message from sctp getsockopt or sctp_opt_info show error

[Michael Tüxen]

On Sep 24, 2011, at 3:43 PM, jyl_2006 wrote:

> Recently , I use getsockopt or sctp_opt_info to get the information of sctp
> association message, both two function return value of 0, and that means
> they work well, but the result of testing show some error.
> 
> Here are the result that getting from function getsockopt or sctp_opt_info:
> 
> NO. ASSOC-ID STATE             RWND     UNACKDATA PENDDATA INSTRMS OUTSTRMS
> FRAG-POINT SPINFO-STATE SPINFO-CWDN SPINFO-SRTT SPINFO-RTO SPINFO-MTU
> 1   36       ESTABLISHED       57344    0         0        10      10      
> 1452       ACTIVE       4380        0           3000       1500
> 
> other datas have same value with the data show above.
> 
> But the message I get from wireshark ,show the value of RWND is changed
> ,when I get a sack.
It seems that you are using multiple socket options to get the above values.
It doesn't matter whether you use getsockopt() or sctp_opt_info() on FreeBSD.

Regarding the RWND: I assume that you print sasoc_peer_rwnd field of the
sctp_assocparams structure retrieved via the SCTP_ASSOCINFO socket option.

The number provided by the stack is the a_rwnd provided by the peer minus
the outstanding data. Doesn't that match you observation? If not, please
let me know how to reproduce the problem and which version of FreeBSD you
are using.

Best regards
Michael
> 
> So can anyone point out something we did wrong or steps we missed? 
> Thanks in advance. 
> 
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