Re: [RFC V1 1/1] net: extend VXLAN header to support more extensions

[Gavin Li <gavinl@nvidia.com>]

On 2/19/2024 11:44 AM, Gavin Li wrote:
> 
> 
> On 2/9/2024 11:32 PM, Thomas Monjalon wrote:
>> 09/02/2024 15:58, Ferruh Yigit:
>>> On 2/9/2024 1:44 PM, Thomas Monjalon wrote:
>>>> 09/02/2024 13:11, Ferruh Yigit:
>>>>> On 2/9/2024 10:12 AM, Thomas Monjalon wrote:
>>>>>> 09/02/2024 00:54, Ferruh Yigit:
>>>>>>> On 1/30/2024 11:25 AM, Gavin Li wrote:
>>>>>>>> Currently, DPDK supports VXLAN and VXLAN-GPE with similar header
>>>>>>>> structures and we are working on adding support for VXLAN-GBP 
>>>>>>>> which is
>>>>>>>> another extension to VXLAN. More extension of VXLAN may be added 
>>>>>>>> in the
>>>>>>>> future.
>>>>>>>>
>>>>>>>> VXLAN and VXLAN-GBP use the same UDP port(4789) while VXLAN-GPE 
>>>>>>>> uses a
>>>>>>>> different one, 4790. The three protocols have the same header 
>>>>>>>> length and
>>>>>>>> overall similar header structure as below.
>>>>>>>>      0                   1                   2                   3
>>>>>>>>      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 
>>>>>>>> 0 1
>>>>>>>>     
>>>>>>>> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>>>>>>>     |R|R|R|R|I|R|R|R|            
>>>>>>>> Reserved                           |
>>>>>>>>     
>>>>>>>> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>>>>>>>     |                VXLAN Network Identifier (VNI) |   
>>>>>>>> Reserved    |
>>>>>>>>     
>>>>>>>> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>>>>>>>
>>>>>>>>                             Figure 1: VXLAN Header
>>>>>>>>
>>>>>>>>      0                   1                   2                   3
>>>>>>>>      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 
>>>>>>>> 0 1
>>>>>>>>     
>>>>>>>> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>>>>>>>     |R|R|Ver|I|P|B|O|       Reserved                |Next 
>>>>>>>> Protocol  |
>>>>>>>>     
>>>>>>>> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>>>>>>>     |                VXLAN Network Identifier (VNI) |   
>>>>>>>> Reserved    |
>>>>>>>>     
>>>>>>>> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>>>>>>>
>>>>>>>>                           Figure 2: VXLAN-GPE Header
>>>>>>>>
>>>>>>>>      0                   1                   2                   3
>>>>>>>>      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 
>>>>>>>> 0 1
>>>>>>>>     
>>>>>>>> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>>>>>>>     |G|R|R|R|I|R|R|R|R|D|R|R|A|R|R|R|        Group Policy 
>>>>>>>> ID        |
>>>>>>>>     
>>>>>>>> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>>>>>>>     |          VXLAN Network Identifier (VNI)       |   
>>>>>>>> Reserved    |
>>>>>>>>     
>>>>>>>> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>>>>>>>
>>>>>>>>                            Figure 3: VXLAN-GBP Extension
>>>>>>>>
>>>>>>>> Both VXLAN-GPE and VXLAN-GBP extended VXLAN by redefining its 
>>>>>>>> reserved
>>>>>>>> bits, which means the packets can be processed with same pattern 
>>>>>>>> and most
>>>>>>>> of the code can be reused. Instead of adding more new items by
>>>>>>>> copying/pasting code for the VXLAN extensions in the future, 
>>>>>>>> it’s better
>>>>>>>> to use existing VXLAN infrastructure and add support code in it.
>>>>>>>>
>>>>>>>
>>>>>>> Hi Gavin,
>>>>>>>
>>>>>>> The motivation is to prevent code duplication, and the code 
>>>>>>> mentioned is
>>>>>>>   the driver code, right?
>>>>>>
>>>>>> The motivation is mainly to provide a unified and more explicit API.
>>>>>>
>>>>>
>>>>>  From user perspective, I think existing approach is more explicit,
>>>>> because it sets VXLAN or VXLAN_GPE flow types.
>>>>>
>>>>> I am trying to understand the benefit, how unifying flow type in 
>>>>> the API
>>>>> helps to the user?
>>>>>
>>>>>>> Overall OK to unify "struct rte_vxlan_hdr" although it makes the 
>>>>>>> struct
>>>>>>> a little complex, perhaps we can consider extraction some nested 
>>>>>>> structs
>>>>>>> as named struct, no strong opinion.
>>>>>>>
>>>>>>>
>>>>>>> But not sure about removing the flow item types for VXLAN-GPE, or 
