This change splits the definition of pkg/cri/os.ResolveSymbolicLink by
platform (windows/!windows), and switches to an alternate implementation
for Windows. This aims to fix the issue described in containerd/containerd#5405.
The previous implementation which just called filepath.EvalSymlinks has
historically had issues on Windows. One of these issues we were able to
fix in Go, but EvalSymlinks's behavior is not well specified on
Windows, and there could easily be more issues in the future, so it
seems prudent to move to a separate implementation for Windows.
The new implementation uses the Windows GetFinalPathNameByHandle API,
which takes a handle to an open file or directory and some flags, and
returns the "real" name for the object. See comments in the code for
details on the implementation.
I have tested this change with a variety of mounts and everything seems
to work as expected. Functions that make incorrect assumptions on what a
Windows path can look like may have some trouble with the \\?\ path
syntax. For instance EvalSymlinks fails when given a \\?\UNC\ path. For
this reason, the resolvePath implementation modifies the returned path
to translate to the more common form (\\?\UNC\server\share ->
\\server\share).
Signed-off-by: Kevin Parsons <kevpar@microsoft.com>
