, caddr_t buf, u_int offset, void *src,
       u_int len)
   {
   
           BPFD_LOCK_ASSERT(d);
   
           switch (d->bd_bufmode) {
           case BPF_BUFMODE_BUFFER:
                   return (bpf_buffer_append_bytes(d, buf, offset, src, len));
   
           case BPF_BUFMODE_ZBUF:
                   d->bd_zcopy++;
                   return (bpf_zerocopy_append_bytes(d, buf, offset, src, len));
   
           default:
                   panic("bpf_buf_append_bytes");
           }
   }
   
   static void
   bpf_append_mbuf(struct bpf_d *d, caddr_t buf, u_int offset, void *src,
       u_int len)
   {
   
           BPFD_LOCK_ASSERT(d);
   
           switch (d->bd_bufmode) {
           case BPF_BUFMODE_BUFFER:
                   return (bpf_buffer_append_mbuf(d, buf, offset, src, len));
   
           case BPF_BUFMODE_ZBUF:
                   d->bd_zcopy++;
                   return (bpf_zerocopy_append_mbuf(d, buf, offset, src, len));
   
           default:
                   panic("bpf_buf_append_mbuf");
           }
   }
   
   /*
    * This function gets called when the free buffer is re-assigned.
    */
   static void
   bpf_buf_reclaimed(struct bpf_d *d)
   {
   
           BPFD_LOCK_ASSERT(d);
   
           switch (d->bd_bufmode) {
           case BPF_BUFMODE_BUFFER:
                   return;
   
           case BPF_BUFMODE_ZBUF:
                   bpf_zerocopy_buf_reclaimed(d);
                   return;
   
           default:
                   panic("bpf_buf_reclaimed");
           }
   }
   
   /*
    * If the buffer mechanism has a way to decide that a held buffer can be made
    * free, then it is exposed via the bpf_canfreebuf() interface.  (1) is
    * returned if the buffer can be discarded, (0) is returned if it cannot.
    */
   static int
   bpf_canfreebuf(struct bpf_d *d)
   {
   
           BPFD_LOCK_ASSERT(d);
   
           switch (d->bd_bufmode) {
           case BPF_BUFMODE_ZBUF:
                   return (bpf_zerocopy_canfreebuf(d));
           }
           return (0);
   }
   
   /*
    * Allow the buffer model to indicate that the current store buffer is
    * immutable, regardless of the appearance of space.  Return (1) if the
    * buffer is writable, and (0) if not.
    */
   static int
   bpf_canwritebuf(struct bpf_d *d)
   {
           BPFD_LOCK_ASSERT(d);
   
           switch (d->bd_bufmode) {
           case BPF_BUFMODE_ZBUF:
                   return (bpf_zerocopy_canwritebuf(d));
           }
           return (1);
   }
   
   /*
    * Notify buffer model that an attempt to write to the store buffer has
    * resulted in a dropped packet, in which case the buffer may be considered
    * full.
    */
   static void
   bpf_buffull(struct bpf_d *d)
   {
   
           BPFD_LOCK_ASSERT(d);
   
           switch (d->bd_bufmode) {
           case BPF_BUFMODE_ZBUF:
                   bpf_zerocopy_buffull(d);
                   break;
           }
   }
   
   /*
    * Notify the buffer model that a buffer has moved into the hold position.
    */
   void
   bpf_bufheld(struct bpf_d *d)
   {
   
           BPFD_LOCK_ASSERT(d);
   
           switch (d->bd_bufmode) {
           case BPF_BUFMODE_ZBUF:
                   bpf_zerocopy_bufheld(d);
                   break;
           }
   }
   
   static void
   bpf_free(struct bpf_d *d)
   {
   
           switch (d->bd_bufmode) {
           case BPF_BUFMODE_BUFFER:
                   return (bpf_buffer_free(d));
   
           case BPF_BUFMODE_ZBUF:
                   return (bpf_zerocopy_free(d));
   
           default:
                   panic("bpf_buf_free");
           }
   }
   
   static int
   bpf_uiomove(struct bpf_d *d, caddr_t buf, u_int len, struct uio *uio)
   {
   
           if (d->bd_bufmode != BPF_BUFMODE_BUFFER)
                   return (EOPNOTSUPP);
           return (bpf_buffer_uiomove(d, buf, len, uio));
   }
   
   static int
   bpf_ioctl_sblen(struct bpf_d *d, u_int *i)
   {
   
           if (d->bd_bufmode != BPF_BUFMODE_BUFFER)
                   return (EOPNOTSUPP);
           return (bpf_buffer_ioctl_sblen(d, i));
   }
   
   static int
   bpf_ioctl_getzmax(struct thread *td, struct bpf_d *d, size_t *i)
   {
   
           if (d->bd_bufmode != BPF_BUFMODE_ZBUF)
                   return (EOPNOTSUPP);
           return (bpf_zerocopy_ioctl_getzmax(td, d, i));
   }
   
   static int
   bpf_ioctl_rotzbuf(struct thread *td, struct bpf_d *d, struct bpf_zbuf *bz)
   {
   
           if (d->bd_bufmode != BPF_BUFMODE_ZBUF)
                   return (EOPNOTSUPP);
           return (bpf_zerocopy_ioctl_rotzbuf(td, d, bz));
   }
   
   static int
   bpf_ioctl_setzbuf(struct thread *td, struct bpf_d *d, struct bpf_zbuf *bz)
   {
   
           if (d->bd_bufmode != BPF_BUFMODE_ZBUF)
                   return (EOPNOTSUPP);
           return (bpf_zerocopy_ioctl_setzbuf(td, d, bz));
   }
   
   /*
    * General BPF functions.
    */
   static int
   bpf_movein(struct uio *uio, int linktype, struct ifnet *ifp, struct mbuf **mp,
       struct sockaddr *sockp, int *hdrlen, struct bpf_insn *wfilter)
   {
           const struct ieee80211_bpf_params *p;
           struct ether_header *eh;
           struct mbuf *m;
           int error;
           int len;
           int hlen;
           int slen;
   
           /*
            * Build a sockaddr based on the data link layer type.
            * We do this at this level because the ethernet header
            * is copied directly into the data field of the sockaddr.
            * In the case of SLIP, there is no header and the packet
            * is forwarded as is.
            * Also, we are careful to leave room at the front of the mbuf
            * for the link level header.
            */
           switch (linktype) {
   
           case DLT_SLIP:
                   sockp->sa_family = AF_INET;
                   hlen = 0;
                   break;
   
           case DLT_EN10MB:
                   sockp->sa_family = AF_UNSPEC;
                   /* XXX Would MAXLINKHDR be better? */
                   hlen = ETHER_HDR_LEN;
                   break;
   
           case DLT_FDDI:
                   sockp->sa_family = AF_IMPLINK;
                   hlen = 0;
                   break;
   
           case DLT_RAW:
                   sockp->sa_family = AF_UNSPEC;
                   hlen = 0;
                   break;
   
           case DLT_NULL:
                   /*
                    * null interface types require a 4 byte pseudo header which
                    * corresponds to the address family of the packet.
                    */
                   sockp->sa_family = AF_UNSPEC;
                   hlen = 4;
                   break;
   
           case DLT_ATM_RFC1483:
                   /*
                    * en atm driver requires 4-byte atm pseudo header.
                    * though it isn't standard, vpi:vci needs to be
                    * specified anyway.
                    */
                   sockp->sa_family = AF_UNSPEC;
                   hlen = 12;      /* XXX 4(ATM_PH) + 3(LLC) + 5(SNAP) */
                   break;
   
           case DLT_PPP:
                   sockp->sa_family = AF_UNSPEC;
                   hlen = 4;       /* This should match PPP_HDRLEN */
                   break;
   
           case DLT_IEEE802_11:            /* IEEE 802.11 wireless */
                   sockp->sa_family = AF_IEEE80211;
                   hlen = 0;
                   break;
   
           case DLT_IEEE802_11_RADIO:      /* IEEE 802.11 wireless w/ phy params */
                   sockp->sa_family = AF_IEEE80211;
                   sockp->sa_len = 12;     /* XXX != 0 */
                   hlen = sizeof(struct ieee80211_bpf_params);
                   break;
   
           default:
                   return (EIO);
           }
   
           len = uio->uio_resid;
   
           if (len - hlen > ifp->if_mtu)
                   return (EMSGSIZE);
   
           if ((unsigned)len > MJUM16BYTES)
                   return (EIO);
   
           if (len <= MHLEN)
                   MGETHDR(m, M_WAIT, MT_DATA);
           else if (len <= MCLBYTES)
                   m = m_getcl(M_WAIT, MT_DATA, M_PKTHDR);
           else
                   m = m_getjcl(M_WAIT, MT_DATA, M_PKTHDR,
   #if (MJUMPAGESIZE > MCLBYTES)
                       len <= MJUMPAGESIZE ? MJUMPAGESIZE :
   #endif
                       (len <= MJUM9BYTES ? MJUM9BYTES : MJUM16BYTES));
           m->m_pkthdr.len = m->m_len = len;
           m->m_pkthdr.rcvif = NULL;
           *mp = m;
   
           if (m->m_len < hlen) {
                   error = EPERM;
                   goto bad;
           }
   
           error = uiomove(mtod(m, u_char *), len, uio);
           if (error)
                   goto bad;
   
           slen = bpf_filter(wfilter, mtod(m, u_char *), len, len);
           if (slen == 0) {
                   error = EPERM;
                   goto bad;
           }
   
           /* Check for multicast destination */
           switch (linktype) {
           case DLT_EN10MB:
                   eh = mtod(m, struct ether_header *);
                   if (ETHER_IS_MULTICAST(eh->ether_dhost)) {
                           if (bcmp(ifp->if_broadcastaddr, eh->ether_dhost,
                               ETHER_ADDR_LEN) == 0)
                                   m->m_flags |= M_BCAST;
                           else
                                   m->m_flags |= M_MCAST;
                   }
                   break;
           }
   
