Fix FakeIP metadata async save

Co-authored-by: Sway-Chan <nz8r488bbc@privaterelay.appleid.com>

experimental/cachefile/cache.go

@@ -38,21 +38,23 @@ var (
 var _ adapter.CacheFile = (*CacheFile)(nil)
 
 type CacheFile struct {
-	ctx               context.Context
-	path              string
-	cacheID           []byte
-	storeFakeIP       bool
-	storeRDRC         bool
-	rdrcTimeout       time.Duration
-	DB                *bbolt.DB
-	resetAccess       sync.Mutex
-	saveMetadataTimer *time.Timer
-	saveFakeIPAccess  sync.RWMutex
-	saveDomain        map[netip.Addr]string
-	saveAddress4      map[string]netip.Addr
-	saveAddress6      map[string]netip.Addr
-	saveRDRCAccess    sync.RWMutex
-	saveRDRC          map[saveRDRCCacheKey]bool
+	ctx                context.Context
+	path               string
+	cacheID            []byte
+	storeFakeIP        bool
+	storeRDRC          bool
+	rdrcTimeout        time.Duration
+	DB                 *bbolt.DB
+	resetAccess        sync.Mutex
+	saveMetadataAccess sync.Mutex
+	saveMetadata       *adapter.FakeIPMetadata
+	saveMetadataTimer  *time.Timer
+	saveFakeIPAccess   sync.RWMutex
+	saveDomain         map[netip.Addr]string
+	saveAddress4       map[string]netip.Addr
+	saveAddress6       map[string]netip.Addr
+	saveRDRCAccess     sync.RWMutex
+	saveRDRC           map[saveRDRCCacheKey]bool
 }
 
 type saveRDRCCacheKey struct {

experimental/cachefile/fakeip.go

@@ -59,9 +59,17 @@ func (c *CacheFile) FakeIPSaveMetadata(metadata *adapter.FakeIPMetadata) error {
 }
 
 func (c *CacheFile) FakeIPSaveMetadataAsync(metadata *adapter.FakeIPMetadata) {
+	c.saveMetadataAccess.Lock()
+	defer c.saveMetadataAccess.Unlock()
+	c.saveMetadata = metadata
 	if c.saveMetadataTimer == nil {
 		c.saveMetadataTimer = time.AfterFunc(C.FakeIPMetadataSaveInterval, func() {
-			_ = c.FakeIPSaveMetadata(metadata)
+			c.saveMetadataAccess.Lock()
+			savedMetadata := c.saveMetadata
+			c.saveMetadataAccess.Unlock()
+			if savedMetadata != nil {
+				_ = c.FakeIPSaveMetadata(savedMetadata)
+			}
 		})
 	} else {
 		c.saveMetadataTimer.Reset(C.FakeIPMetadataSaveInterval)