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gethnamaddr.c

/*
 * ++Copyright++ 1985, 1988, 1993
 * -
 * Copyright (c) 1985, 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.
 * -
 * --Copyright--
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)gethostnamadr.c     8.1 (Berkeley) 6/4/93";
static char rcsid[] = "$Id: gethnamaddr.c,v 1.44 2003/01/01 16:29:36 aj Exp $";
#endif /* LIBC_SCCS and not lint */

#include <sys/types.h>
#include <sys/param.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <arpa/nameser.h>

#include <stdio.h>
#include <netdb.h>
#include <resolv.h>
#include <ctype.h>
#include <errno.h>
#include <syslog.h>

#define RESOLVSORT

#ifndef LOG_AUTH
# define LOG_AUTH 0
#endif

#define MULTI_PTRS_ARE_ALIASES 1    /* XXX - experimental */

#if defined(BSD) && (BSD >= 199103) && defined(AF_INET6)
# include <stdlib.h>
# include <string.h>
#else
# include "../conf/portability.h"
#endif

#if defined(USE_OPTIONS_H)
# include <../conf/options.h>
#endif

#ifdef SPRINTF_CHAR
# define SPRINTF(x) strlen(sprintf/**/x)
#else
# define SPRINTF(x) ((size_t)sprintf x)
#endif

#define     MAXALIASES  35
#define     MAXADDRS    35

static const char AskedForGot[] =
                    "gethostby*.getanswer: asked for \"%s\", got \"%s\"";

static char *h_addr_ptrs[MAXADDRS + 1];

static struct hostent host;
static char *host_aliases[MAXALIASES];
static char hostbuf[8*1024];
static u_char host_addr[16];  /* IPv4 or IPv6 */
static FILE *hostf = NULL;
static int stayopen = 0;

static void map_v4v6_address __P((const char *src, char *dst));
static void map_v4v6_hostent __P((struct hostent *hp, char **bp, int *len));

#ifdef RESOLVSORT
extern void addrsort __P((char **, int));
#endif

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

/* As per RFC 1034 and 1035 a host name cannot exceed 255 octets in length.  */
#ifdef MAXHOSTNAMELEN
# undef MAXHOSTNAMELEN
#endif
#define MAXHOSTNAMELEN 256

typedef union {
    HEADER hdr;
    u_char buf[MAXPACKET];
} querybuf;

typedef union {
    int32_t al;
    char ac;
} align;

#ifndef h_errno
extern int h_errno;
#endif

#ifdef DEBUG
static void
dprintf(msg, num)
      char *msg;
      int num;
{
      if (_res.options & RES_DEBUG) {
            int save = errno;

            printf(msg, num);
            __set_errno (save);
      }
}
#else
# define dprintf(msg, num) /*nada*/
#endif

#define BOUNDED_INCR(x) \
      do { \
            cp += x; \
            if (cp > eom) { \
                  __set_h_errno (NO_RECOVERY); \
                  return (NULL); \
            } \
      } while (0)

#define BOUNDS_CHECK(ptr, count) \
      do { \
            if ((ptr) + (count) > eom) { \
                  __set_h_errno (NO_RECOVERY); \
                  return (NULL); \
            } \
      } while (0)


static struct hostent *
getanswer(answer, anslen, qname, qtype)
      const querybuf *answer;
      int anslen;
      const char *qname;
      int qtype;
{
      register const HEADER *hp;
      register const u_char *cp;
      register int n;
      const u_char *eom, *erdata;
      char *bp, **ap, **hap;
      int type, class, buflen, ancount, qdcount;
      int haveanswer, had_error;
      int toobig = 0;
      char tbuf[MAXDNAME];
      const char *tname;
      int (*name_ok) __P((const char *));

