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

On 11/22/2013 03:27 PM, Vlad Yasevich wrote:

On 11/22/2013 02:49 AM, Chang Xiangzhong wrote:

quoted

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.

quoted

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 <redacted>
---
  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

quoted

  		} else {
  			if (tchunk->tsn_gap_acked) {
  				pr_debug("%s: receiver reneged on data TSN:0x%x\n",