m_spanningtree Propagate topic changes via FTOPIC in order to prevent desync when two TOPIC messages cross

TOPIC is no longer accepted from servers using the new protocol

1 files changed, 44 insertions, 5 deletions

diff --git a/src/modules/m_spanningtree/ftopic.cpp b/src/modules/m_spanningtree/ftopic.cpp
index 0a4a95f9e..bd15489a2 100644
--- a/src/modules/m_spanningtree/ftopic.cpp
+++ b/src/modules/m_spanningtree/ftopic.cpp
@@ -44,26 +44,65 @@ CmdResult CommandFTopic::Handle(User* user, std::vector<std::string>& params)
 	if (ts < c->topicset)
 		return CMD_FAILURE;
 
+	// The topic text is always the last parameter
+	const std::string& newtopic = params.back();
+
+	// If there is a setter in the message use that, otherwise use the message source
+	const std::string& setter = ((params.size() > 4) ? params[3] : (ServerInstance->Config->FullHostInTopic ? user->GetFullHost() : user->nick));
+
 	/*
 	 * If the topics were updated at the exact same second, accept
 	 * the remote only when it's "bigger" than ours as defined by
 	 * string comparision, so non-empty topics always overridde
 	 * empty topics if their timestamps are equal
+	 *
+	 * Similarly, if the topic texts are equal too, keep one topic
+	 * setter and discard the other
 	 */
-	if ((ts == c->topicset) && (c->topic > params[4]))
-		return CMD_FAILURE; // Topics were set at the exact same time, keep our topic and setter
+	if (ts == c->topicset)
+	{
+		// Discard if their topic text is "smaller"
+		if (c->topic > newtopic)
+			return CMD_FAILURE;
 
-	if (c->topic != params[4])
+		// If the texts are equal in addition to the timestamps, decide which setter to keep
+		if ((c->topic == newtopic) && (c->setby >= setter))
+			return CMD_FAILURE;
+	}
+
+	if (c->topic != newtopic)
 	{
 		// Update topic only when it differs from current topic
-		c->topic.assign(params[4], 0, ServerInstance->Config->Limits.MaxTopic);
+		c->topic.assign(newtopic, 0, ServerInstance->Config->Limits.MaxTopic);
 		c->WriteChannel(user, "TOPIC %s :%s", c->name.c_str(), c->topic.c_str());
 	}
 
 	// Update setter and settime
-	c->setby.assign(params[3], 0, 127);
+	c->setby.assign(setter, 0, 128);
 	c->topicset = ts;
 
+	FOREACH_MOD(OnPostTopicChange, (user, c, c->topic));
+
 	return CMD_SUCCESS;
 }
 
+// Used when bursting and in reply to RESYNC, contains topic setter as the 4th parameter
+CommandFTopic::Builder::Builder(Channel* chan)
+	: CmdBuilder("FTOPIC")
+{
+	push(chan->name);
+	push_int(chan->age);
+	push_int(chan->topicset);
+	push(chan->setby);
+	push_last(chan->topic);
+}
+
+// Used when changing the topic, the setter is the message source
+CommandFTopic::Builder::Builder(User* user, Channel* chan)
+	: CmdBuilder(user, "FTOPIC")
+{
+	push(chan->name);
+	push_int(chan->age);
+	push_int(chan->topicset);
+	push_last(chan->topic);
+}