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
+	}
+}

common/netutils/dns.go

@@ -0,0 +1,102 @@
+/*
+ * SPDX-License-Identifier: AGPL-3.0-only
+ * Copyright (c) since 2023, mzz2017 <mzz@tuta.io>
+ */
+
+package netutils
+
+import (
+	"context"
+	"fmt"
+	"github.com/mzz2017/softwind/pool"
+	"golang.org/x/net/dns/dnsmessage"
+	"golang.org/x/net/proxy"
+	"net/netip"
+	"strings"
+)
+
+func ResolveNetip(ctx context.Context, d proxy.Dialer, dns netip.AddrPort, host string, typ dnsmessage.Type) (addrs []netip.Addr, err error) {
+	if addr, err := netip.ParseAddr(host); err == nil {
+		if (addr.Is4() || addr.Is4In6()) && typ == dnsmessage.TypeA {
+			return []netip.Addr{addr}, nil
+		} else if addr.Is6() && typ == dnsmessage.TypeAAAA {
+			return []netip.Addr{addr}, nil
+		}
+		return nil, nil
+	}
+	switch typ {
+	case dnsmessage.TypeA, dnsmessage.TypeAAAA:
+	default:
+		return nil, fmt.Errorf("only support to lookup A/AAAA record")
+	}
+	// Build DNS req.
+	builder := dnsmessage.NewBuilder(nil, dnsmessage.Header{})
+	if err = builder.StartQuestions(); err != nil {
+		return nil, err
+	}
+	fqdn := host
+	if !strings.HasSuffix(fqdn, ".") {
+		fqdn += "."
+	}
+	if err = builder.Question(dnsmessage.Question{
+		Name:  dnsmessage.MustNewName(fqdn),
+		Type:  typ,
+		Class: dnsmessage.ClassINET,
+	}); err != nil {
+		return nil, err
+	}
+	b, err := builder.Finish()
+	if err != nil {
+		return nil, err
+	}
+
+	// Dial and write.
+	cd := ContextDialer{d}
+	c, err := cd.DialContext(ctx, "udp", dns.String())
+	if err != nil {
+		return nil, err
+	}
+	defer c.Close()
+	_, err = c.Write(b)
+	if err != nil {
+		return nil, err
+	}
+	ch := make(chan error, 1)
+	go func() {
+		buf := pool.Get(512)
+		n, err := c.Read(buf)
+		if err != nil {
+			ch <- err
+			return
+		}
+		// Resolve DNS response and extract A/AAAA record.
+		var msg dnsmessage.Message
+		if err = msg.Unpack(buf[:n]); err != nil {
+			ch <- err
+			return
+		}
+		for _, ans := range msg.Answers {
+			if ans.Header.Type != typ {
+				continue
+			}
+			switch typ {
+			case dnsmessage.TypeA:
+				a := ans.Body.(*dnsmessage.AResource)
+				addrs = append(addrs, netip.AddrFrom4(a.A))
+			case dnsmessage.TypeAAAA:
+				a := ans.Body.(*dnsmessage.AAAAResource)
+				addrs = append(addrs, netip.AddrFrom16(a.AAAA))
+			}
+		}
+		ch <- nil
+	}()
+	select {
+	case <-ctx.Done():
+		return nil, fmt.Errorf("timeout")
+	case err = <-ch:
+		if err != nil {
+			return nil, err
+		}
+		return addrs, nil
+	}
+}

common/netutils/url.go

@@ -0,0 +1,25 @@
+/*
+ * SPDX-License-Identifier: AGPL-3.0-only
+ * Copyright (c) since 2023, mzz2017 <mzz@tuta.io>
+ */
+
+package netutils
+
+import "net/url"
+
+type URL struct {
+	*url.URL
+}
+
+func (u *URL) Port() string {
+	if port := u.URL.Port(); port != "" {
+		return port
+	}
+	switch u.Scheme {
+	case "http":
+		return "80"
+	case "https":
+		return "443"
+	}
+	return ""
+}