1/*	$OpenBSD: inet_ntop.c,v 1.8 2008/12/09 19:38:38 otto 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/* OPENBSD ORIGINAL: lib/libc/net/inet_ntop.c */
20
21#include "includes.h"
22
23#ifndef HAVE_INET_NTOP
24
25#include <sys/types.h>
26#include <sys/socket.h>
27#include <netinet/in.h>
28#include <arpa/inet.h>
29#include <arpa/nameser.h>
30#include <string.h>
31#include <errno.h>
32#include <stdio.h>
33
34#ifndef IN6ADDRSZ
35#define IN6ADDRSZ   16   /* IPv6 T_AAAA */
36#endif
37
38#ifndef INT16SZ
39#define INT16SZ     2    /* for systems without 16-bit ints */
40#endif
41
42/*
43 * WARNING: Don't even consider trying to compile this on a system where
44 * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
45 */
46
47static const char *inet_ntop4(const u_char *src, char *dst, size_t size);
48static const char *inet_ntop6(const u_char *src, char *dst, size_t size);
49
50/* char *
51 * inet_ntop(af, src, dst, size)
52 *	convert a network format address to presentation format.
53 * return:
54 *	pointer to presentation format address (`dst'), or NULL (see errno).
55 * author:
56 *	Paul Vixie, 1996.
57 */
58const char *
59inet_ntop(int af, const void *src, char *dst, socklen_t size)
60{
61	switch (af) {
62	case AF_INET:
63		return (inet_ntop4(src, dst, (size_t)size));
64	case AF_INET6:
65		return (inet_ntop6(src, dst, (size_t)size));
66	default:
67		errno = EAFNOSUPPORT;
68		return (NULL);
69	}
70	/* NOTREACHED */
71}
72
73/* const char *
74 * inet_ntop4(src, dst, size)
75 *	format an IPv4 address, more or less like inet_ntoa()
76 * return:
77 *	`dst' (as a const)
78 * notes:
79 *	(1) uses no statics
80 *	(2) takes a u_char* not an in_addr as input
81 * author:
82 *	Paul Vixie, 1996.
83 */
84static const char *
85inet_ntop4(const u_char *src, char *dst, size_t size)
86{
87	static const char fmt[] = "%u.%u.%u.%u";
88	char tmp[sizeof "255.255.255.255"];
89	int l;
90
91	l = snprintf(tmp, size, fmt, src[0], src[1], src[2], src[3]);
92	if (l <= 0 || l >= size) {
93		errno = ENOSPC;
94		return (NULL);
95	}
96	strlcpy(dst, tmp, size);
97	return (dst);
98}
99
100/* const char *
101 * inet_ntop6(src, dst, size)
102 *	convert IPv6 binary address into presentation (printable) format
103 * author:
104 *	Paul Vixie, 1996.
105 */
106static const char *
107inet_ntop6(const u_char *src, char *dst, size_t size)
108{
109	/*
110	 * Note that int32_t and int16_t need only be "at least" large enough
111	 * to contain a value of the specified size.  On some systems, like
112	 * Crays, there is no such thing as an integer variable with 16 bits.
113	 * Keep this in mind if you think this function should have been coded
114	 * to use pointer overlays.  All the world's not a VAX.
115	 */
116	char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"];
117	char *tp, *ep;
118	struct { int base, len; } best, cur;
119	u_int words[IN6ADDRSZ / INT16SZ];
120	int i;
121	int advance;
122
123	/*
124	 * Preprocess:
125	 *	Copy the input (bytewise) array into a wordwise array.
126	 *	Find the longest run of 0x00's in src[] for :: shorthanding.
127	 */
128	memset(words, '\0', sizeof words);
129	for (i = 0; i < IN6ADDRSZ; i++)
130		words[i / 2] |= (src[i] << ((1 - (i % 2)) << 3));
131	best.base = -1;
132	cur.base = -1;
133	for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++) {
134		if (words[i] == 0) {
135			if (cur.base == -1)
136				cur.base = i, cur.len = 1;
137			else
138				cur.len++;
139		} else {
140			if (cur.base != -1) {
141				if (best.base == -1 || cur.len > best.len)
142					best = cur;
143				cur.base = -1;
144			}
145		}
146	}
147	if (cur.base != -1) {
148		if (best.base == -1 || cur.len > best.len)
149			best = cur;
150	}
151	if (best.base != -1 && best.len < 2)
152		best.base = -1;
153
154	/*
155	 * Format the result.
156	 */
157	tp = tmp;
158	ep = tmp + sizeof(tmp);
159	for (i = 0; i < (IN6ADDRSZ / INT16SZ) && tp < ep; i++) {
160		/* Are we inside the best run of 0x00's? */
161		if (best.base != -1 && i >= best.base &&
162		    i < (best.base + best.len)) {
163			if (i == best.base) {
164				if (tp + 1 >= ep)
165					return (NULL);
166				*tp++ = ':';
167			}
168			continue;
169		}
170		/* Are we following an initial run of 0x00s or any real hex? */
171		if (i != 0) {
172			if (tp + 1 >= ep)
173				return (NULL);
174			*tp++ = ':';
175		}
176		/* Is this address an encapsulated IPv4? */
177		if (i == 6 && best.base == 0 &&
178		    (best.len == 6 || (best.len == 5 && words[5] == 0xffff))) {
179			if (!inet_ntop4(src+12, tp, (size_t)(ep - tp)))
180				return (NULL);
181			tp += strlen(tp);
182			break;
183		}
184		advance = snprintf(tp, ep - tp, "%x", words[i]);
185		if (advance <= 0 || advance >= ep - tp)
186			return (NULL);
187		tp += advance;
188	}
189	/* Was it a trailing run of 0x00's? */
190	if (best.base != -1 && (best.base + best.len) == (IN6ADDRSZ / INT16SZ)) {
191		if (tp + 1 >= ep)
192			return (NULL);
193		*tp++ = ':';
194	}
195	if (tp + 1 >= ep)
196		return (NULL);
197	*tp++ = '\0';
198
199	/*
200	 * Check for overflow, copy, and we're done.
201	 */
202	if ((size_t)(tp - tmp) > size) {
203		errno = ENOSPC;
204		return (NULL);
205	}
206	strlcpy(dst, tmp, size);
207	return (dst);
208}
209
210#endif /* !HAVE_INET_NTOP */
211