busybox/libbb/safe_gethostname.c

/* vi: set sw=4 ts=4: */
/*
 * Safe gethostname implementation for busybox
 *
 * Copyright (C) 2008 Tito Ragusa <farmatito@tiscali.it>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 */

/*
 * SUSv2 guarantees that "Host names are limited to 255 bytes"
 * POSIX.1-2001 guarantees that "Host names (not including the terminating
 * null byte) are limited to HOST_NAME_MAX bytes" (64 bytes on my box).
 *
 * RFC1123 says:
 *
 * The syntax of a legal Internet host name was specified in RFC-952
 * [DNS:4].  One aspect of host name syntax is hereby changed: the
 * restriction on the first character is relaxed to allow either a
 * letter or a digit.  Host software MUST support this more liberal
 * syntax.
 *
 * Host software MUST handle host names of up to 63 characters and
 * SHOULD handle host names of up to 255 characters.
 */

#include "libbb.h"
#include <sys/utsname.h>

/*
 * On success return the current malloced and NUL terminated hostname.
 * On error return malloced and NUL terminated string "?".
 * This is an illegal first character for a hostname.
 * The returned malloced string must be freed by the caller.
 */
char* FAST_FUNC safe_gethostname(void)
{
	struct utsname uts;

	/* The length of the arrays in a struct utsname is unspecified;
	 * the fields are terminated by a null byte.
	 * Note that there is no standard that says that the hostname
	 * set by sethostname(2) is the same string as the nodename field of the
	 * struct returned by uname (indeed, some systems allow a 256-byte host-
	 * name and an 8-byte nodename), but this is true on Linux. The same holds
	 * for setdomainname(2) and the domainname field.
	 */

	/* Uname can fail only if you pass a bad pointer to it. */
	uname(&uts);
	return xstrndup(!uts.nodename[0] ? "?" : uts.nodename, sizeof(uts.nodename));
}

/*
 * On success return the current malloced and NUL terminated domainname.
 * On error return malloced and NUL terminated string "?".
 * This is an illegal first character for a domainname.
 * The returned malloced string must be freed by the caller.
 */
char* FAST_FUNC safe_getdomainname(void)
{
#if defined(__linux__)
/* The field domainname of struct utsname is Linux specific. */
	struct utsname uts;
	uname(&uts);
	return xstrndup(!uts.domainname[0] ? "?" : uts.domainname, sizeof(uts.domainname));
#else
	/* We really don't care about people with domain names wider than most screens */
	char buf[256];
	int r = getdomainname(buf, sizeof(buf));
	buf[sizeof(buf)-1] = '\0';
	return xstrdup(r < 0 ? "?" : buf);
#endif
}
1	niro	816	/* 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			*/
36			char* 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			*/
60			char* FAST_FUNC safe_getdomainname(void)
61			{
62	niro	1123	#if defined(__linux__)
63			/* The field domainname of struct utsname is Linux specific. */
64	niro	816	struct utsname uts;
65			uname(&uts);
66			return xstrndup(!uts.domainname[0] ? "?" : uts.domainname, sizeof(uts.domainname));
67	niro	1123	#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	niro	816	}