[PATCH net-next 2/5] netdevsim: add ndo_xdp_xmit

[Jakub Kicinski <kuba@kernel.org>]

Bonding refuses a slave which has no ndo_xdp_xmit once the bond runs an
XDP program, so netdevsim can't currently be enslaved into an XDP bond
and the propagation of XDP down to lower devices has no test coverage
at all.

There is no data path behind it. netdevsim does not advertise
NETDEV_XDP_ACT_NDO_XMIT, so nothing should be redirecting frames here;
anything which does anyway is counted and freed rather than dropped
silently.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 drivers/net/netdevsim/netdev.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/net/netdevsim/netdev.c b/drivers/net/netdevsim/netdev.c
index eebc02ccc4a9..3790b6eb4083 100644
--- a/drivers/net/netdevsim/netdev.c
+++ b/drivers/net/netdevsim/netdev.c
@@ -185,6 +185,25 @@ static netdev_tx_t nsim_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	return NETDEV_TX_OK;
 }
 
+/* Do not advertise NETDEV_XDP_ACT_NDO_XMIT, no real datapath.
+ * This is a "stub" which allows netdevsim to be put under a bond with XDP.
+ */
+static int nsim_xdp_xmit(struct net_device *dev, int n,
+			 struct xdp_frame **frames, u32 flags)
+{
+	int i;
+
+	if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK))
+		return -EINVAL;
+
+	for (i = 0; i < n; i++) {
+		dev_dstats_tx_dropped(dev);
+		xdp_return_frame(frames[i]);
+	}
+
+	return n;
+}
+
 static netdev_tx_t nsim_start_xmit_vf(struct sk_buff *skb,
 				      struct net_device *dev)
 {
@@ -651,6 +670,7 @@ static const struct net_device_ops nsim_netdev_ops = {
 	.ndo_set_features	= nsim_set_features,
 	.ndo_get_iflink		= nsim_get_iflink,
 	.ndo_bpf		= nsim_bpf,
+	.ndo_xdp_xmit		= nsim_xdp_xmit,
 	.ndo_open		= nsim_open,
 	.ndo_stop		= nsim_stop,
 	.ndo_vlan_rx_add_vid	= nsim_vlan_rx_add_vid,
-- 
2.55.0