netdev - Re: [patch net-next 00/34] net: sched: allow qdiscs to share filter block instances

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Date:   Fri, 13 Oct 2017 16:24:44 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     David Ahern <dsahern@...il.com>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, jhs@...atatu.com,
        xiyou.wangcong@...il.com, mlxsw@...lanox.com, andrew@...n.ch,
        vivien.didelot@...oirfairelinux.com, f.fainelli@...il.com,
        michael.chan@...adcom.com, ganeshgr@...lsio.com,
        jeffrey.t.kirsher@...el.com, saeedm@...lanox.com,
        matanb@...lanox.com, leonro@...lanox.com, idosch@...lanox.com,
        jakub.kicinski@...ronome.com, ast@...nel.org, daniel@...earbox.net,
        simon.horman@...ronome.com, pieter.jansenvanvuuren@...ronome.com,
        john.hurley@...ronome.com, edumazet@...gle.com,
        alexander.h.duyck@...el.com, john.fastabend@...il.com,
        willemb@...gle.com
Subject: Re: [patch net-next 00/34] net: sched: allow qdiscs to share filter
 block instances

Fri, Oct 13, 2017 at 04:20:38PM CEST, dsahern@...il.com wrote:
>On 10/13/17 12:26 AM, Jiri Pirko wrote:
>> Thu, Oct 12, 2017 at 11:37:30PM CEST, dsahern@...il.com wrote:
>>> On 10/12/17 11:17 AM, Jiri Pirko wrote:
>>>> So back to the example. First, we create 2 qdiscs. Both will share
>>>> block number 22. "22" is just an identification. If we don't pass any
>>>> block number, a new one will be generated by kernel:
>>>>
>>>> $ tc qdisc add dev ens7 ingress block 22
>>>>                                 ^^^^^^^^
>>>> $ tc qdisc add dev ens8 ingress block 22
>>>>                                 ^^^^^^^^
>>>>
>>>> Now if we list the qdiscs, we will see the block index in the output:
>>>>
>>>> $ tc qdisc
>>>> qdisc ingress ffff: dev ens7 parent ffff:fff1 block 22 
>>>> qdisc ingress ffff: dev ens8 parent ffff:fff1 block 22 
>>>>
>>>> Now we can add filter to any of qdiscs sharing the same block:
>>>>
>>>> $ tc filter add dev ens7 parent ffff: protocol ip pref 25 flower dst_ip 192.168.0.0/16 action drop
>>>>
>>>>
>>>> We will see the same output if we list filters for ens7 and ens8, including stats:
>>>>
>>>> $ tc -s filter show dev ens7 ingress
>>>> filter protocol ip pref 25 flower chain 0 
>>>> filter protocol ip pref 25 flower chain 0 handle 0x1 
>>>>   eth_type ipv4
>>>>   dst_ip 192.168.0.0/16
>>>>   not_in_hw
>>>>         action order 1: gact action drop
>>>>          random type none pass val 0
>>>>          index 1 ref 1 bind 1 installed 39 sec used 2 sec
>>>>         Action statistics:
>>>>         Sent 3108 bytes 37 pkt (dropped 37, overlimits 0 requeues 0) 
>>>>         backlog 0b 0p requeues 0 
>>>>
>>>> $ tc -s filter show dev ens8 ingress
>>>> filter protocol ip pref 25 flower chain 0 
>>>> filter protocol ip pref 25 flower chain 0 handle 0x1 
>>>>   eth_type ipv4
>>>>   dst_ip 192.168.0.0/16
>>>>   not_in_hw
>>>>         action order 1: gact action drop
>>>>          random type none pass val 0
>>>>          index 1 ref 1 bind 1 installed 40 sec used 3 sec
>>>>         Action statistics:
>>>>         Sent 3108 bytes 37 pkt (dropped 37, overlimits 0 requeues 0) 
>>>>         backlog 0b 0p requeues 0
>>>
>>> This seems like really odd semantics to me ... a filter added to one
>>> device shows up on another.
>> 
>> Why is it odd? They share the same block, so it is natural that rule
>> added to one shows in list of rules for all devices that share the same
>> block.
>> 
>> 
>>>
>>> Why not make the shared block a standalone object that is configured
>>> through its own set of commands and then referenced by both devices?
>> 
>> I was thinking about that for a long time. That would require entirely
>> new set of netlink api and internal kernel handling just for this. Lots
>> of duplications. The reason is, the current API is strictly build around
>> ifindex. But the new API would not solve anything. As a user, I still
>> want so see shared rules in individial device listing, because they
>> would get processed for the device. So I believe that the proposed
>> behaviour is correct.
>> 
>
>netconf has NETCONFA_IFINDEX_ALL to keep the device concept but to relay
>information that applies to more than 1 device. You could have something
>similar for tc and shared blocks. Admin is done on this device index
>(e.g., your shared block 22 becomes dev index -22) and the filters are
>attached to another device for sharing using the 'qdisc add' command above.

It can be extended like this I guess. But still, the original rule adding
has to work.