A readdir of /data/alias is dispatched at /data/real and answers with
that directory's entries, but the marks were read off the typed path,
so every link inside an aliased directory came back unmarked: a wasi
guest read a directory link there as a directory and walked into it.
link_names_under resolves a link prefix now, the way the listing itself
is resolved. link_stats_under needs no such resolution, since it is
handed the path the router already rewrote.
The python door also reads the marks after the listing rather than
before, so a directory that will not list fails as readdir rather than
as the mark read.
Zecheng Zhang
4cd8c64fa2