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 5.2 (Berkeley) 03/29/88"; 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 * Caller must parse answer and determine whether it answers the question. 46 */ 47 res_query(name, class, type, answer, anslen) 48 char *name; /* domain name */ 49 int class, type; /* class and type of query */ 50 u_char *answer; /* buffer to put answer */ 51 int anslen; /* size of answer buffer */ 52 { 53 char buf[MAXPACKET]; 54 HEADER *hp; 55 int n; 56 57 if ((_res.options & RES_INIT) == 0 && res_init() == -1) 58 return (-1); 59 #ifdef DEBUG 60 if (_res.options & RES_DEBUG) 61 printf("res_query(%s, %d, %d)\n", name, class, type); 62 #endif 63 n = res_mkquery(QUERY, name, class, type, (char *)NULL, 0, NULL, 64 buf, sizeof(buf)); 65 66 if (n <= 0) { 67 #ifdef DEBUG 68 if (_res.options & RES_DEBUG) 69 printf("res_query: mkquery failed\n"); 70 #endif 71 h_errno = NO_RECOVERY; 72 return (n); 73 } 74 n = res_send(buf, n, answer, anslen); 75 if (n < 0) { 76 #ifdef DEBUG 77 if (_res.options & RES_DEBUG) 78 printf("res_query: send error\n"); 79 #endif 80 h_errno = TRY_AGAIN; 81 return(n); 82 } 83 84 hp = (HEADER *) answer; 85 if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) { 86 #ifdef DEBUG 87 if (_res.options & RES_DEBUG) 88 printf("rcode = %d, ancount=%d\n", hp->rcode, 89 ntohs(hp->ancount)); 90 #endif 91 switch (hp->rcode) { 92 case NXDOMAIN: 93 h_errno = HOST_NOT_FOUND; 94 break; 95 case SERVFAIL: 96 h_errno = TRY_AGAIN; 97 break; 98 case NOERROR: 99 h_errno = NO_ADDRESS; 100 break; 101 case FORMERR: 102 case NOTIMP: 103 case REFUSED: 104 default: 105 h_errno = NO_RECOVERY; 106 break; 107 } 108 return (-1); 109 } 110 return(n); 111 } 112 113 /* 114 * Formulate a normal query, send, and retrieve answer in supplied buffer. 115 * Return the size of the response on success, -1 on error. 116 * If enabled, implement search rules until answer or unrecoverable failure 117 * is detected. Error number is left in h_errno. 118 * Only useful for queries in the same name hierarchy as the local host 119 * (not, for example, for host address-to-name lookups in domain in-addr.arpa). 120 */ 121 res_search(name, class, type, answer, anslen) 122 char *name; /* domain name */ 123 int class, type; /* class and type of query */ 124 u_char *answer; /* buffer to put answer */ 125 int anslen; /* size of answer */ 126 { 127 register char *cp, **domain; 128 int n, ret; 129 char *hostalias(); 130 131 if ((_res.options & RES_INIT) == 0 && res_init() == -1) 132 return (-1); 133 134 errno = 0; 135 for (cp = name, n = 0; *cp; cp++) 136 if (*cp == '.') 137 n++; 138 if (n == 0 && (cp = hostalias(name))) 139 return (res_query(cp, class, type, answer, anslen)); 140 141 if ((n == 0 || *--cp != '.') && (_res.options & RES_DEFNAMES)) 142 for (domain = _res.dnsrch; *domain; domain++) { 143 ret = res_querydomain(name, *domain, class, type, 144 answer, anslen); 145 if (ret > 0) 146 return (ret); 147 /* 148 * If no server present, give up. 149 * If name isn't found in this domain, 150 * keep trying higher domains in the search list 151 * (if that's enabled). 152 * On a NO_ADDRESS error, keep trying, otherwise 153 * a wildcard entry of another type could keep us 154 * from finding this entry higher in the domain. 155 * If we get some other error (non-authoritative negative 156 * answer or server failure), then stop searching up, 157 * but try the input name below in case it's fully-qualified. 158 */ 159 if (errno == ECONNREFUSED) { 160 h_errno = TRY_AGAIN; 161 return (-1); 162 } 163 if ((h_errno != HOST_NOT_FOUND && h_errno != NO_ADDRESS) || 164 (_res.options & RES_DNSRCH) == 0) 165 break; 166 h_errno = 0; 167 } 168 /* 169 * If the search/default failed, try the name as fully-qualified, 170 * but only if it contained at least one dot (even trailing). 171 */ 172 if (n) 173 return (res_querydomain(name, (char *)NULL, class, type, 174 answer, anslen)); 175 h_errno = HOST_NOT_FOUND; 176 return (-1); 177 } 178 179 /* 180 * Perform a call on res_query on the concatenation of name and domain, 181 * removing a trailing dot from name if domain is NULL. 182 */ 183 res_querydomain(name, domain, class, type, answer, anslen) 184 char *name, *domain; 185 int class, type; /* class and type of query */ 186 u_char *answer; /* buffer to put answer */ 187 int anslen; /* size of answer */ 188 { 189 char nbuf[2*MAXDNAME+2]; 190 char *longname = nbuf; 191 int n; 192 193 if (domain == NULL) { 194 /* 195 * Check for trailing '.'; 196 * copy without '.' if present. 197 */ 198 n = strlen(name) - 1; 199 if (name[n] == '.' && n < sizeof(nbuf) - 1) { 200 bcopy(name, nbuf, n); 201 nbuf[n] = '\0'; 202 } else 203 longname = name; 204 } else 205 (void)sprintf(nbuf, "%.*s.%.*s", 206 MAXDNAME, name, MAXDNAME, domain); 207 208 return (res_query(longname, class, type, answer, anslen)); 209 } 210 211 char * 212 hostalias(name) 213 register char *name; 214 { 215 register char *C1, *C2; 216 FILE *fp; 217 char *file, *getenv(), *strcpy(), *strncpy(); 218 char buf[BUFSIZ]; 219 static char abuf[MAXDNAME]; 220 221 file = getenv("HOSTALIASES"); 222 if (file == NULL || (fp = fopen(file, "r")) == NULL) 223 return (NULL); 224 buf[sizeof(buf) - 1] = '\0'; 225 while (fgets(buf, sizeof(buf), fp)) { 226 for (C1 = buf; *C1 && !isspace(*C1); ++C1); 227 if (!*C1) 228 break; 229 *C1 = '\0'; 230 if (!strcasecmp(buf, name)) { 231 while (isspace(*++C1)); 232 if (!*C1) 233 break; 234 for (C2 = C1 + 1; *C2 && !isspace(*C2); ++C2); 235 abuf[sizeof(abuf) - 1] = *C2 = '\0'; 236 (void)strncpy(abuf, C1, sizeof(abuf) - 1); 237 fclose(fp); 238 return (abuf); 239 } 240 } 241 fclose(fp); 242 return (NULL); 243 } 244