source: rtems/cpukit/libnetworking/libc/res_query.c @ 029c374c

/*
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. 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.
 */

/*
 * 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.
 */

#if HAVE_CONFIG_H
#include "config.h"
#endif

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

#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, int type,    /* class and 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) {
#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, int type,    /* class and type of query */
        u_char *answer,         /* buffer to put answer */
        int anslen)             /* size of answer */
{
        const char *cp, * const *domain;
        HEADER *hp = (HEADER *) answer;
        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:
                                if (hp->rcode == SERVFAIL) {
                                        /* try next search element, if any */
                                        got_servfail++;
                                        break;
                                }
                                /* 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, int type,    /* class and 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:"<Nil>", 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)
{
        register 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((int)*cp1); ++cp1)
                        ;
                if (!*cp1)
                        break;
                *cp1 = '\0';
                if (!strcasecmp(buf, name)) {
                        while (isspace((int)*++cp1))
                                ;
                        if (!*cp1)
                                break;
                        for (cp2 = cp1 + 1; *cp2 && !isspace((int)*cp2); ++cp2)
                                ;
                        abuf[sizeof(abuf) - 1] = *cp2 = '\0';
                        strncpy(abuf, cp1, sizeof(abuf) - 1);
                        fclose(fp);
                        return (abuf);
                }
        }
        fclose(fp);
        return (NULL);
}