sysdeps/unix/sysv/linux/if_index.c - nest-cam/v366/glibc - Git at Google

 /* Copyright (C) 1997, 1998, 1999, 2000, 2002, 2003, 2004, 2005, 2007
    Free Software Foundation, Inc.
    This file is part of the GNU C Library.

    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, write to the Free
    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
    02111-1307 USA.  */

 #include <alloca.h>
 #include <errno.h>
 #include <string.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <net/if.h>
 #include <sys/socket.h>
 #include <sys/ioctl.h>
 #include <bits/libc-lock.h>
 #include <not-cancel.h>
 #include <kernel-features.h>

 #include "netlinkaccess.h"


 /* Variable to signal whether SIOCGIFCONF is not available.  */
 # if __ASSUME_SIOCGIFNAME == 0
 static int old_siocgifconf;
 #else
 # define old_siocgifconf 0
 #endif


 unsigned int
 if_nametoindex (const char *ifname)
 {
 #ifndef SIOCGIFINDEX
   __set_errno (ENOSYS);
   return 0;
 #else
   struct ifreq ifr;
   int fd = __opensock ();

   if (fd < 0)
     return 0;

   strncpy (ifr.ifr_name, ifname, sizeof (ifr.ifr_name));
   if (__ioctl (fd, SIOCGIFINDEX, &ifr) < 0)
     {
       int saved_errno = errno;
       close_not_cancel_no_status (fd);
       if (saved_errno == EINVAL)
 	__set_errno (ENOSYS);
       return 0;
     }
   close_not_cancel_no_status (fd);
   return ifr.ifr_ifindex;
 #endif
 }
 libc_hidden_def (if_nametoindex)


 void
 if_freenameindex (struct if_nameindex *ifn)
 {
   struct if_nameindex *ptr = ifn;
   while (ptr->if_name || ptr->if_index)
     {
       free (ptr->if_name);
       ++ptr;
     }
   free (ifn);
 }
 libc_hidden_def (if_freenameindex)


 #if __ASSUME_NETLINK_SUPPORT == 0
 static struct if_nameindex *
 if_nameindex_ioctl (void)
 {
   int fd = __opensock ();
   struct ifconf ifc;
   unsigned int nifs, i;
   int rq_len;
   struct if_nameindex *idx = NULL;
 # define RQ_IFS	4

   if (fd < 0)
     return NULL;

   ifc.ifc_buf = NULL;

   /* We may be able to get the needed buffer size directly, rather than
      guessing.  */
   if (! old_siocgifconf)
     {
       ifc.ifc_buf = NULL;
       ifc.ifc_len = 0;
       if (__ioctl (fd, SIOCGIFCONF, &ifc) < 0 || ifc.ifc_len == 0)
 	{
 # if __ASSUME_SIOCGIFNAME == 0
 	  old_siocgifconf = 1;
 # endif
 	  rq_len = RQ_IFS * sizeof (struct ifreq);
 	}
       else
 	rq_len = ifc.ifc_len;
     }
   else
     rq_len = RQ_IFS * sizeof (struct ifreq);

   /* Read all the interfaces out of the kernel.  */
   ifc.ifc_buf = alloca (rq_len);
   ifc.ifc_len = rq_len;
   while (1)
     {
         if (__ioctl (fd, SIOCGIFCONF, &ifc) < 0)
 	{
 	  close_not_cancel_no_status (fd);
 	  return NULL;
 	}
       if (ifc.ifc_len < rq_len || ! old_siocgifconf)
 	break;

       ifc.ifc_buf = extend_alloca (ifc.ifc_buf, rq_len, 2 * rq_len);
       ifc.ifc_len = rq_len;
     }

   nifs = ifc.ifc_len / sizeof (struct ifreq);

   idx = malloc ((nifs + 1) * sizeof (struct if_nameindex));
   if (idx == NULL)
     {
       close_not_cancel_no_status (fd);
       __set_errno (ENOBUFS);
       return NULL;
     }

