/*      $NetBSD: if_tun.c,v 1.14 1994/06/29 06:36:25 cgd Exp $  */
/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (C) 1999-2000 by Maksim Yevmenkin <m_evmenkin@yahoo.com>
 * All rights reserved.
 * Copyright (c) 2019 Kyle Evans <kevans@FreeBSD.org>
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
 *
 * BASED ON:
 * -------------------------------------------------------------------------
 *
 * Copyright (c) 1988, Julian Onions <jpo@cs.nott.ac.uk>
 * Nottingham University 1987.
 *
 * This source may be freely distributed, however I would be interested
 * in any changes that are made.
 *
 * This driver takes packets off the IP i/f and hands them up to a
 * user process to have its wicked way with. This driver has it's
 * roots in a similar driver written by Phil Cockcroft (formerly) at
 * UCL. This driver is based much more on read/write/poll mode of
 * operation though.
 */

#include "opt_inet.h"
#include "opt_inet6.h"

#include <sys/param.h>
#include <sys/lock.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/systm.h>
#include <sys/jail.h>
#include <sys/mbuf.h>
#include <sys/module.h>
#include <sys/socket.h>
#include <sys/eventhandler.h>
#include <sys/fcntl.h>
#include <sys/filio.h>
#include <sys/sockio.h>
#include <sys/sx.h>
#include <sys/syslog.h>
#include <sys/ttycom.h>
#include <sys/poll.h>
#include <sys/selinfo.h>
#include <sys/signalvar.h>
#include <sys/filedesc.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <sys/conf.h>
#include <sys/uio.h>
#include <sys/malloc.h>
#include <sys/random.h>
#include <sys/ctype.h>
#include <sys/osd.h>

#include <net/ethernet.h>
#include <net/if.h>
#include <net/if_var.h>
#include <net/if_clone.h>
#include <net/if_dl.h>
#include <net/if_media.h>
#include <net/if_private.h>
#include <net/if_types.h>
#include <net/if_vlan_var.h>
#include <net/netisr.h>
#include <net/route.h>
#include <net/vnet.h>
#include <netinet/in.h>
#ifdef INET
#include <netinet/ip.h>
#endif
#ifdef INET6
#include <netinet/ip6.h>
#include <netinet6/ip6_var.h>
#endif
#include <netinet/udp.h>
#include <netinet/tcp.h>
#include <netinet/tcp_lro.h>
#include <net/bpf.h>
#include <net/if_tap.h>
#include <net/if_tun.h>

#include <dev/virtio/network/virtio_net.h>

#include <sys/queue.h>
#include <sys/condvar.h>
#include <security/mac/mac_framework.h>

struct tuntap_driver;

/*
 * tun_list is protected by global tunmtx.  Other mutable fields are
 * protected by tun->tun_mtx, or by their owning subsystem.  tun_dev is
 * static for the duration of a tunnel interface.
 */
struct tuntap_softc {
        TAILQ_ENTRY(tuntap_softc)        tun_list;
        struct cdev                     *tun_alias;
        struct cdev                     *tun_dev;
        u_short                          tun_flags;     /* misc flags */
#define TUN_OPEN        0x0001
#define TUN_INITED      0x0002
#define TUN_UNUSED1     0x0008
#define TUN_UNUSED2     0x0010
#define TUN_LMODE       0x0020
#define TUN_RWAIT       0x0040
#define TUN_ASYNC       0x0080
#define TUN_IFHEAD      0x0100
#define TUN_DYING       0x0200
#define TUN_L2          0x0400
#define TUN_VMNET       0x0800
#define TUN_TRANSIENT   0x1000

#define TUN_DRIVER_IDENT_MASK   (TUN_L2 | TUN_VMNET)
#define TUN_READY               (TUN_OPEN | TUN_INITED)

        pid_t                    tun_pid;       /* owning pid */
        struct epoch_context     tun_epoch_ctx;
        struct ifnet            *tun_ifp;       /* the interface */
        struct sigio            *tun_sigio;     /* async I/O info */
        struct tuntap_driver    *tun_drv;       /* appropriate driver */
        struct selinfo           tun_rsel;      /* read select */
        struct mtx               tun_mtx;       /* softc field mutex */
        struct cv                tun_cv;        /* for ref'd dev destroy */
        struct ether_addr        tun_ether;     /* remote address */
        int                      tun_busy;      /* busy count */
        int                      tun_vhdrlen;   /* virtio-net header length */
        struct lro_ctrl          tun_lro;       /* for TCP LRO */
        bool                     tun_lro_ready; /* TCP LRO initialized */
};
#define TUN2IFP(sc)     ((sc)->tun_ifp)

#define TUNDEBUG        if (tundebug) if_printf

#define TUN_LOCK(tp)            mtx_lock(&(tp)->tun_mtx)
#define TUN_UNLOCK(tp)          mtx_unlock(&(tp)->tun_mtx)
#define TUN_LOCK_ASSERT(tp)     mtx_assert(&(tp)->tun_mtx, MA_OWNED);

#define TUN_VMIO_FLAG_MASK      0x0fff

/*
 * Interface capabilities of a tap device that supports the virtio-net
 * header.
 */
#define TAP_VNET_HDR_CAPS       (IFCAP_HWCSUM | IFCAP_HWCSUM_IPV6       \
                                | IFCAP_VLAN_HWCSUM                     \
                                | IFCAP_TSO | IFCAP_LRO                 \
                                | IFCAP_VLAN_HWTSO)

#define TAP_ALL_OFFLOAD         (CSUM_TSO | CSUM_TCP | CSUM_UDP |\
                                    CSUM_TCP_IPV6 | CSUM_UDP_IPV6)

/*
 * All mutable global variables in if_tun are locked using tunmtx, with
 * the exception of tundebug, which is used unlocked, and the drivers' *clones,
 * which are static after setup.
 */
static struct mtx tunmtx;
static eventhandler_tag rename_tag;
static eventhandler_tag clone_tag;
static int tuntap_osd_jail_slot;
static const char tunname[] = "tun";
static const char tapname[] = "tap";
static const char vmnetname[] = "vmnet";
static MALLOC_DEFINE(M_TUN, tunname, "Tunnel Interface");
static int tundebug = 0;
static int tundclone = 1;
static int tap_allow_uopen = 0; /* allow user devfs cloning */
static int tapuponopen = 0;     /* IFF_UP on open() */
static int tapdclone = 1;       /* enable devfs cloning */

static TAILQ_HEAD(,tuntap_softc)        tunhead = TAILQ_HEAD_INITIALIZER(tunhead);
SYSCTL_INT(_debug, OID_AUTO, if_tun_debug, CTLFLAG_RW, &tundebug, 0, "");

static struct sx tun_ioctl_sx;
SX_SYSINIT(tun_ioctl_sx, &tun_ioctl_sx, "tun_ioctl");

SYSCTL_DECL(_net_link);
/* tun */
static SYSCTL_NODE(_net_link, OID_AUTO, tun, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "IP tunnel software network interface");
SYSCTL_INT(_net_link_tun, OID_AUTO, devfs_cloning, CTLFLAG_RWTUN, &tundclone, 0,
    "Enable legacy devfs interface creation");

/* tap */
static SYSCTL_NODE(_net_link, OID_AUTO, tap, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "Ethernet tunnel software network interface");
SYSCTL_INT(_net_link_tap, OID_AUTO, user_open, CTLFLAG_RW, &tap_allow_uopen, 0,
    "Enable legacy devfs interface creation for all users");
SYSCTL_INT(_net_link_tap, OID_AUTO, up_on_open, CTLFLAG_RW, &tapuponopen, 0,
    "Bring interface up when /dev/tap is opened");
SYSCTL_INT(_net_link_tap, OID_AUTO, devfs_cloning, CTLFLAG_RWTUN, &tapdclone, 0,
    "Enable legacy devfs interface creation");
SYSCTL_INT(_net_link_tap, OID_AUTO, debug, CTLFLAG_RW, &tundebug, 0, "");

static int      tun_create_device(struct tuntap_driver *drv, int unit,
    struct ucred *cr, struct cdev **dev, const char *name);
static int      tun_busy_locked(struct tuntap_softc *tp);
static void     tun_unbusy_locked(struct tuntap_softc *tp);
static int      tun_busy(struct tuntap_softc *tp);
static void     tun_unbusy(struct tuntap_softc *tp);

static int      tuntap_name2info(const char *name, int *unit, int *flags);
static void     tunclone(void *arg, struct ucred *cred, char *name,
                    int namelen, struct cdev **dev);
static void     tuncreate(struct cdev *dev);
static void     tundtor(void *data);
static void     tunrename(void *arg, struct ifnet *ifp);
static int      tunifioctl(struct ifnet *, u_long, caddr_t);
static void     tuninit(struct ifnet *);
static void     tunifinit(void *xtp);
static int      tuntapmodevent(module_t, int, void *);
static int      tunoutput(struct ifnet *, struct mbuf *,
                    const struct sockaddr *, struct route *ro);
static void     tunstart(struct ifnet *);
static void     tunstart_l2(struct ifnet *);

static int      tun_clone_match(struct if_clone *ifc, const char *name);
static int      tap_clone_match(struct if_clone *ifc, const char *name);
static int      vmnet_clone_match(struct if_clone *ifc, const char *name);
static int      tun_clone_create(struct if_clone *, char *, size_t,
                    struct ifc_data *, struct ifnet **);
static int      tun_clone_destroy(struct if_clone *, struct ifnet *, uint32_t);
static void     tun_vnethdr_set(struct ifnet *ifp, int vhdrlen);

