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Re: avoiding overload on port 587

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  • Wietse Venema
    ... I don t know the fine details, but I do know that these systems have have very mature hardware support for virtualization and multiprocessing. There are
    Message 1 of 54 , Dec 1, 2012
      Stan Hoeppner:
      > On 12/1/2012 2:26 PM, Wietse Venema wrote:
      > > Stan Hoeppner:
      > >> ...and I have no experience and pay no
      > >> attention to what Oracle is doing with Solaris virtualization,
      > >> "containers" I believe they call it.
      > >
      > > Solaris containers are descendants from FreeBSD jails: they provide
      > > different userland namespaces(*) on top of a shared OS kernel.
      > >
      > > Hardware virtualization on the other hand provides different hardware
      > > namespaces(*) on top of a shared hypervisor.
      > >
      > > These are basically sandboxing methods with different levels of
      > > isolation and performance. I would not expect that jails/containers
      > > introduce new challenges with respect to missing interrupts.
      > >
      > > Wietse
      > >
      > > (*) Not just file or device names, but also
      > > memory addresses, disk blocks, and so on.
      >
      > Wietse you work in a "small corner" of IBM and may not know, but if you
      > do or know who to ask, I'd like to know how IBM handles Linux guest
      > clocks on zSeries, and pSeries for that matter. Is there an IBM
      > document on this maybe?

      I don't know the fine details, but I do know that these systems
      have have very mature hardware support for virtualization and
      multiprocessing.

      There are many IBM documents, too many for me to make a quick
      selection for you.

      Wietse
    • /dev/rob0
      ... Or better yet: replace it with postscreen. ... To clarify, I meant that if those Outlook Expresses are not yet compromised by malware, they will be, soon.
      Message 54 of 54 , Dec 4, 2012
        On Tue, Dec 04, 2012 at 07:46:10AM -0600, /dev/rob0 wrote:
        > On Tue, Dec 04, 2012 at 11:59:01PM +1300, Peter wrote:
        > > I would still also set up port 587 on the mail.example.com
        > > IP as submission as well and try to encourage your users (at
        > > least the ones you can) to use port 587 from now on.
        >
        > What I would do, on Linux with IPv4 only, is create the submission
        > port and use an iptables redirect for the alternate IP address:
        >
        > # iptables -vt nat -A PREROUTING -p tcp --dport smtp -d \
        > mail.example.com -j REDIRECT --to-port submission
        >
        > This saves the overhead (system and administrative) of running
        > another smtpd on [mail.example.com]:25; he can leave his "smtp ...
        > smtpd" service alone in master.cf.

        Or better yet: replace it with postscreen.

        > I should also add as a reply to Stan in the other subthread: look
        > above at the first quoted paragraph: "Outlook Expresses setup with
        > ... default configuration."
        >
        > Yikes, bad news, very bad. If not doing content filtering nor
        > policy limitation of submission now, he will be soon. And possibly
        > losing his job in any case. Tomas is not in a good place right now.

        To clarify, I meant that if those Outlook Expresses are not yet
        compromised by malware, they will be, soon.
        --
        http://rob0.nodns4.us/ -- system administration and consulting
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