7888 installboot: print version info of the file

[unleashed.git] / kernel / net / ip / ip_multi.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 1991, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 1990 Mentat Inc.
 */

#include <sys/types.h>
#include <sys/stream.h>
#include <sys/dlpi.h>
#include <sys/stropts.h>
#include <sys/strsun.h>
#include <sys/ddi.h>
#include <sys/cmn_err.h>
#include <sys/sdt.h>
#include <sys/zone.h>

#include <sys/param.h>
#include <sys/socket.h>
#include <sys/sockio.h>
#include <net/if.h>
#include <sys/systm.h>
#include <sys/strsubr.h>
#include <net/route.h>
#include <netinet/in.h>
#include <net/if_dl.h>
#include <netinet/ip6.h>
#include <netinet/icmp6.h>

#include <inet/common.h>
#include <inet/mi.h>
#include <inet/nd.h>
#include <inet/arp.h>
#include <inet/ip.h>
#include <inet/ip6.h>
#include <inet/ip_if.h>
#include <inet/ip_ndp.h>
#include <inet/ip_multi.h>
#include <inet/ipclassifier.h>
#include <inet/ipsec_impl.h>
#include <inet/sctp_ip.h>
#include <inet/ip_listutils.h>
#include <inet/udp_impl.h>

/* igmpv3/mldv2 source filter manipulation */
static void     ilm_bld_flists(conn_t *conn, void *arg);
static void     ilm_gen_filter(ilm_t *ilm, mcast_record_t *fmode,
    slist_t *flist);

static ilm_t    *ilm_add(ill_t *ill, const in6_addr_t *group,
    ilg_stat_t ilgstat, mcast_record_t ilg_fmode, slist_t *ilg_flist,
    zoneid_t zoneid);
static void     ilm_delete(ilm_t *ilm);
static int      ilm_numentries(ill_t *, const in6_addr_t *);

static ilm_t    *ip_addmulti_serial(const in6_addr_t *, ill_t *, zoneid_t,
    ilg_stat_t, mcast_record_t, slist_t *, int *);
static ilm_t    *ip_addmulti_impl(const in6_addr_t *, ill_t *,
    zoneid_t, ilg_stat_t, mcast_record_t, slist_t *, int *);
static int      ip_delmulti_serial(ilm_t *, boolean_t, boolean_t);
static int      ip_delmulti_impl(ilm_t *, boolean_t, boolean_t);

static int      ip_ll_multireq(ill_t *ill, const in6_addr_t *group,
    t_uscalar_t);
static ilg_t    *ilg_lookup(conn_t *, const in6_addr_t *, ipaddr_t ifaddr,
    uint_t ifindex);

static int      ilg_add(conn_t *connp, const in6_addr_t *group,
    ipaddr_t ifaddr, uint_t ifindex, ill_t *ill, mcast_record_t fmode,
    const in6_addr_t *v6src);
static void     ilg_delete(conn_t *connp, ilg_t *ilg, const in6_addr_t *src);
static mblk_t   *ill_create_dl(ill_t *ill, uint32_t dl_primitive,
    uint32_t *addr_lenp, uint32_t *addr_offp);
static int      ip_opt_delete_group_excl(conn_t *connp,
    const in6_addr_t *v6group, ipaddr_t ifaddr, uint_t ifindex,
    mcast_record_t fmode, const in6_addr_t *v6src);

static  ilm_t   *ilm_lookup(ill_t *, const in6_addr_t *, zoneid_t);

static int      ip_msfilter_ill(conn_t *, mblk_t *, const ip_ioctl_cmd_t *,
    ill_t **);

static void     ilg_check_detach(conn_t *, ill_t *);
static void     ilg_check_reattach(conn_t *, ill_t *);

/*
 * MT notes:
 *
 * Multicast joins operate on both the ilg and ilm structures. Multiple
 * threads operating on an conn (socket) trying to do multicast joins
 * need to synchronize when operating on the ilg. Multiple threads
 * potentially operating on different conn (socket endpoints) trying to
 * do multicast joins could eventually end up trying to manipulate the
 * ilm simulatenously and need to synchronize on the access to the ilm.
 * The access and lookup of the ilm, as well as other ill multicast state,
 * is under ill_mcast_lock.
 * The modifications and lookup of ilg entries is serialized using conn_ilg_lock
 * rwlock. An ilg will not be freed until ilg_refcnt drops to zero.
 *
 * In some cases we hold ill_mcast_lock and then acquire conn_ilg_lock, but
 * never the other way around.
 *
 * An ilm is an IP data structure used to track multicast join/leave.
 * An ilm is associated with a <multicast group, ipif> tuple in IPv4 and
 * with just <multicast group> in IPv6. ilm_refcnt is the number of ilg's
 * referencing the ilm.
 * The modifications and lookup of ilm entries is serialized using the
 * ill_mcast_lock rwlock; that lock handles all the igmp/mld modifications
 * of the ilm state.
 * ilms are created / destroyed only as writer. ilms
 * are not passed around. The datapath (anything outside of this file
 * and igmp.c) use functions that do not return ilms - just the number
 * of members. So we don't need a dynamic refcount of the number
 * of threads holding reference to an ilm.
 *
 * In the cases where we serially access the ilg and ilm, which happens when
 * we handle the applications requests to join or leave groups and sources,
 * we use the ill_mcast_serializer mutex to ensure that a multithreaded
 * application which does concurrent joins and/or leaves on the same group on
 * the same socket always results in a consistent order for the ilg and ilm
 * modifications.
 *
 * When a multicast operation results in needing to send a message to
 * the driver (to join/leave a L2 multicast address), we use ill_dlpi_queue()
 * which serialized the DLPI requests. The IGMP/MLD code uses ill_mcast_queue()
 * to send IGMP/MLD IP packet to avoid dropping the lock just to send a packet.
 */

#define GETSTRUCT(structure, number)    \
        ((structure *)mi_zalloc(sizeof (structure) * (number)))

/*
 * Caller must ensure that the ilg has not been condemned
 * The condemned flag is only set in ilg_delete under conn_ilg_lock.
 *
 * The caller must hold conn_ilg_lock as writer.
 */
static void
ilg_refhold(ilg_t *ilg)
{
        ASSERT(ilg->ilg_refcnt != 0);
        ASSERT(!ilg->ilg_condemned);
        ASSERT(RW_WRITE_HELD(&ilg->ilg_connp->conn_ilg_lock));

        ilg->ilg_refcnt++;
}

static void
ilg_inactive(ilg_t *ilg)
{
        ASSERT(ilg->ilg_ill == NULL);
        ASSERT(ilg->ilg_ilm == NULL);
        ASSERT(ilg->ilg_filter == NULL);
        ASSERT(ilg->ilg_condemned);

        /* Unlink from list */
        *ilg->ilg_ptpn = ilg->ilg_next;
        if (ilg->ilg_next != NULL)
                ilg->ilg_next->ilg_ptpn = ilg->ilg_ptpn;
        ilg->ilg_next = NULL;
        ilg->ilg_ptpn = NULL;

        ilg->ilg_connp = NULL;
        kmem_free(ilg, sizeof (*ilg));
}

/*
 * The caller must hold conn_ilg_lock as writer.
 */
static void
ilg_refrele(ilg_t *ilg)
{
        ASSERT(RW_WRITE_HELD(&ilg->ilg_connp->conn_ilg_lock));
        ASSERT(ilg->ilg_refcnt != 0);
        if (--ilg->ilg_refcnt == 0)
                ilg_inactive(ilg);
}

/*
 * Acquire reference on ilg and drop reference on held_ilg.
 * In the case when held_ilg is the same as ilg we already have
 * a reference, but the held_ilg might be condemned. In that case
 * we avoid the ilg_refhold/rele so that we can assert in ire_refhold
 * that the ilg isn't condemned.
 */
static void
ilg_transfer_hold(ilg_t *held_ilg, ilg_t *ilg)
{
        if (held_ilg == ilg)
                return;

        ilg_refhold(ilg);
        if (held_ilg != NULL)
                ilg_refrele(held_ilg);
}

/*
 * Allocate a new ilg_t and links it into conn_ilg.
 * Returns NULL on failure, in which case `*errp' will be
 * filled in with the reason.
 *
 * Assumes connp->conn_ilg_lock is held.
 */
static ilg_t *
conn_ilg_alloc(conn_t *connp, int *errp)
{
        ilg_t *ilg;

        ASSERT(RW_WRITE_HELD(&connp->conn_ilg_lock));

        /*
         * If CONN_CLOSING is set, conn_ilg cleanup has begun and we must not
         * create any ilgs.
         */
        if (connp->conn_state_flags & CONN_CLOSING) {
                *errp = EINVAL;
                return (NULL);
        }

        ilg = kmem_zalloc(sizeof (ilg_t), KM_NOSLEEP);
        if (ilg == NULL) {
                *errp = ENOMEM;
                return (NULL);
        }

        ilg->ilg_refcnt = 1;

        /* Insert at head */
        if (connp->conn_ilg != NULL)
                connp->conn_ilg->ilg_ptpn = &ilg->ilg_next;
        ilg->ilg_next = connp->conn_ilg;
        ilg->ilg_ptpn = &connp->conn_ilg;
        connp->conn_ilg = ilg;

        ilg->ilg_connp = connp;
        return (ilg);
}

typedef struct ilm_fbld_s {
        ilm_t           *fbld_ilm;
        int             fbld_in_cnt;
        int             fbld_ex_cnt;
        slist_t         fbld_in;
        slist_t         fbld_ex;
        boolean_t       fbld_in_overflow;
} ilm_fbld_t;

/*
 * Caller must hold ill_mcast_lock
 */
static void
ilm_bld_flists(conn_t *connp, void *arg)
{
        ilg_t *ilg;
        ilm_fbld_t *fbld = (ilm_fbld_t *)(arg);
        ilm_t *ilm = fbld->fbld_ilm;
        in6_addr_t *v6group = &ilm->ilm_v6addr;

        if (connp->conn_ilg == NULL)
                return;

        /*
         * Since we can't break out of the ipcl_walk once started, we still
         * have to look at every conn.  But if we've already found one
         * (EXCLUDE, NULL) list, there's no need to keep checking individual
         * ilgs--that will be our state.
         */
        if (fbld->fbld_ex_cnt > 0 && fbld->fbld_ex.sl_numsrc == 0)
                return;

        /*
         * Check this conn's ilgs to see if any are interested in our
         * ilm (group, interface match).  If so, update the master
         * include and exclude lists we're building in the fbld struct
         * with this ilg's filter info.
         *
         * Note that the caller has already serialized on the ill we care
         * about.
         */
        ASSERT(MUTEX_HELD(&ilm->ilm_ill->ill_mcast_serializer));

        rw_enter(&connp->conn_ilg_lock, RW_READER);
        for (ilg = connp->conn_ilg; ilg != NULL; ilg = ilg->ilg_next) {
                if (ilg->ilg_condemned)
                        continue;

                /*
                 * Since we are under the ill_mcast_serializer we know
                 * that any ilg+ilm operations on this ilm have either
                 * not started or completed, except for the last ilg
                 * (the one that caused us to be called) which doesn't
                 * have ilg_ilm set yet. Hence we compare using ilg_ill
                 * and the address.
                 */
                if ((ilg->ilg_ill == ilm->ilm_ill) &&
                    IN6_ARE_ADDR_EQUAL(&ilg->ilg_v6group, v6group)) {
                        if (ilg->ilg_fmode == MODE_IS_INCLUDE) {
                                fbld->fbld_in_cnt++;
                                if (!fbld->fbld_in_overflow)
                                        l_union_in_a(&fbld->fbld_in,
                                            ilg->ilg_filter,
                                            &fbld->fbld_in_overflow);
                        } else {
                                fbld->fbld_ex_cnt++;
                                /*
                                 * On the first exclude list, don't try to do
                                 * an intersection, as the master exclude list
                                 * is intentionally empty.  If the master list
                                 * is still empty on later iterations, that
                                 * means we have at least one ilg with an empty
                                 * exclude list, so that should be reflected
                                 * when we take the intersection.
                                 */
                                if (fbld->fbld_ex_cnt == 1) {
                                        if (ilg->ilg_filter != NULL)
                                                l_copy(ilg->ilg_filter,
                                                    &fbld->fbld_ex);
                                } else {
                                        l_intersection_in_a(&fbld->fbld_ex,
                                            ilg->ilg_filter);
                                }
                        }
                        /* there will only be one match, so break now. */
                        break;
                }
        }
        rw_exit(&connp->conn_ilg_lock);
}

/*
 * Caller must hold ill_mcast_lock
 */
static void
ilm_gen_filter(ilm_t *ilm, mcast_record_t *fmode, slist_t *flist)
{
        ilm_fbld_t fbld;
        ip_stack_t *ipst = ilm->ilm_ipst;

        fbld.fbld_ilm = ilm;
        fbld.fbld_in_cnt = fbld.fbld_ex_cnt = 0;
        fbld.fbld_in.sl_numsrc = fbld.fbld_ex.sl_numsrc = 0;
        fbld.fbld_in_overflow = B_FALSE;

        /* first, construct our master include and exclude lists */
        ipcl_walk(ilm_bld_flists, (caddr_t)&fbld, ipst);

        /* now use those master lists to generate the interface filter */

        /* if include list overflowed, filter is (EXCLUDE, NULL) */
        if (fbld.fbld_in_overflow) {
                *fmode = MODE_IS_EXCLUDE;
                flist->sl_numsrc = 0;
                return;
        }

        /* if nobody interested, interface filter is (INCLUDE, NULL) */
        if (fbld.fbld_in_cnt == 0 && fbld.fbld_ex_cnt == 0) {
                *fmode = MODE_IS_INCLUDE;
                flist->sl_numsrc = 0;
                return;
        }

        /*
         * If there are no exclude lists, then the interface filter
         * is INCLUDE, with its filter list equal to fbld_in.  A single
         * exclude list makes the interface filter EXCLUDE, with its
         * filter list equal to (fbld_ex - fbld_in).
         */
        if (fbld.fbld_ex_cnt == 0) {
                *fmode = MODE_IS_INCLUDE;
                l_copy(&fbld.fbld_in, flist);
        } else {
                *fmode = MODE_IS_EXCLUDE;
                l_difference(&fbld.fbld_ex, &fbld.fbld_in, flist);
        }
}

/*
 * Caller must hold ill_mcast_lock
 */
static int
ilm_update_add(ilm_t *ilm, ilg_stat_t ilgstat, slist_t *ilg_flist)
{
        mcast_record_t fmode;
        slist_t *flist;
        boolean_t fdefault;
        char buf[INET6_ADDRSTRLEN];
        ill_t *ill = ilm->ilm_ill;

        /*
         * There are several cases where the ilm's filter state
         * defaults to (EXCLUDE, NULL):
         *      - we've had previous joins without associated ilgs
         *      - this join has no associated ilg
         *      - the ilg's filter state is (EXCLUDE, NULL)
         */
        fdefault = (ilm->ilm_no_ilg_cnt > 0) ||
            (ilgstat == ILGSTAT_NONE) || SLIST_IS_EMPTY(ilg_flist);

        /* attempt mallocs (if needed) before doing anything else */
        if ((flist = l_alloc()) == NULL)
                return (ENOMEM);
        if (!fdefault && ilm->ilm_filter == NULL) {
                ilm->ilm_filter = l_alloc();
                if (ilm->ilm_filter == NULL) {
                        l_free(flist);
                        return (ENOMEM);
                }
        }

        if (ilgstat != ILGSTAT_CHANGE)
                ilm->ilm_refcnt++;

        if (ilgstat == ILGSTAT_NONE)
                ilm->ilm_no_ilg_cnt++;

        /*
         * Determine new filter state.  If it's not the default
         * (EXCLUDE, NULL), we must walk the conn list to find
         * any ilgs interested in this group, and re-build the
         * ilm filter.
         */
        if (fdefault) {
                fmode = MODE_IS_EXCLUDE;
                flist->sl_numsrc = 0;
        } else {
                ilm_gen_filter(ilm, &fmode, flist);
        }