      tname = qname;
      host.h_name = NULL;
      eom = answer->buf + anslen;
      switch (qtype) {
      case T_A:
      case T_AAAA:
            name_ok = res_hnok;
            break;
      case T_PTR:
            name_ok = res_dnok;
            break;
      default:
            return (NULL);    /* XXX should be abort(); */
      }
      /*
       * find first satisfactory answer
       */
      hp = &answer->hdr;
      ancount = ntohs(hp->ancount);
      qdcount = ntohs(hp->qdcount);
      bp = hostbuf;
      buflen = sizeof hostbuf;
      cp = answer->buf;
      BOUNDED_INCR(HFIXEDSZ);
      if (qdcount != 1) {
            __set_h_errno (NO_RECOVERY);
            return (NULL);
      }
      n = dn_expand(answer->buf, eom, cp, bp, buflen);
      if ((n < 0) || !(*name_ok)(bp)) {
            __set_h_errno (NO_RECOVERY);
            return (NULL);
      }
      BOUNDED_INCR(n + QFIXEDSZ);
      if (qtype == T_A || qtype == T_AAAA) {
            /* res_send() has already verified that the query name is the
             * same as the one we sent; this just gets the expanded name
             * (i.e., with the succeeding search-domain tacked on).
             */
            n = strlen(bp) + 1;           /* for the \0 */
            if (n >= MAXHOSTNAMELEN) {
                  __set_h_errno (NO_RECOVERY);
                  return (NULL);
            }
            host.h_name = bp;
            bp += n;
            buflen -= n;
            /* The qname can be abbreviated, but h_name is now absolute. */
            qname = host.h_name;
      }
      ap = host_aliases;
      *ap = NULL;
      host.h_aliases = host_aliases;
      hap = h_addr_ptrs;
      *hap = NULL;
      host.h_addr_list = h_addr_ptrs;
      haveanswer = 0;
      had_error = 0;
      while (ancount-- > 0 && cp < eom && !had_error) {
            n = dn_expand(answer->buf, eom, cp, bp, buflen);
            if ((n < 0) || !(*name_ok)(bp)) {
                  had_error++;
                  continue;
            }
            cp += n;                /* name */
            BOUNDS_CHECK(cp, 3 * INT16SZ + INT32SZ);
            type = ns_get16(cp);
            cp += INT16SZ;                /* type */
            class = ns_get16(cp);
            cp += INT16SZ + INT32SZ;      /* class, TTL */
            n = ns_get16(cp);
            cp += INT16SZ;                /* len */
            BOUNDS_CHECK(cp, n);
            erdata = cp + n;
            if (class != C_IN) {
                  /* XXX - debug? syslog? */
                  cp += n;
                  continue;         /* XXX - had_error++ ? */
            }
            if ((qtype == T_A || qtype == T_AAAA) && type == T_CNAME) {
                  if (ap >= &host_aliases[MAXALIASES-1])
                        continue;
                  n = dn_expand(answer->buf, eom, cp, tbuf, sizeof tbuf);
                  if ((n < 0) || !(*name_ok)(tbuf)) {
                        had_error++;
                        continue;
                  }
                  cp += n;
                  if (cp != erdata) {
                        __set_h_errno (NO_RECOVERY);
                        return (NULL);
                  }
                  /* Store alias. */
                  *ap++ = bp;
                  n = strlen(bp) + 1;     /* for the \0 */
                  if (n >= MAXHOSTNAMELEN) {
                        had_error++;
                        continue;
                  }
                  bp += n;
                  buflen -= n;
                  /* Get canonical name. */
                  n = strlen(tbuf) + 1;   /* for the \0 */
                  if (n > buflen || n >= MAXHOSTNAMELEN) {
                        had_error++;
                        continue;
                  }
                  strcpy(bp, tbuf);
                  host.h_name = bp;
                  bp += n;
                  buflen -= n;
                  continue;
            }
            if (qtype == T_PTR && type == T_CNAME) {
                  n = dn_expand(answer->buf, eom, cp, tbuf, sizeof tbuf);
                  if (n < 0 || !res_dnok(tbuf)) {
                        had_error++;
                        continue;
                  }
                  cp += n;
                  if (cp != erdata) {
                        __set_h_errno (NO_RECOVERY);
                        return (NULL);
                  }
                  /* Get canonical name. */
                  n = strlen(tbuf) + 1;   /* for the \0 */
                  if (n > buflen || n >= MAXHOSTNAMELEN) {
                        had_error++;
                        continue;
                  }
                  strcpy(bp, tbuf);
                  tname = bp;
                  bp += n;
                  buflen -= n;
                  continue;
            }
            if ((type == T_SIG) || (type == T_KEY) || (type == T_NXT)) {
                  /* We don't support DNSSEC yet.  For now, ignore
                   * the record and send a low priority message
                   * to syslog.
                   */
                  syslog(LOG_DEBUG|LOG_AUTH,
             "gethostby*.getanswer: asked for \"%s %s %s\", got type \"%s\"",
                         qname, p_class(C_IN), p_type(qtype),
                         p_type(type));
                  cp += n;
                  continue;
            }
            if (type != qtype) {
                  syslog(LOG_NOTICE|LOG_AUTH,
             "gethostby*.getanswer: asked for \"%s %s %s\", got type \"%s\"",
                         qname, p_class(C_IN), p_type(qtype),
                         p_type(type));
                  cp += n;
                  continue;         /* XXX - had_error++ ? */
            }
            switch (type) {
            case T_PTR:
                  if (strcasecmp(tname, bp) != 0) {
                        syslog(LOG_NOTICE|LOG_AUTH,
                               AskedForGot, qname, bp);
                        cp += n;
                        continue;   /* XXX - had_error++ ? */
                  }
                  n = dn_expand(answer->buf, eom, cp, bp, buflen);
                  if ((n < 0) || !res_hnok(bp)) {
                        had_error++;
                        break;
                  }
#if MULTI_PTRS_ARE_ALIASES
                  cp += n;
                  if (cp != erdata) {
                        __set_h_errno (NO_RECOVERY);
                        return (NULL);
                  }
                  if (!haveanswer)
                        host.h_name = bp;
                  else if (ap < &host_aliases[MAXALIASES-1])
                        *ap++ = bp;
                  else
                        n = -1;
                  if (n != -1) {
                        n = strlen(bp) + 1;     /* for the \0 */
                        if (n >= MAXHOSTNAMELEN) {
                              had_error++;
                              break;
                        }
                        bp += n;
                        buflen -= n;
                  }
                  break;
#else
                  host.h_name = bp;
                  if (_res.options & RES_USE_INET6) {
                        n = strlen(bp) + 1;     /* for the \0 */
                        if (n >= MAXHOSTNAMELEN) {
                              had_error++;
                              break;
                        }
                        bp += n;
                        buflen -= n;
                        map_v4v6_hostent(&host, &bp, &buflen);
                  }
                  __set_h_errno (NETDB_SUCCESS);
                  return (&host);
#endif
            case T_A:
            case T_AAAA:
                  if (strcasecmp(host.h_name, bp) != 0) {
                        syslog(LOG_NOTICE|LOG_AUTH,
                               AskedForGot, host.h_name, bp);
                        cp += n;
                        continue;   /* XXX - had_error++ ? */
                  }
                  if (n != host.h_length) {
                        cp += n;
                        continue;
                  }
                  if (!haveanswer) {
                        register int nn;

