/*      $NetBSD: gethnamaddr.c,v 1.95 2023/08/10 20:38:00 mrg Exp $     */

/*
 * ++Copyright++ 1985, 1988, 1993
 * -
 * Copyright (c) 1985, 1988, 1993
 *    The Regents of the University of California.  All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * -
 * Portions Copyright (c) 1993 by Digital Equipment Corporation.
 * 
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies, and that
 * the name of Digital Equipment Corporation not be used in advertising or
 * publicity pertaining to distribution of the document or software without
 * specific, written prior permission.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
 * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
 * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
 * SOFTWARE.
 * -
 * --Copyright--
 */

#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
#if 0
static char sccsid[] = "@(#)gethostnamadr.c     8.1 (Berkeley) 6/4/93";
static char rcsid[] = "Id: gethnamaddr.c,v 8.21 1997/06/01 20:34:37 vixie Exp ";
#else
__RCSID("$NetBSD: gethnamaddr.c,v 1.95 2023/08/10 20:38:00 mrg Exp $");
#endif
#endif /* LIBC_SCCS and not lint */

#if defined(_LIBC)
#include "namespace.h"
#endif
#include <sys/param.h>
#include <sys/socket.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 <stdarg.h>
#include <stdio.h>
#include <syslog.h>

#ifndef LOG_AUTH
# define LOG_AUTH 0
#endif

#define MULTI_PTRS_ARE_ALIASES 1        /* XXX - experimental */

#include <nsswitch.h>
#include <stdlib.h>
#include <string.h>
#include <libutil.h>

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

#include "hostent.h"

#if defined(_LIBC) && defined(__weak_alias)
__weak_alias(gethostbyaddr,_gethostbyaddr)
__weak_alias(gethostbyname,_gethostbyname)
__weak_alias(gethostent,_gethostent)
#endif

#define maybe_ok(res, nm, ok) (((res)->options & RES_NOCHECKNAME) != 0U || \
                               (ok)(nm) != 0)
#define maybe_hnok(res, hn) maybe_ok((res), (hn), res_hnok)
#define maybe_dnok(res, dn) maybe_ok((res), (dn), res_dnok)

#define addalias(d, s, arr, siz) do {                   \
        if (d >= &arr[siz]) {                           \
                ptrdiff_t _off = d - arr;               \
                char **xptr = realloc(arr, (siz + 10) * sizeof(*arr)); \
                if (xptr == NULL)                       \
                        goto nospc;                     \
                d = xptr + _off;                        \
                arr = xptr;                             \
                siz += 10;                              \
        }                                               \
        *d++ = s;                                       \
} while (0)

#define setup(arr, siz) do {                            \
        arr = malloc((siz = 10) * sizeof(*arr));        \
        if (arr == NULL)                                \
                goto nospc;                             \
} while (0)


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


#ifdef YP
static char *__ypdomain;
#endif

#define MAXPACKET       (64*1024)

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

typedef union {
        int32_t al;
        char ac;
} align;

#ifdef DEBUG
static void debugprintf(const char *, res_state, ...)
        __attribute__((__format__(__printf__, 1, 3)));
#endif
static struct hostent *getanswer(const querybuf *, int, const char *, int,
    res_state, struct hostent *, char *, size_t, int *);
static void map_v4v6_address(const char *, char *);
static void map_v4v6_hostent(struct hostent *, char **, char *);
static void addrsort(char **, int, res_state);

void dns_service(void);
#undef dn_skipname
int dn_skipname(const u_char *, const u_char *);

#ifdef YP
static struct hostent *_yp_hostent(char *, int, struct getnamaddr *);
#endif

static struct hostent *gethostbyname_internal(const char *, int, res_state,
    struct hostent *, char *, size_t, int *);

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


#ifdef DEBUG
static void
debugprintf(const char *msg, res_state res, ...)
{
        _DIAGASSERT(msg != NULL);

        if (res->options & RES_DEBUG) {
                int save = errno;
                va_list ap;

                va_start (ap, res);
                vprintf(msg, ap);
                va_end (ap);
                
                errno = save;
        }
}
#else
# define debugprintf(msg, res, num) /*nada*/
#endif

#define BOUNDED_INCR(x) \
        do { \
                cp += (x); \
                if (cp > eom) \
                        goto no_recovery; \
        } while (0)

#define BOUNDS_CHECK(ptr, count) \
        do { \
                if ((ptr) + (count) > eom) \
                        goto no_recovery; \
        } while (0)

static struct hostent *
getanswer(const querybuf *answer, int anslen, const char *qname, int qtype,
    res_state res, struct hostent *hent, char *buf, size_t buflen, int *he)
{
        const HEADER *hp;
        const u_char *cp;
        int n;
        size_t qlen;
        const u_char *eom, *erdata;
        char *bp, **ap, **hap, *ep;
        int type, class, ancount, qdcount;
        int haveanswer, had_error;
        int toobig = 0;
        char tbuf[MAXDNAME];
        char **aliases;
        size_t maxaliases;
        char *addr_ptrs[MAXADDRS];
        const char *tname;
        int (*name_ok)(const char *);

