This moves bridge hooks to a register-when-needed scheme.
We use a device notifier to register the 'call-iptables' netfilter hooks
only once a bridge gets added.
This means that if the initial namespace uses a bridge, newly created
network namespaces no longer get the PRE_ROUTING ipt_sabotage hook.
It will registered in that network namespace once a bridge is created
within that namespace.
A few modules still use global hooks:
- conntrack
- bridge PF_BRIDGE hooks
- IPVS
- CLUSTER match (deprecated)
- SYNPROXY
As long as these modules are not loaded/used, a new network namespace has
empty hook list and NF_HOOK() will boil down to single list_empty test even
if initial namespace does stateless packet filtering.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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