Correctly initialize tuntap_mbuf_queue::size

[tuntaposx.git] / tuntap / src / tuntap.cc

/*
 * ip tunnel/ethertap device for MacOSX. Common functionality of tap_interface and tun_interface.
 *
 * tuntap_interface class definition
 */
/*
 * Copyright (c) 2004, 2005, 2006, 2007, 2008 Mattias Nissler <mattias.nissler@gmx.de>
 *
 * 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. The name of the author may not be used to endorse or promote products derived from this
 *      software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 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.
 */

#include "tuntap.h"

#if 0
#define dprintf(...)                    log(LOG_INFO, __VA_ARGS__)
#else
#define dprintf(...)
#endif

extern "C" {

#include <sys/conf.h>
#include <sys/syslog.h>
#include <sys/param.h>
#include <sys/filio.h>
#include <sys/sockio.h>
#include <sys/fcntl.h>
#include <sys/kpi_socket.h>

#include <vm/vm_kern.h>

#include <net/if_types.h>
#include <net/if_var.h>
#include <net/if_dl.h>
#include <net/if_arp.h>

#include <miscfs/devfs/devfs.h>

}

extern "C" {

/* interface service functions that delegate to the appropriate tuntap_interface instance */
errno_t
tuntap_if_output(ifnet_t ifp, mbuf_t m)
{
        if (ifp != NULL) {
                tuntap_interface *ttif = (tuntap_interface *) ifnet_softc(ifp);
                if (ttif != NULL)
                        return ttif->if_output(m);
        }

        if (m != NULL)
                mbuf_freem_list(m);

        return ENODEV;
}

errno_t
tuntap_if_ioctl(ifnet_t ifp, u_int32_t cmd, void *arg)
{
        if (ifp != NULL) {
                tuntap_interface *ttif = (tuntap_interface *) ifnet_softc(ifp);
                if (ttif != NULL)
                        return ttif->if_ioctl(cmd, arg);
        }

        return ENODEV;
}

errno_t
tuntap_if_set_bpf_tap(ifnet_t ifp, bpf_tap_mode mode, int (*cb)(ifnet_t, mbuf_t))
{
        if (ifp != NULL) {
                tuntap_interface *ttif = (tuntap_interface *) ifnet_softc(ifp);
                if (ttif != NULL)
                        return ttif->if_set_bpf_tap(mode, cb);
        }

        return ENODEV;
}

errno_t
tuntap_if_demux(ifnet_t ifp, mbuf_t m, char *header, protocol_family_t *proto)
{
        if (ifp != NULL) {
                tuntap_interface *ttif = (tuntap_interface *) ifnet_softc(ifp);
                if (ttif != NULL)
                        return ttif->if_demux(m, header, proto);
        }

        return ENODEV;
}

errno_t
tuntap_if_framer(ifnet_t ifp, mbuf_t *m, const struct sockaddr *dest, const char *dest_linkaddr,
                const char *frame_type)
{
        if (ifp != NULL) {
                tuntap_interface *ttif = (tuntap_interface *) ifnet_softc(ifp);
                if (ttif != NULL)
                        return ttif->if_framer(m, dest, dest_linkaddr, frame_type);
        }

        return ENODEV;
}

errno_t
tuntap_if_add_proto(ifnet_t ifp, protocol_family_t proto, const struct ifnet_demux_desc *ddesc,
                u_int32_t ndesc)
{
        if (ifp != NULL) {
                tuntap_interface *ttif = (tuntap_interface *) ifnet_softc(ifp);
                if (ttif != NULL)
                        return ttif->if_add_proto(proto, ddesc, ndesc);
        }

        return ENODEV;
}

errno_t
tuntap_if_del_proto(ifnet_t ifp, protocol_family_t proto)
{
        if (ifp != NULL) {
                tuntap_interface *ttif = (tuntap_interface *) ifnet_softc(ifp);
                if (ttif != NULL)
                        return ttif->if_del_proto(proto);
        }

        return ENODEV;
}

errno_t
tuntap_if_check_multi(ifnet_t ifp, const struct sockaddr* maddr)
{
        if (ifp != NULL)
        {
                tuntap_interface *ttif = (tuntap_interface *) ifnet_softc(ifp);
                if (ttif != NULL)
                        return ttif->if_check_multi(maddr);
        }

        return ENODEV;
}

void
tuntap_if_detached(ifnet_t ifp)
{
        if (ifp != NULL) {
                tuntap_interface *ttif = (tuntap_interface *) ifnet_softc(ifp);
                if (ttif != NULL)
                        ttif->if_detached();
        }
}

errno_t
tuntap_if_noop_output(ifnet_t, mbuf_t)
{
        return ENODEV;
}

errno_t
tuntap_if_noop_demux(ifnet_t, mbuf_t, char*, protocol_family_t*)
{
        return ENODEV;
}

errno_t
tuntap_if_noop_add_proto(ifnet_t, protocol_family_t, const struct ifnet_demux_desc*, u_int32_t)
{
        return ENODEV;
}

errno_t
tuntap_if_noop_del_proto(ifnet_t, protocol_family_t)
{
        return ENODEV;
}

