netdev - Re: [PATCH bpf-next 0/7] Add XDP_ATTACH bind() flag to AF

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Date:   Fri, 7 Dec 2018 13:21:08 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Björn Töpel <bjorn.topel@...il.com>
Cc:     magnus.karlsson@...el.com, magnus.karlsson@...il.com,
        ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org,
        Björn Töpel <bjorn.topel@...el.com>,
        brouer@...hat.com, u9012063@...il.com, qi.z.zhang@...el.com
Subject: Re: [PATCH bpf-next 0/7] Add XDP_ATTACH bind() flag to AF_XDP sockets

On Fri, Dec 07, 2018 at 12:44:24PM +0100, Björn Töpel wrote:
> From: Björn Töpel <bjorn.topel@...el.com>
> 
> Hi!
> 
> This patch set adds support for a new XDP socket bind option,
> XDP_ATTACH.
> 
> The rationale behind attach is performance and ease of use. Many XDP
> socket users just need a simple way of creating/binding a socket and
> receiving frames right away without loading an XDP program.
> 
> XDP_ATTACH adds a mechanism we call "builtin XDP program" that simply
> is a kernel provided XDP program that is installed to the netdev when
> XDP_ATTACH is being passed as a bind() flag.
> 
> The builtin program is the simplest program possible to redirect a
> frame to an attached socket. In restricted C it would look like this:
>     
>   SEC("xdp")
>   int xdp_prog(struct xdp_md *ctx)
>   {
>         return bpf_xsk_redirect(ctx);
>   }
>     
> The builtin program loaded via XDP_ATTACH behaves, from an
> install-to-netdev/uninstall-from-netdev point of view, differently
> from regular XDP programs. The easiest way to look at it is as a
> 2-level hierarchy, where regular XDP programs has precedence over the
> builtin one.

The feature makes sense to me.
May be XDP_ATTACH_BUILTIN would be a better name ?
Also I think it needs another parameter to say which builtin
program to use.
This unconditional xsk_redirect is fine for performance
benchmarking, but for production I suspect the users would want
an easy way to stay safe when they're playing with AF_XDP.
So another builtin program that redirects ssh and ping traffic
back to the kernel would be a nice addition.