11 May
2023
11 May
'23
4 p.m.
We added a listen on localhost and forced the outside application server to
return 127.0.0.1 instead of the IP of Kamailio. This worked as expected,
but wasn't the solution we were looking for.
It turns out that enabling sysctl net.ipv4.ip_forward=1 resolves the
original issue. Is IP Forwarding a normal requirement for Kamailio in
general?
For reference, running "ip route get _interface_ip_" on other Linux servers
confirms that the "lo" interface is used when sending packets to an
assigned Ethernet IP address.
On Thu, May 11, 2023 at 3:19 AM Henning Westerholt <hw(a)gilawa.com> wrote:
Hello,
usally there are not special requirements regarding the localhost. Is
kamailio actually listening on the localhost? You could check e.g. with
netstat or kamcmd/kamcli commands.
Cheers,
Henning
*From:* Calvin E. <calvine(a)gmail.com>
*Sent:* Dienstag, 9. Mai 2023 16:21
*To:* sr-users(a)lists.kamailio.org
*Subject:* [SR-Users] ICMP Port Unreachable using loopback interface with
ethernet IP
The scenario is Kamailio on Debian 11 talking to an external application
server that returns a 302 with a Contact that contains Kamailio's own IP
and a different port. Kamailio is listening on the correct port via at the
given IP address. However, when Kamailio creates the packet to talk to
itself, it it send over the loopback adapter "lo" and gets an ICMP port
reply:
listen=udp:KAMAILIO_INTERNAL_FLOATING_IP:8888
10.z.a.b.5000 > 10.z.x.y.5060: SIP, length: 849
SIP/2.0 302 Moved Temporarily
Contact: <sip:44123456...@10.z.x.y:8888>
15:39:00.548722 lo In IP (tos 0x10, ttl 64, id 5431, offset 0, flags
[none], proto UDP (17), length 949)
10.z.x.y.5060 > 10.z.x.y.8888: SIP, length: 921
15:39:00.548732 lo In IP (tos 0xd0, ttl 64, id 19038, offset 0, flags
[none], proto ICMP (1), length 576)
10.z.x.y > 10.z.x.y: ICMP 10.44.7.136 udp port 8888 unreachable,
length 556
Do I need to configure something in the OS or Kamailio to allow the
ethernet IP to work via the loopback adapter? I haven't set up any special
networking to cause this, it appears to be a Linux kernel behavior.