[PATCH v6 bpf-next 7/8] net: xdp: add multi-buff support to xdp_build_skb_from_fram

[Lorenzo Bianconi <lorenzo@xxxxxxxxxx>]

Introduce xdp multi-buff support to
__xdp_build_skb_from_frame/xdp_build_skb_from_fram utility
routines.

Signed-off-by: Lorenzo Bianconi <lorenzo@xxxxxxxxxx>
---
 net/core/xdp.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/net/core/xdp.c b/net/core/xdp.c
index af9b9c1194fc..a7cd1ffbab6b 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -592,9 +592,21 @@ struct sk_buff *__xdp_build_skb_from_frame(struct xdp_frame *xdpf,
 					   struct sk_buff *skb,
 					   struct net_device *dev)
 {
+	skb_frag_t frag_list[MAX_SKB_FRAGS];
 	unsigned int headroom, frame_size;
+	int i, num_frags = 0;
 	void *hard_start;
 
+	/* XDP multi-buff frame */
+	if (unlikely(xdpf->mb)) {
+		struct xdp_shared_info *xdp_sinfo;
+
+		xdp_sinfo = xdp_get_shared_info_from_frame(xdpf);
+		num_frags = xdp_sinfo->nr_frags;
+		memcpy(frag_list, xdp_sinfo->frags,
+		       sizeof(skb_frag_t) * num_frags);
+	}
+
 	/* Part of headroom was reserved to xdpf */
 	headroom = sizeof(*xdpf) + xdpf->headroom;
 
@@ -613,6 +625,20 @@ struct sk_buff *__xdp_build_skb_from_frame(struct xdp_frame *xdpf,
 	if (xdpf->metasize)
 		skb_metadata_set(skb, xdpf->metasize);
 
+	/* Single-buff XDP frame */
+	if (likely(!num_frags))
+		goto out;
+
+	for (i = 0; i < num_frags; i++) {
+		struct page *page = xdp_get_frag_page(&frag_list[i]);
+
+		skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags,
+				page, xdp_get_frag_offset(&frag_list[i]),
+				xdp_get_frag_size(&frag_list[i]),
+				xdpf->frame_sz);
+	}
+
+out:
 	/* Essential SKB info: protocol and skb->dev */
 	skb->protocol = eth_type_trans(skb, dev);
 
-- 
2.29.2