path: root/sysdeps/posix/getaddrinfo.c

/* The Inner Net License, Version 2.00

  The author(s) grant permission for redistribution and use in source and
binary forms, with or without modification, of the software and documentation
provided that the following conditions are met:

0. If you receive a version of the software that is specifically labelled
   as not being for redistribution (check the version message and/or README),
   you are not permitted to redistribute that version of the software in any
   way or form.
1. All terms of the all other applicable copyrights and licenses must be
   followed.
2. Redistributions of source code must retain the authors' copyright
   notice(s), this list of conditions, and the following disclaimer.
3. Redistributions in binary form must reproduce the authors' copyright
   notice(s), this list of conditions, and the following disclaimer in the
   documentation and/or other materials provided with the distribution.
4. [The copyright holder has authorized the removal of this clause.]
5. Neither the name(s) of the author(s) 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 ITS AUTHORS 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 AUTHORS 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.

  If these license terms cause you a real problem, contact the author.  */

/* This software is Copyright 1996 by Craig Metz, All Rights Reserved.  */

#include <assert.h>
#include <errno.h>
#include <ifaddrs.h>
#include <netdb.h>
#include <resolv.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <sys/un.h>
#include <sys/utsname.h>
#include <net/if.h>
#include <nsswitch.h>
#include <not-cancel.h>

extern int __idna_to_ascii_lz (const char *input, char **output, int flags);
#define IDNA_SUCCESS 0

#define GAIH_OKIFUNSPEC 0x0100
#define GAIH_EAI        ~(GAIH_OKIFUNSPEC)

#ifndef UNIX_PATH_MAX
#define UNIX_PATH_MAX  108
#endif

struct gaih_service
  {
    const char *name;
    int num;
  };

struct gaih_servtuple
  {
    struct gaih_servtuple *next;
    int socktype;
    int protocol;
    int port;
  };

static const struct gaih_servtuple nullserv;

struct gaih_addrtuple
  {
    struct gaih_addrtuple *next;
    int family;
    char addr[16];
    uint32_t scopeid;
  };

struct gaih_typeproto
  {
    int socktype;
    int protocol;
    char name[4];
    int protoflag;
  };

/* Values for `protoflag'.  */
#define GAI_PROTO_NOSERVICE	1
#define GAI_PROTO_PROTOANY	2

static const struct gaih_typeproto gaih_inet_typeproto[] =
{
  { 0, 0, "", 0 },
  { SOCK_STREAM, IPPROTO_TCP, "tcp", 0 },
  { SOCK_DGRAM, IPPROTO_UDP, "udp", 0 },
  { SOCK_RAW, 0, "raw", GAI_PROTO_PROTOANY|GAI_PROTO_NOSERVICE },
  { 0, 0, "", 0 }
};

struct gaih
  {
    int family;
    int (*gaih)(const char *name, const struct gaih_service *service,
		const struct addrinfo *req, struct addrinfo **pai);
  };

static const struct addrinfo default_hints =
  {
    .ai_flags = AI_DEFAULT,
    .ai_family = PF_UNSPEC,
    .ai_socktype = 0,
    .ai_protocol = 0,
    .ai_addrlen = 0,
    .ai_addr = NULL,
    .ai_canonname = NULL,
    .ai_next = NULL
  };


#if 0
/* Using Unix sockets this way is a security risk.  */
static int
gaih_local (const char *name, const struct gaih_service *service,
	    const struct addrinfo *req, struct addrinfo **pai)
{
  struct utsname utsname;

  if ((name != NULL) && (req->ai_flags & AI_NUMERICHOST))
    return GAIH_OKIFUNSPEC | -EAI_NONAME;

  if ((name != NULL) || (req->ai_flags & AI_CANONNAME))
    if (uname (&utsname) < 0)
      return -EAI_SYSTEM;

  if (name != NULL)
    {
      if (strcmp(name, "localhost") &&
	  strcmp(name, "local") &&
	  strcmp(name, "unix") &&
	  strcmp(name, utsname.nodename))
	return GAIH_OKIFUNSPEC | -EAI_NONAME;
    }

  if (req->ai_protocol || req->ai_socktype)
    {
      const struct gaih_typeproto *tp = gaih_inet_typeproto + 1;

      while (tp->name[0]
	     && ((tp->protoflag & GAI_PROTO_NOSERVICE) != 0
		 || (req->ai_socktype != 0 && req->ai_socktype != tp->socktype)
		 || (req->ai_protocol != 0
		     && !(tp->protoflag & GAI_PROTO_PROTOANY)
		     && req->ai_protocol != tp->protocol)))
	++tp;

      if (! tp->name[0])
	{
	  if (req->ai_socktype)
	    return (GAIH_OKIFUNSPEC | -EAI_SOCKTYPE);
	  else
	    return (GAIH_OKIFUNSPEC | -EAI_SERVICE);
	}
    }

  *pai = malloc (sizeof (struct addrinfo) + sizeof (struct sockaddr_un)
		 + ((req->ai_flags & AI_CANONNAME)
		    ? (strlen(utsname.nodename) + 1): 0));
  if (*pai == NULL)
    return -EAI_MEMORY;

  (*pai)->ai_next = NULL;
  (*pai)->ai_flags = req->ai_flags;
  (*pai)->ai_family = AF_LOCAL;
  (*pai)->ai_socktype = req->ai_socktype ? req->ai_socktype : SOCK_STREAM;
  (*pai)->ai_protocol = req->ai_protocol;
  (*pai)->ai_addrlen = sizeof (struct sockaddr_un);
  (*pai)->ai_addr = (void *) (*pai) + sizeof (struct addrinfo);

#if SALEN
  ((struct sockaddr_un *) (*pai)->ai_addr)->sun_len =
    sizeof (struct sockaddr_un);
#endif /* SALEN */

