net: move somaxconn init from sysctl code

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 ef547f2 (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 <[email protected]> Signed-off-by: David S. Miller <[email protected]>
berg · May 25, 2017 · 7c3f187 · 7c3f187
1 parent 65d786c
commit 7c3f187
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Showing 2 changed files with 19 additions and 2 deletions.
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
@@ -315,6 +315,25 @@ static __net_init int setup_net(struct net *net, struct user_namespace *user_ns)
 	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 ucounts *inc_net_namespaces(struct user_namespace *ns)

diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
@@ -479,8 +479,6 @@ static __net_init int sysctl_core_net_init(struct net *net)
 {
 	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);