[NET]: Introduce the sk_detach_filter() call

Filter is attached in a separate function, so do the
same for filter detaching.

This also removes one variable sock_setsockopt().
Signed-off-by: NPavel Emelyanov <xemul@openvz.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/linux/filter.h

@@ -146,6 +146,7 @@ struct sock;
 
 extern unsigned int sk_run_filter(struct sk_buff *skb, struct sock_filter *filter, int flen);
 extern int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk);
+extern int sk_detach_filter(struct sock *sk);
 extern int sk_chk_filter(struct sock_filter *filter, int flen);
 #endif /* __KERNEL__ */
 

net/core/filter.c

@@ -433,5 +433,21 @@ int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
 	return err;
 }
 
+int sk_detach_filter(struct sock *sk)
+{
+	int ret = -ENOENT;
+	struct sk_filter *filter;
+
+	rcu_read_lock_bh();
+	filter = rcu_dereference(sk->sk_filter);
+	if (filter) {
+		rcu_assign_pointer(sk->sk_filter, NULL);
+		sk_filter_release(sk, filter);
+		ret = 0;
+	}
+	rcu_read_unlock_bh();
+	return ret;
+}
+
 EXPORT_SYMBOL(sk_chk_filter);
 EXPORT_SYMBOL(sk_run_filter);

net/core/sock.c

@@ -428,7 +428,6 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
 		    char __user *optval, int optlen)
 {
 	struct sock *sk=sock->sk;
-	struct sk_filter *filter;
 	int val;
 	int valbool;
 	struct linger ling;
@@ -652,16 +651,7 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
 		break;
 
 	case SO_DETACH_FILTER:
-		rcu_read_lock_bh();
-		filter = rcu_dereference(sk->sk_filter);
-		if (filter) {
-			rcu_assign_pointer(sk->sk_filter, NULL);
-			sk_filter_release(sk, filter);
-			rcu_read_unlock_bh();
-			break;
-		}
-		rcu_read_unlock_bh();
-		ret = -ENONET;
+		ret = sk_detach_filter(sk);
 		break;
 
 	case SO_PASSSEC: