Re: [PATCH net-next v5 2/3] net: dsa: rzn1-a5psw: add support for .port_bridge_flags

From: Vladimir Oltean <olteanv@gmail.com>
To: "Alexis Lothoré" <alexis.lothore@bootlin.com>
Cc: "Clément Leger" <clement@clement-leger.fr>,
	"Andrew Lunn" <andrew@lunn.ch>,
	"Florian Fainelli" <f.fainelli@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	"Eric Dumazet" <edumazet@google.com>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"Paolo Abeni" <pabeni@redhat.com>,
	linux-renesas-soc@vger.kernel.org, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	"Miquel Raynal" <miquel.raynal@bootlin.com>,
	"Milan Stevanovic" <milan.stevanovic@se.com>,
	"Jimmy Lalande" <jimmy.lalande@se.com>,
	"Pascal Eberhard" <pascal.eberhard@se.com>,
	"Thomas Petazzoni" <thomas.petazzoni@bootlin.com>
Subject: Re: [PATCH net-next v5 2/3] net: dsa: rzn1-a5psw: add support for .port_bridge_flags
Date: Thu, 17 Aug 2023 20:35:29 +0300	[thread overview]
Message-ID: <20230817173529.mmic4a7g5cgswnbf@skbuf> (raw)
In-Reply-To: <252cdb0b-3630-9e29-45a6-ea0474f0d983@bootlin.com>

Hi Alexis,

On Fri, Aug 11, 2023 at 04:42:18PM +0200, Alexis Lothoré wrote:
> > These 3 port masks will only do what you expect while the bridge has
> > vlan_filtering=0, correct? When vlan_filtering=1, packets classified to
> > a VLAN which don't hit any FDB entry will be always flooded to all ports
> > in that VLAN, correct?
> 
> After thoroughly reading the A5PSW doc again, I feel that this sentence is not
> exactly true. If I refer to section 4.5.3.9, paragraph 3.c:
> 
> The VLAN table is used for both, VLAN domain verification [...] as well as VLAN
> resolution. Once the frame has passed any VLAN domain verification (i.e. will
> not be discarded by the verification function already), the forwarding
> resolution applies.
> [...]
> - If the destination MAC address (Unicast or Multicast) is not found in the MAC
> address table, or if the destination address is the Broadcast address, the frame
> is forwarded according to the following rules:
>   - The destination port mask is loaded from the respective register
> U/M/BCAST_DEFAULT_MASK depending on unicast, multicast or broadcast. Then the
> following filtering on this mask applies.
>     - If the frame carries a VLAN tag, the VLAN resolution table is searched for
> a matching VLAN ID and the frame is sent only to ports that are associated with
> the VLAN ID.
>     - If the frame carries a VLAN tag and the VLAN ID does not match any entry
> in the VLAN Resolution Table, or the frame does not carry a VLAN tag, the frame
> is forwarded to all ports that are enabled by the default mask.
>     - If it cannot be associated with any VLAN group and if the default group
> has been set to all zero, the frame is discarded.
> [...]
> 
> I understand from the second bullet that even when vlan filtering is enabled
> (which occurs as first step), the first flooding filter (used in second step,
> resolution) remains the flooding masks from unicast/multicast/broadcast default
> mask registers. The vlan resolution is then applied over it as a second filter,
> and only make the flooding more "restrictive", it does not bypass it (so if a
> port is in the vlan which VID is in an incoming packet but the port is not also
> defined in the U/M/B default mask, incoming packet won't be flooded to it).

Thanks for the clarification. In this case, the code is fine. I must have left
with the wrong impression from the previous discussion with Clément.