[SR-Users] Help with rewriting headers for NAT manually

[Ovidiu Sas]

Hello Chad,

The floating IPs that you have, are they both private IPs or one
private IP and the other one a public IP?

If you have to two floating private IPs, then you need a config like this:
listen=FLOATING_UDP_PRIVATE1 advertise PUBLIC_UDP_IP
listen=FLOATING_UDP_PRIVATE2

In the config, before relaying the initial INVITE you need to detect
the direction of the call and set $fs accordingly:
if (CAL_FROM_PRIVATE_TO_PUBLIC) {
    $fs = udp:FLOATING_UDP_PRIVATE1
}
else {
    $fs = udp:FLOATING_UDP_PRIVATE2
}

If you have a floating private IPs and a floating public IP, then you
need a config like this:
listen=FLOATING_UDP_PRIVATE
listen=FLOATING_UDP_PUBLIC

There should be no need to force the socket, but if you do, there's no
harm (actually it's better and faster).

Hope this clarifies things and helps,
-ovidiu

On Sat, Jan 15, 2022 at 9:48 AM Chad <ccolumbu at hotmail.com> wrote:
>
> Ovidiu,
> Thank you for your response.
>
> I have done that, in addition to the linux ip_nonlocal_bind I have also set the Kamailio ip_free_bind=1 and it does not
> work.
> Here are my relevant config lines:
> listen=LISTEN_UDP_PRIVATE advertise MY_PUBLIC_IP:5060
> listen=LISTEN_UDP_PUBLIC
>
> mhomed=1
> ip_free_bind=1
>
>
> In my /etc/sysctl.conf I have (yes I applied it with sysctl -p, and I have been using it for a long time and have
> rebooted as well):
> net.ipv4.ip_nonlocal_bind=1
> --
> ^C
>
>
> On 1/15/22 4:55 AM, Ovidiu Sas wrote:
> > Hello Chad,
> >
> > You can add a listen directive to your config for the virtual IPs
> > (both public and private) and then you don't need to manually modify
> > any headers or use force_send_socket().
> > You need to enable non local IP binding so kamailio can start on the
> > server that doesn't have the virtual IP:
> > echo 1 > /proc/sys/net/ipv4/ip_nonlocal_bind
> > To make the change permanent, edit your sysctl.conf file and enable it there:
> > net/ipv4/ip_nonlocal_bind = 1
> >
> > Regards
> > Ovidiu Sas
> >
> >
> > On Sat, Jan 15, 2022 at 4:16 AM Chad <ccolumbu at hotmail.com> wrote:
> >>
> >> We are looking for some help (possibly a paid consultant) to help us with our Kamailio setup.
> >> To keep this as short as possible: we use Kamailio as a NAT proxy to bridge our external IP and our private IP asterisk
> >> servers (via dispatcher).
> >> However both the external IP and the internal IP that the Kamailio server uses are virtual IPs created by keepalived.
> >> Because of that neither mhomed nor fix_nated_contact work, and we use force_send_socket to direct the traffic.
> >> We run linux Debian 10 for the OS.
> >> Also we do not use a DB at all, everything is done with local config files.
> >>
> >> The problem is that when traffic goes out the Contact header has a private IP in it, like:
> >> Contact: <sip:##########@10.10.10.###]:5060>
> >>
> >> There are 2 possible solutions to this:
> >> 1. Make changes to linux, keepalived and/or Kamailio so that Kamailio recognize the virtual IPs so that mhomed and
> >> fix_nated_contact work as usual.
> >>
> >> 2. Create a manual header rewrite system.
> >>
> >> If solution #2:
> >> What we need to do is create a way to rewrite the contact header to the external IP on the way out, and on the way back
> >> rewrite it back to the internal server that the call is already connected to.
> >>
> >> Not sure if we will need to store those paths on the server or if we can do some kind of cheat with another persistant
> >> header like P-Preferred-Identity or P-Asserted-Identity (i.e. store the internal IP in the name field or something).
> >>
> >> If anyone out there know of a way to do this or wants to give it a try please reach out to me.
> >>
> >> Thank you all for your time.
> >>
> >> --
> >> ^C
> >> Chad
> >>
> >> __________________________________________________________
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> >
> >
> >
> > --
> > VoIP Embedded, Inc.
> > http://www.voipembedded.com
> >
> > __________________________________________________________
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> >    * sr-users at lists.kamailio.org
> > Important: keep the mailing list in the recipients, do not reply only to the sender!
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