[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
Constants renamed following a suggestion by Arnaldo.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/dccp/ackvec.c b/net/dccp/ackvec.c
index a086c63..01030f3 100644
--- a/net/dccp/ackvec.c
+++ b/net/dccp/ackvec.c
@@ -157,7 +157,7 @@
if (av != NULL) {
av->dccpav_buf_head = DCCP_MAX_ACKVEC_LEN - 1;
- av->dccpav_buf_ackno = DCCP_MAX_SEQNO + 1;
+ av->dccpav_buf_ackno = UINT48_MAX + 1;
av->dccpav_buf_nonce = av->dccpav_buf_nonce = 0;
av->dccpav_time.tv_sec = 0;
av->dccpav_time.tv_usec = 0;
diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index e33a9ed..a2c20a2 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -92,6 +92,32 @@
extern int sysctl_dccp_feat_send_ndp_count;
extern int sysctl_dccp_tx_qlen;
+/*
+ * 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);
+}
+
+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)
{
@@ -313,26 +339,7 @@
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;
-}
+#define DCCP_PKT_WITHOUT_ACK_SEQ (UINT48_MAX << 2)
static inline void dccp_hdr_set_seq(struct dccp_hdr *dh, const u64 gss)
{
