* One question regarding the SCTP write buffer free mechanism
@ 2020-03-26 5:22 Mao, Jinhui (NSB - CN/Hangzhou)
2020-03-26 19:29 ` Marcelo Ricardo Leitner
2020-03-27 4:57 ` Mao, Jinhui (NSB - CN/Hangzhou)
0 siblings, 2 replies; 3+ messages in thread
From: Mao, Jinhui (NSB - CN/Hangzhou) @ 2020-03-26 5:22 UTC (permalink / raw)
To: linux-sctp
Dear Linux SCTP experts.
Recently we found a SCTP problem in our product, the scenario can be described as follow
Endpoint A Endpoint Z
{App sends 3 messages; strm 0} DATA [TSN=6] ---------------> (ack)
DATA [TSN=7] ---------------> (lost)
DATA [TSN=8] ---------------> (gap detected,immediately send ack)
/----- SACK [TSN Ack=6,Block=1, Start=2,End=2]
<-----/
......
DATA [TSN\x10] ---------------> (gap detected,immediately send ack)
/----- SACK [TSN Ack=6,Block=1, Start=2,End=4]
<-----/ (3 SACK to indicate that TSN=7 lost, fast re-trans triggered)
Re-trans DATA [TSN=7] ---------------> (also lost)
DATA [TSN\x11] ---------------> (gap detected,immediately send ack)
/----- SACK [TSN Ack=6,Block=1, Start=2,End=5]
<-----/
......
DATA [TSN40] ---------------> (gap detected,immediately send ack)
/----- SACK [TSN Ack=6,Block=1, Start=2,End34]
<-----/
Error happened on Endpoint A when calling SCTP sendmsg to send more to Endpoint B, the error is "Resource temporarily unavailable". Association is not destroyed at this time.
1 second later RTO Timeout 2nd Re-trans DATA [TSN=7] ---------------> (Acked)
So could you please help to comments on the following question?
- Does this means that if an gap is found in the SACK, those packages sent after this lost packet will stay in the write buffer until the gap is filled? Even if they are successfully SACKed?
Thanks a lot!
Best Regards!
Mao Jinhui
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: One question regarding the SCTP write buffer free mechanism
2020-03-26 5:22 One question regarding the SCTP write buffer free mechanism Mao, Jinhui (NSB - CN/Hangzhou)
@ 2020-03-26 19:29 ` Marcelo Ricardo Leitner
2020-03-27 4:57 ` Mao, Jinhui (NSB - CN/Hangzhou)
1 sibling, 0 replies; 3+ messages in thread
From: Marcelo Ricardo Leitner @ 2020-03-26 19:29 UTC (permalink / raw)
To: linux-sctp
On Thu, Mar 26, 2020 at 05:22:46AM +0000, Mao, Jinhui (NSB - CN/Hangzhou) wrote:
...
> Error happened on Endpoint A when calling SCTP sendmsg to send more to Endpoint B, the error is "Resource temporarily unavailable". Association is not destroyed at this time.
> 1 second later RTO Timeout 2nd Re-trans DATA [TSN=7] ---------------> (Acked)
>
>
> So could you please help to comments on the following question?
> - Does this means that if an gap is found in the SACK, those packages sent after this lost packet will stay in the write buffer until the gap is filled? Even if they are successfully SACKed?
Yes and yes. Because the receiver is allowed to drop any data acked in
a gap block if it needs more memory to fill in the gap, and in this
case, the sender would have to retransmit it.
Seems you're using non-block sockets, otherwise that last sendmsg()
would have blocked waiting for the sndbuf space to be available, btw.
Cheers,
Marcelo
^ permalink raw reply [flat|nested] 3+ messages in thread
* RE: One question regarding the SCTP write buffer free mechanism
2020-03-26 5:22 One question regarding the SCTP write buffer free mechanism Mao, Jinhui (NSB - CN/Hangzhou)
2020-03-26 19:29 ` Marcelo Ricardo Leitner
@ 2020-03-27 4:57 ` Mao, Jinhui (NSB - CN/Hangzhou)
1 sibling, 0 replies; 3+ messages in thread
From: Mao, Jinhui (NSB - CN/Hangzhou) @ 2020-03-27 4:57 UTC (permalink / raw)
To: linux-sctp
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^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2020-03-27 4:57 UTC | newest]
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2020-03-26 5:22 One question regarding the SCTP write buffer free mechanism Mao, Jinhui (NSB - CN/Hangzhou)
2020-03-26 19:29 ` Marcelo Ricardo Leitner
2020-03-27 4:57 ` Mao, Jinhui (NSB - CN/Hangzhou)
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