/* * Copyright (c) 1988, 1993 * The Regents of the University of California. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * @(#)res_query.c 8.1 (Berkeley) 6/4/93 * $From: Id: res_query.c,v 8.14 1997/06/09 17:47:05 halley Exp $ * $FreeBSD: src/lib/libc/net/res_query.c,v 1.19.2.2 2002/07/07 11:34:42 robert Exp $ * $DragonFly: src/lib/libc/net/res_query.c,v 1.6 2005/11/13 02:04:47 swildner Exp $ */ /* * Portions Copyright (c) 1993 by Digital Equipment Corporation. * * Permission to use, copy, modify, and distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies, and that * the name of Digital Equipment Corporation not be used in advertising or * publicity pertaining to distribution of the document or software without * specific, written prior permission. * * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL DIGITAL EQUIPMENT * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS * SOFTWARE. */ /* * Portions Copyright (c) 1996 by Internet Software Consortium. * * Permission to use, copy, modify, and distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS * SOFTWARE. */ #include #include #include #include #include #include #include #include #include #include #include #include #include "res_config.h" #if PACKETSZ > 1024 #define MAXPACKET PACKETSZ #else #define MAXPACKET 1024 #endif /* * Formulate a normal query, send, and await answer. * Returned answer is placed in supplied buffer "answer". * Perform preliminary check of answer, returning success only * if no error is indicated and the answer count is nonzero. * Return the size of the response on success, -1 on error. * Error number is left in h_errno. * * Caller must parse answer and determine whether it answers the question. */ int res_query(const char *name, /* domain name */ int class, /* class of query */ int type, /* type of query */ u_char *answer, /* buffer to put answer */ int anslen) /* size of answer buffer */ { u_char buf[MAXPACKET]; HEADER *hp = (HEADER *) answer; int n; hp->rcode = NOERROR; /* default */ if ((_res.options & RES_INIT) == 0 && res_init() == -1) { h_errno = NETDB_INTERNAL; return (-1); } #ifdef DEBUG if (_res.options & RES_DEBUG) printf(";; res_query(%s, %d, %d)\n", name, class, type); #endif n = res_mkquery(QUERY, name, class, type, NULL, 0, NULL, buf, sizeof(buf)); if (n > 0 && (_res.options & RES_USE_EDNS0) != 0) n = res_opt(n, buf, sizeof(buf), anslen); if (n <= 0) { #ifdef DEBUG if (_res.options & RES_DEBUG) printf(";; res_query: mkquery failed\n"); #endif h_errno = NO_RECOVERY; return (n); } n = res_send(buf, n, answer, anslen); if (n < 0) { #ifdef DEBUG if (_res.options & RES_DEBUG) printf(";; res_query: send error\n"); #endif h_errno = TRY_AGAIN; return (n); } if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) { #ifdef DEBUG if (_res.options & RES_DEBUG) printf(";; rcode = %d, ancount=%d\n", hp->rcode, ntohs(hp->ancount)); #endif switch (hp->rcode) { case NXDOMAIN: h_errno = HOST_NOT_FOUND; break; case SERVFAIL: h_errno = TRY_AGAIN; break; case NOERROR: h_errno = NO_DATA; break; case FORMERR: case NOTIMP: case REFUSED: default: h_errno = NO_RECOVERY; break; } return (-1); } return (n); } /* * Formulate a normal query, send, and retrieve answer in supplied buffer. * Return the size of the response on success, -1 on error. * If enabled, implement search rules until answer or unrecoverable failure * is detected. Error code, if any, is left in h_errno. */ int res_search(const char *name, /* domain name */ int class, /* class of query */ int type, /* type of query */ u_char *answer, /* buffer to put answer */ int anslen) /* size of answer */ { const char *cp, * const *domain; u_int dots; int trailing_dot, ret, saved_herrno; int got_nodata = 0, got_servfail = 0, tried_as_is = 0; if ((_res.options & RES_INIT) == 0 && res_init() == -1) { h_errno = NETDB_INTERNAL; return (-1); } errno = 0; h_errno = HOST_NOT_FOUND; /* default, if we never query */ dots = 0; for (cp = name; *cp; cp++) dots += (*cp == '.'); trailing_dot = 0; if (cp > name && *--cp == '.') trailing_dot++; /* If there aren't any dots, it could be a user-level alias */ if (!dots && (cp = hostalias(name)) != NULL) return (res_query(cp, class, type, answer, anslen)); /* * If there are dots in the name already, let's just give it a try * 'as is'. The threshold can be set with the "ndots" option. */ saved_herrno = -1; if (dots >= _res.ndots) { ret = res_querydomain(name, NULL, class, type, answer, anslen); if (ret > 0) return (ret); saved_herrno = h_errno; tried_as_is++; } /* * We do at least one level of search if * - there is no dot and RES_DEFNAME is set, or * - there is at least one dot, there is no trailing dot, * and RES_DNSRCH is set. */ if ((!dots && (_res.options & RES_DEFNAMES)) || (dots && !trailing_dot && (_res.options & RES_DNSRCH))) { int done = 0; for (domain = (const char * const *)_res.dnsrch; *domain && !done; domain++) { ret = res_querydomain(name, *domain, class, type, answer, anslen); if (ret > 0) return (ret); /* * If no server present, give up. * If name isn't found in this domain, * keep trying higher domains in the search list * (if that's enabled). * On a NO_DATA error, keep trying, otherwise * a wildcard entry of another type could keep us * from finding this entry higher in the domain. * If we get some other error (negative answer or * server failure), then stop searching up, * but try the input name below in case it's * fully-qualified. */ if (errno == ECONNREFUSED) { h_errno = TRY_AGAIN; return (-1); } switch (h_errno) { case NO_DATA: got_nodata++; /* FALLTHROUGH */ case HOST_NOT_FOUND: /* keep trying */ break; case TRY_AGAIN: /* * This can occur due to a server failure * (that is, all listed servers have failed), * or all listed servers have timed out. * hp->rcode may not be set to SERVFAIL in the * case of a timeout. * * Either way we must terminate the search * and return TRY_AGAIN in order to avoid * non-deterministic return codes. For * example, loaded name servers or races * against network startup/validation (dhcp, * ppp, etc) can cause the search to timeout * on one search element, e.g. 'fu.bar.com', * and return a definitive failure on the * next search element, e.g. 'fu.'. */ ++got_servfail; /* FALLTHROUGH */ default: /* anything else implies that we're done */ done++; } /* if we got here for some reason other than DNSRCH, * we only wanted one iteration of the loop, so stop. */ if (!(_res.options & RES_DNSRCH)) done++; } } /* * If we have not already tried the name "as is", do that now. * note that we do this regardless of how many dots were in the * name or whether it ends with a dot unless NOTLDQUERY is set. */ if (!tried_as_is && (dots || !(_res.options & RES_NOTLDQUERY))) { ret = res_querydomain(name, NULL, class, type, answer, anslen); if (ret > 0) return (ret); } /* if we got here, we didn't satisfy the search. * if we did an initial full query, return that query's h_errno * (note that we wouldn't be here if that query had succeeded). * else if we ever got a nodata, send that back as the reason. * else send back meaningless h_errno, that being the one from * the last DNSRCH we did. */ if (saved_herrno != -1) h_errno = saved_herrno; else if (got_nodata) h_errno = NO_DATA; else if (got_servfail) h_errno = TRY_AGAIN; return (-1); } /* * Perform a call on res_query on the concatenation of name and domain, * removing a trailing dot from name if domain is NULL. */ int res_querydomain(const char *name, const char *domain, int class, /* class of query */ int type, /* type of query */ u_char *answer, /* buffer to put answer */ int anslen) /* size of answer */ { char nbuf[MAXDNAME]; const char *longname = nbuf; int n, d; if ((_res.options & RES_INIT) == 0 && res_init() == -1) { h_errno = NETDB_INTERNAL; return (-1); } #ifdef DEBUG if (_res.options & RES_DEBUG) printf(";; res_querydomain(%s, %s, %d, %d)\n", name, domain?domain:"", class, type); #endif if (domain == NULL) { /* * Check for trailing '.'; * copy without '.' if present. */ n = strlen(name); if (n >= MAXDNAME) { h_errno = NO_RECOVERY; return (-1); } n--; if (n >= 0 && name[n] == '.') { strncpy(nbuf, name, n); nbuf[n] = '\0'; } else longname = name; } else { n = strlen(name); d = strlen(domain); if (n + d + 1 >= MAXDNAME) { h_errno = NO_RECOVERY; return (-1); } sprintf(nbuf, "%s.%s", name, domain); } return (res_query(longname, class, type, answer, anslen)); } const char * hostalias(const char *name) { char *cp1, *cp2; FILE *fp; char *file; char buf[BUFSIZ]; static char abuf[MAXDNAME]; if (_res.options & RES_NOALIASES) return (NULL); if (issetugid()) return (NULL); file = getenv("HOSTALIASES"); if (file == NULL || (fp = fopen(file, "r")) == NULL) return (NULL); setbuf(fp, NULL); buf[sizeof(buf) - 1] = '\0'; while (fgets(buf, sizeof(buf), fp)) { for (cp1 = buf; *cp1 && !isspace((unsigned char)*cp1); ++cp1) ; if (!*cp1) break; *cp1 = '\0'; if (!strcasecmp(buf, name)) { while (isspace((unsigned char)*++cp1)) ; if (!*cp1) break; for (cp2 = cp1 + 1; *cp2 && !isspace((unsigned char)*cp2); ++cp2) ; abuf[sizeof(abuf) - 1] = *cp2 = '\0'; strncpy(abuf, cp1, sizeof(abuf) - 1); fclose(fp); return (abuf); } } fclose(fp); return (NULL); } /* * Weak aliases for applications that use certain private entry points, * and fail to include . */ #undef res_query __weak_reference(__res_query, res_query); #undef res_search __weak_reference(__res_search, res_search); #undef res_querydomain __weak_reference(__res_querydomain, res_querydomain);