linux-kernel - Re: [PATCH v4] add stealth mode

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Date:	Wed, 23 Sep 2015 10:29:52 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Matteo Croce <matteo@...nwrt.org>
Cc:	Florian Westphal <fw@...len.de>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] add stealth mode

On Wed, 2015-09-23 at 18:36 +0200, Matteo Croce wrote:
> 2015-09-16 13:06 GMT+02:00 Florian Westphal <fw@...len.de>:
> >
> > Matteo Croce <matteo@...nwrt.org> wrote:
> > > Add option to disable any reply not related to a listening socket,
> > > like RST/ACK for TCP and ICMP Port-Unreachable for UDP.
> > > Also disables ICMP replies to echo request and timestamp.
> > > The stealth mode can be enabled selectively for a single interface.
> >
> > I think it would make more sense to extend the socket match
> > in xtables if it can't be used to achive this already.
> >
> > seems like
> > *filter
> > :INPUT ACCEPT [0:0]
> > -A INPUT -p tcp -m socket --nowildcard -j ACCEPT
> > -A INPUT -p tcp -j DROP
> > COMMIT
> >
> > Already does what you want for tcp, udp should work too.
> > I'd much rather see xtables and/or nftables to be extended
> > with whatever feature(s) are needed to configure such a policy
> > rather than pushing this into the core network stack.
> 
> The point is to do the filtering without *tables at all,
> like /proc/sys/net/ipv4/icmp_echo_ignore_all does for pings

Yes, but this adds code in many places, even for people not caring of
such protection.

The point is : people wanting firewall like protections should instead
use netfilter framework.


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