Merge commit 'b1e7e97d3b60469b243b3b2e22c7d8cbd11c7c90'

[unleashed.git] / kernel / net / ip / ip_ftable.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) 2006, 2010, Oracle and/or its affiliates. All rights reserved.
 */

/*
 * This file contains consumer routines of the IPv4 forwarding engine
 */

#include <sys/types.h>
#include <sys/stream.h>
#include <sys/stropts.h>
#include <sys/strlog.h>
#include <sys/dlpi.h>
#include <sys/ddi.h>
#include <sys/cmn_err.h>
#include <sys/policy.h>

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

#include <inet/ipsec_impl.h>
#include <inet/common.h>
#include <inet/mi.h>
#include <inet/mib2.h>
#include <inet/ip.h>
#include <inet/ip_impl.h>
#include <inet/ip6.h>
#include <inet/ip_ndp.h>
#include <inet/arp.h>
#include <inet/ip_if.h>
#include <inet/ip_ire.h>
#include <inet/ip_ftable.h>
#include <inet/ip_rts.h>
#include <inet/nd.h>

#include <net/pfkeyv2.h>
#include <inet/sadb.h>
#include <inet/tcp.h>
#include <inet/ipclassifier.h>
#include <sys/zone.h>
#include <net/radix.h>

#define IS_DEFAULT_ROUTE(ire)   \
        (((ire)->ire_type & IRE_DEFAULT) || \
            (((ire)->ire_type & IRE_INTERFACE) && ((ire)->ire_addr == 0)))

#define IP_SRC_MULTIHOMING(isv6, ipst)                  \
        (isv6 ? ipst->ips_ipv6_strict_src_multihoming : \
        ipst->ips_ip_strict_src_multihoming)

static ire_t    *route_to_dst(const struct sockaddr *, zoneid_t, ip_stack_t *);
static void     ire_del_host_redir(ire_t *, char *);
static boolean_t ire_find_best_route(struct radix_node *, void *);

/*
 * Lookup a route in forwarding table. A specific lookup is indicated by
 * passing the required parameters and indicating the match required in the
 * flag field.
 *
 * Supports IP_BOUND_IF by following the ipif/ill when recursing.
 */
ire_t *
ire_ftable_lookup_v4(ipaddr_t addr, ipaddr_t mask, ipaddr_t gateway,
    int type, const ill_t *ill, zoneid_t zoneid, int flags, uint32_t xmit_hint,
    ip_stack_t *ipst, uint_t *generationp)
{
        ire_t *ire;
        struct rt_sockaddr rdst, rmask;
        struct rt_entry *rt;
        ire_ftable_args_t margs;

        ASSERT(ill == NULL || !ill->ill_isv6);

        /*
         * ire_match_args() will dereference ill if MATCH_IRE_ILL
         * is set.
         */
        if ((flags & (MATCH_IRE_ILL|MATCH_IRE_SRC_ILL)) && (ill == NULL))
                return (NULL);

        bzero(&rdst, sizeof (rdst));
        rdst.rt_sin_len = sizeof (rdst);
        rdst.rt_sin_family = AF_INET;
        rdst.rt_sin_addr.s_addr = addr;

        bzero(&rmask, sizeof (rmask));
        rmask.rt_sin_len = sizeof (rmask);
        rmask.rt_sin_family = AF_INET;
        rmask.rt_sin_addr.s_addr = mask;

        bzero(&margs, sizeof (margs));
        margs.ift_addr = addr;
        margs.ift_mask = mask;
        margs.ift_gateway = gateway;
        margs.ift_type = type;
        margs.ift_ill = ill;
        margs.ift_zoneid = zoneid;
        margs.ift_flags = flags;

        /*
         * The flags argument passed to ire_ftable_lookup may cause the
         * search to return, not the longest matching prefix, but the
         * "best matching prefix", i.e., the longest prefix that also
         * satisfies constraints imposed via the permutation of flags
         * passed in. To achieve this, we invoke ire_match_args() on
         * each matching leaf in the  radix tree. ire_match_args is
         * invoked by the callback function ire_find_best_route()
         * We hold the global tree lock in read mode when calling
         * rn_match_args. Before dropping the global tree lock, ensure
         * that the radix node can't be deleted by incrementing ire_refcnt.
         */
        RADIX_NODE_HEAD_RLOCK(ipst->ips_ip_ftable);
        rt = (struct rt_entry *)ipst->ips_ip_ftable->rnh_matchaddr_args(&rdst,
            ipst->ips_ip_ftable, ire_find_best_route, &margs);
        ire = margs.ift_best_ire;
        if (rt == NULL) {
                RADIX_NODE_HEAD_UNLOCK(ipst->ips_ip_ftable);
                return (NULL);
        }
        ASSERT(ire != NULL);

        DTRACE_PROBE2(ire__found, ire_ftable_args_t *, &margs, ire_t *, ire);

        /*
         * round-robin only if we have more than one route in the bucket.
         * ips_ip_ecmp_behavior controls when we do ECMP
         *      2:      always
         *      1:      for IRE_DEFAULT and /0 IRE_INTERFACE
         *      0:      never
         */
        if (ire->ire_bucket->irb_ire_cnt > 1 && !(flags & MATCH_IRE_GW)) {
                if (ipst->ips_ip_ecmp_behavior == 2 ||
                    (ipst->ips_ip_ecmp_behavior == 1 &&
                    IS_DEFAULT_ROUTE(ire))) {
                        ire_t   *next_ire;

                        margs.ift_best_ire = NULL;
                        next_ire = ire_round_robin(ire->ire_bucket, &margs,
                            xmit_hint, ire, ipst);
                        if (next_ire == NULL) {
                                /* keep ire if next_ire is null */
                                goto done;
                        }
                        ire_refrele(ire);
                        ire = next_ire;
                }
        }

done:
        /* Return generation before dropping lock */
        if (generationp != NULL)
                *generationp = ire->ire_generation;

        RADIX_NODE_HEAD_UNLOCK(ipst->ips_ip_ftable);

        /*
         * For shared-IP zones we need additional checks to what was
         * done in ire_match_args to make sure IRE_LOCALs are handled.
         *
         * When ip_restrict_interzone_loopback is set, then
         * we ensure that IRE_LOCAL are only used for loopback
         * between zones when the logical "Ethernet" would
         * have looped them back. That is, if in the absense of
         * the IRE_LOCAL we would have sent to packet out the
         * same ill.
         */
        if ((ire->ire_type & IRE_LOCAL) && zoneid != ALL_ZONES &&
            ire->ire_zoneid != zoneid && ire->ire_zoneid != ALL_ZONES &&
            ipst->ips_ip_restrict_interzone_loopback) {
                ire = ire_alt_local(ire, zoneid, ill, generationp);
                ASSERT(ire != NULL);
        }
        return (ire);
}

/*
 * This function is called by
 * ip_input/ire_route_recursive when doing a route lookup on only the
 * destination address.
 *
 * The optimizations of this function over ire_ftable_lookup are:
 *      o removing unnecessary flag matching
 *      o doing longest prefix match instead of overloading it further
 *        with the unnecessary "best_prefix_match"
 *
 * If no route is found we return IRE_NOROUTE.
 */
ire_t *
ire_ftable_lookup_simple_v4(ipaddr_t addr, uint32_t xmit_hint, ip_stack_t *ipst,
    uint_t *generationp)
{
        ire_t *ire;
        struct rt_sockaddr rdst;
        struct rt_entry *rt;
        irb_t *irb;

        rdst.rt_sin_len = sizeof (rdst);
        rdst.rt_sin_family = AF_INET;
        rdst.rt_sin_addr.s_addr = addr;

