[apple/xnu.git] / iokit / Drivers / network / AppleBPF / bpf.c

/*
 * Copyright (c) 1998-2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This Original Code and all software distributed under the License are
 * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/* Copyright (c) 1995 NeXT Computer, Inc. All Rights Reserved */
/*
 * Copyright (c) 1990, 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that 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       8.4 (Berkeley) 1/9/95
 */

#define BPFDRV

#ifndef BPFDRV
#include <net/bpfilter.h>
#endif /* not BPFDRV */

#include <string.h>
#include <sys/param.h>
#include <sys/systm.h>
#if 0
#ifdef BPFDRV
#include <machine/spl.h>
#endif /* BPFDRV */
#endif
#include <sys/mbuf.h>
#include <sys/buf.h>
#include <sys/time.h>
#include <sys/proc.h>
#include <sys/user.h>
#include <sys/ioctl.h>

#include <sys/file.h>
#if defined(sparc) && BSD < 199103
#include <sys/stream.h>
#endif
#include <sys/tty.h>
#include <sys/uio.h>

#include <sys/protosw.h>
#include <sys/socket.h>
#include <net/if.h>

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

#include <sys/errno.h>

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

/*
 * Older BSDs don't have kernel malloc.
 */
#if BSD < 199103
extern bcopy();
static caddr_t bpf_alloc();
#include <net/bpf_compat.h>
#define BPF_BUFSIZE (MCLBYTES-8)
#define UIOMOVE(cp, len, code, uio) uiomove(cp, len, code, uio)
#else
#include <sys/malloc.h>
#define BPF_BUFSIZE 4096
#define UIOMOVE(cp, len, code, uio) uiomove(cp, len, uio)
#endif

#define PRINET  26                      /* interruptible */

/*
 * The default read buffer size is patchable.
 */
#ifndef BPFDRV
int bpf_bufsize = BPF_BUFSIZE;
#else
extern int bpf_bufsize;
#endif /* BPFDRV */

/*
 *  bpf_iflist is the list of interfaces; each corresponds to an ifnet
 *  bpf_dtab holds the descriptors, indexed by minor device #
 */
#ifdef BPFDRV
extern struct bpf_if    *bpf_iflist;
extern struct bpf_d     *bpf_dtab;
extern int nbpfilter;
#else
struct bpf_if   *bpf_iflist;
struct bpf_d    bpf_dtab[NBPFILTER];
int nbpfilter = NBPFILTER;
#endif

#ifdef BPFDRV
#if BSD >= 199207
/*
 * bpfilterattach() is called at boot time in new systems.  We do
 * nothing here since old systems will not call this.
 */
/* ARGSUSED */
void
bpfilterattach(n)
        int n;
{
}
#endif
#endif /* BPFDRV */

static int      bpf_allocbufs __P((struct bpf_d *));
static int      bpf_allocbufs __P((struct bpf_d *));
static void     bpf_freed __P((struct bpf_d *));
static void     bpf_freed __P((struct bpf_d *));
static void     bpf_ifname __P((struct ifnet *, struct ifreq *));
static void     bpf_ifname __P((struct ifnet *, struct ifreq *));
static void     bpf_mcopy __P((const void *, void *, u_int));
static int      bpf_movein __P((struct uio *, int,
                    struct mbuf **, struct sockaddr *, int *));
static int      bpf_setif __P((struct bpf_d *, struct ifreq *));
static int      bpf_setif __P((struct bpf_d *, struct ifreq *));
static __inline void
                bpf_wakeup __P((struct bpf_d *));
static void     catchpacket __P((struct bpf_d *, u_char *, u_int,
                    u_int, void (*)(const void *, void *, u_int)));
static void     reset_d __P((struct bpf_d *));

#ifdef BPFDRV
static int
bpf_movein(uio, linktype, mp, sockp, datlen)
        register struct uio *uio;
        int linktype, *datlen;
        register struct mbuf **mp;
        register struct sockaddr *sockp;
{
        struct mbuf *m;
        int error;
        int len;
        int hlen;

        /*
         * 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_PPP:
                sockp->sa_family = AF_UNSPEC;
                hlen = 0;
                break;

        case DLT_EN10MB:
                sockp->sa_family = AF_UNSPEC;
                /* XXX Would MAXLINKHDR be better? */
                hlen = sizeof(struct ether_header);
                break;

        case DLT_FDDI:
                sockp->sa_family = AF_UNSPEC;
                /* XXX 4(FORMAC)+6(dst)+6(src)+3(LLC)+5(SNAP) */
                hlen = 24;
                break;

