[cifs-protocol] [EXTERNAL] Trying to let a Windows client use MS-SWN against a samba cluster
Kristian Smith
Kristian.Smith at microsoft.com
Mon Dec 11 21:15:57 UTC 2023
Hi Metze,
I'm reaching out with regard to question 10 from your mail below.
---------------------------------------------------------------------------------------------------------
Question 10:
MS-SWM 3.1.6.1 Server Application Notifies of an Interface Being Enabled or Disabled
The calling application provides the interface group name, IPv4 and/or IPv6
addresses, and state.
...
Then for each entry in the WitnessRegistrationList where
WitnessRegistration.NetworkName
matches the application-provided interface group name ...
This seems to indicate that there's actually just a single
InterfaceGroupName matching the single NetworkName.
---------------------------------------------------------------------------------------------------------
WitnessRegistration.NetworkName is the NetName provided by the client when registering.
InterfaceGroupName is provided by the Server Cluster application.
If there are no current registered witnesses (clients), the Interface.InterfaceGroupName would still exist, but there would be no WitnessRegistration.NetworkName
This check (referenced in your question) compares the server-application-provided InterfaceGroupName (the one that underwent a state change) to those in the list of registered witnesses. This ensures that the client receives a message about the state change.
Please let me know if there are lingering concerns with Question 10 and I'd be happy to dig back in.
Regards,
Kristian Smith
Support Escalation Engineer | Azure DevOps, Windows Protocols | Microsoft® Corporation
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________________________________
From: Stefan Metzmacher <metze at samba.org>
Sent: Tuesday, November 7, 2023 6:29 AM
To: Interoperability Documentation Help <dochelp at microsoft.com>
Cc: cifs-protocol at lists.samba.org <cifs-protocol at lists.samba.org>
Subject: [EXTERNAL] Trying to let a Windows client use MS-SWN against a samba cluster
Hi DocHelp,
I'm currently implementing MS-SWN for samba
in order to allow clients to move to a different
network interface or cluster node if a specific interface
or a complete cluster node gets offline.
In a Samba cluster we have multiple nodes, but just a single netname for all of
them, so there's only a single computer with it's sAMAccountName in active
directory. But each node can have multiple ip addresses,
which may move around between nodes, but some can be
node local.
Now my goal is to let a Windows client use the witness service
in order to get notified about ip addresses going down,
because the interface link or a whole node gets offline.
In order to archive that I need to understand the
exact client behavior implemented in the Windows
clients (also with possible differences of various
Windows versions).
However this is hard from just reading the existing docs...
MS-SWN "3.2 Witness Client Details" doesn't contain
any detail for the logical processing, e.g.
- 3.2.4.1 Application Requests Witness Register
doesn't say that WITNESS_INTERFACE_INFO.InterfaceGroupName
is that name used as part of the servicePrincipalName
(after being prefixed by 'CIFS/') passed to the authentication
layer (spnego, kerberos, ntlm), but I'm seeing this
behavior from a Windows 2022 server as client.
In older version (Windows 2012) I saw that the principal
was requested by the method from MS-RPCE 2.2.1.3.4
rpc_mgmt_inq_princ_name.
Question 1:
Can you please update this with a product behavior note reflecting
the reality with all Windows versions.
- 3.2.4.2 Application Requests Witness Event Notification
only says: ...
The status and any received RESP_ASYNC_NOTIFY result obtained from
the server in the previous step MUST be returned to the caller.
- 3.2.4.3 Application Requests Witness UnRegister
Has the following notable section:
... or if the WitnessRegistration.WitnessNotifyRequest is TRUE,
the client MUST stop processing and return an implementation-defined
local error to the caller.
So it seems with a pending AsyncNotify request the Unregister
seems to be skipped.
With that I'd expect the core logic/behavior of a Windows client
being specified in MS-SMB2, when I look there I found the following
3.2.5.2 Receiving an SMB2 NEGOTIATE Response
...
