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

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Date:	Sat, 18 Jun 2016 18:38:54 -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 Thu, Jun 16, 2016 at 10:53 PM, Simon Horman
<simon.horman@...ronome.com> wrote:
> On Tue, Jun 07, 2016 at 03:45:27PM -0700, pravin shelar wrote:
>> On Mon, Jun 6, 2016 at 8:08 PM, Simon Horman <simon.horman@...ronome.com> wrote:
>> > On Thu, Jun 02, 2016 at 03:01:47PM -0700, pravin shelar wrote:
>> >> 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.
....
....
>> >         eth_type = eth_type_trans(skb, skb->dev);
>> >         skb->mac_len = skb->data - skb_mac_header(skb);
>> >         __skb_push(skb, skb->mac_len);
>> >
>> >         if (eth_type == htons(ETH_P_8021Q))
>> >                 skb->mac_len += VLAN_HLEN;
>> >
>> > Perhaps that logic ought to be in a helper used by both internal_dev_xmit()
>> > and netdev_port_receive(). Or somehow centralised in ovs_vport_receive().
>>
>> This does looks bit complex. Can we use other skb metadata like
>> skb_mac_header_was_set()?
>
> Yes, I think that can be made to work if skb->mac_header is unset
> for l3 packets in netdev_port_receive(). The following is an incremental
> patch on the entire series. Is this the kind of thing you had in mind?
>
> diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c
> index 86f2cfb19de3..42587d5bf894 100644
> --- a/net/openvswitch/flow.c
> +++ b/net/openvswitch/flow.c
> @@ -729,7 +729,7 @@ int ovs_flow_key_extract(const struct ip_tunnel_info *tun_info,
>         key->phy.skb_mark = skb->mark;
>         ovs_ct_fill_key(skb, key);
>         key->ovs_flow_hash = 0;
> -       key->phy.is_layer3 = skb->mac_len == 0;
> +       key->phy.is_layer3 = skb_mac_header_was_set(skb) == 0;
>         key->recirc_id = 0;
>
>         err = key_extract(skb, key);
> diff --git a/net/openvswitch/vport-internal_dev.c b/net/openvswitch/vport-internal_dev.c
> index 484ba529c682..8973d4db509b 100644
> --- a/net/openvswitch/vport-internal_dev.c
> +++ b/net/openvswitch/vport-internal_dev.c
> @@ -50,7 +50,6 @@ static int internal_dev_xmit(struct sk_buff *skb, struct net_device *netdev)
>
>         skb->protocol = eth_type_trans(skb, netdev);
>         skb_push(skb, ETH_HLEN);
> -       skb_reset_mac_len(skb);
>
>         len = skb->len;
>         rcu_read_lock();
> diff --git a/net/openvswitch/vport-netdev.c b/net/openvswitch/vport-netdev.c
> index 3df36df62ee9..4cf3f12ffc99 100644
> --- a/net/openvswitch/vport-netdev.c
> +++ b/net/openvswitch/vport-netdev.c
> @@ -60,22 +60,9 @@ static void netdev_port_receive(struct sk_buff *skb)
>         if (vport->dev->type == ARPHRD_ETHER) {
>                 skb_push(skb, ETH_HLEN);
>                 skb_postpush_rcsum(skb, skb->data, ETH_HLEN);
> -       } else if (vport->dev->type == ARPHRD_NONE) {
> -               if (skb->protocol == htons(ETH_P_TEB)) {
> -                       __be16 eth_type;
> -
> -                       if (unlikely(skb->len < ETH_HLEN))
> -                               goto error;
> -
> -                       eth_type = eth_type_trans(skb, skb->dev);
> -                       skb->mac_len = skb->data - skb_mac_header(skb);
> -                       __skb_push(skb, skb->mac_len);
> -
> -                       if (eth_type == htons(ETH_P_8021Q))
> -                               skb->mac_len += VLAN_HLEN;
> -               } else {
> -                       skb->mac_len = 0;
> -               }
> +       } else if (vport->dev->type == ARPHRD_NONE &&
> +                  skb->protocol != htons(ETH_P_TEB)) {
> +               skb->mac_header = (typeof(skb->mac_header))~0U;
>         }
>
>         ovs_vport_receive(vport, skb, skb_tunnel_info(skb));

This certainly looks better. I was wondering if we can unset the mac
header offset in L3 tunnel devices itself. So there is no need to have
this check here.