netdev - RE: [PATCH bpf v2 3/4] bpf: Use EOPNOTSUPP in bpf_tcp_check

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Date:   Mon, 24 Jan 2022 23:06:29 -0800
From:   John Fastabend <john.fastabend@...il.com>
To:     Maxim Mikityanskiy <maximmi@...dia.com>, bpf@...r.kernel.org,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, netdev@...r.kernel.org
Cc:     Tariq Toukan <tariqt@...dia.com>, Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Petar Penkov <ppenkov@...gle.com>,
        Lorenz Bauer <lmb@...udflare.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Maxim Mikityanskiy <maximmi@...dia.com>
Subject: RE: [PATCH bpf v2 3/4] bpf: Use EOPNOTSUPP in bpf_tcp_check_syncookie

Maxim Mikityanskiy wrote:
> When CONFIG_SYN_COOKIES is off, bpf_tcp_check_syncookie returns
> ENOTSUPP. It's a non-standard and deprecated code. The related function
> bpf_tcp_gen_syncookie and most of the other functions use EOPNOTSUPP if
> some feature is not available. This patch changes ENOTSUPP to EOPNOTSUPP
> in bpf_tcp_check_syncookie.
> 
> Fixes: 399040847084 ("bpf: add helper to check for a valid SYN cookie")
> Signed-off-by: Maxim Mikityanskiy <maximmi@...dia.com>
> Reviewed-by: Tariq Toukan <tariqt@...dia.com>

This came up in another thread? Or was it the same and we lost the context
in the commit msg. Either way I don't think we should start one-off
changing these user facing error codes. Its not the only spot we do this
and its been this way for sometime.

Is it causing a real problem?

> ---
>  net/core/filter.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 780e635fb52a..2c9106704821 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -6814,7 +6814,7 @@ BPF_CALL_5(bpf_tcp_check_syncookie, struct sock *, sk, void *, iph, u32, iph_len
>  
>  	return -ENOENT;
>  #else
> -	return -ENOTSUPP;
> +	return -EOPNOTSUPP;
>  #endif
>  }
>  
> -- 
> 2.30.2
>