   for (i = 0; i < nifs; ++i)
     {
       struct ifreq *ifr = &ifc.ifc_req[i];
       idx[i].if_name = __strdup (ifr->ifr_name);
       if (idx[i].if_name == NULL
 	  || __ioctl (fd, SIOCGIFINDEX, ifr) < 0)
 	{
 	  int saved_errno = errno;
 	  unsigned int j;

 	  for (j =  0; j < i; ++j)
 	    free (idx[j].if_name);
 	  free (idx);
 	  close_not_cancel_no_status (fd);
 	  if (saved_errno == EINVAL)
 	    saved_errno = ENOSYS;
 	  else if (saved_errno == ENOMEM)
 	    saved_errno = ENOBUFS;
 	  __set_errno (saved_errno);
 	  return NULL;
 	}
       idx[i].if_index = ifr->ifr_ifindex;
     }

   idx[i].if_index = 0;
   idx[i].if_name = NULL;

   close_not_cancel_no_status (fd);
   return idx;
 }
 #endif


 static struct if_nameindex *
 if_nameindex_netlink (void)
 {
   struct netlink_handle nh = { 0, 0, 0, NULL, NULL };
   struct if_nameindex *idx = NULL;

   if (__no_netlink_support || __netlink_open (&nh) < 0)
     return NULL;


   /* Tell the kernel that we wish to get a list of all
      active interfaces.  Collect all data for every interface.  */
   if (__netlink_request (&nh, RTM_GETLINK) < 0)
     goto exit_free;

   /* Count the interfaces.  */
   unsigned int nifs = 0;
   for (struct netlink_res *nlp = nh.nlm_list; nlp; nlp = nlp->next)
     {
       struct nlmsghdr *nlh;
       size_t size = nlp->size;

       if (nlp->nlh == NULL)
 	continue;

       /* Walk through all entries we got from the kernel and look, which
          message type they contain.  */
       for (nlh = nlp->nlh; NLMSG_OK (nlh, size); nlh = NLMSG_NEXT (nlh, size))
 	{
 	  /* Check if the message is what we want.  */
 	  if ((pid_t) nlh->nlmsg_pid != nh.pid || nlh->nlmsg_seq != nlp->seq)
 	    continue;

 	  if (nlh->nlmsg_type == NLMSG_DONE)
 	    break;		/* ok */

 	  if (nlh->nlmsg_type == RTM_NEWLINK)
 	    ++nifs;
 	}
     }

   idx = malloc ((nifs + 1) * sizeof (struct if_nameindex));
   if (idx == NULL)
     {
     nomem:
       __set_errno (ENOBUFS);
       goto exit_free;
     }

   /* Add the interfaces.  */
   nifs = 0;
   for (struct netlink_res *nlp = nh.nlm_list; nlp; nlp = nlp->next)
     {
       struct nlmsghdr *nlh;
       size_t size = nlp->size;

       if (nlp->nlh == NULL)
 	continue;

       /* Walk through all entries we got from the kernel and look, which
          message type they contain.  */
       for (nlh = nlp->nlh; NLMSG_OK (nlh, size); nlh = NLMSG_NEXT (nlh, size))
 	{
 	  /* Check if the message is what we want.  */
 	  if ((pid_t) nlh->nlmsg_pid != nh.pid || nlh->nlmsg_seq != nlp->seq)
 	    continue;

 	  if (nlh->nlmsg_type == NLMSG_DONE)
 	    break;		/* ok */

 	  if (nlh->nlmsg_type == RTM_NEWLINK)
 	    {
 	      struct ifinfomsg *ifim = (struct ifinfomsg *) NLMSG_DATA (nlh);
 	      struct rtattr *rta = IFLA_RTA (ifim);
 	      size_t rtasize = IFLA_PAYLOAD (nlh);

 	      idx[nifs].if_index = ifim->ifi_index;