        /* make sure state actually changed; nothing to do if not. */
        if ((ilm->ilm_fmode == fmode) &&
            !lists_are_different(ilm->ilm_filter, flist)) {
                l_free(flist);
                return (0);
        }

        /* send the state change report */
        if (!IS_LOOPBACK(ill)) {
                if (ill->ill_isv6)
                        mld_statechange(ilm, fmode, flist);
                else
                        igmp_statechange(ilm, fmode, flist);
        }

        /* update the ilm state */
        ilm->ilm_fmode = fmode;
        if (flist->sl_numsrc > 0)
                l_copy(flist, ilm->ilm_filter);
        else
                CLEAR_SLIST(ilm->ilm_filter);

        ip1dbg(("ilm_update: new if filter mode %d, group %s\n", ilm->ilm_fmode,
            inet_ntop(AF_INET6, &ilm->ilm_v6addr, buf, sizeof (buf))));

        l_free(flist);
        return (0);
}

/*
 * Caller must hold ill_mcast_lock
 */
static int
ilm_update_del(ilm_t *ilm)
{
        mcast_record_t fmode;
        slist_t *flist;
        ill_t *ill = ilm->ilm_ill;

        ip1dbg(("ilm_update_del: still %d left; updating state\n",
            ilm->ilm_refcnt));

        if ((flist = l_alloc()) == NULL)
                return (ENOMEM);

        /*
         * If present, the ilg in question has already either been
         * updated or removed from our list; so all we need to do
         * now is walk the list to update the ilm filter state.
         *
         * Skip the list walk if we have any no-ilg joins, which
         * cause the filter state to revert to (EXCLUDE, NULL).
         */
        if (ilm->ilm_no_ilg_cnt != 0) {
                fmode = MODE_IS_EXCLUDE;
                flist->sl_numsrc = 0;
        } else {
                ilm_gen_filter(ilm, &fmode, flist);
        }

        /* check to see if state needs to be updated */
        if ((ilm->ilm_fmode == fmode) &&
            (!lists_are_different(ilm->ilm_filter, flist))) {
                l_free(flist);
                return (0);
        }

        if (!IS_LOOPBACK(ill)) {
                if (ill->ill_isv6)
                        mld_statechange(ilm, fmode, flist);
                else
                        igmp_statechange(ilm, fmode, flist);
        }

        ilm->ilm_fmode = fmode;
        if (flist->sl_numsrc > 0) {
                if (ilm->ilm_filter == NULL) {
                        ilm->ilm_filter = l_alloc();
                        if (ilm->ilm_filter == NULL) {
                                char buf[INET6_ADDRSTRLEN];
                                ip1dbg(("ilm_update_del: failed to alloc ilm "
                                    "filter; no source filtering for %s on %s",
                                    inet_ntop(AF_INET6, &ilm->ilm_v6addr,
                                    buf, sizeof (buf)), ill->ill_name));
                                ilm->ilm_fmode = MODE_IS_EXCLUDE;
                                l_free(flist);
                                return (0);
                        }
                }
                l_copy(flist, ilm->ilm_filter);
        } else {
                CLEAR_SLIST(ilm->ilm_filter);
        }

        l_free(flist);
        return (0);
}

/*
 * Create/update the ilm for the group/ill. Used by other parts of IP to
 * do the ILGSTAT_NONE (no ilg), MODE_IS_EXCLUDE, with no slist join.
 * Returns with a refhold on the ilm.
 *
 * The unspecified address means all multicast addresses for in both the
 * case of IPv4 and IPv6.
 *
 * The caller should have already mapped an IPMP under ill to the upper.
 */
ilm_t *
ip_addmulti(const in6_addr_t *v6group, ill_t *ill, zoneid_t zoneid,
    int *errorp)
{
        ilm_t *ilm;

        /* Acquire serializer to keep assert in ilm_bld_flists happy */
        mutex_enter(&ill->ill_mcast_serializer);
        ilm = ip_addmulti_serial(v6group, ill, zoneid, ILGSTAT_NONE,
            MODE_IS_EXCLUDE, NULL, errorp);
        mutex_exit(&ill->ill_mcast_serializer);
        /*
         * Now that all locks have been dropped, we can send any
         * deferred/queued DLPI or IP packets
         */
        ill_mcast_send_queued(ill);
        ill_dlpi_send_queued(ill);
        return (ilm);
}

/*
 * Create/update the ilm for the group/ill. If ILGSTAT_CHANGE is not set
 * then this returns with a refhold on the ilm.
 *
 * Internal routine which assumes the caller has already acquired
 * ill_mcast_serializer. It is the caller's responsibility to send out
 * queued DLPI/multicast packets after all locks are dropped.
 *
 * The unspecified address means all multicast addresses for in both the
 * case of IPv4 and IPv6.
 *
 * ilgstat tells us if there's an ilg associated with this join,
 * and if so, if it's a new ilg or a change to an existing one.
 * ilg_fmode and ilg_flist give us the current filter state of
 * the ilg (and will be EXCLUDE {NULL} in the case of no ilg).
 *
 * The caller should have already mapped an IPMP under ill to the upper.
 */
static ilm_t *
ip_addmulti_serial(const in6_addr_t *v6group, ill_t *ill, zoneid_t zoneid,
    ilg_stat_t ilgstat, mcast_record_t ilg_fmode, slist_t *ilg_flist,
    int *errorp)
{
        ilm_t *ilm;

        ASSERT(MUTEX_HELD(&ill->ill_mcast_serializer));

        if (ill->ill_isv6) {
                if (!IN6_IS_ADDR_MULTICAST(v6group) &&
                    !IN6_IS_ADDR_UNSPECIFIED(v6group)) {
                        *errorp = EINVAL;
                        return (NULL);
                }
        } else {
                if (IN6_IS_ADDR_V4MAPPED(v6group)) {
                        ipaddr_t v4group;

                        IN6_V4MAPPED_TO_IPADDR(v6group, v4group);
                        ASSERT(!IS_UNDER_IPMP(ill));
                        if (!CLASSD(v4group)) {
                                *errorp = EINVAL;
                                return (NULL);
                        }
                } else if (!IN6_IS_ADDR_UNSPECIFIED(v6group)) {
                        *errorp = EINVAL;
                        return (NULL);
                }
        }

        if (IS_UNDER_IPMP(ill)) {
                *errorp = EINVAL;
                return (NULL);
        }

        rw_enter(&ill->ill_mcast_lock, RW_WRITER);
        /*
         * We do the equivalent of a lookup by checking after we get the lock
         * This is needed since the ill could have been condemned after
         * we looked it up, and we need to check condemned after we hold
         * ill_mcast_lock to synchronize with the unplumb code.
         */
        if (ill->ill_state_flags & ILL_CONDEMNED) {
                rw_exit(&ill->ill_mcast_lock);
                *errorp = ENXIO;
                return (NULL);
        }
        ilm = ip_addmulti_impl(v6group, ill, zoneid, ilgstat, ilg_fmode,
            ilg_flist, errorp);
        rw_exit(&ill->ill_mcast_lock);

        ill_mcast_timer_start(ill->ill_ipst);
        return (ilm);
}

static ilm_t *
ip_addmulti_impl(const in6_addr_t *v6group, ill_t *ill, zoneid_t zoneid,
    ilg_stat_t ilgstat, mcast_record_t ilg_fmode, slist_t *ilg_flist,
    int *errorp)
{
        ilm_t   *ilm;
        int     ret = 0;

        ASSERT(RW_WRITE_HELD(&ill->ill_mcast_lock));
        *errorp = 0;

        /*
         * An ilm is uniquely identified by the tuple of (group, ill) where
         * `group' is the multicast group address, and `ill' is the interface
         * on which it is currently joined.
         */

        ilm = ilm_lookup(ill, v6group, zoneid);
        if (ilm != NULL) {
                /* ilm_update_add bumps ilm_refcnt unless ILGSTAT_CHANGE */
                ret = ilm_update_add(ilm, ilgstat, ilg_flist);
                if (ret == 0)
                        return (ilm);

                *errorp = ret;
                return (NULL);
        }

        /*
         * The callers checks on the ilg and the ilg+ilm consistency under
         * ill_mcast_serializer ensures that we can not have ILGSTAT_CHANGE
         * and no ilm.
         */
        ASSERT(ilgstat != ILGSTAT_CHANGE);
        ilm = ilm_add(ill, v6group, ilgstat, ilg_fmode, ilg_flist, zoneid);
        if (ilm == NULL) {
                *errorp = ENOMEM;
                return (NULL);
        }

        if (IN6_IS_ADDR_UNSPECIFIED(v6group)) {
                /*
                 * If we have more then one we should not tell the driver
                 * to join this time.
                 */
                if (ilm_numentries(ill, v6group) == 1) {
                        ret = ill_join_allmulti(ill);
                }
        } else {
                if (!IS_LOOPBACK(ill)) {
                        if (ill->ill_isv6)
                                mld_joingroup(ilm);
                        else
                                igmp_joingroup(ilm);
                }

                /*
                 * If we have more then one we should not tell the driver
                 * to join this time.
                 */
                if (ilm_numentries(ill, v6group) == 1) {
                        ret = ip_ll_multireq(ill, v6group, DL_ENABMULTI_REQ);
                }
        }
        if (ret != 0) {
                if (ret == ENETDOWN) {
                        char buf[INET6_ADDRSTRLEN];

                        ip0dbg(("ip_addmulti: ENETDOWN for %s on %s",
                            inet_ntop(AF_INET6, &ilm->ilm_v6addr,
                            buf, sizeof (buf)), ill->ill_name));
                }
                ilm_delete(ilm);
                *errorp = ret;
                return (NULL);
        } else {
                return (ilm);
        }
}

/*
 * Looks up the list of multicast physical addresses this interface
 * listens to. Add to the list if not present already.
 */
boolean_t
ip_mphysaddr_add(ill_t *ill, uchar_t *hw_addr)
{
        multiphysaddr_t *mpa = NULL;
        int     hw_addr_length = ill->ill_phys_addr_length;

        mutex_enter(&ill->ill_lock);
        for (mpa = ill->ill_mphysaddr_list; mpa != NULL; mpa = mpa->mpa_next) {
                if (bcmp(hw_addr, &(mpa->mpa_addr[0]), hw_addr_length) == 0) {
                        mpa->mpa_refcnt++;
                        mutex_exit(&ill->ill_lock);
                        return (B_FALSE);
                }
        }

        mpa = kmem_zalloc(sizeof (multiphysaddr_t), KM_NOSLEEP);
        if (mpa == NULL) {
                /*
                 * We risk not having the multiphysadd structure. At this
                 * point we can't fail. We can't afford to not send a
                 * DL_ENABMULTI_REQ also. It is better than pre-allocating
                 * the structure and having the code to track it also.
                 */
                ip0dbg(("ip_mphysaddr_add: ENOMEM. Some multicast apps"
                    " may have issues. hw_addr: %p ill_name: %s\n",
                    (void *)hw_addr, ill->ill_name));
                mutex_exit(&ill->ill_lock);
                return (B_TRUE);
        }
        bcopy(hw_addr, &(mpa->mpa_addr[0]), hw_addr_length);
        mpa->mpa_refcnt = 1;
        mpa->mpa_next = ill->ill_mphysaddr_list;
        ill->ill_mphysaddr_list = mpa;
        mutex_exit(&ill->ill_lock);
        return (B_TRUE);
}

/*
 * Look up hw_addr from the list of physical multicast addresses this interface
 * listens to.
 * Remove the entry if the refcnt is 0
 */
boolean_t
ip_mphysaddr_del(ill_t *ill, uchar_t *hw_addr)
{
        multiphysaddr_t *mpap = NULL, **mpapp = NULL;
        int hw_addr_length = ill->ill_phys_addr_length;
        boolean_t ret = B_FALSE;

        mutex_enter(&ill->ill_lock);
        for (mpapp = &ill->ill_mphysaddr_list; (mpap = *mpapp) != NULL;
            mpapp = &(mpap->mpa_next)) {
                if (bcmp(hw_addr, &(mpap->mpa_addr[0]), hw_addr_length) == 0)
                        break;
        }
        if (mpap == NULL) {
                /*
                 * Should be coming here only when there was a memory
                 * exhaustion and we were not able to allocate
                 * a multiphysaddr_t. We still send a DL_DISABMULTI_REQ down.
                 */

                ip0dbg(("ip_mphysaddr_del: No entry for this addr. Some "
                    "multicast apps might have had issues. hw_addr: %p "
                    " ill_name: %s\n", (void *)hw_addr, ill->ill_name));
                ret = B_TRUE;
        } else if (--mpap->mpa_refcnt == 0) {
                *mpapp = mpap->mpa_next;
                kmem_free(mpap, sizeof (multiphysaddr_t));
                ret = B_TRUE;
        }
        mutex_exit(&ill->ill_lock);
        return (ret);
}

/*
 * Send a multicast request to the driver for enabling or disabling
 * multicast reception for v6groupp address. The caller has already
 * checked whether it is appropriate to send one or not.
 *
 * For IPMP we switch to the cast_ill since it has the right hardware
 * information.
 */
static int
ip_ll_send_multireq(ill_t *ill, const in6_addr_t *v6groupp, t_uscalar_t prim)
{
        mblk_t  *mp;
        uint32_t addrlen, addroff;
        ill_t *release_ill = NULL;
        uchar_t *cp;
        int err = 0;

        ASSERT(RW_LOCK_HELD(&ill->ill_mcast_lock));

        if (IS_IPMP(ill)) {
                /* On the upper IPMP ill. */
                release_ill = ipmp_illgrp_hold_cast_ill(ill->ill_grp);
                if (release_ill == NULL) {
                        /*
                         * Avoid sending it down to the ipmpstub.
                         * We will be called again once the members of the
                         * group are in place
                         */
                        ip1dbg(("ip_ll_send_multireq: no cast_ill for %s %d\n",
                            ill->ill_name, ill->ill_isv6));
                        return (0);
                }
                ill = release_ill;
        }
        /* Create a DL_ENABMULTI_REQ or DL_DISABMULTI_REQ message. */
        mp = ill_create_dl(ill, prim, &addrlen, &addroff);
        if (mp == NULL) {
                err = ENOMEM;
                goto done;
        }

        mp = ndp_mcastreq(ill, v6groupp, addrlen, addroff, mp);
        if (mp == NULL) {
                ip0dbg(("null from ndp_mcastreq(ill %s)\n", ill->ill_name));
                err = ENOMEM;
                goto done;
        }
        cp = mp->b_rptr;

        switch (((union DL_primitives *)cp)->dl_primitive) {
        case DL_ENABMULTI_REQ:
                cp += ((dl_enabmulti_req_t *)cp)->dl_addr_offset;
                if (!ip_mphysaddr_add(ill, cp)) {
                        freemsg(mp);
                        err = 0;
                        goto done;
                }
                mutex_enter(&ill->ill_lock);
                /* Track the state if this is the first enabmulti */
                if (ill->ill_dlpi_multicast_state == IDS_UNKNOWN)
                        ill->ill_dlpi_multicast_state = IDS_INPROGRESS;
                mutex_exit(&ill->ill_lock);
                break;
        case DL_DISABMULTI_REQ:
                cp += ((dl_disabmulti_req_t *)cp)->dl_addr_offset;
                if (!ip_mphysaddr_del(ill, cp)) {
                        freemsg(mp);
                        err = 0;
                        goto done;
                }
        }
        ill_dlpi_queue(ill, mp);
done:
        if (release_ill != NULL)
                ill_refrele(release_ill);
        return (err);
}

/*
 * Send a multicast request to the driver for enabling multicast
 * membership for v6group if appropriate.
 */
static int
ip_ll_multireq(ill_t *ill, const in6_addr_t *v6groupp, t_uscalar_t prim)
{
        if (ill->ill_net_type != IRE_IF_RESOLVER ||
            ill->ill_ipif->ipif_flags & IPIF_POINTOPOINT) {
                ip1dbg(("ip_ll_multireq: not resolver\n"));
                return (0);     /* Must be IRE_IF_NORESOLVER */
        }

        if (ill->ill_phyint->phyint_flags & PHYI_MULTI_BCAST) {
                ip1dbg(("ip_ll_multireq: MULTI_BCAST\n"));
                return (0);
        }
        return (ip_ll_send_multireq(ill, v6groupp, prim));
}

