[SR-Users] call forking using dbaliases not working for un-NATed clients

[Klaus Darilion]

I suspect that the branch route is first executed for the NATed client. 
Then the 'received' column is used as destination URI. When executing 
the branch route again, the destination URI is still the value from the 
previous branch, and lookup() will not overwrite is as 'received' is not 
available. Then Kamailio sends the INVITE again to the first client.

You can try to set $du to Null before lookup(). ($du=null or $du=$null, 
not sure what the correct syntax is).

Another workaround is to use fix_nated_register() for every client (the 
pragmatic and more secure approach).

regards
Klaus

On 18.09.2012 15:16, Yufei Tao wrote:
> Hi
>
> I have a strange problem on forking calls to a group of users. For
> example I have two users y2 and y3 in dbaliases, both with
> alias_username 'group'. And y2 and y3 both registers with Kamailio fine.
> When I make a call to 'group' from a third client y1, what my
> kamailio.cfg does is: do an alias_db_lookup("dbaliases"), and goes to
> BRANCH_ALIASDB, where a lookup location will be done for each of the
> username resulting from lookup of dbaliases, something like this:
>
> y1--INVITE 'group'-->lookup dbaliase-->[BRANCH_ALIASDB]--->'y2'-->lookup
> location---¬
>
> |                                                 |-->relay
>                                    ---->[BRANCH_ALIASDB]--->'y3'-->lookup
> location----
>
> The all works well as long as all clients are NAT'ed. However when they
> are not NAT'ed, e.g. all on the same LAN with Kamailio, the call only
> goes to one of the group members, e.g. y2 only. When checking the log,
> it seemed to have done the dbaliases lookup fine, and each location
> lookup successfully. But Kamailio only relayed y2's IP, e.g. to the
> client, while y3's to itself.
>
> When comparing the location table when clients are NAT'ed or not, I find
> that the 'received' column is only populated when I do
> fix_nated_register. And group calls only works when 'received' column is
> populated. That explains why when clients are NAT'ed group calls work,
> as I only do fix_nated_register if nat_uac_test returns true.
>
> But if this is the only reason, if two clients register using the same
> username, e.g. both as y3, and when 'received' column of location table
> is empty (no fix_nated_register done), I would expect a call to y3
> should also only make 1 client ring. But in fact both of them rang! The
> flow is like:
>
> y1--INVITE 'y3'-->lookup location for 'y3'----> IP of 1st client
> registered as 'y3'
>                                             |
>                                             ---> IP of 2nd client
> registered as 'y3'
>
> While a call to 'group' (thus dbaliases lookup took place) under such
> un-NAT'ed set up made only 1 client ring.
>
> So I can make it work by always doing fix_nated_register. But I'm not
> clear about these things:
> - why does a lookup of dbaliases before lookup of location make such
> difference?
> - does lookup location work differently depending on whether it is
> called from trunk or from a route called from a branch route?
>
>
> Following is relevant parts from my config file:
>
> #############################################################
> route[LOCATION]
> {
>     if ( alias_db_lookup("dbaliases") )
>     {
>       t_on_branch("BRANCH_ALIASDB"); # in branch_route[BRANCH_ALIASDB],
>                                      # call another route that looks up
> location,
>                                      # if not existent, call drop()
>
>     }
>     else
>     {
>       xlog("L_DBG","LOCATION: not alias - go to lookup location trunk\n");
>       route(LOCATION_TRUNK); # normal look up location and sending of 404 etc
>     }
>
> ... ...
> }
> #############################################################
> branch_route[BRANCH_ALIASDB]
> {
>     xlog("L_DBG", "BRANCH_ALIASDB: $fU@$fd ->  $rU@$rd; Method:$rm\n");
>     route(LOCATION_BRANCH);
> }
>
> route[LOCATION_BRANCH]
> {
>     if (!lookup("location"))
>     {
>       # Drop this branch - it's going nowhere
>       drop();
>     }
> }
> #############################################################
> route[RELAY] {
>     xlog("L_DBG","RELAY: method=$rm, callid=$ci, cseq=$cs\n");
>
>
> #!ifdef WITH_NAT
>     if (check_route_param("nat=yes")) {
>       setbflag(FLB_NATB);
>     }
>     if (isflagset(FLT_NATS) || isbflagset(FLB_NATB)) {
>       xlog("L_DBG", "RELAY: about to call RTPPROXY\n");
>       route(RTPPROXY);
>     }
> #!endif
>
>     /* example how to enable some additional event routes */
>     if (is_method("INVITE")) {
>       t_on_reply("REPLY_ONE");
>       t_on_failure("FAIL_ONE");
>     }
>
>     if (!t_relay()) {
>       sl_reply_error();
>     }
>
>     exit;
> }
>
> ############################################################
> route[NAT] {
> #!ifdef WITH_NAT
>    xlog("L_DBG","NAT: method=$rm, callid=$ci, cseq=$cs\n");
>
>      force_rport();
>      if (nat_uac_test("2")) {
>          if (method=="REGISTER") {
>              fix_nated_register();
>              xlog("L_DBG","NAT: Just done fix_nated_register in REGISTER
> message in NAT route\n");
>          } else {
>            xlog("L_DBG","NAT: fix_nated_contact\n");
>              fix_nated_contact();
>          }
>          setflag(FLT_NATS);
>      }
>
> #    setflag(FLT_NATS); ## -- YT: set NAT flag for all, so will force
> media relay
> #!endif
>      return;
> }
>
> #############################################################
> And in the main route, route LOCATION and RELAY are the last two routes:
> route {
> ...
>     route(NAT);
>
>     ... ...
>
>     # user location service
>     route(LOCATION);
>
>     route(RELAY);
> }
>
> Hope I have made it clear. Thanks very much!
>
> Yufei
> --
> Yufei Tao
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