linux-kernel - Re: [PATCH 08/14] net: vlan: remove invalid VLAN protocol warning

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Message-ID: <20221107215745.ascdvnxqrbw4meuv@skbuf>
Date:   Mon, 7 Nov 2022 23:57:45 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Felix Fietkau <nbd@....name>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/14] net: vlan: remove invalid VLAN protocol warning

On Mon, Nov 07, 2022 at 07:54:46PM +0100, Felix Fietkau wrote:
> On MTK SoC ethernet, using NETIF_F_HW_VLAN_CTAG_RX in combination with hardware
> special tag parsing can pass the special tag port metadata as VLAN protocol ID.
> When the results is added as a skb hwaccel VLAN tag, it triggers a warning from
> vlan_do_receive before calling the DSA tag receive function.
> Remove this warning in order to properly pass the tag to the DSA receive function,
> which will parse and clear it.
> 
> Signed-off-by: Felix Fietkau <nbd@....name>
> ---
>  net/8021q/vlan.h | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/net/8021q/vlan.h b/net/8021q/vlan.h
> index 5eaf38875554..3f9c0406b266 100644
> --- a/net/8021q/vlan.h
> +++ b/net/8021q/vlan.h
> @@ -44,7 +44,6 @@ static inline int vlan_proto_idx(__be16 proto)
>  	case htons(ETH_P_8021AD):
>  		return VLAN_PROTO_8021AD;
>  	default:
> -		WARN(1, "invalid VLAN protocol: 0x%04x\n", ntohs(proto));

Why would you ever want to remove a warning that's telling you you're
doing something wrong?

Aren't you calling __vlan_hwaccel_put_tag() with the wrong thing (i.e.
htons(RX_DMA_VPID()) as opposed to VPID translated to something
digestible by the rest of the network stack.. ETH_P_8021Q, ETH_P_8021AD
etc)?

>  		return -EINVAL;
>  	}
>  }
> -- 
> 2.38.1
>