[libvirt] [v0.9.12-maint 2/5] build: more workarounds for if_bridge.h

[Eric Blake]

This is a second attempt at fixing the problem first attempted
in commit 2df8d99; basically undoing the fact that it was
reverted in commit 43cee32f, plus fixing two more issues: the
code in configure.ac has to EXACTLY match virnetdevbridge.c
with regards to declaring in6 types before using if_bridge.h,
and the fact that RHEL 5 has even more conflicts:

In file included from util/virnetdevbridge.c:49:
/usr/include/linux/in6.h:47: error: conflicting types for 'in6addr_any'
/usr/include/netinet/in.h:206: error: previous declaration of 'in6addr_any' was here
/usr/include/linux/in6.h:49: error: conflicting types for 'in6addr_loopback'
/usr/include/netinet/in.h:207: error: previous declaration of 'in6addr_loopback' was here

The rest of this commit message borrows from the original try
of 2df8d99:

A fresh checkout on a RHEL 6 machine with these packages:
kernel-headers-2.6.32-405.el6.x86_64
glibc-2.12-1.128.el6.x86_64
failed to configure with this message:
checking for linux/if_bridge.h... no
configure: error: You must install kernel-headers in order to compile libvirt with QEMU or LXC support

Digging in config.log, we see that the problem is identical to
what we fixed earlier in commit d12c2811:

configure:98831: checking for linux/if_bridge.h
configure:98853: gcc -std=gnu99 -c -g -O2  conftest.c >&5
In file included from /usr/include/linux/if_bridge.h:17,
                 from conftest.c:559:
/usr/include/linux/in6.h:31: error: redefinition of 'struct in6_addr'
/usr/include/linux/in6.h:48: error: redefinition of 'struct sockaddr_in6'
/usr/include/linux/in6.h:56: error: redefinition of 'struct ipv6_mreq'
configure:98860: $? = 1

I had not hit it earlier because I was using incremental builds,
where config.cache had shielded me from the kernel-headers breakage.

* configure.ac (if_bridge.h): Avoid conflicting type definitions.
* src/util/virnetdevbridge.c (includes): Also sanitize for RHEL 5.

Signed-off-by: Eric Blake <eblake at redhat.com>
(cherry picked from commit 70024dc9192038575ab5217ac35080b038e5b13e)

Done in one patch rather than a series for bisectability reasons
(as intermediate patches suffer from various problems on various
platforms), and because the intermediate patches include a revert,
but it is pointless to backport two patches where one undoes the
other.  Intermediate patches include: 9a2f36e, c308a9a, 1bf661c,
d12c281, 2df8d99, 43cee32 (phew, that's a mouthful).

Conflicts:
	configure.ac - skip the churn of all intermediate patches
	src/util/virnetdevbridge.c - ditto
---
 configure.ac               | 20 +++++++++++++++++---
 src/util/virnetdevbridge.c | 18 ++++++++++++++++++
 2 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/configure.ac b/configure.ac
index a6894ae..fa9d537 100644
--- a/configure.ac
+++ b/configure.ac
@@ -848,9 +848,23 @@ fi
 dnl
 dnl check for kernel headers required by src/bridge.c
 dnl
-if test "$with_qemu" = "yes" || test "$with_lxc" = "yes" ; then
-  AC_CHECK_HEADERS([linux/param.h linux/sockios.h linux/if_bridge.h linux/if_tun.h],,
-                   AC_MSG_ERROR([You must install kernel-headers in order to compile libvirt with QEMU or LXC support]))
+if test "$with_linux" = "yes"; then
+  if test "$with_qemu" = "yes" || test "$with_lxc" = "yes" ; then
+    AC_CHECK_HEADERS([linux/param.h linux/sockios.h linux/if_bridge.h linux/if_tun.h],,
+      [AC_MSG_ERROR([You must install kernel-headers in order to compile libvirt with QEMU or LXC support])],
+      [[/* The kernel folks broke their headers when used with particular
+         * glibc versions; although the structs are ABI compatible, the
+         * C type system doesn't like struct redefinitions.  We work around
+         * the problem here in the same manner as in virnetdevbridge.c.  */
+        #include <netinet/in.h>
+        #define in6_addr in6_addr_
+        #define sockaddr_in6 sockaddr_in6_
+        #define ipv6_mreq ipv6_mreq_
+        #define in6addr_any in6addr_any_
+        #define in6addr_loopback in6addr_loopback_
+        #include <linux/in6.h>
+      ]])
+  fi
 fi


diff --git a/src/util/virnetdevbridge.c b/src/util/virnetdevbridge.c
index 08c8f5c..84ab89d 100644
--- a/src/util/virnetdevbridge.c
+++ b/src/util/virnetdevbridge.c
@@ -30,13 +30,31 @@
 #include "intprops.h"

 #include <sys/ioctl.h>
+#include <sys/socket.h>
 #ifdef HAVE_NET_IF_H
 # include <net/if.h>
 #endif
+#include <netinet/in.h>
+
 #ifdef __linux__
 # include <linux/sockios.h>
 # include <linux/param.h>     /* HZ                 */
+/* Depending on the version of kernel vs. glibc, there may be a collision
+ * between <net/in.h> and kernel IPv6 structures.  The different types
+ * are ABI compatible, but choke the C type system; work around it by
+ * using temporary redefinitions.  */
+# define in6_addr in6_addr_
+# define sockaddr_in6 sockaddr_in6_
+# define ipv6_mreq ipv6_mreq_
+# define in6addr_any in6addr_any_
+# define in6addr_loopback in6addr_loopback_
+# include <linux/in6.h>
 # include <linux/if_bridge.h> /* SYSFS_BRIDGE_ATTR  */
+# undef in6_addr
+# undef sockaddr_in6
+# undef ipv6_mreq
+# undef in6addr_any
+# undef in6addr_loopback

 # define JIFFIES_TO_MS(j) (((j)*1000)/HZ)
 # define MS_TO_JIFFIES(ms) (((ms)*HZ)/1000)
-- 
1.8.3.1