Deduplicate resolv/nss_dns/dns-host.c

[glibc.git] / resolv / nss_dns / dns-host.c

/* Copyright (C) 1996-2014 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Extended from original form by Ulrich Drepper <drepper@cygnus.com>, 1996.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

/* Parts of this file are plain copies of the file `gethtnamadr.c' from
   the bind package and it has the following copyright.  */

/*
 * ++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--
 */

#include <assert.h>
#include <ctype.h>
#include <errno.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <string.h>
#include <sys/syslog.h>

#include "nsswitch.h"

/* Get implementation for some internal functions.  */
#include <resolv/mapv4v6addr.h>
#include <resolv/mapv4v6hostent.h>

#define RESOLVSORT

#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

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


/* We need this time later.  */
typedef union querybuf
{
  HEADER hdr;
  u_char buf[MAXPACKET];
} querybuf;

/* These functions are defined in res_comp.c.  */
#define NS_MAXCDNAME    255     /* maximum compressed domain name */
extern int __ns_name_ntop (const u_char *, char *, size_t);
extern int __ns_name_unpack (const u_char *, const u_char *,
                             const u_char *, u_char *, size_t);


static enum nss_status getanswer_r (const querybuf *answer, int anslen,
                                    const char *qname, int qtype,
                                    struct hostent *result, char *buffer,
                                    size_t buflen, int *errnop, int *h_errnop,
                                    int map, int32_t *ttlp, char **canonp);

static enum nss_status gaih_getanswer (const querybuf *answer1, int anslen1,
                                       const querybuf *answer2, int anslen2,
                                       const char *qname,
                                       struct gaih_addrtuple **pat,
                                       char *buffer, size_t buflen,
                                       int *errnop, int *h_errnop,
                                       int32_t *ttlp);

extern enum nss_status _nss_dns_gethostbyname3_r (const char *name, int af,
                                                  struct hostent *result,
                                                  char *buffer, size_t buflen,
                                                  int *errnop, int *h_errnop,
                                                  int32_t *ttlp,
                                                  char **canonp);
hidden_proto (_nss_dns_gethostbyname3_r)

enum nss_status
_nss_dns_gethostbyname3_r (const char *name, int af, struct hostent *result,
                           char *buffer, size_t buflen, int *errnop,
                           int *h_errnop, int32_t *ttlp, char **canonp)
{
  union
  {
    querybuf *buf;
    u_char *ptr;
  } host_buffer;
  querybuf *orig_host_buffer;
  char tmp[NS_MAXDNAME];
  int size, type, n;
  const char *cp;
  int map = 0;
  int olderr = errno;
  enum nss_status status;

  if (__res_maybe_init (&_res, 0) == -1)
    return NSS_STATUS_UNAVAIL;

  switch (af) {
  case AF_INET:
    size = INADDRSZ;
    type = T_A;
    break;
  case AF_INET6:
    size = IN6ADDRSZ;
    type = T_AAAA;
    break;
  default:
    *h_errnop = NO_DATA;
    *errnop = EAFNOSUPPORT;
    return NSS_STATUS_UNAVAIL;
  }

  result->h_addrtype = af;
  result->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, '.') == NULL
      && (cp = res_hostalias (&_res, name, tmp, sizeof (tmp))) != NULL)
    name = cp;

  host_buffer.buf = orig_host_buffer = (querybuf *) alloca (1024);

  n = __libc_res_nsearch (&_res, name, C_IN, type, host_buffer.buf->buf,
                          1024, &host_buffer.ptr, NULL, NULL, NULL);
  if (n < 0)
    {
      switch (errno)
        {
        case ESRCH:
          status = NSS_STATUS_TRYAGAIN;
          h_errno = TRY_AGAIN;
          break;
        /* System has run out of file descriptors.  */
        case EMFILE:
        case ENFILE:
          h_errno = NETDB_INTERNAL;
          /* Fall through.  */
        case ECONNREFUSED:
        case ETIMEDOUT:
          status = NSS_STATUS_UNAVAIL;
          break;
        default:
          status = NSS_STATUS_NOTFOUND;
          break;
        }
      *h_errnop = h_errno;
      if (h_errno == TRY_AGAIN)
        *errnop = EAGAIN;
      else
        __set_errno (olderr);

