netdev - Re: [PATCH net-next 02/10] net: bridge: add document for IFLA

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Date: Tue, 21 Nov 2023 11:10:58 +0800
From: Hangbin Liu <liuhangbin@...il.com>
To: Vladimir Oltean <olteanv@...il.com>
Cc: netdev@...r.kernel.org, "David S . Miller" <davem@...emloft.net>,
	David Ahern <dsahern@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Ido Schimmel <idosch@...sch.org>,
	Nikolay Aleksandrov <razor@...ckwall.org>,
	Roopa Prabhu <roopa@...dia.com>,
	Stephen Hemminger <stephen@...workplumber.org>,
	Florian Westphal <fw@...len.de>, Andrew Lunn <andrew@...n.ch>,
	Florian Fainelli <f.fainelli@...il.com>,
	Jiri Pirko <jiri@...nulli.us>, Marc Muehlfeld <mmuehlfe@...hat.com>
Subject: Re: [PATCH net-next 02/10] net: bridge: add document for IFLA_BRPORT
 enum

On Mon, Nov 20, 2023 at 01:31:27PM +0200, Vladimir Oltean wrote:
> On Fri, Nov 17, 2023 at 05:31:37PM +0800, Hangbin Liu wrote:
> > + * @IFLA_BRPORT_LEARNING
> > + *   Controls whether a given port will learn *source* MAC addresses from
> > + *   received traffic or not. By default this flag is on.
> 
> Also controls whether dynamic FDB entries (which can also be added by
> software) will be refreshed by incoming traffic.
> 
> This is subtle but important in certain use cases (below).
> 
> > + * @IFLA_BRPORT_LOCKED
> > + *   Controls whether a port will be locked, meaning that hosts behind the
> > + *   port will not be able to communicate through the port unless an FDB
> > + *   entry with the unit's MAC address is in the FDB. The common use case is
> > + *   that hosts are allowed access through authentication with the IEEE 802.1X
> > + *   protocol or based on whitelists. By default this flag is off.
> 
> Here seems like a good place to add this warning:
> 
> Secure 802.1X deployments should always use the BR_BOOLOPT_NO_LL_LEARN
> flag, to not permit the bridge to populate its FDB based on link-local
> (EAPOL) traffic received on the port.
> 
> > + *
> > + * @IFLA_BRPORT_MAB
> 
> Controls whether a port will use MAC Authentication Bypass (MAB), a
> technique through which select MAC addresses may be allowed on a locked
> port, without using 802.1X authentication. Packets with an unknown source
> MAC address generate a "locked" FDB entry on the incoming bridge port.
> The common use case is for user space to react to these bridge FDB
> notifications and optionally replace the locked FDB entry with a normal
> one, allowing traffic to pass for whitelisted MAC addresses.
> 
> Setting this flag also requires IFLA_BRPORT_LOCKED and IFLA_BRPORT_LEARNING.
> IFLA_BRPORT_LOCKED ensures that unauthorized data packets are dropped,
> and IFLA_BRPORT_LEARNING allows the dynamic FDB entries installed by
> user space (as replacements for the locked FDB entries) to be refreshed
> and/or aged out.
> 
> (source: https://lore.kernel.org/netdev/20221018165619.134535-11-netdev@kapio-technology.com/)

Tanks for the doc, I will update the patch.

Hangbin