linux-kernel - Re: [PATCH v8 net-next 01/12] net: bridge: add locked entry fdb flag to extend locked port feature

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Message-ID: <Y1FE6WFnsH8hcFY2@shredder>
Date:   Thu, 20 Oct 2022 15:54:01 +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 01/12] net: bridge: add locked entry fdb flag
 to extend locked port feature

On Tue, Oct 18, 2022 at 06:56:08PM +0200, Hans J. Schultz wrote:
> Add an intermediate state for clients behind a locked port to allow for
> possible opening of the port for said clients. The clients mac address
> will be added with the locked flag set, denying access through the port

The entry itself is not denying the access through the port, but
rather the fact that the port is locked and there is no matching FDB
entry.

> for the mac address, but also creating a new FDB add event giving
> userspace daemons the ability to unlock the mac address. This feature
> corresponds to the Mac-Auth and MAC Authentication Bypass (MAB) named
> features. The latter defined by Cisco.

Worth mentioning that the feature is enabled via the 'mab' bridge port
option (BR_PORT_MAB).

> 
> Only the kernel can set this FDB entry flag, while userspace can read
> the flag and remove it by replacing or deleting the FDB entry.
> 
> Locked entries will age out with the set bridge ageing time.
> 
> Signed-off-by: Hans J. Schultz <netdev@...io-technology.com>

Overall looks OK to me. See one comment below.

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

[...]

> @@ -1178,6 +1192,14 @@ int br_fdb_add(struct ndmsg *ndm, struct nlattr *tb[],
>  		vg = nbp_vlan_group(p);
>  	}
>  
> +	if (tb[NDA_FLAGS_EXT])
> +		ext_flags = nla_get_u32(tb[NDA_FLAGS_EXT]);
> +
> +	if (ext_flags & NTF_EXT_LOCKED) {
> +		pr_info("bridge: RTM_NEWNEIGH has invalid extended flags\n");

I understand this function makes use of pr_info(), but it already gets
extack and it's a matter of time until the pr_info() instances will be
converted to extack. I would just use extack here like you are doing in
the next patch.

Also, I find this message more helpful:

"Cannot add FDB entry with \"locked\" flag set"

> +		return -EINVAL;
> +	}
> +
>  	if (tb[NDA_FDB_EXT_ATTRS]) {
>  		attr = tb[NDA_FDB_EXT_ATTRS];
>  		err = nla_parse_nested(nfea_tb, NFEA_MAX, attr,