From: Jiri Pirko <jiri@xxxxxxxxxxx>
Date: Fri, 8 Nov 2013 08:52:01 +0100
> Fri, Nov 08, 2013 at 12:54:53AM CET, davem@xxxxxxxxxxxxx wrote:
>>From: Jiri Pirko <jiri@xxxxxxxxxxx>
>>Date: Wed, 6 Nov 2013 17:52:19 +0100
>>
>>> 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@xxxxxxxxxxx>
>> ...
>>
>>> 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);
>>
>>Jiri are you sure that you don't need to take GSO into account in the
>>new part you are adding to the test?
>
>
> For gso skb, we need co cap outgoing fragments by the original frag size
> as well. So I believe that this code is correct for that case as well.
I'm still not so sure I agree, even after having taken a second look
at this.
Look at ipv4's logic for this same facility:
if (skb->len > ip_skb_dst_mtu(skb) && !skb_is_gso(skb))
return ip_fragment(skb, ip_finish_output2);
Strictly, we only call ip_fragment() if skb_is_gso() is false. And then
in ip_fragment():
if (unlikely(((iph->frag_off & htons(IP_DF)) && !skb->local_df) ||
(IPCB(skb)->frag_max_size &&
IPCB(skb)->frag_max_size > dst_mtu(&rt->dst)))) {
And that second branch of this test is what you're trying to duplicate
into ipv6.
Perhaps I don't understand completely the intentions and logic of
dst_allfrag() in the ipv6 case, and maybe you can explain it to me.
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