slackhq/nebula · error

LocalAddr returned invalid IP address: %s

Error message

LocalAddr returned invalid IP address: %s

What it means

Type-guard failure in GenericConn.LocalAddr: the local address's IP slice failed netip.AddrFromSlice conversion (invalid length), so it cannot become a netip.AddrPort. Indicates corrupt address data from the runtime rather than user error.

Source

Thrown at udp/udp_generic.go:67

	written := 0
	for i, b := range bufs {
		if _, err := u.UDPConn.WriteToUDPAddrPort(b, addrs[i]); err == nil {
			written++
		} else {
			u.l.Debug("failed to write packet in batch", "udpAddr", addrs[i], "error", err)
		}
	}
	return written, nil
}

func (u *GenericConn) LocalAddr() (netip.AddrPort, error) {
	a := u.UDPConn.LocalAddr()

	switch v := a.(type) {
	case *net.UDPAddr:
		addr, ok := netip.AddrFromSlice(v.IP)
		if !ok {
			return netip.AddrPort{}, fmt.Errorf("LocalAddr returned invalid IP address: %s", v.IP)
		}
		return netip.AddrPortFrom(addr, uint16(v.Port)), nil

	default:
		return netip.AddrPort{}, fmt.Errorf("LocalAddr returned: %#v", a)
	}
}

func (u *GenericConn) ReloadConfig(c *config.C) {

}

func NewUDPStatsEmitter(udpConns []Conn) func() {
	// No UDP stats for non-linux
	return func() {}
}

type rawMessage struct {

View on GitHub (pinned to dd8f660c0a)

Solutions

1. netip.AddrFromSlice failed on the UDPAddr.IP, which is nil or not 4/16 bytes — usually means the socket is bound to an invalid or unspecified address; set a concrete valid listen.host in the nebula config
2. Check for inherited/activated sockets (systemd, container) with no bound address; bind explicitly instead
3. Restart nebula after fixing the listen address; the local address is resolved once during NewListener via LocalAddr
4. If persistent across valid configs, report with Go version — this would indicate unexpected *net.UDPAddr behavior

When it happens

Trigger: Thrown at udp/udp_generic.go:67 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of slackhq/nebula@dd8f660c0a (2026-09-03). Data as JSON: /api/errors/59577b76c0034faf. Report an issue: GitHub.