openbsd-compat/getrrsetbyname.c - platform/external/openssh - Gitiles

 /* $OpenBSD: getrrsetbyname.c,v 1.7 2003/03/07 07:34:14 itojun Exp $ */

 /*
  * Copyright (c) 2001 Jakob Schlyter. 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.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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) 1999-2001 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.
  */

 #include "includes.h"

 #if defined(DNS) && !defined(HAVE_GETRRSETBYNAME)

 #include "getrrsetbyname.h"

 /* #include "thread_private.h" */

 #define ANSWER_BUFFER_SIZE 1024*64

 struct dns_query {
 	char			*name;
 	u_int16_t		type;
 	u_int16_t		class;
 	struct dns_query	*next;
 };

 struct dns_rr {
 	char			*name;
 	u_int16_t		type;
 	u_int16_t		class;
 	u_int16_t		ttl;
 	u_int16_t		size;
 	void			*rdata;
 	struct dns_rr		*next;
 };

 struct dns_response {
 	HEADER			header;
 	struct dns_query	*query;
 	struct dns_rr		*answer;
 	struct dns_rr		*authority;
 	struct dns_rr		*additional;
 };

 static struct dns_response *parse_dns_response(const u_char *, int);
 static struct dns_query *parse_dns_qsection(const u_char *, int,
     const u_char **, int);
 static struct dns_rr *parse_dns_rrsection(const u_char *, int, const u_char **,
     int);

 static void free_dns_query(struct dns_query *);
 static void free_dns_rr(struct dns_rr *);
 static void free_dns_response(struct dns_response *);

 static int count_dns_rr(struct dns_rr *, u_int16_t, u_int16_t);

 /*
  * Inline versions of get/put short/long.  Pointer is advanced.
  *
  * These macros demonstrate the property of C whereby it can be
  * portable or it can be elegant but rarely both.
  */

 #ifndef INT32SZ
 # define INT32SZ	4
 #endif
 #ifndef INT16SZ
 # define INT16SZ	2
 #endif

 #ifndef GETSHORT
 #define GETSHORT(s, cp) { \
 	register u_char *t_cp = (u_char *)(cp); \
 	(s) = ((u_int16_t)t_cp[0] << 8) \
 	    | ((u_int16_t)t_cp[1]) \
 	    ; \
 	(cp) += INT16SZ; \
 }
 #endif

 #ifndef GETLONG
 #define GETLONG(l, cp) { \
 	register u_char *t_cp = (u_char *)(cp); \
 	(l) = ((u_int32_t)t_cp[0] << 24) \
 	    | ((u_int32_t)t_cp[1] << 16) \
 	    | ((u_int32_t)t_cp[2] << 8) \
 	    | ((u_int32_t)t_cp[3]) \
 	    ; \
 	(cp) += INT32SZ; \
 }
 #endif

 /*
  * Routines to insert/extract short/long's.
  */

 static u_int16_t
 _getshort(msgp)
 	register const u_char *msgp;
 {
 	register u_int16_t u;

 	GETSHORT(u, msgp);
 	return (u);
 }

 static u_int32_t
 _getlong(msgp)
 	register const u_char *msgp;
 {
 	register u_int32_t u;

 	GETLONG(u, msgp);
 	return (u);
 }

 int
 getrrsetbyname(const char *hostname, unsigned int rdclass,
     unsigned int rdtype, unsigned int flags,
     struct rrsetinfo **res)
 {
 	struct __res_state *_resp = &_res;
 	int result;
 	struct rrsetinfo *rrset = NULL;
 	struct dns_response *response;
 	struct dns_rr *rr;
 	struct rdatainfo *rdata;
 	int length;
 	unsigned int index_ans, index_sig;
 	u_char answer[ANSWER_BUFFER_SIZE];

 	/* check for invalid class and type */
 	if (rdclass > 0xffff || rdtype > 0xffff) {
 		result = ERRSET_INVAL;
 		goto fail;
 	}

 	/* don't allow queries of class or type ANY */
 	if (rdclass == 0xff || rdtype == 0xff) {
 		result = ERRSET_INVAL;
 		goto fail;
 	}

 	/* don't allow flags yet, unimplemented */
 	if (flags) {
 		result = ERRSET_INVAL;
 		goto fail;
 	}

