tipc: simplify connection congestion handling

As a consequence of the recently introduced serialized access
to the socket in commit 8d94168a761819d10252bab1f8de6d7b202c3baa
("tipc: same receive code path for connection protocol and data
messages") we can make a number of simplifications in the
detection and handling of connection congestion situations.

- We don't need to keep two counters, one for sent messages and one
  for acked messages. There is no longer any risk for races between
  acknowledge messages arriving in BH and data message sending
  running in user context. So we merge this into one counter,
  'sent_unacked', which is incremented at sending and subtracted
  from at acknowledge reception.

- We don't need to set the 'congested' field in tipc_port to
  true before we sent the message, and clear it when sending
  is successful. (As a matter of fact, it was never necessary;
  the field was set in link_schedule_port() before any wakeup
  could arrive anyway.)

- We keep the conditions for link congestion and connection connection
  congestion separated. There would otherwise be a risk that an arriving
  acknowledge message may wake up a user sleeping because of link
  congestion.

- We can simplify reception of acknowledge messages.

We also make some cosmetic/structural changes:

- We rename the 'congested' field to the more correct 'link_cong´.

- We rename 'conn_unacked' to 'rcv_unacked'

- We move the above mentioned fields from struct tipc_port to
  struct tipc_sock.

Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Reviewed-by: Erik Hugne <erik.hugne@ericsson.com>
Reviewed-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 0 deletions

diff --git a/net/tipc/socket.h b/net/tipc/socket.h
index 69fd06b..2cdede9 100644
--- a/net/tipc/socket.h
+++ b/net/tipc/socket.h
@@ -48,6 +48,9 @@
  * @peer_name: the peer of the connection, if any
  * @conn_timeout: the time we can wait for an unresponded setup request
  * @dupl_rcvcnt: number of bytes counted twice, in both backlog and rcv queue
+ * @link_cong: non-zero if owner must sleep because of link congestion
+ * @sent_unacked: # messages sent by socket, and not yet acked by peer
+ * @rcv_unacked: # messages read by user, but not yet acked back to peer
  */
 
 struct tipc_sock {
@@ -55,6 +58,9 @@ struct tipc_sock {
 	struct tipc_port port;
 	unsigned int conn_timeout;
 	atomic_t dupl_rcvcnt;
+	int link_cong;
+	uint sent_unacked;
+	uint rcv_unacked;
 };
 
 static inline struct tipc_sock *tipc_sk(const struct sock *sk)
@@ -72,6 +78,11 @@ static inline void tipc_sock_wakeup(struct tipc_sock *tsk)
 	tsk->sk.sk_write_space(&tsk->sk);
 }
 
+static inline int tipc_sk_conn_cong(struct tipc_sock *tsk)
+{
+	return tsk->sent_unacked >= TIPC_FLOWCTRL_WIN;
+}
+
 int tipc_sk_rcv(struct sk_buff *buf);
 
 #endif