/*      $KAME: getaddrinfo.c,v 1.14 2001/01/06 09:41:15 jinmei Exp $    */

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

/*! \file
 * Issues to be discussed:
 *\li  Thread safe-ness must be checked.
 *\li  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.
 *\li  IPv4 classful (shortened) form.  RFC2553 is silent about it.  XNET 5.2
 *   says to use inet_aton() to convert IPv4 numeric to binary (allows
 *   classful form as a result).
 *   current code - disallow classful form for IPv4 (due to use of inet_pton).
 *\li  freeaddrinfo(NULL).  RFC2553 is silent about it.  XNET 5.2 says it is
 *   invalid.
 *   current code - SEGV on freeaddrinfo(NULL)
 * Note:
 *\li  We use getipnodebyname() just for thread-safeness.  There's no intent
 *   to let it do PF_UNSPEC (actually we never pass PF_UNSPEC to
 *   getipnodebyname().
 *\li  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?
 *\li  (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?
 * \par Additional Issue:
 *  To avoid search order issue, we have a big amount of code duplicate
 *   from gethnamaddr.c and some other places.  The issues that there's no
 *   lower layer function to lookup "IPv4 or IPv6" record.  Calling
 *   gethostbyname2 from getaddrinfo will end up in wrong search order, as
 *   follows:
 *      \li The code makes use of following calls when asked to resolver with
 *        ai_family  = PF_UNSPEC:
 *\code         getipnodebyname(host, AF_INET6);
 *              getipnodebyname(host, AF_INET);
 *\endcode
 *      \li  This will result in the following queries if the node is configure to
 *        prefer /etc/hosts than DNS:
 *\code
 *              lookup /etc/hosts for IPv6 address
 *              lookup DNS for IPv6 address
 *              lookup /etc/hosts for IPv4 address
 *              lookup DNS for IPv4 address
 *\endcode
 *        which may not meet people's requirement.
 *       \li The right thing to happen is to have underlying layer which does
 *        PF_UNSPEC lookup (lookup both) and return chain of addrinfos.
 *        This would result in a bit of code duplicate with _dns_ghbyname() and
 *        friends.
 */

#include "port_before.h"

#include <sys/types.h>
#include <sys/param.h>
#include <sys/socket.h>

#include <net/if.h>
#include <netinet/in.h>

#include <arpa/inet.h>
#include <arpa/nameser.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 <stdarg.h>

#include <irs.h>
#include <isc/assertions.h>

#include "port_after.h"

#include "irs_data.h"

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

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

static const struct afd {
        int a_af;
        int a_addrlen;
        int a_socklen;
        int a_off;
        const char *a_addrany;
        const char *a_loopback;
        int a_scoped;
} afdl [] = {
        {PF_INET6, sizeof(struct in6_addr),
         sizeof(struct sockaddr_in6),
         offsetof(struct sockaddr_in6, sin6_addr),
         in6_addrany, in6_loopback, 1},
        {PF_INET, sizeof(struct in_addr),
         sizeof(struct sockaddr_in),
         offsetof(struct sockaddr_in, sin_addr),
         in_addrany, in_loopback, 0},
        {0, 0, 0, 0, NULL, NULL, 0},
};

struct explore {
        int e_af;
        int e_socktype;
        int e_protocol;
        const char *e_protostr;
        int e_wild;
#define WILD_AF(ex)             ((ex)->e_wild & 0x01)
#define WILD_SOCKTYPE(ex)       ((ex)->e_wild & 0x02)
#define WILD_PROTOCOL(ex)       ((ex)->e_wild & 0x04)
};

static const struct explore explore[] = {
#if 0
        { PF_LOCAL, 0, ANY, ANY, NULL, 0x01 },
#endif
        { PF_INET6, SOCK_DGRAM, IPPROTO_UDP, "udp", 0x07 },
        { PF_INET6, SOCK_STREAM, IPPROTO_TCP, "tcp", 0x07 },
        { PF_INET6, SOCK_RAW, ANY, NULL, 0x05 },
        { PF_INET, SOCK_DGRAM, IPPROTO_UDP, "udp", 0x07 },
        { PF_INET, SOCK_STREAM, IPPROTO_TCP, "tcp", 0x07 },
        { PF_INET, SOCK_RAW, ANY, NULL, 0x05 },
        { -1, 0, 0, NULL, 0 },
};

