libresolv-25.tar.gz

[apple/libresolv.git] / res_query.c

/*
 * Copyright (c) 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * 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.
 */

/*
 * Portions Copyright (c) 1996-1999 by Internet Software Consortium.
 *
 * 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.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
 * CONSORTIUM 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.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static const char sccsid[] = "@(#)res_query.c   8.1 (Berkeley) 6/4/93";
static const char rcsid[] = "$Id: res_query.c,v 1.1 2006/03/01 19:01:38 majka Exp $";
#endif /* LIBC_SCCS and not lint */

#ifndef __APPLE__
#include "port_before.h"
#endif
#include <sys/types.h>
#include <sys/param.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <arpa/nameser.h>
#include <ctype.h>
#include <errno.h>
#include <netdb.h>
#include <resolv.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "res_private.h"
#include <dns_sd.h>
#include <sys/event.h>
#include <sys/time.h>
#include <time.h>
#include <unistd.h>
#ifndef __APPLE__
#include "port_after.h"
#endif

/* Options.  Leave them on. */
#define DEBUG

#if PACKETSZ > 1024
#define MAXPACKET       PACKETSZ
#else
#define MAXPACKET       1024
#endif

#define BILLION 1000000000

/* length of a reverse DNS IPv6 address query name, e.g. "9.4.a.f.c.e.e.f.e.e.1.5.4.1.4.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.e.f.ip6.arpa" */
#define IPv6_REVERSE_LEN 72

/* index of the trailing char that must be "8", "9", "A", "a", "b", or "B" */
#define IPv6_REVERSE_LINK_LOCAL_TRAILING_CHAR 58

/* index of low-order nibble of embedded scope id */
#define IPv6_REVERSE_LINK_LOCAL_SCOPE_ID_LOW 48

const static uint8_t hexval[128] =
{
        0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,          /*  0 - 15 */
        0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,          /* 16 - 31 */
        0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,          /* 32 - 47 */
        0,  1,  2,  3,  4,  5,  6,  7,  8,  9,  0,  0,  0,  0,  0,  0,          /* 48 - 63 */
        0, 10, 11, 12, 13, 14, 15,  0,  0,  0,  0,  0,  0,  0,  0,  0,          /* 64 - 79 */
        0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,          /* 80 - 95 */
        0, 10, 11, 12, 13, 14, 15,  0,  0,  0,  0,  0,  0,  0,  0,  0,          /* 96 - 111 */
        0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0           /* 112 - 127 */
};

struct res_query_context
{
        u_char *answer;
        size_t anslen;
        size_t ansmaxlen;
        uint32_t ifnum;
        DNSServiceFlags flags;
        DNSServiceErrorType error;
};

static void
res_query_callback(DNSServiceRef sdRef, DNSServiceFlags flags, uint32_t ifIndex, DNSServiceErrorType errorCode, const char *fullname, uint16_t rrtype, uint16_t rrclass, uint16_t rdlen, const void *rdata, uint32_t ttl, void *ctx)
{
        struct res_query_context *context;
        int n;
        size_t buflen;
        u_char *dnlist[2], *cp;
        HEADER *ans;
        struct in6_addr a6;

        context = (struct res_query_context *)ctx;

        context->flags = flags;
        context->error = errorCode;

        if (errorCode != kDNSServiceErr_NoError) return;

        buflen = context->ansmaxlen - context->anslen;
        if (buflen < NS_HFIXEDSZ) return;

        dnlist[0] = context->answer + NS_HFIXEDSZ;
        dnlist[1] = NULL;

        cp = context->answer + context->anslen;

        n = dn_comp((char *)fullname, cp, buflen, dnlist, &dnlist[1]);
        if (n < 0) return;

        /*
         * Check that there is enough space in the buffer for the resource name (n),
         * the resource record data (rdlen) and the resource record header (10).
         */
        if (buflen < n + rdlen + 10) return;

        cp += n;
        buflen -= n;

        putshort(rrtype, cp);
        cp += sizeof(uint16_t);

        putshort(rrclass, cp);
        cp += sizeof(uint16_t);

        putlong(ttl, cp);
        cp += sizeof(uint32_t);

        putshort(rdlen, cp);
        cp += sizeof(uint16_t);

        memcpy(cp, rdata, rdlen);
        cp += rdlen;

        ans = (HEADER *)context->answer;
        ans->ancount = htons(ntohs(ans->ancount) + 1);

        context->anslen = (size_t)(cp - context->answer);