           /*
            * Make room for link header, and copy it to sockaddr
            */
           if (hlen != 0) {
                   if (sockp->sa_family == AF_IEEE80211) {
                           /*
                            * Collect true length from the parameter header
                            * NB: sockp is known to be zero'd so if we do a
                            *     short copy unspecified parameters will be
                            *     zero.
                            * NB: packet may not be aligned after stripping
                            *     bpf params
                            * XXX check ibp_vers
                            */
                           p = mtod(m, const struct ieee80211_bpf_params *);
                           hlen = p->ibp_len;
                           if (hlen > sizeof(sockp->sa_data)) {
                                   error = EINVAL;
                                   goto bad;
                           }
                   }
                   bcopy(m->m_data, sockp->sa_data, hlen);
           }
           *hdrlen = hlen;
   
           return (0);
   bad:
           m_freem(m);
           return (error);
   }
   
   /*
    * Attach file to the bpf interface, i.e. make d listen on bp.
    */
   static void
   bpf_attachd(struct bpf_d *d, struct bpf_if *bp)
   {
           int op_w;
   
           BPF_LOCK_ASSERT();
   
           /*
            * Save sysctl value to protect from sysctl change
            * between reads
            */
           op_w = V_bpf_optimize_writers;
   
           if (d->bd_bif != NULL)
                   bpf_detachd_locked(d);
           /*
            * Point d at bp, and add d to the interface's list.
            * Since there are many applicaiotns using BPF for
            * sending raw packets only (dhcpd, cdpd are good examples)
            * we can delay adding d to the list of active listeners until
            * some filter is configured.
            */
   
           BPFIF_WLOCK(bp);
           BPFD_LOCK(d);
   
           d->bd_bif = bp;
   
           if (op_w != 0) {
                   /* Add to writers-only list */
                   LIST_INSERT_HEAD(&bp->bif_wlist, d, bd_next);
                   /*
                    * We decrement bd_writer on every filter set operation.
                    * First BIOCSETF is done by pcap_open_live() to set up
                    * snap length. After that appliation usually sets its own filter
                    */
                   d->bd_writer = 2;
           } else
                   LIST_INSERT_HEAD(&bp->bif_dlist, d, bd_next);
   
           BPFD_UNLOCK(d);
           BPFIF_WUNLOCK(bp);
   
           bpf_bpfd_cnt++;
   
           CTR3(KTR_NET, "%s: bpf_attach called by pid %d, adding to %s list",
               __func__, d->bd_pid, d->bd_writer ? "writer" : "active");
   
           if (op_w == 0)
                   EVENTHANDLER_INVOKE(bpf_track, bp->bif_ifp, bp->bif_dlt, 1);
   }
   
   /*
    * Add d to the list of active bp filters.
    * Reuqires bpf_attachd() to be called before
    */
   static void
   bpf_upgraded(struct bpf_d *d)
   {
           struct bpf_if *bp;
   
           BPF_LOCK_ASSERT();
   
           bp = d->bd_bif;
   
           /*
            * Filter can be set several times without specifying interface.
            * Mark d as reader and exit.
            */
           if (bp == NULL) {
                   BPFD_LOCK(d);
                   d->bd_writer = 0;
                   BPFD_UNLOCK(d);
                   return;
           }
   
           BPFIF_WLOCK(bp);
           BPFD_LOCK(d);
   
           /* Remove from writers-only list */
           LIST_REMOVE(d, bd_next);
           LIST_INSERT_HEAD(&bp->bif_dlist, d, bd_next);
           /* Mark d as reader */
           d->bd_writer = 0;
   
           BPFD_UNLOCK(d);
           BPFIF_WUNLOCK(bp);
   
           CTR2(KTR_NET, "%s: upgrade required by pid %d", __func__, d->bd_pid);
   
           EVENTHANDLER_INVOKE(bpf_track, bp->bif_ifp, bp->bif_dlt, 1);
   }
   
   /*
    * Detach a file from its interface.
    */
   static void
   bpf_detachd(struct bpf_d *d)
   {
           BPF_LOCK();
           bpf_detachd_locked(d);
           BPF_UNLOCK();
   }
   
   static void
   bpf_detachd_locked(struct bpf_d *d)
   {
           int error;
           struct bpf_if *bp;
           struct ifnet *ifp;
   
           CTR2(KTR_NET, "%s: detach required by pid %d", __func__, d->bd_pid);
   
           BPF_LOCK_ASSERT();
   
           /* Check if descriptor is attached */
           if ((bp = d->bd_bif) == NULL)
                   return;
   
           BPFIF_WLOCK(bp);
           BPFD_LOCK(d);
   
           /* Save bd_writer value */
           error = d->bd_writer;
   
           /*
            * Remove d from the interface's descriptor list.
            */
           LIST_REMOVE(d, bd_next);
   
           ifp = bp->bif_ifp;
           d->bd_bif = NULL;
           BPFD_UNLOCK(d);
           BPFIF_WUNLOCK(bp);
   
           bpf_bpfd_cnt--;
   
           /* Call event handler iff d is attached */
           if (error == 0)
                   EVENTHANDLER_INVOKE(bpf_track, ifp, bp->bif_dlt, 0);
   
           /*
            * Check if this descriptor had requested promiscuous mode.
            * If so, turn it off.
            */
           if (d->bd_promisc) {
                   d->bd_promisc = 0;
                   CURVNET_SET(ifp->if_vnet);
                   error = ifpromisc(ifp, 0);
                   CURVNET_RESTORE();
                   if (error != 0 && error != ENXIO) {
                           /*
                            * ENXIO can happen if a pccard is unplugged
                            * Something is really wrong if we were able to put
                            * the driver into promiscuous mode, but can't
                            * take it out.
                            */
                           if_printf(bp->bif_ifp,
                                   "bpf_detach: ifpromisc failed (%d)\n", error);
                   }
           }
   }
   
   /*
    * Close the descriptor by detaching it from its interface,
    * deallocating its buffers, and marking it free.
    */
   static void
   bpf_dtor(void *data)
   {
           struct bpf_d *d = data;
   
           BPFD_LOCK(d);
           if (d->bd_state == BPF_WAITING)
                   callout_stop(&d->bd_callout);
           d->bd_state = BPF_IDLE;
           BPFD_UNLOCK(d);
           funsetown(&d->bd_sigio);
           bpf_detachd(d);
   #ifdef MAC
           mac_bpfdesc_destroy(d);
   #endif /* MAC */
           seldrain(&d->bd_sel);
           knlist_destroy(&d->bd_sel.si_note);
           callout_drain(&d->bd_callout);
           bpf_freed(d);
           free(d, M_BPF);
   }
   
   /*
    * Open ethernet device.  Returns ENXIO for illegal minor device number,
    * EBUSY if file is open by another process.
    */
   /* ARGSUSED */
   static  int
   bpfopen(struct cdev *dev, int flags, int fmt, struct thread *td)
   {
           struct bpf_d *d;
           int error, size;
   
           d = malloc(sizeof(*d), M_BPF, M_WAITOK | M_ZERO);
           error = devfs_set_cdevpriv(d, bpf_dtor);
           if (error != 0) {
                   free(d, M_BPF);
                   return (error);
           }
   
           /*
            * For historical reasons, perform a one-time initialization call to
            * the buffer routines, even though we're not yet committed to a
            * particular buffer method.
            */
           bpf_buffer_init(d);
           d->bd_bufmode = BPF_BUFMODE_BUFFER;
           d->bd_sig = SIGIO;
           d->bd_direction = BPF_D_INOUT;
           BPF_PID_REFRESH(d, td);
   #ifdef MAC
           mac_bpfdesc_init(d);
           mac_bpfdesc_create(td->td_ucred, d);
   #endif
           mtx_init(&d->bd_lock, devtoname(dev), "bpf cdev lock", MTX_DEF);
           callout_init_mtx(&d->bd_callout, &d->bd_lock, 0);
           knlist_init_mtx(&d->bd_sel.si_note, &d->bd_lock);
   
           /* Allocate default buffers */
           size = d->bd_bufsize;
           bpf_buffer_ioctl_sblen(d, &size);
   
           return (0);
   }
   
   /*
    *  bpfread - read next chunk of packets from buffers
    */
   static  int
   bpfread(struct cdev *dev, struct uio *uio, int ioflag)
   {
           struct bpf_d *d;
           int error;
           int non_block;
           int timed_out;
   
           error = devfs_get_cdevpriv((void **)&d);
           if (error != 0)
                   return (error);
   
           /*
            * Restrict application to use a buffer the same size as
            * as kernel buffers.
            */
           if (uio->uio_resid != d->bd_bufsize)
                   return (EINVAL);
   
           non_block = ((ioflag & O_NONBLOCK) != 0);
   
           BPFD_LOCK(d);
           BPF_PID_REFRESH_CUR(d);
           if (d->bd_bufmode != BPF_BUFMODE_BUFFER) {
                   BPFD_UNLOCK(d);
                   return (EOPNOTSUPP);
           }
           if (d->bd_state == BPF_WAITING)
                   callout_stop(&d->bd_callout);
           timed_out = (d->bd_state == BPF_TIMED_OUT);
           d->bd_state = BPF_IDLE;
           /*
            * If the hold buffer is empty, then do a timed sleep, which
            * ends when the timeout expires or when enough packets
            * have arrived to fill the store buffer.
            */
           while (d->bd_hbuf == NULL) {
                   if (d->bd_slen != 0) {
                           /*
                            * A packet(s) either arrived since the previous
                            * read or arrived while we were asleep.
                            */
                           if (d->bd_immediate || non_block || timed_out) {
                                   /*
                                    * Rotate the buffers and return what's here
                                    * if we are in immediate mode, non-blocking
                                    * flag is set, or this descriptor timed out.
                                    */
                                   ROTATE_BUFFERS(d);
                                   break;
                           }
                   }
   
