1 /*	$OpenBSD: inet_ntop.c,v 1.5 2002/08/23 16:27:31 itojun 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 "includes.h"
20 
21 #ifndef HAVE_INET_NTOP
22 
23 #if defined(LIBC_SCCS) && !defined(lint)
24 #if 0
25 static char rcsid[] = "$From: inet_ntop.c,v 8.7 1996/08/05 08:41:18 vixie Exp $";
26 #else
27 static char rcsid[] = "$OpenBSD: inet_ntop.c,v 1.5 2002/08/23 16:27:31 itojun 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 
57 static const char *inet_ntop4(const u_char *src, char *dst, size_t size);
58 static const char *inet_ntop6(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  */
68 const char *
69 inet_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  */
98 static const char *
99 inet_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 	int l;
107 
108 	l = snprintf(tmp, size, fmt, src[0], src[1], src[2], src[3]);
109 	if (l <= 0 || 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  */
123 static const char *
124 inet_ntop6(src, dst, size)
125 	const u_char *src;
126 	char *dst;
127 	size_t size;
128 {
129 	/*
130 	 * Note that int32_t and int16_t need only be "at least" large enough
131 	 * to contain a value of the specified size.  On some systems, like
132 	 * Crays, there is no such thing as an integer variable with 16 bits.
133 	 * Keep this in mind if you think this function should have been coded
134 	 * to use pointer overlays.  All the world's not a VAX.
135 	 */
136 	char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"];
137 	char *tp, *ep;
138 	struct { int base, len; } best, cur;
139 	u_int words[IN6ADDRSZ / INT16SZ];
140 	int i;
141 	int advance;
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 < IN6ADDRSZ; i++)
150 		words[i / 2] |= (src[i] << ((1 - (i % 2)) << 3));
151 	best.base = -1;
152 	cur.base = -1;
153 	for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++) {
154 		if (words[i] == 0) {
155 			if (cur.base == -1)
156 				cur.base = i, cur.len = 1;
157 			else
158 				cur.len++;
159 		} else {
160 			if (cur.base != -1) {
161 				if (best.base == -1 || cur.len > best.len)
162 					best = cur;
163 				cur.base = -1;
164 			}
165 		}
166 	}
167 	if (cur.base != -1) {
168 		if (best.base == -1 || cur.len > best.len)
169 			best = cur;
170 	}
171 	if (best.base != -1 && best.len < 2)
172 		best.base = -1;
173 
174 	/*
175 	 * Format the result.
176 	 */
177 	tp = tmp;
178 	ep = tmp + sizeof(tmp);
179 	for (i = 0; i < (IN6ADDRSZ / INT16SZ) && tp < ep; i++) {
180 		/* Are we inside the best run of 0x00's? */
181 		if (best.base != -1 && i >= best.base &&
182 		    i < (best.base + best.len)) {
183 			if (i == best.base) {
184 				if (tp + 1 >= ep)
185 					return (NULL);
186 				*tp++ = ':';
187 			}
188 			continue;
189 		}
190 		/* Are we following an initial run of 0x00s or any real hex? */
191 		if (i != 0) {
192 			if (tp + 1 >= ep)
193 				return (NULL);
194 			*tp++ = ':';
195 		}
196 		/* Is this address an encapsulated IPv4? */
197 		if (i == 6 && best.base == 0 &&
198 		    (best.len == 6 || (best.len == 5 && words[5] == 0xffff))) {
199 			if (!inet_ntop4(src+12, tp, (size_t)(ep - tp)))
200 				return (NULL);
201 			tp += strlen(tp);
202 			break;
203 		}
204 		advance = snprintf(tp, ep - tp, "%x", words[i]);
205 		if (advance <= 0 || advance >= ep - tp)
206 			return (NULL);
207 		tp += advance;
208 	}
209 	/* Was it a trailing run of 0x00's? */
210 	if (best.base != -1 && (best.base + best.len) == (IN6ADDRSZ / INT16SZ)) {
211 		if (tp + 1 >= ep)
212 			return (NULL);
213 		*tp++ = ':';
214 	}
215 	if (tp + 1 >= ep)
216 		return (NULL);
217 	*tp++ = '\0';
218 
219 	/*
220 	 * Check for overflow, copy, and we're done.
221 	 */
222 	if ((size_t)(tp - tmp) > size) {
223 		errno = ENOSPC;
224 		return (NULL);
225 	}
226 	strlcpy(dst, tmp, size);
227 	return (dst);
228 }
229 
230 #endif /* !HAVE_INET_NTOP */
231