So basically L4 grants IO caps to the network card's io ports to whatever task acts as the network driver, and it's the driver task's job to bang on the card's I/O and hook up with whatever other tasks represent packet/protocol/whatever layers of the ISO 7 layer stack. On Mon, Nov 2, 2015 at 5:48 PM, Tim Newsham wrote:

seL4 does not provide a network stack or even network device drivers. An OS on top of seL4 would have to provide their own drivers and stack and is free to put them in a single server or in different servers and choose how to communicate between them.

On Mon, Nov 2, 2015 at 2:38 PM, Yuxin Ren wrote:

...

Hi,

I have a few questions about network stack in sel4.

Is network stack implemented in the kernel or user level? If in user level, are different protocols (IP/TCP) implemented in a single server or different servers? If in different servers, how do they communicate with each other?

Is there any example code to show how to use network? How to send and receive TCP or UDP packets? How can I set up the network environment on bare metal machine? Is there documentation or instruction?

Thanks a lot! Yuxin

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So the kernel itself doesn't actually "own" any capabilities, just does the bookkeeping and enforcement? On Mon, Nov 2, 2015 at 7:05 PM, Gernot Heiser wrote:

On 3 Nov 2015, at 12:58 , Raymond Jennings wrote:

So basically L4 grants IO caps to the network card's io ports to whatever task acts as the network driver, and it's the driver task's job to bang on the card's I/O and hook up with whatever other tasks represent packet/protocol/whatever layers of the ISO 7 layer stack.

More precisely: seL4 hands all rights to all resources to the initial process, whose job is then to initialise the desired system. It would be that process that hands caps to drivers etc.

Gernot

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Thank you all. But are there any projects on top of sel4 microkernel which implement network functionality? I don't think I need to build the whole network stack from bare metal. It is best for me to just refer some existing projects and run simple network application on top of it. Yuxin On Mon, Nov 2, 2015 at 10:54 PM, Gernot Heiser wrote:

...

On 3 Nov 2015, at 14:46 , Raymond Jennings wrote:

So the kernel itself doesn't actually "own" any capabilities, just does the bookkeeping and enforcement?

Caps are like keys: they authenticate access. The kernel doesn’t need them for its own purposes. However, our integrity and confidentiality proofs show that the kernel will not on its own access user memory, unless on behalf of a thread who demonstrates that it is authorised by presenting an appropriate caps.

Gernot

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