Fix client instability / crashes when zoning frequently

src/main/resources/application.conf

@@ -580,6 +580,14 @@ network {
 
     # How many attempts at resolving missing packets with anticipated subslot numbers
     in-subslot-missing-attempts = 10
+
+    # How many recently-sent reliable SlottedMetaPackets are retained for retransmission.
+    # When the client requests a resend (RelatedA) of a subslot older than this window, the packet
+    # has been evicted and cannot be recovered, wedging the client. A zone load bursts a large number
+    # of reliable ObjectCreate packets, so this must comfortably exceed the biggest single-zone
+    # burst; frequent zoning is the case that drives the requirement.
+    # Cost is roughly (length * MTU) bytes of retained packet data per session.
+    smp-history-length = 1024
   }
 
   session {

src/main/scala/net/psforever/actors/net/MiddlewareActor.scala

@@ -275,7 +275,7 @@ class MiddlewareActor(
     MiddlewareActor.propertyOverrideMessageGuard
   )
 
-  private val smpHistoryLength: Int = 100
+  private val smpHistoryLength: Int = Config.app.network.middleware.smpHistoryLength
 
   /** History of created `SlottedMetaPacket`s.
     * In case the client does not register receiving a packet by checking against packet subslot index numbers,
@@ -585,11 +585,15 @@ class MiddlewareActor(
 
           case RelatedA(slot, subslot) =>
             val requestedSubslot = subslot - 1
-            preparedSlottedMetaPackets.find(_.subslot == requestedSubslot) match {
+            //the history ring is pre-sized and holds null slots until it fills, so the predicate must be null-safe
+            preparedSlottedMetaPackets.find(p => p != null && p.subslot == requestedSubslot) match {
               case Some(_packet) =>
                 outQueueBundled.enqueue(_packet)
               case None if requestedSubslot < acceptedSmpSubslot =>
-                log.warn(s"Client indicated an smp of slot $slot prior to $subslot that is no longer logged")
+                log.warn(
+                  s"Client indicated an smp of slot $slot prior to $subslot that is no longer logged " +
+                    s"(retransmit history holds $smpHistoryLength packets; raise network.middleware.smp-history-length if this recurs)"
+                )
               case None =>
                 log.warn(s"Client indicated an smp of slot $slot prior to $subslot that is not found")
             }

src/main/scala/net/psforever/actors/session/SessionActor.scala

@@ -230,8 +230,8 @@ class SessionActor(middlewareActor: typed.ActorRef[MiddlewareActor.Command], con
       logic.general.handleRenewCharSavedTimerMsg()
 
     /* common messages (maybe once every respawn) */
-    case ICS.SpawnPointResponse(response) =>
-      data.zoning.handleSpawnPointResponse(response)
+    case ICS.SpawnPointResponse(response, token) =>
+      data.zoning.handleSpawnPointResponse(response, token)
 
     case SessionActor.NewPlayerLoaded(tplayer) =>
       data.zoning.spawn.handleNewPlayerLoaded(tplayer)
@@ -298,6 +298,12 @@ class SessionActor(middlewareActor: typed.ActorRef[MiddlewareActor.Command], con
     case ZoningOperations.AvatarAwardMessageBundle(pkts, delay) =>
       data.zoning.spawn.performAvatarAwardMessageDelivery(pkts, delay)
 
+    case ZoningOperations.ZoningCountdownTick(runnable) =>
+      data.zoning.beginZoningCountdown(runnable)
+
+    case msg: ZoningOperations.ZoningSpawnPointRespawn =>
+      data.zoning.spawn.handleZoningSpawnPointRespawn(msg)
+
     case CommonMessages.ProgressEvent(delta, finishedAction, stepAction, tick) =>
       data.general.handleProgressChange(delta, finishedAction, stepAction, tick)
 

src/main/scala/net/psforever/actors/session/normal/LocalHandlerLogic.scala

@@ -245,7 +245,8 @@ class LocalHandlerLogic(val ops: SessionLocalHandlers, implicit val context: Act
           zone.Number,
           player.Faction,
           Seq(SpawnGroup.Facility, SpawnGroup.Tower, SpawnGroup.AMS),
-          context.self
+          context.self,
+          token = sessionLogic.zoning.nextSpawnPointToken()
         )
       }
   }