send an ack if we receive a packet and don't have any return traffic, keeping a legacy 4-second keep-alive in case there's no traffic at all to send (to be removed later, after nodes have upgraded), ideally we should either remove ReadTimeout or use it for the switch idle timeout instead

src/util/util.go

@@ -3,6 +3,7 @@ package util
 // These are misc. utility functions that didn't really fit anywhere else
 
 import "runtime"
+import "time"
 
 // A wrapper around runtime.Gosched() so it doesn't need to be imported elsewhere.
 func Yield() {
@@ -44,3 +45,14 @@ func PutBytes(bs []byte) {
 	default:
 	}
 }
+
+// This is a workaround to go's broken timer implementation
+func TimerStop(t *time.Timer) bool {
+	if !t.Stop() {
+		select {
+		case <-t.C:
+		default:
+		}
+	}
+	return true
+}