/*      $KAME: getaddrinfo.c,v 1.15 2000/07/09 04:37:24 itojun Exp $    */

/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * 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.
 */

/*
 * Issues to be discussed:
 * - Return values.  There are nonstandard return values defined and used
 *   in the source code.  This is because RFC2553 is silent about which error
 *   code must be returned for which situation.
 * - freeaddrinfo(NULL).  RFC2553 is silent about it.  XNET 5.2 says it is
 *   invalid.  Current code accepts NULL to be compatible with other OSes.
 *
 * Note:
 * - The code filters out AFs that are not supported by the kernel,
 *   when globbing NULL hostname (to loopback, or wildcard).  Is it the right
 *   thing to do?  What is the relationship with post-RFC2553 AI_ADDRCONFIG
 *   in ai_flags?
 * - (post-2553) semantics of AI_ADDRCONFIG itself is too vague.
 *   (1) what should we do against numeric hostname (2) what should we do
 *   against NULL hostname (3) what is AI_ADDRCONFIG itself.  AF not ready?
 *   non-loopback address configured?  global address configured?
 *
 * OS specific notes for freebsd4:
 * - FreeBSD supported $GAI.  The code does not.
 */

#include "namespace.h"
#include <sys/param.h>
#include <sys/socket.h>
#include <net/if.h>
#include <netinet/in.h>
#include <net/if_types.h>
#include <ifaddrs.h>
#include <sys/queue.h>
#ifdef INET6
#include <sys/sysctl.h>
#include <sys/ioctl.h>
#include <netinet6/in6_var.h>
#include <netinet6/nd6.h>
#endif
#include <arpa/inet.h>
#include <arpa/nameser.h>
#include <rpc/rpc.h>
#include <rpcsvc/yp_prot.h>
#include <rpcsvc/ypclnt.h>
#include <netdb.h>
#include <resolv.h>
#include <string.h>
#include <stdlib.h>
#include <stddef.h>
#include <ctype.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>

#include "res_config.h"

#ifdef DEBUG
#include <syslog.h>
#endif

#include <stdarg.h>
#include <nsswitch.h>
#include "un-namespace.h"
#include "netdb_private.h"
#include "libc_private.h"
#ifdef NS_CACHING
#include "nscache.h"
#endif

#define ANY 0
#define YES 1
#define NO  0

static const char in_addrany[] = { 0, 0, 0, 0 };
static const char in_loopback[] = { 127, 0, 0, 1 };
#ifdef INET6
static const char in6_addrany[] = {
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};
static const char in6_loopback[] = {
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1
};
#endif

struct policyqueue {
        TAILQ_ENTRY(policyqueue) pc_entry;
#ifdef INET6
        struct in6_addrpolicy pc_policy;
#endif
};
TAILQ_HEAD(policyhead, policyqueue);

static const struct afd {
        int a_af;
        int a_addrlen;
        socklen_t a_socklen;
        int a_off;
        const char *a_addrany;
        const char *a_loopback;
        int a_scoped;
} afdl [] = {
#ifdef INET6
#define N_INET6 0
        {PF_INET6, sizeof(struct in6_addr),
         sizeof(struct sockaddr_in6),
         offsetof(struct sockaddr_in6, sin6_addr),
         in6_addrany, in6_loopback, 1},
#define N_INET 1
#define N_LOCAL 2
#else
#define N_INET 0
#define N_LOCAL 1
#endif
        {PF_INET, sizeof(struct in_addr),
         sizeof(struct sockaddr_in),
         offsetof(struct sockaddr_in, sin_addr),
         in_addrany, in_loopback, 0},
#define sizeofmember(type, member)      (sizeof(((type *)0)->member))
        {PF_LOCAL, sizeofmember(struct sockaddr_un, sun_path),
         sizeof(struct sockaddr_un),
         offsetof(struct sockaddr_un, sun_path),
         NULL, NULL, 0},
        {0, 0, 0, 0, NULL, NULL, 0},
};

struct explore {
        int e_af;
        int e_socktype;
        int e_protocol;
        int e_wild;
#define AF_ANY          0x01
#define SOCKTYPE_ANY    0x02
#define PROTOCOL_ANY    0x04
#define WILD_AF(ex)             ((ex)->e_wild & AF_ANY)
#define WILD_SOCKTYPE(ex)       ((ex)->e_wild & SOCKTYPE_ANY)
#define WILD_PROTOCOL(ex)       ((ex)->e_wild & PROTOCOL_ANY)
};

static const struct explore explore[] = {
#ifdef INET6
        { PF_INET6, SOCK_DGRAM,  IPPROTO_UDP,
            AF_ANY | SOCKTYPE_ANY | PROTOCOL_ANY },
        { PF_INET6, SOCK_STREAM, IPPROTO_TCP,
            AF_ANY | SOCKTYPE_ANY | PROTOCOL_ANY },
        { PF_INET6, SOCK_STREAM, IPPROTO_SCTP,
            AF_ANY | SOCKTYPE_ANY },
        { PF_INET6, SOCK_SEQPACKET, IPPROTO_SCTP,
            AF_ANY | SOCKTYPE_ANY | PROTOCOL_ANY },
        { PF_INET6, SOCK_DGRAM, IPPROTO_UDPLITE,
            AF_ANY | SOCKTYPE_ANY },
        { PF_INET6, SOCK_RAW, ANY,
            AF_ANY | PROTOCOL_ANY },
#endif
        { PF_INET, SOCK_DGRAM, IPPROTO_UDP,
            AF_ANY | SOCKTYPE_ANY | PROTOCOL_ANY },
        { PF_INET, SOCK_STREAM, IPPROTO_TCP,
            AF_ANY | SOCKTYPE_ANY | PROTOCOL_ANY },
        { PF_INET, SOCK_STREAM, IPPROTO_SCTP,
            AF_ANY | SOCKTYPE_ANY },
        { PF_INET, SOCK_SEQPACKET, IPPROTO_SCTP,
            AF_ANY | SOCKTYPE_ANY | PROTOCOL_ANY },
        { PF_INET, SOCK_DGRAM, IPPROTO_UDPLITE,
            AF_ANY | SOCKTYPE_ANY },
        { PF_INET, SOCK_RAW, ANY,
            AF_ANY | PROTOCOL_ANY },
        { PF_LOCAL, SOCK_DGRAM, ANY,
            AF_ANY | SOCKTYPE_ANY | PROTOCOL_ANY },
        { PF_LOCAL, SOCK_STREAM, ANY,
            AF_ANY | SOCKTYPE_ANY | PROTOCOL_ANY },
        { PF_LOCAL, SOCK_SEQPACKET, ANY,
            AF_ANY | SOCKTYPE_ANY | PROTOCOL_ANY },
        { -1, 0, 0, 0 },
};

#ifdef INET6
#define PTON_MAX        16
#else
#define PTON_MAX        4
#endif

#define AIO_SRCFLAG_DEPRECATED  0x1

struct ai_order {
        union {
                struct sockaddr_storage aiou_ss;
                struct sockaddr aiou_sa;
        } aio_src_un;
#define aio_srcsa aio_src_un.aiou_sa
        u_int32_t aio_srcflag;
        int aio_srcscope;
        int aio_dstscope;
        struct policyqueue *aio_srcpolicy;
        struct policyqueue *aio_dstpolicy;
        struct addrinfo *aio_ai;
        int aio_matchlen;
        int aio_initial_sequence;
};

static const ns_src default_dns_files[] = {
        { NSSRC_FILES,  NS_SUCCESS },
        { NSSRC_DNS,    NS_SUCCESS },
        { 0 }
};

struct res_target {
        struct res_target *next;
        const char *name;       /* domain name */
        int qclass, qtype;      /* class and type of query */
        u_char *answer;         /* buffer to put answer */
        int anslen;             /* size of answer buffer */
        int n;                  /* result length */
};

#define MAXPACKET       (64*1024)

typedef union {
        HEADER hdr;
        u_char buf[MAXPACKET];
} querybuf;

static int str2number(const char *, int *);
static int explore_copy(const struct addrinfo *, const struct addrinfo *,
        struct addrinfo **);
static int explore_null(const struct addrinfo *,
        const char *, struct addrinfo **);
static int explore_numeric(const struct addrinfo *, const char *,
        const char *, struct addrinfo **, const char *);
static int explore_numeric_scope(const struct addrinfo *, const char *,
        const char *, struct addrinfo **);
static int get_canonname(const struct addrinfo *,
        struct addrinfo *, const char *);
static struct addrinfo *get_ai(const struct addrinfo *,
        const struct afd *, const char *);
static struct addrinfo *copy_ai(const struct addrinfo *);
static int get_portmatch(const struct addrinfo *, const char *);
static int get_port(struct addrinfo *, const char *, int);
static const struct afd *find_afd(int);
static int addrconfig(struct addrinfo *);
#ifdef INET6
static int is_ifdisabled(char *);
#endif
static void set_source(struct ai_order *, struct policyhead *);
static int comp_dst(const void *, const void *);
#ifdef INET6
static int ip6_str2scopeid(char *, struct sockaddr_in6 *, u_int32_t *);
#endif
static int gai_addr2scopetype(struct sockaddr *);

static int explore_fqdn(const struct addrinfo *, const char *,
        const char *, struct addrinfo **);

static int reorder(struct addrinfo *);
static int get_addrselectpolicy(struct policyhead *);
static void free_addrselectpolicy(struct policyhead *);
static struct policyqueue *match_addrselectpolicy(struct sockaddr *,
        struct policyhead *);
static int matchlen(struct sockaddr *, struct sockaddr *);

static struct addrinfo *getanswer(const querybuf *, int, const char *, int,
        const struct addrinfo *, res_state);
#if defined(RESOLVSORT)
static int addr4sort(struct addrinfo *, res_state);
#endif
static int _dns_getaddrinfo(void *, void *, va_list);
static void _sethtent(FILE **);
static void _endhtent(FILE **);
static struct addrinfo *_gethtent(FILE **, const char *,
        const struct addrinfo *);
static int _files_getaddrinfo(void *, void *, va_list);
#ifdef YP
static struct addrinfo *_yphostent(char *, const struct addrinfo *);
static int _yp_getaddrinfo(void *, void *, va_list);
#endif
#ifdef NS_CACHING
static int addrinfo_id_func(char *, size_t *, va_list, void *);
static int addrinfo_marshal_func(char *, size_t *, void *, va_list, void *);
static int addrinfo_unmarshal_func(char *, size_t, void *, va_list, void *);
#endif

static int res_queryN(const char *, struct res_target *, res_state);
static int res_searchN(const char *, struct res_target *, res_state);
static int res_querydomainN(const char *, const char *,
        struct res_target *, res_state);

/* XXX macros that make external reference is BAD. */

#define GET_AI(ai, afd, addr) \
do { \
        /* external reference: pai, error, and label free */ \
        (ai) = get_ai(pai, (afd), (addr)); \
        if ((ai) == NULL) { \
                error = EAI_MEMORY; \
                goto free; \
        } \
} while (/*CONSTCOND*/0)

#define GET_PORT(ai, serv) \
do { \
        /* external reference: error and label free */ \
        error = get_port((ai), (serv), 0); \
        if (error != 0) \
                goto free; \
} while (/*CONSTCOND*/0)

#define GET_CANONNAME(ai, str) \
do { \
        /* external reference: pai, error and label free */ \
        error = get_canonname(pai, (ai), (str)); \
        if (error != 0) \
                goto free; \
} while (/*CONSTCOND*/0)

#define ERR(err) \
do { \
        /* external reference: error, and label bad */ \
        error = (err); \
        goto bad; \
        /*NOTREACHED*/ \
} while (/*CONSTCOND*/0)

