Function write_link_packet 

pub fn write_link_packet(
    link_id: &LinkId,
    link_key: &LinkKey,
    mtu: usize,
    context: WireContext,
    plaintext: &[u8],
    iv: &[u8; 16],
    buf: &mut [u8],
) -> Result<usize, LinkDataError>

A sealed link data packet framed under the given wire context: WireContext::None for plain link data, or a resource-family context (an advertisement, a part request, a hashmap update).