Snark gets stuck before download complete

[zzz]

All peers go uninteresting, even seeds, when a leech gets close to the end.

Have seen and fixed bugs like this before but it's back, possibly caused by bEP 6 changes in 0.9.21. Leech is not in end game yet, still ~40 pieces left.

Workaround: Stop and restart torrent.

[somewon]

<+dg> obscuratus: zzz speculated it was to do with the BEP 8(?) changes
< obscuratus> dg: I was sepeculating about the BEP 6 changes. When I revert the LPQ change, I didn't get a stall.
< obscuratus> I left the BEP 6 change intact.
< obscuratus> Bleh, s/I/zzz/
< obscuratus> dg: Anyhow, I'll leave it verbally for you also... Think LPQ (Linked Blocking Queue) in addition to the possiblity of the BEP 6 stuff.

[zzz]

See also ​http://zzz.i2p/topics/1930

Investigation started.

I believe that PeerState?.rejectMessage() needs to return the partial piece via PeerCoordinator?.savePartialPieces() when no requests remain outstanding for that piece.

If true this is a bug of omission. I don't see any issues in the code that was added, we just need some more code.

May be some complication in tracking what portion of the piece is doenloaded. TBD.

[zzz]

Fix for this and several related issues, and fixes for bad data handling, in a95d5fd3f953820b2ad073a9ef12b26c0fc22137 0.9.21-2