[NETFILTER]: nf_conntrack: support for layer 3 protocol load on demand

x_tables matches and targets that require nf_conntrack_ipv[4|6] to work
don't have enough information to load on demand these modules. This
patch introduces the following changes to solve this issue:

o nf_ct_l3proto_try_module_get: try to load the layer 3 connection
tracker module and increases the refcount.
o nf_ct_l3proto_module put: drop the refcount of the module.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 31 insertions, 0 deletions

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index c28840656451cd..0ae281d9bfc3f1 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -23,6 +23,8 @@
  * 26 Jan 2006: Harald Welte <laforge@netfilter.org>
  * 	- restructure nf_conn (introduce nf_conn_help)
  * 	- redesign 'features' how they were originally intended
+ * 26 Feb 2006: Pablo Neira Ayuso <pablo@eurodev.net>
+ * 	- add support for L3 protocol module load on demand.
  *
  * Derived from net/ipv4/netfilter/ip_conntrack_core.c
  */
@@ -241,6 +243,35 @@ void nf_ct_l3proto_put(struct nf_conntrack_l3proto *p)
 	module_put(p->me);
 }
 
+int
+nf_ct_l3proto_try_module_get(unsigned short l3proto)
+{
+	int ret;
+	struct nf_conntrack_l3proto *p;
+
+retry:	p = nf_ct_l3proto_find_get(l3proto);
+	if (p == &nf_conntrack_generic_l3proto) {
+		ret = request_module("nf_conntrack-%d", l3proto);
+		if (!ret)
+			goto retry;
+
+		return -EPROTOTYPE;
+	}
+
+	return 0;
+}
+
+void nf_ct_l3proto_module_put(unsigned short l3proto)
+{
+	struct nf_conntrack_l3proto *p;
+
+	preempt_disable();
+	p = __nf_ct_l3proto_find(l3proto);
+	preempt_enable();
+
+	module_put(p->me);
+}
+
 static int nf_conntrack_hash_rnd_initted;
 static unsigned int nf_conntrack_hash_rnd;