xref: /src/sys/netinet6/in6_src.c

/*	$NetBSD: in6_src.c,v 1.83 2017/11/24 14:03:25 roy Exp $	*/
/*	$KAME: in6_src.c,v 1.159 2005/10/19 01:40:32 t-momose Exp $	*/

/*
 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the project nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * Copyright (c) 1982, 1986, 1991, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)in_pcb.c	8.2 (Berkeley) 1/4/94
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: in6_src.c,v 1.83 2017/11/24 14:03:25 roy Exp $");

#ifdef _KERNEL_OPT
#include "opt_inet.h"
#endif

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/ioctl.h>
#include <sys/errno.h>
#include <sys/time.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/kauth.h>

#include <net/if.h>
#include <net/if_types.h>
#include <net/route.h>

#include <netinet/in.h>
#include <netinet/in_var.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/in_pcb.h>
#include <netinet/portalgo.h>
#include <netinet6/in6_var.h>
#include <netinet/ip6.h>
#include <netinet6/in6_pcb.h>
#include <netinet6/ip6_var.h>
#include <netinet6/ip6_private.h>
#include <netinet6/nd6.h>
#include <netinet6/scope6_var.h>

#include <net/net_osdep.h>

#ifdef MIP6
#include <netinet6/mip6.h>
#include <netinet6/mip6_var.h>
#include "mip.h"
#if NMIP > 0
#include <net/if_mip.h>
#endif /* NMIP > 0 */
#endif /* MIP6 */

#include <netinet/tcp_vtw.h>

#define ADDR_LABEL_NOTAPP (-1)
struct in6_addrpolicy defaultaddrpolicy;

int ip6_prefer_tempaddr = 0;

static int in6_selectif(struct sockaddr_in6 *, struct ip6_pktopts *,
	struct ip6_moptions *, struct route *, struct ifnet **, struct psref *);

static struct in6_addrpolicy *lookup_addrsel_policy(struct sockaddr_in6 *);

static void init_policy_queue(void);
static int add_addrsel_policyent(struct in6_addrpolicy *);
static int delete_addrsel_policyent(struct in6_addrpolicy *);
static int walk_addrsel_policy(int (*)(struct in6_addrpolicy *, void *),
				    void *);
static int dump_addrsel_policyent(struct in6_addrpolicy *, void *);
static struct in6_addrpolicy *match_addrsel_policy(struct sockaddr_in6 *);

/*
 * Return an IPv6 address, which is the most appropriate for a given
 * destination and user specified options.
 * If necessary, this function lookups the routing table and returns
 * an entry to the caller for later use.
 */
#if 0				/* disabled ad-hoc */
#define REPLACE(r) do {\
	char _buf1[INET6_ADDRSTRLEN], _buf2[INET6_ADDRSTRLEN]; \
	if ((r) < sizeof(ip6stat.ip6s_sources_rule) / \
		sizeof(ip6stat.ip6s_sources_rule[0])) /* check for safety */ \
		ip6stat.ip6s_sources_rule[(r)]++; \
	printf("%s: replace %s with %s by %d\n", __func__, ia_best ? \
	    IN6_PRINT(_buf1, &ia_best->ia_addr.sin6_addr) : "none", \
	    IN6_PRINT(_buf2, &ia->ia_addr.sin6_addr), (r)); \
	goto replace; \
} while(/*CONSTCOND*/0)
#define NEXT(r) do {\
	if ((r) < sizeof(ip6stat.ip6s_sources_rule) / \
		sizeof(ip6stat.ip6s_sources_rule[0])) /* check for safety */ \
		ip6stat.ip6s_sources_rule[(r)]++; \
	printf("%s: keep %s against %s by %d\n", ia_best ? \
	    IN6_PRINT(_buf1, &ia_best->ia_addr.sin6_addr) : "none", \
	    IN6_PRINT(_buf2, &ia->ia_addr.sin6_addr), (r)); \
	goto next; 		/* XXX: we can't use 'continue' here */ \
} while(/*CONSTCOND*/0)
#define BREAK(r) do { \
	if ((r) < sizeof(ip6stat.ip6s_sources_rule) / \
		sizeof(ip6stat.ip6s_sources_rule[0])) /* check for safety */ \
		ip6stat.ip6s_sources_rule[(r)]++; \
	goto out; 		/* XXX: we can't use 'break' here */ \
} while(/*CONSTCOND*/0)
#else
#define REPLACE(r) goto replace
#define NEXT(r) goto next
#define BREAK(r) goto out
#endif

