[IPV6]: Fix reversed local_df test in ip6_fragment

I managed to reverse the local_df test when forward-porting this
patch so it actually makes things worse by never fragmenting at
all.

Thanks to David Stevens for testing and reporting this bug.

Bill Fink pointed out that the local_df setting is also the wrong
way around.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/ip6_output.c

@@ -621,7 +621,7 @@ static int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
 	 * or if the skb it not generated by a local socket.  (This last
 	 * check should be redundant, but it's free.)
 	 */
-	if (skb->local_df) {
+	if (!skb->local_df) {
 		skb->dev = skb->dst->dev;
 		icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu, skb->dev);
 		IP6_INC_STATS(ip6_dst_idev(skb->dst), IPSTATS_MIB_FRAGFAILS);
@@ -1421,7 +1421,7 @@ int ip6_push_pending_frames(struct sock *sk)
 	}
 
 	/* Allow local fragmentation. */
-	if (np->pmtudisc >= IPV6_PMTUDISC_DO)
+	if (np->pmtudisc < IPV6_PMTUDISC_DO)
 		skb->local_df = 1;
 
 	ipv6_addr_copy(final_dst, &fl->fl6_dst);