add keepalive for ssh

internal/util/ssh/session.go

@@ -0,0 +1,126 @@
+package ssh
+
+import (
+	"context"
+	"net"
+	"time"
+
+	"github.com/go-gost/core/logger"
+	"golang.org/x/crypto/ssh"
+)
+
+const (
+	defaultKeepaliveInterval = 30 * time.Second
+	defaultKeepaliveTimeout  = 15 * time.Second
+	defaultkeepaliveRetries  = 1
+)
+
+type Session struct {
+	net.Conn
+	client *ssh.Client
+	closed chan struct{}
+	dead   chan struct{}
+	log    logger.Logger
+}
+
+func NewSession(c net.Conn, client *ssh.Client, log logger.Logger) *Session {
+	return &Session{
+		Conn:   c,
+		client: client,
+		closed: make(chan struct{}),
+		dead:   make(chan struct{}),
+		log:    log,
+	}
+}
+
+func (s *Session) OpenChannel(name string) (ssh.Channel, <-chan *ssh.Request, error) {
+	return s.client.OpenChannel(name, nil)
+}
+
+func (s *Session) IsClosed() bool {
+	select {
+	case <-s.dead:
+		return true
+	case <-s.closed:
+		return true
+	default:
+	}
+	return false
+}
+
+func (s *Session) Wait() error {
+	defer close(s.closed)
+
+	return s.client.Wait()
+}
+
+func (s *Session) WaitClose() {
+	defer s.client.Close()
+
+	select {
+	case <-s.dead:
+		s.log.Debugf("session is dead")
+	case <-s.closed:
+		s.log.Debugf("session is closed")
+	}
+}
+
+func (s *Session) Keepalive(interval, timeout time.Duration, retries int) {
+	if interval <= 0 {
+		interval = defaultKeepaliveInterval
+	}
+	if timeout <= 0 {
+		timeout = defaultKeepaliveTimeout
+	}
+	if retries <= 0 {
+		retries = defaultkeepaliveRetries
+	}
+
+	s.log.Debugf("keepalive is enabled, interval: %v, timeout: %v, retries: %d", interval, timeout, retries)
+	defer close(s.dead)
+
+	t := time.NewTicker(interval)
+	defer t.Stop()
+
+	count := retries
+	for {
+		select {
+		case <-t.C:
+			start := time.Now()
+			err := func() error {
+				ctx, cancel := context.WithTimeout(context.Background(), timeout)
+				defer cancel()
+
+				select {
+				case err := <-s.ping():
+					return err
+				case <-ctx.Done():
+					return ctx.Err()
+				}
+			}()
+			if err != nil {
+				s.log.Debugf("ssh ping: %v", err)
+				count--
+				if count == 0 {
+					return
+				}
+				continue
+			}
+			s.log.Debugf("ssh ping OK, RTT: %v", time.Since(start))
+			count = retries
+		case <-s.closed:
+			return
+		}
+	}
+}
+
+func (s *Session) ping() <-chan error {
+	ch := make(chan error, 1)
+	go func() {
+		defer close(ch)
+		if _, _, err := s.client.SendRequest("ping", true, nil); err != nil {
+			ch <- err
+		}
+	}()
+	return ch
+}