Feature: add dhcp type dns client (#1509)

adapter/outbound/direct.go

@@ -24,7 +24,7 @@ func (d *Direct) DialContext(ctx context.Context, metadata *C.Metadata) (C.Conn,
 
 // DialUDP implements C.ProxyAdapter
 func (d *Direct) DialUDP(metadata *C.Metadata) (C.PacketConn, error) {
-	pc, err := dialer.ListenPacket("udp", "")
+	pc, err := dialer.ListenPacket(context.Background(), "udp", "")
 	if err != nil {
 		return nil, err
 	}

adapter/outbound/shadowsocks.go

@@ -89,7 +89,7 @@ func (ss *ShadowSocks) DialContext(ctx context.Context, metadata *C.Metadata) (_
 
 // DialUDP implements C.ProxyAdapter
 func (ss *ShadowSocks) DialUDP(metadata *C.Metadata) (C.PacketConn, error) {
-	pc, err := dialer.ListenPacket("udp", "")
+	pc, err := dialer.ListenPacket(context.Background(), "udp", "")
 	if err != nil {
 		return nil, err
 	}

adapter/outbound/shadowsocksr.go

@@ -74,7 +74,7 @@ func (ssr *ShadowSocksR) DialContext(ctx context.Context, metadata *C.Metadata)
 
 // DialUDP implements C.ProxyAdapter
 func (ssr *ShadowSocksR) DialUDP(metadata *C.Metadata) (C.PacketConn, error) {
-	pc, err := dialer.ListenPacket("udp", "")
+	pc, err := dialer.ListenPacket(context.Background(), "udp", "")
 	if err != nil {
 		return nil, err
 	}

adapter/outbound/socks5.go

@@ -110,7 +110,7 @@ func (ss *Socks5) DialUDP(metadata *C.Metadata) (_ C.PacketConn, err error) {
 		return
 	}
 
-	pc, err := dialer.ListenPacket("udp", "")
+	pc, err := dialer.ListenPacket(context.Background(), "udp", "")
 	if err != nil {
 		return
 	}

adapter/provider/vehicle.go

@@ -3,6 +3,7 @@ package provider
 import (
 	"context"
 	"io/ioutil"
+	"net"
 	"net/http"
 	"net/url"
 	"time"
@@ -71,7 +72,9 @@ func (h *HTTPVehicle) Read() ([]byte, error) {
 		IdleConnTimeout:       90 * time.Second,
 		TLSHandshakeTimeout:   10 * time.Second,
 		ExpectContinueTimeout: 1 * time.Second,
-		DialContext:           dialer.DialContext,
+		DialContext: func(ctx context.Context, network, address string) (net.Conn, error) {
+			return dialer.DialContext(ctx, network, address)
+		},
 	}
 
 	client := http.Client{Transport: transport}

component/dhcp/conn.go

@@ -0,0 +1,18 @@
+package dhcp
+
+import (
+	"context"
+	"net"
+	"runtime"
+
+	"github.com/Dreamacro/clash/component/dialer"
+)
+
+func ListenDHCPClient(ctx context.Context, ifaceName string) (net.PacketConn, error) {
+	listenAddr := "0.0.0.0:68"
+	if runtime.GOOS == "linux" || runtime.GOOS == "android" {
+		listenAddr = "255.255.255.255:68"
+	}
+
+	return dialer.ListenPacket(ctx, "udp4", listenAddr, dialer.WithInterface(ifaceName), dialer.WithAddrReuse(true))
+}

