Re: [nf PATCH] netfilter: nft_fib: Fix for rpath check with VRF devices

[Phil Sutter <phil@nwl.cc>]

On Wed, Sep 21, 2022 at 12:48:27AM +0200, Florian Westphal wrote:
> Phil Sutter <phil@nwl.cc> wrote:
> > Analogous to commit b575b24b8eee3 ("netfilter: Fix rpfilter
> > dropping vrf packets by mistake") but for nftables fib expression:
> > Add special treatment of VRF devices so that typical reverse path
> > filtering via 'fib saddr . iif oif' expression works as expected.
> > 
> > Fixes: f6d0cbcf09c50 ("netfilter: nf_tables: add fib expression")
> > Signed-off-by: Phil Sutter <phil@nwl.cc>
> > ---
> >  net/ipv4/netfilter/nft_fib_ipv4.c | 3 +++
> >  net/ipv6/netfilter/nft_fib_ipv6.c | 7 ++++++-
> >  2 files changed, 9 insertions(+), 1 deletion(-)
> > 
> > diff --git a/net/ipv4/netfilter/nft_fib_ipv4.c b/net/ipv4/netfilter/nft_fib_ipv4.c
> > index b75cac69bd7e6..7ade04ff972d7 100644
> > --- a/net/ipv4/netfilter/nft_fib_ipv4.c
> > +++ b/net/ipv4/netfilter/nft_fib_ipv4.c
> > @@ -83,6 +83,9 @@ void nft_fib4_eval(const struct nft_expr *expr, struct nft_regs *regs,
> >  	else
> >  		oif = NULL;
> >  
> > +	if (priv->flags & NFTA_FIB_F_IIF)
> > +		fl4.flowi4_oif = l3mdev_master_ifindex_rcu(oif);
> > +
> >  	if (nft_hook(pkt) == NF_INET_PRE_ROUTING &&
> >  	    nft_fib_is_loopback(pkt->skb, nft_in(pkt))) {
> >  		nft_fib_store_result(dest, priv, nft_in(pkt));
> > diff --git a/net/ipv6/netfilter/nft_fib_ipv6.c b/net/ipv6/netfilter/nft_fib_ipv6.c
> > index 8970d0b4faeb4..3f860e331580d 100644
> > --- a/net/ipv6/netfilter/nft_fib_ipv6.c
> > +++ b/net/ipv6/netfilter/nft_fib_ipv6.c
> > @@ -170,6 +170,10 @@ void nft_fib6_eval(const struct nft_expr *expr, struct nft_regs *regs,
> >  	else if (priv->flags & NFTA_FIB_F_OIF)
> >  		oif = nft_out(pkt);
> >  
> > +	if ((priv->flags & NFTA_FIB_F_IIF) &&
> > +	    (netif_is_l3_master(oif) || netif_is_l3_slave(oif)))
> > +		fl6.flowi6_oif = oif->ifindex;
> > +
> 
> I was about to apply this, but this initialisation comes before
> nft_fib6_flowi_init(), should this be *after*, or part of
> nft_fib6_flowi_init() function instead?

Oh, I missed that one, sorry. I'll make it part of
nft_fib6_flowi_init() to better align with ip6t_rpfilter.c.

Thanks, Phil