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(-)
--
2.19.1.6.gb485710b
