XEP-0198: Improve handling of too large 'h' values

If the client says that it handled more stanzas than we sent (due to a
bug in the client's or in our code), increase our outgoing stanza count
accordingly.  There's no point in sticking to the old value even if it
was correct, as the client surely won't fix its count during the current
session.

diff --git a/src/ejabberd_c2s.erl b/src/ejabberd_c2s.erl
index 0897730a59e80fac45036bf66846ed9d3ce5ae36..9ce66d0431895400c9e0eb29487dc544c26146f4 100644 (file)
--- a/src/ejabberd_c2s.erl
+++ b/src/ejabberd_c2s.erl
@@ -2686,16 +2686,13 @@ handle_r(StateData) ->
     send_element(StateData, Res),
     StateData.
 
-handle_a(#state{jid = JID, mgmt_stanzas_out = NumStanzasOut} = StateData,
-        Attrs) ->
+handle_a(StateData, Attrs) ->
     case catch jlib:binary_to_integer(xml:get_attr_s(<<"h">>, Attrs)) of
       H when is_integer(H), H >= 0 ->
-         ?DEBUG("~s acknowledged ~B of ~B stanzas",
-                [jlib:jid_to_string(JID), H, NumStanzasOut]),
-         mgmt_queue_drop(StateData, H);
+         check_h_attribute(StateData, H);
       _ ->
          ?DEBUG("Ignoring invalid ACK element from ~s",
-                [jlib:jid_to_string(JID)]),
+                [jlib:jid_to_string(StateData#state.jid)]),
          StateData
     end.
 
@@ -2728,7 +2725,7 @@ handle_resume(StateData, Attrs) ->
        end,
     case R of
       {ok, ResumedState, NumHandled} ->
-         NewState = mgmt_queue_drop(ResumedState, NumHandled),
+         NewState = check_h_attribute(ResumedState, NumHandled),
          AttrXmlns = NewState#state.mgmt_xmlns,
          AttrId = make_resume_id(NewState),
          AttrH = jlib:integer_to_binary(NewState#state.mgmt_stanzas_in),
@@ -2754,6 +2751,16 @@ handle_resume(StateData, Attrs) ->
          error
     end.
 
+check_h_attribute(#state{mgmt_stanzas_out = NumStanzasOut} = StateData, H)
+    when H > NumStanzasOut ->
+    ?DEBUG("~s acknowledged ~B stanzas, but only ~B were sent",
+          [jlib:jid_to_string(StateData#state.jid), H, NumStanzasOut]),
+    mgmt_queue_drop(StateData#state{mgmt_stanzas_out = H}, NumStanzasOut);
+check_h_attribute(#state{mgmt_stanzas_out = NumStanzasOut} = StateData, H) ->
+    ?DEBUG("~s acknowledged ~B of ~B stanzas",
+          [jlib:jid_to_string(StateData#state.jid), H, NumStanzasOut]),
+    mgmt_queue_drop(StateData, H).
+
 update_num_stanzas_in(#state{mgmt_state = active} = StateData, El) ->
     NewNum = case {is_stanza(El), StateData#state.mgmt_stanzas_in} of
               {true, 4294967295} ->