#define PTON_MAX        16

static int str_isnumber __P((const char *));
static int explore_fqdn __P((const struct addrinfo *, const char *,
        const char *, struct addrinfo **));
static int explore_copy __P((const struct addrinfo *, const struct addrinfo *,
        struct addrinfo **));
static int explore_null __P((const struct addrinfo *,
        const char *, struct addrinfo **));
static int explore_numeric __P((const struct addrinfo *, const char *,
        const char *, struct addrinfo **));
static int explore_numeric_scope __P((const struct addrinfo *, const char *,
        const char *, struct addrinfo **));
static int get_canonname __P((const struct addrinfo *,
        struct addrinfo *, const char *));
static struct addrinfo *get_ai __P((const struct addrinfo *,
        const struct afd *, const char *));
static struct addrinfo *copy_ai __P((const struct addrinfo *));
static int get_portmatch __P((const struct addrinfo *, const char *));
static int get_port __P((const struct addrinfo *, const char *, int));
static const struct afd *find_afd __P((int));
static int addrconfig __P((int));
static int ip6_str2scopeid __P((char *, struct sockaddr_in6 *,
                                u_int32_t *scopeidp));
static struct net_data *init __P((void));

struct addrinfo *hostent2addrinfo __P((struct hostent *,
                                       const struct addrinfo *));
struct addrinfo *addr2addrinfo __P((const struct addrinfo *,
                                    const char *));

#if 0
static const char *ai_errlist[] = {
        "Success",
        "Address family for hostname not supported",    /*%< EAI_ADDRFAMILY */
        "Temporary failure in name resolution",         /*%< EAI_AGAIN */
        "Invalid value for ai_flags",                   /*%< EAI_BADFLAGS */
        "Non-recoverable failure in name resolution",   /*%< EAI_FAIL */
        "ai_family not supported",                      /*%< EAI_FAMILY */
        "Memory allocation failure",                    /*%< EAI_MEMORY */
        "No address associated with hostname",          /*%< EAI_NODATA */
        "hostname nor servname provided, or not known", /*%< EAI_NONAME */
        "servname not supported for ai_socktype",       /*%< EAI_SERVICE */
        "ai_socktype not supported",                    /*%< EAI_SOCKTYPE */
        "System error returned in errno",               /*%< EAI_SYSTEM */
        "Invalid value for hints",                      /*%< EAI_BADHINTS */
        "Resolved protocol is unknown",                 /*%< EAI_PROTOCOL */
        "Unknown error",                                /*%< EAI_MAX */
};
#endif

/* 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)

#ifndef SOLARIS2
#define SETERROR(err) \
do { \
        /* external reference: error, and label bad */ \
        error = (err); \
        goto bad; \
        /*NOTREACHED*/ \
} while (/*CONSTCOND*/0)
#else
#define SETERROR(err) \
do { \
        /* external reference: error, and label bad */ \
        error = (err); \
        if (error == error) \
                goto bad; \
} while (/*CONSTCOND*/0)
#endif


#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)))

#if 0                           /*%< bind8 has its own version */
char *
gai_strerror(ecode)
        int ecode;
{
        if (ecode < 0 || ecode > EAI_MAX)
                ecode = EAI_MAX;
        return ai_errlist[ecode];
}
#endif

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

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

static int
str_isnumber(p)
        const char *p;
{
        char *ep;

        if (*p == '\0')
                return NO;
        ep = NULL;
        errno = 0;
        (void)strtoul(p, &ep, 10);
        if (errno == 0 && ep && *ep == '\0')
                return YES;
        else
                return NO;
}

int
getaddrinfo(hostname, servname, hints, res)
        const char *hostname, *servname;
        const struct addrinfo *hints;
        struct addrinfo **res;
{
        struct addrinfo sentinel;
        struct addrinfo *cur;
        int error = 0;
        struct addrinfo ai, ai0, *afai = NULL;
        struct addrinfo *pai;
        const struct explore *ex;

