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

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Date:   Wed, 2 Nov 2016 17:58:39 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Gao Feng <fgao@...ai8.com>, Cong Wang <xiyou.wangcong@...il.com>
Cc:     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

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