inet_ntop.c

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/*
 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
 * Copyright (c) 1996-1999 by Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static const char rcsid[] = "$Id: inet_ntop.c,v 1.3.18.2 2005/11/03 23:02:22 marka Exp $";
#endif /* LIBC_SCCS and not lint */
#include <sys/cdefs.h>
__FBSDID("$BSDSUniX$");

#include <sys/param.h>
#include <sys/socket.h>
#include <sys/systm.h>

#include <netinet/in.h>

/*%
 * WARNING: Don't even consider trying to compile this on a system where
 * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
 */

static char     *inet_ntop4(const u_char *src, char *dst, socklen_t size);
static char     *inet_ntop6(const u_char *src, char *dst, socklen_t size);

/* char *
 * inet_ntop(af, src, dst, size)
 *      convert a network format address to presentation format.
 * return:
 *      pointer to presentation format address (`dst'), or NULL (see errno).
 * author:
 *      Paul Vixie, 1996.
 */
char *
inet_ntop(int af, const void *src, char *dst, socklen_t size)
{
        switch (af) {
        case AF_INET:
                return (inet_ntop4(src, dst, size));
        case AF_INET6:
                return (inet_ntop6(src, dst, size));
        default:
                return (NULL);
        }
        /* NOTREACHED */
}

/* const char *
 * inet_ntop4(src, dst, size)
 *      format an IPv4 address
 * return:
 *      `dst' (as a const)
 * notes:
 *      (1) uses no statics
 *      (2) takes a u_char* not an in_addr as input
 * author:
 *      Paul Vixie, 1996.
 */
static char *
inet_ntop4(const u_char *src, char *dst, socklen_t size)
{
        static const char fmt[] = "%u.%u.%u.%u";
        char tmp[sizeof "255.255.255.255"];
        int l;

        l = snprintf(tmp, sizeof(tmp), fmt, src[0], src[1], src[2], src[3]);
        if (l <= 0 || (socklen_t) l >= size) {
                return (NULL);
        }
        strlcpy(dst, tmp, size);
        return (dst);
}

/* const char *
 * inet_ntop6(src, dst, size)
 *      convert IPv6 binary address into presentation (printable) format
 * author:
 *      Paul Vixie, 1996.
 */
static char *
inet_ntop6(const u_char *src, char *dst, socklen_t size)
{
        /*
         * Note that int32_t and int16_t need only be "at least" large enough
         * to contain a value of the specified size.  On some systems, like
         * Crays, there is no such thing as an integer variable with 16 bits.
         * Keep this in mind if you think this function should have been coded
         * to use pointer overlays.  All the world's not a VAX.
         */
        char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
        struct { int base, len; } best, cur;
#define NS_IN6ADDRSZ    16
#define NS_INT16SZ      2
        u_int words[NS_IN6ADDRSZ / NS_INT16SZ];
        int i;

        /*
         * Preprocess:
         *      Copy the input (bytewise) array into a wordwise array.
         *      Find the longest run of 0x00's in src[] for :: shorthanding.
         */
        memset(words, '\0', sizeof words);
        for (i = 0; i < NS_IN6ADDRSZ; i++)
                words[i / 2] |= (src[i] << ((1 - (i % 2)) << 3));
        best.base = -1;
        best.len = 0;
        cur.base = -1;
        cur.len = 0;
        for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
                if (words[i] == 0) {
                        if (cur.base == -1)
                                cur.base = i, cur.len = 1;
                        else
                                cur.len++;
                } else {
                        if (cur.base != -1) {
                                if (best.base == -1 || cur.len > best.len)
                                        best = cur;
                                cur.base = -1;
                        }
                }
        }
        if (cur.base != -1) {
                if (best.base == -1 || cur.len > best.len)
                        best = cur;
        }
        if (best.base != -1 && best.len < 2)
                best.base = -1;

        /*
         * Format the result.
         */
        tp = tmp;
        for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
                /* Are we inside the best run of 0x00's? */
                if (best.base != -1 && i >= best.base &&
                    i < (best.base + best.len)) {
                        if (i == best.base)
                                *tp++ = ':';
                        continue;
                }
                /* Are we following an initial run of 0x00s or any real hex? */
                if (i != 0)
                        *tp++ = ':';
                /* Is this address an encapsulated IPv4? */
                if (i == 6 && best.base == 0 && (best.len == 6 ||
                    (best.len == 7 && words[7] != 0x0001) ||
                    (best.len == 5 && words[5] == 0xffff))) {
                        if (!inet_ntop4(src+12, tp, sizeof tmp - (tp - tmp)))
                                return (NULL);
                        tp += strlen(tp);
                        break;
                }
                tp += sprintf(tp, "%x", words[i]);
        }
        /* Was it a trailing run of 0x00's? */
        if (best.base != -1 && (best.base + best.len) == 
            (NS_IN6ADDRSZ / NS_INT16SZ))
                *tp++ = ':';
        *tp++ = '\0';

        /*
         * Check for overflow, copy, and we're done.
         */
        if ((socklen_t)(tp - tmp) > size) {
                return (NULL);
        }
        strcpy(dst, tmp);
        return (dst);
}