xref: /csrg-svn/lib/libc/net/res_query.c (revision 47045)
133736Sbostic /*
233736Sbostic  * Copyright (c) 1988 Regents of the University of California.
333736Sbostic  * All rights reserved.
433736Sbostic  *
542627Sbostic  * %sccs.include.redist.c%
633736Sbostic  */
733736Sbostic 
833736Sbostic #if defined(LIBC_SCCS) && !defined(lint)
9*47045Sbostic static char sccsid[] = "@(#)res_query.c	5.11 (Berkeley) 03/06/91";
1033736Sbostic #endif /* LIBC_SCCS and not lint */
1133736Sbostic 
1233736Sbostic #include <sys/param.h>
1333736Sbostic #include <netinet/in.h>
1446604Sbostic #include <arpa/inet.h>
1546604Sbostic #include <arpa/nameser.h>
1633736Sbostic #include <netdb.h>
1746604Sbostic #include <resolv.h>
1833736Sbostic #include <stdio.h>
1946606Sbostic #include <ctype.h>
2033736Sbostic #include <errno.h>
2146604Sbostic #include <stdlib.h>
2242026Sbostic #include <string.h>
2333736Sbostic 
2433736Sbostic #if PACKETSZ > 1024
2533736Sbostic #define MAXPACKET	PACKETSZ
2633736Sbostic #else
2733736Sbostic #define MAXPACKET	1024
2833736Sbostic #endif
2933736Sbostic 
3033736Sbostic int h_errno;
3133736Sbostic 
3233736Sbostic /*
3333736Sbostic  * Formulate a normal query, send, and await answer.
3433736Sbostic  * Returned answer is placed in supplied buffer "answer".
3533736Sbostic  * Perform preliminary check of answer, returning success only
3633736Sbostic  * if no error is indicated and the answer count is nonzero.
3733736Sbostic  * Return the size of the response on success, -1 on error.
3833736Sbostic  * Error number is left in h_errno.
3933826Skarels  * Caller must parse answer and determine whether it answers the question.
4033736Sbostic  */
4133736Sbostic res_query(name, class, type, answer, anslen)
4233736Sbostic 	char *name;		/* domain name */
4333736Sbostic 	int class, type;	/* class and type of query */
4433736Sbostic 	u_char *answer;		/* buffer to put answer */
4533736Sbostic 	int anslen;		/* size of answer buffer */
4633736Sbostic {
4733736Sbostic 	char buf[MAXPACKET];
4833736Sbostic 	HEADER *hp;
4933736Sbostic 	int n;
5033736Sbostic 
5133736Sbostic 	if ((_res.options & RES_INIT) == 0 && res_init() == -1)
5233736Sbostic 		return (-1);
5333736Sbostic #ifdef DEBUG
5433736Sbostic 	if (_res.options & RES_DEBUG)
5533736Sbostic 		printf("res_query(%s, %d, %d)\n", name, class, type);
5633736Sbostic #endif
5733736Sbostic 	n = res_mkquery(QUERY, name, class, type, (char *)NULL, 0, NULL,
5833736Sbostic 	    buf, sizeof(buf));
5933736Sbostic 
6033736Sbostic 	if (n <= 0) {
6133736Sbostic #ifdef DEBUG
6233736Sbostic 		if (_res.options & RES_DEBUG)
6333736Sbostic 			printf("res_query: mkquery failed\n");
6433736Sbostic #endif
6533736Sbostic 		h_errno = NO_RECOVERY;
6633736Sbostic 		return (n);
6733736Sbostic 	}
6846604Sbostic 	n = res_send(buf, n, (char *)answer, anslen);
6933736Sbostic 	if (n < 0) {
7033736Sbostic #ifdef DEBUG
7133736Sbostic 		if (_res.options & RES_DEBUG)
7233736Sbostic 			printf("res_query: send error\n");
7333736Sbostic #endif
7433736Sbostic 		h_errno = TRY_AGAIN;
7533736Sbostic 		return(n);
7633736Sbostic 	}
7733736Sbostic 
7833736Sbostic 	hp = (HEADER *) answer;
7933736Sbostic 	if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
8033736Sbostic #ifdef DEBUG
8133736Sbostic 		if (_res.options & RES_DEBUG)
8233736Sbostic 			printf("rcode = %d, ancount=%d\n", hp->rcode,
8333736Sbostic 			    ntohs(hp->ancount));
8433736Sbostic #endif
8533736Sbostic 		switch (hp->rcode) {
8633736Sbostic 			case NXDOMAIN:
8733826Skarels 				h_errno = HOST_NOT_FOUND;
8833736Sbostic 				break;
8933736Sbostic 			case SERVFAIL:
9033736Sbostic 				h_errno = TRY_AGAIN;
9133736Sbostic 				break;
9233736Sbostic 			case NOERROR:
9333977Skarels 				h_errno = NO_DATA;
9433736Sbostic 				break;
9533736Sbostic 			case FORMERR:
9633736Sbostic 			case NOTIMP:
9733736Sbostic 			case REFUSED:
9833826Skarels 			default:
9933736Sbostic 				h_errno = NO_RECOVERY;
10033826Skarels 				break;
10133736Sbostic 		}
10233736Sbostic 		return (-1);
10333736Sbostic 	}
10433736Sbostic 	return(n);
10533736Sbostic }
10633736Sbostic 
10733736Sbostic /*
10833736Sbostic  * Formulate a normal query, send, and retrieve answer in supplied buffer.
