[RFC 1/2] netvsc: invoke xdp_generic from VF frame handler

[Stephen Hemminger <stephen@networkplumber.org>]

XDP generic does not work correctly with the Hyper-V/Azure netvsc
device because of packet processing order. Only packets on the
synthetic path get seen by the XDP program. The VF device packets
are not seen.

By the time the packets that arrive on the VF are handled by
netvsc after the first pass of XDP generic (on the VF) has already
been done.

A fix for the netvsc device is to do this in the VF packet handler.
by directly calling do_xdp_generic() if XDP program is present
on the parent device.

A riskier but maybe better alternative would be to do this netdev core
code after the receive handler is invoked (if RX_HANDLER_ANOTHER
is returned).

Fixes: 0c195567a8f6 ("netvsc: transparent VF management")
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
---
 drivers/net/hyperv/netvsc_drv.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index 06393b215102..bb0fc1869bde 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -1999,9 +1999,15 @@ static rx_handler_result_t netvsc_vf_handle_frame(struct sk_buff **pskb)
 	struct net_device_context *ndev_ctx = netdev_priv(ndev);
 	struct netvsc_vf_pcpu_stats *pcpu_stats
 		 = this_cpu_ptr(ndev_ctx->vf_stats);
+	struct bpf_prog *xdp_prog;
 
 	skb->dev = ndev;
 
+	xdp_prog = rcu_dereference(ndev->xdp_prog);
+	if (xdp_prog &&
+	    do_xdp_generic(xdp_prog, skb) != XDP_PASS)
+		return RX_HANDLER_CONSUMED;
+
 	u64_stats_update_begin(&pcpu_stats->syncp);
 	pcpu_stats->rx_packets++;
 	pcpu_stats->rx_bytes += skb->len;
-- 
2.20.1