Bug#544292: exim4: please configure IPv6 per default

[Andreas Metzler]

On 2009-08-30 Konrad Rosenbaum <konrad at silmor.de> wrote:
> On Sunday 30 August 2009, Andreas Metzler wrote:
> > OTOH for the other setups (no remote mail, smarthost) the default
> > value for the listening interfaces indeed only includes 127.0.0.1. Is
> > it actually a good idea to change this? I expect that this could cause
> > problems on ipv4-only hosts.

> I just tried it out on a minimal lenny installation that did not have IPv6 
> pre-loaded on startup. Putting ::1 into the configuration will cause the 
> kernel to automatically "modprobe ipv6". I personally do not think this is 
> a bad thing - a lot of other packages do this anyway.

> If the ipv6.ko kernel module is removed (or renamed) the exim startup does 
> not work if it requires IPv6. But I do not think that this is a very 
> realistic scenario in 2009 - we've got only 28 IPv4 A-blocks left in the 
> IANA pool!

Hello,

actually completly disabling ipv6 is probably still a smart choice
at least in Europe. Getting IPv6 is still hard.[1] And having apps trying
to use  IPv6 just slows things down. (Just look at how complicated
google does this. http://www.google.com/intl/en/ipv6/)

<mode rant>No chance of IPv6 success while it is not an automatic
service instead of a special (pricy) option </> ;-)

> Someone who is capable of deliberately shooting himself that big 
> a hole into the foot, is also capable of changing the exim config - don't 
> you think?... ;-)

Point taken.

> > Do people actually run ipv6-only hosts
> > (not even loopback ipv4)? Is this a usecase we should optimize for?

> I don't think there are many IPv6-only hosts yet (and I don't think there 
> will be many before maybe 2015). My proposed setup would break with 
> IPv6-only hosts by the way: exim would panic because of a lack of IPv4.

> What I am concerned about is dual-stack hosts with localhost pointing to ::1 
> instead of or in addition to 127.0.0.1 (often this is under the control of 
> the DNS admin, not the host admin). Having exim listen on both makes things 
> run a little bit smoother, IMHO.

Hm, if I have 

ametzler at argenau:~$ grep ^host /etc/nsswitch.conf
hosts:          files dns

/etc/hosts should win over DNS, shouldnt it?

cu andreas

[1] Yes, I know about 6to4, but a) it is a slow crutch b) it does not work
behind a NATing ADSL Modem/Router.
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