vm: fix a null dereference on out-of-memory

[minix.git] / lib / libc / net / getaddrinfo.c

/*      $NetBSD: getaddrinfo.c,v 1.95 2009/10/02 07:41:08 wiz Exp $     */
/*      $KAME: getaddrinfo.c,v 1.29 2000/08/31 17:26:57 itojun 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.
 */

/*
 * 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.
 * - IPv4 classful (shortened) form.  RFC2553 is silent about it.  XNET 5.2
 *   says to use inet_aton() to convert IPv4 numeric to binary (alows
 *   classful form as a result).
 *   current code - disallow classful form for IPv4 (due to use of inet_pton).
 * - freeaddrinfo(NULL).  RFC2553 is silent about it.  XNET 5.2 says it is
 *   invalid.
 *   current code - SEGV on freeaddrinfo(NULL)
 * 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?
 */

#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
__RCSID("$NetBSD: getaddrinfo.c,v 1.95 2009/10/02 07:41:08 wiz Exp $");
#endif /* LIBC_SCCS and not lint */

#include "namespace.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 <assert.h>
#include <ctype.h>
#include <errno.h>
#include <netdb.h>
#include <resolv.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <syslog.h>
#include <stdarg.h>
#include <nsswitch.h>

#ifdef YP
#include <rpc/rpc.h>
#include <rpcsvc/yp_prot.h>
#include <rpcsvc/ypclnt.h>
#endif

#include "servent.h"

#ifdef __weak_alias
__weak_alias(getaddrinfo,_getaddrinfo)
__weak_alias(freeaddrinfo,_freeaddrinfo)
__weak_alias(gai_strerror,_gai_strerror)
#endif

#define SUCCESS 0
#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

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 [] = {
#ifdef INET6
        {PF_INET6, sizeof(struct in6_addr),
         sizeof(struct sockaddr_in6),
         offsetof(struct sockaddr_in6, sin6_addr),
         in6_addrany, in6_loopback, 1},
#endif
        {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
#ifdef INET6
        { PF_INET6, SOCK_DGRAM, IPPROTO_UDP, "udp", 0x07 },
        { PF_INET6, SOCK_STREAM, IPPROTO_TCP, "tcp", 0x07 },
        { PF_INET6, SOCK_RAW, ANY, NULL, 0x05 },
#endif
        { PF_INET, SOCK_DGRAM, IPPROTO_UDP, "udp", 0x07 },
        { PF_INET, SOCK_STREAM, IPPROTO_TCP, "tcp", 0x07 },
        { PF_INET, SOCK_RAW, ANY, NULL, 0x05 },
        { PF_UNSPEC, SOCK_DGRAM, IPPROTO_UDP, "udp", 0x07 },
        { PF_UNSPEC, SOCK_STREAM, IPPROTO_TCP, "tcp", 0x07 },
        { PF_UNSPEC, SOCK_RAW, ANY, NULL, 0x05 },
        { -1, 0, 0, NULL, 0 },
};

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

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

#define MAXPACKET       (64*1024)

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

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 */
};

static int str2number(const char *);
static int explore_fqdn(const struct addrinfo *, const char *,
        const char *, struct addrinfo **, struct servent_data *);
static int explore_null(const struct addrinfo *,
        const char *, struct addrinfo **, struct servent_data *);
static int explore_numeric(const struct addrinfo *, const char *,
        const char *, struct addrinfo **, const char *, struct servent_data *);
static int explore_numeric_scope(const struct addrinfo *, const char *,
        const char *, struct addrinfo **, struct servent_data *);
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 int get_portmatch(const struct addrinfo *, const char *,
    struct servent_data *);
static int get_port(const struct addrinfo *, const char *, int,
    struct servent_data *);
static const struct afd *find_afd(int);
#ifdef INET6
static int ip6_str2scopeid(char *, struct sockaddr_in6 *, u_int32_t *);
#endif

static struct addrinfo *getanswer(const querybuf *, int, const char *, int,
        const struct addrinfo *);
static void aisort(struct addrinfo *s, res_state res);
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

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);

static const char * const 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   */
        "Argument buffer overflow",                     /* EAI_OVERFLOW   */
        "Unknown error",                                /* EAI_MAX        */
};

