ipv4: ip_gre: Convert to dst_neigh_lookup()

The conversion is very similar to that made to ipv6's SIT code.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/ip_gre.c

@@ -730,10 +730,12 @@ static netdev_tx_t ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev
 		}
 #if IS_ENABLED(CONFIG_IPV6)
 		else if (skb->protocol == htons(ETH_P_IPV6)) {
-			struct neighbour *neigh = dst_get_neighbour_noref(skb_dst(skb));
 			const struct in6_addr *addr6;
+			struct neighbour *neigh;
+			bool do_tx_error_icmp;
 			int addr_type;
 
+			neigh = dst_neigh_lookup(skb_dst(skb), &ipv6_hdr(skb)->daddr);
 			if (neigh == NULL)
 				goto tx_error;
 
@@ -746,9 +748,14 @@ static netdev_tx_t ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev
 			}
 
 			if ((addr_type & IPV6_ADDR_COMPATv4) == 0)
+				do_tx_error_icmp = true;
+			else {
+				do_tx_error_icmp = false;
+				dst = addr6->s6_addr32[3];
+			}
+			neigh_release(neigh);
+			if (do_tx_error_icmp)
 				goto tx_error_icmp;
-
-			dst = addr6->s6_addr32[3];
 		}
 #endif
 		else