netdev - Re: [PATCH net-next 4/6] net: dsa: tag_rtl8_4: add realtek 8 byte protocol 4 tag

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Date:   Wed, 13 Oct 2021 09:52:04 +0000
From:   Alvin Šipraga <ALSI@...g-olufsen.dk>
To:     DENG Qingfang <dqfext@...il.com>,
        Alvin Šipraga <alvin@...s.dk>
CC:     Linus Walleij <linus.walleij@...aro.org>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 4/6] net: dsa: tag_rtl8_4: add realtek 8 byte
 protocol 4 tag

On 10/13/21 11:45 AM, DENG Qingfang wrote:
> On Tue, Oct 12, 2021 at 02:35:53PM +0200, Alvin Šipraga wrote:
>> +static struct sk_buff *rtl8_4_tag_rcv(struct sk_buff *skb,
>> +				      struct net_device *dev)
>> +{
>> +	__be16 *tag;
>> +	u16 etype;
>> +	u8 proto;
>> +	u8 port;
>> +
>> +	if (unlikely(!pskb_may_pull(skb, RTL8_4_TAG_LEN)))
>> +		return NULL;
>> +
>> +	tag = dsa_etype_header_pos_rx(skb);
>> +
>> +	/* Parse Realtek EtherType */
>> +	etype = ntohs(tag[0]);
>> +	if (unlikely(etype != ETH_P_REALTEK)) {
>> +		dev_warn_ratelimited(&dev->dev,
>> +				     "non-realtek ethertype 0x%04x\n", etype);
>> +		return NULL;
>> +	}
>> +
>> +	/* Parse Protocol */
>> +	proto = ntohs(tag[1]) >> 8;
>> +	if (unlikely(proto != RTL8_4_PROTOCOL_RTL8365MB)) {
>> +		dev_warn_ratelimited(&dev->dev,
>> +				     "unknown realtek protocol 0x%02x\n",
>> +				     proto);
>> +		return NULL;
>> +	}
>> +
>> +	/* Parse TX (switch->CPU) */
>> +	port = ntohs(tag[3]) & 0xf; /* Port number is the LSB 4 bits */
>> +	skb->dev = dsa_master_find_slave(dev, 0, port);
>> +	if (!skb->dev) {
>> +		dev_warn_ratelimited(&dev->dev,
>> +				     "could not find slave for port %d\n",
>> +				     port);
>> +		return NULL;
>> +	}
>> +
>> +	/* Remove tag and recalculate checksum */
>> +	skb_pull_rcsum(skb, RTL8_4_TAG_LEN);
>> +
>> +	dsa_strip_etype_header(skb, RTL8_4_TAG_LEN);
>> +
>> +	dsa_default_offload_fwd_mark(skb);
> 
> This should not be set if the REASON is trapped to CPU.

Thanks, you're right. Although with the current state of the driver, 
skb->offload_fwd_mark will never get set, because the bridge is not 
offloaded onto the HW. But I will fix this up in v2.

> 
>> +
>> +	return skb;
>> +}