Re: [PATCH v13 bpf-next 05/18] net: xdp: add xdp_update_skb_shared_info utility routine

[...]

Do we need to clear gso_type here as it is shared/union with xdp_frags_size
?
(see below ... it is already cleared before call)

quoted

+}
+
  /* Avoids inlining WARN macro in fast-path */
  void xdp_warn(const char *msg, const char *func, const int line);
  #define XDP_WARN(msg) xdp_warn(msg, __func__, __LINE__)

diff --git a/net/core/xdp.c b/net/core/xdp.c
index cc92ccb38432..504be3ce3ca9 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c

@@ -531,8 +531,20 @@ struct sk_buff *__xdp_build_skb_from_frame(struct xdp_frame *xdpf,
  					   struct sk_buff *skb,
  					   struct net_device *dev)
  {
+	unsigned int frag_size, frag_tsize;
  	unsigned int headroom, frame_size;
  	void *hard_start;
+	u8 nr_frags;
+
+	/* xdp multi-buff frame */
+	if (unlikely(xdp_frame_is_mb(xdpf))) {
+		struct skb_shared_info *sinfo;
+
+		sinfo = xdp_get_shared_info_from_frame(xdpf);
+		frag_tsize = sinfo->xdp_frags_tsize;
+		frag_size = sinfo->xdp_frags_size;
+		nr_frags = sinfo->nr_frags;
+	}
  	/* Part of headroom was reserved to xdpf */
  	headroom = sizeof(*xdpf) + xdpf->headroom;

@@ -552,6 +564,11 @@ struct sk_buff *__xdp_build_skb_from_frame(struct xdp_frame *xdpf,
  	if (xdpf->metasize)
  		skb_metadata_set(skb, xdpf->metasize);
+	if (unlikely(xdp_frame_is_mb(xdpf)))
+		xdp_update_skb_shared_info(skb, nr_frags,
+					   frag_size, frag_tsize,
+					   xdp_frame_is_frag_pfmemalloc(xdpf));
+

There is a build_skb_around() call before this call, which via
__build_skb_around() will clear top part of skb_shared_info.
(Thus, clearing gso_type not needed ... see above)

yes, this is why I need save sinfo->nr_frags, sinfo->xdp_frags_size, ...

Regards,
Lorenzo

quoted

  	/* Essential SKB info: protocol and skb->dev */
  	skb->protocol = eth_type_trans(skb, dev);

Acked-by: Jesper Dangaard Brouer <redacted>