|Date:||March 30, 2006 / year-entry #114|
|Summary:||Okay, everybody, here's your chance to solve a compatibility problem. There is no answer yet; I'm looking to see how you folks would attack it. This is a real bug in the Windows Vista database. A beta tester reported that Explorer fails to show more than about a hundred files per directory from file servers...|
Okay, everybody, here's your chance to solve a compatibility problem. There is no answer yet; I'm looking to see how you folks would attack it. This is a real bug in the Windows Vista database.
A beta tester reported that Explorer fails to show more than about a hundred files per directory from file servers running a particular brand of the file server software. The shell and networking teams investigated the problem together and tracked it down to the server incorrectly handling certain types of directory queries. Although the server claims to support both slow and fast queries, if you try a fast query, it returns only the first hundred or so files and then gives up with a strange error code. On the other hand, if Explorer switches to the slow query, then everything works fine. (Windows XP always used the slow query.) Additional data: An update to the server software was released earlier this year which claims to fix the bug. However (as of this writing), all of the vendor's distributors continue to ship the buggy version of the driver.
What should we do? Here are some options. Choose of of the below or make up your own!
Make no accomodation for this particular buggy protocol implementation. People who are running that particular implementation will get incomplete directory listings. Publish a Knowledge Base article describing the problem and directing customers to contact the vendor for an updated driver.
Auto-detect the buggy driver and put up a warning dialog
Explorer should recognize the strange error code and display an error message to the user saying, "The server \\servername appears to be running an old version of the XYZ driver that does not report the contents of large directories properly. Not all items in the directory are shown here. Please contact the administrator of the machine \\servername to have the driver upgraded." (Possibly with a "Don't show this dialog again" check-box.)
Auto-detect the buggy driver and work around it next time
Explorer should recognize the strange error code and say, "Oh, this server must have the buggy driver. It's too late to do anything about the current directory information, but I'll remember that I should do things the slow way in the future when talking to this server."
To avoid denial-of-service attacks, remember only the last 16 (say) servers that exhibit the problem. (If the list of "known bad" servers were unbounded, then an attacker could consume all the memory on your computer by creating a server that responded to a billion different names and using HTTP redirects to get you to visit all of those servers in turn.)
Have a configuration setting to put the network client into "slow mode"
Add a configuration setting to the Windows network client to tell it "If somebody asks whether a server supports fast queries, always say No, even if the server says Yes." In this manner, no program will attempt to use fast queries; they will all use slow queries. Directory queries will run slower, but at least they will work.
Have a configuration setting to put Explorer into "slow mode"
Add a configuration setting to Explorer to tell it "Always issue slow queries; never issue fast queries." Directory queries will run slower, but at least they will work. But this affects only Explorer; other programs which ask the server "Do you support fast queries?" will receive an affirmative response and attempt to use fast queries, only to rediscover the problem that Explorer worked around.
Disable "fast mode" by default
Stop supporting "fast mode" in the network client since it is unreliable; there are some servers that don't handle "fast mode" correctly. This forces all programs to use "slow mode". Optionally, have a configuration setting to re-enable "fast mode".
Be creative. Make sure to list both advantages and disadvantages of your proposal.
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