xref: /freebsd/sys/net/if_vlan.c (revision 6d3a3ab73503e1e4a32a90ecaf6cc769e7fc983d)

/*-
 * Copyright 1998 Massachusetts Institute of Technology
 *
 * Permission to use, copy, modify, and distribute this software and
 * its documentation for any purpose and without fee is hereby
 * granted, provided that both the above copyright notice and this
 * permission notice appear in all copies, that both the above
 * copyright notice and this permission notice appear in all
 * supporting documentation, and that the name of M.I.T. not be used
 * in advertising or publicity pertaining to distribution of the
 * software without specific, written prior permission.  M.I.T. makes
 * no representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied
 * warranty.
 *
 * THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''.  M.I.T. DISCLAIMS
 * ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
 * SHALL M.I.T. 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.
 *
 * $FreeBSD$
 */

/*
 * if_vlan.c - pseudo-device driver for IEEE 802.1Q virtual LANs.
 * Might be extended some day to also handle IEEE 802.1p priority
 * tagging.  This is sort of sneaky in the implementation, since
 * we need to pretend to be enough of an Ethernet implementation
 * to make arp work.  The way we do this is by telling everyone
 * that we are an Ethernet, and then catch the packets that
 * ether_output() left on our output queue when it calls
 * if_start(), rewrite them for use by the real outgoing interface,
 * and ask it to send them.
 */

#include "opt_inet.h"

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/module.h>
#include <sys/queue.h>
#include <sys/socket.h>
#include <sys/sockio.h>
#include <sys/sysctl.h>
#include <sys/systm.h>

#include <net/bpf.h>
#include <net/ethernet.h>
#include <net/if.h>
#include <net/if_clone.h>
#include <net/if_arp.h>
#include <net/if_dl.h>
#include <net/if_types.h>
#include <net/if_vlan_var.h>

#ifdef INET
#include <netinet/in.h>
#include <netinet/if_ether.h>
#endif

#define VLANNAME	"vlan"

struct vlan_mc_entry {
	struct ether_addr		mc_addr;
	SLIST_ENTRY(vlan_mc_entry)	mc_entries;
};

struct	ifvlan {
	struct	ifnet *ifv_ifp;
	struct	ifnet *ifv_p;	/* parent inteface of this vlan */
	int	ifv_pflags;	/* special flags we have set on parent */
	struct	ifv_linkmib {
		int	ifvm_parent;
		int	ifvm_encaplen;	/* encapsulation length */
		int	ifvm_mtufudge;	/* MTU fudged by this much */
		int	ifvm_mintu;	/* min transmission unit */
		u_int16_t ifvm_proto; /* encapsulation ethertype */
		u_int16_t ifvm_tag; /* tag to apply on packets leaving if */
	}	ifv_mib;
	SLIST_HEAD(__vlan_mchead, vlan_mc_entry)	vlan_mc_listhead;
	LIST_ENTRY(ifvlan) ifv_list;
};
#define	ifv_tag	ifv_mib.ifvm_tag
#define	ifv_encaplen	ifv_mib.ifvm_encaplen
#define	ifv_mtufudge	ifv_mib.ifvm_mtufudge
#define	ifv_mintu	ifv_mib.ifvm_mintu

/* Special flags we should propagate to parent */
static struct {
	int flag;
	int (*func)(struct ifnet *, int);
} vlan_pflags[] = {
	{IFF_PROMISC, ifpromisc},
	{IFF_ALLMULTI, if_allmulti},
	{0, NULL}
};

SYSCTL_DECL(_net_link);
SYSCTL_NODE(_net_link, IFT_L2VLAN, vlan, CTLFLAG_RW, 0, "IEEE 802.1Q VLAN");
SYSCTL_NODE(_net_link_vlan, PF_LINK, link, CTLFLAG_RW, 0, "for consistency");

static MALLOC_DEFINE(M_VLAN, VLANNAME, "802.1Q Virtual LAN Interface");
static LIST_HEAD(, ifvlan) ifv_list;

