[PATCH v2] uapi glibc compat: fix compile errors when glibc net/if.h included before linux/if.h

From: Mikko Rapeli
Date: Sun Apr 24 2016 - 11:46:53 EST

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glibc's net/if.h contains copies of definitions from linux/if.h and these
conflict and cause build failures if both files are included by application
source code. Changes in uapi headers, which fixed header file dependencies to
include linux/if.h when it was needed, e.g. commit 1ffad83d, made the
net/if.h and linux/if.h incompatibilities visible as build failures for
userspace applications like iproute2 and xtables-addons.

This patch fixes compile errors when glibc net/if.h is included before
linux/if.h:

./linux/if.h:99:21: error: redeclaration of enumerator âIFF_NOARPâ
./linux/if.h:98:23: error: redeclaration of enumerator âIFF_RUNNINGâ
./linux/if.h:97:26: error: redeclaration of enumerator âIFF_NOTRAILERSâ
./linux/if.h:96:27: error: redeclaration of enumerator âIFF_POINTOPOINTâ
./linux/if.h:95:24: error: redeclaration of enumerator âIFF_LOOPBACKâ
./linux/if.h:94:21: error: redeclaration of enumerator âIFF_DEBUGâ
./linux/if.h:93:25: error: redeclaration of enumerator âIFF_BROADCASTâ
./linux/if.h:92:19: error: redeclaration of enumerator âIFF_UPâ
./linux/if.h:252:8: error: redefinition of âstruct ifconfâ
./linux/if.h:203:8: error: redefinition of âstruct ifreqâ
./linux/if.h:169:8: error: redefinition of âstruct ifmapâ
./linux/if.h:107:23: error: redeclaration of enumerator âIFF_DYNAMICâ
./linux/if.h:106:25: error: redeclaration of enumerator âIFF_AUTOMEDIAâ
./linux/if.h:105:23: error: redeclaration of enumerator âIFF_PORTSELâ
./linux/if.h:104:25: error: redeclaration of enumerator âIFF_MULTICASTâ
./linux/if.h:103:21: error: redeclaration of enumerator âIFF_SLAVEâ
./linux/if.h:102:22: error: redeclaration of enumerator âIFF_MASTERâ
./linux/if.h:101:24: error: redeclaration of enumerator âIFF_ALLMULTIâ
./linux/if.h:100:23: error: redeclaration of enumerator âIFF_PROMISCâ

The cases where linux/if.h is included before net/if.h need a similar fix in
the glibc side, or the order of include files can be changed userspace
code as a workaround.

This change was tested in x86 userspace on Debian unstable with
scripts/headers_compile_test.sh:

$ make headers_install && \
cd usr/include && ../../scripts/headers_compile_test.sh -l -k
...
cc -Wall -c -nostdinc -I /usr/lib/gcc/i586-linux-gnu/5/include -I /usr/lib/gcc/i586-linux-gnu/5/include-fixed -I . -I /home/mcfrisk/src/linux-2.6/usr/headers_compile_test_include.2uX2zH -I /home/mcfrisk/src/linux-2.6/usr/headers_compile_test_include.2uX2zH/i586-linux-gnu -o /dev/null ./linux/if.h_libc_before_kernel.h
PASSED libc before kernel test: ./linux/if.h

Reported-by: Jan Engelhardt <jengelh@xxxxxxx>
Reported-by: Josh Boyer <jwboyer@xxxxxxxxxxxxxxxxx>
Reported-by: Stephen Hemminger <shemming@xxxxxxxxxxx>
Reported-by: Waldemar Brodkorb <mail@xxxxxxxxxxxxxxxxxxxx>
Cc: Gabriel Laskar <gabriel@xxxxxxxxxxxx>
Signed-off-by: Mikko Rapeli <mikko.rapeli@xxxxxx>
---
include/uapi/linux/if.h | 28 +++++++++++++++++++++++++
include/uapi/linux/libc-compat.h | 44 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 72 insertions(+)

v1:
http://marc.info/?l=linux-kernel&m=145485386721798&w=2

v2:
Added handling for net_device_flags IFF_LOWER_UP, IFF_DORMANT and IFF_ECHO
which are unknown to glibc as suggested by David Miller in
http://marc.info/?l=linux-kernel&m=145650410726228&w=2

diff --git a/include/uapi/linux/if.h b/include/uapi/linux/if.h
index f802775..e601c8c 100644
--- a/include/uapi/linux/if.h
+++ b/include/uapi/linux/if.h
@@ -19,14 +19,20 @@
#ifndef _LINUX_IF_H
#define _LINUX_IF_H

+#include <linux/libc-compat.h> /* for compatibility with glibc */
#include <linux/types.h> /* for "__kernel_caddr_t" et al */
#include <linux/socket.h> /* for "struct sockaddr" et al */
#include <linux/compiler.h> /* for "__user" et al */

+#if __UAPI_DEF_IF_IFNAMSIZ
#define IFNAMSIZ 16
+#endif /* __UAPI_DEF_IF_IFNAMSIZ */
#define IFALIASZ 256
#include <linux/hdlc/ioctl.h>

