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-rw-r--r--include/net/codel.h19
1 files changed, 15 insertions, 4 deletions
diff --git a/include/net/codel.h b/include/net/codel.h
index 389cf621161d..3b04ff5f6f8d 100644
--- a/include/net/codel.h
+++ b/include/net/codel.h
@@ -72,10 +72,21 @@ static inline codel_time_t codel_get_time(void)
return ns >> CODEL_SHIFT;
}
-#define codel_time_after(a, b) ((s32)(a) - (s32)(b) > 0)
-#define codel_time_after_eq(a, b) ((s32)(a) - (s32)(b) >= 0)
-#define codel_time_before(a, b) ((s32)(a) - (s32)(b) < 0)
-#define codel_time_before_eq(a, b) ((s32)(a) - (s32)(b) <= 0)
+/* Dealing with timer wrapping, according to RFC 1982, as desc in wikipedia:
+ * https://en.wikipedia.org/wiki/Serial_number_arithmetic#General_Solution
+ * codel_time_after(a,b) returns true if the time a is after time b.
+ */
+#define codel_time_after(a, b) \
+ (typecheck(codel_time_t, a) && \
+ typecheck(codel_time_t, b) && \
+ ((s32)((a) - (b)) > 0))
+#define codel_time_before(a, b) codel_time_after(b, a)
+
+#define codel_time_after_eq(a, b) \
+ (typecheck(codel_time_t, a) && \
+ typecheck(codel_time_t, b) && \
+ ((s32)((a) - (b)) >= 0))
+#define codel_time_before_eq(a, b) codel_time_after_eq(b, a)
/* Qdiscs using codel plugin must use codel_skb_cb in their own cb[] */
struct codel_skb_cb {