linux-kernel - Re: [PATCH] usb: gadget: u_ether: Re-attach netif device to mirror detachment

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Date: Thu, 28 Dec 2023 22:59:59 +0100
From: Luca Weiss <luca@...tu.xyz>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Hardik Gajjar <hgajjar@...adit-jv.com>, linux-usb@...r.kernel.org,
 linux-kernel@...r.kernel.org, Richard Acayan <mailingradian@...il.com>
Cc: Richard Acayan <mailingradian@...il.com>,
 Thorsten Leemhuis <regressions@...mhuis.info>,
 Caleb Connolly <caleb.connolly@...aro.org>
Subject:
 Re: [PATCH] usb: gadget: u_ether: Re-attach netif device to mirror detachment

On Montag, 18. Dezember 2023 17:45:33 CET Richard Acayan wrote:
> In 6.7-rc1, there was a netif_device_detach call added to the
> gether_disconnect function. This clears the __LINK_STATE_PRESENT bit of
> the netif device and suppresses pings (ICMP messages) and TCP connection
> requests from the connected host. If userspace temporarily disconnects
> the gadget, such as by temporarily removing configuration in the gadget
> configfs interface, network activity should continue to be processed
> when the gadget is re-connected. Mirror the netif_device_detach call
> with a netif_device_attach call in gether_connect to fix re-connecting
> gadgets.

(+Cc Thorsten Leemhuis)

This appears to fix the regression on a 6.7-rc5-based build for
qcom-msm8974pro-fairphone-fp2, that the NCM network gadget doesn't work.
I've also heard reports from qcom-sdm845 and a PXA1908-based phone (if
I see this correctly) about issues on 6.7.

In postmarketOS on the device side the usb0 interface doesn't get the IP
address assigned correctly it seems, but it seems to behave a bit
inconsistently - but always broken.

Anyways, with this patch everything looks good again. I hope this makes
it for 6.7 final still.

Tested-by: Luca Weiss <luca@...tu.xyz>


> 
> Link: https://gitlab.com/postmarketOS/pmaports/-/tree/6002e51b7090aeeb42947e0ca7ec22278d7227d0/main/postmarketos-base-ui/rootfs-usr-lib-NetworkManager-dispatcher.d-50-tethering.sh
> Fixes: f49449fbc21e ("usb: gadget: u_ether: Replace netif_stop_queue with netif_device_detach")
> Signed-off-by: Richard Acayan <mailingradian@...il.com>
> ---
>  drivers/usb/gadget/function/u_ether.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c
> index 9d1c40c152d8..3c5a6f6ac341 100644
> --- a/drivers/usb/gadget/function/u_ether.c
> +++ b/drivers/usb/gadget/function/u_ether.c
> @@ -1163,6 +1163,8 @@ struct net_device *gether_connect(struct gether *link)
> if (netif_running(dev->net))
>  			eth_start(dev, GFP_ATOMIC);
> 
> +		netif_device_attach(dev->net);
> +
>  	/* on error, disable any endpoints  */
>  	} else {
>  		(void) usb_ep_disable(link->out_ep);