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

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Message-Id: <20190829.150851.713654232867665043.davem@davemloft.net>
Date:   Thu, 29 Aug 2019 15:08:51 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     idosch@...sch.org
Cc:     andrew@...n.ch, jiri@...nulli.us, 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.

From: Ido Schimmel <idosch@...sch.org>
Date: Thu, 29 Aug 2019 20:57:59 +0300

> On a software switch, when you run tcpdump without '-p', do you incur
> major packet loss? No. Will this happen when you punt several Tbps to
> your CPU on the hardware switch? Yes.
> 
> Extending the definition of promiscuous mode to mean punt all traffic to
> the CPU is wrong, IMO. You will not be able to capture all the packets

This is so illogical, it is mind boggling.

How different is this to using tcpdump/wireshark on a 100GB or 1TB
network interface?

There is no difference.

Please stop portraying switches as special in this regard, they are
not.