Re: [dpdk-dev] [PATCH v2] doc: announce API changes for Windows compatibility

[John Alexander <John.Alexander@datapath.co.uk>]

> -----Original Message-----
> From: dev <dev-bounces@dpdk.org> On Behalf Of Dmitry Kozlyuk
> Sent: 10 March 2021 23:54
> To: dev@dpdk.org
> Cc: Ferruh Yigit <ferruh.yigit@intel.com>; Pallavi Kadam
> <pallavi.kadam@intel.com>; Dmitry Malloy <dmitrym@microsoft.com>;
> Narcisa Ana Maria Vasile <navasile@linux.microsoft.com>; Stephen
> Hemminger <stephen@networkplumber.org>; Tyler Retzlaff
> <roretzla@linux.microsoft.com>; Declan Doherty
> <declan.doherty@intel.com>; Fiona Trahe <fiona.trahe@intel.com>; Ashish
> Gupta <ashish.gupta@marvell.com>; Dmitry Kozlyuk
> <dmitry.kozliuk@gmail.com>; Ray Kinsella <mdr@ashroe.eu>; Neil Horman
> <nhorman@tuxdriver.com>
> Subject: [dpdk-dev] [PATCH v2] doc: announce API changes for Windows
> compatibility
> 
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> links or open attachments unless you recognize the sender and know the
> content is safe.
> 
> Windows socket headers define `s_addr`, `min`, and `max` macros which
> break structure definitions containing fields with one of these names.
> Undefining those macros would break some consumers as well.
> 
> 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 */
> 
> It is proposed to rename the conflicting fields on DPDK side, because Win32
> API has wider use and is slower and harder to change.
> 
> New names are left unspecified, open suggestions:
> 
> * `struct rte_ether_hdr` (by Stephen Hemminger):
> 
>     * `s_addr` -> `ether_shost`
>     * `d_addr` -> `ether_dhost` (for consistency)
> 
> * `struct rte_param_log2_range`, `struct rte_crypto_param_range`:
> 
>     * `min` -> `minimum`
>     * `max` -> `maximum`


The min/max macros in the Windows headers cause issues with C++ projects also (breaks std::min/std::max).  The fix there is to "#define NOMINMAX" prior to including windows.h, maybe that's appropriate here too?

> 
> For `s_addr`, a workaround is possible to use it until 21.11.
> For `min` and `max`, no workaround seems available. If cryptodev or
> compressdev is going to be enabled on Windows before 21.11, the only
> option seems to use a new name on Windows (using #ifdef).
> 
> Workaround for `s_addr` 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):
> 
>     #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")
> 
> Signed-off-by: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
> ---
> v2: * Propose to rename all problematic fields identified so far.
>     * Leave future names unspecified, no need to promise now.
>     * Propose better names for MAC addresses (Stephen Hemminger).
> 
> Thread about `s_addr` workaround:
> https://mails.dpdk.org/archives/dev/2021-March/200700.html
> Tyler Retzlaff confirmed offline that Microsoft took similar approach.
> 
>  doc/guides/rel_notes/deprecation.rst | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/doc/guides/rel_notes/deprecation.rst
> b/doc/guides/rel_notes/deprecation.rst
> index 64629e0641..854618f091 100644
> --- a/doc/guides/rel_notes/deprecation.rst
> +++ b/doc/guides/rel_notes/deprecation.rst
> @@ -130,3 +130,12 @@ 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 in DPDK 20.11 to avoid conflict with Windows Sockets
> headers.
> +
> +* compressdev: ``min`` and ``max`` fields of ``rte_param_log2_range``
> +structure
> +  will be renamed in DPDK 20.11 to avoid conflict with Windows Sockets
> headers.
> +
> +* cryptodev: ``min`` and ``max`` fields of ``rte_crypto_param_range``
> +structure
> +  will be renamed in DPDK 20.11 to avoid conflict with Windows Sockets
> headers.
> --
> 2.29.2