[systemd-devel] Fwd: dovecot and systemd

[Michal Hlavinka]

On 03/17/2012 02:19 AM, Lennart Poettering wrote:
> On Fri, 16.03.12 15:55, Michal Hlavinka (mhlavink at redhat.com) wrote:
>
>>>> For example, lets have dovecot configured to listen for imap(s) and lets
>>>> have systemd dovecot socket configured to listen for all protocols -
>>>> pop3(s) and imap(s). When dovecot is configured to start on boot,
>>>> systemd will start it and dovecot will listen on imap(s) ports. But when
>>>> dovecot.socket is enabled, it'll listen on pop3(s) too and when new pop3
>>>> connection comes, it'll pass it to dovecot and dovecot will serve it.
>>>> The question is: Should this happen? What exactly should happen when
>>>> dovecot.conf does not match dovecot.socket configuration?
>>>>
>>>> Michal
>>>
>>> Dovecot's systemd code was written by one of you Redhat guys. I had some
>>> similar thoughts when I applied the patch, but didn't really know what
>>> to do about it, so I didn't do anything. So: I don't know. Maybe some
>>> other project has solved this somehow already?
>>>
>>> Dovecot anyway needs its own internal UNIX listeners. Should all
>>> internal inet listeners be disabled? Could Dovecot somehow talk to
>>> systemd and ask what listeners it's using for Dovecot and log warnings
>>> if they don't match?
>
> So here's what I recommend in cases where the configuration file of the
> service itself and the systemd sockets passed do not match up: honour
> both. i.e. go through the list of sockets passed and match them up with
> the configuration as good as possible, but also listen on all sockets
> which are configured in the config file but not passed and on all
> sockets passed that are not configured in the config file.
>
> This is what we do in CUPS and what I think is a nice approach since it
> basically means that any user configuration is always taken into
> account.

Unfortunately, this can't be used here. CUPS offers only one service, so 
it always know what to expect on any connection. Dovecot, on the other 
hand, provides five services (imap, imaps, pop3, pop3s, managesieve) and 
when it gets connection on port that is not configured in it's config 
files, it can't know what to do with the connection.

So if the connection comes to extra port, it won't be served. There are 
three possibilities what can happen next:
1) just log message that configuration does not match, do nothing
2) log message and close socket that listens on port dovecot won't serve
3) log message and terminate dovecot

I think the 2nd option is the best one here. Does systemd provide any 
API to close those sockets?

Michal