IB/{hfi1, ipoib, rdma}: Broadcast ping sent packets which exceeded mtu size

When in connected mode ipoib sent broadcast pings which exceeded the mtu
size for broadcast addresses.

Add an mtu attribute to the rdma_netdev structure which ipoib sets to its
mcast mtu size.

The RDMA netdev uses this value to determine if the skb length is too long
for the mtu specified and if it is, drops the packet and logs an error
about the errant packet.

Link: https://lore.kernel.org/r/20200511160655.173205.14546.stgit@awfm-01.aw.intel.com
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Gary Leshner <Gary.S.Leshner@intel.com>
Signed-off-by: Kaike Wan <kaike.wan@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/ulp/ipoib/ipoib_main.c

@@ -1896,6 +1896,7 @@ static int ipoib_ndo_init(struct net_device *ndev)
 {
 	struct ipoib_dev_priv *priv = ipoib_priv(ndev);
 	int rc;
+	struct rdma_netdev *rn = netdev_priv(ndev);
 
 	if (priv->parent) {
 		ipoib_child_init(ndev);
@@ -1908,6 +1909,7 @@ static int ipoib_ndo_init(struct net_device *ndev)
 	/* MTU will be reset when mcast join happens */
 	ndev->mtu = IPOIB_UD_MTU(priv->max_ib_mtu);
 	priv->mcast_mtu = priv->admin_mtu = ndev->mtu;
+	rn->mtu = priv->mcast_mtu;
 	ndev->max_mtu = IPOIB_CM_MTU;
 
 	ndev->neigh_priv_len = sizeof(struct ipoib_neigh);

drivers/infiniband/ulp/ipoib/ipoib_multicast.c

@@ -246,6 +246,7 @@ static int ipoib_mcast_join_finish(struct ipoib_mcast *mcast,
 		if (priv->mcast_mtu == priv->admin_mtu)
 			priv->admin_mtu = IPOIB_UD_MTU(mtu);
 		priv->mcast_mtu = IPOIB_UD_MTU(mtu);
+		rn->mtu = priv->mcast_mtu;
 
 		priv->qkey = be32_to_cpu(priv->broadcast->mcmember.qkey);
 		spin_unlock_irq(&priv->lock);

drivers/infiniband/ulp/ipoib/ipoib_vlan.c

@@ -97,6 +97,7 @@ int __ipoib_vlan_add(struct ipoib_dev_priv *ppriv, struct ipoib_dev_priv *priv,
 {
 	struct net_device *ndev = priv->dev;
 	int result;
+	struct rdma_netdev *rn = netdev_priv(ndev);
 
 	ASSERT_RTNL();
 
@@ -117,6 +118,8 @@ int __ipoib_vlan_add(struct ipoib_dev_priv *ppriv, struct ipoib_dev_priv *priv,
 		goto out_early;
 	}
 
+	rn->mtu = priv->mcast_mtu;
+
 	priv->parent = ppriv->dev;
 	priv->pkey = pkey;
 	priv->child_type = type;