1 /* $OpenBSD: inet_ntop.c,v 1.7 2005/08/06 20:30:03 espie 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 <sys/param.h>
20 #include <sys/types.h>
21 #include <sys/socket.h>
22 #include <netinet/in.h>
23 #include <arpa/inet.h>
24 #include "arpa_nameser.h"
25 #include <string.h>
26 #include <errno.h>
27 #include <stdio.h>
28
29 /*
30 * WARNING: Don't even consider trying to compile this on a system where
31 * sizeof(int) < 4. sizeof(int) > 4 is fine; all the world's not a VAX.
32 */
33
34 static const char *inet_ntop4(const u_char *src, char *dst, size_t size);
35 static const char *inet_ntop6(const u_char *src, char *dst, size_t size);
36
37 /* char *
38 * inet_ntop(af, src, dst, size)
39 * convert a network format address to presentation format.
40 * return:
41 * pointer to presentation format address (`dst'), or NULL (see errno).
42 * author:
43 * Paul Vixie, 1996.
44 */
45 const char *
inet_ntop(int af,const void * src,char * dst,size_t size)46 inet_ntop(int af, const void *src, char *dst, size_t size)
47 {
48 switch (af) {
49 case AF_INET:
50 return (inet_ntop4(src, dst, size));
51 case AF_INET6:
52 return (inet_ntop6(src, dst, size));
53 default:
54 errno = EAFNOSUPPORT;
55 return (NULL);
56 }
57 /* NOTREACHED */
58 }
59
60 /* const char *
61 * inet_ntop4(src, dst, size)
62 * format an IPv4 address, more or less like inet_ntoa()
63 * return:
64 * `dst' (as a const)
65 * notes:
66 * (1) uses no statics
67 * (2) takes a u_char* not an in_addr as input
68 * author:
69 * Paul Vixie, 1996.
70 */
71 static const char *
inet_ntop4(const u_char * src,char * dst,size_t size)72 inet_ntop4(const u_char *src, char *dst, size_t size)
73 {
74 static const char fmt[] = "%u.%u.%u.%u";
75 char tmp[sizeof "255.255.255.255"];
76 int l;
77
78 l = snprintf(tmp, size, fmt, src[0], src[1], src[2], src[3]);
79 if (l <= 0 || (size_t)l >= size) {
80 errno = ENOSPC;
81 return (NULL);
82 }
83 strlcpy(dst, tmp, size);
84 return (dst);
85 }
86
87 /* const char *
88 * inet_ntop6(src, dst, size)
89 * convert IPv6 binary address into presentation (printable) format
90 * author:
91 * Paul Vixie, 1996.
92 */
93 static const char *
inet_ntop6(const u_char * src,char * dst,size_t size)94 inet_ntop6(const u_char *src, char *dst, size_t size)
95 {
96 /*
97 * Note that int32_t and int16_t need only be "at least" large enough
98 * to contain a value of the specified size. On some systems, like
99 * Crays, there is no such thing as an integer variable with 16 bits.
100 * Keep this in mind if you think this function should have been coded
101 * to use pointer overlays. All the world's not a VAX.
102 */
103 char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"];
104 char *tp, *ep;
105 struct { int base, len; } best, cur;
106 u_int words[IN6ADDRSZ / INT16SZ];
107 int i;
108 int advance;
109
110 /*
111 * Preprocess:
112 * Copy the input (bytewise) array into a wordwise array.
113 * Find the longest run of 0x00's in src[] for :: shorthanding.
114 */
115 memset(words, '\0', sizeof words);
116 for (i = 0; i < IN6ADDRSZ; i++)
117 words[i / 2] |= (src[i] << ((1 - (i % 2)) << 3));
118 best.base = -1;
119 best.len = 0;
120 cur.base = -1;
121 cur.len = 0;
122 for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++) {
123 if (words[i] == 0) {
124 if (cur.base == -1)
125 cur.base = i, cur.len = 1;
126 else
127 cur.len++;
128 } else {
129 if (cur.base != -1) {
130 if (best.base == -1 || cur.len > best.len)
131 best = cur;
132 cur.base = -1;
133 }
134 }
135 }
136 if (cur.base != -1) {
137 if (best.base == -1 || cur.len > best.len)
138 best = cur;
139 }
140 if (best.base != -1 && best.len < 2)
141 best.base = -1;
142
143 /*
144 * Format the result.
145 */
146 tp = tmp;
147 ep = tmp + sizeof(tmp);
148 for (i = 0; i < (IN6ADDRSZ / INT16SZ) && tp < ep; i++) {
149 /* Are we inside the best run of 0x00's? */
150 if (best.base != -1 && i >= best.base &&
151 i < (best.base + best.len)) {
152 if (i == best.base) {
153 if (tp + 1 >= ep)
154 return (NULL);
155 *tp++ = ':';
156 }
157 continue;
158 }
159 /* Are we following an initial run of 0x00s or any real hex? */
160 if (i != 0) {
161 if (tp + 1 >= ep)
162 return (NULL);
163 *tp++ = ':';
164 }
165 /* Is this address an encapsulated IPv4? */
166 if (i == 6 && best.base == 0 &&
167 (best.len == 6 || (best.len == 5 && words[5] == 0xffff))) {
168 if (!inet_ntop4(src+12, tp, (size_t)(ep - tp)))
169 return (NULL);
170 tp += strlen(tp);
171 break;
172 }
173 advance = snprintf(tp, ep - tp, "%x", words[i]);
174 if (advance <= 0 || advance >= ep - tp)
175 return (NULL);
176 tp += advance;
177 }
178 /* Was it a trailing run of 0x00's? */
179 if (best.base != -1 && (best.base + best.len) == (IN6ADDRSZ / INT16SZ)) {
180 if (tp + 1 >= ep)
181 return (NULL);
182 *tp++ = ':';
183 }
184 if (tp + 1 >= ep)
185 return (NULL);
186 *tp++ = '\0';
187
188 /*
189 * Check for overflow, copy, and we're done.
190 */
191 if ((size_t)(tp - tmp) > size) {
192 errno = ENOSPC;
193 return (NULL);
194 }
195 strlcpy(dst, tmp, size);
196 return (dst);
197 }
198