/************************************************************************
*
* cidrtest.c - Example program to test if an IPv4 address exists 
*              inside of a network, based on a CIDR value.
*
* Copyright 2016 Todd Shadburn <tshadburn@opencomputingsolutions.com>
* 
* Licensed under the GNU GPL version 2
* 
************************************************************************/


#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>


int main (int argc, char**argv)
{
	struct in_addr ipaddr;
	struct in_addr network;
	uint32_t	netmask;
	uint32_t	cidrbits;
	uint8_t		bit;

	if (argc < 4) {
		fprintf(stderr, "Usage: %s network cidrmask ipaddr\n", argv[0]);
		exit (2);
	}
	if (inet_aton(argv[1], &network) == 0) {
		fprintf(stderr, "Invalid network address.\n");
		exit (2);
	}
	cidrbits = atoi(argv[2]);
	if (cidrbits < 1 || cidrbits > 32) {
		fprintf(stderr, "Invalid cidrmask.\n");
		exit (2);
	}
	if (inet_aton(argv[3], &ipaddr) == 0) {
		fprintf(stderr, "Invalid IP address.\n");
		exit (2);
	}

	netmask = 0L;
	for (bit=31 ; bit>(31-cidrbits) ; bit--)
		netmask |= (1<<bit);
	netmask = htonl(netmask);
	fprintf(stderr, "netmask = %x\n", netmask);
	
	if ((network.s_addr & netmask) == (ipaddr.s_addr & netmask))
		fprintf(stdout, "IP address is in network.\n");
	else
		fprintf(stdout, "IP address is not in network.\n");

	return 0;
}