Throw on received message if the responsible RequestOnConn has fini…

…shed

Fixes #309.

When a RoC of a multi-node request finishes, it RoC stays registered in the
`RequestOnConnSet` until all other RoCs have finished, too. During that
time the client can receive a message for this request through this
connection. It then looks the RoC up in the RoCset, finds it and calls
`RequestOnConn.setReceivedPayload`, which attempts to resume the fiber -
but the fiber has terminated so it cannot be resumed, and an assertion
fails.
This is the case of a protocol error, the client has finished handling the
request while the node is still sending messages. Handle it by tracking
which of the RoCs in the RoCset have finished and throwing `ProtocolError`
when attempting to use one.

src/swarm/neo/client/Connection.d

@@ -602,7 +602,8 @@ public final class Connection: ConnectionBase
     {
         if (auto request = this.request_set.getRequest(id))
         {
-            return request.getRequestOnConnForNode(this.node_address);
+            return request.getRequestOnConnForNode(this.node_address,
+                this.protocol_error_);
         }
         else
         {

src/swarm/neo/client/IRequestSet.d

@@ -48,7 +48,8 @@ interface IRequest
         FinishedNotifier;
 
     import swarm.neo.AddrPort;
-    IRequestOnConn getRequestOnConnForNode ( AddrPort node_address );
+    import swarm.neo.protocol.ProtocolError;
+    IRequestOnConn getRequestOnConnForNode ( AddrPort node_address, ProtocolError e );
 }
 
 /*******************************************************************************

src/swarm/neo/client/RequestOnConnSet.d

@@ -252,25 +252,29 @@ public struct RequestOnConnSet
 
     /***************************************************************************
 
-        Decrements the `num_active` counter and returns whether it is now 0.
+        Registers `roc` as inactive, decrements the `num_active` counter and
+        returns whether the counter is now 0.
+
+        Params:
+            roc = the `RequestOnConn` instance that has finished
 
         Returns:
             true if `num_active` is 0
 
     ***************************************************************************/
 
-    public bool finished ( )
+    public bool finished ( RequestOnConn roc )
     in
     {
         assert(this.num_active);
     }
     body
     {
-        // TODO: Consider `this.all_nodes.remove(request_on_conn)` instead of
-        // using the `active` flag. Not doing this now for a patch release to
-        // avoid potentially introducing a bug if there is an unobvious reason
-        // why it isn't done.
-        request_on_conn.active = false;
+        // TODO: Consider `this.all_nodes.remove(roc)` instead of using the
+        // `active` flag. Not doing this now for a patch release to avoid
+        // potentially introducing a bug if there is an unobvious reason why it
+        // isn't done.
+        roc.active = false;
         return --this.num_active == 0;
     }
 

src/swarm/neo/client/RequestSet.d

@@ -439,7 +439,7 @@ public final class RequestSet: IRequestSet
         }
         body
         {
-            if ( this.getRequestOnConnForNode(connection.remote_address) !is null )
+            if ( this.request_on_conns.get(connection.remote_address) !is null )
                 return;
 
             auto request_on_conn = this.request_on_conns.add(
@@ -452,21 +452,37 @@ public final class RequestSet: IRequestSet
         /***********************************************************************
 
             Obtains the handler of this request that is currently communicating
-            with a node, if any.
+            with a node, if any. Expects the handler to be active and throws `e`
+            if not.
 
             Params:
                 node_address = the address of the node to look up the handler
                                for
+                e = the exception to throw if a handler was found that is not
+                    active any more but has finished
 
             Returns:
                 the handler of this request that is currently communicating with
                 the node or null if none is doing that right now.
 
+            Throws:
+                `ProtocolError` if a handler was found that is not active any
+                more but has finished.
+
         ***********************************************************************/
 
-        public RequestOnConn getRequestOnConnForNode ( AddrPort node_address )
+        public RequestOnConn getRequestOnConnForNode ( AddrPort node_address,
+            ProtocolError e )
         {
-            return this.request_on_conns.get(node_address);
+            if (auto roc = this.request_on_conns.get(node_address))
+            {
+                if (roc.active)
+                    return roc;
+                else
+                    throw e.set("Unexpected incoming message");
+            }
+            else
+                return null;
         }
 
         /***********************************************************************
@@ -617,7 +633,7 @@ public final class RequestSet: IRequestSet
 
         public void handlerFinished ( RequestOnConn request_on_conn )
         {
-            if (this.request_on_conns.finished())
+            if (this.request_on_conns.finished(request_on_conn))
             {
                 scope working_data_iter = new RequestWorkingData;
                 this.finished_notifier(this.context, working_data_iter);