netdev - Re: [PATCH net 1/1] uapi: fix big endian definition of ipv6_rpl_sr

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Message-ID: <20210123205444.5e1df187@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Sat, 23 Jan 2021 20:54:44 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Justin Iurman <justin.iurman@...ege.be>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, alex.aring@...il.com
Subject: Re: [PATCH net 1/1] uapi: fix big endian definition of
 ipv6_rpl_sr_hdr

On Thu, 21 Jan 2021 23:00:44 +0100 Justin Iurman wrote:
> Following RFC 6554 [1], the current order of fields is wrong for big
> endian definition. Indeed, here is how the header looks like:
> 
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> |  Next Header  |  Hdr Ext Len  | Routing Type  | Segments Left |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> | CmprI | CmprE |  Pad  |               Reserved                |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> 
> This patch reorders fields so that big endian definition is now correct.
> 
>   [1] https://tools.ietf.org/html/rfc6554#section-3
> 
> Signed-off-by: Justin Iurman <justin.iurman@...ege.be>

Are you sure? This looks right to me.

> diff --git a/include/uapi/linux/rpl.h b/include/uapi/linux/rpl.h
> index 1dccb55cf8c6..708adddf9f13 100644
> --- a/include/uapi/linux/rpl.h
> +++ b/include/uapi/linux/rpl.h
> @@ -28,10 +28,10 @@ struct ipv6_rpl_sr_hdr {
>  		pad:4,
>  		reserved1:16;
>  #elif defined(__BIG_ENDIAN_BITFIELD)
> -	__u32	reserved:20,
> +	__u32	cmpri:4,
> +		cmpre:4,
>  		pad:4,
> -		cmpri:4,
> -		cmpre:4;
> +		reserved:20;
>  #else
>  #error  "Please fix <asm/byteorder.h>"
>  #endif