by Xiaoliang Yang

[permalink] [raw]

Subject: RE: [EXT] Re: [PATCH v1 net-next 4/6] net: mscc: ocelot: VCAP IS1 support

Hi Allan,

> Hi Vladimir,
>
> On 06.05.2020 13:53, Vladimir Oltean wrote:
[snip]
> >At the moment, the driver does not support more than 1 action. We might
> >need to change that, but we can still install more filters with the
> >same key and still be fine (see more below). When there is more than 1
> >action, the IS1 stuff will be combined into a single rule programmed
> >into IS1, and the IS2 stuff will be combined into a single new rule
> >with the same keys installed into VCAP IS2. Would that not work?
> >
> >> The SW model have these two rules in the same table, and can stop
> >> process at the first match. SW will do the action of the first frame
> >> matching.
> >>
> >
> >Actually I think this is an incorrect assumption - software stops at
> >the first action only if told to do so. Let me copy-paste a text from a
> >different email thread.
>
> I'm still not able to see how this proposal will give us the same behavioral in SW and in HW.
>
> A simple example:
>
> tc qdisc add dev enp0s3 ingress
> tc filter add dev enp0s3 protocol 802.1Q parent ffff: \
> prio 10 flower vlan_id 5 action vlan modify id 10 tc filter add dev enp0s3 protocol 802.1Q parent ffff: \
> prio 20 flower src_mac 00:00:00:00:00:08 action drop
>
> We can then inject a frame with VID 5 and smac ::08:
> $ ef tx tap0 eth smac 00:00:00:00:00:08 ctag vid 5
>
> We can then check the filter and see that it only hit the first rule:
>
> $ tc -s filter show dev enp0s3 ingress
> filter protocol 802.1Q pref 10 flower chain 0 filter protocol 802.1Q pref 10 flower chain 0 handle 0x1
> vlan_id 5
> not_in_hw
> action order 1: vlan modify id 10 protocol 802.1Q priority 0 pipe
> index 1 ref 1 bind 1 installed 19 sec used 6 sec
> Action statistics:
> Sent 42 bytes 1 pkt (dropped 0, overlimits 0 requeues 0)
> backlog 0b 0p requeues 0
>
> filter protocol 802.1Q pref 20 flower chain 0 filter protocol 802.1Q pref 20 flower chain 0 handle 0x1
> src_mac 00:00:00:00:00:08
> not_in_hw
> action order 1: gact action drop
> random type none pass val 0
> index 1 ref 1 bind 1 installed 11 sec used 11 sec
> Action statistics:
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> backlog 0b 0p requeues 0
>
> If this was done with the proposed HW offload, then both rules would have been hit and we would have a different behavioral.
>
> This can be fixed by adding the "continue" action to the first rule:

> tc filter add dev enp0s3 protocol 802.1Q parent ffff: \
> prio 10 flower vlan_id 5 action vlan modify id 10 continue tc filter add dev enp0s3 protocol 802.1Q parent ffff: \
> prio 20 flower src_mac 00:00:00:00:00:08 action drop
>
> But that would again break if we add 2 rules manipulating the VLAN (as the HW does not continue with in a single TCAM).
>
> My point is: I do not think we can hide the fact that this is done in independent TCAMs in the silicon.
>
> I think it is possible to do this with the chain feature (even though it is not a perfect match), but it would require more analysis.
>
> /Allan

Do you mean it's better to set vlan modify filters in a different chain, and write the filter entries with a same chain in the same VCAP TCAM?
For example:
tc filter add dev enp0s3 protocol 802.1Q chain 11 parent ffff: prio 10 flower skip_sw vlan_id 5 action vlan modify id 10
tc filter add dev enp0s3 protocol 802.1Q chain 22 parent ffff: prio 20 flower skip_sw src_mac 00:00:00:00:00:08 action drop
for this usage, we only need to ensure a chain corresponding to a VCAP in ocelot ace driver. I'm not sure is my understanding right?

regards,
Xiaoliang

2020-05-07 19:31:18

by [email protected]

[permalink] [raw]

Subject: Re: [EXT] Re: [PATCH v1 net-next 4/6] net: mscc: ocelot: VCAP IS1 support

