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SubjectRe: [PATCH] sctp: Restore 'resent' bit to avoid retransmitted chunks for RTT measurements
On 11/22/2013 10:18 PM, Vlad Yasevich wrote:
> On 11/22/2013 03:30 AM, Xufeng Zhang wrote:
>
>> From: Signed-off-by: Xufeng Zhang<xufeng.zhang@windriver.com>
>>
>> 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@windriver.com>
>> ---
>> include/net/sctp/structs.h | 1 +
>> net/sctp/output.c | 23 +++++++++++++----------
>> net/sctp/outqueue.c | 3 +++
>> net/sctp/sm_make_chunk.c | 1 +
>> 4 files changed, 18 insertions(+), 10 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..32c214d 100644
>> --- a/net/sctp/output.c
>> +++ b/net/sctp/output.c
>> @@ -467,17 +467,20 @@ int sctp_packet_transmit(struct sctp_packet *packet)
>> list_for_each_entry_safe(chunk, tmp,&packet->chunk_list, list) {
>> list_del_init(&chunk->list);
>> if (sctp_chunk_is_data(chunk)) {
>> - /* 6.3.1 C4) When data is in flight and when allowed
>> - * by rule C5, a new RTT measurement MUST be made each
>> - * round trip. Furthermore, new RTT measurements
>> - * SHOULD be made no more than once per round-trip
>> - * for a given destination transport address.
>> - */
>> -
>> - if (!tp->rto_pending) {
>> - chunk->rtt_in_progress = 1;
>> - tp->rto_pending = 1;
>> + if (!chunk->resent) {
>> + /* 6.3.1 C4) When data is in flight and when allowed
>> + * by rule C5, a new RTT measurement MUST be made each
>> + * round trip. Furthermore, new RTT measurements
>> + * SHOULD be made no more than once per round-trip
>> + * for a given destination transport address.
>> + */
>> +
>> + if (!tp->rto_pending) {
>>
> Could be combined as
> if (!chunk->resent&& !tp->rto_pending) {
>

Got it!

>
>> + 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;
>> diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
>> index fe69032..8fe89f8 100644
>> --- a/net/sctp/sm_make_chunk.c
>> +++ b/net/sctp/sm_make_chunk.c
>> @@ -1321,6 +1321,7 @@ struct sctp_chunk *sctp_chunkify(struct sk_buff *skb,
>> INIT_LIST_HEAD(&retval->list);
>> retval->skb = skb;
>> retval->asoc = (struct sctp_association *)asoc;
>> + retval->resent = 0;
>>
> Not needed due to zeroed out malloc.
>

Thank you!
Will send V2 later.



Thanks,
Xufeng

> -vlad
>
>
>> retval->singleton = 1;
>>
>> retval->fast_retransmit = SCTP_CAN_FRTX;
>>
>>
>
>



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