blob: 1290f4ca719fc7016f433705e0ad880de8f15739 [file] [log] [blame]
Denis Vlasenkod6864822008-02-25 23:24:32 +00001/* vi: set sw=4 ts=4: */
2/*
3 * Safe gethostname implementation for busybox
4 *
5 * Copyright (C) 2008 Tito Ragusa <farmatito@tiscali.it>
6 *
7 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
8 */
9
10/*
11 * SUSv2 guarantees that "Host names are limited to 255 bytes"
12 * POSIX.1-2001 guarantees that "Host names (not including the terminating
13 * null byte) are limited to HOST_NAME_MAX bytes" (64 bytes on my box).
14 *
15 * RFC1123 says:
16 *
17 * The syntax of a legal Internet host name was specified in RFC-952
18 * [DNS:4]. One aspect of host name syntax is hereby changed: the
19 * restriction on the first character is relaxed to allow either a
20 * letter or a digit. Host software MUST support this more liberal
21 * syntax.
22 *
23 * Host software MUST handle host names of up to 63 characters and
24 * SHOULD handle host names of up to 255 characters.
25 */
26
27#include "libbb.h"
28#include <sys/utsname.h>
29
30/*
31 * On success return the current malloced and NUL terminated hostname.
32 * On error return malloced and NUL terminated string "?".
33 * This is an illegal first character for a hostname.
34 * The returned malloced string must be freed by the caller.
35 */
36char *safe_gethostname(void)
37{
38 struct utsname uts;
39
40 /* The length of the arrays in a struct utsname is unspecified;
41 * the fields are terminated by a null byte.
42 * Note that there is no standard that says that the hostname
43 * set by sethostname(2) is the same string as the nodename field of the
44 * struct returned by uname (indeed, some systems allow a 256-byte host-
45 * name and an 8-byte nodename), but this is true on Linux. The same holds
46 * for setdomainname(2) and the domainname field.
47 */
48
49 /* Uname can fail only if you pass a bad pointer to it. */
50 uname(&uts);
51
52 return xstrndup(!*(uts.nodename) ? "?" : uts.nodename, sizeof(uts.nodename));
53}