virtio_net: Add XDP meta data support

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.

Signed-off-by: Yuya Kusakabe <yuya.kusakabe@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Link: https://lore.kernel.org/bpf/20200225033212.437563-2-yuya.kusakabe@gmail.com

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index f39d021..12d115e 100644 (file)
--- 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++;
@@ -740,6 +744,9 @@ static struct sk_buff *receive_small(struct net_device *dev,
                memcpy(skb_vnet_hdr(skb), buf, vi->hdr_len);
        } /* keep zeroed vnet hdr since XDP is loaded */
 
+       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))