netdev - [PATCH net-next] net: dsa: tag_8021q: only call skb_push/skb_pull around __skb_vlan

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Date:   Tue, 15 Feb 2022 22:47:22 +0200
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Mans Rullgard <mans@...sr.com>
Subject: [PATCH net-next] net: dsa: tag_8021q: only call skb_push/skb_pull around __skb_vlan_pop

__skb_vlan_pop() needs skb->data to point at the mac_header, while
skb_vlan_tag_present() and skb_vlan_tag_get() don't, because they don't
look at skb->data at all.

So we can avoid uselessly moving around skb->data for the case where the
VLAN tag was offloaded by the DSA master.

Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
---
 net/dsa/tag_8021q.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/dsa/tag_8021q.c b/net/dsa/tag_8021q.c
index 27712a81c967..114f663332d0 100644
--- a/net/dsa/tag_8021q.c
+++ b/net/dsa/tag_8021q.c
@@ -577,14 +577,14 @@ void dsa_8021q_rcv(struct sk_buff *skb, int *source_port, int *switch_id)
 {
 	u16 vid, tci;
 
-	skb_push_rcsum(skb, ETH_HLEN);
 	if (skb_vlan_tag_present(skb)) {
 		tci = skb_vlan_tag_get(skb);
 		__vlan_hwaccel_clear_tag(skb);
 	} else {
+		skb_push_rcsum(skb, ETH_HLEN);
 		__skb_vlan_pop(skb, &tci);
+		skb_pull_rcsum(skb, ETH_HLEN);
 	}
-	skb_pull_rcsum(skb, ETH_HLEN);
 
 	vid = tci & VLAN_VID_MASK;
 
-- 
2.25.1