net: move somaxconn init from sysctl code (7c3f1875) · Commits · 戴 / test

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 (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>

net/core/net_namespace.c

+19 −0

Original line number	Diff line number	Diff line
		@@ -315,6 +315,25 @@ 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 ucounts inc_net_namespaces(struct user_namespace ns)

net/core/sysctl_net_core.c

+0 −2

Original line number	Diff line number	Diff line
		@@ -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);

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