        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;
#if defined(sun) && defined(_SOCKLEN_T) && defined(__sparcv9)
        /*
         * clear _ai_pad to preserve binary
         * compatibility with previously compiled 64-bit
         * applications in a pre-SUSv3 environment by
         * guaranteeing the upper 32-bits are empty.
         */
        pai->_ai_pad = 0;
#endif
        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)
                        SETERROR(EAI_BADHINTS); /*%< xxx */
                if (hints->ai_flags & ~AI_MASK)
                        SETERROR(EAI_BADFLAGS);
                switch (hints->ai_family) {
                case PF_UNSPEC:
                case PF_INET:
                case PF_INET6:
                        break;
                default:
                        SETERROR(EAI_FAMILY);
                }
                memcpy(pai, hints, sizeof(*pai));

#if defined(sun) && defined(_SOCKLEN_T) && defined(__sparcv9)
                /*
                 * We need to clear _ai_pad to preserve binary
                 * compatibility.  See prior comment.
                 */
                pai->_ai_pad = 0;
#endif
                /*
                 * 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 (pai->ai_family != ex->e_af)
                                        continue;
                                if (ex->e_socktype == ANY)
                                        continue;
                                if (ex->e_protocol == ANY)
                                        continue;
                                if (pai->ai_socktype == ex->e_socktype &&
                                    pai->ai_protocol != ex->e_protocol) {
                                        SETERROR(EAI_BADHINTS);
                                }
                        }
                }
        }

        /*
         * post-2553: AI_ALL and AI_V4MAPPED are effective only against
         * AF_INET6 query.  They needs to be ignored if specified in other
         * occassions.
         */
        switch (pai->ai_flags & (AI_ALL | AI_V4MAPPED)) {
        case AI_V4MAPPED:
        case AI_ALL | AI_V4MAPPED:
                if (pai->ai_family != AF_INET6)
                        pai->ai_flags &= ~(AI_ALL | AI_V4MAPPED);
                break;
        case AI_ALL:
#if 1
                /* illegal */
                SETERROR(EAI_BADFLAGS);
#else
                pai->ai_flags &= ~(AI_ALL | AI_V4MAPPED);
                break;
#endif
        }

        /*
         * 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)
                        SETERROR(error);

                *pai = ai0;
        }

        ai0 = *pai;

        /* NULL hostname, or numeric hostname */
        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 (hostname == NULL) {
                        /*
                         * filter out AFs that are not supported by the kernel
                         * XXX errno?
                         */
                        if (!addrconfig(pai->ai_family))
                                continue;
                        error = explore_null(pai, servname, &cur->ai_next);
                } else
                        error = explore_numeric_scope(pai, hostname, servname,
                            &cur->ai_next);

                if (error)
                        goto free;

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

        /*
         * XXX
         * If numreic representation of AF1 can be interpreted as FQDN
         * representation of AF2, we need to think again about the code below.
         */
        if (sentinel.ai_next)
                goto good;

        if (pai->ai_flags & AI_NUMERICHOST)
                SETERROR(EAI_NONAME);
        if (hostname == NULL)
                SETERROR(EAI_NONAME);

        /*
         * hostname as alphabetical name.
         * We'll make sure that
         * - if returning addrinfo list is empty, return non-zero error
         *   value (already known one or EAI_NONAME).
         * - otherwise,
         *   + if we haven't had any errors, return 0 (i.e. success).
         *   + if we've had an error, free the list and return the error.
         * without any assumption on the behavior of explore_fqdn().
         */

        /* first, try to query DNS for all possible address families. */
        *pai = ai0;
        error = explore_fqdn(pai, hostname, servname, &afai);
        if (error) {
                if (afai != NULL)
                        freeaddrinfo(afai);
                goto free;
        }
        if (afai == NULL) {
                error = EAI_NONAME; /*%< we've had no errors. */
                goto free;
        }

        /*
         * we would like to prefer AF_INET6 than AF_INET, so we'll make an
         * outer loop by AFs.
         */
        for (ex = explore; ex->e_af >= 0; ex++) {
                *pai = ai0;

                if (pai->ai_family == PF_UNSPEC)
                        pai->ai_family = ex->e_af;

                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;
                }

#ifdef AI_ADDRCONFIG
                /*
                 * If AI_ADDRCONFIG is specified, check if we are
                 * expected to return the address family or not.
                 */
                if ((pai->ai_flags & AI_ADDRCONFIG) != 0 &&
                    !addrconfig(pai->ai_family))
                        continue;
#endif

