Overview

This repository defines a ROS2 application implementing the CCSDS File Delivery Protocol (CFDP), as implemented by the open-source Python3 CFDP library. This dependency can be installed with pip install cfdp

This application receives local commands through ROS2 service calls as described below.

It communicates to remote entities by exchanging PDUs (of the ROS CfdpPdu type) on topics of the form /cfdp/pdu/entity#, where # is the target entity number. For example, if this instance is instantiated with a local entity ID of 1, and a second instance exists with an entity ID of 2, then it will listen for messages at /cfdp/pdu/entity1 and send to /cfdp/pdu/entity2.

It is left for other ROS entities to bridge the PDU content to interface with external entities. For example, by appending a CCSDS Command (including primary and secondary header) and sending over a UDP socket to a cFE instance running ci_lab, while receiving PDUs from to_lab in an equivalent pattern. The translation bridge should map entity IDs to distinct CCSDS MIDs and/or other appropriate routing details.

sequenceDiagram
box ROS GSW
participant RGSW_CFDP
participant RGSW_BRIDGE
end

box CFE FSW
participant ci_lab
participant to_lab
participant sbn
participant cfdp
end

box ROS FSW
participant RFSW_SBN
participant RFSW_CFDP
end

rect rgb(200, 250, 255)
note right of RGSW_CFDP: Upload file from ROS GSW to ROS FSW via bridges
RGSW_CFDP->>RGSW_BRIDGE: Send PDU
RGSW_BRIDGE->>ci_lab: Forward PDU (/w CCSDS header prepended)
ci_lab->>sbn: Forward packet over SBN
sbn->>RFSW_SBN: SBN to SBN transfer
RFSW_SBN->>RFSW_CFDP: Receive PDU, SBN will strip SBN + CCSDS headers leaving original PDU to parse

Note right of RGSW_CFDP: Reverse message flow for ACKs if using Acknowledged (Class2) Mode

end %% Region Rect

rect rgb(255, 250, 200)
note right of RGSW_CFDP: Request file from cFE

RGSW_CFDP->>RGSW_BRIDGE: Put request for file
RGSW_BRIDGE->>ci_lab: Receive PDU cmd and publish on SB
ci_lab->>cfdp: Process PDU and begin requested tranfer
cfdp->>to_lab: Send PDU ACKs and data packets
to_lab->>RGSW_BRIDGE: Forward PDUs to ground
RGSW_BRIDGE->>RGSW_CFDP: Receive PDUs and assemble file

end %% End cfe file request

Local Commands

Local commands can be issued from the local ROS instance, for example:

ros2 service call /cfdp/cmd/put cfdp_msgs/srv/CfdpXfrCmd "{src: '/test.txt', dst: '/test.txt.dst', dstid: 1}"

All commands are named with the topic format /cfdp/cmd/$CMD. All paths are as defined by the entity. For instances of this application, they are relative to the directory the service was started from.

ls

Generate a directory listing and transfer it to the local instance as a file with the specified name.

WARNING: This command may not be supported by all CFDP clients (does not appear to work with the open-source cFE CF application).

This command uses the CfdpXfrCmd message type where:

• dstid is the CFDP Entity ID to execute the directory listing on
• src is the directory path to list
• dst is the desired name of the file to save the directory listing to.
• ack is a boolean. If true, use CFDP class 2, Acknowledged Mode. Else use unacknowledged class 1.

get

Transfer a file from the remote entity to the local entity. This is implemented as a Proxy request for the remote entity to PUT a file to this instance.

This command uses the CfdpXfrCmd message type where:

• dstid is the CFDP Entity ID to execute the directory listing on
• src is the remote file to send
• dst is the desired name of the file to be saved locally.
• ack is a boolean. If true, use CFDP class 2, Acknowledged Mode. Else use unacknowledged class 1.

put

Transfer a file from the local entity to the remote entity.

This command uses the CfdpXfrCmd message type where:

• dstid is the CFDP Entity ID to execute the directory listing on
• src is the local file to send
• dst is the desired name of the file to be saved on the remote entity.
• ack is a boolean. If true, use CFDP class 2, Acknowledged Mode. Else use unacknowledged class 1.

File operations

The following commands operate on a single (remote) file or directory and support the following parameters:

• dstid is the CFDP Entity ID to execute the directory listing on
• tgt is the desired file/folder to manipulate on the remote entity.
• ack is a boolean. If true, use CFDP class 2, Acknowledged Mode. Else use unacknowledged class 1.

mkdir

Create a directory on the remote insteance identified by dstid.

rmdir

Delete a directory on the remote instance.

Note: Remote instance may not permit deletion of non-empty directories.

touch

Create a blank file on the remote instance.

rm

Delete a single file on the remote instance.

Configuration

A configuration file (specified as the ROS parameter 'config') points to a YAML file defining a listing of all known CFDP Entities and relevant configuration details. This definition should match that available to all other entities (including cFE's CFDP app via it's table services). A default configuration can be found in cfdp_wrapper/config.

