fix: sing内核删除用户逻辑不正确BUG

core/xray/app/dispatcher/default.go

@@ -45,8 +45,14 @@ func (r *cachedReader) Cache(b *buf.Buffer) {
 	if !mb.IsEmpty() {
 		r.cache, _ = buf.MergeMulti(r.cache, mb)
 	}
-	b.Clear()
-	rawBytes := b.Extend(buf.Size)
+	cacheLen := r.cache.Len()
+	if cacheLen <= b.Cap() {
+		b.Clear()
+	} else {
+		b.Release()
+		*b = *buf.NewWithSize(cacheLen)
+	}
+	rawBytes := b.Extend(cacheLen)
 	n := r.cache.Copy(rawBytes)
 	b.Resize(0, int32(n))
 	r.Unlock()
@@ -106,7 +112,7 @@ func init() {
 	common.Must(common.RegisterConfig((*Config)(nil), func(ctx context.Context, config interface{}) (interface{}, error) {
 		d := new(DefaultDispatcher)
 		if err := core.RequireFeatures(ctx, func(om outbound.Manager, router routing.Router, pm policy.Manager, sm stats.Manager, dc dns.Client) error {
-			core.RequireFeatures(ctx, func(fdns dns.FakeDNSEngine) {
+			core.OptionalFeatures(ctx, func(fdns dns.FakeDNSEngine) {
 				d.fdns = fdns
 			})
 			return d.Init(config.(*Config), om, router, pm, sm, dc)