src/java.base/windows/native/libnet/net_util_md.c

rev 53867 : 8250521: Configure initial RTO to use minimal retry for loopback connections on Windows
Reviewed-by: alanb

*** 783,792 ****
--- 783,843 ----
                            NULL,
                            NULL);
      return result == SOCKET_ERROR ? WSAGetLastError() : 0;
  }
  
+ int
+ IsWindows10RS3OrGreater() {
+     OSVERSIONINFOEXW osvi = { sizeof(osvi), 0, 0, 0, 0, {0}, 0, 0 };
+     DWORDLONG const cond_mask = VerSetConditionMask(
+         VerSetConditionMask(
+           VerSetConditionMask(
+             0, VER_MAJORVERSION, VER_GREATER_EQUAL),
+                VER_MINORVERSION, VER_GREATER_EQUAL),
+                VER_BUILDNUMBER,  VER_GREATER_EQUAL);
+ 
+     osvi.dwMajorVersion = HIBYTE(_WIN32_WINNT_WIN10);
+     osvi.dwMinorVersion = LOBYTE(_WIN32_WINNT_WIN10);
+     osvi.dwBuildNumber  = 16299; // RS3 (Redstone 3)
+ 
+     return VerifyVersionInfoW(&osvi, VER_MAJORVERSION | VER_MINORVERSION | VER_BUILDNUMBER, cond_mask) != 0;
+ }
+ 
+ /**
+  * Shortens the default Windows socket
+  * connect timeout. Recommended for usage
+  * on the loopback adapter only.
+  */
+ JNIEXPORT jint JNICALL
+ NET_EnableFastTcpLoopbackConnect(int fd) {
+     TCP_INITIAL_RTO_PARAMETERS rto = {
+         TCP_INITIAL_RTO_UNSPECIFIED_RTT,    // Use the default or overriden by the Administrator
+         1                                   // Minimum possible value before Windows 10 RS3
+     };
+ 
+     /**
+      * In Windows 10 RS3+ we can use the no retransmissions flag to
+      * completely remove the timeout delay, which is fixed to 500ms
+      * if Windows receives RST when the destination port is not open.
+      */
+     if (IsWindows10RS3OrGreater()) {
+         rto.MaxSynRetransmissions = TCP_INITIAL_RTO_NO_SYN_RETRANSMISSIONS;
+     }
+ 
+     DWORD result_byte_count = -1;
+     int result = WSAIoctl(fd,                       // descriptor identifying a socket
+                           SIO_TCP_INITIAL_RTO,      // dwIoControlCode
+                           &rto,                     // pointer to TCP_INITIAL_RTO_PARAMETERS structure
+                           sizeof(rto),              // size, in bytes, of the input buffer
+                           NULL,                     // pointer to output buffer
+                           0,                        // size of output buffer
+                           &result_byte_count,       // number of bytes returned
+                           NULL,                     // OVERLAPPED structure
+                           NULL);                    // completion routine
+     return (result == SOCKET_ERROR) ? WSAGetLastError() : 0;
+ }
+ 
  /**
   * See net_util.h for documentation
   */
  JNIEXPORT int JNICALL
  NET_InetAddressToSockaddr(JNIEnv *env, jobject iaObj, int port,