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 08:20:38 -0600
From:   David Ahern <dsahern@...il.com>
To:     Jiri Pirko <jiri@...nulli.us>
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

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.