Here is the documentation:
http://wiki.untangle.com/index.php/IPsec_VPN
I don't think anyone has added the parameters for sonicwall yet, if you figure it out, please post them here or just add them directly. I've heard it works but I don't know the details.
Attention: Support and help on the Untangle Forums is provided by volunteers and community members like yourself.
If you need Untangle support please call or email support@untangle.com