netlink: add netlink_kernel_cfg parameter to netlink_kernel_create

This patch adds the following structure:

struct netlink_kernel_cfg {
        unsigned int    groups;
        void            (*input)(struct sk_buff *skb);
        struct mutex    *cb_mutex;
};

That can be passed to netlink_kernel_create to set optional configurations
for netlink kernel sockets.

I've populated this structure by looking for NULL and zero parameters at the
existing code. The remaining parameters that always need to be set are still
left in the original interface.

That includes optional parameters for the netlink socket creation. This allows
easy extensibility of this interface in the future.

This patch also adapts all callers to use this new interface.

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

2 files changed, 17 insertions, 9 deletions

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index b3025a6..43a124f 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1503,14 +1503,16 @@ static void netlink_data_ready(struct sock *sk, int len)
  */
 
 struct sock *
-netlink_kernel_create(struct net *net, int unit, unsigned int groups,
-		      void (*input)(struct sk_buff *skb),
-		      struct mutex *cb_mutex, struct module *module)
+netlink_kernel_create(struct net *net, int unit,
+		      struct module *module,
+		      struct netlink_kernel_cfg *cfg)
 {
 	struct socket *sock;
 	struct sock *sk;
 	struct netlink_sock *nlk;
 	struct listeners *listeners = NULL;
+	struct mutex *cb_mutex = cfg ? cfg->cb_mutex : NULL;
+	unsigned int groups;
 
 	BUG_ON(!nl_table);
 
@@ -1532,16 +1534,18 @@ netlink_kernel_create(struct net *net, int unit, unsigned int groups,
 	sk = sock->sk;
 	sk_change_net(sk, net);
 
-	if (groups < 32)
+	if (!cfg || cfg->groups < 32)
 		groups = 32;
+	else
+		groups = cfg->groups;
 
 	listeners = kzalloc(sizeof(*listeners) + NLGRPSZ(groups), GFP_KERNEL);
 	if (!listeners)
 		goto out_sock_release;
 
 	sk->sk_data_ready = netlink_data_ready;
-	if (input)
-		nlk_sk(sk)->netlink_rcv = input;
+	if (cfg && cfg->input)
+		nlk_sk(sk)->netlink_rcv = cfg->input;
 
 	if (netlink_insert(sk, net, 0))
 		goto out_sock_release;
diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index 2cc7c1e..32761b5 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -915,10 +915,14 @@ static struct genl_multicast_group notify_grp = {
 
 static int __net_init genl_pernet_init(struct net *net)
 {
+	struct netlink_kernel_cfg cfg = {
+		.input		= genl_rcv,
+		.cb_mutex	= &genl_mutex,
+	};
+
 	/* we'll bump the group number right afterwards */
-	net->genl_sock = netlink_kernel_create(net, NETLINK_GENERIC, 0,
-					       genl_rcv, &genl_mutex,
-					       THIS_MODULE);
+	net->genl_sock = netlink_kernel_create(net, NETLINK_GENERIC,
+					       THIS_MODULE, &cfg);
 
 	if (!net->genl_sock && net_eq(net, &init_net))
 		panic("GENL: Cannot initialize generic netlink\n");