Astro

Decode CFDP Protocol Data Units (CCSDS 727.0-B-5).

Subcommands

Command	Description
`astro cfdp decode`	Decode a PDU: the fixed header, then its directive or file data

astro cfdp decode

Decode the fixed header, then the file directive or file data the PDU carries.

A file directive names itself in the first octet of its data field (table 5-4), so the body is decoded properly rather than shown as octets. EOF, Finished, ACK, Metadata, NAK and Prompt are all read down to their fields.

File data is not interpreted (it is your file, and the PDU says nothing about its contents) so it comes back as octets with a note saying so.

The CRC is verified when the header says one is present, and a mismatch is an error. Clause 4.1.2 requires the receiver to discard such a PDU, so decoding it into something plausible would be wrong.

astro cfdp decode [file] [flags]

Flags

Flag	Default	Description
`--input`	`hex`	Input format: `hex` or `bin`
`--format`	`text`	Output format: `text` or `json`

Examples

astro cfdp decode --input hex < pdu.hex
astro cfdp decode --input bin pdu.bin --format json

Part 2: the User Operations

Section 6 puts proxy, directory, remote status, suspend and resume operations in a Message to User TLV in an ordinary transaction's metadata, not in PDUs of their own. So they surface when you decode a Metadata PDU, and decode names each one and reads its content.

A Message to User is a protocol message only if it opens with the four ASCII characters cfdp. Anything else is an application message and is left alone, which is what that identifier exists for.

astro cfdp decode --input hex < metadata.hex

CFDP File Directive PDU: Metadata
  ...
User operations (2 message(s)):
  Proxy Put Request
  Beneficiary ....... 3
  Source file ....... /remote/a.dat
  Destination file .. /local/a.dat
  Originating Transaction ID
  Originating transaction: entity 1, sequence 100

Limits

The message formats of Part 2 are implemented. The user behaviour around them is not, and the standard makes that the CFDP user's job: which primitive to call on receipt, and how to queue concurrent suspension orders, which clause 6.5.4.1.2 says outright is "an implementation matter".

See also: the protocol page for the standard and the Go API, and the conformance statement for what is and is not implemented.