Re: [dpdk-dev] [PATCH] doc: announce renaming of rte_ether_hdr fields

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 5/20/2021 5:16 PM, Dmitry Kozlyuk wrote:
> 2021-05-20 17:04 (UTC+0100), Ferruh Yigit:
>> On 5/20/2021 4:50 PM, Dmitry Kozlyuk wrote:
>>> 2021-05-20 16:27 (UTC+0100), Ferruh Yigit:  
>>>> On 5/20/2021 4:06 PM, Dmitry Kozlyuk wrote:  
>>>>> 2021-05-20 15:24 (UTC+0100), Ferruh Yigit:    
>>>>>> On 3/3/2021 10:51 PM, Dmitry Kozlyuk wrote:    
>>>>> [...]    
>>>>>>>
>>>>>>> It is not mandatory to rename `d_addr`, this is for consistency only.
>>>>>>> Naming in `rte_ether_hdr` will also resemble `rte_ipv4/6_hdr`.
>>>>>>>
>>>>>>> Workaround is to define `struct rte_ether_hdr` in such a away that
>>>>>>> it can be used with or without `s_addr` macro (as defined on Windows)
>>>>>>> This can be done for Windows only or for all platforms to save space.
>>>>>>>
>>>>>>>     #pragma push_macro("s_addr")
>>>>>>>     #ifdef s_addr
>>>>>>>     #undef s_addr
>>>>>>>     #endif
>>>>>>>
>>>>>>>     struct rte_ether_hdr {
>>>>>>>         struct rte_ether_addr d_addr; /**< Destination address. */
>>>>>>>         RTE_STD_C11
>>>>>>>         union {
>>>>>>>             struct rte_ether_addr s_addr; /**< Source address. */
>>>>>>>             struct {
>>>>>>>                 struct rte_ether_addr S_un;
>>>>>>>                 /**< MUST NOT be used directly, only via s_addr */
>>>>>>>             } S_addr;
>>>>>>>             /*< MUST NOT be used directly, only via s_addr */
>>>>>>>         };
>>>>>>>         uint16_t ether_type; /**< Frame type. */
>>>>>>>     } __rte_aligned(2);
>>>>>>>
>>>>>>>     #pragma pop_macro("s_addr")
>>>>>>>       
>>>>>>
>>>>>> What is the problem with the workaround, why we can't live with it?
>>>>>>
>>>>>> It requires an order in include files, right?    
>>>>>
>>>>> There's no problem except a tricky structure definition with fields that
>>>>> violate DPDK coding rules. It works with any include order.
>>>>>
>>>>> Will fix typos in v3, thanks.
>>>>>     
>>>>
>>>> For following case, won't compiler take 's_addr' as macro?
>>>>
>>>>     #include <rte_ether.h>
>>>>     #include <winsock2.h>
>>>>     struct rte_ether_hdr eh;
>>>>     /* eh.s_addr.addr_bytes[0] = 0;
>>>>  
>>>
>>> Yes, it will. The macro will expand to `S_addr.S_un` and compile successfully.  
>>
>> will 'eh.S_addr.S_un.addr_bytes[0] = 0;' compile successfully?
> 
> Yes, only it's `S_un.S_addr`, sorry for the typo in my explanation.
> Both code snippets from commit message compile successfully.
> 

Ah, I was missing the union on the struct, yes it will build,

And +1 to deprecation notice and clean the "struct rte_ether_hdr" whenever possible.

>>
>>> In theory, Microsoft can change the definition of `s_addr`, and while I doubt
>>> they will, it's a valid concern and a reason to remove workaround in 21.11.
>>>   
>>
>