netlink: add nlk->netlink_bind hook for module auto-loading

This patch adds a hook in the binding path of netlink.

This is used by ctnetlink to allow module autoloading for the case
in which one user executes:

 conntrack -E

So far, this resulted in nfnetlink loaded, but not
nf_conntrack_netlink.

I have received in the past many complains on this behaviour.

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

1 files changed, 19 insertions, 0 deletions

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 43a124feaad8..5463969da45b 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -80,6 +80,7 @@ struct netlink_sock {
 	struct mutex		*cb_mutex;
 	struct mutex		cb_def_mutex;
 	void			(*netlink_rcv)(struct sk_buff *skb);
+	void			(*netlink_bind)(int group);
 	struct module		*module;
 };
 
@@ -124,6 +125,7 @@ struct netlink_table {
 	unsigned int		groups;
 	struct mutex		*cb_mutex;
 	struct module		*module;
+	void			(*bind)(int group);
 	int			registered;
 };
 
@@ -444,6 +446,7 @@ static int netlink_create(struct net *net, struct socket *sock, int protocol,
 	struct module *module = NULL;
 	struct mutex *cb_mutex;
 	struct netlink_sock *nlk;
+	void (*bind)(int group);
 	int err = 0;
 
 	sock->state = SS_UNCONNECTED;
@@ -468,6 +471,7 @@ static int netlink_create(struct net *net, struct socket *sock, int protocol,
 	else
 		err = -EPROTONOSUPPORT;
 	cb_mutex = nl_table[protocol].cb_mutex;
+	bind = nl_table[protocol].bind;
 	netlink_unlock_table();
 
 	if (err < 0)
@@ -483,6 +487,7 @@ static int netlink_create(struct net *net, struct socket *sock, int protocol,
 
 	nlk = nlk_sk(sock->sk);
 	nlk->module = module;
+	nlk->netlink_bind = bind;
 out:
 	return err;
 
@@ -683,6 +688,15 @@ static int netlink_bind(struct socket *sock, struct sockaddr *addr,
 	netlink_update_listeners(sk);
 	netlink_table_ungrab();
 
+	if (nlk->netlink_bind && nlk->groups[0]) {
+		int i;
+
+		for (i=0; i<nlk->ngroups; i++) {
+			if (test_bit(i, nlk->groups))
+				nlk->netlink_bind(i);
+		}
+	}
+
 	return 0;
 }
 
@@ -1239,6 +1253,10 @@ static int netlink_setsockopt(struct socket *sock, int level, int optname,
 		netlink_update_socket_mc(nlk, val,
 					 optname == NETLINK_ADD_MEMBERSHIP);
 		netlink_table_ungrab();
+
+		if (nlk->netlink_bind)
+			nlk->netlink_bind(val);
+
 		err = 0;
 		break;
 	}
@@ -1559,6 +1577,7 @@ netlink_kernel_create(struct net *net, int unit,
 		rcu_assign_pointer(nl_table[unit].listeners, listeners);
 		nl_table[unit].cb_mutex = cb_mutex;
 		nl_table[unit].module = module;
+		nl_table[unit].bind = cfg ? cfg->bind : NULL;
 		nl_table[unit].registered = 1;
 	} else {
 		kfree(listeners);