From f07951f34841b499388ea97789a7ec1c3cd84141 Mon Sep 17 00:00:00 2001
From: Inada Naoki <songofacandy@gmail.com>
Date: Tue, 11 Jun 2024 22:34:45 +0900
Subject: [PATCH] fix some write error handling (#1595)

interpolateParams() returned ErrInvalidConn without closing the connection.
Since database/sql doesn't understand ErrInvalidConn, there is a risk
that database/sql reuse this connection and ErrInvalidConn is returned
repeatedly.
---
 connection.go | 6 ++++--
 packets.go    | 2 ++
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/connection.go b/connection.go
index eff978d93..9c771b83c 100644
--- a/connection.go
+++ b/connection.go
@@ -217,8 +217,10 @@ func (mc *mysqlConn) interpolateParams(query string, args []driver.Value) (strin
 	buf, err := mc.buf.takeCompleteBuffer()
 	if err != nil {
 		// can not take the buffer. Something must be wrong with the connection
-		mc.log(err)
-		return "", ErrInvalidConn
+		mc.cleanup()
+		// interpolateParams would be called before sending any query.
+		// So its safe to retry.
+		return "", driver.ErrBadConn
 	}
 	buf = buf[:0]
 	argPos := 0
diff --git a/packets.go b/packets.go
index 90a34728b..3bcba1c92 100644
--- a/packets.go
+++ b/packets.go
@@ -116,6 +116,8 @@ func (mc *mysqlConn) writePacket(data []byte) error {
 		// Write packet
 		if mc.writeTimeout > 0 {
 			if err := mc.netConn.SetWriteDeadline(time.Now().Add(mc.writeTimeout)); err != nil {
+				mc.cleanup()
+				mc.log(err)
 				return err
 			}
 		}