        /*
         * This is basically inlining  a simpler version of ire_match_args
         */
        RADIX_NODE_HEAD_RLOCK(ipst->ips_ip_ftable);

        rt = (struct rt_entry *)ipst->ips_ip_ftable->rnh_matchaddr_args(&rdst,
            ipst->ips_ip_ftable, NULL, NULL);

        if (rt == NULL)
                goto bad;

        irb = &rt->rt_irb;
        if (irb->irb_ire_cnt == 0)
                goto bad;

        rw_enter(&irb->irb_lock, RW_READER);
        ire = irb->irb_ire;
        if (ire == NULL) {
                rw_exit(&irb->irb_lock);
                goto bad;
        }
        while (IRE_IS_CONDEMNED(ire)) {
                ire = ire->ire_next;
                if (ire == NULL) {
                        rw_exit(&irb->irb_lock);
                        goto bad;
                }
        }

        /* we have a ire that matches */
        ire_refhold(ire);
        rw_exit(&irb->irb_lock);

        /*
         * round-robin only if we have more than one route in the bucket.
         * ips_ip_ecmp_behavior controls when we do ECMP
         *      2:      always
         *      1:      for IRE_DEFAULT and /0 IRE_INTERFACE
         *      0:      never
         *
         * Note: if we found an IRE_IF_CLONE we won't look at the bucket with
         * other ECMP IRE_INTERFACEs since the IRE_IF_CLONE is a /128 match
         * and the IRE_INTERFACESs are likely to be shorter matches.
         */
        if (ire->ire_bucket->irb_ire_cnt > 1) {
                if (ipst->ips_ip_ecmp_behavior == 2 ||
                    (ipst->ips_ip_ecmp_behavior == 1 &&
                    IS_DEFAULT_ROUTE(ire))) {
                        ire_t   *next_ire;
                        ire_ftable_args_t margs;

                        bzero(&margs, sizeof (margs));
                        margs.ift_addr = addr;
                        margs.ift_zoneid = ALL_ZONES;

                        next_ire = ire_round_robin(ire->ire_bucket, &margs,
                            xmit_hint, ire, ipst);
                        if (next_ire == NULL) {
                                /* keep ire if next_ire is null */
                                if (generationp != NULL)
                                        *generationp = ire->ire_generation;
                                RADIX_NODE_HEAD_UNLOCK(ipst->ips_ip_ftable);
                                return (ire);
                        }
                        ire_refrele(ire);
                        ire = next_ire;
                }
        }
        /* Return generation before dropping lock */
        if (generationp != NULL)
                *generationp = ire->ire_generation;

        RADIX_NODE_HEAD_UNLOCK(ipst->ips_ip_ftable);

        /*
         * Since we only did ALL_ZONES matches there is no special handling
         * of IRE_LOCALs needed here. ire_ftable_lookup_v4 has to handle that.
         */
        return (ire);

bad:
        if (generationp != NULL)
                *generationp = IRE_GENERATION_VERIFY;

        RADIX_NODE_HEAD_UNLOCK(ipst->ips_ip_ftable);
        return (ire_reject(ipst, B_FALSE));
}

/*
 * Find the ill matching a multicast group.
 * Allows different routes for multicast addresses
 * in the unicast routing table (akin to 224.0.0.0 but could be more specific)
 * which point at different interfaces. This is used when IP_MULTICAST_IF
 * isn't specified (when sending) and when IP_ADD_MEMBERSHIP doesn't
 * specify the interface to join on.
 *
 * Supports link-local addresses by using ire_route_recursive which follows
 * the ill when recursing.
 *
 * This is used in ip_set_destination etc to set ixa_postfragfn for multicast.
 * We have a setsrcp argument for the same reason.
 */
ill_t *
ire_lookup_multi_ill_v4(ipaddr_t group, zoneid_t zoneid, ip_stack_t *ipst,
    ipaddr_t *setsrcp)
{
        ire_t   *ire;
        ill_t   *ill;

        ire = ire_route_recursive_v4(group, 0, NULL, zoneid, MATCH_IRE_DSTONLY,
            IRR_NONE, 0, ipst, setsrcp, NULL);
        ASSERT(ire != NULL);
        if (ire->ire_flags & (RTF_REJECT|RTF_BLACKHOLE)) {
                ire_refrele(ire);
                return (NULL);
        }

        ill = ire_nexthop_ill(ire);
        ire_refrele(ire);
        return (ill);
}

/*
 * Delete the passed in ire if the gateway addr matches
 */
void
ire_del_host_redir(ire_t *ire, char *gateway)
{
        if ((ire->ire_flags & RTF_DYNAMIC) &&
            (ire->ire_gateway_addr == *(ipaddr_t *)gateway))
                ire_delete(ire);
}

/*
 * Search for all IRE_HOST RTF_DYNAMIC (aka redirect) routes that are
 * pointing at the specified gateway and
 * delete them. This routine is called only
 * when a default gateway is going away.
 */
void
ire_delete_host_redirects(ipaddr_t gateway, ip_stack_t *ipst)
{
        struct rtfuncarg rtfarg;

        bzero(&rtfarg, sizeof (rtfarg));
        rtfarg.rt_func = ire_del_host_redir;
        rtfarg.rt_arg = (void *)&gateway;
        rtfarg.rt_zoneid = ALL_ZONES;
        rtfarg.rt_ipst = ipst;
        (void) ipst->ips_ip_ftable->rnh_walktree_mt(ipst->ips_ip_ftable,
            rtfunc, &rtfarg, irb_refhold_rn, irb_refrele_rn);
}

/*
 * Obtain the rt_entry and rt_irb for the route to be added to
 * the ips_ip_ftable.
 * First attempt to add a node to the radix tree via rn_addroute. If the
 * route already exists, return the bucket for the existing route.
 *
 * Locking notes: Need to hold the global radix tree lock in write mode to
 * add a radix node. To prevent the node from being deleted, ire_get_bucket()
 * returns with a ref'ed irb_t. The ire itself is added in ire_add_v4()
 * while holding the irb_lock, but not the radix tree lock.
 */
irb_t *
ire_get_bucket(ire_t *ire)
{
        struct radix_node *rn;
        struct rt_entry *rt;
        struct rt_sockaddr rmask, rdst;
        irb_t *irb = NULL;
        ip_stack_t *ipst = ire->ire_ipst;

        ASSERT(ipst->ips_ip_ftable != NULL);

        /* first try to see if route exists (based on rtalloc1) */
        bzero(&rdst, sizeof (rdst));
        rdst.rt_sin_len = sizeof (rdst);
        rdst.rt_sin_family = AF_INET;
        rdst.rt_sin_addr.s_addr = ire->ire_addr;

        bzero(&rmask, sizeof (rmask));
        rmask.rt_sin_len = sizeof (rmask);
        rmask.rt_sin_family = AF_INET;
        rmask.rt_sin_addr.s_addr = ire->ire_mask;

        /*
         * add the route. based on BSD's rtrequest1(RTM_ADD)
         */
        R_Malloc(rt, rt_entry_cache,  sizeof (*rt));
        /* kmem_alloc failed */
        if (rt == NULL)
                return (NULL);

        bzero(rt, sizeof (*rt));
        rt->rt_nodes->rn_key = (char *)&rt->rt_dst;
        rt->rt_dst = rdst;
        irb = &rt->rt_irb;
        irb->irb_marks |= IRB_MARK_DYNAMIC; /* dynamically allocated/freed */
        irb->irb_ipst = ipst;
        rw_init(&irb->irb_lock, NULL, RW_DEFAULT, NULL);
        RADIX_NODE_HEAD_WLOCK(ipst->ips_ip_ftable);
        rn = ipst->ips_ip_ftable->rnh_addaddr(&rt->rt_dst, &rmask,
            ipst->ips_ip_ftable, (struct radix_node *)rt);
        if (rn == NULL) {
                RADIX_NODE_HEAD_UNLOCK(ipst->ips_ip_ftable);
                Free(rt, rt_entry_cache);
                rt = NULL;
                irb = NULL;
                RADIX_NODE_HEAD_RLOCK(ipst->ips_ip_ftable);
                rn = ipst->ips_ip_ftable->rnh_lookup(&rdst, &rmask,
                    ipst->ips_ip_ftable);
                if (rn != NULL && ((rn->rn_flags & RNF_ROOT) == 0)) {
                        /* found a non-root match */
                        rt = (struct rt_entry *)rn;
                }
        }
        if (rt != NULL) {
                irb = &rt->rt_irb;
                irb_refhold(irb);
        }
        RADIX_NODE_HEAD_UNLOCK(ipst->ips_ip_ftable);
        return (irb);
}

