Re: Controlling ports used by natd

From: Brett Glass (brett_at_lariat.org)
Date: 12/12/03

  • Next message: Anthony Volodkin: "Re: mpd vpn" 
    Date: Fri, 12 Dec 2003 10:41:50 -0700
To: Barney Wolff <barney@databus.com>

    At 01:35 AM 12/12/2003, Barney Wolff wrote:

    >Oops, sorry for the confusion. How fancy a change is up to you,
    >but changing ALIAS_PORT_BASE and ALIAS_PORT_MASK (and _EVEN)
    >would let you confine the port range without much work.

    The current algorithm works so long as the blocked ports have
    numbers less than 32768. But there are now lots of Trojans and
    worms that use higher ports, and admins may want to block them.
    So, there ought to be a way to tell libalias "don't assign anything
    in this set of ports" -- via a list or a bitmap.

    If one can tap directly into libalias and make this a global
    restriction, it might be that other programs (e.g. ppp) could
    remain blissfully ignorant of it. If the restrictions were allowed
    to be different for different instances of programs that used
    libalias (for example, several instances of natd, each handling
    an interface with unique restrictions), one would have to modify
    the API of libalias, which might break code if not done carefully.

    --Brett

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