Re: [PATCH -next] netfilter: meta: add support for setting skb->pkttype

[Florian Westphal <fw@strlen.de>]

Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> On Thu, Dec 03, 2015 at 04:56:41PM +0100, Florian Westphal wrote:
> > This allows to redirect bridged packets to local machine.
> > 
> > ether type ip ether daddr set aa:53:08:12:34:56 meta pkttype set unicast
> > 
> > Without 'set unicast', ip stack discards PACKET_OTHERHOST skbs.
> > 
> > Signed-off-by: Florian Westphal <fw@strlen.de>
> > ---
> >  Hi Patrick,
> > 
> >  as discussed this adds meta set support for pkttype.
> > 
> >  I'm not sure how restricted it should be; this only allows
> >  changing PACKET_OTHERHOST to something else, but I'm not sure
> >  if this should do more checks on value (e.g. only allow
> >  PACKET_HOST?) or even less (e.g. also allow mangling
> >  mcast and the like?).
> >
> >  It only allows NETDEV and BRIDGE families but thats mainly
> >  because the other ones make no sense (PACKET_OTHERHOST
> >  cannot happen w. IPV4, 6, INET since stack already drops them earlier).
> 
> With a 'hash' expression and this mangling, we can emulate the cluster
> match (hence its CLUSTERIP target predecesor too).

I forgot about -m cluster, so we definitely want to be able to change
MULTICAST to HOST.

So the only question is wheter we should allow setting it to arbitrary
value (e.g. PACKET_LOOPBACK).  I'm reasonably sure HOST/BROAD/MULTICAST
are okay.

I'll dig if that might cause any problems (esp. when considering
mangling happens in a netns).

> If mangling doesn't crash the kernel, ie. nonsense configuration just
> results in a drop, then I would make no restrictions.

Makes sense.

An updated patch to also permit MCAST will arrive in any case,
moved patchwork state to 'changes requested'.

Thanks!