/*
 * Locking: one lock is used to guard both the ifv_list and modification
 * to vlan data structures.  We are rather conservative here; probably
 * more than necessary.
 */
static struct mtx ifv_mtx;
#define	VLAN_LOCK_INIT()	mtx_init(&ifv_mtx, VLANNAME, NULL, MTX_DEF)
#define	VLAN_LOCK_DESTROY()	mtx_destroy(&ifv_mtx)
#define	VLAN_LOCK_ASSERT()	mtx_assert(&ifv_mtx, MA_OWNED)
#define	VLAN_LOCK()	mtx_lock(&ifv_mtx)
#define	VLAN_UNLOCK()	mtx_unlock(&ifv_mtx)

static	void vlan_start(struct ifnet *ifp);
static	void vlan_ifinit(void *foo);
static	void vlan_input(struct ifnet *ifp, struct mbuf *m);
static	int vlan_ioctl(struct ifnet *ifp, u_long cmd, caddr_t addr);
static	int vlan_setflag(struct ifnet *ifp, int flag, int status,
    int (*func)(struct ifnet *, int));
static	int vlan_setflags(struct ifnet *ifp, int status);
static	int vlan_setmulti(struct ifnet *ifp);
static	int vlan_unconfig(struct ifnet *ifp);
static	int vlan_config(struct ifvlan *ifv, struct ifnet *p);
static	void vlan_link_state(struct ifnet *ifp, int link);

static	struct ifnet *vlan_clone_match_ethertag(struct if_clone *,
    const char *, int *);
static	int vlan_clone_match(struct if_clone *, const char *);
static	int vlan_clone_create(struct if_clone *, char *, size_t);
static	int vlan_clone_destroy(struct if_clone *, struct ifnet *);

static	struct if_clone vlan_cloner = IFC_CLONE_INITIALIZER(VLANNAME, NULL,
    IF_MAXUNIT, NULL, vlan_clone_match, vlan_clone_create, vlan_clone_destroy);

/*
 * Program our multicast filter. What we're actually doing is
 * programming the multicast filter of the parent. This has the
 * side effect of causing the parent interface to receive multicast
 * traffic that it doesn't really want, which ends up being discarded
 * later by the upper protocol layers. Unfortunately, there's no way
 * to avoid this: there really is only one physical interface.
 *
 * XXX: There is a possible race here if more than one thread is
 *      modifying the multicast state of the vlan interface at the same time.
 */
static int
vlan_setmulti(struct ifnet *ifp)
{
	struct ifnet		*ifp_p;
	struct ifmultiaddr	*ifma, *rifma = NULL;
	struct ifvlan		*sc;
	struct vlan_mc_entry	*mc = NULL;
	struct sockaddr_dl	sdl;
	int			error;

	/*VLAN_LOCK_ASSERT();*/

	/* Find the parent. */
	sc = ifp->if_softc;
	ifp_p = sc->ifv_p;

	/*
	 * If we don't have a parent, just remember the membership for
	 * when we do.
	 */
	if (ifp_p == NULL)
		return (0);

	bzero((char *)&sdl, sizeof(sdl));
	sdl.sdl_len = sizeof(sdl);
	sdl.sdl_family = AF_LINK;
	sdl.sdl_index = ifp_p->if_index;
	sdl.sdl_type = IFT_ETHER;
	sdl.sdl_alen = ETHER_ADDR_LEN;

	/* First, remove any existing filter entries. */
	while (SLIST_FIRST(&sc->vlan_mc_listhead) != NULL) {
		mc = SLIST_FIRST(&sc->vlan_mc_listhead);
		bcopy((char *)&mc->mc_addr, LLADDR(&sdl), ETHER_ADDR_LEN);
		error = if_delmulti(ifp_p, (struct sockaddr *)&sdl);
		if (error)
			return (error);
		SLIST_REMOVE_HEAD(&sc->vlan_mc_listhead, mc_entries);
		free(mc, M_VLAN);
	}

	/* Now program new ones. */
	TAILQ_FOREACH(ifma, &ifp->if_multiaddrs, ifma_link) {
		if (ifma->ifma_addr->sa_family != AF_LINK)
			continue;
		mc = malloc(sizeof(struct vlan_mc_entry), M_VLAN, M_NOWAIT);
		if (mc == NULL)
			return (ENOMEM);
		bcopy(LLADDR((struct sockaddr_dl *)ifma->ifma_addr),
		    (char *)&mc->mc_addr, ETHER_ADDR_LEN);
		SLIST_INSERT_HEAD(&sc->vlan_mc_listhead, mc, mc_entries);
		bcopy(LLADDR((struct sockaddr_dl *)ifma->ifma_addr),
		    LLADDR(&sdl), ETHER_ADDR_LEN);
		error = if_addmulti(ifp_p, (struct sockaddr *)&sdl, &rifma);
		if (error)
			return (error);
	}

	return (0);
}

/*
 * VLAN support can be loaded as a module.  The only place in the
 * system that's intimately aware of this is ether_input.  We hook
 * into this code through vlan_input_p which is defined there and
 * set here.  Noone else in the system should be aware of this so
 * we use an explicit reference here.
 *
 * NB: Noone should ever need to check if vlan_input_p is null or
 *     not.  This is because interfaces have a count of the number
 *     of active vlans (if_nvlans) and this should never be bumped
 *     except by vlan_config--which is in this module so therefore
 *     the module must be loaded and vlan_input_p must be non-NULL.
 */
extern	void (*vlan_input_p)(struct ifnet *, struct mbuf *);

