Re: Debian 11: How to disable IPv6
Hello,
On Sat, Jul 09, 2022 at 04:52:27PM +0200, Roger Price wrote:
> When I try to start fetchmail I get the error message
>
> Jul 09 10:22:57 titan fetchmail[7286]:
> reading message
> mailbox@rogerprice.org@mail.gandi.net:1 of 7 (8954 octets)
> (log message incomplete)
> Jul 09 10:22:57 titan fetchmail[7286]:
> Connection errors for this poll:
> name 0: connection to localhost:smtp [127.0.0.1/25] failed:
> Connection refused.
> name 1: connection to localhost:smtp [127.0.0.1/25] failed:
> Connection refused.
> Jul 09 10:22:57 titan fetchmail[7286]: SMTP connect to localhost failed
>
> I understand this to mean that my Debian 11 machine cannot connect to itself
> on port 25 despite the netfilter rule "iif lo accept", so I assumed it was
> an IPv6 problem with fetchmail trying to use IPv6 with exim4.
There's nothing in the above that references IPv6. There isn't a
single IPv6 address in that text. There is an IPv4 address though
(127.0.0.1).
> As a check, I tried:
>
> root@titan ~ telnet localhost 25
> Trying 127.0.0.1...
> Trying ::1...
> telnet: Unable to connect to remote host: Address family not supported by protocol
This shows that nothing is listening on port 25 of 127.0.0.1 (or
it's firewalled with a rule that returns TCP RST) and that there is
something wrong with your IPv6, maybe because you disabled it or
maybe because this variant of telnet you're using doesn't support
it. But whatever the case, it seems like port 25 of your (IPv4)
localhost is the main issue here.
I don't use fetchmail but I guess you are wanting it to connect to
your Exim, so you should check that Exim is actually set to listen
on port 25 of 127.0.0.1.
Thing is, I think that Exim by default does listen on localhost:25
on Debian, so in order for yours to not do that you probably have
altered its config in some way. Or it could be the firewall.
> There is nothing I can find in the exim4 configuration that would inhibit IPv6.
You disabling IPv6 inhibits IPv6 but I really don't know what the
fixation is with IPv6 (and why it must be disabled).
Cheers,
Andy
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