netfilter: conntrack: add nf_conntrack_default_on sysctl

This switch (default on) can be used to disable automatic registration
of connection tracking functionality in newly created network
namespaces.

This means that when net namespace goes down (or the tracker protocol
module is unloaded) we *might* have to unregister the hooks.

We can either add another per-netns variable that tells if
the hooks got registered by default, or, alternatively, just call
the protocol _put() function and have the callee deal with a possible
'extra' put() operation that doesn't pair with a get() one.

This uses the latter approach, i.e. a put() without a get has no effect.

Conntrack is still enabled automatically regardless of the new sysctl
setting if the new net namespace requires connection tracking, e.g. when
NAT rules are created.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Florian Westphal
2016-11-15 21:36:44 +01:00
committed by Pablo Neira Ayuso
parent 0c66dc1ea3
commit 481fa37347
4 changed files with 48 additions and 1 deletions

View File

@@ -96,6 +96,17 @@ nf_conntrack_max - INTEGER
Size of connection tracking table. Default value is
nf_conntrack_buckets value * 4.
nf_conntrack_default_on - BOOLEAN
0 - don't register conntrack in new net namespaces
1 - register conntrack in new net namespaces (default)
This controls wheter newly created network namespaces have connection
tracking enabled by default. It will be enabled automatically
regardless of this setting if the new net namespace requires
connection tracking, e.g. when NAT rules are created.
This setting is only visible in initial user namespace, it has no
effect on existing namespaces.
nf_conntrack_tcp_be_liberal - BOOLEAN
0 - disabled (default)
not 0 - enabled