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 <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/linux/skbuff.h

···
 	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)
 {

include/net/dst.h

···
 	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)));
 }

net/ipv4/ip_fragment.c

···
 			memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
 			if (ip_defrag(skb, user))
 				return NULL;
-			skb->rxhash = 0;
+			skb_clear_hash(skb);
 		}
 	}
 	return skb;

net/ipv4/ip_tunnel_core.c

···
 
 	skb_scrub_packet(skb, xnet);
 
-	skb->rxhash = 0;
+	skb_clear_hash(skb);
 	skb_dst_set(skb, &rt->dst);
 	memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
 
···
 
 	nf_reset(skb);
 	secpath_reset(skb);
-	if (!skb->l4_rxhash)
-		skb->rxhash = 0;
+	skb_clear_hash_if_not_l4(skb);
 	skb_dst_drop(skb);
 	skb->vlan_tci = 0;
 	skb_set_queue_mapping(skb, 0);

net/openvswitch/actions.c

···
 	}
 
 	csum_replace4(&nh->check, *addr, new_addr);
-	skb->rxhash = 0;
+	skb_clear_hash(skb);
 	*addr = new_addr;
 }
 
···
 	if (recalculate_csum)
 		update_ipv6_checksum(skb, l4_proto, addr, new_addr);
 
-	skb->rxhash = 0;
+	skb_clear_hash(skb);
 	memcpy(addr, new_addr, sizeof(__be32[4]));
 }
 
···
 {
 	inet_proto_csum_replace2(check, skb, *port, new_port, 0);
 	*port = new_port;
-	skb->rxhash = 0;
+	skb_clear_hash(skb);
 }
 
 static void set_udp_port(struct sk_buff *skb, __be16 *port, __be16 new_port)
···
 			uh->check = CSUM_MANGLED_0;
 	} else {
 		*port = new_port;
-		skb->rxhash = 0;
+		skb_clear_hash(skb);
 	}
 }
 
···
 		/* Carry any checksum errors through. */
 		sh->checksum = old_csum ^ old_correct_csum ^ new_csum;
 
-		skb->rxhash = 0;
+		skb_clear_hash(skb);
 	}
 
 	return 0;