        /* 
         * Save the interface number for the first AAAA record for link-local addresses.
         * It's used by getaddrinfo to set the scope id.
         */
        if ((context->ifnum == 0) && (rrtype == ns_t_aaaa))
        {
                memset(&a6, 0, sizeof(struct in6_addr));
                memcpy(&a6, rdata, sizeof(struct in6_addr));
                if (IN6_IS_ADDR_LINKLOCAL(&a6)) context->ifnum = ifIndex;
        }
}

static void
h_errno_for_dnssd_err(DNSServiceErrorType dnssd_err, int *h_errno_err)
{
        switch (dnssd_err)
        {
                case kDNSServiceErr_NoError:
                        *h_errno_err = NETDB_SUCCESS;
                        break;
                case kDNSServiceErr_Unknown:
                        *h_errno_err = NO_RECOVERY;
                        break;
                case kDNSServiceErr_NoSuchRecord:
                        *h_errno_err = NO_DATA;
                        break;
                case kDNSServiceErr_NoSuchName:
                        *h_errno_err = HOST_NOT_FOUND;
                        break;
                case kDNSServiceErr_NoMemory:
                default:
                        *h_errno_err = NETDB_INTERNAL;
                        break;
        }
}

static int
_is_rev_link_local(const char *name)
{
        int len, i;

        if (name == NULL) return 0;

        len = strlen(name);
        if (len == 0) return 0;

        /* check for trailing '.' */
        if (name[len - 1] == '.') len--;

        if (len != IPv6_REVERSE_LEN) return 0;

        i = IPv6_REVERSE_LINK_LOCAL_TRAILING_CHAR;
        if ((name[i] != '8') && (name[i] != '9') && (name[i] != 'A') && (name[i] != 'a') && (name[i] != 'B') && (name[i] != 'b')) return 0;

        i = IPv6_REVERSE_LINK_LOCAL_TRAILING_CHAR + 1;
        if (strncasecmp(name + i, ".e.f.ip6.arpa", 13)) return 0;

        for (i = 0; i < IPv6_REVERSE_LINK_LOCAL_TRAILING_CHAR; i += 2)
        {
                if (name[i] < '0') return 0;
                if ((name[i] > '9') && (name[i] < 'A')) return 0;
                if ((name[i] > 'F') && (name[i] < 'a')) return 0;
                if (name[i] > 'f') return 0;
                if (name[i + 1] != '.') return 0;
        }

        return 1;
}

__private_extern__ int
res_query_mDNSResponder(res_state statp, const char *name, int class, int type, u_char *answer, int anslen, struct sockaddr *from, uint32_t *fromlen)
{
        DNSServiceRef sdRef;
        DNSServiceErrorType result;
        struct res_query_context context;
        int i, kq, n, wait;
        struct kevent kv;
        struct timeval ctv;
        struct timespec now, finish, timeout;
        HEADER *ans;
        uint32_t iface;
        uint16_t nibble;
        char *qname;
        result = 0;
        kq = -1;
        ans = (HEADER *)answer;

        ans->rcode = 0;

        memset(&context, 0, sizeof(struct res_query_context));

        /* Build a dummy DNS header with question for the answer */
        context.answer = answer;
        context.ansmaxlen = anslen;
        context.anslen = res_nmkquery(statp, ns_o_query, name, class, type, NULL, 0, NULL, answer, anslen);
        if (context.anslen <= 0) return 0;

        /* Mark DNS packet as a response */
        ans->qr = 1;
        ans->qr = htons(ans->qr);

        /* Pull out Scope ID in link-local reverse queries */
        qname = (char *)name;
        iface = 0;
        if (_is_rev_link_local(name))
        {
                /* _is_rev_link_local rejects chars > 127 so it's safe to index into hexval */
                i = IPv6_REVERSE_LINK_LOCAL_SCOPE_ID_LOW;
                nibble = hexval[(uint32_t)name[i]];
                iface = nibble;

                i += 2;
                nibble = hexval[(uint32_t)name[i]];
                iface += (nibble << 4);

                i += 2;
                nibble = hexval[(uint32_t)name[i]];
                iface += (nibble << 8);

                i += 2;
                nibble = hexval[(uint32_t)name[i]];
                iface += (nibble << 12);

                if (iface != 0)
                {
                        qname = strdup(name);
                        if (qname == NULL)
                        {
                                h_errno = NO_RECOVERY;
                                errno = ENOMEM;
                                return -1;
                        }

