Patch "net: move somaxconn init from sysctl code" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

net: move somaxconn init from sysctl code

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
net-move-somaxconn-init-from-sysctl-code.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Roman Kapl <[email protected]>
Date: Wed, 24 May 2017 10:22:22 +0200
Subject: net: move somaxconn init from sysctl code

From: Roman Kapl <[email protected]>

[ 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.

---
 net/core/net_namespace.c   |   19 +++++++++++++++++++
 net/core/sysctl_net_core.c |    2 --
 2 files changed, 19 insertions(+), 2 deletions(-)

@@ -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;

@@ -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);

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/net-move-somaxconn-init-from-sysctl-code.patch