[Devel] [Users] nathelper/rtpproxy when both SIP UA are behind same NAT
Norman Brandinger
norm at goes.com
Mon Dec 5 02:53:49 CET 2005
Hi Tavis,
I tried your suggestion.
First, thanks for the information about using avp_printf() to save a
pseudo variable to an AVP. Either I overlooked the doc in regard to
this or there isn't any doc. Do you know if it's documented ? Seem to
recall a comment about this on the mailing list a while ago...??
It in my testing, $si = public IP address of the NAT Router which is
what was expected. However, $rd = the private IP of the callee.
Unfortunately the private ip isn't useful. A quick look at the location
table shows that the private IP stored in the "contact" column. It
appears that the value from the "received" column is what is needed. I
guess the question is: "after a lookup(), is the "received" column saved
in a pseudo variable ?
Regards,
Norm
Tavis P wrote:
> actually, this would be better
>
> avp_printf("i:401", "$rd");
>
> if ( avp_check("i:401", "eq/$src_ip/g") )
> {
> xlog("L_INFO", "\"$si\" == \"$rd\" ");
> }
>
> Tavis P wrote:
>
>
>> Opps i made a mistake, instead of "avp_write" you need to use
>> "avp_printf" to store the pseudo variable into an AVP
>> and when you are doing the comparison with avp_check you need an alias
>> defined for the second AVP otherwise you might end up comparing the AVP
>> with a literal value
>>
>>
>> modparam( "avpops", "avp_aliases", "dest_ip=i:401" )
>>
>> avp_printf("i:400", "$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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