/* For if_link_state_change() eyes only... */
extern	void (*vlan_link_state_p)(struct ifnet *, int);

static int
vlan_modevent(module_t mod, int type, void *data)
{

	switch (type) {
	case MOD_LOAD:
		LIST_INIT(&ifv_list);
		VLAN_LOCK_INIT();
		vlan_input_p = vlan_input;
		vlan_link_state_p = vlan_link_state;
		if_clone_attach(&vlan_cloner);
		break;
	case MOD_UNLOAD:
		if_clone_detach(&vlan_cloner);
		vlan_input_p = NULL;
		vlan_link_state_p = NULL;
		while (!LIST_EMPTY(&ifv_list))
			vlan_clone_destroy(&vlan_cloner,
			    LIST_FIRST(&ifv_list)->ifv_ifp);
		VLAN_LOCK_DESTROY();
		break;
	default:
		return (EOPNOTSUPP);
	}
	return (0);
}

static moduledata_t vlan_mod = {
	"if_vlan",
	vlan_modevent,
	0
};

DECLARE_MODULE(if_vlan, vlan_mod, SI_SUB_PSEUDO, SI_ORDER_ANY);
MODULE_DEPEND(if_vlan, miibus, 1, 1, 1);

static struct ifnet *
vlan_clone_match_ethertag(struct if_clone *ifc, const char *name, int *tag)
{
	const char *cp;
	struct ifnet *ifp;
	int t = 0;

	/* Check for <etherif>.<vlan> style interface names. */
	IFNET_RLOCK();
	TAILQ_FOREACH(ifp, &ifnet, if_link) {
		if (ifp->if_type != IFT_ETHER)
			continue;
		if (strncmp(ifp->if_xname, name, strlen(ifp->if_xname)) != 0)
			continue;
		cp = name + strlen(ifp->if_xname);
		if (*cp != '.')
			continue;
		for(; *cp != '\0'; cp++) {
			if (*cp < '0' || *cp > '9')
				continue;
			t = (t * 10) + (*cp - '0');
		}
		if (tag != NULL)
			*tag = t;
		break;
	}
	IFNET_RUNLOCK();

	return (ifp);
}

static int
vlan_clone_match(struct if_clone *ifc, const char *name)
{
	const char *cp;

	if (vlan_clone_match_ethertag(ifc, name, NULL) != NULL)
		return (1);

	if (strncmp(VLANNAME, name, strlen(VLANNAME)) != 0)
		return (0);
	for (cp = name + 4; *cp != '\0'; cp++) {
		if (*cp < '0' || *cp > '9')
			return (0);
	}

	return (1);
}

static int
vlan_clone_create(struct if_clone *ifc, char *name, size_t len)
{
	char *dp;
	int wildcard;
	int unit;
	int error;
	int tag;
	int ethertag;
	struct ifvlan *ifv;
	struct ifnet *ifp;
	struct ifnet *p;
	u_char eaddr[6] = {0,0,0,0,0,0};

	if ((p = vlan_clone_match_ethertag(ifc, name, &tag)) != NULL) {
		ethertag = 1;
		unit = -1;
		wildcard = 0;

		/*
		 * Don't let the caller set up a VLAN tag with
		 * anything except VLID bits.
		 */
		if (tag & ~EVL_VLID_MASK)
			return (EINVAL);
	} else {
		ethertag = 0;

		error = ifc_name2unit(name, &unit);
		if (error != 0)
			return (error);

		wildcard = (unit < 0);
	}

	error = ifc_alloc_unit(ifc, &unit);
	if (error != 0)
		return (error);

