netdev - [PATCH net-next 2/2] ipv6: replace ip_hdr() with skb->data for optimization

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Date:   Tue,  5 Jun 2018 08:04:22 -0400
From:   Yafang Shao <laoar.shao@...il.com>
To:     edumazet@...gle.com, davem@...emloft.net
Cc:     netdev@...r.kernel.org, inux-kernel@...r.kernel.org,
        Yafang Shao <laoar.shao@...il.com>
Subject: [PATCH net-next 2/2] ipv6: replace ip_hdr() with skb->data for optimization

In ipv6 receive path, when ip header hasn't been pulled yet, ip_hdr()
and skb->data are pointing to the same byte.

In ipv6 output path, when ip header is just pushed, ip_hdr() and skb->data
are pointing to the same byte.

As ip_hdr() is more expensive than using skb->data, so replace ip_hdr()
with skb->data in these situations for optimization.

Signed-off-by: Yafang Shao <laoar.shao@...il.com>
---
 net/ipv6/ip6_input.c  | 4 ++--
 net/ipv6/ip6_output.c | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c
index f08d344..2ff4fe8 100644
--- a/net/ipv6/ip6_input.c
+++ b/net/ipv6/ip6_input.c
@@ -113,7 +113,7 @@ int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt
 	if (unlikely(!pskb_may_pull(skb, sizeof(*hdr))))
 		goto err;
 
-	hdr = ipv6_hdr(skb);
+	hdr = (const struct ipv6hdr *)skb->data;
 
 	if (hdr->version != 6)
 		goto err;
@@ -189,7 +189,7 @@ int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt
 			__IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
 			goto drop;
 		}
-		hdr = ipv6_hdr(skb);
+		hdr = (const struct ipv6hdr *)skb->data;
 	}
 
 	if (hdr->nexthdr == NEXTHDR_HOP) {
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 021e5ae..8bb3bc1 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -235,7 +235,7 @@ int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,
 
 	skb_push(skb, sizeof(struct ipv6hdr));
 	skb_reset_network_header(skb);
-	hdr = ipv6_hdr(skb);
+	hdr = (struct ipv6hdr *)skb->data;
 
 	/*
 	 *	Fill in the IPv6 header
@@ -1659,7 +1659,7 @@ struct sk_buff *__ip6_make_skb(struct sock *sk,
 
 	skb_push(skb, sizeof(struct ipv6hdr));
 	skb_reset_network_header(skb);
-	hdr = ipv6_hdr(skb);
+	hdr = (struct ipv6hdr *)skb->data;
 
 	ip6_flow_hdr(hdr, v6_cork->tclass,
 		     ip6_make_flowlabel(net, skb, fl6->flowlabel,
-- 
1.8.3.1