/*
 * Delete the ilm. Used by other parts of IP for the case of no_ilg/leaving
 * being true.
 */
int
ip_delmulti(ilm_t *ilm)
{
        ill_t *ill = ilm->ilm_ill;
        int error;

        /* Acquire serializer to keep assert in ilm_bld_flists happy */
        mutex_enter(&ill->ill_mcast_serializer);
        error = ip_delmulti_serial(ilm, B_TRUE, B_TRUE);
        mutex_exit(&ill->ill_mcast_serializer);
        /*
         * Now that all locks have been dropped, we can send any
         * deferred/queued DLPI or IP packets
         */
        ill_mcast_send_queued(ill);
        ill_dlpi_send_queued(ill);
        return (error);
}


/*
 * Delete the ilm.
 * Assumes ill_mcast_serializer is held by the caller.
 * Caller must send out queued dlpi/multicast packets after dropping
 * all locks.
 */
static int
ip_delmulti_serial(ilm_t *ilm, boolean_t no_ilg, boolean_t leaving)
{
        ill_t *ill = ilm->ilm_ill;
        int ret;

        ASSERT(MUTEX_HELD(&ill->ill_mcast_serializer));
        ASSERT(!(IS_UNDER_IPMP(ill)));

        rw_enter(&ill->ill_mcast_lock, RW_WRITER);
        ret = ip_delmulti_impl(ilm, no_ilg, leaving);
        rw_exit(&ill->ill_mcast_lock);
        ill_mcast_timer_start(ill->ill_ipst);
        return (ret);
}

static int
ip_delmulti_impl(ilm_t *ilm, boolean_t no_ilg, boolean_t leaving)
{
        ill_t *ill = ilm->ilm_ill;
        int error;
        in6_addr_t v6group;

        ASSERT(RW_WRITE_HELD(&ill->ill_mcast_lock));

        /* Update counters */
        if (no_ilg)
                ilm->ilm_no_ilg_cnt--;

        if (leaving)
                ilm->ilm_refcnt--;

        if (ilm->ilm_refcnt > 0)
                return (ilm_update_del(ilm));

        v6group = ilm->ilm_v6addr;

        if (IN6_IS_ADDR_UNSPECIFIED(&ilm->ilm_v6addr)) {
                ilm_delete(ilm);
                /*
                 * If we have some left then one we should not tell the driver
                 * to leave.
                 */
                if (ilm_numentries(ill, &v6group) != 0)
                        return (0);

                ill_leave_allmulti(ill);

                return (0);
        }

        if (!IS_LOOPBACK(ill)) {
                if (ill->ill_isv6)
                        mld_leavegroup(ilm);
                else
                        igmp_leavegroup(ilm);
        }

        ilm_delete(ilm);
        /*
         * If we have some left then one we should not tell the driver
         * to leave.
         */
        if (ilm_numentries(ill, &v6group) != 0)
                return (0);

        error = ip_ll_multireq(ill, &v6group, DL_DISABMULTI_REQ);
        /* We ignore the case when ill_dl_up is not set */
        if (error == ENETDOWN) {
                char buf[INET6_ADDRSTRLEN];

                ip0dbg(("ip_delmulti: ENETDOWN for %s on %s",
                    inet_ntop(AF_INET6, &v6group, buf, sizeof (buf)),
                    ill->ill_name));
        }
        return (error);
}

/*
 * Make the driver pass up all multicast packets.
 */
int
ill_join_allmulti(ill_t *ill)
{
        mblk_t          *promiscon_mp, *promiscoff_mp = NULL;
        uint32_t        addrlen, addroff;
        ill_t           *release_ill = NULL;

        ASSERT(RW_WRITE_HELD(&ill->ill_mcast_lock));

        if (IS_LOOPBACK(ill))
                return (0);

        if (!ill->ill_dl_up) {
                /*
                 * Nobody there. All multicast addresses will be re-joined
                 * when we get the DL_BIND_ACK bringing the interface up.
                 */
                return (ENETDOWN);
        }

        if (IS_IPMP(ill)) {
                /* On the upper IPMP ill. */
                release_ill = ipmp_illgrp_hold_cast_ill(ill->ill_grp);
                if (release_ill == NULL) {
                        /*
                         * Avoid sending it down to the ipmpstub.
                         * We will be called again once the members of the
                         * group are in place
                         */
                        ip1dbg(("ill_join_allmulti: no cast_ill for %s %d\n",
                            ill->ill_name, ill->ill_isv6));
                        return (0);
                }
                ill = release_ill;
                if (!ill->ill_dl_up) {
                        ill_refrele(ill);
                        return (ENETDOWN);
                }
        }

        /*
         * Create a DL_PROMISCON_REQ message and send it directly to the DLPI
         * provider.  We don't need to do this for certain media types for
         * which we never need to turn promiscuous mode on.  While we're here,
         * pre-allocate a DL_PROMISCOFF_REQ message to make sure that
         * ill_leave_allmulti() will not fail due to low memory conditions.
         */
        if ((ill->ill_net_type == IRE_IF_RESOLVER) &&
            !(ill->ill_phyint->phyint_flags & PHYI_MULTI_BCAST)) {
                promiscon_mp = ill_create_dl(ill, DL_PROMISCON_REQ,
                    &addrlen, &addroff);
                if (ill->ill_promiscoff_mp == NULL)
                        promiscoff_mp = ill_create_dl(ill, DL_PROMISCOFF_REQ,
                            &addrlen, &addroff);
                if (promiscon_mp == NULL ||
                    (ill->ill_promiscoff_mp == NULL && promiscoff_mp == NULL)) {
                        freemsg(promiscon_mp);
                        freemsg(promiscoff_mp);
                        if (release_ill != NULL)
                                ill_refrele(release_ill);
                        return (ENOMEM);
                }
                if (ill->ill_promiscoff_mp == NULL)
                        ill->ill_promiscoff_mp = promiscoff_mp;
                ill_dlpi_queue(ill, promiscon_mp);
        }
        if (release_ill != NULL)
                ill_refrele(release_ill);
        return (0);
}

/*
 * Make the driver stop passing up all multicast packets
 */
void
ill_leave_allmulti(ill_t *ill)
{
        mblk_t  *promiscoff_mp;
        ill_t   *release_ill = NULL;

        ASSERT(RW_WRITE_HELD(&ill->ill_mcast_lock));

        if (IS_LOOPBACK(ill))
                return;

        if (!ill->ill_dl_up) {
                /*
                 * Nobody there. All multicast addresses will be re-joined
                 * when we get the DL_BIND_ACK bringing the interface up.
                 */
                return;
        }

        if (IS_IPMP(ill)) {
                /* On the upper IPMP ill. */
                release_ill = ipmp_illgrp_hold_cast_ill(ill->ill_grp);
                if (release_ill == NULL) {
                        /*
                         * Avoid sending it down to the ipmpstub.
                         * We will be called again once the members of the
                         * group are in place
                         */
                        ip1dbg(("ill_leave_allmulti: no cast_ill on %s %d\n",
                            ill->ill_name, ill->ill_isv6));
                        return;
                }
                ill = release_ill;
                if (!ill->ill_dl_up)
                        goto done;
        }

        /*
         * In the case of IPMP and ill_dl_up not being set when we joined
         * we didn't allocate a promiscoff_mp. In that case we have
         * nothing to do when we leave.
         * Ditto for PHYI_MULTI_BCAST
         */
        promiscoff_mp = ill->ill_promiscoff_mp;
        if (promiscoff_mp != NULL) {
                ill->ill_promiscoff_mp = NULL;
                ill_dlpi_queue(ill, promiscoff_mp);
        }
done:
        if (release_ill != NULL)
                ill_refrele(release_ill);
}

int
ip_join_allmulti(uint_t ifindex, boolean_t isv6, ip_stack_t *ipst)
{
        ill_t           *ill;
        int             ret;
        ilm_t           *ilm;

        ill = ill_lookup_on_ifindex(ifindex, isv6, ipst);
        if (ill == NULL)
                return (ENODEV);

        /*
         * The ip_addmulti() function doesn't allow IPMP underlying interfaces
         * to join allmulti since only the nominated underlying interface in
         * the group should receive multicast.  We silently succeed to avoid
         * having to teach IPobs (currently the only caller of this routine)
         * to ignore failures in this case.
         */
        if (IS_UNDER_IPMP(ill)) {
                ill_refrele(ill);
                return (0);
        }
        mutex_enter(&ill->ill_lock);
        if (ill->ill_ipallmulti_cnt > 0) {
                /* Already joined */
                ASSERT(ill->ill_ipallmulti_ilm != NULL);
                ill->ill_ipallmulti_cnt++;
                mutex_exit(&ill->ill_lock);
                goto done;
        }
        mutex_exit(&ill->ill_lock);

        ilm = ip_addmulti(&ipv6_all_zeros, ill, ill->ill_zoneid, &ret);
        if (ilm == NULL) {
                ASSERT(ret != 0);
                ill_refrele(ill);
                return (ret);
        }

        mutex_enter(&ill->ill_lock);
        if (ill->ill_ipallmulti_cnt > 0) {
                /* Another thread added it concurrently */
                (void) ip_delmulti(ilm);
                mutex_exit(&ill->ill_lock);
                goto done;
        }
        ASSERT(ill->ill_ipallmulti_ilm == NULL);
        ill->ill_ipallmulti_ilm = ilm;
        ill->ill_ipallmulti_cnt++;
        mutex_exit(&ill->ill_lock);
done:
        ill_refrele(ill);
        return (0);
}

int
ip_leave_allmulti(uint_t ifindex, boolean_t isv6, ip_stack_t *ipst)
{
        ill_t           *ill;
        ilm_t           *ilm;

        ill = ill_lookup_on_ifindex(ifindex, isv6, ipst);
        if (ill == NULL)
                return (ENODEV);

        if (IS_UNDER_IPMP(ill)) {
                ill_refrele(ill);
                return (0);
        }

        mutex_enter(&ill->ill_lock);
        if (ill->ill_ipallmulti_cnt == 0) {
                /* ip_purge_allmulti could have removed them all */
                mutex_exit(&ill->ill_lock);
                goto done;
        }
        ill->ill_ipallmulti_cnt--;
        if (ill->ill_ipallmulti_cnt == 0) {
                /* Last one */
                ilm = ill->ill_ipallmulti_ilm;
                ill->ill_ipallmulti_ilm = NULL;
        } else {
                ilm = NULL;
        }
        mutex_exit(&ill->ill_lock);
        if (ilm != NULL)
                (void) ip_delmulti(ilm);

done:
        ill_refrele(ill);
        return (0);
}

/*
 * Delete the allmulti memberships that were added as part of
 * ip_join_allmulti().
 */
void
ip_purge_allmulti(ill_t *ill)
{
        ilm_t   *ilm;

        ASSERT(IAM_WRITER_ILL(ill));

        mutex_enter(&ill->ill_lock);
        ilm = ill->ill_ipallmulti_ilm;
        ill->ill_ipallmulti_ilm = NULL;
        ill->ill_ipallmulti_cnt = 0;
        mutex_exit(&ill->ill_lock);

        if (ilm != NULL)
                (void) ip_delmulti(ilm);
}

/*
 * Create a dlpi message with room for phys+sap. Later
 * we will strip the sap for those primitives which
 * only need a physical address.
 */
static mblk_t *
ill_create_dl(ill_t *ill, uint32_t dl_primitive,
    uint32_t *addr_lenp, uint32_t *addr_offp)
{
        mblk_t  *mp;
        uint32_t        hw_addr_length;
        char            *cp;
        uint32_t        offset;
        uint32_t        length;
        uint32_t        size;

        *addr_lenp = *addr_offp = 0;

        hw_addr_length = ill->ill_phys_addr_length;
        if (!hw_addr_length) {
                ip0dbg(("ip_create_dl: hw addr length = 0\n"));
                return (NULL);
        }

        switch (dl_primitive) {
        case DL_ENABMULTI_REQ:
                length = sizeof (dl_enabmulti_req_t);
                size = length + hw_addr_length;
                break;
        case DL_DISABMULTI_REQ:
                length = sizeof (dl_disabmulti_req_t);
                size = length + hw_addr_length;
                break;
        case DL_PROMISCON_REQ:
        case DL_PROMISCOFF_REQ:
                size = length = sizeof (dl_promiscon_req_t);
                break;
        default:
                return (NULL);
        }
        mp = allocb(size, BPRI_HI);
        if (!mp)
                return (NULL);
        mp->b_wptr += size;
        mp->b_datap->db_type = M_PROTO;

        cp = (char *)mp->b_rptr;
        offset = length;

        switch (dl_primitive) {
        case DL_ENABMULTI_REQ: {
                dl_enabmulti_req_t *dl = (dl_enabmulti_req_t *)cp;

                dl->dl_primitive = dl_primitive;
                dl->dl_addr_offset = offset;
                *addr_lenp = dl->dl_addr_length = hw_addr_length;
                *addr_offp = offset;
                break;
        }
        case DL_DISABMULTI_REQ: {
                dl_disabmulti_req_t *dl = (dl_disabmulti_req_t *)cp;

                dl->dl_primitive = dl_primitive;
                dl->dl_addr_offset = offset;
                *addr_lenp = dl->dl_addr_length = hw_addr_length;
                *addr_offp = offset;
                break;
        }
        case DL_PROMISCON_REQ:
        case DL_PROMISCOFF_REQ: {
                dl_promiscon_req_t *dl = (dl_promiscon_req_t *)cp;

                dl->dl_primitive = dl_primitive;
                dl->dl_level = DL_PROMISC_MULTI;
                break;
        }
        }
        ip1dbg(("ill_create_dl: addr_len %d, addr_off %d\n",
            *addr_lenp, *addr_offp));
        return (mp);
}

/*
 * Rejoin any groups for which we have ilms.
 *
 * This is only needed for IPMP when the cast_ill changes since that
 * change is invisible to the ilm. Other interface changes are handled
 * by conn_update_ill.
 */
void
ill_recover_multicast(ill_t *ill)
{
        ilm_t   *ilm;
        char    addrbuf[INET6_ADDRSTRLEN];

        ill->ill_need_recover_multicast = 0;

        rw_enter(&ill->ill_mcast_lock, RW_WRITER);
        for (ilm = ill->ill_ilm; ilm; ilm = ilm->ilm_next) {
                /*
                 * If we have more then one ilm for the group (e.g., with
                 * different zoneid) then we should not tell the driver
                 * to join unless this is the first ilm for the group.
                 */
                if (ilm_numentries(ill, &ilm->ilm_v6addr) > 1 &&
                    ilm_lookup(ill, &ilm->ilm_v6addr, ALL_ZONES) != ilm) {
                        continue;
                }

                ip1dbg(("ill_recover_multicast: %s\n", inet_ntop(AF_INET6,
                    &ilm->ilm_v6addr, addrbuf, sizeof (addrbuf))));

                if (IN6_IS_ADDR_UNSPECIFIED(&ilm->ilm_v6addr)) {
                        (void) ill_join_allmulti(ill);
                } else {
                        if (ill->ill_isv6)
                                mld_joingroup(ilm);
                        else
                                igmp_joingroup(ilm);

                        (void) ip_ll_multireq(ill, &ilm->ilm_v6addr,
                            DL_ENABMULTI_REQ);
                }
        }
        rw_exit(&ill->ill_mcast_lock);
        /* Send any deferred/queued DLPI or IP packets */
        ill_mcast_send_queued(ill);
        ill_dlpi_send_queued(ill);
        ill_mcast_timer_start(ill->ill_ipst);
}

