netdev - Re: [PATCH bpf-next v3 00/15] Introducing AF

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Message-ID: <20180503233819.2tplfjd32auudys2@ast-mbp>
Date:   Thu, 3 May 2018 16:38:21 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     Björn Töpel <bjorn.topel@...il.com>,
        magnus.karlsson@...el.com, alexander.h.duyck@...el.com,
        alexander.duyck@...il.com, john.fastabend@...il.com, ast@...com,
        brouer@...hat.com, willemdebruijn.kernel@...il.com, mst@...hat.com,
        netdev@...r.kernel.org,
        Björn Töpel <bjorn.topel@...el.com>,
        michael.lundkvist@...csson.com, jesse.brandeburg@...el.com,
        anjali.singhai@...el.com, qi.z.zhang@...el.com
Subject: Re: [PATCH bpf-next v3 00/15] Introducing AF_XDP support

On Fri, May 04, 2018 at 12:49:09AM +0200, Daniel Borkmann wrote:
> On 05/02/2018 01:01 PM, Björn Töpel wrote:
> > From: Björn Töpel <bjorn.topel@...el.com>
> > 
> > This patch set introduces a new address family called AF_XDP that is
> > optimized for high performance packet processing and, in upcoming
> > patch sets, zero-copy semantics. In this patch set, we have removed
> > all zero-copy related code in order to make it smaller, simpler and
> > hopefully more review friendly. This patch set only supports copy-mode
> > for the generic XDP path (XDP_SKB) for both RX and TX and copy-mode
> > for RX using the XDP_DRV path. Zero-copy support requires XDP and
> > driver changes that Jesper Dangaard Brouer is working on. Some of his
> > work has already been accepted. We will publish our zero-copy support
> > for RX and TX on top of his patch sets at a later point in time.
> 
> +1, would be great to see it land this cycle. Saw few minor nits here
> and there but nothing to hold it up, for the series:
> 
> Acked-by: Daniel Borkmann <daniel@...earbox.net>
> 
> Thanks everyone!

Great stuff!

Applied to bpf-next, with one condition.
Upcoming zero-copy patches for both RX and TX need to be posted
and reviewed within this release window.
If netdev community as a whole won't be able to agree on the zero-copy
bits we'd need to revert this feature before the next merge window.

Few other minor nits:
patch 3:
+struct xdp_ring {
+       __u32 producer __attribute__((aligned(64)));
+       __u32 consumer __attribute__((aligned(64)));
+};
It kinda begs for ____cacheline_aligned_in_smp to be introduced for uapi headers.

patch 5:
+struct sockaddr_xdp {
+       __u16 sxdp_family;
+       __u32 sxdp_ifindex;
Not great to have a hole in uapi struct. Please fix it in the follow up.

patch 7:
Has a lot of synchronize_net(). I think udpate/delete side
can be improved to avoid them. Otherwise users may unknowingly DoS.

As the next steps I suggest to prioritize the highest to ship
zero-copy rx/tx patches and to add selftests.

Thanks!