linux-kernel - Re: [PATCH] usbnet: ipheth: fix connectivity with iOS 14

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Date:   Fri, 20 Nov 2020 12:15:24 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...il.com>
To:     Yves-Alexis Perez <corsac@...sac.net>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Martin Habets <mhabets@...arflare.com>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Shannon Nelson <snelson@...sando.io>,
        "Michael S. Tsirkin" <mst@...hat.com>, linux-usb@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Matti Vuorela <matti.vuorela@...factor.fi>, stable@...r.kernel.org
Subject: Re: [PATCH] usbnet: ipheth: fix connectivity with iOS 14

Hello!

On 19.11.2020 20:24, Yves-Alexis Perez wrote:

> Starting with iOS 14 released in September 2020, connectivity using the
> personal hotspot USB tethering function of iOS devices is broken.
> 
> Communication between the host and the device (for example ICMP traffic
> or DNS resolution using the DNS service running in the device itself)
> works fine, but communication to endpoints further away doesn't work.
> 
> Investigation on the matter shows that UDP and ICMP traffic from the
                                         ^ "no" missing?

> tethered host is reaching the Internet at all. For TCP traffic there are
> exchanges between tethered host and server but packets are modified in
> transit leading to impossible communication.
> 
> After some trials Matti Vuorela discovered that reducing the URB buffer
> size by two bytes restored the previous behavior. While a better
> solution might exist to fix the issue, since the protocol is not
> publicly documented and considering the small size of the fix, let's do
> that.
> 
> Tested-by: Matti Vuorela <matti.vuorela@...factor.fi>
> Signed-off-by: Yves-Alexis Perez <corsac@...sac.net>
> Link: https://lore.kernel.org/linux-usb/CAAn0qaXmysJ9vx3ZEMkViv_B19ju-_ExN8Yn_uSefxpjS6g4Lw@mail.gmail.com/
> Link: https://github.com/libimobiledevice/libimobiledevice/issues/1038
> Cc: stable@...r.kernel.org
[...]

MBR, Sergei