inet_ntop.c

/*      Id: inet_ntop.c,v 1.4 2001/04/17 07:53:47 lukem Exp     */
/*      $NetBSD: inet_ntop.c,v 1.9 2000/01/22 22:19:16 mycroft Exp $    */

/* Copyright (c) 1996 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 INTERNET SOFTWARE CONSORTIUM DISCLAIMS
 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
 * CONSORTIUM 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.
 */

#include <net-snmp/net-snmp-config.h>

#if HAVE_ARPA_NAMESER_H
#include <arpa/nameser.h>
#endif

#include <errno.h>
#include <stdio.h>
#if HAVE_STRING_H
#include <string.h>
#else
#include <strings.h>
#endif

#include <net-snmp/types.h>

#include "inet_ntop.h"

#ifndef EAFNOSUPPORT
#define EAFNOSUPPORT            WSAEAFNOSUPPORT
#endif

#ifndef IN6ADDRSZ
#define IN6ADDRSZ       16
#endif

#ifndef INT16SZ
#define INT16SZ         2
#endif

#ifdef SPRINTF_CHAR
# define SPRINTF(x) strlen(sprintfx)
#else
# define SPRINTF(x) ((size_t)sprintf x)
#endif

/*
 * 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 const char *inet_ntop4(const u_char *src, char *dst, size_t size);
#ifdef NETSNMP_ENABLE_IPV6
static const char *inet_ntop6(const u_char *src, char *dst, size_t size);
#endif /* NETSNMP_ENABLE_IPV6 */

/* 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.
 */
const char *
inet_ntop(int af, const void *src, char *dst, size_t size)
{

        switch (af) {
        case AF_INET:
                return (inet_ntop4(src, dst, size));
#ifdef NETSNMP_ENABLE_IPV6
        case AF_INET6:
                return (inet_ntop6(src, dst, size));
#endif
        default:
                errno = EAFNOSUPPORT;
                return (NULL);
        }
        /* NOTREACHED */
}

/* const char *
 * inet_ntop4(src, dst, size)
 *      format an IPv4 address, more or less like inet_ntoa()
 * 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 const char *
inet_ntop4(const u_char *src, char *dst, size_t size)
{
        static const char fmt[] = "%u.%u.%u.%u";
        char tmp[sizeof "255.255.255.255"];

        if (SPRINTF((tmp, fmt, src[0], src[1], src[2], src[3])) > size) {
                errno = ENOSPC;
                return (NULL);
        }
        strcpy(dst, tmp);
        return (dst);
}

#ifdef NETSNMP_ENABLE_IPV6
/* const char *
 * inet_ntop6(src, dst, size)
 *      convert IPv6 binary address into presentation (printable) format
 * author:
 *      Paul Vixie, 1996.
 */
static const char *
inet_ntop6(const u_char *src, char *dst, size_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;
        u_int words[IN6ADDRSZ / 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 < IN6ADDRSZ; i++)
                words[i / 2] |= (src[i] << ((1 - (i % 2)) << 3));
        best.base = -1;
        cur.base = -1;
        for (i = 0; i < (IN6ADDRSZ / 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 < (IN6ADDRSZ / 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 == 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) == (IN6ADDRSZ / INT16SZ))
                *tp++ = ':';
        *tp++ = '\0';

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