Prepare for using libcap-ng

configure.in

@@ -768,6 +768,49 @@ AM_CONDITIONAL([HAVE_NUMACTL], [test "$with_numactl" != "no"])
 AC_SUBST([NUMACTL_CFLAGS])
 AC_SUBST([NUMACTL_LIBS])
 
+
+
+dnl libcap-ng
+AC_ARG_WITH([capng],
+  [  --with-capng         use libcap-ng to reduce libvirtd privileges],
+  [],
+  [with_capng=check])
+
+dnl
+dnl This check looks for 'capng_updatev' since that was
+dnl introduced in 0.4.0 release which need as minimum
+dnl
+CAPNG_CFLAGS=
+CAPNG_LIBS=
+if test "$with_qemu" = "yes" -a "$with_capng" != "no"; then
+  old_cflags="$CFLAGS"
+  old_libs="$LIBS"
+  if test "$with_capng" = "check"; then
+    AC_CHECK_HEADER([cap-ng.h],[],[with_capng=no])
+    AC_CHECK_LIB([cap-ng], [capng_updatev],[],[with_capng=no])
+    if test "$with_capng" != "no"; then
+      with_capng="yes"
+    fi
+  else
+    fail=0
+    AC_CHECK_HEADER([cap-ng.h],[],[fail=1])
+    AC_CHECK_LIB([cap-ng], [capng_updatev],[],[fail=1])
+    test $fail = 1 &&
+      AC_MSG_ERROR([You must install the capng >= 0.4.0 development package in order to compile and run libvirt])
+  fi
+  CFLAGS="$old_cflags"
+  LIBS="$old_libs"
+fi
+if test "$with_capng" = "yes"; then
+  CAPNG_LIBS="-lcap-ng"
+  AC_DEFINE_UNQUOTED([HAVE_CAPNG], 1, [whether capng is available for privilege reduction])
+fi
+AM_CONDITIONAL([HAVE_CAPNG], [test "$with_capng" != "no"])
+AC_SUBST([CAPNG_CFLAGS])
+AC_SUBST([CAPNG_LIBS])
+
+
+
 dnl virsh libraries
 AC_CHECK_HEADERS([readline/readline.h])
 
@@ -1492,6 +1535,11 @@ AC_MSG_NOTICE([ numactl: $NUMACTL_CFLAGS $NUMACTL_LIBS])
 else
 AC_MSG_NOTICE([ numactl: no])
 fi
+if test "$with_capng" = "yes" ; then
+AC_MSG_NOTICE([   capng: $CAPNG_CFLAGS $CAPNG_LIBS])
+else
+AC_MSG_NOTICE([   capng: no])
+fi
 if test "$with_xen" = "yes" ; then
 AC_MSG_NOTICE([     xen: $XEN_CFLAGS $XEN_LIBS])
 else