Return a better error when join fails

net.go

@@ -55,6 +55,7 @@ const (
 	encryptMsg
 	nackRespMsg
 	hasCrcMsg
+	errMsg
 )
 
 // compressionType is used to specify the compression algorithm
@@ -105,6 +106,11 @@ type nackResp struct {
 	SeqNo uint32
 }
 
+// err response is sent to relay the error from the remote end
+type errResp struct {
+	Error string
+}
+
 // suspect is broadcast when we suspect a node is dead
 type suspect struct {
 	Incarnation uint32
@@ -209,6 +215,19 @@ func (m *Memberlist) handleConn(conn net.Conn) {
 	if err != nil {
 		if err != io.EOF {
 			m.logger.Printf("[ERR] memberlist: failed to receive: %s %s", err, LogConn(conn))
+
+			resp := errResp{err.Error()}
+			out, err := encode(errMsg, &resp)
+			if err != nil {
+				m.logger.Printf("[ERR] memberlist: Failed to encode error response: %s", err)
+				return
+			}
+
+			err = m.rawSendMsgStream(conn, out.Bytes())
+			if err != nil {
+				m.logger.Printf("[ERR] memberlist: Failed to send error: %s %s", err, LogConn(conn))
+				return
+			}
 		}
 		return
 	}
@@ -726,6 +745,14 @@ func (m *Memberlist) sendAndReceiveState(addr string, join bool) ([]pushNodeStat
 		return nil, nil, err
 	}
 
+	if msgType == errMsg {
+		var resp errResp
+		if err := dec.Decode(&resp); err != nil {
+			return nil, nil, err
+		}
+		return nil, nil, fmt.Errorf("remote error: %v", resp.Error)
+	}
+
 	// Quit if not push/pull
 	if msgType != pushPullMsg {
 		err := fmt.Errorf("received invalid msgType (%d), expected pushPullMsg (%d) %s", msgType, pushPullMsg, LogConn(conn))

net_test.go

@@ -785,3 +785,30 @@ func TestIngestPacket_CRC(t *testing.T) {
 		t.Fatalf("bad: %s", logs.String())
 	}
 }
+
+func TestGossip_MismatchedKeys(t *testing.T) {
+	c1 := testConfig()
+	c2 := testConfig()
+
+	// Create two agents with different gossip keys
+	c1.SecretKey = []byte("4W6DGn2VQVqDEceOdmuRTQ==")
+	c2.SecretKey = []byte("XhX/w702/JKKK7/7OtM9Ww==")
+
+	m1, err := Create(c1)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	defer m1.Shutdown()
+
+	m2, err := Create(c2)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	defer m2.Shutdown()
+
+	// Make sure we get this error on the joining side
+	_, err = m2.Join([]string{c1.BindAddr})
+	if err == nil || !strings.Contains(err.Error(), "No installed keys could decrypt the message") {
+		t.Fatalf("bad: %s", err)
+	}
+}