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author | Ivo Calado <ivocalado@embedded.ufcg.edu.br> | 2010-10-11 20:40:04 +0200 |
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committer | Gerrit Renker <gerrit@erg.abdn.ac.uk> | 2010-10-12 06:57:42 +0200 |
commit | d196c9a5d4e150cdff675662214c80c69b906958 (patch) | |
tree | 0819ea92cdfe9c2ae9716a3eef920849a98c01b9 /net/dccp | |
parent | baf9e782e1dc4991edecfa3b8700cf8739c40259 (diff) | |
download | linux-stable-d196c9a5d4e150cdff675662214c80c69b906958.tar.gz linux-stable-d196c9a5d4e150cdff675662214c80c69b906958.tar.bz2 linux-stable-d196c9a5d4e150cdff675662214c80c69b906958.zip |
dccp: generalise data-loss condition
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@embedded.ufcg.edu.br>
Signed-off-by: Erivaldo Xavier <desadoc@gmail.com>
Signed-off-by: Leandro Sales <leandroal@gmail.com>
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Diffstat (limited to 'net/dccp')
-rw-r--r-- | net/dccp/dccp.h | 21 |
1 files changed, 15 insertions, 6 deletions
diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h index e051c774ef5c..60f4f9622ab3 100644 --- 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 { |