 	/* initialize resolver */
 	if ((_resp->options & RES_INIT) == 0 && res_init() == -1) {
 		result = ERRSET_FAIL;
 		goto fail;
 	}

 #ifdef DEBUG
 	_resp->options |= RES_DEBUG;
 #endif /* DEBUG */

 #ifdef RES_USE_DNSSEC
 	/* turn on DNSSEC if EDNS0 is configured */
 	if (_resp->options & RES_USE_EDNS0)
 		_resp->options |= RES_USE_DNSSEC;
 #endif /* RES_USE_DNSEC */

 	/* make query */
 	length = res_query(hostname, (signed int) rdclass, (signed int) rdtype,
 	    answer, sizeof(answer));
 	if (length < 0) {
 		switch(h_errno) {
 		case HOST_NOT_FOUND:
 			result = ERRSET_NONAME;
 			goto fail;
 		case NO_DATA:
 			result = ERRSET_NODATA;
 			goto fail;
 		default:
 			result = ERRSET_FAIL;
 			goto fail;
 		}
 	}

 	/* parse result */
 	response = parse_dns_response(answer, length);
 	if (response == NULL) {
 		result = ERRSET_FAIL;
 		goto fail;
 	}

 	if (response->header.qdcount != 1) {
 		result = ERRSET_FAIL;
 		goto fail;
 	}

 	/* initialize rrset */
 	rrset = calloc(1, sizeof(struct rrsetinfo));
 	if (rrset == NULL) {
 		result = ERRSET_NOMEMORY;
 		goto fail;
 	}
 	rrset->rri_rdclass = response->query->class;
 	rrset->rri_rdtype = response->query->type;
 	rrset->rri_ttl = response->answer->ttl;
 	rrset->rri_nrdatas = response->header.ancount;

 	/* check for authenticated data */
 	if (response->header.ad == 1)
 		rrset->rri_flags |= RRSET_VALIDATED;

 	/* copy name from answer section */
 	length = strlen(response->answer->name);
 	rrset->rri_name = malloc(length + 1);
 	if (rrset->rri_name == NULL) {
 		result = ERRSET_NOMEMORY;
 		goto fail;
 	}
 	strlcpy(rrset->rri_name, response->answer->name, length + 1);

 	/* count answers */
 	rrset->rri_nrdatas = count_dns_rr(response->answer, rrset->rri_rdclass,
 	    rrset->rri_rdtype);
 	rrset->rri_nsigs = count_dns_rr(response->answer, rrset->rri_rdclass,
 	    T_SIG);

 	/* allocate memory for answers */
 	rrset->rri_rdatas = calloc(rrset->rri_nrdatas,
 	    sizeof(struct rdatainfo));
 	if (rrset->rri_rdatas == NULL) {
 		result = ERRSET_NOMEMORY;
 		goto fail;
 	}

 	/* allocate memory for signatures */
 	rrset->rri_sigs = calloc(rrset->rri_nsigs, sizeof(struct rdatainfo));
 	if (rrset->rri_sigs == NULL) {
 		result = ERRSET_NOMEMORY;
 		goto fail;
 	}

 	/* copy answers & signatures */
 	for (rr = response->answer, index_ans = 0, index_sig = 0;
 	    rr; rr = rr->next) {

 		rdata = NULL;

 		if (rr->class == rrset->rri_rdclass &&
 		    rr->type  == rrset->rri_rdtype)
 			rdata = &rrset->rri_rdatas[index_ans++];

 		if (rr->class == rrset->rri_rdclass &&
 		    rr->type  == T_SIG)
 			rdata = &rrset->rri_sigs[index_sig++];

 		if (rdata) {
 			rdata->rdi_length = rr->size;
 			rdata->rdi_data   = malloc(rr->size);

 			if (rdata->rdi_data == NULL) {
 				result = ERRSET_NOMEMORY;
 				goto fail;
 			}
 			memcpy(rdata->rdi_data, rr->rdata, rr->size);
 		}
 	}