      /* If we are looking for an IPv6 address and mapping is enabled
         by having the RES_USE_INET6 bit in _res.options set, we try
         another lookup.  */
      if (af == AF_INET6 && (_res.options & RES_USE_INET6))
        n = __libc_res_nsearch (&_res, name, C_IN, T_A, host_buffer.buf->buf,
                                host_buffer.buf != orig_host_buffer
                                ? MAXPACKET : 1024, &host_buffer.ptr,
                                NULL, NULL, NULL);

      if (n < 0)
        {
          if (host_buffer.buf != orig_host_buffer)
            free (host_buffer.buf);
          return status;
        }

      map = 1;

      result->h_addrtype = AF_INET;
      result->h_length = INADDRSZ;
    }

  status = getanswer_r (host_buffer.buf, n, name, type, result, buffer, buflen,
                        errnop, h_errnop, map, ttlp, canonp);
  if (host_buffer.buf != orig_host_buffer)
    free (host_buffer.buf);
  return status;
}
hidden_def (_nss_dns_gethostbyname3_r)


enum nss_status
_nss_dns_gethostbyname2_r (const char *name, int af, struct hostent *result,
                           char *buffer, size_t buflen, int *errnop,
                           int *h_errnop)
{
  return _nss_dns_gethostbyname3_r (name, af, result, buffer, buflen, errnop,
                                    h_errnop, NULL, NULL);
}


enum nss_status
_nss_dns_gethostbyname_r (const char *name, struct hostent *result,
                          char *buffer, size_t buflen, int *errnop,
                          int *h_errnop)
{
  enum nss_status status = NSS_STATUS_NOTFOUND;

  if (_res.options & RES_USE_INET6)
    status = _nss_dns_gethostbyname3_r (name, AF_INET6, result, buffer,
                                        buflen, errnop, h_errnop, NULL, NULL);
  if (status == NSS_STATUS_NOTFOUND)
    status = _nss_dns_gethostbyname3_r (name, AF_INET, result, buffer,
                                        buflen, errnop, h_errnop, NULL, NULL);

  return status;
}


enum nss_status
_nss_dns_gethostbyname4_r (const char *name, struct gaih_addrtuple **pat,
                           char *buffer, size_t buflen, int *errnop,
                           int *herrnop, int32_t *ttlp)
{
  if (__res_maybe_init (&_res, 0) == -1)
    return NSS_STATUS_UNAVAIL;

  /*
   * 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, '.') == NULL)
    {
      char *tmp = alloca (NS_MAXDNAME);
      const char *cp = res_hostalias (&_res, name, tmp, NS_MAXDNAME);
      if (cp != NULL)
        name = cp;
    }

  int anslen = 2048;
  union
  {
    querybuf *buf;
    u_char *ptr;
  } host_buffer;
  querybuf *orig_host_buffer;
  host_buffer.buf = orig_host_buffer = (querybuf *) alloca (anslen);
  u_char *ans2p = NULL;
  int nans2p = 0;
  int resplen2 = 0;

  int olderr = errno;
  enum nss_status status;
  int n = __libc_res_nsearch (&_res, name, C_IN, T_UNSPEC,
                              host_buffer.buf->buf, anslen, &host_buffer.ptr,
                              &ans2p, &nans2p, &resplen2);
  if (n >= 0)
    {
      status = gaih_getanswer (host_buffer.buf, n, (const querybuf *) ans2p,
                               resplen2, name, pat, buffer, buflen,
                               errnop, herrnop, ttlp);
    }
  else
    {
      switch (errno)
        {
        case ESRCH:
          status = NSS_STATUS_TRYAGAIN;
          h_errno = TRY_AGAIN;
          break;
        /* System has run out of file descriptors.  */
        case EMFILE:
        case ENFILE:
          h_errno = NETDB_INTERNAL;
          /* Fall through.  */
        case ECONNREFUSED:
        case ETIMEDOUT:
          status = NSS_STATUS_UNAVAIL;
          break;
        default:
          status = NSS_STATUS_NOTFOUND;
          break;
        }

      *herrnop = h_errno;
      if (h_errno == TRY_AGAIN)
        *errnop = EAGAIN;
      else
        __set_errno (olderr);
    }

