netdev - Re: [PATCH net] vxlan: fix missing options_len update on RX with collect metadata

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Message-ID: <56D8F17E.1020607@iogearbox.net>
Date:	Fri, 04 Mar 2016 03:22:54 +0100
From:	Daniel Borkmann <daniel@...earbox.net>
To:	Cong Wang <xiyou.wangcong@...il.com>
CC:	David Miller <davem@...emloft.net>, Thomas Graf <tgraf@...g.ch>,
	Pravin B Shelar <pshelar@...ira.com>, jesse@...nel.org,
	Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH net] vxlan: fix missing options_len update on RX with
 collect metadata

On 03/04/2016 01:16 AM, Cong Wang wrote:
> On Thu, Mar 3, 2016 at 12:58 AM, Daniel Borkmann <daniel@...earbox.net> wrote:
>> On 03/03/2016 02:21 AM, Cong Wang wrote:
>>>
>>> Why not set it in tun_rx_dst() where it is allocated?
>>
>> Nope, current convention is to only fill options_len when an actual
>> option was detected on RX, f.e. see ip_tunnel_info_opts_set() in
>> geneve. Consumers like ovs_flow_key_extract() check for options_len
>> and not TUNNEL_OPTIONS_PRESENT to copy it via ip_tunnel_info_opts_get()
>> from there.
>
> But the APIs suck...
>
> You expect to use ip_tunnel_info_opts_{get,set}() to read or write
> the tun_info, but actually this is not the case here for vxlan.

Yep, since depending on the working mode either skb->mark is populated
or the tunnel opts buffer.

> Also, ip_tunnel_info_opts_set() could write out of range if the len is
> bigger than the allocated length. I know existing callers are fine, but this API
> is problematic.

Current call sites are good agree, API could probably be better, yeah.

> I think this is why we had this bug.