IB/core: Do not resolve VLAN if already resolved

For RoCE, resolution of layer 2 address attributes forces no VLAN if
link-local GIDs are used.  This patch allows applications to choose
the VLAN ID for link-local based RoCE GIDs by setting IB_QP_VID in
their QP attribute mask, and prevents the core from overriding this
choice.

Cc: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: Moni Shoua <monis@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/core/verbs.c

@@ -879,7 +879,8 @@ int ib_resolve_eth_l2_attrs(struct ib_qp *qp,
 		if (rdma_link_local_addr((struct in6_addr *)qp_attr->ah_attr.grh.dgid.raw)) {
 			rdma_get_ll_mac((struct in6_addr *)qp_attr->ah_attr.grh.dgid.raw, qp_attr->ah_attr.dmac);
 			rdma_get_ll_mac((struct in6_addr *)sgid.raw, qp_attr->smac);
-			qp_attr->vlan_id = rdma_get_vlan_id(&sgid);
+			if (!(*qp_attr_mask & IB_QP_VID))
+				qp_attr->vlan_id = rdma_get_vlan_id(&sgid);
 		} else {
 			ret = rdma_addr_find_dmac_by_grh(&sgid, &qp_attr->ah_attr.grh.dgid,
 					qp_attr->ah_attr.dmac, &qp_attr->vlan_id);