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);
    if(parts.length < 4) return -1;

    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 (slower, but more readable):
   if (ip >= dottedQuadToInt('224.0.0.0') && ip <= dottedQuadToInt('239.255.255.255')) return false;

   return true;
}

Answer 3

Multicast IP addresses are defined as those with 1110 as their high-order four bits (see http://www.iana.org/assignments/multicast-addresses/multicast-addresses.xhtml and https://www.rfc-editor.org/rfc/rfc1112). In hex the 1110 is expressed as 0xE (decimal value of 14, remember each hex digit is worth 4 binary bits) so if this value is in the high order 4 bits of 32 bit integer (big endian) the hex would be 0xE0000000. If you first convert the IP address to a 32 bit number and then & it with 0xF0000000, if the resulting value is equal to 0xE0000000 (1110 in the high-order four bits) then it is a multicast IPv4 address (same logic used in Java Inet4Address.isMulticastAddress()).

var ipNum = IPToNumber(sTestIP);
var isMulticast = ((ipNum & 0xF0000000) == 0xE0000000);

Here is a table to prove the point (notice that valid mutlicast IP addresses in hex format all start with 0xE, also the int values are signed 32 bit numbers):

// not a multicast, starts with 0xD
ip [223.000.000.000] hex [0xDF000000] int [-553648128] unsigned [3741319168]
ip [223.255.255.255] hex [0xDFFFFFFF] int [-536870913] unsigned [3758096383]    

// is a multicast, starts with 0xE
ip [224.000.000.000] hex [0xE0000000] int [-536870912] unsigned [3758096384]
ip [224.255.255.255] hex [0xE0FFFFFF] int [-520093697] unsigned [3774873599]
ip [225.000.000.000] hex [0xE1000000] int [-520093696] unsigned [3774873600]
ip [225.255.255.255] hex [0xE1FFFFFF] int [-503316481] unsigned [3791650815]
ip [226.000.000.000] hex [0xE2000000] int [-503316480] unsigned [3791650816]
ip [226.255.255.255] hex [0xE2FFFFFF] int [-486539265] unsigned [3808428031]
ip [227.000.000.000] hex [0xE3000000] int [-486539264] unsigned [3808428032]
ip [227.255.255.255] hex [0xE3FFFFFF] int [-469762049] unsigned [3825205247]
ip [228.000.000.000] hex [0xE4000000] int [-469762048] unsigned [3825205248]
ip [228.255.255.255] hex [0xE4FFFFFF] int [-452984833] unsigned [3841982463]
ip [229.000.000.000] hex [0xE5000000] int [-452984832] unsigned [3841982464]
ip [229.255.255.255] hex [0xE5FFFFFF] int [-436207617] unsigned [3858759679]
ip [230.000.000.000] hex [0xE6000000] int [-436207616] unsigned [3858759680]
ip [230.255.255.255] hex [0xE6FFFFFF] int [-419430401] unsigned [3875536895]
ip [231.000.000.000] hex [0xE7000000] int [-419430400] unsigned [3875536896]
ip [231.255.255.255] hex [0xE7FFFFFF] int [-402653185] unsigned [3892314111]
ip [232.000.000.000] hex [0xE8000000] int [-402653184] unsigned [3892314112]
ip [232.255.255.255] hex [0xE8FFFFFF] int [-385875969] unsigned [3909091327]
ip [233.000.000.000] hex [0xE9000000] int [-385875968] unsigned [3909091328]
ip [233.255.255.255] hex [0xE9FFFFFF] int [-369098753] unsigned [3925868543]
ip [234.000.000.000] hex [0xEA000000] int [-369098752] unsigned [3925868544]
ip [234.255.255.255] hex [0xEAFFFFFF] int [-352321537] unsigned [3942645759]
ip [235.000.000.000] hex [0xEB000000] int [-352321536] unsigned [3942645760]
ip [235.255.255.255] hex [0xEBFFFFFF] int [-335544321] unsigned [3959422975]
ip [236.000.000.000] hex [0xEC000000] int [-335544320] unsigned [3959422976]
ip [236.255.255.255] hex [0xECFFFFFF] int [-318767105] unsigned [3976200191]
ip [237.000.000.000] hex [0xED000000] int [-318767104] unsigned [3976200192]
ip [237.255.255.255] hex [0xEDFFFFFF] int [-301989889] unsigned [3992977407]
ip [238.000.000.000] hex [0xEE000000] int [-301989888] unsigned [3992977408]
ip [238.255.255.255] hex [0xEEFFFFFF] int [-285212673] unsigned [4009754623]
ip [239.000.000.000] hex [0xEF000000] int [-285212672] unsigned [4009754624] 
ip [239.255.255.255] hex [0xEFFFFFFF] int [-268435457] unsigned [4026531839]
    
// not a multicast, starts with 0xF
ip [240.000.000.000] hex [0xF0000000] int [-268435456] unsigned [4026531840]
ip [240.255.255.255] hex [0xF0FFFFFF] int [-251658241] unsigned [4043309055]

Answer 4

/**
 * 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!
}