netdev - Re: [patch net-next 3/5] net: sched: introduce block mechanism to handle netif_keep

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Message-ID: <59FD9796.5030904@iogearbox.net>
Date:   Sat, 04 Nov 2017 11:33:58 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Jiri Pirko <jiri@...nulli.us>
CC:     netdev@...r.kernel.org, davem@...emloft.net, nogahf@...lanox.com,
        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, saeedm@...lanox.com, matanb@...lanox.com,
        leonro@...lanox.com, idosch@...lanox.com,
        jakub.kicinski@...ronome.com, simon.horman@...ronome.com,
        pieter.jansenvanvuuren@...ronome.com, john.hurley@...ronome.com,
        alexander.h.duyck@...el.com, ogerlitz@...lanox.com,
        john.fastabend@...il.com, alexei.starovoitov@...il.com
Subject: Re: [patch net-next 3/5] net: sched: introduce block mechanism to
 handle netif_keep_dst calls

On 11/04/2017 10:55 AM, Jiri Pirko wrote:
> Fri, Nov 03, 2017 at 09:15:54PM CET, daniel@...earbox.net wrote:
>> On 11/03/2017 06:19 PM, Jiri Pirko wrote:
>>> From: Jiri Pirko <jiri@...lanox.com>
>>>
>>> Couple of classifiers call netif_keep_dst directly on q->dev. That is
>>> not possible to do directly for shared blocke where multiple qdiscs are
>>> owning the block. So introduce a infrastructure to keep track of the
>>> block owners in list and use this list to implement block variant of
>>> netif_keep_dst.
>>>
>>> Signed-off-by: Jiri Pirko <jiri@...lanox.com>
>> [...]
>>> +struct tcf_block_owner_item {
>>> +	struct list_head list;
>>> +	struct Qdisc *q;
>>> +	enum tcf_block_binder_type binder_type;
>>> +};
>>> +
>>> +static void
>>> +tcf_block_owner_netif_keep_dst(struct tcf_block *block,
>>> +			       struct Qdisc *q,
>>> +			       enum tcf_block_binder_type binder_type)
>>> +{
>>> +	if (block->keep_dst &&
>>> +	    binder_type != TCF_BLOCK_BINDER_TYPE_CLSACT_INGRESS)
>>
>> Why we need to keep dst on TCF_BLOCK_BINDER_TYPE_CLSACT_EGRESS ?
>> I presume this enum means sch_handle_egress() ? dst is dropped
>> later ...
>
> This is because of the bpf check:
>         if (fp->dst_needed && !(tp->q->flags & TCQ_F_INGRESS))
>                 netif_keep_dst(qdisc_dev(tp->q));
>
> I just maintain the same logic here.

No, that's a wrong claim, really ...

clsact in general hooks into the same logic as ingress, so TC_H_CLSACT
as major needs to reuse TC_H_INGRESS, and qdiscs set up as such set
TCQ_F_INGRESS as flags. For clsact that means both your block binder
types for clsact here (ingress/egress).

Please make sure that your other changes don't have similar assumption.