[asterisk-dev] Problems with the ASTERISK-27206 patch.

[Joshua Colp]

On Tue, Jan 2, 2018, at 7:14 PM, Richard Mudgett wrote:
> The patch for https://issues.asterisk.org/jira/browse/ASTERISK-27206 which
> is committed in 7385d1e017e562afe64431606e857e704f86a16d causes a
> configuration regression by requiring the endpoint and identifier method
> to agree to match the endpoint.  Doing so is redundant for methods that
> explicitly specify which endpoints they match.  The redundancy allows
> configuration errors that cannot be caught when the configuration is
> loaded.

Can you clarify what the precise regression you are referring to is? Even after reading this email I'm still unclear.

> 
> Relevant endpoint 101 configuration values:
> 
> [global]
> ; The order by which endpoint identifier methods are given priority.
> ; The endpoint_identifier_order default is
> ;endpoint_identifier_order=ip,username,anonymous
> 
> [101]
> type=endpoint
> ; The identify_by default is
> ;identify_by=username
> 
> [identify_me]
> type=identify
> endpoint=101
> ; Match by some IP address
> match=127.0.0.1/24
> 
> Before the patch, the 101 endpoint above would identify by either the
> username endpoint identifier method or the
> res_pjsip_endpoint_identifier_ip endpoint identifier method's
> [identify_me] section.
> 
> After the patch, the 101 endpoint is still matched by either method.
> However, the identify_by default had to change to "username,ip" and the
> option meaning had to change slightly do it.  I think this is wrong.  If
> you went to the trouble to create an [identify_me] section which must
> explicitly specify the endpoint it matches then the endpoint should not
> need to also specify in the identify_by value that it is identified by the
> res_pjsip_endpoint_identifier_ip method.  Doing so is redundant and will
> cause unnecessary configuration errors.

I think removing the redundant requirement is a nice improvement for the future, but that comes at a cost to do it in a way that is user friendly and automatic.
 
> The goal of ASTERISK-27206 is to prevent the endpoint from being
> identified by the username identification method so it could only be
> identified by the res_pjsip_endpoint_identifier_ip method.  The key
> difference between the two methods is the username identification method
> has no other configuration than the endpoint's identify_by value available
> to specify to which endpoint the method applies.
> 
> I think the previous and current identify_by documentation is a bit
> misleading in any case.  The identify_by option historically specified
> which identification methods that have no other configuration requirements
> can match the endpoint.  i.e., The username and auth_username
> identification methods.  To satisfy ASTERISK-27206, what is needed for the
> identify_by option is a value to prevent methods that have no other
> configuration requirements from matching the endpoint.

The identify_by option was originally an option which listed the endpoint identifiers that an endpoint could be identified by. That was its original goal. It later evolved slightly with the addition of auth_username to also influence how. The addition of "ip" goes back to its original goal. Over all the option has muddied meaning.

I disagree that whether an endpoint identifier is configurable or not has a bearing on its naming or meaning in identify_by. The configuration may imply that it should only be matched using that identifier, but that is not currently something that is done and is of a greater scope. I think having a global identify_by option which could actually mean multiple endpoint identifiers by itself is also confusing and hard to define the behavior of.

Really what this just illustrates is that the option itself has evolved and hasn't been clearly defined with a strict purpose. I don't think now is the right time to solve that particular problem. If there is a defined use case which is currently broken by the change though, that is something we need to fix.

-- 
Joshua Colp
Digium, Inc. | Senior Software Developer
445 Jan Davis Drive NW - Huntsville, AL 35806 - US
Check us out at: www.digium.com & www.asterisk.org