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

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Message-ID: <20171104095531.GG2024@nanopsycho>
Date:   Sat, 4 Nov 2017 10:55:31 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     Daniel Borkmann <daniel@...earbox.net>
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
Subject: Re: [patch net-next 3/5] net: sched: introduce block mechanism to
 handle netif_keep_dst calls

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.