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res_query.c

/*
 * 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.
 * 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) 1996-1999 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 defined(LIBC_SCCS) && !defined(lint)
static const char sccsid[] = "@(#)res_query.c   8.1 (Berkeley) 6/4/93";
static const char rcsid[] = "$BINDId: res_query.c,v 8.20 2000/02/29 05:39:12 vixie Exp $";
#endif /* LIBC_SCCS and not lint */

#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>

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

#if PACKETSZ > 65536
#define MAXPACKET PACKETSZ
#else
#define MAXPACKET 65536
#endif

#define QUERYSIZE (HFIXEDSZ + QFIXEDSZ + MAXCDNAME + 1)

static int
__libc_res_nquerydomain(res_state statp, const char *name, const char *domain,
                  int class, int type, u_char *answer, int anslen,
                  u_char **answerp);

/*
 * 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
__libc_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 **answerp)     /* if buffer needs to be enlarged */
{
      u_char *buf;
      HEADER *hp = (HEADER *) answer;
      int n, use_malloc = 0;

      hp->rcode = NOERROR;    /* default */

      buf = alloca (QUERYSIZE);

#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, QUERYSIZE);
      if (__builtin_expect (n <= 0, 0)) {
            /* Retry just in case res_nmkquery failed because of too
               short buffer.  Shouldn't happen.  */
            buf = malloc (MAXPACKET);
            if (buf != NULL) {
                  use_malloc = 1;
                  n = res_nmkquery(statp, QUERY, name, class, type, NULL,
                               0, NULL, buf, MAXPACKET);
            }           
      }
      if (__builtin_expect (n <= 0, 0)) {
#ifdef DEBUG
            if (statp->options & RES_DEBUG)
                  printf(";; res_query: mkquery failed\n");
#endif
            RES_SET_H_ERRNO(statp, NO_RECOVERY);
            if (use_malloc)
                  free (buf);
            return (n);
      }
      n = __libc_res_nsend(statp, buf, n, answer, anslen, answerp);
      if (use_malloc)
            free (buf);
      if (n < 0) {
#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 = %d, ancount=%d\n", hp->rcode,
                      ntohs(hp->ancount));
#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);
}

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 */
{
      return __libc_res_nquery(statp, name, class, type, answer, anslen,
                         NULL);
}

/*
 * 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
__libc_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 */
          u_char **answerp)
{
      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;

      __set_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 (__libc_res_nquery(statp, cp, class, type, answer,
                                anslen, answerp));

      /*
       * 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 = __libc_res_nquerydomain(statp, name, NULL, class, type,
                                    answer, anslen, answerp);
            if (ret > 0 || trailing_dot)
                  return (ret);
            saved_herrno = h_errno;
            tried_as_is++;
            if (answerp && *answerp != answer) {
                  answer = *answerp;
                  anslen = MAXPACKET;
            }
      }

      /*
       * 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) != 0) ||
          (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0)) {
            int done = 0;

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

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

                  ret = __libc_res_nquerydomain(statp, name, *domain,
                                          class, type,
                                          answer, anslen, answerp);
                  if (ret > 0)
                        return (ret);

                  if (answerp && *answerp != answer) {
                        answer = *answerp;
                        anslen = MAXPACKET;
                  }

                  /*
                   * 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) == 0)
                        done++;
            }
      }

      /*
       * If the name has any dots at all, and no earlier 'as-is' query
       * for the name, and "." is not on the search list, then try an as-is
       * query now.
       */
      if (statp->ndots && !(tried_as_is || root_on_list)) {
            ret = __libc_res_nquerydomain(statp, name, NULL, class, type,
                                    answer, anslen, answerp);
            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);
}

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 */
{
      return __libc_res_nsearch(statp, name, class, type, answer,
                          anslen, NULL);
}

/*
 * Perform a call on res_query on the concatenation of name and domain,
 * removing a trailing dot from name if domain is NULL.
 */
static int
__libc_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 */
          u_char **answerp)
{
      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 (__libc_res_nquery(statp, longname, class, type, answer,
                          anslen, answerp));
}

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 */
{
      return __libc_res_nquerydomain(statp, name, domain, class, type,
                               answer, anslen, NULL);
}

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

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