Subject: Re: [Bridge] [PATCH 1/2] net: bridge: fix tc added QinQ forwarding

From: Zahari Doychev <[email-masked]>
Date: Thu, 17 Jan 2019 09:17:07 +0100

On Tue, Jan 15, 2019 at 03:11:28PM +0900, Toshiaki Makita wrote:
> On 2019/01/13 22:59, Zahari Doychev wrote:
> > Use the skb->mac_len instead of using the ETH_HLEN when pushing the skb
> > data pointer. This fixes sending incorrect packets when more than one
> > vlan tags are pushed by tc-vlan and the mac header length is bigger than
> > ETH_HLEN. In this way the vlan tagged contained in the skb is inserted at
> > right offset in the packet payload before sending the packet.
> > 
> > Signed-off-by: Zahari Doychev <[email-masked]>
> > ---
> >  net/bridge/br_forward.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/net/bridge/br_forward.c b/net/bridge/br_forward.c
> > index 5372e2042adf..55f928043f77 100644
> > --- a/net/bridge/br_forward.c
> > +++ b/net/bridge/br_forward.c
> > @@ -39,7 +39,7 @@ int br_dev_queue_push_xmit(struct net *net, struct sock *sk, struct sk_buff *skb
> >  	if (!is_skb_forwardable(skb->dev, skb))
> >  		goto drop;
> >  
> > -	skb_push(skb, ETH_HLEN);
> > +	skb_push(skb, skb->mac_len);
> >  	br_drop_fake_rtable(skb);
> >  
> >  	if (skb->ip_summed == CHECKSUM_PARTIAL &&
> > 
> 
> I guess you mean skb->data points to mac_header + ETH_HLEN + VLAN_HLEN
> when bridge receives skbs in br_handle_frame()?

yes, this is what I see.

> If so, the behavior of act_vlan is odd. Normal double tagged skbs from
> hardware devices should have skb->data pointing to mac_header + ETH_HLEN
> because they just call eth_type_trans() before entering
> netif_receive_skb()...
> I think act_vlan needs some fix.

The act_valn is using the skb_vlan_push(...) to add the vlan tags and in this
way increasing the skb->data and mac_len. So I think I can add a fix there to
set the skb->data to point to mac_header + ETH_HLEN when more tags are added.

Thanks
Zahari

> -- 
> Toshiaki Makita