net: Only do flow_dissector hash computation once per packet

Add sw_hash flag to skbuff to indicate that skb->hash was computed
from flow_dissector. This flag is checked in skb_get_hash to avoid
repeatedly trying to compute the hash (ie. in the case that no L4 hash
can be computed).

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index c5f3912dad4c..5f362c1d0332 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -256,6 +256,8 @@ void __skb_get_hash(struct sk_buff *skb)
         if (keys.ports)
                 skb->l4_hash = 1;
 
+        skb->sw_hash = 1;
+
         skb->hash = __flow_hash_from_keys(&keys);
 }
 EXPORT_SYMBOL(__skb_get_hash);