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

        default:
                return (EIO);
        }

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

        MGETHDR(m, M_WAIT, MT_DATA);
        if (m == 0)
                return (ENOBUFS);
        if (len > MHLEN) {
#if BSD >= 199103
                MCLGET(m, M_WAIT);
                if ((m->m_flags & M_EXT) == 0) {
#else
                MCLGET(m);
                if (m->m_len != MCLBYTES) {
#endif
                        error = ENOBUFS;
                        goto bad;
                }
        }
        m->m_len = len;
        m->m_pkthdr.len = len;
        *mp = m;
        /*
         * Make room for link header.
         */
        if (hlen != 0) {
                m->m_len -= hlen;
                m->m_pkthdr.len -= hlen;
#if BSD >= 199103
                m->m_data += hlen; /* XXX */
#else
                m->m_off += hlen;
#endif
                error = UIOMOVE((caddr_t)sockp->sa_data, hlen, UIO_WRITE, uio);
                if (error)
                        goto bad;
        }
        error = UIOMOVE(mtod(m, caddr_t), len - hlen, UIO_WRITE, uio);
        if (!error)
                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(d, bp)
        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;
        d->bd_next = bp->bif_dlist;
        bp->bif_dlist = d;

/*      *bp->bif_driverp = bp; */
}

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

        bp = d->bd_bif;
        /*
         * Check if this descriptor had requested promiscuous mode.
         * If so, turn it off.
         */
        if (d->bd_promisc) {
                d->bd_promisc = 0;
                if (ifpromisc(bp->bif_ifp, 0))
                        /*
                         * Something is really wrong if we were able to put
                         * the driver into promiscuous mode, but can't
                         * take it out.
                         */
                        panic("bpf: ifpromisc failed");
        }
        /* Remove d from the interface's descriptor list. */
        p = &bp->bif_dlist;
        while (*p != d) {
                p = &(*p)->bd_next;
                if (*p == 0)
                        panic("bpf_detachd: descriptor not in list");
        }
        *p = (*p)->bd_next;
        if (bp->bif_dlist == 0)
                /*
                 * Let the driver know that there are no more listeners.
                 */
            /* *d->bd_bif->bif_driverp = 0 */;
        d->bd_bif = 0;
}
#endif /* BPFDRV */

#ifdef BPFDRV
/*
 * Open ethernet device.  Returns ENXIO for illegal minor device number,
 * EBUSY if file is open by another process.
 */
/* ARGSUSED */
int
bpfopen(dev, flag)
        dev_t dev;
        int flag;
{
        register struct bpf_d *d;

        if (minor(dev) >= nbpfilter)
                return (ENXIO);
        /*
         * Each minor can be opened by only one process.  If the requested
         * minor is in use, return EBUSY.
         */
        d = &bpf_dtab[minor(dev)];
        if (!D_ISFREE(d))
                return (EBUSY);

        /* Mark "free" and do most initialization. */
        bzero((char *)d, sizeof(*d));
        d->bd_bufsize = bpf_bufsize;

        return (0);
}

/*
 * Close the descriptor by detaching it from its interface,
 * deallocating its buffers, and marking it free.
 */
/* ARGSUSED */
int
bpfclose(dev, flag)
        dev_t dev;
        int flag;
{
        register struct bpf_d *d = &bpf_dtab[minor(dev)];
        register int s;

        s = splimp();
        if (d->bd_bif)
                bpf_detachd(d);
        splx(s);
        bpf_freed(d);

        return (0);
}

/*
 * Support for SunOS, which does not have tsleep.
 */
#if BSD < 199103
static
bpf_timeout(arg)
        caddr_t arg;
{
        struct bpf_d *d = (struct bpf_d *)arg;
        d->bd_timedout = 1;
        wakeup(arg);
}

