common/inet/inet_cidr_ntop.c

/*
 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
 * Copyright (c) 1998,1999 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_cidr_ntop.c,v 1.7 2006/10/11 02:18:18 marka Exp $";
#endif

#include "port_before.h"

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <arpa/inet.h>

#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include "port_after.h"

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

static char *
inet_cidr_ntop_ipv4(const u_char *src, int bits, char *dst, size_t size);
static char *
inet_cidr_ntop_ipv6(const u_char *src, int bits, char *dst, size_t size);

/*%
 * char *
 * inet_cidr_ntop(af, src, bits, dst, size)
 *  convert network address from network to presentation format.
 *  "src"'s size is determined from its "af".
 * return:
 *  pointer to dst, or NULL if an error occurred (check errno).
 * note:
 *  192.5.5.1/28 has a nonzero host part, which means it isn't a network
 *  as called for by inet_net_ntop() but it can be a host address with
 *  an included netmask.
 * author:
 *  Paul Vixie (ISC), October 1998
 */
char *
inet_cidr_ntop(int af, const void *src, int bits, char *dst, size_t size) {
    switch (af) {
    case AF_INET:
        return (inet_cidr_ntop_ipv4(src, bits, dst, size));
    case AF_INET6:
        return (inet_cidr_ntop_ipv6(src, bits, dst, size));
    default:
        errno = EAFNOSUPPORT;
        return (NULL);
    }
}

static int
decoct(const u_char *src, int bytes, char *dst, size_t size) {
    char *odst = dst;
    char *t;
    int b;

    for (b = 1; b <= bytes; b++) {
        if (size < sizeof "255.")
            return (0);
        t = dst;
        dst += SPRINTF((dst, "%u", *src++));
        if (b != bytes) {
            *dst++ = '.';
            *dst = '\0';
        }
        size -= (size_t)(dst - t);
    }
    return (dst - odst);
}

/*%
 * static char *
 * inet_cidr_ntop_ipv4(src, bits, dst, size)
 *  convert IPv4 network address from network to presentation format.
 *  "src"'s size is determined from its "af".
 * return:
 *  pointer to dst, or NULL if an error occurred (check errno).
 * note:
 *  network byte order assumed.  this means 192.5.5.240/28 has
 *  0b11110000 in its fourth octet.
 * author:
 *  Paul Vixie (ISC), October 1998
 */
static char *
inet_cidr_ntop_ipv4(const u_char *src, int bits, char *dst, size_t size) {
    char *odst = dst;
    size_t len = 4;
    size_t b;
    size_t bytes;

    if ((bits < -1) || (bits > 32)) {
        errno = EINVAL;
        return (NULL);
    }

    /* Find number of significant bytes in address. */
    if (bits == -1)
        len = 4;
    else
        for (len = 1, b = 1 ; b < 4U; b++)
            if (*(src + b))
                len = b + 1;

    /* Format whole octets plus nonzero trailing octets. */
    bytes = (((bits <= 0) ? 1 : bits) + 7) / 8;
    if (len > bytes)
        bytes = len;
    b = decoct(src, bytes, dst, size);
    if (b == 0U)
        goto emsgsize;
    dst += b;
    size -= b;

    if (bits != -1) {
        /* Format CIDR /width. */
        if (size < sizeof "/32")
            goto emsgsize;
        dst += SPRINTF((dst, "/%u", bits));
    }

    return (odst);

 emsgsize:
    errno = EMSGSIZE;
    return (NULL);
}

static char *
inet_cidr_ntop_ipv6(const u_char *src, int bits, 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:255.255.255.255/128"];
    char *tp;
    struct { int base, len; } best, cur;
    u_int words[NS_IN6ADDRSZ / NS_INT16SZ];
    int i;

    if ((bits < -1) || (bits > 128)) {
        errno = EINVAL;
        return (NULL);
    }

    /*
     * 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))) {
            int n;

            if (src[15] || bits == -1 || bits > 120)
                n = 4;
            else if (src[14] || bits > 112)
                n = 3;
            else
                n = 2;
            n = decoct(src+12, n, tp, sizeof tmp - (tp - tmp));
            if (n == 0) {
                errno = EMSGSIZE;
                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';

    if (bits != -1)
        tp += SPRINTF((tp, "/%u", bits));

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

/*! \file */