  /* Check whether ans2p was separately allocated.  */
  if (host_buffer.buf != orig_host_buffer)
    anslen = MAXPACKET;
  if (ans2p != NULL
      && (ans2p < host_buffer.ptr || ans2p >= host_buffer.ptr + anslen))
    free (ans2p);

  if (host_buffer.buf != orig_host_buffer)
    free (host_buffer.buf);

  return status;
}


extern enum nss_status _nss_dns_gethostbyaddr2_r (const void *addr,
                                                  socklen_t len, int af,
                                                  struct hostent *result,
                                                  char *buffer, size_t buflen,
                                                  int *errnop, int *h_errnop,
                                                  int32_t *ttlp);
hidden_proto (_nss_dns_gethostbyaddr2_r)

enum nss_status
_nss_dns_gethostbyaddr2_r (const void *addr, socklen_t len, int af,
                           struct hostent *result, char *buffer, size_t buflen,
                           int *errnop, int *h_errnop, int32_t *ttlp)
{
  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 };
  static const u_char v6local[] = { 0,0, 0,1 };
  const u_char *uaddr = (const u_char *)addr;
  struct host_data
  {
    char *aliases[MAX_NR_ALIASES];
    unsigned char host_addr[16];        /* IPv4 or IPv6 */
    char *h_addr_ptrs[MAX_NR_ADDRS + 1];
    char linebuffer[0];
  } *host_data = (struct host_data *) buffer;
  union
  {
    querybuf *buf;
    u_char *ptr;
  } host_buffer;
  querybuf *orig_host_buffer;
  char qbuf[MAXDNAME+1], *qp = NULL;
  size_t size;
  int n, status;
  int olderr = errno;

 uintptr_t pad = -(uintptr_t) buffer % __alignof__ (struct host_data);
 buffer += pad;
 buflen = buflen > pad ? buflen - pad : 0;

 if (__glibc_unlikely (buflen < sizeof (struct host_data)))
   {
     *errnop = ERANGE;
     *h_errnop = NETDB_INTERNAL;
     return NSS_STATUS_TRYAGAIN;
   }

 host_data = (struct host_data *) buffer;

  if (__res_maybe_init (&_res, 0) == -1)
    return NSS_STATUS_UNAVAIL;

  if (af == AF_INET6 && len == IN6ADDRSZ
      && (memcmp (uaddr, mapped, sizeof mapped) == 0
          || (memcmp (uaddr, tunnelled, sizeof tunnelled) == 0
              && memcmp (&uaddr[sizeof tunnelled], v6local, sizeof v6local))))
    {
      /* 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:
      *errnop = EAFNOSUPPORT;
      *h_errnop = NETDB_INTERNAL;
      return NSS_STATUS_UNAVAIL;
    }
  if (size > len)
    {
      *errnop = EAFNOSUPPORT;
      *h_errnop = NETDB_INTERNAL;
      return NSS_STATUS_UNAVAIL;
    }

  host_buffer.buf = orig_host_buffer = (querybuf *) alloca (1024);

  switch (af)
    {
    case AF_INET:
      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:
      /* Only lookup with the byte string format if the user wants it.  */
      if (__glibc_unlikely (_res.options & RES_USEBSTRING))
        {
          qp = stpcpy (qbuf, "\\[x");
          for (n = 0; n < IN6ADDRSZ; ++n)
            qp += sprintf (qp, "%02hhx", uaddr[n]);
          strcpy (qp, "].ip6.arpa");
          n = __libc_res_nquery (&_res, qbuf, C_IN, T_PTR,
                                 host_buffer.buf->buf, 1024, &host_buffer.ptr,
                                 NULL, NULL, NULL);
          if (n >= 0)
            goto got_it_already;
        }
      qp = qbuf;
      for (n = IN6ADDRSZ - 1; n >= 0; n--)
        {
          static const char nibblechar[16] = "0123456789abcdef";
          *qp++ = nibblechar[uaddr[n] & 0xf];
          *qp++ = '.';
          *qp++ = nibblechar[(uaddr[n] >> 4) & 0xf];
          *qp++ = '.';
        }
      strcpy(qp, "ip6.arpa");
      break;
    default:
      /* Cannot happen.  */
      break;
    }

  n = __libc_res_nquery (&_res, qbuf, C_IN, T_PTR, host_buffer.buf->buf,
                         1024, &host_buffer.ptr, NULL, NULL, NULL);
  if (n < 0 && af == AF_INET6 && (_res.options & RES_NOIP6DOTINT) == 0)
    {
      strcpy (qp, "ip6.int");
      n = __libc_res_nquery (&_res, qbuf, C_IN, T_PTR, host_buffer.buf->buf,
                             host_buffer.buf != orig_host_buffer
                             ? MAXPACKET : 1024, &host_buffer.ptr,
                             NULL, NULL, NULL);
    }
  if (n < 0)
    {
      *h_errnop = h_errno;
      __set_errno (olderr);
      if (host_buffer.buf != orig_host_buffer)
        free (host_buffer.buf);
      return errno == ECONNREFUSED ? NSS_STATUS_UNAVAIL : NSS_STATUS_NOTFOUND;
    }

 got_it_already:
  status = getanswer_r (host_buffer.buf, n, qbuf, T_PTR, result, buffer, buflen,
                        errnop, h_errnop, 0 /* XXX */, ttlp, NULL);
  if (host_buffer.buf != orig_host_buffer)
    free (host_buffer.buf);
  if (status != NSS_STATUS_SUCCESS)
    return status;

