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

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Date:   Tue, 25 Jun 2019 14:22:37 -0600
From:   David Ahern <dsahern@...il.com>
To:     Stephen Suryaputra <ssuryaextr@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH net] vrf: reset rt_iif for recirculated mcast out pkts

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.

> +					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 */