bpf, devmap: Move drop error path to devmap for XDP_REDIRECT

We want to change the current ndo_xdp_xmit drop semantics because it will
allow us to implement better queue overflow handling. This is working
towards the larger goal of a XDP TX queue-hook. Move XDP_REDIRECT error
path handling from each XDP ethernet driver to devmap code. According to
the new APIs, the driver running the ndo_xdp_xmit pointer, will break tx
loop whenever the hw reports a tx error and it will just return to devmap
caller the number of successfully transmitted frames. It will be devmap
responsibility to free dropped frames.

Move each XDP ndo_xdp_xmit capable driver to the new APIs:

- veth
- virtio-net
- mvneta
- mvpp2
- socionext
- amazon ena
- bnxt
- freescale (dpaa2, dpaa)
- xen-frontend
- qede
- ice
- igb
- ixgbe
- i40e
- mlx5
- ti (cpsw, cpsw-new)
- tun
- sfc

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Camelia Groza <camelia.groza@nxp.com>
Acked-by: Edward Cree <ecree.xilinx@gmail.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Shay Agroskin <shayagr@amazon.com>
Link: https://lore.kernel.org/bpf/ed670de24f951cfd77590decf0229a0ad7fd12f6.1615201152.git.lorenzo@kernel.org

1 files changed, 9 insertions, 6 deletions

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index fc86da7f1628..6e55697315de 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1181,8 +1181,7 @@ static int tun_xdp_xmit(struct net_device *dev, int n,
 	struct tun_struct *tun = netdev_priv(dev);
 	struct tun_file *tfile;
 	u32 numqueues;
-	int drops = 0;
-	int cnt = n;
+	int nxmit = 0;
 	int i;
 
 	if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK))
@@ -1212,9 +1211,9 @@ resample:
 
 		if (__ptr_ring_produce(&tfile->tx_ring, frame)) {
 			atomic_long_inc(&dev->tx_dropped);
-			xdp_return_frame_rx_napi(xdp);
-			drops++;
+			break;
 		}
+		nxmit++;
 	}
 	spin_unlock(&tfile->tx_ring.producer_lock);
 
@@ -1222,17 +1221,21 @@ resample:
 		__tun_xdp_flush_tfile(tfile);
 
 	rcu_read_unlock();
-	return cnt - drops;
+	return nxmit;
 }
 
 static int tun_xdp_tx(struct net_device *dev, struct xdp_buff *xdp)
 {
 	struct xdp_frame *frame = xdp_convert_buff_to_frame(xdp);
+	int nxmit;
 
 	if (unlikely(!frame))
 		return -EOVERFLOW;
 
-	return tun_xdp_xmit(dev, 1, &frame, XDP_XMIT_FLUSH);
+	nxmit = tun_xdp_xmit(dev, 1, &frame, XDP_XMIT_FLUSH);
+	if (!nxmit)
+		xdp_return_frame_rx_napi(frame);
+	return nxmit;
 }
 
 static const struct net_device_ops tap_netdev_ops = {