linux-kernel - Re: [RFC PATCH v2 net-next 03/16] net: dsa: inherit the actual bridge port flags at join time

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Message-ID: <2d10377e-88d0-6dea-ff12-469dab1aced0@gmail.com>
Date:   Fri, 19 Mar 2021 15:08:46 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Vladimir Oltean <olteanv@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Tobias Waldekranz <tobias@...dekranz.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Roopa Prabhu <roopa@...dia.com>,
        Nikolay Aleksandrov <nikolay@...dia.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Ido Schimmel <idosch@...sch.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        UNGLinuxDriver@...rochip.com, Vadym Kochan <vkochan@...vell.com>,
        Taras Chornyi <tchornyi@...vell.com>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Ioana Ciornei <ioana.ciornei@....com>,
        Ivan Vecera <ivecera@...hat.com>, linux-omap@...r.kernel.org,
        Vladimir Oltean <vladimir.oltean@....com>
Subject: Re: [RFC PATCH v2 net-next 03/16] net: dsa: inherit the actual bridge
 port flags at join time



On 3/18/2021 4:18 PM, Vladimir Oltean wrote:
> From: Vladimir Oltean <vladimir.oltean@....com>
> 
> DSA currently assumes that the bridge port starts off with this
> constellation of bridge port flags:
> 
> - learning on
> - unicast flooding on
> - multicast flooding on
> - broadcast flooding on
> 
> just by virtue of code copy-pasta from the bridge layer (new_nbp).
> This was a simple enough strategy thus far, because the 'bridge join'
> moment always coincided with the 'bridge port creation' moment.
> 
> But with sandwiched interfaces, such as:
> 
>  br0
>   |
> bond0
>   |
>  swp0
> 
> it may happen that the user has had time to change the bridge port flags
> of bond0 before enslaving swp0 to it. In that case, swp0 will falsely
> assume that the bridge port flags are those determined by new_nbp, when
> in fact this can happen:
> 
> ip link add br0 type bridge
> ip link add bond0 type bond
> ip link set bond0 master br0
> ip link set bond0 type bridge_slave learning off
> ip link set swp0 master br0
> 
> Now swp0 has learning enabled, bond0 has learning disabled. Not nice.
> 
> Fix this by "dumpster diving" through the actual bridge port flags with
> br_port_flag_is_set, at bridge join time.
> 
> We use this opportunity to split dsa_port_change_brport_flags into two
> distinct functions called dsa_port_inherit_brport_flags and
> dsa_port_clear_brport_flags, now that the implementation for the two
> cases is no longer similar.
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
> ---
>  net/dsa/port.c | 123 ++++++++++++++++++++++++++++++++-----------------
>  1 file changed, 82 insertions(+), 41 deletions(-)
> 
> diff --git a/net/dsa/port.c b/net/dsa/port.c
> index fcbe5b1545b8..346c50467810 100644
> --- a/net/dsa/port.c
> +++ b/net/dsa/port.c
> @@ -122,26 +122,82 @@ void dsa_port_disable(struct dsa_port *dp)
>  	rtnl_unlock();
>  }
>  
> -static void dsa_port_change_brport_flags(struct dsa_port *dp,
> -					 bool bridge_offload)
> +static void dsa_port_clear_brport_flags(struct dsa_port *dp,
> +					struct netlink_ext_ack *extack)
>  {
>  	struct switchdev_brport_flags flags;
> -	int flag;
>  
> -	flags.mask = BR_LEARNING | BR_FLOOD | BR_MCAST_FLOOD | BR_BCAST_FLOOD;
> -	if (bridge_offload)
> -		flags.val = flags.mask;
> -	else
> -		flags.val = flags.mask & ~BR_LEARNING;
> +	flags.mask = BR_LEARNING;
> +	flags.val = 0;
> +	dsa_port_bridge_flags(dp, flags, extack);

Would not you want to use the same for_each_set_bit() loop that
dsa_port_change_br_flags() uses, that would be a tad more compact.
-- 
Florian