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Commit 5b7d611f authored by Heng Qi's avatar Heng Qi Committed by Greg Kroah-Hartman
Browse files

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: 4f49129b ("virtio-net: Set RXCSUM feature if GUEST_CSUM is available")
Signed-off-by: default avatarHeng Qi <hengqi@linux.alibaba.com>
Reviewed-by: default avatarJiri Pirko <jiri@nvidia.com>
Acked-by: default avatarJason Wang <jasowang@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 0d8a2d28

drivers/net/virtio_net.c

+10 −2
Original line number Diff line number Diff line
@@ -3157,8 +3157,16 @@ 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))



	/* 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;