Prevent instability and crash due to message flood

This patch adds a rate limiting to selected patches. The underlying rate limiter
used is the Leaky-Bucket algorithm. It allows for a burst of messages, but
limits them after a specified amount of messages within a time frame.

1 files changed, 29 insertions, 0 deletions

diff --git a/src/murmur/ServerUser.h b/src/murmur/ServerUser.h
index 28e582739..0a3828205 100644
--- a/src/murmur/ServerUser.h
+++ b/src/murmur/ServerUser.h
@@ -14,6 +14,13 @@
 #include <winsock2.h>
 #endif
 
+// <chrono> was introduced in C++11
+#if __cplusplus > 199711LL
+#include <chrono>
+#else
+#include <ctime>
+#endif
+
 #include "Connection.h"
 #include "Timer.h"
 #include "User.h"
@@ -55,6 +62,26 @@ struct WhisperTarget {
 
 class Server;
 
+#if __cplusplus > 199711L
+        typedef std::chrono::time_point<std::chrono::steady_clock> time_point;
+#else
+        typedef clock_t time_point;
+#endif
+
+// Simple algorithm for rate limiting
+class LeakyBucket {
+	private:
+		unsigned int tokensPerSec, maxTokens;
+		long currentTokens;
+		time_point lastUpdate;
+
+	public:
+		// Returns true if packets should be dropped
+		bool ratelimit(int tokens);
+
+		LeakyBucket();
+};
+
 class ServerUser : public Connection, public User {
 	private:
 		Q_OBJECT
@@ -103,6 +130,8 @@ class ServerUser : public Connection, public User {
 		QMap<int, TargetCache> qmTargetCache;
 		QMap<QString, QString> qmWhisperRedirect;
 
+		LeakyBucket leakyBucket;
+
 		int iLastPermissionCheck;
 		QMap<int, unsigned int> qmPermissionSent;
 #ifdef Q_OS_UNIX