Re: [PATCH net-next v11 05/23] ovpn: keep carrier always on

[Sergey Ryazanov <ryazanov.s.a@gmail.com>]

On 29.10.2024 12:47, Antonio Quartulli wrote:
> An ovpn interface will keep carrier always on and let the user
> decide when an interface should be considered disconnected.
> 
> This way, even if an ovpn interface is not connected to any peer,
> it can still retain all IPs and routes and thus prevent any data
> leak.
> 
> Signed-off-by: Antonio Quartulli <antonio@openvpn.net>
> Reviewed-by: Andrew Lunn <andrew@lunn.ch>
> ---
>   drivers/net/ovpn/main.c | 7 +++++++
>   1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/net/ovpn/main.c b/drivers/net/ovpn/main.c
> index eead7677b8239eb3c48bb26ca95492d88512b8d4..eaa83a8662e4ac2c758201008268f9633643c0b6 100644
> --- a/drivers/net/ovpn/main.c
> +++ b/drivers/net/ovpn/main.c
> @@ -31,6 +31,13 @@ static void ovpn_struct_free(struct net_device *net)
>   
>   static int ovpn_net_open(struct net_device *dev)
>   {
> +	/* ovpn keeps the carrier always on to avoid losing IP or route
> +	 * configuration upon disconnection. This way it can prevent leaks
> +	 * of traffic outside of the VPN tunnel.
> +	 * The user may override this behaviour by tearing down the interface
> +	 * manually.
> +	 */
> +	netif_carrier_on(dev);

If a user cares about the traffic leaking, then he can create a 
blackhole route with huge metric:

# ip route add blackhole default metric 10000

Why the network interface should implicitly provide this functionality? 
And on another hand, how a routing daemon can learn a topology change 
without indication from the interface?

>   	netif_tx_start_all_queues(dev);
>   	return 0;
>   }
>