inet_ntop.c revision 98937 
1/*	$OpenBSD: inet_ntop.c,v 1.1 1997/03/13 19:07:32 downsj Exp $	*/
2
3/* Copyright (c) 1996 by Internet Software Consortium.
4 *
5 * Permission to use, copy, modify, and 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 INTERNET SOFTWARE CONSORTIUM DISCLAIMS
10 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
11 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
12 * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
13 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
14 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
15 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
16 * SOFTWARE.
17 */
18
19#include "config.h"
20
21#ifndef HAVE_INET_NTOP
22
23#if defined(LIBC_SCCS) && !defined(lint)
24#if 0
25static char rcsid[] = "$From: inet_ntop.c,v 8.7 1996/08/05 08:41:18 vixie Exp $";
26#else
27static char rcsid[] = "$OpenBSD: inet_ntop.c,v 1.1 1997/03/13 19:07:32 downsj Exp $";
28#endif
29#endif /* LIBC_SCCS and not lint */
30
31#include <sys/param.h>
32#include <sys/types.h>
33#include <sys/socket.h>
34#include "openbsd-compat/fake-socket.h"
35#include <netinet/in.h>
36#include <arpa/inet.h>
37#ifndef HAVE_CYGWIN
38#include <arpa/nameser.h>
39#endif
40#include <string.h>
41#include <errno.h>
42#include <stdio.h>
43
44#ifndef IN6ADDRSZ
45#define IN6ADDRSZ   16   /* IPv6 T_AAAA */
46#endif
47
48#ifndef INT16SZ
49#define INT16SZ     2    /* for systems without 16-bit ints */
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 __P((const u_char *src, char *dst, size_t size));
58static const char *inet_ntop6 __P((const u_char *src, char *dst, size_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(af, src, dst, size)
70	int af;
71	const void *src;
72	char *dst;
73	size_t size;
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(src, dst, size)
100	const u_char *src;
101	char *dst;
102	size_t size;
103{
104	static const char fmt[] = "%u.%u.%u.%u";
105	char tmp[sizeof "255.255.255.255"];
106
107	if (snprintf(tmp, sizeof(tmp), fmt, src[0], src[1], src[2],
108	    src[3]) > size) {
109		errno = ENOSPC;
110		return (NULL);
111	}
112	strcpy(dst, tmp);
113	return (dst);
114}
115
116/* const char *
117 * inet_ntop6(src, dst, size)
118 *	convert IPv6 binary address into presentation (printable) format
119 * author:
120 *	Paul Vixie, 1996.
121 */
122static const char *
123inet_ntop6(src, dst, size)
124	const u_char *src;
125	char *dst;
126	size_t size;
127{
128	/*
129	 * Note that int32_t and int16_t need only be "at least" large enough
130	 * to contain a value of the specified size.  On some systems, like
131	 * Crays, there is no such thing as an integer variable with 16 bits.
132	 * Keep this in mind if you think this function should have been coded
133	 * to use pointer overlays.  All the world's not a VAX.
134	 */
135	char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
136	struct { int base, len; } best, cur;
137	u_int words[IN6ADDRSZ / INT16SZ];
138	int i;
139
140	/*
141	 * Preprocess:
142	 *	Copy the input (bytewise) array into a wordwise array.
143	 *	Find the longest run of 0x00's in src[] for :: shorthanding.
144	 */
145	memset(words, '\0', sizeof words);
146	for (i = 0; i < IN6ADDRSZ; i++)
147		words[i / 2] |= (src[i] << ((1 - (i % 2)) << 3));
148	best.base = -1;
149	cur.base = -1;
150	for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++) {
151		if (words[i] == 0) {
152			if (cur.base == -1)
153				cur.base = i, cur.len = 1;
154			else
155				cur.len++;
156		} else {
157			if (cur.base != -1) {
158				if (best.base == -1 || cur.len > best.len)
159					best = cur;
160				cur.base = -1;
161			}
162		}
163	}
164	if (cur.base != -1) {
165		if (best.base == -1 || cur.len > best.len)
166			best = cur;
167	}
168	if (best.base != -1 && best.len < 2)
169		best.base = -1;
170
171	/*
172	 * Format the result.
173	 */
174	tp = tmp;
175	for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++) {
176		/* Are we inside the best run of 0x00's? */
177		if (best.base != -1 && i >= best.base &&
178		    i < (best.base + best.len)) {
179			if (i == best.base)
180				*tp++ = ':';
181			continue;
182		}
183		/* Are we following an initial run of 0x00s or any real hex? */
184		if (i != 0)
185			*tp++ = ':';
186		/* Is this address an encapsulated IPv4? */
187		if (i == 6 && best.base == 0 &&
188		    (best.len == 6 || (best.len == 5 && words[5] == 0xffff))) {
189			if (!inet_ntop4(src+12, tp, sizeof tmp - (tp - tmp)))
190				return (NULL);
191			tp += strlen(tp);
192			break;
193		}
194		snprintf(tp, sizeof(tmp - (tp - tmp)), "%x", words[i]);
195		tp += strlen(tp);
196	}
197	/* Was it a trailing run of 0x00's? */
198	if (best.base != -1 && (best.base + best.len) == (IN6ADDRSZ / INT16SZ))
199		*tp++ = ':';
200	*tp++ = '\0';
201
202	/*
203	 * Check for overflow, copy, and we're done.
204	 */
205	if ((size_t)(tp - tmp) > size) {
206		errno = ENOSPC;
207		return (NULL);
208	}
209	strcpy(dst, tmp);
210	return (dst);
211}
212
213#endif /* !HAVE_INET_NTOP */
214