#define MATCH_FAMILY(x, y, w) \
        ((x) == (y) || (/*CONSTCOND*/(w) && ((x) == PF_UNSPEC || (y) == PF_UNSPEC)))
#define MATCH(x, y, w) \
        ((x) == (y) || (/*CONSTCOND*/(w) && ((x) == ANY || (y) == ANY)))

void
freeaddrinfo(struct addrinfo *ai)
{
        struct addrinfo *next;

        while (ai != NULL) {
                next = ai->ai_next;
                free(ai->ai_canonname);
                /* no need to free(ai->ai_addr) */
                free(ai);
                ai = next;
        }
}

static int
str2number(const char *p, int *portp)
{
        char *ep;
        unsigned long v;

        if (*p == '\0')
                return -1;
        ep = NULL;
        errno = 0;
        v = strtoul(p, &ep, 10);
        if (errno == 0 && ep && *ep == '\0' && v <= UINT_MAX) {
                *portp = v;
                return 0;
        } else
                return -1;
}

int
getaddrinfo(const char *hostname, const char *servname,
    const struct addrinfo *hints, struct addrinfo **res)
{
        struct addrinfo sentinel;
        struct addrinfo *cur;
        int error = 0;
        struct addrinfo ai, ai0, *afai;
        struct addrinfo *pai;
        const struct afd *afd;
        const struct explore *ex;
        struct addrinfo *afailist[nitems(afdl)];
        struct addrinfo *afai_unspec;
        int found;
        int numeric = 0;

        /* ensure we return NULL on errors */
        *res = NULL;

        memset(&ai, 0, sizeof(ai));

        memset(afailist, 0, sizeof(afailist));
        afai_unspec = NULL;

        memset(&sentinel, 0, sizeof(sentinel));
        cur = &sentinel;
        pai = &ai;
        pai->ai_flags = 0;
        pai->ai_family = PF_UNSPEC;
        pai->ai_socktype = ANY;
        pai->ai_protocol = ANY;
        pai->ai_addrlen = 0;
        pai->ai_canonname = NULL;
        pai->ai_addr = NULL;
        pai->ai_next = NULL;

        if (hostname == NULL && servname == NULL)
                return EAI_NONAME;
        if (hints) {
                /* error check for hints */
                if (hints->ai_addrlen || hints->ai_canonname ||
                    hints->ai_addr || hints->ai_next)
                        ERR(EAI_BADHINTS); /* xxx */
                if (hints->ai_flags & ~AI_MASK)
                        ERR(EAI_BADFLAGS);
                switch (hints->ai_family) {
                case PF_UNSPEC:
                case PF_LOCAL:
                case PF_INET:
#ifdef INET6
                case PF_INET6:
#endif
                        break;
                default:
                        ERR(EAI_FAMILY);
                }
                memcpy(pai, hints, sizeof(*pai));

                /*
                 * if both socktype/protocol are specified, check if they
                 * are meaningful combination.
                 */
                if (pai->ai_socktype != ANY && pai->ai_protocol != ANY) {
                        for (ex = explore; ex->e_af >= 0; ex++) {
                                if (!MATCH_FAMILY(pai->ai_family, ex->e_af,
                                    WILD_AF(ex)))
                                        continue;
                                if (!MATCH(pai->ai_socktype, ex->e_socktype,
                                    WILD_SOCKTYPE(ex)))
                                        continue;
                                if (!MATCH(pai->ai_protocol, ex->e_protocol,
                                    WILD_PROTOCOL(ex)))
                                        continue;

                                /* matched */
                                break;
                        }

                        if (ex->e_af < 0)
                                ERR(EAI_BADHINTS);
                }
        }

        /*
         * RFC 3493: AI_ALL and AI_V4MAPPED are effective only against
         * AF_INET6 query.  They need to be ignored if specified in other
         * occasions.
         */
        switch (pai->ai_flags & (AI_ALL | AI_V4MAPPED)) {
        case AI_V4MAPPED:
        case AI_ALL | AI_V4MAPPED:
#ifdef INET6
                if (pai->ai_family != AF_INET6)
                        pai->ai_flags &= ~(AI_ALL | AI_V4MAPPED);
                break;
#endif
        case AI_ALL:
                pai->ai_flags &= ~(AI_ALL | AI_V4MAPPED);
                break;
        }

        /*
         * check for special cases.  (1) numeric servname is disallowed if
         * socktype/protocol are left unspecified. (2) servname is disallowed
         * for raw and other inet{,6} sockets.
         */
        if (MATCH_FAMILY(pai->ai_family, PF_INET, 1)
#ifdef PF_INET6
            || MATCH_FAMILY(pai->ai_family, PF_INET6, 1)
#endif
            ) {
                ai0 = *pai;     /* backup *pai */

                if (pai->ai_family == PF_UNSPEC) {
#ifdef PF_INET6
                        pai->ai_family = PF_INET6;
#else
                        pai->ai_family = PF_INET;
#endif
                }
                error = get_portmatch(pai, servname);
                if (error)
                        goto bad;

                *pai = ai0;
        }

        ai0 = *pai;

        /*
         * NULL hostname, or numeric hostname.
         * If numeric representation of AF1 can be interpreted as FQDN
         * representation of AF2, we need to think again about the code below.
         */
        found = 0;
        for (afd = afdl; afd->a_af; afd++) {
                *pai = ai0;

                if (!MATCH_FAMILY(pai->ai_family, afd->a_af, 1))
                        continue;

                if (pai->ai_family == PF_UNSPEC)
                        pai->ai_family = afd->a_af;

                if (hostname == NULL) {
                        error = explore_null(pai, servname,
                            &afailist[afd - afdl]);

                        /*
                         * Errors from explore_null should be unexpected and
                         * be caught to avoid returning an incomplete result.
                         */
                        if (error != 0)
                                goto bad;
                } else {
                        error = explore_numeric_scope(pai, hostname, servname,
                            &afailist[afd - afdl]);

                        /*
                         * explore_numeric_scope returns an error for address
                         * families that do not match that of hostname.
                         * Thus we should not catch the error at this moment. 
                         */
                }

                if (!error && afailist[afd - afdl])
                        found++;
        }
        if (found) {
                numeric = 1;
                goto globcopy;
        }

        if (hostname == NULL)
                ERR(EAI_NONAME);        /* used to be EAI_NODATA */
        if (pai->ai_flags & AI_NUMERICHOST)
                ERR(EAI_NONAME);

        if ((pai->ai_flags & AI_ADDRCONFIG) != 0 && !addrconfig(&ai0))
                ERR(EAI_FAIL);

        /*
         * hostname as alphabetical name.
         */
        *pai = ai0;
        error = explore_fqdn(pai, hostname, servname, &afai_unspec);

globcopy:
        for (ex = explore; ex->e_af >= 0; ex++) {
                *pai = ai0;

                if (!MATCH_FAMILY(pai->ai_family, ex->e_af, WILD_AF(ex)))
                        continue;
                if (!MATCH(pai->ai_socktype, ex->e_socktype,
                    WILD_SOCKTYPE(ex)))
                        continue;
                if (!MATCH(pai->ai_protocol, ex->e_protocol,
                    WILD_PROTOCOL(ex)))
                        continue;

                if (pai->ai_family == PF_UNSPEC)
                        pai->ai_family = ex->e_af;
                if (pai->ai_socktype == ANY && ex->e_socktype != ANY)
                        pai->ai_socktype = ex->e_socktype;
                if (pai->ai_protocol == ANY && ex->e_protocol != ANY)
                        pai->ai_protocol = ex->e_protocol;

                /*
                 * if the servname does not match socktype/protocol, ignore it.
                 */
                if (get_portmatch(pai, servname) != 0)
                        continue;

                if (afai_unspec)
                        afai = afai_unspec;
                else {
                        if ((afd = find_afd(pai->ai_family)) == NULL)
                                continue;
                        /* XXX assumes that afd points inside afdl[] */
                        afai = afailist[afd - afdl];
                }
                if (!afai)
                        continue;

                error = explore_copy(pai, afai, &cur->ai_next);
                if (error != 0)
                        goto bad;

                while (cur && cur->ai_next)
                        cur = cur->ai_next;
        }

        /*
         * ensure we return either:
         * - error == 0, non-NULL *res
         * - error != 0, NULL *res
         */
        if (error == 0) {
                if (sentinel.ai_next) {
                        /*
                         * If the returned entry is for an active connection,
                         * and the given name is not numeric, reorder the
                         * list, so that the application would try the list
                         * in the most efficient order.  Since the head entry
                         * of the original list may contain ai_canonname and
                         * that entry may be moved elsewhere in the new list,
                         * we keep the pointer and will  restore it in the new
                         * head entry.  (Note that RFC3493 requires the head
                         * entry store it when requested by the caller).
                         */
                        if (hints == NULL || !(hints->ai_flags & AI_PASSIVE)) {
                                if (!numeric) {
                                        char *canonname;

                                        canonname =
                                            sentinel.ai_next->ai_canonname;
                                        sentinel.ai_next->ai_canonname = NULL;
                                        (void)reorder(&sentinel);
                                        if (sentinel.ai_next->ai_canonname ==
                                            NULL) {
                                                sentinel.ai_next->ai_canonname
                                                    = canonname;
                                        } else if (canonname != NULL)
                                                free(canonname);
                                }
                        }
                        *res = sentinel.ai_next;
                } else
                        error = EAI_FAIL;
        }

bad:
        if (afai_unspec)
                freeaddrinfo(afai_unspec);
        for (afd = afdl; afd->a_af; afd++) {
                if (afailist[afd - afdl])
                        freeaddrinfo(afailist[afd - afdl]);
        }
        if (!*res)
                if (sentinel.ai_next)
                        freeaddrinfo(sentinel.ai_next);

        return (error);
}

static int
reorder(struct addrinfo *sentinel)
{
        struct addrinfo *ai, **aip;
        struct ai_order *aio;
        int i, n;
        struct policyhead policyhead;

        /* count the number of addrinfo elements for sorting. */
        for (n = 0, ai = sentinel->ai_next; ai != NULL; ai = ai->ai_next, n++)
                ;

        /*
         * If the number is small enough, we can skip the reordering process.
         */
        if (n <= 1)
                return(n);

        /* allocate a temporary array for sort and initialization of it. */
        if ((aio = calloc(n, sizeof(*aio))) == NULL)
                return(n);      /* give up reordering */

        /* retrieve address selection policy from the kernel */
        TAILQ_INIT(&policyhead);
        if (!get_addrselectpolicy(&policyhead)) {
                /* no policy is installed into kernel, we don't sort. */
                free(aio);
                return (n);
        }

        for (i = 0, ai = sentinel->ai_next; i < n; ai = ai->ai_next, i++) {
                aio[i].aio_ai = ai;
                aio[i].aio_dstscope = gai_addr2scopetype(ai->ai_addr);
                aio[i].aio_dstpolicy = match_addrselectpolicy(ai->ai_addr,
                                                              &policyhead);
                set_source(&aio[i], &policyhead);
                aio[i].aio_initial_sequence = i;
        }

        /* perform sorting. */
        qsort(aio, n, sizeof(*aio), comp_dst);

        /* reorder the addrinfo chain. */
        for (i = 0, aip = &sentinel->ai_next; i < n; i++) {
                *aip = aio[i].aio_ai;
                aip = &aio[i].aio_ai->ai_next;
        }
        *aip = NULL;

