netfilter: nf_conntrack_helper: dynamically allocate struct nf_conntrack_helper

Adapt all existing helpers to use a modified version of
nf_ct_helper_init(), to dynamically allocate struct nf_conntrack_helper.

Allocate expect_policy[] built-in into the helper to ensure this area is
reachable after helper removal since a follow up patch adds refcount to
track use of the nf_conntrack_helper structure from packet path so it
remains around until last reference from ct helper extension is dropped.

Export __nf_conntrack_helper_register() which allows to register
nfnetlink_cthelper dynamically allocated helper. Adapt nfnetlink_cthelper
to use the built-in expect_policy[].

This is a preparation patch to add packet path refcounting to helpers.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 16 insertions, 11 deletions

diff --git a/net/ipv4/netfilter/nf_nat_snmp_basic_main.c b/net/ipv4/netfilter/nf_nat_snmp_basic_main.c
index 717b726504fe..0ede138dfd29 100644
--- a/net/ipv4/netfilter/nf_nat_snmp_basic_main.c
+++ b/net/ipv4/netfilter/nf_nat_snmp_basic_main.c
@@ -202,29 +202,34 @@ static const struct nf_conntrack_expect_policy snmp_exp_policy = {
 	.timeout	= 180,
 };
 
-static struct nf_conntrack_helper snmp_trap_helper __read_mostly = {
-	.me			= THIS_MODULE,
-	.help			= help,
-	.expect_policy		= &snmp_exp_policy,
-	.name			= "snmp_trap",
-	.tuple.src.l3num	= AF_INET,
-	.tuple.src.u.udp.port	= cpu_to_be16(SNMP_TRAP_PORT),
-	.tuple.dst.protonum	= IPPROTO_UDP,
-};
+static struct nf_conntrack_helper snmp_trap_helper __read_mostly;
+static struct nf_conntrack_helper *snmp_trap_helper_ptr __read_mostly;
 
 static int __init nf_nat_snmp_basic_init(void)
 {
+	int err;
+
 	BUG_ON(nf_nat_snmp_hook != NULL);
 	RCU_INIT_POINTER(nf_nat_snmp_hook, help);
 
-	return nf_conntrack_helper_register(&snmp_trap_helper);
+	nf_ct_helper_init(&snmp_trap_helper, AF_INET, IPPROTO_UDP,
+			  "snmp_trap", SNMP_TRAP_PORT, SNMP_TRAP_PORT, SNMP_TRAP_PORT,
+			  &snmp_exp_policy, 0, help, NULL, THIS_MODULE);
+
+	err = nf_conntrack_helper_register(&snmp_trap_helper, &snmp_trap_helper_ptr);
+	if (err < 0) {
+		RCU_INIT_POINTER(nf_nat_snmp_hook, NULL);
+		return err;
+	}
+
+	return 0;
 }
 
 static void __exit nf_nat_snmp_basic_fini(void)
 {
 	RCU_INIT_POINTER(nf_nat_snmp_hook, NULL);
 	synchronize_rcu();
-	nf_conntrack_helper_unregister(&snmp_trap_helper);
+	nf_conntrack_helper_unregister(snmp_trap_helper_ptr);
 }
 
 module_init(nf_nat_snmp_basic_init);