What causes "can't find ip for interface %s" in k3s-io/k3s?

Check what is assigned: ip addr show - is there a non-169.254/non-fe80 address?

can't find ip for interface %s

Error message

can't find ip for interface %s

What it means

Fallback error when the interface is found and up but has no global unicast IPv4 and no global unicast IPv6 address: none of the branches that return an address matched, so there is nothing to return. Loopback and link-local addresses (169.254.x.x, fe80::) are deliberately excluded.

Source

Thrown at pkg/util/net.go:312

			continue
		}
		if ip.IsGlobalUnicast() {
			globalUnicasts = append(globalUnicasts, ip.String())
		}
	}

	if len(globalUnicasts) > 1 {
		return "", fmt.Errorf("multiple global unicast addresses defined for %s, please set ip from one of %v", ifaceName, globalUnicasts)
	}
	if len(globalUnicasts) == 1 && len(globalUnicastsIPv6) == 0 {
		return globalUnicasts[0], nil
	} else if len(globalUnicastsIPv6) > 0 && len(globalUnicasts) == 1 {
		return globalUnicasts[0] + "," + globalUnicastsIPv6[0], nil
	} else if len(globalUnicastsIPv6) > 0 {
		return globalUnicastsIPv6[0], nil
	}

	return "", fmt.Errorf("can't find ip for interface %s", ifaceName)
}

type multiListener struct {
	listeners []net.Listener
	closing   chan struct{}
	conns     chan acceptRes
}

type acceptRes struct {
	conn net.Conn
	err  error
}

// explicit interface check
var _ net.Listener = &multiListener{}

var loopbacks = []string{"127.0.0.1", "::1"}

View on GitHub (pinned to 6ba341e396)

Solutions

Check what is assigned: ip addr show <iface> - is there a non-169.254/non-fe80 address?
Fix address acquisition (DHCP client running, static config applied, VLAN correct) and restart the service
If the address arrives late, delay the component until the network is online (network-online.target, readiness checks)
Alternatively set the node IP explicitly via config instead of deriving it from this interface

Defensive patterns

Strategy: validation

Validate before calling

func waitForGlobalUnicast(name string, timeout time.Duration) error {
	deadline := time.Now().Add(timeout)
	for time.Now().Before(deadline) {
		iface, err := net.InterfaceByName(name)
		if err == nil && iface.Flags&net.FlagUp != 0 {
			addrs, _ := iface.Addrs()
			for _, a := range addrs {
				if ip, _, err := net.ParseCIDR(a.String()); err == nil && ip.IsGlobalUnicast() {
					return nil
				}
			}
		}
		time.Sleep(time.Second)
	}
	return fmt.Errorf("interface %s never got a global unicast address", name)
}

Try / catch

ip, err := util.GetIPFromInterface(name)
if err != nil && strings.Contains(err.Error(), "can't find ip for interface") {
	// DHCP/addressing may still be converging: surface which interface and check
	// `ip addr show <iface>` for link-local-only state before retrying
}
if err != nil {
	return "", err
}

Prevention

Ensure DHCP is reliable (or use static IPs) on the interface the node derives its IP from
Delay startup until the network is online instead of racing address assignment
Treat 169.254.x.x on the interface as a DHCP failure signal
Set node-ip explicitly when the preferred interface has no simple unicast address

When it happens

Trigger: The interface is up but only carries link-local or loopback addresses: DHCP failed or has not run yet, the static IP was not applied yet, or the interface only got an APIPA 169.254.x.x address.

Common situations: VMs booting before DHCP completes; interfaces configured after the service starts; agent containers that see the interface before the host assigns its address; misrouted VLANs where DHCP never answers.

Related errors

AI-assisted analysis of k3s-io/k3s@6ba341e396 (2026-08-15). Data as JSON: /api/errors/67f8fe05cc4bb7bd. Report an issue: GitHub.