#define BPF_SLEEP(chan, pri, s, t) bpf_sleep((struct bpf_d *)chan)

int
bpf_sleep(d)
        register struct bpf_d *d;
{
        register int rto = d->bd_rtout;
        register int st;

        if (rto != 0) {
                d->bd_timedout = 0;
                timeout(bpf_timeout, (caddr_t)d, rto);
        }
        st = sleep((caddr_t)d, PRINET|PCATCH);
        if (rto != 0) {
                if (d->bd_timedout == 0)
                        untimeout(bpf_timeout, (caddr_t)d);
                else if (st == 0)
                        return EWOULDBLOCK;
        }
        return (st != 0) ? EINTR : 0;
}
#else
#define BPF_SLEEP tsleep
#endif

/*
 * 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 = 0;
/*
 *  bpfread - read next chunk of packets from buffers
 */
int
bpfread(dev, uio)
        dev_t dev;
        register struct uio *uio;
{
        register struct bpf_d *d = &bpf_dtab[minor(dev)];
        int error;
        int s;

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

        s = splimp();
        /*
         * 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 == 0) {
                if (d->bd_immediate && d->bd_slen != 0) {
                        /*
                         * 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;
                }
                error = BPF_SLEEP((caddr_t)d, PRINET|PCATCH, "bpf",
                                  d->bd_rtout);
                if (error == EINTR || error == ERESTART) {
                        splx(s);
                        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) {
                                splx(s);
                                return (0);
                        }
                        ROTATE_BUFFERS(d);
                        break;
                }
        }
        /*
         * At this point, we know we have something in the hold slot.
         */
        splx(s);

        /*
         * 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, UIO_READ, uio);

        s = splimp();
        d->bd_fbuf = d->bd_hbuf;
        d->bd_hbuf = 0;
        d->bd_hlen = 0;
        splx(s);

        return (error);
}


/*
 * If there are processes sleeping on this descriptor, wake them up.
 */
static __inline void
bpf_wakeup(d)
        register struct bpf_d *d;
{
        wakeup((caddr_t)d);
        selwakeup(&d->bd_sel);
        d->bd_sel.si_thread = 0;
}

int
bpfwrite(dev, uio)
        dev_t dev;
        struct uio *uio;
{
        register struct bpf_d *d = &bpf_dtab[minor(dev)];
        struct ifnet *ifp;
        struct mbuf *m;
        int error, s;
        static struct sockaddr dst;
        int datlen;

        if (d->bd_bif == 0)
                return (ENXIO);

        ifp = d->bd_bif->bif_ifp;

        if (uio->uio_resid == 0)
                return (0);

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

        if (datlen > ifp->if_mtu)
                return (EMSGSIZE);

        s = splnet();
#if BSD >= 199103
        error = (*ifp->if_output)(ifp, m, &dst, (struct rtentry *)0);
#else
        error = (*ifp->if_output)(ifp, m, &dst);
#endif
        splx(s);
        /*
         * The driver frees the mbuf.
         */
        return (error);
}

/*
 * Reset a descriptor by flushing its packet buffer and clearing the
 * receive and drop counts.  Should be called at splimp.
 */
static void
reset_d(d)
        struct bpf_d *d;
{
        if (d->bd_hbuf) {
                /* Free the hold buffer. */
                d->bd_fbuf = d->bd_hbuf;
                d->bd_hbuf = 0;
        }
        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.
 *  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.
 */
/* ARGSUSED */
int
bpfioctl(dev, cmd, addr, flag)
        dev_t dev;
        u_long cmd;
        caddr_t addr;
        int flag;
{
        register struct bpf_d *d = &bpf_dtab[minor(dev)];
        int s, error = 0;

        switch (cmd) {

        default:
                error = EINVAL;
                break;

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

                        s = splimp();
                        n = d->bd_slen;
                        if (d->bd_hbuf)
                                n += d->bd_hlen;
                        splx(s);

                        *(int *)addr = n;
                        break;
                }

        case SIOCGIFADDR:
                {
                        struct ifnet *ifp;

                        if (d->bd_bif == 0)
                                error = EINVAL;
                        else {
                                ifp = d->bd_bif->bif_ifp;
                                error = (*ifp->if_ioctl)(ifp, cmd, addr);
                        }
                        break;
                }

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

        /*
         * Set buffer length.
         */
        case BIOCSBLEN:
#if BSD < 199103
                error = EINVAL;
#else
                if (d->bd_bif != 0)
                        error = EINVAL;
                else {
                        register u_int size = *(u_int *)addr;

