It seems that there have been a rash of JavaScript virtual machines running Linux lately (or maybe I just travel in really weird circles). However until now none of them had network support, so they weren't too terribly useful. Sebastian Macke'sjor1k project uses asm.js to produce a very fast emulation of the OpenCores OpenRISC processor (or1k) along with a HTML5 canvas framebuffer for graphics support. Recently Ben Burns contributed an emulated OpenCores ethmac ethernet adapter to the project. This sends ethernet frames to a gateway server via websocket where they are switched and/or piped into TAP virtual ethernet adapter. With this you can build whatever kind of network appliance you'd like for the myriad of fast, sandboxed VMs running in your users' browsers. For the live demo all VMs connect to a single private LAN (subnet 10.5.0.0/16). The websocket gateway also NATs traffic from that LAN out to the open Internet."