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
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 (sprintf(tmp, fmt, src[0], src[1], src[2], src[3]) > size) {
108 		errno = ENOSPC;
109 		return (NULL);
110 	}
111 	strcpy(dst, tmp);
112 	return (dst);
113 }
114 
115 /* const char *
116  * inet_ntop6(src, dst, size)
117  *	convert IPv6 binary address into presentation (printable) format
118  * author:
119  *	Paul Vixie, 1996.
120  */
121 static const char *
122 inet_ntop6(src, dst, size)
123 	const u_char *src;
124 	char *dst;
125 	size_t size;
126 {
127 	/*
128 	 * Note that int32_t and int16_t need only be "at least" large enough
129 	 * to contain a value of the specified size.  On some systems, like
130 	 * Crays, there is no such thing as an integer variable with 16 bits.
131 	 * Keep this in mind if you think this function should have been coded
132 	 * to use pointer overlays.  All the world's not a VAX.
133 	 */
134 	char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
135 	struct { int base, len; } best, cur;
136 	u_int words[IN6ADDRSZ / INT16SZ];
137 	int i;
138 
139 	/*
140 	 * Preprocess:
141 	 *	Copy the input (bytewise) array into a wordwise array.
142 	 *	Find the longest run of 0x00's in src[] for :: shorthanding.
143 	 */
144 	memset(words, '\0', sizeof words);
145 	for (i = 0; i < IN6ADDRSZ; i++)
146 		words[i / 2] |= (src[i] << ((1 - (i % 2)) << 3));
147 	best.base = -1;
148 	cur.base = -1;
149 	for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++) {
150 		if (words[i] == 0) {
151 			if (cur.base == -1)
152 				cur.base = i, cur.len = 1;
153 			else
154 				cur.len++;
155 		} else {
156 			if (cur.base != -1) {
157 				if (best.base == -1 || cur.len > best.len)
158 					best = cur;
159 				cur.base = -1;
160 			}
161 		}
162 	}
163 	if (cur.base != -1) {
164 		if (best.base == -1 || cur.len > best.len)
165 			best = cur;
166 	}
167 	if (best.base != -1 && best.len < 2)
168 		best.base = -1;
169 
170 	/*
171 	 * Format the result.
172 	 */
173 	tp = tmp;
174 	for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++) {
175 		/* Are we inside the best run of 0x00's? */
176 		if (best.base != -1 && i >= best.base &&
177 		    i < (best.base + best.len)) {
178 			if (i == best.base)
179 				*tp++ = ':';
180 			continue;
181 		}
182 		/* Are we following an initial run of 0x00s or any real hex? */
183 		if (i != 0)
184 			*tp++ = ':';
185 		/* Is this address an encapsulated IPv4? */
186 		if (i == 6 && best.base == 0 &&
187 		    (best.len == 6 || (best.len == 5 && words[5] == 0xffff))) {
188 			if (!inet_ntop4(src+12, tp, sizeof tmp - (tp - tmp)))
189 				return (NULL);
190 			tp += strlen(tp);
191 			break;
192 		}
193 		tp += sprintf(tp, "%x", words[i]);
194 	}
195 	/* Was it a trailing run of 0x00's? */
196 	if (best.base != -1 && (best.base + best.len) == (IN6ADDRSZ / INT16SZ))
197 		*tp++ = ':';
198 	*tp++ = '\0';
199 
200 	/*
201 	 * Check for overflow, copy, and we're done.
202 	 */
203 	if ((size_t)(tp - tmp) > size) {
204 		errno = ENOSPC;
205 		return (NULL);
206 	}
207 	strcpy(dst, tmp);
208 	return (dst);
209 }
210 
211 #endif /* !HAVE_INET_NTOP */
212