Re: [PATCH net] gso: do GSO for local skb with size bigger than MTU

[Jesse Gross <jesse@nicira.com>]

On Thu, Dec 4, 2014 at 1:26 AM, Thomas Graf <tgraf@suug.ch> wrote:
> On 12/03/14 at 05:51pm, Jesse Gross wrote:
>> I think it depends on where you put the PMTU check. If routing is
>> happening in OVS where it is decomposed in several discrete actions
>> like set MAC and decrement TTL then perhaps there is another explicit
>> action to check the MTU. If it is happening in the context of the IP
>> stack, then ICMP generation occurs automatically and if you get that
>> if you write a flow to send a packet there. In each case, it seems
>> like a flow would be steering you by way of an action to do routing so
>> you would have fine grained control. I don't see this as conflicting
>> with L3 ACLs in an L2 context in the same way that you don't have to
>> automatically decrement the TTL.
>
> OK, I was under the impression that you would detect L3 behaviour
> desire in OVS without an explicit action. Hence the worry on wrong
> classification for L3 ACLs.
>
> Whether we mark the packet and defer the MTU check or we check right
> in the action is an implementation detail in the end. I think we
> agree on concept level that we need an API to control behaviour.

Yes, I agree.