/* 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, svd)                                 \
do {                                                            \
        /* external reference: error and label free */          \
        error = get_port((ai), (serv), 0, (svd));               \
        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)))

const char *
gai_strerror(int ecode)
{
        if (ecode < 0 || ecode > EAI_MAX)
                ecode = EAI_MAX;
        return ai_errlist[ecode];
}

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

        _DIAGASSERT(ai != NULL);

        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
str2number(const char *p)
{
        char *ep;
        unsigned long v;

        _DIAGASSERT(p != NULL);

        if (*p == '\0')
                return -1;
        ep = NULL;
        errno = 0;
        v = strtoul(p, &ep, 10);
        if (errno == 0 && ep && *ep == '\0' && v <= UINT_MAX)
                return v;
        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;
        struct addrinfo ai0;
        struct addrinfo *pai;
        const struct explore *ex;
        struct servent_data svd;

        /* hostname is allowed to be NULL */
        /* servname is allowed to be NULL */
        /* hints is allowed to be NULL */
        _DIAGASSERT(res != NULL);

        (void)memset(&svd, 0, sizeof(svd));
        memset(&sentinel, 0, sizeof(sentinel));
        cur = &sentinel;
        memset(&ai, 0, sizeof(ai));
        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_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 (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) {
                                        ERR(EAI_BADHINTS);
                                }
                        }
                }
        }

        /*
         * 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, &svd);
                if (error)
                        ERR(error);

                *pai = ai0;
        }

        ai0 = *pai;

        /* NULL hostname, or numeric hostname */
        for (ex = explore; ex->e_af >= 0; ex++) {
                *pai = ai0;

                /* PF_UNSPEC entries are prepared for DNS queries only */
                if (ex->e_af == PF_UNSPEC)
                        continue;

                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 (hostname == NULL)
                        error = explore_null(pai, servname, &cur->ai_next,
                            &svd);
                else
                        error = explore_numeric_scope(pai, hostname, servname,
                            &cur->ai_next, &svd);

                if (error)
                        goto free;

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

        /*
         * XXX
         * If numeric 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 (hostname == NULL)
                ERR(EAI_NODATA);
        if (pai->ai_flags & AI_NUMERICHOST)
                ERR(EAI_NONAME);

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

                /* require exact match for family field */
                if (pai->ai_family != ex->e_af)
                        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_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;

                error = explore_fqdn(pai, hostname, servname, &cur->ai_next,
                    &svd);

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

        /* XXX */
        if (sentinel.ai_next)
                error = 0;

        if (error)
                goto free;

        if (sentinel.ai_next) {
 good:
                endservent_r(&svd);
                *res = sentinel.ai_next;
                return SUCCESS;
        } else
                error = EAI_FAIL;
 free:
 bad:
        endservent_r(&svd);
        if (sentinel.ai_next)
                freeaddrinfo(sentinel.ai_next);
        *res = NULL;
        return error;
}

/*
 * FQDN hostname, DNS lookup
 */
static int
explore_fqdn(const struct addrinfo *pai, const char *hostname,
    const char *servname, struct addrinfo **res, struct servent_data *svd)
{
        struct addrinfo *result;
        struct addrinfo *cur;
        int error = 0;
        static const ns_dtab dtab[] = {
                NS_FILES_CB(_files_getaddrinfo, NULL)
                { NSSRC_DNS, _dns_getaddrinfo, NULL },  /* force -DHESIOD */
                NS_NIS_CB(_yp_getaddrinfo, NULL)
                NS_NULL_CB
        };

        _DIAGASSERT(pai != NULL);
        /* hostname may be NULL */
        /* servname may be NULL */
        _DIAGASSERT(res != NULL);

        result = NULL;

        /*
         * if the servname does not match socktype/protocol, ignore it.
         */
        if (get_portmatch(pai, servname, svd) != 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_NODATA;
                goto free;
        case NS_SUCCESS:
                error = 0;
                for (cur = result; cur; cur = cur->ai_next) {
                        GET_PORT(cur, servname, svd);
                        /* canonname should be filled already */
                }
                break;
        }