                   /*
                    * No data is available, check to see if the bpf device
                    * is still pointed at a real interface.  If not, return
                    * ENXIO so that the userland process knows to rebind
                    * it before using it again.
                    */
                   if (d->bd_bif == NULL) {
                           BPFD_UNLOCK(d);
                           return (ENXIO);
                   }
   
                   if (non_block) {
                           BPFD_UNLOCK(d);
                           return (EWOULDBLOCK);
                   }
                   error = msleep(d, &d->bd_lock, PRINET|PCATCH,
                        "bpf", d->bd_rtout);
                   if (error == EINTR || error == ERESTART) {
                           BPFD_UNLOCK(d);
                           return (error);
                   }
                   if (error == EWOULDBLOCK) {
                           /*
                            * On a timeout, return what's in the buffer,
                            * which may be nothing.  If there is something
                            * in the store buffer, we can rotate the buffers.
                            */
                           if (d->bd_hbuf)
                                   /*
                                    * We filled up the buffer in between
                                    * getting the timeout and arriving
                                    * here, so we don't need to rotate.
                                    */
                                   break;
   
                           if (d->bd_slen == 0) {
                                   BPFD_UNLOCK(d);
                                   return (0);
                           }
                           ROTATE_BUFFERS(d);
                           break;
                   }
           }
           /*
            * At this point, we know we have something in the hold slot.
            */
           BPFD_UNLOCK(d);
   
           /*
            * Move data from hold buffer into user space.
            * We know the entire buffer is transferred since
            * we checked above that the read buffer is bpf_bufsize bytes.
            *
            * XXXRW: More synchronization needed here: what if a second thread
            * issues a read on the same fd at the same time?  Don't want this
            * getting invalidated.
            */
           error = bpf_uiomove(d, d->bd_hbuf, d->bd_hlen, uio);
   
           BPFD_LOCK(d);
           d->bd_fbuf = d->bd_hbuf;
           d->bd_hbuf = NULL;
           d->bd_hlen = 0;
           bpf_buf_reclaimed(d);
           BPFD_UNLOCK(d);
   
           return (error);
   }
   
   /*
    * If there are processes sleeping on this descriptor, wake them up.
    */
   static __inline void
   bpf_wakeup(struct bpf_d *d)
   {
   
           BPFD_LOCK_ASSERT(d);
           if (d->bd_state == BPF_WAITING) {
                   callout_stop(&d->bd_callout);
                   d->bd_state = BPF_IDLE;
           }
           wakeup(d);
           if (d->bd_async && d->bd_sig && d->bd_sigio)
                   pgsigio(&d->bd_sigio, d->bd_sig, 0);
   
           selwakeuppri(&d->bd_sel, PRINET);
           KNOTE_LOCKED(&d->bd_sel.si_note, 0);
   }
   
   static void
   bpf_timed_out(void *arg)
   {
           struct bpf_d *d = (struct bpf_d *)arg;
   
           BPFD_LOCK_ASSERT(d);
   
           if (callout_pending(&d->bd_callout) || !callout_active(&d->bd_callout))
                   return;
           if (d->bd_state == BPF_WAITING) {
                   d->bd_state = BPF_TIMED_OUT;
                   if (d->bd_slen != 0)
                           bpf_wakeup(d);
           }
   }
   
   static int
   bpf_ready(struct bpf_d *d)
   {
   
           BPFD_LOCK_ASSERT(d);
   
          if (!bpf_canfreebuf(d) && d->bd_hlen != 0)
                  return (1);
          if ((d->bd_immediate || d->bd_state == BPF_TIMED_OUT) &&
              d->bd_slen != 0)
                  return (1);
          return (0);
  }
  
  static int
  bpfwrite(struct cdev *dev, struct uio *uio, int ioflag)
  {
          struct bpf_d *d;
          struct ifnet *ifp;
          struct mbuf *m, *mc;
          struct sockaddr dst;
          int error, hlen;
  
          error = devfs_get_cdevpriv((void **)&d);
          if (error != 0)
                  return (error);
  
          BPF_PID_REFRESH_CUR(d);
          d->bd_wcount++;
          /* XXX: locking required */
          if (d->bd_bif == NULL) {
                  d->bd_wdcount++;
                  return (ENXIO);
          }
  
          ifp = d->bd_bif->bif_ifp;
  
          if ((ifp->if_flags & IFF_UP) == 0) {
                  d->bd_wdcount++;
                  return (ENETDOWN);
          }
  
          if (uio->uio_resid == 0) {
                  d->bd_wdcount++;
                  return (0);
          }
  
          bzero(&dst, sizeof(dst));
          m = NULL;
          hlen = 0;
          /* XXX: bpf_movein() can sleep */
          error = bpf_movein(uio, (int)d->bd_bif->bif_dlt, ifp,
              &m, &dst, &hlen, d->bd_wfilter);
          if (error) {
                  d->bd_wdcount++;
                  return (error);
          }
          d->bd_wfcount++;
          if (d->bd_hdrcmplt)
                  dst.sa_family = pseudo_AF_HDRCMPLT;
  
          if (d->bd_feedback) {
                  mc = m_dup(m, M_DONTWAIT);
                  if (mc != NULL)
                          mc->m_pkthdr.rcvif = ifp;
                  /* Set M_PROMISC for outgoing packets to be discarded. */
                  if (d->bd_direction == BPF_D_INOUT)
                          m->m_flags |= M_PROMISC;
          } else
                  mc = NULL;
  
          m->m_pkthdr.len -= hlen;
          m->m_len -= hlen;
          m->m_data += hlen;      /* XXX */
  
          CURVNET_SET(ifp->if_vnet);
  #ifdef MAC
          BPFD_LOCK(d);
          mac_bpfdesc_create_mbuf(d, m);
          if (mc != NULL)
                  mac_bpfdesc_create_mbuf(d, mc);
          BPFD_UNLOCK(d);
  #endif
  
          error = (*ifp->if_output)(ifp, m, &dst, NULL);
          if (error)
                  d->bd_wdcount++;
  
          if (mc != NULL) {
                  if (error == 0)
                          (*ifp->if_input)(ifp, mc);
                  else
                          m_freem(mc);
          }
          CURVNET_RESTORE();
  
          return (error);
  }
  
  /*
   * Reset a descriptor by flushing its packet buffer and clearing the receive
   * and drop counts.  This is doable for kernel-only buffers, but with
   * zero-copy buffers, we can't write to (or rotate) buffers that are
   * currently owned by userspace.  It would be nice if we could encapsulate
   * this logic in the buffer code rather than here.
   */
  static void
  reset_d(struct bpf_d *d)
  {
  
          BPFD_LOCK_ASSERT(d);
  
          if ((d->bd_hbuf != NULL) &&
              (d->bd_bufmode != BPF_BUFMODE_ZBUF || bpf_canfreebuf(d))) {
                  /* Free the hold buffer. */
                  d->bd_fbuf = d->bd_hbuf;
                  d->bd_hbuf = NULL;
                  d->bd_hlen = 0;
                  bpf_buf_reclaimed(d);
          }
          if (bpf_canwritebuf(d))
                  d->bd_slen = 0;
          d->bd_rcount = 0;
          d->bd_dcount = 0;
          d->bd_fcount = 0;
          d->bd_wcount = 0;
          d->bd_wfcount = 0;
          d->bd_wdcount = 0;
          d->bd_zcopy = 0;
  }
  
  /*
   *  FIONREAD            Check for read packet available.
   *  SIOCGIFADDR         Get interface address - convenient hook to driver.
   *  BIOCGBLEN           Get buffer len [for read()].
   *  BIOCSETF            Set read filter.
   *  BIOCSETFNR          Set read filter without resetting descriptor.
   *  BIOCSETWF           Set write filter.
   *  BIOCFLUSH           Flush read packet buffer.
   *  BIOCPROMISC         Put interface into promiscuous mode.
   *  BIOCGDLT            Get link layer type.
   *  BIOCGETIF           Get interface name.
   *  BIOCSETIF           Set interface.
   *  BIOCSRTIMEOUT       Set read timeout.
   *  BIOCGRTIMEOUT       Get read timeout.
   *  BIOCGSTATS          Get packet stats.
   *  BIOCIMMEDIATE       Set immediate mode.
   *  BIOCVERSION         Get filter language version.
   *  BIOCGHDRCMPLT       Get "header already complete" flag
   *  BIOCSHDRCMPLT       Set "header already complete" flag
   *  BIOCGDIRECTION      Get packet direction flag
   *  BIOCSDIRECTION      Set packet direction flag
   *  BIOCLOCK            Set "locked" flag
   *  BIOCFEEDBACK        Set packet feedback mode.
   *  BIOCSETZBUF         Set current zero-copy buffer locations.
   *  BIOCGETZMAX         Get maximum zero-copy buffer size.
   *  BIOCROTZBUF         Force rotation of zero-copy buffer
   *  BIOCSETBUFMODE      Set buffer mode.
   *  BIOCGETBUFMODE      Get current buffer mode.
   */
  /* ARGSUSED */
  static  int
  bpfioctl(struct cdev *dev, u_long cmd, caddr_t addr, int flags,
      struct thread *td)
  {
          struct bpf_d *d;
          int error;
  
          error = devfs_get_cdevpriv((void **)&d);
          if (error != 0)
                  return (error);
  
