netfilter: nat: remove module reference counting from NAT protocols

The only remaining user of NAT protocol module reference counting is NAT
ctnetlink support. Since this is a fairly short sequence of code, convert
over to use RCU and remove module reference counting.

Module unregistration is already protected by RCU using synchronize_rcu(),
so no further changes are necessary.

Signed-off-by: Patrick McHardy <[e-mail]>
Signed-off-by: Pablo Neira Ayuso <[e-mail]>

include/net/netfilter/nf_nat_protocol.h

···
 	/* Protocol number. */
 	unsigned int protonum;
 
-	struct module *me;
-
 	/* Translate a packet to the target according to manip type.
 	   Return true if succeeded. */
 	bool (*manip_pkt)(struct sk_buff *skb,

net/ipv4/netfilter/nf_nat_core.c

···
 #include <linux/netfilter/nfnetlink.h>
 #include <linux/netfilter/nfnetlink_conntrack.h>
 
-static const struct nf_nat_protocol *
-nf_nat_proto_find_get(u_int8_t protonum)
-{
-	const struct nf_nat_protocol *p;
-
-	rcu_read_lock();
-	p = __nf_nat_proto_find(protonum);
-	if (!try_module_get(p->me))
-		p = &nf_nat_unknown_protocol;
-	rcu_read_unlock();
-
-	return p;
-}
-
-static void
-nf_nat_proto_put(const struct nf_nat_protocol *p)
-{
-	module_put(p->me);
-}
-
 static const struct nla_policy protonat_nla_policy[CTA_PROTONAT_MAX+1] = {
 	[CTA_PROTONAT_PORT_MIN]	= { .type = NLA_U16 },
 	[CTA_PROTONAT_PORT_MAX]	= { .type = NLA_U16 },
···
 	if (err < 0)
 		return err;
 
-	npt = nf_nat_proto_find_get(nf_ct_protonum(ct));
+	rcu_read_lock();
+	npt = __nf_nat_proto_find(nf_ct_protonum(ct));
 	if (npt->nlattr_to_range)
 		err = npt->nlattr_to_range(tb, range);
-	nf_nat_proto_put(npt);
+	rcu_read_unlock();
 	return err;
 }
 

net/ipv4/netfilter/nf_nat_proto_dccp.c

···
 
 static const struct nf_nat_protocol nf_nat_protocol_dccp = {
 	.protonum		= IPPROTO_DCCP,
-	.me			= THIS_MODULE,
 	.manip_pkt		= dccp_manip_pkt,
 	.in_range		= nf_nat_proto_in_range,
 	.unique_tuple		= dccp_unique_tuple,

net/ipv4/netfilter/nf_nat_proto_gre.c

···
 
 static const struct nf_nat_protocol gre = {
 	.protonum		= IPPROTO_GRE,
-	.me			= THIS_MODULE,
 	.manip_pkt		= gre_manip_pkt,
 	.in_range		= nf_nat_proto_in_range,
 	.unique_tuple		= gre_unique_tuple,

net/ipv4/netfilter/nf_nat_proto_icmp.c

···
 
 const struct nf_nat_protocol nf_nat_protocol_icmp = {
 	.protonum		= IPPROTO_ICMP,
-	.me			= THIS_MODULE,
 	.manip_pkt		= icmp_manip_pkt,
 	.in_range		= icmp_in_range,
 	.unique_tuple		= icmp_unique_tuple,

net/ipv4/netfilter/nf_nat_proto_sctp.c

···
 
 static const struct nf_nat_protocol nf_nat_protocol_sctp = {
 	.protonum		= IPPROTO_SCTP,
-	.me			= THIS_MODULE,
 	.manip_pkt		= sctp_manip_pkt,
 	.in_range		= nf_nat_proto_in_range,
 	.unique_tuple		= sctp_unique_tuple,

net/ipv4/netfilter/nf_nat_proto_tcp.c

···
 
 const struct nf_nat_protocol nf_nat_protocol_tcp = {
 	.protonum		= IPPROTO_TCP,
-	.me			= THIS_MODULE,
 	.manip_pkt		= tcp_manip_pkt,
 	.in_range		= nf_nat_proto_in_range,
 	.unique_tuple		= tcp_unique_tuple,

net/ipv4/netfilter/nf_nat_proto_udp.c

···
 
 const struct nf_nat_protocol nf_nat_protocol_udp = {
 	.protonum		= IPPROTO_UDP,
-	.me			= THIS_MODULE,
 	.manip_pkt		= udp_manip_pkt,
 	.in_range		= nf_nat_proto_in_range,
 	.unique_tuple		= udp_unique_tuple,

net/ipv4/netfilter/nf_nat_proto_udplite.c

···
 
 static const struct nf_nat_protocol nf_nat_protocol_udplite = {
 	.protonum		= IPPROTO_UDPLITE,
-	.me			= THIS_MODULE,
 	.manip_pkt		= udplite_manip_pkt,
 	.in_range		= nf_nat_proto_in_range,
 	.unique_tuple		= udplite_unique_tuple,

net/ipv4/netfilter/nf_nat_proto_unknown.c

···
 }
 
 const struct nf_nat_protocol nf_nat_unknown_protocol = {
-	/* .me isn't set: getting a ref to this cannot fail. */
 	.manip_pkt		= unknown_manip_pkt,
 	.in_range		= unknown_in_range,
 	.unique_tuple		= unknown_unique_tuple,