Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Feedback-ID: i494840e7:Fastmail
Date:   Thu, 26 May 2022 17:13:22 +0300
From:   Ido Schimmel <idosch@idosch.org>
To:     Hans Schultz <schultz.hans@gmail.com>
Cc:     davem@davemloft.net, kuba@kernel.org, netdev@vger.kernel.org,
        Hans Schultz <schultz.hans+netdev@gmail.com>,
        Andrew Lunn <andrew@lunn.ch>,
        Vivien Didelot <vivien.didelot@gmail.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Vladimir Oltean <olteanv@gmail.com>,
        Eric Dumazet <edumazet@google.com>,
        Paolo Abeni <pabeni@redhat.com>, Jiri Pirko <jiri@resnulli.us>,
        Ivan Vecera <ivecera@redhat.com>,
        Roopa Prabhu <roopa@nvidia.com>,
        Nikolay Aleksandrov <razor@blackwall.org>,
        Shuah Khan <shuah@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Ido Schimmel <idosch@nvidia.com>, linux-kernel@vger.kernel.org,
        bridge@lists.linux-foundation.org, linux-kselftest@vger.kernel.org
Subject: Re: [PATCH V3 net-next 1/4] net: bridge: add fdb flag to extent
 locked port feature
Message-ID: <Yo+LAj1vnjq0p36q@shredder>
References: <20220524152144.40527-1-schultz.hans+netdev@gmail.com>
 <20220524152144.40527-2-schultz.hans+netdev@gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20220524152144.40527-2-schultz.hans+netdev@gmail.com>
Precedence: bulk

On Tue, May 24, 2022 at 05:21:41PM +0200, Hans Schultz wrote:
> Add an intermediate state for clients behind a locked port to allow for
> possible opening of the port for said clients. This feature corresponds
> to the Mac-Auth and MAC Authentication Bypass (MAB) named features. The
> latter defined by Cisco.
> Locked FDB entries will be limited in number, so as to prevent DOS
> attacks by spamming the port with random entries. The limit will be
> a per port limit as it is a port based feature and that the port flushes
> all FDB entries on link down.

Why locked FDB entries need a special treatment compared to regular
entries? A port that has learning enabled can be spammed with random
source MACs just as well.

The authorization daemon that is monitoring FDB notifications can have a
policy to shut down a port if the rate / number of locked entries is
above a given threshold.

I don't think this kind of policy belongs in the kernel. If it resides
in user space, then the threshold can be adjusted. Currently it's hard
coded to 64 and I don't see how user space can change or monitor it.