handle SIGUSR1 as a signal to dump state

daemon.go

@@ -64,6 +64,7 @@ func NewDaemon(ctx context.Context, maddr ma.Multiaddr, dhtEnabled bool, dhtClie
 	d.listener = l
 
 	go d.listen()
+	go d.trapSignals()
 
 	return d, nil
 }

trap_nonposix.go

@@ -0,0 +1,8 @@
+// +build windows plan9 nacl js
+
+package p2pd
+
+func (d *Daemon) trapSignals() {
+	// TODO: define signals we want to trap on Windows, if any.
+	return
+}

trap_posix.go

@@ -0,0 +1,34 @@
+// +build !windows,!plan9,!nacl,!js
+
+package p2pd
+
+import (
+	"os"
+	"os/signal"
+	"syscall"
+)
+
+func (d *Daemon) trapSignals() {
+	ch := make(chan os.Signal, 1)
+	signal.Notify(ch, syscall.SIGUSR1)
+	for {
+		select {
+		case s := <-ch:
+			switch s {
+			case syscall.SIGUSR1:
+				d.handleSIGUSR1()
+			default:
+				log.Warningf("unexpected signal %d", s)
+			}
+		case <-d.ctx.Done():
+			return
+		}
+	}
+}
+
+func (d *Daemon) handleSIGUSR1() {
+	// this is the state dump signal; for now just dht routing table if present
+	if d.dht != nil {
+		d.dht.RoutingTable().Print()
+	}
+}