[RFC PATCH net-next 1/7] xfrm: allow packet offload drivers to own transmit

[Jihong Min <hurryman2212@gmail.com>]

Packet offload drivers can currently program state and validate whether an skb can be offloaded, but they cannot take ownership of a packet that needs driver-specific TX preparation before the regular XFRM output path continues.

Add an optional xdo_dev_packet_xmit() callback. Drivers that implement it consume the skb and return the final TX status; all other drivers keep the existing XFRM output path.

Signed-off-by: Jihong Min <hurryman2212@gmail.com>
---
 include/linux/netdevice.h |  8 ++++++++
 net/xfrm/xfrm_output.c    | 11 +++++++++++
 2 files changed, 19 insertions(+)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 7f4f0837c09f..1552eb81ddf0 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1048,6 +1048,14 @@ struct xfrmdev_ops {
 	int	(*xdo_dev_policy_add) (struct xfrm_policy *x, struct netlink_ext_ack *extack);
 	void	(*xdo_dev_policy_delete) (struct xfrm_policy *x);
 	void	(*xdo_dev_policy_free) (struct xfrm_policy *x);
+	/* Optional packet-offload TX path for devices that need
+	 * driver-specific transmit preparation instead of continuing through
+	 * the regular XFRM output path, such as adding offload metadata or
+	 * steering the packet to a private transmit queue. The driver consumes
+	 * skb and returns the final transmit status.
+	 */
+	int	(*xdo_dev_packet_xmit)(struct sk_buff *skb,
+				       struct xfrm_state *x);
 };
 #endif
 
diff --git a/net/xfrm/xfrm_output.c b/net/xfrm/xfrm_output.c
index cc35c2fcbbe0..9f11559b0221 100644
--- a/net/xfrm/xfrm_output.c
+++ b/net/xfrm/xfrm_output.c
@@ -770,6 +770,17 @@ int xfrm_output(struct sock *sk, struct sk_buff *skb)
 	}
 
 	if (x->xso.type == XFRM_DEV_OFFLOAD_PACKET) {
+#ifdef CONFIG_XFRM_OFFLOAD
+		const struct xfrmdev_ops *ops;
+#endif
+
+#ifdef CONFIG_XFRM_OFFLOAD
+		ops = x->xso.dev->xfrmdev_ops;
+		/* Callback validates, consumes skb and returns final TX status. */
+		if (ops && ops->xdo_dev_packet_xmit)
+			return ops->xdo_dev_packet_xmit(skb, x);
+#endif
+
 		if (!xfrm_dev_offload_ok(skb, x)) {
 			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
 			kfree_skb(skb);
-- 
2.53.0