1 /*-
2 * Copyright (c) 1988, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * %sccs.include.redist.c%
6 * -
7 * Portions Copyright (c) 1993 by Digital Equipment Corporation.
8 *
9 * Permission to use, copy, modify, and distribute this software for any
10 * purpose with or without fee is hereby granted, provided that the above
11 * copyright notice and this permission notice appear in all copies, and that
12 * the name of Digital Equipment Corporation not be used in advertising or
13 * publicity pertaining to distribution of the document or software without
14 * specific, written prior permission.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
17 * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL DIGITAL EQUIPMENT
19 * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
20 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
21 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
22 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
23 * SOFTWARE.
24 * -
25 * --Copyright--
26 */
27
28 #if defined(LIBC_SCCS) && !defined(lint)
29 static char sccsid[] = "@(#)res_query.c 8.1 (Berkeley) 06/04/93";
30 static char rcsid[] = "$Id: res_query.c,v 1.1 1993/06/01 09:42:14 vixie Exp vixie $";
31 #endif /* LIBC_SCCS and not lint */
32
33 #include <sys/param.h>
34 #include <netinet/in.h>
35 #include <arpa/inet.h>
36 #include <arpa/nameser.h>
37 #include <netdb.h>
38 #include <resolv.h>
39 #include <stdio.h>
40 #include <ctype.h>
41 #include <errno.h>
42 #include <stdlib.h>
43 #include <string.h>
44
45 #if PACKETSZ > 1024
46 #define MAXPACKET PACKETSZ
47 #else
48 #define MAXPACKET 1024
49 #endif
50
51 int h_errno;
52
53 /*
54 * Formulate a normal query, send, and await answer.
55 * Returned answer is placed in supplied buffer "answer".
56 * Perform preliminary check of answer, returning success only
57 * if no error is indicated and the answer count is nonzero.
58 * Return the size of the response on success, -1 on error.
59 * Error number is left in h_errno.
60 * Caller must parse answer and determine whether it answers the question.
61 */
res_query(name,class,type,answer,anslen)62 res_query(name, class, type, answer, anslen)
63 char *name; /* domain name */
64 int class, type; /* class and type of query */
65 u_char *answer; /* buffer to put answer */
66 int anslen; /* size of answer buffer */
67 {
68 char buf[MAXPACKET];
69 HEADER *hp;
70 int n;
71
72 if ((_res.options & RES_INIT) == 0 && res_init() == -1)
73 return (-1);
74 #ifdef DEBUG
75 if (_res.options & RES_DEBUG)
76 printf(";; res_query(%s, %d, %d)\n", name, class, type);
77 #endif
78 n = res_mkquery(QUERY, name, class, type, (char *)NULL, 0, NULL,
79 buf, sizeof(buf));
80
81 if (n <= 0) {
82 #ifdef DEBUG
83 if (_res.options & RES_DEBUG)
84 printf(";; res_query: mkquery failed\n");
85 #endif
86 h_errno = NO_RECOVERY;
87 return (n);
88 }
89 n = res_send(buf, n, (char *)answer, anslen);
90 if (n < 0) {
91 #ifdef DEBUG
92 if (_res.options & RES_DEBUG)
93 printf(";; res_query: send error\n");
94 #endif
95 h_errno = TRY_AGAIN;
96 return(n);
97 }
98
99 hp = (HEADER *) answer;
100 if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
101 #ifdef DEBUG
102 if (_res.options & RES_DEBUG)
103 printf(";; rcode = %d, ancount=%d\n", hp->rcode,
104 ntohs(hp->ancount));
105 #endif
106 switch (hp->rcode) {
107 case NXDOMAIN:
108 h_errno = HOST_NOT_FOUND;
109 break;
110 case SERVFAIL:
111 h_errno = TRY_AGAIN;
112 break;
113 case NOERROR:
114 h_errno = NO_DATA;
115 break;
116 case FORMERR:
117 case NOTIMP:
118 case REFUSED:
119 default:
120 h_errno = NO_RECOVERY;
121 break;
122 }
123 return (-1);
124 }
125 return(n);
126 }
127
128 /*
129 * Formulate a normal query, send, and retrieve answer in supplied buffer.
130 * Return the size of the response on success, -1 on error.
131 * If enabled, implement search rules until answer or unrecoverable failure
132 * is detected. Error number is left in h_errno.
133 * Only useful for queries in the same name hierarchy as the local host
134 * (not, for example, for host address-to-name lookups in domain in-addr.arpa).
135 */
136 int
res_search(name,class,type,answer,anslen)137 res_search(name, class, type, answer, anslen)
138 char *name; /* domain name */
139 int class, type; /* class and type of query */
140 u_char *answer; /* buffer to put answer */
141 int anslen; /* size of answer */
142 {
143 register char *cp, **domain;
144 int n, ret, got_nodata = 0;
145 char *__hostalias();
146
147 if ((_res.options & RES_INIT) == 0 && res_init() == -1)
148 return (-1);
149
150 errno = 0;
151 h_errno = HOST_NOT_FOUND; /* default, if we never query */
152 for (cp = name, n = 0; *cp; cp++)
153 if (*cp == '.')
