Yep, works fine for me, compiled and run it on our three virtual machines and looks the same as with my original patch. I also had a quick look at the json output and I think the patch should not have broken anything of that either, but a json-expert should have a look at it again. Also it might make sense to introduce something comparable to the subgraphing-feature of the dot-file-format to the json output, wouldn't it? Otherwise you will still see seperated graphs with json output if nodes are having multiple interfaces. So someone might have to write and commit a patch for that sometime in the future as well.
Thanks for reviewing the patch.
Cheers, Linus