	/* In the wildcard case, we need to update the name. */
	if (wildcard) {
		for (dp = name; *dp != '\0'; dp++);
		if (snprintf(dp, len - (dp-name), "%d", unit) >
		    len - (dp-name) - 1) {
			panic("%s: interface name too long", __func__);
		}
	}

	ifv = malloc(sizeof(struct ifvlan), M_VLAN, M_WAITOK | M_ZERO);
	ifp = ifv->ifv_ifp = if_alloc(IFT_ETHER);
	if (ifp == NULL) {
		ifc_free_unit(ifc, unit);
		free(ifv, M_VLAN);
		return (ENOSPC);
	}
	SLIST_INIT(&ifv->vlan_mc_listhead);

	ifp->if_softc = ifv;
	/*
	 * Set the name manually rather than using if_initname because
	 * we don't conform to the default naming convention for interfaces.
	 */
	strlcpy(ifp->if_xname, name, IFNAMSIZ);
	ifp->if_dname = ifc->ifc_name;
	ifp->if_dunit = unit;
	/* NB: flags are not set here */
	ifp->if_linkmib = &ifv->ifv_mib;
	ifp->if_linkmiblen = sizeof(ifv->ifv_mib);
	/* NB: mtu is not set here */

	ifp->if_init = vlan_ifinit;
	ifp->if_start = vlan_start;
	ifp->if_ioctl = vlan_ioctl;
	ifp->if_snd.ifq_maxlen = ifqmaxlen;
	ether_ifattach(ifp, eaddr);
	/* Now undo some of the damage... */
	ifp->if_baudrate = 0;
	ifp->if_type = IFT_L2VLAN;
	ifp->if_hdrlen = ETHER_VLAN_ENCAP_LEN;

	VLAN_LOCK();
	LIST_INSERT_HEAD(&ifv_list, ifv, ifv_list);
	VLAN_UNLOCK();

	if (ethertag) {
		VLAN_LOCK();
		error = vlan_config(ifv, p);
		if (error != 0) {
			/*
			 * Since we've partialy failed, we need to back
			 * out all the way, otherwise userland could get
			 * confused.  Thus, we destroy the interface.
			 */
			LIST_REMOVE(ifv, ifv_list);
			vlan_unconfig(ifp);
			VLAN_UNLOCK();
			ether_ifdetach(ifp);
			if_free_type(ifp, IFT_ETHER);
			free(ifv, M_VLAN);

			return (error);
		}
		ifv->ifv_tag = tag;
		ifp->if_drv_flags |= IFF_DRV_RUNNING;
		VLAN_UNLOCK();

		/* Update flags on the parent, if necessary. */
		vlan_setflags(ifp, 1);
	}

	return (0);
}

static int
vlan_clone_destroy(struct if_clone *ifc, struct ifnet *ifp)
{
	int unit;
	struct ifvlan *ifv = ifp->if_softc;

	unit = ifp->if_dunit;

	VLAN_LOCK();
	LIST_REMOVE(ifv, ifv_list);
	vlan_unconfig(ifp);
	VLAN_UNLOCK();

	ether_ifdetach(ifp);
	if_free_type(ifp, IFT_ETHER);

	free(ifv, M_VLAN);

	ifc_free_unit(ifc, unit);

	return (0);
}

/*
 * The ifp->if_init entry point for vlan(4) is a no-op.
 */
static void
vlan_ifinit(void *foo)
{

}

/*
 * The if_start method for vlan(4) interface. It doesn't
 * raises the IFF_DRV_OACTIVE flag, since it is called
 * only from IFQ_HANDOFF() macro in ether_output_frame().
 * If the interface queue is full, and vlan_start() is
 * not called, the queue would never get emptied and
 * interface would stall forever.
 */
static void
vlan_start(struct ifnet *ifp)
{
	struct ifvlan *ifv;
	struct ifnet *p;
	struct ether_vlan_header *evl;
	struct mbuf *m;
	int error;

	ifv = ifp->if_softc;
	p = ifv->ifv_p;

	for (;;) {
		IF_DEQUEUE(&ifp->if_snd, m);
		if (m == 0)
			break;
		BPF_MTAP(ifp, m);

		/*
		 * Do not run parent's if_start() if the parent is not up,
		 * or parent's driver will cause a system crash.
		 */
		if (!((p->if_flags & IFF_UP) &&
		    (p->if_drv_flags & IFF_DRV_RUNNING))) {
			m_freem(m);
			ifp->if_collisions++;
			continue;
		}

