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FIX: Both sides of a TCP connection are closed when the client or remote application half-closes the TCP connection in a Forefront Threat Management Gateway 2010 environment

Consider the following scenario:
  • You have internal clients who are trying to access non-web-based application servers in a Microsoft Forefront Threat Management Gateway (TMG) 2010 environment.
  • The client traffic passes through an application filter in Forefront TMG that data-flows the traffic in user mode.
  • The client or the remote application server half-closes the TCP connection by sending a FIN/ACK packet. In doing this, the client or the remote application server expects the other half of the TCP connection to stay active.

In this scenario, you may notice that both sides of the TCP connection are closed immediately by the FIN/ACK packet.
When traffic is passed through a user-mode data flow, both sockets are closed after a FIN packet is received on one of them. This prevents Forefront TMG from supporting half-closed TCP connections as supported in the kernel-mode data flow.
To resolve this issue, install the hotfix package that is described in the following Microsoft Knowledge Base article:
2649961 Rollup 1 for Forefront Threat Management Gateway (TMG) 2010 Service Pack 2
To enable this fix, follow these steps:
  1. Start Notepad. To do this, click Start, click Run, type notepad.exe in the Open box, and then click OK.
  2. Paste the following script to a new file in Notepad:
    set curArray = CreateObject("FPC.Root").GetContainingArray()Const SE_VPS_GUID = "{143F5698-103B-12D4-FF34-1F34767DEabc}"Const SE_VPS_NAME = "AllowHalfClosedConnection"Const SE_VPS_VALUE = TrueSub SetValue()    ' Create the root obect.    Dim root  ' The FPCLib.FPC root object    Set root = CreateObject("FPC.Root")     'Declare the other objects needed.    Dim array       ' An FPCArray object    Dim VendorSets  ' An FPCVendorParametersSets collection    Dim VendorSet   ' An FPCVendorParametersSet object     ' Get references to the array object    ' and the network rules collection.    Set array = curArray     Set VendorSets = array.VendorParametersSets     On Error Resume Next    Set VendorSet = VendorSets.Item( SE_VPS_GUID )     If Err.Number <> 0 Then        Err.Clear         ' Add the item        Set VendorSet = VendorSets.Add( SE_VPS_GUID )        CheckError        WScript.Echo "New VendorSet added... " & VendorSet.Name     Else        WScript.Echo "Existing VendorSet found... value- " &  VendorSet.Value(SE_VPS_NAME)    End If     if VendorSet.Value(SE_VPS_NAME) <> SE_VPS_VALUE Then         Err.Clear        VendorSet.Value(SE_VPS_NAME) = SE_VPS_VALUE         If Err.Number <> 0 Then            CheckError        Else            VendorSets.Save false, true            CheckError             If Err.Number = 0 Then                WScript.Echo "Done with " & SE_VPS_NAME & ", saved!"            End If        End If    Else       WScript.Echo "Done with " & SE_VPS_NAME & ", no change!"    End If End Sub Sub CheckError()     If Err.Number <> 0 Then        WScript.Echo "An error occurred: 0x" & Hex(Err.Number) & " " & Err.Description        Err.Clear    End If End SubSetValue
  3. Save the file as AllowHalfClosedConnection.vbs, and then exit Notepad.
  4. On a Forefront TMG server, open an administrative command prompt.
  5. Move to the location to which you saved the AllowHalfClosedConnection.vbs script, and then type the following command:
    Cscript.exe AllowHalfClosedConnection.vbs
This fix lets Forefront TMG enable half-closed TCP connections in user-mode data flows.

Note To change the functionality back to the default behavior, change the following line in the script by changing the value from True to False, and then run the script:
Const SE_VPS_VALUE = True
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates

Note This is a "FAST PUBLISH" article created directly from within the Microsoft support organization. The information contained herein is provided as-is in response to emerging issues. As a result of the speed in making it available, the materials may include typographical errors and may be revised at any time without notice. See Terms of Use for other considerations.

Article ID: 2636183 - Last Review: 01/11/2012 18:07:00 - Revision: 1.0

Microsoft Forefront Threat Management Gateway 2010 Service Pack 2, Microsoft Forefront Threat Management Gateway 2010 Enterprise, Microsoft Forefront Threat Management Gateway 2010 Standard

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