 	*res = rrset;
 	return (ERRSET_SUCCESS);

 fail:
 	if (rrset != NULL)
 		freerrset(rrset);
 	return (result);
 }

 void
 freerrset(struct rrsetinfo *rrset)
 {
 	u_int16_t i;

 	if (rrset == NULL)
 		return;

 	if (rrset->rri_rdatas) {
 		for (i = 0; i < rrset->rri_nrdatas; i++) {
 			if (rrset->rri_rdatas[i].rdi_data == NULL)
 				break;
 			free(rrset->rri_rdatas[i].rdi_data);
 		}
 		free(rrset->rri_rdatas);
 	}

 	if (rrset->rri_sigs) {
 		for (i = 0; i < rrset->rri_nsigs; i++) {
 			if (rrset->rri_sigs[i].rdi_data == NULL)
 				break;
 			free(rrset->rri_sigs[i].rdi_data);
 		}
 		free(rrset->rri_sigs);
 	}

 	if (rrset->rri_name)
 		free(rrset->rri_name);
 	free(rrset);
 }

 /*
  * DNS response parsing routines
  */
 static struct dns_response *
 parse_dns_response(const u_char *answer, int size)
 {
 	struct dns_response *resp;
 	const u_char *cp;

 	/* allocate memory for the response */
 	resp = calloc(1, sizeof(*resp));
 	if (resp == NULL)
 		return (NULL);

 	/* initialize current pointer */
 	cp = answer;

 	/* copy header */
 	memcpy(&resp->header, cp, HFIXEDSZ);
 	cp += HFIXEDSZ;

 	/* fix header byte order */
 	resp->header.qdcount = ntohs(resp->header.qdcount);
 	resp->header.ancount = ntohs(resp->header.ancount);
 	resp->header.nscount = ntohs(resp->header.nscount);
 	resp->header.arcount = ntohs(resp->header.arcount);

 	/* there must be at least one query */
 	if (resp->header.qdcount < 1) {
 		free_dns_response(resp);
 		return (NULL);
 	}

 	/* parse query section */
 	resp->query = parse_dns_qsection(answer, size, &cp,
 	    resp->header.qdcount);
 	if (resp->header.qdcount && resp->query == NULL) {
 		free_dns_response(resp);
 		return (NULL);
 	}

 	/* parse answer section */
 	resp->answer = parse_dns_rrsection(answer, size, &cp,
 	    resp->header.ancount);
 	if (resp->header.ancount && resp->answer == NULL) {
 		free_dns_response(resp);
 		return (NULL);
 	}

 	/* parse authority section */
 	resp->authority = parse_dns_rrsection(answer, size, &cp,
 	    resp->header.nscount);
 	if (resp->header.nscount && resp->authority == NULL) {
 		free_dns_response(resp);
 		return (NULL);
 	}

 	/* parse additional section */
 	resp->additional = parse_dns_rrsection(answer, size, &cp,
 	    resp->header.arcount);
 	if (resp->header.arcount && resp->additional == NULL) {
 		free_dns_response(resp);
 		return (NULL);
 	}

 	return (resp);
 }

 static struct dns_query *
 parse_dns_qsection(const u_char *answer, int size, const u_char **cp, int count)
 {
 	struct dns_query *head, *curr, *prev;
 	int i, length;
 	char name[MAXDNAME];

 	for (i = 1, head = NULL, prev = NULL; i <= count; i++, prev = curr) {

 		/* allocate and initialize struct */
 		curr = calloc(1, sizeof(struct dns_query));
 		if (curr == NULL) {
 			free_dns_query(head);
 			return (NULL);
 		}
 		if (head == NULL)
 			head = curr;
 		if (prev != NULL)
 			prev->next = curr;

 		/* name */
 		length = dn_expand(answer, answer + size, *cp, name,
 		    sizeof(name));
 		if (length < 0) {
 			free_dns_query(head);
 			return (NULL);
 		}
 		curr->name = strdup(name);
 		if (curr->name == NULL) {
 			free_dns_query(head);
 			return (NULL);
 		}
 		*cp += length;

 		/* type */
 		curr->type = _getshort(*cp);
 		*cp += INT16SZ;