        /* cleanup and return */
        free(aio);
        free_addrselectpolicy(&policyhead);
        return(n);
}

static int
get_addrselectpolicy(struct policyhead *head)
{
#ifdef INET6
        int mib[] = { CTL_NET, PF_INET6, IPPROTO_IPV6, IPV6CTL_ADDRCTLPOLICY };
        size_t l;
        char *buf;
        struct in6_addrpolicy *pol, *ep;

        if (sysctl(mib, nitems(mib), NULL, &l, NULL, 0) < 0)
                return (0);
        if (l == 0)
                return (0);
        if ((buf = malloc(l)) == NULL)
                return (0);
        if (sysctl(mib, nitems(mib), buf, &l, NULL, 0) < 0) {
                free(buf);
                return (0);
        }

        ep = (struct in6_addrpolicy *)(buf + l);
        for (pol = (struct in6_addrpolicy *)buf; pol + 1 <= ep; pol++) {
                struct policyqueue *new;

                if ((new = malloc(sizeof(*new))) == NULL) {
                        free_addrselectpolicy(head); /* make the list empty */
                        break;
                }
                new->pc_policy = *pol;
                TAILQ_INSERT_TAIL(head, new, pc_entry);
        }

        free(buf);
        return (1);
#else
        return (0);
#endif
}

static void
free_addrselectpolicy(struct policyhead *head)
{
        struct policyqueue *ent, *nent;

        for (ent = TAILQ_FIRST(head); ent; ent = nent) {
                nent = TAILQ_NEXT(ent, pc_entry);
                TAILQ_REMOVE(head, ent, pc_entry);
                free(ent);
        }
}

static struct policyqueue *
match_addrselectpolicy(struct sockaddr *addr, struct policyhead *head)
{
#ifdef INET6
        struct policyqueue *ent, *bestent = NULL;
        struct in6_addrpolicy *pol;
        int matchlen, bestmatchlen = -1;
        u_char *mp, *ep, *k, *p, m;
        struct sockaddr_in6 key;

        switch(addr->sa_family) {
        case AF_INET6:
                key = *(struct sockaddr_in6 *)addr;
                break;
        case AF_INET:
                /* convert the address into IPv4-mapped IPv6 address. */
                memset(&key, 0, sizeof(key));
                key.sin6_family = AF_INET6;
                key.sin6_len = sizeof(key);
                _map_v4v6_address(
                    (char *)&((struct sockaddr_in *)addr)->sin_addr,
                    (char *)&key.sin6_addr);
                break;
        default:
                return(NULL);
        }

        for (ent = TAILQ_FIRST(head); ent; ent = TAILQ_NEXT(ent, pc_entry)) {
                pol = &ent->pc_policy;
                matchlen = 0;

                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 (matchlen > bestmatchlen) {
                        bestent = ent;
                        bestmatchlen = matchlen;
                }

          next:
                continue;
        }

        return(bestent);
#else
        return(NULL);
#endif

}

static void
set_source(struct ai_order *aio, struct policyhead *ph)
{
        struct addrinfo ai = *aio->aio_ai;
        struct sockaddr_storage ss;
        socklen_t srclen;
        int s;

        /* set unspec ("no source is available"), just in case */
        aio->aio_srcsa.sa_family = AF_UNSPEC;
        aio->aio_srcscope = -1;

        switch(ai.ai_family) {
        case AF_INET:
#ifdef INET6
        case AF_INET6:
#endif
                break;
        default:                /* ignore unsupported AFs explicitly */
                return;
        }

        /* XXX: make a dummy addrinfo to call connect() */
        ai.ai_socktype = SOCK_DGRAM;
        ai.ai_protocol = IPPROTO_UDP; /* is UDP too specific? */
        ai.ai_next = NULL;
        memset(&ss, 0, sizeof(ss));
        memcpy(&ss, ai.ai_addr, ai.ai_addrlen);
        ai.ai_addr = (struct sockaddr *)&ss;
        get_port(&ai, "1", 0);

        /* open a socket to get the source address for the given dst */
        if ((s = _socket(ai.ai_family, ai.ai_socktype | SOCK_CLOEXEC,
            ai.ai_protocol)) < 0)
                return;         /* give up */
#ifdef INET6
        if (ai.ai_family == AF_INET6) {
                struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)ai.ai_addr;
                int off = 0;

                if (IN6_IS_ADDR_V4MAPPED(&sin6->sin6_addr))
                        (void)_setsockopt(s, IPPROTO_IPV6, IPV6_V6ONLY,
                            (char *)&off, sizeof(off));
        }
#endif
        if (_connect(s, ai.ai_addr, ai.ai_addrlen) < 0)
                goto cleanup;
        srclen = ai.ai_addrlen;
        if (_getsockname(s, &aio->aio_srcsa, &srclen) < 0) {
                aio->aio_srcsa.sa_family = AF_UNSPEC;
                goto cleanup;
        }
        aio->aio_srcscope = gai_addr2scopetype(&aio->aio_srcsa);
        aio->aio_srcpolicy = match_addrselectpolicy(&aio->aio_srcsa, ph);
        aio->aio_matchlen = matchlen(&aio->aio_srcsa, aio->aio_ai->ai_addr);
#ifdef INET6
        if (ai.ai_family == AF_INET6) {
                struct in6_ifreq ifr6;
                u_int32_t flags6;

                memset(&ifr6, 0, sizeof(ifr6));
                memcpy(&ifr6.ifr_addr, ai.ai_addr, ai.ai_addrlen);
                if (_ioctl(s, SIOCGIFAFLAG_IN6, &ifr6) == 0) {
                        flags6 = ifr6.ifr_ifru.ifru_flags6;
                        if ((flags6 & IN6_IFF_DEPRECATED))
                                aio->aio_srcflag |= AIO_SRCFLAG_DEPRECATED;
                }
        }
#endif

  cleanup:
        _close(s);
        return;
}

static int
matchlen(struct sockaddr *src, struct sockaddr *dst)
{
        int match = 0;
        u_char *s, *d;
        u_char *lim, r;
        int addrlen;

        switch (src->sa_family) {
#ifdef INET6
        case AF_INET6:
                s = (u_char *)&((struct sockaddr_in6 *)src)->sin6_addr;
                d = (u_char *)&((struct sockaddr_in6 *)dst)->sin6_addr;
                addrlen = sizeof(struct in6_addr);
                lim = s + addrlen;
                break;
#endif
        case AF_INET:
                s = (u_char *)&((struct sockaddr_in *)src)->sin_addr;
                d = (u_char *)&((struct sockaddr_in *)dst)->sin_addr;
                addrlen = sizeof(struct in_addr);
                lim = s + addrlen;
                break;
        default:
                return(0);
        }

        while (s < lim)
                if ((r = (*d++ ^ *s++)) != 0) {
                        while ((r & 0x80) == 0) {
                                match++;
                                r <<= 1;
                        }
                        break;
                } else
                        match += 8;
        return(match);
}

static int
comp_dst(const void *arg1, const void *arg2)
{
        const struct ai_order *dst1 = arg1, *dst2 = arg2;

        /*
         * Rule 1: Avoid unusable destinations.
         * XXX: we currently do not consider if an appropriate route exists.
         */
        if (dst1->aio_srcsa.sa_family != AF_UNSPEC &&
            dst2->aio_srcsa.sa_family == AF_UNSPEC) {
                return(-1);
        }
        if (dst1->aio_srcsa.sa_family == AF_UNSPEC &&
            dst2->aio_srcsa.sa_family != AF_UNSPEC) {
                return(1);
        }

        /* Rule 2: Prefer matching scope. */
        if (dst1->aio_dstscope == dst1->aio_srcscope &&
            dst2->aio_dstscope != dst2->aio_srcscope) {
                return(-1);
        }
        if (dst1->aio_dstscope != dst1->aio_srcscope &&
            dst2->aio_dstscope == dst2->aio_srcscope) {
                return(1);
        }

        /* Rule 3: Avoid deprecated addresses. */
        if (dst1->aio_srcsa.sa_family != AF_UNSPEC &&
            dst2->aio_srcsa.sa_family != AF_UNSPEC) {
                if (!(dst1->aio_srcflag & AIO_SRCFLAG_DEPRECATED) &&
                    (dst2->aio_srcflag & AIO_SRCFLAG_DEPRECATED)) {
                        return(-1);
                }
                if ((dst1->aio_srcflag & AIO_SRCFLAG_DEPRECATED) &&
                    !(dst2->aio_srcflag & AIO_SRCFLAG_DEPRECATED)) {
                        return(1);
                }
        }

        /* Rule 4: Prefer home addresses. */
        /* XXX: not implemented yet */

        /* Rule 5: Prefer matching label. */
#ifdef INET6
        if (dst1->aio_srcpolicy && dst1->aio_dstpolicy &&
            dst1->aio_srcpolicy->pc_policy.label ==
            dst1->aio_dstpolicy->pc_policy.label &&
            (dst2->aio_srcpolicy == NULL || dst2->aio_dstpolicy == NULL ||
             dst2->aio_srcpolicy->pc_policy.label !=
             dst2->aio_dstpolicy->pc_policy.label)) {
                return(-1);
        }
        if (dst2->aio_srcpolicy && dst2->aio_dstpolicy &&
            dst2->aio_srcpolicy->pc_policy.label ==
            dst2->aio_dstpolicy->pc_policy.label &&
            (dst1->aio_srcpolicy == NULL || dst1->aio_dstpolicy == NULL ||
             dst1->aio_srcpolicy->pc_policy.label !=
             dst1->aio_dstpolicy->pc_policy.label)) {
                return(1);
        }
#endif

        /* Rule 6: Prefer higher precedence. */
#ifdef INET6
        if (dst1->aio_dstpolicy &&
            (dst2->aio_dstpolicy == NULL ||
             dst1->aio_dstpolicy->pc_policy.preced >
             dst2->aio_dstpolicy->pc_policy.preced)) {
                return(-1);
        }
        if (dst2->aio_dstpolicy &&
            (dst1->aio_dstpolicy == NULL ||
             dst2->aio_dstpolicy->pc_policy.preced >
             dst1->aio_dstpolicy->pc_policy.preced)) {
                return(1);
        }
#endif

        /* Rule 7: Prefer native transport. */
        /* XXX: not implemented yet */

        /* Rule 8: Prefer smaller scope. */
        if (dst1->aio_dstscope >= 0 &&
            dst1->aio_dstscope < dst2->aio_dstscope) {
                return(-1);
        }
        if (dst2->aio_dstscope >= 0 &&
            dst2->aio_dstscope < dst1->aio_dstscope) {
                return(1);
        }

        /*
         * Rule 9: Use longest matching prefix.
         * We compare the match length in a same AF only.
         */
        if (dst1->aio_ai->ai_addr->sa_family ==
            dst2->aio_ai->ai_addr->sa_family &&
            dst1->aio_ai->ai_addr->sa_family != AF_INET) {
                if (dst1->aio_matchlen > dst2->aio_matchlen) {
                        return(-1);
                }
                if (dst1->aio_matchlen < dst2->aio_matchlen) {
                        return(1);
                }
        }

