Explicitly close connection on ErrBadConn

connection.go

@@ -109,11 +109,16 @@ func (mc *mysqlConn) Begin() (driver.Tx, error) {
 }
 
 func (mc *mysqlConn) Close() (err error) {
-	mc.writeCommandPacket(comQuit)
+	// Makes Close idempotent
+	if mc.netConn != nil {
+		mc.writeCommandPacket(comQuit)
+		mc.netConn.Close()
+		mc.netConn = nil
+	}
+
 	mc.cfg = nil
 	mc.buf = nil
-	mc.netConn.Close()
-	mc.netConn = nil
+
 	return
 }
 

packets.go

@@ -29,6 +29,7 @@ func (mc *mysqlConn) readPacket() (data []byte, err error) {
 	data, err = mc.buf.readNext(4)
 	if err != nil {
 		errLog.Print(err.Error())
+		mc.Close()
 		return nil, driver.ErrBadConn
 	}
 
@@ -37,6 +38,7 @@ func (mc *mysqlConn) readPacket() (data []byte, err error) {
 
 	if pktLen < 1 {
 		errLog.Print(errMalformPkt.Error())
+		mc.Close()
 		return nil, driver.ErrBadConn
 	}
 
@@ -51,8 +53,7 @@ func (mc *mysqlConn) readPacket() (data []byte, err error) {
 	mc.sequence++
 
 	// Read packet body [pktLen bytes]
-	data, err = mc.buf.readNext(pktLen)
-	if err == nil {
+	if data, err = mc.buf.readNext(pktLen); err == nil {
 		if pktLen < maxPacketSize {
 			return data, nil
 		}
@@ -66,6 +67,9 @@ func (mc *mysqlConn) readPacket() (data []byte, err error) {
 			return append(buf, data...), nil
 		}
 	}
+
+	// err case
+	mc.Close()
 	errLog.Print(err.Error())
 	return nil, driver.ErrBadConn
 }

rows.go

@@ -38,11 +38,15 @@ func (rows *mysqlRows) Columns() (columns []string) {
 func (rows *mysqlRows) Close() (err error) {
 	// Remove unread packets from stream
 	if !rows.eof {
-		if rows.mc == nil {
+		if rows.mc == nil || rows.mc.netConn == nil {
 			return errInvalidConn
 		}
 
 		err = rows.mc.readUntilEOF()
+
+		// explicitly set because readUntilEOF might return early in case of an
+		// error
+		rows.eof = true
 	}
 
 	rows.mc = nil
@@ -55,7 +59,7 @@ func (rows *mysqlRows) Next(dest []driver.Value) (err error) {
 		return io.EOF
 	}
 
-	if rows.mc == nil {
+	if rows.mc == nil || rows.mc.netConn == nil {
 		return errInvalidConn
 	}
 

statement.go

@@ -21,6 +21,10 @@ type mysqlStmt struct {
 }
 
 func (stmt *mysqlStmt) Close() (err error) {
+	if stmt.mc == nil || stmt.mc.netConn == nil {
+		return errInvalidConn
+	}
+
 	err = stmt.mc.writeCommandPacketUint32(comStmtClose, stmt.id)
 	stmt.mc = nil
 	return

transaction.go

@@ -14,12 +14,18 @@ type mysqlTx struct {
 }
 
 func (tx *mysqlTx) Commit() (err error) {
+	if tx.mc == nil {
+		return errInvalidConn
+	}
 	err = tx.mc.exec("COMMIT")
 	tx.mc = nil
 	return
 }
 
 func (tx *mysqlTx) Rollback() (err error) {
+	if tx.mc == nil {
+		return errInvalidConn
+	}
 	err = tx.mc.exec("ROLLBACK")
 	tx.mc = nil
 	return