feat: support independent tcp4, tcp6, udp4, udp6 connectivity check

common/netutils/context_dialer.go

@@ -0,0 +1,39 @@
+/*
+ * SPDX-License-Identifier: AGPL-3.0-only
+ * Copyright (c) since 2023, mzz2017 <mzz@tuta.io>
+ */
+
+package netutils
+
+import (
+	"context"
+	"golang.org/x/net/proxy"
+	"net"
+)
+
+type ContextDialer struct {
+	Dialer proxy.Dialer
+}
+
+func (d *ContextDialer) DialContext(ctx context.Context, network, addr string) (c net.Conn, err error) {
+	var done = make(chan struct{})
+	go func() {
+		c, err = d.Dialer.Dial(network, addr)
+		if err != nil {
+			close(done)
+			return
+		}
+		select {
+		case <-ctx.Done():
+			_ = c.Close()
+		default:
+			close(done)
+		}
+	}()
+	select {
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	case <-done:
+		return c, err
+	}
+}