v2: * Separate out the return status fix. * Replace IP4_MASK_MAX with IP4_MASK_NUM. * Remove the ON_EXIT label. This patch is used to add the wrong/invalid subnet check. Cc: Santhapur Naveen <naveens@amiindia.co.in> Cc: Laszlo Ersek <lersek@redhat.com> Cc: Ye Ting <ting.ye@intel.com> Cc: Fu Siyuan <siyuan.fu@intel.com> Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Jiaxin Wu <jiaxin.wu@intel.com> Reviewed-by: Ye Ting <ting.ye@intel.com> Reviewed-by: Laszlo Ersek <lersek@redhat.com>