0.8.0 made private the constant "NETLINK_HEADER_LEN" in use in `innernet` netlink-request

[issackelly]

Could we put this back into pub scope?

pub const NETLINK_HEADER_LEN: usize = PAYLOAD.start;

[cathay4t]

Could you try NetlinkHeader::default().buffer_len()?

Instead of exposing a constant, I prefer adding NetlinkHeader::LEN constant.

May I know why you need that constant?

[cathay4t]

#40 created for NetlinkHeader::LEN.