+extern int sysctl_dccp_sync_ratelimit;
+
+/*
+ * 48-bit sequence number arithmetic (signed and unsigned)
+ */
+#define INT48_MIN 0x800000000000LL /* 2^47 */
+#define UINT48_MAX 0xFFFFFFFFFFFFLL /* 2^48 - 1 */
+#define COMPLEMENT48(x) (0x1000000000000LL - (x)) /* 2^48 - x */
+#define TO_SIGNED48(x) (((x) < INT48_MIN)? (x) : -COMPLEMENT48( (x)))
+#define TO_UNSIGNED48(x) (((x) >= 0)? (x) : COMPLEMENT48(-(x)))
+#define ADD48(a, b) (((a) + (b)) & UINT48_MAX)
+#define SUB48(a, b) ADD48((a), COMPLEMENT48(b))
+
+static inline void dccp_set_seqno(u64 *seqno, u64 value)
+{
+ *seqno = value & UINT48_MAX;
+}
+
+static inline void dccp_inc_seqno(u64 *seqno)
+{
+ *seqno = ADD48(*seqno, 1);
+}
+
+/* signed mod-2^48 distance: pos. if seqno1 < seqno2, neg. if seqno1 > seqno2 */
+static inline s64 dccp_delta_seqno(const u64 seqno1, const u64 seqno2)
+{
+ u64 delta = SUB48(seqno2, seqno1);
+
+ return TO_SIGNED48(delta);
+}