the warning was:
iproute.c:301:12: warning: 'val' may be used uninitialized in this
function [-Wmaybe-uninitialized]
   features &= ~RTAX_FEATURE_ECN;
            ^
iproute.c:575:10: note: 'val' was declared here
   __u32 val;
	  ^
Signed-off-by: Zhang Shengju <zhangshengju@cmss.chinamobile.com>