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

        tname = qname;
        hent->h_name = NULL;
        eom = answer->buf + anslen;
        switch (qtype) {
        case T_A:
        case T_AAAA:
                name_ok = res_hnok;
                break;
        case T_PTR:
                name_ok = res_dnok;
                break;
        default:
                *he = NO_RECOVERY;
                return NULL;    /* XXX should be abort(); */
        }

        setup(aliases, maxaliases);
        /*
         * find first satisfactory answer
         */
        hp = &answer->hdr;
        ancount = ntohs(hp->ancount);
        qdcount = ntohs(hp->qdcount);
        bp = buf;
        ep = buf + buflen;
        cp = answer->buf;
        BOUNDED_INCR(HFIXEDSZ);
        if (qdcount != 1)
                goto no_recovery;

        n = dn_expand(answer->buf, eom, cp, bp, (int)(ep - bp));
        if ((n < 0) || !maybe_ok(res, bp, name_ok))
                goto no_recovery;

        BOUNDED_INCR(n + QFIXEDSZ);
        if (qtype == T_A || qtype == T_AAAA) {
                /* 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 = (int)strlen(bp) + 1;                /* for the \0 */
                if (n >= MAXHOSTNAMELEN)
                        goto no_recovery;
                hent->h_name = bp;
                bp += n;
                /* The qname can be abbreviated, but h_name is now absolute. */
                qname = hent->h_name;
        }
        hent->h_aliases = ap = aliases;
        hent->h_addr_list = hap = addr_ptrs;
        *ap = NULL;
        *hap = NULL;
        haveanswer = 0;
        had_error = 0;
        while (ancount-- > 0 && cp < eom && !had_error) {
                n = dn_expand(answer->buf, eom, cp, bp, (int)(ep - bp));
                if ((n < 0) || !maybe_ok(res, bp, name_ok)) {
                        had_error++;
                        continue;
                }
                cp += n;                        /* name */
                BOUNDS_CHECK(cp, 3 * INT16SZ + INT32SZ);
                type = _getshort(cp);
                cp += INT16SZ;                  /* type */
                class = _getshort(cp);
                cp += INT16SZ + INT32SZ;        /* class, TTL */
                n = _getshort(cp);
                cp += INT16SZ;                  /* len */
                BOUNDS_CHECK(cp, n);
                erdata = cp + n;
                if (class != C_IN) {
                        /* XXX - debug? syslog? */
                        cp += n;
                        continue;               /* XXX - had_error++ ? */
                }
                if ((qtype == T_A || qtype == T_AAAA) && type == T_CNAME) {
                        n = dn_expand(answer->buf, eom, cp, tbuf,
                            (int)sizeof tbuf);
                        if ((n < 0) || !maybe_ok(res, tbuf, name_ok)) {
                                had_error++;
                                continue;
                        }
                        cp += n;
                        if (cp != erdata)
                                goto no_recovery;
                        /* Store alias. */
                        addalias(ap, bp, aliases, maxaliases);
                        n = (int)strlen(bp) + 1;        /* for the \0 */
                        if (n >= MAXHOSTNAMELEN) {
                                had_error++;
                                continue;
                        }
                        bp += n;
                        /* Get canonical name. */
                        n = (int)strlen(tbuf) + 1;      /* for the \0 */
                        if (n > ep - bp || n >= MAXHOSTNAMELEN) {
                                had_error++;
                                continue;
                        }
                        strlcpy(bp, tbuf, (size_t)(ep - bp));
                        hent->h_name = bp;
                        bp += n;
                        continue;
                }
                if (qtype == T_PTR && type == T_CNAME) {
                        n = dn_expand(answer->buf, eom, cp, tbuf,
                            (int)sizeof tbuf);
                        if (n < 0 || !maybe_dnok(res, tbuf)) {
                                had_error++;
                                continue;
                        }
                        cp += n;
                        if (cp != erdata)
                                goto no_recovery;
                        /* Get canonical name. */
                        n = (int)strlen(tbuf) + 1;      /* for the \0 */
                        if (n > ep - bp || n >= MAXHOSTNAMELEN) {
                                had_error++;
                                continue;
                        }
                        strlcpy(bp, tbuf, (size_t)(ep - bp));
                        tname = bp;
                        bp += n;
                        continue;
                }
                if (type != qtype) {
                        if (type != T_KEY && type != T_SIG && type != T_DNAME)
                                syslog(LOG_NOTICE|LOG_AUTH,
               "gethostby*.getanswer: asked for \"%s %s %s\", got type \"%s\"",
                                       qname, p_class(C_IN), p_type(qtype),
                                       p_type(type));
                        cp += n;
                        continue;               /* XXX - had_error++ ? */
                }
                switch (type) {
                case T_PTR:
                        if (strcasecmp(tname, bp) != 0) {
                                syslog(LOG_NOTICE|LOG_AUTH,
                                       AskedForGot, qname, bp);
                                cp += n;
                                continue;       /* XXX - had_error++ ? */
                        }
                        n = dn_expand(answer->buf, eom, cp, bp, (int)(ep - bp));
                        if ((n < 0) || !maybe_hnok(res, bp)) {
                                had_error++;
                                break;
                        }
#if MULTI_PTRS_ARE_ALIASES
                        cp += n;
                        if (cp != erdata)
                                goto no_recovery;
                        if (!haveanswer)
                                hent->h_name = bp;
                        else
                                addalias(ap, bp, aliases, maxaliases);
                        if (n != -1) {
                                n = (int)strlen(bp) + 1;        /* for the \0 */
                                if (n >= MAXHOSTNAMELEN) {
                                        had_error++;
                                        break;
                                }
                                bp += n;
                        }
                        break;
#else
                        hent->h_name = bp;
                        if (res->options & RES_USE_INET6) {
                                n = strlen(bp) + 1;     /* for the \0 */
                                if (n >= MAXHOSTNAMELEN) {
                                        had_error++;
                                        break;
                                }
                                bp += n;
                                map_v4v6_hostent(hent, &bp, ep);
                        }
                        goto success;
#endif
                case T_A:
                case T_AAAA:
                        if (strcasecmp(hent->h_name, bp) != 0) {
                                syslog(LOG_NOTICE|LOG_AUTH,
                                       AskedForGot, hent->h_name, bp);
                                cp += n;
                                continue;       /* XXX - had_error++ ? */
                        }
                        if (n != hent->h_length) {
                                cp += n;
                                continue;
                        }
                        if (type == T_AAAA) {
                                struct in6_addr in6;
                                memcpy(&in6, cp, NS_IN6ADDRSZ);
                                if (IN6_IS_ADDR_V4MAPPED(&in6)) {
                                        cp += n;
                                        continue;
                                }
                        }
                        if (!haveanswer) {
                                int nn;

