I run an open-source Go library that also does packet capture/encode/decode (http://code.google.com/p/gopacket). Would you be at all interested in adding results for gopacket to your benchmarks page? If so, I'm happy to write up the code to actually run the benchmarks, then send it over to you so it can be run on your benchmarking machine.
Is it possible to manipulate traffic / drop it? A long time ago, I've been trying to build transparent tunnels, so that the user does not have to configure anything special to use it. The biggest difficulty I faced was to drop the original traffic to only allow the newly crafted one.
You can't drop the original traffic using the library. You could capture it, modify it and send it though. That + some iptables rules to drop the original traffic would be sufficient I guess.
I started this project with a colleague near the end of 2012, and I've continued development on my own since 2013. The first months of development implied a lot of work, but then just a couple of hours a week to fix bugs or improve some mechanisms.
I've managed to compile it on Windows using Visual Studio. It's in my TODO list to write a tutorial on the site on how to do so. Hopefully I'll do that on the next few days.