9 May
2023
9 May
'23
4:21 p.m.
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.
11 May
11 May
12:19 p.m.
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.
10 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.
11:54 p.m.
On 11/05/2023 16.00, [EXT] Calvin E. wrote:
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.
That is quite surprising as IP forwarding is something very much
different, and definitely shouldn't be required for normal communication
with a locally bound address (and with that communication going over the
`lo` interface being completely expected).
You mentioned the address being a floating address. Was this address
perhaps not bound when Kamailio was started? (Doing this requires the
`ip_nonlocal_bind` sysctl to be enabled, although in that case I guess
the :5060 port also wouldn't be open.)
"Port unreachable" could also indicate a REJECT firewall rule, perhaps
something restricting `lo` to be used only with localhost addresses,
and/or something restricting the external IP address only to its
respective eth interface? (Although enabling IP forwarding wouldn't
change anything in that case.)
Cheers
360
days inactive
362
days old
3 comments
3 participants
participants (3)
-
Calvin E. -
Henning Westerholt -
Richard Fuchs