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1 | /* |
2 | * Copyright (c) 1988 Regents of the University of California. | |
3 | * All rights reserved. | |
4 | * | |
5 | * Redistribution and use in source and binary forms are permitted | |
3ec8dabc MK |
6 | * provided that the above copyright notice and this paragraph are |
7 | * duplicated in all such forms and that any documentation, | |
8 | * advertising materials, and other materials related to such | |
9 | * distribution and use acknowledge that the software was developed | |
10 | * by the University of California, Berkeley. The name of the | |
11 | * University may not be used to endorse or promote products derived | |
12 | * from this software without specific prior written permission. | |
13 | * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR | |
14 | * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED | |
15 | * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE. | |
345feb69 KB |
16 | */ |
17 | ||
18 | #if defined(LIBC_SCCS) && !defined(lint) | |
3ec8dabc | 19 | static char sccsid[] = "@(#)res_query.c 5.5 (Berkeley) %G%"; |
345feb69 KB |
20 | #endif /* LIBC_SCCS and not lint */ |
21 | ||
22 | #include <sys/param.h> | |
23 | #include <sys/socket.h> | |
24 | #include <netinet/in.h> | |
25 | #include <ctype.h> | |
26 | #include <netdb.h> | |
27 | #include <stdio.h> | |
28 | #include <errno.h> | |
29 | #include <strings.h> | |
30 | #include <arpa/inet.h> | |
31 | #include <arpa/nameser.h> | |
32 | #include <resolv.h> | |
33 | ||
34 | #if PACKETSZ > 1024 | |
35 | #define MAXPACKET PACKETSZ | |
36 | #else | |
37 | #define MAXPACKET 1024 | |
38 | #endif | |
39 | ||
40 | extern int errno; | |
41 | int h_errno; | |
42 | ||
43 | /* | |
44 | * Formulate a normal query, send, and await answer. | |
45 | * Returned answer is placed in supplied buffer "answer". | |
46 | * Perform preliminary check of answer, returning success only | |
47 | * if no error is indicated and the answer count is nonzero. | |
48 | * Return the size of the response on success, -1 on error. | |
49 | * Error number is left in h_errno. | |
a5e08740 | 50 | * Caller must parse answer and determine whether it answers the question. |
345feb69 KB |
51 | */ |
52 | res_query(name, class, type, answer, anslen) | |
53 | char *name; /* domain name */ | |
54 | int class, type; /* class and type of query */ | |
55 | u_char *answer; /* buffer to put answer */ | |
56 | int anslen; /* size of answer buffer */ | |
57 | { | |
58 | char buf[MAXPACKET]; | |
59 | HEADER *hp; | |
60 | int n; | |
61 | ||
62 | if ((_res.options & RES_INIT) == 0 && res_init() == -1) | |
63 | return (-1); | |
64 | #ifdef DEBUG | |
65 | if (_res.options & RES_DEBUG) | |
66 | printf("res_query(%s, %d, %d)\n", name, class, type); | |
67 | #endif | |
68 | n = res_mkquery(QUERY, name, class, type, (char *)NULL, 0, NULL, | |
69 | buf, sizeof(buf)); | |
70 | ||
71 | if (n <= 0) { | |
72 | #ifdef DEBUG | |
73 | if (_res.options & RES_DEBUG) | |
74 | printf("res_query: mkquery failed\n"); | |
75 | #endif | |
76 | h_errno = NO_RECOVERY; | |
77 | return (n); | |
78 | } | |
79 | n = res_send(buf, n, answer, anslen); | |
80 | if (n < 0) { | |
81 | #ifdef DEBUG | |
82 | if (_res.options & RES_DEBUG) | |
83 | printf("res_query: send error\n"); | |
84 | #endif | |
