1/* Copyright (C) 1995-2023 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
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.
8
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.
13
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/>. */
17
18#include <errno.h>
19#include <fcntl.h>
20#include <unistd.h>
21#include <netdb.h>
22#include <not-cancel.h>
23#include <stdbool.h>
24
25#define HOSTIDFILE "/etc/hostid"
26
27#ifdef SET_PROCEDURE
28int
29sethostid (long int id)
30{
31 int fd;
32 ssize_t written;
33 int32_t id32 = id;
34
35 /* Test for appropriate rights to set host ID. */
36 if (__libc_enable_secure)
37 {
38 __set_errno (EPERM);
39 return -1;
40 }
41
42 /* Make sure the ID is not too large. Needed for bi-arch support. */
43 if (id32 != id)
44 {
45 __set_errno (EOVERFLOW);
46 return -1;
47 }
48
49 /* Open file for writing. Everybody is allowed to read this file. */
50 fd = __open_nocancel (HOSTIDFILE, O_CREAT|O_WRONLY|O_TRUNC, 0644);
51 if (fd < 0)
52 return -1;
53
54 written = __write_nocancel (fd, &id32, sizeof (id32));
55
56 __close_nocancel_nostatus (fd);
57
58 return written != sizeof (id32) ? -1 : 0;
59}
60
61#else
62# include <string.h>
63# include <sys/param.h>
64# include <resolv/netdb.h>
65# include <netinet/in.h>
66# include <scratch_buffer.h>
67
68long int
69gethostid (void)
70{
71 char hostname[MAXHOSTNAMELEN + 1];
72 struct hostent hostbuf, *hp;
73 int32_t id;
74 struct in_addr in;
75 int herr;
76 int fd;
77
78 /* First try to get the ID from a former invocation of sethostid. */
79 fd = __open_nocancel (HOSTIDFILE, O_RDONLY|O_LARGEFILE, 0);
80 if (fd >= 0)
81 {
82 ssize_t n = __read_nocancel (fd, &id, sizeof (id));
83
84 __close_nocancel_nostatus (fd);
85
86 if (n == sizeof (id))
87 return id;
88 }
89
90 /* Getting from the file was not successful. An intelligent guess
91 for a unique number of a host is its IP address. To get the IP
92 address we need to know the host name. */
93 if (__gethostname (hostname, MAXHOSTNAMELEN) < 0 || hostname[0] == '\0')
94 /* This also fails. Return and arbitrary value. */
95 return 0;
96
97 /* Determine the IP address of the host name. */
98 struct scratch_buffer tmpbuf;
99 scratch_buffer_init (&tmpbuf);
100 while (true)
101 {
102 int ret = __gethostbyname_r (hostname, &hostbuf,
103 tmpbuf.data, tmpbuf.length, &hp, &herr);
104 if (ret == 0 && hp != NULL)
105 break;
106 else
107 {
108 /* Enlarge the buffer on ERANGE. */
109 if (ret != 0 && herr == NETDB_INTERNAL && errno == ERANGE)
110 {
111 if (!scratch_buffer_grow (&tmpbuf))
112 return 0;
113 }
114 /* Other errors are a failure. Return an arbitrary value. */
115 else
116 {
117 scratch_buffer_free (&tmpbuf);
118 return 0;
119 }
120 }
121 }
122
123 in.s_addr = 0;
124 memcpy (&in, hp->h_addr,
125 (int) sizeof (in) < hp->h_length ? (int) sizeof (in) : hp->h_length);
126 scratch_buffer_free (&tmpbuf);
127 /* For the return value to be not exactly the IP address we do some
128 bit fiddling. */
129 return (int32_t) (in.s_addr << 16 | in.s_addr >> 16);
130}
131#endif
132