netdev - Re: [PATCH net-next] net: dlink: count tx_dropped when dropping skb on link down

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Message-Id: <DFNFEBZPHG3I.1YEOOHK1BTI3N@gmail.com>
Date: Tue, 13 Jan 2026 20:30:45 +0900
From: "Yeounsu Moon" <yyyynoom@...il.com>
To: "Andrew Lunn" <andrew@...n.ch>, "Yeounsu Moon" <yyyynoom@...il.com>
Cc: "Andrew Lunn" <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>, "Eric Dumazet" <edumazet@...gle.com>, "Jakub
 Kicinski" <kuba@...nel.org>, "Paolo Abeni" <pabeni@...hat.com>,
 <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next] net: dlink: count tx_dropped when dropping skb
 on link down

On Tue Jan 6, 2026 at 10:44 PM KST, Andrew Lunn wrote:
> On Tue, Jan 06, 2026 at 09:23:51PM +0900, Yeounsu Moon wrote:
>> Increment tx_dropped when dropping the skb due to link down.
>> 
>> Tested-on: D-Link DGE-550T Rev-A3
>> Signed-off-by: Yeounsu Moon <yyyynoom@...il.com>
>> ---
>>  drivers/net/ethernet/dlink/dl2k.c | 1 +
>>  1 file changed, 1 insertion(+)
>> 
>> diff --git a/drivers/net/ethernet/dlink/dl2k.c b/drivers/net/ethernet/dlink/dl2k.c
>> index 846d58c769ea..edc6cd64ac56 100644
>> --- a/drivers/net/ethernet/dlink/dl2k.c
>> +++ b/drivers/net/ethernet/dlink/dl2k.c
>> @@ -733,6 +733,7 @@ start_xmit (struct sk_buff *skb, struct net_device *dev)
>>  	u64 tfc_vlan_tag = 0;
>>  
>>  	if (np->link_status == 0) {	/* Link Down */
>> +		dev->stats.tx_dropped++;
>
> Do you see this being hit very often? It should be that as soon as you
> know the link is down, you tell the core, and it will stop calling
> start_xmit. If you see this counter being incremented a lot, it
> indicates there is a problem somewhere else.
>
> You might want to consider converting this driver to phylink.
>
> 	  Andrew

Sorry for the late reply. I recently started my first job and have been
a bit busy settling in.

To answer your question: this path is hit extremely rarely. In practice,
I only observed it in rather extreme cases, such as forcibly
disconnecting the physical link (e.g. unplugging the Ethernet cable). I
have not seen it occurring during normal operation.

Given that, dropping the packet in this situation seems reasonable, so I
added a counter to make such cases visible. However, I am not entirely
sure whether this is the right direction, or whether this is just
masking a problem that should be handled elsewhere.

Do you think this should instead be addressed by improving how link-down
is propagted to the core, or would converting this driver to phylink
help avoid or improve this situation?

    Yeounsu