rds: add transport specific tos_map hook

RDMA transport maps user tos to underline virtual lanes(VL)
for IB or DSCP values. RDMA CM transport abstract thats for
RDS. TCP transport makes use of default priority 0 and maps
all user tos values to it.

Reviewed-by: Sowmini Varadhan <[e-mail]>
Signed-off-by: Santosh Shilimkar <[e-mail]>
[[e-mail]: Adapted original patch with ipv6 changes]
Signed-off-by: Zhu Yanjun <[e-mail]>

net/rds/af_rds.c

···
 static int rds_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
 {
 	struct rds_sock *rs = rds_sk_to_rs(sock->sk);
-	rds_tos_t tos;
+	rds_tos_t utos, tos = 0;
 
 	switch (cmd) {
 	case SIOCRDSSETTOS:
-		if (get_user(tos, (rds_tos_t __user *)arg))
+		if (get_user(utos, (rds_tos_t __user *)arg))
 			return -EFAULT;
 
 		if (rs->rs_transport &&
-		    rs->rs_transport->t_type == RDS_TRANS_TCP)
-			tos = 0;
+		    rs->rs_transport->get_tos_map)
+			tos = rs->rs_transport->get_tos_map(utos);
+		else
+			return -ENOIOCTLCMD;
 
 		spin_lock_bh(&rds_sock_lock);
 		if (rs->rs_tos || rs->rs_conn) {

net/rds/ib.c

···
 	rds_ib_mr_exit();
 }
 
+static u8 rds_ib_get_tos_map(u8 tos)
+{
+	/* 1:1 user to transport map for RDMA transport.
+	 * In future, if custom map is desired, hook can export
+	 * user configurable map.
+	 */
+	return tos;
+}
+
 struct rds_transport rds_ib_transport = {
 	.laddr_check		= rds_ib_laddr_check,
 	.xmit_path_complete	= rds_ib_xmit_path_complete,
···
 	.sync_mr		= rds_ib_sync_mr,
 	.free_mr		= rds_ib_free_mr,
 	.flush_mrs		= rds_ib_flush_mrs,
+	.get_tos_map		= rds_ib_get_tos_map,
 	.t_owner		= THIS_MODULE,
 	.t_name			= "infiniband",
 	.t_unloading		= rds_ib_is_unloading,

net/rds/rds.h

···
 	void (*free_mr)(void *trans_private, int invalidate);
 	void (*flush_mrs)(void);
 	bool (*t_unloading)(struct rds_connection *conn);
+	u8 (*get_tos_map)(u8 tos);
 };
 
 /* Bind hash table key length.  It is the sum of the size of a struct

net/rds/tcp.c

···
 
 static void rds_tcp_exit(void);
 
+static u8 rds_tcp_get_tos_map(u8 tos)
+{
+	/* all user tos mapped to default 0 for TCP transport */
+	return 0;
+}
+
 struct rds_transport rds_tcp_transport = {
 	.laddr_check		= rds_tcp_laddr_check,
 	.xmit_path_prepare	= rds_tcp_xmit_path_prepare,
···
 	.inc_free		= rds_tcp_inc_free,
 	.stats_info_copy	= rds_tcp_stats_info_copy,
 	.exit			= rds_tcp_exit,
+	.get_tos_map		= rds_tcp_get_tos_map,
 	.t_owner		= THIS_MODULE,
 	.t_name			= "tcp",
 	.t_type			= RDS_TRANS_TCP,