Bug#544292: exim4: please configure IPv6 per default

[Andreas Metzler]

On 2009-08-30 Konrad Rosenbaum <konrad at silmor.de> wrote:
> Package: exim4
> Version: 4.69-9
> Severity: wishlist

> Default installations of exim4 do not include IPv6 addresses, so it does not 
> work as expected
> on IPv6 systems. This affects the dc_local_interfaces 
> in /etc/exim4/update-exim4.conf.conf:

> for local configurations set it to '::::1:127.0.0.1'
> for all others set it to: '::::0:0.0.0.0'

> (::1 is localhost in IPv6, :: is the any address of IPv6, exim doubles the 
> colons)

Hello,

afaict the important part of your bugreport is already solved. The
default value for configurations with a remotely accessible SMTP
listener ("internet") does not set exim's main configuration option
local_interfaces. And this yields

argenau:~$ netstat -tl | grep smtp
tcp        0      0 *:smtp                  *:*                     LISTEN
tcp6       0      0 [::]:smtp               [::]:*                  LISTEN

because it is the builtin default value to also listen on IPV6 if
possible.

Quoting spec.txt:
| 13.2 Special IP listening addresses
| -----------------------------------
[...]
| The default value of local_interfaces is
| 
| local_interfaces = 0.0.0.0
| 
| when Exim is built without IPv6 support; otherwise it is:
| 
| local_interfaces = <; ::0 ; 0.0.0.0
|
| Thus, by default, Exim listens on all available interfaces, on the SMTP
| port.


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

thanks, cu andreas