		/*
		 * If underlying interface can do VLAN tag insertion itself,
		 * just pass the packet along. However, we need some way to
		 * tell the interface where the packet came from so that it
		 * knows how to find the VLAN tag to use, so we attach a
		 * packet tag that holds it.
		 */
		if (p->if_capenable & IFCAP_VLAN_HWTAGGING) {
			struct m_tag *mtag = m_tag_alloc(MTAG_VLAN,
							 MTAG_VLAN_TAG,
							 sizeof(u_int),
							 M_NOWAIT);
			if (mtag == NULL) {
				ifp->if_oerrors++;
				m_freem(m);
				continue;
			}
			VLAN_TAG_VALUE(mtag) = ifv->ifv_tag;
			m_tag_prepend(m, mtag);
			m->m_flags |= M_VLANTAG;
		} else {
			M_PREPEND(m, ifv->ifv_encaplen, M_DONTWAIT);
			if (m == NULL) {
				if_printf(ifp,
				    "unable to prepend VLAN header\n");
				ifp->if_oerrors++;
				continue;
			}
			/* M_PREPEND takes care of m_len, m_pkthdr.len for us */

			if (m->m_len < sizeof(*evl)) {
				m = m_pullup(m, sizeof(*evl));
				if (m == NULL) {
					if_printf(ifp,
					    "cannot pullup VLAN header\n");
					ifp->if_oerrors++;
					continue;
				}
			}

			/*
			 * Transform the Ethernet header into an Ethernet header
			 * with 802.1Q encapsulation.
			 */
			bcopy(mtod(m, char *) + ifv->ifv_encaplen,
			      mtod(m, char *), ETHER_HDR_LEN);
			evl = mtod(m, struct ether_vlan_header *);
			evl->evl_proto = evl->evl_encap_proto;
			evl->evl_encap_proto = htons(ETHERTYPE_VLAN);
			evl->evl_tag = htons(ifv->ifv_tag);
#ifdef DEBUG
			printf("%s: %*D\n", __func__, (int)sizeof(*evl),
			    (unsigned char *)evl, ":");
#endif
		}

		/*
		 * Send it, precisely as ether_output() would have.
		 * We are already running at splimp.
		 */
		IFQ_HANDOFF(p, m, error);
		if (!error)
			ifp->if_opackets++;
		else
			ifp->if_oerrors++;
	}
}

static void
vlan_input(struct ifnet *ifp, struct mbuf *m)
{
	struct ether_vlan_header *evl;
	struct ifvlan *ifv;
	struct m_tag *mtag;
	u_int tag;

	if (m->m_flags & M_VLANTAG) {
		/*
		 * Packet is tagged, but m contains a normal
		 * Ethernet frame; the tag is stored out-of-band.
		 */
		mtag = m_tag_locate(m, MTAG_VLAN, MTAG_VLAN_TAG, NULL);
		KASSERT(mtag != NULL,
			("%s: M_VLANTAG without m_tag", __func__));
		tag = EVL_VLANOFTAG(VLAN_TAG_VALUE(mtag));
		m_tag_delete(m, mtag);
		m->m_flags &= ~M_VLANTAG;
	} else {
		/*
		 * Packet is tagged in-band as specified by 802.1q.
		 */
		mtag = NULL;
		switch (ifp->if_type) {
		case IFT_ETHER:
			if (m->m_len < sizeof(*evl) &&
			    (m = m_pullup(m, sizeof(*evl))) == NULL) {
				if_printf(ifp, "cannot pullup VLAN header\n");
				return;
			}
			evl = mtod(m, struct ether_vlan_header *);
			KASSERT(ntohs(evl->evl_encap_proto) == ETHERTYPE_VLAN,
				("%s: bad encapsulation protocol (%u)",
				 __func__, ntohs(evl->evl_encap_proto)));

			tag = EVL_VLANOFTAG(ntohs(evl->evl_tag));

			/*
			 * Restore the original ethertype.  We'll remove
			 * the encapsulation after we've found the vlan
			 * interface corresponding to the tag.
			 */
			evl->evl_encap_proto = evl->evl_proto;
			break;
		default:
			tag = (u_int) -1;
#ifdef INVARIANTS
			panic("%s: unsupported if_type (%u)",
			      __func__, ifp->if_type);
#endif
			break;
		}
	}

	VLAN_LOCK();
	LIST_FOREACH(ifv, &ifv_list, ifv_list)
		if (ifp == ifv->ifv_p && tag == ifv->ifv_tag)
			break;

	if (ifv == NULL || (ifv->ifv_ifp->if_flags & IFF_UP) == 0) {
		VLAN_UNLOCK();
		m_freem(m);
		ifp->if_noproto++;
#ifdef DEBUG
		printf("%s: tag %d, no interface\n", __func__, tag);
#endif
		return;
	}
	VLAN_UNLOCK();		/* XXX extend below? */
#ifdef DEBUG
	printf("%s: tag %d, parent %s\n", __func__, tag, ifv->ifv_p->if_xname);
#endif

	if (mtag == NULL) {
		/*
		 * Packet had an in-line encapsulation header;
		 * remove it.  The original header has already
		 * been fixed up above.
		 */
		bcopy(mtod(m, caddr_t),
		      mtod(m, caddr_t) + ETHER_VLAN_ENCAP_LEN,
		      ETHER_HDR_LEN);
		m_adj(m, ETHER_VLAN_ENCAP_LEN);
	}

	m->m_pkthdr.rcvif = ifv->ifv_ifp;
	ifv->ifv_ifp->if_ipackets++;