        /* Rule 10: Otherwise, leave the order unchanged. */

        /* 
         * Note that qsort is unstable; so, we can't return zero and 
         * expect the order to be unchanged.
         * That also means we can't depend on the current position of
         * dst2 being after dst1.  We must enforce the initial order
         * with an explicit compare on the original position.
         * The qsort specification requires that "When the same objects 
         * (consisting of width bytes, irrespective of their current 
         * positions in the array) are passed more than once to the 
         * comparison function, the results shall be consistent with one 
         * another."  
         * In other words, If A < B, then we must also return B > A.
         */
        if (dst2->aio_initial_sequence < dst1->aio_initial_sequence)
                return(1);

        return(-1);
}

/*
 * Copy from scope.c.
 * XXX: we should standardize the functions and link them as standard
 * library.
 */
static int
gai_addr2scopetype(struct sockaddr *sa)
{
#ifdef INET6
        struct sockaddr_in6 *sa6;
#endif
        struct sockaddr_in *sa4;

        switch(sa->sa_family) {
#ifdef INET6
        case AF_INET6:
                sa6 = (struct sockaddr_in6 *)sa;
                if (IN6_IS_ADDR_MULTICAST(&sa6->sin6_addr)) {
                        /* just use the scope field of the multicast address */
                        return(sa6->sin6_addr.s6_addr[2] & 0x0f);
                }
                /*
                 * Unicast addresses: map scope type to corresponding scope
                 * value defined for multcast addresses.
                 * XXX: hardcoded scope type values are bad...
                 */
                if (IN6_IS_ADDR_LOOPBACK(&sa6->sin6_addr))
                        return(1); /* node local scope */
                if (IN6_IS_ADDR_LINKLOCAL(&sa6->sin6_addr))
                        return(2); /* link-local scope */
                if (IN6_IS_ADDR_SITELOCAL(&sa6->sin6_addr))
                        return(5); /* site-local scope */
                return(14);     /* global scope */
                break;
#endif
        case AF_INET:
                /*
                 * IPv4 pseudo scoping according to RFC 3484.
                 */
                sa4 = (struct sockaddr_in *)sa;
                /* IPv4 autoconfiguration addresses have link-local scope. */
                if (((u_char *)&sa4->sin_addr)[0] == 169 &&
                    ((u_char *)&sa4->sin_addr)[1] == 254)
                        return(2);
                /* Private addresses have site-local scope. */
                if (((u_char *)&sa4->sin_addr)[0] == 10 ||
                    (((u_char *)&sa4->sin_addr)[0] == 172 &&
                     (((u_char *)&sa4->sin_addr)[1] & 0xf0) == 16) ||
                    (((u_char *)&sa4->sin_addr)[0] == 192 &&
                     ((u_char *)&sa4->sin_addr)[1] == 168))
                        return(14);     /* XXX: It should be 5 unless NAT */
                /* Loopback addresses have link-local scope. */
                if (((u_char *)&sa4->sin_addr)[0] == 127)
                        return(2);
                return(14);
                break;
        default:
                errno = EAFNOSUPPORT; /* is this a good error? */
                return(-1);
        }
}

static int
explore_copy(const struct addrinfo *pai, const struct addrinfo *src0,
    struct addrinfo **res)
{
        int error;
        struct addrinfo sentinel, *cur;
        const struct addrinfo *src;

        error = 0;
        sentinel.ai_next = NULL;
        cur = &sentinel;

        for (src = src0; src != NULL; src = src->ai_next) {
                if (src->ai_family != pai->ai_family)
                        continue;

                cur->ai_next = copy_ai(src);
                if (!cur->ai_next) {
                        error = EAI_MEMORY;
                        goto fail;
                }

                cur->ai_next->ai_socktype = pai->ai_socktype;
                cur->ai_next->ai_protocol = pai->ai_protocol;
                cur = cur->ai_next;
        }

        *res = sentinel.ai_next;
        return 0;

fail:
        freeaddrinfo(sentinel.ai_next);
        return error;
}

/*
 * hostname == NULL.
 * passive socket -> anyaddr (0.0.0.0 or ::)
 * non-passive socket -> localhost (127.0.0.1 or ::1)
 */
static int
explore_null(const struct addrinfo *pai, const char *servname,
    struct addrinfo **res)
{
        int s;
        const struct afd *afd;
        struct addrinfo *ai;
        int error;

        *res = NULL;
        ai = NULL;

        if (pai->ai_family == PF_LOCAL)
                return (0);

        /*
         * filter out AFs that are not supported by the kernel
         * XXX errno?
         */
        s = _socket(pai->ai_family, SOCK_DGRAM | SOCK_CLOEXEC, 0);
        if (s < 0) {
                if (errno != EMFILE)
                        return 0;
        } else
                _close(s);

        afd = find_afd(pai->ai_family);
        if (afd == NULL)
                return 0;

        if (pai->ai_flags & AI_PASSIVE) {
                GET_AI(ai, afd, afd->a_addrany);
                GET_PORT(ai, servname);
        } else {
                GET_AI(ai, afd, afd->a_loopback);
                GET_PORT(ai, servname);
        }

        *res = ai;
        return 0;

free:
        if (ai != NULL)
                freeaddrinfo(ai);
        return error;
}

/*
 * numeric hostname
 */
static int
explore_numeric(const struct addrinfo *pai, const char *hostname,
    const char *servname, struct addrinfo **res, const char *canonname)
{
        const struct afd *afd;
        struct addrinfo *ai, ai0;
        int error;
        char pton[PTON_MAX], path[PATH_MAX], *p;

#ifdef CTASSERT
        CTASSERT(sizeofmember(struct sockaddr_un, sun_path) <= PATH_MAX);
#endif
        *res = NULL;
        ai = NULL;

        afd = find_afd(pai->ai_family);
        if (afd == NULL)
                return 0;

        switch (afd->a_af) {
        case AF_LOCAL:
                if (hostname[0] != '/')
                        ERR(EAI_NONAME);
                if (strlen(hostname) > afd->a_addrlen)
                        ERR(EAI_MEMORY);
                /* NUL-termination does not need to be guaranteed. */
                strncpy(path, hostname, afd->a_addrlen);
                p = &path[0];
                break;
        case AF_INET:
                /*
                 * RFC3493 requires getaddrinfo() to accept AF_INET formats
                 * that are accepted by inet_addr() and its family.  The
                 * accepted forms includes the "classful" one, which inet_pton
                 * does not accept.  So we need to separate the case for
                 * AF_INET.
                 */
                if (inet_aton(hostname, (struct in_addr *)pton) != 1 ||
                    hostname[strspn(hostname, "0123456789.xabcdefXABCDEF")] != '\0')
                        return 0;
                p = pton;
                break;
        default:
                if (inet_pton(afd->a_af, hostname, pton) != 1) {
                        if (pai->ai_family != AF_INET6 ||
                            (pai->ai_flags & AI_V4MAPPED) != AI_V4MAPPED)
                                return 0;
                        if (inet_aton(hostname, (struct in_addr *)pton) != 1)
                                return 0;
                        afd = &afdl[N_INET];
                        ai0 = *pai;
                        ai0.ai_family = AF_INET;
                        pai = &ai0;
                }
                p = pton;
                break;
        }

        if (pai->ai_family == afd->a_af) {
                GET_AI(ai, afd, p);
                GET_PORT(ai, servname);
                if ((pai->ai_family == AF_INET ||
                     pai->ai_family == AF_INET6) &&
                    (pai->ai_flags & AI_CANONNAME)) {
                        /*
                         * Set the numeric address itself as the canonical
                         * name, based on a clarification in RFC3493.
                         */
                        GET_CANONNAME(ai, canonname);
                }
        } else {
                /*
                 * XXX: This should not happen since we already matched the AF
                 * by find_afd.
                 */
                ERR(EAI_FAMILY);
        }

        *res = ai;
        return 0;

free:
bad:
        if (ai != NULL)
                freeaddrinfo(ai);
        return error;
}

/*
 * numeric hostname with scope
 */
static int
explore_numeric_scope(const struct addrinfo *pai, const char *hostname,
    const char *servname, struct addrinfo **res)
{
#if !defined(SCOPE_DELIMITER) || !defined(INET6)
        return explore_numeric(pai, hostname, servname, res, hostname);
#else
        const struct afd *afd;
        struct addrinfo *cur;
        int error;
        char *cp, *hostname2 = NULL, *scope, *addr;
        struct sockaddr_in6 *sin6;

        afd = find_afd(pai->ai_family);
        if (afd == NULL)
                return 0;

        if (!afd->a_scoped)
                return explore_numeric(pai, hostname, servname, res, hostname);

        cp = strchr(hostname, SCOPE_DELIMITER);
        if (cp == NULL)
                return explore_numeric(pai, hostname, servname, res, hostname);

        /*
         * Handle special case of <scoped_address><delimiter><scope id>
         */
        hostname2 = strdup(hostname);
        if (hostname2 == NULL)
                return EAI_MEMORY;
        /* terminate at the delimiter */
        hostname2[cp - hostname] = '\0';
        addr = hostname2;
        scope = cp + 1;

        error = explore_numeric(pai, addr, servname, res, hostname);
        if (error == 0) {
                u_int32_t scopeid;

                for (cur = *res; cur; cur = cur->ai_next) {
                        if (cur->ai_family != AF_INET6)
                                continue;
                        sin6 = (struct sockaddr_in6 *)(void *)cur->ai_addr;
                        if (ip6_str2scopeid(scope, sin6, &scopeid) == -1) {
                                free(hostname2);
                                freeaddrinfo(*res);
                                *res = NULL;
                                return(EAI_NONAME); /* XXX: is return OK? */
                        }
                        sin6->sin6_scope_id = scopeid;
                }
        }

        free(hostname2);

        if (error && *res) {
                freeaddrinfo(*res);
                *res = NULL;
        }
        return error;
#endif
}

static int
get_canonname(const struct addrinfo *pai, struct addrinfo *ai, const char *str)
{
        if ((pai->ai_flags & AI_CANONNAME) != 0) {
                ai->ai_canonname = strdup(str);
                if (ai->ai_canonname == NULL)
                        return EAI_MEMORY;
        }
        return 0;
}

static struct addrinfo *
get_ai(const struct addrinfo *pai, const struct afd *afd, const char *addr)
{
        char *p;
        struct addrinfo *ai;
#ifdef INET6
        struct in6_addr mapaddr;

        if (afd->a_af == AF_INET && (pai->ai_flags & AI_V4MAPPED) != 0) {
                afd = &afdl[N_INET6];
                _map_v4v6_address(addr, (char *)&mapaddr);
                addr = (char *)&mapaddr;
        }
#endif

        ai = (struct addrinfo *)malloc(sizeof(struct addrinfo)
                + (afd->a_socklen));
        if (ai == NULL)
                return NULL;

        memcpy(ai, pai, sizeof(struct addrinfo));
        ai->ai_addr = (struct sockaddr *)(void *)(ai + 1);
        memset(ai->ai_addr, 0, (size_t)afd->a_socklen);
        ai->ai_addr->sa_len = afd->a_socklen;
        ai->ai_addrlen = afd->a_socklen;
        if (ai->ai_family == PF_LOCAL) {
                size_t n = strnlen(addr, afd->a_addrlen);

                ai->ai_addrlen -= afd->a_addrlen - n;
                ai->ai_addr->sa_len -= afd->a_addrlen - n;
        }
        ai->ai_addr->sa_family = ai->ai_family = afd->a_af;
        p = (char *)(void *)(ai->ai_addr);
        memcpy(p + afd->a_off, addr, (size_t)afd->a_addrlen);
        return ai;
}