#ifdef SUNSECURITY
  This is not implemented because it is not possible to use the current
  source from bind in a multi-threaded program.
#endif

  result->h_addrtype = af;
  result->h_length = len;
  memcpy (host_data->host_addr, addr, len);
  host_data->h_addr_ptrs[0] = (char *) host_data->host_addr;
  host_data->h_addr_ptrs[1] = NULL;
#if 0
  /* XXX I think this is wrong.  Why should an IPv4 address be
     converted to IPv6 if the user explicitly asked for IPv4?  */
  if (af == AF_INET && (_res.options & RES_USE_INET6))
    {
      map_v4v6_address ((char *) host_data->host_addr,
                        (char *) host_data->host_addr);
      result->h_addrtype = AF_INET6;
      result->h_length = IN6ADDRSZ;
    }
#endif
  *h_errnop = NETDB_SUCCESS;
  return NSS_STATUS_SUCCESS;
}
hidden_def (_nss_dns_gethostbyaddr2_r)


enum nss_status
_nss_dns_gethostbyaddr_r (const void *addr, socklen_t len, int af,
                          struct hostent *result, char *buffer, size_t buflen,
                          int *errnop, int *h_errnop)
{
  return _nss_dns_gethostbyaddr2_r (addr, len, af, result, buffer, buflen,
                                    errnop, h_errnop, NULL);
}

#ifdef RESOLVSORT
static void addrsort (char **ap, int num);

static void
addrsort (char **ap, int num)
{
  int i, j;
  char **p;
  short aval[MAX_NR_ADDRS];
  int needsort = 0;

  p = ap;
  if (num > MAX_NR_ADDRS)
    num = MAX_NR_ADDRS;
  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 - 2; 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;
}
#endif

static enum nss_status
getanswer_r (const querybuf *answer, int anslen, const char *qname, int qtype,
             struct hostent *result, char *buffer, size_t buflen,
             int *errnop, int *h_errnop, int map, int32_t *ttlp, char **canonp)
{
  struct host_data
  {
    char *aliases[MAX_NR_ALIASES];
    unsigned char host_addr[16];        /* IPv4 or IPv6 */
    char *h_addr_ptrs[0];
  } *host_data;
  int linebuflen;
  const HEADER *hp;
  const u_char *end_of_message, *cp;
  int n, ancount, qdcount;
  int haveanswer, had_error;
  char *bp, **ap, **hap;
  char tbuf[MAXDNAME];
  const char *tname;
  int (*name_ok) (const char *);
  u_char packtmp[NS_MAXCDNAME];
  int have_to_map = 0;
  uintptr_t pad = -(uintptr_t) buffer % __alignof__ (struct host_data);
  buffer += pad;
  if (__glibc_unlikely (buflen < sizeof (struct host_data) + pad))
    {
      /* The buffer is too small.  */
    too_small:
      *errnop = ERANGE;
      *h_errnop = NETDB_INTERNAL;
      return NSS_STATUS_TRYAGAIN;
    }
  host_data = (struct host_data *) buffer;
  linebuflen = buflen - sizeof (struct host_data);
  if (buflen - sizeof (struct host_data) != linebuflen)
    linebuflen = INT_MAX;

  tname = qname;
  result->h_name = NULL;
  end_of_message = 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:
      *errnop = ENOENT;
      return NSS_STATUS_UNAVAIL;  /* XXX should be abort(); */
    }

  /*
   * find first satisfactory answer
   */
  hp = &answer->hdr;
  ancount = ntohs (hp->ancount);
  qdcount = ntohs (hp->qdcount);
  cp = answer->buf + HFIXEDSZ;
  if (__builtin_expect (qdcount, 1) != 1)
    {
      *h_errnop = NO_RECOVERY;
      return NSS_STATUS_UNAVAIL;
    }
  if (sizeof (struct host_data) + (ancount + 1) * sizeof (char *) >= buflen)
    goto too_small;
  bp = (char *) &host_data->h_addr_ptrs[ancount + 1];
  linebuflen -= (ancount + 1) * sizeof (char *);

