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73319a8ee1
Supporting a 1:n relationship between nft_hook and nf_hook_ops is convenient since a chain's or flowtable's nft_hooks may remain in place despite matching interfaces disappearing. This stabilizes ruleset dumps in that regard and opens the possibility to claim newly added interfaces which match the spec. Also it prepares for wildcard interface specs since these will potentially match multiple interfaces. All spots dealing with hook registration are updated to handle a list of multiple nf_hook_ops, but nft_netdev_hook_alloc() only adds a single item for now to retain the old behaviour. The only expected functional change here is how vanishing interfaces are handled: Instead of dropping the respective nft_hook, only the matching nf_hook_ops are dropped. To safely remove individual ops from the list in netdev handlers, an rcu_head is added to struct nf_hook_ops so kfree_rcu() may be used. There is at least nft_flowtable_find_dev() which may be iterating through the list at the same time. Signed-off-by: Phil Sutter <phil@nwl.cc> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>