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

[Ovidiu Sas]

You have a different problem then.
Having private IPs in Contact is fine. You need to lose route the
calls (kamailio will add two Record-Route headers) and the origination
server will set the RURI to the private IP from Contact, but it will
send the in-dialog requests to the public IP of kamailio. This has
nothing to do with virtual IPs.
Maybe you have a buggy client that doesn't do proper loose routing.

-ovidiu

On Sat, Jan 15, 2022 at 11:50 AM Chad <ccolumbu at hotmail.com> wrote:
>
> Ovidiu,
> Thank you again for your response.
> One is public (an internet IP) and one is private (a 10.x ip).
> Apparently this is a known problem with virtual IPs, it does not work.
> When the asterisk server responds to the invite it sends a contact header with the private IP and Kamailio does not
> rewrite it to the advertised public IP. So the originating server sees the private IP in the Contact header and tries to
> send the traffic to the 10.x IP (which is non-routable) and the call dies.
> I have been trying things for a long time to fix this (years) what you are saying will not fix it because of the virtual
> IPs.
> If it was a normal IP it would work fine. It has something to do with the routing table and how mhomed detects networks.
>
> --
> ^C
>
>
> On 1/15/22 8:36 AM, Ovidiu Sas wrote:
> > 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
> >>>
> >>> __________________________________________________________
> >>> Kamailio - Users Mailing List - Non Commercial Discussions
> >>>     * 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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> >
> >
> >



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