Debugging a hung connection

[J. Bruce Fields]

On Wed, May 21, 2008 at 10:14:15AM -0400, Dave Quigley wrote:
> 
> On Wed, 2008-05-21 at 09:59 -0400, Norman Elton wrote:
> > I've got an NFSv4 writable mount that seems to be hung. I can do an
> > "ls", but neither read (cat) nor write (echo) operations succeed. Both
> > hang until I kill the process. Other clients are able to continue to
> > read/write without a problem. I've got a packet capture, and there
> > don't seem be any packets getting dropped by firewall, etc.
> > 
> > I'm not entirely sure how to pin down the problem. I've got PCAPs of a
> > working and nonworking client. I see NFS4 calls going back and forth,
> > but am not quite sure what I'm looking at. Is there a good resource to
> > explain what the different operations mean, and how/where they would
> > be failing?

Well, the simplest thing to look for would just be any rpc calls that
don't get replies.  What exactly are the client and server?

> In terms of linux implementation specifics I haven't found much other
> than the code as a reference. The Umich guys have a small page on kernel
> hacking/debugging NFSv4 which can be found at [1].

You remind me that hasn't been updated in a while....  So I did a global
s/ethereal/wireshark, added a mention of "rpcdebug" and some git
details, and fixed up one or two small things.  Corrections welcome.

--b.

> I have found that
> turning on the extra debug statements really helps in figure out what is
> going wrong. If you want to understand what each of the NFSv4 operations
> does the best reference for that is the NFSv4.1 specification [2].
> 
> [1] http://www.citi.umich.edu/projects/nfsv4/linux/nfsv4-hacking.html
> [2] http://www.nfsv4-editor.org/draft23/draft-ietf-nfsv4-minorversion1-23.txt
> 
> Dave
> 
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