                                hent->h_name = bp;
                                nn = (int)strlen(bp) + 1;       /* for the \0 */
                                bp += nn;
                        }

                        bp += sizeof(align) -
                            (size_t)((u_long)bp % sizeof(align));

                        if (bp + n >= ep) {
                                debugprintf("size (%d) too big\n", res, n);
                                had_error++;
                                continue;
                        }
                        if (hap >= &addr_ptrs[MAXADDRS - 1]) {
                                if (!toobig++) {
                                        debugprintf("Too many addresses (%d)\n",
                                                res, MAXADDRS);
                                }
                                cp += n;
                                continue;
                        }
                        (void)memcpy(*hap++ = bp, cp, (size_t)n);
                        bp += n;
                        cp += n;
                        if (cp != erdata)
                                goto no_recovery;
                        break;
                default:
                        abort();
                }
                if (!had_error)
                        haveanswer++;
        }
        if (haveanswer) {
                *ap = NULL;
                *hap = NULL;
                /*
                 * Note: we sort even if host can take only one address
                 * in its return structures - should give it the "best"
                 * address in that case, not some random one
                 */
                if (res->nsort && haveanswer > 1 && qtype == T_A)
                        addrsort(addr_ptrs, haveanswer, res);
                if (!hent->h_name) {
                        n = (int)strlen(qname) + 1;     /* for the \0 */
                        if (n > ep - bp || n >= MAXHOSTNAMELEN)
                                goto no_recovery;
                        strlcpy(bp, qname, (size_t)(ep - bp));
                        hent->h_name = bp;
                        bp += n;
                }
                if (res->options & RES_USE_INET6)
                        map_v4v6_hostent(hent, &bp, ep);
                goto success;
        }
no_recovery:
        free(aliases);
        *he = NO_RECOVERY;
        return NULL;
success:
        bp = (char *)ALIGN(bp);
        n = (int)(ap - aliases);
        qlen = (n + 1) * sizeof(*hent->h_aliases);
        if ((size_t)(ep - bp) < qlen)
                goto nospc;
        hent->h_aliases = (void *)bp;
        memcpy(bp, aliases, qlen);
        free(aliases);
        aliases = NULL;

        bp += qlen;
        n = (int)(hap - addr_ptrs);
        qlen = (n + 1) * sizeof(*hent->h_addr_list);
        if ((size_t)(ep - bp) < qlen)
                goto nospc;
        hent->h_addr_list = (void *)bp;
        memcpy(bp, addr_ptrs, qlen);
        *he = NETDB_SUCCESS;
        return hent;
nospc:
        free(aliases);
        errno = ENOSPC;
        *he = NETDB_INTERNAL;
        return NULL;
}

struct hostent *
gethostbyname_r(const char *name, struct hostent *hp, char *buf, int buflen,
    int *he)
{
        res_state res = __res_get_state();

        if (res == NULL) {
                *he = NETDB_INTERNAL;
                return NULL;
        }