	/* Pass it back through the parent's input routine. */
	(*ifp->if_input)(ifv->ifv_ifp, m);
}

static int
vlan_config(struct ifvlan *ifv, struct ifnet *p)
{
	struct ifaddr *ifa1, *ifa2;
	struct ifnet *ifp;
	struct sockaddr_dl *sdl1, *sdl2;

	VLAN_LOCK_ASSERT();

	if (p->if_type != IFT_ETHER)
		return (EPROTONOSUPPORT);
	if (ifv->ifv_p)
		return (EBUSY);

	ifv->ifv_encaplen = ETHER_VLAN_ENCAP_LEN;
	ifv->ifv_mintu = ETHERMIN;
	ifv->ifv_pflags = 0;

	/*
	 * The active VLAN counter on the parent is used
	 * at various places to see if there is a vlan(4)
	 * attached to this physical interface.
	 */
	p->if_nvlans++;

	/*
	 * If the parent supports the VLAN_MTU capability,
	 * i.e. can Tx/Rx larger than ETHER_MAX_LEN frames,
	 * use it.
	 */
	if (p->if_capenable & IFCAP_VLAN_MTU) {
		/*
		 * No need to fudge the MTU since the parent can
		 * handle extended frames.
		 */
		ifv->ifv_mtufudge = 0;
	} else {
		/*
		 * Fudge the MTU by the encapsulation size.  This
		 * makes us incompatible with strictly compliant
		 * 802.1Q implementations, but allows us to use
		 * the feature with other NetBSD implementations,
		 * which might still be useful.
		 */
		ifv->ifv_mtufudge = ifv->ifv_encaplen;
	}

	ifv->ifv_p = p;
	ifp = ifv->ifv_ifp;
	ifp->if_mtu = p->if_mtu - ifv->ifv_mtufudge;
	/*
	 * Copy only a selected subset of flags from the parent.
	 * Other flags are none of our business.
	 */
#define VLAN_COPY_FLAGS \
    (IFF_BROADCAST | IFF_MULTICAST | IFF_SIMPLEX | IFF_POINTOPOINT)
	ifp->if_flags &= ~VLAN_COPY_FLAGS;
	ifp->if_flags |= p->if_flags & VLAN_COPY_FLAGS;
#undef VLAN_COPY_FLAGS

	ifp->if_link_state = p->if_link_state;

#if 0
	/*
	 * Not ready yet.  We need notification from the parent
	 * when hw checksumming flags in its if_capenable change.
	 * Flags set in if_capabilities only are useless.
	 */
	/*
	 * If the parent interface can do hardware-assisted
	 * VLAN encapsulation, then propagate its hardware-
	 * assisted checksumming flags.
	 */
	if (p->if_capabilities & IFCAP_VLAN_HWTAGGING)
		ifp->if_capabilities |= p->if_capabilities & IFCAP_HWCSUM;
#endif

	/*
	 * Set up our ``Ethernet address'' to reflect the underlying
	 * physical interface's.
	 */
	ifa1 = ifaddr_byindex(ifp->if_index);
	ifa2 = ifaddr_byindex(p->if_index);
	sdl1 = (struct sockaddr_dl *)ifa1->ifa_addr;
	sdl2 = (struct sockaddr_dl *)ifa2->ifa_addr;
	sdl1->sdl_type = IFT_ETHER;
	sdl1->sdl_alen = ETHER_ADDR_LEN;
	bcopy(LLADDR(sdl2), LLADDR(sdl1), ETHER_ADDR_LEN);
	bcopy(LLADDR(sdl2), IFP2ENADDR(ifp), ETHER_ADDR_LEN);

	/*
	 * Configure multicast addresses that may already be
	 * joined on the vlan device.
	 */
	(void)vlan_setmulti(ifp); /* XXX: VLAN lock held */

	return (0);
}

static int
vlan_unconfig(struct ifnet *ifp)
{
	struct ifaddr *ifa;
	struct sockaddr_dl *sdl;
	struct vlan_mc_entry *mc;
	struct ifvlan *ifv;
	struct ifnet *p;
	int error;

