drop packets that have been queued for longer than some timeout (currently 25ms) instead of using fixed length queues

src/yggdrasil/switch.go

@@ -586,36 +586,66 @@ func (t *switchTable) handleIn(packet []byte, idle map[switchPort]struct{}) bool
 	}
 }
 
+// Info about a buffered packet
+type switch_packetInfo struct {
+	bytes []byte
+	time  time.Time // Timestamp of when the packet arrived
+}
+
+// Used to keep track of buffered packets
+type switch_buffer struct {
+	packets []switch_packetInfo // Currently buffered packets, which may be dropped if it grows too large
+	count   uint64              // Total queue size, including dropped packets
+}
+
+func (b *switch_buffer) dropTimedOut() {
+	// TODO figure out what timeout makes sense
+	const timeout = 25 * time.Millisecond
+	now := time.Now()
+	for len(b.packets) > 0 && now.Sub(b.packets[0].time) > timeout {
+		util_putBytes(b.packets[0].bytes)
+		b.packets = b.packets[1:]
+	}
+}
+
 // Handles incoming idle notifications
 // Loops over packets and sends the newest one that's OK for this peer to send
 // Returns true if the peer is no longer idle, false if it should be added to the idle list
-func (t *switchTable) handleIdle(port switchPort, buffs map[string][][]byte) bool {
+func (t *switchTable) handleIdle(port switchPort, buffs map[string]switch_buffer) bool {
 	to := t.core.peers.getPorts()[port]
 	if to == nil {
 		return true
 	}
 	var best string
-	var bestSize int
-	for streamID, packets := range buffs {
+	var bestSize uint64
+	for streamID, buf := range buffs {
 		// Filter over the streams that this node is closer to
 		// Keep the one with the smallest queue
-		packet := packets[0]
-		coords := switch_getPacketCoords(packet)
-		if (bestSize == 0 || len(packets) < bestSize) && t.portIsCloser(coords, port) {
+		buf.dropTimedOut()
+		if len(buf.packets) == 0 {
+			delete(buffs, streamID)
+			continue
+		}
+		buffs[streamID] = buf
+		packet := buf.packets[0]
+		coords := switch_getPacketCoords(packet.bytes)
+		if (bestSize == 0 || buf.count < bestSize) && t.portIsCloser(coords, port) {
 			best = streamID
-			bestSize = len(packets)
+			bestSize = buf.count
 		}
 	}
 	if bestSize != 0 {
-		packets := buffs[best]
-		var packet []byte
-		packet, packets = packets[0], packets[1:]
-		if len(packets) == 0 {
+		buf := buffs[best]
+		var packet switch_packetInfo
+		// TODO decide if this should be LIFO or FIFO
+		packet, buf.packets = buf.packets[0], buf.packets[1:]
+		buf.count--
+		if len(buf.packets) == 0 {
 			delete(buffs, best)
 		} else {
-			buffs[best] = packets
+			buffs[best] = buf
 		}
-		to.sendPacket(packet)
+		to.sendPacket(packet.bytes)
 		return true
 	} else {
 		return false
@@ -624,7 +654,7 @@ func (t *switchTable) handleIdle(port switchPort, buffs map[string][][]byte) boo
 
 // The switch worker does routing lookups and sends packets to where they need to be
 func (t *switchTable) doWorker() {
-	buffs := make(map[string][][]byte)    // Packets per PacketStreamID (string)
+	buffs := make(map[string]switch_buffer) // Packets per PacketStreamID (string)
 	idle := make(map[switchPort]struct{})   // this is to deduplicate things
 	for {
 		select {
@@ -633,12 +663,12 @@ func (t *switchTable) doWorker() {
 			if !t.handleIn(packet, idle) {
 				// There's nobody free to take it right now, so queue it for later
 				streamID := switch_getPacketStreamID(packet)
-				packets := append(buffs[streamID], packet)
-				for len(packets) > 32 {
-					util_putBytes(packets[0])
-					packets = packets[1:]
-				}
-				buffs[streamID] = packets
+				buf := buffs[streamID]
+				buf.dropTimedOut()
+				pinfo := switch_packetInfo{packet, time.Now()}
+				buf.packets = append(buf.packets, pinfo)
+				buf.count++
+				buffs[streamID] = buf
 			}
 		case port := <-t.idleIn:
 			// Try to find something to send to this peer