k3s-io/k3s · error

no IPv6 address found

Error message

no IPv6 address found

What it means

getFirst6 in pkg/util/net.go returns the first IPv6 address from a []net.IP (checked with netutils.IsIPv6), or 'no IPv6 address found' when none qualifies. It backs GetFirst6String and is used on dual-stack paths that must derive an IPv6 address (e.g. v6 node addresses or CIDRs for dual-stack networking).

Source

Thrown at pkg/util/net.go:94

func JoinIP4Nets(elems []*net.IPNet) string {
	var strs []string
	for _, elem := range elems {
		if elem != nil && elem.IP.To4() != nil {
			strs = append(strs, elem.String())
		}
	}
	return strings.Join(strs, ",")
}

// getFirst6 returns the first IPv6 address from the list of IP addresses.
// If no IPv6 addresses are found, an error is raised.
func getFirst6(elems []net.IP) (net.IP, error) {
	for _, elem := range elems {
		if elem != nil && netutils.IsIPv6(elem) {
			return elem, nil
		}
	}
	return nil, errors.New("no IPv6 address found")
}

// getFirst6Net returns the first IPv4 network from the list of IP networks.
// If no IPv6 addresses are found, an error is raised.
func getFirst6Net(elems []*net.IPNet) (*net.IPNet, error) {
	for _, elem := range elems {
		if elem != nil && netutils.IsIPv6(elem.IP) {
			return elem, nil
		}
	}
	return nil, errors.New("no IPv6 CIDRs found")
}

// GetFirst6String returns the first IPv6 address from a list of IP address strings.
// If no IPv6 addresses are found, an error is raised.
func GetFirst6String(elems []string) (string, error) {
	ips := []net.IP{}
	for _, elem := range elems {

View on GitHub (pinned to 6ba341e396)

Solutions

1. Add an IPv6 to the relevant list: --node-ip=192.0.2.10,2001:db8::10 so a valid v6 exists.
2. Ensure the chosen interface has a global unicast IPv6 address (ip -6 addr show scope global).
3. If dual-stack is not intended, disable the dual-stack options so v6 derivation is not attempted.
4. Sanitize inputs: net.ParseIP each comma-separated entry and reject nils before passing them in.

Example fix

# before: dual-stack enabled but no v6 supplied -> error
k3s server --node-ip=192.0.2.10 --cluster-cidr=10.42.0.0/16,fd00:42::/56

# after: node-ip includes the v6 address
k3s server --node-ip=192.0.2.10,2001:db8::10 --cluster-cidr=10.42.0.0/16,fd00:42::/56

// Equivalent of GetFirst6String pre-check
count := 0
for _, s := range strings.Split(nodeIPFlag, ",") {
    if ip := net.ParseIP(s); ip != nil && netutils.IsIPv6(ip) {
        count++
    }
}
if count == 0 {
    return errors.New("no IPv6 in node-ip list for dual-stack path")
}

if err != nil && strings.Contains(err.Error(), "no IPv6 address found") {
    // supply a global unicast v6 via --node-ip or disable dual-stack
}

When it happens

Trigger: Dual-stack configuration paths calling getFirst6/GetFirst6String with a list containing only IPv4 addresses or unparsable strings (net.ParseIP returns nil for garbage, which is skipped) - e.g. --node-ip lacking a v6 entry on a dual-stack cluster, or an interface with no global v6 address.

Common situations: Enabling dual-stack without providing IPv6 addresses; v6 privacy extensions or link-local-only interfaces; flags copy-pasted from single-stack setups.

Related errors

• no IPv4 address found
• no IPv4 CIDRs found
• no IPv6 CIDRs found
• cluster-cidr: %v and service-cidr: %v, must share the same I
• invalid node-ip: %w

AI-assisted analysis of k3s-io/k3s@6ba341e396 (2026-08-15). Data as JSON: /api/errors/2ea81d45e3e44bba. Report an issue: GitHub.