/*
 * Called inside pserialize critical section. Don't sleep/block.
 */
static struct in6_ifaddr *
in6_select_best_ia(struct sockaddr_in6 *dstsock, struct in6_addr *dst,
    const struct ifnet *ifp, const struct ip6_pktopts *opts,
    const u_int32_t odstzone)
{
	struct in6_ifaddr *ia, *ia_best = NULL;
	int dst_scope = -1, best_scope = -1, best_matchlen = -1;
	struct in6_addrpolicy *dst_policy = NULL, *best_policy = NULL;

	IN6_ADDRLIST_READER_FOREACH(ia) {
		int new_scope = -1, new_matchlen = -1;
		struct in6_addrpolicy *new_policy = NULL;
		u_int32_t srczone, osrczone, dstzone;
		struct in6_addr src;
		struct ifnet *ifp1 = ia->ia_ifp;
		int prefer_tempaddr;

		/*
		 * We'll never take an address that breaks the scope zone
		 * of the destination.  We also skip an address if its zone
		 * does not contain the outgoing interface.
		 * XXX: we should probably use sin6_scope_id here.
		 */
		if (in6_setscope(dst, ifp1, &dstzone) ||
		    odstzone != dstzone) {
			continue;
		}
		src = ia->ia_addr.sin6_addr;

		/* Skip the scope test in impossible cases */
		if (!(ifp->if_flags & IFF_LOOPBACK) &&
		    IN6_IS_ADDR_LOOPBACK(&src))
			continue;

		if (in6_setscope(&src, ifp, &osrczone) ||
		    in6_setscope(&src, ifp1, &srczone) ||
		    osrczone != srczone) {
			continue;
		}

		/* avoid unusable addresses */
		if ((ia->ia6_flags & (IN6_IFF_DUPLICATED | IN6_IFF_ANYCAST)))
			continue;
		/* Prefer validated addresses */
		if (!(ia->ia6_flags & (IN6_IFF_TENTATIVE | IN6_IFF_DETACHED)) &&
		    ia_best != NULL &&
		    ia_best->ia6_flags & (IN6_IFF_TENTATIVE | IN6_IFF_DETACHED))
			REPLACE(0);

		if (!ip6_use_deprecated && IFA6_IS_DEPRECATED(ia))
			continue;

#if defined(MIP6) && NMIP > 0
		/* avoid unusable home addresses. */
		if ((ia->ia6_flags & IN6_IFF_HOME) &&
		    !mip6_ifa6_is_addr_valid_hoa(ia))
			continue;
#endif /* MIP6 && NMIP > 0 */

		/* Rule 1: Prefer same address */
		if (IN6_ARE_ADDR_EQUAL(dst, &ia->ia_addr.sin6_addr)) {
			ia_best = ia;
			BREAK(1); /* there should be no better candidate */
		}

		if (ia_best == NULL)
			REPLACE(1);

		/* Rule 2: Prefer appropriate scope */
		if (dst_scope < 0)
			dst_scope = in6_addrscope(dst);
		new_scope = in6_addrscope(&ia->ia_addr.sin6_addr);
		if (IN6_ARE_SCOPE_CMP(best_scope, new_scope) < 0) {
			if (IN6_ARE_SCOPE_CMP(best_scope, dst_scope) < 0)
				REPLACE(2);
			NEXT(2);
		} else if (IN6_ARE_SCOPE_CMP(new_scope, best_scope) < 0) {
			if (IN6_ARE_SCOPE_CMP(new_scope, dst_scope) < 0)
				NEXT(2);
			REPLACE(2);
		}

		/*
		 * Rule 3: Avoid deprecated addresses.  Note that the case of
		 * !ip6_use_deprecated is already rejected above.
		 */
		if (!IFA6_IS_DEPRECATED(ia_best) && IFA6_IS_DEPRECATED(ia))
			NEXT(3);
		if (IFA6_IS_DEPRECATED(ia_best) && !IFA6_IS_DEPRECATED(ia))
			REPLACE(3);

		/* Rule 4: Prefer home addresses */
#if defined(MIP6) && NMIP > 0
		if (!MIP6_IS_MN)
			goto skip_rule4;

		if ((ia_best->ia6_flags & IN6_IFF_HOME) == 0 &&
		    (ia->ia6_flags & IN6_IFF_HOME) == 0) {
			/* both address are not home addresses. */
			goto skip_rule4;
		}