10933736Sbostic  * Return the size of the response on success, -1 on error.
11033736Sbostic  * If enabled, implement search rules until answer or unrecoverable failure
11133736Sbostic  * is detected.  Error number is left in h_errno.
11233736Sbostic  * Only useful for queries in the same name hierarchy as the local host
11333736Sbostic  * (not, for example, for host address-to-name lookups in domain in-addr.arpa).
11433736Sbostic  */
11533736Sbostic res_search(name, class, type, answer, anslen)
11633736Sbostic 	char *name;		/* domain name */
11733736Sbostic 	int class, type;	/* class and type of query */
11833736Sbostic 	u_char *answer;		/* buffer to put answer */
11933736Sbostic 	int anslen;		/* size of answer */
12033736Sbostic {
12133736Sbostic 	register char *cp, **domain;
12233977Skarels 	int n, ret, got_nodata = 0;
123*47045Sbostic 	char *__hostalias();
12433736Sbostic 
12533736Sbostic 	if ((_res.options & RES_INIT) == 0 && res_init() == -1)
12633736Sbostic 		return (-1);
12733736Sbostic 
12833736Sbostic 	errno = 0;
12933977Skarels 	h_errno = HOST_NOT_FOUND;		/* default, if we never query */
13033736Sbostic 	for (cp = name, n = 0; *cp; cp++)
13133736Sbostic 		if (*cp == '.')
13233736Sbostic 			n++;
133*47045Sbostic 	if (n == 0 && (cp = __hostalias(name)))
13433736Sbostic 		return (res_query(cp, class, type, answer, anslen));
13533736Sbostic 
13635655Skarels 	/*
13735655Skarels 	 * We do at least one level of search if
13835655Skarels 	 *	- there is no dot and RES_DEFNAME is set, or
13935655Skarels 	 *	- there is at least one dot, there is no trailing dot,
14035655Skarels 	 *	  and RES_DNSRCH is set.
14135655Skarels 	 */
14235655Skarels 	if ((n == 0 && _res.options & RES_DEFNAMES) ||
14335655Skarels 	   (n != 0 && *--cp != '.' && _res.options & RES_DNSRCH))
14435655Skarels 	     for (domain = _res.dnsrch; *domain; domain++) {
14533736Sbostic 		ret = res_querydomain(name, *domain, class, type,
14633736Sbostic 		    answer, anslen);
14733736Sbostic 		if (ret > 0)
14833736Sbostic 			return (ret);
14933736Sbostic 		/*
15033736Sbostic 		 * If no server present, give up.
15133736Sbostic 		 * If name isn't found in this domain,
15233736Sbostic 		 * keep trying higher domains in the search list
15333736Sbostic 		 * (if that's enabled).
15433977Skarels 		 * On a NO_DATA error, keep trying, otherwise
15533736Sbostic 		 * a wildcard entry of another type could keep us
15633736Sbostic 		 * from finding this entry higher in the domain.
15735655Skarels 		 * If we get some other error (negative answer or
15835655Skarels 		 * server failure), then stop searching up,
15933736Sbostic 		 * but try the input name below in case it's fully-qualified.
16033736Sbostic 		 */
16133736Sbostic 		if (errno == ECONNREFUSED) {
16233736Sbostic 			h_errno = TRY_AGAIN;
16333736Sbostic 			return (-1);
16433736Sbostic 		}
16533977Skarels 		if (h_errno == NO_DATA)
16633977Skarels 			got_nodata++;
16733977Skarels 		if ((h_errno != HOST_NOT_FOUND && h_errno != NO_DATA) ||
16833736Sbostic 		    (_res.options & RES_DNSRCH) == 0)
16933736Sbostic 			break;
17033736Sbostic 	}
17133736Sbostic 	/*
17233736Sbostic 	 * If the search/default failed, try the name as fully-qualified,
17333736Sbostic 	 * but only if it contained at least one dot (even trailing).
