Implement localhop forwarding

[pulsejet]

localhop forwards only one hop (confirm from NFD spec)

[yoursunny]

"/localhop forwards only one hop" is not part of the NDN protocol, but simply a convention adopted by NFD.

In 2016, Prof @beichuan asserted that the forwarder does not need to understand names, but can simply follow routing tables and strategies.
I immediately asked about /localhost and /localhop.
His answer was that, /localhop could be realized by a forwarding strategy that chooses not to forward any Interest received from a non-local face to a non-local face.

Therefore, I'd recommend NDNd forwarder to adopt this approach:

• Build a forwarding strategy that does not forward an Interest received from a non-local face to a non-local face.
• Assign this strategy to /localhop in the initial strategy choice.

[pulsejet]

@yoursunny I took a go at this but it doesn't cover all use cases. /localhop itself can be best-route (DV) or multicast (NLSR), so we'd need two strategies to support this (too complicated).

Unrelated, accessing the face table creates a import cycle so this will also need a major refactor of the forwarder.