net: move somaxconn init from sysctl code

[ 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>

diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 572af0011997a2057f30ba0b5022760e11493d98..9195a109ea790ce07a8dc3b113fc2693095801ff 100644 (file)
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -268,6 +268,25 @@ 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;

diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index f5ef2115871f72b657611c399ab9573dadd71c12..a9a4276609efe5cbdfee9ef97a974a5657cdc368 100644 (file)
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -423,8 +423,6 @@ 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);