netdev - Re: [PATCH net-next 1/2] net: dsa: tag_ks8995: Add the KS8995 tag handling

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Message-ID: <1fc53a59-a4f2-4376-ae06-5947e366ccc4@lunn.ch>
Date: Wed, 7 Jan 2026 17:01:16 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Linus Walleij <linusw@...nel.org>
Cc: Vladimir Oltean <olteanv@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 1/2] net: dsa: tag_ks8995: Add the KS8995 tag
 handling

> +static struct sk_buff *ks8995_rcv(struct sk_buff *skb, struct net_device *dev)
> +{
> +	unsigned int port;
> +	__be16 *p;
> +	u16 etype;
> +	u16 tci;
> +
> +	if (unlikely(!pskb_may_pull(skb, KS8995_TAG_LEN))) {
> +		netdev_err(dev, "dropping packet, cannot pull\n");
> +		return NULL;
> +	}
> +
> +	p = dsa_etype_header_pos_rx(skb);
> +	etype = ntohs(p[0]);
> +
> +	if (etype == ETH_P_8021Q) {
> +		/* That's just an ordinary VLAN tag, pass through */
> +		return skb;

Should that actually happen? Normally all frames use the tag, and
anything without a tag we drop because we don't expect it.

> +	}
> +
> +	if ((etype & 0xFFF0U) != ETH_P_8021Q) {
> +		/* Not custom, just pass through */
> +		netdev_dbg(dev, "non-KS8995 ethertype 0x%04x\n", etype);
> +		return skb;
> +	}

Same here.

     Andrew