From a343408ccba57a719b27390ec19c55e8bd058355 Mon Sep 17 00:00:00 2001
From: raffertyyu <raffertyyu@tencent.com>
Date: Mon, 11 Nov 2024 11:40:27 +0800
Subject: [PATCH 1/2] send client connect attrs according to whether mysql
 server supports CLIENT_CONNECT_ATTRS

---
 packets.go | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/packets.go b/packets.go
index eb4e0cef..0552bd82 100644
--- a/packets.go
+++ b/packets.go
@@ -210,10 +210,12 @@ func (mc *mysqlConn) readHandshakePacket() (data []byte, plugin string, err erro
 	if len(data) > pos {
 		// character set [1 byte]
 		// status flags [2 bytes]
+		pos += 1 + 2
 		// capability flags (upper 2 bytes) [2 bytes]
+		mc.flags |= clientFlag(binary.LittleEndian.Uint16(data[pos:pos+2])) << 16
 		// length of auth-plugin-data [1 byte]
 		// reserved (all [00]) [10 bytes]
-		pos += 1 + 2 + 2 + 1 + 10
+		pos += 2 + 1 + 10
 
 		// second part of the password cipher [minimum 13 bytes],
 		// where len=MAX(13, length of auth-plugin-data - 8)
@@ -261,9 +263,11 @@ func (mc *mysqlConn) writeHandshakeResponsePacket(authResp []byte, plugin string
 		clientLocalFiles |
 		clientPluginAuth |
 		clientMultiResults |
-		clientConnectAttrs |
+		mc.flags&clientConnectAttrs |
 		mc.flags&clientLongFlag
 
+	serverSupportClientConnectAttrs := mc.flags&clientConnectAttrs != 0
+
 	if mc.cfg.ClientFoundRows {
 		clientFlags |= clientFoundRows
 	}
@@ -295,11 +299,14 @@ func (mc *mysqlConn) writeHandshakeResponsePacket(authResp []byte, plugin string
 		pktLen += n + 1
 	}
 
+	var connAttrsLEI []byte
 	// encode length of the connection attributes
-	var connAttrsLEIBuf [9]byte
-	connAttrsLen := len(mc.connector.encodedAttributes)
-	connAttrsLEI := appendLengthEncodedInteger(connAttrsLEIBuf[:0], uint64(connAttrsLen))
-	pktLen += len(connAttrsLEI) + len(mc.connector.encodedAttributes)
+	if serverSupportClientConnectAttrs {
+		var connAttrsLEIBuf [9]byte
+		connAttrsLen := len(mc.connector.encodedAttributes)
+		connAttrsLEI = appendLengthEncodedInteger(connAttrsLEIBuf[:0], uint64(connAttrsLen))
+		pktLen += len(connAttrsLEI) + len(mc.connector.encodedAttributes)
+	}
 
 	// Calculate packet length and get buffer with that size
 	data, err := mc.buf.takeBuffer(pktLen + 4)
@@ -382,8 +389,10 @@ func (mc *mysqlConn) writeHandshakeResponsePacket(authResp []byte, plugin string
 	pos++
 
 	// Connection Attributes
-	pos += copy(data[pos:], connAttrsLEI)
-	pos += copy(data[pos:], []byte(mc.connector.encodedAttributes))
+	if serverSupportClientConnectAttrs {
+		pos += copy(data[pos:], connAttrsLEI)
+		pos += copy(data[pos:], []byte(mc.connector.encodedAttributes))
+	}
 
 	// Send Auth packet
 	return mc.writePacket(data[:pos])

From 782166f670b9031c629d002c9b96203d5e695015 Mon Sep 17 00:00:00 2001
From: Inada Naoki <songofacandy@gmail.com>
Date: Mon, 11 Nov 2024 15:32:42 +0900
Subject: [PATCH 2/2] code styling

---
 packets.go | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/packets.go b/packets.go
index 0552bd82..a2e7ef95 100644
--- a/packets.go
+++ b/packets.go
@@ -210,12 +210,13 @@ func (mc *mysqlConn) readHandshakePacket() (data []byte, plugin string, err erro
 	if len(data) > pos {
 		// character set [1 byte]
 		// status flags [2 bytes]
-		pos += 1 + 2
+		pos += 3
 		// capability flags (upper 2 bytes) [2 bytes]
 		mc.flags |= clientFlag(binary.LittleEndian.Uint16(data[pos:pos+2])) << 16
+		pos += 2
 		// length of auth-plugin-data [1 byte]
 		// reserved (all [00]) [10 bytes]
-		pos += 2 + 1 + 10
+		pos += 11
 
 		// second part of the password cipher [minimum 13 bytes],
 		// where len=MAX(13, length of auth-plugin-data - 8)
@@ -266,7 +267,7 @@ func (mc *mysqlConn) writeHandshakeResponsePacket(authResp []byte, plugin string
 		mc.flags&clientConnectAttrs |
 		mc.flags&clientLongFlag
 
-	serverSupportClientConnectAttrs := mc.flags&clientConnectAttrs != 0
+	sendConnectAttrs := mc.flags&clientConnectAttrs != 0
 
 	if mc.cfg.ClientFoundRows {
 		clientFlags |= clientFoundRows
@@ -299,9 +300,9 @@ func (mc *mysqlConn) writeHandshakeResponsePacket(authResp []byte, plugin string
 		pktLen += n + 1
 	}
 
-	var connAttrsLEI []byte
 	// encode length of the connection attributes
-	if serverSupportClientConnectAttrs {
+	var connAttrsLEI []byte
+	if sendConnectAttrs {
 		var connAttrsLEIBuf [9]byte
 		connAttrsLen := len(mc.connector.encodedAttributes)
 		connAttrsLEI = appendLengthEncodedInteger(connAttrsLEIBuf[:0], uint64(connAttrsLen))
@@ -389,7 +390,7 @@ func (mc *mysqlConn) writeHandshakeResponsePacket(authResp []byte, plugin string
 	pos++
 
 	// Connection Attributes
-	if serverSupportClientConnectAttrs {
+	if sendConnectAttrs {
 		pos += copy(data[pos:], connAttrsLEI)
 		pos += copy(data[pos:], []byte(mc.connector.encodedAttributes))
 	}