netdev - Re: [PATCH v5 net] stmmac: 802.1ad tag stripping fix

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Date:   Wed, 30 May 2018 09:16:03 +0300
From:   Elad Nachman <eladv6@...il.com>
To:     Toshiaki Makita <makita.toshiaki@....ntt.co.jp>
Cc:     David Miller <davem@...emloft.net>,
        Jose Abreu <Jose.Abreu@...opsys.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        netdev@...r.kernel.org, peppe.cavallaro@...com,
        alexandre.torgue@...com, eladv6@...il.com
Subject: Re: [PATCH v5 net] stmmac: 802.1ad tag stripping fix

Interesting question. That's the way the driver was originally written and I tried to minimize the changes in the patch.
Anyway, common.h (included by stmmac_main.c) contains the following:

#if IS_ENABLED(CONFIG_VLAN_8021Q)
#define STMMAC_VLAN_TAG_USED
#include <linux/if_vlan.h>
#endif

So the define in question kicks in only once you enable 802.1Q support in the kernel .config .

Thanks,

Elad.

On 30/05/18 09:08, Toshiaki Makita wrote:
> On 2018/05/30 14:48, Elad Nachman wrote:
>> stmmac reception handler calls stmmac_rx_vlan() to strip the vlan before calling napi_gro_receive().
>>
>> The function assumes VLAN tagged frames are always tagged with 802.1Q protocol,
>> and assigns ETH_P_8021Q to the skb by hard-coding the parameter on call to __vlan_hwaccel_put_tag() .
>>
>> This causes packets not to be passed to the VLAN slave if it was created with 802.1AD protocol
>> (ip link add link eth0 eth0.100 type vlan proto 802.1ad id 100).
>>
>> This fix passes the protocol from the VLAN header into __vlan_hwaccel_put_tag()
>> instead of using the hard-coded value of ETH_P_8021Q.
>> NETIF_F_HW_VLAN_CTAG_RX check was removed and NETIF_F_HW_VLAN_STAG_RX feature was added to be in line with the driver actual abilities.
>>
>> Signed-off-by: Elad Nachman <eladn@...at.com>
>>
>> ---
>>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 16 ++++++++--------
>>  1 file changed, 8 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> index b65e2d1..f680bcf 100644
>> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> @@ -3293,17 +3293,17 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
>>  
>>  static void stmmac_rx_vlan(struct net_device *dev, struct sk_buff *skb)
>>  {
>> -	struct ethhdr *ehdr;
>> +	struct vlan_ethhdr *veth;
>>  	u16 vlanid;
>> +	__be16 vlan_proto;
>>  
>> -	if ((dev->features & NETIF_F_HW_VLAN_CTAG_RX) ==
>> -	    NETIF_F_HW_VLAN_CTAG_RX &&
>> -	    !__vlan_get_tag(skb, &vlanid)) {
>> +	if (!__vlan_get_tag(skb, &vlanid)) {
>>  		/* pop the vlan tag */
>> -		ehdr = (struct ethhdr *)skb->data;
>> -		memmove(skb->data + VLAN_HLEN, ehdr, ETH_ALEN * 2);
>> +		veth = (struct vlan_ethhdr *)skb->data;
>> +		vlan_proto = veth->h_vlan_proto;
>> +		memmove(skb->data + VLAN_HLEN, veth, ETH_ALEN * 2);
>>  		skb_pull(skb, VLAN_HLEN);
>> -		__vlan_hwaccel_put_tag(skb, htons(ETH_P_8021Q), vlanid);
>> +		__vlan_hwaccel_put_tag(skb, vlan_proto, vlanid);
>>  	}
> 
> Should this function contents be surrounded by
> #ifdef STMMAC_VLAN_TAG_USED, since the features is enabled only when it
> is defined?
> Otherwise looks good to me from the perspective of vlan features.
> 
>>  }
>>  
>> @@ -4344,7 +4344,7 @@ int stmmac_dvr_probe(struct device *device,
>>  	ndev->watchdog_timeo = msecs_to_jiffies(watchdog);
>>  #ifdef STMMAC_VLAN_TAG_USED
>>  	/* Both mac100 and gmac support receive VLAN tag detection */
>> -	ndev->features |= NETIF_F_HW_VLAN_CTAG_RX;
>> +	ndev->features |= NETIF_F_HW_VLAN_CTAG_RX | NETIF_F_HW_VLAN_STAG_RX;
>>  #endif
>>  	priv->msg_enable = netif_msg_init(debug, default_msg_level);
>>  
>>
>