Subject: RE: [PATCH bpf v2 3/4] bpf: Use EOPNOTSUPP in bpf_tcp_check_syncookie

From: John Fastabend <[email-masked]>
Date: Mon, 24 Jan 2022 23:06:29 -0800

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 <[email-masked]>
> Reviewed-by: Tariq Toukan <[email-masked]>

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
>