[Devel] [Users] nathelper/rtpproxy when both SIP UA are behind same NAT

[Tavis P]

Opps i made a mistake, instead of "avp_write" you need to use
"avp_printf" to store the pseudo variable into an AVP
and when you are doing the comparison with avp_check you need an alias
defined for the second AVP otherwise you might end up comparing the AVP
with a literal value


        modparam( "avpops", "avp_aliases", "dest_ip=i:401" )

        avp_printf("i:400", "$si");
        avp_printf("i:401", "$rd");

        if ( avp_check("i:400", "eq/$dest_ip/g") )
        {
            xlog("L_INFO", "\"$si\" == \"$rd\"  ");
        }


Norman Brandinger wrote:

> I agree that the solution that was presented is BAD for the reasons
> stated by both of us and probably more :)
>
> Perhaps using $Ri after the successful lookup() and comparing it to
> the $src_ip AVP would work.
>
> The problem was trying to compare a pseudo variable with an AVP.
>
>
> The doc <snipped below> does not state that pseudo variables can be
> used by avp_write().
>
> Pseudo-variables can be used with following modules of OpenSER:
>
> * avpops - function “avp_printf()”
> * xlog - functions “xlog()” and “xdbg()”
>
> I did try to use avp_write() to save a pseudo variable to an AVP but
> was unsuccessful.
>
> Do you have an example of writing a pseudo variable to an AVP ?
>
> Regards,
> Norm
>
>
>
> Tavis P wrote:
>
>> Another, more lightweight solution, is:
>>
>> After a successful lookup(location) you can compare the received IP
>> address ($si) with the destination domain/ip address returned from the
>> "lookup" function call ($rd), i think these two pieces of information
>> are reliable for this purpose
>>
>> This way you don't have to make extra database calls to determine
>> locality
>>
>> Also if you want to compare pseudo variables you can first write them to
>> an AVP using "avp_write" and then you can make use of "avp_check" with
>> data sourced from a pseudo variable
>>
>> Norman Brandinger wrote:
>>
>>  
>>
>>> I have looked into the problem related to saving saving resources by
>>> not calling rtpproxy or mediaproxy when both the caller and callee are
>>> behind the same NAT.
>>>
>>> This topic has been discussed many times however, there have been no
>>> "working" examples, or even partial examples posted (that I'm aware
>>> of).
>>>
>>> Below is a solution to the problem, but is a BAD hack at best.
>>>
>>> This solution is BAD because AVP's are added to the usr_preferences
>>> table during the registration process, but there is no notification
>>> that a registration has expired and is no longer valid.  A cron job
>>> could be run periodically to delete all received_ip AVP's with no
>>> matching entry in the location table, but this is another hack to fix
>>> the first hack.
>>>
>>> The solution is BAD because a database calls must be made to save the
>>> received_ip address into an AVP, then another database call must be
>>> made to reload the value just so that it can be tested against the
>>> caller's $src_ip.  A pseudo variable $Ri already exists that contains
>>> the value we use in received_ip, but I have not been able to find a
>>> way for avp_check() to use $Ri.
>>>
>>> The solution is BAD because it will fail when the SIP device(s) are
>>> behind more than a single NAT router.  I believe this is not an issue
>>> for 95% of the users and 99% of the small office or home users.
>>>
>>> I think that a better solution would be to enhance avp_check() to
>>> accept pseudo variables for the "value" parameter.  This would remove
>>> the need for any database calls.
>>>
>>> I'm cross-posting this response to the developers list to bring this
>>> to their attention and ask for suggestions (it's possible that I've
>>> totally missed something).  If a decision is made to open the avpops
>>> module to pseudo variables (other than just avp_print()), I would
>>> suggest the following be looked at:
>>>
>>> avp_check() the value parm should accept pseudo variables
>>> avp_write() the value parm should accept pseudo variables
>>> avp_pushto() the name parameter should accept pseudo variables
>>> avp_op() the value parameter should accept pseudo variables
>>>
>>> Regards,
>>> Norm
>>>
>>>
>>> 1) During REGISTER processing, place the following code.  I would
>>> suggest that you put the code "after" all authentication checks and
>>> "after" the save("location") statement.
>>>
>>>  # Delete any previously saved IP addressess from the user.
>>>  avp_db_delete("$from/username","s:received_ip");
>>>
>>>  # Save the source IP address of the user into an AVP called
>>> received_ip.
>>>  # The saved IP address should be the public address of the NAT router.
>>>  avp_write("$src_ip", "s:received_ip");
>>>
>>>  # Save the AVP received_ip into the usr_preferences tables associated
>>> with the user that just registered
>>>  avp_db_store("$from/username","s:received_ip");
>>>
>>> 2) During INVITE processing (or wherever you make the decision to use
>>> or not use rtpproxy / mediaproxy) , place the following code.
>>>
>>>  
>>> #---------------------------------------------------------------------------
>>>
>>>
>>>  # Are the caller and callee behind the same NAT ?
>>>  
>>> #---------------------------------------------------------------------------
>>>
>>>
>>>  avp_db_load("$to/username", "s:received_ip");
>>>  if (avp_check("s:received_ip", "eq/$src_ip")) {
>>>    setflag(CALLER_AND_CALLEE_ ARE_BEHIND_THE_SAME_NAT);
>>>  };
>>>
>>>
>>>
>>> _______________________________________________
>>> Devel mailing list
>>> Devel at openser.org
>>> http://openser.org/cgi-bin/mailman/listinfo/devel
>>>
>>>
>>>     
>>
>>
>>
>>
>>   
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