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/include/net/tcp.h b/include/net/tcp.h
index 56b7602..03a49c7 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -394,13 +394,13 @@
 					       int __user *optlen);
 extern int			tcp_setsockopt(struct sock *sk, int level, 
 					       int optname, char __user *optval, 
-					       int optlen);
+					       unsigned int optlen);
 extern int			compat_tcp_getsockopt(struct sock *sk,
 					int level, int optname,
 					char __user *optval, int __user *optlen);
 extern int			compat_tcp_setsockopt(struct sock *sk,
 					int level, int optname,
-					char __user *optval, int optlen);
+					char __user *optval, unsigned int optlen);
 extern void			tcp_set_keepalive(struct sock *sk, int val);
 extern int			tcp_recvmsg(struct kiocb *iocb, struct sock *sk,
 					    struct msghdr *msg,