This is a note to let you know that I've just added the patch titled
virtio_net: checksum offloading handling fix
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
virtio_net-checksum-offloading-handling-fix.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 23d9dc56de730ed72d093334714112b0fc26fe7a
Author: Heng Qi <hengqi@xxxxxxxxxxxxxxxxx>
Date: Mon Jun 17 21:15:23 2024 +0800
virtio_net: checksum offloading handling fix
[ Upstream commit 604141c036e1b636e2a71cf6e1aa09d1e45f40c2 ]
In virtio spec 0.95, VIRTIO_NET_F_GUEST_CSUM was designed to handle
partially checksummed packets, and the validation of fully checksummed
packets by the device is independent of VIRTIO_NET_F_GUEST_CSUM
negotiation. However, the specification erroneously stated:
"If VIRTIO_NET_F_GUEST_CSUM is not negotiated, the device MUST set flags
to zero and SHOULD supply a fully checksummed packet to the driver."
This statement is inaccurate because even without VIRTIO_NET_F_GUEST_CSUM
negotiation, the device can still set the VIRTIO_NET_HDR_F_DATA_VALID flag.
Essentially, the device can facilitate the validation of these packets'
checksums - a process known as RX checksum offloading - removing the need
for the driver to do so.
This scenario is currently not implemented in the driver and requires
correction. The necessary specification correction[1] has been made and
approved in the virtio TC vote.
[1] https://lists.oasis-open.org/archives/virtio-comment/202401/msg00011.html
Fixes: 4f49129be6fa ("virtio-net: Set RXCSUM feature if GUEST_CSUM is available")
Signed-off-by: Heng Qi <hengqi@xxxxxxxxxxxxxxxxx>
Reviewed-by: Jiri Pirko <jiri@xxxxxxxxxx>
Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 6a655bd442fe3..bd0cb3a03b7b2 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -3211,8 +3211,16 @@ static int virtnet_probe(struct virtio_device *vdev)
dev->features |= dev->hw_features & NETIF_F_ALL_TSO;
/* (!csum && gso) case will be fixed by register_netdev() */
}
- if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_CSUM))
- dev->features |= NETIF_F_RXCSUM;
+
+ /* 1. With VIRTIO_NET_F_GUEST_CSUM negotiation, the driver doesn't
+ * need to calculate checksums for partially checksummed packets,
+ * as they're considered valid by the upper layer.
+ * 2. Without VIRTIO_NET_F_GUEST_CSUM negotiation, the driver only
+ * receives fully checksummed packets. The device may assist in
+ * validating these packets' checksums, so the driver won't have to.
+ */
+ dev->features |= NETIF_F_RXCSUM;
+
if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO4) ||
virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO6))
dev->features |= NETIF_F_GRO_HW;
