From: "Allan W. Nielsen" <allan.nielsen@microchip.com>
To: Jiri Pirko <jiri@resnulli.us>
Cc: David Miller <davem@davemloft.net>, <idosch@idosch.org>,
<andrew@lunn.ch>, <horatiu.vultur@microchip.com>,
<alexandre.belloni@bootlin.com>, <UNGLinuxDriver@microchip.com>,
<ivecera@redhat.com>, <f.fainelli@gmail.com>,
<netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 1/2] net: core: Notify on changes to dev->promiscuity.
Date: Mon, 2 Sep 2019 19:42:31 +0200 [thread overview]
Message-ID: <20190902174229.uur7r7duq4dvbnqq@lx-anielsen.microsemi.net> (raw)
In-Reply-To: <20190830063624.GN2312@nanopsycho>
Hi Jiri,
Sorry for joining the discussion this late, but I have been without mail access
for the last few days.
The 08/30/2019 08:36, Jiri Pirko wrote:
> Fri, Aug 30, 2019 at 08:02:33AM CEST, davem@davemloft.net wrote:
> >From: Jiri Pirko <jiri@resnulli.us>
> >Date: Fri, 30 Aug 2019 07:39:40 +0200
> >
> >> Because the "promisc mode" would gain another meaning. Now how the
> >> driver should guess which meaning the user ment when he setted it?
> >> filter or trap?
> >>
> >> That is very confusing. If the flag is the way to do this, let's
> >> introduce another flag, like IFF_TRAPPING indicating that user wants
> >> exactly this.
> >
> >I don't understand how the meaning of promiscuous mode for a
> >networking device has suddenly become ambiguous, when did this start
> >happening?
>
> 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.
> But if there is hw fwd datapath, rx filter is still off, all rxed packets
> are processed. But that does not mean they should be trapped to cpu.
>
> Simple example:
> I need to see slowpath packets, for example arps/stp/bgp/... that
> are going to cpu, I do:
> tcpdump -i swp1
How is this different from "tcpdump -p -i swp1"
> I don't want to get all the traffic running over hw running this cmd.
> This is a valid usecase.
>
> To cope with hw fwd datapath devices, I believe that tcpdump has to have
> notion of that. Something like:
>
> tcpdump -i swp1 --hw-trapping-mode
>
> The logic can be inverse:
> tcpdump -i swp1
> tcpdump -i swp1 --no-hw-trapping-mode
>
> However, that would provide inconsistent behaviour between existing and
> patched tcpdump/kernel.
>
> All I'm trying to say, there are 2 flags
> needed (if we don't use tc trap).
I have been reading through this thread several times and I still do not get it.
As far as I understand you are arguing that we need 3 modes:
- tcpdump -i swp1
- tcpdump -p -i swp1
- tcpdump -i swp1 --hw-trapping-mode
Would you mind provide an example of the traffic you want to see in the 3 cases
(or the traffic which you do not want to see).
/Allan
next prev parent reply other threads:[~2019-09-02 17:42 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-29 9:22 [PATCH v3 0/2] net: core: Notify on changes to dev->promiscuity Horatiu Vultur
2019-08-29 9:22 ` [PATCH v3 1/2] " Horatiu Vultur
2019-08-29 9:51 ` Jiri Pirko
2019-08-29 10:56 ` Horatiu Vultur
2019-08-29 12:18 ` Jiri Pirko
2019-08-29 12:44 ` Horatiu Vultur
2019-08-29 12:55 ` Ivan Vecera
2019-08-29 13:15 ` Andrew Lunn
2019-08-29 13:39 ` Ivan Vecera
2019-08-29 13:15 ` Horatiu Vultur
2019-08-29 13:26 ` Andrew Lunn
2019-08-29 13:49 ` Jiri Pirko
2019-08-29 14:37 ` Andrew Lunn
2019-08-29 17:57 ` Ido Schimmel
2019-08-29 18:29 ` Andrew Lunn
2019-08-29 19:36 ` Ido Schimmel
2019-08-29 22:12 ` David Miller
2019-08-30 5:39 ` Jiri Pirko
2019-08-30 6:02 ` David Miller
2019-08-30 6:36 ` Jiri Pirko
2019-08-30 6:54 ` Ivan Vecera
2019-08-30 7:13 ` David Miller
2019-08-30 7:12 ` David Miller
2019-08-30 7:21 ` Jiri Pirko
2019-08-30 7:32 ` David Miller
2019-08-30 8:01 ` Jiri Pirko
2019-09-02 17:42 ` Allan W. Nielsen [this message]
2019-09-02 17:51 ` Jiri Pirko
2019-09-02 18:05 ` Allan W. Nielsen
2019-09-02 18:45 ` Jiri Pirko
2019-09-03 6:13 ` Ido Schimmel
2019-09-03 8:14 ` Allan W. Nielsen
2019-09-08 10:15 ` Ido Schimmel
2019-08-30 9:43 ` Ido Schimmel
2019-08-31 19:35 ` Andrew Lunn
2019-08-31 20:47 ` Ido Schimmel
2019-09-01 18:48 ` Andrew Lunn
2019-09-02 17:55 ` Allan W. Nielsen
2019-09-01 6:54 ` Jiri Pirko
2019-08-29 22:10 ` David Miller
2019-08-29 22:08 ` David Miller
2019-08-30 6:13 ` Jiri Pirko
2019-08-30 6:18 ` David Miller
2019-08-30 7:26 ` Ivan Vecera
2019-08-29 9:22 ` [PATCH v3 2/2] net: mscc: Implement promisc mode Horatiu Vultur
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