                        i = IPv6_REVERSE_LINK_LOCAL_SCOPE_ID_LOW;
                        qname[i] = '0';
                        qname[i + 2] = '0';
                        qname[i + 4] = '0';
                        qname[i + 6] = '0';
                }
        }

        result = DNSServiceQueryRecord(&sdRef, kDNSServiceFlagsReturnIntermediates, iface, qname, type, class, res_query_callback, &context);
        if (iface != 0) free(qname);

        if (result != 0) return 0;

        /* Use a kqueue to wait for a response from mDNSResponder */
        kq = kqueue();

        /* determine the maximum time to wait for a result */
        gettimeofday(&ctv, NULL);

        /* N.B. statp->retrans is actually the total timeount in seconds */
        timeout.tv_sec = statp->retrans;
        timeout.tv_nsec = 0;

        finish.tv_sec = ctv.tv_sec + statp->retrans;
        finish.tv_nsec = ctv.tv_usec * 1000;

        EV_SET(&kv, DNSServiceRefSockFD(sdRef), EVFILT_READ, EV_ADD | EV_ONESHOT, 0, 0, 0);

        wait = 1;
        while (wait == 1)
        {
                n = kevent(kq, &kv, 1, &kv, 1, &timeout);

                if (n < 0)
                {
                        if (errno == EINTR) goto keep_waiting;
                        h_errno = NO_RECOVERY;
                        wait = 0;
                }
                else if ((n == 0) && (ans->ancount == 0))
                {
                        h_errno = TRY_AGAIN;
                        wait = 0;
                }
                else
                {
                        result = DNSServiceProcessResult(sdRef);
                        if ((result != 0) || (context.error != 0))
                        {
                                if (result == 0) result = context.error;
                                h_errno_for_dnssd_err(result, &h_errno);
                                wait = 0;
                        }

                        if ((ans->ancount > 0) && ((context.flags & kDNSServiceFlagsMoreComing) == 0)) wait = 0;
                }

        keep_waiting:

                if (wait == 1)
                {
                        /* calculate remaining timeout */
                        gettimeofday(&ctv, NULL);

                        now.tv_sec = ctv.tv_sec;
                        now.tv_nsec = ctv.tv_usec * 1000;

                        timeout.tv_sec = finish.tv_sec - now.tv_sec;
                        if (finish.tv_nsec >= now.tv_nsec)
                        {
                                timeout.tv_nsec = finish.tv_nsec - now.tv_nsec;
                        }
                        else
                        {
                                timeout.tv_nsec = BILLION - now.tv_nsec + finish.tv_nsec;
                                timeout.tv_sec--;
                        }
                }
        }

        DNSServiceRefDeallocate(sdRef);
        close(kq);

        if (ans->ancount == 0) context.anslen = -1;

        if ((from != NULL) && (fromlen != NULL) && (context.ifnum != 0))
        {
                ((struct sockaddr_in6 *)from)->sin6_len = sizeof(struct sockaddr_in6);
                ((struct sockaddr_in6 *)from)->sin6_family = AF_INET6;
                ((struct sockaddr_in6 *)from)->sin6_addr.__u6_addr.__u6_addr8[15] = 1;
                ((struct sockaddr_in6 *)from)->sin6_scope_id = context.ifnum;
                *fromlen = sizeof(struct sockaddr_in6);
        }

        return context.anslen;
}

static int
res_soa_minimum(const u_char *msg, int len)
{
        ns_msg handle;
        const u_char *eom;
        uint32_t i, b;
        int min, soa_min;

        eom = msg + len;

        handle._msg = msg;
        handle._eom = eom;

        if (msg + NS_INT16SZ > eom) return -1;
        NS_GET16(handle._id, msg);

        if (msg + NS_INT16SZ > eom) return -1;
        NS_GET16(handle._flags, msg);

        for (i = 0; i < ns_s_max; i++)
        {
                if (msg + NS_INT16SZ > eom) return -1;
                NS_GET16(handle._counts[i], msg);
        }

        if (handle._counts[ns_s_ns] == 0) return -1;

        /* Skip forward to nameserver section */
        for (i = 0; i < ns_s_ns; i++)
        {
                if (handle._counts[i] == 0) handle._sections[i] = NULL;
                else
                {
                        b = ns_skiprr(msg, eom, (ns_sect)i, handle._counts[i]);
                        if (b < 0) return -1;

