Validate IP address is not 0.0.0.0 or multicast address

Question

Using JavaScript how would I validate an IP address "x.x.x.x" is a valid IPV4 unicast address e.g. is not 0.0.0.0 or multicast (224.0.0.0 to 224.0.0.255, 224.0.1.0 to 238.255.255.255, 239.0.0.0 to 239.255.255.255)?

Answer 1

First you need to get it into a number, use this function:-

function IPToNumber(s)
{
 var arr = s.split(".");
 var n = 0
 for (var i = 0; i < 4; i++)
 {
  n = n * 256
  n += parseInt(arr[i],10)

 }
 return n;
}

Looking at you spec, whilst you seem to list a series of ranges those ranges appear to be contiguous to me, that is can be simplified to (224.0.0.0 to 239.255.255.255). Hence you can test with:-

var min = IPToNumber("224.0.0.0");
var max = IPToNumber("239.255.255.255");

var ipNum = IPToNumber(sTestIP);

var isValid = (ipNum != 0 && (ipNum < min || ipNum > max))

Note of course that without knowledge of the destinations subnet you can't tell whether the address is the network address or the broadcast address for that subnet.

Answer 2

The dotted quad notation you're seeing is just that: a notation that makes it easier on human eyes. An IP Address is really a 32 bit integer. I suggest you convert your address to that integer and then just check that it's in a valid range (ie, > 0 for the first requirement).

To that end:

function dottedQuadToInt(ip)
{      
    var parts = ip.split('.', 4);
    var result = 0, base = 1;
    for (var i = 3;i>=0;i--)
    {
       //validation
       if (parts[i].length == 0 || parts[i].length > 3) return -1;

       var segment = parseInt(parts[i],10);
       if (isNaN(segment) || segment<0 || segment > 255) return -1;

       //compute next segment
       result += base * segment;
       base = base << 8;
    }
    return result;
}

and then:

function isValidIP(ip)
{
   ip = dottedQuadToInt(ip);
   if (ip <= 0) return false;

   //mulitcast range:
   if (ip >= 3758096384 && ip <= 4026531839) return false;

   //alternate way to check multicast:
   if (ip >= dottedQuadToInt('224.0.0.0') && ip <= dottedQuadToInt('239.255.255.255')) return false;

   return true;
}

Answer 3

/**
 * Converts an IPv4 address to a (signed) 32-bit integer.
 */
function parse_ipv4_address(str) {
    var arr = str.split('.');
    for (var i = 0, val = 0; i < 4; i++) {
        val += parseInt(arr[i], 10) << (8 * (3 - i));
    }

    return val;
}

var min = parse_ipv4_address('224.0.0.0');
var max = parse_ipv4_address('239.255.255.255');

var myIp = parse_ipv4_address(myIpStr);

// because the values are signed ints, min and max will be
// negative and we need to reverse the comparison operators :(
if (myIp == 0 || (myIp <= min && myIp >= max)) {
    // multicast!
}