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

On 02/10/2014 07:17 AM, Laine Stump wrote: > In order to make a client-only build successful on RHEL4, commit > 3ed2e54 modified src/util/virnetdev.c so that the functional version I wonder if that was a typo in the 3ed2e54 commit message - we generally only care about RHEL5, not RHEL4. > 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_TRY_COMPILE(), and #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. > --- > configure.ac | 10 ++++++++++ > src/util/virnetdev.c | 4 ++-- > 2 files changed, 12 insertions(+), 2 deletions(-) > > +AC_MSG_CHECKING([for GET_VLAN_VID_CMD in /usr/linux/if_vlan.h]) > +AC_TRY_COMPILE([ #include <linux/if_vlan.h> ], > + [ int x = GET_VLAN_VID_CMD; ], > + [ have_get_vlan_vid_cmd=yes ], > + [ have_get_vlan_vid_cmd=no ]) Unusual style - most autoconf macro calls don't put spaces between the [] quoting.

Also, AC_TRY_COMPILE is marked deprecated in the autoconf manual, with the recommendation to use AC_COMPILE_IFELSE. But see below... > +if test "$have_get_vlan_vid_cmd" = "yes"; then > + AC_DEFINE_UNQUOTED([HAVE_GET_VLAN_VID_CMD], 1, > + [whether the kernel SIOCGIFVLAN ioctl supports GET_VLAN_VID_CMD]) > +fi > +AC_MSG_RESULT([$have_get_vlan_vid_cmd]) > AC_CHECK_DECLS is more compact;

for example, see how we probe for MACVLAN_MODE_PASSTHRU, at which point the rest of the code can use HAVE_DECL_MACVLAN_MODE_PASSTHRU.