        _DIAGASSERT(name != NULL);

        if (res->options & RES_USE_INET6) {
                struct hostent *nhp = gethostbyname_internal(name, AF_INET6,
                    res, hp, buf, buflen, he);
                if (nhp) {
                        __res_put_state(res);
                        return nhp;
                }
        }
        hp = gethostbyname_internal(name, AF_INET, res, hp, buf, buflen, he);
        __res_put_state(res);
        return hp;
}

struct hostent *
gethostbyname2_r(const char *name, int af, struct hostent *hp, char *buf,
    size_t buflen, int *he)
{
        res_state res = __res_get_state();

        if (res == NULL) {
                *he = NETDB_INTERNAL;
                return NULL;
        }
        hp = gethostbyname_internal(name, af, res, hp, buf, buflen, he);
        __res_put_state(res);
        return hp;
}

static struct hostent *
gethostbyname_internal(const char *name, int af, res_state res,
    struct hostent *hp, char *buf, size_t buflen, int *he)
{
        const char *cp;
        struct getnamaddr info;
        char hbuf[MAXHOSTNAMELEN];
        size_t size;
        static const ns_dtab dtab[] = {
                NS_FILES_CB(_hf_gethtbyname, NULL)
                { NSSRC_DNS, _dns_gethtbyname, NULL },  /* force -DHESIOD */
                NS_NIS_CB(_yp_gethtbyname, NULL)
                NS_NULL_CB
        };

        _DIAGASSERT(name != NULL);

        switch (af) {
        case AF_INET:
                size = NS_INADDRSZ;
                break;
        case AF_INET6:
                size = NS_IN6ADDRSZ;
                break;
        default:
                *he = NETDB_INTERNAL;
                errno = EAFNOSUPPORT;
                return NULL;
        }
        if (buflen < size)
                goto nospc;

        hp->h_addrtype = af;
        hp->h_length = (int)size;

        /*
         * if there aren't any dots, it could be a user-level alias.
         * this is also done in res_nquery() since we are not the only
         * function that looks up host names.
         */
        if (!strchr(name, '.') && (cp = res_hostalias(res, name,
            hbuf, sizeof(hbuf))))
                name = cp;

        /*
         * disallow names consisting only of digits/dots, unless
         * they end in a dot.
         */
        if (isdigit((u_char) name[0]))
                for (cp = name;; ++cp) {
                        if (!*cp) {
                                if (*--cp == '.')
                                        break;
                                /*
                                 * All-numeric, no dot at the end.
                                 * Fake up a hostent as if we'd actually
                                 * done a lookup.
                                 */
                                goto fake;
                        }
                        if (!isdigit((u_char) *cp) && *cp != '.') 
                                break;
                }
        if ((isxdigit((u_char) name[0]) && strchr(name, ':') != NULL) ||
            name[0] == ':')
                for (cp = name;; ++cp) {
                        if (!*cp) {
                                if (*--cp == '.')
                                        break;
                                /*
                                 * All-IPv6-legal, no dot at the end.
                                 * Fake up a hostent as if we'd actually
                                 * done a lookup.
                                 */
                                goto fake;
                        }
                        if (!isxdigit((u_char) *cp) && *cp != ':' && *cp != '.')
                                break;
                }

        *he = NETDB_INTERNAL;
        info.hp = hp;
        info.buf = buf;
        info.buflen = buflen;
        info.he = he;
        if (nsdispatch(&info, dtab, NSDB_HOSTS, "gethostbyname",
            default_dns_files, name, strlen(name), af) != NS_SUCCESS)
                return NULL;
        *he = NETDB_SUCCESS;
        return hp;
nospc:
        *he = NETDB_INTERNAL;
        errno = ENOSPC;
        return NULL;
fake:
        HENT_ARRAY(hp->h_addr_list, 1, buf, buflen);
        HENT_ARRAY(hp->h_aliases, 0, buf, buflen);

        hp->h_aliases[0] = NULL;
        if (size > buflen)
                goto nospc;

        if (inet_pton(af, name, buf) <= 0) {
                *he = HOST_NOT_FOUND;
                return NULL;
        }
        hp->h_addr_list[0] = buf;
        hp->h_addr_list[1] = NULL;
        buf += size;
        buflen -= size;
        HENT_SCOPY(hp->h_name, name, buf, buflen);
        if (res->options & RES_USE_INET6)
                map_v4v6_hostent(hp, &buf, buf + buflen);
        *he = NETDB_SUCCESS;
        return hp;
}

struct hostent *
gethostbyaddr_r(const void *addr, int len, int af,
        struct hostent *hp, char *buf, int buflen, int *he)
{
        const u_char *uaddr = (const u_char *)addr;
        socklen_t size;
        struct getnamaddr info;
        static const ns_dtab dtab[] = {
                NS_FILES_CB(_hf_gethtbyaddr, NULL)
                { NSSRC_DNS, _dns_gethtbyaddr, NULL },  /* force -DHESIOD */
                NS_NIS_CB(_yp_gethtbyaddr, NULL)
                NS_NULL_CB
        };
        
