Drop incoming messages with stale join refs

Author: chrismccord

lib/phoenix/socket.ex

@@ -765,9 +765,19 @@ defmodule Phoenix.Socket do
     end
   end
 
-  defp handle_in({pid, _ref, _status}, message, state, socket) do
-    send(pid, message)
-    {:ok, {state, socket}}
+  defp handle_in({pid, _ref, _status}, msg, state, socket) do
+    %{topic: topic, join_ref: join_ref} = msg
+
+    case state.channels_inverse do
+      # we need to match on nil to handle v1 protocol
+      %{^pid => {^topic, existing_join_ref}} when existing_join_ref in [join_ref, nil] ->
+        send(pid, msg)
+        {:ok, {state, socket}}
+
+      # the client has sent a stale message to a previous join_ref, ignore
+      %{^pid => {^topic, _old_join_ref}} ->
+        {:ok, {state, socket}}
+    end
   end
 
   defp handle_in(

test/phoenix/integration/long_poll_channels_test.exs

@@ -436,14 +436,16 @@ defmodule Phoenix.Integration.LongPollChannelsTest do
 
         test "#{@mode}: publishing events" do
           Phoenix.PubSub.subscribe(__MODULE__, "room:lobby")
-          session = join("/ws", "room:lobby", @vsn, "1", @mode)
+          join_ref = "1"
+          session = join("/ws", "room:lobby", @vsn, join_ref, @mode)
 
           # Publish successfully
           resp =
             poll(:post, "/ws", @vsn, session, %{
               "topic" => "room:lobby",
               "event" => "new_msg",
               "ref" => "1",
+              "join_ref" => join_ref,
               "payload" => %{"body" => "hi!"}
             })