                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 ((error = explore_copy(pai, afai, &cur->ai_next)) != 0) {
                        freeaddrinfo(afai);
                        goto free;
                }

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

        freeaddrinfo(afai);     /*%< afai must not be NULL at this point. */

        if (sentinel.ai_next) {
good:
                *res = sentinel.ai_next;
                return(SUCCESS);
        } else {
                /*
                 * All the process succeeded, but we've had an empty list.
                 * This can happen if the given hints do not match our
                 * candidates.
                 */
                error = EAI_NONAME;
        }

free:
bad:
        if (sentinel.ai_next)
                freeaddrinfo(sentinel.ai_next);
        *res = NULL;
        return(error);
}

/*%
 * FQDN hostname, DNS lookup
 */
static int
explore_fqdn(pai, hostname, servname, res)
        const struct addrinfo *pai;
        const char *hostname;
        const char *servname;
        struct addrinfo **res;
{
        struct addrinfo *result;
        struct addrinfo *cur;
        struct net_data *net_data = init();
        struct irs_ho *ho;
        int error = 0;
        char tmp[NS_MAXDNAME];
        const char *cp;

        INSIST(res != NULL && *res == NULL);

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

        if (!net_data || !(ho = net_data->ho))
                return(0);
#if 0                           /*%< XXX (notyet) */
        if (net_data->ho_stayopen && net_data->ho_last &&
            net_data->ho_last->h_addrtype == af) {
                if (ns_samename(name, net_data->ho_last->h_name) == 1)
                        return (net_data->ho_last);
                for (hap = net_data->ho_last->h_aliases; hap && *hap; hap++)
                        if (ns_samename(name, *hap) == 1)
                                return (net_data->ho_last);
        }
#endif
        if (!strchr(hostname, '.') &&
            (cp = res_hostalias(net_data->res, hostname,
                                tmp, sizeof(tmp))))
                hostname = cp;
        result = (*ho->addrinfo)(ho, hostname, pai);
        if (!net_data->ho_stayopen) {
                (*ho->minimize)(ho);
        }
        if (result == NULL) {
                int e = h_errno;

                switch(e) {
                case NETDB_INTERNAL:
                        error = EAI_SYSTEM;
                        break;
                case TRY_AGAIN:
                        error = EAI_AGAIN;
                        break;
                case NO_RECOVERY:
                        error = EAI_FAIL;
                        break;
                case HOST_NOT_FOUND:
                case NO_DATA:
                        error = EAI_NONAME;
                        break;
                default:
                case NETDB_SUCCESS: /*%< should be impossible... */
                        error = EAI_NONAME;
                        break;
                }
                goto free;
        }

        for (cur = result; cur; cur = cur->ai_next) {
                GET_PORT(cur, servname); /*%< XXX: redundant lookups... */
                /* canonname should already be filled. */
        }

        *res = result;

        return(0);

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

static int
explore_copy(pai, src0, res)
        const struct addrinfo *pai;     /*%< seed */
        const struct addrinfo *src0;    /*%< source */
        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(pai, servname, res)
        const struct addrinfo *pai;
        const char *servname;
        struct addrinfo **res;
{
        const struct afd *afd;
        struct addrinfo *cur;
        struct addrinfo sentinel;
        int error;

        *res = NULL;
        sentinel.ai_next = NULL;
        cur = &sentinel;

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

        if (pai->ai_flags & AI_PASSIVE) {
                GET_AI(cur->ai_next, afd, afd->a_addrany);
                /* xxx meaningless?
                 * GET_CANONNAME(cur->ai_next, "anyaddr");
                 */
                GET_PORT(cur->ai_next, servname);
        } else {
                GET_AI(cur->ai_next, afd, afd->a_loopback);
                /* xxx meaningless?
                 * GET_CANONNAME(cur->ai_next, "localhost");
                 */
                GET_PORT(cur->ai_next, servname);
        }
        cur = cur->ai_next;

        *res = sentinel.ai_next;
        return 0;

free:
        if (sentinel.ai_next)
                freeaddrinfo(sentinel.ai_next);
        return error;
}

/*%
 * numeric hostname
 */
static int
explore_numeric(pai, hostname, servname, res)
        const struct addrinfo *pai;
        const char *hostname;
        const char *servname;
        struct addrinfo **res;
{
        const struct afd *afd;
        struct addrinfo *cur;
        struct addrinfo sentinel;
        int error;
        char pton[PTON_MAX];

