use ErrBadConn only if nothing is written

Author: arnehormann

connection.go

@@ -107,7 +107,9 @@ func (mc *mysqlConn) Begin() (driver.Tx, error) {
 	if err == nil {
 		return &mysqlTx{mc}, err
 	}
-
+	if err == errNoWrite {
+		return driver.ErrBadConn
+	}
 	return nil, err
 }
 
@@ -137,6 +139,9 @@ func (mc *mysqlConn) Prepare(query string) (driver.Stmt, error) {
 	// Send command
 	err := mc.writeCommandPacketStr(comStmtPrepare, query)
 	if err != nil {
+		if err == errNoWrite {
+			return nil, driver.ErrBadConn
+		}
 		return nil, err
 	}
 
@@ -177,6 +182,9 @@ func (mc *mysqlConn) Exec(query string, args []driver.Value) (driver.Result, err
 				insertId:     int64(mc.insertId),
 			}, err
 		}
+		if err == errNoWrite {
+			return nil, driver.ErrBadConn
+		}
 		return nil, err
 	}
 
@@ -231,6 +239,9 @@ func (mc *mysqlConn) Query(query string, args []driver.Value) (driver.Rows, erro
 				return rows, err
 			}
 		}
+		if err == errNoWrite {
+			return nil, driver.ErrBadConn
+		}
 		return nil, err
 	}
 
@@ -243,6 +254,9 @@ func (mc *mysqlConn) Query(query string, args []driver.Value) (driver.Rows, erro
 func (mc *mysqlConn) getSystemVar(name string) ([]byte, error) {
 	// Send command
 	if err := mc.writeCommandPacketStr(comQuery, "SELECT @@"+name); err != nil {
+		if err == errNoWrite {
+			return nil, driver.ErrBadConn
+		}
 		return nil, err
 	}
 

driver.go

@@ -118,6 +118,9 @@ func (d MySQLDriver) Open(dsn string) (driver.Conn, error) {
 	maxap, err := mc.getSystemVar("max_allowed_packet")
 	if err != nil {
 		mc.Close()
+		if err == driver.ErrBadConn {
+			err = ErrInvalidConn
+		}
 		return nil, err
 	}
 	mc.maxPacketAllowed = stringToInt(maxap) - 1

errors.go

@@ -28,6 +28,7 @@ var (
 	ErrPktSyncMul  = errors.New("Commands out of sync. Did you run multiple statements at once?")
 	ErrPktTooLarge = errors.New("Packet for query is too large. You can change this value on the server by adjusting the 'max_allowed_packet' variable.")
 	ErrBusyBuffer  = errors.New("Busy buffer")
+	errNoWrite     = errors.New("No data written")
 )
 
 var errLog Logger = log.New(os.Stderr, "[MySQL] ", log.Ldate|log.Ltime|log.Lshortfile)

packets.go

@@ -114,8 +114,12 @@ func (mc *mysqlConn) writePacket(data []byte) error {
 		// Handle error
 		if err == nil { // n != len(data)
 			errLog.Print(ErrMalformPkt)
-		} else {
-			errLog.Print(err)
+			return ErrMalformPkt
+		}
+		errLog.Print(err)
+		if n == 0 && pktLen == len(data)-4 {
+			// first loop iteration, nothing was written
+			return errNoWrite
 		}
 		return ErrInvalidConn
 	}
@@ -731,6 +735,10 @@ func (stmt *mysqlStmt) writeCommandLongData(paramID int, arg []byte) error {
 			data = data[pktLen-dataOffset:]
 			continue
 		}
+		if err == errNoWrite && argLen != len(arg) {
+			// must not relay errNoWrite after first loop iteration
+			return ErrInvalidConn
+		}
 		return err
 
 	}

statement.go

@@ -26,6 +26,9 @@ func (stmt *mysqlStmt) Close() error {
 	}
 
 	err := stmt.mc.writeCommandPacketUint32(comStmtClose, stmt.id)
+	if err == errNoWrite {
+		err = ErrInvalidConn
+	}
 	stmt.mc = nil
 	return err
 }
@@ -42,6 +45,9 @@ func (stmt *mysqlStmt) Exec(args []driver.Value) (driver.Result, error) {
 	// Send command
 	err := stmt.writeExecutePacket(args)
 	if err != nil {
+		if err == errNoWrite {
+			return driver.ErrBadConn
+		}
 		return nil, err
 	}
 
@@ -82,6 +88,9 @@ func (stmt *mysqlStmt) Query(args []driver.Value) (driver.Rows, error) {
 	// Send command
 	err := stmt.writeExecutePacket(args)
 	if err != nil {
+		if err == errNoWrite {
+			return driver.ErrBadConn
+		}
 		return nil, err
 	}