k3s + tailscale + dual-stack ipv6 doesn't start with tailscale advertise-routes error

[m00nwtchr]

Environmental Info:
K3s Version: v1.31.4+k3s1 (a562d09)

Node(s) CPU architecture, OS, and Version: Linux m-server 6.6.69-hardened1 NixOS SMP PREEMPT_DYNAMIC Thu Jan 2 09:32:11 UTC 2025 x86_64 GNU/Linux

Cluster Configuration:
1 server 1 agent

Describe the bug:
After enabling IPv6 dual stack and re-creating the cluster the following error message appears:
flannel exited: failed to register flannel network: failed to run command: tailscale set --accept-routes --advertise-routes=$SUBNET,$IPV6SUBNET Err: exit status 1 Output: ::/0 advertised without its IPv4 counterpart, please also advertise 0.0.0.0/0

Steps To Reproduce:
NixOS k3s module:

{ config, lib, pkgs, ... }:

{
  networking.firewall.allowedTCPPorts = [
    6443 # k3s: required so that pods can reach the API server (running on port 6443 by default)
    2379 # k3s, etcd clients: required if using a "High Availability Embedded etcd" configuration
    2380 # k3s, etcd peers: required if using a "High Availability Embedded etcd" configuration
  ];
  networking.firewall.allowedUDPPorts = [
    8472 # k3s, flannel: required if using multi-node for inter-node networking
  ];

  services.tailscale.enable = true;
  systemd.services.k3s.path = [ pkgs.tailscale pkgs.nftables ];

  services.k3s = {
    enable = true;
    token = "<token>";
    extraFlags = lib.strings.concatStringsSep " " ([
      "--vpn-auth=name=tailscale,joinKey=<tailscale key>"
    ] ++ (if config.services.k3s.role == "server" then [
      "--cluster-cidr=10.42.0.0/16,2001:cafe:42::/56"
      "--service-cidr=10.43.0.0/16,2001:cafe:43::/112"
    ] else []));
  };
}

[brandond]

@manuelbuil any ideas?

[m00nwtchr]

Also, seems like if trying to run in IPv6 only mode, k3s always picks up only the IPv4 address to use to advertise, which creates a apiserver exited: service IP family "2001:cafe:43::/112" must match public address family "100.64.190.109" error, and in an IPv6 only tailnet I just get: "tailscale does not provide an ipv4 address"

[brandond]

What happens if you provide ipv4,ipv6 --node-ip addresses?

[m00nwtchr]

Update for the original issue: Looks like it just randomly went away without changing anything.