Re: [Linphone-users] hoping for help in protocol analyzation

[Boris]

Hej Dennis,

thanks for your hints. This is so much, I will need some time to follow....

Am 22.09.21 um 18:19 schrieb Dennis Filder:
> On Wed, Sep 22, 2021 at 11:28:46AM +0200, boris@cation.de wrote:
>
> > Do I understand correct, that I have to use either a STUN server or
> > a local proxy to make LinPhone work fully?
>
> If you sit behind a router that does NAT then yes.  LEAF apparently
> offers a package named siproxd.lrp.  If you get that to work keep
> detailed notes and consider writing a tutorial for the LEAF wiki.

I like to see that you seem to know LEAF. I'm using it since about 20 
years (oops, I'm shocked) and seem to be quite familiar with it. If 
siproxd.lrp is the way to do it, I'll write the tutorial!

> > As far as I could research until now, DT doesn't serve STUN.
>
>      $ host stun.dtst.de
>      stun.dtst.de is an alias for stun.stunprotocol.org.
>      stun.stunprotocol.org has address 18.191.223.12
>      stun.stunprotocol.org has IPv6 address 2600:1f16:8c5:101::108
>
> I have no idea what the privacy policy of that third party provider
> is, though.  Maybe you can find more somewhere on
> http://stunprotocol.org/.  stun.linphone.org exists, too.  Or maybe
> you can run your own if you have a VPS.

OK, thanks. Some homework to do....

> > And a local proxy would possibly prevent a second SIP service from
> > being used on the LAN?
>
> Not necessarily.  It will depend on how auto-configuration via
> broadcast/zeroconf/Avahi/SRV records is done.  In theory you can use
> as many different SIP servers and proxies on a network as you like,
> but you will probably have to manually configure each client to use a
> static configuration.
>
> > More facs from my local network:
> > a) The router is a full-configurable box based on APU Board with
> > LEAF-software (http://leaf.zetam.org/), which is a purified small Linux.....
> > b) There is a Panasonic KXsomething IP-Phone working all fine within the
> > local network against the DT.
> > c) LinPhone works fine as well against an other SIP-Provider (TNG).
> > d) The disconnection after 15 minutes doesn't happen with Twinkle as
> > softphone.
>
> It would be very interesting to know how these other SIP clients learn
> the public IP address.  LEAF has tcpdump, so it should be easy to
> figure out.  I suspect that they contact a hard-coded publically
> reachable STUN server or do other tricks like that.

OK, more homework.... ;-)

> As for TNG working and DT not working I assume that TNG is your ISP

yes

> which means it can rewrite your outgoing SIP packets on the fly at the
> next hop with a transparent SIP proxy because it knows both your phone
> number and your currently assigned IP address.  I read about Telekom
> doing it this way, and while it sure is convenient it isn't really how
> SIP was intended to be used because it usually also allows any
> stranger walking into your home to plug in an IP phone and perform
> calls on your bill without having to authenticate against the SIP
> provider. 

No. I got some (one for each phone number) credentials from TNG to 
authorizw against their SIP server.

If SIP packets would be rewritten, LinPhone, Twinkle and the Panasonic 
HardPhone wouldn't be able to reach the DT server?

> That's something to keep in mind.  It also gives people
> wrong ideas about how SIP is designed to work.

I obviously belong to exactly these people - regardless of who or what 
is responsible for this.

> Regards.
>
> P.S.: Your reply to the list didn't make it through for some reason.

I found my reply in the list's archive, so it seems it was received?
I try to put that message back on the list.

Thanks very much an regards,

Boris

PS: I'll be back with replies to the technical hints - need some days.....