154 n++;
155 if (n == 0 && (cp = __hostalias(name)))
156 return (res_query(cp, class, type, answer, anslen));
157
158 /*
159 * We do at least one level of search if
160 * - there is no dot and RES_DEFNAME is set, or
161 * - there is at least one dot, there is no trailing dot,
162 * and RES_DNSRCH is set.
163 */
164 if ((n == 0 && _res.options & RES_DEFNAMES) ||
165 (n != 0 && *--cp != '.' && _res.options & RES_DNSRCH))
166 for (domain = _res.dnsrch; *domain; domain++) {
167 ret = res_querydomain(name, *domain, class, type,
168 answer, anslen);
169 if (ret > 0)
170 return (ret);
171 /*
172 * If no server present, give up.
173 * If name isn't found in this domain,
174 * keep trying higher domains in the search list
175 * (if that's enabled).
176 * On a NO_DATA error, keep trying, otherwise
177 * a wildcard entry of another type could keep us
178 * from finding this entry higher in the domain.
179 * If we get some other error (negative answer or
180 * server failure), then stop searching up,
181 * but try the input name below in case it's fully-qualified.
182 */
183 if (errno == ECONNREFUSED) {
184 h_errno = TRY_AGAIN;
185 return (-1);
186 }
187 if (h_errno == NO_DATA)
188 got_nodata++;
189 if ((h_errno != HOST_NOT_FOUND && h_errno != NO_DATA) ||
190 (_res.options & RES_DNSRCH) == 0)
191 break;
192 }
193 /*
194 * If the search/default failed, try the name as fully-qualified,
195 * but only if it contained at least one dot (even trailing).
196 * This is purely a heuristic; we assume that any reasonable query
197 * about a top-level domain (for servers, SOA, etc) will not use
198 * res_search.
199 */
200 if (n && (ret = res_querydomain(name, (char *)NULL, class, type,
201 answer, anslen)) > 0)
202 return (ret);
203 if (got_nodata)
204 h_errno = NO_DATA;
205 return (-1);
206 }
207
208 /*
209 * Perform a call on res_query on the concatenation of name and domain,
210 * removing a trailing dot from name if domain is NULL.
211 */
res_querydomain(name,domain,class,type,answer,anslen)212 res_querydomain(name, domain, class, type, answer, anslen)
213 char *name, *domain;
214 int class, type; /* class and type of query */
215 u_char *answer; /* buffer to put answer */
216 int anslen; /* size of answer */
217 {
218 char nbuf[2*MAXDNAME+2];
219 char *longname = nbuf;
220 int n;
221
222 #ifdef DEBUG
223 if (_res.options & RES_DEBUG)
224 printf(";; res_querydomain(%s, %s, %d, %d)\n",
225 name, domain, class, type);
226 #endif
227 if (domain == NULL) {
228 /*
229 * Check for trailing '.';
230 * copy without '.' if present.
231 */
232 n = strlen(name) - 1;
233 if (name[n] == '.' && n < sizeof(nbuf) - 1) {
234 bcopy(name, nbuf, n);
235 nbuf[n] = '\0';
236 } else
237 longname = name;
238 } else
239 (void)sprintf(nbuf, "%.*s.%.*s",
240 MAXDNAME, name, MAXDNAME, domain);
241
242 return (res_query(longname, class, type, answer, anslen));
243 }
244
245 char *
__hostalias(name)246 __hostalias(name)
247 register const char *name;
248 {
249 register char *C1, *C2;
250 FILE *fp;
251 char *file, *getenv(), *strcpy(), *strncpy();
252 char buf[BUFSIZ];
253 static char abuf[MAXDNAME];
254
255 file = getenv("HOSTALIASES");
256 if (file == NULL || (fp = fopen(file, "r")) == NULL)
257 return (NULL);
258 buf[sizeof(buf) - 1] = '\0';
259 while (fgets(buf, sizeof(buf), fp)) {
260 for (C1 = buf; *C1 && !isspace(*C1); ++C1);
261 if (!*C1)
262 break;
263 *C1 = '\0';
264 if (!strcasecmp(buf, name)) {
265 while (isspace(*++C1));
266 if (!*C1)
267 break;
268 for (C2 = C1 + 1; *C2 && !isspace(*C2); ++C2);
269 abuf[sizeof(abuf) - 1] = *C2 = '\0';
270 (void)strncpy(abuf, C1, sizeof(abuf) - 1);
271 fclose(fp);
272 return (abuf);
273 }
274 }
275 fclose(fp);
276 return (NULL);
277 }
278