feat: resolve peer endpoint with dot

conf.go

@@ -1,69 +1,147 @@
 package main
 
 import (
+	"context"
+	"crypto/tls"
 	"encoding/base64"
 	"encoding/hex"
 	"fmt"
+	"math/rand"
 	"net"
 	"time"
 
 	"golang.zx2c4.com/wireguard/device"
 )
 
+const (
+	resolvePeerInterval = time.Second * 10
+	keepaliveInterval   = "10"
+)
+
+type peer struct {
+	dialer *net.Dialer
+
+	pubKey    string
+	keepalive bool
+
+	addr   string
+	ipPort string
+}
+
+func newPeerEndpoint(opts options) (*peer, error) {
+	pubKey, err := base64.StdEncoding.DecodeString(opts.PeerKey)
+	if err != nil {
+		return nil, fmt.Errorf("parse peer key: %w", err)
+	}
+
+	p := &peer{
+		dialer: &net.Dialer{
+			Resolver: &net.Resolver{
+				PreferGo: true,
+				Dial: func(ctx context.Context, network, address string) (net.Conn, error) {
+					if len(opts.DNS) > 0 {
+						host := opts.DNS[rand.Intn(len(opts.DNS))]
+						port := "53"
+						if opts.DoT != "" {
+							port = opts.DoT
+						}
+						address = net.JoinHostPort(host, port)
+					}
+					logger.Verbosef("Using %s to resolve peer endpoint", address)
+
+					if opts.DoT == "" {
+						var d net.Dialer
+						return d.DialContext(ctx, network, address)
+					}
+					d := tls.Dialer{
+						Config: &tls.Config{
+							InsecureSkipVerify: true,
+						},
+					}
+					return d.DialContext(ctx, "tcp", address)
+				},
+			},
+		},
+		pubKey:    hex.EncodeToString(pubKey),
+		keepalive: opts.ExitMode == "local",
+		addr:      opts.PeerEndpoint,
+	}
+	p.ipPort, err = p.resolveAddr()
+	return p, err
+}
+
+func (p *peer) initConf() string {
+	conf := "public_key=" + p.pubKey + "\n"
+	conf += "endpoint=" + p.ipPort + "\n"
+	conf += "allowed_ip=0.0.0.0/0\n"
+	conf += "allowed_ip=::/0\n"
+
+	if p.keepalive {
+		conf += "persistent_keepalive_interval=" + keepaliveInterval + "\n"
+	}
+
+	return conf
+}
+
+func (p *peer) updateConf() (string, bool) {
+	newIPPort, err := p.resolveAddr()
+	if err != nil {
+		logger.Verbosef("Resolve peer endpoint: %v", err)
+		return "", false
+	}
+	if p.ipPort == newIPPort {
+		return "", false
+	}
+	p.ipPort = newIPPort
+	logger.Verbosef("PeerEndpoint is changed to: %s", p.ipPort)
+
+	conf := "public_key=" + p.pubKey + "\n"
+	conf += "update_only=true\n"
+	conf += "endpoint=" + p.ipPort + "\n"
+	return conf, true
+}
+
+func (p *peer) resolveAddr() (string, error) {
+	c, err := p.dialer.Dial("udp", p.addr)
+	if err != nil {
+		return "", fmt.Errorf("dial %s: %w", p.addr, err)
+	}
+	defer c.Close()
+	return c.RemoteAddr().String(), nil
+}
+
 func ipcSet(dev *device.Device, opts options) error {
 	privateKey, err := base64.StdEncoding.DecodeString(opts.PrivateKey)
 	if err != nil {
 		return fmt.Errorf("parse private key: %w", err)
 	}
-	peerKey, err := base64.StdEncoding.DecodeString(opts.PeerKey)
-	if err != nil {
-		return fmt.Errorf("parse peer key: %w", err)
-	}
 	conf := "private_key=" + hex.EncodeToString(privateKey) + "\n"
-	conf += "public_key=" + hex.EncodeToString(peerKey) + "\n"
 
-	peerAddr, err := net.ResolveUDPAddr("udp", opts.PeerEndpoint)
+	peer, err := newPeerEndpoint(opts)
 	if err != nil {
-		return fmt.Errorf("resolve peer endpoint: %w", err)
-	}
-
-	conf += "endpoint=" + peerAddr.String() + "\n"
-	conf += "allowed_ip=0.0.0.0/0\n"
-	conf += "allowed_ip=::/0\n"
-
-	if opts.ExitMode == "local" {
-		conf += "persistent_keepalive_interval=10\n"
+		return err
 	}
+	conf += peer.initConf()
 
 	if err := dev.IpcSet(conf); err != nil {
 		return fmt.Errorf("set device config: %w", err)
 	}
 
-	if peerAddr.String() != opts.PeerEndpoint {
-		go refreshEndpoint(dev, peerKey, peerAddr.String(), opts.PeerEndpoint)
+	if peer.addr != peer.ipPort {
+		go func() {
+			c := time.Tick(resolvePeerInterval)
+
+			for range c {
+				conf, needUpdate := peer.updateConf()
+				if !needUpdate {
+					continue
+				}
+
+				if err := dev.IpcSet(conf); err != nil {
+					logger.Errorf("Set device config: %v", err)
+				}
+			}
+		}()
 	}
 	return nil
 }
-
-func refreshEndpoint(dev *device.Device, peerKey []byte, currentPeerAddr, peerEndpoint string) {
-	c := time.Tick(10 * time.Second)
-
-	for range c {
-		addr, err := net.ResolveUDPAddr("udp", peerEndpoint)
-		if err != nil {
-			logger.Errorf("Resolve peer endpoint: %v", err)
-			continue
-		}
-		if currentPeerAddr == addr.String() {
-			continue
-		}
-		currentPeerAddr = addr.String()
-		logger.Verbosef("Endpoint is changed to: %s", addr)
-		conf := "public_key=" + hex.EncodeToString(peerKey) + "\n"
-		conf += "update_only=true\n"
-		conf += "endpoint=" + addr.String() + "\n"
-		if err := dev.IpcSet(conf); err != nil {
-			logger.Errorf("Set device config: %v", err)
-		}
-	}
-}