          /*
           * Refresh PID associated with this descriptor.
           */
          BPFD_LOCK(d);
          BPF_PID_REFRESH(d, td);
          if (d->bd_state == BPF_WAITING)
                  callout_stop(&d->bd_callout);
          d->bd_state = BPF_IDLE;
          BPFD_UNLOCK(d);
  
          if (d->bd_locked == 1) {
                  switch (cmd) {
                  case BIOCGBLEN:
                  case BIOCFLUSH:
                  case BIOCGDLT:
                  case BIOCGDLTLIST:
  #ifdef COMPAT_FREEBSD32
                  case BIOCGDLTLIST32:
  #endif
                  case BIOCGETIF:
                  case BIOCGRTIMEOUT:
  #ifdef COMPAT_FREEBSD32
                  case BIOCGRTIMEOUT32:
  #endif
                  case BIOCGSTATS:
                  case BIOCVERSION:
                  case BIOCGRSIG:
                  case BIOCGHDRCMPLT:
                  case BIOCFEEDBACK:
                  case FIONREAD:
                  case BIOCLOCK:
                  case BIOCSRTIMEOUT:
  #ifdef COMPAT_FREEBSD32
                  case BIOCSRTIMEOUT32:
  #endif
                  case BIOCIMMEDIATE:
                  case TIOCGPGRP:
                  case BIOCROTZBUF:
                          break;
                  default:
                          return (EPERM);
                  }
          }
  #ifdef COMPAT_FREEBSD32
          /*
           * If we see a 32-bit compat ioctl, mark the stream as 32-bit so
           * that it will get 32-bit packet headers.
           */
          switch (cmd) {
          case BIOCSETF32:
          case BIOCSETFNR32:
          case BIOCSETWF32:
          case BIOCGDLTLIST32:
          case BIOCGRTIMEOUT32:
          case BIOCSRTIMEOUT32:
                  BPFD_LOCK(d);
                  d->bd_compat32 = 1;
                  BPFD_UNLOCK(d);
          }
  #endif
  
          CURVNET_SET(TD_TO_VNET(td));
          switch (cmd) {
  
          default:
                  error = EINVAL;
                  break;
  
          /*
           * Check for read packet available.
           */
          case FIONREAD:
                  {
                          int n;
  
                          BPFD_LOCK(d);
                          n = d->bd_slen;
                          if (d->bd_hbuf)
                                  n += d->bd_hlen;
                          BPFD_UNLOCK(d);
  
                          *(int *)addr = n;
                          break;
                  }
  
          case SIOCGIFADDR:
                  {
                          struct ifnet *ifp;
  
                          if (d->bd_bif == NULL)
                                  error = EINVAL;
                          else {
                                  ifp = d->bd_bif->bif_ifp;
                                  error = (*ifp->if_ioctl)(ifp, cmd, addr);
                          }
                          break;
                  }
  
          /*
           * Get buffer len [for read()].
           */
          case BIOCGBLEN:
                  BPFD_LOCK(d);
                  *(u_int *)addr = d->bd_bufsize;
                  BPFD_UNLOCK(d);
                  break;
  
          /*
           * Set buffer length.
           */
          case BIOCSBLEN:
                  error = bpf_ioctl_sblen(d, (u_int *)addr);
                  break;
  
          /*
           * Set link layer read filter.
           */
          case BIOCSETF:
          case BIOCSETFNR:
          case BIOCSETWF:
  #ifdef COMPAT_FREEBSD32
          case BIOCSETF32:
          case BIOCSETFNR32:
          case BIOCSETWF32:
  #endif
                  error = bpf_setf(d, (struct bpf_program *)addr, cmd);
                  break;
  
          /*
           * Flush read packet buffer.
           */
          case BIOCFLUSH:
                  BPFD_LOCK(d);
                  reset_d(d);
                  BPFD_UNLOCK(d);
                  break;
  
          /*
           * Put interface into promiscuous mode.
           */
          case BIOCPROMISC:
                  if (d->bd_bif == NULL) {
                          /*
                           * No interface attached yet.
                           */
                          error = EINVAL;
                          break;
                  }
                  if (d->bd_promisc == 0) {
                          error = ifpromisc(d->bd_bif->bif_ifp, 1);
                          if (error == 0)
                                  d->bd_promisc = 1;
                  }
                  break;
  
          /*
           * Get current data link type.
           */
          case BIOCGDLT:
                  BPF_LOCK();
                  if (d->bd_bif == NULL)
                          error = EINVAL;
                  else
                          *(u_int *)addr = d->bd_bif->bif_dlt;
                  BPF_UNLOCK();
                  break;
  
          /*
           * Get a list of supported data link types.
           */
  #ifdef COMPAT_FREEBSD32
          case BIOCGDLTLIST32:
                  {
                          struct bpf_dltlist32 *list32;
                          struct bpf_dltlist dltlist;
  
                          list32 = (struct bpf_dltlist32 *)addr;
                          dltlist.bfl_len = list32->bfl_len;
                          dltlist.bfl_list = PTRIN(list32->bfl_list);
                          BPF_LOCK();
                          if (d->bd_bif == NULL)
                                  error = EINVAL;
                          else {
                                  error = bpf_getdltlist(d, &dltlist);
                                  if (error == 0)
                                          list32->bfl_len = dltlist.bfl_len;
                          }
                          BPF_UNLOCK();
                          break;
                  }
  #endif
  
          case BIOCGDLTLIST:
                  BPF_LOCK();
                  if (d->bd_bif == NULL)
                          error = EINVAL;
                  else
                          error = bpf_getdltlist(d, (struct bpf_dltlist *)addr);
                  BPF_UNLOCK();
                  break;
  
          /*
           * Set data link type.
           */
          case BIOCSDLT:
                  BPF_LOCK();
                  if (d->bd_bif == NULL)
                          error = EINVAL;
                  else
                          error = bpf_setdlt(d, *(u_int *)addr);
                  BPF_UNLOCK();
                  break;
  
          /*
           * Get interface name.
           */
          case BIOCGETIF:
                  BPF_LOCK();
                  if (d->bd_bif == NULL)
                          error = EINVAL;
                  else {
                          struct ifnet *const ifp = d->bd_bif->bif_ifp;
                          struct ifreq *const ifr = (struct ifreq *)addr;
  
                          strlcpy(ifr->ifr_name, ifp->if_xname,
                              sizeof(ifr->ifr_name));
                  }
                  BPF_UNLOCK();
                  break;
  
          /*
           * Set interface.
           */
          case BIOCSETIF:
                  BPF_LOCK();
                  error = bpf_setif(d, (struct ifreq *)addr);
                  BPF_UNLOCK();
                  break;
  
          /*
           * Set read timeout.
           */
          case BIOCSRTIMEOUT:
  #ifdef COMPAT_FREEBSD32
          case BIOCSRTIMEOUT32:
  #endif
                  {
                          struct timeval *tv = (struct timeval *)addr;
  #ifdef COMPAT_FREEBSD32
                          struct timeval32 *tv32;
                          struct timeval tv64;
  
                          if (cmd == BIOCSRTIMEOUT32) {
                                  tv32 = (struct timeval32 *)addr;
                                  tv = &tv64;
                                  tv->tv_sec = tv32->tv_sec;
                                  tv->tv_usec = tv32->tv_usec;
                          } else
  #endif
                                  tv = (struct timeval *)addr;
  
                          /*
                           * Subtract 1 tick from tvtohz() since this isn't
                           * a one-shot timer.
                           */
                          if ((error = itimerfix(tv)) == 0)
                                  d->bd_rtout = tvtohz(tv) - 1;
                          break;
                  }
  
          /*
           * Get read timeout.
           */
          case BIOCGRTIMEOUT:
  #ifdef COMPAT_FREEBSD32
          case BIOCGRTIMEOUT32:
  #endif
                  {
                          struct timeval *tv;
  #ifdef COMPAT_FREEBSD32
                          struct timeval32 *tv32;
                          struct timeval tv64;
  
                          if (cmd == BIOCGRTIMEOUT32)
                                  tv = &tv64;
                          else
  #endif
                                  tv = (struct timeval *)addr;
  
                          tv->tv_sec = d->bd_rtout / hz;
                          tv->tv_usec = (d->bd_rtout % hz) * tick;
  #ifdef COMPAT_FREEBSD32
                          if (cmd == BIOCGRTIMEOUT32) {
                                  tv32 = (struct timeval32 *)addr;
                                  tv32->tv_sec = tv->tv_sec;
                                  tv32->tv_usec = tv->tv_usec;
                          }
  #endif
  
                          break;
                  }
  
          /*
           * Get packet stats.
           */
          case BIOCGSTATS:
                  {
                          struct bpf_stat *bs = (struct bpf_stat *)addr;
  
                          /* XXXCSJP overflow */
                          bs->bs_recv = d->bd_rcount;
                          bs->bs_drop = d->bd_dcount;
                          break;
                  }
  
          /*
           * Set immediate mode.
           */
          case BIOCIMMEDIATE:
                  BPFD_LOCK(d);
                  d->bd_immediate = *(u_int *)addr;
                  BPFD_UNLOCK(d);
                  break;
  
          case BIOCVERSION:
                  {
                          struct bpf_version *bv = (struct bpf_version *)addr;
  
                          bv->bv_major = BPF_MAJOR_VERSION;
                          bv->bv_minor = BPF_MINOR_VERSION;
                          break;
                  }
  
          /*
           * Get "header already complete" flag
           */
          case BIOCGHDRCMPLT:
                  BPFD_LOCK(d);
                  *(u_int *)addr = d->bd_hdrcmplt;
                  BPFD_UNLOCK(d);
                  break;
  
          /*
           * Set "header already complete" flag
           */
          case BIOCSHDRCMPLT:
                  BPFD_LOCK(d);
                  d->bd_hdrcmplt = *(u_int *)addr ? 1 : 0;
                  BPFD_UNLOCK(d);
                  break;
  
          /*
           * Get packet direction flag
           */
          case BIOCGDIRECTION:
                  BPFD_LOCK(d);
                  *(u_int *)addr = d->bd_direction;
                  BPFD_UNLOCK(d);
                  break;
  