        _DIAGASSERT(addr != NULL);

        if (af == AF_INET6 && len == NS_IN6ADDRSZ &&
            (IN6_IS_ADDR_LINKLOCAL((const struct in6_addr *)addr) ||
             IN6_IS_ADDR_SITELOCAL((const struct in6_addr *)addr))) {
                *he = HOST_NOT_FOUND;
                return NULL;
        }
        if (af == AF_INET6 && len == NS_IN6ADDRSZ &&
            (IN6_IS_ADDR_V4MAPPED((const struct in6_addr *)addr) ||
             IN6_IS_ADDR_V4COMPAT((const struct in6_addr *)addr))) {
                /* Unmap. */
                uaddr += NS_IN6ADDRSZ - NS_INADDRSZ;
                addr = uaddr;
                af = AF_INET;
                len = NS_INADDRSZ;
        }
        switch (af) {
        case AF_INET:
                size = NS_INADDRSZ;
                break;
        case AF_INET6:
                size = NS_IN6ADDRSZ;
                break;
        default:
                errno = EAFNOSUPPORT;
                *he = NETDB_INTERNAL;
                return NULL;
        }
        if (size != len) {
                errno = EINVAL;
                *he = NETDB_INTERNAL;
                return NULL;
        }
        info.hp = hp;
        info.buf = buf;
        info.buflen = buflen;
        info.he = he;
        *he = NETDB_INTERNAL;
        if (nsdispatch(&info, dtab, NSDB_HOSTS, "gethostbyaddr",
            default_dns_files, uaddr, len, af) != NS_SUCCESS)
                return NULL;
        *he = NETDB_SUCCESS;
        return hp;
}

struct hostent *
gethostent_r(FILE *hf, struct hostent *hent, char *buf, size_t buflen, int *he)
{
        char *p, *name;
        char *cp, **q;
        int af, len;
        size_t anum;
        char **aliases;
        size_t maxaliases;
        struct in6_addr host_addr;

        if (hf == NULL) {
                *he = NETDB_INTERNAL;
                errno = EINVAL;
                return NULL;
        }
        p = NULL;
        setup(aliases, maxaliases);
        for (;;) {
                free(p);
                p = fparseln(hf, NULL, NULL, NULL, FPARSELN_UNESCALL);
                if (p == NULL) {
                        free(aliases);
                        *he = HOST_NOT_FOUND;
                        return NULL;
                }
                if (!(cp = strpbrk(p, " \t")))
                        continue;
                *cp++ = '\0';
                if (inet_pton(AF_INET6, p, &host_addr) > 0) {
                        af = AF_INET6;
                        len = NS_IN6ADDRSZ;
                } else {
                        if (inet_pton(AF_INET, p, &host_addr) <= 0)
                                continue;

                        {
                        res_state res = __res_get_state();
                        if (res == NULL)
                                goto nospc;
                        if (res->options & RES_USE_INET6) {
                                map_v4v6_address(buf, buf);
                                af = AF_INET6;
                                len = NS_IN6ADDRSZ;
                        } else {
                                af = AF_INET;
                                len = NS_INADDRSZ;
                        }
                        __res_put_state(res);
                        }
                }

                /* if this is not something we're looking for, skip it. */
                if (hent->h_addrtype != 0 && hent->h_addrtype != af)
                        continue;
                if (hent->h_length != 0 && hent->h_length != len)
                        continue;

                while (*cp == ' ' || *cp == '\t')
                        cp++;
                if ((cp = strpbrk(name = cp, " \t")) != NULL)
                        *cp++ = '\0';
                q = aliases;
                while (cp && *cp) {
                        if (*cp == ' ' || *cp == '\t') {
                                cp++;
                                continue;
                        }
                        addalias(q, cp, aliases, maxaliases);
                        if ((cp = strpbrk(cp, " \t")) != NULL)
                                *cp++ = '\0';
                }
                break;
        }
        hent->h_length = len;
        hent->h_addrtype = af;
        HENT_ARRAY(hent->h_addr_list, 1, buf, buflen);
        anum = (size_t)(q - aliases);
        HENT_ARRAY(hent->h_aliases, anum, buf, buflen);
        HENT_COPY(hent->h_addr_list[0], &host_addr, hent->h_length, buf,
            buflen);
        hent->h_addr_list[1] = NULL;

        HENT_SCOPY(hent->h_name, name, buf, buflen);
        {
        size_t i;
        for (i = 0; i < anum; i++)
                HENT_SCOPY(hent->h_aliases[i], aliases[i], buf, buflen);
        }
        hent->h_aliases[anum] = NULL;

        *he = NETDB_SUCCESS;
        free(p);
        free(aliases);
        return hent;
nospc:
        free(p);
        free(aliases);
        errno = ENOSPC;
        *he = NETDB_INTERNAL;
        return NULL;
}

static void
map_v4v6_address(const char *src, char *dst)
{
        u_char *p = (u_char *)dst;
        char tmp[NS_INADDRSZ];
        int i;

        _DIAGASSERT(src != NULL);
        _DIAGASSERT(dst != NULL);

