133 lines
3.4 KiB
C
133 lines
3.4 KiB
C
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/* Copyright (C) 1995-2022 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <alloca.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <netdb.h>
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#include <not-cancel.h>
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#include <stdbool.h>
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#define HOSTIDFILE "/etc/hostid"
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#ifdef SET_PROCEDURE
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int
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sethostid (long int id)
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{
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int fd;
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ssize_t written;
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int32_t id32 = id;
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/* Test for appropriate rights to set host ID. */
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if (__libc_enable_secure)
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{
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__set_errno (EPERM);
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return -1;
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}
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/* Make sure the ID is not too large. Needed for bi-arch support. */
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if (id32 != id)
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{
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__set_errno (EOVERFLOW);
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return -1;
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}
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/* Open file for writing. Everybody is allowed to read this file. */
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fd = __open_nocancel (HOSTIDFILE, O_CREAT|O_WRONLY|O_TRUNC, 0644);
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if (fd < 0)
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return -1;
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written = __write_nocancel (fd, &id32, sizeof (id32));
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__close_nocancel_nostatus (fd);
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return written != sizeof (id32) ? -1 : 0;
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}
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#else
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# include <string.h>
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# include <sys/param.h>
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# include <resolv/netdb.h>
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# include <netinet/in.h>
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# include <scratch_buffer.h>
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long int
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gethostid (void)
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{
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char hostname[MAXHOSTNAMELEN + 1];
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struct hostent hostbuf, *hp;
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int32_t id;
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struct in_addr in;
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int herr;
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int fd;
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/* First try to get the ID from a former invocation of sethostid. */
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fd = __open_nocancel (HOSTIDFILE, O_RDONLY|O_LARGEFILE, 0);
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if (fd >= 0)
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{
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ssize_t n = __read_nocancel (fd, &id, sizeof (id));
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__close_nocancel_nostatus (fd);
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if (n == sizeof (id))
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return id;
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}
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/* Getting from the file was not successful. An intelligent guess
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for a unique number of a host is its IP address. To get the IP
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address we need to know the host name. */
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if (__gethostname (hostname, MAXHOSTNAMELEN) < 0 || hostname[0] == '\0')
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/* This also fails. Return and arbitrary value. */
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return 0;
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/* Determine the IP address of the host name. */
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struct scratch_buffer tmpbuf;
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scratch_buffer_init (&tmpbuf);
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while (true)
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{
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int ret = __gethostbyname_r (hostname, &hostbuf,
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tmpbuf.data, tmpbuf.length, &hp, &herr);
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if (ret == 0 && hp != NULL)
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break;
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else
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{
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/* Enlarge the buffer on ERANGE. */
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if (ret != 0 && herr == NETDB_INTERNAL && errno == ERANGE)
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{
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if (!scratch_buffer_grow (&tmpbuf))
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return 0;
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}
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/* Other errors are a failure. Return an arbitrary value. */
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else
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{
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scratch_buffer_free (&tmpbuf);
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return 0;
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}
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}
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}
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in.s_addr = 0;
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memcpy (&in, hp->h_addr,
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(int) sizeof (in) < hp->h_length ? (int) sizeof (in) : hp->h_length);
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scratch_buffer_free (&tmpbuf);
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/* For the return value to be not exactly the IP address we do some
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bit fiddling. */
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return (int32_t) (in.s_addr << 16 | in.s_addr >> 16);
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}
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#endif
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