Changes: 1.Simplify f-stack startup arguments:"--conf, --proc-type, --proc-id". 2.add a function `ff_fdisused` to check if fd is used in f-stack.
RX: VLAN strip, CRC strip, IP/TCP/UDP checksum. TX: IP/TCP/UDP checksum, TSO. Note that TSO has a problem: when enable TSO, F-Stack is much slower(Temporarily not resolved). So TSO is disabled by default. Edit config.ini to enable it.
In some cases such as AWS EC2, we must strip vlan tag. Edit the config.ini, set port.vlanstrip = 1.