Svc/FileDownlink radio feedback

[timcanham]

In the current FileDownling to radio scheme, the radio signals it is done by returning the FileDownlink packet buffer in FileDownlink ::bufferReturn_handler The return port is of type Fw.BufferSend.

The issue is that if the radio link goes down (on purpose or otherwise), the FileDownlink stalls waiting for a buffer to return. The radio should return the buffer if it knows the link is down, but it has no way to communicate that. If the buffer is returned to FileDownlink, it will just send the next buffer, and the radio would presumably just send it back. When the file is "done", FileDownlink would return the file send status complete to users like DpCatalog, which could request further files. What should happen is that the radio should tell FileDownlink that the link has closed, and FileDownlink should stop sending packets and inform upstream users so they can cancel their activities. Downlink file automation is broken IMHO if we don't fix this.

The answer is to not use the generic Fw.BufferSend port between FileDownlink and framers/radios/etc. We need to define another port that carries status back.