chore: cleanup dns client code

dns/client.go

@@ -16,53 +16,49 @@ import (
 )
 
 type client struct {
-	*D.Client
-	port   string
-	host   string
-	dialer *dnsDialer
-	addr   string
+	port           string
+	host           string
+	dialer         *dnsDialer
+	schema         string
+	skipCertVerify bool
 }
 
 var _ dnsClient = (*client)(nil)
 
 // Address implements dnsClient
 func (c *client) Address() string {
-	if len(c.addr) != 0 {
-		return c.addr
-	}
-	schema := "udp"
-	if strings.HasPrefix(c.Client.Net, "tcp") {
-		schema = "tcp"
-		if strings.HasSuffix(c.Client.Net, "tls") {
-			schema = "tls"
-		}
-	}
-
-	c.addr = fmt.Sprintf("%s://%s", schema, net.JoinHostPort(c.host, c.port))
-	return c.addr
+	return fmt.Sprintf("%s://%s", c.schema, net.JoinHostPort(c.host, c.port))
 }
 
 func (c *client) ExchangeContext(ctx context.Context, m *D.Msg) (*D.Msg, error) {
 	network := "udp"
-	if strings.HasPrefix(c.Client.Net, "tcp") {
+	if c.schema != "udp" {
 		network = "tcp"
 	}
 
-	tlsConfig, err := ca.GetTLSConfig(ca.Option{
-		TLSConfig: c.Client.TLSConfig,
-	})
-	if err != nil {
-		return nil, err
-	}
-
 	addr := net.JoinHostPort(c.host, c.port)
 	conn, err := c.dialer.DialContext(ctx, network, addr)
 	if err != nil {
 		return nil, err
 	}
-	defer func() {
-		_ = conn.Close()
-	}()
+	defer conn.Close()
+
+	if c.schema == "tls" {
+		tlsConfig, err := ca.GetTLSConfig(ca.Option{
+			TLSConfig: &tls.Config{
+				ServerName:         c.host,
+				InsecureSkipVerify: c.skipCertVerify,
+			},
+		})
+		if err != nil {
+			return nil, err
+		}
+		tlsConn := tls.Client(conn, tlsConfig)
+		if err := tlsConn.HandshakeContext(ctx); err != nil {
+			return nil, err
+		}
+		conn = tlsConn
+	}
 
 	// miekg/dns ExchangeContext doesn't respond to context cancel.
 	// this is a workaround
@@ -72,34 +68,30 @@ func (c *client) ExchangeContext(ctx context.Context, m *D.Msg) (*D.Msg, error)
 	}
 	ch := make(chan result, 1)
 	go func() {
-		if strings.HasSuffix(c.Client.Net, "tls") {
-			conn = tls.Client(conn, tlsConfig)
+		dClient := &D.Client{
+			UDPSize: 4096,
+			Timeout: 5 * time.Second,
 		}
-
 		dConn := &D.Conn{
-			Conn:         conn,
-			UDPSize:      c.Client.UDPSize,
-			TsigSecret:   c.Client.TsigSecret,
-			TsigProvider: c.Client.TsigProvider,
+			Conn:    conn,
+			UDPSize: dClient.UDPSize,
 		}
 
-		msg, _, err := c.Client.ExchangeWithConn(m, dConn)
+		msg, _, err := dClient.ExchangeWithConn(m, dConn)
 
 		// Resolvers MUST resend queries over TCP if they receive a truncated UDP response (with TC=1 set)!
 		if msg != nil && msg.Truncated && network == "udp" {
-			tcpClient := *c.Client // copy a client
-			tcpClient.Net = "tcp"
 			network = "tcp"
 			log.Debugln("[DNS] Truncated reply from %s:%s for %s over UDP, retrying over TCP", c.host, c.port, m.Question[0].String())
-			dConn.Conn, err = c.dialer.DialContext(ctx, network, addr)
+			var tcpConn net.Conn
+			tcpConn, err = c.dialer.DialContext(ctx, network, addr)
 			if err != nil {
 				ch <- result{msg, err}
 				return
 			}
-			defer func() {
-				_ = conn.Close()
-			}()
-			msg, _, err = tcpClient.ExchangeWithConn(m, dConn)
+			defer tcpConn.Close()
+			dConn.Conn = tcpConn
+			msg, _, err = dClient.ExchangeWithConn(m, dConn)
 		}
 
 		ch <- result{msg, err}
@@ -118,20 +110,19 @@ func (c *client) ResetConnection() {}
 func newClient(addr string, resolver *Resolver, netType string, params map[string]string, proxyAdapter C.ProxyAdapter, proxyName string) *client {
 	host, port, _ := net.SplitHostPort(addr)
 	c := &client{
-		Client: &D.Client{
-			Net: netType,
-			TLSConfig: &tls.Config{
-				ServerName: host,
-			},
-			UDPSize: 4096,
-			Timeout: 5 * time.Second,
-		},
 		port:   port,
 		host:   host,
 		dialer: newDNSDialer(resolver, proxyAdapter, proxyName),
+		schema: "udp",
+	}
+	if strings.HasPrefix(netType, "tcp") {
+		c.schema = "tcp"
+		if strings.HasSuffix(netType, "tls") {
+			c.schema = "tls"
+		}
 	}
 	if params["skip-cert-verify"] == "true" {
-		c.TLSConfig.InsecureSkipVerify = true
+		c.skipCertVerify = true
 	}
 	return c
 }