1 | /* Copyright (C) 1995-2016 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 | <http://www.gnu.org/licenses/>. */ |
17 | |
18 | #include <alloca.h> |
19 | #include <errno.h> |
20 | #include <fcntl.h> |
21 | #include <unistd.h> |
22 | #include <netdb.h> |
23 | #include <not-cancel.h> |
24 | |
25 | #define HOSTIDFILE "/etc/hostid" |
26 | |
27 | #ifdef SET_PROCEDURE |
28 | int |
29 | sethostid (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_not_cancel (HOSTIDFILE, O_CREAT|O_WRONLY|O_TRUNC, 0644); |
51 | if (fd < 0) |
52 | return -1; |
53 | |
54 | written = write_not_cancel (fd, &id32, sizeof (id32)); |
55 | |
56 | close_not_cancel_no_status (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 | |
67 | long int |
68 | gethostid (void) |
69 | { |
70 | char hostname[MAXHOSTNAMELEN + 1]; |
71 | size_t buflen; |
72 | char *buffer; |
73 | struct hostent hostbuf, *hp; |
74 | int32_t id; |
75 | struct in_addr in; |
76 | int herr; |
77 | int fd; |
78 | |
79 | /* First try to get the ID from a former invocation of sethostid. */ |
80 | fd = open_not_cancel (HOSTIDFILE, O_RDONLY|O_LARGEFILE, 0); |
81 | if (fd >= 0) |
82 | { |
83 | ssize_t n = read_not_cancel (fd, &id, sizeof (id)); |
84 | |
85 | close_not_cancel_no_status (fd); |
86 | |
87 | if (n == sizeof (id)) |
88 | return id; |
89 | } |
90 | |
91 | /* Getting from the file was not successful. An intelligent guess for |
92 | a unique number of a host is its IP address. Return this. */ |
93 | if (__gethostname (hostname, MAXHOSTNAMELEN) < 0 || hostname[0] == '\0') |
94 | /* This also fails. Return and arbitrary value. */ |
95 | return 0; |
96 | |
97 | buflen = 1024; |
98 | buffer = __alloca (buflen); |
99 | |
100 | /* To get the IP address we need to know the host name. */ |
101 | while (__gethostbyname_r (hostname, &hostbuf, buffer, buflen, &hp, &herr) |
102 | != 0 |
103 | || hp == NULL) |
104 | if (herr != NETDB_INTERNAL || errno != ERANGE) |
105 | return 0; |
106 | else |
107 | /* Enlarge buffer. */ |
108 | buffer = extend_alloca (buffer, buflen, 2 * buflen); |
109 | |
110 | in.s_addr = 0; |
111 | memcpy (&in, hp->h_addr, |
112 | (int) sizeof (in) < hp->h_length ? (int) sizeof (in) : hp->h_length); |
113 | |
114 | /* For the return value to be not exactly the IP address we do some |
115 | bit fiddling. */ |
116 | return (int32_t) (in.s_addr << 16 | in.s_addr >> 16); |
117 | } |
118 | #endif |
119 | |