kernel - Fix some rare pmap races in i386 and x86_64.

[dragonfly.git] / 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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 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       8.2 (Berkeley) 3/28/94
 *
 * $FreeBSD: src/sys/net/bpf.c,v 1.59.2.12 2002/04/14 21:41:48 luigi Exp $
 * $DragonFly: src/sys/net/bpf.c,v 1.50 2008/09/23 11:28:49 sephe Exp $
 */

#include "use_bpf.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/conf.h>
#include <sys/device.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/time.h>
#include <sys/proc.h>
#include <sys/signalvar.h>
#include <sys/filio.h>
#include <sys/sockio.h>
#include <sys/ttycom.h>
#include <sys/filedesc.h>

#include <sys/poll.h>

#include <sys/socket.h>
#include <sys/vnode.h>

#include <sys/thread2.h>
#include <sys/mplock2.h>

#include <net/if.h>
#include <net/bpf.h>
#include <net/bpfdesc.h>
#include <net/netmsg2.h>

#include <netinet/in.h>
#include <netinet/if_ether.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>

#include <sys/devfs.h>

struct netmsg_bpf_output {
        struct netmsg   nm_netmsg;
        struct mbuf     *nm_mbuf;
        struct ifnet    *nm_ifp;
        struct sockaddr *nm_dst;
};

MALLOC_DEFINE(M_BPF, "BPF", "BPF data");
DEVFS_DECLARE_CLONE_BITMAP(bpf);

#if NBPF <= 1
#define BPF_PREALLOCATED_UNITS  4
#else
#define BPF_PREALLOCATED_UNITS  NBPF
#endif

#if NBPF > 0

/*
 * The default read buffer size is patchable.
 */
static int bpf_bufsize = BPF_DEFAULTBUFSIZE;
SYSCTL_INT(_debug, OID_AUTO, bpf_bufsize, CTLFLAG_RW,
           &bpf_bufsize, 0, "");
int bpf_maxbufsize = BPF_MAXBUFSIZE;
SYSCTL_INT(_debug, OID_AUTO, bpf_maxbufsize, CTLFLAG_RW,
           &bpf_maxbufsize, 0, "");

/*
 *  bpf_iflist is the list of interfaces; each corresponds to an ifnet
 */
static struct bpf_if    *bpf_iflist;

static int      bpf_allocbufs(struct bpf_d *);
static void     bpf_attachd(struct bpf_d *d, struct bpf_if *bp);
static void     bpf_detachd(struct bpf_d *d);
static void     bpf_resetd(struct bpf_d *);
static void     bpf_freed(struct bpf_d *);
static void     bpf_mcopy(const void *, void *, size_t);
static int      bpf_movein(struct uio *, int, struct mbuf **,
                           struct sockaddr *, int *, struct bpf_insn *);
static int      bpf_setif(struct bpf_d *, struct ifreq *);
static void     bpf_timed_out(void *);
static void     bpf_wakeup(struct bpf_d *);
static void     catchpacket(struct bpf_d *, u_char *, u_int, u_int,
                            void (*)(const void *, void *, size_t),
                            const struct timeval *);
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     bpf_drvinit(void *unused);

static d_open_t         bpfopen;
static d_clone_t        bpfclone;
static d_close_t        bpfclose;
static d_read_t         bpfread;
static d_write_t        bpfwrite;
static d_ioctl_t        bpfioctl;
static d_poll_t         bpfpoll;

#define CDEV_MAJOR 23
static struct dev_ops bpf_ops = {
        { "bpf", CDEV_MAJOR, 0 },
        .d_open =       bpfopen,
        .d_close =      bpfclose,
        .d_read =       bpfread,
        .d_write =      bpfwrite,
        .d_ioctl =      bpfioctl,
        .d_poll =       bpfpoll,
};


static int
bpf_movein(struct uio *uio, int linktype, struct mbuf **mp,
           struct sockaddr *sockp, int *datlen, struct bpf_insn *wfilter)
{
        struct mbuf *m;
        int error;
        int len;
        int hlen;
        int slen;

        *datlen = 0;
        *mp = NULL;

        /*
         * 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 = sizeof(struct ether_header);
                break;

        case DLT_RAW:
        case DLT_NULL:
                sockp->sa_family = AF_UNSPEC;
                hlen = 0;
                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;

        default:
                return(EIO);
        }

        len = uio->uio_resid;
        *datlen = len - hlen;
        if ((unsigned)len > MCLBYTES)
                return(EIO);

        m = m_getl(len, MB_WAIT, MT_DATA, M_PKTHDR, NULL);
        if (m == NULL)
                return(ENOBUFS);
        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;
        }

