Re: [PATCH net 8/9] netfilter: ip6_tables: set F_PROTO when proto value is nonzero

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

On Tue, Sep 08, 2026 at 06:04:04PM +0000, netdev-bot+sashiko@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 1 potential
> issue(s) to consider:
> 
> Critical: 0 · High: 0 · Medium: 0 · Low: 1
> 
> - [Low] Stale/contradicted UAPI documentation for `struct
>   ip6t_ip6::proto`.
> 
> --
> 
> netfilter: ip6_tables: set F_PROTO when proto value is nonzero
> 
> This makes the kernel set IP6T_F_PROTO for any rule that carries a nonzero
> ipv6.proto, so ip6_packet_match() always performs the protocol comparison
> and extension header walk instead of skipping it when userspace left the
> flag clear. It mirrors the normalisation already done in nft_compat.c.
> 
> > diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
> > index f42fb96ef64b6..313c4aac377aa 100644
> > --- a/net/ipv6/netfilter/ip6_tables.c
> > +++ b/net/ipv6/netfilter/ip6_tables.c
> > @@ -647,6 +647,11 @@ check_entry_size_and_hooks(struct ip6t_entry *e,
> >  	/* Clear counters and comefrom */
> >  	e->counters = ((struct xt_counters) { 0, 0 });
> >  	e->comefrom = 0;
> > +
> > +	/* set F_PROTO, else ip6_packet_match won't do the right thing. */
> > +	if (e->ipv6.proto)
> > +		e->ipv6.flags |= IP6T_F_PROTO;
> > +
> >  	return 0;
> >  }
> 
> [Severity: Low]
> Should the uapi header comment be updated in the same patch?  The
> description of struct ip6t_ip6::proto in
> include/uapi/linux/netfilter_ipv6/ip6_tables.h still documents the
> opposite contract:
> 
> 	/* Upper protocol number
> 	 * ...
> 	 * - You also need to set IP6T_FLAGS_PROTO to "flags" to check protocol.
> 	 */

That is still the indeed recommended practise, so no, comment must be
not updated.

This is just makes a work-around for broken userspace code that has no
real usecase other than triggering a bug.

Quite a bit of noise from LLM, one pre-existing issue found, but other
than that, just lengthy text noise.