Merge pull request #542 from Arceliar/switch

Switch

src/yggdrasil/switch.go

@@ -143,6 +143,7 @@ type switchPort uint64
 type tableElem struct {
 	port    switchPort
 	locator switchLocator
+	time    time.Time
 }
 
 // This is the subset of the information about all peers needed to make routing decisions, and it stored separately in an atomically accessed table, which gets hammered in the "hot loop" of the routing logic (see: peer.handleTraffic in peers.go).
@@ -175,7 +176,7 @@ type switchTable struct {
 	table       atomic.Value               // lookupTable
 	phony.Inbox                            // Owns the below
 	queues      switch_buffers             // Queues - not atomic so ONLY use through the actor
-	idle        map[switchPort]time.Time   // idle peers - not atomic so ONLY use through the actor
+	idle        map[switchPort]struct{}    // idle peers - not atomic so ONLY use through the actor
 }
 
 // Minimum allowed total size of switch queues.
@@ -201,7 +202,7 @@ func (t *switchTable) init(core *Core) {
 		}
 		core.config.Mutex.RUnlock()
 		t.queues.bufs = make(map[string]switch_buffer)
-		t.idle = make(map[switchPort]time.Time)
+		t.idle = make(map[switchPort]struct{})
 	})
 }
 
@@ -562,6 +563,7 @@ func (t *switchTable) updateTable() {
 		newTable.elems[pinfo.port] = tableElem{
 			locator: loc,
 			port:    pinfo.port,
+			time:    pinfo.time,
 		}
 	}
 	t.table.Store(newTable)
@@ -581,7 +583,7 @@ func (t *switchTable) start() error {
 }
 
 type closerInfo struct {
-	port switchPort
+	elem tableElem
 	dist int
 }
 
@@ -598,7 +600,7 @@ func (t *switchTable) getCloser(dest []byte) []closerInfo {
 	for _, info := range table.elems {
 		dist := info.locator.dist(dest)
 		if dist < myDist {
-			t.queues.closer = append(t.queues.closer, closerInfo{info.port, dist})
+			t.queues.closer = append(t.queues.closer, closerInfo{info, dist})
 		}
 	}
 	return t.queues.closer
@@ -662,7 +664,7 @@ func (t *switchTable) bestPortForCoords(coords []byte) switchPort {
 // Handle an incoming packet
 // Either send it to ourself, or to the first idle peer that's free
 // Returns true if the packet has been handled somehow, false if it should be queued
-func (t *switchTable) _handleIn(packet []byte, idle map[switchPort]time.Time) bool {
+func (t *switchTable) _handleIn(packet []byte, idle map[switchPort]struct{}) bool {
 	coords := switch_getPacketCoords(packet)
 	closer := t.getCloser(coords)
 	if len(closer) == 0 {
@@ -671,49 +673,48 @@ func (t *switchTable) _handleIn(packet []byte, idle map[switchPort]time.Time) bo
 		self.sendPacketsFrom(t, [][]byte{packet})
 		return true
 	}
-	var best *peer
-	var bestDist int
-	var bestTime time.Time
+	var best *closerInfo
 	ports := t.core.peers.getPorts()
 	for _, cinfo := range closer {
-		to := ports[cinfo.port]
-		thisTime, isIdle := idle[cinfo.port]
+		to := ports[cinfo.elem.port]
 		var update bool
 		switch {
 		case to == nil:
 			// no port was found, ignore it
-		case !isIdle:
-			// the port is busy, ignore it
 		case best == nil:
 			// this is the first idle port we've found, so select it until we find a
 			// better candidate port to use instead
 			update = true
-		case cinfo.dist < bestDist:
+		case cinfo.dist < best.dist:
 			// the port takes a shorter path/is more direct than our current
 			// candidate, so select that instead
 			update = true
-		case cinfo.dist > bestDist:
+		case cinfo.dist > best.dist:
 			// the port takes a longer path/is less direct than our current candidate,
 			// ignore it
-		case thisTime.After(bestTime):
-			// all else equal, this port was used more recently than our current
-			// candidate, so choose that instead. this should mean that, in low
-			// traffic scenarios, we consistently pick the same link which helps with
-			// packet ordering
+		case cinfo.elem.locator.tstamp > best.elem.locator.tstamp:
+			// has a newer tstamp from the root, so presumably a better path
+			update = true
+		case cinfo.elem.locator.tstamp < best.elem.locator.tstamp:
+			// has a n older tstamp, so presumably a worse path
+		case cinfo.elem.time.Before(best.elem.time):
+			// same tstamp, but got it earlier, so presumably a better path
 			update = true
 		default:
 			// the search for a port has finished
 		}
 		if update {
-			best = to
-			bestDist = cinfo.dist
-			bestTime = thisTime
+			b := cinfo // because cinfo gets mutated by the iteration
+			best = &b
 		}
 	}
 	if best != nil {
 		// Send to the best idle next hop
-		delete(idle, best.port)
-		best.sendPacketsFrom(t, [][]byte{packet})
+		if _, isIdle := idle[best.elem.port]; !isIdle {
+			return false
+		}
+		delete(idle, best.elem.port)
+		ports[best.elem.port].sendPacketsFrom(t, [][]byte{packet})
 		return true
 	}
 	// Didn't find anyone idle to send it to
@@ -870,6 +871,6 @@ func (t *switchTable) _idleIn(port switchPort) {
 	// Try to find something to send to this peer
 	if !t._handleIdle(port) {
 		// Didn't find anything ready to send yet, so stay idle
-		t.idle[port] = time.Now()
+		t.idle[port] = struct{}{}
 	}
 }