ipv6: Don't send packet to big messages to self

Calling icmpv6_send() on a local message size error leads to an
incorrect update of the path mtu in the case when IPsec is used.
So use ipv6_local_error() instead to notify the socket about the
error.
Reported-by: NJiri Bohac <jbohac@suse.cz>
Signed-off-by: NSteffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/ip6_output.c

@@ -242,9 +242,8 @@ int ip6_xmit(struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,
 			       dst->dev, dst_output);
 	}
 
-	net_dbg_ratelimited("IPv6: sending pkt_too_big to self\n");
 	skb->dev = dst->dev;
-	icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
+	ipv6_local_error(sk, EMSGSIZE, fl6, mtu);
 	IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_FRAGFAILS);
 	kfree_skb(skb);
 	return -EMSGSIZE;