Date:   Tue, 6 Aug 2019 19:53:23 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     David Ahern <dsahern@...il.com>
Cc:     Jakub Kicinski <jakub.kicinski@...ronome.com>,
        netdev@...r.kernel.org, davem@...emloft.net,
        sthemmin@...rosoft.com, mlxsw@...lanox.com
Subject: Re: [patch net-next v2 1/3] net: devlink: allow to change namespaces

Tue, Aug 06, 2019 at 07:34:59PM CEST, dsahern@...il.com wrote:
>On 8/5/19 9:20 AM, Jiri Pirko wrote:
>> Mon, Aug 05, 2019 at 04:51:22PM CEST, dsahern@...il.com wrote:
>>> On 8/5/19 8:49 AM, Jiri Pirko wrote:
>>>>> Your commit 5fc494225c1eb81309cc4c91f183cd30e4edb674 changed that from a
>>>>> per-namepace accounting to all namespaces managed by a single devlink
>>>>> instance in init_net - which is completely wrong.
>>>> No. Not "all namespaces". Only the one where the devlink is. And that is
>>>> always init_net, until this patchset.
>>>>
>>>>
>>>
>>> Jiri: your change to fib.c does not take into account namespace when
>>> doing rules and routes accounting. you broke it. fix it.
>> 
>> What do you mean by "account namespace"? It's a device resource, why to
>> tight it with namespace? What if you have 2 netdevsim-devlink instances
>> in one namespace? Why the setting should be per-namespace?
>> 
>
>Jiri:
>
>Here's an example of how your 5.2 change to netdevsim broke the resource
>controller:
>
>Create a netdevsim device:
>$ modprobe netdevsim
>$  echo "0 1" > /sys/bus/netdevsim/new_device
>
>Get the current number of IPv4 routes:
>$ n=$(ip -4 ro ls table all | wc -l)
>$ echo $n
>13
>
>Prevent any more from being added. This limit should apply solely to
>this namespace, init_net:
>
>$ devlink resource set netdevsim/netdevsim0 path /IPv4/fib size $n
>$ devlink dev reload netdevsim/netdevsim0
>Error: netdevsim: New size is less than current occupancy.
>devlink answers: Invalid argument
>
>So that is the first breakage: accounting is off - maybe. Note there are
>no other visible namespaces, but who knows what systemd or other
>processes are doing with namespaces. Perhaps this accounting is another
>example of your changes not properly handling namespaces:
>
>$ devlink resource show netdevsim/netdevsim0
>netdevsim/netdevsim0:
>  name IPv4 size unlimited unit entry size_min 0 size_max unlimited
>size_gran 1 dpipe_tables none
>    resources:
>      name fib size 13 occ 17 unit entry size_min 0 size_max unlimited
>size_gran 1 dpipe_tables none
>      name fib-rules size unlimited occ 6 unit entry size_min 0 size_max
>unlimited size_gran 1 dpipe_tables none
>  name IPv6 size unlimited unit entry size_min 0 size_max unlimited
>size_gran 1 dpipe_tables none
>    resources:
>      name fib size unlimited occ 10 unit entry size_min 0 size_max
>unlimited size_gran 1 dpipe_tables none
>      name fib-rules size unlimited occ 4 unit entry size_min 0 size_max
>unlimited size_gran 1 dpipe_tables none
>
>So the occupancy does not match the tables for init_net.
>
>Reset the max to 17, the current occupancy:
>$ devlink resource set netdevsim/netdevsim0 path /IPv4/fib size 17
>$ devlink dev reload netdevsim/netdevsim0
>$ devlink resource show netdevsim/netdevsim0
>netdevsim/netdevsim0:
>  name IPv4 size unlimited unit entry size_min 0 size_max unlimited
>size_gran 1 dpipe_tables none
>    resources:
>      name fib size 17 occ 17 unit entry size_min 0 size_max unlimited
>size_gran 1 dpipe_tables none
>      name fib-rules size unlimited occ 6 unit entry size_min 0 size_max
>unlimited size_gran 1 dpipe_tables none
>  name IPv6 size unlimited unit entry size_min 0 size_max unlimited
>size_gran 1 dpipe_tables none
>    resources:
>      name fib size unlimited occ 10 unit entry size_min 0 size_max
>unlimited size_gran 1 dpipe_tables none
>      name fib-rules size unlimited occ 4 unit entry size_min 0 size_max
>unlimited size_gran 1 dpipe_tables none
>
>Create a new namespace, bring up lo which attempts to add more route
>entries:
>$ unshare -n
>$ ip li set lo up
>
>If you list routes you see the lo routes failed to installed because of
>the limits, but it is a silent failure. Try to add a new route and you
>see the cross namespace accounting now:
>$ ip ro add 192.168.1.0/24 dev lo
>Error: netdevsim: Exceeded number of supported fib entries.
>
>
>Contrast that behavior with 5.1 and you see the new namespaces have no
>bearing on accounting in init_net and limits in init_net do not affect
>other namespaces.
>
>That behavior needs to be restored in 5.2 and 5.3.

Let's figure out the devlink-controlling-kernel-resources thread first.
What you describe here is exactly that.

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