[SR-Users] Kamailio Routing Logic

[Paul Smith]

Hi Zaka
You have misunderstood this line : if (!t_relay()) {

That line explicitly calls t_relay() and the packet is relayed at that time.  If the packet cannot be relayed then the t_relay() function returns an error and the conditional block is executed.

Paul Smith



On 13 Nov 2014, at 09:10, Zaka Ul Isam <Zaka.Ul at albtelecom.al> wrote:

> Morning Paul:
> 
> Thanks a million, mate!
> So, if I understood correctly, in the: 
> 
> if (!t_relay()) {
> sl_reply_error();
> 
> !t_relay will check the error condition in sending out the stateful message.  However, in this code snippet, t_relay is not explicitly called. Therefore, as in kamailio-advanced-config, route[relay] should be performing this. 
> 
> But it is not the case. Instead the main routing block first calls several other routes:
> 
> route(REQINIT);
> route(NATDETECT);
> 
> and then # CANCEL processing
>     if (is_method("CANCEL")) {
>         if (t_check_trans())   ????????
>             t_relay();
>         exit;
> 
> Please forgive my ignorance, but I am baffled here.
> 
> The next occurrence of t_relay is:
> 
> if ( is_method("ACK") ) {
>         if ( t_check_trans() ) {
>             # no loose-route, but stateful ACK;
>             # must be an ACK after a 487
>             # or e.g. 404 from upstream server
>             t_relay();
>             exit;
> 
> 
> Many anticipatory thanks again!
> 
> Have an awesome day!
> 
> Zaka
> 
> ________________________________________
> From: sr-users-bounces at lists.sip-router.org [sr-users-bounces at lists.sip-router.org] on behalf of Paul Smith [paul.smith at claritytele.com]
> Sent: Thursday, November 13, 2014 9:38 AM
> To: sr-users at lists.sip-router.org
> Subject: Re: [SR-Users] Kamailio Routing Logic
> 
> Hi Zaka,
> The stageful forwarding takes place in the t_relay() function. If relaying is unsuccessful then an error is returned and the conditional block executed to send an error back to the originator using sl_reply_error().
> 
> Your other question is about why to use the call to route(1): Yes you could just put the content of route[1] into the main route block and it would work fine. In more complex scripts it is neater to put code which is executed in lots of different place into a separate block and then call the block. That way if you need to modify that code you only have one place to maintain. The t_relay() function is a good example of a block of functionality that is reached from loads of places … so generally a route[relay] block is a good idea.
> 
> Paul Smith
> 
> On 13 Nov 2014, at 07:52, Zaka Ul Isam <Zaka.Ul at albtelecom.al> wrote:
> 
> > Hello Friends and Gurus:
> >
> > I am struggling with routing and need a bit of clarification WRT following:
> >
> > route {
> > if ($fU=="601"&&is_method("INVITE"))
> > record_route();
> > rewritehost("10.0.10.111"); //SS IP
> > route(1);
> > }
> > route[1] {
> > # send it out now; use stateful forwarding as it works reliably
> > # even for UDP2TCP
> > if (!t_relay()) {
> > sl_reply_error();
> > };
> > exit;
> > }
> > * In the above stateful forwarding what is the rationale of calling route (1) within main route block? Could the t_relay statement afyer rewriting the host part of URI not have performed the stateful forwarding?
> >
> > ** In route[1] there is is only an expression abt logical not condition about t_relay() (if methods in this function are not invoked??)
> > I wonder where exactly is stateful forwarding taking place?
> >
> > 1- Is it the default action?
> > 2- Or in function sl_reply_error()?
> >
> > Thanks a lot in advance!
> >
> > Zaka
> >
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