dumbpipe doesn't seem to signal when the pipe operation has "ended"

I'm using dumbpipe to cat a file over a network connection and receive it on the computer that's connected to a tape drive (/dev/nst0), to write the file to tape.

When the cat file | dumbpipe connect [ticket] side is done, it doesn't seem to signal that to the dumbpipe listen | mbuffer -o /dev/nst0 on the other machine, so I need to do these steps in this order:

• press Ctrl+c on the sending end.
• press Enter on the receiving end (which seems cause some 'closing' action on either mbuffer or dumbpipe).

If I instead Ctrl+c out on the receiving end, it seems mbuffer doesn't flush the final bit of data, which results in the last 40 or so kilobytes never being written to tape.

Start by reproducing the two commands described: cat file | dumbpipe connect [ticket] and dumbpipe listen | mbuffer -o /dev/nst0. Trace the sender and receiver shutdown paths to determine why completion is not signaled and why interrupting the receiver loses buffered data. Done means the receiving pipe observes end-of-input and mbuffer can flush the complete file without manual Ctrl+c or Enter.