func (u uint128) and(m uint128) uint128 {
	return uint128{u.hi & m.hi, u.lo & m.lo}
}
and returns the bitwise AND of u and m (u&m).
package netaddr
import "math/bits"
type uint128 struct {
	hi uint64
	lo uint64
}
func (u uint128) isZero() bool { return u.hi|u.lo == 0 }