17435655Skarels 	 * This is purely a heuristic; we assume that any reasonable query
17535655Skarels 	 * about a top-level domain (for servers, SOA, etc) will not use
17635655Skarels 	 * res_search.
17733736Sbostic 	 */
17835655Skarels 	if (n && (ret = res_querydomain(name, (char *)NULL, class, type,
17935655Skarels 	    answer, anslen)) > 0)
18035655Skarels 		return (ret);
18133977Skarels 	if (got_nodata)
18233977Skarels 		h_errno = NO_DATA;
18333736Sbostic 	return (-1);
18433736Sbostic }
18533736Sbostic 
18633736Sbostic /*
18733736Sbostic  * Perform a call on res_query on the concatenation of name and domain,
18833736Sbostic  * removing a trailing dot from name if domain is NULL.
18933736Sbostic  */
19033736Sbostic res_querydomain(name, domain, class, type, answer, anslen)
19133736Sbostic 	char *name, *domain;
19233736Sbostic 	int class, type;	/* class and type of query */
19333736Sbostic 	u_char *answer;		/* buffer to put answer */
19433736Sbostic 	int anslen;		/* size of answer */
19533736Sbostic {
19633736Sbostic 	char nbuf[2*MAXDNAME+2];
19733736Sbostic 	char *longname = nbuf;
19833736Sbostic 	int n;
19933736Sbostic 
20033977Skarels #ifdef DEBUG
20133977Skarels 	if (_res.options & RES_DEBUG)
20233977Skarels 		printf("res_querydomain(%s, %s, %d, %d)\n",
20333977Skarels 		    name, domain, class, type);
20433977Skarels #endif
20533736Sbostic 	if (domain == NULL) {
20633736Sbostic 		/*
20733736Sbostic 		 * Check for trailing '.';
20833736Sbostic 		 * copy without '.' if present.
20933736Sbostic 		 */
21033736Sbostic 		n = strlen(name) - 1;
21133736Sbostic 		if (name[n] == '.' && n < sizeof(nbuf) - 1) {
21233736Sbostic 			bcopy(name, nbuf, n);
21333736Sbostic 			nbuf[n] = '\0';
21433736Sbostic 		} else
21533736Sbostic 			longname = name;
21633736Sbostic 	} else
21733736Sbostic 		(void)sprintf(nbuf, "%.*s.%.*s",
21833736Sbostic 		    MAXDNAME, name, MAXDNAME, domain);
21933736Sbostic 
22033736Sbostic 	return (res_query(longname, class, type, answer, anslen));
22133736Sbostic }
22233736Sbostic 
223*47045Sbostic char *
224*47045Sbostic __hostalias(name)
225*47045Sbostic 	register const char *name;
22633736Sbostic {
22733736Sbostic 	register char *C1, *C2;
22833736Sbostic 	FILE *fp;
22933736Sbostic 	char *file, *getenv(), *strcpy(), *strncpy();
23033736Sbostic 	char buf[BUFSIZ];
23133736Sbostic 	static char abuf[MAXDNAME];
23233736Sbostic 
23333736Sbostic 	file = getenv("HOSTALIASES");
23433736Sbostic 	if (file == NULL || (fp = fopen(file, "r")) == NULL)
23533736Sbostic 		return (NULL);
23633736Sbostic 	buf[sizeof(buf) - 1] = '\0';
23733736Sbostic 	while (fgets(buf, sizeof(buf), fp)) {
23833736Sbostic 		for (C1 = buf; *C1 && !isspace(*C1); ++C1);
23933736Sbostic 		if (!*C1)
24033736Sbostic 			break;
24133736Sbostic 		*C1 = '\0';
24233736Sbostic 		if (!strcasecmp(buf, name)) {
24333736Sbostic 			while (isspace(*++C1));
24433736Sbostic 			if (!*C1)
24533736Sbostic 				break;
24633736Sbostic 			for (C2 = C1 + 1; *C2 && !isspace(*C2); ++C2);
24733736Sbostic 			abuf[sizeof(abuf) - 1] = *C2 = '\0';
24833736Sbostic 			(void)strncpy(abuf, C1, sizeof(abuf) - 1);
24933736Sbostic 			fclose(fp);
25033736Sbostic 			return (abuf);
25133736Sbostic 		}
25233736Sbostic 	}
25333736Sbostic 	fclose(fp);
25433736Sbostic 	return (NULL);
25533736Sbostic }
256