datapath: geneve: Relax MTU constraints.

Upstream commit:
    Allow the MTU of geneve devices to be set to large values, in order to
    exploit underlying networks with larger frame sizes.

    GENEVE does not have a fixed encapsulation overhead (an openvswitch
    rule can add variable length options), so there is no relevant maximum
    MTU to enforce.  A maximum of IP_MAX_MTU is used instead.
    Encapsulated packets that are too big for the underlying network will
    get dropped on the floor.

    Signed-off-by: David Wragg <david@weave.works>
    Signed-off-by: David S. Miller <davem@davemloft.net>
Upstream: 55e5bfb53cff ("geneve: Relax MTU constraints")
Signed-off-by: Joe Stringer <joe@ovn.org>
Acked-by: Jesse Gross <jesse@kernel.org>

diff --git a/datapath/linux/compat/geneve.c b/datapath/linux/compat/geneve.c
index 297593c..29a65a0 100644 (file)
--- a/datapath/linux/compat/geneve.c
+++ b/datapath/linux/compat/geneve.c
@@ -742,6 +742,17 @@ static netdev_tx_t geneve_dev_xmit(struct sk_buff *skb, struct net_device *dev)
        return NETDEV_TX_OK;
 }
 
+static int geneve_change_mtu(struct net_device *dev, int new_mtu)
+{
+       /* GENEVE overhead is not fixed, so we can't enforce a more
+        * precise max MTU.
+        */
+       if (new_mtu < 68 || new_mtu > IP_MAX_MTU)
+               return -EINVAL;
+       dev->mtu = new_mtu;
+       return 0;
+}
+
 static const struct net_device_ops geneve_netdev_ops = {
 #ifdef HAVE_DEV_TSTATS
        .ndo_init               = geneve_init,
@@ -751,7 +762,7 @@ static const struct net_device_ops geneve_netdev_ops = {
        .ndo_open               = geneve_open,
        .ndo_stop               = geneve_stop,
        .ndo_start_xmit         = geneve_dev_xmit,
-       .ndo_change_mtu         = eth_change_mtu,
+       .ndo_change_mtu         = geneve_change_mtu,
        .ndo_validate_addr      = eth_validate_addr,
        .ndo_set_mac_address    = eth_mac_addr,
 };