		/*
		 * If SA is simultaneously a home address and care-of
		 * address and SB is not, then prefer SA. Similarly,
		 * if SB is simultaneously a home address and care-of
		 * address and SA is not, then prefer SB.
		 */
		if (((ia_best->ia6_flags & IN6_IFF_HOME) != 0 &&
			ia_best->ia_ifp->if_type != IFT_MIP)
		    &&
		    ((ia->ia6_flags & IN6_IFF_HOME) != 0 &&
			ia->ia_ifp->if_type == IFT_MIP))
			NEXT(4);
		if (((ia_best->ia6_flags & IN6_IFF_HOME) != 0 &&
			ia_best->ia_ifp->if_type == IFT_MIP)
		    &&
		    ((ia->ia6_flags & IN6_IFF_HOME) != 0 &&
			ia->ia_ifp->if_type != IFT_MIP))
			REPLACE(4);
		if (ip6po_usecoa == 0) {
			/*
			 * If SA is just a home address and SB is just
			 * a care-of address, then prefer
			 * SA. Similarly, if SB is just a home address
			 * and SA is just a care-of address, then
			 * prefer SB.
			 */
			if ((ia_best->ia6_flags & IN6_IFF_HOME) != 0 &&
			    (ia->ia6_flags & IN6_IFF_HOME) == 0) {
				NEXT(4);
			}
			if ((ia_best->ia6_flags & IN6_IFF_HOME) == 0 &&
			    (ia->ia6_flags & IN6_IFF_HOME) != 0) {
				REPLACE(4);
			}
		} else {
			/*
			 * a sender don't want to use a home address
			 * because:
			 *
			 * 1) we cannot use.  (ex. NS or NA to global
			 * addresses.)
			 *
			 * 2) a user specified not to use.
			 * (ex. mip6control -u)
			 */
			if ((ia_best->ia6_flags & IN6_IFF_HOME) == 0 &&
			    (ia->ia6_flags & IN6_IFF_HOME) != 0) {
				/* XXX breaks stat */
				NEXT(0);
			}
			if ((ia_best->ia6_flags & IN6_IFF_HOME) != 0 &&
			    (ia->ia6_flags & IN6_IFF_HOME) == 0) {
				/* XXX breaks stat */
				REPLACE(0);
			}
		}
	skip_rule4:
#endif /* MIP6 && NMIP > 0 */

		/* Rule 5: Prefer outgoing interface */
		if (ia_best->ia_ifp == ifp && ia->ia_ifp != ifp)
			NEXT(5);
		if (ia_best->ia_ifp != ifp && ia->ia_ifp == ifp)
			REPLACE(5);

		/*
		 * Rule 6: Prefer matching label
		 * Note that best_policy should be non-NULL here.
		 */
		if (dst_policy == NULL)
			dst_policy = lookup_addrsel_policy(dstsock);
		if (dst_policy->label != ADDR_LABEL_NOTAPP) {
			new_policy = lookup_addrsel_policy(&ia->ia_addr);
			if (dst_policy->label == best_policy->label &&
			    dst_policy->label != new_policy->label)
				NEXT(6);
			if (dst_policy->label != best_policy->label &&
			    dst_policy->label == new_policy->label)
				REPLACE(6);
		}

		/*
		 * Rule 7: Prefer public addresses.
		 * We allow users to reverse the logic by configuring
		 * a sysctl variable, so that privacy conscious users can
		 * always prefer temporary addresses.
		 */
		if (opts == NULL ||
		    opts->ip6po_prefer_tempaddr == IP6PO_TEMPADDR_SYSTEM) {
			prefer_tempaddr = ip6_prefer_tempaddr;
		} else if (opts->ip6po_prefer_tempaddr ==
		    IP6PO_TEMPADDR_NOTPREFER) {
			prefer_tempaddr = 0;
		} else
			prefer_tempaddr = 1;
		if (!(ia_best->ia6_flags & IN6_IFF_TEMPORARY) &&
		    (ia->ia6_flags & IN6_IFF_TEMPORARY)) {
			if (prefer_tempaddr)
				REPLACE(7);
			else
				NEXT(7);
		}
		if ((ia_best->ia6_flags & IN6_IFF_TEMPORARY) &&
		    !(ia->ia6_flags & IN6_IFF_TEMPORARY)) {
			if (prefer_tempaddr)
				NEXT(7);
			else
				REPLACE(7);
		}

		/*
		 * Rule 8: prefer addresses on alive interfaces.
		 * This is a KAME specific rule.
		 */
		if ((ia_best->ia_ifp->if_flags & IFF_UP) &&
		    !(ia->ia_ifp->if_flags & IFF_UP))
			NEXT(8);
		if (!(ia_best->ia_ifp->if_flags & IFF_UP) &&
		    (ia->ia_ifp->if_flags & IFF_UP))
			REPLACE(8);

		/*
		 * Rule 9: prefer addresses on "preferred" interfaces.
		 * This is a KAME specific rule.
		 */
#ifdef notyet			/* until introducing address selection */
#define NDI_BEST ND_IFINFO(ia_best->ia_ifp)
#define NDI_NEW  ND_IFINFO(ia->ia_ifp)
		if ((NDI_BEST->flags & ND6_IFF_PREFER_SOURCE) &&
		    !(NDI_NEW->flags & ND6_IFF_PREFER_SOURCE))
			NEXT(9);
		if (!(NDI_BEST->flags & ND6_IFF_PREFER_SOURCE) &&
		    (NDI_NEW->flags & ND6_IFF_PREFER_SOURCE))
			REPLACE(9);
#undef NDI_BEST
#undef NDI_NEW
#endif

