openwrt/target/linux/ipq40xx/patches-5.15/700-skbuff-add-DSA-specific-data-to-struct-skb_shared_in.patch

From da75807ac41175e9db8c95f7a172b4133763b744 Mon Sep 17 00:00:00 2001
From: Gabor Juhos <j4g8y7@gmail.com>
Date: Mon, 11 Jan 2021 17:49:36 +0100
Subject: [PATCH] skbuff: add DSA specific data to struct skb_shared_info

All of the already existing DSA tagging protocol drivers
are storing the tagging data directly into the skb. In most
cases that is the only way to send the required information
to the underlying ethernet switch.

However on certain platforms (like the Qualcomm IPQ40xx
SoCs) the built-in ethernet switch is connected directly
to an ethernet MAC, and the tagging information must be
sent out-of-band which is done directly via the hardware
TX descriptors of the ethernet MAC.

In such cases, putting the information into the skb causes
unneccesary overhead, because the ethernet driver must
remove that before sending the ethernet frame towards to
the hardware.

This change adds two new DSA specific fields to struct
skb_shared_info which makes it possible to send the
tagging information via skb->shinfo. With this approach,
the twofold modifications of the skb data can be avoided.

Signed-off-by: Gabor Juhos <j4g8y7@gmail.com>
---
 include/linux/skbuff.h | 3 +++
 1 file changed, 3 insertions(+)

--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -563,6 +563,9 @@ struct skb_shared_info {
 	unsigned int	gso_type;
 	u32		tskey;
 
+	unsigned int	dsa_tag_proto;
+	unsigned char	dsa_tag_data[8];
+
 	/*
 	 * Warning : all fields before dataref are cleared in __alloc_skb()
 	 */