On Tue, Nov 13, 2012 at 07:46:20AM +0100, Schoch Christian wrote:
> The calculation of RTTVAR involves the subtraction of two unsigned
> numbers which
> may causes rollover and results in very high values of RTTVAR when RTT > SRTT.
> With this patch it is possible to set RTOmin = 1 to get the minimum of RTO at
> 4 times the clock granularity.
>
>
> Change Notes:
>
> v2)
> *Replaced abs() by abs64() and long by __s64, changed patch
> description.
>
> Signed-off-by: Christian Schoch <e0326715@xxxxxxxxxxxxxxxxxxxx>
> CC: Vlad Yasevich <vyasevich@xxxxxxxxx>
> CC: Sridhar Samudrala <sri@xxxxxxxxxx>
> CC: Neil Horman <nhorman@xxxxxxxxxxxxx>
> CC: linux-sctp@xxxxxxxxxxxxxxx
> ---
>
> diff --git a/net/sctp/transport.c b/net/sctp/transport.c
> index 953c21e..206cf52 100644
> --- a/net/sctp/transport.c
> +++ b/net/sctp/transport.c
> @@ -331,7 +331,7 @@ void sctp_transport_update_rto(struct
> sctp_transport *tp, __u32 rtt)
> * 1/8, rto_alpha would be expressed as 3.
> */
> tp->rttvar = tp->rttvar - (tp->rttvar >> net->sctp.rto_beta)
> - + ((abs(tp->srtt - rtt)) >> net->sctp.rto_beta);
> + + (((__u32)abs64((__s64)tp->srtt -
> (__s64)rtt)) >> net->sctp.rto_beta);
> tp->srtt = tp->srtt - (tp->srtt >> net->sctp.rto_alpha)
> + (rtt >> net->sctp.rto_alpha);
> } else {
> --
>
> --
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>
Acked-by: Neil Horman <nhorman@xxxxxxxxxxxxx>
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