                        if (size > BPF_MAXBUFSIZE)
                                *(u_int *)addr = size = BPF_MAXBUFSIZE;
                        else if (size < BPF_MINBUFSIZE)
                                *(u_int *)addr = size = BPF_MINBUFSIZE;
                        d->bd_bufsize = size;
                }
#endif
                break;

        /*
         * Set link layer read filter.
         */
        case BIOCSETF:
                error = bpf_setf(d, (struct bpf_program *)addr);
                break;

        /*
         * Flush read packet buffer.
         */
        case BIOCFLUSH:
                s = splimp();
                reset_d(d);
                splx(s);
                break;

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

        /*
         * Get device parameters.
         */
        case BIOCGDLT:
                if (d->bd_bif == 0)
                        error = EINVAL;
                else
                        *(u_int *)addr = d->bd_bif->bif_dlt;
                break;

        /*
         * Set interface name.
         */
        case BIOCGETIF:
                if (d->bd_bif == 0)
                        error = EINVAL;
                else
                        bpf_ifname(d->bd_bif->bif_ifp, (struct ifreq *)addr);
                break;

        /*
         * Set interface.
         */
        case BIOCSETIF:
                error = bpf_setif(d, (struct ifreq *)addr);
                break;

        /*
         * Set read timeout.
         */
        case BIOCSRTIMEOUT:
                {
                        struct timeval *tv = (struct timeval *)addr;
                        u_long msec;

                        /* Compute number of milliseconds. */
                        msec = tv->tv_sec * 1000 + tv->tv_usec / 1000;
                        /* Scale milliseconds to ticks.  Assume hard
                           clock has millisecond or greater resolution
                           (i.e. tick >= 1000).  For 10ms hardclock,
                           tick/1000 = 10, so rtout<-msec/10. */
                        d->bd_rtout = msec / (tick / 1000);
                        break;
                }

        /*
         * Get read timeout.
         */
        case BIOCGRTIMEOUT:
                {
                        struct timeval *tv = (struct timeval *)addr;
                        u_long msec = d->bd_rtout;

                        msec *= tick / 1000;
                        tv->tv_sec = msec / 1000;
                        tv->tv_usec = msec % 1000;
                        break;
                }

        /*
         * Get packet stats.
         */
        case BIOCGSTATS:
                {
                        struct bpf_stat *bs = (struct bpf_stat *)addr;

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

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

        case BIOCVERSION:
                {
                        struct bpf_version *bv = (struct bpf_version *)addr;

                        bv->bv_major = BPF_MAJOR_VERSION;
                        bv->bv_minor = BPF_MINOR_VERSION;
                        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.
 */
int
bpf_setf(d, fp)
        struct bpf_d *d;
        struct bpf_program *fp;
{
        struct bpf_insn *fcode, *old;
        u_int flen, size;
        int s;

        old = d->bd_filter;
        if (fp->bf_insns == 0) {
                if (fp->bf_len != 0)
                        return (EINVAL);
                s = splimp();
                d->bd_filter = 0;
                reset_d(d);
                splx(s);
                if (old != 0)
                        FREE((caddr_t)old, M_DEVBUF);
                return (0);
        }
        flen = fp->bf_len;
        if (flen > BPF_MAXINSNS)
                return (EINVAL);

        size = flen * sizeof(*fp->bf_insns);
        MALLOC(fcode, struct bpf_insn *, size, M_DEVBUF, M_WAITOK);
        if (copyin((caddr_t)fp->bf_insns, (caddr_t)fcode, size) == 0 &&
            bpf_validate(fcode, (int)flen)) {
                s = splimp();
                d->bd_filter = fcode;
                reset_d(d);
                splx(s);
                if (old != 0)
                        FREE((caddr_t)old, M_DEVBUF);

                return (0);
        }
        FREE((caddr_t)fcode, M_DEVBUF);
        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(d, ifr)
        struct bpf_d *d;
        struct ifreq *ifr;
{
        struct bpf_if *bp;
        char *cp;
        int unit, s, error;