 	      while (RTA_OK (rta, rtasize))
 		{
 		  char *rta_data = RTA_DATA (rta);
 		  size_t rta_payload = RTA_PAYLOAD (rta);

 		  if (rta->rta_type == IFLA_IFNAME)
 		    {
 		      idx[nifs].if_name = __strndup (rta_data, rta_payload);
 		      if (idx[nifs].if_name == NULL)
 			{
 			  idx[nifs].if_index = 0;
 			  if_freenameindex (idx);
 			  idx = NULL;
 			  goto nomem;
 			}
 		      break;
 		    }

 		  rta = RTA_NEXT (rta, rtasize);
 		}

 	      ++nifs;
 	    }
 	}
     }

   idx[nifs].if_index = 0;
   idx[nifs].if_name = NULL;

  exit_free:
   __netlink_free_handle (&nh);
   __netlink_close (&nh);

   return idx;
 }


 struct if_nameindex *
 if_nameindex (void)
 {
 #ifndef SIOCGIFINDEX
   __set_errno (ENOSYS);
   return NULL;
 #else
   struct if_nameindex *result = if_nameindex_netlink ();
 # if __ASSUME_NETLINK_SUPPORT == 0
   if (__no_netlink_support)
     result = if_nameindex_ioctl ();
 # endif
   return result;
 #endif
 }
 libc_hidden_def (if_nameindex)


 char *
 if_indextoname (unsigned int ifindex, char *ifname)
 {
 #if !defined SIOCGIFINDEX && __ASSUME_SIOCGIFNAME == 0
   __set_errno (ENOSYS);
   return NULL;
 #else
 # if __ASSUME_SIOCGIFNAME == 0
   struct if_nameindex *idx;
   struct if_nameindex *p;
   char *result = NULL;
 # endif

 # if defined SIOCGIFNAME || __ASSUME_SIOCGIFNAME > 0
   /* We may be able to do the conversion directly, rather than searching a
      list.  This ioctl is not present in kernels before version 2.1.50.  */
   struct ifreq ifr;
   int fd;
 #  if __ASSUME_SIOCGIFNAME == 0
   static int siocgifname_works_not;

   if (!siocgifname_works_not)
 #  endif
     {
 #  if __ASSUME_SIOCGIFNAME == 0
       int serrno = errno;
 #  endif
       int status;

       fd = __opensock ();

       if (fd < 0)
 	return NULL;

       ifr.ifr_ifindex = ifindex;
       status = __ioctl (fd, SIOCGIFNAME, &ifr);

       close_not_cancel_no_status (fd);

       if (status  < 0)
 	{
 #  if __ASSUME_SIOCGIFNAME == 0
 	  if (errno == EINVAL)
 	    siocgifname_works_not = 1; /* Don't make the same mistake twice. */
 	  else
 #  endif
 	    {
 	      if (errno == ENODEV)
 		/* POSIX requires ENXIO.  */
 		__set_errno (ENXIO);

 	      return NULL;
 	    }
 	}
       else
 	return strncpy (ifname, ifr.ifr_name, IFNAMSIZ);

 #  if __ASSUME_SIOCGIFNAME == 0
       __set_errno (serrno);
 #  endif
     }
 # endif

 # if __ASSUME_SIOCGIFNAME == 0
   idx = if_nameindex ();

   if (idx != NULL)
     {
       for (p = idx; p->if_index || p->if_name; ++p)
 	if (p->if_index == ifindex)
 	  {
 	    result = strncpy (ifname, p->if_name, IFNAMSIZ);
 	    break;
 	  }

       if_freenameindex (idx);

       if (result == NULL)
 	__set_errno (ENXIO);
     }
   return result;
 # endif
 #endif
 }
 libc_hidden_def (if_indextoname)


 #if 0
 void
 internal_function
 __protocol_available (int *have_inet, int *have_inet6)
 {
   int fd = __opensock ();
   unsigned int nifs;
   int rq_len;
   struct ifconf ifc;
 # define RQ_IFS	4

