netdev - Re: [PATCH] af_packet: Fix softirq mismatch in tpacket

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Message-ID: <05765015-f727-2f30-58da-2ad6fa7ea99f@candelatech.com>
Date: Thu, 19 Sep 2024 14:40:51 -0700
From: Ben Greear <greearb@...delatech.com>
To: David Ahern <dsahern@...nel.org>,
 Willem de Bruijn <willemdebruijn.kernel@...il.com>, netdev@...r.kernel.org,
 Ido Schimmel <idosch@...dia.com>
Subject: Re: [PATCH] af_packet: Fix softirq mismatch in tpacket_rcv

On 9/19/24 13:00, David Ahern wrote:
> On 9/19/24 10:44 AM, Willem de Bruijn wrote:
>> Yes, it seems that VRF calls dev_queue_xmit_nit without the same BH
>> protections that it expects.
>>
>> I suspect that the fix is in VRF, to disable BH the same way that
>> __dev_queue_xmit does, before calling dev_queue_xmit_nit.
>>
> 
> commit 504fc6f4f7f681d2a03aa5f68aad549d90eab853 removed the bh around
> dev_queue_xmit_nit:
> 
> diff --git a/drivers/net/vrf.c b/drivers/net/vrf.c
> index 6043e63b42f9..43f374444684 100644
> --- a/drivers/net/vrf.c
> +++ b/drivers/net/vrf.c
> @@ -638,9 +638,7 @@ static void vrf_finish_direct(struct sk_buff *skb)
>                  eth_zero_addr(eth->h_dest);
>                  eth->h_proto = skb->protocol;
> 
> -               rcu_read_lock_bh();
>                  dev_queue_xmit_nit(skb, vrf_dev);
> -               rcu_read_unlock_bh();
> 
>                  skb_pull(skb, ETH_HLEN);
>          }

So I guess we should revert this?  Maybe original testing passed because veth doesn't do
xmit/rcv quite like a real Eth driver will?

Thanks,
Ben

-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com