Message-ID: <8097c38e-e88e-66ad-74d3-2f4a9e3734f4@arista.com>
Date:   Mon, 22 Aug 2022 21:35:53 +0100
From:   Dmitry Safonov <dima@...sta.com>
To:     David Ahern <dsahern@...nel.org>,
        Leonard Crestez <cdleonard@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Ard Biesheuvel <ardb@...nel.org>,
        Bob Gilligan <gilligan@...sta.com>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Eric Biggers <ebiggers@...nel.org>,
        Francesco Ruggeri <fruggeri@...sta.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Ivan Delalande <colona@...sta.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Salam Noureddine <noureddine@...sta.com>,
        Shuah Khan <shuah@...nel.org>, netdev@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/31] net/tcp: Add TCP-AO support

Hi Leonard, David,

On 8/22/22 00:51, David Ahern wrote:
> On 8/21/22 2:34 PM, Leonard Crestez wrote:
>> On 8/18/22 19:59, Dmitry Safonov wrote:
>>> This patchset implements the TCP-AO option as described in RFC5925. There
>>> is a request from industry to move away from TCP-MD5SIG and it seems
>>> the time
>>> is right to have a TCP-AO upstreamed. This TCP option is meant to replace
>>> the TCP MD5 option and address its shortcomings. Specifically, it
>>> provides
>>> more secure hashing, key rotation and support for long-lived connections
>>> (see the summary of TCP-AO advantages over TCP-MD5 in (1.3) of RFC5925).
>>> The patch series starts with six patches that are not specific to TCP-AO
>>> but implement a general crypto facility that we thought is useful
>>> to eliminate code duplication between TCP-MD5SIG and TCP-AO as well as
>>> other
>>> crypto users. These six patches are being submitted separately in
>>> a different patchset [1]. Including them here will show better the gain
>>> in code sharing. Next are 18 patches that implement the actual TCP-AO
>>> option,
>>> followed by patches implementing selftests.
>>>
>>> The patch set was written as a collaboration of three authors (in
>>> alphabetical
>>> order): Dmitry Safonov, Francesco Ruggeri and Salam Noureddine.
>>> Additional
>>> credits should be given to Prasad Koya, who was involved in early
>>> prototyping
>>> a few years back. There is also a separate submission done by Leonard
>>> Crestez
>>> whom we thank for his efforts getting an implementation of RFC5925
>>> submitted
>>> for review upstream [2]. This is an independent implementation that makes
>>> different design decisions.
>>
>> Is this based on something that Arista has had running for a while now
>> or is a recent new development?
>>
> 
> ...
> 
>> Seeing an entirely distinct unrelated implementation is very unexpected.
>> What made you do this?
>>
> 
> I am curious as well. You are well aware of Leonard's efforts which go
> back a long time, why go off and do a separate implementation?

When I started working on this, there was a prototype that was neither
good for upstream, nor for customers. At the moment Leonard submitted
his RFC, I was already giving feedback/reviews to local code and
patches. So, as I was aware of the details of TCP-AO, I started giving
Leonard feedback and reviews, based on what I've learned from RFC/code.
I thought whatever code will make it upstream, it can benefit from my
reviews. Some of my comments were based on a better code I saw locally,
or a way of improving it that I've suggested to both sides.

I'm quite happy that Leonard addressed some of my comments (i.e.
extendable syscalls), I see that it improved his patches.
On the other hand, some of the comments I've left moved to "known
limitations" with no foreseeable plan to fix them, while they were
addressed in local/Arista code.

And now a little bit more than a year later, it seems that the quality
of local patches has reached a point where they can be submitted for
an upstream review. So, please don't misunderstand me, it's not that
"drop your implementation, take ours" and it's not that we've
intentionally hidden that we're working on TCP-AO. It's that it is the
first moment we can make upstream aware of an alternative implementation.

Personally, I think it's best for opensource community:
- Arista's implementation is now public
- there are now at least 4 people that understand RFC5925 and the
  code/details
- in a discussion, it will be possible to find what will be the best
  from both implementations for Linux and come up with better code

At this particular moment, it seems neither of patch sets is ready to be
merged "as-is". But it seems that there's enough interest from both
sides and likely it guarantees that there will be enough effort to make
something merge-able, that will work for all interested parties.

As for my part, I'm interested in the best code upstream, regardless who
is the author. This includes:
- reusing the existing TCP-MD5 code, rather than copying'n'pasting for
  TCP-AO with intent to refactor it some day later
- making setsockopt()s and other syscalls extendable
- cover functionality with selftests
- following RFC5925 in implementation, especially "required" and "must"
  parts

I hope that clarifies how and why now there are two patch sets that
implement the same RFC/functionality.

Thanks,
          Dmitry

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