Hi Daniel,
I'm trying to understand why skb_metadata_differs() needed to block GRO ?
I was looking at XDP storing information in metadata area that also
survives into SKBs layer. E.g. the RX timestamp.
Then I noticed that GRO code (gro_list_prepare) will not allow
aggregating if metadata isn't the same in all packets via
skb_metadata_differs(). Is this really needed?
Can we lift/remove this limitation?
E.g. if I want to store a timestamp, then it will differ per packet.
--Jesper
Git history says it dates back to the original commit that added meta
pointer de8f3a83b0a0 ("bpf: add meta pointer for direct access") (author
Daniel).
diff --git a/net/core/gro.c b/net/core/gro.c
index 0759277dc14e..7fb6a6a24288 100644
--- a/net/core/gro.c
+++ b/net/core/gro.c
@@ -341,7 +341,7 @@ static void gro_list_prepare(const struct list_head
*head,
diffs = (unsigned long)p->dev ^ (unsigned long)skb->dev;
diffs |= p->vlan_all ^ skb->vlan_all;
- diffs |= skb_metadata_differs(p, skb);
+ diffs |= skb_metadata_differs(p, skb); // Why?
if (maclen == ETH_HLEN)
diffs |= compare_ether_header(skb_mac_header(p),
