netdev - [PATCH v2 3/3] uapi/if_ether.h: prevent redefinition of struct ethhdr

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Message-Id: <20170418210036.26039-4-hauke@hauke-m.de>
Date:   Tue, 18 Apr 2017 23:00:36 +0200
From:   Hauke Mehrtens <hauke@...ke-m.de>
To:     davem@...emloft.net, netdev@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, jarod@...hat.com, jogo@...nwrt.org,
        david.heidelberger@...t.cz, maillist-linux@...fooze.de,
        mikko.rapeli@....fi, dwmw2@...radead.org,
        Hauke Mehrtens <hauke@...ke-m.de>
Subject: [PATCH v2 3/3] uapi/if_ether.h: prevent redefinition of struct ethhdr

From: David Heidelberger <david.heidelberger@...t.cz>

Musl provides its own ethhdr struct definition. Add a guard to prevent
its definition of the appropriate musl header has already been included.

Acked-by: Mikko Rapeli <mikko.rapeli@....fi>
Signed-off-by: John Spencer <maillist-linux@...fooze.de>
Tested-by: David Heidelberger <david.heidelberger@...t.cz>
Signed-off-by: Jonas Gorski <jogo@...nwrt.org>
Signed-off-by: Hauke Mehrtens <hauke@...ke-m.de>
---
 include/uapi/linux/if_ether.h    |  3 +++
 include/uapi/linux/libc-compat.h | 11 +++++++++++
 2 files changed, 14 insertions(+)

diff --git a/include/uapi/linux/if_ether.h b/include/uapi/linux/if_ether.h
index 5bc9bfd816b7..fb5ab8c1e753 100644
--- a/include/uapi/linux/if_ether.h
+++ b/include/uapi/linux/if_ether.h
@@ -22,6 +22,7 @@
 #define _UAPI_LINUX_IF_ETHER_H
 
 #include <linux/types.h>
+#include <linux/libc-compat.h>
 
 /*
  *	IEEE 802.3 Ethernet magic constants.  The frame sizes omit the preamble
@@ -142,11 +143,13 @@
  *	This is an Ethernet frame header.
  */
 
+#if __UAPI_DEF_ETHHDR
 struct ethhdr {
 	unsigned char	h_dest[ETH_ALEN];	/* destination eth addr	*/
 	unsigned char	h_source[ETH_ALEN];	/* source ether addr	*/
 	__be16		h_proto;		/* packet type ID field	*/
 } __attribute__((packed));
+#endif
 
 
 #endif /* _UAPI_LINUX_IF_ETHER_H */
diff --git a/include/uapi/linux/libc-compat.h b/include/uapi/linux/libc-compat.h
index ce2fa8a4ced6..c92d32f213d1 100644
--- a/include/uapi/linux/libc-compat.h
+++ b/include/uapi/linux/libc-compat.h
@@ -87,6 +87,14 @@
 
 #endif /* _NET_IF_H */
 
+/* musl defines the ethhdr struct itself in its netinet/if_ether.h.
+ * Glibc just includes the kernel header and uses a different guard. */
+#if defined(_NETINET_IF_ETHER_H)
+#define __UAPI_DEF_ETHHDR		0
+#else
+#define __UAPI_DEF_ETHHDR		1
+#endif
+
 /* Coordinate with glibc netinet/in.h header. */
 #if defined(_NETINET_IN_H)
 
@@ -182,6 +190,9 @@
 /* For the future if glibc adds IFF_LOWER_UP, IFF_DORMANT and IFF_ECHO */
 #define __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO 1
 
+/* Definitions for if_ether.h */
+#define __UAPI_DEF_ETHHDR 		1
+
 /* Definitions for in.h */
 #define __UAPI_DEF_IN_ADDR		1
 #define __UAPI_DEF_IN_IPPROTO		1
-- 
2.11.0