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@xxxxxxxxxxxxx>
> > ---
> > 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.
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