Are there any good (Linux) tools for diffing two XML files?

Ideally, I would like to be able configure it to some things strict, or loosen some things, like whitespace, or attribute order. I'll often care that the files are functionally the same, but diff by itself, would be annoying to use, especially if the XML file doesn't have a lot of linebreaks. For example, the following should really be okay to me:

<tag att1="one" att2="two">
  content
</tag>

<tag att2="two" att1="one">
  content
</tag>

On Linux, how could I generate a diff between two XML files?

Ideally, I would like to be able configure it to some things strict, or loosen some things, like whitespace, or attribute order. 

I'll often care that the files are functionally the same, but diff by itself, would be annoying to use, especially if the XML file doesn't have a lot of linebreaks. 

For example, the following should really be okay to me:

<tag att1="one" att2="two">
  content
</tag>

<tag att2="two" att1="one">
  content
</tag>