Hi, I am very interested in SEL4, partly because I was assured it was impossible to use Formal Methods in kernel development, partly because it's a fascinating project in its own right, but right now because there are some embedded applications that could do with the high level of reliability and security that provable correctness implies. Unfortunately, said applications need a comprehensive network stack and a powerful packet filtering/mangling engine. The latter could imaginably be done in the kernel, as it's deterministic, but I don't see any obvious value. Nonetheless, if someone has coded such a system as a third-party add-on, I would be very interested. There are good arguments for why the former can't be done, in a way that can be proven, and I really want the correctness. In terms of userspace, I believe I could use something like L4Linux (as long as it is still maintained), and I think there's one supplied, but are there other options? Has anyone ported OpenBSD to it? To be honest, I'm not sure I need a multitasking userspace, but I do absolutely need the network stack and packet filter. Everything else can be ported, albeit with difficulty. However, network operating systems are thin on the ground and tend to be proprietary, exactly what I don't want. For those curious, I'm looking to end up with a system with strong bounds on robustness and security, and that can handle things like multipath TCP, network failover, QoS and OpenFlow. However, all of these requirements boil down to a sequential process. Unnecessary complexity is where you end up with problems. If current wisdom says that there's nothing suitable in userspace, then does anyone know if there are there any existing Coloured Petri Nets that I could use to build what I need into the kernel? Even if I can't get better than a quasi-guarantee, it would be something.