> I tracked the problem down. Depending on how you look at it, it is a > bug in openssh's sftp or in sshfs. > > The problem is that when sending a file data, sshfs will just keep > sending without waiting for the server to catch up. This does not need > to be a problem, as the sftp server should just stop receiving TCP > packets when the buffers are full, causing TCP resends and > automatically slowing down the sending. > > However, the openssh sftp server loop (openssh:sftp-server.c) will > just keep trying to read from stdin. It will read from stdin to its > input buffer at most once per loop, and dispatch at most one sftp > packet per loop. But as each read from stdin can read up to 8 sftp > packets into the input buffer then the input buffer risks running out > of space. When it runs out of space then it just kills itself > (openssh:buffer.c:buffer_append_space). > > I note that the openssh sftp client has a mechanism to limit the > number of unanswered requests, which probably means unlike sshfs, it > is not affected. > > I found that a reliable way to trigger this bug was to start a > parallel process which hogs the disk, causing the consuming sftp > server loop to slow down. > -sshfs-mount localhost:/tmp test > -ionice -c1 cp large_file /tmp/deleteme > -dd if=/dev/zero of=test/deleteme2 > > The error I get is > dd: writing to `test/deleteme2': Input/output error > dd: closing output file `test/deleteme2': Transport endpoint is not connected > > It is somewhat a matter of opinion, but I would say that it is openssh > which should be fixed. If I look at
Great bug hunting! :) The "Transport endpoint is not connected" error means, that sshfs crashed, which it should not do even with a buggy sftp server. Also it's probably not too hard to work around this in sshfs as well. I'll have a look at these. But you're right, that there's definitely something wrong with the server as well, which should also be fixed. Thanks, Miklos -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