/* XXX need to malloc() the same way we do from other functions! */
static struct addrinfo *
copy_ai(const struct addrinfo *pai)
{
        struct addrinfo *ai;
        size_t l;

        l = sizeof(*ai) + pai->ai_addrlen;
        if ((ai = calloc(1, l)) == NULL)
                return NULL;
        memcpy(ai, pai, sizeof(*ai));
        ai->ai_addr = (struct sockaddr *)(void *)(ai + 1);
        memcpy(ai->ai_addr, pai->ai_addr, pai->ai_addrlen);

        if (pai->ai_canonname) {
                l = strlen(pai->ai_canonname) + 1;
                if ((ai->ai_canonname = malloc(l)) == NULL) {
                        free(ai);
                        return NULL;
                }
                strlcpy(ai->ai_canonname, pai->ai_canonname, l);
        } else {
                /* just to make sure */
                ai->ai_canonname = NULL;
        }

        ai->ai_next = NULL;

        return ai;
}

static int
get_portmatch(const struct addrinfo *ai, const char *servname)
{

        /* get_port does not touch first argument when matchonly == 1. */
        /* LINTED const cast */
        return get_port((struct addrinfo *)ai, servname, 1);
}

static int
get_port(struct addrinfo *ai, const char *servname, int matchonly)
{
        const char *proto;
        struct servent *sp;
        int port, error;
        int allownumeric;

        if (servname == NULL)
                return 0;
        switch (ai->ai_family) {
        case AF_LOCAL:
                /* AF_LOCAL ignores servname silently. */
                return (0);
        case AF_INET:
#ifdef AF_INET6
        case AF_INET6:
#endif
                break;
        default:
                return 0;
        }

        switch (ai->ai_socktype) {
        case SOCK_RAW:
                return EAI_SERVICE;
        case SOCK_DGRAM:
        case SOCK_STREAM:
        case SOCK_SEQPACKET:
                allownumeric = 1;
                break;
        case ANY:
                switch (ai->ai_family) {
                case AF_INET:
#ifdef AF_INET6
                case AF_INET6:
#endif
                        allownumeric = 1;
                        break;
                default:
                        allownumeric = 0;
                        break;
                }
                break;
        default:
                return EAI_SOCKTYPE;
        }

        error = str2number(servname, &port);
        if (error == 0) {
                if (!allownumeric)
                        return EAI_SERVICE;
                if (port < 0 || port > 65535)
                        return EAI_SERVICE;
                port = htons(port);
        } else {
                if (ai->ai_flags & AI_NUMERICSERV)
                        return EAI_NONAME;

                switch (ai->ai_protocol) {
                case IPPROTO_UDP:
                        proto = "udp";
                        break;
                case IPPROTO_TCP:
                        proto = "tcp";
                        break;
                case IPPROTO_SCTP:
                        proto = "sctp";
                        break;
                case IPPROTO_UDPLITE:
                        proto = "udplite";
                        break;
                default:
                        proto = NULL;
                        break;
                }

                if ((sp = getservbyname(servname, proto)) == NULL)
                        return EAI_SERVICE;
                port = sp->s_port;
        }

        if (!matchonly) {
                switch (ai->ai_family) {
                case AF_INET:
                        ((struct sockaddr_in *)(void *)
                            ai->ai_addr)->sin_port = port;
                        break;
#ifdef INET6
                case AF_INET6:
                        ((struct sockaddr_in6 *)(void *)
                            ai->ai_addr)->sin6_port = port;
                        break;
#endif
                }
        }

        return 0;
}

static const struct afd *
find_afd(int af)
{
        const struct afd *afd;

        if (af == PF_UNSPEC)
                return NULL;
        for (afd = afdl; afd->a_af; afd++) {
                if (afd->a_af == af)
                        return afd;
        }
        return NULL;
}

/*
 * RFC 3493: AI_ADDRCONFIG check.  Determines which address families are
 * configured on the local system and correlates with pai->ai_family value.
 * If an address family is not configured on the system, it will not be
 * queried for.  For this purpose, loopback addresses are not considered
 * configured addresses.
 *
 * XXX PF_UNSPEC -> PF_INET6 + PF_INET mapping needs to be in sync with
 * _dns_getaddrinfo.
 */
static int
addrconfig(struct addrinfo *pai)
{
        struct ifaddrs *ifaddrs, *ifa;
        struct sockaddr_in *sin;
#ifdef INET6
        struct sockaddr_in6 *sin6;
#endif
        int seen_inet = 0, seen_inet6 = 0;

        if (getifaddrs(&ifaddrs) != 0)
                return (0);

        for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) {
                if (ifa->ifa_addr == NULL || (ifa->ifa_flags & IFF_UP) == 0)
                        continue;
                switch (ifa->ifa_addr->sa_family) {
                case AF_INET:
                        if (seen_inet)
                                continue;
                        sin = (struct sockaddr_in *)(ifa->ifa_addr);
                        if (htonl(sin->sin_addr.s_addr) == INADDR_LOOPBACK)
                                continue;
                        seen_inet = 1;
                        break;
#ifdef INET6
                case AF_INET6:
                        if (seen_inet6)
                                continue;
                        sin6 = (struct sockaddr_in6 *)(ifa->ifa_addr);
                        if (IN6_IS_ADDR_LOOPBACK(&sin6->sin6_addr))
                                continue;
                        if ((ifa->ifa_flags & IFT_LOOP) != 0 &&
                            IN6_IS_ADDR_LINKLOCAL(&sin6->sin6_addr))
                                continue;
                        if (is_ifdisabled(ifa->ifa_name))
                                continue;
                        seen_inet6 = 1;
                        break;
#endif
                }
        }
        freeifaddrs(ifaddrs);

        switch(pai->ai_family) {
        case AF_INET6:
                return (seen_inet6);
        case AF_INET:
                return (seen_inet);
        case AF_UNSPEC:
                if (seen_inet == seen_inet6)
                        return (seen_inet);
                pai->ai_family = seen_inet ? AF_INET : AF_INET6;
                return (1);
        }
        return (1);
}

#ifdef INET6
static int
is_ifdisabled(char *name)
{
        struct in6_ndireq nd;
        int fd;

        if ((fd = _socket(AF_INET6, SOCK_DGRAM | SOCK_CLOEXEC, 0)) < 0)
                return (-1);
        memset(&nd, 0, sizeof(nd));
        strlcpy(nd.ifname, name, sizeof(nd.ifname));
        if (_ioctl(fd, SIOCGIFINFO_IN6, &nd) < 0) {
                _close(fd);
                return (-1);
        }
        _close(fd);
        return ((nd.ndi.flags & ND6_IFF_IFDISABLED) != 0);
}

/* convert a string to a scope identifier. XXX: IPv6 specific */
static int
ip6_str2scopeid(char *scope, struct sockaddr_in6 *sin6, u_int32_t *scopeid)
{
        u_long lscopeid;
        struct in6_addr *a6;
        char *ep;

        a6 = &sin6->sin6_addr;

        /* empty scopeid portion is invalid */
        if (*scope == '\0')
                return -1;

        if (IN6_IS_ADDR_LINKLOCAL(a6) || IN6_IS_ADDR_MC_LINKLOCAL(a6) ||
            IN6_IS_ADDR_MC_NODELOCAL(a6)) {
                /*
                 * We currently assume a one-to-one mapping between links
                 * and interfaces, so we simply use interface indices for
                 * like-local scopes.
                 */
                *scopeid = if_nametoindex(scope);
                if (*scopeid == 0)
                        goto trynumeric;
                return 0;
        }

        /* still unclear about literal, allow numeric only - placeholder */
        if (IN6_IS_ADDR_SITELOCAL(a6) || IN6_IS_ADDR_MC_SITELOCAL(a6))
                goto trynumeric;
        if (IN6_IS_ADDR_MC_ORGLOCAL(a6))
                goto trynumeric;
        else
                goto trynumeric;        /* global */

        /* try to convert to a numeric id as a last resort */
  trynumeric:
        errno = 0;
        lscopeid = strtoul(scope, &ep, 10);
        *scopeid = (u_int32_t)(lscopeid & 0xffffffffUL);
        if (errno == 0 && ep && *ep == '\0' && *scopeid == lscopeid)
                return 0;
        else
                return -1;
}
#endif


#ifdef NS_CACHING
static int
addrinfo_id_func(char *buffer, size_t *buffer_size, va_list ap,
    void *cache_mdata)
{
        res_state statp;
        u_long res_options;

        const int op_id = 0;    /* identifies the getaddrinfo for the cache */
        char *hostname;
        struct addrinfo *hints;

        char *p;
        int ai_flags, ai_family, ai_socktype, ai_protocol;
        size_t desired_size, size;

        statp = __res_state();
        res_options = statp->options & (RES_RECURSE | RES_DEFNAMES |
            RES_DNSRCH | RES_NOALIASES | RES_USE_INET6);

        hostname = va_arg(ap, char *);
        hints = va_arg(ap, struct addrinfo *);

        desired_size = sizeof(res_options) + sizeof(int) + sizeof(int) * 4;
        if (hostname != NULL) {
                size = strlen(hostname);
                desired_size += size + 1;
        } else
                size = 0;

        if (desired_size > *buffer_size) {
                *buffer_size = desired_size;
                return (NS_RETURN);
        }

        if (hints == NULL)
                ai_flags = ai_family = ai_socktype = ai_protocol = 0;
        else {
                ai_flags = hints->ai_flags;
                ai_family = hints->ai_family;
                ai_socktype = hints->ai_socktype;
                ai_protocol = hints->ai_protocol;
        }

        p = buffer;
        memcpy(p, &res_options, sizeof(res_options));
        p += sizeof(res_options);

        memcpy(p, &op_id, sizeof(int));
        p += sizeof(int);

        memcpy(p, &ai_flags, sizeof(int));
        p += sizeof(int);

        memcpy(p, &ai_family, sizeof(int));
        p += sizeof(int);

        memcpy(p, &ai_socktype, sizeof(int));
        p += sizeof(int);

        memcpy(p, &ai_protocol, sizeof(int));
        p += sizeof(int);

        if (hostname != NULL)
                memcpy(p, hostname, size);

        *buffer_size = desired_size;
        return (NS_SUCCESS);
}

static int
addrinfo_marshal_func(char *buffer, size_t *buffer_size, void *retval,
    va_list ap, void *cache_mdata)
{
        struct addrinfo *ai, *cai;
        char *p;
        size_t desired_size, size, ai_size;

        ai = *((struct addrinfo **)retval);

        desired_size = sizeof(size_t);
        ai_size = 0;
        for (cai = ai; cai != NULL; cai = cai->ai_next) {
                desired_size += sizeof(struct addrinfo) + cai->ai_addrlen;
                if (cai->ai_canonname != NULL)
                        desired_size += sizeof(size_t) +
                            strlen(cai->ai_canonname);
                ++ai_size;
        }

        if (desired_size > *buffer_size) {
                /* this assignment is here for future use */
                errno = ERANGE;
                *buffer_size = desired_size;
                return (NS_RETURN);
        }

        memset(buffer, 0, desired_size);
        p = buffer;

        memcpy(p, &ai_size, sizeof(size_t));
        p += sizeof(size_t);
        for (cai = ai; cai != NULL; cai = cai->ai_next) {
                memcpy(p, cai, sizeof(struct addrinfo));
                p += sizeof(struct addrinfo);

                memcpy(p, cai->ai_addr, cai->ai_addrlen);
                p += cai->ai_addrlen;

                if (cai->ai_canonname != NULL) {
                        size = strlen(cai->ai_canonname);
                        memcpy(p, &size, sizeof(size_t));
                        p += sizeof(size_t);

                        memcpy(p, cai->ai_canonname, size);
                        p += size;
                }
        }

        return (NS_SUCCESS);
}

static int
addrinfo_unmarshal_func(char *buffer, size_t buffer_size, void *retval,
    va_list ap, void *cache_mdata)
{
        struct addrinfo new_ai, *result, *sentinel, *lasts;

        char *p;
        size_t ai_size, ai_i, size;

        p = buffer;
        memcpy(&ai_size, p, sizeof(size_t));
        p += sizeof(size_t);

        result = NULL;
        lasts = NULL;
        for (ai_i = 0; ai_i < ai_size; ++ai_i) {
                memcpy(&new_ai, p, sizeof(struct addrinfo));
                p += sizeof(struct addrinfo);
                size = new_ai.ai_addrlen + sizeof(struct addrinfo) +
                        _ALIGNBYTES;

                sentinel = calloc(1, size);

                memcpy(sentinel, &new_ai, sizeof(struct addrinfo));
                sentinel->ai_addr = (struct sockaddr *)_ALIGN((char *)sentinel +
                    sizeof(struct addrinfo));

                memcpy(sentinel->ai_addr, p, new_ai.ai_addrlen);
                p += new_ai.ai_addrlen;

                if (new_ai.ai_canonname != NULL) {
                        memcpy(&size, p, sizeof(size_t));
                        p += sizeof(size_t);

                        sentinel->ai_canonname = calloc(1, size + 1);

                        memcpy(sentinel->ai_canonname, p, size);
                        p += size;
                }

                if (result == NULL) {
                        result = sentinel;
                        lasts = sentinel;
                } else {
                        lasts->ai_next = sentinel;
                        lasts = sentinel;
                }
        }

        *((struct addrinfo **)retval) = result;
        return (NS_SUCCESS);
}
#endif /* NS_CACHING */

/*
 * FQDN hostname, DNS lookup
 */
static int
explore_fqdn(const struct addrinfo *pai, const char *hostname,
    const char *servname, struct addrinfo **res)
{
        struct addrinfo *result;
        struct addrinfo *cur;
        int error = 0;

#ifdef NS_CACHING
        static const nss_cache_info cache_info =
        NS_COMMON_CACHE_INFO_INITIALIZER(
                hosts, NULL, addrinfo_id_func, addrinfo_marshal_func,
                addrinfo_unmarshal_func);
#endif
        static const ns_dtab dtab[] = {
                NS_FILES_CB(_files_getaddrinfo, NULL)
                { NSSRC_DNS, _dns_getaddrinfo, NULL },  /* force -DHESIOD */
                NS_NIS_CB(_yp_getaddrinfo, NULL)
#ifdef NS_CACHING
                NS_CACHE_CB(&cache_info)
#endif
                { 0 }
        };

        result = NULL;

        /*
         * if the servname does not match socktype/protocol, ignore it.
         */
        if (get_portmatch(pai, servname) != 0)
                return 0;

        switch (_nsdispatch(&result, dtab, NSDB_HOSTS, "getaddrinfo",
                        default_dns_files, hostname, pai)) {
        case NS_TRYAGAIN:
                error = EAI_AGAIN;
                goto free;
        case NS_UNAVAIL:
                error = EAI_FAIL;
                goto free;
        case NS_NOTFOUND:
                error = EAI_NONAME;
                goto free;
        case NS_ADDRFAMILY:
                error = EAI_ADDRFAMILY;
                goto free;
        case NS_SUCCESS:
                error = 0;
                for (cur = result; cur; cur = cur->ai_next) {
                        GET_PORT(cur, servname);
                        /* canonname should be filled already */
                }
                break;
        }

        *res = result;

        return 0;

free:
        if (result)
                freeaddrinfo(result);
        return error;
}

#ifdef DEBUG
static const char AskedForGot[] =
        "gethostby*.getanswer: asked for \"%s\", got \"%s\"";
#endif

static struct addrinfo *
getanswer(const querybuf *answer, int anslen, const char *qname, int qtype,
    const struct addrinfo *pai, res_state res)
{
        struct addrinfo sentinel, *cur;
        struct addrinfo ai;
        const struct afd *afd;
        char *canonname;
        const HEADER *hp;
        const u_char *cp;
        int n;
        const u_char *eom;
        char *bp, *ep;
        int type, class, ancount, qdcount;
        int haveanswer, had_error;
        char tbuf[MAXDNAME];
        int (*name_ok)(const char *);
        char hostbuf[8*1024];

        memset(&sentinel, 0, sizeof(sentinel));
        cur = &sentinel;

        canonname = NULL;
        eom = answer->buf + anslen;
        switch (qtype) {
        case T_A:
        case T_AAAA:
        case T_ANY:     /*use T_ANY only for T_A/T_AAAA lookup*/
                name_ok = res_hnok;
                break;
        default:
                return (NULL);  /* XXX should be abort(); */
        }
        /*
         * find first satisfactory answer
         */
        hp = &answer->hdr;
        ancount = ntohs(hp->ancount);
        qdcount = ntohs(hp->qdcount);
        bp = hostbuf;
        ep = hostbuf + sizeof hostbuf;
        cp = answer->buf + HFIXEDSZ;
        if (qdcount != 1) {
                RES_SET_H_ERRNO(res, NO_RECOVERY);
                return (NULL);
        }
        n = dn_expand(answer->buf, eom, cp, bp, ep - bp);
        if ((n < 0) || !(*name_ok)(bp)) {
                RES_SET_H_ERRNO(res, NO_RECOVERY);
                return (NULL);
        }
        cp += n + QFIXEDSZ;
        if (qtype == T_A || qtype == T_AAAA || qtype == T_ANY) {
                /* res_send() has already verified that the query name is the
                 * same as the one we sent; this just gets the expanded name
                 * (i.e., with the succeeding search-domain tacked on).
                 */
                n = strlen(bp) + 1;             /* for the \0 */
                if (n >= MAXHOSTNAMELEN) {
                        RES_SET_H_ERRNO(res, NO_RECOVERY);
                        return (NULL);
                }
                canonname = bp;
                bp += n;
                /* The qname can be abbreviated, but h_name is now absolute. */
                qname = canonname;
        }
        haveanswer = 0;
        had_error = 0;
        while (ancount-- > 0 && cp < eom && !had_error) {
                n = dn_expand(answer->buf, eom, cp, bp, ep - bp);
                if ((n < 0) || !(*name_ok)(bp)) {
                        had_error++;
                        continue;
                }
                cp += n;                        /* name */
                type = _getshort(cp);
                cp += INT16SZ;                  /* type */
                class = _getshort(cp);
                cp += INT16SZ + INT32SZ;        /* class, TTL */
                n = _getshort(cp);
                cp += INT16SZ;                  /* len */
                if (class != C_IN) {
                        /* XXX - debug? syslog? */
                        cp += n;
                        continue;               /* XXX - had_error++ ? */
                }
                if ((qtype == T_A || qtype == T_AAAA || qtype == T_ANY) &&
                    type == T_CNAME) {
                        n = dn_expand(answer->buf, eom, cp, tbuf, sizeof tbuf);
                        if ((n < 0) || !(*name_ok)(tbuf)) {
                                had_error++;
                                continue;
                        }
                        cp += n;
                        /* Get canonical name. */
                        n = strlen(tbuf) + 1;   /* for the \0 */
                        if (n > ep - bp || n >= MAXHOSTNAMELEN) {
                                had_error++;
                                continue;
                        }
                        strlcpy(bp, tbuf, ep - bp);
                        canonname = bp;
                        bp += n;
                        continue;
                }
                if (qtype == T_ANY) {
                        if (!(type == T_A || type == T_AAAA)) {
                                cp += n;
                                continue;
                        }
                } else if (type != qtype) {
#ifdef DEBUG
                        if (type != T_KEY && type != T_SIG &&
                            type != T_DNAME && type != T_RRSIG)
                                syslog(LOG_NOTICE|LOG_AUTH,
               "gethostby*.getanswer: asked for \"%s %s %s\", got type \"%s\"",
                                       qname, p_class(C_IN), p_type(qtype),
                                       p_type(type));
#endif
                        cp += n;
                        continue;               /* XXX - had_error++ ? */
                }
                switch (type) {
                case T_A:
                case T_AAAA:
                        if (strcasecmp(canonname, bp) != 0) {
#ifdef DEBUG
                                syslog(LOG_NOTICE|LOG_AUTH,
                                       AskedForGot, canonname, bp);
#endif
                                cp += n;
                                continue;       /* XXX - had_error++ ? */
                        }
                        if (type == T_A && n != INADDRSZ) {
                                cp += n;
                                continue;
                        }
                        if (type == T_AAAA && n != IN6ADDRSZ) {
                                cp += n;
                                continue;
                        }
#ifdef FILTER_V4MAPPED
                        if (type == T_AAAA) {
                                struct in6_addr in6;
                                memcpy(&in6, cp, sizeof(in6));
                                if (IN6_IS_ADDR_V4MAPPED(&in6)) {
                                        cp += n;
                                        continue;
                                }
                        }
#endif
                        if (!haveanswer) {
                                int nn;

                                canonname = bp;
                                nn = strlen(bp) + 1;    /* for the \0 */
                                bp += nn;
                        }

                        /* don't overwrite pai */
                        ai = *pai;
                        ai.ai_family = (type == T_A) ? AF_INET : AF_INET6;
                        afd = find_afd(ai.ai_family);
                        if (afd == NULL) {
                                cp += n;
                                continue;
                        }
                        cur->ai_next = get_ai(&ai, afd, (const char *)cp);
                        if (cur->ai_next == NULL)
                                had_error++;
                        while (cur && cur->ai_next)
                                cur = cur->ai_next;
                        cp += n;
                        break;
                default:
                        abort();
                }
                if (!had_error)
                        haveanswer++;
        }
        if (haveanswer) {
#if defined(RESOLVSORT)
                /*
                 * We support only IPv4 address for backward
                 * compatibility against gethostbyname(3).
                 */
                if (res->nsort && qtype == T_A) {
                        if (addr4sort(&sentinel, res) < 0) {
                                freeaddrinfo(sentinel.ai_next);
                                RES_SET_H_ERRNO(res, NO_RECOVERY);
                                return NULL;
                        }
                }
#endif /*RESOLVSORT*/
                if (!canonname)
                        (void)get_canonname(pai, sentinel.ai_next, qname);
                else
                        (void)get_canonname(pai, sentinel.ai_next, canonname);
                RES_SET_H_ERRNO(res, NETDB_SUCCESS);
                return sentinel.ai_next;
        }

        /*
         * We could have walked a CNAME chain, but the ultimate target
         * may not have what we looked for.
         */
        RES_SET_H_ERRNO(res, ntohs(hp->ancount) > 0 ? NO_DATA : NO_RECOVERY);
        return NULL;
}

#ifdef RESOLVSORT
struct addr_ptr {
        struct addrinfo *ai;
        int aval;
};

static int
addr4sort(struct addrinfo *sentinel, res_state res)
{
        struct addrinfo *ai;
        struct addr_ptr *addrs, addr;
        struct sockaddr_in *sin;
        int naddrs, i, j;
        int needsort = 0;

        if (!sentinel)
                return -1;
        naddrs = 0;
        for (ai = sentinel->ai_next; ai; ai = ai->ai_next)
                naddrs++;
        if (naddrs < 2)
                return 0;               /* We don't need sorting. */
        if ((addrs = malloc(sizeof(struct addr_ptr) * naddrs)) == NULL)
                return -1;
        i = 0;
        for (ai = sentinel->ai_next; ai; ai = ai->ai_next) {
                sin = (struct sockaddr_in *)ai->ai_addr;
                for (j = 0; (unsigned)j < res->nsort; j++) {
                        if (res->sort_list[j].addr.s_addr ==
                            (sin->sin_addr.s_addr & res->sort_list[j].mask))
                                break;
                }
                addrs[i].ai = ai;
                addrs[i].aval = j;
                if (needsort == 0 && i > 0 && j < addrs[i - 1].aval)
                        needsort = i;
                i++;
        }
        if (!needsort) {
                free(addrs);
                return 0;
        }

        while (needsort < naddrs) {
                for (j = needsort - 1; j >= 0; j--) {
                        if (addrs[j].aval > addrs[j+1].aval) {
                                addr = addrs[j];
                                addrs[j] = addrs[j + 1];
                                addrs[j + 1] = addr;
                        } else
                                break;
                }
                needsort++;
        }

        ai = sentinel;
        for (i = 0; i < naddrs; ++i) {
                ai->ai_next = addrs[i].ai;
                ai = ai->ai_next;
        }
        ai->ai_next = NULL;
        free(addrs);
        return 0;
}
#endif /*RESOLVSORT*/

