netdev - Re: [PATCH net-next v11 04/23] ovpn: add basic interface creation/destruction/management routines

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Message-ID: <855e6fee-5f0a-439d-a6c5-6829db4ecbfa@openvpn.net>
Date: Tue, 19 Nov 2024 09:45:51 +0100
From: Antonio Quartulli <antonio@...nvpn.net>
To: Sergey Ryazanov <ryazanov.s.a@...il.com>
Cc: Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Donald Hunter <donald.hunter@...il.com>,
 Shuah Khan <shuah@...nel.org>, sd@...asysnail.net,
 Andrew Lunn <andrew@...n.ch>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH net-next v11 04/23] ovpn: add basic interface
 creation/destruction/management routines

On 19/11/2024 04:08, Sergey Ryazanov wrote:
> On 15.11.2024 16:03, Antonio Quartulli wrote:
>> On 10/11/2024 21:42, Sergey Ryazanov wrote:
>>> Missed the most essential note regarding this patch :)
>>>
>>> On 29.10.2024 12:47, Antonio Quartulli wrote:
>>>> +static int ovpn_net_open(struct net_device *dev)
>>>> +{
>>>> +    netif_tx_start_all_queues(dev);
>>>> +    return 0;
>>>> +}
>>>> +
>>>> +static int ovpn_net_stop(struct net_device *dev)
>>>> +{
>>>> +    netif_tx_stop_all_queues(dev);
>>>
>>> Here we stop a user generated traffic in downlink. Shall we take care 
>>> about other kinds of traffic: keepalive, uplink?
>>
>> Keepalive is "metadata" and should continue to flow, regardless of 
>> whether the user interface is brought down.
>>
>> Uplink traffic directed to *this* device should just be dropped at 
>> delivery time.
>>
>> Incoming traffic directed to other peers will continue to work.
> 
> How it's possible? AFAIU, the module uses the kernel IP routing 
> subsystem. Putting the interface down will effectively block a client- 
> to-client packet to reenter the interface.

True.
At least part of the traffic is stopped (traffic directed to the VPN IP 
of a peer will still flow as it does not require a routing table lookup).

I circled this discussion through the other devs to see what perspective 
they would bring and we also agree that if something is stopping, better 
stop the entire infra.

Also, if a user is fumbling with the link state, they are probably 
trying to bring the VPN down.

I will go that way and basically perform the same cleanup as if the 
interface is being deleted.

"the party is over"[cit.] :)

Regards,

-- 
Antonio Quartulli
OpenVPN Inc.