netdev - Re: [PATCH bpf-next v3 2/3] bpf_xdp_redirect_map: Perform map lookup in eBPF helper

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Date:   Wed, 12 Jun 2019 12:45:59 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>
Cc:     netdev@...r.kernel.org, Jesper Dangaard Brouer <brouer@...hat.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        David Miller <davem@...emloft.net>,
        Jonathan Lemon <jonathan.lemon@...il.com>
Subject: Re: [PATCH bpf-next v3 2/3] bpf_xdp_redirect_map: Perform map
 lookup in eBPF helper

On Wed, 12 Jun 2019 11:49:17 +0200, Toke Høiland-Jørgensen wrote:
> Jakub Kicinski <jakub.kicinski@...ronome.com> writes:
> 
> > On Tue, 11 Jun 2019 17:44:00 +0200, Toke Høiland-Jørgensen wrote:  
> >> +#define XDP_REDIRECT_INVALID_MASK (XDP_ABORTED | XDP_DROP | XDP_PASS | XDP_TX)  
> >
> > It feels a little strange to OR in values which are not bits, even if
> > it happens to work today (since those are values of 0, 1, 2, 3)...  
> 
> Yeah, I agree. But it also nicely expresses the extent in code.
> Otherwise that would need to be in a comment, like
> 
> // we allow return codes of ABORTED/DROP/PASS/TX
> #define XDP_REDIRECT_INVALID_MASK 3
> 
> 
> Or do you have a better idea?

flags > XDP_TX

In the future when we add more fields in flags:

if (flags & ~XDP_REDIRECT_FLAGS_MASK)
	return -EBLA;
if ((flags & XDP_REDIRECT_RETCODE_MASK) > XDP_TX))
	return -EFOO;

?