>>>>>>> not
>>>>>>> adding for VXLAN-GBP.
>>>>>>>
>>>>>>> Think about a case user adding a rule, which has a item type as 
>>>>>>> VXLAN
>>>>>>> and in the protocol header some bits are set, lets say first 
>>>>>>> word, last
>>>>>>> byte is set, how driver will know if to take it as GPE "next 
>>>>>>> protocol"
>>>>>>> or "group policy id".
>>>>>>
>>>>>> The driver may decide depending on the UDP port and some 
>>>>>> distinguishing flags.
>>>>>> If you want to match on GBP, you should includes the GBP flag in 
>>>>>> your pattern,
>>>>>> no need to use a separate item.
>>>>>>
>>>>>
>>>>> Why not be more explicit?
>>>>> It helps to driver to know more about the pattern to be able to create
>>>>> proper flow rule, if there is an obvious way for driver to 
>>>>> differentiate
>>>>> these protocol extensions, and flow item type is redundant, I can
>>>>> understand the proposal, but otherwise I think better to keep flow 
>>>>> items
>>>>> for extensions.
>>>>
>>>> In any case we need the simple VXLAN item.
>>>> If we have GPE and GBP specialized items,
>>>> what means a match on the simple VXLAN?
>>>> Does it include packets with other extensions or exclude them?
>>>> Matching the bits in the protocol make such decision explicit.
>>>>
>>>>> When a rule is set in HW, HW may not care about the protocol, as 
>>>>> long as
>>>>> bits in the rule match with the packet, HW can apply the action.
>>>>> But for driver to be able to set the rule properly, it needs more
>>>>> explicit information.
>>>>
>>>> Yes information is in the pattern to match.
>>>>
>>>>> Lets assume driver API get a pattern with 'RTE_FLOW_ITEM_TYPE_VXLAN'
>>>>> type and "struct rte_flow_item_vxlan", at this point driver doesn't 
>>>>> know
>>>>> if it is VXLAN or any of the extensions.
>>>>
>>>> Yes it knows because of the matched bits in the pattern.
>>>> If the rule specify a match on GBP flag = 1, it is GBP only.
>>>> If the rule specify a match on GBP flag = 0, it excludes GBP.
>>>> If the rule does not mask GBP flag, it includes GBP.
>>>>
>>>
>>>
>>> OK, VXLAN-GBP protocol has a GBP flag that gives a way to differentiate
>>> the extension, so flow item for it becomes redundant and we can get rid
>>> of it.
>>
>> Yes I think so.
>>
>>> Is it same for the other extensions?
>>> If we use VXLAN flow item and by setting specific field in pattern can
>>> we differentiate VXLAN and any other extension?
>>> Or in some cases other information, like UDP port, needs to be taken
>>> into account to differentiate protocol/extension?
>>
>> For VXLAN-GPE, differentiation is on UDP port.
>> Remember we have an API to fill some UDP ports:
>> rte_eth_dev_udp_tunnel_port_add with RTE_ETH_TUNNEL_TYPE_VXLAN_GPE
>>
>> The UDP port value/mask may be part of the flow rule pattern.
>>
>>
>>> I found a spec for VXLAN-GBP, but it shows as sub-header for VXLAN-GPE,
>>> different than what this RFC describes:
>>> https://datatracker.ietf.org/doc/html/draft-lemon-vxlan-gpe-gbp
>>>
>>> Can you please share link for VXLAN-GBP Extension spec?
>>
>> I will let Gavin explain here, I'm not an expert.
> 
> Sorry for the wrong format of my last mail. Let me try again.
> 
> The RFC mentioned, aka draft-lemon-vxlan-gpe-gbp was to define VXLAN-GBP
> as a sub header of VXLAN-GPE by assigning a next protocol num of 
> VXLAN-GPE for VXLAN-GBP, which has been obsoleted since 
> draft-ietf-nvo3-vxlan-gpe-09, the latest is 
> draft-ietf-nvo3-vxlan-gpe-13. It was temporarily valid from 
> draft-ietf-nvo3-vxlan-gpe-05 to draft-ietf-nvo3-vxlan-gpe-08.
> 
> The VXLAN-GBP we are discussing in this thread is an VXLAN extension 
> parallel to VXLAN-GPE.
> 
> The RFC introduced VXLAN-GBP sub header to VXLAN-GPE is 
> https://datatracker.ietf.org/doc/html/draft-ietf-nvo3-vxlan-gpe-05.
> 
> The RFC obsoleted the sub header is 
> https://datatracker.ietf.org/doc/html/draft-ietf-nvo3-vxlan-gpe-09.
> 
> The latest RFC of VXLAN-GPE is 
> https://datatracker.ietf.org/doc/html/draft-ietf-nvo3-vxlan-gpe-13.

And the latest RFC of VXLAN-GPB is 
https://datatracker.ietf.org/doc/html/draft-smith-vxlan-group-policy-05.

> 
> 
>>
>>