[net-next,v3,0/2] virtio-net: avoid conflicts between XDP and GUEST_CSUM

Message

Heng Qi June 26, 2023, 12:02 p.m. UTC

virtio-net needs to clear the VIRTIO_NET_F_GUEST_CSUM feature when
loading XDP. The main reason for doing this is because
VIRTIO_NET_F_GUEST_CSUM allows to receive packets marked as
VIRTIO_NET_HDR_F_NEEDS_CSUM. Such packets are not compatible with
XDP programs, because we cannot guarantee that the csum_{start, offset}
fields are correct after XDP modifies the packets.

There is also an existing problem, in the same host vm-vm (eg
[vm]<->[ovs vhost-user]<->[vm]) scenario, loading XDP will cause packet loss.

To solve the above problems, we have discussed in the [1] proposal, and
now try to solve it through the method of reprobing fields suggested
by Jason.

[1] https://lists.oasis-open.org/archives/virtio-dev/202305/msg00318.html

---
v2->v3:
  - Use skb_checksum_setup() instead of virtnet_flow_dissect_udp_tcp().
    The two operations are different, skb_checksum_setup() operates as
    skb->data==>iphdr, and virtnet_flow_dissect_udp_tcp() operates as
    skb->data==>ethhdr. Essentially equivalent. @Jason Wang

v1->v2:
  - Squash v1's patch [1/4] and patch [2/4] into v2's patch [1/3]. @Michael S. Tsirkin
  - Some minor modifications.

Heng Qi (2):
  virtio-net: support coexistence of XDP and GUEST_CSUM
  virtio-net: remove GUEST_CSUM check for XDP

 drivers/net/virtio_net.c | 90 +++++++++++++++++++++++++++++++++-------
 1 file changed, 74 insertions(+), 16 deletions(-)