Losing the last network only flipped the availability state: the dead management, signal and relay sockets stayed silently connected until their own timeouts, so the client kept reporting Connected with no network at all.
Introduce client/netevents with a Manager that ties the availability state, the connection sweeper and the status recorder together, and move the netstate and netsweep packages under it (netsweep renamed to sweep). SetNetworkAvailable(false) now also sweeps the registered connections so their owners redial and the listener reaches the NoNetwork state.
The Android and iOS bindings own a Manager instance and inject it through the constructors; consumers hold the concrete *Manager whose nil zero value reports always-online and never sweeps, with interfaces kept only as parameter contracts. The relay guard settle wait moved into the Manager as WaitSettled, removing the netevents import from the relay package.
On network changes the client restarted the whole engine. That is heavy-handed and slow: it tears down working state to recover from a transition the engine could handle itself. This replaces the restart with proper network event handling.
Suspend the retry loops while no network is available. Instead of burning through backoff intervals against an unreachable network, the reconnection loops park until the OS reports a usable network again.
Reconnect immediately on a network switch. When the OS hands us a new network, connections bound to the old one are swept and re-dialed right away, rather than waiting for a timeout to notice they are dead.
* [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.
