On Wed, Jan 18, 2017 at 10:53 PM, Michael Tuexen
<Michael.Tuexen@xxxxxxxxxxxxxxxxx> wrote:
>> On 18 Jan 2017, at 07:01, Xin Long <lucien.xin@xxxxxxxxx> wrote:
>>
>> On Wed, Jan 18, 2017 at 12:38 AM, Marcelo Ricardo Leitner
>> <marcelo.leitner@xxxxxxxxx> wrote:
>>> On Tue, Jan 17, 2017 at 02:07:52PM +0100, Julian Cordes wrote:
>>>> When a FORWARD-TSN-Chunk with a relative high cum-tsn-value is injected
>>>> then the linux kernel ignores this valid FORWARD-TSN-Chunk.
>>>> It should instead send an SACK-Chunk where the cum_tsn is equal to the
>>>> cum_tsn specified in the FORWARD-TSN.
>>>
>>> You mean, with the cum_tsn specified on the *injected* FORWARD-TSN.
>>> Is that so?
>> from the test script
>> +0.0 < sctp: FORWARD_TSN[cum_tsn=99999, ids=[{1, 1}]]
>> I think so.
>>
>> But 99999 is so high relative to the base_tsn of tsnmap,
>> it overflowed tsnmap, such a big gap is disallowed in linux
>> sctp. it has to drop this packet.
>>
>> /* Verify that we can hold this TSN and that it will not
>> * overlfow our map
>> */
>> if (!TSN_lt(tsn, map->base_tsn + SCTP_TSN_MAP_SIZE))
>> return -1;
>>
>> Hi, Julian, maybe you can improve your script by using a lower
>> value for linux.
> but this would mean that Linux only supports the peer skipping some small number of TSN's.
> Isn't this a limitation of the implementation?
not really, there is map->base_tsn, it will grow when the tsn has been sacked.
like tsn=8000 and below 8000 have been sacked, map->base_tsn could be
8000, then the map range would be 8000 ~ 8000 + SCTP_TSN_MAP_SIZE.
But the test case sent tsn=1, then try to skip tsn=99999, that's really not
a normal case.
and to set SCTP_TSN_MAP_SIZE=4096 for reasons:
/* Guess at how big to make the TSN mapping array.
* We guarantee that we can handle at least this big a gap between the
* cumulative ACK and the highest TSN. In practice, we can often
* handle up to twice this value.
*
* NEVER make this more than 32767 (2^15-1). The Gap Ack Blocks in a
* SACK (see section 3.3.4) are only 16 bits, so 2*SCTP_TSN_MAP_SIZE
* must be less than 65535 (2^16 - 1), or we will have overflow
* problems creating SACK's.
*/
#define SCTP_TSN_MAP_INITIAL BITS_PER_LONG
#define SCTP_TSN_MAP_INCREMENT SCTP_TSN_MAP_INITIAL
#define SCTP_TSN_MAP_SIZE 4096
>
> Best regards
> Michael
>>
>>>
>>>>
>>>> Testscript available at:
>>>> https://github.com/nplab/PR_SCTP_Testsuite/blob/master/forward-tsn/receiver-side-implementation/receiver-side-implementation-11.pkt
>>>
>>>
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