Re: [dpdk-dev] [PATCH v3 0/3] ethdev: add generic L2/L3 tunnel encapsulation actions

[Andrew Rybchenko <arybchenko@solarflare.com>]

On 10/9/18 7:48 PM, Ferruh Yigit wrote:
> On 10/7/2018 1:57 PM, Ori Kam wrote:
>> This series implement the generic L2/L3 tunnel encapsulation actions
>> and is based on rfc [1] "add generic L2/L3 tunnel encapsulation actions"
>>
>> Currenlty the encap/decap actions only support encapsulation
>> of VXLAN and NVGRE L2 packets (L2 encapsulation is where
>> the inner packet has a valid Ethernet header, while L3 encapsulation
>> is where the inner packet doesn't have the Ethernet header).
>> In addtion the parameter to to the encap action is a list of rte items,
>> this results in 2 extra translation, between the application to the action
>> and from the action to the NIC. This results in negetive impact on the
>> insertion performance.
>>      
>> Looking forward there are going to be a need to support many more tunnel
>> encapsulations. For example MPLSoGRE, MPLSoUDP.
>> Adding the new encapsulation will result in duplication of code.
>> For example the code for handling NVGRE and VXLAN are exactly the same,
>> and each new tunnel will have the same exact structure.
>>      
>> This series introduce a generic encapsulation for L2 tunnel types, and
>> generic encapsulation for L3 tunnel types. In addtion the new
>> encapsulations commands are using raw buffer inorder to save the
>> converstion time, both for the application and the PMD.
>>
>> [1]https://mails.dpdk.org/archives/dev/2018-August/109944.html
>>
>> v3:
>>   * rebase on tip.
>>
>> v2:
>>   * add missing decap_l3 structure.
>>   * fix typo.
>>
>>
>> Ori Kam (3):
>>    ethdev: add generic L2/L3 tunnel encapsulation actions
>>    app/testpmd: convert testpmd encap commands to new API
>>    ethdev: remove vxlan and nvgre encapsulation commands
> Reminder of this patchset, any reviews welcome.

I've added the author of previous actions in recipients.

I like the idea to generalize encap/decap actions. It makes a bit harder
for reader to find which encap/decap actions are supported in fact,
but it changes nothing for automated usage in the code - just try it
(as a generic way used in rte_flow).

Arguments about a way of encap/decap headers specification (flow items
vs raw) sound sensible, but I'm not sure about it.
It would be simpler if the tunnel header is added appended or removed
as is, but as I understand it is not true. For example, IPv4 ID will be
different in incoming packets to be decapsulated and different values
should be used on encapsulation. Checksums will be different (but
offloaded in any case).

Current way allows to specify which fields do not matter and which one
must match. It allows to say that, for example, VNI match is sufficient
to decapsulate.

Also arguments assume that action input is accepted as is by the HW.
It could be true, but could be obviously false and HW interface may
require parsed input (i.e. driver must parse the input buffer and extract
required fields of packet headers).

So, I'd say no. It should be better motivated if we change existing
approach (even advertised as experimental).