+
+#if defined(TCP_FASTOPEN) && defined(MSG_FASTOPEN)
+/* TCP Fast Open, if the system has a cookie from a previous call to
+this peer, can send data in the SYN packet. The peer can send data
+before it gets our ACK of its SYN,ACK - the latter is useful for
+the SMTP banner. Is there any usage where the former might be?
+We might extend the ip_connect() args for data if so. For now,
+connect in FASTOPEN mode but with zero data.
+*/
+
+if (fastopen)
+ {
+ if ( (rc = sendto(sock, NULL, 0, MSG_FASTOPEN, s_ptr, s_len)) < 0
+ && errno == EOPNOTSUPP
+ )
+ {
+ DEBUG(D_transport)
+ debug_printf("Tried TCP Fast Open but apparently not enabled by sysctl\n");
+ rc = connect(sock, s_ptr, s_len);
+ }
+ }
+else
+#endif
+ rc = connect(sock, s_ptr, s_len);
+