        /*
         * Make room for link header, and copy it to sockaddr.
         */
        if (hlen != 0) {
                bcopy(m->m_data, sockp->sa_data, hlen);
                m->m_pkthdr.len -= hlen;
                m->m_len -= hlen;
                m->m_data += hlen; /* XXX */
        }
        return (0);
bad:
        m_freem(m);
        return(error);
}

/*
 * Attach file to the bpf interface, i.e. make d listen on bp.
 * Must be called at splimp.
 */
static void
bpf_attachd(struct bpf_d *d, struct bpf_if *bp)
{
        /*
         * Point d at bp, and add d to the interface's list of listeners.
         * Finally, point the driver's bpf cookie at the interface so
         * it will divert packets to bpf.
         */
        d->bd_bif = bp;
        SLIST_INSERT_HEAD(&bp->bif_dlist, d, bd_next);
        *bp->bif_driverp = bp;
}

/*
 * Detach a file from its interface.
 */
static void
bpf_detachd(struct bpf_d *d)
{
        int error;
        struct bpf_if *bp;
        struct ifnet *ifp;

        bp = d->bd_bif;
        ifp = bp->bif_ifp;

        /* Remove d from the interface's descriptor list. */
        SLIST_REMOVE(&bp->bif_dlist, d, bpf_d, bd_next);

        if (SLIST_EMPTY(&bp->bif_dlist)) {
                /*
                 * Let the driver know that there are no more listeners.
                 */
                *bp->bif_driverp = NULL;
        }
        d->bd_bif = NULL;
        /*
         * Check if this descriptor had requested promiscuous mode.
         * If so, turn it off.
         */
        if (d->bd_promisc) {
                d->bd_promisc = 0;
                error = ifpromisc(ifp, 0);
                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(ifp, "bpf_detach: ifpromisc failed(%d)\n",
                                  error);
                }
        }
}

/*
 * Open ethernet device.  Returns ENXIO for illegal minor device number,
 * EBUSY if file is open by another process.
 */
/* ARGSUSED */
static int
bpfopen(struct dev_open_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        struct bpf_d *d;

        if (ap->a_cred->cr_prison)
                return(EPERM);

        d = dev->si_drv1;
        /*
         * Each minor can be opened by only one process.  If the requested
         * minor is in use, return EBUSY.
         */
        if (d != NULL)
                return(EBUSY);

        MALLOC(d, struct bpf_d *, sizeof *d, M_BPF, M_WAITOK | M_ZERO);
        dev->si_drv1 = d;
        d->bd_bufsize = bpf_bufsize;
        d->bd_sig = SIGIO;
        d->bd_seesent = 1;
        callout_init(&d->bd_callout);
        return(0);
}

static int
bpfclone(struct dev_clone_args *ap)
{
        int unit;

        unit = devfs_clone_bitmap_get(&DEVFS_CLONE_BITMAP(bpf), 0);
        ap->a_dev = make_only_dev(&bpf_ops, unit, 0, 0, 0600, "bpf%d", unit);

        return 0;
}

/*
 * Close the descriptor by detaching it from its interface,
 * deallocating its buffers, and marking it free.
 */
/* ARGSUSED */
static int
bpfclose(struct dev_close_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        struct bpf_d *d = dev->si_drv1;

        funsetown(d->bd_sigio);
        crit_enter();
        if (d->bd_state == BPF_WAITING)
                callout_stop(&d->bd_callout);
        d->bd_state = BPF_IDLE;
        if (d->bd_bif != NULL)
                bpf_detachd(d);
        crit_exit();
        bpf_freed(d);
        dev->si_drv1 = NULL;
        if (dev->si_uminor >= BPF_PREALLOCATED_UNITS) {
                devfs_clone_bitmap_put(&DEVFS_CLONE_BITMAP(bpf), dev->si_uminor);
                destroy_dev(dev);
        }
        kfree(d, M_BPF);
        return(0);
}

/*
 * Rotate the packet buffers in descriptor d.  Move the store buffer
 * into the hold slot, and the free buffer into the store slot.
 * Zero the length of the new store buffer.
 */
#define ROTATE_BUFFERS(d) \
        (d)->bd_hbuf = (d)->bd_sbuf; \
        (d)->bd_hlen = (d)->bd_slen; \
        (d)->bd_sbuf = (d)->bd_fbuf; \
        (d)->bd_slen = 0; \
        (d)->bd_fbuf = NULL;
/*
 *  bpfread - read next chunk of packets from buffers
 */
static int
bpfread(struct dev_read_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        struct bpf_d *d = dev->si_drv1;
        int timed_out;
        int error;