        /*
         * Separate string into name part and unit number.  Put a null
         * byte at the end of the name part, and compute the number.
         * If the a unit number is unspecified, the default is 0,
         * as initialized above.  XXX This should be common code.
         */
        unit = 0;
        cp = ifr->ifr_name;
        cp[sizeof(ifr->ifr_name) - 1] = '\0';
        while (*cp++) {
                if (*cp >= '0' && *cp <= '9') {
                        unit = *cp - '0';
                        *cp++ = '\0';
                        while (*cp)
                                unit = 10 * unit + *cp++ - '0';
                        break;
                }
        }
        /*
         * Look through attached interfaces for the named one.
         */
        for (bp = bpf_iflist; bp != 0; bp = bp->bif_next) {
                struct ifnet *ifp = bp->bif_ifp;

                if (ifp == 0 || unit != ifp->if_unit
                    || strcmp(ifp->if_name, ifr->ifr_name) != 0)
                        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) == 0)
                        return (ENETDOWN);

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

                        bpf_attachd(d, bp);
                }
                reset_d(d);
                splx(s);
                return (0);
        }
        /* Not found. */
        return (ENXIO);
}

/*
 * Convert an interface name plus unit number of an ifp to a single
 * name which is returned in the ifr.
 */
static void
bpf_ifname(ifp, ifr)
        struct ifnet *ifp;
        struct ifreq *ifr;
{
        char *s = ifp->if_name;
        char *d = ifr->ifr_name;

        while ((*d++ = *s++) != 0)
                continue;
        /* XXX Assume that unit number is less than 10. */
        *d++ = ifp->if_unit + '0';
        *d = '\0';
}

/*
 * The new select interface passes down the proc pointer; the old select
 * stubs had to grab it out of the user struct.  This glue allows either case.
 */
#if BSD < 199103
int
bpfselect(dev, rw)
        register dev_t dev;
        int rw;
{
        return (bpf_select(dev, rw, u.u_procp));
}
#endif

/*
 * Support for select() system call
 *
 * Return true iff the specific operation will not block indefinitely.
 * Otherwise, return false but make a note that a selwakeup() must be done.
 */
int
bpf_select(dev, rw, p)
        register dev_t dev;
        int rw;
        struct proc *p;
{
        register struct bpf_d *d;
        register int s;

        if (rw != FREAD)
                return (0);
        /*
         * An imitation of the FIONREAD ioctl code.
         */
        d = &bpf_dtab[minor(dev)];

        s = splimp();
        if (d->bd_hlen != 0 || (d->bd_immediate && d->bd_slen != 0)) {
                /*
                 * There is data waiting.
                 */
                splx(s);
                return (1);
        }
#if BSD >= 199103
        selrecord(p, &d->bd_sel);
#else
        /*
         * No data ready.  If there's already a select() waiting on this
         * minor device then this is a collision.  This shouldn't happen
         * because minors really should not be shared, but if a process
         * forks while one of these is open, it is possible that both
         * processes could select on the same descriptor.
         */
        if (d->bd_selproc && d->bd_selproc->p_wchan == (caddr_t)&selwait)
                d->bd_selcoll = 1;
        else
                d->bd_selproc = p;
#endif
        splx(s);
        return (0);
}
#endif /* BPFDRV */

/*
 * 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.
 */
#ifdef BPFDRV
void
bpf_tap(arg, pkt, pktlen)
        struct ifnet *ifp;
        register u_char *pkt;
        register u_int pktlen;
{
        struct bpf_if *bp;
        register struct bpf_d *d;
        register u_int slen;
        /*
         * 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.
         */
        bp = (struct bpf_if *)arg;
        for (d = bp->bif_dlist; d != 0; d = d->bd_next) {
                ++d->bd_rcount;
                slen = bpf_filter(d->bd_filter, pkt, pktlen, pktlen);
                if (slen != 0)
                        catchpacket(d, pkt, pktlen, slen, bcopy);
        }
}

/*
 * 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(src_arg, dst_arg, len)
        const void *src_arg;
        void *dst_arg;
        register u_int len;
{
        register const struct mbuf *m;
        register u_int count;
        u_char *dst;

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

#ifdef BPFDRV
/*
 * Incoming linkage from device drivers, when packet is in an mbuf chain.
 */
void
bpf_mtap(arg, m)
        caddr_t arg;
        struct mbuf *m;
{
        struct bpf_if *bp = (struct bpf_if *)arg;
        struct bpf_d *d;
        u_int pktlen, slen;
        struct mbuf *m0;

        pktlen = 0;
        for (m0 = m; m0 != 0; m0 = m0->m_next)
                pktlen += m0->m_len;

        for (d = bp->bif_dlist; d != 0; d = d->bd_next) {
                ++d->bd_rcount;
                slen = bpf_filter(d->bd_filter, (u_char *)m, pktlen, 0);
                if (slen != 0)
                        catchpacket(d, (u_char *)m, pktlen, slen, bpf_mcopy);
        }
}
#endif /* BPFDRV */

