[Asterisk-Dev] [BUG?] chan_sip, RFC 3261 and multiple UACs registering for one account

[Kevin P. Fleming]

Hartwig Deneke wrote:

> I respect the decision of Asterisk developers to  support only one 
> device per channel. However, from a usability perspective, it seems 
> terrible to let the REGISTER requests of two devices succeed 
> successfully, making both devices think they are in REGISTERed state, 
> while this is actually not the case. It would be far better to fail the 
> second registration then.

If you can give us an absolutely 100% guaranteed way to know that the 
second REGISTER is not coming from the same device (which has just 
moved), then we can reject the second one.

However, I already know the answer to that question: you can't. There is 
no way to conclusively prove that a REGISTER is not coming from the same 
device that already registered with us.

> sipsak indeed sends no Contact header, if empty is specified as 
> command-line parameter. Asterisk does not find the Contact field, and 
> assumes an empty contact, which is used to overwrite the previous 
> contact. So anyone wanting to query for currently registered contacts, 
> e.g. to verify a successful registration  will kick out just this 
> registration.

That is a bug, please post it. Thanks for the debugging :-)