                        handle._sections[i] = msg;
                        msg += b;
                }
        }

        min = -1;
        for (i = 0; i < handle._counts[ns_s_ns]; i++)
        {
                b = ns_skiprr(msg, eom, ns_s_ns, 1);
                if (b < 0) return -1;

                memcpy(&soa_min, msg + b - sizeof(int32_t), sizeof(int32_t));
                soa_min = ntohl(soa_min);
                if ((i == 0) || (soa_min < min)) min = soa_min;
                msg += b;
        }

        return min;
}

/*
 * 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.
 */
__private_extern__ int
res_nquery_soa_min(res_state statp, const char *name, int class, int type, u_char *answer, int anslen, struct sockaddr *from, int *fromlen, int *min)
{
        u_char buf[MAXPACKET];
        HEADER *hp = (HEADER *) answer;
        int n;
        u_int oflags;

        if (min != NULL) *min = -1;

        oflags = statp->_flags;

again:
        __h_errno_set(statp, 0);
        hp->rcode = ns_r_noerror;       /* default */

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

        n = res_nmkquery(statp, ns_o_query, name, class, type, NULL, 0, NULL, buf, sizeof(buf));
#ifdef RES_USE_EDNS0
        if (n > 0 && (statp->_flags & RES_F_EDNS0ERR) == 0 && (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0)
                n = res_nopt(statp, n, buf, sizeof(buf), anslen);
#endif
        if (n <= 0)
        {
#ifdef DEBUG
                if (statp->options & RES_DEBUG) printf(";; res_query: mkquery failed\n");
#endif
                __h_errno_set(statp, NO_RECOVERY);
                return (n);
        }

        n = res_nsend_2(statp, buf, n, answer, anslen, from, fromlen);
        if (n < 0)
        {
#ifdef RES_USE_EDNS0
                /* if the query choked with EDNS0, retry without EDNS0 */
                if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0 && ((oflags ^ statp->_flags) & RES_F_EDNS0ERR) != 0)
                {
                        statp->_flags |= RES_F_EDNS0ERR;
                        if (statp->options & RES_DEBUG) printf(";; res_nquery: retry without EDNS0\n");
                        goto again;
                }
#endif
#ifdef DEBUG
                if (statp->options & RES_DEBUG) printf(";; res_query: send error\n");
#endif
                __h_errno_set(statp, TRY_AGAIN);
                return (n);
        }

        if ((hp->rcode == ns_r_nxdomain) || ((hp->rcode == ns_r_noerror) && (ntohs(hp->ancount) == 0)))
        {
                if (min != NULL)
                {
                        *min = res_soa_minimum(answer, anslen);
                        if (statp->options & RES_DEBUG) printf(";; res_nquery: SOA minimum TTL = %d\n", *min);
                }
        }

        if (hp->rcode != ns_r_noerror || ntohs(hp->ancount) == 0)
        {
#ifdef DEBUG
                if (statp->options & RES_DEBUG) printf(";; rcode = %d, ancount=%d\n", hp->rcode, ntohs(hp->ancount));
#endif
                switch (hp->rcode)
                {
                        case ns_r_nxdomain:
                                __h_errno_set(statp, HOST_NOT_FOUND);
                                break;
                        case ns_r_servfail:
                                __h_errno_set(statp, TRY_AGAIN);
                                break;
                        case ns_r_noerror:
                                __h_errno_set(statp, NO_DATA);
                                break;
                        case ns_r_formerr:
                        case ns_r_notimpl:
                        case ns_r_refused:
                        default:
                                __h_errno_set(statp, NO_RECOVERY);
                                break;
                }

                return (-1);
        }

        return (n);
}

int
res_nquery_2(res_state statp, const char *name, int class, int type, u_char *answer, int anslen, struct sockaddr *from, int *fromlen)
{
        int unused = 0;

        return res_nquery_soa_min(statp, name, class, type, answer, anslen, from, fromlen, &unused);
}

int
res_nquery(res_state statp, const char *name, int class, int type, u_char *answer, int anslen)
{
        struct sockaddr_storage f;
        int l;

        l = sizeof(struct sockaddr_storage);

        return res_nquery_2(statp, name, class, type, answer, anslen, (struct sockaddr *)&f, &l);
}

