Subject: Re: [PATCH] For for each TSN t being newly acked (Not only cumulatively, but also SELECTIVELY) cacc_saw_newack should be set to 1.

From: Vlad Yasevich <[email-masked]>
Date: Tue, 15 Oct 2013 13:25:06 -0400

On 10/15/2013 12:59 PM, Chang Xiangzhong wrote:
> Signed-off-by: Xiangzhong Chang <[email-masked]>
> ---
>   net/sctp/outqueue.c |  142 ++++++++++++++++++++++++---------------------------
>   1 file changed, 68 insertions(+), 74 deletions(-)
>
> diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
> index 94df758..f10d848 100644
> --- a/net/sctp/outqueue.c
> +++ b/net/sctp/outqueue.c
> @@ -1357,84 +1357,78 @@ static void sctp_check_transmitted(struct sctp_outq *q,
>
>   		tsn = ntohl(tchunk->subh.data_hdr->tsn);
>   		if (sctp_acked(sack, tsn)) {
> -			/* If this queue is the retransmit queue, the
> -			 * retransmit timer has already reclaimed
> -			 * the outstanding bytes for this chunk, so only
> -			 * count bytes associated with a transport.
> -			 */
> -			if (transport) {
> -				/* If this chunk is being used for RTT
> -				 * measurement, calculate the RTT and update
> -				 * the RTO using this value.
> -				 *
> -				 * 6.3.1 C5) Karn's algorithm: RTT measurements
> -				 * MUST NOT be made using packets that were
> -				 * retransmitted (and thus for which it is
> -				 * ambiguous whether the reply was for the
> -				 * first instance of the packet or a later
> -				 * instance).
> -				 */
> -				if (!tchunk->tsn_gap_acked &&
> -				    tchunk->rtt_in_progress) {
> -					tchunk->rtt_in_progress = 0;
> -					rtt = jiffies - tchunk->sent_at;
> -					sctp_transport_update_rto(transport,
> -								  rtt);
> -				}
> -			}
> -
> -			/* If the chunk hasn't been marked as ACKED,
> -			 * mark it and account bytes_acked if the
> -			 * chunk had a valid transport (it will not
> -			 * have a transport if ASCONF had deleted it
> -			 * while DATA was outstanding).
> -			 */
>   			if (!tchunk->tsn_gap_acked) {
> -				tchunk->tsn_gap_acked = 1;
> -				*highest_new_tsn_in_sack = tsn;
> -				bytes_acked += sctp_data_size(tchunk);
> -				if (!tchunk->transport)
> -					migrate_bytes += sctp_data_size(tchunk);
> -				forward_progress = true;
> +			    /* If this queue is the retransmit queue, the
> +			     * retransmit timer has already reclaimed
> +			     * the outstanding bytes for this chunk, so only
> +			     * count bytes associated with a transport.
> +			     *
> +			     * If this chunk is being used for RTT
> +			     * measurement, calculate the RTT and update
> +			     * the RTO using this value.
> +			     *
> +			     * 6.3.1 C5) Karn's algorithm: RTT measurements
> +			     * MUST NOT be made using packets that were
> +			     * retransmitted (and thus for which it is
> +			     * ambiguous whether the reply was for the
> +			     * first instance of the packet or a later
> +			     * instance).
> +			     */
> +			    if (transport && tchunk->rtt_in_progress) {
> +				tchunk->rtt_in_progress = 0;
> +				rtt = jiffies - tchunk->sent_at;
> +				sctp_transport_update_rto(transport,
> +					rtt);
> +			    }
> +
> +			    /* If the chunk hasn't been marked as ACKED,
> +			     * mark it and account bytes_acked if the
> +			     * chunk had a valid transport (it will not
> +			     * have a transport if ASCONF had deleted it
> +			     * while DATA was outstanding).
> +			     */
> +			    tchunk->tsn_gap_acked = 1;
> +			    *highest_new_tsn_in_sack = tsn;
> +			    bytes_acked += sctp_data_size(tchunk);
> +			    if (!tchunk->transport)
> +				migrate_bytes += sctp_data_size(tchunk);
> +			    forward_progress = true;
> +
> +			    /*
> +			     * SFR-CACC algorithm:
> +			     * 2) If the SACK contains gap acks
> +			     * and the flag CHANGEOVER_ACTIVE is
> +			     * set the receiver of the SACK MUST
> +			     * take the following action:
> +			     *
> +			     * B) For each TSN t being acked that
> +			     * has not been acked in any SACK so
> +			     * far, set cacc_saw_newack to 1 for
> +			     * the destination that the TSN was
> +			     * sent to.
> +			     */
> +			    if (transport &&
> +				    sack->num_gap_ack_blocks &&
> +				    q->asoc->peer.primary_path->cacc.
> +				    changeover_active)
> +				transport->cacc.cacc_saw_newack = 1;
>   			}

