1 /* 2 * Copyright (c) 1988 Regents of the University of California. 3 * All rights reserved. 4 * 5 * %sccs.include.redist.c% 6 */ 7 8 #if defined(LIBC_SCCS) && !defined(lint) 9 static char sccsid[] = "@(#)res_query.c 5.9 (Berkeley) 02/24/91"; 10 #endif /* LIBC_SCCS and not lint */ 11 12 #include <sys/param.h> 13 #include <netinet/in.h> 14 #include <arpa/inet.h> 15 #include <arpa/nameser.h> 16 #include <netdb.h> 17 #include <resolv.h> 18 #include <stdio.h> 19 #include <errno.h> 20 #include <stdlib.h> 21 #include <string.h> 22 23 #if PACKETSZ > 1024 24 #define MAXPACKET PACKETSZ 25 #else 26 #define MAXPACKET 1024 27 #endif 28 29 int h_errno; 30 31 /* 32 * Formulate a normal query, send, and await answer. 33 * Returned answer is placed in supplied buffer "answer". 34 * Perform preliminary check of answer, returning success only 35 * if no error is indicated and the answer count is nonzero. 36 * Return the size of the response on success, -1 on error. 37 * Error number is left in h_errno. 38 * Caller must parse answer and determine whether it answers the question. 39 */ 40 res_query(name, class, type, answer, anslen) 41 char *name; /* domain name */ 42 int class, type; /* class and type of query */ 43 u_char *answer; /* buffer to put answer */ 44 int anslen; /* size of answer buffer */ 45 { 46 char buf[MAXPACKET]; 47 HEADER *hp; 48 int n; 49 50 if ((_res.options & RES_INIT) == 0 && res_init() == -1) 51 return (-1); 52 #ifdef DEBUG 53 if (_res.options & RES_DEBUG) 54 printf("res_query(%s, %d, %d)\n", name, class, type); 55 #endif 56 n = res_mkquery(QUERY, name, class, type, (char *)NULL, 0, NULL, 57 buf, sizeof(buf)); 58 59 if (n <= 0) { 60 #ifdef DEBUG 61 if (_res.options & RES_DEBUG) 62 printf("res_query: mkquery failed\n"); 63 #endif 64 h_errno = NO_RECOVERY; 65 return (n); 66 } 67 n = res_send(buf, n, (char *)answer, anslen); 68 if (n < 0) { 69 #ifdef DEBUG 70 if (_res.options & RES_DEBUG) 71 printf("res_query: send error\n"); 72 #endif 73 h_errno = TRY_AGAIN; 74 return(n); 75 } 76 77 hp = (HEADER *) answer; 78 if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) { 79 #ifdef DEBUG 80 if (_res.options & RES_DEBUG) 81 printf("rcode = %d, ancount=%d\n", hp->rcode, 82 ntohs(hp->ancount)); 83 #endif 84 switch (hp->rcode) { 85 case NXDOMAIN: 86 h_errno = HOST_NOT_FOUND; 87 break; 88 case SERVFAIL: 89 h_errno = TRY_AGAIN; 90 break; 91 case NOERROR: 92 h_errno = NO_DATA; 93 break; 94 case FORMERR: 95 case NOTIMP: 96 case REFUSED: 97 default: 98 h_errno = NO_RECOVERY; 99 break; 100 } 101 return (-1); 102 } 103 return(n); 104 } 105 106 /* 107 * Formulate a normal query, send, and retrieve answer in supplied buffer. 108 * Return the size of the response on success, -1 on error. 109 * If enabled, implement search rules until answer or unrecoverable failure 110 * is detected. Error number is left in h_errno. 111 * Only useful for queries in the same name hierarchy as the local host 112 * (not, for example, for host address-to-name lookups in domain in-addr.arpa). 113 */ 114 res_search(name, class, type, answer, anslen) 115 char *name; /* domain name */ 116 int class, type; /* class and type of query */ 117 u_char *answer; /* buffer to put answer */ 118 int anslen; /* size of answer */ 119 { 120 register char *cp, **domain; 121 int n, ret, got_nodata = 0; 122 static char *hostalias(); 123 124 if ((_res.options & RES_INIT) == 0 && res_init() == -1) 125 return (-1); 126 127 errno = 0; 128 h_errno = HOST_NOT_FOUND; /* default, if we never query */ 129 for (cp = name, n = 0; *cp; cp++) 130 if (*cp == '.') 