	VLAN_LOCK_ASSERT();

	ifv = ifp->if_softc;
	p = ifv->ifv_p;

	if (p) {
		struct sockaddr_dl sdl;

		/*
		 * Since the interface is being unconfigured, we need to
		 * empty the list of multicast groups that we may have joined
		 * while we were alive from the parent's list.
		 */
		bzero((char *)&sdl, sizeof(sdl));
		sdl.sdl_len = sizeof(sdl);
		sdl.sdl_family = AF_LINK;
		sdl.sdl_index = p->if_index;
		sdl.sdl_type = IFT_ETHER;
		sdl.sdl_alen = ETHER_ADDR_LEN;

		while(SLIST_FIRST(&ifv->vlan_mc_listhead) != NULL) {
			mc = SLIST_FIRST(&ifv->vlan_mc_listhead);
			bcopy((char *)&mc->mc_addr, LLADDR(&sdl),
			    ETHER_ADDR_LEN);
			error = if_delmulti(p, (struct sockaddr *)&sdl);
			if (error)
				return (error);
			SLIST_REMOVE_HEAD(&ifv->vlan_mc_listhead, mc_entries);
			free(mc, M_VLAN);
		}

		vlan_setflags(ifp, 0); /* clear special flags on parent */
		p->if_nvlans--;
	}

	/* Disconnect from parent. */
	if (ifv->ifv_pflags)
		if_printf(ifp, "%s: ifv_pflags unclean\n", __func__);
	ifv->ifv_p = NULL;
	ifv->ifv_ifp->if_mtu = ETHERMTU;		/* XXX why not 0? */
	ifv->ifv_ifp->if_link_state = LINK_STATE_UNKNOWN;

	/* Clear our MAC address. */
	ifa = ifaddr_byindex(ifv->ifv_ifp->if_index);
	sdl = (struct sockaddr_dl *)ifa->ifa_addr;
	sdl->sdl_type = IFT_ETHER;
	sdl->sdl_alen = ETHER_ADDR_LEN;
	bzero(LLADDR(sdl), ETHER_ADDR_LEN);
	bzero(IFP2ENADDR(ifv->ifv_ifp), ETHER_ADDR_LEN);

	return (0);
}

/* Handle a reference counted flag that should be set on the parent as well */
static int
vlan_setflag(struct ifnet *ifp, int flag, int status,
	     int (*func)(struct ifnet *, int))
{
	struct ifvlan *ifv;
	int error;

	/* XXX VLAN_LOCK_ASSERT(); */

	ifv = ifp->if_softc;
	status = status ? (ifp->if_flags & flag) : 0;
	/* Now "status" contains the flag value or 0 */

	/*
	 * See if recorded parent's status is different from what
	 * we want it to be.  If it is, flip it.  We record parent's
	 * status in ifv_pflags so that we won't clear parent's flag
	 * we haven't set.  In fact, we don't clear or set parent's
	 * flags directly, but get or release references to them.
	 * That's why we can be sure that recorded flags still are
	 * in accord with actual parent's flags.
	 */
	if (status != (ifv->ifv_pflags & flag)) {
		error = (*func)(ifv->ifv_p, status);
		if (error)
			return (error);
		ifv->ifv_pflags &= ~flag;
		ifv->ifv_pflags |= status;
	}
	return (0);
}

/*
 * Handle IFF_* flags that require certain changes on the parent:
 * if "status" is true, update parent's flags respective to our if_flags;
 * if "status" is false, forcedly clear the flags set on parent.
 */
static int
vlan_setflags(struct ifnet *ifp, int status)
{
	int error, i;

	for (i = 0; vlan_pflags[i].flag; i++) {
		error = vlan_setflag(ifp, vlan_pflags[i].flag,
				     status, vlan_pflags[i].func);
		if (error)
			return (error);
	}
	return (0);
}

/* Inform all vlans that their parent has changed link state */
static void
vlan_link_state(struct ifnet *ifp, int link)
{
	struct ifvlan *ifv;

