On 2019/7/9 上午6:38, Daniel Borkmann wrote:
On 07/02/2019 04:11 PM, Yuya Kusakabe wrote:On 7/2/19 5:33 PM, Jason Wang wrote:On 2019/7/2 下午4:16, Yuya Kusakabe wrote:This adds XDP meta data support to both receive_small() and receive_mergeable(). Fixes: de8f3a83b0a0 ("bpf: add meta pointer for direct access") Signed-off-by: Yuya Kusakabe <yuya.kusak...@gmail.com> --- 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 | 45 +++++++++++++++++++++++++++------------- 1 file changed, 31 insertions(+), 14 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 4f3de0ac8b0b..03a1ae6fe267 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) 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 +689,13 @@ 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 by XDP meta data */ + memcpy(xdp.data_hard_start - vi->hdr_len, xdp.data - vi->hdr_len, vi->hdr_len);I'm not fully sure if I'm following this one correctly, probably just missing something. Isn't the vnet header based on how we set up xdp.data_hard_start earlier already in front of it? Wouldn't we copy invalid data from xdp.data - vi->hdr_len into the vnet header at that point (given there can be up to 256 bytes of headroom between the two)? If it's relative to xdp.data and headroom is >0, then BPF prog could otherwise mangle this; something doesn't add up to me here. Could you clarify? Thx
Vnet headr sits just in front of xdp.data not xdp.data_hard_start. So it could be overwrote by metadata, that's why we need a copy here.
Thanks
What happens if we have a large metadata that occupies all headroom here? ThanksDo you mean a large "XDP" metadata? If a large metadata is a large "XDP" metadata, I think we can not use a metadata that occupies all headroom. The size of metadata limited by bpf_xdp_adjust_meta() as below. bpf_xdp_adjust_meta() in net/core/filter.c: if (unlikely((metalen & (sizeof(__u32) - 1)) || (metalen > 32))) return -EACCES; Thanks.act = bpf_prog_run_xdp(xdp_prog, &xdp); stats->xdp_packets++; @@ -695,9 +704,11 @@ 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; xdpf = convert_to_xdp_frame(&xdp); if (unlikely(!xdpf)) goto err_xdp; @@ -736,10 +747,12 @@ static struct sk_buff *receive_small(struct net_device *dev, skb_reserve(skb, headroom - delta); skb_put(skb, len); if (!delta) { - 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 +773,8 @@ 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 +806,7 @@ 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 +853,8 @@ 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 +866,9 @@ 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 +878,15 @@ 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; xdpf = convert_to_xdp_frame(&xdp); if (unlikely(!xdpf)) goto err_xdp; @@ -921,7 +937,8 @@ 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))
