Arch Linux

Fingel

Member

Registered: 2009-02-28

Posts: 105

Mystery bridge appears on boot and causes havoc

Hello,

I have arch running on a computer in a network which I sometimes log into remotely via VPN. I noticed a few weeks ago I could not reach it. After some digging I found that my route table was wrong:

$ route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         172.16.5.253    0.0.0.0         UG    202    0        0 eno1
172.16.4.0      0.0.0.0         255.255.252.0   U     202    0        0 eno1
172.17.0.0      0.0.0.0         255.255.0.0     U     0      0        0 docker0
172.18.0.0      0.0.0.0         255.255.0.0     U     0      0        0 br-dace97159602

172.18.0.0 should be routing to the internal network, but there is this mystery bridge br-dace97159602 instead and I have no idea where it is coming from.

$ brctl show
bridge name     bridge id               STP enabled     interfaces
br-dace97159602         8000.02421d4af862       no
docker0         8000.02425508cb56       no              veth78a6c07
                                                        vethe5069d4

Every time I reboot (locally), I have to bring down the bridge and remove it, or else I can't ssh in via the vpn later. So I do the following:

sudo ip link set br-dace97159602 down; sudo brctl  delbr br-dace97159602

This works, and I can successfully log in via ssh over the vpn from outside the network. But it is annoying, especially because I don't know what is causing it. I thought perhaps it was KVM, so I removed all libvirt and qemu stuff I could find (I don't really use it) to no avail. Another candidate would be docker - but I can't find any configuration that would create an additional bridge besides the docker0 one.

I am not running Networkmanager or Wicd or anything like that. Just system-dhcpcd@eno1.service (desktop machine) Anyone have any ideas?

JohnBobSmith

Member

From: Canada

Registered: 2014-11-29

Posts: 804

Re: Mystery bridge appears on boot and causes havoc

Wow... a google search for br-dace97159602 yielded no results. No really, try it. That sucks. Anyhow, did any hardware change recently? New computer, router, phone, or otherwise?? Is it possible that something could have been renamed to br-dace97159602? This is bizarre indeed, keep us posted.

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Fingel

Member

Registered: 2009-02-28

Posts: 105

Re: Mystery bridge appears on boot and causes havoc

Wow... a google search for br-dace97159602 yielded no results. No really, try it. That sucks. Anyhow, did any hardware change recently? New computer, router, phone, or otherwise?? Is it possible that something could have been renamed to br-dace97159602? This is bizarre indeed, keep us posted.

The first thing I tried was googling it. The bridge name does look pseudo random but the bizarre thing is that every time I remove the bridge and reboot, it comes back with the *exact* same name. So it looks pseudo random, but it is deterministic due to something on my system. No new hardware since the Arch install, must be software related somehow.

ewaller

Administrator

From: Pasadena, CA

Registered: 2009-07-13

Posts: 20,349

Re: Mystery bridge appears on boot and causes havoc

Just thinking out loud here, any kernel modules for VMWare, Virtualbox?
Any kernel modules loading that you don't know what they are for?
How about an Smart Phone attached via USB?  Or an embedded processor development system?

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Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Sometimes it is the people no one can imagine anything of who do the things no one can imagine. -- Alan Turing
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Fingel

Member

Registered: 2009-02-28

Posts: 105

Re: Mystery bridge appears on boot and causes havoc

I've never installed VMWare or Virtualbox.
As far as kernel modules go, I'm not sure. I pretty much stopped paying attention to kernel modules once the whole dynamic loading thing happened. Here is the output of lsmod:
https://www.pastery.net/dgbdyy/
I just rebooted with nothing plugged in, no cell phones, arduinos, anything like that. The bridge is back.

alphaniner

Member

From: Ancapistan

Registered: 2010-07-12

Posts: 2,810

Re: Mystery bridge appears on boot and causes havoc

It might help to look back in the journal and see what was updated/installed before the bridge first appeared.

When all else fails

grep -rli "bridge" /etc 2>/dev/null

...the hope being that whatever creates it has the word bridge in its config file. Maybe also do the same with your home folder.

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