		/*
		 * Rule 14: Use longest matching prefix.
		 * Note: in the address selection draft, this rule is
		 * documented as "Rule 8".  However, since it is also
		 * documented that this rule can be overridden, we assign
		 * a large number so that it is easy to assign smaller numbers
		 * to more preferred rules.
		 */
		new_matchlen = in6_matchlen(&ia->ia_addr.sin6_addr, dst);
		if (best_matchlen < new_matchlen)
			REPLACE(14);
		if (new_matchlen < best_matchlen)
			NEXT(14);

		/* Rule 15 is reserved. */

		/*
		 * Last resort: just keep the current candidate.
		 * Or, do we need more rules?
		 */
		continue;

	  replace:
		ia_best = ia;
		best_scope = (new_scope >= 0 ? new_scope :
			      in6_addrscope(&ia_best->ia_addr.sin6_addr));
		best_policy = (new_policy ? new_policy :
			       lookup_addrsel_policy(&ia_best->ia_addr));
		best_matchlen = (new_matchlen >= 0 ? new_matchlen :
				 in6_matchlen(&ia_best->ia_addr.sin6_addr,
					      dst));

	  next:
		continue;

	  out:
		break;
	}

	return ia_best;
}
#undef REPLACE
#undef BREAK
#undef NEXT

int
in6_selectsrc(struct sockaddr_in6 *dstsock, struct ip6_pktopts *opts,
	struct ip6_moptions *mopts, struct route *ro, struct in6_addr *laddr,
	struct ifnet **ifpp, struct psref *psref, struct in6_addr *ret_ia6)
{
	struct in6_addr dst;
	struct ifnet *ifp = NULL;
	struct in6_ifaddr *ia = NULL;
	struct in6_pktinfo *pi = NULL;
	u_int32_t odstzone;
	int error = 0, iferror;
#if defined(MIP6) && NMIP > 0
	u_int8_t ip6po_usecoa = 0;
#endif /* MIP6 && NMIP > 0 */
	struct psref local_psref;
	int bound = curlwp_bind();
#define PSREF (psref == NULL) ? &local_psref : psref
	int s;

	KASSERT((ifpp != NULL && psref != NULL) ||
	        (ifpp == NULL && psref == NULL));

	dst = dstsock->sin6_addr; /* make a copy for local operation */
	if (ifpp)
		*ifpp = NULL;

	/*
	 * Try to determine the outgoing interface for the given destination.
	 * We do this regardless of whether the socket is bound, since the
	 * caller may need this information as a side effect of the call
	 * to this function (e.g., for identifying the appropriate scope zone
	 * ID).
	 */
	iferror = in6_selectif(dstsock, opts, mopts, ro, &ifp, PSREF);
	if (ifpp != NULL)
		*ifpp = ifp;

	/*
	 * If the source address is explicitly specified by the caller,
	 * check if the requested source address is indeed a unicast address
	 * assigned to the node, and can be used as the packet's source
	 * address.  If everything is okay, use the address as source.
	 */
	if (opts && (pi = opts->ip6po_pktinfo) &&
	    !IN6_IS_ADDR_UNSPECIFIED(&pi->ipi6_addr)) {
		struct sockaddr_in6 srcsock;
		struct in6_ifaddr *ia6;
		int _s;
		struct ifaddr *ifa;

		/*
		 * Determine the appropriate zone id of the source based on
		 * the zone of the destination and the outgoing interface.
		 * If the specified address is ambiguous wrt the scope zone,
		 * the interface must be specified; otherwise, ifa_ifwithaddr()
		 * will fail matching the address.
		 */
		memset(&srcsock, 0, sizeof(srcsock));
		srcsock.sin6_family = AF_INET6;
		srcsock.sin6_len = sizeof(srcsock);
		srcsock.sin6_addr = pi->ipi6_addr;
		if (ifp) {
			error = in6_setscope(&srcsock.sin6_addr, ifp, NULL);
			if (error != 0)
				goto exit;
		}

		_s = pserialize_read_enter();
		ifa = ifa_ifwithaddr(sin6tosa(&srcsock));
		if ((ia6 = ifatoia6(ifa)) == NULL ||
		    ia6->ia6_flags &
		    (IN6_IFF_ANYCAST | IN6_IFF_NOTREADY)) {
			pserialize_read_exit(_s);
			error = EADDRNOTAVAIL;
			goto exit;
		}
		pi->ipi6_addr = srcsock.sin6_addr; /* XXX: this overrides pi */
		if (ifpp)
			*ifpp = ifp;
		*ret_ia6 = ia6->ia_addr.sin6_addr;
		pserialize_read_exit(_s);
		goto exit;
	}

