[NTTCP-7] handleConnectionRequest should not blindly believe theirAddress

[Imported from JIRA. Reported by Alexander Kjeldaas @ak) as NTTCP-7 on 2014-07-19 23:28:20]
From casually reading the code, I'm worried about believing the received EndPointAddress in handleConnectionRequest.

In an environment where not all processes have the same credentials, this opens up the ability to spoof other processes.

If node A connects to node B and presents itself as node C, then this is a spoofing attempt.

(Not fixing this severely restricts the use-cases for CH).

Rather, I think what should be done is by default to screen the incoming EndPointAddress against Network.Socket.getPeerName and reject anything that does not match.

Bonus points for having a callback that can act as a "firewall" in case the transport is going through a NAT (in which case accepting the EndPointAddress is essential in getting bi-directional connectivity).

Start by reading handleConnectionRequest and the surrounding transport code, then inspect how Network.Socket.getPeerName can be used to compare the peer with the received EndPointAddress. Define the default rejection behavior for mismatches and the callback boundary needed for NAT cases. Done means spoofed identities are rejected by default while legitimate NAT connectivity remains configurable.