> Le 25 janv. 2021 à 20:32, Jakub Kicinski <k...@kernel.org> a écrit :
>
>> On Sun, 24 Jan 2021 11:57:03 -0700 David Ahern wrote:
>> On 1/24/21 2:57 AM, Justin Iurman wrote:
>>>> De: "Jakub Kicinski" <k...@kernel.org>
>>>> À: "Justin Iurman" <justin.iur...@uliege.be>
>>>> Cc: netdev@vger.kernel.org, da...@davemloft.net, "alex aring"
>>>> <alex.ar...@gmail.com>
>>>> Envoyé: Dimanche 24 Janvier 2021 05:54:44
>>>> Objet: 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.iur...@uliege.be>
>>>>
>>>> Are you sure? This looks right to me.
>>>
>>> AFAIK, yes. Did you mean the old (current) one looks right, or the new one?
>
> Old one / existing is correct.
>
>>> If you meant the old/current one, well, I don't understand why the big
>>> endian definition would look like this:
>>>
>>> #elif defined(__BIG_ENDIAN_BITFIELD)
>>> __u32 reserved:20,
>>> pad:4,
>>> cmpri:4,
>>> cmpre:4;
>>>
>>> When the RFC defines the header as follows:
>>>
>>> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>> | CmprI | CmprE | Pad | Reserved |
>>> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>>
>>> The little endian definition looks fine. But, when it comes to big endian,
>>> you define fields as you see them on the wire with the same order, right?
>>> So the current big endian definition makes no sense. It looks like it was a
>>> wrong mix with the little endian conversion.
>
> Well, you don't list the bit positions in the quote from the RFC, and
> I'm not familiar with the IETF parlor. I'm only
Indeed, sorry for that. Bit positions are available if you follow the link to
the RFC I referenced in the patch. It is always defined as network byte order
by default (=BE).
> comparing the LE
> definition with the BE. If you claim the BE is wrong, then the LE is
> wrong, too.
Actually, no, it’s not. If you have a look at the header definition from the
RFC, you can see that the LE is correct (valid translation from BE, the *new*
BE in this patch).
>>>>> 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
>>
>> cross-checking with other headers - tcp and vxlan-gpe - this patch looks
>> correct.
>
> What are you cross-checking?
