flowlabel_put
expect_pass(flowlabel_put(fd, 1));
expect_pass(flowlabel_put(fd, 1));
expect_fail(flowlabel_put(fd, 1));
expect_pass(flowlabel_put(fd, 2));
expect_fail(flowlabel_put(fd, 1));
expect_pass(flowlabel_put(fd, 1));