85 | h_errno = TRY_AGAIN; | |
86 | return(n); | |
87 | } | |
88 | ||
89 | hp = (HEADER *) answer; | |
90 | if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) { | |
91 | #ifdef DEBUG | |
92 | if (_res.options & RES_DEBUG) | |
93 | printf("rcode = %d, ancount=%d\n", hp->rcode, | |
94 | ntohs(hp->ancount)); | |
95 | #endif | |
96 | switch (hp->rcode) { | |
97 | case NXDOMAIN: | |
a5e08740 | 98 | h_errno = HOST_NOT_FOUND; |
345feb69 KB |
99 | break; |
100 | case SERVFAIL: | |
101 | h_errno = TRY_AGAIN; | |
102 | break; | |
103 | case NOERROR: | |
d7ec9b41 | 104 | h_errno = NO_DATA; |
345feb69 KB |
105 | break; |
106 | case FORMERR: | |
107 | case NOTIMP: | |
108 | case REFUSED: | |
a5e08740 | 109 | default: |
345feb69 | 110 | h_errno = NO_RECOVERY; |
a5e08740 | 111 | break; |
345feb69 KB |
112 | } |
113 | return (-1); | |
114 | } | |
115 | return(n); | |
116 | } | |
117 | ||
118 | /* | |
119 | * Formulate a normal query, send, and retrieve answer in supplied buffer. | |
120 | * Return the size of the response on success, -1 on error. | |
121 | * If enabled, implement search rules until answer or unrecoverable failure | |
122 | * is detected. Error number is left in h_errno. | |
123 | * Only useful for queries in the same name hierarchy as the local host | |
124 | * (not, for example, for host address-to-name lookups in domain in-addr.arpa). | |
125 | */ | |
126 | res_search(name, class, type, answer, anslen) | |
127 | char *name; /* domain name */ | |
128 | int class, type; /* class and type of query */ | |
129 | u_char *answer; /* buffer to put answer */ | |
130 | int anslen; /* size of answer */ | |
131 | { | |
132 | register char *cp, **domain; | |
d7ec9b41 | 133 | int n, ret, got_nodata = 0; |
345feb69 KB |
134 | char *hostalias(); |
135 | ||
136 | if ((_res.options & RES_INIT) == 0 && res_init() == -1) | |
137 | return (-1); | |
138 | ||
139 | errno = 0; | |
d7ec9b41 | 140 | h_errno = HOST_NOT_FOUND; /* default, if we never query */ |
345feb69 KB |
141 | for (cp = name, n = 0; *cp; cp++) |
142 | if (*cp == '.') | |
143 | n++; | |
144 | if (n == 0 && (cp = hostalias(name))) | |
145 | return (res_query(cp, class, type, answer, anslen)); | |
146 | ||
3ec8dabc MK |
147 | /* |
148 | * We do at least one level of search if | |
149 | * - there is no dot and RES_DEFNAME is set, or | |
150 | * - there is at least one dot, there is no trailing dot, | |
151 | * and RES_DNSRCH is set. | |
152 | */ | |
153 | if ((n == 0 && _res.options & RES_DEFNAMES) || | |
154 | (n != 0 && *--cp != '.' && _res.options & RES_DNSRCH)) | |
155 | for (domain = _res.dnsrch; *domain; domain++) { | |
345feb69 KB |
156 | ret = res_querydomain(name, *domain, class, type, |
157 | answer, anslen); | |
158 | if (ret > 0) | |
159 | return (ret); | |
160 | /* | |
161 | * If no server present, give up. | |
162 | * If name isn't found in this domain, | |
163 | * keep trying higher domains in the search list | |
164 | * (if that's enabled). | |
d7ec9b41 | 165 | * On a NO_DATA error, keep trying, otherwise |
345feb69 KB |
166 | * a wildcard entry of another type could keep us |
167 | * from finding this entry higher in the domain. | |
3ec8dabc MK |
168 | * If we get some other error (negative answer or |
169 | * server failure), then stop searching up, | |
345feb69 KB |
