mirror of
https://github.com/slackhq/nebula.git
synced 2026-10-03 17:56:38 +02:00
Wade Simmons
11528c6e02
Lanes were established for every slot as soon as the base tunnel came up, so a host with `routines: N` paid N-1 extra Noise handshakes, sessions and keepalives for every peer it talked to, including peers it exchanges a trickle with. Only routines that actually carry traffic to a peer need a lane. Add a per-slot demand flag to laneState. sendInsideMessage already loads txLanes[laneSlot] on every direct-path packet; that load missing is now the signal, and EnsureLanes only starts slots the data plane asked for. The miss path is unchanged otherwise: the packet rides the base tunnel, the same fallback used while a lane is down. noteLaneDemand load-guards its store so repeated misses on a lane-less slot are plain reads rather than a cache line ping-ponging between the routines sharing it. The demand check is EnsureLanes' last condition, so a slot that is pending or inside its backoff keeps the flag for the tick that can act on it. Consuming the flag also stops a lane whose routine went quiet from being rebuilt forever after it dies. The wire format, lane negotiation and port-offset scheme are untouched, so a lazy node interoperates with an eager one in both directions, and inbound lane handshakes from a busy peer are still accepted regardless of our own demand.