Re: [PATCH net-next V2 3/3] tun: add eBPF based queue selection method

[Jason Wang]

On 2017å11æ04æ 08:56, Willem de Bruijn wrote:
> On Fri, Nov 3, 2017 at 5:56 PM, Willem de Bruijn
> <willemdebruijn.kernel@xxxxxxxxx> wrote:
> > On Tue, Oct 31, 2017 at 7:32 PM, Jason Wang <jasowang@xxxxxxxxxx> wrote:
> > > This patch introduces an eBPF based queue selection method based on
> > > the flow steering policy ops. Userspace could load an eBPF program
> > > through TUNSETSTEERINGEBPF. This gives much more flexibility compare
> > > to simple but hard coded policy in kernel.
> > >
> > > Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> > > ---
> > > +static int tun_set_steering_ebpf(struct tun_struct *tun, void __user *data)
> > > +{
> > > +       struct bpf_prog *prog;
> > > +       u32 fd;
> > > +
> > > +       if (copy_from_user(&fd, data, sizeof(fd)))
> > > +               return -EFAULT;
> > > +
> > > +       prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_SOCKET_FILTER);
> > If the idea is to allow guests to pass BPF programs down to the host,
> > you may want to define a new program type that is more restrictive than
> > socket filter.
> >
> > The external functions allowed for socket filters (sk_filter_func_proto)
> > are relatively few (compared to, say, clsact), but may still leak host
> > information to a guest. More importantly, guest security considerations
> > limits how we can extend socket filters later.
> Unless the idea is for the hypervisor to prepared the BPF based on a
> limited set of well defined modes that the guest can configure. Then
> socket filters are fine, as the BPF is prepared by a regular host process.

Yes, I think the idea is to let qemu to build a BPF program now.

Passing eBPF program from guest to host is interesting, but an obvious 
issue is how to deal with the accessing of map.

Thanks