          /*
           * Set packet direction flag
           */
          case BIOCSDIRECTION:
                  {
                          u_int   direction;
  
                          direction = *(u_int *)addr;
                          switch (direction) {
                          case BPF_D_IN:
                          case BPF_D_INOUT:
                          case BPF_D_OUT:
                                  BPFD_LOCK(d);
                                  d->bd_direction = direction;
                                  BPFD_UNLOCK(d);
                                  break;
                          default:
                                  error = EINVAL;
                          }
                  }
                  break;
  
          case BIOCFEEDBACK:
                  BPFD_LOCK(d);
                  d->bd_feedback = *(u_int *)addr;
                  BPFD_UNLOCK(d);
                  break;
  
          case BIOCLOCK:
                  BPFD_LOCK(d);
                  d->bd_locked = 1;
                  BPFD_UNLOCK(d);
                  break;
  
          case FIONBIO:           /* Non-blocking I/O */
                  break;
  
          case FIOASYNC:          /* Send signal on receive packets */
                  BPFD_LOCK(d);
                  d->bd_async = *(int *)addr;
                  BPFD_UNLOCK(d);
                  break;
  
          case FIOSETOWN:
                  /*
                   * XXX: Add some sort of locking here?
                   * fsetown() can sleep.
                   */
                  error = fsetown(*(int *)addr, &d->bd_sigio);
                  break;
  
          case FIOGETOWN:
                  BPFD_LOCK(d);
                  *(int *)addr = fgetown(&d->bd_sigio);
                  BPFD_UNLOCK(d);
                  break;
  
          /* This is deprecated, FIOSETOWN should be used instead. */
          case TIOCSPGRP:
                  error = fsetown(-(*(int *)addr), &d->bd_sigio);
                  break;
  
          /* This is deprecated, FIOGETOWN should be used instead. */
          case TIOCGPGRP:
                  *(int *)addr = -fgetown(&d->bd_sigio);
                  break;
  
          case BIOCSRSIG:         /* Set receive signal */
                  {
                          u_int sig;
  
                          sig = *(u_int *)addr;
  
                          if (sig >= NSIG)
                                  error = EINVAL;
                          else {
                                  BPFD_LOCK(d);
                                  d->bd_sig = sig;
                                  BPFD_UNLOCK(d);
                          }
                          break;
                  }
          case BIOCGRSIG:
                  BPFD_LOCK(d);
                  *(u_int *)addr = d->bd_sig;
                  BPFD_UNLOCK(d);
                  break;
  
          case BIOCGETBUFMODE:
                  BPFD_LOCK(d);
                  *(u_int *)addr = d->bd_bufmode;
                  BPFD_UNLOCK(d);
                  break;
  
          case BIOCSETBUFMODE:
                  /*
                   * Allow the buffering mode to be changed as long as we
                   * haven't yet committed to a particular mode.  Our
                   * definition of commitment, for now, is whether or not a
                   * buffer has been allocated or an interface attached, since
                   * that's the point where things get tricky.
                   */
                  switch (*(u_int *)addr) {
                  case BPF_BUFMODE_BUFFER:
                          break;
  
                  case BPF_BUFMODE_ZBUF:
                          if (bpf_zerocopy_enable)
                                  break;
                          /* FALLSTHROUGH */
  
                  default:
                          CURVNET_RESTORE();
                          return (EINVAL);
                  }
  
                  BPFD_LOCK(d);
                  if (d->bd_sbuf != NULL || d->bd_hbuf != NULL ||
                      d->bd_fbuf != NULL || d->bd_bif != NULL) {
                          BPFD_UNLOCK(d);
                          CURVNET_RESTORE();
                          return (EBUSY);
                  }
                  d->bd_bufmode = *(u_int *)addr;
                  BPFD_UNLOCK(d);
                  break;
  
          case BIOCGETZMAX:
                  error = bpf_ioctl_getzmax(td, d, (size_t *)addr);
                  break;
  
          case BIOCSETZBUF:
                  error = bpf_ioctl_setzbuf(td, d, (struct bpf_zbuf *)addr);
                  break;
  
          case BIOCROTZBUF:
                  error = bpf_ioctl_rotzbuf(td, d, (struct bpf_zbuf *)addr);
                  break;
          }
          CURVNET_RESTORE();
          return (error);
  }
  
  /*
   * Set d's packet filter program to fp.  If this file already has a filter,
   * free it and replace it.  Returns EINVAL for bogus requests.
   *
   * Note we need global lock here to serialize bpf_setf() and bpf_setif() calls
   * since reading d->bd_bif can't be protected by d or interface lock due to
   * lock order.
   *
   * Additionally, we have to acquire interface write lock due to bpf_mtap() uses
   * interface read lock to read all filers.
   *
   */
  static int
  bpf_setf(struct bpf_d *d, struct bpf_program *fp, u_long cmd)
  {
  #ifdef COMPAT_FREEBSD32
          struct bpf_program fp_swab;
          struct bpf_program32 *fp32;
  #endif
          struct bpf_insn *fcode, *old;
  #ifdef BPF_JITTER
          bpf_jit_filter *jfunc, *ofunc;
  #endif
          size_t size;
          u_int flen;
          int need_upgrade;
  
  #ifdef COMPAT_FREEBSD32
          switch (cmd) {
          case BIOCSETF32:
          case BIOCSETWF32:
          case BIOCSETFNR32:
                  fp32 = (struct bpf_program32 *)fp;
                  fp_swab.bf_len = fp32->bf_len;
                  fp_swab.bf_insns = (struct bpf_insn *)(uintptr_t)fp32->bf_insns;
                  fp = &fp_swab;
                  switch (cmd) {
                  case BIOCSETF32:
                          cmd = BIOCSETF;
                          break;
                  case BIOCSETWF32:
                          cmd = BIOCSETWF;
                          break;
                  }
                  break;
          }
  #endif
  
          fcode = NULL;
  #ifdef BPF_JITTER
          jfunc = ofunc = NULL;
  #endif
          need_upgrade = 0;
  
          /*
           * Check new filter validness before acquiring any locks.
           * Allocate memory for new filter, if needed.
           */
          flen = fp->bf_len;
          if (flen > bpf_maxinsns || (fp->bf_insns == NULL && flen != 0))
                  return (EINVAL);
          size = flen * sizeof(*fp->bf_insns);
          if (size > 0) {
                  /* We're setting up new filter.  Copy and check actual data. */
                  fcode = malloc(size, M_BPF, M_WAITOK);
                  if (copyin(fp->bf_insns, fcode, size) != 0 ||
                      !bpf_validate(fcode, flen)) {
                          free(fcode, M_BPF);
                          return (EINVAL);
                  }
  #ifdef BPF_JITTER
                  /* Filter is copied inside fcode and is perfectly valid. */
                  jfunc = bpf_jitter(fcode, flen);
  #endif
          }
  
          BPF_LOCK();
  
          /*
           * Set up new filter.
           * Protect filter change by interface lock.
           * Additionally, we are protected by global lock here.
           */
          if (d->bd_bif != NULL)
                  BPFIF_WLOCK(d->bd_bif);
          BPFD_LOCK(d);
          if (cmd == BIOCSETWF) {
                  old = d->bd_wfilter;
                  d->bd_wfilter = fcode;
          } else {
                  old = d->bd_rfilter;
                  d->bd_rfilter = fcode;
  #ifdef BPF_JITTER
                  ofunc = d->bd_bfilter;
                  d->bd_bfilter = jfunc;
  #endif
                  if (cmd == BIOCSETF)
                          reset_d(d);
  
                  if (fcode != NULL) {
                          /*
                           * Do not require upgrade by first BIOCSETF
                           * (used to set snaplen) by pcap_open_live().
                           */
                          if (d->bd_writer != 0 && --d->bd_writer == 0)
                                  need_upgrade = 1;
                          CTR4(KTR_NET, "%s: filter function set by pid %d, "
                              "bd_writer counter %d, need_upgrade %d",
                              __func__, d->bd_pid, d->bd_writer, need_upgrade);
                  }
          }
          BPFD_UNLOCK(d);
          if (d->bd_bif != NULL)
                  BPFIF_WUNLOCK(d->bd_bif);
          if (old != NULL)
                  free(old, M_BPF);
  #ifdef BPF_JITTER
          if (ofunc != NULL)
                  bpf_destroy_jit_filter(ofunc);
  #endif
  
          /* Move d to active readers list. */
          if (need_upgrade)
                  bpf_upgraded(d);
  
          BPF_UNLOCK();
          return (0);
  }
  
  /*
   * Detach a file from its current interface (if attached at all) and attach
   * to the interface indicated by the name stored in ifr.
   * Return an errno or 0.
   */
  static int
  bpf_setif(struct bpf_d *d, struct ifreq *ifr)
  {
          struct bpf_if *bp;
          struct ifnet *theywant;
  
          BPF_LOCK_ASSERT();
  
          theywant = ifunit(ifr->ifr_name);
          if (theywant == NULL || theywant->if_bpf == NULL)
                  return (ENXIO);
  
          bp = theywant->if_bpf;
  
          /* Check if interface is not being detached from BPF */
          BPFIF_RLOCK(bp);
          if (bp->flags & BPFIF_FLAG_DYING) {
                  BPFIF_RUNLOCK(bp);
                  return (ENXIO);
          }
          BPFIF_RUNLOCK(bp);
  
          /*
           * Behavior here depends on the buffering model.  If we're using
           * kernel memory buffers, then we can allocate them here.  If we're
           * using zero-copy, then the user process must have registered
           * buffers by the time we get here.  If not, return an error.
           */
          switch (d->bd_bufmode) {
          case BPF_BUFMODE_BUFFER:
          case BPF_BUFMODE_ZBUF:
                  if (d->bd_sbuf == NULL)
                          return (EINVAL);
                  break;
  
          default:
                  panic("bpf_setif: bufmode %d", d->bd_bufmode);
          }
          if (bp != d->bd_bif)
                  bpf_attachd(d, bp);
          BPFD_LOCK(d);
          reset_d(d);
          BPFD_UNLOCK(d);
          return (0);
  }
  
