Re: [PATCH] KVM Test: add -w parameter in nc command in kvm_utils.py

[Feng Yang <fyang@redhat.com>]

----- "Michael Goldish" <mgoldish@redhat.com> wrote:

> From: "Michael Goldish" <mgoldish@redhat.com>
> To: "Feng Yang" <fyang@redhat.com>
> Cc: autotest@test.kernel.org, kvm@vger.kernel.org
> Sent: Wednesday, October 20, 2010 5:11:32 PM GMT +08:00 Beijing / Chongqing / Hong Kong / Urumqi
> Subject: Re: [PATCH] KVM Test: add -w parameter in nc command in kvm_utils.py
>
> On 10/20/2010 08:55 AM, Feng Yang wrote:
> > If a connection and stdin are idle for more than timeout seconds,
> > then the connection is silently closed. withou this paramter,
> > nc will listen forever for a connection. This may cause our test
> > hang. redmine issue:
> > http://redmine.englab.nay.redhat.com/issues/show/6947
> > Add -w parameter should fix this issue.
> > 
> > Signed-off-by: Feng Yang <fyang@redhat.com>
> > ---
> >  client/tests/kvm/kvm_utils.py |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> > 
> > diff --git a/client/tests/kvm/kvm_utils.py
> b/client/tests/kvm/kvm_utils.py
> > index a51c857..526d38d 100644
> > --- a/client/tests/kvm/kvm_utils.py
> > +++ b/client/tests/kvm/kvm_utils.py
> > @@ -733,7 +733,7 @@ def remote_login(client, host, port, username,
> password, prompt, linesep="\n",
> >      elif client == "telnet":
> >          cmd = "telnet -l %s %s %s" % (username, host, port)
> >      elif client == "nc":
> > -        cmd = "nc %s %s" % (host, port)
> > +        cmd = "nc %s %s -w %s" % (host, port, timeout)
> >      else:
> >          logging.error("Unknown remote shell client: %s" % client)
> >          return
> 
> I don't understand how remote_login() can stall here.
> kvm_utils._remote_login() doesn't rely on nc's self-termination.  If
> no
> shell prompt is available after 10 seconds, nc is forcefully
> terminated
> and _remote_login() fails.  If it somehow stalls this might indicate
> a
> bug somewhere.
It is really rarely reproduce. Only meet this issue when guest panic or core dump.
nc stall. Do not know why it is not terminated after 10s.

I think -w parameter is helpful in this situation.
If it does not cause other issue,  we'd better add -w in nc command.

Thanks for your command. What do you think?

Feng Yang