netdev - Re: [PATCH v3 1/2] net: core: Notify on changes to dev->promiscuity.

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Date:   Fri, 30 Aug 2019 10:01:31 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     David Miller <davem@...emloft.net>
Cc:     idosch@...sch.org, andrew@...n.ch, horatiu.vultur@...rochip.com,
        alexandre.belloni@...tlin.com, UNGLinuxDriver@...rochip.com,
        allan.nielsen@...rochip.com, ivecera@...hat.com,
        f.fainelli@...il.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] net: core: Notify on changes to dev->promiscuity.

Fri, Aug 30, 2019 at 09:32:25AM CEST, davem@...emloft.net wrote:
>From: Jiri Pirko <jiri@...nulli.us>
>Date: Fri, 30 Aug 2019 09:21:33 +0200
>
>> Fri, Aug 30, 2019 at 09:12:23AM CEST, davem@...emloft.net wrote:
>>>From: Jiri Pirko <jiri@...nulli.us>
>>>Date: Fri, 30 Aug 2019 08:36:24 +0200
>>>
>>>> The promiscuity is a way to setup the rx filter. So promics == rx filter
>>>> off. For normal nics, where there is no hw fwd datapath,
>>>> this coincidentally means all received packets go to cpu.
>>>
>>>You cannot convince me that the HW datapath isn't a "rx filter" too, sorry.
>> 
>> If you look at it that way, then we have 2: rx_filter and hw_rx_filter.
>> The point is, those 2 are not one item, that is the point I'm trying to
>> make :/
>
>And you can turn both of them off when I ask for promiscuous mode, that's
>a detail of the device not a semantic issue.

Well, bridge asks for promiscuous mode during enslave -> hw_rx_filter off
When you, want to see all traffic in tcpdump -> rx_filter off

So basically there are 2 flavours of promiscuous mode we have to somehow
distinguish between, so the driver knows what to do.

Nothe that the hw_rx_filter off is not something special to bridge.
There is a usecase for this when no bridge is there, only TC filters for
example.