On 2020/2/4 下午3:16, 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 and copy vnet header to the front of xdp.data_hard_start
to avoid overwriting it, where on program return with pass verdict,
we call into skb_metadata_set().
Fixes: de8f3a83b0a0 ("bpf: add meta pointer for direct access")
Signed-off-by: Yuya Kusakabe <yuya.kusakabe@xxxxxxxxx>
---
drivers/net/virtio_net.c | 47 ++++++++++++++++++++++++++++------------
1 file changed, 33 insertions(+), 14 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 2fe7a3188282..5fdd6ea0e3f1 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)
hdr_valid means no XDP, so I think we can remove the check for metasize
here and add a comment instead?
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 +689,15 @@ 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 it by XDP meta data.
+ */
+ memcpy(xdp.data_hard_start - vi->hdr_len,
+ xdp.data - vi->hdr_len, vi->hdr_len);
I think we don't need this. And it looks to me there's a bug in the
current code.
Commit 436c9453a1ac0 ("virtio-net: keep vnet header zeroed after
processing XDP") leave the a corner case for receive_small() which still
use:
if (!delta) {
buf += header_offset;
memcpy(skb_vnet_hdr(skb), buf, vi->hdr_len);
} /* keep zeroed vnet hdr since packet was changed by bpf */
Which seems wrong, we need check xdp_prog instead of delta.
With this fixed, there's no need to care about the vnet header here
since we don't know whether or not packet is modified by XDP.
act = bpf_prog_run_xdp(xdp_prog, &xdp);
stats->xdp_packets++;
@@ -695,9 +706,11 @@ 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++;
+ xdp.data_meta = xdp.data;
I think we should remove the xdp_set_data_meta_invalid() at least? And
move this initialization just after xdp.data is initialized.
Testing receive_small() requires to disable mrg_rxbuf, guest_tso4,
guest_tso6 and guest_ufo from qemu command line.
xdpf = convert_to_xdp_frame(&xdp);
if (unlikely(!xdpf))
goto err_xdp;
@@ -736,10 +749,12 @@ static struct sk_buff *receive_small(struct net_device *dev,
skb_reserve(skb, headroom - delta);
skb_put(skb, len);
if (!delta) {
Need to check xdp_prog (need another patch).
- buf += header_offset;
- memcpy(skb_vnet_hdr(skb), buf, vi->hdr_len);
+ memcpy(skb_vnet_hdr(skb), buf + VIRTNET_RX_PAD, vi->hdr_len);
} /* keep zeroed vnet hdr since packet was changed by bpf */
+ if (metasize)
+ skb_metadata_set(skb, metasize);
+
err:
return skb;
@@ -760,8 +775,8 @@ 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 +808,7 @@ 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 +855,8 @@ 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);
@@ -852,8 +868,9 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
* adjustments. Note other cases do not build an
* skb and avoid using offset
*/
- offset = xdp.data -
- page_address(xdp_page) - vi->hdr_len;
+ metasize = xdp.data - xdp.data_meta;
+ offset = xdp.data - page_address(xdp_page) -
+ vi->hdr_len - metasize;
/* recalculate len if xdp.data or xdp.data_end were
* adjusted
@@ -863,14 +880,15 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
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;
case XDP_TX:
stats->xdp_tx++;
+ xdp.data_meta = xdp.data;
Any reason for doing this?
Thanks
xdpf = convert_to_xdp_frame(&xdp);
if (unlikely(!xdpf))
goto err_xdp;
@@ -921,7 +939,8 @@ 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))
