[dpdk-dev] [PATCH 2/2] vhost: fix IP csum not calculated

[Jianfeng Tan]

There is no way to bypass IP checksum verification in Linux
kernel, no matter skb->ip_summed is assigned as CHECKSUM_UNNECESSARY
or CHECKSUM_PARTIAL.

So any packets with bad IP checksum will be dropped at VM IP layer.

To correct, we check this flag PKT_TX_IP_CKSUM to calculate IP csum.

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

Cc: Yuanhan Liu <yuanhan.liu at linux.intel.com>
Cc: Maxime Coquelin <maxime.coquelin at redhat.com>
Cc: Jiayu Hu <jiayu.hu at intel.com>
Signed-off-by: Jianfeng Tan <jianfeng.tan at intel.com>
---
 lib/librte_vhost/virtio_net.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index 0a7e023..cf7c5ac 100644
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -143,6 +143,15 @@ virtio_enqueue_offload(struct rte_mbuf *m_buf, struct virtio_net_hdr *net_hdr)
 		ASSIGN_UNLESS_EQUAL(net_hdr->flags, 0);
 	}
 
+	/* IP cksum verification cannot be bypassed, then calculate here */
+	if (m_buf->ol_flags & PKT_TX_IP_CKSUM) {
+		struct ipv4_hdr *ipv4_hdr;
+
+		ipv4_hdr = rte_pktmbuf_mtod_offset(m_buf, struct ipv4_hdr *,
+						   m_buf->l2_len);
+		ipv4_hdr->hdr_checksum = rte_ipv4_cksum(ipv4_hdr);
+	}
+
 	if (m_buf->ol_flags & PKT_TX_TCP_SEG) {
 		if (m_buf->ol_flags & PKT_TX_IPV4)
 			net_hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
-- 
2.7.4