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Date:	Thu, 3 Apr 2025 14:28:17 -0700 (PDT)
X-X-Sender:	jeremyd AT resin DOT csoft DOT net
To:	cygwin AT cygwin DOT com
cc:	Ms-nfs41-client-devel AT lists DOT sourceforge DOT net
Subject:	Re: Windows Remote Driver Identification Re: Cygwin wishlist for
	NFSv4.2 driver?
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From:	Jeremy Drake via Cygwin <cygwin AT cygwin DOT com>
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On Wed, 2 Apr 2025, Cedric Blancher via Cygwin wrote:

> On Tue, 1 Apr 2025 at 13:54, Corinna Vinschen via Cygwin
> <cygwin AT cygwin DOT com> wrote:
> > No, but if we want to *better* support this driver, we need either a
> > patch (preferred) or at least info how to distinguish in
> > fs_info::update(*) between the MSFT driver and the NFSv4.2 driver.
>
> That is actually easy: Roland implemented support for
> FileRemoteProtocolInformation in
> https://github.com/kofemann/ms-nfs41-client/commit/e9f72b61494bebd9e26fefec2659a4511a05b0fd
>  , and the FILE_REMOTE_PROTOCOL_INFORMATION->Protocol field can be
> used to identify the type of driver.
>
> Examples:
> Windows NFSv3 driver uses WNNC_NET_MS_NFS,
> OpenAFS uses WNNC_NET_OPENAFS, ms-nfs41-client uses
> WNNC_NET_RDR2SAMPLE, and OpenText NFS also uses WNNC_NET_RDR2SAMPLE.
>
> Plan for ms-nfs42-client is to obtain an own WNNC_NET_MSNFS42CLIENT
> tag, and also tags for DOKANY.

I thought using WNNC to identify was brought up before and rejected.  At
this point, it's querying *volume* information, and has a volume handle.
It looks like you get FileRemoteProtocolInformation by querying a *file*
handle.  I could be wrong, and maybe that handle can be queried for
FileRemoteProtocolInformation, but it's not like that returns a unique
identifier either.

What I'm seeing of the things that come through volume information:
FileSystemName is either NFS or DEBUG-NFS41 (the latter at least looks
unique, if not intended for public consumption).  The VolumeLabel is
PnfsVolume, the VolumeSerialNumber is always 0xBABAFACE (that's got to
suck for the "unique per-drive/share hash" mentioned in mount.cc), the
flags are set in
https://github.com/kofemann/ms-nfs41-client/blob/bf8d343ba2465926f3bfafa8407a69e79649cf46/daemon/nfs41_superblock.c#L173

What stands out to me in the flags is that they include
FILE_SUPPORTS_REMOTE_STORAGE.  I'm not sure what that's supposed to
mean, above and beyond FILE_REMOTE_DEVICE.  MS NFS only seems to set
FILE_CASE_PRESERVED_NAMES (2), so the existing flag song-and-dance could
probably be extended to tell the difference here.

They're also always setting
SSINFO_FLAGS_ALIGNED_DEVICE|SSINFO_FLAGS_PARTITION_ALIGNED_ON_DEVIVE|
SSINFO_FLAGS_NO_SEEK_PENALTY.

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