@@ -1,3 +1,5 @@
 module .com/go-sql-driver/mysql
 
 go 1.18
+
+require golang.org/x/sys v0.10.0 // indirect

@@ -0,0 +1,2 @@
+golang.org/x/sys v0.10.0 h1:SqMFp9UcQJZa+pmYuAKjd9xq1f0j5rLcDIk0mj4qAsA=
+golang.org/x/sys v0.10.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=

@@ -14,6 +14,7 @@ import (
 "database/sql/driver"
 "encoding/binary"
 "encoding/json"
+"errors"
 "fmt"
 "io"
 "math"
@@ -44,12 +45,24 @@ func (mc *mysqlConn) readPacket() ([]byte, error) {
 
 // check packet sync [8 bit]
 if data[3] != mc.sequence {
+var syncErr error
 if data[3] > mc.sequence {
-return nil, ErrPktSyncMul
+syncErr = ErrPktSyncMul
+} else {
+syncErr = ErrPktSync
 }
-return nil, ErrPktSync
+
+if prevData != nil {
+return nil, syncErr
+} else {
+// log and ignore seqno mismatch error.
+// MySQL sometimes sends wrong sequence no.
+mc.cfg.Logger.Print(syncErr)
+mc.sequence = data[3] + 1
+}
+} else {
+mc.sequence++
 }
-mc.sequence++
 
 // packets with length 0 terminate a previous packet which is a
 // multiple of (2^24)-1 bytes long
@@ -89,6 +102,9 @@ func (mc *mysqlConn) readPacket() ([]byte, error) {
 }
 }
 
+// used in conncheck.go
+var errUnexpectedEvent = errors.New("recieved unexpected event")
+
 // Write packet buffer 'data'
 func (mc *mysqlConn) writePacket(data []byte) error {
 pktLen := len(data) - 4
@@ -111,18 +127,29 @@ func (mc *mysqlConn) writePacket(data []byte) error {
 }
 var err error
 if mc.cfg.CheckConnLiveness {
-if mc.cfg.ReadTimeout != 0 {
-err = conn.SetReadDeadline(time.Now().Add(mc.cfg.ReadTimeout))
-}
-if err == nil {
-err = connCheck(conn)
+err = connCheck(conn)
+if err != nil {
+if err == errUnexpectedEvent {
+_ = conn.SetReadDeadline(time.Now().Add(time.Second))
+var data []byte
+data, err = mc.readPacket()
+
+if err == nil {
+if data[0] == iERR {
+err = mc.handleErrorPacket(data)
+} else {
+err = fmt.Errorf("unexpected packet: % x", data[:128])
+}
+} else {
+err = fmt.Errorf("readPacket(): %w", err)
+}
+}
+
+mc.cfg.Logger.Print("checkConn() failed: ", err)
+mc.Close()
+return driver.ErrBadConn
 }
 }
-if err != nil {
-mc.cfg.Logger.Print("closing bad idle connection: ", err)
-mc.Close()
-return driver.ErrBadConn
-}
 }
 
 for {

@@ -11,6 +11,7 @@ package mysql
 import (
 "bytes"
 "errors"
+"fmt"
 "net"
 "testing"
 "time"
@@ -132,31 +133,57 @@ func TestReadPacketSingleByte(t *testing.T) {
 }
 }
 
+type mockLogger struct {
+bytes.Buffer
+}
+
+func (ml *mockLogger) Print(v ...any) {
+ml.WriteString(fmt.Sprint(v...) + "\n")
+}
+
 func TestReadPacketWrongSequenceID(t *testing.T) {
 conn := new(mockConn)
 mc := &mysqlConn{
 buf: newBuffer(conn),
+cfg: NewConfig(),
 }
+logger := &mockLogger{}
+mc.cfg.Logger = Logger(logger)
 
 // too low sequence id
 conn.data = []byte{0x01, 0x00, 0x00, 0x00, 0xff}
 conn.maxReads = 1
 mc.sequence = 1
-_, err := mc.readPacket()
-if err != ErrPktSync {
-t.Errorf("expected ErrPktSync, got %v", err)
+data, err := mc.readPacket()
+if err != nil {
+t.Errorf("expected nil, got %v", err)
+}
+if len(data) != 1 || data[0] != 0xff {
+t.Errorf("expected [0xff], got % x", data)
+}
+logMsg := logger.String()
+if logMsg != ErrPktSync.Error()+"\n" {
+t.Errorf("expected ErrPktSync.Error(), got %q", logMsg)
 }
 
 // reset
 conn.reads = 0
 mc.sequence = 0
 mc.buf = newBuffer(conn)
+logger.Reset()
 
 // too high sequence id
 conn.data = []byte{0x01, 0x00, 0x00, 0x42, 0xff}
-_, err = mc.readPacket()
-if err != ErrPktSyncMul {
-t.Errorf("expected ErrPktSyncMul, got %v", err)
+data, err = mc.readPacket()
+if err != nil {
+t.Errorf("expected nil, got %v", err)
+}
+if len(data) != 1 || data[0] != 0xff {
+t.Errorf("expected [0xff], got % x", data)
+}
+logMsg = logger.String()
+if logMsg != ErrPktSyncMul.Error()+"\n" {
+t.Errorf("expected ErrPktSync.Error(), got %q", logMsg)
 }
 }