Feature: add default-nameserver and outbound interface

component/dialer/dialer.go

@@ -2,7 +2,10 @@ package dialer
 
 import (
 	"context"
+	"errors"
 	"net"
+
+	"github.com/Dreamacro/clash/component/resolver"
 )
 
 func Dialer() *net.Dialer {
@@ -28,11 +31,124 @@ func Dial(network, address string) (net.Conn, error) {
 }
 
 func DialContext(ctx context.Context, network, address string) (net.Conn, error) {
-	dailer := Dialer()
-	return dailer.DialContext(ctx, network, address)
+	switch network {
+	case "tcp4", "tcp6", "udp4", "udp6":
+		host, port, err := net.SplitHostPort(address)
+		if err != nil {
+			return nil, err
+		}
+
+		dialer := Dialer()
+
+		var ip net.IP
+		switch network {
+		case "tcp4", "udp4":
+			ip, err = resolver.ResolveIPv4(host)
+		default:
+			ip, err = resolver.ResolveIPv6(host)
+		}
+
+		if err != nil {
+			return nil, err
+		}
+
+		if DialHook != nil {
+			DialHook(dialer, network, ip)
+		}
+		return dialer.DialContext(ctx, network, net.JoinHostPort(ip.String(), port))
+	case "tcp", "udp":
+		return dualStackDailContext(ctx, network, address)
+	default:
+		return nil, errors.New("network invalid")
+	}
 }
 
 func ListenPacket(network, address string) (net.PacketConn, error) {
 	lc := ListenConfig()
+
+	if ListenPacketHook != nil && address == "" {
+		ip := ListenPacketHook()
+		if ip != nil {
+			address = net.JoinHostPort(ip.String(), "0")
+		}
+	}
 	return lc.ListenPacket(context.Background(), network, address)
 }
+
+func dualStackDailContext(ctx context.Context, network, address string) (net.Conn, error) {
+	host, port, err := net.SplitHostPort(address)
+	if err != nil {
+		return nil, err
+	}
+
+	returned := make(chan struct{})
+	defer close(returned)
+
+	type dialResult struct {
+		net.Conn
+		error
+		resolved bool
+		ipv6     bool
+		done     bool
+	}
+	results := make(chan dialResult)
+	var primary, fallback dialResult
+
+	startRacer := func(ctx context.Context, network, host string, ipv6 bool) {
+		dialer := Dialer()
+		result := dialResult{ipv6: ipv6, done: true}
+		defer func() {
+			select {
+			case results <- result:
+			case <-returned:
+				if result.Conn != nil {
+					result.Conn.Close()
+				}
+			}
+		}()
+
+		var ip net.IP
+		if ipv6 {
+			ip, result.error = resolver.ResolveIPv6(host)
+		} else {
+			ip, result.error = resolver.ResolveIPv4(host)
+		}
+		if result.error != nil {
+			return
+		}
+		result.resolved = true
+
+		if DialHook != nil {
+			DialHook(dialer, network, ip)
+		}
+		result.Conn, result.error = dialer.DialContext(ctx, network, net.JoinHostPort(ip.String(), port))
+	}
+
+	go startRacer(ctx, network+"4", host, false)
+	go startRacer(ctx, network+"6", host, true)
+
+	for {
+		select {
+		case res := <-results:
+			if res.error == nil {
+				return res.Conn, nil
+			}
+
+			if !res.ipv6 {
+				primary = res
+			} else {
+				fallback = res
+			}
+
+			if primary.done && fallback.done {
+				if primary.resolved {
+					return nil, primary.error
+				} else if fallback.resolved {
+					return nil, fallback.error
+				} else {
+					return nil, primary.error
+				}
+			}
+		}
+	}
+}