netdev - [PATCH net 3/4] ip_gre: set tunnel hlen properly in erspan_tunnel

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Date:   Sun,  1 Oct 2017 22:00:55 +0800
From:   Xin Long <lucien.xin@...il.com>
To:     network dev <netdev@...r.kernel.org>
Cc:     davem@...emloft.net, Dmitry Kozlov <xeb@...l.ru>,
        William Tu <u9012063@...il.com>
Subject: [PATCH net 3/4] ip_gre: set tunnel hlen properly in erspan_tunnel_init

According to __gre_tunnel_init, tunnel->hlen should be set as the
headers' length between inner packet and outer iphdr.

It would be used especially to calculate a proper mtu when updating
mtu in tnl_update_pmtu. Now without setting it, a bigger mtu value
than expected would be updated, which hurts performance a lot.

This patch is to fix it by setting tunnel->hlen with:
   tunnel->tun_hlen + tunnel->encap_hlen + sizeof(struct erspanhdr)

Fixes: 84e54fe0a5ea ("gre: introduce native tunnel support for ERSPAN")
Signed-off-by: Xin Long <lucien.xin@...il.com>
---
 net/ipv4/ip_gre.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 2a4ef9d..fad0bb1 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -1245,7 +1245,9 @@ static int erspan_tunnel_init(struct net_device *dev)
 
 	tunnel->tun_hlen = 8;
 	tunnel->parms.iph.protocol = IPPROTO_GRE;
-	t_hlen = tunnel->hlen + sizeof(struct iphdr) + sizeof(struct erspanhdr);
+	tunnel->hlen = tunnel->tun_hlen + tunnel->encap_hlen +
+		       sizeof(struct erspanhdr);
+	t_hlen = tunnel->hlen + sizeof(struct iphdr);
 
 	dev->needed_headroom = LL_MAX_HEADER + t_hlen + 4;
 	dev->mtu = ETH_DATA_LEN - t_hlen - 4;
-- 
2.1.0