netdev - [PATCH bpf-next v3 07/17] veth: Call skb_metadata_set when skb->data points at metadata end

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Message-Id: <20260107-skb-meta-safeproof-netdevs-rx-only-v3-7-0d461c5e4764@cloudflare.com>
Date: Wed, 07 Jan 2026 15:28:07 +0100
From: Jakub Sitnicki <jakub@...udflare.com>
To: bpf@...r.kernel.org
Cc: netdev@...r.kernel.org, "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>, 
 Stanislav Fomichev <sdf@...ichev.me>, Simon Horman <horms@...nel.org>, 
 Andrii Nakryiko <andrii@...nel.org>, 
 Martin KaFai Lau <martin.lau@...ux.dev>, 
 Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
 Yonghong Song <yonghong.song@...ux.dev>, KP Singh <kpsingh@...nel.org>, 
 Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
 kernel-team@...udflare.com
Subject: [PATCH bpf-next v3 07/17] veth: Call skb_metadata_set when
 skb->data points at metadata end

Prepare to track skb metadata location independently of MAC header offset.

Following changes will make skb_metadata_set() record where metadata ends
relative to skb->head. Hence the helper must be called when skb->data
points right past the metadata area.

Unlike other drivers, veth calls skb_metadata_set() after eth_type_trans(),
which pulls the Ethernet header and moves skb->data. This violates the
future calling convention.

Adjust the driver to pull the MAC header after calling skb_metadata_set().

Signed-off-by: Jakub Sitnicki <jakub@...udflare.com>
---
 drivers/net/veth.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index 14e6f2a2fb77..1d1dbfa2e5ef 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -874,11 +874,11 @@ static struct sk_buff *veth_xdp_rcv_skb(struct veth_rq *rq,
 	else
 		skb->data_len = 0;

-	skb->protocol = eth_type_trans(skb, rq->dev);
-
 	metalen = xdp->data - xdp->data_meta;
 	if (metalen)
 		skb_metadata_set(skb, metalen);
+
+	skb->protocol = eth_type_trans(skb, rq->dev);
 out:
 	return skb;
 drop:

-- 
2.43.0