mesos git commit: Windows: Added legacy support for admin-only symlinks.

[an...@apache.org]

Repository: mesos
Updated Branches:
  refs/heads/master ca6729315 -> 4bf96153a


Windows: Added legacy support for admin-only symlinks.

Some users are regrettably stuck on versions of Windows before this
feature was added. If the `ALLOW_UNPRIVILEGED` flag is unsupported, the
creation of the symlink will fail with `ERROR_INVALID_PARAMETER`.

Review: https://reviews.apache.org/r/64461


Project: http://git-wip-us.apache.org/repos/asf/mesos/repo
Commit: http://git-wip-us.apache.org/repos/asf/mesos/commit/4bf96153
Tree: http://git-wip-us.apache.org/repos/asf/mesos/tree/4bf96153
Diff: http://git-wip-us.apache.org/repos/asf/mesos/diff/4bf96153

Branch: refs/heads/master
Commit: 4bf96153abfde2c5b18373072a5a85c377293086
Parents: ca67293
Author: Andrew Schwartzmeyer <an...@schwartzmeyer.com>
Authored: Fri Dec 8 13:11:44 2017 -0800
Committer: Andrew Schwartzmeyer <an...@schwartzmeyer.com>
Committed: Thu Dec 14 13:23:02 2017 -0800

----------------------------------------------------------------------
 .../stout/internal/windows/reparsepoint.hpp     | 40 ++++++++++++--------
 1 file changed, 24 insertions(+), 16 deletions(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/mesos/blob/4bf96153/3rdparty/stout/include/stout/internal/windows/reparsepoint.hpp
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diff --git a/3rdparty/stout/include/stout/internal/windows/reparsepoint.hpp b/3rdparty/stout/include/stout/internal/windows/reparsepoint.hpp
index 158f445..858b3c7 100644
--- a/3rdparty/stout/include/stout/internal/windows/reparsepoint.hpp
+++ b/3rdparty/stout/include/stout/internal/windows/reparsepoint.hpp
@@ -328,29 +328,37 @@ inline Try<Nothing> create_symbolic_link(
   // Bail out if target is already a reparse point.
   Try<bool> attribute_set = reparse_point_attribute_set(longpath(target));
   if (attribute_set.isSome() && attribute_set.get()) {
-    return Error(
-        "Path '" + target + "' is already a reparse point");
+    return Error("Path '" + target + "' is already a reparse point");
   }
 
-  // Avoid requiring administrative privileges to create symbolic links.
-  DWORD flags = SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE;
-  if (target_is_folder) {
-    flags |= SYMBOLIC_LINK_FLAG_DIRECTORY;
-  }
+  DWORD flags = target_is_folder ? SYMBOLIC_LINK_FLAG_DIRECTORY : 0;
+
+  // Lambda to create symlink with given flags.
+  auto link = [&reparse_point, &target](const DWORD flags) {
+    return ::CreateSymbolicLinkW(
+        // Path to link.
+        longpath(reparse_point).data(),
+        // Path to target.
+        longpath(target).data(),
+        flags);
+  };
 
   // `CreateSymbolicLink` normally adjusts the process token's privileges to
   // allow for symlink creation; however, we explicitly avoid this with the
-  // above flag.
-  if (!::CreateSymbolicLinkW(
-          // Path to link.
-          longpath(reparse_point).data(),
-          // Path to target.
-          longpath(target).data(),
-          flags)) {
-    return WindowsError();
+  // following flag to not require administrative privileges.
+  if (link(flags | SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE)) {
+    return Nothing();
+  }
+
+  // If this failed because the non-symbolic link feature was not supported,
+  // try again without the feature. This is for legacy support.
+  if (::GetLastError() == ERROR_INVALID_PARAMETER) {
+    if (link(flags)) {
+      return Nothing();
+    }
   }
 
-  return Nothing();
+  return WindowsError();
 }
 
 } // namespace windows {