static d_open_t         tunopen;
static d_read_t         tunread;
static d_write_t        tunwrite;
static d_ioctl_t        tunioctl;
static d_poll_t         tunpoll;
static d_kqfilter_t     tunkqfilter;

static int              tunkqread(struct knote *, long);
static int              tunkqwrite(struct knote *, long);
static void             tunkqdetach(struct knote *);

static const struct filterops tun_read_filterops = {
        .f_isfd =       1,
        .f_attach =     NULL,
        .f_detach =     tunkqdetach,
        .f_event =      tunkqread,
        .f_copy =       knote_triv_copy,
};

static const struct filterops tun_write_filterops = {
        .f_isfd =       1,
        .f_attach =     NULL,
        .f_detach =     tunkqdetach,
        .f_event =      tunkqwrite,
        .f_copy =       knote_triv_copy,
};

static struct tuntap_driver {
        struct cdevsw            cdevsw;
        int                      ident_flags;
        struct unrhdr           *unrhdr;
        struct clonedevs        *clones;
        ifc_match_f             *clone_match_fn;
        ifc_create_f            *clone_create_fn;
        ifc_destroy_f           *clone_destroy_fn;
} tuntap_drivers[] = {
        {
                .ident_flags =  0,
                .cdevsw =       {
                    .d_version =        D_VERSION,
                    .d_flags =          D_NEEDMINOR,
                    .d_open =           tunopen,
                    .d_read =           tunread,
                    .d_write =          tunwrite,
                    .d_ioctl =          tunioctl,
                    .d_poll =           tunpoll,
                    .d_kqfilter =       tunkqfilter,
                    .d_name =           tunname,
                },
                .clone_match_fn =       tun_clone_match,
                .clone_create_fn =      tun_clone_create,
                .clone_destroy_fn =     tun_clone_destroy,
        },
        {
                .ident_flags =  TUN_L2,
                .cdevsw =       {
                    .d_version =        D_VERSION,
                    .d_flags =          D_NEEDMINOR,
                    .d_open =           tunopen,
                    .d_read =           tunread,
                    .d_write =          tunwrite,
                    .d_ioctl =          tunioctl,
                    .d_poll =           tunpoll,
                    .d_kqfilter =       tunkqfilter,
                    .d_name =           tapname,
                },
                .clone_match_fn =       tap_clone_match,
                .clone_create_fn =      tun_clone_create,
                .clone_destroy_fn =     tun_clone_destroy,
        },
        {
                .ident_flags =  TUN_L2 | TUN_VMNET,
                .cdevsw =       {
                    .d_version =        D_VERSION,
                    .d_flags =          D_NEEDMINOR,
                    .d_open =           tunopen,
                    .d_read =           tunread,
                    .d_write =          tunwrite,
                    .d_ioctl =          tunioctl,
                    .d_poll =           tunpoll,
                    .d_kqfilter =       tunkqfilter,
                    .d_name =           vmnetname,
                },
                .clone_match_fn =       vmnet_clone_match,
                .clone_create_fn =      tun_clone_create,
                .clone_destroy_fn =     tun_clone_destroy,
        },
};
#define NDRV    nitems(tuntap_drivers)

VNET_DEFINE_STATIC(struct if_clone *, tuntap_driver_cloners[NDRV]);
#define V_tuntap_driver_cloners VNET(tuntap_driver_cloners)

/*
 * Mechanism for marking a tunnel device as busy so that we can safely do some
 * orthogonal operations (such as operations on devices) without racing against
 * tun_destroy.  tun_destroy will wait on the condvar if we're at all busy or
 * open, to be woken up when the condition is alleviated.
 */
static int
tun_busy_locked(struct tuntap_softc *tp)
{

        TUN_LOCK_ASSERT(tp);
        if ((tp->tun_flags & TUN_DYING) != 0) {
                /*
                 * Perhaps unintuitive, but the device is busy going away.
                 * Other interpretations of EBUSY from tun_busy make little
                 * sense, since making a busy device even more busy doesn't
                 * sound like a problem.
                 */
                return (EBUSY);
        }

        ++tp->tun_busy;
        return (0);
}

static void
tun_unbusy_locked(struct tuntap_softc *tp)
{

        TUN_LOCK_ASSERT(tp);
        KASSERT(tp->tun_busy != 0, ("tun_unbusy: called for non-busy tunnel"));

        --tp->tun_busy;
        /* Wake up anything that may be waiting on our busy tunnel. */
        if (tp->tun_busy == 0)
                cv_broadcast(&tp->tun_cv);
}

static int
tun_busy(struct tuntap_softc *tp)
{
        int ret;

        TUN_LOCK(tp);
        ret = tun_busy_locked(tp);
        TUN_UNLOCK(tp);
        return (ret);
}

static void
tun_unbusy(struct tuntap_softc *tp)
{

        TUN_LOCK(tp);
        tun_unbusy_locked(tp);
        TUN_UNLOCK(tp);
}

/*
 * Sets unit and/or flags given the device name.  Must be called with correct
 * vnet context.
 */
static int
tuntap_name2info(const char *name, int *outunit, int *outflags)
{
        struct tuntap_driver *drv;
        char *dname;
        int flags, unit;
        bool found;

        if (name == NULL)
                return (EINVAL);

        /*
         * Needed for dev_stdclone, but dev_stdclone will not modify, it just
         * wants to be able to pass back a char * through the second param. We
         * will always set that as NULL here, so we'll fake it.
         */
        dname = __DECONST(char *, name);
        found = false;

        for (u_int i = 0; i < NDRV; i++) {
                drv = &tuntap_drivers[i];

                if (strcmp(name, drv->cdevsw.d_name) == 0) {
                        found = true;
                        unit = -1;
                        flags = drv->ident_flags;
                        break;
                }

                if (dev_stdclone(dname, NULL, drv->cdevsw.d_name, &unit) == 1) {
                        found = true;
                        flags = drv->ident_flags;
                        break;
                }
        }

        if (!found)
                return (ENXIO);

        if (outunit != NULL)
                *outunit = unit;
        if (outflags != NULL)
                *outflags = flags;
        return (0);
}

static struct if_clone *
tuntap_cloner_from_flags(int tun_flags)
{

        for (u_int i = 0; i < NDRV; i++)
                if ((tun_flags & TUN_DRIVER_IDENT_MASK) ==
                    tuntap_drivers[i].ident_flags)
                        return (V_tuntap_driver_cloners[i]);

        return (NULL);
}

/*
 * Get driver information from a set of flags specified.  Masks the identifying
 * part of the flags and compares it against all of the available
 * tuntap_drivers.
 */
static struct tuntap_driver *
tuntap_driver_from_flags(int tun_flags)
{

        for (u_int i = 0; i < NDRV; i++)
                if ((tun_flags & TUN_DRIVER_IDENT_MASK) ==
                    tuntap_drivers[i].ident_flags)
                        return (&tuntap_drivers[i]);

        return (NULL);
}

static int
tun_clone_match(struct if_clone *ifc, const char *name)
{
        int tunflags;

        if (tuntap_name2info(name, NULL, &tunflags) == 0) {
                if ((tunflags & TUN_L2) == 0)
                        return (1);
        }

        return (0);
}

static int
tap_clone_match(struct if_clone *ifc, const char *name)
{
        int tunflags;

        if (tuntap_name2info(name, NULL, &tunflags) == 0) {
                if ((tunflags & (TUN_L2 | TUN_VMNET)) == TUN_L2)
                        return (1);
        }

        return (0);
}

static int
vmnet_clone_match(struct if_clone *ifc, const char *name)
{
        int tunflags;

        if (tuntap_name2info(name, NULL, &tunflags) == 0) {
                if ((tunflags & TUN_VMNET) != 0)
                        return (1);
        }

        return (0);
}

/*
 * Create a clone via the ifnet cloning mechanism.  Note that this is invoked
 * indirectly by tunclone() below.
 */
static int
tun_clone_create(struct if_clone *ifc, char *name, size_t len,
    struct ifc_data *ifd, struct ifnet **ifpp)
{
        struct tuntap_driver *drv;
        struct cdev *dev;
        int err, i, tunflags, unit;

        tunflags = 0;
        /* The name here tells us exactly what we're creating */
        err = tuntap_name2info(name, &unit, &tunflags);
        if (err != 0)
                return (err);

        drv = tuntap_driver_from_flags(tunflags);
        if (drv == NULL)
                return (ENXIO);

        if (unit != -1) {
                /* If this unit number is still available that's okay. */
                if (alloc_unr_specific(drv->unrhdr, unit) == -1)
                        return (EEXIST);
        } else {
                unit = alloc_unr(drv->unrhdr);
        }

        snprintf(name, IFNAMSIZ, "%s%d", drv->cdevsw.d_name, unit);

