CCSDS Frame Security Report (FSR)
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# fsr
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CCSDS Frame Security Report (FSR) for OCaml.
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The Frame Security Report is a 32-bit status word transmitted from
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the recipient to the initiator of a [SDLS][sdls]-secured space link.
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It reports per-frame acceptance status and security events: bad
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sequence number, bad MAC, bad security association. Specified in
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CCSDS [355.1-B-1][fsr] §4.2.
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[sdls]: https://public.ccsds.org/Pubs/355x0b2.pdf
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[fsr]: https://public.ccsds.org/Pubs/355x1b1.pdf
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## Installation
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Install with opam:
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<!-- $MDX skip -->
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```sh
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$ opam install fsr
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```
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If opam cannot find the package, it may not yet be released in the
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public `opam-repository`. Add the overlay repository, then install
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it:
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<!-- $MDX skip -->
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```sh
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$ opam repo add samoht https://tangled.org/gazagnaire.org/opam-overlay.git
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$ opam update
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$ opam install fsr
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```
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## Usage
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Encode a clean report, then round-trip through the 32-bit wire
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format:
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```ocaml
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# let fsr =
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Fsr.v ~alarm:false ~bad_sn:false ~bad_mac:false ~bad_sa:false
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~spi:0x0042 ~arsn_lsb:0x7b in
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let word = Fsr.encode fsr in
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Result.map (fun r -> (r.Fsr.spi, r.Fsr.arsn_lsb)) (Fsr.decode word)
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- : (int * int, [ `Invalid_version of int | `Not_fsr ]) result = Ok (66, 123)
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```
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`update` drops in the per-frame flags and auto-raises the persistent
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alarm if any of them is true:
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```ocaml
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# let fsr =
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Fsr.initial
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|> Fsr.update ~bad_mac:true ~spi:0x0042 ~arsn_lsb:0x01 in
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(Fsr.has_error fsr, fsr.alarm)
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- : bool * bool = (true, true)
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```
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`decode` rejects non-FSR words — a Control Word Type of 0 indicates
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a CLCW, not an FSR:
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```ocaml
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# Fsr.decode 0l
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- : (Fsr.t, [ `Invalid_version of int | `Not_fsr ]) result = Error `Not_fsr
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```
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## Licence
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ISC
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