Tim,
So are you telling me that when you see the wireshark trace the
custom attribute you added is present but in a corrupted state? I don't
think that pjmedia_sdp_conn_clone is corrupting your attribute, coz if u
see the definition of that function it shudn't be affected in anyway!
I am suspecting that something is done wrongly in Create_DH_HMAC_SDP_Attribute
fucntion of yours. I wud be helpful if barebone expansion of this function
is known.
On Wed, Jan 16, 2013 at 6:01 PM, McLeod, Tim <Tim.McLeod at cassidian.com>wrote:
> Sandeep,
>
>
>
> |Good day to you, I hope that you are well?
>
>
>
> I think we are moving forward, but my engineer is now experiencing
> problems whereby it seems that the message is becoming corrupted before the
> outgoing message can be transmitted. The following is my engineer?s
> description of the problem:
>
>
>
> Using ?transport_adapter_sample.c? as an example, I am trying to add an
> attribute to the outgoing SDP message.
>
>
>
> I have modified the example code as follows:
>
>
>
> /* You may do anything to the local_sdp, e.g. adding new
> attributes, or
>
> * even modifying the SDP if you want.
>
> */
>
> if (1)
>
> {
>
> /* Say we add a proprietary attribute here.. */
>
> pjmedia_sdp_attr *mikey_attr;
>
>
>
> mikey_attr = PJ_POOL_ALLOC_T(sdp_pool, pjmedia_sdp_attr);
>
>
>
> pj_strdup2(sdp_pool, &mikey_attr->name, "key-mgmt");
>
> pj_strdup2(sdp_pool, &mikey_attr->value, "mikey ");
>
>
>
> Create_DH_HMAC_SDP_Attribute(sdp_pool, local_sdp, mikey_attr);
>
>
>
> pjmedia_sdp_attr_add(&local_sdp->attr_count,
> local_sdp->attr, my_attr);
>
> }
>
>
>
> Create_DH_HMAC_SDP_Attribute creates a base64 encoded attribute and
> appends it to ?mikey_attr->value?.
>
>
>
> using
>
> pj_strcat2(&mikey_atrr->value, base64_buffer);
>
>
>
> This appears to work okay, and the attribute is added to the local_sdp,
> and results in an attribute pj_string something like
>
>
>
> ?mikey AQcF/kkSBAA????.? About 157 bytes in length.
>
>
>
> When I step through the routine pjsua_media_channel_create_sdp in
> pjsua_media.c a call is made to
>
>
>
> sdp->conn = pjmedia_sdp_conn_clone(pool, m->conn);
>
>
>
> which then overwrites my attribute, resulting in a corrupted message being
> sent.
>
>
>
> Any thoughts/suggestions would be extremely welcome.
>
>
>
> Many thanks?
>
>
>
> Tim
>
>
>
> *From:* McLeod, Tim
> *Sent:* 11 January 2013 11:02
> *To:* 'pjsip list'
> *Subject:* RE: [pjsip] Custom Session Negotiation
>
>
>
> Sandeep,
>
>
>
> Thank you for your very quick response. I have passed your suggestion to
> my engineer who has confirmed that this is exactly the information he
> needed. Excellent work.
>
>
>
> Thanks again?
>
>
>
> Tim
>
>
>
> *From:* pjsip [mailto:pjsip-bounces at lists.pjsip.org] *On Behalf Of *Sandeep
> Karanth
> *Sent:* 11 January 2013 05:17
> *To:* pjsip list
> *Subject:* Re: [pjsip] Custom Session Negotiation
>
>
>
> Hi Tim,
>
> I guess probably you are using below part of *transport_encode_sdp()
> *function * *to add your custom attribute to sdp.
>
>
>
> if (1)
>
> {
>
> /* Say we add a proprietary attribute here.. */
>
> pjmedia_sdp_attr *my_attr;
>
>
>
> my_attr = PJ_POOL_ALLOC_T(sdp_pool, pjmedia_sdp_attr);
>
> pj_strdup2(sdp_pool, &my_attr->name, "X-adapter");
>
> pj_strdup2(sdp_pool, &my_attr->value, "some value");
>
>
>
> pjmedia_sdp_attr_add(&local_sdp->media[media_index]->attr_count,
> local_sdp->media[media_index]->attr, my_attr);
>
> }
>
>
>
> I think you are probably substituting in the above block 'X-adapter' with
> your custom attribute. The problem is that pjmedia_sdp_attr_add function
> highlighted above is adding that parameter as a media parameter and hence
> it will come as a media parameter.
>
>
>
> You can instead substitute the above line with
> pjmedia_sdp_attr_add(&local_sdp->attr_count,local_sdp->attr,my_attr); and
> try again. Hopefully this should solve your problem!
>
>
>
> Regards,
>
> Sandeep
>
> On Fri, Jan 11, 2013 at 10:20 AM, Sandeep Karanth <sandeepk.kdp at gmail.com>
> wrote:
>
> Correct me if am wrong! So what you are looking to do is to add a session
> level attribute i.e a=somevalue before any of the media parameter (m) lines
>
> but instead it is getting added after some (m) parameter and hence it is
> effect your custom "a" attribute in effect is becoming a media level
> attribute??
>
> On Thu, Jan 10, 2013 at 7:40 PM, McLeod, Tim <Tim.McLeod at cassidian.com>
> wrote:
>
> Furthering our project for experimenting with various methods of
> providing secure VoIP communications we have a need to provide custom
> negotiation mechanisms. My engineer is currently looking into how this
> might be incorporated into the existing pjsua functionality. He is
> encountering difficulties.
>
>
>
> He is attempting to insert MIKEY session attributes into SDP message, i.e.
> a=key-mgmt: mikey {base64 encoded mikey message} by using the function
> ?transport_encode_sdp? in the transport adapter to add the desired mikey
> message. When capturing the SIP invite message in Wireshark, the coding is
> translated as a media attribute, the suspicion being that this is the case
> because it is added to the message after the media description. Is there a
> clean way to add a session description before the media attribute?
>
>
>
> Your help would (once again) be very much appreciated.
>
>
>
> Tim McLeod MBCS CITP
>
> Principal Engineer
>
> Tel: +44 1633 715097
>
> Mob: +44 7765 088364
>
> Email: tim.mcleod at cassidian.com
>
> RLI: tim.mcleod at eads.r.mil.uk
>
> Website: www.cassidian.com
>
>
>
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