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diff --git a/src/shrpx_connect_blocker.h b/src/shrpx_connect_blocker.h
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+/*
+ * nghttp2 - HTTP/2 C Library
+ *
+ * Copyright (c) 2014 Tatsuhiro Tsujikawa
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+#ifndef SHRPX_CONNECT_BLOCKER_H
+#define SHRPX_CONNECT_BLOCKER_H
+
+#include "shrpx.h"
+
+#include <random>
+#include <functional>
+
+#include <ev.h>
+
+namespace shrpx {
+
+class ConnectBlocker {
+public:
+  ConnectBlocker(std::mt19937 &gen, struct ev_loop *loop,
+                 std::function<void()> block_func,
+                 std::function<void()> unblock_func);
+  ~ConnectBlocker();
+
+  // Returns true if making connection is not allowed.
+  bool blocked() const;
+  // Call this function if connect operation succeeded.  This will
+  // reset sleep_ to minimum value.
+  void on_success();
+  // Call this function if connect operations failed.  This will start
+  // timer and blocks connection establishment with exponential
+  // backoff.
+  void on_failure();
+
+  size_t get_fail_count() const;
+
+  // Peer is now considered offline.  This effectively means that the
+  // connection is blocked until online() is called.
+  void offline();
+
+  // Peer is now considered online
+  void online();
+
+  // Returns true if peer is considered offline.
+  bool in_offline() const;
+
+  void call_block_func();
+  void call_unblock_func();
+
+private:
+  std::mt19937 &gen_;
+  // Called when blocking is started
+  std::function<void()> block_func_;
+  // Called when unblocked
+  std::function<void()> unblock_func_;
+  ev_timer timer_;
+  struct ev_loop *loop_;
+  // The number of consecutive connection failure.  Reset to 0 on
+  // success.
+  size_t fail_count_;
+  // true if peer is considered offline.
+  bool offline_;
+};
+
+} // namespace shrpx
+
+#endif // SHRPX_CONNECT_BLOCKER_H