Rename the ConnRacer type to FallbackOpener and its constructor to
NewFallbackOpener. Rename fallback.go to fallback_opener.go and
foreign_relays.go to foreign_relays_store.go so file names mirror their
primary struct.
When a peer advertises a relay different from the home relay, open the
peer connection by racing the home relay and the remote peer's relay in
parallel: start the preferred one (controller prefers home, otherwise the
remote relay), fall back to the other after a delay, use whichever connects
first and drain the loser.
Expose the foreign relay cache as ForeignRelaysStore and the race as
ConnRacer. The manager passes the remote relay as a RelayServer{Addr, IP}.
OpenConn no longer returns the winning server address; the worker derives it
from the returned conn's RemoteAddr to register the close listener, matching
the previous main-branch behavior.
Move the foreign-relay client cache out of Manager into a foreignRelays
type. Concurrent first-time connects to the same server are deduplicated
with singleflight, so the cache mutex is never held during a network
connect (removing the previous stall where a slow connect blocked all map
operations). A per-entry in-use refcount prevents the cleanup loop from
closing a client while a connection is being opened on it.
This drops RelayTrack, its per-track lock and the hand-over-hand locking
between the map lock and the track lock. The exported API is unchanged.
* [relay] evict foreign client cache on disconnect
When a foreign relay's TCP connection drops, the manager's
onServerDisconnected handler only triggered reconnect logic for the
home server; the disconnected foreign entry stayed in the relayClients
cache. Subsequent OpenConn calls reused the closed client until the
60-second cleanup tick evicted it, breaking peer connectivity through
that relay for up to a minute.
Evict the foreign entry from the cache on disconnect so the next
OpenConn dials a fresh client.
Also:
- Make the reconnect backoff cap configurable via WithMaxBackoffInterval
ManagerOption; the previous hard-coded 60s constant forced
TestAutoReconnect to sleep ~61s. Test now polls Ready() and finishes
in ~2s.
- Add NB_HOME_RELAY_SERVERS env var that overrides the relay URL list
received from management, so a peer can be pinned to a specific home
relay (used by the netbird-conn-lab Edge 4 reproducer).
* [client] treat empty NB_HOME_RELAY_SERVERS as unset
Returning (urls=[], ok=true) when the env var contained only separators or
whitespace caused callers to wipe the mgmt-provided relay list, leaving the
peer with no relays. Treat a parsed-empty result the same as an unset env.
Zoltan Papp