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| author | Heng Qi <hengqi@linux.alibaba.com> | 2024-06-17 16:15:23 +0300 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2024-06-19 12:52:44 +0300 |
| commit | 604141c036e1b636e2a71cf6e1aa09d1e45f40c2 (patch) | |
| tree | bf5c880919fa8ef35c7f6d0616a2e6625071e8c0 /drivers/net/virtio_net.c | |
| parent | 7be4cb7189f747b4e5b6977d0e4387bde3204e62 (diff) | |
| download | linux-604141c036e1b636e2a71cf6e1aa09d1e45f40c2.tar.xz | |
virtio_net: checksum offloading handling fix
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@linux.alibaba.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/virtio_net.c')
| -rw-r--r-- | drivers/net/virtio_net.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 61a57d134544..aa70a7ed8072 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -5666,8 +5666,16 @@ 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; |