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authorEric Dumazet <edumazet@google.com>2018-03-08 12:51:41 -0800
committerDavid S. Miller <davem@davemloft.net>2018-03-09 11:23:11 -0500
commit79134e6ce2c9d1a00eab4d98cb48f975dd2474cb (patch)
treeb5f8a1d1f2036315e6955d015fd181c538ed8ebf /net/core/sysctl_net_core.c
parent2b3905de8b3d8511aee1d4acbf063197291cdd3f (diff)
net: do not create fallback tunnels for non-default namespaces
fallback tunnels (like tunl0, gre0, gretap0, erspan0, sit0, ip6tnl0, ip6gre0) are automatically created when the corresponding module is loaded. These tunnels are also automatically created when a new network namespace is created, at a great cost. In many cases, netns are used for isolation purposes, and these extra network devices are a waste of resources. We are using thousands of netns per host, and hit the netns creation/delete bottleneck a lot. (Many thanks to Kirill for recent work on this) Add a new sysctl so that we can opt-out from this automatic creation. Note that these tunnels are still created for the initial namespace, to be the least intrusive for typical setups. Tested: lpk43:~# cat add_del_unshare.sh for i in `seq 1 40` do (for j in `seq 1 100` ; do unshare -n /bin/true >/dev/null ; done) & done wait lpk43:~# echo 0 >/proc/sys/net/core/fb_tunnels_only_for_init_net lpk43:~# time ./add_del_unshare.sh real 0m37.521s user 0m0.886s sys 7m7.084s lpk43:~# echo 1 >/proc/sys/net/core/fb_tunnels_only_for_init_net lpk43:~# time ./add_del_unshare.sh real 0m4.761s user 0m0.851s sys 1m8.343s lpk43:~# Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core/sysctl_net_core.c')
-rw-r--r--net/core/sysctl_net_core.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index d714f65782b7..4f47f92459cc 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -32,6 +32,9 @@ static int max_skb_frags = MAX_SKB_FRAGS;
static int net_msg_warn; /* Unused, but still a sysctl */
+int sysctl_fb_tunnels_only_for_init_net __read_mostly = 0;
+EXPORT_SYMBOL(sysctl_fb_tunnels_only_for_init_net);
+
#ifdef CONFIG_RPS
static int rps_sock_flow_sysctl(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
@@ -513,6 +516,15 @@ static struct ctl_table net_core_table[] = {
.proc_handler = proc_dointvec_minmax,
.extra1 = &zero,
},
+ {
+ .procname = "fb_tunnels_only_for_init_net",
+ .data = &sysctl_fb_tunnels_only_for_init_net,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &zero,
+ .extra2 = &one,
+ },
{ }
};