[PATCH net 1/2] virtio-net: disable guest csum during XDP set

[Jason Wang]

We don't disable VIRTIO_NET_F_GUEST_CSUM if XDP was set. This means we
can receive partial csumed packets with metadata kept in the
vnet_hdr. This may have several side effects:

- It could be overridden by header adjustment, thus is might be not
  correct after XDP processing.
- There's no way to pass such metadata information through
  XDP_REDIRECT to another driver.
- XDP does not support checksum offload right now.

So simply disable guest csum if possible in this the case of XDP.

Fixes: 3f93522ffab2d ("virtio-net: switch off offloads on demand if possible on XDP set")
Reported-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
Cc: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
Cc: Pavel Popa <pashinho1990@xxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
---
 drivers/net/virtio_net.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 3e2c041d76ac..9b5ace538824 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -70,7 +70,8 @@ static const unsigned long guest_offloads[] = {
 	VIRTIO_NET_F_GUEST_TSO4,
 	VIRTIO_NET_F_GUEST_TSO6,
 	VIRTIO_NET_F_GUEST_ECN,
-	VIRTIO_NET_F_GUEST_UFO
+	VIRTIO_NET_F_GUEST_UFO,
+	VIRTIO_NET_F_GUEST_CSUM
 };
 
 struct virtnet_stat_desc {
@@ -2334,9 +2335,6 @@ static int virtnet_clear_guest_offloads(struct virtnet_info *vi)
 	if (!vi->guest_offloads)
 		return 0;
 
-	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM))
-		offloads = 1ULL << VIRTIO_NET_F_GUEST_CSUM;
-
 	return virtnet_set_guest_offloads(vi, offloads);
 }
 
@@ -2346,8 +2344,6 @@ static int virtnet_restore_guest_offloads(struct virtnet_info *vi)
 
 	if (!vi->guest_offloads)
 		return 0;
-	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM))
-		offloads |= 1ULL << VIRTIO_NET_F_GUEST_CSUM;
 
 	return virtnet_set_guest_offloads(vi, offloads);
 }
-- 
2.17.1