libssh2-hs can't send 3megabyte file

[aycanirican]

I am able to send small files but libssh2 blocks when I try to send a 3mb file.

[grpala]

It's not just 3MiB... a 180KiB file blocks it too... I've been trying to fix this for the past 3 hours, got no results yet. HELP!

[grpala]

OK, found the bug. I'd submit a pull request but I'm not sure of the correctness of my fix. The problem is as follows:
When sending a file and the server replies an EAGAIN (this doesn't happen for very small files), threadWaitSession will first block the thread waiting for read, but since there's nothing to read whatsoever it blocks forever.

I made transfers work (https://gist.github.com/5428276) but this doesn't feel all right since there are 3 possible states for session direction: [INBOUND], [OUTBOUND], [INBOUND, OUTBOUND] (as seen in int2dir).

During file transfers, the observed direction is the latest, and in this case it only needs to threadWaitWrite, but what if there were a case where it needed to threadWaitRead too? This "fix" would undoubtedly break.

In any case, take this patch as a proof of concept as to where the bug is.

[portnov]

Applied that patch to master for now. If anyone has better solutions, you are welcome.