        /* find any existing device, or allocate new unit number */
        dev = NULL;
        i = clone_create(&drv->clones, &drv->cdevsw, &unit, &dev, 0);
        /* No preexisting struct cdev *, create one */
        if (i != 0)
                i = tun_create_device(drv, unit, NULL, &dev, name);
        if (i == 0) {
                struct tuntap_softc *tp;

                tuncreate(dev);
                tp = dev->si_drv1;
                *ifpp = tp->tun_ifp;
        }

        return (i);
}

/*
 * Create a clone via devfs access.
 */
static void
tunclone(void *arg, struct ucred *cred, char *name, int namelen,
    struct cdev **dev)
{
        char devname[SPECNAMELEN + 1];
        struct tuntap_driver *drv;
        int append_unit, i, u, tunflags;
        bool mayclone;

        if (*dev != NULL)
                return;

        tunflags = 0;
        CURVNET_SET(CRED_TO_VNET(cred));
        if (tuntap_name2info(name, &u, &tunflags) != 0)
                goto out;       /* Not recognized */

        if (u != -1 && u > IF_MAXUNIT)
                goto out;       /* Unit number too high */

        mayclone = priv_check_cred(cred, PRIV_NET_IFCREATE) == 0;
        if ((tunflags & TUN_L2) != 0) {
                /* tap/vmnet allow user open with a sysctl */
                mayclone = (mayclone || tap_allow_uopen) && tapdclone;
        } else {
                mayclone = mayclone && tundclone;
        }

        /*
         * If tun cloning is enabled, only the superuser can create an
         * interface.
         */
        if (!mayclone)
                goto out;

        if (u == -1)
                append_unit = 1;
        else
                append_unit = 0;

        drv = tuntap_driver_from_flags(tunflags);
        if (drv == NULL)
                goto out;

        /* find any existing device, or allocate new unit number */
        i = clone_create(&drv->clones, &drv->cdevsw, &u, dev, 0);
        if (i) {
                if (append_unit) {
                        namelen = snprintf(devname, sizeof(devname), "%s%d",
                            name, u);
                        name = devname;
                }

                i = tun_create_device(drv, u, cred, dev, name);
        } else {
                /* Consumed by the dev_clone invoker. */
                dev_ref(*dev);
        }
        if (i == 0)
                if_clone_create(name, namelen, NULL);
out:
        CURVNET_RESTORE();
}

static void
tunfree(struct epoch_context *ctx)
{
        struct tuntap_softc *tp;

        tp = __containerof(ctx, struct tuntap_softc, tun_epoch_ctx);

        /* Any remaining resources that would be needed by a concurrent open. */
        mtx_destroy(&tp->tun_mtx);
        free(tp, M_TUN);
}

static int
tun_destroy(struct tuntap_softc *tp, bool may_intr)
{
        int error;

        TUN_LOCK(tp);

        /*
         * Transient tunnels may have set TUN_DYING if we're being destroyed as
         * a result of the last close, which we'll allow.
         */
        MPASS((tp->tun_flags & (TUN_DYING | TUN_TRANSIENT)) != TUN_DYING);
        tp->tun_flags |= TUN_DYING;
        error = 0;
        while (tp->tun_busy != 0) {
                if (may_intr)
                        error = cv_wait_sig(&tp->tun_cv, &tp->tun_mtx);
                else
                        cv_wait(&tp->tun_cv, &tp->tun_mtx);
                if (error != 0 && tp->tun_busy != 0) {
                        tp->tun_flags &= ~TUN_DYING;
                        TUN_UNLOCK(tp);
                        return (error);
                }
        }
        TUN_UNLOCK(tp);

        CURVNET_SET(TUN2IFP(tp)->if_vnet);

        mtx_lock(&tunmtx);
        TAILQ_REMOVE(&tunhead, tp, tun_list);
        mtx_unlock(&tunmtx);

        /*
         * destroy_dev will take care of any alias.  For transient tunnels,
         * we're being called from close(2) so we can't destroy it ourselves
         * without deadlocking, but we already know that we can cleanup
         * everything else and just continue to prevent it from being reopened.
         */
        if ((tp->tun_flags & TUN_TRANSIENT) != 0) {
                atomic_store_ptr(&tp->tun_dev->si_drv1, tp->tun_dev);
                destroy_dev_sched(tp->tun_dev);
        } else {
                destroy_dev(tp->tun_dev);
        }
        seldrain(&tp->tun_rsel);
        knlist_clear(&tp->tun_rsel.si_note, 0);
        knlist_destroy(&tp->tun_rsel.si_note);
        if ((tp->tun_flags & TUN_L2) != 0) {
                ether_ifdetach(TUN2IFP(tp));
        } else {
                bpfdetach(TUN2IFP(tp));
                if_detach(TUN2IFP(tp));
        }
        sx_xlock(&tun_ioctl_sx);
        TUN2IFP(tp)->if_softc = NULL;
        sx_xunlock(&tun_ioctl_sx);
        free_unr(tp->tun_drv->unrhdr, TUN2IFP(tp)->if_dunit);
        if_free(TUN2IFP(tp));
        cv_destroy(&tp->tun_cv);
        NET_EPOCH_CALL(tunfree, &tp->tun_epoch_ctx);
        CURVNET_RESTORE();

        return (0);
}

static int
tun_clone_destroy(struct if_clone *ifc __unused, struct ifnet *ifp, uint32_t flags)
{
        struct tuntap_softc *tp = ifp->if_softc;

        return (tun_destroy(tp, true));
}

static void
vnet_tun_init(const void *unused __unused)
{

        for (u_int i = 0; i < NDRV; ++i) {
                struct if_clone_addreq req = {
                        .match_f = tuntap_drivers[i].clone_match_fn,
                        .create_f = tuntap_drivers[i].clone_create_fn,
                        .destroy_f = tuntap_drivers[i].clone_destroy_fn,
                };
                V_tuntap_driver_cloners[i] =
                    ifc_attach_cloner(tuntap_drivers[i].cdevsw.d_name, &req);
        };
}
VNET_SYSINIT(vnet_tun_init, SI_SUB_PROTO_IF, SI_ORDER_ANY,
                vnet_tun_init, NULL);

static void
tun_uninit(const void *unused __unused)
{
        struct tuntap_driver *drv;
        struct tuntap_softc *tp;
        int i;

        EVENTHANDLER_DEREGISTER(ifnet_rename_event, rename_tag);
        EVENTHANDLER_DEREGISTER(dev_clone, clone_tag);

        CURVNET_SET(vnet0);
        for (u_int i = 0; i < NDRV; i++) {
                if_clone_detach(V_tuntap_driver_cloners[i]);
                V_tuntap_driver_cloners[i] = NULL;
        }
        CURVNET_RESTORE();

        if (tuntap_osd_jail_slot != 0)
                osd_jail_deregister(tuntap_osd_jail_slot);

        mtx_lock(&tunmtx);
        while ((tp = TAILQ_FIRST(&tunhead)) != NULL) {
                mtx_unlock(&tunmtx);
                /* tun_destroy() will remove it from the tailq. */
                tun_destroy(tp, false);
                mtx_lock(&tunmtx);
        }
        mtx_unlock(&tunmtx);
        for (i = 0; i < nitems(tuntap_drivers); ++i) {
                drv = &tuntap_drivers[i];
                destroy_dev_drain(&drv->cdevsw);
                delete_unrhdr(drv->unrhdr);
                clone_cleanup(&drv->clones);
        }
        NET_EPOCH_DRAIN_CALLBACKS();
        mtx_destroy(&tunmtx);
}
SYSUNINIT(tun_uninit, SI_SUB_PROTO_IF, SI_ORDER_ANY, tun_uninit, NULL);

static struct tuntap_driver *
tuntap_driver_from_ifnet(const struct ifnet *ifp)
{
        struct tuntap_driver *drv;
        int i;

        if (ifp == NULL)
                return (NULL);

        for (i = 0; i < nitems(tuntap_drivers); ++i) {
                drv = &tuntap_drivers[i];
                if (strcmp(ifp->if_dname, drv->cdevsw.d_name) == 0)
                        return (drv);
        }

        return (NULL);
}

/*
 * Remove devices that were created by devfs cloning, as they hold references
 * which prevent the prison from collapsing, in which state VNET sysuninits will
 * not be invoked.
 */
static int
tuntap_prison_remove(void *obj, void *data __unused)
{
#ifdef VIMAGE
        struct prison *pr;

        pr = obj;
        if (prison_owns_vnet(pr)) {
                CURVNET_SET(pr->pr_vnet);
                for (u_int i = 0; i < NDRV; i++) {
                        if_clone_detach(V_tuntap_driver_cloners[i]);
                        V_tuntap_driver_cloners[i] = NULL;
                }
                CURVNET_RESTORE();
        }
#endif
        return (0);
}

static int
tuntapmodevent(module_t mod, int type, void *data)
{
        struct tuntap_driver *drv;
        int i;

        switch (type) {
        case MOD_LOAD:
                mtx_init(&tunmtx, "tunmtx", NULL, MTX_DEF);
                for (i = 0; i < nitems(tuntap_drivers); ++i) {
                        drv = &tuntap_drivers[i];
                        clone_setup(&drv->clones);
                        drv->unrhdr = new_unrhdr(0, IF_MAXUNIT, &tunmtx);
                }
                osd_method_t methods[PR_MAXMETHOD] = {
                        [PR_METHOD_REMOVE] = tuntap_prison_remove,
                };
                tuntap_osd_jail_slot = osd_jail_register(NULL, methods);
                rename_tag = EVENTHANDLER_REGISTER(ifnet_rename_event,
                    tunrename, NULL, EVENTHANDLER_PRI_ANY);
                clone_tag = EVENTHANDLER_REGISTER(dev_clone, tunclone, NULL,
                    EVENTHANDLER_PRI_ANY);
                break;
        case MOD_UNLOAD:
                /* See tun_uninit(). */
                break;
        default:
                return EOPNOTSUPP;
        }
        return 0;
}

static moduledata_t tuntap_mod = {
        "if_tuntap",
        tuntapmodevent,
        0
};

