summaryrefslogtreecommitdiffstats
path: root/net/ipv6/ip6_gre.c
diff options
context:
space:
mode:
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/ipv6/ip6_gre.c
parent2b3905de8b3d8511aee1d4acbf063197291cdd3f (diff)
downloadlinux-79134e6ce2c9d1a00eab4d98cb48f975dd2474cb.tar.bz2
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/ipv6/ip6_gre.c')
-rw-r--r--net/ipv6/ip6_gre.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index 18a3dfbd0300..7d8775c9570d 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -236,7 +236,7 @@ static struct ip6_tnl *ip6gre_tunnel_lookup(struct net_device *dev,
return t;
dev = ign->fb_tunnel_dev;
- if (dev->flags & IFF_UP)
+ if (dev && dev->flags & IFF_UP)
return netdev_priv(dev);
return NULL;
@@ -1472,6 +1472,8 @@ static int __net_init ip6gre_init_net(struct net *net)
struct ip6gre_net *ign = net_generic(net, ip6gre_net_id);
int err;
+ if (!net_has_fallback_tunnels(net))
+ return 0;
ign->fb_tunnel_dev = alloc_netdev(sizeof(struct ip6_tnl), "ip6gre0",
NET_NAME_UNKNOWN,
ip6gre_tunnel_setup);