skliper
commented
6 months ago TX and RX PDU sizes can be different. Transmit maximum size is configurable via table using outgoing_file_chunk_size as defined below. Note the actual TX PDU also includes the PDU header which is variable size. The CCSDS header also needs to be accounted for to get to the final size over the SB. https://github.com/nasa/CF/blob/27dcaf507f79631b1105dcf4a261d8ce60b6aedd/config/default_cf_tblstruct.h#L51-L52
CF_MAX_PDU_SIZE is defined in the interface header here, note this includes the PDU headers but not the CCSDS header: https://github.com/nasa/CF/blob/27dcaf507f79631b1105dcf4a261d8ce60b6aedd/config/default_cf_interface_cfg.h#L94-L95
The outgoing_file_chunk_size is limited by this structure size: https://github.com/nasa/CF/blob/27dcaf507f79631b1105dcf4a261d8ce60b6aedd/fsw/src/cf_cfdp_pdu.h#L371-L381
Note the comment below is actually misleading, since CF gets a buffer from SB and writes from the file to it directly: https://github.com/nasa/CF/blob/27dcaf507f79631b1105dcf4a261d8ce60b6aedd/docs/dox_src/cfs_cf.dox#L460-L462
On the receive side the PDU is processed "in place", so it isn't restricted by local CF buffer sizes. There's a misleading comment here: https://github.com/nasa/CF/blob/27dcaf507f79631b1105dcf4a261d8ce60b6aedd/docs/dox_src/cfs_cf.dox#L455-L458
Note that there is a structure defined below, but it's only used for size checking of outgoing_file_chunk_size and not directly: https://github.com/nasa/CF/blob/27dcaf507f79631b1105dcf4a261d8ce60b6aedd/fsw/src/cf_cfdp_pdu.h#L371-L381
This comment is also wrong, since outgoing_file_chunk_size is common across channels: https://github.com/nasa/CF/blob/27dcaf507f79631b1105dcf4a261d8ce60b6aedd/config/default_cf_interface_cfg.h#L87-L89
Also no longer applicable: https://github.com/nasa/CF/blob/27dcaf507f79631b1105dcf4a261d8ce60b6aedd/fsw/src/cf_cfdp_types.h#L413-L415
This issue was imported from the GSFC issue tracking system
Imported from: [GSFCCFS-1196] Investigate whether TX and RX PDU sizes need to be different Originally submitted by: Timmons, Elizabeth J. (GSFC-5820) on Mon Jul 20 13:37:06 2020
Original Description: Need to investigate uses cases where TX and RX PDU sizes need to be different. Need to investigate the impact of making a change to allow that.