Distributor should excert backpressure due to filtering overhead

lib/floof/distributor.ex

@@ -58,7 +58,7 @@ defmodule Floof.Distributor do
   end
 
   @impl true
-  def handle_cast({:xfer, {origin, dcdhash, dcd}}, state) do
+  def handle_call({:xfer, {origin, dcdhash, dcd}}, _, state) do
     # we split the state such that only the parts necessary get
     # copied into the spawned-off process
     fconf = dstate(state, :fconf)
@@ -99,7 +99,7 @@ defmodule Floof.Distributor do
       end)
     end
 
-    {:noreply, state}
+    {:reply, :ok, state}
   end
 
   @impl true

lib/floof/message.ex

@@ -6,7 +6,7 @@ defmodule Floof.Message do
   def emit(xf) do
     {:XferBlob, _, _, _, xfinner} = xf
     mhash = :crypto.hash(:blake2b, xfinner)
-    GenServer.cast(Floof.Distributor, {:xfer, {self(), mhash, xf}})
+    GenServer.call(Floof.Distributor, {:xfer, {self(), mhash, xf}})
     mhash
   end