} /* extern "C" */

/* tuntap_mbuf_queue */
tuntap_mbuf_queue::tuntap_mbuf_queue()
{
        head = tail = NULL;
        size = 0;
}

tuntap_mbuf_queue::~tuntap_mbuf_queue()
{
        clear();
}

bool
tuntap_mbuf_queue::enqueue(mbuf_t mb)
{
        if (size == QUEUE_SIZE)
                return false;

        mbuf_setnextpkt(mb, NULL);

        if (head == NULL)
                head = tail = mb;
        else {
                mbuf_setnextpkt(tail, mb);
                tail = mb;
        }
        size++;

        return true;
}

mbuf_t
tuntap_mbuf_queue::dequeue()
{
        mbuf_t ret;

        /* check wether there is a packet in the queue */
        if (head == NULL)
                return NULL;

        /* fetch it */
        ret = head;
        head = mbuf_nextpkt(head);
        mbuf_setnextpkt(ret, NULL);
        size--;

        return ret;
}

void
tuntap_mbuf_queue::clear()
{
        /* free mbufs that are in the queue */
        if (head != NULL)
                mbuf_freem_list(head);

        head = NULL;
        tail = NULL;
        size = 0;
}

/* tuntap_interface members */
tuntap_interface::tuntap_interface()
{
        /* initialize the members */
        ifp = NULL;
        open = false;
        block_io = true;
        dev_handle = NULL;
        pid = 0;
        selthreadclear(&rsel);
        bpf_mode = BPF_MODE_DISABLED;
        bpf_callback = NULL;
        bzero(unique_id, UIDLEN);
}

tuntap_interface::~tuntap_interface()
{
}

bool
tuntap_interface::register_chardev(unsigned short major)
{
        /* register character device */
        dev_handle = devfs_make_node(makedev(major, unit), DEVFS_CHAR, 0, 0, 0660, "%s%d",
                        family_name, (int) unit);

        if (dev_handle == NULL) {
                log(LOG_ERR, "tuntap: could not make /dev/%s%d\n", family_name, (int) unit);
                return false;
        }

        return true;
}

void
tuntap_interface::unregister_chardev()
{
        dprintf("unregistering character device\n");

        /* unregister character device */
        if (dev_handle != NULL)
                devfs_remove(dev_handle);
        dev_handle = NULL;
}

bool
tuntap_interface::register_interface(const struct sockaddr_dl* lladdr, void *bcaddr,
                u_int32_t bcaddrlen)
{
        struct ifnet_init_params ip;
        errno_t err;

        dprintf("register_interface\n");

        /* initialize an initialization info struct */
        ip.uniqueid_len = UIDLEN;
        ip.uniqueid = unique_id;
        ip.name = family_name;
        ip.unit = unit;
        ip.family = family;
        ip.type = type;
        ip.output = tuntap_if_output;
        ip.demux = tuntap_if_demux;
        ip.add_proto = tuntap_if_add_proto;
        ip.del_proto = tuntap_if_del_proto;
        ip.check_multi = tuntap_if_check_multi;
        ip.framer = tuntap_if_framer;
        ip.softc = this;
        ip.ioctl = tuntap_if_ioctl;
        ip.set_bpf_tap = tuntap_if_set_bpf_tap;
        ip.detach = tuntap_if_detached;
        ip.event = NULL;
        ip.broadcast_addr = bcaddr;
        ip.broadcast_len = bcaddrlen;

        dprintf("tuntap: tuntap_if_check_multi is at 0x%08x\n", (void*) tuntap_if_check_multi);

        /* allocate the interface */
        err = ifnet_allocate(&ip, &ifp);
        if (err) {
                log(LOG_ERR, "tuntap: could not allocate interface for %s%d: %d\n", family_name,
                                (int) unit, err);
                ifp = NULL;
                return false;
        }

