1 /*	$OpenBSD: inet_ntop.c,v 1.8 2008/12/09 19:38:38 otto 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 /* OPENBSD ORIGINAL: lib/libc/net/inet_ntop.c */
20 
21 #include "includes.h"
22 
23 #ifndef HAVE_INET_NTOP
24 
25 #include <sys/param.h>
26 #include <sys/types.h>
27 #include <sys/socket.h>
28 #include <netinet/in.h>
29 #include <arpa/inet.h>
30 #include <arpa/nameser.h>
31 #include <string.h>
32 #include <errno.h>
33 #include <stdio.h>
34 
35 #ifndef IN6ADDRSZ
36 #define IN6ADDRSZ   16   /* IPv6 T_AAAA */
37 #endif
38 
39 #ifndef INT16SZ
40 #define INT16SZ     2    /* for systems without 16-bit ints */
41 #endif
42 
43 /*
44  * WARNING: Don't even consider trying to compile this on a system where
45  * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
46  */
47 
48 static const char *inet_ntop4(const u_char *src, char *dst, size_t size);
49 static const char *inet_ntop6(const u_char *src, char *dst, size_t size);
50 
51 /* char *
52  * inet_ntop(af, src, dst, size)
53  *	convert a network format address to presentation format.
54  * return:
55  *	pointer to presentation format address (`dst'), or NULL (see errno).
56  * author:
57  *	Paul Vixie, 1996.
58  */
59 const char *
inet_ntop(int af,const void * src,char * dst,socklen_t size)60 inet_ntop(int af, const void *src, char *dst, socklen_t size)
61 {
62 	switch (af) {
63 	case AF_INET:
64 		return (inet_ntop4(src, dst, (size_t)size));
65 	case AF_INET6:
66 		return (inet_ntop6(src, dst, (size_t)size));
67 	default:
68 		errno = EAFNOSUPPORT;
69 		return (NULL);
70 	}
71 	/* NOTREACHED */
72 }
73 
74 /* const char *
75  * inet_ntop4(src, dst, size)
76  *	format an IPv4 address, more or less like inet_ntoa()
77  * return:
78  *	`dst' (as a const)
79  * notes:
80  *	(1) uses no statics
81  *	(2) takes a u_char* not an in_addr as input
82  * author:
83  *	Paul Vixie, 1996.
84  */
85 static const char *
inet_ntop4(const u_char * src,char * dst,size_t size)86 inet_ntop4(const u_char *src, char *dst, size_t size)
87 {
88 	static const char fmt[] = "%u.%u.%u.%u";
89 	char tmp[sizeof "255.255.255.255"];
90 	int l;
91 
92 	l = snprintf(tmp, size, fmt, src[0], src[1], src[2], src[3]);
93 	if (l <= 0 || l >= size) {
94 		errno = ENOSPC;
95 		return (NULL);
96 	}
97 	strlcpy(dst, tmp, size);
98 	return (dst);
99 }
100 
101 /* const char *
102  * inet_ntop6(src, dst, size)
103  *	convert IPv6 binary address into presentation (printable) format
104  * author:
105  *	Paul Vixie, 1996.
106  */
107 static const char *
inet_ntop6(const u_char * src,char * dst,size_t size)108 inet_ntop6(const u_char *src, char *dst, size_t size)
109 {
110 	/*
111 	 * Note that int32_t and int16_t need only be "at least" large enough
112 	 * to contain a value of the specified size.  On some systems, like
113 	 * Crays, there is no such thing as an integer variable with 16 bits.
114 	 * Keep this in mind if you think this function should have been coded
115 	 * to use pointer overlays.  All the world's not a VAX.
116 	 */
117 	char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"];
118 	char *tp, *ep;
119 	struct { int base, len; } best, cur;
120 	u_int words[IN6ADDRSZ / INT16SZ];
121 	int i;
122 	int advance;
123 
124 	/*
125 	 * Preprocess:
126 	 *	Copy the input (bytewise) array into a wordwise array.
127 	 *	Find the longest run of 0x00's in src[] for :: shorthanding.
128 	 */
129 	memset(words, '\0', sizeof words);
130 	for (i = 0; i < IN6ADDRSZ; i++)
131 		words[i / 2] |= (src[i] << ((1 - (i % 2)) << 3));
132 	best.base = -1;
133 	cur.base = -1;
134 	for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++) {
135 		if (words[i] == 0) {
136 			if (cur.base == -1)
137 				cur.base = i, cur.len = 1;
138 			else
139 				cur.len++;
140 		} else {
141 			if (cur.base != -1) {
142 				if (best.base == -1 || cur.len > best.len)
143 					best = cur;
144 				cur.base = -1;
145 			}
146 		}
147 	}
148 	if (cur.base != -1) {
149 		if (best.base == -1 || cur.len > best.len)
150 			best = cur;
151 	}
152 	if (best.base != -1 && best.len < 2)
153 		best.base = -1;
154 
155 	/*
156 	 * Format the result.
157 	 */
158 	tp = tmp;
159 	ep = tmp + sizeof(tmp);
160 	for (i = 0; i < (IN6ADDRSZ / INT16SZ) && tp < ep; i++) {
161 		/* Are we inside the best run of 0x00's? */
162 		if (best.base != -1 && i >= best.base &&
163 		    i < (best.base + best.len)) {
164 			if (i == best.base) {
165 				if (tp + 1 >= ep)
166 					return (NULL);
167 				*tp++ = ':';
168 			}
169 			continue;
170 		}
171 		/* Are we following an initial run of 0x00s or any real hex? */
172 		if (i != 0) {
173 			if (tp + 1 >= ep)
174 				return (NULL);
175 			*tp++ = ':';
176 		}
177 		/* Is this address an encapsulated IPv4? */
178 		if (i == 6 && best.base == 0 &&
179 		    (best.len == 6 || (best.len == 5 && words[5] == 0xffff))) {
180 			if (!inet_ntop4(src+12, tp, (size_t)(ep - tp)))
181 				return (NULL);
182 			tp += strlen(tp);
183 			break;
184 		}
185 		advance = snprintf(tp, ep - tp, "%x", words[i]);
186 		if (advance <= 0 || advance >= ep - tp)
187 			return (NULL);
188 		tp += advance;
189 	}
190 	/* Was it a trailing run of 0x00's? */
191 	if (best.base != -1 && (best.base + best.len) == (IN6ADDRSZ / INT16SZ)) {
192 		if (tp + 1 >= ep)
193 			return (NULL);
194 		*tp++ = ':';
195 	}
196 	if (tp + 1 >= ep)
197 		return (NULL);
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 	strlcpy(dst, tmp, size);
208 	return (dst);
209 }
210 
211 #endif /* !HAVE_INET_NTOP */
212