Module flags 

Constants

LAST_CHUNK

This is the final chunk of its file.

REUSE_LOCAL

This chunk is byte-for-byte what the receiver already holds at the same offset in its existing copy, so it carries no payload either. The receiver copies the block locally instead of receiving it.

SEALED

Payload carries an AEAD tag after the ciphertext.

ZERO

The chunk is entirely zero bytes and carries no payload at all. Lets a sparse or preallocated file cross the wire as its holes rather than as gigabytes of zeros.