[Dovecot] [ Re: best practises for mail systems]

[Timo Sirainen]

On 9.6.2012, at 4.55, Matthias-Christian Ott wrote:

> Yes, there is. You have to replicate the entire state of the IMAP
> session (protocol states, buffers, TLS state etc.) and the TCP state of
> the connection. The state of the IMAP session is (in theory) easily
> replicable (although you probably have to rely on internals of the TLS
> implementation; OpenSSL can serialise TLS sessions from/into ASN.1 via
> i2d_SSL_SESSION, though this is meant to resume session via TLS)

Interesting! I thought OpenSSL didn't have a way to [de]serialize the session state. The first time I wanted to do that was 13 years ago. I see there are some google hits for i2d_SSL_SESSION, but do you already know a good web page / example code I could look at?

> and for
> TCP there is RTCP [1]. RTCP intercepts the TCP session is able to
> recover the TCP state. It works without any modification of the
> operating system (at the moment limited to Linux).

Thanks for this too.

> If this would be implemented in Dovecot it would really set it apart
> from other IMAP servers and software that I've seen so far. Being able
> to transparently handle failover of a TCP connection is unique.

Yes.