Re: [PATCH] net: sctp: set chunk->tsn_gap_acked at the end of cycle

[Chang]

On 11/22/2013 03:27 PM, Vlad Yasevich wrote:
> On 11/22/2013 02:49 AM, Chang Xiangzhong wrote:
> > tsn_gap_acked is an important state flag in chunk, which indicates if the
> > chunk has been acked in gap reports before.
> Actually, this bit indicates simply that the chunk has been acked.  It
> doesn't state whether it's been acked in a gap report or via cumulative tsn.
Thanks for pointing this out. Sorry for not having made that clear.
> > SFR-CACC algorithm depends on this
> > variable. So set this at the end of each iteration, otherwise the SFR-CACC
> > algorithm would never be toggled.
> >
> > Signed-off-by: Chang Xiangzhong <changxiangzhong@xxxxxxxxx>
> > ---
> >   net/sctp/outqueue.c | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
> > index 1b494fa..bff828c 100644
> > --- a/net/sctp/outqueue.c
> > +++ b/net/sctp/outqueue.c
> > @@ -1396,7 +1396,6 @@ static void sctp_check_transmitted(struct sctp_outq *q,
> >   			 * while DATA was outstanding).
> >   			 */
> >   			if (!tchunk->tsn_gap_acked) {
> > -				tchunk->tsn_gap_acked = 1;
> >   				if (TSN_lt(*highest_new_tsn_in_sack, tsn))
> >   					*highest_new_tsn_in_sack = tsn;
> >   				bytes_acked += sctp_data_size(tchunk);
> > @@ -1460,6 +1459,8 @@ static void sctp_check_transmitted(struct sctp_outq *q,
> >   				 */
> >   				list_add_tail(lchunk, &tlist);
> >   			}
> > +
> > +			tchunk->tsn_gap_acked = 1;
> The current code will set the state if it hasn't been set yet.  Why is
> this needed?
Because in line 1420 ~ 1440 The SFR-CACC algorithms use tsn_gap_acked. 
That "if block" would never be triggered because the varaiable's been 
set. That's why I move the "state changing sentence" to the end of the 
iteration.
> Now there is an issue with tracking highest_new_tsn_in_sack.  The spec
> is a little vague on this, but the highest_new_tsn_in_sack only supposed
> to track tsns that have not been resent.  If a tsn has been reneged, and
> then sent again, it is not considered 'new' thus should not count
> toward highest_new_tsn_in_sack.  We currently do not track this right.
I'll try to figure this out.
> -vlad
>
> -vlad
>
> >   		} else {
> >   			if (tchunk->tsn_gap_acked) {
> >   				pr_debug("%s: receiver reneged on data TSN:0x%x\n",

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