  ((struct sockaddr_un *)(*pai)->ai_addr)->sun_family = AF_LOCAL;
  memset(((struct sockaddr_un *)(*pai)->ai_addr)->sun_path, 0, UNIX_PATH_MAX);

  if (service)
    {
      struct sockaddr_un *sunp = (struct sockaddr_un *) (*pai)->ai_addr;

      if (strchr (service->name, '/') != NULL)
	{
	  if (strlen (service->name) >= sizeof (sunp->sun_path))
	    return GAIH_OKIFUNSPEC | -EAI_SERVICE;

	  strcpy (sunp->sun_path, service->name);
	}
      else
	{
	  if (strlen (P_tmpdir "/") + 1 + strlen (service->name) >=
	      sizeof (sunp->sun_path))
	    return GAIH_OKIFUNSPEC | -EAI_SERVICE;

	  __stpcpy (__stpcpy (sunp->sun_path, P_tmpdir "/"), service->name);
	}
    }
  else
    {
      /* This is a dangerous use of the interface since there is a time
	 window between the test for the file and the actual creation
	 (done by the caller) in which a file with the same name could
	 be created.  */
      char *buf = ((struct sockaddr_un *) (*pai)->ai_addr)->sun_path;

      if (__builtin_expect (__path_search (buf, L_tmpnam, NULL, NULL, 0),
			    0) != 0
	  || __builtin_expect (__gen_tempname (buf, __GT_NOCREATE), 0) != 0)
	return -EAI_SYSTEM;
    }

  if (req->ai_flags & AI_CANONNAME)
    (*pai)->ai_canonname = strcpy ((char *) *pai + sizeof (struct addrinfo)
				   + sizeof (struct sockaddr_un),
				   utsname.nodename);
  else
    (*pai)->ai_canonname = NULL;
  return 0;
}
#endif	/* 0 */

static int
gaih_inet_serv (const char *servicename, const struct gaih_typeproto *tp,
	       const struct addrinfo *req, struct gaih_servtuple *st)
{
  struct servent *s;
  size_t tmpbuflen = 1024;
  struct servent ts;
  char *tmpbuf;
  int r;

  do
    {
      tmpbuf = __alloca (tmpbuflen);

      r = __getservbyname_r (servicename, tp->name, &ts, tmpbuf, tmpbuflen,
			     &s);
      if (r != 0 || s == NULL)
	{
	  if (r == ERANGE)
	    tmpbuflen *= 2;
	  else
	    return GAIH_OKIFUNSPEC | -EAI_SERVICE;
	}
    }
  while (r);

  st->next = NULL;
  st->socktype = tp->socktype;
  st->protocol = ((tp->protoflag & GAI_PROTO_PROTOANY)
		  ? req->ai_protocol : tp->protocol);
  st->port = s->s_port;

  return 0;
}

#define gethosts(_family, _type) \
 {									      \
  int i, herrno;							      \
  size_t tmpbuflen;							      \
  struct hostent th;							      \
  char *tmpbuf = NULL;							      \
  tmpbuflen = 512;							      \
  no_data = 0;								      \
  do {									      \
    tmpbuf = extend_alloca (tmpbuf, tmpbuflen, 2 * tmpbuflen);		      \
    rc = __gethostbyname2_r (name, _family, &th, tmpbuf,		      \
         tmpbuflen, &h, &herrno);					      \
  } while (rc == ERANGE && herrno == NETDB_INTERNAL);			      \
  if (rc != 0)								      \
    {									      \
      if (herrno == NETDB_INTERNAL)					      \
	{								      \
	  __set_h_errno (herrno);					      \
	  return -EAI_SYSTEM;						      \
	}								      \
      if (herrno == TRY_AGAIN)						      \
	no_data = EAI_AGAIN;						      \
      else								      \
	no_data = herrno == NO_DATA;					      \
    }									      \
  else if (h != NULL)							      \
    {									      \
      for (i = 0; h->h_addr_list[i]; i++)				      \
	{								      \
	  if (*pat == NULL) {						      \
	    *pat = __alloca (sizeof (struct gaih_addrtuple));		      \
	    (*pat)->scopeid = 0;					      \
	  }								      \
	  (*pat)->next = NULL;						      \
	  (*pat)->family = _family;					      \
	  memcpy ((*pat)->addr, h->h_addr_list[i],			      \
		 sizeof(_type));					      \
	  pat = &((*pat)->next);					      \
	}								      \
      if (_family == AF_INET6)						      \
	got_ipv6 = true;						      \
    }									      \
  else if (_family == AF_INET6 && (req->ai_flags & AI_V4MAPPED))	      \
    {									      \
      /* We have to add V4 mapped addresses.  Maybe we discard them	      \
         later again but we get them anyhow for now.  */		      \
      while ((rc = __gethostbyname2_r (name, AF_INET6, &th, tmpbuf,	      \
				       tmpbuflen, &h, &herrno)) == ERANGE     \
	     && herrno == NETDB_INTERNAL)				      \
	tmpbuf = extend_alloca (tmpbuf, tmpbuflen, 2 * tmpbuflen);	      \
									      \
      if (rc != 0)							      \
	{								      \
	  if (herrno == NETDB_INTERNAL)					      \
	    {								      \
	      __set_h_errno (herrno);					      \
	      return -EAI_SYSTEM;					      \
	    }								      \
	  if (herrno == TRY_AGAIN)					      \
	    no_data = EAI_AGAIN;					      \
	  else								      \
	    no_data = herrno == NO_DATA;				      \
	}								      \
      else if (h != NULL)						      \
	{								      \
	  for (i = 0; h->h_addr_list[i]; ++i)				      \
	    {								      \
	      if (*pat == NULL)						      \
		{							      \
		  *pat = __alloca (sizeof (struct gaih_addrtuple));	      \
		  (*pat)->scopeid = 0;					      \
		}							      \
	      uint32_t *addr = (uint32_t *) (*pat)->addr;		      \
	      (*pat)->next = NULL;					      \
	      (*pat)->family = _family;					      \
	      addr[3] = *(uint32_t *) h->h_addr_list[i];		      \
	      addr[2] = htonl (0xffff);					      \
	      addr[1] = 0;						      \
	      addr[0] = 0;						      \
	      pat = &((*pat)->next);					      \
	    }								      \
	}								      \
    }									      \
 }


