Add resolver for outbound dialer

adapter/inbound.go

@@ -1,6 +1,8 @@
 package adapter
 
 import (
+	"context"
+
 	M "github.com/sagernet/sing/common/metadata"
 )
 
@@ -17,6 +19,7 @@ type InboundContext struct {
 	Destination M.Socksaddr
 	Domain      string
 	Protocol    string
+	Outbound    string
 
 	// cache
 
@@ -26,3 +29,26 @@ type InboundContext struct {
 	SourceGeoIPCode string
 	GeoIPCode       string
 }
+
+type inboundContextKey struct{}
+
+func WithContext(ctx context.Context, inboundContext *InboundContext) context.Context {
+	return context.WithValue(ctx, (*inboundContextKey)(nil), inboundContext)
+}
+
+func ContextFrom(ctx context.Context) *InboundContext {
+	metadata := ctx.Value((*inboundContextKey)(nil))
+	if metadata == nil {
+		return nil
+	}
+	return metadata.(*InboundContext)
+}
+
+func AppendContext(ctx context.Context) (context.Context, *InboundContext) {
+	metadata := ContextFrom(ctx)
+	if metadata != nil {
+		return ctx, metadata
+	}
+	metadata = new(InboundContext)
+	return WithContext(ctx, metadata), nil
+}