        /* activate the interface */
        err = ifnet_attach(ifp, lladdr);
        if (err) {
                log(LOG_ERR, "tuntap: could not attach interface %s%d: %d\n", family_name,
                                (int) unit, err);
                ifnet_release(ifp);
                ifp = NULL;
                return false;
        }

        dprintf("setting interface flags\n");

        /* set interface flags */
        ifnet_set_flags(ifp, IFF_RUNNING | IFF_MULTICAST | IFF_SIMPLEX, (u_int16_t) ~0UL);

        dprintf("flags: %x\n", ifnet_flags(ifp));
        
        return true;
}

void
tuntap_interface::unregister_interface()
{
        errno_t err;

        dprintf("unregistering network interface\n");

        if (ifp != NULL) {
                interface_detached = false;

                /* detach interface */
                err = ifnet_detach(ifp);
                if (err)
                        log(LOG_ERR, "tuntap: error detaching interface %s%d: %d\n",
                                        family_name, unit, err);

                dprintf("interface detaching\n");

                /* Wait until the interface has completely been detached. */
                detach_lock.lock();
                while (!interface_detached)
                        detach_lock.sleep(&interface_detached, NULL);
                detach_lock.unlock();

                dprintf("interface detached\n");

                /* release the interface */
                ifnet_release(ifp);

                ifp = NULL;

#if 0
                /* Here goes another hack that we need to prevent darwin from crashing.
                 * Unfortunately, not all of the interface service function pointers are cleared on
                 * detach properly. In particular, I had crashes from calling the demux() interface
                 * function after the kernel module had been unloaded. So we need to make sure all
                 * our function pointers get out of the ifnet struct. We do that by allocating the
                 * interface again, this time passing NULLs for the optional functions and pointers
                 * to noop-dummies for the required functions. Then, we release the interface again.
                 */
                struct ifnet_init_params ip;
                errno_t err;

                dprintf("re-registering interface\n");

                /* initialize an initialization info struct */
                ip.uniqueid_len = UIDLEN;
                ip.uniqueid = unique_id;
                ip.name = family_name;
                ip.unit = unit;
                ip.family = family;
                ip.type = type;
                ip.output = tuntap_if_noop_output;
                ip.demux = tuntap_if_noop_demux;
                ip.add_proto = tuntap_if_noop_add_proto;
                ip.del_proto = tuntap_if_noop_del_proto;
                ip.check_multi = NULL;
                ip.framer = NULL;
                ip.softc = this;
                ip.ioctl = NULL;
                ip.set_bpf_tap = NULL;
                ip.detach = NULL;
                ip.event = NULL;
                ip.broadcast_addr = NULL;
                ip.broadcast_len = 0;

                /* re-register the interface */
                err = ifnet_allocate(&ip, &ifp);
                if (err) {
                        log(LOG_ERR, "tuntap: dummy-allocate interface for %s%d: %d\n", family_name,
                                        (int) unit, err);
                        /* well, bail out. this error shouldn't occur anyway. */
                }
                else
                {
                        /* give it back */
                        ifnet_release(ifp);
                }
#endif

                /* finally done. */
                ifp = NULL;
        }

        dprintf("network interface unregistered\n");
}

void
tuntap_interface::cleanup_interface()
{
        errno_t err;
        ifaddr_t *addrs;
        ifaddr_t *a;
        struct ifreq ifr;
        socket_t sock;

        /* mark the interface down */
        ifnet_set_flags(ifp, 0, IFF_UP | IFF_RUNNING);

        /* Unregister all interface addresses. This works around a deficiency in the Darwin kernel.
         * If we don't remove all IP addresses that are attached to the interface it can happen that
         * the IP code fails to clean them up itself. When the interface is recycled, the IP code
         * might then think some addresses are still attached to the interface...
         */

        err = ifnet_get_address_list(ifp, &addrs);
        if (!err) {

                /* Execute a SIOCDIFADDR ioctl for each address. For technical reasons, we can only
                 * do that with a socket of the appropriate family. So try to create a dummy socket.
                 * I know this is a little expensive, but better than crashing...
                 *
                 * This really sucks.
                 */
                for (a = addrs; *a != NULL; a++) {
                        /* initialize the request parameters */
                        snprintf(ifr.ifr_name, sizeof(ifr.ifr_name), "%s%d",
                                ifnet_name(ifp), ifnet_unit(ifp));
                        ifaddr_address(*a, &(ifr.ifr_addr), sizeof(ifr.ifr_addr));

                        dprintf("trying to delete address of family %d\n", ifr.ifr_addr.sa_family);

