Re: [RFC v4] Add TCP encap_rcv hook (repost)
From: Jesse Gross <hidden>
Date: 2012-04-25 17:17:25
On Wed, Apr 25, 2012 at 1:39 AM, Simon Horman [off-list ref] wrote:
On Tue, Apr 24, 2012 at 04:02:41PM +0000, Kyle Mestery (kmestery) wrote:quoted
On Apr 23, 2012, at 9:25 PM, Simon Horman wrote:quoted
On Mon, Apr 23, 2012 at 03:59:24PM -0700, Jesse Gross wrote:quoted
On Mon, Apr 23, 2012 at 3:32 PM, Simon Horman [off-list ref] wrote:quoted
On Mon, Apr 23, 2012 at 02:38:07PM -0700, Jesse Gross wrote:quoted
On Mon, Apr 23, 2012 at 2:08 PM, David Miller [off-list ref] wrote:quoted
From: Jesse Gross <redacted> Date: Mon, 23 Apr 2012 13:53:42 -0700quoted
On Mon, Apr 23, 2012 at 1:13 PM, David Miller [off-list ref] wrote:quoted
From: Jesse Gross <redacted> Date: Mon, 23 Apr 2012 13:08:49 -0700quoted
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 takingDid 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?
This was what I had originally written a while back, although it's more about OVS internally and less about how to connect to the in-tree code: http://openvswitch.org/pipermail/dev/2012-February/014779.html In order to flexibly implement support for current and future tunnel protocols OVS needs to be able to get/set information about the outer tunnel header when processing the inner packet. At the very least this is src/dst IP addresses and the key/ID/VNI/etc. In the upstream tunnel implementations those are implicitly encoded in the device that sends or receives the packet. However, this has a two problems: number of devices and ability to handle unknown values. We addressed part of this problem by allowing the tunnel ID to be set and matched through the OVS flow table and an action. In order to do this with the in-tree tunneling code, we obviously need a way of passing this information around since it would currently get lost as we pass through the Linux device layer. The plan to deal with that is to add a function to the in-tree tunneling code that allows a skb to be encapsulated with specific parameters and conversely a hook to receive decapsulated packets along with header info. This would make all of the kernel tunneling code common, while still giving OVS userspace the ability to implement essentially any type of tunneling policy. In many ways, this is very similar to how vlans look in OVS today. While it would be possible to implement the hook to use the in-tree tunnel code today without a lot of changes, we already know that we want to move away from port-based model in the OVS kernel module towards the flow model. As we push this upstream the userspace/kernel API should be the correct one, so that's why these two things are tied together. _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev