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 "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 1.1 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 
57 static const char *inet_ntop4 __P((const u_char *src, char *dst, size_t size));
58 static 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  */
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 
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  */
122 static const char *
123 inet_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