linux-kernel - [PATCH 4.4 119/143] uapi/if_ether.h: prevent redefinition of struct ethhdr

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Date:   Mon, 18 Feb 2019 14:44:07 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hauke Mehrtens <hauke@...ke-m.de>,
        "David S. Miller" <davem@...emloft.net>,
        Linus Walleij <linus.walleij@...aro.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.4 119/143] uapi/if_ether.h: prevent redefinition of struct ethhdr

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

commit 6926e041a8920c8ec27e4e155efa760aa01551fd upstream.

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

glibc does not implement this header, but when glibc will implement this
they can just define __UAPI_DEF_ETHHDR 0 to make it work with the
kernel.

Signed-off-by: Hauke Mehrtens <hauke@...ke-m.de>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 include/uapi/linux/if_ether.h    | 3 +++
 include/uapi/linux/libc-compat.h | 6 ++++++
 2 files changed, 9 insertions(+)

diff --git a/include/uapi/linux/if_ether.h b/include/uapi/linux/if_ether.h
index 064d2026ab38..cb490cd9376f 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
@@ -136,11 +137,13 @@
  *	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 e4f048ee7043..5da44c571cdd 100644
--- a/include/uapi/linux/libc-compat.h
+++ b/include/uapi/linux/libc-compat.h
@@ -184,4 +184,10 @@
 
 #endif /* __GLIBC__ */
 
+/* Definitions for if_ether.h */
+/* allow libcs like musl to deactivate this, glibc does not implement this. */
+#ifndef __UAPI_DEF_ETHHDR
+#define __UAPI_DEF_ETHHDR		1
+#endif
+
 #endif /* _UAPI_LIBC_COMPAT_H */
-- 
2.19.1