/* We'll only ever have these two, so no need for a macro. */
static moduledata_t tun_mod = { "if_tun", NULL, 0 };
static moduledata_t tap_mod = { "if_tap", NULL, 0 };

DECLARE_MODULE(if_tuntap, tuntap_mod, SI_SUB_PSEUDO, SI_ORDER_ANY);
MODULE_VERSION(if_tuntap, 1);
DECLARE_MODULE(if_tun, tun_mod, SI_SUB_PSEUDO, SI_ORDER_ANY);
MODULE_VERSION(if_tun, 1);
DECLARE_MODULE(if_tap, tap_mod, SI_SUB_PSEUDO, SI_ORDER_ANY);
MODULE_VERSION(if_tap, 1);

static int
tun_create_device(struct tuntap_driver *drv, int unit, struct ucred *cr,
    struct cdev **dev, const char *name)
{
        struct make_dev_args args;
        struct tuntap_softc *tp;
        int error;

        tp = malloc(sizeof(*tp), M_TUN, M_WAITOK | M_ZERO);
        mtx_init(&tp->tun_mtx, "tun_mtx", NULL, MTX_DEF);
        cv_init(&tp->tun_cv, "tun_condvar");
        tp->tun_flags = drv->ident_flags;
        tp->tun_drv = drv;

        make_dev_args_init(&args);
        if (cr != NULL)
                args.mda_flags = MAKEDEV_REF | MAKEDEV_CHECKNAME;
        args.mda_devsw = &drv->cdevsw;
        args.mda_cr = cr;
        args.mda_uid = UID_UUCP;
        args.mda_gid = GID_DIALER;
        args.mda_mode = 0600;
        args.mda_unit = unit;
        args.mda_si_drv1 = tp;
        error = make_dev_s(&args, dev, "%s", name);
        if (error != 0) {
                mtx_destroy(&tp->tun_mtx);
                cv_destroy(&tp->tun_cv);
                free(tp, M_TUN);
                return (error);
        }

        KASSERT((*dev)->si_drv1 != NULL,
            ("Failed to set si_drv1 at %s creation", name));
        tp->tun_dev = *dev;
        knlist_init_mtx(&tp->tun_rsel.si_note, &tp->tun_mtx);
        mtx_lock(&tunmtx);
        TAILQ_INSERT_TAIL(&tunhead, tp, tun_list);
        mtx_unlock(&tunmtx);
        return (0);
}

static void
tunstart(struct ifnet *ifp)
{
        struct tuntap_softc *tp = ifp->if_softc;
        struct mbuf *m;

        TUNDEBUG(ifp, "starting\n");
        if (ALTQ_IS_ENABLED(&ifp->if_snd)) {
                IFQ_LOCK(&ifp->if_snd);
                IFQ_POLL_NOLOCK(&ifp->if_snd, m);
                if (m == NULL) {
                        IFQ_UNLOCK(&ifp->if_snd);
                        return;
                }
                IFQ_UNLOCK(&ifp->if_snd);
        }

        TUN_LOCK(tp);
        if (tp->tun_flags & TUN_RWAIT) {
                tp->tun_flags &= ~TUN_RWAIT;
                wakeup(tp);
        }
        selwakeuppri(&tp->tun_rsel, PZERO);
        KNOTE_LOCKED(&tp->tun_rsel.si_note, 0);
        if (tp->tun_flags & TUN_ASYNC && tp->tun_sigio) {
                TUN_UNLOCK(tp);
                pgsigio(&tp->tun_sigio, SIGIO, 0);
        } else
                TUN_UNLOCK(tp);
}

/*
 * tunstart_l2
 *
 * queue packets from higher level ready to put out
 */
static void
tunstart_l2(struct ifnet *ifp)
{
        struct tuntap_softc     *tp = ifp->if_softc;

        TUNDEBUG(ifp, "starting\n");

        /*
         * do not junk pending output if we are in VMnet mode.
         * XXX: can this do any harm because of queue overflow?
         */

        TUN_LOCK(tp);
        if (((tp->tun_flags & TUN_VMNET) == 0) &&
            ((tp->tun_flags & TUN_READY) != TUN_READY)) {
                struct mbuf *m;

                /* Unlocked read. */
                TUNDEBUG(ifp, "not ready, tun_flags = 0x%x\n", tp->tun_flags);

                for (;;) {
                        IF_DEQUEUE(&ifp->if_snd, m);
                        if (m != NULL) {
                                m_freem(m);
                                if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
                        } else
                                break;
                }
                TUN_UNLOCK(tp);

                return;
        }

        ifp->if_drv_flags |= IFF_DRV_OACTIVE;

        if (!IFQ_IS_EMPTY(&ifp->if_snd)) {
                if (tp->tun_flags & TUN_RWAIT) {
                        tp->tun_flags &= ~TUN_RWAIT;
                        wakeup(tp);
                }

                if ((tp->tun_flags & TUN_ASYNC) && (tp->tun_sigio != NULL)) {
                        TUN_UNLOCK(tp);
                        pgsigio(&tp->tun_sigio, SIGIO, 0);
                        TUN_LOCK(tp);
                }

                selwakeuppri(&tp->tun_rsel, PZERO);
                KNOTE_LOCKED(&tp->tun_rsel.si_note, 0);
                if_inc_counter(ifp, IFCOUNTER_OPACKETS, 1); /* obytes are counted in ether_output */
        }

        ifp->if_drv_flags &= ~IFF_DRV_OACTIVE;
        TUN_UNLOCK(tp);
} /* tunstart_l2 */

static int
tap_transmit(struct ifnet *ifp, struct mbuf *m)
{
        int error;

        BPF_MTAP(ifp, m);
        IFQ_HANDOFF(ifp, m, error);
        return (error);
}

static void
tuncreate(struct cdev *dev)
{
        struct tuntap_driver *drv;
        struct tuntap_softc *tp;
        struct ifnet *ifp;
        struct ether_addr eaddr;
        int iflags;
        u_char type;

        tp = dev->si_drv1;
        KASSERT(tp != NULL,
            ("si_drv1 should have been initialized at creation"));

        drv = tp->tun_drv;
        iflags = IFF_MULTICAST;
        if ((tp->tun_flags & TUN_L2) != 0) {
                type = IFT_ETHER;
                iflags |= IFF_BROADCAST | IFF_SIMPLEX;
        } else {
                type = IFT_PPP;
                iflags |= IFF_POINTOPOINT;
        }
        ifp = tp->tun_ifp = if_alloc(type);
        ifp->if_softc = tp;
        if_initname(ifp, drv->cdevsw.d_name, dev2unit(dev));
        ifp->if_ioctl = tunifioctl;
        ifp->if_flags = iflags;
        IFQ_SET_MAXLEN(&ifp->if_snd, ifqmaxlen);
        ifp->if_capabilities |= IFCAP_LINKSTATE | IFCAP_MEXTPG;
        if ((tp->tun_flags & TUN_L2) != 0)
                ifp->if_capabilities |=
                    IFCAP_RXCSUM | IFCAP_RXCSUM_IPV6 | IFCAP_LRO;
        ifp->if_capenable |= IFCAP_LINKSTATE | IFCAP_MEXTPG;

        if ((tp->tun_flags & TUN_L2) != 0) {
                ifp->if_init = tunifinit;
                ifp->if_start = tunstart_l2;
                ifp->if_transmit = tap_transmit;
                ifp->if_qflush = if_qflush;

                ether_gen_addr(ifp, &eaddr);
                ether_ifattach(ifp, eaddr.octet);
        } else {
                ifp->if_mtu = TUNMTU;
                ifp->if_start = tunstart;
                ifp->if_output = tunoutput;

                ifp->if_snd.ifq_drv_maxlen = 0;
                IFQ_SET_READY(&ifp->if_snd);

                if_attach(ifp);
                bpfattach(ifp, DLT_NULL, sizeof(u_int32_t));
        }

        TUN_LOCK(tp);
        tp->tun_flags |= TUN_INITED;
        TUN_UNLOCK(tp);

        TUNDEBUG(ifp, "interface %s is created, minor = %#x\n",
            ifp->if_xname, dev2unit(dev));
}

static void
tunrename(void *arg __unused, struct ifnet *ifp)
{
        struct tuntap_softc *tp;
        int error;

        if (tuntap_driver_from_ifnet(ifp) == NULL)
                return;

        /*
         * We need to grab the ioctl sx long enough to make sure the softc is
         * still there.  If it is, we can safely try to busy the tun device.
         * The busy may fail if the device is currently dying, in which case
         * we do nothing.  If it doesn't fail, the busy count stops the device
         * from dying until we've created the alias (that will then be
         * subsequently destroyed).
         */
        sx_xlock(&tun_ioctl_sx);
        tp = ifp->if_softc;
        if (tp == NULL) {
                sx_xunlock(&tun_ioctl_sx);
                return;
        }
        error = tun_busy(tp);
        sx_xunlock(&tun_ioctl_sx);
        if (error != 0)
                return;
        if (tp->tun_alias != NULL) {
                destroy_dev(tp->tun_alias);
                tp->tun_alias = NULL;
        }

        if (strcmp(ifp->if_xname, tp->tun_dev->si_name) == 0)
                goto out;