#define gethosts2(_family, _type) \
 {									      \
  int i, herrno;							      \
  size_t tmpbuflen;							      \
  struct hostent th;							      \
  char *tmpbuf = NULL;							      \
  tmpbuflen = 512;							      \
  no_data = 0;								      \
  do {									      \
    tmpbuf = extend_alloca (tmpbuf, tmpbuflen, 2 * tmpbuflen);		      \
    rc = 0;								      \
    status = DL_CALL_FCT (fct, (name, _family, &th, tmpbuf,		      \
           tmpbuflen, &rc, &herrno));					      \
  } while (rc == ERANGE && herrno == NETDB_INTERNAL);			      \
  if (status == NSS_STATUS_SUCCESS && rc == 0)				      \
    h = &th;								      \
  else									      \
    h = NULL;								      \
  if (rc != 0)								      \
    {									      \
      if (herrno == NETDB_INTERNAL)					      \
	{								      \
	  __set_h_errno (herrno);					      \
	  return -EAI_SYSTEM;						      \
	}								      \
      if (herrno == TRY_AGAIN)						      \
	no_data = EAI_AGAIN;						      \
      else								      \
	no_data = herrno == NO_DATA;					      \
    }									      \
  else if (h != NULL)							      \
    {									      \
      for (i = 0; h->h_addr_list[i]; i++)				      \
	{								      \
	  if (*pat == NULL) {						      \
	    *pat = __alloca (sizeof (struct gaih_addrtuple));		      \
	    (*pat)->scopeid = 0;					      \
	  }								      \
	  (*pat)->next = NULL;						      \
	  (*pat)->family = _family;					      \
	  memcpy ((*pat)->addr, h->h_addr_list[i],			      \
		 sizeof(_type));					      \
	  pat = &((*pat)->next);					      \
	}								      \
    }									      \
 }

typedef enum nss_status (*nss_gethostbyname2_r)
  (const char *name, int af, struct hostent *host,
   char *buffer, size_t buflen, int *errnop,
   int *h_errnop);
extern service_user *__nss_hosts_database attribute_hidden;

static int
gaih_inet (const char *name, const struct gaih_service *service,
	   const struct addrinfo *req, struct addrinfo **pai)
{
  const struct gaih_typeproto *tp = gaih_inet_typeproto;
  struct gaih_servtuple *st = (struct gaih_servtuple *) &nullserv;
  struct gaih_addrtuple *at = NULL;
  int rc;
  bool got_ipv6 = false;

  if (req->ai_protocol || req->ai_socktype)
    {
      ++tp;

      while (tp->name[0]
	     && ((req->ai_socktype != 0 && req->ai_socktype != tp->socktype)
		 || (req->ai_protocol != 0
		     && !(tp->protoflag & GAI_PROTO_PROTOANY)
		     && req->ai_protocol != tp->protocol)))
	++tp;

      if (! tp->name[0])
	{
	  if (req->ai_socktype)
	    return (GAIH_OKIFUNSPEC | -EAI_SOCKTYPE);
	  else
	    return (GAIH_OKIFUNSPEC | -EAI_SERVICE);
	}
    }

  if (service != NULL)
    {
      if ((tp->protoflag & GAI_PROTO_NOSERVICE) != 0)
	return (GAIH_OKIFUNSPEC | -EAI_SERVICE);

      if (service->num < 0)
	{
	  if (tp->name[0])
	    {
	      st = (struct gaih_servtuple *)
		__alloca (sizeof (struct gaih_servtuple));

	      if ((rc = gaih_inet_serv (service->name, tp, req, st)))
		return rc;
	    }
	  else
	    {
	      struct gaih_servtuple **pst = &st;
	      for (tp++; tp->name[0]; tp++)
		{
		  struct gaih_servtuple *newp;

		  if ((tp->protoflag & GAI_PROTO_NOSERVICE) != 0)
		    continue;

		  if (req->ai_socktype != 0
		      && req->ai_socktype != tp->socktype)
		    continue;
		  if (req->ai_protocol != 0
		      && !(tp->protoflag & GAI_PROTO_PROTOANY)
		      && req->ai_protocol != tp->protocol)
		    continue;

		  newp = (struct gaih_servtuple *)
		    __alloca (sizeof (struct gaih_servtuple));

		  if ((rc = gaih_inet_serv (service->name, tp, req, newp)))
		    {
		      if (rc & GAIH_OKIFUNSPEC)
			continue;
		      return rc;
		    }

		  *pst = newp;
		  pst = &(newp->next);
		}
	      if (st == (struct gaih_servtuple *) &nullserv)
		return (GAIH_OKIFUNSPEC | -EAI_SERVICE);
	    }
	}
      else
	{
	  st = __alloca (sizeof (struct gaih_servtuple));
	  st->next = NULL;
	  st->socktype = tp->socktype;
	  st->protocol = ((tp->protoflag & GAI_PROTO_PROTOANY)
			  ? req->ai_protocol : tp->protocol);
	  st->port = htons (service->num);
	}
    }
  else if (req->ai_socktype || req->ai_protocol)
    {
      st = __alloca (sizeof (struct gaih_servtuple));
      st->next = NULL;
      st->socktype = tp->socktype;
      st->protocol = ((tp->protoflag & GAI_PROTO_PROTOANY)
		      ? req->ai_protocol : tp->protocol);
      st->port = 0;
    }
  else
    {
      /* Neither socket type nor protocol is set.  Return all socket types
	 we know about.  */
      struct gaih_servtuple **lastp = &st;
      for (++tp; tp->name[0]; ++tp)
	{
	  struct gaih_servtuple *newp;

	  newp = __alloca (sizeof (struct gaih_servtuple));
	  newp->next = NULL;
	  newp->socktype = tp->socktype;
	  newp->protocol = tp->protocol;
	  newp->port = 0;

