Firewalling Rules (Was: Linux Kernels)

Matthew Kirkwood (weejock@ferret.lmh.ox.ac.uk)
Fri, 31 Oct 1997 15:04:50 +0000 (GMT)


On Fri, 31 Oct 1997, Richard B. Johnson wrote:

> > Here's what you do: write a utility that reads the /etc/packet.deny
> > file, and translate it into ipfwadm commands. No need to change the
> > kernel.
>
> #
> # This keeps Micro$oft garbage packets out of this machine
> #
> ipfwadm -I -f
[snip rack of f/w rules]

Having heard various (and unconvincing) horror stories about the effect
that having many firewalling rules can have on network latency, I thought
up this foolish plan: firewall modules

Compile up a (or perhaps more than one) little module with enough code in
it to handle, in an intelligent way all of the firewalling that you
require.

Compile it with -O8 (or turn the 8 on its side :), and insmod the thing so
that your rules are, in essence, hardcoded and (of course :-) written
cunningly to minimise time taken in refusing all packets from 207.68.x.x.

It is, perhaps, unacceptably hacky, but could save a few cycles every now
and then...

So -- Am I a fool, or should I make some hacking time this weekend? :)

Matthew.

--
Matthew Kirkwood  |  Mail:  matthew.kirkwood@lmh.ox.ac.uk
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