/*
 * The opposite of ill_recover_multicast() -- leaves all multicast groups
 * that were explicitly joined.
 *
 * This is only needed for IPMP when the cast_ill changes since that
 * change is invisible to the ilm. Other interface changes are handled
 * by conn_update_ill.
 */
void
ill_leave_multicast(ill_t *ill)
{
        ilm_t   *ilm;
        char    addrbuf[INET6_ADDRSTRLEN];

        ill->ill_need_recover_multicast = 1;

        rw_enter(&ill->ill_mcast_lock, RW_WRITER);
        for (ilm = ill->ill_ilm; ilm; ilm = ilm->ilm_next) {
                /*
                 * If we have more then one ilm for the group (e.g., with
                 * different zoneid) then we should not tell the driver
                 * to leave unless this is the first ilm for the group.
                 */
                if (ilm_numentries(ill, &ilm->ilm_v6addr) > 1 &&
                    ilm_lookup(ill, &ilm->ilm_v6addr, ALL_ZONES) != ilm) {
                        continue;
                }

                ip1dbg(("ill_leave_multicast: %s\n", inet_ntop(AF_INET6,
                    &ilm->ilm_v6addr, addrbuf, sizeof (addrbuf))));

                if (IN6_IS_ADDR_UNSPECIFIED(&ilm->ilm_v6addr)) {
                        ill_leave_allmulti(ill);
                } else {
                        if (ill->ill_isv6)
                                mld_leavegroup(ilm);
                        else
                                igmp_leavegroup(ilm);

                        (void) ip_ll_multireq(ill, &ilm->ilm_v6addr,
                            DL_DISABMULTI_REQ);
                }
        }
        rw_exit(&ill->ill_mcast_lock);
        /* Send any deferred/queued DLPI or IP packets */
        ill_mcast_send_queued(ill);
        ill_dlpi_send_queued(ill);
        ill_mcast_timer_start(ill->ill_ipst);
}

/*
 * Interface used by IP input/output.
 * Returns true if there is a member on the ill for any zoneid.
 */
boolean_t
ill_hasmembers_v6(ill_t *ill, const in6_addr_t *v6group)
{
        ilm_t           *ilm;

        rw_enter(&ill->ill_mcast_lock, RW_READER);
        ilm = ilm_lookup(ill, v6group, ALL_ZONES);
        rw_exit(&ill->ill_mcast_lock);
        return (ilm != NULL);
}

/*
 * Interface used by IP input/output.
 * Returns true if there is a member on the ill for any zoneid.
 *
 * The group and source can't be INADDR_ANY here so no need to translate to
 * the unspecified IPv6 address.
 */
boolean_t
ill_hasmembers_v4(ill_t *ill, ipaddr_t group)
{
        in6_addr_t      v6group;

        IN6_IPADDR_TO_V4MAPPED(group, &v6group);
        return (ill_hasmembers_v6(ill, &v6group));
}

/*
 * Interface used by IP input/output.
 * Returns true if there is a member on the ill for any zoneid except skipzone.
 */
boolean_t
ill_hasmembers_otherzones_v6(ill_t *ill, const in6_addr_t *v6group,
    zoneid_t skipzone)
{
        ilm_t           *ilm;

        rw_enter(&ill->ill_mcast_lock, RW_READER);
        for (ilm = ill->ill_ilm; ilm; ilm = ilm->ilm_next) {
                if (IN6_ARE_ADDR_EQUAL(&ilm->ilm_v6addr, v6group) &&
                    ilm->ilm_zoneid != skipzone) {
                        rw_exit(&ill->ill_mcast_lock);
                        return (B_TRUE);
                }
        }
        rw_exit(&ill->ill_mcast_lock);
        return (B_FALSE);
}

/*
 * Interface used by IP input/output.
 * Returns true if there is a member on the ill for any zoneid except skipzone.
 *
 * The group and source can't be INADDR_ANY here so no need to translate to
 * the unspecified IPv6 address.
 */
boolean_t
ill_hasmembers_otherzones_v4(ill_t *ill, ipaddr_t group, zoneid_t skipzone)
{
        in6_addr_t      v6group;

        IN6_IPADDR_TO_V4MAPPED(group, &v6group);
        return (ill_hasmembers_otherzones_v6(ill, &v6group, skipzone));
}

/*
 * Interface used by IP input.
 * Returns the next numerically larger zoneid that has a member. If none exist
 * then returns -1 (ALL_ZONES).
 * The normal usage is for the caller to start with a -1 zoneid (ALL_ZONES)
 * to find the first zoneid which has a member, and then pass that in for
 * subsequent calls until ALL_ZONES is returned.
 *
 * The implementation of ill_hasmembers_nextzone() assumes the ilms
 * are sorted by zoneid for efficiency.
 */
zoneid_t
ill_hasmembers_nextzone_v6(ill_t *ill, const in6_addr_t *v6group,
    zoneid_t zoneid)
{
        ilm_t           *ilm;

        rw_enter(&ill->ill_mcast_lock, RW_READER);
        for (ilm = ill->ill_ilm; ilm; ilm = ilm->ilm_next) {
                if (IN6_ARE_ADDR_EQUAL(&ilm->ilm_v6addr, v6group) &&
                    ilm->ilm_zoneid > zoneid) {
                        zoneid = ilm->ilm_zoneid;
                        rw_exit(&ill->ill_mcast_lock);
                        return (zoneid);
                }
        }
        rw_exit(&ill->ill_mcast_lock);
        return (ALL_ZONES);
}

/*
 * Interface used by IP input.
 * Returns the next numerically larger zoneid that has a member. If none exist
 * then returns -1 (ALL_ZONES).
 *
 * The group and source can't be INADDR_ANY here so no need to translate to
 * the unspecified IPv6 address.
 */
zoneid_t
ill_hasmembers_nextzone_v4(ill_t *ill, ipaddr_t group, zoneid_t zoneid)
{
        in6_addr_t      v6group;

        IN6_IPADDR_TO_V4MAPPED(group, &v6group);

        return (ill_hasmembers_nextzone_v6(ill, &v6group, zoneid));
}

/*
 * Find an ilm matching the ill, group, and zoneid.
 */
static ilm_t *
ilm_lookup(ill_t *ill, const in6_addr_t *v6group, zoneid_t zoneid)
{
        ilm_t   *ilm;

        ASSERT(RW_LOCK_HELD(&ill->ill_mcast_lock));

        for (ilm = ill->ill_ilm; ilm; ilm = ilm->ilm_next) {
                if (!IN6_ARE_ADDR_EQUAL(&ilm->ilm_v6addr, v6group))
                        continue;
                if (zoneid != ALL_ZONES && zoneid != ilm->ilm_zoneid)
                        continue;

                ASSERT(ilm->ilm_ill == ill);
                return (ilm);
        }
        return (NULL);
}

/*
 * How many members on this ill?
 * Since each shared-IP zone has a separate ilm for the same group/ill
 * we can have several.
 */
static int
ilm_numentries(ill_t *ill, const in6_addr_t *v6group)
{
        ilm_t   *ilm;
        int i = 0;

        ASSERT(RW_LOCK_HELD(&ill->ill_mcast_lock));
        for (ilm = ill->ill_ilm; ilm; ilm = ilm->ilm_next) {
                if (IN6_ARE_ADDR_EQUAL(&ilm->ilm_v6addr, v6group)) {
                        i++;
                }
        }
        return (i);
}

/* Caller guarantees that the group is not already on the list */
static ilm_t *
ilm_add(ill_t *ill, const in6_addr_t *v6group, ilg_stat_t ilgstat,
    mcast_record_t ilg_fmode, slist_t *ilg_flist, zoneid_t zoneid)
{
        ilm_t   *ilm;
        ilm_t   *ilm_cur;
        ilm_t   **ilm_ptpn;

        ASSERT(RW_WRITE_HELD(&ill->ill_mcast_lock));
        ilm = GETSTRUCT(ilm_t, 1);
        if (ilm == NULL)
                return (NULL);
        if (ilgstat != ILGSTAT_NONE && !SLIST_IS_EMPTY(ilg_flist)) {
                ilm->ilm_filter = l_alloc();
                if (ilm->ilm_filter == NULL) {
                        mi_free(ilm);
                        return (NULL);
                }
        }
        ilm->ilm_v6addr = *v6group;
        ilm->ilm_refcnt = 1;
        ilm->ilm_zoneid = zoneid;
        ilm->ilm_timer = INFINITY;
        ilm->ilm_rtx.rtx_timer = INFINITY;

        ilm->ilm_ill = ill;
        DTRACE_PROBE3(ill__incr__cnt, (ill_t *), ill,
            (char *), "ilm", (void *), ilm);
        ill->ill_ilm_cnt++;

        ASSERT(ill->ill_ipst);
        ilm->ilm_ipst = ill->ill_ipst;  /* No netstack_hold */

        /* The ill/ipif could have just been marked as condemned */

        /*
         * To make ill_hasmembers_nextzone_v6 work we keep the list
         * sorted by zoneid.
         */
        ilm_cur = ill->ill_ilm;
        ilm_ptpn = &ill->ill_ilm;
        while (ilm_cur != NULL && ilm_cur->ilm_zoneid < ilm->ilm_zoneid) {
                ilm_ptpn = &ilm_cur->ilm_next;
                ilm_cur = ilm_cur->ilm_next;
        }
        ilm->ilm_next = ilm_cur;
        *ilm_ptpn = ilm;

        /*
         * If we have an associated ilg, use its filter state; if not,
         * default to (EXCLUDE, NULL) and set no_ilg_cnt to track this.
         */
        if (ilgstat != ILGSTAT_NONE) {
                if (!SLIST_IS_EMPTY(ilg_flist))
                        l_copy(ilg_flist, ilm->ilm_filter);
                ilm->ilm_fmode = ilg_fmode;
        } else {
                ilm->ilm_no_ilg_cnt = 1;
                ilm->ilm_fmode = MODE_IS_EXCLUDE;
        }

        return (ilm);
}

void
ilm_inactive(ilm_t *ilm)
{
        FREE_SLIST(ilm->ilm_filter);
        FREE_SLIST(ilm->ilm_pendsrcs);
        FREE_SLIST(ilm->ilm_rtx.rtx_allow);
        FREE_SLIST(ilm->ilm_rtx.rtx_block);
        ilm->ilm_ipst = NULL;
        mi_free((char *)ilm);
}

/*
 * Unlink ilm and free it.
 */
static void
ilm_delete(ilm_t *ilm)
{
        ill_t           *ill = ilm->ilm_ill;
        ilm_t           **ilmp;
        boolean_t       need_wakeup;

        /*
         * Delete under lock protection so that readers don't stumble
         * on bad ilm_next
         */
        ASSERT(RW_WRITE_HELD(&ill->ill_mcast_lock));

        for (ilmp = &ill->ill_ilm; *ilmp != ilm; ilmp = &(*ilmp)->ilm_next)
                ;

        *ilmp = ilm->ilm_next;

        mutex_enter(&ill->ill_lock);
        /*
         * if we are the last reference to the ill, we may need to wakeup any
         * pending FREE or unplumb operations. This is because conn_update_ill
         * bails if there is a ilg_delete_all in progress.
         */
        need_wakeup = B_FALSE;
        DTRACE_PROBE3(ill__decr__cnt, (ill_t *), ill,
            (char *), "ilm", (void *), ilm);
        ASSERT(ill->ill_ilm_cnt > 0);
        ill->ill_ilm_cnt--;
        if (ILL_FREE_OK(ill))
                need_wakeup = B_TRUE;

        ilm_inactive(ilm); /* frees this ilm */

        if (need_wakeup) {
                /* drops ill lock */
                ipif_ill_refrele_tail(ill);
        } else {
                mutex_exit(&ill->ill_lock);
        }
}

/*
 * Lookup an ill based on the group, ifindex, ifaddr, and zoneid.
 * Applies to both IPv4 and IPv6, although ifaddr is only used with
 * IPv4.
 * Returns an error for IS_UNDER_IPMP and VNI interfaces.
 * On error it sets *errorp.
 */
static ill_t *
ill_mcast_lookup(const in6_addr_t *group, ipaddr_t ifaddr, uint_t ifindex,
    zoneid_t zoneid, ip_stack_t *ipst, int *errorp)
{
        ill_t *ill;
        ipaddr_t v4group;

        if (IN6_IS_ADDR_V4MAPPED(group)) {
                IN6_V4MAPPED_TO_IPADDR(group, v4group);

                if (ifindex != 0) {
                        ill = ill_lookup_on_ifindex_zoneid(ifindex, zoneid,
                            B_FALSE, ipst);
                } else if (ifaddr != INADDR_ANY) {
                        ipif_t *ipif;

                        ipif = ipif_lookup_addr(ifaddr, NULL, zoneid, ipst);
                        if (ipif == NULL) {
                                ill = NULL;
                        } else {
                                ill = ipif->ipif_ill;
                                ill_refhold(ill);
                                ipif_refrele(ipif);
                        }
                } else {
                        ill = ill_lookup_group_v4(v4group, zoneid, ipst, NULL);
                }
        } else {
                if (ifindex != 0) {
                        ill = ill_lookup_on_ifindex_zoneid(ifindex, zoneid,
                            B_TRUE, ipst);
                } else {
                        ill = ill_lookup_group_v6(group, zoneid, ipst, NULL);
                }
        }
        if (ill == NULL) {
                if (ifindex != 0)
                        *errorp = ENXIO;
                else
                        *errorp = EADDRNOTAVAIL;
                return (NULL);
        }
        /* operation not supported on the virtual network interface */
        if (IS_UNDER_IPMP(ill) || IS_VNI(ill)) {
                ill_refrele(ill);
                *errorp = EINVAL;
                return (NULL);
        }
        return (ill);
}

/*
 * Looks up the appropriate ill given an interface index (or interface address)
 * and multicast group.  On success, returns 0, with *illpp pointing to the
 * found struct.  On failure, returns an errno and *illpp is set to NULL.
 *
 * Returns an error for IS_UNDER_IPMP and VNI interfaces.
 *
 * Handles both IPv4 and IPv6. The ifaddr argument only applies in the
 * case of IPv4.
 */
int
ip_opt_check(conn_t *connp, const in6_addr_t *v6group,
    const in6_addr_t *v6src, ipaddr_t ifaddr, uint_t ifindex, ill_t **illpp)
{
        boolean_t src_unspec;
        ill_t *ill = NULL;
        ip_stack_t *ipst = connp->conn_netstack->netstack_ip;
        int error = 0;

        *illpp = NULL;

        src_unspec = IN6_IS_ADDR_UNSPECIFIED(v6src);

        if (IN6_IS_ADDR_V4MAPPED(v6group)) {
                ipaddr_t v4group;
                ipaddr_t v4src;

                if (!IN6_IS_ADDR_V4MAPPED(v6src) && !src_unspec)
                        return (EINVAL);
                IN6_V4MAPPED_TO_IPADDR(v6group, v4group);
                if (src_unspec) {
                        v4src = INADDR_ANY;
                } else {
                        IN6_V4MAPPED_TO_IPADDR(v6src, v4src);
                }
                if (!CLASSD(v4group) || CLASSD(v4src))
                        return (EINVAL);
        } else {
                if (IN6_IS_ADDR_V4MAPPED(v6src) && !src_unspec)
                        return (EINVAL);
                if (!IN6_IS_ADDR_MULTICAST(v6group) ||
                    IN6_IS_ADDR_MULTICAST(v6src)) {
                        return (EINVAL);
                }
        }

        ill = ill_mcast_lookup(v6group, ifaddr, ifindex, IPCL_ZONEID(connp),
            ipst, &error);
        *illpp = ill;
        return (error);
}

static int
ip_get_srcfilter(conn_t *connp, struct group_filter *gf,
    struct ip_msfilter *imsf, const struct in6_addr *group, boolean_t issin6)
{
        ilg_t *ilg;
        int i, numsrc, fmode, outsrcs;
        struct sockaddr_in *sin;
        struct sockaddr_in6 *sin6;
        struct in_addr *addrp;
        slist_t *fp;
        boolean_t is_v4only_api;
        ipaddr_t ifaddr;
        uint_t ifindex;

        if (gf == NULL) {
                ASSERT(imsf != NULL);
                ASSERT(!issin6);
                is_v4only_api = B_TRUE;
                outsrcs = imsf->imsf_numsrc;
                ifaddr = imsf->imsf_interface.s_addr;
                ifindex = 0;
        } else {
                ASSERT(imsf == NULL);
                is_v4only_api = B_FALSE;
                outsrcs = gf->gf_numsrc;
                ifaddr = INADDR_ANY;
                ifindex = gf->gf_interface;
        }