/*
 * This function is used when the caller wants to know the outbound
 * interface for a packet given only the address.
 * If this is a offlink IP address and there are multiple
 * routes to this destination, this routine will utilise the
 * first route it finds to IP address
 * Return values:
 *      0       - FAILURE
 *      nonzero - ifindex
 */
uint_t
ifindex_lookup(const struct sockaddr *ipaddr, zoneid_t zoneid)
{
        uint_t ifindex = 0;
        ire_t *ire;
        ill_t *ill;
        netstack_t *ns;
        ip_stack_t *ipst;

        if (zoneid == ALL_ZONES)
                ns = netstack_find_by_zoneid(GLOBAL_ZONEID);
        else
                ns = netstack_find_by_zoneid(zoneid);
        ASSERT(ns != NULL);

        /*
         * For exclusive stacks we set the zoneid to zero
         * since IP uses the global zoneid in the exclusive stacks.
         */
        if (ns->netstack_stackid != GLOBAL_NETSTACKID)
                zoneid = GLOBAL_ZONEID;
        ipst = ns->netstack_ip;

        ASSERT(ipaddr->sa_family == AF_INET || ipaddr->sa_family == AF_INET6);

        if ((ire = route_to_dst(ipaddr, zoneid, ipst)) != NULL) {
                ill = ire_nexthop_ill(ire);
                if (ill != NULL) {
                        ifindex = ill->ill_phyint->phyint_ifindex;
                        ill_refrele(ill);
                }
                ire_refrele(ire);
        }
        netstack_rele(ns);
        return (ifindex);
}

/*
 * Routine to find the route to a destination. If a ifindex is supplied
 * it tries to match the route to the corresponding ipif for the ifindex
 */
static  ire_t *
route_to_dst(const struct sockaddr *dst_addr, zoneid_t zoneid, ip_stack_t *ipst)
{
        ire_t *ire = NULL;
        int match_flags;

        match_flags = MATCH_IRE_DSTONLY;

        if (dst_addr->sa_family == AF_INET) {
                ire = ire_route_recursive_v4(
                    ((struct sockaddr_in *)dst_addr)->sin_addr.s_addr, 0, NULL,
                    zoneid, match_flags, IRR_ALLOCATE, 0, ipst, NULL, NULL);
        } else {
                ire = ire_route_recursive_v6(
                    &((struct sockaddr_in6 *)dst_addr)->sin6_addr, 0, NULL,
                    zoneid, match_flags, IRR_ALLOCATE, 0, ipst, NULL, NULL);
        }
        ASSERT(ire != NULL);
        if (ire->ire_flags & (RTF_REJECT|RTF_BLACKHOLE)) {
                ire_refrele(ire);
                return (NULL);
        }
        return (ire);
}

/*
 * This routine is called by IP Filter to send a packet out on the wire
 * to a specified dstination (which may be onlink or offlink). The ifindex may
 * or may not be 0. A non-null ifindex indicates IP Filter has stipulated
 * an outgoing interface and requires the nexthop to be on that interface.
 * IP WILL NOT DO the following to the data packet before sending it out:
 *      a. manipulate ttl
 *      b. ipsec work
 *      c. fragmentation
 *
 * If the packet has been prepared for hardware checksum then it will be
 * passed off to ip_send_align_cksum() to check that the flags set on the
 * packet are in alignment with the capabilities of the new outgoing NIC.
 *
 * Return values:
 *      0:              IP was able to send of the data pkt
 *      ECOMM:          Could not send packet
 *      ENONET          No route to dst. It is up to the caller
 *                      to send icmp unreachable error message,
 *      EINPROGRESS     The macaddr of the onlink dst or that
 *                      of the offlink dst's nexthop needs to get
 *                      resolved before packet can be sent to dst.
 *                      Thus transmission is not guaranteed.
 *                      Note: No longer have visibility to the ARP queue
 *                      hence no EINPROGRESS.
 */
int
ipfil_sendpkt(const struct sockaddr *dst_addr, mblk_t *mp, uint_t ifindex,
    zoneid_t zoneid)
{
        ipaddr_t nexthop;
        netstack_t *ns;
        ip_stack_t *ipst;
        ip_xmit_attr_t ixas;
        int error;

        ASSERT(mp != NULL);

        if (zoneid == ALL_ZONES)
                ns = netstack_find_by_zoneid(GLOBAL_ZONEID);
        else
                ns = netstack_find_by_zoneid(zoneid);
        ASSERT(ns != NULL);

        /*
         * For exclusive stacks we set the zoneid to zero
         * since IP uses the global zoneid in the exclusive stacks.
         */
        if (ns->netstack_stackid != GLOBAL_NETSTACKID)
                zoneid = GLOBAL_ZONEID;
        ipst = ns->netstack_ip;

        ASSERT(dst_addr->sa_family == AF_INET ||
            dst_addr->sa_family == AF_INET6);

        bzero(&ixas, sizeof (ixas));
        /*
         * No IPsec, no fragmentation, and don't let any hooks see
         * the packet.
         */
        ixas.ixa_flags = IXAF_NO_IPSEC | IXAF_DONTFRAG | IXAF_NO_PFHOOK;
        ixas.ixa_cred = kcred;
        ixas.ixa_cpid = NOPID;
        ixas.ixa_ipst = ipst;
        ixas.ixa_ifindex = ifindex;

        if (dst_addr->sa_family == AF_INET) {
                ipha_t *ipha = (ipha_t *)mp->b_rptr;

                ixas.ixa_flags |= IXAF_IS_IPV4;
                nexthop = ((struct sockaddr_in *)dst_addr)->sin_addr.s_addr;
                if (nexthop != ipha->ipha_dst) {
                        ixas.ixa_flags |= IXAF_NEXTHOP_SET;
                        ixas.ixa_nexthop_v4 = nexthop;
                }
                ixas.ixa_multicast_ttl = ipha->ipha_ttl;
        } else {
                ip6_t *ip6h = (ip6_t *)mp->b_rptr;
                in6_addr_t *nexthop6;

                nexthop6 = &((struct sockaddr_in6 *)dst_addr)->sin6_addr;
                if (!IN6_ARE_ADDR_EQUAL(nexthop6, &ip6h->ip6_dst)) {
                        ixas.ixa_flags |= IXAF_NEXTHOP_SET;
                        ixas.ixa_nexthop_v6 = *nexthop6;
                }
                ixas.ixa_multicast_ttl = ip6h->ip6_hops;
        }
        error = ip_output_simple(mp, &ixas);
        ixa_cleanup(&ixas);

        netstack_rele(ns);
        switch (error) {
        case 0:
                break;

        case EHOSTUNREACH:
        case ENETUNREACH:
                error = ENONET;
                break;

        default:
                error = ECOMM;
                break;
        }
        return (error);
}

/*
 * callback function provided by ire_ftable_lookup when calling
 * rn_match_args(). Invoke ire_match_args on each matching leaf node in
 * the radix tree.
 */
boolean_t
ire_find_best_route(struct radix_node *rn, void *arg)
{
        struct rt_entry *rt = (struct rt_entry *)rn;
        irb_t *irb_ptr;
        ire_t *ire;
        ire_ftable_args_t *margs = arg;
        ipaddr_t match_mask;

        ASSERT(rt != NULL);

        irb_ptr = &rt->rt_irb;

        if (irb_ptr->irb_ire_cnt == 0)
                return (B_FALSE);

        rw_enter(&irb_ptr->irb_lock, RW_READER);
        for (ire = irb_ptr->irb_ire; ire != NULL; ire = ire->ire_next) {
                if (IRE_IS_CONDEMNED(ire))
                        continue;
                ASSERT((margs->ift_flags & MATCH_IRE_SHORTERMASK) == 0);
                if (margs->ift_flags & MATCH_IRE_MASK)
                        match_mask = margs->ift_mask;
                else
                        match_mask = ire->ire_mask;

                if (ire_match_args(ire, margs->ift_addr, match_mask,
                    margs->ift_gateway, margs->ift_type, margs->ift_ill,
                    margs->ift_zoneid, margs->ift_flags)) {
                        ire_refhold(ire);
                        rw_exit(&irb_ptr->irb_lock);
                        margs->ift_best_ire = ire;
                        return (B_TRUE);
                }
        }
        rw_exit(&irb_ptr->irb_lock);
        return (B_FALSE);
}

