condition: greatly improve processing speed

Replace the loop over all possible condvars by a simple deref. This
changes the runtime from O(n) to O(1) at the expense of only 8 bytes
for rule.

extensions/xt_condition.h

@@ -8,6 +8,9 @@ enum {
 struct xt_condition_mtinfo {
 	char name[CONDITION_NAME_LEN];
 	__u8 invert;
+
+	/* Used internally by the kernel */
+	void *condvar __attribute__((aligned(8)));
 };
 
 #endif /* _XT_CONDITION_H */