Function construct_aad 

pub fn construct_aad(
    frame_type: u8,
    flags: u8,
    session_id: &[u8; 6],
    nonce_counter: u64,
) -> [u8; 16]

Available on crate feature crypto only.

Construct AAD (Additional Authenticated Data) for a data frame.

Layout (exactly 16 bytes):

[ frame_type (1) | flags (1) | session_id (6) | nonce_counter (8) ]