RDMA/core: Calculate UDP source port based on flow label or lqpn/rqpn

Calculate and set UDP source port based on the flow label. If flow label
is not defined in GRH then calculate it based on lqpn/rqpn.

Link: https://lore.kernel.org/r/20220106180359.2915060-2-yanjun.zhu@linux.dev
Signed-off-by: Zhu Yanjun <yanjun.zhu@linux.dev>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

include/rdma/ib_verbs.h

@@ -4749,6 +4749,23 @@ static inline u32 rdma_calc_flow_label(u32 lqpn, u32 rqpn)
 	return (u32)(v & IB_GRH_FLOWLABEL_MASK);
 }
 
+/**
+ * rdma_get_udp_sport - Calculate and set UDP source port based on the flow
+ *                      label. If flow label is not defined in GRH then
+ *                      calculate it based on lqpn/rqpn.
+ *
+ * @fl:                 flow label from GRH
+ * @lqpn:               local qp number
+ * @rqpn:               remote qp number
+ */
+static inline u16 rdma_get_udp_sport(u32 fl, u32 lqpn, u32 rqpn)
+{
+	if (!fl)
+		fl = rdma_calc_flow_label(lqpn, rqpn);
+
+	return rdma_flow_label_to_udp_sport(fl);
+}
+
 const struct ib_port_immutable*
 ib_port_immutable_read(struct ib_device *dev, unsigned int port);
 #endif /* IB_VERBS_H */