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From: Eric Dumazet <edumazet@google.com>
To: Leonard Crestez <cdleonard@gmail.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
	Dmitry Safonov <0x7f454c46@gmail.com>,
	David Ahern <dsahern@kernel.org>,
	"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 <netdev@vger.kernel.org>,
	"open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
	<linux-crypto@vger.kernel.org>,
	"open list:KERNEL SELFTEST FRAMEWORK" 
	<linux-kselftest@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Shuah Khan <shuah@kernel.org>
Subject: Re: [RFCv3 05/15] tcp: authopt: Add crypto initialization
Date: Wed, 25 Aug 2021 10:55:49 -0700	[thread overview]
Message-ID: <CANn89iJPyQpJTxrDMGszEOrgKwaEdYz1xaRK7vKbS4qj9tV23g@mail.gmail.com> (raw)
In-Reply-To: <27e56f61-3267-de50-0d49-5fcfc59af93c@gmail.com>

On Wed, Aug 25, 2021 at 9:35 AM Leonard Crestez <cdleonard@gmail.com> wrote:
>
> 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).

Well, do not use arrays of NR_CPUS and instead use normal per_cpu
accessors (as in __tcp_alloc_md5sig_pool)

>
> 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.

What I meant is that __tcp_alloc_md5sig_pool() allocates stuff one time,
we do not care about tcp_md5sig_pool_populated going back to false.

Otherwise, a single user application constantly allocating a socket,
enabling MD5 (or authopt), then closing the socket would incur
a big cost on hosts with a lot of cpus.

>
> 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

  reply	other threads:[~2021-08-25 17:56 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-24 21:34 [RFCv3 00/15] tcp: Initial support for RFC5925 auth option Leonard Crestez
2021-08-24 21:34 ` [RFCv3 01/15] tcp: authopt: Initial support and key management Leonard Crestez
2021-08-31 19:04   ` Dmitry Safonov
2021-09-03 14:26     ` Leonard Crestez
2021-08-24 21:34 ` [RFCv3 02/15] docs: Add user documentation for tcp_authopt Leonard Crestez
2021-08-24 21:34 ` [RFCv3 03/15] selftests: Initial tcp_authopt test module Leonard Crestez
2021-08-24 21:34 ` [RFCv3 04/15] selftests: tcp_authopt: Initial sockopt manipulation Leonard Crestez
2021-08-24 21:34 ` [RFCv3 05/15] tcp: authopt: Add crypto initialization Leonard Crestez
2021-08-24 23:02   ` Eric Dumazet
2021-08-24 23:34   ` Eric Dumazet
2021-08-25  8:08     ` Herbert Xu
2021-08-25 14:55       ` Eric Dumazet
2021-08-25 16:04       ` Ard Biesheuvel
2021-08-25 16:31         ` Leonard Crestez
2021-08-25 16:35     ` Leonard Crestez
2021-08-25 17:55       ` Eric Dumazet [this message]
2021-08-25 18:56         ` Leonard Crestez
2021-08-24 21:34 ` [RFCv3 06/15] tcp: authopt: Compute packet signatures Leonard Crestez
2021-08-24 21:34 ` [RFCv3 07/15] tcp: authopt: Hook into tcp core Leonard Crestez
2021-08-24 22:59   ` Eric Dumazet
2021-08-25 16:32     ` Leonard Crestez
2021-08-24 21:34 ` [RFCv3 08/15] tcp: authopt: Add snmp counters Leonard Crestez
2021-08-24 21:34 ` [RFCv3 09/15] selftests: tcp_authopt: Test key address binding Leonard Crestez
2021-08-25  5:18   ` David Ahern
2021-08-25 16:37     ` Leonard Crestez
2021-08-24 21:34 ` [RFCv3 10/15] selftests: tcp_authopt: Capture and verify packets Leonard Crestez
2021-08-24 21:34 ` [RFCv3 11/15] selftests: Initial tcp_authopt support for nettest Leonard Crestez
2021-08-24 21:34 ` [RFCv3 12/15] selftests: Initial tcp_authopt support for fcnal-test Leonard Crestez
2021-08-24 21:34 ` [RFCv3 13/15] selftests: Add -t tcp_authopt option for fcnal-test.sh Leonard Crestez
2021-08-24 21:34 ` [RFCv3 14/15] tcp: authopt: Add key selection controls Leonard Crestez
2021-08-24 21:34 ` [RFCv3 15/15] selftests: tcp_authopt: Add tests for rollover Leonard Crestez

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