IB/cm: Block processing alternate path handling RoCE Rx cm messages

Due to below reasons, it is better to not support alternate path receive
messages for RoCE in near term.

1. Alternate path for RoCE is not supported at rdmacm layer.
2. It is not supported in uverbs/core layer for RoCE.
3. Alternate path for IPv6 for link local address cannot resolve route
determinstically without a valid incoming interface id whose usecase
make sense only with dual port mode.
4. init_av_from_path while processing LAP messages for IB and RoCE can
lead to adding duplicate entry of AV into the port list, leads to list
corruption.
5. rdma-core userspace a well known userspace implementation has removed
support of libucm which use ucm.ko module, which is the only module that
can trigger alternate path related messages.
6. ucm kernel module is requested to be removed from the IB core in
patch [1].

[1] https://patchwork.kernel.org/patch/10268503/Signed-off-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/core/cm.c

@@ -3175,6 +3175,13 @@ static int cm_lap_handler(struct cm_work *work)
 	struct ib_mad_send_buf *msg = NULL;
 	int ret;
 
+	/* Currently Alternate path messages are not supported for
+	 * RoCE link layer.
+	 */
+	if (rdma_protocol_roce(work->port->cm_dev->ib_device,
+			       work->port->port_num))
+		return -EINVAL;
+
 	/* todo: verify LAP request and send reject APR if invalid. */
 	lap_msg = (struct cm_lap_msg *)work->mad_recv_wc->recv_buf.mad;
 	cm_id_priv = cm_acquire_id(lap_msg->remote_comm_id,
@@ -3324,6 +3331,13 @@ static int cm_apr_handler(struct cm_work *work)
 	struct cm_apr_msg *apr_msg;
 	int ret;
 
+	/* Currently Alternate path messages are not supported for
+	 * RoCE link layer.
+	 */
+	if (rdma_protocol_roce(work->port->cm_dev->ib_device,
+			       work->port->port_num))
+		return -EINVAL;
+
 	apr_msg = (struct cm_apr_msg *)work->mad_recv_wc->recv_buf.mad;
 	cm_id_priv = cm_acquire_id(apr_msg->remote_comm_id,
 				   apr_msg->local_comm_id);