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 6 * provided that this notice is preserved and that due credit is given 7 * to the University of California at Berkeley. The name of the University 8 * may not be used to endorse or promote products derived from this 9 * software without specific prior written permission. This software 10 * is provided ``as is'' without express or implied warranty. 11 */ 12 13 #if defined(LIBC_SCCS) && !defined(lint) 14 static char sccsid[] = "@(#)res_query.c 5.1 (Berkeley) 03/14/88"; 15 #endif /* LIBC_SCCS and not lint */ 16 17 #include <sys/param.h> 18 #include <sys/socket.h> 19 #include <netinet/in.h> 20 #include <ctype.h> 21 #include <netdb.h> 22 #include <stdio.h> 23 #include <errno.h> 24 #include <strings.h> 25 #include <arpa/inet.h> 26 #include <arpa/nameser.h> 27 #include <resolv.h> 28 29 #if PACKETSZ > 1024 30 #define MAXPACKET PACKETSZ 31 #else 32 #define MAXPACKET 1024 33 #endif 34 35 extern int errno; 36 int h_errno; 37 38 /* 39 * Formulate a normal query, send, and await answer. 40 * Returned answer is placed in supplied buffer "answer". 41 * Perform preliminary check of answer, returning success only 42 * if no error is indicated and the answer count is nonzero. 43 * Return the size of the response on success, -1 on error. 44 * Error number is left in h_errno. 45 */ 46 res_query(name, class, type, answer, anslen) 47 char *name; /* domain name */ 48 int class, type; /* class and type of query */ 49 u_char *answer; /* buffer to put answer */ 50 int anslen; /* size of answer buffer */ 51 { 52 char buf[MAXPACKET]; 53 HEADER *hp; 54 int n; 55 56 if ((_res.options & RES_INIT) == 0 && res_init() == -1) 57 return (-1); 58 #ifdef DEBUG 59 if (_res.options & RES_DEBUG) 60 printf("res_query(%s, %d, %d)\n", name, class, type); 61 #endif 62 n = res_mkquery(QUERY, name, class, type, (char *)NULL, 0, NULL, 63 buf, sizeof(buf)); 64 65 if (n <= 0) { 66 #ifdef DEBUG 67 if (_res.options & RES_DEBUG) 68 printf("res_query: mkquery failed\n"); 69 #endif 70 h_errno = NO_RECOVERY; 71 return (n); 72 } 73 n = res_send(buf, n, answer, anslen); 74 if (n < 0) { 75 #ifdef DEBUG 76 if (_res.options & RES_DEBUG) 77 printf("res_query: send error\n"); 78 #endif 79 h_errno = TRY_AGAIN; 80 return(n); 81 } 82 83 hp = (HEADER *) answer; 84 if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) { 85 #ifdef DEBUG 86 if (_res.options & RES_DEBUG) 87 printf("rcode = %d, ancount=%d\n", hp->rcode, 88 ntohs(hp->ancount)); 89 #endif 90 switch (hp->rcode) { 91 case NXDOMAIN: 92 /* Check if it's an authoritive answer */ 93 if (hp->aa) 94 h_errno = HOST_NOT_FOUND; 95 else 96 h_errno = TRY_AGAIN; 97 break; 98 case SERVFAIL: 99 h_errno = TRY_AGAIN; 100 break; 101 case NOERROR: 102 if (hp->aa) 103 h_errno = NO_ADDRESS; 104 else 105 h_errno = TRY_AGAIN; 106 break; 107 case FORMERR: 108 case NOTIMP: 109 case REFUSED: 110 h_errno = NO_RECOVERY; 111 } 112 return (-1); 113 } 114 return(n); 115 } 116 117 /* 118 * Formulate a normal query, send, and retrieve answer in supplied buffer. 119 * Return the size of the response on success, -1 on error. 120 * If enabled, implement search rules until answer or unrecoverable failure 121 * is detected. Error number is left in h_errno. 122 * Only useful for queries in the same name hierarchy as the local host 123 * (not, for example, for host address-to-name lookups in domain in-addr.arpa). 