netdev - Re: [PATCH net 1/1] driver: veth: Return the actual value instead return NETDEV_TX

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Date:   Thu, 3 Nov 2016 09:04:43 +0800
From:   Gao Feng <fgao@...ai8.com>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Cong Wang <xiyou.wangcong@...il.com>,
        David Miller <davem@...emloft.net>,
        Cong Wang <cwang@...pensource.com>,
        Vijay Pandurangan <vijayp@...ayp.ca>,
        Evan Jones <ej@...njones.ca>, pabeni@...hat.com,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH net 1/1] driver: veth: Return the actual value instead
 return NETDEV_TX_OK always

Hi Florian,

On Thu, Nov 3, 2016 at 8:58 AM, Florian Fainelli <f.fainelli@...il.com> wrote:
> On 11/02/2016 05:52 PM, Gao Feng wrote:
>> Hi Cong,
>>
>> On Thu, Nov 3, 2016 at 4:22 AM, Cong Wang <xiyou.wangcong@...il.com> wrote:
>>> On Wed, Nov 2, 2016 at 2:59 AM,  <fgao@...ai8.com> wrote:
>>>> From: Gao Feng <fgao@...ai8.com>
>>>>
>>>> Current veth_xmit always returns NETDEV_TX_OK whatever if it is really
>>>> sent successfully. Now return the actual value instead of NETDEV_TX_OK
>>>> always.
>>>>
>>>> Signed-off-by: Gao Feng <fgao@...ai8.com>
>>>> ---
>>>>  drivers/net/veth.c | 7 +++++--
>>>>  1 file changed, 5 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/net/veth.c b/drivers/net/veth.c
>>>> index fbc853e..769a3bd 100644
>>>> --- a/drivers/net/veth.c
>>>> +++ b/drivers/net/veth.c
>>>> @@ -111,15 +111,18 @@ static netdev_tx_t veth_xmit(struct sk_buff *skb, struct net_device *dev)
>>>>         struct veth_priv *priv = netdev_priv(dev);
>>>>         struct net_device *rcv;
>>>>         int length = skb->len;
>>>> +       int ret = NETDEV_TX_OK;
>>>>
>>>>         rcu_read_lock();
>>>>         rcv = rcu_dereference(priv->peer);
>>>>         if (unlikely(!rcv)) {
>>>>                 kfree_skb(skb);
>>>> +               ret = NET_RX_DROP;
>>>
>>>
>>> Returning NET_RX_DROP doesn't look correct in a xmit function.
>>
>> Yes. But I don't find good macro.
>> NETDEV_TX_BUSY or NET_RX_DROP, which is better ?
>
> There is no much choice you need to return a correct value from the
> netdev_tx_t enum, which NET_RX_DROP is not part of, so that probably
> means using NETDEV_TX_OK here, the packet has been freed, and there is
> no flow control problem mandating the return of NETDEV_TX_BUSY it seems...
> --
> Florian

Thanks your explanation.
It means the veth_xmit must return NETDEV_TX_OK.

Regards
Feng