	VLAN_LOCK();
	LIST_FOREACH(ifv, &ifv_list, ifv_list) {
		if (ifv->ifv_p == ifp)
			if_link_state_change(ifv->ifv_ifp,
			    ifv->ifv_p->if_link_state);
	}
	VLAN_UNLOCK();
}

static int
vlan_ioctl(struct ifnet *ifp, u_long cmd, caddr_t data)
{
	struct ifaddr *ifa;
	struct ifnet *p;
	struct ifreq *ifr;
	struct ifvlan *ifv;
	struct vlanreq vlr;
	int error = 0;

	ifr = (struct ifreq *)data;
	ifa = (struct ifaddr *)data;
	ifv = ifp->if_softc;

	switch (cmd) {
	case SIOCSIFADDR:
		ifp->if_flags |= IFF_UP;

		switch (ifa->ifa_addr->sa_family) {
#ifdef INET
		case AF_INET:
			arp_ifinit(ifv->ifv_ifp, ifa);
			break;
#endif
		default:
			break;
		}
		break;

	case SIOCGIFADDR:
		{
			struct sockaddr *sa;

			sa = (struct sockaddr *) &ifr->ifr_data;
			bcopy(IFP2ENADDR(ifp), (caddr_t)sa->sa_data,
			    ETHER_ADDR_LEN);
		}
		break;

	case SIOCGIFMEDIA:
		VLAN_LOCK();
		if (ifv->ifv_p != NULL) {
			error = (*ifv->ifv_p->if_ioctl)(ifv->ifv_p,
					SIOCGIFMEDIA, data);
			VLAN_UNLOCK();
			/* Limit the result to the parent's current config. */
			if (error == 0) {
				struct ifmediareq *ifmr;

				ifmr = (struct ifmediareq *)data;
				if (ifmr->ifm_count >= 1 && ifmr->ifm_ulist) {
					ifmr->ifm_count = 1;
					error = copyout(&ifmr->ifm_current,
						ifmr->ifm_ulist,
						sizeof(int));
				}
			}
		} else {
			VLAN_UNLOCK();
			error = EINVAL;
		}
		break;

	case SIOCSIFMEDIA:
		error = EINVAL;
		break;

	case SIOCSIFMTU:
		/*
		 * Set the interface MTU.
		 */
		VLAN_LOCK();
		if (ifv->ifv_p != NULL) {
			if (ifr->ifr_mtu >
			     (ifv->ifv_p->if_mtu - ifv->ifv_mtufudge) ||
			    ifr->ifr_mtu <
			     (ifv->ifv_mintu - ifv->ifv_mtufudge))
				error = EINVAL;
			else
				ifp->if_mtu = ifr->ifr_mtu;
		} else
			error = EINVAL;
		VLAN_UNLOCK();
		break;

	case SIOCSETVLAN:
		error = copyin(ifr->ifr_data, &vlr, sizeof(vlr));
		if (error)
			break;
		if (vlr.vlr_parent[0] == '\0') {
			VLAN_LOCK();
			vlan_unconfig(ifp);
			if (ifp->if_flags & IFF_UP)
				if_down(ifp);
			ifp->if_drv_flags &= ~IFF_DRV_RUNNING;
			VLAN_UNLOCK();
			break;
		}
		p = ifunit(vlr.vlr_parent);
		if (p == 0) {
			error = ENOENT;
			break;
		}
		/*
		 * Don't let the caller set up a VLAN tag with
		 * anything except VLID bits.
		 */
		if (vlr.vlr_tag & ~EVL_VLID_MASK) {
			error = EINVAL;
			break;
		}
		VLAN_LOCK();
		error = vlan_config(ifv, p);
		if (error) {
			VLAN_UNLOCK();
			break;
		}
		ifv->ifv_tag = vlr.vlr_tag;
		ifp->if_drv_flags |= IFF_DRV_RUNNING;
		VLAN_UNLOCK();

		/* Update flags on the parent, if necessary. */
		vlan_setflags(ifp, 1);
		break;

	case SIOCGETVLAN:
		bzero(&vlr, sizeof(vlr));
		VLAN_LOCK();
		if (ifv->ifv_p) {
			strlcpy(vlr.vlr_parent, ifv->ifv_p->if_xname,
			    sizeof(vlr.vlr_parent));
			vlr.vlr_tag = ifv->ifv_tag;
		}
		VLAN_UNLOCK();
		error = copyout(&vlr, ifr->ifr_data, sizeof(vlr));
		break;

	case SIOCSIFFLAGS:
		/*
		 * We should propagate selected flags to the parent,
		 * e.g., promiscuous mode.
		 */
		if (ifv->ifv_p != NULL)
			error = vlan_setflags(ifp, 1);
		break;

	case SIOCADDMULTI:
	case SIOCDELMULTI:
		/*VLAN_LOCK();*/
		error = vlan_setmulti(ifp);
		/*VLAN_UNLOCK();*/
		break;
	default:
		error = EINVAL;
	}

	return (error);
}