Merge pull request #123 from lightninglabs/fix-gbn-transport-timeouts

gbn+mailbox: fix transport timeouts, add dynamic pong, harden with rapid tests

Author: ViktorT-11

gbn/config.go

@@ -78,6 +78,28 @@ func WithBoostPercent(boostPercent float32) TimeoutOptions {
 	}
 }
 
+// WithDynamicPongTimeout enables dynamic pong timeout based on observed RTT.
+// When enabled, the pong timeout is computed as max(basePongTime,
+// pongMultiplier * smoothedRTT), capped at maxPongTime and never allowed to
+// exceed the local ping interval. This is useful for relay-based transports
+// where the round-trip time through the relay can vary significantly based on
+// network conditions.
+func WithDynamicPongTimeout(pongMultiplier int,
+	maxPongTime time.Duration) TimeoutOptions {
+
+	return func(manager *TimeoutManager) {
+		manager.dynamicPongTime = true
+
+		if pongMultiplier > 0 {
+			manager.pongMultiplier = pongMultiplier
+		}
+
+		if maxPongTime > 0 {
+			manager.maxPongTime = maxPongTime
+		}
+	}
+}
+
 // config holds the configuration values for an instance of GoBackNConn.
 type config struct {
 	// n is the window size. The sender can send a maximum of n packets

gbn/gbn_conn.go

@@ -411,21 +411,22 @@ func (g *GoBackNConn) sendPacketsForever() error {
 			continue
 
 		case <-g.pingTicker.Ticks():
-			// If we have expected a sync after sending the previous
-			// ping, both the pingTicker and pongTicker may have
-			// ticked when waiting to sync. In that case, we can't
-			// be sure which of the signals we receive over first in
-			// the above select. We therefore need to check if the
-			// pong ticker has ticked here to ensure that it get's
-			// prioritized over the ping ticker.
+			// The pong timeout is capped at the ping interval, so
+			// if we're still waiting for a response to the previous
+			// ping then both tickers may fire at roughly the same
+			// time. In that case the keepalive timeout must win
+			// over sending a new ping.
 			select {
 			case <-g.pongTicker.Ticks():
 				return errKeepaliveTimeout
 			default:
 			}
 
-			// Start the pong timer.
-			g.pongTicker.Reset()
+			// Start the pong timer. We use ResetWithInterval
+			// to pick up any dynamic pong timeout changes
+			// based on observed RTT.
+			pongTime := g.timeoutManager.GetPongTime()
+			g.pongTicker.ResetWithInterval(pongTime)
 			g.pongTicker.Resume()
 
 			// Also reset the ping timer.