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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 ef547f2ac1 (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>
This commit is contained in:
Roman Kapl 2017-05-24 10:22:22 +02:00 committed by David S. Miller
parent 65d786c21b
commit 7c3f1875c6
2 changed files with 19 additions and 2 deletions
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19
net/core/net_namespace.c
View File

@ -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)

2
net/core/sysctl_net_core.c
View File

@ -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);