[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 <step...@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