linux-kernel - Re: [PATCH net] bridge: ebtables: fix reception of frames DNAT-ed to bridge device

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Message-ID: <20170315104211.GA24409@salvia>
Date:   Wed, 15 Mar 2017 11:42:11 +0100
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Florian Westphal <fw@...len.de>
Cc:     Linus Lüssing <linus.luessing@...3.blue>,
        netdev@...r.kernel.org, "David S . Miller" <davem@...emloft.net>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
        bridge@...ts.linux-foundation.org, netfilter-devel@...r.kernel.org,
        coreteam@...filter.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] bridge: ebtables: fix reception of frames DNAT-ed to
 bridge device

On Wed, Mar 15, 2017 at 11:26:08AM +0100, Florian Westphal wrote:
> Linus Lüssing <linus.luessing@...3.blue> wrote:
> > When trying to redirect bridged frames to the bridge device itself
> > via the ebtables nat-prerouting chain and the dnat target then this
> > currently fails:
> > 
> > The ethernet destination of the frame is dnat'ed to the MAC address of
> > the bridge itself just fine and the correctly altered frame can even
> > be captured via a tcpdump on br0 (with or without promisc mode).
> >
> > However, the IP code drops it in the beginning of ip_input.c/ip_rcv()
> > as the dnat target did not update the skb->pkt_type.
> 
> Right, thats the reason why ebtables also has ebt_redirect target
> which does this pkt_type fixup.

I'm missing then why redirect is not then just enough for Linus usecase.