[SOLVED] What enabled ip_forward in my arch installation?

munzirtaha · 2014-02-27 04:26:06

Hi,
I know the default is to have ip_forward = 0 in the kernel but somehow my system have ip_forward enabled. I couldn't figure out which application enabled it!

% grep -r ip_forward /etc/sysctl.d || sysctl net.ipv4.ip_forward
net.ipv4.ip_forward = 1

Last edited by munzirtaha (2014-03-02 18:28:09)

Rexilion · 2014-02-27 18:56:57

I don't have it. Maybe it's installed with NetworkManager. You seem to have solved this issue yourself. But it's not clear to me where that file would be coming from.

This box does not have it.

munzirtaha · 2014-02-28 13:33:03

I checked another system with NetworkManager and ip_forwarding is not enabled so it's not the culprit. I didn't understand when you said I have solved the issue!

Rexilion wrote:

I don't have it. Maybe it's installed with NetworkManager. You seem to have solved this issue yourself. But it's not clear to me where that file would be coming from.
This box does not have it.

Rexilion · 2014-02-28 13:43:41

I have misread your initial post. Sorry.

Maybe this?

grep -R ip_forward /usr/lib/sysctl.d/

I'm guessing it's SystemD.

munzirtaha · 2014-02-28 14:08:28

grep -R ip_forward /usr/lib/sysctl.d/

reveals nothing

Rexilion · 2014-02-28 14:36:07

What software are you using for your network on this machine?

munzirtaha · 2014-03-01 22:53:05

I am using networkmanager 0.9.8.8-3

Rexilion · 2014-03-02 06:39:09

I'm out of idea's. It could be that NetworkManager is doing it behind your back. Maybe boot without starting it and see if that helps?

munzirtaha · 2014-03-02 12:27:23

I did a systemctl disable NetworkManager and rebooted and still ip_forward = 1. It's something else. There should be a way to track which application set which value in /proc, ain't it?

Rexilion · 2014-03-02 13:38:09

munzirtaha wrote:

I did a systemctl disable NetworkManager and rebooted and still ip_forward = 1. It's something else. There should be a way to track which application set which value in /proc, ain't it?

Yes. It does not have to go through sysctl. But you could replace the sysctl with a script that echo's the parent pid and then looks it up with ps or top.

I would have no idea how to do that if it were to change it through /proc...

Spider.007 · 2014-03-02 14:07:34

I would append '1' to the grub commandline to boot to single-user mode. Then use systemctl to start all the services that normally start on boot. Between each systemctl command; check if ip_forward is still disabled. This also tells you if the setting is hidden in /etc somewhere (when ip_forward would be enabled when entering single-user mode)

ewaller · 2014-03-02 16:52:49

Just a guess, but do you have visualization software installed. VMWare? VirtualBox? Qemu? These provide virtual networks to their guest environments. They enable bridging and/or NAT to provide connectivity from the virtual world to the real world networks.

munzirtaha · 2014-03-02 18:25:49

@Spider.007: I ended up using your method by booting in rescue mode and enabling the services one by one. I found it's libvirtd that enables ip forwarding. Thanks a lot.

@ewaller: you guessed it right!

Arch Linux

#1 2014-02-27 04:26:06

[SOLVED] What enabled ip_forward in my arch installation?

#2 2014-02-27 18:56:57

Re: [SOLVED] What enabled ip_forward in my arch installation?

#3 2014-02-28 13:33:03

Re: [SOLVED] What enabled ip_forward in my arch installation?

#4 2014-02-28 13:43:41

Re: [SOLVED] What enabled ip_forward in my arch installation?

#5 2014-02-28 14:08:28

Re: [SOLVED] What enabled ip_forward in my arch installation?

#6 2014-02-28 14:36:07

Re: [SOLVED] What enabled ip_forward in my arch installation?

#7 2014-03-01 22:53:05

Re: [SOLVED] What enabled ip_forward in my arch installation?

#8 2014-03-02 06:39:09

Re: [SOLVED] What enabled ip_forward in my arch installation?

#9 2014-03-02 12:27:23

Re: [SOLVED] What enabled ip_forward in my arch installation?

#10 2014-03-02 13:38:09

Re: [SOLVED] What enabled ip_forward in my arch installation?

#11 2014-03-02 14:07:34

Re: [SOLVED] What enabled ip_forward in my arch installation?

#12 2014-03-02 16:52:49

Re: [SOLVED] What enabled ip_forward in my arch installation?

#13 2014-03-02 18:25:49

Re: [SOLVED] What enabled ip_forward in my arch installation?

Board footer