131 n++; 132 if (n == 0 && (cp = hostalias(name))) 133 return (res_query(cp, class, type, answer, anslen)); 134 135 /* 136 * We do at least one level of search if 137 * - there is no dot and RES_DEFNAME is set, or 138 * - there is at least one dot, there is no trailing dot, 139 * and RES_DNSRCH is set. 140 */ 141 if ((n == 0 && _res.options & RES_DEFNAMES) || 142 (n != 0 && *--cp != '.' && _res.options & RES_DNSRCH)) 143 for (domain = _res.dnsrch; *domain; domain++) { 144 ret = res_querydomain(name, *domain, class, type, 145 answer, anslen); 146 if (ret > 0) 147 return (ret); 148 /* 149 * If no server present, give up. 150 * If name isn't found in this domain, 151 * keep trying higher domains in the search list 152 * (if that's enabled). 153 * On a NO_DATA error, keep trying, otherwise 154 * a wildcard entry of another type could keep us 155 * from finding this entry higher in the domain. 156 * If we get some other error (negative answer or 157 * server failure), then stop searching up, 158 * but try the input name below in case it's fully-qualified. 159 */ 160 if (errno == ECONNREFUSED) { 161 h_errno = TRY_AGAIN; 162 return (-1); 163 } 164 if (h_errno == NO_DATA) 165 got_nodata++; 166 if ((h_errno != HOST_NOT_FOUND && h_errno != NO_DATA) || 167 (_res.options & RES_DNSRCH) == 0) 168 break; 169 } 170 /* 171 * If the search/default failed, try the name as fully-qualified, 172 * but only if it contained at least one dot (even trailing). 173 * This is purely a heuristic; we assume that any reasonable query 174 * about a top-level domain (for servers, SOA, etc) will not use 175 * res_search. 176 */ 177 if (n && (ret = res_querydomain(name, (char *)NULL, class, type, 178 answer, anslen)) > 0) 179 return (ret); 180 if (got_nodata) 181 h_errno = NO_DATA; 182 return (-1); 183 } 184 185 /* 186 * Perform a call on res_query on the concatenation of name and domain, 187 * removing a trailing dot from name if domain is NULL. 188 */ 189 res_querydomain(name, domain, class, type, answer, anslen) 190 char *name, *domain; 191 int class, type; /* class and type of query */ 192 u_char *answer; /* buffer to put answer */ 193 int anslen; /* size of answer */ 194 { 195 char nbuf[2*MAXDNAME+2]; 196 char *longname = nbuf; 197 int n; 198 199 #ifdef DEBUG 200 if (_res.options & RES_DEBUG) 201 printf("res_querydomain(%s, %s, %d, %d)\n", 202 name, domain, class, type); 203 #endif 204 if (domain == NULL) { 205 /* 206 * Check for trailing '.'; 207 * copy without '.' if present. 208 */ 209 n = strlen(name) - 1; 210 if (name[n] == '.' && n < sizeof(nbuf) - 1) { 211 bcopy(name, nbuf, n); 212 nbuf[n] = '\0'; 213 } else 214 longname = name; 215 } else 216 (void)sprintf(nbuf, "%.*s.%.*s", 217 MAXDNAME, name, MAXDNAME, domain); 218 219 return (res_query(longname, class, type, answer, anslen)); 220 } 221 222 static char * 223 hostalias(name) 224 register char *name; 225 { 226 register char *C1, *C2; 227 FILE *fp; 228 char *file, *getenv(), *strcpy(), *strncpy(); 229 char buf[BUFSIZ]; 230 static char abuf[MAXDNAME]; 231 232 file = getenv("HOSTALIASES"); 233 if (file == NULL || (fp = fopen(file, "r")) == NULL) 234 return (NULL); 235 buf[sizeof(buf) - 1] = '\0'; 236 while (fgets(buf, sizeof(buf), fp)) { 237 for (C1 = buf; *C1 && !isspace(*C1); ++C1); 238 if (!*C1) 239 break; 240 *C1 = '\0'; 241 if (!strcasecmp(buf, name)) { 242 while (isspace(*++C1)); 243 if (!*C1) 244 break; 245 for (C2 = C1 + 1; *C2 && !isspace(*C2); ++C2); 246 abuf[sizeof(abuf) - 1] = *C2 = '\0'; 247 (void)strncpy(abuf, C1, sizeof(abuf) - 1); 248 fclose(fp); 249 return (abuf); 250 } 251 } 252 fclose(fp); 253 return (NULL); 254 } 255