Re: question about eth and vlan item in flow pattern

[Jie Hai <haijie1@huawei.com>]

Hi, Ivan Malov,
Sorry for the late reply.
On 2024/4/10 21:19, Ivan Malov wrote:
> Hi Jie,
> 
> Consider the following examples:
> 1) flow create 0 ingress pattern eth / ipv4 proto is 17 / udp / end \
>     actions queue index 1 / end
> 2) flow create 0 ingress pattern eth / ipv4 / udp / end \
>     actions queue index 1 / end
> 
> Generally speaking, these two rules might be equivalent, with "proto is 
> 17" in
> the first one probably being redundant (the very presence of "udp" item 
> might
> stand for the same match criterion -- the protocol ID being 17).
I can understand that.
> 
> And I'd be tempted to treat the "has_vlan" case similarly. Consider:
> 3) flow create 0 ingress pattern eth has_vlan is 1 / vlan / end \
>     actions queue index 1 / end
> 4) flow create 0 ingress pattern eth / vlan / end \
>     actions queue index 1 / end
> 
> (rule (3) is similar to "rule-0" from your example)
> 
> Rules (3) and (4) seem equivalent to me -- the "has_vlan is 1" bit might be
> redundant in flow (3) -- the presence of item "vlan" sort of means the 
> same.

> Rule (3) and (4) should probably match both single-tagged and double-tagged
> packets because, in both cases, the pattern does not clarify which protocol
> follows the outermost VLAN tag. If one needs to exclude double-tag match,
> they should clarify the rule in one of the possible ways, in example:
> 
> - pattern eth / vlan has_more_vlan is 0 / end
> - pattern eth / vlan tpid is 0x0800 / end
> - pattern eth / vlan / ipv4 / end
> 
> (the "tpid" goes to the "hdr.eth_proto" of "struct rte_flow_item_vlan").
> 
As mentioned above, `has_vlan is 1` and `vlan` are the same,
which means `vlan` stands for any-tagged vlan,
Then, is the introduction of `has_vlan` and `has_more_vlan` unnecessary?

There are drivers seeing `vlan` an one vlan layer and match 
'eth/vlan/end' with single-tagged packets, e.g.bnxt, hns3, etc.
I think this meaning makes it easier to distinguish the functions of the 
two.

The `has_more_vlan is 1` is defined and used by some drivers, like mlx5.
While the `has_more_vlan is 0` is not defined.
Here you give the meaning as `having no vlan after this vlan`.
Then, What should the follow rule mean? single-tagged or double tagged?

- pattern eth / vlan tpid is 0x8100 has_more_vlan is 0 / end

> With regard to the question about VLAN ID match, "pattern eth / vlan vid 
> is 10",
> as well as "pattern eth has_vlan is 1 / vlan vid is 10", should probably 
> match
> only on the outermost tag ID, -- that is, not on the inner one and not 
> on both.
I agree with it.
> That is because the "vid is 10" criterion relates to the specific header,
> as per the match item it sits in. If the user wants to match on the
> inner VLAN ID (say, 11), they should clarify specify it as follows:
> 
> - pattern eth / vlan vid is 10 / vlan vid is 11 / end
> - pattern eth / vlan / vlan vid is 11 / end
>

> Hopefully, the rest of DPDK vendor community can correct me in case I got
> that wrong. Should you have more questions, please feel free to ask such.
> 
> Thank you.
> 
> On Wed, 10 Apr 2024, Jie Hai wrote:
> 
>> Hi, all,
>>
>> I have some questions about the sub-options for ``VLAN`` and ``ETH`` 
>> item.
>>
>> According to the documentation, ``has_vlan`` is sub-option of ``ETH``
>> item and it means that the pattern contains at least one vlan.
>> The ``VLAN`` item is used to match tagged packets and have some
>> sub-options such as ``vid``, ``tci``, etc.
>>
>> If we combine them, what should the effect be?
>> For instance,
>>
>> rule-0: flow create 0 ingress pattern  eth  has_vlan is 1 / vlan  / 
>> end actions queue index 2 / end
>> rule-1: flow create 0 ingress pattern  eth  has_vlan is 1 / vlan vid 
>> is 10 / end actions queue index 2 / end
>>
>> For rule-0, should it match single-tagged packets only or multi-tagged 
>> only or both?
>> That is to say, which one will take effect, `has_vlan is 1`  or `vlan` 
>> or both?
>>
>> For rule-2, which packets should it match, with inner VLAN id 10, or 
>> outer VLAN id 10, or both 10?
>>
>> The hns3 driver supports only the exact matching of VLAN numer.
>> And it is planned to adapt ``has_vlan`` and ``has_more_vlan`` to the
>> meaning of one VLAN for hns3 driver. Therefore, if the preceding 
>> combinations are supported, we need to confirm the exact meanings.
>>
>> So, what are your views on the above question?
>>
>>
>>
>>
> .