lib/model: Consider weak hash on recheckFile (#6797)

lib/model/model.go

@@ -1524,7 +1524,7 @@ func (m *model) Request(deviceID protocol.DeviceID, folder, name string, size in
 	}
 
 	if !scanner.Validate(res.data, hash, weakHash) {
-		m.recheckFile(deviceID, folder, name, offset, hash)
+		m.recheckFile(deviceID, folder, name, offset, hash, weakHash)
 		l.Debugf("%v REQ(in) failed validating data: %s: %q / %q o=%d s=%d", m, deviceID, folder, name, offset, size)
 		return nil, protocol.ErrNoSuchFile
 	}
@@ -1558,7 +1558,7 @@ func newLimitedRequestResponse(size int, limiters ...*byteSemaphore) *requestRes
 	return res
 }
 
-func (m *model) recheckFile(deviceID protocol.DeviceID, folder, name string, offset int64, hash []byte) {
+func (m *model) recheckFile(deviceID protocol.DeviceID, folder, name string, offset int64, hash []byte, weakHash uint32) {
 	cf, ok := m.CurrentFolderFile(folder, name)
 	if !ok {
 		l.Debugf("%v recheckFile: %s: %q / %q: no current file", m, deviceID, folder, name)
@@ -1583,6 +1583,10 @@ func (m *model) recheckFile(deviceID protocol.DeviceID, folder, name string, off
 		l.Debugf("%v recheckFile: %s: %q / %q i=%d: hash mismatch %x != %x", m, deviceID, folder, name, blockIndex, block.Hash, hash)
 		return
 	}
+	if weakHash != 0 && block.WeakHash != weakHash {
+		l.Debugf("%v recheckFile: %s: %q / %q i=%d: weak hash mismatch %v != %v", m, deviceID, folder, name, blockIndex, block.WeakHash, weakHash)
+		return
+	}
 
 	// The hashes provided part of the request match what we expect to find according
 	// to what we have in the database, yet the content we've read off the filesystem doesn't

lib/model/model_test.go

@@ -3174,9 +3174,9 @@ func TestIssue5002(t *testing.T) {
 	}
 	blockSize := int32(file.BlockSize())
 
-	m.recheckFile(protocol.LocalDeviceID, "default", "foo", file.Size-int64(blockSize), []byte{1, 2, 3, 4})
-	m.recheckFile(protocol.LocalDeviceID, "default", "foo", file.Size, []byte{1, 2, 3, 4}) // panic
-	m.recheckFile(protocol.LocalDeviceID, "default", "foo", file.Size+int64(blockSize), []byte{1, 2, 3, 4})
+	m.recheckFile(protocol.LocalDeviceID, "default", "foo", file.Size-int64(blockSize), []byte{1, 2, 3, 4}, 0)
+	m.recheckFile(protocol.LocalDeviceID, "default", "foo", file.Size, []byte{1, 2, 3, 4}, 0) // panic
+	m.recheckFile(protocol.LocalDeviceID, "default", "foo", file.Size+int64(blockSize), []byte{1, 2, 3, 4}, 0)
 }
 
 func TestParentOfUnignored(t *testing.T) {