Re: [v3,net-next 1/4] net: qos: introduce a gate control flow action

[Dave Taht]

On Wed, Apr 22, 2020 at 12:31 PM Vladimir Oltean <olteanv@xxxxxxxxx> wrote:
>
> Hi Allan,
>
> On Wed, 22 Apr 2020 at 22:20, Allan W. Nielsen
> <allan.nielsen@xxxxxxxxxxxxx> wrote:
> >
> > Hi Po,
> >
> > Nice to see even more work on the TSN standards in the upstream kernel.
> >
> > On 22.04.2020 10:48, Po Liu wrote:
> > >EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> > >
> > >Introduce a ingress frame gate control flow action.
> > >Tc gate action does the work like this:
> > >Assume there is a gate allow specified ingress frames can be passed at
> > >specific time slot, and be dropped at specific time slot. Tc filter
> > >chooses the ingress frames, and tc gate action would specify what slot
> > >does these frames can be passed to device and what time slot would be
> > >dropped.
> > >Tc gate action would provide an entry list to tell how much time gate
> > >keep open and how much time gate keep state close. Gate action also
> > >assign a start time to tell when the entry list start. Then driver would
> > >repeat the gate entry list cyclically.
> > >For the software simulation, gate action requires the user assign a time
> > >clock type.
> > >
> > >Below is the setting example in user space. Tc filter a stream source ip
> > >address is 192.168.0.20 and gate action own two time slots. One is last
> > >200ms gate open let frame pass another is last 100ms gate close let
> > >frames dropped. When the frames have passed total frames over 8000000
> > >bytes, frames will be dropped in one 200000000ns time slot.
> > >
> > >> tc qdisc add dev eth0 ingress
> > >
> > >> tc filter add dev eth0 parent ffff: protocol ip \
> > >           flower src_ip 192.168.0.20 \
> > >           action gate index 2 clockid CLOCK_TAI \
> > >           sched-entry open 200000000 -1 8000000 \
> > >           sched-entry close 100000000 -1 -1
> >
> > First of all, it is a long time since I read the 802.1Qci and when I did
> > it, it was a draft. So please let me know if I'm completly off here.
> >
> > I know you are focusing on the gate control in this patch serie, but I
> > assume that you later will want to do the policing and flow-meter as
> > well. And it could make sense to consider how all of this work
> > toghether.
> >
> > A common use-case for the policing is to have multiple rules pointing at
> > the same policing instance. Maybe you want the sum of the traffic on 2
> > ports to be limited to 100mbit. If you specify such action on the
> > individual rule (like done with the gate), then you can not have two
> > rules pointing at the same policer instance.
> >
> > Long storry short, have you considered if it would be better to do
> > something like:
> >
> >    tc filter add dev eth0 parent ffff: protocol ip \
> >             flower src_ip 192.168.0.20 \
> >             action psfp-id 42
> >
> > And then have some other function to configure the properties of psfp-id
> > 42?
> >
> >
> > /Allan
> >
>
> It is very good that you brought it up though, since in my opinion too
> it is a rather important aspect, and it seems that the fact this
> feature is already designed-in was a bit too subtle.
>
> "psfp-id" is actually his "index" argument.
>
> You can actually do this:
> tc filter add dev eth0 ingress \
>         flower skip_hw dst_mac 01:80:c2:00:00:0e \
>         action gate index 1 clockid CLOCK_TAI \
>         base-time 200000000000 \
>         sched-entry OPEN 200000000 -1 -1 \
>         sched-entry CLOSE 100000000 -1 -1
> tc filter add dev eth0 ingress \
>         flower skip_hw dst_mac 01:80:c2:00:00:0f \
>         action gate index 1
>
> Then 2 filters get created with the same action:
>
> tc -s filter show dev swp2 ingress
> filter protocol all pref 49151 flower chain 0
> filter protocol all pref 49151 flower chain 0 handle 0x1
>   dst_mac 01:80:c2:00:00:0f
>   skip_hw
>   not_in_hw
>         action order 1:
>         priority wildcard       clockid TAI     flags 0x6404f
>         base-time 200000000000                  cycle-time 300000000
>          cycle-time-ext 0
>          number    0    gate-state open         interval 200000000
>          ipv wildcard    max-octets wildcard
>          number    1    gate-state close        interval 100000000
>          ipv wildcard    max-octets wildcard
>         pipe
>          index 2 ref 2 bind 2 installed 168 sec used 168 sec
>         Action statistics:
>         Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
>         backlog 0b 0p requeues 0
>
> filter protocol all pref 49152 flower chain 0
> filter protocol all pref 49152 flower chain 0 handle 0x1
>   dst_mac 01:80:c2:00:00:0e
>   skip_hw
>   not_in_hw
>         action order 1:
>         priority wildcard       clockid TAI     flags 0x6404f
>         base-time 200000000000                  cycle-time 300000000
>          cycle-time-ext 0
>          number    0    gate-state open         interval 200000000
>          ipv wildcard    max-octets wildcard
>          number    1    gate-state close        interval 100000000
>          ipv wildcard    max-octets wildcard
>         pipe
>          index 2 ref 2 bind 2 installed 168 sec used 168 sec
>         Action statistics:
>         Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
>         backlog 0b 0p requeues 0
>
> Actually my only concern is that maybe this mechanism should (?) have
> been more generic. At the moment, this patch series implements it via
> a TCA_GATE_ENTRY_INDEX netlink attribute, so every action which wants
> to be shared across filters needs to reinvent this wheel.
>
> Thoughts, everyone?

I don't have anything valuable to add, aside from commenting this
whole thing makes my brain hurt.

> Thanks,
> -Vladimir



-- 
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Dave TÃht
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http://www.teklibre.com
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