Constant rubble::link::MIN_PACKET_BUF

pub const MIN_PACKET_BUF: usize = 1 /* preamble */ +
    4 /* access addr */ +
    MIN_PDU_BUF +
    3; // 0x0000_0000_0000_002fusize

Min. size a buffer for Link-Layer packets must have to comply with the spec.

The packet contains everything that ends up being transmitted over the air: Preamble, Access Address, the actual PDU, and the CRC checksum.

Bluetooth 4.2 also allows exchanging larger packets than this using the Packet Length Extension.