[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Hangs when downloading large files


It didn't work to add "-l DEBUG2" to Subsystem--it complained about "garbage (-l)" at the end of the line. My path is slightly different, though:

 Subsystem       sftp    /usr/libexec/openssh/sftp-server

so maybe this has to do with the version. I tried adding "LogLevel DEBUG2" to the file, though, and it seems to have worked--at least, I get what looks like level-2 debugging from the server. I've attached the server's debug output, and Sawmill+libssh debug output.

I captured the server output with "tail -f" on /var/log/messages; when the client hung, I typed "(at this point I press control-C in the client window)" in the window of tail -f, and then terminated the client. So you'll see the line I typed in the server log, so you can see where it hung. It was after about 10 seconds of hang. The point of the hang seems to be here:

Mar  9 08:58:55 wisteria sshd[21822]: debug2: channel 0: rcvd adjust 128000
Mar  9 08:59:09 wisteria last message repeated 177 times

I ran it again and let it hang longer, and it still was 177 times.

If this is a server bug, I will be content to just document it, especially if there's a newer version of the server which fixes it. Do you know if there is?

I don't understand the sshfs code enough to know what we would have to do similarly. Is this a change that would be made in libssh, or is this a change I could make in my client program? I suspect the former; it seems to have to do with throttling the amount of outstanding data somehow, and I don't think the libssh API provides any functionality for determining what's outstanding. Is there some way I can implement this on my end?


Andreas Schneider wrote:
On Tuesday 09 March 2010 01:58:02 you wrote:

Here is the debug output from the client, and from Sawmill (our
software). I didn't turn on logging in the server because I never have
(or maybe once), and I'll have to do some research to know how--if this
doesn't give you enough, please let me know and I'll log it from the
server side too.

Edit /etc/ssh/sshd_config and add -l DEBUG2

Subsystem       sftp    /usr/lib64/ssh/sftp-server -l DEBUG2

I want to see both sides to figure out what it is happening. This looks like a bug in openssh, as it works for thousands of users and just your client with this server version is hitting the problem.

sshfs fixed the sftp server bug by working around it. See:



	-- andreas

Attachment: serverlog.txt.gz
Description: GNU Zip compressed data

Attachment: sawmill_libssh.log.gz
Description: GNU Zip compressed data

Re: Hangs when downloading large filesAndreas Schneider <mail@xxxxxxxxxxxx>
Re: Hangs when downloading large filesAndreas Schneider <mail@xxxxxxxxxxxx>
Re: Hangs when downloading large filesGreg Ferrar <ferrar@xxxxxxxxxxxxxx>
Re: Hangs when downloading large filesAndreas Schneider <mail@xxxxxxxxxxxx>
Archive administrator: postmaster@lists.cynapses.org