xref: /csrg-svn/lib/libc/net/res_query.c (revision 61023)
1*61023Skarels /*-
233736Sbostic  * Copyright (c) 1988 Regents of the University of California.
333736Sbostic  * All rights reserved.
433736Sbostic  *
542627Sbostic  * %sccs.include.redist.c%
6*61023Skarels  * -
7*61023Skarels  * Portions Copyright (c) 1993 by Digital Equipment Corporation.
8*61023Skarels  *
9*61023Skarels  * Permission to use, copy, modify, and distribute this software for any
10*61023Skarels  * purpose with or without fee is hereby granted, provided that the above
11*61023Skarels  * copyright notice and this permission notice appear in all copies, and that
12*61023Skarels  * the name of Digital Equipment Corporation not be used in advertising or
13*61023Skarels  * publicity pertaining to distribution of the document or software without
14*61023Skarels  * specific, written prior permission.
15*61023Skarels  *
16*61023Skarels  * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
17*61023Skarels  * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
18*61023Skarels  * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
19*61023Skarels  * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
20*61023Skarels  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
21*61023Skarels  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
22*61023Skarels  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
23*61023Skarels  * SOFTWARE.
24*61023Skarels  * -
25*61023Skarels  * --Copyright--
2633736Sbostic  */
2733736Sbostic 
2833736Sbostic #if defined(LIBC_SCCS) && !defined(lint)
29*61023Skarels static char sccsid[] = "@(#)res_query.c	5.12 (Berkeley) 06/02/93";
30*61023Skarels static char rcsid[] = "$Id: res_query.c,v 1.1 1993/06/01 09:42:14 vixie Exp vixie $";
3133736Sbostic #endif /* LIBC_SCCS and not lint */
3233736Sbostic 
3333736Sbostic #include <sys/param.h>
3433736Sbostic #include <netinet/in.h>
3546604Sbostic #include <arpa/inet.h>
3646604Sbostic #include <arpa/nameser.h>
3733736Sbostic #include <netdb.h>
3846604Sbostic #include <resolv.h>
3933736Sbostic #include <stdio.h>
4046606Sbostic #include <ctype.h>
4133736Sbostic #include <errno.h>
4246604Sbostic #include <stdlib.h>
4342026Sbostic #include <string.h>
4433736Sbostic 
4533736Sbostic #if PACKETSZ > 1024
4633736Sbostic #define MAXPACKET	PACKETSZ
4733736Sbostic #else
4833736Sbostic #define MAXPACKET	1024
4933736Sbostic #endif
5033736Sbostic 
5133736Sbostic int h_errno;
5233736Sbostic 
5333736Sbostic /*
5433736Sbostic  * Formulate a normal query, send, and await answer.
5533736Sbostic  * Returned answer is placed in supplied buffer "answer".
5633736Sbostic  * Perform preliminary check of answer, returning success only
5733736Sbostic  * if no error is indicated and the answer count is nonzero.
5833736Sbostic  * Return the size of the response on success, -1 on error.
5933736Sbostic  * Error number is left in h_errno.
6033826Skarels  * Caller must parse answer and determine whether it answers the question.
6133736Sbostic  */
6233736Sbostic res_query(name, class, type, answer, anslen)
6333736Sbostic 	char *name;		/* domain name */
6433736Sbostic 	int class, type;	/* class and type of query */
6533736Sbostic 	u_char *answer;		/* buffer to put answer */
6633736Sbostic 	int anslen;		/* size of answer buffer */
6733736Sbostic {
6833736Sbostic 	char buf[MAXPACKET];
6933736Sbostic 	HEADER *hp;
7033736Sbostic 	int n;
7133736Sbostic 
7233736Sbostic 	if ((_res.options & RES_INIT) == 0 && res_init() == -1)
7333736Sbostic 		return (-1);
7433736Sbostic #ifdef DEBUG
7533736Sbostic 	if (_res.options & RES_DEBUG)
76*61023Skarels 		printf(";; res_query(%s, %d, %d)\n", name, class, type);
7733736Sbostic #endif
7833736Sbostic 	n = res_mkquery(QUERY, name, class, type, (char *)NULL, 0, NULL,
7933736Sbostic 	    buf, sizeof(buf));
8033736Sbostic 
8133736Sbostic 	if (n <= 0) {
8233736Sbostic #ifdef DEBUG
8333736Sbostic 		if (_res.options & RES_DEBUG)
84*61023Skarels 			printf(";; res_query: mkquery failed\n");
8533736Sbostic #endif
8633736Sbostic 		h_errno = NO_RECOVERY;
8733736Sbostic 		return (n);
8833736Sbostic 	}
8946604Sbostic 	n = res_send(buf, n, (char *)answer, anslen);
