cifs: fix IPv6 address length check

For IPv6 the userspace mount helper sends an address in the "ip="
option.  This check fails if the length is > 35 characters. I have no
idea where the magic 35 character limit came from, but it's clearly not
enough for IPv6. Fix it by making it use the INET6_ADDRSTRLEN #define.

While we're at it, use the same #define for the address length in SPNEGO
upcalls.

Reported-by: Charles R. Anderson <cra@wpi.edu>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 8ae563f..74b5a87 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -35,6 +35,7 @@
 #include <linux/namei.h>
 #include <asm/uaccess.h>
 #include <asm/processor.h>
+#include <linux/inet.h>
 #include <net/ipv6.h>
 #include "cifspdu.h"
 #include "cifsglob.h"
@@ -960,7 +961,8 @@
 		} else if (strnicmp(data, "ip", 2) == 0) {
 			if (!value || !*value) {
 				vol->UNCip = NULL;
-			} else if (strnlen(value, 35) < 35) {
+			} else if (strnlen(value, INET6_ADDRSTRLEN) <
+							INET6_ADDRSTRLEN) {
 				vol->UNCip = value;
 			} else {
 				printk(KERN_WARNING "CIFS: ip address "