xref: /titanic_51/usr/src/lib/libresolv/res_query.c (revision 13bb89069ebe3cbce237b2708bda9946a2ff4607)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License, Version 1.0 only
6  * (the "License").  You may not use this file except in compliance
7  * with the License.
8  *
9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10  * or http://www.opensolaris.org/os/licensing.
11  * See the License for the specific language governing permissions
12  * and limitations under the License.
13  *
14  * When distributing Covered Code, include this CDDL HEADER in each
15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16  * If applicable, add the following below this CDDL HEADER, with the
17  * fields enclosed by brackets "[]" replaced with your own identifying
18  * information: Portions Copyright [yyyy] [name of copyright owner]
19  *
20  * CDDL HEADER END
21  */
22 /*
23  * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
24  * Use is subject to license terms.
25  */
26 
27 /*	Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T	*/
28 /*	  All Rights Reserved  	*/
29 
30 /*
31  * University Copyright- Copyright (c) 1982, 1986, 1988
32  * The Regents of the University of California
33  * All Rights Reserved
34  *
35  * University Acknowledgment- Portions of this document are derived from
36  * software developed by the University of California, Berkeley, and its
37  * contributors.
38  */
39 
40 #pragma ident	"%Z%%M%	%I%	%E% SMI"
41 
42 #include "synonyms.h"
43 
44 #include <sys/param.h>
45 #include <sys/socket.h>
46 #include <netinet/in.h>
47 #include <ctype.h>
48 #include <netdb.h>
49 #include <stdio.h>
50 #include <errno.h>
51 #include <string.h>
52 #include <arpa/inet.h>
53 #include <arpa/nameser.h>
54 #include <resolv.h>
55 
56 #if PACKETSZ > 1024
57 #define	MAXPACKET	PACKETSZ
58 #else
59 #define	MAXPACKET	1024
60 #endif
61 
62 int h_errno;
63 
64 /*
65  * Formulate a normal query, send, and await answer.
66  * Returned answer is placed in supplied buffer "answer".
67  * Perform preliminary check of answer, returning success only
68  * if no error is indicated and the answer count is nonzero.
69  * Return the size of the response on success, -1 on error.
70  * Error number is left in h_errno.
71  * Caller must parse answer and determine whether it answers the question.
72  */
73 int
74 res_query(name, class, type, answer, anslen)
75 	char *name;		/* domain name */
76 	int class, type;	/* class and type of query */
77 	u_char *answer;		/* buffer to put answer */
78 	int anslen;		/* size of answer buffer */
79 {
80 	char buf[MAXPACKET];
81 	HEADER *hp;
82 	int n;
83 
84 	if ((_res.options & RES_INIT) == 0 && res_init() == -1)
85 		return (-1);
86 #ifdef DEBUG
87 	if (_res.options & RES_DEBUG)
88 		printf("res_query(%s, %d, %d)\n", name, class, type);
89 #endif
90 	n = res_mkquery(QUERY, name, class, type, (char *)NULL, 0, NULL,
91 	    buf, sizeof (buf));
92 
93 	if (n <= 0) {
94 #ifdef DEBUG
95 		if (_res.options & RES_DEBUG)
96 			printf("res_query: mkquery failed\n");
97 #endif
98 		h_errno = NO_RECOVERY;
99 		return (n);
100 	}
101 	n = res_send(buf, n, answer, anslen);
102 	if (n < 0) {
103 #ifdef DEBUG
104 		if (_res.options & RES_DEBUG)
105 			printf("res_query: send error\n");
106 #endif
107 		h_errno = TRY_AGAIN;
108 		return (n);
109 	}
110 
111 	hp = (HEADER *) answer;
112 	if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
113 #ifdef DEBUG
114 		if (_res.options & RES_DEBUG)
115 			printf("rcode = %d, ancount=%d\n", hp->rcode,
116 			    ntohs(hp->ancount));
117 #endif
118 		switch (hp->rcode) {
119 			case NXDOMAIN:
120 				h_errno = HOST_NOT_FOUND;
121 				break;
122 			case SERVFAIL:
123 				h_errno = TRY_AGAIN;
124 				break;
125 			case NOERROR:
126 				h_errno = NO_DATA;
127 				break;
128 			case FORMERR:
129 			case NOTIMP:
130 			case REFUSED:
131 			default:
132 				h_errno = NO_RECOVERY;
133 				break;
134 		}
135 		return (-1);
136 	}
137 	if (hp->rcode == NOERROR && ntohs(hp->ancount) > 0)
138 		h_errno = 0;
139 	return (n);
140 }
141 
142 /*
143  * Formulate a normal query, send, and retrieve answer in supplied buffer.
144  * Return the size of the response on success, -1 on error.
145  * If enabled, implement search rules until answer or unrecoverable failure
146  * is detected.  Error number is left in h_errno.
147  * Only useful for queries in the same name hierarchy as the local host
148  * (not, for example, for host address-to-name lookups in domain in-addr.arpa).
149  */
150 int
151 res_search(name, class, type, answer, anslen)
152 	char *name;		/* domain name */
153 	int class, type;	/* class and type of query */
154 	u_char *answer;		/* buffer to put answer */
155 	int anslen;		/* size of answer */
156 {
157 	register char *cp, **domain;
158 	int n, ret, got_nodata = 0;
159 	char *hostalias();
160 
161 	if ((_res.options & RES_INIT) == 0 && res_init() == -1)
162 		return (-1);
163 
164 	errno = 0;
165 	h_errno = HOST_NOT_FOUND;		/* default, if we never query */
166 	for (cp = name, n = 0; *cp; cp++)
167 		if (*cp == '.')
