Hi Marco!

As Patrick suggested, adding the a:sendonly line in RTP should instruct the caller not to send any RTP. However, if I remember correctly, I've seen legitimate clients that still send RTP. On a different note, they are sending RTP to a media gateway, right? And most likely the B part will ignore all the RTP.

Best regards,

Răzvan Crainea
OpenSIPS Solutions
www.opensips-solutions.com

On 01/22/2015 02:50 PM, Patrick Wakano wrote:
Ok Marco,
Your concern is with hackers and not misuse! Really valid nowadays!

Patrick

On Thu, Jan 22, 2015 at 8:32 AM, Marco Hierl <[email protected] <mailto:[email protected]>> wrote:

    Hi Patrik,

    thanks for this idea!

    I did not say clear enough: I’m afraid that anybody can cheat us.
    My intention is to assure that our interconnection partners (or
    their customers) do not have the possibility to make a
    conversation without being charged.

    Sending the indication “a:sendonly” only means, that the client is
    told not to send RTP, but IF it send RTP anyway then the RTPproxy
    leads in on to the callee. So, it is not in my hands then!

    Best regards from Hamburg

      Marco

    *Von:*[email protected]
    <mailto:[email protected]>
    [mailto:[email protected]
    <mailto:[email protected]>] *Im Auftrag von
    *Patrick Wakano
    *Gesendet:* Donnerstag, 22. Januar 2015 11:16
    *An:* OpenSIPS users mailling list

    *Betreff:* Re: [OpenSIPS-Users] rtpproxy sends rtp from caller to
    callee before 200OK

    Have you tried to insert a "a:sendonly" line in your SDP body when
    sending it to the caller?
    If the client receives such line it should not send media...

    Then in the 200Ok you can put an "a:sendrecv" line to establish
    full media path!

    It's just an idea, I'm not sure if it will really work...

    Patrick

    On Thu, Jan 22, 2015 at 6:51 AM, Marco Hierl
    <[email protected] <mailto:[email protected]>>
    wrote:

    Hi Răzvan,

    Ok, thanks for your answer!

    Unfortunately we are offering „early media“ to our customers (call
    center, radio station, and other companies) and lots of them like
    to play a free-of-charge announcement in the beginning. But if we
    started to get cheated, maybe we need to go for this workaround.

    But apart from that: Mostly the SDP is NOT repeated in the 200OK.
    Can I call rtpproxy_answer() when receiving the 200OK anyway?

    Thanks and best regards

      Marco

    *Von:*[email protected]
    <mailto:[email protected]>
    [mailto:[email protected]
    <mailto:[email protected]>] *Im Auftrag von *Razvan
    Crainea
    *Gesendet:* Donnerstag, 22. Januar 2015 09:36
    *An:* [email protected] <mailto:[email protected]>
    *Betreff:* Re: [OpenSIPS-Users] rtpproxy sends rtp from caller to
    callee before 200OK

    Hi, Marco!

    From RTPProxy point of view, you can't differentiate between SIP
    replies, because for all of them you call the same function -
    rtpproxy_answer().
    Now, if the client decides to send RTP for 183 (and indeed, I've
    seen this several times), there's not that much that you can do.
    Although it's kind of a hack, all I can think of is to not call
    rtpproxy_answer() for 180/183 and strip the body to prevent the
    client from sending RTP directly to the callee.
    I hope this works for you.

    Best regards,

    Răzvan Crainea

    OpenSIPS Solutions

    www.opensips-solutions.com  <http://www.opensips-solutions.com>

    On 01/21/2015 04:07 PM, Marco Hierl wrote:

        Dear all,

        first of all I need to apologize that I was not able to find
        information about this issue although I’m sure that I’m not
        the first one complaining!

        The caller is sending an INVITE via OpenSIPS and
        rtpproxy_offer() is executed, callee answers with REPLY 180 or
        REPLY 183 (with SDP) and rtpproxy_answer() is made. In this
        status it should be ok that the rtp stream from callee to
        caller is transferred via the rtpproxy (e.g. for
        announcements), but I can see that rtp stream from caller to
        callee is transferred too!!! This means that there can be a
        conversation without receiving the 200OK and what is the real
        problem: that means (at least for me) they can talk to each
        other without any charging !! A timer will stop the conversion
        after the a while, but this can take time.

        How can I overcome this problem? How can prevent RTP to be
        send to the callee before REPLY 200 is received?

        I can’t find any help in the RTPproxy protocol
        http://www.b2bua.org/wiki/RTPproxy/Protocol, nor in the
        rtpproxy module description in OpenSIPS.

        Thanks for your ideas, and best regards

          Marco



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