inet_ntop.c revision 270838 
1/*
2 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
3 * Copyright (c) 1996-1999 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 ISC DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
15 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18#if defined(LIBC_SCCS) && !defined(lint)
19static const char rcsid[] = "$Id: inet_ntop.c,v 1.5 2005/11/03 22:59:52 marka Exp $";
20#endif /* LIBC_SCCS and not lint */
21#include <sys/cdefs.h>
22__FBSDID("$FreeBSD: stable/10/lib/libc/inet/inet_ntop.c 270838 2014-08-30 10:16:25Z ume $");
23
24#include "port_before.h"
25
26#include <sys/param.h>
27#include <sys/types.h>
28#include <sys/socket.h>
29
30#include <netinet/in.h>
31#include <arpa/inet.h>
32#include <arpa/nameser.h>
33
34#include <errno.h>
35#include <stdio.h>
36#include <string.h>
37
38#include "port_after.h"
39
40/*%
41 * WARNING: Don't even consider trying to compile this on a system where
42 * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
43 */
44
45static const char *inet_ntop4(const u_char *src, char *dst, socklen_t size);
46static const char *inet_ntop6(const u_char *src, char *dst, socklen_t size);
47
48/* char *
49 * inet_ntop(af, src, dst, size)
50 *	convert a network format address to presentation format.
51 * return:
52 *	pointer to presentation format address (`dst'), or NULL (see errno).
53 * author:
54 *	Paul Vixie, 1996.
55 */
56const char *
57inet_ntop(int af, const void * __restrict src, char * __restrict dst,
58    socklen_t size)
59{
60	switch (af) {
61	case AF_INET:
62		return (inet_ntop4(src, dst, size));
63	case AF_INET6:
64		return (inet_ntop6(src, dst, size));
65	default:
66		errno = EAFNOSUPPORT;
67		return (NULL);
68	}
69	/* NOTREACHED */
70}
71
72/* const char *
73 * inet_ntop4(src, dst, size)
74 *	format an IPv4 address
75 * return:
76 *	`dst' (as a const)
77 * notes:
78 *	(1) uses no statics
79 *	(2) takes a u_char* not an in_addr as input
80 * author:
81 *	Paul Vixie, 1996.
82 */
83static const char *
84inet_ntop4(const u_char *src, char *dst, socklen_t size)
85{
86	static const char fmt[] = "%u.%u.%u.%u";
87	char tmp[sizeof "255.255.255.255"];
88	int l;
89
90	l = snprintf(tmp, sizeof(tmp), fmt, src[0], src[1], src[2], src[3]);
91	if (l <= 0 || (socklen_t) l >= size) {
92		errno = ENOSPC;
93		return (NULL);
94	}
95	strlcpy(dst, tmp, size);
96	return (dst);
97}
98
99/* const char *
100 * inet_ntop6(src, dst, size)
101 *	convert IPv6 binary address into presentation (printable) format
102 * author:
103 *	Paul Vixie, 1996.
104 */
105static const char *
106inet_ntop6(const u_char *src, char *dst, socklen_t size)
107{
108	/*
109	 * Note that int32_t and int16_t need only be "at least" large enough
110	 * to contain a value of the specified size.  On some systems, like
111	 * Crays, there is no such thing as an integer variable with 16 bits.
112	 * Keep this in mind if you think this function should have been coded
113	 * to use pointer overlays.  All the world's not a VAX.
114	 */
115	char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
116	struct { int base, len; } best, cur;
117	u_int words[NS_IN6ADDRSZ / NS_INT16SZ];
118	int i;
119
120	/*
121	 * Preprocess:
122	 *	Copy the input (bytewise) array into a wordwise array.
123	 *	Find the longest run of 0x00's in src[] for :: shorthanding.
124	 */
125	memset(words, '\0', sizeof words);
126	for (i = 0; i < NS_IN6ADDRSZ; i++)
127		words[i / 2] |= (src[i] << ((1 - (i % 2)) << 3));
128	best.base = -1;
129	best.len = 0;
130	cur.base = -1;
131	cur.len = 0;
132	for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
133		if (words[i] == 0) {
134			if (cur.base == -1)
135				cur.base = i, cur.len = 1;
136			else
137				cur.len++;
138		} else {
139			if (cur.base != -1) {
140				if (best.base == -1 || cur.len > best.len)
141					best = cur;
142				cur.base = -1;
143			}
144		}
145	}
146	if (cur.base != -1) {
147		if (best.base == -1 || cur.len > best.len)
148			best = cur;
149	}
150	if (best.base != -1 && best.len < 2)
151		best.base = -1;
152
153	/*
154	 * Format the result.
155	 */
156	tp = tmp;
157	for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
158		/* Are we inside the best run of 0x00's? */
159		if (best.base != -1 && i >= best.base &&
160		    i < (best.base + best.len)) {
161			if (i == best.base)
162				*tp++ = ':';
163			continue;
164		}
165		/* Are we following an initial run of 0x00s or any real hex? */
166		if (i != 0)
167			*tp++ = ':';
168		/* Is this address an encapsulated IPv4? */
169		if (i == 6 && best.base == 0 && (best.len == 6 ||
170		    (best.len == 7 && words[7] != 0x0001) ||
171		    (best.len == 5 && words[5] == 0xffff))) {
172			if (!inet_ntop4(src+12, tp, sizeof tmp - (tp - tmp)))
173				return (NULL);
174			tp += strlen(tp);
175			break;
176		}
177		tp += sprintf(tp, "%x", words[i]);
178	}
179	/* Was it a trailing run of 0x00's? */
180	if (best.base != -1 && (best.base + best.len) ==
181	    (NS_IN6ADDRSZ / NS_INT16SZ))
182		*tp++ = ':';
183	*tp++ = '\0';
184
185	/*
186	 * Check for overflow, copy, and we're done.
187	 */
188	if ((socklen_t)(tp - tmp) > size) {
189		errno = ENOSPC;
190		return (NULL);
191	}
192	strcpy(dst, tmp);
193	return (dst);
194}
195
196/*
197 * Weak aliases for applications that use certain private entry points,
198 * and fail to include <arpa/inet.h>.
199 */
200#undef inet_ntop
201__weak_reference(__inet_ntop, inet_ntop);
202
203/*! \file */
204