mod_ping: Fix double response to internal ping When responding to a ping from elsewhere in the same Prosody the send function will be host_send from core.hostmanager, which does not return anything. Tailcalling it therefore lets the iq event fall trough to handle_unhandled_stanza in core.stanza_router, which responds with an error. This error also goes into handle_unhandled_stanza which discards it. Noticed because I have a module that points out when a stanza error reply is created without a text argument.

--- a/plugins/mod_ping.lua	Fri Feb 21 23:01:43 2020 +0100
+++ b/plugins/mod_ping.lua	Fri Feb 21 23:30:47 2020 +0100
@@ -11,7 +11,8 @@
 module:add_feature("urn:xmpp:ping");
 
 local function ping_handler(event)
-	return event.origin.send(st.reply(event.stanza));
+	event.origin.send(st.reply(event.stanza));
+	return true;
 end
 
 module:hook("iq-get/bare/urn:xmpp:ping:ping", ping_handler);