        /* Stash a temporary copy so our caller can update in place. */
        (void)memcpy(tmp, src, NS_INADDRSZ);
        /* Mark this ipv6 addr as a mapped ipv4. */
        for (i = 0; i < 10; i++)
                *p++ = 0x00;
        *p++ = 0xff;
        *p++ = 0xff;
        /* Retrieve the saved copy and we're done. */
        (void)memcpy(p, tmp, NS_INADDRSZ);
}

static void
map_v4v6_hostent(struct hostent *hp, char **bpp, char *ep)
{
        char **ap;

        _DIAGASSERT(hp != NULL);
        _DIAGASSERT(bpp != NULL);
        _DIAGASSERT(ep != NULL);

        if (hp->h_addrtype != AF_INET || hp->h_length != NS_INADDRSZ)
                return;
        hp->h_addrtype = AF_INET6;
        hp->h_length = NS_IN6ADDRSZ;
        for (ap = hp->h_addr_list; *ap; ap++) {
                int i = (int)(sizeof(align) -
                    (size_t)((u_long)*bpp % sizeof(align)));

                if (ep - *bpp < (i + NS_IN6ADDRSZ)) {
                        /* Out of memory.  Truncate address list here.  XXX */
                        *ap = NULL;
                        return;
                }
                *bpp += i;
                map_v4v6_address(*ap, *bpp);
                *ap = *bpp;
                *bpp += NS_IN6ADDRSZ;
        }
}

static void
addrsort(char **ap, int num, res_state res)
{
        int i, j;
        char **p;
        short aval[MAXADDRS];
        int needsort = 0;

        _DIAGASSERT(ap != NULL);

        p = ap;
        for (i = 0; i < num; i++, p++) {
            for (j = 0 ; (unsigned)j < res->nsort; j++)
                if (res->sort_list[j].addr.s_addr == 
                    (((struct in_addr *)(void *)(*p))->s_addr &
                    res->sort_list[j].mask))
                        break;
            aval[i] = j;
            if (needsort == 0 && i > 0 && j < aval[i-1])
                needsort = i;
        }
        if (!needsort)
            return;

        while (needsort < num) {
            for (j = needsort - 1; j >= 0; j--) {
                if (aval[j] > aval[j+1]) {
                    char *hp;

                    i = aval[j];
                    aval[j] = aval[j+1];
                    aval[j+1] = i;

                    hp = ap[j];
                    ap[j] = ap[j+1];
                    ap[j+1] = hp;
                } else
                    break;
            }
            needsort++;
        }
}


/*ARGSUSED*/
int
_dns_gethtbyname(void *rv, void *cb_data, va_list ap)
{
        querybuf *buf;
        int n, type;
        struct hostent *hp;
        const char *name;
        res_state res;
        struct getnamaddr *info = rv;

        _DIAGASSERT(rv != NULL);

        name = va_arg(ap, char *);
        /* NOSTRICT skip string len */(void)va_arg(ap, int);
        info->hp->h_addrtype = va_arg(ap, int);

        switch (info->hp->h_addrtype) {
        case AF_INET:
                info->hp->h_length = NS_INADDRSZ;
                type = T_A;
                break;
        case AF_INET6:
                info->hp->h_length = NS_IN6ADDRSZ;
                type = T_AAAA;
                break;
        default:
                return NS_UNAVAIL;
        }
        buf = malloc(sizeof(*buf));
        if (buf == NULL) {
                *info->he = NETDB_INTERNAL;
                return NS_NOTFOUND;
        }
        res = __res_get_state();
        if (res == NULL) {
                free(buf);
                *info->he = NETDB_INTERNAL;
                return NS_NOTFOUND;
        }
        n = res_nsearch(res, name, C_IN, type, buf->buf, (int)sizeof(buf->buf));
        if (n < 0) {
                free(buf);
                debugprintf("res_nsearch failed (%d)\n", res, n);
                __res_put_state(res);
                return NS_NOTFOUND;
        }
        hp = getanswer(buf, n, name, type, res, info->hp, info->buf,
            info->buflen, info->he);
        free(buf);
        __res_put_state(res);
        if (hp == NULL)
                switch (*info->he) {
                case HOST_NOT_FOUND:
                        return NS_NOTFOUND;
                case TRY_AGAIN:
                        return NS_TRYAGAIN;
                default:
                        return NS_UNAVAIL;
                }
        return NS_SUCCESS;
}

/*ARGSUSED*/
int
_dns_gethtbyaddr(void *rv, void *cb_data, va_list ap)
{
        char qbuf[MAXDNAME + 1], *qp, *ep;
        int n;
        querybuf *buf;
        struct hostent *hp;
        const unsigned char *uaddr;
        int advance;
        res_state res;
        char *bf;
        size_t blen;
        struct getnamaddr *info = rv;

