DX > SYN > server
DX < SYN ACK < server (start SYN_RECV timer, retries=0)
DX > ACK > server... TCP_DEFER_ACCEPT? yes! packet_has_data? no! drop 6!

... some time later: SYN_RECV timeout, so
DX < SYN ACK < server (start SYN_RECV timer, retries=1)
DX > ACK > server... TCP_DEFER_ACCEPT? yes! packet_has_data? no! drop 6!

... some time later: SYN_RECV timeout, so
DX < SYN ACK < server (start SYN_RECV timer, retries=2)
DX > ACK > server... TCP_DEFER_ACCEPT? yes! packet_has_data? no! drop 6!

... some time later: SYN_RECV timeout, so
DX < SYN ACK < server (start SYN_RECV timer, retries=3)
DX > ACK > server... TCP_DEFER_ACCEPT? yes! packet_has_data? no! drop 6!

... some time later: SYN_RECV timeout, so
DX < SYN ACK < server (start SYN_RECV timer, retries=4)
DX > ACK > server... TCP_DEFER_ACCEPT? yes! packet_has_data? no! drop 6!

... some time later: SYN_RECV timeout, so
DX < SYN ACK < server (start SYN_RECV timer, retries=5)
DX > ACK > server... TCP_DEFER_ACCEPT? yes! packet_has_data? no! drop 6!

... some time later: SYN_RECV timeout, retries >=5 so close half-open connection

DX > ACK + data > server... Seq # invalid, so
DX < RST < server