   /* Wirst case assumption.  */
   *have_inet = 0;
   *have_inet6 = 0;

   if (fd < 0)
     /* We cannot open the socket.  No networking at all?  */
     return;

   /* We may be able to get the needed buffer size directly, rather than
      guessing.  */
   if (! old_siocgifconf)
     {
       ifc.ifc_buf = NULL;
       ifc.ifc_len = 0;
       if (__ioctl (fd, SIOCGIFCONF, &ifc) < 0 || ifc.ifc_len == 0)
 	{
 # if __ASSUME_SIOCGIFNAME == 0
 	  old_siocgifconf = 1;
 # endif
 	  rq_len = RQ_IFS * sizeof (struct ifreq);
 	}
       else
 	rq_len = ifc.ifc_len;
     }
   else
     rq_len = RQ_IFS * sizeof (struct ifreq);

   /* Read all the interfaces out of the kernel.  */
   do
     {
       ifc.ifc_buf = alloca (ifc.ifc_len = rq_len);
       if (__ioctl (fd, SIOCGIFCONF, &ifc) < 0)
 	{
 	  close_not_cancel_no_status (fd);
 	  return;
 	}
       rq_len *= 2;
     }
   while (ifc.ifc_len == rq_len && old_siocgifconf);

   nifs = ifc.ifc_len / sizeof (struct ifreq);

   /* Go through all the interfaces and get the address.  */
   while (nifs-- > 0)
     if (__ioctl (fd, SIOCGIFADDR, &ifc.ifc_req[nifs]) >= 0)
       {
 	/* We successfully got information about this interface.  Now
 	   test whether it is an IPv4 or IPv6 address.  */
 	if (ifc.ifc_req[nifs].ifr_addr.sa_family == AF_INET)
 	  *have_inet = 1;
 	else if (ifc.ifc_req[nifs].ifr_addr.sa_family == AF_INET6)
 	  *have_inet6 = 1;

 	/* Note, this is & not &&.  It works since the values are always
 	   0 or 1.  */
 	if (*have_inet & *have_inet6)
 	  /* We can stop early.  */
 	  break;
       }

   close_not_cancel_no_status (fd);
 }
 #endif
	/* Copyright (C) 1997, 1998, 1999, 2000, 2002, 2003, 2004, 2005, 2007
	Free Software Foundation, Inc.
	This file is part of the GNU C Library.

	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, write to the Free
	Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
	02111-1307 USA. */

	#include <alloca.h>
	#include <errno.h>
	#include <string.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <unistd.h>
	#include <net/if.h>
	#include <sys/socket.h>
	#include <sys/ioctl.h>
	#include <bits/libc-lock.h>
	#include <not-cancel.h>
	#include <kernel-features.h>

	#include "netlinkaccess.h"


	/* Variable to signal whether SIOCGIFCONF is not available. */
	# if __ASSUME_SIOCGIFNAME == 0
	static int old_siocgifconf;
	#else
	# define old_siocgifconf 0
	#endif


	unsigned int
	if_nametoindex (const char *ifname)
	{
	#ifndef SIOCGIFINDEX
	__set_errno (ENOSYS);
	return 0;
	#else
	struct ifreq ifr;
	int fd = __opensock ();

	if (fd < 0)
	return 0;

	strncpy (ifr.ifr_name, ifname, sizeof (ifr.ifr_name));
	if (__ioctl (fd, SIOCGIFINDEX, &ifr) < 0)
	{
	int saved_errno = errno;
	close_not_cancel_no_status (fd);
	if (saved_errno == EINVAL)
	__set_errno (ENOSYS);
	return 0;
	}
	close_not_cancel_no_status (fd);
	return ifr.ifr_ifindex;
	#endif
	}
	libc_hidden_def (if_nametoindex)


	void
	if_freenameindex (struct if_nameindex *ifn)
	{
	struct if_nameindex *ptr = ifn;
	while (ptr->if_name \|\| ptr->if_index)
	{
	free (ptr->if_name);
	++ptr;
	}
	free (ifn);
	}
	libc_hidden_def (if_freenameindex)