                        /* create the dummy socket. */
                        err = sock_socket(ifr.ifr_addr.sa_family, SOCK_RAW, 0, NULL, NULL, &sock);
                        if (err)
                                /* failed to create the socket? Ignore this address... */
                                continue;

                        /* issue the ioctl */
                        err = sock_ioctl(sock, SIOCDIFADDR, &ifr);

                        dprintf("ifnet_ioctl returned %d\n", err);

                        /* get rid of the socket */
                        sock_close(sock);
                }

                /* release the address list */
                ifnet_free_address_list(addrs);
        }
}

bool
tuntap_interface::idle()
{
        return !(open);
}

void
tuntap_interface::notify_bpf(mbuf_t mb, bool out)
{
        auto_lock l(&bpf_lock);

        if ((out && bpf_mode == BPF_MODE_OUTPUT)
                        || (!out && bpf_mode == BPF_MODE_INPUT)
                        || (bpf_mode == BPF_MODE_INPUT_OUTPUT))
                (*bpf_callback)(ifp, mb);
}

/* character device service methods */
int
tuntap_interface::cdev_open(int flags, int devtype, proc_t p)
{
        dprintf("tuntap: cdev_open()\n");

        /* grab the lock so that there can only be one thread inside */
        auto_lock l(&lock);

        /* check wether it is already open */
        if (open)
                return EBUSY;

        /* bring the network interface up */
        int error = initialize_interface();
        if (error)
                return error;

        open = true;
        pid = proc_pid(p);

        return 0;
}

int
tuntap_interface::cdev_close(int flags, int devtype, proc_t p)
{
        dprintf("tuntap: cdev_close()\n");

        auto_lock l(&lock);

        if (open) {
                open = false;

                /* shut down the network interface */
                shutdown_interface();

                /* clear the queue */
                send_queue.clear();

                /* wakeup the cdev thread and notify selects */
                wakeup(this);
                selwakeup(&rsel);

                return 0;
        }

        return EBADF;
}

int
tuntap_interface::cdev_read(uio_t uio, int ioflag)
{
        auto_lock l(&lock);

        unsigned int nb = 0;
        int error;

        dprintf("tuntap: cdev read\n");

        if (!open || ifp == NULL || !(ifnet_flags(ifp) & IFF_UP))
                return EIO;

        /* fetch a new mbuf from the queue if necessary */
        mbuf_t cur_mbuf = NULL;
        while (cur_mbuf == NULL) {
                dprintf("tuntap: fetching new mbuf\n");

                cur_mbuf = send_queue.dequeue();
                if (cur_mbuf == NULL) {
                        /* nothing in queue, block or return */
                        if (!block_io) {
                                dprintf("tuntap: aborting (nbio)\n");
                                return EWOULDBLOCK;
                        } else {
                                /* block */
                                dprintf("tuntap: waiting\n");
                                /* release the lock while waiting */
                                l.unlock();
                                error = msleep(this, NULL, PZERO | PCATCH, "tuntap", NULL);

                                l.lock();

                                if (error)
                                        return error;

                                /* see whether the device was closed in the meantime */
                                if (!open || ifp == NULL || !(ifnet_flags(ifp) & IFF_UP))
                                        return EIO;

                        }
                }
        }

        /* notify bpf */
        notify_bpf(cur_mbuf, true);

        /* output what we have */
        do {
                dprintf("tuntap: got new mbuf: %p uio_resid: %d\n", cur_mbuf, uio_resid(uio));

                /* now we have an mbuf */
                int chunk_len = min(mbuf_len(cur_mbuf), uio_resid(uio));
                error = uiomove((char *) mbuf_data(cur_mbuf), chunk_len, uio);
                if (error) {
                        mbuf_freem(cur_mbuf);
                        return error;
                }
                nb += chunk_len;

                dprintf("tuntap: moved %d bytes to userspace uio_resid: %d\n", chunk_len,
                                uio_resid(uio));

                /* update cur_mbuf */
                cur_mbuf = mbuf_free(cur_mbuf);

        } while (uio_resid(uio) > 0 && cur_mbuf != NULL);

        /* update statistics */
        ifnet_stat_increment_out(ifp, 1, nb, 0);

        /* still data left? forget about that ;-) */
        if (cur_mbuf != NULL)
                mbuf_freem(cur_mbuf);

        dprintf("tuntap: read done\n");

        return 0;
}

int
tuntap_interface::cdev_write(uio_t uio, int ioflag)
{
        auto_lock l(&lock);

        if (!open || ifp == NULL || !(ifnet_flags(ifp) & IFF_UP))
                return EIO;

        dprintf("tuntap: cdev write. uio_resid: %d\n", uio_resid(uio));

