On 4 March 2010 17:46, Bo Shi <bs1984@gmail.com> wrote:
Hi All,
I've been struggling with this issue off and on for the better part of a month now. Having implemented a simple git SSH server using some of the Conch examples in the official documentation, I encountered an issue that would cause a git client to throw an error only part of the time.
I think it's a bug in conch.
The little program to reproduce the issue is found at
(raw version for download) http://gist.github.com/raw/321403/82ab2111a2709c8fe50a77aabb08565749087408/g...
and can be executed to start the sample server. Run a command like
# The /abspath/to/git/repo should be readable by the server user $ git clone ssh://user@localhost:2222/abspath/to/git/repo (password "user")
To test the server. On my workstation, I am able to reproduce the error at least once every 5 tries. It's definitely not consistent. The behavior I see is attached at the end of this email. The client fails due to a premature inConnectionLost() call in the SSHSessionProcessProtocol that sends an EOF.
As a workaround, when TraceProcessProtocol.inConnectionLost() is overriden to do nothing, the client error goes away. This is somewhat foreign territory for me so I'm not sure whether it's a bug in git or whether it's a bug in the twisted ProcessProtocol implementation. RFC 4254 isn't terribly helpful here:
5.3. Closing a Channel
When a party will no longer send more data to a channel, it SHOULD send SSH_MSG_CHANNEL_EOF.
So on the surface the current behavior of sending an EOF appears fine, however, I can't really find any definitive cases of this type of problem popping up via, say, default OpenSSH/git combinations.
Any advice? Is the gitconnbug.py implementation flawed? Should I open a ticket? Any git experts know of a case where git-upload-pack might close it's stdout pipe?
I think what's actually happening here is that git-upload-pack is closing its *stdin*. Why conch reacts to that by shutting down the channel, I don't really know -- it doesn't seem right to me. Maybe it's a simple logic error and it method should be 'outConnectionClosed' instead? At any rate, I think this is a bug -- please file a ticket. And thanks for the complete example! Cheers, mwh