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 4cbf692a0fbe6d5668526467664dd5b4b2862f57..0958b6d25d0f3e522524452bcb8e87281e3368fb 100644
--- a/net/socket/tcp_socket_libevent.h
+++ b/net/socket/tcp_socket_libevent.h
@@ -88,52 +88,72 @@ class NET_EXPORT TCPSocketLibevent {
 
  private:
   // States that using a socket with TCP FastOpen can lead to.
-  enum FastOpenStatus {
-    FAST_OPEN_STATUS_UNKNOWN,
+  enum TCPFastOpenStatus {
+    TCP_FASTOPEN_STATUS_UNKNOWN,
 
-    // The initial TCP FastOpen connect attempted returned synchronously,
+    // The initial FastOpen connect attempted returned synchronously,
     // indicating that we had and sent a cookie along with the initial data.
-    FAST_OPEN_FAST_CONNECT_RETURN,
+    TCP_FASTOPEN_FAST_CONNECT_RETURN,
 
-    // The initial TCP FastOpen connect attempted returned asynchronously,
+    // The initial FastOpen connect attempted returned asynchronously,
     // indicating that we did not have a cookie for the server.
-    FAST_OPEN_SLOW_CONNECT_RETURN,
+    TCP_FASTOPEN_SLOW_CONNECT_RETURN,
 
     // Some other error occurred on connection, so we couldn't tell if
-    // TCP FastOpen would have worked.
-    FAST_OPEN_ERROR,
+    // FastOpen would have worked.
+    TCP_FASTOPEN_ERROR,
 
-    // An attempt to do a TCP FastOpen succeeded immediately
-    // (FAST_OPEN_FAST_CONNECT_RETURN) and we later confirmed that the server
+    // An attempt to do a FastOpen succeeded immediately
+    // (TCP_FASTOPEN_FAST_CONNECT_RETURN) and we later confirmed that the server
     // had acked the data we sent.
-    FAST_OPEN_SYN_DATA_ACK,
+    TCP_FASTOPEN_SYN_DATA_ACK,
 
-    // An attempt to do a TCP FastOpen succeeded immediately
-    // (FAST_OPEN_FAST_CONNECT_RETURN) and we later confirmed that the server
+    // An attempt to do a FastOpen succeeded immediately
+    // (TCP_FASTOPEN_FAST_CONNECT_RETURN) and we later confirmed that the server
     // had nacked the data we sent.
-    FAST_OPEN_SYN_DATA_NACK,
+    TCP_FASTOPEN_SYN_DATA_NACK,
 
-    // An attempt to do a TCP FastOpen succeeded immediately
-    // (FAST_OPEN_FAST_CONNECT_RETURN) and our probe to determine if the
-    // socket was using TCP FastOpen failed.
-    FAST_OPEN_SYN_DATA_FAILED,
+    // An attempt to do a FastOpen succeeded immediately
+    // (TCP_FASTOPEN_FAST_CONNECT_RETURN) and our probe to determine if the
+    // socket was using FastOpen failed.
+    TCP_FASTOPEN_SYN_DATA_GETSOCKOPT_FAILED,
 
-    // An attempt to do a TCP FastOpen failed (FAST_OPEN_SLOW_CONNECT_RETURN)
+    // An attempt to do a FastOpen failed (TCP_FASTOPEN_SLOW_CONNECT_RETURN)
     // and we later confirmed that the server had acked initial data.  This
     // should never happen (we didn't send data, so it shouldn't have
     // been acked).
-    FAST_OPEN_NO_SYN_DATA_ACK,
+    TCP_FASTOPEN_NO_SYN_DATA_ACK,
 
-    // An attempt to do a TCP FastOpen failed (FAST_OPEN_SLOW_CONNECT_RETURN)
+    // An attempt to do a FastOpen failed (TCP_FASTOPEN_SLOW_CONNECT_RETURN)
     // and we later discovered that the server had nacked initial data.  This
-    // is the expected case results for FAST_OPEN_SLOW_CONNECT_RETURN.
-    FAST_OPEN_NO_SYN_DATA_NACK,
+    // is the expected case results for TCP_FASTOPEN_SLOW_CONNECT_RETURN.
+    TCP_FASTOPEN_NO_SYN_DATA_NACK,
 
-    // An attempt to do a TCP FastOpen failed (FAST_OPEN_SLOW_CONNECT_RETURN)
+    // An attempt to do a FastOpen failed (TCP_FASTOPEN_SLOW_CONNECT_RETURN)
     // and our later probe for ack/nack state failed.
-    FAST_OPEN_NO_SYN_DATA_FAILED,
-
-    FAST_OPEN_MAX_VALUE
+    TCP_FASTOPEN_NO_SYN_DATA_GETSOCKOPT_FAILED,
+
+    // The initial FastOpen connect+write succeeded immediately
+    // (TCP_FASTOPEN_FAST_CONNECT_RETURN) and a subsequent attempt to read from
+    // the connection failed.
+    TCP_FASTOPEN_FAST_CONNECT_READ_FAILED,
+
+    // The initial FastOpen connect+write failed
+    // (TCP_FASTOPEN_SLOW_CONNECT_RETURN)
+    // and a subsequent attempt to read from the connection failed.
+    TCP_FASTOPEN_SLOW_CONNECT_READ_FAILED,
+
+    // We didn't try FastOpen because it had failed in the past
+    // (g_tcp_fastopen_has_failed was true.)
+    // NOTE: This status is currently registered before a connect/write call
+    // is attempted, and may capture some cases where the status is registered
+    // but no connect is subsequently attempted.
+    // TODO(jri): The expectation is that such cases are not the common case
+    // with TCP FastOpen for SSL sockets however. Change code to be more
+    // accurate when TCP FastOpen is used for more than just SSL sockets.
+    TCP_FASTOPEN_PREVIOUSLY_FAILED,
+
+    TCP_FASTOPEN_MAX_VALUE
   };
 
   void AcceptCompleted(scoped_ptr<TCPSocketLibevent>* tcp_socket,
@@ -158,14 +178,14 @@ 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();
+  // Called after the first read completes on a TCP FastOpen socket.
+  void UpdateTCPFastOpenStatusAfterRead();
 
   scoped_ptr<SocketLibevent> socket_;
   scoped_ptr<SocketLibevent> accept_socket_;
@@ -173,9 +193,14 @@ 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_;