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

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

On 3/3/2021 10:51 PM, Dmitry Kozlyuk wrote:
> It is proposed to rename fields of `struct rte_ether_hdr`,
> `s_addr` tp `src_addr` and `d_addr` to `dst_addr`,

s/tp/to/

> due to the clash with system macro on Windows.
> Until remaining is done in 21.11, a workaround can be used.

s/remaining/renaming/  ??

> 
> Windows Sockets headers contain `#define s_addr S_un.S_addr`, which
> conflicts with `s_addr` field of `struct rte_ether_hdr`. Undefining
> this macro in <rte_ether.h> is breaking some usages of DPDK
> and Windows headers in one file.
> 
> Example 1:
> 
>     #include <winsock2.h>
>     #include <rte_ether.h>
>     struct in_addr addr;
>     /* addr.s_addr = 0;     ERROR: s_addr undefined by DPDK */
> 
> Example 2:
> 
>     #include <rte_ether.h>
>     #include <winsock2.h>
>     struct rte_ether_hdr eh;
>     /* eh.s_addr.addr_bytes[0] = 0;     ERROR: `addr_s` is a macro */

s/addr_s/s_addr/  ??

> 
> 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?


> Signed-off-by: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
> ---
>  doc/guides/rel_notes/deprecation.rst | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/doc/guides/rel_notes/deprecation.rst b/doc/guides/rel_notes/deprecation.rst
> index 82c1a90a3..f7be10543 100644
> --- a/doc/guides/rel_notes/deprecation.rst
> +++ b/doc/guides/rel_notes/deprecation.rst
> @@ -125,3 +125,7 @@ Deprecation Notices
>  * cmdline: ``cmdline`` structure will be made opaque to hide platform-specific
>    content. On Linux and FreeBSD, supported prior to DPDK 20.11,
>    original structure will be kept until DPDK 21.11.
> +
> +* net: ``s_addr`` and ``d_addr`` fields of ``rte_ether_hdr`` structure
> +  will be renamed to ``src_addr`` and ``dst_addr`` respectively in DPDK 20.11

v21.11

> +  in order to avoid conflict with Windows Sockets headers.
>