netdev - Re: [PATCH net] bpf: make error reporting in bpf_warn_invalid_xdp

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Date:   Fri, 08 Sep 2017 21:13:35 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     daniel@...earbox.net
Cc:     ast@...com, john.fastabend@...il.com, netdev@...r.kernel.org
Subject: Re: [PATCH net] bpf: make error reporting in
 bpf_warn_invalid_xdp_action more clear

From: Daniel Borkmann <daniel@...earbox.net>
Date: Sat,  9 Sep 2017 01:40:35 +0200

> Differ between illegal XDP action code and just driver
> unsupported one to provide better feedback when we throw
> a one-time warning here. Reason is that with 814abfabef3c
> ("xdp: add bpf_redirect helper function") not all drivers
> support the new XDP return code yet and thus they will
> fall into their 'default' case when checking for return
> codes after program return, which then triggers a
> bpf_warn_invalid_xdp_action() stating that the return
> code is illegal, but from XDP perspective it's not.
> 
> I decided not to place something like a XDP_ACT_MAX define
> into uapi i) given we don't have this either for all other
> program types, ii) future action codes could have further
> encoding there, which would render such define unsuitable
> and we wouldn't be able to rip it out again, and iii) we
> rarely add new action codes.
> 
> Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
> Acked-by: Alexei Starovoitov <ast@...nel.org>

Applied.