9033736Sbostic 	if (n < 0) {
9133736Sbostic #ifdef DEBUG
9233736Sbostic 		if (_res.options & RES_DEBUG)
93*61023Skarels 			printf(";; res_query: send error\n");
9433736Sbostic #endif
9533736Sbostic 		h_errno = TRY_AGAIN;
9633736Sbostic 		return(n);
9733736Sbostic 	}
9833736Sbostic 
9933736Sbostic 	hp = (HEADER *) answer;
10033736Sbostic 	if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
10133736Sbostic #ifdef DEBUG
10233736Sbostic 		if (_res.options & RES_DEBUG)
103*61023Skarels 			printf(";; rcode = %d, ancount=%d\n", hp->rcode,
10433736Sbostic 			    ntohs(hp->ancount));
10533736Sbostic #endif
10633736Sbostic 		switch (hp->rcode) {
10733736Sbostic 			case NXDOMAIN:
10833826Skarels 				h_errno = HOST_NOT_FOUND;
10933736Sbostic 				break;
11033736Sbostic 			case SERVFAIL:
11133736Sbostic 				h_errno = TRY_AGAIN;
11233736Sbostic 				break;
11333736Sbostic 			case NOERROR:
11433977Skarels 				h_errno = NO_DATA;
11533736Sbostic 				break;
11633736Sbostic 			case FORMERR:
11733736Sbostic 			case NOTIMP:
11833736Sbostic 			case REFUSED:
11933826Skarels 			default:
12033736Sbostic 				h_errno = NO_RECOVERY;
12133826Skarels 				break;
12233736Sbostic 		}
12333736Sbostic 		return (-1);
12433736Sbostic 	}
12533736Sbostic 	return(n);
12633736Sbostic }
12733736Sbostic 
12833736Sbostic /*
12933736Sbostic  * Formulate a normal query, send, and retrieve answer in supplied buffer.
13033736Sbostic  * Return the size of the response on success, -1 on error.
13133736Sbostic  * If enabled, implement search rules until answer or unrecoverable failure
13233736Sbostic  * is detected.  Error number is left in h_errno.
13333736Sbostic  * Only useful for queries in the same name hierarchy as the local host
13433736Sbostic  * (not, for example, for host address-to-name lookups in domain in-addr.arpa).
13533736Sbostic  */
136*61023Skarels int
13733736Sbostic res_search(name, class, type, answer, anslen)
13833736Sbostic 	char *name;		/* domain name */
13933736Sbostic 	int class, type;	/* class and type of query */
14033736Sbostic 	u_char *answer;		/* buffer to put answer */
14133736Sbostic 	int anslen;		/* size of answer */
14233736Sbostic {
14333736Sbostic 	register char *cp, **domain;
14433977Skarels 	int n, ret, got_nodata = 0;
14547045Sbostic 	char *__hostalias();
14633736Sbostic 
14733736Sbostic 	if ((_res.options & RES_INIT) == 0 && res_init() == -1)
14833736Sbostic 		return (-1);
14933736Sbostic 
15033736Sbostic 	errno = 0;
151*61023Skarels 	h_errno = HOST_NOT_FOUND;	/* default, if we never query */
15233736Sbostic 	for (cp = name, n = 0; *cp; cp++)
15333736Sbostic 		if (*cp == '.')
15433736Sbostic 			n++;
15547045Sbostic 	if (n == 0 && (cp = __hostalias(name)))
15633736Sbostic 		return (res_query(cp, class, type, answer, anslen));
15733736Sbostic 
15835655Skarels 	/*
15935655Skarels 	 * We do at least one level of search if
16035655Skarels 	 *	- there is no dot and RES_DEFNAME is set, or
16135655Skarels 	 *	- there is at least one dot, there is no trailing dot,
16235655Skarels 	 *	  and RES_DNSRCH is set.
16335655Skarels 	 */
16435655Skarels 	if ((n == 0 && _res.options & RES_DEFNAMES) ||
16535655Skarels 	   (n != 0 && *--cp != '.' && _res.options & RES_DNSRCH))
16635655Skarels 	     for (domain = _res.dnsrch; *domain; domain++) {
16733736Sbostic 		ret = res_querydomain(name, *domain, class, type,
16833736Sbostic 		    answer, anslen);
16933736Sbostic 		if (ret > 0)
17033736Sbostic 			return (ret);
17133736Sbostic 		/*
17233736Sbostic 		 * If no server present, give up.
17333736Sbostic 		 * If name isn't found in this domain,
17433736Sbostic 		 * keep trying higher domains in the search list
17533736Sbostic 		 * (if that's enabled).
17633977Skarels 		 * On a NO_DATA error, keep trying, otherwise
17733736Sbostic 		 * a wildcard entry of another type could keep us
17833736Sbostic 		 * from finding this entry higher in the domain.
17935655Skarels 		 * If we get some other error (negative answer or
18035655Skarels 		 * server failure), then stop searching up,
18133736Sbostic 		 * but try the input name below in case it's fully-qualified.
