netdev - Re: [PATCH net-next v3 1/2] net: dsa: untag the bridge pvid from rx skbs

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Message-ID: <20200923214852.x2z5gb6pzaphpfvv@skbuf>
Date:   Wed, 23 Sep 2020 21:48:53 +0000
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Florian Fainelli <f.fainelli@...il.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "olteanv@...il.com" <olteanv@...il.com>,
        "nikolay@...dia.com" <nikolay@...dia.com>
Subject: Re: [PATCH net-next v3 1/2] net: dsa: untag the bridge pvid from rx
 skbs

On Wed, Sep 23, 2020 at 02:40:37PM -0700, Florian Fainelli wrote:
> From: Vladimir Oltean <vladimir.oltean@....com>
> +	/* The sad part about attempting to untag from DSA is that we
> +	 * don't know, unless we check, if the skb will end up in
> +	 * the bridge's data path - br_allowed_ingress() - or not.
> +	 * For example, there might be an 8021q upper for the
> +	 * default_pvid of the bridge, which will steal VLAN-tagged traffic
> +	 * from the bridge's data path. This is a configuration that DSA
> +	 * supports because vlan_filtering is 0. In that case, we should
> +	 * definitely keep the tag, to make sure it keeps working.
> +	 */
> +	netdev_for_each_upper_dev_rcu(dev, upper_dev, iter) {
> +		if (!is_vlan_dev(upper_dev))
> +			continue;
> +
> +		if (vid == vlan_dev_vlan_id(upper_dev))
> +			return skb;
> +	}

Argh...
So I wanted to ask you how's performance with a few 8021q uppers, then I
remembered that vlan_do_receive() probably does something more efficient
here than a complete lookup, like hashing or something, then I found the
vlan_find_dev() helper function.... Sorry for not noticing it in the
first place.