[PATCH] ipvlan: fix ipvlan MTU limits

[<liuqifa@huawei.com>]

From: Keefe Liu <liuqifa@huawei.com>

The MTU of ipvlan interface should not bigger than the phy device, When we
run following scripts, we will find there are some problems.
Step1:
	ip link add link eth0 name ipv1 type ipvlan mode l2
	ip netns add net1
	ip link set dev ipv1 netns net1
Step2:
	ip netns exec net1 ip link set dev ipv1 mtu 1501
	RTNETLINK answers: Invalid argument
	dmesg info: "ipv1: Invalid MTU 1501 requested, hw max 1500"
Step3:
	ip link set dev eth0 mtu 1600
	ip netns exec net1 ip link set dev ipv1 mtu 1501
	RTNETLINK answers: Invalid argument
	dmesg info: "ipv1: Invalid MTU 1501 requested, hw max 1500"
Step4:
	ip link set dev eth0 mtu 1400
	ip netns exec net1 ip link set dev ipv1 mtu 1500
The result of Step2 is we expected, but the result of Step3 and Step4
are not.

This patch set ipvlan's maximum MTU to ETH_MAX_MTU, and when we change
the ipvlan device's MTU, ipvlan_change_mtu() will make sure the new MTU
no larger than the phy device's MTU.

Signed-off-by: Keefe Liu <liuqifa@huawei.com>
---
 drivers/net/ipvlan/ipvlan_main.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/net/ipvlan/ipvlan_main.c b/drivers/net/ipvlan/ipvlan_main.c
index 30cb803..84c007d 100644
--- a/drivers/net/ipvlan/ipvlan_main.c
+++ b/drivers/net/ipvlan/ipvlan_main.c
@@ -380,12 +380,24 @@ static int ipvlan_get_iflink(const struct net_device *dev)
 	return ipvlan->phy_dev->ifindex;
 }
 
+static int ipvlan_change_mtu(struct net_device *dev, int new_mtu)
+{
+	struct ipvl_dev *ipvlan = netdev_priv(dev);
+
+	if (ipvlan->phy_dev->mtu < new_mtu)
+		return -EINVAL;
+
+	dev->mtu = new_mtu;
+	return 0;
+}
+
 static const struct net_device_ops ipvlan_netdev_ops = {
 	.ndo_init		= ipvlan_init,
 	.ndo_uninit		= ipvlan_uninit,
 	.ndo_open		= ipvlan_open,
 	.ndo_stop		= ipvlan_stop,
 	.ndo_start_xmit		= ipvlan_start_xmit,
+	.ndo_change_mtu		= ipvlan_change_mtu,
 	.ndo_fix_features	= ipvlan_fix_features,
 	.ndo_change_rx_flags	= ipvlan_change_rx_flags,
 	.ndo_set_rx_mode	= ipvlan_set_multicast_mac_filter,
@@ -680,6 +692,8 @@ void ipvlan_link_setup(struct net_device *dev)
 {
 	ether_setup(dev);
 
+	dev->min_mtu = 0;
+	dev->max_mtu = ETH_MAX_MTU;
 	dev->priv_flags &= ~(IFF_XMIT_DST_RELEASE | IFF_TX_SKB_SHARING);
 	dev->priv_flags |= IFF_UNICAST_FLT | IFF_NO_QUEUE;
 	dev->netdev_ops = &ipvlan_netdev_ops;
-- 
1.8.3.1