[SR-Users] How to uniquely identify SIP WS / WSS endpoint

[Vitaliy Aleksandrov]

When kamailio processes a request script writer can check if there any 
Route header or valid  R-URI or R-URI alias parameter to determine the 
destination. You can check it manually maybe reusing kamailio sip parser.

As you've already said to find a destination where kamailio is going to 
send a reply you can parse via header or its "received" and "rport" 
parameters. Even when via doesn't have valid destination (ws/wss 
transport) it has correct "received" and "rport" parameters which 
kamailio adds during a request processing.

"Via" header in INVITE received from WSS client and forwarded to a 
destination looks like this:
"Via: SIP/2.0/WSS 
df7jal23ls0d.invalid;received=1.2.3.4;branch=z9hG4bKTp9lzCApgHsdbRUrFcZ4XTCI49EZbbDf;rport=37213"


> Not really, the main context of this question is in reference to this 
> thread,
>
> https://www.mail-archive.com/sr-users@lists.sip-router.org/msg19962.html
>
> A patched to allow network IO intercept in kamailio corex module was 
> add to trunk as discussed in this thread,
>
> https://www.mail-archive.com/sr-users@lists.sip-router.org/msg20183.html
>
> Currently i am able to compress / decompress entire sip message coming 
> from or going to remote endpoint in kamailio server. It works fine. 
> Now i want to try ITV encryption algorithm for this on-wire data.
>
> https://github.com/mshary/itv
>
> For this i need to keep track of remote endpoint. At this low level, i 
> only have raw data received from or being transmitted to remote UA, 
> without even the remote socket address, so i have no choice but to 
> look at this raw data to determine the identity of remote endpoint. 
> For non-WS transport, i can easily  look at topmost VIA and extract 
> network address to use as "unique identification" of endpoint who sent 
> the data or would receive the data. However, for WS transport this 
> topmost VIA is useless static constant string. So VIA checking is 
> pointless (all remote endpoints will or may have same top most VIA).
>
> So i was thinking if there is another way to do it? I thought of using 
> GRUU, but it is not always present, especially in SIP replies.
>
> Thank you.
>
>
>
>
> On Mon, Aug 25, 2014 at 3:24 PM, Vitaliy Aleksandrov 
> <vitalik.voip at gmail.com <mailto:vitalik.voip at gmail.com>> wrote:
>
>     On 22.08.14 03:26, Muhammad Shahzad wrote:
>
>         Sorry for putting this question on both dev and user mailing
>         lists, as it is a rather theoretical question and i hope some
>         SIP guru on either mail list will answer.
>
>         For non-WS endpoints which use TCP or UDP for SIP transport,
>         each upstream request has top most VIA header pointing to the
>         previous hop which forwarded the request to current hop while
>         each downstream request has top most VIA header pointing to
>         next hop to which it will be forwarded from current hop.
>
>         But for WS endpoints, the top most VIA has dummy static value,
>         so there is no way to identify who sent this request or to
>         whom the reply is going to.
>
>         Please note that i am not specifically interested in network
>         address of remote endpoint (though VIA header is suppose to
>         provide it), i only need to match requests and responses from
>         / to a specific device using SIP v2.0 standard.
>
>         Any help is highly appreciated.
>
>         Thank you.
>
>
>     Can you provide an example of scenario you want to create ?
>     Do you want to understand how transaction and dialog matching
>     works in SIP ?
>
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>
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