niceSOFT/inetutils

libinetutils/localhost.c
100 строк2 KB
Alfred M. Szmidt
Updated to GPLv3.
29 июн 2007, 20:29
29 июн 2007, 20:295dc26ad
/* A slightly more convenient wrapper for gethostname

   Copyright (C) 1996, 1997, 2000, 2005, 2006, 2007 Free Software Foundation, Inc.

   Written by Miles Bader <miles@gnu.ai.mit.edu>

   This program is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License as
   published by the Free Software Foundation; either version 3, or (at
   your option) any later version.

   This program 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
   General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include <unistd.h>
#ifdef HAVE_MALLOC_H
# include <malloc.h>
#endif
#if defined(STDC_HEADERS) || defined(HAVE_STDLIB_H)
# include <stdlib.h>
#endif
#include <stdint.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>

/* Return the name of the localhost.  This is just a wrapper for gethostname,
   which takes care of allocating a big enough buffer, and caches the result
   after the first call (so the result should be copied before modification).
   If something goes wrong, 0 is returned, and errno set.  */
/* We know longer use static buffers, is to dangerous and
   cause subtile bugs.  */
char *
localhost (void)
{
  char *buf = NULL;
  size_t buf_len = 0;
  int status = 0;

  do
    {
      char *tmp;
      errno = 0;

      buf_len += 256;		/* Initial guess */
      tmp = realloc (buf, buf_len);
      if (tmp == NULL)
	{
	  errno = ENOMEM;
	  free (buf);
	  return 0;
	}
      else
	buf = tmp;
    }
  while (((status = gethostname (buf, buf_len)) == 0
	  && !memchr (buf, '\0', buf_len))
#ifdef ENAMETOOLONG
	 || errno == ENAMETOOLONG
#endif
    );

  if (status != 0 && errno != 0)
    /* gethostname failed, abort.  */
    {
      free (buf);
      buf = 0;
    }
  else
    /* Determine FQDN */
    {
      struct hostent *hp = gethostbyname (buf);
      
      if (hp)
	{
	  struct in_addr addr;
	  addr.s_addr = *(unsigned int *) hp->h_addr;
	  hp = gethostbyaddr ((char *) &addr, sizeof (addr), AF_INET);
	  if (hp)
	    {
	      free (buf);
	      buf = strdup (hp->h_name);
	    }
	}
    }
  return buf;
}