/*
 * ftable irb_t structures are dynamically allocated, and we need to
 * check if the irb_t (and associated ftable tree attachment) needs to
 * be cleaned up when the irb_refcnt goes to 0. The conditions that need
 * be verified are:
 * - no other walkers of the irebucket, i.e., quiescent irb_refcnt,
 * - no other threads holding references to ire's in the bucket,
 *   i.e., irb_nire == 0
 * - no active ire's in the bucket, i.e., irb_ire_cnt == 0
 * - need to hold the global tree lock and irb_lock in write mode.
 */
void
irb_refrele_ftable(irb_t *irb)
{
        for (;;) {
                rw_enter(&irb->irb_lock, RW_WRITER);
                ASSERT(irb->irb_refcnt != 0);
                if (irb->irb_refcnt != 1) {
                        /*
                         * Someone has a reference to this radix node
                         * or there is some bucket walker.
                         */
                        irb->irb_refcnt--;
                        rw_exit(&irb->irb_lock);
                        return;
                } else {
                        /*
                         * There is no other walker, nor is there any
                         * other thread that holds a direct ref to this
                         * radix node. Do the clean up if needed. Call
                         * to ire_unlink will clear the IRB_MARK_CONDEMNED flag
                         */
                        if (irb->irb_marks & IRB_MARK_CONDEMNED)  {
                                ire_t *ire_list;

                                ire_list = ire_unlink(irb);
                                rw_exit(&irb->irb_lock);

                                if (ire_list != NULL)
                                        ire_cleanup(ire_list);
                                /*
                                 * more CONDEMNED entries could have
                                 * been added while we dropped the lock,
                                 * so we have to re-check.
                                 */
                                continue;
                        }

                        /*
                         * Now check if there are still any ires
                         * associated with this radix node.
                         */
                        if (irb->irb_nire != 0) {
                                /*
                                 * someone is still holding on
                                 * to ires in this bucket
                                 */
                                irb->irb_refcnt--;
                                rw_exit(&irb->irb_lock);
                                return;
                        } else {
                                /*
                                 * Everything is clear. Zero walkers,
                                 * Zero threads with a ref to this
                                 * radix node, Zero ires associated with
                                 * this radix node. Due to lock order,
                                 * check the above conditions again
                                 * after grabbing all locks in the right order
                                 */
                                rw_exit(&irb->irb_lock);
                                if (irb_inactive(irb))
                                        return;
                                /*
                                 * irb_inactive could not free the irb.
                                 * See if there are any walkers, if not
                                 * try to clean up again.
                                 */
                        }
                }
        }
}

/*
 * IRE iterator used by ire_ftable_lookup to process multiple equal
 * routes. Given a starting point in the hash list (hash), walk the IREs
 * in the bucket skipping deleted entries. We treat the bucket as a circular
 * list for the purposes of walking it.
 * Returns the IRE (held) that corresponds to the hash value. If that IRE is
 * not applicable (ire_match_args failed) then it returns a subsequent one.
 * If we fail to find an IRE we return NULL.
 *
 * Assumes that the caller holds a reference on the IRE bucket and a read lock
 * on the radix_node_head (for IPv4) or the ip6_ire_head (for IPv6).
 *
 * Applies to IPv4 and IPv6.
 *
 * Due to shared-IP zones we check that an IRE_OFFLINK has a gateway that is
 * reachable from the zone i.e., that the ire_gateway_addr is in a subnet
 * in which the zone has an IP address. We check this for the global zone
 * even if no shared-IP zones are configured.
 */
ire_t *
ire_round_robin(irb_t *irb_ptr, ire_ftable_args_t *margs, uint_t hash,
    ire_t *orig_ire, ip_stack_t *ipst)
{
        ire_t           *ire, *maybe_ire = NULL;
        uint_t          maybe_badcnt;
        uint_t          maxwalk;

        /* Fold in more bits from the hint/hash */
        hash = hash ^ (hash >> 8) ^ (hash >> 16);

        rw_enter(&irb_ptr->irb_lock, RW_WRITER);
        maxwalk = irb_ptr->irb_ire_cnt; /* Excludes condemned */
        if (maxwalk == 0) {
                rw_exit(&irb_ptr->irb_lock);
                return (NULL);
        }

        hash %= maxwalk;
        irb_refhold_locked(irb_ptr);
        rw_exit(&irb_ptr->irb_lock);

        /*
         * Round-robin the routers list looking for a route that
         * matches the passed in parameters.
         * First we skip "hash" number of non-condemned IREs.
         * Then we match the IRE.
         * If we find an ire which has a non-zero ire_badcnt then we remember
         * it and keep on looking for a lower ire_badcnt.
         * If we come to the end of the list we continue (treat the
         * bucket list as a circular list) but we match less than "max"
         * entries.
         */
        ire = irb_ptr->irb_ire;
        while (maxwalk > 0) {
                if (IRE_IS_CONDEMNED(ire))
                        goto next_ire_skip;

                /* Skip the first "hash" entries to do ECMP */
                if (hash != 0) {
                        hash--;
                        goto next_ire_skip;
                }

                /*
                 * Note: Since IPv6 has hash buckets instead of radix
                 * buckers we need to explicitly compare the addresses.
                 * That makes this less efficient since we will be called
                 * even if there is no alternatives just because the
                 * bucket has multiple IREs for different addresses.
                 */
                if (ire->ire_ipversion == IPV6_VERSION) {
                        if (!IN6_ARE_ADDR_EQUAL(&orig_ire->ire_addr_v6,
                            &ire->ire_addr_v6))
                                goto next_ire;
                }

                /*
                 * For some reason find_best_route uses ire_mask. We do
                 * the same.
                 */
                if (ire->ire_ipversion == IPV4_VERSION ?
                    !ire_match_args(ire, margs->ift_addr,
                    ire->ire_mask, margs->ift_gateway,
                    margs->ift_type, margs->ift_ill, margs->ift_zoneid,
                    margs->ift_flags) :
                    !ire_match_args_v6(ire, &margs->ift_addr_v6,
                    &ire->ire_mask_v6, &margs->ift_gateway_v6,
                    margs->ift_type, margs->ift_ill, margs->ift_zoneid,
                    margs->ift_flags))
                        goto next_ire;

                if (margs->ift_zoneid != ALL_ZONES &&
                    (ire->ire_type & IRE_OFFLINK)) {
                        /*
                         * When we're in a zone, we're only
                         * interested in routers that are
                         * reachable through ipifs within our zone.
                         */
                        if (ire->ire_ipversion == IPV4_VERSION) {
                                if (!ire_gateway_ok_zone_v4(
                                    ire->ire_gateway_addr, margs->ift_zoneid,
                                    ire->ire_ill, ipst, B_TRUE))
                                        goto next_ire;
                        } else {
                                if (!ire_gateway_ok_zone_v6(
                                    &ire->ire_gateway_addr_v6,
                                    margs->ift_zoneid, ire->ire_ill,
                                    ipst, B_TRUE))
                                        goto next_ire;
                        }
                }
                mutex_enter(&ire->ire_lock);
                /* Look for stale ire_badcnt and clear */
                if (ire->ire_badcnt != 0 &&
                    (TICK_TO_SEC(ddi_get_lbolt64()) - ire->ire_last_badcnt >
                    ipst->ips_ip_ire_badcnt_lifetime))
                        ire->ire_badcnt = 0;
                mutex_exit(&ire->ire_lock);

