[ovs-dev] [RFC v4] Add TCP encap_rcv hook (repost)

[Kyle Mestery (kmestery)]

On Apr 25, 2012, at 3:39 AM, Simon Horman wrote:
> On Tue, Apr 24, 2012 at 04:02:41PM +0000, Kyle Mestery (kmestery) wrote:
>> On Apr 23, 2012, at 9:25 PM, Simon Horman wrote:
>>> On Mon, Apr 23, 2012 at 03:59:24PM -0700, Jesse Gross wrote:
>>>> On Mon, Apr 23, 2012 at 3:32 PM, Simon Horman <horms at verge.net.au> wrote:
>>>>> On Mon, Apr 23, 2012 at 02:38:07PM -0700, Jesse Gross wrote:
>>>>>> On Mon, Apr 23, 2012 at 2:08 PM, David Miller <davem at davemloft.net> wrote:
>>>>>>> From: Jesse Gross <jesse at nicira.com>
>>>>>>> Date: Mon, 23 Apr 2012 13:53:42 -0700
>>>>>>> 
>>>>>>>> On Mon, Apr 23, 2012 at 1:13 PM, David Miller <davem at davemloft.net> wrote:
>>>>>>>>> From: Jesse Gross <jesse at nicira.com>
>>>>>>>>> Date: Mon, 23 Apr 2012 13:08:49 -0700
>>>>>>>>> 
>>>>>>>>>> Assuming that the TCP stack generates large TSO frames on transmit
>>>>>>>>>> (which could be the local stack; something sent by a VM; or packets
>>>>>>>>>> received, coalesced by GRO and then encapsulated by STT) then you can
>>>>>>>>>> just prepend the STT header (possibly slightly adjusting things like
>>>>>>>>>> requested MSS, number of segments, etc. slightly).  After that it's
>>>>>>>>>> possible to just output the resulting frame through the IP stack like
>>>>>>>>>> all tunnels do today.
>>>>>>>>> 
>>>>>>>>> Which seems to potentially suggest a stronger intergration of the STT
>>>>>>>>> tunnel transmit path into our IP stack rather than the approach Simon
>>>>>>>>> is taking
>>>>>>>> 
>>>>>>>> Did you have something in mind?
>>>>>>> 
>>>>>>> A normal bonafide tunnel netdevice driver like GRE instead of the
>>>>>>> openvswitch approach Simon is using.
>>>>>> 
>>>>>> Ahh, yes, that I agree with.  Independent of this, there's work being
>>>>>> done to make it so that OVS can use the normal in-tree tunneling code
>>>>>> and not need its own.  Once that's done I expect that STT will follow
>>>>>> the same model.
>>>>> 
>>>>> Hi Jesse,
>>>>> 
>>>>> I am wondering how firm the plans to on allowing OVS to use in-tree tunnel
>>>>> code are. I'm happy to move my efforts over to an in-tree STT implementation
>>>>> but ultimately I would like to get STT running in conjunction with OVS.
>>>> 
>>>> I would say that it's a firm goal but the implementation probably
>>>> still has a ways to go.  Kyle Mestery (CC'ed) has volunteered to work
>>>> on this in support of adding VXLAN, which needs some additional
>>>> flexibility that this approach would also provide.  You might want to
>>>> talk to him to see if there are ways that you guys can work together
>>>> on it if you are interested.  Having better integration with upstream
>>>> tunneling is definitely a step that OVS needs to make and sooner would
>>>> be better than later.
>>> 
>>> Hi Jesse, Hi Kyle,
>>> 
>>> that sounds like an excellent plan.
>>> 
>>> Kyle, do you have any thoughts on how we might best work together on this?
>>> Perhaps there are some patches floating around that I could take a look at?
>>> 
>> 
>> Hi Simon:
>> 
>> The VXLAN work has been slow going for me at this point. What I have works, but is far from complete. It's available here:
>> 
>> https://github.com/mestery/ovs-vxlan/tree/vxlan
>> 
>> This is based on a fairly recent version of OVS. I'm currently working to allow tunnels to be flow-based rather than port-based, as they currently exist.
>> As Jesse may have mentioned, doing this allows us to move most tunnel state into user space. The outer header can now be part of the flow lookup and can
>> be passed to user space, so things like multicast learning for VXLAN become possible.
>> 
>> With regards to working together, ping me off-list and we can work something out, I'm very much in favor of this!
> 
> Hi Kyle,
> 
> the component that is of most interest to me is enabling OVS to use in-tree
> tunnelling code - as it seems that makes most sense for an implementation
> of STT. I have taken a brief look over your vxlan work and it isn't clear
> to me if it is moving towards being an in-tree implementation.  Moreover,
> I'm a rather unclear on what changes need to be made to OVS in order for
> in-tree tunneling to be used.
> 
> My recollection is that OVS did make use of in-tree tunnelling code
> but this was removed in favour of the current implementation for various
> reasons (performance being one IIRC). I gather that revisiting in-tree
> tunnelling won't revisit the previous set of problems. But I'm unclear how.
> 
> Jesse, is it possible for you to describe that in a little detail
> or point me to some information?

Simon:

The changes I have in there now are taking the first step of trying to add support for flow-based tunneling, in the case of VXLAN. Once we do that, we can remove (if we want) the existing port-based tunneling code. I was planning this as a first step. I would also to understand from Jesse better the direction with regards to moving to in-tree tunneling. I assume the changes Jesse and I had talked about a few months back around flow-based tunneling will still be compatible with the in-tree tunneling as well.

Thanks,
Kyle