[SIS-CFDPV1] Improvements for CCSDS CFDP

[muellerr]

Good Morning,

I am currently working on a high-level implementation of CFDP state 
machines using Python as part
of the tmtccmd library: https://github.com/robamu-org/tmtccmd

I have one suggestion to improve the standard:

I extended the directory operations reserved message with a directory 
listing options message type, which augments
the current directory listing request similarly to how the Proxy 
Transmission Mode or Proxy Closure Requested manipulate
the current Proxy Put Request.

These options currently contains the recursive option and the all option 
for me, which translate to the -r and -a flag
of the ls command for a UNIX system. Of course, there might be other 
options to consider, but I think such an options
message type might also be useful in the standard.

Another point: I am currently trying to fully implement 6.2.4 and 6.2.5 
which specify how to respond to a Proxy Put Request.
The whole process is done via the CFDP user, so this becomes a bit 
tricky when trying to implement this as
a library, but it is certainly possible with smart design. One thing I 
noticed is that I probably need some way to
figure out whether a transaction indication was triggered by a proxy put 
request, so that I can request a new FDU
with the proxy put response and the originating ID. This currently means 
that I would have to add some new API to my CFDP user
base class, so that I can register that some transaction indication was 
due to a proxy put request. Would it for example be
possible to extend the Transaction.Indication primitive to somehow 
contain the information, for example via an optional
originating transaction ID parameter?

Kind Regards
Robin Müller