 		/* class */
 		curr->class = _getshort(*cp);
 		*cp += INT16SZ;
 	}

 	return (head);
 }

 static struct dns_rr *
 parse_dns_rrsection(const u_char *answer, int size, const u_char **cp, int count)
 {
 	struct dns_rr *head, *curr, *prev;
 	int i, length;
 	char name[MAXDNAME];

 	for (i = 1, head = NULL, prev = NULL; i <= count; i++, prev = curr) {

 		/* allocate and initialize struct */
 		curr = calloc(1, sizeof(struct dns_rr));
 		if (curr == NULL) {
 			free_dns_rr(head);
 			return (NULL);
 		}
 		if (head == NULL)
 			head = curr;
 		if (prev != NULL)
 			prev->next = curr;

 		/* name */
 		length = dn_expand(answer, answer + size, *cp, name,
 		    sizeof(name));
 		if (length < 0) {
 			free_dns_rr(head);
 			return (NULL);
 		}
 		curr->name = strdup(name);
 		if (curr->name == NULL) {
 			free_dns_rr(head);
 			return (NULL);
 		}
 		*cp += length;

 		/* type */
 		curr->type = _getshort(*cp);
 		*cp += INT16SZ;

 		/* class */
 		curr->class = _getshort(*cp);
 		*cp += INT16SZ;

 		/* ttl */
 		curr->ttl = _getlong(*cp);
 		*cp += INT32SZ;

 		/* rdata size */
 		curr->size = _getshort(*cp);
 		*cp += INT16SZ;

 		/* rdata itself */
 		curr->rdata = malloc(curr->size);
 		if (curr->rdata == NULL) {
 			free_dns_rr(head);
 			return (NULL);
 		}
 		memcpy(curr->rdata, *cp, curr->size);
 		*cp += curr->size;
 	}

 	return (head);
 }

 static void
 free_dns_query(struct dns_query *p)
 {
 	if (p == NULL)
 		return;

 	if (p->name)
 		free(p->name);
 	free_dns_query(p->next);
 	free(p);
 }

 static void
 free_dns_rr(struct dns_rr *p)
 {
 	if (p == NULL)
 		return;

 	if (p->name)
 		free(p->name);
 	if (p->rdata)
 		free(p->rdata);
 	free_dns_rr(p->next);
 	free(p);
 }

 static void
 free_dns_response(struct dns_response *p)
 {
 	if (p == NULL)
 		return;

 	free_dns_query(p->query);
 	free_dns_rr(p->answer);
 	free_dns_rr(p->authority);
 	free_dns_rr(p->additional);
 	free(p);
 }

 static int
 count_dns_rr(struct dns_rr *p, u_int16_t class, u_int16_t type)
 {
 	int n = 0;

 	while(p) {
 		if (p->class == class && p->type == type)
 			n++;
 		p = p->next;
 	}

 	return (n);
 }

 #endif /* defined(DNS) && !defined(HAVE_GETRRSETBYNAME) */
	/* $OpenBSD: getrrsetbyname.c,v 1.7 2003/03/07 07:34:14 itojun Exp $ */

	/*
	* Copyright (c) 2001 Jakob Schlyter. 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.
	*
	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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) 1999-2001 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.
	*/

	#include "includes.h"

	#if defined(DNS) && !defined(HAVE_GETRRSETBYNAME)

	#include "getrrsetbyname.h"

	/* #include "thread_private.h" */

	#define ANSWER_BUFFER_SIZE 1024*64

	struct dns_query {
	char *name;
	u_int16_t type;
	u_int16_t class;
	struct dns_query *next;
	};

	struct dns_rr {
	char *name;
	u_int16_t type;
	u_int16_t class;
	u_int16_t ttl;
	u_int16_t size;
	void *rdata;
	struct dns_rr *next;
	};

	struct dns_response {
	HEADER header;
	struct dns_query *query;
	struct dns_rr *answer;
	struct dns_rr *authority;
	struct dns_rr *additional;
	};

	static struct dns_response parse_dns_response(const u_char , int);
	static struct dns_query parse_dns_qsection(const u_char , int,
	const u_char **, int);
	static struct dns_rr parse_dns_rrsection(const u_char , int, const u_char **,
	int);

	static void free_dns_query(struct dns_query *);
	static void free_dns_rr(struct dns_rr *);
	static void free_dns_response(struct dns_response *);

	static int count_dns_rr(struct dns_rr *, u_int16_t, u_int16_t);

	/*
	* Inline versions of get/put short/long. Pointer is advanced.
	*
	* These macros demonstrate the property of C whereby it can be
	* portable or it can be elegant but rarely both.
	*/

