Add resolver for outbound dialer

common/dialer/detour.go

@@ -0,0 +1,62 @@
+package dialer
+
+import (
+	"context"
+	"net"
+	"sync"
+
+	E "github.com/sagernet/sing/common/exceptions"
+	M "github.com/sagernet/sing/common/metadata"
+	N "github.com/sagernet/sing/common/network"
+
+	"github.com/sagernet/sing-box/adapter"
+)
+
+type DetourDialer struct {
+	router   adapter.Router
+	detour   string
+	dialer   N.Dialer
+	initOnce sync.Once
+	initErr  error
+}
+
+func NewDetour(router adapter.Router, detour string) N.Dialer {
+	return &DetourDialer{router: router, detour: detour}
+}
+
+func (d *DetourDialer) Start() error {
+	_, err := d.Dialer()
+	return err
+}
+
+func (d *DetourDialer) Dialer() (N.Dialer, error) {
+	d.initOnce.Do(func() {
+		var loaded bool
+		d.dialer, loaded = d.router.Outbound(d.detour)
+		if !loaded {
+			d.initErr = E.New("outbound detour not found: ", d.detour)
+		}
+	})
+	return d.dialer, d.initErr
+}
+
+func (d *DetourDialer) DialContext(ctx context.Context, network string, destination M.Socksaddr) (net.Conn, error) {
+	dialer, err := d.Dialer()
+	if err != nil {
+		return nil, err
+	}
+	return dialer.DialContext(ctx, network, destination)
+}
+
+func (d *DetourDialer) ListenPacket(ctx context.Context, destination M.Socksaddr) (net.PacketConn, error) {
+	dialer, err := d.Dialer()
+	if err != nil {
+		return nil, err
+	}
+	return dialer.ListenPacket(ctx, destination)
+}
+
+func (d *DetourDialer) Upstream() any {
+	detour, _ := d.Dialer()
+	return detour
+}