  n = __ns_name_unpack (answer->buf, end_of_message, cp,
                        packtmp, sizeof packtmp);
  if (n != -1 && __ns_name_ntop (packtmp, bp, linebuflen) == -1)
    {
      if (__builtin_expect (errno, 0) == EMSGSIZE)
        goto too_small;

      n = -1;
    }

  if (n > 0 && bp[0] == '.')
    bp[0] = '\0';

  if (__builtin_expect (n < 0 || ((*name_ok) (bp) == 0 && (errno = EBADMSG)),
                        0))
    {
      *errnop = errno;
      *h_errnop = NO_RECOVERY;
      return NSS_STATUS_UNAVAIL;
    }
  cp += 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)
        {
          *h_errnop = NO_RECOVERY;
          *errnop = ENOENT;
          return NSS_STATUS_TRYAGAIN;
        }
      result->h_name = bp;
      bp += n;
      linebuflen -= n;
      if (linebuflen < 0)
        goto too_small;
      /* The qname can be abbreviated, but h_name is now absolute. */
      qname = result->h_name;
    }

  ap = host_data->aliases;
  *ap = NULL;
  result->h_aliases = host_data->aliases;
  hap = host_data->h_addr_ptrs;
  *hap = NULL;
  result->h_addr_list = host_data->h_addr_ptrs;
  haveanswer = 0;
  had_error = 0;

  while (ancount-- > 0 && cp < end_of_message && had_error == 0)
    {
      int type, class;

      n = __ns_name_unpack (answer->buf, end_of_message, cp,
                            packtmp, sizeof packtmp);
      if (n != -1 && __ns_name_ntop (packtmp, bp, linebuflen) == -1)
        {
          if (__builtin_expect (errno, 0) == EMSGSIZE)
            goto too_small;

          n = -1;
        }

      if (__glibc_unlikely (n < 0 || (*name_ok) (bp) == 0))
        {
          ++had_error;
          continue;
        }
      cp += n;                          /* name */

      if (__glibc_unlikely (cp + 10 > end_of_message))
        {
          ++had_error;
          continue;
        }

      type = __ns_get16 (cp);
      cp += INT16SZ;                    /* type */
      class = __ns_get16 (cp);
      cp += INT16SZ;                    /* class */
      int32_t ttl = __ns_get32 (cp);
      cp += INT32SZ;                    /* TTL */
      n = __ns_get16 (cp);
      cp += INT16SZ;                    /* len */
      if (__glibc_unlikely (class != C_IN))
        {
          /* XXX - debug? syslog? */
          cp += n;
          continue;                     /* XXX - had_error++ ? */
        }

      if ((qtype == T_A || qtype == T_AAAA) && type == T_CNAME)
        {
          /* A CNAME could also have a TTL entry.  */
          if (ttlp != NULL && ttl < *ttlp)
              *ttlp = ttl;

          if (ap >= &host_data->aliases[MAX_NR_ALIASES - 1])
            continue;
          n = dn_expand (answer->buf, end_of_message, cp, tbuf, sizeof tbuf);
          if (__glibc_unlikely (n < 0 || (*name_ok) (tbuf) == 0))
            {
              ++had_error;
              continue;
            }
          cp += n;
          /* Store alias.  */
          *ap++ = bp;
          n = strlen (bp) + 1;          /* For the \0.  */
          if (__builtin_expect (n, 0) >= MAXHOSTNAMELEN)
            {
              ++had_error;
              continue;
            }
          bp += n;
          linebuflen -= n;
          /* Get canonical name.  */
          n = strlen (tbuf) + 1;        /* For the \0.  */
          if (__glibc_unlikely (n > linebuflen))
            goto too_small;
          if (__builtin_expect (n, 0) >= MAXHOSTNAMELEN)
            {
              ++had_error;
              continue;
            }
          result->h_name = bp;
          bp = __mempcpy (bp, tbuf, n); /* Cannot overflow.  */
          linebuflen -= n;
          continue;
        }

