common/resolv/res_query.c

/*
 * Portions Copyright (C) 2004, 2005, 2008  Internet Systems Consortium, Inc. ("ISC")
 * Portions Copyright (C) 1996-2001, 2003  Internet Software Consortium.
 *
 * Permission to use, copy, modify, and/or 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 ISC DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS.  IN NO EVENT SHALL ISC 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.
 */

/*
 * 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.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static const char sccsid[] = "@(#)res_query.c   8.1 (Berkeley) 6/4/93";
static const char rcsid[] = "$Id: res_query.c,v 1.11 2008/11/14 02:36:51 marka Exp $";
#endif /* LIBC_SCCS and not lint */

#include "port_before.h"
#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 "port_after.h"

/* Options.  Leave them on. */
#define DEBUG

#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_nquery(res_state statp,
       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;
    u_int oflags;
    u_char *rdata;
    int n;

    oflags = statp->_flags;

again:
    hp->rcode = NOERROR;    /*%< default */
#ifdef DEBUG
    if (statp->options & RES_DEBUG)
        printf(";; res_query(%s, %d, %d)\n", name, class, type);
#endif

    n = res_nmkquery(statp, QUERY, name, class, type, NULL, 0, NULL,
             buf, sizeof(buf));
#ifdef RES_USE_EDNS0
    if (n > 0 && (statp->_flags & RES_F_EDNS0ERR) == 0 &&
        (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC|RES_NSID))) {
        n = res_nopt(statp, n, buf, sizeof(buf), anslen);
        rdata = &buf[n];
        if (n > 0 && (statp->options & RES_NSID) != 0U) {
            n = res_nopt_rdata(statp, n, buf, sizeof(buf), rdata,
                       NS_OPT_NSID, 0, NULL);
        }
    }
#endif
    if (n <= 0) {
#ifdef DEBUG
        if (statp->options & RES_DEBUG)
            printf(";; res_query: mkquery failed\n");
#endif
        RES_SET_H_ERRNO(statp, NO_RECOVERY);
        return (n);
    }

    n = res_nsend(statp, buf, n, answer, anslen);
    if (n < 0) {
#ifdef RES_USE_EDNS0
        /* if the query choked with EDNS0, retry without EDNS0 */
        if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0U &&
            ((oflags ^ statp->_flags) & RES_F_EDNS0ERR) != 0) {
            statp->_flags |= RES_F_EDNS0ERR;
            if (statp->options & RES_DEBUG)
                printf(";; res_nquery: retry without EDNS0\n");
            goto again;
        }
#endif
#ifdef DEBUG
        if (statp->options & RES_DEBUG)
            printf(";; res_query: send error\n");
#endif
        RES_SET_H_ERRNO(statp, TRY_AGAIN);
        return (n);
    }

    if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
#ifdef DEBUG
        if (statp->options & RES_DEBUG)
            printf(";; rcode = (%s), counts = an:%d ns:%d ar:%d\n",
                   p_rcode(hp->rcode),
                   ntohs(hp->ancount),
                   ntohs(hp->nscount),
                   ntohs(hp->arcount));
#endif
        switch (hp->rcode) {
        case NXDOMAIN:
            RES_SET_H_ERRNO(statp, HOST_NOT_FOUND);
            break;
        case SERVFAIL:
            RES_SET_H_ERRNO(statp, TRY_AGAIN);
            break;
        case NOERROR:
            RES_SET_H_ERRNO(statp, NO_DATA);
            break;
        case FORMERR:
        case NOTIMP:
        case REFUSED:
        default:
            RES_SET_H_ERRNO(statp, 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_nsearch(res_state statp,
        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;
    char tmp[NS_MAXDNAME];
    u_int dots;
    int trailing_dot, ret, saved_herrno;
    int got_nodata = 0, got_servfail = 0, root_on_list = 0;
    int tried_as_is = 0;
    int searched = 0;

    errno = 0;
    RES_SET_H_ERRNO(statp, HOST_NOT_FOUND);  /*%< True if we never query. */
    dots = 0;
    for (cp = name; *cp != '\0'; 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 = res_hostalias(statp, name, tmp, sizeof tmp))!= NULL)
        return (res_nquery(statp, cp, class, type, answer, anslen));

    /*
     * If there are enough dots in the name, let's just give it a
     * try 'as is'. The threshold can be set with the "ndots" option.
     * Also, query 'as is', if there is a trailing dot in the name.
     */
    saved_herrno = -1;
    if (dots >= statp->ndots || trailing_dot) {
        ret = res_nquerydomain(statp, name, NULL, class, type,
                     answer, anslen);
        if (ret > 0 || trailing_dot)
            return (ret);
        saved_herrno = statp->res_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 && (statp->options & RES_DEFNAMES) != 0U) ||
        (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0U)) {
        int done = 0;

        for (domain = (const char * const *)statp->dnsrch;
             *domain && !done;
             domain++) {
            searched = 1;

            if (domain[0][0] == '\0' ||
                (domain[0][0] == '.' && domain[0][1] == '\0'))
                root_on_list++;

            ret = res_nquerydomain(statp, 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) {
                RES_SET_H_ERRNO(statp, TRY_AGAIN);
                return (-1);
            }

            switch (statp->res_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 ((statp->options & RES_DNSRCH) == 0U)
                done++;
        }
    }

    /*
     * If the query has not already been tried as is then try it
     * unless RES_NOTLDQUERY is set and there were no dots.
     */
    if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0U) &&
        !(tried_as_is || root_on_list)) {
        ret = res_nquerydomain(statp, 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)
        RES_SET_H_ERRNO(statp, saved_herrno);
    else if (got_nodata)
        RES_SET_H_ERRNO(statp, NO_DATA);
    else if (got_servfail)
        RES_SET_H_ERRNO(statp, 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_nquerydomain(res_state statp,
        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;

#ifdef DEBUG
    if (statp->options & RES_DEBUG)
        printf(";; res_nquerydomain(%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) {
            RES_SET_H_ERRNO(statp, 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) {
            RES_SET_H_ERRNO(statp, NO_RECOVERY);
            return (-1);
        }
        sprintf(nbuf, "%s.%s", name, domain);
    }
    return (res_nquery(statp, longname, class, type, answer, anslen));
}

const char *
res_hostalias(const res_state statp, const char *name, char *dst, size_t siz) {
    char *file, *cp1, *cp2;
    char buf[BUFSIZ];
    FILE *fp;

    if (statp->options & RES_NOALIASES)
        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 (ns_samename(buf, name) == 1) {
            while (isspace((unsigned char)*++cp1))
                ;
            if (!*cp1)
                break;
            for (cp2 = cp1 + 1; *cp2 &&
                 !isspace((unsigned char)*cp2); ++cp2)
                ;
            *cp2 = '\0';
            strncpy(dst, cp1, siz - 1);
            dst[siz - 1] = '\0';
            fclose(fp);
            return (dst);
        }
    }
    fclose(fp);
    return (NULL);
}

/*! \file */