inet_cidr_ntop.c

/*-
 * SPDX-License-Identifier: ISC
 *
 * 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.
 */

#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 */