      if (qtype == T_PTR && type == T_CNAME)
        {
          n = dn_expand (answer->buf, end_of_message, cp, tbuf, sizeof tbuf);
          if (__glibc_unlikely (n < 0 || res_dnok (tbuf) == 0))
            {
              ++had_error;
              continue;
            }
          cp += n;
          /* Get canonical name.  */
          n = strlen (tbuf) + 1;   /* For the \0.  */
          if (__glibc_unlikely (n > linebuflen))
            goto too_small;
          if (__builtin_expect (n, 0) >= MAXHOSTNAMELEN)
            {
              ++had_error;
              continue;
            }
          tname = bp;
          bp = __mempcpy (bp, tbuf, n); /* Cannot overflow.  */
          linebuflen -= n;
          continue;
        }
      if (__builtin_expect (type == T_SIG, 0)
          || __builtin_expect (type == T_KEY, 0)
          || __builtin_expect (type == T_NXT, 0))
        {
          /* 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 == T_A && qtype == T_AAAA && map)
        have_to_map = 1;
      else if (__glibc_unlikely (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 (__glibc_unlikely (strcasecmp (tname, bp) != 0))
            {
              syslog (LOG_NOTICE | LOG_AUTH, AskedForGot, qname, bp);
              cp += n;
              continue;                 /* XXX - had_error++ ? */
            }

          n = __ns_name_unpack (answer->buf, end_of_message, cp,
                                packtmp, sizeof packtmp);
          if (n != -1 && __ns_name_ntop (packtmp, bp, linebuflen) == -1)
            {
              if (__builtin_expect (errno, 0) == EMSGSIZE)
                goto too_small;

              n = -1;
            }

          if (__glibc_unlikely (n < 0 || res_hnok (bp) == 0))
            {
              ++had_error;
              break;
            }
#if MULTI_PTRS_ARE_ALIASES
          cp += n;
          if (haveanswer == 0)
            result->h_name = bp;
          else if (ap < &host_data->aliases[MAXALIASES-1])
            *ap++ = bp;
          else
            n = -1;
          if (n != -1)
            {
              n = strlen (bp) + 1;      /* for the \0 */
              if (__builtin_expect (n, 0) >= MAXHOSTNAMELEN)
                {
                  ++had_error;
                  break;
                }
              bp += n;
              linebuflen -= n;
            }
          break;
#else
          result->h_name = bp;
          if (have_to_map)
            {
              n = strlen (bp) + 1;      /* for the \0 */
              if (__glibc_unlikely (n >= MAXHOSTNAMELEN))
                {
                  ++had_error;
                  break;
                }
              bp += n;
              linebuflen -= n;
              if (map_v4v6_hostent (result, &bp, &linebuflen))
                goto too_small;
            }
          *h_errnop = NETDB_SUCCESS;
          return NSS_STATUS_SUCCESS;
#endif
        case T_A:
        case T_AAAA:
          if (__builtin_expect (strcasecmp (result->h_name, bp), 0) != 0)
            {
              syslog (LOG_NOTICE | LOG_AUTH, AskedForGot, result->h_name, bp);
              cp += n;
              continue;                 /* XXX - had_error++ ? */
            }
          if (n != result->h_length)
            {
              cp += n;
              continue;
            }
          if (!haveanswer)
            {
              int nn;

              /* We compose a single hostent out of the entire chain of
                 entries, so the TTL of the hostent is essentially the lowest
                 TTL in the chain.  */
              if (ttlp != NULL && ttl < *ttlp)
                *ttlp = ttl;
              if (canonp != NULL)
                *canonp = bp;
              result->h_name = bp;
              nn = strlen (bp) + 1;     /* for the \0 */
              bp += nn;
              linebuflen -= nn;
            }

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

          if (__glibc_unlikely (n > linebuflen))
            goto too_small;
          bp = __mempcpy (*hap++ = bp, cp, n);
          cp += n;
          linebuflen -= n;
          break;
        default:
          abort ();
        }
      if (had_error == 0)
        ++haveanswer;
    }

  if (haveanswer > 0)
    {
      *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 (host_data->h_addr_ptrs, haveanswer);
#endif /*RESOLVSORT*/

      if (result->h_name == NULL)
        {
          n = strlen (qname) + 1;       /* For the \0.  */
          if (n > linebuflen)
            goto too_small;
          if (n >= MAXHOSTNAMELEN)
            goto no_recovery;
          result->h_name = bp;
          bp = __mempcpy (bp, qname, n);        /* Cannot overflow.  */
          linebuflen -= n;
        }

      if (have_to_map)
        if (map_v4v6_hostent (result, &bp, &linebuflen))
          goto too_small;
      *h_errnop = NETDB_SUCCESS;
      return NSS_STATUS_SUCCESS;
    }
 no_recovery:
  *h_errnop = NO_RECOVERY;
  *errnop = ENOENT;
  /* Special case here: if the resolver sent a result but it only
     contains a CNAME while we are looking for a T_A or T_AAAA record,
     we fail with NOTFOUND instead of TRYAGAIN.  */
  return ((qtype == T_A || qtype == T_AAAA) && ap != host_data->aliases
           ? NSS_STATUS_NOTFOUND : NSS_STATUS_TRYAGAIN);
}


