src/cidr/cidr_addr.c

/*
 * Functions to generate various addresses based on a CIDR
 */
#include "config.h"

#include <errno.h>
#include <string.h>
#include "../include/cidr.h"

/* Create a network address */
CIDR *cidr_addr_network(const CIDR * addr)
{
	int i, j;
	CIDR *toret;

	toret = cidr_alloc();
	toret->proto = addr->proto;

	/* The netmask is the same */
	memcpy(toret->mask, addr->mask, (16 * sizeof(toret->mask[0])));

	/* Now just figure out the network address and spit it out */
	for (i = 0; i <= 15; i++) {
		for (j = 7; j >= 0; j--) {
			/* If we're into host bits, hop out */
			if ((addr->mask[i] & 1 << j) == 0)
				return (toret);

			/* Else, copy this network bit */
			toret->addr[i] |= (addr->addr[i] & 1 << j);
		}
	}

	/*
	 * We only get here on host (/32 or /128) addresses; shorter masks
	 * return earlier.  But it's as correct as can be to just say the
	 * same here, so...
	 */
	return (toret);
}

/* And a broadcast */
CIDR *cidr_addr_broadcast(const CIDR * addr)
{
	int i, j;
	CIDR *toret;

	toret = cidr_alloc();
	toret->proto = addr->proto;

	/* The netmask is the same */
	memcpy(toret->mask, addr->mask, (16 * sizeof(toret->mask[0])));

	/* Copy all the network bits */
	for (i = 0; i <= 15; i++) {
		for (j = 7; j >= 0; j--) {
			/* If we're into host bits, hop out */
			if ((addr->mask[i] & 1 << j) == 0)
				goto post;

			/* Else, copy this network bit */
			toret->addr[i] |= (addr->addr[i] & 1 << j);

		}
	}

 post:
	/* Now set the remaining bits to 1 */
	for ( /* i */ ; i <= 15; i++) {
		for ( /* j */ ; j >= 0; j--)
			toret->addr[i] |= (1 << j);

		j = 7;
	}

	/* And send it back */
	return (toret);
}

/* Get the first host in a CIDR block */
CIDR *cidr_addr_hostmin(const CIDR * addr)
{
	CIDR *toret;

	toret = cidr_addr_network(addr);
	if (toret == NULL)
		return (NULL);	/* Preserve errno */

	toret->addr[15] |= 1;

	return (toret);
}

/* Get the last host in a CIDR block */
CIDR *cidr_addr_hostmax(const CIDR * addr)
{
	CIDR *toret;

	toret = cidr_addr_broadcast(addr);
	if (toret == NULL)
		return (NULL);	/* Preserve errno */

	toret->addr[15] &= 0xfe;

	return (toret);
}