netdev - Re: [PATCH 1/1] net: usb: qmi_wwan: restore mtu min/max values after raw

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Date:   Mon, 24 Feb 2020 09:38:25 +0100
From:   Daniele Palmas <dnlplm@...il.com>
To:     Bjørn Mork <bjorn@...k.no>
Cc:     netdev@...r.kernel.org, "David S . Miller" <davem@...emloft.net>
Subject: Re: [PATCH 1/1] net: usb: qmi_wwan: restore mtu min/max values after
 raw_ip switch

Il giorno dom 23 feb 2020 alle ore 14:41 Bjørn Mork <bjorn@...k.no> ha scritto:
>
> Daniele Palmas <dnlplm@...il.com> writes:
>
> > usbnet creates network interfaces with min_mtu = 0 and
> > max_mtu = ETH_MAX_MTU.
> >
> > These values are not modified by qmi_wwan when the network interface
> > is created initially, allowing, for example, to set mtu greater than 1500.
> >
> > When a raw_ip switch is done (raw_ip set to 'Y', then set to 'N') the mtu
> > values for the network interface are set through ether_setup, with
> > min_mtu = ETH_MIN_MTU and max_mtu = ETH_DATA_LEN, not allowing anymore to
> > set mtu greater than 1500 (error: mtu greater than device maximum).
> >
> > The patch restores the original min/max mtu values set by usbnet after a
> > raw_ip switch.
> >
> > Signed-off-by: Daniele Palmas <dnlplm@...il.com>
>
> Great! I tried to look up the origin of this bug, and it seems to be a
> hard-to-spot fallout from the 'centralized MTU checking'.  Not easy to
> see the hidden connection in usbnet.c and eth.c. Thanks for finding and
> fixing it!
>
> This should probably go to stable as well?
>

Yes, I think it won't hurt.

Thanks,
Daniele

> Acked-by: Bjørn Mork <bjorn@...k.no>