        /*
         * Restrict application to use a buffer the same size as
         * as kernel buffers.
         */
        if (ap->a_uio->uio_resid != d->bd_bufsize)
                return(EINVAL);

        crit_enter();
        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_immediate || (ap->a_ioflag & IO_NDELAY) || timed_out)
                    && d->bd_slen != 0) {
                        /*
                         * A packet(s) either arrived since the previous,
                         * We're in immediate mode, or are reading
                         * in non-blocking mode, and a packet(s)
                         * either arrived since the previous
                         * read or arrived while we were asleep.
                         * Rotate the buffers and return what's here.
                         */
                        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) {
                        crit_exit();
                        return(ENXIO);
                }

                if (ap->a_ioflag & IO_NDELAY) {
                        crit_exit();
                        return(EWOULDBLOCK);
                }
                error = tsleep(d, PCATCH, "bpf", d->bd_rtout);
                if (error == EINTR || error == ERESTART) {
                        crit_exit();
                        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) {
                                crit_exit();
                                return(0);
                        }
                        ROTATE_BUFFERS(d);
                        break;
                }
        }
        /*
         * At this point, we know we have something in the hold slot.
         */
        crit_exit();

        /*
         * 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.
         */
        error = uiomove(d->bd_hbuf, d->bd_hlen, ap->a_uio);

        crit_enter();
        d->bd_fbuf = d->bd_hbuf;
        d->bd_hbuf = NULL;
        d->bd_hlen = 0;
        crit_exit();

        return(error);
}


/*
 * If there are processes sleeping on this descriptor, wake them up.
 */
static void
bpf_wakeup(struct bpf_d *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);

        get_mplock();
        selwakeup(&d->bd_sel);
        rel_mplock();
        /* XXX */
        d->bd_sel.si_pid = 0;
}

static void
bpf_timed_out(void *arg)
{
        struct bpf_d *d = (struct bpf_d *)arg;

        crit_enter();
        if (d->bd_state == BPF_WAITING) {
                d->bd_state = BPF_TIMED_OUT;
                if (d->bd_slen != 0)
                        bpf_wakeup(d);
        }
        crit_exit();
}

static void
bpf_output_dispatch(struct netmsg *nmsg)
{
        struct netmsg_bpf_output *bmsg = (struct netmsg_bpf_output *)nmsg;
        struct ifnet *ifp = bmsg->nm_ifp;
        int error;

        /*
         * The driver frees the mbuf.
         */
        error = ifp->if_output(ifp, bmsg->nm_mbuf, bmsg->nm_dst, NULL);
        lwkt_replymsg(&nmsg->nm_lmsg, error);
}

static int
bpfwrite(struct dev_write_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        struct bpf_d *d = dev->si_drv1;
        struct ifnet *ifp;
        struct mbuf *m;
        int error;
        struct sockaddr dst;
        int datlen;
        struct netmsg_bpf_output bmsg;

        if (d->bd_bif == NULL)
                return(ENXIO);

        ifp = d->bd_bif->bif_ifp;

        if (ap->a_uio->uio_resid == 0)
                return(0);

        error = bpf_movein(ap->a_uio, (int)d->bd_bif->bif_dlt, &m,
                           &dst, &datlen, d->bd_wfilter);
        if (error)
                return(error);

        if (datlen > ifp->if_mtu) {
                m_freem(m);
                return(EMSGSIZE);
        }

        if (d->bd_hdrcmplt)
                dst.sa_family = pseudo_AF_HDRCMPLT;

        netmsg_init(&bmsg.nm_netmsg, NULL, &curthread->td_msgport,
                    MSGF_MPSAFE, bpf_output_dispatch);
        bmsg.nm_mbuf = m;
        bmsg.nm_ifp = ifp;
        bmsg.nm_dst = &dst;

        return lwkt_domsg(cpu_portfn(0), &bmsg.nm_netmsg.nm_lmsg, 0);
}

/*
 * Reset a descriptor by flushing its packet buffer and clearing the
 * receive and drop counts.  Should be called at splimp.
 */
static void
bpf_resetd(struct bpf_d *d)
{
        if (d->bd_hbuf) {
                /* Free the hold buffer. */
                d->bd_fbuf = d->bd_hbuf;
                d->bd_hbuf = NULL;
        }
        d->bd_slen = 0;
        d->bd_hlen = 0;
        d->bd_rcount = 0;
        d->bd_dcount = 0;
}

