net: Add utility functions to clear rxhash

In several places 'skb->rxhash = 0' is being done to clear the
rxhash value in an skb.  This does not clear l4_rxhash which could
still be set so that the rxhash wouldn't be recalculated on subsequent
call to skb_get_rxhash.  This patch adds an explict function to clear
all the rxhash related information in the skb properly.

skb_clear_hash_if_not_l4 clears the rxhash only if it is not marked as
l4_rxhash.

Fixed up places where 'skb->rxhash = 0' was being called.

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

2 files changed, 14 insertions, 3 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 4725b953e00d..7deb7ad65914 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -712,6 +712,18 @@ static inline __u32 skb_get_hash(struct sk_buff *skb)
         return skb->rxhash;
 }
 
+static inline void skb_clear_hash(struct sk_buff *skb)
+{
+        skb->rxhash = 0;
+        skb->l4_rxhash = 0;
+}
+
+static inline void skb_clear_hash_if_not_l4(struct sk_buff *skb)
+{
+        if (!skb->l4_rxhash)
+                skb_clear_hash(skb);
+}
+
 #ifdef NET_SKBUFF_DATA_USES_OFFSET
 static inline unsigned char *skb_end_pointer(const struct sk_buff *skb)
 {
diff --git a/include/net/dst.h b/include/net/dst.h
index 44995c13e941..77eb53fabfb0 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -322,12 +322,11 @@ static inline void __skb_tunnel_rx(struct sk_buff *skb, struct net_device *dev,
         skb->dev = dev;
 
         /*
-         * Clear rxhash so that we can recalulate the hash for the
+         * Clear hash so that we can recalulate the hash for the
          * encapsulated packet, unless we have already determine the hash
          * over the L4 4-tuple.
          */
-        if (!skb->l4_rxhash)
-                skb->rxhash = 0;
+        skb_clear_hash_if_not_l4(skb);
         skb_set_queue_mapping(skb, 0);
         skb_scrub_packet(skb, !net_eq(net, dev_net(dev)));
 }