                        host.h_name = bp;
                        nn = strlen(bp) + 1;    /* for the \0 */
                        bp += nn;
                        buflen -= nn;
                  }

                  /* XXX: when incrementing bp, we have to decrement
                   * buflen by the same amount --okir */
                  buflen -= sizeof(align) - ((u_long)bp % sizeof(align));

                  bp += sizeof(align) - ((u_long)bp % sizeof(align));

                  if (bp + n >= &hostbuf[sizeof hostbuf]) {
                        dprintf("size (%d) too big\n", n);
                        had_error++;
                        continue;
                  }
                  if (hap >= &h_addr_ptrs[MAXADDRS-1]) {
                        if (!toobig++) {
                              dprintf("Too many addresses (%d)\n",
                                    MAXADDRS);
                        }
                        cp += n;
                        continue;
                  }
                  memmove(*hap++ = bp, cp, n);
                  bp += n;
                  buflen -= n;
                  cp += n;
                  if (cp != erdata) {
                        __set_h_errno (NO_RECOVERY);
                        return (NULL);
                  }
                  break;
            default:
                  abort();
            }
            if (!had_error)
                  haveanswer++;
      }
      if (haveanswer) {
            *ap = NULL;
            *hap = NULL;
# if defined(RESOLVSORT)
            /*
             * Note: we sort even if host can take only one address
             * in its return structures - should give it the "best"
             * address in that case, not some random one
             */
            if (_res.nsort && haveanswer > 1 && qtype == T_A)
                  addrsort(h_addr_ptrs, haveanswer);
# endif /*RESOLVSORT*/
            if (!host.h_name) {
                  n = strlen(qname) + 1;  /* for the \0 */
                  if (n > buflen || n >= MAXHOSTNAMELEN)
                        goto no_recovery;
                  strcpy(bp, qname);
                  host.h_name = bp;
                  bp += n;
                  buflen -= n;
            }
            if (_res.options & RES_USE_INET6)
                  map_v4v6_hostent(&host, &bp, &buflen);
            __set_h_errno (NETDB_SUCCESS);
            return (&host);
      }
 no_recovery:
      __set_h_errno (NO_RECOVERY);
      return (NULL);
}