        /* No need to use ill_mcast_serializer for the reader */
        rw_enter(&connp->conn_ilg_lock, RW_READER);
        ilg = ilg_lookup(connp, group, ifaddr, ifindex);
        if (ilg == NULL) {
                rw_exit(&connp->conn_ilg_lock);
                return (EADDRNOTAVAIL);
        }

        /*
         * In the kernel, we use the state definitions MODE_IS_[IN|EX]CLUDE
         * to identify the filter mode; but the API uses MCAST_[IN|EX]CLUDE.
         * So we need to translate here.
         */
        fmode = (ilg->ilg_fmode == MODE_IS_INCLUDE) ?
            MCAST_INCLUDE : MCAST_EXCLUDE;
        if ((fp = ilg->ilg_filter) == NULL) {
                numsrc = 0;
        } else {
                for (i = 0; i < outsrcs; i++) {
                        if (i == fp->sl_numsrc)
                                break;
                        if (issin6) {
                                sin6 = (struct sockaddr_in6 *)&gf->gf_slist[i];
                                sin6->sin6_family = AF_INET6;
                                sin6->sin6_addr = fp->sl_addr[i];
                        } else {
                                if (is_v4only_api) {
                                        addrp = &imsf->imsf_slist[i];
                                } else {
                                        sin = (struct sockaddr_in *)
                                            &gf->gf_slist[i];
                                        sin->sin_family = AF_INET;
                                        addrp = &sin->sin_addr;
                                }
                                IN6_V4MAPPED_TO_INADDR(&fp->sl_addr[i], addrp);
                        }
                }
                numsrc = fp->sl_numsrc;
        }

        if (is_v4only_api) {
                imsf->imsf_numsrc = numsrc;
                imsf->imsf_fmode = fmode;
        } else {
                gf->gf_numsrc = numsrc;
                gf->gf_fmode = fmode;
        }

        rw_exit(&connp->conn_ilg_lock);

        return (0);
}

/*
 * Common for IPv4 and IPv6.
 */
static int
ip_set_srcfilter(conn_t *connp, struct group_filter *gf,
    struct ip_msfilter *imsf, const struct in6_addr *group, ill_t *ill,
    boolean_t issin6)
{
        ilg_t *ilg;
        int i, err, infmode, new_fmode;
        uint_t insrcs;
        struct sockaddr_in *sin;
        struct sockaddr_in6 *sin6;
        struct in_addr *addrp;
        slist_t *orig_filter = NULL;
        slist_t *new_filter = NULL;
        mcast_record_t orig_fmode;
        boolean_t leave_group, is_v4only_api;
        ilg_stat_t ilgstat;
        ilm_t *ilm;
        ipaddr_t ifaddr;
        uint_t ifindex;

        if (gf == NULL) {
                ASSERT(imsf != NULL);
                ASSERT(!issin6);
                is_v4only_api = B_TRUE;
                insrcs = imsf->imsf_numsrc;
                infmode = imsf->imsf_fmode;
                ifaddr = imsf->imsf_interface.s_addr;
                ifindex = 0;
        } else {
                ASSERT(imsf == NULL);
                is_v4only_api = B_FALSE;
                insrcs = gf->gf_numsrc;
                infmode = gf->gf_fmode;
                ifaddr = INADDR_ANY;
                ifindex = gf->gf_interface;
        }

        /* Make sure we can handle the source list */
        if (insrcs > MAX_FILTER_SIZE)
                return (ENOBUFS);

        /*
         * setting the filter to (INCLUDE, NULL) is treated
         * as a request to leave the group.
         */
        leave_group = (infmode == MCAST_INCLUDE && insrcs == 0);

        mutex_enter(&ill->ill_mcast_serializer);
        rw_enter(&connp->conn_ilg_lock, RW_WRITER);
        ilg = ilg_lookup(connp, group, ifaddr, ifindex);
        if (ilg == NULL) {
                /*
                 * if the request was actually to leave, and we
                 * didn't find an ilg, there's nothing to do.
                 */
                if (leave_group) {
                        rw_exit(&connp->conn_ilg_lock);
                        mutex_exit(&ill->ill_mcast_serializer);
                        return (0);
                }
                ilg = conn_ilg_alloc(connp, &err);
                if (ilg == NULL) {
                        rw_exit(&connp->conn_ilg_lock);
                        mutex_exit(&ill->ill_mcast_serializer);
                        return (err);
                }
                ilgstat = ILGSTAT_NEW;
                ilg->ilg_v6group = *group;
                ilg->ilg_ill = ill;
                ilg->ilg_ifaddr = ifaddr;
                ilg->ilg_ifindex = ifindex;
        } else if (leave_group) {
                /*
                 * Make sure we have the correct serializer. The ill argument
                 * might not match ilg_ill.
                 */
                ilg_refhold(ilg);
                mutex_exit(&ill->ill_mcast_serializer);
                ill = ilg->ilg_ill;
                rw_exit(&connp->conn_ilg_lock);

                mutex_enter(&ill->ill_mcast_serializer);
                rw_enter(&connp->conn_ilg_lock, RW_WRITER);
                ilm = ilg->ilg_ilm;
                ilg->ilg_ilm = NULL;
                ilg_delete(connp, ilg, NULL);
                ilg_refrele(ilg);
                rw_exit(&connp->conn_ilg_lock);
                if (ilm != NULL)
                        (void) ip_delmulti_serial(ilm, B_FALSE, B_TRUE);
                mutex_exit(&ill->ill_mcast_serializer);
                /*
                 * Now that all locks have been dropped, we can send any
                 * deferred/queued DLPI or IP packets
                 */
                ill_mcast_send_queued(ill);
                ill_dlpi_send_queued(ill);
                return (0);
        } else {
                ilgstat = ILGSTAT_CHANGE;
                /* Preserve existing state in case ip_addmulti() fails */
                orig_fmode = ilg->ilg_fmode;
                if (ilg->ilg_filter == NULL) {
                        orig_filter = NULL;
                } else {
                        orig_filter = l_alloc_copy(ilg->ilg_filter);
                        if (orig_filter == NULL) {
                                rw_exit(&connp->conn_ilg_lock);
                                mutex_exit(&ill->ill_mcast_serializer);
                                return (ENOMEM);
                        }
                }
        }

        /*
         * Alloc buffer to copy new state into (see below) before
         * we make any changes, so we can bail if it fails.
         */
        if ((new_filter = l_alloc()) == NULL) {
                rw_exit(&connp->conn_ilg_lock);
                err = ENOMEM;
                goto free_and_exit;
        }

        if (insrcs == 0) {
                CLEAR_SLIST(ilg->ilg_filter);
        } else {
                slist_t *fp;
                if (ilg->ilg_filter == NULL) {
                        fp = l_alloc();
                        if (fp == NULL) {
                                if (ilgstat == ILGSTAT_NEW)
                                        ilg_delete(connp, ilg, NULL);
                                rw_exit(&connp->conn_ilg_lock);
                                err = ENOMEM;
                                goto free_and_exit;
                        }
                } else {
                        fp = ilg->ilg_filter;
                }
                for (i = 0; i < insrcs; i++) {
                        if (issin6) {
                                sin6 = (struct sockaddr_in6 *)&gf->gf_slist[i];
                                fp->sl_addr[i] = sin6->sin6_addr;
                        } else {
                                if (is_v4only_api) {
                                        addrp = &imsf->imsf_slist[i];
                                } else {
                                        sin = (struct sockaddr_in *)
                                            &gf->gf_slist[i];
                                        addrp = &sin->sin_addr;
                                }
                                IN6_INADDR_TO_V4MAPPED(addrp, &fp->sl_addr[i]);
                        }
                }
                fp->sl_numsrc = insrcs;
                ilg->ilg_filter = fp;
        }
        /*
         * In the kernel, we use the state definitions MODE_IS_[IN|EX]CLUDE
         * to identify the filter mode; but the API uses MCAST_[IN|EX]CLUDE.
         * So we need to translate here.
         */
        ilg->ilg_fmode = (infmode == MCAST_INCLUDE) ?
            MODE_IS_INCLUDE : MODE_IS_EXCLUDE;

        /*
         * Save copy of ilg's filter state to pass to other functions,
         * so we can release conn_ilg_lock now.
         */
        new_fmode = ilg->ilg_fmode;
        l_copy(ilg->ilg_filter, new_filter);

        rw_exit(&connp->conn_ilg_lock);

        /*
         * Now update the ill. We wait to do this until after the ilg
         * has been updated because we need to update the src filter
         * info for the ill, which involves looking at the status of
         * all the ilgs associated with this group/interface pair.
         */
        ilm = ip_addmulti_serial(group, ill, connp->conn_zoneid, ilgstat,
            new_fmode, new_filter, &err);

        rw_enter(&connp->conn_ilg_lock, RW_WRITER);
        /*
         * Must look up the ilg again since we've not been holding
         * conn_ilg_lock. The ilg could have disappeared due to an unplumb
         * having called conn_update_ill, which can run once we dropped the
         * conn_ilg_lock above.
         */
        ilg = ilg_lookup(connp, group, ifaddr, ifindex);
        if (ilg == NULL) {
                rw_exit(&connp->conn_ilg_lock);
                if (ilm != NULL) {
                        (void) ip_delmulti_serial(ilm, B_FALSE,
                            (ilgstat == ILGSTAT_NEW));
                }
                err = ENXIO;
                goto free_and_exit;
        }

        if (ilm != NULL) {
                if (ilg->ilg_ill == NULL) {
                        /* some other thread is re-attaching this.  */
                        rw_exit(&connp->conn_ilg_lock);
                        (void) ip_delmulti_serial(ilm, B_FALSE,
                            (ilgstat == ILGSTAT_NEW));
                        err = 0;
                        goto free_and_exit;
                }
                /* Succeeded. Update the ilg to point at the ilm */
                if (ilgstat == ILGSTAT_NEW) {
                        if (ilg->ilg_ilm == NULL) {
                                ilg->ilg_ilm = ilm;
                                ilm->ilm_ifaddr = ifaddr; /* For netstat */
                        } else {
                                /* some other thread is re-attaching this. */
                                rw_exit(&connp->conn_ilg_lock);
                                (void) ip_delmulti_serial(ilm, B_FALSE, B_TRUE);
                                err = 0;
                                goto free_and_exit;
                        }
                } else {
                        /*
                         * ip_addmulti didn't get a held ilm for
                         * ILGSTAT_CHANGE; ilm_refcnt was unchanged.
                         */
                        ASSERT(ilg->ilg_ilm == ilm);
                }
        } else {
                ASSERT(err != 0);
                /*
                 * Failed to allocate the ilm.
                 * Restore the original filter state, or delete the
                 * newly-created ilg.
                 * If ENETDOWN just clear ill_ilg since so that we
                 * will rejoin when the ill comes back; don't report ENETDOWN
                 * to application.
                 */
                if (ilgstat == ILGSTAT_NEW) {
                        if (err == ENETDOWN) {
                                ilg->ilg_ill = NULL;
                                err = 0;
                        } else {
                                ilg_delete(connp, ilg, NULL);
                        }
                } else {
                        ilg->ilg_fmode = orig_fmode;
                        if (SLIST_IS_EMPTY(orig_filter)) {
                                CLEAR_SLIST(ilg->ilg_filter);
                        } else {
                                /*
                                 * We didn't free the filter, even if we
                                 * were trying to make the source list empty;
                                 * so if orig_filter isn't empty, the ilg
                                 * must still have a filter alloc'd.
                                 */
                                l_copy(orig_filter, ilg->ilg_filter);
                        }
                }
        }
        rw_exit(&connp->conn_ilg_lock);

free_and_exit:
        mutex_exit(&ill->ill_mcast_serializer);
        ill_mcast_send_queued(ill);
        ill_dlpi_send_queued(ill);
        l_free(orig_filter);
        l_free(new_filter);

        return (err);
}

/*
 * Process the SIOC[GS]MSFILTER and SIOC[GS]IPMSFILTER ioctls.
 */
/* ARGSUSED */
int
ip_sioctl_msfilter(ipif_t *ipif, sin_t *dummy_sin, queue_t *q, mblk_t *mp,
    ip_ioctl_cmd_t *ipip, void *ifreq)
{
        struct iocblk *iocp = (struct iocblk *)mp->b_rptr;
        /* existence verified in ip_wput_nondata() */
        mblk_t *data_mp = mp->b_cont->b_cont;
        int datalen, err, cmd, minsize;
        uint_t expsize = 0;
        conn_t *connp;
        boolean_t isv6, is_v4only_api, getcmd;
        struct sockaddr_in *gsin;
        struct sockaddr_in6 *gsin6;
        ipaddr_t v4group;
        in6_addr_t v6group;
        struct group_filter *gf = NULL;
        struct ip_msfilter *imsf = NULL;
        mblk_t *ndp;
        ill_t *ill;

        connp = Q_TO_CONN(q);
        err = ip_msfilter_ill(connp, mp, ipip, &ill);
        if (err != 0)
                return (err);

        if (data_mp->b_cont != NULL) {
                if ((ndp = msgpullup(data_mp, -1)) == NULL)
                        return (ENOMEM);
                freemsg(data_mp);
                data_mp = ndp;
                mp->b_cont->b_cont = data_mp;
        }

        cmd = iocp->ioc_cmd;
        getcmd = (cmd == SIOCGIPMSFILTER || cmd == SIOCGMSFILTER);
        is_v4only_api = (cmd == SIOCGIPMSFILTER || cmd == SIOCSIPMSFILTER);
        minsize = (is_v4only_api) ? IP_MSFILTER_SIZE(0) : GROUP_FILTER_SIZE(0);
        datalen = MBLKL(data_mp);

        if (datalen < minsize)
                return (EINVAL);

        /*
         * now we know we have at least have the initial structure,
         * but need to check for the source list array.
         */
        if (is_v4only_api) {
                imsf = (struct ip_msfilter *)data_mp->b_rptr;
                isv6 = B_FALSE;
                expsize = IP_MSFILTER_SIZE(imsf->imsf_numsrc);
        } else {
                gf = (struct group_filter *)data_mp->b_rptr;
                if (gf->gf_group.ss_family == AF_INET6) {
                        gsin6 = (struct sockaddr_in6 *)&gf->gf_group;
                        isv6 = !(IN6_IS_ADDR_V4MAPPED(&gsin6->sin6_addr));
                } else {
                        isv6 = B_FALSE;
                }
                expsize = GROUP_FILTER_SIZE(gf->gf_numsrc);
        }
        if (datalen < expsize)
                return (EINVAL);

        if (isv6) {
                gsin6 = (struct sockaddr_in6 *)&gf->gf_group;
                v6group = gsin6->sin6_addr;
                if (getcmd) {
                        err = ip_get_srcfilter(connp, gf, NULL, &v6group,
                            B_TRUE);
                } else {
                        err = ip_set_srcfilter(connp, gf, NULL, &v6group, ill,
                            B_TRUE);
                }
        } else {
                boolean_t issin6 = B_FALSE;
                if (is_v4only_api) {
                        v4group = (ipaddr_t)imsf->imsf_multiaddr.s_addr;
                        IN6_IPADDR_TO_V4MAPPED(v4group, &v6group);
                } else {
                        if (gf->gf_group.ss_family == AF_INET) {
                                gsin = (struct sockaddr_in *)&gf->gf_group;
                                v4group = (ipaddr_t)gsin->sin_addr.s_addr;
                                IN6_IPADDR_TO_V4MAPPED(v4group, &v6group);
                        } else {
                                gsin6 = (struct sockaddr_in6 *)&gf->gf_group;
                                IN6_V4MAPPED_TO_IPADDR(&gsin6->sin6_addr,
                                    v4group);
                                issin6 = B_TRUE;
                        }
                }
                /*
                 * INADDR_ANY is represented as the IPv6 unspecifed addr.
                 */
                if (v4group == INADDR_ANY)
                        v6group = ipv6_all_zeros;
                else
                        IN6_IPADDR_TO_V4MAPPED(v4group, &v6group);

                if (getcmd) {
                        err = ip_get_srcfilter(connp, gf, imsf, &v6group,
                            issin6);
                } else {
                        err = ip_set_srcfilter(connp, gf, imsf, &v6group, ill,
                            issin6);
                }
        }
        ill_refrele(ill);

        return (err);
}

/*
 * Determine the ill for the SIOC*MSFILTER ioctls
 *
 * Returns an error for IS_UNDER_IPMP interfaces.
 *
 * Finds the ill based on information in the ioctl headers.
 */
static int
ip_msfilter_ill(conn_t *connp, mblk_t *mp, const ip_ioctl_cmd_t *ipip,
    ill_t **illp)
{
        int cmd = ipip->ipi_cmd;
        int err = 0;
        ill_t *ill;
        /* caller has verified this mblk exists */
        char *dbuf = (char *)mp->b_cont->b_cont->b_rptr;
        struct ip_msfilter *imsf;
        struct group_filter *gf;
        ipaddr_t v4addr, v4group;
        in6_addr_t v6group;
        uint32_t index;
        ip_stack_t *ipst;

        ipst = connp->conn_netstack->netstack_ip;