+/* For glibc compatibility. An empty enum does not compile. */
+#if __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO != 0 && \
+ __UAPI_DEF_IF_NET_DEVICE_FLAGS != 0
/**
* enum net_device_flags - &struct net_device flags
*
@@ -68,6 +74,8 @@
* @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 +92,17 @@ 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 */
+#if __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO
IFF_LOWER_UP = 1<<16, /* volatile */
IFF_DORMANT = 1<<17, /* volatile */
IFF_ECHO = 1<<18, /* volatile */
+#endif /* __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO */
};
+#endif /* __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO != 0 && __UAPI_DEF_IF_NET_DEVICE_FLAGS != 0 */

+/* 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
@@ -105,9 +119,13 @@ 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 */
+
+#if __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO
#define IFF_LOWER_UP IFF_LOWER_UP
#define IFF_DORMANT IFF_DORMANT
#define IFF_ECHO IFF_ECHO
+#endif /* __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO */

#define IFF_VOLATILE (IFF_LOOPBACK|IFF_POINTOPOINT|IFF_BROADCAST|IFF_ECHO|\
IFF_MASTER|IFF_SLAVE|IFF_RUNNING|IFF_LOWER_UP|IFF_DORMANT)
@@ -166,6 +184,8 @@ enum {
* being very small might be worth keeping for clean configuration.
*/

+/* for compatibility with glibc net/if.h */
+#if __UAPI_DEF_IF_IFMAP
struct ifmap {
unsigned long mem_start;
unsigned long mem_end;
@@ -175,6 +195,7 @@ struct ifmap {
unsigned char port;
/* 3 bytes spare */
};
+#endif /* __UAPI_DEF_IF_IFMAP */

struct if_settings {
unsigned int type; /* Type of physical device or protocol */
@@ -200,6 +221,8 @@ struct if_settings {
* remainder may be interface specific.
*/

+/* for compatibility with glibc net/if.h */
+#if __UAPI_DEF_IF_IFREQ
struct ifreq {
#define IFHWADDRLEN 6
union
@@ -223,6 +246,7 @@ struct ifreq {
struct if_settings ifru_settings;
} 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 */
@@ -249,6 +273,8 @@ struct ifreq {
* must know all networks accessible).
*/

+/* for compatibility with glibc net/if.h */
+#if __UAPI_DEF_IF_IFCONF
struct ifconf {
int ifc_len; /* size of buffer */
union {
@@ -256,6 +282,8 @@ struct ifconf {
struct ifreq __user *ifcu_req;
} ifc_ifcu;
};
+#endif /* __UAPI_DEF_IF_IFCONF */
+
#define ifc_buf ifc_ifcu.ifcu_buf /* buffer address */
#define ifc_req ifc_ifcu.ifcu_req /* array of structures */

diff --git a/include/uapi/linux/libc-compat.h b/include/uapi/linux/libc-compat.h
index 7d024ce..d5e38c7 100644
--- a/include/uapi/linux/libc-compat.h
+++ b/include/uapi/linux/libc-compat.h
@@ -51,6 +51,40 @@
/* We have included glibc headers... */
#if defined(__GLIBC__)

+/* Coordinate with glibc net/if.h header. */
+#if defined(_NET_IF_H)
+
+/* GLIBC headers included first so don't define anything
+ * that would already be defined. */
+
+#define __UAPI_DEF_IF_IFCONF 0
+#define __UAPI_DEF_IF_IFMAP 0
+#define __UAPI_DEF_IF_IFNAMSIZ 0
+#define __UAPI_DEF_IF_IFREQ 0
+/* Everything up to IFF_DYNAMIC, matches net/if.h until glibc 2.23 */
+#define __UAPI_DEF_IF_NET_DEVICE_FLAGS 0
+/* For the future if glibc adds IFF_LOWER_UP, IFF_DORMANT and IFF_ECHO */
+#ifndef __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO
+#define __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO 1
+#endif /* __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO */
+
+#else /* _NET_IF_H */
+
+/* Linux headers included first, and we must define everything
+ * we need. The expectation is that glibc will check the
+ * __UAPI_DEF_* defines and adjust appropriately. */
+
+#define __UAPI_DEF_IF_IFCONF 1
+#define __UAPI_DEF_IF_IFMAP 1
+#define __UAPI_DEF_IF_IFNAMSIZ 1
+#define __UAPI_DEF_IF_IFREQ 1
+/* Everything up to IFF_DYNAMIC, matches net/if.h until glibc 2.23 */
+#define __UAPI_DEF_IF_NET_DEVICE_FLAGS 1
+/* 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
+
+#endif /* _NET_IF_H */
+
/* Coordinate with glibc netinet/in.h header. */
#if defined(_NETINET_IN_H)

@@ -117,6 +151,16 @@
* that we need. */
#else /* !defined(__GLIBC__) */

+/* Definitions for if.h */
+#define __UAPI_DEF_IF_IFCONF 1
+#define __UAPI_DEF_IF_IFMAP 1
+#define __UAPI_DEF_IF_IFNAMSIZ 1
+#define __UAPI_DEF_IF_IFREQ 1
+/* Everything up to IFF_DYNAMIC, matches net/if.h until glibc 2.23 */
+#define __UAPI_DEF_IF_NET_DEVICE_FLAGS 1
+/* 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 in.h */
#define __UAPI_DEF_IN_ADDR 1
#define __UAPI_DEF_IN_IPPROTO 1
--
2.8.0.rc3

Next message: Pavel Machek: "Re: [PATCH 1/2] extcon: arizona: Add device bindings for the micd configurations"
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