Re: tcp heisenbug

[Andrew Morton <akpm@osdl.org>]

"David S. Miller" <davem@davemloft.net> wrote:
>
> On Fri, 8 Oct 2004 01:41:51 -0700
> Andrew Morton <akpm@osdl.org> wrote:
> 
> > fetchmail broke.  It's fetching mail from localhost (ssh port-forwarded to
> > remote servers) and then for some reason it wants to open an SMTP
> > connection to localhost.  It was failing, some error message about that
> > SMTP connection.
> > 
> > While I was poking at it, it started to work.  `uptime' said 6 minutes.  So
> > I'd be suspecting that there's a jiffy wrap bug in TCP-to-localhost
> > introduced since 2.6.9-rc3.
> 
> That's possible.
> 
> It could also be something that only happens the first time you try
> to talk to a remote system.

It doesn't seem like that.  I'd already established three ssh sessions to
three remote servers (zip,  digeo, osdl) and fetchmail was able to contact
those three servers via connection to the three local ssh clients.

It was only when fetchmail tried to talk to sendmail on localhost that
things failed.

> You're using e1000 on x86 right?

Yup.  At 100 mbps

>  Maybe force TSO off via ethtool
> right after the interface is brought up and see if that makes it
> go away?

The problem went away on subsequent reboots :(

But the failure was when communicating with sendmail on localhost.