static enum nss_status
gaih_getanswer_slice (const querybuf *answer, int anslen, const char *qname,
                      struct gaih_addrtuple ***patp,
                      char **bufferp, size_t *buflenp,
                      int *errnop, int *h_errnop, int32_t *ttlp, int *firstp)
{
  char *buffer = *bufferp;
  size_t buflen = *buflenp;

  struct gaih_addrtuple **pat = *patp;
  const HEADER *hp = &answer->hdr;
  int ancount = ntohs (hp->ancount);
  int qdcount = ntohs (hp->qdcount);
  const u_char *cp = answer->buf + HFIXEDSZ;
  const u_char *end_of_message = answer->buf + anslen;
  if (__glibc_unlikely (qdcount != 1))
    {
      *h_errnop = NO_RECOVERY;
      return NSS_STATUS_UNAVAIL;
    }

  u_char packtmp[NS_MAXCDNAME];
  int n = __ns_name_unpack (answer->buf, end_of_message, cp,
                            packtmp, sizeof packtmp);
  /* We unpack the name to check it for validity.  But we do not need
     it later.  */
  if (n != -1 && __ns_name_ntop (packtmp, buffer, buflen) == -1)
    {
      if (__builtin_expect (errno, 0) == EMSGSIZE)
        {
        too_small:
          *errnop = ERANGE;
          *h_errnop = NETDB_INTERNAL;
          return NSS_STATUS_TRYAGAIN;
        }

      n = -1;
    }

  if (__builtin_expect (n < 0 || (res_hnok (buffer) == 0
                                  && (errno = EBADMSG)), 0))
    {
      *errnop = errno;
      *h_errnop = NO_RECOVERY;
      return NSS_STATUS_UNAVAIL;
    }
  cp += n + QFIXEDSZ;

  int haveanswer = 0;
  int had_error = 0;
  char *canon = NULL;
  char *h_name = NULL;
  int h_namelen = 0;

  if (ancount == 0)
    return NSS_STATUS_NOTFOUND;

  while (ancount-- > 0 && cp < end_of_message && had_error == 0)
    {
      n = __ns_name_unpack (answer->buf, end_of_message, cp,
                            packtmp, sizeof packtmp);
      if (n != -1 &&
          (h_namelen = __ns_name_ntop (packtmp, buffer, buflen)) == -1)
        {
          if (__builtin_expect (errno, 0) == EMSGSIZE)
            goto too_small;

          n = -1;
        }
      if (__glibc_unlikely (n < 0 || res_hnok (buffer) == 0))
        {
          ++had_error;
          continue;
        }
      if (*firstp && canon == NULL)
        {
          h_name = buffer;
          buffer += h_namelen;
          buflen -= h_namelen;
        }

      cp += n;                          /* name */

      if (__glibc_unlikely (cp + 10 > end_of_message))
        {
          ++had_error;
          continue;
        }

      int type = __ns_get16 (cp);
      cp += INT16SZ;                    /* type */
      int class = __ns_get16 (cp);
      cp += INT16SZ;                    /* class */
      int32_t ttl = __ns_get32 (cp);
      cp += INT32SZ;                    /* TTL */
      n = __ns_get16 (cp);
      cp += INT16SZ;                    /* len */

      if (class != C_IN)
        {
          cp += n;
          continue;
        }

      if (type == T_CNAME)
        {
          char tbuf[MAXDNAME];

          /* A CNAME could also have a TTL entry.  */
          if (ttlp != NULL && ttl < *ttlp)
              *ttlp = ttl;

          n = dn_expand (answer->buf, end_of_message, cp, tbuf, sizeof tbuf);
          if (__glibc_unlikely (n < 0 || res_hnok (tbuf) == 0))
            {
              ++had_error;
              continue;
            }
          cp += n;

          if (*firstp)
            {
              /* Reclaim buffer space.  */
              if (h_name + h_namelen == buffer)
                {
                  buffer = h_name;
                  buflen += h_namelen;
                }

              n = strlen (tbuf) + 1;
              if (__glibc_unlikely (n > buflen))
                goto too_small;
              if (__glibc_unlikely (n >= MAXHOSTNAMELEN))
                {
                  ++had_error;
                  continue;
                }

              canon = buffer;
              buffer = __mempcpy (buffer, tbuf, n);
              buflen -= n;
              h_namelen = 0;
            }
          continue;
        }
#if 1
      // We should not see any types other than those explicitly listed
      // below.  Some types sent by server seem missing, though.  Just
      // collect the data for now.
      if (__glibc_unlikely (type != T_A && type != T_AAAA))
#else
      if (__builtin_expect (type == T_SIG, 0)
          || __builtin_expect (type == T_KEY, 0)
          || __builtin_expect (type == T_NXT, 0)
          || __builtin_expect (type == T_PTR, 0)
          || __builtin_expect (type == T_DNAME, 0))
#endif
        {
          /* We don't support DNSSEC yet.  For now, ignore the record
             and send a low priority message to syslog.

