Windows doesn't allow folder names ending with a period (if you try to create "somefolder." on Windows it instead makes "somefolder"). I used Konqueror's libsmbclient ioslave to make one on a Windows XP machine from a computer running Ubuntu. The folder and its contents work fine through samba, but trying to open, rename, move, or delete it in Windows results in an error message complaining that Windows can't find the folder.
If Windows actually created the folder, that means that it accepts creating folders with a trailing dot when requested via the network. libsmbclient can't do anything that some other Windows client wouldn't be able to do (except that currently, there may be no Windows clients that will let you enter a folder name with a trailing dot).
I don't think it's a good idea to put code in libsmbclient to prevent issuing such a request. If the server wants not to support folder names with trailing dots, it should refuse the request. I don't believe it's the client's job to modify the request. That would mean that if a future version of Windows *did* allow creating folders with a trailing dot, we wouldn't be able to do it via libsmbclient.
Have you experimented with putting files into that folder you created? Can you then read them via libsmbclient even though the folder is inaccessible directly by Windows? My mind would possibly change on this issue if we found that even libsmbclient could not access files in the folder that it just created. Even then, though, I'm not sure. This is really a server issue...
It's certainly an issue with Windows, as libsmbclient has no difficulty at all with these folders, but it was a nuisance to figure out what was going on. I'm not sure what action (if any) should be taken -- maybe some kind of message warning that the folder might not be readable on windows, if that's possible.
It couldn't hurt, in some circumstances, for a message to be displayed to the user. That belongs in the application which is making use of libsmbclient, though, not in libsmbclient itself. Some applications will want to display such a warning while others will not. Just as a Windows client currently does not allow folder names with a trailing dot, the "user interface" portion of a libsmbclient application could provide the same limitation if it so desires.
Thanks for the report! I'm closing this out. If you find other evidence that there is reason for libsmbclient to be enforcing this, feel free to re-open this.