| Message ID | 20170524082222.14208-1-roman.kapl@sysgo.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Roman Kapl <roman.kapl@sysgo.com> Date: Wed, 24 May 2017 10:22:22 +0200 > 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> This looks better, applied, thanks.
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c index 1934efd..26bbfab 100644 --- 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 index ea23254..b7cd9aa 100644 --- 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);
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> --- net/core/net_namespace.c | 19 +++++++++++++++++++ net/core/sysctl_net_core.c | 2 -- 2 files changed, 19 insertions(+), 2 deletions(-)