On 07.05.2020 11:23, Xiaoliang Yang wrote:
>EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>
>Hi Allan,
>
>
>> Hi Vladimir,
>>
>> On 06.05.2020 13:53, Vladimir Oltean wrote:
>[snip]
>> >At the moment, the driver does not support more than 1 action. We might
>> >need to change that, but we can still install more filters with the
>> >same key and still be fine (see more below). When there is more than 1
>> >action, the IS1 stuff will be combined into a single rule programmed
>> >into IS1, and the IS2 stuff will be combined into a single new rule
>> >with the same keys installed into VCAP IS2. Would that not work?
>> >
>> >> The SW model have these two rules in the same table, and can stop
>> >> process at the first match. SW will do the action of the first frame
>> >> matching.
>> >>
>> >
>> >Actually I think this is an incorrect assumption - software stops at
>> >the first action only if told to do so. Let me copy-paste a text from a
>> >different email thread.
>>
>> I'm still not able to see how this proposal will give us the same behavioral in SW and in HW.
>>
>> A simple example:
>>
>> tc qdisc add dev enp0s3 ingress
>> tc filter add dev enp0s3 protocol 802.1Q parent ffff: \
>> prio 10 flower vlan_id 5 action vlan modify id 10 tc filter add dev enp0s3 protocol 802.1Q parent ffff: \
>> prio 20 flower src_mac 00:00:00:00:00:08 action drop
>>
>> We can then inject a frame with VID 5 and smac ::08:
>> $ ef tx tap0 eth smac 00:00:00:00:00:08 ctag vid 5
>>
>> We can then check the filter and see that it only hit the first rule:
>>
>> $ tc -s filter show dev enp0s3 ingress
>> filter protocol 802.1Q pref 10 flower chain 0 filter protocol 802.1Q pref 10 flower chain 0 handle 0x1
>> vlan_id 5
>> not_in_hw
>> action order 1: vlan modify id 10 protocol 802.1Q priority 0 pipe
>> index 1 ref 1 bind 1 installed 19 sec used 6 sec
>> Action statistics:
>> Sent 42 bytes 1 pkt (dropped 0, overlimits 0 requeues 0)
>> backlog 0b 0p requeues 0
>>
>> filter protocol 802.1Q pref 20 flower chain 0 filter protocol 802.1Q pref 20 flower chain 0 handle 0x1
>> src_mac 00:00:00:00:00:08
>> not_in_hw
>> action order 1: gact action drop
>> random type none pass val 0
>> index 1 ref 1 bind 1 installed 11 sec used 11 sec
>> Action statistics:
>> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
>> backlog 0b 0p requeues 0
>>
>> If this was done with the proposed HW offload, then both rules would have been hit and we would have a different behavioral.
>>
>> This can be fixed by adding the "continue" action to the first rule:
>
>> tc filter add dev enp0s3 protocol 802.1Q parent ffff: \
>> prio 10 flower vlan_id 5 action vlan modify id 10 continue tc filter add dev enp0s3 protocol 802.1Q parent ffff: \
>> prio 20 flower src_mac 00:00:00:00:00:08 action drop
>>
>> But that would again break if we add 2 rules manipulating the VLAN (as the HW does not continue with in a single TCAM).
>>
>> My point is: I do not think we can hide the fact that this is done in independent TCAMs in the silicon.
>>
>> I think it is possible to do this with the chain feature (even though it is not a perfect match), but it would require more analysis.
>>
>> /Allan
>
>Do you mean it's better to set vlan modify filters in a different chain, and write the filter entries with a same chain in the same VCAP TCAM?
>For example:
> tc filter add dev enp0s3 protocol 802.1Q chain 11 parent ffff: prio 10 flower skip_sw vlan_id 5 action vlan modify id 10
> tc filter add dev enp0s3 protocol 802.1Q chain 22 parent ffff: prio 20 flower skip_sw src_mac 00:00:00:00:00:08 action drop
>for this usage, we only need to ensure a chain corresponding to a VCAP in ocelot ace driver. I'm not sure is my understanding right?

I still have not found a satisfying solution to this. As I understand
the chains, they require the "goto" action to be used to tie them
together.

We could use that to represent a single lookup in is1 and link that to a
lookup in is2. Not sure if we should, it will also require
(non-backwards compatible) changes in how the existing IS2 support is
working.

Again, I do not have the answer (I'm also looking for it), but I think
we need something where it is clear to the user that this end up in
different lists.

/Allan