netdev - Re: [PATCH net-next v10 2/5] openvswitch: set skb protocol and mac

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Date:	Thu, 2 Jun 2016 15:01:47 -0700
From:	pravin shelar <pshelar@....org>
To:	Simon Horman <simon.horman@...ronome.com>
Cc:	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	ovs dev <dev@...nvswitch.org>
Subject: Re: [PATCH net-next v10 2/5] openvswitch: set skb protocol and
 mac_len when receiving on internal device

On Wed, Jun 1, 2016 at 11:24 PM, Simon Horman
<simon.horman@...ronome.com> wrote:
> * Set skb protocol based on contents of packet. I have observed this is
>   necessary to get actual protocol of a packet when it is injected into an
>   internal device e.g. by libnet in which case skb protocol will be set to
>   ETH_ALL.
>
> * Set the mac_len which has been observed to not be set up correctly when
>   an ARP packet is generated and sent via an openvswitch bridge.
>   My test case is a scenario where there are two open vswtich bridges.
>   One outputs to a tunnel port which egresses on the other.
>
> The motivation for this is that support for outputting to layer 3 (non-tap)
> GRE tunnels as implemented by a subsequent patch depends on protocol and
> mac_len being set correctly on receive.
>
> Signed-off-by: Simon Horman <simon.horman@...ronome.com>
>
> ---
> v10
> * Set mac_len
>
> v9
> * New patch
> ---
>  net/openvswitch/vport-internal_dev.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/net/openvswitch/vport-internal_dev.c b/net/openvswitch/vport-internal_dev.c
> index 2ee48e447b72..f89b1efa88f1 100644
> --- a/net/openvswitch/vport-internal_dev.c
> +++ b/net/openvswitch/vport-internal_dev.c
> @@ -48,6 +48,10 @@ static int internal_dev_xmit(struct sk_buff *skb, struct net_device *netdev)
>  {
>         int len, err;
>
> +       skb->protocol = eth_type_trans(skb, netdev);
> +       skb_push(skb, ETH_HLEN);
> +       skb_reset_mac_len(skb);
> +
resetting mac-len breaks the assumption about mac_len for referencing
MPLS header ref: skb_mpls_header().