[PATCH][WIP] query smb3 reparse tags for special files

[Aurélien Aptel]

Steve French <smfrench at gmail.com> writes:
> smbfsctl.h:#define IO_REPARSE_TAG_LX_SYMLINK    0xA000001D
> smbfsctl.h:#define IO_REPARSE_TAG_LX_FIFO            0x80000024
> smbfsctl.h:#define IO_REPARSE_TAG_LX_CHR             0x80000025
> smbfsctl.h:#define IO_REPARSE_TAG_LX_BLK             0x80000026
>
> These also make sense for us to use more broadly because it simplifies readdir
>
> but ... my first attempt at querying this using infolevel 33
> FileReparsePointInformation (see MS-FSCC section 2.4.35) failed ...
> with Windows 10 returning STATUS_NOT_SUPPORTED when querying various
> reparse points (created by WSL indirectly) including fifos, symlinks
> and char devices.
>
> I can switch approaches and try to do the smb3 fsctl to query reparse
> info instead but was hoping that query info would work.  Any idea if
> there is another info level that would allow me to query the tag?

According to [MS-FSCC] if the file has the REPARSE_TAG attribute, the
EaSize field must be interpreted as a reparse tag for these info levels:

* FileFullDirectoryInfo
* FileBothDirectoryInfo
* FileIdFullDirectoryInfo
* FileIdBothDirectoryInfo

Otherwise we have code for querying the reparse tag in
smb2_query_symlink():

	rc = SMB2_ioctl_init(tcon, server,
			     &rqst[1], fid.persistent_fid,
			     fid.volatile_fid, FSCTL_GET_REPARSE_POINT,
			     true /* is_fctl */, NULL, 0,
			     CIFSMaxBufSize -
			     MAX_SMB2_CREATE_RESPONSE_SIZE -
			     MAX_SMB2_CLOSE_RESPONSE_SIZE);

-- 
Aurélien Aptel / SUSE Labs Samba Team
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