inet_ntop.c revision f51d3e87671110c508f0f71d9bcb1bf54c22ca3b 
1/*	$OpenBSD: inet_ntop.c,v 1.10 2014/05/17 18:16:14 tedu 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 <sys/param.h>
20#include <sys/types.h>
21#include <sys/socket.h>
22#include <netinet/in.h>
23#include <arpa/inet.h>
24#include <arpa/nameser.h>
25#include <string.h>
26#include <errno.h>
27#include <stdio.h>
28
29/*
30 * WARNING: Don't even consider trying to compile this on a system where
31 * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
32 */
33
34static const char *inet_ntop4(const u_char *src, char *dst, size_t size);
35static const char *inet_ntop6(const u_char *src, char *dst, size_t size);
36
37/* const char *
38 * inet_ntop(af, src, dst, size)
39 *	convert a network format address to presentation format.
40 * return:
41 *	pointer to presentation format address (`dst'), or NULL (see errno).
42 * author:
43 *	Paul Vixie, 1996.
44 */
45const char *
46inet_ntop(int af, const void *src, char *dst, socklen_t size)
47{
48	switch (af) {
49	case AF_INET:
50		return (inet_ntop4(src, dst, (size_t)size));
51	case AF_INET6:
52		return (inet_ntop6(src, dst, (size_t)size));
53	default:
54		errno = EAFNOSUPPORT;
55		return (NULL);
56	}
57	/* NOTREACHED */
58}
59
60/* const char *
61 * inet_ntop4(src, dst, size)
62 *	format an IPv4 address, more or less like inet_ntoa()
63 * return:
64 *	`dst' (as a const)
65 * notes:
66 *	(1) uses no statics
67 *	(2) takes a u_char* not an in_addr as input
68 * author:
69 *	Paul Vixie, 1996.
70 */
71static const char *
72inet_ntop4(const u_char *src, char *dst, size_t size)
73{
74	char tmp[sizeof "255.255.255.255"];
75	int l;
76
77	l = snprintf(tmp, sizeof(tmp), "%u.%u.%u.%u",
78	    src[0], src[1], src[2], src[3]);
79	if (l <= 0 || l >= size) {
80		errno = ENOSPC;
81		return (NULL);
82	}
83	strlcpy(dst, tmp, size);
84	return (dst);
85}
86
87/* const char *
88 * inet_ntop6(src, dst, size)
89 *	convert IPv6 binary address into presentation (printable) format
90 * author:
91 *	Paul Vixie, 1996.
92 */
93static const char *
94inet_ntop6(const u_char *src, char *dst, size_t size)
95{
96	/*
97	 * Note that int32_t and int16_t need only be "at least" large enough
98	 * to contain a value of the specified size.  On some systems, like
99	 * Crays, there is no such thing as an integer variable with 16 bits.
100	 * Keep this in mind if you think this function should have been coded
101	 * to use pointer overlays.  All the world's not a VAX.
102	 */
103	char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"];
104	char *tp, *ep;
105	struct { int base, len; } best, cur;
106	u_int words[IN6ADDRSZ / INT16SZ];
107	int i;
108	int advance;
109
110	/*
111	 * Preprocess:
112	 *	Copy the input (bytewise) array into a wordwise array.
113	 *	Find the longest run of 0x00's in src[] for :: shorthanding.
114	 */
115	memset(words, '\0', sizeof words);
116	for (i = 0; i < IN6ADDRSZ; i++)
117		words[i / 2] |= (src[i] << ((1 - (i % 2)) << 3));
118	best.base = -1;
119	cur.base = -1;
120	for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++) {
121		if (words[i] == 0) {
122			if (cur.base == -1)
123				cur.base = i, cur.len = 1;
124			else
125				cur.len++;
126		} else {
127			if (cur.base != -1) {
128				if (best.base == -1 || cur.len > best.len)
129					best = cur;
130				cur.base = -1;
131			}
132		}
133	}
134	if (cur.base != -1) {
135		if (best.base == -1 || cur.len > best.len)
136			best = cur;
137	}
138	if (best.base != -1 && best.len < 2)
139		best.base = -1;
140
141	/*
142	 * Format the result.
143	 */
144	tp = tmp;
145	ep = tmp + sizeof(tmp);
146	for (i = 0; i < (IN6ADDRSZ / INT16SZ) && tp < ep; i++) {
147		/* Are we inside the best run of 0x00's? */
148		if (best.base != -1 && i >= best.base &&
149		    i < (best.base + best.len)) {
150			if (i == best.base) {
151				if (tp + 1 >= ep) {
152					errno = ENOSPC;
153					return (NULL);
154				}
155				*tp++ = ':';
156			}
157			continue;
158		}
159		/* Are we following an initial run of 0x00s or any real hex? */
160		if (i != 0) {
161			if (tp + 1 >= ep) {
162				errno = ENOSPC;
163				return (NULL);
164			}
165			*tp++ = ':';
166		}
167		/* Is this address an encapsulated IPv4? */
168		if (i == 6 && best.base == 0 &&
169		    (best.len == 6 || (best.len == 5 && words[5] == 0xffff))) {
170			if (!inet_ntop4(src+12, tp, (size_t)(ep - tp)))
171				return (NULL);
172			tp += strlen(tp);
173			break;
174		}
175		advance = snprintf(tp, ep - tp, "%x", words[i]);
176		if (advance <= 0 || advance >= ep - tp) {
177			errno = ENOSPC;
178			return (NULL);
179		}
180		tp += advance;
181	}
182	/* Was it a trailing run of 0x00's? */
183	if (best.base != -1 && (best.base + best.len) == (IN6ADDRSZ / INT16SZ)) {
184		if (tp + 1 >= ep) {
185			errno = ENOSPC;
186			return (NULL);
187		}
188		*tp++ = ':';
189	}
190	if (tp + 1 >= ep) {
191		errno = ENOSPC;
192		return (NULL);
193	}
194	*tp++ = '\0';
195
196	/*
197	 * Check for overflow, copy, and we're done.
198	 */
199	if ((size_t)(tp - tmp) > size) {
200		errno = ENOSPC;
201		return (NULL);
202	}
203	strlcpy(dst, tmp, size);
204	return (dst);
205}
206