[PATCH] skb: add a comment to skb_csum_unnecessary to avoid miuse

[Koki Sanagi <sanagi.koki@jp.fujitsu.com>]

Due to its name and appearance, someone thinks this only checks if ip_summed is
CHECKSUM_UNNECESARRY.  But actually, this returns true even if ip_summed is
CHECKSUM_PARTIAL.  To avoid misuse, this patch a comment which specifies that
CHECKSUM_PARTIAL is OK.

Signed-off-by: Koki Sanagi <sanagi.koki@jp.fujitsu.com>
---
 include/linux/skbuff.h |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 8b2256e..bc41f64 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2522,6 +2522,16 @@ void skb_complete_wifi_ack(struct sk_buff *skb, bool acked);
 extern __sum16 __skb_checksum_complete_head(struct sk_buff *skb, int len);
 extern __sum16 __skb_checksum_complete(struct sk_buff *skb);
 
+/**
+ * skb_csum_unnecessary - check if the checksum needs to be verified
+ * @skb: skb to check
+ *
+ * check if the checksum of this skb needs to be verified.  This function is
+ * effective only against skbs on inbound path.
+ *
+ * NB: This returns true if ip_summed is CHECKSUM_UNNECESSARY or
+ *     CHECKSUM_PARTIAL.
+ **/
 static inline int skb_csum_unnecessary(const struct sk_buff *skb)
 {
 	return skb->ip_summed & CHECKSUM_UNNECESSARY;