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

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Date:   Wed, 8 Nov 2017 14:28:53 +0900
From:   Jason Wang <jasowang@...hat.com>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc:     Network Development <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Tom Herbert <tom@...bertland.com>
Subject: Re: [PATCH net-next V2 3/3] tun: add eBPF based queue selection
 method



On 2017年11月04日 08:56, Willem de Bruijn wrote:
> On Fri, Nov 3, 2017 at 5:56 PM, Willem de Bruijn
> <willemdebruijn.kernel@...il.com> wrote:
>> On Tue, Oct 31, 2017 at 7:32 PM, Jason Wang <jasowang@...hat.com> 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@...hat.com>
>>> ---
>>> +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