netdev - Re: [PATCH bpf-next v3] virtio_net: add XDP meta data support

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Date:   Mon, 3 Feb 2020 22:52:00 +0900
From:   Yuya Kusakabe <yuya.kusakabe@...il.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>, davem@...emloft.net,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        John Fastabend <john.fastabend@...il.com>,
        Martin KaFai Lau <kafai@...com>,
        "Michael S. Tsirkin" <mst@...hat.com>, netdev@...r.kernel.org,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>
Subject: Re: [PATCH bpf-next v3] virtio_net: add XDP meta data support

I'm sorry for the late reply.

I saw the status of this patch is "Awaiting Upstream" on
https://patchwork.ozlabs.org/patch/1126046/. What is "Awaiting
Upstream"? Is there anything that I can do?

Thank you,
Yuya

On Wed, Jul 10, 2019 at 11:30 AM Jason Wang <jasowang@...hat.com> wrote:
>
>
> On 2019/7/10 上午4:03, Daniel Borkmann wrote:
> > On 07/09/2019 05:04 AM, Jason Wang wrote:
> >> On 2019/7/9 上午6:38, Daniel Borkmann wrote:
> >>> On 07/02/2019 04:11 PM, Yuya Kusakabe wrote:
> >>>> On 7/2/19 5:33 PM, Jason Wang wrote:
> >>>>> On 2019/7/2 下午4:16, Yuya Kusakabe wrote:
> >>>>>> This adds XDP meta data support to both receive_small() and
> >>>>>> receive_mergeable().
> >>>>>>
> >>>>>> Fixes: de8f3a83b0a0 ("bpf: add meta pointer for direct access")
> >>>>>> Signed-off-by: Yuya Kusakabe <yuya.kusakabe@...il.com>
> >>>>>> ---
> >>>>>> v3:
> >>>>>>     - fix preserve the vnet header in receive_small().
> >>>>>> v2:
> >>>>>>     - keep copy untouched in page_to_skb().
> >>>>>>     - preserve the vnet header in receive_small().
> >>>>>>     - fix indentation.
> >>>>>> ---
> >>>>>>     drivers/net/virtio_net.c | 45 +++++++++++++++++++++++++++-------------
> >>>>>>     1 file changed, 31 insertions(+), 14 deletions(-)
> >>>>>>
> >>>>>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> >>>>>> index 4f3de0ac8b0b..03a1ae6fe267 100644
> >>>>>> --- a/drivers/net/virtio_net.c
> >>>>>> +++ b/drivers/net/virtio_net.c
> >>>>>> @@ -371,7 +371,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
> >>>>>>                        struct receive_queue *rq,
> >>>>>>                        struct page *page, unsigned int offset,
> >>>>>>                        unsigned int len, unsigned int truesize,
> >>>>>> -                   bool hdr_valid)
> >>>>>> +                   bool hdr_valid, unsigned int metasize)
> >>>>>>     {
> >>>>>>         struct sk_buff *skb;
> >>>>>>         struct virtio_net_hdr_mrg_rxbuf *hdr;
> >>>>>> @@ -393,7 +393,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
> >>>>>>         else
> >>>>>>             hdr_padded_len = sizeof(struct padded_vnet_hdr);
> >>>>>>     -    if (hdr_valid)
> >>>>>> +    if (hdr_valid && !metasize)
> >>>>>>             memcpy(hdr, p, hdr_len);
> >>>>>>           len -= hdr_len;
> >>>>>> @@ -405,6 +405,11 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
> >>>>>>             copy = skb_tailroom(skb);
> >>>>>>         skb_put_data(skb, p, copy);
> >>>>>>     +    if (metasize) {
> >>>>>> +        __skb_pull(skb, metasize);
> >>>>>> +        skb_metadata_set(skb, metasize);
> >>>>>> +    }
> >>>>>> +
> >>>>>>         len -= copy;
> >>>>>>         offset += copy;
> >>>>>>     @@ -644,6 +649,7 @@ static struct sk_buff *receive_small(struct net_device *dev,
> >>>>>>         unsigned int delta = 0;
> >>>>>>         struct page *xdp_page;
> >>>>>>         int err;
> >>>>>> +    unsigned int metasize = 0;
> >>>>>>           len -= vi->hdr_len;
> >>>>>>         stats->bytes += len;
> >>>>>> @@ -683,10 +689,13 @@ static struct sk_buff *receive_small(struct net_device *dev,
> >>>>>>               xdp.data_hard_start = buf + VIRTNET_RX_PAD + vi->hdr_len;
> >>>>>>             xdp.data = xdp.data_hard_start + xdp_headroom;
> >>>>>> -        xdp_set_data_meta_invalid(&xdp);
> >>>>>>             xdp.data_end = xdp.data + len;
> >>>>>> +        xdp.data_meta = xdp.data;
> >>>>>>             xdp.rxq = &rq->xdp_rxq;
> >>>>>>             orig_data = xdp.data;
> >>>>>> +        /* Copy the vnet header to the front of data_hard_start to avoid
> >>>>>> +         * overwriting by XDP meta data */
> >>>>>> +        memcpy(xdp.data_hard_start - vi->hdr_len, xdp.data - vi->hdr_len, vi->hdr_len);
> >>> I'm not fully sure if I'm following this one correctly, probably just missing
> >>> something. Isn't the vnet header based on how we set up xdp.data_hard_start
> >>> earlier already in front of it? Wouldn't we copy invalid data from xdp.data -
> >>> vi->hdr_len into the vnet header at that point (given there can be up to 256
> >>> bytes of headroom between the two)? If it's relative to xdp.data and headroom
> >>> is >0, then BPF prog could otherwise mangle this; something doesn't add up to
> >>> me here. Could you clarify? Thx
> >> Vnet headr sits just in front of xdp.data not xdp.data_hard_start. So it could be overwrote by metadata, that's why we need a copy here.
> > For the current code, you can adjust the xdp.data with a positive/negative offset
> > already via bpf_xdp_adjust_head() helper. If vnet headr sits just in front of
> > xdp.data, couldn't this be overridden today as well then? Anyway, just wondering
> > how this is handled differently?
>
>
> We will invalidate the vnet header in this case. But for the case of
> metadata adjustment without header adjustment, we want to seek a way to
> preserve that.
>
> Thanks
>
>
> >
> > Thanks,
> > Daniel



-- 
Yuya Kusakabe