	  *lastp = newp;
	  lastp = &newp->next;
	}
    }

  if (name != NULL)
    {
      at = __alloca (sizeof (struct gaih_addrtuple));

      at->family = AF_UNSPEC;
      at->scopeid = 0;
      at->next = NULL;

#ifdef HAVE_LIBIDN
      if (req->ai_flags & AI_IDN)
	{
	  char *p = NULL;
	  rc = __idna_to_ascii_lz (name, &p, 0);
	  if (rc != IDNA_SUCCESS)
	    return -EAI_IDN_ENCODE;
	  name = strdupa (p);
	  free (p);
	}
#endif

      if (inet_pton (AF_INET, name, at->addr) > 0)
	{
	  if (req->ai_family == AF_UNSPEC || req->ai_family == AF_INET)
	    at->family = AF_INET;
	  else if (req->ai_flags & AI_V4MAPPED)
	    {
	      ((uint32_t *) at->addr)[3] = *(uint32_t *) at->addr;
	      ((uint32_t *) at->addr)[2] = htonl (0xffff);
	      ((uint32_t *) at->addr)[1] = 0;
	      ((uint32_t *) at->addr)[0] = 0;
	    }
	  else
	    return -EAI_ADDRFAMILY;
	}

      if (at->family == AF_UNSPEC)
	{
	  char *namebuf = strdupa (name);
	  char *scope_delim;

	  scope_delim = strchr (namebuf, SCOPE_DELIMITER);
	  if (scope_delim != NULL)
	    *scope_delim = '\0';

	  if (inet_pton (AF_INET6, namebuf, at->addr) > 0)
	    {
	      if (req->ai_family == AF_UNSPEC || req->ai_family == AF_INET6)
		at->family = AF_INET6;
	      else if (IN6_IS_ADDR_V4MAPPED (at->addr))
		*(uint32_t *) at->addr = ((uint32_t *) at->addr)[3];
	      else
		return -EAI_ADDRFAMILY;

	      if (scope_delim != NULL)
		{
		  int try_numericscope = 0;
		  if (IN6_IS_ADDR_LINKLOCAL (at->addr)
		      || IN6_IS_ADDR_MC_LINKLOCAL (at->addr))
		    {
		      at->scopeid = if_nametoindex (scope_delim + 1);
		      if (at->scopeid == 0)
			try_numericscope = 1;
		    }
		  else
		    try_numericscope = 1;

		  if (try_numericscope != 0)
		    {
		      char *end;
		      assert (sizeof (uint32_t) <= sizeof (unsigned long));
		      at->scopeid = (uint32_t) strtoul (scope_delim + 1, &end,
							10);
		      if (*end != '\0')
			return GAIH_OKIFUNSPEC | -EAI_NONAME;
		    }
		}
	    }
	}

      if (at->family == AF_UNSPEC && (req->ai_flags & AI_NUMERICHOST) == 0)
	{
	  struct hostent *h;
	  struct gaih_addrtuple **pat = &at;
	  int no_data = 0;
	  int no_inet6_data = 0;
	  /* If we are looking for both IPv4 and IPv6 address we don't
	     want the lookup functions to automatically promote IPv4
	     addresses to IPv6 addresses.  Currently this is decided
	     by setting the RES_USE_INET6 bit in _res.options.  */
	  if (req->ai_family == AF_UNSPEC)
	    {
	      service_user *nip = NULL;
	      enum nss_status inet6_status, status = NSS_STATUS_UNAVAIL;
	      int no_more;
	      nss_gethostbyname2_r fct;
	      int old_res_options;

	      if (__nss_hosts_database != NULL)
		{
		  no_more = 0;
		  nip = __nss_hosts_database;
		}
	      else
		no_more = __nss_database_lookup ("hosts", NULL,
						 "dns [!UNAVAIL=return] files", &nip);

	      if ((_res.options & RES_INIT) == 0 && __res_ninit(&_res) == -1)
		no_more = 1;
	      old_res_options = _res.options;
	      _res.options &= ~RES_USE_INET6;

	      while (!no_more)
		{
		  fct = __nss_lookup_function (nip, "gethostbyname2_r");

		  if (fct != NULL)
		    {
		      gethosts2 (AF_INET6, struct in6_addr);
		      no_inet6_data = no_data;
		      inet6_status = status;
		      gethosts2 (AF_INET, struct in_addr);

		      /* If we found one address for AF_INET or AF_INET6,
			 don't continue the search.  */
		      if (inet6_status == NSS_STATUS_SUCCESS ||
			  status == NSS_STATUS_SUCCESS)
			break;

		      /* We can have different states for AF_INET
			 and AF_INET6. Try to find a usefull one for
			 both.  */
		      if (inet6_status == NSS_STATUS_TRYAGAIN)
			status = NSS_STATUS_TRYAGAIN;
		      else if (status == NSS_STATUS_UNAVAIL &&
			       inet6_status != NSS_STATUS_UNAVAIL)
			status = inet6_status;
		    }

		  if (nss_next_action (nip, status) == NSS_ACTION_RETURN)
		    break;

		  if (nip->next == NULL)
		    no_more = -1;
		  else
		    nip = nip->next;
		}

	      _res.options = old_res_options;
	    }
	  else if (req->ai_family == AF_INET6)
	    {
	      gethosts (AF_INET6, struct in6_addr);
	      no_inet6_data = no_data;
	    }
	  else if (req->ai_family == AF_INET)
	    {
	      gethosts (AF_INET, struct in_addr);
	      no_inet6_data = no_data;
	    }

	  if (no_data != 0 && no_inet6_data != 0)
	    {
	      /* If both requests timed out report this.  */
	      if (no_data == EAI_AGAIN && no_inet6_data == EAI_AGAIN)
		return -EAI_AGAIN;

