Make resumed sessions try to deliver possibly queued messages to new session

Between receiving resume request and being closed by new session, it's
possible (even if not very likely) that new messages would arrive to
process that is resumed. In that case try to reroute messages that were
received after we sent resume reply to new process.

src/mod_stream_mgmt.erl

@@ -192,7 +192,7 @@ c2s_handle_recv(State, _, _) ->
 
 c2s_handle_send(#{mgmt_state := MgmtState, mod := Mod,
 		  lang := Lang} = State, Pkt, SendResult)
-  when MgmtState == pending; MgmtState == active ->
+  when MgmtState == pending; MgmtState == active; MgmtState == resumed ->
     IsStanza = xmpp:is_stanza(Pkt),
     case Pkt of
 	_ when IsStanza ->
@@ -214,6 +214,8 @@ c2s_handle_send(#{mgmt_state := MgmtState, mod := Mod,
 	    end;
 	#stream_error{} ->
 	    case MgmtState of
+		resumed ->
+		    State;
 		active ->
 		    State;
 		pending ->
@@ -230,7 +232,7 @@ c2s_handle_call(#{sid := {Time, _}, mod := Mod, mgmt_queue := Queue} = State,
 		{resume_session, Time}, From) ->
     State1 = State#{mgmt_queue => p1_queue:file_to_ram(Queue)},
     Mod:reply(From, {resume, State1}),
-    {stop, State#{mgmt_state => resumed}};
+    {stop, State#{mgmt_state => resumed, mgmt_queue => p1_queue:clear(Queue)}};
 c2s_handle_call(#{mod := Mod} = State, {resume_session, _}, From) ->
     Mod:reply(From, {error, session_not_found}),
     {stop, State};
@@ -282,6 +284,7 @@ c2s_terminated(#{mgmt_state := resumed, sid := SID, jid := JID} = State, _Reason
 	   [jid:encode(JID)]),
     {U, S, R} = jid:tolower(JID),
     ejabberd_sm:close_session(SID, U, S, R),
+    route_late_queue_after_resume(State),
     ejabberd_c2s:bounce_message_queue(SID, JID),
     {stop, State};
 c2s_terminated(#{mgmt_state := MgmtState, mgmt_stanzas_in := In,
@@ -544,6 +547,18 @@ check_queue_length(#{mgmt_queue := Queue, mgmt_max_queue := Limit} = State) ->
 	    State
     end.
 
+-spec route_late_queue_after_resume(state()) -> ok.
+route_late_queue_after_resume(#{mgmt_queue := Queue, jid := JID})
+    when ?qlen(Queue) > 0 ->
+    ?DEBUG("Re-routing ~B late queued packets to ~ts",
+	   [p1_queue:len(Queue), jid:encode(JID)]),
+    p1_queue:foreach(
+	fun({_, _Time, Pkt}) ->
+	    ejabberd_router:route(Pkt)
+	end, Queue);
+route_late_queue_after_resume(_State) ->
+    ok.
+
 -spec resend_unacked_stanzas(state()) -> state().
 resend_unacked_stanzas(#{mgmt_state := MgmtState,
 			 mgmt_queue := Queue,