[IPV6]: Reload skb->dst after xfrm6_route_forward()

While replacing dst_pmtu in ip6_output I found this little gem.  In
ip6_forward we're not reloading the dst pointer after calling
xfrm6_route_forward.  So all subsequent dereferences of dst will
refer to its pre-IPsec value.

The solution is of course to refresh its value.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6_output.c

@@ -397,6 +397,7 @@ int ip6_forward(struct sk_buff *skb)
 		IP6_INC_STATS(IPSTATS_MIB_INDISCARDS);
 		goto drop;
 	}
+	dst = skb->dst;
 
 	/* IPv6 specs say nothing about it, but it is clear that we cannot
 	   send redirects to source routed frames.