fix(agent): retire replaced tunnel sessions (#541)

go-gost/x/dialer/kcp/conn.go

@@ -19,20 +19,23 @@ func (session *muxSession) Accept() (net.Conn, error) {
 }
 
 func (session *muxSession) Close() error {
-	if session.session == nil {
+	if session == nil || session.session == nil {
 		return nil
 	}
 	return session.session.Close()
 }
 
 func (session *muxSession) IsClosed() bool {
-	if session.session == nil {
+	if session == nil || session.session == nil {
 		return true
 	}
 	return session.session.IsClosed()
 }
 
 func (session *muxSession) NumStreams() int {
+	if session == nil || session.session == nil {
+		return 0
+	}
 	return session.session.NumStreams()
 }
 

go-gost/x/dialer/kcp/dialer.go

@@ -11,6 +11,7 @@ import (
 	"github.com/go-gost/core/logger"
 	md "github.com/go-gost/core/metadata"
 	kcp_util "github.com/go-gost/x/internal/util/kcp"
+	"github.com/go-gost/x/internal/util/sessionretire"
 	mdutil "github.com/go-gost/x/metadata/util"
 	"github.com/go-gost/x/registry"
 	"github.com/xtaci/kcp-go/v5"
@@ -25,6 +26,7 @@ func init() {
 type kcpDialer struct {
 	sessions     map[string]*muxSession
 	sessionMutex sync.Mutex
+	retired      bool
 	logger       logger.Logger
 	md           metadata
 	options      dialer.Options
@@ -64,6 +66,9 @@ func (d *kcpDialer) Dial(ctx context.Context, addr string, opts ...dialer.DialOp
 
 	d.sessionMutex.Lock()
 	defer d.sessionMutex.Unlock()
+	if d.retired {
+		return nil, net.ErrClosed
+	}
 
 	session, ok := d.sessions[addr]
 	if session != nil && session.IsClosed() {
@@ -171,3 +176,36 @@ func (d *kcpDialer) initSession(ctx context.Context, addr net.Addr, conn net.Pac
 func (d *kcpDialer) Multiplex() bool {
 	return true
 }
+
+// Retire drains existing streams and closes their backing sessions once idle.
+func (d *kcpDialer) Retire() {
+	for _, session := range d.detachSessions() {
+		sessionretire.Gracefully(session)
+	}
+}
+
+// Close immediately releases all cached multiplex sessions.
+func (d *kcpDialer) Close() error {
+	var errs []error
+	for _, session := range d.detachSessions() {
+		errs = append(errs, session.Close())
+	}
+	return errors.Join(errs...)
+}
+
+func (d *kcpDialer) detachSessions() []*muxSession {
+	if d == nil {
+		return nil
+	}
+	d.sessionMutex.Lock()
+	d.retired = true
+	sessions := make([]*muxSession, 0, len(d.sessions))
+	for _, session := range d.sessions {
+		if session != nil {
+			sessions = append(sessions, session)
+		}
+	}
+	d.sessions = make(map[string]*muxSession)
+	d.sessionMutex.Unlock()
+	return sessions
+}

go-gost/x/dialer/kcp/dialer_test.go

@@ -0,0 +1,17 @@
+package kcp
+
+import (
+	"context"
+	"errors"
+	"net"
+	"testing"
+)
+
+func TestRetiredDialerRejectsNewConnections(t *testing.T) {
+	dialer := NewDialer().(*kcpDialer)
+	dialer.Retire()
+
+	if _, err := dialer.Dial(context.Background(), "127.0.0.1:1"); !errors.Is(err, net.ErrClosed) {
+		t.Fatalf("Dial error = %v, want net.ErrClosed", err)
+	}
+}