Re: [PATCH bpf-next v5] virtio_net: add XDP meta data support
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2020-02-21 11:02:11
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On Fri, Feb 21, 2020 at 05:36:08PM +0900, Yuya Kusakabe wrote:
On 2/21/20 1:23 PM, Jason Wang wrote:quoted
On 2020/2/20 下午4:55, Yuya Kusakabe wrote:quoted
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.
Fixes basically means "must be backported to any kernel that has de8f3a83b0a0 in order to fix a bug". This looks more like a feature than a bug though, so I'm not sure Fixes is approproate. Correct me if I'm wrong.
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Signed-off-by: Yuya Kusakabe <redacted> --- 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. ThanksI see. So I need to revert to delta from xdp_prog? Thank you.quoted
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+ 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))