/*
 *  FIONREAD            Check for read packet available.
 *  SIOCGIFADDR         Get interface address - convenient hook to driver.
 *  BIOCGBLEN           Get buffer len [for read()].
 *  BIOCSETF            Set ethernet read filter.
 *  BIOCSETWF           Set ethernet 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
 *  BIOCGSEESENT        Get "see packets sent" flag
 *  BIOCSSEESENT        Set "see packets sent" flag
 *  BIOCLOCK            Set "locked" flag
 */
/* ARGSUSED */
static int
bpfioctl(struct dev_ioctl_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        struct bpf_d *d = dev->si_drv1;
        int error = 0;

        crit_enter();
        if (d->bd_state == BPF_WAITING)
                callout_stop(&d->bd_callout);
        d->bd_state = BPF_IDLE;
        crit_exit();

        if (d->bd_locked == 1) {
                switch (ap->a_cmd) {
                case BIOCGBLEN:
                case BIOCFLUSH:
                case BIOCGDLT:
                case BIOCGDLTLIST: 
                case BIOCGETIF:
                case BIOCGRTIMEOUT:
                case BIOCGSTATS:
                case BIOCVERSION:
                case BIOCGRSIG:
                case BIOCGHDRCMPLT:
                case FIONREAD:
                case BIOCLOCK:
                case BIOCSRTIMEOUT:
                case BIOCIMMEDIATE:
                case TIOCGPGRP:
                        break;
                default:
                        return (EPERM);
                }
        }
        switch (ap->a_cmd) {
        default:
                error = EINVAL;
                break;

        /*
         * Check for read packet available.
         */
        case FIONREAD:
                {
                        int n;

                        crit_enter();
                        n = d->bd_slen;
                        if (d->bd_hbuf)
                                n += d->bd_hlen;
                        crit_exit();

                        *(int *)ap->a_data = n;
                        break;
                }

        case SIOCGIFADDR:
                {
                        struct ifnet *ifp;

                        if (d->bd_bif == NULL) {
                                error = EINVAL;
                        } else {
                                ifp = d->bd_bif->bif_ifp;
                                ifnet_serialize_all(ifp);
                                error = ifp->if_ioctl(ifp, ap->a_cmd,
                                                      ap->a_data, ap->a_cred);
                                ifnet_deserialize_all(ifp);
                        }
                        break;
                }

        /*
         * Get buffer len [for read()].
         */
        case BIOCGBLEN:
                *(u_int *)ap->a_data = d->bd_bufsize;
                break;

        /*
         * Set buffer length.
         */
        case BIOCSBLEN:
                if (d->bd_bif != NULL) {
                        error = EINVAL;
                } else {
                        u_int size = *(u_int *)ap->a_data;

                        if (size > bpf_maxbufsize)
                                *(u_int *)ap->a_data = size = bpf_maxbufsize;
                        else if (size < BPF_MINBUFSIZE)
                                *(u_int *)ap->a_data = size = BPF_MINBUFSIZE;
                        d->bd_bufsize = size;
                }
                break;

        /*
         * Set link layer read filter.
         */
        case BIOCSETF:
        case BIOCSETWF:
                error = bpf_setf(d, (struct bpf_program *)ap->a_data, 
                        ap->a_cmd);
                break;

        /*
         * Flush read packet buffer.
         */
        case BIOCFLUSH:
                crit_enter();
                bpf_resetd(d);
                crit_exit();
                break;

        /*
         * Put interface into promiscuous mode.
         */
        case BIOCPROMISC:
                if (d->bd_bif == NULL) {
                        /*
                         * No interface attached yet.
                         */
                        error = EINVAL;
                        break;
                }
                crit_enter();
                if (d->bd_promisc == 0) {
                        error = ifpromisc(d->bd_bif->bif_ifp, 1);
                        if (error == 0)
                                d->bd_promisc = 1;
                }
                crit_exit();
                break;

        /*
         * Get device parameters.
         */
        case BIOCGDLT:
                if (d->bd_bif == NULL)
                        error = EINVAL;
                else
                        *(u_int *)ap->a_data = d->bd_bif->bif_dlt;
                break;

        /*
         * Get a list of supported data link types.
         */
        case BIOCGDLTLIST:
                if (d->bd_bif == NULL) {
                        error = EINVAL;
                } else {
                        error = bpf_getdltlist(d,
                                (struct bpf_dltlist *)ap->a_data);
                }
                break;

        /*
         * Set data link type.
         */
        case BIOCSDLT:
                if (d->bd_bif == NULL)
                        error = EINVAL;
                else
                        error = bpf_setdlt(d, *(u_int *)ap->a_data);
                break;