        /*
         * Failure's ok, aliases are created on a best effort basis.  If a
         * tun user/consumer decides to rename the interface to conflict with
         * another device (non-ifnet) on the system, we will assume they know
         * what they are doing.  make_dev_alias_p won't touch tun_alias on
         * failure, so we use it but ignore the return value.
         */
        make_dev_alias_p(MAKEDEV_CHECKNAME, &tp->tun_alias, tp->tun_dev, "%s",
            ifp->if_xname);
out:
        tun_unbusy(tp);
}

static int
tunopen(struct cdev *dev, int flag, int mode, struct thread *td)
{
        struct epoch_tracker et;
        struct ifnet    *ifp;
        struct tuntap_softc *tp;
        void            *p;
        int error __diagused, tunflags;

        /*
         * Transient tunnels do deferred destroy of the tun device but want
         * to immediately cleanup state, so they clobber si_drv1 to avoid a
         * use-after-free in case someone does happen to open it in the interim.
         * We avoid using NULL to be able to distinguish from an uninitialized
         * cdev.
         *
         * We use the net epoch here to let a concurrent tun_destroy() schedule
         * freeing our tuntap_softc, in case we entered here and loaded si_drv1
         * before it was swapped out.  If we managed to load this while it was
         * still a softc, then the concurrent tun_destroy() hasn't yet scheduled
         * it to be free- that will take place sometime after the epoch we just
         * entered, so we can safely use it.
         */
        NET_EPOCH_ENTER(et);
        p = atomic_load_ptr(&dev->si_drv1);
        if (p == dev) {
                NET_EPOCH_EXIT(et);
                return (ENXIO);
        }

        tunflags = 0;
        CURVNET_SET(TD_TO_VNET(td));
        error = tuntap_name2info(dev->si_name, NULL, &tunflags);
        if (error != 0) {
                CURVNET_RESTORE();
                NET_EPOCH_EXIT(et);
                return (error); /* Shouldn't happen */
        }

        tp = p;
        KASSERT(tp != NULL,
            ("si_drv1 should have been initialized at creation"));

        TUN_LOCK(tp);
        if ((tp->tun_flags & TUN_INITED) == 0) {
                TUN_UNLOCK(tp);
                CURVNET_RESTORE();
                NET_EPOCH_EXIT(et);
                return (ENXIO);
        }
        if ((tp->tun_flags & (TUN_OPEN | TUN_DYING)) != 0) {
                TUN_UNLOCK(tp);
                CURVNET_RESTORE();
                NET_EPOCH_EXIT(et);
                return (EBUSY);
        }

        NET_EPOCH_EXIT(et);
        error = tun_busy_locked(tp);
        KASSERT(error == 0, ("Must be able to busy an unopen tunnel"));
        ifp = TUN2IFP(tp);

        if ((tp->tun_flags & TUN_L2) != 0) {
                bcopy(IF_LLADDR(ifp), tp->tun_ether.octet,
                    sizeof(tp->tun_ether.octet));

                ifp->if_drv_flags |= IFF_DRV_RUNNING;
                ifp->if_drv_flags &= ~IFF_DRV_OACTIVE;

                if (tapuponopen)
                        ifp->if_flags |= IFF_UP;
        }

        tp->tun_pid = td->td_proc->p_pid;
        tp->tun_flags |= TUN_OPEN;

        if_link_state_change(ifp, LINK_STATE_UP);
        TUNDEBUG(ifp, "open\n");
        TUN_UNLOCK(tp);

        /*
         * This can fail with either ENOENT or EBUSY.  This is in the middle of
         * d_open, so ENOENT should not be possible.  EBUSY is possible, but
         * the only cdevpriv dtor being set will be tundtor and the softc being
         * passed is constant for a given cdev.  We ignore the possible error
         * because of this as either "unlikely" or "not actually a problem."
         */
        (void)devfs_set_cdevpriv(tp, tundtor);
        CURVNET_RESTORE();
        return (0);
}

/*
 * tundtor - tear down the device - mark i/f down & delete
 * routing info
 */
static void
tundtor(void *data)
{
        struct proc *p;
        struct tuntap_softc *tp;
        struct ifnet *ifp;
        bool l2tun;

        tp = data;
        p = curproc;
        ifp = TUN2IFP(tp);

        TUN_LOCK(tp);

        /*
         * Realistically, we can't be obstinate here.  This only means that the
         * tuntap device was closed out of order, and the last closer wasn't the
         * controller.  These are still good to know about, though, as software
         * should avoid multiple processes with a tuntap device open and
         * ill-defined transfer of control (e.g., handoff, TUNSIFPID, close in
         * parent).
         */
        if (p->p_pid != tp->tun_pid) {
                log(LOG_INFO,
                    "pid %d (%s), %s: tun/tap protocol violation, non-controlling process closed last.\n",
                    p->p_pid, p->p_comm, tp->tun_dev->si_name);
        }

        /*
         * junk all pending output
         */
        CURVNET_SET(ifp->if_vnet);

        l2tun = false;
        if ((tp->tun_flags & TUN_L2) != 0) {
                l2tun = true;
                IF_DRAIN(&ifp->if_snd);
        } else {
                IFQ_PURGE(&ifp->if_snd);
        }

        /* For vmnet, we won't do most of the address/route bits */
        if ((tp->tun_flags & TUN_VMNET) != 0 ||
            (l2tun && (ifp->if_flags & IFF_LINK0) != 0))
                goto out;
#if defined(INET) || defined(INET6)
        if (l2tun && tp->tun_lro_ready) {
                TUNDEBUG (ifp, "LRO disabled\n");
                tcp_lro_free(&tp->tun_lro);
                tp->tun_lro_ready = false;
        }
#endif
        if (ifp->if_flags & IFF_UP) {
                TUN_UNLOCK(tp);
                if_down(ifp);
                TUN_LOCK(tp);
        }

        /* Delete all addresses and routes which reference this interface. */
        if (ifp->if_drv_flags & IFF_DRV_RUNNING) {
                ifp->if_drv_flags &= ~IFF_DRV_RUNNING;
                TUN_UNLOCK(tp);
                if_purgeaddrs(ifp);
                TUN_LOCK(tp);
        }

out:
        if_link_state_change(ifp, LINK_STATE_DOWN);
        CURVNET_RESTORE();

        funsetown(&tp->tun_sigio);
        selwakeuppri(&tp->tun_rsel, PZERO);
        KNOTE_LOCKED(&tp->tun_rsel.si_note, 0);
        TUNDEBUG (ifp, "closed\n");
        tp->tun_flags &= ~TUN_OPEN;
        tp->tun_pid = 0;
        tun_vnethdr_set(ifp, 0);

        tun_unbusy_locked(tp);
        if ((tp->tun_flags & TUN_TRANSIENT) != 0) {
                struct if_clone *cloner;
                int error __diagused;

                /* Mark it busy so that nothing can re-open it. */
                tp->tun_flags |= TUN_DYING;
                TUN_UNLOCK(tp);

                CURVNET_SET_QUIET(ifp->if_home_vnet);
                cloner = tuntap_cloner_from_flags(tp->tun_flags);
                CURVNET_RESTORE();

                error = if_clone_destroyif(cloner, ifp);
                MPASS(error == 0 || error == EINTR || error == ERESTART);
                return;
        }

        TUN_UNLOCK(tp);
}

static void
tuninit(struct ifnet *ifp)
{
        struct tuntap_softc *tp = ifp->if_softc;

        TUNDEBUG(ifp, "tuninit\n");

        TUN_LOCK(tp);
        ifp->if_drv_flags |= IFF_DRV_RUNNING;
        if ((tp->tun_flags & TUN_L2) == 0) {
                ifp->if_flags |= IFF_UP;
                getmicrotime(&ifp->if_lastchange);
                TUN_UNLOCK(tp);
        } else {
#if defined(INET) || defined(INET6)
                if (tcp_lro_init(&tp->tun_lro) == 0) {
                        TUNDEBUG(ifp, "LRO enabled\n");
                        tp->tun_lro.ifp = ifp;
                        tp->tun_lro_ready = true;
                } else {
                        TUNDEBUG(ifp, "Could not enable LRO\n");
                        tp->tun_lro_ready = false;
                }
#endif
                ifp->if_drv_flags &= ~IFF_DRV_OACTIVE;
                TUN_UNLOCK(tp);
                /* attempt to start output */
                tunstart_l2(ifp);
        }

}

/*
 * Used only for l2 tunnel.
 */
static void
tunifinit(void *xtp)
{
        struct tuntap_softc *tp;

        tp = (struct tuntap_softc *)xtp;
        tuninit(tp->tun_ifp);
}

/*
 * To be called under TUN_LOCK. Update ifp->if_hwassist according to the
 * current value of ifp->if_capenable.
 */
static void
tun_caps_changed(struct ifnet *ifp)
{
        uint64_t hwassist = 0;