/*ARGSUSED*/
static int
_dns_getaddrinfo(void *rv, void *cb_data, va_list ap)
{
        struct addrinfo *ai, ai0;
        querybuf *buf, *buf2;
        const char *hostname;
        const struct addrinfo *pai;
        struct addrinfo sentinel, *cur;
        struct res_target q, q2;
        res_state res;

        ai = NULL;

        hostname = va_arg(ap, char *);
        pai = va_arg(ap, const struct addrinfo *);

        memset(&q, 0, sizeof(q));
        memset(&q2, 0, sizeof(q2));
        memset(&sentinel, 0, sizeof(sentinel));
        cur = &sentinel;

        res = __res_state();

        buf = malloc(sizeof(*buf));
        if (!buf) {
                RES_SET_H_ERRNO(res, NETDB_INTERNAL);
                return NS_NOTFOUND;
        }
        buf2 = malloc(sizeof(*buf2));
        if (!buf2) {
                free(buf);
                RES_SET_H_ERRNO(res, NETDB_INTERNAL);
                return NS_NOTFOUND;
        }

        if (pai->ai_family == AF_INET6 &&
            (pai->ai_flags & AI_V4MAPPED) == AI_V4MAPPED) {
                ai0 = *pai;
                ai0.ai_family = AF_UNSPEC;
                pai = &ai0;
        }

        switch (pai->ai_family) {
        case AF_UNSPEC:
                q.name = hostname;
                q.qclass = C_IN;
                q.qtype = T_A;
                q.answer = buf->buf;
                q.anslen = sizeof(buf->buf);
                q.next = &q2;
                q2.name = hostname;
                q2.qclass = C_IN;
                q2.qtype = T_AAAA;
                q2.answer = buf2->buf;
                q2.anslen = sizeof(buf2->buf);
                break;
        case AF_INET:
                q.name = hostname;
                q.qclass = C_IN;
                q.qtype = T_A;
                q.answer = buf->buf;
                q.anslen = sizeof(buf->buf);
                break;
        case AF_INET6:
                q.name = hostname;
                q.qclass = C_IN;
                q.qtype = T_AAAA;
                q.answer = buf->buf;
                q.anslen = sizeof(buf->buf);
                break;
        default:
                free(buf);
                free(buf2);
                return NS_UNAVAIL;
        }

        if ((res->options & RES_INIT) == 0 && res_ninit(res) == -1) {
                RES_SET_H_ERRNO(res, NETDB_INTERNAL);
                free(buf);
                free(buf2);
                return NS_NOTFOUND;
        }

        if (res_searchN(hostname, &q, res) < 0) {
                free(buf);
                free(buf2);
                switch (res->res_h_errno) {
                case NO_DATA:
                        return (NS_ADDRFAMILY);
                case TRY_AGAIN:
                        return (NS_TRYAGAIN);
                default:
                        return (NS_NOTFOUND);
                }
        }
        /* prefer IPv6 */
        if (q.next) {
                ai = getanswer(buf2, q2.n, q2.name, q2.qtype, pai, res);
                if (ai != NULL) {
                        cur->ai_next = ai;
                        while (cur && cur->ai_next)
                                cur = cur->ai_next;
                }
        }
        if (ai == NULL || pai->ai_family != AF_UNSPEC ||
            (pai->ai_flags & (AI_ALL | AI_V4MAPPED)) != AI_V4MAPPED) {
                ai = getanswer(buf, q.n, q.name, q.qtype, pai, res);
                if (ai != NULL)
                        cur->ai_next = ai;
        }
        free(buf);
        free(buf2);
        if (sentinel.ai_next == NULL)
                switch (res->res_h_errno) {
                case HOST_NOT_FOUND:
                        return (NS_NOTFOUND);
                case NO_DATA:
                        return (NS_ADDRFAMILY);
                case TRY_AGAIN:
                        return (NS_TRYAGAIN);
                default:
                        return (NS_UNAVAIL);
                }
        *((struct addrinfo **)rv) = sentinel.ai_next;
        return (NS_SUCCESS);
}

static void
_sethtent(FILE **hostf)
{
        if (!*hostf)
                *hostf = fopen(_PATH_HOSTS, "re");
        else
                rewind(*hostf);
}

static void
_endhtent(FILE **hostf)
{
        if (*hostf) {
                (void) fclose(*hostf);
                *hostf = NULL;
        }
}

static struct addrinfo *
_gethtent(FILE **hostf, const char *name, const struct addrinfo *pai)
{
        char *p;
        char *cp, *tname, *cname;
        struct addrinfo hints, *res0, *res;
        int error;
        const char *addr;
        char hostbuf[8*1024];

        if (!*hostf && !(*hostf = fopen(_PATH_HOSTS, "re")))
                return (NULL);
again:
        if (!(p = fgets(hostbuf, sizeof hostbuf, *hostf)))
                return (NULL);
        if (*p == '#')
                goto again;
        cp = strpbrk(p, "#\n");
        if (cp != NULL)
                *cp = '\0';
        if (!(cp = strpbrk(p, " \t")))
                goto again;
        *cp++ = '\0';
        addr = p;
        cname = NULL;
        /* if this is not something we're looking for, skip it. */
        while (cp && *cp) {
                if (*cp == ' ' || *cp == '\t') {
                        cp++;
                        continue;
                }
                tname = cp;
                if (cname == NULL)
                        cname = cp;
                if ((cp = strpbrk(cp, " \t")) != NULL)
                        *cp++ = '\0';
                if (strcasecmp(name, tname) == 0)
                        goto found;
        }
        goto again;

found:
        /* we should not glob socktype/protocol here */
        memset(&hints, 0, sizeof(hints));
        hints.ai_family = pai->ai_family;
        hints.ai_socktype = SOCK_DGRAM;
        hints.ai_protocol = 0;
        hints.ai_flags = AI_NUMERICHOST;
        if (pai->ai_family == AF_INET6 &&
            (pai->ai_flags & AI_V4MAPPED) == AI_V4MAPPED)
                hints.ai_flags |= AI_V4MAPPED;
        error = getaddrinfo(addr, "0", &hints, &res0);
        if (error)
                goto again;
#ifdef FILTER_V4MAPPED
        /* XXX should check all items in the chain */
        if (res0->ai_family == AF_INET6 &&
            IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)res0->ai_addr)->sin6_addr)) {
                freeaddrinfo(res0);
                goto again;
        }
#endif
        for (res = res0; res; res = res->ai_next) {
                /* cover it up */
                res->ai_flags = pai->ai_flags;
                res->ai_socktype = pai->ai_socktype;
                res->ai_protocol = pai->ai_protocol;

                if (pai->ai_flags & AI_CANONNAME) {
                        if (get_canonname(pai, res, cname) != 0) {
                                freeaddrinfo(res0);
                                goto again;
                        }
                }
        }
        return res0;
}

static struct addrinfo *
_getht(FILE **hostf, const char *name, const struct addrinfo *pai,
     struct addrinfo *cur)
{
        struct addrinfo *p;

        while ((p = _gethtent(hostf, name, pai)) != NULL) {
                cur->ai_next = p;
                while (cur && cur->ai_next)
                        cur = cur->ai_next;
        }
        return (cur);
}

/*ARGSUSED*/
static int
_files_getaddrinfo(void *rv, void *cb_data, va_list ap)
{
        const char *name;
        const struct addrinfo *pai;
        struct addrinfo sentinel, *cur;
        FILE *hostf = NULL;

        name = va_arg(ap, char *);
        pai = va_arg(ap, struct addrinfo *);

        memset(&sentinel, 0, sizeof(sentinel));
        cur = &sentinel;

        _sethtent(&hostf);
        if (pai->ai_family == AF_INET6 &&
            (pai->ai_flags & (AI_ALL | AI_V4MAPPED)) == AI_V4MAPPED) {
                struct addrinfo ai0 = *pai;

                ai0.ai_flags &= ~AI_V4MAPPED;
                cur = _getht(&hostf, name, &ai0, cur);
                if (sentinel.ai_next == NULL) {
                        _sethtent(&hostf);
                        ai0.ai_flags |= AI_V4MAPPED;
                        cur = _getht(&hostf, name, &ai0, cur);
                }
        } else
                cur = _getht(&hostf, name, pai, cur);
        _endhtent(&hostf);

        *((struct addrinfo **)rv) = sentinel.ai_next;
        if (sentinel.ai_next == NULL)
                return NS_NOTFOUND;
        return NS_SUCCESS;
}

#ifdef YP
/*ARGSUSED*/
static struct addrinfo *
_yphostent(char *line, const struct addrinfo *pai)
{
        struct addrinfo sentinel, *cur;
        struct addrinfo hints, *res, *res0;
        int error;
        char *p = line;
        const char *addr, *canonname;
        char *nextline;
        char *cp;

        addr = canonname = NULL;

        memset(&sentinel, 0, sizeof(sentinel));
        cur = &sentinel;

nextline:
        /* terminate line */
        cp = strchr(p, '\n');
        if (cp) {
                *cp++ = '\0';
                nextline = cp;
        } else
                nextline = NULL;

        cp = strpbrk(p, " \t");
        if (cp == NULL) {
                if (canonname == NULL)
                        return (NULL);
                else
                        goto done;
        }
        *cp++ = '\0';

        addr = p;

        while (cp && *cp) {
                if (*cp == ' ' || *cp == '\t') {
                        cp++;
                        continue;
                }
                if (!canonname)
                        canonname = cp;
                if ((cp = strpbrk(cp, " \t")) != NULL)
                        *cp++ = '\0';
        }

        hints = *pai;
        hints.ai_flags = AI_NUMERICHOST;
        if (pai->ai_family == AF_INET6 &&
            (pai->ai_flags & AI_V4MAPPED) == AI_V4MAPPED)
                hints.ai_flags |= AI_V4MAPPED;
        error = getaddrinfo(addr, NULL, &hints, &res0);
        if (error == 0) {
                for (res = res0; res; res = res->ai_next) {
                        /* cover it up */
                        res->ai_flags = pai->ai_flags;

                        if (pai->ai_flags & AI_CANONNAME)
                                (void)get_canonname(pai, res, canonname);
                }
        } else
                res0 = NULL;
        if (res0) {
                cur->ai_next = res0;
                while (cur && cur->ai_next)
                        cur = cur->ai_next;
        }

        if (nextline) {
                p = nextline;
                goto nextline;
        }

done:
        return sentinel.ai_next;
}

/*ARGSUSED*/
static int
_yp_getaddrinfo(void *rv, void *cb_data, va_list ap)
{
        struct addrinfo sentinel, *cur;
        struct addrinfo *ai = NULL;
        char *ypbuf;
        int ypbuflen, r;
        const char *name;
        const struct addrinfo *pai;
        char *ypdomain;

        if (_yp_check(&ypdomain) == 0)
                return NS_UNAVAIL;

        name = va_arg(ap, char *);
        pai = va_arg(ap, const struct addrinfo *);

        memset(&sentinel, 0, sizeof(sentinel));
        cur = &sentinel;

        /* ipnodes.byname can hold both IPv4/v6 */
        r = yp_match(ypdomain, "ipnodes.byname", name,
                (int)strlen(name), &ypbuf, &ypbuflen);
        if (r == 0) {
                ai = _yphostent(ypbuf, pai);
                if (ai) {
                        cur->ai_next = ai;
                        while (cur && cur->ai_next)
                                cur = cur->ai_next;
                }
                free(ypbuf);
        }

        if (ai != NULL) {
                struct sockaddr_in6 *sin6;

                switch (ai->ai_family) {
                case AF_INET:
                        goto done;
                case AF_INET6:
                        sin6 = (struct sockaddr_in6 *)ai->ai_addr;
                        if (IN6_IS_ADDR_V4MAPPED(&sin6->sin6_addr))
                                goto done;
                        break;
                }
        }

        /* hosts.byname is only for IPv4 (Solaris8) */
        if (pai->ai_family == AF_UNSPEC || pai->ai_family == AF_INET ||
            ((pai->ai_family == AF_INET6 &&
             (pai->ai_flags & AI_V4MAPPED) == AI_V4MAPPED) &&
              (ai == NULL || (pai->ai_flags & AI_ALL) == AI_ALL))) {
                r = yp_match(ypdomain, "hosts.byname", name,
                        (int)strlen(name), &ypbuf, &ypbuflen);
                if (r == 0) {
                        struct addrinfo ai4;

