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/* Copyright (C) 1995-2021 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, see
<https://www.gnu.org/licenses/>. */
#include <alloca.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <netdb.h>
#include <not-cancel.h>
#include <stdbool.h>
#define HOSTIDFILE "/etc/hostid"
#ifdef SET_PROCEDURE
int
sethostid (long int id)
{
int fd;
ssize_t written;
int32_t id32 = id;
/* Test for appropriate rights to set host ID. */
if (__libc_enable_secure)
{
__set_errno (EPERM);
return -1;
}
/* Make sure the ID is not too large. Needed for bi-arch support. */
if (id32 != id)
{
__set_errno (EOVERFLOW);
return -1;
}
/* Open file for writing. Everybody is allowed to read this file. */
fd = __open_nocancel (HOSTIDFILE, O_CREAT|O_WRONLY|O_TRUNC, 0644);
if (fd < 0)
return -1;
written = __write_nocancel (fd, &id32, sizeof (id32));
__close_nocancel_nostatus (fd);
return written != sizeof (id32) ? -1 : 0;
}
#else
# include <string.h>
# include <sys/param.h>
# include <resolv/netdb.h>
# include <netinet/in.h>
# include <scratch_buffer.h>
long int
gethostid (void)
{
char hostname[MAXHOSTNAMELEN + 1];
struct hostent hostbuf, *hp;
int32_t id;
struct in_addr in;
int herr;
int fd;
/* First try to get the ID from a former invocation of sethostid. */
fd = __open_nocancel (HOSTIDFILE, O_RDONLY|O_LARGEFILE, 0);
if (fd >= 0)
{
ssize_t n = __read_nocancel (fd, &id, sizeof (id));
__close_nocancel_nostatus (fd);
if (n == sizeof (id))
return id;
}
/* Getting from the file was not successful. An intelligent guess
for a unique number of a host is its IP address. To get the IP
address we need to know the host name. */
if (__gethostname (hostname, MAXHOSTNAMELEN) < 0 || hostname[0] == '\0')
/* This also fails. Return and arbitrary value. */
return 0;
/* Determine the IP address of the host name. */
struct scratch_buffer tmpbuf;
scratch_buffer_init (&tmpbuf);
while (true)
{
int ret = __gethostbyname_r (hostname, &hostbuf,
tmpbuf.data, tmpbuf.length, &hp, &herr);
if (ret == 0 && hp != NULL)
break;
else
{
/* Enlarge the buffer on ERANGE. */
if (ret != 0 && herr == NETDB_INTERNAL && errno == ERANGE)
{
if (!scratch_buffer_grow (&tmpbuf))
return 0;
}
/* Other errors are a failure. Return an arbitrary value. */
else
{
scratch_buffer_free (&tmpbuf);
return 0;
}
}
}
in.s_addr = 0;
memcpy (&in, hp->h_addr,
(int) sizeof (in) < hp->h_length ? (int) sizeof (in) : hp->h_length);
scratch_buffer_free (&tmpbuf);
/* For the return value to be not exactly the IP address we do some
bit fiddling. */
return (int32_t) (in.s_addr << 16 | in.s_addr >> 16);
}
#endif
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