124 */ 125 res_search(name, class, type, answer, anslen) 126 char *name; /* domain name */ 127 int class, type; /* class and type of query */ 128 u_char *answer; /* buffer to put answer */ 129 int anslen; /* size of answer */ 130 { 131 register char *cp, **domain; 132 int n, ret; 133 char *hostalias(); 134 135 if ((_res.options & RES_INIT) == 0 && res_init() == -1) 136 return (-1); 137 138 errno = 0; 139 for (cp = name, n = 0; *cp; cp++) 140 if (*cp == '.') 141 n++; 142 if (n == 0 && (cp = hostalias(name))) 143 return (res_query(cp, class, type, answer, anslen)); 144 145 if ((n == 0 || *--cp != '.') && (_res.options & RES_DEFNAMES)) 146 for (domain = _res.dnsrch; *domain; domain++) { 147 ret = res_querydomain(name, *domain, class, type, 148 answer, anslen); 149 if (ret > 0) 150 return (ret); 151 /* 152 * If no server present, give up. 153 * If name isn't found in this domain, 154 * keep trying higher domains in the search list 155 * (if that's enabled). 156 * On a NO_ADDRESS error, keep trying, otherwise 157 * a wildcard entry of another type could keep us 158 * from finding this entry higher in the domain. 159 * If we get some other error (non-authoritative negative 160 * answer or server failure), then stop searching up, 161 * but try the input name below in case it's fully-qualified. 162 */ 163 if (errno == ECONNREFUSED) { 164 h_errno = TRY_AGAIN; 165 return (-1); 166 } 167 if ((h_errno != HOST_NOT_FOUND && h_errno != NO_ADDRESS) || 168 (_res.options & RES_DNSRCH) == 0) 169 break; 170 h_errno = 0; 171 } 172 /* 173 * If the search/default failed, try the name as fully-qualified, 174 * but only if it contained at least one dot (even trailing). 175 */ 176 if (n) 177 return (res_querydomain(name, (char *)NULL, class, type, 178 answer, anslen)); 179 h_errno = HOST_NOT_FOUND; 180 return (-1); 181 } 182 183 /* 184 * Perform a call on res_query on the concatenation of name and domain, 185 * removing a trailing dot from name if domain is NULL. 186 */ 187 res_querydomain(name, domain, class, type, answer, anslen) 188 char *name, *domain; 189 int class, type; /* class and type of query */ 190 u_char *answer; /* buffer to put answer */ 191 int anslen; /* size of answer */ 192 { 193 char nbuf[2*MAXDNAME+2]; 194 char *longname = nbuf; 195 int n; 196 197 if (domain == NULL) { 198 /* 199 * Check for trailing '.'; 200 * copy without '.' if present. 201 */ 202 n = strlen(name) - 1; 203 if (name[n] == '.' && n < sizeof(nbuf) - 1) { 204 bcopy(name, nbuf, n); 205 nbuf[n] = '\0'; 206 } else 207 longname = name; 208 } else 209 (void)sprintf(nbuf, "%.*s.%.*s", 210 MAXDNAME, name, MAXDNAME, domain); 211 212 return (res_query(longname, class, type, answer, anslen)); 213 } 214 215 char * 216 hostalias(name) 217 register char *name; 218 { 219 register char *C1, *C2; 220 FILE *fp; 221 char *file, *getenv(), *strcpy(), *strncpy(); 222 char buf[BUFSIZ]; 223 static char abuf[MAXDNAME]; 224 225 file = getenv("HOSTALIASES"); 226 if (file == NULL || (fp = fopen(file, "r")) == NULL) 227 return (NULL); 228 buf[sizeof(buf) - 1] = '\0'; 229 while (fgets(buf, sizeof(buf), fp)) { 230 for (C1 = buf; *C1 && !isspace(*C1); ++C1); 231 if (!*C1) 232 break; 233 *C1 = '\0'; 234 if (!strcasecmp(buf, name)) { 235 while (isspace(*++C1)); 236 if (!*C1) 237 break; 238 for (C2 = C1 + 1; *C2 && !isspace(*C2); ++C2); 239 abuf[sizeof(abuf) - 1] = *C2 = '\0'; 240 (void)strncpy(abuf, C1, sizeof(abuf) - 1); 241 fclose(fp); 242 return (abuf); 243 } 244 } 245 fclose(fp); 246 return (NULL); 247 } 248