ip6_output: fragment outgoing reassembled skb properly

[ Upstream commit 9037c357 ]

If reassembled packet would fit into outdev MTU, it is not fragmented
according the original frag size and it is send as single big packet.

The second case is if skb is gso. In that case fragmentation does not happen
according to the original frag size.

This patch fixes these.
Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

net/ipv6/ip6_output.c

@@ -125,7 +125,8 @@ static int ip6_finish_output2(struct sk_buff *skb)
 static int ip6_finish_output(struct sk_buff *skb)
 {
 	if ((skb->len > ip6_skb_dst_mtu(skb) && !skb_is_gso(skb)) ||
-	    dst_allfrag(skb_dst(skb)))
+	    dst_allfrag(skb_dst(skb)) ||
+	    (IP6CB(skb)->frag_max_size && skb->len > IP6CB(skb)->frag_max_size))
 		return ip6_fragment(skb, ip6_finish_output2);
 	else
 		return ip6_finish_output2(skb);