net/ipv4: add dst cache support for gre lwtunnels

Paolo Abeni · davem330 · commit 3c1cb4d2604c · 2016-02-16T20:21:49.000-05:00
In case of UDP traffic with datagram length below MTU this
gives about 4% performance increase

Signed-off-by: Paolo Abeni &lt;pabeni@redhat.com&gt;
Suggested-and-Acked-by: Hannes Frederic Sowa &lt;hannes@stressinduktion.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
@@ -540,9 +540,16 @@ static void gre_fb_xmit(struct sk_buff *skb, struct net_device *dev)
 		goto err_free_skb;
 
 	key = &tun_info->key;
-	rt = gre_get_rt(skb, dev, &fl, key);
-	if (IS_ERR(rt))
-		goto err_free_skb;
+	rt = !skb->mark ? dst_cache_get_ip4(&tun_info->dst_cache, &fl.saddr) :
+			 NULL;
+	if (!rt) {
+		rt = gre_get_rt(skb, dev, &fl, key);
+		if (IS_ERR(rt))
+				goto err_free_skb;
+		if (!skb->mark)
+			dst_cache_set_ip4(&tun_info->dst_cache, &rt->dst,
+					  fl.saddr);
+	}
 
 	tunnel_hlen = ip_gre_calc_hlen(key->tun_flags);
 