Protocol Data Units (PDUs) are transmitted on a ROS topic of /cfdp/pdu/entity$entityID.

entityID is a required parameter to this application, currently defaulitng to a value of 2. This field defines the entityID of this application instance. This value is automatically populated in outgoing PDUs, and is used to construct the topic (/cfdp/pdu/entity$entityID) we listen on for incoming PDUs.

altServices is a boolean parameter that causes this instance to append /entity$entityId to all command services it is listening on. This allows multiple CFDP application instances to operate on a single ROS instance for test purposes (be sure to also specify an alternate ROS Node name for each).

Usage & Configuration Examples

CFDP Entities

This table shows CFDP Entity IDs, the corresponding container name (when using brash_docker demo), and the corresponding ROS Topic prefixes. PDUs are sent by default on topics of the form /$prefix/cfdp/pdu

Identifiers

This is a listing of all identifiers (topics, ids, etc.) involved when using the example brash_docker (or multihost) configuration

• See the Comands section below for sample commands corresponding to each cmd column with an entry. Blank cells represent combinations that are not applicable, or not currently possible.
• The Cfe CH column is used internally by the CFE CF application and is not currently used for ros-to-ros transfers.
• 'gsw-topic' refers to the topic generated on rosgsw, with 'cmd' being messages sent out and 'tlm' being packets received
• 'sbn'-topic' similarly refers to rosfsw topics as sent on the SBN bridge ('tlm') or received ('cmd'). Note: Despite the naming convention, the CCSDS packets can be of CMD or TLM variants in either direction.
• This table reflects the IDs/topics for messages flowing from src to dst only. Any replies, including ACKs/NAKs, will use the MIDS/topics for the row corresponding to that message flow.

Commands

The following series of example commands starts 2 instances of the service under a single ROS machine and executes a series of commands.

Start CFDP ROS Fsw and Gsw instances using explicit parameters. Default values are suitable for RosFsw instance when RosGsw is on a discrete Ros machine.

• ros2 run cfdp_wrapper cfdp_wrapper.py --ros-args -r __node:=cfdpgsw -p entityID:=1 -p "filestore:=cfdp/rosgsw"
• ros2 run cfdp_wrapper cfdp_wrapper.py --ros-args -r __node:=cfdpfsw -p entityID:=2 -p altServices:=True -p "filestore:=cfdp/rosfsw" -p "pduTopicPrefix:=/rosfsw/cfdp/pdu/entity"

Directory listing

• rosfsw listing requested by rosgsw: ros2 service call /cfdp/cmd/ls cfdp_msgs/srv/CfdpXfrCmd "{src: '/', dst: '/dst1_dirlisting.txt', dstid: 2}"
• rosgsw listing requested by rosfsw: ros2 service call /cfdp/cmd/ls cfdp_msgs/srv/CfdpXfrCmd "{src: '/', dst: '/dst2_dirlisting.txt', dstid: 1}"
• fsw listing: NOT AVAILABLE (limitation of nasa CF application)

Transfer a file from RosGsw to RosFsw

• Put from rosgsw: ros2 service call /cfdp/cmd/put cfdp_msgs/srv/CfdpXfrCmd "{src: '/dst1_dirlisting.txt', dst: '/echodst1_dirlisting.txt', dstid: 2}"
• Get from rosfsw: ros2 service call /cfdp/cmd/get cfdp_msgs/srv/CfdpXfrCmd "{dst: '/dst1_dirlisting.txt', src: '/echodst1_dirlisting.txt', dstid: 1}"

Transfer a file from RosFsw to RosGsw

• Get from rosgsw: ros2 service call /cfdp/cmd/get cfdp_msgs/srv/CfdpXfrCmd "{src: '/echodst1_dirlisting.txt', dst: '/echodst1_dirlisting.txt', dstid: 2}"
• Put from rosfsw: ros2 service call /cfdp/cmd/put cfdp_msgs/srv/CfdpXfrCmd "{src: '/echodst1_dirlisting.txt', dst: '/echodst1_dirlisting.txt', dstid: 1}"

Transfer a file to FSW (from either rosfsw or rosgsw)

• ros2 service call /cfdp/cmd/put cfdp_msgs/srv/CfdpXfrCmd '{\"src\": \"gswtest.txt\", \"dst\": \"/cf/gswtestdst724c.txt\", \"dstid\":25}'

CFDP Fsw to RosFsw (put)

• `ros2 topic pub --once /groundsystem/cfdp_tx_cmd cfe_msgs/msg/CFTxFileCmd '{"cfdp_class":1,"keep":1,"chan_num":0,"priority":0,"dest_id":1,"src_filename":"/cf/cf.so","dst_filename":"fsw2rgsw1.txt"}'

Caveats:

• ls and get commands do NOT work against the cFE CF[DP] application at this time (not supported). Use the CF app commands instead for equivalent functionality.