pkg/systemd/systemd_client.go

// Copyright 2021 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package systemd

import (
	"bytes"
	"fmt"
	"os/exec"
	"policy-manager/pkg/sysapi"
	"strings"
)

// SystemdClient implements the SystemdClient interface.
type SystemdClient struct {
	// systemctlCmd is a string to pass appropriate command.
	systemctlCmd string
}

// NewSystemdClient returns a new SystemdClient.
func NewSystemdClient(systemctlCmd string) *SystemdClient {
	return &SystemdClient{systemctlCmd}
}

func (systemd *SystemdClient) IsUnitActiveRunning(name string) (bool, error) {
	cmd := exec.Command(systemd.systemctlCmd, "is-active", name)
	var stdout bytes.Buffer
	cmd.Stdout = &stdout

	err := cmd.Run()
	output := strings.TrimSpace(string(stdout.Bytes()))

	if err != nil {
		if exitError, ok := err.(*exec.ExitError); ok {
			code := exitError.ExitCode()
			if code == 3 || code == 4 {
				return false, nil
			}
		}
		return false, err
	}
	if output == "active" {
		return true, nil
	}
	return false, nil
}

func (systemd *SystemdClient) StartUnit(name string) error {
	_, _, err := sysapi.RunCommand(systemd.systemctlCmd, "start", name)
	return err
}

func (systemd *SystemdClient) StopUnit(name string) error {
	_, _, err := sysapi.RunCommand(systemd.systemctlCmd, "stop", name)
	return err
}

// ServiceExists checks if a systemd service exists (is loaded).
func (systemd *SystemdClient) ServiceExists(name string) (bool, error) {
	stdout, _, err := sysapi.RunCommand(systemd.systemctlCmd, "show", name, "-p", "LoadState")
	if err != nil {
		return false, err
	}
	output := strings.TrimSpace(string(stdout))
	if !strings.HasPrefix(output, "LoadState=") {
		return false, fmt.Errorf("unexpected output from systemctl show: %q", output)
	}
	return !strings.Contains(output, "LoadState=not-found"), nil
}