support client connection attributes on the server side

server/conn.go

@@ -20,6 +20,7 @@ type Conn struct {
 	capability     uint32
 	charset        uint8
 	authPluginName string
+	attributes     map[string]string
 	connectionID   uint32
 	status         uint16
 	warnings       uint16
@@ -160,6 +161,10 @@ func (c *Conn) Charset() uint8 {
 	return c.charset
 }
 
+func (c *Conn) Attributes() map[string]string {
+	return c.attributes
+}
+
 func (c *Conn) ConnectionID() uint32 {
 	return c.connectionID
 }

server/handshake_resp.go

@@ -38,7 +38,14 @@ func (c *Conn) readHandshakeResponse() error {
 		return nil
 	}
 
-	// ignore connect attrs for now, the proxy does not support passing attrs to actual MySQL server
+	// read connection attributes
+	if c.capability&CLIENT_CONNECT_ATTRS > 0 {
+		// readAttributes returns new position for further processing of data
+		_, err = c.readAttributes(data, pos)
+		if err != nil {
+			return err
+		}
+	}
 
 	// try to authenticate the client
 	return c.compareAuthData(c.authPluginName, authData)
@@ -198,3 +205,35 @@ func (c *Conn) handleAuthMatch(authData []byte, pos int) (bool, error) {
 	}
 	return true, nil
 }
+
+func (c *Conn) readAttributes(data []byte, pos int) (int, error) {
+	attrs := make(map[string]string)
+	i := 0
+	var key string
+
+	for {
+		str, isNull, strLen, err := LengthEncodedString(data[pos:])
+
+		if err != nil {
+			return -1, err
+		}
+
+		if isNull {
+			break
+		}
+
+		// reading keys or values
+		if i%2 == 0 {
+			key = string(str)
+		} else {
+			attrs[key] = string(str)
+		}
+
+		pos += strLen
+		i++
+	}
+
+	c.attributes = attrs
+
+	return pos, nil
+}

server/handshake_resp_test.go

@@ -52,3 +52,58 @@ func TestDecodeFirstPart(t *testing.T) {
 		t.Fatalf("unexpected capability, got %d", c.capability)
 	}
 }
+
+func TestReadAttributes(t *testing.T) {
+	var err error
+	// example data from
+	// https://dev.mysql.com/doc/internals/en/connection-phase-packets.html#packet-Protocol::HandshakeResponse41
+	data := []byte{
+		0xb2, 0x00, 0x00, 0x01, 0x85, 0xa2, 0x1e, 0x00, 0x00, 0x00,
+		0x00, 0x40, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x72, 0x6f, 0x6f, 0x74, 0x00, 0x14, 0x22, 0x50, 0x79, 0xa2,
+		0x12, 0xd4, 0xe8, 0x82, 0xe5, 0xb3, 0xf4, 0x1a, 0x97, 0x75, 0x6b, 0xc8,
+		0xbe, 0xdb, 0x9f, 0x80, 0x6d, 0x79, 0x73, 0x71, 0x6c, 0x5f, 0x6e, 0x61,
+		0x74, 0x69, 0x76, 0x65, 0x5f, 0x70, 0x61, 0x73, 0x73, 0x77, 0x6f, 0x72,
+		0x64, 0x00, 0x61, 0x03, 0x5f, 0x6f, 0x73, 0x09, 0x64, 0x65, 0x62, 0x69,
+		0x61, 0x6e, 0x36, 0x2e, 0x30, 0x0c, 0x5f, 0x63, 0x6c, 0x69, 0x65, 0x6e,
+		0x74, 0x5f, 0x6e, 0x61, 0x6d, 0x65, 0x08, 0x6c, 0x69, 0x62, 0x6d, 0x79,
+		0x73, 0x71, 0x6c, 0x04, 0x5f, 0x70, 0x69, 0x64, 0x05, 0x32, 0x32, 0x33,
+		0x34, 0x34, 0x0f, 0x5f, 0x63, 0x6c, 0x69, 0x65, 0x6e, 0x74, 0x5f, 0x76,
+		0x65, 0x72, 0x73, 0x69, 0x6f, 0x6e, 0x08, 0x35, 0x2e, 0x36, 0x2e, 0x36,
+		0x2d, 0x6d, 0x39, 0x09, 0x5f, 0x70, 0x6c, 0x61, 0x74, 0x66, 0x6f, 0x72,
+		0x6d, 0x06, 0x78, 0x38, 0x36, 0x5f, 0x36, 0x34, 0x03, 0x66, 0x6f, 0x6f,
+		0x03, 0x62, 0x61, 0x72,
+	}
+	pos := 85
+
+	c := &Conn{}
+
+	pos, err = c.readAttributes(data, pos)
+	if err != nil {
+		t.Fatalf("unexpected error: got %v", err)
+	}
+
+	if pos != 182 {
+		t.Fatalf("unexpected position: got %d", pos)
+	}
+
+	if len(c.attributes) != 6 {
+		t.Fatalf("unexpected attribute length: got %d", len(c.attributes))
+	}
+
+	fixture := map[string]string{
+		"_client_name":    "libmysql",
+		"_client_version": "5.6.6-m9",
+		"_os":             "debian6.0",
+		"_pid":            "22344",
+		"_platform":       "x86_64",
+		"foo":             "bar",
+	}
+
+	for k, v := range fixture {
+		if vv := c.attributes[k]; vv != v {
+			t.Fatalf("unexpected value for %s, got %s instead of %s", k, vv, v)
+		}
+	}
+}

server/server_conf.go

@@ -78,7 +78,8 @@ func NewServer(serverVersion string, collationId uint8, defaultAuthMethod string
 	//	panic(fmt.Sprintf("default auth method is not one of the allowed auth methods"))
 	//}
 	var capFlag = CLIENT_LONG_PASSWORD | CLIENT_LONG_FLAG | CLIENT_CONNECT_WITH_DB | CLIENT_PROTOCOL_41 |
-		CLIENT_TRANSACTIONS | CLIENT_SECURE_CONNECTION | CLIENT_PLUGIN_AUTH | CLIENT_PLUGIN_AUTH_LENENC_CLIENT_DATA
+		CLIENT_TRANSACTIONS | CLIENT_SECURE_CONNECTION | CLIENT_PLUGIN_AUTH | CLIENT_CONNECT_ATTRS |
+		CLIENT_PLUGIN_AUTH_LENENC_CLIENT_DATA
 	if tlsConfig != nil {
 		capFlag |= CLIENT_SSL
 	}