Re: [PATCH] xfrm: interface: Don't hide plain packets from netfilter

[Steffen Klassert <steffen.klassert@secunet.com>]

On Mon, Dec 07, 2020 at 02:03:03PM +0100, Phil Sutter wrote:
> With an IPsec tunnel without dedicated interface, netfilter sees locally
> generated packets twice as they exit the physical interface: Once as "the
> inner packet" with IPsec context attached and once as the encrypted
> (ESP) packet.
> 
> With xfrm_interface, the inner packet did not traverse NF_INET_LOCAL_OUT
> hook anymore, making it impossible to match on both inner header values
> and associated IPsec data from that hook.
> 
> Fix this by looping packets transmitted from xfrm_interface through
> NF_INET_LOCAL_OUT before passing them on to dst_output(), which makes
> behaviour consistent again from netfilter's point of view.
> 
> Fixes: f203b76d78092 ("xfrm: Add virtual xfrm interfaces")
> Signed-off-by: Phil Sutter <phil@nwl.cc>
> ---
>  net/xfrm/xfrm_interface.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/net/xfrm/xfrm_interface.c b/net/xfrm/xfrm_interface.c
> index aa4cdcf69d471..24af61c95b4d4 100644
> --- a/net/xfrm/xfrm_interface.c
> +++ b/net/xfrm/xfrm_interface.c
> @@ -317,7 +317,8 @@ xfrmi_xmit2(struct sk_buff *skb, struct net_device *dev, struct flowi *fl)
>  	skb_dst_set(skb, dst);
>  	skb->dev = tdev;
>  
> -	err = dst_output(xi->net, skb->sk, skb);
> +	err = NF_HOOK(skb_dst(skb)->ops->family, NF_INET_LOCAL_OUT, xi->net,
> +		      skb->sk, skb, NULL, skb_dst(skb)->dev, dst_output);
>  	if (net_xmit_eval(err) == 0) {
>  		struct pcpu_sw_netstats *tstats = this_cpu_ptr(dev->tstats);

This is networking code, so please send your patch also to the netdev list:
netdev@vger.kernel.org