Re: [PATCH bpf-next v5] virtio_net: add XDP meta data support

From: Yuya Kusakabe
Date: Fri Feb 21 2020 - 03:36:25 EST

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On 2/21/20 1:23 PM, Jason Wang wrote:
>
> On 2020/2/20 äå4:55, Yuya Kusakabe wrote:
>> Implement support for transferring XDP meta data into skb for
>> virtio_net driver; before calling into the program, xdp.data_meta points
>> to xdp.data, where on program return with pass verdict, we call
>> into skb_metadata_set().
>>
>> Tested with the script at
>> https://github.com/higebu/virtio_net-xdp-metadata-test.
>>
>> Fixes: de8f3a83b0a0 ("bpf: add meta pointer for direct access")
>
>
> I'm not sure this is correct since virtio-net claims to not support metadata by calling xdp_set_data_meta_invalid()?

virtio_net doesn't support by calling xdp_set_data_meta_invalid() for now.

https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/tree/drivers/net/virtio_net.c?id=e42da4c62abb547d9c9138e0e7fcd1f36057b5e8#n686
https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/tree/drivers/net/virtio_net.c?id=e42da4c62abb547d9c9138e0e7fcd1f36057b5e8#n842

And xdp_set_data_meta_invalid() are added by de8f3a83b0a0.

$ git blame ./drivers/net/virtio_net.c | grep xdp_set_data_meta_invalid
de8f3a83b0a0f (Daniel Borkmann 2017-09-25 02:25:51 +0200 686) xdp_set_data_meta_invalid(&xdp);
de8f3a83b0a0f (Daniel Borkmann 2017-09-25 02:25:51 +0200 842) xdp_set_data_meta_invalid(&xdp);

So I added `Fixes: de8f3a83b0a0 ("bpf: add meta pointer for direct access")` to the comment.

