We currently have a method in Geo UDF that takes an IP address from the remote host header and the X-Forwarded-For value and attempts to identify the originating client IP address by following a simple algorithm as follows:

GetClientIP(remote_host, X-Forwarded-For)

IF X-Forwarded-For value is not valid:

return remote_host

ELSE:

FOR EACH valid IP address, proxy_ip, in the comma-separated X-Forwarded-For value:

IF proxy_ip does not start with "127.0" or "192.168" or "10." or "169.254":

return proxy_ip

What are the ways in which this naive algorithm can be improved? For example, is it better to maintain a separate list of IP address to ignore (currently only 4)? If yes, how do we ensure that the list is exhaustive? Any other improvements?

Thanks,

Ananth