18233736Sbostic 		 */
18333736Sbostic 		if (errno == ECONNREFUSED) {
18433736Sbostic 			h_errno = TRY_AGAIN;
18533736Sbostic 			return (-1);
18633736Sbostic 		}
18733977Skarels 		if (h_errno == NO_DATA)
18833977Skarels 			got_nodata++;
18933977Skarels 		if ((h_errno != HOST_NOT_FOUND && h_errno != NO_DATA) ||
19033736Sbostic 		    (_res.options & RES_DNSRCH) == 0)
19133736Sbostic 			break;
19233736Sbostic 	}
19333736Sbostic 	/*
19433736Sbostic 	 * If the search/default failed, try the name as fully-qualified,
19533736Sbostic 	 * but only if it contained at least one dot (even trailing).
19635655Skarels 	 * This is purely a heuristic; we assume that any reasonable query
19735655Skarels 	 * about a top-level domain (for servers, SOA, etc) will not use
19835655Skarels 	 * res_search.
19933736Sbostic 	 */
20035655Skarels 	if (n && (ret = res_querydomain(name, (char *)NULL, class, type,
20135655Skarels 	    answer, anslen)) > 0)
20235655Skarels 		return (ret);
20333977Skarels 	if (got_nodata)
20433977Skarels 		h_errno = NO_DATA;
20533736Sbostic 	return (-1);
20633736Sbostic }
20733736Sbostic 
20833736Sbostic /*
20933736Sbostic  * Perform a call on res_query on the concatenation of name and domain,
21033736Sbostic  * removing a trailing dot from name if domain is NULL.
21133736Sbostic  */
21233736Sbostic res_querydomain(name, domain, class, type, answer, anslen)
21333736Sbostic 	char *name, *domain;
21433736Sbostic 	int class, type;	/* class and type of query */
21533736Sbostic 	u_char *answer;		/* buffer to put answer */
21633736Sbostic 	int anslen;		/* size of answer */
21733736Sbostic {
21833736Sbostic 	char nbuf[2*MAXDNAME+2];
21933736Sbostic 	char *longname = nbuf;
22033736Sbostic 	int n;
22133736Sbostic 
22233977Skarels #ifdef DEBUG
22333977Skarels 	if (_res.options & RES_DEBUG)
224*61023Skarels 		printf(";; res_querydomain(%s, %s, %d, %d)\n",
22533977Skarels 		    name, domain, class, type);
22633977Skarels #endif
22733736Sbostic 	if (domain == NULL) {
22833736Sbostic 		/*
22933736Sbostic 		 * Check for trailing '.';
23033736Sbostic 		 * copy without '.' if present.
23133736Sbostic 		 */
23233736Sbostic 		n = strlen(name) - 1;
23333736Sbostic 		if (name[n] == '.' && n < sizeof(nbuf) - 1) {
23433736Sbostic 			bcopy(name, nbuf, n);
23533736Sbostic 			nbuf[n] = '\0';
23633736Sbostic 		} else
23733736Sbostic 			longname = name;
23833736Sbostic 	} else
23933736Sbostic 		(void)sprintf(nbuf, "%.*s.%.*s",
24033736Sbostic 		    MAXDNAME, name, MAXDNAME, domain);
24133736Sbostic 
24233736Sbostic 	return (res_query(longname, class, type, answer, anslen));
24333736Sbostic }
24433736Sbostic 
24547045Sbostic char *
24647045Sbostic __hostalias(name)
24747045Sbostic 	register const char *name;
24833736Sbostic {
24933736Sbostic 	register char *C1, *C2;
25033736Sbostic 	FILE *fp;
25133736Sbostic 	char *file, *getenv(), *strcpy(), *strncpy();
25233736Sbostic 	char buf[BUFSIZ];
25333736Sbostic 	static char abuf[MAXDNAME];
25433736Sbostic 
25533736Sbostic 	file = getenv("HOSTALIASES");
25633736Sbostic 	if (file == NULL || (fp = fopen(file, "r")) == NULL)
25733736Sbostic 		return (NULL);
25833736Sbostic 	buf[sizeof(buf) - 1] = '\0';
25933736Sbostic 	while (fgets(buf, sizeof(buf), fp)) {
26033736Sbostic 		for (C1 = buf; *C1 && !isspace(*C1); ++C1);
26133736Sbostic 		if (!*C1)
26233736Sbostic 			break;
26333736Sbostic 		*C1 = '\0';
26433736Sbostic 		if (!strcasecmp(buf, name)) {
26533736Sbostic 			while (isspace(*++C1));
26633736Sbostic 			if (!*C1)
26733736Sbostic 				break;
26833736Sbostic 			for (C2 = C1 + 1; *C2 && !isspace(*C2); ++C2);
26933736Sbostic 			abuf[sizeof(abuf) - 1] = *C2 = '\0';
27033736Sbostic 			(void)strncpy(abuf, C1, sizeof(abuf) - 1);
27133736Sbostic 			fclose(fp);
27233736Sbostic 			return (abuf);
27333736Sbostic 		}
27433736Sbostic 	}
27533736Sbostic 	fclose(fp);
27633736Sbostic 	return (NULL);
27733736Sbostic }
278