	      /* We made requests but they turned out no data.  The name
		 is known, though.  */
	      return (GAIH_OKIFUNSPEC | -EAI_NODATA);
	    }
	}

      if (at->family == AF_UNSPEC)
	return (GAIH_OKIFUNSPEC | -EAI_NONAME);
    }
  else
    {
      struct gaih_addrtuple *atr;
      atr = at = __alloca (sizeof (struct gaih_addrtuple));
      memset (at, '\0', sizeof (struct gaih_addrtuple));

      if (req->ai_family == 0)
	{
	  at->next = __alloca (sizeof (struct gaih_addrtuple));
	  memset (at->next, '\0', sizeof (struct gaih_addrtuple));
	}

      if (req->ai_family == 0 || req->ai_family == AF_INET6)
	{
	  at->family = AF_INET6;
	  if ((req->ai_flags & AI_PASSIVE) == 0)
	    memcpy (at->addr, &in6addr_loopback, sizeof (struct in6_addr));
	  atr = at->next;
	}

      if (req->ai_family == 0 || req->ai_family == AF_INET)
	{
	  atr->family = AF_INET;
	  if ((req->ai_flags & AI_PASSIVE) == 0)
	    *(uint32_t *) atr->addr = htonl (INADDR_LOOPBACK);
	}
    }

  if (pai == NULL)
    return 0;

  {
    const char *c = NULL;
    struct gaih_servtuple *st2;
    struct gaih_addrtuple *at2 = at;
    size_t socklen, namelen;
    sa_family_t family;

    /*
      buffer is the size of an unformatted IPv6 address in printable format.
     */
    while (at2 != NULL)
      {
	if (req->ai_flags & AI_CANONNAME)
	  {
	    struct hostent *h = NULL;

	    int herrno;
	    struct hostent th;
	    size_t tmpbuflen = 512;
	    char *tmpbuf = NULL;

	    do
	      {
		tmpbuf = extend_alloca (tmpbuf, tmpbuflen, tmpbuflen * 2);
		rc = __gethostbyaddr_r (at2->addr,
					((at2->family == AF_INET6)
					 ? sizeof(struct in6_addr)
					 : sizeof(struct in_addr)),
					at2->family, &th, tmpbuf, tmpbuflen,
					&h, &herrno);

	      }
	    while (rc == ERANGE && herrno == NETDB_INTERNAL);

	    if (rc != 0 && herrno == NETDB_INTERNAL)
	      {
		__set_h_errno (herrno);
		return -EAI_SYSTEM;
	      }

	    if (h != NULL)
	      c = h->h_name;
	    else
	      {
		/* We have to try to get the canonical in some other
		   way.  If we are looking for either AF_INET or
		   AF_INET6 try the other line.  */
		if (req->ai_family == AF_UNSPEC)
		  {
		    struct addrinfo *p = NULL;
		    struct addrinfo **end = &p;
		    struct addrinfo localreq = *req;
		    struct addrinfo *runp;

		    localreq.ai_family = AF_INET + AF_INET6 - at2->family;
		    (void) gaih_inet (name, service, &localreq, end);

		    runp = p;
		    while (runp != NULL)
		      {
			if (p->ai_canonname != name)
			  {
			    c = strdupa (p->ai_canonname);
			    break;
			  }
			runp = runp->ai_next;
		      }

		    freeaddrinfo (p);
		  }

		/* If this code is used the missing canonical name is
		   substituted with the name passed in by the user.  */
		if (c == NULL)
		  c = name;
	      }

	    if (c == NULL)
	      return GAIH_OKIFUNSPEC | -EAI_NONAME;

	    namelen = strlen (c) + 1;
	  }
	else
	  namelen = 0;

	if (at2->family == AF_INET6)
	  {
	    family = AF_INET6;
	    socklen = sizeof (struct sockaddr_in6);

	    /* If we looked up IPv4 mapped address discard them here if
	       the caller isn't interested in all address and we have
	       found at least one IPv6 address.  */
	    if (! got_ipv6
		&& (req->ai_flags & (AI_V4MAPPED|AI_ALL)) == AI_V4MAPPED
		&& IN6_IS_ADDR_V4MAPPED (at2->addr))
	      goto ignore;
	  }
	else
	  {
	    family = AF_INET;
	    socklen = sizeof (struct sockaddr_in);
	  }

	for (st2 = st; st2 != NULL; st2 = st2->next)
	  {
	    *pai = malloc (sizeof (struct addrinfo) + socklen + namelen);
	    if (*pai == NULL)
	      return -EAI_MEMORY;

	    (*pai)->ai_flags = req->ai_flags;
	    (*pai)->ai_family = family;
	    (*pai)->ai_socktype = st2->socktype;
	    (*pai)->ai_protocol = st2->protocol;
	    (*pai)->ai_addrlen = socklen;
	    (*pai)->ai_addr = (void *) (*pai) + sizeof (struct addrinfo);
#if SALEN
	    (*pai)->ai_addr->sa_len = socklen;
#endif /* SALEN */
	    (*pai)->ai_addr->sa_family = family;

	    if (family == AF_INET6)
	      {
		struct sockaddr_in6 *sin6p =
		  (struct sockaddr_in6 *) (*pai)->ai_addr;

		sin6p->sin6_flowinfo = 0;
		memcpy (&sin6p->sin6_addr,
			at2->addr, sizeof (struct in6_addr));
		sin6p->sin6_port = st2->port;
		sin6p->sin6_scope_id = at2->scopeid;
	      }
	    else
	      {
		struct sockaddr_in *sinp =
		  (struct sockaddr_in *) (*pai)->ai_addr;
		memcpy (&sinp->sin_addr,
			at2->addr, sizeof (struct in_addr));
		sinp->sin_port = st2->port;
		memset (sinp->sin_zero, '\0', sizeof (sinp->sin_zero));
	      }

	    if (c)
	      {
		(*pai)->ai_canonname = ((void *) (*pai) +
					sizeof (struct addrinfo) + socklen);
		strcpy ((*pai)->ai_canonname, c);
	      }
	    else
	      (*pai)->ai_canonname = NULL;