struct hostent *
gethostbyname(name)
      const char *name;
{
      struct hostent *hp;

      if ((_res.options & RES_INIT) == 0 && __res_ninit(&_res) == -1) {
            __set_h_errno (NETDB_INTERNAL);
            return (NULL);
       }
      if (_res.options & RES_USE_INET6) {
            hp = gethostbyname2(name, AF_INET6);
            if (hp)
                  return (hp);
      }
      return (gethostbyname2(name, AF_INET));
}

struct hostent *
gethostbyname2(name, af)
      const char *name;
      int af;
{
      union
      {
        querybuf *buf;
        u_char *ptr;
      } buf;
      querybuf *origbuf;
      register const char *cp;
      char *bp;
      int n, size, type, len;
      struct hostent *ret;
      extern struct hostent *_gethtbyname2();

      if ((_res.options & RES_INIT) == 0 && __res_ninit(&_res) == -1) {
            __set_h_errno (NETDB_INTERNAL);
            return (NULL);
      }

      switch (af) {
      case AF_INET:
            size = INADDRSZ;
            type = T_A;
            break;
      case AF_INET6:
            size = IN6ADDRSZ;
            type = T_AAAA;
            break;
      default:
            __set_h_errno (NETDB_INTERNAL);
            __set_errno (EAFNOSUPPORT);
            return (NULL);
      }

      host.h_addrtype = af;
      host.h_length = size;

      /*
       * if there aren't any dots, it could be a user-level alias.
       * this is also done in res_query() since we are not the only
       * function that looks up host names.
       */
      if (!strchr(name, '.') && (cp = __hostalias(name)))
            name = cp;

      /*
       * disallow names consisting only of digits/dots, unless
       * they end in a dot.
       */
      if (isdigit(name[0]))
            for (cp = name;; ++cp) {
                  if (!*cp) {
                        if (*--cp == '.')
                              break;
                        /*
                         * All-numeric, no dot at the end.
                         * Fake up a hostent as if we'd actually
                         * done a lookup.
                         */
                        if (inet_pton(af, name, host_addr) <= 0) {
                              __set_h_errno (HOST_NOT_FOUND);
                              return (NULL);
                        }
                        strncpy(hostbuf, name, MAXDNAME);
                        hostbuf[MAXDNAME] = '\0';
                        bp = hostbuf + MAXDNAME;
                        len = sizeof hostbuf - MAXDNAME;
                        host.h_name = hostbuf;
                        host.h_aliases = host_aliases;
                        host_aliases[0] = NULL;
                        h_addr_ptrs[0] = (char *)host_addr;
                        h_addr_ptrs[1] = NULL;
                        host.h_addr_list = h_addr_ptrs;
                        if (_res.options & RES_USE_INET6)
                              map_v4v6_hostent(&host, &bp, &len);
                        __set_h_errno (NETDB_SUCCESS);
                        return (&host);
                  }
                  if (!isdigit(*cp) && *cp != '.')
                        break;
               }
      if ((isxdigit(name[0]) && strchr(name, ':') != NULL) ||
          name[0] == ':')
            for (cp = name;; ++cp) {
                  if (!*cp) {
                        if (*--cp == '.')
                              break;
                        /*
                         * All-IPv6-legal, no dot at the end.
                         * Fake up a hostent as if we'd actually
                         * done a lookup.
                         */
                        if (inet_pton(af, name, host_addr) <= 0) {
                              __set_h_errno (HOST_NOT_FOUND);
                              return (NULL);
                        }
                        strncpy(hostbuf, name, MAXDNAME);
                        hostbuf[MAXDNAME] = '\0';
                        bp = hostbuf + MAXDNAME;
                        len = sizeof hostbuf - MAXDNAME;
                        host.h_name = hostbuf;
                        host.h_aliases = host_aliases;
                        host_aliases[0] = NULL;
                        h_addr_ptrs[0] = (char *)host_addr;
                        h_addr_ptrs[1] = NULL;
                        host.h_addr_list = h_addr_ptrs;
                        __set_h_errno (NETDB_SUCCESS);
                        return (&host);
                  }
                  if (!isxdigit(*cp) && *cp != ':' && *cp != '.')
                        break;
            }