        *res = result;

        return 0;

free:
        if (result)
                freeaddrinfo(result);
        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, struct servent_data *svd)
{
        int s;
        const struct afd *afd;
        struct addrinfo *cur;
        struct addrinfo sentinel;
        int error;

        _DIAGASSERT(pai != NULL);
        /* servname may be NULL */
        _DIAGASSERT(res != NULL);

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

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

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

        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, svd);
        } else {
                GET_AI(cur->ai_next, afd, afd->a_loopback);
                /* xxx meaningless?
                 * GET_CANONNAME(cur->ai_next, "localhost");
                 */
                GET_PORT(cur->ai_next, servname, svd);
        }
        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(const struct addrinfo *pai, const char *hostname,
    const char *servname, struct addrinfo **res, const char *canonname,
    struct servent_data *svd)
{
        const struct afd *afd;
        struct addrinfo *cur;
        struct addrinfo sentinel;
        int error;
        char pton[PTON_MAX];

        _DIAGASSERT(pai != NULL);
        /* hostname may be NULL */
        /* servname may be NULL */
        _DIAGASSERT(res != NULL);

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

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

        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, svd);
                                if ((pai->ai_flags & AI_CANONNAME)) {
                                        /*
                                         * Set the numeric address itself as
                                         * the canonical name, based on a
                                         * clarification in rfc2553bis-03.
                                         */
                                        GET_CANONNAME(cur->ai_next, canonname);
                                }
                                while (cur && cur->ai_next)
                                        cur = cur->ai_next;
                        } else
                                ERR(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, svd);
                                if ((pai->ai_flags & AI_CANONNAME)) {
                                        /*
                                         * Set the numeric address itself as
                                         * the canonical name, based on a
                                         * clarification in rfc2553bis-03.
                                         */
                                        GET_CANONNAME(cur->ai_next, canonname);
                                }
                                while (cur->ai_next)
                                        cur = cur->ai_next;
                        } else
                                ERR(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(const struct addrinfo *pai, const char *hostname,
    const char *servname, struct addrinfo **res, struct servent_data *svd)
{
#if !defined(SCOPE_DELIMITER) || !defined(INET6)
        return explore_numeric(pai, hostname, servname, res, hostname, svd);
#else
        const struct afd *afd;
        struct addrinfo *cur;
        int error;
        char *cp, *hostname2 = NULL, *scope, *addr;
        struct sockaddr_in6 *sin6;

        _DIAGASSERT(pai != NULL);
        /* hostname may be NULL */
        /* servname may be NULL */
        _DIAGASSERT(res != NULL);

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

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

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

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

        /*
         * 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, svd);
        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);
                                return(EAI_NODATA); /* XXX: is return OK? */
                        }
                        sin6->sin6_scope_id = scopeid;
                }
        }

        free(hostname2);

        return error;
#endif
}

static int
get_canonname(const struct addrinfo *pai, struct addrinfo *ai, const char *str)
{

        _DIAGASSERT(pai != NULL);
        _DIAGASSERT(ai != NULL);
        _DIAGASSERT(str != NULL);

        if ((pai->ai_flags & AI_CANONNAME) != 0) {
                ai->ai_canonname = strdup(str);
                if (ai->ai_canonname == NULL)
                        return EAI_MEMORY;
        }
        return 0;
}

struct addrinfo *
allocaddrinfo(socklen_t addrlen)
{
        struct addrinfo *ai;

        ai = calloc(sizeof(struct addrinfo) + addrlen, 1);
        if (ai) {
                ai->ai_addr = (void *)(ai+1);
#ifndef __minix
                ai->ai_addrlen = ai->ai_addr->sa_len = addrlen;
#else /* __minix */
                ai->ai_addrlen = addrlen;
#endif

        }

        return ai;
}

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

        _DIAGASSERT(pai != NULL);
        _DIAGASSERT(afd != NULL);
        _DIAGASSERT(addr != NULL);

        ai = allocaddrinfo((socklen_t)afd->a_socklen);
        if (ai == NULL)
                return NULL;

        save = ai->ai_addr;
        memcpy(ai, pai, sizeof(struct addrinfo));

        /* since we just overwrote all of ai, we have
           to restore ai_addr and ai_addrlen */
        ai->ai_addr = save;
        ai->ai_addrlen = (socklen_t)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;
}

