Re: Operating Postfix with IPv6 (dual-stack)

[lst_hoe02]

Zitat von Wietse Venema <wie...@porcupine.org>:

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

Regards

Andreas

Is the last point still on todo list or considered worth to be included in the future?

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