Function to determine if IP is in CIDR network?

[jason_lau]

Is there an existing script class I can use to determine if an IP address is in a given CIDR range?

Basically I want to make a call like: isInCIDR(ip_addr, cidr) and it returns true or false. I'd like to do this without first converting CIDR to range and then using SncIPRangeV4 for example.

Or as a corollary, is there a function I can call where given an IP address, it will return the IP Network (cmdb_ci_ip_network) that IP belongs to, regardless if I have that IP address mapped in CMDB.

[Chuck Tomasi · Accepted solution]

Hi Jason,

Thanks for the inquiry. As far as I know, there's nothing OOB. It sounded like a fun thing to build on a weekend so... here's a script include you can use.

var CidrUtil = Class.create();
CidrUtil.prototype = {
   initialize: function() {
   },

   ipIsInCidr : function(ip, cidr) {
             var cidrIp = cidr.split('/')[0];
             var cidrSm = cidr.split('/')[1];

             return (this.IPnumber(ip) & this.IPmask(cidrSm)) == this.IPnumber(cidrIp);
   },

   IPnumber : function (IPaddress) {
             var ip = IPaddress.match(/^(\d+)\.(\d+)\.(\d+)\.(\d+)$/);
             if(ip) {
                       return (+ip[1]<<24) + (+ip[2]<<16) + (+ip[3]<<8) + (+ip[4]);
             }
             // else ... ?
             return null;
   },

   IPmask : function(maskSize) {
             return -1<<(32-maskSize);
   },
   type: 'CidrUtil'
};

Here's a small example how it can be used:

var ip = '192.168.1.4';
var cidr = '192.168.1.0/24';

var cu = new CidrUtil();
gs.log(cu.ipIsInCidr(ip, cidr));

[A Westervelt]

Jason,

I was just working on this the other week actually. Below is a Business Rule on the cmdb_ci table where it will match the update of an IP address to an existing IP Network record. I recommend adding more qualifiers to your IP Networks (line 6-8) to be more precise on your results.

Condition: current.ip_address.changes() && !current.location.changes()

var ip = current.ip_address;
var location = '';


var netGR = new GlideRecord('cmdb_ci_ip_network');
//netGR.addQuery('discover', true);
netGR.addNotNullQuery('location');
//netGR.addQuery('state', 'Processed');
netGR.orderBy('location');
netGR.query();


while (netGR.next()){

 if (inSubNet(ip, netGR.subnet)){
   location = netGR.location.sys_id;
   break;
 }
}


current.location = location;

function ip2long(ip){
       var components;


       if(components = ip.match(/^(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})$/)){
               var iplong = 0;
               var power   = 1;
               for(var i=4; i>=1; i-=1)
               {
                       iplong += power * parseInt(components[i]);
                       power   *= 256;
               }
               return iplong;
       }
       else return -1;
}


function inSubNet(ip, subnet){     
       var mask, base_ip, long_ip = ip2long(ip);
       if( (mask = subnet.match(/^(.*?)\/(\d{1,2})$/)) && ((base_ip=ip2long(mask[1])) >= 0) ){
               var freedom = Math.pow(2, 32 - parseInt(mask[2]));
               return (long_ip > base_ip) && (long_ip < base_ip + freedom - 1);
       }
       else return false;
}

[jason_lau]

Thanks Andrew, this is very helpful. We have strructured vlans (each VLAN maps to a business unit) so if I add BU information to network object, I can use that to populate some fields in the server CI as they're discovered (owner, etc).

[jason_lau]

Thanks Chuck! Would be great if this could be built into an OOB servicenow class for IP utils. I know there's a few classes already out there but hard to chase down documention.