netdev - [PATCH 1/2 bpf] xdp: add XDP extension to skb

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Message-ID: <20251028160200.4204-1-fmancera@suse.de>
Date: Tue, 28 Oct 2025 17:01:59 +0100
From: Fernando Fernandez Mancera <fmancera@...e.de>
To: bpf@...r.kernel.org
Cc: netdev@...r.kernel.org,
	magnus.karlsson@...el.com,
	maciej.fijalkowski@...el.com,
	sdf@...ichev.me,
	kerneljasonxing@...il.com,
	fw@...len.de,
	Fernando Fernandez Mancera <fmancera@...e.de>
Subject: [PATCH 1/2 bpf] xdp: add XDP extension to skb

This patch adds a new skb extension for XDP representing the number of
cq descriptors and a linked list of umem addresses.

This is going to be used from the xsk skb destructor to put the umem
addresses onto pool's completion queue.

Signed-off-by: Fernando Fernandez Mancera <fmancera@...e.de>
---
Note: CC'ing Florian Westphal in case I am missing something
while implementing/using the skb extension.
---
 include/linux/skbuff.h | 3 +++
 include/net/xdp_sock.h | 5 +++++
 net/core/skbuff.c      | 4 ++++
 net/xdp/Kconfig        | 1 +
 4 files changed, 13 insertions(+)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index fb3fec9affaa..1c4a598b6564 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -4910,6 +4910,9 @@ enum skb_ext_id {
 #endif
 #if IS_ENABLED(CONFIG_INET_PSP)
 	SKB_EXT_PSP,
+#endif
+#if IS_ENABLED(CONFIG_XDP_SOCKETS)
+	SKB_EXT_XDP,
 #endif
 	SKB_EXT_NUM, /* must be last */
 };
diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h
index ce587a225661..94c607093768 100644
--- a/include/net/xdp_sock.h
+++ b/include/net/xdp_sock.h
@@ -120,6 +120,11 @@ struct xsk_tx_metadata_ops {
 	void	(*tmo_request_launch_time)(u64 launch_time, void *priv);
 };
 
+struct xdp_skb_ext {
+	u32 num_descs;
+	struct list_head addrs_list;
+};
+
 #ifdef CONFIG_XDP_SOCKETS
 
 int xsk_generic_rcv(struct xdp_sock *xs, struct xdp_buff *xdp);
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 6be01454f262..f3966b8c61ee 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -81,6 +81,7 @@
 #include <net/page_pool/helpers.h>
 #include <net/psp/types.h>
 #include <net/dropreason.h>
+#include <net/xdp_sock.h>
 
 #include <linux/uaccess.h>
 #include <trace/events/skb.h>
@@ -5066,6 +5067,9 @@ static const u8 skb_ext_type_len[] = {
 #if IS_ENABLED(CONFIG_INET_PSP)
 	[SKB_EXT_PSP] = SKB_EXT_CHUNKSIZEOF(struct psp_skb_ext),
 #endif
+#if IS_ENABLED(CONFIG_XDP_SOCKETS)
+	[SKB_EXT_XDP] = SKB_EXT_CHUNKSIZEOF(struct xdp_skb_ext),
+#endif
 };
 
 static __always_inline unsigned int skb_ext_total_length(void)
diff --git a/net/xdp/Kconfig b/net/xdp/Kconfig
index 71af2febe72a..89546c48ac2a 100644
--- a/net/xdp/Kconfig
+++ b/net/xdp/Kconfig
@@ -2,6 +2,7 @@
 config XDP_SOCKETS
 	bool "XDP sockets"
 	depends on BPF_SYSCALL
+	select SKB_EXTENSIONS
 	default n
 	help
 	  XDP sockets allows a channel between XDP programs and
-- 
2.51.0