From: Ivo Calado <ivocalado@xxxxxxxxxxxxxxxxxxxx>
This patch generalises the task of determining data loss from RFC 4340, 7.7.1.
Let S_A, S_B be sequence numbers such that S_B is "after" S_A, and let
N_B be the NDP count of packet S_B. Then, using modulo-2^48 arithmetic,
D = S_B - S_A - 1 is an upper bound of the number of lost data packets,
D - N_B is an approximation of the number of lost data packets
(there are cases where this is not exact).
The patch implements this as
dccp_loss_count(S_A, S_B, N_B) := max(S_B - S_A - 1 - N_B, 0)
Signed-off-by: Ivo Calado <ivocalado@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Erivaldo Xavier <desadoc@xxxxxxxxx>
Signed-off-by: Leandro Sales <leandroal@xxxxxxxxx>
Signed-off-by: Gerrit Renker <gerrit@xxxxxxxxxxxxxx>
---
net/dccp/dccp.h | 21 +++++++++++++++------
1 files changed, 15 insertions(+), 6 deletions(-)
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -153,18 +153,27 @@ static inline u64 max48(const u64 seq1, const u64 seq2)
}
/**
- * dccp_loss_free - Evaluates condition for data loss from RFC 4340, 7.7.1
- * @s1: start sequence number
- * @s2: end sequence number
+ * dccp_loss_count - Approximate the number of lost data packets in a burst loss
+ * @s1: last known sequence number before the loss ('hole')
+ * @s2: first sequence number seen after the 'hole'
* @ndp: NDP count on packet with sequence number @s2
- * Returns true if the sequence range s1...s2 has no data loss.
*/
-static inline bool dccp_loss_free(const u64 s1, const u64 s2, const u64 ndp)
+static inline u64 dccp_loss_count(const u64 s1, const u64 s2, const u64 ndp)
{
s64 delta = dccp_delta_seqno(s1, s2);
WARN_ON(delta < 0);
- return (u64)delta <= ndp + 1;
+ delta -= ndp + 1;
+
+ return delta > 0 ? delta : 0;
+}
+
+/**
+ * dccp_loss_free - Evaluate condition for data loss from RFC 4340, 7.7.1
+ */
+static inline bool dccp_loss_free(const u64 s1, const u64 s2, const u64 ndp)
+{
+ return dccp_loss_count(s1, s2, ndp) == 0;
}
enum {
--
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