netdev - Re: [patch net-next v6 06/11] net: sched: use block index as a handle instead of qdisc when block is shared

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Date:   Sun, 7 Jan 2018 14:46:38 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     Jamal Hadi Salim <jhs@...atatu.com>
Cc:     netdev@...r.kernel.org, davem@...emloft.net,
        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,
        daniel@...earbox.net, dsahern@...il.com
Subject: Re: [patch net-next v6 06/11] net: sched: use block index as a
 handle instead of qdisc when block is shared

Sun, Jan 07, 2018 at 02:11:19PM CET, jhs@...atatu.com wrote:
>On 18-01-06 03:43 PM, Jiri Pirko wrote:
>
>
>> 
>> > @@ -886,8 +887,13 @@ static int tcf_fill_node(struct net *net, struct sk_buff *skb,
>> > 	tcm->tcm_family = AF_UNSPEC;
>> > 	tcm->tcm__pad1 = 0;
>> > 	tcm->tcm__pad2 = 0;
>> > -	tcm->tcm_ifindex = qdisc_dev(q)->ifindex;
>> > -	tcm->tcm_parent = parent;
>> > +	if (q) {
>> > +		tcm->tcm_ifindex = qdisc_dev(q)->ifindex;
>> > +		tcm->tcm_parent = parent;
>> > +	} else {
>> > +		tcm->tcm_ifindex = 0; /* block index is stored in parent */
>> > +		tcm->tcm_parent = block->index;
>> > +	}
>> 
>> Please guys, please look at this reuse (also on clt side). I would like
>> you to double-check this reuse of existing API for balock_index carrying
>> purpose. I believe it's UAPI safe. But please, check it out carefully.
>> 
>
>
>Should not break any ABI/UAPI AFAIK. Maybe go for a negative ifindex
>(not sure if zero means something speacial to someone).

Like -1 means parent is block_index?

Why would 0 mean something special? Could you point to a code that
suggests it?

>
>cheers,
>jamal
>