/*
 * Perform a call on res_query on the concatenation of name and domain,
 * removing a trailing dot from name if domain is NULL.
 */
int
res_nquerydomain_2(res_state statp, const char *name, const char *domain, int class, int type, u_char *answer, int anslen, struct sockaddr *from, int *fromlen)
{
        char nbuf[NS_MAXDNAME];
        const char *longname = nbuf;
        int n, d;

#ifdef DEBUG
        if (statp->options & RES_DEBUG) printf(";; res_nquerydomain(%s, %s, %d, %d)\n", name, domain?domain:"<Nil>", class, type);
#endif
        if (domain == NULL)
        {
                /*
                 * Check for trailing '.';
                 * copy without '.' if present.
                 */
                n = strlen(name);
                if (n >= NS_MAXDNAME)
                {
                        __h_errno_set(statp, NO_RECOVERY);
                        return (-1);
                }

                n--;
                if (n >= 0 && name[n] == '.')
                {
                        strncpy(nbuf, name, n);
                        nbuf[n] = '\0';
                }
                else
                {
                        longname = name;
                }
        }
        else
        {
                n = strlen(name);
                d = strlen(domain);
                if (n + d + 1 >= NS_MAXDNAME)
                {
                        __h_errno_set(statp, NO_RECOVERY);
                        return (-1);
                }

                sprintf(nbuf, "%s.%s", name, domain);
        }

        return (res_nquery_2(statp, longname, class, type, answer, anslen, from, fromlen));
}

int
res_nquerydomain(res_state statp, const char *name, const char *domain, int class, int type, u_char *answer, int anslen)
{
        struct sockaddr_storage f;
        int l;

        l = sizeof(struct sockaddr_storage);

        return res_nquerydomain_2(statp, name, domain, class, type, answer, anslen, (struct sockaddr *)&f, &l);
}

/*
 * 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.
 */
int
res_nsearch_2(res_state statp, const char *name, int class, int type, u_char *answer, int anslen, struct sockaddr *from, int *fromlen)
{
        const char *cp, * const *domain;
        HEADER *hp = (HEADER *) answer;
        char tmp[NS_MAXDNAME];
        u_int dots;
        int trailing_dot, ret, saved_herrno;
        int got_nodata = 0, got_servfail = 0, root_on_list = 0;
        int tried_as_is = 0;
        int searched = 0;

        errno = 0;
        __h_errno_set(statp, HOST_NOT_FOUND);  /* True if we never query. */

        dots = 0;
        for (cp = name; *cp != '\0'; cp++) dots += (*cp == '.');

        trailing_dot = 0;
        if (cp > name && *--cp == '.') trailing_dot++;

        /* If there aren't any dots, it could be a user-level alias. */
        if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp))!= NULL)
                return (res_nquery(statp, cp, class, type, answer, anslen));

        /*
         * If there are enough dots in the name, let's just give it a
         * try 'as is'. The threshold can be set with the "ndots" option.
         * Also, query 'as is', if there is a trailing dot in the name.
         */
        saved_herrno = -1;
        if (dots >= statp->ndots || trailing_dot)
        {
                ret = res_nquerydomain_2(statp, name, NULL, class, type, answer, anslen, from, fromlen);
                if (ret > 0 || trailing_dot) 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 && (statp->options & RES_DEFNAMES) != 0) || (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0))
        {
                int done = 0;

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

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

                        ret = res_nquerydomain_2(statp, name, *domain, class, type, answer, anslen, from, fromlen);
                        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_set(statp, TRY_AGAIN);
                                return (-1);
                        }

                        switch (statp->res_h_errno)
                        {
                                case NO_DATA:
                                        got_nodata++;
                                        /* FALLTHROUGH */
                                case HOST_NOT_FOUND:
                                        /* keep trying */
                                        break;
                                case TRY_AGAIN:
                                        if (hp->rcode == ns_r_refused)
                                        {
                                                /* 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 ((statp->options & RES_DNSRCH) == 0) done++;
                }
        }

