Bug#544292: exim4: please configure IPv6 per default

[Konrad Rosenbaum]

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! 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?... ;-)

> 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.


	Konrad
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