[dpdk-dev] [PATCH 1/2] virtio: don't falsely claim to do IP checksum

[Stephen Hemminger]

The virtio driver is confused about the meaning of the ip_checksum
flag.  In DPDK, ip_checksum means the hardware is capable of checking
the Layer 3 IP checksum.  But KVM/QEMU does not do that. The flag
VIRTIO_NET_F_GUEST_CSUM controls whether the receive side does
Layer 4 (TCP/UDP) checksum offload.

Fix by erroring out any requests to do IP checksum.

Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
---
 drivers/net/virtio/virtio_ethdev.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
index 5c826f47740c..ca607904fa37 100644
--- a/drivers/net/virtio/virtio_ethdev.c
+++ b/drivers/net/virtio/virtio_ethdev.c
@@ -1664,8 +1664,13 @@ virtio_dev_configure(struct rte_eth_dev *dev)
 
 	PMD_INIT_LOG(DEBUG, "configure");
 	req_features = VIRTIO_PMD_DEFAULT_GUEST_FEATURES;
-	if (rxmode->hw_ip_checksum)
-		req_features |= (1ULL << VIRTIO_NET_F_GUEST_CSUM);
+
+	/* Virtio does L4 checksum but not L3! */
+	if (rxmode->hw_ip_checksum) {
+		PMD_DRV_LOG(NOTICE,
+			    "virtio does not support IP checksum");
+		return -ENOTSUP;
+	}
 	if (rxmode->enable_lro)
 		req_features |=
 			(1ULL << VIRTIO_NET_F_GUEST_TSO4) |
@@ -1678,13 +1683,6 @@ virtio_dev_configure(struct rte_eth_dev *dev)
 			return ret;
 	}
 
-	if (rxmode->hw_ip_checksum &&
-		!vtpci_with_feature(hw, VIRTIO_NET_F_GUEST_CSUM)) {
-		PMD_DRV_LOG(NOTICE,
-			"rx ip checksum not available on this host");
-		return -ENOTSUP;
-	}
-
 	if (rxmode->enable_lro &&
 		(!vtpci_with_feature(hw, VIRTIO_NET_F_GUEST_TSO4) ||
 			!vtpci_with_feature(hw, VIRTIO_NET_F_GUEST_TSO4))) {
-- 
2.11.0