        /* pack the data into an mbuf chain */
        mbuf_t first, mb;

        /* first we need an mbuf having a header */
        mbuf_gethdr(MBUF_WAITOK, MBUF_TYPE_DATA, &first);
        if (first == NULL) {
                log(LOG_ERR, "tuntap: could not get mbuf.\n");
                return ENOMEM;
        }
        mbuf_setlen(first, 0);

        unsigned int mlen = mbuf_maxlen(first);
        unsigned int chunk_len;
        unsigned int copied = 0;
        int error;

        /* stuff the data into the mbuf(s) */
        mb = first;
        while (uio_resid(uio) > 0) {
                /* copy a chunk. enforce mtu (don't know if this is correct behaviour) */
                chunk_len = min(ifnet_mtu(ifp), min(uio_resid(uio), mlen));
                error = uiomove((caddr_t) mbuf_data(mb), chunk_len, uio);
                if (error) {
                        log(LOG_ERR, "tuntap: could not copy data from userspace: %d\n", error);
                        mbuf_freem(first);
                        return error;
                }

                dprintf("tuntap: copied %d bytes, uio_resid %d\n", chunk_len,
                                uio_resid(uio));

                mlen -= chunk_len;
                mbuf_setlen(mb, mbuf_len(mb) + chunk_len);
                copied += chunk_len;

                /* if done, break the loop */
                if (uio_resid(uio) <= 0 || copied >= ifnet_mtu(ifp))
                        break;

                /* allocate a new mbuf if the current is filled */
                if (mlen == 0) {
                        mbuf_t next;
                        mbuf_get(MBUF_WAITOK, MBUF_TYPE_DATA, &next);
                        if (next == NULL) {
                                log(LOG_ERR, "tuntap: could not get mbuf.\n");
                                mbuf_freem(first);
                                return ENOMEM;
                        }
                        mbuf_setnext(mb, next);
                        mb = next;
                        mbuf_setlen(mb, 0);
                        mlen = mbuf_maxlen(mb);
                }
        }

        /* fill in header info */
        mbuf_pkthdr_setrcvif(first, ifp);
        mbuf_pkthdr_setlen(first, copied);
        mbuf_pkthdr_setheader(first, mbuf_data(first));
        mbuf_set_csum_performed(first, 0, 0);

        /* update statistics */
        ifnet_stat_increment_in(ifp, 1, copied, 0);

        dprintf("tuntap: mbuf chain constructed. first: %p mb: %p len: %d data: %p\n",
                        first, mb, mbuf_len(first), mbuf_data(first));

        /* notify bpf */
        notify_bpf(first, false);

        /* need to adjust the data pointer to point directly behind the linklevel header. The header
         * itself is later accessed via m_pkthdr.header. Well, if something is ugly, here is it.
         */
        mbuf_adj(first, ifnet_hdrlen(ifp));

        /* pass the packet over to the network stack */
        error = ifnet_input(ifp, first, NULL);

        if (error) {
                log(LOG_ERR, "tuntap: could not input packet into network stack.\n");
                mbuf_freem(first);
                return error;
        }

        return 0;
}

int
tuntap_interface::cdev_ioctl(u_long cmd, caddr_t data, int fflag, proc_t p)
{
        auto_lock l(&lock);

        dprintf("tuntap: cdev ioctl: %d\n", (int) (cmd & 0xff));

        switch (cmd) {
                case FIONBIO:
                        /* set i/o mode */
                        block_io = *((int *) data) ? false : true;
                        return 0;
                case FIOASYNC:
                        /* don't allow switching it on */
                        if (*((int *) data))
                                return ENOTTY;
                        return 0;
        }

        return ENOTTY;
}

int
tuntap_interface::cdev_select(int which, void *wql, proc_t p)
{
        auto_lock l(&lock);

        int ret = 0;

        dprintf("tuntap: select. which: %d\n", which);

        switch (which) {
                case FREAD:
                        /* check wether data is available */
                        {
                                if (!send_queue.empty())
                                        ret = 1;
                                else {
                                        dprintf("tuntap: select: waiting\n");
                                        selrecord(p, &rsel, wql);
                                }
                        }
                        break;
                case FWRITE:
                        /* we are always writeable */
                        ret = 1;
        }

        return ret;
}

/* interface service methods */
errno_t
tuntap_interface::if_output(mbuf_t m)
{
        mbuf_t pkt;

        dprintf("tuntap: if output\n");

