Let a throttling callback discard a received message

This can be used as a simple form of overload protection, discarding the
message before it's passed into diameter to become one more request
process in a flood. Replying with 3004 would be more appropriate when
the request has been directed at a specific server (the RFC's
requirement) however, and possibly it should be possible for a callback
to do this as well.

1 files changed, 9 insertions, 0 deletions

diff --git a/lib/diameter/src/transport/diameter_tcp.erl b/lib/diameter/src/transport/diameter_tcp.erl
index 7f9255c097..b68a16b521 100644
--- a/lib/diameter/src/transport/diameter_tcp.erl
+++ b/lib/diameter/src/transport/diameter_tcp.erl
@@ -892,6 +892,15 @@ throttle({NPid, F}, #transport{throttled = Msg} = S)
   when is_pid(NPid), is_binary(Msg) ->
     throttle(NPid, S#transport{throttle_cb = F});
 
+%% Callback to accept a received message says to discard it.
+throttle(discard, #transport{throttled = Msg} = S)
+  when is_binary(Msg) ->
+    throttle(S#transport{throttled = true});
+
+throttle({discard = T, F}, #transport{throttled = Msg} = S)
+  when is_binary(Msg) ->
+    throttle(T, S#transport{throttle_cb = F});
+
 %% Callback says to ask again in the specified number of milliseconds.
 throttle({timeout, Tmo}, #transport{} = S) ->
     erlang:send_after(Tmo, self(), throttle),