Solution (source code)

= Solution

Outside the ingoing null shell the enclosed mass is $E$, so use the ingoing <Ingoing Eddington-Finkelstein coordinates>
$$
ds^2=-(1-2E/r)dv^2+2\,dv\,dr+r^2dΩ^2.
$$
This is the <Schwarzschild spacetime>[Schwarzschild metric] of mass $E$, regular across $r=2E$ and valid for $r>0$ on the exterior side of the shell.