[RFC net-next 3/8] virtio_net: introduce virtnet_xdp_handler() to seprate the logic of run xdp

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At present, we have two similar logic to perform the XDP prog.

Therefore, this PATCH separates the code of executing XDP, which is
conducive to later maintenance.

Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
---
 drivers/net/virtio_net.c | 142 +++++++++++++++++++++------------------
 1 file changed, 75 insertions(+), 67 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index f4d01693e568..13c43b609465 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -300,6 +300,15 @@ struct padded_vnet_hdr {
 	char padding[12];
 };
 
+enum {
+	/* xdp pass */
+	VIRTNET_XDP_RES_PASS,
+	/* drop packet. the caller needs to release the page. */
+	VIRTNET_XDP_RES_DROP,
+	/* packet is consumed by xdp. the caller needs to do nothing. */
+	VIRTNET_XDP_RES_CONSUMED,
+};
+
 static void virtnet_rq_free_unused_buf(struct virtqueue *vq, void *buf);
 static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void *buf);
 static void check_sq_full(struct virtnet_info *vi, struct net_device *dev,
@@ -719,6 +728,59 @@ static int virtnet_xdp_xmit(struct net_device *dev,
 	return ret;
 }
 
+static int virtnet_xdp_handler(struct bpf_prog *xdp_prog, struct xdp_buff *xdp,
+			       struct net_device *dev,
+			       unsigned int *xdp_xmit,
+			       struct virtnet_rq_stats *stats)
+{
+	struct xdp_frame *xdpf;
+	int err;
+	u32 act;
+
+	act = bpf_prog_run_xdp(xdp_prog, xdp);
+	stats->xdp_packets++;
+
+	switch (act) {
+	case XDP_PASS:
+		return VIRTNET_XDP_RES_PASS;
+
+	case XDP_TX:
+		stats->xdp_tx++;
+		xdpf = xdp_convert_buff_to_frame(xdp);
+		if (unlikely(!xdpf))
+			return VIRTNET_XDP_RES_DROP;
+
+		err = virtnet_xdp_xmit(dev, 1, &xdpf, 0);
+		if (unlikely(!err)) {
+			xdp_return_frame_rx_napi(xdpf);
+		} else if (unlikely(err < 0)) {
+			trace_xdp_exception(dev, xdp_prog, act);
+			return VIRTNET_XDP_RES_DROP;
+		}
+
+		*xdp_xmit |= VIRTIO_XDP_TX;
+		return VIRTNET_XDP_RES_CONSUMED;
+
+	case XDP_REDIRECT:
+		stats->xdp_redirects++;
+		err = xdp_do_redirect(dev, xdp, xdp_prog);
+		if (err)
+			return VIRTNET_XDP_RES_DROP;
+
+		*xdp_xmit |= VIRTIO_XDP_REDIR;
+		return VIRTNET_XDP_RES_CONSUMED;
+
+	default:
+		bpf_warn_invalid_xdp_action(dev, xdp_prog, act);
+		fallthrough;
+	case XDP_ABORTED:
+		trace_xdp_exception(dev, xdp_prog, act);
+		fallthrough;
+	case XDP_DROP:
+		return VIRTNET_XDP_RES_DROP;
+	}
+}
+
 static unsigned int virtnet_get_headroom(struct virtnet_info *vi)
 {
 	return vi->xdp_enabled ? VIRTIO_XDP_HEADROOM : 0;
@@ -806,7 +868,6 @@ static struct sk_buff *receive_small(struct net_device *dev,
 	struct page *page = virt_to_head_page(buf);
 	unsigned int delta = 0;
 	struct page *xdp_page;
-	int err;
 	unsigned int metasize = 0;
 
 	len -= vi->hdr_len;
@@ -828,7 +889,6 @@ static struct sk_buff *receive_small(struct net_device *dev,
 	xdp_prog = rcu_dereference(rq->xdp_prog);
 	if (xdp_prog) {
 		struct virtio_net_hdr_mrg_rxbuf *hdr = buf + header_offset;
-		struct xdp_frame *xdpf;
 		struct xdp_buff xdp;
 		void *orig_data;
 		u32 act;
@@ -861,46 +921,22 @@ static struct sk_buff *receive_small(struct net_device *dev,
 		xdp_prepare_buff(&xdp, buf + VIRTNET_RX_PAD + vi->hdr_len,
 				 xdp_headroom, len, true);
 		orig_data = xdp.data;
-		act = bpf_prog_run_xdp(xdp_prog, &xdp);
-		stats->xdp_packets++;
+
+		act = virtnet_xdp_handler(xdp_prog, &xdp, dev, xdp_xmit, stats);
 
