OpenConn held relayClientMu for the whole call, including the network-bound
FallbackOpener.Run, which blocked onServerDisconnected/storeClient from taking
the write lock and delayed reconnect by up to the race timeout. Snapshot the
home relay client under the read lock, release it, and run the foreign check
and the race on the snapshot. isForeignServer now takes the client so it uses
the snapshot instead of re-reading the field after the lock is dropped.
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.
