FIX: The FTP service stops responding if the "Access IP restrictions" option has been set for an FTP site

View products that this article applies to.

SYMPTOMS

If the "Access IP restrictions" option has been set for an FTP site, the FTP service may stop responding, and users may not be able to connect to the restricted FTP site.

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This behavior occurs because unauthorized IP addresses are rejected if the "Access IP restrictions" option is set for an FTP site. These rejected requests are not closed correctly, and the FTP service stops responding when the number of rejected requests exceeds the number of available sockets.

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RESOLUTION

A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Only apply it to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next Microsoft Internet Information Services service pack or security update that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:

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

Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

Prerequisites

You must be running one of the following to install this hotfix:

Microsoft Windows NT 4.0 Server Service Pack 6 (SP6)
Microsoft Windows 2000 Server Service Pack 3 (SP3) or later
Microsoft Windows 2000 Advanced Server Service Pack 3 (SP3) or later

Restart requirement

You must restart your 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) 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 tool in Control Panel.

   Date         Time   Version            Size    File name
   --------------------------------------------------------------
   27-Aug-2003  16:20  5.0.2195.6808     118,032  Ftpsvc2.dll

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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

When IP restriction is used to control access to a Microsoft FTP site, and a client that has an unauthorized IP address tries to access that FTP site, the socket that is used to open the connection is never closed. One socket handle is created for each connect request. When a connect request is blocked by the access IP restriction, the socket handle is not closed. When the socket handle is not closed, the socket remains in a CLOSE_WAIT state indefinitely. The available pool of sockets is eventually exhausted, and the restricted FTP site does not reply to requests.

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