wraith-ircbot/src/compat/inet_ntop.c

/*
 * inet_ntop.c --
 *
 *	provides inet_ntop()
 */


#include "common.h"
#include "inet_ntop.h"

#ifndef HAVE_INET_NTOP

#include <sys/param.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>

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

#define NS_INADDRSZ     4       /* IPv4 T_A */
#define NS_IN6ADDRSZ    16      /* IPv6 T_AAAA */
#define NS_INT16SZ      2       /* #/bytes of data in a u_int16_t */

/*
 * 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 *egg_inet_ntop4 (const u_char *src, char *dst, socklen_t size);
static const char *egg_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.
 */
const char *
egg_inet_ntop(int af, const void *src, char *dst, socklen_t size)
{
	switch (af) {
	case AF_INET:
		return (egg_inet_ntop4((const u_char *) src, dst, size));
#ifdef USE_IPV6
	case AF_INET6:
		return (egg_inet_ntop6((const u_char *) src, dst, size));
#endif /* USE_IPV6 */
	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 const char *
egg_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"];

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

/* const char *
 * inet_ntop6(src, dst, size)
 *	convert IPv6 binary address into presentation (printable) format
 * author:
 *	Paul Vixie, 1996.
 */
static const char *
egg_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;
	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.
	 */
	egg_memset(words, '\0', sizeof words);
	for (i = 0; i < NS_IN6ADDRSZ; i += 2)
		words[i >> 1] = (src[i] << 8) | src[i + 1];
	best.base = -1;
	cur.base = -1;
	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 == 5 && words[5] == 0xffff))) {
			if (!egg_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);
	}
	return strcpy(dst, tmp);
}
#endif /* !HAVE_INET_NTOP */