      buf.buf = origbuf = (querybuf *) alloca (1024);

      if ((n = __libc_res_nsearch(&_res, name, C_IN, type, buf.buf->buf, 1024,
                            &buf.ptr)) < 0) {
            if (buf.buf != origbuf)
                  free (buf.buf);
            dprintf("res_nsearch failed (%d)\n", n);
            if (errno == ECONNREFUSED)
                  return (_gethtbyname2(name, af));
            return (NULL);
      }
      ret = getanswer(buf.buf, n, name, type);
      if (buf.buf != origbuf)
            free (buf.buf);
      return ret;
}

struct hostent *
gethostbyaddr(addr, len, af)
      const void *addr;
      socklen_t len;
      int af;
{
      const u_char *uaddr = (const u_char *)addr;
      static const u_char mapped[] = { 0,0, 0,0, 0,0, 0,0, 0,0, 0xff,0xff };
      static const u_char tunnelled[] = { 0,0, 0,0, 0,0, 0,0, 0,0, 0,0 };
      int n;
      socklen_t size;
      union
      {
        querybuf *buf;
        u_char *ptr;
      } buf;
      querybuf *orig_buf;
      register struct hostent *hp;
      char qbuf[MAXDNAME+1], *qp = NULL;
#ifdef SUNSECURITY
      register struct hostent *rhp;
      char **haddr;
      u_long old_options;
      char hname2[MAXDNAME+1];
#endif /*SUNSECURITY*/
      extern struct hostent *_gethtbyaddr();

      if ((_res.options & RES_INIT) == 0 && __res_ninit(&_res) == -1) {
            __set_h_errno (NETDB_INTERNAL);
            return (NULL);
      }
      if (af == AF_INET6 && len == IN6ADDRSZ &&
          (!bcmp(uaddr, mapped, sizeof mapped) ||
           !bcmp(uaddr, tunnelled, sizeof tunnelled))) {
            /* Unmap. */
            addr += sizeof mapped;
            uaddr += sizeof mapped;
            af = AF_INET;
            len = INADDRSZ;
      }
      switch (af) {
      case AF_INET:
            size = INADDRSZ;
            break;
      case AF_INET6:
            size = IN6ADDRSZ;
            break;
      default:
            __set_errno (EAFNOSUPPORT);
            __set_h_errno (NETDB_INTERNAL);
            return (NULL);
      }
      if (size != len) {
            __set_errno (EINVAL);
            __set_h_errno (NETDB_INTERNAL);
            return (NULL);
      }
      switch (af) {
      case AF_INET:
            (void) sprintf(qbuf, "%u.%u.%u.%u.in-addr.arpa",
                         (uaddr[3] & 0xff),
                         (uaddr[2] & 0xff),
                         (uaddr[1] & 0xff),
                         (uaddr[0] & 0xff));
            break;
      case AF_INET6:
            qp = qbuf;
            for (n = IN6ADDRSZ - 1; n >= 0; n--) {
                  qp += SPRINTF((qp, "%x.%x.",
                               uaddr[n] & 0xf,
                               (uaddr[n] >> 4) & 0xf));
            }
            strcpy(qp, "ip6.arpa");
            break;
      default:
            abort();
      }

      buf.buf = orig_buf = (querybuf *) alloca (1024);

