tipc: change socket buffer overflow control to respect sk_rcvbuf

As per feedback from the netdev community, we change the buffer
overflow protection algorithm in receiving sockets so that it
always respects the nominal upper limit set in sk_rcvbuf.

Instead of scaling up from a small sk_rcvbuf value, which leads to
violation of the configured sk_rcvbuf limit, we now calculate the
weighted per-message limit by scaling down from a much bigger value,
still in the same field, according to the importance priority of the
received message.

To allow for administrative tunability of the socket receive buffer
size, we create a tipc_rmem sysctl variable to allow the user to
configure an even bigger value via sysctl command.  It is a size of
three (min/default/max) to be consistent with things like tcp_rmem.

By default, the value initialized in tipc_rmem[1] is equal to the
receive socket size needed by a TIPC_CRITICAL_IMPORTANCE message.
This value is also set as the default value of sk_rcvbuf.

Originally-by: Jon Maloy <jon.maloy@ericsson.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: Jon Maloy <jon.maloy@ericsson.com>
[Ying: added sysctl variation to Jon's original patch]
Signed-off-by: Ying Xue <ying.xue@windriver.com>
[PG: don't compile sysctl.c if not config'd; add Documentation]
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 2 deletions

diff --git a/net/tipc/core.c b/net/tipc/core.c
index 7ec2c1eb94f1..b0e42a087291 100644
--- a/net/tipc/core.c
+++ b/net/tipc/core.c
@@ -39,6 +39,7 @@
 #include "name_table.h"
 #include "subscr.h"
 #include "config.h"
+#include "port.h"
 
 #include <linux/module.h>
 
@@ -50,7 +51,7 @@ u32 tipc_own_addr __read_mostly;
 int tipc_max_ports __read_mostly;
 int tipc_net_id __read_mostly;
 int tipc_remote_management __read_mostly;
-
+int sysctl_tipc_rmem[3] __read_mostly;	/* min/default/max */
 
 /**
  * tipc_buf_acquire - creates a TIPC message buffer
@@ -118,6 +119,7 @@ static void tipc_core_stop(void)
 	tipc_nametbl_stop();
 	tipc_ref_table_stop();
 	tipc_socket_stop();
+	tipc_unregister_sysctl();
 }
 
 /**
@@ -142,13 +144,14 @@ static int tipc_core_start(void)
 		res = tipc_netlink_start();
 	if (!res)
 		res = tipc_socket_init();
+	if (!res)
+		res = tipc_register_sysctl();
 	if (res)
 		tipc_core_stop();
 
 	return res;
 }
 
-
 static int __init tipc_init(void)
 {
 	int res;
@@ -160,6 +163,11 @@ static int __init tipc_init(void)
 	tipc_max_ports = CONFIG_TIPC_PORTS;
 	tipc_net_id = 4711;
 
+	sysctl_tipc_rmem[0] = CONN_OVERLOAD_LIMIT >> 4 << TIPC_LOW_IMPORTANCE;
+	sysctl_tipc_rmem[1] = CONN_OVERLOAD_LIMIT >> 4 <<
+			      TIPC_CRITICAL_IMPORTANCE;
+	sysctl_tipc_rmem[2] = CONN_OVERLOAD_LIMIT;
+
 	res = tipc_core_start();
 	if (res)
 		pr_err("Unable to start in single node mode\n");