linux-kernel - Re: [PATCH net] virtio-net: unbreak cusmed packet for small buffer XDP

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Message-ID: <7068053c-50da-6779-5ff2-6588e01e616d@redhat.com>
Date:   Wed, 28 Jun 2017 10:14:34 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] virtio-net: unbreak cusmed packet for small buffer
 XDP



On 2017年06月28日 10:02, Michael S. Tsirkin wrote:
> On Wed, Jun 28, 2017 at 09:54:03AM +0800, Jason Wang wrote:
>> We should allow csumed packet for small buffer, otherwise XDP_PASS
>> won't work correctly.
>>
>> Fixes commit bb91accf2733 ("virtio-net: XDP support for small buffers")
>> Signed-off-by: Jason Wang <jasowang@...hat.com>
> The issue would be VIRTIO_NET_HDR_F_DATA_VALID might be set.
> What do you think?

I think it's safe. For XDP_PASS, it work like in the past. For XDP_TX, 
we zero the vnet header. For adjusting header, XDP prog should deal with 
csum.

Thanks

>
>> ---
>> The patch is needed for -stable.
>> ---
>>   drivers/net/virtio_net.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index 143d8a9..499fcc9 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -413,7 +413,7 @@ static struct sk_buff *receive_small(struct net_device *dev,
>>   		void *orig_data;
>>   		u32 act;
>>   
>> -		if (unlikely(hdr->hdr.gso_type || hdr->hdr.flags))
>> +		if (unlikely(hdr->hdr.gso_type))
>>   			goto err_xdp;
>>   
>>   		xdp.data_hard_start = buf + VIRTNET_RX_PAD + vi->hdr_len;
>> -- 
>> 2.7.4