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/* Copyright (C) 1995 Free Software Foundation, Inc.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 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
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#define HOSTIDFILE "/var/adm/hostid"
#ifdef SET_PROCEDURE
int
sethostid (id)
long int id;
{
int fd;
ssize_t written;
/* Test for appropriate rights to set host ID. */
if (geteuid () || getuid ())
{
errno = EPERM;
return -1;
}
/* Open file for writing. Everybody is allowed to read this file. */
fd = __open (HOSTIDFILE, O_CREAT|O_WRONLY, 0644);
if (fd < 0)
return -1;
written = __write (fd, &id, sizeof (id));
__close (fd);
return written != sizeof (id) ? -1 : 0;
}
#else
# include <sys/param.h>
# include <resolv/netdb.h>
# include <netinet/in.h>
long int
gethostid ()
{
char hostname[MAXHOSTNAMELEN + 1];
struct hostent *hp;
unsigned long id;
struct in_addr in;
int fd;
/* First try to get the ID from a former invocation of sethostid. */
fd = __open (HOSTIDFILE, O_RDONLY);
if (fd >= 0)
{
ssize_t n = __read (fd, &id, sizeof (id));
__close (fd);
if (n == sizeof (id))
return id;
}
/* Getting from the file was not succesful. An intelligent guess for
a unique number of a host is its IP address. Return this. */
if (gethostname (hostname, MAXHOSTNAMELEN) < 0 || hostname[0] == '\0')
/* This also fails. Return and arbitrary value. */
return 0;
/* To get the IP address we need to knoe the host name. */
hp = gethostbyname (hostname);
if (hp == NULL)
return 0;
in.s_addr = 0;
memcpy (&in, hp->h_addr,
sizeof (in) < hp->h_length ? sizeof (in) : hp->h_length);
/* For the return value to be not exactly the IP address we do some
bit fiddling. */
return in.s_addr << 16 | in.s_addr >> 16;
}
#endif
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