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

        _DIAGASSERT(ai != NULL);
        /* servname may be NULL */

        return get_port(ai, servname, 1, svd);
}

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

        _DIAGASSERT(ai != NULL);
        /* servname may be NULL */

        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:
                /*
                 * This was 0.  It is now 1 so that queries specifying
                 * a NULL hint, or hint without socktype (but, hopefully,
                 * with protocol) and numeric address actually work.
                 */
                allownumeric = 1;
                break;
        default:
                return EAI_SOCKTYPE;
        }

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

                switch (ai->ai_socktype) {
                case SOCK_DGRAM:
                        proto = "udp";
                        break;
                case SOCK_STREAM:
                        proto = "tcp";
                        break;
                default:
                        proto = NULL;
                        break;
                }

                sp = getservbyname_r(servname, proto, &sv, svd);
                if (sp == 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;
}

#ifdef INET6
/* 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;

        _DIAGASSERT(scope != NULL);
        _DIAGASSERT(sin6 != NULL);
        _DIAGASSERT(scopeid != NULL);

        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)) {
                /*
                 * 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

/* code duplicate with gethnamaddr.c */

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

static struct addrinfo *
getanswer(const querybuf *answer, int anslen, const char *qname, int qtype,
    const struct addrinfo *pai)
{
        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];

        _DIAGASSERT(answer != NULL);
        _DIAGASSERT(qname != NULL);
        _DIAGASSERT(pai != NULL);

        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) {
                h_errno = NO_RECOVERY;
                return (NULL);
        }
        n = dn_expand(answer->buf, eom, cp, bp, ep - bp);
        if ((n < 0) || !(*name_ok)(bp)) {
                h_errno = 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) {
                        h_errno = 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, (size_t)(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) {
                        if (type != T_KEY && type != T_SIG) {
                                struct syslog_data sd = SYSLOG_DATA_INIT;
                                syslog_r(LOG_NOTICE|LOG_AUTH, &sd,
               "gethostby*.getanswer: asked for \"%s %s %s\", got type \"%s\"",
                                       qname, p_class(C_IN), p_type(qtype),
                                       p_type(type));
                        }
                        cp += n;
                        continue;               /* XXX - had_error++ ? */
                }
                switch (type) {
                case T_A:
                case T_AAAA:
                        if (strcasecmp(canonname, bp) != 0) {
                                struct syslog_data sd = SYSLOG_DATA_INIT;
                                syslog_r(LOG_NOTICE|LOG_AUTH, &sd,
                                       AskedForGot, canonname, bp);
                                cp += n;
                                continue;       /* XXX - had_error++ ? */
                        }
                        if (type == T_A && n != INADDRSZ) {
                                cp += n;
                                continue;
                        }
                        if (type == T_AAAA && n != IN6ADDRSZ) {
                                cp += n;
                                continue;
                        }
                        if (type == T_AAAA) {
                                struct in6_addr in6;
                                memcpy(&in6, cp, IN6ADDRSZ);
                                if (IN6_IS_ADDR_V4MAPPED(&in6)) {
                                        cp += n;
                                        continue;
                                }
                        }
                        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 (!canonname)
                        (void)get_canonname(pai, sentinel.ai_next, qname);
                else
                        (void)get_canonname(pai, sentinel.ai_next, canonname);
                h_errno = NETDB_SUCCESS;
                return sentinel.ai_next;
        }

        h_errno = NO_RECOVERY;
        return NULL;
}

#define SORTEDADDR(p)   (((struct sockaddr_in *)(void *)(p->ai_next->ai_addr))->sin_addr.s_addr)
#define SORTMATCH(p, s) ((SORTEDADDR(p) & (s).mask) == (s).addr.s_addr)

static void
aisort(struct addrinfo *s, res_state res)
{
        struct addrinfo head, *t, *p;
        int i;

        head.ai_next = NULL;
        t = &head;

        for (i = 0; i < res->nsort; i++) {
                p = s;
                while (p->ai_next) {
                        if ((p->ai_next->ai_family != AF_INET)
                        || SORTMATCH(p, res->sort_list[i])) {
                                t->ai_next = p->ai_next;
                                t = t->ai_next;
                                p->ai_next = p->ai_next->ai_next;
                        } else {
                                p = p->ai_next;
                        }
                }
        }

