netdev - Re: [PATCH net-next v12 7/9] openvswitch: add Ethernet push and pop actions

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Message-ID: <CAOrHB_Bj+0DNePDKQ64Gtx9SyxS4cy20Y-1RLC4Dpd3DKJpsjA@mail.gmail.com>
Date:   Thu, 20 Oct 2016 21:22:21 -0700
From:   Pravin Shelar <pshelar@....org>
To:     Jiri Benc <jbenc@...hat.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        ovs dev <dev@...nvswitch.org>,
        Lorand Jakab <lojakab@...co.com>,
        Simon Horman <simon.horman@...ronome.com>
Subject: Re: [PATCH net-next v12 7/9] openvswitch: add Ethernet push and pop actions

On Mon, Oct 17, 2016 at 6:02 AM, Jiri Benc <jbenc@...hat.com> wrote:
> It's not allowed to push Ethernet header in front of another Ethernet
> header.
>
> It's not allowed to pop Ethernet header if there's a vlan tag. This
> preserves the invariant that L3 packet never has a vlan tag.
>
> Based on previous versions by Lorand Jakab and Simon Horman.
>
> Signed-off-by: Lorand Jakab <lojakab@...co.com>
> Signed-off-by: Simon Horman <simon.horman@...ronome.com>
> Signed-off-by: Jiri Benc <jbenc@...hat.com>
> ---
>  include/uapi/linux/openvswitch.h | 15 ++++++++++++
>  net/openvswitch/actions.c        | 49 ++++++++++++++++++++++++++++++++++++++++
>  net/openvswitch/flow_netlink.c   | 18 +++++++++++++++
>  3 files changed, 82 insertions(+)
>
...
...
> diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
> index 064cbcb7b0c5..a63572fb878e 100644
> --- a/net/openvswitch/actions.c
> +++ b/net/openvswitch/actions.c
> @@ -317,6 +317,47 @@ static int set_eth_addr(struct sk_buff *skb, struct sw_flow_key *flow_key,
>         return 0;
>  }
>
> +/* pop_eth does not support VLAN packets as this action is never called
> + * for them.
> + */
> +static int pop_eth(struct sk_buff *skb, struct sw_flow_key *key)
> +{
> +       skb_pull_rcsum(skb, ETH_HLEN);
> +       skb_reset_mac_header(skb);
> +       skb->mac_len -= ETH_HLEN;
> +
> +       /* safe right before invalidate_flow_key */
> +       key->mac_proto = MAC_PROTO_NONE;
> +       invalidate_flow_key(key);
> +       return 0;
> +}
> +
> +static int push_eth(struct sk_buff *skb, struct sw_flow_key *key,
> +                   const struct ovs_action_push_eth *ethh)
> +{
> +       struct ethhdr *hdr;
> +
> +       /* Add the new Ethernet header */
> +       if (skb_cow_head(skb, ETH_HLEN) < 0)
> +               return -ENOMEM;
> +
> +       skb_push(skb, ETH_HLEN);
> +       skb_reset_mac_header(skb);
> +       skb->mac_len = ETH_HLEN;
> +

The eth pop substracts ETH_HLEN but here the length is set. I think it
should be consistent with respect to eth-pop.