Re: [dpdk-dev] about rx checksum flags

[Olivier MATZ <olivier.matz@6wind.com>]

Hi,

On 05/31/2016 12:08 PM, Adrien Mazarguil wrote:
> On Tue, May 31, 2016 at 10:43:29AM +0800, Tan, Jianfeng wrote:
>> Why not take care of PKT_RX_IP_CKSUM_BAD? Is it too easy for sw to handle?
> 
> I thought PKT_RX_IP_CKSUM_BAD was to be modified in a similar fashion, but
> since you raise the issue, mlx4/mlx5 need this as well. These boards only
> report "good" checksums for L3 and L4.

Yep, maybe it was not so clear in my initial mail, but I think the L4
example should apply to IP as well.

>> For virtio, there's only one bit, VIRTIO_NET_HDR_F_DATA_VALID, to indicate
>> that checksum is valid. Shall we differentiate L3 checksum and L4 checksum
>> in rte_mbuf.ol_flags?

>From what I understand from the specification, when the driver
(virtio-net) receives a packet with the VIRTIO_NET_HDR_F_NEEDS_CSUM
flag, it can be assumed that all checksums before hdr->csum_start are
valid. Here we would set PKT_RX_IP_CKSUM_GOOD and PKT_RX_L4_CKSUM_NONE.

In case of VIRTIO_NET_HDR_F_DATA_VALID, I understand that both L3 and
L4 of the outer header is valid. Here we would set PKT_RX_IP_CKSUM_GOOD
and PKT_RX_L4_CKSUM_GOOD.

Regards,
Olivier