extern BOOL system_filtering; /* TRUE when running system filter */
extern BOOL tcp_fastopen_ok; /* appears to be supported by kernel */
+extern blob tcp_fastopen_nodata; /* for zero-data TFO connect requests */
+extern BOOL tcp_in_fastopen; /* conn usefully used fastopen */
+extern BOOL tcp_in_fastopen_logged; /* one-time logging */
extern BOOL tcp_nodelay; /* Controls TCP_NODELAY on daemon */
+extern int tcp_out_fastopen; /* 0: no 1: conn used 2: useful */
+extern BOOL tcp_out_fastopen_logged; /* one-time logging */
#ifdef USE_TCP_WRAPPERS
extern uschar *tcp_wrappers_daemon_name; /* tcpwrappers daemon lookup name */
#endif