>NAT gateway has been >detected as a ignore-the-source UDP forwarder 2.4 kernels: NAT doesn't work without ip_conntrack, and ip_conntrack always keeps track of source IP addresses (hence its function). I can't think of a situation for any Linux machine which allows inbound UDP replies from other sources. Spoofing the original sender's address is a different story, but that is pandemic of any stateless AND insecure protocol. >I posted about this in March of 2000, the kernel development team response >was that many RPC services require this functionality and it would not be >fixed. The reason is that many UDP-based RPC services will respond back >to requests from an alternative interface using a different IP address >entirely. Just recently someone has written a conntrack handler to traverse firewalls with RPC as you describe. No leaks to my knowledge, although I am not too familiar with this module.