#ifdef BPFDRV
/*
 * 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(d, pkt, pktlen, snaplen, cpfn)
        register struct bpf_d *d;
        register u_char *pkt;
        register u_int pktlen, snaplen;
        register void (*cpfn) __P((const void *, void *, u_int));
{
        register struct bpf_hdr *hp;
        register int totlen, curlen;
        register 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 == 0) {
                        /*
                         * 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)
                /*
                 * Immediate mode is set.  A packet arrived so any
                 * reads should be woken up.
                 */
                bpf_wakeup(d);

        /*
         * Append the bpf header.
         */
        hp = (struct bpf_hdr *)(d->bd_sbuf + curlen);
#if BSD >= 199103
        microtime(&hp->bh_tstamp);
#elif defined(sun)
        uniqtime(&hp->bh_tstamp);
#else
        hp->bh_tstamp = time;
#endif
        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(d)
        register struct bpf_d *d;
{
        MALLOC(d->bd_fbuf, caddr_t, d->bd_bufsize, M_DEVBUF, M_WAITOK);
        if (d->bd_fbuf == 0)
                return (ENOBUFS);

        MALLOC(d->bd_sbuf, caddr_t, d->bd_bufsize, M_DEVBUF, M_WAITOK);
        if (d->bd_sbuf == 0) {
                FREE(d->bd_fbuf, M_DEVBUF);
                return (ENOBUFS);
        }
        d->bd_slen = 0;
        d->bd_hlen = 0;
        return (0);
}

/*
 * Free buffers currently in use by a descriptor.
 * Called on close.
 */
static void
bpf_freed(d)
        register 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 != 0) {
                FREE(d->bd_sbuf, M_DEVBUF);
                if (d->bd_hbuf != 0)
                        FREE(d->bd_hbuf, M_DEVBUF);
                if (d->bd_fbuf != 0)
                        FREE(d->bd_fbuf, M_DEVBUF);
        }
        if (d->bd_filter)
                FREE((caddr_t)d->bd_filter, M_DEVBUF);

        D_MARKFREE(d);
}
#endif /* BPFDRV */

#ifdef BPFDRV
#if BSD >= 199103
/* XXX This routine belongs in net/if.c. */
/*
 * Set/clear promiscuous mode on interface ifp based on the truth value
 * of pswitch.  The calls are reference counted so that only the first
 * "on" request actually has an effect, as does the final "off" request.
 * Results are undefined if the "off" and "on" requests are not matched.
 */
int
ifpromisc(ifp, pswitch)
        struct ifnet *ifp;
        int pswitch;
{
        struct ifreq ifr;
        /*
         * If the device is not configured up, we cannot put it in
         * promiscuous mode.
         */
        if ((ifp->if_flags & IFF_UP) == 0)
                return (ENETDOWN);

        if (pswitch) {
                if (ifp->if_pcount++ != 0)
                        return (0);
                ifp->if_flags |= IFF_PROMISC;
        } else {
                if (--ifp->if_pcount > 0)
                        return (0);
                ifp->if_flags &= ~IFF_PROMISC;
        }
        ifr.ifr_flags = ifp->if_flags;
        return ((*ifp->if_ioctl)(ifp, SIOCSIFFLAGS, (caddr_t)&ifr));
}
#endif

#if BSD < 199103
/*
 * Allocate some memory for bpf.  This is temporary SunOS support, and
 * is admittedly a hack.
 * If resources unavaiable, return 0.
 */
static caddr_t
bpf_alloc(size, canwait)
        register int size;
        register int canwait;
{
        register struct mbuf *m;

        if ((unsigned)size > (MCLBYTES-8))
                return 0;

        MGET(m, canwait, MT_DATA);
        if (m == 0)
                return 0;
        if ((unsigned)size > (MLEN-8)) {
                MCLGET(m);
                if (m->m_len != MCLBYTES) {
                        m_freem(m);
                        return 0;
                }
        }
        *mtod(m, struct mbuf **) = m;
        return mtod(m, caddr_t) + 8;
}
#endif
#endif /* BPFDRV */