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, 64 insertions, 0 deletions

diff --git a/net/tipc/sysctl.c b/net/tipc/sysctl.c
new file mode 100644
index 000000000000..f3fef93325a8
--- /dev/null
+++ b/net/tipc/sysctl.c
@@ -0,0 +1,64 @@
+/*
+ * net/tipc/sysctl.c: sysctl interface to TIPC subsystem
+ *
+ * Copyright (c) 2013, Wind River Systems
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the names of the copyright holders nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * Alternatively, this software may be distributed under the terms of the
+ * GNU General Public License ("GPL") version 2 as published by the Free
+ * Software Foundation.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "core.h"
+
+#include <linux/sysctl.h>
+
+static struct ctl_table_header *tipc_ctl_hdr;
+
+static struct ctl_table tipc_table[] = {
+	{
+		.procname	= "tipc_rmem",
+		.data		= &sysctl_tipc_rmem,
+		.maxlen		= sizeof(sysctl_tipc_rmem),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{}
+};
+
+int tipc_register_sysctl(void)
+{
+	tipc_ctl_hdr = register_net_sysctl(&init_net, "net/tipc", tipc_table);
+	if (tipc_ctl_hdr == NULL)
+		return -ENOMEM;
+	return 0;
+}
+
+void tipc_unregister_sysctl(void)
+{
+	unregister_net_sysctl_table(tipc_ctl_hdr);
+}