netdev - Re: [PATCH] net: arp, ipv6: handle special case of tap device

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Message-ID: <87muru2g2d.fsf@codeaurora.org>
Date:   Thu, 04 Oct 2018 12:53:46 +0300
From:   Kalle Valo <kvalo@...eaurora.org>
To:     Vladis Dronov <vdronov@...hat.com>
Cc:     David Miller <davem@...emloft.net>, kuznet@....inr.ac.ru,
        yoshfuji@...ux-ipv6.org, netdev@...r.kernel.org,
        syzkaller@...glegroups.com, linux-kernel@...r.kernel.org,
        linux-wireless@...r.kernel.org
Subject: Re: [PATCH] net: arp, ipv6: handle special case of tap device

Vladis Dronov <vdronov@...hat.com> writes:

>> From: "David Miller" <davem@...emloft.net>
>> Sent: Wednesday, October 3, 2018 7:25:40 AM
>>
>> > Probably, this functionality is already used by some userspace, so I
>> > believe, I cannot just remove TUNSETLINK ioctl.
>> 
>> Who uses it, how do they use it, and what do they sanely expect about
>> the link layer header properties of a tap device which has had ->type
>> changed?
>
> Honestly, I have no idea. I was working on a syzkaller bug report and
> found that the reason for that bug was TUNSETLINK ioctl.
>
> This ioctl was introduced 13 years ago with ff4cc3ac93e1d and it says:
>
>> For use with
>> wireless and other networking types it should be possible to set the
>> ARP type via an ioctl.
>
> , that's all. Let me try to prepare a patch that sets dev->addr_len and
> dev->broadcast according to dev->type. I would probably need an advise
> what other fields must be adjusted too.
>
> Otherwise, we can just to remove the TUNSETLINK ioctl.

Let's add linux-wireless in case someone there knows about the ioctl.

-- 
Kalle Valo