168 			n++;
169 	if (n == 0 && (cp = hostalias(name)))
170 		return (res_query(cp, class, type, answer, anslen));
171 
172 	/*
173 	 * We do at least one level of search if
174 	 *	- there is no dot and RES_DEFNAME is set, or
175 	 *	- there is at least one dot, there is no trailing dot,
176 	 *	  and RES_DNSRCH is set.
177 	 */
178 	if ((n == 0 && _res.options & RES_DEFNAMES) ||
179 		(n != 0 && *--cp != '.' && _res.options & RES_DNSRCH)) {
180 		for (domain = _res.dnsrch; *domain; domain++) {
181 			ret = res_querydomain(name, *domain, class, type,
182 							answer, anslen);
183 			if (ret > 0)
184 				return (ret);
185 		/*
186 		 * If no server present, give up.
187 		 * If name isn't found in this domain,
188 		 * keep trying higher domains in the search list
189 		 * (if that's enabled).
190 		 * On a NO_DATA error, keep trying, otherwise
191 		 * a wildcard entry of another type could keep us
192 		 * from finding this entry higher in the domain.
193 		 * If we get some other error (negative answer or
194 		 * server failure), then stop searching up,
195 		 * but try the input name below in case it's fully-qualified.
196 		 */
197 			if (errno == ECONNREFUSED) {
198 				h_errno = TRY_AGAIN;
199 				return (-1);
200 			}
201 			if (h_errno == NO_DATA)
202 				got_nodata++;
203 			if ((h_errno != HOST_NOT_FOUND && h_errno != NO_DATA) ||
204 				(_res.options & RES_DNSRCH) == 0)
205 				break;
206 		}
207 	}
208 	/*
209 	 * If the search/default failed, try the name as fully-qualified,
210 	 * but only if it contained at least one dot (even trailing).
211 	 * This is purely a heuristic; we assume that any reasonable query
212 	 * about a top-level domain (for servers, SOA, etc) will not use
213 	 * res_search.
214 	 */
215 	if (n && (ret = res_querydomain(name, (char *)NULL, class, type,
216 	    answer, anslen)) > 0)
217 		return (ret);
218 	if (got_nodata)
219 		h_errno = NO_DATA;
220 	return (-1);
221 }
222 
223 /*
224  * Perform a call on res_query on the concatenation of name and domain,
225  * removing a trailing dot from name if domain is NULL.
226  */
227 int
228 res_querydomain(name, domain, class, type, answer, anslen)
229 	char *name, *domain;
230 	int class, type;	/* class and type of query */
231 	u_char *answer;		/* buffer to put answer */
232 	int anslen;		/* size of answer */
233 {
234 	char nbuf[2*MAXDNAME+2];
235 	char *longname = nbuf;
236 	int n;
237 
238 #ifdef DEBUG
239 	if (_res.options & RES_DEBUG) {
240 		if (domain == (char *)NULL)
241 			printf("res_querydomain(%s, NULL, %d, %d)\n",
242 					    name, class, type);
243 		else
244 			printf("res_querydomain(%s, %s, %d, %d)\n",
245 					    name, domain, class, type);
246 	}
247 #endif
248 	if (domain == NULL) {
249 		/*
250 		 * Check for trailing '.';
251 		 * copy without '.' if present.
252 		 */
253 		n = strlen(name) - 1;
254 		if (name[n] == '.' && n < sizeof (nbuf) - 1) {
255 #ifdef SYSV
256 			memcpy((void *)nbuf, (void *)name, n);
257 #else
258 			bcopy(name, nbuf, n);
259 #endif
260 			nbuf[n] = '\0';
261 		} else
262 			longname = name;
263 	} else
264 		(void) sprintf(nbuf, "%.*s.%.*s",
265 		    MAXDNAME, name, MAXDNAME, domain);
266 
267 	return (res_query(longname, class, type, answer, anslen));
268 }
269 
270 char *
271 hostalias(name)
272 	register char *name;
273 {
274 	register char *C1, *C2;
275 	FILE *fp;
276 	char *file, *getenv(), *strcpy(), *strncpy();
277 	char buf[BUFSIZ];
278 	static char abuf[MAXDNAME];
279 
280 	file = getenv("HOSTALIASES");
281 	if (file == NULL || (fp = fopen(file, "r")) == NULL)
282 		return (NULL);
283 	buf[sizeof (buf) - 1] = '\0';
284 	while (fgets(buf, sizeof (buf), fp)) {
285 		for (C1 = buf; *C1 && !isspace(*C1); ++C1);
286 		if (!*C1)
287 			break;
288 		*C1 = '\0';
289 		if (!strcasecmp(buf, name)) {
290 			while (isspace(*++C1));
291 			if (!*C1)
292 				break;
293 			for (C2 = C1 + 1; *C2 && !isspace(*C2); ++C2);
294 			abuf[sizeof (abuf) - 1] = *C2 = '\0';
295 			(void) strncpy(abuf, C1, sizeof (abuf) - 1);
296 			fclose(fp);
297 			return (abuf);
298 		}
299 	}
300 	fclose(fp);
301 	return (NULL);
302 }
303