Subject: Re: [PATCH net-next] net: PIM register decapsulation and Forwarding.

From: Jakub Kicinski <[email-masked]>
Date: Tue, 17 May 2022 17:10:26 -0700

On Mon, 16 May 2022 04:29:06 -0700 Saranya Panjarathina wrote:
> PIM register packet is decapsulated but not forwarded in RP
> 
> __pim_rcv decapsulates the PIM register packet and reinjects for forwarding
> after replacing the skb->dev to reg_dev (vif with VIFF_Register)
> 
> Ideally the incoming device should be same as skb->dev where the
> original PIM register packet is received. mcache would not have
> reg_vif as IIF. Decapsulated packet forwarding is failing
> because of IIF mismatch. In RP for this S,G RPF interface would be
> skb->dev vif only, so that would be IIF for the cache entry.
> 
> Signed-off-by: Saranya Panjarathina <[email-masked]>

Not sure if this can cause any trouble. And why it had become 
a problem now, seems like the code has been this way forever.
David? Ido?

> diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
> index 13e6329784fb..7b9586335fb7 100644
> --- a/net/ipv4/ipmr.c
> +++ b/net/ipv4/ipmr.c
> @@ -598,7 +598,7 @@ static int __pim_rcv(struct mr_table *mrt, struct sk_buff *skb,
>  	skb->protocol = htons(ETH_P_IP);
>  	skb->ip_summed = CHECKSUM_NONE;
>  
> -	skb_tunnel_rx(skb, reg_dev, dev_net(reg_dev));
> +	skb_tunnel_rx(skb, skb->dev, dev_net(skb->dev));
>  
>  	netif_rx(skb);
>  
> diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
> index 4e74bc61a3db..147e29a818ca 100644
> --- a/net/ipv6/ip6mr.c
> +++ b/net/ipv6/ip6mr.c
> @@ -566,7 +566,7 @@ static int pim6_rcv(struct sk_buff *skb)
>  	skb->protocol = htons(ETH_P_IPV6);
>  	skb->ip_summed = CHECKSUM_NONE;
>  
> -	skb_tunnel_rx(skb, reg_dev, dev_net(reg_dev));
> +	skb_tunnel_rx(skb, skb->dev, net);
>  
>  	netif_rx(skb);
>