        /*
         * Get interface name.
         */
        case BIOCGETIF:
                if (d->bd_bif == NULL) {
                        error = EINVAL;
                } else {
                        struct ifnet *const ifp = d->bd_bif->bif_ifp;
                        struct ifreq *const ifr = (struct ifreq *)ap->a_data;

                        strlcpy(ifr->ifr_name, ifp->if_xname,
                                sizeof ifr->ifr_name);
                }
                break;

        /*
         * Set interface.
         */
        case BIOCSETIF:
                error = bpf_setif(d, (struct ifreq *)ap->a_data);
                break;

        /*
         * Set read timeout.
         */
        case BIOCSRTIMEOUT:
                {
                        struct timeval *tv = (struct timeval *)ap->a_data;

                        /*
                         * Subtract 1 tick from tvtohz() since this isn't
                         * a one-shot timer.
                         */
                        if ((error = itimerfix(tv)) == 0)
                                d->bd_rtout = tvtohz_low(tv);
                        break;
                }

        /*
         * Get read timeout.
         */
        case BIOCGRTIMEOUT:
                {
                        struct timeval *tv = (struct timeval *)ap->a_data;

                        tv->tv_sec = d->bd_rtout / hz;
                        tv->tv_usec = (d->bd_rtout % hz) * ustick;
                        break;
                }

        /*
         * Get packet stats.
         */
        case BIOCGSTATS:
                {
                        struct bpf_stat *bs = (struct bpf_stat *)ap->a_data;

                        bs->bs_recv = d->bd_rcount;
                        bs->bs_drop = d->bd_dcount;
                        break;
                }

        /*
         * Set immediate mode.
         */
        case BIOCIMMEDIATE:
                d->bd_immediate = *(u_int *)ap->a_data;
                break;

        case BIOCVERSION:
                {
                        struct bpf_version *bv = (struct bpf_version *)ap->a_data;

                        bv->bv_major = BPF_MAJOR_VERSION;
                        bv->bv_minor = BPF_MINOR_VERSION;
                        break;
                }

        /*
         * Get "header already complete" flag
         */
        case BIOCGHDRCMPLT:
                *(u_int *)ap->a_data = d->bd_hdrcmplt;
                break;

        /*
         * Set "header already complete" flag
         */
        case BIOCSHDRCMPLT:
                d->bd_hdrcmplt = *(u_int *)ap->a_data ? 1 : 0;
                break;

        /*
         * Get "see sent packets" flag
         */
        case BIOCGSEESENT:
                *(u_int *)ap->a_data = d->bd_seesent;
                break;

        /*
         * Set "see sent packets" flag
         */
        case BIOCSSEESENT:
                d->bd_seesent = *(u_int *)ap->a_data;
                break;

        case FIOASYNC:          /* Send signal on receive packets */
                d->bd_async = *(int *)ap->a_data;
                break;

        case FIOSETOWN:
                error = fsetown(*(int *)ap->a_data, &d->bd_sigio);
                break;

        case FIOGETOWN:
                *(int *)ap->a_data = fgetown(d->bd_sigio);
                break;

        /* This is deprecated, FIOSETOWN should be used instead. */
        case TIOCSPGRP:
                error = fsetown(-(*(int *)ap->a_data), &d->bd_sigio);
                break;

        /* This is deprecated, FIOGETOWN should be used instead. */
        case TIOCGPGRP:
                *(int *)ap->a_data = -fgetown(d->bd_sigio);
                break;

        case BIOCSRSIG:         /* Set receive signal */
                {
                        u_int sig;

                        sig = *(u_int *)ap->a_data;

                        if (sig >= NSIG)
                                error = EINVAL;
                        else
                                d->bd_sig = sig;
                        break;
                }
        case BIOCGRSIG:
                *(u_int *)ap->a_data = d->bd_sig;
                break;
        case BIOCLOCK:
                d->bd_locked = 1;
                break;
        }
        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.
 */
static int
bpf_setf(struct bpf_d *d, struct bpf_program *fp, u_long cmd)
{
        struct bpf_insn *fcode, *old;
        u_int wfilter, flen, size;

        if (cmd == BIOCSETWF) {
                old = d->bd_wfilter;
                wfilter = 1;
        } else {
                wfilter = 0;
                old = d->bd_rfilter;
        }
        if (fp->bf_insns == NULL) {
                if (fp->bf_len != 0)
                        return(EINVAL);
                crit_enter();
                if (wfilter)
                        d->bd_wfilter = NULL;
                else
                        d->bd_rfilter = NULL;
                bpf_resetd(d);
                crit_exit();
                if (old != NULL)
                        kfree(old, M_BPF);
                return(0);
        }
        flen = fp->bf_len;
        if (flen > BPF_MAXINSNS)
                return(EINVAL);

