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

[Daniel Borkmann <daniel@iogearbox.net>]

On 11/04/2017 10:55 AM, Jiri Pirko wrote:
> Fri, Nov 03, 2017 at 09:15:54PM CET, daniel@iogearbox.net wrote:
>> On 11/03/2017 06:19 PM, Jiri Pirko wrote:
>>> From: Jiri Pirko <jiri@mellanox.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@mellanox.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.