                if (ire->ire_badcnt == 0) {
                        /* We found one with a zero badcnt; done */
                        ire_refhold(ire);
                        /*
                         * Care needed since irb_refrele grabs WLOCK to free
                         * the irb_t.
                         */
                        if (ire->ire_ipversion == IPV4_VERSION) {
                                RADIX_NODE_HEAD_UNLOCK(ipst->ips_ip_ftable);
                                irb_refrele(irb_ptr);
                                RADIX_NODE_HEAD_RLOCK(ipst->ips_ip_ftable);
                        } else {
                                rw_exit(&ipst->ips_ip6_ire_head_lock);
                                irb_refrele(irb_ptr);
                                rw_enter(&ipst->ips_ip6_ire_head_lock,
                                    RW_READER);
                        }
                        return (ire);
                }
                /*
                 * keep looking to see if there is a better (lower
                 * badcnt) matching IRE, but save this one as a last resort.
                 * If we find a lower badcnt pick that one as the last* resort.
                 */
                if (maybe_ire == NULL) {
                        maybe_ire = ire;
                        maybe_badcnt = ire->ire_badcnt;
                } else if (ire->ire_badcnt < maybe_badcnt) {
                        maybe_ire = ire;
                        maybe_badcnt = ire->ire_badcnt;
                }

next_ire:
                maxwalk--;
next_ire_skip:
                ire = ire->ire_next;
                if (ire == NULL)
                        ire = irb_ptr->irb_ire;
        }
        if (maybe_ire != NULL)
                ire_refhold(maybe_ire);

        /* Care needed since irb_refrele grabs WLOCK to free the irb_t. */
        if (ire->ire_ipversion == IPV4_VERSION) {
                RADIX_NODE_HEAD_UNLOCK(ipst->ips_ip_ftable);
                irb_refrele(irb_ptr);
                RADIX_NODE_HEAD_RLOCK(ipst->ips_ip_ftable);
        } else {
                rw_exit(&ipst->ips_ip6_ire_head_lock);
                irb_refrele(irb_ptr);
                rw_enter(&ipst->ips_ip6_ire_head_lock, RW_READER);
        }
        return (maybe_ire);
}

void
irb_refhold_rn(struct radix_node *rn)
{
        if ((rn->rn_flags & RNF_ROOT) == 0)
                irb_refhold(&((rt_t *)(rn))->rt_irb);
}

void
irb_refrele_rn(struct radix_node *rn)
{
        if ((rn->rn_flags & RNF_ROOT) == 0)
                irb_refrele_ftable(&((rt_t *)(rn))->rt_irb);
}


/*
 * ip_select_src_ill() is used by ip_select_route() to find the src_ill
 * to be used for source-aware routing table lookup. This function will
 * ignore IPIF_UNNUMBERED interface addresses, and will only return a
 * numbered interface (ipif_lookup_addr_nondup() will ignore UNNUMBERED
 * interfaces).
 */
static ill_t *
ip_select_src_ill(const in6_addr_t *v6src, zoneid_t zoneid, ip_stack_t *ipst)
{
        ipif_t *ipif;
        ill_t *ill;
        boolean_t isv6 = !IN6_IS_ADDR_V4MAPPED(v6src);
        ipaddr_t v4src;

        if (isv6) {
                ipif = ipif_lookup_addr_nondup_v6(v6src, NULL, zoneid, ipst);
        } else {
                IN6_V4MAPPED_TO_IPADDR(v6src, v4src);
                ipif = ipif_lookup_addr_nondup(v4src, NULL, zoneid, ipst);
        }
        if (ipif == NULL)
                return (NULL);
        ill = ipif->ipif_ill;
        ill_refhold(ill);
        ipif_refrele(ipif);
        return (ill);
}

/*
 * verify that v6src is configured on ill
 */
static boolean_t
ip_verify_src_on_ill(const in6_addr_t v6src, ill_t *ill, zoneid_t zoneid)
{
        ipif_t *ipif;
        ip_stack_t *ipst;
        ipaddr_t v4src;

        if (ill == NULL)
                return (B_FALSE);
        ipst = ill->ill_ipst;

        if (ill->ill_isv6) {
                ipif = ipif_lookup_addr_nondup_v6(&v6src, ill, zoneid, ipst);
        } else {
                IN6_V4MAPPED_TO_IPADDR(&v6src, v4src);
                ipif = ipif_lookup_addr_nondup(v4src, ill, zoneid, ipst);
        }

        if (ipif != NULL) {
                ipif_refrele(ipif);
                return (B_TRUE);
        } else {
                return (B_FALSE);
        }
}

/*
 * Select a route for IPv4 and IPv6. Except for multicast, loopback and reject
 * routes this routine sets up a ire_nce_cache as well. The caller needs to
 * lookup an nce for the multicast case.
 *
 * When src_multihoming is set to 2 (strict src multihoming) we use the source
 * address to select the interface and route. If IP_BOUND_IF etc are
 * specified, we require that they specify an interface on which the
 * source address is assigned.
 *
 * When src_multihoming is set to 1 (preferred src aware route
 * selection)  the unicast lookup prefers a matching source
 * (i.e., that the route points out an ill on which the source is assigned), but
 * if no such route is found we fallback to not considering the source in the
 * route lookup.
 *
 * We skip the src_multihoming check when the source isn't (yet) set, and
 * when IXAF_VERIFY_SOURCE is not set. The latter allows RAW sockets to send
 * with bogus source addresses as allowed by IP_HDRINCL and IPV6_PKTINFO
 * when secpolicy_net_rawaccess().
 */
ire_t *
ip_select_route(const in6_addr_t *v6dst, const in6_addr_t v6src,
    ip_xmit_attr_t *ixa, uint_t *generationp, in6_addr_t *setsrcp,
    int *errorp)
{
        uint_t          match_args;
        uint_t          ire_type;
        ill_t           *ill = NULL;
        ire_t           *ire;
        ip_stack_t      *ipst = ixa->ixa_ipst;
        ipaddr_t        v4dst;
        in6_addr_t      v6nexthop;
        iaflags_t       ixaflags = ixa->ixa_flags;
        nce_t           *nce;
        boolean_t       preferred_src_aware = B_FALSE;
        boolean_t       verify_src;
        boolean_t       isv6 = !(ixa->ixa_flags & IXAF_IS_IPV4);
        int             src_multihoming = IP_SRC_MULTIHOMING(isv6, ipst);

        /*
         * We only verify that the src has been configured on a selected
         * interface if the src is not :: or INADDR_ANY, and if the
         * IXAF_VERIFY_SOURCE flag is set.
         */
        verify_src = (!V6_OR_V4_INADDR_ANY(v6src) &&
            (ixa->ixa_flags & IXAF_VERIFY_SOURCE));

        match_args = 0;
        IN6_V4MAPPED_TO_IPADDR(v6dst, v4dst);
        if (setsrcp != NULL)
                ASSERT(IN6_IS_ADDR_UNSPECIFIED(setsrcp));
        if (errorp != NULL)
                ASSERT(*errorp == 0);

        /*
         * The content of the ixa will be different if IP_NEXTHOP,
         * SO_DONTROUTE, IP_BOUND_IF, IP_PKTINFO etc are set
         */

        if (isv6 ? IN6_IS_ADDR_MULTICAST(v6dst) : CLASSD(v4dst)) {
                /* Pick up the IRE_MULTICAST for the ill */
                if (ixa->ixa_multicast_ifindex != 0) {
                        ill = ill_lookup_on_ifindex(ixa->ixa_multicast_ifindex,
                            isv6, ipst);
                } else if (ixaflags & IXAF_SCOPEID_SET) {
                        /* sin6_scope_id takes precedence over ixa_ifindex */
                        ASSERT(ixa->ixa_scopeid != 0);
                        ill = ill_lookup_on_ifindex(ixa->ixa_scopeid,
                            isv6, ipst);
                } else if (ixa->ixa_ifindex != 0) {
                        /*
                         * In the ipmp case, the ixa_ifindex is set to
                         * point at an under_ill and we would return the
                         * ire_multicast() corresponding to that under_ill.
                         */
                        ill = ill_lookup_on_ifindex(ixa->ixa_ifindex,
                            isv6, ipst);
                } else if (src_multihoming != 0 && verify_src) {
                        /* Look up the ill based on the source address */
                        ill = ip_select_src_ill(&v6src, ixa->ixa_zoneid, ipst);
                        /*
                         * Since we looked up the ill from the source there
                         * is no need to verify that the source is on the ill
                         * below.
                         */
                        verify_src = B_FALSE;
                        if (ill != NULL && IS_VNI(ill)) {
                                ill_t *usesrc = ill;

                                ill = ill_lookup_usesrc(usesrc);
                                ill_refrele(usesrc);
                        }
                } else if (!isv6) {
                        ipaddr_t        v4setsrc = INADDR_ANY;

                        ill = ill_lookup_group_v4(v4dst, ixa->ixa_zoneid,
                            ipst, &v4setsrc);
                        if (setsrcp != NULL)
                                IN6_IPADDR_TO_V4MAPPED(v4setsrc, setsrcp);
                } else {
                        ill = ill_lookup_group_v6(v6dst, ixa->ixa_zoneid,
                            ipst, setsrcp);
                }
                if (ill != NULL && IS_VNI(ill)) {
                        ill_refrele(ill);
                        ill = NULL;
                }
                if (ill == NULL) {
                        if (errorp != NULL)
                                *errorp = ENXIO;
                        /* Get a hold on the IRE_NOROUTE */
                        ire = ire_reject(ipst, isv6);
                        return (ire);
                }
                if (!(ill->ill_flags & ILLF_MULTICAST)) {
                        ill_refrele(ill);
                        if (errorp != NULL)
                                *errorp = EHOSTUNREACH;
                        /* Get a hold on the IRE_NOROUTE */
                        ire = ire_reject(ipst, isv6);
                        return (ire);
                }
                /*
                 * If we are doing the strictest src_multihoming, then
                 * we check that IP_MULTICAST_IF, IP_BOUND_IF, etc specify
                 * an interface that is consistent with the source address.
                 */
                if (verify_src && src_multihoming == 2 &&
                    !ip_verify_src_on_ill(v6src, ill, ixa->ixa_zoneid)) {
                        if (errorp != NULL)
                                *errorp = EADDRNOTAVAIL;
                        ill_refrele(ill);
                        /* Get a hold on the IRE_NOROUTE */
                        ire = ire_reject(ipst, isv6);
                        return (ire);
                }
                /* Get a refcnt on the single IRE_MULTICAST per ill */
                ire = ire_multicast(ill);
                ill_refrele(ill);
                if (generationp != NULL)
                        *generationp = ire->ire_generation;
                if (errorp != NULL &&
                    (ire->ire_flags & (RTF_REJECT|RTF_BLACKHOLE))) {
                        *errorp = EHOSTUNREACH;
                }
                return (ire);
        }

        /* Now for unicast */
        if (ixa->ixa_ifindex != 0 || (ixaflags & IXAF_SCOPEID_SET)) {
                if (ixaflags & IXAF_SCOPEID_SET) {
                        /* sin6_scope_id takes precedence over ixa_ifindex */
                        ASSERT(ixa->ixa_scopeid != 0);
                        ill = ill_lookup_on_ifindex(ixa->ixa_scopeid,
                            isv6, ipst);
                } else {
                        ASSERT(ixa->ixa_ifindex != 0);
                        ill = ill_lookup_on_ifindex(ixa->ixa_ifindex,
                            isv6, ipst);
                }
                if (ill != NULL && IS_VNI(ill)) {
                        ill_refrele(ill);
                        ill = NULL;
                }
                if (ill == NULL) {
                        if (errorp != NULL)
                                *errorp = ENXIO;
                        /* Get a hold on the IRE_NOROUTE */
                        ire = ire_reject(ipst, isv6);
                        return (ire);
                }

                match_args |= MATCH_IRE_ILL;

                /*
                 * icmp_send_reply_v6 uses scopeid, and mpathd sets IP*_BOUND_IF
                 * so for both of them we need to be able look for an under
                 * interface.
                 */
                if (IS_UNDER_IPMP(ill))
                        match_args |= MATCH_IRE_TESTHIDDEN;

                /*
                 * If we are doing the strictest src_multihoming, then
                 * we check that IP_BOUND_IF, IP_PKTINFO, etc specify
                 * an interface that is consistent with the source address.
                 */
                if (src_multihoming == 2 &&
                    !ip_verify_src_on_ill(v6src, ill, ixa->ixa_zoneid)) {
                        if (errorp != NULL)
                                *errorp = EADDRNOTAVAIL;
                        ill_refrele(ill);
                        /* Get a hold on the IRE_NOROUTE */
                        ire = ire_reject(ipst, isv6);
                        return (ire);
                }
        } else if (src_multihoming != 0 && verify_src) {
                /* Look up the ill based on the source address */
                ill = ip_select_src_ill(&v6src, ixa->ixa_zoneid, ipst);
                if (ill == NULL) {
                        char addrbuf[INET6_ADDRSTRLEN];

                        ip3dbg(("%s not a valid src for unicast",
                            inet_ntop(AF_INET6, &v6src, addrbuf,
                            sizeof (addrbuf))));
                        if (errorp != NULL)
                                *errorp = EADDRNOTAVAIL;
                        /* Get a hold on the IRE_NOROUTE */
                        ire = ire_reject(ipst, isv6);
                        return (ire);
                }
                match_args |= MATCH_IRE_SRC_ILL;
                preferred_src_aware = (src_multihoming == 1);
        }

        if (ixaflags & IXAF_NEXTHOP_SET) {
                /* IP_NEXTHOP was set */
                v6nexthop = ixa->ixa_nexthop_v6;
        } else {
                v6nexthop = *v6dst;
        }

        ire_type = 0;

        /*
         * If SO_DONTROUTE is set or if IP_NEXTHOP is set, then
         * we only look for an onlink IRE.
         */
        if (ixaflags & (IXAF_DONTROUTE|IXAF_NEXTHOP_SET)) {
                match_args |= MATCH_IRE_TYPE;
                ire_type = IRE_ONLINK;
        }

retry:
        if (!isv6) {
                ipaddr_t        v4nexthop;
                ipaddr_t        v4setsrc = INADDR_ANY;

                IN6_V4MAPPED_TO_IPADDR(&v6nexthop, v4nexthop);
                ire = ire_route_recursive_v4(v4nexthop, ire_type, ill,
                    ixa->ixa_zoneid, match_args, IRR_ALLOCATE,
                    ixa->ixa_xmit_hint, ipst, &v4setsrc, generationp);
                if (setsrcp != NULL)
                        IN6_IPADDR_TO_V4MAPPED(v4setsrc, setsrcp);
        } else {
                ire = ire_route_recursive_v6(&v6nexthop, ire_type, ill,
                    ixa->ixa_zoneid, match_args, IRR_ALLOCATE,
                    ixa->ixa_xmit_hint, ipst, setsrcp, generationp);
        }

#ifdef DEBUG
        if (match_args & MATCH_IRE_TESTHIDDEN) {
                ip3dbg(("looking for hidden; dst %x ire %p\n",
                    v4dst, (void *)ire));
        }
#endif
        if (ill != NULL) {
                ill_refrele(ill);
                ill = NULL;
        }
        if ((ire->ire_flags & (RTF_REJECT|RTF_BLACKHOLE)) ||
            (ire->ire_type & IRE_MULTICAST)) {
                if (preferred_src_aware) {
                        /*
                         * "Preferred Source Aware" send mode. If we cannot
                         * find an ire whose ire_ill had the desired source
                         * address retry after relaxing the ill matching
                         * constraint.
                         */
                        ire_refrele(ire);
                        preferred_src_aware = B_FALSE;
                        match_args &= ~MATCH_IRE_SRC_ILL;
                        goto retry;
                }
                /* No ire_nce_cache */
                return (ire);
        }

        /* Setup ire_nce_cache if it doesn't exist or is condemned. */
        mutex_enter(&ire->ire_lock);
        nce = ire->ire_nce_cache;
        if (nce == NULL || nce->nce_is_condemned) {
                mutex_exit(&ire->ire_lock);
                (void) ire_revalidate_nce(ire);
        } else {
                mutex_exit(&ire->ire_lock);
        }
        return (ire);
}