        size = flen * sizeof *fp->bf_insns;
        fcode = (struct bpf_insn *)kmalloc(size, M_BPF, M_WAITOK);
        if (copyin(fp->bf_insns, fcode, size) == 0 &&
            bpf_validate(fcode, (int)flen)) {
                crit_enter();
                if (wfilter)
                        d->bd_wfilter = fcode;
                else
                        d->bd_rfilter = fcode;
                bpf_resetd(d);
                crit_exit();
                if (old != NULL)
                        kfree(old, M_BPF);

                return(0);
        }
        kfree(fcode, M_BPF);
        return(EINVAL);
}

/*
 * 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;
        int error;
        struct ifnet *theywant;

        theywant = ifunit(ifr->ifr_name);
        if (theywant == NULL)
                return(ENXIO);

        /*
         * Look through attached interfaces for the named one.
         */
        for (bp = bpf_iflist; bp != NULL; bp = bp->bif_next) {
                struct ifnet *ifp = bp->bif_ifp;

                if (ifp == NULL || ifp != theywant)
                        continue;
                /* skip additional entry */
                if (bp->bif_driverp != &ifp->if_bpf)
                        continue;
                /*
                 * We found the requested interface.
                 * If it's not up, return an error.
                 * Allocate the packet buffers if we need to.
                 * If we're already attached to requested interface,
                 * just flush the buffer.
                 */
                if (!(ifp->if_flags & IFF_UP))
                        return(ENETDOWN);

                if (d->bd_sbuf == NULL) {
                        error = bpf_allocbufs(d);
                        if (error != 0)
                                return(error);
                }
                crit_enter();
                if (bp != d->bd_bif) {
                        if (d->bd_bif != NULL) {
                                /*
                                 * Detach if attached to something else.
                                 */
                                bpf_detachd(d);
                        }

                        bpf_attachd(d, bp);
                }
                bpf_resetd(d);
                crit_exit();
                return(0);
        }

        /* Not found. */
        return(ENXIO);
}

/*
 * 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 dev_poll_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        struct bpf_d *d;
        int revents;

        d = dev->si_drv1;
        if (d->bd_bif == NULL)
                return(ENXIO);

        revents = ap->a_events & (POLLOUT | POLLWRNORM);
        crit_enter();
        if (ap->a_events & (POLLIN | POLLRDNORM)) {
                /*
                 * An imitation of the FIONREAD ioctl code.
                 * XXX not quite.  An exact imitation:
                 *      if (d->b_slen != 0 ||
                 *          (d->bd_hbuf != NULL && d->bd_hlen != 0)
                 */
                if (d->bd_hlen != 0 ||
                    ((d->bd_immediate || d->bd_state == BPF_TIMED_OUT) &&
                    d->bd_slen != 0)) {
                        revents |= ap->a_events & (POLLIN | POLLRDNORM);
                } else {
                        selrecord(curthread, &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;
                        }
                }
        }
        crit_exit();
        ap->a_events = revents;
        return(0);
}

/*
 * Process the packet pkt of length pktlen.  The packet is parsed
 * by each listener's 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;
        struct timeval tv;
        int gottime = 0;
        u_int slen;

        get_mplock();

        /* Re-check */
        if (bp == NULL) {
                rel_mplock();
                return;
        }

        /*
         * Note that the ipl does not have to be raised at this point.
         * The only problem that could arise here is that if two different
         * interfaces shared any data.  This is not the case.
         */
        SLIST_FOREACH(d, &bp->bif_dlist, bd_next) {
                ++d->bd_rcount;
                slen = bpf_filter(d->bd_rfilter, pkt, pktlen, pktlen);
                if (slen != 0) {
                        if (!gottime) {
                                microtime(&tv);
                                gottime = 1;
                        }
                        catchpacket(d, pkt, pktlen, slen, ovbcopy, &tv);
                }
        }

        rel_mplock();
}

/*
 * Copy data from an mbuf chain into a buffer.  This code is derived
 * from m_copydata in sys/uipc_mbuf.c.
 */
static void
bpf_mcopy(const void *src_arg, void *dst_arg, size_t len)
{
        const struct mbuf *m;
        u_int count;
        u_char *dst;

        m = src_arg;
        dst = dst_arg;
        while (len > 0) {
                if (m == NULL)
                        panic("bpf_mcopy");
                count = min(m->m_len, len);
                bcopy(mtod(m, void *), dst, count);
                m = m->m_next;
                dst += count;
                len -= count;
        }
}