        _DIAGASSERT(rv != NULL);

        uaddr = va_arg(ap, unsigned char *);
        info->hp->h_length = va_arg(ap, int);
        info->hp->h_addrtype = va_arg(ap, int);

        switch (info->hp->h_addrtype) {
        case AF_INET:
                (void)snprintf(qbuf, sizeof(qbuf), "%u.%u.%u.%u.in-addr.arpa",
                    (uaddr[3] & 0xff), (uaddr[2] & 0xff),
                    (uaddr[1] & 0xff), (uaddr[0] & 0xff));
                break;

        case AF_INET6:
                qp = qbuf;
                ep = qbuf + sizeof(qbuf) - 1;
                for (n = NS_IN6ADDRSZ - 1; n >= 0; n--) {
                        advance = snprintf(qp, (size_t)(ep - qp), "%x.%x.",
                            uaddr[n] & 0xf,
                            ((unsigned int)uaddr[n] >> 4) & 0xf);
                        if (advance > 0 && qp + advance < ep)
                                qp += advance;
                        else
                                goto norecovery;
                }
                if (strlcat(qbuf, "ip6.arpa", sizeof(qbuf)) >= sizeof(qbuf))
                        goto norecovery;
                break;
        default:
                goto norecovery;
        }

        buf = malloc(sizeof(*buf));
        if (buf == NULL) {
                goto nospc;
        }
        res = __res_get_state();
        if (res == NULL) {
                free(buf);
                goto nospc;
        }
        n = res_nquery(res, qbuf, C_IN, T_PTR, buf->buf, (int)sizeof(buf->buf));
        if (n < 0) {
                free(buf);
                debugprintf("res_nquery failed (%d)\n", res, n);
                __res_put_state(res);
                *info->he = HOST_NOT_FOUND;
                return NS_NOTFOUND;
        }
        hp = getanswer(buf, n, qbuf, T_PTR, res, info->hp, info->buf,
            info->buflen, info->he);
        free(buf);
        if (hp == NULL) {
                __res_put_state(res);
                switch (*info->he) {
                case HOST_NOT_FOUND:
                        return NS_NOTFOUND;
                case TRY_AGAIN:
                        return NS_TRYAGAIN;
                default:
                        return NS_UNAVAIL;
                }
        }

        bf = (void *)(hp->h_addr_list + 2);
        blen = (size_t)(bf - info->buf);
        if (blen + info->hp->h_length > info->buflen)
                goto nospc;
        hp->h_addr_list[0] = bf;
        hp->h_addr_list[1] = NULL;
        (void)memcpy(bf, uaddr, (size_t)info->hp->h_length);
        if (info->hp->h_addrtype == AF_INET && (res->options & RES_USE_INET6)) {
                if (blen + NS_IN6ADDRSZ > info->buflen) {
                        __res_put_state(res);
                        goto nospc;
                }
                map_v4v6_address(bf, bf);
                hp->h_addrtype = AF_INET6;
                hp->h_length = NS_IN6ADDRSZ;
        }

        __res_put_state(res);
        *info->he = NETDB_SUCCESS;
        return NS_SUCCESS;
nospc:
        *info->he = NETDB_INTERNAL;
        return NS_UNAVAIL;
norecovery:
        *info->he = NO_RECOVERY;
        return NS_UNAVAIL;
}

#ifdef YP
/*ARGSUSED*/
static struct hostent *
_yp_hostent(char *line, int af, struct getnamaddr *info)
{
        struct in6_addr host_addrs[MAXADDRS];
        char **aliases;
        size_t maxaliases;
        char *p = line;
        char *cp, **q, *ptr;
        size_t len, anum, i;
        int addrok;
        int more;
        size_t naddrs;
        struct hostent *hp = info->hp;

        _DIAGASSERT(line != NULL);

        hp->h_name = NULL;
        hp->h_addrtype = af;
        switch (af) {
        case AF_INET:
                hp->h_length = NS_INADDRSZ;
                break;
        case AF_INET6:
                hp->h_length = NS_IN6ADDRSZ;
                break;
        default:
                return NULL;
        }
        setup(aliases, maxaliases);
        naddrs = 0;
        q = aliases;

nextline:
        /* check for host_addrs overflow */
        if (naddrs >= __arraycount(host_addrs))
                goto done;

        more = 0;
        cp = strpbrk(p, " \t");
        if (cp == NULL)
                goto done;
        *cp++ = '\0';

        /* p has should have an address */
        addrok = inet_pton(af, p, &host_addrs[naddrs]);
        if (addrok != 1) {
                /* skip to the next line */
                while (cp && *cp) {
                        if (*cp == '\n') {
                                cp++;
                                goto nextline;
                        }
                        cp++;
                }
                goto done;
        }
        naddrs++;

        while (*cp == ' ' || *cp == '\t')
                cp++;
        p = cp;
        cp = strpbrk(p, " \t\n");
        if (cp != NULL) {
                if (*cp == '\n')
                        more = 1;
                *cp++ = '\0';
        }
        if (!hp->h_name)
                hp->h_name = p;
        else if (strcmp(hp->h_name, p) == 0)
                ;
        else
                addalias(q, p, aliases, maxaliases);
        p = cp;
        if (more)
                goto nextline;

        while (cp && *cp) {
                if (*cp == ' ' || *cp == '\t') {
                        cp++;
                        continue;
                }
                if (*cp == '\n') {
                        cp++;
                        goto nextline;
                }
                addalias(q, cp, aliases, maxaliases);
                cp = strpbrk(cp, " \t");
                if (cp != NULL)
                        *cp++ = '\0';
        }

done:
        if (hp->h_name == NULL) {
                free(aliases);
                return NULL;
        }

        ptr = info->buf;
        len = info->buflen;

        anum = (size_t)(q - aliases);
        HENT_ARRAY(hp->h_addr_list, naddrs, ptr, len);
        HENT_ARRAY(hp->h_aliases, anum, ptr, len);

        for (i = 0; i < naddrs; i++)
                HENT_COPY(hp->h_addr_list[i], &host_addrs[i], hp->h_length,
                    ptr, len);
        hp->h_addr_list[naddrs] = NULL;

