function_modify_sv_packet

    pub fn modify_sv_packet(frame: &EthernetFrame) -> EthernetFrame{
        let destination =   frame.destination;
        let source =        frame.source;
        let tpid =              TPID;
        let tci =               TCI;
        let ethertype =         frame.ethertype;
        let payload =         frame.payload.clone();
        let fcs =           frame.fcs;
        let mut frame_received = EthernetFrame {
            destination,
            source,
            tpid,
            tci,
            ethertype,
            payload,
            fcs, // Temporary FCS
        };

    // Calculate the FCS using crc32fast
    let frame_bytes = frame_received.to_bytes();
    let fcs = crc32(&frame_bytes[..frame_bytes.len() - 4]).to_be_bytes();
    frame_received.fcs = [fcs[0], fcs[1], fcs[2], fcs[3]];

    frame_received
    }