[sr-dev] appending a new branch in route block

[Daniel-Constantin Mierla]

On 5/17/10 5:47 PM, Juha Heinanen wrote:
> Juha Heinanen writes:
>
>    
>> any pointer on how to do the same from lcr module?  i guess i need to
>> load tm api and call some tm function?
>>      
> i think i was able to figure this out.  the corresponding tm api
> function is t_gett().
>    

yes, t_gett() is the way. For the reference, if someone needs to play 
with tm api, looking at tmx module is a good example, since it uses 
couple of them. also k sl module uses transaction detection for 
send_reply().

> so i went and changed next_gw() implementation so that if no transaction
> exists, it rewrites request uri and if it exists, it clears possible old
> branches and appends a new one.
>
> still next_gw() does not work as it should, i.e., second next_gw() call
> after failing t_relay() results in destination set with two sip uris
> (the first one and the second one).
>
> then i went and added some more debug to script:
>
>   	    # relay the request
> 	    if (t_relay()) {
> 		    xlog("Relaying succeeded with result $rc\n");
> 			exit;
> 		} else {	
> 		    xlog("Relaying failed with result $rc\n");
> 		    if (t_check_trans()) {
> 			    xlog("Transaction exists\n");
> 		    } else {
> 		       xlog("Transaction does not exist\n");
> 		    };
> 		};
>
> what happens now is that execution of the script stops at
> t_check_trans() test, i.e., nothing gets printed to syslog after this:
>
> May 17 18:26:09 localhost /usr/sbin/sip-proxy[30400]: ERROR: Relaying failed with result -478
>
> even if t_check_trans() would not be a proper function to call at this
> point, i don't understand why it does not return.
>    

t_check_trans() returns 0 if transaction exists, iirc, to absorb 
retransmission.

> anyway, then i then went and changed in above t_check_trans() to
> t_lookup_request() and execution of the script went on and printed this:
>
> May 17 18:36:35 localhost /usr/sbin/sip-proxy[30693]: INFO: Relaying
> INVITE<sip:00358407058055 at sars.tutpro.com;transport=tcp>  to gw
> May 17 18:36:35 localhost /usr/sbin/sip-proxy[30693]: ERROR: tm [ut.h:295]: ERROR: uri2dst: failed to resolve "sars.tutpro.com" :unresolvable A or AAAA request (-7)
> May 17 18:36:35 localhost /usr/sbin/sip-proxy[30693]: ERROR: tm [t_fwd.c:1391]: ERROR: t_forward_nonack: failure to add branches
> May 17 18:36:35 localhost /usr/sbin/sip-proxy[30693]: ERROR: Relaying failed with result -478
> May 17 18:36:35 localhost /usr/sbin/sip-proxy[30693]: ERROR: Transaction exists
> May 17 18:36:36 localhost /usr/sbin/sip-proxy[30693]: ERROR: Calling next_gw()
> May 17 18:36:36 localhost /usr/sbin/sip-proxy[30693]: ERROR: found next
> gw<Contact: sip:00358407058055 at sars.tutpro.com;transport=tcp,
> sip:00358407058055 at lohi.tutpro.com:5060>
> May 17 18:36:36 localhost /usr/sbin/sip-proxy[30693]: INFO: Relaying
> INVITE<sip:00358407058055 at sars.tutpro.com;transport=tcp>  to gw
> ...
>
> so even if t_relay() failed with result -478, transaction was created.
> as result, next_gw() thought that it must now append a new branch
> instead of rewriting request uri, which resulted in trying the first gw
> the second time.
>
> i don't understand, how it is possible that transaction was created, but
> request uri was not marked as used.  also, i don't understand how i can
> ever get this to work, because i don't have no way to know if i should
> rewrite request uri or append a branch.
>    

I haven't got into this config situation yet. I will try to look into 
sources, but might take a bit since I travel. I will ping Andrei, maybe 
he can give a hint faster.

Cheers,
Daniel

> andrei, are you around?  perhaps you can shed some light on this or
> better yet implement opensips behavior about which i posted a request
> to the tracker, which would allow me always just to rewrite request uri
> and be done with it.
>
> -- juha
>
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>    

-- 
Daniel-Constantin Mierla
Kamailio (OpenSER) Advanced Training
Miami, Fl, USA - June 21-23, 2010
http://www.asipto.com/index.php/kamailio-advanced-training/