	#if __ASSUME_NETLINK_SUPPORT == 0
	static struct if_nameindex *
	if_nameindex_ioctl (void)
	{
	int fd = __opensock ();
	struct ifconf ifc;
	unsigned int nifs, i;
	int rq_len;
	struct if_nameindex *idx = NULL;
	# define RQ_IFS 4

	if (fd < 0)
	return NULL;

	ifc.ifc_buf = NULL;

	/* We may be able to get the needed buffer size directly, rather than
	guessing. */
	if (! old_siocgifconf)
	{
	ifc.ifc_buf = NULL;
	ifc.ifc_len = 0;
	if (__ioctl (fd, SIOCGIFCONF, &ifc) < 0 \|\| ifc.ifc_len == 0)
	{
	# if __ASSUME_SIOCGIFNAME == 0
	old_siocgifconf = 1;
	# endif
	rq_len = RQ_IFS * sizeof (struct ifreq);
	}
	else
	rq_len = ifc.ifc_len;
	}
	else
	rq_len = RQ_IFS * sizeof (struct ifreq);

	/* Read all the interfaces out of the kernel. */
	ifc.ifc_buf = alloca (rq_len);
	ifc.ifc_len = rq_len;
	while (1)
	{
	if (__ioctl (fd, SIOCGIFCONF, &ifc) < 0)
	{
	close_not_cancel_no_status (fd);
	return NULL;
	}
	if (ifc.ifc_len < rq_len \|\| ! old_siocgifconf)
	break;

	ifc.ifc_buf = extend_alloca (ifc.ifc_buf, rq_len, 2 * rq_len);
	ifc.ifc_len = rq_len;
	}

	nifs = ifc.ifc_len / sizeof (struct ifreq);

	idx = malloc ((nifs + 1) * sizeof (struct if_nameindex));
	if (idx == NULL)
	{
	close_not_cancel_no_status (fd);
	__set_errno (ENOBUFS);
	return NULL;
	}

	for (i = 0; i < nifs; ++i)
	{
	struct ifreq *ifr = &ifc.ifc_req[i];
	idx[i].if_name = __strdup (ifr->ifr_name);
	if (idx[i].if_name == NULL
	\|\| __ioctl (fd, SIOCGIFINDEX, ifr) < 0)
	{
	int saved_errno = errno;
	unsigned int j;

	for (j = 0; j < i; ++j)
	free (idx[j].if_name);
	free (idx);
	close_not_cancel_no_status (fd);
	if (saved_errno == EINVAL)
	saved_errno = ENOSYS;
	else if (saved_errno == ENOMEM)
	saved_errno = ENOBUFS;
	__set_errno (saved_errno);
	return NULL;
	}
	idx[i].if_index = ifr->ifr_ifindex;
	}

	idx[i].if_index = 0;
	idx[i].if_name = NULL;

	close_not_cancel_no_status (fd);
	return idx;
	}
	#endif


	static struct if_nameindex *
	if_nameindex_netlink (void)
	{
	struct netlink_handle nh = { 0, 0, 0, NULL, NULL };
	struct if_nameindex *idx = NULL;

	if (__no_netlink_support \|\| __netlink_open (&nh) < 0)
	return NULL;


	/* Tell the kernel that we wish to get a list of all
	active interfaces. Collect all data for every interface. */
	if (__netlink_request (&nh, RTM_GETLINK) < 0)
	goto exit_free;

	/* Count the interfaces. */
	unsigned int nifs = 0;
	for (struct netlink_res *nlp = nh.nlm_list; nlp; nlp = nlp->next)
	{
	struct nlmsghdr *nlh;
	size_t size = nlp->size;

	if (nlp->nlh == NULL)
	continue;

