RDMA/cma: Initialize the flow label of CM's route path record

If flow label is not set by the user or it's not IPv4, initialize it with
the cma src/dst based on the "Kernighan and Ritchie's hash function".

Link: https://lore.kernel.org/r/20200504051935.269708-5-leon@kernel.org
Signed-off-by: Mark Zhang <markz@mellanox.com>
Reviewed-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/core/cma.c

@@ -2909,6 +2909,24 @@ static int iboe_tos_to_sl(struct net_device *ndev, int tos)
 		return 0;
 }
 
+static __be32 cma_get_roce_udp_flow_label(struct rdma_id_private *id_priv)
+{
+	struct sockaddr_in6 *addr6;
+	u16 dport, sport;
+	u32 hash, fl;
+
+	addr6 = (struct sockaddr_in6 *)cma_src_addr(id_priv);
+	fl = be32_to_cpu(addr6->sin6_flowinfo) & IB_GRH_FLOWLABEL_MASK;
+	if ((cma_family(id_priv) != AF_INET6) || !fl) {
+		dport = be16_to_cpu(cma_port(cma_dst_addr(id_priv)));
+		sport = be16_to_cpu(cma_port(cma_src_addr(id_priv)));
+		hash = (u32)sport * 31 + dport;
+		fl = hash & IB_GRH_FLOWLABEL_MASK;
+	}
+
+	return cpu_to_be32(fl);
+}
+
 static int cma_resolve_iboe_route(struct rdma_id_private *id_priv)
 {
 	struct rdma_route *route = &id_priv->id.route;
@@ -2975,6 +2993,11 @@ static int cma_resolve_iboe_route(struct rdma_id_private *id_priv)
 		goto err2;
 	}
 
+	if (rdma_protocol_roce_udp_encap(id_priv->id.device,
+					 id_priv->id.port_num))
+		route->path_rec->flow_label =
+			cma_get_roce_udp_flow_label(id_priv);
+
 	cma_init_resolve_route_work(work, id_priv);
 	queue_work(cma_wq, &work->work);