linux-kernel - Re: [PATCH v6 01/21] net/tcp: Prepare tcp_md5sig

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Message-ID: <eb6d0724-92d6-3c3f-b698-9734adc7e1b9@arista.com>
Date:   Mon, 15 May 2023 17:25:55 +0100
From:   Dmitry Safonov <dima@...sta.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     linux-kernel@...r.kernel.org, David Ahern <dsahern@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Andy Lutomirski <luto@...capital.net>,
        Ard Biesheuvel <ardb@...nel.org>,
        Bob Gilligan <gilligan@...sta.com>,
        Dan Carpenter <error27@...il.com>,
        David Laight <David.Laight@...lab.com>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Eric Biggers <ebiggers@...nel.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Francesco Ruggeri <fruggeri05@...il.com>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Ivan Delalande <colona@...sta.com>,
        Leonard Crestez <cdleonard@...il.com>,
        Salam Noureddine <noureddine@...sta.com>,
        netdev@...r.kernel.org
Subject: Re: [PATCH v6 01/21] net/tcp: Prepare tcp_md5sig_pool for TCP-AO

On 5/15/23 05:48, Herbert Xu wrote:
> On Fri, May 12, 2023 at 09:22:51PM +0100, Dmitry Safonov wrote:
>> TCP-AO, similarly to TCP-MD5, needs to allocate tfms on a slow-path,
>> which is setsockopt() and use crypto ahash requests on fast paths,
>> which are RX/TX softirqs. Also, it needs a temporary/scratch buffer
>> for preparing the hash.
>>
>> Rework tcp_md5sig_pool in order to support other hashing algorithms
>> than MD5. It will make it possible to share pre-allocated crypto_ahash
>> descriptors and scratch area between all TCP hash users.
>>
>> Internally tcp_sigpool preferences crypto_clone_ahash() API over
>> pre-allocating per-CPU crypto requests. Kudos to Herbert, who provided
>> this new crypto API [1]. Currently, there's still per-CPU crypto request
>> allocation fallback, that is needed for ciphers, that yet don't support
>> cloning (TCP-AO requires cmac(aes128) in RFC5925).
>>
>> I was a little concerned over GFP_ATOMIC allocations of ahash and
>> crypto_request in RX/TX (see tcp_sigpool_start()), so I benchmarked both
>> "backends" with different algorithms, using patched version of iperf3[2].
>> On my laptop with i7-7600U @ 2.80GHz:
>>
>>                          clone-tfm                per-CPU-requests
>> TCP-MD5                  2.25 Gbits/sec           2.30 Gbits/sec
>> TCP-AO(hmac(sha1))       2.53 Gbits/sec           2.54 Gbits/sec
>> TCP-AO(hmac(sha512))     1.67 Gbits/sec           1.64 Gbits/sec
>> TCP-AO(hmac(sha384))     1.77 Gbits/sec           1.80 Gbits/sec
>> TCP-AO(hmac(sha224))     1.29 Gbits/sec           1.30 Gbits/sec
>> TCP-AO(hmac(sha3-512))    481 Mbits/sec            480 Mbits/sec
>> TCP-AO(hmac(md5))        2.07 Gbits/sec           2.12 Gbits/sec
>> TCP-AO(hmac(rmd160))     1.01 Gbits/sec            995 Mbits/sec
>> TCP-AO(cmac(aes128))     [not supporetd yet]      2.11 Gbits/sec
>>
>> So, it seems that my concerns don't have strong grounds and per-CPU
>> crypto_request allocation can be dropped/removed from tcp_sigpool once
>> ciphers get crypto_clone_ahash() support.
> 
> This support is now in the upstream kernel.  Please let me know
> if you run into any issues using it.

Hi Herbert, thanks for your patches. Could you point me to the repo that
has ciphers clone-tfm support? I've looked in Torvald's/master, your
cryptodev-2.6.git and in linux-next, but I can't see anywhere in
cmac_create() something of inst->alg.base.clone_tfm = cmac_clone_tfm kind.

As I wrote two paragraphs above, it's required for TCP-AO to provide
cmac(aes128) support. Let me know if you have cmac clone-tfm somewhere
or if you're cooking it. On the cover-letter for this patch set, it's in
TODO.

Thanks,
         Dmitry