[V2 PATCH] sctp: Restore 'resent' bit to avoid retransmitted chunks for RTT measurements

From: Xufeng Zhang
Date: Sun Nov 24 2013 - 22:23:23 EST


Currently retransmitted DATA chunks could also be used for
RTT measurements since there are no flag to identify whether
the transmitted DATA chunk is a new one or a retransmitted one.
This problem is introduced by commit ae19c5486 ("sctp: remove
'resent' bit from the chunk") which inappropriately removed the
'resent' bit completely, instead of doing this, we should set
the resent bit only for the retransmitted DATA chunks.

Signed-off-by: Xufeng Zhang <xufeng.zhang@xxxxxxxxxxxxx>
---
v1->v2:
Rmoved initialization for resent bit.
Combined two if clause

include/net/sctp/structs.h | 1 +
net/sctp/output.c | 3 ++-
net/sctp/outqueue.c | 3 +++
3 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index 2174d8d..ea0ca5f 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -629,6 +629,7 @@ struct sctp_chunk {
#define SCTP_NEED_FRTX 0x1
#define SCTP_DONT_FRTX 0x2
__u16 rtt_in_progress:1, /* This chunk used for RTT calc? */
+ resent:1, /* Has this chunk ever been resent. */
has_tsn:1, /* Does this chunk have a TSN yet? */
has_ssn:1, /* Does this chunk have a SSN yet? */
singleton:1, /* Only chunk in the packet? */
diff --git a/net/sctp/output.c b/net/sctp/output.c
index e650978..0e2644d 100644
--- a/net/sctp/output.c
+++ b/net/sctp/output.c
@@ -474,10 +474,11 @@ int sctp_packet_transmit(struct sctp_packet *packet)
* for a given destination transport address.
*/

- if (!tp->rto_pending) {
+ if (!chunk->resent && !tp->rto_pending) {
chunk->rtt_in_progress = 1;
tp->rto_pending = 1;
}
+
has_data = 1;
}

diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
index 94df758..70f4f56 100644
--- a/net/sctp/outqueue.c
+++ b/net/sctp/outqueue.c
@@ -446,6 +446,8 @@ void sctp_retransmit_mark(struct sctp_outq *q,
transport->rto_pending = 0;
}

+ chunk->resent = 1;
+
/* Move the chunk to the retransmit queue. The chunks
* on the retransmit queue are always kept in order.
*/
@@ -1375,6 +1377,7 @@ static void sctp_check_transmitted(struct sctp_outq *q,
* instance).
*/
if (!tchunk->tsn_gap_acked &&
+ !tchunk->resent &&
tchunk->rtt_in_progress) {
tchunk->rtt_in_progress = 0;
rtt = jiffies - tchunk->sent_at;
--
1.7.0.2

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/