        TUN_LOCK_ASSERT((struct tuntap_softc *)ifp->if_softc);
        if (ifp->if_capenable & IFCAP_TXCSUM)
                hwassist |= CSUM_TCP | CSUM_UDP;
        if (ifp->if_capenable & IFCAP_TXCSUM_IPV6)
                hwassist |= CSUM_TCP_IPV6
                    | CSUM_UDP_IPV6;
        if (ifp->if_capenable & IFCAP_TSO4)
                hwassist |= CSUM_IP_TSO;
        if (ifp->if_capenable & IFCAP_TSO6)
                hwassist |= CSUM_IP6_TSO;
        ifp->if_hwassist = hwassist;
}

/*
 * To be called under TUN_LOCK. Update tp->tun_vhdrlen and adjust
 * if_capabilities and if_capenable as needed.
 */
static void
tun_vnethdr_set(struct ifnet *ifp, int vhdrlen)
{
        struct tuntap_softc *tp = ifp->if_softc;

        TUN_LOCK_ASSERT(tp);

        if (tp->tun_vhdrlen == vhdrlen)
                return;

        /*
         * Update if_capabilities to reflect the
         * functionalities offered by the virtio-net
         * header.
         */
        if (vhdrlen != 0)
                ifp->if_capabilities |=
                        TAP_VNET_HDR_CAPS;
        else
                ifp->if_capabilities &=
                        ~TAP_VNET_HDR_CAPS;
        /*
         * Disable any capabilities that we don't
         * support anymore.
         */
        ifp->if_capenable &= ifp->if_capabilities;
        tun_caps_changed(ifp);
        tp->tun_vhdrlen = vhdrlen;

        TUNDEBUG(ifp, "vnet_hdr_len=%d, if_capabilities=%x\n",
            vhdrlen, ifp->if_capabilities);
}

/*
 * Process an ioctl request.
 */
static int
tunifioctl(struct ifnet *ifp, u_long cmd, caddr_t data)
{
        struct ifreq *ifr = (struct ifreq *)data;
        struct tuntap_softc *tp;
        struct ifstat *ifs;
        struct ifmediareq       *ifmr;
        int             dummy, error = 0;
        bool            l2tun;

        ifmr = NULL;
        sx_xlock(&tun_ioctl_sx);
        tp = ifp->if_softc;
        if (tp == NULL) {
                error = ENXIO;
                goto bad;
        }
        l2tun = (tp->tun_flags & TUN_L2) != 0;
        switch(cmd) {
        case SIOCGIFSTATUS:
                ifs = (struct ifstat *)data;
                TUN_LOCK(tp);
                if (tp->tun_pid)
                        snprintf(ifs->ascii, sizeof(ifs->ascii),
                            "\tOpened by PID %d\n", tp->tun_pid);
                else
                        ifs->ascii[0] = '\0';
                TUN_UNLOCK(tp);
                break;
        case SIOCSIFADDR:
                if (l2tun)
                        error = ether_ioctl(ifp, cmd, data);
                else
                        tuninit(ifp);
                if (error == 0)
                    TUNDEBUG(ifp, "address set\n");
                break;
        case SIOCSIFMTU:
                ifp->if_mtu = ifr->ifr_mtu;
                TUNDEBUG(ifp, "mtu set\n");
                break;
        case SIOCSIFFLAGS:
        case SIOCADDMULTI:
        case SIOCDELMULTI:
                break;
        case SIOCGIFMEDIA:
                if (!l2tun) {
                        error = EINVAL;
                        break;
                }

                ifmr = (struct ifmediareq *)data;
                dummy = ifmr->ifm_count;
                ifmr->ifm_count = 1;
                ifmr->ifm_status = IFM_AVALID;
                ifmr->ifm_active = IFM_ETHER | IFM_FDX | IFM_1000_T;
                if (tp->tun_flags & TUN_OPEN)
                        ifmr->ifm_status |= IFM_ACTIVE;
                ifmr->ifm_current = ifmr->ifm_active;
                if (dummy >= 1) {
                        int media = IFM_ETHER;
                        error = copyout(&media, ifmr->ifm_ulist, sizeof(int));
                }
                break;
        case SIOCSIFCAP:
                TUN_LOCK(tp);
                ifp->if_capenable = ifr->ifr_reqcap;
                tun_caps_changed(ifp);
                TUN_UNLOCK(tp);
                VLAN_CAPABILITIES(ifp);
                break;
        default:
                if (l2tun) {
                        error = ether_ioctl(ifp, cmd, data);
                } else {
                        error = EINVAL;
                }
        }
bad:
        sx_xunlock(&tun_ioctl_sx);
        return (error);
}

/*
 * tunoutput - queue packets from higher level ready to put out.
 */
static int
tunoutput(struct ifnet *ifp, struct mbuf *m0, const struct sockaddr *dst,
    struct route *ro)
{
        struct tuntap_softc *tp = ifp->if_softc;
        u_short cached_tun_flags;
        int error;
        u_int32_t af;

        TUNDEBUG (ifp, "tunoutput\n");

#ifdef MAC
        error = mac_ifnet_check_transmit(ifp, m0);
        if (error) {
                m_freem(m0);
                return (error);
        }
#endif

        /* Could be unlocked read? */
        TUN_LOCK(tp);
        cached_tun_flags = tp->tun_flags;
        TUN_UNLOCK(tp);
        if ((cached_tun_flags & TUN_READY) != TUN_READY) {
                TUNDEBUG (ifp, "not ready 0%o\n", tp->tun_flags);
                m_freem (m0);
                return (EHOSTDOWN);
        }

        if ((ifp->if_flags & IFF_UP) != IFF_UP) {
                m_freem (m0);
                return (EHOSTDOWN);
        }

        /* BPF writes need to be handled specially. */
        if (dst->sa_family == AF_UNSPEC || dst->sa_family == pseudo_AF_HDRCMPLT)
                bcopy(dst->sa_data, &af, sizeof(af));
        else
                af = RO_GET_FAMILY(ro, dst);

        BPF_MTAP2(ifp, &af, sizeof(af), m0);

        /* prepend sockaddr? this may abort if the mbuf allocation fails */
        if (cached_tun_flags & TUN_LMODE) {
                /* allocate space for sockaddr */
                M_PREPEND(m0, dst->sa_len, M_NOWAIT);

                /* if allocation failed drop packet */
                if (m0 == NULL) {
                        if_inc_counter(ifp, IFCOUNTER_IQDROPS, 1);
                        if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
                        return (ENOBUFS);
                } else {
                        bcopy(dst, m0->m_data, dst->sa_len);
                }
        }

        if (cached_tun_flags & TUN_IFHEAD) {
                /* Prepend the address family */
                M_PREPEND(m0, 4, M_NOWAIT);

                /* if allocation failed drop packet */
                if (m0 == NULL) {
                        if_inc_counter(ifp, IFCOUNTER_IQDROPS, 1);
                        if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
                        return (ENOBUFS);
                } else
                        *(u_int32_t *)m0->m_data = htonl(af);
        } else {
#ifdef INET
                if (af != AF_INET)
#endif
                {
                        m_freem(m0);
                        return (EAFNOSUPPORT);
                }
        }

        error = (ifp->if_transmit)(ifp, m0);
        if (error)
                return (ENOBUFS);
        if_inc_counter(ifp, IFCOUNTER_OPACKETS, 1);
        return (0);
}

/*
 * the cdevsw interface is now pretty minimal.
 */
static  int
tunioctl(struct cdev *dev, u_long cmd, caddr_t data, int flag,
    struct thread *td)
{
        struct ifreq ifr, *ifrp;
        struct tuntap_softc *tp = dev->si_drv1;
        struct ifnet *ifp = TUN2IFP(tp);
        struct tuninfo *tunp;
        int error, iflags, ival;
        bool    l2tun;

        l2tun = (tp->tun_flags & TUN_L2) != 0;
        if (l2tun) {
                /* tap specific ioctls */
                switch(cmd) {
                /* VMware/VMnet port ioctl's */
#if defined(COMPAT_FREEBSD6) || defined(COMPAT_FREEBSD5) || \
    defined(COMPAT_FREEBSD4)
                case _IO('V', 0):
                        ival = IOCPARM_IVAL(data);
                        data = (caddr_t)&ival;
                        /* FALLTHROUGH */
#endif
                case VMIO_SIOCSIFFLAGS: /* VMware/VMnet SIOCSIFFLAGS */
                        iflags = *(int *)data;
                        iflags &= TUN_VMIO_FLAG_MASK;
                        iflags &= ~IFF_CANTCHANGE;
                        iflags |= IFF_UP;

                        TUN_LOCK(tp);
                        ifp->if_flags = iflags |
                            (ifp->if_flags & IFF_CANTCHANGE);
                        TUN_UNLOCK(tp);

                        return (0);
                case SIOCGIFADDR:       /* get MAC address of the remote side */
                        TUN_LOCK(tp);
                        bcopy(&tp->tun_ether.octet, data,
                            sizeof(tp->tun_ether.octet));
                        TUN_UNLOCK(tp);

                        return (0);
                case SIOCSIFADDR:       /* set MAC address of the remote side */
                        TUN_LOCK(tp);
                        bcopy(data, &tp->tun_ether.octet,
                            sizeof(tp->tun_ether.octet));
                        TUN_UNLOCK(tp);

