Re: [PATCH bpf-next v5] virtio_net: add XDP meta data support
From: Jason Wang
Date: Thu Feb 20 2020 - 23:23:58 EST
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()?
Signed-off-by: Yuya Kusakabe <yuya.kusakabe@xxxxxxxxx>
---
v5:
- page_to_skb(): copy vnet header if hdr_valid without checking metasize.
- receive_small(): do not copy vnet header if xdp_prog is availavle.
- __virtnet_xdp_xmit_one(): remove the xdp_set_data_meta_invalid().
- improve comments.
v4:
- improve commit message
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 | 54 ++++++++++++++++++++++++----------------
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,
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;
@@ -393,6 +393,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
else
hdr_padded_len = sizeof(struct padded_vnet_hdr);
+ /* hdr_valid means no XDP, so we can copy the vnet header */
if (hdr_valid)
memcpy(hdr, p, hdr_len);
@@ -405,6 +406,11 @@ 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;
@@ -450,10 +456,6 @@ static int __virtnet_xdp_xmit_one(struct virtnet_info *vi,
struct virtio_net_hdr_mrg_rxbuf *hdr;
int err;
- /* virtqueue want to use data area in-front of packet */
- if (unlikely(xdpf->metasize > 0))
- return -EOPNOTSUPP;
-
if (unlikely(xdpf->headroom < vi->hdr_len))
return -EOVERFLOW;
@@ -644,6 +646,7 @@ 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;
@@ -683,8 +686,8 @@ 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;
act = bpf_prog_run_xdp(xdp_prog, &xdp);
@@ -695,6 +698,7 @@ static struct sk_buff *receive_small(struct net_device *dev,
/* Recalculate length in case bpf program changed it */
delta = orig_data - xdp.data;
len = xdp.data_end - xdp.data;
+ metasize = xdp.data - xdp.data_meta;
break;
case XDP_TX:
stats->xdp_tx++;
@@ -735,11 +739,14 @@ static struct sk_buff *receive_small(struct net_device *dev,
}
skb_reserve(skb, headroom - delta);
skb_put(skb, len);
- if (!delta) {
+ if (!xdp_prog) {
buf += header_offset;
memcpy(skb_vnet_hdr(skb), buf, vi->hdr_len);
} /* 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
+ if (metasize)
+ skb_metadata_set(skb, metasize);
+
err:
return skb;
@@ -760,8 +767,8 @@ static struct sk_buff *receive_big(struct net_device *dev,
struct virtnet_rq_stats *stats)
{
struct page *page = buf;
- struct sk_buff *skb = page_to_skb(vi, rq, page, 0, len,
- PAGE_SIZE, true);
+ struct sk_buff *skb =
+ page_to_skb(vi, rq, page, 0, len, PAGE_SIZE, true, 0);
stats->bytes += len - vi->hdr_len;
if (unlikely(!skb))
@@ -793,6 +800,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
unsigned int truesize;
unsigned int headroom = mergeable_ctx_to_headroom(ctx);
int err;
+ unsigned int metasize = 0;
head_skb = NULL;
stats->bytes += len - vi->hdr_len;
@@ -839,8 +847,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
data = page_address(xdp_page) + offset;
xdp.data_hard_start = data - VIRTIO_XDP_HEADROOM + vi->hdr_len;
xdp.data = data + vi->hdr_len;
- xdp_set_data_meta_invalid(&xdp);
xdp.data_end = xdp.data + (len - vi->hdr_len);
+ xdp.data_meta = xdp.data;
xdp.rxq = &rq->xdp_rxq;
act = bpf_prog_run_xdp(xdp_prog, &xdp);
@@ -848,24 +856,27 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
switch (act) {
case XDP_PASS:
+ metasize = xdp.data - xdp.data_meta;
+
/* recalculate offset to account for any header
- * adjustments. Note other cases do not build an
- * skb and avoid using offset
+ * adjustments and minus the metasize to copy the
+ * metadata in page_to_skb(). Note other cases do not
+ * build an skb and avoid using offset
*/
- offset = xdp.data -
- page_address(xdp_page) - vi->hdr_len;
+ offset = xdp.data - page_address(xdp_page) -
+ vi->hdr_len - metasize;
- /* recalculate len if xdp.data or xdp.data_end were
- * adjusted
+ /* recalculate len if xdp.data, xdp.data_end or
+ * xdp.data_meta were adjusted
*/
- len = xdp.data_end - xdp.data + vi->hdr_len;
+ len = xdp.data_end - xdp.data + vi->hdr_len + metasize;
/* We can only create skb based on xdp_page. */
if (unlikely(xdp_page != page)) {
rcu_read_unlock();
put_page(page);
- head_skb = page_to_skb(vi, rq, xdp_page,
- offset, len,
- PAGE_SIZE, false);
+ head_skb = page_to_skb(vi, rq, xdp_page, offset,
+ len, PAGE_SIZE, false,
+ metasize);
return head_skb;
}
break;
@@ -921,7 +932,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
goto err_skb;
}
- head_skb = page_to_skb(vi, rq, page, offset, len, truesize, !xdp_prog);
+ head_skb = page_to_skb(vi, rq, page, offset, len, truesize, !xdp_prog,
+ metasize);
curr_skb = head_skb;
if (unlikely(!curr_skb))