        *res = NULL;
        sentinel.ai_next = NULL;
        cur = &sentinel;

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

        switch (afd->a_af) {
#if 0 /*X/Open spec*/
        case AF_INET:
                if (inet_aton(hostname, (struct in_addr *)pton) == 1) {
                        if (pai->ai_family == afd->a_af ||
                            pai->ai_family == PF_UNSPEC /*?*/) {
                                GET_AI(cur->ai_next, afd, pton);
                                GET_PORT(cur->ai_next, servname);
                                while (cur->ai_next)
                                        cur = cur->ai_next;
                        } else
                                SETERROR(EAI_FAMILY);   /*xxx*/
                }
                break;
#endif
        default:
                if (inet_pton(afd->a_af, hostname, pton) == 1) {
                        if (pai->ai_family == afd->a_af ||
                            pai->ai_family == PF_UNSPEC /*?*/) {
                                GET_AI(cur->ai_next, afd, pton);
                                GET_PORT(cur->ai_next, servname);
                                while (cur->ai_next)
                                        cur = cur->ai_next;
                        } else
                                SETERROR(EAI_FAMILY);   /*xxx*/
                }
                break;
        }

        *res = sentinel.ai_next;
        return 0;

free:
bad:
        if (sentinel.ai_next)
                freeaddrinfo(sentinel.ai_next);
        return error;
}

/*%
 * numeric hostname with scope
 */
static int
explore_numeric_scope(pai, hostname, servname, res)
        const struct addrinfo *pai;
        const char *hostname;
        const char *servname;
        struct addrinfo **res;
{
#ifndef SCOPE_DELIMITER
        return explore_numeric(pai, hostname, servname, res);
#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);

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

        /*
         * 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);
        if (error == 0) {
                u_int32_t scopeid = 0;

                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)) {
                                free(hostname2);
                                return(EAI_NONAME); /*%< XXX: is return OK? */
                        }
#ifdef HAVE_SIN6_SCOPE_ID
                        sin6->sin6_scope_id = scopeid;
#endif
                }
        }

        free(hostname2);

        return error;
#endif
}

static int
get_canonname(pai, ai, str)
        const struct addrinfo *pai;
        struct addrinfo *ai;
        const char *str;
{
        if ((pai->ai_flags & AI_CANONNAME) != 0) {
                ai->ai_canonname = (char *)malloc(strlen(str) + 1);
                if (ai->ai_canonname == NULL)
                        return EAI_MEMORY;
                strcpy(ai->ai_canonname, str);
        }
        return 0;
}

static struct addrinfo *
get_ai(pai, afd, addr)
        const struct addrinfo *pai;
        const struct afd *afd;
        const char *addr;
{
        char *p;
        struct addrinfo *ai;

        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);
#ifdef HAVE_SA_LEN
        ai->ai_addr->sa_len = afd->a_socklen;
#endif
        ai->ai_addrlen = afd->a_socklen;
        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(pai)
        const struct addrinfo *pai;
{
        struct addrinfo *ai;
        size_t l;

        l = sizeof(*ai) + pai->ai_addrlen;
        if ((ai = (struct addrinfo *)malloc(l)) == NULL)
                return NULL;
        memset(ai, 0, l);
        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;
                }
                strcpy(ai->ai_canonname, pai->ai_canonname);    /* (checked) */
        } 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((const struct addrinfo *)ai, servname, 1);
}

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

        if (servname == NULL)
                return 0;
        switch (ai->ai_family) {
        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:
                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;
        }

        if (str_isnumber(servname)) {
                if (!allownumeric)
                        return EAI_SERVICE;
                port = atoi(servname);
                if (port < 0 || port > 65535)
                        return EAI_SERVICE;
                port = htons(port);
        } else {
                switch (ai->ai_socktype) {
                case SOCK_DGRAM:
                        proto = "udp";
                        break;
                case SOCK_STREAM:
                        proto = "tcp";
                        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;
                case AF_INET6:
                        ((struct sockaddr_in6 *)(void *)
                            ai->ai_addr)->sin6_port = port;
                        break;
                }
        }

        return 0;
}

static const struct afd *
find_afd(af)
        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;
}

