This PR introduces a new inactivity package responsible for monitoring peer activity and notifying when peers become inactive.
Introduces a new Signal message type to close the peer connection after the idle timeout is reached.
Periodically checks the last activity of registered peers via a Bind interface.
Notifies via a channel when peers exceed a configurable inactivity threshold.
Default settings
DefaultInactivityThreshold is set to 15 minutes, with a minimum allowed threshold of 1 minute.
Limitations
This inactivity check does not support kernel WireGuard integration. In kernel–user space communication, the user space side will always be responsible for closing the connection.
In the conn_mgr we must distinguish two contexts. One is relevant for lazy-manager, and one (engine context) is relevant for peer creation. If we use the incorrect context, then when we disable the lazy connection feature, we cancel the peer connections too, instead of just the lazy manager.
With the lazy connection feature, the peer will connect to target peers on-demand. The trigger can be any IP traffic.
This feature can be enabled with the NB_ENABLE_EXPERIMENTAL_LAZY_CONN environment variable.
When the engine receives a network map, it binds a free UDP port for every remote peer, and the system configures WireGuard endpoints for these ports. When traffic appears on a UDP socket, the system removes this listener and starts the peer connection procedure immediately.
Key changes
Fix slow netbird status -d command
Move from engine.go file to conn_mgr.go the peer connection related code
Refactor the iface interface usage and moved interface file next to the engine code
Add new command line flag and UI option to enable feature
The peer.Conn struct is reusable after it has been closed.
Change connection states
Connection states
Idle: The peer is not attempting to establish a connection. This typically means it's in a lazy state or the remote peer is expired.
Connecting: The peer is actively trying to establish a connection. This occurs when the peer has entered an active state and is continuously attempting to reach the remote peer.
Connected: A successful peer-to-peer connection has been established and communication is active.
