Date: Mon, 16 Aug 1999 20:37:09 -0700 (PDT) From: "Rodney W. Grimes" <freebsd@gndrsh.dnsmgr.net> To: archie@whistle.com (Archie Cobbs) Cc: current@FreeBSD.ORG Subject: Re: Dropping connections without RST Message-ID: <199908170337.UAA10246@gndrsh.dnsmgr.net> In-Reply-To: <199908170133.SAA25256@bubba.whistle.com> from Archie Cobbs at "Aug 16, 1999 06:33:51 pm"
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> Geoff Rehmet writes:
> > After the discussions regarding the "log_in_vain"
> > sysctls, I was thinking about a feature I would
> > like to implement:
> >
> > Instead of sending a RST (for TCP) or Port Unreachable
> > (for UDP) where the box is not listening on a socket,
> > I would like to implement a sysctl, which disables the
> > sending of the RST or the Port unreachable. This is
> > basically for public servers (like DNS servers), which
> > I want to turn into black holes on ports where they
> > are not listening. (This confuses things if someone
> > strobes the machines, and also makes life a little
> > more difficult for anyone who tries to portscan them.)
> >
> > In default configuration, everything would behave as per
> > normal, and you would have to set a sysctl MIB before the
> > behaviour that I have described is displayed.
> >
> > Can anyone think of any reason why this feature should
> > not be implemented?
>
> I like that idea... net.inet.{tcp,udp}.drop_in_vain ?
>
I kinda like the idea of this, but can't that really just
be done easily with a few ipfw rules, the last two being
the important ones:
for port in "22 53" ; do
ipfw add allow udp from any to ${myip} ${port}
ipfw add allow udp from ${myip} ${port} to any
ipfw add allow tcp from any to ${myip} ${port}
ipfw add allow tcp from ${myip} ${port} to any
done
ipfw add deny udp from any to ${myip}
ipfw add deny tcp from any to ${myip}
Why should we special case this?
--
Rod Grimes - KD7CAX - (RWG25) rgrimes@gndrsh.dnsmgr.net
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