net: Make setsockopt() optlen be unsigned.

This provides safety against negative optlen at the type
level instead of depending upon (sometimes non-trivial)
checks against this sprinkled all over the the place, in
each and every implementation.

Based upon work done by Arjan van de Ven and feedback
from Linus Torvalds.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/udp_impl.h b/net/ipv6/udp_impl.h
index 6bb3034..d757104 100644
--- a/net/ipv6/udp_impl.h
+++ b/net/ipv6/udp_impl.h
@@ -16,10 +16,10 @@
 extern int	udpv6_getsockopt(struct sock *sk, int level, int optname,
 				 char __user *optval, int __user *optlen);
 extern int	udpv6_setsockopt(struct sock *sk, int level, int optname,
-				 char __user *optval, int optlen);
+				 char __user *optval, unsigned int optlen);
 #ifdef CONFIG_COMPAT
 extern int	compat_udpv6_setsockopt(struct sock *sk, int level, int optname,
-					char __user *optval, int optlen);
+					char __user *optval, unsigned int optlen);
 extern int	compat_udpv6_getsockopt(struct sock *sk, int level, int optname,
 				       char __user *optval, int __user *optlen);
 #endif