  /*
   * Support for select() and poll() system calls
   *
   * Return true iff the specific operation will not block indefinitely.
   * Otherwise, return false but make a note that a selwakeup() must be done.
   */
  static int
  bpfpoll(struct cdev *dev, int events, struct thread *td)
  {
          struct bpf_d *d;
          int revents;
  
          if (devfs_get_cdevpriv((void **)&d) != 0 || d->bd_bif == NULL)
                  return (events &
                      (POLLHUP|POLLIN|POLLRDNORM|POLLOUT|POLLWRNORM));
  
          /*
           * Refresh PID associated with this descriptor.
           */
          revents = events & (POLLOUT | POLLWRNORM);
          BPFD_LOCK(d);
          BPF_PID_REFRESH(d, td);
          if (events & (POLLIN | POLLRDNORM)) {
                  if (bpf_ready(d))
                          revents |= events & (POLLIN | POLLRDNORM);
                  else {
                          selrecord(td, &d->bd_sel);
                          /* Start the read timeout if necessary. */
                          if (d->bd_rtout > 0 && d->bd_state == BPF_IDLE) {
                                  callout_reset(&d->bd_callout, d->bd_rtout,
                                      bpf_timed_out, d);
                                  d->bd_state = BPF_WAITING;
                          }
                  }
          }
          BPFD_UNLOCK(d);
          return (revents);
  }
  
  /*
   * Support for kevent() system call.  Register EVFILT_READ filters and
   * reject all others.
   */
  int
  bpfkqfilter(struct cdev *dev, struct knote *kn)
  {
          struct bpf_d *d;
  
          if (devfs_get_cdevpriv((void **)&d) != 0 ||
              kn->kn_filter != EVFILT_READ)
                  return (1);
  
          /*
           * Refresh PID associated with this descriptor.
           */
          BPFD_LOCK(d);
          BPF_PID_REFRESH_CUR(d);
          kn->kn_fop = &bpfread_filtops;
          kn->kn_hook = d;
          knlist_add(&d->bd_sel.si_note, kn, 1);
          BPFD_UNLOCK(d);
  
          return (0);
  }
  
  static void
  filt_bpfdetach(struct knote *kn)
  {
          struct bpf_d *d = (struct bpf_d *)kn->kn_hook;
  
          knlist_remove(&d->bd_sel.si_note, kn, 0);
  }
  
  static int
  filt_bpfread(struct knote *kn, long hint)
  {
          struct bpf_d *d = (struct bpf_d *)kn->kn_hook;
          int ready;
  
          BPFD_LOCK_ASSERT(d);
          ready = bpf_ready(d);
          if (ready) {
                  kn->kn_data = d->bd_slen;
                  if (d->bd_hbuf)
                          kn->kn_data += d->bd_hlen;
          } else if (d->bd_rtout > 0 && d->bd_state == BPF_IDLE) {
                  callout_reset(&d->bd_callout, d->bd_rtout,
                      bpf_timed_out, d);
                  d->bd_state = BPF_WAITING;
          }
  
          return (ready);
  }
  
  /*
   * Incoming linkage from device drivers.  Process the packet pkt, of length
   * pktlen, which is stored in a contiguous buffer.  The packet is parsed
   * by each process' filter, and if accepted, stashed into the corresponding
   * buffer.
   */
  void
  bpf_tap(struct bpf_if *bp, u_char *pkt, u_int pktlen)
  {
          struct bpf_d *d;
  #ifdef BPF_JITTER
          bpf_jit_filter *bf;
  #endif
          u_int slen;
          int gottime;
          struct timeval tv;
  
          gottime = 0;
  
          BPFIF_RLOCK(bp);
  
          LIST_FOREACH(d, &bp->bif_dlist, bd_next) {
                  /*
                   * We are not using any locks for d here because:
                   * 1) any filter change is protected by interface
                   * write lock
                   * 2) destroying/detaching d is protected by interface
                   * write lock, too
                   */
  
                  /* XXX: Do not protect counter for the sake of performance. */
                  ++d->bd_rcount;
                  /*
                   * NB: We dont call BPF_CHECK_DIRECTION() here since there is no
                   * way for the caller to indiciate to us whether this packet
                   * is inbound or outbound.  In the bpf_mtap() routines, we use
                   * the interface pointers on the mbuf to figure it out.
                   */
  #ifdef BPF_JITTER
                  bf = bpf_jitter_enable != 0 ? d->bd_bfilter : NULL;
                  if (bf != NULL)
                          slen = (*(bf->func))(pkt, pktlen, pktlen);
                  else
  #endif
                  slen = bpf_filter(d->bd_rfilter, pkt, pktlen, pktlen);
                  if (slen != 0) {
                          /*
                           * Filter matches. Let's to acquire write lock.
                           */
                          BPFD_LOCK(d);
  
                          d->bd_fcount++;
                          if (!gottime) {
                                  microtime(&tv);
                                  gottime = 1;
                          }
  #ifdef MAC
                          if (mac_bpfdesc_check_receive(d, bp->bif_ifp) == 0)
  #endif
                                  catchpacket(d, pkt, pktlen, slen,
                                      bpf_append_bytes, &tv);
                          BPFD_UNLOCK(d);
                  }
          }
          BPFIF_RUNLOCK(bp);
  }
  
  #define BPF_CHECK_DIRECTION(d, r, i)                            \
              (((d)->bd_direction == BPF_D_IN && (r) != (i)) ||   \
              ((d)->bd_direction == BPF_D_OUT && (r) == (i)))
  
  /*
   * Incoming linkage from device drivers, when packet is in an mbuf chain.
   * Locking model is explained in bpf_tap().
   */
  void
  bpf_mtap(struct bpf_if *bp, struct mbuf *m)
  {
          struct bpf_d *d;
  #ifdef BPF_JITTER
          bpf_jit_filter *bf;
  #endif
          u_int pktlen, slen;
          int gottime;
          struct timeval tv;
  
          /* Skip outgoing duplicate packets. */
          if ((m->m_flags & M_PROMISC) != 0 && m->m_pkthdr.rcvif == NULL) {
                  m->m_flags &= ~M_PROMISC;
                  return;
          }
  
          gottime = 0;
  
          pktlen = m_length(m, NULL);
  
          BPFIF_RLOCK(bp);
  
          LIST_FOREACH(d, &bp->bif_dlist, bd_next) {
                  if (BPF_CHECK_DIRECTION(d, m->m_pkthdr.rcvif, bp->bif_ifp))
                          continue;
                  ++d->bd_rcount;
  #ifdef BPF_JITTER
                  bf = bpf_jitter_enable != 0 ? d->bd_bfilter : NULL;
                  /* XXX We cannot handle multiple mbufs. */
                  if (bf != NULL && m->m_next == NULL)
                          slen = (*(bf->func))(mtod(m, u_char *), pktlen, pktlen);
                  else
  #endif
                  slen = bpf_filter(d->bd_rfilter, (u_char *)m, pktlen, 0);
                  if (slen != 0) {
                          BPFD_LOCK(d);
  
                          d->bd_fcount++;
                          if (!gottime) {
                                  microtime(&tv);
                                  gottime = 1;
                          }
  #ifdef MAC
                          if (mac_bpfdesc_check_receive(d, bp->bif_ifp) == 0)
  #endif
                                  catchpacket(d, (u_char *)m, pktlen, slen,
                                      bpf_append_mbuf, &tv);
                          BPFD_UNLOCK(d);
                  }
          }
          BPFIF_RUNLOCK(bp);
  }
  
  /*
   * Incoming linkage from device drivers, when packet is in
   * an mbuf chain and to be prepended by a contiguous header.
   */
  void
  bpf_mtap2(struct bpf_if *bp, void *data, u_int dlen, struct mbuf *m)
  {
          struct mbuf mb;
          struct bpf_d *d;
          u_int pktlen, slen;
          int gottime;
          struct timeval tv;
  
          /* Skip outgoing duplicate packets. */
          if ((m->m_flags & M_PROMISC) != 0 && m->m_pkthdr.rcvif == NULL) {
                  m->m_flags &= ~M_PROMISC;
                  return;
          }
  
          gottime = 0;
  
          pktlen = m_length(m, NULL);
          /*
           * Craft on-stack mbuf suitable for passing to bpf_filter.
           * Note that we cut corners here; we only setup what's
           * absolutely needed--this mbuf should never go anywhere else.
           */
          mb.m_next = m;
          mb.m_data = data;
          mb.m_len = dlen;
          pktlen += dlen;
  
  
          BPFIF_RLOCK(bp);
  
          LIST_FOREACH(d, &bp->bif_dlist, bd_next) {
                  if (BPF_CHECK_DIRECTION(d, m->m_pkthdr.rcvif, bp->bif_ifp))
                          continue;
                  ++d->bd_rcount;
                  slen = bpf_filter(d->bd_rfilter, (u_char *)&mb, pktlen, 0);
                  if (slen != 0) {
                          BPFD_LOCK(d);
  
                          d->bd_fcount++;
                          if (!gottime) {
                                  microtime(&tv);
                                  gottime = 1;
                          }
  #ifdef MAC
                          if (mac_bpfdesc_check_receive(d, bp->bif_ifp) == 0)
  #endif
                                  catchpacket(d, (u_char *)&mb, pktlen, slen,
                                      bpf_append_mbuf, &tv);
                          BPFD_UNLOCK(d);
                  }
          }
          BPFIF_RUNLOCK(bp);
  }
  
