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

From: Mikko Rapeli
Date: Sun Feb 07 2016 - 09:04:22 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, made the net/if.h and linux/if.h
incompatibilities visible as build failures for userspace applications
like iproute2.

This patch fixes the cases where glibc net/if.h is included before linux/if.h
by using the linux/libc-compat.h approach.

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 after 'make headers_install' and
combining these headers with plain glibc and gcc headers. The test included
not just net/if.h but all compiling glibc headers with linux/if.h and it
compiles now without errors and warnings.

$ cat usr/libc_conflict_test/libc_headers.h
#include <aio.h>
#include <aliases.h>
#include <alloca.h>
#include <argp.h>
#include <argz.h>
#include <ar.h>
//these conflict with each other
// #include <arpa/ftp.h>
// #include <arpa/inet.h>
// #include <arpa/nameser_compat.h>
// #include <arpa/nameser.h>
// #include <arpa/telnet.h>
// #include <arpa/tftp.h>
#include <assert.h>
#include <byteswap.h>
#include <complex.h>
#include <cpio.h>
#include <crypt.h>
#include <ctype.h>
#include <dirent.h>
#include <dlfcn.h>
#include <elf.h>
#include <endian.h>
#include <envz.h>
#include <err.h>
#include <errno.h>
#include <error.h>
#include <execinfo.h>
#include <fcntl.h>
#include <features.h>
#include <fenv.h>
#include <fmtmsg.h>
#include <fnmatch.h>
#include <fstab.h>
#include <fts.h>
#include <ftw.h>
#include <_G_config.h>
#include <gconv.h>
#include <getopt.h>
#include <glob.h>
#include <gnu-versions.h>
#include <grp.h>
#include <gshadow.h>
#include <iconv.h>
#include <ifaddrs.h>
#include <inttypes.h>
#include <langinfo.h>
#include <lastlog.h>
#include <libgen.h>
#include <libintl.h>
#include <libio.h>
#include <limits.h>
#include <link.h>
#include <locale.h>
#include <malloc.h>
#include <math.h>
#include <mcheck.h>
#include <memory.h>
#include <mntent.h>
#include <monetary.h>
#include <mqueue.h>
#include <netash/ash.h>
#include <netatalk/at.h>
#include <netax25/ax25.h>
#include <netdb.h>
#include <neteconet/ec.h>
#include <net/ethernet.h>
#include <net/if_arp.h>
#include <net/if.h>
#include <net/if_packet.h>
#include <net/if_ppp.h>
#include <net/if_shaper.h>
#include <net/if_slip.h>
#include <netinet/ether.h>
#include <netinet/icmp6.h>
#include <netinet/if_ether.h>
#include <netinet/if_fddi.h>
#include <netinet/if_tr.h>
#include <netinet/igmp.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip6.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <netinet/tcp.h>
#include <netinet/udp.h>
#include <netipx/ipx.h>
#include <netiucv/iucv.h>
#include <netpacket/packet.h>
#include <net/ppp-comp.h>
#include <net/ppp_defs.h>
#include <netrom/netrom.h>
#include <netrose/rose.h>
#include <net/route.h>
#include <nl_types.h>
#include <nss.h>
#include <obstack.h>
#include <paths.h>
#include <poll.h>
#include <printf.h>
#include <protocols/routed.h>
#include <protocols/rwhod.h>
// conflicts with arap headers
//#include <protocols/talkd.h>
#include <protocols/timed.h>
#include <pthread.h>
#include <pty.h>
#include <pwd.h>
#include <re_comp.h>
#include <regex.h>
// conflicts with arpa headers
//#include <resolv.h>
#include <sched.h>
#include <scsi/scsi.h>
#include <scsi/scsi_ioctl.h>
#include <scsi/sg.h>
#include <search.h>
#include <semaphore.h>
#include <setjmp.h>
#include <sgtty.h>
#include <shadow.h>
#include <signal.h>
#include <spawn.h>
#include <stab.h>
#include <stdc-predef.h>
#include <stdint.h>
#include <stdio_ext.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <stropts.h>
#include <syscall.h>
#include <sysexits.h>
#include <syslog.h>
#include <tar.h>
#include <termio.h>
#include <termios.h>
#include <tgmath.h>
#include <thread_db.h>
#include <time.h>
#include <ttyent.h>
#include <uchar.h>
#include <ucontext.h>
#include <ulimit.h>
#include <unistd.h>
#include <ustat.h>
#include <utime.h>
#include <utmp.h>
#include <utmpx.h>
#include <values.h>
#include <wait.h>
#include <wchar.h>
#include <wctype.h>
#include <wordexp.h>
#include <xlocale.h>

$ cat iproute2_bug.h
#include <libc_headers.h>
#include <linux/if.h>

$ cc -Wall -c -nostdinc -I ../include/ -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.ddxtNf -I /home/mcfrisk/src/linux-2.6/usr/headers_compile_test_include.ddxtNf/i586-linux-gnu -o /dev/null ./iproute2_bug.h

Reported-by: Stephen Hemminger <shemming@xxxxxxxxxxx>
Reported-by: Josh Boyer <jwboyer@xxxxxxxxxxxxxxxxx>
Signed-off-by: Mikko Rapeli <mikko.rapeli@xxxxxx>
---
include/uapi/linux/if.h | 21 +++++++++++++++++++++
include/uapi/linux/libc-compat.h | 33 +++++++++++++++++++++++++++++++++
2 files changed, 54 insertions(+)

diff --git a/include/uapi/linux/if.h b/include/uapi/linux/if.h
index 9cf2394..5a07a67 100644
--- a/include/uapi/linux/if.h
+++ b/include/uapi/linux/if.h
@@ -19,11 +19,15 @@
#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 */

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

@@ -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 */
};

+/* 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
@@ -166,6 +177,8 @@ 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 +188,7 @@ 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 +214,8 @@ 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 +239,7 @@ 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 +266,8 @@ 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 +275,8 @@ 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..9211e52 100644
--- a/include/uapi/linux/libc-compat.h
+++ b/include/uapi/linux/libc-compat.h
@@ -51,6 +51,32 @@
/* 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
+#define __UAPI_DEF_IF_NET_DEVICE_FLAGS 0
+
+#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
+#define __UAPI_DEF_IF_NET_DEVICE_FLAGS 1
+
+#endif /* _NET_IF_H */
+
/* Coordinate with glibc netinet/in.h header. */
#if defined(_NETINET_IN_H)

@@ -117,6 +143,13 @@
* 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
+#define __UAPI_DEF_IF_NET_DEVICE_FLAGS 1
+
/* Definitions for in.h */
#define __UAPI_DEF_IN_ADDR 1
#define __UAPI_DEF_IN_IPPROTO 1
--
2.7.0.rc3

Next message: Gabriel L. Somlo: "Re: [PATCH v8 2/4] kobject: export kset_find_obj() for module use"
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