        /* just to be sure */
        if (m == NULL)
                return 0;

        if (!open || ifp == NULL || !(ifnet_flags(ifp) & IFF_UP)) {
                mbuf_freem_list(m);
                return EHOSTDOWN;
        }

        /* check whether packet has a header */
        if ((mbuf_flags(m) & MBUF_PKTHDR) == 0) {
                log(LOG_ERR, "tuntap: packet to be output has no mbuf header.\n");
                mbuf_freem_list(m);
                return EINVAL;
        }

        /* put the packet(s) into the output queue */
        while (m != NULL) {
                /* keep pointer, iterate */
                pkt = m;
                m = mbuf_nextpkt(m);
                mbuf_setnextpkt(pkt, NULL);

                auto_lock l(&lock);

                if (!send_queue.enqueue(pkt)) {
                        mbuf_freem(pkt);
                        mbuf_freem_list(m);
                        return ENOBUFS;
                }
        }

        /* wakeup the cdev thread and notify selects */
        wakeup(this);
        selwakeup(&rsel);

        return 0;
}

errno_t
tuntap_interface::if_ioctl(u_int32_t cmd, void *arg)
{
        dprintf("tuntap: if ioctl: %d\n", (int) (cmd & 0xff));

        switch (cmd) {
                case SIOCSIFADDR:
                        dprintf("tuntap: if_ioctl: SIOCSIFADDR\n");

                        /* Unfortunately, ifconfig sets the address family field of an INET netmask
                         * to zero. However, this makes mDNSresponder ignore the interface. Fix that
                         * here. This one is of the category "ugly workaround". Dumb Darwin...
                         *
                         * Btw. If you configure other network interfaces using ifconfig, you run
                         * into the same problem. I still don't know how to make the tap devices
                         * show up in the network configuration panel...
                         */
                        struct ifaddr *ifa = (struct ifaddr *) arg;
                        if (ifa != NULL && ifa->ifa_netmask != NULL && ifa->ifa_addr != NULL) {

                                dprintf("tuntap: if_ioctl: addr af %d netmask af %d\n",
                                                ifa->ifa_netmask->sa_family,
                                                ifa->ifa_addr->sa_family);

                                if (ifa->ifa_netmask->sa_family != ifa->ifa_addr->sa_family)
                                {
                                        /* Fix the address family field of the netmask */
                                        dprintf("tuntap: if_ioctl: fixing netmask af.\n");
                                        ifa->ifa_netmask->sa_family = ifa->ifa_addr->sa_family;
                                }
                        }
                        return 0;
                                        
                case SIOCSIFFLAGS:
                        return 0;

                case SIOCGIFSTATUS:
                        {
                                struct ifstat *stat = (struct ifstat *) arg;
                                int len;
                                char *p;

                                if (stat == NULL)
                                        return EINVAL;

                                /* print status */
                                len = strlen(stat->ascii);
                                p = stat->ascii + len;
                                if (open) {
                                        snprintf(p, IFSTATMAX - len, "\topen (pid %u)\n", pid);
                                } else {
                                        snprintf(p, IFSTATMAX - len, "\tclosed\n");
                                }

                                return 0;
                        }

                case SIOCSIFMTU:
                        {
                                struct ifreq *ifr = (struct ifreq *) arg;

                                if (ifr == NULL)
                                        return EINVAL;

                                ifnet_set_mtu(ifp, ifr->ifr_mtu);

                                return 0;
                        }

                case SIOCDIFADDR:
                        return 0;

        }

        return EOPNOTSUPP;
}

errno_t
tuntap_interface::if_set_bpf_tap(bpf_tap_mode mode, int (*cb)(ifnet_t, mbuf_t))
{
        dprintf("tuntap: mode %d\n", mode);

        auto_lock l(&bpf_lock);

        bpf_callback = cb;
        bpf_mode = mode;

        return 0;
}

errno_t
tuntap_interface::if_check_multi(const struct sockaddr *maddr)
{
        dprintf("tuntap: if_check_multi\n");

        return EOPNOTSUPP;
}

void
tuntap_interface::if_detached()
{
        dprintf("tuntap: if_detached\n");

        /* wake unregister_interface() */
        detach_lock.lock();
        interface_detached = true;
        detach_lock.wakeup(&interface_detached);
        detach_lock.unlock();

        dprintf("if_detached done\n");
}