[tialaramex]

No. If you mean "I don't know" that's not non_exhaustive that's "I don't know".

For a network protocol or C FFI you probably want a primitive integer type not any of Rust's fancier types such as enum, because while you might believe this byte should have one of six values, 0x01 through 0x06 maybe somebody decided the top bit is a flag now, so 0x83 is "the same" as 0x03 but with a flag set.

Trying to unsafely transmute things from arbitrary blobs of data to a Rust type is likely to end in tears, this attribute does not fix that.