	/*
	 * If the socket has already bound the source, just use it.  We don't
	 * care at the moment whether in6_selectif() succeeded above, even
	 * though it would eventually cause an error.
	 */
	if (laddr && !IN6_IS_ADDR_UNSPECIFIED(laddr)) {
		*ret_ia6 = *laddr;
		goto exit;
	}

	/*
	 * The outgoing interface is crucial in the general selection procedure
	 * below.  If it is not known at this point, we fail.
	 */
	if (ifp == NULL) {
		error = iferror;
		goto exit;
	}

	/*
	 * If the address is not yet determined, choose the best one based on
	 * the outgoing interface and the destination address.
	 */

#if defined(MIP6) && NMIP > 0
	/*
	 * a caller can specify IP6PO_USECOA to not to use a home
	 * address.  for example, the case that the neighbour
	 * unreachability detection to the global address.
	 */
	if (opts != NULL &&
	    (opts->ip6po_flags & IP6PO_USECOA) != 0) {
		ip6po_usecoa = 1;
	}
#endif /* MIP6 && NMIP > 0 */

	error = in6_setscope(&dst, ifp, &odstzone);
	if (error != 0)
		goto exit;

	s = pserialize_read_enter();

	ia = in6_select_best_ia(dstsock, &dst, ifp, opts, odstzone);
	if (ia == NULL) {
		pserialize_read_exit(s);
		error = EADDRNOTAVAIL;
		goto exit;
	}
	*ret_ia6 = ia->ia_addr.sin6_addr;

	pserialize_read_exit(s);
exit:
	if (ifpp == NULL)
		if_put(ifp, PSREF);
	curlwp_bindx(bound);
	return error;
#undef PSREF
}

int
in6_selectroute(struct sockaddr_in6 *dstsock, struct ip6_pktopts *opts,
    struct route **ro, struct rtentry **retrt, bool count_discard)
{
	int error = 0;
	struct rtentry *rt = NULL;
	union {
		struct sockaddr		dst;
		struct sockaddr_in6	dst6;
	} u;

	KASSERT(ro != NULL);
	KASSERT(*ro != NULL);
	KASSERT(retrt != NULL);

#if 0
	if (dstsock->sin6_addr.s6_addr32[0] == 0 &&
	    dstsock->sin6_addr.s6_addr32[1] == 0 &&
	    !IN6_IS_ADDR_LOOPBACK(&dstsock->sin6_addr)) {
		char ip6buf[INET6_ADDRSTRLEN];
		printf("%s: strange destination %s\n", __func__,
		       IN6_PRINT(ip6buf, &dstsock->sin6_addr));
	} else {
		char ip6buf[INET6_ADDRSTRLEN];
		printf("%s: destination = %s%%%d\n", __func__,
		       IN6_PRINT(ip6buf, &dstsock->sin6_addr),
		       dstsock->sin6_scope_id); /* for debug */
	}
#endif

	/*
	 * If the next hop address for the packet is specified by the caller,
	 * use it as the gateway.
	 */
	if (opts && opts->ip6po_nexthop) {
		struct route *ron;
		struct sockaddr_in6 *sin6_next;

		sin6_next = satosin6(opts->ip6po_nexthop);

		/* at this moment, we only support AF_INET6 next hops */
		if (sin6_next->sin6_family != AF_INET6) {
			error = EAFNOSUPPORT; /* or should we proceed? */
			goto done;
		}

		/*
		 * If the next hop is an IPv6 address, then the node identified
		 * by that address must be a neighbor of the sending host.
		 */
		ron = &opts->ip6po_nextroute;
		rt = rtcache_lookup(ron, sin6tosa(sin6_next));
		if (rt == NULL || (rt->rt_flags & RTF_GATEWAY) != 0 ||
		    !nd6_is_addr_neighbor(sin6_next, rt->rt_ifp)) {
			if (rt != NULL) {
				if (count_discard)
					in6_ifstat_inc(rt->rt_ifp,
					    ifs6_out_discard);
				rtcache_unref(rt, ron);
				rt = NULL;
			}
			rtcache_free(ron);
			error = EHOSTUNREACH;
			goto done;
		}
		*ro = ron;

		goto done;
	}

	/*
	 * Use a cached route if it exists and is valid, else try to allocate
	 * a new one.  Note that we should check the address family of the
	 * cached destination, in case of sharing the cache with IPv4.
	 */
	u.dst6 = *dstsock;
	u.dst6.sin6_scope_id = 0;
	rt = rtcache_lookup1(*ro, &u.dst, 1);

	if (rt == NULL)
		error = EHOSTUNREACH;

