netdev - Re: [PATCH 1/1] qmi_wwan: add MTU default to qmap network interface

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Date:   Fri, 04 Jan 2019 14:24:23 +0100
From:   Bjørn Mork <bjorn@...k.no>
To:     Daniele Palmas <dnlplm@...il.com>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH 1/1] qmi_wwan: add MTU default to qmap network interface

Daniele Palmas <dnlplm@...il.com> writes:

> This patch adds MTU default value to qmap network interface in
> order to avoid "RTNETLINK answers: No buffer space available"
> error when setting an ipv6 address.
>
> Signed-off-by: Daniele Palmas <dnlplm@...il.com>
> ---
>  drivers/net/usb/qmi_wwan.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/net/usb/qmi_wwan.c b/drivers/net/usb/qmi_wwan.c
> index 774e1ff..735ad83 100644
> --- a/drivers/net/usb/qmi_wwan.c
> +++ b/drivers/net/usb/qmi_wwan.c
> @@ -123,6 +123,7 @@ static void qmimux_setup(struct net_device *dev)
>  	dev->addr_len        = 0;
>  	dev->flags           = IFF_POINTOPOINT | IFF_NOARP | IFF_MULTICAST;
>  	dev->netdev_ops      = &qmimux_netdev_ops;
> +	dev->mtu             = 1500;
>  	dev->needs_free_netdev = true;
>  }

Setting some value makes sense, but hard coding 1500 feels wrong.
Should this relate to the real device mtu somehow?  Do we need a
ndo_change_mtu to enforce this relationship?  Should qmimux_rx_fixup()
respect the qmap device mtu?

I'm fine with this patch as a first step and immediate fix, so

Acked-by: Bjørn Mork <bjorn@...k.no>