netdev - Re: [PATCH net] vrf: reset rt_iif for recirculated mcast out pkts

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Date:   Tue, 25 Jun 2019 16:42:53 -0400
From:   Stephen Suryaputra <ssuryaextr@...il.com>
To:     David Ahern <dsahern@...il.com>
Cc:     netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net] vrf: reset rt_iif for recirculated mcast out pkts

On Tue, Jun 25, 2019 at 4:22 PM David Ahern <dsahern@...il.com> wrote:
>
> On 6/25/19 4:33 AM, Stephen Suryaputra wrote:
> > @@ -363,10 +376,20 @@ int ip_mc_output(struct net *net, struct sock *sk, struct sk_buff *skb)
> >  #endif
> >                  ) {
> >                       struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
> > -                     if (newskb)
> > +                     if (newskb) {
> > +                             /* Reset rt_iif so that inet_iif() will return
> > +                              * skb->dev->ifIndex which is the VRF device for
> > +                              * socket lookup. Setting this to VRF ifindex
> > +                              * causes ipi_ifindex in in_pktinfo to be
> > +                              * overwritten, see ipv4_pktinfo_prepare().
> > +                              */
> > +                             if (netif_is_l3_slave(dev))
>
> seems like the rt_iif is a problem for recirculated mcast packets in
> general, not just ones tied to a VRF.

It seems so to me too but I wonder why this hasn't been seen...
Can I get more feedbacks on this? If there is an agreement to fix this
generally, I will remove the if clause and respin the patch with more
accurate changelog.

>
> > +                                     ip_mc_reset_rt_iif(net, rt, newskb);
> > +
> >                               NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
> >                                       net, sk, newskb, NULL, newskb->dev,
> >                                       ip_mc_finish_output);
> > +                     }
> >               }
> >
> >               /* Multicasts with ttl 0 must not go beyond the host */

Thanks.