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