	#ifndef INT32SZ
	# define INT32SZ 4
	#endif
	#ifndef INT16SZ
	# define INT16SZ 2
	#endif

	#ifndef GETSHORT
	#define GETSHORT(s, cp) { \
	register u_char t_cp = (u_char )(cp); \
	(s) = ((u_int16_t)t_cp[0] << 8) \
	\| ((u_int16_t)t_cp[1]) \
	; \
	(cp) += INT16SZ; \
	}
	#endif

	#ifndef GETLONG
	#define GETLONG(l, cp) { \
	register u_char t_cp = (u_char )(cp); \
	(l) = ((u_int32_t)t_cp[0] << 24) \
	\| ((u_int32_t)t_cp[1] << 16) \
	\| ((u_int32_t)t_cp[2] << 8) \
	\| ((u_int32_t)t_cp[3]) \
	; \
	(cp) += INT32SZ; \
	}
	#endif

	/*
	* Routines to insert/extract short/long's.
	*/

	static u_int16_t
	_getshort(msgp)
	register const u_char *msgp;
	{
	register u_int16_t u;

	GETSHORT(u, msgp);
	return (u);
	}

	static u_int32_t
	_getlong(msgp)
	register const u_char *msgp;
	{
	register u_int32_t u;

	GETLONG(u, msgp);
	return (u);
	}

	int
	getrrsetbyname(const char *hostname, unsigned int rdclass,
	unsigned int rdtype, unsigned int flags,
	struct rrsetinfo **res)
	{
	struct __res_state *_resp = &_res;
	int result;
	struct rrsetinfo *rrset = NULL;
	struct dns_response *response;
	struct dns_rr *rr;
	struct rdatainfo *rdata;
	int length;
	unsigned int index_ans, index_sig;
	u_char answer[ANSWER_BUFFER_SIZE];

	/* check for invalid class and type */
	if (rdclass > 0xffff \|\| rdtype > 0xffff) {
	result = ERRSET_INVAL;
	goto fail;
	}

	/* don't allow queries of class or type ANY */
	if (rdclass == 0xff \|\| rdtype == 0xff) {
	result = ERRSET_INVAL;
	goto fail;
	}

	/* don't allow flags yet, unimplemented */
	if (flags) {
	result = ERRSET_INVAL;
	goto fail;
	}

	/* initialize resolver */
	if ((_resp->options & RES_INIT) == 0 && res_init() == -1) {
	result = ERRSET_FAIL;
	goto fail;
	}

	#ifdef DEBUG
	_resp->options \|= RES_DEBUG;
	#endif /* DEBUG */

	#ifdef RES_USE_DNSSEC
	/* turn on DNSSEC if EDNS0 is configured */
	if (_resp->options & RES_USE_EDNS0)
	_resp->options \|= RES_USE_DNSSEC;
	#endif /* RES_USE_DNSEC */

	/* make query */
	length = res_query(hostname, (signed int) rdclass, (signed int) rdtype,
	answer, sizeof(answer));
	if (length < 0) {
	switch(h_errno) {
	case HOST_NOT_FOUND:
	result = ERRSET_NONAME;
	goto fail;
	case NO_DATA:
	result = ERRSET_NODATA;
	goto fail;
	default:
	result = ERRSET_FAIL;
	goto fail;
	}
	}

	/* parse result */
	response = parse_dns_response(answer, length);
	if (response == NULL) {
	result = ERRSET_FAIL;
	goto fail;
	}

	if (response->header.qdcount != 1) {
	result = ERRSET_FAIL;
	goto fail;
	}

	/* initialize rrset */
	rrset = calloc(1, sizeof(struct rrsetinfo));
	if (rrset == NULL) {
	result = ERRSET_NOMEMORY;
	goto fail;
	}
	rrset->rri_rdclass = response->query->class;
	rrset->rri_rdtype = response->query->type;
	rrset->rri_ttl = response->answer->ttl;
	rrset->rri_nrdatas = response->header.ancount;

	/* check for authenticated data */
	if (response->header.ad == 1)
	rrset->rri_flags \|= RRSET_VALIDATED;