	    (*pai)->ai_next = NULL;
	    pai = &((*pai)->ai_next);
	  }

      ignore:
	at2 = at2->next;
      }
  }
  return 0;
}

static struct gaih gaih[] =
  {
    { PF_INET6, gaih_inet },
    { PF_INET, gaih_inet },
#if 0
    { PF_LOCAL, gaih_local },
#endif
    { PF_UNSPEC, NULL }
  };

struct sort_result
{
  struct addrinfo *dest_addr;
  struct sockaddr_storage source_addr;
  bool got_source_addr;
};


static int
get_scope (const struct sockaddr_storage *ss)
{
  int scope;
  if (ss->ss_family == PF_INET6)
    {
      const struct sockaddr_in6 *in6 = (const struct sockaddr_in6 *) ss;

      if (! IN6_IS_ADDR_MULTICAST (&in6->sin6_addr))
	{
	  if (IN6_IS_ADDR_LINKLOCAL (&in6->sin6_addr))
	    scope = 2;
	  else if (IN6_IS_ADDR_SITELOCAL (&in6->sin6_addr))
	    scope = 5;
	  else
	    /* XXX Is this the correct default behavior?  */
	    scope = 14;
	}
      else
	scope = in6->sin6_addr.s6_addr[1] & 0xf;
    }
  else if (ss->ss_family == PF_INET)
    {
      const struct sockaddr_in *in = (const struct sockaddr_in *) ss;
      const uint8_t *addr = (const uint8_t *) &in->sin_addr;

      /* RFC 3484 specifies how to map IPv6 addresses to scopes.
	 169.254/16 and 127/8 are link-local.  */
      if ((addr[0] == 169 && addr[1] == 254) || addr[0] == 127)
	scope = 2;
      else if (addr[0] == 10 || (addr[0] == 172 && addr[1] == 16)
	       || (addr[0] == 192 && addr[1] == 168))
	scope = 5;
      else
	scope = 14;
    }
  else
    /* XXX What is a good default?  */
    scope = 15;

  return scope;
}


/* XXX The system administrator should be able to install other
   tables.  We need to make this configurable.  The problem is that
   the kernel is also involved since it needs the same table.  */
static const struct prefixlist
{
  struct in6_addr prefix;
  unsigned int bits;
  int val;
} default_labels[] =
  {
    /* See RFC 3484 for the details.  */
    { { .in6_u = { .u6_addr16 = { 0x0000, 0x0000, 0x0000, 0x0000,
				  0x0000, 0x0000, 0x0000, 0x0001 } } },
      128, 0 },
    { { .in6_u = { .u6_addr16 = { 0x2002, 0x0000, 0x0000, 0x0000,
				  0x0000, 0x0000, 0x0000, 0x0000 } } },
      16, 2 },
    { { .in6_u = { .u6_addr16 = { 0x0000, 0x0000, 0x0000, 0x0000,
				  0x0000, 0x0000, 0x0000, 0x0000 } } },
      96, 3 },
    { { .in6_u = { .u6_addr16 = { 0x0000, 0x0000, 0x0000, 0x0000,
				  0x0000, 0xffff, 0x0000, 0x0000 } } },
      96, 4 },
    { { .in6_u = { .u6_addr16 = { 0x0000, 0x0000, 0x0000, 0x0000,
				  0x0000, 0x0000, 0x0000, 0x0000 } } },
      0, 1 }
  };


static const struct prefixlist default_precedence[] =
  {
    /* See RFC 3484 for the details.  */
    { { .in6_u = { .u6_addr16 = { 0x0000, 0x0000, 0x0000, 0x0000,
				  0x0000, 0x0000, 0x0000, 0x0001 } } },
      128, 50 },
    { { .in6_u = { .u6_addr16 = { 0x2002, 0x0000, 0x0000, 0x0000,
				  0x0000, 0x0000, 0x0000, 0x0000 } } },
      16, 30 },
    { { .in6_u = { .u6_addr16 = { 0x0000, 0x0000, 0x0000, 0x0000,
				  0x0000, 0x0000, 0x0000, 0x0000 } } },
      96, 20 },
    { { .in6_u = { .u6_addr16 = { 0x0000, 0x0000, 0x0000, 0x0000,
				  0x0000, 0xffff, 0x0000, 0x0000 } } },
      96, 10 },
    { { .in6_u = { .u6_addr16 = { 0x0000, 0x0000, 0x0000, 0x0000,
				  0x0000, 0x0000, 0x0000, 0x0000 } } },
      0, 40 }
  };


static int
match_prefix (const struct sockaddr_storage *ss, const struct prefixlist *list,
	      int default_val)
{
  int idx;
  struct sockaddr_in6 in6_mem;
  const struct sockaddr_in6 *in6;

  if (ss->ss_family == PF_INET6)
    in6 = (const struct sockaddr_in6 *) ss;
  else if (ss->ss_family == PF_INET)
    {
      const struct sockaddr_in *in = (const struct sockaddr_in *) ss;

      /* Convert to IPv6 address.  */
      in6_mem.sin6_family = PF_INET6;
      in6_mem.sin6_port = in->sin_port;
      in6_mem.sin6_flowinfo = 0;
      if (in->sin_addr.s_addr == htonl (0x7f000001))
	in6_mem.sin6_addr = (struct in6_addr) IN6ADDR_LOOPBACK_INIT;
      else
	{
	  /* Construct a V4-to-6 mapped address.  */
	  memset (&in6_mem.sin6_addr, '\0', sizeof (in6_mem.sin6_addr));
	  in6_mem.sin6_addr.s6_addr16[5] = 0xffff;
	  in6_mem.sin6_addr.s6_addr32[3] = in->sin_addr.s_addr;
	  in6_mem.sin6_scope_id = 0;
	}

      in6 = &in6_mem;
    }
  else
    return default_val;

  for (idx = 0; ; ++idx)
    {
      unsigned int bits = list[idx].bits;
      uint8_t *mask = list[idx].prefix.s6_addr;
      uint8_t *val = in6->sin6_addr.s6_addr;

      while (bits > 8)
	{
	  if (*mask != *val)
	    break;

