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common/rfb/Blacklist.h

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+/* Copyright (C) 2002-2005 RealVNC Ltd.  All Rights Reserved.
+ * 
+ * This is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ * 
+ * This software is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this software; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,
+ * USA.
+ */
+
+//
+// Blacklist.h - Handling of black-listed entities.
+// Just keeps a table mapping strings to timing information, including
+// how many times the entry has been black-listed and when to next
+// put it on probation (e.g. allow a connection in from the host, and
+// re-blacklist it if that fails). 
+//
+
+#ifndef __RFB_BLACKLIST_H__
+#define __RFB_BLACKLIST_H__
+
+#include <string.h>
+#include <time.h>
+#include <map>
+
+#include <rfb/Configuration.h>
+#include <rfb/util.h>
+
+namespace rfb {
+
+  //
+  // -=- Blacklist handler
+  //
+  // Parameters include a threshold after which to blacklist the named
+  // host, and a timeout after which to re-consider them.
+  //
+  // Threshold means that isBlackmarked can be called that number of times
+  // before it will return true.
+  //
+  // Timeout means that after that many seconds, the next call to isBlackmarked
+  // will return false.  At the same time, the timeout is doubled, so that the
+  // next calls will fail, until the timeout expires again or clearBlackmark is
+  // called.
+  //
+  // When clearBlackMark is called, the corresponding entry is completely
+  // removed, causing the next isBlackmarked call to return false.
+
+  // KNOWN BUG:  Client can keep making rejected requests, thus increasing
+  // their timeout.  If client does this for 30 years, timeout may wrap round
+  // to a very small value again.
+
+  // THIS CLASS IS NOT THREAD-SAFE!
+
+  class Blacklist {
+  public:
+    Blacklist();
+    ~Blacklist();
+
+    bool isBlackmarked(const char* name);
+    void clearBlackmark(const char* name);
+
+    static IntParameter threshold;
+    static IntParameter initialTimeout;
+
+  protected:
+    struct ltStr {
+      bool operator()(const char* s1, const char* s2) const {
+        return strcmp(s1, s2) < 0;
+      };
+    };
+    struct BlacklistInfo {
+      int marks;
+      time_t blockUntil;
+      unsigned int blockTimeout;
+    };
+    typedef std::map<const char*,BlacklistInfo,ltStr> BlacklistMap;
+    BlacklistMap blm;
+  };
+
+}
+
+#endif
+