Javascript and 6RD...

Ok, this time is not about flying or holiday, but, rather about a simple javascript code to detect whether IPv6 connectivity is established through a 6RD tunnel... Prerequisite is to know your (or your CPE) IPv4 address and your IPv6 address. It is based on an idea of Hugo Kaczmarek and Arthur Lacoste.

The idea is very simple: look inside the IPv6 address whether part of the IPv4 address appears...

Code is:

function is6RD(addr4, addr6) {        var bytes = addr4.split('.') ;        var i, addr4Bits, addr6Bits, chunk, index ;
        // Now process the IPv4 address by generating a string of 32 '0' or '1' based on the host address        addr4Bits = '' ;        for (i = 0 ; i < 4 ; i++) {                chunk = parseInt(bytes[i], 10).toString(2) ;                while (chunk.length < 8)                        chunk = '0' + chunk ;                addr4Bits = addr4Bits + chunk ;        }
        // Now process the IPv6 address by generating a string of 64 '0' or '1' based on the /64 prefix        bytes = addr6.split(':') ;        addr6Bits = '' ;        for (i = 0 ; i < 4 ; i++) {                chunk = parseInt(bytes[i], 16).toString(2) ;                while (chunk.length < 16)                        chunk = '0' + chunk ;                addr6Bits = addr6Bits + chunk ;        }
        // Now check whether full or at least 16 bits of the IPv4 is embedded into the IPv6 prefix        while (addr4Bits.length > 16) {                index = addr6Bits.indexOf(addr4Bits) ; // Is part of the IPv4 address embedded in the /64 of IPv6?                if (index >= 0)                                                                                                                                     return addr4Bits.length + " bits of the IPv4 address are embedded in the IPv6 address starting at " + index ;                       // Else, remove one leading bit of addr4                                                                                  
 
                addr4Bits = addr4Bits.substr(1, addr4Bits.length-1) ;                                                                               }                                                                                                                                           return 0                                                                                                                          
 
}

This code can be tried at http://test-ipv6.vyncke.org