/*
 * 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 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 <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
#ifdef notdef
static const char rcsid[] = "Id: inet_net_ntop.c,v 1.1.2.1 2002/08/02 02:17:21 marka Exp ";
#else
__RCSID("$NetBSD: inet_net_ntop.c,v 1.5 2026/04/08 14:12:06 christos Exp $");
#endif
#endif

#include "port_before.h"

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

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

#include "port_after.h"

#ifdef __weak_alias
__weak_alias(inet_net_ntop,_inet_net_ntop)
#endif

static char *   inet_net_ntop_ipv4(const u_char *src, int bits,
                                        char *dst, size_t size);
static char *   inet_net_ntop_ipv6(const u_char *src, int bits,
                                        char *dst, size_t size);

/*
 * char *
 * inet_net_ntop(af, src, bits, dst, size)
 *      convert network number from network to presentation format.
 *      generates CIDR style result always.
 * return:
 *      pointer to dst, or NULL if an error occurred (check errno).
 * author:
 *      Paul Vixie (ISC), July 1996
 */
char *
inet_net_ntop(int af, const void *src, int bits, char *dst, size_t size)
{
        switch (af) {
        case AF_INET:
                return (inet_net_ntop_ipv4(src, bits, dst, size));
        case AF_INET6:
                return (inet_net_ntop_ipv6(src, bits, dst, size));
        default:
                errno = EAFNOSUPPORT;
                return (NULL);
        }
}

/*
 * static char *
 * inet_net_ntop_ipv4(src, bits, dst, size)
 *      convert IPv4 network number from network to presentation format.
 *      generates CIDR style result always.
 * 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), July 1996
 */
static char *
inet_net_ntop_ipv4(const u_char *src, int bits, char *dst, size_t size)
{
        size_t t;
        u_int m;
        int b, l;

        if (bits < 0 || bits > 32) {
                errno = EINVAL;
                return (NULL);
        }


        t = 0;
        if (bits == 0)
                ADDC('0');

        /* Format whole octets. */
        t = 0;
        for (b = bits / 8; b > 0; b--) {
                ADDS(snprintf(dst + t, size - t, "%u", *src++));
                if (b > 1)
                        ADDC('.');
        }

        /* Format partial octet. */
        b = bits % 8;
        if (b > 0) {
                if (t)
                        ADDC('.');
                m = ((1 << b) - 1) << (8 - b);
                ADDS(snprintf(dst + t, size - t, "%u", *src & m));
        }

        /* Format CIDR /width. */
        ADDS(snprintf(dst + t, size - t, "/%u", bits));
        return dst;

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

/*
 * static char *
 * inet_net_ntop_ipv6(src, bits, fakebits, dst, size)
 *      convert IPv6 network number from network to presentation format.
 *      generates CIDR style result always. Picks the shortest representation
 *      unless the IP is really IPv4.
 *      always prints specified number of bits (bits).
 * 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
 *      0x11110000 in its fourth octet.
 * author:
 *      Vadim Kogan (UCB), June 2001
 *  Original version (IPv4) by Paul Vixie (ISC), July 1996
 */

static char *
inet_net_ntop_ipv6(const u_char *src, int bits, char *dst, size_t size)
{
        u_int   m;
        int     b, t, l;
        size_t  p;
        size_t  zero_s, zero_l, tmp_zero_s, tmp_zero_l;
        size_t  i;
        int     is_ipv4 = 0;
        unsigned char inbuf[16];
        size_t  words;
        u_char  *s;

        if (bits < 0 || bits > 128) {
                errno = EINVAL;
                return (NULL);
        }

        t = 0;
        if (bits == 0) {
                ADDC(':');
                ADDC(':');
        } else {
                /* Copy src to private buffer.  Zero host part. */      
                p = (bits + 7) / 8;
                memcpy(inbuf, src, p);
                memset(inbuf + p, 0, 16 - p);
                b = bits % 8;
                if (b != 0) {
                        m = ~0u << (8 - b);
                        inbuf[p-1] &= m;
                }

                s = inbuf;

                /* how many words need to be displayed in output */
                words = (bits + 15) / 16;
                if (words == 1)
                        words = 2;
                
                /* Find the longest substring of zero's */
                zero_s = zero_l = tmp_zero_s = tmp_zero_l = 0;
                for (i = 0; i < (words * 2); i += 2) {
                        if ((s[i] | s[i+1]) == 0) {
                                if (tmp_zero_l == 0)
                                        tmp_zero_s = i / 2;
                                tmp_zero_l++;
                        } else {
                                if (tmp_zero_l && zero_l < tmp_zero_l) {
                                        zero_s = tmp_zero_s;
                                        zero_l = tmp_zero_l;
                                        tmp_zero_l = 0;
                                }
                        }
                }

                if (tmp_zero_l && zero_l < tmp_zero_l) {
                        zero_s = tmp_zero_s;
                        zero_l = tmp_zero_l;
                }

                if (zero_l != words && zero_s == 0 && ((zero_l == 6) ||
                    ((zero_l == 5 && s[10] == 0xff && s[11] == 0xff) ||
                    ((zero_l == 7 && s[14] != 0 && s[15] != 1)))))
                        is_ipv4 = 1;

                /* Format whole words. */
                for (p = 0; p < words; p++) {
                        if (zero_l != 0 && p >= zero_s && p < zero_s + zero_l) {
                                /* Time to skip some zeros */
                                if (p == zero_s)
                                        ADDC(':');
                                if (p == words - 1)
                                        ADDC(':');
                                s++;
                                s++;
                                continue;
                        }

                        if (is_ipv4 && p > 5 ) {
                                ADDS(snprintf(dst + t, size - t, "%c%u",
                                    (p == 6) ? ':' : '.', *s++));
                                /* we can potentially drop the last octet */
                                if (p != 7 || bits > 120) {
                                        ADDS(snprintf(dst + t, size - t, ".%u",
                                            *s++));
                                }
                        } else {
                                if (t)
                                        ADDC(':');
                                ADDS(snprintf(dst + t, size - t, "%x",
                                    *s * 256 + s[1]));
                                s += 2;
                        }
                }
        }
        /* Format CIDR /width. */
        ADDS(snprintf(dst + t, size - t, "/%u", bits));
        return (dst);

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