        /* add rest of list and reset s to the new list*/
        t->ai_next = s->ai_next;
        s->ai_next = head.ai_next;
}

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

        name = 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;

        buf = malloc(sizeof(*buf));
        if (buf == NULL) {
                h_errno = NETDB_INTERNAL;
                return NS_NOTFOUND;
        }
        buf2 = malloc(sizeof(*buf2));
        if (buf2 == NULL) {
                free(buf);
                h_errno = NETDB_INTERNAL;
                return NS_NOTFOUND;
        }

        switch (pai->ai_family) {
        case AF_UNSPEC:
                /* prefer IPv6 */
                q.name = name;
                q.qclass = C_IN;
                q.qtype = T_AAAA;
                q.answer = buf->buf;
                q.anslen = sizeof(buf->buf);
                q.next = &q2;
                q2.name = name;
                q2.qclass = C_IN;
                q2.qtype = T_A;
                q2.answer = buf2->buf;
                q2.anslen = sizeof(buf2->buf);
                break;
        case AF_INET:
                q.name = name;
                q.qclass = C_IN;
                q.qtype = T_A;
                q.answer = buf->buf;
                q.anslen = sizeof(buf->buf);
                break;
        case AF_INET6:
                q.name = name;
                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;
        }

        res = __res_get_state();
        if (res == NULL) {
                free(buf);
                free(buf2);
                return NS_NOTFOUND;
        }

        if (res_searchN(name, &q, res) < 0) {
                __res_put_state(res);
                free(buf);
                free(buf2);
                return NS_NOTFOUND;
        }
        ai = getanswer(buf, q.n, q.name, q.qtype, pai);
        if (ai) {
                cur->ai_next = ai;
                while (cur && cur->ai_next)
                        cur = cur->ai_next;
        }
        if (q.next) {
                ai = getanswer(buf2, q2.n, q2.name, q2.qtype, pai);
                if (ai)
                        cur->ai_next = ai;
        }
        free(buf);
        free(buf2);
        if (sentinel.ai_next == NULL) {
                __res_put_state(res);
                switch (h_errno) {
                case HOST_NOT_FOUND:
                        return NS_NOTFOUND;
                case TRY_AGAIN:
                        return NS_TRYAGAIN;
                default:
                        return NS_UNAVAIL;
                }
        }

        if (res->nsort)
                aisort(&sentinel, res);

        __res_put_state(res);

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

static void
_sethtent(FILE **hostf)
{

        if (!*hostf)
                *hostf = fopen(_PATH_HOSTS, "r" );
        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];

        _DIAGASSERT(name != NULL);
        _DIAGASSERT(pai != NULL);

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

found:
        hints = *pai;
        hints.ai_flags = AI_NUMERICHOST;
        error = getaddrinfo(addr, NULL, &hints, &res0);
        if (error)
                goto again;
        for (res = res0; res; res = res->ai_next) {
                /* cover it up */
                res->ai_flags = pai->ai_flags;

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

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

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

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

        _sethtent(&hostf);
        while ((p = _gethtent(&hostf, name, pai)) != NULL) {
                cur->ai_next = p;
                while (cur && cur->ai_next)
                        cur = cur->ai_next;
        }
        _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;
        const char *addr, *canonname;
        char *nextline;
        char *cp;

        _DIAGASSERT(line != NULL);
        _DIAGASSERT(pai != NULL);

        p = line;
        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;
        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->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;

        /* hosts.byname is only for IPv4 (Solaris8) */
        if (pai->ai_family == PF_UNSPEC || pai->ai_family == PF_INET) {
                r = yp_match(ypdomain, "hosts.byname", name,
                        (int)strlen(name), &ypbuf, &ypbuflen);
                if (r == 0) {
                        struct addrinfo ai4;

                        ai4 = *pai;
                        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);
        }

        /* 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;
                free(ypbuf);
        }

        if (sentinel.ai_next == NULL) {
                h_errno = 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, /* domain name */ struct res_target *target,
    res_state res)
{
        u_char buf[MAXPACKET];
        HEADER *hp;
        int n;
        struct res_target *t;
        int rcode;
        int ancount;

