fix/optimize: reroute if necessary and add opendns as bootstrap dns

common/netutils/dns.go

@@ -28,6 +28,8 @@ var (
 	systemDnsNextUpdateAfter time.Time
 
 	BadDnsAnsError = fmt.Errorf("bad dns answer")
+
+	BootstrapDns = netip.MustParseAddrPort("208.67.222.222:5353")
 )
 
 func TryUpdateSystemDns() (err error) {
@@ -61,7 +63,17 @@ func tryUpdateSystemDns() (err error) {
 		err = fmt.Errorf("no valid dns server in /etc/resolv.conf")
 		return err
 	}
-	systemDns = netip.MustParseAddrPort(dnsConf.servers[0])
+	systemDns = netip.AddrPort{}
+	for _, s := range dnsConf.servers {
+		ipPort := netip.MustParseAddrPort(s)
+		if !ipPort.Addr().IsLoopback() {
+			systemDns = ipPort
+			break
+		}
+	}
+	if !systemDns.IsValid() {
+		systemDns = BootstrapDns
+	}
 	return nil
 }
 

component/dns/upstream.go

@@ -92,7 +92,7 @@ func NewUpstream(ctx context.Context, upstream *url.URL) (up *Upstream, err erro
 		return nil, fmt.Errorf("failed to resolve dns_upstream: %w", err)
 	}
 	if !ip46.Ip4.IsValid() && !ip46.Ip6.IsValid() {
-		return nil, fmt.Errorf("dns_upstream has no record")
+		return nil, fmt.Errorf("dns_upstream %v has no record", upstream.String())
 	}
 
 	return &Upstream{

control/control_plane.go

@@ -491,8 +491,8 @@ func (c *ControlPlane) dnsUpstreamReadyCallback(dnsUpstream *dns.Upstream) (err
 	return nil
 }
 
-func (c *ControlPlane) ChooseDialTarget(outbound consts.OutboundIndex, dst netip.AddrPort, domain string) (dialTarget string, dialMode consts.DialMode) {
+func (c *ControlPlane) ChooseDialTarget(outbound consts.OutboundIndex, dst netip.AddrPort, domain string) (dialTarget string, shouldReroute bool) {
-	dialMode = consts.DialMode_Ip
+	dialMode := consts.DialMode_Ip
 
 	if !outbound.IsReserved() && domain != "" {
 		switch c.dialMode {
@@ -521,6 +521,9 @@ func (c *ControlPlane) ChooseDialTarget(outbound consts.OutboundIndex, dst netip
 							c.muRealDomainSet.Lock()
 							c.realDomainSet.AddString(domain)
 							c.muRealDomainSet.Unlock()
+
+							// Should use this domain to reroute
+							shouldReroute = true
 						}
 					}
 				}
@@ -553,7 +556,7 @@ func (c *ControlPlane) ChooseDialTarget(outbound consts.OutboundIndex, dst netip
 			"to":   dialTarget,
 		}).Debugln("Rewrite dial target to domain")
 	}
-	return dialTarget, dialMode
+	return dialTarget, shouldReroute
 }
 
 type Listener struct {
@@ -758,7 +761,7 @@ func (c *ControlPlane) chooseBestDnsDialer(
 			default:
 				return nil, fmt.Errorf("unexpected ipversion: %v", ver)
 			}
-			outboundIndex, mark, _, err := c.Route(req.realSrc, netip.AddrPortFrom(dAddr, dnsUpstream.Port), "", proto.ToL4ProtoType(), req.routingResult)
+			outboundIndex, mark, _, err := c.Route(req.realSrc, netip.AddrPortFrom(dAddr, dnsUpstream.Port), dnsUpstream.Hostname, proto.ToL4ProtoType(), req.routingResult)
 			if err != nil {
 				return nil, err
 			}

control/tcp.go

@@ -68,6 +68,11 @@ func (c *ControlPlane) handleConn(lConn net.Conn) (err error) {
 		outboundIndex = consts.OutboundControlPlaneRouting
 	}
 
+	dialTarget, shouldReroute := c.ChooseDialTarget(outboundIndex, dst, domain)
+	if shouldReroute {
+		outboundIndex = consts.OutboundControlPlaneRouting
+	}
+
 	switch outboundIndex {
 	case consts.OutboundDirect:
 	case consts.OutboundControlPlaneRouting:
@@ -82,6 +87,8 @@ func (c *ControlPlane) handleConn(lConn net.Conn) (err error) {
 				outboundIndex.String(),
 			)
 		}
+		// Reset dialTarget.
+		dialTarget, _ = c.ChooseDialTarget(outboundIndex, dst, domain)
 	default:
 	}
 	// TODO: Set-up ip to domain mapping and show domain if possible.
@@ -99,7 +106,6 @@ func (c *ControlPlane) handleConn(lConn net.Conn) (err error) {
 		return fmt.Errorf("failed to select dialer from group %v (%v): %w", outbound.Name, networkType.String(), err)
 	}
 
-	dialTarget, _ := c.ChooseDialTarget(outboundIndex, dst, domain)
 	if c.log.IsLevelEnabled(logrus.InfoLevel) {
 		c.log.WithFields(logrus.Fields{
 			"network":  networkType.String(),

control/udp.go

@@ -143,6 +143,11 @@ func (c *ControlPlane) handlePkt(lConn *net.UDPConn, data []byte, src, pktDst, r
 		outboundIndex = consts.OutboundControlPlaneRouting
 	}
 
+	dialTarget, shouldReroute := c.ChooseDialTarget(outboundIndex, realDst, domain)
+	if shouldReroute {
+		outboundIndex = consts.OutboundControlPlaneRouting
+	}
+
 	if routingResult.Must > 0 {
 		isDns = false // Regard as plain traffic.
 	}
@@ -164,6 +169,8 @@ func (c *ControlPlane) handlePkt(lConn *net.UDPConn, data []byte, src, pktDst, r
 				outboundIndex.String(),
 			)
 		}
+		// Reset dialTarget.
+		dialTarget, _ = c.ChooseDialTarget(outboundIndex, realDst, domain)
 	default:
 	}
 	if isDns {
@@ -197,7 +204,6 @@ func (c *ControlPlane) handlePkt(lConn *net.UDPConn, data []byte, src, pktDst, r
 	// TODO: Rewritten domain should not use full-cone (such as VMess Packet Addr).
 	// 		Maybe we should set up a mapping for UDP: Dialer + Target Domain => Remote Resolved IP.
 	//		However, games may not use QUIC for communication, thus we cannot use domain to dial, which is fine.
-	dialTarget, _ := c.ChooseDialTarget(outboundIndex, realDst, domain)
 
 	// Get udp endpoint.
 	var ue *UdpEndpoint