From: David Wragg <david@weave.works>
Date: Wed, 10 Feb 2016 00:05:55 +0000 (+0000)
Subject: datapath: vxlan: Relax MTU constraints.
X-Git-Url: http://git.cascardo.eti.br/?p=cascardo%2Fovs.git;a=commitdiff_plain;h=27e39e3e9f9d628ee80c321e8876b2595f7a8be2

datapath: vxlan: Relax MTU constraints.

Upstream commit:
    Allow the MTU of vxlan devices without an underlying device to be set
    to larger values (up to a maximum based on IP packet limits and vxlan
    overhead).

    Previously, their MTUs could not be set to higher than the
    conventional ethernet value of 1500.  This is a very arbitrary value
    in the context of vxlan, and prevented vxlan devices from being able
    to take advantage of jumbo frames etc.

    The default MTU remains 1500, for compatibility.

    Signed-off-by: David Wragg <david@weave.works>
    Acked-by: Roopa Prabhu <roopa@cumulusnetworks.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>

Upstream: 72564b59ffc4 ("vxlan: Relax MTU constraints")
Signed-off-by: Joe Stringer <joe@ovn.org>
Acked-by: Jesse Gross <jesse@kernel.org>
---

diff --git a/datapath/linux/compat/vxlan.c b/datapath/linux/compat/vxlan.c
index dd0015d01..f443a1b03 100644
--- a/datapath/linux/compat/vxlan.c
+++ b/datapath/linux/compat/vxlan.c
@@ -1608,29 +1608,43 @@ static void vxlan_set_multicast_list(struct net_device *dev)
 {
 }
 
-static int vxlan_change_mtu(struct net_device *dev, int new_mtu)
+static int __vxlan_change_mtu(struct net_device *dev,
+			      struct net_device *lowerdev,
+			      struct vxlan_rdst *dst, int new_mtu, bool strict)
 {
-	struct vxlan_dev *vxlan = netdev_priv(dev);
-	struct vxlan_rdst *dst = &vxlan->default_dst;
-	struct net_device *lowerdev;
-	int max_mtu;
+	int max_mtu = IP_MAX_MTU;
 
-	lowerdev = __dev_get_by_index(vxlan->net, dst->remote_ifindex);
-	if (lowerdev == NULL)
-		return eth_change_mtu(dev, new_mtu);
+	if (lowerdev)
+		max_mtu = lowerdev->mtu;
 
 	if (dst->remote_ip.sa.sa_family == AF_INET6)
-		max_mtu = lowerdev->mtu - VXLAN6_HEADROOM;
+		max_mtu -= VXLAN6_HEADROOM;
 	else
-		max_mtu = lowerdev->mtu - VXLAN_HEADROOM;
+		max_mtu -= VXLAN_HEADROOM;
 
-	if (new_mtu < 68 || new_mtu > max_mtu)
+	if (new_mtu < 68)
 		return -EINVAL;
 
+	if (new_mtu > max_mtu) {
+		if (strict)
+			return -EINVAL;
+
+		new_mtu = max_mtu;
+	}
+
 	dev->mtu = new_mtu;
 	return 0;
 }
 
+static int vxlan_change_mtu(struct net_device *dev, int new_mtu)
+{
+	struct vxlan_dev *vxlan = netdev_priv(dev);
+	struct vxlan_rdst *dst = &vxlan->default_dst;
+	struct net_device *lowerdev = __dev_get_by_index(vxlan->net,
+							 dst->remote_ifindex);
+	return __vxlan_change_mtu(dev, lowerdev, dst, new_mtu, true);
+}
+
 static netdev_tx_t vxlan_dev_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	/* Drop All packets coming from networking stack. OVS-CB is