             We also don't expect T_PTR or T_DNAME messages.  */
          syslog (LOG_DEBUG | LOG_AUTH,
                  "getaddrinfo*.gaih_getanswer: got type \"%s\"",
                  p_type (type));
          cp += n;
          continue;
        }
      if (type != T_A && type != T_AAAA)
        abort ();

      if (*pat == NULL)
        {
          uintptr_t pad = (-(uintptr_t) buffer
                           % __alignof__ (struct gaih_addrtuple));
          buffer += pad;
          buflen = buflen > pad ? buflen - pad : 0;

          if (__builtin_expect (buflen < sizeof (struct gaih_addrtuple),
                                0))
            goto too_small;

          *pat = (struct gaih_addrtuple *) buffer;
          buffer += sizeof (struct gaih_addrtuple);
          buflen -= sizeof (struct gaih_addrtuple);
        }

      (*pat)->name = NULL;
      (*pat)->next = NULL;

      if (*firstp)
        {
          /* We compose a single hostent out of the entire chain of
             entries, so the TTL of the hostent is essentially the lowest
             TTL in the chain.  */
          if (ttlp != NULL && ttl < *ttlp)
            *ttlp = ttl;

          (*pat)->name = canon ?: h_name;

          *firstp = 0;
        }

      (*pat)->family = type == T_A ? AF_INET : AF_INET6;
      if (__builtin_expect ((type == T_A && n != INADDRSZ)
                            || (type == T_AAAA && n != IN6ADDRSZ), 0))
        {
          ++had_error;
          continue;
        }
      memcpy ((*pat)->addr, cp, n);
      cp += n;
      (*pat)->scopeid = 0;

      pat = &((*pat)->next);

      haveanswer = 1;
    }

  if (haveanswer)
    {
      *patp = pat;
      *bufferp = buffer;
      *buflenp = buflen;

      *h_errnop = NETDB_SUCCESS;
      return NSS_STATUS_SUCCESS;
    }

  /* Special case here: if the resolver sent a result but it only
     contains a CNAME while we are looking for a T_A or T_AAAA record,
     we fail with NOTFOUND instead of TRYAGAIN.  */
  return canon == NULL ? NSS_STATUS_TRYAGAIN : NSS_STATUS_NOTFOUND;
}


static enum nss_status
gaih_getanswer (const querybuf *answer1, int anslen1, const querybuf *answer2,
                int anslen2, const char *qname,
                struct gaih_addrtuple **pat, char *buffer, size_t buflen,
                int *errnop, int *h_errnop, int32_t *ttlp)
{
  int first = 1;

  enum nss_status status = NSS_STATUS_NOTFOUND;

  if (anslen1 > 0)
    status = gaih_getanswer_slice(answer1, anslen1, qname,
                                  &pat, &buffer, &buflen,
                                  errnop, h_errnop, ttlp,
                                  &first);
  if ((status == NSS_STATUS_SUCCESS || status == NSS_STATUS_NOTFOUND
       || (status == NSS_STATUS_TRYAGAIN
           /* We want to look at the second answer in case of an
              NSS_STATUS_TRYAGAIN only if the error is non-recoverable, i.e.
              *h_errnop is NO_RECOVERY. If not, and if the failure was due to
              an insufficient buffer (ERANGE), then we need to drop the results
              and pass on the NSS_STATUS_TRYAGAIN to the caller so that it can
              repeat the query with a larger buffer.  */
           && (*errnop != ERANGE || *h_errnop == NO_RECOVERY)))
      && answer2 != NULL && anslen2 > 0)
    {
      enum nss_status status2 = gaih_getanswer_slice(answer2, anslen2, qname,
                                                     &pat, &buffer, &buflen,
                                                     errnop, h_errnop, ttlp,
                                                     &first);
      if (status != NSS_STATUS_SUCCESS && status2 != NSS_STATUS_NOTFOUND)
        status = status2;
    }

  return status;
}