lib/libresolv/res_query.c

	res_query.c revision 2
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*  Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/*    All Rights Reserved   */

/*
 * University Copyright- Copyright (c) 1982, 1986, 1988
 * The Regents of the University of California
 * All Rights Reserved
 *
 * University Acknowledgment- Portions of this document are derived from
 * software developed by the University of California, Berkeley, and its
 * contributors.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#include <sys/param.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <ctype.h>
#include <netdb.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <arpa/inet.h>
#include <arpa/nameser.h>
#include <resolv.h>

#if PACKETSZ > 1024
#define MAXPACKET   PACKETSZ
#else
#define MAXPACKET   1024
#endif

int h_errno;

/*
 * 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(name, class, type, answer, anslen)
    char *name;     /* domain name */
    int class, type;    /* class and type of query */
    u_char *answer;     /* buffer to put answer */
    int anslen;     /* size of answer buffer */
{
    char buf[MAXPACKET];
    HEADER *hp;
    int n;

    if ((_res.options & RES_INIT) == 0 && res_init() == -1)
        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, (char *)NULL, 0, NULL,
        buf, sizeof (buf));

    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);
    }

    hp = (HEADER *) answer;
    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);
    }
    if (hp->rcode == NOERROR && ntohs(hp->ancount) > 0)
        h_errno = 0;
    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 number is left in h_errno.
 * Only useful for queries in the same name hierarchy as the local host
 * (not, for example, for host address-to-name lookups in domain in-addr.arpa).
 */
int
res_search(name, class, type, answer, anslen)
    char *name;     /* domain name */
    int class, type;    /* class and type of query */
    u_char *answer;     /* buffer to put answer */
    int anslen;     /* size of answer */
{
    register char *cp, **domain;
    int n, ret, got_nodata = 0;
    char *hostalias();

    if ((_res.options & RES_INIT) == 0 && res_init() == -1)
        return (-1);

    errno = 0;
    h_errno = HOST_NOT_FOUND;       /* default, if we never query */
    for (cp = name, n = 0; *cp; cp++)
        if (*cp == '.')
            n++;
    if (n == 0 && (cp = hostalias(name)))
        return (res_query(cp, class, type, answer, anslen));

    /*
     * 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 ((n == 0 && _res.options & RES_DEFNAMES) ||
        (n != 0 && *--cp != '.' && _res.options & RES_DNSRCH)) {
        for (domain = _res.dnsrch; *domain; 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);
            }
            if (h_errno == NO_DATA)
                got_nodata++;
            if ((h_errno != HOST_NOT_FOUND && h_errno != NO_DATA) ||
                (_res.options & RES_DNSRCH) == 0)
                break;
        }
    }
    /*
     * If the search/default failed, try the name as fully-qualified,
     * but only if it contained at least one dot (even trailing).
     * This is purely a heuristic; we assume that any reasonable query
     * about a top-level domain (for servers, SOA, etc) will not use
     * res_search.
     */
    if (n && (ret = res_querydomain(name, (char *)NULL, class, type,
        answer, anslen)) > 0)
        return (ret);
    if (got_nodata)
        h_errno = NO_DATA;
    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(name, domain, class, type, answer, anslen)
    char *name, *domain;
    int class, type;    /* class and type of query */
    u_char *answer;     /* buffer to put answer */
    int anslen;     /* size of answer */
{
    char nbuf[2*MAXDNAME+2];
    char *longname = nbuf;
    int n;

#ifdef DEBUG
    if (_res.options & RES_DEBUG) {
        if (domain == (char *)NULL)
            printf("res_querydomain(%s, NULL, %d, %d)\n",
                        name, class, type);
        else
            printf("res_querydomain(%s, %s, %d, %d)\n",
                        name, domain, class, type);
    }
#endif
    if (domain == NULL) {
        /*
         * Check for trailing '.';
         * copy without '.' if present.
         */
        n = strlen(name) - 1;
        if (name[n] == '.' && n < sizeof (nbuf) - 1) {
#ifdef SYSV
            memcpy((void *)nbuf, (void *)name, n);
#else
            bcopy(name, nbuf, n);
#endif
            nbuf[n] = '\0';
        } else
            longname = name;
    } else
        (void) sprintf(nbuf, "%.*s.%.*s",
            MAXDNAME, name, MAXDNAME, domain);

    return (res_query(longname, class, type, answer, anslen));
}

char *
hostalias(name)
    register char *name;
{
    register char *C1, *C2;
    FILE *fp;
    char *file, *getenv(), *strcpy(), *strncpy();
    char buf[BUFSIZ];
    static char abuf[MAXDNAME];

    file = getenv("HOSTALIASES");
    if (file == NULL || (fp = fopen(file, "r")) == NULL)
        return (NULL);
    buf[sizeof (buf) - 1] = '\0';
    while (fgets(buf, sizeof (buf), fp)) {
        for (C1 = buf; *C1 && !isspace(*C1); ++C1);
        if (!*C1)
            break;
        *C1 = '\0';
        if (!strcasecmp(buf, name)) {
            while (isspace(*++C1));
            if (!*C1)
                break;
            for (C2 = C1 + 1; *C2 && !isspace(*C2); ++C2);
            abuf[sizeof (abuf) - 1] = *C2 = '\0';
            (void) strncpy(abuf, C1, sizeof (abuf) - 1);
            fclose(fp);
            return (abuf);
        }
    }
    fclose(fp);
    return (NULL);
}