        HENT_SCOPY(hp->h_name, hp->h_name, ptr, len);

        for (i = 0; i < anum; i++)
                HENT_SCOPY(hp->h_aliases[i], aliases[i], ptr, len);
        hp->h_aliases[anum] = NULL;
        free(aliases);

        return hp;
nospc:
        free(aliases);
        *info->he = NETDB_INTERNAL;
        errno = ENOSPC;
        return NULL;
}

/*ARGSUSED*/
int
_yp_gethtbyaddr(void *rv, void *cb_data, va_list ap)
{
        struct hostent *hp = NULL;
        char *ypcurrent;
        int ypcurrentlen, r;
        char name[INET6_ADDRSTRLEN];    /* XXX enough? */
        const unsigned char *uaddr;
        int af;
        const char *map;
        struct getnamaddr *info = rv;

        _DIAGASSERT(rv != NULL);

        uaddr = va_arg(ap, unsigned char *);
        /* NOSTRICT skip len */(void)va_arg(ap, int);
        af = va_arg(ap, int);
        
        if (!__ypdomain) {
                if (_yp_check(&__ypdomain) == 0)
                        return NS_UNAVAIL;
        }
        /*
         * XXX unfortunately, we cannot support IPv6 extended scoped address
         * notation here.  gethostbyaddr() is not scope-aware.  too bad.
         */
        if (inet_ntop(af, uaddr, name, (socklen_t)sizeof(name)) == NULL)
                return NS_UNAVAIL;
        switch (af) {
        case AF_INET:
                map = "hosts.byaddr";
                break;
        default:
                map = "ipnodes.byaddr";
                break;
        }
        ypcurrent = NULL;
        r = yp_match(__ypdomain, map, name,
                (int)strlen(name), &ypcurrent, &ypcurrentlen);
        if (r == 0)
                hp = _yp_hostent(ypcurrent, af, info);
        else
                hp = NULL;
        free(ypcurrent);
        if (hp == NULL) {
                *info->he = HOST_NOT_FOUND;
                return NS_NOTFOUND;
        }
        return NS_SUCCESS;
}

/*ARGSUSED*/
int
_yp_gethtbyname(void *rv, void *cb_data, va_list ap)
{
        struct hostent *hp;
        char *ypcurrent;
        int ypcurrentlen, r;
        const char *name;
        int af;
        const char *map;
        struct getnamaddr *info = rv;

        _DIAGASSERT(rv != NULL);

        name = va_arg(ap, char *);
        /* NOSTRICT skip string len */(void)va_arg(ap, int);
        af = va_arg(ap, int);

        if (!__ypdomain) {
                if (_yp_check(&__ypdomain) == 0)
                        return NS_UNAVAIL;
        }
        switch (af) {
        case AF_INET:
                map = "hosts.byname";
                break;
        default:
                map = "ipnodes.byname";
                break;
        }
        ypcurrent = NULL;
        r = yp_match(__ypdomain, map, name,
                (int)strlen(name), &ypcurrent, &ypcurrentlen);
        if (r == 0)
                hp = _yp_hostent(ypcurrent, af, info);
        else
                hp = NULL;
        free(ypcurrent);
        if (hp == NULL) {
                *info->he = HOST_NOT_FOUND;
                return NS_NOTFOUND;
        }
        return NS_SUCCESS;
}
#endif

/*
 * Non-reentrant versions.
 */
FILE *_h_file;
static struct hostent h_ent;
static char h_buf[16384];

struct hostent *
gethostbyaddr(const void *addr, socklen_t len, int af) {
        return gethostbyaddr_r(addr, len, af, &h_ent, h_buf, sizeof(h_buf),
            &h_errno);
}

struct hostent *
gethostbyname(const char *name) {
        return gethostbyname_r(name, &h_ent, h_buf, sizeof(h_buf), &h_errno);
}

struct hostent *
gethostbyname2(const char *name, int af) {
        return gethostbyname2_r(name, af, &h_ent, h_buf, sizeof(h_buf),
            &h_errno);
}

struct hostent *
gethostent(void)
{
        if (_h_file == NULL) {
                sethostent_r(&_h_file);
                if (_h_file == NULL) {
                        h_errno = NETDB_INTERNAL;
                        return NULL;
                }
        }
        memset(&h_ent, 0, sizeof(h_ent));
        return gethostent_r(_h_file, &h_ent, h_buf, sizeof(h_buf), &h_errno);
}