        *illp = NULL;

        /* don't allow multicast operations on a tcp conn */
        if (IPCL_IS_TCP(connp))
                return (ENOPROTOOPT);

        if (cmd == SIOCSIPMSFILTER || cmd == SIOCGIPMSFILTER) {
                /* don't allow v4-specific ioctls on v6 socket */
                if (connp->conn_family == AF_INET6)
                        return (EAFNOSUPPORT);

                imsf = (struct ip_msfilter *)dbuf;
                v4addr = imsf->imsf_interface.s_addr;
                v4group = imsf->imsf_multiaddr.s_addr;
                IN6_IPADDR_TO_V4MAPPED(v4group, &v6group);
                ill = ill_mcast_lookup(&v6group, v4addr, 0, IPCL_ZONEID(connp),
                    ipst, &err);
                if (ill == NULL && v4addr != INADDR_ANY)
                        err = ENXIO;
        } else {
                gf = (struct group_filter *)dbuf;
                index = gf->gf_interface;
                if (gf->gf_group.ss_family == AF_INET6) {
                        struct sockaddr_in6 *sin6;

                        sin6 = (struct sockaddr_in6 *)&gf->gf_group;
                        v6group = sin6->sin6_addr;
                } else if (gf->gf_group.ss_family == AF_INET) {
                        struct sockaddr_in *sin;

                        sin = (struct sockaddr_in *)&gf->gf_group;
                        v4group = sin->sin_addr.s_addr;
                        IN6_IPADDR_TO_V4MAPPED(v4group, &v6group);
                } else {
                        return (EAFNOSUPPORT);
                }
                ill = ill_mcast_lookup(&v6group, INADDR_ANY, index,
                    IPCL_ZONEID(connp), ipst, &err);
        }
        *illp = ill;
        return (err);
}

/*
 * The structures used for the SIOC*MSFILTER ioctls usually must be copied
 * in in two stages, as the first copyin tells us the size of the attached
 * source buffer.  This function is called by ip_wput_nondata() after the
 * first copyin has completed; it figures out how big the second stage
 * needs to be, and kicks it off.
 *
 * In some cases (numsrc < 2), the second copyin is not needed as the
 * first one gets a complete structure containing 1 source addr.
 *
 * The function returns 0 if a second copyin has been started (i.e. there's
 * no more work to be done right now), or 1 if the second copyin is not
 * needed and ip_wput_nondata() can continue its processing.
 */
int
ip_copyin_msfilter(queue_t *q, mblk_t *mp)
{
        struct iocblk *iocp = (struct iocblk *)mp->b_rptr;
        int cmd = iocp->ioc_cmd;
        /* validity of this checked in ip_wput_nondata() */
        mblk_t *mp1 = mp->b_cont->b_cont;
        int copysize = 0;
        int offset;

        if (cmd == SIOCSMSFILTER || cmd == SIOCGMSFILTER) {
                struct group_filter *gf = (struct group_filter *)mp1->b_rptr;
                if (gf->gf_numsrc >= 2) {
                        offset = sizeof (struct group_filter);
                        copysize = GROUP_FILTER_SIZE(gf->gf_numsrc) - offset;
                }
        } else {
                struct ip_msfilter *imsf = (struct ip_msfilter *)mp1->b_rptr;
                if (imsf->imsf_numsrc >= 2) {
                        offset = sizeof (struct ip_msfilter);
                        copysize = IP_MSFILTER_SIZE(imsf->imsf_numsrc) - offset;
                }
        }
        if (copysize > 0) {
                mi_copyin_n(q, mp, offset, copysize);
                return (0);
        }
        return (1);
}

/*
 * Handle the following optmgmt:
 *      IP_ADD_MEMBERSHIP               must not have joined already
 *      IPV6_JOIN_GROUP                 must not have joined already
 *      MCAST_JOIN_GROUP                must not have joined already
 *      IP_BLOCK_SOURCE                 must have joined already
 *      MCAST_BLOCK_SOURCE              must have joined already
 *      IP_JOIN_SOURCE_GROUP            may have joined already
 *      MCAST_JOIN_SOURCE_GROUP         may have joined already
 *
 * fmode and src parameters may be used to determine which option is
 * being set, as follows (IPV6_JOIN_GROUP and MCAST_JOIN_GROUP options
 * are functionally equivalent):
 *      opt                     fmode                   v6src
 *      IP_ADD_MEMBERSHIP       MODE_IS_EXCLUDE         unspecified
 *      IPV6_JOIN_GROUP         MODE_IS_EXCLUDE         unspecified
 *      MCAST_JOIN_GROUP        MODE_IS_EXCLUDE         unspecified
 *      IP_BLOCK_SOURCE         MODE_IS_EXCLUDE         IPv4-mapped addr
 *      MCAST_BLOCK_SOURCE      MODE_IS_EXCLUDE         v6 addr
 *      IP_JOIN_SOURCE_GROUP    MODE_IS_INCLUDE         IPv4-mapped addr
 *      MCAST_JOIN_SOURCE_GROUP MODE_IS_INCLUDE         v6 addr
 *
 * Changing the filter mode is not allowed; if a matching ilg already
 * exists and fmode != ilg->ilg_fmode, EINVAL is returned.
 *
 * Verifies that there is a source address of appropriate scope for
 * the group; if not, EADDRNOTAVAIL is returned.
 *
 * The interface to be used may be identified by an IPv4 address or by an
 * interface index.
 *
 * Handles IPv4-mapped IPv6 multicast addresses by associating them
 * with the IPv4 address.  Assumes that if v6group is v4-mapped,
 * v6src is also v4-mapped.
 */
int
ip_opt_add_group(conn_t *connp, boolean_t checkonly,
    const in6_addr_t *v6group, ipaddr_t ifaddr, uint_t ifindex,
    mcast_record_t fmode, const in6_addr_t *v6src)
{
        ill_t *ill;
        char buf[INET6_ADDRSTRLEN];
        int     err;

        err = ip_opt_check(connp, v6group, v6src, ifaddr, ifindex, &ill);
        if (err != 0) {
                ip1dbg(("ip_opt_add_group: no ill for group %s/"
                    "index %d\n", inet_ntop(AF_INET6, v6group, buf,
                    sizeof (buf)), ifindex));
                return (err);
        }

        if (checkonly) {
                /*
                 * do not do operation, just pretend to - new T_CHECK
                 * semantics. The error return case above if encountered
                 * considered a good enough "check" here.
                 */
                ill_refrele(ill);
                return (0);
        }
        mutex_enter(&ill->ill_mcast_serializer);
        /*
         * Multicast groups may not be joined on interfaces that are either
         * already underlying interfaces in an IPMP group, or in the process
         * of joining the IPMP group. The latter condition is enforced by
         * checking the value of ill->ill_grp_pending under the
         * ill_mcast_serializer lock.  We cannot serialize the
         * ill_grp_pending check on the ill_g_lock across ilg_add() because
         *  ill_mcast_send_queued -> ip_output_simple -> ill_lookup_on_ifindex
         * will take the ill_g_lock itself. Instead, we hold the
         * ill_mcast_serializer.
         */
        if (ill->ill_grp_pending || IS_UNDER_IPMP(ill)) {
                DTRACE_PROBE2(group__add__on__under, ill_t *, ill,
                    in6_addr_t *, v6group);
                mutex_exit(&ill->ill_mcast_serializer);
                ill_refrele(ill);
                return (EADDRNOTAVAIL);
        }
        err = ilg_add(connp, v6group, ifaddr, ifindex, ill, fmode, v6src);
        mutex_exit(&ill->ill_mcast_serializer);
        /*
         * We have done an addmulti_impl and/or delmulti_impl.
         * All locks have been dropped, we can send any
         * deferred/queued DLPI or IP packets
         */
        ill_mcast_send_queued(ill);
        ill_dlpi_send_queued(ill);
        ill_refrele(ill);
        return (err);
}

/*
 * Common for IPv6 and IPv4.
 * Here we handle ilgs that are still attached to their original ill
 * (the one ifaddr/ifindex points at), as well as detached ones.
 * The detached ones might have been attached to some other ill.
 */
static int
ip_opt_delete_group_excl(conn_t *connp, const in6_addr_t *v6group,
    ipaddr_t ifaddr, uint_t ifindex, mcast_record_t fmode,
    const in6_addr_t *v6src)
{
        ilg_t   *ilg;
        boolean_t leaving;
        ilm_t *ilm;
        ill_t *ill;
        int err = 0;

retry:
        rw_enter(&connp->conn_ilg_lock, RW_WRITER);
        ilg = ilg_lookup(connp, v6group, ifaddr, ifindex);
        if (ilg == NULL) {
                rw_exit(&connp->conn_ilg_lock);
                /*
                 * Since we didn't have any ilg we now do the error checks
                 * to determine the best errno.
                 */
                err = ip_opt_check(connp, v6group, v6src, ifaddr, ifindex,
                    &ill);
                if (ill != NULL) {
                        /* The only error was a missing ilg for the group */
                        ill_refrele(ill);
                        err = EADDRNOTAVAIL;
                }
                return (err);
        }

        /* If the ilg is attached then we serialize using that ill */
        ill = ilg->ilg_ill;
        if (ill != NULL) {
                /* Prevent the ill and ilg from being freed */
                ill_refhold(ill);
                ilg_refhold(ilg);
                rw_exit(&connp->conn_ilg_lock);
                mutex_enter(&ill->ill_mcast_serializer);
                rw_enter(&connp->conn_ilg_lock, RW_WRITER);
                if (ilg->ilg_condemned) {
                        /* Disappeared */
                        ilg_refrele(ilg);
                        rw_exit(&connp->conn_ilg_lock);
                        mutex_exit(&ill->ill_mcast_serializer);
                        ill_refrele(ill);
                        goto retry;
                }
        }

        /*
         * Decide if we're actually deleting the ilg or just removing a
         * source filter address; if just removing an addr, make sure we
         * aren't trying to change the filter mode, and that the addr is
         * actually in our filter list already.  If we're removing the
         * last src in an include list, just delete the ilg.
         */
        if (IN6_IS_ADDR_UNSPECIFIED(v6src)) {
                leaving = B_TRUE;
        } else {
                if (fmode != ilg->ilg_fmode)
                        err = EINVAL;
                else if (ilg->ilg_filter == NULL ||
                    !list_has_addr(ilg->ilg_filter, v6src))
                        err = EADDRNOTAVAIL;
                if (err != 0) {
                        if (ill != NULL)
                                ilg_refrele(ilg);
                        rw_exit(&connp->conn_ilg_lock);
                        goto done;
                }
                if (fmode == MODE_IS_INCLUDE &&
                    ilg->ilg_filter->sl_numsrc == 1) {
                        leaving = B_TRUE;
                        v6src = NULL;
                } else {
                        leaving = B_FALSE;
                }
        }
        ilm = ilg->ilg_ilm;
        if (leaving)
                ilg->ilg_ilm = NULL;

        ilg_delete(connp, ilg, v6src);
        if (ill != NULL)
                ilg_refrele(ilg);
        rw_exit(&connp->conn_ilg_lock);

        if (ilm != NULL) {
                ASSERT(ill != NULL);
                (void) ip_delmulti_serial(ilm, B_FALSE, leaving);
        }
done:
        if (ill != NULL) {
                mutex_exit(&ill->ill_mcast_serializer);
                /*
                 * Now that all locks have been dropped, we can
                 * send any deferred/queued DLPI or IP packets
                 */
                ill_mcast_send_queued(ill);
                ill_dlpi_send_queued(ill);
                ill_refrele(ill);
        }
        return (err);
}

/*
 * Handle the following optmgmt:
 *      IP_DROP_MEMBERSHIP              will leave
 *      IPV6_LEAVE_GROUP                will leave
 *      MCAST_LEAVE_GROUP               will leave
 *      IP_UNBLOCK_SOURCE               will not leave
 *      MCAST_UNBLOCK_SOURCE            will not leave
 *      IP_LEAVE_SOURCE_GROUP           may leave (if leaving last source)
 *      MCAST_LEAVE_SOURCE_GROUP        may leave (if leaving last source)
 *
 * fmode and src parameters may be used to determine which option is
 * being set, as follows:
 *      opt                      fmode                  v6src
 *      IP_DROP_MEMBERSHIP       MODE_IS_INCLUDE        unspecified
 *      IPV6_LEAVE_GROUP         MODE_IS_INCLUDE        unspecified
 *      MCAST_LEAVE_GROUP        MODE_IS_INCLUDE        unspecified
 *      IP_UNBLOCK_SOURCE        MODE_IS_EXCLUDE        IPv4-mapped addr
 *      MCAST_UNBLOCK_SOURCE     MODE_IS_EXCLUDE        v6 addr
 *      IP_LEAVE_SOURCE_GROUP    MODE_IS_INCLUDE        IPv4-mapped addr
 *      MCAST_LEAVE_SOURCE_GROUP MODE_IS_INCLUDE        v6 addr
 *
 * Changing the filter mode is not allowed; if a matching ilg already
 * exists and fmode != ilg->ilg_fmode, EINVAL is returned.
 *
 * The interface to be used may be identified by an IPv4 address or by an
 * interface index.
 *
 * Handles IPv4-mapped IPv6 multicast addresses by associating them
 * with the IPv4 address.  Assumes that if v6group is v4-mapped,
 * v6src is also v4-mapped.
 */
int
ip_opt_delete_group(conn_t *connp, boolean_t checkonly,
    const in6_addr_t *v6group, ipaddr_t ifaddr, uint_t ifindex,
    mcast_record_t fmode, const in6_addr_t *v6src)
{

        /*
         * In the normal case below we don't check for the ill existing.
         * Instead we look for an existing ilg in _excl.
         * If checkonly we sanity check the arguments
         */
        if (checkonly) {
                ill_t   *ill;
                int     err;

                err = ip_opt_check(connp, v6group, v6src, ifaddr, ifindex,
                    &ill);
                /*
                 * do not do operation, just pretend to - new T_CHECK semantics.
                 * ip_opt_check is considered a good enough "check" here.
                 */
                if (ill != NULL)
                        ill_refrele(ill);
                return (err);
        }
        return (ip_opt_delete_group_excl(connp, v6group, ifaddr, ifindex,
            fmode, v6src));
}

/*
 * Group mgmt for upper conn that passes things down
 * to the interface multicast list (and DLPI)
 * These routines can handle new style options that specify an interface name
 * as opposed to an interface address (needed for general handling of
 * unnumbered interfaces.)
 */

