slackhq/nebula · error

LocalAddr returned: %#v

Error message

LocalAddr returned: %#v

What it means

Type-guard failure in GenericConn.LocalAddr: UDPConn.LocalAddr() returned a type other than *net.UDPAddr (printed with %#v), so conversion to netip.AddrPort is impossible. Defensive branch; effectively unreachable for a real UDP socket.

Source

Thrown at udp/udp_generic.go:72

			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 {
	Len uint32
}

func (u *GenericConn) ListenOut(r EncReader, flush func()) error {
	buffer := make([]byte, MTU)

View on GitHub (pinned to dd8f660c0a)

Solutions

1. GenericConn.LocalAddr received a LocalAddr result that is not *net.UDPAddr — not expected for a UDP socket; update Go and nebula to current versions
2. Ensure nothing wraps or replaces the underlying *net.UDPConn (custom listeners, test harnesses, socket libraries)
3. Include the %#v detail from the error message in a bug report; it names the actual type returned
4. Re-run with an explicit, valid UDP listen address in the nebula config

When it happens

Trigger: Thrown at udp/udp_generic.go:72 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/67226ab2464a4e47. Report an issue: GitHub.