component/dhcp/dhcp.go

@@ -0,0 +1,94 @@
+package dhcp
+
+import (
+	"context"
+	"errors"
+	"math/rand"
+	"net"
+
+	"github.com/insomniacslk/dhcp/dhcpv4"
+)
+
+var (
+	ErrNotResponding = errors.New("DHCP not responding")
+	ErrNotFound      = errors.New("DNS option not found")
+)
+
+func ResolveDNSFromDHCP(context context.Context, ifaceName string) ([]net.IP, error) {
+	conn, err := ListenDHCPClient(context, ifaceName)
+	if err != nil {
+		return nil, err
+	}
+	defer conn.Close()
+
+	result := make(chan []net.IP, 1)
+
+	discovery, err := dhcpv4.NewDiscovery(randomHardware(), dhcpv4.WithBroadcast(true), dhcpv4.WithRequestedOptions(dhcpv4.OptionDomainNameServer))
+	if err != nil {
+		return nil, err
+	}
+
+	go receiveOffer(conn, discovery.TransactionID, result)
+
+	_, err = conn.WriteTo(discovery.ToBytes(), &net.UDPAddr{IP: net.IPv4bcast, Port: 67})
+	if err != nil {
+		return nil, err
+	}
+
+	select {
+	case r, ok := <-result:
+		if !ok {
+			return nil, ErrNotFound
+		}
+		return r, nil
+	case <-context.Done():
+		return nil, ErrNotResponding
+	}
+}
+
+func receiveOffer(conn net.PacketConn, id dhcpv4.TransactionID, result chan<- []net.IP) {
+	defer close(result)
+
+	buf := make([]byte, dhcpv4.MaxMessageSize)
+
+	for {
+		n, _, err := conn.ReadFrom(buf)
+		if err != nil {
+			return
+		}
+
+		pkt, err := dhcpv4.FromBytes(buf[:n])
+		if err != nil {
+			continue
+		}
+
+		if pkt.MessageType() != dhcpv4.MessageTypeOffer {
+			continue
+		}
+
+		if pkt.TransactionID != id {
+			continue
+		}
+
+		dns := pkt.DNS()
+		if len(dns) == 0 {
+			return
+		}
+
+		result <- dns
+
+		return
+	}
+}
+
+func randomHardware() net.HardwareAddr {
+	addr := make(net.HardwareAddr, 6)
+
+	addr[0] = 0xff
+
+	for i := 1; i < len(addr); i++ {
+		addr[i] = byte(rand.Intn(254) + 1)
+	}
+
+	return addr
+}

component/dialer/bind_darwin.go

@@ -3,51 +3,57 @@ package dialer
 import (
 	"net"
 	"syscall"
+
+	"golang.org/x/sys/unix"
+
+	"github.com/Dreamacro/clash/component/iface"
 )
 
 type controlFn = func(network, address string, c syscall.RawConn) error
 
-func bindControl(ifaceIdx int) controlFn {
-	return func(network, address string, c syscall.RawConn) error {
+func bindControl(ifaceIdx int, chain controlFn) controlFn {
+	return func(network, address string, c syscall.RawConn) (err error) {
+		defer func() {
+			if err == nil && chain != nil {
+				err = chain(network, address, c)
+			}
+		}()
+
 		ipStr, _, err := net.SplitHostPort(address)
 		if err == nil {
 			ip := net.ParseIP(ipStr)
 			if ip != nil && !ip.IsGlobalUnicast() {
-				return nil
+				return
 			}
 		}
 
 		return c.Control(func(fd uintptr) {
 			switch network {
 			case "tcp4", "udp4":
-				syscall.SetsockoptInt(int(fd), syscall.IPPROTO_IP, syscall.IP_BOUND_IF, ifaceIdx)
+				unix.SetsockoptInt(int(fd), unix.IPPROTO_IP, unix.IP_BOUND_IF, ifaceIdx)
 			case "tcp6", "udp6":
-				syscall.SetsockoptInt(int(fd), syscall.IPPROTO_IPV6, syscall.IPV6_BOUND_IF, ifaceIdx)
+				unix.SetsockoptInt(int(fd), unix.IPPROTO_IPV6, unix.IPV6_BOUND_IF, ifaceIdx)
 			}
 		})
 	}
 }
 
-func bindIfaceToDialer(dialer *net.Dialer, ifaceName string) error {
-	iface, err, _ := ifaceSingle.Do(func() (interface{}, error) {
-		return net.InterfaceByName(ifaceName)
-	})
+func bindIfaceToDialer(ifaceName string, dialer *net.Dialer, _ string, _ net.IP) error {
+	ifaceObj, err := iface.ResolveInterface(ifaceName)
 	if err != nil {
 		return err
 	}
 
-	dialer.Control = bindControl(iface.(*net.Interface).Index)
+	dialer.Control = bindControl(ifaceObj.Index, dialer.Control)
 	return nil
 }
 
-func bindIfaceToListenConfig(lc *net.ListenConfig, ifaceName string) error {
-	iface, err, _ := ifaceSingle.Do(func() (interface{}, error) {
-		return net.InterfaceByName(ifaceName)
-	})
+func bindIfaceToListenConfig(ifaceName string, lc *net.ListenConfig, _, address string) (string, error) {
+	ifaceObj, err := iface.ResolveInterface(ifaceName)
 	if err != nil {
-		return err
+		return "", err
 	}
 
-	lc.Control = bindControl(iface.(*net.Interface).Index)
-	return nil
+	lc.Control = bindControl(ifaceObj.Index, lc.Control)
+	return address, nil
 }