Re: [dpdk-dev] [PATCH 1/2] vhost: fix TCP csum not set

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 06/07/2017 08:41 AM, Jianfeng Tan wrote:
> As PKT_TX_TCP_SEG flag in mbuf->ol_flags implies PKT_TX_TCP_CKSUM,
> applications, e.g., testpmd, don't set PKT_TX_TCP_CKSUM when TSO
> is set.
> 
> This leads to that packets get dropped in VM tcp stack layer because
> of bad TCP csum.
> 
> To fix this, we make sure TCP NEEDS_CSUM info is set into virtio net
> header when PKT_TX_TCP_SEG is set, so that VM tcp stack will not
> check the TCP csum.
> 
> Fixes: 859b480d5afd ("vhost: add guest offload setting")
> Cc: stable@dpdk.org
> 
> Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com>
> Cc: Maxime Coquelin <maxime.coquelin@redhat.com>
> Cc: Jiayu Hu <jiayu.hu@intel.com>
> Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>

Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

Thanks,
Maxime
> ---
>   lib/librte_vhost/virtio_net.c | 9 +++++++--
>   1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
> index 48219e0..0a7e023 100644
> --- a/lib/librte_vhost/virtio_net.c
> +++ b/lib/librte_vhost/virtio_net.c
> @@ -114,11 +114,16 @@ update_shadow_used_ring(struct vhost_virtqueue *vq,
>   static void
>   virtio_enqueue_offload(struct rte_mbuf *m_buf, struct virtio_net_hdr *net_hdr)
>   {
> -	if (m_buf->ol_flags & PKT_TX_L4_MASK) {
> +	uint64_t csum_l4 = m_buf->ol_flags & PKT_TX_L4_MASK;
> +
> +	if (m_buf->ol_flags & PKT_TX_TCP_SEG)
> +		csum_l4 |= PKT_TX_TCP_CKSUM;
> +
> +	if (csum_l4) {
>   		net_hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
>   		net_hdr->csum_start = m_buf->l2_len + m_buf->l3_len;
>   
> -		switch (m_buf->ol_flags & PKT_TX_L4_MASK) {
> +		switch (csum_l4) {
>   		case PKT_TX_TCP_CKSUM:
>   			net_hdr->csum_offset = (offsetof(struct tcp_hdr,
>   						cksum));
>