netdev - Re: [PATCH 2/3 nf-next] netfilter: nf_tables: allow to bind table to net

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Date:	Wed, 27 May 2015 10:08:16 +0900
From:	Simon Horman <simon.horman@...ronome.com>
To:	Pablo Neira Ayuso <pablo@...filter.org>
Cc:	netfilter-devel@...r.kernel.org, kaber@...sh.net,
	netdev@...r.kernel.org
Subject: Re: [PATCH 2/3 nf-next] netfilter: nf_tables: allow to bind table to
 net_device

On Tue, May 26, 2015 at 11:58:24AM +0200, Pablo Neira Ayuso wrote:
> On Tue, May 26, 2015 at 09:48:41AM +0900, Simon Horman wrote:
> > Hi Pablo,
> > 
> > On Mon, May 25, 2015 at 02:46:41PM +0200, Pablo Neira Ayuso wrote:
> > > This patch adds the internal NFT_AF_NEEDS_DEV flag to indicate that you must
> > > attach this table to a net_device.
> > > 
> > > This change is required by the follow up patch that introduces the new netdev
> > > table.
> > > 
> > > Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
> > > ---
> > >  include/net/netfilter/nf_tables.h        |    8 ++++++
> > >  include/uapi/linux/netfilter/nf_tables.h |    2 ++
> > >  net/netfilter/nf_tables_api.c            |   46 ++++++++++++++++++++++++++----
> > >  3 files changed, 51 insertions(+), 5 deletions(-)
> > 
> > [snip]
> > 
> > > diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
> > > index 5fa1cd0..89a671e 100644
> > > --- a/include/uapi/linux/netfilter/nf_tables.h
> > > +++ b/include/uapi/linux/netfilter/nf_tables.h
> > 
> > [snip]
> > 
> > > @@ -423,6 +425,10 @@ static int nf_tables_fill_table_info(struct sk_buff *skb, struct net *net,
> > >  	    nla_put_be32(skb, NFTA_TABLE_USE, htonl(table->use)))
> > >  		goto nla_put_failure;
> > >  
> > > +	if (table->dev &&
> > > +	    nla_put_string(skb, NFTA_TABLE_DEV, table->dev->name))
> > > +		goto nla_put_failure;
> > > +
> > >  	nlmsg_end(skb, nlh);
> > >  	return 0;
> > >  
> > > @@ -608,6 +614,11 @@ static int nf_tables_updtable(struct nft_ctx *ctx)
> > >  	if (flags == ctx->table->flags)
> > >  		return 0;
> > >  
> > > +	if ((ctx->afi->flags & NFT_AF_NEEDS_DEV) &&
> > > +	    ctx->nla[NFTA_TABLE_DEV] &&
> > > +	    nla_strcmp(ctx->nla[NFTA_TABLE_DEV], ctx->table->dev->name))
> > > +		return -EOPNOTSUPP;
> > > +
> > >  	trans = nft_trans_alloc(ctx, NFT_MSG_NEWTABLE,
> > >  				sizeof(struct nft_trans_table));
> > >  	if (trans == NULL)
> > 
> > I'm a little unsure of the above logic.
> > 
> > Is it ok for NFT_AF_NEEDS_DEV to be set but ctx->nla[NFTA_TABLE_DEV] to
> > be absent?
> 
> This path is only run if the table already exists.
> 
> So it basically checks if we're trying to update the binding, in that
> case we hit -EOPNOTSUPP.
> 
> If we don't pass any NFTA_TABLE_DEV, then we assume we stick to the
> existing binding.
> 
> This allows us to update the table flags without indicating the
> binding, eg.
> 
>         nft add table netdev filter { flags dormant\; }
> 
> which basically disables the entire table content.

Thanks Pablo, that is clear to me now.
I have no objections.
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