[OpenSIPS-Users] Opensips should reply "SIP/2.0 200 canceling" to CANCEL after forwarding ? or wait after reply

[Julien Chavanton]

Hi, regarding handling of CANCEL request,
 
Please correct me if I am wrong,
 
I have glare condition on how Opensips handled Cancel requests.
The problem is taht Opensips respond "487 Request terminated" strait after forwarding the CANCEL but it does not know if the targe UA will accept it.
 
I think it should wait after the target UA to reply before, as this can create out of sync situation if there is a problem with the target.
in this senario the "200 OK" is  received at the same time as the CANCEL is sent, in this case the target UA as the right to ignore the CANCEL because it as generated a final response.
 
 
UA -----> CANCEL ------------------------> osips
UA <------ SIP/2.0 200 canceling --------> osips
                                           osips <--- 200 OK <-- UA
                                           osips ---> CANCEL --> UA
UA <---- SIP/2.0 487 Request Terminated -> osips
 
 
 
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