Subject: Re: [PATCH net 7/9] virtio-net: forbid XDP when VIRTIO_NET_F_GUEST_UFO is support

From: John Fastabend <[email-masked]>
Date: Fri, 23 Dec 2016 08:10:06 -0800

On 16-12-23 08:02 AM, John Fastabend wrote:
> On 16-12-23 06:37 AM, Jason Wang wrote:
>> When VIRTIO_NET_F_GUEST_UFO is negotiated, host could still send UFO
>> packet that exceeds a single page which could not be handled
>> correctly by XDP. So this patch forbids setting XDP when GUEST_UFO is
>> supported. While at it, forbid XDP for ECN (which comes only from GRO)
>> too to prevent user from misconfiguration.
>>

Is sending packets greater than single page though normal in this case?
I don't have any need to support big packet mode other than MST asked
for it. And I wasn't seeing this in my tests. MTU is capped at 4k - hdr
when XDP is enabled.

.John

>> Cc: John Fastabend <[email-masked]>
>> Signed-off-by: Jason Wang <[email-masked]>
>> ---
>>  drivers/net/virtio_net.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index 77ae358..c1f66d8 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -1684,7 +1684,9 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog)
>>  	int i, err;
>>  
>>  	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO4) ||
>> -	    virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO6)) {
>> +	    virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO6) ||
>> +	    virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_ECN) ||
>> +	    virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_UFO)) {
>>  		netdev_warn(dev, "can't set XDP while host is implementing LRO, disable LRO first\n");
>>  		return -EOPNOTSUPP;
>>  	}
>>
> 
> Acked-by: John Fastabend <[email-masked]>
>