[libvirt] [PATCHv3] 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>
---

Good thing I'm waiting for a review - that waiting time was enough
for me to test on RHEL 5 and find another issue.
v3: also work around RHEL 5 - yet ANOTHER symptom of broken if_bridge.h

 configure.ac               | 12 +++++++++++-
 src/util/virnetdevbridge.c |  4 ++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index a155790..d3219ce 100644
--- a/configure.ac
+++ b/configure.ac
@@ -997,7 +997,17 @@ 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])],
-      [[#include <netinet/in.h>
+      [[/* 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 5d52e23..e4daa27 100644
--- a/src/util/virnetdevbridge.c
+++ b/src/util/virnetdevbridge.c
@@ -46,11 +46,15 @@
 # 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