 		switch (act) {
-		case XDP_PASS:
+		case VIRTNET_XDP_RES_PASS:
 			/* Recalculate length in case bpf program changed it */
 			delta = orig_data - xdp.data;
 			len = xdp.data_end - xdp.data;
 			metasize = xdp.data - xdp.data_meta;
 			break;
-		case XDP_TX:
-			stats->xdp_tx++;
-			xdpf = xdp_convert_buff_to_frame(&xdp);
-			if (unlikely(!xdpf))
-				goto err_xdp;
-			err = virtnet_xdp_xmit(dev, 1, &xdpf, 0);
-			if (unlikely(!err)) {
-				xdp_return_frame_rx_napi(xdpf);
-			} else if (unlikely(err < 0)) {
-				trace_xdp_exception(vi->dev, xdp_prog, act);
-				goto err_xdp;
-			}
-			*xdp_xmit |= VIRTIO_XDP_TX;
-			rcu_read_unlock();
-			goto xdp_xmit;
-		case XDP_REDIRECT:
-			stats->xdp_redirects++;
-			err = xdp_do_redirect(dev, &xdp, xdp_prog);
-			if (err)
-				goto err_xdp;
-			*xdp_xmit |= VIRTIO_XDP_REDIR;
+
+		case VIRTNET_XDP_RES_CONSUMED:
 			rcu_read_unlock();
 			goto xdp_xmit;
-		default:
-			bpf_warn_invalid_xdp_action(vi->dev, xdp_prog, act);
-			fallthrough;
-		case XDP_ABORTED:
-			trace_xdp_exception(vi->dev, xdp_prog, act);
-			goto err_xdp;
-		case XDP_DROP:
+
+		case VIRTNET_XDP_RES_DROP:
 			goto err_xdp;
 		}
 	}
@@ -1207,7 +1243,6 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 	if (xdp_prog) {
 		unsigned int xdp_frags_truesz = 0;
 		struct skb_shared_info *shinfo;
-		struct xdp_frame *xdpf;
 		struct page *xdp_page;
 		struct xdp_buff xdp;
 		void *data;
@@ -1224,49 +1259,22 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 		if (unlikely(err))
 			goto err_xdp_frags;
 
-		act = bpf_prog_run_xdp(xdp_prog, &xdp);
-		stats->xdp_packets++;
+		act = virtnet_xdp_handler(xdp_prog, &xdp, dev, xdp_xmit, stats);
 
 		switch (act) {
-		case XDP_PASS:
+		case VIRTNET_XDP_RES_PASS:
 			head_skb = build_skb_from_xdp_buff(dev, vi, &xdp, xdp_frags_truesz);
 			if (unlikely(!head_skb))
 				goto err_xdp_frags;
 
 			rcu_read_unlock();
 			return head_skb;
-		case XDP_TX:
-			stats->xdp_tx++;
-			xdpf = xdp_convert_buff_to_frame(&xdp);
-			if (unlikely(!xdpf)) {
-				netdev_dbg(dev, "convert buff to frame failed for xdp\n");
-				goto err_xdp_frags;
-			}
-			err = virtnet_xdp_xmit(dev, 1, &xdpf, 0);
-			if (unlikely(!err)) {
-				xdp_return_frame_rx_napi(xdpf);
-			} else if (unlikely(err < 0)) {
-				trace_xdp_exception(vi->dev, xdp_prog, act);
-				goto err_xdp_frags;
-			}
-			*xdp_xmit |= VIRTIO_XDP_TX;
-			rcu_read_unlock();
-			goto xdp_xmit;
-		case XDP_REDIRECT:
-			stats->xdp_redirects++;
-			err = xdp_do_redirect(dev, &xdp, xdp_prog);
-			if (err)
-				goto err_xdp_frags;
-			*xdp_xmit |= VIRTIO_XDP_REDIR;
+
+		case VIRTNET_XDP_RES_CONSUMED:
 			rcu_read_unlock();
 			goto xdp_xmit;
-		default:
-			bpf_warn_invalid_xdp_action(vi->dev, xdp_prog, act);
-			fallthrough;
-		case XDP_ABORTED:
-			trace_xdp_exception(vi->dev, xdp_prog, act);
-			fallthrough;
-		case XDP_DROP:
+
+		case VIRTNET_XDP_RES_DROP:
 			goto err_xdp_frags;
 		}
 err_xdp_frags:
-- 
2.32.0.3.g01195cf9f

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