>
>
>> Signed-off-by: Yuya Kusakabe <yuya.kusakabe@xxxxxxxxx>
>> ---
>> v5:
>> Â - page_to_skb(): copy vnet header if hdr_valid without checking metasize.
>> Â - receive_small(): do not copy vnet header if xdp_prog is availavle.
>> Â - __virtnet_xdp_xmit_one(): remove the xdp_set_data_meta_invalid().
>> Â - improve comments.
>> v4:
>> Â - improve commit message
>> v3:
>> Â - fix preserve the vnet header in receive_small().
>> v2:
>> Â - keep copy untouched in page_to_skb().
>> Â - preserve the vnet header in receive_small().
>> Â - fix indentation.
>> ---
>> Â drivers/net/virtio_net.c | 54 ++++++++++++++++++++++++----------------
>> Â 1 file changed, 33 insertions(+), 21 deletions(-)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index 2fe7a3188282..4ea0ae60c000 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,
>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ struct receive_queue *rq,
>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ struct page *page, unsigned int offset,
>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ unsigned int len, unsigned int truesize,
>> -ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ bool hdr_valid)
>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ bool hdr_valid, unsigned int metasize)
>> Â {
>> ÂÂÂÂÂ struct sk_buff *skb;
>> ÂÂÂÂÂ struct virtio_net_hdr_mrg_rxbuf *hdr;
>> @@ -393,6 +393,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
>> ÂÂÂÂÂ else
>> ÂÂÂÂÂÂÂÂÂ hdr_padded_len = sizeof(struct padded_vnet_hdr);
>> Â +ÂÂÂ /* hdr_valid means no XDP, so we can copy the vnet header */
>> ÂÂÂÂÂ if (hdr_valid)
>> ÂÂÂÂÂÂÂÂÂ memcpy(hdr, p, hdr_len);
>> Â @@ -405,6 +406,11 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
>> ÂÂÂÂÂÂÂÂÂ copy = skb_tailroom(skb);
>> ÂÂÂÂÂ skb_put_data(skb, p, copy);
>> Â +ÂÂÂ if (metasize) {
>> +ÂÂÂÂÂÂÂ __skb_pull(skb, metasize);
>> +ÂÂÂÂÂÂÂ skb_metadata_set(skb, metasize);
>> +ÂÂÂ }
>> +
>> ÂÂÂÂÂ len -= copy;
>> ÂÂÂÂÂ offset += copy;
>> Â @@ -450,10 +456,6 @@ static int __virtnet_xdp_xmit_one(struct virtnet_info *vi,
>> ÂÂÂÂÂ struct virtio_net_hdr_mrg_rxbuf *hdr;
>> ÂÂÂÂÂ int err;
>> Â -ÂÂÂ /* virtqueue want to use data area in-front of packet */
>> -ÂÂÂ if (unlikely(xdpf->metasize > 0))
>> -ÂÂÂÂÂÂÂ return -EOPNOTSUPP;
>> -
>> ÂÂÂÂÂ if (unlikely(xdpf->headroom < vi->hdr_len))
>> ÂÂÂÂÂÂÂÂÂ return -EOVERFLOW;
>> Â @@ -644,6 +646,7 @@ static struct sk_buff *receive_small(struct net_device *dev,
>> ÂÂÂÂÂ unsigned int delta = 0;
>> ÂÂÂÂÂ struct page *xdp_page;
>> ÂÂÂÂÂ int err;
>> +ÂÂÂ unsigned int metasize = 0;
>> Â ÂÂÂÂÂ len -= vi->hdr_len;
>> ÂÂÂÂÂ stats->bytes += len;
>> @@ -683,8 +686,8 @@ static struct sk_buff *receive_small(struct net_device *dev,
>> Â ÂÂÂÂÂÂÂÂÂ xdp.data_hard_start = buf + VIRTNET_RX_PAD + vi->hdr_len;
>> ÂÂÂÂÂÂÂÂÂ xdp.data = xdp.data_hard_start + xdp_headroom;
>> -ÂÂÂÂÂÂÂ xdp_set_data_meta_invalid(&xdp);
>> ÂÂÂÂÂÂÂÂÂ xdp.data_end = xdp.data + len;
>> +ÂÂÂÂÂÂÂ xdp.data_meta = xdp.data;
>> ÂÂÂÂÂÂÂÂÂ xdp.rxq = &rq->xdp_rxq;
>> ÂÂÂÂÂÂÂÂÂ orig_data = xdp.data;
>> ÂÂÂÂÂÂÂÂÂ act = bpf_prog_run_xdp(xdp_prog, &xdp);
>> @@ -695,6 +698,7 @@ static struct sk_buff *receive_small(struct net_device *dev,
>> ÂÂÂÂÂÂÂÂÂÂÂÂÂ /* Recalculate length in case bpf program changed it */
>> ÂÂÂÂÂÂÂÂÂÂÂÂÂ delta = orig_data - xdp.data;
>> ÂÂÂÂÂÂÂÂÂÂÂÂÂ len = xdp.data_end - xdp.data;
>> +ÂÂÂÂÂÂÂÂÂÂÂ metasize = xdp.data - xdp.data_meta;
>> ÂÂÂÂÂÂÂÂÂÂÂÂÂ break;
>> ÂÂÂÂÂÂÂÂÂ case XDP_TX:
>> ÂÂÂÂÂÂÂÂÂÂÂÂÂ stats->xdp_tx++;
>> @@ -735,11 +739,14 @@ static struct sk_buff *receive_small(struct net_device *dev,
>> ÂÂÂÂÂ }
>> ÂÂÂÂÂ skb_reserve(skb, headroom - delta);
>> ÂÂÂÂÂ skb_put(skb, len);
>> -ÂÂÂ if (!delta) {
>> +ÂÂÂ if (!xdp_prog) {
>> ÂÂÂÂÂÂÂÂÂ buf += header_offset;
>> ÂÂÂÂÂÂÂÂÂ memcpy(skb_vnet_hdr(skb), buf, vi->hdr_len);
>> ÂÂÂÂÂ } /* keep zeroed vnet hdr since packet was changed by bpf */
>
>
> I prefer to make this an independent patch and cc stable.
>
> Other looks good.
>
> Thanks

I see. So I need to revert to delta from xdp_prog?

Thank you.

