arp: Inherit metadata dst when creating ARP requests

If output device wants to see the dst, inherit the dst of the
original skb and pass it on to generate the ARP request.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/arp.c

@@ -291,6 +291,40 @@ static void arp_error_report(struct neighbour *neigh, struct sk_buff *skb)
 	kfree_skb(skb);
 }
 
+/* Create and send an arp packet. */
+static void arp_send_dst(int type, int ptype, __be32 dest_ip,
+			 struct net_device *dev, __be32 src_ip,
+			 const unsigned char *dest_hw,
+			 const unsigned char *src_hw,
+			 const unsigned char *target_hw, struct sk_buff *oskb)
+{
+	struct sk_buff *skb;
+
+	/* arp on this interface. */
+	if (dev->flags & IFF_NOARP)
+		return;
+
+	skb = arp_create(type, ptype, dest_ip, dev, src_ip,
+			 dest_hw, src_hw, target_hw);
+	if (!skb)
+		return;
+
+	if (oskb)
+		skb_dst_copy(skb, oskb);
+
+	arp_xmit(skb);
+}
+
+void arp_send(int type, int ptype, __be32 dest_ip,
+	      struct net_device *dev, __be32 src_ip,
+	      const unsigned char *dest_hw, const unsigned char *src_hw,
+	      const unsigned char *target_hw)
+{
+	arp_send_dst(type, ptype, dest_ip, dev, src_ip, dest_hw, src_hw,
+		     target_hw, NULL);
+}
+EXPORT_SYMBOL(arp_send);
+
 static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb)
 {
 	__be32 saddr = 0;
@@ -346,8 +380,9 @@ static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb)
 		}
 	}
 
-	arp_send(ARPOP_REQUEST, ETH_P_ARP, target, dev, saddr,
-		 dst_hw, dev->dev_addr, NULL);
+	arp_send_dst(ARPOP_REQUEST, ETH_P_ARP, target, dev, saddr,
+		     dst_hw, dev->dev_addr, NULL,
+		     dev->priv_flags & IFF_XMIT_DST_RELEASE ? NULL : skb);
 }
 
 static int arp_ignore(struct in_device *in_dev, __be32 sip, __be32 tip)
@@ -596,32 +631,6 @@ void arp_xmit(struct sk_buff *skb)
 }
 EXPORT_SYMBOL(arp_xmit);
 
-/*
- *	Create and send an arp packet.
- */
-void arp_send(int type, int ptype, __be32 dest_ip,
-	      struct net_device *dev, __be32 src_ip,
-	      const unsigned char *dest_hw, const unsigned char *src_hw,
-	      const unsigned char *target_hw)
-{
-	struct sk_buff *skb;
-
-	/*
-	 *	No arp on this interface.
-	 */
-
-	if (dev->flags&IFF_NOARP)
-		return;
-
-	skb = arp_create(type, ptype, dest_ip, dev, src_ip,
-			 dest_hw, src_hw, target_hw);
-	if (!skb)
-		return;
-
-	arp_xmit(skb);
-}
-EXPORT_SYMBOL(arp_send);
-
 /*
  *	Process an arp request.
  */