Indents should be tab based.
This is a bit more of a re-write that is needed for the this particualar 
patch.  What's wrong with just doing this?

@@ -1396,6 +1396,25 @@ static void sctp_check_transmitted(struct 
sctp_outq *q,
                                 if (!tchunk->transport)
                                         migrate_bytes += 
sctp_data_size(tchunk);
                                 forward_progress = true;
+
+                               /*
+                                * SFR-CACC algorithm:
+                                * 2) If the SACK contains gap acks
+                                * and the flag CHANGEOVER_ACTIVE is
+                                * set the receiver of the SACK MUST
+                                * take the following action:
+                                *
+                                * B) For each TSN t being acked that
+                                * has not been acked in any SACK so
+                                * far, set cacc_saw_newack to 1 for
+                                * the destination that the TSN was
+                                * sent to.
+                                */
+                               if (transport &&
+                                   sack->num_gap_ack_blocks &&
+                                   q->asoc->peer.primary_path->cacc.
+                                   changeover_active)
+                                       transport->cacc.cacc_saw_newack = 1;
                         }

                         if (TSN_lte(tsn, sack_ctsn)) {

-vlad

>
>   			if (TSN_lte(tsn, sack_ctsn)) {
> -				/* RFC 2960  6.3.2 Retransmission Timer Rules
> -				 *
> -				 * R3) Whenever a SACK is received
> -				 * that acknowledges the DATA chunk
> -				 * with the earliest outstanding TSN
> -				 * for that address, restart T3-rtx
> -				 * timer for that address with its
> -				 * current RTO.
> -				 */
> -				restart_timer = 1;
> -				forward_progress = true;
> -
> -				if (!tchunk->tsn_gap_acked) {
> -					/*
> -					 * SFR-CACC algorithm:
> -					 * 2) If the SACK contains gap acks
> -					 * and the flag CHANGEOVER_ACTIVE is
> -					 * set the receiver of the SACK MUST
> -					 * take the following action:
> -					 *
> -					 * B) For each TSN t being acked that
> -					 * has not been acked in any SACK so
> -					 * far, set cacc_saw_newack to 1 for
> -					 * the destination that the TSN was
> -					 * sent to.
> -					 */
> -					if (transport &&
> -					    sack->num_gap_ack_blocks &&
> -					    q->asoc->peer.primary_path->cacc.
> -					    changeover_active)
> -						transport->cacc.cacc_saw_newack
> -							= 1;
> -				}
> -
> -				list_add_tail(&tchunk->transmitted_list,
> -					      &q->sacked);
> +			    /* RFC 2960  6.3.2 Retransmission Timer Rules
> +			     *
> +			     * R3) Whenever a SACK is received
> +			     * that acknowledges the DATA chunk
> +			     * with the earliest outstanding TSN
> +			     * for that address, restart T3-rtx
> +			     * timer for that address with its
> +			     * current RTO.
> +			     */
> +			    restart_timer = 1;
> +			    forward_progress = true;
> +
> +			    list_add_tail(&tchunk->transmitted_list,
> +				    &q->sacked);
>   			} else {
>   				/* RFC2960 7.2.4, sctpimpguide-05 2.8.2
>   				 * M2) Each time a SACK arrives reporting
>