/*%
 * post-2553: AI_ADDRCONFIG check.  if we use getipnodeby* as backend, backend
 * will take care of it.
 * the semantics of AI_ADDRCONFIG is not defined well.  we are not sure
 * if the code is right or not.
 */
static int
addrconfig(af)
        int af;
{
        int s;

        /* XXX errno */
        s = socket(af, SOCK_DGRAM, 0);
        if (s < 0) {
                if (errno != EMFILE)
                        return 0;
        } else
                close(s);
        return 1;
}

/* convert a string to a scope identifier. XXX: IPv6 specific */
static int
ip6_str2scopeid(char *scope, struct sockaddr_in6 *sin6,
                u_int32_t *scopeidp)
{
        u_int32_t scopeid;
        u_long lscopeid;
        struct in6_addr *a6 = &sin6->sin6_addr;
        char *ep;

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

#ifdef USE_IFNAMELINKID
        if (IN6_IS_ADDR_LINKLOCAL(a6) || IN6_IS_ADDR_MC_LINKLOCAL(a6) ||
            IN6_IS_ADDR_MC_NODELOCAL(a6)) {
                /*
                 * Using interface names as link indices can be allowed
                 * only when we can assume a one-to-one mappings between
                 * links and interfaces.  See comments in getnameinfo.c.
                 */
                scopeid = if_nametoindex(scope);
                if (scopeid == 0)
                        goto trynumeric;
                *scopeidp = scopeid;
                return (1);
        }
#endif

        /* 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 = lscopeid & 0xffffffff;
        if (errno == 0 && ep && *ep == '\0' && scopeid == lscopeid) {
                *scopeidp = scopeid;
                return (1);
        } else
                return (0);
}

struct addrinfo *
hostent2addrinfo(hp, pai)
        struct hostent *hp;
        const struct addrinfo *pai;
{
        int i, af, error = 0;
        char **aplist = NULL, *ap;
        struct addrinfo sentinel, *cur;
        const struct afd *afd;

        af = hp->h_addrtype;
        if (pai->ai_family != AF_UNSPEC && af != pai->ai_family)
                return(NULL);

        afd = find_afd(af);
        if (afd == NULL)
                return(NULL);

        aplist = hp->h_addr_list;

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

        for (i = 0; (ap = aplist[i]) != NULL; i++) {
#if 0                           /*%< the trick seems too much */
                af = hp->h_addr_list;
                if (af == AF_INET6 &&
                    IN6_IS_ADDR_V4MAPPED((struct in6_addr *)ap)) {
                        af = AF_INET;
                        ap = ap + sizeof(struct in6_addr)
                                - sizeof(struct in_addr);
                }
                afd = find_afd(af);
                if (afd == NULL)
                        continue;
#endif /* 0 */

                GET_AI(cur->ai_next, afd, ap);

                /* GET_PORT(cur->ai_next, servname); */
                if ((pai->ai_flags & AI_CANONNAME) != 0) {
                        /*
                         * RFC2553 says that ai_canonname will be set only for
                         * the first element.  we do it for all the elements,
                         * just for convenience.
                         */
                        GET_CANONNAME(cur->ai_next, hp->h_name);
                }
                while (cur->ai_next) /*%< no need to loop, actually. */
                        cur = cur->ai_next;
                continue;

        free:
                if (cur->ai_next)
                        freeaddrinfo(cur->ai_next);
                cur->ai_next = NULL;
                /* continue, without tht pointer CUR advanced. */
        }

        return(sentinel.ai_next);
}

struct addrinfo *
addr2addrinfo(pai, cp)
        const struct addrinfo *pai;
        const char *cp;
{
        const struct afd *afd;

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

        return(get_ai(pai, afd, cp));
}

static struct net_data *
init()
{
        struct net_data *net_data;

        if (!(net_data = net_data_init(NULL)))
                goto error;
        if (!net_data->ho) {
                net_data->ho = (*net_data->irs->ho_map)(net_data->irs);
                if (!net_data->ho || !net_data->res) {
error:
                        errno = EIO;
                        if (net_data && net_data->res)
                                RES_SET_H_ERRNO(net_data->res, NETDB_INTERNAL);
                        return (NULL);
                }

                (*net_data->ho->res_set)(net_data->ho, net_data->res, NULL);
        }

        return (net_data);
}