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273679Re: Operating Postfix with IPv6 (dual-stack)

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  • Wietse Venema
    Feb 1, 2011
      lst_hoe02@...:
      > Zitat von Wietse Venema <wietse@...>:
      >
      > > lst_hoe02@...:
      > >> 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
      >
      > Is the last point still on todo list or considered worth to be
      > included in the future?

      It is not a high priority. Moreover, this means ripping up a
      low-level API, so it would take longer. I'm still fixing code
      that was merged into Postfix 9 years ago.

      Wietse
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