Replace the direct use of ptr_ring in the vhost-net virtqueue with
tun/tap ring wrapper helpers. Instead of storing an rx_ring pointer,
the virtqueue now stores the interface type (IF_TUN, IF_TAP, or IF_NONE)
and dispatches to the corresponding tun/tap helpers for ring
produce, consume, and unconsume operations.

Routing ring operations through the tun/tap helpers enables netdev
queue wakeups, which are required for upcoming netdev queue flow
control support shared by tun/tap and vhost-net.

No functional change is intended beyond switching to the wrapper
helpers.

Co-developed-by: Tim Gebauer <redacted>
Signed-off-by: Tim Gebauer <redacted>
Co-developed by: Jon Kohler [off-list ref]
Signed-off-by: Jon Kohler <redacted>
Signed-off-by: Simon Schippers <redacted>
---
 drivers/vhost/net.c | 92 +++++++++++++++++++++++++++++----------------
 1 file changed, 60 insertions(+), 32 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 7f886d3dba7d..215556f7cd40 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c

@@ -90,6 +90,12 @@ enum {
        VHOST_NET_VQ_MAX = 2,
 };

+enum if_type {
+       IF_NONE = 0,
+       IF_TUN = 1,
+       IF_TAP = 2,
+};