                        return (0);
                case TAPSVNETHDR:
                        ival = *(int *)data;
                        if (ival != 0 &&
                            ival != sizeof(struct virtio_net_hdr) &&
                            ival != sizeof(struct virtio_net_hdr_mrg_rxbuf)) {
                                return (EINVAL);
                        }
                        TUN_LOCK(tp);
                        tun_vnethdr_set(ifp, ival);
                        TUN_UNLOCK(tp);

                        return (0);
                case TAPGVNETHDR:
                        TUN_LOCK(tp);
                        *(int *)data = tp->tun_vhdrlen;
                        TUN_UNLOCK(tp);

                        return (0);
                }

                /* Fall through to the common ioctls if unhandled */
        } else {
                switch (cmd) {
                case TUNSLMODE:
                        TUN_LOCK(tp);
                        if (*(int *)data) {
                                tp->tun_flags |= TUN_LMODE;
                                tp->tun_flags &= ~TUN_IFHEAD;
                        } else
                                tp->tun_flags &= ~TUN_LMODE;
                        TUN_UNLOCK(tp);

                        return (0);
                case TUNSIFHEAD:
                        TUN_LOCK(tp);
                        if (*(int *)data) {
                                tp->tun_flags |= TUN_IFHEAD;
                                tp->tun_flags &= ~TUN_LMODE;
                        } else
                                tp->tun_flags &= ~TUN_IFHEAD;
                        TUN_UNLOCK(tp);

                        return (0);
                case TUNGIFHEAD:
                        TUN_LOCK(tp);
                        *(int *)data = (tp->tun_flags & TUN_IFHEAD) ? 1 : 0;
                        TUN_UNLOCK(tp);

                        return (0);
                case TUNSIFMODE:
                        /* deny this if UP */
                        if (TUN2IFP(tp)->if_flags & IFF_UP)
                                return (EBUSY);

                        switch (*(int *)data & ~IFF_MULTICAST) {
                        case IFF_POINTOPOINT:
                        case IFF_BROADCAST:
                                TUN_LOCK(tp);
                                TUN2IFP(tp)->if_flags &=
                                    ~(IFF_BROADCAST|IFF_POINTOPOINT|IFF_MULTICAST);
                                TUN2IFP(tp)->if_flags |= *(int *)data;
                                TUN_UNLOCK(tp);

                                break;
                        default:
                                return (EINVAL);
                        }

                        return (0);
                case TUNSIFPID:
                        TUN_LOCK(tp);
                        tp->tun_pid = curthread->td_proc->p_pid;
                        TUN_UNLOCK(tp);

                        return (0);
                }
                /* Fall through to the common ioctls if unhandled */
        }

        switch (cmd) {
        case TUNGIFNAME:
                ifrp = (struct ifreq *)data;
                strlcpy(ifrp->ifr_name, TUN2IFP(tp)->if_xname, IFNAMSIZ);

                return (0);
        case TUNSIFINFO:
                tunp = (struct tuninfo *)data;
                if (TUN2IFP(tp)->if_type != tunp->type)
                        return (EPROTOTYPE);
                TUN_LOCK(tp);
                if (TUN2IFP(tp)->if_mtu != tunp->mtu) {
                        strlcpy(ifr.ifr_name, if_name(TUN2IFP(tp)), IFNAMSIZ);
                        ifr.ifr_mtu = tunp->mtu;
                        CURVNET_SET(TUN2IFP(tp)->if_vnet);
                        error = ifhwioctl(SIOCSIFMTU, TUN2IFP(tp),
                            (caddr_t)&ifr, td);
                        CURVNET_RESTORE();
                        if (error) {
                                TUN_UNLOCK(tp);
                                return (error);
                        }
                }
                TUN2IFP(tp)->if_baudrate = tunp->baudrate;
                TUN_UNLOCK(tp);
                break;
        case TUNGIFINFO:
                tunp = (struct tuninfo *)data;
                TUN_LOCK(tp);
                tunp->mtu = TUN2IFP(tp)->if_mtu;
                tunp->type = TUN2IFP(tp)->if_type;
                tunp->baudrate = TUN2IFP(tp)->if_baudrate;
                TUN_UNLOCK(tp);
                break;
        case TUNSDEBUG:
                tundebug = *(int *)data;
                break;
        case TUNGDEBUG:
                *(int *)data = tundebug;
                break;
        case TUNSTRANSIENT:
                TUN_LOCK(tp);
                if (*(int *)data)
                        tp->tun_flags |= TUN_TRANSIENT;
                else
                        tp->tun_flags &= ~TUN_TRANSIENT;
                TUN_UNLOCK(tp);
                break;
        case TUNGTRANSIENT:
                TUN_LOCK(tp);
                *(int *)data = (tp->tun_flags & TUN_TRANSIENT) != 0;
                TUN_UNLOCK(tp);
                break;
        case FIONBIO:
                break;
        case FIOASYNC:
                TUN_LOCK(tp);
                if (*(int *)data)
                        tp->tun_flags |= TUN_ASYNC;
                else
                        tp->tun_flags &= ~TUN_ASYNC;
                TUN_UNLOCK(tp);
                break;
        case FIONREAD:
                if (!IFQ_IS_EMPTY(&TUN2IFP(tp)->if_snd)) {
                        struct mbuf *mb;
                        IFQ_LOCK(&TUN2IFP(tp)->if_snd);
                        IFQ_POLL_NOLOCK(&TUN2IFP(tp)->if_snd, mb);
                        for (*(int *)data = 0; mb != NULL; mb = mb->m_next)
                                *(int *)data += mb->m_len;
                        IFQ_UNLOCK(&TUN2IFP(tp)->if_snd);
                } else
                        *(int *)data = 0;
                break;
        case FIOSETOWN:
                return (fsetown(*(int *)data, &tp->tun_sigio));

        case FIOGETOWN:
                *(int *)data = fgetown(&tp->tun_sigio);
                return (0);

        /* This is deprecated, FIOSETOWN should be used instead. */
        case TIOCSPGRP:
                return (fsetown(-(*(int *)data), &tp->tun_sigio));

        /* This is deprecated, FIOGETOWN should be used instead. */
        case TIOCGPGRP:
                *(int *)data = -fgetown(&tp->tun_sigio);
                return (0);

        default:
                return (ENOTTY);
        }
        return (0);
}

/*
 * The cdevsw read interface - reads a packet at a time, or at
 * least as much of a packet as can be read.
 */
static  int
tunread(struct cdev *dev, struct uio *uio, int flag)
{
        struct tuntap_softc *tp = dev->si_drv1;
        struct ifnet    *ifp = TUN2IFP(tp);
        struct mbuf     *m;
        size_t          len;
        int             error = 0;

        TUNDEBUG (ifp, "read\n");
        TUN_LOCK(tp);
        if ((tp->tun_flags & TUN_READY) != TUN_READY) {
                TUN_UNLOCK(tp);
                TUNDEBUG (ifp, "not ready 0%o\n", tp->tun_flags);
                return (EHOSTDOWN);
        }

        tp->tun_flags &= ~TUN_RWAIT;

        for (;;) {
                IFQ_DEQUEUE(&ifp->if_snd, m);
                if (m != NULL)
                        break;
                if (flag & O_NONBLOCK) {
                        TUN_UNLOCK(tp);
                        return (EWOULDBLOCK);
                }
                tp->tun_flags |= TUN_RWAIT;
                error = mtx_sleep(tp, &tp->tun_mtx, PCATCH | PZERO,
                    "tunread", 0);
                if (error != 0) {
                        TUN_UNLOCK(tp);
                        return (error);
                }
        }
        TUN_UNLOCK(tp);

        len = min(tp->tun_vhdrlen, uio->uio_resid);
        if (len > 0) {
                struct virtio_net_hdr_mrg_rxbuf vhdr;

                bzero(&vhdr, sizeof(vhdr));
                if (m->m_pkthdr.csum_flags & TAP_ALL_OFFLOAD) {
                        m = virtio_net_tx_offload(ifp, m, false, &vhdr.hdr);
                }

                TUNDEBUG(ifp, "txvhdr: f %u, gt %u, hl %u, "
                    "gs %u, cs %u, co %u\n", vhdr.hdr.flags,
                    vhdr.hdr.gso_type, vhdr.hdr.hdr_len,
                    vhdr.hdr.gso_size, vhdr.hdr.csum_start,
                    vhdr.hdr.csum_offset);
                error = uiomove(&vhdr, len, uio);
        }
        if (error == 0)
                error = m_mbuftouio(uio, m, 0);
        m_freem(m);
        return (error);
}

static int
tunwrite_l2(struct tuntap_softc *tp, struct mbuf *m,
            struct virtio_net_hdr_mrg_rxbuf *vhdr)
{
        struct epoch_tracker et;
        struct ether_header *eh;
        struct ifnet *ifp;

        ifp = TUN2IFP(tp);

