Re: [libvirt] [PATCHv2] build: correctly check for SOICGIFVLAN GET_VLAN_VID_CMD command

In order to make a client-only build successful on RHEL4, commit 3ed2e54 modified src/util/virnetdev.c so that the functional version of virNetDevGetVLanID() was only compiled if GET_VLAN_VID_CMD was defined. However, it is *never* defined, but is only an enum value, so the proper version was no longer compiled even on platforms that support it. This resulted in the vlan tag not being properly set for guest traffic on VEPA mode guest macvtap interfaces that were bound to a vlan interface (that's the only place that libvirt currently uses virNetDevGetVLanID) Since there is no way to compile conditionally based on the presence of an enum value, this patch modifies configure.ac to check for said enum value with AC_CHECK_DECLS(), which #defines HAVE_GET_VLAN_VID_CMD if it's successful compiling a test program that uses GET_VLAN_VID_CMD. We can then make the compilation of virNetDevGetVLanID() conditional on that #define instead. --- Difference from V1: Use the amazingly compact AC_CHECK_DECLS() instead of deprecated AC_TRY_COMPILE() + extra trappings. configure.ac | 2 ++ src/util/virnetdev.c | 4 ++-- 2 files changed, 4 insertions(+), 2 deletions(-)

-#if defined(SIOCGIFVLAN) && defined(HAVE_STRUCT_IFREQ) && defined(GET_VLAN_VID_CMD) +#if defined(SIOCGIFVLAN) && defined(HAVE_STRUCT_IFREQ) && defined(HAVE_GET_VLAN_VID_CMD)