	/* copy name from answer section */
	length = strlen(response->answer->name);
	rrset->rri_name = malloc(length + 1);
	if (rrset->rri_name == NULL) {
	result = ERRSET_NOMEMORY;
	goto fail;
	}
	strlcpy(rrset->rri_name, response->answer->name, length + 1);

	/* count answers */
	rrset->rri_nrdatas = count_dns_rr(response->answer, rrset->rri_rdclass,
	rrset->rri_rdtype);
	rrset->rri_nsigs = count_dns_rr(response->answer, rrset->rri_rdclass,
	T_SIG);

	/* allocate memory for answers */
	rrset->rri_rdatas = calloc(rrset->rri_nrdatas,
	sizeof(struct rdatainfo));
	if (rrset->rri_rdatas == NULL) {
	result = ERRSET_NOMEMORY;
	goto fail;
	}

	/* allocate memory for signatures */
	rrset->rri_sigs = calloc(rrset->rri_nsigs, sizeof(struct rdatainfo));
	if (rrset->rri_sigs == NULL) {
	result = ERRSET_NOMEMORY;
	goto fail;
	}

	/* copy answers & signatures */
	for (rr = response->answer, index_ans = 0, index_sig = 0;
	rr; rr = rr->next) {

	rdata = NULL;

	if (rr->class == rrset->rri_rdclass &&
	rr->type == rrset->rri_rdtype)
	rdata = &rrset->rri_rdatas[index_ans++];

	if (rr->class == rrset->rri_rdclass &&
	rr->type == T_SIG)
	rdata = &rrset->rri_sigs[index_sig++];

	if (rdata) {
	rdata->rdi_length = rr->size;
	rdata->rdi_data = malloc(rr->size);

	if (rdata->rdi_data == NULL) {
	result = ERRSET_NOMEMORY;
	goto fail;
	}
	memcpy(rdata->rdi_data, rr->rdata, rr->size);
	}
	}

	*res = rrset;
	return (ERRSET_SUCCESS);

	fail:
	if (rrset != NULL)
	freerrset(rrset);
	return (result);
	}

	void
	freerrset(struct rrsetinfo *rrset)
	{
	u_int16_t i;

	if (rrset == NULL)
	return;

	if (rrset->rri_rdatas) {
	for (i = 0; i < rrset->rri_nrdatas; i++) {
	if (rrset->rri_rdatas[i].rdi_data == NULL)
	break;
	free(rrset->rri_rdatas[i].rdi_data);
	}
	free(rrset->rri_rdatas);
	}

	if (rrset->rri_sigs) {
	for (i = 0; i < rrset->rri_nsigs; i++) {
	if (rrset->rri_sigs[i].rdi_data == NULL)
	break;
	free(rrset->rri_sigs[i].rdi_data);
	}
	free(rrset->rri_sigs);
	}

	if (rrset->rri_name)
	free(rrset->rri_name);
	free(rrset);
	}

	/*
	* DNS response parsing routines
	*/
	static struct dns_response *
	parse_dns_response(const u_char *answer, int size)
	{
	struct dns_response *resp;
	const u_char *cp;

	/* allocate memory for the response */
	resp = calloc(1, sizeof(*resp));
	if (resp == NULL)
	return (NULL);

	/* initialize current pointer */
	cp = answer;

	/* copy header */
	memcpy(&resp->header, cp, HFIXEDSZ);
	cp += HFIXEDSZ;

	/* fix header byte order */
	resp->header.qdcount = ntohs(resp->header.qdcount);
	resp->header.ancount = ntohs(resp->header.ancount);
	resp->header.nscount = ntohs(resp->header.nscount);
	resp->header.arcount = ntohs(resp->header.arcount);

	/* there must be at least one query */
	if (resp->header.qdcount < 1) {
	free_dns_response(resp);
	return (NULL);
	}

	/* parse query section */
	resp->query = parse_dns_qsection(answer, size, &cp,
	resp->header.qdcount);
	if (resp->header.qdcount && resp->query == NULL) {
	free_dns_response(resp);
	return (NULL);
	}

	/* parse answer section */
	resp->answer = parse_dns_rrsection(answer, size, &cp,
	resp->header.ancount);
	if (resp->header.ancount && resp->answer == NULL) {
	free_dns_response(resp);
	return (NULL);
	}

