Don't allow users to set a zero channel limit.

Closes #451.

docs/conf/inspircd.conf.example

@@ -610,6 +610,11 @@
          # banned from the server.
          xlinemessage="You're banned! Email irc@example.com with the ERROR line below for help."
 
+         # allowzerolimit: If enabled then allow a limit of 0 to be set on channels.
+         # This is non-standard behaviour and should only be enabled if you need to
+         # link with servers running 2.0. Defaults to yes.
+         allowzerolimit="no"
+
          # exemptchanops: exemptions for channel access restrictions based on prefix.
          exemptchanops="nonick:v flood:o"
 

src/coremods/core_channel/cmode_l.cpp

@@ -24,6 +24,7 @@
 
 ModeChannelLimit::ModeChannelLimit(Module* Creator)
 	: ParamMode<ModeChannelLimit, LocalIntExt>(Creator, "limit", 'l')
+	, minlimit(0)
 {
 }
 
@@ -35,8 +36,8 @@ bool ModeChannelLimit::ResolveModeConflict(std::string &their_param, const std::
 
 ModeAction ModeChannelLimit::OnSet(User* user, Channel* chan, std::string& parameter)
 {
-	int limit = ConvToInt(parameter);
-	if (limit < 0)
+	size_t limit = ConvToNum<size_t>(parameter);
+	if (limit < minlimit)
 		return MODEACTION_DENY;
 
 	ext.set(chan, limit);

src/coremods/core_channel/core_channel.cpp

@@ -104,6 +104,11 @@ class CoreModChannel : public Module, public CheckExemption::EventListener
 			exempts[restriction] = prefix;
 		}
 		exemptions.swap(exempts);
+
+		// In 2.0 we allowed limits of 0 to be set. This is non-standard behaviour
+		// and will be removed in the next major release.
+		limitmode.minlimit = optionstag->getBool("allowzerolimit", true) ? 0 : 1;
+
 		banmode.DoRehash();
 	}
 

src/coremods/core_channel/core_channel.h

@@ -168,6 +168,7 @@ class ModeChannelKey : public ParamMode<ModeChannelKey, LocalStringExt>
 class ModeChannelLimit : public ParamMode<ModeChannelLimit, LocalIntExt>
 {
  public:
+	size_t minlimit;
 	ModeChannelLimit(Module* Creator);
 	bool ResolveModeConflict(std::string& their_param, const std::string& our_param, Channel* channel) CXX11_OVERRIDE;
 	void SerializeParam(Channel* chan, intptr_t n, std::string& out);