Before this change, NetBird Agent wasn't handling
peer interface configuration changes dynamically.
Also, remote peer configuration changes have
not been applied (e.g. AllowedIPs changed).
Not a very common cause, but still it should be handled.
Now, Agent reacts to PeerConfig changes sent from the
management service and restarts remote connections
if AllowedIps have been changed.
When stopping engine, all peer conns have to be closed
and for each peer WireGuard iface is called
to remove WireGuard peer.
This operation happens in a goroutine causing
Engine to remove the whole WireGuard interface before.
Therefore consequent calls to RemovePeer are unsuccessful.
This fix just adds a small delay before removing interface.
When one of the peers has a static public host IP
or both peers are in the same local network
we establish a direct Wireguard connection
bypassing proxy usage.
This helps reduce FD usage and improves
performance.
* Create temp file before saving data
On the event of full disk, we may encounter the case where the
destination file get replaced by an empty file as the
ioutil.WriteFile truncates the destination before write.
* Close the tempFile instance before moving it
* Blacklist Wireguard interfaces for ICE checks
* feature: support new management service protocol
* chore: add more logging to track networkmap serial
* refactor: organize peer update code in engine
* chore: fix lint issues
* refactor: extract Signal client interface
* test: add signal client mock
* refactor: introduce Management Service client interface
* chore: place management and signal clients mocks to respective packages
* test: add Serial test to the engine
* fix: lint issues
* test: unit tests for a networkMapUpdate
* test: unit tests Sync update