	/*
	 * Check if the outgoing interface conflicts with
	 * the interface specified by ipi6_ifindex (if specified).
	 * Note that loopback interface is always okay.
	 * (this may happen when we are sending a packet to one of
	 *  our own addresses.)
	 */
	if (opts && opts->ip6po_pktinfo && opts->ip6po_pktinfo->ipi6_ifindex) {
		if (rt != NULL && !(rt->rt_ifp->if_flags & IFF_LOOPBACK) &&
		    rt->rt_ifp->if_index != opts->ip6po_pktinfo->ipi6_ifindex) {
			if (count_discard)
				in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
			error = EHOSTUNREACH;
			rt = NULL;
		}
	}

done:
	if (error == EHOSTUNREACH)
		IP6_STATINC(IP6_STAT_NOROUTE);
	*retrt = rt;
	return error;
}

static int
in6_selectif(struct sockaddr_in6 *dstsock, struct ip6_pktopts *opts,
	struct ip6_moptions *mopts, struct route *ro, struct ifnet **retifp,
	struct psref *psref)
{
	int error = 0;
	struct rtentry *rt = NULL;
	struct in6_addr *dst;
	struct in6_pktinfo *pi = NULL;

	KASSERT(retifp != NULL);
	*retifp = NULL;
	dst = &dstsock->sin6_addr;

	/* If the caller specify the outgoing interface explicitly, use it. */
	if (opts && (pi = opts->ip6po_pktinfo) != NULL && pi->ipi6_ifindex) {
		/* XXX boundary check is assumed to be already done. */
		*retifp = if_get_byindex(pi->ipi6_ifindex, psref);
		if (*retifp != NULL)
			return 0;
		goto getroute;
	}

	/*
	 * If the destination address is a multicast address and the outgoing
	 * interface for the address is specified by the caller, use it.
	 */
	if (IN6_IS_ADDR_MULTICAST(dst) && mopts != NULL) {
		*retifp = if_get_byindex(mopts->im6o_multicast_if_index, psref);
		if (*retifp != NULL)
			return 0; /* we do not need a route for multicast. */
	}

getroute:
	error = in6_selectroute(dstsock, opts, &ro, &rt, false);
	if (error != 0)
		return error;

	*retifp = if_get_byindex(rt->rt_ifp->if_index, psref);

	/*
	 * do not use a rejected or black hole route.
	 * XXX: this check should be done in the L2 output routine.
	 * However, if we skipped this check here, we'd see the following
	 * scenario:
	 * - install a rejected route for a scoped address prefix
	 *   (like fe80::/10)
	 * - send a packet to a destination that matches the scoped prefix,
	 *   with ambiguity about the scope zone.
	 * - pick the outgoing interface from the route, and disambiguate the
	 *   scope zone with the interface.
	 * - ip6_output() would try to get another route with the "new"
	 *   destination, which may be valid.
	 * - we'd see no error on output.
	 * Although this may not be very harmful, it should still be confusing.
	 * We thus reject the case here.
	 */
	if ((rt->rt_flags & (RTF_REJECT | RTF_BLACKHOLE))) {
		error = (rt->rt_flags & RTF_HOST ? EHOSTUNREACH : ENETUNREACH);
		/* XXX: ifp can be returned with psref even if error */
		goto out;
	}

	/*
	 * Adjust the "outgoing" interface.  If we're going to loop the packet
	 * back to ourselves, the ifp would be the loopback interface.
	 * However, we'd rather know the interface associated to the
	 * destination address (which should probably be one of our own
	 * addresses.)
	 */
	if (rt->rt_ifa && rt->rt_ifa->ifa_ifp &&
	    rt->rt_ifa->ifa_ifp != *retifp &&
	    !if_is_deactivated(rt->rt_ifa->ifa_ifp)) {
		if_put(*retifp, psref);
		*retifp = rt->rt_ifa->ifa_ifp;
		if_acquire(*retifp, psref);
	}
out:
	rtcache_unref(rt, ro);
	return error;
}

/*
 * Default hop limit selection. The precedence is as follows:
 * 1. Hoplimit value specified via ioctl.
 * 2. (If the outgoing interface is detected) the current
 *     hop limit of the interface specified by router advertisement.
 * 3. The system default hoplimit.
*/
int
in6_selecthlim(struct in6pcb *in6p, struct ifnet *ifp)
{
	if (in6p && in6p->in6p_hops >= 0)
		return (in6p->in6p_hops);
	else if (ifp)
		return (ND_IFINFO(ifp)->chlim);
	else
		return (ip6_defhlim);
}

int
in6_selecthlim_rt(struct in6pcb *in6p)
{
	struct rtentry *rt;

	if (in6p == NULL)
		return in6_selecthlim(in6p, NULL);

	rt = rtcache_validate(&in6p->in6p_route);
	if (rt != NULL) {
		int ret = in6_selecthlim(in6p, rt->rt_ifp);
		rtcache_unref(rt, &in6p->in6p_route);
		return ret;
	} else
		return in6_selecthlim(in6p, NULL);
}

