mod_s2s: Fire 's2s-ondrain' event, mirroring mod_c2s

Signals that any pending outgoing stanzas that were in the write buffer
have at least been sent off to the Kernel and maybe even sent out over
the network.

See 7a703af90c9c for mod_c2s commit

1 files changed, 7 insertions, 0 deletions

diff --git a/plugins/mod_s2s.lua b/plugins/mod_s2s.lua
index 1e0fb955..75eb15ca 100644
--- a/plugins/mod_s2s.lua
+++ b/plugins/mod_s2s.lua
@@ -853,6 +853,13 @@ function listener.onreadtimeout(conn)
 	end
 end
 
+function listener.ondrain(conn)
+	local session = sessions[conn];
+	if session then
+		return (hosts[session.host] or prosody).events.fire_event("s2s-ondrain", { session = session });
+	end
+end
+
 function listener.register_outgoing(conn, session)
 	sessions[conn] = session;
 	initialize_session(session);