[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: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 91b2e3b..ddfa037 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -146,6 +146,7 @@
 
 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__ */