+# ------------------------------------------------------------------------------
+
+AC_CHECK_HEADERS_ONCE([
+ ctype.h
+ errno.h
+ linux/netlink.h
+ net/if.h
+ stdarg.h
+ stdio.h
+ stdlib.h
+ string.h
+ syslog.h
+])
+
+AC_CHECK_FUNCS([ \
+ __secure_getenv \
+ secure_getenv \
+])
+
+# ------------------------------------------------------------------------------
+
+AC_ARG_ENABLE([debug],
+ AS_HELP_STRING([--enable-debug], [enable debug messages @<:@default=disabled@:>@]),
+ [], [enable_debug=no])
+AS_IF([test "x$enable_debug" = "xyes"], [
+ AC_DEFINE(ENABLE_DEBUG, [1], [Debug messages.])
+])
+