Send PING to check the status of the SPDY connection.

net/spdy/spdy_session.h

Index: net/spdy/spdy_session.h
===================================================================
--- net/spdy/spdy_session.h	(revision 105257)
+++ net/spdy/spdy_session.h	(working copy)
@@ -104,7 +104,8 @@
   // NOTE:  This function can have false negatives on some platforms.
   bool VerifyDomainAuthentication(const std::string& domain);
 
-  // Send the SYN frame for |stream_id|.
+  // Send the SYN frame for |stream_id|. This also sends PING message to check
+  // the status of the connection.
   int WriteSynStream(
       spdy::SpdyStreamId stream_id,
       RequestPriority priority,
@@ -271,12 +272,14 @@
                  const linked_ptr<spdy::SpdyHeaderBlock>& headers);
   void OnRst(const spdy::SpdyRstStreamControlFrame& frame);
   void OnGoAway(const spdy::SpdyGoAwayControlFrame& frame);
+  void OnPing(const spdy::SpdyPingControlFrame& frame);
   void OnSettings(const spdy::SpdySettingsControlFrame& frame);
   void OnWindowUpdate(const spdy::SpdyWindowUpdateControlFrame& frame);
 
   // IO Callbacks
   void OnReadComplete(int result);
   void OnWriteComplete(int result);
+  void OnWriteCompleteInternal(int result, bool ping_frame);
 
   // Send relevant SETTINGS.  This is generally called on connection setup.
   void SendSettings();
@@ -285,6 +288,24 @@
   // SETTINGS ontrol frame, update our SpdySession accordingly.
   void HandleSettings(const spdy::SpdySettings& settings);
 
+  // Send the PING (pre-PING and post-PING) frames for |stream_id|.
+  int SendPing(spdy::SpdyStreamId stream_id);
+
+  // Send PING if there are no PINGs in flight and we haven't heard from server.
+  int SendPrePing(spdy::SpdyStreamId stream_id);
+
+  // Send a delayed PING if there is no |follower_ping_pending_|. This PING
+  // makes sure the request has been received by the server.
+  int SendPostPing(spdy::SpdyStreamId stream_id);
+
+  // Send the PING frame for |stream_id|.
+  int WritePingFrame(spdy::SpdyStreamId stream_id);
+
+  // Check the status of the connection. It does |DeleteStream| if we haven't
+  // received any data in |kHungInterval|.
+  void CheckStatus(spdy::SpdyStreamId stream_id,
+                   base::TimeTicks last_check_time);
+
   // Start reading from the socket.
   // Returns OK on success, or an error on failure.
   net::Error ReadSocket();
@@ -431,6 +452,18 @@
                             // frame.
   int stalled_streams_;     // Count of streams that were ever stalled.
 
+  // This list keeps track of all pings (unique_ids) that are in flight.
+  int64 pings_in_flight_;
+
+  // This is the next unique_id to be sent in PING frame.
+  uint32  unique_id_counter_;
+
+  // This is the last time we had received data.
+  base::TimeTicks received_data_time_;
+
+  // Flag if we have a pending follower ping.
+  bool follower_ping_pending_;
+
   // Initial send window size for the session; can be changed by an
   // arriving SETTINGS frame; newly created streams use this value for the
   // initial send window size.