        _DIAGASSERT(name != NULL);
        /* XXX: target may be NULL??? */

        rcode = NOERROR;
        ancount = 0;

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

                hp = (HEADER *)(void *)t->answer;
                hp->rcode = NOERROR;    /* default */

                /* make it easier... */
                class = t->qclass;
                type = t->qtype;
                answer = t->answer;
                anslen = t->anslen;
#ifdef DEBUG
                if (res->options & RES_DEBUG)
                        printf(";; res_nquery(%s, %d, %d)\n", name, class, type);
#endif

                n = res_nmkquery(res, QUERY, name, class, type, NULL, 0, NULL,
                    buf, sizeof(buf));
#ifdef RES_USE_EDNS0
                if (n > 0 && (res->options & RES_USE_EDNS0) != 0)
                        n = res_nopt(res, n, buf, sizeof(buf), anslen);
#endif
                if (n <= 0) {
#ifdef DEBUG
                        if (res->options & RES_DEBUG)
                                printf(";; res_nquery: mkquery failed\n");
#endif
                        h_errno = NO_RECOVERY;
                        return n;
                }
                n = res_nsend(res, buf, n, answer, anslen);
#if 0
                if (n < 0) {
#ifdef DEBUG
                        if (res->options & RES_DEBUG)
                                printf(";; res_query: send error\n");
#endif
                        h_errno = TRY_AGAIN;
                        return n;
                }
#endif

                if (n < 0 || 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;
        }

        if (ancount == 0) {
                switch (rcode) {
                case NXDOMAIN:
                        h_errno = HOST_NOT_FOUND;
                        break;
                case SERVFAIL:
                        h_errno = TRY_AGAIN;
                        break;
                case NOERROR:
                        h_errno = NO_DATA;
                        break;
                case FORMERR:
                case NOTIMP:
                case REFUSED:
                default:
                        h_errno = 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;
        u_int dots;
        int trailing_dot, ret, saved_herrno;
        int got_nodata = 0, got_servfail = 0, tried_as_is = 0;

        _DIAGASSERT(name != NULL);
        _DIAGASSERT(target != NULL);

        hp = (HEADER *)(void *)target->answer;  /*XXX*/

        errno = 0;
        h_errno = 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 = __hostalias(name)) != NULL) {
                ret = res_queryN(cp, target, res);
                return ret;
        }

        /*
         * If there are dots in the name already, let's just give it a try
         * 'as is'.  The threshold can be set with the "ndots" option.
         */
        saved_herrno = -1;
        if (dots >= res->ndots) {
                ret = res_querydomainN(name, NULL, target, res);
                if (ret > 0)
                        return (ret);
                saved_herrno = 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++) {

                        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.
                         */
                        if (errno == ECONNREFUSED) {
                                h_errno = TRY_AGAIN;
                                return -1;
                        }

                        switch (h_errno) {
                        case NO_DATA:
                                got_nodata++;
                                /* FALLTHROUGH */
                        case HOST_NOT_FOUND:
                                /* keep trying */
                                break;
                        case TRY_AGAIN:
                                if (hp->rcode == SERVFAIL) {
                                        /* try next search element, if any */
                                        got_servfail++;
                                        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++;
                }
        }

        /*
         * if we have not already tried the name "as is", do that now.
         * note that we do this regardless of how many dots were in the
         * name or whether it ends with a dot.
         */
        if (!tried_as_is) {
                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.
         */
        if (saved_herrno != -1)
                h_errno = saved_herrno;
        else if (got_nodata)
                h_errno = NO_DATA;
        else if (got_servfail)
                h_errno = 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;

        _DIAGASSERT(name != NULL);
        /* XXX: target may be NULL??? */

#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 + 1 > sizeof(nbuf)) {
                        h_errno = 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 + 1 + d + 1 > sizeof(nbuf)) {
                        h_errno = NO_RECOVERY;
                        return -1;
                }
                snprintf(nbuf, sizeof(nbuf), "%s.%s", name, domain);
        }
        return res_queryN(longname, target, res);
}