What are the use case(s) of truncate “outside” of sampling/mirroring ?
The use of truncation in the context of sampling/mirroring is well known.
On 5/10/17, 7:56 AM, "ovs-dev-boun...@openvswitch.org on behalf of William Tu"
<ovs-dev-boun...@openvswitch.org on behalf of u9012...@gmail.com> wrote:
> It may be cleaner if we add a new trunc action for the datapath, say
> trunc2 that applies
> to all outputs within the clone.
>
> So the translation will look like: clone(trunc2, native tunnel
> translation). Would this
> approach work?
>
Or how about we apply actual packet truncation when clone action
follows truncate action?
Now we apply actual packet truncation when:
actions=trunc, output
actions=trunc, tunnel_push
actions=trunc, sample
If we add clone as another truncate target, then
actions = trunc(100), clone(tnl(...)), actionX,
Inside clone will see packet of size 100, and actionX sees original
size. Then I think we don't need to introduce trunc2?
Regards,
William
>>
>> Without the "Avoid recirculation" patch we have two datapath flows,
because the
>> packet is recirculated. At the end of the first flow the packet size is
changed
>> and the packet with modified size enters the OF pipeline again.
>>
>> What is the reason not to change packet size when truncate action is
applied?
>>
>
> One of the reasons could be that we introduced trunc before clone.
Otherwise, a
> clone(trunc2, output:x) is equivalent to trunc, output:x. Note that
> the trunc datapath
> action is different than other datapath actions, which usually applies
> to all following
> actions. Native tunneling may be the first use case that motivates
> trunc2, which should
> have the normal datapath action behavior.
>
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