/*
 * Find an empty port and set it to the specified PCB.
 */
int
in6_pcbsetport(struct sockaddr_in6 *sin6, struct in6pcb *in6p, struct lwp *l)
{
	struct socket *so = in6p->in6p_socket;
	struct inpcbtable *table = in6p->in6p_table;
	u_int16_t lport, *lastport;
	enum kauth_network_req req;
	int error = 0;

	if (in6p->in6p_flags & IN6P_LOWPORT) {
#ifndef IPNOPRIVPORTS
		req = KAUTH_REQ_NETWORK_BIND_PRIVPORT;
#else
		req = KAUTH_REQ_NETWORK_BIND_PORT;
#endif
		lastport = &table->inpt_lastlow;
	} else {
		req = KAUTH_REQ_NETWORK_BIND_PORT;

		lastport = &table->inpt_lastport;
	}

	/* XXX-kauth: KAUTH_REQ_NETWORK_BIND_AUTOASSIGN_{,PRIV}PORT */
	error = kauth_authorize_network(l->l_cred, KAUTH_NETWORK_BIND, req, so,
	    sin6, NULL);
	if (error)
		return (EACCES);

       /*
        * Use RFC6056 randomized port selection
        */
	error = portalgo_randport(&lport, &in6p->in6p_head, l->l_cred);
	if (error)
		return error;

	in6p->in6p_flags |= IN6P_ANONPORT;
	*lastport = lport;
	in6p->in6p_lport = htons(lport);
	in6_pcbstate(in6p, IN6P_BOUND);
	return (0);		/* success */
}

void
addrsel_policy_init(void)
{
	init_policy_queue();

	/* initialize the "last resort" policy */
	memset(&defaultaddrpolicy, 0, sizeof(defaultaddrpolicy));
	defaultaddrpolicy.label = ADDR_LABEL_NOTAPP;
}

/*
 * XXX: NOMPSAFE if a policy is set
 */
static struct in6_addrpolicy *
lookup_addrsel_policy(struct sockaddr_in6 *key)
{
	struct in6_addrpolicy *match = NULL;

	match = match_addrsel_policy(key);

	if (match == NULL)
		match = &defaultaddrpolicy;
	else
		match->use++;

	return (match);
}

/*
 * Subroutines to manage the address selection policy table via sysctl.
 */
struct sel_walkarg {
	size_t	w_total;
	size_t	w_given;
	void *	w_where;
	void *w_limit;
};

int sysctl_net_inet6_addrctlpolicy(SYSCTLFN_ARGS);
int
sysctl_net_inet6_addrctlpolicy(SYSCTLFN_ARGS)
{
	int error = 0;
	int s;

	s = splsoftnet();

	if (newp) {
		error = EPERM;
		goto end;
	}
	if (oldp && oldlenp == NULL) {
		error = EINVAL;
		goto end;
	}
	if (oldp || oldlenp) {
		struct sel_walkarg w;
		size_t oldlen = *oldlenp;

		memset(&w, 0, sizeof(w));
		w.w_given = oldlen;
		w.w_where = oldp;
		if (oldp)
			w.w_limit = (char *)oldp + oldlen;

		error = walk_addrsel_policy(dump_addrsel_policyent, &w);

		*oldlenp = w.w_total;
		if (oldp && w.w_total > oldlen && error == 0)
			error = ENOMEM;
	}

  end:
	splx(s);

	return (error);
}

int
in6_src_ioctl(u_long cmd, void *data)
{
	int i;
	struct in6_addrpolicy ent0;

	if (cmd != SIOCAADDRCTL_POLICY && cmd != SIOCDADDRCTL_POLICY)
		return (EOPNOTSUPP); /* check for safety */

	ent0 = *(struct in6_addrpolicy *)data;

	if (ent0.label == ADDR_LABEL_NOTAPP)
		return (EINVAL);
	/* check if the prefix mask is consecutive. */
	if (in6_mask2len(&ent0.addrmask.sin6_addr, NULL) < 0)
		return (EINVAL);
	/* clear trailing garbages (if any) of the prefix address. */
	for (i = 0; i < 4; i++) {
		ent0.addr.sin6_addr.s6_addr32[i] &=
			ent0.addrmask.sin6_addr.s6_addr32[i];
	}
	ent0.use = 0;

	switch (cmd) {
	case SIOCAADDRCTL_POLICY:
		return (add_addrsel_policyent(&ent0));
	case SIOCDADDRCTL_POLICY:
		return (delete_addrsel_policyent(&ent0));
	}

	return (0);		/* XXX: compromise compilers */
}

/*
 * The followings are implementation of the policy table using a
 * simple tail queue.
 * XXX such details should be hidden.
 * XXX implementation using binary tree should be more efficient.
 */
struct addrsel_policyent {
	TAILQ_ENTRY(addrsel_policyent) ape_entry;
	struct in6_addrpolicy ape_policy;
};

