I don't know. Truth is I needed to get the Flow Label from packets in a somewhat less dirty way than (grep|cut|awk)ing through tcpdump -vvvvvvn. So for all you IPv6 enthousiasts who need the Flow Label and do not know where to start, the somewhat minimal working example below might be of help. Mind you, I'm by no means a pro C-coder nor a libpcap-wizard, so if you see essential improvements, please rant at this GitHub gist. And until I've fixed the layout glitches on my blog, you may also prefer to peek at the code over there.
Getting the IPv6 Flow Label
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