[PATCH v2 2/6] vhost: fix missing enqueue pseudo-header calculation

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

The Virtio specification requires that in case of checksum
offloading, the pseudo-header checksum must be set in the
L4 header.

When received from another Vhost-user port, the packet
checksum might already contain the pseudo-header checksum
but we have no way to know it. So we have no other choice
than doing the pseudo-header checksum systematically.

This patch handles this using the rte_net_intel_cksum_prepare()
helper.

Fixes: 859b480d5afd ("vhost: add guest offload setting")
Cc: stable@dpdk.org

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>
---
 lib/vhost/virtio_net.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c
index 68a26eb17d..ce22e3ac79 100644
--- a/lib/vhost/virtio_net.c
+++ b/lib/vhost/virtio_net.c
@@ -596,6 +596,16 @@ virtio_enqueue_offload(struct rte_mbuf *m_buf, struct virtio_net_hdr *net_hdr)
 		csum_l4 |= RTE_MBUF_F_TX_TCP_CKSUM;
 
 	if (csum_l4) {
+		/*
+		 * Pseudo-header checksum must be set as per Virtio spec.
+		 *
+		 * Note: We don't propagate rte_net_intel_cksum_prepare()
+		 * errors, as it would have an impact on performance, and an
+		 * error would mean the packet is dropped by the guest instead
+		 * of being dropped here.
+		 */
+		rte_net_intel_cksum_prepare(m_buf);
+
 		net_hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
 		net_hdr->csum_start = m_buf->l2_len + m_buf->l3_len;
 
-- 
2.35.3