dovecot - Oct 2012 - Dovecot 2 and TCP-Keepalive

Hi!

I am about to migrate a perdition-based IMAP/POP3 proxy to Dovecot.

Unfortunately some users are behind a firewall/NAT setup which throws
away seemingly idle TCP connections sooner than the established default
of 24 hours (more likely after 30 minutes ...) resulting in all kinds of
weird client behavior.

And unfortunately? this firewall/NAT setup is outside of my control and
I have no means of correcting this (in my opinion) flawed configuration.

Now, with perdition I was able to use the --tcp_keepalive option which
totally solved the mentioned weird client behavior.

My question is: does Dovecot2 use TCP-Keepalive on its sockets per
default or do I need to enable it some way I have not yet discovered?

The manual and wiki only talk about "keepalive" in connection with the
IMAP protocol and IDLE and my C-fu is too weak to understand the source
code.

Gr??e,
Sven.


-- 
Sigmentation fault. Core dumped.

On 20.10.2012, at 19.39, Sven Hartge wrote:
> I am about to migrate a perdition-based IMAP/POP3 proxy to Dovecot.
> 
> Unfortunately some users are behind a firewall/NAT setup which throws
> away seemingly idle TCP connections sooner than the established default
> of 24 hours (more likely after 30 minutes ...) resulting in all kinds of
> weird client behavior.
> 
> And unfortunately? this firewall/NAT setup is outside of my control and
> I have no means of correcting this (in my opinion) flawed configuration.
> 
> Now, with perdition I was able to use the --tcp_keepalive option which
> totally solved the mentioned weird client behavior.
> 
> My question is: does Dovecot2 use TCP-Keepalive on its sockets per
> default or do I need to enable it some way I have not yet discovered?
It's the default yes. Of course Linux's default keepalive interval is
something like 90 minutes, so have you changed that already?..
> The manual and wiki only talk about "keepalive" in connection
with the
> IMAP protocol and IDLE and my C-fu is too weak to understand the source
> code.
imap_idle_notify_interval (default 2 min) causes Dovecot to send data to IDLEing
connections, which pretty much makes the TCP keepalive irrelevant. For non-IDLE
connections Dovecot has a disconnect timeout of 30 minutes.