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

[Jianfeng Tan <jianfeng.tan@intel.com>]

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>
---
 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));
-- 
2.7.4