/*
 * Process the packet in the mbuf chain m.  The packet is parsed by each
 * listener's filter, and if accepted, stashed into the corresponding
 * buffer.
 */
void
bpf_mtap(struct bpf_if *bp, struct mbuf *m)
{
        struct bpf_d *d;
        u_int pktlen, slen;
        struct timeval tv;
        int gottime = 0;

        get_mplock();

        /* Re-check */
        if (bp == NULL) {
                rel_mplock();
                return;
        }

        /* Don't compute pktlen, if no descriptor is attached. */
        if (SLIST_EMPTY(&bp->bif_dlist)) {
                rel_mplock();
                return;
        }

        pktlen = m_lengthm(m, NULL);

        SLIST_FOREACH(d, &bp->bif_dlist, bd_next) {
                if (!d->bd_seesent && (m->m_pkthdr.rcvif == NULL))
                        continue;
                ++d->bd_rcount;
                slen = bpf_filter(d->bd_rfilter, (u_char *)m, pktlen, 0);
                if (slen != 0) {
                        if (!gottime) {
                                microtime(&tv);
                                gottime = 1;
                        }
                        catchpacket(d, (u_char *)m, pktlen, slen, bpf_mcopy,
                                    &tv);
                }
        }

        rel_mplock();
}

void
bpf_mtap_family(struct bpf_if *bp, struct mbuf *m, sa_family_t family)
{
        u_int family4;

        KKASSERT(family != AF_UNSPEC);

        family4 = (u_int)family;
        bpf_ptap(bp, m, &family4, sizeof(family4));
}

/*
 * Process the packet in the mbuf chain m with the header in m prepended.
 * The packet is parsed by each listener's filter, and if accepted,
 * stashed into the corresponding buffer.
 */
void
bpf_ptap(struct bpf_if *bp, struct mbuf *m, const void *data, u_int dlen)
{
        struct mbuf mb;

        /*
         * Craft on-stack mbuf suitable for passing to bpf_mtap.
         * 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 = __DECONST(void *, data); /* LINTED */
        mb.m_len = dlen;
        mb.m_pkthdr.rcvif = m->m_pkthdr.rcvif;

        bpf_mtap(bp, &mb);
}

/*
 * Move the packet data from interface memory (pkt) into the
 * store buffer.  Return 1 if it's time to wakeup a listener (buffer full),
 * otherwise 0.  "copy" is the routine called to do the actual data
 * transfer.  bcopy is passed in to copy contiguous chunks, while
 * bpf_mcopy 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)(const void *, void *, size_t),
            const struct timeval *tv)
{
        struct bpf_hdr *hp;
        int totlen, curlen;
        int hdrlen = d->bd_bif->bif_hdrlen;
        /*
         * 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.
         */
        curlen = BPF_WORDALIGN(d->bd_slen);
        if (curlen + totlen > d->bd_bufsize) {
                /*
                 * This packet will overflow the storage buffer.
                 * Rotate the buffers if we can, then wakeup any
                 * pending reads.
                 */
                if (d->bd_fbuf == NULL) {
                        /*
                         * We haven't completed the previous read yet,
                         * so drop the packet.
                         */
                        ++d->bd_dcount;
                        return;
                }
                ROTATE_BUFFERS(d);
                bpf_wakeup(d);
                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.
                 */
                bpf_wakeup(d);
        }

        /*
         * Append the bpf header.
         */
        hp = (struct bpf_hdr *)(d->bd_sbuf + curlen);
        hp->bh_tstamp = *tv;
        hp->bh_datalen = pktlen;
        hp->bh_hdrlen = hdrlen;
        /*
         * Copy the packet data into the store buffer and update its length.
         */
        (*cpfn)(pkt, (u_char *)hp + hdrlen, (hp->bh_caplen = totlen - hdrlen));
        d->bd_slen = curlen + totlen;
}

/*
 * Initialize all nonzero fields of a descriptor.
 */
static int
bpf_allocbufs(struct bpf_d *d)
{
        d->bd_fbuf = kmalloc(d->bd_bufsize, M_BPF, M_WAITOK);
        d->bd_sbuf = kmalloc(d->bd_bufsize, M_BPF, M_WAITOK);
        d->bd_slen = 0;
        d->bd_hlen = 0;
        return(0);
}

