On Mon, Oct 19, 2009 at 02:16, Gerrit Renker <gerrit@xxxxxxxxxxxxxx> wrote:
> dccp: Generalise data-loss condition
>
> This patch is thanks to Ivo Calado who had integrated this function into one
> of the TFRC-SP patches.
>
> It generalises the task of determining data loss from RFC 43430, 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 module-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: Gerrit Renker <gerrit@xxxxxxxxxxxxxx>
> ---
> net/dccp/dccp.h | 21 +++++++++++++++------
> 1 file 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,
> }
>
> /**
> - * 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 {
>
Agree
--
Ivo Augusto Andrade Rocha Calado
MSc. Candidate
Embedded Systems and Pervasive Computing Lab - http://embedded.ufcg.edu.br
Systems and Computing Department - http://www.dsc.ufcg.edu.br
Electrical Engineering and Informatics Center - http://www.ceei.ufcg.edu.br
Federal University of Campina Grande - http://www.ufcg.edu.br
PGP: 0x03422935
Putt's Law:
Technology is dominated by two types of people:
Those who understand what they do not manage.
Those who manage what they do not understand.
--
To unsubscribe from this list: send the line "unsubscribe dccp" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
