netdev - [PATCH] mpls: defer ttl decrement in mpls

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Date:   Fri, 23 Jul 2021 03:50:28 +0900
From:   Kangmin Park <l4stpr0gr4m@...il.com>
To:     "David S. Miller" <davem@...emloft.net>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        Martin Varghese <martin.varghese@...ia.com>,
        Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Guillaume Nault <gnault@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] mpls: defer ttl decrement in mpls_forward()

Defer ttl decrement to optimize in tx_err case. There is no need
to decrease ttl in the case of goto tx_err.

Signed-off-by: Kangmin Park <l4stpr0gr4m@...il.com>
---
 net/mpls/af_mpls.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c
index 05a21dd072df..ffeb2df8be7a 100644
--- a/net/mpls/af_mpls.c
+++ b/net/mpls/af_mpls.c
@@ -407,7 +407,6 @@ static int mpls_forward(struct sk_buff *skb, struct net_device *dev,
 	/* Verify ttl is valid */
 	if (dec.ttl <= 1)
 		goto err;
-	dec.ttl -= 1;
 
 	/* Find the output device */
 	out_dev = rcu_dereference(nh->nh_dev);
@@ -431,6 +430,7 @@ static int mpls_forward(struct sk_buff *skb, struct net_device *dev,
 	skb->dev = out_dev;
 	skb->protocol = htons(ETH_P_MPLS_UC);
 
+	dec.ttl -= 1;
 	if (unlikely(!new_header_size && dec.bos)) {
 		/* Penultimate hop popping */
 		if (!mpls_egress(dev_net(out_dev), rt, skb, dec))
-- 
2.26.2