From: Andy Lutomirski Subject: Re: [PATCH net-next v3 02/17] zinc: introduce minimal cryptography library Date: Sun, 16 Sep 2018 21:09:11 -0700 Message-ID: References: <20180911214737.GA81235@gmail.com> <20180911233015.GD11474@lunn.ch> <20180911.165739.2032677219588723041.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Cc: andrew@lunn.ch, "Jason A. Donenfeld" , Eric Biggers , Greg KH , Ard Biesheuvel , LKML , Network Development , Andrew Lutomirski , Samuel Neves , Jean-Philippe Aumasson , Linux Crypto Mailing List To: "David S. Miller" Return-path: In-Reply-To: <20180911.165739.2032677219588723041.davem@davemloft.net> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-crypto.vger.kernel.org On Tue, Sep 11, 2018 at 4:57 PM David Miller wrote: > > From: Andrew Lunn > Date: Wed, 12 Sep 2018 01:30:15 +0200 > > > Just as an FYI: > > > > 1) I don't think anybody in netdev has taken a serious look at the > > network code yet. There is little point until the controversial part > > of the code, Zinc, has been sorted out. > > > > 2) I personally would be surprised if DaveM took this code without > > having an Acked-by from the crypto subsystem people. In the same way, > > i doubt the crypto people would take an Ethernet driver without having > > DaveM's Acked-by. > > Both of Andrew's statements are completely true. > > I'm not looking at any of the networking bits until the crypto stuff > is fully sorted and fully supported and Ack'd by crypto folks. So, as a process question, whom exactly are we waiting for: CRYPTO API M: Herbert Xu M: "David S. Miller" L: linux-crypto@vger.kernel.org Herbert hasn't replied to any of these submissions. You're the other maintainer :) To the extent that you (DaveM) want my ack, here's what I think of the series so far: The new APIs to the crypto primitives are good. For code that wants to do a specific known crypto operation, they are much, much more pleasant to use than the existing crypto API. The code cleanups in the big keys patch speak for themselves IMO. I have no problem with the addition of a brand-new API to the kernel, especially when it's a nice one like Zinc's, even if that API starts out with only a couple of users. Zinc's arrangement of arch code is just fine. Sure, there are arguments that putting arch-specific code in arch/ is better, but this is mostly bikeshedding IMO. There has been some discussion of the exact best way to handle simd_relax() and some other minor nitpicks of API details. This kind of stuff doesn't need to block the series -- it can always be reworked down the road if needed. There are two things I don't like right now, though: 1. Zinc conflates the addition of a new API with the replacement of some algorithm implementations. This is problematic. Look at the recent benchmarks of ipsec before and after this series. Apparently big packets get faster and small packets get slower. It would be really nice to bisect the series to narrow down *where* the regression came from, but, as currently structured, you can't. The right way to do this is to rearrange the series. First, the new Zinc APIs should be added, and they should be backed with the *existing* crypto code. (If the code needs to be moved or copied to a new location, so be it. The patch will be messy because somehow the Zinc API is going to have to dispatch to the arch-specific code, and the way that the crypto API handles it is not exactly friendly to this type of use. So be it.) Then another patch should switch the crypto API to use the Zinc interface. That patch, *by itself*, can be benchmarked. If it causes a regression for small ipsec packets, then it can be tracked down relatively easily. Once this is all done, the actual crypto implementation can be changed, and that changed can be reviewed on its own merits. As a simplistic example, I wrote this code a while back: https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git/commit/?h=crypto/sha256_bpf&id=e9e12f056f2abed50a30b762db9185799f5864e6 and its two parents. This series added a more Zinc-like API to SHA256. And it did it without replacing the SHA256 implementation. Doing this for Zinc would be a bit more complication, since the arch code would need to be invoked too, but it should be doable. FWIW, Wireguard should not actually depend on the replacement of the crypto implementation. 2. The new Zinc crypto implementations look like they're brand new. I realize that they have some history, some of them are derived from OpenSSL, etc, but none of this is really apparent in the patches themselves. It would be great if the kernel could literally share the same code as something like OpenSSL, since OpenSSL gets much more attention than the kernel's crypto. Failing that, it would be nice if the patches made it more clear how the code differs from its origin. At the very least, though, if the replacement of the crypto code were, as above, a patch that just replaced the crypto code, it would be much easier to review and benchmark intelligently. --Andy