The WTSQuerySessionInformation function on a Windows Server 2008-based terminal server returns ambiguous IPv6 address data

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SYMPTOMS

Consider the following scenario:

On a Windows Server 2008-based terminal server, an application calls the WTSQuerySessionInformation function to query the IP address of a terminal server client.
The terminal server client has an IPv6 address that contains several contiguous blocks of zeros.

In this scenario, the WTSQuerySessionInformation function returns ambiguous data. Therefore, the application cannot rely on this function to retrieve the IPv6 address of the terminal server client.

For example, the following is the actual client IPv6 address:

fe80:0000:0000:0000:385f:e84b:ac02:f69c

In compliance with the IPv6 specification, this address can be abbreviated by using double-colon characters (::). Therefore, the following is the abbreviated form of the address:

fe80::385f:e84b:ac02:f69c

However, the WTSQuerySessionInformation function returns a WTS_CLIENT_ADDRESS structure that resembles the following:

typedef struct _WTS_CLIENT_ADDRESS {
DWORD AddressFamily; 17 00 00 00
BYTE Address[20]; 00 00 FE 80 00 00 38 5F E8 4B AC 02 F6 9C 00 00 00 00 00 00
} ;

In this example, the double-colon characters are returned as "00 00" instead of as the correct number of zeros. In this situation, the application cannot interpret which one of the following is the correct full IPv6 address:

fe80:0000:385f:e84b:ac02:f69c:0000:0000
fe80:0000:0000:385f:e84b:ac02:f69c:0000
fe80:0000:0000:0000:385f:e84b:ac02:f69c

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RESOLUTION

Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, submit a request to Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support (http://support.microsoft.com/contactus/?ws=support)

Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

Prerequisites

No prerequisites are required.

Restart requirement

You must restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any other hotfixes.

File information

The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.

Windows Server 2008, x86-based versions

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File name	File version	File size	Date	Time	Platform
Rdpwd.sys	6.0.6001.22152	180,736	08-Apr-2008	06:13	x86

Windows Server 2008, x64-based versions

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File name	File version	File size	Date	Time	Platform
Rdpwd.sys	6.0.6001.22152	209,920	08-Apr-2008	06:47	x64

Windows Server 2008, Itanium-based versions

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File name	File version	File size	Date	Time	Platform
Rdpwd.sys	6.0.6001.22152	475,648	08-Apr-2008	02:24	IA-64

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STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

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MORE INFORMATION

Request for Comments (RFC) 4291

Because of how certain styles of IPv6 addresses are allocated, some addresses may contain long strings of zero bits. There is a special syntax to simplify the presentation of these zero bits. That is, double-colon characters (::) can be used to indicate one or more groups of 16 bits of zero. These double-colon characters can also be used to compress leading zeros or trailing zeros in an address.

Note The double-colon characters can appear only one time in a particular address.

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