netdev - Re: [PATCH net-next 2/3] net: mpls: Fixups for GSO

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Message-ID: <CAOrHB_Dw1MJnfeD034HzGWkMrzEhP6PUKGFP3jDJzeNyRSZcHg@mail.gmail.com>
Date:   Wed, 24 Aug 2016 10:41:24 -0700
From:   pravin shelar <pshelar@....org>
To:     David Ahern <dsa@...ulusnetworks.com>
Cc:     Simon Horman <simon.horman@...ronome.com>,
        Pravin B Shelar <pshelar@...ira.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>, buytenh@...tstofly.org,
        "Eric W. Biederman" <ebiederm@...ssion.com>, rshearma@...cade.com,
        tom@...bertland.com, Thomas Graf <tgraf@...g.ch>,
        olivier.dugeon@...nge.com,
        Alexander Duyck <alexander.duyck@...il.com>,
        roopa@...ulusnetworks.com
Subject: Re: [PATCH net-next 2/3] net: mpls: Fixups for GSO

On Wed, Aug 24, 2016 at 9:37 AM, David Ahern <dsa@...ulusnetworks.com> wrote:
> On 8/24/16 10:28 AM, pravin shelar wrote:
>>> How do you feel about implementing the do_output() idea I suggested above?
>>> I'm happy to provide testing and review.
>>
>> I am not sure about changing do_output(). why not just use same scheme
>> to track mpls header in OVS datapath as done in mpls device?
>>
>
> was just replying with the same.
>
> Something like this should be able to handle multiple labels. The inner network header is set once and the outer one pointing to MPLS is adjusted each time a label is pushed:
>
> diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
> index 1ecbd7715f6d..0f37b17e3a73 100644
> --- a/net/openvswitch/actions.c
> +++ b/net/openvswitch/actions.c
> @@ -162,10 +162,16 @@ static int push_mpls(struct sk_buff *skb, struct sw_flow_key *key,
>         if (skb_cow_head(skb, MPLS_HLEN) < 0)
>                 return -ENOMEM;
>
> +       if (!skb->inner_protocol) {
> +               skb_set_inner_network_header(skb, skb->mac_len);
> +               skb_set_inner_protocol(skb, skb->protocol);
> +       }
> +
>         skb_push(skb, MPLS_HLEN);
>         memmove(skb_mac_header(skb) - MPLS_HLEN, skb_mac_header(skb),
>                 skb->mac_len);
>         skb_reset_mac_header(skb);
> +       skb_set_network_header(skb, skb->mac_len);
>
>         new_mpls_lse = (__be32 *)skb_mpls_header(skb);
>         *new_mpls_lse = mpls->mpls_lse;
> @@ -173,8 +179,7 @@ static int push_mpls(struct sk_buff *skb, struct sw_flow_key *key,
>         skb_postpush_rcsum(skb, new_mpls_lse, MPLS_HLEN);
>
>         update_ethertype(skb, eth_hdr(skb), mpls->mpls_ethertype);
> -       if (!skb->inner_protocol)
> -               skb_set_inner_protocol(skb, skb->protocol);
> +
>         skb->protocol = mpls->mpls_ethertype;
>
>         invalidate_flow_key(key);
>
>
>
>
> If it does, what else needs to be changed in OVS to handle the network layer now pointing to the MPLS labels?
>
You also need to change pop_mpls().

Anyways I was thinking about the neigh output functions skb pull
issue, where it is using network-header offset. Can we use mac_len?
this way we would not use any inner offsets for MPLS skb and current
scheme used by OVS datapath works.