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/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index f5e0682..14f54eb 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -123,7 +123,7 @@
 }
 
 static int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
-		    char __user *optval, int optlen)
+		    char __user *optval, unsigned int optlen)
 {
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct net *net = sock_net(sk);
@@ -773,7 +773,7 @@
 }
 
 int ipv6_setsockopt(struct sock *sk, int level, int optname,
-		    char __user *optval, int optlen)
+		    char __user *optval, unsigned int optlen)
 {
 	int err;
 
@@ -801,7 +801,7 @@
 
 #ifdef CONFIG_COMPAT
 int compat_ipv6_setsockopt(struct sock *sk, int level, int optname,
-			   char __user *optval, int optlen)
+			   char __user *optval, unsigned int optlen)
 {
 	int err;