/*
 * Free buffers and packet filter program 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.
         */
        if (d->bd_sbuf != NULL) {
                kfree(d->bd_sbuf, M_BPF);
                if (d->bd_hbuf != NULL)
                        kfree(d->bd_hbuf, M_BPF);
                if (d->bd_fbuf != NULL)
                        kfree(d->bd_fbuf, M_BPF);
        }
        if (d->bd_rfilter)
                kfree(d->bd_rfilter, M_BPF);
        if (d->bd_wfilter)
                kfree(d->bd_wfilter, M_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 supported).
 */
void
bpfattach(struct ifnet *ifp, u_int dlt, u_int hdrlen)
{
        bpfattach_dlt(ifp, dlt, hdrlen, &ifp->if_bpf);
}

void
bpfattach_dlt(struct ifnet *ifp, u_int dlt, u_int hdrlen, struct bpf_if **driverp)
{
        struct bpf_if *bp;

        bp = kmalloc(sizeof *bp, M_BPF, M_WAITOK | M_ZERO);

        SLIST_INIT(&bp->bif_dlist);
        bp->bif_ifp = ifp;
        bp->bif_dlt = dlt;
        bp->bif_driverp = driverp;
        *bp->bif_driverp = NULL;

        bp->bif_next = bpf_iflist;
        bpf_iflist = bp;

        /*
         * 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, and leaving bd_bif NULL.  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, *bp_prev;
        struct bpf_d *d;

        crit_enter();

        /* Locate BPF interface information */
        bp_prev = NULL;
        for (bp = bpf_iflist; bp != NULL; bp = bp->bif_next) {
                if (ifp == bp->bif_ifp)
                        break;
                bp_prev = bp;
        }

        /* Interface wasn't attached */
        if (bp->bif_ifp == NULL) {
                crit_exit();
                kprintf("bpfdetach: %s was not attached\n", ifp->if_xname);
                return;
        }

        while ((d = SLIST_FIRST(&bp->bif_dlist)) != NULL) {
                bpf_detachd(d);
                bpf_wakeup(d);
        }

        if (bp_prev != NULL)
                bp_prev->bif_next = bp->bif_next;
        else
                bpf_iflist = bp->bif_next;

        kfree(bp, M_BPF);

        crit_exit();
}

/*
 * 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;

        ifp = d->bd_bif->bif_ifp;
        n = 0;
        error = 0;
        for (bp = bpf_iflist; bp != NULL; bp = bp->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;

        if (d->bd_bif->bif_dlt == dlt)
                return (0);
        ifp = d->bd_bif->bif_ifp;
        for (bp = bpf_iflist; bp != NULL; bp = bp->bif_next) {
                if (bp->bif_ifp == ifp && bp->bif_dlt == dlt)
                        break;
        }
        if (bp != NULL) {
                opromisc = d->bd_promisc;
                crit_enter();
                bpf_detachd(d);
                bpf_attachd(d, bp);
                bpf_resetd(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;
                        }
                }
                crit_exit();
        }
        return(bp == NULL ? EINVAL : 0);
}

static void
bpf_drvinit(void *unused)
{
        int i;

        make_autoclone_dev(&bpf_ops, &DEVFS_CLONE_BITMAP(bpf),
                bpfclone, 0, 0, 0600, "bpf");
        for (i = 0; i < BPF_PREALLOCATED_UNITS; i++) {
                make_dev(&bpf_ops, i, 0, 0, 0600, "bpf%d", i);
                devfs_clone_bitmap_set(&DEVFS_CLONE_BITMAP(bpf), i);
        }
}

static void
bpf_drvuninit(void *unused)
{
        devfs_clone_handler_del("bpf");
        dev_ops_remove_all(&bpf_ops);
        devfs_clone_bitmap_uninit(&DEVFS_CLONE_BITMAP(bpf));
}

SYSINIT(bpfdev,SI_SUB_DRIVERS,SI_ORDER_MIDDLE+CDEV_MAJOR,bpf_drvinit,NULL)
SYSUNINIT(bpfdev, SI_SUB_DRIVERS,SI_ORDER_MIDDLE+CDEV_MAJOR,bpf_drvuninit, NULL);

#else /* !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.
 */

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_ptap(struct bpf_if *bp, struct mbuf *m, const void *data, u_int dlen)
{
}

void
bpfattach(struct ifnet *ifp, u_int dlt, u_int hdrlen)
{
}

void
bpfattach_dlt(struct ifnet *ifp, u_int dlt, u_int hdrlen, struct bpf_if **driverp)
{
}

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 */
}

#endif /* !BPF */