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    SubjectRe: Network Security hole (was -> Re: arp bug )

    Russell King <> wrote:

    > On Sat, Mar 02, 2002 at 04:21:24PM -0800, wrote:
    > > The fact that the routing layer and application layers of Linux's
    > > TCP/IP stack are one and the same is a difficulty here which the
    > > IP firewalling code in Linux does not fix. I.e. if I wanted to
    > > have routing as well, but not accept any packets internally *not*
    > > destined for my interface, I'm not sure how to specify it without
    > > something like TCP wrappers, as sleazy as they can be, and they
    > > don't offer this kind of capability in general as is.
    > Linux 2.4 netfilter:
    > Incoming Outgoing
    > interface interface
    > ----+------------------- FORWARD -----------------+------->
    > | ^
    > v |
    > INPUT -------------> Application -----------> OUTPUT
    > The names in capitals are the names of the tables. You can control
    > packets that the local machine sees completely independently of what
    > gets routed through the machine with a kernel supporting iptables
    > by adding the appropriate rules to the input and forward tables.

    Hmm. This would seem to be false in the RH 7.2 kernel 2.4.9-21
    kernel I'm working with.

    My IP masquerading rule (which claims to be in the "forward"
    chain, with target "MASQ"), was blocked when I did input address

    I.e. Yes, I actually tested this before posting.

    If you're calling it a bug, then so be it. But the result would be
    a bit better than how my Linux system works now.

    Erich Stefan Boleyn <>
    "Reality is truly stranger than fiction; Probably why fiction is so popular"
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