[DCCP]: 48-bit sequence number arithmetic
This patch
* organizes the sequence arithmetic functions into one corner of dccp.h
* performs a small modification of dccp_set_seqno to make it more widely reusable
(now it is safe to use any number, since it performs modulo-2^48 assignment)
* adds functions and generic macros for 48-bit sequence arithmetic:
--48 bit complement
--modulo-48 addition and modulo-48 subtraction
--dccp_inc_seqno now a special case of add48
Signed-off-by: Gerrit Renker <gerrit@xxxxxxxxxxxxxx>
Acked-by: Ian McDonald <ian.mcdonald@xxxxxxxxxxx>
---
net/dccp/dccp.h | 45 ++++++++++++++++++++++++++-------------------
1 file changed, 26 insertions(+), 19 deletions(-)
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -92,6 +92,32 @@ extern int sysctl_dccp_feat_send_ack_ve
extern int sysctl_dccp_feat_send_ndp_count;
extern int sysctl_dccp_tx_qlen;
+/*
+ * 48-bit sequence number arithmetic
+ */
+#define S48_NEG_MIN 0x800000000000LL /* 2^47 */
+#define DCCP_MAX_SEQNO 0xFFFFFFFFFFFFLL /* 2^48 - 1 */
+#define COMPLEMENT48(x) (0x1000000000000LL - (x)) /* 2^48 - x */
+#define TO_SIGNED48(x) (((x) < S48_NEG_MIN)? (x) : -COMPLEMENT48( (x)))
+#define TO_UNSIGNED48(x) (((x) >= 0)? (x) : COMPLEMENT48(-(x)))
+#define ADD48(a, b) (((a) + (b)) & DCCP_MAX_SEQNO)
+#define SUB48(a, b) ADD48((a), COMPLEMENT48(b))
+
+static inline void dccp_set_seqno(u64 *seqno, u64 value)
+{
+ *seqno = value & DCCP_MAX_SEQNO;
+}
+
+static inline void dccp_inc_seqno(u64 *seqno)
+{
+ *seqno = ADD48(*seqno, 1);
+}
+
+static inline u64 dccp_delta_seqno(u64 seqno1, u64 seqno2)
+{
+ return ((seqno2 << 16) - (seqno1 << 16)) >> 16;
+}
+
/* is seq1 < seq2 ? */
static inline int before48(const u64 seq1, const u64 seq2)
{
@@ -313,27 +339,8 @@ static inline int dccp_packet_without_ac
return type == DCCP_PKT_DATA || type == DCCP_PKT_REQUEST;
}
-#define DCCP_MAX_SEQNO ((((u64)1) << 48) - 1)
#define DCCP_PKT_WITHOUT_ACK_SEQ (DCCP_MAX_SEQNO << 2)
-static inline void dccp_set_seqno(u64 *seqno, u64 value)
-{
- if (value > DCCP_MAX_SEQNO)
- value -= DCCP_MAX_SEQNO + 1;
- *seqno = value;
-}
-
-static inline u64 dccp_delta_seqno(u64 seqno1, u64 seqno2)
-{
- return ((seqno2 << 16) - (seqno1 << 16)) >> 16;
-}
-
-static inline void dccp_inc_seqno(u64 *seqno)
-{
- if (++*seqno > DCCP_MAX_SEQNO)
- *seqno = 0;
-}
-
static inline void dccp_hdr_set_seq(struct dccp_hdr *dh, const u64 gss)
{
struct dccp_hdr_ext *dhx = (struct dccp_hdr_ext *)((void *)dh +
-
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