Re: issues with vxlan RX checksum offload under OVS datapath

[Pravin Shelar <pshelar@nicira.com>]

On Sun, Jan 19, 2014 at 2:05 PM, Or Gerlitz <ogerlitz@mellanox.com> wrote:
> Hi Pravin,
>
> While testing the gro udp patches over a setup with openvswitch I noted that
> the RX checksum offload support introduced by Joseph's commit 0afb166
> "vxlan: Add capability of Rx checksum offload for inner packet" works fine
> when you use a setup made of
>
> NIC --> IP stack --> vxlan device --> bridge --> tap
>
> but not when its
>
> NIC --> IP stack --> ovs vxlan port --> OVS DP --> tap
>
> I narrowed it down to the fact the when going the OVS pathskb->encapsulation
> remains true also after the decap is done. Basically, this is the original
> hunk
>
>
>> @@ -607,7 +607,17 @@ static int vxlan_udp_encap_recv(struct sock *sk,
>> struct sk_buff *skb)
>>
>>         __skb_tunnel_rx(skb, vxlan->dev);
>>         skb_reset_network_header(skb);
>> -       skb->ip_summed = CHECKSUM_NONE;
>> +
>> +       /* If the NIC driver gave us an encapsulated packet with
>> +        * CHECKSUM_UNNECESSARY and Rx checksum feature is enabled,
>> +        * leave the CHECKSUM_UNNECESSARY, the device checksummed it
>> +        * for us. Otherwise force the upper layers to verify it.
>> +        */
>> +       if (skb->ip_summed != CHECKSUM_UNNECESSARY || !skb->encapsulation
>> ||
>> +           !(vxlan->dev->features & NETIF_F_RXCSUM))
>> +               skb->ip_summed = CHECKSUM_NONE;
>> +
>> +       skb->encapsulation = 0;
>
>
> which was moved by your commits
>
> 5cfccc5 vxlan: Add vxlan recv demux.
> 7ce0475 vxlan: Restructure vxlan receive.
>
> to a code which isn't shared by the vxlan driver and ovs vxlan datapath
> code, and I was thinking lets just move it back to vxlan_udp_encap_recv.
> However, we can't really make the "vxlan->dev->features & NETIF_F_RXCSUM"
> check - since there's no vxlan device for ovs datapath, any idea how to
> overcome this.
>
> Moving this to shared code (while removing the check for
> vxlan->dev->features) made things to work on my setup, but this misses one
> of the original conditions, ideas?
>
I kept csum check in vxlan-device recv path for same reason. As of now
there is no efficient way to get ovs-dev features.
May be we can cache device features in struct datapath from datapath-netdev.

> I believe its too late for 3.13 unless there is going to be -rc9, but lets
> first see what's the right fix.
>
> Or.