linux-kernel - Re: [PATCH] uapi glibc compat: fix cases where glibc net/if.h is included before linux/if.h

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Message-Id: <20160217.104620.239734387234680136.davem@davemloft.net>
Date:	Wed, 17 Feb 2016 10:46:20 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	mikko.rapeli@....fi
Cc:	shemming@...cade.com, linux-api@...r.kernel.org,
	linux-kernel@...r.kernel.org, jwboyer@...oraproject.org,
	pablo@...filter.org, netdev@...r.kernel.org,
	netfilter-devel@...r.kernel.org
Subject: Re: [PATCH] uapi glibc compat: fix cases where glibc net/if.h is
 included before linux/if.h

From: Mikko Rapeli <mikko.rapeli@....fi>
Date: Sun,  7 Feb 2016 16:03:21 +0200

> @@ -68,6 +72,8 @@
>   * @IFF_ECHO: echo sent packets. Volatile.
>   */
>  enum net_device_flags {
> +/* for compatibility with glibc net/if.h */
> +#if __UAPI_DEF_IF_NET_DEVICE_FLAGS
>  	IFF_UP				= 1<<0,  /* sysfs */
>  	IFF_BROADCAST			= 1<<1,  /* volatile */
>  	IFF_DEBUG			= 1<<2,  /* sysfs */
> @@ -84,11 +90,14 @@ enum net_device_flags {
>  	IFF_PORTSEL			= 1<<13, /* sysfs */
>  	IFF_AUTOMEDIA			= 1<<14, /* sysfs */
>  	IFF_DYNAMIC			= 1<<15, /* sysfs */
> +#endif /* __UAPI_DEF_IF_NET_DEVICE_FLAGS */
>  	IFF_LOWER_UP			= 1<<16, /* volatile */
>  	IFF_DORMANT			= 1<<17, /* volatile */
>  	IFF_ECHO			= 1<<18, /* volatile */
>  };

This is going to get messy is IFF_LOWER_UP, IFF_DORMANT, and IFF_ECHO
get added the the glibc header.  Why not just handle it now with
another __UAPI_DEF_FOO guard so that the additions to net/if.h can
deal with this case too.

> +/* for compatibility with glibc net/if.h */
> +#if __UAPI_DEF_IF_NET_DEVICE_FLAGS
>  #define IFF_UP				IFF_UP
>  #define IFF_BROADCAST			IFF_BROADCAST
>  #define IFF_DEBUG			IFF_DEBUG
> @@ -105,6 +114,8 @@ enum net_device_flags {
>  #define IFF_PORTSEL			IFF_PORTSEL
>  #define IFF_AUTOMEDIA			IFF_AUTOMEDIA
>  #define IFF_DYNAMIC			IFF_DYNAMIC
> +#endif /* __UAPI_DEF_IF_NET_DEVICE_FLAGS */
> +
>  #define IFF_LOWER_UP			IFF_LOWER_UP
>  #define IFF_DORMANT			IFF_DORMANT
>  #define IFF_ECHO			IFF_ECHO

Likewise.