1/*	$NetBSD: inet_ntop.c,v 1.9 2012/03/20 17:08:13 matt Exp $	*/
2
3/*
4 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
5 * Copyright (c) 1996-1999 by Internet Software Consortium.
6 *
7 * Permission to use, copy, modify, and distribute this software for any
8 * purpose with or without fee is hereby granted, provided that the above
9 * copyright notice and this permission notice appear in all copies.
10 *
11 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
12 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
13 * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
14 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
15 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
16 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
17 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
18 */
19
20#include <sys/cdefs.h>
21#if defined(LIBC_SCCS) && !defined(lint)
22#if 0
23static const char rcsid[] = "Id: inet_ntop.c,v 1.5 2005/11/03 22:59:52 marka Exp";
24#else
25__RCSID("$NetBSD: inet_ntop.c,v 1.9 2012/03/20 17:08:13 matt Exp $");
26#endif
27#endif /* LIBC_SCCS and not lint */
28
29#include "port_before.h"
30
31#include "namespace.h"
32#include <sys/param.h>
33#include <sys/types.h>
34#include <sys/socket.h>
35
36#include <netinet/in.h>
37#include <arpa/inet.h>
38#include <arpa/nameser.h>
39
40#include <assert.h>
41#include <errno.h>
42#include <stdio.h>
43#include <stdlib.h>
44#include <string.h>
45
46#include "port_after.h"
47
48#ifdef __weak_alias
49__weak_alias(inet_ntop,_inet_ntop)
50#endif
51
52/*%
53 * WARNING: Don't even consider trying to compile this on a system where
54 * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
55 */
56
57static const char *inet_ntop4(const u_char *src, char *dst, socklen_t size);
58static const char *inet_ntop6(const u_char *src, char *dst, socklen_t size);
59
60/* char *
61 * inet_ntop(af, src, dst, size)
62 *	convert a network format address to presentation format.
63 * return:
64 *	pointer to presentation format address (`dst'), or NULL (see errno).
65 * author:
66 *	Paul Vixie, 1996.
67 */
68const char *
69inet_ntop(int af, const void *src, char *dst, socklen_t size)
70{
71
72	_DIAGASSERT(src != NULL);
73	_DIAGASSERT(dst != NULL);
74
75	switch (af) {
76	case AF_INET:
77		return (inet_ntop4(src, dst, size));
78	case AF_INET6:
79		return (inet_ntop6(src, dst, size));
80	default:
81		errno = EAFNOSUPPORT;
82		return (NULL);
83	}
84	/* NOTREACHED */
85}
86
87/* const char *
88 * inet_ntop4(src, dst, size)
89 *	format an IPv4 address, more or less like inet_ntoa()
90 * return:
91 *	`dst' (as a const)
92 * notes:
93 *	(1) uses no statics
94 *	(2) takes a u_char* not an in_addr as input
95 * author:
96 *	Paul Vixie, 1996.
97 */
98static const char *
99inet_ntop4(const u_char *src, char *dst, socklen_t size)
100{
101	char tmp[sizeof "255.255.255.255"];
102	int l;
103
104	_DIAGASSERT(src != NULL);
105	_DIAGASSERT(dst != NULL);
106
107	l = snprintf(tmp, sizeof(tmp), "%u.%u.%u.%u",
108	    src[0], src[1], src[2], src[3]);
109	if (l <= 0 || (socklen_t) l >= size) {
110		errno = ENOSPC;
111		return (NULL);
112	}
113	strlcpy(dst, tmp, size);
114	return (dst);
115}
116
117/* const char *
118 * inet_ntop6(src, dst, size)
119 *	convert IPv6 binary address into presentation (printable) format
120 * author:
121 *	Paul Vixie, 1996.
122 */
123static const char *
124inet_ntop6(const u_char *src, char *dst, socklen_t size)
125{
126	/*
127	 * Note that int32_t and int16_t need only be "at least" large enough
128	 * to contain a value of the specified size.  On some systems, like
129	 * Crays, there is no such thing as an integer variable with 16 bits.
130	 * Keep this in mind if you think this function should have been coded
131	 * to use pointer overlays.  All the world's not a VAX.
132	 */
133	char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"];
134	char *tp, *ep;
135	struct { int base, len; } best, cur;
136	u_int words[NS_IN6ADDRSZ / NS_INT16SZ];
137	int i;
138	int advance;
139
140	_DIAGASSERT(src != NULL);
141	_DIAGASSERT(dst != NULL);
142
143	/*
144	 * Preprocess:
145	 *	Copy the input (bytewise) array into a wordwise array.
146	 *	Find the longest run of 0x00's in src[] for :: shorthanding.
147	 */
148	memset(words, '\0', sizeof words);
149	for (i = 0; i < NS_IN6ADDRSZ; i++)
150		words[i / 2] |= (src[i] << ((1 - (i % 2)) << 3));
151	best.base = -1;
152	best.len = 0;
153	cur.base = -1;
154	cur.len = 0;
155	for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
156		if (words[i] == 0) {
157			if (cur.base == -1)
158				cur.base = i, cur.len = 1;
159			else
160				cur.len++;
161		} else {
162			if (cur.base != -1) {
163				if (best.base == -1 || cur.len > best.len)
164					best = cur;
165				cur.base = -1;
166			}
167		}
168	}
169	if (cur.base != -1) {
170		if (best.base == -1 || cur.len > best.len)
171			best = cur;
172	}
173	if (best.base != -1 && best.len < 2)
174		best.base = -1;
175
176	/*
177	 * Format the result.
178	 */
179	tp = tmp;
180	ep = tmp + sizeof(tmp);
181	for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
182		/* Are we inside the best run of 0x00's? */
183		if (best.base != -1 && i >= best.base &&
184		    i < (best.base + best.len)) {
185			if (i == best.base)
186				*tp++ = ':';
187			continue;
188		}
189		/* Are we following an initial run of 0x00s or any real hex? */
190		if (i != 0) {
191			if (tp + 1 >= ep)
192				return (NULL);
193			*tp++ = ':';
194		}
195		/* Is this address an encapsulated IPv4? */
196		if (i == 6 && best.base == 0 &&
197		    (best.len == 6 ||
198		    (best.len == 7 && words[7] != 0x0001) ||
199		    (best.len == 5 && words[5] == 0xffff))) {
200			if (!inet_ntop4(src+12, tp, (socklen_t)(ep - tp)))
201				return (NULL);
202			tp += strlen(tp);
203			break;
204		}
205		advance = snprintf(tp, (size_t)(ep - tp), "%x", words[i]);
206		if (advance <= 0 || advance >= ep - tp)
207			return (NULL);
208		tp += advance;
209	}
210	/* Was it a trailing run of 0x00's? */
211	if (best.base != -1 && (best.base + best.len) ==
212	    (NS_IN6ADDRSZ / NS_INT16SZ)) {
213		if (tp + 1 >= ep)
214			return (NULL);
215		*tp++ = ':';
216	}
217	if (tp + 1 >= ep)
218		return (NULL);
219	*tp++ = '\0';
220
221	/*
222	 * Check for overflow, copy, and we're done.
223	 */
224	if ((size_t)(tp - tmp) > size) {
225		errno = ENOSPC;
226		return (NULL);
227	}
228	strlcpy(dst, tmp, size);
229	return (dst);
230}
231
232/*! \file */
233