Multiple network interface support

[jiegec]

Where to put sockets?

1. Interface
2. Global

How to implement global routing table?

[jiegec]

Answer:

1. Interface: when to bind socket to specific interface?
2. Global: does interface ignore sockets that do not belong to it?

Ask for routing table in each interface.

How to bind to 0.0.0.0?

• It should work out of the box.

[jiegec]

Steps to make:

• [x] Merge protocol specific functions in kernel/src/syscall/net.rs
• [x] Move socket to global
• [ ] User land ip raw socket forwarding