	/* Walk through all entries we got from the kernel and look, which
	message type they contain. */
	for (nlh = nlp->nlh; NLMSG_OK (nlh, size); nlh = NLMSG_NEXT (nlh, size))
	{
	/* Check if the message is what we want. */
	if ((pid_t) nlh->nlmsg_pid != nh.pid \|\| nlh->nlmsg_seq != nlp->seq)
	continue;

	if (nlh->nlmsg_type == NLMSG_DONE)
	break; /* ok */

	if (nlh->nlmsg_type == RTM_NEWLINK)
	++nifs;
	}
	}

	idx = malloc ((nifs + 1) * sizeof (struct if_nameindex));
	if (idx == NULL)
	{
	nomem:
	__set_errno (ENOBUFS);
	goto exit_free;
	}

	/* Add the interfaces. */
	nifs = 0;
	for (struct netlink_res *nlp = nh.nlm_list; nlp; nlp = nlp->next)
	{
	struct nlmsghdr *nlh;
	size_t size = nlp->size;

	if (nlp->nlh == NULL)
	continue;

	/* Walk through all entries we got from the kernel and look, which
	message type they contain. */
	for (nlh = nlp->nlh; NLMSG_OK (nlh, size); nlh = NLMSG_NEXT (nlh, size))
	{
	/* Check if the message is what we want. */
	if ((pid_t) nlh->nlmsg_pid != nh.pid \|\| nlh->nlmsg_seq != nlp->seq)
	continue;

	if (nlh->nlmsg_type == NLMSG_DONE)
	break; /* ok */

	if (nlh->nlmsg_type == RTM_NEWLINK)
	{
	struct ifinfomsg ifim = (struct ifinfomsg ) NLMSG_DATA (nlh);
	struct rtattr *rta = IFLA_RTA (ifim);
	size_t rtasize = IFLA_PAYLOAD (nlh);

	idx[nifs].if_index = ifim->ifi_index;

	while (RTA_OK (rta, rtasize))
	{
	char *rta_data = RTA_DATA (rta);
	size_t rta_payload = RTA_PAYLOAD (rta);

	if (rta->rta_type == IFLA_IFNAME)
	{
	idx[nifs].if_name = __strndup (rta_data, rta_payload);
	if (idx[nifs].if_name == NULL)
	{
	idx[nifs].if_index = 0;
	if_freenameindex (idx);
	idx = NULL;
	goto nomem;
	}
	break;
	}

	rta = RTA_NEXT (rta, rtasize);
	}

	++nifs;
	}
	}
	}

	idx[nifs].if_index = 0;
	idx[nifs].if_name = NULL;

	exit_free:
	__netlink_free_handle (&nh);
	__netlink_close (&nh);

	return idx;
	}


	struct if_nameindex *
	if_nameindex (void)
	{
	#ifndef SIOCGIFINDEX
	__set_errno (ENOSYS);
	return NULL;
	#else
	struct if_nameindex *result = if_nameindex_netlink ();
	# if __ASSUME_NETLINK_SUPPORT == 0
	if (__no_netlink_support)
	result = if_nameindex_ioctl ();
	# endif
	return result;
	#endif
	}
	libc_hidden_def (if_nameindex)


	char *
	if_indextoname (unsigned int ifindex, char *ifname)
	{
	#if !defined SIOCGIFINDEX && __ASSUME_SIOCGIFNAME == 0
	__set_errno (ENOSYS);
	return NULL;
	#else
	# if __ASSUME_SIOCGIFNAME == 0
	struct if_nameindex *idx;
	struct if_nameindex *p;
	char *result = NULL;
	# endif

