[Intel-wired-lan] [PATCH net-next 01/10] net: Document skb_metadata_set contract with the drivers

[Jakub Sitnicki]

Prepare to copy XDP metadata into an skb extension chunk. To access the
metadata contents, we need to know where it is located. Document the
expectation - skb->data must point right past the metadata when
skb_metadata_set gets called.

Signed-off-by: Jakub Sitnicki <jakub at cloudflare.com>
---
 include/linux/skbuff.h | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 86737076101d..df001283076f 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -4554,6 +4554,13 @@ static inline bool skb_metadata_differs(const struct sk_buff *skb_a,
 	       true : __skb_metadata_differs(skb_a, skb_b, len_a);
 }
 
+/**
+ * skb_metadata_set - Record packet metadata length.
+ * @skb: packet carrying the metadata
+ * @meta_len: number of bytes of metadata preceding skb->data
+ *
+ * Must be called when skb->data already points past the metadata area.
+ */
 static inline void skb_metadata_set(struct sk_buff *skb, u8 meta_len)
 {
 	skb_shinfo(skb)->meta_len = meta_len;

-- 
2.43.0