If SMB2_GLOBAL_CAP_PERSISTENT_HANDLES is set in the Capabilities field of the
SMB2 NEGOTIATE Response, the client SHOULD invoke the event as specified in
[MS-SWN] section 3.2.4.1 by providing Connection.ServerName as Netname
parameter.
Question 2:
I don't see this happening from a Windows Server 2022 acting as client.
Can you please update this with a product behavior note reflecting
the reality with all Windows versions.
3.2.5.5 Receiving an SMB2 TREE_CONNECT Response
...
- TreeConnect.IsCAShare MUST be set to TRUE, if the
SMB2_SHARE_CAP_CONTINUOUS_AVAILABILITY bit is set in the Capabilities
field of the response.
...
If Connection.Dialect belongs to the SMB 3.x dialect family and the Capabilities
field in the response includes SMB2_SHARE_CAP_CLUSTER bit, the client SHOULD
invoke the event as specified in [MS-SWN] section 3.2.4.1 by providing
Connection.ServerName as Netname parameter.
...
If Connection.Dialect belongs to the SMB 3.x dialect family and the Capabilities
field in the response includes the SMB2_SHARE_CAP_SCALEOUT bit, the client MUST
set TreeConnect.IsScaleoutShare to TRUE.
...
If Connection.Dialect is "3.0.2" or "3.1.1" and the Capabilities field in the
response includes the SMB2_SHARE_CAP_ASYMMETRIC bit, the client MUST verify
whether both of the following conditions are true:
...
If the SMB2 TREE_CONNECT request is successful, the client SHOULD invoke the
event as specified in [MS-SWN] section 3.2.4.1 by providing
Connection.ServerName as the Netname parameter and TreeConnect.ShareName as the
ShareName parameter, and by setting the IsShareNameNotificationRequired
parameter to TRUE.
Question 3:
I don't see this happening from a Windows Server 2022 acting as client.
The only relevant flags in order to let the client try a witness connection
are SMB2_SHARE_CAP_CONTINUOUS_AVAILABILITY together with SMB2_SHARE_CAP_CLUSTER.
Can you please update this with a product behavior note reflecting
the reality with all Windows versions.
3.2.5.6 Receiving an SMB2 TREE_DISCONNECT Response
... If Connection.Dialect belongs to the SMB 3.x dialect family and if
Session.TreeConnectTable is empty in all sessions in the Connection.SessionTable
for which Connection.ServerName matches the server name, the client SHOULD
invoke the event as specified in [MS-SWN] section 3.2.4.3.
Question 4:
I don't see this happening from a Windows Server 2022 acting as client.
The witness registration stays until a reboot.
There's also no new witness registration after a reconnect to
a different ip, which means that the smb connection and witness connection
may stay on the same server ip address, which means there's no benefit from it.
Can you please update this with a product behavior note reflecting
the reality with all Windows versions.
3.2.7.1 Handling a Network Disconnect
...
If Connection.Dialect belongs to the SMB 3.x dialect family and if
Session.TreeConnectTable is empty in all sessions in the Connection.SessionTable
for which Connection.ServerName matches the server name, the client SHOULD
invoke the event as specified in [MS-SWN] section 3.2.4.3.
Question 5:
I don't see this happening from a Windows Server 2022 acting as client.
The witness registration stays until a reboot.
There's also no new witness registration after a reconnect to
a different ip, which means that the smb connection and witness connection
may stay on the same server ip address, which means there's no benefit from it.
Can you please update this with a product behavior note reflecting
the reality with all Windows versions.
3.2.4.3.5 Application Requests Creating a File Opened for Durable Operation
...
- If TreeConnect.IsCAShare is TRUE, the client MUST set the
SMB2_DHANDLE_FLAG_PERSISTENT bit in the Flags field. Otherwise, the client SHOULD
perform one of the following:
- Request a batch oplock by setting RequestedOplockLevel in the create request to
SMB2_OPLOCK_LEVEL_BATCH.
- Request a handle caching lease by including an SMB2_CREATE_REQUEST_LEASE or
SMB2_CREATE_REQUEST_LEASE_V2 Create Context in the create request with a
LeaseState that includes SMB2_LEASE_HANDLE_CACHING.
...
Question 6:
From the documentation the above is the only reference that is
impacted by SMB2_SHARE_CAP_CONTINUOUS_AVAILABILITY and it seems
that it implicitly disables handle caching, is that really true?
And SMB2_DHANDLE_FLAG_PERSISTENT doesn't seem to be impacted by
SMB2_GLOBAL_CAP_PERSISTENT_HANDLES, which is strange.
Can you please cross-check this?
3.2.4.27 Application Notifies Offline Status of a Server
This optional interface is applicable only for the SMB 3.x dialect family. The
application provides the following:
- ServerName: The name of the server which became unavailable.
For each Connection in the ConnectionTable where Connection.ServerName matches
ServerName, the client MUST determine if any TreeConnect exists in the
Session.TreeConnectTable with TreeConnect.IsScaleoutShare set to TRUE.
If a tree connect entry is found, the client MUST do the following:
- Disconnect the connection by performing the steps as specified in section 3.2.7.1.
- Invoke the event as specified in section 3.2.4.28 with ServerName set to the
caller-supplied ServerName.
If no tree connect entry is found, the client MUST disconnect the connection
by performing the steps as specified in section 3.2.7.1.
Question 7:
The above section is the only place in the whole documentation
that references SMB2_SHARE_CAP_SCALEOUT, is that really correct?
And it seems to be required in order trigger an immediate reconnect.
Can you please cross-check this?
3.2.4.28 Application Notifies Online Status of a Server
This optional interface is applicable only for the SMB 3.x dialect family. The
application provides the following:
- ServerName: The name of the server which became available.
For each Open in the GlobalFileTable, where Open.Session.ChannelList is empty
and the server name identified from Open.FileName matches ServerName, the client
MUST re-establish the durable open as specified in section 3.2.4.4.
3.2.4.29 Application Requests Moving to a Server Instance
This optional interface is applicable only for SMB 3.x dialect family. The
application provides the following:
- ServerName: The name of the server.
- NewServerAddress: The IPv4 or IPv6 address of the server which the client
is required to move to.
For each Connection in the ConnectionTable where Connection.ServerName matches
ServerName, the client MUST disconnect the connection by performing the steps as
specified in section 3.2.7.1.
For each Open in the GlobalFileTable, where Open.Session.ChannelList is empty
and the server name identified from Open.FileName matches ServerName, the client
MUST re-establish the durable open as specified in section 3.2.4.4, and by using
NewServerAddress as the TransportIdentifier for the rules specified in section
3.2.4.2.
Question 8:
The impact of SMB2_SHARE_CAP_CONTINUOUS_AVAILABILITY
without SMB2_GLOBAL_CAP_PERSISTENT_HANDLES is a very
important part of this.
Question 9:
Section 3.2.4.27-3.2.4.29 seems to actions triggered when
the client receives an RESP_ASYNC_NOTIFY, but there's no
specification on how the individual witness registrations
handle specific notification events. E.g. based on the
different posibilities for RESOURCE_CHANGE.ResourceName
Is a CLIENT_MOVE_NOTIFICATION a better choice when using
a single InterfaceGroupName for all nodes?
Question 10:
MS-SWM 3.1.6.1 Server Application Notifies of an Interface Being Enabled or Disabled
The calling application provides the interface group name, IPv4 and/or IPv6
addresses, and state.
...
Then for each entry in the WitnessRegistrationList where
WitnessRegistration.NetworkName
matches the application-provided interface group name ...
This seems to indicate that there's actually just a single
InterfaceGroupName matching the single NetworkName.
Question 11:
I'm also wondering if ServerGlobalName is really a single name,
as I can the client can use a dns or netbios name of the server!
Thanks!
metze
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