RDS: TCP: Enable multipath RDS for TCP

Use RDS probe-ping to compute how many paths may be used with
the peer, and to synchronously start the multiple paths. If mprds is
supported, hash outgoing traffic to one of multiple paths in rds_sendmsg()
when multipath RDS is supported by the transport.

CC: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 23 insertions, 2 deletions

diff --git a/net/rds/rds.h b/net/rds/rds.h
index 6ef07bd27227..b2d17f0fafa8 100644
--- a/net/rds/rds.h
+++ b/net/rds/rds.h
@@ -85,7 +85,9 @@ enum {
 #define RDS_RECV_REFILL		3
 
 /* Max number of multipaths per RDS connection. Must be a power of 2 */
-#define	RDS_MPATH_WORKERS	1
+#define	RDS_MPATH_WORKERS	8
+#define	RDS_MPATH_HASH(rs, n) (jhash_1word((rs)->rs_bound_port, \
+			       (rs)->rs_hash_initval) & ((n) - 1))
 
 /* Per mpath connection state */
 struct rds_conn_path {
@@ -131,7 +133,8 @@ struct rds_connection {
 	__be32			c_laddr;
 	__be32			c_faddr;
 	unsigned int		c_loopback:1,
-				c_pad_to_32:31;
+				c_ping_triggered:1,
+				c_pad_to_32:30;
 	int			c_npaths;
 	struct rds_connection	*c_passive;
 	struct rds_transport	*c_trans;
@@ -147,6 +150,7 @@ struct rds_connection {
 	unsigned long		c_map_queued;
 
 	struct rds_conn_path	c_path[RDS_MPATH_WORKERS];
+	wait_queue_head_t	c_hs_waitq; /* handshake waitq */
 };
 
 static inline
@@ -166,6 +170,17 @@ void rds_conn_net_set(struct rds_connection *conn, struct net *net)
 #define RDS_FLAG_RETRANSMITTED	0x04
 #define RDS_MAX_ADV_CREDIT	255
 
+/* RDS_FLAG_PROBE_PORT is the reserved sport used for sending a ping
+ * probe to exchange control information before establishing a connection.
+ * Currently the control information that is exchanged is the number of
+ * supported paths. If the peer is a legacy (older kernel revision) peer,
+ * it would return a pong message without additional control information
+ * that would then alert the sender that the peer was an older rev.
+ */
+#define RDS_FLAG_PROBE_PORT	1
+#define	RDS_HS_PROBE(sport, dport) \
+		((sport == RDS_FLAG_PROBE_PORT && dport == 0) || \
+		 (sport == 0 && dport == RDS_FLAG_PROBE_PORT))
 /*
  * Maximum space available for extension headers.
  */
@@ -225,6 +240,11 @@ struct rds_ext_header_rdma_dest {
 	__be32			h_rdma_offset;
 };
 
+/* Extension header announcing number of paths.
+ * Implicit length = 2 bytes.
+ */
+#define RDS_EXTHDR_NPATHS	4
+
 #define __RDS_EXTHDR_MAX	16 /* for now */
 
 struct rds_incoming {
@@ -545,6 +565,7 @@ struct rds_sock {
 	/* Socket options - in case there will be more */
 	unsigned char		rs_recverr,
 				rs_cong_monitor;
+	u32			rs_hash_initval;
 };
 
 static inline struct rds_sock *rds_sk_to_rs(const struct sock *sk)