1/* 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* FAST_FUNC 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	return xstrndup(!uts.nodename[0] ? "?" : uts.nodename, sizeof(uts.nodename));
52}
53
54/*
55 * On success return the current malloced and NUL terminated domainname.
56 * On error return malloced and NUL terminated string "?".
57 * This is an illegal first character for a domainname.
58 * The returned malloced string must be freed by the caller.
59 */
60char* FAST_FUNC safe_getdomainname(void)
61{
62#if defined(__linux__)
63/* The field domainname of struct utsname is Linux specific. */
64	struct utsname uts;
65	uname(&uts);
66	return xstrndup(!uts.domainname[0] ? "?" : uts.domainname, sizeof(uts.domainname));
67#else
68	/* We really don't care about people with domain names wider than most screens */
69	char buf[256];
70	int r = getdomainname(buf, sizeof(buf));
71	buf[sizeof(buf)-1] = '\0';
72	return xstrdup(r < 0 ? "?" : buf);
73#endif
74}
75