                        ai4 = *pai;
                        if (pai->ai_family == AF_UNSPEC)
                                ai4.ai_family = AF_INET;
                        ai = _yphostent(ypbuf, &ai4);
                        if (ai) {
                                cur->ai_next = ai;
                                while (cur && cur->ai_next)
                                        cur = cur->ai_next;
                        }
                        free(ypbuf);
                }
        }

done:
        if (sentinel.ai_next == NULL) {
                RES_SET_H_ERRNO(__res_state(), HOST_NOT_FOUND);
                return NS_NOTFOUND;
        }
        *((struct addrinfo **)rv) = sentinel.ai_next;
        return NS_SUCCESS;
}
#endif

/* resolver logic */

/*
 * Formulate a normal query, send, and await answer.
 * Returned answer is placed in supplied buffer "answer".
 * Perform preliminary check of answer, returning success only
 * if no error is indicated and the answer count is nonzero.
 * Return the size of the response on success, -1 on error.
 * Error number is left in h_errno.
 *
 * Caller must parse answer and determine whether it answers the question.
 */
static int
res_queryN(const char *name, struct res_target *target, res_state res)
{
        u_char *buf;
        HEADER *hp;
        int n;
        u_int oflags;
        struct res_target *t;
        u_int rcode;
        int ancount;

        /*
         * Extend rcode values in the scope of this function.  The DNS header
         * rcode we use in this function (hp->rcode) is limited by 4 bits, so
         * anything starting from 16 is safe wrt aliasing.  However, nameser.h
         * already has extended enum __ns_rcode, so for future safety let's use
         * even larger values.
         */
#define RCODE_UNREACH   32
#define RCODE_TIMEDOUT  33
        rcode = NOERROR;
        ancount = 0;

        buf = malloc(MAXPACKET);
        if (!buf) {
                RES_SET_H_ERRNO(res, NETDB_INTERNAL);
                return -1;
        }

        for (t = target; t; t = t->next) {
                int class, type;
                u_char *answer;
                int anslen;

                hp = (HEADER *)(void *)t->answer;

                /* make it easier... */
                class = t->qclass;
                type = t->qtype;
                answer = t->answer;
                anslen = t->anslen;

                oflags = res->_flags;

again:
                hp->rcode = NOERROR;    /* default */

#ifdef DEBUG
                if (res->options & RES_DEBUG)
                        printf(";; res_query(%s, %d, %d)\n", name, class, type);
#endif

                n = res_nmkquery(res, QUERY, name, class, type, NULL, 0, NULL,
                    buf, MAXPACKET);
                if (n > 0 && (res->_flags & RES_F_EDNS0ERR) == 0 &&
                    (res->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0U)
                        n = res_nopt(res, n, buf, MAXPACKET, anslen);
                if (n <= 0) {
#ifdef DEBUG
                        if (res->options & RES_DEBUG)
                                printf(";; res_query: mkquery failed\n");
#endif
                        free(buf);
                        RES_SET_H_ERRNO(res, NO_RECOVERY);
                        return (n);
                }
                n = res_nsend(res, buf, n, answer, anslen);
                if (n < 0) {
                        /*
                         * if the query choked with EDNS0, retry
                         * without EDNS0
                         */
                        if ((res->options & (RES_USE_EDNS0|RES_USE_DNSSEC))
                            != 0U &&
                            ((oflags ^ res->_flags) & RES_F_EDNS0ERR) != 0) {
                                res->_flags |= RES_F_EDNS0ERR;
                                if (res->options & RES_DEBUG)
                                        printf(";; res_nquery: retry without EDNS0\n");
                                goto again;
                        }
                        /*
                         * Historically if a DNS server replied with ICMP port
                         * unreach res_nsend() would signal that with
                         * ECONNREFUSED and the upper layers would convert that
                         * into TRY_AGAIN.  See 3a0b3b673936b and deeper.
                         * Also, res_nsend() may set errno to ECONNREFUSED due
                         * to internal failures.  This may not be intentional,
                         * but we also treat that as soft failures.
                         *
                         * A more practical case is when a DNS server(s) were
                         * queried and didn't respond anything, which usually
                         * indicates a soft network failure.
                         */
                        switch (errno) {
                        case ECONNREFUSED:
                                rcode = RCODE_UNREACH;
                                break;
                        case ETIMEDOUT:
                                rcode = RCODE_TIMEDOUT;
                                break;
                        default:
                                rcode = hp->rcode;
                        }
#ifdef DEBUG
                        if (res->options & RES_DEBUG)
                                printf(";; res_query: send error\n");
#endif
                        continue;
                }

                if (n > anslen)
                        hp->rcode = FORMERR; /* XXX not very informative */
                if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
                        rcode = hp->rcode;      /* record most recent error */
#ifdef DEBUG
                        if (res->options & RES_DEBUG)
                                printf(";; rcode = %u, ancount=%u\n", hp->rcode,
                                    ntohs(hp->ancount));
#endif
                        continue;
                }

                ancount += ntohs(hp->ancount);

                t->n = n;
        }

        free(buf);

        if (ancount == 0) {
                switch (rcode) {
                case NXDOMAIN:
                        RES_SET_H_ERRNO(res, HOST_NOT_FOUND);
                        break;
                case RCODE_UNREACH:
                case RCODE_TIMEDOUT:
                case SERVFAIL:
                        RES_SET_H_ERRNO(res, TRY_AGAIN);
                        break;
                case NOERROR:
                        RES_SET_H_ERRNO(res, NO_DATA);
                        break;
                case FORMERR:
                case NOTIMP:
                case REFUSED:
                default:
                        RES_SET_H_ERRNO(res, NO_RECOVERY);
                        break;
                }
                return (-1);
        }
        return (ancount);
}

/*
 * Formulate a normal query, send, and retrieve answer in supplied buffer.
 * Return the size of the response on success, -1 on error.
 * If enabled, implement search rules until answer or unrecoverable failure
 * is detected.  Error code, if any, is left in h_errno.
 */
static int
res_searchN(const char *name, struct res_target *target, res_state res)
{
        const char *cp, * const *domain;
        HEADER *hp = (HEADER *)(void *)target->answer;  /*XXX*/
        u_int dots;
        int trailing_dot, ret, saved_herrno;
        int got_nodata = 0, got_servfail = 0, root_on_list = 0;
        int tried_as_is = 0;
        int searched = 0;
        char abuf[MAXDNAME];

        errno = 0;
        RES_SET_H_ERRNO(res, HOST_NOT_FOUND); /* default, if we never query */
        dots = 0;
        for (cp = name; *cp; cp++)
                dots += (*cp == '.');
        trailing_dot = 0;
        if (cp > name && *--cp == '.')
                trailing_dot++;

        /*
         * if there aren't any dots, it could be a user-level alias
         */
        if (!dots &&
            (cp = res_hostalias(res, name, abuf, sizeof(abuf))) != NULL)
                return (res_queryN(cp, target, res));

        /*
         * If there are enough dots in the name, let's just give it a
         * try 'as is'. The threshold can be set with the "ndots" option.
         * Also, query 'as is', if there is a trailing dot in the name.
         */
        saved_herrno = -1;
        if (dots >= res->ndots || trailing_dot) {
                ret = res_querydomainN(name, NULL, target, res);
                if (ret > 0 || trailing_dot)
                        return (ret);
                switch (res->res_h_errno) {
                case NO_DATA:
                case HOST_NOT_FOUND:
                        break;
                case TRY_AGAIN:
                        if (hp->rcode == SERVFAIL)
                                break;
                        /* FALLTHROUGH */
                default:
                        return (-1);
                }
                saved_herrno = res->res_h_errno;
                tried_as_is++;
        }

        /*
         * We do at least one level of search if
         *      - there is no dot and RES_DEFNAME is set, or
         *      - there is at least one dot, there is no trailing dot,
         *        and RES_DNSRCH is set.
         */
        if ((!dots && (res->options & RES_DEFNAMES)) ||
            (dots && !trailing_dot && (res->options & RES_DNSRCH))) {
                int done = 0;

                for (domain = (const char * const *)res->dnsrch;
                   *domain && !done;
                   domain++) {
                        searched = 1;

                        if (domain[0][0] == '\0' ||
                            (domain[0][0] == '.' && domain[0][1] == '\0'))
                                root_on_list++;

                        if (root_on_list && tried_as_is)
                                continue;

                        ret = res_querydomainN(name, *domain, target, res);
                        if (ret > 0)
                                return (ret);
                        /*
                         * If no server present, give up.
                         * If name isn't found in this domain,
                         * keep trying higher domains in the search list
                         * (if that's enabled).
                         * On a NO_DATA error, keep trying, otherwise
                         * a wildcard entry of another type could keep us
                         * from finding this entry higher in the domain.
                         * If we get some other error (negative answer or
                         * server failure), then stop searching up,
                         * but try the input name below in case it's
                         * fully-qualified.
                         */
                        switch (res->res_h_errno) {
                        case NO_DATA:
                                got_nodata++;
                                /* FALLTHROUGH */
                        case HOST_NOT_FOUND:
                                /* keep trying */
                                break;
                        case TRY_AGAIN:
                                if (hp->rcode == SERVFAIL) {
                                        got_servfail++;
                                        /* try next search element, if any */
                                        break;
                                }
                                /* FALLTHROUGH */
                        default:
                                /* anything else implies that we're done */
                                done++;
                        }
                        /*
                         * if we got here for some reason other than DNSRCH,
                         * we only wanted one iteration of the loop, so stop.
                         */
                        if (!(res->options & RES_DNSRCH))
                                done++;
                }
        }

        switch (res->res_h_errno) {
        case NO_DATA:
        case HOST_NOT_FOUND:
                break;
        case TRY_AGAIN:
                if (hp->rcode == SERVFAIL)
                        break;
                /* FALLTHROUGH */
        default:
                goto giveup;
        }

        /*
         * If the query has not already been tried as is then try it
         * unless RES_NOTLDQUERY is set and there were no dots.
         */
        if ((dots || !searched || !(res->options & RES_NOTLDQUERY)) &&
            !(tried_as_is || root_on_list)) {
                ret = res_querydomainN(name, NULL, target, res);
                if (ret > 0)
                        return (ret);
        }

        /*
         * if we got here, we didn't satisfy the search.
         * if we did an initial full query, return that query's h_errno
         * (note that we wouldn't be here if that query had succeeded).
         * else if we ever got a nodata, send that back as the reason.
         * else send back meaningless h_errno, that being the one from
         * the last DNSRCH we did.
         */
giveup:
        if (saved_herrno != -1)
                RES_SET_H_ERRNO(res, saved_herrno);
        else if (got_nodata)
                RES_SET_H_ERRNO(res, NO_DATA);
        else if (got_servfail)
                RES_SET_H_ERRNO(res, TRY_AGAIN);
        return (-1);
}

/*
 * Perform a call on res_query on the concatenation of name and domain,
 * removing a trailing dot from name if domain is NULL.
 */
static int
res_querydomainN(const char *name, const char *domain,
    struct res_target *target, res_state res)
{
        char nbuf[MAXDNAME];
        const char *longname = nbuf;
        size_t n, d;

#ifdef DEBUG
        if (res->options & RES_DEBUG)
                printf(";; res_querydomain(%s, %s)\n",
                        name, domain?domain:"<Nil>");
#endif
        if (domain == NULL) {
                /*
                 * Check for trailing '.';
                 * copy without '.' if present.
                 */
                n = strlen(name);
                if (n >= MAXDNAME) {
                        RES_SET_H_ERRNO(res, NO_RECOVERY);
                        return (-1);
                }
                if (n > 0 && name[--n] == '.') {
                        strncpy(nbuf, name, n);
                        nbuf[n] = '\0';
                } else
                        longname = name;
        } else {
                n = strlen(name);
                d = strlen(domain);
                if (n + d + 1 >= MAXDNAME) {
                        RES_SET_H_ERRNO(res, NO_RECOVERY);
                        return (-1);
                }
                snprintf(nbuf, sizeof(nbuf), "%s.%s", name, domain);
        }
        return (res_queryN(longname, target, res));
}