IpStack-Geph

A fork of narrowlink/ipstack. Main changes:

• Not tightly coupled to TUN interfaces. Instead, packets are passed in and out of the stack in a generic fashion using channels.
• Built on tokio: the background processing loop is spawned onto the tokio runtime and the streams implement the tokio I/O traits (tokio::io::{AsyncRead, AsyncWrite}). IpStack::new must be called from within a tokio runtime.