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Using Tunnelbroker to make Lavalink balance its requests over many IPv6 addresses

Freya Arbjerg

24 Mar 2020

When scraping metadata with Lavalink, it may be useful to have a large block of IPv6 addresses available. Allocating a large prefix of addresses to a machine can be difficult, as this is dependent on the configuration of the IP addresses, which is generally out of your control if you are renting a server.

We can use the free Tunnelbroker service from Hurricane Electric to get a routed IPv6 prefix. This can also work if your server does not even have an IPv6 address to begin with. If you intend to use Tunnelbroker, bear in mind that it is a free service and it may break.

Important: Always be careful about making changes to live production systems. Mistakes here could mess up your network and make you unable to access your server. Consider testing on a disposable VPS.

Please read the entire guide

Several weeks later I am still being contacted by people who have trouble with this guide. Most people's problems are fixed by following the troubleshooting guide. I'm still happy to help if you've read this entire guide.

Acquiring a /48 block

  1. Register an account at https://tunnelbroker.net/
  2. Create a new (regular) tunnel
  3. Enter your IPv4 IP address and select a nearby region. Your IPv4 must be pingable.
  4. Request a new /48 by clicking assign /48. We could use a /64, however a /64 is much more likely to be blocked.

Configuring your block

The first thing you will need to do is enable IPv6 binding in Linux. This enables Lavalink (and other programs) to bind to local addresses that would otherwise be considered illegal:

# Enable now
sysctl -w net.ipv6.ip_nonlocal_bind=1
# Persist for next boot
echo 'net.ipv6.ip_nonlocal_bind = 1' >> /etc/sysctl.conf

Next you will need to configure your network system. This diverges a lot depending on your distribution. Hurricane Electric provides a lot of examples. Common for them all is that you need to take two extra steps:

ip -6 route replace local YOUR_48_BLOCK dev lo

Test your configuration

Before setting up Lavalink, you can test if your IPv6 configuration actually works.

# Test that IPv6 works in the first place
ping6 google.com

# If you have the IPv6 block 1234:1234:1234::/48
# You should be able to use any of the IPs within that block
ping6 -I 1234:1234:1234:: google.com
ping6 -I 1234:1234:1234::1 google.com
ping6 -I 1234:1234:1234:dead::beef google.com

# Make sure your /48 block appears when running this command
ip -6 route

This is the easy part. Add the ratelimit block to your config:

lavalink:
  server:
    # ...
    ratelimit:
      ipBlocks: ["1234:1234:1234::/48"]
      strategy: "LoadBalance"
      searchTriggersFail: true

You can read more about the different strategies in ROUTEPLANNERS.md

When using docker

If you use Docker, you will need to set your network mode to "host". This will let your container use the network as if it was not in a container.

Troubleshooting

Ubuntu: Editing /etc/network/interfaces on a Netplan system

Don't edit /etc/network/interfaces if your system relies on a /etc/netplan/ configuration. See the Netplan example on the Tunnelbroker website.

Using the /64 block instead of the /48 block

Make sure the /64 block is not being used in your config. You must replace it in the examples that Tunnelbroker provides.

You probably haven't configured your routes properly. See the “Test your configuration” section.

It is also possible that you have an existing IPv6 configuration that is interfering with your tunnel.

You did not enable net.ipv6.ip_nonlocal_bind as described above.

You're using a nano strategy for a block larger than a /64 block. This doesn't work. The other strategies still pick out random values for the last 64 bits, so there would be no point anywaysIndex out of bounds for the CombinedBlock.

You're running Lavalink in a docker container without host as your network mode.

If that isn't it, check your DNS config. Your DNS server is not returning IPv6 records for whatever reason.

ifup: add tunnel "sit0" failed: No buffer space available

According to duncte123, removing the ttl line in your /etc/network/interfaces file might help.

The steps for that are as following:

  1. Run sudo ip tun del he-ipv6
  2. Comment out the ttl line in your /etc/network/interfaces
  3. Run sudo ifup he-ipv6, this command should run without errors
  4. Remove the comment in front of the ttl line in your /etc/network/interfaces
  5. Run sudo systemctl restart networking, this command should also run without any errors

Why does that work?

These steps work because Ubuntu does not like the ttl line for some reason, commenting the line out allows your server to initialize tunnel properly. You cannot leave the ttl line commented out because your requests will time out within lavalink if you do so. Once the tunnel is created on your system a final restart of the networking interface will also set the ttl on the tunnel and allows lavalink to actually work.

This might also help: https://askubuntu.com/questions/109709/hurricane-ipv6-buffer-space-error/272097

“Help, I've tried everything!”

If you've followed this entire guide and you have a problem not listed here, please open an issue on the #help forum on the Lavalink Discord server. Please provide the following info:

  1. Which distro you are on
  2. The network config you wrote based on one of the Tunnelbroker examples
  3. A screenshot of the Tunnelbroker website with your tunnel details
  4. The output of ip -6 route
  5. Don't say “doesn't work”. Describe your problem in details
  6. A list of everything you have tried

If you fail to get a response from the Lavalink community, feel free to bring the thread to my attention. I will refuse to help if you do not provide the information above.