Adds TCP FastOpen blackhole recovery code to avoid getting persistently blackholed.

net/socket/tcp_socket_libevent.h

Index: net/socket/tcp_socket_libevent.h
diff --git a/net/socket/tcp_socket_libevent.h b/net/socket/tcp_socket_libevent.h
index 89b6a22bdd08d24b05529b6a9f2031351098d256..08844c37eff928bd6af87c850b957cfdf7032908 100644
--- a/net/socket/tcp_socket_libevent.h
+++ b/net/socket/tcp_socket_libevent.h
@@ -88,7 +88,7 @@ class NET_EXPORT TCPSocketLibevent {
 
  private:
   // States that a fast open socket attempt can result in.
-  enum FastOpenStatus {
+  enum TCPFastOpenStatus {
     FAST_OPEN_STATUS_UNKNOWN,
 
     // The initial fast open connect attempted returned synchronously,
@@ -103,6 +103,14 @@ class NET_EXPORT TCPSocketLibevent {
     // fast open would have worked.
     FAST_OPEN_ERROR,
 
+    // The initial fast open connect succeeded immediately
+    // (FAST_OPEN_FAST_CONNECT_RETURN) and the attempt to write SYN+DATA failed.
+    FAST_OPEN_FAST_CONNECT_FAILED,
+
+    // The initial fast open connect failed (FAST_OPEN_SLOW_CONNECT_RETURN)
+    // and the first attempt to write data failed.
+    FAST_OPEN_SLOW_CONNECT_FAILED,

[mmenke, 2014/09/23 15:21:01]

These should be added at the end of the list, since they're used in a UMA
histogram.

[Jana, 2014/09/24 00:51:27]

Thanks for catching this! Done.

+
     // An attempt to do a fast open succeeded immediately
     // (FAST_OPEN_FAST_CONNECT_RETURN) and we later confirmed that the server
     // had acked the data we sent.
@@ -158,14 +166,14 @@ class NET_EXPORT TCPSocketLibevent {
 
   void WriteCompleted(const scoped_refptr<IOBuffer>& buf,
                       const CompletionCallback& callback,
-                      int rv) const;
-  int HandleWriteCompleted(IOBuffer* buf, int rv) const;
+                      int rv);
+  int HandleWriteCompleted(IOBuffer* buf, int rv);
   int TcpFastOpenWrite(IOBuffer* buf,
                        int buf_len,
                        const CompletionCallback& callback);
 
   // Called when the socket is known to be in a connected state.
-  void RecordFastOpenStatus();
+  void RecordTCPFastOpenStatus();
 
   scoped_ptr<SocketLibevent> socket_;
   scoped_ptr<SocketLibevent> accept_socket_;
@@ -173,9 +181,14 @@ class NET_EXPORT TCPSocketLibevent {
   // Enables experimental TCP FastOpen option.
   bool use_tcp_fastopen_;
 
+  // True when TCP FastOpen is in use and we have attempted the
+  // connect with write.
+  bool tcp_fastopen_write_attempted_;
+
   // True when TCP FastOpen is in use and we have done the connect.
   bool tcp_fastopen_connected_;
-  FastOpenStatus fast_open_status_;
+
+  TCPFastOpenStatus tcp_fastopen_status_;
 
   bool logging_multiple_connect_attempts_;