From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 67DDC33768B; Wed, 15 Oct 2025 16:43:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760546614; cv=none; b=JuT+/EJAyvtyGEOOIHMui4Kfo/2qjCaNwZDx1/lhV/v0q9lXLzm5Uz3JC6Wu+AmA9mamTCIH+C/R20uFfPWFhCy4NX5vRhXEMFDVtkptO+6YAi4Sw8r7QGY7Gf4E3XMsNAJEmvNf4Re7564ZUnrFMoba6yolt0k1eKPbTL1XY+8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760546614; c=relaxed/simple; bh=4nrEEDuiqojf/f9RqiSpynaXP0mqkulPdbzuB7ofuXY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=VgyqZUExMIyp5HUMxH/iADbmInMoVS03V794KPTp3fPf8UzovFXUs8tKxs2AI+8rOE092Z5THhEhKuKaA8g8ZkZVkSr8nk1tUSaauYOmku+9PmJKzHLEBoA6QzWD8sSCCko9u/gmGUdpdOVLZQoTGXFFJyngMKo/AZdBbTdsn0U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YYN4w4Yy; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YYN4w4Yy" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DDCE6C4CEF8; Wed, 15 Oct 2025 16:43:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1760546613; bh=4nrEEDuiqojf/f9RqiSpynaXP0mqkulPdbzuB7ofuXY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=YYN4w4Yy8DJ8eml8J9REG94kgUAktX7OJjE8ISwCJONcX+3na55LYmctaeMGbfXTZ 2wYXXd3JtrGQS08GyiVKLuxmbXWrWkoWZ+xwgDLVUJlie9fHeHbMqydBRAru+wRwfM aVrMcFYzYG7ygPwq7eCYFKObyB4JCiJqgc11hsS/Du/LhW2D0GrgzxhRi3V/128rFG 4UScwXsilq3wlQgakwOd/HgeKtbNNAGaKfFi04DPPF+8FvG+VNaV6SVj6W4o3ayyUj OwKS2Zc8//B35GVcAowdxCyzBMN/DOfUVBkVd2ARaVPp2/3NhdkTdyD9JMeH/w+S4v DV1kO2ObKWT/w== Date: Wed, 15 Oct 2025 17:43:29 +0100 From: Simon Horman To: Jonas Gorski Cc: Andrew Lunn , Vladimir Oltean , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , =?utf-8?B?w4FsdmFybyBGZXJuw6FuZGV6?= Rojas , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net] net: dsa: tag_brcm: legacy: fix untagged rx on unbridged ports for bcm63xx Message-ID: References: <20251015070854.36281-1-jonas.gorski@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Wed, Oct 15, 2025 at 06:24:33PM +0200, Jonas Gorski wrote: > On Wed, Oct 15, 2025 at 6:12 PM Simon Horman wrote: > > > > On Wed, Oct 15, 2025 at 09:08:54AM +0200, Jonas Gorski wrote: > > > The internal switch on BCM63XX SoCs will unconditionally add 802.1Q VLAN > > > tags on egress to CPU when 802.1Q mode is enabled. We do this > > > unconditionally since commit ed409f3bbaa5 ("net: dsa: b53: Configure > > > VLANs while not filtering"). > > > > > > This is fine for VLAN aware bridges, but for standalone ports and vlan > > > unaware bridges this means all packets are tagged with the default VID, > > > which is 0. > > > > > > While the kernel will treat that like untagged, this can break userspace > > > applications processing raw packets, expecting untagged traffic, like > > > STP daemons. > > > > > > This also breaks several bridge tests, where the tcpdump output then > > > does not match the expected output anymore. > > > > > > Since 0 isn't a valid VID, just strip out the VLAN tag if we encounter > > > it, unless the priority field is set, since that would be a valid tag > > > again. > > > > > > Fixes: 964dbf186eaa ("net: dsa: tag_brcm: add support for legacy tags") > > > Signed-off-by: Jonas Gorski > > > > ... > > > > > @@ -237,8 +239,14 @@ static struct sk_buff *brcm_leg_tag_rcv(struct sk_buff *skb, > > > if (!skb->dev) > > > return NULL; > > > > > > - /* VLAN tag is added by BCM63xx internal switch */ > > > - if (netdev_uses_dsa(skb->dev)) > > > + /* The internal switch in BCM63XX SoCs will add a 802.1Q VLAN tag on > > > + * egress to the CPU port for all packets, regardless of the untag bit > > > + * in the VLAN table. VID 0 is used for untagged traffic on unbridged > > > + * ports and vlan unaware bridges. If we encounter a VID 0 tagged > > > + * packet, we know it is supposed to be untagged, so strip the VLAN > > > + * tag as well in that case. > > > > Maybe it isn't important, but here it is a TCI 0 that is being checked: > > VID 0, PCP 0, and DEI 0. > > Right, that is intentional (I tried to convey it in the commit > message, though should probably also extend it here). Thanks, I see that more clearly now. > If any of the fields is non-zero, then the tag is meaningful, and we > don't want to strip it (e.g. 802.1p tagged packets). I guess there are already a lot of words there. But, FWIIW, I would lean to wards tightening up the comment a bit.