  #undef  BPF_CHECK_DIRECTION
  
  /*
   * Move the packet data from interface memory (pkt) into the
   * store buffer.  "cpfn" is the routine called to do the actual data
   * transfer.  bcopy is passed in to copy contiguous chunks, while
   * bpf_append_mbuf is passed in to copy mbuf chains.  In the latter case,
   * pkt is really an mbuf.
   */
  static void
  catchpacket(struct bpf_d *d, u_char *pkt, u_int pktlen, u_int snaplen,
      void (*cpfn)(struct bpf_d *, caddr_t, u_int, void *, u_int),
      struct timeval *tv)
  {
          struct bpf_hdr hdr;
  #ifdef COMPAT_FREEBSD32
          struct bpf_hdr32 hdr32;
  #endif
          int totlen, curlen;
          int hdrlen = d->bd_bif->bif_hdrlen;
          int do_wakeup = 0;
  
          BPFD_LOCK_ASSERT(d);
  
          /*
           * Detect whether user space has released a buffer back to us, and if
           * so, move it from being a hold buffer to a free buffer.  This may
           * not be the best place to do it (for example, we might only want to
           * run this check if we need the space), but for now it's a reliable
           * spot to do it.
           */
          if (d->bd_fbuf == NULL && bpf_canfreebuf(d)) {
                  d->bd_fbuf = d->bd_hbuf;
                  d->bd_hbuf = NULL;
                  d->bd_hlen = 0;
                  bpf_buf_reclaimed(d);
          }
  
          /*
           * Figure out how many bytes to move.  If the packet is
           * greater or equal to the snapshot length, transfer that
           * much.  Otherwise, transfer the whole packet (unless
           * we hit the buffer size limit).
           */
          totlen = hdrlen + min(snaplen, pktlen);
          if (totlen > d->bd_bufsize)
                  totlen = d->bd_bufsize;
  
          /*
           * Round up the end of the previous packet to the next longword.
           *
           * Drop the packet if there's no room and no hope of room
           * If the packet would overflow the storage buffer or the storage
           * buffer is considered immutable by the buffer model, try to rotate
           * the buffer and wakeup pending processes.
           */
  #ifdef COMPAT_FREEBSD32
          if (d->bd_compat32)
                  curlen = BPF_WORDALIGN32(d->bd_slen);
          else
  #endif
                  curlen = BPF_WORDALIGN(d->bd_slen);
          if (curlen + totlen > d->bd_bufsize || !bpf_canwritebuf(d)) {
                  if (d->bd_fbuf == NULL) {
                          /*
                           * There's no room in the store buffer, and no
                           * prospect of room, so drop the packet.  Notify the
                           * buffer model.
                           */
                          bpf_buffull(d);
                          ++d->bd_dcount;
                          return;
                  }
                  ROTATE_BUFFERS(d);
                  do_wakeup = 1;
                  curlen = 0;
          } else if (d->bd_immediate || d->bd_state == BPF_TIMED_OUT)
                  /*
                   * Immediate mode is set, or the read timeout has already
                   * expired during a select call.  A packet arrived, so the
                   * reader should be woken up.
                   */
                  do_wakeup = 1;
  #ifdef COMPAT_FREEBSD32
          /*
           * If this is a 32-bit stream, then stick a 32-bit header at the
           * front and copy the data into the buffer.
           */
          if (d->bd_compat32) {
                  bzero(&hdr32, sizeof(hdr32));
                  hdr32.bh_tstamp.tv_sec = tv->tv_sec;
                  hdr32.bh_tstamp.tv_usec = tv->tv_usec;
                  hdr32.bh_datalen = pktlen;
                  hdr32.bh_hdrlen = hdrlen;
                  hdr.bh_caplen = hdr32.bh_caplen = totlen - hdrlen;
                  bpf_append_bytes(d, d->bd_sbuf, curlen, &hdr32, sizeof(hdr32));
                  goto copy;
          }
  #endif
  
          /*
           * Append the bpf header.  Note we append the actual header size, but
           * move forward the length of the header plus padding.
           */
          bzero(&hdr, sizeof(hdr));
          hdr.bh_tstamp = *tv;
          hdr.bh_datalen = pktlen;
          hdr.bh_hdrlen = hdrlen;
          hdr.bh_caplen = totlen - hdrlen;
          bpf_append_bytes(d, d->bd_sbuf, curlen, &hdr, sizeof(hdr));
  
          /*
           * Copy the packet data into the store buffer and update its length.
           */
  #ifdef COMPAT_FREEBSD32
   copy:
  #endif
          (*cpfn)(d, d->bd_sbuf, curlen + hdrlen, pkt, hdr.bh_caplen);
          d->bd_slen = curlen + totlen;
  
          if (do_wakeup)
                  bpf_wakeup(d);
  }
  
  /*
   * Free buffers currently in use by a descriptor.
   * Called on close.
   */
  static void
  bpf_freed(struct bpf_d *d)
  {
  
          /*
           * We don't need to lock out interrupts since this descriptor has
           * been detached from its interface and it yet hasn't been marked
           * free.
           */
          bpf_free(d);
          if (d->bd_rfilter != NULL) {
                  free((caddr_t)d->bd_rfilter, M_BPF);
  #ifdef BPF_JITTER
                  if (d->bd_bfilter != NULL)
                          bpf_destroy_jit_filter(d->bd_bfilter);
  #endif
          }
          if (d->bd_wfilter != NULL)
                  free((caddr_t)d->bd_wfilter, M_BPF);
          mtx_destroy(&d->bd_lock);
  }
  
  /*
   * Attach an interface to bpf.  dlt is the link layer type; hdrlen is the
   * fixed size of the link header (variable length headers not yet supported).
   */
  void
  bpfattach(struct ifnet *ifp, u_int dlt, u_int hdrlen)
  {
  
          bpfattach2(ifp, dlt, hdrlen, &ifp->if_bpf);
  }
  
  /*
   * Attach an interface to bpf.  ifp is a pointer to the structure
   * defining the interface to be attached, dlt is the link layer type,
   * and hdrlen is the fixed size of the link header (variable length
   * headers are not yet supporrted).
   */
  void
  bpfattach2(struct ifnet *ifp, u_int dlt, u_int hdrlen, struct bpf_if **driverp)
  {
          struct bpf_if *bp;
  
          bp = malloc(sizeof(*bp), M_BPF, M_NOWAIT | M_ZERO);
          if (bp == NULL)
                  panic("bpfattach");
  
          LIST_INIT(&bp->bif_dlist);
          LIST_INIT(&bp->bif_wlist);
          bp->bif_ifp = ifp;
          bp->bif_dlt = dlt;
          rw_init(&bp->bif_lock, "bpf interface lock");
          KASSERT(*driverp == NULL, ("bpfattach2: driverp already initialized"));
          *driverp = bp;
  
          BPF_LOCK();
          LIST_INSERT_HEAD(&bpf_iflist, bp, bif_next);
          BPF_UNLOCK();
  
          /*
           * Compute the length of the bpf header.  This is not necessarily
           * equal to SIZEOF_BPF_HDR because we want to insert spacing such
           * that the network layer header begins on a longword boundary (for
           * performance reasons and to alleviate alignment restrictions).
           */
          bp->bif_hdrlen = BPF_WORDALIGN(hdrlen + SIZEOF_BPF_HDR) - hdrlen;
  
          if (bootverbose)
                  if_printf(ifp, "bpf attached\n");
  }
  
  /*
   * Detach bpf from an interface. This involves detaching each descriptor
   * associated with the interface. Notify each descriptor as it's detached
   * so that any sleepers wake up and get ENXIO.
   */
  void
  bpfdetach(struct ifnet *ifp)
  {
          struct bpf_if   *bp;
          struct bpf_d    *d;
  #ifdef INVARIANTS
          int ndetached;
  
          ndetached = 0;
  #endif
  
          BPF_LOCK();
          /* Find all bpf_if struct's which reference ifp and detach them. */
          do {
                  LIST_FOREACH(bp, &bpf_iflist, bif_next) {
                          if (ifp == bp->bif_ifp)
                                  break;
                  }
                  if (bp != NULL)
                          LIST_REMOVE(bp, bif_next);
  
                  if (bp != NULL) {
  #ifdef INVARIANTS
                          ndetached++;
  #endif
                          while ((d = LIST_FIRST(&bp->bif_dlist)) != NULL) {
                                  bpf_detachd_locked(d);
                                  BPFD_LOCK(d);
                                  bpf_wakeup(d);
                                  BPFD_UNLOCK(d);
                          }
                          /* Free writer-only descriptors */
                          while ((d = LIST_FIRST(&bp->bif_wlist)) != NULL) {
                                  bpf_detachd_locked(d);
                                  BPFD_LOCK(d);
                                  bpf_wakeup(d);
                                  BPFD_UNLOCK(d);
                          }
  
                          /*
                           * Delay freing bp till interface is detached
                           * and all routes through this interface are removed.
                           * Mark bp as detached to restrict new consumers.
                           */
                          BPFIF_WLOCK(bp);
                          bp->flags |= BPFIF_FLAG_DYING;
                          BPFIF_WUNLOCK(bp);
                  }
          } while (bp != NULL);
          BPF_UNLOCK();
  
  #ifdef INVARIANTS
          if (ndetached == 0)
                  printf("bpfdetach: %s was not attached\n", ifp->if_xname);
  #endif
  }
  
  /*
   * Interface departure handler.
   * Note departure event does not guarantee interface is going down.
   */
  static void
  bpf_ifdetach(void *arg __unused, struct ifnet *ifp)
  {
          struct bpf_if *bp;
  
          BPF_LOCK();
          if ((bp = ifp->if_bpf) == NULL) {
                  BPF_UNLOCK();
                  return;
          }
  
          /* Check if bpfdetach() was called previously */
          if ((bp->flags & BPFIF_FLAG_DYING) == 0) {
                  BPF_UNLOCK();
                  return;
          }
  
