IB/mlx4: Fix wrong usage of IPv4 protocol for multicast attach/detach

commit e9a7faf1 upstream.

The MLX4_PROT_IB_IPV4 protocol should only be used with RoCEv2 and such.
Removing this wrong usage allows to run multicast applications over RoCE.

Fixes: d487ee77 ("IB/mlx4: Use IBoE (RoCE) IP based GIDs in the port GID table")
Reported-by: Carol Soto <clsoto@linux.vnet.ibm.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

drivers/infiniband/hw/mlx4/main.c

@@ -1170,8 +1170,7 @@ static int mlx4_ib_mcg_attach(struct ib_qp *ibqp, union ib_gid *gid, u16 lid)
 	struct mlx4_ib_qp *mqp = to_mqp(ibqp);
 	u64 reg_id;
 	struct mlx4_ib_steering *ib_steering = NULL;
-	enum mlx4_protocol prot = (gid->raw[1] == 0x0e) ?
-		MLX4_PROT_IB_IPV4 : MLX4_PROT_IB_IPV6;
+	enum mlx4_protocol prot = MLX4_PROT_IB_IPV6;
 
 	if (mdev->dev->caps.steering_mode ==
 	    MLX4_STEERING_MODE_DEVICE_MANAGED) {
@@ -1184,8 +1183,10 @@ static int mlx4_ib_mcg_attach(struct ib_qp *ibqp, union ib_gid *gid, u16 lid)
 				    !!(mqp->flags &
 				       MLX4_IB_QP_BLOCK_MULTICAST_LOOPBACK),
 				    prot, &reg_id);
-	if (err)
+	if (err) {
+		pr_err("multicast attach op failed, err %d\n", err);
 		goto err_malloc;
+	}
 
 	err = add_gid_entry(ibqp, gid);
 	if (err)
@@ -1233,8 +1234,7 @@ static int mlx4_ib_mcg_detach(struct ib_qp *ibqp, union ib_gid *gid, u16 lid)
 	struct net_device *ndev;
 	struct mlx4_ib_gid_entry *ge;
 	u64 reg_id = 0;
-	enum mlx4_protocol prot = (gid->raw[1] == 0x0e) ?
-		MLX4_PROT_IB_IPV4 : MLX4_PROT_IB_IPV6;
+	enum mlx4_protocol prot =  MLX4_PROT_IB_IPV6;
 
 	if (mdev->dev->caps.steering_mode ==
 	    MLX4_STEERING_MODE_DEVICE_MANAGED) {