Add Fake DNS support (#309)

Co-authored-by: Xiaokang Wang <xiaokangwang@outlook.com>
Co-authored-by: loyalsoldier <10487845+Loyalsoldier@users.noreply.github.com>
Co-authored-by: kslr <kslrwang@gmail.com>

common/cache/lru.go

@@ -0,0 +1,85 @@
+package cache
+
+import (
+	"container/list"
+	sync "sync"
+)
+
+// Lru simple, fast lru cache implementation
+type Lru interface {
+	Get(key interface{}) (value interface{}, ok bool)
+	GetKeyFromValue(value interface{}) (key interface{}, ok bool)
+	PeekKeyFromValue(value interface{}) (key interface{}, ok bool) // Peek means check but NOT bring to top
+	Put(key, value interface{})
+}
+
+type lru struct {
+	capacity         int
+	doubleLinkedlist *list.List
+	keyToElement     *sync.Map
+	valueToElement   *sync.Map
+	mu               *sync.Mutex
+}
+
+type lruElement struct {
+	key   interface{}
+	value interface{}
+}
+
+// NewLru init a lru cache
+func NewLru(cap int) Lru {
+	return lru{
+		capacity:         cap,
+		doubleLinkedlist: list.New(),
+		keyToElement:     new(sync.Map),
+		valueToElement:   new(sync.Map),
+		mu:               new(sync.Mutex),
+	}
+}
+
+func (l lru) Get(key interface{}) (value interface{}, ok bool) {
+	if v, ok := l.keyToElement.Load(key); ok {
+		element := v.(*list.Element)
+		l.doubleLinkedlist.MoveBefore(element, l.doubleLinkedlist.Front())
+		return element.Value.(lruElement).value, true
+	}
+	return nil, false
+}
+
+func (l lru) GetKeyFromValue(value interface{}) (key interface{}, ok bool) {
+	if k, ok := l.valueToElement.Load(value); ok {
+		element := k.(*list.Element)
+		l.doubleLinkedlist.MoveBefore(element, l.doubleLinkedlist.Front())
+		return element.Value.(lruElement).key, true
+	}
+	return nil, false
+}
+
+func (l lru) PeekKeyFromValue(value interface{}) (key interface{}, ok bool) {
+	if k, ok := l.valueToElement.Load(value); ok {
+		element := k.(*list.Element)
+		return element.Value.(lruElement).key, true
+	}
+	return nil, false
+}
+
+func (l lru) Put(key, value interface{}) {
+	e := lruElement{key, value}
+	if v, ok := l.keyToElement.Load(key); ok {
+		element := v.(*list.Element)
+		element.Value = e
+		l.doubleLinkedlist.MoveBefore(element, l.doubleLinkedlist.Front())
+	} else {
+		l.mu.Lock()
+		element := l.doubleLinkedlist.PushFront(e)
+		l.keyToElement.Store(key, element)
+		l.valueToElement.Store(value, element)
+		if l.doubleLinkedlist.Len() > l.capacity {
+			toBeRemove := l.doubleLinkedlist.Back()
+			l.doubleLinkedlist.Remove(toBeRemove)
+			l.keyToElement.Delete(toBeRemove.Value.(lruElement).key)
+			l.valueToElement.Delete(toBeRemove.Value.(lruElement).value)
+		}
+		l.mu.Unlock()
+	}
+}

common/cache/lru_test.go

@@ -0,0 +1,86 @@
+package cache_test
+
+import (
+	"testing"
+
+	. "github.com/xtls/xray-core/common/cache"
+)
+
+func TestLruReplaceValue(t *testing.T) {
+	lru := NewLru(2)
+	lru.Put(2, 6)
+	lru.Put(1, 5)
+	lru.Put(1, 2)
+	v, _ := lru.Get(1)
+	if v != 2 {
+		t.Error("should get 2", v)
+	}
+	v, _ = lru.Get(2)
+	if v != 6 {
+		t.Error("should get 6", v)
+	}
+}
+
+func TestLruRemoveOld(t *testing.T) {
+	lru := NewLru(2)
+	v, ok := lru.Get(2)
+	if ok {
+		t.Error("should get nil", v)
+	}
+	lru.Put(1, 1)
+	lru.Put(2, 2)
+	v, _ = lru.Get(1)
+	if v != 1 {
+		t.Error("should get 1", v)
+	}
+	lru.Put(3, 3)
+	v, ok = lru.Get(2)
+	if ok {
+		t.Error("should get nil", v)
+	}
+	lru.Put(4, 4)
+	v, ok = lru.Get(1)
+	if ok {
+		t.Error("should get nil", v)
+	}
+	v, _ = lru.Get(3)
+	if v != 3 {
+		t.Error("should get 3", v)
+	}
+	v, _ = lru.Get(4)
+	if v != 4 {
+		t.Error("should get 4", v)
+	}
+}
+
+func TestGetKeyFromValue(t *testing.T) {
+	lru := NewLru(2)
+	lru.Put(3, 3)
+	lru.Put(2, 2)
+	lru.GetKeyFromValue(3)
+	lru.Put(1, 1)
+	v, ok := lru.GetKeyFromValue(2)
+	if ok {
+		t.Error("should get nil", v)
+	}
+	v, _ = lru.GetKeyFromValue(3)
+	if v != 3 {
+		t.Error("should get 3", v)
+	}
+}
+
+func TestPeekKeyFromValue(t *testing.T) {
+	lru := NewLru(2)
+	lru.Put(3, 3)
+	lru.Put(2, 2)
+	lru.PeekKeyFromValue(3)
+	lru.Put(1, 1)
+	v, ok := lru.PeekKeyFromValue(3)
+	if ok {
+		t.Error("should get nil", v)
+	}
+	v, _ = lru.PeekKeyFromValue(2)
+	if v != 2 {
+		t.Error("should get 2", v)
+	}
+}