[PATCH v2] Coordinate if.h definitions for Linux and glibc (BZ #21367)

[Aurelien Jarno]

This commit coordinates the definition of structures and enum already
defined the Linux kernel UAPI headers, following the procedure described
on https://sourceware.org/glibc/wiki/Synchronizing_Headers.

With this change, it is safe to include <net/if.h> and <linux/if.h> in
any order in a a userspace application.

Note: this as been fixed in commit 4a91cb61bb995 on the Linux side.

Changelog:
	[BZ #21367]
	* sysdeps/gnu/net/if.h: wrap IFF_* enums in
	!defined __UAPI_DEF_IF_NET_DEVICE_FLAGS defines.
	(struct ifmap): Wrap in !defined __UAPI_DEF_IF_IFMAP defines.
	(struct ifreq): Wrap in !defined __UAPI_DEF_IF_IFREQ defines.
	(struct ifconf): Wrap in !defined __UAPI_DEF_IF_IFCONF defines.
---
 ChangeLog            | 9 +++++++++
 sysdeps/gnu/net/if.h | 9 +++++++++
 2 files changed, 18 insertions(+)

Changes v1 -> v2:
  Use '#ifndef' instead of '#if !' so that it also works with -Werror=undef

diff --git a/ChangeLog b/ChangeLog
index b72d52164e..21b96bb35e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2017-04-09 Aurelien Jarno  <aurelien@aurel32.net>
+
+	[BZ #21367]
+	* sysdeps/gnu/net/if.h: wrap IFF_* enums in
+	!defined __UAPI_DEF_IF_NET_DEVICE_FLAGS defines.
+	(struct ifmap): Wrap in !defined __UAPI_DEF_IF_IFMAP defines.
+	(struct ifreq): Wrap in !defined __UAPI_DEF_IF_IFREQ defines.
+	(struct ifconf): Wrap in !defined __UAPI_DEF_IF_IFCONF defines.
+
 2017-04-07  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* sysdeps/i386/fpu/fclrexcpt.c (__feclearexcept): Use
diff --git a/sysdeps/gnu/net/if.h b/sysdeps/gnu/net/if.h
index 0afce08238..a330fe0755 100644
--- a/sysdeps/gnu/net/if.h
+++ b/sysdeps/gnu/net/if.h
@@ -39,6 +39,7 @@ struct if_nameindex
 
 #ifdef __USE_MISC
 /* Standard interface flags. */
+# ifndef __UAPI_DEF_IF_NET_DEVICE_FLAGS
 enum
   {
     IFF_UP = 0x1,		/* Interface is up.  */
@@ -79,6 +80,7 @@ enum
     IFF_DYNAMIC = 0x8000	/* Dialup device with changing addresses.  */
 # define IFF_DYNAMIC	IFF_DYNAMIC
   };
+# endif /* !defined __UAPI_DEF_IF_NET_DEVICE_FLAGS */
 
 /* The ifaddr structure contains information about one address of an
    interface.  They are maintained by the different address families,
@@ -108,6 +110,7 @@ struct ifaddr
    handy for debugging things. The set side is fine for now and being
    very small might be worth keeping for clean configuration.  */
 
+# ifndef __UAPI_DEF_IF_IFMAP
 struct ifmap
   {
     unsigned long int mem_start;
@@ -118,11 +121,13 @@ struct ifmap
     unsigned char port;
     /* 3 bytes spare */
   };
+# endif /* !defined __UAPI_DEF_IF_IFMAP */
 
 /* Interface request structure used for socket ioctl's.  All interface
    ioctl's must have parameter definitions which begin with ifr_name.
    The remainder may be interface specific.  */
 
+# ifndef __UAPI_DEF_IF_IFREQ
 struct ifreq
   {
 # define IFHWADDRLEN	6
@@ -148,6 +153,8 @@ struct ifreq
 	__caddr_t ifru_data;
       } ifr_ifru;
   };
+# endif /* !__UAPI_DEF_IF_IFREQ */
+
 # define ifr_name	ifr_ifrn.ifrn_name	/* interface name 	*/
 # define ifr_hwaddr	ifr_ifru.ifru_hwaddr	/* MAC address 		*/
 # define ifr_addr	ifr_ifru.ifru_addr	/* address		*/
@@ -173,6 +180,7 @@ struct ifreq
    configuration for machine (useful for programs which must know all
    networks accessible).  */
 
+# ifndef __UAPI_DEF_IF_IFCONF
 struct ifconf
   {
     int	ifc_len;			/* Size of buffer.  */
@@ -182,6 +190,7 @@ struct ifconf
 	struct ifreq *ifcu_req;
       } ifc_ifcu;
   };
+# endif /* !defined __UAPI_DEF_IF_IFCONF */
 # define ifc_buf	ifc_ifcu.ifcu_buf	/* Buffer address.  */
 # define ifc_req	ifc_ifcu.ifcu_req	/* Array of structures.  */
 # define _IOT_ifconf _IOT(_IOTS(struct ifconf),1,0,0,0,0) /* not right */
-- 
2.11.0