IB/rxe: Drop QP0 silently

According to "Annex A16: RDMA over Converged Ethernet (RoCE)":

A16.4.3 MANAGEMENT INTERFACES

As defined in the base specification, a special Queue Pair, QP0 is defined
solely for communication between subnet manager(s) and subnet management
agents. Since such an IB-defined subnet management architecture is outside
the scope of this annex, it follows that there is also no requirement that
a port which conforms to this annex be associated with a QP0. Thus, for
end nodes designed to conform to this annex, the concept of QP0 is
undefined and unused for any port connected to an Ethernet network.

CA16-8: A packet arriving at a RoCE port containing a BTH with the
destination QP field set to QP0 shall be silently dropped.
Signed-off-by: Zhu Yanjun <yanjun.zhu@oracle.com>
Acked-by: Moni Shoua <monis@mellanox.com>
Reviewed-by: Yuval Shaia <yuval.shaia@oracle.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/sw/rxe/rxe_recv.c

@@ -225,9 +225,14 @@ static int hdr_check(struct rxe_pkt_info *pkt)
 		goto err1;
 	}
 
+	if (unlikely(qpn == 0)) {
+		pr_warn_once("QP 0 not supported");
+		goto err1;
+	}
+
 	if (qpn != IB_MULTICAST_QPN) {
-		index = (qpn == 0) ? port->qp_smi_index :
-			((qpn == 1) ? port->qp_gsi_index : qpn);
+		index = (qpn == 1) ? port->qp_gsi_index : qpn;
+
 		qp = rxe_pool_get_index(&rxe->qp_pool, index);
 		if (unlikely(!qp)) {
 			pr_warn_ratelimited("no qp matches qpn 0x%x\n", qpn);