[SR-Users] SIP communication does not reach phone when STUN is used

[Sergiu Pojoga]

Aside from the obvious question: why do you need to use STUN in the first
place considering you already have a proxy that handles far-end NAT
traversal...?

All those FLT/FLB NAT related flags are quite frankly confusing, especially
if you didn't take your time to really understand what's going on. You
don't need all that, none I'd say. Just get to really understand what is to
be done at the proxy level when a request/reply is received.

The default NATMANAGE route is written to handle phones registering
directly with the proxy. Your setup is different by interacting between
UACs and Asterisk on the other side, which has his own techniques of
handling NAT (another hint for you here).

One last but important thing: do yourself a favor and install sngrep
<https://github.com/irontec/sngrep>. Use it and you'll find the problem in
no time.

Good luck.

On Fri, Oct 5, 2018 at 8:40 AM Kevin Olbrich <ko at sv01.de> wrote:

> Hi!
>
> I noticed a minor problem when I set up the STUN config of my phone.
> When the server is set, I am unable to reach the endpoint from kamailio
> (Phone1 -> Kamailio -> Asterisk -> same Kamilio -> no outgoing SIP flow to
> Phone2).
> If I do not set it, it seems to fallback to it's RFC1918 address which is
> then detected by nat_uac_test() and I can reach the phone.
>
> During my tests with Asterisk directly, this did not make any difference.
> Seems like Asterisk checks more than FLAG 19/8 in nat_uac_test().
> If I am right, I strictly used the SIP source port for answers instead of
> any self-detection using STUN or similar.
>
> My kamailio node is connected to the internet directly and 95 percent of
> (planned) phones are behind random NATs.
>
> In example kamailio.cfg there are these settings:
>
> # Caller NAT detection
>> route[NATDETECT] {
>> #!ifdef WITH_NAT
>> force_rport();
>> if (nat_uac_test("19")) {
>> if (is_method("REGISTER")) {
>> fix_nated_register();
>> } else {
>> if(is_first_hop()) {
>> set_contact_alias();
>> }
>> }
>> setflag(FLT_NATS);
>> }
>> #!endif
>> return;
>> }
>
>
> AND (modified for direct RTP flow):
>
>  # RTPProxy control and signaling updates for NAT traversal
>> route[NATMANAGE] {
>> #!ifdef WITH_NAT
>> if (is_request()) {
>> if(has_totag()) {
>> if(check_route_param("nat=yes")) {
>> setbflag(FLB_NATB);
>> }
>> }
>> }
>> if (!(isflagset(FLT_NATS) || isbflagset(FLB_NATB))) return;
>> if(nat_uac_test("8")) {
>> fix_nated_sdp("15");
>> if (is_request()) {
>> if (!has_totag()) {
>> if(t_is_branch_route()) {
>> add_rr_param(";nat=yes");
>> }
>> }
>> }
>> if (is_reply()) {
>> if(isbflagset(FLB_NATB)) {
>> if(is_first_hop())
>> set_contact_alias();
>> }
>> }
>> #!endif
>> return;
>> }
>
>
> I checked the docs but I am not sure which FLAGs are safe to use (or break
> things).
>
> Any thoughts or hints are welcome.
>
> Thank you very much!
>
> Kind regards
> Kevin
> _______________________________________________
> Kamailio (SER) - Users Mailing List
> sr-users at lists.kamailio.org
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>
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