          CTR3(KTR_NET, "%s: freing BPF instance %p for interface %p",
              __func__, bp, ifp);
  
          ifp->if_bpf = NULL;
          BPF_UNLOCK();
  
          rw_destroy(&bp->bif_lock);
          free(bp, M_BPF);
  }
  
  /*
   * Get a list of available data link type of the interface.
   */
  static int
  bpf_getdltlist(struct bpf_d *d, struct bpf_dltlist *bfl)
  {
          int n, error;
          struct ifnet *ifp;
          struct bpf_if *bp;
  
          BPF_LOCK_ASSERT();
  
          ifp = d->bd_bif->bif_ifp;
          n = 0;
          error = 0;
          LIST_FOREACH(bp, &bpf_iflist, bif_next) {
                  if (bp->bif_ifp != ifp)
                          continue;
                  if (bfl->bfl_list != NULL) {
                          if (n >= bfl->bfl_len)
                                  return (ENOMEM);
                          error = copyout(&bp->bif_dlt,
                              bfl->bfl_list + n, sizeof(u_int));
                  }
                  n++;
          }
          bfl->bfl_len = n;
          return (error);
  }
  
  /*
   * Set the data link type of a BPF instance.
   */
  static int
  bpf_setdlt(struct bpf_d *d, u_int dlt)
  {
          int error, opromisc;
          struct ifnet *ifp;
          struct bpf_if *bp;
  
          BPF_LOCK_ASSERT();
  
          if (d->bd_bif->bif_dlt == dlt)
                  return (0);
          ifp = d->bd_bif->bif_ifp;
  
          LIST_FOREACH(bp, &bpf_iflist, bif_next) {
                  if (bp->bif_ifp == ifp && bp->bif_dlt == dlt)
                          break;
          }
  
          if (bp != NULL) {
                  opromisc = d->bd_promisc;
                  bpf_attachd(d, bp);
                  BPFD_LOCK(d);
                  reset_d(d);
                  BPFD_UNLOCK(d);
                  if (opromisc) {
                          error = ifpromisc(bp->bif_ifp, 1);
                          if (error)
                                  if_printf(bp->bif_ifp,
                                          "bpf_setdlt: ifpromisc failed (%d)\n",
                                          error);
                          else
                                  d->bd_promisc = 1;
                  }
          }
          return (bp == NULL ? EINVAL : 0);
  }
  
  static void
  bpf_drvinit(void *unused)
  {
          struct cdev *dev;
  
          mtx_init(&bpf_mtx, "bpf global lock", NULL, MTX_DEF);
          LIST_INIT(&bpf_iflist);
  
          dev = make_dev(&bpf_cdevsw, 0, UID_ROOT, GID_WHEEL, 0600, "bpf");
          /* For compatibility */
          make_dev_alias(dev, "bpf0");
  
          /* Register interface departure handler */
          bpf_ifdetach_cookie = EVENTHANDLER_REGISTER(
                      ifnet_departure_event, bpf_ifdetach, NULL,
                      EVENTHANDLER_PRI_ANY);
  }
  
  /*
   * Zero out the various packet counters associated with all of the bpf
   * descriptors.  At some point, we will probably want to get a bit more
   * granular and allow the user to specify descriptors to be zeroed.
   */
  static void
  bpf_zero_counters(void)
  {
          struct bpf_if *bp;
          struct bpf_d *bd;
  
          BPF_LOCK();
          LIST_FOREACH(bp, &bpf_iflist, bif_next) {
                  BPFIF_RLOCK(bp);
                  LIST_FOREACH(bd, &bp->bif_dlist, bd_next) {
                          BPFD_LOCK(bd);
                          bd->bd_rcount = 0;
                          bd->bd_dcount = 0;
                          bd->bd_fcount = 0;
                          bd->bd_wcount = 0;
                          bd->bd_wfcount = 0;
                          bd->bd_zcopy = 0;
                          BPFD_UNLOCK(bd);
                  }
                  BPFIF_RUNLOCK(bp);
          }
          BPF_UNLOCK();
  }
  
  /*
   * Fill filter statistics
   */
  static void
  bpfstats_fill_xbpf(struct xbpf_d *d, struct bpf_d *bd)
  {
  
          bzero(d, sizeof(*d));
          BPFD_LOCK_ASSERT(bd);
          d->bd_structsize = sizeof(*d);
          /* XXX: reading should be protected by global lock */
          d->bd_immediate = bd->bd_immediate;
          d->bd_promisc = bd->bd_promisc;
          d->bd_hdrcmplt = bd->bd_hdrcmplt;
          d->bd_direction = bd->bd_direction;
          d->bd_feedback = bd->bd_feedback;
          d->bd_async = bd->bd_async;
          d->bd_rcount = bd->bd_rcount;
          d->bd_dcount = bd->bd_dcount;
          d->bd_fcount = bd->bd_fcount;
          d->bd_sig = bd->bd_sig;
          d->bd_slen = bd->bd_slen;
          d->bd_hlen = bd->bd_hlen;
          d->bd_bufsize = bd->bd_bufsize;
          d->bd_pid = bd->bd_pid;
          strlcpy(d->bd_ifname,
              bd->bd_bif->bif_ifp->if_xname, IFNAMSIZ);
          d->bd_locked = bd->bd_locked;
          d->bd_wcount = bd->bd_wcount;
          d->bd_wdcount = bd->bd_wdcount;
          d->bd_wfcount = bd->bd_wfcount;
          d->bd_zcopy = bd->bd_zcopy;
          d->bd_bufmode = bd->bd_bufmode;
  }
  
  /*
   * Handle `netstat -B' stats request
   */
  static int
  bpf_stats_sysctl(SYSCTL_HANDLER_ARGS)
  {
          struct xbpf_d *xbdbuf, *xbd, zerostats;
          int index, error;
          struct bpf_if *bp;
          struct bpf_d *bd;
  
          /*
           * XXX This is not technically correct. It is possible for non
           * privileged users to open bpf devices. It would make sense
           * if the users who opened the devices were able to retrieve
           * the statistics for them, too.
           */
          error = priv_check(req->td, PRIV_NET_BPF);
          if (error)
                  return (error);
          /*
           * Check to see if the user is requesting that the counters be
           * zeroed out.  Explicitly check that the supplied data is zeroed,
           * as we aren't allowing the user to set the counters currently.
           */
          if (req->newptr != NULL) {
                  if (req->newlen != sizeof(zerostats))
                          return (EINVAL);
                  bzero(&zerostats, sizeof(zerostats));
                  xbd = req->newptr;
                  if (bcmp(xbd, &zerostats, sizeof(*xbd)) != 0)
                          return (EINVAL);
                  bpf_zero_counters();
                  return (0);
          }
          if (req->oldptr == NULL)
                  return (SYSCTL_OUT(req, 0, bpf_bpfd_cnt * sizeof(*xbd)));
          if (bpf_bpfd_cnt == 0)
                  return (SYSCTL_OUT(req, 0, 0));
          xbdbuf = malloc(req->oldlen, M_BPF, M_WAITOK);
          BPF_LOCK();
          if (req->oldlen < (bpf_bpfd_cnt * sizeof(*xbd))) {
                  BPF_UNLOCK();
                  free(xbdbuf, M_BPF);
                  return (ENOMEM);
          }
          index = 0;
          LIST_FOREACH(bp, &bpf_iflist, bif_next) {
                  BPFIF_RLOCK(bp);
                  /* Send writers-only first */
                  LIST_FOREACH(bd, &bp->bif_wlist, bd_next) {
                          xbd = &xbdbuf[index++];
                          BPFD_LOCK(bd);
                          bpfstats_fill_xbpf(xbd, bd);
                          BPFD_UNLOCK(bd);
                  }
                  LIST_FOREACH(bd, &bp->bif_dlist, bd_next) {
                          xbd = &xbdbuf[index++];
                          BPFD_LOCK(bd);
                          bpfstats_fill_xbpf(xbd, bd);
                          BPFD_UNLOCK(bd);
                  }
                  BPFIF_RUNLOCK(bp);
          }
          BPF_UNLOCK();
          error = SYSCTL_OUT(req, xbdbuf, index * sizeof(*xbd));
          free(xbdbuf, M_BPF);
          return (error);
  }
  
  SYSINIT(bpfdev,SI_SUB_DRIVERS,SI_ORDER_MIDDLE,bpf_drvinit,NULL);
  
  #else /* !DEV_BPF && !NETGRAPH_BPF */
  /*
   * NOP stubs to allow bpf-using drivers to load and function.
   *
   * A 'better' implementation would allow the core bpf functionality
   * to be loaded at runtime.
   */
  static struct bpf_if bp_null;
  
  void
  bpf_tap(struct bpf_if *bp, u_char *pkt, u_int pktlen)
  {
  }
  
  void
  bpf_mtap(struct bpf_if *bp, struct mbuf *m)
  {
  }
  
  void
  bpf_mtap2(struct bpf_if *bp, void *d, u_int l, struct mbuf *m)
  {
  }
  
  void
  bpfattach(struct ifnet *ifp, u_int dlt, u_int hdrlen)
  {
  
          bpfattach2(ifp, dlt, hdrlen, &ifp->if_bpf);
  }
  
  void
  bpfattach2(struct ifnet *ifp, u_int dlt, u_int hdrlen, struct bpf_if **driverp)
  {
  
          *driverp = &bp_null;
  }
  
  void
  bpfdetach(struct ifnet *ifp)
  {
  }
  
  u_int
  bpf_filter(const struct bpf_insn *pc, u_char *p, u_int wirelen, u_int buflen)
  {
          return -1;      /* "no filter" behaviour */
  }
  
  int
  bpf_validate(const struct bpf_insn *f, int len)
  {
          return 0;               /* false */
  }
  
  #endif /* !DEV_BPF && !NETGRAPH_BPF */

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