Message ID | 20091019051642.GA3366@gerrit.erg.abdn.ac.uk |
---|---|
State | Not Applicable, archived |
Delegated to: | David Miller |
Headers | show |
On Mon, Oct 19, 2009 at 02:16, Gerrit Renker <gerrit@erg.abdn.ac.uk> 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@erg.abdn.ac.uk> > --- > 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
--- 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 {
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@erg.abdn.ac.uk> --- net/dccp/dccp.h | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html