        /*
         * If the query has not already been tried as is then try it
         * unless RES_NOTLDQUERY is set and there were no dots.
         */
        if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0) && !(tried_as_is || root_on_list))
        {
                ret = res_nquerydomain_2(statp, name, NULL, class, type, answer, anslen, from, fromlen);
                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_set(statp, saved_herrno);
        else if (got_nodata)
                __h_errno_set(statp, NO_DATA);
        else if (got_servfail)
                __h_errno_set(statp, TRY_AGAIN);
        return (-1);
}

int
__res_nsearch_list_2(res_state statp, const char *name, int class, int type, u_char *answer, int anslen, struct sockaddr *from, int *fromlen, int nsearch, char **search)
{
        const char *cp, *domain;
        HEADER *hp = (HEADER *) answer;
        char tmp[NS_MAXDNAME];
        u_int dots;
        int trailing_dot, ret, saved_herrno, i;
        int got_nodata = 0, got_servfail = 0, root_on_list = 0;
        int tried_as_is = 0;
        int searched = 0;

        errno = 0;
        __h_errno_set(statp, HOST_NOT_FOUND);  /* True if we never query. */

        dots = 0;
        for (cp = name; *cp != '\0'; cp++) dots += (*cp == '.');

        trailing_dot = 0;
        if (cp > name && *--cp == '.') trailing_dot++;

        /* If there aren't any dots, it could be a user-level alias. */
        if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp)) != NULL)
                return (res_nquery(statp, cp, class, type, answer, anslen));

        /*
         * If there are enough dots in the name, let's just give it a
         * try 'as is'. The threshold can be set with the "ndots" option.
         * Also, query 'as is', if there is a trailing dot in the name.
         */
        saved_herrno = -1;
        if (dots >= statp->ndots || trailing_dot)
        {
                ret = res_nquerydomain(statp, name, NULL, class, type, answer, anslen);
                if (ret > 0 || trailing_dot) 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 && (statp->options & RES_DEFNAMES) != 0) || (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0))
        {
                int done = 0;

                for (i = 0; i < nsearch; i++)
                {
                        domain = search[i];
                        searched = 1;

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

                        ret = res_nquerydomain_2(statp, name, domain, class, type, answer, anslen, from, fromlen);
                        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_set(statp, TRY_AGAIN);
                                return -1;
                        }

                        switch (statp->res_h_errno)
                        {
                                case NO_DATA:
                                        got_nodata++;
                                        /* FALLTHROUGH */
                                case HOST_NOT_FOUND:
                                        /* keep trying */
                                        break;
                                case TRY_AGAIN:
                                        if (hp->rcode == ns_r_refused)
                                        {
                                                /* 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 ((statp->options & RES_DNSRCH) == 0) done++;
                }
        }

        /*
         * If the query has not already been tried as is then try it
         * unless RES_NOTLDQUERY is set and there were no dots.
         */
        if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0) && !(tried_as_is || root_on_list))
        {
                ret = res_nquerydomain_2(statp, name, NULL, class, type, answer, anslen, from, fromlen);
                if (ret > 0) return ret;
        }

        /*
         * 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_set(statp, saved_herrno);
        else if (got_nodata) __h_errno_set(statp, NO_DATA);
        else if (got_servfail) __h_errno_set(statp, TRY_AGAIN);
        return -1;
}
                          
int
res_nsearch(res_state statp, const char *name, int class, int type, u_char *answer, int anslen)
{
        struct sockaddr_storage f;
        int l;

        l = sizeof(struct sockaddr_storage);

        return res_nsearch_2(statp, name, class, type, answer, anslen, (struct sockaddr *)&f, &l);
}

const char *
res_hostalias(const res_state statp, const char *name, char *dst, size_t siz)
{
        char *file, *cp1, *cp2;
        char buf[BUFSIZ];
        FILE *fp;

        if (statp->options & RES_NOALIASES) return (NULL);

        file = getenv("HOSTALIASES");
        if (file == NULL || (fp = fopen(file, "r")) == NULL) return (NULL);

        setbuf(fp, NULL);
        buf[sizeof(buf) - 1] = '\0';
        while (fgets(buf, sizeof(buf), fp))
        {
                for (cp1 = buf; *cp1 && !isspace((unsigned char)*cp1); ++cp1) ;

                if (!*cp1) break;
                *cp1 = '\0';

                if (ns_samename(buf, name) == 1)
                {
                        while (isspace((unsigned char)*++cp1)) ;

                        if (!*cp1) break;

                        for (cp2 = cp1 + 1; *cp2 && !isspace((unsigned char)*cp2); ++cp2) ;

                        *cp2 = '\0';
                        strncpy(dst, cp1, siz - 1);
                        dst[siz - 1] = '\0';
                        fclose(fp);
                        return (dst);
                }
        }

        fclose(fp);
        return (NULL);
}