lst_ho...@kwsoft.de:
> Hello
>
> we are on the way to IPv6 and some question arise about Postfix IPv6
> behaviour in dual stack setup.
You mean dual-protocol. Unlike some versions of Linux, there exist
systems that have a single unified TCP/IP stack implementation (the
protocols have a fair amount of behavior in common).
> 1.) Do the lookups for AAAA when resolving MX records occur in
> parallel to A queries, or is some additional latency expected due to
> the fact that many AAAA queries fail by timeout and others resolving
> errors?
With smtp_host_lookup=dns, all SMTP client lookups are sequential.
With smtp_host_lookup=native (or dns,native) Postfix in dual-protocol
mode will invoke getaddrinfo() with hints.ai_family=PF_UNSPEC.
The internals of getaddrinfo() are system dependent.
> 2.) Do AAAA/ip6.arpa lookup occur on client connects from IPv4
> addresses or only when a client connects by IPv6 (name/reverse lookups)?
The Postfix SMTP server's FCRDNS lookups use the getnameinfo() and
getaddrinfo() system library functions. In dual-protocol mode,
Postfix invokes getaddrinfo() with hints.ai_family=PF_UNSPEC; it
would be smarter to pass the client's address family instead.
Wietse
> Additionally any hints and feedback about potential pitfalls from
> people already doing IPv6 is welcome.
>
> Many Thanks
>
> Andreas
>
>
