Received-SPF: pass (google.com: domain of linux-crypto-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Leonard Crestez <cdleonard@gmail.com>
Subject: Re: [RFCv3 05/15] tcp: authopt: Add crypto initialization
To:     Eric Dumazet <eric.dumazet@gmail.com>,
        Dmitry Safonov <0x7f454c46@gmail.com>,
        David Ahern <dsahern@kernel.org>
Cc:     Eric Dumazet <edumazet@google.com>,
        "David S. Miller" <davem@davemloft.net>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Kuniyuki Iwashima <kuniyu@amazon.co.jp>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        Jakub Kicinski <kuba@kernel.org>,
        Yuchung Cheng <ycheng@google.com>,
        Francesco Ruggeri <fruggeri@arista.com>,
        Mat Martineau <mathew.j.martineau@linux.intel.com>,
        Christoph Paasch <cpaasch@apple.com>,
        Ivan Delalande <colona@arista.com>,
        Priyaranjan Jha <priyarjha@google.com>,
        Menglong Dong <dong.menglong@zte.com.cn>,
        netdev@vger.kernel.org, linux-crypto@vger.kernel.org,
        linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org,
        Shuah Khan <shuah@kernel.org>
References: <cover.1629840814.git.cdleonard@gmail.com>
 <abb720b34b9eef1cc52ef68017334e27a2af83c6.1629840814.git.cdleonard@gmail.com>
 <30f73293-ea03-d18f-d923-0cf499d4b208@gmail.com>
Message-ID: <27e56f61-3267-de50-0d49-5fcfc59af93c@gmail.com>
Date:   Wed, 25 Aug 2021 19:35:42 +0300
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101
 Thunderbird/78.11.0
MIME-Version: 1.0
In-Reply-To: <30f73293-ea03-d18f-d923-0cf499d4b208@gmail.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 25.08.2021 02:34, Eric Dumazet wrote:
> On 8/24/21 2:34 PM, Leonard Crestez wrote:
>> The crypto_shash API is used in order to compute packet signatures. The
>> API comes with several unfortunate limitations:
>>
>> 1) Allocating a crypto_shash can sleep and must be done in user context.
>> 2) Packet signatures must be computed in softirq context
>> 3) Packet signatures use dynamic "traffic keys" which require exclusive
>> access to crypto_shash for crypto_setkey.
>>
>> The solution is to allocate one crypto_shash for each possible cpu for
>> each algorithm at setsockopt time. The per-cpu tfm is then borrowed from
>> softirq context, signatures are computed and the tfm is returned.
>>
> 
> I could not see the per-cpu stuff that you mention in the changelog.

That's a little embarrasing, I forgot to implement the actual per-cpu 
stuff. tcp_authopt_alg_imp.tfm is meant to be an array up to NR_CPUS and 
tcp_authopt_alg_get_tfm needs no locking other than preempt_disable 
(which should already be the case).

The reference counting would still only happen from very few places: 
setsockopt, close and openreq. This would only impact request/response 
traffic and relatively little.

Performance was not a major focus so far. Preventing impact on non-AO 
connections is important but typical AO usecases are long-lived 
low-traffic connections.

--
Regards,
Leonard