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

[Chad]

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
>>>>
>>>> __________________________________________________________
>>>> 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!
>>>> Edit mailing list options or unsubscribe:
>>>>     * https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users
>>>
>>>
>>>
>>> --
>>> 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!
>>> Edit mailing list options or unsubscribe:
>>>     * https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users
> 
> 
>