Re: WRT FAQ: slow logins

"Karsten M. Self" <[email protected]>
Newsgroups gmane.os.openbsd.www
Message-ID <[email protected]>
Janne:  thanks for your response.

on Wed, Nov 24, 2010 at 09:08:27AM +0100, Janne Johansson
([email protected]) wrote:
> 2010/11/11 Karsten M. Self <[email protected]>
>
> > FAQ 3.3: ssh(1) takes a long time to connect or log in.
> >
> > I've also seen this happen due to either kerberos being enabled, or
> > GSSAPI being used.
> >
> > I forget the solution to the kerberos problem, though IIRC it involved
> > removing kerberised SSH from the shell search PATH.
> >
> > In the case of GSSAPI:
> >
> >    GSSAPIAuthentication no
> >
> > (at the command line, in ~/.ssh/config, or /etc/ssh/ssh_config) resolves
> > the issue.  With the option enabled, I see a ~30s delay in connections,
> > visible at two points in the process with 'ssh -v <hostname>'
> >
> >
> This feels all weird to me. First of all, openssh doesnt ship with
> GSSAPIAuthentication enabled by default,

I don't recall if this was enabled by default or if I'd enabled it for
some specific reason (I don't recall that I did).  And there's enough
wonkiness going on with our DNS at work that reverse lookups are a
pretty likely suspect.

That said:  disabling GSSAPIAuthentication at the command line or in
user or host configs fixes the problem.  Pretty convincingly, and for
multiple users.

> secondly if you actually use krb5 and enable GSSAPI it does not in itself
> cause any 30 second timeouts
> unless you have something broken, like reverse DNS mappings, which still
> makes the FAQ suggestion apply.
>
> If your site needs/uses GSSAPI, then removing "kerberized ssh from the
> $PATH" or taking out GSSAPI from the
> local ssh_config is definately not the correct solution and only hides the
> symptoms of a broken site.

The site doesn't use/need GSSAPI.  Disabling the option results in no
functionality loss and far faster session set-up.

Any suggestions on further isolating DNS as the culprit?


Peace.

> --
>  To our sweethearts and wives.  May they never meet. -- 19th century toast

I love that saying.  It's an old sailor's toast, as I recall.  We use it
frequently at the rowing club ;-)


--
Karsten M. Self <[email protected]>
http://linuxmafia.com/~karsten
 What part of "gestalt" don't you understand?

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