	/* parse authority section */
	resp->authority = parse_dns_rrsection(answer, size, &cp,
	resp->header.nscount);
	if (resp->header.nscount && resp->authority == NULL) {
	free_dns_response(resp);
	return (NULL);
	}

	/* parse additional section */
	resp->additional = parse_dns_rrsection(answer, size, &cp,
	resp->header.arcount);
	if (resp->header.arcount && resp->additional == NULL) {
	free_dns_response(resp);
	return (NULL);
	}

	return (resp);
	}

	static struct dns_query *
	parse_dns_qsection(const u_char answer, int size, const u_char *cp, int count)
	{
	struct dns_query head, curr, *prev;
	int i, length;
	char name[MAXDNAME];

	for (i = 1, head = NULL, prev = NULL; i <= count; i++, prev = curr) {

	/* allocate and initialize struct */
	curr = calloc(1, sizeof(struct dns_query));
	if (curr == NULL) {
	free_dns_query(head);
	return (NULL);
	}
	if (head == NULL)
	head = curr;
	if (prev != NULL)
	prev->next = curr;

	/* name */
	length = dn_expand(answer, answer + size, *cp, name,
	sizeof(name));
	if (length < 0) {
	free_dns_query(head);
	return (NULL);
	}
	curr->name = strdup(name);
	if (curr->name == NULL) {
	free_dns_query(head);
	return (NULL);
	}
	*cp += length;

	/* type */
	curr->type = _getshort(*cp);
	*cp += INT16SZ;

	/* class */
	curr->class = _getshort(*cp);
	*cp += INT16SZ;
	}

	return (head);
	}

	static struct dns_rr *
	parse_dns_rrsection(const u_char answer, int size, const u_char *cp, int count)
	{
	struct dns_rr head, curr, *prev;
	int i, length;
	char name[MAXDNAME];

	for (i = 1, head = NULL, prev = NULL; i <= count; i++, prev = curr) {

	/* allocate and initialize struct */
	curr = calloc(1, sizeof(struct dns_rr));
	if (curr == NULL) {
	free_dns_rr(head);
	return (NULL);
	}
	if (head == NULL)
	head = curr;
	if (prev != NULL)
	prev->next = curr;

	/* name */
	length = dn_expand(answer, answer + size, *cp, name,
	sizeof(name));
	if (length < 0) {
	free_dns_rr(head);
	return (NULL);
	}
	curr->name = strdup(name);
	if (curr->name == NULL) {
	free_dns_rr(head);
	return (NULL);
	}
	*cp += length;

	/* type */
	curr->type = _getshort(*cp);
	*cp += INT16SZ;

	/* class */
	curr->class = _getshort(*cp);
	*cp += INT16SZ;

	/* ttl */
	curr->ttl = _getlong(*cp);
	*cp += INT32SZ;

	/* rdata size */
	curr->size = _getshort(*cp);
	*cp += INT16SZ;

	/* rdata itself */
	curr->rdata = malloc(curr->size);
	if (curr->rdata == NULL) {
	free_dns_rr(head);
	return (NULL);
	}
	memcpy(curr->rdata, *cp, curr->size);
	*cp += curr->size;
	}

	return (head);
	}

	static void
	free_dns_query(struct dns_query *p)
	{
	if (p == NULL)
	return;

	if (p->name)
	free(p->name);
	free_dns_query(p->next);
	free(p);
	}

	static void
	free_dns_rr(struct dns_rr *p)
	{
	if (p == NULL)
	return;

	if (p->name)
	free(p->name);
	if (p->rdata)
	free(p->rdata);
	free_dns_rr(p->next);
	free(p);
	}

	static void
	free_dns_response(struct dns_response *p)
	{
	if (p == NULL)
	return;

	free_dns_query(p->query);
	free_dns_rr(p->answer);
	free_dns_rr(p->authority);
	free_dns_rr(p->additional);
	free(p);
	}

	static int
	count_dns_rr(struct dns_rr *p, u_int16_t class, u_int16_t type)
	{
	int n = 0;

	while(p) {
	if (p->class == class && p->type == type)
	n++;
	p = p->next;
	}

	return (n);
	}

	#endif /* defined(DNS) && !defined(HAVE_GETRRSETBYNAME) */