      n = __libc_res_nquery(&_res, qbuf, C_IN, T_PTR, buf.buf->buf, 1024,
                        &buf.ptr);
      if (n < 0 && af == AF_INET6) {
            strcpy(qp, "ip6.int");
            n = __libc_res_nquery(&_res, qbuf, C_IN, T_PTR, buf.buf->buf,
                              buf.buf != orig_buf ? MAXPACKET : 1024,
                              &buf.ptr);
      }
      if (n < 0) {
            if (buf.buf != orig_buf)
                  free (buf.buf);
            dprintf("res_nquery failed (%d)\n", n);
            if (errno == ECONNREFUSED)
                  return (_gethtbyaddr(addr, len, af));
            return (NULL);
      }
      hp = getanswer(buf.buf, n, qbuf, T_PTR);
      if (buf.buf != orig_buf)
            free (buf.buf);
      if (!hp)
            return (NULL);    /* h_errno was set by getanswer() */
#ifdef SUNSECURITY
      if (af == AF_INET) {
          /*
           * turn off search as the name should be absolute,
           * 'localhost' should be matched by defnames
           */
          strncpy(hname2, hp->h_name, MAXDNAME);
          hname2[MAXDNAME] = '\0';
          old_options = _res.options;
          _res.options &= ~RES_DNSRCH;
          _res.options |= RES_DEFNAMES;
          if (!(rhp = gethostbyname(hname2))) {
            syslog(LOG_NOTICE|LOG_AUTH,
                   "gethostbyaddr: No A record for %s (verifying [%s])",
                   hname2, inet_ntoa(*((struct in_addr *)addr)));
            _res.options = old_options;
            __set_h_errno (HOST_NOT_FOUND);
            return (NULL);
          }
          _res.options = old_options;
          for (haddr = rhp->h_addr_list; *haddr; haddr++)
            if (!memcmp(*haddr, addr, INADDRSZ))
                  break;
          if (!*haddr) {
            syslog(LOG_NOTICE|LOG_AUTH,
                   "gethostbyaddr: A record of %s != PTR record [%s]",
                   hname2, inet_ntoa(*((struct in_addr *)addr)));
            __set_h_errno (HOST_NOT_FOUND);
            return (NULL);
          }
      }
#endif /*SUNSECURITY*/
      hp->h_addrtype = af;
      hp->h_length = len;
      memmove(host_addr, addr, len);
      h_addr_ptrs[0] = (char *)host_addr;
      h_addr_ptrs[1] = NULL;
      if (af == AF_INET && (_res.options & RES_USE_INET6)) {
            map_v4v6_address((char*)host_addr, (char*)host_addr);
            hp->h_addrtype = AF_INET6;
            hp->h_length = IN6ADDRSZ;
      }
      __set_h_errno (NETDB_SUCCESS);
      return (hp);
}

void
_sethtent(f)
      int f;
{
      if (!hostf)
            hostf = fopen(_PATH_HOSTS, "r" );
      else
            rewind(hostf);
      stayopen = f;
}

void
_endhtent()
{
      if (hostf && !stayopen) {
            (void) fclose(hostf);
            hostf = NULL;
      }
}

struct hostent *
_gethtent()
{
      char *p;
      register char *cp, **q;
      int af, len;

      if (!hostf && !(hostf = fopen(_PATH_HOSTS, "r" ))) {
            __set_h_errno (NETDB_INTERNAL);
            return (NULL);
      }
 again:
      if (!(p = fgets(hostbuf, sizeof hostbuf, hostf))) {
            __set_h_errno (HOST_NOT_FOUND);
            return (NULL);
      }
      if (*p == '#')
            goto again;
      if (!(cp = strpbrk(p, "#\n")))
            goto again;
      *cp = '\0';
      if (!(cp = strpbrk(p, " \t")))
            goto again;
      *cp++ = '\0';
      if (inet_pton(AF_INET6, p, host_addr) > 0) {
            af = AF_INET6;
            len = IN6ADDRSZ;
      } else if (inet_pton(AF_INET, p, host_addr) > 0) {
            if (_res.options & RES_USE_INET6) {
                  map_v4v6_address((char*)host_addr, (char*)host_addr);
                  af = AF_INET6;
                  len = IN6ADDRSZ;
            } else {
                  af = AF_INET;
                  len = INADDRSZ;
            }
      } else {
            goto again;
      }
      h_addr_ptrs[0] = (char *)host_addr;
      h_addr_ptrs[1] = NULL;
      host.h_addr_list = h_addr_ptrs;
      host.h_length = len;
      host.h_addrtype = af;
      while (*cp == ' ' || *cp == '\t')
            cp++;
      host.h_name = cp;
      q = host.h_aliases = host_aliases;
      if ((cp = strpbrk(cp, " \t")))
            *cp++ = '\0';
      while (cp && *cp) {
            if (*cp == ' ' || *cp == '\t') {
                  cp++;
                  continue;
            }
            if (q < &host_aliases[MAXALIASES - 1])
                  *q++ = cp;
            if ((cp = strpbrk(cp, " \t")))
                  *cp++ = '\0';
      }
      *q = NULL;
      __set_h_errno (NETDB_SUCCESS);
      return (&host);
}

struct hostent *
_gethtbyname(name)
      const char *name;
{
      extern struct hostent *_gethtbyname2();
      struct hostent *hp;

      if (_res.options & RES_USE_INET6) {
            hp = _gethtbyname2(name, AF_INET6);
            if (hp)
                  return (hp);
      }
      return (_gethtbyname2(name, AF_INET));
}

struct hostent *
_gethtbyname2(name, af)
      const char *name;
      int af;
{
      register struct hostent *p;
      register char **cp;

