100 lines
2.1 KiB
Go
100 lines
2.1 KiB
Go
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package crypticnet
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import (
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"errors"
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"fmt"
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"io/fs"
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"os"
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"path/filepath"
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"github.com/shirou/gopsutil/process"
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)
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var errDaemonNotRunning = errors.New("no cryptic-net daemon process running")
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// ProcLock is used to lock a process.
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type ProcLock interface {
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// WriteLock creates a new lock, or errors if the lock is alread held.
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WriteLock() error
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// AssertLock returns an error if the lock already exists.
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AssertLock() error
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}
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type procLock struct {
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dir string
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}
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// NewProcLock returns a ProcLock which will use a file in the given directory
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// to lock the process.
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func NewProcLock(dir string) ProcLock {
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return &procLock{dir: dir}
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}
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func (pl *procLock) path() string {
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return filepath.Join(pl.dir, "lock")
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}
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func (pl *procLock) WriteLock() error {
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lockFilePath := pl.path()
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lockFile, err := os.OpenFile(
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lockFilePath, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0400,
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)
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if errors.Is(err, os.ErrExist) {
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return fmt.Errorf(
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"lock file %q already exists, if the cryptic-net daemon is not already running you can safely delete this file",
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lockFilePath,
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)
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} else if err != nil {
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return fmt.Errorf("opening lockfile %q: %w", lockFilePath, err)
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}
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defer lockFile.Close()
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if _, err := fmt.Fprintf(lockFile, "%d\n", os.Getpid()); err != nil {
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return fmt.Errorf("writing pid to %q: %w", lockFilePath, err)
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}
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return nil
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}
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// checks that the lock file exists and that the process which created it also
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// still exists.
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func (pl *procLock) AssertLock() error {
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lockFilePath := pl.path()
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lockFile, err := os.Open(lockFilePath)
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if errors.Is(err, fs.ErrNotExist) {
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return errDaemonNotRunning
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} else if err != nil {
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return fmt.Errorf("checking lock file %q: %w", lockFilePath, err)
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}
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defer lockFile.Close()
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var pid int32
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if _, err := fmt.Fscan(lockFile, &pid); err != nil {
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return fmt.Errorf("scanning pid from lock file %q: %w", lockFilePath, err)
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}
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procExists, err := process.PidExists(pid)
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if err != nil {
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return fmt.Errorf("checking if process %d exists: %w", pid, err)
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} else if !procExists {
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return errDaemonNotRunning
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}
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return nil
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}
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