linux-kernel - Re: [RFCv2 1/9] tcp: authopt: Initial support and key management

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Message-ID: <18235a42-72ad-8471-c940-c70b476cf0e0@gmail.com>
Date:   Wed, 11 Aug 2021 22:11:08 +0300
From:   Leonard Crestez <cdleonard@...il.com>
To:     David Ahern <dsahern@...il.com>,
        Leonard Crestez <cdleonard@...il.com>,
        Dmitry Safonov <0x7f454c46@...il.com>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Kuniyuki Iwashima <kuniyu@...zon.co.jp>,
        David Ahern <dsahern@...nel.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Yuchung Cheng <ycheng@...gle.com>,
        Francesco Ruggeri <fruggeri@...sta.com>,
        Mat Martineau <mathew.j.martineau@...ux.intel.com>,
        Christoph Paasch <cpaasch@...le.com>,
        Ivan Delalande <colona@...sta.com>,
        Priyaranjan Jha <priyarjha@...gle.com>,
        Menglong Dong <dong.menglong@....com.cn>,
        open list <linux-kernel@...r.kernel.org>,
        linux-crypto@...r.kernel.org,
        Network Development <netdev@...r.kernel.org>,
        Dmitry Safonov <dima@...sta.com>
Subject: Re: [RFCv2 1/9] tcp: authopt: Initial support and key management

On 11.08.2021 16:42, David Ahern wrote:
> On 8/11/21 2:29 AM, Leonard Crestez wrote:
>> On 8/10/21 11:41 PM, Dmitry Safonov wrote:
>>> Hi Leonard,
>>>
>>> On Tue, 10 Aug 2021 at 02:50, Leonard Crestez <cdleonard@...il.com>
>>> wrote:
>>> [..]
>>>> +/* Representation of a Master Key Tuple as per RFC5925 */
>>>> +struct tcp_authopt_key_info {
>>>> +       struct hlist_node node;
>>>> +       /* Local identifier */
>>>> +       u32 local_id;
>>>
>>> There is no local_id in RFC5925, what's that?
>>> An MKT is identified by (send_id, recv_id), together with
>>> (src_addr/src_port, dst_addr/dst_port).
>>> Why introducing something new to already complicated RFC?
>>
>> It was there to simplify user interface and initial implementation.
>>
>> But it seems that BGP listeners already needs to support multiple
>> keychains for different peers so identifying the key by (send_id,
>> recv_id, binding) is easier for userspace to work with. Otherwise they
>> need to create their own local_id mapping internally.
>>
> 
> any proposed simplification needs to be well explained and how it
> relates to the RFC spec.

The local_id only exists between userspace and kernel so it's not really 
covered by the RFC.

There are objections to this and it seems to be unhelpful for userspace 
zo I will replace it with match by binding.

BTW: another somewhat dubious simplification is that I offloaded the RFC 
requirement to never add overlapping keys to userspace. So if userspace 
adds keys with same recvid that match the same TCP 4-tuple then 
connections will just start failing.

It's arguably fine to allow userspace misconfiguration to cause failures.

--
Regards,
Leonard