netdev - [PATCH net] virtio-net: drop the multi-buffer XDP packet in zerocopy

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Message-ID: <20250603150613.83802-1-minhquangbui99@gmail.com>
Date: Tue,  3 Jun 2025 22:06:13 +0700
From: Bui Quang Minh <minhquangbui99@...il.com>
To: netdev@...r.kernel.org
Cc: "Michael S. Tsirkin" <mst@...hat.com>,
	Jason Wang <jasowang@...hat.com>,
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Eugenio Pérez <eperezma@...hat.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	virtualization@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	bpf@...r.kernel.org,
	Bui Quang Minh <minhquangbui99@...il.com>,
	stable@...r.kernel.org
Subject: [PATCH net] virtio-net: drop the multi-buffer XDP packet in zerocopy

In virtio-net, we have not yet supported multi-buffer XDP packet in
zerocopy mode when there is a binding XDP program. However, in that
case, when receiving multi-buffer XDP packet, we skip the XDP program
and return XDP_PASS. As a result, the packet is passed to normal network
stack which is an incorrect behavior. This commit instead returns
XDP_DROP in that case.

Fixes: 99c861b44eb1 ("virtio_net: xsk: rx: support recv merge mode")
Cc: stable@...r.kernel.org
Signed-off-by: Bui Quang Minh <minhquangbui99@...il.com>
---
 drivers/net/virtio_net.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index e53ba600605a..4c35324d6e5b 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1309,9 +1309,14 @@ static struct sk_buff *virtnet_receive_xsk_merge(struct net_device *dev, struct
 	ret = XDP_PASS;
 	rcu_read_lock();
 	prog = rcu_dereference(rq->xdp_prog);
-	/* TODO: support multi buffer. */
-	if (prog && num_buf == 1)
-		ret = virtnet_xdp_handler(prog, xdp, dev, xdp_xmit, stats);
+	if (prog) {
+		/* TODO: support multi buffer. */
+		if (num_buf == 1)
+			ret = virtnet_xdp_handler(prog, xdp, dev, xdp_xmit,
+						  stats);
+		else
+			ret = XDP_DROP;
+	}
 	rcu_read_unlock();
 
 	switch (ret) {
-- 
2.43.0