netdev - [PATCH net-next] xdp: add xdp_skb_reserve

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Message-ID: <20250430182921.1704021-1-jon@nutanix.com>
Date: Wed, 30 Apr 2025 11:29:20 -0700
From: Jon Kohler <jon@...anix.com>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Jason Wang <jasowang@...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>,
        Simon Horman <horms@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Cc: Jon Kohler <jon@...anix.com>
Subject: [PATCH net-next] xdp: add xdp_skb_reserve_put helper

Add helper for calling skb_{put|reserve} to reduce repetitive pattern
across various drivers.

Plumb into tap and tun to start.

No functional change intended.

Signed-off-by: Jon Kohler <jon@...anix.com>
---
 drivers/net/tap.c | 3 +--
 drivers/net/tun.c | 3 +--
 include/net/xdp.h | 8 ++++++++
 net/core/xdp.c    | 3 +--
 4 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/net/tap.c b/drivers/net/tap.c
index d4ece538f1b2..54ce492da5e9 100644
--- a/drivers/net/tap.c
+++ b/drivers/net/tap.c
@@ -1062,8 +1062,7 @@ static int tap_get_user_xdp(struct tap_queue *q, struct xdp_buff *xdp)
 		goto err;
 	}
 
-	skb_reserve(skb, xdp->data - xdp->data_hard_start);
-	skb_put(skb, xdp->data_end - xdp->data);
+	xdp_skb_reserve_put(xdp, skb);
 
 	skb_set_network_header(skb, ETH_HLEN);
 	skb_reset_mac_header(skb);
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 7babd1e9a378..30701ad5c27d 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -2415,8 +2415,7 @@ static int tun_xdp_one(struct tun_struct *tun,
 		goto out;
 	}
 
-	skb_reserve(skb, xdp->data - xdp->data_hard_start);
-	skb_put(skb, xdp->data_end - xdp->data);
+	xdp_skb_reserve_put(xdp, skb);
 
 	/* The externally provided xdp_buff may have no metadata support, which
 	 * is marked by xdp->data_meta being xdp->data + 1. This will lead to a
diff --git a/include/net/xdp.h b/include/net/xdp.h
index 48efacbaa35d..0e7414472464 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -345,6 +345,14 @@ struct sk_buff *xdp_build_skb_from_frame(struct xdp_frame *xdpf,
 					 struct net_device *dev);
 struct xdp_frame *xdpf_clone(struct xdp_frame *xdpf);
 
+static __always_inline
+void xdp_skb_reserve_put(const struct xdp_buff *xdp,
+			 struct sk_buff *skb)
+{
+	skb_reserve(skb, xdp->data - xdp->data_hard_start);
+	__skb_put(skb, xdp->data_end - xdp->data);
+}
+
 static inline
 void xdp_convert_frame_to_buff(const struct xdp_frame *frame,
 			       struct xdp_buff *xdp)
diff --git a/net/core/xdp.c b/net/core/xdp.c
index f86eedad586a..1fca2aa1d1fe 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -646,8 +646,7 @@ struct sk_buff *xdp_build_skb_from_buff(const struct xdp_buff *xdp)
 	if (unlikely(!skb))
 		return NULL;
 
-	skb_reserve(skb, xdp->data - xdp->data_hard_start);
-	__skb_put(skb, xdp->data_end - xdp->data);
+	xdp_skb_reserve_put(xdp, skb);
 
 	metalen = xdp->data - xdp->data_meta;
 	if (metalen > 0)
-- 
2.43.0