        /*
         * Only pass a unicast frame to ether_input(), if it would
         * actually have been received by non-virtual hardware.
         */
        if (m->m_len < sizeof(struct ether_header)) {
                m_freem(m);
                return (0);
        }

        eh = mtod(m, struct ether_header *);

        if ((ifp->if_flags & IFF_PROMISC) == 0 &&
            !ETHER_IS_MULTICAST(eh->ether_dhost) &&
            bcmp(eh->ether_dhost, IF_LLADDR(ifp), ETHER_ADDR_LEN) != 0) {
                m_freem(m);
                return (0);
        }

        if (vhdr != NULL) {
                if (virtio_net_rx_csum(m, &vhdr->hdr)) {
                        m_freem(m);
                        return (0);
                }
        } else {
                switch (ntohs(eh->ether_type)) {
#ifdef INET
                case ETHERTYPE_IP:
                        if (ifp->if_capenable & IFCAP_RXCSUM) {
                                m->m_pkthdr.csum_flags |=
                                    CSUM_IP_CHECKED | CSUM_IP_VALID |
                                    CSUM_DATA_VALID | CSUM_SCTP_VALID |
                                    CSUM_PSEUDO_HDR;
                                m->m_pkthdr.csum_data = 0xffff;
                        }
                        break;
#endif
#ifdef INET6
                case ETHERTYPE_IPV6:
                        if (ifp->if_capenable & IFCAP_RXCSUM_IPV6) {
                                m->m_pkthdr.csum_flags |=
                                    CSUM_DATA_VALID_IPV6 | CSUM_SCTP_VALID |
                                    CSUM_PSEUDO_HDR;
                                m->m_pkthdr.csum_data = 0xffff;
                        }
                        break;
#endif
                }
        }

        /* Pass packet up to parent. */
        CURVNET_SET(ifp->if_vnet);
        NET_EPOCH_ENTER(et);
#if defined(INET) || defined(INET6)
        if (tp->tun_lro_ready && ifp->if_capenable & IFCAP_LRO &&
            tcp_lro_rx(&tp->tun_lro, m, 0) == 0)
                tcp_lro_flush_all(&tp->tun_lro);
        else
#endif
                (*ifp->if_input)(ifp, m);
        NET_EPOCH_EXIT(et);
        CURVNET_RESTORE();
        /* ibytes are counted in parent */
        if_inc_counter(ifp, IFCOUNTER_IPACKETS, 1);
        return (0);
}

static int
tunwrite_l3(struct tuntap_softc *tp, struct mbuf *m)
{
        struct epoch_tracker et;
        struct ifnet *ifp;
        int family, isr;

        ifp = TUN2IFP(tp);
        /* Could be unlocked read? */
        TUN_LOCK(tp);
        if (tp->tun_flags & TUN_IFHEAD) {
                TUN_UNLOCK(tp);
                if (m->m_len < sizeof(family) &&
                (m = m_pullup(m, sizeof(family))) == NULL)
                        return (ENOBUFS);
                family = ntohl(*mtod(m, u_int32_t *));
                m_adj(m, sizeof(family));
        } else {
                TUN_UNLOCK(tp);
                family = AF_INET;
        }

        BPF_MTAP2(ifp, &family, sizeof(family), m);

        switch (family) {
#ifdef INET
        case AF_INET:
                isr = NETISR_IP;
                break;
#endif
#ifdef INET6
        case AF_INET6:
                isr = NETISR_IPV6;
                break;
#endif
        default:
                m_freem(m);
                return (EAFNOSUPPORT);
        }
        random_harvest_queue(m, sizeof(*m), RANDOM_NET_TUN);
        if_inc_counter(ifp, IFCOUNTER_IBYTES, m->m_pkthdr.len);
        if_inc_counter(ifp, IFCOUNTER_IPACKETS, 1);
        CURVNET_SET(ifp->if_vnet);
        M_SETFIB(m, ifp->if_fib);
        NET_EPOCH_ENTER(et);
        netisr_dispatch(isr, m);
        NET_EPOCH_EXIT(et);
        CURVNET_RESTORE();
        return (0);
}

/*
 * the cdevsw write interface - an atomic write is a packet - or else!
 */
static  int
tunwrite(struct cdev *dev, struct uio *uio, int flag)
{
        struct virtio_net_hdr_mrg_rxbuf vhdr;
        struct tuntap_softc *tp;
        struct ifnet    *ifp;
        struct mbuf     *m;
        uint32_t        mru;
        int             align, vhdrlen, error;
        bool            l2tun;

        tp = dev->si_drv1;
        ifp = TUN2IFP(tp);
        TUNDEBUG(ifp, "tunwrite\n");
        if ((ifp->if_flags & IFF_UP) != IFF_UP)
                /* ignore silently */
                return (0);

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

        l2tun = (tp->tun_flags & TUN_L2) != 0;
        mru = l2tun ? TAPMRU : TUNMRU;
        vhdrlen = tp->tun_vhdrlen;
        align = 0;
        if (l2tun) {
                align = ETHER_ALIGN;
                mru += vhdrlen;
        } else if ((tp->tun_flags & TUN_IFHEAD) != 0)
                mru += sizeof(uint32_t);        /* family */
        if (uio->uio_resid < 0 || uio->uio_resid > mru) {
                TUNDEBUG(ifp, "len=%zd!\n", uio->uio_resid);
                return (EIO);
        }

        if (vhdrlen > 0) {
                error = uiomove(&vhdr, vhdrlen, uio);
                if (error != 0)
                        return (error);
                TUNDEBUG(ifp, "txvhdr: f %u, gt %u, hl %u, "
                    "gs %u, cs %u, co %u\n", vhdr.hdr.flags,
                    vhdr.hdr.gso_type, vhdr.hdr.hdr_len,
                    vhdr.hdr.gso_size, vhdr.hdr.csum_start,
                    vhdr.hdr.csum_offset);
        }

        if ((m = m_uiotombuf(uio, M_NOWAIT, 0, align, M_PKTHDR)) == NULL) {
                if_inc_counter(ifp, IFCOUNTER_IERRORS, 1);
                return (ENOBUFS);
        }

        m->m_pkthdr.rcvif = ifp;
#ifdef MAC
        mac_ifnet_create_mbuf(ifp, m);
#endif

        if (l2tun)
                return (tunwrite_l2(tp, m, vhdrlen > 0 ? &vhdr : NULL));

        return (tunwrite_l3(tp, m));
}

/*
 * tunpoll - the poll interface, this is only useful on reads
 * really. The write detect always returns true, write never blocks
 * anyway, it either accepts the packet or drops it.
 */
static  int
tunpoll(struct cdev *dev, int events, struct thread *td)
{
        struct tuntap_softc *tp = dev->si_drv1;
        struct ifnet    *ifp = TUN2IFP(tp);
        int             revents = 0;

        TUNDEBUG(ifp, "tunpoll\n");

        if (events & (POLLIN | POLLRDNORM)) {
                IFQ_LOCK(&ifp->if_snd);
                if (!IFQ_IS_EMPTY(&ifp->if_snd)) {
                        TUNDEBUG(ifp, "tunpoll q=%d\n", ifp->if_snd.ifq_len);
                        revents |= events & (POLLIN | POLLRDNORM);
                } else {
                        TUNDEBUG(ifp, "tunpoll waiting\n");
                        selrecord(td, &tp->tun_rsel);
                }
                IFQ_UNLOCK(&ifp->if_snd);
        }
        revents |= events & (POLLOUT | POLLWRNORM);

        return (revents);
}

/*
 * tunkqfilter - support for the kevent() system call.
 */
static int
tunkqfilter(struct cdev *dev, struct knote *kn)
{
        struct tuntap_softc     *tp = dev->si_drv1;
        struct ifnet    *ifp = TUN2IFP(tp);

        switch(kn->kn_filter) {
        case EVFILT_READ:
                TUNDEBUG(ifp, "%s kqfilter: EVFILT_READ, minor = %#x\n",
                    ifp->if_xname, dev2unit(dev));
                kn->kn_fop = &tun_read_filterops;
                break;

        case EVFILT_WRITE:
                TUNDEBUG(ifp, "%s kqfilter: EVFILT_WRITE, minor = %#x\n",
                    ifp->if_xname, dev2unit(dev));
                kn->kn_fop = &tun_write_filterops;
                break;

        default:
                TUNDEBUG(ifp, "%s kqfilter: invalid filter, minor = %#x\n",
                    ifp->if_xname, dev2unit(dev));
                return(EINVAL);
        }

        kn->kn_hook = tp;
        knlist_add(&tp->tun_rsel.si_note, kn, 0);

        return (0);
}

/*
 * Return true of there is data in the interface queue.
 */
static int
tunkqread(struct knote *kn, long hint)
{
        int                     ret;
        struct tuntap_softc     *tp = kn->kn_hook;
        struct cdev             *dev = tp->tun_dev;
        struct ifnet    *ifp = TUN2IFP(tp);

        if ((kn->kn_data = ifp->if_snd.ifq_len) > 0) {
                TUNDEBUG(ifp,
                    "%s have data in the queue.  Len = %d, minor = %#x\n",
                    ifp->if_xname, ifp->if_snd.ifq_len, dev2unit(dev));
                ret = 1;
        } else {
                TUNDEBUG(ifp,
                    "%s waiting for data, minor = %#x\n", ifp->if_xname,
                    dev2unit(dev));
                ret = 0;
        }

        return (ret);
}

/*
 * Always can write, always return MTU in kn->data.
 */
static int
tunkqwrite(struct knote *kn, long hint)
{
        struct tuntap_softc     *tp = kn->kn_hook;
        struct ifnet    *ifp = TUN2IFP(tp);

        kn->kn_data = ifp->if_mtu;

        return (1);
}

static void
tunkqdetach(struct knote *kn)
{
        struct tuntap_softc     *tp = kn->kn_hook;

        knlist_remove(&tp->tun_rsel.si_note, kn, 0);
}