/*
 * Find a route given some xmit attributes and a packet.
 * Generic for IPv4 and IPv6
 *
 * This never returns NULL. But when it returns the IRE_NOROUTE
 * it might set errorp.
 */
ire_t *
ip_select_route_pkt(mblk_t *mp, ip_xmit_attr_t *ixa, uint_t *generationp,
    int *errorp)
{
        if (ixa->ixa_flags & IXAF_IS_IPV4) {
                ipha_t          *ipha = (ipha_t *)mp->b_rptr;
                in6_addr_t      v6dst, v6src;

                IN6_IPADDR_TO_V4MAPPED(ipha->ipha_dst, &v6dst);
                IN6_IPADDR_TO_V4MAPPED(ipha->ipha_src, &v6src);

                return (ip_select_route(&v6dst, v6src, ixa, generationp,
                    NULL, errorp));
        } else {
                ip6_t   *ip6h = (ip6_t *)mp->b_rptr;

                return (ip_select_route(&ip6h->ip6_dst, ip6h->ip6_src,
                    ixa, generationp, NULL, errorp));
        }
}

ire_t *
ip_select_route_v4(ipaddr_t dst, ipaddr_t src, ip_xmit_attr_t *ixa,
    uint_t *generationp, ipaddr_t *v4setsrcp, int *errorp)
{
        in6_addr_t      v6dst, v6src;
        ire_t           *ire;
        in6_addr_t      setsrc;

        ASSERT(ixa->ixa_flags & IXAF_IS_IPV4);

        IN6_IPADDR_TO_V4MAPPED(dst, &v6dst);
        IN6_IPADDR_TO_V4MAPPED(src, &v6src);

        setsrc = ipv6_all_zeros;
        ire = ip_select_route(&v6dst, v6src, ixa, generationp, &setsrc, errorp);
        if (v4setsrcp != NULL)
                IN6_V4MAPPED_TO_IPADDR(&setsrc, *v4setsrcp);
        return (ire);
}

/*
 * Recursively look for a route to the destination. Can also match on
 * the zoneid and ill. Used for the data paths. See also
 * ire_route_recursive.
 *
 * If IRR_ALLOCATE is not set then we will only inspect the existing IREs; never
 * create an IRE_IF_CLONE. This is used on the receive side when we are not
 * forwarding.
 * If IRR_INCOMPLETE is set then we return the IRE even if we can't correctly
 * resolve the gateway.
 *
 * Note that this function never returns NULL. It returns an IRE_NOROUTE
 * instead.
 *
 * If we find any IRE_LOCAL|BROADCAST etc past the first iteration it
 * is an error.
 * Allow at most one RTF_INDIRECT.
 */
ire_t *
ire_route_recursive_impl_v4(ire_t *ire,
    ipaddr_t nexthop, uint_t ire_type, const ill_t *ill_arg,
    zoneid_t zoneid, uint_t match_args, uint_t irr_flags, uint32_t xmit_hint,
    ip_stack_t *ipst, ipaddr_t *setsrcp, uint_t *generationp)
{
        int             i, j;
        ire_t           *ires[MAX_IRE_RECURSION];
        uint_t          generation;
        uint_t          generations[MAX_IRE_RECURSION];
        boolean_t       need_refrele = B_FALSE;
        boolean_t       invalidate = B_FALSE;
        ill_t           *ill = NULL;
        uint_t          maskoff = (IRE_LOCAL|IRE_LOOPBACK|IRE_BROADCAST);

        if (setsrcp != NULL)
                ASSERT(*setsrcp == INADDR_ANY);

        /*
         * We iterate up to three times to resolve a route, even though
         * we have four slots in the array. The extra slot is for an
         * IRE_IF_CLONE we might need to create.
         */
        i = 0;
        while (i < MAX_IRE_RECURSION - 1) {
                /* ire_ftable_lookup handles round-robin/ECMP */
                if (ire == NULL) {
                        ire = ire_ftable_lookup_v4(nexthop, 0, 0, ire_type,
                            (ill != NULL? ill : ill_arg), zoneid, match_args,
                            xmit_hint, ipst, &generation);
                } else {
                        /* Caller passed it; extra hold since we will rele */
                        ire_refhold(ire);
                        if (generationp != NULL)
                                generation = *generationp;
                        else
                                generation = IRE_GENERATION_VERIFY;
                }
                if (ire == NULL) {
                        if (i > 0 && (irr_flags & IRR_INCOMPLETE)) {
                                ire = ires[0];
                                ire_refhold(ire);
                        } else {
                                ire = ire_reject(ipst, B_FALSE);
                        }
                        goto error;
                }

                /* Need to return the ire with RTF_REJECT|BLACKHOLE */
                if (ire->ire_flags & (RTF_REJECT|RTF_BLACKHOLE))
                        goto error;

                ASSERT(!(ire->ire_type & IRE_MULTICAST)); /* Not in ftable */
                /*
                 * Verify that the IRE_IF_CLONE has a consistent generation
                 * number.
                 */
                if ((ire->ire_type & IRE_IF_CLONE) && !ire_clone_verify(ire)) {
                        ire_refrele(ire);
                        ire = NULL;
                        continue;
                }

                /*
                 * Don't allow anything unusual past the first iteration.
                 * After the first lookup, we should no longer look for
                 * (IRE_LOCAL|IRE_LOOPBACK|IRE_BROADCAST) or RTF_INDIRECT
                 * routes.
                 *
                 * In addition, after we have found a direct IRE_OFFLINK,
                 * we should only look for interface or clone routes.
                 */
                match_args |= MATCH_IRE_DIRECT; /* no more RTF_INDIRECTs */

                if ((ire->ire_type & IRE_OFFLINK) &&
                    !(ire->ire_flags & RTF_INDIRECT)) {
                        ire_type = IRE_IF_ALL;
                } else {
                        /*
                         * no more local, loopback, broadcast routes
                         */
                        if (!(match_args & MATCH_IRE_TYPE))
                                ire_type = (IRE_OFFLINK|IRE_ONLINK);
                        ire_type &= ~maskoff;
                }
                match_args |= MATCH_IRE_TYPE;

                /* We have a usable IRE */
                ires[i] = ire;
                generations[i] = generation;
                i++;

                /* The first RTF_SETSRC address is passed back if setsrcp */
                if ((ire->ire_flags & RTF_SETSRC) &&
                    setsrcp != NULL && *setsrcp == INADDR_ANY) {
                        ASSERT(ire->ire_setsrc_addr != INADDR_ANY);
                        *setsrcp = ire->ire_setsrc_addr;
                }

                /*
                 * Check if we have a short-cut pointer to an IRE for this
                 * destination, and that the cached dependency isn't stale.
                 * In that case we've rejoined an existing tree towards a
                 * parent, thus we don't need to continue the loop to
                 * discover the rest of the tree.
                 */
                mutex_enter(&ire->ire_lock);
                if (ire->ire_dep_parent != NULL &&
                    ire->ire_dep_parent->ire_generation ==
                    ire->ire_dep_parent_generation) {
                        mutex_exit(&ire->ire_lock);
                        ire = NULL;
                        goto done;
                }
                mutex_exit(&ire->ire_lock);

                /*
                 * If this type should have an ire_nce_cache (even if it
                 * doesn't yet have one) then we are done. Includes
                 * IRE_INTERFACE with a full 32 bit mask.
                 */
                if (ire->ire_nce_capable) {
                        ire = NULL;
                        goto done;
                }
                ASSERT(!(ire->ire_type & IRE_IF_CLONE));
                /*
                 * For an IRE_INTERFACE we create an IRE_IF_CLONE for this
                 * particular destination
                 */
                if (ire->ire_type & IRE_INTERFACE) {
                        in6_addr_t      v6nexthop;
                        ire_t           *clone;

                        ASSERT(ire->ire_masklen != IPV4_ABITS);

