netdev - [PATCH v1 3/4] netfilter: Split ip6t_unregister_table() into pre

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Message-Id: <20200622171014.975-4-dwilder@us.ibm.com>
Date:   Mon, 22 Jun 2020 10:10:13 -0700
From:   David Wilder <dwilder@...ibm.com>
To:     netdev@...r.kernel.org
Cc:     netfilter-devel@...r.kernel.org, fw@...len.de, wilder@...ibm.com,
        mkubecek@...e.com
Subject: [PATCH v1 3/4] netfilter: Split ip6t_unregister_table() into pre_exit and exit helpers.

The pre_exit will un-register the underlying hook and .exit will do
the table freeing. The netns core does an unconditional synchronize_rcu
after the pre_exit hooks insuring no packets are in flight that have
picked up the pointer before completing the un-register.

Signed-off-by: David Wilder <dwilder@...ibm.com>
---
 include/linux/netfilter_ipv6/ip6_tables.h |  3 +++
 net/ipv6/netfilter/ip6_tables.c           | 15 ++++++++++++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/include/linux/netfilter_ipv6/ip6_tables.h b/include/linux/netfilter_ipv6/ip6_tables.h
index 8225f78..1547d5f 100644
--- a/include/linux/netfilter_ipv6/ip6_tables.h
+++ b/include/linux/netfilter_ipv6/ip6_tables.h
@@ -29,6 +29,9 @@ int ip6t_register_table(struct net *net, const struct xt_table *table,
 			const struct nf_hook_ops *ops, struct xt_table **res);
 void ip6t_unregister_table(struct net *net, struct xt_table *table,
 			   const struct nf_hook_ops *ops);
+void ip6t_unregister_table_pre_exit(struct net *net, struct xt_table *table,
+				    const struct nf_hook_ops *ops);
+void ip6t_unregister_table_exit(struct net *net, struct xt_table *table);
 extern unsigned int ip6t_do_table(struct sk_buff *skb,
 				  const struct nf_hook_state *state,
 				  struct xt_table *table);
diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index e273934..e96a431 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -1807,11 +1807,22 @@ int ip6t_register_table(struct net *net, const struct xt_table *table,
 	return ret;
 }
 
+void ip6t_unregister_table_pre_exit(struct net *net, struct xt_table *table,
+				    const struct nf_hook_ops *ops)
+{
+	nf_unregister_net_hooks(net, ops, hweight32(table->valid_hooks));
+}
+
+void ip6t_unregister_table_exit(struct net *net, struct xt_table *table)
+{
+	__ip6t_unregister_table(net, table);
+}
+
 void ip6t_unregister_table(struct net *net, struct xt_table *table,
 			   const struct nf_hook_ops *ops)
 {
 	if (ops)
-		nf_unregister_net_hooks(net, ops, hweight32(table->valid_hooks));
+		ip6t_unregister_table_pre_exit(net, table, ops);
 	__ip6t_unregister_table(net, table);
 }
 
@@ -1969,6 +1980,8 @@ static void __exit ip6_tables_fini(void)
 
 EXPORT_SYMBOL(ip6t_register_table);
 EXPORT_SYMBOL(ip6t_unregister_table);
+EXPORT_SYMBOL(ip6t_unregister_table_pre_exit);
+EXPORT_SYMBOL(ip6t_unregister_table_exit);
 EXPORT_SYMBOL(ip6t_do_table);
 
 module_init(ip6_tables_init);
-- 
1.8.3.1