	  ++mask;
	  ++val;
	  bits -= 8;
	}

      if (bits < 8)
	{
	  if ((*mask & (0xff00 >> bits)) == (*val & (0xff00 >> bits)))
	    /* Match!  */
	    break;
	}
    }

  return list[idx].val;
}


static int
get_label (const struct sockaddr_storage *ss)
{
  /* XXX What is a good default value?  */
  return match_prefix (ss, default_labels, INT_MAX);
}


static int
get_precedence (const struct sockaddr_storage *ss)
{
  /* XXX What is a good default value?  */
  return match_prefix (ss, default_precedence, 0);
}


static int
rfc3484_sort (const void *p1, const void *p2)
{
  const struct sort_result *a1 = (const struct sort_result *) p1;
  const struct sort_result *a2 = (const struct sort_result *) p2;

  /* Rule 1: Avoid unusable destinations.
     We have the got_source_addr flag set if the destination is reachable.  */
  if (a1->got_source_addr && ! a2->got_source_addr)
    return -1;
  if (! a1->got_source_addr && a2->got_source_addr)
    return 1;


  /* Rule 2: Prefer matching scope.  Only interesting if both
     destination addresses are IPv6.  */
  int a1_dst_scope
    = get_scope ((struct sockaddr_storage *) a1->dest_addr->ai_addr);

  int a2_dst_scope
    = get_scope ((struct sockaddr_storage *) a2->dest_addr->ai_addr);

  if (a1->got_source_addr)
    {
      int a1_src_scope = get_scope (&a1->source_addr);
      int a2_src_scope = get_scope (&a2->source_addr);

      if (a1_dst_scope == a1_src_scope && a2_dst_scope != a2_src_scope)
	return -1;
      if (a1_dst_scope != a1_src_scope && a2_dst_scope == a2_src_scope)
	return 1;
    }


  /* Rule 3: Avoid deprecated addresses.
     That's something only the kernel could decide.  */

  /* Rule 4: Prefer home addresses.
     Another thing only the kernel can decide.  */

  /* Rule 5: Prefer matching label.  */
  if (a1->got_source_addr)
    {
      int a1_dst_label
	= get_label ((struct sockaddr_storage *) a1->dest_addr->ai_addr);
      int a1_src_label = get_label (&a1->source_addr);

      int a2_dst_label
	= get_label ((struct sockaddr_storage *) a2->dest_addr->ai_addr);
      int a2_src_label = get_label (&a2->source_addr);

      if (a1_dst_label == a1_src_label && a2_dst_label != a2_src_label)
	return -1;
      if (a1_dst_label != a1_src_label && a2_dst_label == a2_src_label)
	return 1;
    }


  /* Rule 6: Prefer higher precedence.  */
  int a1_prec
    = get_precedence ((struct sockaddr_storage *) a1->dest_addr->ai_addr);
  int a2_prec
    = get_precedence ((struct sockaddr_storage *) a2->dest_addr->ai_addr);

  if (a1_prec > a2_prec)
    return -1;
  if (a1_prec < a2_prec)
    return 1;


  /* Rule 7: Prefer native transport.
     XXX How to recognize tunnels?  */


  /* Rule 8: Prefer smaller scope.  */
  if (a1_dst_scope < a2_dst_scope)
    return -1;
  if (a1_dst_scope > a2_dst_scope)
    return 1;


  /* Rule 9: Use longest matching prefix.  */
  if (a1->got_source_addr
      && a1->dest_addr->ai_family == a2->dest_addr->ai_family)
    {
      int bit1 = 0;
      int bit2 = 0;

      if (a1->dest_addr->ai_family == PF_INET)
	{
	  assert (a1->source_addr.ss_family == PF_INET);
	  assert (a2->source_addr.ss_family == PF_INET);

	  struct sockaddr_in *in1_dst;
	  struct sockaddr_in *in1_src;
	  struct sockaddr_in *in2_dst;
	  struct sockaddr_in *in2_src;

	  in1_dst = (struct sockaddr_in *) a1->dest_addr->ai_addr;
	  in1_src = (struct sockaddr_in *) &a1->source_addr;
	  in2_dst = (struct sockaddr_in *) a2->dest_addr->ai_addr;
	  in2_src = (struct sockaddr_in *) &a2->source_addr;

	  bit1 = ffs (in1_dst->sin_addr.s_addr ^ in1_src->sin_addr.s_addr);
	  bit2 = ffs (in2_dst->sin_addr.s_addr ^ in2_src->sin_addr.s_addr);
	}
      else if (a1->dest_addr->ai_family == PF_INET6)
	{
	  assert (a1->source_addr.ss_family == PF_INET6);
	  assert (a2->source_addr.ss_family == PF_INET6);

	  struct sockaddr_in6 *in1_dst;
	  struct sockaddr_in6 *in1_src;
	  struct sockaddr_in6 *in2_dst;
	  struct sockaddr_in6 *in2_src;

	  in1_dst = (struct sockaddr_in6 *) a1->dest_addr->ai_addr;
	  in1_src = (struct sockaddr_in6 *) &a1->source_addr;
	  in2_dst = (struct sockaddr_in6 *) a2->dest_addr->ai_addr;
	  in2_src = (struct sockaddr_in6 *) &a2->source_addr;

	  int i;
	  for (i = 0; i < 4; ++i)
	    if (in1_dst->sin6_addr.s6_addr32[i]
		!= in1_src->sin6_addr.s6_addr32[i]
		|| (in2_dst->sin6_addr.s6_addr32[i]
		    != in2_src->sin6_addr.s6_addr32[i]))
	      break;

	  if (i < 4)
	    {
	      bit1 = ffs (in1_dst->sin6_addr.s6_addr32[i]
			  ^ in1_src->sin6_addr.s6_addr32[i]);
	      bit2 = ffs (in2_dst->sin6_addr.s6_addr32[i]
			  ^ in2_src->sin6_addr.s6_addr32[i]);
	    }
	}

