AdGuardHome/internal/aghos/os.go

175 lines
4.5 KiB
Go

// Package aghos contains utilities for functions requiring system calls and
// other OS-specific APIs. OS-specific network handling should go to aghnet
// instead.
package aghos
import (
"bufio"
"fmt"
"io"
"io/fs"
"os"
"os/exec"
"path"
"runtime"
"strconv"
"strings"
"github.com/AdguardTeam/golibs/errors"
"github.com/AdguardTeam/golibs/log"
)
// UnsupportedError is returned by functions and methods when a particular
// operation Op cannot be performed on the current OS.
type UnsupportedError struct {
Op string
OS string
}
// Error implements the error interface for *UnsupportedError.
func (err *UnsupportedError) Error() (msg string) {
return fmt.Sprintf("%s is unsupported on %s", err.Op, err.OS)
}
// Unsupported is a helper that returns an *UnsupportedError with the Op field
// set to op and the OS field set to the current OS.
func Unsupported(op string) (err error) {
return &UnsupportedError{
Op: op,
OS: runtime.GOOS,
}
}
// SetRlimit sets user-specified limit of how many fd's we can use.
//
// See https://github.com/AdguardTeam/AdGuardHome/internal/issues/659.
func SetRlimit(val uint64) (err error) {
return setRlimit(val)
}
// HaveAdminRights checks if the current user has root (administrator) rights.
func HaveAdminRights() (bool, error) {
return haveAdminRights()
}
// MaxCmdOutputSize is the maximum length of performed shell command output.
const MaxCmdOutputSize = 2 * 1024
// RunCommand runs shell command.
func RunCommand(command string, arguments ...string) (int, string, error) {
cmd := exec.Command(command, arguments...)
out, err := cmd.Output()
if len(out) > MaxCmdOutputSize {
out = out[:MaxCmdOutputSize]
}
if errors.As(err, new(*exec.ExitError)) {
return cmd.ProcessState.ExitCode(), string(out), nil
} else if err != nil {
return 1, "", fmt.Errorf("exec.Command(%s) failed: %w: %s", command, err, string(out))
}
return cmd.ProcessState.ExitCode(), string(out), nil
}
// PIDByCommand searches for process named command and returns its PID ignoring
// the PIDs from except. If no processes found, the error returned.
func PIDByCommand(command string, except ...int) (pid int, err error) {
// Don't use -C flag here since it's a feature of linux's ps
// implementation. Use POSIX-compatible flags instead.
//
// See https://github.com/AdguardTeam/AdGuardHome/issues/3457.
cmd := exec.Command("ps", "-A", "-o", "pid=", "-o", "comm=")
var stdout io.ReadCloser
if stdout, err = cmd.StdoutPipe(); err != nil {
return 0, fmt.Errorf("getting the command's stdout pipe: %w", err)
}
if err = cmd.Start(); err != nil {
return 0, fmt.Errorf("start command executing: %w", err)
}
var instNum int
pid, instNum, err = parsePSOutput(stdout, command, except)
if err != nil {
return 0, err
}
if err = cmd.Wait(); err != nil {
return 0, fmt.Errorf("executing the command: %w", err)
}
switch instNum {
case 0:
// TODO(e.burkov): Use constant error.
return 0, fmt.Errorf("no %s instances found", command)
case 1:
// Go on.
default:
log.Info("warning: %d %s instances found", instNum, command)
}
if code := cmd.ProcessState.ExitCode(); code != 0 {
return 0, fmt.Errorf("ps finished with code %d", code)
}
return pid, nil
}
// parsePSOutput scans the output of ps searching the largest PID of the process
// associated with cmdName ignoring PIDs from ignore. A valid line from
// r should look like these:
//
// 123 ./example-cmd
// 1230 some/base/path/example-cmd
// 3210 example-cmd
//
func parsePSOutput(r io.Reader, cmdName string, ignore []int) (largest, instNum int, err error) {
s := bufio.NewScanner(r)
for s.Scan() {
fields := strings.Fields(s.Text())
if len(fields) != 2 || path.Base(fields[1]) != cmdName {
continue
}
cur, aerr := strconv.Atoi(fields[0])
if aerr != nil || cur < 0 || intIn(cur, ignore) {
continue
}
instNum++
if cur > largest {
largest = cur
}
}
if err = s.Err(); err != nil {
return 0, 0, fmt.Errorf("scanning stdout: %w", err)
}
return largest, instNum, nil
}
// intIn returns true if nums contains n.
func intIn(n int, nums []int) (ok bool) {
for _, nn := range nums {
if n == nn {
return true
}
}
return false
}
// IsOpenWrt returns true if host OS is OpenWrt.
func IsOpenWrt() (ok bool) {
return isOpenWrt()
}
// RootDirFS returns the fs.FS rooted at the operating system's root.
func RootDirFS() (fsys fs.FS) {
// Use empty string since os.DirFS implicitly prepends a slash to it. This
// behavior is undocumented but it currently works.
return os.DirFS("")
}