>
>> Â +ÂÂÂ if (metasize)
>> +ÂÂÂÂÂÂÂ skb_metadata_set(skb, metasize);
>> +
>> Â err:
>> ÂÂÂÂÂ return skb;
>> Â @@ -760,8 +767,8 @@ static struct sk_buff *receive_big(struct net_device *dev,
>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ struct virtnet_rq_stats *stats)
>> Â {
>> ÂÂÂÂÂ struct page *page = buf;
>> -ÂÂÂ struct sk_buff *skb = page_to_skb(vi, rq, page, 0, len,
>> -ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ PAGE_SIZE, true);
>> +ÂÂÂ struct sk_buff *skb =
>> +ÂÂÂÂÂÂÂ page_to_skb(vi, rq, page, 0, len, PAGE_SIZE, true, 0);
>> Â ÂÂÂÂÂ stats->bytes += len - vi->hdr_len;
>> ÂÂÂÂÂ if (unlikely(!skb))
>> @@ -793,6 +800,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
>> ÂÂÂÂÂ unsigned int truesize;
>> ÂÂÂÂÂ unsigned int headroom = mergeable_ctx_to_headroom(ctx);
>> ÂÂÂÂÂ int err;
>> +ÂÂÂ unsigned int metasize = 0;
>> Â ÂÂÂÂÂ head_skb = NULL;
>> ÂÂÂÂÂ stats->bytes += len - vi->hdr_len;
>> @@ -839,8 +847,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
>> ÂÂÂÂÂÂÂÂÂ data = page_address(xdp_page) + offset;
>> ÂÂÂÂÂÂÂÂÂ xdp.data_hard_start = data - VIRTIO_XDP_HEADROOM + vi->hdr_len;
>> ÂÂÂÂÂÂÂÂÂ xdp.data = data + vi->hdr_len;
>> -ÂÂÂÂÂÂÂ xdp_set_data_meta_invalid(&xdp);
>> ÂÂÂÂÂÂÂÂÂ xdp.data_end = xdp.data + (len - vi->hdr_len);
>> +ÂÂÂÂÂÂÂ xdp.data_meta = xdp.data;
>> ÂÂÂÂÂÂÂÂÂ xdp.rxq = &rq->xdp_rxq;
>> Â ÂÂÂÂÂÂÂÂÂ act = bpf_prog_run_xdp(xdp_prog, &xdp);
>> @@ -848,24 +856,27 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
>> Â ÂÂÂÂÂÂÂÂÂ switch (act) {
>> ÂÂÂÂÂÂÂÂÂ case XDP_PASS:
>> +ÂÂÂÂÂÂÂÂÂÂÂ metasize = xdp.data - xdp.data_meta;
>> +
>> ÂÂÂÂÂÂÂÂÂÂÂÂÂ /* recalculate offset to account for any header
>> -ÂÂÂÂÂÂÂÂÂÂÂÂ * adjustments. Note other cases do not build an
>> -ÂÂÂÂÂÂÂÂÂÂÂÂ * skb and avoid using offset
>> +ÂÂÂÂÂÂÂÂÂÂÂÂ * adjustments and minus the metasize to copy the
>> +ÂÂÂÂÂÂÂÂÂÂÂÂ * metadata in page_to_skb(). Note other cases do not
>> +ÂÂÂÂÂÂÂÂÂÂÂÂ * build an skb and avoid using offset
>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ */
>> -ÂÂÂÂÂÂÂÂÂÂÂ offset = xdp.data -
>> -ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ page_address(xdp_page) - vi->hdr_len;
>> +ÂÂÂÂÂÂÂÂÂÂÂ offset = xdp.data - page_address(xdp_page) -
>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ vi->hdr_len - metasize;
>> Â -ÂÂÂÂÂÂÂÂÂÂÂ /* recalculate len if xdp.data or xdp.data_end were
>> -ÂÂÂÂÂÂÂÂÂÂÂÂ * adjusted
>> +ÂÂÂÂÂÂÂÂÂÂÂ /* recalculate len if xdp.data, xdp.data_end or
>> +ÂÂÂÂÂÂÂÂÂÂÂÂ * xdp.data_meta were adjusted
>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ */
>> -ÂÂÂÂÂÂÂÂÂÂÂ len = xdp.data_end - xdp.data + vi->hdr_len;
>> +ÂÂÂÂÂÂÂÂÂÂÂ len = xdp.data_end - xdp.data + vi->hdr_len + metasize;
>> ÂÂÂÂÂÂÂÂÂÂÂÂÂ /* We can only create skb based on xdp_page. */
>> ÂÂÂÂÂÂÂÂÂÂÂÂÂ if (unlikely(xdp_page != page)) {
>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ rcu_read_unlock();
>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ put_page(page);
>> -ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ head_skb = page_to_skb(vi, rq, xdp_page,
>> -ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ offset, len,
>> -ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ PAGE_SIZE, false);
>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ head_skb = page_to_skb(vi, rq, xdp_page, offset,
>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ len, PAGE_SIZE, false,
>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ metasize);
>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ return head_skb;
>> ÂÂÂÂÂÂÂÂÂÂÂÂÂ }
>> ÂÂÂÂÂÂÂÂÂÂÂÂÂ break;
>> @@ -921,7 +932,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
>> ÂÂÂÂÂÂÂÂÂ goto err_skb;
>> ÂÂÂÂÂ }
>> Â -ÂÂÂ head_skb = page_to_skb(vi, rq, page, offset, len, truesize, !xdp_prog);
>> +ÂÂÂ head_skb = page_to_skb(vi, rq, page, offset, len, truesize, !xdp_prog,
>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ metasize);
>> ÂÂÂÂÂ curr_skb = head_skb;
>> Â ÂÂÂÂÂ if (unlikely(!curr_skb))
>

Next message: Greg Kroah-Hartman: "[PATCH 5.4 126/344] media: v4l2-device.h: Explicitly compare grp{id,mask} to zero in v4l2_device macros"
Previous message: Greg Kroah-Hartman: "[PATCH 5.4 130/344] fore200e: Fix incorrect checks of NULL pointer dereference"
In reply to: Jason Wang: "Re: [PATCH bpf-next v5] virtio_net: add XDP meta data support"
Next in thread: Michael S. Tsirkin: "Re: [PATCH bpf-next v5] virtio_net: add XDP meta data support"
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