From ea32d9f4bc5ce4fc07a421845da8f5aeec520f43 Mon Sep 17 00:00:00 2001
From: Tzu-Chiao Yeh <su3g4284zo6y7@gmail.com>
Date: Sat, 5 Sep 2020 09:58:16 +0800
Subject: [PATCH] Ensure backward compatibility with legacy EOF format

---
 connection.go | 25 ++++++++++++++-----------
 packets.go    | 51 ++++++++++++++++-----------------------------------
 rows.go       |  2 +-
 3 files changed, 31 insertions(+), 47 deletions(-)

diff --git a/connection.go b/connection.go
index 425cc5952..90aec6439 100644
--- a/connection.go
+++ b/connection.go
@@ -180,16 +180,16 @@ func (mc *mysqlConn) Prepare(query string) (driver.Stmt, error) {
 
 	// Read Result
 	columnCount, err := stmt.readPrepareResultPacket()
-	if err != nil {
-		return stmt, err
-	}
-
-	if err := mc.readPackets(stmt.paramCount); err != nil {
-		return nil, err
-	}
+	if err == nil {
+		if stmt.paramCount > 0 {
+			if err = mc.readUntilEOF(); err != nil {
+				return nil, err
+			}
+		}
 
-	if err := mc.readPackets(int(columnCount)); err != nil {
-		return nil, err
+		if columnCount > 0 {
+			err = mc.readUntilEOF()
+		}
 	}
 
 	return stmt, err
@@ -415,8 +415,11 @@ func (mc *mysqlConn) getSystemVar(name string) ([]byte, error) {
 		rows.mc = mc
 		rows.rs.columns = []mysqlField{{fieldType: fieldTypeVarChar}}
 
-		if err := mc.readPackets(resLen); err != nil {
-			return nil, err
+		if resLen > 0 {
+			// Columns
+			if err := mc.readUntilEOF(); err != nil {
+				return nil, err
+			}
 		}
 
 		dest := make([]driver.Value, resLen)
diff --git a/packets.go b/packets.go
index 422278fe1..6cec68228 100644
--- a/packets.go
+++ b/packets.go
@@ -614,7 +614,7 @@ func readStatus(b []byte) statusFlag {
 }
 
 // Ok Packet
-// http://dev.mysql.com/doc/internals/en/generic-response-packets.html#packet-OK_Packet
+// https://dev.mysql.com/doc/internals/en/packet-OK_Packet.html
 func (mc *mysqlConn) handleOkPacket(data []byte) error {
 	// 0x00 or 0xFE [1 byte]
 	n := 1
@@ -640,8 +640,12 @@ func (mc *mysqlConn) handleOkPacket(data []byte) error {
 
 // isEOFPacket will return true if the data is either a EOF-Packet or OK-Packet
 // acting as an EOF.
-func isEOFPacket(data []byte) bool {
-	return data[0] == iEOF && len(data) < 9
+func (mc *mysqlConn) isEOFPacket(data []byte) bool {
+	// Legacy EOF packet
+	if data[0] == iEOF && (len(data) == 5 || len(data) == 1) && mc.flags&clientDeprecateEOF == 0 {
+		return true
+	}
+	return data[0] == iEOF && len(data) < 9 && mc.flags&clientDeprecateEOF != 0
 }
 
 // Read Packets as Field Packets until EOF-Packet or an Error appears
@@ -649,13 +653,13 @@ func isEOFPacket(data []byte) bool {
 func (mc *mysqlConn) readColumns(count int) ([]mysqlField, error) {
 	columns := make([]mysqlField, count)
 
-	for i := 0; i < count; i++ {
+	for i := 0; ; i++ {
 		data, err := mc.readPacket()
 		if err != nil {
 			return nil, err
 		}
 
-		if mc.flags&clientDeprecateEOF == 0 && isEOFPacket(data) {
+		if mc.isEOFPacket(data) {
 			if i == count {
 				return columns, nil
 			}
@@ -741,7 +745,6 @@ func (mc *mysqlConn) readColumns(count int) ([]mysqlField, error) {
 		//	defaultVal, _, err = bytesToLengthCodedBinary(data[pos:])
 		//}
 	}
-	return columns, nil
 }
 
 // Read Packets as Field Packets until EOF/OK-Packet or an Error appears
@@ -759,12 +762,13 @@ func (rows *textRows) readRow(dest []driver.Value) error {
 	}
 
 	// EOF Packet
-	if isEOFPacket(data) {
+	if mc.isEOFPacket(data) {
 		if mc.flags&clientDeprecateEOF == 0 {
 			// server_status [2 bytes]
 			rows.mc.status = readStatus(data[3:])
 		} else {
 			if err := mc.handleOkPacket(data); err != nil {
+				rows.mc = nil
 				return err
 			}
 		}
@@ -830,39 +834,15 @@ func (mc *mysqlConn) readUntilEOF() error {
 		switch {
 		case data[0] == iERR:
 			return mc.handleErrorPacket(data)
-		case isEOFPacket(data):
+		case mc.isEOFPacket(data):
 			if mc.flags&clientDeprecateEOF == 0 {
 				mc.status = readStatus(data[3:])
-			} else {
-				return mc.handleOkPacket(data)
+				return nil
 			}
-			return nil
-		}
-	}
-}
-
-func (mc *mysqlConn) readPackets(num int) error {
-
-	// we need to read EOF as well
-	if mc.flags&clientDeprecateEOF == 0 {
-		num++
-	}
 
-	for i := 0; i < num; i++ {
-		data, err := mc.readPacket()
-		if err != nil {
-			return err
-		}
-
-		switch {
-		case data[0] == iERR:
-			return mc.handleErrorPacket(data)
-		case mc.flags&clientDeprecateEOF == 0 && isEOFPacket(data):
-			mc.status = readStatus(data[3:])
-			return nil
+			return mc.handleOkPacket(data)
 		}
 	}
-	return nil
 }
 
 /******************************************************************************
@@ -1223,11 +1203,12 @@ func (rows *binaryRows) readRow(dest []driver.Value) error {
 
 	// packet indicator [1 byte]
 	if data[0] != iOK {
-		if isEOFPacket(data) {
+		if rows.mc.isEOFPacket(data) {
 			if rows.mc.flags&clientDeprecateEOF == 0 {
 				rows.mc.status = readStatus(data[3:])
 			} else {
 				if err := rows.mc.handleOkPacket(data); err != nil {
+					rows.mc = nil
 					return err
 				}
 			}
diff --git a/rows.go b/rows.go
index 888bdb5f0..5567a7287 100644
--- a/rows.go
+++ b/rows.go
@@ -215,7 +215,7 @@ func (rows *textRows) Next(dest []driver.Value) error {
 		if err := mc.error(); err != nil {
 			return err
 		}
-
+		errLog.Print("perform next read")
 		// Fetch next row from stream
 		return rows.readRow(dest)
 	}