/*
 * Add a group to an upper conn group data structure and pass things down
 * to the interface multicast list (and DLPI)
 * Common for IPv4 and IPv6; for IPv4 we can have an ifaddr.
 */
static int
ilg_add(conn_t *connp, const in6_addr_t *v6group, ipaddr_t ifaddr,
    uint_t ifindex, ill_t *ill, mcast_record_t fmode, const in6_addr_t *v6src)
{
        int     error = 0;
        ilg_t   *ilg;
        ilg_stat_t ilgstat;
        slist_t *new_filter = NULL;
        int     new_fmode;
        ilm_t *ilm;

        if (!(ill->ill_flags & ILLF_MULTICAST))
                return (EADDRNOTAVAIL);

        /* conn_ilg_lock protects the ilg list. */
        ASSERT(MUTEX_HELD(&ill->ill_mcast_serializer));
        rw_enter(&connp->conn_ilg_lock, RW_WRITER);
        ilg = ilg_lookup(connp, v6group, ifaddr, ifindex);

        /*
         * Depending on the option we're handling, may or may not be okay
         * if group has already been added.  Figure out our rules based
         * on fmode and src params.  Also make sure there's enough room
         * in the filter if we're adding a source to an existing filter.
         */
        if (IN6_IS_ADDR_UNSPECIFIED(v6src)) {
                /* we're joining for all sources, must not have joined */
                if (ilg != NULL)
                        error = EADDRINUSE;
        } else {
                if (fmode == MODE_IS_EXCLUDE) {
                        /* (excl {addr}) => block source, must have joined */
                        if (ilg == NULL)
                                error = EADDRNOTAVAIL;
                }
                /* (incl {addr}) => join source, may have joined */

                if (ilg != NULL &&
                    SLIST_CNT(ilg->ilg_filter) == MAX_FILTER_SIZE)
                        error = ENOBUFS;
        }
        if (error != 0) {
                rw_exit(&connp->conn_ilg_lock);
                return (error);
        }

        /*
         * Alloc buffer to copy new state into (see below) before
         * we make any changes, so we can bail if it fails.
         */
        if ((new_filter = l_alloc()) == NULL) {
                rw_exit(&connp->conn_ilg_lock);
                return (ENOMEM);
        }

        if (ilg == NULL) {
                if ((ilg = conn_ilg_alloc(connp, &error)) == NULL) {
                        rw_exit(&connp->conn_ilg_lock);
                        l_free(new_filter);
                        return (error);
                }
                ilg->ilg_ifindex = ifindex;
                ilg->ilg_ifaddr = ifaddr;
                if (!IN6_IS_ADDR_UNSPECIFIED(v6src)) {
                        ilg->ilg_filter = l_alloc();
                        if (ilg->ilg_filter == NULL) {
                                ilg_delete(connp, ilg, NULL);
                                rw_exit(&connp->conn_ilg_lock);
                                l_free(new_filter);
                                return (ENOMEM);
                        }
                        ilg->ilg_filter->sl_numsrc = 1;
                        ilg->ilg_filter->sl_addr[0] = *v6src;
                }
                ilgstat = ILGSTAT_NEW;
                ilg->ilg_v6group = *v6group;
                ilg->ilg_fmode = fmode;
                ilg->ilg_ill = ill;
        } else {
                int index;

                if (ilg->ilg_fmode != fmode || IN6_IS_ADDR_UNSPECIFIED(v6src)) {
                        rw_exit(&connp->conn_ilg_lock);
                        l_free(new_filter);
                        return (EINVAL);
                }
                if (ilg->ilg_filter == NULL) {
                        ilg->ilg_filter = l_alloc();
                        if (ilg->ilg_filter == NULL) {
                                rw_exit(&connp->conn_ilg_lock);
                                l_free(new_filter);
                                return (ENOMEM);
                        }
                }
                if (list_has_addr(ilg->ilg_filter, v6src)) {
                        rw_exit(&connp->conn_ilg_lock);
                        l_free(new_filter);
                        return (EADDRNOTAVAIL);
                }
                ilgstat = ILGSTAT_CHANGE;
                index = ilg->ilg_filter->sl_numsrc++;
                ilg->ilg_filter->sl_addr[index] = *v6src;
        }

        /*
         * Save copy of ilg's filter state to pass to other functions,
         * so we can release conn_ilg_lock now.
         */
        new_fmode = ilg->ilg_fmode;
        l_copy(ilg->ilg_filter, new_filter);

        rw_exit(&connp->conn_ilg_lock);

        /*
         * Now update the ill. We wait to do this until after the ilg
         * has been updated because we need to update the src filter
         * info for the ill, which involves looking at the status of
         * all the ilgs associated with this group/interface pair.
         */
        ilm = ip_addmulti_serial(v6group, ill, connp->conn_zoneid, ilgstat,
            new_fmode, new_filter, &error);

        rw_enter(&connp->conn_ilg_lock, RW_WRITER);
        /*
         * Must look up the ilg again since we've not been holding
         * conn_ilg_lock. The ilg could have disappeared due to an unplumb
         * having called conn_update_ill, which can run once we dropped the
         * conn_ilg_lock above.
         */
        ilg = ilg_lookup(connp, v6group, ifaddr, ifindex);
        if (ilg == NULL) {
                rw_exit(&connp->conn_ilg_lock);
                if (ilm != NULL) {
                        (void) ip_delmulti_serial(ilm, B_FALSE,
                            (ilgstat == ILGSTAT_NEW));
                }
                error = ENXIO;
                goto free_and_exit;
        }
        if (ilm != NULL) {
                if (ilg->ilg_ill == NULL) {
                        /* some other thread is re-attaching this.  */
                        rw_exit(&connp->conn_ilg_lock);
                        (void) ip_delmulti_serial(ilm, B_FALSE,
                            (ilgstat == ILGSTAT_NEW));
                        error = 0;
                        goto free_and_exit;
                }
                /* Succeeded. Update the ilg to point at the ilm */
                if (ilgstat == ILGSTAT_NEW) {
                        if (ilg->ilg_ilm == NULL) {
                                ilg->ilg_ilm = ilm;
                                ilm->ilm_ifaddr = ifaddr; /* For netstat */
                        } else {
                                /* some other thread is re-attaching this. */
                                rw_exit(&connp->conn_ilg_lock);
                                (void) ip_delmulti_serial(ilm, B_FALSE, B_TRUE);
                                error = 0;
                                goto free_and_exit;
                        }
                } else {
                        /*
                         * ip_addmulti didn't get a held ilm for
                         * ILGSTAT_CHANGE; ilm_refcnt was unchanged.
                         */
                        ASSERT(ilg->ilg_ilm == ilm);
                }
        } else {
                ASSERT(error != 0);
                /*
                 * Failed to allocate the ilm.
                 * Need to undo what we did before calling ip_addmulti()
                 * If ENETDOWN just clear ill_ilg since so that we
                 * will rejoin when the ill comes back; don't report ENETDOWN
                 * to application.
                 */
                if (ilgstat == ILGSTAT_NEW && error == ENETDOWN) {
                        ilg->ilg_ill = NULL;
                        error = 0;
                } else {
                        in6_addr_t delsrc =
                            (ilgstat == ILGSTAT_NEW) ? ipv6_all_zeros : *v6src;

                        ilg_delete(connp, ilg, &delsrc);
                }
        }
        rw_exit(&connp->conn_ilg_lock);

free_and_exit:
        l_free(new_filter);
        return (error);
}

/*
 * Find an IPv4 ilg matching group, ill and source.
 * The group and source can't be INADDR_ANY here so no need to translate to
 * the unspecified IPv6 address.
 */
boolean_t
conn_hasmembers_ill_withsrc_v4(conn_t *connp, ipaddr_t group, ipaddr_t src,
    ill_t *ill)
{
        in6_addr_t v6group, v6src;
        int i;
        boolean_t isinlist;
        ilg_t *ilg;

        rw_enter(&connp->conn_ilg_lock, RW_READER);
        IN6_IPADDR_TO_V4MAPPED(group, &v6group);
        for (ilg = connp->conn_ilg; ilg != NULL; ilg = ilg->ilg_next) {
                if (ilg->ilg_condemned)
                        continue;

                /* ilg_ill could be NULL if an add is in progress */
                if (ilg->ilg_ill != ill)
                        continue;

                /* The callers use upper ill for IPMP */
                ASSERT(!IS_UNDER_IPMP(ill));
                if (IN6_ARE_ADDR_EQUAL(&ilg->ilg_v6group, &v6group)) {
                        if (SLIST_IS_EMPTY(ilg->ilg_filter)) {
                                /* no source filter, so this is a match */
                                rw_exit(&connp->conn_ilg_lock);
                                return (B_TRUE);
                        }
                        break;
                }
        }
        if (ilg == NULL) {
                rw_exit(&connp->conn_ilg_lock);
                return (B_FALSE);
        }

        /*
         * we have an ilg with matching ill and group; but
         * the ilg has a source list that we must check.
         */
        IN6_IPADDR_TO_V4MAPPED(src, &v6src);
        isinlist = B_FALSE;
        for (i = 0; i < ilg->ilg_filter->sl_numsrc; i++) {
                if (IN6_ARE_ADDR_EQUAL(&v6src, &ilg->ilg_filter->sl_addr[i])) {
                        isinlist = B_TRUE;
                        break;
                }
        }

        if ((isinlist && ilg->ilg_fmode == MODE_IS_INCLUDE) ||
            (!isinlist && ilg->ilg_fmode == MODE_IS_EXCLUDE)) {
                rw_exit(&connp->conn_ilg_lock);
                return (B_TRUE);
        }
        rw_exit(&connp->conn_ilg_lock);
        return (B_FALSE);
}

/*
 * Find an IPv6 ilg matching group, ill, and source
 */
boolean_t
conn_hasmembers_ill_withsrc_v6(conn_t *connp, const in6_addr_t *v6group,
    const in6_addr_t *v6src, ill_t *ill)
{
        int i;
        boolean_t isinlist;
        ilg_t *ilg;

        rw_enter(&connp->conn_ilg_lock, RW_READER);
        for (ilg = connp->conn_ilg; ilg != NULL; ilg = ilg->ilg_next) {
                if (ilg->ilg_condemned)
                        continue;

                /* ilg_ill could be NULL if an add is in progress */
                if (ilg->ilg_ill != ill)
                        continue;

                /* The callers use upper ill for IPMP */
                ASSERT(!IS_UNDER_IPMP(ill));
                if (IN6_ARE_ADDR_EQUAL(&ilg->ilg_v6group, v6group)) {
                        if (SLIST_IS_EMPTY(ilg->ilg_filter)) {
                                /* no source filter, so this is a match */
                                rw_exit(&connp->conn_ilg_lock);
                                return (B_TRUE);
                        }
                        break;
                }
        }
        if (ilg == NULL) {
                rw_exit(&connp->conn_ilg_lock);
                return (B_FALSE);
        }

        /*
         * we have an ilg with matching ill and group; but
         * the ilg has a source list that we must check.
         */
        isinlist = B_FALSE;
        for (i = 0; i < ilg->ilg_filter->sl_numsrc; i++) {
                if (IN6_ARE_ADDR_EQUAL(v6src, &ilg->ilg_filter->sl_addr[i])) {
                        isinlist = B_TRUE;
                        break;
                }
        }

        if ((isinlist && ilg->ilg_fmode == MODE_IS_INCLUDE) ||
            (!isinlist && ilg->ilg_fmode == MODE_IS_EXCLUDE)) {
                rw_exit(&connp->conn_ilg_lock);
                return (B_TRUE);
        }
        rw_exit(&connp->conn_ilg_lock);
        return (B_FALSE);
}

/*
 * Find an ilg matching group and ifaddr/ifindex.
 * We check both ifaddr and ifindex even though at most one of them
 * will be non-zero; that way we always find the right one.
 */
static ilg_t *
ilg_lookup(conn_t *connp, const in6_addr_t *v6group, ipaddr_t ifaddr,
    uint_t ifindex)
{
        ilg_t   *ilg;

        ASSERT(RW_LOCK_HELD(&connp->conn_ilg_lock));

        for (ilg = connp->conn_ilg; ilg != NULL; ilg = ilg->ilg_next) {
                if (ilg->ilg_condemned)
                        continue;

                if (ilg->ilg_ifaddr == ifaddr &&
                    ilg->ilg_ifindex == ifindex &&
                    IN6_ARE_ADDR_EQUAL(&ilg->ilg_v6group, v6group))
                        return (ilg);
        }
        return (NULL);
}

/*
 * If a source address is passed in (src != NULL and src is not
 * unspecified), remove the specified src addr from the given ilg's
 * filter list, else delete the ilg.
 */
static void
ilg_delete(conn_t *connp, ilg_t *ilg, const in6_addr_t *src)
{
        ASSERT(RW_WRITE_HELD(&connp->conn_ilg_lock));
        ASSERT(ilg->ilg_ptpn != NULL);
        ASSERT(!ilg->ilg_condemned);

        if (src == NULL || IN6_IS_ADDR_UNSPECIFIED(src)) {
                FREE_SLIST(ilg->ilg_filter);
                ilg->ilg_filter = NULL;

                ASSERT(ilg->ilg_ilm == NULL);
                ilg->ilg_ill = NULL;
                ilg->ilg_condemned = B_TRUE;

                /* ilg_inactive will unlink from the list */
                ilg_refrele(ilg);
        } else {
                l_remove(ilg->ilg_filter, src);
        }
}

/*
 * Called from conn close. No new ilg can be added or removed
 * because CONN_CLOSING has been set by ip_close. ilg_add / ilg_delete
 * will return error if conn has started closing.
 *
 * We handle locking as follows.
 * Under conn_ilg_lock we get the first ilg. As we drop the conn_ilg_lock to
 * proceed with the ilm part of the delete we hold a reference on both the ill
 * and the ilg. This doesn't prevent changes to the ilg, but prevents it from
 * being deleted.
 *
 * Since the ilg_add code path uses two locks (conn_ilg_lock for the ilg part,
 * and ill_mcast_lock for the ip_addmulti part) we can run at a point between
 * the two. At that point ilg_ill is set, but ilg_ilm hasn't yet been set. In
 * that case we delete the ilg here, which makes ilg_add discover that the ilg
 * has disappeared when ip_addmulti returns, so it will discard the ilm it just
 * added.
 */
void
ilg_delete_all(conn_t *connp)
{
        ilg_t   *ilg, *next_ilg, *held_ilg;
        ilm_t   *ilm;
        ill_t   *ill;
        boolean_t need_refrele;

        /*
         * Can not run if there is a conn_update_ill already running.
         * Wait for it to complete. Caller should have already set CONN_CLOSING
         * which prevents any new threads to run in conn_update_ill.
         */
        mutex_enter(&connp->conn_lock);
        ASSERT(connp->conn_state_flags & CONN_CLOSING);
        while (connp->conn_state_flags & CONN_UPDATE_ILL)
                cv_wait(&connp->conn_cv, &connp->conn_lock);
        mutex_exit(&connp->conn_lock);

        rw_enter(&connp->conn_ilg_lock, RW_WRITER);
        ilg = connp->conn_ilg;
        held_ilg = NULL;
        while (ilg != NULL) {
                if (ilg->ilg_condemned) {
                        ilg = ilg->ilg_next;
                        continue;
                }
                /* If the ilg is detached then no need to serialize */
                if (ilg->ilg_ilm == NULL) {
                        next_ilg = ilg->ilg_next;
                        ilg_delete(connp, ilg, NULL);
                        ilg = next_ilg;
                        continue;
                }
                ill = ilg->ilg_ilm->ilm_ill;

