Author: sawbona Date: To: exim-users Subject: Re: [exim] Exim4 delay at boot
Hello:
On 13 Nov 2021 at 11:50, Heiko Schlittermann via Exim-users wrote:
> JHM via Exim-users <exim-users@???> (Fr 12 Nov 2021 22:14:12 CET):
> > [code]
> > disable_ipv6 = true
> > [/code]
>
> Shooting into the dark as well. If IPv6 is enabled, Exim tries to
> resolve names as A and as AAAA records. Independend on your system's
> IPV6 setup. Yes, that's probably it.
But it is the cause of the problem.
In my opinion as desktop end user, if the box where Exim is being
installed does *not* have IPv6 enabled (and is explicitly disabled), then
it should *not* be configured by default with IPv6 enabled.
What I think would be a good idea is that at installation time ie: when
dpkg-reconfigure-exim4-config runs, the installer looks to check if IPv6
is configured or maybe just ask if IPv6 is to be configured.
And not assume that it should be enabled by default.
I think we're quite a few years from IPv6 being used by default
everywhere.
eg: just reading the kernel command line to see if the ipv6.disable=1 bit
is present would be quite enough for a basic check to decide how to
configure Exim when installing.
Adding the /etc/hosts file to the files to read would add yet a second
layer of certainty.
At the very least, adding the line I added to the exim4.conf.template with
the proper comments would have been of great help to me.
I spent a great many hours attempting to solve this problem.
Could have been avoided. 8^ )
> ... but in parts of the code Exim doesn't rely on the gethostinfo(3)
> call, but talks directly to the resolver (found in /etc/resolv.conf).
My name server (Unbound) runs on a VBox virtual machine which also runs
Pi-hole:
Just like the host, the virtual machine has IPv6 explicily disabled in the
same way. IPv6 is also disabled in my ADSL router. So, no IPv6 *anywhere*.
> So, if you resolver behaves strange ...
> ... the root cause of delay is outside of Exim ...
I beg to differ.
Exim was installed on a machine with IPv6 disabled, like I have pointed
out, from the kernel command line onwards.
If it installed with IPv6 enabled by default on such a machine, I cannot
but conclude that the problem is with the Exim installation routine and
not elsewhere.
> .... disable_ipv6 = true is a good mitigation. It was the solution to the problem, one which could easily be avoided.
