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Subject[PATCH 4.4 076/190] net: move somaxconn init from sysctl code
Date
4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Roman Kapl <roman.kapl@sysgo.com>


[ Upstream commit 7c3f1875c66fbc19762760097cabc91849ea0bbb ]

The default value for somaxconn is set in sysctl_core_net_init(), but this
function is not called when kernel is configured without CONFIG_SYSCTL.

This results in the kernel not being able to accept TCP connections,
because the backlog has zero size. Usually, the user ends up with:
"TCP: request_sock_TCP: Possible SYN flooding on port 7. Dropping request. Check SNMP counters."
If SYN cookies are not enabled the connection is rejected.

Before ef547f2ac16 (tcp: remove max_qlen_log), the effects were less
severe, because the backlog was always at least eight slots long.

Signed-off-by: Roman Kapl <roman.kapl@sysgo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/core/net_namespace.c | 19 +++++++++++++++++++
net/core/sysctl_net_core.c | 2 --
2 files changed, 19 insertions(+), 2 deletions(-)

--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -310,6 +310,25 @@ out_undo:
goto out;
}

+static int __net_init net_defaults_init_net(struct net *net)
+{
+ net->core.sysctl_somaxconn = SOMAXCONN;
+ return 0;
+}
+
+static struct pernet_operations net_defaults_ops = {
+ .init = net_defaults_init_net,
+};
+
+static __init int net_defaults_init(void)
+{
+ if (register_pernet_subsys(&net_defaults_ops))
+ panic("Cannot initialize net default settings");
+
+ return 0;
+}
+
+core_initcall(net_defaults_init);

#ifdef CONFIG_NET_NS
static struct kmem_cache *net_cachep;
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -429,8 +429,6 @@ static __net_init int sysctl_core_net_in
{
struct ctl_table *tbl;

- net->core.sysctl_somaxconn = SOMAXCONN;
-
tbl = netns_core_table;
if (!net_eq(net, &init_net)) {
tbl = kmemdup(tbl, sizeof(netns_core_table), GFP_KERNEL);

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