TAILQ_HEAD(addrsel_policyhead, addrsel_policyent);

struct addrsel_policyhead addrsel_policytab;

static void
init_policy_queue(void)
{
	TAILQ_INIT(&addrsel_policytab);
}

static int
add_addrsel_policyent(struct in6_addrpolicy *newpolicy)
{
	struct addrsel_policyent *newpol, *pol;

	/* duplication check */
	TAILQ_FOREACH(pol, &addrsel_policytab, ape_entry) {
		if (IN6_ARE_ADDR_EQUAL(&newpolicy->addr.sin6_addr,
		    &pol->ape_policy.addr.sin6_addr) &&
		    IN6_ARE_ADDR_EQUAL(&newpolicy->addrmask.sin6_addr,
		    &pol->ape_policy.addrmask.sin6_addr)) {
			return (EEXIST);	/* or override it? */
		}
	}

	newpol = malloc(sizeof(*newpol), M_IFADDR, M_WAITOK|M_ZERO);

	/* XXX: should validate entry */
	newpol->ape_policy = *newpolicy;

	TAILQ_INSERT_TAIL(&addrsel_policytab, newpol, ape_entry);

	return (0);
}

static int
delete_addrsel_policyent(struct in6_addrpolicy *key)
{
	struct addrsel_policyent *pol;

	/* search for the entry in the table */
	for (pol = TAILQ_FIRST(&addrsel_policytab); pol;
	     pol = TAILQ_NEXT(pol, ape_entry)) {
		if (IN6_ARE_ADDR_EQUAL(&key->addr.sin6_addr,
		    &pol->ape_policy.addr.sin6_addr) &&
		    IN6_ARE_ADDR_EQUAL(&key->addrmask.sin6_addr,
		    &pol->ape_policy.addrmask.sin6_addr)) {
			break;
		}
	}
	if (pol == NULL) {
		return (ESRCH);
	}

	TAILQ_REMOVE(&addrsel_policytab, pol, ape_entry);

	return (0);
}

static int
walk_addrsel_policy(int (*callback)(struct in6_addrpolicy *, void *), void *w)
{
	struct addrsel_policyent *pol;
	int error = 0;

	TAILQ_FOREACH(pol, &addrsel_policytab, ape_entry) {
		if ((error = (*callback)(&pol->ape_policy, w)) != 0)
			return error;
	}

	return error;
}

static int
dump_addrsel_policyent(struct in6_addrpolicy *pol, void *arg)
{
	int error = 0;
	struct sel_walkarg *w = arg;

	if (w->w_where && (char *)w->w_where + sizeof(*pol) <= (char *)w->w_limit) {
		if ((error = copyout(pol, w->w_where, sizeof(*pol))) != 0)
			return error;
		w->w_where = (char *)w->w_where + sizeof(*pol);
	}
	w->w_total += sizeof(*pol);

	return error;
}

static struct in6_addrpolicy *
match_addrsel_policy(struct sockaddr_in6 *key)
{
	struct addrsel_policyent *pent;
	struct in6_addrpolicy *bestpol = NULL, *pol;
	int matchlen, bestmatchlen = -1;
	u_char *mp, *ep, *k, *p, m;

	for (pent = TAILQ_FIRST(&addrsel_policytab); pent;
	     pent = TAILQ_NEXT(pent, ape_entry)) {
		matchlen = 0;

		pol = &pent->ape_policy;
		mp = (u_char *)&pol->addrmask.sin6_addr;
		ep = mp + 16;	/* XXX: scope field? */
		k = (u_char *)&key->sin6_addr;
		p = (u_char *)&pol->addr.sin6_addr;
		for (; mp < ep && *mp; mp++, k++, p++) {
			m = *mp;
			if ((*k & m) != *p)
				goto next; /* not match */
			if (m == 0xff) /* short cut for a typical case */
				matchlen += 8;
			else {
				while (m >= 0x80) {
					matchlen++;
					m <<= 1;
				}
			}
		}

		/* matched.  check if this is better than the current best. */
		if (bestpol == NULL ||
		    matchlen > bestmatchlen) {
			bestpol = pol;
			bestmatchlen = matchlen;
		}

	  next:
		continue;
	}

	return (bestpol);
}