Re: [PATCH RESEND] netfilter: bridge: unshare bridge info before change it

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Wed, Nov 19, 2014 at 12:17:20PM +0100, Pablo Neira Ayuso wrote:
> On Wed, Nov 19, 2014 at 10:11:25AM +0800, Gao feng wrote:
> > On 11/19/2014 02:34 AM, Pablo Neira Ayuso wrote:
> > > On Mon, Nov 17, 2014 at 01:48:43PM +0800, Gao feng wrote:
> > >> diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c
> > >> index 1a4f32c..b4612b9 100644
> > >> --- a/net/bridge/br_netfilter.c
> > >> +++ b/net/bridge/br_netfilter.c
> > >> @@ -653,7 +643,11 @@ static int br_nf_forward_finish(struct sk_buff *skb)
> > >>  		in = nf_bridge->physindev;
> > >>  		if (nf_bridge->mask & BRNF_PKT_TYPE) {
> > >>  			skb->pkt_type = PACKET_OTHERHOST;
> > >> -			nf_bridge->mask ^= BRNF_PKT_TYPE;
> > >> +
> > >> +			if (!nf_bridge_unset_mask(skb, BRNF_PKT_TYPE)) {
> > >> +				kfree_skb(skb);
> > >> +				return 0;
> > >> +			}
> > > 
> > > This can now release the packet and, thus, drop it.
> > > 
> > > However, br_nf_forward_ip() always returns NF_STOLEN.
> > > 
> > > Could you revisit the error paths and confirm they are correct?
> > 
> > Since br_nf_forward_ip() returns NF_STOLEN, br_nf_forward_finish should make
> > sure this skb will be released. if unser_mask for this skb is failed, we free
> > it. if unset successed, the hooks on NF_BR_FORWARD or br_forward_finish will
> > free this skb.
> 
> OK, but I think this should return NF_DROP instead of NF_STOLEN so you
> don't explicitly need to kfree_skb it.

After a further look, I noticed what I suggest needs to replace:

        NF_HOOK_THRESH(...);
        return 0;

by:
        return NF_HOOK_THRESH(...);

And review the return value of all the existing okfn() functions so
they return netfilter verdicts.

The existing code always returns NF_STOLEN from many other hooks, not
only when dropped but also when accepted to make this work...

I'm going to have a look at your v2. Thanks.