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/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index 5a06935..0c0b6e3 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -440,7 +440,7 @@
  */
 
 static int do_ip_setsockopt(struct sock *sk, int level,
-			    int optname, char __user *optval, int optlen)
+			    int optname, char __user *optval, unsigned int optlen)
 {
 	struct inet_sock *inet = inet_sk(sk);
 	int val = 0, err;
@@ -950,7 +950,7 @@
 }
 
 int ip_setsockopt(struct sock *sk, int level,
-		int optname, char __user *optval, int optlen)
+		int optname, char __user *optval, unsigned int optlen)
 {
 	int err;
 
@@ -975,7 +975,7 @@
 
 #ifdef CONFIG_COMPAT
 int compat_ip_setsockopt(struct sock *sk, int level, int optname,
-			 char __user *optval, int optlen)
+			 char __user *optval, unsigned int optlen)
 {
 	int err;