Alright, solution for this, in case anyone needs it, is to edit /usr/local/pkg/squid.inc:
Go to section:
// Set up the external authentication programs
There's a switch function there, go to the LDAP section and modify the $port variable assignment to look like this:
$port = (isset($settings['auth_server_port']) ? "-p {$settings['auth_server_port']}" : '');
In bold the -p oprion I believe is missing in the original .inc file.
As a matter of facts, right below LDAP auth options, come RADIUS options and there the "-p" is present:
case 'radius':
$port = (isset($settings['auth_server_port']) ? "-p {$settings['auth_server_port']}" : '');
Cheers.
