commit ac341176da5bbe99a9b07353f6e9790575ce1493
from: Alexander Barton <alex@barton.de>
date: Sun Mar 11 20:01:45 2018 UTC

Only send TOPIC updates to a channel when the topic actually changed

This prevents the channel from becoming flooded by unecessary TOPIC
update messages, that can happen when IRC services try to enforce a
certain topic but which is already set (at least on the local server),
for example. Therefore still forward it to all servers, but don't inform
local clients (still update setter and timestamp information, though!)

commit - 6a622c0084ec69563609804520e2753501254503
commit + ac341176da5bbe99a9b07353f6e9790575ce1493
blob - 4ea25bb044e61d7744e0d427faac7a35fa44e3f8
blob + 812429bbf33eadc2a0dbd5174522bb673572f121
--- src/ngircd/irc-channel.c
+++ src/ngircd/irc-channel.c
@@ -1,6 +1,6 @@
 /*
  * ngIRCd -- The Next Generation IRC Daemon
- * Copyright (c)2001-2015 Alexander Barton (alex@barton.de) and Contributors.
+ * Copyright (c)2001-2018 Alexander Barton (alex@barton.de) and Contributors.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -497,7 +497,7 @@ IRC_TOPIC( CLIENT *Client, REQUEST *Req )
 		topic_power = true;
 
 	if (Req->argc == 1) {
-		/* Request actual topic */
+		/* Request current topic */
 		topic = Channel_Topic(chan);
 		if (*topic) {
 			r = IRC_WriteStrClient(from, RPL_TOPIC_MSG,
@@ -532,8 +532,6 @@ IRC_TOPIC( CLIENT *Client, REQUEST *Req )
 						  Channel_Name(chan));
 	}
 
-	/* Set new topic */
-	Channel_SetTopic(chan, from, Req->argv[1]);
 	LogDebug("%s \"%s\" set topic on \"%s\": %s",
 		 Client_TypeText(from), Client_Mask(from), Channel_Name(chan),
 		 Req->argv[1][0] ? Req->argv[1] : "<none>");
@@ -545,9 +543,17 @@ IRC_TOPIC( CLIENT *Client, REQUEST *Req )
 	if (!Channel_IsLocal(chan))
 		IRC_WriteStrServersPrefix(Client, from, "TOPIC %s :%s",
 					  Req->argv[0], Req->argv[1]);
-	IRC_WriteStrChannelPrefix(Client, chan, from, false, "TOPIC %s :%s",
-				  Req->argv[0], Req->argv[1]);
+
+	/* Infrom local clients, but only when the topic really changed. */
+	if (strcmp(Req->argv[1], Channel_Topic(chan)) != 0)
+		IRC_WriteStrChannelPrefix(Client, chan, from, false,
+					    "TOPIC %s :%s", Req->argv[0],
+					    Req->argv[1]);
 
+	/* Update topic, setter, and timestamp. */
+	Channel_SetTopic(chan, from, Req->argv[1]);
+
+	/* Send confirmation when the local client is a user. */
 	if (Client_Type(Client) == CLIENT_USER)
 		return IRC_WriteStrClientPrefix(Client, Client, "TOPIC %s :%s",
 						Req->argv[0], Req->argv[1]);