trick77.com – …gadgeteers at work

OVH server loses Internet connectivity after 1 hour

I have a dedicated server at OVH on which I’m hosting a few KVM guests. Recently, I upgraded the OS to Debian 11 Bullseye. The upgrade went without a hitch but the host consistently started to lose Internet connectivity after 1 hour (a bit less actually, +-56 minutes) after a restart. I was able ping the default gateway though at all times, but nothing else behind this first hop. The KVM guests were unaffected (since bridged and using their pre-defined MAC address), and IPv6 kept working on the host as well. It was only IPv4 connectivity that got lost (beyond the switch), always after an hour after a reboot. Very strange! It took me quite a while to figure out the root cause. I suspected a problem with the hosts MAC address and started pinging a public IP address while running tcpdump with the -e parameter. That’s when I noticed that the ping was sent with the MAC address of my br0 bridge instead of the physical interface’s MAC address. Here’s what happened: starting with Debian Bullseye, bridges get randomly generated MAC addresses assigned. While in Debian 10 Buster, the bridge’s MAC address was inherited from the physical interface associated with the bridge.

The solution was to manually set the bridge’s MAC address to the same address as the physical interface using the hwaddress instruction:

rename eno1=eth0
auto eth0
iface eth0 inet manual 
auto br0
iface br0 inet static
  hwaddress ether 0a:c4:7a:42:53:e2 # <-- from eth0
  address 5.196.nnn.nnn
  netmask 255.255.255.0
  network 5.196.nnn.nnn
  broadcast 5.196.nnn.nnn
  gateway 5.196.nnn.nnn
  bridge_ports eth0
  bridge_fd 0
  bridge_stp off
  bridge_maxwait 0

It looks like OVH’s switch in front of my server was allowing unknown MAC addresses passing through, but only for an hour and then silently dropped all IPv4 packets until the next NIC reset. Yeah, obviously OVH’s support was clueless even though the hint about the 56 minutes and then losing access should have been a strong pointer for them. That’s why I’m posting the solution here, hopefully it helps someone else with the same problem.

Slow oh-my-zsh loading on macOS 11

At some point, starting a zsh (I’m using iTerm2 here) took almost 10 seconds on macOS 11 Big Sur. This only happened the first time when I opened iTerm2 after a reboot. After mentally going through all the software changes I had done to my rig, I was pretty sure this happened right after installing Xcode. After some debugging in the oh-my-zsh code I found the culprit: it’s related to Apple’s git version which comes with Xcode. After installing the Homebrew version of git, the delay no longer occurred. It’s important though that the Homebrew git binary is found first when calling git from the command line.

GA-Z97X-UD5H and macOS 11 Big Sur with OpenCore

Interestingly, my 6 year old Hackintosh rig is still going strong and so I decided to upgrade it from macOS X Mojave to macOS 11 Big Sur. Since OpenCore is pretty well documented by now, I wanted to give it a try and replace Clover (which seems to use OpenCore as well by now).
However, the transition from Clover to OpenCore wasn’t smooth at all. OpenCore has quite a steep learning curve and I spent almost an entire, foggy November Sunday to get it all up and running.

The best cloud desktop solution for Linux is… Windows!?

I like using a remote desktop work/office environment for various reasons, travelling being on of them. This is also known as a cloud desktop. Thanks to the awesome Apache Guacamole remote desktop gateway software, I can access it everywhere, just by using a web browser (and an Internet connection).

While I love Linux, it sucks when it comes to running a remote desktop server using non-commercial software. Yes, I’ve tried xrdp. While it works, the graphics performance/latency sucks even though I was using the low resource environment xfce4. Obviously there is commercial remote desktop server software like RealVNC or NoMachine but I don’t want to shell out cash for my cloud desktop and in the case of NoMachine, its proprietary NX protocol isn’t supported by Guacamole.

How to use IPv6 on Quickline/WWZ and pfSense firewall

Here’s how to configure your pfSense firewall for IPv6 on Quickline/WWZ. The settings may work with other ISPs too but YMMV. I’m assuming your modem is already in bridge mode and pfSense is up and running for IPv4 DHCP on the WAN interface.