170 | * but try the input name below in case it's fully-qualified. |
171 | */ | |
172 | if (errno == ECONNREFUSED) { | |
173 | h_errno = TRY_AGAIN; | |
174 | return (-1); | |
175 | } | |
d7ec9b41 MK |
176 | if (h_errno == NO_DATA) |
177 | got_nodata++; | |
178 | if ((h_errno != HOST_NOT_FOUND && h_errno != NO_DATA) || | |
345feb69 KB |
179 | (_res.options & RES_DNSRCH) == 0) |
180 | break; | |
345feb69 KB |
181 | } |
182 | /* | |
183 | * If the search/default failed, try the name as fully-qualified, | |
184 | * but only if it contained at least one dot (even trailing). | |
3ec8dabc MK |
185 | * This is purely a heuristic; we assume that any reasonable query |
186 | * about a top-level domain (for servers, SOA, etc) will not use | |
187 | * res_search. | |
345feb69 | 188 | */ |
3ec8dabc MK |
189 | if (n && (ret = res_querydomain(name, (char *)NULL, class, type, |
190 | answer, anslen)) > 0) | |
191 | return (ret); | |
d7ec9b41 MK |
192 | if (got_nodata) |
193 | h_errno = NO_DATA; | |
345feb69 KB |
194 | return (-1); |
195 | } | |
196 | ||
197 | /* | |
198 | * Perform a call on res_query on the concatenation of name and domain, | |
199 | * removing a trailing dot from name if domain is NULL. | |
200 | */ | |
201 | res_querydomain(name, domain, class, type, answer, anslen) | |
202 | char *name, *domain; | |
203 | int class, type; /* class and type of query */ | |
204 | u_char *answer; /* buffer to put answer */ | |
205 | int anslen; /* size of answer */ | |
206 | { | |
207 | char nbuf[2*MAXDNAME+2]; | |
208 | char *longname = nbuf; | |
209 | int n; | |
210 | ||
d7ec9b41 MK |
211 | #ifdef DEBUG |
212 | if (_res.options & RES_DEBUG) | |
213 | printf("res_querydomain(%s, %s, %d, %d)\n", | |
214 | name, domain, class, type); | |
215 | #endif | |
345feb69 KB |
216 | if (domain == NULL) { |
217 | /* | |
218 | * Check for trailing '.'; | |
219 | * copy without '.' if present. | |
220 | */ | |
221 | n = strlen(name) - 1; | |
222 | if (name[n] == '.' && n < sizeof(nbuf) - 1) { | |
223 | bcopy(name, nbuf, n); | |
224 | nbuf[n] = '\0'; | |
225 | } else | |
226 | longname = name; | |
227 | } else | |
228 | (void)sprintf(nbuf, "%.*s.%.*s", | |
229 | MAXDNAME, name, MAXDNAME, domain); | |
230 | ||
231 | return (res_query(longname, class, type, answer, anslen)); | |
232 | } | |
233 | ||
234 | char * | |
235 | hostalias(name) | |
236 | register char *name; | |
237 | { | |
238 | register char *C1, *C2; | |
239 | FILE *fp; | |
240 | char *file, *getenv(), *strcpy(), *strncpy(); | |
241 | char buf[BUFSIZ]; | |
242 | static char abuf[MAXDNAME]; | |
243 | ||
244 | file = getenv("HOSTALIASES"); | |
245 | if (file == NULL || (fp = fopen(file, "r")) == NULL) | |
246 | return (NULL); | |
247 | buf[sizeof(buf) - 1] = '\0'; | |
248 | while (fgets(buf, sizeof(buf), fp)) { | |
249 | for (C1 = buf; *C1 && !isspace(*C1); ++C1); | |
250 | if (!*C1) | |
251 | break; | |
252 | *C1 = '\0'; | |
253 | if (!strcasecmp(buf, name)) { | |
254 | while (isspace(*++C1)); | |
255 | if (!*C1) | |
256 | break; | |
257 | for (C2 = C1 + 1; *C2 && !isspace(*C2); ++C2); | |
258 | abuf[sizeof(abuf) - 1] = *C2 = '\0'; | |
259 | (void)strncpy(abuf, C1, sizeof(abuf) - 1); | |
260 | fclose(fp); | |
261 | return (abuf); | |
262 | } | |
263 | } | |
264 | fclose(fp); | |
265 | return (NULL); | |
266 | } |