DOS applications dosn't work with VBox Guest Additions shared folders

[Dimitar Nanev]

Hello,

There is a problem with DOS applications working on folders shared through VBox Guest Additions.

The test configuration is:

Host: Win XP, 32-bit /problem also confirmed on Win7 64-bit host/

Guest: Win XP, 32-bit

Shared folder: 'D:\' on host shared as 'D'; Drive F: on the guest is mapped to \vboxsvr\D;

Problem: A DOS application running on the guest cannot find any file residing on a shared folder. The standard DOS FindFirst function call (INT 21/AH=4E) always fails despite there is files matching to the search criteria. For example FindFirst("F:\Temp\*.*") always got error is 0x12 (NO MORE FILES), but there are files in F:\Temp. Furthermore if you call GetExtendedError (INT 21/AH=59h) afterwards it reports error 0xEA which looks meaningless and unrelated to the error returned by FindFirst.

The problem occurs only if you are searching for files on a shares through VirtualBox Guest Additions. It's working correctly with classic SMB network shares.

I tested FindFirst for files on a network drive (e.g. drive 'G:' mapped to a network share) and it works. But if you map G: to \vboxsvr\some-shared-folder then you always got error as described above.

Another test by running 4DOS command shell on the guest shows similar behaviour (4DOS is a popular 16-bit DOS shell like COMMAND.COM). If you type "dir F:\*.*", where F: is mapped to \vboxsvr\some-shared-folder you see empty directory listing.

Described problem also appears also on a different machine with Windows 7, 64-bit host.