PayPal WPP requires IPv4

The following patch addresses both of the above issues. I added an IPv4 check in the patch because I think it might help developers more quickly identify any IP version issues. It appears that currently Paypal WPP API only accepts IPv4 addresses so I figured the module might as well check that before sending out it's request.

Glad to help out.

I did notice one thing in your referenced commit (line 197). Should $billing_address_found instead be $valid_billing_address? Those conditions were part of the original if() statement, and it would seem should follow the pattern of setting $valid_billing_address to FALSE.

I think converting the IPv6 of localhost to IPv4 is a good idea. Preventing the transaction doesn't get one farther along in testing Paypal. They might just end up burning a lot of time trying to get MAMP configured, or hardcoding 127.0.0.1 into the .module file to get it to work, which I did both of :-)

Also, I think keeping an IPv4 general validation function is a good idea. Something like: if ip_address=IPv6 then check if it's localhost, if it is then convert and proceed with transaction, if it isn't then prevent transaction and post error message. This way if somebody is developing on a hosted server they could figure it out with their provider.

I'm not familiar with the possible ranges the loopback address can have in IPv6 (or what the standard format is), but it seems like ::1 is the only one. The IPv6 loopback block is given in CIDR notation as '::1/128. Here's what the mighty Wikipedia said:

" ::1/128 represents the IPv6 loopback address. Its prefix size is 128, i.e. the size of the address itself, indicating that this facility consists of only this one address."

http://en.wikipedia.org/wiki/CIDR_notation

One possible solution I was thinking of:

$ip_address = ip_address();

//is it IPv4? 
if (filter_var($ip_address, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4)) {
//proceed with transaction
}
  else {
  //is it localhost? This is the tricky part...
  if ($ip_address == '::1' //???) {
    //convert and proceed
  }
  else {
    //post error message
  }
}

Works great on my setup! Transaction was processed, and watchdog logged the warning that my localhost was converted. Looks like the Paypal module is on the road to world domination :-)