      _sethtent(0);
      while ((p = _gethtent())) {
            if (p->h_addrtype != af)
                  continue;
            if (strcasecmp(p->h_name, name) == 0)
                  break;
            for (cp = p->h_aliases; *cp != 0; cp++)
                  if (strcasecmp(*cp, name) == 0)
                        goto found;
      }
 found:
      _endhtent();
      return (p);
}

struct hostent *
_gethtbyaddr(addr, len, af)
      const char *addr;
      size_t len;
      int af;
{
      register struct hostent *p;

      _sethtent(0);
      while ((p = _gethtent()))
            if (p->h_addrtype == af && !bcmp(p->h_addr, addr, len))
                  break;
      _endhtent();
      return (p);
}

static void
map_v4v6_address(src, dst)
      const char *src;
      char *dst;
{
      u_char *p = (u_char *)dst;
      char tmp[INADDRSZ];
      int i;

      /* Stash a temporary copy so our caller can update in place. */
      memcpy(tmp, src, INADDRSZ);
      /* Mark this ipv6 addr as a mapped ipv4. */
      for (i = 0; i < 10; i++)
            *p++ = 0x00;
      *p++ = 0xff;
      *p++ = 0xff;
      /* Retrieve the saved copy and we're done. */
      memcpy((void*)p, tmp, INADDRSZ);
}

static void
map_v4v6_hostent(hp, bpp, lenp)
      struct hostent *hp;
      char **bpp;
      int *lenp;
{
      char **ap;

      if (hp->h_addrtype != AF_INET || hp->h_length != INADDRSZ)
            return;
      hp->h_addrtype = AF_INET6;
      hp->h_length = IN6ADDRSZ;
      for (ap = hp->h_addr_list; *ap; ap++) {
            int i = sizeof(align) - ((u_long)*bpp % sizeof(align));

            if (*lenp < (i + IN6ADDRSZ)) {
                  /* Out of memory.  Truncate address list here.  XXX */
                  *ap = NULL;
                  return;
            }
            *bpp += i;
            *lenp -= i;
            map_v4v6_address(*ap, *bpp);
            *ap = *bpp;
            *bpp += IN6ADDRSZ;
            *lenp -= IN6ADDRSZ;
      }
}

#ifdef RESOLVSORT
extern void
addrsort(ap, num)
      char **ap;
      int num;
{
      int i, j;
      char **p;
      short aval[MAXADDRS];
      int needsort = 0;

      p = ap;
      for (i = 0; i < num; i++, p++) {
          for (j = 0 ; (unsigned)j < _res.nsort; j++)
            if (_res.sort_list[j].addr.s_addr ==
                (((struct in_addr *)(*p))->s_addr & _res.sort_list[j].mask))
                  break;
          aval[i] = j;
          if (needsort == 0 && i > 0 && j < aval[i-1])
            needsort = i;
      }
      if (!needsort)
          return;

      while (needsort < num) {
          for (j = needsort - 1; j >= 0; j--) {
            if (aval[j] > aval[j+1]) {
                char *hp;

                i = aval[j];
                aval[j] = aval[j+1];
                aval[j+1] = i;

                hp = ap[j];
                ap[j] = ap[j+1];
                ap[j+1] = hp;

            } else
                break;
          }
          needsort++;
      }
}
#endif

#if defined(BSD43_BSD43_NFS) || defined(sun)
/* some libc's out there are bound internally to these names (UMIPS) */
void
ht_sethostent(stayopen)
      int stayopen;
{
      _sethtent(stayopen);
}

void
ht_endhostent()
{
      _endhtent();
}

struct hostent *
ht_gethostbyname(name)
      char *name;
{
      return (_gethtbyname(name));
}

struct hostent *
ht_gethostbyaddr(addr, len, af)
      const char *addr;
      size_t len;
      int af;
{
      return (_gethtbyaddr(addr, len, af));
}

struct hostent *
gethostent()
{
      return (_gethtent());
}

void
dns_service()
{
      return;
}

#undef dn_skipname
dn_skipname(comp_dn, eom)
      const u_char *comp_dn, *eom;
{
      return (__dn_skipname(comp_dn, eom));
}
#endif /*old-style libc with yp junk in it*/

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