Subject: Re: [PATCH] net: dsa: lan9303: handle hwaccel VLAN tags

From: Måns Rullgård <[email-masked]>
Date: Wed, 16 Feb 2022 12:48:03 +0000

Vladimir Oltean <[email-masked]> writes:

> On Tue, Feb 15, 2022 at 02:59:13PM +0000, Mans Rullgard wrote:
>> Check for a hwaccel VLAN tag on rx and use it if present.  Otherwise,
>> use __skb_vlan_pop() like the other tag parsers do.  This fixes the case
>> where the VLAN tag has already been consumed by the master.
>> 
>> Signed-off-by: Mans Rullgard <[email-masked]>
>> ---
>>  net/dsa/tag_lan9303.c | 21 +++++++--------------
>>  1 file changed, 7 insertions(+), 14 deletions(-)
>> 
>> diff --git a/net/dsa/tag_lan9303.c b/net/dsa/tag_lan9303.c
>> index cb548188f813..7fe180941ac4 100644
>> --- a/net/dsa/tag_lan9303.c
>> +++ b/net/dsa/tag_lan9303.c
>> @@ -77,7 +77,6 @@ static struct sk_buff *lan9303_xmit(struct sk_buff *skb, struct net_device *dev)
>>  
>>  static struct sk_buff *lan9303_rcv(struct sk_buff *skb, struct net_device *dev)
>>  {
>> -	__be16 *lan9303_tag;
>>  	u16 lan9303_tag1;
>>  	unsigned int source_port;
>>  
>> @@ -87,14 +86,15 @@ static struct sk_buff *lan9303_rcv(struct sk_buff *skb, struct net_device *dev)
>>  		return NULL;
>>  	}
>>  
>> -	lan9303_tag = dsa_etype_header_pos_rx(skb);
>> -
>> -	if (lan9303_tag[0] != htons(ETH_P_8021Q)) {
>> -		dev_warn_ratelimited(&dev->dev, "Dropping packet due to invalid VLAN marker\n");
>> -		return NULL;
>> +	skb_push_rcsum(skb, ETH_HLEN);
>> +	if (skb_vlan_tag_present(skb)) {
>> +		lan9303_tag1 = skb_vlan_tag_get(skb);
>> +		__vlan_hwaccel_clear_tag(skb);
>> +	} else {
>> +		__skb_vlan_pop(skb, &lan9303_tag1);
>
> Sorry for the bad example, there is no reason to call skb_push_rcsum()
> and skb_pull_rcsum() if we go through the skb_vlan_tag_present() code
> path, just the "else" branch.

I could have realised that myself, had I not simply blindly copied the
example.  Anyway, new patch sent.

-- 
Måns Rullgård