fix: keep fake-ip allocation state when cloning the pool on reload (#3283)

component/fakeip/pool.go

@@ -88,7 +88,18 @@ func (p *Pool) IPNet() netip.Prefix {
 
 // CloneFrom clone cache from old pool
 func (p *Pool) CloneFrom(o *Pool) {
+	p.mux.Lock()
+	defer p.mux.Unlock()
+
+	o.mux.Lock()
+	defer o.mux.Unlock()
+
 	o.store.CloneTo(p.store)
+
+	// the allocation state only matches the cloned entries if both pools cover the same range
+	if o.first == p.first && o.last == p.last {
+		p.offset, p.cycle = o.offset, o.cycle
+	}
 }
 
 func (p *Pool) get(host string) netip.Addr {

component/fakeip/pool_test.go

@@ -212,6 +212,33 @@ func TestPool_Clone(t *testing.T) {
 	assert.True(t, lastExist)
 }
 
+func TestPool_CloneKeepsAllocationState(t *testing.T) {
+	ipnet := netip.MustParsePrefix("192.168.0.1/24")
+	pool, _ := New(Options{
+		IPNet: ipnet,
+		Size:  10,
+	})
+
+	foo := pool.Lookup("foo.com")
+	bar := pool.Lookup("bar.com")
+
+	newPool, _ := New(Options{
+		IPNet: ipnet,
+		Size:  10,
+	})
+	newPool.CloneFrom(pool)
+
+	// a fresh allocation must not overwrite the retained mappings
+	baz := newPool.Lookup("baz.com")
+	assert.NotEqual(t, foo, baz)
+	assert.NotEqual(t, bar, baz)
+	assert.Equal(t, foo, newPool.Lookup("foo.com"))
+	assert.Equal(t, bar, newPool.Lookup("bar.com"))
+	host, ok := newPool.LookBack(foo)
+	assert.True(t, ok)
+	assert.Equal(t, "foo.com", host)
+}
+
 func TestPool_Error(t *testing.T) {
 	ipnet := netip.MustParsePrefix("192.168.0.1/31")
 	_, err := New(Options{