                        /*
                         * In the case of ip_input and ILLF_FORWARDING not
                         * being set, and in the case of RTM_GET, there is
                         * no point in allocating an IRE_IF_CLONE. We return
                         * the IRE_INTERFACE. Note that !IRR_ALLOCATE can
                         * result in a ire_dep_parent which is IRE_IF_*
                         * without an IRE_IF_CLONE.
                         * We recover from that when we need to send packets
                         * by ensuring that the generations become
                         * IRE_GENERATION_VERIFY in this case.
                         */
                        if (!(irr_flags & IRR_ALLOCATE)) {
                                invalidate = B_TRUE;
                                ire = NULL;
                                goto done;
                        }

                        IN6_IPADDR_TO_V4MAPPED(nexthop, &v6nexthop);

                        clone = ire_create_if_clone(ire, &v6nexthop,
                            &generation);
                        if (clone == NULL) {
                                /*
                                 * Temporary failure - no memory.
                                 * Don't want caller to cache IRE_NOROUTE.
                                 */
                                invalidate = B_TRUE;
                                ire = ire_blackhole(ipst, B_FALSE);
                                goto error;
                        }
                        /*
                         * Make clone next to last entry and the
                         * IRE_INTERFACE the last in the dependency
                         * chain since the clone depends on the
                         * IRE_INTERFACE.
                         */
                        ASSERT(i >= 1);
                        ASSERT(i < MAX_IRE_RECURSION);

                        ires[i] = ires[i-1];
                        generations[i] = generations[i-1];
                        ires[i-1] = clone;
                        generations[i-1] = generation;
                        i++;

                        ire = NULL;
                        goto done;
                }

                /*
                 * We only match on the type and optionally ILL when
                 * recursing. The type match is used by some callers
                 * to exclude certain types (such as IRE_IF_CLONE or
                 * IRE_LOCAL|IRE_LOOPBACK).
                 *
                 * In the MATCH_IRE_SRC_ILL case, ill_arg may be the 'srcof'
                 * ire->ire_ill, and we want to find the IRE_INTERFACE for
                 * ire_ill, so we set ill to the ire_ill;
                 */
                match_args &= (MATCH_IRE_TYPE | MATCH_IRE_DIRECT);
                nexthop = ire->ire_gateway_addr;
                if (ill == NULL && ire->ire_ill != NULL) {
                        ill = ire->ire_ill;
                        need_refrele = B_TRUE;
                        ill_refhold(ill);
                        match_args |= MATCH_IRE_ILL;
                }
                ire = NULL;
        }
        ASSERT(ire == NULL);
        ire = ire_reject(ipst, B_FALSE);

error:
        ASSERT(ire != NULL);
        if (need_refrele)
                ill_refrele(ill);

cleanup:
        /* cleanup ires[i] */
        ire_dep_unbuild(ires, i);
        for (j = 0; j < i; j++)
                ire_refrele(ires[j]);

        ASSERT((ire->ire_flags & (RTF_REJECT|RTF_BLACKHOLE)) ||
            (irr_flags & IRR_INCOMPLETE));
        /*
         * Use IRE_GENERATION_VERIFY to ensure that ip_output will redo the
         * ip_select_route since the reject or lack of memory might be gone.
         */
        if (generationp != NULL)
                *generationp = IRE_GENERATION_VERIFY;
        return (ire);

done:
        ASSERT(ire == NULL);
        if (need_refrele) {
                ill_refrele(ill);
                ill = NULL;
        }

        /* Build dependencies */
        if (i > 1 && !ire_dep_build(ires, generations, i)) {
                /* Something in chain was condemned; tear it apart */
                ire = ire_reject(ipst, B_FALSE);
                goto cleanup;
        }

        /*
         * Release all refholds except the one for ires[0] that we
         * will return to the caller.
         */
        for (j = 1; j < i; j++)
                ire_refrele(ires[j]);

        if (invalidate) {
                /*
                 * Since we needed to allocate but couldn't we need to make
                 * sure that the dependency chain is rebuilt the next time.
                 */
                ire_dep_invalidate_generations(ires[0]);
                generation = IRE_GENERATION_VERIFY;
        } else {
                /*
                 * IREs can have been added or deleted while we did the
                 * recursive lookup and we can't catch those until we've built
                 * the dependencies. We verify the stored
                 * ire_dep_parent_generation to catch any such changes and
                 * return IRE_GENERATION_VERIFY (which will cause
                 * ip_select_route to be called again so we can redo the
                 * recursive lookup next time we send a packet.
                 */
                if (ires[0]->ire_dep_parent == NULL)
                        generation = ires[0]->ire_generation;
                else
                        generation = ire_dep_validate_generations(ires[0]);
                if (generations[0] != ires[0]->ire_generation) {
                        /* Something changed at the top */
                        generation = IRE_GENERATION_VERIFY;
                }
        }
        if (generationp != NULL)
                *generationp = generation;

        return (ires[0]);
}

ire_t *
ire_route_recursive_v4(ipaddr_t nexthop, uint_t ire_type, const ill_t *ill,
    zoneid_t zoneid, uint_t match_args, uint_t irr_flags, uint32_t xmit_hint,
    ip_stack_t *ipst, ipaddr_t *setsrcp, uint_t *generationp)
{
        return (ire_route_recursive_impl_v4(NULL, nexthop, ire_type, ill,
            zoneid, match_args, irr_flags, xmit_hint, ipst, setsrcp,
            generationp));
}

/*
 * Recursively look for a route to the destination.
 * We only handle a destination match here, yet we have the same arguments
 * as the full match to allow function pointers to select between the two.
 *
 * Note that this function never returns NULL. It returns an IRE_NOROUTE
 * instead.
 *
 * If we find any IRE_LOCAL|BROADCAST etc past the first iteration it
 * is an error.
 * Allow at most one RTF_INDIRECT.
 */
ire_t *
ire_route_recursive_dstonly_v4(ipaddr_t nexthop, uint_t irr_flags,
    uint32_t xmit_hint, ip_stack_t *ipst)
{
        ire_t   *ire;
        ire_t   *ire1;
        uint_t  generation;

        /* ire_ftable_lookup handles round-robin/ECMP */
        ire = ire_ftable_lookup_simple_v4(nexthop, xmit_hint, ipst,
            &generation);
        ASSERT(ire != NULL);
        /*
         * If the IRE has a current cached parent we know that the whole
         * parent chain is current, hence we don't need to discover and
         * build any dependencies by doing a recursive lookup.
         */
        mutex_enter(&ire->ire_lock);
        if (ire->ire_dep_parent != NULL) {
                if (ire->ire_dep_parent->ire_generation ==
                    ire->ire_dep_parent_generation) {
                        mutex_exit(&ire->ire_lock);
                        return (ire);
                }
                mutex_exit(&ire->ire_lock);
        } else {
                mutex_exit(&ire->ire_lock);
                /*
                 * If this type should have an ire_nce_cache (even if it
                 * doesn't yet have one) then we are done. Includes
                 * IRE_INTERFACE with a full 32 bit mask.
                 */
                if (ire->ire_nce_capable)
                        return (ire);
        }

        /*
         * Fallback to loop in the normal code starting with the ire
         * we found. Normally this would return the same ire.
         */
        ire1 = ire_route_recursive_impl_v4(ire, nexthop, 0, NULL, ALL_ZONES,
            MATCH_IRE_DSTONLY, irr_flags, xmit_hint, ipst, NULL, &generation);
        ire_refrele(ire);
        return (ire1);
}

/*
 * Verify that the generation numbers in the chain leading to an IRE_IF_CLONE
 * are consistent. Return FALSE (and delete the IRE_IF_CLONE) if they
 * are not consistent, and TRUE otherwise.
 */
boolean_t
ire_clone_verify(ire_t *ire)
{
        ASSERT((ire->ire_type & IRE_IF_CLONE) != 0);
        mutex_enter(&ire->ire_lock);
        if (ire->ire_dep_parent != NULL &&
            ire->ire_dep_parent->ire_generation !=
            ire->ire_dep_parent_generation) {
                mutex_exit(&ire->ire_lock);
                ire_delete(ire);
                return (B_FALSE);
        }
        mutex_exit(&ire->ire_lock);
        return (B_TRUE);
}