linux-kernel - Re: [PATCH v8 net-next 02/12] net: bridge: add blackhole fdb entry flag

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Date:   Thu, 20 Oct 2022 16:06:01 +0300
From:   Ido Schimmel <idosch@...dia.com>
To:     "Hans J. Schultz" <netdev@...io-technology.com>
Cc:     davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Kurt Kanzenbach <kurt@...utronix.de>,
        Hauke Mehrtens <hauke@...ke-m.de>,
        Woojung Huh <woojung.huh@...rochip.com>,
        UNGLinuxDriver@...rochip.com, Sean Wang <sean.wang@...iatek.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        DENG Qingfang <dqfext@...il.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Ivan Vecera <ivecera@...hat.com>,
        Roopa Prabhu <roopa@...dia.com>,
        Nikolay Aleksandrov <razor@...ckwall.org>,
        Shuah Khan <shuah@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Christian Marangi <ansuelsmth@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Yuwei Wang <wangyuweihx@...il.com>,
        Petr Machata <petrm@...dia.com>,
        Florent Fourcot <florent.fourcot@...irst.fr>,
        Hans Schultz <schultz.hans@...il.com>,
        Joachim Wiberg <troglobit@...il.com>,
        Amit Cohen <amcohen@...dia.com>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        bridge@...ts.linux-foundation.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v8 net-next 02/12] net: bridge: add blackhole fdb entry
 flag

On Tue, Oct 18, 2022 at 06:56:09PM +0200, Hans J. Schultz wrote:
> Add a 'blackhole' fdb flag, ensuring that no forwarding from any port
> to a destination MAC that has a FDB entry with this flag on will occur.
> The packets will thus be dropped.
> 
> When the blackhole fdb flag is set, the 'local' flag will also be enabled
> as blackhole entries are not associated with any port.

It reads as if the kernel will enable the 'local' flag automatically,
which is not true anymore. The bridge driver enforces that
'NUD_PERMANENT' is set if 'NTF_EXT_BLACKHOLE' is specified.

> 
> Thus the command will be alike to:
> bridge fdb add MAC dev br0 local blackhole
> 
> Signed-off-by: Hans J. Schultz <netdev@...io-technology.com>

Looks OK to me. See one comment below.

Reviewed-by: Ido Schimmel <idosch@...dia.com>

[...]

> @@ -1140,7 +1148,7 @@ static int __br_fdb_add(struct ndmsg *ndm, struct net_bridge *br,
>  		err = br_fdb_external_learn_add(br, p, addr, vid, true);
>  	} else {
>  		spin_lock_bh(&br->hash_lock);
> -		err = fdb_add_entry(br, p, addr, ndm, nlh_flags, vid, nfea_tb);
> +		err = fdb_add_entry(br, p, addr, ndm, nlh_flags, vid, ext_flags, nfea_tb);

I believe the preference is to wrap to 80 columns when possible.

>  		spin_unlock_bh(&br->hash_lock);
>  	}