Re: [PATCH v6 01/21] net/tcp: Prepare tcp_md5sig_pool for TCP-AO

[Herbert Xu]

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.

Thanks,
-- 
Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt