/*      $NetBSD: res_query.c,v 1.1.1.2 2012/09/09 16:08:08 christos Exp $       */

/*
* 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 */

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