[SOLVED] Duplicate URL

[m4ss4cr4t10n]

Hi,
I'm from Brazil, and I'm new with Prestashop.

I have some products in my store, and I have afraid to have a duplicate url problem, because I can access the page of the product by two ways:

http://www.mydomain.com/maincategory/21-product-description.html
or
http://www.mydomain.com/21-product-description.html

I want to redirect http://www.mydomain.com/21-product-description.html to http://www.mydomain.com/maincategory/21-product-description.html.

And at a moment, my website is with Canonical URL module deactivated, because I had a problem with Facebook by URL duplication, like:
http://www.mydomain.com/mydomain.com.br/maincategory/21-product-description.html

So,
Anyone knows how can I solve this problem?

[m4ss4cr4t10n]

I solved my problem with this module:

http://www.presto-changeo.com/prestashop-modules/25-duplicate-url-redirect.html

The topic can be closed. Thanks.