inet_ntop.c revision 290001 
1/*
2 * Copyright (C) 2004, 2005, 2007, 2009  Internet Systems Consortium, Inc. ("ISC")
3 * Copyright (C) 1996-2001  Internet Software Consortium.
4 *
5 * Permission to use, copy, modify, and/or distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
10 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
11 * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
12 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
13 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
14 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
15 * PERFORMANCE OF THIS SOFTWARE.
16 */
17
18/*! \file */
19
20#if defined(LIBC_SCCS) && !defined(lint)
21static char rcsid[] =
22	"$Id: inet_ntop.c,v 1.21 2009/07/17 23:47:41 tbox Exp $";
23#endif /* LIBC_SCCS and not lint */
24
25#include <config.h>
26
27#include <errno.h>
28#include <stdio.h>
29#include <string.h>
30
31#include <isc/net.h>
32#include <isc/print.h>
33
34#define NS_INT16SZ	 2
35#define NS_IN6ADDRSZ	16
36
37/*
38 * WARNING: Don't even consider trying to compile this on a system where
39 * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
40 */
41
42static const char *inet_ntop4(const unsigned char *src, char *dst,
43			      size_t size);
44
45#ifdef AF_INET6
46static const char *inet_ntop6(const unsigned char *src, char *dst,
47			      size_t size);
48#endif
49const char *isc_net_ntop(int af, const void *src, char *dst, size_t size);
50
51/*! char *
52 * isc_net_ntop(af, src, dst, size)
53 *	convert a network format address to presentation format.
54 * \return
55 *	pointer to presentation format address (`dst'), or NULL (see errno).
56 * \author
57 *	Paul Vixie, 1996.
58 */
59const char *
60isc_net_ntop(int af, const void *src, char *dst, size_t size)
61{
62	switch (af) {
63	case AF_INET:
64		return (inet_ntop4(src, dst, size));
65#ifdef AF_INET6
66	case AF_INET6:
67		return (inet_ntop6(src, dst, size));
68#endif
69	default:
70		errno = EAFNOSUPPORT;
71		return (NULL);
72	}
73	/* NOTREACHED */
74}
75
76/*! const char *
77 * inet_ntop4(src, dst, size)
78 *	format an IPv4 address
79 * \return
80 *	`dst' (as a const)
81 * \note
82 *	(1) uses no statics
83 * \note
84 *	(2) takes a unsigned char* not an in_addr as input
85 * \author
86 *	Paul Vixie, 1996.
87 */
88static const char *
89inet_ntop4(const unsigned char *src, char *dst, size_t size)
90{
91	static const char *fmt = "%u.%u.%u.%u";
92	char tmp[sizeof("255.255.255.255")];
93	int len;
94
95	len = snprintf(tmp, sizeof(tmp), fmt, src[0], src[1], src[2], src[3]);
96	if (len < 0 || (size_t)len >= size)
97	{
98		errno = ENOSPC;
99		return (NULL);
100	}
101	memcpy(dst, tmp, 1 + len);
102
103	return (dst);
104}
105
106/*! const char *
107 * isc_inet_ntop6(src, dst, size)
108 *	convert IPv6 binary address into presentation (printable) format
109 * \author
110 *	Paul Vixie, 1996.
111 */
112#ifdef AF_INET6
113static const char *
114inet_ntop6(const unsigned char *src, char *dst, size_t size)
115{
116	/*
117	 * Note that int32_t and int16_t need only be "at least" large enough
118	 * to contain a value of the specified size.  On some systems, like
119	 * Crays, there is no such thing as an integer variable with 16 bits.
120	 * Keep this in mind if you think this function should have been coded
121	 * to use pointer overlays.  All the world's not a VAX.
122	 */
123	char tmp[sizeof("ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255")], *tp;
124	struct { int base, len; } best, cur;
125	unsigned int words[NS_IN6ADDRSZ / NS_INT16SZ];
126	int i;
127
128	/*
129	 * Preprocess:
130	 *	Copy the input (bytewise) array into a wordwise array.
131	 *	Find the longest run of 0x00's in src[] for :: shorthanding.
132	 */
133	memset(words, '\0', sizeof(words));
134	for (i = 0; i < NS_IN6ADDRSZ; i++)
135		words[i / 2] |= (src[i] << ((1 - (i % 2)) << 3));
136	best.base = -1;
137	cur.base = -1;
138	best.len = cur.len = 0;
139	for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
140		if (words[i] == 0) {
141			if (cur.base == -1)
142				cur.base = i, cur.len = 1;
143			else
144				cur.len++;
145		} else {
146			if (cur.base != -1) {
147				if (best.base == -1 || cur.len > best.len)
148					best = cur;
149				cur.base = -1;
150			}
151		}
152	}
153	if (cur.base != -1) {
154		if (best.base == -1 || cur.len > best.len)
155			best = cur;
156	}
157	if (best.base != -1 && best.len < 2)
158		best.base = -1;
159
160	/*
161	 * Format the result.
162	 */
163	tp = tmp;
164	for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
165		/* Are we inside the best run of 0x00's? */
166		if (best.base != -1 && i >= best.base &&
167		    i < (best.base + best.len)) {
168			if (i == best.base)
169				*tp++ = ':';
170			continue;
171		}
172		/* Are we following an initial run of 0x00s or any real hex? */
173		if (i != 0)
174			*tp++ = ':';
175		/* Is this address an encapsulated IPv4? */
176		if (i == 6 && best.base == 0 && (best.len == 6 ||
177		    (best.len == 7 && words[7] != 0x0001) ||
178		    (best.len == 5 && words[5] == 0xffff))) {
179			if (!inet_ntop4(src+12, tp,
180					sizeof(tmp) - (tp - tmp)))
181				return (NULL);
182			tp += strlen(tp);
183			break;
184		}
185		tp += snprintf(tp, sizeof(tmp) - (tp - tmp), "%x", words[i]);
186	}
187	/* Was it a trailing run of 0x00's? */
188	if (best.base != -1 && (best.base + best.len) ==
189	    (NS_IN6ADDRSZ / NS_INT16SZ))
190		*tp++ = ':';
191	*tp++ = '\0';
192
193	/*
194	 * Check for overflow, copy, and we're done.
195	 */
196	if ((size_t)(tp - tmp) > size) {
197		errno = ENOSPC;
198		return (NULL);
199	}
200	memcpy(dst, tmp, (size_t)(tp - tmp));
201	return (dst);
202}
203#endif /* AF_INET6 */
204