  The Einstein equations are integrated in the presence of two (incoming and
outgoing) streams of null dust, under the assumptions of spherical symmetry and
staticity. The solution is also written in double null and radiation
coordinates and it is reinterpreted as an anisotropic fluid. Interior matching
with a static fluid and exterior matching with the Vaidya solution along null
hypersurfaces is discussed. The connection with two-dimensional dilaton gravity
is established.
