IPv4/IPv6 mismatches of doveadm: Fatal: connect(fd00:b::1:12345) failed: Connection refused

[Michael Grimm]

Hi —

I recently extendend my IPsec tunnel between two mail servers to deal with IPv4 
addresses in addition to IPv6 ones. (No specific reason for that.)
I ran into an issue worth reporting. This is Dovecot v2.2.27 (c0f36b0) at 
FreeBSD STABLE-11.

Previously:

        dovecot.conf:
                plugin { 
                        mail_replica = tcp:remote.test
                }
                service doveadm {
                inet_listener {
                        address = [::]
                        }
                }       

        | local> host remote.test:      
        remote.test has IPv6 address fd00:b::1

        working well.

Currently:

        dovecot.conf:
                plugin { 
                        mail_replica = tcp:remote.test
                }
                service doveadm {
                inet_listener {
                        address = *
                        }
                }       

        | local> host remote.test:      
        remote.test has address 10.2.0.1
        remote.test has IPv6 address fd00:b::1



Now, Replication stops and throws an error like:

        | <mail.crit> local.test dovecot: doveadm(user): Fatal: 
connect(fd00:b::1:12345) failed: Connection refused


If I either

        #) remove IPv6 from my lokal DNS, 
        #) use "mail_replica = tcp:10.2.0.1", or 
        #) define the appropriate IPv4 address of remote.test in /etc/hosts, 

then replication works as usual.

Hmm, shouldn't doveadm be more persistent in using every IP address of that 
entry of mail_replica *before* throwing a "Fatal:" error?
Or do I miss something, and it's a feature, instead?

Regards,
Michael