if I want to transfer files to a webdav share, can I do that directly to the server that the share originates from, or does it need to be mounted on the machine that I send the rsync to? The thing is, I sort of can't mount that webdav share anywhere, but it's accessible through a browser. That'll let me download things, but not upload via rsync. So I'm wondering, can I get rsync to put things on the webdav share while it isn't mounted anywhere? I figure authentication might be a problem, because afaik rsync uses the ssh protocol, so how can I make it authenticate to webdav?
You can only use rsync to connect to the webdav share if you first mount the webdav share on a system that you can ssh to. For example, in linux you can use something like davfs. After you do that, the webdav share will appear as a regular filesystem on your system.
So for example, if you used davfs to mount the webdav share on your linux machine 'foo.example.com', you could then run rsync on another machine and connect to foo.example.com over ssh to access your files.