                /*
                 * In order to serialize on the ill we try to enter
                 * and if that fails we unlock and relock and then
                 * check that we still have an ilm.
                 */
                need_refrele = B_FALSE;
                if (!mutex_tryenter(&ill->ill_mcast_serializer)) {
                        ill_refhold(ill);
                        need_refrele = B_TRUE;
                        ilg_refhold(ilg);
                        if (held_ilg != NULL)
                                ilg_refrele(held_ilg);
                        held_ilg = ilg;
                        rw_exit(&connp->conn_ilg_lock);
                        mutex_enter(&ill->ill_mcast_serializer);
                        rw_enter(&connp->conn_ilg_lock, RW_WRITER);
                        if (ilg->ilg_condemned) {
                                ilg = ilg->ilg_next;
                                goto next;
                        }
                }
                ilm = ilg->ilg_ilm;
                ilg->ilg_ilm = NULL;
                next_ilg = ilg->ilg_next;
                ilg_delete(connp, ilg, NULL);
                ilg = next_ilg;
                rw_exit(&connp->conn_ilg_lock);

                if (ilm != NULL)
                        (void) ip_delmulti_serial(ilm, B_FALSE, B_TRUE);

        next:
                mutex_exit(&ill->ill_mcast_serializer);
                /*
                 * Now that all locks have been dropped, we can send any
                 * deferred/queued DLPI or IP packets
                 */
                ill_mcast_send_queued(ill);
                ill_dlpi_send_queued(ill);
                if (need_refrele) {
                        /* Drop ill reference while we hold no locks */
                        ill_refrele(ill);
                }
                rw_enter(&connp->conn_ilg_lock, RW_WRITER);
        }
        if (held_ilg != NULL)
                ilg_refrele(held_ilg);
        rw_exit(&connp->conn_ilg_lock);
}

/*
 * Attach the ilg to an ilm on the ill. If it fails we leave ilg_ill as NULL so
 * that a subsequent attempt can attach it. Drops and reacquires conn_ilg_lock.
 */
static void
ilg_attach(conn_t *connp, ilg_t *ilg, ill_t *ill)
{
        ilg_stat_t      ilgstat;
        slist_t         *new_filter;
        int             new_fmode;
        in6_addr_t      v6group;
        ipaddr_t        ifaddr;
        uint_t          ifindex;
        ilm_t           *ilm;
        int             error = 0;

        ASSERT(RW_WRITE_HELD(&connp->conn_ilg_lock));
        /*
         * Alloc buffer to copy new state into (see below) before
         * we make any changes, so we can bail if it fails.
         */
        if ((new_filter = l_alloc()) == NULL)
                return;

        /*
         * Save copy of ilg's filter state to pass to other functions, so
         * we can release conn_ilg_lock now.
         * Set ilg_ill so that an unplumb can find us.
         */
        new_fmode = ilg->ilg_fmode;
        l_copy(ilg->ilg_filter, new_filter);
        v6group = ilg->ilg_v6group;
        ifaddr = ilg->ilg_ifaddr;
        ifindex = ilg->ilg_ifindex;
        ilgstat = ILGSTAT_NEW;

        ilg->ilg_ill = ill;
        ASSERT(ilg->ilg_ilm == NULL);
        rw_exit(&connp->conn_ilg_lock);

        ilm = ip_addmulti_serial(&v6group, ill, connp->conn_zoneid, ilgstat,
            new_fmode, new_filter, &error);
        l_free(new_filter);

        rw_enter(&connp->conn_ilg_lock, RW_WRITER);
        /*
         * Must look up the ilg again since we've not been holding
         * conn_ilg_lock. The ilg could have disappeared due to an unplumb
         * having called conn_update_ill, which can run once we dropped the
         * conn_ilg_lock above. Alternatively, the ilg could have been attached
         * when the lock was dropped
         */
        ilg = ilg_lookup(connp, &v6group, ifaddr, ifindex);
        if (ilg == NULL || ilg->ilg_ilm != NULL) {
                if (ilm != NULL) {
                        rw_exit(&connp->conn_ilg_lock);
                        (void) ip_delmulti_serial(ilm, B_FALSE,
                            (ilgstat == ILGSTAT_NEW));
                        rw_enter(&connp->conn_ilg_lock, RW_WRITER);
                }
                return;
        }
        if (ilm == NULL) {
                ilg->ilg_ill = NULL;
                return;
        }
        ilg->ilg_ilm = ilm;
        ilm->ilm_ifaddr = ifaddr;       /* For netstat */
}

/*
 * Called when an ill is unplumbed to make sure that there are no
 * dangling conn references to that ill. In that case ill is non-NULL and
 * we make sure we remove all references to it.
 * Also called when we should revisit the ilg_ill used for multicast
 * memberships, in which case ill is NULL.
 *
 * conn is held by caller.
 *
 * Note that ipcl_walk only walks conns that are not yet condemned.
 * condemned conns can't be refheld. For this reason, conn must become clean
 * first, i.e. it must not refer to any ill/ire and then only set
 * condemned flag.
 *
 * We leave ixa_multicast_ifindex in place. We prefer dropping
 * packets instead of sending them out the wrong interface.
 *
 * We keep the ilg around in a detached state (with ilg_ill and ilg_ilm being
 * NULL) so that the application can leave it later. Also, if ilg_ifaddr and
 * ilg_ifindex are zero, indicating that the system should pick the interface,
 * then we attempt to reselect the ill and join on it.
 *
 * Locking notes:
 * Under conn_ilg_lock we get the first ilg. As we drop the conn_ilg_lock to
 * proceed with the ilm part of the delete we hold a reference on both the ill
 * and the ilg. This doesn't prevent changes to the ilg, but prevents it from
 * being deleted.
 *
 * Note: if this function is called when new ill/ipif's arrive or change status
 * (SIOCSLIFINDEX, SIOCSLIFADDR) then we will attempt to attach any ilgs with
 * a NULL ilg_ill to an ill/ilm.
 */
static void
conn_update_ill(conn_t *connp, caddr_t arg)
{
        ill_t   *ill = (ill_t *)arg;

        /*
         * We have to prevent ip_close/ilg_delete_all from running at
         * the same time. ip_close sets CONN_CLOSING before doing the ilg_delete
         * all, and we set CONN_UPDATE_ILL. That ensures that only one of
         * ilg_delete_all and conn_update_ill run at a time for a given conn.
         * If ilg_delete_all got here first, then we have nothing to do.
         */
        mutex_enter(&connp->conn_lock);
        if (connp->conn_state_flags & (CONN_CLOSING|CONN_UPDATE_ILL)) {
                /* Caller has to wait for ill_ilm_cnt to drop to zero */
                mutex_exit(&connp->conn_lock);
                return;
        }
        connp->conn_state_flags |= CONN_UPDATE_ILL;
        mutex_exit(&connp->conn_lock);

        if (ill != NULL)
                ilg_check_detach(connp, ill);

        ilg_check_reattach(connp, ill);

        /* Do we need to wake up a thread in ilg_delete_all? */
        mutex_enter(&connp->conn_lock);
        connp->conn_state_flags &= ~CONN_UPDATE_ILL;
        if (connp->conn_state_flags & CONN_CLOSING)
                cv_broadcast(&connp->conn_cv);
        mutex_exit(&connp->conn_lock);
}

/* Detach from an ill that is going away */
static void
ilg_check_detach(conn_t *connp, ill_t *ill)
{
        char    group_buf[INET6_ADDRSTRLEN];
        ilg_t   *ilg, *held_ilg;
        ilm_t   *ilm;

        mutex_enter(&ill->ill_mcast_serializer);
        rw_enter(&connp->conn_ilg_lock, RW_WRITER);
        held_ilg = NULL;
        for (ilg = connp->conn_ilg; ilg != NULL; ilg = ilg->ilg_next) {
                if (ilg->ilg_condemned)
                        continue;

                if (ilg->ilg_ill != ill)
                        continue;

                /* Detach from current ill */
                ip1dbg(("ilg_check_detach: detach %s on %s\n",
                    inet_ntop(AF_INET6, &ilg->ilg_v6group,
                    group_buf, sizeof (group_buf)),
                    ilg->ilg_ill->ill_name));

                /* Detach this ilg from the ill/ilm */
                ilm = ilg->ilg_ilm;
                ilg->ilg_ilm = NULL;
                ilg->ilg_ill = NULL;
                if (ilm == NULL)
                        continue;

                /* Prevent ilg from disappearing */
                ilg_transfer_hold(held_ilg, ilg);
                held_ilg = ilg;
                rw_exit(&connp->conn_ilg_lock);

                (void) ip_delmulti_serial(ilm, B_FALSE, B_TRUE);
                rw_enter(&connp->conn_ilg_lock, RW_WRITER);
        }
        if (held_ilg != NULL)
                ilg_refrele(held_ilg);
        rw_exit(&connp->conn_ilg_lock);
        mutex_exit(&ill->ill_mcast_serializer);
        /*
         * Now that all locks have been dropped, we can send any
         * deferred/queued DLPI or IP packets
         */
        ill_mcast_send_queued(ill);
        ill_dlpi_send_queued(ill);
}

/*
 * Check if there is a place to attach the conn_ilgs. We do this for both
 * detached ilgs and attached ones, since for the latter there could be
 * a better ill to attach them to. oill is non-null if we just detached from
 * that ill.
 */
static void
ilg_check_reattach(conn_t *connp, ill_t *oill)
{
        ill_t   *ill;
        char    group_buf[INET6_ADDRSTRLEN];
        ilg_t   *ilg, *held_ilg;
        ilm_t   *ilm;
        zoneid_t zoneid = IPCL_ZONEID(connp);
        int     error;
        ip_stack_t *ipst = connp->conn_netstack->netstack_ip;

        rw_enter(&connp->conn_ilg_lock, RW_WRITER);
        held_ilg = NULL;
        for (ilg = connp->conn_ilg; ilg != NULL; ilg = ilg->ilg_next) {
                if (ilg->ilg_condemned)
                        continue;

                /* Check if the conn_ill matches what we would pick now */
                ill = ill_mcast_lookup(&ilg->ilg_v6group, ilg->ilg_ifaddr,
                    ilg->ilg_ifindex, zoneid, ipst, &error);

                /*
                 * Make sure the ill is usable for multicast and that
                 * we can send the DL_ADDMULTI_REQ before we create an
                 * ilm.
                 */
                if (ill != NULL &&
                    (!(ill->ill_flags & ILLF_MULTICAST) || !ill->ill_dl_up)) {
                        /* Drop locks across ill_refrele */
                        ilg_transfer_hold(held_ilg, ilg);
                        held_ilg = ilg;
                        rw_exit(&connp->conn_ilg_lock);
                        ill_refrele(ill);
                        ill = NULL;
                        rw_enter(&connp->conn_ilg_lock, RW_WRITER);
                        /* Note that ilg could have become condemned */
                }

                /*
                 * Is the ill unchanged, even if both are NULL?
                 * Did we just detach from that ill?
                 */
                if (ill == ilg->ilg_ill || (ill != NULL && ill == oill)) {
                        if (ill != NULL) {
                                /* Drop locks across ill_refrele */
                                ilg_transfer_hold(held_ilg, ilg);
                                held_ilg = ilg;
                                rw_exit(&connp->conn_ilg_lock);
                                ill_refrele(ill);
                                rw_enter(&connp->conn_ilg_lock, RW_WRITER);
                        }
                        continue;
                }

                /* Something changed; detach from old first if needed */
                if (ilg->ilg_ill != NULL) {
                        ill_t *ill2 = ilg->ilg_ill;
                        boolean_t need_refrele = B_FALSE;

                        /*
                         * In order to serialize on the ill we try to enter
                         * and if that fails we unlock and relock.
                         */
                        if (!mutex_tryenter(&ill2->ill_mcast_serializer)) {
                                ill_refhold(ill2);
                                need_refrele = B_TRUE;
                                ilg_transfer_hold(held_ilg, ilg);
                                held_ilg = ilg;
                                rw_exit(&connp->conn_ilg_lock);
                                mutex_enter(&ill2->ill_mcast_serializer);
                                rw_enter(&connp->conn_ilg_lock, RW_WRITER);
                                /* Note that ilg could have become condemned */
                        }
                        /*
                         * Check that nobody else re-attached the ilg while we
                         * dropped the lock.
                         */
                        if (ilg->ilg_ill == ill2) {
                                ASSERT(!ilg->ilg_condemned);
                                /* Detach from current ill */
                                ip1dbg(("conn_check_reattach: detach %s/%s\n",
                                    inet_ntop(AF_INET6, &ilg->ilg_v6group,
                                    group_buf, sizeof (group_buf)),
                                    ill2->ill_name));

                                ilm = ilg->ilg_ilm;
                                ilg->ilg_ilm = NULL;
                                ilg->ilg_ill = NULL;
                        } else {
                                ilm = NULL;
                        }
                        ilg_transfer_hold(held_ilg, ilg);
                        held_ilg = ilg;
                        rw_exit(&connp->conn_ilg_lock);
                        if (ilm != NULL)
                                (void) ip_delmulti_serial(ilm, B_FALSE, B_TRUE);
                        mutex_exit(&ill2->ill_mcast_serializer);
                        /*
                         * Now that all locks have been dropped, we can send any
                         * deferred/queued DLPI or IP packets
                         */
                        ill_mcast_send_queued(ill2);
                        ill_dlpi_send_queued(ill2);
                        if (need_refrele) {
                                /* Drop ill reference while we hold no locks */
                                ill_refrele(ill2);
                        }
                        rw_enter(&connp->conn_ilg_lock, RW_WRITER);
                        /*
                         * While we dropped conn_ilg_lock some other thread
                         * could have attached this ilg, thus we check again.
                         */
                        if (ilg->ilg_ill != NULL) {
                                if (ill != NULL) {
                                        /* Drop locks across ill_refrele */
                                        ilg_transfer_hold(held_ilg, ilg);
                                        held_ilg = ilg;
                                        rw_exit(&connp->conn_ilg_lock);
                                        ill_refrele(ill);
                                        rw_enter(&connp->conn_ilg_lock,
                                            RW_WRITER);
                                }
                                continue;
                        }
                }
                if (ill != NULL) {
                        /*
                         * In order to serialize on the ill we try to enter
                         * and if that fails we unlock and relock.
                         */
                        if (!mutex_tryenter(&ill->ill_mcast_serializer)) {
                                /* Already have a refhold on ill */
                                ilg_transfer_hold(held_ilg, ilg);
                                held_ilg = ilg;
                                rw_exit(&connp->conn_ilg_lock);
                                mutex_enter(&ill->ill_mcast_serializer);
                                rw_enter(&connp->conn_ilg_lock, RW_WRITER);
                                /* Note that ilg could have become condemned */
                        }
                        ilg_transfer_hold(held_ilg, ilg);
                        held_ilg = ilg;
                        /*
                         * Check that nobody else attached the ilg and that
                         * it wasn't condemned while we dropped the lock.
                         */
                        if (ilg->ilg_ill == NULL && !ilg->ilg_condemned) {
                                /*
                                 * Attach to the new ill. Can fail in which
                                 * case ilg_ill will remain NULL. ilg_attach
                                 * drops and reacquires conn_ilg_lock.
                                 */
                                ip1dbg(("conn_check_reattach: attach %s/%s\n",
                                    inet_ntop(AF_INET6, &ilg->ilg_v6group,
                                    group_buf, sizeof (group_buf)),
                                    ill->ill_name));
                                ilg_attach(connp, ilg, ill);
                                ASSERT(RW_WRITE_HELD(&connp->conn_ilg_lock));
                        }
                        /* Drop locks across ill_refrele */
                        rw_exit(&connp->conn_ilg_lock);
                        mutex_exit(&ill->ill_mcast_serializer);
                        /*
                         * Now that all locks have been
                         * dropped, we can send any
                         * deferred/queued DLPI or IP packets
                         */
                        ill_mcast_send_queued(ill);
                        ill_dlpi_send_queued(ill);
                        ill_refrele(ill);
                        rw_enter(&connp->conn_ilg_lock, RW_WRITER);
                }
        }
        if (held_ilg != NULL)
                ilg_refrele(held_ilg);
        rw_exit(&connp->conn_ilg_lock);
}

/*
 * Called when an ill is unplumbed to make sure that there are no
 * dangling conn references to that ill. In that case ill is non-NULL and
 * we make sure we remove all references to it.
 * Also called when we should revisit the ilg_ill used for multicast
 * memberships, in which case ill is NULL.
 */
void
update_conn_ill(ill_t *ill, ip_stack_t *ipst)
{
        ipcl_walk(conn_update_ill, (caddr_t)ill, ipst);
}