	# if defined SIOCGIFNAME \|\| __ASSUME_SIOCGIFNAME > 0
	/* We may be able to do the conversion directly, rather than searching a
	list. This ioctl is not present in kernels before version 2.1.50. */
	struct ifreq ifr;
	int fd;
	# if __ASSUME_SIOCGIFNAME == 0
	static int siocgifname_works_not;

	if (!siocgifname_works_not)
	# endif
	{
	# if __ASSUME_SIOCGIFNAME == 0
	int serrno = errno;
	# endif
	int status;

	fd = __opensock ();

	if (fd < 0)
	return NULL;

	ifr.ifr_ifindex = ifindex;
	status = __ioctl (fd, SIOCGIFNAME, &ifr);

	close_not_cancel_no_status (fd);

	if (status < 0)
	{
	# if __ASSUME_SIOCGIFNAME == 0
	if (errno == EINVAL)
	siocgifname_works_not = 1; /* Don't make the same mistake twice. */
	else
	# endif
	{
	if (errno == ENODEV)
	/* POSIX requires ENXIO. */
	__set_errno (ENXIO);

	return NULL;
	}
	}
	else
	return strncpy (ifname, ifr.ifr_name, IFNAMSIZ);

	# if __ASSUME_SIOCGIFNAME == 0
	__set_errno (serrno);
	# endif
	}
	# endif

	# if __ASSUME_SIOCGIFNAME == 0
	idx = if_nameindex ();

	if (idx != NULL)
	{
	for (p = idx; p->if_index \|\| p->if_name; ++p)
	if (p->if_index == ifindex)
	{
	result = strncpy (ifname, p->if_name, IFNAMSIZ);
	break;
	}

	if_freenameindex (idx);

	if (result == NULL)
	__set_errno (ENXIO);
	}
	return result;
	# endif
	#endif
	}
	libc_hidden_def (if_indextoname)


	#if 0
	void
	internal_function
	__protocol_available (int have_inet, int have_inet6)
	{
	int fd = __opensock ();
	unsigned int nifs;
	int rq_len;
	struct ifconf ifc;
	# define RQ_IFS 4

	/* Wirst case assumption. */
	*have_inet = 0;
	*have_inet6 = 0;

	if (fd < 0)
	/* We cannot open the socket. No networking at all? */
	return;

	/* We may be able to get the needed buffer size directly, rather than
	guessing. */
	if (! old_siocgifconf)
	{
	ifc.ifc_buf = NULL;
	ifc.ifc_len = 0;
	if (__ioctl (fd, SIOCGIFCONF, &ifc) < 0 \|\| ifc.ifc_len == 0)
	{
	# if __ASSUME_SIOCGIFNAME == 0
	old_siocgifconf = 1;
	# endif
	rq_len = RQ_IFS * sizeof (struct ifreq);
	}
	else
	rq_len = ifc.ifc_len;
	}
	else
	rq_len = RQ_IFS * sizeof (struct ifreq);

	/* Read all the interfaces out of the kernel. */
	do
	{
	ifc.ifc_buf = alloca (ifc.ifc_len = rq_len);
	if (__ioctl (fd, SIOCGIFCONF, &ifc) < 0)
	{
	close_not_cancel_no_status (fd);
	return;
	}
	rq_len *= 2;
	}
	while (ifc.ifc_len == rq_len && old_siocgifconf);

	nifs = ifc.ifc_len / sizeof (struct ifreq);

	/* Go through all the interfaces and get the address. */
	while (nifs-- > 0)
	if (__ioctl (fd, SIOCGIFADDR, &ifc.ifc_req[nifs]) >= 0)
	{
	/* We successfully got information about this interface. Now
	test whether it is an IPv4 or IPv6 address. */
	if (ifc.ifc_req[nifs].ifr_addr.sa_family == AF_INET)
	*have_inet = 1;
	else if (ifc.ifc_req[nifs].ifr_addr.sa_family == AF_INET6)
	*have_inet6 = 1;

	/* Note, this is & not &&. It works since the values are always
	0 or 1. */
	if (have_inet & have_inet6)
	/* We can stop early. */
	break;
	}

	close_not_cancel_no_status (fd);
	}
	#endif