[NET]: unify netlink kernel socket recognition

There are currently two ways to determine whether the netlink socket is a
kernel one or a user one. This patch creates a single inline call for
this purpose and unifies all the calls in the af_netlink.c

No similar calls are found outside af_netlink.c.
Signed-off-by: NDenis V. Lunev <den@openvz.org>
Acked-by: NAlexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/netlink/af_netlink.c

@@ -92,6 +92,11 @@ static inline struct netlink_sock *nlk_sk(struct sock *sk)
 	return container_of(sk, struct netlink_sock, sk);
 }
 
+static inline int netlink_is_kernel(struct sock *sk)
+{
+	return nlk_sk(sk)->flags & NETLINK_KERNEL_SOCKET;
+}
+
 struct nl_pid_hash {
 	struct hlist_head *table;
 	unsigned long rehash_time;
@@ -489,7 +494,7 @@ static int netlink_release(struct socket *sock)
 	module_put(nlk->module);
 
 	netlink_table_grab();
-	if (nlk->flags & NETLINK_KERNEL_SOCKET) {
+	if (netlink_is_kernel(sk)) {
 		kfree(nl_table[sk->sk_protocol].listeners);
 		nl_table[sk->sk_protocol].module = NULL;
 		nl_table[sk->sk_protocol].registered = 0;
@@ -716,7 +721,7 @@ static struct sock *netlink_getsockbypid(struct sock *ssk, u32 pid)
 
 	/* Don't bother queuing skb if kernel socket has no input function */
 	nlk = nlk_sk(sock);
-	if ((nlk->pid == 0 && !nlk->data_ready) ||
+	if ((netlink_is_kernel(sock) && !nlk->data_ready) ||
 	    (sock->sk_state == NETLINK_CONNECTED &&
 	     nlk->dst_pid != nlk_sk(ssk)->pid)) {
 		sock_put(sock);
@@ -762,7 +767,7 @@ int netlink_attachskb(struct sock *sk, struct sk_buff *skb, int nonblock,
 	    test_bit(0, &nlk->state)) {
 		DECLARE_WAITQUEUE(wait, current);
 		if (!timeo) {
-			if (!ssk || nlk_sk(ssk)->pid == 0)
+			if (!ssk || netlink_is_kernel(ssk))
 				netlink_overrun(sk);
 			sock_put(sk);
 			kfree_skb(skb);
@@ -861,7 +866,7 @@ int netlink_has_listeners(struct sock *sk, unsigned int group)
 	int res = 0;
 	unsigned long *listeners;
 
-	BUG_ON(!(nlk_sk(sk)->flags & NETLINK_KERNEL_SOCKET));
+	BUG_ON(!netlink_is_kernel(sk));
 
 	rcu_read_lock();
 	listeners = rcu_dereference(nl_table[sk->sk_protocol].listeners);