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Date:   Sat, 2 May 2020 04:48:05 -0400
From:   Jamal Hadi Salim <jhs@...atatu.com>
To:     Cong Wang <xiyou.wangcong@...il.com>, netdev@...r.kernel.org
Cc:     Jiri Pirko <jiri@...nulli.us>
Subject: Re: [Patch net v2] net_sched: fix tcm_parent in tc filter dump

On 2020-04-30 11:53 p.m., Cong Wang wrote:
> When we tell kernel to dump filters from root (ffff:ffff),
> those filters on ingress (ffff:0000) are matched, but their
> true parents must be dumped as they are. However, kernel
> dumps just whatever we tell it, that is either ffff:ffff
> or ffff:0000:
> 
>   $ nl-cls-list --dev=dummy0 --parent=root
>   cls basic dev dummy0 id none parent root prio 49152 protocol ip match-all
>   cls basic dev dummy0 id :1 parent root prio 49152 protocol ip match-all
>   $ nl-cls-list --dev=dummy0 --parent=ffff:
>   cls basic dev dummy0 id none parent ffff: prio 49152 protocol ip match-all
>   cls basic dev dummy0 id :1 parent ffff: prio 49152 protocol ip match-all
> 
> This is confusing and misleading, more importantly this is
> a regression since 4.15, so the old behavior must be restored.
> 
> And, when tc filters are installed on a tc class, the parent
> should be the classid, rather than the qdisc handle. Commit
> edf6711c9840 ("net: sched: remove classid and q fields from tcf_proto")
> removed the classid we save for filters, we can just restore
> this classid in tcf_block.
> 
> Steps to reproduce this:
>   ip li set dev dummy0 up
>   tc qd add dev dummy0 ingress
>   tc filter add dev dummy0 parent ffff: protocol arp basic action pass
>   tc filter show dev dummy0 root
> 
> Before this patch:
>   filter protocol arp pref 49152 basic
>   filter protocol arp pref 49152 basic handle 0x1
> 	action order 1: gact action pass
> 	 random type none pass val 0
> 	 index 1 ref 1 bind 1
> 
> After this patch:
>   filter parent ffff: protocol arp pref 49152 basic
>   filter parent ffff: protocol arp pref 49152 basic handle 0x1
>   	action order 1: gact action pass
>   	 random type none pass val 0
> 	 index 1 ref 1 bind 1

Note:
tc filter show dev dummy0 root
should not show that filter. OTOH,
tc filter show dev dummy0 parent ffff:
should.

root and ffff: are distinct/unique installation hooks.

cheers,
jamal

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