      if (bit1 > bit2)
	return -1;
      if (bit1 < bit2)
	return 1;
    }


  /* Rule 10: Otherwise, leave the order unchanged.  */
  return 0;
}


int
getaddrinfo (const char *name, const char *service,
	     const struct addrinfo *hints, struct addrinfo **pai)
{
  int i = 0, j = 0, last_i = 0;
  int nresults = 0;
  struct addrinfo *p = NULL, **end;
  struct gaih *g = gaih, *pg = NULL;
  struct gaih_service gaih_service, *pservice;
  struct addrinfo local_hints;

  if (name != NULL && name[0] == '*' && name[1] == 0)
    name = NULL;

  if (service != NULL && service[0] == '*' && service[1] == 0)
    service = NULL;

  if (name == NULL && service == NULL)
    return EAI_NONAME;

  if (hints == NULL)
    hints = &default_hints;

  if (hints->ai_flags
      & ~(AI_PASSIVE|AI_CANONNAME|AI_NUMERICHOST|AI_ADDRCONFIG|AI_V4MAPPED
#ifdef HAVE_LIBIDN
	  |AI_IDN
#endif
	  |AI_ALL))
    return EAI_BADFLAGS;

  if ((hints->ai_flags & AI_CANONNAME) && name == NULL)
    return EAI_BADFLAGS;

  if (hints->ai_flags & AI_ADDRCONFIG)
    {
      /* Determine whether we have IPv4 or IPv6 interfaces or both.
	 We cannot cache the results since new interfaces could be
	 added at any time.  */
      bool seen_ipv4;
      bool seen_ipv6;
      __check_pf (&seen_ipv4, &seen_ipv6);

      /* Now make a decision on what we return, if anything.  */
      if (hints->ai_family == PF_UNSPEC)
	{
	  /* If we haven't seen both IPv4 and IPv6 interfaces we can
	     narrow down the search.  */
	  if (! seen_ipv4 || ! seen_ipv6)
	    {
	      local_hints = *hints;
	      local_hints.ai_family = seen_ipv4 ? PF_INET : PF_INET6;
	      hints = &local_hints;
	    }
	}
      else if ((hints->ai_family == PF_INET && ! seen_ipv4)
	       || (hints->ai_family == PF_INET6 && ! seen_ipv6))
	/* We cannot possibly return a valid answer.  */
	return EAI_NONAME;
    }

  if (service && service[0])
    {
      char *c;
      gaih_service.name = service;
      gaih_service.num = strtoul (gaih_service.name, &c, 10);
      if (*c)
	gaih_service.num = -1;
      else
	/* Can't specify a numerical socket unless a protocol family was
	   given. */
        if (hints->ai_socktype == 0 && hints->ai_protocol == 0)
          return EAI_SERVICE;
      pservice = &gaih_service;
    }
  else
    pservice = NULL;

  if (pai)
    end = &p;
  else
    end = NULL;

  while (g->gaih)
    {
      if (hints->ai_family == g->family || hints->ai_family == AF_UNSPEC)
	{
	  j++;
	  if (pg == NULL || pg->gaih != g->gaih)
	    {
	      pg = g;
	      i = g->gaih (name, pservice, hints, end);
	      if (i != 0)
		{
		  /* EAI_NODATA is a more specific result as it says that
		     we found a result but it is not usable.  */
		  if (last_i != (GAIH_OKIFUNSPEC | -EAI_NODATA))
		    last_i = i;

		  if (hints->ai_family == AF_UNSPEC && (i & GAIH_OKIFUNSPEC))
		    {
		      ++g;
		      continue;
		    }

		  freeaddrinfo (p);

		  return -(i & GAIH_EAI);
		}
	      if (end)
		while (*end)
		  {
		    end = &((*end)->ai_next);
		    ++nresults;
		  }
	    }
	}
      ++g;
    }

  if (j == 0)
    return EAI_FAMILY;

  if (nresults > 1)
    {
      /* Sort results according to RFC 3484.  */
      struct sort_result results[nresults];
      struct addrinfo *q;

      for (i = 0, q = p; q != NULL; ++i, q = q->ai_next)
	{
	  results[i].dest_addr = q;
	  results[i].got_source_addr = false;

	  /* We overwrite the type with SOCK_DGRAM since we do not
	     want connect() to connect to the other side.  If we
	     cannot determine the source address remember this
	     fact.  */
	  int fd = __socket (q->ai_family, SOCK_DGRAM, IPPROTO_IP);
	  if (fd != -1)
	    {
	      socklen_t sl = sizeof (results[i].source_addr);
	      if (__connect (fd, q->ai_addr, q->ai_addrlen) == 0
		  && __getsockname (fd,
				    (struct sockaddr *) &results[i].source_addr,
				    &sl) == 0)
		results[i].got_source_addr = true;

	      close_not_cancel_no_status (fd);
	    }
	}

      /* We got all the source addresses we can get, now sort using
	 the information.  */
      qsort (results, nresults, sizeof (results[0]), rfc3484_sort);

      /* Queue the results up as they come out of sorting.  */
      q = p = results[0].dest_addr;
      for (i = 1; i < nresults; ++i)
	q = q->ai_next = results[i].dest_addr;
      q->ai_next = NULL;
    }

  if (p)
    {
      *pai = p;
      return 0;
    }

  if (pai == NULL && last_i == 0)
    return 0;

  freeaddrinfo (p);

  return last_i ? -(last_i & GAIH_EAI) : EAI_NONAME;
}
libc_hidden_def (getaddrinfo)

static_link_warning (getaddrinfo)

void
freeaddrinfo (struct addrinfo *ai)
{
  struct addrinfo *p;

  while (ai != NULL)
    {
      p = ai;
      ai = ai->ai_next;
      free (p);
    }
}
libc_hidden_def (freeaddrinfo)