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git.ipfire.org Git - thirdparty/glibc.git/blob - sysdeps/unix/sysv/linux/gethostid.c
50a4707f71f42edc9370b7189b23c3cc56f4fe34
1 /* Copyright (C) 1995-2020 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
23 #include <not-cancel.h>
26 #define HOSTIDFILE "/etc/hostid"
30 sethostid (long int id
)
36 /* Test for appropriate rights to set host ID. */
37 if (__libc_enable_secure
)
43 /* Make sure the ID is not too large. Needed for bi-arch support. */
46 __set_errno (EOVERFLOW
);
50 /* Open file for writing. Everybody is allowed to read this file. */
51 fd
= __open_nocancel (HOSTIDFILE
, O_CREAT
|O_WRONLY
|O_TRUNC
, 0644);
55 written
= __write_nocancel (fd
, &id32
, sizeof (id32
));
57 __close_nocancel_nostatus (fd
);
59 return written
!= sizeof (id32
) ? -1 : 0;
64 # include <sys/param.h>
65 # include <resolv/netdb.h>
66 # include <netinet/in.h>
67 # include <scratch_buffer.h>
72 char hostname
[MAXHOSTNAMELEN
+ 1];
73 struct hostent hostbuf
, *hp
;
79 /* First try to get the ID from a former invocation of sethostid. */
80 fd
= __open_nocancel (HOSTIDFILE
, O_RDONLY
|O_LARGEFILE
, 0);
83 ssize_t n
= __read_nocancel (fd
, &id
, sizeof (id
));
85 __close_nocancel_nostatus (fd
);
91 /* Getting from the file was not successful. An intelligent guess
92 for a unique number of a host is its IP address. To get the IP
93 address we need to know the host name. */
94 if (__gethostname (hostname
, MAXHOSTNAMELEN
) < 0 || hostname
[0] == '\0')
95 /* This also fails. Return and arbitrary value. */
98 /* Determine the IP address of the host name. */
99 struct scratch_buffer tmpbuf
;
100 scratch_buffer_init (&tmpbuf
);
103 int ret
= __gethostbyname_r (hostname
, &hostbuf
,
104 tmpbuf
.data
, tmpbuf
.length
, &hp
, &herr
);
105 if (ret
== 0 && hp
!= NULL
)
109 /* Enlarge the buffer on ERANGE. */
110 if (ret
!= 0 && herr
== NETDB_INTERNAL
&& errno
== ERANGE
)
112 if (!scratch_buffer_grow (&tmpbuf
))
115 /* Other errors are a failure. Return an arbitrary value. */
118 scratch_buffer_free (&tmpbuf
);
125 memcpy (&in
, hp
->h_addr
,
126 (int) sizeof (in
) < hp
->h_length
? (int) sizeof (in
) : hp
->h_length
);
127 scratch_buffer_free (&tmpbuf
);
128 /* For the return value to be not exactly the IP address we do some
130 return (int32_t) (in
.s_addr
<< 16 | in
.s_addr
>> 16);